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Defects in SIPOS film studied through ESR
Abstracts
The relaxation process of photoeonductivity and the effect of trap in a-Si:H film Gong Daoben, Physics Department, Zhangnan National University, Wuhan, 430074 Hubei, China This paper gives the experimental result of the relaxation process of photoconductivity in amorphous silicon (a-Si:H) under the conditions of non-steady state light illumination, as this subject has not been widely researched. A part of the beginning of both the rising curve and the dropping curve closes the exponential curve. It shows that in the aSi: H film under weak light its photoconductivity approximately agrees with a monomolecular recombination law. However, all curves relative to exponential curve have different degrees of deviation. The longer the time of stopping the light illumination, the more the curve deviates from the exponential curve and the longer the relaxation time of the rising curve when next illuminated. Holes are trapped by minority carrier traps. It has an increased lifetime of majority carrier so that it has the decay of photoconductivity slowly. Then the text considers that the action of the minority carrier trap only increases the relaxation time of photoconductivity exponentially, and subsequently affects of majority carrier trapping, mainly as the relaxation process has to obviously deviate from the exponential curve. Because when photoelectrons increase (or decrease) at same time it is accompanied with a gradually filling (or discharging) process of majority carrier trap. It obviously increases relaxation time of photoconductivity. It shows that there are a lot of deep electron traps in a-Si : H.
Silane plasma parameters and their dependence on the deposition conditions of PECVD a-Si:H films Xi Zhonghe, Yang Fan, Xu Feng and Zhang Guanghuai, Radio-
Electronics Department, Peking University, Beijing 100871, China; Lin Hongyi, Electronics Department, Beijing Institute of Technology, Beijing, China; and Hu Jianfang, Physics Department, Chinese National Institute, Beijing, China Amorphous-Si: H films have attracted a considerable amount of interest because of their applications in a variety of areas and their significance in disordered solid physics. In this paper, electron temperature Te and density Are of Sill 4 plasma generated in a typical rf glow discharge (PECVD) system are investigated using a double floating probe so as to improve the understanding of the plasma feature and the early process of a-Si:H deposition. Measurements show complex dependence of Te and N, on the deposition parameters (e.g. rf power, gas pressure, flow rate and deposition temperature) and a wide variation : 4-20 eV in T~, 108 10 9 c m 3 in Ne. A simple model based on the consideration of the mean electron energy restricted closely by the retention time is proposed and is shown to be successful to explain the relation of the macroscopic and microscopic parameters. A conception of 'renewal rate' of the discharge gas is first introduced and it seems to be one of the essential parameters for the flowing plasma usually met in plasma deposition and etching. Spatial distribution is measured for the plasma parameters, and a heterogeneous profile with an extreme value before the earth plate is found along the axis. Probe contamination and rf-jam are the main technical difficulties in the experiments. Contaminative ~ V curves usually 1080
show an additional equivalent resistance and a steep slope due to the expanded probe sheath. The dependence of the contamination behavior on the deposition conditions and the measurement techniques in relation to reducing the probe contamination are also discussed.
Defects in SIPOS film studied through ESR Wang Yunzhen and Pan Yaoling, East China Normal University,
Shanghai 200062, China In the present paper, we used the datum of g factor value, linewidth AHpe and Spin density Ns from ESR measurements to investigate the defects in the SIPOS film. There are four defects related to the different Si tetrahedral structure Si-(Si 4 yOy) in SIPOS film. These defects are named defect 1, defect 2, defect 3 and defect 4. The ESR spectrum found for a specific oxygen content is assumed to be a linear superposition of the resonances of these four defects. The g value is the statistical average of four g values of corresponding defects. Using the above model of defects, the variations of linewidth and spin densities of SIPOS film with different oxygen content and annealing conditions can be well described.
Diffusion in a random thin film on a crystal substrate Igor S Branovitsky, Scientific Industrial Association 'Luch'
Podolsk, Moscow 142100, USSR Hopping transport in a random thin film (RTF) on a crystal substrate is studied when non-zero probability of particles transfer into a substrate exists. The lattice model is considered where the RTF is represented by one layer of sites with random values of transfer rate between nearest neighbours. The transfer rate in the substrate is a non-random value. A self-consistent effective-medium approximation is presented for the problem of diffusion in the film with diagonal disorder (symmetric hopping rates between neighbouring sites). It is shown that self consistency condition differs from that for the two-dimensional random system. Therefore one cannot consider RTF as an isolated random medium. The frequency dependence of the diffusion coefficient in RTF is analysed when the jump rate (between RTF sites) obeys a bimodal distribution. Diffusion in RTF with general non-symmetric long-range correlated disorder is studied by means of the perturbation theory and diagram technique. The analysis shows that anomalous diffusion conditions for RTF on a substrate are more rigid than that for a free two-dimensional random system. The model in consideration is suitable for analysis of transport processes in such systems as amorphous semiconductor film on crystal substrate, rough surface, disordered grain boundary and others.
Study on the current transport mechanisms in thin SiOxNy films Yang Bingliang, Liu Baiyong and Chen Dounan, Department of
Physics, South China University of Technology, Guangzhou 510641, China; and Y C Cheng, Department of Electrical and Electronic Engineering, University of Hong Kong, Hong Kong Since 1980, the properties and applications of the thin thermally
The relaxation process of photoeonductivity and the effect of trap in a-Si:H film Gong Daoben, Physics Department, Zhangnan National University, Wuhan, 430074 Hubei, China This paper gives the experimental result of the relaxation process of photoconductivity in amorphous silicon (a-Si:H) under the conditions of non-steady state light illumination, as this subject has not been widely researched. A part of the beginning of both the rising curve and the dropping curve closes the exponential curve. It shows that in the aSi: H film under weak light its photoconductivity approximately agrees with a monomolecular recombination law. However, all curves relative to exponential curve have different degrees of deviation. The longer the time of stopping the light illumination, the more the curve deviates from the exponential curve and the longer the relaxation time of the rising curve when next illuminated. Holes are trapped by minority carrier traps. It has an increased lifetime of majority carrier so that it has the decay of photoconductivity slowly. Then the text considers that the action of the minority carrier trap only increases the relaxation time of photoconductivity exponentially, and subsequently affects of majority carrier trapping, mainly as the relaxation process has to obviously deviate from the exponential curve. Because when photoelectrons increase (or decrease) at same time it is accompanied with a gradually filling (or discharging) process of majority carrier trap. It obviously increases relaxation time of photoconductivity. It shows that there are a lot of deep electron traps in a-Si : H.
Silane plasma parameters and their dependence on the deposition conditions of PECVD a-Si:H films Xi Zhonghe, Yang Fan, Xu Feng and Zhang Guanghuai, Radio-
Electronics Department, Peking University, Beijing 100871, China; Lin Hongyi, Electronics Department, Beijing Institute of Technology, Beijing, China; and Hu Jianfang, Physics Department, Chinese National Institute, Beijing, China Amorphous-Si: H films have attracted a considerable amount of interest because of their applications in a variety of areas and their significance in disordered solid physics. In this paper, electron temperature Te and density Are of Sill 4 plasma generated in a typical rf glow discharge (PECVD) system are investigated using a double floating probe so as to improve the understanding of the plasma feature and the early process of a-Si:H deposition. Measurements show complex dependence of Te and N, on the deposition parameters (e.g. rf power, gas pressure, flow rate and deposition temperature) and a wide variation : 4-20 eV in T~, 108 10 9 c m 3 in Ne. A simple model based on the consideration of the mean electron energy restricted closely by the retention time is proposed and is shown to be successful to explain the relation of the macroscopic and microscopic parameters. A conception of 'renewal rate' of the discharge gas is first introduced and it seems to be one of the essential parameters for the flowing plasma usually met in plasma deposition and etching. Spatial distribution is measured for the plasma parameters, and a heterogeneous profile with an extreme value before the earth plate is found along the axis. Probe contamination and rf-jam are the main technical difficulties in the experiments. Contaminative ~ V curves usually 1080
show an additional equivalent resistance and a steep slope due to the expanded probe sheath. The dependence of the contamination behavior on the deposition conditions and the measurement techniques in relation to reducing the probe contamination are also discussed.
Defects in SIPOS film studied through ESR Wang Yunzhen and Pan Yaoling, East China Normal University,
Shanghai 200062, China In the present paper, we used the datum of g factor value, linewidth AHpe and Spin density Ns from ESR measurements to investigate the defects in the SIPOS film. There are four defects related to the different Si tetrahedral structure Si-(Si 4 yOy) in SIPOS film. These defects are named defect 1, defect 2, defect 3 and defect 4. The ESR spectrum found for a specific oxygen content is assumed to be a linear superposition of the resonances of these four defects. The g value is the statistical average of four g values of corresponding defects. Using the above model of defects, the variations of linewidth and spin densities of SIPOS film with different oxygen content and annealing conditions can be well described.
Diffusion in a random thin film on a crystal substrate Igor S Branovitsky, Scientific Industrial Association 'Luch'
Podolsk, Moscow 142100, USSR Hopping transport in a random thin film (RTF) on a crystal substrate is studied when non-zero probability of particles transfer into a substrate exists. The lattice model is considered where the RTF is represented by one layer of sites with random values of transfer rate between nearest neighbours. The transfer rate in the substrate is a non-random value. A self-consistent effective-medium approximation is presented for the problem of diffusion in the film with diagonal disorder (symmetric hopping rates between neighbouring sites). It is shown that self consistency condition differs from that for the two-dimensional random system. Therefore one cannot consider RTF as an isolated random medium. The frequency dependence of the diffusion coefficient in RTF is analysed when the jump rate (between RTF sites) obeys a bimodal distribution. Diffusion in RTF with general non-symmetric long-range correlated disorder is studied by means of the perturbation theory and diagram technique. The analysis shows that anomalous diffusion conditions for RTF on a substrate are more rigid than that for a free two-dimensional random system. The model in consideration is suitable for analysis of transport processes in such systems as amorphous semiconductor film on crystal substrate, rough surface, disordered grain boundary and others.
Study on the current transport mechanisms in thin SiOxNy films Yang Bingliang, Liu Baiyong and Chen Dounan, Department of
Physics, South China University of Technology, Guangzhou 510641, China; and Y C Cheng, Department of Electrical and Electronic Engineering, University of Hong Kong, Hong Kong Since 1980, the properties and applications of the thin thermally