Browsing by Author "Wu, JP"

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An efficient method for characterizing time-evolutional interface state and its correlation with the device degradation in LDD n-MOSFET's
(1996-06-01)
Lee, RGH
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Wu, JP
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Chung, SS
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電子工程學系及電子研究所
;
電控工程研究所
A new characterization method is proposed to study the relationship between the hot-carrier-induced interface state N-it(x) and the device drain current degradation of submicron LDD n-MOSFET's. In this method, by making use of the conventional charge pumping measurement in combination with the power-lay dependence of interface damages on stress time, the spatial distribution N-it(x) and the effective damaged length L(dam) can be easily extracted. The time evolution of the interface state generation and its correlation with the device degradation can then be well explained. It is worthwhile to note that this newly-developed method requires no repetitive charge pumping measurements, and hence avoids he likely imposition of se-stress on tested devices. By combining the characterized L(dam) and N-it quantitatively, the results show that the damage at V-GS approximate to V-DS/2 is most highly localized among various stress biases, which can explain why the generated interface states will dominate the device drain current degradation at this bias after long-term operating conditions.
Influence of thermal boundary resistance on bolometric response of high-T-c superconducting films
(1998-09-01)
Wu, JP
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Shih, CU
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Chu, HS
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機械工程學系
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Department of Mechanical Engineering
This work presents a thermal analysis on predicting the temperature increase and the voltage response of high-T-c superconducting bolometers. To consider the thermal boundary resistance between film and substrate, an acoustic mismatch model (AMM), a diffusive mismatch model (DMM), and an interfacial layer model (ILM) are employed. The thermal boundary resistance significantly influences the voltage response. Additionally, several common substrates are examined. SrTiO3 (100) or LaAlO3 (100) is a better substrate for high-T-c superconducting bolometers. Furthermore, we demonstrated that there are several factors to affect the voltage response, such as the pulse duration for a constant total incident energy or a fixed highest incident heat flux, the pulse distribution function in time, optical penetration depth, the thermal conductivities of the film and substrate, initial operating temperature, thickness ratio, and the amount of incident heat flux. One interesting finding was that when compared with experimental data, all the theoretical values from the present study as well as the other previously theoretical treatment overestimate the voltage response near the transition temperature. (C) 1998 Elsevier Science Ltd. All rights reserved.
Intrinsic thermal stability and quenching recovery of thin-film superconductors with thermal boundary resistance
(1997-05-01)
Wu, JP
;
Chu, HS
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機械工程學系
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Department of Mechanical Engineering
The stability behaviour of a thin-film superconductor under a localized release of thermal disturbance is investigated. Two-dimensional conjugate film/substrate conduction equation with anisotropic thermal conductivity of the film, and Joule heat are employed to investigate effects of substrate and thermal properties on the intrinsic stability and quenching recovery. To consider the thermal boundary resistance between film and substrate, an interfacial-layer model (ILM) with very low diffusivity and an acoustic mismatch model (AMM) are employed. Results show that the thermal boundary resistance influences strongly the intrinsic stability. Thermal boundary resistance increases intrinsic stability if the thermal conductivity of the substrate or the disturbance energy is large. Higher Riot numbers and thermal conductivity ratios of film to substrate in longitudinal direction influence stability favorably. We demonstrate also that operation of a film/substrate system, such as YBCO/MgO, is either intrinsically stable or irrecoverably unstable.
Intrinsic thermal stability and quenching recovery of thin-film superconductors with thermal boundary resistance
(1997-05-01)
Wu, JP
;
Chu, HS
;
交大名義發表
;
機械工程學系
;
National Chiao Tung University
The stability behaviour of a thin-film superconductor under a localized release of thermal disturbance is investigated. Two-dimensional conjugate film/substrate conduction equation with anisotropic thermal conductivity of the film, and Joule heat are employed to investigate effects of substrate and thermal properties on the intrinsic stability and quenching recovery. To consider the thermal boundary resistance between film and substrate, an interfacial-layer model (ILM) with very low diffusivity and an acoustic mismatch model (AMM) are employed. Results show that the thermal boundary resistance influences strongly the intrinsic stability. Thermal boundary resistance increases intrinsic stability if the thermal conductivity of the substrate or the disturbance energy is large. Higher Riot numbers and thermal conductivity ratios of film to substrate in longitudinal direction influence stability favorably. We demonstrate also that operation of a film/substrate system, such as YBCO/MgO, is either intrinsically stable or irrecoverably unstable.
Propagation and reflection of thermal waves in a rectangular plate
(1999-07-01)
Wu, JP
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Chu, HS
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機械工程學系
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Department of Mechanical Engineering
The wave nature of heat propagation in a two-dimensional rectangular plate with an instantaneous thermal disturbance released in an arbitrary position is investigated by solving the hyperbolic heat conduction equation. The exact analytical solutions are developed for the temperature field and heat flux using the Green's function technique to deal with two limiting boundary conditions, the constant wall temperature and the adiabatic condition, around the region. The disturbance gives rise to a severe thermal wave front, which differs completely front that obtained through one-dimensional analysis, traveling through the medium at a finite speed with a sharp peak at the leading edge. The significant findings in these results are that a negative trailer is generated and follows behind the wave front. In addition, the magnitude of the front is significantly attenuated from the side adjacent to the trailer because the increasing area available to it for diffusion, and decays exponentially along its path of travel, since the thermal energy is dissipated in the wake of the moving wave front. The results also reveal that different boundary conditions strongly influence the reflection of a thermal wave front from the exterior surfaces and the reflection and interaction among thermal waves are more complicated than those found through one-dimensional analysis.
Substrate effects on intrinsic thermal stability and quench recovery for thin-film superconductors
(1996-11-01)
Wu, JP
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Chu, HS
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交大名義發表
;
機械工程學系
;
National Chiao Tung University
Two-dimensional conjugate film/substrate conduction equations considering an instantaneous release of energy in the form of a line source, anisotropic thermal conductivity of the film, and Joule heat are employed to investigate substrate effects on the intrinsic thermal stability and quenching recovery of thin-film superconductors. The results show that substrate effects exert significant influences on thermal stability of superconductors, because the higher thermal conductivity of substrates than those of films can cause heat feedback from the substrates. Both critical current densities related to intrinsic stability and recovery are calculated for different ratios of thermal conductivity and thickness of film to substrate, substrate materials, superconductors, Blot numbers, and operating temperatures. (C) 1996 Elsevier Science Limited
Transient heat-transfer phenomenon of two-dimensional hyperbolic heat conduction problem
(1998-05-08)
Wu, JP
;
Shu, YP
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Chu, HS
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機械工程學系
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Department of Mechanical Engineering
This article presents a numerical analysis of the two-dimensional hyperbolic heat conduction problem in an anisotropic medium under a point heat source with different boundary conditions. A simple model has been developed to solve the anisotropic problem. In this analysis, the second-order total variation diminishing (TVD) scheme is employed to solve this problem. The effects of boundary conditions and anisotropy on the thermal wave induced by different types of heat sources in the medium are examined in detail. The results show that the transient behavior of the propagation of the two-dimensional thermal wave is much more complicated than that of the one-dimensional thermal wave due to a circular wave formed to propagate uniformly in all directions, reflections by boundaries, interaction with each other, and serious discontinuity on the wavefront.