Browsing by Author "Hwang, CC"

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A self-propagating high-temperature synthesis method for Ni-ferrite powder synthesis
(2004-03-25)
Peng, CH
;
Hwang, CC
;
Hong, CK
;
Chen, SY
;
材料科學與工程學系
Ni-ferrite (NiFe2O4) powder was synthesized by a self-propagating high-temperature synthesis (SHS) process using Fe, Fe2O3 and various Ni-containing species (Ni-CSs) as reactants. The reactants were thoroughly mixed and pressed into a cylindrical compact. The compact was ignited by electrical heating under oxygen partial pressures varying between 0.02 and 1.5 MPa. The effects of the type of Ni-containing species, the reactant composition, the oxygen pressure on the combustion temperature, and the product conversion were investigated. X-ray diffraction (XRD) analysis showed that oxygen pressure promoted product conversion. Among several Ni-containing species tested, Ni2O3 was found to give the highest conversion. The product conversion increased with increasing iron content and then decreased with further increase in iron content. Scanning electron microscope (SEM) observations showed that the product synthesized is mostly in the form of agglomerated fine particles with submicron size (0.1-0.5 mum). Hysteresis behavior analysis showed that the product as synthesized possessed better soft magnetic properties when compared with commercial Ni-ferrite prepared by the solid reaction method. (C) 2004 Elsevier B.V. All rights reserved.
Characteristics of low-temperature-prepared (Ba, Sr)TiO3 films post treated by novel excimer laser annealing
(2002)
Shye, DC
;
Chiou, BS
;
Hwang, CC
;
Chen, JS
;
Su, IW
Thin (Ba0.5Sr0.5)TiO3 (BST) films were sputtered on Pt[FiN/Ti/Si multilayer substrates at very low temperature (150degrees C). A novel process, using wavelength 248-nm KrF excimer laser annealing (ELA), has been undertaken to implement barium strontium titanate (BST) films at a low process temperature of 300degrees C. The crystallinity and dielectric constant are greatly improved after ELA treatment. In this work, the variation of texture was investigated. Besides, the escaped oxygen atoms from BST films were detected in-situ using a residual gas analyzer (RGA) during ELA process. Thus, the degradation of upper surface is strongly influenced by the laser energy fluence for an ELA-BST film.
Combustion synthesis of Ni-Zn ferrite powder - influence of oxygen balance value
(2005-01-01)
Hwang, CC
;
Tsai, JS
;
Huang, TH
;
Peng, CH
;
Chen, SY
In this study, Ni0.5Zn0.5FC2O4 powder was synthesized via an exothermic reaction between nitrates [Ni(NO3)(2).6H(2)O, Zn(NO3)(2).6H(2)O, Fe(NO3)(3).9H(2)O, and NH4NO3] and glycine [NH2CH2COOH]. By adjusting the glycine-to-nitrates ratio, the oxygen balance (OB) values of the reactant mixtures can be varied in which the combustion phenomena is altered and thereby the as-synthesized products with different characteristics are obtained. An interpretation based on the measurement of maximum combustion temperature (T-c) and the amounts of gas evolved during reaction for various OB values has been proposed regarding the nature of combustion and its correlation with the characteristics of as-synthesized products. After instrumental analyses, it is shown that the as-synthesized powders are nanoscale crystallites with a large specific surface area and they inherit a superparamagnetic behavior. (C) 2004 Elsevier Inc. All rights reserved.
Dynamic Java program corpus analysis - Part 1: The analyzer
(2001-05-01)
Hwang, CC
;
Chen, DJ
;
Huang, SK
;
Lin, MS
;
交大名義發表
Program corpus analysis is important in the optimization of runtime systems. Conventional linguistic analysis is static in nature and cannot reflect dynamic behaviors revealed by versatile object-oriented programming languages. We propose a pattern-based runtime profiler in this article. Unlike a conventional profiler or runtime visualization tools, representative program corpora accumulated and benchmarked not only shows monolithic functions that introduce excessive runtime overhead, hut also reflect their correlated code patterns, We propose a pattern-based analysis to address a program runtime bottleneck in a sequence of method invocations. It will reveal more semantic meanings in performance bottleneck rendered by object-oriented programming systems.
Dynamic Java program corpus analysis - Part 2: The control pattern analysis
(2001-06-01)
Hwang, CC
;
Chen, DJ
;
Huang, SK
;
Lin, MS
;
交大名義發表
Code patterns are statically recurring structures specific to a programming language, Control patterns are dynamically recurring structures invoked during program execution time, We have proposed a runtime profiler based on control patterns and demonstrate that all runtime traces can be represented by these patterns, A transformed form can be fed into a data-mining(1,2) analyzer(3) to find out if the recurring structures represent runtime behaviors.
Effect of diatomic islands on step morphological stability of a terrace edge in molecular beam epitaxy
(1999-09-29)
Lin, SP
;
Hwang, CC
;
Chu, HS
;
機械工程學系
;
Department of Mechanical Engineering
The effect of two-dimensional diatomic-island nucleation on the linear stability of the step morphology during molecular beam epitaxy is investigated numerically via shooting methods. It is found that the effect of diatomic islands on the step morphological stability is significant. The greater the effects of diatomic islands, the more stable the step morphology. increasing capture efficiency can decrease the critical surface capillary length and shift the critical wave number toward short-wavelength regimes. The unstable region is shrunk with increasing capture efficiency. Further, increasing flux coverage and/or surface coverage can decrease the critical surface capillary length and shift the critical wave number toward short-wavelength regimes. (C) 1999 Elsevier Science S.A. All rights reserved.
Effect of diatomic islands on step morphological stability of a terrace edge in molecular beam epitaxy (vol 353, pg 174, 1999)
(2000-01-31)
Lin, SP
;
Hwang, CC
;
Chu, HS
;
機械工程學系
;
Department of Mechanical Engineering
Effect of rapid thermal annealed TiN barrier layer on BST capacitors prepared by RF magnetron cosputter system at low substrate temperatures
(2000-12-01)
Hwang, CC
;
Jaing, CC
;
Lai, MJ
;
Chen, JS
;
Huang, S
This work reports on rapid-thermal-annealed TiN as a barrier for Pt/BST/Pt/TiN/Ti/Si capacitors. Experimental results indicate that the diffusion of Ti and Si from the Ti adhesion layer and Si plug, respectively, degrade the capacitor for the gigabit dynamic random access memories (DRAMs) using barium strontium titanate (BST) as a dielectric material. Although the diffusion barrier TiN between the bottom electrode Pt and Ti adhesion layer has been conventionally used to release the issue, the interdiffusion of Ti and Si occurs due to the thermal budget of the BST deposition. A rapid thermal annealing process is applied to the as-deposited TiN barrier against the interdiffusion. Excellent electrical characteristics, including high dielectric constant (epsilon (r) = 320), low leakage current (1.5 x 10(-8) A/cm(2)) under 0.1 MV/cm, and a lifetime greater than 10 years under 1.5 MV/cm are obtained. Our results further demonstrate that the proposed technique is highly promising for future high-density DRAMs. (C) 2000 The Electrochemical Society. S1099-0062(00)07-005-X. All rights reserved.
Effect of rapid-thermal-annealed TiN barrier layer on the Pt/BST/Pt capacitors prepared by RF magnetron co-sputter technique at low substrate temperature
(2001-01-01)
Hwang, CC
;
Juang, MH
;
Lai, MJ
;
Jaing, CC
;
Chen, JS
This investigation reports the effect of rapid-thermal-annealing (RTA) on metallic barrier TiN against the interdiffusions of Ti and Si into barium strontium titanate (BST) in Pt/BST/Pt/TiN/Ti/Si capacitors. In the integration of BST capacitors, the thermal budget of the BST deposition would cause the inter-diffusions of Ti and Si from Ti adhesion layer and Si plug respectively. This event would degrade the BST capacitors. To address this issue. rapid-thermal-annealed TiN barriers were deposited between the bottom electrode Pt and adhesion layer Ti. Optimal RTA condition for TiN were found ill this: experiment. Excellent electrical characteristics of Pt/BST/Pt/TiN/Ti/Si capacitors. including high dielectric constant (epsilon (r) = 320). low leakage current (1.5 x 10(-8) A/cm(2)) under 0.1 MV/cm, and greater than 10 year lifetime under 1.6 MV/cm were obtained with Ar + O-2 mixed ambient at a low substrate temperature (300 degreesC). (C) 2001 Elsevier Science Ltd. All rights reserved.
Effect of TiN treated by rapid thermal annealing on properties of BST capacitors prepared by RF magnetron co-sputter system at low substrate temperature
(2000)
Teng, TH
;
Hwang, CC
;
Lai, MJ
;
Huang, SC
;
Chen, JS
In this work, (Ba0.7Sr0.3)TiO3 thin films on Pt/TiN/Ti/Si substrate were deposited by an RF magnetron co-sputter system at 300 degrees C in an Ar+O-2 mixed ambient. In the integration of BST capacitors, the diffusion barrier (TiN) under bottom electrodes is one of the key issues. To obtain a stable and excellent diffusion barrier against inter-diffusion between Pt and Si, as well as against being oxidized during BST deposition, TiN was treated by a rapid thermal annealing (RTA) process. Experimental results indicated that proper RTA treatments resulted in a superior TiN barrier layer. In addition, low substrate temperature during BST deposition suppressed the phenomena of inter-diffusion and barrier oxidation. Furthermore, Pt hillocking, another problem during BST deposition because of high thermal budget, was also solved by reducing substrate temperature during BST deposition. The MIM (Pt/BST/Pt) structure was used in the experiments for electrical properties measurement. High dielectric constant (epsilon (r)=300), low leakage current (1.5x10(-8) A/cm(2)) under 0.1MV/cm, and 10 year lifetime under 1.6MV/cm were achieved with an Ar+O-2 mixed ambient at a low substrate temperature (300 degrees C).
Effects of post-oxygen plasma treatment on Pt/(Ba,Sr)TiO3/Pt capacitors at low substrate temperatures
(2003-02-01)
Shye, DC
;
Hwang, CC
;
Lai, MJ
;
Jaing, CC
;
Chen, JS
We investigated how oxygen plasma post-treatment improves leakage characteristics of Pt/(Ba,Sr)TiO3 (BST)/Pt capacitors prepared by the radio-frequency (RF) cosputtering technique. Experimental results indicate that oxygen plasma treatment can effectively passivate the oxygen vacancies of (Ba,Sr)TiO3 (BST) films, thus decreasing the electric conduction paths of leakage currents. By this low-temperature (250degreesC), and short-duration (similar to5 min) process, the leakage current is reduced by as many as two orders of magnitude. The reliability characteristics of time-dependent dielectric breakdown (TDDB) are improved as well. However, the usage of oxygen plasma treatment is not unrestricted. Plasma treatment for an extended period (more than 10 min) degrades both the leakage and reliability characteristics, due to plasma damage. Excellent electrical characteristics, including low leakage current (1.5 x 10(-8) A/cm(2)) under 0.1 MV/cm, high dielectric constant (288), and a lifetime longer than 10 years under 2 MV/cm can be achieved. Therefore, the proposed technique for as-deposited BST films is a highly promising means of improving the electrical characteristics of BST thin films.
Low temperature radio-frequency-sputtered (Ba, Sr)TiO3 films on Pt/TiN/Ti/Si substrates with various oxygen/argon mixing ratios
(2003-02-01)
Shye, DC
;
Chiou, BS
;
Lai, MJ
;
Hwang, CC
;
Jiang, CC
(Ba, Sr) TiO3 (BST) films were fabricated on Pt/TiN/Ti/Si substrates by low temperature radio frequency magnetron cosputtering at 300degreesC. Material and electrical properties of BST films sputtered at low temperatures are significantly affected by the O-2/(Ar + O-2) mixing ratio (OMR). Plasma emission spectra indicate that the deposition rate declines at a higher OMR due to oxide formation on the target surface. The dielectric constant of the BST films can reach a maximum of 364 at 5% OMR. The ten-year lifetime of the time-dependent dielectric breakdown implies that the reliability of the capacitor can be enhanced at a higher OMR due to compensation of oxygen vacancies and smaller grain sizes. Current-voltage analysis indicates that the leakage current of the Pt/BST/Pt capacitor is limited by Schottky emission (SE)/Poole-Frenkel emission (PF) at a lower/higher applied field. The applied field boundary between SE and PF shifts toward higher field as OMR increases. Moreover, an energy band model was proposed and this leakage mechanism was discussed. (C) 2003 The Electrochemical Society.
Low-temperature process to improve the leakage current of (Ba, Sr)TiO3 films on Pt/TiN/Ti/Si substrates
(2000-12-15)
Hwang, CC
;
Lai, MJ
;
Jaing, CC
;
Chen, JS
;
Huang, S
In this study, we employed an oxygen plasma post-treatment to improve the leakage characteristics of Pt/(Ba, Sr)TiO3(BST)/Pt capacitors prepared by the RF cosputtering technique. Applying oxygen plasma treatment to BST thin films can effectively passivate the oxygen vacancies of the BST films, thus decreasing the electric conduction paths of leakage current. The leakage current is reduced by as many as two orders of magnitude by this low-temperature (250 degreesC) and short duration (similar to5 min) process. However, the usage of oxygen plasma treatment is not unrestricted. Plasma treatment over a long time (more than 10 min) degrades the leakage characteristics, due to plasma damage. Therefore, a proper oxygen plasma treatment for as-deposited BST films is desired to improve leakage characteristics of BST thin films.
Microwave-absorbing characteristics for the composites of thermal-plastic polyurethane (TPU)-bonded NiZn-ferrites prepared by combustion synthesis method
(2005-02-25)
Peng, CH
;
Hwang, CC
;
Wan, J
;
Tsai, JS
;
Chen, SY
NiZn ferrite with the chemical formula Ni0.5-xZn0.5-xM2xFe2O4 (M = Co, Cu, or Mg, and x = 0 or 0.05) was synthesized by a combustion synthesis method using metal nitrates and urea ((NH2)(2)CO) as reactants. The narrocrystallite of these materials were mixed with a thermal-plastic polyurethane (TPU) elastomer to be converted into a microwave-absorbing composite. The complex relative permittivity (epsilon(r) = epsilon'-jepsilon") and permeability (mu(r)=mu'-jmu") of the absorber were measured in a frequency range of 2-12GHz. The reflection loss (R.L.), matching frequency (f(m)) and matching thickness (d(m)) were calculated using the theory of the absorbing wall. Effects of both the particle size of ferrite and the dopant presented in the ferrite on the electromagnetic properties and microwave-absorbing characteristics were investigated. It was found that nanoparticles around 40 nm exhibit higher reflection loss than both those obtained from micro-sized powders and those with size less than 25 nm. Also, it was shown that the Co-doped, Mg-doped, and Cu-doped NiZn ferrite-TPU composites could be designed to be more negative than -20 dB, in a frequency range of 2-12 GHz, to become promising materials for microwave-absorbing application. These doped ferrite-containing composites have more effective microwave-absorbing characteristics compared to undoped one. (C) 2004 Elsevier B.V. All rights reserved.
Mining control patterns from Java program corpora
(2004-01-01)
Chen, DJ
;
Hwang, CC
;
Huang, SK
;
Chen, DTK
;
資訊工程學系
Java programming, based on the Object-Oriented (OO) paradigm, has played a major role in program design and implementation due to the fact that it is extensible, maintainable, and reusable in software system construction. Experiences with using Java programming have indicated that there also exist disadvantages with respect to its execution inefficiency and complicated runtime behaviors. Code-patterns are statically recurring structures specifically related to a programming language. They can be used in parallel to help programmer design software systems to solve particular problems. In opposition to the role of code-patterns in assisting compilation, control-pattems are dynamically recurring structures invoked during program execution time. They can be used to understand the run-time behaviors of OO-programs with respect to the underlying architecture, such as Java-VM. A control pattern describes the model of control transfer among objects during OO program execution. In this paper, several control patterns are proposed and discussed. We have analyzed and collected several control patterns from several Java program corpora. The experimental results show that control patterns do exist and provide information for quantitative analysis. Simple patterns, compound patterns, and complex patterns have different ratios depending on their source programs. Collected control patterns can be used to provide guidelines for Java programmers so that they can write more effective Java programs.
Molecular dynamics simulation of microscopic droplet spread on rough surfaces
(2001-09-01)
Hwang, CC
;
Jeng, YR
;
Hsu, YL
;
Chang, JG
;
機械工程學系
This study uses molecular dynamics simulations to elucidate the spreading behaviour of a liquid droplet oil a rough solid surface. The Lennard-Jones potential energy model is adopted as the interaction model between the liquid and the solid molecules. The paper considers two typos of rough surface: periodic and random. These surfaces are characterized by their roughness height and their spatial variation. For a periodic surface, the roughness height is defined by the amplitude, A, while for a random surface, it is defined in terms of the standard deviation of the roughness height, sigma. Regarding the spatial variation of the surface, a periodic surface is characterized by the wavelength, lambda, while the random surface is characterized by its autocorrelation length, L. Simulation results indicate that the characteristics of the rough surface can significantly influence spreading behaviour, in terms of final equilibrium time, spreading radius, and spreading topography. It is observed that the effects of roughness height and spatial variation are broadly similar for both periodic and random surfaces. It is found that increasing roughness height and decreasing spatial periodicity both prolong the final equilibrium time, and that the filial spreading radius decreases with increasing roughness height and increases with larger spatial periodicity.
Nonlinear diffusion-induced stresses in a long bar of square cross section
(1999-01-01)
Hwang, CC
;
Lin, SP
;
Chu, HS
;
Lee, WS
;
機械工程學系
This paper is to investigate the nonlinear effect of the self-induced electric field on the diffusion-induced stresses in a long bar. We first approximate the nonlinear concentration-dependent diffusivity asa series of third-degree polynomials by the least-squares curve-fitting techniques, and then calculate the distributions of concentration by the Galerkin method. Afterwards, the diffusion-induced stresses inside the bar are determined analytically by introducing the Goodier displacement potential and Airy stress function. It is found that the nonlinear self-induced electric fields can depress both the concentration gradient and the maximum diffusion-induced stresses apparently, and these effects are more significant at short times than at long times. (C) 1998 Elsevier Science Ltd. All rights reserved.
Object-oriented program behavior analysis based on control patterns
(2001)
Hwang, CC
;
Huang, SK
;
Chen, DJ
;
Chen, DTK
;
資訊工程學系
Code-patterns are statically recurring structure specific to a programming language. It can be parallel to aid in designing software systems for solving particular problems. Contrary to compilation assistance of code-patterns, control-patterns are dynamically recurring structures invoked during program execution time. It can be used for benchmarking OO-programs and underlying architecture like Java and Java-VM. We have proposed a run-rime profiler based on control patterns and show that all run-time trace can be represented by, a directed graph, a constrained output and a Boolean function. A transformed graph can be fed into a data-mining analyzer to find out the recurring structure representing run-time behaviors.
On striping traffic over multiple IEEE 802.11(b) wireless channels
(2006-06-01)
Wang, SY
;
Hwang, CC
;
Chou, CL
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資訊工程學系
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Department of Computer Science
Due to interference, path loss, multipath fading, background noise, and many other factors, wireless communication normally cannot provide a wireless link with both a high data rate and a long transmission range. To address this problem, striping network traffic in parallel over multiple lower-data-rate but longer-transmission-range wireless channels may be used. In this paper, we propose a new striping method and evaluate its performances over multiple IEEE 802.11(b) channels under various conditions. Our extensive simulation results show that this method is quite effective for such an application.
Preparation and characterization of YBa2Cu3O7-x superconductor by means of a novel method combining sol-gel and combustion synthesis techniques
(2004-06-15)
Peng, CH
;
Hwang, CC
;
Hong, CK
;
Chen, SY
;
材料科學與工程學系