Browsing by Issue Date, starting with "2007-05-21"

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High-performance bottom-contact devices based on an air-stable n-type organic semiconductor N,N-bis (4-trifluoromethoxybenzyl)-1,4,5,8-naphthalene-tetracarboxylic di-imide
(2007-05-21)
Kao, Chia-Chun
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Lin, Pang
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Lee, Cheng-Chung
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Wang, Yi-Kai
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Ho, Jia-Chong
N,N-bis(4-trifluoromethoxybenzyl)-1,4,5,8-naphthalene-tetracarboxylic di-imide was applied to organic semiconductors for bottom-contact thin-film transistors. The carrier mobility was 1.6x10(-2) cm(2) V-1 s(-1), the threshold voltage (V-T) was +5.5 V, and the on/off current ratio was 8.6x10(5). Devices without any further surface treatments were tested in an ambient environment. The threshold voltage shift (Delta V-T) was verified by gate bias stress measurements. A prototype compound, N,N-bis(4-trifluoromethylbenzyl)naphthalene-1,4,5,8-tetracarboxylic di-imide, shows direct correlation to the bottom-contact device with the varied molecular structure. (c) 2007 American Institute of Physics.
Using double layer CoSi2 nanocrystals to improve the memory effects of nonvolatile memory devices
(2007-05-21)
Yang, F. M.
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Chang, T. C.
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Liu, P. T.
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Yeh, P. H.
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Chen, U. S.
The nonvolatile memory device with multilayer nanocrystals has advantages such as the memory effects can be increased by the increasing density of the nanocrystals and the whole retention characteristic can be improved. There are much more electrons that can be stored in the double layer than single layer nanocrystal memory device. The double layer CoSi2 nanocrystals have better retention characteristic than the single layer. The good retention characteristic of the double layer device is due to the Coulomb-blockage effects on the top layer nanocrystals from the bottom layer nanocrystals. So, the memory effects of the nonvolatile memory device can be improved by using the double layer nanocrystals. (c) 2007 American Institute of Physics.
Exciton energy transfer between optically forbidden states of molecular aggregates
(2007-05-21)
Kobayashi, Takayoshi
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Taneichi, Takashi
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Takasaka, Shigehiro
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電子物理學系
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先進超快雷射研究中心
3-ethyl-2-[3-(3-ethyl-2(3H)-benzoxazolylidene)-1-propenyl]benzoxazolium iodide (dye I) and pseudoisocyanine bromide are employed to form H aggregates as donors and J aggregates as acceptors. The energy of an H band of the H aggregates is higher than that of a J band of the J aggregates. It was confirmed that excitation of the H band does not emit fluorescence by comparison of excitation spectra of dye I H aggregates with that of dye I monomer. Absorption, fluorescence, and excitation spectra of spin-coated films of H aggregates mixed with various quantities of J aggregates have been observed. Excitation spectra probed at the J band are found to have a component of the H band. Fluorescence spectra originated from excitation of the H band are extracted and qualitatively analyzed. It is confirmed that excitation of the H band causes to emit fluorescence of a J band of the J aggregates. These phenomena show that exciton energy can transfer from the lowest energy in electronic states of the H aggregate, which state is optically forbidden, to electronic state of the J aggregate. (C) 2007 American Institute of Physics.
交大e-News第002期
(2007-05-21)
Secretariat
;
國立交通大學秘書室
Micellar morphologies of self-associated diblock copolymers in acetone solution
(2007-05-21)
Tung, Pao-Hsiang
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Kuo, Shiao-Wei
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Chen, Shih-Chien
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Lin, Chen-Lung
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Chang, Feng-Chih
We describe the synthesis and solution morphologies of poly(vinyl phenol-b-styrene) (PVPh-b-PS) micelles and the effects that changing the copolymer composition and concentration have on self-assembly structures of PVPh-b-PS in acetone (a good solvent for PVPh). These PVPh-b-PS copolymers aggregated into spherical, rod-like, and vesicular morphologies. The transformations of the PVPh-b-PS block copolymer micelles in acetone depended on a number of parameters, including the relative block lengths, their concentrations, and the degree of self-association through hydrogen bonding of the coronal PVPh chains. We also investigated the morphologies of the micelles formed from acetone solutions of poly (4-tert-butoxystyrene-b-styrene) (PtBOS-b-PS) copolymers having the same degree of polymerization as the precursor of PVPh-b-PS copolymer before hydrolysis reaction. Our results indicate that the micelles formed from PVPh-b-PS copolymers in acetone were more complicated than those prepared from PtBOS-b-PS copolymers in acetone because hydrogen bonding occurs in the micelle corona of the PVPh block. Finally, we also discussed the morphology transition when the self-association hydrogen bonding of PVPh block was destroyed by adding proton acceptor poly(4-vinylpyridine) (P4vp). (c) 2007 Elsevier Ltd. All rights reserved.
Polybenzoxazine as a mold-release agent for nanoimprint lithography
(2007-05-22)
Wang, Chih-Feng
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Chiou, Shih-Feng
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Ko, Fu-Hsiang
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Chen, Jem-Kun
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Chou, Cheng-Tung
One of the most important tasks remaining to be resolved in nanoimprint lithography is the elimination of the resist sticking to the mold during demolding. Previously, the main approach was to apply a thin layer of fluorinated alkyl silane mold-release agent on the surface on the mold; however, this involves complicated steps and high costs. The low surface free energy material polybenzoxazine provides an efficient mold-release agent for silicon molds that is easier to process, costs less, and has no side reactions.
Dynamic structure factor of liquid Ga close to the melting point: spectral linewidth at high momentum transfer
(2007-05-23)
Tsai, K. H.
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Wu, Ten-Ming
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Tsay, Shiow-Fon
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Yang, Tzong-Jer
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電子物理學系
By simulating an interatomic pair potential obtained from the first-principles generalized energy-independent nonlocal model-pseudopotential (GEINMP) theory, we have reproduced the high-wavevector shoulder in the static structure factor and the recently observed anomaly in the linewidth of the dynamic structure factor of liquid Ga close to the melting point. Our results indicate that the two anomalies have the same physical origin, which is associated with the Friedel oscillations induced by conduction electrons. The anomaly in the dynamics can be well described by the revised Enskog theory for the hard-sphere (HS) system, with the effective HS diameter determined by the position at the first peak of the radial distribution function. We interpret the occurrence of the anomaly in the dynamics by the physical picture of cage diffusion.
Dissociation of energy-selected CH3CN+ in a region 15.1-16.5 eV: Vibrationally enhanced dissociation and mechanisms
(2007-05-25)
Huang, Chuan-Keng
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Lin, I.-Feng
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Chiang, Su-Yu
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應用化學系
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Department of Applied Chemistry
Threshold photoelectron-photoion coincidence spectra of CH3CN were measured in a region 15.1-16.5 eV. We observed a small vibrational enhancement on dissociation of CH3CN+ and obtained kinetic energy releases for channels C2HN+ + H-2 and CH2+ + HCN. The kinetic energies released in channel C2HN+ + H-2 are substantial; a linearly extrapolated dissociation threshold of 14.68 +/- 0.01 eV agrees with a Gaussian-3 B3LYP prediction 14.70 eV for formation of HCCN+ + H-2. In contrast, the small releases for channel CH2+ + HCN agree with a statistical calculation. We describe a plausible dissociation mechanism with the Gaussian-3 B3LYP method to rationalize experimental results. (c) 2007 Elsevier B.V. All rights reserved.
Contact to ZnO and intrinsic resistances of individual ZnO nanowires with a circular cross section
(2007-05-28)
Lin, Yen-Fu
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Jian, Wen-Bin
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Wang, C. P.
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Suen, Yuen-Wuu
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Wu, Zhong-Yi
Single crystalline ZnO nanowires (NWs) with a circular cross section and similar to 40 nm in diameter have been synthesized and utilized to fabricate two-contact ZnO NW devices. The electrical properties of the NW devices can be categorized into two classes according to the magnitude of their room-temperature resistances. I-V curves of low-resistance devices exhibit downward bending features and their temperature dependent resistances demonstrate thermal activation transport in the ZnO NWs. The high-resistance NW devices can be modeled as back-to-back Schottky contacts and the electron transport through the contacts reveals a variable-range-hopping mechanism. (C) 2007 American Institute of Physics.
Quantum limit of optimum four-level ASK signals with direct detection optically preamplified receivers
(2007-05-28)
Peng, Wei-Ren
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Chi, Sien
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光電工程學系
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Department of Photonics
We analytically obtain the exact fundamental limit of 4- level amplitude shifted keying formats (4ASK) with direct detection optically preamplified receivers. The optimum multilevel spacing and the corresponding decision thresholds, which depend both on the signal to noise ratio and optical bandwidth, are obtained numerically considering the Chis-quared distribution of each level. The quantum limit under the optimum level spacing is 127.5 photons/bit, which is about 0.2 dB smaller than the results by the Gaussian approximation. Over a broad range of the signal to noise ratio and the optical bandwidth, we have found that not only the bit error rate but also the optimum level spacing are well predicted by Gaussian method, although the three decision thresholds are all underestimated. (C) 2007 Optical Society of America.
Near-infrared femtosecond laser crystallized poly-Si thin film transistors
(2007-05-28)
Wang, Yi-Chao
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Shieh, Jia-Min
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Zan, Hsiao-Wen
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Pan, Ci-Ling
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光電工程學系
Polycrystalline silicon (poly-Si) thin film transistors (TFTs) fabricated by near-infrared femtosecond laser annealing (FLA) are demonstrated. The FLA-annealed poly-Si channels exhibit low tail-state, deep-state, and midgap-state densities of grain traps. Characteristics such as field-effect mobility, threshold voltage, and subthreshold slope for FLA-annealed poly-TFTs are comparable to those of conventional approaches. A wide process window for annealing laser fluences was confirmed by examining the changes in electrical parameters for transistors with various channel dimensions. (C) 2006 Optical Society of America.
Effects of supercritical CO2 fluid on sputter-deposited hafnium oxide
(2007-05-28)
Liu, Po-Tsun
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Tsai, Chih-Tsung
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Yang, Po-Yu
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光電工程學系
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顯示科技研究所
Low-temperature supercritical fluid (SCF) technology is employed to improve the dielectric characteristics of metal oxide film deposited at low temperature. In this investigation, hafnium oxide (HfO2) film was sputter deposited at room temperature and post-treated with SCF at 150 degrees C, replacing typical high-temperature annealing process. From Fourier transformation infrared and thermal desorption spectroscopy measurement, the absorption peaks of Hf-O-Hf bonding and the oxygen content in HfO2 film have, respectively, shown apparent raise. The leakage current density of the low-temperature deposited HfO2 film is reduced significantly, and the conduction mechanism is modified from trap-assisted quantum tunneling to thermionic emission process, since SCF treatment effectively reduces the number of traps in HfO2 film. (C) 2007 American Institute of Physics.
Nickel nanocrystals with HfO2 blocking oxide for nonvolatile memory application
(2007-05-28)
Yang, F. M.
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Chang, T. C.
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Liu, P. T.
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Chen, U. S.
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Yeh, P. H.
A distributed charge storage with Ni nanocrystals embedded in the SiO2 and HfO2 layer has been fabricated in this study. The mean size and aerial density of the Ni nanocrystals are estimated to be about 5 nm and 3.9x10(12)/cm(2), respectively. The nonvolatile memory device with Ni nanocrystals exhibits 1 V threshold voltage shift under 4 V write operation. The device has a long retention time with a small charge lose rate. Besides, the endurance of the memory device is not degraded up to 10(6) write/erase cycles. (C) 2007 American Institute of Physics.
Operations of poly-Si nanowire thin-film transistors with a multiple-gated configuration
(2007-05-30)
Su, C. J.
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Lin, H. C.
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Tsai, H. H.
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Hsu, H. H.
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Wang, T. M.
In this study, a novel multiple-gated (MG) thin-film transistor (TFT) with poly-Si nanowire ( NW) channels is fabricated using a simple process flow. In the proposed new transistors, poly-Si NWs were formed in a self-aligned manner and were precisely positioned with respect to the source/drain, and the side-gate. Moreover, the NW channels are surrounded by three gates, i.e., top-gate, side-gate and bottom-gate, resulting in much stronger gate controllability over the NW channels, and greatly enhanced device performance over the conventional single-gated TFTs. Furthermore, the independently applied top-gate and/or bottom-gate biases could be utilized to adjust the threshold voltage of NW channels in a reliable manner, making the scheme suitable for practical applications.
Device and method for integrating sound effect processing and active noise control
(2007-05-31)
Bai, Mingsian R.
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Ou, Kuen-Ying
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Lin, Jain-Liang
A device and a method for integrating 3D sound effect processing and active noise control are proposed. A digital signal processor incorporates an artificial reverberator and a 3D spatial audio processor into an audio module. The audio signal is presented via an earphone. Next, a microphone embedded in the vicinity of the loudspeaker inside the headset is used to sense an external noise while playing, and feed it back to an active noise controller, which generates an anti-noise to eliminate the external noise. Therefore, the signal to noise ratio can be increased and the 3D sound field effect can be significantly enhanced. In addition, a head-related transfer function is more efficiently implemented on the basis of an interaural transfer function in the spatial audio processing to reduce the filter order lower and hence the computation loading.
Method and apparatus for telephone routing between PTN and PSTN
(2007-05-31)
Chang, Ming-Feng
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Lin, Yi-Bing
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Liang, Ching-Feng
Disclosed is a method and apparatus applicable to an interface between PSTN and PTN for telephone routing. The interface includes a branch switch, a key system, a network branch switch, and media gateway, etc. The telephone routing method and apparatus of the present invention creates, maintains, and utilizes a call-back routing table to enable a specified PSTN user to call the callback external leased line to reach a specified PTN user in a one-stage dialing manner. The process of one-stage dialing includes PTN call origination to PSTN, PSTN call origination to PTN, and callback tag insertion in the call-back routing table. The call-back routing table consists of a plurality of call-back tags. Each call-back tag consists of at least a data triple, i.e. PTN user identifier, PSTN called party telephone number, and callback leased line identifier.
Vertical-channel organic thin-film transistors with meshed electrode and low leakage current
(2007-06-01)
Zan, Hsiao-Wen
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Yen, Kuo-Hsi
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光電工程學系
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顯示科技研究所
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Department of Photonics
In this study, we have successfully fabricated vertical-channel organic thin-film transistors with a channel length smaller than 100nm. It is found that Fowler-Nordheim tunneling is the dominant mechanism determining the ultra short-channel device behavior. To improve the gate control capability, a meshed source electrode pad had been used. This significantly lowers the gate and drain driving voltages (<10V), improves the saturation characteristics and reduces the leakage current. The improvement may be due to the fringing field around the source electrode, which suppresses the tunneling effect.
Chaos in a modified van der Pol system and in its fractional order systenis
(2007-06-01)
Ge, Zheng-Ming
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Zhang, An-Ray
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機械工程學系
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Department of Mechanical Engineering
Chaos in a modified van der Pot system and in its fractional order systems is studied in this paper. It is found that chaos exists both in the system and in the fractional order systems with order from 1.8 down to 0.8 much less than the number of states of the system, two. By phase portraits, Poincare maps and bifurcation diagrams, the chaotic behaviors of fractional order modified van der Pot systems are presented. (c) 2005 Elsevier Ltd. All rights reserved.
Universal share for the sharing of multiple images
(2007-06-01)
Fang, Wen-Pinn
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Lin, Ja-Chen
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資訊工程學系
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Department of Computer Science
To share numerous grey-valued images (or numerous color-valued images), this study presents a system with a universal share. A company organizer can use this universal share to attend the recovery meeting of any shared image. No storage space is wasted; i.e. for each shared image, the total storage space occupied by all generated shares (including the universal share) is identical to the image size.
Magneto-electrodynamical modeling and design of a microspeaker used for mobile phones with considerations of diaphragm corrugation and air closures
(2007-06-01)
Chao, Paul C. -P.
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Chiu, Chi-Wei
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Hsu-Pang, Yuan
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電控工程研究所
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Institute of Electrical and Control Engineering
Recent design trends for modern mobile phones are evolving to be miniaturized and versatile sounds in quality. To these ends, a microspeaker with a corrugated diaphragm is employed to broaden the sound frequency range. Due to the fact that diaphragm corrugation and air closures were not considered in any past studies, this study presents comprehensive modeling with the consideration of diaphragm corrugations and air closures. It starts with the modeling on the subsystems of the voice coil motor (VCM) in the speaker. The magnetic field of the VCM is modeled by one set of finite elements, while the corrugated diaphragm is modeled by another set of finite elements. In addition, the air closures above or below the diaphragm are modeled by the third group of finite elements based on basic acoustics. Simulations are conducted with and without air closures. It is found that: 1) the speaker with 45 degrees corrugation exhibits overall higher (better) sound pressure levels (SPLs), while 2) the 75 degrees corrugation leads to unsatisfied, low SPLs below 1 kHz and two undesired antiresonances at higher frequencies. The theoretical findings are successfully validated by experiments.