Browsing by Author "Su, FC"

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An effective method for evaluating the image-sticking effect of TFT-LCDs by interpretative modelling of optical measurements
(2000-07-01)
Chen, PL
;
Chen, SH
;
Su, FC
;
光電工程學系
;
Department of Photonics
The conventional method of evaluating the image-sticking effect of a LCD module is inspection by sight, because the residual optical difference between two stressing areas is small and viewing angle-dependent, so that it is difficult to obtain a significant optical difference value by instrumental measurement. We propose an effective method for evaluating the image-sticking effect of a TFT-LCD module by directly measuring its time evolution of transmission with the TFT glass turned off after a period of pattern stress. In this way, the liquid crystal system under charge equilibrium in constant-charge mode shows a dramatically amplified optical difference. Further, we interpret the measured results by a modelling that combines the calculation of liquid crystal director orientation and ionic charge distribution. It is supposed that there are four time constants that dominate the overall sticking phenomenon and belong to four transient processes: adsorption of ions, desorption of free ions, desorption of stuck ions, and TFT leakage. The modelling shows good accordance between measured and simulated results when fitting parameters are properly chosen.
Effects of the rear interface states and fixed charges on the electrical characteristics of thin film transistors with thin amorphous silicon layers
(1996-06-01)
Tai, YH
;
Su, FC
;
Feng, MS
;
Cheng, HC
;
材料科學與工程學系
The electrical characteristics of the thin film transistors (TFT's) with hydrogenated amorphous silicon (a-Si:H) films thinner than 0.1 mu m have been carefully studied to show that the interface states and fixed charges at the rear interface will play the comparable effects to those at the front interface on the field effect conductance. It is dearly demonstrated that as the thickness of the active layer is smaller than the theoretically expected width of the space charge region, the potential at the rear interface will be affected by the gate voltage. This is very different from the conventional case with a thicker active layer. Since the TFT's at present have smaller typical thicknesses of the semiconductor films than the expected width of the space charge region, the effects of the interface states and the fixed charges at both the rear and front interfaces, as well as the bulk states of the thin a-Si:H films, must be taken into account concurrently.
Electrical properties of amorphous silicon films with different thicknesses in metal/insulator/semiconductor structures
(1996-05-01)
Tai, YH
;
Su, FC
;
Chang, WS
;
Feng, MS
;
Cheng, HC
The density of states (DOS) of hydrogenated amorphous silicon (a-Si:H) is an important issue in the study of the physics of amorphous semiconductors. In many earlier reports concerning the analysis of the field-effect conductance metal/insulator/ a-Si:H structures, namely, thin-film transistors (TFTs), the potential at the semiconductor surface apart from the gate insulator/a-Si:H interface, i.e., the rear interface, was assumed to be zero. However, in principle, as the thickness of the semiconductor film is smaller than the theoretically expected width of the space charge region, this assumption no longer holds. Hence, it is necessary to reconsider the band-bending phenomena of the a-Si:H active layers. It was found that the DOS, which was extracted previously from the field-effect conductance of the TFTs based on the assumption of the zero-potential rear interface, was appropriate only for the thick a-Si:H films. As for the thin semiconductor films, the accurate DOS can be obtained by fitting the calculated field-effect conductance, with a surmised possible DOS, to the experimentally measured data via the method developed.
Fault diagnosis of rotating machinery using an intelligent order tracking system
(2005-02-23)
Bai, MS
;
Huang, JM
;
Hong, MH
;
Su, FC
;
機械工程學系
This research focuses on the development of an intelligent diagnostic system for rotating machinery. The system is composed of a signal processing module and a state inference module. In the signal processing module, the recursive least square (RLS) algorithm and the Kalman filter are exploited to extract the order amplitudes of vibration signals, followed by fault classification using the fuzzy state inference module. The RLS algorithm and Kalman filter provide advantages in order tracking over conventional Fourier-based techniques in that they are insensitive to smearing problems arising from closely spaced orders or crossing orders. On the basis of thus obtained order features, the potential fault types are then deduced with the aid of a state inference engine. Human diagnostic rules are fuzzified for various common faults, including the single fault and double fault situations. This system is implemented on the platform of a floating point digital signal processor, where a photo switch and an accelerometer supply the shaft speed and acceleration signals, respectively. Experiments were carried out for a rotor kit and a practical four-cylinder engine to show the effectiveness of the proposed system in tracking the rotating order with precise inference. (C) 2003 Elsevier Ltd. All rights reserved.
Process-related instability mechanisms for the hydrogenated amorphous silicon thin film transistors
(1995)
Tai, YH
;
Su, FC
;
Feng, MS
;
Cheng, HC
;
電子工程學系及電子研究所
Reducing threshold voltage shifts in amorphous silicon thin film transistors by hydrogenating the gate nitride prior to amorphous silicon deposition
(1997-09-01)
Tsai, JW
;
Huang, CY
;
Tai, YH
;
Cheng, HC
;
Su, FC
A short H-2 plasma treatment of the gate SiNx before depositing amorphous silicon (a-Si:H) is found to significantly decrease the threshold shifts in the bias stress, inverted a-Si:H thin film transistors (TFTs). The reduced threshold voltage shift is attributed to a plasma induced reconstruction of SiNx precursors leading to the removal of the weak bonds. A prolonged plasma treatment, however, degraded the TFT characteristics; this was traced H-2 plasma damage which eventually generated a rough a-Si:H/SiNx interface. (C) 1997 American Institute of Physics.
Reducing threshold voltage shifts in amorphous silicon thin film transistors by hydrogenating the gate nitride prior to amorphous silicon deposition
(1997-09-01)
Tsai, JW
;
Huang, CY
;
Tai, YH
;
Cheng, HC
;
Su, FC
A short H-2 plasma treatment of the gate SiNx before depositing amorphous silicon (a-Si:H) is found to significantly decrease the threshold shifts in the bias stress, inverted a-Si:H thin film transistors (TFTs). The reduced threshold voltage shift is attributed to a plasma induced reconstruction of SiNx precursors leading to the removal of the weak bonds. A prolonged plasma treatment, however, degraded the TFT characteristics; this was traced H-2 plasma damage which eventually generated a rough a-Si:H/SiNx interface. (C) 1997 American Institute of Physics.
The electrical characteristics of the amorphous silicon thin film transistors with dual intrinsic layers
(1997-08-01)
Tsai, JW
;
Cheng, HC
;
Chou, A
;
Su, FC
;
Luo, FC
The amorphous silicon thin film transistors (a-Si:H TFTs) with dual intrinsic layers, namely, a bottom a-Si:H deposited at a low deposition rate and an upper layer at a high deposition rate, were investigated to improve the manufacturing throughput. It was found that the high deposition rate for the upper layer resulted in high density of states and low mobility and high threshold voltage. Although a-Si:H TFTs with high deposition rates for the upper layer still had an I-on/I-off ratios higher than 10(6) and saturation mobility higher than 0.4 cm(2)/V s, the deposition rates of 1786 and 3340 Angstrom/min exhibited a significant current crowding and led to low mobility and on-current in the linear region. On the other hand, a-Si:H TFTs with deposition rate of 1170 Angstrom/min for the upper layer achieved similar characteristics as those with single layer deposited at deposition rate of 482 Angstrom/min. Furthermore, the stress stability for deposition rate of 1170 Angstrom/min also showed a threshold voltage shift similar to that of a single-layer one. This indicated that the deposition rate of the upper layer for dual-layer a-Si:H TFTs must be properly chosen for applications in high resolution LCDs.