The 18th International Symposium on the Physics
of Semiconductors and Applications
Abstracts
July 3 - 7, 2016
Ramada Plaza Jeju Hotel, Jeju, Korea
http://www.ispsa.or.kr
Hosted by
Organized by
Sponsored by
Supported by
The 18th International Symposium on the Physics
of Semiconductors and Applications
Abstracts
July 3 - 7, 2016
Ramada Plaza Jeju Hotel, Jeju, Korea
http://www.ispsa.or.kr
Hosted by
Organized by
Sponsored by
Supported by
CONTENTS
Program Summary
10:00 Dec. 8 (Monday) ~ 13: 00 Dec. 11 (Thursday)
Exhibition for Scientific Equipments (Ballroom Lobby)
A1-I-01
Electron transport in 3D topological insulators
Sungjae Cho
Physics Department, Korea Advanced Institute of Science and Technology, Daejeon 305-701, Korea
* E-mail address: sungjae.cho@kaist.ac.kr
The three dimensional topological insulator (3D TI) is a new class of materials having metallic
surface states while the bulk is insulating. The surface states have gapless Dirac dispersions
with novel properties such as momentum-spin locking. Moreover, coupling the surface states
to an s-wave superconductor is predicted to produce so-called Majorana fermions, which may
be applicable to fault-tolerant topological quantum computations. In this talk, I will discuss my
transport experiments on Bi2Se3, a 3D TI having large bulk bandgap of 0.3eV and a single
surface state. Thin (10~15nm) Bi2Se3 films and nanowires are mechanically exfoliated to
fabricate gate tunable transport devices. Electrolyte gating and/or molecular doping methods
are used to tune the chemical potential into the bulk bandgap through the Dirac point [1-3].
Electronic transport measurements reveal an ambipolar metallic electronic transport in the
topological surface of an insulating bulk [1]. Next, I will discuss my measurements of dc
Josephson effects in TI-superconductor junctions [2]. I will compare my results with threedimensional quantum transport simulations and show that the supercurrent is largely carried by
surface states regardless of disorders. The results clarify key open issues regarding the nature
of supercurrents in topological insulators. Finally, I will discuss my recent experiments on
electron transport in 3D TI nanowires. TI nanowires with an insulating bulk can be described
as a hollow metallic cylinder, showing Aharonov-Bohm oscillations upon magnetic flux
threaded through the axis. Angular-momentum quantization in TI nanowires allows only half
integer angular-momenta due to a Berry phase π and induces a surface gap at zero magnetic
fields. When half quantum magnetic flux (Φ0/2) through the nanowire axis cancels the Berry
phase, a gapless Dirac-mode is predicted to appear. Hence, by measuring the
magnetoconductance of TI nanowire near the Dirac point, a Berry phase of curved TI surfaces
can be detected. The conductance at the Dirac point is expected to have a minimum at Φ = 0
and a maximum (~ e2/h) at Φ = Φ0/2 while oscillating with a period of Φ0 [3]. I will discuss my
four-probe magnetoconductance measurements in a TI (Bi2Se3) nanowire while the gate
voltage is tuned through the Dirac point. My measurement of Aharonov-Bohm effects near the
Dirac point shows the first evidence of 1D gapless Dirac-mode and a Berry phase in a TI
nanowire.
References
[1] Dohun Kim*, Sungjae Cho*(equal contribution), Nicholas P. Butch, Paul Syers, Kevin
Kirshenbaum, Shaffique Adam, Johnpierre Paglione, Michael S. Fuhrer, Nature Physics 8, 460
(2012)
[2] Sungjae Cho, Brian Dellabetta, Alina Yang, John Schneeloch, Zhijun Xu, Tonica Valla,
Genda Gu, Matthew J. Gilbert, Nadya Mason, Nature Communication 4, 1689 (2013)
[3] Sungjae Cho*, Brian Dellabetta, Alina Yang, John Schneeloch, Zhijun Xu, Genda Gu,
Matthew J. Gilbert, Nadya Mason* Nature Communication 6, 7634 (2015)
A1-O-01
Effective high dielectric constant of SrTiO3 thin film in graphene device
Haeyong Kang1, Jeongmin Park1,2, Kyeong Tae Kang1,3, Young Hee Lee1,2, Woo Seok Choi3,
and Dongseok Suh1,2,*
2
1
Deparment of Energy Science, Sungkyunkwan University, Suwon 16419, Korea
IBS center for integrated Nanostructure Physics, Sungkyunkwan University, Suwon 16419, Korea
3
Department of Physics, Sungkyunkwan University, Suwon 16419, Korea
* E-mail address: energy.suh@skku.edu
The voltage scaling was successfully demonstrated in graphene device using an ultrahigh-k
dielectric material, SrTiO3 (STO), with a thickness of 300 nm [1]. STO has been expected to
reveal new quantum physical properties of graphene due to huge enhancement of its dielectric
constant at low temperature. However, unexpected leakage current and doping effect in thin
film prevented STO from playing a role of gate dielectric. In our study, well-grown epitaxial
STO thin film showed low level of leakage current and graphene device on STO exhibited a
non-hysteretic behavior with typical ambipolar property at all measured temperature range.
Reduced gate voltage for device operation was successfully achieved by its high dielectric
constant and thin layer. STO-graphene device showed the well-developed quantum
conductance behaviors under the magnetic field, where the lowest quantum Hall state still
remained at a high temperature of 200 K. Moreover, universal quantum behavior allowed us to
estimate the effective dielectric constant of STO in the device, which was consistent with the
results from capacitance measurement. Throughout our study, we believe two-dimensional
semiconducting materials on the thin film STO with high dielectric constant makes it possible
to greatly reduce subthreshold swing for electronic devices.
References
1. J. Park, H. Kang, K. T. Kang, Y. Yun, Y. H. Lee, W. S. Choi, and D. Suh, Nano Lett., 16,
1754 (2016).
A1-O-02
Toward large-area transition metal dischalcogendide
Ki Kang Kim*
Dongguk University, 10105 New-Engineering Building, 30 Pildong-ro 1 gi, Korea
* E-mail address: kkkim@dongguk.edu
Semiconducting transition metal dichalcogenides (s-TMdCs) have been interested due to their
exceptional physical, chemical, and optical properties. In this presentation, we present the way
to prepare the large-area and high-quality s-TMdCs by means of chemical vapor deposition.
First, we introduce new precursors to increase the coverage of monolayer s-TMdCs on the
growth substrate. Second, we suggest new substrates to grow s-TMdCs. Our strategies will not
only pave the way to synthesize large-area and high-quality 2D, but also promote their real
applications.
A2-I-01
Novel 2D interfaces with silicon, graphene, MoTe2 and Ca2N
Heejun Yang1*
1
Deparment of Energy Science, Sungkyunkwan University, Suwon 16419, Korea
* E-mail address: h.yang@skku.edu
Two-dimensional (2D) interfaces with diverse three-dimensional materials' contact have long
been an issue familiar to scientists and engineers. These days, together with 2D materials and
emerging 1D edge contact, the 2D interfaces are attracting renewed interests for various
applications such as next-generation devices. In particular, polymorph engineering in group 6
TMDs, such as MX2 with M=(Mo, W) and X=(S, Se, Te), has allowed an intriguing theme in
the interface science, a formation of homojunction in a single material.
In this talk, I will briefly review interesting features of 2D interface including graphene [1].
Then, homojunctions between metallic (1T') and semiconducting (2H) MoTe2, generated by
two methods (laser irradiation and contacting to low work function material), will be discussed
[2]. The synthesis of high quality MoTe2 has been a key for these studies [3]. We demonstrate
that our high quality single-crystalline and semimetallic 1T'-MoTe2 exhibits a maximum carrier
mobility of 4,000 cm2V-1s-1 and a giant magnetoresistance of 16,000% in a magnetic field of
14 Tesla at 1.8 Kelvin in the bulk form, and the few-layered 1T’-MoTe2 reveals a bandgap of
up to 60 meV in its monoclinic form. The small energy difference between 2H and 1T'-MoTe2,
resulting in the presence of the two polymorphs, is also used for a novel way of structural phase
transition, contact-driven phase change. Extremely low work function of Ca2N, ~2.3 eV,
realizes a large charge transfer that can switch the material's symmetry in a long range of ~100
nm. These interface studies suggest novel contact-based 2D materials design and applications.
References
1. Heejun Yang et al., Science 336, 1140 (2012).
2. S. Cho et al., Science 349, 625 (2015).
3. D. H. Keum et al., Nature Physics 11, 482 (2015).
A2-O-01
Highly Sensitive NH3 Detection in Fluorine Doped 2D Tungsten Disulfides
Young In Jhon, Younghee Kim, Chulki Kim, Taikjin Lee, and Young Min Jhon*
Sensor System Research Center, Korea Institute of Science and Technology, Seoul 136-791, Republic of Korea
* E-mail address: ymjhon@kist.re.kr
Recently, 2D transition-metal dichalcogenides, which consist of hexagonally arranged
transition metal atoms that are sandwiched between two layers of chalcogen atoms, have gained
great attention due to their unique superb optoelectronic properties. In particular, the reduced
dielectric screening in these 2D materials and the heavy effective mass of charge carriers
arising from d-orbitals of the transition-metal atoms significantly increase the Coulombic
interaction between the electrons and holes that are optically generated in them, creating stable
electron-hole pairs (excitons) even at room temperature. These excitons can further become
charged by binding an additional electron or hole to form charged excitons named trions
resulting in characteristic exciton and trion dynamics.
Among 2D transition-metal dichalcogenides, monolayer (1L) MoS2 and WS2 exhibit a
significantly low photoluminescence (PL) than that expected in high-quality direct band-gap
semiconductors due to the abundance of trions in their naturally n-doped states1,2, and this low
PL intensity can be substantially enhanced by decreasing the electron density and thus inducing
the trion-to-exciton transition. Consequently, these 2D semiconductors exhibit ultrasensitive
PL response to environmental gases. However, they can only detect p-type gases such as NO2
so far since they are inherently electron-rich.
Here, for the first time, we show that fluorine plasma functionalization can effectively
enhance PL intensity of 1L WS2 via charge transfer, accompanied by significant modification
of its electronic states, and this fluorine doped 1L WS2 (Figure 1a) can serve as an excellent
PL sensor for NO2 gases while pristine 1L WS2 cannot (Figure 1b and 1c). The spectrum weight
analysis on excitons and trions indicates that this is achieved by the charge of electron density
in 1L WS2, indicating possible fabrication of resistive NO2 sensor elements using this material
as well. An efficient method of controlling fluorine functionalization level is also suggested for
tuning the sensing signal strength for a wide range of gas detection.
Fig. 1. (a) Schematic of fluorine doped WS2 sensor for NO2 gases; (b-c) The PL responses of pristine and
fluorine-doped 1L WS2 samples under periodic and stepwise increasing dose of NO2 gases, respectively.
References
1. Mak, K. F. et al. Tightly Bound Trions in Monolayer MoS2. Nat. Mater. 12, 207–211
(2013).
2. Ross, J. S. et al. Electrical Control of Neutral and Charged Excitons in a Monolayer
Semiconductor. Nat. Commun. 4, (2013).
A2-O-02
Boron-ion implantation for p-type doping of graphene by using PMMA as
a stopping layer
Chan Wook Jang1, Jung Hyun Kim1 , Sung Kim1, Suk-Ho Choi1,*, and R. G. Elliman2
1
Department of Applied Physics, Kyung Hee University, Yongin 446-701, Korea
Department of Electronic Materials Engineering, Research School of Physics and Engineering, The Australian
National University, Canberra ACT 0200, Australia
*E-mail address: sukho@khu.ac.kr
2
We report a new method of ion implantation for hole doping of graphene. For this, the surface
of the graphene is properly coated with polymethyl methacrylate (PMMA) as a stopping layer
for making B ions distributed in the graphene layer. PMMA/graphene/Cu-foil stacks of 2 x 2
cm2 area were implanted with 35 keV B- ions to nominal fluences (ϕB) of 0.5 - 50 x 1010 cm-2
at room temperature and heated by rapid thermal annealing (1000 oC for 10 s under vacuum)
to anneal the radiation damage and activate the implanted B. [1] At a ϕB of 0.5 x 1010 cm-2, a
big shift of the average data point (ωG, ω2D) in the Raman G-2D frequency (ωG–ω2D) space is
observed in the uniaxial stress direction with its negligible shift in the charge-doping direction.
As ϕB increases from 0.5 x 1010 to 50 x 1010 cm-2, the (ωG, ω2D) points of doped graphene are
almost placed in the charge-doping direction, indicating that the charge-doping effect is more
dominant than the strain effect at larger ϕB. The sharp reduction of electron and hole mobilities
by doping at ϕB = 0.5 x 1010 cm-2 can be attributed to the strain effect, as proved from the
Raman-scattering data. Above ϕB = 0.5 x 1010 cm-2, the electron and hole mobilities increase
with increasing ϕB, as estimated from the Dirac curves, because the charge-doping effect is
more dominant than the stain effect, consistent with the increase of carrier concentration above
ϕB = 0.5 x 1010 cm-2. At the highest ϕB of 50 x 1010 cm-2, the hole mobility reaches 1703 cm2V1 -1
s . These results and theoretical considerations suggest that the electrical properties of the Bdoped graphene are governed by the strain effect at low ϕB, but by the charge-doping effect at
high ϕB. These results and the physical mechanisms underpinning them will be discussed.
References
1. M. Telychko, P. Mutombo, M. Ondracek, P. Hapala, F. C. Bocquet, J. Kolorenc, M.
Vondracek, P. Jelınek, and M. Svec, ACS Nano 7, 7318 (2014).
A2-O-03
Quantum spin Hall insulators with tunable topological edge states in 1T’ –
MoX2(X=S, Se, Te) nanoribbons
Duk-Hyun Choe1 , Kee Joo Chang1 and Ha Jun Sung1*
1
KAIST, Daehak-ro, Daejeon, Korea
*E-mail address: kjchang@kaist.ac.kr
Recently, layered transition metal dichalcogenides (TMDs) with 1T’ structure have been
predicted to be two-dimensional (2D) topological insulators (TIs), namely, quantum spin Hall
(QSH) insulators. Topological insulators have attracted much attention owing to their
fundamental interests and potential applications. QSH insulators possess a bulk insulating gap
as well as gapless edge states. The edge states exhibit a linear dispersion giving rise to a Dirac
fermion behavior, which can lead to an efficient transport of charge carriers. However, to date,
the QSH effect only occurs at very low temperatures, below 10K for HgTe/CdTe and
InAs/GaSb quantum wells, due to the small band gaps. For practical applications of QSH
insulators, large band gaps and edge states within the band gap are desirable because they allow
for device operation at room temperature and quantum transport without dissipation.
Furthermore, applications of TIs to a wide range of devices would require a manipulation of
the properties of the topological edge states while keeping the bulk sufficiently insulating.
In this work, we systematically study the electronic structure of QSH insulators based on 1T’MoX2 with X = (S, Se, Te) through first-principles density functional calculations. Our focus
is on identifying the range of strain where the topological edge states exist within the bulk gap
in 1T’-MoX2 nanoribbons. Although the location of the Dirac point depends on the chalcogen
species, we show the possibility of tuning the Dirac point in the band gap by applying
compressive or tensile strain. The bulk gaps can reach up to 167, 228, and 362 meV under
tensile strain for X= S, Se, and Te, respectively, which are sufficiently large enough for device
operation at room temperature. Especially, considering the band gap size and the location of
the Dirac point, we suggest that, among TMDs, MoSe2 would be the best candidate for QSHbased device operation.
A2-O-04
Epitaxially Grown Monolayer ZnO on 2D Materials
Hyo-Ki Hong1, Junhyeon Jo1, Daeyeon Hwang4, Jongyeong Lee1, Na Yeon Kim1,2,
Seungwoo Son1, Jung Hwa Kim1, Mi-jin Jin1, Young Chul Jun1, Rolf Erni3, Sang Kyu
Kwak4, Jung-Woo Yoo1, Zonghoon Lee1,2,*
1
School of Materials Science and Engineering, Ulsan National Institute of Science and Technology (UNIST),
Ulsan 44919, Rep. of Korea
2
Center for Multidimensional Carbon Materials, Institute for Basic Science (IBS), Ulsan 44919, Rep. of Korea
3
Electron Microscopy Center, Empa – Swiss Federal Laboratories for Materials Science and Technology, CH8600 Dübendorf, Switzerland
4
School of Energy and Chemical Engineering, Ulsan National Institute of Science and Technology (UNIST),
Ulsan 44919, Rep. of Korea
* E-mail address: zhlee@unist.ac.kr
ZnO, which has many forms, such as nanowire, quantum dot, and nanotube, has been widely studied
because of its unique optical, electronic, and magnetic properties [1-3]. To date, however, only a few
reports have demonstrated two dimensional ZnO formations on graphene substrate [4]. Here, we show
experimental evidence of epitaxial growth of ZnO monolayer on graphene using atomic resolution
transmission electron microscopy and corresponding image simulations. Binding energy calculation
confirms relative misorientation angle of epitaxially grown ZnO monolayer on graphene.
Misorientation angle of 0° and 30° counted to be the most popular ZnO growth on graphene. We also
demonstrate in situ observations of zinc and oxygen atom-by-atom growth at zigzag edge of ZnO
monolayer on graphene at atomic scale. This graphene-like ZnO monolayer shows different properties
as compared to other ZnO structures.
References
1. Bonaccorso, F. et al. Nature Photonics 4, p.611–622 (2010)
2. Kim, Y. D. et al. Nature Nanotechnology 10, p.676–781 (2015)
3. Bao, Q. et al. ACS Nano 6, p.3677-3694 (2012)
4. Quang, H. T. et al. ACS Nano 9, p.11408-11413 (2015)
A3-I-01
The application of semiconductor plasmon lasers
Ren-Min Ma*
State Key Lab for Mesoscopic Physics and School of Physics, Peking University,
Beijing 100871, China
* renminma@pku.edu.cn
Lasers are the coherent sources of high frequency electromagnetic radiation with
applications spanning all physical sciences and technology. In contrast to classical lasers,
plasmon lasers amplify light coupled to oscillating electrons enabling their physical size and
mode volume to shrink below the diffraction limit. With unprecedented small physical size and
mode volume, new features of plasmon laser are evident. The recent emergence of plasmon
lasers also stimulates the exploration of nanometer-scale science and application towards the
rich physics of deep sub-wavelength optics and the development of high performance devices.
In this talk, I will review our recent works of plasmon laser applications in on-chip optical
interconnector and sensing.
References
[1] Ma, R-M., Yin, X. B., Oulton, R. F., Sorger, V. J. & Zhang, X. “Multiplexed and
electrically modulated plasmon laser circuit” Nano Lett. 12, 5396–5402 (2012).
[2] Ma, R. M., Ota, S., Li, Y. M., Yang, S. and Zhang, X., “Explosive Detection in a Lasing
Plasmon Nanocavity” Nature Nanotechnology, 9, 600, 2014.
[3] X.-Y. Wang, Y.-L. Wang, S. Wang, B. Li, X.-W. Zhang, L. Dai, R.-M. Ma, “Lasing
Enhanced Surface Plasmon Resonance Sensing” Nanophotonics DOI: 10.1515/nanoph-20160006, 2016.
A3-O-01
Localized Surface Plasmon – Colloidal Quantum Dot Coupling in Large
Area of Metallic Nanodisk Arrays for Light Emitting Device Applications
Hyun-Chul Park1, Isnaeni2, Su-Hyun Gong2,and Yong-Hoon Cho2,*
1
Graduate School of Nanoscience and Technology, Korea Advanced Institute of Science and Technology
(KAIST), Daejeon 34141, Republic of Korea
2
Department of Physics, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141,
Republic of Korea
* E-mail address: yhc@kaist.ac.kr
The study of coupling between localized surface plasmons (LSPs) that occur at the metaldielectric interface and light emitters for enhancement of their fluorescence for applications in
light emitting diodes (LEDs) has been very active in the recent years [1]. LSP coupling has
been studied in various different types of LEDs, such as epitaxial LEDs, organic LEDs and
quantum dot (QD) LEDs, where enhancements of PL and electroluminescence (EL) intensities
were observed. However, detailed analysis of the enhancement process is lacking in these
works due to the random distribution of metallic nanostructures. There is an interplay of three
different factors that contribute to the overall enhancement process of an emitter in the vicinity
of a metallic nanostructure: Excitation enhancement [2], spontaneous emission enhancement
[3], and improved scattering of light [4]. In this work, the interaction between colloidal
quantum dots (cQDs) and metallic nanodisks (NDs) in an optical down-conversion LED
structure is investigated. A blue LED with 455 nm emission wavelength is used as the
excitation source, and enhancements of red QDs and green QDs by silver nanodisks (Ag NDs)
and aluminium nanodisks (Al NDs) respectively in a substrate of 500 µm x 500 µm size is
studied in detail. A finite-difference time-domain method is used in order to simulate the
contributions from each aforementioned factor in hexagonal arrays of Ag NDs and Al NDs
interaction with dipoles that represent cQDs. Then a simple model is constructed to estimate
the overall enhancement factor in the whole substrate. Finally, electron-beam lithography is
used to fabricate the hexagonal arrays of the nanodisks and PL experiment is conducted in
order to compare the enhancement factors with the simulated results. Experimental PL
enhancement results for red QD – Ag ND structure and green QD – Al ND structure are around
2.5 fold and 2.3 fold respectively, and are in good agreement with the calculated enhancement
factors from the simulation.
Fig. 1. (a), (b) Schematic images (not in scale) of red QDs on Ag ND array substrate and green QDs on Al ND
array substrate respectively. (c) Hexagonal array of metallic nanodisk fabricated by electron beam lithography.
References
1. E. Urena et al, Adv. Mater., vol. 24, OP314-OP320 (2012)
2. C. Geddes and J. Lakowicz, Journal of Fluorescence, vol. 12 (2002)
3. W. L. Barnes, J. Modern Optics, vol. 45, 661-699 (1998)
4. F. Tam et al, Nano Letters, vol. 7, 496-501 (2007)
A3-O-02
Vertical Efficient Optical Coupling of Long-range Surface Plasmon
Polaritons for Intersubband Transition Photodetector
Shuai Wang1, Jun Zhang1, Feng Wu1, Ju He1, Jiang Nan Dai1 and Chang Qing Chen1,*
1
Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan
430074, China
* E-mail address: cqchen@mail.hust.edu.cn
The surface plasmon polaritons (SPP) have attractive potential applications in the
photodetectors based on intersubband transition [1], especially for focal plane arrays (FPAs)
which requires normal illumination [2]. In this paper, significant enhancement of vertical
optical coupling of AlGaN/GaN quantum well infrared photodetector (QWIP) has been
obtained via a two-dimensional gold grating with Si3N4 cap layer by introducing the coupling
of long-range surface plasmon polaritons (LRSPPs) with the incident electromagnetic. The
electromagnetic field, energy flow and current density are analyzed by an algorithm of finite
element method (FEM). In time domain, the electric field component Ez and current density Jz
perpendicular to the multi-quantum wells (MQWs) are symmetric and asymmetric distribution
over the gold grating respectively, which precisely prove the existence of LRSPPs [3]. By
comparing the enhancement ratios for SPP-coupled AlGaN MQWs with three different
dielectric materials air, SiO2 and Si3N4, it can be concluded that the Si3N4 layer over the grating
matches well with the QWIP which can induce the two SPP modes over the grating coupling
into the LRSPPs as well as decreasing the Fresnel reflection. As a result, the averaged |Ez|2
across the MQWs region reaches 1.51 (V/m)2 when the electric field intensity (|E0|2) of normal
incidence is 1 (V/m)2 at 4.65 μm.
(a)
(b)
Fig. 1. (a) Schematic view of a periodic unit for the hybrid grating combined with the QWIP. The gray area
represents different dielectric materials (air, SiO2, Si3N4); (b) Spectrums of averaged |Ez|2 across the whole
quantum well region with different dielectric materials.
Fig. 2. Distributions of Ez and Jz component over the y-z plane across the centre of basic unit in time domain
with 500nm Si3N4 as cap layer.
References
1. B. F. Levine, J. Appl. Phys. 74, R1-R81(1993).
2. A. Rogalski, Opto-Electron. Rev. 12, 221-245(2004).
3. P. Berini, Adv. Opt. Photon. 1, 484-588(2009).
A3-O-03 [NO SHOW]
Guided modes of Surface Plasmon Polaritons of an symmetric
metamaterial slab waveguide with a ε-negative metamaterials for fluid
sensing
Cherl-Hee Lee and Young Ki Cho
IT College, Kyungpook National University, Daegu 702-701, Korea
* E-mail address: cherlhee@ee.knu.ac.kr
We studied the properties of surface plasmon polaritons (SPPs) of an asymmetric slab waveguide
consisting of metamaterials (MTM) cladding, a hollow core, and a ε-negative metamaterials (ENG) for
fluid sensing. SPP is a kind of surface wave that propagates along the interface and decays exponentially
in the transverse direction. If the hollow core of the slab is filled with air, SPP modes will not be guided
along the surface. However, when a fluid fills the hollow core, the slab supports SPP modes that can
provide highly sensitive measurements of the fluid. The mode characteristics of the SPPs were
graphically derived by new dispersion equations in a one-dimensional five-layered structure, and the
field distributions of the surface guided modes were developed.
(a)
(b)
Fig. 1. (a) Structure of the presented; (b) SPP eigenmode
Figure 1 (a) shows a one-dimensional five-layered slab which is infinite to y- and z-axes. The slab
consists of a first semi-infinite air layer, a second MTM layer with thickness of (d1-d2), a third hollow
core layer with thickness of (d2-d3), a fourth ENG layer with thickness of d4, and a fifth semi-infinite
air layer. Each layer has permeability µi (i=1~5), permittivity εi (i=1~5), and refractive index ni (i=1~5).
The hollow core layer with positive permeability µ3 and permittivity ε3 is inserted between MTM layers
that are surrounded by air. Figure 1 (b) shows field distribution of the SPP mode, which are calculated
by the characteristic equation with the following constitutional parameters: λ=1.6 µm, (µ1 = 1, ε1 = 1),
(µ2 = -1.12, ε2 = -2), (µ3 = 2, ε3 = 2), and (µ4 = -1.12, ε4 = -2), (µ5 = 1, ε5 = 1), (d2 = 0.18 µm), and (d1d2 = 1 µm).
References
1. K. L. Tsakmakidis, C. Hermann, A. Klaedtke, C. Jamois, and O. Hess, Phys. Rev. B. 73, 085104
(2006).
2. H.-F. Zhang, d. Cao, F. Tao, X.-H. Yang, Y. Wang, X.-N. Yan, and L.-H. Bai, Chin. Phys. B 19,
027301 (2010).
A3-O-04
[NO SHOW]
Bands structures and magneto-transport in GaAs/Al0.3Ga0.7As nanostru
cture superlattice at very low temperature
Abdelhakim Nafidi*, Driss Barkissy , Abderrazak Boutramine, Ali Khalal, Thami El Gouti
and Mustapha Massaq
Laboratory of Condensed Matter Physics and Nano Re, University Ibn Zohr, Agadir, Morocco
* E-mail address: nafidi21@yahoo.fr
The realization of type I nanostructures superlattices (SLs), consisting of alternating GaAs and
AlxGa1-xAs compounds, was associated with different fundamental studies, since they are promising in
different applications fields, like in optoelectronics [1] and in detectors [2,3].
We have investigated the band structures E(d1), E(kz, kp) in Fig 1. (a) and the effective mass m*/m0
along the growth axis and in the plane of GaAs(d1=19 nm)/Al0.3Ga0.7As(d2=5 nm) nanostructure
superlattice, based on the envelope function formalism.
1,712
1,740
N=4 N=3N=2
Ek2z=0
Ek2p=0
1,700
E (eV)
GaAs/Al0.3Ga0.7As Ekz=0
1
1,675 190 Å / 50 Å
Λ = 175 meV
HHk1z=0
T= 0.4 K
0,17
0,16
-0,018-1 -0,012
-kp(Å )
-0,006
(a)
0,000
Γ
N=0
1,704
HHk1p=0
E1
1,700
HH1
0,172
GaAs/Al0.15Ga0.85As
190 Å / 50 Å
Λ = 175 meV
T = 0.4 K
HHk2p=0
N=0
N=4
0,006
0,012
kz(Å-1)
(b)
EF
Ek1p=0
hk1p=0
hk1z=0
HHk2z=0
EF
Eg
N=1
1,708
E(eV)
1,725
0,168
0
N=3 N=2
3
6
N=1
9
12
B(T)
15
18
21
Fig. 1: (a) Dispersion bands in the kz wave vector direction and in the plane kp of the superlattice, respectively.
(b) Energy position of the calculated Landau levels of the first conduction and valence sub-bands as a function of
magnetic field. The position of the Fermi level EF is also shown as a function of the magnetic field.
At 0.4 K, the band gap 1.53 eV situates this sample as near infrared detector. The electronic states
are quantized and discrete along kz direction because of the thick (d2= 50 Å) barrier thickness, which
separates two adjacent wells GaAs, leading to a weakly coupled system. In this case the electronic
transport is dominated in the plane of this superlattice, in particular, in the GaAs layer with a large
confinement of carriers charge. We have also interpreted in the Fig. 1.(b) the oscillations in the magnetoresistance (Shubnikov-de Haas effect) observed by Smrčka et al [4] and the quantum Hall effect in the
GaAs quantum wells. At 0.4 K, the electrons effective mass, the sheet carrier density and the Fermi
level of the two dimensional electron gas (2DEG) are, respectively, m*E1= 0.13m0, n2D= 4.4 1011 cm2
and EF= 1.710 eV. Therefore, this sample exhibits n type conductivity.
References
1. F. Janiak, M. Dyksik, M. Motyka, K. Ryczko, J. Misiewicz, K. Kosiel and M. Bugajski, Opt.
Quantum Electron, Vol. 47, 945–652, (2015).
2. P. Martyniuk, M. Kopytko and A. Rogalski, Opto-Electronics Rev, Vol. 22, (2014).
3. D. Barkissy, A. Nafidi, A. Boutramine, H. Charifi, A. Elanique and M. Massaq, J. Low Temp. Phys,
Vol.182, 185–191, (2016).
4. L. Smrčka, N. A. Goncharuk, P. Svoboda, P. Vašek, Y. Krupko, and W. Wegscheider,
Microelectronics J, Vol. 39, No. 3–4, 411–413, (2008).
A3-I-02
Deep-ultraviolet Raman scattering studies of monolayer materials
Hsiang-Lin Liu1*
1Deparment
of Physics, National Taiwan Normal University, Taipei 11677, Taiwan
* E-mail address: hliu@ntnu.edu.tw
We present joint experimental and theoretical investigations of the deep-ultraviolet Raman
scattering spectra of monolayer materials. The Raman scattering intensities from the secondorder phonon modes of monolayer graphene and transition metal dichalcogenides thin films
are revealed to be decreased or enhanced anomalously by the deep-ultraviolet excitation
wavelength [1,2]. We demonstrate theoretically that such resonant behavior has a strong
correlation with the absorption properties and electron-phonon interactions in these materials.
These results advance our understanding of the double resonance Raman scattering process in
monolayer nanomaterials and provide a foundation for the technological development of these
materials in the deep-ultraviolet frequency range.
References
[1] H. L. Liu, S. Siregar, E. H. Hasdeo, Y. Kumamoto, C. C. Shen, C. C. Cheng, L. J. Li, R. Saito, and S. Kawata,
Carbon 81, 807 (2015).
[2] H. L. Liu, H. Guo, T. Yang, Z. Zhang, Y. Kumamoto, C. C. Shen, Y. T. Hsu, L. J. Li, R. Saito, and S. Kawata,
Physical Chemistry Chemical Physics 17, 14561 (2015)..
A4-I-01
Nonlinear optics in emerging two-dimensional materials
Joon Jang1* and Yong Soo Kim2
1Binghamton
2Ulsan
University, 4400 Vestal Pkwy E, Binghamton, USA
University, Daehangno, Nam-gu, 93,Ulsan, Korea
* E-mail address: jjoon@binghamton.edu
Nonlinear optics deals with light-matter interaction where the dielectric polarization of a
medium responds nonlinearly to the electric field of light. The most important nonlinear
optical processes in hard condensed matter are harmonic generation and multiphoton
absorption, which typically require a large interaction volume for the coherent buildup of the
effects. Owing to their highly polarizable nature, however, monolayers of transition metal
dichalcogenides (TMDs) have emerged as ideal materials for exploring strong nonlinear lightmatter interaction in a two-dimensional world with additional control of the spin-valley degree
of freedom. Indeed, TMD monolayers are believed to be the thinnest materials exhibiting
highly efficient second harmonic generation (SHG).
Although atomically thin, the
monolayers can be excited by simultaneous absorption of two photons in accordance with twophoton selection rules. In this talk, I will first describe how SHG can be utilized to
characterize the crystal and electronic structures of TMD monolayers. Then I will present our
recent endeavors to enhance the SHG efficiency of the TMD system at strong exciton
resonance through bandgap engineering and vertical hetero stacking. Finally, feasibility of
SHG for probing dark exciton states at the K(K’) valley in TMDs will be discussed. These
optically forbidden states cannot be directly accessed by ordinary one- or two-photon
absorption, but are known to crucially affect optoelectronic properties of TMDs for nanoscale
electronic and photonic applications.
A4-I-02
Defect engineering in two dimensional materials
Zhenhua Ni1*
1Southeast
University, Nanjing, China
* E-mail address: zhni@seu.edu.cn
The optical and electrical properties of two dimensional transitional metal dichalcogenides
(TMDs) are strongly influenced by the amount of structural defects inside. Here, we provide
an optical spectroscopic characterization approach to correlate the amount of structural defects
and the electrical performance of WSe2 devices. Low temperature PL spectra of electron-beam
processed WeS2 present a clear defect-induced PL emission due to excitons bound to defect
sites, which are confirmed to be Se vacancies induced by e-beam irradiation. The defects in
WSe2 behave as scattering sources and strongly degrade its electrical performance, e.g. carrier
mobility. We also report a strong PL enhancement of monolayer MoS2 through defect
engineering and oxygen bonding. High resolution micro- PL and Raman images clearly reveal
that the PL enhancement occurs at defect sites of MoS2. The main reasons of such enhancement
include the following: (1) the oxygen chemical adsorption induced heavy p doping and the
conversion from trion to exciton; (2) the suppression of nonradiative recombination of excitons
at defect sites. The above work would not only provide an in-situ, time efficient and
nondestructive method to monitor the defects in TMDs, but also a new route to modulate the
optical and electrical properties of TMDs.
A4-O-01
P-type doping of monolayer MoS2 via graphene oxide
Hye Min Oh1,2 ,Ұ, Hyun Jeong 3,Ұ, Young Hee Lee1,2,* Mun Seok Jeong1,2,*
1
Center for Integrated Nanostructure Physics, Institute for Basic Science (IBS), Sungkyunkwan University,
Suwon 440-746, Republic of Korea.
2
Department of Energy Science, Department of Physics, Sungkyunkwan University, Suwon 440-746, Republic of
Korea.
3Laboratoire de Nanotechnologie et d’Instrumentation Optique, Institut Charles Delaunay, CNRS-UMR 6281,
Université de Technologie de Troyes, BP 2060, 10010 Troyes, France.
* E-mail address: mjeong@skku
Recently, few-layer or monolayer transition metal dichalcogenides (TMDs), MX2 (M = Mo,
W; X = S), have attracted considerable attention for use in next-generation electronic and
optoelectronic devices.[1-3] The electrical and optical properties of these TMDs are widely
known to depend on the number of constituent layers. In particular, monolayer (1L) MoS2
demonstrates potential for application in photodetectors, light-emitting devices, and solar cells,
owing to the direct bandgap formation in contrast to the bulk. Recently, several researchers
have reported various methods for modulating the optical and electrical properties of few-layer
and 1L-MoS2
We demonstrate tuning of the electronic properties of large-area monolayer (1L) MoS2 via a
simple coating of graphene oxide (GO). The GO sheets act as a p-type dopant because of a
large number of functional groups that exhibit electron-withdrawing characteristics. We reveal
tuned optical and electronic properties of 1L-MoS2 through the enhanced photoluminescence
(PL) intensity and considerable change in the Raman spectrum. We measured the current
versus voltage (I-V) curves of 1L-MoS2 field effect transistors with and without GO; these
results support the conclusion that the electron concentration of 1L-MoS2 was reduced by the
presence of the GO coating. Furthermore, clear current rectification was observed from I-V
curve of lateral 1L-MoS2 − 1L-MoS2/GO structure, which supports significantly reduced
electron concentration of GO/1L-MoS2.
References
1. Wang, Q. H.; Kalantar-Zadeh, K.; Kis, A.; Coleman, J. N.; Strano, M. S. Nat. Nanotechnol.
7, (11), 699-712 (2012)
2. Tsai, D.-S.; Liu, K.-K.; Lien, D.-H.; Tsai, M.-L.; Kang, C.-F.; Lin, C.-A.; Li, L.-J.; He, J.H. ACS Nano 7, (5), 3905-3911. (2013)
3. Ross, J. S.; Klement, P.; Jones, A. M.; Ghimire, N. J.; Yan, J.; Mandrus, D. G.; Taniguchi,
T.; Watanabe, K.; Kitamura, K.; Yao, W.; Cobden, D. H.; Xu, X. Nat. Nanotechnol. 9, (4),
268-272 (2014)
A4-O-02
Electrical characterization of MoS2 thin layers on ferroelectric domains
Hye-Jin Jin and William Jo*
Department of Physics, Ewha Womans University, Seoul, 03760, Korea
* E-mail address: wmjo@ewha.ac.kr
Transition metal dichalcogenides (TMDCs) are promising materials showing high
performance in electronic properties. In addition, TMDCs are a substitute for graphene because
it has a bandgap. Electrical performance can be varied depending on the bandgap and the
bandgap can be tuned by the number of TMDCs layer. In this study, a few MoS2 layers on
PbTiO3 (PTO) epitaxial thin films were prepared. Polarization states in PTO thin films can give
variation in electrical performance in MoS2 layer. Electrical characterization of MoS2-PTO
heterostructures is directly related to application of field-effect transistors (FETs). The MoS2PTO heterostructures were characterized by scanning probe microscopy. Electrical transport
measurement was conducted by conductive-atomic force microscopy. Kelvin probe force
microscopy was used to investigate variation in surface potential depending on the thickness
of MoS2 layer. In addition, electrical performance of MoS2 layer was varied depending on the
polarization state of PTO. Therefore, we can control the electrical characteristics of MoS2 by
controlling the ferroelectric characteristics.
A4-O-03
Ambient Effects on Electrical Characteristics of MoS2 Thin Films Grown
by Chemical Vapor Deposition
Yunae CHO1, Ahrum SOHN1, Sujung KIM1, Dong-Wook KIM1,*, Byungjin CHO2,
Myung Gwan HAHM2, and Dong-Ho KIM2
1
Department of Physics, Ewha Womans University, Seoul 120-750, Korea
Advanced Functional Thin Films Department, Korea Institute of Materials Science (KIMS), Changwon 642831, Korea
* E-mail address: dwkim@ewha.ac.kr
2
Recently, two-dimensional transition metal dichalcogenides (TMDCs) have attracted
tremendous research attention owing to their unique physical properties. Chemical vapor
deposition (CVD) techniques have been widely used to grow large area TMDC thin films,
which are very useful for electronic and optoelectronic device applications. Since the TMDC
thin films consist of several atomic layers, their electrical properties are very sensitive to the
ambient conditions. In this work, we studied the relationship between the resistance (R) and
surface work function (WF) of CVD-grown MoS2 thin films in N2, O2, and H2/N2. The
measured R and WF were varied depending on the ambient gas. We also studied the roles of
Au nanoparticles (NPs) on the electrical properties of MoS2 thin films, since decoration of
metal NPs has been used as a useful means to tailor the transport properties of MoS2 thin films.
To clarify the roles of the Au NPs, we also studied the ambient-dependent electrical properties
of the NP-coated MoS2 thin films. The quantitative analyses of the measured data of either bare
or the NP-coated samples couldn’t confirm the validity of the gas adsorption and charge
transfer scenario. Our results suggested that the defects (e.g., S vacancies) and their interaction
with the ambient gas played important roles in the ambient-dependence of our CVD-grown
MoS2 thin films.
A5-I-01
Excited-state optical properties and carrier dynamics
of atomically thin transition metal dichalcogenides
A. Steinhoff1, J.-H. Kim3, F. Jahnke1, M. Rösner1,2, M. Florian1, M. Lorke1,
D.-S. Kim3, C. Lee4, G.H. Han4, M. S. Jeong3,4, T. Wehling1,2, and C. Gies1
1
Institute for Theoretical Physics, University of Bremen, 28334 Bremen, Germany
2
Bremen Center for Computational Material Science, University of Bremen
3
Center for Integrated Nanostructure Physics, Institute for Basic Science (IBS), Suwon, Republic of
Korea
4
Department of Energy Science, Sungkyunkwan University, Suwon, Republic of Korea
Abstract
Atomically thin layers of transition-metal dichalcogenides have emerged in the wake of graphene as
new class of optically active materials. We discuss their optical properties in the presence of excited
carriers on the basis of microscopic theories. Our approach combines atomistic ab-initio electronic
properties with semiconductor many-body calculations of optical transitions beyond the reach of
GW/BSE methods, which are typically restricted to the description of ground-state properties.
Many-body effects lead to carrier-density dependent energy renormalizations and screening of the
Coulomb interaction, reflected in the absorption spectra as lineshifts and bleaching of the excitonic
resonances [1]. At the Mott-transition of the MoS2 A-exciton, band-gap shrinkage of about 0.5 eV is
predicted.
For photoluminescence, optical recombination at the A and B exciton resonances relies on the presence
of carriers in the corresponding K-valleys of the band structure. Based on calculations of carrier
dynamics [2], we discuss two different excitation scenarios: Above-band gap excitation leads to a quasiequilibrium distribution of carriers in the Brillouin zone on a timescale of 200fs. The second scheme is
quasi-resonant excitation, which takes place within the single-particle band gap and is only possible
due to the existence of bound excitonic states. Here, carriers are created according to the corresponding
position of the bound-state wave function in reciprocal space. This excitation scenario enables enhanced
B-peak emission in agreement with PL measurements performed at excitation wavelengths of 405 nm
(above) and 473, 532 and 633 nm (below the band gap) [3]. We observe efficient PL even in case of an
indirect band gap, providing a possible explanation for significant photoluminescence observed in
bilayer MoS2, which is an indirect band-gap semiconductor [4].
[1] A. Steinhoff, M. Rösner, F. Jahnke, T. O. Wehling, and C. Gies, Influence of excited carriers on
the optical and electronic properties of MoS2. Nano Letters, 14, 3743 (2014)
[2] A. Steinhoff, M. Florian, M. Rösner, M. Lorke, T. O. Wehling, C. Gies, and F. Jahnke,
Nonequilibrium Carrier Dynamics in Transition Metal Dichalcogenide Semiconductors.
arXiv:1603.03633 (2016)
[3] A. Steinhoff, J.-H. Kim, F. Jahnke, M. Rösner, D.-S. Kim, C. Lee, G.H. Han, M. S. Jeong, T.
Wehling, and C. Gies, Efficient Excitonic Photoluminescence in Direct and Indirect Band Gap
Monolayer MoS2. Nano Letters DOI: 10.1021/acs.nanolett.5b02719 (2015)
[4] H. J. Conley, B. Wang, J. Ziegler, R. Haglund, S. Pantelides, and K. Bolotin, Bandgap
engineering of strained monolayer and bilayer MoS2. Nano Letters 13, 3626 (2013)
A5-I-02
Confined Light-Exciton Interactions in Monolayer TMDs
Jeongyong Kim
1
Center for Integrated Nanostructure Physics, Institute for Basic Science, Sungkyunkwan University, Suwon
440-746, Korea,
2
Department of Energy Science, Sungkyunkwan University, Suwon 440-746, Korea
* E-mail address: j.kim@skku.edu
Transition-metal dichalcogenide (TMD) monolayers are atomically thin two-dimensional
(2D) semiconductors with the direct bandgap [1], providing ideal platforms to study the
interaction between light and confined excitons. Due to the 2D nature and strong Coulomb
interaction resulting in large binding energies, these TMD monolayers host various exciton
complexes of not only neutral excitons also charged excitons (trions) and biexcitons, routinely
observable in room temperature [2-4]. Using nanoscale optical imaging and spectroscopy, we
will show that these exciton complexes coexist competing for the light emission, which largely
depend on the surface conditions such as local defects or excess charge carrier [4,5] and the
enhanced optical properties can be engineered by heterostructures of TMD monolayers [6].
Another advantageous aspect of TMD monolayers are their flat lateral nature and the
efficient light emission which make the coupling of surface plasmons using metallic
nanostructures highly efficient, suitable for nanophotonics applications. We will discuss that
surface plasmons can be generated, propagated and detected by using simple configuration of
overlaying Ag nanowires on monolayer MoS2. This hybrid system displayed the high coupling
efficiency of 32% and a resonant interaction of neutral excitons and surface plasmons [7,8].
References
1. K. F. Mak et al., Phys. Rev. Lett. 105, 031112 (2010).
2. K. P. Dhakal and J. Kim et al., Nanoscale 6, 13028 (2014).
3. S. K. Park, M. S. Kim and J. Kim et al., ACS Nano 9, 11042 (2015).
4. M. S. Kim and J. Kim et al., ACS Nano 10, 2399 (2016).
5. Y. J. Lee and J. Kim et al., Nanoscale 7, 11909 (2015).
6. M. S. Kim and J. Kim et al., Submitted.
7. H. S. Lee and J. Kim et al., Adv. Opt. Mater. 9, 943 (2015).
8. H. S. Lee and J. Kim et al., Phys. Rev. Lett. 115, 226801 (2015).
A5-I-03
Energy dissipation and light emission in graphene
Myung-Ho Bae
Korea Research Institute of Standards and Science, Daejeon 34113, Republic of Korea
Department of Nano Science, University of Science and Technology, Daejeon 34113, Republic of Korea
* E-mail address: mhbae@kriss.re.kr
Energy dissipation in nanoscale electronics has become an important subject in modern
electronic industry and energy conversion system. From this perspective, graphene with very
high mobility and thermal conductivity, which are about ten times higher than silicon, is a very
attractive nano-material to study energy dissipation in nano-electronics. My talk will present
recent studies for the gate-controllable Joule heating, Peltier cooling and light emission in
graphene devices. I will also talk about the in-plane thermal conductivity of graphene
nanoribbons, to explore the nano-engineering of phonon flow.
A6-I-01
Steep sub-threshold slope in short-channel InGaAs TFET
Yasuyuki MIYAMOTO1,2)*, Wenbo LIN1) , Shinjiro IWATA2), and Koichi FUKUDA1,3)
1 Department of Electrical and Electronics Engineering, 2 Department of Physical Electronics,
Tokyo Institute of Technology, O-okayama, Meguro, Tokyo, 152-8552, Japan
3 National Institute of Advanced Industrial Science and Technology,
Umezono, Tsukuba, Ibaraki 305-8560, Japan.
* E-mail address: miya@ee.e.titech.ac.jp
Tunnel FETs with a sub-60-mV/dec subthreshold slope (SS) have been proposed as transistors
for CMOS logic circuits1,2). Since the high-speed operation of CMOS circuits requires a high
drive current, introduction of heterojunctions in the tunnel FETs is an attractive option. The high
electron mobility provided by InGaAs channels can result in a high current density. Thus, we
have studied the InGaAs/GaAsSb type-II heterojunction double-gate tunnel FETs3-5). In general,
the minimum current of tunnel FETs is determined by the ambipolar behavior that is caused by
the source-to-channel tunneling and the channel-to-drain tunneling. However, the direct sourceto-drain tunneling increases in the case of short channels and it may be the dominant tunneling
mechanism of off-state currents, although the reduction of the channel length of MOSFETs
decreases the gate capacitance and lowers the dynamic power consumption. In this report, we
classify the tunneling current based on numerical simulations. We also discuss the off-state
current in short-channel tunnel FETs using the classified tunneling current. Fig.1 shows simulated
I-V characteristics classified by the starting and ending points of the tunneling path when channel
length is 10 nm. When direct source-to-drain tunneling becomes dominant. steep sub-threshold
characteristics is degraded. More precise calculation will be discussed.
References
1) A. C. Seabaugh and Q. Zhang:Proc. IEEE 98(2010)2095.
2) A.M. Ionescu and H. Riel:Nature479(2011)329.
3) M. Fujimatsu, H. Saito, and Y. Miyamoto:IPRM(2012)Mo-1 D.2.
4) K. Ohashi, M. Fujimatsu, S. Iwata, and Y. Miyamoto:Jpn. J. Appl. Phys. 54(2015)04DF10.
5) S. Iwata, W. Lin, K. Fukuda, and Y. Miyamoto:SSDM(2015)PS-6-25.
A6-O-01
Comparative study of electronical prosperity and current collapse in
AlGaN/GaN MIS HEMT on sapphire and native GaN substrates
Shichuang Sun1,2, Kai Fu2, Guohao Yu2, Zhili Zhang2, Liang Song2, Yong Cai2, Jiangnan Dai1, Changqing
Chen1*, Baoshun Zhang2*
1Wuhan
2Key
National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan 430074, China
Laboratory of Nanodevices and Applications, Suzhou Institute of Nano-tech and Nano-bionics, CAS, Suzhou 215123,
People’s Republic of China
*E-mail address: cqchen@mail.hust.edu.cn,
bszhang2009@sinano.ac.cn
GaN based metal-insulator-semiconductor high electron mobility transistors (MIS-HEMTs) have
been highly desired because of their potentially excellent performance in radio frequency (RF) and
power switching applications with high-efficiency operation at high power, high frequency, and high
temperature. Low density defects and dislocations of AlGaN/GaN HEMT materials would be promising
for improved reliability and reduced current collapse[1-2]. In this paper, a comparative study of
electronical prosperity and current collapse in AlGaN/GaN MIS HEMTs on sapphire and native GaN
substrates, respectively, have been conducted. The as-grown substrates were characterized by atomic
force microscopy (AFM) to quantify surface roughness. Characterized by an Agilent B1505A, the
transfer and output characteristics of MIS AlGaN/GaN HEMT on native GaN substrate have shown a
higher saturation current density, owing to the higher 2DEG density on native GaN substrate. The
current collapse characteristics varied with the drain off stress voltage (VDS-Off), after switching to on
state from various drain off stress voltage (VDS-Off) of 10, 20, 30, 40, 50V at an off stress voltage off
stress time (TOff-stress) of 10ms. A longer stress time results in a lower post stress on state current (IDS)
and a larger increase in ON-resistance, suggesting that the OFF-state stress itself is leading to an
increase in current collapse. Particularly, it can be clearly seen that the current collapse phenomenon
are suppressed by a AlGaN/GaN MISHEMT on native GaN substrate with a low density defect.
Fig.1. (a) AFM images of surface of AlGaN/GaN HEMT on GaN and sapphire substrate. (b) The transfers
characters
Fig.2. Ron-dynamic/Ron ratio as a function of drain off stress voltage (VDS-Off)
Reference: [1] Travis J. Anderson,et.al IEEE Electron Device Lett.1, 28-30(2016)
[2] J. K. Hite, et.al Electron. Lett. 50, 1722–1724(2014).
A6-O-02
Fabrication of Phosphor-Free, White Light-Emitting Diodes Using Three
Dimensional GaN Structures
Seung-Hyuk Lim, Young-Ho Ko, Christophe Rodriguez,
Su-Hyun Gong, and Yong-Hoon Cho*
1
Deparment of Physics, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141,
Republic of Korea
* E-mail address: yhc@kaist.ac.kr
White light-emitting diodes (LEDs), commonly used as an illuminator or back light units
of display, is already commercialized. For creating white light, two promising strategies are
commonly used, such as (i) combination of LEDs with different color and (ii) LED with
phosphor(s).[1] However, case (i) suffers from expensive cost and complicated operation. In
case of (ii), energy conversion loss is unavoidable and thermal stability is much reduced.
Therefore, the concern with single chip phosphor-free white LEDs has been growing for the
last several years.
Here, we present fabrication and characterization of phosphor-free white LEDs using threedimensional (3D) GaN structures. The 3D GaN structures are fabricated by metal-organic
chemical vapor deposition with selective area growth technique. A scanning electron
microscopy image of a single structure, a.k.a. double concentric truncated pyramid, is shown
in Fig. 1. To analysis the origin of illumination, cathodoluminescence and high angle annular
dark field transmission electron microscopy experiment on 3D GaN structure are performed.
Finally, phosphor-free white LEDs are electrically driven and the spectrum is plotted in Fig. 1.
The photography of white emission is also shown in inset of Fig. 1.[2]
Fig. 1. A single 3D structure SEM image and its spectrum; (inset) phosphor-free white light illumination
References
1. E. F. Schubert and J. K. Kim, Science 308, 1274 (2005).
2. S. H. Lim, Y. H. Ko, C. Rodriguez, S. H. Gong, and Y. H. Cho, Light Sci Appl 5, e16030
(2016).
A6-O-03
Single-Photon Emissions with Small Inhomogeneous Broadening
from InGaN/GaN Quantum-dots in Nano-pyramids
Y. M. Kim1, Jong-Hoi Cho1, Hwan-Seop Yeo1, Seung-Hyuk Lim1,
Sejeong Kim1, Su-Hyun Gong1 and Yong-Hoon Cho1,*
Department of Physics, Korea Advanced Institute of Science and Technology (KAIST),
Daejeon 34141, Republic of Korea
*
Email address: yhc@kaist.ac.kr
The feasibility of generating non-classical lights with strong linear polarizability at
high temperature makes InGaN/GaN quantum-dots (QDs) attractive material candidate for
semiconductor quantum emitters [1-2]. However, the presence of built-in electric field, a wellknown phenomenon in III-nitride material could cause considerable inhomogeneous
broadening in the photon emissions via spectral diffusion, which could randomize the
coherence property for achieving indistinguishability.
Here, we present an unconventional InGaN/GaN QD potential in a nano-pyramid
structure where a decoupling of single exciton emission from the influence of built-in electric
field was manifested. Through morphological as well as detailed optical characterizations, we
report a sharp emission linewidth with negligible quantum-confined Stark effect, and estimated
the homogeneous linewidth beyond the spectral resolution limit via Fourier-transform
spectroscopy. We report that these emitted photons exhibited sub-Poissonian statistics which
retained its antibunching characteristics at an elevated temperature. Furthermore, we
investigated the acoustic-phonon coupling with excitons in our system, and discuss its
fundamental as well as practical implications.
Fig. 1. µ − PL spectrum of InGaN/GaN single QD at 10 K. (inset) SEM tilt view image of GaN nano-pyramid.
Reference
1. J. H. Kim et al., Scientific Reports 3, 2150 (2013)
2. S. H. Gong et al., Proceeding of the National Academy of Sciences 112, 5280 (2015)
A7-IK-01
Tip-enhanced Raman Scattering Studies of Graphene
Yukihiro OZAKI1*
1
School of Science and Technology, Kwansei Gakuin University, Sanda 669-1337, Japan
* E-mail address: ozaki@kwansei.ac.jp
Real graphene samples are not always flat, perfect honeycomb as usually portrayed. This
is especially pronounced in graphene grown on the C-face of SiC due to the relatively weak
substrate interaction. Despite its extremely high electron mobility, large sheet and minimal
defects, nanoscale features such as steps and ridges are usually occurred on its sheet. In this
study, these nanostructures were studied using tip-enhanced Raman spectroscopy (TERS).
TERS spectroscopy, a combination of scanning probe microscopy (SPM) and surfaceenhanced Raman scattering (SERS), has high spatial resolution beyond the diffraction limit of
light. Therefore, TERS is a powerful tool for obtaining structural information from nm scale
area. We developed a bulk silver tip-enhanced Raman scattering (TERS) and obtain TERS
spectra of epitaxial graphene on the carbon face of 4H-SiC (000-1) with a high signal-to noise
ratio.1 Thanks to the high quality of TERS spectra we firstly find that the G band in the TERS
spectra exhibits position-by-position variations in both lower wavenumber shifts and spectral
broadening. The analysis of the variations reveals that the shifts and broadenings have a linear
correlation between each other, indicating that the variations are induced by the position
dependent local stress on graphene based on a uniaxial strain model.1
As the second study,2 step, ridge, and crack submicro/ nanostructures of epitaxial graphene
on 4H-SiC (000-1) were characterized using tip-enhanced Raman scattering (TERS). The
results of this TERS study illustrate that the exceptional spatial resolution of TERS allows
spectroscopic measurements of individual nanostructures, a feat which normal Raman
spectroscopy is not capable of. By analyzing TERS spectra, the change of local strain on the
nanoridge and decreased graphene content in the submicrometer crack were detected.
References
1. Suzuki, T.; Itoh, T.; Vantasin, S.; Minami, S.; Kutsuma, Y.; Ashida, K.; Kaneko, T.;
Morisawa, Y.; Miura, T.; Ozaki, Y, Phys. Chem. Chem. Phys. 2014, 16, 20236-20240.
2. Vantasin, S.; Tanabe, I.; Tanaka, Y.; Itoh, T.; Suzuki, T.; Kutsuma, Y.; Ashida, K.; Kaneko,
T.; Ozaki, Y, J. Phys. Chem. C 2014, 118, 25809-25815.
A7-I-02
Two-Dimensional van der Waals Heterostructures for Device Applications
Gwan-Hyoung Lee 1,*
1
Department of Materials Science and Engineering, Yonsei University, Seoul 03722, Korea
* E-mail address: gwanlee@yonsei.ac.kr
Graphene has brought a great deal of excitement to nanoscience community with its
attractive and unique properties. Such excellent characteristics have triggered highly active
researches on other two-dimensional (2D) materials, such as hexagonal boron nitride (hBN),
molybdenum disulfide (MoS2), tungsten diselenide (WSe2) and so on. Especially, these
emerging 2D semiconductors are promising candidates for flexible and transparent electronics.
Furthermore, new physics observed in 2D semiconductors allow for development of newconcept devices by using their valleys, tunneling effect, photoluminescence, and optical
responsivity. Recently, van der Waals heterostructures (vdWH) have been achieved by putting
these 2D materials onto another, in the similar way to build Lego blocks. This enables us to
investigate intrinsic physical properties of atomically-sharp heterostructure interfaces and
fabricate high performance optoelectronic devices for advanced applications. In this talk,
fundamental properties of various 2D materials will be introduced, including growth
techniques for graphene and 2D semiconductors.[1-3] Then, I will show high performance
electronic/optoelectronic devices of vdWH, such as transistors,[4-6] memories,[7] and solar
cells.[8] Our works paves a way toward future devices based on 2D materials.
References
1. Gwan-Hyoung Lee, Ryan C. Cooper, Sung Joo An, Sunwoo Lee, Arend van der Zande, Nicholas
Petrone, Alexandra G. Hammerberg, Changgu Lee, Bryan Crawford, Warren Oliver, Jeffrey W.
Kysar, and James Hone, Science 340, 1073-1076 (2013).
2. Arend M. van der Zande, Pinshane Y. Huang, Daniel A. Chenet, Timothy C. Berkelbach, Yu Meng
You, Gwan-Hyoung Lee, Tony F. Heinz, David R. Reichman, David A. Muller, and James Hone,
Nature Materials 12, 554-561 (2013).
3. Ardavan Zandiatashbar, Gwan-Hyoung Lee, Sung Joo An, Sunwoo Lee, Nithin Mathew, Mauricio
Terrones, Takuya Hayashi, Catalin R. Picu, James Hone , and Nikhil Koratkar, Nature
Communications 5, 3186 (2014).
4. X. Cui, Gwan-Hyoung Lee, Young Duck Kim, Ghidewon Arefe, Pinshane Y. Huang, Chul-Ho Lee,
Daniel A. Chenet, Xian Zhang, Lei Wang, Fan Ye, Filippo Pizzocchero, Bjarke S. Jessen, Kenji
Watanabe, Takashi Taniguchi, David A. Muller, Tony Low, Philip Kim, and James Hone, Nature
Nanotech. 10, 534–540 (2015)
5. Gwan-Hyoung Lee, Xu Cui, Young Duck Kim, Ghidewon Arefe, Xian Zhang, Chul-Ho Lee, Fan
Ye, Kenji Watanabe, Takashi Taniguchi, Philip Kim, and James Hone, ACS Nano 9, 7019–7026
(2015).
6. Gwan-Hyoung Lee, Young-Jun Yu, Xu Cui, Nicholas Petrone , Chul-Ho Lee , Min Sup Choi, DaeYeong Lee , Changgu Lee , Won Jong Yoo , Kenji Watanabe , Takashi Taniguchi , Colin Nuckolls,
Philip Kim , and James Hone, ACS Nano 7, 7931–7936 (2013).
7. Min Sup Choi, Gwan-Hyoung Lee, Young-Jun Yu, Dae-Yeong Lee, Seung Hwan Lee, Philip Kim,
James Hone, and Won Jong Yoo, Nature Communications 4, 1624 (2013).
8. Chul-Ho Lee, Gwan-Hyoung Lee, Arend M. van der Zande, Wenchao Chen, Yilei Li, Minyong
Han, Xu Cui, Ghidewon Arefe, Colin Nuckolls, Tony F. Heinz, Jing Guo, James Hone, and Philip
Kim, Nature Nanotech. 9, 676-681 (2014).
A7-O-01
Surface Potential Mapping to Visualize Band Bending at Metal/MoS2
Contacts
Ahrum SOHN, Hankyoul MOON, Ja-yeong KIM, Seokhyun YOON, and Dong-Wook KIM*
Department of Physics, Ewha Womans University, Seoul 120-750, Korea
* E-mail address: dwkim@ewha.ac.kr
Molybdenum disulphide (MoS2), one of the most intensively studied atomically thin 2D
semiconductors (2D-SCs), has surfaced as a strong candidate material for electronics and
optoelectronics applications. In any kind of devices, it is essential to understand and control
the electrical properties of metal/semiconductor contacts. In this regard, many research groups
have been studying contacts consisting of metal electrodes and MoS2 layers. Such efforts have
revealed that conventional electrical measurements and analyses based on 3D bulk band theory
cannot be applied to the metal/MoS2 contacts. Quantum confinement effects due to extremely
thin semiconductor layers and van der Waals force (rather than covalent bonding) are the main
origins to cause the distinct features of metal/2D-SC contacts, compared with metal/3D
semiconductor contacts. However, a simple and reliable technique to characterize band profiles
at metal/2D-SC contacts is not available now. In this work, we measured the work function of
the MoS2 flakes exfoliated on SiO2/Si substrates using Kelvin probe force microscopy (KPFM).
Also, we investigated the surface potential of the MoS2 flakes on 100-nm-thick Ag thin films
using KPFM. The thickness-dependence of the work function and the surface potential of the
MoS2 samples with various thicknesses allowed us to reveal the band bending at the Ag/MoS2
contacts.
A7-O-02
New Strategy for High-Yield Exfoliation of Two-Dimensional Materials in
aqueous solution: Size Control of Polymeric Micelles with Alcohol
Changbong Yeon1,2, Sun Jin Yun1,2*
1
ICT Materials & Components Research Laboratory, Electronics and Telecommunications Research Institute,
218 Gajeongno, Yuseong-gu, Daejeon 305-700, Korea
2
Department of Advanced Device Engineering, University of Science and Technology, 217 Gajeongno,
Yuseong-gu, Daejeon 305-350, Korea
One of the important issues in research of exfoliation of 2D materials in an aqueous solution
is to increase the exfoliation yield.1,2 For the exfoliation of 2D materials in an aqueous solution,
dispersing agents such as ionic and non-ionic surfactants are necessary because of their
hydrophobicity. Among them, non-ionic polyethylene oxide-polypropylene oxidepolyethylene oxide (PEO-PPO-PEO) triblock copolymer, known by the trade name of Pluronic
(which is generally used as one of ingredients of cosmetics and pharmaceuticals) is effective
for the exfoliation of 2D materials.3
The unimers of the PEO-PPO-PEO copolymer form spherical micelles due to their selfassembling nature in an aqueous solution when the solution concentration exceeds the critical
micelle concentration (cmc).4 For the surfactant-assisted exfoliation, it has been conventionally
accepted that the concentration of surfactants has to exceed the cmc regardless the size of
micelles. However, the effect of micellar size on the exfoliation of 2D materials has not been
studied until quite recently.
In this work, we clarified that the micellar size has a great influence on the exfoliation
efficiency, and systematically investigated the effect of the micellar size of Pluronic F-68
copolymer on the exfoliation of 2D materials such as MoS2, graphene, and h-BN. As a result,
the smaller size form such as unimer and very small size micelle is much more efficient for
obtaining a high-concentrated dispersion of atomically thin 2D materials than larger micelles.
For example, the highest exfoliation yield (2.83%) of MoS2 could be achieved in an aqueous
solution in which 8 nm size unimers mainly existed. The yield was 16.6 times higher than the
exfoliation yield (0.17%) obtained using large micelles.
Fig. 1. Schematic of unimer exfoliation of MoS2 flakes.
References
1. S. M. Notley, Langmuir 28, 14110-14113 (2012).
2. L. Guardia, M. J. Ferna´ndez-Merino, J. I. Paredes, P. Solı´s-Ferna´ndez, S. Villar-Rodil,
A. Martı´nez-Alonso, J. M. D. Tasco´n, Carbon 49, 1653-1662 (2011).
3. J. T. Seo, A. A. Green, A. L. Antaris, M. C. Hersam, J. Phys. Chem. Let. 2, 1004-1008
(2011).
4. O. Glatter, G. Scherf, Macromolecules 27, 6046-6054 (1994).
A7-O-03
All Two-Dimensional Field-effect Transistor with alloyed junction
Ah Ra Kim1, Sun Young Choi1, Yonghun Kim1, Myung Gwan Hahm2, and Byungjin Cho1,*
1
Advanced Functional Thin Films Department, Surface Technology Division, Korea Institute of Materials
Science (KIMS), Changwon 51508, Republic of Korea
2
School of Materials Science and Engineering, Inha University, Incheon 22212, Republic of Korea
* E-mail address: bjcho@kims.re.kr
Two-dimensional (2D) materials, such as graphene, hexagonal boron nitride (h-BN), and
transition metal dichalcogenides (TMDs), have been attracting great attention due to their
intriguing physical properties. Further the structures are applicable to diverse device in
compliance with unique components. In particular, atomically thin TMDs are excellent 2D
semiconductors due to their finite bandgaps and various other interesting electronic properties.
In addition to drawing interest due to their potential use in individual-atomic-layer devices,
combinations of atomic layers with different compositions into van der Waals (vdW)
heterostructures have gained interest because of the possibility of generating a large number of
electronically variant systems. In these multiple-atomic-layer devices, the Schottky barriers
originating from Fermi level misalignment present a critical issue that must be addressed.
Here, we report that the composition of interfacial transition region between
semiconducting WSe2 atomic layer channels and metallic NbSe2 contact layers can be
engineered through interfacial doping with Nb atoms. For this, we design a simple bottom-gate
field-effect transistor (FET) with a WSe2 channel and NbSe2 electrodes including WxNb1−xSe2
alloyed interfacial layer (Figure 1a). 2D WxNb1-xSe2 junction regions considerably lower the
barrier height of the junction, significantly enhancing the performance of the corresponding
WSe2-based field-effect transistor devices (Figure 1b). The creation of such alloyed 2D
junctions between dissimilar atomic layer domains would be one of the important factors in
controlling the electronic properties of 2D junctions and the design and fabrication of 2D
atomic layer devices. [1]
Fig. 1. (a) Optical image and schematic drawing of WSe2-based bottom-gate FET with NbSe2 electrode. (b)
Transfer characteristics (IDS−VBG) of MS (Pd-WSe2), vdW (NbSe2-WSe2), and m-vdW (NbSe2- WxNb1−xSe2WSe2): 1, 3, and 5 cycle junction devices.
[1] Kim et al., Nano Lett., 2016, 16, 1890–1895.
A8-I-01
III-V/Ge Tunneling FET technology for ultralow power LSIs
Shinichi Takagi1,2,*, Munetaka Noguchi1, Minsoo Kim1,2, Daehwan Ahn1,2
and Mitsuru Takenaka1,2
1
Department of Electrical Engineering and Information Systems, The University of Tokyo, 7-3-1 Hongo,
Bunkyo-ku, Tokyo, 113-8656, Japan
2
JST-CREST, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan
* E-mail address: takagi@ee.t.u-tokyo.ac.jp
Low power consumption is of paramount importance for advanced CMOS-based logic LSI and
integrated systems mainly because of the difficulty in supply voltage (Vdd) reduction under realistic
CMOS device design. A strategy for the reduction in Vdd is to introduce devices with steep slope
of the channel current change in sub-threshold region. This way can contribute to the reduction in
Vdd by decreasing the gate voltage swing in the sub-threshold region. Here, the inverse of the slope
of the channel current change with respect to Vg defined as the sub-threshold slope (S.S.), which is
the Vg change necessary to change channel currents by one order of the magnitude, is known to
have the minimum value of ~60 mV/dec. at room temperature for conventional MOSFETs.
One of the most promising steep slope devices is tunneling FETs (TFETs) [1], where tunneling
probability and resulting tunneling current are modulated by Vg. This is because a variety of
simulation results have reported the excellent performance of TFETs with the steep slopes. Also,
fabrication of some TFETs can be regarded as highly compatible with the Si CMOS platform.
However, one of the drawbacks in TFETs is the low current drive. Particularly, Si-based TFETs
are known to have the essential limitation in Ion and S.S., because of the high Eg and the indirect
bandgap. Thus, III-V/Ge is promising for the materials used in TFETs as well, because of lower Eg,
direct bandgap in III-V and various possible combinations of the hetero-structures, which lead to
the higher tunneling probability. Here, it is known that the source/channel junctions composed of
type-II hetero-structures are effective in enhancing Ion of TFETs with maintaining low off current.
The effectiveness of Ge/III-V materials on TFETs through the enhancement of tunneling
probability has been demonstrated in this study [2, 3]. One of the key issues is the formation of the
steep and high quality source junctions, which provide both high tunneling current and low off
current. We address two types of planar TFETs utilizing the Ge/strained Si type-II hetero-structure
and the InGaAs channels, where in-situ doping p+ Ge/sSi and Zn-diffused p+ InGaAs source
junctions are employed for realizing steep and defect-less tunneling junction formation. Ge/tensilystrained Si n-TFETs with the type-II hetero-interfaces have also been found to exhibit high Ion/Ioff
ratio and low minimum S.S., because of reduction in effective Eg, steep B profiles by in-situ B
doping in Ge and improved MOS interface properties with both Ge and strained Si. Tensile strain
in Si channels combined with the Ge source can enhance the tunneling current because of the
reduced effective bandgap. The fabricated Ge/sSOI (1.1 %) TFETs show high Ion/Ioff ratio over 107
and steep minimum S.S. of 28 mV/dec. The p+/n junction formation in InGaAs using Zn diffusion
has realized excellent planar In0.53Ga0.47As n-TFET characteristics. Solid-phase Zn diffusion can
realize steep-profile and defect-less p+/n source junctions. The small S.S. of 64 mV/dec and large
Ion/Ioff ratio over 106 have been realized in the planar-type III-V TFETs.
References
1. A. C. Seabaugh et al., IEEE Proc. 98, 2095 (2010).
2. M. Noguchi et al., IEDM, 683 (2013); J. Appl. Phys. 118, 045712 (2015).
3. M.-S. Kim et al., IEDM, 331 (2014).
A8-O-01
Ultrafast dynamics of center-of-mass excitons confined in a quasi-2
dimensional structure by time-resolved ellipsometry and magneto Kerr
rotation
Minju Kim1, Juyeong Jang1, Sengho Park1, Minwoo Kim1, Woojin Lee1, Akihiro Murayama2
and Kwangseuk Kyhm1,3,*
1
Dept. of Opto-mechatronics and Cogno-mechatronics Engineering, Dept. Physics Educaion, RCDAMP, Pusan
Nat’l University, Busan, 609-735, Republic of Korea
2
Graduate School of Information Science and Technology, Hokkaido University, Kita 14, Nishi 9 Kita-ku,
Sapporo, 060-0814, Japan
* E-mail address: kskyhm@pusan.ac.kr
Center-of-mass exciton (CMX) confinement in a quasi-two dimensional structure is quite novel,
where individual electrons and holes are not fully confined but the center-of-mass exciton is
confined as a single particle confinement. In this case, large optical nonlinearities are expected due
to the large wavefunction size of CMXs [1,2]. Although the confined energy levels of CMXs were
studied mainly in terms of linear optical properties, their optical nonlinearities are barely known so
far.
We have investigated ultrafast dynamics of CMXs confined in a quasi-two dimensional
structure in terms of optical nonlinearities, where time-resolved ellipsometry and magneto Kerrrotation were utilized. Transient phase retardation was analyzed in terms of Stokes parameters,
which give rise to ultrafast change of elliptical polarizations. The polarization dynamics was
mapped in the Poincare sphere. Additionally, the maximum pump-probe signals were plotted for
the central wavelength of a pump pulse in order to clarify the ground state. The Rabi oscillation of
CMXs was also obtained for increasing excitation intensity, where we found the full saturation
occurs at relatively low excitation compared to common quantum well structures.
Finally, we also performed time-resolved Kerr rotation experiment to observe electron spin
precession in CMXs, where the Larmor precession of CMXs under resonant excitation was
observed.
Fig. 1. (a) Time-resolved Stokes parameters were mapped in the Poincare sphere at 4K for resonant excitation to
CMXs. (b) The experimental Time-resolved Kerr rotation signal under the magnetic field of 5T at 4K for resonant
excitation to CMXs. The g-factor is 1.637 and coherence time of spin is 23ps.
References
1. J. Hours, P. Senellart, E. Peter, A. Cavanna, and J. Bloch, Phys. Rev. B 71, 161306(R) (2005)
2. H. Tuffigo, R. T. Cox, and N. Magnea, Phys. Rev. B 37, 8 (1988)
A8-O-02
Efficient stress-relaxation of InGaN/GaN light-emitting diodes by carbon
nanotubes-assisted nanoepitaxy
Gun Hee Lee,1 Ah Hyun Park,1 S. Chandramohan,1 Tae Hoon Seo,2 Kyung Hyun Min,1 Hee
Soo Kim,1 Dong Kyu Yeo,1 Myung Jong Kim, 2 and Eun-Kyung Suh1*
1
School of semiconductor and Chemical Engineering, Semiconductor Physics Research Center,
Chonbuk National University, JeonJu 54896, Republic of Korea
2
Soft Innovative Materials Research Center, Korea Institute of Science and Technology,
Jeonbuk 55324, Republic of Korea
* E-mail address: eksuh@jbnu.ac.kr
The InGaN/GaN light-eimittng diodes (LEDs) has suffered from the compressive residual
stresses with strain-induced internal piezoelectric field and high density of threading
dislocations by the lattice and thermal expansion mismatch between GaN and sapphire. [1] In
this study, the dependence of efficiency droop on strain state of the undoped GaN and Si-doped
GaN was investigated through strain engineering of the respective layers by using singlewalled carbon nanotubes (SWCNTs) as nanomasks on sapphire substrate or undoped GaN
underlayer. Micro-Raman, high-resolution x-ray diffraction (HRXRD) and photoluminescence
studies revealed a substantial relaxation in the compressive residual stress and suppression of
threading dislocations. The SWCNTs allow epitaxial lateral overgrowth of GaN to occur,
leading to the suppression of dislocations and stress relaxation by up to 0.3 GPa. In HRXRD
rocking curve, the full width at half maximum (FWHM) of the (002) plane did not vary for the
two samples whereas the FWHM of the (102) plane decreased from 587 arcsec to 488 arcsec
for the n-GaN grown on SWCNTs. The internal quantum efficiency of InGaN/GaN LEDs on
SWCNTs was enhanced by up to 77 % and the significant increase in the light output power
and remarkably reduced efficiency droop, with the effect being more prominent at high
injection current levels.
Fig. 1. (a, b) HRXRD rocking curve for the symmetric (002) and asymmetric (102) planes of the n-GaN. (c)
Cross-sectional and (d) bird’s eye view FESEM images of the n-GaN on SWCNTs coated undoped GaN. The
scale bar is 10µm
References
1. G. Pozina, R. Ciechonski, Z. Bi, L. Samuelson, and B. Monemar, Appl. Phys. Lett. 107,
251106 (2015).
A8-O-03
Controlled fabrication of GaN nanorod arrays as a high-stability field
emitter
H.W. Seo,1* Q.Y. Chen,2 L.W. Tu,2 N. Badi,3 X. M. Wang,4 M. Chen,2 Y.J. Tu,2 C.L. Hsiao,5
L. Shao,6 A. Bensaoula,3 Milko Ileiv,4 and W. K. Chu4
1
Department of Physics, Jeju National University, Jeju, South Korea
Department of Physics and Center for Nanoscience & Nanotechnology, National Sun Yat-Sen University,
Kaohsiung, Taiwan.
3
Department of Physics and SVEC, University of Houston, Houston, Texas, USA
4
Department of Physics and TcSUH, University of Houston, Houston, Texas, USA.
5
Department of Physics, Chemistry and Biology, Linkoping University, Linkoping, Sweden
6
Department of Nuclear Engineering, Texas A&M University, College Station, Texas, USA.
2
* E-mail address: hwseo@jejunu.ac.kr
Patterned arrays of epitaxial GaN (0001) nanorods by Si-ion bombardment of Si (111)
substrates have been fabricated for the field emitters. The field emission characteristics of the
fabricated GaN nanorod arrays were measured using the flat tungsten tip at the high-vacuum
condition; both GaN nanorods on self-implanted and GaN matrix on unimplanted Si substrates.
The current densities as high as 10 mA/cm2 have been observed for GaN nanorod arrays under
applied electrical field of about 67 V/µm, while the stability of field emission at 3.9 mA/cm2
has been tested up to 8 hours without observable degradation. The new processes for GaN
nanorod-array fabrications provide an enabling method for large-scale field emitting devices.
2.0
5.0
VST = 67 V/µm
1.5
Current Density (mA/cm2)
Current Density (mA/cm2)
Implanted 5 x 1014/cm2
Unimplanted
1.0
0.5
JAV = 3.9 mA/cm2
Stability-7KV-100microns
annealed at 400 oC
4.5
4.0
3.5
0.0
20
40
Electrical Field ( V/µm)
60
0
6000
12000
18000
24000
Time (S)
Fig. 1. (a) Emission current density as function of the applied electric field for GaN nanorods on Si in linear
scale, and (b) Time stability of field emission current density of GaN nanorod arrays.
A8-O-04
Excitation polarization dependence of exciton dipole-dipole interaction in a
coupled quantum dot molecule
Heedae Kim+,#, Kwangseuk Kyhm*, Jongsu Kim&
+Clarendon
Laboratory, Department of Physics, University of Oxford, Oxford, OX1,
3PU, United Kingdom
# Institute for Integrative Nanosciences, IFW Dresden, Helmholtzstraße 20, 01069,
Dresden, Germany
*Graduate School of Cogno-mechatronics, Department of Physics Education,
RCDAMP, Pusan Nat’l University, Busan 609-735, Korea
&Department of Physics, Yeungnam University, Gyeongsan, 712-749, Korea
As a building-block of quantum bits, various coupled quantum dot molecule (CQM) structures
have been studied in terms of coupling and entangling of quantum states [1]. A conventional
approach in coupling states was focused on vertically coupled quantum dot molecule which
the inter-dot distance can be easily controlled. Here, we found that exciton-exciton interaction
in a laterally coupled quantum dot molecule depends on excitation polarization via dipoledipole interaction. When excitation intensity of linearly polarized light parallel to the coupled
direction of [11-0] is increased, excitons and local biexcitons of the two different quantum dots
show redshift along with coupled biexcitons, whilst both coupled biexciton and redshift are not
observed for the polarization perpendicular to the coupled direction ([110]). The redshift of
excitons was manifested theoretically by exciton dipole-dipole interaction, and the diamagnetic
coefficient of coupled biexcitons was observed nearly twice compared to that of local
biexcitons.
Figure 1(a) Atomic force microscope (AFM) image and dipole-dipole interaction schematics of CQM fabricated on the AlGaAs
surface, (b) Magneto-micro PL spectra for excitons and local/coupled biexcitons, (c) Time-resolved PL spectra were measured
under excitation power of 6W/cm^2
References
[1] M. Bayer et al., Science 291, 451 (2001)
A8-O-05
Photoelectrochemical analysis of InGaN/GaN core-shell nanowire for solar
water splitting
Jin-Ho Kang1, Mohamed Ebaid1, and Sang-Wan Ryu1,2,*
1
Deparment of Physics, Chonnam National University, Gwangju 61186, Korea
Optoelectronics Convergence Research Center, Chonnam National University, Gwangju 61186, Korea
* E-mail address: sangwan@chonnam.ac.kr
2
We investigated the fabrication of GaN-based nanowires (NWs) to work as solar light harvesting media in the
PEC-WS process. Initially we focused on the fabrication and detailed characterization of various GaN-based
nanostructures such as GaN, InGaN, and InGaN/GaN multi-quantum well coaxial NWs (MQW-CNWs). The
growth mechanisms that can lead to the production of high quality nanoscale building blocks have been
investigated. As a result, high crystal quality GaN-based NWs with large aspect-ratio and good substrate surface
coverage were synthesized using a metal assisted vapor-liquid-solid (VLS) growth mechanism in a metalorganic
chemical vapor deposition (MOCVD) system, as shown in Fig. 1. The detailed microstructure at the atomic scale
of the as-grown NWs was investigated using high resolution transmission electron microscopy (TEM), which
showed highly crystalline NWs. Additionally, the optical properties were studied using photoluminescence (PL)
and cathodoluminescence (CL) spectroscopies. For the deep evaluation of the optical properties, the as-grown
NWs were further characterized using time-resolved PL to understand the carrier dynamics with respect to the
different growth parameters.
To evaluate the PEC-WS performance of the GaN-based NWs, they were used in a home-made PEC cell as
photoanodes and irradiated with a simulated solar light source. The high crystal quality and the large surface-tovolume ratio of the NW geometry led to improved PEC-WS performance, especially in the case of InGaN/GaN
MQW-CNWs that added the merits of low band gap and high carrier collection efficiency. The low band gap of
the InGaN alloy provided the capture of lower energy photons and realized the hydrogen fuel generation in the
visible range of the solar spectrum, which is not easily accessible in the commonly used wide band gap materials
such as ZnO and TiO2. The applied-bias-photon-to-current efficiency (ABPC) and incident-photon-to-current
conversion efficiency (IPCE) were further measured, which showed values comparable with those in the natural
photosynthesis. The PEC-WS mechanism was investigated based on the physical phenomena occurred in the
GaN-based NW photoelectrodes during the light irradiation in water-based electrolytes such as exciton
localization and defect induced recombination.
Fig. 1. Typical FE-SEM surface images of (a) agglomerated Ni/In/Ga nanocatalysts, (b) GaN cores grown with
the VLS mechanism, and (c) the nanowires containing six periods of InGaN/GaN shells by the VS mechanism.
B1-I-01
R-matrix Theory and Real Space DFT Simulation of
Si Nanowire Transistors
Nobuya MORI1,*, Gennady MIL'NIKOV1, Jun-Ichi IWATA2, and Atsushi OSHIYAMA2
1
Department of Electronic Engineering, Osaka University, 2-1 Yamada-oka, Suita, Osaka 565-0871, Japan
2
Department of Applied Physics, The University of Tokyo, Hongo, Tokyo 113-8656, Japan
* E-mail address: nobuya.mori@eei.eng.osaka-u.ac.jp
Semiconductor nanowires have recently attracted great attention as potential active
components of future integrated circuits. In nanoscale regime, there are a countable number of
atoms in the conducting channel and quantum transport simulations require an atomistic device
structure and atomic-scale variations, such as the random impurity distribution. However,
application of realistic electronic structure models such as tight-binding approach or more
advanced density functional theory (DFT) has been proven to be numerically challenging and
efficiency of the numerical methods remains an important issue for realistic device simulations.
In this talk we present a recently developed R-matrix method [1] for atomistic quantum
transport in ballistic regime. Similar to the popular recursive Green’s function method, our
scheme makes use of the localized nature of atomistic device Hamiltonian in order to perform
recursive calculations of the mobile charge density. However, unlike the conventional approach,
the R-matrix method enables one to treat an open device as a set of close subsystems which are
independent on the external conditions at the contacts and can be chosen in arbitrary way. The
propagated quantity in our scheme is the R-matrix which has been defined as a boundary part
of the Green’s function in the close system. It is then shown that the real-valued R-matrix can
be constructed recursively in a device of arbitrary geometry. The size of the matrix inversion
operations in the propagation scheme is controlled by the local size of the close subsystems
and can be made arbitrary small.
The method has no limitations on the device geometry and provides a lot of freedom for
handling size of computer operations and efficient parallelization. We present mathematical
details of the method and discuss its application to self-consistent non-equilibrium Green’s
function (NEGF) transport simulation of Si nanowire transistors, based on tight-binding models
and DFT Hamiltonian in the real space representation [2].
References
1. G. Mil’nikov, N. Mori, and Y. Kamakura, Phys. Rev. B 79, 235337 (2009).
2. J. Iwata, D. Takahashi, A. Oshiyama, T. Boku, K. Shiraishi, S. Okada, and K. Yabana, J.
Comput. Phys. 229, 2339 (2010).
B1-O-01
Low-Temperature Growth of GeSn on Si (100) Substrate and Structural
Characterization
Jeongmin Lee1and Seongjae Cho1,2,*
1
Deparment of IT Convergence Engineering, 2Department of Electronic Engineering, Gachon University
1342 Seongnamdaero, Sujeong-gu, Seongnam-si, Gyeonggi-do 13120, Republic of Korea
* E-mail address: felixcho@gachon.ac.kr
GeSn is one of the most promising materials for scalable and Si-compatible photonic devices
in the optical interconnect system due to its capability of indirect-to-direct band transition at
Sn fraction of 7–8 % and bandgap tunability by controlling the Sn fraction. Although chemical
vapor deposition (CVD) has been mainly adopted for epitaxially growing GeSn on various
platforms, the Ge and Sn precursors are toxic and unstable [1–2]. In this study, GeSn films
were deposited on Si (100) substrates at various deposition rates using e-beam evaporation with
GeSn pellets having 12 at. % Sn. Then, 40-nm-thick SiO2 layers were deposited for capping
and post-deposition annealing (PDA) was performed in sequence at 400~600 ºC by rapid
thermal annealing (RTA) in the 4:1 N2/H2 forming gas, by 50 ºC step, in order to form crystal
domains. After the sample preparation, characterization of the GeSn thin films were carried out
by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The deposition rate was
precisely controlled to be 0.5 Å/s for densified GeSn deposition (Fig. 1) and the lowest value
of 2θ of 26.796º was obtained from (111) GeSn matrices at the PDA temperature of 500 ºC
(Fig. 2). The corresponding lattice constant is calculated to be a⊥ = 5.756 Å; the extracted Sn
fraction is 12.4% high enough for the direct-band transition [3–4].
Acknowledgment This work was supported by the National Research Foundation of Korea (NRF)
funded by the Ministry of Science, ICT & Future Planning (Grant No. NRF-2014R1A1A1003644).
Fig. 1. SEM image of the GeSn thin film after a PDA
at 500 ºC (320 nm). Deposition rate = 0.5 Å/s.
Fig. 2. XRD patterns of GeSn thin films after PDAs
at different annealing temperatures.
References
[1] J. S. Harris, R. Chen, H. Lin, Y. Huo, E. Fei, S. Paik, S. Cho, and T. Kamins, ECS Trans. 50, 601 (2012).
[2] C. G. Littlejohns, A. Z. Khokhar, D. J. Thomson, Y. Hu, L. Basset, S. A. Reynolds, G. Z. Mashanovich, G. T. Reed,
and F. Y. Gardes, IEEE Photonics J. 7, 6802408 (2015).
[3] N. Bhargava, M. Coppinger, J. P. Gupta, L. Wielunski, and J. Kolodzey, Appl. Phys. Lett. 103, 041908 (2013).
[4] Y. Cho, O. Rubel, and S. Cho, Abstract of Korean Conference on Semiconductors (KCS), WG1-F-3, Feb. 2016.
B1-O-02
First-principle study of GeSn alloys and its application to tunneling fieldeffect transistor
Yongbeom Cho1, Oleg Rubel2, and Seongjae Cho1,3,*
1
Deparment of Electronic Engineering, Gachon University, Seongnam-si, Gyeonggi-do 13120, Korea
Department of Materials Science and Engineering, McMaster University, Hamilton L8S4L8, Canada
3
Graduate School of IT convergence Engineering, Gachon University, Seongnam-si, Gyeonggi-do 13120, Korea
* E-mail address: felixcho@gachon.ac.kr
2
GeSn is getting increasing popularity as a candidate material for both group-IV-driven advanced Si
CMOS and photonics technologies owing to the virtues of its high carrier mobilities and bandgap
tunability, by which higher chances for low-power electronics and Si-compatible optical interconnect
are expected [1]. By incorporating Sn atoms, the optical bandgap Ge is reduced accompanying the
transition to a direct-bandgap material at Sn fraction of near 7%. By the narrow bandgap of GeSn with
a permissibly large Sn fraction, GeSn can be adopted for source junction material in tunneling fieldeffect transistor (TFET). Although the current drivability by band-to-band tunneling is mainly
determined by the energy bandgap, density of states (DOS) should be considered at the same time for
more accurate calculating of the on-state current (Ion). In this work, a study on DOS as a function of Sn
fraction is made by ab initio calculation of the electronic structures of GeSn alloys. The Two-atom
triclinic primitive unit cell usesd in constructing the whole supercells with different Sn fractions as
shown in Fig. 1. Various models were used in cooperation for higher accuracy and credibility: (i) the
supercells were volume-optimized considering local density approximation (LDA) and spin-orbital (SO)
coupling effect [2–3]. (ii) more realistic energy bandgaps were obtained by modified Becke-Johnson
(mBJ) exchange potential model with LDA [4–6]. DOS was calculated with SO coupling taking the
split-off valence band into account. Fig. 2 demonstrates the DOS (upper) and effective DOS (lower) of
GeSn matrices with different Sn fractions. As more Sn atoms are incorporated, the effective DOS in the
valence band decreases while that in the conduction band is insignificantly small. Although GeSn with
a high Sn fraction can be applied to source junction of a heterojunction TFET for higher Ion [7], the
degradation in number of valence electrons that potentially can participate in the band-to-band tunneling
needs to be considered for material design of GeSn in TFETs.
Acknowledgment This work was supported by NRF funded by MSIP (NRF-2014R1A1A1003644).
Fig. 1. Primitive unit cell for the diamond structure.
Conventional (left) and new two-atom ones (right).
Fig. 2. DOS (top) and effective DOS (bottom)
obtained by ab initio calculations and
integration.
References [1] G. He and H. A. Atwater, Phys. Rev. Lett. 79, 1937 (1997) [2] J. P. Perdew, Chem. Phys. Lett. 64,
127 (1979) [3] W. Kohn and L. J. Sham, Phys. Rev. 140, A1133 (1965) [4] É. Germaneau, G. Su, and Q. R. Zheng,
Comput. Phys. Commun. 184, 1697 (2013) [5] D. Koller, F. Tran, and P. Blaha, Phys. Rev. B. 83, 195134 (2011)
[6] P. V. Smith, M. W. Radney, and G. A. Shah, J. Phys. Condens. Matter. 25, 056007 (2013) [7] S. Cho, I. M.
Kang, T. I. Kamins, B.-G. Park, and J. S. Harris, Jr., Appl. Phys. Lett. 99, 243505 (2011).
B1-O-03
Simultaneously Controlled Strain Enhancement and Photoluminescence
Blue-shift in Ge-on-Si
Chulwon Lee1, Buguen Ki2, Yang-Seok Yoo1, Min-Ho Jang1, Seung-Hyuk Lim1, Jungwoo
Oh2, and Yong-Hoon Cho1*
1
Department of Physics and KI for the NanoCentury, Daejeon, Republic of Korea
2
School of Integrated Technology, Yonsei University, Incheon, Republic of Korea
E-mail address: yhc@kaist.ac.kr
Recently, strained Ge has attracted much attention due to its promising properties as a future
semiconductor light source for optical communication applications.[1,2,3] Especially, since
there has been a numerous demand on Si compatible light source for optical interconnection
for on-chip scale, a variety of attempts have been shown to achieve on-chip light source with
strained Ge to achieve telecommunication wavelength for the on-chip or chip-to-chip optical
interconnection.[1] However, owing to its indirect bandgap, its poor quantum efficiency at low
tensile strain requires greater strain enhancement. To overcome the poor efficiency, highly
strained micro- and nano-structures have been suggested to achieve higher recombination rate,
yet the higher value of strain leads to linearly red-shifted emission wavelength of
photoluminescence.[3]
In this study, photoluminescence (PL) blue-shift and tensile strain enhancement could be
simultaneously achieved by simply annealing Ge-on-Si. It has clearly been observed that the
thermal annealing process provides strain enhancement. However, at a specific condition of
annealing, the annealed Ge-on-Si shows blue-shifted emission in spite of its enhanced strain.
To find the origin of simultaneous strain enhancement and PL blue shift, depth dependent
optical properties of Ge-on-Si have been investigated by simply etching the surface of the Geon-Si. It turned out that the thermally annealed Ge-on-Si exhibits both increasing strain and PL
peak energy as the etched depth increases. Since the thermal annealing and cooling cycle
enhances the value of tensile strain as well as the composition of Si atoms in the Ge layer, the
bandgap globally increases and the emission gets blue-shifted. This result could be confirmed
by performing optical characterization as well as Energy-dispersive X-ray Spectroscopy
analysis on the samples with different etched depth. Our research may provide a possibility of
practical Ge based light source with telecommunication wavelength.
References
1. Y. Ishikawa, K. Wada, D. D. Cannon, J. F. Liu, H. C. Luan and L. C. Kimerling, “Stran-induced
band gap shrinkage in Ge grown on Si substrate,”Appl. Phys. Lett. 82, 2044 (2003)
2. J. Liu, X. Sun, R. Camacho-Aguilera, L. C. Kimerling, and J. Michel, “Ge-on-Si laser operating
at room temperature,” Opt. Lett. 35, 5 (2010)
3. Suess, M. J., et al. "Analysis of enhanced light emission from highly strained germanium
microbridges." Nat Photon 7, 466 (2013)
B2-IK-01
Device Innovation for the Future Automotive and IoT Applications
Bich-Yen Nguyen, Mariam Sadaka, Manuel Sellier and Christophe Maleville
Soitec | Parc Technologique des Fontaines, 38190 Bernin (France)
There is an undisputed consensus: Internet of Thing (IoT) will have an enormous economic impact and is a big
driver for the growth of the semiconductor market after the smartphone. Sensors, microcontrollers,
microprocessors, embedded non-volatile memory (eNVM) and analog/RF technologies will be the key drivers for
IoT. At the core of it: IoT is about having electronic devices connected to the Internet, capable of identifying
themselves and communicating data to other devices on the network.
The connected car has been a familiar example of IoT technology, making the automotive industry an enormous
driver for IoT growth in the next 5 years. Cars rely on greater intelligence, connectivity and sophisticated
electronics as illustrated in Figure 1a (1). Today, consumers demand cars that sync with smartphones and invehicle infotainment capability; and governments mandate improvement in safety and fuel efficiency. Over the
next decades, it is predicted that more than 100 million cars worldwide will have autonomous-driving features
and simultaneous connectivity, both vehicle-to-vehicle and vehicle-to-infrastructure. This will continue to drive
the automotive electronic content to beyond 30% of the total vehicle bill of material (2).
To address the requirements of this strong emerging industry trend, electronic content must have; high degrees of
functional integration and superior reliability in harsh environment (automotive); all while maintaining excellent
power/performance and cost benefits. In this talk, we will discuss FDSOI, as shown in Figure 1b, as a candidate
technology for enabling future automotive and IOT applications based on providing minimum energy
consumption, better performance and RF/analog co-integration capabilities with the least process and design
disruption for low cost and fast time to market. FDSOI on ultra-thin box enables a wide range of back bias which
can be used to further reduce power consumption without adding process complexity for multi-threshold voltage
option as used in bulk devices (Figure 1c, (3)). The forward bias can also be used to provide a higher drive current
for operating stacked embedded emerging memory such as MRAM.
Automotive electronics require much more stringent reliability requirements compared to consumer electronics.
Ultra-thin body FDSOI devices are totally isolated with the buried oxide, which tremendously improves the soft
error rate, as shown in Figure 1d (4), and thus enhances the reliability and reduces the need for error correction
and redundancy with scaling. Furthermore, FDSOI devices allows operating at a wide temperature range (-40C to
150C), unattainable by bulk devices especially at high temperatures due to extreme low junction leakage current.
References:
1. Clemson University Vehicular Electronics Lab, http://www.cvel.clemson.edu/auto/systems/auto-systems.html
2. Globalfoundries, “FD-SOI Technology Innovations Extend Moore’s Law” white paper, Sept. 2015,
http://globalfoundries.com
3. Q. Liu et al, IEEE IEDM 2013
4. P. Roche et al, IEEE IEDM 2013
B2-I-02
Modeling of FinFET and Nanowire Transistor using industry standard
BSIM-CMG model
Yogesh Singh Chauhan*
* Department of Electrical Engineering, India Institute of Technology Kanpur, India-208016
Multi-gate devices have become the requirement of time to effectively control the short
channel effects (SCE) that become severe in extremely scaled MOSFETs. In multi-gate device family,
FinFET having three gates with silicon as channel material is already being used from 22nm and beyond
technology nodes. The nanowire having gates all around is competent to replace the FinFETs structure
below 10nm technology nodes due to its better control on channel over the FinFETs. To enhance the
performance of multi-gate devices, different high mobility channel materials such as germanium, III-V,
2-D layered material etc. are being actively explored to replace silicon in channel region. The circuit
designers need robust compact models to perform circuit simulation. BSIM-CMG is the industry
standard compact model for silicon channel based multi-gate devices and it also accurately models the
devices having channel materials from group III-V or Ge [1]. We are also developing models for
transistors with alternate channel materials that may be used below 10nm node [2, 3].
Figure 1. BSIM-CMG model validation for FinFET, nanowire and triangular FETs having Si, Ge and InGaAs as channel materials from (a)–
(f) [4]; (g) gate capacitance of a dedicated model in InGaAs channel FinFETs is shown where gate capacitance has lower value than oxide
capacitance due to presence of quantum capacitance [3].
References
[1] Y. S. Chauhan et al., Academic Press, 2015.
[2] S. Khandelwal et al., IEEE EDL, Feb. 2016.
[3] C. Yadav et al., IEEE TED, Nov. 2015.
[4] S. Khandelwal et al., IEEE VLSIT, June 2015.
B2-O-01
The electronic and optical properties of Ge/Sn core-shell nanowires
Elisabeth Pratidhina, Sunghyun Kim, and Kee Joo Chang*
Department of Physics, Korea Advanced Institute of Science and Technology, Daejon 34141, Korea
*E-mail address: kjchang@kaist.ac.kr
Germanium (Ge) is considered as a potential candidate material for integrated lasers due to
its compatibility with the current Si-based complementary metal-oxide-semiconductor
technology. However, the indirect band gap nature of Ge is an obstacle to the fabrication of
efficient light emitters. Although Ge has the indirect band gap at the L point in the Brillouin
zone, the direct band gap at the Γ point only differs by 0.14 eV from the indirect band gap.
The small difference between the indirect and direct band gaps has promoted extensive studies
for the band gap engineering of Ge via several routes such as strain engineering and alloying
with other group-IV elements.
In this work, we investigate the electronic properties of Ge/Sn core-shell nanowires (NWs)
through first-principles density functional calculations. We report the discovery of Ge/Sn coreshell NWs with direct band gaps and efficient optical transitions, especially oriented along the
[111] direction. We find that strain is induced to the Ge core by the lattice mismatch between
Ge and Sn, and it drives an indirect-to-direct band gap transition. The intrinsic tensile strain on
the Ge core is inversely proportional to the Ge core size, whereas it is proportional to the Sn
shell thickness. The band gaps of Ge/Sn core-shell NWs can be tuned by controlling the coreshell ratio and the diameter of NWs. The squared dipole matrix elements of the direct transition
at the Γ point are comparable to that of GaAs. Furthermore, we demonstrate that an external
tensile strain along the [111] direction can trigger an indirect-to-direct band gap transition for
NWs with the intrinsically indirect band gaps.
B3-I-01
Magneto-optical studies in II-VI quantum Hall systems
Yasutaka IMANAKA1
1Tsukuba Magnet Laboratory, National Institute for Materials Science, Tsukuba, Ibaraki 305-0003, Japan
* E-mail address: IMANAKA.Yasutaka@nims.go.jp
Inter- and intra-band optical studies under high magnetic fields are quite essential for
understanding the band structure of semiconducting materials. Moreover, such “magneto-optical”
experiments sometimes give us another approach for detecting electron “transport” phenomena of
semiconductor nano-structures like quantum Hall systems [1].
Recent progresses of the epitaxial growth technique enable us to study both the integer and the
fractional quantum Hall effects for various III-V and II-VI compound semiconductors. The
Shubnikov-de Haas (SdH) oscillation and the quantum Hall plateau are observed evidently in
various two-dimensional electron systems even at low magnetic fields. The high frequency study
of the quantum Hall effect is also attractive from the viewpoints as the topological protected
features.
In this talk, I will present the magneto-transmission results in ZnO and CdTe quantum all systems
with using millimeter and terahertz waves under high magnetic fields. The ffective mass and the
mobility of two-dimensional electron were discussed from both yclotron resonance experiments
and magneto-transport measurements.
Figure 1 shows the cyclotron resonance (red) and the magneto-transport (blue) results of a ZnO
heterstructure sample under magnetic fields up to B=15T. The cyclotron resonant dip appears
around B=8T when the millimeter wave frequency is f=632GHz. The 2D polaron mass is obtained
as m*~0.32m0 from the magnetic field dependence of the resonance because of the large electronphonon coupling in ZnO. The electron mobility is also obtained from the resonant width as
μ~2,500cm2/Vs at liq.He temperatures.
Above the resonant field, the oscillatory behavior of the transmission is observed in the cyclotron
resonance data. The oscillation period is perfectly consistent with the one in the transport data,
indicating that the optical-detected SdH oscillation (ODSdH) is occurred in the dense twodimensional electron systems.
In CdTe two-dimensional electron systems, we have just carried out to observe the ODSdH at
the fractional filling factors under high magnetic fields.
Fig. 1. Magneto-transmission (red) and magneto-transport (blue) results in a ZnO heterostructure at low
temperatures. The cyclotron resonance with the oscillatory behavior is clearly observed by the millimeter wave
transmisson. The oscillation period is perfectly consistent with the one of the magneto-transport result.
References
1. Y. Imanaka, J. Low Temp. Phys. 170, 389-396 (2013).
B3-I-02
Vertical Organic Transistors for Information Tag and Display Applications
Kazuhiro Kudo* and Masatoshi Sakai
Graduate School of Engineering, Chiba University, Chiba, Japan
* E-mail address: kudo@faculty.chiba-u.jp
Conventional organic field-effect transistors (OFETs) have low-speed, low-power, and
relatively high operational voltage mainly due to their low-mobility and high-resistivity. From
these points of view, various vertical-type OFETs with a short channel length have been
reported. In this report, we report step-edge vertical channel OFETs (SVC-OFETs) for
achieving a submicron channel-length by a simple fabrication process [1] and their applications.
Basic FET characteristics of SVC-OFETs were investigated. SVC-OFETs showed
excellent device performances and high cut-off frequency of approximately 4 MHz was
obtained. These results demonstrate that SVC-OFETs are able to fabricate by simple printing
process and have a potential to produce high-speed logic circuits, radio-frequency
identification (RFID) tags, display devices, etc. Figure 1 shows typical examples of (a) an
active antenna [2] and (b) a layout of active-matrix (AM) OLED display [3] using SVC-OFETs.
The characteristics of active antenna can be changed from 0 turn to N turn loop by operating
SVC-OFETs. The effective emission area (OLED part) in one pixel using a SVC-OFET is
larger than that of a conventional device layout. Because SVC-OFETs can be fabricated on
AM wire edges such as common, data, and scan lines. As described above, SVC-OFETs are
suitable not only for RFID tags, but also AM display backplanes, owing to their highperformance operation and compact layout. Furthermore, the matching capacitor of active
antenna and storage capacitor of AM display circuits can be controlled by adjusting the overlap
area between the gate line and source electrode.
(a) Active antenna of RFID tag
Fig. 1.
(b) Layout of AM OLED display using SVC-OFETs.
Application to (a) active antenna, (b) active-matrix OLED display using SVC-OFETs.
References
1. K. Kudo, H. Yamauchi and M. Sakai, Jpn. J. Appl. Phys., 51, 11PD05-1-4 (2012).
2. K. Kudo, S. Kuniyoshi, H. Yamauchi, M. Iizuka and M. Sakai, IEICE Trans.
Electron., E96-C(3), 340-343 (2013).
3. K.Nakamura, T.Hata, A.Yoshizawa, K.Obata, H.Endo and K.Kudo, Appl. Phys. Lett., 89,
103525-1-3 (2006).
B3-O-01
The atomic and electronic properties of coordination defects in amorphous
oxide semiconductors
Woo Hyun Han* and Kee Joo Chang
Department of physics, Korea Advanced Institute of Science and Technology, Daejeon 34141, Korea
*E-mail address: hanwooh@kaist.ac.kr
Amorphous oxide semiconductors (AOSs), such as amorphous In-Ga-Zn-O (a-IGZO) and
Zn-Sn-O (a-ZTO), are considered as a promising channel material in transparent thin-film
transistors (TFTs) because of their superior material properties such as large band gaps,
intrinsic n-type conductivity, uniform film growth, and high mobility. However, there remain
critical instability issues in AOS-based TFTs, such as large negative shifts of the threshold
voltage under negative bias illumination stress and positive threshold-voltage shifts under
positive bias stress, which should be overcome for their practical applications. Several
theoretical models based on disorder and defects have been proposed to explain the origin of
the instability problems. While disorder-induced anions cause the valence band tail states as
well as the deep subgap states in AOSs, the role of disordered cations is poorly understood.
In this work, we perform first-principles density functional calculations to investigate the
atomic and electronic properties of cation- and anion-related defects in amorphous oxide
semiconductors. For a-IGZO, a-ZTO, and a-ZnO, we generate non-stoichiometric amorphous
samples through melt-and-quench ab initio molecular dynamics simulations. We find that
undercoordinated cation defects commonly occur under O-deficient conditions, which are
classified into two types, undercoordinated cation pair and undercoordinated single cation
defects. Based on hybrid functional calculations, we find that cation pair defects induce deep
subgap states in the band gap, similar to those of O-vacancy defects. In the case of
undercoordinated single cation defects, localized subgap states near the conduction band edge
are formed. Under O-rich conditions, excess O atoms form O-O dimers with the host O atoms
and these dimers act as electron traps. We discuss the role of cation- and anion-related defects
in the instability problems and a way to improve the performance of AOS-based devices.
B3-O-02 [NO SHOW]
Modification of ZnO film surface by C60 molecules: Raman and
Photoluminescent spectroscopy of the interface ZnO–C60
Erkin A. Zakhidov*, Abdumutallib M. Kokhkharov, Sherzod Q. Nematov,
Rafael A. Nusretov, Vakhobjon O. Quvondikov, Aziz A. Saparbaev
Institute of Ion-Plasma and Laser Technologies, Uzbekistan Academy of Sciences, Tashkent, Uzbekistan
* E-mail address: ezakhidov@hotmail.com
ZnO, a metal oxide semiconductor with a wide band gap (3.37 eV), large exciton
binding energy (60 meV) and high mechanical and thermal stabilities is a promising candidate
material for new generations of devices such as UV light emitting diodes, solar cells,
photocatalysists, and high-temperature and harsh environment electronic materials. Currently,
a variety of synthesis techniques is available for the growth of high quality ZnO thin films for
use in advanced devices applications. Physical properties of ZnO thin films can be significantly
modified by C60 molecules deposited on the surface of such a semiconductor. However,
control of the electronic and optical characteristics of the composition ZnO + C60 required for
using in aboveindicated applications is still a big challenge.
Fullerene molecules, because of their extensively conjugated three-dimensional π-system
having a closed-shell configuration, are suitable for the efficient electron transfer with
minimal changes in their structure and energy. This allows fullerene molecules to accept up
to 6 electrons from organic electron-donor molecules, such as Zn-porphyrin, and to compose
a molecular donor-acceptor pair with the absorption spectrum, covering a substantial part of
the sunlight energy. The most intriguing aspect in this case is that ZnO can, in turn, serve as
an effective secondary electron acceptor from C60 molecules inhibiting back recombination
of separated charges, and thus, ZnO-C60 interface may be considered as a key element for
constructing new types of organic photovoltaic or systems of artificial photosynthesis.
In this presentation, Raman and photoluminescence spectra of the composition of ZnO film
with a C60 solution in toluene on the film surface are studied separately in each of its
component and in the integrated structure as a whole. Thin (approx. 100 nm) film of ZnO was
deposited on a quartz glass by spray-pyrolysis method. Further, ~2 mm layer of C60 solution
in toluene was placed on the surface of ZnO film. Raman and photoluminescence spectra of
the composition were measured by Renishaw micro-Raman spectrometer 2000 at laser
excitation in visible, 532 nm, (non-resonant) and UV, 325 nm, (resonant) regions. Using
backscattering geometry and 90x microscope objective the spatial resolution of measurements
up to ~ l μm has been gained, when intensities of Raman scattering from nano-scaled ZnO film
and C60 layer were comparable to those from SiO2 substrate or toluene. Comparison of the
Raman spectra measured before and after evaporation of toluene on the ZnO film surface
revealed physical conditions favorable for interaction in ZnO-C60 interface.
In addition to well known Raman lines of C60 (270 cm-1, 490 cm-1, and 1467 cm-1) and
ZnO (430 cm-1), Raman spectra of the interface ZnO-C60 revealed new bands at 780 cm-1,
1080 cm-1 and 1350 cm-1. Spectral positions and intensities of these bands were substantially
depended on the physical conditions in that area, in particular, the roughness of the ZnO film
surface, concentration of C60 molecules and temperature of samples. The photoluminescence
spectra shown the possibility of charge separation and charge transfer induced quenching in
specific wavelengths related to absorption of C60.
B3-O-03
Switching characteristics of ZnO/graphene hybrid devices
Bok Ki Min1, Seong K. Kim1, Seong Jun Kim1, Min-A Kang1, Sung Ho Kim1, Wooseok
Song1, Sung Myung1, Jongsun Lim1, and Ki-Seok An1,*
1
Thin Film Materials Research Center, Korea Research Institute of Chemical Technology (KRICT), Yuseong P.
O. Box 107, Daejeon 305-600, Republic of Korea
* E-mail address: ksan@krict.re.kr
We present the fabrication of a simple ZnO/graphene two-dimensional thin-film device
exhibiting ambipolar switching behavior with both a high on-off ratio of 105 and excellent
carrier mobility of 329.7 ± 16.9 cm2/V·s [1]. Conventional ZnO thin-film transistors (TFTs)
often suffer from relatively low carrier mobility, while the performance of typical graphene
TFTs is largely limited by the linear dispersion band structure. These TFTs operate through the
formation of a channel with a high density of charge carriers induced by a gate bias. We believe
that the unique switching characteristic of our device originates from current passing across a
series of ZnO/graphene heterojunctions, as in graphene barristors. Graphene barristors are a
novel type of electronic switching device with excellent performance, which surpass the low
on-off ratios that limit the operation of conventional graphene transistors. In barristors, a gate
bias is used to vary graphene’s Fermi level, which in turn controls the height and resistance of
a Schottky barrier at graphene/semiconductor heterojunction. We demonstrate that the
switching characteristic of a ZnO/ graphene device with simple geometry results from
tunneling current across the Schottky barriers formed at the ZnO/graphene heterojunctions.
Direct characterization of the current-voltage-temperature relationship of the heterojunctions
by ac-impedance spectroscopy reveals that this relationship is controlled predominantly by
field emission, unlike most graphene barristors in which thermionic emission is observed [2].
This governing mechanism makes the device unique among graphene barristors, while also
having the advantages of simple fabrication and outstanding performance.
Fig. 1. Schematic diagram for the current conduction by field emission across a ZnO/graphene heterojunction and
the effective mobilities for the ZnO, thickness-controlled ZnO/graphene, and graphene
References
1. W. Song, S. Y. Kwon, S. Myung, M. W. Jung, S. J. Kim, B. K. Min, M.-A. Kang, S. H. Kim,
J. Lim, and K.-S. An, Sci. Rep. 4, 4064 (2014).
2. E. M. Mills, B. K. Min, S. K. Kim, S. J. Kim, M.-A. Kang, W. Song, S. Myung, J. Lim, K.S. An, J. Jung, and S. Kim, ACS Appl. Mater. Inter. 7, 18300 (2015).
B4-I-01
Ultrathin nanorod-type solar cells with silicon germanium active layer
R.E.I. Schropp1,*, L.W. Veldhuizen1, Y. Kuang1, M.C. van Lare2, J.K. Rath3, A. Polman2,
S.J. Yun4
1
Department of Applied Physics, Plasma & Materials Processing, Eindhoven University of Technology (TUE), P.O. Box
513, 5600 MB Eindhoven, The Netherlands
2Center for Nanophotonics, FOM Institute AMOLF, Science Park 104, 1098 XG Amsterdam, The Netherlands
3Physics of Devices, Debye Institute for Nanomaterials Science, Utrecht University, High Tech Campus 21, 5656 AE
Eindhoven, The Netherlands
4Solar Cell Technology Research Section, Electronics and Telecommunications Research Institute, 138 Gajeongno,
Yuseong-gu, Daejeon 305-700, Korea
*E-mail address: r.e.i.schropp@tue.nl
Thin-film silicon and its alloys are attractive for the photovoltaic (PV) market because of
versatile deposition procedures (such as roll-to-roll fabrication) and potential applications in
lightweight and flexible form. However, hydrogenated amorphous silicon (a-Si:H) in thin-film
solar cells suffers from a high defect density, leading to a high recombination rate. Bulk
recombination is mitigated by using thinner layers, which has added advantages of increased
production throughput and reduced light-induced degradation. On the other hand, cells have to
be thick enough to efficiently absorb the near-bandgap part of the solar spectrum. Therefore
light-trapping schemes that increase optical absorption are crucial. Light scattering in thin-film
solar cells is traditionally achieved by the usage of a textured transparent conductive oxide
(TCO) layer, such as commercially available SnO2:F with a randomly textured surface.
Recently, radial junction solar cells based on elongated nanostructures such as nanowires,
nanorods, nanopillars, nanodomes, and nanopyramid have attracted strong attention. Here we
present a simple, low-cost, and scalable approach for the fabrication of efficient nanorod-based
solar cells. Templates with arrays of self-assembled ZnO nanorods with tuneable morphology
have been synthesized by chemical bath deposition at a low temperature of 80°C. The nanorod
templates are conformally coated with a-Si:H light absorber layers of 100 nm and 200 nm
thickness. An initial efficiency of up to 9.0% is achieved for the optimized design. External
quantum efficiency (EQE) measurements of the nanorod cells show a substantial photocurrent
enhancement in both the red and the blue part of the solar spectrum.
We also demonstrate single junction and tandem solar cells using an ultrathin (35 nm)
hydrogenated amorphous silicon-germanium (a-SiGe:H) absorber that is deposited by hot wire
chemical vapor deposition (HWCVD) within only 90 s. When fabricating solar cells on
morphologies consisting of ZnO nanorods we take advantage of the extremely small thickness
of the absorber layer and the capability of HWCVD to create conformal layers,. We also made
solar cells in tandem configuration using the a-SiGe:H absorber layer in the bottom cell. We
show that the nanorod morphology particularly improves the current generation in the bottom
cell.
Key insights in the light trapping mechanisms in these arrays are obtained via a
combination of three-dimensional finite-difference time-domain (3D FDTD) simulations,
optical absorption, and EQE measurements. Front-surface patterns enhance the in-coupling of
light in the blue, while rear-side patterns lead to enhanced light trapping in the red. The red
response in the nanorod cells is limited by absorption in the patterned Ag back contact. With
these findings we experimentally realized a further advanced design with patterned front and
back side while keeping the Ag reflector flat, showing significantly enhanced scattering from
the back reflector with reduced parasitic absorption in the Ag and thus higher photocurrent
generation. Many of the findings in this work can serve to provide insights for further
optimization of nanostructures for thin-film solar cells in a broad range of materials.
B4-I-02
Defect Engineering for High Performance Thermoelectric Energy
Conversion
Sung Wng Kim
Department of Energy Science, Sungkyunkwan University, Suwon, Korea
E-Mail address (corresponding author): kimsungwng@skku.edu
The practical use of thermoelectric technology is constrained by a low conversion
efficiency of thermoelectric systems depending largely on the performance of thermoel
ectric bulk materials. It has been demonstrated that the dimensionless figure of merit,
ZT of bulk alloys can be enhanced by reducing lattice thermal conductivity through n
anostructuring, which has been exclusively focused on the installation of nanosized de
fects and modification of grain structure to stimulate phonon scattering [1]. Recently, a
ll-scale hierarchical architecturing of thermoelectric bulk alloys was reported as a new
approach to enhance the ZT of bulk alloys over threshold number of 2.0 [2]. Howeve
r, this approach is rather difficult to apply to the all state-of-the-art materials such as
Bi-Te and Co-Sb systems. Thus, we introduce an uncontroversial approach in which the
independent control of scattering mechanism for phonon and electron is possible via the
engineering of phase and grain boundaries of bulk thermoelectric materials. This approach can
be a general way for “beyond nanostructuring and hierarchical architecturing” to enhance the
ZT of all thermoelectric bulk materials using scalable sintering processes.
For an example, the grain boundary engineering of p-type Bi-Sb-Te system, leading to a
record-high value around 2.0 at 320 K will be introduced [3]. This achievement was realized
with the reduced lattice thermal conductivity originated in the formation of highly dense
dislocation arrays at grain boundaries. Importantly, we demonstrate a full-spectrum phonon
scattering strategy by adding a new phonon scattering mechanism with the dislocation arrays
embedded in low energy grain boundaries, targeting the mid-frequency phonons with
∼− and ∼−dependences that are between that for point defect and
grain boundary scattering (Figure 1). This is the first example of engineering the grain
boundary structure by introducing a defect that allows a compounding effect not found in
randomly dispersed dislocations. This enables phonon scattering in the full frequency spectrum,
while maintaining the high carrier mobility at the same time. Further, we demonstrate the highperformance of Peltier cooling devices by adapting our Bi0.5Sb1.5Te3 alloys with dislocation
arrays embedded in grain boundaries. The performance was confirmed in a single stage Peltier
cooler, exhibiting an unprecedented ∆Tmax of 81 K with 300 K hot side which outperforms all
commercialized Peltier cooling devices with 64 K < ∆Tmax < 72 K.
References
[1] Poudel et. al, Science 320, 634 (2008).
[2] Biswas et. al, Nature 489, 414 (2012).
[3] Kim et. al, Submitted (2014).
B4-O-01
Freestanding Triboelectric Nanogenerator as a Mobile Cover and its selfpowered Applications
Arunkumar Chandrasekhar1, Nagamalleswara Rao Alluri2, Sang-Jae Kim1*
1
Department of Mechatronics Engineering, Nanomaterials and System Lab,
2
Department of Mechanical Engineering, Nanomaterials and System Lab,
Jeju National University, Jeju 690-756, Republic of Korea.
A lightweight, flexible, cost effective and robust, freestanding triboelectric nanogenerator is
introduced as a promising eco-friendly approach for harvesting energy from the living
environment, for use in integrated self-powered systems. An effective method for harvesting
biomechanical energy from human motion such as walking, running, and sitting, utilizing
widely adaptable cloths as contact materials (nylon, jeans, cotton, and polyester) is
demonstrated. The working mechanism of the MC-TENG (Mobile Cover -TENG) is based on
the generation and transfer of triboelectric charge carriers between the active layer and userfriendly contact materials. The performance of MC-TENG (180V and 300 μA) is
systematically studied and demonstrated in a range of applications including a self-powered
flash light and as a self-powered pedometer This feasibility study confirms that MC-TENG is
a suitable technology for energy harvesting from human motion during transportation, which
could be used to operate a variety of wireless devices, GPS systems, electronic devices and
other sensors during travel.
*Corresponding author:
Tel: +82-64-754-3715;
Fax: +82-64-756-3886
Email:kimsangj@jejunu.ac.kr (Prof. Sang-Jae Kim)
Acknowledgement
This work was supported by the National Research Foundation of Korea (NRF) funded by the
Korea Government GRANT (2013R1A2A2A01068926, 2013R1A1A2064471), and by the
Jeju Sea Grant College Program 2016 Funded by the Ministry of Oceans and Fisheries (MOF),
Korea.
B4-O-02
High Performance Piezoelectric-Triboelectric Nanogenerator using
Irregular Surface Morphology
Nagamalleswara Rao Alluri1, Arunkumar Chandrashekar2, Sophia Selvarajan3,
Ji Hyun Jeong4, Sang Jae Kim2,*
1,4
Nanomaterials and System Lab, Mechanical Engineering, JeJu National University, Jeju-690756, Korea
Nanomaterials and System Lab, Mechatronics Engineering, JeJu National University, Jeju-690756, Korea
3
Nanomaterials and System Lab, Convergence Technology, JeJu National University Jeju-690756, Korea
2
Presenting author Email: allure@jejunu.ac.kr
*Corresponding author: Email: kimsangj@jejunu.ac.kr,
Abstract:
Hybrid Nanogenerators (H-NGs) are reliable portable power sources to drive micro sensors. In
present work, piezoelectric (PNG), triboelectric (TENG) and hybrid nanogenrator (H-NG)
performance was evaluated using 0.3(Ba0.7Ca0.3TiO3)-0.7(BaSn0.12Ti0.88O3)/PDMS composite
with different surface morphology. The substitution of Sn, Ca atoms into BaTiO3 lattice will
enhance piezoelectric property due to the morphotropic phase boundary causes a very low
energy barrier for polarization rotation and lattice distortion. The H-NGs (3 cm x 2.5 cm) with
different surface morphologies such as micro pillars, irregular network shows few fold
increment in output as compared to the flat surface morphology of H-NG and piezoelectric
nanogenerator output. High performance is due to the combined effect of piezoelectric effect
and generation of triboelectric charge carriers with respect to composite surface roughness. HNGs have the ability to drive 100 LEDs, and LCD without using an energy storage device.
Keywords:
Hybrid nanogenerator, 0.3(Ba0.7Ca0.3TiO3)-0.7(BaSn0.12Ti0.88O3) piezoelectric nanoparticles,
surface roughness, triboelectric nanogenerator, irregular network.
Acknowledgement:
This Research was supported by Basic Science Research Program through the National
Research Foundation of Korea (NRF) (2013R1A2A2A01068926) and by the Sea Grant
College Program 2016 Jeju Funded by the Ministry of Oceans and Fisheries (MOF), Korea.
B4-O-03
Laser irradiation time-dependent charge carrier dynamics in organo-lead
halide perovskite single crystals
Hye Ryung Byun1, 2, Tanzila Tasnim3, Dae Young Park1, 2, Gon Namkoong3 and Mun Seok Jeong1,2*
1
Center for Integrated Nanostructure Physics (CINAP), Institute for basic Science (IBS), Sungkyunkwan
University, Suwon 446-746, Korea
2
Department of Energy Science, Sungkyunkwan University, Suwon 446-746, Korea
3
Department of Electrical and Computer Engineering, Old Dominion University, Applied Research Center,
12050 Jefferson Avenue, Newport News, VA 23606, USA.
*E-mail: mjeong@skku.edu
Abstract: The optical characteristics of organo-lead halide perovskite single crystals (MAPbX3;
MA=CH3NH3+, X=Cl-, Br-, or I-) have been investigated by using steady-state photoluminescence (PL)
and time-resolved PL (TRPL) spectroscopies. Perovskite single crystals (MAPbCl3-xBrx, MAPbBr3-xIx)
were synthesized using the inverse temperature crystallization (ITC) with proper solvents. Then, the PL
spectra were performed using confocal micro-spectroscopy (NTEGRA spectra, NT-MDT) equipped
with a solid state laser with 405 nm and an objective lens with numerical aperture of 0.7, yielding a
high spatial resolution of ~380 nm. For an analysis of carrier dynamics for the single crystals, TRPL,
multifunctional confocal microscopy including a time-correlated single photon counting (TCSPC)
system was employed (NTEGRA, NT-MDT). Figure 1 shows an evolution of PL spectra of the
MAPbBr3 and MAPbBr2.5I0.5 as functions of laser irradiation times. As shown, the sharp contrast
between MAPbBr3 and MAPbBr2.5I0.5 PL spectra was observed. The PL spectra of MAPbBr3 remained
with a band edge peak of ~530 nm. However, the MAPbBr2.5I0.5 developed the additional satellite peaks
at lower energy bandgaps while the bandgap peak of 540 nm gradually disappeared. Interestingly, when
the single crystals are left for 15 minutes in the dark, the PL spectra reverted to the initial PL states,
indicating these photo induced changes are completely reversible. To further understand the nature of
lower energy peaks, power and temperature dependent PL measurements were investigated and will be
further discussed.
Figure 1. Photoluminescence (PL) spectra of (a) MAPbBr3 and (b) MAPbBr2.5I0.5 with increasing laser irradiation
time.
B5-I-01
Ionic semiconductors and their applications in photovoltaics
Yiyang Sun
Department of Physics, Applied Physics and Astronomy, Rensselaer Polytechnic Institute, Troy, New York
12180, USA
* E-mail address: suny4@rpi.edu
The high-efficiency solar cells with power conversion efficiency (PCE) > 20% have been
exclusively based on materials derived from the diamond structure, such as Si, GaAs, InP,
CdTe, and CIGS. The four-fold coordination of all atoms in these materials implies dominant
covalency in the bonding. The organic-inorganic halide perovskite materials, in particular,
CH3NH3PbI3, represents the first non-four-fold coordinate material that achieved PCE above
20%. In this talk, I will discuss the advantage of the perovskite materials from a point of view
of intrinsic defects. The current theoretical study suggests that CH3NH3PbI3 could be free of
intrinsic deep-level defects serving as recombination centers, if the Fermi level is controlled
~0.3 eV away from the band edges [1]. Experiments support this conclusion by showing that
the dominant recombination process in this material is indeed a second order, instead of a firstorder defect-mediated (or Shockley-Read-Hall), process. The apparent disadvantage of
CH3NH3PbI3 is its toxicity and instability. In this aspect, I will discuss the possibility of
chalcogenide perovskites as potential photovoltaic materials, which we have theoretically
proposed and partly validated by experiment recently [2,3,4].
References
1. M. L. Agiorgousis, Y. Y. Sun, H. Zeng, and S. B. Zhang, “Strong Covalency-Induced
Recombination Centers in Perovskite Solar Cell Material CH3NH3PbI3”, J. Am. Chem.
Soc. 136, 14570 (2014).
2. Y. Y. Sun, M. L. Agiorgousis, P. Zhang, and S. B. Zhang, “Chalcogenide Perovskites for
Photovoltaics”, Nano Lett. 15, 581 (2015).
3. S. Perera, et al., “Chalcogenide perovskites – an emerging class of ionic semiconductors”,
Nano Energy 22, 129 (2016).
4. Y. Y. Sun, et al., “Discovering lead-free perovskite solar materials with a split-anion
approach”, Nanoscale 8, 6284 (2016).
B5-I-02
Structural and Electronic Defects in Perovskite Oxides
Anderson Janotti*
Delaware University, Newark, DE, USA
* E-mail address: janotti@udel.edu
Control of defects and charge carriers is key to the development of oxides as electronic
materials. In SrTiO3, defects such as oxygen vacancies easily form and strongly affect the
electrical and optical properties. Experiments indicate that the oxygen vacancy displays a
paradoxical behavior: it simultaneously acts as a shallow donor that contributes to n-type
conductivity and as a deep center that causes luminescence well below the band-gap energy.
Using first-principles calculations we investigate the role of oxygen, strontium, and titanium
vacancies in SrTiO3. We find that oxygen vacancies are double donors, and that one electron
is easily ionized, explaining the shallow donor behavior. The second electron is trapped in the
form of a small polaron, and this additional binding energy explains the behavior as a deep
center that gives rise to blue luminescence. At low temperatures, holes become self-trapped,
and recombination of free electrons with self-trapped holes gives rise to green luminescence.
These results explain the intricate interplay between the observed green and blue luminescence
in SrTiO3, and form a framework for interpreting similar phenomena in other complex oxides.
B5-I-03
Computational design of photovoltaic solar cell materials
by controlling spinodal decomposition
Kazunori Sato1, *, Haruki Okumura1, Tomoyuki Kakeshita1, and Hiroshi Katayama-Yoshida2
1Division
of Materials and Manufacturing Science, Graduate School of Engineering, Osaka University,
2-1 Yamadaoka, Suita, Osaka 565-0871, Japan
2Center for Spintronics Research Network, Graduate School of Engineering Science, Osaka University,
1-3 Machikaneyama, Toyonaka, Osaka 560-8531, Japan
* E-mail address: ksato@mat.eng.osaka-u.ac.jp
For establishing photovoltaic solar cells (PVSC) as a sustainable energy source, it is
indispensable to fabricate PVSC materials with high conversion efficiency based on earthabundant elements. Owing to the recent development of first-principles method, computational
design of PVSC materials is now becoming realistic and used for such materials exploring.
Recently, we propose novel approach for enhancing conversion efficiency of PVSC materials.
In the approach, we control phase separation in alloy semiconductors to fabricate nanostructures by self-organization [1]. If the interface between the nano-structures shows Type-2
band alignment, we can expect efficient electron-hole separation which causes efficiency
enhancement [2]. In this talk, we will show some materials design based on this idea.
Firstly, as typical materials design based on such ‘spinodal nanotechnology’ for PVSC
materials, we show some materials design of charcopyrite semiconductors such as CuIn1xGaxSe2 (CIGS), Cu2ZnSn(S1-xSex)4 (CZTSSe) and CdTe-based PVCS based on the
calculations of the mixing energy by using the Korringa-Kohn-Rostoker coherent potential
approximation [2].
Next, we apply this strategy to oxide-based PVSC materials. We focus on newly fabricated
β-CuGaO2, which is expected to be a promising candidate for an oxide PVSC material [3]. βCuGaO2 (pseudo Wurtzite structure) is p-type semiconductor with band-gap energy (Eg) of
1.47 eV. It is fabricated by using the ion exchange technique. We have calculated electronic
structure and optical properties of β-CuGaO2 by using the hybrid method (HSE06)
implemented in the VASP [4]. It is found that accurate structure optimization is necessary to
reproduce experimental Eg. Upper limit (Shockley-Queisser limit) of the conversion efficiency
is calculated to be 24% for 0.5
m absorber.
Orbital Hamiltonian Population [5] indicates that the states at the valence band maximum are
anti-bonding like states between Cu-3d and O-2p, and this fact might explain p-type conduction
of this material. Since the lattice matching between β-CuGaO2 and ZnO is rather good, we can
expect coherent interface between these materials. We will discuss possibility of spinodal
decomposition and electronic structure in alloy semiconductors with β-CuGaO2 and ZnO.
References
1. T. Dietl, K. Sato, T. Fukushima, A. Bonanni, M. Jamet, A. Barski, S. Kuroda, M. Tanaka,
P. H. Hai, and H. Katayama-Yoshida, Rev. Mod. Phys. 87, 1311 (2015).
2. Y. Tani et al., Appl. Phys. Express 3, 101201 (2010), Jpn. J. Appl. Phys. 51, 050202 (2012).
3. T. Omata et al., J. Am. Chem. Soc. 136, 3378 (2014), Sci. Technol. Adv. Mater. 16, 024902
(2015).
4. G. Kresse and J. Furthmueller, Phys. Rev. B 54, 11169 (1996).
5. R. Dronskowski and P. E. Bloechl, J. Phys. Chem, 97, 8617 (1993).
B5-O-01
Computational search for dipole‐allowed direct band gap silicon allotropes
based on global optimization
Sunghyun Kim1*, Young Jun Oh1, In-Ho Lee2,3, Jooyoung Lee3, and Kee Joo Chang1
1
Department of Physics, Korea Advanced Institute of Science and Technology, Daejeon 34141, Korea
2
Korea Research Institute of Standards and Science, Daejeon 34113, Korea
3
Center for In Silico Protein Science, School of Computational Science, Korea Institute for Advanced Study,
Seoul 02455, Korea
* E-mail address: kimsunghyun@kaist.ac.kr
Recently, the inverse method of materials design has drawn much attention, where
specific material properties are initially assigned and target materials are subsequently
searched. For successful applications to specific problems, the inverse method needs a very
efficient scheme for global optimization which enables us to explore the configuration space
spanned by atomic positions and lattice parameters under various environments, such as
dimensionality, pressure, composition, and stoichiometry. Very recently, we have developed
an efficient protocol named AMADEUS (Ab initio MAterials DEsign Using conformational
Space annealing) [1], in which the conformational space annealing algorithm for global
optimization is combined with first-principles density functional calculations.
In this work, we show the discovery of direct band gap Si allotropes with efficient optical
transitions and demonstrate the successful applications of AMADEUS, which is designed to
search for new structures and new functional materials. Cubic diamond Si (c-Si) is the key
element in modern electronic devices, however, its optical properties are rather poor due to
the indirect band gap nature, limiting applications to optoelectronic devices. We find several
Si allotropes with direct band gaps as well as a family of direct band gap Si superlattices
[2,3]. We show that these Si allotropes exhibit excellent optical transitions at the threshold
energy, with photovoltaic efficiencies comparable to those of best known non-silicon
photovoltaic materials, suggesting that the designed allotropes can serve as promising
materials for solar-cell applications. We discuss the dynamical and thermal stabilities of the
allotropes and a possible route to synthesis.
Fig. 1. Direct band gap Si superlattices composed of Si(111) layers (green) and a defective layer containing
Seiwatz chains (orange).
References
1. I.-H. Lee, Y.J. Oh, S. Kim, J. Lee, and K.J. Chang, Comp. Phys. Commun., in presss (2016);
DOI:10.1016/j.cpc.2016.02.011.
2. I.-H. Lee, J. Lee, Y.J. Oh, S. Kim, and K.J. Chang, Phys. Rev. B 90, 115209 (2014).
3. Y.J. Oh, I.-H. Lee, S. Kim, J. Lee, and K.J. Chang, Sci. Rep. 5, 18086 (2015).
B6-I-01
A two-qubit logic gate in silicon
Menno Veldhorst1*
1
QuTech / TU Delft, Lorentzweg 1, Delft, Netherlands
* E-mail address: m.veldhorst@tudelft.nl
Quantum computation requires qubits that can be coupled in a scalable manner, together
with universal and high-fidelity one- and two-qubit logic gates. Many physical realizations of
qubits exist, including single photons, trapped ions, superconducting circuits, single defects or
atoms in diamond and silicon, and semiconductor quantum dots, with single-qubit fidelities
that exceed the stringent thresholds required for fault-tolerant quantum computing. Despite this,
high-fidelity two-qubit gates in the solid
state that can be manufactured using standard lithographic techniques have so far been limited
to superconducting qubits, owing to the difficulties of coupling qubits and dephasing in
semiconductor systems.
In this talk, I will present our recent demonstration of universal quantum logic, based
on single spins in isotopically enriched silicon and realized by performing single- and twoqubit operations in a quantum dot system using the exchange interaction, as envisaged in the
original Loss–DiVincenzo proposal. We realize CNOT gates via controlled-phase operations
combined with single-qubit operations. Direct gate-voltage control provides single-qubit
addressability, together with a switchable exchange interaction that is used in the two-qubit
controlled-phase gate. By independently reading out both qubits, we measure clear
anticorrelations in the two-spin probabilities of the CNOT gate.
B6-O-01
Self assembled Wigner crystals as mediators of spin currents and quantum
Abolfazl Bayat1 , Sanjeev Kumar2, Bobby Antonio1, Sougato Bose1, and Michael Pepper2
1Department
2London
of Physics and Astronomy, University College London, London, United Kingdom
Centre for Nanotechnology, University College London, London, United Kingdom
* E-mail address: abolfazl.bayat@gmail.com
Quantum simulators are excellent test beds for realising certain many-body strongly
correlated systems. Heisenberg interaction is one of the key models in many-body physics
which has been extensively studied for its static (namely ground state) and dynamical
properties. We show [1] that the trapped electrons forming a Wigner crystal in a quantum
wire, realized by a quantum point contact which has been blocked at one end, can simulate
Heisenberg Hamiltonian. The transverse trapping potential changes the charge configuration
of the trapped electrons from linear to zig-zag (See Fig. 1a below) providing a wide range of
spin interactions from nearest neighbours and beyond. We compute the spin exchange
interaction using a semi-classical method. In fact, the spin exchange couplings can be tuned
from one to tens of micro eV enabling the system to operate in current dilution refrigerators.
We propose this system for mediating the interaction between two distant quantum
dots each confining a single electron. The natural time evolution of the system may
realize quantum state transfer between the two distant dots. To do that, an arbitrary
quantum state is prepared in the spin degrees of freedom of the electron in the first
dot. Then by decreasing the gate barrier between the dots the system starts to evolve
under the action of the global Heisenberg interaction. The natural time evolution
propagates the quantum state from one side of the system to another. A schematic
picture of the proposal is shown in Fig. 1b below. Such preliminary results are very
encouraging and open avenues to investigate such quantum effects experimentally.
B7-I-01
New Approaches for Diagnosis and Therapy Using Microfluidic Devices
Manabu Tokeshi1-3,*
1
2
Division of Applied Chemistry, Hokkaido University, Kita 13 Nishi 8, Kita-ku, Sapporo, Japan
ImPACT Research Center for Advanced Nanodevices, Nagoya University, Furo-cho, Chikusa-ku, Nagoya,
Japan
3Innovation of Future Society, Nagoya University, Furo-cho, Chikusa-ku, Nagoya University, Japan
* E-mail address: tokeshi@eng.hokudai.ac.jp
Microfluidic devices have great potential for medical and life science applications. Recent
progresses in microfluidic devices have enabled rapid and easy-to-use analysis of a small
amount of protein in serum or urine, and preparation of highly functional nanoparticles. We
have developed that several immunoassay systems for the detection of biomarkers using the
microfluidic devices [1-3], and have fabricated functional nanoparticles for drug delivery
system (DDS) applications using the microfluidic devices [4, 5].
In this presentation, I will present the following topics: on-chip immunoassay systems for
point-of-care testing and on-chip fabrication and delivery of lipid nanoparticles for DDS.
Moreover, future challenges and potentials of microfluidic devices for biotechnology, medicine,
and clinical diagnostics will be also discussed.
References
[1] M. Ikami, A. Kawakami, M. Kakuta, Y. Okamoto, N. Kaji, M. Tokeshi, Y. Baba, Lab Chip,
10, 3335-3340 (2010).
[2] W. Jin, K. Yamada, M. Ikami, N. Kaji, M. Tokeshi, Y. Atsumi, M. Mizutani, A. Murai, A.
Okamoto, T. Namikawa, Y. Baba, M. Ohta, J. Microbiol. Methods, 92, 323-331 (2013).
[3] T. Kasama, M. Ikami, W. Jin, K. Yamada, N. Kaji, Y. Atsumi, M. Mizutani, A. Murai, A.
Okamoto, T. Namikawa, M. Ohta, M. Tokeshi, Y. Baba, Anal. Methods, 7, 5092-5095
(2015).
[4] M. Maeki, T. Saito, Y. Sato, T. Yasui, N. Kaji, A. Ishida, H. Tani, Y. Baba, H. Harashima,
M. Tokeshi, RSC Adv., 5, 46181-46185 (2015).
[5] Y. Sato, Y. Note, M. Maeki, N. Kaji, Y. Baba, M. Tokeshi, H. Harashima, J. Control.
Release, 229, 48-57 (2016).
B7-I-02
Zn(II) -Coordinated Nanosensors for the Detection of Protein
Kinases/Phosphatase Activity
Jin Oh Lee1, Butaek Lim1, and Young-Pil Kim1,2*
1
Deparment of Life Science, Hanyang University, Seoul 04763, Korea
Institute of Nano Science and Technology, Hanyang University, Seoul 04763, Korea
* E-mail address: ypilkim@hanyang.ac.kr
2
Protein phosphorylation and dephosphorylation regulate molecular signal transduction in
living cells, and its abnormal process causes major diseases. Rapid detection of their catalytic
activities, therefore, is very crucial to identify their functional roles in a myriad of biological
events. In general, protein kinase activity has been elucidated using ATP-radiolabeled method
or antibody-based immunoblotting. However, these methods sill remain challenging due to
labor-intensity and time-consuming process. Here we describe simple detection of
(de)phosphorylation of peptide substrate using Zn(II)-mediated nanosensors: i) gold
colorimetric nanosensor for protein phosphatase activity assay and ii) quantum dot (QD)fluorescence resonance energy transfer (FRET) nanosensor for protein kinase activity assay.
Interestingly, upon enzyme reaction, Zn(II) enabled the phosphorylated peptides to be strongly
attached on the carboxyl groups of the gold nanoparticle (AuNP) or QD surface via metal
coordination, thus leading to remarkable transducing signal changes (colorimetric signal in
AuNPs or fluorescent signal in QD-FRET). Contrast to Zn(II), other divalent ions (such as
Ni(II), Co(II), and Cu(II)) and trivalent ion ((Fe(III)) did not give rise to a significant change.
As a result, protein kinase or protein phosphatase activity in intermixed solution was efficiently
detected by AuNP or QD-FRET via Zn(II) coordination in combination with
immunoprecipitation. We suggest that this approach is expected to find applications for
studying physiological function and signal transduction with respect to protein
phosphatase/kinase activity.
References
1. J. O. Lee, E.-J. Kim, B. Lim, T.-W. Kim, and Y.-P. Kim, Anal. Chem. 87(2), 1257 (2015).
2. B. Lim, J.-I. Park, K.J. Lee, J.-W. Lee, T.-W. Kim, and Y.-P. Kim, Sensors 15(8), 17977
(2015).
3. J. H. Lim, G.C. Park, S.M. Lee, J.H. Lee, B. Lim, S.M. Hwang, J.H. Kim, H. Park, J. Joo
and Y.-P. Kim, Small 11(28), 3469 (2015).
B7-I-03
Nanoparticle plasmonics:
Application to single-molecule catalytic reactions and
nanoscopic chemical imaging
Zee Hwan Kima
a
Department of Chemistry, Seoul National University, Seoul 151-747, Seoul, Korea
The nano-particle plasmonics, the resonant oscillation of electrons driven by light, offers many
possibilities ranging from trace-level detection of molecules to opto-electronic devices. In this
talk, I will present my research group’s recent investigation on how the localized plasmon of a
nanoparticle interacts with another plasmon, and with nearby molecules. First, I will
demonstrate the use of scattering-type scanning near-field microscopy (s-SNOM) to directly
visualize the capacitive / conductive coupling in dimeric nanoparticles and heterometallic
nanorods. Second, I will talk about the use of gap-plasmons to locally induce photochemical
reactions, and to follow chemical kinetics of individual organic molecules using the gapplasmons. Finally, I will talk about the use of near-field coupling between a scanning probe
and 2D-materials to visualize / identify the stacking domains (e. g., ABA versus ABC-type
stacking in triple layer) hidden in multilayer graphenes.
(top) the infrared nanoscopy imaging of trilayer graphene; (bottom) time-dependent SERS
spectra of single-molecule dimercapto-azobenzene reaction intermediates
B7-O-01
Monitoring of the Complex Motion of One-dimensional Particles
Gi-Hyun Go1, Seungjin Heo1, Jong-Hoi Cho1, Yang-Seok Yoo1, Min-Kwan Kim1, ChungHyun Park1 and Yong-Hoon Cho1,*
1
Department of Physics and Graduate School of Nano Science and Technology,
Korea Advanced Institute of Science and Technology(KAIST), Daejeon, 305-701, Republic of Korea
* E-mail address: yhc@kaist.ac.kr
As the interest in the anisotropic particle in various research fields increases, the tracking
method of such particle has been one of most desirable techniques. In the case of anisotropic
shaped particle like a single nanowire (SNW), there is complex coupling of translational and
rotational motions [1], which is not normally observed in the case of sphere. Previous
researches measured the translation motion of a nanowire by neglecting rotational motion [2]
or observed the rotational motion indirectly by using a cross-correlation of the transverse
signals of a quadrant photodiode [3].
We studied coupling translational and rotational Brownian dynamics of a GaN nanowire
confined in an optical trap. We developed the dual particle tracking system which can track the
lateral positions of the nanowire at different vertical positions by using the diffraction pattern
tracking method [4], and obtained the isolated angular fluctuations extracted from rotational
Brownian motions. We measured the physical properties of scanning probe in optical trap such
as stiffness and torsional constants, depending on laser power, polarization direction. This
suggests an accurate measurement Brownian motions and physical properties of nanowire as a
scanning probe in a photonic force microscopy.
Fig. 1. The significant optical trapping parameters such as stiffness and torque constants acting on the SNW in
optical trap can be obtained from the analysis of the motion of the GaN nanowire. (a) Stiffness is proportional to
the trapping laser power, and shows (b) sinusoidal polarization dependence.
References
1. A. Shelton, D. Bonin, and G. Walker, Physical Review, 71, 036204, (2005)
2. J. Reece, J. Toe, F. Wang, S. Paiman, Q. Gao, H. Tan, and C. Jagadish, Nanoletters, 11,
2375-2381, (2011)
3. M. Marago, H. Jones, F. Bonaccorso, V.Scardaci, G. Gucciardi, G. Rozhin, C. Ferrari,
Nanoletters 8, 3211-3216, (2008)
4. C. Gosse and V. Croquette, Biophysical journal, 82, 3314, (2002).
C1-I-01
Chiral Nano-scale Skyrmions in Ultrathin Transition Metal Films:
From Fundamentals to Potential Applications
Pin-Jui HSU and Roland WIESENDANGER*
Interdisciplinary Nanoscience Center Hamburg, University of Hamburg, D-20355 Hamburg
*Email address: wiesendanger@physnet.uni-hamburg.de
Magnetism in ultrathin films can significantly deviate from commonly known bulk magnetism
due to low dimensionality, hybridization effects, changes of the lattice constant, stacking
dependencies, and broken inversion symmetry at interfaces. This can lead to complex non-collinear
spin states such as chiral spin spirals or skyrmions. Especially chiral magnetic skyrmions with their
non-trivial topology are interesting objects for both fundamental as well as application-oriented
research due to their possible utilization in future magnetic data storage.
Based on the development of atomic-resolution spin-polarized scanning tunneling microscopy
(SP-STM) and spectroscopy [1], operated within 3D superconducting magnet systems, we have
discovered chiral nanoskyrmion lattices in single atomic layers of transition metals on particular
substrates exhibiting a large spin-orbit coupling, such as monolayer (ML) Fe films on Ir(111) [25]. In this case, skyrmionic lattices with a periodicity of only one nanometer can be stabilized even
in zero external field by the chiral Dzyaloshinskii-Moriya interaction combined with the breaking
of inversion symmetry at surfaces and interfaces [6].
More recently, we have made use of multiple interface engineering in bilayer and multilayer
systems in order to demonstrate the direct observation and manipulation of individual skyrmions
of single-digit nanometer-scale size [7]. In particular, we resolved the atomic-scale spin structure
of individual isolated chiral skyrmions in real space by SP-STM [8]. Their axial symmetry as well
as their unique rotational sense has been revealed by using both out-of-plane and in-plane sensitive
SP-STM tips. The size and shape of skyrmions change as a function of magnetic field. An analytical
expression for the description of skyrmions has been proposed in order to connect the experimental
data to the original theoretical model describing chiral skyrmions [9].
By locally injecting spin-polarized electrons from an atomically sharp SP-STM tip, we were able
to write and delete individual skyrmions one-by-one, making use of spin-transfer torque exerted by
the injected high-energy spin-polarized electrons [7]. Switching rate and direction can be controlled
by the parameters used for current injection. Alternatively, individual skyrmions can be created
and deleted by local electric fields, which can be of great advantage in view of energy-saving
skyrmionic device concepts. The creation and annihilation of individual magnetic skyrmions
demonstrates their great potential for future nanospintronic devices making use of individual
topological charges as information carriers.
References:
[1] R. Wiesendanger, Rev. Mod. Phys. 81, 1495 (2009).
[2] S. Heinze et al., Nature Physics 7, 713 (2011).
[3] A. Sonntag et al., Phys. Rev. Lett. 113, 077202 (2014).
[4] J. Brede et al., Nature Nanotechnology 9, 1018 (2014).
[5]K. von Bergmann et al., Nano Lett. 15, 3280 (2015).
[6] A. A. Khajetoorians et al., Nature Commun. 7, 10620 (2016).
[7] N. Romming et al., Science 341, 6146 (2013).
[8] N. Romming et al., Phys. Rev. Lett. 114, 177203 (2015).
[9]A. Bogdanov and D.A. Yablonskii, Sov. Phys. JETP 68, 101 (1989).
C1-I-02
Topological Phase Transitions in Topological Insulators Driven by
Dimensional Reduction and Magnetic Perturbations
Jae Hoon Kim
Department of Physics, Yonsei University, Seoul 03722 Republic of Korea
Topological insulators exhibit novel quantum states known as topological surface states
originating from strong spin-orbit interaction and time-reversal symmetry of the bulk. We show
that dimensional reduction realized in ultrathin, few-quintuple layer films leads to a number of
topological phase transitions from three-dimensional topological insulators (3DTI) to twodimensional hybrid topological insulators (2DHTI) and finally to two-dimensional trivial
insulators. Along with these transitions, there follows a series of quantized conductances and
concomitant changes in the electron-phonon interaction as evidenced by a Fano effect.
Magnetic impurities can also be incorporated into topological insulators to hybridize the
topological surfaces states with impurity states, again leading to ordinary insulators. Our
experiment demonstrates the feasibility to control and utilize the topological surfaces states for
practical electronic and photonic applications.
C1-O-01
Light Spins of Free-Space Electromagnetic Waves with Parallel Electric
and Magnetic Fields
Hyoung-In LEE1,*,JinsikMOK2,DmitryA.KUZMIN3,andIgorV.BYCHOV3
1
Research Institute of Mathematics, Seoul National University, Gwanak-Gu, Seoul, 08826, Korea
Department of Industrial and Management Engineering, Sunmooon Univ., Asan, Choongnam, 31460 Korea
3
Chelyabinsk State University, 129 Kashirinykh Street, Chelyabinsk 454001, Russian Federation
2
* E-mail address: hileesam@naver.com
Physical phenomena of topological nature involve oftentimes applied magnetic field and/or
magneto-optical materials. For instance, transport and optics on and around graphenes or
graphene-coated cylindrical media can be controlled by varying degrees of doping [1]. Here,
we consider a configuration where field variables depend only on two space coordinates on a
plane as a setting for discussing topological physics. We thus follow the idea of rotationally
symmetric gauge fields where a constant magnetic field is externally applied in the direction
perpendicular to the plane of interest. Instead of such imposed magnetic fields, we consider a
possibility of electromagnetic waves in altering the kinetic momenta for solving a proper
Schroedinger equation.
In this aspect, it is known that electromagnetic waves with the electric-field vector parallel
to the magnetic-field vector can be established for certain standing waves [2]. This finding is
in apparent contradiction to the usual electromagnetic waves with the electric-field vector
perpendicular to the magnetic-field vector. Notice that the latter conventional waves involve
propagating waves with the wave-propagation vector is perpendicular to both the electric- and
magnetic-field vectors. We are to analyze the light field and chirality associated with such
electromagnetic fields with parallel electric and magnetic fields [3]. In this way, we are to
examine the implications of non-linear vector potentials employed in the kinetic momenta and
the resulting alterations of Landau levels.
Fig. 1. Electromagnetic waves with the electric-field vector parallel to the magnetic-field vector. The waves are
standing in the axial (out-of-pane) direction. (a) A schematic for axial and azimuthal (in-plane) components of
light spin. An angular rotation is assumed. (b) The radial distribution of the axial component of light spin
normalized by electromagnetic energy.
References
1. D. A. Kuzmin, et. al, “Plasmonically induced magnetic field in graphene-coated nanowires”, Opt. Lett. 41, 396
(2016)
2. K. Uehara, T. Kawai, and K. Shimoda, "Non-Transverse Electromagnetic Waves with Parallel Electric and
Magnetic Fields", J. Phys. Soc. Jpn. 58, pp. 3570-3575 (1989)
3. K. Y. Bliokh and F. Nori, “Transverse and longitudinal angular momenta of light”, Physics Reports 592, 1–38
(2015)
C1-O-02
Structural phase transition and superconductivity in MoTe2
Suyeon Cho, SeHwang Kang, Hosung Yu (Sungkyunkwan Univ., Korea), Hyo won Kim,
Won Hee Ko (Samsung Adv. Inst. Tech., Korea), Duk-Hyun Choe, K. J. Chang (KAIST,
Korea), Young Hee Lee, Heejun Yang and SungWng Kim* (Sungkyunkwan Univ., Korea)
Recently, distorted transition metal ditelluride systems, MoTe2, WTe2 and IrTe2, show
fascinating behaviors with high mobility, large magnetoresistance(MR) and Shubnikov-de
Haas oscillation having strong spin-orbit coupling. Those distorted transition metal
ditelluride series have rather enhanced inter-layer interaction while planar hexagonal TMDs
have weak van der Waals interaction. The competition between inter-layer and intra-layer
interaction could lead to the phase transition in distorted transition metal ditelluride system.
We synthesized 1T'-MoTe2 single crystal using Flux method. We conducted high resolution
powder x-ray diffraction varying measurement temperature from 10 K to 300 K. We found
that the structural phase transition from 1T' to Td structure is occurred around 250 K
accompanying the sign change of Hall coefficient. We also observed the superconducting
behavior with critical temperature around 2 K. Electrical resistivity shows clear anomalies
which might be related with phase transition in MoTe2.
C2-I-01
Electrical switching of an antiferromagnet
Tomas JUNGWIRTH1,2
1
Institute of Physics, Academy of Sciences of the Czech Republic, Czech Republic
2
School of Physics and Astronomy, University of Nottingham, United Kingdom
Louis Néel pointed out in his Nobel lecture that while abundant and interesting from theoretical
viewpoint, antiferromagnets did not seem to have any applications. Indeed, the alternating
directions of magnetic moments on individual atoms and the resulting zero net magnetization
make antiferromagnets hard to control by tools common in ferromagnets. Strong coupling
would be achieved if the externally generated field had a sign alternating on the scale of a
lattice constant at which moments alternate in antiferromagnets. However, generating such a
field has been regarded unfeasible, hindering the research and applications of these abundant
magnetic materials. We have recently predicted that relativistic quantum mechanics may offer
staggered current induced fields with the sign alternating within the magnetic unit cell which
can facilitate a reversible switching of an antiferromagnet by applying electrical currents with
comparable efficiency to ferromagnets. Among suitable materials is a high Néel temperature
antiferromagnet, tetragonal-phase CuMnAs, which we have recently synthesized in the form
of single-crystal epilayers structurally compatible with common semiconductors. We
demonstrate electrical writing and read-out, combined with the insensitivity to magnetic field
perturbations, in a proof-of-concept antiferromagnetic memory device.
References:
[1] P. Wadley et al. Science 351, 587 (2016)
[2] T. Jungwirth et al., Nature Nanotech. 11, 231 (2016)
C2-I-02
Effect of Orbital Magnetism on Dzyaloshinskii-Moriya Interaction
Teruo ONO1
1
Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011, Japan
* E-mail address: ono@scl.kyoto-u.ac.jp
Chiral interaction between two atomic spins due to a strong spin-orbit coupling, which is
known as the Dzyaloshinskii-Moriya interaction (DMI), has attracted intense interest. In
particular, it has been demonstrated that the DMI at the interface between ferromagnetic (FM)
and heavy nonmagnetic metals (HM) plays a major role for the formation of chiral spin textures,
such as the skyrmion [1] and the homochiral Néel-type domain wall [2-4], which are attractive
for the development of future information storage technology.
We show that orbital magnetism plays a crucial role in the emergence of the DMI. The
temperature dependence of the DMI-induced effective field is quantified by magnetic domainwall velocity measurements, while the temperature dependence of the spin and orbital magnetic
moments in FM and HM layers is determined by x-ray magnetic circular dichroism
measurements. We find no direct correlation between the increase of the DMI and the
proximity-induced magnetic moment in a HM layer, which is contradictory to the results of a
previous report [5], but is consistent with recent first-principle calculations [6]. Furthermore,
we establish that the strength of the DMI is proportional to the ratio of the in-plane and out-ofplane orbital moments in a FM layer.
This work was partly supported by Grant-in-Aid for Scientific Research on Innovative
Areas, Grant-in-Aid for Specially Promoted Research, and R & D Project for ICT Key
Technology of MEXT.
References
1.
2.
3.
4.
5.
6.
A. Fert et al., Nat. nanotech. 8, 152 (2013).
S. Emori et al., Nat. Mater. 12, 611 (2013).
K.-S. Ryu et al., Nat. Nanotechnol. 8, 527 (2013).
K. Ueda et al., Appl. Phys. Express 7, 053006 (2014).
K.-S. Ryu et al., Nat. Commun. 5, 3910 (2014).
H. Yang et al., Phys. Rev. Lett. 115, 267210 (2015).
C2-O-01
Field-free switching of perpendicular magnetization through Spin orbit
torque in antiferromagnet/ferromagnet/oxide structures
Young-Wan Oh1*,Seung-heonChrisBaek1,2,YoungMinKim1,HaeYeonLee1,KyeongDongLee1,Chang-GeunYang3,Eun-SangPark4,5,Ki-SeungLee3,Kyoung-Whan Kim6,7,8,9,
Gyungchoon Go3,Byoung-ChulMin5,Hyun-WooLee6,Kyung-JinLee3,4andByong-GukPark1
1
Department of Materials and Science and Engineering, KAIST, Daejeon, Korea
2
School of Electrical Engineering, KAIST, Daejeon 305-701, Korea
3
Department of Materials Science and Engineering, Korea University, Seoul 136-701, Korea
4
KU-KIST Graduate School of Converging Science and Technology, Korea University, Seoul 136-713, Korea
5
Center for Spintronics, , Seoul 136-791, Korea
PCTP and Department of Physics, Pohang University of Science and Technology, Pohang 790-784, Korea
7
Center for Nanoscale Science and Technology, National Institute of Standards and Technology, Gaithersburg,
Maryland 20899, USA
8
Maryland Nanocenter, University of Maryland, College Park, MD 20742, USA
9
Basic Science Research Institute, Pohang University of Science and Technology, Pohang 790-784, Korea
* E-mail address: 50wan@kaist.ac.kr
6
A Control of the magnetization by spin-orbit torque (SOT) has drawn a great attention since it
allows a low-power switching and a high speed domain wall motion. For deterministic SOT
switching, external field along to current direction is required to break symmetry, which is detrimental
for device application. In some research, SOT switching without an external field was reported in the
systems using the lateral symmetry breaking[1] or tilted magnetic anisotropy[2]. Recent reports
revealed that antiferromagnet (AFM) exhibit spin-orbit interaction[3], which means that AFM can be
used as source of SOT in antiferromagnet (AFM) /ferromagnet(FM) structures. Also, field-free
switching can be achieved using the exchange bias existing at the interface between AFM/FM layers.
In this work, we investigated the SOT in a perpendicularly magnetized AFM/FM/oxide
heterostructures. Figures 1(a, b) show the second harmonic Hall voltage for Ta(5nm)/IrMn(0,
9nm)/CoFeB(1nm)/MgO samples. The sign change of the Hall signal by the introduction of the IrMn
layer confirms that the SOT originates from the IrMn layer. Figures 1(d, e) compare the switching
characteristics of the samples with and without IrMn layers. As expected, a preferred magnetization
direction for certain current polarity is revered by the insertion of IrMn layer. We also demonstrated
field-free switching for the Ta/IrMn(9nm)/CoFeB/MgO sample. These results confirm that the IrMn
layer supplies not only spin-orbit torque but also in-plane exchange bias, which enables the field-free
switching.
Fig. 1. (a,b) The second harmonic signal
V2ωforTa/CoFeB/IrMn(tIrMn)/MgOsamples.TheswitchingexperimentunderBxfor(d), the Ta/CoFeB/MgO and (e),
the Ta/IrMn/CoFeB/MgO. (e) Magnetic moment versus in-plane external field of Ta/CoFeB/IrMn(9nm)/MgO
sample. BEBsignifiesexchangebiasfieldestablishedinthefield-annealingdirection
.
References
1. Yu, G. et al, Nature Nanotech. 9, 548-554 (2014).
2. Yoo, L. et al, http://arxiv.org/abs/1409.0620v1 (2014)
3. Mendes, J. B. S. et al. Phys. Rev. B 89, 140406(R) (2014)
C2-O-02
Spin orbit torque induced by all 3d-material underlayer: Ferromagnetic
metal
Seung-heon Chris Baek1,2*,Young-WanOh2,andByong-GukPark2
1
2
School of Electrical Engineering, KAIST, Daejeon, 305-701, Korea
Department of Materials Science and Engineering, KAIST, Daejeon, 305-701, Korea
* E-mail address: secret@kaist.ac.kr
The magnetization of a ferromagnetic (FM) layer in heavy metal (HM)/FM/oxide structure
can
be
controlled
by
in-plane
current
(Ix).Thisphenomenonissocalledspinorbittorque(SOT),whichisinducedbyspinHalleffectandRashbaeffectintheHMandattheHM/FMi
nterface,respectively.[1][2]SincethediscoveryofSOT,ithasbeenwidelyknownthattheamountofi
nducedSOTisrelatedtospinHallangleoftheheavymaterial;thatisnormallylargeforheavyelements
suchasPt,TaandW[3].However,insomepriorresearch,aconsiderablevalueofspinHallanglehasbe
enmeasuredeveninlightelements,suchasferromagneticmetals.Thisimpliesthatferromagneticmet
alscaninduceasizeableamountofSOT,whichwillbeabletoswitchthemagnetizationofsecondFMin
thestructure.
In this work, we report the switching of ferromagnetic CoFeB, with perpendicular magnetic
anisotropy by the SOT induced from an underlayer structure composed of only 3d metals (Ti
and CoFeB). Comparing with control samples of Ta and Ti underlayer, we confirm that SOT
is indeed generated from the FM CoFeB in the underlayer. Our result suggests that not only
heavy elements but also some light elements can be used to create SOT, which will widen the
choice of materials for future SOT applications and research.
Fig. 1. (a) Schematic of the system. Switching operation of a (b) Ta/CoFeB/MgO
(c)[Ti/CoFeB/Ti]/CoFeB/MgOstructures
References
1. Miron, I.M. et al. Perpendicular switching of a single ferromagnetic layer induced by in-plane current injection.
Nature 476, 189-193 (2011).
2. Liu, L., Pai, C.-F., Li, Y., Tseng, H.W., Ralph, D.C. & Buhrman, R.A. Spin-torque switching with the giant
spin Hall effect of Tantalum. Science 336, 555-558 (2012).
3. Cho, S. et al. Large spin Hall magnetoresistance and its correlation to the spin-orbit torque in W/CoFeB/MgO
structures. Sci. Rep. 5, 14668
C3-I-01
Electrical control of magnetism induced by interfacial orbital
reconstruction
Cheng SONG*, Bin CUI, and Feng PAN
School of Materials Science and Engineering, Tsinghua University, Beijing 100084, China
* E-mail address: songcheng@mail.tsinghua.edu.cn
Electrical control of magnetism with profound physics and enormous potential applications
has provoked extensive research activities.1 In this talk, we will present the reversible orbital
reconstruction driven by ferroelectric polarization modulates the magnetic performance of
ferroelectric/ferromagnetic [BaTiO3/(La,Sr)MnO3] heterostructure. In-plane Mn orbital
occupancy and related interfacial magnetic state are enhanced and weakened by the negative
and positive electric-field, respectively.2 Furthermore, with the aid of ionic liquid, the
modulation of magnetism extends to bulk part of the ferromagnet. The Ti-O-Mn covalent bond
at the interface controls the field effect by enhancing or blocking the channel for electron
injection and extraction in the bulk of film, serving as an orbital switch at atomic scale for the
manipulation of magnetism.3 Our findings thus not only present a broad opportunity to fill the
missing member—orbital in the mechanism of electrical control of magnetism, but also make
the orbits straight forward to the application in microelectronic device.
Fig. 1. Left panel: Representative HAADF-STEM image of the BaTiO3/(La,Sr)MnO3 interface areas under
negative (Pup)andpositive (Pdown)VG. The corresponding sketch for the interfacial orbital reconstruction under
different polarization states is shown in the middle panel. Right panel: the dependence of Curie temperature (TC)
and planar magnetoresistance (pMR) under PupandPdownon(La,Sr)MnO3thickness.
References
1. F. Matsukura, Y. Tokura, H. Ohno, Nat. Nanotechnol. 10, 209 (2015).
2. B. Cui, C. Song, H. Mao, H. Wu, F. Li, J. Peng, G. Wang, F. Zeng, and F. Pan, Adv. Mater.
27, 6651 (2015).
3. B. Cui, C. Song, H. J. Mao, Y. N. Yan, F. Li, S. Gao, J. J. Peng, F. Zeng, and F. Pan. Adv.
Funct. Mater. 26, 753 (2016).
C3-I-02
Electrical detection of spin Hall and Rashba effects in a semiconductor
channel
Hyun Cheol Koo1,2,*WonYoungChoi1,2,HyungjunKim1,JoonyeonChang1,SukHeeHan1,andMarkJohnson3
1
Center for Spintronics, Korea Institute of Science and Technology, Seoul 02792, Korea
KU-KIST Graduate School of Converging Science and Technology, Korea University, Seoul, 02841, Korea
3
Naval Research Laboratory, Washington DC 20375, USA
* E-mail address: hckoo@kist.re.kr
2
The Rashba and the spin Hall effects are very fascinating phenomena in the field of
spintronics. [1-3] In this work, we combine these two effects to demonstrate the ballistic spin
Hall effect and the gate controlled spin precession. The spin Hall device consists of a
ferromagnet electrode (FM) as a spin injector, and a spin Hall detector made of InAs quantum
well channel as shown in the top of Fig. 1. The applied field sets the FM injector magnetization
to be along the x axis. Spin polarized electrons injected from FM have ballistic trajectories with
coherent spin precession due to the Rashba effective field. Thus, we can get the spin Hall
voltage if we properly select the location of the Hall probe. From the multiple devices, we
obtained the spin Hall signal as a function of channel length as shown in Fig. 1. The dotted line
is a fit to the original Datta–Das wavelength and the solid line fit includes an exponential decay
using mean free path. From a single device of fixed length, we also demonstrate the gate
dependence of channel conductance.
I
Ba
VH,1 VH,2
VH,3
VH,4
VH,5
…..…
VH,n …..…
BR
x=0
Fig. 1. Geometry of spin Hall device and channel length dependence of spin Hall signal.
References
1. S. Datta, and B. Das, Appl. Phys. Lett. 56, 665 (1990).
2. H. C. Koo, J. H. Kwon, J. Eom, J. Chang, S. H. Han, and M. Johnson, Science, 325, 1515
(2009).
3. W. Y. Choi, H.-j. Kim, J. Chang, S. H. Han, H. C. Koo, and M. Johnson, Nat.
Nanotechnol. 10, 666 (2015).
C3-I-03 [NO SHOW]
Surface-termination-dependent magnetism and strong perpendicular
magnetocrystalline anisotropy of an FeRh(001) thin film
Sonny H. Rhim, Soyoung Jekal and Soon Cheol
Physics, U. of Ulsan,Ulsan, Korea
sonny@ulsan.ac.kr
FeRh has attracted for its magnetocaloric effect and huge magnetoresistance. In this talk,
magnetism of FeRh film is studied, which exhibits strong perpendicular magnetocrystalline
anisotropy(MCA). The Rh-terminated film is ferromagnetic with strong perpendicular MCA whose energy 2.1 meV/☐ is two orders magnitude greater than conventional magnetic metals.
(☐ is the two-dimensional area). The Fe-terminated film, on the other hand, is G-type
antiferromagnetic as in the bulk. The surface-termination dependent magnetism is elucidated
within Goodenough-Kanamori-Anderson rule, where the competition between superexchange,
Zener-type direct interaction, and energy gain by Rh magnetism play a crucial role.
C3-O-01
Electric field effect on interfacial magnetic anisotropy with HM/FM/oxide
structures
Kyung-Woong Park12, Dae-Hoon Kim1,Soo-ManSeo2,Sung-WoongChung2
and Byong-Guk Park1
1
Department of Materials and Science and Engineering, KAIST, Daejeon, Korea
2
Research and development division, SK Hynix semiconductor Inc, Gyeonggi-do
*E-mail : kw_park@kaist.ac.kr
Electric field induced magnetic anisotropy control has been interested in spintronics device
because it enables high efficiency and low power consumption for the magnetization
switching.[1] In this present, we studied the electric field effect on the interfacial magnetic
anisotropy of ferromagnet/oxide film with various non-magnetic heavy metal underlayer. The
strong perpendicular mangetic anisotropy is observed in Ta/CFB/MgO, whereas Ta/Pt
underlayer shows canted easy axis from c-axis and Pt underlayer shows in-plane easy axis. The
change of magnetic propety was measured by anomalous hall measuremet method as a function
of applying gate voltage bias. When negative gate bais is applied, the coercivity of PMA sample
increased and saturation magnetic field of cone state decreased, resulting from manipulation of
interfacial perpendicular mangnetic anisotropy by electric field as shown in Fig1. This electric
field effect demonstrates reversible and non-volatile behavior which can provide the
development of low power consuming spintronics memory and logic applications.
0.8
0.6
RH(ohm)
0.4
1_0V
2_+17V
3_0V
4_-17V
0.2
0.0
-0.2
-0.4
-0.6
-0.8
-500
-250
0
250
500
H(Oe)
Figure 1. Electric field control of magnetic property
Reference
[1] Wei-GangWang, Mingen Li, Stephen Hageman and C. L. Chien, Nature materials 11, 64
(2012)
C3-O-02 [NO SHOW]
Spintornics with carbon-based materials
Jung-Woo Yoo
Ulsan National Institute of Science and Technology, unist gil 50, ulsan, Korea
jwyoo@unist.ac.kr
Recent years witnessed increasing research activity in exploiting carbon-based materials as
a spin transporting channel, which introduces a new avenue for device integration and
functionality. In this talk, I will present application of an organic-based magnetic/non-magnetic
semiconductor as an electron spin polarizer/spin transporting layer in the standard spintronic
device geometry [1,2]. The application of organic small molecule films as the spin transporting
layer has been studied extensively recently.
However, conceptual understanding of how the spins are injected into and transport through
these organic semiconductor films was still lacking. With careful study on film thickness,
temperature, and bias dependencies, significant differences between tunneling and giant
magnetoresistance were resolved. In addition, the room temperature organic-based magnet,
V(TCNE)x was successfully incorporated into the standard magnetic tunnel junction devices
in tandem with LSMO(La2/3Sr1/3MnO3) film [2].
The second part of this talk will be devoted for engineering spin dependent dispersion in
graphene and non-local transport study therein. Graphene has been perceived to be an
outstanding material for delivering spin information due to its high electron mobility and weak
spin-orbit coupling. The mandatory requirement for exploiting electron spins in graphene is
facile control of spin-orbit coupling. Instilling spin-orbit coupling into graphene allows
splitting and detecting electron spins via spin Hall and its inverse effect. We introduced
ultrathin metal pad on graphene to enhance spin-orbit coupling and studied non-local signal to
demonstrate alternative spin current generation.
Reference
[1] Jung-Woo Yoo, H. W. Jang, V.N. Prigodin, C. Kao, C.B. Eom, and A.J. Epstein, Phys. Rev.
B 80, 205207 (2009).
[2] Jung-Woo Yoo, C.-Y. Chen, H. W. Jang, C. W. Bark, V. N. Prigodin, C. B. Eom, and A. J.
Epstein, Nature Materials 9, 638 (2010).
C4-IK-01
The quest for perfect 1D electrical conduction
David Goldhaber-Gordon*(Stanford Univ, USA)
C4-I-02
Searching for better quantum anomalous Hall materials
Ke He*(Tsinghua Univ., China)
The recent experimental observation of the quantum anomalous Hall (QAH) effect in thin
films of magnetic topological insulators (TIs) paves the ways for practical applications of
dissipationless quantum Hall edge states and for realizations of the novel quantum
phenomena such as chiral topological superconductivity and axion magnetoelectric effect.
Further studies in these directions require magnetic TI materials able to show the QAH effect
at higher temperature and with lower electrical conduction from bulk states. I will introduce
the recent experimental progresses on the QAH effect aiming to clarify the mechanism of the
QAH effect and to increase its occurring temperature. These results not only give an in-depth
understanding on the nature of the QAH effect but also provide insights into designing and
fabrication of superior QAH materials.
C4-I-03
Electron waves refract negatively in ballistic graphene
Hu-Jong Lee*, Gil-Ho Lee†, Geon-Hyoung Park
Department of Physics, Pohang University of Science and Technology, Pohang 37673, Republic of Korea
†Current
address: Department of Physics, Harvard University, Cambridge, MA 02138 USA
*E-mail address: hjlee@postech.ac.kr
We investigated the electronic current refraction at p-n junctions in ballistic monolayer graphene.
Given the Dirac band structure of the graphene, the transmission of electrons through a p-n junction is
predicted to be similar to the optical refraction at the boundary of metamaterials with negative refractive
index [1]. In consequence, electronic waves injected at a point in one side of a junction can be refocused
into a single point in the other side of the junction, which demonstrates Veselago lensing for the
electrons. By adopting high-yield dry-transfer technique, we fabricated fully ballistic graphene devices
encapsulated by hexagonal boron nitrides with a local top gate. In this talk, we present the signatures
of negative refractive transport behavior of electrons [2] in p-n junctions and the electronic current
focusing in p-n-p heterojunctions (see figures below) in terms of Veselago lensing. Our study confirms
great potential for engineering electronic wave propagation in a ballistic and coherent Dirac medium in
general. This study also demonstrates that, with a long mean free path at room temperature, graphene
promises highly novel components for electronic optics operating at high temperatures.
dI2/dVtg’
I
Ibias
1
V
I
3
I
Vbg (V)
tg
2
Enhancement of I2
Fig. 1. Configuration of a Veselago lens device and the conductance enhancement by electronic lensing.
References
1. V. V. Cheianov, V. Fal'ko, and B. L. Altshuler, Science 315, 1252 (2007).
2. Gil-Ho Lee, Geon-Hyoung Park, and Hu-Jong Lee, Nature Physics 11, 925 (2015), [DOI:
10.1038/nphys3460 (2015).
C5-IK-01
Innovative thermal energy harvesting for future autonomous applications,
S.Monfray*,STMicroelectronics, France
C5-I-02
Inorganic-based High-Performance Flexible Thermoelectric Power
Generator for Wearable Electronics Application
Byung Jin Cho1, Sun Jin Kim1, Ju Hyung We1, Hyeongdo Choi1, Yongjun Kim1 and Ji Sun Shin2
1
Department of Electrical Engineering, KAIST, 335 Gwahak-ro, Yuseong, Daejeon,
Republic of Korea , e-mail: bjcho@kaist.edu
2
TEGway Co, 335 Gwahak-ro, Yuseong, Daejeon, Republic of Korea
Flexible thermoelectric generator (f-TEG) is emerging as a semi-permanent power source to
self-powered sensor that is an important issue for the next generation smart network monitoring
system in the internet-of-things (IoT) era. There have been attempts to realize f-TEG using polymerbased TEG devices, however, those devices suffer poor conversion efficiency which is an inherent
problem of polymer-based TE materials. In this talk, a new approach in realizing f-TEG using
field-proven high performance inorganic TE materials will be discussed. Device design
concept targeting wearable electronics application will also be discussed. Detailed study on
material properties of screen printed BiTe-based TE materials will be presented. Material
processing optimization and new techniques in device fabrication enable us to demonstrate a
f-TEG with a high flexibility and excellent output performance (4.78 mW/cm2 and 20.8 mW/g
at a △T = 25 K). The device can withstand the repeated bending of 8,000 cycles without
noticeable degradation in performance.
C5-O-01
Efficient Polymer Passivation of Methylammonium Lead Trihalide
Perovskites
Hyojung Kim1,2,HyeRyungByun1,2,BoraKim1,2,DaeYoungPark1,2,andMunSeokJeong1,2*
2
1
Deparment of Energy Science, Sungkyunkwan University, Suwon 16419, Republic of Korea
Center for Integrated Nanostructure Physics (CINAP), Institute for Basic Science (IBS), Sungkyunkwan
University, Suwon 16419, Republic of Korea
* E-mail address: mjeong@skku.edu
Methylammonium lead trihalide (MAPbX3) perovskites have attracted considerable attention
due to their high absorption coefficients and tunable optical bandgap. In particular, single
crystals of MAPbBr3 and MAPbI3 show a remarkable low trap density and long carrier
diffusion lengths [1] and have been applied for various optoelectronic devices such as solar
cells, light-emitting diodes (LEDs), and lasing, etc. Despite their unique properties,
perovskite materials suffer from long-term stability in air due to degradation by moisture and
oxygen. In previous work, severe structure damages were observed from the aged perovskite
solar cells, leading to poor device performance [2], and the absorbance of perovskite thin films
was gradually decreased owing to decomposition of MAPbI3 under high humidity [3]. To
prevent degradation process, various passivation materials were studied, for example, pyridine
were coated on perovskite films, resulting in significant enhancement of the radiative
recombination rates [4]. However, organic compound materials usually lack adequate
protection from moisture because of high water permeability, thus stability issue is still
necessary to be concerned for further improvement. Here, we suggest parylene-C as a
passivation layer because it is well known to have high light transmittance, low water
permeability, and low chemical reactivity [5] and will discuss the mechanism of the
degradation from changes of optical properties in single crystal perovskites.
References
1. M. I. Saidaminov, A. L. Abdelhady, B. Murali, E. Alarousu, V. M. Burlakov, W. Peng, I.
Dursun, L. Wang, Y. He, G. Maculan, A. Goriely, T. Wu, O. F. Mohammed, and O. M. Bakr,
Nat. Commun. 6, 7586 (2015).
2. Y. Han, S. Meyer, Y. Dkhissi, K. Weber, J. M. Pringle, U. Bach, L. Spiccia, and Y.-B. Cheng,
J. Mater. Chem. A, 3, 8139 (2015).
3. R. Ruess, F. Benfer, F. Böcher, M. Stumpp, and D. Schlettwein, Chem. Phys. Chem. 17, 18 (2016).
4. N. K. Noel, A. Abate, S. D. Stranks, E. S. Parrott, V. M. Burlakov, A. Goriely, and H. J.
Snaith, ACS Nano, 8(10), 9815 (2014).
5. J. Gao, B. Li, J. Tan, P. Chow, T.-M. Lu, and N. Koratkar, ACS Nano, 10(2), 2628 (2016).
C5-O-02
Fast crystallization of bandgap modulated organic lead halide perovskite
single crystals
Daeyoung Park1,2, Hyeryung Byun1,2,AYoungLee1,2,HoMinChoi1,2,
Seong Chu Lim1,2,MunSeokJeong1,2,*.
1
Center for Integrated Nanostructure Physics(CINAP), Institute for basic Science(IBS), Sungkyunkwan
University, Suwon 446-746, Korea
2
Department of Energy Science, Sungkyunkwan University, Suwon 446-746, Korea
*E-mail : mjeong@skku.edu
Organic lead halide perovskite has been focused by many scientists due to its excellent properties in
photovoltaic and optoelectronics.[1,2] Especially, perovskite solar cell recorded 20.1% power
conversion efficiency despite of short research period. However, high quality of film in devices is
crucial for fabricating high performance device.[3] For improving film quality, some researchers
fabricated devices based on organic lead halide perovskite single crystal and demonstrated high
performance. But, they synthesized only three representative organic lead halide perovskite single
crystals(CH3NH3PbX3,CH3NH3MA,X=Cl,Br,I).[4,5]Fortheexpansionofapplicability,bandgaptuningise
ssential.Therefore,wepreparedbandgapmodulatedorganicleadhalideperovskitesinglecrystals(MAPbCl3xBrx,MAPbBr3-xIx)bychanginghalogenratiowithin24husingretrogradesolubilitypropertyandantisolventdiffusion.SynthesizedsampleswerecharacterizedwithXRD,UVVis,FT-IR,photoluminescence,TGA,SEMandetc.
References
1. Q. Dong, Y. Fang, Y. Shao, P. Mulligan, J. Qiu, L. Cao and J. Huang, Science 347, 967(2015).
2. Y. Liu, Z. Yang, D. Cui, X. Ren, J. Sun, X. Liu, J. Zhang, Q. Wei, H. Fan, F. Yu, X. Zhang, C. Zhao
and S. Liu, Adv. Mater. 27, 5176(2015).
3. W. S. Yang, J. H. Noh, N. J. Jeon, Y. C. Kim, S. C. Ryu, J. W. Seo and S. I. Seok, Science 348,
1234(2015).
4. G. Maculan, A. D. Sheikh, A. L. Abdelhady, M. I. Saidaminov, M. A. Haque, B. Murali, E.
larousu, O. F. Mohammed, T. Wu and O. M. Bakr, J. Phys. Chem. Lett. 6, 3781(2015).
5. M. I. Saidaminov, A. L. Abdelhady, B. Murali, E. Alarousu, V. M. Burlakov, W. Peng, I. Dursun,
L. Wang, Y. He, G. Maculan, A. Goriely, T. Wu, O. F. Mohammed and O. M. Bakr, Nat. Commun.
6, 7586(2015)
C6-I-01
Spin Orbit Coupling and Spin Orbit Torque in Topological Insulators
Xufeng Kou, Kang L Wang* (UCLA, USA)
Device Research Laboratory
Department of Electrical Engineering
University of California, Los Angeles, California 90095 (USA)
The presence of large SOC can render an insulator to a topological insulator exhibiting Dirac electron
surface states with the spin-momentum lock property. When magnetic order is introduced into
topological insulators (TIs), the time-reversal-symmetry (TRS) is broken, and the non-trivial
topological surface is driven into a new massive Dirac-fermions state. By controlling the magnetic
(Cr) doping concentration and the Fermi level position, we show that the quantum anomalous Hall
effect (QAHE) in the macroscopic millimeter-size magnetic-doped TI Cr-doped ((BixSb1-x)2Te3) films.
Furthermore, we find that the stability of the dissipationless chiral edge conductance is wellmaintained as the film thickness varies across the 2D hybridization limit.
TI/Cr-doped TI heterostructures can also be used for the electrical manipulation of magnetization
switching via giant spin–orbit torque (SOT). We demonstrate that the SOT required for
magnetization switching in such magnetic TI-based bilayer structures is three orders of magnitude
more efficient than that of heavy metals. All these exotic magnetic TI-based phenomena will serve
as fundamental steps to further explore the TRS-breaking TI systems. In addition, potential
applications of energy efficient electronics will be discussed.
A short biography:
Kang L. Wang is currently a Distinguished Professor and holds Raytheon Chair Professor in
Physical Science and Electronics in the Electrical Engineering Department of the University
of California, Los Angeles (UCLA). He received his BS degree from National Cheng Kung
University (Taiwan) and his MS and PhD degrees from the Massachusetts Institute of
Technology. He is a Fellow of the IEEE. He also served as the Editor-in-Chief of IEEE
TNANO. His research areas include nanoscale physics and materials, topological insulators,
and spintronics and devices.
*The work was in part supported by ERFC-SHINES, ARO, TANMS, and FAME
C6-O-01
Superconducting proximity effect via Andreev edge states in graphene
Geon-Hyoung Park1,MinsooKim1,TakashiTaniguchi2,KenjiWatanabe2,Hu-JongLee1*
1
Department of Physics, Pohang University of Science and Technology, Korea
National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
* E-mail address: hjlee@postech.ac.kr
2
Andreev reflection (AR), a retro-reflection of an incident electron as a hole at a superconductornormal metal interface, leads to the formation of an Andreev edge state, which consists of a
coherent pair of an electron and a hole in a strong magnetic field [1]. The coexistence of AR
and quantum Hall (QH) effect in semiconducting two-dimensional electron systems has been
confirmed in two-terminal Hall conductance measurement configurations where bulk and
longitudinal contributions are bound to be contained. Here, we report signature of the Andreev
edge state formed in mono- and bi-layer graphene devices with Hall-bar configuration, where
a graphene layer was encapsulated by hexagonal boron nitride crystals [2] and in proximity
contact with a Nb electrode having high critical magnetic field (Hc2~3.5TatT = 150 mK). The
high carrier mobility of our graphene layers allowed the formation of QH edge states in
perpendicular magnetic fields as low as ~1 T. The signature of AR was clearly visible along
with Landau-level modulating signals in the bias dependence of both longitudinal and QH
conductance at QH plateaus corresponding to high filling factors (ν ≥ 28).
References
1. H. Hoppe et al., Phys. Rev. Lett. 84, 1804 (2000).
2. L. Wang et al., Science 342, 614 (2013).
C6-O-02
Quasi-1D transport in a ballistic graphene layer with preserved valley
symmetry
Minsoo Kim1,Ji-HaeChoi1,Sang-HoonLee1,KenjiWatanabe2,TakashiTaniguchi2,SeungHoonJhi1,Hu-JongLee1,*
1
Department of Physics, Pohang University of Science and Technology, Pohang, Korea
2
National Institute for Materials Science, Tsukuba, Japan
* E-mail address: hjlee@postech.ac.kr
Zigzag graphene nanoribbons are predicted to exhibit intrinsic electronic properties
stemming from its Dirac band structure. To date, however, investigation of the properties is
highly limited because of the defects and the roughness at the edges with different valley
properties intermixed. Here, we report the signature of conservation of valley symmetry in
quasi one-dimensional (1D) ballistic graphene of two types of devices; one is a quantum point
contact (QPC) and another is an Aharonov-Bohm (AB) interferometer. Carrier confinement
was realized by the operation of both top and bottom gates along with large difference in the
sheet conductance between different gated regions of high-mobility graphene encapsulated
between clean hexagonal boron nitride layers. Constricted conducting channel of a QPC device
exhibits the conductance quantization in steps of 4e2/h starting from 10e2/h at zero magnetic
field, a behavior similar to the one observed in zigzag graphene nanoribbons of edge-localized
channels. Our tight-binding calculation shows that quasi-1D carrier flow along arbitrary
direction on a graphene plane acts as a zigzag-type nanoribbon. In the AB interferometer, we
observed h/e periodic modulation of magnetoconductance (MC) and the zero-field conductance
minimum with a negative MC background. All these results signify valley-symmetrypreserved quasi-1D transport, which is essential for realizing valleytronics in graphene.
C6-O-03
Realization of Topological One-dimensional Conducting Channel in
Bilayer Graphene
Janghee Lee1, Kenji Watanabe2, Takashi Taniguchi2, and Hu-Jong Lee1,*
1
Deparment of Physics, Pohang University of Science and Technology, Korea
Advanced Materials Laboratory, National Institute for Materials Science, Japan
* E-mail address: hjlee@postech.ac.kr
2
Low-lying energy bands of intrinsic bilayer graphene (BLG) have a parabolic shape
without a band gap. However, the band gap can be induced by applying an external electric
field perpendicular to the plane of BLG. Motivated by the tunability of this bulk energy gap,
a new type of topological zero-energy mode has been predicted in BLG [1]. If the electric
fields in two adjacent regions in BLG are opposite to each other in their direction, the band
gap in each region opens with the chirality opposite to each other, which induces a
topological one-dimensional (1D) conducting channel at the band-inversion boundary
between the two regions in BLG. In this study, we fabricated BLG devices, where a BLG
layer was sandwiched between two atomically clean hexagonal boron nitride (h-BN) single
crystals, with two pairs of split gates arranged on top and bottom h-BN layers. Currentvoltage characteristics showed a large transport gap, which was comparable to the ones
obtained from optical measurements and numerical calculation. For opening of the inverted
band gaps in two adjacent regions of the BLG, metallic conducting behavior was observed
with the conductance of 4e2/h along the boundary between the two insulating regions. This
result indicates that a topological 1D conducting channel formed between the two adjacent
gapped regions in BLG with inverted band gaps.
References
1. I. Martin, Y. M. Blanter, and A. F. Morpurgo, Phys. Rev. Lett. 100, 036804 (2008).
C7-I-01
Holey Two-Dimensional Crystals
Jong-Beom Baek
School of Energy and Chemical Engineering, UNIST
50, UNIST, Ulsan, 44919South Korea
*jbbaek@unist.ac.kr
Two-dimensional (2D) materials with uniformly decorated heteroatoms attract immense
interest beyond graphene due to their multifunctionality such as exceptional electrocatalytic,
electronic, optoelectronic and magnetic properties. Despite recent explorations in 2D materials
science and engineering, easy and scalable methods to produce uniformly doped 2D materials
are limited. To overcome these problems, a new layered 2D network structure with uniformly
distributed holes and nitrogen atoms was synthesized and its stoichiometry of basal plane is
C2N.[1] The structure of the C2N was confirmed by scanning tunneling microscopy (STM)
(Figure 1a). Its calculated and experimental band-gaps are 1.7 and 2.0 eV, respectively, in the
semiconductor region, suggesting a clear advantage over conducting graphene and insulating
h-BN. The C2N structure was used to encapsulate iron (Fe) and cobalt (Co) particles by in situ
reducing and subsequent annealing to give Fe@C2N and Co@C2N, which were used as
catalysts for oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER).
Furthermore, another 2D structure with C3N stoichiometry with uniformly placed nitrogen
atoms in the carbon framework was synthesized by ‘direct’ carbonization of
hexaaminobenezene trihydrochloride single crystal at 500 °C. The topological and electronic
structure of the C3N 2D structure was studied by STM (Figure 1b).[2] The C3N structure could
be a new class of 2D materials with novel properties that can be emerged from the unique
structure.
Figure 1. Atomic resolution STM topography images on Cu(111): (a) C2N crystal (8.5 × 8.5
nm2, Vs = 0.7 V, It = 300 pA); (b) C3N crystal (2.5 × 2.5 nm2, Vs = -1.1 V, It = 1.0 nA).
[1] Mahmood, et al., Nat. Commun. 6, 6486 (2015).
[2] Mahmood, et al., Submitted (2015).
C7-I-02
Local chemical modification of graphene using AFM lithography
Bae Ho Park*
Division of Quantum Phases & Devices, Department of Physics, Konkuk University, Seoul 05029
* E-mail address: baehpark@konkuk.ac.kr
Monolayer
graphene
with
sp2-carbon-atomnetworkisapromisingplatformfornextgenerationelectronicandspintronicdevicesbecuaseofitshighcarriermobilityandlongspinrelaxati
onlength.Uptonow,grapheneintegratedcircuitshavebeendemonstratedbycombininggraphenetra
nsistorsandpassivecomponents.Nextstepintechnologyroadmapistheimplementationofgraphene
system-onchip(SOC)thatcombinestransistorsandmemoriesonasamechip.Themainobstacletorealizationof
grapheneSOCisthecomplexityoffabricationprocessoriginatingfromprocessdifferencesbetweent
ransistorsandmemories.Therefore,itisrequiredtofabricategraphenetransistorsandmemoriesusin
gasimpleandidenticalprocess.Inthispresentation,Iwillreportonlocalchemicalmodificationofgra
pheneusingAFMlithographythatcanprovideasimplemethodfordrawingexquisitelykeyelements
ofdevicesongraphene.Functionalgroupsandtheircoveragesonoxidizedandhydrogenatedgraphen
eareselectivelycontrolledonthenanoscalebyAFMlithography.[1]The
in-plane
graphene/graphene oxide/graphene junction devices exhibit switching of Fowler-Nordheim
tunneling current and resistive memory behavior according to the controlled oxidation
voltage.[2] The combination of high on/off current ratio (~1000) of the switching device and
nonvolatility of the memory device fabricated by the same process demonstrates the possibility
of graphene SOC platform.
References
1. I. S. Byun, W. Kim, D. W. Boukhvalov, I. Hwang, J. W. Son, G. Oh, J. S. Choi, D. Yoon,
H. Cheong, J. Baik, H. J. Shin, H. W. Shiu, C. H. Chen, Y. W. Son, and B. H. Park, NPG
Asia Materials 6, e102 (2014).
2. D. H. Lee, C. K. Kim, J. H. Lee, H. J. Chung, and B. H. Park, Carbon 96, 223 (2016).
C7-I-03
Quantum Transport in van der Waals Junctions of 2D Materials
Tomiki Machida*
Tokyo University, 4-6-1-Ce308 Komaba, Tokyo, Japan
* E-mail address: tmachida@iis.u-tokyo.ac.jp
Recent advances in transfer techniques of atomic layers have enabled one to fabricate van der
Waals junctions of two-dimensional (2D) crystals such as graphene, hexagonal boron nitride
(h-BN), and transition-metal dichalcogenides (TMDs). Here, we present our recent
experiments in graphene/2D crystal van der Waals junctions. First, we demonstrate that highquality Josephson junctions can be built by connecting two exfoliated crystal flakes of a layered
2D superconductor, NbSe2. Current-voltage characteristics showed hysteretic zero-bias current,
indicating the under-damped Josephson effect. Next, we demonstrate that magnetic tunnel
junctions can be built by connecting flakes of layered ferromagnetic dichalcogenide, Fe0.25TaS2.
The Fe0.25TaS2/Fe0.25TaS2 junction exhibited the tunnel magnetoresistance (TMR) effect caused
by the switching between parallel and anti-parallel magnetic configurations in the vdW
junction. Finally, we study quantum Hall effect in twisted bilayer graphene fabricated by
stacking two flakes of mechanically-exfoliated graphene with a twisted angle of 0.4-4.0 degree.
The observed transition of Landau level degeneracy between eightfold and fourfold is
attributed to a topological change of the Fermi surface at van Hove singularity point. In addition,
ballistic carrier transport in graphene npn junctions will be discussed.
C8-I-01
BN Monolayer Induced ZnO Nanorod Array Growth on Cu Foil for a
Transparent and Flexible Piezoelectric Nanogenerator
Duanjun CAI1, 2, *, Abdul Majid SOOMRO2, Chenping WU2, Feipeng SUN2, Huachun
WANG2, Youyang HUANG2, Waseem AHEMDBHUTTO3, Zhiming WU4, and Junyong
KANG2
1
2
Department of Chemistry, Duke University, Durham, NC 27708-0354, USA
Fujian Key Laboratory of Semiconductor Materials and Applications, CI center for OSED, College of Physical
Science and Technology, Xiamen University, Xiamen 361005, China
3
Institute of Physics, University of Sindh, Jamshoro, Sindh, Pakistan
4
Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
* E-mail address: dcai@xmu.edu.cn
Utilization of various energy forms by harvesting through efficient converters has been a longexisting concept and now an extremely important issue in this age, facing the growing power
consumption and serious energy crisis. Recently, rapid progress on nanogenerators which are able to
convert mechanical/thermal energy in our daily life directly into electrical energy, such as triboelectric,
pyroelectric and piezoelectric nanogenerators, has opened up a big field for exploring new energy
sources. Among them, ZnO nanowires based piezoelectric nanoconverter has been widely concerned
due to its non-toxic and biocompatible for the sustainable energy technology used in our living
environment [1]. However, the workable device fabrication requires the mass production of vertically
aligned ZnO array on conductive and flexible substrates, which is very challenging and rarely reported.
In recent years, hexagonal boron nitride (hBN) has been a very attractive 2D material
because of its layered crystalline structure like
graphene and especially many outstanding
properties such as wide bandgap (6.0 eV), high
thermal stability (> 800 ºC), strong mechanical
strength and so on[2]. Considering the atomic
monolayer thickness and single-crystal hexagonal
structure, we realize that the presence h-BN layer
over a substrate surface, even for a polycrystalline
or amorphous substrate, may catalyze the growth
of semiconductor crystalline epilayer or
nanowires.
In this work, we demonstrate the synthesis of Fig. 1. (a) schematic of synthesis of well-aligned
superlong ZnO nanorod (> 15 µm) array directly ZnO Nanorod array on h-BN/Cu substrate by CV
on Cu foil substrate pre-orientated by h-BN D. (b) and (c) SEM and photo of as-grown ZnO
monolayer and the fabrication of highly NRs. (d) Photo of transparent piezoelectric nanoge
transparent
and
flexible
piezoelectric nerator.
nanogenerator. Roll-to-roll growth of 25-inch h-BN monolayer film was achieved by low-pressure
CVD with 2D curling technique. As a pre-orientating layer on Cu foil, h-BN induced the growth of
vertically aligned ZnO nanorod array on Cu foil in an average diameter of ~ 110 nm. By using
PMMA/PDMS as insulating media and Pt/Cu nanowires network as electrodes [3], a ultrathin and
highly transparent piezoelectric nanogenerator film has been achieved for harvesting mechanical energy
of body movements.
References
1. Y. Hu and Z. L. Wang, Nano Energy 14, 3 (2015).
2. C. P. Wu, A. M. Soomro et al., ACS Nano, to be published, (2016).
3. H. M. Xu, H. C. Wang et al., Nanoscale, 7, 10613 (2015).
5.
C8-O-01
Bandgap grading in Cu2ZnSnSe4thin-filmsolarcellsbyin-diffusionofGe
Juran Kim, Gee Yeong Kim, Trang Thi Thu Nguyen, Seokhyun Yoon, and William Jo*
Department of Physics, Ewha Womans University, Seoul, 03760 Korea
* E-mail address: wmjo@ewha.ac.kr
Cu2ZnSnSe4 (CZTSe) is one of promising light absorber candidates for thin-film solar cells.
However, its band gap needs to be improved up to the optimal band gap for the light absorption
efficiency. The present research investigated the front band gap grading of Cu2Zn(Sn,Ge)Se4
(CZTGSe) thin films, and tuned the band gap of it by altering the ratio of Ge/(Ge+Sn). CZTSe
absorber layers were deposited using electron beam co-evaporation on Mo-coated soda lime
glass. For front band gap tuning, Ge layers with different thicknesses are applied on the CZTSe
thin films, and they are annealed during different time each up to 50 min. The front band gap
grading CZTGSe samples were investigated in term of its structural, electrical, and optical
properties. When the annealing time is long, Ge is well diffused into the CZTSe layers. This
leads to the enhancement of the thin film formation and the band gap of it has increased as well.
As the Ge/(Ge+Sn) ratio is high, the phase change of the CZTGSe thin films was observable.
This is because Sn is replaced with Ge. Interestingly, when the annealing time is less than 30
min, the samples show single work function peak. On the other hand, the sample annealed more
than 30 min has several work function peak. In this way, the band alignment between an
absorber layer and a buffer layer can be understood. Consequently, the front band gap tuning
of CZTGSe is expected to show high conversion efficiency.
C8-O-02
Surface potential and carrier transport in CH3NH3Pb(I,Br)3 perovskite
single crystals
Hye Ri Jung1, Trang Thi Thu Nguyen1, Phuong Bich Nguyen1, Hoa Thi Dao1, Gee Yeong
Kim1, Seokhyun Yoon1, William Jo1,*, Won Seok Woo2, Chang Won Ahn2, Shinuk Cho2, and
Ill Won Kim2
1
2
Department of physics, Ewha Womans University, Seoul, 03760, Korea
Department of Physics and Energy Harvest-Storage Research Center, University of Ulsan, Ulsan 44610, Korea
* E-mail address: wmjo@ewha.ac.kr
Organic-inorganic lead halide perovskite, MAPbX3 (MA=CH3NH3+, X=Br- or I-), single
crystals have risen to prominence with regards for their intimate physical properties. We
reported surface potential and carrier transport in perovskite mesoscopic solar cells [1].
However, the grain growth is yet not fully controlled in terms of compositions, textures, and
even believed as a trapping source of ionic migration. We investigate both iodide and bromide
perovskite single crystals for the distribution of surface electric potential and current transport
by Kelvin probe force microscopy and conductive atomic force microscopy, respectively.
Surface potential exhibits about 4.7 eV, which is a similar value for thin-film perovskites [2].
Current level of the grain-boundary free large grains is smaller than thin-films but some spots
exhibit large current values at high external voltage bias. Piezoelectric force microscopic
measurement on the perovskite single crystals was also performed to decipher the potential
ferroelectric properties or inequivalent majority/minority carrier dynamics.
References
1. G. Y. Kim, S. H. Oh, B. P. Nguyen, W. Jo, B. J. Kim, D. G. Lee, H. S. Jung, J. Phys. Chem.
Lett. 6, 2355 (2015)
C8-O-03
Efficient Light Extraction from a Quantum Dot in a Pyramidal Structure
Sejeong Kim1,Su-HyunGong1,Jong-HoiCho1andYong-HoonCho1,*
1
Deparment Physics, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Republic
of Korea
* E-mail address: yhc@kaist.ac.kr
Bright solid-state single-photon sources based on quantum dots (QDs) represent a key
component for quantum information technology [1]. Achieving high collection efficiency of
single photons from QDs to predesigned optical waveguides or a free-space measurement setup
is important task for an application of QDs to quantum information devices [2]. Given that the
collection efficiency of single photons from conventional QD embedded in a high index planar
substrate is less than 5 %, there have been extensive efforts during the past decade to control
the direction of the emission of QDs using various photonics structures [3-4]. However, most
fabrication methods of photonic structures use a top-down approach and rely on chance, which
results in an extremely low fabrication yield.
In this study, we propose that site-controlled QD in a nano-pyramidal structure can be
utilized as unidirectional single-photon sources. Silver-coated nano-pyramid structures grown
by a lateral overgrowth technique cause the emission of QD to be guided in one direction.
Furthermore, we demonstrate nano-pyramid structures which can be detached from a substrate
using an ultraviolet-curable optical adhesive material, thus having great potential in various
applications. We observed highly directional single-photon emission from a QD in the detached
inverted-pyramid structure. We emphasize that this highly directional emission from the nanopyramid structure can easily be integrated with a photonic waveguide system with high
coupling efficiency.
Unlike previous approaches for controlling the direction of single photons, our novel
approach is extremely simple and can be realized for site-controlled QDs on a full-wafer scale
with high productivity. Moreover, it can be applied not only to GaN pyramid structures but
also to any material with a pyramidal structure.
Fig. 1. a, Calculated far-field radiation pattern toward the upper and lower hemisphere at a wavelength of 520
nm. b, SEM image and illustration of the detached nanopyramids embedded in a UV-curable polymer.
References
1. A. J. Shields, Nature Photon., 1, 215 (2007)
2. J. Claudon, et al., Nature Photon., 4, 174 (2010).
3. M. Pelton, et al., Phys. Rev. Lett., 89, 233602 (2002)
4. A. Schwagmann, et al., Appl. Phys. Lett., 99, 261108 (2011)
C8-O-04
InAs/GaAsSb Quantum Dot Solar Cells
Yeongho Kim, Jun Oh Kim, Sam Kyu Noh, and Sang Jun Lee*
Division of Industrial Metrology, Korea Research Institute of Standards and Science, Daejeon 305-340,
Republic of Korea
*E-mail address: sjlee@kriss.re.kr
Self-assembled InAs/GaAs quantum dots (QDs) have shown a potential for optoelectronic
applications of laser diodes, infrared photodetectors, and quantum dot solar cells (QDSCs) due
to discrete density of states and strong quantum confinement in QDs. Recently, much attention
has been focused on QDSCs in an attempt to exceed the Shockley-Queisser efficiency limit of
~31 % for a conventional single-junction solar cell by sub-bandgap photon absorption [1]. As
a promising candidate material, InAs/GaAsSb QDs have been proposed because of high dot
density and long carrier lifetime of QDs, suitable to improve the device performance of QDSCs
[2].
In my presentation, the effect of Sb composition in GaAsSb barriers on the structural
and optical properties of single/multi-stack InAs QDs is firstly addressed. The increase of Sb
composition increases the density of misfit and threading dislocations at the GaAs/GaAsSb
interface, as well as improves carrier recombination lifetime in the QDs as a result of reduced
valence band offset at the InAs/GaAsSb heterojunction [3]. Secondly, GaAsSb barrier
thickness is optimized to obtain high-quality, multi-stack InAs QDs. This optimization is
important in that the barrier thickness can modify strain field distribution around the QDs,
which is correlated to the crystal quality and thermal stability of carriers [4]. Lastly, the material
properties and device characteristics of strain-compensated InAs/GaAsSb QDSCs with GaP
strain compensation layer are systematically studied as a function of GaP coverage. The
compressive strain of the QDs is compensated by the tensile strain of GaP, embedded in
GaAsSb barriers [5]. As a result, the overall crystal quality of QD stacks is enhanced, leading
to boosting the conversion efficiency of the QDSCs with increasing GaP coverage.
References
1. A Luque and A Martí, Adv. Mater. 22, 160 (2010).
2. K.-Y. Ban, S. P. Bremner, G. Liu, S. N. Dahal, P. C. Dippo, A. G. Norman, and C. B.
Honsberg, Appl. Phys. Lett. 96, 183101 (2010).
3. D. Tang, Y. Kim, N. Faleev, C. B. Honsberg, and D. J. Smith, J. Appl. Phys. 118, 094303
(2015).
4. Y. Kim, K.-Y. Ban, A. Boley, D. J. Smith, and C. B. Honsberg, Appl. Phys. Lett. 107, 173109
(2015).
5. Y. Kim, K.-Y. Ban, C. Zhang, J. O. Kim, S. J. Lee, and C. B. Honsberg, Appl. Phys. Lett.
108, 103104 (2016).
D1-I-01
Graphene-nanoribbon (GNR) Tunneling Field-Effect Transistors (TFETs)
Wan Sik Hwang
Korea Aerospace University, 76 hanggongdaehak ro, goyang, Korea
whwang@kau.ac.kr
Graphene-nanoribbon (GNR) tunneling field-effect transistors (TFETs) were demonstrated
using ion-assisted electrostatic doping. The GNR of sub-10 nm width was patterned by
electron-beam lithography and the energy gap of 0.2 eV was extracted by conductance
measurement at 4 K. A p-n junction is formed in the GNR channel using two side gates which
are electrostatically doped with ions in a solid polymer electrolyte. The built-in potential, 1.15
eV, of the p-n junction is much higher than 0.34 eV, which is the highest energy separation
ever reported for a chemically doped junction. From these GNR-TFETs, negative differential
resistance (NDR) was experimentally observed for the first time at the room temperature. The
essence of experimental results was well captured by analytical modeling and a numerical
atomistic simulation.
D1-I-02
Toward Graphene Integration from the Bottom-Up
Patrick Han
Tohoku Univ., Japan
D1-I-03
A charge-insensitive single-atomspin-orbit qubit in silicon
Dimi Culcer*
The Univ. of New South Wales, Australia
High fidelity entanglement of an on-chip array of spin qubits poses many challenges. Spinorbit coupling (SOC) can ease some of these challenges by enabling long-ranged entanglement
via electric dipole-dipole interactions, microwave photons, or phonons. However, SOC exposes
conventional spin qubits to decoherence from electrical noise. Here we propose an acceptorbased spin-orbit qubit in silicon offering long-range entanglement at a sweet spot where the
qubit is protected from electrical noise. The qubit relies on quadrupolar SOC with the interface
and gate potentials. As required for surface codes, 105 electrically mediated single-qubit and
104 dipole-dipole mediated two-qubit gates are possible in the predicted spin lifetime.
Moreover, circuit quantum electrodynamics with single spins is feasible, including dispersive
readout, cavity-mediated entanglement, and spin-photon entanglement. An industrially
relevant silicon-based platform is employed.
D2-I-01
Quantum Electrical Transport and Superconducting Proximity Effect in
Topological Insulator Nanowires
Yong-Joo Doh1,* Jihwan Kim2 , Ahreum Hwang2, Sang-Hoon Lee3, Seung-Hoon Jhi3,
Sunghun Lee2, Yun Chang Park4, Hong-Seok Kim1, Bum-Kyu Kim1, Jinhee Kim5, Bongsoo
Kim2
1
Department of Physics and Photon Science, GIST, Gwangju, 61005, Korea
2
Deparment of Chemistry, KAIST, Daejeon 34141, Korea
3
Department of Physics, POSTECH, Pohang 37673,Korea
4
Department of Measurement and Analysis, National Nanofab Center, Daejeon 34141, Korea
5
Korea Research Institute of Standards and Science, Daejeon 34113, Korea
* E-mail address: yjdoh@gist.ac.kr
Single-crystalline β-Ag2Se nanostructures, a new class of three-dimensional topological
insulators (TIs), were synthesized using the chemical vapor transport method. The topological
surface states were verified by measuring electronic transport properties including the weak
antilocalization effect, Aharonov-Bohm oscillations, and Shubnikov-de Haas oscillations.[1]
The band inversion in β-Ag2Se is attributed to a strong spin-orbit coupling and Ag-Se bonding
hybridization. The superconducting junctions of β-Ag2Se nanostructures were also made using
superconducting Al electrodes.[2] Very large supercurrent in the junction enables us to observe
the macroscopic quantum tunneling behavior in the narrow junction limit. These extensive
investigations would provide new meaningful information about silver-chalcogenide TIs that
have anisotropic Dirac cones, which could be useful for spintronics and superconducting
quantum information devices applications.
Fig. 1. Aharonov-Bohm oscillations observed in β-Ag2Se nanoribbon device.
References
1. J. Kim, A. Hwang, S.-H. Lee, S.-H. Jhi, S. Lee, Y. C. Park, S.-I Kim, H.-S. Kim, Y.-J.
Doh, J. Kim, B. Kim, to appear in ACS Nano (2016).
2. B. K. Kim, J. Kim, H.-S. Kim, B. Kim, Y.-J. Doh, (in preparation).
D2-I-02
Electronic Properties of High-Quality Epitaxial Topological Dirac
Semimetal Thin Films
Michael S. Fuhrer1*
1
Monash Centre for Atomically Thin Materials, Monash University, Monash 3800 VIC Australia
* E-mail address: michael.fuhrer@monash.edu
Topological Dirac semimetals (TDS) are three-dimensional analogues of graphene, with
linear electronic dispersions in three dimensions. Electrical measurements so far have been
on bulk TDS crystals and have revealed unusual axion magnetoresistance [1]. Yet the ability
to grow and characterise TDS thin-films on thickness scales ranging from several monolayers
to tens of monolayers with transport and scanning tunnelling microscopy (STM) opens up
numerous new possibilities, including studying the conventional-to-topological quantum
phase transition (QPT) as a function of layer thickness or incorporating gate electrodes to
enable an electric field-tuned QPT, realizing a topological transistor [2].
We combine molecular beam epitaxial growth with a low-temperature STM capable of
magnetotransport at 5 K to study the electronic properties of Na3Bi thin films. Thin films (20
nm) of Na3Bi on α-Al2O3(0001) substrates are found to possess low temperature charge
carrier mobilities exceeding 6000 cm2V-1s-1 with n-type carrier densities below 1 x 1018 cm-3
that are comparable to the best single crystal values [3]. Perpendicular magnetoresistance at
low field shows the perfect weak-antilocalization behaviour expected for Dirac fermions in
the absence of intervalley scattering. Our ongoing efforts to tune the carrier density using
physical and chemical schemes will also be discussed [4].
References
1. J. Xiong et al., Science 350, 413 (2015)
2. X. Xiao, et al., Scientific Reports 5, 7898 (2015)
3. J. Hellerstedt, M. T. Edmonds, N. Ramakrishnan, C. Liu, B. Weber, A. Tadich, K. M.
O’Donnell, S. Adam, M. S. Fuhrer (submitted)
4. M.T. Edmonds, J. Hellerstedt, A. Tadich, K. M. O’Donnell, M. S. Fuhrer (submitted)
D2-I-03
Sign reversal of the hole g-factor in a (311) GaAs quantum point contact
Oleh Klochan*
The university of new south wales, Australia
D3-IK-01
Unique properties of graphene-based vertical-junction diodes and
applications
Suk-Ho Choi*
Department of Applied Physics, Kyung Hee University, Yongin 446-701, Korea
*E-mail address: sukho@khu.ac.kr
Recently, various types of device structures have been reported by employing graphene and its
hybrid structures, but it is still unclear which will be successfully the prototypes for the
practical applications. In this talk, I introduce graphene-based vertical-junction diodes firstly
developed in our group by using solely graphene or its convergence structures and compare
them with those of other device structures. Firstly, I discuss all-graphene p-n vertical tunneling
junctions that were fabricated by chemical vapor deposition and chemical treatment. One of
the most important characteristics of the graphene tunneling junctions is the asymmetric
rectifying behavior showing on/off ratio of ∼103 under bias voltages below ± 10 V without
gating. The observed rectification results from the strongly-corrugated insulating/
semiconducting interlayers, graphene quantum dots (GQDs), or GQDs/silica nanoparticles,
sandwiched between the doped or pristine graphene sheets, which is actually a structure like
metal-insulator-metal or metal-semiconductor-metal tunneling diode. These all-graphene
vertical-tunneling diodes show unique photodetector (PD) characteristics, which follow well
what are expected from its band structure. I also discuss the principles and the device properties
of several graphene-based hybrid structures such as graphene/Si-quantum-dot tunneling diodes
and graphene/Si nanowire DNA sensors. The I-V measurements demonstrate that some of the
tunneling diodes show temperature-dependent negative differential resistance in a voltage
region, i.e., resonant-tunneling behaviors.
D3-I-02
Photonics of two-dimensional materials: graphene and beyond
Qiaoliang Bao1,2,*, Haoran Mu2, Yunzhou Xue2, Yupeng Zhang1, Shaojuan Li2
1 Department of Materials Science & Engineering, Monash University & the Melbourne Centre for
Nanofabrication, Clayton, Victoria 3800, Australia * Email: qiaoliang.bao@monash.edu
2 FUNSOM and Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University,
Suzhou 215123, P. R. China
Here we would like to review our recent progresses on the photonic applications of graphene and other
two-dimensional (2D) layered materials.[1,2] Firstly, we report that the synergetic integration of
graphene and Bi2Te3 by epitaxial growth affords tunable optical properties by controlling the coverage
of Bi2Te3. We further developed it as saturable absorbers and incorporated into a 1.5 µm fiber laser for
both Q-switching and mode-locking pulse generation.[3] In another work, black phosphorus is
encapsulated by polymer matrix to effectively avoid the oxidization and degradation. Our experiments
suggest that black phosphorus could be another efficient saturable absorber to generate high energy Qswitched pulse in fiber laser.[4] We also demonstrated for the first time that self-doped plasmonic 2D
Cu3-xP nanosheets can be used as simple and effective nonlinear absorbers in a 1.5 µm high energy Qswitched laser. [5]
Secondly, we fabricated a highly efficient hybrid photodetector that consists of graphene and
dispersive perovskite (CH3NH3PbBr2I) islands. A photoconductive gain of ~109 and a responsivity of
~6.0×105 AW-1 were achieved, which is attributed to the effective charge transfer and photo-gating
effect.[6] We also demonstrated a broadband photodetector based on graphene-Bi2Te3 heterostructure.
The device not only shows greatly enhanced responsivity (up to 35 AW-1) and an ultra-high
photoconductive gain (up to 83), but also has the capability for broadband photodetection from visible
to NIR wavelengths.[7] Furthermore, we developed new methods to grow and transfer large area single
crystal WS2 [8], continuous MoS2 thin film [9] as well as MoS2/WS2 heterojunction [10]. In an n-n
heterostructure photodetector based on multilayer MoS2 film covered with graphene quantum dots, a
photoresponsivity of 104 AW-1 and a photogain of 107 were achieved.[11] Due to good CMOScompatibility of 2D materials, we fabricate chip-integrated resonator devices and incorporate 2D
heterostructure for the signal modulation and processing.[12] We observed optical bistability in a
Fabry–Perot cavity containing monolayer and bilayer graphene for the first time, which allows us to
explore the promise of using such elements as the building block of digital all-optical circuitry.[13] Last,
we report our recent progress on the synthesis of low-dimensional perovskite as well as its
optoelectronic applications.[14, 15] In summary, the advances of photonics of 2D materials may pave
the way for the integration of next generation hybrid silicon photonic circuit.
Reference
[1] Qiaoliang Bao, Kian Ping Loh. ACS Nano, 2012, 6, 3677. [2] Shaojuan Li，Qiaoliang Bao*, et al., New Carbon Materials, 2014, 5,
329. [3] Haoran Mu, Qiaoliang Bao*, et al., ACS Photonics, 2015, 2, 832. [4] Haoran Mu, Qiaoliang Bao*, et al., Adv. Opt. Mater., 2015, 3,
1447. [5] Zeke Liu, Qiaoliang Bao*, et al., Adv. Mater., 2016, DOI: 10.1002/adma.201504927. [6] Yusheng Wang, Qiaoliang Bao*, et al.,
Adv. Opt. Mater., 2015, 3, 1389. [7] Hong Qiao, Qiaoliang Bao*, et al., ACS Nano, 2015, 9, 1886. [8] Zaiquan Xu, Qiaoliang Bao*, et al.,
ACS Nano, 2015, 9, 6178. [9] Caiyun Chen, Qiaoliang Bao*, et al., Photonic Research, 2015, 3, 110. [10] Yunzhou Xue, Qiaoliang Bao*, et
al., ACS Nano, 2016, 10, 573. [11] Caiyun Chen, Qiaoliang Bao*, et al., Scientific Reports, 2015, 5, 11830. [12] Sheng Gan, Qiaoliang Bao*,
et al., Nanoscale, 2015, 7, 20249. [13] Qiaoliang Bao, Kian Ping Loh, T. Venkatesan, et al., Adv. Opt. Mater., 2015, 3, 744. [14] Ziyu Wang,
Qiaoliang Bao*, et al., Nanoscale, 2016, 8, 6258. [15] Jingying Liu, Qiaoliang Bao*, et al., ACS Nano, 2016, 10, 3536.
D3-I-03
Toward Continuous Synthesis and Patterning of Graphene & 2D Materials
TaejunChoi1,2†, SangJinKim1†, SubeomPark1, TaekyongHwang2,YoungroJeon2, ByungHeeHong1
1 1Department of Chemistry, Seoul National University, Seoul, 151–747, Korea
2 2AppliedTechnologyGroup,SamsungElectro-Mechanics,Suwon,443-743,Korea.
3 Tel: +82-2-882-6569 Fax: +82-2-871-639, Email: byunghee@snu.ac.kr
Graphene has been intensively studied due to their outstanding electrical, mechanical and
optical properties, such as high electrical conductivity, mechanical flexibility, and optical
transmittance. The key challenges to make commercially viable graphene-based electronic
devices are enabling large-area production of high quality graphene and subsequently
patterning graphene into desirable structures. With the recent advances in chemical vapor
deposition (CVD), large-area growth of graphene by CVD on Cu substrates was successfully
demonstrated for industrial applications. However, reliable methods are still required to
transfer the large-area graphene sheet to the application substrate and pattern for the desired
applications without damaging or leaving undesired residues on the graphene surface. Here we
present a roll-to-roll continuous patterning and transfer methods applicable to various
substrates using the two-layer structure film of PET/silicone. Pattern and transfer can be
continuously performed without requiring any additional complex system and the method is
fitted to the roll-to-roll large-scale production. We will also demonstrate that the same
technique can be applied to the synthesis and transfer of various 2D materials.
References
1. S. Bae et al. Nat Nanotechnol. 5, 574-578 (2010).
2. S. J. Kim et al. Nano Letters 15, 3236–3240 (2015).
3. T. Choi et al. Nanoscale 7, 7138-7142 (2015).
D3-I-04
From liquid metals down to two dimensional semiconductors
Benjamin J. Carey, Torben Daeneke and Kourosh Kalantar-zadeh*
RMIT University, School of Engineering,Melbourne VIC, Australia
* E-mail address: kourosh.kalantar@rmit.edu.au
Different deposition methods, either chemical or physical based, for two dimensional
planar crystals have been devised [1-3]. However, the high quality, large scale and consistent
deposition of these materials remain as significant challenges. We introduce a novel approach
for depositing large scale two dimensional (2D) post transition metal chalcogenide compounds
using the self-limiting metal oxide layer of the metal precursor in liquid form.
Ga, In and Sn, which are the post transition metals, have low melting points. In an oxygen
containing atmosphere, these metals quickly form an atomically thin (~0.7 nm) self-limiting
oxide layer [4]. The presence of this protective oxide layer increases the wettability of post
transition liquid metals on oxygen terminated substrates by providing large van der Waals
forces between the two surfaces [5]. After placing this liquid metal with its self-limiting oxide
layer on a substrate, the coating is exfoliated due to the large van der Waals forces onto its
surface oxide. Using this phenomenon, we establish a process that uses low melting point Ga
(29.7°C) to deposit wafer scale printable 2D gallium sulphide from its exfoliated oxide. In this
process, the oxide skin of Ga is exclusively placed onto a substrate. This oxide layer is then
sulfurised via a specifically designed low temperature procedure to produce large area bilayer
(~1.4 nm) 2D gallium sulphide. Controlling the surface chemistry of the substrate allows for
selective patterning [6]. This facile printing method is suitable for large scale fabrication of 2D
post deposition sulphide based devices, overcoming one of the major impediments of the
fabrication of devices based on these 2D materials.
References
1
E. P. Nguyen, B. Carey, T. Daeneke, J. Z. Ou, K. Latham, S. Zhuiykov and K.
Kalantar-zadeh , Chem. Mater. 27, 53–59 (2015).
2
S. Balendhran, J. Z. Ou, M. Bhaskaran, S. Sriram, S. Ippolito, Z. Vasic, E. Kats, S.
Bhargava, S. Zhuiykov, and K. Kalantar-zadeh, Nanoscale 4, 461–466 (2012).
3
S. Balendhran, S. Walia, H. Nili, J. Z Ou., S. Zhuiykov, R. B. Kaner, S. Sriram, M.
Bhaskaran, K. Kalantar-zadeh, Adv. Funct. Mater. 23, 3952–3970 (2013)
4
A. J. Downs, Chemistry of aluminium, gallium, indium, and thallium. (Springer
Science & Business Media, 1993).
5
M. D. Dickey, ACS Appl. Mater. Interfaces 6, 18369-18379 (2014).
6
E. P. Nguyen, B. J. Carey, J. Z. Ou, J. van Embden, F. Della Gaspera, A. F. Chrimes,
M. J. S. Spencer, S. Zhuiykov, K. Kalantar-zadeh and T. Daeneke Adv. Mater. 27,
6225-6229 (2015).
D4-I-01
MOCVD Growth of High Quality AlN and AlGaN Epilayers for Deep
Ultraviolet Light-Emitting Diodes
Changqing Chen1,*, Shuai Wang1, Feng Wu1, Jingwen Chen1, Jun Zhang1, Renli Liang1,
Hanling Long1 and Jiangnan Dai1
1
Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan
430074, China
* E-mail address: cqchen@mail.hust.edu.cn
AlGaN-based deep ultraviolet light-emitting diodes (DUV-LEDs) have attracted increasing
attention in the potential applications in sterilization, water and air purification, medical
phototherapy, biochemical detection, secure communication and so on [1]. However, compared
with the commercially available blue and green LEDs with InGaN active layers on
GaN/sapphire templates, the practical applications of AlGaN-based DUV-LEDs are still held
back on account of their low external quantum efficiency (EQE), which is typically below 15%
[2]. One major reason responsible for the low EQE of DUV-LEDs is the presence of high
threading dislocation density (TDD) in the AlGaN active layers which will induce nonradiative carrier-recombinations, resulting in a low internal quantum efficiency (IQE). In recent
years, great efforts have been made to reduce the threading dislocations in AlGaN materials,
including the adoption of epitaxial lateral overgrowth AlN/sapphire templates [3] and epitaxy
of AlGaN materials on AlN bulk substrates [4]. Nevertheless, the TDD of AlGaN materials is
still high with an order of 109 cm-2, which is a significant restriction on the improvement in the
IQE in DUV-LEDs.
In this report, we combined the pulsed atomic layer epitaxy (PALE) method [5] with midtemperature inserting layer as well as high-temperature, high-growth-rate continuous-flow
mode to improve the crystal quality of AlN epilayer. As a result, a crack-free, atomically flatsurface AlN epilayer with thickness over 3 μm was obtained. The typical full widths at half
maximum (FWHMs) of X-ray diffraction (10-12) and (0002) ω-scan rocking curves of the AlN
were less than 300 and 60 arcsec, respectively. Furthermore, we have also achieved high quality
n-doped AlGaN epilayers, by inserting grading superlattice structures between the AlGaN
epilayers and high-quality AlN/sapphire templates to relax the strain and filter the dislocations.
Typically, the electron concentration of n-AlGaN with the aluminum content of 0.45 was
3×1018 cm-3, and the mobility was 99.7 cm2/V•s. This progress we made on the AlN and AlGaN
materials will contribute to increasing the IQE, which can potentially improve the performance
of AlGaN-based DUV-LEDs.
References
1.
2.
3.
4.
5.
A. Khan, K. Balakrishnan, and T. Katona, Nature Photon. 2, 77-84(2008).
H. Hirayama, N. Maeda, S. Fujikawa, S. Toyoda, and N. Kamata Jpn. J. Appl. Phys. 53, 100209 (2014).
U. Zeimer, V. Kueller, A. Knauer, A. Mogilatenko, M. Weyers, and M. Kneissl, J. Cryst. Growth 377, 3236(2013).
T. Kinoshita, K. Hironaka, T. Obata, T. Nagashima, R. Dalmau, R. Schlesser, B. Moody, J. Q. Xie, S. Inoue,
Y. Kumagai, A. Koukitu, Z. Sitar, T. Kinoshita, K. Hironaka, T. Obata, T. Nagashima, R. Dalmau, R.
Schlesser, B. Moody, J. Q. Xie, Y. Kumagai, and Z. Sitar, Appl. Phys. Express 5, 122101(2012).
J. P. Zhang, A. Khan, W. H. Sun, H. M. Wang, C. Q. Chen, Q. Fareed, E. Kuokstis, and J. W. Yang, Appl.
Phys. Lett. 81, 4392(2002).
D4-I-02
InSb double quantum dots embedded in a superconducting circuit cavity
-Towards strong spin-photon couplingRui Wang1,RussellS.Deacon1,2, Diana Car3, ErikP.A.M.Bakkers3, and Koji Ishibashi1,2,*
1
2
Advanced Device Laboratory, RIKEN, Wako, Japan
Center for Emergent Matter Science (CEMS), RIKEN, Wako, Japan
3
Eindhoven University of Technology, Eindhoven, The Netherlands
* E-mail address: kishiba@riken.jp
Electron spins in a quantum dot (QD) can be an attractive media for quantum processing.
In a future quantum processor, various qubits, such as the superconducting qubits and the spin
qubits, could be coupled through the microwave cavity, and quantum information stored in the
various qubits with various forms (flux, spin, et al.) could be manipulated or transferred among
them. To couple the qubits to the cavity also produces an advantage that the quantum
information can be transferred between the long-distant qubits, which is also advantageous in
terms of scalability. The superconducting qubit would be used for logic operations because
they are easily accessed, while the spin qubit be mainly used for the quantum memory because
the coherence is long. Although the strong qubit-cavity coupling has already been realized for
the superconducting qubit [1], the essential difficulty exists to realize it in the single spin-cavity
system because the dipole interaction between the single-spin magnetic moment and the cavity
magnetic field is very small (< ~1kHz). To overcome the problem, an orbital degree of freedom
could be used, and various theoretical works have been done [2-4], which predict the coupling
strength could be larger than ~MHz. The basic ingredient to couple the spin with the photon in
a cavity would be either to use a material dependent spin orbit interaction (SOI) [5] or an
artificially realized inhomogeneous magnetic field [6]. The most important factor for the strong
coupling is the decoherence of the qubit because “strong” means that the coupling strength
should be much larger than the decoherence rate that varies in various material systems.
In this talk, we discuss the feasibility to realize the strong spin-cavity interaction from the
material point of view and present preliminary measurements on the double QDs made of the
InSb nanowire which were embedded in a superconducting coplanar-waveguide cavity [7]. The
measurements indicate that the present system is still far from the strong coupling regime, but
we discuss how the double QDs were coupled with the cavity in our measurements.
References
1. A. Wallraff, D. I. Schuster, A. Blais, L. Fruzio, R. S. Huang, J. Majer, S. Kumar, S. M. Girvin,
and R. J. Schoelkopf, Nature 449, 162 (2004)
2. G. Burkard and A. Imamoglu, Phys. Rev. B 74, 041307 (2006).
3. Pei-Qing Jin, Michael Marthaler, Alexander Shnirman, and Gerd Schon, Phys. Rev.Lett. 108,
190506 (2012)
4. Xuedong Hu, Yu-xi Liu, and Franco Nori, Phys. Rev. B 86, 035314 (2012)
5. S. Nadj-Perge, S. M. Frolov, E. P. A. M. Bakkers, and L. P. Kouwenhoven, Nature, 468 1084
(2010).
6. Y. Tokura, W. G. van der Wiel, T. Obata, and S. Tarucha, Phys. Rev. Lett. 96, 047202 (2006)
7. R. Wang, R. S. Deacon, D. Car, E. P. A. M. Bakkers, and K. Ishibashi, submitted.
D4-O-01
D4-O-02
Epitaxial growth of antimonide based infrared photodetectors
Jun Oh Kim1, Sang-Woo Kang1, Sooho Bae2, J-W Choe3, Ha Sul Kim4, S. Krishna5, and
Sang Jun Lee1,*
1
Division of Convergence Technology, Korea Research Institute of Standards and Science, Daejeon 305-340,
Korea
2
R&D Center, I3Systems, Daejeon 305-343, Korea
3
Department of Applied Physics, Kyung Hee University, Yongin 449-701, Korea
4
Department of Physics, Chonnam National University, Gwangju 500-757, Korea
5
Center for High Technology Materials, University of New Mexico, Albuquerque 87106, USA
* E-mail address: sjlee@kriss.re.kr
Antimonide (Sb) based semiconductors have attracted much interest as a device materials
for an applications of optoelectronic devices, such as infrared photodetectors [1], solar cell [2]
and light emitting diode [3]. Sb based infrared photodetectors have been widely researched in
recent year and have been used to fabricate focal plane arrays (FPA) for detecting in mid-wave
infrared (MWIR, 3∼5 µ m ) and long-wave infrared (LWIR, 8∼12 µm). In this study,
InAs/GaSb type-II superlattice (T2SL) structures for mid-wave infrared (MWIR) detection
were grown on Te-doped GaSb substrate by a solid source molecular beam epitaxy with As2
and Sb2 cracker cells. The layer structure consists of GaSb buffer and InAsSb etch stop layer,
followed by bottom contact layer. Then, an active layer formed by InAs/GaSb SLS was grown,
followed by top contact layer as shown in Figure 1. For MWIR detection, thickness of InAs
and GaSb was estimated with a semi-empirical theory. After MBE growth of T2SL structure,
the devices were processed in 410×410 µm2 mesas using inductively coupled plasma etching,
followed by the contact metal deposition. We have measured the spectral response of T2SL
based photodetector. Detailed study of device design, fabrication and characterizations for the
T2SL infrared detectors will be presented.
Fig. 1. Schematic of InAs/GaAs T2SL structure.
References
1. D. L. Smith, and C. Mailhiot, J. Appl. Phys. 62, 2545 (1987).
2. R. B. Laghumavarapu, A. Moscho, A. Khoshakhlagh, M. El-Emawy, L. F. Lester and D. L. Huffaker, Appl.
Phys. Lett. 90, 173215 (2007).
3. A. A. Allerman, R. M. Biefeld, and S. R. Kurtz, Appl. Phys. Lett. 69, 465 (1996).
D4-O-03
Temperature-Dependent Resonance Energy Transfer from Semiconductor
Quantum Wells to Graphene
Young-Jun Yu1*, Keun Soo Kim2, Jungtae Nam2, Se Ra Kwon3, Hyeryoung Byun3, Kwanjae
Lee4, Jae-Hyun Ryou 5, Russell D. Dupuis 6, Jeomoh Kim 6, Gwanghyun Ahn7, Sunmin Ryu7,
Mee-Yi Ryu3 and Jin Soo Kim4
1
ICT Materials & Components Basic Research Group, Electronics and Telecommunications Research Institute
(ETRI), 218 Gajeong-ro, Yuseong-gu, Daejeon 305-700, Korea
2
Department of Physics and Graphene Research Institute, Sejong University, Seoul 143-747, Korea
3
Department of Physics, Kangwon National University, Kangwon-Do 200-701, Korea
4
Division of Advanced Materials Engineering, Research Center of Advanced Materials Development (RCAMD),
Chonbuk National University, Jeonju 561-756, Korea
5
Department of Mechanical Engineering and Texas Center for Superconductivity at the University of Houston
(TcSUH), University of Houston, Houston TX 77204-4006, USA
6
Center for Compound Semiconductors and School of Electrical and Computer Engineering, Georgia Institute
of Technology, Atlanta GA 30332-0250, USA
7
Department of Chemistry, Pohang University of Science and Technology, Pohang 790-784, Korea
* E-mail address: yjyu@etri.re.kr
Resonance energy transfer (RET) has been employed for interpreting the energy interaction
of graphene combined with semiconductor materials such as nanoparticles and quantum-well
(QW) heterostructures. Especially, for the application of graphene as a transparent electrode
for semiconductor light emitting diodes (LEDs), the mechanism of exciton recombination
processes such as RET in graphene-semiconductor QW heterojunctions should be understood
clearly. Here, we characterized the temperature-dependent RET behaviors in
graphene/semiconductor QW heterostructures. We then observed the tuning of the RET
efficiency from 5% to 30% in graphene/QW heterostructures with ~60 nm dipole-dipole
coupled distance at temperatures of 300 ~ 10 K. This survey allows us to identify the roles of
localized and free excitons in the RET process from the QWs to graphene as a function of
temperature.[1]
References
1. Y. -J. Yu, K. S. Kim, J. T. Nam, S. R. Kwon, H. Byun, K. Lee, J.-H. Ryou,
R. D. Dupuis, J. Kim, G. Ahn, S. Ryu, M.-Y. Ryu and J. S. Kim, Nano Let
ters 15, 896-902 (2015).
D5-I-01
D5-I-02
Graphene superlattices
Levente Tapaszto*
Centre for Energy Hungarian Academy of Sciences, Budapest 1121, Hungary
* E-mail address: tapaszto@mfa.kfki.hu
The structure of atomically thin materials can be easily modulated in the out-of-plane direction,
a degree of freedom that is usually absent in bulk materials. This opens up an entirely new
route towards engineering their electronic properties. The adherence of graphene and other 2D
materials to various crystalline substrates often leads to a periodic modulation of their atomic
structure due to lattice and/or rotational mismatch. The observed topography of supported
graphene can vary between ultra-flat and periodically rippled surfaces.
Graphene superlattices comprise a rich physics as the periodic modulation of the atomic
structure substantially influences the electronic properties. One can exploit this correlation to
tune the charge density distribution on the graphene sheet as well as alter the band structure
through the periodic structural modulation. Furthermore, the nanoscale landscape emerging
from the interaction of the graphene and the substrate can be employed as a template for
molecular self-assembly.
In this talk we will present our results on graphene superlattices, including one and twodimensional graphene superlattices, suspended as well as supported on various substrates, such
as Cu (111), Cu(110), Au(111) and graphite. Peculiar superlattices have been observed by STM
on Cu (110) due to intercalation and Au (111), where a nanomesh-type superlattice is stabilized
instead of the usually observed protrusion lattice. We will show examples for the modulation
of the charge density distribution and band structure, correlated with the structural graphene
superlattices. Experimental results obtained by us on the superlattices of other 2D crystals will
also be briefly discussed.
(b)
Fig. 1. STM images of concave (a) and convex (b) superlattices emerging graphene deposited on Au(111) and
Cu(111) substrates, respectively .
D5-I-03
D6-I-01
Low-Dimensional Heterogeneities to Engineer 2D Materials Properties
Mina Yoon*
Oak Ridge National Lab, USA
D6-I-02
Probing Electronic Structures of Low-Dimensional Materials by Tunneling
Spectroscopy Measurements
Suyong Jung*
KRISS, Korea
D6-I-03
Manipulating the Properties of Graphene in CVD and Their Potentiality
Keun Soo Kim*
Sejong Univ., Korea
D7-I-01
Exploring the Physics of Graphene with Local Probes
Yue Zhao
South Univ. of Science and Technol. of China, China
D7-I-02
Light Emission on Suspended Graphene Xylophone;
Optical Properties and Applications
Hakseong Kim1,2,DongHoonShin2,KirstieMcAllister2,MiriSeo2,SangWookLee2,*
1
Korea Research Institute of Standards and Science (KRISS), Daejeon 34113, Korea
2
Deparment of Physics, Konkuk University, Seoul 05029, Korea
* E-mail address: leesw@konkuk.ac.kr
In this presentation, optical properties of suspended graphene xylophone structure will be
introduced. Micro contact transfer method is applied to realize the suspended grapheme
structures. Recently developed transfer technique made it possible to pick up a specific
graphene flake from mother substrate to target substrate. Bright visible light emission could be
realized thanks to the suspended structure. Based on the optical absorption and Raman
spectroscopy measurement, the temperature of suspended graphene while the light emission
was estimated. It was also found that the surface of graphene after light emission became clean
without any residues so that high quality graphene material could be obtained. We will show
that the suspended graphene can be used for micro scale crucible by utilizing its endurance at
high temperature while light emission.
Figure1 (a) Electron microscope image of suspended graphene xylophone structure (b)
Frequency tuning of mechanical resonance (c) Light emission from suspended graphene[1]
References
1. Y. D. Kim, H. Kim, Y. Cho, J. H. Ryoo, C.-H. Park, P. Kim, Y. S. Kim, S. Lee, Y. Li, S.-N. Park, Y. S.
Yoo, D. Yoon, V. E. Dorgan, E. Pop, T. Heinz, J. Hone, S.-H. Chun, H. Cheong, S. W. Lee, M.-H.
Bae, and Y. D. Park, "Bright visible light emission from graphene" Nature Nanotechnology 10, 676681 (2015).
D7-I-03
Controlling the Band Structure of Black Phosphorus
Keun Su Kim1,2,*
1
Department of Physics, Pohang University of Science and Technology, Korea
Center for Artificial Low Dimensional Electron Systems, Institute for Basic Science, Korea
* E-mail address: keunsukim@postech.edu
2
Two-dimensional (2D) atomic crystals have emerged as a class of materials that may
impact our future electronics technology1. A key issue is controlling their electronic state to
overcome the limit of natural properties. Black phosphorus is a 2D material, consisting of 2D
phosphorene layers, which attracts rapidly growing interests. The low-energy band structure of
black phosphorus was widely predicted to be tunable by various external perturbations, such
as strain and electric field2. In this talk, I will introduce our recent angle-resolved
photoemission spectroscopy studies on the tunable band structure of black phosphorus.
Through the in-situ deposition of alkali-metal atoms on the surface of black phosphorus, we
found that vertical electric field from dopants modulates the band gap, and tunes the material
from a narrow-gap semiconductor to a band-overlapped semimetal3. At the critical point of this
semiconductor-semimetal transition, the system becomes a 2D Dirac semimetal, whose band
dispersion is highly anisotropic, linear in armchair and quadratic in zigzag directions3.
References
1. E. S. Reich, Nature 506, 19 (2014).
2. H. O. H. Churchill and P. Jarillo-Herrero, Nature Nanotech. 9, 330 (2014).
3. J. Kim et al., Science 349, 723−726 (2015).
M-P-001
Common thermal annealing effect for various substrate of MoS2 Field
Effect Transistor,
Jeongmin Park, Haeyong
Kang, Dongseok Suh
Sungkyunkwan University, Seoul, Korea
Two dimensional (2D) Field Effect Transistors (FET) are very sensitive to environment and
treatment while device fabrication process for electrical transport measurement. The
MoS2 FET is already studied very well as n-type semiconductor device by electrical transport.
But even though MoS2 FETs having same structure, some literatures report respective electrical
transports causing different history from fabrication to measurement. Here, we tried to observe
electrical transport changing by common thermal annealing treatment, and after that, we also
exposed ambient mood to define what influence affect to MoS2 device by the thermal annealing.
Especially, SrTiO3 substrate FETs are focused to get intended device on/off operation.
M-P-002
Enhancement of optical properties of TMD/organic hybrid structure.
Changwon Seo1,2, Jubok Lee1,2, Min Su Kim1, Dongwook Lee3, Jinsang Kim3 and Jeongyong
Kim1,2*
1Center for Integrated Nanostructure Physics (CINAP), Institute for Basic Science (IBS),
Sungkyunkwan University, Suwon 440-746, Korea
2Department of Energy science, Sungkyunkwan University, Suwon 440-746, Korea
3Department of Materials Science and Engineering,University of Michigan, Ann Arbor, Michigan 48109, US
*E-mail address: j.kim@skku.edu
Phosphorescence materials have attracted much attention for alternative light emitting
materials, due to their high electro-optic efficiency. Recently metal-free organic
phosphorescence materials were synthesized because of low cost and the versatility of
molecular design [1,2]. 2D transition metal dichalcogenides (TMDs) have been studied and
applied in wide fields of applications, such as batteries, solar cells, field effect transistor, due
to their high carrier mobility [3]. The carrier mobility is caused by enhanced
photoluminescence which results from quantum confinement effects and larger band gap than
that of measured in the bulk structure. Recently, TMDs materials are used in OLED device
structure for hole injection layer (HIL) and it shows more stability than PEDOT:PSS-based
OLED [4]. According to the results, superior carrier mobility of TMDs effect the phosphore to
enhance the photoluminescence from phosphorescence materials.
Herein, we suggest the use of transition-metal dichalcogenides (TMDs)/phosphorescence
material hybrid structure to enhance the optical properties of TMD materials. We expect two
results: phosphorescence emission from metal-free organic materials could be enhanced by
charge transfer which can be used for developing high efficiency OLDED device structure, or
organic phosphorescence material can act as doping materials for TMDs, which can modulate
electronic structure to increase the light emission. The detailed results of experiment and
analysis will be presented.
References
1. O.Bolton, K.Lee, H.Kim, K.Lin and J. Kim, Nature Chemistry 3, 207–212 (2011)
2. D.Lee, O.Bolton, B.Kim, J.Youk, S.Takayama, and J. Kim, J. Am. Chem. Soc. 135, 6325−6329 (2013)
3. D. Jariwala, V. K. Sangwan, L. J. Lauhon, T. J. Marks, M. C. Hersam, ACS Nano, 8, 1102-1120 (2014)
4. C. Kim, T. P. Nguyen, Q. V. Le, J. Jeon, H. Jang and S. Kim, Adv. Funct. Mater. 25, 4512–4519 (2015)
M-P-004
Growth and characterization of molybdenum disulfide atomic layerby
chemical vapor deposition
Doo-Hyung Kim1, Min-Woo Kim1, Yu-Hyun Cho1,2, Hyun-Sun Park1,2,
Ja-Yeon Kim2, Min-Ki Kwon1,*
2
1
Deparment of photonic engineering, Chosun university, Gwangju 501-759, Korea (South)
DepartmentLED team, Korea Photonics Technology Institute(KOPTI), Gwangju 500-779, Korea (South)
* mkkwon@chosun.ac.kr
PL Intensity (a.u)
Raman Intensity (a.u)
Graphene has shown many fascinating properties as a supplement to silicon-base
semiconductor technologies. However, its high leakage current, due to zero bandgap energy, is
not suitable for many applications in electronics and optics. Recently, monolayers of
semiconducting transition metal dichalcogenides (TMDs) such as molybdenum disulfide
(MoS2) hold significant promise in electronics and optoelectronics due to their unusual
electrostatic coupling, large carrier mobility, high current carrying capacity, and strong
absorption by direct bandgap in the visible frequencies with the their chemical and mechanical
robustness. [1,2] MoS2 is a layered semiconductor with a bandgap in the range 1.2-1.8 eV,
whose properties are significantly thickness dependent. A considerable enhancement of
photoluminescence has been observed as the materials thickness is decreased. While
monolayer of MoS2 can be readily obtained by micromechanical cleavage of synthesis or
natural bulk crystals, large area, high quality and continuous thin film are needed for practical
devices. However, obtaining high crystal quality thin films over a large area remains a
challenge.
Here, we report the controlled vapor phase synthesis of MoS2 atomic layers and elucidate a
fundamental mechanism for the nucleation, growth, and grain boundary formation in its
crystalline monolayers. MoS2 films grown under optimal conditions were found to be of high
structural quality from high resolution X-ray diffraction, transmission electron microscopy,
scanning electron microscopy, Photoluminescence and Raman measurements. The uniformity
in thickness, large grain sizes, and excellent electrical performance signify the high quality and
scalable synthesis of the MoS2 atomic layers.
200
300
400
500
600
550
600
Raman Shift (cm-1)
650
700
750
Wavelength (nm)
Fig. 1 Optical analysis of atomic layered MoS2 film (a) Raman spectrum, (b) PL spectrum
Reference
[1] G. H. Han et. al, Nature Comm., 6, 6128 (2014)
[2] S. Najmaei et. al, Nature Mater., 12, 754 (2013)
M-P-005
Photoresponse properties of large-area MoS2 atomic layer grown by
chemical vapor deposition
Min-Woo Kim1, Doo-Hyung Kim1, Ja-Yeon Kim2, Yu-Hyun Cho1,2, Hyun-Sun Park1,2,
,Seungho Bang3,4,Mun Seok Jeong3,4,Min-Ki Kwon1,*
1
Deparment of photonic engineering, Chosun university, Gwangju 501-759 , Korea (South)
DepartmentLED team, Korea Photonics Technology Institute(KOPTI), Gwangju 500-779, Korea (South)
3
Deparment of Energy Science, Sungkyunkwan University, Suwon 446-746, Republic of Korea
4
Center for Integrated Nanostructure Physics, Institute for Basic Science, Sungkyunkwan University, Suwon
440-746, Republic of Korea
* mkkwon@chosun.ac.kr
2
Transition metal dichalcogenides (TMDs) such as molybdenum disulfide (MoS2) is demonstrated as a
promising candidate that goes beyond graphene of zero-gap characteristic for next generation of
optoelectronics due to the intrinsic and tunable bandgap, relatively high carrier mobility, and strong
coupling of spin and valley degrees. [1] Recently, single or few layer MoS2 have been investigated as
photodiode, phototransistors and optical detectors because it is optically active for its bandgap matches
the visible spectrum well. [1-4] However, up to now, the published literature related to the optical
properties of large area and high quality MoS2 are very scarce.
In this work, we report on the demonstration of photodetectors based on large scale two-dimensional
and high quality MoS2 transition metal dichalcogenides. Excellent film uniformity and precise control
of the MoS2 thickness down to a monolayer (~0.75nm) were achieved by using sapphire substrate
through low-pressure chemical vapor deposition. Raman spectroscopy, scanning electron microscopy,
transmission electron microscope and atomic force microscopy were used to determine the
microstructures and morphologies of the MoS2 film. Furthermore, we studied the behaviors of the
photocurrent and photoresponse of the large area and high crystal quality MoS2 sample as shown in fig.
1.
11
Drain current (nA)
Vg = 10V
10
9
8
7
6
0
100
200
300
400
500
Time (s)
Fig. 1. Photoresponse behavior of back gated MoS2 Photodiode. (a) Gating response (Ids-Vg) of MoS2 photodiode
in dark and in illuminated states. (b) Time resolved photoresponse of the MoS2 photodiode in dark and in
illuminated states. Illumination power is 100W.
References
1. Y. Li et. al, Sci. Rep. 4, 7186 (2014)
2. W. Choi et. al, Adv. Mater. 24, 5832 (2012).
3. Z. Yin et. al, ACS Nano 6, 74 (2012).
4. S. Luo et. al, J. Appl. Phys, 116, 164304 (2014)
M-P-006
Chemically doped three-dimensional porous graphene monoliths for highperformance flexible field emitters
Ho Young Kim1,2, Sooyeon Jeong1, Seung Yol Jeong1, Joong Tark Han1, GeonWoong Lee1* & Mun Seok Jeong2 & Hee Jin Jeong1*
1
Nanocarbon Material Research Group, Korea Electrotechnology Research Institute (KERI), Changwon
642-120, Republic of Korea
2
IBS center for Integrated Nanostructure Physics, Institute for Basic Science, Sungkyunkwan University,
Suwon 440-746, Republic of Korea
E-mail: gwleephd@keri.re.kr
Despite the recent progress in the fabrication of field emitters based on graphene nanosheets, their
morphological and electrical properties, which affect their degree of field enhancement as well as the electron
tunnelling barrier height, should be controlled to allow for better field-emission properties. Here we report a
method that allows the synthesis of graphene-based emitters with a high field-enhancement factor and a low work
function. The method involves forming monolithic three-dimensional (3D) graphene structures by the freezedrying of a highly concentrated graphene paste and subsequent work-function engineering by chemical doping.
Graphene structures with vertically aligned edges were successfully fabricated by the freeze-drying process.
Further, their number density could be controlled by varying the composition of the graphene paste. Al- and Audoped 3D graphene emitters were fabricated by introducing the corresponding dopant solutions into the graphene
sheets. The resulting field-emission characteristics of the resulting emitters are discussed. The synthesized 3D
graphene emitters were highly flexible, maintaining their field-emission properties even when bent at large angles.
This is attributed to the high crystallinity and emitter density and good chemical stability of the 3D graphene
emitters, as well as to the strong interactions between the 3D graphene emitters and the substrate.
a
c
b
Bar coating
d
e
Freeze drying
f
g
Fig. 1. (a) Photograph of a highly concentrated water-based rGO paste. Inset shows SEM image of rGO sheets in the paste. The scale bar is 5
µm. (b) Schematic of fabrication of monolithic 3D rGO structure by the bar coating of a rGO paste and subsequent freeze-drying. (c)
Photograph of a 3D rGO structure fabricated on a flexible polymer substrate. (d) Cross-sectional SEM images of a 3D rGO structure. The
scale bar is 300 µm. (e) and (f) Top-view SEM images with low and high magnifications, respectively. The scale bars are 300 µm and 100
µm, respectively.
(g) TEM image of stacked rGO nanosheets. The scale bar is 400 nm.
M-P-007
Nonvolatile Ferroelectric Memory Using Black Phosphorous Field Effect
Transistors with P(VDF-TrFE) Polymer
Young Tack Lee, Do Kyung Hwang and Won Kook Choi
Two-dimensional van der Waals (2D vdWs) materials are a class of new materials that can provide important
resources for future electronics and materials sciences due to their unique physical properties. Among 2D vdWs
materials, black phosphorous (BP) has exhibited significant potential for use in electronic and optoelectronic
applications because of its allotropic properties, high mobility, and direct and narrow band gap. Here, we
demonstrate a few-layered BP-based nonvolatile memory transistor with a poly(vinylidenefluoridetrifluoroethylene) (P(VDF-TrFE)) ferroelectric top gate insulator. Experiments showed that our BP-based
ferroelectric transistors operate satisfactorily at room temperature in ambient air, and exhibit a clear memory
window. Unlike conventional ambipolar BP transistors, our ferroelectric transistors showed only p-type
characteristics due to the carbon–fluorine (C-F) dipole effect of the P(VDF-TrFE) layer, as well as the highest
linear mobility value of 1159 cm2/V-1s-1 with a 103 on/off current ratio. For more advanced memory applications
beyond unit memory devices, we implemented two memory inverter circuits, a resistive-load inverter circuit and
a complementary inverter circuit, combined with an n-type molybdenum disulphide (MoS2) nanosheet. Our
memory inverter circuits displayed a clear memory window of 15 V and memory output voltage efficiency of
95%.
M-P-008
Exciton Complexes in Transition-Metal Dichalcogenide Heterostructures
by Interlayer Charge Exchanges
Min Su Kim1, Changwon Seo1,2, Hyun Kim1,2, Jubok Lee1,2, Dinh Hoa Luong1,2, Ji-Hoon
Park1, Gang Hee Han1, Jeongyong Kim1,2,*
1
Center for Integrated Nanostructure Physics (CINAP), Institute for Basic Science (IBS), Sungkyunkwan
University, Suwon 440-746, Republic of Korea
2
Department of Energy Science, Sungkyunkwan University, Suwon 440-746, Republic of Korea
* E-mail address: j.kim@skku.edu
Inspired by the recent advancements in graphene, the layered transition-metal
dichalcogenides (LTMDs), such as MoS2, MoSe2, WS2 and WSe2, have attracted considerable
attention as two-dimensional (2D) semiconductors with unique layer-number-dependent
electronic and optical properties. Although LTDMs have the same crystalline structure, their
physical properties, such as bandgap, exciton resonance and spin-orbit coupling strength, can
vary significantly. Therefore, an intriguing possibility is to stack different LTMD monolayers
on top of one another to form 2D heterostructures. In addition, the recently developed ability
to 2D materials heralds a new realm of device physics based on 2D semiconductors and van
der Waals heterostructures. Heterostacking of LTMD monolayers offers a convenient way to
create 2D exciton systems, which have extensively been explored using various LTMD
monolayers of 2D materials. Interlayer interactions and charge exchanges between the
monolayers in heterostacked structures have been shown to yield intriguing phenomena such
as the modulation of electronic structures and emergence of interlayer excitons and charged
excitons, paving the way for a new class of van der Waals-stabilized heterostructures with
unique physical properties. Here we report the improved luminescent efficiency of exciton
complexes in vertically stacked heterostructures at room temperature. By using spatially
resolved PL and Raman spectroscopy and imaging, we showed PL enhancement of the stacked
heterostructures by controlling the distance between the bottom and the top LTMD monolayers
in the heterostructures. We also showed changes in the polarity of trions from negative to
positive when heterostacking the LTMDs. Our results showed that vertically heterostacked
LTMD structures provide a convenient and reliable platform to study intriguing phenomena of
confined exciton complexes driven by interlayer charge exchanges, which can be tunable for
the enhanced optical properties.
M-P-009
Ohmic contact to semipolar (11-22) p-GaN by electrical breakdown
method,
Seonghoon Jeong1, Sung-Nam Lee2 and Hyunsoo Kim1
1 Chonbuk National University, Korea
2 Korea Polytechnic University, Korea
Semipolar GaN semiconductors are of interest for application in high-efficiency optoelectronic
and electronic devices such as light-emitting diodes (LEDs), laser diodes (LDs), sensors, and
heterojunction field-effect transistors (HFETs) since they can overcome polarization-induced
issues in III-nitride semiconductors. In order to fabricate reliable devices using semipolar GaN
semiconductors, it is very essential to obtain low resistance Ohmic contact on p-type layers.
For semipolar p-GaN, however, the Ohmic contact with an excellent linearity could not be
easily obtained. This is due to the large work-function mismatch between p-GaN and metal,
low carrier concentration of ~1017 cm-3, and the presence of a high density of surface states in
the epitaxial semipolar p-GaN (pinning the surface Fermi level). Therefore, the formation of
Ohmic contact via the classical method, e.g., the use of large work function metals such as Pt,
Pd, and Ni, is quite difficult.
Very recently, a universal method to obtain an Ohmic contact, the so-called electrical
breakdown (EBD) method which utilizes a metal/wide bandgap oxides/semiconductor
structure, was demonstrated. In this study, we attempted to obtain low resistance Ohmic contact
on (11-22) semipolar p-GaN using the EBD method. The graded EBD method by which the
electrical stress voltage could be increased up to 70 V in the Ti/SiO2/p-GaN structure produced
Ohmic contact with a specific contact resistance of 3.1X10-3 Ωcm2 without any sudden
degradation in the contact. Detailed structural changes and carrier transport behavior before
and after EBD method were analyzed by the transmission electron microscope and currentvoltage-temperature measurements.
M-P-010
Threshold Voltage Shift of 0.2 μm AlGaN/GaN MISHFET
with Fluorinated Gate Dielectric
Ho-Kyun Ahn*, Min Jeong Shin, Hyun-Wook Jung, Hae-Cheon Kim, Dong-Min Kang,
Sung-Il Kim, Jong-Min Lee, Byoung-Gue Min, Hyoung-Sup Yoon, Eun-Soo Nam and JongWon Lim
ICT Materials and Components Research Laboratory, Electronics and Telecommunications Research Institute,
Daejeon, Korea
* E-mail address: hkahn@etri.re.kr
This paper demonstrates 0.2 μm AlGaN/GaN MISHFETs with the fluorinated Al2O3 gate dielectric.
AlGaN/GaN-based heterostructure on 4-inch semi-insulating sapphire wafer was utilized for the
fabrication of the MISHFETs. After Al2O3 layer as a gate dielectric was deposited by Atomic-Layer
Deposition (ALD), the gate dielectric was treated to the CF4 plasma. As shown in Fig. 1, the analysis
of Al2O3 layer using XPS and AES indicated that F ions were incorporated inside Al2O3 layer. The
MISHFETs with the fluorinated Al2O3 gate dielectric were compared with the untreated device. The
fluorinated MISHFETs exhibited positive threshold voltage shift of about 3 V. The fabricated device
showed the maximum transconductance of 183 mS/mm and drain current of 490 mA/mm at Vgs = 0V.
The device exhibited the hysteresis of 0.1 ~ 0.2V in the transfer curve and significantly degraded offstate performances such as off-state leakage current of 4 × 10 - 7 mA/mm at Vgs = - 5 V. This result in
the device performance was correlated with the degradation of fluorinated Al2O3 film [1].
(a)
(b)
Fig. 1. (a) XPS spectra of Al 2p at the surface and (b) AES depth profile of the Al2O3 layer treated by the CF4
plasma.
(a)
(b)
Fig. 2. (a) Tranfer curves and (b) C-V characteristics of the fabricated MISHFET with the fluorinated Al2O3 gate
dielectric and the reference device.
References
1. Y. Zhang et al, “Threshold voltage control by gate oxide thickness in fluorinated GaN metaloxide-semiconductor high-electron-mobility transistors” Appl.Phys.Lett., vol. 103, No. 3,
2013, 033524.
M-P-011
Influence of Light Concentration on GaAs Solar Cell on Cu Substrate
Dae-Myeong Geum1,2, Min-Su Park2, Chang Zoo Kim3, SangHyeon Kim2*, Won Jun Choi2*, and
Euijoon Yoon1
1
Department of Materials Science and Engineering, Seoul National University, Seoul, Korea
2
Center for Opto-Electronics Materials and Devices, Korea Institute of Science and
Technology (KIST), Seoul, Korea
3
Korea Advanced Nanofab Center (KANC), Suwon-si, Gyeongi-do, Korea
Group III-V concentrator solar cells (SCs) have drawn a strong attention thanks to their very
high efficiency (η) with increasing light concentration ratio [1]. In general, as elevating the
light concentration ratio, the η of SCs increases, whereas the excess light concentration
generates the heat in SCs, resulting in a temperature increase of the SCs. As a result,
unfortunately, a high concentration ratio degrades an open-circuit voltage (VOC) and fill factor
of the SCs, which cause η drop. Therefore the heat dissipation is the key issue to further
improve the performances of III-C concentrator SCs
In this paper, we have investigated the performance of heterogeneously integrated GaAs SC
on Cu. Heterogeneous integration is one of the approaches to handle thermal problems in
concentrator SC. SC on Cu showed the comparable performances to reference SC in 1 sun
illumination condition. Using these devices, we have characterized the SCs under light
concentration.
Figure Photovoltaic performance of reference GaAs SC and GaAs SC on Cu at 1 sun illumination
References
[1] C, Algora et al. A. IEEE Trans. Electron Devices, 48, 5 (2001)
M-P-012
High-performance core/shell InGaN/GaN-multi-quantum-well nanowire
solar cells for heterojunction device array
Hyunho Shin1, Jeongho Park1 and Sung Won Hwang1*
1
Department of Nano Science & Mechatronics Engineering, Interdisciplinary Research center for health and
Nanotechnology Research Center, Konkuk University, Chungju-si 27478, Korea
* E-mail address: swhwang@kku.ac.kr
We demonstrate photovoltaic properties of solar cells made of core/shell InGaN/GaN multi
quantum wells (MQWs)-NW arrays, vertically-grown through oxide-template hole patterns
from n-GaN thin films on n-type Si wafers. Detailed structural properties are analyzed for two
types of the solar cells containing defect-free or defective active layer (MQWs) by highresolution transmission electron microscopy. Photocurrent and external quantum efficiency are
greatly enhanced in the defect-free solar cells due to better charge collection/transport. A
maximum power conversion efficiency (PCE) of ∼5.37% is achieved with an open-circuit
voltage of ∼0.79 V, a short-circuit current density of ∼10.54 mA/cm2, and a fill factor of
∼0.65 in the defect-free solar cells. The performance was dominated by an increase in the
current density, result in an increase in power density. These results suggest that the welldefined active layer in InGaN/GaN MQWs-NWs solar cells are crucial for enhancing their PCE
and further explain why the PCE of the solar cells employing similar structures in the previous
reports are comparatively low.
Fig. 1. HRTEM image and photocurrent-voltage (PC-V) curves of the solar cells containing defective and defectfree InGaN/GaN MQWs NWs, schematics of a single-NW solar cell and its band diagram describing the PV
mechanism.
References
1. Y. Dong, B. Tian, T. J. Kempa, and C. M. Lieber, Nano Lett. 9, 2183 (2009).
2. Y. B. Tang, Z. H. Chen, H. S. Song, C. S. Lee, H. T. Cong, H. M. Cheng, W. J. Zhang, I. Bello, and S. T. Lee,
Nano Lett. 8, 4191 (2008).
3. F. Li, S. H. Lee, J. H. You, T. W. Kim, K. H. Lee, J. Y. Lee, Y. H. Kwon, and T. W. Kang, J. Cryst. Growth
M-P-013
Surface treatment for recessed gate and its effects on the performance of
enhancement-mode AlGaN/GaN HEMTs
Jae-Won Do1,*, Ho-Kyun Ahn1, Hae-Cheon Kim1, Hyun-Wook Jung1, Min Jeong Shin1, Kyu
Jun Cho1, Sung-Jae Chang1, Byoung-Gue Min1, Hyoung-Sup Yoon1, Dong-Young Kim1,
Dong-Min Kang1, Jong-Min Lee1, Seong-Il Kim1, Sang-Heung Lee1, Woo-Jin Chang1, HongGu Ji1, Eun-Soo Nam1, and Jong-Won Lim1
1
ICT Materials & Components Research Laboratory, Electronics and Telecommunications Research Institute
(ETRI), Daejeon 34129, Korea. * E-mail address: jdo@etri.re.kr
The high electron mobility transistors (HEMTs) based on AlGaN/GaN heterostructures have
attracted much attention for high-power and high-frequency applications due to their high mobility of
two-dimensional electron gas (2DEG) and high intrinsic breakdown [1]. Enhancement-mode HEMTs
are of special interest as the normally-off operation enables simple design of driving circuits and
reduced power loss during switching, especially for applications in digital circuits. Recessed-gate
approach is one of the effective methods to realize the enhancement-mode AlGaN/GaN HEMTs
because the threshold voltage and the transconductance can be easily optimized on a wafer scale using
conventional lithography and dry etching techniques.
In this work, enhancement-mode AlGaN/GaN HEMTs are fabricated using both optical and
electron-beam lithography techniques and a dry etching technique by inductively coupled-reactive ion
etch (ICP-RIE) system. Fig. 1a shows a schematic diagram of AlGaN/GaN HEMT with a recessed gate,
and Fig. 1b shows an atomic force microscope (AFM) image of the channel region with the recessed
gate prior to metal deposition. Using AFM analysis, the recess-etch rate and the roughness of the
recessed AlGaN surface are investigated. In addition, the roughened and damaged AlGaN surface from
the dry etching step is treated with tetramethylammonium hydroxide (TMAH), which is known to
effectively remove the damages and the oxide on the AlGaN surface and also anisotropically etch the
AlGaN layer [2]. Fig.2 shows the etched AlGaN surface before and after the TMAH treatment, showing
the AlGaN surface with a greatly reduced roughness. Finally, the electrical performance of the
completed devices with and without the TMAH treatment are compared, and the effects of the surface
treatment is evaluated.
Fig. 1. (a) A schematic diagram of an AlGaN/GaN HEMT with a recessed gate and (b) an AFM image of the
channel region indicated by a red dashed box in Fig. 1a.
Fig. 2. AFM images of the recessed gate region prior to metal deposition (a) before and (b) after the TMAH
treatment.
[1] D. M. Kang et al., Microwave Opt. Technol. Lett. 57, 212 (2015)
[2] K.-S. Im et al., J. Cryst. Growth. 441, 41 (2016) Circuits and System Technology, 475 (2013).
M-P-014
Thermodynamic Modeling for Purification of AlN Powder
Yura Kang1, Seongmin Jeong2,*, Younghee Kim2 and Suklyun Hong1,*
1
Deparment of Physics and Graphene Research Institute, Sejong University, Seoul 143-797, Korea
Energy & Environmental Division, Korea Institute of Ceramic Engineering and Technology, Jinju 52851,
Korea
* E-mail address: ,
2
Aluminum nitride (AlN) single crystal is an attractive wide band gap material giving potential
application for substrate material applicable to deep UV optoelectronics. Currently, 2 inch AlN
substrates were commercialized by physical vapor transport (PVT) method which uses AlN
powder as the source. However, high purity AlN powder is not available in the commercial
market, so the fabrication of good quality source through purification of AlN powder is still
open issue for producing high quality AlN single crystal wafer. In this study, we suggest
suitable thermal annealing process conditions on reduction of metallic impurities in AlN
powder by introducing Cl containing species by performing computational thermodynamic
calculations. Factsage software with FactPS database is used to estimate the stability of metals
acting as impurities in AlN crystal.
.
M-P-015 [NO SHOW]
Photocurrent and Dark Current Characteristics of InP/InGaAs Multiple
Quantum Well Avalanche Photodiode
Hyunseok Seo1, Seung-Hwan Park2 and Doyeol Ahn1*
1Department of Electrical and Computer Engineering and Institute of Quantum Information Processing and
Systems, University of Seoul, Seoul 02504, Republic of Korea 2Electronics Department, Catholic University of
Daegu, Hayang, Kyeongbuk 712-702, Republic of Korea * E-mail address: dahn@uos.ac.kr
The avalanche photodiode(APD) has a high current gain by the avalanche effect in i region on the p-in diode structure under high reverse bias voltage.[1] For the optical communication systems, InGaAs
material is generally used for the photon wavelength 1.55um, but its energy bandgap is so small that
the dark current is increased by the tunneling effect under high reverse bias for the avalanche effect. To
prevent the tunneling effect, InGaAs absorption layer and InP multiplication layer for the avalanche
effect are separated and insert the highly doped InP layer between two layer, so that their electric field
can be separated. This structure is known as the separated absorption and multiplication(SAM)
structure.[2] On the other hand, the InP p-i-n APD, applied InP/InGaAs multiple quantum well(MQW)
in the i region, can absorb photon in InGaAs well region and then photogenerated electron and hole can
make the avalanche effect in InP barrier region. Since the i region consists of InP, it doesn't make
tunneling effect. So we can apply the higher reverse bias and get the higher gain with a very low dark
current. Also in a quantum well, the quantum confined Stark effect(QCSE) increase the absorption
coefficient.[3] In this paper, we designed and simulated the MQW APD structure which has 4 wells and
each well length is 5nm, as shown in Fig.1. The fig.2 shows I-V curves with incident photon wavelength
1.55um and without photon on MQW APD structure as shown in Fig.1. The dark current keep the low
current(below 100fA) as reverse bias increased, but the photocurrent is much higher(above 10nA). Also
we simulated other conditions of structure parameter and analyzed dark current rate(DCR), quantum
efficiency, avalanche gain, absorption rate and recombination rate in QW.
References
1. T. P. Pearsall and M. Papuchon, Appl. Phys. Lett., 33, 640(1978). 2. N. Susa, H. Nakaome, H.
Ando, and H. Kanbe, IEEE J. Quantum Electron., 17, 243(1981). 3. T. H. Wood, Lightwave. Tech. J.,
6, 6(1988)..
M-P-016
Direct comparison of axial InxGa1-xN/GaN heterostructure nanowires
grown by PA-MBE for high indium composition of InGaN segments
J. W. Min1, S. Y. Bae2, H. Y. Hwang3, E. K. Kang3, C. H. Kim3, S. J. Kang3, G. W. Ju3, K.
W. Park4, B. H. Na5, C. Y. Park5, Y. D. Jho3, and Y. T. Lee3,*
1
2
Dep. of Physics and Photon Science, Gwangju Institute of Science and Technology, Gwangju 61005, Korea
Department of Electrical Engineering and Computer Science, Nagoya University, Nagoya 466-8550, Japan
3
School of Info. & Comm., Gwangju Institute of Science and Technology, Gwangju 61005, Korea
4
National Renewable Energy Laboratory, Golden, Colorado 80401, USA
5
Device Lab, Samsung Advanced Institute of Technology, Suwon 443-803, Korea
* E-mail address: ytlee@gist.ac.kr
Due to the tremendous developments of III-nitride materials in the past few decades, the
commercial production of laser diodes (LDs) and light-emitting diodes (LEDs) became
available for solid-state lighting. However, the high efficiency of long wavelength emission (>
550 nm) has been still challenging due to the high density of defects at the InGaN/GaN interface,
usually generated from the large lattice mismatch between InN and GaN in the planar platform.
In contrast, self-catalyst GaN nanowire arrays have unique properties of dislocation- and strainfree nature with high surface-to-volume ratio. Accompanying to these advantages, high indium
incorporation of nanowires are well suitable for next-generation phosphor-free white LEDs—
it enables to emit the full visible color emission.
In this work, catalyst- and mask-free GaN nanowire arrays were grown on Si(111)
substrates under nitrogen-rich condition by plasma-assisted molecular beam epitaxy (PAMBE). Before achieving high-indium-content InGaN/GaN nanowire arrays, the coalescence
degree of GaN nanowire arrays was controlled by AlN buffer layer [1]. Based on GaN nanowire
arrays, 10 InGaN/GaN axial heterostructure nanowires are successfully grown as shown in Fig.
1(a). After that, the average thickness of InGaN QDs and GaN barriers was reduced as a
function of growth time in Fig. 1(b) and its corresponding optical characteristics are
investigated in Fig. 1(c). Further, power- and temperature-dependent photoluminescence
properties are also investigated for the grown nanowires.
Fig. 1. (a) STEM image of InGaN/GaN heterostructure nanowires. (b) SEM tilted view of InGaN/GaN
heterostructure nanowires as a function of growth time. (c) RT-PL results of each nanowire arrays.
References
1. M. Musolino, A. Tahraoui, F. Limbach, J. Lähnemann, U. Jahn, O. Brandt, L. Geelhaar and
H. Riechert, Appl. Phys. Lett. 105, 083505 (2014).
M-P-017
Origin of low leakage current in Fe-doped GaN films on Si(110)
Eui-Young Oh1, Sang-Tae Lee1, Byung-Guon Park1, Ji-Won Hwang1, Moon-Deock Kim1*,
Young-Kyun Noh2, Jae-Eung Oh3
1
Department of Physics, Chungnam National University, Daejeon, 305-764, Korea
2
3
IV Works Co., Ltd., Hanyang University, Ansan, Kyunggi-do, 426-79, Korea
School of Electrical and Computer Engineering, Hanyang University, Ansan, Kyunggi-do, 425-791, Korea
In this study, we have investigated the mechanisms of leakage current in iron (Fe) doped
GaN films grown on Si(110) substrates. Effect of Fe on electrical properties of GaN films with
variation of Fe concentration was investigated in details by current-voltage (I-V), capacitancevoltage, and thermally stimulated current (TSC). In the I-V measurement (Figure 1a)), leakage
currents at
-100 V were -1.03×10-4 , -3.60×10-9, and -2.52×10-5 A for un-doped GaN, lightly
Fe-doped GaN, and heavily Fe-doped GaN, respectively. It was found that a leakage current
significantly decreased for lightly Fe-doped GaN compare to other samples. This decreasing
phenomenon on lightly Fe-doped GaN might be due to compensated residual donors and/or
native defects by deep acceptor Fe (Fe3+/2+). To find the origin of defects related with leakage
current, we measured TSC on un-doped GaN, lightly Fe-doped GaN, and heavily Fe-doped
GaN, respectively. Et trap with Ec-0.18 eV was only observed in un-doped GaN as shown in
figure 1b). From these results, mechanism of leakage current by Fe in GaN films will be
discussed in detail.
Figure 2a) Current-voltage characteristics of un-doped, lightly Fe-doped, and highly heavily Fe-doped
GaN films, b) TSC spectra of un-doped, Fe-doped, and highly Fe-doped GaN films
M-P-018 [NO SHOW]
Effects of hydrogen plasma treatment on the various structure of the
InAs/GaAs quantum dot solar cells
HoSung Kim1,2, MoonHo Park1,2, MinSu Park1, SangHyeon Kim1, JiHoon Kyhm1, JinDong
Song1, SangHyuck Kim1, WonJun Choi1*, and JungHo Park2*
1
Center for Opto-Electronics Materials and Devices, Korea Institute of Science and Technology, Seoul 136-791,
Republic of Korea
2
School of Electrical Engineering, Korea University, Seoul 136-713, Republic of Korea
* E-mail address: wjchoi@kist.re.kr, jhpark@korea.ac.kr
To study effects of hydrogen plasma treatment on the various structures of quantum dot
solar cell (QDSC), which have different defect density, quantum dot (QD) solar cell and dotin-a-well solar cell (DWELLSC) were fabricated. The photoluminescence (PL) intensity of
both hydrogen plasma treated solar cells (SCs) was highly increased than that of the non-treated
SCs due to the reduced non-radiative recombination. As a result, the open-circuit voltage of
hydrogen plasma treated the QD embedded SCs was increased. By analyzing the time resolved
photoluminescence (TRPL), and the external quantum efficiency (EQE) response of QDSC
and DWELLSC, termination of defects in GaAs layers near QDs is very important to further
increase the current limit of the QDSC.
Fig. 3. The J-V curve of control SC, QDSC, DWELLSC and their hydrogenated samples.
Acknolwedgement
This research was supported by the Agency for Defense Development (ADD) of Republic of
Korea and by the Converging Research Center Program through the Ministry of Education,
ICT and Future Planning, Korea (2013K000196) and the Seoul R&BD Program (WR080951),
the Brain Korea 21 Plus Project in 2016 and also supported by the KIST internal program.
M-P-019 [NO SHOW]
Growth of InGaN/InGaN Quantum Wells for Long Wavelength LD/LED
by Molecular Beam Epitaxy
Hyeonseok Woo1,2, Cheong Hyun Roh1, Yong Gon Seo1, Jun Ho Lee1, Hyunsik Im2, CheolKoo Hahn1,*
1
Korea Electronics Technology Institute, Seongnam 463-816, South Korea
Division of Physics and Semiconductor Science, Dongguk University, Seoul 100-715, South Korea
* E-mail address: whs4407@gmail.com
2
InxGa1-xN ternary has attracted attention due to their tunable bandgap (0.7 ~ 3.4 eV),
covering the entire visible spectrum. However compositional pulling effect, phase separation,
and rough InGaN/GaN hetero interface have been main obstacles to realize long wavelength
InxGa1-xN/GaN quantum well (QW) structure. We report growth techniques to obtain high Incontent InGaN films with single phase for long wavelength optical devices.
InxGa1-xN films were grown on c-plane sapphire substrate by plasma assisted molecular
beam epitaxy. For the growth, substrate temperature was in the range from 540 to 640 oC and
the beam flux of Ga and N were in the range of 2~8 and 5~12 ML/min, respectively. The III/V
ratio and Ga/In ratio were adjusted in the range of 1~2 and 1~2, respectively.
Excess metal accumulated under the metal-rich condition induces compositional
inhomogeneity in InGaN layer, and unintentional In-alloy in (In)GaN barrier layer, resulting
an irregular QW interface. To prevent this adverse alloy, metal modulated epitaxy (MME) and
metal covering epitaxy were proposed. We precisely controlled a consumption of In-adlayer
using N-interrupt and Ga-covering technique with monitoring reflection high-energy electron
diffraction (RHEED) patterns and intensity. Streaky patterns and the change of intensity for
RHEED demonstrate smooth QW interface. Indium composition (x) of InGaN layer was
estimated by x-ray diffraction (XRD) and photoluminescence (PL). In0.3Ga0.7N/In0.15Ga0.85N
MQWs structure emitting long wavelength PL signal up to 660 nm (FWHM = 0.29 eV) was
realized. It seems that precise control of metal-adlayer plays a key role in improving crystal
quality and In-incorporation. Detailed experimental results and discussion will be studied in
presentation.
Fig. 1. (a) Photoluminescence signals of InGaN/InGaN QWs as a function of growth temperature, and (b) TEM
image of double QW structure.
References
1. C. A. M. Fabien, et al., Jour. Crys. Growth. 425, 115 (2015)
2. T. Yamaguchi, et al., Jour. Crys. Growth. 377, 123 (2013)
M-P-020
Enhancement of GaInP/GaAs dual-junction solar cells using modified gas
switching sequence for tunnel junction grown by MOVPE
Seokjin Kang , Kwangwook Park,Eunkyu Kang, Heeju Choi , Sookyung Lee , Jungwook Min
Gunwoo Ju, Hyojin Kim and Yongtak Lee
III-V based multi-junction solar cells are utilized as high efficient solar cells such as
concentrated photovoltaics and space solar cells [1]. Commonly, the multi-junction solar cells
are performed by the series connection of sub-cells and tunnel junctions. The ultra-high doped
(>1019 cm-3) pn-junction is required to grow the proper tunnel junction. Generally, an intrinsic
doped p-AlGaAs and a Te doped n-GaAs are used for the high doped p- and n- region. It is
noted that the low V/III ratio (≤10) growth is required to maximize the intrinsic doping for pAlGaAs and minimize the optimum flow of Te precursors for the n-GaAs in order to reduce
Te memory effect [2,3]. However, we found that the surface was not mirror-like when the low
V/III ratio n-GaAs of the tunnel junction was grown on the n-GaInP window using the standard
gas switching sequence (GCS).
In this study, the modified GCS was introduced to get mirror-like surface of
GaInP/GaAs dual-junction solar cells. The epitaxial growth was performed by metal-organic
vapor phase epitaxy in an Aixtron AIX 200/4 reactor. The growth temperature and V/III was
550℃ and 5 for tunnel junction and 650℃ and ~100 for other layers, respectively. The wafer
orientation was (100) 2°-off toward (111)B. Two MLs of GaAs under high V/III ratio was
introduced to enhance the surface morphology and it was effective when V/III was over 10 as
illustrated in Fig 1. Next, GaInP/GaAs dual-junction solar cells was grown and fabricated to
qualifying the modified GCS. The efficiency of the solar cells was enhanced as shown in Fig.
2. When V/III was 50 for 2 MLs buffer, the surface was mirror-like and the efficiency was
27.2% under AM1.5G 1 sun.
M-P-021
Efficient piezoelectric generator based on GaN p-n junction
Jin-Ho Kang1, Dae Kyung Jeong1, Jun-Seok Ha2, and Sang-Wan Ryu1,*
1
Deparment of Physics, Chonnam National University, Gwangju 500-757, Republic of Korea
Optoelectronics Convergence Research Center, Chonnam National University, Gwangju 500-757, Republic of
Korea
* E-mail address: sangwan@chonnam.ac.kr
2
Due to extensive attention for wireless portable electric devices, energy harvesting from the
environment has attracted considerable attention. Recently piezoelectric generators (PGs) have
emerged as promising energy harvester which can produce electric energy from vibrational and
mechanical energy sources. Various piezoelectric materials including ZnO, GaN and lead
zirconate titanate (PZT) have been applied to PGs. However, the low output current and
poisonous lead have limited the integration of these materials and human-related applications.
Despite of low piezoelectric coefficients, the material properties of GaN such as non-toxicity
and good thermal stability have led to the promising candidate for NG.
Unintentionally doped GaN (u-GaN) exhibits n-type conductivity with typical free carrier
concentrations of 1×1016 – 1×1017 cm-3 and electron mobility of about 440 cm2V-1s-1 due to the
native defects in GaN. These defects play a role in the screening effect and degradation of
Schottky barrier formation at the interfaces between metal electrodes and GaN, which
contributes to extraction of generated piezoelectric energy. Free carriers screen the
piezoelectric potential under mechanical deformation, resulting in degradation of piezoelectric
potential-induced power output. Therefore, it is essential to suppress the screening effect by
decreasing the electrical conductivity of GaN and to establish more reliable Schottky rectifying
barriers for preventing leakage current. P-n junction structure is a possible way to improve the
piezoelectric performance via suppressed screening effect and formation of space charge region
at the junction.
In this work, we realized the high efficiency PG based on p-n junction-structured GaN thin
film. The maximum output voltage and current peaks of the GaN thin film PG reached values
up to 3.2 V and 390 nA, respectively. The high piezoelectric performance is believed to be
originated from the formation of p-n junction, which acts as a rectifying barrier. Furthermore,
the suppression of screening effect caused by conductivity-modulated doping may play an
important rule in the enhancement of output power.
Fig. 1. (a) Schematic presentation of a GaN-based PG. (b) Piezoelectric output voltage and (c) current measured
from a GaN-based PG under normal compressive stress.
M-P-022 [NO SHOW]
In Situ Passivated SiN/AlN/GaN Heterostructures
Grown By Ammonia MBE For Normally-Off Transistors
Konstantin Sergeevich ZHURAVLEV1, Timur Valerievich MALIN1, Vladimir Gennadievich
MANSUROV1, Oleg Evgenievich TERESHENKO1, Valerii Evgenievich ZEMLYAKOV2*,
Vladimir Ilich EGORKIN2, Yakov Mikchailovich PARNES3, Vladimir Gennadievich
TIKHOMIROV3
1
Rzhanov Institute of Semiconductor Physics of Russian Academy of Sciences, Novosibirsk, Russian Federation
2
National Research University of Electronic Technology «MIET», Zelenograd, Moscow, Russian Federation
3
CJSC “ Svetlana-Electronpribor”, Saint Petersburg, Russian Federation
* E-mail address: vzml@rambler.ru
AlN/GaN high electron mobility transistors (HEMTs) have evolved as the most promising for high
frequency and power switching and amplification because of high two-dimensional electron gas (2DEG)
densities and large breakdown electric field. AlN/GaN is considered as an ideal candidate for the
realization of normally-off (E-mode) devices since due to a thin barrier it is easy to deplete the channel.
The technology of AlN/GaN HEMT is not yet fully mature, some issues related to long-term memory
effects due to the presence of traps on the surface and inside the device structure are still present. Si3N4
dielectric film is one of most promising passivation materials in AlN/GaN heterostructures.
In the present work an ammonia MBE technology of in situ passivated SiN/AlN/GaN
heterostructures with thin AlN barrier has been developed. The heterostructures consisted of 5 nm AlN
barrier layer, 1.5 µm GaN buffer and 300 nm AlN nucleation layer on an (001)-oriented sapphire
substrate. The Si3N4 dielectric film was deposited at 800 ºC immediately following the AlN barrier layer
growth in the same MBE chamber. Ammonia and silane were used as precursors. The formation of
Si3N4 film was monitored in situ by reflection high electron energy diffraction (RHEED) and ex situ by
X-ray photoelectron spectroscopy (XPS) methods. The (2×2) structure was observed by RHEED on the
initial AlN(0001) surface. The deposition of Si3N4 film causes the appearance in series the (√3×√3)R30°
and (1×1) structures. Finally Si3N4 film becomes amorphous. The N1s и Al2p XPS peaks shift with the
increase of the Si3N4 film thickness because of the decrease of surface band bending due to passivation
of surface states. The analysis of XPS spectra allows to estimate the final thickness of Si3N4 film as 1
nm. A Hall measurement yielded a mobility of 1200 cm2/V s at room temperature with a sheet carrier
density of 1.1×1013 cm−2.
Enhancement-mode HEMTs with a 0.6-μm gate length were fabricated without any post growth
treatments of heterostructures. DC and small signal RF characteristics were measured on these devices.
The HEMTs exhibit a maximum drain current of 1 A/mm, a saturation voltage of 1 V, a maximum
transconductance of 350 mS/mm, a breakdown voltage of 60 V. Pulsed volt-ampere characteristics were
measured for devices biased at different quiescent bias points defined by gate and drain bias voltages
in order to test traps in different regions of the devices. The gate lag and drain lag effects are negligibly
small (<2%) for these transistors because of successful passivation of surface states and the low density
of traps inside heterostructures. The device exhibited the small signal unity current gain, ft of 13 GHz
and the maximum oscillation frequency, fmax of 32 GHz extrapolated from the frequency dependences
of short circuit current gain and maximum stable gain, respectively. These RF performances can be
further improved by the shortening of gate length and the optimization of the device fabrication such as
better ohmic contact formation and gate metallization process.
M-P-023
GaN piezoelectric nanogenerator by a NiO-GaN p-n junction formation
Dae Kyung jeong1, Jin-Ho Kang1, Jun-Seok Ha2, and Sang Wan Ryu1,2*
2
1
Deparment of Physics, Chonnam National University, Gwanju, 500-757, South Korea
Optoelectronics Convergence Research Center, Chonnam National University, Gwanju, 500-757, South Korea
* E-mail address: sanwan@chonnam.ac.kr
With the extensive use of various wireless sensors and portable electronic devices, energy
harvesting from the environment has attracted considerable attention. Piezoelectric
nanogenerators (p-NGs) have been proposed for producing electric energy from vibration and
mechanical energy sources. Therefore, piezoelectric materials such as lead zirconate titanate
(PZT), ZnO and GaN have great potential for sustainable operation of wireless electronic
devices. Among the available piezoelectric materials, PZT is the best material to achieve high
output voltage due to its outstanding piezoelectric coefficients [1]. However, the low output
current and poisonous lead have limited the integration of these materials and human-related
applications. Despite of low piezoelectric coefficients, the material properties of GaN such as
non-toxicity and good thermal stability have led to the promising candidate for NG.
In this work, we fabricated high efficiency GaN NG with a NiO-GaN p-n junction. Nanoporous
(NP) GaN for active element was fabricated by electrochemical etching and then NiO layer
was formed by RF sputter using NiO target at room temperature. Nickel (Ni)/ gold (Au) and
Indium (In) were used as bottom and top electrode material, respectively. Piezoelectric output
power was measured by a potentiometer (PARSTAT 4000/Potentiostat/Galvanostat/ELS
Analyzer) while straining devices.
Two piezoelectric thin film generators as reference and p-NG based on NiO-NP GaN junction
were fabricated. For one device (device A), Ni plays an important role in the enhancement of
piezoelectric output power due to the formation of Schottky barrier between metal and u-GaN
layer. On the other hand, for other device (device B) Ohmic contact was formed between Ni
and NiO after the additional annealing step for metallization. P-n junction acts as a reliable
Schottky rectifying barrier, leading to the enhancement of piezoelectric output power. In this
design, device A shows AC output voltage around 10 mV when cyclic stresses were applied to
device. On the other hand, the output voltage of device B was increased by about 260-fold
compared to device A. the enhancement was caused by p-n junction structure. P-n junction
reduced the free carrier more than Schottky junction, resulting in high degree of carrier
screening suppression. In addition, p-n junction prevented the leakage current through the
interface, which screen piezoelectric potential, more effectively than Schottky contact in device
A.
References
1. Y. Jeon, R. Sood, J. Jeong and S. Kim, Sens. Act. A-Phys, Vol. 122, pp 16-22(2005)
M-P-024
Oxidized digital alloy Al0.98Ga0.02As/GaAs distributed Bragg reflectors
Gun Wu Ju1, Subin Lee2, Byung Hoon Na3 and Yong Tak Lee1*
1
School of Information and Communications, Gwangju Institute of Science and Technology,
Gwangju 61005, Republic of Korea
2
Advanced Photonics Research Institute, Gwangju Institute of Science and Technology,
Gwangju 61005, Republic of Korea
3
Device Laboratory, Samsung Advanced Institute of Technology,
Suwon 16678, Republic of Korea
E-mail : ytlee@gist.ac.kr
High and broadband reflecting distributed Bragg reflectors (DBRs) are essential to improve the
performance of various optical devices, such as semiconductor lasers and photodetectors. To produce
DBRs of high and broadband reflection properties, high refractive index contrast is required. wet
thermally oxidized AlGaAs material has low refractive index (n~1.6) compared to that of GaAs (n~3.5).
Previously, ultra-low threshold VCSEL using oxidized AlAs (AlxOy) and GaAs DBRs were reported
[1]. However, AlAs bulk layer could shrunk after oxidation because of poor mechanical strength.
In this paper, we grew the digital alloy Al0.98Ga0.02As / GaAs DBRs with 2, 4, 6 pairs by DCA P600
MBE. The smaple was exposed in an inert gas within an elevated temperature of 420oC. As a result, we
obtained the relatively stable oxidation rate, more mechanically stable layers, and realization of a highly
reflective and broad stop band DBRs. The oxidized digital alloy DBR 6 pairs showed a peak reflectivity
of 99.98% near 980 nm and a stop band width of 526 nm.
(a)
(b)
GaAs
GaAs 1ML
Oxidized
Bulk-alloys AlAs
Oxidized
Digital-alloys
Al0.98Ga0.02As
AlAs 49ML
…
GaAs
x 10 periods
…
…
69.6 nm
69.6 nm
153.1 nm
153.1 nm
GaAs substrate
GaAs substrate
Figure 4 Schematics of (a) bulk alloy and (b) digital
alloy DBR.
Figure 5 Reflectivity of (a) bulk ally and (b)
digital alloy DBR
[1] I. Suarez et al., “Optimal control of AlAs oxidation via digital alloy heterostructure compositions,”
J. Phys. D: Appl. Phys. 42, 1 (2009).
M-P-025
Internal electric fields due to piezoelectric and spontaneous polarizations in
ZnO/ZnOS quantum well
H. C. Jeon1, S. H. Park2, T. W. Kang1, and S. J. Lee1,*
1
Quantum-functional Semiconductor Research Center, Dongguk University, Seoul, 04620, Korea
Department of Electronics Engineering, Catholic University of Daegu Kyeongbuk, 38430, Korea
* E-mail address: leesj@dongguk.edu
2
Wide band-gap wurtzite semiconductors have attracted much attention due to their potential
applications for optoelectronic devices in blue and ultraviolet regions. So far, practical shortwavelength light-emitting diodes or laser diodes have been fabricated using GaN-related
materials. On the other hand, ZnO and related oxides have been proposed as alternative wide
band-gap semiconductors for short-wavelength optoelectronic applications. ZnO-based
quantum well(QW) structures and their properties are of increasing interest for possible
applications in light-emitting diodes (LEDs) and laser diodes (LDs) operating in the visible and
ultraviolet region, owing to their direct wide band gap (Eg ~ 3.4-3.8 eV) and large binding
energy of excitons (60 meV). In order to design ZnO based optoelectronic devices, quantum
confined structures are essential, which necessitate the modification of the band structure by
alloying. In this regard, a change of the content of the anions or cations in ZnS by introducing
the isoelectronic impurities is important in terms of a band-gap engineering.
Numerous works have been reported related to ZnMgO, ZnBeO and ZnCdO, which modify
the band gap clearly toward higher and lower energies, respectively. However, fewer attentions
have been paid to anions alloying such as S and Se in ZnO, which are also important from the
viewpoint of band gap engineering. On the theoretical side, the above experimental result
suggest that an understanding of the roles of internal electric fields due to piezoelectric (PZ)
and spontaneous (SP) polarizations in wurtzite ZnO-based QW structures is very important in
order to give guidelines on sample growth and a device design. For these results, we investigate
electronic and optical properties of ZnO/ZnOS QW structures numerically with SP and PZ
polarizations by considering many-body effects. The strain-induced piezoelectric polarization
and the spontaneous polarization can be reduced effectively using by the internal field
engineering in the ZnO/ZnOS QW structures. That is, optical properties of ZnO/ZnOS QW
structures resulting in the increased optical gain the fact that the QW potential is flattened as a
result of the compensation of the internal field. We got very high laser gain spectrum compare
with that of without considering droop prevention.
References
1. T. Makino, K. Tamura, C. H. Chia, Y. Segawa, M. Kawasaki, A. Ohtomo, and H. Koinuma,
Appl. Phys. Lett. 81, 2355 (2002).
M-P-026
The two-dimensional electron gas mobility in AlGaAs/InGaAs/AlGaAs
heterostructures with donor-acceptor doping
D.Yu. Protasov‡§, D.V. Gulyaev‡, A.M. Gilinsky‡,
A.K. Bakarov‡, A.I. Toropov‡ and K.S. Zhuravlev‡†
‡
Rzhanov Institute of Semiconductor Physics, Siberian Branch of Russian Academy of Sciences, 13, Lavrentiev
avenue, Novosibirsk, Russia, 630090, e-mail: protasov@isp.nsc.ru
§
Novosibirsk State Technical University, 20, K.Marx avenue, Novosibirsk, Russia, 630073
†
Novosibirsk State University, 2, Pirogov street, Novosibirsk, Russia, 630090
Recently we proposed to increase the effective depth of quantum well (QW) in
AlGaAs/InGaAs/AlGaAs heterostructures by modulation doping of QW's barriers by donors and
acceptors, leading to a 50% output power density increase of pseudomorphic high electron mobility
transistors with donor-acceptor doping (DA-pHEMTs) [1]. However, the electron mobility in DApHEMT heterostructures is reduced by scattering by ionized donors from broadened δ-layers [2].
In the present work we propose to split the δ-layers from every side of QW into two δ-sublayers
with the total donor density in the δ-sublayers nearest to the QW being equal to the 2DEG density.
The calculation of low-field 2DEG mobility which takes into account the scattering by ionized
donors and acceptors, acoustic phonons, alloy disorder and interface roughness in the framework
of a two-subband transport model shows the enhancement of low-temperature mobility by 12%
and 25% for 1 nm and 2 nm δ-layer splitting, respectively. These results were confirmed by the
experimental data.
Electron drift velocity in DA-pHEMTs as a function of electric field was obtained up to about 10
kV/cm from submicrosecond-pulsed current-voltage measurements. It was found that the drift
velocity in DA-pHEMTs is by 30% greater than that in an ordinary pHEMT. An
electroluminescence (EL) study of DA-pHEMTs shows that hot electrons populate the first and
second subbands, whereas the EL from QW’s barriers was not found. The data obtained evidence
the suppression of the real space transfer effect in DA-pHEMTs.
References
[1] V. M. Lukashin, A. B. Pashkovskii, K. S. Zhuravlev et al., Technical Physics Letters, 38(9), pp.
819-821 (2012).
[2] D. V. Gulyaev, K. S. Zhuravlev, A. K. Bakarov et al., J. Phys. D: Appl. Phys., 49(9), 095108
(2016).
M-P-027
Novel defect-related luminescence in InAlAs
grown by molecular beam epitaxy
A.M.Gilinsky, D.V.Dmitriev, A.I.Toropov, and K.S.Zhuravlev
A.V.Rzhanov Institute of Semiconductor Physics, 630090 Novosibirsk, Russia
We report the observation of a novel luminescence in InAlAs grown on InP that is related to defects
in the material, and discuss ways of improving the quality of the material. The InAlAs alloy latticematched to InP has been recently proposed for implementation of the carrier multiplication layer
in high-sensitivity InGaAs/InP-based avalanche photodiodes, promising improved temperature
characteristics and reduced noise level. In practice the achieved device characteristics remain rather
far from the expectation, presumably due to the deep levels in the InAlAs layer, which makes
investigation of the role deep levels play in this material crucial. The samples studied here were
grown on semi-insulating (100) InP substrates by molecular beam epitaxy at various substrate
temperatures and constituent fluxes. As we have found, samples grown under standard conditions
demonstrate a novel long-wavelength photoluminescence (PL) band below the near-band edge
transition (see Fig.1). The novel band is observed in the PL spectra in the intermediate temperature
range 60–160 K only. We consider the dependencies of the long-wavelength PL on temperature and
excitation power and its behavior under transient excitation, and conclude that the novel band in
the PL spectra of InAlAs is caused by defect contents in the layers. We show that by using the
growth regimes that approach the quasi-stoichiometric ones on the growth surface we were able to
grow layers which showed very low intensity of the defect-related PL and a high luminescence
efficiency that is by 1–2 orders of magnitude greater than that in the samples grown under standard
conditions.
hν (eV)
106
1.60
1.50
1.40
1.30
C
3 W/cm2
shallow impurity-related
105
Intensity
A
B
defect-related
104
InP
103
102
750
800
850
900
λ (nm)
950
1000
Fig.1. PL spectra of samples grown in standard (curves A and B) and in optimized (curve C) growth
conditions. The spectra were taken at temperatures of 86 K (sample A), 62 K (sample B) and 70 K
(sample C). The dominating bands correspond to band-to-shallow impurity and inter-impurity
(donor-acceptor) transitions. The long-wavelength part of spectrum B below the bandgap energy
of InP substrate (1.42 eV) is affected by interference.
M-P-028
Morphology Effect of TiO2 photoelectrodes in perovskite-sensitized solar
cells
Kang-Pil Kim*, Dae-Kue Hwang, and Shi-Joon Sung
Convergence Research Center for Solar Energy, DGIST, Daegu 711-873, South Korea
* E-mail address: kkp@dgist.ac.kr
Solid-state sensitized solar cells have received increased interest as promising avenues
affording cost-effective high-efficiency solar power conversion. Many materials have been
extensively researched for their use in nanostructured devices. However, achieving highly
efficient thin-film solar cells remains a challenge. Among many materials that can be used as
an absorber in these cells, CH3NH3PbI3 perovskite nanocrystals have recently attracted much
attention as a new class of light harvesters for fabricating high-efficiency nanostructured
devices. The perovskite solar cells use inorganic–organic perovskite compounds as light
harvesters on mesoporous TiO2 electrodes along with hole-transport materials. In this work,
we have studied the morphology effect of the TiO2 photoelectrodes in perovskite solar cells
according to the different TiO2 electrode structures. We have fabricated the perovskitesensitized solar cells using CH3NH3PbI3 as a light absorber and PTAA as a hole conductor on
the surface of TiO2 electrodes. We adopted a two-step deposition process to prepare the
CH3NH3PbI3 layer. In a two-step deposition process, the spin-coated PbI2 layers were
converted to the CH3NH3PbI3 layers on exposure to a CH3NH3I/2-propanol solution. The
perovskite-sensitized solar cell with the mesoporous TiO2 electrode has shown a better
efficiency than those with the planar and electrospun TiO2 electrodes.
M-P-029
The effect of Surface Modification on LiNi0.801Co0.110Mn0.089O2
cathode material by sugar coating
Ji-Woong Shin, Mi-ra Shin, Jong-Tae Son*
Department of Nano Polymer Science & Engineering, Korea National University of
Transportation, Chungju, Chungbuk, 380-702, Korea
E-mail : jt1234@ut.ac.kr
Abstract
Recently, LiNi1-x-yCoxMnyO2 cathode materials have attracted much attention due to their
relatively low cost and high capacity. However, they were very unstable due to CO2, H2O
absorption and suffered from low capacity. X-ray diffraction (XRD) analysis show that
reduction of Ni3+ to Ni2+ and the formation of Li2CO3 and LiOH for LiNi0.801Co0.110Mn0.089O2
sample after CO2, H2O exposure.[1] In this study, we were coated sugar in cathode material so
as to do reduce Li2CO3 and LiOH and up to improve electrochemical performance. The sugarcoated LiNi0.801Co0.110Mn0.089O2 was characterized transmission electronic microscopy (TEM),
scanning electronic microscopy (SEM) and atomic force microscopy (AFM). Result show that
LiOH reduced than pristine cathode material and coated electrode exhibited high discharge
capacity of 191.75 mAhg-1 at 0.1C (17mAg-1) than bare electrode (163.04 mAhg-1). In addition,
impedance property of sugar coated cathode material is considerably increased.
Keyword: cathode material, sugar coating
References
[1] K.Shizuka, C.Kiyohara, K. Shima, Y.Takeda,
J.Power Sources 166 (2007) 233-238
Acknowledgement
This was supported by Korea National University of Transportation in 2016 and the granted financial
resource from the Ministry of Trade program of the Industry & Energy, Republic of Korea
(G02N03620000901)
M-P-030 [NO SHOW]
Influence of temperature of AlN buffer layer deposition on crystallinity of
GaN,
Shuichi Emura
M-P-031 [NO SHOW]
Optical properties of WO3 powders synthesized by hydrothermal methods
Su-Min Park1, Sung-Myung Yoo1, and Chung-hee Nam1*
1
Department of Photonics and Sensors, Hannam University, Daejeon, Republic of Korea
* chnam@hnu.ac.kr
WO3 materials have much attention due to their various engineering applications such as,
photo-catalyst, electrochromic or photochromic devices, and gas-sensors. Polycrystalline WO3
powder samples have been fabricated by hydrothermal methods at different conditions such as
working temperature, pH, and hydrothermal time [1]. Sodium tungstate solution was dissolved
in deionized water and the HCl was added to the solution followed by stirring at room
temperature. The solution were heated from 80 oC ~ 180 oC for 12 ~ 48 hours in a stirred
autoclave. Finally, the samples were dried in the oven at 50 oC. The optical and SEM images
were seen in the Fig. 1. The morphology and the shape of the samples are dependent on the pH
of the solution, hydrothermal temperature, and the time, as shown in Fig. 1. The nanorod
structures are shown at the condition of pH = 2.0 and lower hydrothermal processing time at
120 oC. The structure properties were characterized by XRD measurements in Fig. 2. The
detailed results of photo-catalytic and optical properties will be presented at the conference.
References
1. C.H. Lu, M. H. Hon, C.Y. Kuan, and I.C. Leu, Jpn. J. Appl. phys. 53, 06JG08(2014)
M-P-032
Self-powered reaction based cysteine sensor and its application for sensing
in urine sample
Sophia Selvarajan1, Nagamalleswara Rao Alluri 2, Arunkumar Chandrasekhar 3,
Sang-Jae Kim1-3,*
1
Department of Advanced Convergence Technology and Science,
2
Department of Mechanical Engineering,
3
Department of Mechatronics Engineering,
Nanomaterial and System Lab, Jeju National University, Jeju-690756, South Korea
*Corresponding author: kimsangj@jejunu.ac.kr
Abstract
Cysteine, an essential amino acid having prominent role in physiological process inside
living organisms has to be maintained properly which otherwise leads to diseases such as
psoriasis, rheumatoid arthritis, parkinson’s disease, alzheimer’s disease, and adverse pregnancy
etc. In our present work, facile fabrication of cysteine responsive film based sensor has been
reported for the first time. NH2 functionalized BaTiO3 nanoparticles suspended in a 3D matrix
of agarose film serves as the sensing element for cysteine detection. The change in surface
charge properties of the film with respect to cysteine concentrations were determined using IV technique. With increase in cysteine concentrations the current response increased in a linear
fashion (linear concentration range is 10µM to 1mM). Self-powered cysteine sensor was
demonstrated by integrating the sensor to a nanogenerator (agarose- BaTiO3 nanoparticles)
whose output voltage was used for driving the sensor. The voltage across the sensor was
measured as a function of different cysteine concentrations. Real time analysis was performed
using urine samples. The proposed sensor has good selectivity and detection limits down to
143nM.
Acknowledgment
This work was supported by the National Research Foundation of Korea (NRF) funded by the
Korea Government GRANT (2013R1A2A2A01068926, 2013R1A1A2064471), and by the
Jeju Sea Grant College Program 2016 Funded by the Ministry of Oceans and Fisheries (MOF),
Korea.
M-P-033
Semi-empirical Analysis for Nano-mechanical Properties
Soyeun Park*
College of Pharmacy, Keimyung University, Daegu 42601, Republic of Korea
* E-mail address: sypark20@gmail.com
Mechanical properties of materials such as polymers, biological cells, and tissues have
gained a special attention. The AFM-based force-distance (f-d) curves were the most widely
used tool to determine mechanical properties of materials on nanoscale. The f-d curves fitted
with the elastic continuum theory assuming the small indentation on thick samples such as the
Hertz model yield the elastic modulus of samples with a reasonably acceptable precision.
However, there is still a challenge to determine mechanical properties of double thin layers due
to the high deformation and the hard substrate effect. In this study, we have utilized the semiempirical model modified from the Hertz model to determine the Young’s moduli of double
thin layers. The hyperbolic fit was applied to f-d curves obtained from polymeric nano-brushes
grafted from nano-patterns. We found that the obtained elastic moduli are close to those of
homogeneous thick polymer films determined from the Hertz model. This result suggest that
the semi-empirical analysis could be effective to provide us with accurate Young’s moduli of
Double thin layers [1].
References
1. S. Silbernagl and B. Cappella. Scanning. 32, 282-293 (2010).
M-P-034 [NO SHOW]
Characteristics of carbon nanotubes fabricated by ink-jet printing
method for counter electrode in dye-sensitized solar cell
Yong Seob Park1,*, Nam-Hun Kim2, and Jaehyeong Lee3
1
Department of Photoelectronics, Chosun College of Science and Technology, Gwangju 61453, Korea
2
Department of Electrical Engineering, Chosun University, Gwangju 61452, Korea
3
School of Information and Communication Engineering, Sungkyunkwan University, Suwon 16419, Korea
*E-mail : yongspark@cst.ac.kr
We fabricated the carbon nanotube (CNT) films for counter electrodes in dye-sensitized solar
cell by using an ink-jet printing method and investigated the electrical, optical, structural and,
physical properties of the CNT films with various thicknesses. It was found that the optimized
condition of the CNT films fabricated on glass substrates significantly depends on its thickness
because the sheet resistance and optical transmittance critically were affected by amount of
number of CNT layers. Ink-jet printed CNT layers were used in counter electrode and all of
counter electrodes prepared on FTO glasses. Also, dye-sensitized solar cell (DSSC) using inkjet printed CNT counter electrodes were fabricated and its performance was measured by solar
simulator. We investigated DSSC fabricated with the ink-jet printed CNT counter electrode
provided good performance in the DSSCs. Consequently, the performance of the DSSC was
determined by the conductivity of the CNT film.
Keywords: carbon nanotube (CNT), ink-jet printing, transparent, resistivity, dye-sensitized
solar cell (DSSC)
M-P-035
Complex Refractive Index Measurement of DNA Materials via
Kramers-Kronig Analysis
Taek Sun Jung, Taewoo Ha, Kyung Ik Sim, Howon Lee, Byung-joo Kong, Kyunghwan Oh
and Jae Hoon Kim
Department of Physics, Yonsei University 50 Yonsei-ro, Seodaemun-gu, Seoul 03722, Republic of Korea
Abstract
We retrieved the phase information of the far-infrared transmission spectra of various DNA
materials by Kramers-Kronig relation. We then applied a linear-frequency compensation to fit
the spectra to the measured phase. From the complex transmission, we also obtain complex
refractive index through non-linear fitting. Even when the phase information is given in the
narrow terahertz spectral region, we can recover the complex refractive index in the far infrared
region from the power transmission alone by anchored Kramers-Kronig analysis.
M-P-036
Structural properties and local density of states in metal-to-insulatortransition VO2 and Ti2O3
Sang-Wook Han*, In-Hui Hwang, Zhenlan Jin, and Chang-In Park
Department of Physics Education and Institute of Fusion Science, Jeonbuk National University, Jeonju 54869,
Korea
*
E-mail: shan@jbnu.ac.kr
VO2 and Ti2O3 are typical metal-insulator-transition(MIT) materials and are known that they
have different origins of the MIT. Ti2O3 is often mentioned as a Mott transition, whereas the
MIT of VO2 is induced by a first order structural transition. However, recent studies on VO2
showed that the structural change many not induce the MIT. Mott proposed that impurity bands
in corundum-symmetry Ti2O3 at high temperatures caused a collapse in the bandgap. However,
the origin of the impurity bands has not yet been clarified. We examine the local structural
properties of metal-to-insulator-transition VO2 and Ti2O3 using in-situ x-ray absorption fine
structure(XAFS) measurements at the V and Ti K edges in the temperature range from 290 to
750 K. XAFS measurements revealed a local structural transition in the films from the
monoclinic(M1) to the rutile(R) phase at ~70°C during their heating; further, temperaturedependent resistance measurements showed a sharp MIT in the films at ~75°C. Extended
XAFS (EXAFS) measurements revealed non-rigid changes of V–O and V–V bond lengths
from the M1 to the R phase via the M2 phase. In-situ EXAFS and R–T measurements showed
that the synthesized VO2 films acted as Mott insulators and that their electrical property change
was not proportional to their structural property change at their MIT temperature. ExtendedXAFS measurements on Ti2O3 reveals a zigzag patterned Ti position and an anomalous
structural disorder in Ti-Ti pairs, accompanied by a bond length expansion of the Ti-Ti pairs
along the c-axis for T > 450 K. The local structural distortion and disorder of the Ti atoms
would induce impurity levels in the band gap between the Ti 3d a1g and egπ bands, resulting in
a collapse of the band gap for T > 450 K. We will discuss the MIT origin of VO2 comparing
with that of Ti2O3 in detail.
M-P-037
High crystallized perovskite solar cell using copper oxide and
ZnO nanorods as carrier transport layers
Hyeon Jun Jeong1, Hyang Mi Yu1, Hong-Sik Kim2, Abdullah Mamun3, Namkoong Gon3*,
Mun Seok Jeong1*
1Center
for Integrated Nanostructure Physics (CINAP), Institute for Basic Science (IBS), Sungkyunkwan University, Suwon
440-746, Republic of Korea
2Photoelectric
and Energy Device Application Lab (PEDAL) and Department of Electrical Engineering,Incheon National
University, 119 Academy Rd. Yeonsu, Incheon 406772, South Korea
3Department
of Electrical and Computer Engineering, Old Dominion University, Applied Research Center, 12050
Jefferson Avenue, Newport News, VA 23606, USA.
Perovskite solar cells are one of most exciting green energy technologies due to superior
characteristics including ideal energy bandgap, strong light absorption, and long charge
diffusion length [1]. During the past few years, the energy conversion efficiency of perovskite
solar cells continuously increased. However, there is still room for improvement incuding the
optimized photon absorbing layers and facilitated electron (hole) transport layers. Particularly,
the ZnO nanorods have been utilized as an electron transport layer (ETL) because of high
mobility, low recombination loss and easy doping [2,3]. However, due to crystal mismatches
between ZnO nanorods and perovskite, it is very difficult to directly grow a high quality of
perovskites on ZnO nanorods [2,3,4]. In this research, perovskite absorber layers were grown
on ZnO nanorods using various approaches including conventional one-step, two-step
processes, and a hot-casting approach while scanning electron microscope (SEM), energydispersive X-ray spectroscopy (EDS), and UV-VIS measurements were performed. Based SEM
and EDS measurements, as shown in Figure 1, it is found that perovskite absorbers were indeed
grown on ZnO narnods using a hot-casting process as one-step approach. It should be noted
that conventional one-step approach does not allow for directly grow perovskite on ZnO
nanorods due to crystal mismatches between ZnO and perovskites. It is well known that a hotcasting method facilitates the thermal energy to form large grains of perovskites during the
spin-casting process, in which the glass slide was heated at near or higher temperature than the
boiling temperature of DMF solvent (153°C) [5]. Therefore, it is conceived that a hot-casting
process facilitated the crystalline process at a higher temperature which allows for overcoming
a mismatch of the ZnO nanorods and perovskite structure. We will further discuss the
comparisions of various approaches, resulting chemistries and crystalline morphologies, and
so on. In addition, copper oxide (CuO, Cu2O) as a hole transporting layer (HTL) as a promising
a hole transport layer (HTL) was investigated and will be further discussed in detail.
[1] Samuel D. Stranks et al., Science 342, 341 (2013).
[2] Khalid Mahmood et al., Advanced Energy Materials 5, 1500568 (2015).
[3] Juan Dong et al., Chem. Commun. 50, 13381 (2014)
[4] Dongqin Bi et al., ACS appl. Mater. Interfaces 6, 18751 (2014).
[5] Wanyi Nie et al., Science 347, 522 (2015).
Element
Wt%
At%
C
4.83
21.64
N
0.74
2.85
O
6.27
21.11
Pb
20.44
5.31
Cl
2.67
4.06
I
20
8.49
Zn
25.89
21.33
Figure 1. SEM image and EDS measurement of hot casting process on ZnO nanorods.
M-P-038 [NO SHOW]
Highly sensitive ppb-level detection of gas molecules using patterned
porous channels of ITO nanoparticles
Jonghyurk Park1,*, Dong-Jin Lee2, Hochan Chang2 and Byung-Yang Lee2,*
1
ICT materials and devices research laboratory, ETRI, Deaejo 305-700, Korea
School of Mechanical Engineerring, Korea University, Seoul 136-713, Korea
* E-mail address: eureka99@etri.re.kr, blee@korea.ac.kr
2
Indium tin oxide is widely utilized as a transparent conducting electrode and its
nanostructure are promising to act as low temperature process compatible
semiconducting/metallic material which can be an important ingredient for smart flexible
applications like wearable/mobile electronics. Hence, we demonstrate the easy fabrication of
ITO nanoparticle-based gas sensing channel without any further annealing treatment. The gassensing channel was made of micro-patterned porous thin ITO film via self-assembly of ITO
nanoparticles on the given substrate. The ITO NP channels were formed by dipping a
molecularly patterned solid substrate into an ITO NP suspension and then pulling it vertically
at a precisely controlled speed. The ITO NPs were self-assembled on the intended regions with
high definition, as the NPs were selectively adsorbed on the polar SiO2 regions avoiding the
non-polar regions. The thickness of the assembled ITO NP patterns could be modulated by
controlling the pulling speed. The NPs formed a dense percolated network through which
current could flow without any post-treatment such as heat annealing. Finally forming metal
electrodes on top of the assembled ITO NP patterns, we realized a simple sensing device for
the detection of gas molecules like NO2 and NH3. The sensor showed a highly sensitive
detection of NH3 and NO2 gas down to some ppb-level at the moderate temperature.
Furthermore, the sensor can be easily modified by coating some catalysts on micro-patterned
porous ITO NP channels to enhance the sensitivity and selectivity of various gas molecules
which is confirmed by an opposite response behavior to reducing NH3 and oxidizing NO2.
References
1. Lee Dong-Jin, Park J.-H., Chang H.-C. Jin J.-H. and Lee B.-Y., Highly Selective sub-ppm
detection of NH3 gas using patterned porous channel of ITO nanoparticles via self-assembly,
Sensors and Actuators B, 216, 482 (2015)
2. Lee Dong-Jin, Heo Kwang, Lee Hyungwoo, Chang Hochan, and Lee Byung Yang,
Selective adsorption of metal nanowires on molecularly patterned substrates using surfaceto-volume ratio-dependent strategies, Applied Physics Express, 7, 115001 (2014)
3. Huh Junghwan, J. Park, J.-Y. Park and G.-T. Kim, Highly sensitive hydrogen detection of
catalyst-free ZnO nanorod networks suspended by lithography-assisted growth,
Nanotechnology, 22, 085502 (2011)
M-P-039
Carrier Dynamics Study of Dopant Level Manipulated Ba1-xLaxSnO3
Probed by Terahertz-Infrared Spectroscopy
Taewoo Ha*, Useong Kim†, Chulkwon Park†, Kyung Ik Sim*, Kookrin Char† and Jae Hoon
Kim*
†
* Department of Physics, Yonsei University, Seoul 03722, Republic of Korea
Center for Strongly Correlated Materials Research, Department of Physics and Astronomy, Seoul National
University, Seoul 08826, Republic of Korea
We have investigated the transport properties of La-doped BaSnO3 (Ba1-xLaxSnO3) thin films
with x = 0−0.06, epitaxially grown on SrTiO3 (001) substrates. The materials represent an
emerging class of transparent conducting oxides (TCOs) with a cubic perovskite structure[1,
2]. We performed the terahertz-infrared spectroscopy and Hall measurements, obtaining
comprehensive information on the dynamical properties over the optical and electronic regimes.
Both experimental data are remarkably consistent for all the series samples, providing the
reliable free-carrier parameters such as the effective mass, scattering rate, and mobility.
Especially, the free carriers in the 4% La-doped sample exhibit the highest mobility reaching
up to 60 cm2/V∙s. This unique behavior can be explained with the simultaneous presence of
threading dislocations, grain boundaries, and ionized impurities, all of which provide
independent scattering mechanisms of the free carriers. This study paves the way for
demonstrating optoelectronics and solar cell devices based on perovskite transparent
conducting oxides.
Figure 6 The Drude model fit results for (a) the real part conductivity (σ1) of Ba1-xLaxSnO3 (x = 0 − 0.06) by
THz-TDS and FTIR-SE. The Drude model fit was used with reliable optical conductivities which were obtained
by THz-TDS range from 3 cm-1 to 10 cm-1 and FTIR-SE range from 600 cm-1 to 3000 cm-1.small. b)
Comparison for BLSO (x = 0.01 − 0.06) of the mobility (μ) determined by Hall measurements (green squares)
and by optical measurements (red circles). The inserted graph in (c) cm2V-1s-1 depicts the trend of scattering time
(τ) versus dopants levels of BLSO in good agreement with the trend of electron mobility.
References
[1] Hyung Joon Kim et al., Applied Physics Express 5, 061102 (2012).
M-P-040
Enhanced Gas Sensing Performance of Palladium and Indium-Codoped
Zinc Oxide Thin Film Gas Sensors
Hyejoon KHEEL1, Gun-Joo SUN1, Tae Kyung KO1, Sangmin LEE2, and Chongmu LEE1,*
1
Deparment of Materials Science and Engineering, Inha University, 253 Yonghyun-dong, Nam-gu, Incheon 402751, Republic of Korea
2
Deparment of Electronic Engineering, Inha University, 253 Yonghyun-dong, Nam-gu, Incheon 402-751,
Republic of Korea
* E-mail address: cmlee@inha.ac.kr
Indium zinc oxide thin films can be utilized in smart window and wearable nose-sensor
applications, where both high optical transparency and gas sensitivity are demanded [1,2]. ZnO
codoped with palladium and indium (Pd-IZO) materials were fabricated, characterized and
tested for their gas sensing properties. These were fabricated into gas sensors. Materials were
characterized using X-ray diffraction (XRD), scanning electron microscopy
(SEM) and energy dispersive X-ray spectroscopy (EDX). Electrical conductivity of all
samples was also calculated. Sensors were exposed to ethanol, methanol, n-butanol and acetone
at concentrations between 5 and 200 ppm. Optimal amount of Pd and In doping enhanced the
conductivity of the IZO sensor. Pd-doping enhanced the ethanol sensing properties of the IZO
sensor to ethanol. Pd and In-codoped IZO sensors show potential for inclusion into an
electronic nose for with the aim of selective alcohol detection.
References
1. H. Choi, J. S. Choi, J.-S. Kim, J.-H. Choe, K. H. Chung, J.-W. Shin, J. T. Kim, D. H. Youn,
K. C. Kim, J. I. Lee, S. Y. Choi, P. Kim, C. G. Choi, and Y. J. Yu, Small 10, 3685 (2014).
2. K. Lee, V. Scardaci, H.-Y. Kim, T. Hallam, H. Nolan, B. E. Bolf, G. S. Maltbie, J. E. Abbott,
and G. S. Duesberg, Sens. Actuators B: Chem. 188, 571 (2013).
M-P-041
Acetone Gas Sensing Properties of WO3/NiO Core-Shell Nanorod Sensors
Gun-Joo SUN1, Hyejoon KHEEL1, Soong Keun HYUN1, Seungbok CHOI2, and Chongmu
LEE1,*
1
Deparment of Materials Science and Engineering, Inha University, 253 Yonghyun-dong, Nam-gu, Incheon 402751, Republic of Korea
2
Deparment of Mechanical Engineering, Inha University, 253 Yonghyun-dong, Nam-gu, Incheon 402-751,
Republic of Korea
* E-mail address: cmlee@inha.ac.kr
In this study WO3 nanorods and WO3-core/NiO-shell nanorods were synthesized using
facile hydrothermal techniques and their acetone sensing properties were examined. X-ray
diffraction and scanning electron microscopy revealed the good crystallinity and uniformity of
the WO3-core/NiO-shell nanorods in terms of shape and size. The WO3-core/NiO-shell
nanorod sensor showed stronger response to acetone than the pristine WO3 nanorod sensor.
The response of the core-shell nanorod sensor to 200 ppm of acetone at 300°C was more than
twice as strong as that of the pristine nanorod sensor under the same conditions. Furthermore,
under these conditions, both the response and recovery times of the core-shell nanorod sensor
were much shorter than those of the pristine one. The core-shell nanorod sensor showed
excellent selectivity to acetone over other volatile organic compound gases. The enhanced
sensing performance of the core-shell nanorod sensor is attributed to modulation of the
conduction channel width and the potential barrier height at the WO3-NiO interface
accompanying the adsorption and desorption of acetone gas as well as enhanced catalytic
oxidation of acetone.
References
1. N. Barsan, and U. Weimer, J. Electroceram. 7, 143 (2011).
2. C. C. Li, Z. F. Du, L. M. Li, H. C. Yu, Q. Wan, and T. H. Wang, Appl. Phys. Lett. 91, 032101
(2007).
3. O. V. Safonova, G. Delabouglise, B. Chenevier, A. M. Gaskov, and M. Labeau, Mater. Sci.
Eng. C 21, 105 (2002).
M-P-042
Simulation of passivation effects on the plasmonic color filter for infrared
image sensor
Hong-Kun Lyu1,*, Eunsu Shin1, Bunyod Allabergenov2, Hui-Sup Cho1, Young-Jin Park1 and
Byeongdae Choi2
Division of IoT‧Robotics Convergence Research, Daegu Gyeongbuk Institute of Science and Technology
(DGIST), Daegu 42988, Korea
2
Division of Nano‧Energy Convergence Research, Daegu Gyeongbuk Institute of Science and Technology
(DGIST), Daegu 42988, Korea
* E-mail address: hklyu@dgist.ac.kr
1
Plasmonic color filters (PCFs) has been studied by many researchers [1] since
subwavelength metal gratings and structures were reported to have extraordinary optical
transmission (EOT) [2]. We investigated that the influence of vertically asymmetrical metallic
apertures to the characteristics of extraordinary optical transmission of the plasmonic color or
infrared filters. To study it, firstly we designed the structure model of the asymmetric
cylindrical aperture. And then, we simulated the spectral variation in the wavelength
transmission. For the computer simulation, we used a commercial computer simulation tool
utilizing the FDTD method. We applied a quartz glass for the substrate insulator and SiO2 for
both side insulator and for the filled material in the cylindrical aperture. We applied Au for the
metal layer, and the dispersion information for Au was derived from the Lorentz–Drude model.
It was presented that the electrical distribution (Ey) with several different conditions at the peak
wavelength of the calculated transmission spectral characteristics. They are all applied the
cover passivation layer with the same material of the substrate (SiO2). Furthermore, we
presented the transmittance spectral characteristics and the highest transmittance compared as
several different conditions [3].
Fig. 1. The transmittance comparison of five aperture types as TR.
References
1. H. S. Lee, Y. T. Yoon, S. S. Lee, S. H. Kim, and K. D. Lee, Opt. Express 15, 15457-15463
(2007).
2. T. W. Ebbesen, H. J. Lezec, H. F. Ghaemi, T. Thio, and P. A. Wolff, Nature 391, 667–669
(1998).
3. H.-K. Lyu, Y.-J. Park, H.-S. Cho, S.-H. Jo, H.-H. Lee, and J.-K. Shin, Sensor Letters 13,
687-692 (2015).
M-P-043 [NO SHOW]
Properties of Optical Quantum Transition of ZnO and Si of ElectronPiezoeletric Interaction System under Two Circularly Oscillating Fields
Su Ho Lee1, Joo Young Jeon1 and Jeoung Young Sug2*
1
Department of Electrical Engineering, Donga University, Busan, 604-714, Korea
2
School of Physics and Energy Science, Kyungpook National University, Daegu 702-701, Korea.
E-mail: leesuho@dau.ac.kr* jysug@knu.ac.kr
We have considered two systems - one is under a right circularly oscillating external fields (RCF)
and the other is under a left circularly oscillating external fields (LCF). The main purpose of this work
is to compare quantum transition line shapes (QTLSs) and optical quantum transition line widths
(QTLWs) under both directions right and left of circularly polarized oscillatory external fields.
We have applied the quantum transport theory (QTR) to the systems in the confinement of electrons
by square well confinement potential. There are many theories regarding the quantum transport
problems in various methodologies, among them we use the projected Liouville equation method with
the Equilibrium Average Projection Scheme (EAPS). The merit of using EAPS is that the quantum
response function and the scattering factor formula can be obtained in a one-step process by expanding
the quantum transport theory. In the previous work, we applied the EAPS theory in Ge and Si, since
there are abundant experimental date in non-confining potential systems. We compared our results of
numerical calculations of the EAPS theory with existing experimental data and showed a good
agreement between them. This indicated that the EAPS theory is useful in analyzing many-body
systems. But, the previous work restricted for non- confining potential systems with the extremely weak
coupling(EWC) approximation. The optical power absorption spectrum of the transitions measured in
experiments is directly related to the electric conductivity tensor, and the spectrum’s linewidth to its
line-shape function. Hence, it is important to obtain an explicit expression of the line-shape function for
a given confining potential system on the basis of a theoretical formulation. Recently, we suggested a
more precise procedure of expanding and application of EAPS in Low-dimensional electron systems
with the moderately weak coupling(MWC) approximation in Ref.[1]. In the MWC scheme, the
distribution components can provide an adequate explanation of the quantum transition processes. In a
previous work of EWC scheme, the intermediate states of quantum transition processes do not appear.
Through numerical calculation, we have analyzed the temperature and magnetic field dependences
of QTLSs and QTLWs under both directions right and left of circularly polarized oscillatory external
fields in various cases. The analysis of various cases is difficult using other theories because they require
the calculation of absorption power to obtain QTLWs. However, we can obtain QTLWs directly using
the EAPS. In order to analyze the quantum transition process, we compare the temperature and magnetic
field dependences of the QTLWs and the QTLSs of two transition processes, the intra and inter-Landau
level transition process.
References
[1] J. Y. Sug, S. H. Lee, J. J. Kim, Cent. Eur. J. Phys. 6(4). 812. (2008)
[2] J. Y. Sug, S. H. Lee, J. Y. Choi, G. Sa-Gong. and J,.J. Kim, Jpn. J. Appl. Phys., 47, 7757(2008).
M-P-044
Molecular beam epitaxial growth of InGaAsSb light emitting diodes for 2.1
µm emission,
Tien Dai Nguyen, Jehwan Hwang, Eui–Tae, Kim Sam Kyu Noh, Jun Oh Kim and Sang Jun
Lee
In the past decade, mid-wavelength infrared (mid-IR) light emitting diode (LED) has been
widely explored for an application of optical gas sensor [1-2]. In this study. we report on the
device performance of mid–IR LED based on In0.35Ga0.65As0.15Sb0.85/Al0.35Ga0.65As0.03Sb0.97
multiple quantum well (QW) design. The mid-IR LED was grown using the solid source
molecular beam epitaxy (SS–MBE) growth with As2 and Sb2 cracker cells on a n–type GaSb
substrate. The active region consists of 3 periods of a 10 nm thick InGaAsSb layer and a 200
nm thick AlGaAsSb layer as shown in the Fig. 1(a). Fig. 1(b) shows the SEM image of active
region. The structural and optical properties of the epitaxial layer was measured by the high–
resolution X–ray diffraction (HR–XRD) and photoluminescence (PL) techniques. The LED
sample was processed into 410 ⅹ 410 ㎛2 using conventional photolithographic technique.
Ohmic contacts were formed by e-beam evaporlation on the p and n sides of the wafer. The
LED chips were mounted onto TO－18 package for the test. The electroluminescence of LED
device measured on a Fourier-transform infrared spectrometer using a calibrated HgCdTe
detector at room temperature. Detailed study of device performance will be presented.
M-P-045
Stacked 1D subwavelength gratings for improved mid-IR polarization
extinction ratio
Boram Oh1,2, Jeonghwan Kim3, Deok-Kee Kim2, Jong Eun Ryu3, Jun Oh Kim1, Augustine
Urbas4, Zahyun Ku4, and Sang Jun Lee1,*
1
Division of Convergence Technology, Korea Research Institute of Standards and Science, Daejeon 34113,
Korea
2
Department of Electrical Engineering, Sejong University, Seoul 05006, Korea
3
Department of Mechanical Engineering, IUPUI, Indianapolis, IN 46202, USA
4
Air Force Research Laboratory, Wright-Patterson AFB, OH 45433, USA
*E-mail: sjlee@kriss.re.kr
Polarimetric imagery has been used in a variety of applications such as military surveillance, remote
sensing and astronomy1. In particular, surface features (shape, roughness and shading of objects) sensed
by polarimetric imagery are used for detection and recognition of targets regardless of the day and the
night and the almost weather. Recently, many researches have been conducted on the integration of
infrared (IR) focal plane devices with plasmonic architectures2 in order to decrease the cost and
complexity of IR imagers, as compared with conventional approach using the optical instruments.
However, no linear polarization extinction using integration of 1D subwavelength grating (1dSG) has
been reported to date as high as using a commercial linear polarizer. This obstacle made us to pay
attention to stacked 1dSGs in MWIR region in order to improve the linear polarization extinction
( ∫ 𝑇𝑇𝑇𝑇𝑇𝑇 𝑑𝑑𝑑𝑑 / ∫ 𝑇𝑇𝑇𝑇𝑇𝑇 𝑑𝑑𝑑𝑑) . In this study, we performed simulations of stacked 1dSGs using a finite
integration technique solver3 to find the optimized structure and to understand the underlying
mechanism. In addition, nanofabrication and FTIR-measurement will be carried out to confirm our
proposed design. Figure 1a shows the illustration of stacked 1dSGs (pitch p, width w (= r ∙ p), spacer
thickness tBCB) which consists of BCB dielectric layer sandwiched by two 1dSGs layers. Figure 1b
shows the transmission spectra of 1dSG (black) and stacked 1dSGs (red) for transvers magnetic (TM)
and transvers electric (TE) polarizations, exhibiting higher TM and lower TE transmissions due to
stacking the 1dSGs, as compared with 1dSG structure. Extinction ratio (Ext-R) map is presented in
color as a function of pitch and BCB thickness (Figure 1c). We can observe the drastic changes of the
Ext-R depending on grating parameters and spacer thickness. For experiment, samples will be
fabricated with various pitches (p = 0.4, 0.7, 1
tm)
spacer
( m).
0.25,
0.45,thickness
0.65
BCB =and
Nanoimprint lithography (NIL for a low cost, simplicity and large area) will be used to define a periodic
1dSG pattern in the NIL resist layer and the fabrication procedure is indicated in Figure 1d.
Figure 1. (a) Schematic view of the stacked 1dSGs on GaAs substrate (p and r are fixed at 0.4
m and 0.7,
respectively). Also, configuration of TM/TE polarizations is depicted. (b) TM/TE transmission spectra of 1dSG
and stacked 1dSGs. (c) Linear polarization extinction ratio colormap as a function of p and tBCB. (d) Fabrication
procedure of stacked 1dSGs using NIL.
Reference
1
Q. Li, Z. F. Li, N. Li et al., “High-Polarization-Discriminating Infrared Detection Using a Single
Quantum Well Sandwiched in Plasmonic
Micro-Cavity,” Scientific Reports, 4, 6332, (2014).
2
G.P. Nordin, J. T. Meier, P. C. Deguzman and M. W. Jones, “Micropolarizer array for infrared imaging
polarimetry,” J. Opt. Soc. Am. A.,
16, 1168-1174 (1999).
3
www.cst.com.
M-P-046
Improvement of optical properties of GaN-based Ultraviolet light-emitting
diode with Ag Nanowire transparent conducting electrode
Yu-Hyun Cho1,2,, Hyun-Sun Park1,2, Doo-Hyung Kim1, Min-Woo Kim1,
Min-Ki Kwon1, Ja-Yeon Kim2*
1
Department of photonic engineering, Chosun university, Gwang Ju 501-759 , Korea (South)
2
Department of Photonics Device Research Center, Korea Photonics Technology Institute(KOPTI), Gwang Ju
500-779, Korea (South)
* jykim@kopti.re.kr
Transparent conducting electrodes are important components of highly efficient ultraviolet light
emitting diodes (UVLEDs). Indium tin oxide (ITO) is commonly used to form a current spreading layer,
but ITO is costly and shows low transparency in the UV range and instability in the presence of acids
or bases. We demonstrate a simple solution-based coating technique to obtain large-area, highly
uniform, and conductive silver-nanowire (NW)-based electrodes that exhibit UV-range optical
transparency better than that of ITO for the same sheet resistance. In this study, we demonstrate an
UVLED with a single Ag NW-based TCE deposited by the simple solution based coating method. After
optimization of deposition condition, the Ag NW-based TCE showed a sheet resistance of 30–40 Ω/sq
and an optical transmittance of over 85% at UV wavelength, which are better than the characteristics of
ITO. With optimization of annealing condition, the measured I-V curves of Ag NW-based TCE exhibit
fairly good Ohmic behavior while that of Ag NW-based TCE before annealing shows Schottky behavior.
The electrical and optical properties of a UVLED with a Ag NW-based TCE were better than those of
a UVLED with an ITO-based TCE. We anticipate the application of the Ag NW-based TCE to a wide
variety of devices, including UVLEDs, with lower fabrication costs and improved performances.
Fig. 1. (a) Current-voltage (I-V) Characteristic (b) Optical output power (L–I characteristic) of 385 nm UVLED
w/o TCE and with AgNW and ITO based TCE
References
1. Ja-Yeon Kim, Jong-Hyun Jeon, and Min-Ki Kwon, ACS applied materials & interfaces,
2015, 7, 7945-7950
M-P-047
Enhanced light matter interaction and spectral selectivity of TMDCs by
plasmonic structure
Jubok Lee1,2, Min Su Kim1, Seki Park1,2, Yongjun Lee1,2, Changwon Seo1,2, Youngbum
Kim1,2, and Jeongyong Kim 1,2,*
1
IBS Center for Integrated Nanostructure Physics, Institute for Basic Science (IBS), Daejeon 305-701, Republic
of Korea
2
Department of Energy Science, Sungkyunkwan University, Suwon, 440-746, Republic of Korea
* E-mail address: j.kim@skku.edu
The optical properties of two-dimensional transition metal dichalcogenides (TMDCs) have
been widely investigated because of their novel properties and applications. Light matter
interactions are strong for TMDCs monolayers at excitonic resonances despite being atomically
thin. But it’s atomically thin nature limits the absolute value of absorption due to optical
absorption length is less than 1nm for monolayer. For practical applications, it is necessary to
enhance the light matter interaction of TMDCs. Recently, there are many tries to enhance the
light matter interaction of TMDCs with using of plasmonic nanostructures. The plasmonic
structures can improve optical absorption in the TMDCs by trapping light by excitation of
localized surface plasmons or trapping and guiding light via SPPs at the metal semiconductor
interface [1]. These plasmonic nanostructures can also be applied to device which showed the
enhanced performance. But, there is room for enhance the spectral selectivity and enhancement.
In this work, we investigated optical property of TMD materials with plasmonic nanostructure
by photoluminescence and absorption spectroscopy.
References
1. Eda, Goki, and Stefan A. Maier. Acs Nano. 7(7) , 5660-5665 (2013).
M-P-048 [NO SHOW]
Surface Plasmon Interference for below 10-nm
Patterning: Simulation
Sang-Kon Kim
Dept. of Science, Hongik Univ., Seoul 121-791 Korea
E-mail address: sangkona@hongik.ac.kr
Due to higher throughput, lower cost, higher resolution, and simplification of system
configuration, surface plasmon interference (SPI) can be a candidate for the next-generation
lithography technologies. Plasmon lithography technologies such as contact nanolithography,
planar lens imaging nanolithography, and direct writing nanolithography, have been developed.
Recent achievement of SPI is 14.6 nm patterning with a 25-nm-thick photoresist by using the
structure under 193-nm illumination. In this paper, SPI process is modeled and simulated for
below 10-nm critical dimension (CD). The near-field intensity of SPI with the plasmonic
phenomena of aperture shapes is described due to aperture parameters by using the rigorous
coupled-wave analysis (RCWA) method and the finite difference time domain (FDTD) method.
SPI parameters of bowtie structures are optimized and improved for the imperfection of the
resist pattern.
M-P-049 [NO SHOW]
Properties of Optical Quantum Transition of GaN and CdS of ElectronPiezoeletric Interaction System under Two Circularly Oscillating Fields
Su Ho Lee1, E. H. Kwon1, C. H. Choi1 and Jeoung Young Sug2*
1
Department of Electrical Engineering, Donga University, Busan, 604-714, Korea
2
School of Physics and Energy Science, Kyungpook University, Daegu 702-701, Korea.
leesuho@dau.ac.kr, corresponding :* jysug@knu.ac.kr
We have applied the quantum transport theory (QTR) to the systems in the confinement of electrons
by square well confinement potential. We compared our results of numerical calculations of the EAPS
theory with existing experimental data and showed a good agreement between them. This indicated that
the EAPS theory is useful in analyzing many-body systems.
When a static magnetic field B = Bz zφ is applied to an electron system, the single electron energy
state is quantized to the Landau levels. We select a system of electrons confined in an infinite square
well potential (SQWP) between z = 0 and z = Lz in the z-direction. We use the eigenvalue and
eigenstate of Ref.[10] of the square well potential system. We suppose that an oscillatory electric field
E (t ) = E0 exp(iωt ) is applied along the z-axis, which gives the absorption power delivered to the
system as P(ω ) = ( E02 / 2) Re{σ (ω )} , where "Re" denotes the real component and σ (ω ) is the optical
conductivity tensor which is the coefficient of the current formula. Here the absorption power represents
the optical QTLS, and the scattering factor function represents the optical QTLW. We consider the
electron-phonon interacting system and then we have the Hamiltonian of the system as
(
)
H s = H e + H P + V = ∑ β h0 β a β+ aβ + ∑ ω q bq+ bq + ∑∑ Cα ,µ (q )aq+ aµ bq + b−+q .
β
q
q α ,µ
Here H e is the electron Hamiltonian, h0 is a single- electron Hamiltonian, H P is the phonon
Hamiltonian and V is the electron-phonon interaction Hamiltonian. The b1 (b2+ ) are the annihilation

operator(creation operator) of boson particle, and q is phonon(or impurity) wave vector. The
interaction Hamiltonian of electron-phonon-interacting system is V ≡ ∑∑ Cα , µ (q )aα+ aµ (bq + b−+q )
q α ,µ
is
matrix element of electron-phonon interaction Cα , µ (q )
 

Cα , µ (q ) ≡ Vq < α | exp(iq ⋅ r ) | µ > , r is the position vector of electron and Vq is coupling
where
the
coupling
coefficient of the materials. Recently, we suggested the absorption power formula in Ref.[2] in
confining potential systems. With the continuous approximation, in a right circularly polarized external
field, the absorption power formula (or the QTLS formula) is obtained finally as
( )
∞

γ R ω
total
c ∑ ∫ dk zα ( N α + 1)( f α − f α +1 )
−
∞


 e ω 
Nα
R
P (ω ) ∝  2 

2
2
R
ω − ω c + γ total
ωc
 π ω  



2
2
c
(
) (
( ))
For the left circularly oscillating external fields, we obtain final result of the absorption power formula
(or the QTLS formula),
( )
∞
γ ( L) ω

total
c ∑ ∫ dk zα ( N α + 1)( f α +1 − f α )
−
∞

.


e
ω
N
α
P ( L ) (ω ) ∝  2  

2
2
(
)
L
ω − ω c + γ total ω c

 π ω  


2
2
c
(
) (
( ))
QTLSs of two transition processes, the intra and inter-Landau level transition process.
M-P-050
Feasibility study of amorphous silicon based radiation detector to monitor
the patient dose in radiotherapy
Tae Seong Baek1, Eun Ji Chung1, Jaeman Son2, and Myonggeun Yoon2,*
1
Department of Radiation Oncology, National Health Insurance Co. Ilsan Hospital, Ilsan, 410-719, Korea
2
Department of Bio-convergence Engineering, Korea University, Seoul, 02841, Korea
* E-mail address: radioyoon@korea.ac.kr
The purpose of this study was to evaluate the effectiveness of an amorphous silicon based
radiation detector to monitor the radiation dose in radiotherapy, and to verify the accuracy of
dose delivery to patients. For this purpose a commercial amorphous silicon based radiation
detector named electronic portal imaging device (EPID) was used to measure the transit dose
in eight patients treated with intensity modulated radiotherapy (IMRT). The calculated dose
map of the treatment planning system (TPS) was compared with the EPID based dose measured
on the same plane with a gamma index method. The plan for each patient was verified prior to
treatment with a diode array (MapCHECK) and portal dose image prediction (PDIP). Based on
3%/3mm criteria, the mean ± SD passing rates of MapCHECK, PDIP, and EPID dosimetry for
47 IMRT fields were 99.8%±0.1%, 99.0%±0.7%, and 90.0%±1.5%, respectively. Setup errors
of 5 and 10 mm reduced the mean passing rates by 1.3% and 3.0%, 2.2% and 4.3%, 5.9% and
10.9%, and 8.9% and 16.3%, respectively. These findings suggest that the an amorphous silicon
based radiation detector based dose verification method, in which the transit dose from patients
is compared with the dose map calculated from the TPS, may provide proper quality assurance
of actual dose delivery to patients in the radiation treatment room.
(a)
(b)
Fig. 1. A commercial amorphous silicon based radiation detector (EPID) measurements of transit doses during
treatment at the posterior surfaces of Patients (a) 1 (maxillary sinus) and 3 (prostate).
References
1. M. Oldham, H. Sakhalkar, P. Guo, and J. Adamovics, Med. Phys. 35, 2072 (2008).
2. M. Sabet, P. Rowshanfarzad, P. Vial, F. W. Menk, and P. B. Greer, Phys. Med. Biol. 57,
N295 (2012).
M-P-051
Observation of Negative-Differential Resistance Behaviors in
Gated p+-i-n+ Silicon Transistors
Namhyun An, Hwauk Lee, Youngmin Lee, Deuk Young Kim, and Sejoon Lee*
Department of Semiconductor Science, Dongguk University-Seoul, Seoul 04620, Korea
*
E-mail Address: sejoon@dongguk.edu
The silicon-based negative-differential resistance transistors (NDR-TRs) were fabricated,
where the channel structure was configured with the p+-i-n+ junction on a ultra-thin silicon-oninsulator. We analyzed the transport characteristics of NDR-TRs and investigated their
operation mechanisms. Through designing the optimal p+-i-n+ channel structure, we could
demonstrate the N-shaped NDR oscillations at room temperature on the fabricated devices. In
addition, we observed that the position and the magnitude of NDR peaks can be precisely tuned
by changing gate and/or drain bias voltages. The largest peak-to-valley current ratio of the
NDR peak was 4-6, and the smallest full-width at half-maximum was < 200 mV. The minimal
subthreshold swing was ∼180 mV/dec. From results of device characterization, we found out
that the N-shape of NDR in our devices is attributed to band-to-band tunneling in the channeldrain junction. Using the NDR oscillations, we eventually demonstrated possible applications
of multi-value logic circuits.
Fig 1. (a) ID-VG curves of the fabricated Si p+-i-n+ NDR-TR and (a) Energy band diagram
representing the NDR behavior.
M-P-052
Feasibility study of integrated AEC grid containing semiconductor x-ray
sensor for the optimization in mammography
K.T. Kim1, R.Y. Yun1, M.J. Han1, Y.J. Heo1, J.H. Kim2,
Y.K. Song3, S.W. Heo3, K.M. Oh4, S.K. Park5 and S.H. Nam1,*
1
Deparment of Biomedical Engineering, Inje University, Gimhae 50834, Korea
Department of Emergency and Disaster Management, Inje University, Gimhae 50834, Korea
3
Medical Physics Research Team, Division of Heavy Ion Clinical Research, Korea Institute of Radiological and
Medical Sciences, Seoul 01812, Korea
4
Radiation Equipment Research Division, Korea Atomic Energy Research Institute, Jeongeup 56212, Korea
5
Department of Radiation Oncology, Busan Paik Hospital, Busan 47392, Korea
* E-mail address: nsh@bme.inje.ac.kr
2
In current radiation diagnosis field, mammography is being used for early detection of breast cancer.
Also, It has been minimize the exposure dose via various attempts and to increased the quality of
medical imaging; There are researches being conducted on grid in order to produce high quality
images. In terms of grid, although the grid ratio, which affects the scattering removal rate, must be
increased to improve image qualities, it has a problem of increasing the total exposure dose. So,
Automatic Exposure Control (AEC) systems play a fundamental role in striking a balance between
patient dose and achieving the best image quality in mammography imaging. [1,2] However, the
currently available AEC device for mammography is attached to the bottom end of the detector,
unlike in general radiography, which makes it vulnerable to influence by the detector and support
structure, and it cannot easily control the beam dose. Against this background, in this study, an
AEC-grid device is introduced. We designed the geometry to implement the grid and AEC to obtain
the optimal image quality as well as to reduction in patient dose by removing scattered radiation
by using the FLAIR geometry editor of the FLUKA additional tool. FLUKA is a fully integrated
MC simulation package tool for calculations of particle transport and interactions with matter.
The integrated AEC-grid device designed in this research was constructed by patterning
radiopaque strip biased at 90 degree angle on top and bottom of Si wafer. Then, electrodes were
introduced in between radiopaque strips to enable measurement of exposure dose. Then, generally
used X-ray was used to perform simulations to predict interactions with X-ray. The results were
compared to a commercially used crossed grid based on which a possibility of using the integrated
AEC-grid device was evaluated. We used the Bucky factor and selectivity as the standard for
evaluating the grid performance. In additional, In an attempt to overcome the difficultly of
controlling the dose with a conventional AEC, with air-equivalent material mounted to the bottom
of a detector ascribable to its position between the detector and the support, we designed a Si-based
AEC integrating the grid positioned at the top of the detector and AEC. We derived its linearity to
evaluate its reaction characteristics to X-rays.
The experimental results demonstrated that the selectivity of the ACE-grid is approximate 5.8%
lower than that of the conventional cross-type grid, however, the Bucky factor is approximately
61.2% higher. Additionally, the absorption property is very high, and the linearity is above 0.95.
These results indicate that the AEC-grid has potential for use as an automatic exposure control
device, if the decreased of scattered radiation via the optimization of the grid performance
parameters is performed.
References
1. Reis, A. Pascoal, T. Sakellaris, and M. Koutalonis, Insights Imaging 4 5 (2013) 539-553.
2. Y. Zhou, A. Scott II, J. Allahverdian and S. Frankel, Journal of X-ray Sci. and Tech. 22 3 (2014)
377-471.
M-P-053
A Study on the x-ray sensor containing compound group IVbased semiconductor for automatic exposure control in digital
radiography
K.T. Kim1, G.Y. Choi1, Y.H. Shin1, Y.J. Heo1, J.H. Kim2,
J.E. Park3, S.K. Park4, S.S. Kang5, J.K. Park5 and S.H. Nam1,*
1
Deparment of Biomedical Engineering, Inje University, Gimhae 50834, Korea
Department of Emergency and Disaster Management, Inje University, Gimhae 50834, Korea
3
Department of Radiation Oncology, Severance Yeonsei Cancer Center, Seoul 03722, Korea
4
Department of Radiation Oncology, Busan Paik Hospital, Busan 47392, Korea
5
Department of Radiological Science, International University of Korea, Jinju 52833, Korea
* E-mail address: nsh@bme.inje.ac.kr
2
In recent years the medical imaging systems using radiation enables it to obtain the images
of appropriate concentration thanks to its wider bandwidth than the existing analogue
technology, but with respect to the image quality determined by various variables, it is hard to
obtain the images of high reproducibility. To solve this problem, a demand for automatic
exposure controller (AEC) which will be able to increase the reproducibility in implementing
images is increasing. AEC is a sensor that automatically controls the exposure to maintain
adequate image quality by judging the amount of under or over exposure required. Among such
AEC chamber, ionization chamber and semiconductor detectors have been widely used. [1,2]
Although such ionization chambers are used in most of today’s AEC systems, they are less
sophisticated and less accurate compared to other types of detector. Compared with ionization
chamber, semiconductor detector offers several advantages such as geometric efficiency due
to low thickness, high sensitivity, fast response time and excellent stability. Thus in this study
the author consider the semiconductor materials applicable to the AEC by evaluating shading
using a semiconductor sensor manufactured by the author, and evaluated their electrical
properties. Additionally, we used group IV-based semiconductor; lead oxide (PbO), lead
dioxide (PbO2) and lead (II) iodide (PbI2).
Furthermore, for the electrical properties, the author evaluated the dark current according to
the applied voltage and the ratio of charge electron according to the dose, and compared the
Silicon diode. The contrast for shading was evaluated. The results of contrast showed 0.060 for
PbO (18 μm), 0.053 for PbO2 (19 μm), 0.070 for PbI2 (18 μm), and 0.041 for Si (347 μm).
Based on these results, it is useful as materials for the AEC. Analysis result of the ratio of
charge electron as a function of the exposure dose, linearity showed 0.9995 for PbO, 0.9956
for PbO2, 0.992 for PbI2, 0.9996 for Si diode. Additionally, sensitivity appeared 0.4988 for
PbO, 0.6695 for PbO2, 0.5178 for PbI2, 0.547 for Si diode. Taken together, group IV-based
semiconductor is expected to perform as x-ray sensor of AEC that a more accurate control of
dose.
References
1. P. Doyle and CJ Martin, Phys. Med. Biol. 51, 21, 5475, (2006).
2. C. Walsh, D. Gorman, P. Byrne, A. Larkin, A. Dowling, and JF Malone, Radiat. Prot.
Dosimetry 129, 1-3, 271 (2008).
M-P-054
Fabrication and characterization of ZnO nanorods/micro-pyramidal silicon
hybrid antireflective structures for photovoltaic applications
Sang Hun Kim1, Soo Hyun Lee1, Dudem Bhaskar1, and Jae Su Yu1,*
1
Deparment of Electronics and Radio Engineering, Kyung Hee University, 1732 Deogyeong-daero, Giheung-gu,
Yongin-si, Gyeonggi-do 17104, Republic of Korea
* E-mail address: jsyu@khu.ac.kr
Photovoltaic devices have been widely investigated because of their high efficiency, strong
reliability, long lifetime, and eco-friendly feature. Particularly, the silicon (Si) based
photovoltaic devices can provide additional advantages such as relatively simple fabrication
processes and cost effectiveness. However, the Fresnel reflection can be induced on the surface
of Si due to the large refractive index contrast between air and Si (n~ 3.4), resulting in the
reduction of device efficiency [1,2]. To overcome this issue, the architectures of antireflective
structures are required. In this study, we fabricated the hybrid structures of ZnO nanorods
grown on micro-pyramidal Si using wet-etching process and hydrothermal synthesis for
antireflective coating applications. The wet-etching process was carried out with various
solution concentrations of potassium hydroxide (KOH) and isopropyl alcohol (IPA). For the
ratio of 10:9 for KOH and IPA, the micro-pyramidal Si structures exhibited the lowest
reflectance of 14.5%. The ZnO nanorods were grown on the as-prepared samples via the
hydrothermal synthesis at three different concentrations. For the ZnO nanorods grown at 25
mM, the optical reflectance was further decreased to 3.6%. These results may provide a deep
insight into the fabrication and antireflective properties of ZnO nanorods/micro-pyramidal
silicon hybrid structures and will be useful to enhance the efficiency of Si-based solar cells in
photovoltaic applications.
References
1. J.W. Leem, Y. M. Song, and J. S. Yu, Opt. Express 19, A1155 (2011).
2. J. Zhao and M. A. Green, IEEE Trans. Electron. Dev. 38, 1925 (1991).
M-P-055 [NO SHOW]
Effects of narrow size on the magneto-electrical properties in Co thin film
Chunghee Nam
1
Deparmentof Photonics and sensors, Hannam Unv., Daejeon South Korea
* E-mail address: chnam@hnu.ac.kr
Magnetic nanostructures have been proposed for various applications in logic-circuits, non-volatile
memory, and bio-sensors. For reliable operation of the magnetic devices, the structure induced electrical
properties should be studied. In this presentation, an artificially narrowed side of the magnetic Co ring
structure was introduced to understand the magneto-electrical signals (anisotropic magnetoresistance –
AMR) in terms of an external magnetic field, as shown in Fig 1. In the magnetic ring structures,
magnetic domain wall(DW) is easily formed along the field direction. DW motion with the magnetic
field results in a change of the AMR signals, as shown in Fig. 2, meaning that the direction of DW
motion and magnetic state can be identified. The details of the experimental results will be presented.,
M-P-056 [NO SHOW]
Direct observation of systematic change in domain wall motions of
Co1-XFeX ferromagnetic systems
Kwang-Su Ryu1 and Sung-Chul Shin2
1
Department of Physics Education, Korea National University of Education (KNUE), Cheongju, Chungbuk
28173, Korea
2
Department of Emerging Materials Science, Daegu Gyeongbuk Institute of Science and Technology (DGIST),
Daegu 711-873, Korea
The domain wall (DW) dynamics in ferromagnetic (FM) films under external magnetic field
continues to be one of the important issues in magnetism fields due to its technical application
in spintronic devices. Also, it has been found that the DW dynamics in in-plane magnetized
FM systems shows the stochastic behavior having discrete and jerky DW jumps [1,2]. In this
work, we report the systematic change of the DW motion mechanism depending on the ratio
of composition x in Co1-xFex ferromagnetic systems (0 ≤ x ≤ 0.8). It was found that all samples
show the clear single DW motions and their magnetization are aligned on the sample plane.
Interestingly, as the Fe composition x increases, the DW motion mechanism is changed from
the stochastic behavior with random DW sizes to the thermal activated behavior with specific
DW sizes, as seen in the time-resolved DW images of Fig 1(a). This result could be understood
by the change of the magnetic angular symmetry from a 4-fold one to a 2-fold one, resulting in
the increase of the thermal activation in the lower DW energy barriers, as seen in Fig 1.
Fig 1.(a) Time-resolved domain wall images observed in Co1-xFex alloy systems by means of a optical
Kerr-microscope and (b) the angular dependences of the 
where 

r/
s
r and
s are the remanent and
the saturation Kerr angles of the Kerr hysteresis loop, respectively.
Reference: [1] K.-S. Ryu et al., Nat. Phys. 3, 547 (2007). [2] H.-S. Lee et al., New J. Phys. 13,
083038 (2011).
M-P-057
Diode-like dynamic behavior of magnetic domain wall in discrete magnetic
nanodot chains
Xiao-Ping Ma1, Seon-Dae Kim1, Hong-Guang Piao1,2, Dong-Hyun Kim1*
1
Department of Physics, Chungbuk National University, Cheongju 28644, Chungbuk, R. Korea
2
College of Science, China Three Gorges University, Yichang 443002, P. R. China
* E-mail address: donghyun@cbnu.ac.kr
For spintronics applications, devices based on magnetic domain wall motion (DW) in
ferromagnetic nanowires have attracted much attention. In ferromagnetic nanowires, it has
been known that the propagating DW dynamics is significantly affected by the nanowire
geometry and dimension. In particular, with including asymmetric artificial defects in nanowire
geometry, possibility of magnetic diode functionality based on a ratchet effect of DW motion
has been numerically and experimentally proposed [1,2]. Since DW dynamic behaviors in
ferromagnetic nanowires are affected by various effects such as the pinning effect and the
Walker breakdown phenomenon, further detailed study is required to fully understand the
ratchet DW behavior along various nanowires. In this work, we numerically investigated the
diode-like DW ratchet effect in the asymmetrically shaped nanodot chains as a magnetic
dissipative system, as shown in Fig. 1. Material parameters of Permalloy are used for
micromagnetic simulations. By changing the strength and the frequency of the AC driving field,
we have systematically analyzed the DW ratchet effect and the dynamic depinning effect,
which might be ascribed to the existence of a dynamic dipolar field interaction between
adjacent nanodots. Further details will be discussed with a systematic variation of the gap
distance between adjacent nanodots to confirm the interaction impact.
Fig. 1. Show the geometry and dimension of the asymmetrically shaped nanodot chains as a magnetic
dissipative system.
References
[1] H.-G. Piao, et al., Appl. Phys. Lett. 99, 192512 (2011).
[2] J. H. Franken, et al., Nature nanotech. 7, 499 (2012).
M-P-058
Intrinsic damping like spin-orbit torque in two dimensional collinear
antiferromagnets
Suik Cheon1*, and Hyun-Woo Lee1
1
Department of Physics, Pohang University of Science and Technology, Pohang 37673, Korea
We consider spin torque generated by an electric current flowing through a twodimensional(2D) collinear antiferromagnetic(AFM) layer subject to the Rashba spin-orbit
coupling. In particular, we focus on the spin-orbit torque (SOT), which is the spin torque
generated by the interplay between the current and the spin-orbit coupling. Considering small
Fermi energy and strong exchange limit, we investigate the damping-like(DL) component of
the SOT, or DL-SOT. Compared to the DL-SOT in a ferromagnetic case, we show that this
torque in the AFM case is more sensitive to the exchange interaction and the Fermi energy.
Moreover while the intrinsic DL-SOT in the ferromagnetic case arises from the whole bands[2],
in the 2D collinear AFM system, which is invariant under combination between time reversal
and lattice translation symmetry operations, we show that certain specific bands are important
to the DL-SOT.
References
[1] Suik Cheon, and Hyun-Woo Lee, in preparation.
[2] H. Kurebayashi et al., Nat. Nanotechnol. 9, 211 (2014).
M-P-059
Evaluation of a portable respiratory training system with the tactile guide
for respiratory gated radiotherapy
Sun Young Moon1, Myonggeun Yoon1, Mijoo Chung2, Weon Kuu Chung2, and Dong Wook
Kim 2,*
1
Department of Bio-Convergence Engineering, Korea University, Seoul, Korea 136-703
2
Department of Radiation Oncology, Kyung Hee University Hospital at Gangdong,
Seoul, Korea 134-727
* E-mail address: joocheck@gmail.com
Purpose
We developed and evaluated the portable respiratory training system based on micro-electromechanical-system (MEMS) that provide the audio-visual and tactile information.
Method
The MEMS was placed on respiratory motion phantom and when the phantom repeatedly had
movement out of designated limitation, electronic signal was released by the portable
respiratory monitoring system. The tactile guide system was connected to oscilloscope and
electronic signal from the monitoring system to the tactile sensor was measured. We compared
time interval out of designated limitation of the phantom and interval of the electronic signal
recorded on the oscilloscope.
Result
Difference between time interval out of designated limitation of the phantom and interval of
the electronic signal recorded on the oscilloscope showed within 1 second.
Conclusion
The tactile guide system connected to the MEMS developed by our team received the electronic
signal within 1 second. This means that when respiratory cycles of patient for respiratory gated
radiotherapy were out of designated limitation, the patient immediately could adjust the
respiratory cycles of one’s own into stable limit.
M-P-060
Carrier Multiplication Induced Non-Thermal Phase Transition in Ge-SbTe Alloys
Junhyeok BANG1,*, Y. Y. SUN2, X.-Q. LIU2, and S. B. ZHANG2
1
Spin Engineering Physics Team, Korea Basic Science Institute (KBSI), Daejeon 305-806, Republic of Korea
2
Department of Physics, Applied Physics, & Astronomy, Rensselaer Polytechnic Institute, Troy, New York
12180, USA
* E-mail address: jbang0312@kbsi.re.kr
Non-thermally driven phase transition has been observed by femtosecond laser experiments
in numerous materials. For decades, the phenomenon has been explained by the plasma
annealing model: excitation of a large fraction of valence electrons to conduction bands
weakens lattices and leads to the structural phase transition in low temperature. In contrast to
ground state carriers, however, excited carriers can undergo several dynamic processes such as
scattering, relaxation, and recombination and the plasma annealing model completely ignores
such a dynamical effect of the carriers. Here, we will discuss recent real-time ab initio timedependent density functional theory studies on the non-thermal phase transition in Ge-Sb-Te
alloys. We find a strong carrier energy dependence in the carrier relaxation process: for low
energy carriers electron-phonon scattering becomes a dominant relaxation process, and for high
energy carriers electron-electron scattering remains a dominant relaxation process. As a result,
we observe significant ionic temperature increase from the initial stage of excitation for low
energy excitation, which aids phase transition by ionic thermal activation, and non-thermal
phase transition for high energy excitation significantly below the melting temperature. The
results show that the excited carrier energy is a key factor in determining the phase transition
mechanism in contrast to the plasma annealing model, in which the excited carrier density is
crucial in the phase transition processes. This provides a new conceptual framework in
understanding fundamental physical phenomenon of the phase transition.
M-P-061
Infrared Spectroscopic Study of
Filling-Controlled Metal-Insulator Transition in (Sr1-xLax)3Ir2O7
Gihyeon Ahn1, S. J. Song1, T. Hogan2,3, S. D. Wilson3, S. J. Moon1,*
1
Department of Physics, Hanyang University, Seoul 04763, Korea
2
Department of Physics, Boston College, Chestnut Hill, Massachusetts 02467, USA
3
Department of Materials, University of California, Santa Barbara, California 93106, USA
E-mail: ahn.gihyeon.25@gmail.com
We investigated the charge dynamics of (Sr1-xLax)3Ir2O7 using infrared spectroscopy. Upon
electron doping, we observed a collapse of the Jeff=1/2 Mott gap accompanying the transfer of
the spectral weight from high energy region to in-gap region, which is a characteristic feature
of correlated electron systems. We found the reduced effective number of carriers in
comparison with the band filling. It is due to the large mass enhancement and it is further
supported by the extended Drude model analysis. Our results indicate that the electronic
correlations play important roles in the electrodynamics of electron-doped Sr3Ir2O7.
M-P-062
Optical spectroscopic study of the electronic structure of La-doped
Sr2IrO4
J. H. Seo, S. J. Song, G. H. Ahn, T. Hogan, S. D. Wilson, and S. J. Moon
M-P-063
Temperature and Doping Evolutions of the Electronic Response of
Sr3(Ir1-xRux)2O7,
Seungjae Song, G. H. Ahn, J. H. Seo, T. Hogan, S. D. Wilson, and S. J. Moon
M-P-064
One-dimensional quantum dot array fabricated with carbon nanotubes
and molecules
Akira Hida1,* and Koji Ishibashi1,2
1
Advanced Device Laboratory, RIKEN, Saitama 351-0198, Japan
RIKEN Center for Emergent Matter Science, Saitama 351-0198, Japan
* E-mail address: hida@riken.jp
2
Carbon nanotube [1] has been attracting attention as a promising material for the nextgeneration electronic and optical devices. In order to design the device characteristics, it is
essential to realize the so-called band engineering of carbon nanotubes. Recently, we fabricated
the heterostructures with single-walled carbon nanotubes (SWNTs) and collagen model
peptides [2]. The confinement potential was formed when collagen model peptides were
connected to both ends of an individual SWNT, and the obtained heterostructure was regarded
as a quantum dot [2]. In the case of applying quantum dots as the device components, it is
important to produce the arrangement structure of the dots as well, not only a single dot. In this
presentation, the effort to fabricate one-dimensional quantum dot array is introduced.
Our strategy is as follows: by connecting SWNTs and collagen model peptides alternately,
multiple quantum dots can get in a line. Both ends of SWNTs were modified with carboxyl
groups in order to attach to the collagen model peptides having carboxyl groups and amino
groups via the formation of carboxylic anhydrides or peptide bonds. We repeated the
condensation reactions while supplying SWNTs and collagen model peptides alternately, and
obtained the one-dimensional array which included five quantum dots. The microscopic
structure and the electronic states of the dot array were investigated directly by using scanning
tunneling microscopy and spectroscopy. The details of the fabrication procedures and the
results of measurements are shown in the presentation.
References
1. S. Iijima, Nature 354, 56 (1991).
1. A. Hida and K. Ishibashi, Appl. Phys. Express 8, 045101 (2015).
W-P-001
Increased Quantum Yield of an Atomically Thin Semiconductor by Silver
Nanowires
Seungho Bang1,2, Jubok Lee1,2, Yu-Hyun Cho3,4, Thanh Ngoc Duong1,2, Anh Duc Nguyen 1, 2,
Chul Ho Park1,2, Hyun Kim1,2, Seok Joon Yun1,2, Gang Hee Han1,2, Min-Ki Kwon3, Ja-Yeon
Kim4, Deok-Soo Kim1, Jeongyong Kim1,2 and Mun Seok Jeong1,2,*
1
Deparment of Energy Science, Sungkyunkwan University, Suwon 446-746, Republic of Korea
Center for Integrated Nanostructure Physics, Institute for Basic Science, Sungkyunkwan University, Suwon
440-746, Republic of Korea
3
Deparment of photonic engineering, Chosun university, Gwang Ju 501-759 , Korea (South)
4
DepartmentLED team, Korea Photonics Technology Institute(KOPTI), Gwang Ju 500-779, Korea (South)
* E-mail address: mjeong@skku.edu
2
Recently, an atomically thin semiconductors are the most promising materials in
optoelectronic field. Among them, especially transition metal dichalcogenides (TMDs) have
direct band gap and broad absorption range from ultraviolet to infra-red regions [1,2]. However,
because of its low quantum yield, it is difficult to applicate to optoelectronic devices such as
photodetector and light emitting diode (LED). So, many researchers have studied for increasing
their quantum yield with doping, free-standing and light-matter coupling by nanostructures of
novel metal [3,4]. In this work, we increased quantum yield of Molybdenum disulfides (MoS2)
which is a kind of TMD, using weblike silver nanowires (Ag NWs). We confirmed strong
plasmonic electric field in weblike Ag NWs from its dark field scattering. And then, we
succeeded to increase more over 100 times intensity of PL and photocurrent using coupling of
between exciton of MoS2 and plasmonic resonance of Ag NWs.
References
1. F. Withers, O. Del Pozo-Zamudio, A. Mishchenko, A. P. Rooney, A. Gholinia, K. Watanabe,
T. Taniguchi, S. J. Haigh, A. K. Geim, A. I. Tartakovskii, K. S. Novoselov, Nat. Mater. 14,
301-306. (2015)
2. Qing Hua Wang, Kourosh Kalantar-Zadeh, Andras Kis, Jonathan N. Coleman, Michael S.
Strano, Nat. Nanotech. 7, 699-712. (2012)
3. Nils Scheuschner, Oliver Ochedowski, Anne-Marie Kaulitz, Roland Gillen, Marika
Schleberger, and Janina Maultzsch, Physical Review B. 89, 125406 (2014)
4. Shinichiro Mouri, Yuhei Miyauchi, Kazunari Matsuda, Nano Lett. 13 (12), (2013)
W-P-002
Optical and Electrical Characteristics of Hybrid Transparent Conductive
Film by Silver Nanowires and Two Dimensional Nano Materials
Kihyuk Yang1,2, Deok Soo Kim1, Ho Young Kim1,2,3, Seungho Bang1,2, Hee Jin Jeong3,4, and
Mun Seok Jeong1,2,*
1
Department of Energy Science, Sungkyunkwan University, Suwon 16419, Korea
Center for Integrated Nanostructure Physics, Institute for Basic Science, Sungkyunkwan University, Suwon
16419, Korea
3
Nano Hybrid Technology Research Center, Korea Electrotechnology Research Institute, Changwon 51543,
Korea
4
Multidimensional Nanomaterials Research Group, Korea Electrotechnology Research Institute, Changwon
51543, Korea
2
* E-mail address: mjeong@skku.edu
In recent display developments, silver nanowires transparent conductive film (Ag
NWs TCF) is the most promising candidate for replacing indium tin oxide (ITO) because of
good optical properties and high flexibility. However, haze in Ag NWs TCF is severe problem
in application area. Thus, some research groups have been tried to minimize haze by covering
TCF with other materials but it was not satisfied yet. Here, we show fabrication and
characterization of Ag NWs hybrid TCF covering with 2D materials such as graphene and
molybdenum disulfide (MoS2) to increase internal connection of wire to wire for improving
electrical performance and reducing haze phenomena. Monolayer of these materials has very
high transmittance and electrical conductivity. We measured optical and electrical properties
of hybrid TCF which were compared with pristine Ag NWs TCF. Then, experimental results
were compared to theoretical predictions. Predictions are calculated using Mie theory and
Percolation theory. Sheet resistance of hybrid structures was much lower than that of pristine
structures, on the other hands transmittance was little decreased. Finally, we can get low sheet
resistance without great loss of transmittance and optical haze from characteristics of Ag NWs
hybrid network.
W-P-003
Raman scattering studies of tungsten disulfide (WS2)
Ja-yeong Kim, Hankyoul Moon, and Seokhyun Yoon*
Department of Physics, Ewha Womans University, Seoul 120-750, Korea
*
E-mail: syoon@ewha.ac.kr
The advent of new facile fabrication techniques of producing the single- and the multi-layered
graphene, has led to large amount of research over other two-dimensional materials such as
MoS2, WS2, MoSe2, WSe2, and MoTe2. These materials in principle can be utilized for
semiconductor devices such as transistors, emitters, and detectors as well as exhibit interesting
two-dimensional physics. Especially, WS2 bilayer shows mobility above 300 cm2V-1S-1 in low
temperature[1] that implies possible low losses through the Joule effect. In this study, we made
WS2 samples by exfoliation method. We deposited WS2 flakes on Si substrates with a 300 nm
SiO2 layer, and the typical size of thin layer of WS2 flakes were about few micrometers. For
measuring basic characteristics such as lattice properties and information regarding the
electronic band structures of the samples, we performed Raman scattering spectroscopy using
four different excitation energies of 457 nm (2.71 eV), 488 nm (2.54 eV), 514.5 nm (2.41 eV),
532 nm (2.33 eV), and 632.8 nm (1.96 eV) in different temperatures. Also, we measured Raman
spectra including the low energy breathing and shear modes. We report anomalous phonon
behavior that depends on the number of layers and the resonant effect reflecting the underlying
electronic band structure.
References
1. Dmitry Ovchinnikov, “Electrical transport properties of Single-Layer WS2,” ACS nano,
10.1021, nn502362b, 2014.
W-P-004
Hybrid Photodetector Based on WSe2 Monolayer and Graphene Quantum
Dot
Anh Duc Nguyen1,2, Thanh Ngoc Duong1,2, Seung Ho Bang1,2, and Mun Seok Jeong1,2,*
1
Center for Integrated Nanostructure Physics, Institute for Basic science, Sungkyunkwan University, Suwon
440-746, Republic of Korea
2
Department of Energy Science, Sungkyunkwan University, Suwon 440-746, Republic of Korea
* E-mail address: mjeong@skku.edu
Recently, hybrid devices combining two-dimensional transition metal dichalcogenides (TMDs)
with other semiconductors have been widely studied for the purpose of enhancing light
absorption and device photosensitivity [1,2]. Among them, heterostructures formed from 2D0D material have emerged as a particularly interesting research field. In this work, we present
a hybrid photodetector that consists of a monolayer WSe2 covered with a thin layer of nitrogendoped graphene quantum dots (N-GQD) which have tunable optical and electronic properties
depending on their functional groups. The improved photodetection performance
(photoconductive gain, time-dependent photoresponse) is attributed to enhanced optical
responsivity resulting from the strong light absorption and charges transfer from N-GQD to
WSe2. The carriers and electrostatic doping effect also have been concerned.
References
1. G. Konstantatos, M. Badioli, L. Gaudreau, J. Osmond, M. Bernechea, F. Pelayo Garcia de
Arquer, F. Gatti, and F. H. L. Koppes, Nature Nanotech. 7, 363-368 (2012).
2. C. Chen, H. Qiao, S. Lin, C. M. Luk, Y. Liu, Z. Xu, J. Song, Y. Xue, D. Li, J. Yuan, W. Yu,
C. Pan, S. P. Lau, and Q. Bao, Sci. Rep. 5, 11830 (2015).
W-P-005
Graphene-based Nanoelectromechanical Switch with Vertical Carbon
Nanotube Tip
Eunae Lee1, Ki-Sub Kim2,*, and Jeong Won Kang2,**
1
Department of IT Convergence, Korea National University of Transportation, Chungju 380-702, Republic of
Korea
2
Department of Chemical and Biological Engineering, Korea National University of Transportation, Chungju
380-702, Republic of Korea
3
Graduate School of Transportation, Korea National University of Transportation, Uiwang-si, Gyeonggi-do
437-763, Republic of Korea
* E-mail address: kks1114@ut.ac.kr ** E-mail addres: jwkang@ut.ac.kr
We present the simple schematics of the three-terminal nanoelectromechanical switch
using the vertical carbon nanotube tip and planar graphene and investigated their operation
dynamics via classical molecular dynamics simulations combined with classical electrostatic
theory. The key operations of the proposed graphene-based nanoelectromechanical switch are
based on two issues: first, the low mass density, the large area, and the flexible deflection of
the graphene and second, narrow and sharp of the carbon nanotube tip. The electromechanical
dynamics of the graphene switch are well balanced by five forces as follows: the capacitive
force between the bottom electrode and the graphene, the van der Waals force between the
bottom electrode and the graphene, the capacitive force between the carbon nanotube tip and
the graphene, the van der Waals force between the carbon nanotube tip electrode and the
graphene, and the elastic force of the graphene.
ACKNOWLEDGEMENTS : This research was partially supported by the MSIP (Ministry
of Science, ICT and Future Planning), Korea, under the C-ITRC (Convergence Information
Technology Research Center) (IITP-2015-H8601-15-1008) supervised by the IITP (Institute
for Information & communications Technology Promotion), and partly supported by Basic
Science Research Program through the National Research Foundation of Korea (NRF) funded
by the Ministry of Education, Science and Technology (2015R1A1A1A05027643).
W-P-006
Development of Charge – coupled Devices with van der
Waals heterostructures
Thanh Ngoc Duong1,2, and Munseok Jeong1,2,*
1
Center for Integrated Nanostructure Physics, Institute for Basic Science (IBS), Sungkyunkwan
University, Suwon 440-746, Republic of Korea
2
Deparment of Energy Science, Sungkyunkwan University, Suwon 440-746, Republic of Korea
* E-mail address:mjeong@skku.edu
The stacking different types of Transition Metal Dichalcogenides (TMDs) creates a wide
range of heterostructures as well as applications from electronics to photonics. Due to
possessing direct band gap, monolayer Molybdenum disulfide (MoS2) benefits significantly in
optoelectronic devices such as photodetectors(1), light-emitting diodes(2) and solar cells(3).
However, research about Charge-coupled Devices (CCD) based on TMDs is quite limited. Here
we prepared Charge-coupled Image Sensors using TMDs of monolayer MoS2 and few layer
MoSe2 vertical heterostructure with high responsivity. After being generated in absorptive
layers (MoSe2) during light exposure, photo-generated carriers accumulate and are trapped by
a potential well of MoS2 monolayer. Then, read out current measurements are also conducted
to extract electrons from trapping layer for next data processing. With developments of twodimensional materials recently, our work also opens a new threshold of research regarding to
cameras, video recorders and light sensing.
References
1. Oriol Lopez-Sanchez, Dominik Lembke, Metin Kayci, Aleksandra Radenovic and Andras
Kis, Nature. Nanotech. 497,501 (2013).
2. F.Withers, O. Del Pozo-Zamudio2 A. Mishchenko, A. P. Rooney, A. Gholinia, K.Watanabe,
T. Taniguchi, S. J. Haigh, A. K. Geim, A. I. Tartakovskii and K. S. Novoselov, Nature.
Mater. 301,306 (2015).
3. Marco M. Furchi, Andreas Pospischil, Florian Libisch, Joachim Burgdorfer, and
Thomas Mueller, Nano. Lett. 4785,4791 (2014).
W-P-007
Fabrication of hybrid structure of transition metal dichalcogenides and
ZnO nanorods
Kang Nyeoung Lee1,2, Chul Ho Park1,2, and Mun Seok Jeong1,2,*
2
1
Deparment of Energy Science, Sungkyunkwan University, Suwon 440-746, Korea
Center for Integrated Nanostructure Physics (CINAP), Institute for Basic Science (IBS), Sungkyunkwan
University, Suwon 440-746, Korea
* E-mail address: mjeong@skku.edu
The structural and optical properties of ZnO nanorods have been actively studied [1]. In
addition, hybrid structures using ZnO nanorods and other materials have been in the limelight
because of their unique electronic and optical properties [2]. In this study, we report structural
and optical interrelation of hybrid structures using various 2-dimentional transition metal
dichalcogenides (TMDs) materials and ZnO nanorods.
Various TMDs materials were prepared by using CVD method on SiO2/Si substrate. Then,
ZnO nanorods were grown by using hydrothermal method. To prepare the reaction solution,
Zinc acetate dehydrate powder was mixed into deionized water. And the strong ammonia
solution was used to adjust pH of the solution. Finally, the autoclave was heated for 2H at low
temperature (150℃) and cooled for 2H at room temperature after putting the TMDs/SiO2/Si
sample and the solution into the autoclave. After this procedure, the structural and optical
properties of the sample were measured with scanning electron microscope and confocal
microscopy system, respectively. We used a 532nm laser (2mW) for the excitation source.
Those analysis sufficiently reveals that TMDs materials as a substrate will affect
improvement of flexible device.
References
1. X. Q. Meng, D. Z. Shen, J. Y. Zhang, D. X. Zhao, Y. M. Lu, L. Dong, Z. Z. Zhang, Y. C.
Liu, X. W. Fan, Sol. Stat. Comm. 135, 179-182 (2005).
2. K. Zhang, Y. Zhang, T. Zhang, W. Dong, T. Wei, Nano Res. 8, 743-750 (2015)
W-P-008
Laser-exfoliation of Few-layer MoS2
by High-power Femtosecond Pulse Laser
Sung-Jin An1,2,Yong-Hwan Kim1,2, Ayoung Lee1,2, Ji-Hee Kim2*, and Mun Seok Jeong1,2*
1
Deparment of Energy Science, Sungkyunkwan University, Suwon 440-746, Republic of Korea
2
Center for Integrated Nanostructure Physics (CINAP), Institute for Basic Science (IBS)
* E-mail address: mjeong@skku.edu, kimj@skku.edu
Since the bandgap energy increases as the thinkness of molybdenum disulfide (MoS2)
decreases, many researchers have attempted to synthesize monolayer MoS2 through various
methods, such as mechanical exfoliation, and chemical vapor deposition (CVD). Mechanical
exfoliation using scotch tape produces a high quality sample, but it takes long time to find
monolayer of MoS2 by optical microscope. Although CVD method is more convenient in
method, the quality of the sample is a bit lower than one prepared by mechanical exfoliation.
Recently, photoexfoliation method using femtosecond pulsed laser is proposed to detach
monolayer graphene sheets from graphite with high surface quality and large quantity [1].
Here we report successful preparation of few-layer MoS2 by the laser-exfoliation method. The
number of layers and morphological characteristics were confirmed by Photoluminescence,
Raman spectroscopy, and SEM measurement, we could confirm the presence of MoS2 thin
films.
Fig. 1 shows the experimental scheme of the laser-exfoliation. An amplified Ti:sapphire laser with
80 fs pulse duration and 800 nm center wavelength was focused on the surface of bulk MoS2, and we
performed the laser-exfoliation under different laser powers (1~2.8 mJ) and three different incident
angles (45°, 70°, and 90°). Di-water and Ethanol was used as a solvent to suspend the sheets
exfoliated. Compared to the previous report [2], Raman spectra that we obtained from the laserexfoliated sample indicate that we successfully produced few-layer MoS2 from the bulk (0.2 nm of
spectral resolution, 1800 lines/mm grating with 500 nm blaze).
Fig. 2 shows the few-layer MoS2 picture of laser-exfoliation. When using Di-water, ratio of Diwater and MoS2 is 10: 1.
Fig. 1. Experimental setup for photoexfoliation of bulk MoS2
Fig. 2. Solution for photoexfoliation of few- MoS2
References
1. Y. Miyamoto, H. Zhang, D. Tomanek, Phys. Rev. Lett. 104, 208302 (2010).
2. H. Li, Q. Zhang, C. Yap, B. Tay, T. Edwin, A. Olivier, and D. Baillargeat, Adv. Funct. Mater. 22, 1385 (2012).
W-P-009
Optical properties of few-layer MoS2
Hanul Kim1, Heesuk Rho1,*, Joo Song Lee2, Soo Min Kim2
2
1
Deparment of Physics, Chonbuk National University, Jeonju 54896, Korea
Soft Innovative Materials Research Center, Korea Institute of Science and Technology, Jeollabuk-Do 55324,
Korea
* E-mail address: rho@chonbuk.ac.kr
We utilized Raman scattering and photoluminescence (PL) from CVD-grown MoS2 layers
to study exciton and phonon behaviors simultaneously as a function of layer thickness. Atomic
force microscope images revealed that triangular-shaped MoS2 layers each were stacked on a
basal monolayer. From a side to the triangle center, MoS2 layer thickness increased gradually
from monolayer to a few layers. Polarized Raman scattering measurements were employed to
1
identify scattering symmetries of optical phonons. For a monolayer MoS2, E2g
and A1g
phonon modes were observed at 385 and 404 cm-1, respectively. Interestingly, these modes
varied systematically in linewidths, intensities, and peak energies with an increase of the layer
thickness, indicating the presence of interlayer interactions. Therefore, it is expected that
exciton characteristics can be modified as a function of layer thickness. PL from monolayer
MoS2 revealed A and B exciton peaks at 1.88 and 2 eV, respectively. With an increase of the
number of layers, the PL emission strength was gradually weakened and finally quenched in
thick MoS2 layer. In addition, PL peak energies and linewidths were changed systematically
with an increase of the layer thickness.
This research was supported by the Basic Science Research Program through the National
Research Foundation of Korea (NRF) funded by the Ministry of Education (Grant No.
2014R1A1A2057173), the Korea Basic Science Institute under the R&D program (Project No.
E36800) supervised by the Ministry of Science, ICT and Future Planning, and the KIST
institutional program.
W-P-010
Single Si-nanowire/graphene-nanoribbon lateral-type heterojunctions
Ju Hwan Kim, Jong Min Kim, Sang Woo Seo, Sung Kim, and Suk-Ho Choi*
Department of Applied Physics, Kyung Hee University, Yongin 446-701, Korea
*E-mail address: sukho@khu.ac.kr
Successful realization of advanced wearable devices requires their building materials to be high-grade especially
in flexibility, transparency, and electrical conductivity. In particular, Si nanowires (NWs) and graphene, the earthabundant materials, have recently attracted much attention due to their excellent physicochemical properties
suitable for such purposes. In this work, we report novel properties of single Si-NW/graphene-nanoribbon (GNR)
lateral-type heterojunctions fabricated based on simple procedures. Metal-assisted chemical etching of Si is
employed to fabricate Si NWs with uniform diameter/length and smooth surface. The prepared Si NWs are
plucked off from the Si substrate and collected in EtOH. The Si-NWs solution is spin-coated on monolayer
graphene that was synthesized by chemical vapor deposition, and subsequently, the Si NWs/graphene sample is
treated by O2 plasma. As a result, the exposed graphene is etched out by O2 plasma, and the graphene underneath
Si NWs is selectively left to be GNRs, resulting in the formation of single Si-NW/GNR junctions. Optical and
structural properties of the Si-NW/GNR junctions are characterized by Raman spectroscopy, scanning electron
microscopy, and atomic force microscopy. The electrical properties of p- and n-type Si NW/GNR junctions are
analyzed by current force microscopy (CFM). The I-V curves obtained from CFM show asymmetric rectifying
behaviors. These and further details of the experimental results are discussed based on possible physical
mechanisms.
Fig. 1. (a) Fabrication procedures of Si-NW/GNR junctions. (b) and (c) Scanning electron microscope
images of single Si NW and GNR, respectively.
W-P-011
Characterization of graphene n-doped with triethylenetetramine
Jung Hyun Kim, Chan Wook Jang, Ha Seung Lee, Sung Kim, and Suk-Ho Choi*
Department of Applied Physics, Kyung Hee University, Yongin 446-701, Korea
*E-mail address: sukho@khu.ac.kr
Doping is an essential part in the studies of graphene because the conductivity and
workfunction of graphene are engineered by doping based on its unique band structure.
Chemical doping method has been extensively used due to its simple process and high doping
strength compared to other methods, but has drawbacks such as instabilities caused by
evaporation of dopants from the surface of graphene. This problem is more serious in n-type
doping because of undesirable reaction between dopants and ambient water and oxygen. It is a
challenge to maintain the doping strength while improving the stability of doping. Advent of
an innovative chemical doping method, vapor-phase doping, could facilitate strong and stable
doping. Here, we employ triethylenetetramine (TETA) as an n-type dopant [1] to change the
doping strength of graphene and enhance its stability. To vary the doping concentration we
control the time for graphene to be exposed to the vapor phase of TETA. We show the
characteristics of graphene can be controlled and tuned delicately by this doping method.
Fig. 1. (a) Raman spectra of doped graphene for various doping concentrations of TETA. (b)
G peak and 2D peak distribution of doped graphene for various doping concentrations of TETA.
References
1. Y. Kim, J. Ryu, M. Park, E. Kim, J. M. Yoo, J. Park, J. H. Kang, B. H. Hong, ACS Nano 8,
868 (2013).
W-P-012
Intermediate band solar cell of AlZnO/ZnTe:Cr/p-Si with InSnO electron
transfer layer
Kyoung Su Lee, Sang Woo Pak, Gyujin Oh, and Eun Kyu Kim*
Department of Physics, Hanyang University
*
E-mail: ek-kim@hanyang.ac.kr
Low-cost, high efficiency solar cells are tremendous interests for the realization of a
renewable and clean energy source. ZnTe based solar cells have a possibility of high efficiency
with formation of an intermediated energy band structure by impurity doping. A pulsed (10 Hz)
Nd:YAG laser operating at a wavelength of 266 nm was used to produce a plasma plume from
an ablated a ZnTe:Cr target, whose density of laser energy was 10 J/cm2. The base pressure of
the chamber was kept at a pressure of approximately 4x10-7 Torr. ZnTe:Cr films with thickness
of 130 nm were grown on p-Si substrate, and then AlZnO thin film with thickness of 150 nm
were grown on ZnTe:Cr film at oxygen partial pressure of 3 mTorr. Growth temperature of all
the films was set to 250 oC. As an electron transfer layer, InSnO thin film with thickness of
100 nm was grown on ZnTe:Cr by using sputter. Finally, grid patterns of Ti/Au and In metal
were deposited on front and back side of the solar cells by using thermal evaporation,
respectively. For the fabricated solar cell, dark current was measured by using Keithley 2600.
Solar cell parameters were obtained under Air Mass 1.5 Global solar simulator with an
irradiation intensity of 100 mW cm−2.
W-P-013
Enhancement of ultraviolet photoresponse properties of Al-doped ZnO thin
films prepared by sol-gel spin coating method
Wookbin Lee and Jae-Young Leem*
* Department of Nano Science & Engineering, Inje University, 197, Inje-ro, Gimhae-si,
Gyeongsangnam-do 621-749, Korea
A recent study on improved ultraviolet (UV) photoresponse properties of zinc oxide (ZnO)
thin films through ZnO buffer layer obtained by evaporation has been reported [1]. However,
we report that Al-doped ZnO (AZO) thin films enhanced UV photoresponse properties without
ZnO buffer layer. The undoped and AZO thin films obtained using sol-gel spin-coating method
on silicon substrates with different Al-doping concentration were prepared for metalsemiconductor-metal (MSM)-type UV photoconductive sensor applications. The absorbance
of AZO thin films in UV region was higher than that of undoped ZnO thin films. The UV
sensor based on AZO thin films exhibited faster reset and decay times as well as a higher UV
responsivity and sensitivity compared with UV sensor based on undoped ZnO thin films.
Therefore, our research may suggest a method of the facile fabrication for high photosensitivity
and fast-response UV sensor.
Figure 7) Photocurrent spectra of the UV sensor based on undoped (a) and 5% AZO (b) thin film under a bias voltage of 1 V in
response to the on/off switching of the UV illumination (λ = 365 nm).
References
[1] M. Kim et al., J. Korean Phys. Soc. 68, 705 (2016).
W-P-014
Optical and Electrical Properties of F-doped ZnO Thin Films Grown on
Muscovite Mica Substrates and Their Optical Constants
Younggyu Kim, Minjae Kim, and Jae-Young Leem *
*Department of Nanoscience & Engineering, Inje University, 197, Inje-ro, Gimhae-si,
Gyoengsangnam-do 621-749, Republic of Korea
Undoped and F-doped ZnO (FZO) thin films with different F concentrations were deposited
on muscovite mica substrates using the sol-gel spin-coating method [1]. All the films exhibited
strong ultra-violet emissions as well as broad peaks in the visible region. The transmittances of
the FZO films were slightly lower than that of the undoped film. The calculated optical band
gap of the FZO films did not show any notable changes with changes in the F concentration,
while the Urbach energy depended significantly on the F concentration. Using the refractive
index values of the films, their optical constants, such as the single-oscillator energy, the
dispersion energy, and the M-1, and M-3 moments, were determined. The electrical properties
of the films improved with an increase in the F concentration up to 9 at. %, and then decreased
slightly for further increase.
Fig. 1
Fig. 2
Figure 1) Normalized RT steady-state PL spectra of the FZO thin films with different F concentrations. The inset
shows the FWHM of the NBE peaks.
Figure 2) Optical transmittance spectra for the wavelengths of 200‒800 nm for the FZO thin films with different
F concentrations
References
[1] G. Nam et al., J. Mater. Chem. C. 2, 9918 (2014)
W-P-015
Oxidation temperature effects on ZnO thin films prepared from
evaporated metallic Zn on muscovite mica substrates
Woosung Jeon and Jae-Young Leem*
* Department of Nano science & Engineering, Inje University, 197, inje-ro, Gimhae-si,
Gyeonsangnam-do, 621-749, Korea
We studied the structural and optical properties of ZnO thin films oxidized by annealing at
different temperatures. Firstly, muscovite mica substrates were heated in order to efficiently
deposit Zn thin films by thermal evaporation and then the Zn thin films were oxidized by
annealing at temperature ranging from 200 to 600 °C. The ZnO thin films were formed by
thermal oxidation of the Zn thin films at oxidation temperature over 400 °C. The average
transmittance of these films in visible region was higher than 80% [1]. The intensity of nearband-edge (NBE) emission of the ZnO films was remarkably observed at 400 and 500°C. In
XRD patterns, Full width at half maximum (FWHM) of the ZnO (002) diffraction peaks was
the lowest at 500 °C. Therefore we found that the highest crystallinity of the ZnO thin film was
obtained at 500 °C.
Figure 8a) RT steady-state PL spectra of the ZnO films oxidized by annealing at temperatures ranging from 200 to 600 °C. b)
Optical transmittance spectra in the 200 to 800 nm range for the ZnO thin films oxidized by annealing at temperatures ranging
from 200 to 600 °C.
References
[1] Y. Kim et al., J. Korean Phys. Soc. 66, 1516 (2015).
W-P-016
Enhanced photoluminescence properties and photoresponse properties of
Li-doped ZnO thin films grown on quartz substrate by using spin-coating
Dongwan Kim and Jae-Young Leem*
* Department of Nanoscience & Engineering, Inje University, 197, Inje-ro, Gimhae-si,
Gyeongsangnam-do 621-749, Korea
Zinc oxide (ZnO) is one of metal oxide semiconductor with wide band gap (3.37 eV), a
large exciton binding energy (60 meV), and high transparent in the visible range.
Accordingly, ZnO has been extensively utilized as encouraging materials for the development
of several optoelectronic and photovoltaic devices such as UV sensors and solar cells.
Undoped ZnO exhibits n-type conductivity due to the native donor defects such as zinc
interstitial and oxygen vacancy [1]. In this paper, we fabricated the Li-doped ZnO thin films
on the quartz substrates by using a sol-gel spin-coating method to create the p-type ZnO. The
doping effect of Li with different concentrations (0, 1, 3, 5, 7, and 9 at.%) on electrical and
optical properties of Li-doped ZnO thin films were investigated. In the PL spectra, the
intensity of near-band-edge (NBE) emission gradually increased with increasing Li
concentration to 5 at.% and decreased with Li concentration from 5 at.% to 9 at.%. The UV
sensor made by Li-doped ZnO thin films has fast response more than UV sensor made by
undoped ZnO thin film and it indicates that UV sensor of the Li-doped ZnO thin film has
better UV photoresponse properties.
Figure 9a) PL spectra of the undoped ZnO films and Li-doped ZnO films. b) Time-resolved photocurrent spectrum at 0.5 V bias
in response to the on/off switch of UV illumination (λ = 365nm) for the undoped ZnO film. c) Time-resolved photocurrent
spectrum at 0.5 V bias in response to the on/off switch of UV illumination (λ = 365nm) for the Li-doped ZnO film.
References
[1] S. B. Zhang et al., Phys. Rev. B 63, 075205 (2001).
W-P-017
Enhanced optical properties of ZnO thin films grown by thermal oxidation
of Zn films on ZnO buffer layer/transparent substrates
Byunggu Kim and Jae-Young Leem*
*Department of Nanoscience and Engineering, Inje University, 197, Inje-ro, Gimhae-si,
Gyeongsangnam-do 621-749, Republic of Korea
In this study, we fabricated ZnO thin films by using thermal oxidation on spin-coated ZnO
buffer layers/corning glass or mica substrates (transparent substrates). Zn thin films were
deposited onto the ZnO buffer layers by using a thermal evaporator [1], and then the deposited
Zn thin films were thermally oxidized in a furnace at 200 – 600 °C for 2 h in air. Oxygen atoms
can diffuse into Zn thin films though the annealing process. Therefore, the intensities of nearband-edge (NBE) emission of the ZnO thin films on buffer layer/transparent substrates
increased significantly with increasing oxidation temperature up to 500 °C. However, the
intensities of NBE emission of the film remarkably decreased at the higher oxidation
temperature than 500°C. Zn thin films oxidized at temperatures of 200 and 300 °C had low
transmittances because Zn thin films were partially oxidized, which were Zn and ZnO phases.
While the Zn thin films oxidized at annealing temperatures of 400, 500, and 600 °C onto ZnO
buffer layer/corning glass and mica substrates had average transmittances of more than 82 %
and 75 %, respectively, because Zn thin films were fully oxidized.
Figure 1) PL spectra at RT of ZnO thin films oxidized at different temperatures onto ZnO buffer layer/transparent substrates.
Figure 2) The optical transmittance spectra of ZnO thin films oxidized at different temperatures onto ZnO buffer layer/transparent substrates.
References
[1] M. Kim et al., J. Korean Phys. Soc. 5, 68 (2016)
W-P-018
Effect of oxidation temperature on structural and optical properties of
thermally oxidized ZnO thin films on indium tin oxide substrates
Jiyun Moon and Jae-Young Leem*
*Department of Nanoscience and Engineering, Inje University, 197, Inje-ro, Gimhae-si,
Gyeongsangnam-do, 621-749, Korea
ZnO thin films were prepared by thermal oxidation of metallic Zn thin films deposited by
thermal evaporation on indium-tin-oxide-coated glass substrates. The Zn thin films were
oxidized by annealing at temperatures ranging from 350 to 650 °C. The ZnO thin films formed
by thermal oxidation at temperatures above 450 °C exhibited transmittances of 90% in the
visible region [1]. The optical band gaps of the oxidized ZnO thin films were blue-shifted upon
increasing the oxidation temperatures up to 450 °C and red-shifted at higher temperatures.
From the calculated Urbach energy, the ZnO thin film oxidized at 450 °C exhibited the best
crystallinity [2]. In the photoluminescence spectra of the oxidized ZnO thin films, the intensity
of the near-band-edge emission peak increased with increasing oxidation temperature up to
450 °C but decreased for further increases in the temperature.
Figure 10a) Plots of (αhν)2 as a function of the photon energy (hν) for ZnO thin films oxidized at 350–650 °C. b) Plots of the
Urbach energy of an as-deposited Zn thin film, the ZnO thin film oxidized at temperatures of 350– 650 °C.
References
[1] G. G. Rusu et al., Supperlattice Microst. 42, 116 (2007)
[2] S. W. Xue et al., J. Alloy. Compd. 448, 21 (2008)
W-P-019 [NO SHOW]
Preparation of well-aligned ZnO nanorods using eletrodeposition combined
with a rotating cathode
Youngbin Park and Jae-Young Leem*
* Department of Nanoscience & Engineering, Inje University, 197, Inje-ro, Gimhae-si,
Gyeongsangnam-do 621-749, Korea
ZnO is a compatible material for the growth of 1D nanostructure exhibiting superior and
unusual properties compared with bulk materials [1]. In case of electrodeposition, the
morphology of ZnO is easily tunable by controlling growth condition. This condition is
essential for both basic fundamental research and industrial applications because the properties
of ZnO nanostructure depend on the morphology, and practical applications can be modulated
by designing their morphology. Specially, the random orientation degrades the performance
of a nanostructure-based device. Thus, a novel approach that easily enhances the c-axis
orientation and controls the morphology of the nanostructure is needed. In this study, we
prepared ZnO nanorods on Au/Si substrates using electrodeposition combined with a rotating
cathode. The effect of various cathode rotation rates on the structural properties of
electrodeposited ZnO nanorods was specifically investigated. By rotating the cathode at
rotation rates of 300 rpm, better aligned ZnO nanorods not only were rapidly grown, but also
exhibited improvement in directional growth along the (002) crystallographic plane.
Figure 11a) Cross-sectional SEM image of electrodeposited ZnO nanorods grown for various times at rotation rates of 0 and
300 rpm and b) plot of rod length for ZnO nanorods as a function of deposition time.
References
[1] R.-J. Chung et al., Thin Solid Films 504, 570 (2014)
W-P-020
Effects of ZnTe separation layer thickness on optical properties of
multilayer CdTe/ZnTe quantum dots
Sung Hwan Jin1, Su Hwan Kim1, Jin Chul Choi1, Sang-Youp Yim2, and Hong Seok Lee3,*
2
1
Department of Physics, Yonsei University, Wonju 26493, Republic of Korea
Advanced Photonics Research Institute, Gwangju Institute of Science and Technology, Gwangju 61005,
Republic of Korea
3
Department of Physics, Chonbuk National University, Jeonju 54896, Republic of Korea
* E-mail address: hslee1@jbnu.ac.kr
Semiconductor QDs have been attractive because of the interest in both investigations of
fundamental physical properties and promising applications in electronic and optoelectronic
devices, such as single-electron transistors, lasers, and infrared photodetectors [1]. In
comparison to quantum well lasers, QD lasers have harnessed the unique properties of QDs to
obtain a high differential gain, low threshold current densities, and temperature-stable
operation. However, the performance of QD lasers still suffers from poor thermal stability and
low carrier collection in the QDs. The multilayer QD structures provide many advantages, such
as larger carrier collection, flexible detection wavelength tuning, more lateral transport, and
higher thermal stability. Among the II-VI QDs, CdTe QDs are of great interest due to their
potential applications in optoelectronic devices operating in the green spectral range. In this
work, we investigate the effects of ZnTe separation layer thickness on optical properties of
multilayer CdTe/ZnTe QDs. The photoluminescence (PL) measurements are shown, as the
ZnTe separation layer increasing the PL peak positions of the QDs are shifted to higher energy
because the interactions of the vertical electronic coupling between QDs are reduced and the
size of QDs are decreased due to the compressive strain of the ZnTe separation layer. And, the
PL intensities of the QDs are increased, which as the ZnTe separation layer increasing because
the much more carriers are confined from barrier into the QDs. In addition, we have observed
from the temperature-dependent PL measurement result that as the thickness of the ZnTe
separation layer increasing the thermal activation energy is increased. From these results we
could understand the optical properties of the multilayer CdTe/ZnTe QDs according to the
thickness of the ZnTe separation layer.
Fig. 1. PL spectra at 25 K for the multilayer CdTe/ZnTe QDs with the ZnTe separation layer thicknesses of 15,
30, 45, and 60 nm.
References
1. S. A. Empedocles and M. G. Bawendi, Science 278, 2114 (1997).
W-P-021
Interband transition and activation energy of multilayer CdTe/ZnTe
quantum dots
Su Hwan Kim1, Sung Hwan Jin1, Jin Chul Choi1, Sang-Youp Yim2, and Hong Seok Lee3,*
2
1
Department of Physics, Yonsei University, Wonju 26493, Republic of Korea
Advanced Photonics Research Institute, Gwangju Institute of Science and Technology, Gwangju 61005,
Republic of Korea
3
Department of Physics, Chonbuk National University, Jeonju 54896, Republic of Korea
* E-mail address: hslee1@jbnu.ac.kr
Potential applications of electronic and optoelectronic devices utilizing semiconductor
nanostructure systems have driven extensive efforts to grow various kinds of quantum
structures [1]. Even though quantum dot (QD) lasers have been expected to obtain a low
threshold current density, a high differential gain, and an ultrahigh temperature stability, the
performance of QD lasers is still not good enough to overcome the stability problems of devices
operating at high temperatures. The multilayer QD structures provide many advantages, such
as larger carrier collection, flexible detection wavelength tuning, more lateral transport, and
higher thermal stability. Wide-gap CdTe/ZnTe nanostructures utilizing their advantages of
higher excitonic binding energies are of great interest because of their potential applications in
optoelectronic devices operating at the green spectral range. In this work, we investigate the
optical properties in the multilayer CdTe/ZnTe QDs with various numbers of the CdTe QDs
layers. The photoluminescence (PL) peak position of the multilayer CdTe/ZnTe QDs shifts to
higher energies with increasing number of the CdTe QDs layers due to the intermixing by the
induced strain of the QDs. The PL intensity of multilayer CdTe/ZnTe QDs increases with
increasing number of the CdTe QDs layers. This behavior is attributed to an increase in the
density of the emitting states. Temperature-dependent PL measurements are carried out in order
to determine the activation energy of the multilayer CdTe/ZnTe QDs with various number of
the CdTe QDs layers. The present observations can help improve understanding of the optical
properties in the multilayer CdTe/ZnTe QDs with various numbers of the CdTe QDs layers.
Fig. 1. Integrated PL intensities as a function of reciprocal temperature for the multilayer CdTe/ZnTe QDs with
1 layer and 12 layers of CdTe QDs. Activation energies of the multilayer CdTe/ZnTe QDs as a function of number
of the CdTe QDs layers.
References
1. S. Facsko, T. Dekorsy, C. Koerdt, C. Trappe, H. Kurz, A. Vogt, and H. L.Hartnage, Science
285, 1551 (1999).
W-P-022
Characteristics of the Pulse Response of AlGaN/GaN HEMT at low
temperatures
Minsung Kang, Jeongjin Kim, Simhoon yuk, Jeonwook Yang and Chel-jong Choi1
1
School of Semiconductor and Chemical Engineering, Chonbuk National Univ, Jeonju 561-756, Korea
* E-mail address:
0.10
0.08
Drain current (A)
200
296K
246K
166K
86K
150
0.06
100
0.04
50
0.02
0
0.00
-12
-10
-8
-6
-4
-2
0
2
4
6
Transconductance (mS/mm)
Pulse response of AlGaN/GaN/HEMT was studied. To investigate the effect of temperatures,
transistor was cool down to 86 K and electrical characteristics were measured. A drain
current density of Ids = 300 mA/mm was obtained at room temperatures and it was increased
to 510 mA/mm at 86 K with a gate voltage of 0 V and a drain voltage of 5 V. Also, the
maximum transconductance was increased from 121 mS/mm to 183 mS/mm by lowering the
temperature as shown in Fig. 1. Transient response of the transistor at the gate pulse from -5
V to 0 V with a frequency of 1kHz, revealed large amount of variation at the temperature
between 296 K and 246 K in Fig. 2. It shows most of the trap influences on the pulse
response exist at near the room temperatures.
Gate voltage (V)
Fig. 1. DC transfer characteristics of AlGaN/GaN HEMT at various temperatures.
0.05
(a)
2.5
(b)
296K
246K
206K
166K
126K
Voltage (V)
Drain current (A)
2.0
0.04
0.03
296K
246K
206K
166K
126K
0.02
0.01
1E-4
1E-3
Time (s)
1.5
1.0
0.5
0.0
-0.5
-0.010
-0.005
0.000
0.005
0.010
Time (s)
Fig. 2 Pulse response with vGS stepped from -5 to 1 V and vDS = 7 V. (a) log scale (b) linear sacle.
W-P-023
Investigation of GaN Channel Quality on the Device Properties in
AlGaN/GaN HEMTs
Sung-Jae Chang1,*, Maruf Amin Bhuiyan2, Hee-Sung Kang3, Hyoung-Sup Yoon1,
Eun-Soo Nam1, Jung-Hee Lee3, Tso-Ping Ma2, and Jong-Won Lim1
1ICT
Materials & Components Research Laboratory, Electronics and Telecommunications Research Institute (ETRI),
Daejeon 305-700, Korea
2Electrical Engineering, Yale University, New Haven, CT 06511, U.S.A.
3School of Electrical Engineering, Kyungpook National University, Daegu 702-701, Korea
* E-mail address: sjchang@etri.re.kr
GaN-based high-electron mobility transistors (HEMTs) have been extensively researched
as possible next-generation power and radio-frequency transistors [1], thanks to the excellent
material properties, such as wide bandgap and high sheet carrier density at the heterojunction
interface. However, performance of the GaN-based HEMTs is mainly limited by the crystalline
quality of the GaN channel, requiring optimization.
We evaluate and discuss the impact of crystalline quality on AlGaN/GaN HEMTs
properties with varying GaN channel thickness (TGaN_Channel = 0.5, 2.0, 3.5 and 6.3 μm). The
schematic cross-section of the AlGaN/GaN HEMTs fabricated in this work is shown in Fig.1.
Systematic measurements were carried out for detailed comparison and characterization of
various GaN channel thickness devices.
X-ray diffraction measurement shows the dislocations which cause the charge trapping in
HEMTs reduces with increasing GaN channel thickness up to 3.5 μm and it saturates shown in
Fig.2. The reason is that threading dislocations originating from the substrate/GaN interface
are attenuated with growing thicker GaN channel layer and then remained beyond a certain
value. Gate-stress measurement was performed by applying two synchronized pulses at gate
and drain in order to observe the extent of trapping in different GaN channel quality devices.
For the quiescent bias points, VGS = -6 V and VDS = 0 V was applied while during the
subsequent measurement the corresponding biases are VGS = -2.5 V and VDS = 1 V. Smaller
threshold voltage shift resulted from the charge trapping [2] is achieved in thicker GaN channel
devices in Fig.3. Accurate effective channel mobility under the gated region considering
contact and sheet resistance between gate and source/drain [3] has been extracted which is
more relevant to the development of advanced device technology. When the GaN channel
thickness is changed from 0.5 to 3.5 μm, the carrier mobility values are varied from 780 to
1100 cm2/Vs (Fig.4). Our electrical measurements reveal that the density of traps reduces and
performance of the device improves with increasing GaN channel thickness up to a certain
value due to the ameliorated crystalline quality of the AlGaN/GaN HEMTs.
Fig.1. Cross-section of
AlGaN/GaN HEMTs.
Fig.2. XRD results. Full
width a half height vs GaN
channel thickness.
Fig.3. Threshold voltage
shift vs stress time for
various GaN channel
thicknesses
References
1.
2.
3.
X. Wang et al., IEEE trans. on Electron Devices, Vol. 61(5), 1341, 2014.
P. Lagger et al., IEDM, 2012 IEEE International, 13.1.1, 2012.
S.-J. Chang et al., Japanese J. Applied Physics, Vol. 55(4), 044104, 2016.
Fig.4. Carrier mobility vs
2DEG carrier density for
various
GaN
channel
thicknesses.
W-P-024
Effect of V/III ratio and Al composition of AlGaN on GaN by MOCVD
Woo Seop Jeong1, Dae-sik Kim1, Seung Hee Cho1, Cheol Kim1 and Dongjin Byun1,*
1
Deparment of Materials Science & Engineering, Korea University,
Anam-dong, Seongbuk-gu, Seoul, 136-713, Republic of Korea
* E-mail address: dbyun@korea.ac.kr
In this study, AlGaN layers on GaN grew for using GaN-based distributed bragg reflector
by metal organic chemical vapor deposition (MOCVD). AlGaN layer was deposited using GaN
template grown on c-plane sapphire. Grown AlGaN layers of bottom DBR for GaN-based light
emitting diode were investigated varied V/III ratio and Al composition. Conditions of V/III
ratio was adjusted to NH3 flow in reactor. Al composition in the growth of AlGaN layer
samples ranges from 0.1 to 0.3. Al composition of AlGaN grown on Si wafer were determined
using energy dispersive spectrometer (EDS). The surface morphology of AlGaN were
characterized using a field emission scanning electron microscope (FE-SEM) and atomic force
microscope (AFM). Properties of the AlGaN samples were obtained from x-ray diffraction
(XRD).
W-P-025
Temperature Dependence of ZnO Growth Mechanism on Si(100) Substrate
by Atomic Layer Deposition
Seunghee Cho1, Seonho Bae1, Dae-sik Kim1, Woo seop Jeong1, Cheol Kim1, Dongjin Byun1*
Department of Material Science and Engineering, Korea University,
Anam-dong, Seungbuk-gu, Seoul 136-713, Republic of Korea
* E-mail address: dbyun@korea.ac.kr
Zinc oxide(ZnO) growth mechanism by atomic layer deposition(ALD) on Si(100) substrate
were investigated. The ALD mechanism was determined using each substrate orientation and
temperature dependent deposition rate. ZnO deposited temperature was confirmed as 75°C ~
150°C and grow per cycle(GPC) was as 1.0Å ~ 2.0Å. The preferred orientation was changed
from (002) to (100) with increasing temperature. The changed preferred orientation was related
the surface activity and surface passivation effect[1]. The ZnO thin films were investigated
using field emission scanning electron microscope(Fe-SEM) and X-ray diffraction (XRD).
(a)
(b)
Fig. 1. SEM image of ZnO thin films deposited at (a) 75°C x100k (b) 150°C x100k
References
1. Z. Baji, et at, Crystal Growth & Design. 12, 5615-5620 (2012).
W-P-026
Growth of CdS Nanowires and Nanostructures catalyzed by Tin Oxide
Man Suk Song1, Seon Bin Choi1, and Yong Kim1,*
1
Deparment of Physics, Dong-A University, Busan 49315, South Korea
* E-mail address: yongkim@dau.ac.kr
CdS nanowires and nanostructures were grown via a physical vapor transport method on
silicon oxide substrate and fluorine-doped tin oxide (FTO) glass, respectively. Firstly, tin oxide
from the FTO glass substrate catalyzed the growth of a hierarchical structure that included a
stem and branches at a growth temperature of 280 °C. The stem nanowires grew along ⟨001⟩
with an unusual zinc blende structure whereas branched nanowires grew along ⟨0001⟩ with a
wurtzite structure. A modified vapor−solid−solid mechanism predominantly controlled by the
diffusion of source species along the surface of the quasi-liquid shell of the catalyst while
keeping its crystalline solid core was proposed based on the finding of a faceted core−shell SnSnO2 catalyst. The tetragonal β-phase Sn structure was observed and may induce the epitaxial
growth of zinc blende CdS nanowires through a thin quasi-liquid interface as a result of the
close lattice match to zinc blende CdS. In contrast, branches were grown via a
vapor−liquid−solid mechanism by SnO2 catalysts, which were vapor-transported from the
higher temperature zone of the substrate, and condensed on the side wall of the stem nanowire.
Next, tin oxide nanoparticle spread on silicon oxide substrate played a catalytic role in growing
CdS nanowires as well. The CdS nanowires presented a polytypic property with a mixture of
CdS zinc blende and wurtzite crystal structure. Both CdS nanostructures showed strong
photoluminescence emission without impurity-related bands indicating high optical quality.
This research was supported by the Basic Science Research Program through the National
Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and
Technology (2015R1D1A3A01015615).
Fig. 1. FESEM image of as-grown branched CdS nanowires on FTO glass substrate.
W-P-027
Normally-off AlGaN/GaN HEMTs using hive shape fin-gate channel
Jeong jin Kim1, Sang Chun Ko2, Gye Mo Yang1, Tae Hoon Jang1, Jeon Wook Yang1
1
Department of Semiconductor Science and Technology/Semiconductor Physics Research Center, Chonbuk
National University, Jeonju, Korea
2
Electronics and Telecommunications Research Institute, Daejeon, Korea
* E-mail address: kjj_jin@jbnu.ac.kr
In this study, nano-sphere lithography and recess etch process were used for fabrication of
multi-fin-gate structure, to obtain normally-off operation of AlGaN/GaN HEMTs. The
AlGaN/GaN HEMTs using fin-gate structure facilitated the realization of normally-off
operation due to fringing effect by narrow channel width under 100 nm. The fin-gate structures
demanded high resolution lithography techniques such as E-beam lithography in order to define
the gate channel width under 100 nm. However, these high resolution lithography equipments
are expensive and/or show poor productivity. In this regard, we investigate the AlGaN/GaN
HEMTs with hive shape channel under gate using self-assembly of nano-spheres of 200 nm
diameter. Fig 1. (a) shows the fabricated device structure which have the gate width of 60 nm
with a shape of hive wall, and the device are fabricated without gate dielectric. The fabricated
device shows the threshold voltage of 0.7 V and maximum drain current density of 216 mA/mm.
(a)
(b)
Fig 1. (a) Device structure and (b) ID-VG characteristics of fabricated AlGaN/GaN HEMTs.
W-P-028
AlZnO/n-ZnO/p-Si heterojunction photovoltaic devices with AlOx barrier
layer
Ji Hoon Kang, Kyoung Su Lee, and Eun Kyu Kim*
Department of Physics, Hanyang University
*
E-mail: ek-kim@hanyang.ac.kr
ZnO semiconductor material has been widely utilized in various applications in
semiconductor device technology owing to its unique electrical and optical features. This is a
promising as solar cell material, because of its low cost, n-type conductivity and wide direct
band gap. In this work, the AlZnO/n-ZnO/p-Si heterojunction diodes with AlOx thin barrier
layer were fabricated by pulsed laser deposition system and thermal evaporator. Aluminum thin
films with different thickness were deposited on p-Si (100) substrate. AlOx film was obtained
by post annealing of Al film in oxygen atmosphere. AlZnO and ZnO layers were grown at 250
o
C on AlOx/p-Si by using pulsed laser deposition respectively. Vacuum chamber was evacuated
to a base pressure of approximately 2x10-6 Torr. A pulsed (10 Hz) Nd:YAG laser operating at a
wavelength of 266 nm was used to produce a plasma plume from ablated AlZnO and ZnO
targets, whose density of laser energy was 10 J/cm2. Thicknesses of AlZnO and ZnO thin films
were about 100 nm and 200 nm respectively. Optical property was characterized by
photoluminescence and crystallinity of AlZnO and ZnO was analyzed by X-ray diffraction.
Photovoltaic devices with AlZnO/n-ZnO/p-Si heterostructure were formed by deposition of
indium metal and Al grid patterns on back and front sides, respectively, by using thermal
evaporator. Finally, the photovoltaic properties were measured by Air Mass 1.5 Global solar
simulator with an irradiation intensity of 100 mW/cm2.
W-P-029
Inspection of Defective Regions of GaN-Based Light-Emitting Diode
Wafers By Photoluminescence Imaging
Jongseok KIM1,*, Hyung Tae KIM1, Seungtaek KIM1, Hoon JEONG1, Kyung Chan JIN1, InSung CHO2, Min Soo NOH2, and Hyundon JUNG3
1Korea
Institute of Industrial Technology, Cheonan31056, Korea
2Soft-Epi, Gwangju 12790, Korea
3Etamax Co., LTD., Suwon 16650, Korea
* E-mail address: jongseok@kitech.re.kr
We present results of photoluminescence (PL) imaging for GaN-based light emitting diode (LED)
epi-wafersand chip-wafers. The PL images of the epi-wafers revealed defective regions as dark
spots, which were Shockley-Read-Hallnonradiative recombinationcenters and caused degraded
optical and electrical properties of LED chips fabricated from the epi-wafer [1]. The PL images
of LED chip-wafers showed dark chips with low optical intensities. The low optical intensities
of the chips could be resulted from forward leakages due to dark spot defects or low resistance
paths. The chips with dark PL images from chip-wafers showeddegraded optical and electrical
properties from LED chip probing results. The dark PLimages of defective regions from LED
wafers were investigatedusing a micro-PL setup. The experimental setup for micro-PL imaging
was composed of a 405nm laser as an excitation source, a diffuser for expansion of the laser
beam, a 425nm longpass filter for directing the excitation laser beam to the objective lens and
selecting PL, microscope optics, and a CCD camera. The PL images at micro-scale showed dark
spot defective regions as observed at the PL images of the large area of LED wafers. MicroscalePL imaging provided with defect regions ofsmaller than 50 μm. The dark spot images were
compared with microscopic inspection resultsof surface defects.Some PL images at micro-scale
showed sub-surface defective regions that were not observed clearlyby a surface inspection using
a microscope, which indicates that the PL imaging could be an effective inspection method for
evaluation of LED wafers.
Fig. 1. Images of defective regions from LED epi-wafers: (a), (c) Microscope image using 20x objective lens
(b), (d) Photoluminescence images of the region under a diffused 400 nm laser excitation
References
1. J. Kim, H. Kim, S. Kim, H. Jeong, I.-S. Cho, M. S. Noh, H. Jung, and K. C. Jin, J. Opt.
Soc. Korea 19, 687 (2015).
W-P-030
Ultra-low rate dry etching conditions for fabrication of normally-off field
effect transistor on AlGaN/GaN heterostructure
Zin-Sig KIM*, Hyung-Seok LEE, Jeho NA, Sang-Choon KO, Eunsoo NAM and Jong-Won
LIM
ICT Materials & Components & Research Laboratory, ETRI, Daejeon 34129, Korea
* E-mail address: synthese@etri.re.kr
Enhancement-mode transistors with uniform turn-on threshold voltage (Vth) can be achieved
by means of low damage and low rate gate recess etching techniques [1]. In this work, the dry
etching condition of AlGaN/GaN heterostructure with ultra-low etching rate of 1.5 nm/min. is
demonstrated. The etching process of AlGaN/GaN heterostructure was performed in Cl2/BCl3
plasma using inductively coupled plasma (ICP). The optimal recess depth was achieved after
examination with various conditions in dependence of recess time. The optimized etching
condition results in the low damages and smooth roughness of the etched AlGaN/GaN surfaces.
The recess of gate region with the fine controlled recess depth was performed for AlGaN/GaN
heterostructure without any etch-stop layer for the fabrication of field effect transistors (FETs)
using conventional processes. The fabricated normally-off Al2O3/AlGaN/GaN MOSFETs
delivered a high positive Vth of +4.8 V with the low off-state leakage current of ~10-6 A/mm.
and lower current collapse.
Figure 12 a) The measured recess depth of AlGaN/GaN vs. the recess time with various conditions. b) Schematic cross
section of the normally-off Al2O3/AlGaN/GaN MOSFET.
Figure 2 a) Measured transfer curve in logarithm scale and b) linear scale, c) the output curve of the fabricated normally-off
Al2O3/AlGaN/GaN MOSFET.
References
[1] S. Lin et al., IEEE Electron Device Lett. 37, 377 (2016)
W-P-031
Temperature dependence of the optical transitions of InP-GaP lateral
nanowires
Yongmin Kim1*, Y.H. Shin1, J.D. Song2
1
Department of Applied Physics Dankook University, Yongin, Korea
2
KIST, Hwarangno 14-gil, Seongbuk-gu, Seoul 5, Korea
* E-mail address: yongmin@dankook.ac.kr
Linearly polarized photoluminescence (PL) measurements were carried out on InP-GaP lateral
nanowires grown using a lateral composition modulation method in pulsed magnetic fields up
to ∼ 50 T and temperature between 4 K and 300 K. In these structures, the energy band
alignment becomes type-I and type-II in In-rich wire and Ga-rich barrier regions, respectively.
It is revealed that the polarization of the type-I PL is oriented along the [1-10] crystal direction,
whereas that of the type-II PL is along the [110] direction in the absence of magnetic field.
These two different PL peaks exhibit anomalous energy shifts with respect to the direction of
the magnetic field due to the variation of the confined energy in the exciton center of mass
potential. The [110] transition also shows strong abnormal behavior by changing temperature
below 100 K. This behavior is due to the internal strain field which changes with respet to
temperature.
W-P-032
Transient absorption spectroscopy of organic-inorganic lead bromide
perovskite quantum dots
Sang Woo Kim1,2, Sung Hyuk Kim 1,2, Dae Young Park1,2, and Mun Seok Jeong1,2,*
2
1
Deparment of Energy science, Sungkyunkwan University, Suwon 440-746, Korea
Center for Integrated Nanostructure Physics (CINAP), Institute for Basic Science (IBS), Sungkyunkwan
University, Suwon 446-746, Korea
* E-mail address: mjeong@skku.edu
Hybrid organic-inorganic lead halide perovskites and their quantum dots (QDs) have recently
been studied owing to their unique characteristics such as a long diffusion length, lifetime and
high absorption coefficient, etc [1,2]. Furthermore, the bandgap is easily tunable in a whole
range of visible, depending on the size of QDs which can be controlled by reaction temperature
and modulation of the amount of halogen. Due to these outstanding properties, they are being
applied in various optoelectronic devices such as solar cell and LED [3]. In spite of many
efforts on fabrication of devices, fundamental properties of perovskite QDs still remain to study.
Using transient absorption (TA) spectroscopy, we study the carrier dynamics of hybrid
organic-inorganic lead bromide perovskite (CH3NH3PbBr3) QDs. To analyze in detail, we
discuss TA spectra and their kinetics with the different pumping powers. The samples were
synthesized with temperature distribution of 0oC to 60oC.
References
1. S. S. Mali, C. S. Shim, and C. K. Hong, NPG Asia Mater. 7, e208 (2015).
2. K. Wu, G. Liang, Q. Shang, Y. Ren, D. Kong and T. Lian, J. Am. Chem. Soc. 137,1279212795 (2015)
3. J. Song, J. Le, X. Li, L. Xu, Y. Dong, and H. Zeng, Adv. Mater. 27, 7162 (2015)
W-P-033
Surface Engineering of Electron Transport Layers for High Performance
of Organic Photovoltaic Cells
Ju Won Lim1,3, Keun Yong Lim2, Won Kook Choi2, Do Kyung Hwang1*, and
Dong Ha Kim3*
1
Center of Opto-Electronic Materials and Devices, Post-Silicon Semiconductor Institute, Korea Institute of
Science and Technology (KIST), Seoul 02792, Republic of Korea
2
Materials and Life Science Research Division, Korea Institute of Science and Technology (KIST), Seoul 02792,
Republic of Korea
3
Department of Chemistry and Nano Science, College of Natural Sciences, Ewha Womans University, 52
Ewhayeodae-gil, Seodaemun-gu, Seoul 03760, Republic of Korea
* E-mail address: dkhwang@kist.re.kr
*E-mail address: dhkim@ewha.ac.kr
Abstract
Modification of electron transport layers (ETLs) has been actively utilized for the development
of high-performance organic photovoltaic (OPV) cells via lowered conduction band energy1,2.
In this article, we systematically engineered the role of surface modifier layer with different
types of device configurations, which can verify the formation of interfacial dipoles at the
surfaces. The low-energy bandgap poly[4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5bA]dithiophene-2,6-diyl][3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]-thiophenediyl]
(PTB7) and [6,6]-phenyl-C70-butyric acid methyl ester (PC70BM) based inverted OPVs with
ZnO/PEIE bilayer showed significantly enhanced power conversion efficiency (PCE) values
of 8.46 % while the other devices exhibited 7.12 % and 7.43 % respectively, which shows more
than 18.8 % and 13.8 % increase in efficiency. As a result, the design of ZnO/PEIE bilayer
shows the best performance in solar cell configuration by improving the resistance and fill
factor.
Fig. 13. Device configurations with different types of electron transport layers.
References
1. S. Woo, W. H. Kim, H. Kim, Y. Yi, H. –K. Lyu, and Y. Kim, Adv. Energy Mater. 4, 1301692
(2014).
2. T. H. Lee, H. Choi, B. Walker, T. Kim, H.-B. Kim, and J. Y. Kim, RSC Adv., 4, 4791–4795
(2014)
W-P-034
Raman spectroscopy of single crystalline organic-inorganic halide
Perovskite
Ayoung Lee1,2, Daeyoung Park1,2, Mun Seok Jeong1,2*
1
Deparment of Energy Science, Sungkyunkwan University, Suwon 440-746, Republic of Korea
2
Center for Integrated Nanostructure Physics (CINAP), Institute for Basic Science (IBS)
* E-mail address: mjeong@skku.edu,
Organic-inorganic halide Perovskite has been spotlighted as a solar cell materials because of
its tunable band gap, high absorption coefficients. Particularly single crystalline Perovskite is
notable for low trap density and long carrier diffusion lengths [1]. Raman spectroscopy is used
to investigate the chemical composition of Perovskite [2]. In high frequencies, organic
component has Raman active mode. Low frequency range, in comparison, is studied for
inorganic component which is halide composition. Here we report low frequency Raman
spectrums single crystalline by two types of crystallization. One is Anti solvent Vapor-assisted
Crystallization (AVC). The other is Inverse Temperature Crystallization (ITC).
We expect
that our results can be used to optimize the crystallization condition of Perovskite crystal.
Fig. 1 shows the single crystalline Perovskite. They changes in color because of different optical
band gap energy (from 2.31 eV to 3.05 eV)
Fig. 2 shows the Raman spectrums of CH3NH3PbI3 at low frequency range. The excitation
wavelength of 532 nm in ambient conditions
Fig. 1. Single crystalline CH3NH3Pb(ClxBr1-x)3
Fig. 2. Raman spectrum measured of CH3NH3PbI3, left spectrum from AVC method and the right from ITC
References
1. Saidaminov. M. I, Abdelhady. A. L, Murali. B, Alarousu. E, Burlakov. V.
M, Peng. W, Dursun. I, Wang. L, He. Y, Maculan. G, Nat. Commun. , 6, 7586 (2015)
2.
Ledinský. M, Löper. P, Niesen. B, Holovský. J, Moon. S.-J, Yum. J.-H, De Wolf. S, Fejfar, Ballif. C,
J. Phys. Chem. Lett. 6, 401, (2015)
W-P-035
High-efficiency Si-quantum-dot solar cells containing pristine and doped
graphene layers as transparent electrodes
Jong Min Kim1, Ju Hwan Kim1, Soo Seok Kang1, Sung Kim1, Suk-Ho Choi1,*, and Kyung
Joong Kim2
1
2
Department of Applied Physics, Kyung Hee University, Yongin 446-701, Korea
Division of Industrial Metrology, Korea Research Institute of Standards and Science, P.O. Box 102, Yuseonggu, Deajeon, Korea
*E-mail address: sukho@khu.ac.kr
Among the various types of solar cells: amorphous Si solar cells, dye-sensitized solar cells, and
perovskite solar cells, Si quantum dots (SQDs)-based solar cells have a particular advantage:
controlling the band gap of SQDs. [1] Here, we report the enhancement of the power
conversion efficiency (PCE) in SQDs solar cells by employing pristine and AuCl3-doped
graphene layers as transparent electrodes. Single-layer graphene sheets were prepared by
chemical vapor deposition, and subsequently transferred on top of the SQDs-embedded oxide
(SQDs:SiO2) multilayers (MLs)/Si wafers. For p-type doping of graphene, AuCl3 solution of 5
to 30 mM concentrations were dropped and spin-coated on the whole surface of the graphene/
SQDs:SiO2 MLs. Al thin films were deposited on graphene and Si substrate as top and bottom
electrodes. Finally, the samples were annealed in the oven to reduce the contact resistance
between graphene and SQDs:SiO2 MLs surface. The quality of graphene and the effect of ptype doping were checked by Raman scattering. The transmittance showed a monotonic
decrease with increasing doping concentration, and reached a level of ~75 % at the highest
doping concentration. The PCE of the SQDs solar cells with pristine graphene showed a highest
value (10.6 %) at 560 oC. For the p-type graphene, the PCE depended strongly on the doping
concentration, and reached the highest value (11.3 %) at 10 mM.
References
1. G. Conibeer, M. A. Green, D. Konig, I. Perez-Wurfl, S. Huang, X. Hao, D. Di, L. Shi, S.
Shrestha, B. Puthen-Veetil, Y. So, B. Zhang, and Z. Wan, Prog. Photovolt: Res. Appl. 19, 813
(2011).
W-P-036
FPGA-based LabVIEW Control Software for Atomic Force Microscopy
Naveed Ullah, Bernard Ouma Alunda, and Yong Joong Lee*
School of Mechanical Engineering, Kyungpook National University, Daegu 702-701, Republic of Korea
* E-mail address: yjlee76@knu.ac.kr
Atomic Force Microscope (AFM) is one of the frequently-used tools for
nanotechnology research involving the visualization of nanostructures and their
characteristics. Typically, it is often difficult to use the default software packages available
with commercial scanning probe microscopes for custom applications. Consequently, there
have been constant needs for more adoptable, flexible and user friendly control software for
various customized tasks. As an attempt to address these needs, we are in the process of
developing a flexible AFM control software using National instrument’s LabVIEW. Real-time
and deterministic control using FPGA hardware allows for higher feedback rates, which
significantly improve stability and accuracy of the control software. Moreover, FPGA control
allows true parallel executions and deterministic response to every task, unlike typical
microprocessors or digital signal processors. Due to the simplicity of design, modularity, and
future expandability offered in an FPGA package, future modifications to the overall code
result in a greatly expanded level of customization. So far, our code is equipped with the
features of oscillator tuning, a digital PID feedback control, scan related parameter controls,
image acquisitions, and on-demand data-file saving. We are currently in the process of
implementing other features necessary for running a tuning fork-based AFM.
References
1. A. J. Berger et al., Rev. Sci. Instrum. 85, 123702 (2014).
2. D. B. Nowak et al., Rev. Sci. Instrum. 82, 103701 (2011).
W-P-037
A Two-Axis Parallel-Kinematic Nano-positioner for High Speed Atomic
Force Microscopy
Bernard Ouma Alunda1, Naveed Ullah1, and Yong Joong Lee1,*
1
School of Mechanical Engineering, Kyungpook National University, Daegu 702-701, Republic of Korea
* E-mail address: yjlee76@knu.ac.kr
Atomic force microscopy (AFM) has been widely used to overcome the limitation of scanning
tunneling microscope because it is capable of acquiring topographical images of nonconducting surfaces. Lately, AFM has been extended to the study of biological samples in a
liquid environment. Many biological processes involving living things are not only static but
also dynamic in nature. Traditional AFM is inadequate for obtaining information about
dynamic processes due to slow scanners used in capturing images. In this work we present a
rigid, simple, high-precision two-axis parallel-kinematic nano-positioner with high resonant
frequencies suitable for high-speed atomic force microscopy. The maximum static deflection
and the resonant modes with their frequencies were predicted using finite element analysis.
The actual displacement and resonant frequency modes were also measured, and the values
agree well with the predictions of finite element analysis.
References
1. P. N. Adrian, W. E. Blake, H. Nahid, D. A. Jonathan, and E. F. Georg, Sci. Rep 5,
11987 (2015).
2. B. J. Kenton and K. K. Leang, IEEE/ASME Trans. Mechatronics 17, 356-369 (2012).
3. A. Toshio, Curr. Opin. Struc. Biol. 28, 63-68 (2014).
4. G. Schitter, J. T. Philipp, and K. H. Paul, Mechatronics. 18, 282-288 (2008).
W-P-038
Well-Aligned ZnO Nanorods Assisted with Close-packed Polystyrene
Monolayer for Quartz Crystal Microbalances
Hyun Ji Choi1,2, Hyeon Jin Seo1, Ki-Hwan Hwang1,2, Jung-Hoon Yu1, Jee Yun Kim1,2, YongMin Lee1, Yulhee Lee1, Dong In Kim1, Sang Hun Nam2 and Jin-Hyo Boo1,2,*
1
Department of chemistry, Sungkyunkwan University, 440-746 Suwon, Republic of Korea
2
Institute of basic science, Sungkyunkwan University, 440-746 Suwon, Republic of Korea
* E-mail address: jhboo@skku.edu
Zinc Oxide (ZnO) is known as a promising material for sensing devices due to piezoelectric
properties. Recently, Quartz crystal microbalances (QCMs) have been widely promising sensor
platforms owing to their high sensitivity and ease of measurement. In particular, the alignment
of ZnO nanostructures into ordered nanoarrays is expected to improve the device sensitivity
due to the large surface area which can be utilized to capture significant quantities of gas
particles. In this study, we investigated nanostructures by adjusting the interval distance of the
arranged ZnO nanorods according to polystyrene (PS) spheres of various sizes (800 nm, 1300
nm and 1600 nm). Therefore, ZnO nanorods were grown on a quartz substrate with patterned
polystyrene monolayer by hydrothermal method. And then, ZnO nanorods modified with
polyvinylidene fluoride (PVDF) was fabricated and used for detection of dimethyl
methlyphosphonate (DMMP) vapor. QCMs were based on the frequency shifts due to the
adsorption of DMMP vapor on the surface of the modified electrodes. The obtained ZnO
nanostructures was characterized by XRD (X-ray diffraction), FE-SEM (Field-emission
scanning electron microscopy), EDS (Energy dispersive x-ray spectroscopy) and QCMs
(Quartz crystal microbalances).
Fig. 1. FE-SEM images of ZnO nanorods growth on quartz substrate by PS monolayer template. PS sphere having
diameters of about (a) 800 nm, (b) 1300 nm, (c) 1600 nm, cross section of (d) 800 nm, (e) 1300 nm and (f) 1600
nm.
References
1. Y. Zhihua, J. Yadong, and Y. Junsheng, Sensors and Actuators B 125, 167-172 (2007).
W-P-039
Preparation of lignin-based carbon aerogels as biomaterials for nanosupercapacitor
Bong Suk YANG, Myung-Joon JEONG and Kyu-Young KANG*
Department of Biological and Environmental Science, Dongguk University-Seoul, Seoul 04620,
Republic of Korea
* E-mail address: kykang@dongguk.edu
1. Introduction: Carbon aerogels are obtained through the procession of carbonization by sol-gel
polycondensation of resorcinol with formaldehyde. Carbon aerogels are regarded as the ideal materials
for fuel cells and supercapacitor because of its excellent electrical conductivity properties and high
surface area. RF aerogel, which is used as a raw material in the production of the petroleum based
phenolic hydroxyl compound known as Resorcinol, can also be used as the aromatic structure
containing phenolic compound in lignin. Therefore, lignin-based aerogels can be a substitute for RF
aerogels. Although lignin is a renewable low-cost natural by-product and a non-toxic resource, it is not
utilized extensively. In this work, lignin-based aerogels were prepared by the sol-gel polycondensation
of lignin, kraft and organosolv lignin, with formaldehyde. The differences in the gel formation, density,
and thermal stability of lignin-based aerogels and microstructure were analyzed.
2. Methods: Lignin was isolated by kraft and organosolv pulping methods from wood. It was
homogenized for 1 hour in aqueous solution by the addition of NaOH as a catalyst. Formaldehyde was
then added to the lignin with the ratio of 1:1 and 1:2 (w/w). The mixture was cured in the oven at 85℃
for 5 days. The density of lignin-based aerogel was measured by apparent density. The thermal
properties were analyzed by TGA, and the stability of gel formation was carried out by measuring the
weight of unreacted portion of the mixture from the gelation process. The microstructures of the
aerogels were observed by SEM.
3. Results: Most of the density readings of lignin came out to 0.1-0.7 g/cm3 compared to the density
distribution of RF carbon aerogel (0.05-0.5 g/cm3). The results from TG analysis showed that the
responses of samples were different before and after temperature at 300℃. Based on SEM images, the
microstructure of kraft lignin-based aerogel has a three-dimensional network, which is similar to the
RF aerogel of existing studies. Organosolv lignin-based aerogel showed hierarchically organized porous
structure.
Lignin(KL)
Lignin-based aerogel(KL)
Lignin(OSL)
Lignin-based aerogel(OSL)
100
90
(b)
(a)
Weight (%)
80
70
60
50
40
30
20
0
100
200
300
400
500
600
Temp. (°C)
Fig. 1. TGA curves of lignin-based
aerogels and lignin.
Fig. 2. SEM images of lignin-based aerogels.
(a) Kraft lignin-based aerogel
(b) Organosolv lignin-based aerogel
References
1. A. Shaheen, J. A. Ritter, Adv. Mater. 15, 101-114 (2003).
2. L.I. Grishechko, A. Celzard, Microporous Mesoporous Mat. 168, 19-29 (2013).
Acknowledgement
This study was carried out with the support of ‘Forest Science & Technology Project (Project No.
S111315L010130)’ provided by Korea Forest Service. This work was also supported by the R&D Program of
MOTIE/KEIT (10049674).
W-P-040
Temperature-dependent local structural and electrical properties of VO2
films
Zhenlan Jin, In-Hui Hwang, Chang-In Park, and Sang-Wook Han*,
Department of Physics Education and Institute of Fusion Science, Jeonbuk National University, Jeonju 54869,
Korea
*
E-mail: shan@jbnu.ac.kr
We examined the local structural and electrical properties of VO2 films showing metal-toinsulator transition (MIT) by using in-situ x-ray absorption fine structure (XAFS)
measurements at the V K edge and resistance measurements in the temperature range 20–120°C.
VO2 films were synthesized on Al2O3 (0001) substrates by DC magnetron sputtering deposition.
X-ray diffraction measurements showed that the films had b-oriented monoclinic-phase
crystals at room temperature. XAFS measurements revealed a local structural transition in the
films from the monoclinic (M1) to the rutile (R) phase at ~70°C during their heating; further,
temperature-dependent resistance (R–T) measurements showed a sharp MIT in the films at
~75°C. Extended XAFS (EXAFS) measurements revealed non-rigid changes of V–O and V–
V bond lengths from the M1 to the R phase via the M2 phase. In-situ EXAFS and R–T
measurements showed that the synthesized VO2 films acted as Mott insulators and that their
electrical property change was not proportional to their structural property change at their MIT
temperature.
W-P-041
Flexible organic solar cells with various silver grid size between PET
substrate and graphene transparent electrodes
Myoung Joo Cha,12 Sung Man Kim,3 Ju Hwan Kang,1 Seong Jun Kang,3 Bright Walker2 and
Jung Hwa Seo1*
1
Department of Materials Physics, DONG-A University, Busan 49315, Republic of Korea
2 School of Energy and Chemical Engineering, Ulsan National Institute of Science and
Technology, Ulsan, 44919, Republic of Korea
3 Department of Advanced Materials Engineering for Information and Electronics,
Kyung Hee University, Yongin, 02447, Republic of Korea
* E-mail address: seojh@dau.ac.kr
We studied the effect of the silver grid size on graphene transparent conducting films for
flexible organic solar cells (OSCs). The silver grid was used an assistant layer of the graphene
to reduce the sheet resistance of substrates. Silver grid with various graphene sizes for
optimizing transmittance and sheet resistance of substrates were fabricated on polyethylene
terephthalate (PET) substrates to form the hybrid films. The optimized grid geometry on the
single layer graphene (SLG) was the grid dimension 200 μm × 200 μm × 50nm × 2μm (length
× width × height × linewidth), where the sheet resistance was 55.73 Ω/square with the average
transmittance of ~ 92.83 % at 550 nm. The properties of the OSCs fabricated using SLG with
optimized silver grids on PET substrates show a short circuit current of 10.9 mA/cm2, an open
circuit voltage of 0.58 V, a fill factor of 60.8 %, and a power conversion efficiency (PCE) of
3.9 %. The PCE was improved about 90.7% than that of the OSCs using the SLG without the
silver grid. These results demonstrate that the optimized grid geometry to the based on the
graphene transparent electrodes contribute to improving the performance of OSCs.
References
1 F. C. Krebs, Sol. Energy Mater. Sol. Cells 93, 394 (2009).
2 C. J. Brabec, S. Gowrisanker, J. J. M. Halls, D. Laird, S. Jia and S. P. Williams, Adv. Mater. 22,
3839 (2010).
3 H.-Y. Chen, J. Hou, S. Zhang, Y. Liang, G. Yang, Y. Yang, Y. Wu, L. Yu, Y. Wu and G. Li, Nat.
Photonics 3, 649 (2009).
4 Z. Yin, S. Sun, T. Salim, S. Wu, X. Huang, Q. He, Y. M. Lam and H. Zhang, ACS Nano 4, 5263
(2010).
5 J. Y. Lee, S. T. Connor, Y. Cui and P. Peumans, Nano Lett. 8, 689 (2008).
6 M. G. Kang, T. Xu, H. J. Park, X. Luo and L. J. Guo, Adv. Mater. 22, 4378 (2010).
7 S.-I. Na, S.-S. Kim, J. Jo and D.-Y. Kim, Adv. Mater. 20, 4061 (2008).
8 J. Zou, H.-L. Yip, S. K. Hau and A. K. Y. Jen, Appl. Phys. Lett. 96, 203301 (2010).
9 M. W. Rowell, M. A. Topinka, M. D. McGehee, H. J. Prall, G. Dennler, N. S. Saricici, L. Hu
and G. Gruner, Appl. Phys. Lett. 88, 233506 (2006).
10 R. C. Tenent, T. M. Barnes, J. D. Bergeson, A. J. Ferguson, B. To, L. M. Gedvulas, M. J. Heben
and J. L. Blackburn, Adv. Mater. 21, 3210 (2009).
11 X. Wan, G. Long, L. Huang and Y. Chen, Adv. Mater. 23, 5342 (2011).
12 Y. Choi, S. J. Kang, H. Kim, W. M. Choi and S. Na, Sol. Energy Mater. Sol. Cells 96, 281
(2012).
13 H. Park, P. R. Brown, V. Bulovic and J. Kong, Nano Lett. 12, 133 (2012).
14 Y. Suh, N. Lu, S. H. Lee, W.-S. Chung, K. Kim, B. Kim, M. J. Ko and M. J. Kim, ACS Appl.
Mater. Interfaces 4, 5118 (2012).
15 J. K. Wassei and R. B. Kaner, Mater. Today 13, 52 (2010).
16 C. Lee, X. Wei, J. W. Kysar and J. Hone, Science 321, 385 (2008).
17 X. Li, Y. Zhu, W. Cai, M. Borysiak, B. Han, D. Chen, R. D. Piner, L. Colombo and R. S. Ruoff,
Nano Lett. 9, 4359 (2009).
18 K. S. Kim, Y. Zhao, H. Jang, S. Y. Lee, J. M. Kim, K. S. Kim, J. H. Ahn, P. Kim, J. Y. Choi
and B. H. Hong, Nature 457, 706 (2009).
19 Y. Shi, K. K. Kim, A. Reina, M. Hofmann, L.-J. Li and J. Kong, ACS Nano 4, 2689 (2010).
20 L. G. De Arco, Y. Zhang, C. W. Schlenker, K. Ryu, M. E. Thompson and C. Zhou, ACS Nano
4, 2865 (2010)
21 M. Cox, A. Gorodetsky, B. Kim, K. S. Kim, Z. Jia, P. Kim, C. Nuckolls and L. Kymissis, Appl.
Phys. Lett. 98, 123303 (2011).
22 Y. Zhu, Z. Sun, Z. Yan, Z. Jin and J. M. Tour, ACS Nano 8, 6472 (2011).
23 S. M. Kim and S. J. Kang, J. Korean Phys. Soc. 64, 177 (2014).
24 S. M. Kim, B. Walker, J. H. Seo and S. J. Kang, Jpn. J. Appl. Phys. 52, 125103 2013).
25 T. Aernouts, P. Vanlaeke, W. Geens, J. Poortmans, P. Heremans, S. Borghs, R. Mertens, R.
Andriessen and L. Leenders, Thin Solid films 22, 451 (2004).
26 M. Glatthaar, M. Niggemann, B. Zimmermann, P. Lewer, M. Riede, A. Hinsch and J. Luther,
Thin Solid films 491, 298 (2005).
27 K. Tvingstedt and O. Inganas, Adv. Mater. 19, 2893 (2007).
28 J.-S. Yu, I. Kim, J.-S. Kim, J. Jo, T. T. Larsen-Olsen, R. R. Søndergaard, M. H¨osel, D. Angmo,
M. Jørgensen and F. C. Krebs, Nanoscale4, 6032 (2012).
29 K. Ellmer, Nat. Photonics 6, 809 (2012).
30 S. Bae, H. Kim, Y. Lee, X. Xu, J.-S. Park, Y. Zheng, J. Balakrishnan, T. Lei, H. Ri Kim, Y. I.
Song, Y.-J. Kim, K. S. Kim, B. ¨Ozyilmaz, J.-H. Ahn, B. H. Hong and S. Iijima, Nat.
Nanotechnol. 5, 574 (2010).
31 B. Walker, A. Tamayo, J. Yang, J. Z. Brzezinski and T.-Q. Nguyen, Appl. Phys. Lett. 93, 063302
(2008).
32 A. Siokou, F. Ravani, S. Karakalos, O. Frank, M. Kalbac and C. Galiotis, Appl. Surf. Sci. 257,
9785 (2011).
33 B. A. Collins, Z. Li, R. Tumbleston, E. Gann, C. R. McNeill and H. Ade, Adv. Energy Mater.
3, 65 (2013).
34 Y. Wang, S. W. Tong, X. F. Xu, B. Ozyilmaz and K. P. Loh, Adv. Mater. 23, 1514 (2011).
35 H. Kim, S. H. Bae, T. H. Han, K. G. Lim, J.-H. Ahn and T. W. Lee, Nanotechnology, 2014, 25,
014012.
W-P-042
Electrical properties of transparent thin film transistors with zinc tin oxide
channel layer
Seunghwan Hong, Gyujin Oh, and Eun Kyu Kim*
Quantum-Function Research Laboratory and Department of Physics, Hanyang University, Seoul 133-791,
Korea
*E-mail address: ek-kim@hanyang.ac.kr
Thin film transistors (TFTs) with a zinc tin oxide (ZTO) channel layer were fabricated by
using an ultra high vacuum (UHV) radio frequency (RF) magnetron sputter. In our previous
study, ZTO thin films deposited on silicon substrates with different oxygen partial pressure
were investigated, and then the best properties appeared in the film grown under no oxygen gas
flow. In this study, ZTO thin films were deposited on SiO2(90-nm-thickness) on Si and sapphire
substrates, respectively. Deposition of ZTO thin films was performed at a base pressure of
5.33x10-8 Pa and a working pressure of 2.66x10-1 Pa. Under the fixed power of 70 W for zinc
oxide (ZnO) sputtering target, the applied power for tin oxide (SnO2) sputtering target was
varied from 15 W to 55 W. After the deposition, ZTO thin films were post-annealed at 300 °C,
450 °C, and 600 °C, respectively. Optical properties of ZTO thin films were observed by
ultraviolet and visible (UV-Vis) spectrophotometer, and their electrical properties were
analyzed by Hall effect and current-voltage measurements. ZTO thin films deposited on
sapphire substrate showed a transmittance more than 85 % in the visible light region, and their
optical band gap was ranging from 3.72 eV to 3.79 eV. Electrical properties of transparent thin
film transistors with zinc tin oxide channel layer will be discussed.
W-P-043
Improved injection in n-type organic field-effect transistors with a nonconjugated polyelectrolyte layer
Yu Jung Park1, Myoung Joo Cha1, Jin Hee Lee1, Shinuk Cho2, Bright Walker3, and Jung Hwa
Seo1,*
1
Department of Materials Physics, Dong-A University, Busan, 604-714, Republic of Korea
Department of Physics and EHSRC, University of Ulsan, Ulsan 680-749, Republic of Korea
3
School of Energy and Chemical Engineering, Ulsan National Institute of Science and Technology, Ulsan, 689798, Republic of Korea
2
* E-mail address: seojh@dau.ac.kr
We characterized the n-type organic field-effect transistors (OFETs) with non-conjugated
polyelectrolytes (NPEs) interlayers as the electron injection layer. Novel NPEs with various
couterions (Cl-, Br-, I-) improved the electron mobilities of up to ~10-2 cm2V-1s-1 with on-off
ratios (Ion/Ioff) of 105 in OFETs based [6,6]-Phenyl-C61-butyric acid methyl ester (PCBM).
Reduced electron injection barrier (ϕe) at NPE/metal electrode interface was induced by dipole
formation and led to increase the electron injection and transport. These findings are important
for understanding how NPEs function in devices, the improvement of device performance, and
the design of new materials for use in optoelectronic devices.
References
1. Tsumura, H. Koezuka, T. Ando, Appl. Phys. Lett., 1986, 49, 1210
2. Hui-Jun Yun , Seok-Ju Kang , Yong Xu , Seul Ong Kim , Yun-Hi Kim , Yong-Young Noh , Soon-Ki Kwon,
Adv. Mater., 2014, 26, 7300–7307.
3. Hanying Li, Benjamin C-K. Tee, Judy J. Cha, Yi Cui, Jong Won Chung, Sang Yoon Lee, Zhenan Bao, J. Am.
Chem. Soc., 2012, 134, 2760–2765.
4. Hsin-Rong Tseng , Hung Phan , Chan Luo , Ming Wang , Louis A. Perez , Shrayesh N. Patel , Lei Ying ,
Edward J. Kramer , Thuc-Quyen Nguyen , Guillermo C. Bazan , Alan J. Heeger, Adv. Mater., 2014, 26,
2993–2998.
5. M. Yamagishi, J. Takeya, Y. Tominari, Y. Nakazawa, T. Kuroda, S. Ikehata, M. Uno, T. Nishikawa, T.
Kawase, Appl. Phys. Lett., 2007, 90, 182117.
6. Jongwan Choi, Heeseok Song, Nakjoong Kim and Felix Sunjoo Kim, Semicond. Sci. Technol., 2015, 30,
064002.
7. Suresh Vasimalla, Satyaprasad P. Senanayak, Meenakshi Sharma, K. S. Narayan, Parameswar Krishnan Iyer,
Chem. Mater. 2014, 26, 4030−4037
8. Nam-Koo Kim, Dongyoon Khim, Yong Xu, Seung-Hoon Lee, Minji Kang, Jihong Kim, Antonio Facchetti,
Yong-Young Noh, Dong-Yu Kim, ACS Appl. Mater. Interfaces, 2014, 6, 9614–9621.
9. Huanli Dong, Xiaolong Fu, Jie Liu, Zongrui Wang, Wenping Hu, Adv. Mater., 2013, 25, 6158–6183.
10. Hisao Ishii, Kiyoshi Sugiyama, Eisuke Ito, Kazuhiko Seki, Adv. Mater., 1999, 11, 605-625.
11. Vidya Raj, Sreenivasan Kunnetheeri, ISRN Analytical Chemistry, 2014, 841857.
12. Jung Hwa Seo, Andrea Gutacker, Yanming Sun, Hongbin Wu, Fei Huang, Yong Cao, Ullrich Scherf, Alan
J. Heeger, and Guillermo C. Bazan, J. Am. Chem. Soc., 2011, 133, 8416–8419.
W-P-044
Effects of Al addition on Resistive-Switching Characteristics of Solution
Processed Zn-Sn-O ReRAMs
Il-Jin Baek, Kwang-Won Jo and Won-Ju Cho*
Department of Electronic Materials Engineering, Kwangwoon University, Seoul 139-701, Korea
* E-mail address: chowj@kw.ac.kr
Resistive random access memory (ReRAM) has been regarded as a very promising
candidate for next-generation non-volatile memory, owing to its simple structure, high speed
operation, high density integration, and low power consumption. According to previous reports,
the resistive switching (RS) phenomena have been observed in various materials, such as metal
oxide, perovskite, solid electrolyte, and organic material. Amorphous InGaZnO (a-IGZO) has
been studied as active layers of thin film transistors (TFTs) and ReRAMs because it has not
only superior electrical properties but also excellent RS characteristics. However, the indium
and gallium are becoming increasingly expensive and potentially scarce. Alternatively, aAlZnSnO (a-AZTO) composed of Al and Sn has attracted considerable interest [1]. AZTO has
many advantages such as low cost, low temperature process ability, high transparency, and
simultaneously available material as active layers of TFTs and ReRAMs. Therefore, a-AZTO
based device is expected to transparent and flexible electronic device for system-on-panel
application [2]. Recently, solution processed TFTs and ReRAMs have attracted considerable
interest owing to its simplicity, low process temperature, large area device application, and cost
effectiveness. But, solution processed metal oxide films have various defects including grain
boundaries, oxygen ions, oxygen vacancy, and organic defects. Especially, oxygen vacancy is
related to formation of conductive filament (CF) and resistive switching characteristics depend
on the composition of materials.
In this study, we fabricated Ti/AZTO/Pt structure ReRAM devices using three different
composition ratio solutions (Al:Zn:Sn=0:1:1, 0.1:1:1 and 0.2:1:1). The fabricated devices
showed a stable bipolar resistive switching behavior. Improved memory endurance
characteristics were obtained with increasing Al addition in AZTO ReRAM devices. All
devices showed a low operation voltage of ~1 V and reliable retention characteristics for 104
sec, confirming the nonvolatile.
Fig. 1. (a) Schematic of AZTO-ReRAM. (b) Typical bipolar resistive switching characteristics of AZTO-ReRAM
depending on Al concentration (0, 0.1, and 0.2 mol %)
References
1. Y. S. Fan, P. T. Liu, L. F. Teng, and C. H. Hsu, Appl. Phys. Lett., 101, 052901 (2012).
2. Y. H. Hwang, H. M. An, and W. J. Cho, Jpn. J. Appl. Phys., 53, 04EJ04 (2014).
W-P-045
Performance enhancement in amorphous In-Ga-Zn-O thin-film transistors
with off-planed dual-work function source/drain structure
Ju-Young Pyo and Won-Ju Cho,*
Department of Electronic Materials Engineering, Kwangwoon University, Seoul 139-701, Korea
* E-mail address: chowj@kw.ac.kr
Recently, thin-film transistor (TFT) based oxide semiconductor has been a lot of attention
for next generation display devices because of a good conductivity and a high transparency in
the visible light region compared to conventional amorphous Si or poly-Si TFTs. The
amorphous InGaZnO (a-IGZO) is a representative oxide semiconductor with excellent optical
and electrical characteristics as a channel material of TFTs acting as switching and driving
elements. Nevertheless, a higher on-current, a lower off-current, and a higher mobility are
necessary in order to emit light through current injection for high-performance display devices
[1]. Accordingly, in order to satisfy these requirements, extensive studies have been conducted,
including the annealing condition, dopant doping, thin-film deposition condition, and device
structure.
In this work, we fabricated a bottom-gate top-contact type a-IGZO TFT of distinctive offplaned source/drain with dual-work function to enhance the electrical performance. In this a
distinctive structure, the source and drain electrodes are not in the same plane and we can select
different materials for respective source and drain contacts. Ti of low work function (ΦTi≒3.8
eV) and Ni of high work function (ΦNi≒4.9 eV) were applied to the source metal and drain
metal contacts, respectively. As a result, the Ni-drain/Ti-source combination showed a higher
driving current of 970 μA at VG = 30 V and a lower leakage current of 50 pA than the Tidrain/Ni-source combination. This implies that we can increase the drive current and reduce
the leakage current by using the low work function at source and high work function at drain
contact, respectively. Therefore, we consider that the off-planed source/drain with dual-work
function is promising candidate for high-performance display backplane device.
Fig. 1. (a) Structure of bottom bottom-gate top-contact type a-IGZO TFT of distinctive off-planed source/drain
with dual-work function. (b) Transfer characteristics for different source/drain materials.
References
1. K. Nomura, H. Ohta, A. Takagi, T.Kamiya, M.Hirano, and H.Hosono, Nat. 432, 488 (2004).
W-P-046
Enhanced emission of green, blue and red phosphor by localized surface
plasmon coupling
Hyun-Sun Park1,2, Ja-Yeon Kim2, Yu-Hyun Cho1,2, Doo-Hyung Kim1
Min-Woo Kim1, Min-Ki Kwon1,*
1
Deparment of photonic engineering, Chosun university, Gwang Ju 501-759 , Korea (South)
DepartmentLED team, Korea Photonics Technology Institute(KOPTI), Gwang Ju 500-779, Korea (South)
* mkkwon@chosun.ac.kr
2
Gallium nitride (GaN) based light emitting diodes (LEDs) have many advantages, such as
energy-saving, longer lifetime and better stability and so on, compared with other conventional
light sources such as florescence. In addition, GaN based LEDs have attracted great interest in
broad applications such as full-color display, solid-state lighting and many other fields. For
that, many efforts have been made in the search of high efficient down converting phosphors
converting ultraviolet (UV) or blue light into a combination of red-green-blue light in order to
obtain white light emission. Commercial white LEDs lamp is generally fabricated by using a
blue InGaN LED chip and the yellow-emittingY3Al5O12:Ce3+ (YAG:Ce) phosphor. However,
such WLEDs were suffered from a poor color rendering index (CRI) and a high correlated
color temperature (CCT) because of lacking a green and red component. To solve these
problems, WLEDs can be also fabricated by pumping blue, green and red phosphors coated on
a near-UV LED. However, efficiency of these WLEDs is lower than that of WLED with blue
InGaN LED:YAG:Ce due to stoke shift. For this reason, it is necessary to improve the emission
efficiency of phosphors. Surface plasmons are the collective oscillations of free electrons in a
metal at the interfaces between metals and dielectrics. Specifically, the collective oscillations
of electrons in noble metal nanoparticles embedded in a dielectric matrix are localized surface
plasmons (LSPs). [1, 2] The overlap of local electromagnetic field with the excitons in QW
results in a coupling effect of effective energy transfer from the excitons in QW into LSP for
emission, creating an alternative emission channel. There, the efficiency of LED can
significantly be improved by increase in spontaneous emission rate. In this letter, we
demonstrate the SP-enhanced blue, green and red phosphor with various metal nanoparticles.
Especially, we analyze the effect of size and density of metal nanoparticle, thickness of spacer
layer and core-shell structure on the optical properties of SP-enhanced phosphor. Up to 1.3 fold
enhancement factor was obtained when density and size of metal nanoparticle and thickness of
spacer layer was optimized. The temperature dependent and time resolved photoluminescence
will be discussed.
Fig. 1 Enhanced emission efficiency of (a) green phosphor and (b) blue phosphor by Au NP and Ag NP,
respectively
References
1. M. K. Kwon et. al, J. of Cryst. Grwoth, 370, 124 (2013) .
2. S. M. Lee, Optics Exp. 18, 12144 (2010).
W-P-047 [NO SHOW]
Enhancement of light extraction efficiency for III-nirtide based LED with
multilayer graphene/ITO p-electrodes
Tae Kyoung Kim, Seung Kyu Oh, Yu-Jung Cha, Joon Seop Kwak*
Department of Printed Electronics Engineering (BK21 plus), Sunchon National University Jeonnam 540-742,
Korea
E-mail :
jskwak@sunchon.ac.kr
III-nitride LED (light emitting diode) with transparent p-electrode having low sheet
resistance, high transmittance and ITO/p-GaN interface ohmic contact are essential. For that
reason, in order to improve properties of the transparent p-electrode, researches of NiOx
contacts, insertion of metallic particle, application of OMO structure on the p-GaN and other
studies are being in progress. In this study, the high transmittance and ohmic contact of ITO/pGaN were formed in ITO electrodes having thin thickness (5 and 10 nm) of III-nitride LED.
Also, transfered MLG on each ITO, III-nitride LEDs having transparent p-electrode of
MLG/ITO hybrid structure were fabricated to improve current spreading effect and decrease
high sheet resistance made by thin thickness of ITO. In this results, III-nitride LEDs applied
ITO 5nm and MLG/ITO 5nm structure showed 3.25 and 3.06V at 20mA, 11.69 and 13.02
mW/sr at 400mA, respectively. After forming MLG on ITO 5nm, electro-optical properties
were enhanced. Otherwise, III-nitride LEDs applied ITO 10nm and MLG/ITO 10nm structure
showed 2.95 and 3.06V at 20mA, 20.28 and 16.74 mW/sr at 400mA, respectively. In contrast
with reserch of other group [1], sheet resistance of transfered MLG on ITO 5nm was
decreased about four times compared to ITO 5nm. But, the ITO 10nm and MLG/ITO 10nm
were almost similar sheet resistance, transmittance of III-nitride LED with ITO 10 nm
decreased to 16 % because of MLG formation on ITO. This study suggested relation between
sheet resistance and transmittance by thickness of ITO affected electro-optical properties of
III-nitride LEDs having transparent p-electrode of MLG/ITO hybrid structure.
80
90
85
80
75
ITO 5nm
ITO 10nm
MLG/ITO 5nm
MLG/ITO 10nm
70
65
60
400
500
600
Wavelength (nm)
700
Current (A)
Transmittance (%)
95
24
ITO 5nm
ITO 10nm
MLG/ITO 5nm
MLG/ITO 10nm
60
40
20
0
0
1
2
3
Voltage (V)
4
5
Radiant intensity (mW/sr)
100
100
20
16
ITO 5nm
ITO 10nm
MLG/ITO 5nm
MLG/ITO 10nm
12
8
4
0
0
100
200
300
400
Current (mA)
Fig. 1) Electro-optical properties of III-nitride LEDs having transparent p-electrode of MLG/ITO
Reference
[1] X Kun, X Chen, D Jun, Z Yanxu, G Weiling, M Mingming, Z Lei and S Jie, Appl. Phys.
Lett. 102, 162102 (2013).
W-P-048
Synthesis and optical charecterization of titanium oxide nanowi
res on transperent substrates for photovolatoic applications
Dong Hyun Kim, Bhaskar Dudem, and Jae Su Yu *
Department of Electronics and Radio Engineering, Kyung Hee University, 1732 Deogyeong-daero, Giheunggu, Yongin-si, Gyeonggi-do 17104, South Korea
Abstract
Metal oxide one-dimensional (1D) nanostructures such as nanowires, nanoneedles, and
nanotubes have been studied in various optoelectronic device applications. The nanostructures
exhibit novel physical, electrical, and optical properties due to their unique geometry with a
high aspect ratio. Recently, several metal oxide nanostructures have been utilized as an antireflection (AR) layer to enhance the efficiency of photovoltaic device by reducing the Fresnel
surface reflections. Moreover, the refractive indices of these nanostructures can be engineered
by adjusting the air volume ratio (i.e., nanostructure dimensions). In this work, we employed
the hydrothermal synthesis to grow tightly packed titanium dioxide (TiO2) nanowires on
transparent substrates as an AR layer. For the hydrothermal synthesis of TiO2 nanowires, the
mild titanium (Ti) precursor solutions were used instead of strong acidic solutions which can
increase the equipment cost and cause environmental damages. Furthermore, we controlled the
dimensions of TiO2 nanowires by changing the growth conditions and investigated its structural
and optical characteristics by using different measurement systems.
*
E-mail address: jsyu@khu.ac.kr Tel.: +82 312013820 Fax: +82 312062820
W-P-049
A metamaterial based antireflection coating layer to improve the
transmission at surface plamon resonance
Jiyeon Jeon,1,2 Khagendra Bhattarai,3 Deok-Kee Kim,2 Jun Oh Kim,1 Jiangfeng Zhou,3 Augustine Urbas,4
Zahyun Ku,4 and Sang Jun Lee1,*
1 Division
of Convergence Technology, Korea Research Institute of Standards and Science, Daejeon, 34113, Korea
2 Department of Electrical Engineering, Sejong University, Seoul, 05006, Korea
3 Department of Physics, University of South Florida, Tampa, FL 33620, USA
4 Air Force Research Laboratory, Wright-Patterson Air Force Base, OH 45433, USA
* E-mail address: sjlee@kriss.re.kr
We experimentally and analytically investigate the phenomenon of improved transmission
due to metamaterial (MM) based antireflection coating (ARC) atop the metal hole array (MHA
used as the surface plasmon (SP) resonance structure) in the mid-infrared region (Figure 1a).
Our MM based ARC consists of a metal disk array (MDA) on top of a benzencyclobutene
(BCB) layer. Figure 1b shows that the transmission obtained by a finite integration technique
based simulation agrees very well with the FTIR-measured transmission. The highest measured
(simulated) enhancement ratio at the first SP resonance wavelength of metal hole array is ~88%
(~82%) as compared with no MM-ARC layered MHA. To understand the underlying
mechanism of MM-ARC, we developed a multiple layer model based on a transfer matrix
method. As shown in the left panel of Figure 1c, it can be clearly seen that the amplitudes of
r12 and α∙r23 are equal at the first SP resonance wavelength (~6.25 µm) and the phase condition
is also satisfied (θ in red crosses π in gray), which leads to R ~ 0 (nearly zero reflection, not
shown here). In effect, a discrepancy between the measured and simulated enhancement ratio
(not shown here) was occurred due to the imperfections in the fabrication, specifically the
misalignment between MDA and MHA. As shown in Figure 1d, the amount of misalignment
(x,y) is represented as the distance from the center of the metal hole to the center of the metal
disk. The misalignment was found to be x = 0.5 µm, y = 0.5 µm using simulation, which is
close to experimental values of enhancement ratio (MDA could be shifted by ~0.28∙p in x and
y direction, compared with the perfect alignment). The results drawn from this work could be
used as a basis to improve the performance of plasmonic structure integrated IR device.
Figure 1. (a) Scanning electron microscope (SEM) image of MM based ARC layer on MHA structure (period p = 1.8 µm). (b) Colormap of
simulated and measured transmission as a function of wavelength and BCB thickness varying from 0.35 µm to 1.55 µm with 0.2 µm step. (c)
Amplitude and phase condition for ARC. (d) Schematic view of misaligned MM-ARC, i.e., misalignment between MDA and MHA
representing (x,y).
W-P-050
Experimental validation of modified InAs quantum dot detectorresponses due to surface plasmon resonance
Jehwan Hwang1,3, Nguyen Tien Dai1, Yeongho Kim1, Jun Oh Kim1, Eun Kyu Kim3, Augustine Urbas2,
Zahyun Ku2, and Sang Jun Lee1,*
1
Division of Convergence Technology, Korea Research Institute of Standards and Science, Daejeon, 305-340, Korea
2
Air Force Research Laboratory, Wright-Patterson Air Force Base, OH 45433, USA
3
Quantum-Function Research Laboratory and Department of Physics, Hanyang University, Seoul 133-791, South Korea
*
sjlee@kriss.re.kr
Spectral infrared imagers have attracted much attention due to various applications such as
mineral exploration, medical diagnostics and military surveillance. Spectral imagery provides
detailed information in individual pixels via bandpass filters, but the filters have reached the
limit for costs, complexity and calibration in optical system. Recently, a novel spectral
detection strategy using plasmon-based tunable superpixels and a spectral-tuning algorithm
was numerically demonstrated for the next generation of spectral sensors, which enables us to
reconstruct the infrared spectral signatures without actual filters [1]. In ref [1], a superpixel
array in the quantum dots-in-a-well (DWELL) focal-plane array (FPA) integrated with surface
plasmon resonance (SPR) architectures was used as the sensing system and each superpixel in
the array was composed of a group of pixels where different metal hole arrays (MHAs used as
SPR structures) are integrated in each pixel to offer spectrally modified DWELL FPAresponses. To realize such a spectral sensor, it is of great importance to achieve the
modification of detector responses using MHAs, however no studies have been experimentally
reported to date. In this study, we validate the SPR capability to modify the detector responses
using the bias tunable DWELL device and MHA with fixed geometric parameters (i.e., pitch,
aperture size and thickness) as illustrated in Figure 1(a). The maximum peaks of DWELLresponses gradually red-shift from 5.70 µm to 6.28 µm as the bias increases from -3.5 V to
+3.0 V with a step of 0.5 V at 77 K as shown in the left panel of Figure 1(b). On the contrary,
the colormap in the right panel of Figure 2(b) indicates the responses of MHA integrated
DWELL device are insensitive to applied bias voltages, which results from strong interaction
between SPR (nearest-hole coupling; 1st order SPR associated with the periodicity of MHA)
and the active layer in DWELL device [2,3].
Normalized response
(a)
(b)
0
1
+3.0
Active
(QDs)
Contact
Si3N4
p
Bias (V)
+2.0
2D-MHA
d
2 µm
+1.0
-0.5
-1.5
-2.5
QDIP
-3.5
4
5
6
7
8
MHA/QDIP
4
5
6
7
8
Wavelength (µm)
Fig. 1. (a) Schematic view of the front side illuminated QDIP and the top view SEM images of the 2D-MHA with
pith = 2 µm (b) the normalized experimental spectral of QDIP and MHA/QDIP.
References
1. Jang, W.-Y., et al., "Plasmonic Superpixel Sensor for Compressive Spectral Sensing." IEEE Transactions on Geoscience
and Remote Sensing, 53, 3471-3480 (2015).
2. Lee, S. J., et al., "A monolithically integrated plasmonic infrared quantum dot camera." Nature communications 2, 286
(2011).
3. Ku, Z., et al., "Analysis of subwavelength metal hole array structure for the enhancement of back-illuminated quantum dot
infrared photodetectors." Optics express 21, 4709-4716 (2013).
W-P-051
Tip-Enhanced Resonant Raman Scattering Study of Monolayer WS2
Chanwoo Lee1,2, Byeong Geun Jeong1,2, Seok Joon Yun1,2, Young Hee Lee1,2,3, and
Mun Seok Jeong1,2,*
1
2
Deparment of Energy Science, Sungkyunkwan University, Suwon 16419, Korea
Center for Integrated Nanostructure Physics (CINAP), Institute for Basic Science (IBS), Suwon 16419, Korea
1
Deparment of Physics, Sungkyunkwan University, Suwon 16419, Korea
* E-mail address: mjeong@skku.edu
Two-dimensional (2D) transition metal dichalcogenide (TMD) materials have been
intensively studied for a long time due to distinctive mechanical, optical and electronic
properties [1]. In particular, monolayer TMD materials which exhibit a direct band gap have
been under the global limelight for optoelectronic applications in atomically thin electronics
[2]. Among the TMD materials, monolayer tungsten disulfide (WS2) has been widely known
as its high photoluminescence (PL) quantum yield, which is more intense than that of
monolayer MoS2 [3]. Owing to such properties, there are lots of studies which are related to
PL and Raman scattering of WS2 [4]. However, the conventional PL and Raman spectroscopy
have a limit to analyze nanoscale structures such as local disorder, grain boundaries, dopants,
edges and wrinkles which affect to the optical properties of WS2. Therefore, more researches
using near-field scanning optical microscope (NSOM) and tip-enhanced Raman spectroscopy
(TERS) are absolutely necessary to analyze the structures on nanometer scale for 2D TMD
materials.
Here, we carry out a systematic study to investigate monolayer WS2 by using tip-enhanced
resonant Raman scattering. As measuring monolayer WS2 on a gold substrate, PL background
can be quenched by a charge transfer. We also measure the surface morphology of WS2 by a
scanning tunneling microscope (STM) to compare TERS mapping images and observe the split
and shift of A1g mode. In addition, Raman signals increase more than 20-fold and an
enhancement factor of TERS reaches values of 2.7 x 104 in our study.
Fig. 1. (a) Schematic of TERS setup. (b) Comparing confocal Raman mapping image with TERS mapping image.
References
1. G. Moody, C. Kavir Dass, K. Hao, C.-H. Chen, L.-J. Li, A. Singh, K. Tran, G. Clark, X. Xu,
G. Berghäuser, E. Malic, A. Knorr, X. Li, Nat. Commun. 6, 8315 (2015).
2. Q. H. Wang, K. Kalantar-Zadeh, A. Kis, J. N. Coleman & M. S. Strano, Nat. Nanotechnol.
7, 699–712 (2012).
3. L. Yuan, L. Huang, Nanoscale 7, 7402−7408 (2015)
4. A. Berkdemir, H. R. Gutierrez, A. R. B.-Mendez, N. P.-Lopez, A. L. Elias, C.-I. Chia, B.
Wang, V. H. Crespi, F. L.-Urias, J.-C. Charlier, H. Terrones & M. Terrones, Sci. Rep. 3,
1755 (2013)
W-P-052
Package effects on device properties of near ultra-violet flip-chip lightemitting diodes
Soo Hyun Lee, Xiang-Yu Guan, and Jae Su Yu*
Department of Electronics and Radio Engineering, Kyung Hee University, 1732 Deogyeong-daero, Giheung-gu,
Yongin-si, Gyeonggi-do 17104, Republic of Korea
* E-mail address: jsyu@khu.ac.kr
Light-emitting diodes (LEDs), which provide high power, low power assumption, long
lifetime, and good stability, have demonstrated a great potential in general illuminations and
full color displays [1]. Recently, near ultra-violet (NUV) LEDs have been intensively focused
to realize white emission by combining with phosphors [2]. However, the increased junction
temperature can significantly degrade the device performance, especially, at high injection
currents. The heat generation can be more accelerated by the device limitations such as the
threading dislocations from lattice mismatch, poor thermal conductivity of sapphire substrate
(k~ 35 Wm-1K-1 at 298 K), and high resistivity of p-GaN layer. Thus, a careful choice in
package design and material selection is required for efficient heat dissipation. In this study,
we characterized and compared the characteristics of NUV flip-chip (FC) LEDs with two
different metal core printed circuit boards (MCPCBs). One MCPCB is composed of metals and
dielectric layers while the other one of metal and ceramic layers. A thermal transient tester was
used to measure their thermal properties such as junction temperature and thermal resistance.
The three-dimensional device modeling and thermal/mechanical simulation were also carried
out to compare the experimental results. These results may provide a deep insight into the
design and material selection of package and will be useful to improve the heat dissipation of
NUV FC LEDs in industrial applications.
References
1. S. J. Tu, M. L. Lee, Y. H. Yeh, F. W. Huang, P. C. Chen, W. C. Lai, C. W. Chen, G. C.
Chi, and J. K. Sheu, IEEE J. Quantum Electron. 48, 1004 (2012).
2. J. K. Sheu, S. J. Chang, C. H. Kuo, Y. K. Su, L. W. Wu, Y. C. Lin, W. C. Lai, J. M. Tsai,
G. C. Chi, and R. K. Wu, IEEE Photon. Technol. Lett. 15, 18 (2003).
W-P-053
Thermal Study on High-Power Ceramic Chip-Scale Package LightEmitting Diodes
Byungjin MA1*, Taehee Jung1, Kwanhun LEE1, Young Jun An, and Kyung-Whan Woo2*
1
Reliability Research Center, Korea Electronics Technology Institute, #25 Saenari-ro, Bundang-gu, Seongnamsi, Gyeonggi-do 13509, Republic of Korea
2
Amosense Co. Ltd.,308 Moshi-ri, Jiksan-eup, Seobuk-gu, Cheonan-si 31040, Republic of Korea
* E-mail address: bjma@keti.re.kr
Light-Emitting Diode (LED) has been adopted in many applications such as mobile, display
and lightings because of its promising advantages over conventional light sources. But, a cost reduction
has strongly been needed in order to survive in this field due to an excessive supply of LED packages.
In order to meet the cost-reduction need, chip-scale package (CSP) LED has attracted attention
because of its small size and simple configuration. However, the size of CSP LED has been limited to
the size of LED chip and Zenor-diode chip for the protection of ESD (electro-static discharge). We
developed a novel CSP LED with embedded-varistor layer in the ceramic substrate without additional
area for the ESD protection. In order to investigate the optimize the substrate size of the CSP LED, we
carried out the 3D fluidic dynamics simulation based on a finite volume method and including
conduction, convection and radiation as shown in Fig.1. There is a trade-off relationship between the
package-size reduction and the thermal management and reliability [1]. 1414 CSP LEDs has been
developed on the basis of the simulation result. Thermal properties such as thermal resistance were
obtained using a thermal transient method. In order to minimize the thermal resistance and meet the
process yield of the CSP LEDs, several substrate structures had been considered. Finally, reliability
tests had carried out for the estimation of lifetime and environmental tolerances such as ESD,
temperature, humidity, etc.
Fig. 1. 3D thermal simulation for CSP LED
References
1. B. Ma et. al, EML, 9(4), pp.541-544
Fig. 2. Simulated junction temperature with respect to
the size of CSP LED
(2013)
W-P-054
Investigations of Absorption of Carbon Monoxide on Metal-incorporated
Porphyrin Molecules using First-principles Calculations
Janghwan Cha1, Hoonkyung Lee2, and Suklyun Hong1,*
1
Department of Physics and Graphene Research Institute, Sejong University, Seoul 143-747, Korea
2
School of Physics, Konkuk University, Seoul 446-701, Korea
* E-mail address: hong@sejong.ac.kr
Carbon monoxide molecules have been known to interrupt transportation of oxygen
molecules in the blood, which can cause carbon monoxide poisoning. In the previous research,
adsorption of not only carbon monoxide molecules but also environmental gas molecules such
as O2, N2, and CO2 on Fe-incorporated porphyrin molecules has been studied. We have
performed density functional theory (DFT) calculations to understand the interaction of carbon
monoxide and environmental gas with porphyrins with Fe and other 3d transition metal atoms.
In particular, we focus on the investigation of binding energy and electronic structure of carbon
monoxide on 3d metal-incorporated porphyrins. The results of Fe-incorporated porphyrin is
compared with the previous ones. In addition, the interaction of carbon monoxide with other
types of oxygen-transporting proteins or their subunits is investigated.
W-P-055
Theoretical investigations of the doping effect by adsorbates on graphene
Dongchul Sung, and Suklyun Hong*
Graphene Research Institute and Department of Physics, Sejong University, Seoul 143-747, Korea
* E-mail address: hong@sejong.ac.kr
The tuning of charge carrier concentration in graphene is one of fundamental issues for
application of graphene in nanodevices such as field effect transistors. Experiments showed
that nitrogen (N2) and oxygen molecules (O2) are dissociated on the graphene surface with the
aid of deep ultraviolet (DUV). The shift of charge-neutrality point toward a positive gate
voltage confirmed p-type doping after DUV irradiation in O2 gas flow, while the shifted chargeneutrality point is restored to that of pristine graphene by DUV irradiation in N2 gas flow. In
this regard, we have performed first-principles electronic structure calculations to examine the
adsorption and desorption mechanism of nitrogen and oxygen atoms on graphene as well as
their recombination to form NO or NO2 molecules. Importantly, we investigate the doping
effect by the adsorbed atoms or molecules on graphene. As a result, we find that the interaction
between adsorbates and graphene can modulate the amount of doping.
W-P-056
Computational study of hybrid structures of carbon nanotube with
bacterial cellulose
Kyung-Ah Min, Dongchul Sung, Jinwoo Park and Suklyun Hong*
Graphene Research Institute and Department of Physics, Sejong University, Seoul 143-747, Korea
* E-mail address: hong@sejong.ac.kr
Carbon nanotubes (CNTs) have been widely explored for application of three-dimensional
(3D) biomedical scaffolds. However, its applications in 3D biomedical scaffolds have been
hampered by aggregation of CNTs and inhomogeneous distribution of nanomaterials. In this
connection, a new way for in situ hybridization of CNT with bacterial cellulose (BC) was
designed by utilizing amphiphilic comb-like polymer (APCLP). Experimentally APCLP
improved the colloidal stability of CNTs and facilitated the hybridization of CNT with BC by
mediating between them, and calculation results to explain the binding behaviors between CNT,
BC and APCLP were mentioned [1]. Here, we present the detailed theoretical investigations of
the mechanism for hybridization of CNTs with BC and APCLP. To understand the
hybridization mechanism between them, we have performed density functional theory (DFT)
calculations and molecular dynamics (MD) simulations. DFT calculations show that the
binding energy between CNT and BC is increased by APCLP, and MD simulations explain
that BCs are homogeneously distributed around APCLP-coated CNT. Such hybridization of
CNT with BC would lead to high bone regeneration efficacy, and this strategy provides a new
insight for biofunctional hybrid scaffold development in regenerative biomedical area.
References
1. S. Park, J. Park, I. Jo, S.-P. Cho, D. Sung, S. Ryu, M. Park, K.-A. Min, J. Kim, S. Hong, B.
H. Hong, and B.-S. Kim, Biomaterials 58, 93-102 (2015).
W-P-057
Evaluation of the Auto Exposure Control sensor based on PIN
type Technology in Digital Radiography
Ye Ji Heo1, Yo Han Shin1, Kyo Tae Kim1, Sung Kwang Park2, Ji Koon Park3, Sang Sick
Kang3 and Sang Hee Nam4,*
1
Deparment of Biomedical Engineering, Inje University, Gimhae 621-749, South Korea
Inje University Busan Paik Hospital, Bokji-ro 75, Busangjin-gu, Busan South Korea
3
Department of Radiology Science, International University of Korea, Jinju 660-759, South Korea
4
Osong Medical Innovation Foundation, Osongsaengmyeong-ro 123, South Korea
* E-mail address: nsh@bse.inje.ac.kr
2
Diagnostic imaging technology using digital radiography (DR) X-ray equipment
requires fast and accurate image acquisition technology for reducing exposure doses
for patients. Recently, image acquisition technologies have been continuously studied
to increase diagnostic image quality while minimizing patient exposure dose by
employing technologies such as anatomical programmable radiology (APR) and
automatic exposure control (AEC) sensor to the DR X-ray equipment as a method to
reduce patient exposure dose. Because the AEC sensor allows the density of image to
be maintained at an adequate level even with excessive X-ray exposure conditions, it
can minimize retake rates and patient exposure doses as well as improve
reproducibility[1–2]. Hence, this study fabricated a new semiconductor-type AEC
sensor and evaluated its electrical properties and images to solve the problems of
conventional semiconductor-type AEC sensors. In order to examine the potential
development of PIN type AEC sensor prepared in this study, an electrical properties
test and Transmission efficiency test designed to analyze the transmission rates were
conducted and the results were compared with the results for the commercial
semiconductor-type AEC sensor. The result of X-ray sensitivity, the excellent
sensitivity characteristics according to changes in the production millimeter sec(ms),
PIN type sensor was found to have a coefficient of determination (R2) Titanium
electrode based PIN type AEC sensor formed to 0.97. Also exposure dose range Curve
fitting was evaluated on the basis of sensitivity by setting up suitable X-ray beam-on
conditions to range from 1–50 μGy. Fig.1 shows the measurement results of X-ray
sensitivity with variations in the micro-absorption dose. PIN-type AEC sensor had a
trend of 0.9959.
Fig. 1. Measurement results of X-ray sensitivity with variations in the micro-absorption dose.
References
1. S.-M. Kwon, C.-H. Park, J.-K. Park, et al., Journal of Korean society of radiography
8(4) (2014).
2. P. Doyle, D. Gentle, and C. J. Martin, Radiat. Prot. Dosim. 114(1–3) (2005).
W-P-058
The etching characteristics of (100) Si surface by KOH solution
Shinae Hwang¹, Kyungsuk Lim¹, Hyeseon Shin¹, Moongyu Jang
1
Dept. of Nano-medical device engineering ,Hallym university,
Chuncheon, Gangwon-do 200-702, South Korea
2
Dept. of materials science and engineering ,Hallym university,
Chuncheon, Gangwon-do 200-702, South Korea
*e-mail address : jangmg@hallym.ac.kr
For the fabrication of MEMS(micro electro machanical system) devices, micromachining
three-dimensional structure is a fundamental process. In order to fabricate it, anisotropic wet
chemical etching of crystalline silicon has been used for a long time. In this study, potassium
hydroxide(KOH) solution, which is one of the most popular etchant for single crystal silicon,
was used as a base solvent. The popularity of the etchant comes from large part by their extreme
anisotropy, easy-preparation, cost-effective and fast etching advantages. For anisotropic silicon
etching, the KOH concentration and etching temperature are key parameters.
In this study, the etching process of (100) silicon wafers in KOH solution has been studied.
Single crystal silicon has orientation-dependent etching rates on different crystallographic
planes and it has been estimated in the wide range of KOH etchant concentration and etching
temperature. First, photo masks which have line and squere patterns with different dimensions
were used in the photolithography process to investigate the etching properties. Next, the
specimen was anisotropically etched with solution of KOH. From the experimental studies, the
square etching formed a pyramidal structure and the line etching created the grating structure.
Also it is found that the etch rate along the silicon (100) direction was determined to be 0.71.0µm/min. On account of the highly anisotropic etching, the V-groove is formed with (111)
single crystal planes. The surface quality and roughness of (100) plane is dependent on the
etching temperature and decreases with and increase in KOH concentration. All morphological
data were analyzed using Scanning Electron Microscope(SEM) and Atomic Force
Microscope(AFM).
W-P-059 [NO SHOW]
Optical Characteristics of Ge-on-Si after Phosphorus Implantation for
Monolithic Integration on Si Platform
Jiwoong Baek1,2, Bugeun Ki1,2, Chulwon Lee3, Yong-Hoon Cho3, Donguk Nam4, and
Jungwoo Oh1,2
1
School of Integrated Technology, Yonsei University, Incheon 21983, Republic of Korea
2
Yonsei Institute of Convergence Technology, Incheon 21983, Republic of Korea
3
Department of Physics, KI for the NanoCentury, KAIST, Daejeon, Republic of Korea
4
Silicon Photonics Research Laboratory, Inha University, Incheon 22212, Republic of Korea
E-mail address:
jungwoo.oh@yonsei.ac.kr
A silicon-based optical source is a key enabler for heterogeneous integration of electronicphotonic components on Si platform. Process compatibility of Ge with Si CMOS and pseudodirect bandgap energy of Ge potentially suggest ideal integration architecture for complete Si
photonics. However, some challenges include a lattice mismatch of heteroepitaxy and
insufficient doping concentration for population inversion. Tensile strain of Ge-on-Si reduces
the difference in direct and indirect bandgap energy. Photoluminescence (PL) of tensile strained
Ge-on-Si is further enhanced by filling sufficient electrons into the L valleys via n-type doping
[1,2,3]. In this study, a systematic analysis shows that the variation of PL intensity after ion
implantation into Ge-on-Si. Ion implantations were conducted in various energies, doses, and
annealing temperatures. Unintentionally doped Ge and in-situ pre-doped Ge-on-Si were
compared as references. When phosphorus implantation was combined with in-situ pre-doped
Ge-on-Si, PL intensity increased substantially after appropriate annealing. Post-implant
annealing was analyzed to evaluate tensile strain, dopant activation, and recrystallization. Four
point probe measurements quantified sheet resistance of Ge-on-Si. Raman analysis verified
sustainable tensile strain and crystal quality after ion implantation into Ge-on-Si.
References
4. J. Liu, L. C. Kimerling and J. Michel, Semicond. Sci. Technol. 27 (2012).
5. Y. Ishikawa, K. Wada, D. D. Cannon, J. F. Liu, H. C. Luan and L. C. Kimerling, Appl. Phys.
Lett. 82, 2044-2046 (2003).
6. L. Ding, Andy Eu-Jin Lim, Jason Tsung-Yang Liow, M. B. Yu, and G.-Q. Lo, Optics Express.
20, 8 (2012).
W-P-060
Effect of corrosion inhibitor using ZrO2 abrasive slurry for tungsten CMP
Taek-hwan Kwon1, Soo-bum Kim1, Jin-Hyung Park2, and Jea-Gun Park1
1
Advanced Semiconductor Materials & Device Development Center,
Hanyang University, Seoul 133-791, Korea
2
UB materials Inc, #10, Hakchon-ro, Yangji-myeon, Cheoin-gu, Yongin-si, Gyeonggi-do, 449-823,
Korea
E-mail : Parkjgl@hanyang.ac.kr
Tungsten CMP compared with Al and Cu is widely used in metal CMP process, which reason is
scratch less than other metal even if abrasive is too hard. Thus, W is being widely used as metal
wiring, gate or plug in manufacturing processes of the semiconductor devices and W CMP studies is
progressing actively for removal rate, high selectivity, surface roughness improvement, etc. In W
CMP, oxidizer is added in the slurry to oxidize W surface. The WO3 layer is easily removed by
abrasive, because the WO3 layer on the W surface is softer than native W layer. Therefore, oxidizer in
the CMP slurry is playing an important role in high removal rate. Surface turned into soft property is
easily polished by abrasive, and then the polishing process is again repeating WO3 layer formed
passivation. Thus, scratch of surface is decreased and uniformity is improved. However, when
passivation is formed, corrosion is formed too. It make the issue such as corrosion pit at W surface,
which make yield decreased. Therefore, during the W CMP, it is important to suppress corrosion in
order to prevent the surface of W film from corrosion and addition agent is needed as corrosion
inhibitor. In this study, we investigated the effects of PAM concentration on W film. We used nano
ZrO2 abrasive, anionic dispersing agent to disperse abrasive stably, H2O2 as oxidizer, (NH4)Fe(SO4)3
as catalyst, and PAM(polyacrylamide) as corrosion inhibitor. We investigated stability of dispersion
through secondary particle size measurement and static etch rate of the sample, which is dipped in the
slurry at ten-minutes at 30°C temperature, for each PAM concentration(0, 0.01, 0.03 wt%) using
Scanning Electron Microscope(SEM). The more PAM concentration, static etch rate decreased from
32.4 to 3.3 Å/min and corrosion pit is decreased at W surface, which is dipped in slurry as Fig2.
Polyacrylamide
O
H
H
C
C
C
H
0 wt% PAM
32.4 Å/min
0.01 wt% PAM
8.1 Å/min
0.03 wt% PAM
3.3 Å/min
NH2
Fig 1. Structures of PAM
Fig 2. W surface corrosion-pit SEM IMAGE as PAM concentration
Acknowledgement
This work was financially supported by the Brain Korea 21 PLUS Program in 2016 and the Research &
Business Development Program Announcement (C0276121) funded by the Small and Medium Business
Administration(SMBA), Republic of Korea.
W-P-061 [NO SHOW]
Enhancement effect of magnetic field response in silicon-based devices
Hong-Guang Piao1,2*, Dong-Hyun Kim2, Seong-Cho Yu2, and Xiaozhong Zhang3
1
Department of Physics, Chungbuk National University, Cheongju 28644, R. Korea
College of Science, China Three Gorges University, Yichang 443002, P. R. China
3
School of Materials Science and Engineering, Tsinghua University, Beijing 100084, P. R. China
* E-mail address: hgpiao@ctgu.edu.cn
2
Magnetoresistance (MR) as a spintronics effect in non-magnetic semiconductors has
attracted a lot of attentions because of its fundamental interests and broad application potential.
In recent years, large MR has been reported in many different non-magnetic semiconductors,
such as AgSe, InSb and also in Si which is the mainstream semiconductor of information
technology. The ordinary MR of Si at room temperature is small because it is a mediate
mobility non-magnetic semiconductor. One pathway to increase room temperature MR is to
utilize nonlinear transport properties of silicon. Current/voltage controlled resistance transition
could be formed and this resistance transition would be modified by the external magnetic field
via some magnetoelectric mechanisms. A large MR could be achieved in the transition region
and the magnitude of MR is related with the sharpness of the resistance transition. However,
the conditions to form resistance transition are either high voltage or connection with other
extrinsic device and the low-magnetic-field MR at room temperature remained small (~10% at
0.05 T) [1-3]. Here, we realize jump-like voltage controlled resistance transition resulted from
current controlled negative differential conductance phenomenon at low voltage (~ 4 V) and
achieve large magnetic field response under the low-magnetic-field in silicon-based devices at
room temperature with the MR reaching about 1,000% at 0.05 T, as shown in Fig.1. This
performance approaching that of magnetic metal-based magnetoelectronics devices, would
pave the way in silicon-based spintronic devices.
Fig. 1. Show the magnetic field response of Si under the deferent electric field.
References
1. M. P. Delmo, S. Yamamoto, S. Kaisa, T. Ono, K. Kobayashi, Nature 457, 1112 (2009).
2. C. Wan, X. Zhang, X. Gao, J. Wang, X. Tan, Nature 477, 304 (2011)
3. D. Yang, F. Wang, Y. Ren, Y. Zuo, Y. Peng, S. Zhou, D. Xue, Adv. Funct. Mater. 23, 2918
(2013)
W-P-062
Thickness dependence of spin Hall Magnetoresistance
in metallic-ferromagnet/non-magnet structures
Jong-Guk Choi1* and Byong-Guk Park1
1
Department of Materials Science and Engineering, KAIST, Daejeon, 305-701, Korea
* E-mail address: cjg000@kaist.ac.kr
New type of magnetoresistance (MR) has been discovered recently in non-magnet
(NM)/ferromagnet (FM) structures, which is called spin Hall magnetoresistance (SMR)
because it originates from the absorption/reflection of a spin Hall effect-induced spin current
at the NM/FM interface [1]. Most studies on the SMR are focused on NM/FM-insulator
structure such as Pt/YIG, where other MR effects are absent because of no current flow in
FM layer. On the other hand, latest research showed that the SMR is also existent in
NM/metallic-FM structures and its strong correlation with spin-orbit torque [2]. Therefore,
systematic study on SMR in metallic structures is indispensable to understand the underlying
physics of spin transport in NM/FM systems.
In this work, we report SMR in various systems of NM/FM, FM/NM/FM, NM/FM/NM
structures, where NM is Pt and FM is metallic CoFeB. Figure 1(a) shows the angular
dependence of SMR in the Pt/CoFeB, Pt/CoFeB/Pt, CoFeB/Pt/CoFeB structures. SMR is the
largest in CoFeB/Pt/CoFeB structure among the samples, in which spin current generated
from spin Hall effect in Pt layer is absorbed/reflected at two adjacent NM/FM interfaces.
Figure 1(b) shows the CoFeB-thickness dependence of SMR in Pt/CoFeB and Pt/CoFeB/Pt
structures. While the SMR values are comparable between the samples for a larger CoFeB
thickness, the difference in the SMR becomes larger for a smaller CoFeB thickness,
indicating a strong interfacial contribution. Figure 1(c) shows the Pt-thickness dependence of
SMR in Pt/CoFeB, Pt/CoFeB/Pt, and CoFeB/Pt/CoFeB structures. The variation of the SMR
with Pt thickness is changed, especially for a smaller Pt thickness region when an additional
FM/NM interface is introduced. This implies that there is an interaction between the
accumulated spin at each FM/NM interface, which is pronounced for a thin FM or NM layer.
Our results suggest that the SMR in fully metallic structures can be modulated by a
multilayer formation.
Fig. 1. (a) Angular dependence of MR in Pt/CoFeB, Pt/CoFeB/Pt and CoFeB/Pt/CoFeB structures. The angle θ
is determined by orientation of applied field direction and orientation of accumulated spin. (b) Thickness
dependency of MR in Pt/CoFeB(t)/Pt and Pt/CoFeB(t) structures. (c) Thickness dependency of MR in
Pt(t)/CoFeB, Pt(t)/CoFeB/Pt, and CoFeB/Pt(t)/CoFeB structures.
References
1. H. Nakayama. et al, Phys. Rev. Lett. 110, 206601 (2013).
2. S. Cho, S-H. C. Baek, Y. Jo, and B.-G. Park, Sci. Rep. 5, 14668 (2015).
W-P-063
Magnetic Tunnel Junction-Based Spin-Torque Oscillator Simulation:
NEGF-LLGS Approach
Seongcheol Noh, Joon-Ho Lee, and Mincheol Shin*
School of Electrical Engineering, Korea Advanced Institute of Science and Technology (KAIST),
Daehak-ro 291, Yuseong-gu, Daejeon 34141, Republic of Korea
* E-mail address: mshin@kaist.ac.kr
It was the past two decades that has brought remarkable improvements on spintronics field.
In recent years, special care has been taken for utilizing ferromagnetic material as a mean of
telecommunication device. Spin-torque oscillator (STO) is considered as a rather recent
telecommunication device which converts DC signal to RF signal, and transmits. In particular,
STO based on magnetic tunnel junction (MTJ) shows its strength in scalability. Fig. 1
represents the tri-layer MTJ structure that we deal with, and the tunneling material, MgO,
separates two ferromagnets. Previous theoretical studies on MTJ-based STO have invoked
Landau-Lifshitz-Gilbert-Slonczewski (LLGS) equation to demonstrate its magnetization
dynamics [1]. The consecutive behavior of magnetization could be exhibited by selfconsistently solving nonequilibrium Green’s function (NEGF) transport on tri-layer MTJ
coupled with LLGS equation, assuming that parabolic effective mass Hamiltonian and
macrospin model were considered [2]. The barrier length-dependent characteristics of
precession frequency are shown in Fig. 2. Each thread in Fig. 2 can be divided into two regions:
the trajectory below the pivot voltage showed in-plane precession (IPP), and the region above
the pivot voltage showed out-of-plane precession (OPP). All the simulation trials show that the
OPPs operate over the wider frequency regions. Consequently, NEGF-LLGS approach
provides the precise calculation as well as it exhibits that the frequency trends are in accordance
with those from the previous constant-current models.
Fig. 1. Tri-layer MTJ structure. The tunneling
barrier, MgO, is sandwiched between the
ferromagnets.
Fig. 2. Applied bias voltage vs. frequency of STO at
various oxide length (1.15nm, 1.25nm, 1.35nm).
References
1. J. C. Slonczewski, J. Magn. Magn. Mater. 247, 324 (2002).
2. A. A. Yanik, G. Klimeck, and S. Datta, Phys. Rev. B 76, 045213 (2007).
W-P-064
Dependence of Magnetic Properties on Ti Contents in
ZnCrTiO Thin Films
Hwauk Lee, Namhyun An, Youngmin Lee, Deuk Young Kim, and Sejoon Lee*
Department of Semiconductor Science, Dongguk University-Seoul, Seoul 04620, Korea
*
E-mail Address: sejoon@dongguk.edu
We investigated the dependence of magnetic properties on Ti contents in ZnCrTiO thin films
(Cr: 1.0 at.% and Ti: 0 – 0.4 at.%). The ZnCrTiO thin films were grown on Al2O3 (0001)
substrates at 600 oC by co-sputtering of ZnCrO and Ti. Regardless of the Ti contents, the
samples clearly showed to have room-temperature ferromagnetism. The samples exhibited a
clear dependence of their spontaneous magnetization (Ms) on the Ti concentration. The
effective magnetic-moment (i.e., Ms per each Cr ion) was dramatically increased with
increasing the Ti content up to 0.2 at.%. We ascribe this behavior to the incorporation of Ti2+
ions into ZnCrO because they provide two excess spins for the ZnCrTiO solid state system.
However, the effective magnetic-moment was decreased again when exceeding the Ti content
> 0.2 at.%. This is thought as arising from the degradation of crystal magnetic anisotropy. In
other words, the high concentration of Ti causes the lattice distortion in ZnCrTiO lattices; then,
the ferromagnetic coupling strength becomes weak.
Fig 1. Effective magnetic moment as a function of Ti contents in ZnCrTiO thin films. The inset
shows the temperature-dependent magnetization for the ZnCrTiO thin film with Cr =
0.1 at.% and Ti = 0.2 at.%.
W-P-065 [NO SHOW]
Peculiarities of the photoluminescence line shape in Ga(N, As, P)/GaP.
Experiment and Monte Carlo simulations.
V.V. Valkovskii1,*, M.K. Shakfa1, K. Jandieri1 , K. Volz1, W. Stolz1, M. Koch1 and
S.D. Baranovskii1
1
Department of Physics and Material Sciences Center, Phillips University Marburg, D-35032 Marburg,
Germany
* E-mail address: vitalii.valkovskii@physik.uni-marburg.de
In the recent years much attention has been paid to the study of such semiconductor quantum
well structures (QW) as (Ga, In)As/InP, Ga(N, As, P)/GaP, Ga(As, Bi)/GaAs and number of other
materials due to their unique physical properties and potential for applications in optoelectronic devices.
In many cases, optical spectra of QW are strongly influenced by disorder. In particular, energy
relaxation of correlated electron-hole pairs through disorder-induced localized states determines the
position and the shape of the photoluminescence (PL) lines. A lot of studies (both experimental and
theoretical with numerical simulations) were conducted to find out the influence of disorder on QW
optical properties. For many materials the dependences of PL lines on temperature and on the excitation
power can be explained in the frame of Baranovskii-Eichmann model (BE) with exponential density of
states (DOS) in the tail of localized states [1]. However, some materials, such as Ga(N,As, P)/GaP,
demonstrate unusual peculiarities in PL response depended on excitation, that cannot be explained in
the frame of the standard BE model. In Fig.1 one can see the typical dependence of the PL peak and
linewidth (FWHM) on the excitation power. At low temperatures (10 K), a strong blue shift of PL line
is observed, while the FWHM significantly reduces, when pump power is increased. The similar
behavior was reported for Ga(As, Bi) QW [2].
0,075
1,445
Experiment
MC Simulation
Experiment
MC Simulation
0,070
1,440
FWHM [Ev]
Peak [Ev]
0,065
1,435
1,430
0,060
0,055
0,050
1,425
0,045
1,420
0,01
0,1
1
Pump Power [mW]
10
100
0,01
0,1
1
10
100
Pump Power [mW]
Fig. 1. Typical dependence of Ga(N, As, P) PL line shape on excitation power at 10 K (black circles) with
Monte Carlo simulations results (red lines).
Still no satisfactory explanation has been given to these phenomena.
In the present work, the explanation of the observed effect and a detailed scheme for numerical
simulations (results in Fig. 1) is given. It is shown that in the frame of BE approach a modification of
the DOS from an exponential one to a combination of an exponential and a Gaussian DOS is required
in order to achieve a good agreement between experiment and numerical simulations.
References
1. S.D. Baranovskii, R. Eichmann, and P. Thomas, Phys. Rev. B 58, 13081 (1998)
2. Yu. I. Mazur et al , J. Appl. Phys. 113, 144308 (2013).
W-P-066
Terahertz Time-Domain Observation of Coherent Spin Precession in
YMn0.1Fe0.9O3
Howon Lee, Taewoo Ha, Jong Hyeon Kim, Young Chan Jo, Kyung Ik Sim, Jangwon Kim, S.
H. Oh, Y .J. Choi and Jae Hoon Kim
Department of Physics, Yonsei University, 50 Yonsei-Ro, Seodaemun-Gu, Seoul 03722,
Republic of Korea
*E-mail address: lhw31221@naver.com
We performed terahertz time-domain spectroscopy on sintered pellet samples of
YMn0.1Fe0.9O3. An elliptic emission due to coherent spin precession associated with a
quasiferromagnetic resonance mode (qFMR) at 0.299 THz was induced by a linearly polarized
terahertz magnetic pulse. Below 100 K, the spin precession signal of the weak ferromagnetic
moment along the c axis disappears, signaling the spin reorientation transition to the Γ2
antiferromagnetic phase.
Figure 1 a) A circular emission of the coherent spin precession was detected by a linearly polarized terahertz
magnetic pulse at 0.299 THz. b) Temperature dependent quasiferromagnetic resonance mode (qFMR) and
quasiantiferromagnetic resonance mode (qAFMR).
W-P-067
Colloidal Synthesis and Thermoelectric Properties of La-doped
SrTiO3 Nanoparticles
Kunsu Park1,2, Sue In Chae1,2, Sanghwa Lee1,2, Taeghwan Hyeon1,2,*
1
Chemical and Biological Engineering, Seoul National University, Seoul, 151-744, Korea
2
Center for Nanoparticle Research, Istitute of Basic Science (IBS), Korea
* E-mail address: thyeon@snu.ac.kr
We describe n-type nanostructured bulk thermoelectric La-doped SrTiO3 materials
produced by spark plasma sintering of chemically synthesized colloidal nanocrystals. The La
doping levels could be readily controlled from 3 to 9.0 at% by varying the experimental
conditions. An enhanced thermoelectric efficiency was observed and attributed to the large
decrease in thermal conductivity obtained with no significant change in the Seebeck coefficient
or electrical conductivity. The nanostructured bulk of the La-doped SrTiO3 exhibited a
maximum ZT of ~0.37 at 937 K at 9.0 at% La doping, which is one of the highest values
reported for doped SrTiO3.
References
1. K. Park et al., J. Mater. Chem. A 2, 4217 (2014).
W-P-068
Native point defect densite s of various transition-metal dichalcogenide
single layers based on STM measurements
Gábor Zsolt MAGDA1,*, János PETŐ1, Péter VANCSÓ1, Ji-Young NOH2, Yong-Sung
KIM2, Chanyong HWANG2, László Péter BIRÓ3, and Levente TAPASZTÓ1
1
Centre for Energy Research, Institute of Technical Physics and Materials Science, 2D Nanoelectronics
"Lendület" Research Group, Budapest, Hungary
2
Korea Research Institute of Standards and Science, Center for Nanometrology, Daejeon, South Korea
5
Centre for Energy Research, Institute of Technical Physics and Materials Science, Nanotechnology
Department, Budapest, Hungary
* E-mail address: magda@mfa.kfki.hu
In the last few years, more and more two dimensional (2D) materials have been isolated,
most of them from the transition-metal dichalcogenide (TMDC) family [1]. In order to use
these materials in future electronic applications, we need experimental data on the realistic
structure and properties of their 2D crystal form. The point defects are responsible for a
significant deviation in the properties of these materials as compared to theoretical expectations.
Therefore, it is important to reveal the native point defect concentration in these materials as it
can help designing more realistic application concepts. This can be done by Scanning
Tunneling Microscopy (STM), as STM is a versatile and non-invasive tool suitable to
investigate the native defect density and distribution without modifying the material.
Furthermore, it can also provide information on the atomic and electronic structure of these
defects. In our work we have performed the detailed atomic resolution STM investigations of
exfoliated single layers of the most common members of the TMDC family (MoS2, MoSe2,
WS2 and WSe2), and compared their native point defect concentrations.
References
1. G. Zs. Magda, et al., Sci. Rep. 5, 14714 (2015).
T-P-001
Resonance Raman scattering studies of tungsten diselenide (WSe2)
Hankyoul Moon, Ja-yeong Kim, and Seokhyun Yoon*
Department of Physics, Ewha Womans University, Seoul 120-750, Korea
*
E-mail: syoon@ewha.ac.kr
Large amount of research has been conducted over two-dimensional materials including
transition metal dichalcogenide monolayers (TMDCs) such as MoS2, WS2, MoSe2, WSe2, and
MoTe2, since production of the single- and the multi-layered graphene. These materials exhibit
not only interesting 2-dimensional physics but also, in principle, can be utilized for
semiconductor devices such as transistors, emitters, and detectors due to layer-dependent band
structures. Moreover, these two-dimensional materials show low losses through the Joule effect
due to very high mobility. For example, a field-effect transistor (FET) made of WSe2 shows
the mobility near 500 cm2V-1S-1 for p-type conductivity and also stable in both acidic and basic
conditions, which make TMDCs even more attractive for applications. Especially, monolayers
of WSe2 are transparent photovoltaic materials with LED properties. In this study, we made
WSe2 samples by exfoliation method. We deposited WSe2 flakes on Si substrates with a 300
nm SiO2 layer. For measuring basic characteristics such as lattice properties and information
regarding the electronic band structures of the samples, we performed Raman scattering
spectroscopy by using five different excitation energies of 457.9 nm (2.71 eV), 488 nm (2.54
eV), 514.5 nm (2.41 eV), 532 nm (2.33 eV), and 632.8 nm (1.96 eV) and also measured
temperature dependence of WSe2. We report anomalous phonon behavior that depends on the
number of layers and the resonant effect reflecting the underlying electronic band structure.
References
1. Wang, Q. H., Kalantar-Zadeh, K., Kis, A., Coleman, J. N., Strano, M. S. "Electronics and
optoelectronics of two-dimensional transition metal dichalcogenides". Nature
Nanotechnology Vol.7, No.11, 699–712.
2. Johnson, D. "Tungsten Diselenide Is New 2-D Optoelectronic Wonder Material",
IEEE Spectrum. Retrieved 19 March 2014
3. Zhang, X., Qiao, X.-F., Shi, W., Wu, J.-B., Jiang, D.-S., Tan, P.-H. "Phonon and
Raman scattering of two-dimensional transition metal dichalcogenides from
monolayer, multilayer to bulk material", Chemical Society Reviews 2015, volume
44, 2757-2785
T-P-002
Low-temperature growth of layered molybdenum disulfide with controlled
clusters
Jihun Mun1, Chegal Won2, Jeong Won Kim2, Taesung Kim3,4 and Sang-Woo Kang1,5*
1
Division of Industrial Metrology, Korea Research Institute of Standards and Science, Daejeon 34113, Korea
2
Division of Convergence Technology, Korea Research Institute of Standards and Science, Daejeon 34113,
Korea
3
School of Mechanical Engineering, Sungkyunkwan University, Suwon 16419, Korea
4
SKKU Advanced Institute of Nanotechnology, Sungkyunkwan University, Suwon 16419, Korea
5
Department of Advanced Device Technology, University of Science and Technology, Daejeon 34113, Korea
* E-mail address: swkang@kriss.re.kr
Layered molybdenum disulfide was grown at a low-temperature of 350 °C using chemical
vapor deposition by elaborately controlling the cluster size. The molybdenum disulfide grown
under various sulfur-reaction-gas to molybdenum-precursor partial-pressure ratios were
examined. Using spectroscopy and microscopy, the effect of the cluster size on the layered
growth was investigated in terms of the morphology, grain size, and impurity incorporation.
Triangular single-crystal domains were grown at an optimized sulfur-reaction-gas to
molybdenum-precursor partial-pressure ratio. Furthermore, it is proved that the nucleation
sites on the silicon-dioxide substrate were related with the grain size. A polycrystalline
monolayer with the 100-nm grain size was grown on a nucleation site confined substrate by
high-vacuum annealing. In addition, a field-effect transistor was fabricated with a MoS2
monolayer and exhibited a mobility and on/off ratio of 0.15 cm2 V−1 s−1 and 105, respectively.
T-P-003
Synthesis of high-quality MoS2 atomic layer using inorganic seeding
promoters
You Joong Kim, Soo Ho Choi, and Woochul Yang*
Dongguk University, Seoul, 04620, South Korea
E-mail address: wyang@dongguk.edu
Molybdenum disulfide (MoS2) is highlighted due to their unique physical and electrical
properties such as ultrathin layered structure, high on/off ratio, and high mobility. The Band
gap of layered-semiconductor MoS2 is changed from 1.2 eV to 1. 9 eV depending on the layered
thickness. Monolayer MoS2 with direct band gap is an optimal material to develop novel
optoelectronic devices. There are many method to prepare monolayer MoS2 such as
mechanically, chemically exfoliation, and chemical vapor deposition (CVD) method. Among
them, the CVD method is inexpensive and easy to synthesize MoS2 films with large scale and
uniform thickness. In the CVD process, the absorption of vapor phase molybdenum and sulfur
on the substrate is a problem for laterally layered growth of MoS2. Recently, Y. H. Lee et al.
reported organic aromatic molecules helps the nucleation of MoS2 in the CVD process [1].
However, the organic materials are easily decomposed due to their thermal instability at the
growth temperature. Herein, we first report the inorganic seeding promoter to grow high quality
MoS2 flakes. The crystalline quality and the thickness of grown MoS2 were confirmed by AFM,
Raman, and PL. The difference of typical Raman peaks of E2g and A1g is lower than ~19 cm-1
with full width half maximum values of 3.8 cm-1 and 4.5 cm-1, respectively. This high quality
is similar with mechanically exfoliated MoS2. In addition, the size of the grown MoS2 flakes
can be tuned by concentration of the seeding promoters. The growth process with seeding
promoters will be suggested in terms of surface reaction and nucleation of participating atoms
and promoters on the surface. Our suggested inorganic seeding promoter will open the way to
grow high quality monolayer MoS2 flakes with scalable size.
References
1. Y. H. Lee, X. Q. Zhang, M. T. Chang, C. T. Lin, K. D. Chang, Y. C. Yu, J. T. W. Wang,
C. S. Chang, L. J. Li, and T. W. Lin, Adv. Mater. 24, 2320 (2012).
T-P-004
Analysis of Electrical Detection of Biomolecules on MoS2 FET
with Surface Potential by KPFM
Heekyeong Park1,†, Minhyung Kim2,†, Jongyeol Baek1, Healin Im1, Seokhwan Jeong1,
Dabin Seol1, Youngki Hong1, Sangwoo Lee2,* and Sunkook Kim1,*
1
Department of Electronics and Radio Engineering, Kyung Hee University,
Yongin-si,Gyunggi-do,449-701, Korea
2
Department of Biomedical Engineering, Yonsei University, Wonju, Gangwon-do, 220-710, Korea
*E-mail address: seonkuk@khu.ac.kr
Nowadays, detection of cancer biomarker for early diagnosis by using field effect transistor
sensor is one of the most popular issues in biotechnology. Furthermore, not only uniformity of
biosensor performance but also its quantitative analysis is the key issue in nanotechnology.
Recently, Lee et al [1] have reported that the nature of hydrophobic MoS2 surface (the contact
angle ~ 75.77˚) affords a physical adsorption to biomolecule binding directly. Another
interesting point is that biomolecules (anti-PSA) on MoS2 channel surface shows positively
charged. These charged biomolecules could induce the surface potential modification of MoS2
channel and then control the channel conductance. Kelvin probe microscopy (KPFM), which
is known as one of the microscopy equipment to investigate surface potential, can recognize
the charge state and the spatial distribution of the biomolecules, and the surface potential on
MoS2 channel surface. In this work, we have analysed the relationship between the current
behavior of MoS2 TFT and the surface potential after anti-PSA-MoS2 surface adsorption by
using I-V measurement and KPFM. Also, we have conducted quantitative analysis of anti-PSA
to find optimum condition on MoS2 FET biosensor. From this work, we supposed the surface
binding and uniformity to confirm an optimized absorption of the biomolecules. Also, this
novel analytical technique, KPFM, to investigate the sensing of the physically absorbed
biomolecules on 2D MoS2 FET biosensor can be useful to optimize and model a FET biosensor
based on 2D materials.
Fig. 1. Surface potential map images observed by KPFM on MoS2 surface after adsorption of biomolecules (anti, (b)
, (c)
, (d)
, (e)
of anti-PSA.
PSA): (a)
References
1. J. H. Lee, P. Dak, Y. S. Lee, H. K. Park, W. Choi, M. A. Alam, and S. K. Kim, Sci. Rep. 4, 7352 (2014).
†
These authors contributed equally to this work
T-P-005
Tailored graphene on silver nanowire as highly reliable and transparent
electrode for light emitting diodes
Kyung Hyun Min1,2, Tae Hoon Seo1, Seula Lee1, S. Chandramohan2, Ah Hyun Park2,
Gun Hee Lee2, Dong Kyu Yeo1,2, Hee Su Kim2, Eun-Kyung Suh2,*, and Myung Jong Kim2,*
1
Soft Innovative Materials Research Center, Korea Institute of Science and Technology, Jeonbuk 565-905,
South Korea
2
School of Semiconductor and Chemical Engineering, Semiconductor Physics Research Center, Chonbuk
National University, Jeonju 561-756, South Korea
* E-mail address: eksuh@jbnu.ac.kr, myung@kist.re.kr
ABSTRACT We demonstrate a highly reliable transparent conductive electrode (TCE) that integrates
silver nanowires (AgNWs) and high-quality graphene as a protecting layer. Graphene with minimized
defects and large graphene domain was successfully achieved by decoupling nucleation step from
growth through a facile two-step growth approach. Ultraviolet light emitting diodes (UV-LEDs) were
fabricated using AgNWs or hybrid electrodes where AgNWs were combined with two-step grown
graphene (A-2GE) or conventional one-step grown graphene (A-1GE). Then, the device performance
and reliability of the UV-LEDs with three different electrodes were compared. The light output power
as a function of injection current for the UV-LED with the three different TCEs examined in this work
after one month is illustrated in Fig. 1. The light output power of the LED with AgNWs is poor, and its
light output power is not observed when the injection current exceeds 40 mA because the device failed
by larger voltage drop caused by AgNWs agglomeration and junction breakdown under high power
operation. When operated at high injection current levels, the devices inevitably generate extreme
amounts of heat, obstructing the reliability and performance of the device. According to Fig. 1, the UVLEDs with A-1GE and A-2GE show stable operation even after one month up to an injection current of
100 mA investigated in our measurements, with bright light emission over the entire emission area as
evidenced from the EL image at 20 mA. This result strongly implies that both devices with graphene
have thermal stability during long-time operation. One can notice that the difference in light output
power between the devices with A-1GE and A-2GE progressively increases as the current elevates,
indicating that the A-2GE as a TCE possesses great thermal as well as long-term stability and reliability
of the device better than those of A-1GE.
Fig. 1. Light output power with increasing current for UV-LED having AgNWs, A-1GE, and A-2GE, respectively
after one month. (inset) EL photographs of respective devices at 20 Ma
T-P-006
Gas barrier characteristic of graphene formed by two-step growth process
and electro-chemical polishing
Seula Lee1,2, Tae Hoon Seo1, Kyung Hyun Min1, Jae Kwan Lee2, Eun-kyung Suh3, and
Myung Jong Kim1,*
1
Soft Innovative Materials Research Center, Korea Institute of Science and Technology, Jeonbuk 565-905,
South Korea
2
School Department of Carbon materials, Chosun University, Gwangju 501-759, Republic of Korea
3
School of Semiconductor and Chemical Engineering, Semiconductor Physics Research Center, Chonbuk
National University, Jeonju 561-756, South Korea
* E-mail address: myung@kist.re.kr
Graphene with chemical inertness and complete impermeability to any gases can be used as a
gas barrier against water and oxygen diffusion and protective layer to prevent the metal
electrodes from oxidation, corrosion, and degradation in electrochemical systems.[1,2] In this
study, we use a combined approach of electro-chemical polishing (ECP) and two-step growth
methods to improve the gas barrier property of graphene without an increase in the layer
numbers or additional fabrication process. Three different graphene layers were prepared as
follows: The first graphene was grown on as-received Cu foil without any treatment by one
step growth (1step-w/o ECP), the second graphene was grown on electrochemically polished
Cu foil by one step growth (1step-ECP) and the third graphene was grown on ECP Cu foil by
two step growth (2step-ECP). Figure 1 shows water vapor transmission rate (WVTR) with time
for three different samples. The formation of graphene on PET leads to a decrease in WVTR
results compared to bare PET. In particular, 2step-ECP graphene on PET exhibits the lowest
WVTR value of 0.665±0.046 g/m2-day, which is 57.9% less than 1.58±0.029 g/m2-day of bare
PET due to large domains and improved graphene quality with minimized defects. The CVD
graphene reported here could open up the possibility for exploring graphene-based gas barrier.
Fig. 1. Water vapor trasmission rate (WVTR) of graphenes formed by various methods on PET.
References 1. J.S. Bunch, S.S. Verbridge, J.S. Alden, A.M.V.D. Zande, J.M. Parpia, H.G. Craighead, P.L.
Mceuen, Nano Lett. 8 (8) (2008) 2458. 2. S. Chen, L. Brown, M. Levendorf, W. Cai, S.-Y. Ju, J. Edgeworth, X.
Li, C.W. Magnuson, A. Velamakanni, R.D. Piner, J. Kang, J. Park, R.S. Ruoff, ACS Nano 5 (2) (2011) 1321.
T-P-007
Fabrication of 2D Multilayer MoSe2 Photodetector Synthesized by
Chemical Vapor Deposition
Chulseung Jung1, Hyunsung Moon1, Na Liu1, Jingon Lee1, Hyosung Kim1, Inturu Omkaram1
and Sunkook Kim1*
1
Deparment of Electronics and Radio Engineering, Kyung Hee University, Yongin-si, South Korea
* E-mail address: seonkuk@khu.ac.kr
Recently, many researchers actively study about transition metal dichalcogenides (TMDs: MX2, M=
Mo, W; X= S, Se, Te) because of their good electrical and optical properties. In particular, TMDs can
be fabricated easily by mechanically exfoliation method using scotch tape. TMDs present extremely
high device performances such as high mobility (> 100 cm2/Vs), high photoresponsivity (~500 A/W)14
, and flexibility for the next-generation electronic devices. However, because of the scotch tape method,
TMDs materials are transferred randomly on the substrate indicating uniformity of device
characteristics. In order to solve the crucial problem, many researchers study about the uniform growth
method of TMDs materials on the diverse substrate using chemical vapor deposition (CVD).
We synthesized the multilayer hexagonal molybdenum diselenide (MoSe2) based on the twodimensional nucleation theory5. The as-grown MoSe2 were annealed by the decomposition temperature
(~650℃) for 10 min to generate Se vacancies which acted as defect between channel and electrode
junction. We also extracted the density of state (DOS) by temperature-dependent behavior of the device
to confirm the effect of the trap sites. Our multilayer MoSe2 thin film transistor (TFT) shows p-type
dominant ambipolar behaviors with large field-effect mobility (~ 10 cm2/Vs). To confirm the photoresponsive behavior, we measured the transfer curves under various illumination conditions (from 20
to 2560 mW/cm2) with a 638nm laser and calculated the reasonably high photoresponsivity (93.7 A/W).
Our multilayer MoSe2 TFTs, which have high electrical and optical properties, were attracted by their
interested potentials for interactive electronics.
(a)
(b)
Fig. 1. (a) 3D schematics image of CVD process for multilayer hexagonal MoSe2 using MoO3 and Se powder
with Ar/H2 gas mixture. (b) Transfer characteristics (Ids-Vgs) of as-grown MoSe2 thin film transistor for calculation
of photoresponsivity in the dark and under the 638nm-red laser with different incident light power densities (Pinc=
20, 40, 80, 160, 320, 640, 1280 and 2560 mW/cm2)
References
1.
2.
3.
4.
5.
Lee, T. H. et al., Adv. Mater. 24, 2320-2325 (2012).
Jeon, J. et al., Nanoscale 7, 1688-1695 (2015)
Schmidt, H. et al., Nano Lett. 14, 1909-1913 (2014)
Lee, Y. –H. et al., Nano Lett. 13, 1852-1857 (2013)
Hirth, J. P. & Pound, G. M. Macmillan, (1963)
6.
T-P-008
[NO SHOW]
Light helicity dependent photocurrent in two dimensional
materials,
Mustafa Eginligil, Bingchen Cao, Zilong Wang, Jingzhi Shang, Chunxiao Cong, Cesare Soci and Ting Yu
T-P-009
Optical Conductivity and Band Gap of Transition Metal Dichalcogenides
Jangwon Kim1, Dongwoo Shin2, H. Y. Choi1, D. G. Oh1 , Taewoo Ha1, Kyung Ik Sim1, Jeehoon
Kim2, Y. J. Choi1 and Jae Hoon Kim1
1
2
Department of Physics, Yonsei University, 50 Yonsei-Ro, Seodaemun-Gu, Seoul 03722, Republic of Korea
Department of Physics, Pohang University of Science and Technology, 77 Cheongam-Ro, Nam-Gu, Pohang,
Gyeongbuk 37673, Republic of Korea
We have investigated the optical properties of several compounds in the transition metal
dichalcogenide(TMDC) family. The experiment was conducted by using terahertz time-domain
spectroscopy and spectroellipsometry. We confirmed the optical band gap of Mo1-xWxSe2. The
result indicates that our TMDC specimens show semiconducting behavior at terahertz
frequencies toward the d.c. limit. The linear conductivity in the infrared region may have a
connection to Weyl semimetal signatures.
T-P-010 [NO SHOW]
Exotic anisotropic magnetoresistance in bulk single crystal LaSb
WonHyuk SHON1, 2, Sung-Jin KIM2, Heon-Jung KIM3, Yong Seung KWON4, Jong-Soo
RHYEE1,*
1
Deparment of Applied Physics, KyungHee Unicersity, YongIn-si 17104, Republic of Korea
Department of Chemistry and Nano Science, Ewha Womans University, Seoul 03760, Republic of Korea
3Department of Physics, Daegu University, Daegu 38453, Republic of Korea
4Department of Emerging Materials Science, DGIST, Daegu 42988, Republic of Korea
* E-mail address: jsrhyee@khu.ac.kr
2
We investigated the angle-resolved electrical transport properties of LaSb single crystal
synthesized by the Bridgman method. The temperature-dependent electrical resistivity showed
unsaturated behavior of ρ(T) and extremely large transverse magnetoresistance (XMR) at low
temperatures. The Hall resistivity measurements with respect to magnetic fields ρxy(H) at
various temperatures exhibited non-linear behavior with magnetic field at low temperatures
(T≤30 K) which is the same temperature region exhibiting XMR. It implies the anomalous Hall
resistivity is related with the XMR behavior. From the angle dependent magnetoresistance both
the rotations with respect to Φ- (sample s1) and θ- directions(sample s2), we observed
unsaturated negative magnetoresistance near 90˚(E∥B). Here we argue that the negative MR
at the special condition E∥B is a signature of chiral anomaly which is the strong indication of
Weyl semimetal character in LaSb.
T-P-012
Fabrication of GaN nanoneedles and their application to optoelectronic
devices based on inorganic-organic structures
Ha Young Lee1, Ji-Yeon Noh1, Injun Jeon1 , Hunsoo Jeon2, Hyung Soo Ahn1,2, Sam Nyung Yi1,2*
Min Jeong Shin3, and Young Moon Yu4
,1
Department of Electronic Materials Engineering, Korea Maritime and Ocean University, Busan 49112,
Korea,2Compound Semiconductor Fabrication Technology Center, Korea Maritime and Ocean University,
Busan 49112, Korea, 3RF Convergence Components Research Section, ICT Materials & Components Research
Laboratory, Electronics and Telecommunications Research Institute (ETRI), Daejeon 34129, Korea, 4LED
Convergence Engineering Department, Specialized Graduate School Science and Technology Convergency,
Pukyong National University, Busan 48513, Korea
GaN-based inorganic semiconductors have been extensively investigated owing to their
potential applicability in high-power/high-frequency electronic and short-wavelength optical
devices such as blue–green and UV LEDs, laser diodes, and high-power/high-temperature
electronics.
We fabricated one-dimensional GaN nanoneedles on a n-GaN epilayer by hydride vapour
phase epitaxy. Nanoneedles were grown at HCl:NH3 gas flow ratios of 1:38 at 600°C. The
vertical growth rate of GaN nanoneedles is higher than the lateral growth rate under the
optimized growth conditions. A pole figure at (101� 1) revealed that GaN nanoneedles grew
on the c-axis in a specific direction and rotated to the substrate.
The organic–inorganic hybrid device was formed with MEH-PPV and GaN nanoneedles for
LED applications. A 0.6 wt% solution of MEH-PPV was prepared by continuously stirring the
MEH-PPV fibre in monochlorobenzene at 30 °C for more than 12 h. The properties of the
hybrid structure were investigated by field emission scanning electron microscopy (FE-SEM),
energy-dispersive X-ray spectroscopy (EDS), Raman spectroscopy, current–voltage (I–V)
characteristics, photoluminescence (PL), and electroluminescence (EL). The I–V curve of the
hybrid device showed its rectification behaviour. PL spectroscopy showed peaks of both GaN
nanoneedles and MEH-PPV, but only one visible emission peak, originating from MEH-PPV,
appeared in the EL spectrum owing to the different potential barriers of electrons and holes at
the interface of MEH-PPV and the GaN nanoneedles.
T-P-013
Common-Source Inductance Reduction in GaN Cascode FET for HighSpeed Switching and High-Efficiency Operation
Woojin Chang1, Young-Rak Park2, Jae-Kyoung Mun2, and Jong-Won Lim1
1
RF Convergence Components Research Section, 2GaN Power Electronics Research Section,
Electronics and Telecommunications Research Institute (ETRI), Daejeon, Korea
* E-mail address: wjchang@etri.re.kr
This paper aims to reduce the most critical parasitic inductance of a GaN cascode FET using an additional
bonding wire interconnected between the source electrode of a low-voltage (LV) normally-off Si MOSFET
and the gate electrode of a high-voltage (HV) normally-on GaN FET for high-speed switching and highefficiency operation. A common-source inductance (CSI) is defined as the inductance shared by the power
loop and driving loop, to be the most critical parasitic element. The CSI acts as negative feedback to slow
down the driver during the turn-on and turn-off transitions, thus, it prolongs the voltage and current crossover
time, and significantly increases the switching loss. In terms of the GaN cascode FET, because Lint3 is the
CSI of the HV normally-on GaN FET and the LV normally-off Si MOSFET, it should be the most critical
inductance, providing the major switching loss [1]. Compared with a conventional GaN cascode FET, shown
in Fig. 1, the proposed GaN cascode FET has an additional inductor (bonding wire, Lgs,int) to reduce the most
critical inductance acting as the CSI. From the measured results of the proposed and conventional GaN
cascode FETs, shown in Table 1, the rising and falling times of the proposed GaN cascode FET were up to
3.4% and 8.0% faster than those of the conventional GaN cascode FET, respectively, under measurement
conditions of 30 V and 5 A. During the rising and falling times, the energy losses of the proposed GaN
cascode FET were up to 0.3% and 6.7% lower than those of the conventional GaN cascode FET, respectively.
The total on/off switching time and energy loss of the proposed GaN cascode FET for one cycle were up to
1.2% and 3.6% lower than those of the conventional GaN cascode FET, respectively, under the same
measurement conditions.
Fig. 1. GaN cascode FETs of (a) conventional structure and (b) proposed structure with additional inductor.
Table 1. Comparison of measured switching characteristics.
Acknowledgements
This work was supported by the “Development of High Efficiency GaN-Based Key Components and Modules for Base and Mobile Stations”
R&D project (No. B0132-15-1006) of Korea Ministry of Science, ICT and Future Planning.
References
1. Z. Liu et al, IEEE Trans. on Power Electronics, vol. 29, no. 4, pp.1977-1985 (2014).
2. W. Saito et al, IEEE Trans. on Electron Devices, vol. 53, no. 2, pp.356-362 (2006).
3. W. Chang et al, ETRI Journal, vol. 38, no. 1, pp.133-140 (2016).
T-P-014
Influence of silicon nitride layer on MIM capacitor for MMIC
Min Jeong Shin1,*, Ho-Kyun Ahn1, Sang-Heung Lee1, Dong-Min Kang1, Dong-Young Kim1,
Kyu Jun Cho1, Jae-Won Do1, Hyun-Wook Jung1, Sung-Jae Chang1, Hae-Cheon Kim1,
Hyoung-Sup Yoon1, Byoung-Gue Min1, Jong-Min Lee1, Seong-Il Kim1, Chul-Won Ju1, EunSoo Nam1, Yongsoon Baek1 and Jong-Won Lim1
1
ICT Materials & Components Research Laboratory, Electronics and Telecommunications Research Institute
(ETRI), Daejeon 305-700, Korea
* E-mail address: mjshin706@etri.re.kr
Metal-Insulator-Metal (MIM) capacitors are one of important passive components in MonolithicMicrowave Integrated Circuit (MMIC), integrated passive device and RF-power amplifier due to its
many functions such as DC-blocking, impedance matching and DC-bias network, etc [1, 2]. We
investigated the correlation between silicon nitride properties and MIM capacitor for MMIC
applications. MIM capacitors were fabricated using silicon nitride layer as dielectric insulator deposited
by plasma-enhanced chemical vapor deposition with different nitride source, ammonia or nitrogen gases.
Figure 1 shows microscopy image and schematic diagram of MIM capacitor. Highly denser silicon
nitride with low impurities, formed by using nitrogen gas caused the electrical properties of MIM
capacitor to be improved. Figure 2 shows capacitance of MIM capacitor with silicon nitride layer
deposited using ammonia gas and nitrogen gas, respectively. We measured the higher κ value of MIM
capacitor (B) fabricated by highly denser silicon nitride. The silicon nitride layers were analyzed by
etch rate, ellipsometer, x-ray photoelectron spectroscopy, Fourier transform infrared and atomic-force
microscopy measurement. Electrical properties such as leakage current, breakdown voltage and
capacitance of MIM capacitors were investigated by I-V and C-V characteristics. Also the simulated
RF modeling results by designing equivalent circuit for MMIC are compared with measured results
from C-V data.
Fig. 1. The microscopy image and schematic diagram of MIM capacitor using silicon nitride layers.
Fig. 2. Permittivity of MIM capacitor with silicon nitride layer deposited by (A) using ammonia gas and (B)
nitrogen gas, respectively.
References
1. L. Wang, R.M. Xu, B. Yan, Progress In Electromagnetics Research 66, 173 (2006).
2. P. Tiwat, Y. Tingting, L. Guoguo, C. Xiaojuan, L. Xinyu, Proceedings of the IEEE International Workshop on
Microwave and Millimeter Wave Circuits and System Technology, 475 (2013).
T-P-015
Fabrication of GaN nanoneedles and their application to optoelectronic
devices based on inorganic-organic structures
Ha Young Lee1, Ji-Yeon Noh1, Injun Jeon1 , Hunsoo Jeon2, Hyung Soo Ahn1,2, Sam Nyung Yi1,2* Min
Jeong Shin3, and Young Moon Yu4
, 1
Department of Electronic Materials Engineering, Korea Maritime and Ocean University, Busan 49112,
Korea,2Compound Semiconductor Fabrication Technology Center, Korea Maritime and Ocean University, Busan
49112, Korea, 3RF Convergence Components Research Section, ICT Materials & Components Research
Laboratory, Electronics and Telecommunications Research Institute (ETRI), Daejeon 34129, Korea, 4LED
Convergence Engineering Department, Specialized Graduate School Science and Technology Convergency,
Pukyong National University, Busan 48513, Korea
GaN-based inorganic semiconductors have been extensively investigated owing to their potential
applicability in high-power/high-frequency electronic and short-wavelength optical devices such as
blue–green and UV LEDs, laser diodes, and high-power/high-temperature electronics.
We fabricated one-dimensional GaN nanoneedles on a n-GaN epilayer by hydride vapour phase
epitaxy. Nanoneedles were grown at HCl:NH3 gas flow ratios of 1:38 at 600°C. The vertical growth rate
of GaN nanoneedles is higher than the lateral growth rate under the optimized growth conditions. A
pole figure at (101� 1) revealed that GaN nanoneedles grew on the c-axis in a specific direction and
rotated to the substrate.
The organic–inorganic hybrid device was formed with MEH-PPV and GaN nanoneedles for LED
applications. A 0.6 wt% solution of MEH-PPV was prepared by continuously stirring the MEH-PPV
fibre in monochlorobenzene at 30 °C for more than 12 h. The properties of the hybrid structure were
investigated by field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray
spectroscopy (EDS), Raman spectroscopy, current–voltage (I–V) characteristics, photoluminescence
(PL), and electroluminescence (EL). The I–V curve of the hybrid device showed its rectification
behaviour. PL spectroscopy showed peaks of both GaN nanoneedles and MEH-PPV, but only one
visible emission peak, originating from MEH-PPV, appeared in the EL spectrum owing to the different
potential barriers of electrons and holes at the interface of MEH-PPV and the GaN nanoneedles.
T-P-016
Enhanced photoresponsivity and electrical transport of ZnO/ZnS core/shell
nanowires for multifunctional nanodevices
Sehee Jeong1, Min Woo Kim2, Wan Gil Jung2, Young-Chul Leem2, Bong-Joong Kim2, and
Seong-Ju Park1,2,*
1
Deparment of Nanobio Materials and Electronics, Gwangju Institute of Science and Technology, Gwangju
500-712, Korea
2
School of Materials Science and Engineering, Gwangju Institute of Science and Technology, Gwangju 500712, Korea
* E-mail address: sjpark@gist.ac.kr
In this study, we synthesized the ZnO/ZnS core/shell nanowires (NWs) using facile solution
method and invesitigated the electrical and optical properties of these NWs compared to ZnO
NWs. [1] In case of ZnO/ZnS core/shell NWs, the valence and conduction bands of the core
materials are lower than those of the shell material, thus it provides a spatial separation of the
electorns and holes in the core and shell. The spatial separation of charge carriers due to their
type-II band structure together with passivation effect on ZnO/ZnS core/shell NWs not only
enhanced their charge carrier transport characteristics by confining the electrons and reducing
surface states in the ZnO channel but also increased the photocurrent under ultraviolet (UV)
illumination by reducing the recombination probability of the photogenerated charge carriers.
Figure 1(a) shows the representative transfer (IDS-VG) curves for the ZnO/ZnS core/shell and
ZnO NW FETs at a drain voltage of 5 V and the inset shows a schematic diagram of a ZnO/ZnS
core/shell NW device with band-diagram. The photoresponse properties of the ZnO/ZnS
core/shell and ZnO NWs were measured under UV illumination of 365 nm, as shown in Figure
1 (b). The ZnO/ZnS core/shell NWs showed a higher photocurrent by 176% compared with
that of the ZnO NWs. The calculated responsivity and external quantum efficiency (EQE) of
the ZnO/ZnS core/shell NW (4.4 x 106 A/W, 1.5 x 109%) was much higher than that of the
ZnO NW (2.5 x 106 A/W, 8.5 x 108%). It is believed that the remarkably high responsivity and
EQE of the ZnO/ZnS core/shell NWs originate from the spatial separation and confinement of
the photogenerated electrons and holes upon illumination, resulting from the type-II band
alignment.
Figure 1. (a) IDS-VG characteristics of ZnO/ZnS core/shell and ZnO NW FETs. The inset
indicates the schematic illustration of a ZnO/ZnS core/shell NWs with its band diagram. (b)
Time-dependent photoresponse currents of ZnO/ZnS core/shell and ZnO NW devices upon
repeated UV illumination (365 nm) at a VDS of 5 V.
References
1. S. Jeong, M. Choe, J.W. Kang, M.W. Kim, W.G. Jung, Y.C. Leem, J. Chun, B. J. Kim, S. J. Park, ACS Appl.
Mater. Interfaces. 6, 6170 (2014)
T-P-017
Enhanced Hydrogen Sensing Characteristics of Pd/GaN Schottky Diodes
Embedded with Interfacial Ag Nano-dots
Kyurin KIM and Hyunsoo KIM*
School of Semiconductor and Chemical Engineering, Semiconductor Physics Research Center, Jeonju 54896,
Korea
* E-mail address: hskim7@jbnu.ac.kr
To use hydrogen sensors in an environmentally harsh condition such as high pressure, high
temperature, and corrosive ambient, the thermally and chemically stable semiconductors such
as SiC or GaN should be employed. Recently, wide bandgap GaN semiconductors showed a
feasible operation in such a harsh environment owing to their wide bandgap energy, physical
and chemical stability. However, GaN Schottky-diode type sensors still suffer from the
relatively poor sensitivity and recovery, which is presumably associated with the large density
of surface state density at the metal/GaN interfaces. In this study, the Pd/GaN Schottky diodes
embedded with an interfacial Ag nano-dot were fabricated to use as an efficient hydrogen
sensors. For this work, the 2 nm-thick Ag film was deposited on the n-GaN substrate, followed
by the thermal annealing at 700 °C for 5 min in N2 ambient. Then, the 100 nm-thick Pd layer
was deposited on the Ag nano-dots as a Schottky contact. As a n-type Ohmic contact, Ti/Al
layer was used. Interestingly, the Pd Schottky diodes embedded with interfacial Ag nano-dots
showed a noticeable increase in the relative change of forward current upon H2 exposure as
compared to the reference Pd diode (without Ag nano-dots), i.e., 1.1×106 for the advanced
sample and 1.1×105 for the reference diode. In addition, the advanced sample also showed a
greater shift of forward voltage after H2 exposure. The detailed hydrogen sensing mechanism
will be discussed in this presentation.
T-P-018
Parameterization of Dielectric Function of InxAl1-xP alloys
Chang Hyun YOO, Tae Jung KIM, Han Gyeol PARK, Van Long LE, Hwa Seob KIM, Hoang
Tung NGUYEN, and Young Dong KIM*
Nano-Optical Property Laboratory and Department of Physics, Kyung Hee University, Seoul 02447, Republic
of Korea
* E-mail address: ydkim@khu.ac.kr
The InxAl1-xP alloys are interesting because they exhibit the smallest refractive index and
largest band gap of any arsenic- or phosphorus-based alloy that is lattice matched to GaAs.
Based on these advantages, InxAl1-xP is used to make high-performance laser diodes and lightemitting diodes in the visible spectral range. To properly design and understand semiconductor
devices, it is needed to know the complex dielectric functions ɛ = ɛ1+iɛ2 of InxAl1-xP alloys as
a continuous function of indium composition (x). In this work, pseudodielectric functions < ɛ
> are obtained from InxAl1-xP ternary alloy films (x = 0, 0.186, 0.310, 0.476, 0.715, 0.810, and
1) by using spectroscopic ellipsometry (SE) and we analytically determine ɛ of InxAl1-xP as a
function of arbitrary x-composition in the spectral range from 1.5 to 6.0 eV at room temperature
and report the parameters that can be used to reconstruct the InxAl1-xP alloys by using dielectric
function parametric model (DFPM). The DFPM provides reasonably convenient means for
accurately establishing the asymmetric characteristics of optical functions of the materials as
the sum of polynomials. The dependence of composition x is determined by the quadratic
function of x so that we could specify dielectric function over the ranges given above. These
results will be useful for high-performance and light-emitting devices based on InxAl1-xP.
25
InP
20
15
ε2
E1
10
E1+∆1
E0'
E2
5
0
E1'
E0+∆0
2
3
4
5
6
E (eV)
Fig. 1. Dielectric function spectra of InxAl1-xP alloy films for x=1, together with the best fit using D
T-P-019
Ⅱ-Ⅵ Compound Semiconductor Crystal Growth,
Characterization of CdMnTe Radiztion detectors
Hyundo Shin, Heejin Ahn, Dongchan Lee, Heungyeol Jo and Youngho Um*
Deparment of physics,Ulsan 689-749, Korea
* E-mail address: yhum@ulsan.ac.kr
In today’s world, nuclear medical imaging is becoming more popular for diagnosing cancer
and other diseases, and control of weapons-grade nuclear materials is becoming more and more
important for national security. All of these needs require high performance nuclear radiation
detectors which can accurately measure the type and amount of radiation being used. One of
the most promising semiconductor materials being considered to create a convenient, fielddeployable radiation detector is cadmium zinc telluride (CdZnTe), CdZnTe is a compound
semiconductor which can detect high-energy gamma-rays at room temperature. It offers high
resistivity (≥ 1010 Ω-cm), a high band gap (1.55 eV), and good electron transport properties.
However, one significant issue with CdZnTe is that there is considerable difficulty in growing
large, homogeneous, defect-free single crystals of CdZnTe. This significantly increases the cost
of producing CdZnTe detectors, making CdZnTe less than ideal for mass-production.
Furthermore, CdZnTe has durability by soft properties of Zinc, which creates significant
problems when using it as a high energy gamma-ray detector.
In this study, investigated the structural, electrical and optical properties of cadmium
manganese telluride (CdMnTe) single crystals. Which is a II-VI compound semiconductors as
promising alternative material to complement the disadvantages of CdZnTe compound
semiconductor. The CdMnTe base properties conform to CdZnTe as Zinc-blende structure,
high resistivity and high band gap energy. In additional CdMnTe has good crystallinity by good
segregation coefficient. CdMnTe single crystals grown by the vertical Bridgman method,
which considered stability of crystal growth furnace for made good quality CdMnTe single
crystal. As a result, we have good quality CdMnTe single crystal is shown in Fig. 1.
Finally, we are annealed under Cd vapor atmosphere to decrease Cd vacancy and other defects
of Te inclusions and dislocations. The quality and electrical and optical properties of the
CdMnTe single crystal before and after annealing were investigated.
Fig. 1. Non-polishing CdMnTe single crystal
T-P-020
The properties of AZO and GZO thin films by using RF magnetron
sputtering for CIGS solar cell
Dongchan Lee, Heejin Ahn, Hyundo Shin, Sujung Park and Youngho Um*
Department of Physics, Ulsan 689-749, Korea
*E-mail address : yhum@ulsan.ac.kr
The transparent conducting oxide (TCO) thin films show low resistivity, high transmittance in
the visible region and high thermal stability. The TCO based on zinc oxide show remarkable
electrical and optical properties. To improve the electrical conductivity of zinc oxide thin film,
elements of group Ⅲ are doped zinc oxide; such as boron(B), aluminum(Al), indium(In), and
gallium(Ga). In this work, structural, morphological, optical and electrical properties of
Aluminum doped zinc oxide (AZO) thin film and gallium doped zinc oxide (GZO) thin film
on soda-lime glass substrate by using radio-frequency (RF) magnetron sputtering with different
conditions are investigated. Morphological, structural properties are studied by FE-SEM, AFM
images and X-ray diffraction (XRD) pattern. Deposition rate of films depends on RF power
and deposition time in sputtering system. XRD patterns of films exhibit a major (002) peak and
intensity increases as the RF power increases. This indicates that thin films are polycrystalline
with the hexagonal wurtzite structure and have a preferred orientation with the c-axis
perpendicular to the substrates. Transmittance of AZO and GZO is about 90% and 91%
respectively. The highest resistivity of GZO is about 3.71╳10-3 Ω∙cm and AZO is about 1.49╳
10-2 Ω∙cm.
T-P-021
The effect of the Na2EDTA and HMTA concentrations on the growth and
properties of CBD ZnS/CIGS films in acidic solution
Heejin Ahn, Dongchan Lee, Sujung Park Hyundo shin and Youngho Um*
Deparment of physics,Ulsan 689-749, Korea
* E-mail address: yhum@ulsan.ac.kr
CBD-ZnS buffer layer needs to have uniform morphologies, pinhole free, good interfacial
adhesion and high growth rate for its application in thin film solar cells and it is resulted in the
improved conversion efficiency. It has been well known that the morphological property of a
CBD-ZnS buffer layer is strongly related to the complexing agents, which control Zn2+ ion
concentration during deposition processing.
Recently, the improved crystal quality of ZnS thin film could in acidic solution. ZnS thin
films were successfully grown with the improved crystal quality and uniform morphology
using Na2EDTA as a less toxic complexing agent in acidic solution. However this additive
agent make long deposition time for a CBD-ZnS buffer layer was resulted in the low conversion
efficiency. Therefore it is necessary to improve the growth rate for ZnS thin film by introducing
a proper complexing agent during CBD process. It is well known that
hexamethylenetetramine(HMTA) easily forms Zn2HMTA in hot reaction solution, which
results in increasing the ZnS formation probability by releasing Zn2+ ions with reaction
proceeds. This characteristic suggested that the growth rate of ZnS thin film could be improved
with keeping smooth and dense micro-structure by proper use of mixed complexing agents.
This study is to improve the growth rate of ZnS thin films by CBD method in acidic solution
on the CIGS thin film at 90oC without changing uniform morphology by using mixed
complexing agent of Na2EDTA and HMTA. The effects of HMTA quantity on the
morphological, chemical, optical properties of ZnS/CIGS films have been reported. FESEM
results showed that very uniform and smooth ZnS/CIGS films were obtained using mixed
complexing agents of Na2EDTA and HMTA. The results will be presented in detail.
Fig 1. The effect of complexing agents on the properties of ZnS thin films
T-P-022
Electron transport mechanism of AZO films
Tae-Soo Jang1 and Dong-Cheol Oh2,*
1
Deparment of Nanobiotronics, Hoseo University, Asan, 31499, Korea
Department of Defense Science & Technology, Hoseo University, Asan, 31499, Korea
* E-mail address: ohdongcheol@hoseo.edu
2
Al-doped ZnO, AZO is noted as one of promising transparent conductive oxide (TCO)
materials replaceable for Sn-doped In2O3, ITO in the near-future due to the development of
various display applications. This is originated from the fact that ZnO with a wide bandgap
of 3.37 eV has transparency to visible light, fabricated ZnO films natively contain a large
density of n-type dopants such as VO and Zni, and Al doping into the ZnO films can effectively
control the n-type conductivity of ZnO films. Moreover, high-quality AZO films can be
fabricated by rf-sputtering, which is suitable for mass production, convenient to system
maintenance, and possible for low-temperature fabrication. MBE is not appropriate to mass
production and MOCVD is not appropriate to low temperature fabrication below 300 oC.
In this work, we prepare various sets of ZnO and AZO films as functions of substrate, substrate
temperature, and post-annealing temperature. ZnO and AZO films are fabricated on glass and
Al2O3 substrates at different substrate temperatures by rf-sputtering, respectively. The ZnO
film deposited on a glass substrate and that on an Al2O3 substrate have extremely different
structural properties, though they are also dependent on each substrate temperature, which
resultedly determine their electrical properties. The ZnO and AZO films are post-annealed in
open-tube furnace, which induces the change of their structural properties and electrical
properties. All electrical parameters and structural parameters of the ZnO and AZO films are
obtained by temperature-dependent Hall measurement and high-resolution X-ray diffraction.
We derive the electron transport mechanism of AZO films in terms of comparing the electron
concentrations and electron mobilities of the ZnO and AZO films and their X-ray diffraction
linewidths and dislocation densities.
Fig. 1. Electron mobility as a function of electron concentration, varied by annealing conditions.1
References
1. D. C. Oh, H. J. Ko, S. K. Han, and S. K. Hong, W. G. Jeong, and T. Yao,
Appl. Phys. Exp.
5, 075801 (2012).
T-P-023 [NO SHOW]
Comparative study about the electrical properties
of ZnO and GaN films and a ZnO/GaN heterostructure
Tae-Soo Jang1 and Dong-Cheol Oh2,*
1
Deparment of Nanobiotronics, Hoseo University, Asan, 31499, Korea
Department of Defense Science & Technology, Hoseo University, Asan, 31499, Korea
* E-mail address: ohdongcheol@hoseo.edu
2
ZnO has attracted a considerable attention as a promising material for the optical devices in the
ultraviolet region and the electronic devices in the communication field due to a direct bandgap
of 3.37 eV, a large exciton-binding energy of 60 meV, a large saturation velocity of
3.1×107cm/sec, and a large cohesive energy of 1.89 eV. Also, ZnO-on-GaN is expected as
another promising material for the high-speed electronic devices due to the fact that the
ZnO/GaN heterostructure has the large conduction band discontinuity of 0.82 eV, whose value
is 3 times larger than the value of 0.29 eV in the Al0.15Ga0.85N/GaN heterostructure.
In this work, we have a comparative study about the electrical properties of ZnO and GaN films
and a ZnO/GaN heterostructure, which were evaluated by using Hall measurements and C-V
measurements. First, we investigate the electron transport mechanism of ZnO films grown
on Al2O3 substrates by rf-sputtering.
Second, we investigate the electron transport
mechanism of GaN films grown on Al2O3 substrates by MOCVD. Third, we investigate the
electron transport mechanism of ZnO/GaN heterostructures, which was fabricated by growing
ZnO films on GaN/Al2O3 templates by rf-sputtering. Those electrical properties were
compared with their structural properties and optical properties.
Fig. 1. Left: Depth profile of electron concentration of a ZnO/GaN heterostructure.1
dependence of electron mobility of GaN bulks.2
Right: Temperature
References
1. D. C. Oh, T. Suzuki, J. J. Kim, H. Makino, T. Hanada, T. Yao, and H. J. Ko, Appl. Phys. Lett.
(2005).
2. D. C. Oh, H. J. Lee, H. J. Ko, and C. G. Jhun, J. Korean Phys. Soc. 65, 1696 (2014).
87, 162104
T-P-024
Narrow band gap (1-1.25 eV) dilute-N-Sb materials for high efficiency
multi-junction solar cell application
TaeWan Kim1,*
1
Vacuum Center, Korea Research Institute of Standards and Science, Daejeon 34113, Korea
* E-mail address: twkim@kriss.re.kr
Recently, record efficiency (44.7%) for III-V multi-junction solar cells have been achieved
under 297.3 × solar concentration using an InGaP/GaAs/(Eg ~ 1 eV) material/Ge four-junction
structure on Ge substrate. These results demonstrate the importance of further developing
materials with close to 1 eV band gap energy for pushing solar cell performance towards higher
efficiency [1]. Multinary bulk films of dilute-nitride materials for narrow energy band gap (Eg
~ 1 eV), such as GaAsN, InGaAsN, GaAsSbN, and InGaAsSbN, are very attractive owing to
the ease of bandgap energy tuning and lattice matching with a small amount of N. There are
several prior successful achievements of single junction solar cells employing dilute-nitride
materials grown by molecular beam epitaxy (MBE) [2.3] and by metalorganic vapor phase
epitaxy (MOVPE) [4,5]. Dilute nitride materials grown by MBE generally have very low
background carrier concentrations (~1x1015 cm-3). By contrast, high background carbon
impurities, which correlates with poor luminescence properties and short minority carrier
diffusion length, is a challenging issue for MOVPE-grown dilute-nitride-antimonide materials
[4,6].
In this study, dilute-nitride-antimonide materials grown by MOVPE have been pursued to
achieve a 1 – 1.25 eV energy band gap materials, which can be easily integrated into multijunction solar cells on Ge and GaAs substrates. Several types of bulk dilute-nitride-antimonide
films (InGaAsN, GaAsSbN, InGaAsSbN), close lattice matched to GaAs or Ge, are optimized
by growth conditions, metal organic sources selection, optical properties, electrical properties,
and carrier dynamics studies. The optimized dilute-nitride-antimonide materials with band gap
energies of 1 – 1.25 eV have been integrated into single hetero- and homo-junction and doublejunction solar cell structures.
References
1. http://phys.org/news/2013-09-world-solar-cell-efficiency.html.
2. David B. Jackrel, Seth R. Bank, Homan B. Yuen, Mark A, Wistey, and James S. Harris,
Aaron J. Ptak, Steven W. Johnston, Daniel J. Friedman, and Sarah R. Kurtz, J. Appl.
Phys. 101, 114916 (2007).
3. Yokiko Kamikawa-Shimizu, Shigeru Niki, Yoshitaka Okada, Solar Energy Materials
& Solar Cells 93, 1120-1123 (2009).
4. T. W. Kim, T. J. Garrod, K. Kim, J. J. Lee, S. D. LaLumondiere, Y. Sin, W. T. Lotshaw,
S. C. Moss, T. F. Kuech, Rao Tatavarti, and L. J. Mawst, Appl. Phys. Lett.100, 121120
(2012).
5. G. Leibiger, C. Krahmer, J. Bauer, H, Herrnberger, V. Gottschalch, J. Cryst.Growth 272,
732-738 (2004).
6. Kerstin. Volz, Torsten Torunski, Bernardette Kunert, Oleg Rubel, Siegfried Nau, Stefan
Reinhard, Wolfgang Stolz, J. Cryst.Growth 272, 739-747 (2004).
T-P-025
Optical phonons in CdTe/ZnTe self-assembled quantum dot structures
Seulki Baik, Hong Seok Lee, and Heesuk Rho*
Department of Physics, Chonbuk National University, Jeonju 54896, Korea
* E-mail address: rho@chonbuk.ac.kr
We report Raman scattering results of CdTe/ZnTe self-assembled quantum dots (QDs).
Photoluminescence (PL) spectra revealed that the ground-state PL peak energies of the CdTe
QDs decreased with increasing QD thickness from 2.0 to 3.5 monolayers (MLs), indicating
that the QDs grew in size. When the CdTe QDs were excited under non-resonant excitation, a
longitudinal optical (LO) phonon response from ZnTe barrier material was mainly observed at
207 cm−1. In contrast, when the CdTe QDs were resonantly excited, while the ZnTe LO phonon
response was considerably weakened, additional phonon modes were newly observed at 167
and 201 cm−1. The 167 cm−1 phonon mode corresponds to the LO phonon from CdTe QDs. To
identify the origin of the 201 cm−1 phonon mode, spatially-resolved Raman scattering
measurements were performed from the side edge of the sample. Interestingly, it was found
that the 201 cm−1 phonon mode was strongly localized at the interface between the CdTe QDs
and ZnTe cap layer. This phonon corresponds to the interface optical (IO) phonon which
propagates with a characteristic frequency lying between the transverse optical (TO) and LO
phonon frequencies. Theoretically calculated result using a dielectric continuum approach with
an assumption of spherical dot boundary agreed well with the experimentally observed IO
phonon energy.
This research was supported by the Basic Science Research Program through the National
Research Foundation of Korea (NRF) funded by the Ministry of Education (Grant No.
2014R1A1A2057173).
T-P-026
T-P-027
MBE growth of GaN Films on Tungsten Carbide/Si Template
Sungmin Cho1, Sungkuk Choi2, Youngji Cho2, Seokhwan Lee1, and Jiho Chang*12
1
Department of Convergence Study on the Ocean Science and Technology, Korea Maritime and Ocean
University, Busan 606-791, Republic of Korea
2
Major of Electronic Material Engineering, Korea Maritime and Ocean University, Busan 606-791, Republic of
Korea
* E-mail address: jiho_chang@KMOU.ac.kr
GaN on Si technology has attracted an interest since it offers a lot of availability that is not
affordable by sapphire substrates. However, requirement of sophisticated interface control has
hindered a wide spreading of this technology[1]. We have introduce a tungsten carbide(WC)
buffer layer for the GaN growth[2]. Actually, WC has been well known as a surface protection
layer for various mechanical tools, due to its superior mechanical and chemical robustness[3].
However, it has not been studied as a buffer layer for the nitrides so far, we have to figure out
the growth condition of tungsten carbide on silicon substrate and evaluate the ability of the
layer for the successive nitrides growth on it.
WC layer has been sputtered on a (111) Si-substrate, and GaN layer has been grown by gassource molecular beam epitaxy. First of all, we have optimized the substrate treatment and
sputtering conditions to grow WC. Also, to assess the possibility of the growth of GaN layer
on it, we have evaluated the WC/Si interface quality and the surface energy of WC layer.
Finally, we have grown GaN layer on WC layer and have tested several well-known defect
reduction methods to obtain a single crystalline GaN layer, although the growth condition has
not been optimized yet. Crystalline quality, luminescence property and residual carrier
concentration of the GaN films grown on WC/Si templates were evaluated by X-ray diffraction,
photoluminescence, and Hall effect measurement, respectively. Fig. 1 shows the rocking curve
results of GaN layers grown on WC/Si template. By using a low temperature GaN buffer, we
could grow single crystalline GaN film easily.
Consequently, we have demonstrated a new way of nitride growth on Si-substrate by using a
sputtered WC buffer layer. We found that a growth of GaN film with high crystal quality is
possible through a simple approach with a WC/Si template.
GaN/WC/(111)Si
Si(111)
GaN (11-22)
GaN (11-20)
GaN (10-13)
GaN (10-12)
XRD intensity (a.u.)
GaN (10-10)
GaN (0002)
GaN (10-11)
(a) without LT-GaN
Si(111)
(b) With LT-GaN
GaN (0002)
Si(222)
GaN (0004)
20
30
40
50
60
2θ-ω scan (degee)
70
80
Fig. 1. XRD patterns of GaN layers on WC/Si temples. (a) without LT-GaN layer, (b) with LT-GaN layer
References
1. Hiroyasu Ishikawa et al, J. Cryst. Growth. 189/190, 172 (1998)
2. Kurlov, Alexey S., Gusev and Aleksandr I., Tungsten Carbides: Structure, Properties and Application in Hardmetals, Springer Science &
Business Media, (2013), 5-22
3. G.Zambrano et al, Surf. Coat. Tech. 108, 323 (1998).
T-P-028
Characteristics of Enhanced-mode AlGaN/GaN MIS HEMTs for
Millimeter Wave Applications
Jong-Min Lee1*, Ho-Kyun Ahn, Dong Min Kang, Min-Jung Shin, Jong-Won Lim
1
RF Convergence Components Research Section, IT Materials and Components Lab.,
Electronics and Telecommunications Research Institute, Daejeon, 305-700, Korea
* E-mail address: leejongmin@etri.re.kr
For mm-wave applications, we fabricated enhanced-mode AlGaN/GaN HEMTs with MIStype gate structure. The devices used in this work were grown on SiC substrate and to shift the
threshold voltage of HEMTs we applied the Al2O3 insulator to the gate structure and adopted
the gate recess technique. To increase the frequency performance the e-beam lithography
technique was used to define the 0.15 um gate length. In this study, we report an electrical
characteristics of the fabricated devices. The threshold voltage was measured to be 0 V by
linear extrapolation from the transfer curve. The device leakage current is comparable with the
depletion mode device. The current gain cut-off frequency and the maximum oscillation
frequency of the E-mode device with a total gate width of 100 um were 46 GHz and 136 GHz,
respectively. To confirm the power performance for mm-wave applications the loadpull test
was performed. The measured power density of 2.4 W/mm was achieved at frequency of 30
GHz.
Fig. 1. Current-voltage characteristics of fabricated AlGaN/GaN MIS HEMT device.
3.0
Pdensity
Pout
Gain
Efficiency
25
2.5
20
2.0
15
1.5
10
1.0
5
0.5
0
0
5
10
15
20
Power density [W/mm]
Pout [dBm] & Gain [dB] & PAE [%]
30
0.0
25
Input Power [dBm]
Fig. 2. Measured output power performance of fabricated AlGaN/GaN MIS HEMT measured at 30 GHz.
References
1. K. J. Chen and C. Zhou, Phys. Status Solidi A 208, 434 (2011).
2. H. Hahn, F. Benkhelifa, O. Ambacher, F. Brunner, A. Noculak, H. Kalisch, and A. Vescan, IEEE Trans.
Electron Devices 62, 538 (2015).
Acknowledgment
This work was supported by Institute for & Information & communications Technology Promotion (IITP) grand
funded by the Korea government (MSIP) (No.B0132-15-1006, Development of High Efficiency GaN-based Key
Components and Modules for Base and Mobile Stations)
T-P-029
Backside Process of AlGaN/GaN HEMT on SiC
with Optimized Via-Hole Etching Conditions
Byoung-Gue MIN*, Hyung Sup YOON, Haecheon KIM, Ho-Kyun AHN, Kyu-Jun CHO,
Jae-Won DO, Hyun-Wook JUNG, Min-Jeong SHIN and Jong-Won LIM1
RF Convergence Components Research Section, ETRI, Daejeon 305-700, Korea
* E-mail address: minbg@etri.re.kr
AlGaN/GaN HEMT on SiC substrate is known to have superior characteristics than on Si or Sapphire substrate
because of the higher thermal conductivity of SiC. The electrical grounding on the front side of the device by
wire-bonding causes a gain reduction problem in case of high frequency operation. So it is necessary to ground
the front source electrodes through substrate via-holes to backside of the device. Intrinsically stable properties of
SiC make it difficult to etch the via-hole on SiC substrate. A specific dry etching system capable of high plasma
density can effectively etch the via-hole at high etch rate with sufficient etch selectivity over GaN epitaxial layers.
In this paper, the whole backside process will be introduced including the etch mask formation and the ground
metallization as well as SiC etching.
HEMT devices were fabricated using AlGaN/GaN epitaxial layers grown on 100 mm-diameter SiC substrate with
the gate length of 0.2 um. The device wafer and a SiC carrier wafer were bonded using the temporary adhesive
having a sufficient thermal stability at high temperatures. Ni was plated as etch-mask after simple processing steps
of the photoresist patterning and the subsequent seed metal deposition. ICP dry etching system (SPTS Synapse)
characterized by high plasma density and sufficient wafer cooling was used for etching via-holes. SF6 and O2 as
the main process gases were used for SiC etching and Cl2 was used for AlGaN/GaN epitaxial layers. The backside
of the wafer including the bottom of the via-holes, which was revealing the front source electrode pad, was
deposited by Ti/Au seed metals and plated by Au. The front side source electrode and the backside ground metal
were connected electrically.
As a result of optimization of etching conditions, the etch-stops were successfully accomplished on the
AlGaN/GaN epitaxial layers and on the source electrode metal, respectively. The etch selectivity of SiC to Ni
mask and to AlGaN/GaN epitaxial layers were shown on Figure 1. The etch profile of via-holes was almost vertical.
The etch rate of SiC was 1.4 um/min. These data are one of the highly optimized values ever reported.
Fig. 1. Vertical SEM images showing etched SiC via-hole and key characteristics of SiC etching.
(* Selectivity is approximate, GaN loss <0.1μm)
Acknowledgements
This work was supported by Institute for Information & communications Technology Promotion(IITP) grant funded by the Korea
government(MSIP) (No. B0132-15-1006, Development of High Efficiency GaN-Based Key Components and Modules for Base and Mobile
Stations).
References
1. J.-W. Lim, H.-K. Ahn, S.-I. Kim, D.-M. Kang, J.-M. Lee, B.-G. Min, S.-H. Lee, H.-S. Yoon, C.-W. Ju, H. Kim, J.-K. Mun, E.-S. Nam
and H.-M. Park, Thin Solid Films, v547, 106-110 (2013).
2. B.-G. Min, S.-I. Kim, J.-M. Lee, H.-S. Yoon, H. Kim, H.-K. Ahn, K.-J. Cho, D.-M. Kang, S.-H. Lee, C.-W. Ju, and J.-W. Lim, J. of
Korean Phys. Soc., v67, 718-722 (2015).
T-P-030 [NO SHOW]
Gate-Aspect-Ratio Induced Short-Channel Characteristics on Scaled Sub-30
Nanometer GaAs MESFETs and AlGaAs/GaAs HEMTs
Jaeheon Han
Department of Electronic Engineering, Kangnam University,
Yongin-city, Kyunggi-do 449-702, Korea
E-mail address: jhan@kangnam.ac.kr
GaAs MESFETs and AlGaAs/GaAs HEMTs with gate lengths ranging up to 10 nm were fabricated using
electron-beam lithography process, in order to examine the fundamental limitation of transistor scaling.
For gate lengths in the tens of nanometer range, where the gradual channel approximation is no longer
valid, it is observed that the transconductance is improved by electron velocity overshoot. On the other
hand, the transconductance enhanced by the velocity overshoot is suppressed by a parasitic gate–fringing
effect due to the incremental degree of the lateral extension and the partially semicircular shape of a
depletion region in reduced gate-aspect-ratio. The electron velocity obtained from the transconductance
becomes the peak at a certain value of a gate length (in our case, 20 to 40 nm) depending on the type of the
devices and other parameters such as the doping concentration and the thickness of the active area, and the
channel thickness. After the peak value, the electron velocity or the transconductance drops again with
further scaling. This drop is the result of the dominance of the gate-fringing over the velocity overshoot.
To investigate these behaviors, a transport model based on the Retarded Langevin equation (RLE) was
used. Here, the field seen by an individual electron changes significantly in a time comparable to the
relaxation times. Our measurements and RLE simulations show that HEMTs are relatively less significant
in gate-fringing and more significant in velocity overshoot than MESFETs. Also, the lightly doped devices
have the same tendency over the heavily doped devices, too. We suggest that the gate-aspect-ratio could
serve as an important design rule or device parameter for determining the extent of short channel effect,
which is the relative ratio of the velocity overshoot over gate-fringing (parasitic channel geometry effect),
for very short nanometer-range FETs.
T-P-031
Velocity Overshoot Degradation in Short-channel AlGaAs/GaAs HEMTs due
to the Minimum Electron Acceleration Lengths
Jaeheon Han
Department of Electronic Engineering, Kangnam University,
Yongin-city, Kyunggi-do 449-702, Korea
E-mail address: jhan@kangnam.ac.kr
Short-channel AlGaAs/GaAs HEMTs with gate lengths ranging up to 15-nm were fabricated using
electron-beam lithography process. These HEMTs were fabricated with a MBE-grown 35- and 15-nm-thick
epitaxial Al0.3Ga0.7As layer with 1 x 1018 cm-3, 2 x 1018 cm-3 and 4 x 1018 cm-3 in Si doping concentration
on semi-insulating Si substrate, respectively. Also, the doping concentration of the 5 nm Si-doped n-GaAs
cap layer were 4 x 1017 cm-3 and 2 x 1018 cm-3, respectively.
Here the rise in the measured transconductance is mainly attributed to electron velocity overshoot. The
transconductances start to rise rapidly as the gate length becomes on the order of the inelastic mean free
path of electrons. After reaching a maximum at around 40 nm, it is observed that both the measured
transconductance and the electron velocity drop rapidly with further reduction in gate length. For gate
lengths below 40 nm, however, the transconductance drops suddenly.
We investigated this behavior with a transient transport model based on the retarded Langevin equation
(RLE), which indicates the existence of a minimum acceleration length needed for the carriers to reach the
overshoot velocity. By solving the retarded Langevin equation with inverse Laplace transformation, X(t),
the time response of the evolution of the velocity of each carrier was solved in a parameterization fitting
routine. First, the initial condition <v(0)> = 0 yields no degradation of the overshoot. Next, the carriers
were given an initial launching velocity corresponding to the injection energy obtained from a non-ideal
ohmic contact. Here, v<(0)> = 1 x 107 cm/s was chosen to represent the conventional case. It clearly shows
a degradation of the overshoot. The degradation becomes larger the low doping case (4 x 1017 cm-3) than
the high doping case (2 x 1018 cm-3) in the 5 nm Si-doped n-GaAs cap layer due to the difference of the
source resistance. However, the degree of the degradation is inverse-proportional to the thickness and the
doping concentration of the Al0.3Ga0.7As active layer due to the smaller gate-fringing effect with the thinner
and/or the lightly-doped active area.
This approach matches the measured data reasonably well and confirms the overshoot is limited by having
a minimum acceleration length to reach the peak value of the overshoot. This shows that a source resistance
must be included as an internal element, or appropriate boundary condition, of relative importance in any
model where the gate length is comparable to the inelastic mean free path of the carriers.
T-P-32
Characterization of 0.18 µm Gate-Length AlGaN/GaN HEMTs on SiC
Fabricated Using Two-Step Gate Recessing
Hyung Sup Yoon*, Byoung-Gue Min, Jong Min Lee, Dong Min Kang, Ho Kyun Ahn, Kyu-Jun Cho,
Jae-Won Do, Min Jeong Shin, Hyun-Wook Jung, Sung Il Kim,
Hae Cheon Kim, and Jong Won Lim
Photonic-Wireless Convergence Components Research Department, ICT Materials & Components Research
laboratory, Electronics and Telecommunications Research Institute, Daejeon City 305-700, Korea
* E-mail address: hsyoon@etri.re.kr
GaN-based high-electron mobility transistors (HEMTs) are attracted promising devices for high
power and microwave low-noise applications[1-2]. The gate-recess technologies using either wet
or dry etching are applied for improving DC and RF characteristics on GaN-based HEMTs. In this
work, we report the characterization of the 0.18 µm T-gate AlGaN/GaN HEMTs on SiC fabricated
using two-step gate recessing with ICP dry etch and, oxygen plasma treatment and HCl-based
cleaning. The GaN HEMT epitaxial layers consists of a nucleation layer, a 2 µm GaN buffer, a 20
nm undoped Al 0.25Ga 0.75N Schottky layer on SiC grown using MOCVD. Ohmic contacts were
achieved by Ti/Al/Ni/Au evaporation and RTA. The device isolation was formed by P+ ion
implantation and 50 nm-PECVD SiN was deposited for gate patterning. T-shaped gate pattern of
0.18 µm was defined by electron-beam lithography process. Gate recess process was executed
using two-step gate etching. After etching SiN, the first gate recess was performed using BCl3/Cl2
ICP etching. The second gate recess was performed using the oxygen plasma treatment and HClbased cleaning. T-gate (30nm Ni/500nm Au) was formed by electron beam evaporator. A gate
width and a source-drain spacing of the device are 200 µm and 5 µm, respectively. The device
exhibited a good pinch-off characteristics, a threshold voltage of – 2.03 V and maximum
transconductance of 353 mS/mm at a gate bias of -1.19 V and a drain bias of 7 V. The device
showed a fT of 48 GHz and fMAX of 130 GHz. Also, the device showed a minimum noise figure
(NFmin) of 0.83 dB for 10 GHz and 1.43 dB for 18 GHz. These devices will be applied for GaN
HEMTs-based high frequency and low noise applications.
400
Vgs= 0 to - 4.5 V
Step= - 0.5 V
Transconductance [mS/mm]
Drain Current [mA]
120
100
80
60
40
20
0
0
5
10
15
120
gm
Ids
350
100
300
80
250
200
60
150
40
100
20
50
0
0
20
Drain Current [mA]
140
-5
-4
-3
Drain Voltage[V]
-2
-1
0
1
Gate Voltage [V]
Fig. 1. DC Characteristics of 0.18 µm T-gate GaN HEMTs fabricated using two-step gate recess etching.
50
20
NFmin
Ga
1.5
12
10
1.0
8
6
0.5
10
16
Ga[dB]
20
18
14
30
NFmin[dB]
h21 and MSG/MAG [dB]
2.0
h21
MSG/MAG
40
4
2
0
1
10
100
Frequency [GHz]
1,000
0.0
2
4
6
8
10
12
14
16
18
0
20
Frequency[GHz]
Fig. 2. RF and Noise Characteristics of 0.18 µm T-gate GaN HEMTs fabricated using two-step gate recess etching.
References
1. Palacios, et al., IEEE Electron Device Lett., 781, 26 (2005).
2. Minko, et al., IEEE Electron Device Lett., 167, 25 (2004).
T-P-033
Study of dual color InAs/GaAs quantum dot infrared photodetectors
Dong-Beom Seo 1, Tien Dai Nguyen 1,2, Je-hwan Hwang1, Eui-Tae Kim2, Sam Kyu Noh1,
Jun Oh Kim1 and Sang Jun Lee1,*
1
Division of Convergence Technology, Korea Research Institute of Standard Science, Daejeon, 305-340,
South Korea
2
Department of Material Science & Engineering, Chungnam National University, Daejeon, 305-764,
South Korea
* E-mail address: sjlee@kriss.re.kr
Abstract. Quantum dot infrared photodetectors (QDIPs) based on Stranski-Karastanov (SK)
and Sub-monolayer (SML) growth mode were grown on SI-GaAs substrate by a molecular
beam epitaxy for dual color infrared detection. The layer structures of two samples with
different QDs are illustrated in Figure. 1. First, a 100 nm thick buffer layer, a 500 nm thick
bottom contact layer and an AlGaAs barrier were grown at 570℃. The active region consists
of 7 periods of the 4 stacks SML-QDs and 2.0 MLs SK-QDs. Photoluminescence (PL)
measurements of both samples were performed at room temperature. The PL emission was
detected using a monochromator and an InGaAs photodiode with lock-in techniques.
Following the growth, 410 ⅹ 410 ㎛2 mesa devices were fabricated using standard optical
lithography and inductively coupled plasma etching. The devices were mounted on leadless
chip carrier, wire-bonded and loaded in a cryostat with a KBr window. The spectral responses
were measured by a Fourier transform infrared spectrometer at 77 K. Detailed study of device
design and characterizations for dual color infrared detectors will be presented.
Figure.1. Schematic view of the SML-QDs and SK-QDs DWELL heterostructure
T-P-034 [NO SHOW]
Influence of the thickness and the temperature on bands structure and
magneto-transport properties in semimetallic two-dimensional InAs/GaSb
far-infrared detector
Abdelhakim Nafidi*, Abderrazak Boutramine, Driss Barkissy, Ali Khalal, Abdelkrim
Hannour and Nassima Benchtaber
Laboratory of Condensed Matter Physics and Nano Re, University Ibn Zohr, Agadir, Morocco
* E-mail address: nafidi21@yahoo.fr
We have employed the envelop function formalism in order to investigate the band structure
E(d), E(kz) and E(kp), respectively, as a function of the SL period, d, in the growth direction
and in-plan of InAs(d1 = 160 Å)/GaSb(d2 = 105 Å) type II superlattice with the valence band
offset Λ=510 meV and d1/d2=1.52. The dependence of band gap energy, Eg(Γ), on d, Λ and
the temperature are examined. The semiconductor-semimetal transition goes to high d and Λ
when the temperature decreases. The spectra of energy E (kz, kp) shows that, when the
temperature increases from 4.2 K to 300 K, Eg(Γ) decreases from -48.2 meV to -98.3 meV
corresponding to a cutoff wavelength, |λc|, in the range of 12.6 µm to 25.7 µm. The latter
situates this sample as a far infrared detector. The position of the determined Fermi level
EF=500.2 meV indicates a p-type semimetallic conductivity at 141 K.
E (meV)
800
50
100
E1kz=0
z=π/d
Ek
1
150
E20<kz<π/d
200
250
InAs(160Å)/GaSb(105Å)
d1=1.52d2
Λ = 510 meV
T = 141K
k =0
HH1z
600 HHkz=π/d
1
300
4.2K
400
81K
200
200
200
50
(b)
Λ = 510 meV
800
h1kz=0
0
InAs(160Å)/GaSb(105Å)
d1=1.52d2
600
z=π/d
hk
1
400
300
1000
λc(µm)
1000
100
150
d (Å)
200
250
0
300
141K
100
300K
0
0
50
100
150
200
d =1.7d1(Å)
250
300
Fig. 1: (a) Calculated subbands energies and bandwidths at 141K for electrons (Ei), heavy holes (HHi)
and light holes (h1), at the centre Γ (kz=0) and at the limit (kz= π /d) of the first Brillouin zone, as a
function of the period, assuming d1= 1.52 d2 for the investigated SL. (b) Evolution of the cutoff
wavelength |λc| versus the SL period. The peaks of |λc| indicates the position of the semiconductor-tosemimetal transition.
On the basis of the classical expression for the Hall coefficient of two-band model, derived
from the Boltzmann equation, we have found: 1.8. 1013 cm−2 , 3.9. 1013 cm−2 ,
3345 cm−2 ⁄V. s , 975 cm−2 ⁄V. s , and 2117 cm−2 ⁄V. s for ne , nh , µe , µh , and µH
respectively. A good fit of the experimental data has been observed.
References
1. G.A. Sai-Halasz, R. Tsu, L. Esaki, Appl. Phys. Lett. 30, 651 (1977).
2. M. Razeghi and Binh-Minh Nguyen, Rep. Prog. Phys, Vol. 77, 082401(17pp) (2014).
3. X. Guo, W. Ma, J. Huang, Y. Zhang, Y. Wei, K. Cui, Y. Cao, Q. Li, Semicond. Sci. Technol. 28, 045004 (2013)
4. A. Boutramine, A. Nafidi, D. Barkissy, E. El Frikhe, H. Charifi, A. Elanique, H. Chaib Appl. Phys. A 122:70 (2016), DOI
10.1007/s00339-015-9561-x.
6. D. M. Symons, M. Lakrimi, M. van der Burgt, T. A. Vaughan, R. J. Nicholas, N. J. Mason, and P. J. Walker, Phys. Rev. B
51: 1729 (1995).
T-P-035
Studying CIGSSe absorber layer under various sulfurization temperatures
by Raman scattering spectroscopy
Trang Thi Thu NGUYEN1, Hankyoul MOON1, Gee Yeong KIM1, William JO1, JungYup
YANG2, Junggyu NAM2, Dong Ho LEE2, Dongseop KIM2, Minsu KWON3, Chan-Wook
JEON3, and Seokhyun YOON1*
1
Department of Physics, Ewha Womans University, Seoul 120-750, Korea
Photovoltaic Technology Team, Samsung SDI, Cheonan 331-300, Korea
3
Department of Chemical Engineering, Yeungnam University, Geyongsan 712-749, Korea
* E-mail address: syoon@ewha.ac.kr
2
Up until now, CuInGa(S,Se)2 (CIGSSe) quaternary semiconductor has been drawing attention
in solar cell fabrication by low cost and potential high efficiency. Raman scattering
spectroscopy has been actively applied for studying various kinds of materials, and also for
studying CIGSSe thin film solar cells recently. In this presentation, we used Raman scattering
spectroscopy to study CIGSSe thin films under various selenization/sulfurization annealing
temperatures of 570 °C, 580 °C and 590 °C [1,2]. We observed phonons of CIGSSe (A1 mode
at 188 cm-1) and CIGS (A1 mode at 287 cm-1) at the surface of thin films and also observed,
with increased annealing temperature, the shift of the CIGSSe peak that is related to the Ga
contents. We also studied spatial variation of thin films near surface and near CIGSSe/Mo
interface regions that were cut by a dimpling method. We observed that the CIGSSe peak red
shifted which is due to decreased Ga content near the absorber region. However, near
CIGSSe/Mo interface, there was no frequency shift of the CIGSSe peak observed and the CIGS
peak disappeared. Moreover, by observing the amount of secondary phase of Cu2-xSe, we
suggest that the best material with intrinsic properties of the CIGSSe phase was the sample
with annealing temperature of 580 °C. These results are completely consistent with local
electrical measurements that show the best annealing temperature for the sulfurization that
provides the highest efficiency of 15% among three samples with different annealing
temperatures is 580 °C [1].
References
1. J. Y. Yang, D. Lee, K. S. Huh, S. J. Jung, J. W. Lee, H. C. Lee, D. H. Baek, B. J. Kim, D.
Kim, J. Nam, G. Y. Kim, and W. Jo, RSC Advances 5, 40719 (2015).
2. J. Nam, Y. Kang, D. Lee, J. Yang, Y. –S. Kim, C. B. Mo, S. Park, D. Kim, Prog. Photovolt:
Res. Appl. (2015) DOI: 10.1002/pip.2653.
T-P-036 [NO SHOW]
Sensorless PMSM Sinusoidal Driver IC
Integrated Three Phase Gate Driver
Jimin Oh
Power Control Device Section, ETRI, Daejeon 305-700, Korea
E-mail address: ojmhiin@etri.re.kr
I. Introduction: PMSM driver chip without several sensors such as position, current, voltage
has various advantages [1, 2]. This paper reports sensorless PMSM driver chip integrated a
gate driver employing three phase current sensing. Adapted sensorless scheme is sliding mode
observer that has robust characteristics about parameter variations [3].
II. Description: Fig. 1 shows architectures of PMSM driver IC. An inverter consists of Super
Junction MOSFETs. Manufactured chip compose of two main blocks: “Speed Controller” is a
digital part and includes estimation functions of motor rotor position and speed (Fig. 1 (b, c)).
“Gate Driver” is an analog part and includes three phase gate driver with high side driving of
N-ch. MOSFET and current sensing for sensorless operations. Fig. 1 (d) shows a photograph
of fabricated PMSM driver chip. This chip is manufactured by 0.18um BCD process. System
operating frequency is 20MHz and chip size is 4.4 mm × 3mm. A Core voltage and I/O are 1.8,
5 V and a gate driver voltage is 5V. Chip package is 64pin QFN type.
III. Experimental Results: Fig. 2 shows startup operation with 1.5 kW PMSM. The startup time
is set to 500 ms. This PMSM is operated with sensorless operation after the startup time.
(d)
Fig. 1. (a) PMSM driver IC (b) Position estimation (c) Speed control and estimation (d) Photograph
Fig. 2. Startup operation in 1.5 kW PMSM
Acknowledgement:
This work was supported by Institute for Information & communications Technology Promotion (IITP) grant funded by the
Korea government (MSIP) (B0186-15-1001, Form factor-free Multi Input and output Power Module Technology for Wearable Devices).
References
1. Toshiba semiconductor, TB6588 datasheet, 2011. Accessed Feb. 24, 2011, http://toshiba.semicon-storage.com/info/docget.jsp?did=11516&
prodName=TB6588FG.
2. G. Wang, R. Yang, and D. Xu, “DSP-based control of sensorless IPMSM drives for wide-speed-range operation”, IEEE Trans. Ind. Electron., vol. 60, no. 2,
Feb. 2013, pp. 720-727.
3. S. Chi, Z. Zhang, and L. Xu, “Sliding-mode sensorless control of direct-drive PM synchronous motors for washing machine applications”, IEEE Trans. Ind.
Appl., vol. 45, no. 2, Mar./Apr. 2009, pp. 582-590.
T-P-037
The Effect of n-type Window Layer on the Performance of Amorphous
Si:H Thin Film Solar Cells
Kwang Hoon Jung1,2, Seong Hyun Lee1,2, Yoo Jeong Lee1,2, Kyu-Sung Lee1,2, Jung Wook
Lim1,2, R.E.I. Schropp3, and Sun Jin Yun1,2*
1
IT Materials Technology Research Section, Electronics and Telecommunications Research Institute,218
Gajeongno, Yuseong-gu, Daejeon 305-700, Korea
2
Department of Advanced Device Engineering, University of Science and Technology, 217 Gajeongno, Yuseonggu, Daejeon 305-350, Korea
3
Eindhoven University of Technology (TU/e), Department of Applied Physics, Plasma & Materials Processing,
P.O. Box 513, 5600 MB Eindhoven, The Netherlands*Corresponding author. E-mail address: sjyun@etri.re.kr
Typical substrate-type hydrogenated amorphous silicon (a-Si:H) thin film solar cells have been
fabricated to have p-type window layer with n-i-p deposition sequence (Fig. 1(a)) on opaque
substrates using multi-chamber PECVD systems. Earlier works have reported that using the pside as a window is advantageous compared to the n-side because holes are the minority carrier
in intrinsic (i-) a-Si:H films, and therefore the hole collection efficiency is limiting the solar
cell conversion efficiency. PECVD i-Si:H is commonly slightly n-type, and multi chamber
PECVD should be used to deposit n-i-p layers in sequence in order to protect i-Si:H from
further contamination by n-type dopant in typical substrate-type a-Si:H solar cells. But, n-type
window (p-i-n sequence deposition in a single chamber PECVD system) would be more
beneficial if substantial i-Si:H or slightly p-type Si:H light absorbing layers are deposited.
In this work, we carried out a “chamber-seasoning” process (pre-deposition of heavily B-doped
Si:H on the single chamber PECVD chamber wall) in order to obtain electronically neutral aSi:H light absorbing layer, and fabricated substrate-type a-Si:H thin film solar cells on stainless
steel(SS) with a p-i-n sequence to have n-type window layer as shown in Fig. 1(b). In these
devices the minority carrier type might have altered from holes to electrons because the p-type
dopants were incorporated into the a-Si:H light absorbing layer [1].
We also fabricated a p-window a-Si:H thin film solar cell on SS substrate with n-i-p sequence
at the same deposition condition to compare with the n-window a-Si:H cell. The conversion
efficiency of the n-window a-Si:H cell was 42.9% higher than that of the p-window cell. To
understand the behavior of n-window a-Si:H cells, the electrical characteristics and impurity
distribution profile of i-Si:H layer were investigated and the dependence of quantum efficiency
on the incident direction of light was evaluated using transparent cells, in detail.
Fig. 1. Schematic diagrams showing (a) p-type window solar cell deposited with n-i-p sequence and (b) ntype window solar cell deposited with p-i-n sequence on SS.
References
1. K. H. Jung, S. J. Yun, S. H. Lee, Y. J. Lee, K. S. Lee, J. W. Lim, K. B. Kim, M. J. Kim, and R. E. I. Schropp, Sol. Energy Mater. Sol.
Cells, 145, 368-374 (2016).
T-P-038 [NO SHOW]
Nano-scale Periodicity in Thermite Composites
Do Joong Shin1, Whi Dong Kim1 and Doh C. Lee1, *
1
Department of Chemical and Biomolecular Engineering, Korea Advanced Institute of Science and Technology
(KAIST), Daejeon 305-701 (Korea)
* E-mail address: dclee@kaist.edu
We investigated the periodical nano-thermite which is composed of aluminum
nanoparticles(NPs) as a fuel and three-dimensionally ordered macroporous (3DOM) copper (II)
oxide frame as an oxidizer. Differential scanning calorimetry analysis revealed that the energy
release in thermite reaction significantly enhanced in the periodical thermite composite
compared with the physically mixed composite which is the mixture of Al nanoparticles and
CuO nanoparticles. The 3DOM CuO/Al nanoparticles composite showed higher reactivity in
the pressure cell test in terms of pressurization rate. We will analyze non-dimensional
correlations with different periodicity of the 3DOM CuO frame. It will reveal systematically
that the 3DOM CuO/Al nanoparticles thermite have a periodical combustion aspect.
Fig. 1. SEM images of (a) PS colloidal crystal template, (b) 3DOM CuO frame.
T-P-039
Evaluation of supercritical CO2 dried cellulose aerogels
as nano-biomaterials
Sinah LEE1, Myung-Joon JEONG1, Antje POTTHAST2, Falk LIEBNER2
and Kyu-Young KANG1,*
1
Department of Biological and Environmental Science, Dongguk University-Seoul, Seoul 04620,
Republic of Korea
2
Department of Chemistry, University of Natural Resources and Life Sciences, Vienna 1190, Austria
* E-mail address: kykang@dongguk.edu
1. Introduction: Cellulose is an attractive alternatives to petroleum based materials, which are
gradually becoming scarce and also causing serious environmental problems. Cellulose is the most
abundant natural polymer, and having strong hydrogen bond in crystalline area, it is not dissolved by
water and typical organic solvents. Among a few of solvents, hydrated calcium thiocyanate molten salt
is one of the most effective solvents for preparing porous material. In this study, cellulose aerogels
dissolved in calcium thiocyanate were supercritical dried, and the properties of cellulose aerogels were
analyzed.
2. Methods: Two types of small-diameter wood, Quercus mongolica and Larix kaempferi and
Whatman filter paper were selected as raw materials. The two types of wood samples were chipped and
chemically pulped in peracetic acid at 70℃ for 6 and 24 hours, respectively. Level-off samples were
prepared with 5% hydrochloric acid under reflux and gentle stirring. In order to make cellulose aerogel,
cellulose was dissolved in hydrated calcium thiocyanate (Hoepfner 2007). The gels were supercritical
carbon dioxide dried at 35 bars for 2 to 5 hours.
3. Results: Cellulose aerogels dissolved in calcium thiocyanate were produced in different molecular
weight. Density of cellulose aerogels which were made of higher molecular weight (R.M.S. 34.6 nm)
was higher than that of lower molecular weight (R.M.S. 28.3 nm) cellulose aerogel; 124 and 76 kg/m3,
respectively. It was observed with SEM images that low molecular weight cellulose aerogels have
bigger pores and randomly structured, whereas high molecular weight cellulose aerogels are uniformly
structured with micro-size pores.
(a)
(b)
Fig. 1. SEM images of cellulose aerogels made of (a) un-hydrolyzed and (b) level-off Whatman filter paper.
References
1. S. Hoepfner, Cellulose 15, 121-129 (2007).
2. H. Jin, Y. Nishiyama, M. Wada, Colloid Surf. A-Physicochem. Eng. Asp. 240, 63 (2004).
Acknowledgement
This study was carried out with the support of ‘Forest Science & Technology Project (Project No. S111315L010130)’ provided
by Korea Forest Service. This work was also supported by the R&D Program of MOTIE/KEIT (10049674)..
T-P-040
Characteristics of Cellulose-Microalgae Composite
Kyo-Jung Hwang, Gu-Joong Kwon, Ji-Wook Yang, Sung-Yeol Kim and Dae-Young Kim*
Department of Biological and Environmental Science, Dongguk University-Seoul, Seoul 100-715, Korea
* E-mail address: sbpkim@dongguk.edu
I. INTRODUCTION
Microalgae has many more advantages than traditional biomass crops, not only the
sustainability but also facile artificial culture, productivity at severe environment, high
performance in carbon capture and cellular multiplication is that 1). Recently, various studies
into cellulose dissolution makes microalgae promising biomass source in development of
functional materials. But there is lack of studies about economic feasibility and its
commercialization. In this research, physical, chemical properties examination will be
conducted on cellulose-microalgae composite gel from LiOH/urea dissolution.
II. EXPERIMENTS
Nostoc Commune was used as microalgae sample, cultured in JM medium, freeze dried.
Cellulose was refined from filter paper (Whatman No. 4), freeze-dried after dissociation.
LiOH/urea/H2O (8:12:80 w/w) was used for dissolution of cellulose. Powder state microalgae
was added to LiOH/urea/H2O solution and cellulose dissolution was proceeded in the solution
at -10℃ condition. The gel from dissolution was regenerated to bead type and washed before
freeze drying. The cellulose concentration was 2% (w/w) and mixing ration of
cellulose/microalgae was 1:0.5, 1:1, 1:1.5 (w/w). Characteristics of the composite was analyzed
by SEM, BET, TGA, FT-IR, methylene blue adsorption test.
III. RESULTS AND DISCUSSION
Fig. 14. SEM image of cross-section of
composite
This figure 1 shows the network structure and
microalgae in cross-section of composite. In the
BET analysis of the composite, decrease of
porosity was observed according to increase of
microalgae mixture ratio. In TGA analysis,
pyrolysis of microalgae was faster than the control.
The Methylene blue adsorption test shows
increase of methylene blue adsorption as
microalgae ratio rise.
REFERENCE
1) T. M. Mata, A. A. Martins and N. S. Caetano. 2010. Microalgae for biodiesel
production and other applications: A review. Renewable and Sustainable Energy
Reviews. 14, 217-232
(Acknowledgements) This subject is supported by Korea Ministry of Environment as "The Ecoinnovation Project" (412-112011).
T-P-041
Cellulose-Chitosan Composite Film prepared from LiBr Solution
Ji-Wook Yang, Gu-Joong Kwon, Kyo-Jung Hwang, Sung-Yeol Kim, Dae-Young Kim*
Department of Biological and Environmental Science, Dongguk University-Seoul, Seoul 100-715, Korea
* E-mail address: sbpkim@dongguk.edu
I. INTRODUCTION
Chitosan films have mainly been applied to the pharmaceutical field and food industry due to
biocompatible, biodegradable, and nontoxic. However, cost of chitosan is expensive and thus
importance is attached to the research on the combination of chitosan and other materials such
as cellulose, alginate, PVA, etc.1 Combination of cellulose and chitosan is most attractive from
the point of view of sample form suitable for a variety of application. In recent research, LiBr
solution can easily dissolved and regenerated cellulose. The purpose of this study was to
investigate the physical properties, chemical properties and anti-bacterial activities of
cellulose-chitosan composite films.
II. EXPERIMENTS
Filter paper (Whatman Filter Paper No.5, USA) and chitosan powder (Sigma-Aldrich, USA)
were used as the cellulose and chitosan samples, and 60 wt% LiBr solution was prepared. 1
wt% each samples in LiBr solution dissolved on 190℃ hot plate for 45 min from room
temperature. Then cellulose solution and chitosan solution with a weight rate of 10:0, 9:1, 8:2,
7:3 were stirred for 10 min. The mixed solution cast on glass plate and cooled down to room
temperature. After then, the cellulose-chitosan composite films were manufactured by washing
and dry. The films were analyzes by SEM, FT-IR, tensile strength, elongation and anti-bacterial
activities.
III. RESULTS AND DISCUSSION
Cellulose-chitosan composite film were made with various ratio of cellulose to chitosan. In
cross-section of the films using SEM analysis, the 10:0-film had a layer-by-layer structure, and
the layers of the film became thicker and rougher as the amount of chitosan increased. The FTIR analysis of the films showed that the crystalline structure of cellulose I was transformed into
cellulose II. The hydroxyl group of cellulose and the hydroxyl and amino groups of chitosan
form hydrogen bonds. When chitosan increased, the films became thicker and E-modulus
decreased. Tensile strength and elongation increased to a certain amount and then decreased.
Cellulose performs as a matrix and chitosan acts as a reinforcing material. It is presumed that
when chitosan was mixed excessively, it caused a weakness in the cellulose gel structure. When
the amount of chitosan in the film increased, the anti-bacterial characteristics improved in S.
aureus and E. coli.
References
1. C. M. Shih, Y. T. Shieh, and Y. K. Twu, Carbohydrate Polymers 78, 169–174 (2009).
(Acknowledgements) This subject is supported by Korea Ministry of Environment as "The
Ecoinnovation Project" (412-112-011).
T-P-042
A Flexible Skin Patch for Continuous Physiological Monitoring
of Mental Disorders
W. I. Jang*, B. K. Lee, J. H. Ryu, I. B. Baek, H. Y. Yu and S. W. Kim1
1
Bio-Medical IT Convergence Research Department, ETRI, Daejeon, 34129, Republic of KOREA1
* E-mail address: wijang@etri.re.kr
To provide clinical-quality health monitoring capabilities for continuous use, soft microfluidic
assemblies of sensors, circuits, and radios for the skin were recently proposed recently [1]. For the early
diagnosis of disease and monitoring health and wellbeing, self-adhesive epidermal CNT/aPDMS
electronics were also reported [2]. In this study, a flexible skin patch was newly suggested for
continuous physiological monitoring of mental disorders. We can monitor the mental health status
through a comprehensive analysis of various biological signals.
The elastic modulus (E) and Poisson’s ratio (ν) are EEcoflex=0.0623MPa and νEcoflex=0.49 for Ecoflex;
ECu=119GPa and νCu=0.34 for copper; and EPI=2.5GPa and νPI=0.34 for PI (polyimide). The yield
strength (σY) is the range of 4.7x104 to 3.2x105 KPa and the fracture strength (σF) is the range of 2x105
to 3.5x105 KPa for copper. In Fig. 1, maximum 1st principal stress by ANSYS simulator was calculated
about 5.5x104 kPa, less than yield strength and fracture strength of copper. Calculated elastic
stretchability (~13%) for stretchable circuits of a copper was less than the maximum elastic
stretchability of the skin (~30%). As a result, analysis results in system design are suitable to effectively
accommodate integration with the soft, textured, curvilinear, and time-dynamic surfaces of the skin. As
shown in Fig. 2, a flexible 0.5mm-thick sheet with polydimethylsiloxane (PDMS)/ soft silicone
adhesive (SSA) tow layers was fabricated for skin adhesive patch application. The SSA (Dow Corning
MG-7 9850) attached on the skin did not cause a skin trouble such as urticaria, rash, itchiness, and so
on, for one day. The PI layer was coated by spin coating and was etched by using O2 plasma etching on
PDMS/silicone adhesives of a glass substrate. A 0.4um-thick copper on 5nm-thick Ti for
interconnection was coated on 100um-thick PI layer for skin adhesive patch application. Self-align and
soldering of IC Chips such as resistor between metal pads on flexible skin patch have also successfully
fabricated for 5min at 180oC in vacuum oven.
We have newly developed a flexible adhesive skin patch with PDMS/SSA tow layers and have also
suggested the possibility of novel interconnection for Cu/Ti on PDMS/PI layer of this flexible substrate.
(a)
(b)
Fig. 1. 1st principal stress(a) and strain(b) distribution by ANSYS.
References
1. Sheng Xu, et al., Science 344, 70 (2014).
2. Seung Min Lee, et al., Scientific Reports, 4, 6074 (2014).
Fig. 2. Fabricated flexible skin patch.
T-P-043 [NO SHOW]
Enhanced Gas Sensing Performance of Palladium and Indium-Codoped
Zinc Oxide Thin Film Gas Sensors
Hyejoon KHEEL1, Gun-Joo SUN1, Tae Kyung KO1, Sangmin LEE2, and Chongmu LEE1,*
1
Deparment of Materials Science and Engineering, Inha University, 253 Yonghyun-dong, Nam-gu, Incheon 402751, Republic of Korea
2
Deparment of Electronic Engineering, Inha University, 253 Yonghyun-dong, Nam-gu, Incheon 402-751,
Republic of Korea
* E-mail address: cmlee@inha.ac.kr
Indium zinc oxide thin films can be utilized in smart window and wearable nose-sensor
applications, where both high optical transparency and gas sensitivity are demanded [1,2]. ZnO
codoped with palladium and indium (Pd-IZO) materials were fabricated, characterized and
tested for their gas sensing properties. These were fabricated into gas sensors. Materials were
characterized using X-ray diffraction (XRD), scanning electron microscopy
(SEM) and energy dispersive X-ray spectroscopy (EDX). Electrical conductivity of all
samples was also calculated. Sensors were exposed to ethanol, methanol, n-butanol and acetone
at concentrations between 5 and 200 ppm. Optimal amount of Pd and In doping enhanced the
conductivity of the IZO sensor. Pd-doping enhanced the ethanol sensing properties of the IZO
sensor to ethanol. Pd and In-codoped IZO sensors show potential for inclusion into an
electronic nose for with the aim of selective alcohol detection.
References
1. H. Choi, J. S. Choi, J.-S. Kim, J.-H. Choe, K. H. Chung, J.-W. Shin, J. T. Kim, D. H. Youn,
K. C. Kim, J. I. Lee, S. Y. Choi, P. Kim, C. G. Choi, and Y. J. Yu, Small 10, 3685 (2014).
2. K. Lee, V. Scardaci, H.-Y. Kim, T. Hallam, H. Nolan, B. E. Bolf, G. S. Maltbie, J. E. Abbott,
and G. S. Duesberg, Sens. Actuators B: Chem. 188, 571 (2013).
T-P-044 [NO SHOW]
Acetone Gas Sensing Properties of WO3/NiO Core-Shell Nanorod Sensors
Gun-Joo SUN1, Hyejoon KHEEL1, Soong Keun HYUN1, Seungbok CHOI2, and Chongmu
LEE1,*
1
Deparment of Materials Science and Engineering, Inha University, 253 Yonghyun-dong, Nam-gu, Incheon 402751, Republic of Korea
2
Deparment of Mechanical Engineering, Inha University, 253 Yonghyun-dong, Nam-gu, Incheon 402-751,
Republic of Korea
* E-mail address: cmlee@inha.ac.kr
In this study WO3 nanorods and WO3-core/NiO-shell nanorods were synthesized using facile
hydrothermal techniques and their acetone sensing properties were examined. X-ray diffraction
and scanning electron microscopy revealed the good crystallinity and uniformity of the WO3core/NiO-shell nanorods in terms of shape and size. The WO3-core/NiO-shell nanorod sensor
showed stronger response to acetone than the pristine WO3 nanorod sensor. The response of
the core-shell nanorod sensor to 200 ppm of acetone at 300°C was more than twice as strong
as that of the pristine nanorod sensor under the same conditions. Furthermore, under these
conditions, both the response and recovery times of the core-shell nanorod sensor were much
shorter than those of the pristine one. The core-shell nanorod sensor showed excellent
selectivity to acetone over other volatile organic compound gases. The enhanced sensing
performance of the core-shell nanorod sensor is attributed to modulation of the conduction
channel width and the potential barrier height at the WO3-NiO interface accompanying the
adsorption and desorption of acetone gas as well as enhanced catalytic oxidation of acetone.
References
1. N. Barsan, and U. Weimer, J. Electroceram. 7, 143 (2011).
2. C. C. Li, Z. F. Du, L. M. Li, H. C. Yu, Q. Wan, and T. H. Wang, Appl. Phys. Lett. 91, 032101
(2007).
3. O. V. Safonova, G. Delabouglise, B. Chenevier, A. M. Gaskov, and M. Labeau, Mater. Sci.
Eng. C 21, 105 (2002).
T-P-045
Low Temperature Processed In-Ga-Zn-O Thin-Film Transistors on
Polyimide Substrate using Microwave Irradiation
Min-Ju Ahn1, and Won-Ju Cho2,*
1
Deparment of Electronic Materials Engineering, Kwangwoon University, 447-1, Wolgye-dong, Nowon-gu,
Seoul 139-701, Korea
* E-mail address: chowj@kw.ac.kr
Flexible displays and electronics have attracted a great deal of interest in the future display
market due to their advantages such as thinner, lighter, unbreakable characteristics on flexible
surfaces and portability. Recently, oxide semiconductor based thin film transistors (TFTs) have
been paying attentions for the applications in next generation display market. Among them, an
In-Ga-Zn-O (IGZO) has received much attention due to their high mobility and stability
characteristics even at a low process temperature, compared with a-Si:H TFTs. In addition, the
IGZO is easy to apply to various substrates, such as glass or plastic due to a high transparency
and a low process temperature [1]. However, for flexible devices manufacturing, it is remained
a challenge to be solved such as high coefficient of thermal expansion, low process temperature,
poor roughness of surface and permeability due to the penetration of oxygen or water vapor in
the atmosphere. Thus, the choice of plastic substrate is most important in order to realize the
flexible electronics exhibiting good electrical performance. Polyimide (PI) is widely suggested
due to their low thermal expansion coefficient and excellent thermal stability (> 300 °C) [2].
However, the IGZO based TFTs is required thermal annealing more than 400 °C to achieve a
satisfactory electrical performance and stability according to previous reports [3].
In the study, we fabricated the IGZO based top-contact top-gate type (TCTG) TFTs on PI
substrate. The roughness and permeability of PI substrate are improved through the O2 plasma
treatment and solution-SiO2 (spin-on-glass, SOG) buffer layer, respectively. In addition, we
applied to a microwave irradiation (MWI) as PDA process which has high energy transfer
efficiency and low thermal budget than the conventional heat treatment (CTA) method.
Therefore, we implemented the flexible TFTs with excellent electrical characteristics using
MWI.
Fig. 1. (a) the schematic structure of TCTG TFT (b) ID-VG curves of TCTG TFTs under various annealing methods.
References
1. A. Nathan and B. R. Chalamala, Proc. IEEE, vol. 93, no. 8, pp. 1391–1393, (2005).
2. C.-Y. Lin et al., IEEE Trans. Electron Devices, vol. 59, no. 7, pp. 1956–1962, (2012).
3. L.-F. Teng, P.-T. Liu, Y.-J. Lo, and Y.-J. Lee, Appl. Phys. Lett. 101. 132901, (2012).
T-P-046
Enhancement of pH sensitivity in Dual Gate IGZO ISFET
Se-Yeon Hwang, and Won-Ju Cho*
Department of Electronic Materials Engineering, Kwangwoon University, Seoul 139-701, Korea
* E-mail address: chowj@kw.ac.kr
With the rapid development of medical industry in recent years, the treatment of various
diseases becomes possible. Nevertheless, early diagnosis is very important in case of
intractable and infectious diseases. Accordingly, an active and vibrant research on the sensors
to detect various diseases is being conducted. In this study, we investigated the ion-sensitive
field effect transistor (ISFET) sensors that convert the biological signal to electrical signal.
ISFET derived from the metal-oxide-semiconductor field effect transistor (MOSFET) have a
liquid electrolyte directly in contact with their gate oxide instead of a metal gate contact. The
dependence of the surface charge on the pH value forms the working principle of ISFETs. The
platform based on the field-effect devices has many advantages such as a real-time,
noninvasive, label-free detection, small size, and low cost. However, the conventional ISFETs
operated by single gate (SG) have been hindered in the commercialization due to a small
sensitivity of 60 mV/pH.
In this study, we fabricated a high performance dual gate (DG) IGZO ISFET and applied to the
biosensor. As a result, we overcame the theoretical limitations sensitivity of conventional
ISFET based on the capacitive coupling effect between top and bottom gate dielectric layers in
DG-IGZO TFTs with a high sensitivity of 321.62 mV/pH and an excellent stability as shown
in Fig. 1.
In conclusion, we demonstrated a high performance DG-IGZO based biosensor capable of
early detection of various intractable and infectious diseases.
Fig. 1. pH sensitivity of DG-IGZO ISFETs for single gate and dual gate modes.
T-P-047
Optical and electrical properties of Sn-doped ZnO thin films studied with
spectroscopic ellipsometery
Hyeon Seob So1, Dae Ho Jung1, Kun Hee Ko1, Sang Bin Hwang1, and Hosun Lee1*
1
Department of Applied Physics, Kyung Hee University, Yong-In 17104, Korea
* E-mail address: hlee@khu.ac.kr
Extinction Coefficient 'k'
Transparent conducting oxides (TCOs) have a wide range of application areas in flat panel
displays, photovoltaics, transparent thin film transistors, and transparent memory devices. TCO
films require a low resistivity (ρ ≤ 10-3 Ω·cm), a high optical transmittance (≥ 80%), and a large
optical band gap energy (≥ 3.5 eV). We investigated the optical and electrical properties of
amorphous and crystalline tin (Sn)-doped zinc oxide (ZnO) thin films grown by using cosputtering deposition method at room temperature. Cosputtered targets were ZnO and Sn (10
wt%) doped targets. Varying the relative power ratio of the two targets, we controlled the Sncomposition of ZnO:Sn. Through annealing, the as-grown amorphous oxides were transformed
to crystalline oxides. We measured the ellipsometry angles, Ψ and ∆, of ZnO:Sn thin films
using spectroscopic ellipsometry. The dielectric functions were obtained from the measured
ellipsometry angles using the Drude and parametric optical constant models. With increasing
Sn doping concentration, the Drude model amplitude increased substantially because the
carrier concentration was larger than 1019 cm-3. We determined the absorption coefficients and
optical gap energies of ZnO:Sn films from the dielectric functions. We measured the carrier
concentrations and mobilities of ZnO:Sn thin films using Hall effect measurements. Comparing
optical and electrical parameters, we estimated the effective masses of ZnO:Sn films. We
discussed the Sn-doping dependence of dielectric function, optical gap energy, and effective
mass of carriers of ZnO:Sn thin films.
0.5
0.4
0.3
0wt%
2wt%
4wt%
6wt%
8wt%
10wt%
0.2
0.1
0.0
0
1
2
3
4
5
6
Photon Energy (eV)
Fig. 1. The extinction coefficients for ZnO:Sn films with varying Sn contents.
T-P-048
Investigation of metal-insulator transitions of low-temperature-grown
VO2 thin films on TiO2-buffered SiO2/Si substrates
using RF magnetron sputtering deposition
Daeho JUNG1, Hyeonseob So1, Kunhee Ko1, Jaegon Ryu and Hosun Lee2,*
1
Deparment of Applied Physics, Kyung Hee University, Yongin, 171-04, Korea
* E-mail address: hlee@khu.ac.kr
Vanadium dioxide (VO2) has been studied intensively owing mostly to its near-room-temperature
phase transition as well as its high phase stability. It undergoes a first-order metal-insulator transition
(MIT) around 68 °C from a high-temperature metallic phase to a low-temperature insulating phase,
which is accompanied by a structural phase transition from a high-temperature tetragonal (Rutile, R)
structure to a low-temperature monoclinic (M1) structure. The MIT transition can be utilized to
develop smart windows, which block (transmit) infrared light in summer (winter). Smart windows can
be used to cool the building interiors without using electric power.
In general, VO2 films are grown at a substrate temperature of 500°C. In order to grow VO2 thin
films on glasses or flexible plastics, we used TiO2 buffer layer on SiO2/Si substrates. VO2 films
grown on flexible plastic substrates can be applied to develop flexible smart windows. VO2 thin films
with ~100 nm in thickness were grown on TiO2-buffered SiO2/Si substrates by RF reactive sputtering
deposition from a VO2 target. Considering the complex phases of vanadium oxide material system,
the growth temperature and sputtering gas ambient were optimized and precisely controlled to yield
high purity VO2 phase. The sputtering pressure was set at 6 mTorr with 10 sccm flow of O2 gas. All
VO2 films were grown at substrate temperature below 250°C, and subsequently annealed with 1 sccm
of O2 gas flow rate for 1 hr at the same temperature. The structural and morphological properties of all
samples were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), and Raman
scattering. The electrical properties of all samples were measured using Keithley 4200.
Low-temperature-grown VO2 thin films grown on TiO2/ Si (TiO2/SiO2/Si) substrates showed the
critical temperature Tc at 42.6 °C (44.2°C). XRD peaks were found at 2θ = 28.0° from (011) plane
and 55.6° from (211) plane of monoclinic phase at RT. Raman spectroscopy measured the phonons at
223.6 cm-1 and 620.8 cm-1, which were identified as Ag modes. We also present low-temperature
growth of VO2 films on flexible plastic substrates using TiO2 buffer layer.
Heating
Cooling
Heating
Cooling
(b)
(a)
Tc = 44.19oC
100000
Tc=42.63oC
100000
10000
10000
1000
1000
100
100
30
40
50
60
Temperature (oC)
70
80
30
40
50
60
70
Temperature (oC)
Fig. 1. (a) is the VO2/TiO2/SiO2/Si Hysteresis and (b) is the VO2/TiO2/Si Hysteresis
References
1. M.Imada, A.Fujimori, and Y. Tokura, Rev. Mod. Phys., 70, 1039, (1998).
80
T-P-049 [NO SHOW]
Electrically Controllable High-Q THz Metamaterial based on VO2 Thin
Film
Han-Cheol Ryu*
1
Department of Car-Mechatronics, Sahmyook University, Seoul, 139-742, Korea
* E-mail address: hcryu@syu.ac.kr
We propose an electrically controllable terahertz wave modulator based on metamaterial and
vanadium dioxide (VO2) thin film. Metamaterials have attracted great attentions owing to their
unique responses for manipulating electromagnetic resonances that were mostly not founded
in natural material. The controllable resonances of the artificially engineered metamaterials can
offer the opportunities to realize the new and novel THz devices for a wide variety of THz
applications [1]. Numerous researches on the realization of the tunable characteristics for the
THz metamaterials have been reported by using semiconductors, graphene, and tunable
functional-material [2, 3]. Tunable metamaterial based on vanadium dioxide (VO2) which has
reversible switching properties caused by insulator-metal transition at a critical temperature at
340 K, is one of promising approach to spatially manipulate the THz wave thanks to easy
fabrication and high tunability. There are several researches on the tunable THz metamaterials
based on the phase transition of VO2 by applying temperature, THz-field, or light [4]. However,
these methods need external devices such as a heater, a THz or a light source; the external
devices make the THz tunable devices more expensive and bulky. Thus, the electrical control
for the phase transition of VO2 is preferred for the practical applications. A loop shape
metamaterial is designed to play roles as a resonating metamaterial and a heater to electrically
control a conductivity of VO2 at the same time. These easily controllable high-Q THz
metamaterials can be used as high-performance modulating filters or sensors.
References
1. J. Doe, A. Smith, and B. Kim, Appl. Phys. Lett. 999, ### (1999).
1. H.-T. Chen, W. J. Padilla, J. M. O. Zide, A. C. Gossard, A. J. Taylor, and R. D. Averitt,
Active terahertz metamaterial devices, Nature, vol. 444, pp. 597-600, (2006).
2. L. Ju, B. Geng, J. Horng, C. Girit, M. Martin, Z. Hao, H. A. Bechtel, X. Liang, A. Zettl, Y.
R. Shen, and F. Wang, Graphene plasmonics for tunable terahertz metamaterials, Nat.
Nanotech., vol. 4, pp. 630-634, (2011).
3. B. Sensale-Rodriguez, R. Yan, M. M. Kelly, T. Fang, K. Tahy, W. S. Hwang, D. Jena, L.
Liu, and H. G. Xing, Broadband graphene terahertz modulators enabled by intraband transition,
Nat. Comm., vol. 3, pp. 1-7, (2012).
4. M. Liu, H. Y. Hwang, H. Tao, A. C. Strikwerda, K. Fan, G. R. Keiser, A. J. Sternbach, K.
G. West, S. Kittiwatanakul, J. Lu, S. A. Wolf, F. G. Omenetto, X. Zhang, K. A. Nelson, and R.
D. Averitt, Terahertz-field-induced insulator-to-metal transition in vanadium dioxide
metamaterial, Nature vol. 487, pp. 345-348, (2012).
T-P-050
Effect of Additives on the Electrical Conductivity of Printed ITO Layers
Jieun Koo1,3, Seokhwan Lee2, Sungmin Cho2, and Jiho Chang*1,2
1
Deparment of Electronic Material Engineering, Korea Maritime and Ocean University, Busan 606-791,
Republic of Korea
2
Major of Convergence Study on the Ocean Science and Technology, Korea Maritime and Ocean University,
Busan 606-791, Republic of Korea
3
International Center for Materials Nanoarchitectonics (MANA), National Institute for Materials Science
(NIMS), Ibaraki, Japan
* E-mail address: jiho_chang@KMOU.ac.kr
The effect of additives on electrical conductivity and methane sensitivity of ITO gas sensor has been
investigated. ITO sensors were prepared through a printing procedure [1]. To improve the sensor
performance, silver (Ag) and carbon-nanotubes (CNT) were adapted as an additive. The morphology
and microstructure of the ITO sensing layer were characterized by scanning electron microscopy (SEM)
and X-ray diffraction (XRD) techniques. The electrical property of the samples was examined by
temperature-dependence Hall effect measurement. Also, sensor performance has been investigated by
I-V source-meter under the methane gas flow driven by mass-flow-controller(MFC). Remarkable
improvement of sensitivity and responsibility was observed as shown in the Fig. 1(a). It was discussed
in terms of Mott variable-range-hopping (VRH) model [2]. Fig. 1(b) shows the conductivity variation
of the ITO layers confirmed by a temperature-dependence Hall effect measurement. From the result,
considerable decrease of the hopping barrier height was observed, which indicates that increase of
carrier mobility is responsible for the improved sensing performance.
8
1.04
ITO layer
ITO: (Ag+CNT)
(b)
ITO layer
ITO:(Ag+CNT) layer
6
1.00
ln (ρ)
Sensitivity (Rg/Ro)
(a) @ RT, V = 5V,
bias
CH4= 100ppm
To = 3.8 x 104 (K)
4
0.96
2
0.92
ON
OFF
ON
OFF
ON
OFF
ON
To = 1.8 (K)
OFF
Gas flow
0
400
800
Time (sec)
1200
0
0.24
0.26
0.28
0.30
0.32
0.34
T-1/4 (K-1/4)
Fig. 1. (a) Improved sensitivity of ITO sensors due to an addiction of Ag and CNT. (b) decrease of hopping barrier;
T0, where ρ=ρ0exp(T0/T)p[2]
References
1. J. Koo et al., Phys. Status Solidi C 10, No. 5, 873–876 (2013)
2. S. S. N. Bharadwaja et al., APPLIED PHYSICS LETTERS 94, 222110 (2009)
This research was a part of the project titled 'Development of Management Technology for HNS Accident', funded by the
Ministry of Oceans and Fisheries, Korea.
T-P-051
Optical phonon characteristics of GaN/AlN nanowire structures
Heesuk Rho1,*, Taegeon Lee1, Jae-Gwan Park2
1
2
Department of Physics, Chonbuk National University, Jeonju 54896, Korea
Nanophotonics Research Center, Korea Institute of Science and Technology, Seoul 02792, Korea
* E-mail address : rho@chonbuk.ac.kr
We report Raman scattering from GaN nanowire (NW), GaN/AlN core−shell NW, and
GaN/AlN hetero-NW structures. GaN-based nanostructures enable one to design novel
optoelectronic applications such as LEDs, lasers, and solar cells. For efficient device
performance, high quality NW growth is required. When a GaN core NW is coated with an
AlN shell layer, compressive strain can be induced in the core NW due to lattice mismatch
between core and shell materials. Raman scattering can probe longitudinal optical (LO) and
transverse optical (TO) phonons, which provide a useful means of understanding crystalline
quality and strain in semiconductor NWs. In addition, surface optical (SO) and interface optical
(IO) phonons can also be explored.
Polarized Raman scattering from a single GaN NW showed strong anisotropic behavior in
agreement with the Raman polarization selection rules for a wurtzite crystal, indicating high
crystalline quality of the NW. A Raman spectrum from a single GaN NW show several optical
phonons, such as A1(TO), A1(LO), and E2(high) phonons at 530, 724, and 567 cm−1,
respectively. When an AlN shell layer formed on the side surface of the GaN core NW, the
GaN A1(LO) phonon energy was shifted upward by 7 cm−1, indicating that a compressive strain
occurred in the GaN core NW. When AlN NW branches formed perpendicular to the GaN/AlN
core−shell NW long axis, the upshifted A1(LO) phonon energy was shifted downward toward
the value of the GaN NW, indicating a relaxation of strain in the GaN core NW. Especially, a
broad phonon response was observed in the low energy shoulder of the GaN A1(LO) phonon
peak. If this phonon corresponded to the SO phonon, the phonon energy should vary when the
GaN NW was embedded in paraffin oil. However, an identical phonon response was observed,
indicating that the broad phonon mode was not the SO phonon.
This research was supported by the Basic Science Research Program through the National
Research Foundation of Korea (NRF) funded by the Ministry of Education (Grant No.
2014R1A1A2057173), the Korea Basic Science Institute under the R&D program (Project No.
E36800) supervised by the Ministry of Science, ICT and Future Planning, and the KIST
institutional program (2E26140).
T-P-052
Absorption Enhancement of 10-µm-thick Si Wafers with Plasmonic Ag
Nanoheptamer Arrays
Sujung KIM, Yunae CHO, Ahrum SOHN, and Dong-Wook KIM*
Department of Physics, Ewha Womans University, Seoul 120-750, Korea
* E-mail address: dwkim@ewha.ac.kr
Among numerous semiconductor materials, Si-based devices have notable advantages of
superior performance, matured fabrication technologies, and long-term reliability. Owing to
these merits, Si-wafer-based solar cells occupy a 90% market share. In very recent days, there
have been intensive research efforts to fabricate ultrathin (< 50 µm) Si-wafer-based cells for
further reduction of power generation cost. The use of such thin wafers requires light trapping
strategies to improve the optical absorption. In this work, we performed finite-difference timedomain simulations to investigate the influence of Ag nanoheptamer (NH) arrays on the optical
absorption spectra of 10-µm-thick Si wafers. The NH arrays increased the absorption of the
ultrathin wafers in very broad wavelength range. For better understanding, we compared the
optical spectra of the wafers with the NH arrays and Ag monomer (MN) arrays. The absorption
enhancement at long wavelengths by the NH arrays was much more significant than that by
the MN arrays, although both the NH and MN arrays consisted of the identical Ag metal
nanoparticles. The scattering cross-section spectra of the NH (MN) arrays on the Si wafer were
very (not much) different from those in air. Near-field interaction between neighboring metal
nanoparticles gives rise to hybridized plasmon modes, which could be largely modified by the
presence of a high refractive index substrate. This work demonstrates that the substrate effects
should be carefully considered for desirable Si-based plasmonic devices.
T-P-053
Light Confinement and Local Surface Photovoltage in P3HT/Si Hybrid
Nanopillar Arrays
Eunah KIM1, Yunae Cho1, Ahrum SOHN1, Heewon Hwang2, Y. U. Lee1, Kyungkon Kim2,
Hyeong-Ho PARK3, Joondong Kim4, J. W. Wu1, and Dong-Wook KIM1,*
1
Department of Physics, Ewha Womans University, Seoul 120-750, Korea
Department of Chemistry and Nano Science, Ewha Womans University, Seoul 120-750, Korea
3
Applied Device and Material Lab., Device Technology Division, Korea Advanced Nanofab Center (KANC),
Suwon 443-270, Korea
4
Department of Electrical Engineering, Incheon National University, Incheon 406-772, Korea
* E-mail address: dwkim@ewha.ac.kr
2
We investigated the influence of Mie-resonance-mediated light confinement on spatial
distributions of photo-generated charge carriers in Si nanopillar (NP) arrays coated with
poly(3-hexylthiophene-2,5-diyl) (P3HT) organic semiconductor layers. Regular NP arrays
were fabricated by electron-beam lithography and dry etching techniques. The optical
reflection spectra of the P3HT/Si NP arrays showed that Mie resonance significantly increased
the scattering cross-sections of the NPs and strongly concentrated incident light in the NPs.
Such confined light should increase local density of photo-generated charge carriers and affect
the spatial redistribution of the carriers. Surface photovoltage (SPV), defined as the difference
of the surface potential in dark and under light, could reveal the creation and separation of the
photo-generated carriers. Especially, Kelvin probe force microscopy (KPFM) technique
allowed us to obtain SPV maps of the P3HT/Si NP arrays with nanoscopic spatial resolution.
The SPV values at the NP tops were much larger than those at the flat regions around the NPs,
as expected. This suggests that KPFM-based SPV characterizations are very useful to study of
hybrid nanostructure-based optoelectronic devices.
T-P-054
Localized surface plasmon-enhanced near-ultraviolet light-emitting diodes
by colloidal silver nanoparticles
Sang-Hyun Hong, Na-Yeong Kim, Sehee Jeong, and Seong-Ju Park*
Department of Nanobio Materials and Electronics, Gwangju Institute of Science and Technology, Gwangju,
South Korea
* E-mail address: sjpark@gist.ac.kr
Near-ultraviolet (NUV) light-emitting diode (LED) are applied in diverse application fields such as fake
bill detector, bio-chemical sensor, medical device, high density storage, light source of photometric
detector, and pumping source for white LEDs [1, 2]. However, it has a problem that the internal quantum
efficiency (IQE) of NUV-LED is relatively low compared to that of blue and green LED due to the low
indium composition of InGaN quantum wells [3].
In this study, we demonstrate the improvement of IQE of NUV-LED (403 nm) by localized surface
plasmons (LSPs) from colloidal Ag nanoparticles (NPs). The spontaneous emission of multiple
quantum wells (MQWs) can be enhanced by resonant coupling between SPs in metal and excitons in
MQWs. Figure 1 shows a schematic diagram of NUV-LEDs with colloidal Ag NPs embedded in pGaN layer. The NUV-MQWs structure (InGaN/GaN MQWs/n-GaN/un-GaN/sapphire substrate) were
grown by MOCVD, followed by a 20-nm-thick p-GaN spacer layer grown between the MQWs and the
colloidal Ag NPs. Pre-synthesized colloidal Ag NPs solution was deposited on p-GaN spacer layer by
pneumatic spray process and then overgrowth of p-GaN layer was performed. Spray process is a
convenient method to control the density of metal NPs than the conventional method which employs
the e-beam evaporation and rapid thermal annealing process to produce metal NPs. Figure 2 shows the
optical output power of NUV-LEDs with colloidal Ag NPs are increased by 48.7% at 20 mA compared
with those of NUV-LEDs without colloidal Ag NPs. Furthermore, the IQE of NUV-LEDs with and
without Ag NPs are calculated to be 19% and 25.1% by comparing the integrated photoluminescence
(PL) intensities. And the time-resolved PL of NUV-LEDs with Ag NPs showed a faster decay time
compared to NUV-LEDs without Ag NPs. These results show that the increase in the spontaneous
emission rate is attributed to the resonant coupling between the excitons in MQWs and LSPs in the Ag
NPs.
Fig. 1. Schematic diagram of the LSP-enhanced
NUV-LEDs with colloidal Ag NPs in p-GaN layer.
Fig. 2. Optical output power of the NUV-LEDs with
and without colloidal Ag NPs.
References
1. A. Khan, K. Balakrishnan, and T. Katona, Nature 2, 77 (2008).
2. A. Knauer, H. Wenzel, T. Kolbe, S. Einfeldt, M. Weyers, M. Kneissl, and G Trankle, Appl. Phys. Lett. 92, 191912 (2008).
3. T. Nishida, H. Saito, and N. Kobayashi, Appl. Phys. Lett. 79, 711 (2001).
T-P-055
Stress evolution in semiconductor multiple quantum well structures
Taegeon Lee1, Heesuk Rho1,*, Won Jun Choi2, Jin Dong Song2
1
2
Department of Physics, Chonbuk National University, Jeonju 54896, Korea
Center for Opto-Electronic Materials and Devices, Korea Institute of Science and Technology, Seoul 02792,
Korea
* E-mail address : rho@chonbuk.ac.kr
We report Raman scattering results from GaAs/AlGaAs multiple quantum well (MQW)
structures grown by molecular beam epitaxy. To improve crystalline quality of the MQW layers,
firstly, InAs quantum dot (QD) layers were grown on a Si substrate. Secondly, GaAs buffer
layers were grown on the QD layers. Finally, the MQW layers were grown on GaAs. During
the growth of the GaAs layers, strain evolves along the growth direction, which, in turn,
strongly affects crystalline quality of the MQW layers.
Raman scattering provides useful means to understand optical phonon behaviors in
semiconductor crystals. Because optical phonon energies are very sensitive to variations in
strain, spatially-resolved Raman scattering is an efficient characterization tool to probe stress
evolution in semiconductors.
Raman scattering from GaAs/AlGaAs MQW structures revealed several transverse optical (TO)
and longitudinal optical (LO) phonons, such as GaAs, GaAs-like, and AlAs-like TO and LO
phonons. To evaluate stress evolution in the GaAs buffer layers, spatially-resolved Raman
experiments were performed along the growth direction from the side edges of the samples.
Interestingly, spatially-resolved Raman spectra obtained across the GaAs layers showed that
doubly degenerate GaAs TO phonons were split into two distinct phonons. We found that,
depending on the growth temperature, the split TO phonon energies evolved differently along
the growth direction. At the optimized growth temperature, two TO phonons merged toward
the top surface of the GaAs layers. Stress profiles in the GaAs buffer layers can be calculated
by using the biaxial assumption and the TO phonon energy shifts.
This research was supported by the Basic Science Research Program through the National
Research Foundation of Korea (NRF) funded by the Ministry of Education (Grant No.
2014R1A1A2057173), the Korea Basic Science Institute under the R&D program (Project No.
E36800) supervised by the Ministry of Science, ICT and Future Planning, and the KIST
institutional program.
T-P-056
Three Dimensional Measurement of Optical Components using Single
Interferogram and Quadrature Transform
Silin Na , Younghun Yu*
Department of Physics, Jeju National University, Jeju 63243, Korea
* E-mail address: yyhyoung@jejunu.ac.kr
During the last years many methods for fringe pattern analysis have been developed. The main
object of these methods is the phase measurements from fringe patterns. Normally phase
information is contained in the modulating phase which depends on the shape, refractive index,
etc [1].
Many types of interference microscopy were developed, such as phase shift interferometric
microscopy (PSIM), digital holography microscopy (DHM), Fourier phase microscopy (FPM).
In order to get the phase information of the sample, the interferogram obtained by
interferometric measurements need to be processed with phase retrieval algorithms. The PSIM
is an interfrometric method which owns the highest sensitivity, but it needs several phase
shifting interferograms by changing phase in measurement. Therefore, it could not use in real
time measurement. For real time measurement, only one interferogram is needed for phase
retrieving. FPM needs only one interferogram to retrieve the phase information. However, the
phase frequency and carrier frequency should be large difference for correct phase retrieving
in FMM. Especially, FMM could not be used in closed type interferogram. To solve these
problems, Quadrature transform (QT), two-dimensional Hilbert transform (HT), is suggested.
The principle of HT is that a modulating double side band signal such as a cosine or sine
contains redundant information; only one side band is needed to extract the modulation
information. Using the HT, one can derive the a single sideband expression for this modulating
signal with no loss of information [2].
In this paper, we have acquired the interferogram of optical component by normal
interferometer, and use QT to get the phase information of the sample. To apply QT,
background of interferogram should be removed and the intensity of the interferogram is
normalized. We have removed background signal and normalize the pattern using two
orthogonal band pass filters. After acquire the wrapped phase information, we use normal phase
unwrapping method to calculate the shape of the optical components.
References
1. S. Gorthi and P. Rastogi, Opt. Lasers Eng. 48, 133 (2019)
2. K. G. Larkin, J. Opt. Soc. Am. A18 (8) 1871 (2001)
T-P-057
Comparison study between Wigner equation and Schrödinger equation by
investigating an interaction between a Gaussian wave packet and a nonreflecting potential.
Joon-Ho Lee and Mincheol Shin*
Department of Electrical Engineering, Korea Advanced Institute of Science and Technology, Daejeon 34141,
South Korea
* E-mail address: mshin@kaist.edu
Comparison study between Wigner equation(WE) and Schrödinger equation(SE) can be conveniently
done by observing an interaction between a Gaussian wave packet and a square barrier, which has been
mostly implemented by Monte Carlo method rather than the deterministic approach. This paper employs
the deterministic solutions of WE to describe the time evolutions of a Gaussian wave packet interacting
with a square barrier, a square well, and a sech-squared well. The deterministic calculation for a
Gaussian wave packet with a small enough initial velocity shows that WE and SE produce the results
that agree closely with each other. Especially, in the sech-squared well known as a non-reflecting
potential the characteristics such as acceleration and reverse diffusion of a wave packet are reconfirmed
by the time dependent Wigner simulation. For more realistic simulation we add the 3 types of scattering
terms introduced by Jonasson et al.[J. Comput. Electron. 14, 879 (2015)]., the functions of which are
energy dissipation, momentum randomization, and spatial decoherence, respectively. Calculation
shows that the non-reflection is maintained with the energy dissipation term but is not with the
momentum randomization term and the spatial decoherence term. The momentum randomization effect
disturbs an ordered movement of a wave packet heading to a direction, which makes non-reflection
fundamentally impossible. The spatial decoherence term gives additional diffusion to a wave packet,
which could make the slow part of the wave packet have negative momentum, causing a failure of nonreflection.
References
1. S. DATTA, Superlattice Microst. 28, 253 (2000).
2. W. R. Frensley, Phys. Rev. B 36, 1570-1580 (1987).
3. Y. Yamada, H. Tsuchiya, and M. Ogawa, IEEE T. Electron Dev. 56, 1396 (2009).
4. S. Barraud, J. Appl. Phys. 106, 063714-7 (2009).
5. O. Jonasson, and I. Knezevic: J. Comput. Electron. 14, 879-887 (2015).
6. L. Shifren and D. K. Ferry, Phys. Lett. A 285, 217 (2001).
7. D. Querlioz, J. Saint-Martin, P. Dollfus, J. Comput. Electron. 9, 224 (2010).
8. S. Shao, J. M. Sellier, J. Comput. Phys. 300, 167-185(2015).
9. S. Shao, T. Lu, and W. Cai, Commun. Comput. Phys. 9, 711-739(2011).
10. R. Li, T. Lu, Y. Wang, W. Yao, Commun. Comput. Phys. 15, 569(2014).
11. A. Dorda, F. Schürrer, J. Comput. Phys. 284, 95-116(2015) .
12. R. Rosati, F. Dolcini, R. C. Iotti,, F. Rossi, Phys. Rev. B 88, 035401-16 (2013).
13. N. Kiriushcheva, S. Kuzmin, Am. J. Phys. 66, 867-872 (1998).
14 J. Lekner,, Am. J. Phys. 75, 1151-1157 (2007).
15 T. Lekner,, J. Lekner, Eur. J. Phys. 29, 671-679 (2008).
16 S. Barraud, J. Appl. Phys. 110, 093710 (2011).
17. K. L. Jensen and F. A. Buot, J. Appl. Phys. 65, 5248-5250 (1989).
18. W. R. Frensley, Rev. Mod. Phys. 62, 745-791 (1990).
T-P-058
Control of plasmonic response by dielectric function engineering
Doojae Park1, Ryan. P. Smith2 and Soo Bong Choi3*
1
Department of Physics, Hallym University, Chuncheon, Korea
Department of Physics, California State University, CA, USA
3
Department of Physics, Incheon National University, Incheon 443-803, Korea
*sbchoi@inu.ac.kr
2
The surface plasmon polariton on the metal/dielectric interface has been studies in many
aspects of light-matter interaction. Especially, the sensitive dependency of geometry of nano
structures give rise to the development of sensing devices in material science, bio detection,
chemical detections, etc. However the geometry gives degree of freedom to control of the
plasmonic responses, the designing of dielectric constant around the metal structure was limited
by detection. Due to the evanescent nature of surface plasmon, conventional microscope cannot
measure the propagation of surface plasmon directly. The most common technique to detect
the surface plasmon between air/metal interface is the Nearfield Scanning Optical Microscope
(NSOM). The non-contact mode of operation would not be applied in liquid environment, so
it has been an obstacle to design and detect the plasmonic respopnses with various dielectric
materials.[1,2]
To avoid the probe scanning technique, we developed wet-NSOM by introducing hybrid mode
operation between fast scan and hoping. With the wet NSOM measurement, the plasmonic
structure can be truly analized by introducing the dielectric function of surrounding materials.
The resonant reponse of SPP in water(n=1.33) was disappeared in dry condition(Air n=1).
0.030
0.030
-80.00
0.025
88.00
1.920
0.20
64.00
0.010
116.0
0.015
144.0
0.010
172.0
0.005
160.0
0.000
0.0
0.5
1.0
1.5
2.0
2.5
3.0
2.140
0.15
2.360
0.10
2.580
112.0
0.005
Distance(µm)
16.00
Distance(µm)
0.020
0.015
1.700
0.25
-32.00
0.020
Distance(µm)
0.30
60.00
0.025
200.0
0.000
0.0
0.5
1.0
1.5
2.0
2.5
3.0
0.05
2.800
0.00
0.0
0.5
1.0
1.5
Distance(µm)
2.0
2.5
3.0
Figure 15 Topography(left),
resonant plasmonic pattern(middle),
non-resonant plasmonic pattern(right)
Distance(µm)
Distance(µm)
References
[1] S. B. Choi, et al, Adv. Opt. Matt. 3(12),1179 (2015)
[2] S. B. Choi, et al, JKPS.67(7) 1158, (2015)
T-P-059
Electron-induced Cleaning of Carbon-contaminated Gold Film
Hyun Tae Kim1, Doo Jae Park2, and Soo Bong Choi1*
1Department
of Physics, Incheon National University, Incheon, 22012 Korea
of Physics, Hallym University, Chuncheon 24252, Korea
* sbchoi@incheon.ac.kr
2Department
A contamination of metal film and corresponding metal patterns is an important issue in fabrication of
devices where metal pattern is used. Such contamination could occur during evaporation process
because of unclean environment including crucible and vacuum chamber. Further, various chemicals
including photo- or electro-resistance which are involved in the etching and pattering procedure also
act as potential contaminants. Hence, finding a method for removing those potential contaminant is
important for preparation of a clean metal films and patterns, and further for improvement of device
performance which utilizes those. We report a method for removing such contaminants, especially
carbon, by simply exposing gold film to electron beam which is irradiated from a conventional SEM
apparatus.
Fig. 1 (a) shows a scanning electron microscope (SEM) image of a gold film fabricated by a
conventional e-beam evaporation method, after about 5 min exposure of electron beam. A clear dark
square image is observed in the center of image, which means that the electron absorption is increased
due to a certain change of film surface including modification of surface potential.
To investigate such changes in detail, we measured this film with an atomic force microscope and lateral
force microscope. As depicted in Fig. 1(b), no significant changes in topography of the film surface
except the edge of the square, which means that physical damage is negligibly small due to electron
beam exposure. However, as can be seen in Fig. 1 (c), a meaningful decrease of lateral force is observed
in the area of electron beam exposure. This strongly suggest that the surface potential has been
effectively changed.
[Fig.1] SEM image(left), AFM image(middle), Lateral(Sheer) force Microscope image(right)
To investigate the origin of the change of the surface potential, we also performed an electron diffraction
spectroscopy. This result shows that the film surface contains a significant amount of carbon, which is
likely due to a contamination of crucible in e-beam evaporator. However, this carbon contaminant is
meaningfully removed due to electron beam exposure. This results strongly suggest that the surface
contamination of gold film can be successfully removed, simply by exposing electron beam.
T-P-060
Three Dimensional Measurement of Optical Components using Single
Interferogram and Quadrature Transform
Silin Na , Younghun Yu*
Department of Physics, Jeju National University, Jeju 63243, Korea
* E-mail address: yyhyoung@jejunu.ac.kr
During the last years many methods for fringe pattern analysis have been developed. The main
object of these methods is the phase measurements from fringe patterns. Normally phase
information is contained in the modulating phase which depends on the shape, refractive index,
etc [1].
Many types of interference microscopy were developed, such as phase shift interferometric
microscopy (PSIM), digital holography microscopy (DHM), Fourier phase microscopy (FPM).
In order to get the phase information of the sample, the interferogram obtained by
interferometric measurements need to be processed with phase retrieval algorithms. The PSIM
is an interfrometric method which owns the highest sensitivity, but it needs several phase
shifting interferograms by changing phase in measurement. Therefore, it could not use in real
time measurement. For real time measurement, only one interferogram is needed for phase
retrieving. FPM needs only one interferogram to retrieve the phase information. However, the
phase frequency and carrier frequency should be large difference for correct phase retrieving
in FMM. Especially, FMM could not be used in closed type interferogram. To solve these
problems, Quadrature transform (QT), two-dimensional Hilbert transform (HT), is suggested.
The principle of HT is that a modulating double side band signal such as a cosine or sine
contains redundant information; only one side band is needed to extract the modulation
information. Using the HT, one can derive the a single sideband expression for this modulating
signal with no loss of information [2].
In this paper, we have acquired the interferogram of optical component by normal
interferometer, and use QT to get the phase information of the sample. To apply QT,
background of interferogram should be removed and the intensity of the interferogram is
normalized. We have removed background signal and normalize the pattern using two
orthogonal band pass filters. After acquire the wrapped phase information, we use normal phase
unwrapping method to calculate the shape of the optical components.
References
1. S. Gorthi and P. Rastogi, Opt. Lasers Eng. 48, 133 (2019)
2. K. G. Larkin, J. Opt. Soc. Am. A18 (8) 1871 (2001)
T-P-061 [NO SHOW]
On the etching method for the double patterning technique of DRAM
Doowhan Choi*, Jingee Kim, Taekyun Kang
Mansoo street in In-cheon, Korea, ASI|KR|KS006|INCHEON
*E-mail address: doowhan1@naver.com
For manufacturing DRAM with dimensions under OO nm, the double patterning techni
que (DPT) has been developed by A and B. It was successfully applied to 20 nm DRAM, but it does not work well for DRAM with the smaller dimensions.
The major problem is that the pattern size has been temporally changed in
manufacturing DRAM with the smaller dimensions, resulting from the various factors
in processes of DPT. For this reason, we have investigated the contribution of the
etching process to the temporal changes of dimensions. According to the present stud
y, it was found that the profile pattern, by-products, and uniformity of the plasma in
the etching process contribute to the temporal change of the pattern size. For this rea
son, the chemical components for the generation of plasma, the power, and pressure h
ave been changed to control the temporal changes of dimensions. The validation again
st the mass production showed that our method works well for the next
T-P-062
Yield improvement of next generation flash memory through
the enhancement of the plasma uniformity
Hundong Lee*1[1], Song-Yi Yang and Daegyu Ban and Byungoh Moon
*Etch Technology Team, Samsung Electronics,Samsung jeonja-ro, Hwaseong-si, Gyeonggido, Republic of Korea
As the aspect ratio of device becomes higher, the number of failures also increases. In particular,
the yield at the edge of wafer is low. Mostly, it resulted from the ion tilts in the etching process.
It is caused by the discontinuity of the electronic density at the edge.
The discontinuous electron density is improved by applying the different voltages at the edge,
changing materials, and enhancing the plasma uniformity. Among of them, Cho and Libermann
(2003) had tried to improve the plasma uniformity. Following them, we have changed the
external parameter for the yield improvement of next generation device.
By modifying the external parameter, the plasma uniformity has been enhanced, but the other
problem appeared in the etching process. The overall etch rate was lower, because modifying
the external parameter induced to change the volume of the process chamber. Due to this, the
larger etch time was applied to the process condition in addition to modifying the external
parameter.
As a result, SEM images showed that there were no ion tilts at the edge, and the heights of hole
satisfied the targets. And then this method was validated against the mass production. The test
showed that the method was successfully applied to the ion tilts. Finally, it leads to the increases
edge of yields..
References
S.Cho and M.A Liebemann, PSST 12(2003) 244-254
T-P-063
High photosensitivity of local bottom gate amorphous silicon thin film
phototransistors
Seongin Hong1, Okjin Kim1, Won Geun Song1, Minjung Kim1, Youngki Hong1, Na Liu1 and
Sunkook Kim1,*
1
Multi-Functional Nano/Bio Electronics Lab, Kyong Hee University, Yongin 446-701, South
Korea
* E-mail address: seonkuk@khu.ac.kr
Common amorphous silicon thin film transistors show low photosensitivity due to a-Si:H
channel which is indirect band gap semiconductor. To enhance the intrinsic characteristic of
this material, this paper presents a high photosensitivity of a-Si:H TFTs with local bottom gate.
Our phototransistors have various gate underlap that gate length is thinner than the channel
length. Our data shows that photocurrent generated by illuminating light can be significantly
enhanced with a larger gate underlap and a higher incident power density. Sensitivity of our
local bottom-gate a-Si:H phototransistor with 3-μm gate underlap and 3.2 W/cm2 could be
significantly larger than that of a global-gate counterpart by 3 orders of magnitude. Our local
bottom-gate a-Si:H TFTs also show excellent time-resolved photo-switching behaviors near
the IR range, which, along with the giant photo-sensitivity, demonstrates the great potential of
our local bottom-gate a-Si:H phototransistors for highly sensitive photosensor applications.
Fig. 1. (a)Optical microscope image which is illustrating top view of the TFT. (b) Transfer
characteristics of the local bottom-gated a-Si:H TFTs at the fixed Vds of 1 V with various
underlapped gate lengths.
References
1.
2.
3.
4.
M. Weiser, Sci. Am. 265, 94 (1991).
S.-E. Ahn, I. Song, S. Jeon, Y. W. Jeon, Y. Kim, C. Kim, B. Ryu, J.-H. Lee, A. Nathan, S. Lee, G. T.
Kim, and U.-I. Chung, Adv. Mater. 24, 2631(2012).
S. Y. Han, D. C. Kim, B. Cho, K. S. Jeon, S. M. Seo, M. S. Seo, S.-W. Jung, K. Jeong, W. K. Kim, S.H. Yang, N.-H. Kim, J. Song, H.-S. Kong, and H. G. Kim, J. Soc. Inf. Disp. 19, 855 (2011).
S. Y. Han, K. S. Jeon, B. Cho, M. S. Seo, J. Song, and H.-S. Kong, IEEE J. Quantum Electron. 48, 952
(2012).
T-P-064
Oxidation effect in Hafnium Disulfide (HfS2)
Youngjo Jin†,‡, and Young Hee Lee*,†,‡
†
Center for Integrated Nanostructure Physics, Institute for Basic Science (IBS),
Department of Energy Science, and
#
Department of Physics, Sungkyunkwan University, Suwon, 440-746, Republic of Korea
‡
*email: leeyoung@skku.edu
Abstract: Atomically smooth van der Waals materials are structurally stable in monolayer and
a few layers but some are susceptible to oxygen-rich environments. In particular, recently
emerging materials such as black phosphorus and perovskite have revealed stronger
environmental sensitivity than other two-dimensional layered materials, often obscuring the
interesting intrinsic electronic and optical properties. Unleashing the true potential of these
materials requires the oxidation-free sample preparation that protects thin flakes from air
exposure. Here, we fabricated the few-layer hafnium disulfide (HfS2) field effect transistors
(FETs) using an integrated vacuum cluster system and study their electronic properties and
stability under ambient conditions. By performing all the device fabrication and
characterization procedure under oxygen- and moisture-free environment, we found that a fewlayer AA-stacking HfS2-FETs display excellent field effect responses (Ion/Ioff = ~107) with
reduced hysteresis compared to the FETs prepared under ambient conditions. Oxidation of HfS2
occurs uniformly over the entire area, increasing film thickness by 250% at a prolonged
oxidation time of >120 hours, while defects on the surface are the preferential initial oxidation
sites. We further demonstrated that the stability of the device in air is significantly improved
by passivating FETs with BN in a vacuum cluster.
Key words: Oxidation, hafnium disulfide, vacuum cluster, glove box, field effect transistor,
boron nitride
T-P-065 [No SHOW]
Improvement of processing result in ashing plasma processing of DRAM
device
SeungHun Yang*,Young HwangBo, JeongJu Park
Samsungjeonja-ro in Hwaseong, Korea, 445701
*e-mail address: sh7035.yang@samsung.com
The critical dimension (CD) of the device has been shrunk in DRAM device manufacturing
etching process and thus, careful processing condition has to be considered to obtain high
quility device perfomance. However, the previous process recipe is often used in plasma
ashing process, even though smaller CD is required. Therfore, one should check or study the
discharge characteristic by applying the previous process recipe in next generation DRAM
process. In this study, we found that the previous ashing condition can affect the new device
performance. Improvement method of processing result and detailed mechanism will be
discussed in this presentation.
T-P-066
Current Characteristics of PNP Si BJT on Fast Neutron Irradiation
Sung Ho Ahn*, Gwang Min Sun, Hani Baek, Seong Bok Jin, and Sy Minh Tuan Hoang
Neutron Utilization Technology Division, Korea Atomic Energy Research Institute,
Daejeon, 34057, Republic of Korea
* E-mail address: shahn2@kaeri.re.kr
Bipolar junction transistors (BJTs) are applied in many industrial fields. BJT is a three-terminal
device with the important feature that the current through two terminals can be controlled by
small changes we make in the current or voltage at the third terminal. This control feature
allows us to amplify small AC signals or to switch the device from an on state and off state and
back. These two operations, amplification and switching, are the basis of a host of electronic
functions. The structure of BJT is divided by PNP and NPN types as the composition of the
emitter, base, and collector. In PNP BJT, the forward-biased junction which injects holes into
the center n-region is called emitter junction, and the reverse-biased junction which collects
the injected holes is called the collector junction. The emitter current can be accounted
physically by following three dominant mechanisms [1]. (a) There must be some recombination
of injected holes with electrons in the base. The electrons lost to recombination must be
resupplied through the base contact. (b) Some electrons will be injected from N to P in the
forward biased emitter junction, even if the emitter is heavily doped compared to the base.
These electrons must also be supplied by the base current. (c) Some electrons are swept into
the base at the reverse-biased collector junction due to thermal generation in the collector. This
small current reduced the base current by supplying electrons to the base. The dominant
mechanism in the base current is usually recombination, and the base current can be often
approximated by calculating the recombination rate in the base.
This study will investigate the current characteristics of PNP Si BJT such as base current,
collector current, and current gain etc. for the fast neutron irradiation. The fast neutron
irradiation causes the lattice damage in the Si bulk, arising from the displacement of silicon
atoms because of bombardment by the fast neutron irradiation. The uniformity of damage can
be obtained by the fast neutron irradiation method. This lattice damage introduces a deep level
in the silicon band gap, which act as recombination center [2]. The lattice damage increases
the base current and decreases the collector current with increasing the recombination rate of
minority carriers at base region and increasing the resistor [3]. Thus, the fast neutron irradiation
will reduce the switching time of the semiconductor devices even though the current gain is
reduced. The experimental results from this study show that increasing of the fast neutron
irradiation fluence increases the base current and decreases the collector current and current
gain. These results can be analyzed that the lattice damage caused by the fast neutron irradiation
increases the recombination rate of minority carriers as well as the resistors on PNP Si BJT.
References
1. J. B. G. Streetman, Solid State Electronic Devices, 2nd Edition, Prentice-Hall Inc., (1980).
2. B. J. Baliga, Fundamentals of Power Semiconductor Devices, Springer, New York (2008)
3. X. T. Wang, H. W. Yang, A. G. Kang, J. L, Wang, H. Y. Jia, P. Y. Chen, P. H. Tsien, Effects of neutron
irradiation on SiGe HBT and Si BJT devices, Journal of Materials Science : Materials in Electronics, 14, 199-203
(2003).
T-P-067
Field-driven domain wall motion under a bias current in Pt/[CoSiB/Pt]N
nanowires
M. H. Jung1*, Y. H. Choi1, Y. Yoshimura2, K.-J. Kim2, K. Lee3, T. W. Kim4, T. Ono2, C.-Y. You5
1
Department of Physics, Sogang University, Seoul 121-742 Korea
Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011, Japan
3
Institute of Physics, Johannes Gutenberg-Universität Mainz, 55128 Mainz, Germany
4
Department of Advanced Materials Engineering, Sejong University, Seoul 143-747 Korea
5
Department of Physics, Inha University, Incheon 402-751, Korea
*E-mail address: mhjung@sogang.ac.kr
2
Materials with perpendicular magnetic anisotropy (PMA) accelerates the developments of
spintronics devices due to their low threshold current density, simple domain wall (DW)
structure, and high spin-transfer-torque (STT) efficiency, compared with in-plane magnetic
anisotropy (IMA) materials. They can be used as one of magnetic components in magnetic
memory and logic devices by manipulating the magnetic domain wall (DW) motion. Thus, it
is important to understand the DW dynamics in PMA materials.
We investigated the DW motion in two extreme regimes of DW flow and creep motions for
the amorphous PMA multilayer with heavy metals, Ta/Pt/[CoSiB/Pt]N nanowire structure, for
different N and w.1 The field-driven DW velocity in the flow regime was found to increase with
N, which is ascribed to the enhancement of DW anisotropy energy with N. The DW motion
under a constant bias current reveals that the DW motion prefers the current flow direction in
thinner layer whereas the DW motion prefers the electron flow direction in thicker layer,
implying that the SHE gradually decreases with increasing the layer thickness while the STT
is constant. We also found that the relative strength of two torques is different depending on
the dynamic regime of DW.
Fig. 1. (a) Sample structure and (b) schematic illustration of the experiment setup of [CoSiB/Pt]N nanowires. A
is the electrode to inject a pulse current and create a DW. DC current is applied into A and B electrodes and the
Hall voltage is measured at C electrode. (c) Normalized Hall resistance RH data of [CoSiB/Pt]N nanowires for N
= 3, 6 and 9. The switching field corresponds to the coercive field. (d) Normalized Hall resistance RH data after
creating DW when perpendicular magnetic field pushes the DW to Hall bar. The switching field corresponds to
the depinning field.
References
1. Y. H. Choi, Y. Yoshimura, K.-J. Kim, K. Lee, T. W. Kim, T. Ono, C.-Y. You, and M. H. Jung, Sci. Rep.
Accepted (2016).
T-P-068
Enhancement of electric-field-induced change of magnetic anisotropy by
interface engineering of MgO magnetic tunnel junctions
Taufik Bonaedy 1, 2 , Jun Woo Choi 1,2*, Chaun Jang 1, Byoung-Chul Min 1, and Joonyeon Chang1
1 Center for Spintronics Research, Korea Institute of Science and Technology, Seoul 02792, Korea
2 Department of Nanomaterials Science and Engineering, Korea University of Science and Technology, Daejon,
Korea
*email address: junwoo@kist.re.kr
The realization of electric field control of magnetic properties enables low power voltage
controlled spintronic devices. In applications, it would be advantageous if the magnitude of the
electric-field-induced modification of magnetic properties is maximized for further reduction
of the operating power. In magnetic tunnel junction (MTJ) systems, one approach to enhance
the electric field effect is to effectively increase the change of electron density at the
ferromagnetic/insulator interface [1]. In earlier studies, ionic liquids and high-k dielectric
materials were utilized to increase the modification of electron density resulting in
enhancement of the electric field effect on the Curie temperature and magnetic anisotropy.
In this work, we use interface engineering to enhance the electric field induced magnetic
anisotropy modification. Two sets of thin film structures Co40Fe40B20/MgO/Co40Fe40B20 and
Co40Fe40B20/ Hf(0.08nm)/MgO/Co40Fe40B20 MTJ were deposited by rf sputtering, and
fabricated into MTJs. In both MTJ systems, the interfacial perpendicular magnetic anisotropy
is enhanced when the electron density at the Co40Fe40B20/MgO interface is increased by
applying voltage. Quantitative comparison between the electric field induced magnetic
anisotropy change in the two systems reveals that the electric field effect is significantly
enhanced
in
Co40Fe40B20/Hf(0.08nm)/MgO/Co40Fe40B20
compared
to
Co40Fe40B20/MgO/Co40Fe40B20. This result shows that insertion of sub-monolyaer (0.08nm) Hf
at the CoFeB/MgO interface can effectively enhance the electric field control of the interfacial
magnetic anisotropy.
References
1. F. Bonell, Y.T. Takahashi, D. D. Lam, S. Yoshida, Y. Shiota, S. Miwa, T. Nakamura, and Y. Suzuki, Appl.
Phys. Lett.102, 152401 (2013).
2. K. Shimamura, D. Chiba, S. Ono, S. Fukami, N. Ishiwata, M. Kawaguchi, K. Kobayashi and T.Ono, Appl.
Phys.Lett. 100, 122402 (2012).
3. M. Kawaguchi, K. Shimamura, S. Ono, S. Fukami, F. Matsukura, H. Ohno, D. Chiba, and T. Ono, Appl.
Phys. Express 5, 063007 (2012).
4. K. Kita, D.W. Abraham, M.J. Gajek, and D.C. Worledge, J. Appl. Phys. 112, 033919 (2012).
T-P-069
Study on verification of difference for the transition between
photoluminescence and cathode-luminescence in GaMnN
Juwon Lee1, Yoon Shon1*, Jae Min Sohn2, Hyungsang Kim3, Hyunsik Im3,
Changsoo Park3 and Eun Kyu Kim3
1
Quantum-functional Semiconductor Research Center, Dongguk University, Seoul 100-715, Republic of Korea,
2
Department of Physics and Semiconductor Science, Dongguk University, Seoul 100-715, Republic of Korea
3
Quantum-Function Spinics Laboratory and Department of Physics, Hanyang University, Seoul 133-791,
Republic of Korea
* E-mail address: sonyun@dongguk.edu
GaN:Mn epilayers were grown on Al2O3 substrate uisng MBE and were subsequently
implanted with Mn+ ions (1 and 10 %). Photoluminescence (PL) with 1 % of Mn showed that
optical transitions related to Mn revealed (D, Mn) at 2.5 eV and (e, Mn) around 3.1 eV, and
YL around 2.20 ~ 2.25 eV. Photoluminescence (PL) with 10 % of Mn showed the same but
enhanced optical transitions as above. However, the new transitions around 1.65 eV for the
sample with 10 % which did not appeared with Mn of 1 % were very weakly produced. The
results of CL with 10 % of Mn showed transitions related to Mn in PL together with new
transitions around 1.72 eV. However, the new transitions around 1.72 eV for the sample with
10 % according to high accelerating voltage were very remarkably activated in contrast with
PL transitions which appeared were very weakly produced in samples with Mn of 10 %.
Transitions around 1.72 eV in CL corresponds to though around 1.65 eV in PL. This result
means that deep donor (probably, VN) is detected with increasing accelerating voltage and MnVN complex is formed. This is supported by strong electron beam sensitivity of the IR emission
bands. It is well known that heavy Mn doping ( > ~1019 Cm-3) leads to a downshift of the Fermi
level and promotes the formation of defect complexes of Mn–VN . In our case, Mn doping
concentration is > ~ 1021 Cm-3. Therefore, it is conjectured that the CL transition around 1.72
eV corresponds to Mn-VN complex.
T-P-070
Effects of Current Cleaning on Graphene Spin Precession
Seoknam Ko and Doyeol Ahn*
Department of Electrical and Computer Engineering and Institute of Quantum Information Processing and
Systems, University of Seoul, Seoul 02504, Republic of Korea
* E-mail address: dahn@uos.ac.kr
Advantages of electrical spin-based devices are non-volatile, scalable, low power and
reprogrammable functionalities.[1] Utilizing graphene opened up the possibility of spintronic
due to its high electron spin coherence time and diffusion length.[2,3] In conventional electrical
spin injection and detection device, conductivity mismatch problem related low spin injection
efficiency was relieved by employing an insulating tunnel barriers between ferromagnetic (FM)
and graphene.[4] Here we studied the effect of current cleaning on spin precession signals.[5]
Standard lithography techniques are used to fabricate spin valve device. Figure 1 shows the
SEM image of typical our graphene spin valve device with ferromagnetic Co electrodes. A
low-frequency ac excitation current is applied across the injection electrodes to generate spin
polarization at the interface between electrode and graphene. Nonlocal voltages differences are
measured using standard lock-in detection techniques with an ac current at low-frequency
below 17Hz. The resistance is measured as a function of magnetic field, swept up and swept
down, to align magnetization into parallel and antiparallel of electrodes.[6,7]
Magnetoresistance (MR) characteristics are measured using the closed cycle refrigerator and
electromagnet in vacuum at 4K. Figure 2 shows the effects of current cleaning on Hanle spin
curve. We find the degrade of spin precession signal which is induced by the interfacial change
between Co electrode and graphene.
References
1. A.L. Friedman, C.H. Li, J.T. Robinson, J. Connell, L.J. Lauhon, O.M.J. van rsquo t Erve, and B.T. Jonker,
Nature Communications 6, 1 (2015).
2. B. Trauzettel, D.V. Bulaev, D. Loss, and G. Burkard, Nature Physics 3, 192 (2007).
3. D. Huertas-Hernando, F. Guinea, and A. Brataas, Phys. Rev. B 74, 155426 (2006).
4. W. Han, K. Pi, K.M. McCreary, Y. Li, J.J.I. Wong, A.G. Swartz, and R.K. Kawakami, Phys. Rev. Lett. 105,
167202 (2010).
5. J. Moser, A. Barreiro, and A. Bachtold, Appl. Phys. Lett. 91, 163513 (2007).
6. C. Jozsa, M. Popinciuc, N. Tombros, H.T. Jonkman, and B.J. van Wees, Phys. Rev. B 79, (2009).
7. W. Han, W. Wang, K. Pi, K. McCreary, W. Bao, Y. Li, F. Miao, C. Lau, and R. Kawakami, Phys. Rev. Lett.
102, 137205 (2009).
T-P-071
Probing plasmonic interaction in 2D layered materials by surface enhanced
Raman spectroscopy
Younghee Kim‡, Joonmo Ahn‡, Jae Hun Kim, Minah Seo, Young Min Jhon*
1
Sensor System Research Center, Korea Institute of Science and Technology, Seoul, 136-791, Republic of Korea
‡
These authors contributed equally to this work
* E-mail address: ymjhon@kist.re.kr
Surface enhanced Raman spectroscopy (SERS) exploits surface plasmon induced by the
incident field in metallic nanostructures to significantly increase the Raman scattering. Twodimensional (2D) layered materials, exhibiting a flat surface, are shown to be strong candidates
for both fundamental studies of the Raman enhancement effect and its extension to meet
practical applications requirements. Recently, the zero-band semi-metallic graphene was
introduced as a prototype material to investigate the electromagnetic mechanisms in the
interaction between metals and graphene1,2 and the graphene-mediated metal SERS substrate
was applied to enable direct, real time and reliable detection of trace amounts of molecules,
such as rhodamine 6G.3 However, the SERS still has many ambiguities regarding the pertinent
enhancement mechanisms. Here, we performed SERS experiments on three different prototype
2D materials of graphene, WTe2, and black phosphorus with metal depositions of gold and
silver nanoparticles to deduce the origin of the SERS effects on the flat substrates. We observe
the layer- and metal thickness-dependent Raman enhancement factors exhibit different
behaviors as shown in Figure 1 (a) and (b). It indicates the interaction between the dipoles in
metal and the induced image dipoles in material depends on the reflectivity of the graphene
layers. In contrast to graphene, few-layer WTe2 with the similar electronic structure as
graphene shows the whole Raman intensity screening (Figure 1(c)). It results from the high
reflectivity of WTe2 materials interrupting the formation of the image dipoles induced from the
metal nanoparticles in the material. The semiconducting black phosphorus reveals the local
mechanical strain caused by the hot electrons at the interface of the semiconductor and metals.
Fig. 1. (a) SERS of 1L-graphene and various thickness gold films. (b) Enhancement factors of G-peak in graphene
as a function of gold film thicknesses. (c) Raman scattering screening of few-layer WTe2 after deposition of gold.
References
1. F. Schedin et al., ACS Nano, 4, 5617 (2009)
2. J. Lee, K. S. Novelselov, H. S. Shin, ACS Nano, 5, 608 (2010)
3. W. Xu et al., Proc. Natl. Aca. Sci. U.S.A., 109, 9281 (2012)
T-P-072
Nonvolatile Charge Injection Memory Effect based on Black Phosphorous
2D Nanosheets
Hyunsu Ju*, Young Tack Lee, Do Kyung Hwang, Won Kook Choi
Korea Institute of Science and Technology(KIST), Seoul 02792, Korea
2D van der Waals materials have caught great attention expected for use in future nanoscale
electronic and optoelectronic applications due to their unique properties such as a tunable
energy band gap by their thickness or number of layers. Recently, a single-component material,
black phosphorous (BP) has attracted significant interest because it has high mobility, a direct
band gap, and exhibits ambipolar transition behavior. In this study charge injection memory
effect are reported with a field-effect transistor on glass substrate, where few-layer BPs’ act as
active channel and charge trapping layers, and Al2O3 films grown by atomic layer deposition
act as tunneling and blocking layers. The ambipolar property of the BP nanosheet enables both
electrons and holes to be involved in the charge trapping process, resulting in bi-directional
threshold voltage shifts with a large memory window of 22 V. Finally, a resistive-load inverter
is implemented that converts analog signals (current) to digital signals (voltage). Such a
memory inverter also shows a clear memory window and distinct memory on/off switching
characteristics.
T-P-073
Size Dependence of Metal-Insulator Transition in Stoichiometric Fe3O4
Nanocrystals
Jaeyoung Hong1, Jisoo Lee1, Soon Gu Kwon1, Je-Geun Park2,* and Taeghwan Hyeon1,*
1
School of Chemical and Biological Engineering, Seoul National University, Seoul 08826, Korea
2
Department of Physics and Astronomy, Seoul National University, Seoul 08826, Korea
1
2
thyeon@snu.ac.kr
jgpark10@snu.ac.kr
* E-mail address:
Magnetite (Fe3O4) is one of the most actively studied materials with a famous metal-insulator
transition (MIT), so-called the Verwey transition at around 123 K.1 Despite the recent progress
in synthesis and characterization of Fe3O4 nanocrystals (NCs), it is still an open question how
the Verwey transition changes on a nanometer scale. We herein report the systematic studies
on size dependence of the Verwey transition of stoichiometric Fe3O4 NCs. We have
successfully synthesized stoichiometric and uniform-sized Fe3O4 NCs with sizes ranging from
5 to 100 nm. These stoichiometric Fe3O4 NCs show the Verwey transition when they are
characterized by conductance, magnetization, cryo-XRD, and heat capacity measurements.
The Verwey transition is weakly size-dependent and becomes suppressed in NCs smaller than
20 nm before disappearing completely for less than 6 nm, which is a clear, yet highly interesting
indication of a size effect of this well-known phenomena.2
Fig. 1. Size dependence of TV for Fe3O4 NCs. The contour plot represents the heat capacity data after removing
the contribution of surfactant . The symbols mark the Verwey transition temperature (TV) determined from three
different types of measurements: heat capacity (green, CP/T), conductance (blue, G), and magnetic moment (red,
m). The size dependence of blocking temperature (TB) is also plotted from the same magnetization measurement
(black). The gray line is a guide to the eye for the size dependence of TB.
References
1. E. J. Verwey, Nature, 144, 327 (1939).
2. J. Lee, S. G. Kwon, J.-G. Park and T. Hyeon, Nano Lett. 15, 4337 (2015).
T-P-074
Neuronal differentiation of human mesenchymal stem cells in response to
grain size of graphene substrate
Yoo-Jung Lee 1, Tae-Hoon Seo2, Myung-Jong Kim2, Hyun-Sik Im3 and Jung-Suk Sung1*
1
Department of Life Science, Dongguk University-Biomedi Campus, Goyang, 410-820, Korea
Soft Innovative Materials Research Center, Korea Institute of Science and Technology, Jeonbuk 565-905,
Korea
3
Department of Semiconductor Science, Dongguk University, Seoul 100-715, Korea
* E-mail address: sungjs@dongguk.edu
2
Graphene is non-cytotoxicity monolayer platform with unique physical, chemical and biological
properties. [1, 2]. It has been demonstrated that graphene substrate provides the promising
biocompatible scaffold for stem cell therapy [3, 4]. To achieve desirable properties for nano-material,
control of individual grain size of graphene is important [5]. However, the biological effects mediated
by differences in graphene grain have not yet been reported. Here, we showed that the neuronal
differentiation of bone marrow-derived human mesenchymal stem cells (hMSCs) was more enhanced
on graphene substrates with grain size of 32 µm2 compared to 105 µm2. The water contact angle of 75.7°
compared to 85.7° for the monolayer graphene containing higher defect density stimulated cellsubstrate adhesion and up-regulated neuronal differentiation of hMSCs. Our results may provide
valuable information on the development of graphene-based scaffold by understanding which properties
of graphene grain influence to cell adhesion efficacy and stem cell differentiation.
Fig. (a) SEM image of graphene substrate of different grain sizes (32 and 105 µm2). (b) hMSC neuronal
differentiation on graphene substrates determined by immunocytochemistry. Stained cells with neuronal markers
(TUJ-1, MAP2) (green) for hMSCs and DAPI (blue) for nuclei (scale bar = 100 µm).
References
1. C. Chung, Y. K. Kim, D. Shin, S. R. Ryoo, B. H. Hong, and D. H. Min, Acc. Chem. Res. 46, 2211-2224 (2013)
2. F. Rodriguez, D. Garcia, S. Aznar, and J. Moraleda, Transl. Res. 166, 399-400 (2015)
3. E. bressan, L. Ferroni, C. Gardin, L. Sbricoli, and B. Zaban, J. Transl. Med. 12, 296 (2014)
4. S. Shah, P. Yin, T. Uehara, S. Chueng, L. Yang, and K. Lee, Adv. Mater. 26, 3673-80 (2014)
5. Q.Yu, L. Jauregui. W. Wu, R. Colby, J. Tian, and Y. Chen., Nat. Mater. 10, 443-449 (2011)