Browsing by Issue Date, starting with "2005-02-03"

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Growth of GaAs epitaixial layers on Si substrate by using a novel GeSi buffer layer
(2005-02-03)
Chang, Edward Y.
;
Luo, Guangli
;
Yang, Tsung Hsi
;
Chang, Chung Yen
This invention provides a process for growing Ge epitaixial layers on Si substrate by using ultra-high vacuum chemical vapor deposition (UHVCVD), and subsequently growing a GaAs layer on Ge film of the surface of said Ge epitaixial layers by using metal organic chemical vapor deposition (MOCVD). The process comprises steps of, firstly, pre-cleaning a silicon wafer in a standard cleaning procedure, dipping it with HF solution and prebaking to remove its native oxide layer. Then, growing a high Ge-composition epitaixial layer, such as Si0.1Ge0.9 in a thickness of 0.8 μm on said Si substrate by using ultra-high vacuum chemical vapor deposition under certain conditions. Thus, many dislocations are generated and located near the interface and in the low of part of Si0.1Ge0.9 due to the large mismatch between this layer and Si substrate. Furthermore, a subsequent 0.8 μm Si0.05Ge0.95 layer, and/or optionally a further 0.8 μm Si0.02Ge0.98 layer, are grown. They form strained interfaces of said layers can bend and terminate the propagated upward dislocation very effectively. Therefore, a film of pure Ge is grown on the surface of said epitaixial layers. Finally, a GaAs epitaixial layer is grown on said Ge film by using MOCVD.
Terahertz phase shifter or retarder based on magnetically controlled birefringence in liquid crystals
(2005-02-03)
Pan, Ci-Ling
;
Chao, Ru-Pin
;
Chen, Chao-Yuan
The present invention enables a means of continuously shifting the phase of electromagnetic waves in the THz (0.1 to 10 THz, 1 THz=10−12 Hz) or sub-millimeter wave range. It is based on magnetically controlled birefringence of liquid crystals. The device consists of an assembly of a liquid crystal cell and rotatable magnets. By varying the angle of the magnet with respect to the incident THz wave, desired phase shift or delay can be achieved. To increase the amount of phase shift, the device employs multiple liquid crystal cells in a compact sandwich structure.
Epitope mapping of a monoclonal antibody specific to bovine dry milk - Involvement of residues 66-76 of strand D in thermal denatured beta-lactoglobulin
(2005-02-04)
Song, CY
;
Chen, WL
;
Yang, MC
;
Huang, JP
;
Mao, SJT
beta-Lactoglobulin (beta-LG) is a bovine milk protein sensitive to thermal denaturation. Previously, we demonstrated that such structural change can be detected by a monoclonal antibody (mAb) specific to denatured beta-LG. In the present study, we show a dramatic increase in beta-LG immunoreactivity when heating raw milk between 70 and 80 degreesC. To map out the specific epitope of beta-LG recognized by this mAb, we used a combined strategy including tryptic and CNBr fragments, chemical modifications (acetylation and carboxymethylation), peptide array containing in situ synthesized peptides, and a synthetic soluble peptide for immunoassays. The antigenic determinant we defined was exactly located within the D strand (residues 66-76) of beta-LG. Circular dichroic spectral analysis shows that carboxymethylation on beta-LG not only resulted in a substantial loss of beta-configuration but also exerted a 10 times increase in immunoreactivity as compared with heated beta-LG. The result suggests that a further disordered structure occurred in beta-LG and thus rendered the mAb recognition. Mutations on each charged residue (three Lys and one Glu) revealed that Lys-69 and Glu-74 were extremely essential in maintaining the antigenic structure. We also show an inverse relationship between the immunoreactivity in heated beta-LG and its binding to retinol or palmitic acid. Most interestingly, pH 9-10, which neutralizes the Lys groups of beta-LG, not only reduced its immunoreactivity but also its binding to palmitic acid implicating a role of Lys-69. Taken together, we concluded that strand D of beta-LG participated in the thermal denaturation between 70 and 80 degreesC and the binding to retinol and palmitic acid. The antigenic and biochemical roles of mAb specific to D strand are discussed in detail.
雪泥
(2005-02-05)
管管
The kinetics of B-a and P-a type copolybenzoxazine via the ring opening process
(2005-02-05)
Su, YC
;
Yei, DR
;
Chang, FC
;
應用化學系
;
Department of Applied Chemistry
The structure of benzoxazines is similar to that of phenolic resin through thermal self-curing of the heterocyclic ring opening reaction that neither requires catalyst nor releases any condensation byproduct. These polybenzoxazine resins have several outstanding properties such as high thermal stability and high glass transition temperature. To better understand the curing kinetics of this copolybenzoxazine thermosetting resin, dynamic and isothermal differential scanning calorimetry measurements were performed. Three models, the Kissinger method, the Flynn-Wall-Osawa method, and the Kamal method, were used to describe the curing process. Dynamic kinetic activation energies based on Kissinger and Flynn-Wall-Osawa methods are 72.11 and 84.06 KJ/mol, respectively. The Kamal method based on an autocatalytic model results in a total order of reaction between 2.66 and 3.03, depending on curing temperature. Its activation energy and Arrhenius preexponential are 50.3 KJ/mol and 7959, respectively. (C) 2004 Wiley Periodicals, Inc.
親嘴的新考據
(2005-02-06)
管管
1.2-ps mode-locked semiconductor optical amplifier fiber laser pulses generated by 60-ps backward dark-optical comb injection and soliton compression
(2005-02-07)
Lin, GR
;
Chiu, IH
;
Wu, MC
;
光電工程學系
;
Department of Photonics
Optically harmonic mode-locking of a semiconductor optical amplifier fiber laser (SOAFL) induced by backward injecting a dark-optical comb is demonstrated for the first time. The dark-optical comb with 60-ps pulsewidth is generated from a Mach-Zehnder modulator, which is driven by an electrical comb at a DC offset of 0.3V(pi). Theoretical simulation indicates that the backward injection of dark-optical comb results in a narrow gain window of 60 ps within one modulating period, providing a cross-gain-modulation induced mode-locking in the SOAFL with a shortest pulsewidth of 15 ps at repetition frequency of 1 GHz. The mode-locked SOAFL pulsewidth can be slightly shortened to 10.8 ps with a 200m-long dispersion compensating fiber. After nonlinearly soliton compression in a 5km-long single mode fiber, the pulsewidth, linewidth and time-bandwidth product become 1.2 ps, 2.06 nm and 0.31, respectively. (C) 2005 Optical Society of America.
Synthesis and characterization of luminescent polyfluorenes incorporating side-chain-tethered polyhedral oligomeric silsesquioxane units
(2005-02-08)
Chou, CH
;
Hsu, SL
;
Dinakaran, K
;
Chiu, MY
;
Wei, KH
Using Suzuki polycondensation, we have synthesized polyhedral silsesquioxane-tethered polyfluorene copolymers, poly(9,9'-dioctylfluorene-co-9,9'-bis[4-(N,N-dipolysilsesquioxane)aminophenyl]fluorene) (PFO-POSS), that have well-defined architectures. This particular PFO-POSS molecular architecture increases the quantum yield of polyfluorene significantly by reducing the degree of interchain aggregation; in addition, these copolymers exhibit a purer and stronger blue light by preventing the formation of keto defects.
Ferroelectric thin film processing for ferroelectric field-effect transistor
(2005-02-08)
Chen
;
San-Yuan
;
Sun
;
Chia-Liang
;
Chin
The present invention relates to a method for manufacturing a ferroelectric field-effect transistor, particularly to a ferroelectric field-effect transistor with a metal/ferroelectric/insulator/semiconductor (MFIS) gate capacitor structure. The method comprises steps of depositing a bismuth layered ferroelectric film on the insulator buffered Si, after a high-temperature thermal treatment, depositing an upper electrode on the bismuth layered ferroelectric film.
New dopant and host materials for blue-light-emitting phosphorescent organic electroluminescent devices
(2005-02-10)
Yeh, SJ
;
Wu, MF
;
Chen, CT
;
Song, YH
;
Chi, Y
Efficient organic light-emitting diodes (OLEDs) incorporating Ir-III bis(4,6-difluorophenylpyridinato)3-(trifluoromethyl)-5-(pyridin-2-yl)-1,2,4-triazolate (FIrtaz) and Ir-III bis(4,6-difluorophenylpyridinato)-5- (pyridin-2-yl)-1H-tetrazolate (FIrN4) demonstrate higher-purity blue-light emission than the long-known Ir-III bis(4,6-difluorophenylpyridinato)-picolate (FIrpic) phosphorophore. New host materials with higher glass-transition temperatures were also found to enhance the OLED performance.
分波多工網路中之光功率監測裝置
(2005-02-11)
祁甡
;
李健仲
;
葉建宏
本案關於一種分波多工網路中之光功率監測裝置，尤指一種藉掃描摻鉺光纖放大器不同的增益頻譜方式而應用於分波多工網路中之光功率監測裝置。本案可藉注入一個飽和頻來對此光放大器作到增益箝制的要求。本案分波多工網路中之光功率監測裝置使用的元件取得方便且價格便宜，對於WDM光通訊系統的頻率及功率的監測具有極大的價值，亦可大幅提高對光纖網路系統波頻監測之解析度。
以邊界聲源表示法為基礎之空間音效混成方法
(2005-02-11)
白明憲
;
歐昆應
一種以邊界聲源表示法為基礎之空間音效混成方法；主要係將密閉空間聲場等效成一個主要聲源以及均勻分布在聲場邊界上的虛擬次要聲源。虛擬次要聲源即是用來模擬聲場的反射以及混響的現象，最後根據這個假設所推導數學模式將符合波動方程式(wave equation)。由這個關係式，利用最小平方法(least-square procedure)來求解反矩陣以得到每個虛擬聲源的強度。所算出來的一組虛擬聲源強度即代表一個特定的聲場所產生的混響效果。在模擬的過程中亦可以設定其聲場的幾何大小，以及與頻率相關的邊界條件如聲場邊界的吸音律。
Synthesis of alpha-galactosyl ceramide and the related glycolipids for evaluation of their activities on mouse splenocytes
(2005-02-14)
Fan, GT
;
Pan, YS
;
Lu, KC
;
Cheng, YP
;
Lin, WC
Phytosphingosine and its short-chain analog were efficiently synthesized with 19% overall yield in 10 steps, respectively, starting from an inexpensive D-lyxose. Galactosyl donors of sulfide and phosphite types bearing benzoyl protecting groups of 4- and 6OH underwent glycosylation in excellent alpha-anomeric selectivity. A variety of alpha-galactosyl, fucosyl and glucosyl ceramides and serine-type lipids were prepared, and their activities involved in the proliferation of mouse splenocytes and the expression of cytokines were elucidated. Besides alpha-galactosyl ceramides, a galactosyl serine-type lipid also exhibited substantial effect on the expression of cytokines IFN-gamma and IL-4. (C) 2004 Elsevier Ltd. All rights reserved.
Preparation and characterization of poly seudorotaxanes based on adamantane-modified polybenzoxazines and beta-cyclodextrin
(2005-02-14)
Su, YC
;
Chen, WC
;
Chang, FC
;
應用化學系
;
Department of Applied Chemistry
P-Cyclodextrin (P-CD) forms inclusion complexes (ICs) with adamantane-modified benzoxazines (2 benzoxazine and 3 benzoxazine). These benzoxazines can readily penetrate into the CD's hydrophobic cavity, causing turbidity of their solutions, from which fine crystalline powders are obtained. We characterized these complexes by powder X-ray diffraction, C-13 and C-13 CP/MAS NMR spectroscopies, DSC, and TGA. The X-ray diffraction and solid-state C-13 CP/MAS NMR spectroscopy indicate that the IC domains of the polypseudorotaxanes maintain their channel-type structures after the ring-opening curing reactions have occurred. Furthermore, DSC measurements indicate that complexing the adamantane-modified benzoxazine units with beta-CDs result in stiffer main chains and, thus, higher glass transition temperature. TGA also indicates that the inclusion complexes have enhanced its thermal stability. (C) 2004 Published by Elsevier Ltd.
A new strategy for the one-step synthesis of block copolymers through simultaneous free radical and ring opening polymerizations using a dual-functional initiator
(2005-02-14)
Huang, CF
;
Kuo, SW
;
Lee, HF
;
Chang, FC
;
應用化學系
Block copolymers are fascinating and complex materials that have been used in a range of diverse scientific and technological capacities. We demonstrate that a single one-step approach based on dual simultaneous polymerizations is a viable technique for the synthesis of a wide range of block copolymers by combining two dissimilar polymerization systems and using a dual-functional initiator. The main advantage of this methodology is that a simple, one-step, and simultaneous polymerization occurs in the bulk, which makes this process very attractive from both industrial and academic points of view. We plan to study the reaction kinetics and evaluate how well the ring opening catalyst [in this case, Sn(oct)(2)] works under reverse ATRP conditions. (C) 2004 Elsevier Ltd. All rights reserved.
Stimulated Raman scattering in a potassium titanyl phosphate crystal: simultaneous self-sum frequency mixing and self-frequency doubling
(2005-02-15)
Chen, YF
;
電子物理學系
;
Department of Electrophysics
A potassium titanyl phosphate crystal is used to achieve efficient stimulated Raman scattering conversion with simultaneous self-sum frequency mixing and self-frequency doubling. Inside a diode-pumped Nd:YAG Q-switched laser cavity, 1.03 W of 1129-nm second Stokes average output power and 0.25 W of 548-nm sum-frequency average power are simultaneously generated with a diode input power of 10 W at a pulse repetition rate of 10 kHz. (C) 2005 Optical Society of America.
Polyfluorene containing diphenylquinoline pendants and their applications in organic light emitting diodes
(2005-02-15)
Su, HJ
;
Wu, FI
;
Shu, CF
;
Tung, YL
;
Yun, C
We present a short, efficient synthetic route for the preparation of a novel polyfluorene copolymer (PF-Q) containing two electron-deficient, 2,4-diphenylquinoline groups functionalized at the C-9 positions of alternate fluorene units that form a three-dimensional cardostructure. The presence of the rigid bulky pendent groups leads to a polyfluorene possessing a high glass-transition temperature (207 degreesC) and very good thermal stability (5% weight loss observed at 460 degreesC). A photoluminescence study revealed that the Forster energy transfer from the excited quinoline groups to the polyfluorene backbone is Very efficient; it also demonstrated that, the commonly observed aggregate/excimer formation in polyfluorenes is suppressed very effectively, in this polymer, even after it has been annealed at 150 degreesC for 20 h. A light emitting diode (LED) device prepared with PF-Q as the emitting layer exhibits a stable blue emission with a maximum brightness of 1121 cd/m(2) at 12 V and a maximum external quantum efficiency of 0.80% at 250 cd/m(2). We also used PF-Q, which contains diphenylquinoline units that behave as electron-transporting side chains, as a host. material and doped it with 2.4 wt % of a red-emitting phosphorescent dye, Os(fppz). to realize a red electrolumineseence with CIE color coordinates of (0.66, 0.34). The doped device exhibits a maximum external quantum efficiency of 6.63% (corresponding a luminance efficiency of 8.71 cd/A) at a current density of 47.8 mV/cm(2) together with a maximum brightness of 10457 cd/m(2). (C) 2005 Wiley Periodicals, Inc.
A two-level scheduling method: an effective parallelizing technique for uniform nested loops on a DSP multiprocessor
(2005-02-15)
Lee, YH
;
Chen, C
;
資訊工程學系
;
Department of Computer Science
A digital signal processor (DSP), which is a special-purpose microprocessor, is designed to achieve higher performance on DSP applications. Because most DSP applications contain many nested loops and permit a very high degree of parallelism, the DSP multiprocessor has a suitable architecture to execute these applications. Unfortunately, conventional scheduling methods used on DSP multiprocessors allocate only one operation to each DSP every time unit, even if the DSP includes several function units that can operate in parallel. Obviously they cannot achieve full function unit utilization. Hence, in this paper, we propose a two-level scheduling method (TSM) to overcome this common failing. TSM contains two approaches, which integrates unimodular transformations, loop tiling technique, and conventional methods used on single DSP, Besides introducing algorithm, we also use an analytic module to analyze its preliminary performance. Based on our analyses the TSM can achieve shorter execution time and more scalable speedup results. In addition, the TSM causes less memory access and synchronization overheads, which are usually negligible in the DSP multiprocessor architecture. (C) 2004 Elsevier Inc. All rights reserved.
Growth of zinc oxide thin films on Y2O3/Si substrates by chemical vapor deposition
(2005-02-15)
Lin, Chih-Wei
;
Cheng, Tsan-Yao
;
Chang, Li
;
Juang, Jenh-Yih
;
電子物理學系
Epitaxial ZnO was deposited on Si(1 1 1) substrate by atmospheric pressure metal-organic chemical vapor deposition (MOCVD) at 500 degrees C. A Y2O3 buffer layer in epitaxy with Si substrate has successfully suppressed the Si oxidation before ZnO deposition. The Y2O3 film was grown by pulsed laser deposition (PLD) on Si(1 1 1) substrate at 800 degrees C. Also, ZnO was deposited by PLD for comparison with MOCVD. X-ray diffraction and cross-sectional transmission electron microscopy was used to characterize microstructures of the ZnO films and their interfaces with Y2O3. The result shows ZnO(0 0 0 2) parallel to Y2O3(1 1 1). With the increase of the deposition time, the grain morphology of ZnO thin films evolved from flat structure to columnar structure. Most of the columnar ZnO grains are c-axis oriented perpendicular to the interface. (C) 2004 Elsevier B. V. All rights reserved.
Synthesis of silicon carbide nanostructures via a simplified Yajima process - Reaction at the vapor-liquid interface
(2005-02-23)
Wang, CH
;
Chang, YH
;
Yen, MY
;
Peng, CW
;
Lee, CY
A preceramic polymer route developed in 1975 has been simplified to efficiently generate beta-SiC nanostructures, including cubic cages (see Figure), cubic shells, and nanoparticles. The nanostructures are generated by the reaction of liquid sodium with the vapors of methylchlorosilanes, with the morphology of the resulting nanostructures dependent upon the interactions between the phase-separated solid products generated at the interface of the vapor-liquid/solid reactions.