Browsing by Issue Date, starting with "1996-03-01"

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Structural and electrical properties of GaSb, AlGaSb and their heterostructures grown on GaAs by metalorganic chemical vapor deposition
(1996-03-01)
Wang, PY
;
Chen, JF
;
Chen, WK
;
電子物理學系
;
Department of Electrophysics
A systematic study of structural and electrical properties of GaSb and AlGaSb grown on GaAs by metalorganic chemical vapor deposition is reported. In general, the results obtained from surface morphologies, X-ray linewidths and Hall properties are consistent with each other and indicate that the optimal growth conditions for GaSb are at 525 degrees C around V/III = 1. A highest hole mobility of 652 cm(2)/V . s at RT (3208 cm(2)/V . s at 77 K) and a lowest concentration of 2.8 x 10(16) cm(-3) (1.2 X 10(15) cm(-3) at 77 K) were obtained for GaSb grown under this optimal condition. Compared to the GaSb growth, a smaller V/III ratio is needed for the AlGaSb growth to protect the surface morphology. When Al was incorporated into GaSb growth, mobility decreased and carrier concentration increased sharply. The AlGaSb grown at 600 degrees C had a background concentration about one order of magnitude lower than the AlGaSb grown at 680 degrees C. Room-temperature current-voltage characteristics of GaSb/AlxGa1-xSb/GaSb show a rectifying feature when Al composition x is higher than 0.3, suggesting a valence-band discontinuity at the AlGaSb/GaSb interface. A leakage current much higher than the value predicted by the thermionic emission theory is observed at 77 K, presumably due to a large number of dislocations generated by the huge lattice mismatch between GaSb and GaAs.
Stability and chaotic motions of a symmetric heavy gyroscope
(1996-03-01)
Ge, ZM
;
Chen, HK
;
交大名義發表
;
機械工程學系
;
National Chiao Tung University
The nonlinear motion of a symmetric heavy gyro mounted on a vibrating base, particularly its long-term dynamic behavior for a wide range of parameters, is investigated, The system exhibits both regular and chaotic motions. Two typical routes to chaos, namely through period-doubling and intermittency, are found in this study, The method of multiple scales is used to analyze the responses and to determine the stability of the trivial fixed point for the system excited by single harmonic force. The stability of the system excited by multiple harmonic forces has been studied by Lyapunov's direct method. As the system is subjected to external disturbance, the Melnikov method is used to show the existence of chaotic motion. The effect of the number of forcing frequencies on the chaotic regions is also established. The numerical results, in which the existence of chaos is demonstrated, are presented in the form of bifurcation diagrams, phase portraits, Poincare maps, and Lyapunov exponents. The effect of the gyroscope's spinning speed is also studied. It is found that increasing the gyroscope's spin speed is the simplest method to overcome the chaotic motion for this system.
Mechanical properties and 95 degrees C aging characteristics of zircon-reinforced Zn-4Al-3Cu alloy
(1996-03-01)
Li, BJ
;
Chao, CG
;
交大名義發表
;
材料科學與工程學系
;
National Chiao Tung University
A process for preparing zinc alloy castings containing dispersions of zircon particles is described. Composites were prepared by stirring zircon particles in Zn-4Al-3Cu (ZAS) alloy melts and subsequently casting these melts in permanent molds. It was found that additions of zircon resulted in an increase in the sliding wear resistance and in the proportional limit in compression. The aging characteristics of the ZAS alloy have also been investigated by hardness tests, dilatometry technique, and transmission electron microscopy observations. There are two kinds of precipitates that occur during the aging process. The alpha-phase precipitates from the eta phase in the early stage of aging and the copper-rich epsilon-phase precipitates from the eta phase in the later stage of aging. Therefore, there are two peaks in the hardening curve caused by both alpha-phase and epsilon-phase precipitation. The alpha-phase precipitation induces the dimensional shrinkage, and the copper-rich epsilon phase precipitation results in dimensional expansion. Zircon particles existing in ZAS alloy reduce the maximum shrinkage from 353 X 10(-6) for the monolith to 167 x 10(-6) for the composite. Two groups of parallel alpha-phase plates had formed within the eta dendrite during aging at 95 degrees C. The orientation relationship between the alpha phase and matrix was determined as [(1) over bar 101](//[l (1) over bar 0](alphaalpha), (11 (2) over bar 0)(eta)//(111)(alpha).
Active noise cancellation in ducts using internal model-based control algorithms
(1996-03-01)
Hu, JS
;
交大名義發表
;
電控工程研究所
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National Chiao Tung University
;
Institute of Electrical and Control Engineering
A feedback control algorithm based on the internal model principle is proposed to solve the active noise control (ANC) problem in ducts. Because of its infinite open-loop gain at selected frequencies, the controller is able, at the cancellation speaker position, to block noise transmission of these frequencies. In other words, the speaker acts like a totally reflective boundary, Stability analysis of the closed-loop system is performed using the Nyquist criterion, Experimental results confirm the theoretical analysis, showing an average noise level reduction of 30 to 40 dB at the target frequencies.
A potential-based approach for shape matching and recognition
(1996-03-01)
Chuang, JH
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交大名義發表
;
資訊工程學系
;
National Chiao Tung University
;
Department of Computer Science
This paper presents a novel potential-based approach for recognizing the shape of a two-dimensional (2D) region by identifying the best match from a selected group of shape templates. The proposed model assumes that the border of every 2D region is uniformly charged. An initially small shape template placed inside a shape sample will experience the repulsive force and torque arising from the potential field. A better match in the shape between the template and the sample can be obtained if the template translates and reorients itself to reduce the potential while growing in size. The shape template with the largest final size corresponds to the best match and represents the shape of the given sample. The potential and the associated repulsive force and torque between the polygonal contours are analytically tractable, hence resulting in high computational efficiency of the matching process. The proposed approach is intrinsically invariant under translation, rotation and size changes of the shape sample. Moreover, not only can the matching be carried out directly for shape contours at different viewscales, but the contours can also be unconnected, provided that the template is confined within the shape sample throughout the matching process.
Dielectric degradation of Cu/SiO2/Si structure during thermal annealing
(1996-03-01)
Chiou, JC
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Wang, HI
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Chen, MC
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電子工程學系及電子研究所
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Department of Electronics Engineering and Institute of Electronics
The impact of Cu on the dielectric SiO2 layer was studied using a Cu/SiO2/Si metal oxide semiconductor capacitor and rapid thermal annealing (RTA) treatment. With the RTA treatment, no chemical reaction was observed up to 900 degrees C; however, dielectric degradation occurred following RTA at 300 degrees C for 60 s and became worse with the increase of annealing temperature. The interface-trap density at the SiO2/Si interface also increased from 5 x 10(10) to 5 x 10(13) eV(-1) cm(-2) after 800 degrees C RTA treatment. The RTA anneal introduced a large number of positive Cu ions into the dielectric SiO2 layer. Under bias-temperature stress, Cu ions drift quickly in the SiO2 layer and may drift across the SiO2/Si interface and enter the Si substrate. With the use of 1200 Angstrom thick TiN and TiW barrier layers, respectively, the dielectric strength of the Cu/(barrier)/SiO2/Si structures was able to remain stable up to 500 and 600 degrees C.
肥了秋陽瘦了乳房
(1996-03-01)
管管
A design strategy for short gate length SOI MESFETs
(1996-03-01)
Hou, CS
;
Wu, CY
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電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
A design strategy for short gate length, self-aligned Si-SOI MESFETs is proposed, in which the design considerations for the important device parameters of the SOI MESFET are studied by using a 2D numerical simulator. It is shown that the sub-threshold I-ds-V-gs characteristics can be used to determine the thickness of silicon film for a given channel doping level under a specified threshold voltage. Moreover, the 2D effect can be suppressed by reducing the thickness of buried oxide to improve the bottom-gate controllability over the channel charges. Moreover, it is shown the backgate bias is also an important controllable parameter for modulating the characteristics of the SOI MESFET in both sub-threshold and saturation regions. An example for designing a very short gate length (0.1 mu m) SOI MESFET has been carried out to verify this strategy. It is shown that the proposed strategy does provide an effective procedure for designing an Si-SOI MESFET with high performance.
Stress analysis of the rotational object under the condition of transient state
(1996-03-01)
Lu, TC
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Jeng, TH
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交大名義發表
;
National Chiao Tung University
A novel method for extracting the metallurgical channel length of MOSFET's using a single device
(1996-03-01)
Li, HH
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Chu, YL
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Wu, CY
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電子工程學系及電子研究所
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Department of Electronics Engineering and Institute of Electronics
A new charge-pumping method with de source/drain biases and specified gate waveforms is proposed to extract the metallurgical channel length of MOSFET's by using a single device. Using two charge-pumping currents of a single nMOSFET measured under different V-GL (V-GH for pMOSFET's), the metallurgical channel length can be easily extracted with an accuracy of 0.02 mu m. It is shown that the proposed novel method is self-consistent with the results obtained by the charge-pumping current measured from multidevices under different gate pulse waveforms and bias conditions.
Modeling of a finger-follower cam system with verification in contact forces
(1996-03-01)
Hsu, WY
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Pisano, AP
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交大名義發表
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機械工程學系
;
National Chiao Tung University
A lumped/distributed-parameter dynamic model is developed to investigate the dynamic responses of a finger-follower cam system by considering a hydraulic lash adjuster with an oscillating pivot, and frictional forces between sliding surfaces. The measured force data at low speed are employed to derive an algorithm to determine the dynamic Coulomb friction coefficients at contact points. The contact position between the earn and the follower with moving pivot is determined by a constraint equation method. A hydraulic lash adjuster acting as the pivot of the follower is also modeled with the effects of oil compressibility and oil refill mechanism. Simulated contact forces at three different speeds are shown to have good agreement with experimental data. The separation between the hydraulic lash adjuster and the follower is predicted at a camshaft speed of 2535 rpm, ana experiment indicates at 2520 rpm.
The stability of the rotation of a magnetized gyro with a fixed point
(1996-03-01)
Ge, ZM
;
Chen, HK
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交大名義發表
;
機械工程學系
;
National Chiao Tung University
In conventional studies about the gyro motion the gyroscopic forces which are produced by the Lorentz action of the magnetic field on the electrical charges moving in space have not been considered. Euler gyro, Lagrange gyro and Kovalveskaya gyro are three representative gyros. In this paper, the stability and instability conditions of the rotation of the three representative gyros under the action of the Lorentz forces both in a uniform force field and in a central force field are obtained by using Liapunov's direct method.
A high-speed algorithm for elliptical object detection
(1996-03-01)
Ho, CT
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Chen, LH
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交大名義發表
;
資訊工程學系
;
National Chiao Tung University
A high-speed method for elliptical object location is proposed. Through the use of the geometric symmetry, it first locates centers of elliptical objects and classifies the boundary points, Then, each point possible on an elliptical object boundary is used to obtain the remaining three parameters of the elliptical object, Since each boundary point is at most transformed to one point on the parameter space, the proposed method is very fast. Some experimental results are also given to show that the proposed method is better than some existing methods under the consideration of space and storage.
Reduction of soliton interactions by sliding-frequency second-order Butterworth filters
(1996-03-01)
Dung, JC
;
Chi, S
;
Wen, SF
;
光電工程學系
;
Department of Photonics
The reduction of the soliton interaction by use of optical sliding-frequency second-order Butterworth filters is studied numerically. It is found that the second-order Butterworth filters can reduce the soliton interaction more effectively than Fabry-Perot filters or third-order Butterworth filters because the second-order Butterworth filter induces larger frequency chirping on the soliton, compressing it as it propagates in the fiber after the filter. (C) 1996 Optical Society of America
The family of universal axes
(1996-03-01)
Lin, JC
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交大名義發表
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資訊工程學系
;
National Chiao Tung University
;
Department of Computer Science
The family of universal axes (UA) is introduced in this paper. This family has infinitely many members, each of which generates a method that is universal in the sense that each generated method can define shape orientation for almost any kind of shape and once the numerical computing system has been set up, the users of this orientation detection system need not supply the system the information about whether a given shape is mirror-symmetric, rotationally symmetric, irregular, etc. Some mathematical properties of the proposed UA are investigated and numerical techniques for implementing UA are discussed. The method of universal principal axes (UPA) introduced recently is just one of the infinitely many members of the proposed family of UA. The UPA method yields at least two orientations for each shape and thus must be combined with another non-universal single-orientation method in order to reduce the time needed to match irregular shapes. Most members of the proposed UA family do not need to be supplemented by a single-orientation method in this way.
Fabrication of thin film transistors by chemical mechanical polished polycrystalline silicon films
(1996-03-01)
Chang, CY
;
Lin, HY
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Lei, TF
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Cheng, JY
;
Chen, LP
A top-gate p-channel polycrystalline thin film transistor (TFT) has been fabricated using the polycrystalline silicon (poly-Si) film as-deposited by ultrahigh vacuum chemical vapor deposition (UHV/CVD) and polished by chemical mechanical polishing (CMP), In this process, long-term recrystallization in channel films is not needed. A maximum field effect mobility of 58 cm(2)/V-s, ON/OFF current ratio of 1.110(7), and threshold voltage of -0.54 V were obtained. The characteristics are not poor. In this work, therefore, we have demonstrated a new method to fabricate poly-Si TFT's.
The influence of Ge-implantation on the electrical characteristics of the ultra-shallow junction formed by using silicide as a diffusion source
(1996-03-01)
Huang, CT
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Lei, TF
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Chu, CH
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Shvu, SH
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電子工程學系及電子研究所
The electrical characteristics of ultra-shallow p(+)/n junctions formed by implanting a 60 keV Ge+ into a TiSi2 layer have been studied. A very low reverse leakage current density (congruent to 0.4 nA/cm(2) at -5 V) and a very good forward ideality factor n (congruent to 1.001) were achieved in these ultra-shallow p(+)/n junctions, From the secondary ion mass spectrometry (SIMS) analysis, the junction depth was measured to be 600 Angstrom and the surface concentration was about 3 times higher than that of the conventional samples.
Fuzzy reliability using a discrete stress-strength interference model
(1996-03-01)
Wang, JD
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Liu, TS
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交大名義發表
;
機械工程學系
;
National Chiao Tung University
This paper uses a fuzzy line-segment method to calculate the fuzzy unreliability of a system when only discrete-interval probabilities of stress & strength inside an interference region are available. The discrete-interval probabilities are treated as fuzzy numbers. A stress-strength interference model and extended operations of fuzzy numbers are used to calculate the fuzzy unreliability, Probability density functions are approximated by piecewise fuzzy line-segments that are expressed by linear fuzzy polynomials; the centroid of the membership function for the fuzzy unreliability is treated as the point estimate of unreliability, This method requires less computer time than previous methods in the literature, and is useful since it does not require information on distribution types of stress & strength, Numerical examples demonstrate the method.
Reducing inventory costs by order splitting in the sole sourcing environment
(1996-03-01)
Chiang, C
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Chiang, WC
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管理科學系
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Department of Management Science
In this paper, we examine the possibility of the arrangement for multiple deliveries in each order cycle for the continuous review inventory system. The problem is mainly found in the retail sector where inventory often makes up the majority of a company's assets. Most works recently have focused on the reduction of safety stock in the multiple sourcing setting. This research, instead, considers the reduction of cycle stock in the sole sourcing environment. The formulation where a predetermined service level serves as a constraint for the objective function is employed throughout this research. We show that splitting the order into multiple deliveries can significantly reduce the inventory carrying cost especially when the interarrival times between deliveries are determined optimally.
Transmitting on various network topologies
(1996-03-01)
Ho, TY
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Hsu, LH
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Sung, TY
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資訊工程學系
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Department of Computer Science
Architectures for interconnection networks can be represented by graphs, while vertices represent processors and edges represent communication links between processors. We use the terms vertices and processors interchangeably. Let G = (V, E) be a graph representing the topology for an interconnection network. Let v(0) be a special vertex outside G, called the host processor, which is connected to each vertex in G. The host processor is the sender or source of the message to be transmitted to all of the vertices in G. In each time unit, the host processor may send an identical message to an arbitrary vertex in G or remain idle. At the same time, each processor in G that has already received the message can send it to all its neighbors in one time unit. A transmitting scheme allowing all processors to receive the message in t time units and requiring the host processor to send the message s times is called a (t, s)-transmitting scheme, where t greater than or equal to s. We call t the transmitting time, and s, the workload of the host processor. We aimed to find an optimal transmitting scheme, i.e., a transmitting scheme such that t is minimized while s is also minimized. In this paper, we present optimal transmitting schemes for linear arrays, rings, complete binary trees, star trees, and (directed) de Bruijn graphs. Furthermore, we present a(t, s)-transmitting scheme for diagonal meshes which are defined slightly different from meshes, and the ratio of t to the optimal transmitting time is approximate to 1.1. (C) 1996 John Wiley & Sons, Inc.