Browsing by Issue Date, starting with "2008-06-09"

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Atomic scale characterization of buried In(x)Ga(1-x)As quantum dots using pulsed laser atom probe tomography
(2008-06-09)
Mueller, M.
;
Cerezo, A.
;
Smith, G. D. W.
;
Chang, L.
;
Gerstl, S. S. A.
Atom probe tomography (APT) has been used to study In(x)Ga(1-x)As quantum dots buried in GaAs. The dots have an average base width of 16.1 +/- 1.1 nm and height of 3.5 +/- 0.3 nm, but a wide range of sizes. APT composition profiles across the dots are similar to a previous study by cross-sectional scanning transmission electron microscopy, but show significant gallium incorporation (average x=0.22 +/- 0.01). The direct three-dimensional nature of the APT data also reveals the complex spatial distribution of indium within the dots. Data such as these are vital for optimizing the performance of quantum dot materials and devices. (c) 2008 American Institute of Physics.
Complementary inverter circuits based on p-SnO2 and n-In2O3 thin film transistors
(2008-06-09)
Dhananjay
;
Chu, Chih-Wei
;
Ou, Chun-Wei
;
Wu, Meng-Chyi
;
Ho, Zhong-Yo
Thin film transistors (TFTs) of indium oxide (In2O3) and tin oxide (SnO2) were fabricated on SiO2 gate dielectric using reactive evaporation process. Structural investigation of the films revealed that In2O3 films were polycrystalline in nature with preferred (222) orientation and SnO2 films exhibited amorphous nature. The x-ray photoelectric spectroscopy measurements suggest that SnO2 films were oxygen rich and presume mixed oxidation states of Sn, namely Sn2+ and Sn4+. While the In2O3 based TFTs possess n-type channel conduction, SnO2 based TFTs exhibited anomalous p-type conductivity. Integration of these n- and p-type devices resulted in complementary inverter with a gain of 11. (C) 2008 American Institute of Physics.
Complementary inverter circuits based on p-SnO(2) and n-In(2)O(3) thin film transistors
(2008-06-09)
Dhananjay
;
Chu, Chih-Wei
;
Ou, Chun-Wei
;
Wu, Meng-Chyi
;
Ho, Zhong-Yo
Thin film transistors (TFTs) of indium oxide (In(2)O(3)) and tin oxide (SnO(2)) were fabricated on SiO(2) gate dielectric using reactive evaporation process. Structural investigation of the films revealed that In(2)O(3) films were polycrystalline in nature with preferred (222) orientation and SnO(2) films exhibited amorphous nature. The x-ray photoelectric spectroscopy measurements suggest that SnO(2) films were oxygen rich and presume mixed oxidation states of Sn, namely Sn(2+) and Sn(4+). While the In(2)O(3) based TFTs possess n-type channel conduction, SnO(2) based TFTs exhibited anomalous p-type conductivity. Integration of these n- and p-type devices resulted in complementary inverter with a gain of 11. (C) 2008 American Institute of Physics.
Broadband and omnidirectional antireflection employing disordered GaN nanopillars
(2008-06-09)
Chiu, C. H.
;
Yu, Peichen
;
Kuo, H. C.
;
Chen, C. C.
;
Lu, T. C.
Disordered GaN nanopillars of three different heights: 300, 550, and 720 nm are fabricated, and demonstrate broad angular and spectral anti-reflective characteristics, up to an incident angle of 60 degrees and for the wavelength range lambda=300-1800nm. An algorithm based on a rigorous coupled-wave analysis (RCWA) method is developed to investigate the correlations between the reflective characteristics and the structural properties of the nanopillars. The broadband and omnidirectional antireflection arises mainly from the refractive-index gradient provided by nanopillars. Calculations show excellent agreement with the measured reflectivities for both s- and p-polarizations. (c) 2008 Optical Society of America.
Highly efficient red organic light-emitting devices based on a fluorene-triphenylamine host doped with an Os(II) phosphor
(2008-06-09)
Wu, Chen-Hao
;
Shih, Ping-I
;
Shu, Ching-Fong
;
Chi, Yun
;
應用化學系
We report highly efficient red-light-emitting devices based on a fluorene-triphenylamine tris[4-(9-phenylfluoren-9-yl)phenyl]amine (TFTPA) host doped with an osmium phosphor. The sterically hindered fluorene peripheries provided a compatible environment for the osmium dopant and alleviated concentration quenching of the phosphor at high doping levels. Increasing the doping concentration from 7 to 21 wt % dramatically decreased the driving voltage of the TFTPA-based devices, leading to improved power efficiency. The 21 wt % Os-doped device exhibited maximum luminous and powder efficiencies of 29.9 cd/A and 25.2 lm/W, combined with high efficiencies at high brightness. At 1000 cd/m(2) the efficiencies remained 29.2 cd/A and 22.2 lm/W. (C) 2008 American Institute of Physics.
Polymers derived from 3,6-fluorene and tetraphenylsilane derivatives: Solution-processable host materials for green phosphorescent OLEDs
(2008-06-10)
Yeh, Huan-Chi
;
Chien, Chen-Han
;
Shih, Ping-I
;
Yuan, Mao-Chuan
;
Shu, Ching-Fong
We have synthesized two fluorene-based polymeric host materials, P1 and P2, through palladium-catalyzed Suzuki couplings of monomers containing tetraphenylsilane and 3,6-disubstituted fluorene frameworks, respectively. The resultant copolymers exhibited high glass transition temperatures (T-g >= 215 degrees C) and excellent thermal stability. The conjugation lengths of polymers P1 and P2 were effectively confined through the presence of the 3,6-linkages and silane units in the polymer skeleton. The structural features endowed these copolymers with UV-violet emissions in the solid state, together with high triplet energies (E-T = 2.60 eV), which were sufficiently high for PI and P2 to serve as appropriate hosts for green-emitting phosphors. In the case of polymer P2, the incorporation of pendent carbazole groups increased the HOMO level markedly and balanced the rates of charge injection and transportation. Employing P2 doped with green-emitting fac-tris(2-phenylpyridine)iridium as the emissive layer, we fabricated highly efficient polymer light-emitting diodes (32 cd/A, 9.2%) that exhibited significantly enhanced EL performance relative to that of the system employing P1 (14.5 cd/A, 4.2%).
可調式光纖放大器與雷射裝置
(2008-06-11)
祁甡
;
陳南光
一種可調式光纖放大器與雷射裝置,主要設有一光芯(Core),以及至少一光殼(cladding);其中該光芯為一可使用電激發或光學激發的光增益介質,該光殼設為一光學色散材料,而該光芯係置於光殼內部, 被光殼所包覆;藉此,利用光殼對溫度的升降變化,使該光芯的材料色散特性隨之改變,進一步使折射率亦隨之變化調整者。
IDENTIFICATION AND ADMINISTRATION SYSTEM APPLIED TO PEER-TO-PEER GATEWAY AND METHOD FOR THE SAME
(2008-06-12)
LIN, Po-Ching
;
Tsai, Meng-Fu
;
Chang, Tsao-Jiang
;
Lin, Ying-Dar
;
Lai, Yuan-Cheng
An identification and administration system applied to P2P gateway and a method for the same are proposed. The system is installed in a kernel space, and a plug-in kernel module is in the kernel space to finish preprocessing and application processing of packets on the kernel space without the need of copying data to the user space for processing. Moreover, a connection cache is provided in the kernel space to process source/destination IP addresses, connection ports and protocol identifiers of all packets to recognize and then block identical request packets in reconnections. Therefore, the throughput of content-level security gateway can be increased, and the processing efficiency of packets can also be enhanced.
Parallel plate denuder for gas absorption
(2008-06-12)
Tsai, Chuen-Jinn
;
Lin, Guan-Yu
This invention provides a high-efficiency parallel plate wet denuder (PPWD) for gas absorption, the absorption surfaces thereof are composed of two hydrophilic porous glass plates on which TiO2 particles are coated and subsequently are irradiated with UV light to form super-hydrophilic surfaces, so that it further enhances the formation of uniform water film and increases gas absorption efficiency. This invention can be used in the manual sampling devices for acidic/basic gases, the gas absorption equipments for acidic/basic gases and gas-particle denuder sampling devices, besides it can also be coupled with an ion chromatograph to make semi-continuous acidic/basic gas-particle monitors.
The Rouse-Mooney model for coherent quasielastic neutron scatterings of single chains well entangled in polymer melts
(2008-06-14)
Lin, Y. -H.
;
Huang, C. -F.
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應用化學系
;
Department of Applied Chemistry
The dynamic structure factor (DSF) for single (labeled) chains well entangled in polymer melts has been developed based on the Rouse-Mooney picture; the DSF functions derived from the Langevin equations of the model in both discrete and continuous forms are given. It is shown that for all practical purposes, it is sufficient to use the continuous form to analyze experimental results in the "safe" q region (q being the magnitude of the scattering wave vector q) where the Rouse-segment-based theories are applicable. The DSF form reduces to the same limiting form as that of the free Rouse chain as q(2)a(2) or q(2)R(2)->infinity (a and R being the entanglement distance and the root mean square end-to-end distance, respectively), confirming what has been expected physically. The natural reduction to the limiting form allows the full range of DSF curves to be displayed in terms of the reduced Rouse variable q(2)(Z(d)t)(0.5) in a unified way. The displayed full range represents a framework or "map," with respect to which effects occurring in different regions of the DSF may be located and studied in a consistent manner. One effect is the significant or noticeable deviations of the theoretical DSF curves from the limiting curve in the region similar to 4>q(2)(Z(d)t)(0.5)>similar to 0.1 (a time region where t
Characterization and properties of infrared NLO crystals: AGeX(3) (A = Rb, Cs; X = Cl, Br)
(2008-06-15)
Lin, Zhi-Guang
;
Tang, Li-Chuan
;
Chou, Chang-Pin
;
機械工程學系
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Department of Mechanical Engineering
innovative infrared nonlinear optical crystals AGeX(3) were synthesized. Their powder X-ray diffraction patterns demonstrated that they had rhombohedral structures with R3m (no. 160) space group symmetry (except RbGeBr3). Their structural distortion increased with Br content, but decreased with Rb content. The Kurtz powder methods revealed that the nonlinear optical efficiency of CsGeBr3 is 9.64 times that of rhombohedral CsGeCl3 and 28.29 times that of KDP; most importantly, AGeX(3) is phasematchable (except RbGeBr3). (C) 2008 Elsevier B.V. All rights reserved.
Mechanical properties of InGaN thin films deposited by metal-organic chemical vapor deposition
(2008-06-15)
Jian, Sheng-Rui
;
Jang, Jason Shian-Ching
;
Lai, Yi-Shao
;
Yang, Ping-Feng
;
Yang, Chu-Shou
We report in this study characteristics of InGaN thin films developed by metal-organic chemical vapor deposition (MOCVD) at various growth temperatures. The effect of deposition temperatures on microstructures and mechanical properties are examined using X-ray diffraction (XRD), scanning probe microscopy (SPM), and nanoindentation techniques. The XRD analysis shows no evidence of phase separation for InGaN thin films. The SPM micrographs indicate that the films have relatively smooth surfaces. Hardness and Young's modulus of InGaN thin films vary according to the deposition temperature. As the deposition temperature increases from 730 to 790 degrees C, the grain size increases from 28 to 52 nm. Hardness for InGaN thin films dropped from 13.8 to 17.6 GPa in accordance with the increase of the grain size. By fitting experimental data with the Hall-Petch equation, a probable lattice friction stress of 3.48 GPa and Hall-Petch constant of 73.15 GPa nm(1/2) are obtained. (C) 2007 Elsevier B.V. All rights reserved.
Design and analysis of an orientation estimation system using coplanar gyro-free inertial measurement unit and magnetic sensors
(2008-06-15)
Kao, C. F.
;
Chen, T. L.
;
機械工程學系
;
Department of Mechanical Engineering
Conventionally, there are two ways to determine the orientation angles of an object. One uses 3-axis accelerometers and 3-axis magnetic sensors, while the other one uses additional 3-axis gyroscopes to achieve a higher sensing accuracy than the first one. This paper presents a novel orientation estimation system that uses seven single-axis linear accelerometers and 3-axis magnetic sensors. These seven linear accelerometers are deployed in a way to form a "coplanar" gyro-free inertial measurement unit (IMU). As such, they can perform the integrated measurements of gravity force and angular velocity for the subsequent sensor fusion algorithms. With the information of the angular velocity, this novel design achieves a comparable performance with the one that includes 3-axis gyroscopes. The analysis of the system observability indicates that the angular velocity measurements can improve the observability of the angle estimation under certain circumstances. This result suggests the possibility of using fewer sensors in an orientation estimation system. Simulation results indicate that the proposed design achieve a sensing accuracy of 0.11 degrees, 0.09 degrees, and 0.2 degrees for the roll, pitch, and yaw angle; this leads to the improvement of 540%, 632%, and 754% over the one that does not include the measurement of the angular velocity. (C) 2008 Elsevier B.V. All rights reserved.
Degradation kinetics of di-(2-ethylhexyl) phthalate (DEHP) and organic matter of sewage sludge during composting
(2008-06-15)
Cheng, Hsiao-Fen
;
Kumar, Mathava
;
Lin, Jih-Gaw
;
環境工程研究所
;
Institute of Environmental Engineering
The potential degradation of di-(2-ethylhexyl) phthalate (DEHP) and organic matter of sewage sludge by composting was investigated using laboratory reactor at different operating conditions (E-1, E-2 and E-3). In all conditions, single stage thermophilic phase was observed within 2 days and almost, 60% of DEHP was degraded under this phase. At the end of composting, total DEHP degradation of more than 85% was observed in all conditions and total carbon reduction was 11.8% in E-1, 7.6% in E-2 and 10.8% in E-3. Similar trend was observed in the degradation of total nitrogen. The reduction of volatile solids (VS) in the composting reactors was 5.4% in E-1 (18 days), 5.5% in E-2 (12 days) and 4.3% in E-3 (18 days). The degradation kinetics of DEHP in thermophilic phase (including initial mesophilic phase) and the phase there after were determined by first order and fractional power kinetics, respectively. The significance of experimental parameters in DEHP degradation was assessed by Pearson correlation approach. Elevated temperature produced during composting was effective for the rapid degradation of DEHP from sewage sludge compared to mesophilic treatment. (c) 2007 Elsevier B.V. All rights reserved.
俺不說
(2008-06-15)
管管
Energy-dependent carrier relaxation in self-assembled InAs quantum dots
(2008-06-15)
Ling, H. S.
;
Lee, C. P.
;
Lo, M. C.
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
Selective excitation photoluminescence spectroscopy was employed to study InAs/GaAs self-assembled quantum dots (QDs). Under different excitation energies, different groups of QDs are selected and then emit light. The excited carriers relax to the ground state through different mechanisms when excited at different energies. Three distinct regions with different mechanisms in carrier excitation and relaxation are identified in the emission spectra. These three regions can be categorized from high energy to low energy, as continuum absorption, electronic state excitation, and multiphonon resonance. The special joint density of state tail of the QD that extends from the wetting layer band edge facilitates carrier relaxation and is posited to explain these spectral results. (C) 2008 American Institute of Physics.
俺不說
(2008-06-15)
管管
俺不說
(2008-06-15)
管管
Conducting polymer blends prepared from polyaniline with n-dodecylbenzenesulfonic acid zinc salt as the secondary dopant
(2008-06-15)
Chao, Liang
;
Han, Yu-Kai
;
Hiseh, Bi-Zen
;
Huang, Ying-Jie
;
Hsieh, Tar-Hwa
A red-shift of the UV-vis spectra of n-dodecylbenzenesulfonic acid doped polyaniline (PANI (DBSA)(0.5)), resulting from the secondary doping of polyaniline backbones, was found in the presence of n-dodecylbenzenesulfonic acid zinc salt (Zn(DBS)(2)). It is proved to behave as steric hindrance spacers to induce the extension of the conjugation length through the straightening effect on the polyaniline backbones and the obtained mixtures (PANI(DBSA)(0.5) plus Zn(DBS)(2)) can be used as master batch materials (MB-13) for blending with regular polypropylene polymer (PP). The thermal degradation accompanied with loss of conductivity for MB-13 can be delayed to over 250 degrees C.when enough Zn(DBS)(2) was secondarily doped on PANI(DBSA)0.5., which allow the performance of its blending with other nonconducting/regular polymers possible. Below 80 rpm, increasing shear rates would induce higher viscosity difference between the MB-13 and PP matrix, resulting in elongation of MB-13 in the PP matrix and higher conductivities of the polyblends. The deviation from the Taylor equation, which is used to estimate the degree of elongation for a polyblend, started when shear rate is over 80 rpm. The leakage of Zn(DBS)(2) out of MB-13 can be confirmed by comparing the DSC thermograms and X-ray diffraction patterns with that of neat PP. Gradual deformation for the conductive fillers (MB-13) and a well-defined and expanded layered structure can be found when processing time is below 15 min with 60 rpm shear rate. The layers started to shrink back after 15 min of procession with the loss of the Zn(DBS)(2) from MB-13 in the PP matrix. (c) 2008 Wiley Periodicals, Inc.
俺不說
(2008-06-15)
管管