Browsing by Author "Chen, Lih-Juann"

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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.
Controlled growth of the silicide nanostructures on Si bicrystal nanotemplate at a precision of a few nanometres
(2011)
Hsin, Cheng-Lun
;
Wu, Wen-Wei
;
Chu, Li-Wei
;
Hsu, Hung-Chang
;
Chen, Lih-Juann
A nanotemplate of Si bicrystal was fabricated by wafer bonding. The surface electronic energy arrangement on the surface of the Si bicrystal has been measured by scanning tunneling microscopy. The stress effect on the stepped growth of titanium silicide nanorods on Si bicrystal was observed in an ultrahigh vacuum transmission electron microscope in real time. The growth behavior of the nanorods was found to be affected by the underlying dislocation arrays significantly. For a dislocation interspacing of 3.1 nm, the dislocation arrays confined the shape of the nanoclusters and nanorods. Compared to the time of the nanorod remaining at the same length, the elongating time is more than two orders of magnitude shorter. The stepped growth behavior is attributed to the stress contour of the surface strain induced by the underlying dislocation network. This study is constructive to the basic understanding of the stress effect on the initial stage of the reaction of metals on Si and the observation may be applied to nanostructure growth for future applications and design.
Diffraction-Unlimited Plasmonic Nanolaser
(2015-01-01)
Lu, Yu-Jung
;
Kim, Jisun
;
Chen, Hung-Ying
;
Wu, Chihhui
;
Dabidian, Nima
Direct observation of melting behaviors at the nanoscale under electron beam and heat to form hollow nanostructures
(2012)
Huang, Chun-Wei
;
Hsin, Cheng-Lun
;
Wang, Chun-Wen
;
Chu, Fu-Hsuan
;
Kao, Chen-Yen
"We report the melting behaviours of ZnO nanowire by heating ZnO-Al2O3 core-shell heterostructures to form Al2O3 nanotubes in an in situ ultrahigh vacuum transmission electron microscope (UHV-TEM). When the ZnO-Al2O3 core-shell nanowire heterostructures were annealed at 600 degrees C under electron irradiation, the amorphous Al2O3 shell became single crystalline and then the ZnO core melted. The average vanishing rate of the ZnO core was measured to be 4.2 nm s(-1). The thickness of the Al2O3 nanotubes can be precisely controlled by the deposition process. Additionally, the inner geometry of nanotubes can be defined by the initial ZnO core. The result shows a promising method to obtain the biocompatible Al2O3 nanotubes, which may be applied in drug delivery, biochemistry and resistive switching random access memory (ReRAM)."
Direct Observation of Sublimation Behaviors in One-Dimensional In2Se3/In2O3 Nanoheterostructures
(2015-06-02)
Hsin, Cheng-Lun
;
Huang, Chun-Wei
;
Chen, Jui-Yuan
;
Liao, Kuo-Cheng
;
Liu, Po-Liang
Recently, in situ transmission electron microscopy (TEM) has provided a route to analyze structural characterization and chemical evolution with its powerful and unique applications. In this paper, we disclose the detailed phenomenon of sublimation on the atomic scale. In2Se3/In2O3 nanowires were synthesized via the vapor-liquid-solid mechanism and studied in an ultra-high-vacuum (UHV) TEM at high temperature in real time. During in situ observation of the sublimation process of the nanowires, the evolution and reconstruction of the exposed In2Se3 surface progressed in different manners with time. The surface structure was decomposed by mass-desorption and stepwise-migration processes, which are also energetically favored processes in the ab initio calculation. This study developed a new concept and will be essential in the development of atomic kinetics.
Dynamic Evolution of Conducting Nanofilament in Resistive Switching Memories
(2013-08-01)
Chen, Jui-Yuan
;
Hsin, Cheng-Lun
;
Huang, Chun-Wei
;
Chiu, Chung-Hua
;
Huang, Yu-Ting
Resistive random access memory (ReRAM) has been considered the most promising next-generation nonvolatile memory. In recent years, the switching behavior has been widely reported, and understanding the switching mechanism can improve the stability and scalability of devices. We designed an innovative sample structure for in situ transmission electron microscopy (TEM) to observe the formation of conductive filaments in the Pt/ZnO/Pt structure in real time. The corresponding current-voltage measurements help us to understand the switching mechanism of ZnO film. In addition, high-resolution transmission electron microscopy (HRTEM) and electron energy loss spectroscopy (EELS) have been used to identify the atomic structure and components of the filament/disrupted region, determining that the conducting paths are caused by the conglomeration of zinc atoms. The behavior of resistive switching is due to the migration of oxygen ions, leading to transformation between Zn-dominated ZnO1-x and ZnO.
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.
Growth of CuInSe(2) and In(2)Se(3)/CuInSe(2) Nano-Heterostructures through Solid State Reactions
(2011-10-01)
Hsin, Cheng-Lun
;
Lee, Wei-Fan
;
Huang, Chi-Te
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Huang, Chun-Wei
;
Wu, Wen-Wei
In(2)Se(3) is an essential phase change material and CuInSe(2) is the fundamental basis of the copper-indium-gallium-diselenide (CIGS) solar energy material. In this paper, we demonstrate the feasibility to transform the phase change material to the solar energy material via the solid state reaction. The In(2)Se(3) nanobelts (NBs) were synthesized via the vapor-liquid-solid mechanism. The chemical composition and the optical properties were investigated by energy dispersive spectroscopy, X-ray photoelectron spectroscopy, and reflectance and photoluminescence spectra. In the in situ observation of the solid state reaction with Cu to form the CuInSe(2) NBs with ultrahigh vacuum transmission electron microscopy, we observed the In(2)Se(3)/CuInSe(2) transformation at atomic scale in real time. The progression of the atomic layer at the interface provided the pertinent information on the kinetic mechanism. In(2)Se(3)/CuInSe(2) nano-heterostructures were also obtained in the present investigation. The approach to the CIGS nanosolar cell was also proposed. This study shall be beneficial in the development of high-performance nanowire solar cells and nanodevices with In(2)Se(3)/CuInSe(2) nano-heterostructures.
Growth of CuInSe2 and In2Se3/CuInSe2 Nano-Heterostructures through Solid State Reactions
(2011-10-01)
Hsin, Cheng-Lun
;
Lee, Wei-Fan
;
Huang, Chi-Te
;
Huang, Chun-Wei
;
Wu, Wen-Wei
In2Se3 is an essential phase change material and CuInSe2 is the fundamental basis of the copper-indium-gallium-diselenide (CIGS) solar energy material. In this paper, we demonstrate the feasibility to transform the phase change material to the solar energy material via the solid state reaction. The In2Se3 nanobelts (NBs) were synthesized via the vapor-liquid-solid mechanism. The chemical composition and the optical properties were investigated by energy dispersive spectroscopy, X-ray photoelectron spectroscopy, and reflectance and photoluminescence spectra. In the in situ observation of the solid state reaction with Cu to form the CuInSe2 NBs with ultrahigh vacuum transmission electron microscopy, we observed the In2Se3/CuInSe2 transformation at atomic scale in real time. The progression of the atomic layer at the interface provided the pertinent information on the kinetic mechanism. In2Se3/CuInSe2 nano-heterostructures were also obtained in the present investigation. The approach to the CIGS nanosolar cell was also proposed. This study shall be beneficial in the development of high-performance nanowire solar cells and nanodevices with In2Se3/CuInSe2 nano-heterostructures.
Heterogeneous and Homogeneous Nucleation of Epitaxial NiSi(2) in [110] Si Nanowires
(2011-01-20)
Chou, Yi-Chia
;
Wu, Wen-Wei
;
Lee, Chung-Yang
;
Liu, Chun-Yi
;
Chen, Lih-Juann
We report here both heterogeneous and homogeneous nucleation of epitaxial suicide of NiSi(2) in Si nanowires grown in [110] direction by in situ observation in high-resolution transmission electron microscopy (TEM). Owing to the excellent lattice match between Si and NiSi(2), a giant epitaxial step of 2-8 nm wide forms at the interface between Si and NiSi(2) during the growth of the latter. The step formation results in two suicide/Si interfaces parallel to each other in TEM observations. Heterogeneous nucleation of NiSi(2) occurs at the intersection where the step meets the interfaces. However, we have also observed the epitaxial growth of NiSi(2) having a single interface with the Si, i.e., without a giant step. Homogeneous nucleation of NiSi(2) occurs on the single interface. Incubation time of heterogeneous nucleation of NiSi(2) has been measured by high-resolution video to be much shorter than that of homogeneous nucleation. The overall growth rate of NiSi(2) for the case of heterogeneous nucleation is faster than that for the case of homogeneous nucleation. Kinetic analysis of both types of nucleation is presented for a direct comparison in order to have a better understanding of the nucleation events.
Heterogeneous and Homogeneous Nucleation of Epitaxial NiSi2 in [110] Si Nanowires
(2011-01-20)
Chou, Yi-Chia
;
Wu, Wen-Wei
;
Lee, Chung-Yang
;
Liu, Chun-Yi
;
Chen, Lih-Juann
We report here both heterogeneous and homogeneous nucleation of epitaxial suicide of NiSi2 in Si nanowires grown in [110] direction by in situ observation in high-resolution transmission electron microscopy (TEM). Owing to the excellent lattice match between Si and NiSi2, a giant epitaxial step of 2-8 nm wide forms at the interface between Si and NiSi2 during the growth of the latter. The step formation results in two suicide/Si interfaces parallel to each other in TEM observations. Heterogeneous nucleation of NiSi2 occurs at the intersection where the step meets the interfaces. However, we have also observed the epitaxial growth of NiSi2 having a single interface with the Si, i.e., without a giant step. Homogeneous nucleation of NiSi2 occurs on the single interface. Incubation time of heterogeneous nucleation of NiSi2 has been measured by high-resolution video to be much shorter than that of homogeneous nucleation. The overall growth rate of NiSi2 for the case of heterogeneous nucleation is faster than that for the case of homogeneous nucleation. Kinetic analysis of both types of nucleation is presented for a direct comparison in order to have a better understanding of the nucleation events.
Homogeneous Nucleation of Epitaxial CoSi(2) and NiSi in Si Nanowires
(2009-06-01)
Chou, Yi-Chia
;
Wu, Wen-Wei
;
Chen, Lih-Juann
;
Tu, King-Ning
;
材料科學與工程學系
Homogeneous nucleation is rare except in theory. We observed repeating events of homogeneous nucleation in epitaxial growth of CoSi(2) and NiSi silicides in nanowires of silicon by using high resolution TEM. The growth of every single atomic layer requires nucleation. Heterogeneous nucleation is prevented because of non-microreversibility between the oxide/Si and oxide/silicide interfaces. We determined the incubation time of homogeneous nucleation. The calculated and the measured nucleation rates are in good agreement. We used Zeldovich factor to estimate the number of molecules in the critical nucleus; it is about 10 and reasonable. A very high supersaturation is found for the homogeneous nucleation.
Homogeneous Nucleation of Epitaxial CoSi2 and NiSi in Si Nanowires
(2009-06-01)
Chou, Yi-Chia
;
Wu, Wen-Wei
;
Chen, Lih-Juann
;
Tu, King-Ning
;
材料科學與工程學系
Homogeneous nucleation is rare except in theory. We observed repeating events of homogeneous nucleation in epitaxial growth of CoSi2 and NiSi silicides in nanowires of silicon by using high resolution TEM. The growth of every single atomic layer requires nucleation. Heterogeneous nucleation is prevented because of non-microreversibility between the oxide/Si and oxide/silicide interfaces. We determined the incubation time of homogeneous nucleation. The calculated and the measured nucleation rates are in good agreement. We used Zeldovich factor to estimate the number of molecules in the critical nucleus; it is about 10 and reasonable. A very high supersaturation is found for the homogeneous nucleation.
In Situ Investigation of Defect-Free Copper Nanowire Growth
(2018-02-01)
Lin, Ting-Yi
;
Chen, Yong-Long
;
Chang, Chia-Fu
;
Huang, Guan-Min
;
Huang, Chun-Wei
The fabrication and placement of high purity nanometals, such as one-dimensional copper (Cu) nanowires, for interconnection in integrated devices have been among the most important technological developments in recent years. Structural stability and oxidation prevention have been the key issues, and the defect control in Cu nanowire growth has been found to be important. Here, we report the synthesis of defect-free single-crystalline Cu nanowires by controlling the surface-assisted heterogeneous nucleation of Cu atomic layering on the graphite-like loop of an amorphous carbon (a-C) lacey film surface. Without a metal-catalyst or induced defects, the high quality Cu nanowires formed with high aspect ratio and high growth rate of 578 nm/s. The dynamic study of the growth of heterogeneous nanowires was conducted in situ with a high-resolution transmission electron microscope. The study illuminates the new mechanism by heterogeneous nucleation control and laying the groundwork for better understanding of heterosurface-assisted nucleation of defect-free Cu nanowire on a-C lacey film.
In Situ Observation of Dehydration-Induced Phase Transformation from Na2Nb2O6-H2O to NaNbO3
(2012-10-25)
Jung, Jong Hoon
;
Chen, Chih-Yen
;
Wu, Wen-Wei
;
Hong, Jung-Il
;
Yun, Byung Kil
We have monitored the phase transformation from a Sandia octahedral molecular sieve Na2Nb2O6-H2O to a piezoelectric NaNbO3 nanowire through in situ X-ray diffraction (XRD) and transmission electron microscopy (TEM) measurements at high temperatures. After dehydration at 288 degrees C, the Na2Nb2O6-H2O becomes significantly destabilized and transforms into NaNbO3 with the increase of time. The phase transformation time is exponentially proportional to the inverse of temperature, for example, similar to 10(5) is at 300 degrees C and similar to 10(1) at 500 degrees C, and follows an Arrhenius equation with the activation energy of 2.0 eV. Real time TEM investigation directly reveals that the phase transformation occurs through a thermally excited atomic rearrangement due to the small difference of Gibbs free energy between two phases. This work may provide a clue of kinetic control for the development of high piezoelectric lead-free alkaline niobates and a deep insight for the crystallization of oxide nanostructures during a hydrothermal process.
In-situ Transmission Electron Microscopy Study of Nanotwinned Copper under Electromigration
(2010)
Liao, Chien-Neng
;
Chen, Kuan-Chia
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Wu, Wen-Wei
;
Chen, Lih-Juann
;
Tu, K. N.
Nanotwinned copper has drawn growing attention recently due to its substantially enhanced mechanical strength and negligible increase in electrical resistivity. The stability of nanotwins under mechanical and electrical stressing becomes a critical consideration. Using a high resolution transmission electron microscopy, we observed that the {112} incoherent twin boundary (TB) and {111} coherent TB migrate at a rate of 0.06 similar to 0.09 nm/s in copper under an electric current density of 2x10(6) A/cm(2). The TB migration is possibly associated with an atomic step moving along either (111) or {112} plane and the TB migration rate is mainly controlled by the incubation time of forming new atomic steps. To form such atomic steps, EM-induced diffusion at junctions where TBs meet a grain boundary or free surface may play an important role.
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.
Kinetic Competition Model and Size-Dependent Phase Selection in 1-D Nanostructures
(2012-06-01)
Chen, Yu
;
Lin, Yung-Chen
;
Huang, Chun-Wei
;
Wang, Chun-Wen
;
Chen, Lih-Juann
The first phase selection and the phase formation sequence between metal and silicon (Si) couples are indispensably significant to microelectronics. With increasing scaling of device dimension to nano regime, established thermodynamic and kinetic models in bulk and thin film fail to apply in 1-D nanostructures. Herein, we present an unique size-dependent first phase formation sequence in 1-D nanostructures, with Ni-Si as the model system. Interfacial-limited phase which forms the last in thin film, NiSi2, appears as the dominant first phase at 300-800 degrees C due to the elimination of continuous grain boundaries in 1-D suicides. On the other hand, theta-Ni2Si, the most competitive diffusion-limited phase takes over NiSi2 and wins out as the first phase in small diameter nanowires at 800 degrees C. Kinetic parameters extracted from in situ transmission electron microscope studies and a modified kinetic growth competition model quantitatively explain this observation. An estimated critical diameter from the model agrees reasonably well with observations.