Browsing by Issue Date, starting with "2009-07-25"

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Developments of Raman spectroscopy in the past 40 years: from a molecule to a living cell
(2009-07-25)
Hamaguchi, Hiro-o
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應用化學系
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應用化學系分子科學碩博班
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Department of Applied Chemistry
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Institute of Molecular science
This article is based on the opening lecture 'Raman spectroscopy at Tokyo: past 40 years and future' delivered at the symposium entitled '80 years of Raman effect: reflections and the future' held at Bangalore from 8 to 10 December 2008. It reviews four research subjects, including (1) anomalous depolarization ratios in resonance Raman scattering, (2) one- way photoisomerization of retinal by nanosecond time-resolved Raman spectroscopy, (3) dynamic polarization model of photoisomerization of stilbene by picosecond time-resolved Raman spectroscopy, and (4) discovery of the 'Raman spectroscopic signature of life' by timeand space-resolved Raman spectroscopy. The future possibilities of Raman spectroscopy are also briefly addressed.
Preparation of phosphated Zr-doped TiO(2) exhibiting high photocatalytic activity through calcination of ligand-capped nanocrystals
(2009-07-25)
Chang, Sue-min
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Hou, Chieh-yao
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Lo, Pin-han
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Chang, Chen-tuan
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環境工程研究所
We incorporated phosphate and pyrophosphate species into the surface lattice of Zr-doped TiO(2) via calcination (>550 degrees C) of triocylphosphine oxide (TOPO)-capped nanocrystals that had been prepared using a non-hydrolytic sol-gel method. The phosphated Zr-doped TiO(2) calcined at 550-750 degrees C exhibited 2.88-5.28-fold higher photocatalytic activities for decomposition of bisphenol A (BPA) than did P25. Moreover, the sample prepared through calcination at 950 degrees C performed an extraordinary activity which was 40.3 times higher than that of P25. The high surface reactivities were resulted from co-doing of TiO(2) surface with Zr(4+) and phosphate/pyrophosphate species. Calcination enhanced the reactivity at elevated temperatures because it changed the microstructures and surface properties of phosphated Zr-doped TiO(2). The average crystallite size increased dramatically from 10.2-10.8 to 16.1 nm when the temperature increased from 750 to 950 degrees C. This change was associated with the formation of pyrophosphate species through condensation of the concentrated phosphate species. Dehydration resulted in substantial amounts of oxygen vacancies (O(M)/M(S) = 1.38) and Ti(3+) ions in the surface layers of the phosphated Zr-doped TiO(2) calcined at 950 degrees C. The dehydrated TiO(2) displayed high affinity toward BPA with a maximum adsorption capacity of 5.35 mg/g. The appearance of signals for Ti(4+)-O(2)(-) in the EPR spectrum of the modified TiO(2) in the dark indicated its high capability for the chemisorption of O(2). In addition, the remarkable decrease in the intensities of trapped electrons in the sample under an O(2) atmosphere revealed that efficient charge transfer occurred from the trapped sites to the electron scavenger. Thus, the phosphated Zr-doped TiO(2) calcined at high temperatures exhibit improved adsorbability toward reactants and enhanced interfacial charge transfer, resulting in outstanding photocatalytic activity. (C) 2009 Elsevier B.V. All rights reserved.
Preparation of phosphated Zr-doped TiO2 exhibiting high photocatalytic activity through calcination of ligand-capped nanocrystals
(2009-07-25)
Chang, Sue-min
;
Hou, Chieh-yao
;
Lo, Pin-han
;
Chang, Chen-tuan
;
環境工程研究所
We incorporated phosphate and pyrophosphate species into the surface lattice of Zr-doped TiO2 via calcination (>550 degrees C) of triocylphosphine oxide (TOPO)-capped nanocrystals that had been prepared using a non-hydrolytic sol-gel method. The phosphated Zr-doped TiO2 calcined at 550-750 degrees C exhibited 2.88-5.28-fold higher photocatalytic activities for decomposition of bisphenol A (BPA) than did P25. Moreover, the sample prepared through calcination at 950 degrees C performed an extraordinary activity which was 40.3 times higher than that of P25. The high surface reactivities were resulted from co-doing of TiO2 surface with Zr4+ and phosphate/pyrophosphate species. Calcination enhanced the reactivity at elevated temperatures because it changed the microstructures and surface properties of phosphated Zr-doped TiO2. The average crystallite size increased dramatically from 10.2-10.8 to 16.1 nm when the temperature increased from 750 to 950 degrees C. This change was associated with the formation of pyrophosphate species through condensation of the concentrated phosphate species. Dehydration resulted in substantial amounts of oxygen vacancies (O-M/M-S = 1.38) and Ti3+ ions in the surface layers of the phosphated Zr-doped TiO2 calcined at 950 degrees C. The dehydrated TiO2 displayed high affinity toward BPA with a maximum adsorption capacity of 5.35 mg/g. The appearance of signals for Ti4+-O-2(-) in the EPR spectrum of the modified TiO2 in the dark indicated its high capability for the chemisorption of O-2. In addition, the remarkable decrease in the intensities of trapped electrons in the sample under an O-2 atmosphere revealed that efficient charge transfer occurred from the trapped sites to the electron scavenger. Thus, the phosphated Zr-doped TiO2 calcined at high temperatures exhibit improved adsorbability toward reactants and enhanced interfacial charge transfer, resulting in outstanding photocatalytic activity. (C) 2009 Elsevier B.V. All rights reserved.
High efficiency light emitting diode with anisotropically etched GaN-sapphire interface
(2009-07-27)
Lo, M. H.
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Tu, P. M.
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Wang, C. H.
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Hung, C. W.
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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
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Liu, Po-Tsun
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Wu, Tai-Bor
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光電工程學系
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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
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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
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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 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
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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
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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.