Browsing by Author "Lu, Ming-Yen"

Now showing 1 - 12 of 12

All-Color Plasmonic Nanolasers with Ultralow Thresholds: Autotuning Mechanism for Single-Mode Lasing
(2014-08-01)
Lu, Yu-Jung
;
Wang, Chun-Yuan
;
Kim, Jisun
;
Chen, Hung-Ying
;
Lu, Ming-Yen
We report on the first demonstration of broadband tunable, single-mode plasmonic nanolasers (spasers) emitting in the full visible spectrum. These nanolasers are based on a single metal oxide semiconductor nanostructure platform comprising of InGaN/GaN semiconductor nanorods supported on an Al2O3-capped epitaxial Ag film. In particular, all-color lasing in subdiffraction plasmonic resonators is achieved via a novel mechanism based on a property of weak size dependence inherent in spasers. Moreover, we have successfully reduced the continuous-wave (CW) lasing thresholds to ultrasmall values for all three primary colors and have clearly demonstrated the possibility of "thresholdless" lasing for the blue plasmonic nanolaser.
All-Color Plasmonic Nanolasers with Ultralow Thresholds: Autotuning Mechanism for Single-Mode Lasing
(2014-08-01)
Lu, Yu-Jung
;
Wang, Chun-Yuan
;
Kim, Jisun
;
Chen, Hung-Ying
;
Lu, Ming-Yen
We report on the first demonstration of broadband tunable, single-mode plasmonic nanolasers (spasers) emitting in the full visible spectrum. These nanolasers are based on a single metal oxide semiconductor nanostructure platform comprising of InGaN/GaN semiconductor nanorods supported on an Al2O3-capped epitaxial Ag film. In particular, all-color lasing in subdiffraction plasmonic resonators is achieved via a novel mechanism based on a property of weak size dependence inherent in spasers. Moreover, we have successfully reduced the continuous-wave (CW) lasing thresholds to ultrasmall values for all three primary colors and have clearly demonstrated the possibility of "thresholdless" lasing for the blue plasmonic nanolaser.
Cobalt Silicide Nanostructures: Synthesis, Electron Transport, and Field Emission Properties
(2009-10-01)
Tsai, Chun-I
;
Yeh, Ping-Hung
;
Wang, Chiu-Yen
;
Wu, Han-Wei
;
Chen, Uei-Shin
Cobalt silicide nanostructures have been synthesized by a spontaneous chemical vapor transport and reaction method. The temperature and the vapor flow rate were shown to critically influence the growth of nanostructures. The effects of two main parameters on the growth of nanostructures were discussed. The phases formed were determined by the Gibbs free energy changes in the reactions. Various phases (CoSi, Co(2)Si) and morphologies, such as single-stern nanowires, three-dimensional (3D) nanowire networks, and aloelike nanostructures, have been synthesized. Very low turn-on field (1.42 V/mu m) and good conductance obtained from field-emission and electrical property measurements, respectively, indicate that CoSi nanowires are potentially useful for electronic devices.
Diffraction-Unlimited Plasmonic Nanolaser
(2015-01-01)
Lu, Yu-Jung
;
Kim, Jisun
;
Chen, Hung-Ying
;
Wu, Chihhui
;
Dabidian, Nima
Germanium Possessing Facet-Specific Trap States and Carrier Lifetimes
(2020-06-18)
Tan, Chih-Shan
;
Lu, Ming-Yen
;
Peng, Wei-Hao
;
Chen, Lih-Juann
;
Huang, Michael H.
Previously, the notable differences in the band structure and changes in bond length and bond distortion between the semiconducting and metal-like planes of germanium have been used to understand the facet-dependent electrical conductivity properties of germanium wafers. To gain further insights into the appearance of electrical facet behaviors, impedance measurements were performed on the Ge{111}, {110}, and {100} wafers. Impedance data and several conductivity-related parameters were used to produce a diagram showing the amount of trap states and the trap state energies. The trap states are found within the germanium band gap with a facet-specific distribution of energies. Compared to the {100} and {110} wafers, the Ge{111} wafer has the lowest trap state density in the probed voltage range. This is consistent with its best conductivity property, as trap states hinder the direct excitation of electrons to the conduction band. Carrier lifetime can also be obtained from the impedance data. The {111} surface generally has the shortest carrier lifetime, which is related to its high electrical conductivity. Interestingly, diffuse reflectance and ultraviolet photoelectron spectral (UPS) measurements yield the smallest Schottky barrier between Ag and the most conductive Ge{111} surface, showing this approach to understanding electrical facet effects can still be useful despite its inadequacy to account for the facet-specific conductivity behaviors of Si wafers. However, one should not rely solely on the experimentally determined Schottky barriers to explain electrical facet effects.
Influences of Contact Metals on the Performances of MoS2 Devices under Strains
(2019-12-19)
Tseng, Sian-Hong
;
Chen, Hung-Yi
;
Hsu, Wei-Ting
;
Wang, Hsiang-Chen
;
Li, Yuan-Yao
The growth of large-area MoS2 films was achieved through atmospheric pressure chemical vapor deposition via vapor management in this study. The thickness of the MoS2 film changed upon varying the amount of vapor deposited on the substrate. Gratifyingly, large-area monolayer MoS2 was obtained under controlled conditions. Studies using transmission electron microscopy and second harmonic generation confirmed that the MoS2 films were composed of grains having sizes ranging from 40 to 70 mu m. Flexible MoS2 device arrays were fabricated on a polyimide substrate; the device arrays displayed high spatial uniformity in their carrier transport properties. The contact metals affected the electrical characteristics of the MoS2 devices under strain; the sensitivity of devices featuring Schottky contacts was higher than that of those with ohmic contacts. Importantly, the device arrays exhibit sensitive and endurance performances under strain cycles of up to 10(5) times. These results suggest a means for the feasible growth of large-area single-layer MoS2 films, as well as the exploitation of flexible MoS2 device arrays in strain and human motion sensor applications.
Intercrossed Sheet-Like Ga-Doped ZnS Nanostructures with Superb Photocatalytic Actvitiy and Photoresponse
(2009-07-23)
Lu, Ming-Yen
;
Lu, Ming-Pei
;
Chung, Yao-An
;
Chen, Ming-Jer
;
Wang, Zhong Lin
Intercrossed ZnS nanostructures doped with Ga (ZnS:Ga nanowalls) have been synthesized in high yield from mixed powders in a vacuum furnace. ZnS:Ga nanowalls were grown vertically on the substrate with the size in the range of several micrometers and the thickness down to similar to 15 nm and have very rough edges. Due to the high surface area and distinctive morphology of ZnS:Ga nanowalls, the photocatalytic activity and the photoresponse show superior properties compared to ZnS:Ga films. The increased conductivity of metal-semiconductor-metal (Ag-ZnS:Ga nanowalls-Ag) Schottky photodetectors under light illumination is attributed to the photogenerated electron-hole pairs, the desorption of oxygen molecules on the ZnS:Ga surface, and the lowering of the Schottky barrier height. The results indicate that ZnS:Ga nanowalls are promising candidate materials for photocatalysts and applicable as photodetectors, optical switches, and sensors in the visible light region.
Layer-Dependent and In-Plane Anisotropic Properties of Low-Temperature Synthesized Few-Layer PdSe2 Single Crystals
(2020-04-28)
Lu, Li-Syuan
;
Chen, Guan-Hao
;
Cheng, Hui-Yu
;
Chuu, Chih-Piao
;
Lu, Kuan-Cheng
Palladium diselenide (PdSe2), a peculiar noble metal dichalcogenide, has emerged as a new two-dimensional material with high predicted carrier mobility and a widely tunable band gap for device applications. The inherent in-plane anisotropy endowed by the pentagonal structure further renders PdSe2 promising for novel electronic, photonic, and thermoelectric applications. However, the direct synthesis of few-layer PdSe2 is still challenging and rarely reported. Here, we demonstrate that few-layer, single-crystal PdSe2 flakes can be synthesized at a relatively low growth temperature (300 degrees C) on sapphire substrates using low-pressure chemical vapor deposition (CVD). The well-defined rectangular domain shape and precisely determined layer number of the CVD-grown PdSe2 enable us to investigate their layer-dependent and in-plane anisotropic properties. The experimentally determined layer-dependent band gap shrinkage combined with first-principle calculations suggest that the interlayer interaction is weaker in few-layer PdSe2 in comparison with that in bulk crystals. Field-effect transistors based on the CVD-grown PdSe2 also show performances comparable to those based on exfoliated samples. The low-temperature synthesis method reported here provides a feasible approach to fabricate high-quality few-layer PdSe2 for device applications.
Optoelectronic Properties of Single-Crystalline Zn2GeO4 Nanowires
(2014-04-17)
Liao, Chi-Hung
;
Huang, Chun-Wei
;
Chen, Jui-Yuan
;
Chiu, Chung-Hua
;
Tsai, TzungChuen
In this work, Zn2GeO4 nanowires (NWs) were successfully synthesized on Si(100) substrates through carbon thermal reduction and a vapor liquid solid method. The NWs were of around 100 nm diameter and high aspect ratio (AR > 150). High-resolution transmission electron microscopy studies indicate that the NWs are single-crystalline with [110] growth direction. Moreover, the atomic resolution high-angle annular dark-field and bright-field images of scanning transmission electron microscopy have distinguished the different elements. They also further identified the structure of Zn2GeO4 and located the positions of the elements. Additionally, we have fabricated devices and measured the electrical properties of a single NW. It is remarkable that individual Zn2GeO4 NW devices exhibited excellent optoelectronic properties with fast switching speed under 254 nm UV illuminations. Furthermore, with short wavelength UV illumination, as we soaked Zn2GeO4 NWs in methyl orange solution, the methyl orange was degraded. Therefore, Zn2GeO4 NWs have potential applications in UV photodetectors and degradation of organic pollutants.
Plasmonic enhancement of Au nanoparticle-embedded single-crystalline ZnO nanowire dye-sensitized solar cells
(2016-02)
Lu, Ming-Yen
;
Tsai, Chen-Yu
;
Chen, Hsueh-An
;
Liang, Ya-Ting
;
Chen, Kuo-Ping
This paper describes the enhanced efficiency of dye-sensitized solar cells (DSSCs) incorporating Au nanoparticle-embedded single-crystalline ZnO nanowire (Au NPs@ZnO NW) arrays. We fabricated these Au NPs@ZnO NW arrays through sequential hydrothermal ZnO growth, with the Au NPs deposited in between the two ZnO growth processes. Interestingly, despite the presence of embedded Au NPs, the ZnO NWs exhibited continuously matched periodic atomic arrangements across the ZnO NW core and shells, indicating that they were single-crystalline. The surface plasmon resonance peaks of the Au NPs on the ZnO NW arrays and of the Au NPs@ZnO NW arrays appeared near 526 and 574 nm, respectively; the red-shift of the latter signal confirmed the embedded geometry of the Au NPs in the ZnO NW arrays. Photovoltaic measurements of the Au NPs ZnO NW DSSCs revealed enhancements in efficiency that depended on the lengths of the ZnO NWs in the arrays; these efficiencies were all greater than those of corresponding ZnO NW-only DSSCs by at least 20%. In accordance with the geometry of our devices and the improved dye absorption within them, it appears that the near-field localized surface plasmon of the Au NPs in the ZnO NWs was the principal factor governing the enhanced power conversion efficiency. (C) 2015 Elsevier Ltd. All rights reserved.
Plasmonic Nanolaser Using Epitaxially Grown Silver Film
(1970-01-01)
Lu, Yu-Jung
;
Kim, Jisun
;
Chen, Hung-Ying
;
Wu, Chihhui
;
Dabidian, Nima
"A nanolaser is a key component for on-chip optical communications and computing systems. Here, we report on the low-threshold, continuous-wave operation of a subdiffraction nanolaser based on surface plasmon amplification by stimulated emission of radiation. The plasmonic nanocavity is formed between an atomically smooth epitaxial silver film and a single optically pumped nanorod consisting of an epitaxial gallium nitride shell and an indium gallium nitride core acting as gain medium. The atomic smoothness of the metallic film is crucial for reducing the modal volume and plasmonic losses. Bimodal lasing with similar pumping thresholds was experimentally observed, and polarization properties of the two modes were used to unambiguously identify them with theoretically predicted modes. The all-epitaxial approach opens a scalable platform for low-loss, active nanoplasmonics."
Plasmonic Nanolaser Using Epitaxially Grown Silver Film
(2012-01-01)
Lu, Yu-Jung
;
Kim, Jisun
;
Chen, Hung-Ying
;
Wu, Chihhui
;
Dabidian, Nima
Successful development of epitaxial Ag as a new plasmonic platform has enabled low-threshold, continuous-wave (CW) operation of a SPASER-enabled nanolaser comprised of a subdiffraction plasmonic cavity and a single InGaN@GaN core-shell nanorod gain medium.