Browsing by Issue Date, starting with "2009-07-27"

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High efficiency light emitting diode with anisotropically etched GaN-sapphire interface
(2009-07-27)
Lo, M. H.
;
Tu, P. M.
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Wang, C. H.
;
Hung, C. W.
;
Hsu, S. C.
We report the fabrication and study of high efficiency ultraviolet light emitting diodes with inverted micropyramid structures at GaN-sapphire interface. The micropyramid structures were created by anisotropic chemical wet etching. The pyramid structures have significantly enhanced the light output efficiency and at the same time also improved the crystal quality by partially relieving the strain and reducing the dislocation defects in GaN. The electroluminescent output power at normal direction was enhanced by 120% at 20 mA injection current and the output power integrated over all directions was enhanced by 85% compared to a reference sample.
Effect of bias stress on mechanically strained low temperature polycrystalline silicon thin film transistor on stainless steel substrate
(2009-07-27)
Peng, I-Hsuan
;
Liu, Po-Tsun
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Wu, Tai-Bor
;
光電工程學系
;
顯示科技研究所
This paper reported the variation in performance of bias stressed low-temperature polycrystalline silicon thin film transistors (LTPS TFTs) fabricated on metal foil substrate for flexible display applications. The mobility, threshold voltage (V(th)), and trap density (N(t)) of the proposed p-channel poly-Si TFT as a function of curvature radii were investigated. The significant increase in V(th) by 9% was observed as the compressive or tensile mechanical strain increases to 0.1%. In addition, the hole mobility increases by 7% due to an increased compressive strain of 0.1%, while hole mobility decreases by 3.5% with the increase in tensile strain of 0.1%. After dc bias stressing, the LTPS TFT with mechanical strain had better performance than that on flat state in both the mobility drop and V(th) shift. Mechanical strain influences the lattice arrangement and electric field at the drain electrode region that resisted device degradation in early stressing period.
Multicolored parallelisms of Hamiltonian cycles
(2009-07-28)
Fu, Hung-Lin
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Lo, Yuan-Hsun
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應用數學系
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Department of Applied Mathematics
A subgraph in an edge-colored graph is multicolored if all its edges receive distinct colors. In this paper, we prove that a complete graph on 2m + 1 vertices K(2m+1) can be properly edge-colored with 2m + 1 colors in such a way that the edges of K(2m+1) can be partitioned into m multicolored Hamiltonian cycles. (C) 2009 Published by Elsevier B.V.
Directed 3-cycle decompositions of complete directed graphs with quadratic leaves
(2009-07-28)
Pu, Liqun
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Fu, Hung-Lin
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Shen, Hao
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應用數學系
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Department of Applied Mathematics
Let G be a vertex-disjoint union of directed cycles in the complete directed graph D(t), let vertical bar E(G)vertical bar be the number of directed edges of G and suppose G not equal 54 (C) over right arrow (2) boolean OR (C) over right arrow (3) or (C) over right arrow (5) if t = 5, and G not equal (C) over right arrow (3) boolean OR (C) over right arrow (3) if t = 6. It is proved in this paper that for each positive integer t, there exist (C) over right arrow (3)-decompositions for D(t) - G if and only if t(t - 1) -vertical bar E(G)vertical bar equivalent to 0 (mod 3). (C) 2008 Elsevier B.V. All rights reserved.
Using Click Chemistry To Fabricate Ultrathin Thermoresponsive Microcapsules through Direct Covalent Layer-by-Layer Assembly
(2009-07-28)
Huang, Cheng-Jyun
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Chang, Feng-Chih
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應用化學系
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Department of Applied Chemistry
We report the syntheses of azido- and acetylene-functionalized poly(N-isopropylacrylamide) (PNIPAm) copolymers and their use in the fabrication of ultrathin thermoresponsive microcapsules through direct covalent layer-by-layer (LbL) assembly using click chemistry. The clickable copolymers poly[N-isopropylacrylamide-co-(trimethylsilyl)propargylacrylamide] and poly(N-isoropylacrylamide-co-3-azideo-propylacrylamide) were prepared through atom transfer radical polymerization (ATRP) at 0 degrees C using a synthesized dansyl-labeled initiator and the CuBr/Me(6)TREN (hexamethylated tris[2-(dimethylamino)ethyl]amine) catalyst complex in 2-propanol. After removing the protective trimethylsilyl groups, these clickable PNIPAm copolymers assemble alternately onto azido-modified silica particles in aqueous media through click reactions catalyzed by copper sulfate and sodium ascorbate. After removing the template, the microcapsules remained stable because of the presence of the covalently bonded triazole units; the microcapsules exhibited thermoresponsive and thermoreversible swelling/deswelling behaviors upon changing the temperature of the medium. Adjusting the number of clickable functionalities resulted in changes to the degree of cross-linking, thereby allowing control over the surface morphology and thickness of the covalently stabilized PNIPAm multilayer thin films. The microcapsules fabricated close to the lower critical solution temperature of PNIPAm exhibited extremely low surface roughnesses and thick multilayer films as a result of their compact chain conformation in aqueous solution, leading to tighter packing of the PNIPAm structure. We further postfunctionalized the surface of the multilayer thin film through click reactions with an azido-modified lissamine rhodamin dye to demonstrate the feasibility of further modification with potentially useful functionalities. Finally, preliminary study on the permeability of microcapsules was presented by using different molecular weigh tetramethylrhodamine isothiocyanate (TRITC)-labeled dextran and rhodamine 6G as probe molecules, and the results revealed that the microcapsules with tighter packing wall are selectively permeable to molecules and show potential applications for the encapsulation of a variety of materials.
Error-correcting pooling designs associated with some distance-regular graphs
(2009-07-28)
Bai, Yujuan
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Huang, Tayuan
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Wang, Kaishun
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應用數學系
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Department of Applied Mathematics
Motivated by the pooling designs over the incidence matrices of matchings with various sizes of the complete graph K(2n) considered by Ngo and Du [Ngo and Du, Discrete Math. 243 (2003) 167-170]. two families of pooling designs over the incidence matrices of t-cliques (resp. strongly t-cliques) with various sizes of the Johnson graph J(n. t) (resp. the Grassmann graph J(q) (n, t)) are considered. Their performances as pooling designs are better than those given by Ngo and Du. Moreover, pooling designs associated with other special distance-regular graphs are also considered. (C) 2009 Elsevier B.V. All rights reserved.
Pulse-train modulation in a picosecond self-mode-locked laser
(2009-07-28)
Hsu, Chih-Chang
;
Lin, Ja-Hon
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Hsieh, Wen-Feng
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光電工程學系
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Department of Photonics
Pulse-train modulation was observed in a picosecond self-mode-locked Ti:sapphire laser with pump-power dependence when it was operated around the degenerate cavity configuration. By increasing the optical pumping power, the envelope of the periodic amplitude modulation splits into two or three clusters with enhanced modulation depth, and the amplitude modulation eventually becomes disordered at higher pump power. The amplitude modulation may be supported by exciting two sets of non-degenerate longitudinally mode-locked supermodes due to spatially inhomogeneous gain modulation in the Ti: sapphire crystal.
Excessive near 1-factorizations
(2009-07-28)
Cariolaro, David
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Fu, Hung-Lin
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應用數學系
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Department of Applied Mathematics
We begin the study of sets of near 1-factors of graphs G of odd order whose union contains all the edges of G and determine, for a few classes of graphs, the mini mum number of near 1-factors in such sets. (C) 2008 Elsevier B.V. All rights reserved.
Interfacial energy levels and related properties of atomic-layer-deposited Al2O3 films on nanoporous TiO2 electrodes of dye-sensitized solar cells
(2009-07-29)
Tien, Ta-Chang
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Pan, Fu-Ming
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Wang, Lih-Ping
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Lee, Chia-Hua
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Tung, Yung-Liang
Low-temperature (similar to 150 degrees C), atomic-layer-deposited Al2O3 films on nanoporous TiO2 electrodes of dye-sensitized solar cells (DSSCs) were investigated using electron spectroscopy. The power conversion efficiency (PCE) of the DSSCs was increased from 5.7% to 6.5%, an improvement of 14%, with one monolayer of Al2O3 with a thickness of similar to 0.2 nm. The formation of Ti-O-Al(OH)(2) and interfacial dipole layers exhibited a strong influence on the work function of the Al2O3 over-layers, while the thicker Al2O3 over-layers caused the values of valence band maximum and band gap to approach the values associated with pure Al2O3. A work function difference (Delta Phi(A-T)) of 0.4 eV and a recombination barrier height (epsilon(RB)) of 0.1 eV were associated with the highest PCE achieved by the first monolayer of the Al2O3 layer. Thicker Al2O3 over-layers, however, caused significant reduction of PCE with negative Delta Phi(T-A) and increased interfacial energy barrier height (*epsilon(IB)) between the N719 dyes and TiO2 electrodes. It was concluded that the PCE of the DSSCs may correlate with Delta Phi(A-T), epsilon(RB), and *epsilon(IB) resulting from various thicknesses of the Al2O3 over-layers and that interfacial reactions, such as the formation of Ti-O-Al(OH)(2) and dipole layers, play an important role in determining the interfacial energy levels required to achieve optimal performance of dye-sensitized TiO2 solar cells.
Interfacial energy levels and related properties of atomic-layer-deposited Al(2)O(3) films on nanoporous TiO(2) electrodes of dye-sensitized solar cells
(2009-07-29)
Tien, Ta-Chang
;
Pan, Fu-Ming
;
Wang, Lih-Ping
;
Lee, Chia-Hua
;
Tung, Yung-Liang
Low-temperature (similar to 150 degrees C), atomic-layer-deposited Al(2)O(3) films on nanoporous TiO(2) electrodes of dye-sensitized solar cells (DSSCs) were investigated using electron spectroscopy. The power conversion efficiency (PCE) of the DSSCs was increased from 5.7% to 6.5%, an improvement of 14%, with one monolayer of Al(2)O(3) with a thickness of similar to 0.2 nm. The formation of Ti-O-Al(OH)(2) and interfacial dipole layers exhibited a strong influence on the work function of the Al(2)O(3) over-layers, while the thicker Al(2)O(3) over-layers caused the values of valence band maximum and band gap to approach the values associated with pure Al(2)O(3). A work function difference (Delta Phi(A-T)) of 0.4 eV and a recombination barrier height (epsilon(RB)) of 0.1 eV were associated with the highest PCE achieved by the first monolayer of the Al(2)O(3) layer. Thicker Al(2)O(3) over-layers, however, caused significant reduction of PCE with negative Delta Phi(T-A) and increased interfacial energy barrier height (*epsilon(IB)) between the N719 dyes and TiO(2) electrodes. It was concluded that the PCE of the DSSCs may correlate with Delta Phi(A-T), epsilon(RB), and *epsilon(IB) resulting from various thicknesses of the Al(2)O(3) over-layers and that interfacial reactions, such as the formation of Ti-O-Al(OH)(2) and dipole layers, play an important role in determining the interfacial energy levels required to achieve optimal performance of dye-sensitized TiO(2) solar cells.
Observation of localized surface plasmons in spatially controlled array structures
(2009-07-29)
Chou, J. W.
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Lin, Kao-Chin
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Lee, Yao-Jen
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Yuan, Chi-Tsu
;
Hsueh, Fu-Kuo
We observed the reflectance spectra of three different nano-scale array structures of Au-coated silicon nanorods. The trends of the reflectance spectra indicate that the localized surface plasmon modes can be spatially controlled by manipulating geometric parameters, namely the lattice constants of the array. In addition, the experimental results were compared with 2D numerical simulations based on the finite element method. Satisfactory agreement between the experimental observations and numerical results was obtained.
Novel morphology and solidification behavior of eutectic bismuth-tin (Bi-Sn) nanowires
(2009-07-29)
Chen, Shih Hsun
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Chen, Chien Chon
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Chao, Chuen Guang
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材料科學與工程學系
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Department of Materials Science and Engineering
In the present work we show a simple and robust fabrication process for dense and continuous bismuth-tin (Bi-Sn) eutectic nanowires. The Bi-Sn eutectic nanowires of 200 nm diameter and several tens of mu m, in length were fabricated by a vacuum hydraulic force method. The alloy melt was injected into an anodic aluminum oxide (AAO) template to form nanowires after melt solidification. For this process, nanowires were formed from non-atomic deposition with liquid alloy; in this way, the composition of nanowires can be controlled precisely in stoichiometry. The Bi-Sn melt was restricted inside the AAO which has a low thermo-conduction and long period cooling rate around the melt. On the other hand, the heat flow is along the tube Z-axis and the melt is solidified from the AAO bottom to top because of the open pore on the AAO top. The eutectic nanowires were found to be dense and continuous with a uniform diameter throughout the length of the wires and with a lamellar microstructure along the wires' Z-axis. In addition, the alternative segmental compositions showed that the ratio of tin to bismuth is approximately 33:1. (C) 2009 Elsevier B.V. All rights reserved.
蛍光材料と発光装置
(2009-07-30)
陳登銘
;
戴筱萍
【課題】一連の新奇性を有する化学組成蛍光材料を提供すること。【解決手段】本発明は、化学式をＡm（Ｂａ1-xＥｕx2+）nＰyＯzとし、式中ＡはＬｉ、ＮａおよびＫにより構成された群から選ばれた少なくとも１つであり、かつ０＜ｍ＜１０、０＜ｎ＜１０、０＜ｙ＜１０、ｍ＋ｎ＋ｙ＝３／４ｚ、０．００１＜ｘ＜０．８である一連の蛍光材料を提供する。【選択図】図１
Characterizations of gallium-doped ZnO films on glass substrate prepared by atmospheric pressure metal-organic chemical vapor deposition
(2009-07-31)
Huang, Yen-Chin
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Li, Zhen-Yu
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Chen, Hung-hsin
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Uen, Wu-Yih
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Lan, Shan-Ming
Ga-doped zinc oxide (ZnO:Ga) films were grown on glass substrate by atmospheric pressure metal-organic chemical vapor deposition (AP-MOCVD) using diethylzinc and water as reactant gases and triethyl gallium (TEG) as an n-type dopant gas. The structural, electrical and optical properties of ZnO:Ga films obtained at various flow rates of TEG ranging from 1.5 to 10 sccm were investigated. X-ray diffraction patterns and scanning electron microscopy images indicated that Ga-doping plays an important role in forming microstructures in ZnO films. A smooth surface with a predominant orientation of (101) was obtained for the ZnO:Ga film grown at a flow rate of TEG=7.5 sccm. Moreover, a lowest resistivity of 3.6 x 10(-4) Omega cm and a highest mobility of 30.4 cm(2) V(-1) s(-1) were presented by the same sample, as evaluated by Hall measurement. Otherwise. as the flow rate of TEG was increased, the average transmittance of ZnO:Ga films increased from 75% to more than 85% in the wavelength range of 400-800 nm, simultaneously with a blue-shift in the absorption edge. The results obtained suggest that low-resistivity and high-transparency ZnO films can be obtained by AP-MOCVD using Ga-doping sufficiently to make the films grow degenerate and effect the Burstein-Moss shift to raise the band-gap energy from 3.26 to 3.71 eV. (C) 2009 Elsevier B.V. All rights reserved.
Effect of Ta2O5 Doping on Electrical Characteristics of SrTiO3 Metal-Insulator-Metal Capacitors
(2009-08-01)
Huang, Ching-Chien
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Cheng, Chun-Hu
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Liou, Bo-Heng
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Yeh, Fon-Shan
;
Chin, Albert
The effect of Ta2O5 doping on electrical characteristics of SrTiO3 (STO) metal-insulator-metal (MIM) capacitors was studied for the first time. Using Ta2O5-doped STO dielectrics, an absolute quadratic voltage coefficient of capacitance (VCC-alpha) of 510 ppm/V-2 and a high capacitance density of similar to 20 fF/mu m(2) are achieved. These are approximately one order of magnitude lower than those of the MIM capacitor fabricated using a pure STO. In addition, the degradation of electrical properties (capacitance variation versus voltage, VCC-alpha, and long-term reliability) after electrical stressing is reduced, compared with that of an MIM capacitor fabricated using a pure STO. (C) 2009 The Japan Society of Applied Physics
Diode-pumped passively mode-locked 1342 nm Nd:YVO(4) laser with an AlGaInAs quantum-well saturable absorber
(2009-08-01)
Huang, S. C.
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Cheng, H. L.
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Chen, Yi-Fan
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Su, K. W.
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Chen, Y. F.
We demonstrate what we believe to be the first use of AlGaInAs quantum wells (QWs) as a saturable absorber for a diode-pumped passively mode locked Nd:YVO(4) laser at 1342 nm. The QWs are grown on a Fedoped InP substrate that is transparent at lasing wavelength. At an incident pump power of 13.5 W an average output power of 1.05 W with a continuous mode-locked pulse duration of 26.4 ps at a repetition rate of 152 MHz was generated. (C) 2009 Optical Society of America
Role conflicts, emotional exhaustion and health problems: a study of police officers in Taiwan
(2009-08-01)
Wu, Chia-huei
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經營管理研究所
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Institute of Business and Management
This study focused on the role conflicts faced by police officers in Taiwan and investigated the relationship between role conflicts, emotional exhaustion and health problems based on the job demands and resources model (JD-R model). Firstly, in addition to work-family conflict, an inter-role conflict, this study identified an intrasender role conflict for police officers called uncompromising-friendly conflict. Secondly, according to the JD-R model, it was hypothesized that emotional exhaustion has a complete mediation effect on the relationships between role conflicts and health problems. The survey data in Huang's study were analysed. A total of 672 police officers at Kaohsiung, Taiwan provided completed data for analysis. Correlation analysis showed that role conflicts, emotional exhaustion and health problems were positively correlated. Results of the structural equation model further suggested that the positive effect of role conflicts on health problems was partially mediated by emotional exhaustion. Copyright (C) 2009 John Wiley & Sons, Ltd.
Adaptation to the edge of chaos in a self-starting Kerr-lens mode-locked laser
(2009-08-01)
Hsu, C. C.
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Lin, J. H.
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Hsieh, W. F.
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光電工程學系
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Department of Photonics
We experimentally and numerically demonstrated that self-focusing acts as a slow-varying control parameter that suppresses the transient chaos to reach a stable mode-locking (ML) state in a self-starting Kerr-lens mode-locked Ti:sapphire laser without external modulation and feedback control. Based on Fox-Li's approach, including the self-focusing effect, the theoretical simulation reveals that the self-focusing effect is responsible for the self-adaptation. The self-adaptation occurs at the boundary between the chaotic and continuous output regions in which the laser system begins with a transient chaotic state with fractal correlation dimension, and then evolves with reducing dimension into the stable ML state.
Sample size determination for production yield estimation with multiple independent process characteristics
(2009-08-01)
Hsu, Ya-Chen
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Pearn, W. L.
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Chuang, Ya-Fei
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工業工程與管理學系
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Department of Industrial Engineering and Management
Capability measure for processes yield with single characteristic has been investigated extensively, but is still comparatively neglected for processes with multiple characteristics. Wu and Pearn [Wu, C.W., Pearn, W.L. 2005. Measuring manufacturing capability for couplers and wavelength division multiplexers (WDM). International journal of Advanced Manufacturing Technology 25(5/6), 533-541] proposed a capability index for multiple characteristics called C(PU)(T), which provides an exact measure on process yield for multiple characteristics with each characteristic normally distributed. However, the exact sampling distribution of C(PU)(T)(multiple characteristics) is analytically intractable. In this paper, we apply the bootstrap method for calculating the lower confidence bounds of the index C(PU)(T), and determine the sample size for a specified estimation accuracy. In order to obtain a desired estimation quality assurance, the sample size determination is essential as it provides the accuracy of the lower bound obtained from the bootstrap method. For convenience of applications, we tabulate the sample size required for various designated accuracy for the engineers/practitioners to use. A real-world example from manufacturing process with multiple characteristics is investigated to illustrate the applicability of the proposed approach. (C) 2008 Published by Elsevier B.V.
Effects of Plasma Damage on Metal-insulator-Metal Capacitors and Transistors for Advanced Mixed-Signal/Radio-Frequency Metal-Oxide-Semiconductor Field-Effect Transistor Technology
(2009-08-01)
Weng, Wu-Te
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Lee, Yao-Jen
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Lin, Hong-Chih
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Huang, Tiao-Yuan
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電子工程學系及電子研究所
The effects of damage on mixed-signal (MS)/radio-frequency (RF) circuits integrated with metal-insulator-metal (MIM) capacitors and advanced metal-oxide-semiconductor field-effect transistors (MOSFETs) are studied in this work. The impact of damage on an MIM oxide is evaluated by connecting its capacitor top metal (CTM) to an upper-level metal with a large antenna ratio (AR(CTM)) used in an actual CTM circuit connected to an interconnect. In addition to the dielectric degradation of a transistor, we also investigate the damage-enhanced negative bias temperature instability (NBTI) degradation of a transistor with its gate electrode connected to an MIM capacitor with a large ARCTM for various gate oxide thicknesses. A model is proposed to explain the experimentally observed dependence of NBTI degradation on AR(CTM) and accurately simulate failure distributions in the presence of plasma damage. (C) 2009 The Japan Society of Applied Physics