光CVD法によるa-Si生成の初期過程

抄録

The initial process of a-Si: H formation by photo-induced chemical vapor deposition (photo-CVD) was studied by making use of a new technique of pre-amplification of small Si nuclei to colloidal silver, followed by examination with a transmission electron microscope. The variation of Si nucleus density with irradiation time revealed a clearly definite saturation. The saturation density decreased with substrate temperature. The initial nucleation rate, however, showed a tendency to increase with substrate temperature. Structural surface defects induced by a mechanical scratch largely increased the nucleus density at high substrate tem-peratures. These results manifest the contribution of surface diffusion and desorption of active radicals in the initial process of photo-CVD and suggest that some chemical reac-tion is involved at the uucleation step. From the effect of gas phase pressure on the nucleus density, independent of substrate temperature, it is concluded that the active radicals are pro-vided mostly by the photodecomposition of gas phase molecules. A simple model of the initial process of photo-CVD is presented.