Advanced Computation& Modeling
張亞中 (YiaChung Chang) –
Nanostructure
electronics &
photonics
馬尚德 (Alec Maassen
van den Brink)–
Quantum computing
謝東翰(Tung-Han
Hsieh) – Web computing
New Hire: Shu-Wei Chang
關肇正 (Chao-Cheng
Kaun)– Ab initio transport
Vladimir Nazarov-CDFT
-Nanophotonics
Missions
 To carry out theoretical modeling in
targeted areas of importance in applied
sciences, including:
1) Nanostructure optoelectronic devices
2) Quantum information devices
3) Optical metrology and nanophotonics
 Provide theoretical guidance and analysis to
experimental groups within RCAS
Progress in Nanophotonics
•
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•
•
•
•
•
•
•
•
•
Efficiency Enhancement of GaAs Photovoltaics Employing Antireflective Indium
Tin Oxide Nanocolumns, (with P. Yu, NCTU) [ Adv. Mater., 20, 1–4 (2008); Y. Z.
Hsu Scientific Paper Award, 2010]
Aspect-ratio-dependent ultra-low reflection and luminescence of dry-etched Si
nanopillars on Si substrate [Nanotechnology, 20, 035303, (2009)]
Spatial filtering by using cascading plasmonic gratings [Optics Express 17, 6218
(2009).]
Effective dielectric properties of biological cells: Generalization of the spectral
density function approach [J. Phys. Chem. B 113 (29), 9924–9931 (2009)]
Dielectric response of AlSb from 0.7 to 5.0 eV determined by in situ ellipsometry
[Appl. Phys. Lett. 94, 231913 (2009)]
T-shaped plasmonic array as a narrow-band thermal emitter or biosensor [Optics
Exp. 17, 13526-31 (2009)]
Interband transitions of InAsxSb1−x alloy films [Appl. Phys. Lett. 95,111902 (2009)]
Manipulative depolarization and reflectance spectra of morphologically controlled
nano-pillars and nano-rods [Optics Exp., 17, 20824-32 (2009)]
Optical metrology of randomly-distributed Au colloids on a multilayer film [Optics
Exp. 18, 1310-15 (2010)]
Plasmon-polariton band structures of asymmetric T-shaped plasmonic gratings
[Optics Exp. 18, 2509-14 (2010)]
Surface plasmon resonance ellipsometry based sensor for studying biomolecular
interaction [Biosensors and Bioelectronics 25, 2633 (2010)]
Research progress in nanoelectronics
 Superconducting nanowires： Interplay of discrete transverse
modes with supercurrent (Kaun)[Phys. Rev. B 80, 024513 (2009)]
 Submonolayer quantum dot infrared photodetector [Appl. Phys.
Lett. 94, 1 (2009)]
 Bistable states of quantum dot array junctions for high-density
memory [Jpn. J. Appl. Phys., 48, 104504 (2009)]
 Cesium doped and undoped ZnO Nanocrystalline thin films: a comparative
study of structural and Micro-Raman investigation of optical phonons, R.
Thangavel [J. Ram. Spect. DOI 10.1002/jrs.2599 (2010)]
 Surface States/Modes in One-Dimensional Semi-infinite Crystals, [Annals
of Physics 325, 937-947 (2010)]
 Thermoelectric and thermal rectification properties of quantum
dot junctions, [Phys. Rev. B 81, 205321 (2010)]
Progress in DFT & quantum structures
 Exact dynamical exchange-correlation kernel of a weakly inhomogeneous
electron gas [Phys. Rev. Lett., 102, 113001 (2009)]
 Open a way for interpolation between low- and high frequency behavior of
the xc kernel of an arbitrary system by expressing it in the high-frequency
limit through a few ground-state properties. (Nazarov) [Phys. Rev. B 81,
245101 (2010)]
 On the relation between the scalar and tensor exchange-correlation kernels
of the time-dependent density-functional theory [J. Chem. Phys.. in press
(2010)
 Enhancement factor, electrostatic force and emission current in nanoneedle
emitter [Euro Phys. Lett. 85, 17001 (2009) ]
 Field enhancement factor and field emission from a hemi-ellipsoidal metallic
needle [Ultramicroscopy 109, 373 (2009)]
 Van der Waals interaction between two crossed carbon nanotubes [ACS
nano, in press (2010)]
 Corrected field enhancement factor for the floating sphere model of carbon
nanotube emitter [J. Appl. Phys., in press (2010)]
 Development of GPU computing environment and Investigation of the novel
"Adaptive Thick Restart Lanczos Algorithm" for low-lying eigenmode
projection for large sparse Hermition matrix. (TH Hsieh)
Optical nanometrology
Nanometrology allows optical inspection of the
geometry of nanostructures down to 10nm scale.
It uses a best fit to the measured ellipsometric spectra
via theoretical simulation (with efficient software) to
determine the critical dimension.
If done correctly, one can reconstruct images of nm
resolution by using an optical instrument (with
wavelengths 100nm-1000nm).
It is noninvasive and capable of probing buried
structures and biological systems
SEM of Au Nanoparticles of different sizes
d = 20nm
d = 40nm
d = 60nm
d = 80nm
Ellipsometry Results – Au NP@60o
o
o
Au NP, 60
Au NP, 60
18
80
70
16
60 nm
60
20 nm
12
80 nm
10
40 nm
8
50
 (degree)
 (degree)
14
40
30
10 nm
20 nm
40 nm
60 nm
80 nm
20
10
6
10 nm
0
4
1
2
3
4
5
6
Photon energy (eV)
7
8
1
2
3
4
5
6
Photon energy (eV)
7
8
Ellipsometry Measurement vs. simulation
 Au nanoparticles: 20, 40, 60, 80 nm
 angle of incidence: 60º
Fitting by a lattice model
o
Au NP, 60
26
26
20 nm
40 nm
60 nm
80 nm
24
22
20
22
20
18
16
14
18
16
14
12
12
10
10
8
8
6
6
4
4
1
2
3
4
5
6
Photon energy (eV)
7
20 nm
40 nm
60 nm
80 nm
24
 (degree)
 (degree)
o
AuNP, 60
8
1
2
3
4
5
6
7
Photon energy (eV)
8
9
Effects of Site Disorder
∫
f
Simplified model for structure factor
S(g) = 1 + f ∑j≠0 exp{i (k-k0) ∙Rj}
L
= 1+ f 2π ∫a rdr J0(gr) /Ac
= 1 + f [Nδk,k0 – 2π(a2/Ac)J1(ga) /ga],
f = similarity factor
N= total number of atoms considered,
g = k - k0
Ac = average cell volume
[S.-H. Hsu, Y.-C. Chang*, Y.-C. Chen, P.-K. Wei, Y. D. Kim, Optics Exp. 18, 1310 (2010)]
Au NP 20~60 nm, random (without clusters)
16
experiment
14
14
12
12
 (degree)
 (degree)
16
10
8
6
10
8
6
4
2
1
model
20 nm:
40 nm:
2
o
55
o
55
3
4
5
6
7
Photon energy (eV)
o
60
o
60
8
4
60 nm:
2
1
2
55
o
3
4
5
6
7
Photon energy (eV)
60
8
o
Au NP 20~60 nm, random (without clusters)
180
20 nm:
40 nm:
60 nm:
160
140
o
55
o
55
o
55
160
140
 (degree)
120
 (degree)
180
o
60
o
60
o
60
100
80
60
120
100
80
60
40
40
20
20
experiment
0
1
2
3
4
5
6
7
Photon energy (eV)
8
model
0
1
2
3
4
5
6
7
Photon energy (eV)
8
GF results (random, no clusters)
 substrate: glass slide coated with a buffer layer (e = 2.0)
 parameters:


m=7
isur = 1
nominal
size
20 nm
40 nm
60 nm
radial
k
slices particle size
mesh
18  16 nm
35
15
18  16 nm
42  32 nm
37
19
40  36 nm
60  55 nm
39
23
60  57 nm


cc = 1.0
gst = 2
sk0
pitch
0.9
1.0
0.9
1.0
0.8
0.9
42 nm
42 nm
140 nm
155 nm
170 nm
180 nm
buffer
thicknes MSE
s
11.75
2 nm
11.64
27.54
2 nm
24.28
2 nm 32.00
0 nm 31.62
Comparison of modeling based on
random and periodic distributions
SEM estimation
Random distribution
Nominal
size
Average
(nm)
distance (nm)
Average
distance
(nm)
20
40 - 42
40
Periodic distribution
MSEa
Periodicity
(nm)
MSEa
42
12.2 (11.0)
80
13.1 (12.5)
135 - 140
140
26.4 (14.7)
200
25.6 (15.7)
60
156 - 175
175
35.6 (18.7)
220
35.1 (23.3)
80
210 - 249
235
31.6 (17.2)
300
32.2 (23.2)
aValues
in parentheses are for fitting in the 2-9 eV range.
Effects of clustering
2
Modeling potential for clusters
V2
V3
V4
Au NP 40 & 60 nm, random (with
clusters)
16
experiment
14
14
12
12
 (degree)
 (degree)
16
10
8
6
10
8
6
40 nm:
60 nm:
4
2
1
model
2
o
55
o
55
3
4
5
6
7
Photon energy (eV)
o
60
o
60
8
4
2
1
2
3
4
5
6
7
Photon energy (eV)
8
Au NP 40 & 60 nm, random (with
clusters)
180
40 nm:
60 nm:
180
o
60
o
60
160
140
140
120
120
 (degree)
 (degree)
160
o
55
o
55
100
80
60
100
80
60
40
40
20
20
experiment
0
1
2
3
4
5
6
7
Photon energy (eV)
model
0
8
1
2
3
4
5
6
7
Photon energy (eV)
8
GF (random, with clustering)
 angle of incidence: 55º, 60º
 substrate: pseudo-dielectric constants from APTES w/o BSC modeling
 common parameters:




m=8
radial k mesh = 45
ns = 4
size (nm)
slice
s
p


fc
fv
Dc
sk0 = gst = 1
cc = 1.0
isurf = 1
MSE (1~9 eV)
MSE (2~9
eV)
13.20
11.07
13.11
11.52
20
21.44
18.17
15
21.51
17.93
21.24
17.27
21.28
16.96
ds
0.04
42  36
60  57
80  72
19
23
25
145 nm 0.04 0.30
5
90
180 nm 0.05 0.30 125
235 nm 0.05
230 nm 0.04
0.45 160
15
20
Summary
Samples with different sizes of Gold nanoparticles immobilized on
a glass substrate are investigated by variable-angle spectroscopic
ellipsometry (VASE) in the UV to near IR region.
Both the Green’s function method and rigorous coupled-wave
analysis (RCWA) were used to model the ellipsometric spectra
GF method is 10 – 100 times more efficient than RCWA in most
cases for lattice model calculation.
For random scattering problem, only GF method is used, and it is
faster by another order of magnitude.
Our model calculations show reasonable agreement with the
ellipsometric measurements.
This demonstrates that the spectroscopic ellipsometry could be a
useful tool to provide information about the size and distribution of
nanoparticles deposited on insulating substrate.
The technique can be extended to inspect buried nanostructures
Microscopic imaging ellipsometer
Multiskop
 original capabilities
 single-wavelength measurement
 variable-angle ellipsometry/reflectance (spatial resolution: ~ mm)
 imagine ellipsometry (spatial resolution: 5~10 mm)
 Ongoing upgrades
 intense white-light source + monochromator
 spectroscopic measurement
 in-house software
 scatterometry (scattering-type ellipsometry/reflectance)
 atomic force microscope (AFM)
 increased spatial resolution (100 nm), tip-enhanced measurement
 projected-field electromagnet
 magnetism-related studies
Introduction
• Measures polarization change (ψ and Δ) when
light reflects from a surface.
tanΨ =
Rp
Rs
and    p   s
Properties of Interest:
Film Thickness
Refractive Index
Surface Roughness
Interfacial Regions
Anisotropy
Uniformity
Composition
Crystallinity
Biosensing
Source: J. A. Woollam Co., Inc.
Figure (a) Ellipsometry measurement showing light reflected from sample surface parallel
to the sample stage.
(b) SPR ellipsometry showing light reflected from sample surface perpendicular to the
sample stage.
Sample preparation process
AuNPs(13nm)
SiO2(~4nm)
Gold(40nm)
Ti(5nm)
Gold nanoparticle on gold substrate
1min
5min
1min
5min
SPR dip with different surface coverage of Gold nanoparticles on Gold film
Gold=40nm
Ti
Glass
EMA layer
Gold=40nm
Ti
Glass
Gold nanoparticle is slice into
2EMA layers- 5 and 10 minutes
3EMA layers - 20, 60 and 120 minutes
1st EMA
AuNP
2nd EMA or Au thin layer
3rd EMA
Metal substrate
Non-uniform medium
Image dipole,
multipole effect
Bulk sensitivity measurement for bare Gold film and Gold nanoparticles coated on Gold film
Bare gold film
AuNPs/ gold film (1min)
Bare gold film
AuNPs/ gold film (1min)
Dynamic measurement
BSA / Anti-BSA interaction
Ti
Glass slide
Gold
Ti/Glass slide
Au/Ti/Glass
slide
BSA
anti-BSA
Bare gold substrate
Bare 13nm AuNPS
After attachment of BSA + anti-BSA
After attachment of
BSA + anti-BSA
Current study on BSA / Anti-BSA interaction
Surface mass density of BSA
adsorption on gold surface
Solutions
Fitting
Paramete
r An
Fitting
Paramete
r Bn
Mean
Square
Error
(MSE)
Thicknes
s (nm)
PBS
1.340
0.00023
5
6.978
BSA
1.338
0.01
1.715
6.9
Anti-BSA
1.342
0.01
1.655
22.2
Dynamic measurement on various samples for BSA / Anti-BSA interaction
Dynamic measurement on bare gold film for BSA / Anti-BSA interaction
A comparison on biomolecular interaction study
Comparison on sensitivity of various samples for BSA / Anti-BSA interaction
Conclusion
– A very simple and promising technique is presented and
further extended its potential application to investigate both
spectroscopic and real time response of bio-molecular
interaction based on the ellipsometry optical signals.
– Surface Plasmon Resonance(SPR) of the gold film can be
tune with various distribution of AuNPs coated on gold film.
– Bulk refractive indices measurement shows that more
densely packed AuNPs on gold film give higher refractive
index (RI) resolution.
– However, local refractive index change corresponding to the
adsorption of BSA and subsequent attachment of anti-BSA
measurement shows that sample dipped in AuNPs for 1
minute shows better sensitivity as compare to other dipping
time as well as bare gold film.
– Hence, direct correlation on sensitivity from bulk to local
refractive index change is trivial and need further
investigation.
– SPR ellipsometry does make a unique tool to investigate
various challenging issues in terms high affinity bio-detection
Application software development
• LED/light scattering Simulator:
Optical simulation for LED devices and optical
metrology.
• LASTO package:
An abinitio computation package based on
Linear Augmented Slater-Type Orbitals basis.
• Nanostructure Simulator:
Effective bond-orbital method for microsopic
strain distribution, electronic states, and optical
properties of semiconductor nanostructures
computatio
• GPU software development (Hsieh)
Future goals of ACM group
Development of multiscale modeling package for
future generation nanoscale optoelectronic devices
(combining modeling techniques for electron transport,
interface characteristics, optical properties and heat
dissipation.
Couple theoretical modeling with experimental studies
for development of novel nanometrology technology.
Modeling for spintronics, quantum information, and
magnetic RAM.