Browsing by Issue Date, starting with "2007-07-07"

Now showing 1 - 20 of 59408

Cross-sectional transmission electron microscopy observations on the Berkovich indentation-induced deformation microstructures in GaN thin films
(2007-07-07)
Chien, Chi-Hui
;
Jian, Sheng-Rui
;
Wang, Chung-Ting
;
Juang, Jenh-Yih
;
Huang, J. C.
Nanoindentation-induced mechanical deformation in GaN thin films prepared by metal-organic chemical-vapour deposition was investigated using the Berkovich diamond tip in combination with the cross-sectional transmission electron microscopy (XTEM). By using focused ion beam milling to accurately position the cross-section of the indented region, the XTEM results demonstrate that the major plastic deformation was taking place through the propagation of dislocations. The present observations are in support of attributing the pop-ins that appeared in the load-displacement curves to the massive dislocation activities occurring underneath the indenter during the loading cycle. The absence of indentation-induced new phases might have been due to the stress relaxation via the substrate and is also consistent with the fact that no discontinuity was found upon unloading.
Dislocation reduction in GaN grown on stripe patterned r-plane sapphire substrates
(2007-07-09)
Chen, Hou-Guang
;
Ko, Tsung-Shine
;
Ling, Shih-Chun
;
Lu, Tien-Chang
;
Kuo, Hao-Chung
Extended defect reduction in GaN can be achieved via direct growth on stripe patterned (1(-)1 02) r-plane sapphire substrates by metal organic chemical vapor deposition. The striped mesa is along [11 (-)2 0] with two etched sides in {0001} and {1 (-)1 01} faces. GaN grown on both etched facets in epitaxy exhibit different crystallographic relationships with sapphire substrate which are (1 (-)1 02)(sapphire)parallel to(11 (-)2 0)(GaN) and [11 (-)2 0](sapphire)parallel to[ (-)1 100](GaN), and (0001)(sapphire)parallel to(0001)(GaN) and [11 (-)2 0](sapphire)parallel to[ (-)1 100](GaN), respectively. The dislocation densities can be significantly reduced through epitaxial growth on the inclined lateral faces of mesas. Dislocation density in the order of similar to 10(7) cm(-2) can be achieved in the tilted GaN. (C) 2007 American Institute of Physics.
n(+)-doped-layer-free microcrystalline silicon thin film transistors fabricated with the CuMg as source/drain metal
(2007-07-09)
Wang, M. C.
;
Chang, T. C.
;
Liu, Po-Tsun
;
Xiao, R. W.
;
Lin, L. F.
The feasibility of using CuMg as source/drain metal electrodes for n(+)-doped-layer-free microcrystalline silicon thin film transistors (mu-Si:H TFTs) has been investigated. The Ohmic-contact characteristic has been achieved by using the CuMg alloy as source/drain metal. Furthermore, a wet etching process of Cu alloy source/drain metal has been completed by using the ferric chloride base etchant. The proposed mu-Si:H TFT has shown similar electrical characteristic with the mu-Si:H TFT with n(+)-doped layer. The experimental result also showed that the CuMg alloy was suitable for the replacement of n(+)-doped layer in thin film transistor liquid-crystal displays. (C) 2007 American Institute of Physics.
Multi-slope handoff algorithm for controlling dynamic communication quality in wireless communications
(2007-07-10)
Huang
;
Ching Yao
;
Tsai
;
Ming Yuan
;
Huang
A multi-slope handoff algorithm for controlling dynamic communication quality in wireless communications is proposed to let a mobile node adjust the handoff slope according to different communication connection situations for setting the optimum add/drop connection trigger thresholds. The algorithm comprises the following steps. First, a mobile node receives pilot strengths of its service pilot and nearby pilots to produce an aggregate strength. Next, the mobile node determines whether to perform handoff according to the magnitude of the aggregate strength. The handoff action is then controlled by multi-slope handoff operations to set an appropriate slope and to calculate the add/drop connection trigger thresholds when performing handoff. Finally, the pilot to be connected is selected based on the communication quality at that time. In this way, the quality of the communication service can be enhanced, the connection power consumption can be lowered, and the communication channel usage can be reduced.
Method of combining multilevel memory cells for an error correction scheme
(2007-07-10)
Wu
;
Jieh-Tsorng
;
Wang
;
Ta-Hui
;
Chang
A memory combines plural memory cells for storing data wherein the differential stages voltage levels of memory cells are not limited in square value of 2 and can be improved linearly. The feature of the present invention can also increase memory capacity without increasing memory area. Furthermore it can remain voltage levels which cannot express 0 and 1 combination for error erasure messages when data is read. For efficient usage of memory, the increased memory capacity is not only for storing data but also for storing error correction scheme to assure the veracity of the storing data and improve producing yield and reliability for multilevel memory systems.
Structural evolution of poly(styrene-b-4-vinylpyridine) diblock copolymer/gold nanoparticle mixtures from solution to solid state
(2007-07-10)
Huang, Ching-Mao
;
Wei, Kung-Hwa
;
Jeng, U-Ser
;
Liang, Keng S.
;
材料科學與工程學系
We used in situ annealing small-angle X-ray scattering to monitor the structural evolution of a spherical poly(styrene-b-4-vinylpyridine) diblock copolymer (PS-b-P4VP)/2-phenylethanethiol-coated Au nanoparticle (AuSC2Ph) mixture in the solid state during its thermal annealing. We found that the Au nanoparticles (NPs) that existed initially in a random state with some cluster packing in the PS domain diffused to the interface of the amphiphilic PS-b-P4VP diblock copolymer within 4 h at 170 degrees C under vacuum to form NP-filled shell-like assemblies, as further evidenced from transmission electron microscopy imaging. From the X-ray photoelectron spectroscopy data, we speculate that this interfacial activity of AuSC2Ph results from the fact that the initially hydrophobic Au NP surfaces became increasingly hydrophilic as most of the 2-phenylethanethiol ligands had evaporated off. The Au NP nanoshell assemblies located at the interface between PS and P4VP were quite stable even after redissolving in toluene; they remained in the form of PS-Au-P4VP core/shell/corona onion micelles, as evidenced from solution state small-angle X-ray scattering data.
Transient evolution of carbon monoxide poisoning effect of PBI membrane fuel cells
(2007-07-10)
Wang, Chien-Ping
;
Chu, Hsin-Sen
;
Yan, Yi-Yie
;
Hsueh, Kan-Lin
;
機械工程學系
High temperature poly benzimidazole membrane fuel cells are the focus of attention due to high CO tolerance and overcoming water managements. This paper develops a transient. one-dimensional mathematical model to predict CO tolerance, and validates it with experiments. Experimental results are measured at different temperatures. Fuel cell performance degradations with time are also measured under various fuel compositions. Transient evolutions of current density, H-2 coverage, CO coverage, and ionic potential are shown during the CO poisoning process. The theoretical results show that hydrogen coverage decreases with time, reducing hydrogen oxidation reactions and dropping ionic potential loss. The effects of temperature. CO contents. and H-2 dilutions on fuel cell performance and the time to reach steady t(ss) are all investigated. Predictions of fuel cell current density degradation also show good agreement with experimental results. (c) 2007 Elsevier B.V. All rights reserved.
Kernel support for zero-loss Internet service restart
(2007-07-10)
Chang, Da-Wei
;
Tsai, Chuan-Ming
;
Li, Wei-Kou
;
Lee, Tzu-Rung
;
資訊工程學系
Owing to long serving time and huge numbers of clients, Internet services can easily suffer from transient faults. Although restarting a service can solve this problem, information of the on-line requests will be lost owing to the service restart, which is unacceptable for many commercial or transaction-based services. In this paper, we propose an approach to achieve the goal of zero-loss restart for Internet services. Under this approach, a kernel subsystem is responsible for detecting the transient faults, retaining the I/O channels of the service, and managing the service restart How. In addition, some straightforward modifications to the service should be made to take advantage of the kernel support. To demonstrate the feasibility of our approach, we implemented the subsystem in the Linux kernel. Moreover, we modified a Web server and a CGI program to take advantage of the kernel support. According to the experimental results, our approach incurs little runtime overhead (i.e. less than 3.2%). When the service crashes, it can be restarted quickly (i.e. within 210 mu s) with no information loss. Furthermore, the performance impact due to the service crash is small. These results show that the approach can efficiently achieve the goal of zero-loss restart for Internet services. Copyright (C) 2006 John Wiley & Sons, Ltd.
Copper metalized ohmic contact electrode of compound device
(2007-07-12)
Lee, Cheng-Shih
;
Chang, Edward Yi
;
Chen, Ke-Shian
The present invention provides an ohmic contact for a copper metallization whose heat diffusion is improved and cost is reduced. Therein, the ohmic contact is formed through a depositing and an annealing of three metal layers of Pd, Ge and Cu; and, the contact resistance of the ohmic contact is adjusted by the thicknesses of the three layers.
Staggered source/drain and thin-channel TFT structure and fabrication method thereof
(2007-07-12)
Chang, Kow-Ming
;
Lin, Gin-Min
This invention relates to a process for fabricating a staggered source/drain and thin-channel TFT structure, which simplifies the conventional process for fabricating the structure by decreasing the number of mask steps and achieving better results at suppressing the electric field near the drain junction and reducing the leakage current. The process comprises (1) re-crystallizing a-Si into poly-Si (02), which is performed by depositing an a-Si layer on a substrate and then applying a general photolithographic step and a RIE etching step for defining the amorphous Si islands provided with higher regions and lower regions, wherein the residual width of the thin channel of the a-Si is about 5 to 200 nm after etching; then the a-Si is changed into poly-Si (02) after a subsequent annealing; (2) defining the gate region (05), source/drain region (07) and the channel; (3) applying the implantation; and (4) applying the connection.
Pragmatical generalized synchronization of chaotic systems with uncertain parameters by adaptive control
(2007-07-15)
Ge, Zheng-Ming
;
Yang, Cheng-Hsiung
;
機械工程學系
;
Department of Mechanical Engineering
A new kind of generalized synchronization of two chaotic systems with uncertain parameters is proposed. Based on a pragmatical asymptotical stability theorem and an assumption of equal probability for ergodic initial conditions, an adaptive control law is derived so that it can be proved strictly that the common null solution of error dynamics and of parameter dynamics is actually asymptotically stable, i.e. these two identical systems are in generalized synchronization and the estimated parameters approach the uncertain values. It is called pragmatical generalized synchronization. Finally, two numerical examples are studied for two Quantum-CNN oscillator chaotic systems to show the effectiveness of the proposed generalized synchronization strategy with a double Duffing chaotic system as a goal system. (C) 2007 Elsevier B.V. All rights reserved.
White electroluminescence from a single polymer: A blue-emitting polyfluorene incorporating orange-emitting benzoselenadiazole segments on its main chain
(2007-07-15)
Chien, Chen-Han
;
Shih, Ping-I
;
Shu, Ching-Fong
;
應用化學系
;
Department of Applied Chemistry
We have developed efficient white-light-emitting polymers through the incorporation of low-bandgap orange-light-emitting benzoselenadiazole (BSeD) moieties into the backbone of a blue-light-emitting bipolar polyfluorene (PF) copolymer, which contains hole-transporting triphenylamine and electron-transporting oxadiazole pendent groups. By carefully controlling the concentrations of the low-energy-emitting species in the resulting copolymers, partial energy transfer from the blue-fluorescent PF backbone to the orange-fluorescent segments led to a single polymer emitting white light and exhibiting two balanced blue and orange emissions simultaneously. Efficient polymer light-emitting devices prepared using this copolymer exhibited luminance efficiencies as high as 4.1 cd/A with color coordinates (0.30, 0.36) located in the white-light region. Moreover, the color coordinates remained almost unchanged over a range of operating potentials. A mechanistic study revealed that energy transfer from the PF backbone to the low-bandgap segments, rather than charge trapping, was the main operating process involved in the electroluminescence process. (c) 2007 Wiley Periodicals, Inc. Inc.
Influences of Ti, TiN, Ta and TaN layers on integration of low-k SiOC : H and Cu
(2007-07-15)
Tsai, Kou-Chiang
;
Wu, Wen-Fa
;
Chao, Chuen-Guang
;
Hsu, Jwo-Lun
;
Chiang, Chiu-Fen
The interactions between low-k material hydrogenated silicon oxycarbide (SiOC:H) and barrier layers, Ta, TaN, physical-vapor deposition (PVD) and chemical-vapor deposition (CVD) Ti and TiN, have been investigated. The results show these barriers except TaN can react with SiOC:H at evaluated temperature. Furthermore, significant interactions of carbon and oxygen due to the degradation of the SiOC:H films upon annealing exist for all barrier/SiOC:H structures. The CVD-TiN structure can retard the hydrogen out-diffusion, while PVD-TiN structure induces the H out-diffusion from the SiOC:H films. By studying flat band voltage shift in C-V tests, it is demonstrated that Cu+ ions drift into SiOC:H under electric field at elevated temperatures. A thin layer of TaN is proven to be good Cu drift barrier layer with SiOC:H dielectrics. (c) 2007 Elsevier B.V. All rights reserved.
Synthesis and characterization of a polyfluorene containing carbazole and oxadiazole dipolar pendent groups and its application to electroluminescent devices
(2007-07-15)
Yuan, Mao-Chuan
;
Shih, Ping-I
;
Chien, Chen-Han
;
Shu, Ching-Fong
;
應用化學系
We have synthesized a blue-light-emitting polyfluorene (PF) derivative (PF-CBZ-OXD) that presents bulky bole-transporting carbazole and electron-transporting oxadiazole pendent groups functionalized. at the C-9 positions of alternating fluorene units. The results from photoluminescence and electrochemical measurements indicate that both the side chains and the PF main chain retain their own electronic characteristics in the copolymer. An electroluminescent device incorporating this polymer as the emitting layer was turned on at 4.5 V; it exhibited a stable blue emission with a maximum external quantum efficiency of 1.1%. Moreover, we doped PF-CBZ-OXD and its analogue PF-TPA-OXD with a red-light-emitting iridium phosphor for use as components of phosphorescent red-light emitters to investigate the effect of the host's HOMO energy level on the degree of charge trapping and on the electrophosphorescent efficiency. We found that spectral overlap and individual energy level matching between the host and guest were both crucial features affecting the performance of the electroluminescence devices. Atomic force microscopy measurements indicated that the dipolar nature of PF-CBZ-OXD, in contrast to the general nonpolarity of polydialkylfluorenes, provided a stabilizing environment that allowed homogeneous dispersion of the polar iridium triplet dopant. (c) 2007 Wiley Periodicals, Inc.
Evolution of self-assembled InAs quantum ring formation
(2007-07-15)
Ling, Hong-Shi
;
Lee, Chien-Ping
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
The evolution of InAs quantum ring (QR) formation and the corresponding optical properties were investigated by atomic force microscopy (AFM) and photoluminescence (PL) spectroscopy. Just like a nanoscale volcanic eruption, the transformation from quantum dots (QDs) to QRs using the capping and annealing process depends on how much InAs is removed from the center of the dots to the surrounding areas. The final structure was found to depend on the annealing temperature and the cap layer thickness. We have investigated the QR formation at different stages using various growth conditions. The findings provided a clear picture on the mechanism of ring formation. We were able to obtain QRs with various geometries by controlling these growth parameters. (c) 2007 American Institute of Physics.
Thermal properties of polystyrene nanocomposites formed from rigid intercalation agent-treated montmorillonite
(2007-07-15)
Yei, Ding-Ru
;
Fu, Hue-Kuan
;
Chang, Yu-Hsin
;
Kuo, Shiao-Wei
;
Huang, Jieh-Ming
Polystyrene (PS)/clay nanocomposites were prepared with two different new intercalation organophilic clays, the phosphonium salt (APP) and the ammonium 4-(4-adamantylphenoxy)-1-butanamine (APB) salts, by emulsion polymerization technique. X-ray diffraction and transmission electron microscopy were performed to characterize the layered structures of APB- and APP-treated polymer-clay nanocomposites, and both resulted in exfoliated structures. Molecular weights of PS obtained from these nanocomposites are slightly lower than the virgin PS formed under similar polymerization conditions. Coefficient of thermal expansion showed approximately a 44-55% decrease for APB- and APP-intercalated clay nanocomposites relative to the pure PS. Both T-g and thermal decomposition temperature of the PS component in the nanocomposite are higher than the virgin PS, implying that the presence of clay is able to enhance thermal stabilities of the PS. (c) 2007 Wiley Periodicals, Inc.
Electro-optical properties of poly(1-(difluorophenyl)-2(4-alkylcyclohexyl phenyl)acetylene) organic light-emitting diodes
(2007-07-16)
Huang, Chun-Hao
;
Lee, Chih-Wen
;
Hsu, Chain-Shu
;
Renaud, Cedric
;
Nguyen, Thien-Phap
For organic light-emitting diodes (OLEDs) applications, we have investigated novel polymers, using substituted polyacetylenes (PA), poly(I (fluorophenyl)-2-(alkylcyclohexylphenyl)acetylene) (PDPA-nF) (n =1 or n = 2) which exhibit air stability, better solubility in common organic solvent and higher luminescence than polyacetylene. In this study, we have used poly[(1-(3,4-difluorophenyl)-2-(4-pentylcyclohexylphenyl) acetylene)] (PDPA-2F) as an emitter in OLEDs and their performance was determined by measuring the cuffent-voltage-luminance characteristic. The devices have a maximum brightness of 827 candela (cd)/M-2 at 12 V and a maximum current efficiency of 0. 7 8 cd/A at 9 V with a maximum luminescence at 536 nm. Influence of the metal electrode on the charge injection was studied using several cathode configurations (Ca, Al and Au) for the devices. Furthermore, the charge injection and transport processes were correlated to the presence of traps inside the polymer, determined by deep level transient spectroscopy (DLTS). (c) 2007 Elsevier B.V. All rights reserved.
在無線通訊系統下適應性RTO的預測方法
(2007-07-16)
羅文嶽
因為舊有的TCP傳輸控制方法直接應用在無線通訊上會產生錯誤,例如一些錯誤的控制數據估測導致誤判為網路壅塞,本發明提出一個為適應性RTO(Retransmission Time Out)控制方法來修正。這個控制方法可以動態改變來回傳輸時間的預測値來適應現在的頻寬狀況。因為正確的RTO數値可以藉由新的適應性的來回傳輸時間的預測値來計算出來,所以可以解決由於因頻寬變動造成不正確的RTO數値所造成誤判網路狀況和不必的重新傳輸問題,從而增加TCP在無線系統下的效能。
表情轉換比對之人臉表情辨識技術
(2007-07-16)
連振昌
;
張揚凱
;
黃仲陵
本發明係提供一種表情轉換比對之人臉表情辨識技術,其係以訓練方式得到各種表情間的特徵轉換矩陣,並可依實際需求調整特徵轉換矩陣的維度大小以控制系統的準確度及運算時間,再以特徵轉換矩陣建立出各種表情模型,將該表情模型應用於臉部表情辨識比對上。在過程中並不需要接觸或穿戴任何裝置,且可有效降低運算量,節省運算時間達到即時辨識之功效。
堆疊式源／汲極與薄通道之複晶矽薄膜電晶體結構，及其製作方法
(2007-07-16)
張國明
;
林俊銘
本發明提供堆疊式源/汲極複晶矽薄膜電晶體結構之製造方法,其簡化了習知製作堆疊式源/汲極複晶矽薄膜電晶體結構之光罩數量且可有效降低汲極附近的高電場並具有降低漏電電流的功效。本發明步驟包括:(1)將非晶矽層再結晶為複晶矽層(02)之步驟;先於基板上沈積一非晶矽層,再進行一般曝光微影以及利用RIE蝕刻技術以定義出具有高區間與低區間之非晶矽島狀物,其中蝕刻後之非晶矽薄通道區剩餘厚度約5-200nm,然後再進行退火以使該非晶矽層再結晶為複晶矽層(02);(2)定義閘極區(05)、源/汲極區(07)與通道區之步驟;(3)佈植步驟;以及(4)接線步驟。