Browsing by Author "Horng, RH"

Now showing 1 - 3 of 3

Characterization of NH3 plasma-treated Ba0.7Sr0.3TiO3 thin films
(2000-04-01)
Wuu, DS
;
Horng, RH
;
Liao, FC
;
Leu, CC
;
Huang, TY
The effects of plasma surface treatment, using NH3 gas, of Ba0.7Sr0.3TiO3 (BST) films on the leakage and dielectric characteristics of a Pt/BST/Pt capacitor were investigated. As a result of the exposure of BST to the plasma, the leakage current density of the BST capacitor can be improved by three orders of magnitude as compared to that of the nonplasma-treated sample at an applied voltage of 1.5 V. Nevertheless, the surface morphology of BST was also changed by the NH3 plasma, as explored by atomic force microscopy. From the X-ray photoelectron spectroscopy examination, the existence of the N 1 s peak was observed in the plasma-treated sample. It induces the additional space charge and results in the reduction of the dielectric constant. (C) 2000 Elsevier Science Ltd. All rights reserved.
Effects of O-2 plasma treatment on the electric and dielectric characteristics of Ba0.7Sr0.3TiO3 thin films
(2000-04-01)
Leu, CC
;
Chan, SH
;
Chen, HY
;
Horng, RH
;
Wuu, DS
The effects of the O-2 plasma treatment on the electric and dielectric characteristics of Ba0.7Sr0.3TiO3 (BST) thin films were investigated. As a result of the exposure of the as-deposited or the annealed BST films to the O-2 plasma, the leakage current density of the BST films can be improved. Typically, the leakage current density can decrease by three orders of magnitude as compared that of the non-plasma treated sample at an applied voltage of 1.5 V. It is found that the plasma treatment changes the surface morphology. The capacitance of the BST films was reduced by 10%similar to 30%. The improvement of the leakage current density and the reduction of a dielectric constant for the plasma treated samples could be attributed to the reduction of carbon contaminations of BST thin films. The 10 year life time of the time-dependent dielectric breakdown (TDDB) studies indicates that all the samples have a life time of over 10 years of operation at a voltage bias of 1 V. (C) 2000 Elsevier Science Ltd. Al rights reserved.
Stable shaft-sensorless control of permanent magnet synchronous motors using a sliding torque observer
(2003-06-01)
Horng, RH
;
Chin, KP
;
機械工程學系
;
Department of Mechanical Engineering
Two nonlinear sliding observers are developed for speed-sensorless control of permanent magnet synchronous motors. One of the observers estimates the rotor position and velocity based on the measurement of the motor current, while the other estimates load torque as well as rotor position and velocity. The lower bounds of the sliding gain, which guarantee the existence of the sliding manifold, and the upper bounds, which guarantee the stability of the digital implementation of the sliding observers, are also presented. Both theoretical analyses and experimental results demonstrate that, regardless of the observer used for speed-sensorless control, the steady-state velocity error converges even when an external load torque is applied to the rotor. However, when an external load is present, the position estimation error of the control system with torque estimation and compensation is significantly smaller than that of the system without torque estimation and compensation.