Browsing by Issue Date, starting with "2001-12-01"

Now showing 1 - 20 of 76092

Simultaneous observation of second-harmonic emission and three-photon excited photoluminescence from hybrid vapor phase epitaxy-grown GaN film
(2001-12-01)
Lee, CK
;
Kao, FJ
;
Wang, SC
;
Pan, CL
;
光電工程學系
Nonlinear optical properties of the undoped hybrid vapor phase epitaxy-grown (GaTN film sample) were investigated and analyzed using a tunable femtosecond laser as an excitation source. As the laser wavelength was tuned from 762-796 nm, the sample emitted signals corresponding to the second-harmonic wavelength from 381-398 nm with a quadratic power dependence. A strong three-photon-process-related signal at 367 nm with cubic power dependence was simultaneously observed for the first time.
Preparation and crystallization behavior of syndiotactic polystyrene-clay nanocomposites
(2001-12-01)
Tseng, CR
;
Wu, JY
;
Lee, HY
;
Chang, FC
;
應用化學系
Syndiotactic polystyrene/modified-clay nanocomposites have been prepared by solution blending by mixing pure s-PS and organophilic clay with adsorbed cetyl pyridium chloride (CPC) in dichlorobenzene. The dispersability of the clay in syndiotactic polystyrene/modified-clay nanocomposites was studied using X-ray and transmission electron microscopy. The clay is well dispersed into the s-PS matrix using solution blending with scale in 1-2 nm or in a few tenths similar to 100 nm depending on surfactant treatment. The CPC is partially compatible with s-PS and allows syndiotactic polystyrene chains intercalating into clay layers. The crystallization behavior of alpha- and beta -crystals for syndiotactic polystyrene nanocomposite has been thoroughly examined using the Fourier transform infrared and differential scanning calorimetry. Our results further demonstrate that the presence of the clay plays a vital role in facilitating the formation on the thermodynamically more favorable beta form crystal when the s-PS is melt- or cold-crystallized. (C) 2001 Elsevier Science Ltd. All rights reserved.
Synthesis and physical properties of linear and branch phenoxies
(2001-12-01)
Chen, JR
;
Li, YS
;
Chang, FC
;
應用化學系
;
Department of Applied Chemistry
Linear and branch phenoxies have been synthesized by reacting difunctional epoxy and diphenol or triphenol monomer, using phosphonium salt as the catalyst. The reaction kinetics is analyzed by the ASTM E 698 method, which is suitable for a first order reaction system. The bulky structure of the bisphenol Z moiety retards the reaction; therefore, the reaction temperature required is higher- at 200 degreesC, compared to 190 degreesC for the bisphenol A based system. The introduction of a branch structure increases both molecular weight and the polydispersity of the phenoxy. A slightly branched structure tends to increase the distance between the polymer chains and results in a lower shear viscosity for easier processing. A higher branch results in light crosslinking and decreases the mobility of the polymer. The branch structure has a negligible effect on its glass transition temperature because the average distance between branches is substantially longer than the critical mainchain length for T-1's Brownian motion. The 100/1 (bisphenol/ trisphenol) system has the lowest viscosity, but its mechanical properties and the gas permeation properties are poorer than those of the others. The bisphenol Z based phenoxy shows superior mechanical properties, higher T-g, lower coefficient of thermal expansion, and lower gas permeation properties than the corresponding bisphenol A based phenoxy because of the steric hindrance structure of the bisphenol Z moiety.
Design on the low-capacitance bond pad for high-frequency I/O circuits in CMOS technology
(2001-12-01)
Ker, MD
;
Jiang, HC
;
Chang, CY
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
A new structure design of bond pad is proposed to reduce its parasitic capacitance in general CMOS processes without extra process modification. The proposed bond pad is constructed by connecting multilayer metals and inserting additional diffusion layers into the substrate below the metal layers. The metal layers except top metal layer are designed with special patterns, which have smaller area than that in the traditional bond pad. Both the additional diffusion layers and patterned metal layers are used to reduce the parasitic capacitance of bond pad. An experimental test chip has been designed and fabricated to investigate the reduction of parasitic capacitance of the bond pad. The bonding reliability tests on the fabricated bond pad, including the ball-shear and wire-pull tests, are also used to verify the bonding adhesion. The experimental results show that the proposed low-capacitance bond pad has a capacitance less than 50% of that in the traditional bond pad. The new proposed bond pads can also keep the same good bonding reliability as that of a traditional bond pad.
The effects of low-pressure rapid thermal post-annealing on the properties of (Ba,Sr)TiO3 thin films deposited by liquid source misted chemical deposition
(2001-12-01)
Yang, MJ
;
Chien, CH
;
Leu, CC
;
Zhang, RJ
;
Wu, SC
The technique of low-pressure post-annealing process with additional second-step annealing for preparation of the Ba0.7Sr0.3TiO3 thin films deposited by liquid source misted chemical deposition (LSMCD) has been proposed. With employing this annealing procedure, the leakage current density can be significantly eliminated by approximately one order of magnitude at 2 V. In particular, process temperature can be reduced from 650 degreesC to 600 degreesC without suffering deteriorated crystallinity issue, which is identified by both C-V measurement and X-ray diffraction spectrum. The extracted dielectric constant is 310 with extreamly low loss tangent of 0.005. The spectrum of atomic force microscopy (AFM) shows that this low-pressure process results in smoother surface topography. Moreover, thermal desorption spectrums assure that less residual organics and contaminations were left after low pressure post-annealing. This may be one of the reasons for lowering crystallization temperature and the improved electrical properties.
Effects of yttrium codoping on photoluminescence of erbium-doped TiO2 films
(2001-12-01)
Ting, CC
;
Chen, SY
;
Hsieh, WF
;
Lee, HY
;
材料科學與工程學系
Er3+-Y3+ codoped TiO2 films were prepared on a fused silica substrate by the sol-gel process. The effect of Y3+ codoping on the similar to1.54 mum photoluminescence (PL) properties of Er3+-doped TiO2 films are investigated. Enhancement of PL properties due to Y3+ codoping by a factor of 10 for intensity and of 1.5 for the full width at half maximum in comparison with the Er3+-Al3+ codoped SiO2 system has been observed in the film annealed at Er3+:Y3+:Ti4+=5:30(similar to 50):100. Extended x-ray absorption fine structure measurements show that the local chemical environment of Er3+ ions in the Er3+-Y3+ codoped TiO2 films is similar to that in Er2O3. The average spatial distance between Er3+ ions is enlarged due to the partial substitution of Y3+ for Er3+ ions in the Er2O3-like local structure. It is believed that the more intense PL emission of the Er3+-Y3+ codoped TiO2 films can be attributed to the better dispersion and distorted local structure of Er3+ ions in the TiO2 host matrix by yttrium codoping. (C) 2001 American Institute of Physics.
Unsupervised texture segmentation by determining the interior of texture regions based on wavelet transform
(2001-12-01)
Lee, KL
;
Chen, LH
;
資訊工程學系
;
Department of Computer Science
Traditional approaches for texture segmentation via wavelet transform usually adopt textural features to achieve segmentation purposes. However, for a natural image, the characteristics of the pixels in a texture region are not similar everywhere from a global viewpoint, and over-segmentation often occurs. To deal with this issue, an unsupervised texture segmentation method based on determining the interior of texture regions is proposed. The key idea of the proposed method is that if the pixels of the input image can be classified into interior pixels (pixels within a texture region) and boundary ones, then the segmentation can be achieved by applying region growing on the interior pixels and reclassifying boundary pixels. Based on the fact that each pixel P within a texture region will have similar characteristics with its neighbors, after applying wavelet transform, pixel P will have similar response with its neighbors in each transformed subimage. Thus, by applying a multilevel thresholding technique to segment each subimage into several regions, pixel P and its neighbors will be assigned to the same region in most subimages. Based on these segmented results, an interior pixels finding algorithm is then provided to find all interior pixels of textural regions. The algorithm considers a pixel which is in the same region as its neighbors in most subimages as an interior pixel. The effectiveness of this method is proved by successfully segmenting natural texture images and comparing with other methods.
Composition and retrieval of visual information for video databases
(2001-12-01)
Cheng, PJ
;
Yang, WP
;
資訊工程學系
;
Department of Computer Science
This paper presents a new visual aggregation model for representing visual information about moving objects in video data. Based on available automatic scene segmentation and object tracking algorithms, the proposed model provides eight operations to calculate object motions at various levels of semantic granularity. It represents trajectory, color and dimensions of a single moving object and the directional and topological relations among multiple objects over a time interval. Each representation of a motion can be normalized to improve computational cost and storage utilization. To facilitate query processing, there are two optimal approximate matching algorithms designed to match time-series visual features of moving objects. Experimental results indicate that the proposed algorithms outperform the conventional subsequence matching methods substantially in the similarity between the two trajectories. Finally, the visual aggregation model is integrated into a relational database system and a prototype content-based video retrieval system has been implemented as well. (C) 2001 Academic Press.
Investigation of electron-optical phonon interactions in moderate wide InxGa1-xAs/GaAs strained quantum wells
(2001-12-01)
Lin, SD
;
Lee, HC
;
Sun, KW
;
Lee, CP
;
電子工程學系及電子研究所
In this presentation, we have calculated the electron-optical phonon scattering rate of GaAs/AlAs quantum wells and average electron energy loss rate as a function of well width of the GaAs/AlxGa1-xAs quantum wells. We have also studied the Raman and hot electron-neutral acceptor luminescence in moderate wide InxGa1-xAs/GaAs strained quantum wells (with 10 nm in well width and 30 nm in barrier width) to determine the dominant phonon mode emitted by the hot electrons in the wells at 15 K. The hot electron-neutral acceptor luminescence spectrum of the strained quantum well sample shows an oscillation period of about 22 meV which indicates that the hot electrons relaxed mostly through emissions of the InAs confined phonons. (C) 2001 Elsevier Science B.V. All rights reserved.
Generalized interconnect delay time and crosstalk models: I. Applications of interconnect optimization design
(2001-12-01)
Lee, TGY
;
Tseng, TY
;
Wong, SC
;
Yang, CJ
;
Liang, MS
New analytical models for estimating the delay time of single line and coupled interconnect for ramp input waveform are derived, The accuracy of the signal delay time and crosstalk noise voltage models for various driver resistances, loading capacitances, and input-ramping rates has also been verified by simulation program with integrated circuit emphasis (SPICE) simulation. Based on the delay and crosstalk models, interconnect optimization design can be discussed thoroughly. The proposed guaranteed-performance interconnect design method is also discussed. These models are useful for performance estimation and layout optimization in VLSI synthesis as well as process optimization in technology development.
Effectiveness of NH3 plasma treatment in preventing wet stripper damage to low-k hydrogen silsesquioxane (HSQ)
(2001-12-01)
Chang, TC
;
Mor, YS
;
Liu, PT
;
Tsai, TM
;
Chen, CW
Wet stripper is commonly used to remove photoresist in IC integration processing. However, the high alkalinity of the wet stripper solution often leads to the hydrolysis of hydrogen silsesquioxane (HSQ) film and induces water uptake. As a result, both the leakage current and dielectric constant of HSQ increase. In this study, NH3 plasma treatment was applied to the HSQ film to form a thin nitrogen-containing layer on the HSQ surface and prevents the hydrolysis of HSQ during photoresist stripping. Dielectric degradation can be prevented by NH3 plasma treatment.
New CMOS 2V low-power IF fully differential Rm-C bandpass amplifier for RF wireless receivers
(2001-12-01)
Cheng, Y
;
Gong, J
;
Wu, CY
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
A new CMOS fully differential bandpass amplifier (BPA) based on the structure of a transresistance (Rm) amplifier and capacitor is proposed and analysed. In this design, the Rill amplifier is realised by a simple inverter with tunable shunt-shunt feedback MOS resistor and tunable negative resistance realised by crosscoupled MOS transistors in parallel with a current source. The capacitor is in series with the input of the Rm amplifier, which realises the filter function and blocks the DC voltage. Under a 2V supply voltage, the post-tuning capability of the gain can be as high as 55 dB whereas the tunable frequency range is 41-178 MHz. The power consumption is 14mW and the dynamic range (DR) is 50 dB. The differential-mode gain is 20 dB and the common-mode gain is -25 dB so that the CMRR is 45 dB. Simple structure, good frequency response and low power dissipation make the proposed bandpass amplifier quite feasible for application in the IF stage of RF receivers.
A general invariance principle for nonlinear time-varying systems and its applications
(2001-12-01)
Lee, TC
;
Liaw, DC
;
Chen, BS
;
電控工程研究所
;
Institute of Electrical and Control Engineering
A general invariance principle, from the output-to-state point of view, is proposed for the dynamical analysis of nonlinear time-varying systems. This is achieved by the construction of a simple and intuitive criterion using integral inequality of the output function and modified detectability conditions. The proposed scheme can be viewed as an extension of the integral invariance principle (Byrnes and Martin, 1995) for time-invariant systems to time-varying systems. Such extension is nontrivial and can be used in various research areas such as adaptive control, tracking control and the control of driftless systems. An application to global tracking control of four-wheeled mobile robots is given to demonstrate the feasibility and validity of the proposed approach.
Finding multiple possible critical paths using fuzzy PERT
(2001-12-01)
Chen, SM
;
Chang, TH
;
資訊工程學系
;
Department of Computer Science
Program evaluation and review techniques (PERT) is an efficient tool for large project management. In actual project control decisions, PERT has successfully been applied to business management, industry production, project scheduling control, logistics support, etc. However, classical PERT requires a crisp duration time representation for each activity. This requirement is often difficult for the decision-makers due to the fact that they usually can not estimate these values precisely. In recent years, some fuzzy PERT methods have been proposed based on fuzzy set theory for project management. However, there is a drawback in the existing fuzzy PERT methods, i.e., sometimes they maybe cannot rind a critical path in a fuzzy project network. In this paper, we propose a fuzzy PERT algorithm to find multiple possible critical paths in a fuzzy project network, where the duration time of each activity in a fuzzy project network is represented by a fuzzy number. The proposed algorithm can overcome the drawback of the existing fuzzy PERT methods.
A spread spectrum clock generator for EMI reduction
(2001-12-01)
Chen, HW
;
Wu, JC
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
This paper described a new method to generate a spread spectrum clock for the purpose of EMI reduction. This method uses two phase-locked loops (PLL). The output of the first PLL is locked to its input of 14.318-MHz, The VCO in this PLL is used to produce 32 outputs with the same frequency and each with 11.25 degrees phase variation. A digital spread spectrum generator uses these 32 signals to generate the desired spread spectrum signal by phase hopping technique. These two circuits form a spread spect ruin digital PLL (SSDPLL). The second PLL is configured as a conventional frequency synthesizer. It can be programmed to generate the desired frequencies. The second PLL also serves as a low pass filter of the output of the SSDPLL to smooth out frequency variation. This circuit was implemented with a 0.6 mum single poly CMOS process. The active areas of the SSDPLL and the synthesizer are 826 x 396 mum(2) and 790 x 298 mum(2), respectively. The, total power consumption is 99 mW at 3.3 V supply. The peak power of the spread spectrum clock is reduced by 10 dBm at 14.318 MHz output with a 2.34% frequency spreading. The reduction of peak power increases with output frequency.
An investigation of a block moving back and forth on a heat plate under a slot jet. Part II (the effects of block moving distance and vacant distance)
(2001-12-01)
Fu, WS
;
Wang, KN
;
機械工程學系
;
Department of Mechanical Engineering
A continuous investigation of a block moving back and forth on a heat plate under a slot jet was studied numerically. This study investigates the effects of block moving distance and vacant distance between the block and heat plate on the heat transfer of heat plate. This subject belongs to a kind of moving boundary problems, and the modified Arbitrary Lagrangian Eulerian (ALE) method is suitable for solving this subject. The results show that the increment of the heat transfer rate of heat plate is not direct proportion to the block moving distance, and the smaller vacant distance is expected for obtaining the larger heat transfer rate of heat plate. (C) 2001 Elsevier Science Ltd. All rights reserved.
Modal identification of structures from ambient vibration, free vibration, and seismic response data via subspace approach
(2001-12-01)
Huang, CS
;
Lin, HL
;
土木工程學系
;
Department of Civil Engineering
This work presents a unified procedure for determining the natural frequencies, modal damping ratios and modal shapes of a structure from its ambient vibration, free vibration and earthquake response data. To evaluate the coefficient matrices of a state-space model, the proposed procedure applies a subspace approach cooperating with an instrumental variable concept. The dynamic characteristics of a structure are determined from the coefficient matrices. The feasibility of the procedure is demonstrated through processing an in situ ambient vibration measurement of a five-storey steel frame, an impulse response measurement of a three-span continuous bridge, and simulated earthquake responses of five-storey steel frames from shaking table tests. The excellent agreement of the results obtained herein with those published previously confirms the feasibility of the present procedure. Copyright (C) 2001 John Wiley & Sons, Ltd.
An efficient IP routing lookup by using routing interval
(2001-12-01)
Wang, PC
;
Chan, CT
;
Chen, YC
;
資訊工程學系
;
Department of Computer Science
Nowadays, the commonly used table lookup scheme for IP routing is based on the so-called classless interdomain routing (CIDR). With CIDR, routers must find out the best matching prefix (BMP) for IP packets forwarding, this complicates the IP lookup. Currently, this process is mainly performed in software and several schemes have been proposed for hardware implementation. Since the IP lookup performance is a major design issue for the new generation routers, in this article we investigate the properties of the routing table and present a new approach for IP lookups, our approach is not based on BMP and significantly reduces the complexity, thus the computation cost of existing schemes can be significantly reduced. We also propose an efficient IP lookup algorithm, with which we improve the binary search on prefixes to 30 millions of packets per second (MPPS) and 5,000 route updates/s under the same experiment setup with an even larger routing table.
Comparison of InGaP/InGaAs/GaAs and InGaPtInGaAs/AlGaAs pseudomorphic high electron mobility transistors
(2001-12-01)
Huang, CE
;
Lee, CP
;
Huang, RT
;
Chang, MCF
;
電子工程學系及電子研究所
We have studied the DC and RF characteristics of InGaP/InGaAs/AlGaAs and InGaP/InGaAs/GaAs pseudomorphic high electron mobility transistors (PHEMTs). The InGaP gate barrier provides adequate carrier confinement for the channel carriers and at the same time eliminates the problems associated with AlGaAs. Excellent device performance was obtained for both types of devices. No short channel effect was observed at a gate length as low as 0.3 mum. The InGaP/InGaAs/AlGaAs PHEMTS are superior in that they have higher transconductance, higher current carrying capability and better RF performance. This is attributed to the better carrier confinement at the back channel. These results demonstrate that InGaP/InGaAs/AlGaAs PHEMTs are favorable candidates for microwave applications.
Edge hole direct Tunneling leakage in ultrathin gate oxide p-channel MOSFETs
(2001-12-01)
Yang, KN
;
Huang, HT
;
Chen, MJ
;
Lin, YM
;
Yu, MC
This paper examines the edge direct tunneling (EDT) of holes from p(+) polysilicon to underlying p-type drain extensions in off-state p-channel MOSFETs having ultrathin gate oxides that are 1.2 nm-2.2 nm thick. It is for the first time found that for thinner oxides, hole EDT is more pronounced than both conventional gate-induced drain leakage (GIDL) and gate-to-channel tunneling. As a result, the induced gate and drain leakage is more accurately measured per unit gate width. Terminal currents versus input voltage are measured from a CMOS inverter with gate oxide thickness T-OX = 1.23 nm, exhibiting the impact of EDT in two standby modes. For the first time, a physical model is derived for the oxide field E-OX at the gate edge by accounting for the heavy and light holes' subbands in the quantized accumulation polysilicon surface. This model relates E-OX to the gate-to-drain voltage, oxide thickness, and doping concentration of the drain extension. Once E-OX is known, an existing direct tunneling (DT) model consistently reproduces EDT current-voltage (I-V), and the tunneling path size extracted falls adequately within the gate-to-drain overlap region. The ultimate oxide thickness limit due to hole EDT is projected.