RESEARCH ARTICLE
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On-Chip Monolithically Integrated
Ultraviolet Low-Threshold Plasmonic Metal‒Semiconductor
Heterojunction Nanolasers
Jia-Yuan Sun, Duc Huy Nguyen, Jia-Ming Liu, Chia-Yao Lo, Yuan-Ron Ma, Yi-Jia Chen,
Jui-Yun Yi, Jian-Zhi Huang, Hien Giap, Hai Yen Thi Nguyen, Chun-Da Liao, Ming-Yi Lin,
and Chien-Chih Lai*
The metal‒semiconductor heterojunction is imperative for the realization of
electrically driven nanolasers for chip-level platforms. Progress in developing
such nanolasers has hitherto rarely been realized, however, because of their
complexity in heterojunction fabrication and the need to use noble metals that
are incompatible with microelectronic manufacturing. Most plasmonic
nanolasers lase either above a high threshold (101 ‒103 MW cm−2 ) or at a
cryogenic temperature, and lasing is possible only after they are removed
from the substrate to avoid the large ohmic loss and the low modal reflectivity,
making monolithic fabrication impossible. Here, for the first time,
record-low-threshold, room-temperature ultraviolet (UV) lasing of
plasmon-coupled core‒shell nanowires that are directly grown on silicon is
demonstrated. The naturally formed core‒shell metal‒semiconductor
heterostructure of the nanowires leads to a 100-fold improvement in growth
density over previous results. This unprecedentedly high nanowire density
creates intense plasmonic resonance, which is outcoupled to the resonant
Fabry‒Pérot microcavity. By boosting the emission strength by a factor of 100,
the hybrid photonic‒plasmonic system successfully facilitates a record-low
laser threshold of 12 kW cm−2 with a spontaneous emission coupling factor
as high as ≈0.32 in the 340‒360 nm range. Such architecture is simple and
cost-competitive for future UV sources in silicon integration.
J.-Y. Sun, D. H. Nguyen, Y.-R. Ma, H. Giap, H. Y. T. Nguyen, C.-C. Lai
Department of Physics
National Dong Hwa University
Hualien 974301, Taiwan
E-mail: cclai@gms.ndhu.edu.tw
J.-M. Liu
Department of Electrical and Computer Engineering
University of California
Los Angeles, CA 90095, USA
The ORCID identification number(s) for the author(s) of this article
can be found under https://doi.org/10.1002/advs.202301493
© 2023 The Authors. Advanced Science published by Wiley-VCH GmbH.
This is an open access article under the terms of the Creative Commons
Attribution License, which permits use, distribution and reproduction in
any medium, provided the original work is properly cited.
DOI: 10.1002/advs.202301493
Adv. Sci. 2023, 2301493
1. Introduction
With the booming interest in nanotechnology and nanoscience, strong demands for
tight interconnection between on-chip photonics and electronics have spurred pronounced studies into the development of
nanolasers. The limited progress in ultraviolet (UV) nanolasers so far is caused by challenges in extending the emission to short
wavelengths due to the high optical absorption of existing nanolaser materials in the
UV region, particularly at wavelengths below 360 nm (near the bandgap of gallium
nitride (GaN)). To date, lasing of nanolasers
in the UV region is a long-standing goal that
has been eagerly pursued in white light, information storage, and biomedical science
across a wide variety of applications.[1–3]
In light of this, the exploration of materials emitting in the UV spectral region as
relevant alternatives to the existing GaN
and aluminium GaN (AlGaN) materials
is essential to achieving UV nanolasers,
that are compatible with the fabrication
J.-M. Liu
Institute of Photonics
National Yang Ming Chiao Tung University
Tainan 711010, Taiwan
J.-M. Liu
Institute of Optoelectronics
National Chung Hsing University
Taichung 402202, Taiwan
C.-Y. Lo
Department of Optoelectronics and Materials Technology
National Taiwan Ocean University
Keelung 202301, Taiwan
Y.-J. Chen
Department of Materials Science and Engineering
National Dong Hwa University
Hualien 974301, Taiwan
J.-Y. Yi
Department of Electrical Engineering
National Kaohsiung Normal University
Kaohsiung 824004, Taiwan
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requirement of silicon-based on-chip microelectronic manufacturing. For this purpose, two recognized requirements have to
be fulfilled: i) An easily accessible wide-bandgap optical gain
medium for monolithic integration with Si has to be developed.
ii) Efficient UV lasers operating at room temperature (RT) require effective cavity feedback, efficient optical amplification, and
high optical gain. These two requirements are of concern to ultracompact all-optical interconnect on silicon (Si).[4]
In place of using bulky solid-state lasers via off-chip nonlinear frequency conversions for UV laser emission, the use of
wide-bandgap materials as active nano emitters that emit directly in the UV region engenders superior features, including miniaturization and compatibility with chip-level integration.
Within the family of wide-bandgap materials, zinc oxide (ZnO) is
one of the most widely used metallic oxide semiconductors for
UV light-emitting diodes and laser diodes because of its naturally wide bandgap in the near-UV region and its large exciton binding energy. However, the poor crystal quality and defectrelated deep-level emission of the p-type wide-bandgap ZnO are
of great concern,[5] which precludes the interest in developing
UV-luminescent homojunction devices through a facile route at
a competitive cost (Table S1). As an alternative, group III‒nitride
semiconductors have proven feasible under optical pumping in
the UV band (Table S2). However, some problems with the Alrich AlGaN epilayers arise with regard to their low crystal quality,
high dislocation density, and large residual strain. Moreover, owing to the delicate growth procedure and the prerequisite expensive equipment, successful development of GaN nanolasers that
lase at wavelengths shorter than 360 nm has hitherto been hindered, thus severely restricting the feasibility of GaN nanolasers
for practical applications (Table S3).
Among the existing nanolaser schemes, metal‒semiconductor
heterojunctions and plasmonics are at the heart of present
electrically driven nano-electronics and nano-photonics.
Despite the success in realizing nanolasers using either
metal‒insulator‒metal
or
metal‒insulator‒semiconductor
architectures,[6,7] the insulating barrier limits the implementation of on-chip electrically driven lasers. Moreover, the
abovementioned success significantly depends on ultra-flat
single-crystalline metal films that require atomically controlled
growth involving expensive interfacial epitaxy.[8–12] This severely
hinders the development of facile and cost-competitive fabrication processes for future mass production. The ideal feature
of a plasmon-enhanced UV laser with a metal‒semiconductor
heterojunction scheme is a spectral overlap between the surface
J.-Z. Huang, C.-C. Lai
Department of Opto-Electronic Engineering
National Dong Hwa University
Hualien 974301, Taiwan
C.-D. Liao
R&D Center
Taiwan Semiconductor Manufacturing Company
Hsinchu 300091, Taiwan
M.-Y. Lin
Department of Dermatology
National Taiwan University Hospital and College of Medicine
National Taiwan University
Taipei 100229, Taiwan
Adv. Sci. 2023, 2301493
plasmon resonance (SPR) of the hot spot and the photoluminescence (PL) of the gain medium. Thus, the combination of
bandgap engineering and surface-plasmon-enhanced luminescence in heterostructures has been considered as an effective
bridge between on-chip nano-photonics and micro-photonics.
However, this spectral overlap requires bandgap alignment and
shifts, which are difficult to accomplish. For most plasmonic
nanolasers that operate after being separated from the substrate,
either pumping above a megawatt cm−2 -level threshold or operating at a cryogenic temperature is needed to overcome the large
ohmic losses and the low modal reflectivity. These limitations
make monolithic fabrication impossible. To this end, the design
of effective cavity feedback of SPR and the use of accessible laser
materials that are compatible with existing Si-based photonics
are highly desirable.
Herein, we focus on the use of the low-cost and
semiconductor-manufacturing-compatible bismuth (Bi) as a
UV hybrid photonic‒plasmonic host.[13–17] To date, it remains
challenging to fabricate large quantities of high-quality 1D Bi
nanostructures.[18–20] In this work, we experimentally demonstrate a fabrication process of combining the UV SPR-coupled
architecture with eco-friendly and low-cost Bi nanowires (NWs)
by using a simple, scalable, and template-free vapor‒solid (VS)
technique.[21–25] The developed and modified VS technique
requires neither an inert environment, nor any costly noble
metal, nor an epitaxial system. It thus possesses many attractive advantages such as a low cost and a fast growth rate. By
exposing the Bi NWs to an oxygen-containing atmosphere, a
self-terminating bismuth oxide (Bi2 O3 ) shell naturally forms
on each of the as-grown high-yield Bi NWs due to its negative
Gibbs free energy.[26–28] As the gain medium, the NWs have the
core‒shell metal‒semiconductor heterostructure with a 100-fold
improvement in density over existing gain materials for UV
emission.
Specifically, the UV SPR excited at the Bi/Bi2 O3 heterojunction
interface can modulate the local field and further overcome the
optical loss. It is then outcoupled to the Fabry‒Pérot (F‒P) lasing
modes. Hence, the Bi NW lasers outperform other NW lasers by
simultaneously providing a low lasing threshold of ≈12 kW cm−2
and a remarkably high spontaneous emission coupling factor 𝛽 of
≈0.32 at RT. In contrast to most single-NW lasers, the enhanced
Fresnel reflection of ensemble NWs can suppress the optical loss
and preferentially enhance the radiative photons by up to 100
folds through a hybrid SPR-coupled F‒P microcavity, suitable for
monolithical on-chip silicon integration. It is in principle an ideal
form for the nanolasers in light of the essential requirements of
facile fabrications, competitive cost, and effective miniaturization
for industrial mass production.
2. Results and Discussion
2.1. Investigation of Core‒Shell Metal‒Semiconductor
Heterojunction NWs
Numerous modified growth techniques have been developed
over the past decades; however, each of these approaches suffered from expensive equipment, time-consuming procedures,
or complexity from vapor deposition. Here, a controlled lowcost VS technique, by which target sources are deposited on a
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Figure 1. Morphological characterizations of a core‒shell metal‒semiconductor heterojunction NW device. a) Schematic of a dense and oriented NW
array realized by the scalable, high-yield, and template-free VS technique. b,c) Planar- and side-view SEM images of densely packed heterojunction NWs
directly grown on silicon, showing an average thickness of ≈6.1 μm. d) Low-magnification TEM image of a single truncated NW with a conical tapering
as further resolved in Figure 2.
crystalline substrate, is the key to delivering dense Bi-core Bi2 O3 shell heterojunction NWs on a Si substrate. Thermodynamically,
the high-throughput VS growth in our work can be ascribed to
a synergistic effect from the small millimeter distance and the
large thermally-induced stress at a high temperature (Figure
S1, in which the thermally induced compressive strain occurs
between the Bi film and the substrate). The details of the fabrication, characterization, and growth of these NWs are described
in Figures S2–S6, Sections S1–S3, and Section S8 (Supporting
Information).
A device configuration, consisting primarily of a thin native
SiO2 layer along with Bi nanograins beneath dense Bi-core Bi2 O3 shell heterojunction NWs, is schematically illustrated in Figure
1a. For the sample analyzed here, the average thickness of the
core‒shell heterojunction NWs is ≈6.1 μm and the average diameter is ≈50‒100 nm, corresponding to a surprisingly high density of ≈3×109 cm−2 (refer to Discussion in Supporting Information for details), as assessed from planar-view and side-view scanning electron microscopy (SEM) images (Figure 1b,c; Figures
S4 and S6, Supporting Information) together with lengthwise
cross-sectional transmission electron microscopy (TEM) images
(Figure 2 and Figure S5, Supporting Information). Since all the
NWs are oblique, the average length of the NWs is greater than
the thickness. By scrutinizing >20 cross-sectional SEM images,
the average length of the core‒shell heterojunction NWs is found
to be ≈7.8 μm.
In the low magnification high-resolution TEM (HRTEM)
image shown in Figure 1d, the truncated core‒shell NW exhibits a strong tapering located near the apex, giving a conical
growth front of a high aspect ratio (i.e., length-to-diameter ratio). The highest aspect ratio is 78 to 156 (i.e., 7.8 μm/100 nm
Adv. Sci. 2023, 2301493
to 7.8 μm/50 nm). As a promising alternative to costly indium
tin oxide, high aspect-ratio NWs as transparent conducting electrodes have demonstrated exceptional levels of electrical performance and mechanical flexibility.[29–32] However, the facile, lowcost, and reproducible production of extremely dense and high
aspect-ratio NWs, which is critical for achieving novel nanodevices, remains challenging.
Our strategy presented here differs conceptually from previous studies on forming low-density Bi NWs. The previously
recorded values of Bi NW density were of the order of only
104 to 107 cm−2 .[20,33,34] Thanks to the millimeter-spacing sublimation and the high-temperature-induced stress, it was expected that there would be a thin supporting Bi film containing a substantial amount of tiny grains (Figures S4 and S5, Supporting Information).[35] The presence of tiny grains promotes a
high growth density that is different from the low growth density resulting from larger grain sizes (i.e., thicker Bi film).[36]
Figure 2a shows the HRTEM image of a representative NW,
and Figure 2b,c shows the corresponding selected area electron
diffraction (SAED) pattern and restructured lattice image, respectively. These images indicate an atomically abrupt core‒shell
metal‒semiconductor heterojunction. The core arranges in a
close-packed manner of rhombohedral Bi lattice as well as in
̄ growth direction as reported earlier.[33,35–41]
the reciprocal [011]
̄
Note that the [011] direction in the rhombohedral structure is
[110] in the hexagonal structure. Sharp and bright SAED spots are
clearly visible in Figure 2b, demonstrating a high-crystallinity Bi
̄
core that is predominantly perpendicular to the [100]
zone axis
when viewed edge-on. The shell formed by native oxidation is
a self-terminating Bi2 O3 semiconductor, which preserves the Bi
crystalline core, as found for aluminium, copper, and gallium,
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Figure 2. Nanostructure characterizations of the core‒shell metal‒semiconductor heterojunction NWs fabricated by the high-yield VS technique and
the high-temperature treatment. a) Atomic lattice image coupled with b) its SAED pattern of the NW in Figure 1d, indicating that the Bi crystal core is
free of defect and encapsulated by an amorphous 𝛽-Bi2 O3 thin shell with a tapered feature. c) Reconstructed lattice image of (a) by the inverse Fourier
̄
transform using all the diffraction spots revealing a high crystallinity with a rhombohedral structure having well-developed crystalline facets in the [100]
zone axis. d,e) Low-magnification TEM image showing a growth direction along the [012] of the hexagonal structure as outlined by its SAED pattern in
(e). f) Representative high-angle annular dark-field image showing a bifurcated core surrounded by a protective shell with an amorphous signature. g)
Raman signal showing a predominant crystalline Bi core with an amorphous 𝛽-Bi2 O3 shell having a frequency-shift than those of Bi bulk (refer to text).
h) XPS spectrum of the same sample in Figure 1. Note that no relevant signals of bi-, tetra-, or penta-valent states were detectable in all the samples,
implying that the oxide shell consists primarily of a Bi (III) oxidation state. i) XRD trace with sharp diffraction of the orientations labeled, indicating the
̄
crystallization of metallic Bi (space group: R3m)
of rhombohedral structure on a cubic Si substrate.
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respectively.[42–44] This result is consistent with the Raman and
X-ray diffraction (XRD) data (addressed in the following).
Further examination of certain NW apexes using TEM shows
another growth direction along <012> in the hexagonal scheme
(Figure 2d,e, and Figure S5, Supporting Information), besides
aforementioned predominant <110> for a Bi NW. This protective oxide shell of a thickness of a few to tens of nanometers also
acts as the active luminescent gain region for this study (Figure 2f
and Figure S5, Supporting Information), as discussed further in
the following. It is also noteworthy that, on careful inspection using SEM (Figure S6, Supporting Information), the presence of
cross-over originates from the difference in anisotropic growth
rates that account for the length differences among NWs shown
in Figure 1c, by analogy to the NWs grown by the physical vapor
deposition.[45] These evidence also supports that the Bi NWs were
grown through the preferential surface diffusion of Bi atoms
from their base Bi thin film in such a manner that they have
well-developed crystalline facets at the core–shell interface. From
the above atomic-scale inspections, it can be concluded that the
core‒shell NWs presented here have these prominent features:
i) the core–shell interface is atomically sharp, and the shape and
growth facet are well-defined; ii) each core‒shell NW shows high
crystallinity, thus superb plasmonic properties essential for an efficient nanophotonic device; iii) the proposed and demonstrated
synthesis method is facile and easy to cost-effectively scale up for
the present Si manufacturing on account of its simple process
and high-yield nature without using sophisticated equipment.
Although HRTEM is a promising technique for the characterization of the degree of crystallinity of NWs, it is rather difficult
to verify the overall crystalline quality on the micrometer scale
by using this technique. Alternatively, the confocal Raman microscopy with its direct and rapid testing nature has been employed to study the NW quality with a submicron spatial resolution. Based on the Gaussian beam relation (refer to Section
S5, Supporting Information), we can estimate the focus spot diameter at the 633-nm wavelength to be 310 nm (or a radius of
155 nm), which contains a few NWs. In the experiment, a longer
exposure time of several minutes was required to acquire substantial Raman signals. As presented in Figure 2g, two prominent Raman peaks can be specified based on the group theory
prediction. The doubly degenerate Eg (≈72 cm−1 ) and the nondegenerate A1g active modes (≈97 cm−1 ) are due to the Bi metal
core, whereas the broad and faint vibration hump (≈312 cm−1 )
belongs to featured Bi-O bond stretches and can be assigned to
the 𝛽-Bi2 O3 semiconductor shell,[46] as identified by the HRTEM
images mentioned above. The observed Bi Raman peaks exhibit
a frequency shift as compared to those of Bi in the bulk form
(71 and 98 cm−1 );[47] this frequency shift may be elucidated by
quantum confinement effects in view of a relatively large lengthto-diameter ratio,[48–50] as described above.
To further confirm the presence of an oxide phase within
the NWs, the quantitative compositions of the NWs were analyzed by X-ray photoelectron spectroscopy (XPS) recorded over
a millimeter-sized area. Figure 2h shows the high-resolution
XPS spectrum of the Bi 4f state of an as-grown core‒shell
metal‒semiconductor heterojunction NW sample fitted with a
Gaussian shape, which reveals two symmetrical oxide shell spectra (Bi2 O3 4f7/2 and 4f5/2 at 158.8 and 164.1 eV, respectively) aside
from two broad sidebands of the metallic core (Bi 4f7/2 and 4f5/2 at
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157.6 and 162.7 eV, respectively). Both the locations of the peaks
and their separation (≈5.3 eV) are consistent with those reported
in the literature.[51,52] From Figure 2h, the Bi3+ peaks are predominant and the Bi0 peaks are suppressed because the depth of analysis for an XPS measurement is typically <10 nm.[53] The same
sample was further verified by the XRD spectrum, confirming the
orientation and the high crystallinity of the as-grown core-shell
heterojunction NWs on a Si substrate (Figure 2i). Achieving lasing in the UV region requires a high structural factor and thus a
good internal quantum efficiency. The XRD pattern is indexed to
a well-crystallized rhombohedral Bi structure (Joint Committee
̄
on Powder Diffraction Standards No. 05–0519, R3m),
and it suḡ and [110] perpengests a growth direction of the NWs with [011]
dicular to the substrate. Distinct XRD signals are observed, indicating the presence of lattice planes and hence a single crystalline
phase, as supported also by the HRTEM investigation (Figure 2
and Figure S5, Supporting Information). These observations unambiguously confirm that the pristine Bi core provides the template for native oxidation, bridging the core and the outer 𝛽-Bi2 O3
shell together. The above results clearly provide direct information about the core‒shell heterojunction structure and the presence of quantum confinement in the sample.
2.2. Correlation between Photonics and Plasmonics among
Core‒Shell Metal‒Semiconductor Heterojunction NWs
Most SPR-assisted nanolasers have, so far, used exorbitant and
scarce noble metals, such as gold (Au) or silver (Ag), which are not
compatible with microelectronic manufacturing technologies. In
this study, we focus on the use of cost-effective Bi as an efficient
UV scatterer because of its availability, facile synthesis, and microelectronic compatibility.[13,14] In fact, Bi has been the SPR material of choice for broad tunability across the UV and visible
(VIS) spectral regions.[15–17,54]
Figure 3a shows the real (𝜖 r ) and the imaginary (𝜖 i ) parts of the
dielectric function of metallic Bi, along with those of two widely
used plasmonic materials, Au and Ag, for comparison. As seen
in Figure 3b, it is important to point out that the dielectric response of Bi falls in the UV region (<360 nm), which leads to an
enhancement factor, EF, of the SPR intensity to be higher than
those of the noble Au and Ag. The enhancement factor is defined
as[55]
EF =
[
]
2
2(𝜀(𝜔) − 1) 2 (2𝜀r − 2) + 4𝜀2i
|E|2
=
=
𝜀(𝜔) + 2
|E0 |2
(𝜀r + 2)2 + 𝜀2i
| |
(1)
where |E0 |2 is the intensity of an external field. As shown in
Figure S7 (Supporting Information), Bi has a higher EF than
those of common toxic and costly plasmonic metals of gallium and indium in the 300‒400 nm wavelength range because of its negative real dielectric response.[42,55–57] The literature values shown in Figure 3a for Bi, Au, and Ag are from
Toudert,[15] McPeak,[58] and Werner,[59] respectively. The parameters from Toudert in a Bi nanostructure were chosen as a reference throughout this work. We reasoned that those highly dense
core‒shell NWs would create considerable plasmonic hot spots
in the near field, which in turn would greatly promote sustained
optical gain, as discussed in detail below.
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Figure 3. Spectroscopic characterizations and lasing performance of a core‒shell metal‒semiconductor heterojunction NW device. a) Theoretical dielectric functions of Bi, Au, and Ag, which were employed for the extracted enhancement factor, EF, in (b). 𝜖 i and 𝜖 r represent the real and the imaginary
parts of the dielectric function, respectively. b) Predicted EF for the SPR in Bi, Au, and Ag, respectively, indicating the potential of Bi as an efficient SPR
agent below ≈360 nm. c) Extinction, PL, and CL spectra of the demonstrated heterojunction NW device, shown alongside the extinction spectrum of
pure 𝛽-Bi2 O3 shell for comparison. An overlap between the extinction (purple) and PL (red) spectra ensures efficient SPR coupling, leading to a strong
interband transition for spontaneous emission and, thus, an enhanced stimulated emission. The main reason for slow modulations (denoted by the
gray arrows) is given in the main text. d) Nanolaser performance with increasing excitation power density in linear scale clearly shows a threshold of
≈12 kW cm−2 . The solid curve is a fit to rate equations (for details see Section S6, Supporting Information). e) Representative emission spectra below
and above the lasing threshold. f) Pseudo-color map of primary lasing peaks under various excitation levels, suggesting that the resonance modes were
effectively amplified among the NWs, as detailed in Figure S11 (Supporting Information).
Leveraging on the wide-bandgap nature of 𝛽-Bi2 O3 ,[60,61] the
heterojunction NWs could engender UV operation at wavelengths much shorter than those previously obtained from
conventional GaN or ZnO materials. To study the contribution
of the SPR from the Bi cores, one of the as-grown samples (Bi
core with 𝛽-Bi2 O3 shell) was intentionally treated in an oxygen
condition and thereby was fully transformed into 𝛽-Bi2 O3 NWs
for comparison, as confirmed by the Raman measurement in
Figure S8 (Supporting Information). Figure 3c presents the
extinction spectrum of pure 𝛽-Bi2 O3 NWs (blue), as well as the
extinction (purple) and PL (red) spectra of our device (i.e., Bi-𝛽Bi2 O3 core‒shell NWs); in the core‒shell structure, the 𝛽-Bi2 O3
shell serves as the gain medium in this study. From Figure 3c,
the ensemble of pure 𝛽-Bi2 O3 NWs has an extinction spectrum
peaked at ≈230 nm, corresponding to a bandgap energy (Eg ) of
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≈4.4 eV (Figure S9, Supporting Information), analogous to the
case prepared in a hydrothermal reaction (≈4 eV).[61] Notably,
the measured blueshifted bandgap of the pure 𝛽-Bi2 O3 NWs in
comparison with that of bulk forms (≈2.3‒2.6 eV) seemingly
reveals the effect of quantum confinement due to the small NW
size,[61–65] which is similar to gold and silver nanoforms.[66–69]
The above result is supported also by the Raman investigation
(Figure 2g). Further, the observed extinction spectrum of the
as-grown core‒shell heterojunction NWs exhibits a large broadening and a redshift (purple, Figure 3c), which also indicates that
the ensemble Bi NWs are distinctly inhomogeneous in either geometry or orientation, as previously demonstrated in disordered
plasmonic nanostructures.[28,70,71] This feature can be inferred
from both SEM and TEM images (Figures S1, S4, and S5,
Supporting Information). Apparently, in our case, the significant
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orientation dispersion enables multicolored tuning of SPR over
a broad UV‒VIS region rather than an ordered conformation.
The red curve in Figure 3c is a representative PL spectrum
of ensemble heterojunction Bi NWs. This spectrum has a feeble emission band of a power density lower than 1 kW cm−2
at 290 nm, which is attributed to the near-band-edge transitions, and two broad and dominant luminescence peaks in the
325‒600 nm range originated from the trapping state and the
electron-hole recombination of band transition, respectively, as
observed in 𝛽-Bi2 O3 nanoflowers and nanohooks.[60,72–75] Meanwhile, the clear luminescence peaks at ≈340 and 510 nm in
the cathodoluminescence (CL) spectrum of single heterojunction
NW (orange, Figure 3c) are indicative of the PL spectrum (red,
Figure 3c) of an ensemble of heterojunction NWs. Further, as
summarized in Figure S10 (Supporting Information), the exemplary CL spectra of three individual NWs for the present sample were observed to vary from one NW to another (i.e., positiondependent CL emissions); however, they exhibited a similar spectral feature, i.e., a board emission in the 300‒600 nm range. This
also suggests that the measured PL of the device is the emission
of an ensemble of Bi NWs.
Surprisingly, notwithstanding the previously reported broadband characteristic of UV-excited PL spectrum,[72,73,76–79] the PL
spectrum of our NWs for excitation at a power density higher
than 1 kW cm−2 shows much more distinct cavity modes protruding at ≈340 nm rather than at ≈350 nm for excitation at a power
density lower than 1 kW cm−2 . We ascribe this blueshift to the
band-filling effect because the measured shift of the optical-gain
peak with excitation is in good accordance with the peak of the
extinction spectrum at ≈340 nm (refer to Figure S11a, Supporting Information). The spectral widths of the optical-gain peak in
Figure S11b are found to be from 11 to 28 nm for the four cavity modes, which discretize the broad PL spectrum (Figure 3c).
This feature indicates the effective cavity resonance established
by densely packed core‒shell NWs, which provides the necessary
feedback for lasing. The process is similar to the optical feedback via total internal reflection in a plasmonic laser of thin CdS
nanosquares,[80] as inferred from the mode selection addressed
later.
Typically, periodic spectral fluctuations would occur in the extinction and PL spectra owing to the F‒P interference. In the
extinction spectrum, distinct oscillation peaks were not found,
but slowly modulated patterns were generated, as denoted by the
gray arrows in Figure 3c. This is attributable to the tapered apexes
with sharp corners relative to those with rounded structures.[81]
The extinction properties for a specified plasmonic nanostructure are significantly affected by the increase in the number of
nanocones, as shown in the present study. Polarization dependence has been shown to modify the resonance signature of extinction responses.[82] In our experiment, unpolarized white illumination was used, which may be another dominant factor that
diminishes the oscillatory behavior.
Based on the guided PL spectrum shown in Figure S12 (bottom panel), the comparative spectral responses indicated consistency among several oscillatory peaks marked by the dashed
lines. Because the direction of the polarized excitation field can be
unrestrictedly rotated during the experiment, it was obtained by
slightly adjusting the incident polarization. The spectral modulation in the guided PL spectrum would be further suppressed ow-
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ing to the strong optical absorption of the metallic Bi core across
the entire spectral region, as observed in the case of core‒shell
NWs.[83] Based on the metallic absorption-loss spectrum shown
in Figure S11b (Supporting Information), the linewidth broadening of the cavity modes reflects the energy loss within the device,
i.e., the linewidth of the resonant cavity modes increases gradually with the emission wavelength, and the parasitic metallic loss
exhibits the same trend.
In a core‒shell heterostructure, it is speculated by considering the large surface-to-volume ratio of core‒shell heterojunction
NWs that the 290-nm near-band-edge emission is governed by
the quantum size effect because bulk 𝛽-Bi2 O3 crystals exhibit no
PL.[84] This result corroborates the aforementioned Raman spectra and blueshifted bandgap obtained from ensemble Bi-core 𝛽Bi2 O3 -shell NWs and pure 𝛽-Bi2 O3 NWs, respectively (Figure 2 g
and Figure S8, Supporting Information). In the present case,
strong UV scattering becomes prevalent as the PL spectrum is
well within that of the SPR of the core‒shell heterojunction NWs.
Figure 3c also clearly shows that the emitted photon energy of
the 𝛽-Bi2 O3 -shell NWs at 350 nm is in satisfactory agreement
with the SPR energy of the Bi core at 330 nm. Despite the fact
that the optical loss in Bi metals is larger than that in 𝛽-Bi2 O3
semiconductors, a Bi metal core not only enhances plasmonic
absorption but also facilitates the plasmonic gain, leading to an
overall resonance-dependent net gain.[85] Based on this result,
as of concern to a potential plasmonic nanolaser, it is expected
that the strong SPR coupling allows an interband transition and
further readies band-to-band recombination for efficient spontaneous and stimulated emissions from the core‒shell heterojunction NWs.
2.3. UV Low-Threshold Lasing in a Photonic‒Plasmonic-Coupled
NW Device and its Underlying Mechanism
In conjunction with the VS technique endowed with inherently easy handling, and high yield yet high crystallinity, we
demonstrate that achieving the densely disordered NWs and
optically flat F‒P microcavity formed by a naturally formed
metal‒semiconductor heterostructure. These NWs represent
a significant step toward the SPR-coupled nanoemitter. The
photonic‒plasmonic-coupled NW ensemble is optically pumped
by a 263-nm nanosecond-pulsed laser at RT (Figure S3, Supporting Information). Figure 3d shows that the integrated output intensity and the full width at half-maximum (FWHM) of its
spectrum against the excitation power density follow a nonlinear response, delineating clear features of the onset of lasing. We
spectroscopically observed an FWHM reduction from the typical
broad spectral width of the PL down to ≈0.7 nm when the excitation power density was increased, as observed for the disordered
nanolaser analogy.[86] This characteristic demonstrates that the
cavity modes are selectively amplified by optical feedback in the
dense heterojunction NW cavity. Importantly, Figure S13 (Supporting Information) shows the interference fringes above the
laser threshold; furthermore, it clearly indicates the onset of lasing. Figure S14 (Supporting Information) shows a photograph of
the far-field pattern of the lasing output, where a sensor card was
placed 30 cm in front of the nanolaser device. The high directionality and coherence of the device were demonstrated.
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The representative emission spectra for different excitation
power densities below and above the lasing threshold are shown
in Figure 3e. Nearly equidistant longitudinal modes at 340.1,
350.1, and 360.0 nm can be clearly resolved. At an excitation level
above 12 kW cm−2 , the emission remarkably intensifies, and the
mode at 340.1 nm stands out over the broad spontaneous emission band with a significantly reduced FWHM down to ≈0.7 nm.
(The observed lasing linewidths of ≈0.7 nm were limited by the
resolution of the detection system.) Thus, the lasing threshold is
determined to be at 12 kW cm−2 . Above the lasing threshold, the
FWHMs of the three adjacent lasing modes are all below 0.8 nm
(Figure S15), far narrower than that of the broad PL spectrum.
The narrowed linewidths are comparable with the previously reported RT UV lasers (Tables S1‒S3, Supporting Information),
confirming that the observed sharp spectral peaks represent UV
lasing. It should be noted that the f-element lanthanides typically
result in a set of narrow lines. However, severe lanthanide-related
signals would occur in both the XPS survey scan (Figure S2, Supporting Information) and Raman spectrum (Figure 2g) if they
were included in this study. XPS and Raman analyses can provide direct elemental information regarding the presence of unintentionally introduced dopants owing to their high quantitative
and qualitative sensitivities. Notably, we have never performed
lanthanide-based experiments previously; hence, contamination
can be precluded.
Moreover, from the SEM image in Figure 1c, the cavity length
L is ≈6.1 μm; therefore, the corresponding lasing wavelength 𝜆L
for the lasing mode can be theoretically predicted by introducing the mode spacing △𝜆 and the effective refractive index n
into the classical F‒P cavity model: 𝜆L 2 = △𝜆{2L[n-𝜆L (dn/d𝜆L )]}.
The effective n is estimated by considering both the core-to-shell
volume fraction (≈70%) and the filling factor (≈17.5%). Figure
S16 (Supporting Information) presents the corresponding dispersion relation. By taking △𝜆, L, and n to have the values of
10 nm, 6.1 μm, and 1.23, respectively, the value of 𝜆L is found
to be ≈349.3 nm, which is close to the experimentally observed
value of 350.1 nm determined from the lasing spectrum shown
in Figure 3e, thus verifying that the laser action arises from a vertical F‒P microcavity. Furthermore, the presence of a series of
narrow lasing peaks also indicates that the top and bottom end
faces of the densely packed NWs effectively act as two partial mirrors for the F‒P microcavity.[87]
By using our proposed technique, high-quality Bi NWs can be
facilely grown, with a precisely controlled thickness, on a Si substrate. Although some of the Bi NWs protruded from the surface
of the ensemble NWs (Figure 1c), we discovered that they minimally affected the resonance when the amount of protrusion in
the present sample was significantly lower than that in the ensemble counterpart. On the other hand, because the free spectral
range is governed by the thickness of the Bi NWs, the variation in
the lasing peaks is attributable to the thickness-dependent optical
properties. However, we observed the lasing behavior only in the
sample with an average thickness of ≈6.1 μm. One important parameter that determines the laser action is the net optical gain of
the device, which is related not only to the enhanced plasmonic
gain but also to the metallic absorption loss. For a thinner sample,
the most intuitive conclusion may be a reduction in the hot-spot
densities when the thickness decreases, which consequently re-
Adv. Sci. 2023, 2301493
sults in an insufficient plasmonic optical gain. By contrast, as the
sample thickness increases, the metallic core volume increases
significantly within the device, thus resulting in a high metallic
absorption loss. This may be related to the absence of laser action
in a thicker sample.
Yet, at this stage, the typical photonic model is inadequate
for explaining the observed narrow lasing linewidths on account
of the low reflectivities at both the air/NWs and the NWs/Sisubstrate interfaces, which could be alternatively attributed to
the enhanced light‒matter interactions within the core‒shell heterojunctions, as further discussed below. Figure 3f presents the
representative spectral map as a function of the excitation power
density. It is apparent that the lasing peaks are fixed and independent of the excitation level above the threshold. This result
supplies further evidence that the UV lasing does not stem from
the resonant feedback in a closed-loop light-scattering manner, as
usually found for random schemes.[88–90] Having demonstrated
that UV lasing in naturally formed heterojunction NWs and light
confinement in the vertical microcavity was well interpreted by
the F‒P model, here we raise another question: it is intriguing to
speculate whether the aforementioned lasing behavior only originates from general F‒P resonance. Remarkably, on the basis of
a rate-equation model (see Figure 4a and Section S6, Supporting Information), the theoretical fit and the measured data agree
well (Figures 3d and 4b), manifesting the low-threshold UV lasing from the synergistic photonic‒plasmonic coupling, as elaborated in detail below. Note that the metallic absorption-loss spectrum (Figure S11b, Supporting Information) shows considerable
energy losses across the entire spectral region. This implies that
whereas light is incident on the test samples, the PL emission is
relatively weak at excitation intensities below 1 kW cm−2 , as similarly indicated by the x-axis intercept of both the simulation and
experiment.
Meanwhile, an analysis of Figure 3d yields a high coupling factor of 𝛽 ≈0.32 (Figure S17 in Supporting Information). This is
also evidenced by the temporal development of laser spiking associated with relaxation oscillations, in which the turn-on surge
emerges as the round-trip gain overcomes the total round-trip
loss (Figure 4c,d). It is also noteworthy that the lasing threshold
is as low as 12 kW cm−2 , which is the lowest ever reported among
nanolasers operated either at RT or at a wavelength shorter than
360 nm (Tables S1‒S3, Supporting Information). Furthermore,
the output intensity of the same device against the input power
density was tested again after one year, as shown in Figure S18a
(Supporting Information). Although the lasing threshold was
slightly increased to ≈13 kW cm−2 , in conjunction with the spectral evolution shown in Figure S18b (Supporting Information),
the strong emission clearly indicates the robust reliability of our
NW device and that of the demonstrated VS technique for mass
production.
Given the exceptionally low-threshold and high-𝛽 lasing at RT,
we then delved deeper into the effect of the photon‒plasmon coupling strength on the laser action and its underlying mechanism.
Phenomenologically, we simulated the intracavity properties
without and with involving plasmonic couplings to unravel their
spectral responses. In this regard, the corresponding enhanced
effective reflectivity was thus obtained. The spectrum in the
top panel of Figure 5a was determined by the classical F‒P
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Figure 4. Temporal dynamics of the hybrid photonic‒plasmonic-coupled F‒P nanolaser. a) Schematic of the resonant intermodal coupling between the
photonic cavity modes and the SPR-enhanced modes. b) Dependence of the lasing intensity on the incident power density, the same data presented in
Figure 3d. The solid curve was simulated for the experiment using a coupled time-dependent model having a high 𝛽 factor of 0.317. c,d) Turn-on lasing
dynamics of the excited-state carrier number (N2 ) and the photon intensity (IL ), showing the transient state from spontaneous emission to stimulated
emission.
model (Equation (2)) without plasmonic coupling, whereas that
in the center panel of Figure 5a was calculated by using the
finite element method (FEM) via a variable frequency to excite
the hybrid photonic‒plasmonic modes (details refer to Section
S4, Supporting Information). Note that, due to the intrinsically
dense nature of the core‒shell heterojunction NWs, one can
reasonably simplify the present form, comprising of denselypacked NWs standing on a thin supporting Bi/Bi2 O3 interlayer,
as an F‒P thin film on a Si substrate, as schematically illustrated
in Figure 1a. Herein, the intracavity spectral response I due to
interference within the thin film of a thickness d can be extracted
based on the known relation in terms of the intensity of the
incident wave I0 , the reflectivities R1 and R2 at the air/NWs
Adv. Sci. 2023, 2301493
and NWs/Si-substrate interfaces, respectively, and the refractive
index n, through the longitudinal mode function:[91]
)2
√
√
I0 (
= 1 − R1 R2 + 4 R1 R2 sin2 (𝜋nd∕𝜆)
I
(2)
In the above expression, the employed values of I0 , R1 , R2 ,
n, and d for the core‒shell heterojunction NWs were 1, 1.03%,
38.48%, 1.23, and 6.1 μm, respectively. Even though the oscillatory characteristics in the top panel of Figure 5a exhibit strong
modulations and the positions of maximum intensities correspond well to those of the experimentally observed lasing peaks
(bottom panel, Figure 5a), its rather broad undulating FWHMs
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Figure 5. Simulated spectral and spatial responses of the hybrid photonic‒plasmonic-coupled F‒P laser action. a) Top panel: plot of spectral response
calculated by Equation (2) showing a rather broad modulation due to multiple interferences at each interface, as expected from the classical Fresnel
relation. Center panel: FEM simulated spectrum with plasmonic coupling, showing a series of narrow resonances with the F‒P characteristics in good
agreement with the experimental spectrum given in the bottom panel. Bottom panel: Experimentally recorded lasing spectrum. b) Computational model
reconstructed from a realistic NW geometry based on SEM and HRTEM images. c) Spatial E-field maps of (b) for in-plane and out-of-plane polarization.
d) Plot of the E field between the two adjoining NWs for a slice of the E-field intensity (red dashed line in (c)) from the top to the bottom. e,f) Enlargements
of (c) on the top and the bottom of the NWs, witnessing the synergy of localized SPR and the significant standing-wave character. Blue represents zero
E field; red max E field.
do not support the result of narrowed lasing linewidths. The narrowed linewidth features multiple interferences within a thin
layer with two partially reflective mirrors formed by Fresnel reflections. Undoubtedly, the low reflectivities, R1 (≈1.03%) and R2
(≈38.48%), of the two interfaces are not able to effectively sustain
the optical resonance, particularly for the stimulated emission,
which indicates that there are other mechanisms involved in the
UV laser action.
To further shed light on the contribution of the
photonic‒plasmonic-coupled lasing mode, we performed
2D FEM simulations to determine the spectral response (center
panel, Figure 5a) and the corresponding spatial map of the
electric field (E field) in both the xz and yz planes (Figure 5b–f).
This model was based on a realistic representation (i.e., the
average thickness, diameter, and spacing) of the core‒shell
nanostructures and the bottom supporting Bi/Bi2 O3 interlayer
and was constructed by identifying the morphology and geometry found in the aforementioned SEM and HRTEM images,
respectively. As seen in Figure 5a, the agreement between the
numerically simulated (center panel) and the experimentally
observed (bottom panel) spectra is excellent. This conspicuous
spectral correspondence in Figure 5a unambiguously manifests
that the SPs indeed play a key role in the low-threshold RT operation of the UV laser action. Note that to qualitatively reproduce
the plasmonic properties in a randomly distributed manner, the
Adv. Sci. 2023, 2301493
hot-spot features should be modeled in 3D space. However, 3D
disordered finite element modeling was not performed owing to
the significant amount of time and the corresponding computational burden required for solving 3D geometries. Hence, a 2D
periodically ordered model was used to model densely packed Bi
NWs. Our fabrication strategy indicated a 100-fold improvement
in growth density as compared with previous strategies. As
mentioned earlier, the present form comprising densely packed
NWs can be reasonably simplified to an F‒P thin film on a Si
substrate. Additionally, the effective cavity resonance established
by densely packed core‒shell NWs provides the necessary feedback for lasing. Meanwhile, the spectral agreement shown in
Figure 5a may be regarded as further support for validating the
abovementioned F‒P thin-film approximation.
A simulated spatial map of the E field among the NWs, which
is shown alongside that for a slice of the E-field intensity as a
function of the position in Figure 5d, is shown in Figure 5c.
The result presents a reasonable mimic of intermodal coupling, predicting many of its intriguing features. Particularly, the
photonic‒plasmonic-coupled resonances among the NWs have
primarily a standing-wave characteristic with much of the E field
localized in the periphery of the shell, as evidenced in the magnified images of Figure 5e. suggests the existence of centered
hot spots near the apex of the NWs because nanostructures with
sharp cones promote charge separation more easily than smooth
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shapes. It is clear that there are pronounced E-field enhancements on the top (Figure 5e) and the bottom (Figure 5f) of the
NWs owing to the unique tapered nanostructures.[92–94] Meanwhile, the randomness of the orientally tapered NWs provides
a variety of diameters, and it efficiently traps incoming photons
and transmits them down to the substrate,[95–99] as implied by
the broadband extinction spectrum presented in Figure 3c. Note
that Figure 5e depicts further evidence that the tapered apexes
function as nanoantennae and thus facilitate the coupling of incident light into SPR at the Bi/Bi2 O3 heterojunction interface.
Actually, the core‒shell metal‒semiconductor heterojunction is
expected to intensify the light‒matter interplays because of the
extent of hybrid coupling between the photons (i.e., photonics)
and the SPR (i.e., plasmonics).[100] In this connection, the gain
layer consists primarily of densely distributed nanometer-sized
apexes, leading to the generation of a substantial amount of the
strong and localized E fields across the whole F‒P microcavity
and hence the SPR-assisted UV laser action.
From the center panel in Figure 5a, we see that there are a considerable number of longitudinal modes within the gain bandwidth. A key factor is the wavelength range of the mode selection in relation to that of the parasitic metallic loss (Sections S7
and S9, Supporting Information). This is particularly clear as one
looks into the absorption and emission cross-sections. The oscillatory laser modes are determined by the optical-gain spectra and
the parasitic metallic loss. (Figure S19 and Section S10, Supporting Information). If a series of sharp emission lines were due
solely to F‒P resonance involving an emission cross-section that
is of the order of 10−13 m2 , then the optical gain of the material
is not able to overcome the intrinsic metallic loss across a broadband span (Figure S19a), suggesting no laser action. This is not
the case in reality. A refined calculation based on coupled rate
equations in which the emission cross-section is modified by a
100-fold enhancement highlights the requirement for adequate
net gain (Figure S19b). This result rationalizes the fact that the
SPR plays a key role in intensifying the effective amplification
and stimulated emission within the NW microcavity.
We now turn to consider the SPR-enhanced effects on the
effective cavity reflectivities, R, in our system. For our device,
an analytical expression in terms of the quality factor and the
parasitic metallic absorption loss at the lasing wavelength enables us to clarify the physical parameters in sustaining the stimulated emission (Section S11, Supporting Information). From
the derived R-value of ≈75.9%, it becomes evident that the SPR
effect is expected to significantly enhance the reflectivity. The
increased R can then overcome the intrinsically high metallic
loss and the low modal reflectivity, thereby achieving a lowthreshold UV nanolaser. The developed nanolaser can serve as
a compact and cost-effective alternative to either bulky solidstate or gas UV lasers emitting below 360 nm for bioanalytical applications.[101–103] Our proposed simple yet high-yield vapor‒solid technique does not involve expensive prerequisites but
enables a scalable yet low-cost approach for developing compact integrated devices. This technique is practical for a wide
range of metal‒semiconductor heterojunction NWs. Thus, by
adopting plasmonic aluminium,[58] indium,[55] or Ag,[104] we expect on-chip low-threshold heterojunction nanolasers for UV-B
(280‒320 nm), UV-C (< 280 nm), or VIS/near-infrared bands to
be realizable on Si substrates.
Adv. Sci. 2023, 2301493
3. Conclusion
In summary, we have experimentally demonstrated and theoretically studied the core‒shell metal‒semiconductor heterojunction
NWs that are grown directly on a large-area Si substrate as a route
toward a compact and low-threshold UV nanolaser. To fully meet
the requirements of facile and scalable fabrication, each of the
densely packed and optically flat metallic Bi cores of a high crystallinity was grown with a self-terminating Bi2 O3 native semiconductor shell, thus forming a vertical F‒P microcavity for the circulation of light through effective multiple reflections in each NW.
Unlike most single-NW lasers that lase after they are removed
from the substrate, we show that direct lasing of the ensemble
NWs on a Si substrate with enhanced Fresnel reflection between
two opposing parallel crystalline facets is possible because the
densely packed ensemble NWs that form the gain medium also
serve as an efficient F‒P resonator for the formation of cavity
modes. Additionally, the good overlap between the SPR band and
the PL spectrum of the optical gain material delineates beneficial
SPR-field enhancement that underpins the PL enhancement by
up to 100 times. In light of this, through the intermodal coupling
between the photonic cavity modes and the plasmonic resonance
modes, UV lasing with a record-low threshold and a high-𝛽 factor were successfully achieved. The results presented in this paper demonstrate the promising prospects of the proposed heterojunction platform for the integration of active optical devices in
silicon-based nanophotonic systems.
Supporting Information
Supporting Information is available from the Wiley Online Library or from
the author.
Acknowledgements
J.Y.S and D.H.N contributed equally to this work. The authors were grateful
to R. C. S from Delta Electronics for his support in numerical calculations.
The authors also thank L. C. W, Y. W. C, and M. L. L for their assistance
with the nanoscale inspections, especially the use of facilities at the Joint
Center for High Valued Instruments of the National Sun Yat-sen University
and Core Facility Center of the National Cheng Kung University. C. C. L
acknowledges strong funding from the Ministry of Science and Technology
of Taiwan under the received grant nos. MOST 111-2112-M-259-015 and
MOST 110-2112-M-259-008.
Conflict of Interest
The authors declare no conflict of interest.
Data Availability Statement
The data that support the findings of this study are available in the supplementary material of this article.
Keywords
heterojunction, nanolaser, nanowire, plasmonics, ultraviolet
2301493 (11 of 13)
Received: March 7, 2023
Revised: July 16, 2023
Published online:
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[1] W. Telford, L. Stickland, M. Koschorreck, Cytom. Part A 2017, 91,
314.
[2] S. Chu, G. Wang, W. Zhou, Y. Lin, L. Chernyak, J. Zhao, J. Kong, L. Li,
J. Ren, J. Liu, Nat. Nanotechnol. 2011, 6, 506.
[3] H. Guo, X. F. Wang, J. D. Chen, F. Li, Opt. Express 2010, 18, 18900.
[4] Q. Zhang, G. Li, X. Liu, F. Qian, Y. Li, T. C. Sum, C. M. Lieber, Q.
Xiong, Nat. Commun. 2014, 5, 4953.
[5] C. T. Plass, V. Bonino, M. Ritzer, L. R. Jäger, V. Rey-Bakaikoa, M.
Hafermann, J. Segura-Ruiz, G. Martínez-Criado, C. Ronning, Adv.
Sci. 2022, 10, 2205304.
[6] S. I. Azzam, A. V. Kildishev, R. M. Ma, C. Z. Ning, R. Oulton, V. M.
Shalaev, M. I. Stockman, J. L. Xu, X. Zhang, Light Sci. Appl. 2020, 9,
90.
[7] Y. Liang, C. Li, Y. Z. Huang, Q. Zhang, ACS Nano 2020, 14, 14375.
[8] C. J. Lee, H. Yeh, F. Cheng, P. H. Su, T. H. Her, Y. C. Chen, C. Y. Wang,
S. Gwo, S. R. Bank, C. K. Shih, W. H. Chang, ACS Photonics 2017, 4,
1431.
[9] Y. H. Chou, Y. M. Wu, K. B. Hong, B. T. Chou, J. H. Shih, Y. C. Chung,
P. Y. Chen, T. R. Lin, C. C. Lin, S. D. Lin, T. C. Lu, Nano Lett. 2016,
16, 3179.
[10] B. T. Chou, Y. H. Chou, Y. M. Wu, Y. C. Chung, W. J. Hsueh, S. W. Lin,
T. C. Lu, T. R. Lin, S. D. Lin, Sci. Rep. 2016, 6, 19887.
[11] Y. J. Lu, C. Y. Wang, J. Kim, H. Y. Chen, M. Y. Lu, Y. C. Chen, W. H.
Chang, L. J. Chen, M. I. Stockman, C. K. Shih, S. Gwo, Nano Lett.
2014, 14, 4381.
[12] Y. J. Lu, J. Kim, H. Y. Chen, C. Wu, N. Dabidian, C. E. Sanders, C. Y.
Wang, M. Y. Lu, B. H. Li, X. Qiu, W. H. Chang, L. J. Chen, G. Shvets,
C. K. Shih, S. Gwo, Science 2012, 337, 450.
[13] P. C. Shen, C. Su, Y. Lin, A. S. Chou, C. C. Cheng, J. H. Park, M. H.
Chiu, A. Y. Lu, H. L. Tang, M. M. Tavakoli, G. Pitner, X. Ji, Z. Cai, N.
Mao, J. Wang, V. Tung, J. Li, J. Bokor, A. Zettl, C. I. Wu, T. Palacios,
L. J. Li, J. Kong, Nature 2021, 593, 211.
[14] W. Huang, J. Zhu, M. Wang, L. Hu, Y. Tang, Y. Shu, Z. Xie, H. Zhang,
Adv. Funct. Mater. 2020, 31, 2007584.
[15] J. Toudert, R. Serna, I. Camps, J. Wojcik, P. Mascher, E. Rebollar, T.
A. Ezquerra, J. Phys. Chem. C 2017, 121, 3511.
[16] J. Toudert, R. Serna, Opt. Mater. Express 2017, 7, 2299.
[17] J. Toudert, R. Serna, M. J. Castro, J. Phys. Chem. C 2012, 116, 20530.
[18] B. Wei, X. Zhang, C. Zhang, Y. Jiang, Y. Y. Fu, C. Yu, S. K. Sun, X. P.
Yan, ACS Appl. Mater. Interfaces 2016, 8, 12720.
[19] Y. Li, Y. Zhao, G. Wu, J. Zhao, Inorg. Chem. 2016, 55, 4897.
[20] M. Liu, J. Tao, C. Y. Nam, K. Kisslinger, L. Zhang, D. Su, Nano Lett.
2014, 14, 5630.
[21] T. Y. Lin, Y. L. Chen, C. F. Chang, G. M. Huang, C. W. Huang, C. Y.
Hsieh, Y. C. Lo, K. C. Lu, W. W. Wu, L. J. Chen, Nano Lett. 2018, 18,
778.
[22] J. Midya, S. K. Das, Phys. Rev. Lett. 2017, 118, 165701.
[23] Z. Zhang, J. Chen, H. Li, Z. Zhang, Y. Wang, Cryst. Growth Des. 2017,
17, 11.
[24] Z. Zhang, Y. Wang, H. Li, W. Yuan, X. Zhang, C. Sun, Z. Zhang, ACS
Nano 2016, 10, 763.
[25] S. Rackauskas, H. Jiang, J. B. Wagner, S. D. Shandakov, T. W.
Hansen, E. I. Kauppinen, A. G. Nasibulin, Nano Lett. 2014, 14, 5810.
[26] M. Jia, J. T. Newberg, Appl. Surf. Sci. 2021, 539, 148219.
[27] D. Leng, T. Wang, Y. F. Li, Z. Huang, H. Wang, Y. Wan, X. Pei, J. Wang,
Inorg. Chem. 2021, 60, 17258.
[28] M. Chen, Y. Li, Z. Wang, Y. Gao, Y. Huang, J. Cao, W. Ho, S. Lee, Ind.
Eng. Chem. Res. 2017, 56, 10251.
[29] A. Garcia-Gil, S. Biswas, D. McNulty, A. Roy, K. M. Ryan, V. Nicolosi,
J. D. Holmes, Adv. Mater. Interfaces 2022, 9, 2201170.
[30] X. Zhu, Q. Xu, H. Li, M. Liu, Z. Li, K. Yang, J. Zhao, L. Qian, Z.
Peng, G. Zhang, J. Yang, F. Wang, D. Li, H. Lan, Adv. Mater. 2019,
31, 1902479.
Adv. Sci. 2023, 2301493
[31] H. Guo, N. Lin, Y. Chen, Z. Wang, Q. Xie, T. Zheng, N. Gao, S. Li, J.
Kang, D. Cai, D. L. Peng, Sci. Rep. 2013, 3, 2323.
[32] A. R. Rathmell, B. J. Wiley, Adv. Mater. 2011, 23, 4798.
[33] B. K. Wu, H. Y. Lee, M. Y. Chern, Appl. Phys. Express 2013, 6, 035504.
[34] H. Kim, J. S. Noh, J. Ham, W. Lee, J. Nanosci. Nanotechnol. 2011, 11,
2047.
[35] J. Ham, W. Shim, D. H. Kim, K. H. Oh, P. W. Voorhees, W. Lee, Appl.
Phys. Lett. 2011, 98, 043102.
[36] W. Shim, J. Ham, K. Lee, W. Y. Jeung, M. Johnson, W. Lee, Nano Lett.
2009, 9, 18.
[37] F. Kong, W. Ning, A. Wang, Y. Liu, M. Tian, J. Alloys Compd. 2018,
737, 484.
[38] V. T. Volkov, A. Yu. Kasumov, Yu. A. Kasumov, I. I. Khodos, Appl.
Phys. A 2017, 123, 503.
[39] J. W. Roh, K. Hippalgaonkar, J. H. Ham, R. Chen, M. Z. Li, P. Ercius,
A. Majumdar, W. Kim, W. Lee, ACS Nano 2011, 5, 3954.
[40] S. Lee, J. Ham, K. Jeon, J. S. Noh, W. Lee, Nanotechnology 2010, 21,
405701.
[41] S. Cao, C. Guo, Y. Wang, J. Miao, Z. Zhang, Q. Liu, Solid State Commun. 2009, 149, 87.
[42] M. W. Knight, T. Coenen, Y. Yang, B. J. M. Brenny, M. Losurdo, A. S.
Brown, H. O. Everitt, A. Polman, ACS Nano 2015, 9, 2049.
[43] M. W. Knight, N. S. King, L. Liu, H. O. Everitt, P. Nordlander, N. J.
Halas, ACS Nano 2014, 8, 834.
[44] T. Ghodselahi, H. Zahrabi, M. H. Heidari Saani, M. A. Vesaghi, J.
Phys. Chem. C 2011, 115, 22126.
[45] S. A. Stanley, C. Stuttle, A. J. Caruana, M. D. Cropper, A. S. O. Walton,
J. Phys. D: Appl. Phys. 2012, 45, 435304.
[46] A. L. J. Pereira, J. A. Sans, R. Vilaplana, O. Gomis, F. J. Manjón, P.
Rodríguez-Hernández, A. Muñoz, C. Popescu, A. Beltrán, J. Phys.
Chem. C 2014, 118, 23189.
[47] J. A. Steele, R. A. Lewis, Opt. Mater. Express 2014, 4, 2133.
[48] W. Wang, M. Liu, Z. Yang, W. Mai, J. Gong, Physica E 2012, 44, 1142.
[49] T. W. Cornelius, M. E. Toimil-Molares, R. Neumann, G. Fahsold, R.
Lovrincic, A. Pucci, S. Karim, Appl. Phys. Lett. 2006, 88, 103114.
[50] E. Haro-Poniatowski, M. Jouanne, J. F. Morhange, M. Kanehisa, R.
Serna, C. N. Afonso, Phys. Rev. B 1999, 60, 10080.
[51] W. Sun, H. Zhang, J. Lin, J. Phys. Chem. C 2014, 118, 17626.
[52] K. Brezesinski, R. Ostermann, P. Hartmann, J. Perlich, T.
Brezesinski, Chem. Mater. 2010, 22, 3079.
[53] T. K. Sham, M. S. Lazarus, Chem. Phys. Lett. 1979, 68, 426.
[54] Y. P. Chen, C. C. Lai, W. S. Tsai, Opt. Express 2020, 28, 24511.
[55] Y. Kumamoto, A. Taguchi, M. Honda, K. Watanabe, Y. Saito, S.
Kawata, ACS Photonics 2014, 1, 598.
[56] Y. Yang, J. M. Callahan, T. H. Kim, A. S. Brown, H. O. Everitt, Nano
Lett. 2013, 13, 2837.
[57] J. C. Lemonnier, G. Jezequel, J. Thomas, J. Phys. C: Solid State Phys.
1975, 8, 2812.
[58] K. M. McPeak, S. V. Jayanti, S. J. P. Kress, S. Meyer, S. Iotti, A.
Rossinelli, D. J. Norris, ACS Photonics 2015, 2, 326.
[59] W. S. M. Werner, K. Glantschning, C. Ambrosch-Draxl, J. Phys. Chem.
Ref. Data 2009, 38, 1013.
[60] W. Li, Mater. Chem. Phys. 2006, 99, 174.
[61] B. Yang, M. Mo, H. Hu, C. Li, X. Yang, Q. Li, Y. Qian, Eur. J. Inorg.
Chem. 2004, 9, 1758.
[62] T. Kanagaraja, P. S. M. Kumar, R. Thomas, R. Kulandaivelu, R.
Subramani, R. N. Mohamed, S. Lee, S. W. Chang, W. J. Chung, D.
D. Nguyen, Environ. Res. 2022, 205, 112439.
[63] Q. Y. Li, Z. Y. Zhao, Phys. Lett. A 2015, 379, 2766.
[64] V. Dolocan, Appl. Phys. 1978, 16, 405.
[65] H. Gobrecht, S. Seeck, H. E. Bergt, A. Märtens, K. Kossmann, Phys.
Stat. Sol. 1969, 33, 599.
[66] J. Qin, Y. H. Chen, B. Ding, R. J. Blaikie, M. Qiu, J. Phys. Chem. C
2017, 121, 24740.
2301493 (12 of 13)
© 2023 The Authors. Advanced Science published by Wiley-VCH GmbH
www.advancedsciencenews.com
www.advancedscience.com
[67] V. Juvé, M. F. Cardinal, A. Lombardi, A. Crut, P. Maioli, J. PérezJuste, L. M. Liz-Marzán, N. D. Fatti, F. Vallée, Nano Lett. 2013, 13,
2234.
[68] H. Kuwata, H. Tamaru, K. Esumi, K. Miyano, Appl. Phys. Lett. 2003,
83, 4625.
[69] S. Link, M. A. El-Sayed, J. Phys. Chem. B 1999, 103, 8410.
[70] Z. Wang, C. Jiang, R. Huang, H. Peng, X. Tang, J. Phys. Chem. C 2014,
118, 1155.
[71] J. M. McMahon, G. C. Schatz, S. K. Gray, Phys. Chem. Chem. Phys.
2013, 15, 5415.
[72] R. A. Patil, M. K. Wei, P. H. Yeh, J. B. Liang, W. T. Gao, J. H. Lin, Y.
Liou, Y. R. Ma, Nanoscale 2016, 8, 3565.
[73] Y. Huang, W. Wang, Q. Zhang, J. J. Cao, R. J. Huang, W. Ho, S. C.
Lee, Sci. Rep. 2016, 6, 23435.
[74] L. Kumari, J. H. Lin, Y. R. Ma, Nanotechnology 2007, 18, 295605.
[75] L. Kumari, J. H. Lin, Y. R. Ma, J. Phys. Condens. Matter. 2007, 19,
406204.
[76] J. Hou, C. Yang, Z. Wang, W. Zhou, S. Jiao, H. Zhu, Appl. Catal. B
2013, 142, 504.
[77] H. W. Kim, Thin Solid Film 2008, 516, 3665.
[78] H. W. Kim, J. W. Lee, S. H. Shim, Sens. Actuators B 2007, 126, 306.
[79] W. Dong, C. Zhu, J. Phys. Chem. Solids 2003, 64, 265.
[80] R. M. Ma, R. F. Oulton, V. J. Sorger, G. Bartal, X. Zhang, Nat. Mater.
2011, 10, 110.
[81] B. J. Wiley, S. H. Im, Z. Y. Li, J. McLellan, A. Siekkinen, Y. Xia, J. Phys.
Chem. B 2006, 110, 15666.
[82] M. A. Schmidt, D. Y. Lei, L. Wondraczek, V. Nazabal, S. A. Maier,
Nat. Commun. 2012, 3, 1108.
[83] T. Khudiyev, E. Ozgur, M. Yaman, M. Bayindir, Nano Lett. 2011, 11,
4661.
[84] D. P. Dutta, M. Roy, A. K. Tyagi, Dalton Trans. 2012, 41, 10238.
[85] D. B. Li, C. Z. Ning, Appl. Phys. Lett. 2010, 96, 181109.
[86] J. Liu, P. D. Garcia, S. Ek, N. Gregersen, T. Suhr, M. Schubert, J.
Mørk, S. Stobbe, P. Lodahl, Nat. Nanotechnol. 2014, 9, 285.
[87] L. Yang, J. Motohisa, T. Fukui, L. X. Jia, L. Zhang, M. M. Geng, P.
Chen, Y. L. Liu, Opt. Express 2009, 17, 9337.
Adv. Sci. 2023, 2301493
[88] Y. Wu, J. Li, H. Zhu, Y. Ren, G. Lou, Z. Chen, X. Gui, Z. Tang, Opt.
Express 2018, 26, 17511.
[89] X. Meng, K. Fujita, Y. Zong, S. Murai, K. Tanaka, Appl. Phys. Lett.
2008, 92, 201112.
[90] H. Cao, Y. G. Zhao, S. T. Ho, E. W. Seelig, Q. H. Wang, R. P. H. Chang,
Phys. Rev. Lett. 1999, 82, 2278.
[91] N. Ismail, C. C. Kores, D. Geskus, M. Pollnau, Opt. Express 2016, 24,
16366.
[92] R. M. Córdova-Castro1, A. V. Krasavin1, M. E. Nasir, A. V. Zayats, W.
Dickson, Nanotechnology 2018, 30, 055301.
[93] Y. Li, M. Li, P. Fu, R. Li, D. Song, C. Shen, Y. Zhao, Sci. Rep. 2015, 5,
11532.
[94] H. Lin, F. Xiu, M. Fang, S. P. Yip, H. Y. Cheung, F. Wang, N. Han, K.
S. Chan, C. Y. Wong, J. C. Ho, ACS Nano 2014, 8, 3752.
[95] H. Hu, J. Gao, W. Wang, S. Tang, L. Zhou, Q. He, H. Wu, X. Zheng,
X. Li, X. Li, A. A. Rogachev, H. Cao, Appl. Mater. Today 2022, 26,
101266.
[96] S. Magdi, J. El-Rifai, M. A. Swillam, Sci. Rep. 2018, 8, 4001.
[97] A. Ghobadi, S. A. Dereshgi, H. Hajian, G. Birant, B. Butun, A. Bek,
E. Ozbay, Nanoscale 2017, 9, 16652.
[98] A. J. Smith, C. Wang, D. Guo, C. Sun, J. Huang, Nat. Commun. 2014,
5, 5517.
[99] Q. G. Du, C. H. Kam, H. V. Demir, H. Y. Yu, X. W. Sun, Opt. Lett.
2011, 36, 1884.
[100] J. P. Reithmaier, G. Sek,
˛ A. Löffler, C. Hofmann, S. Kuhn, S.
Reitzenstein, L. V. Keldysh, V. D. Kulakovskii, T. L. Reinecke, A.
Forchel, Nature 2004, 432, 197.
[101] O. Rodenko, P. Tidemand-Lichtenberg, C. Pedersen, Opt. Express
2018, 26, 20614.
[102] H. Yoshida, Y. Yamashita, M. Kuwabara, H. Kan, Nat. Photonics 2008,
2, 551.
[103] B. W. Chwirot, S. Chwirot, W. Jedrzejczyk, M. Jackowski, A. M.
Raczyńska, J. Winczakiewicz, J. Dobber, Lasers Surg. Med. 1997, 21,
149.
[104] M. Rycenga, C. M. Cobley, J. Zeng, W. Li, C. H. Moran, Q. Zhang, D.
Qin, Y. Xia, Chem. Rev. 2011, 111, 3669.
2301493 (13 of 13)
© 2023 The Authors. Advanced Science published by Wiley-VCH GmbH