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.
Various metal ions were implanted to colorless synthetic quartz to doses of metal ions from 4×1016 to 5×1017 ions/cm2 with an energy of 20 KeV. The part of quartz implanted with Cu+ ions showed tint of light purple-red, while parts implanted with Fe+ ions or Nb+ ions showed yellowish brown or light blue, respectively, after annealing for 3 hours in air at 1000°C. Transparencies of the implanted sample in the visible range and the depth profile of Cu were measured.
Using the Langmuir-Blodgett method, mon-omolecular layers were easily deposited on a flat surface. The thickness of these layers (LB films) can be controlled with very high accuracy. The frictional coefficient and elec-trical contact resistance were measured be-tween a steel ball and a flat copper surface covered with several layers of stearic acid-LB films. The ratio of metallic contact was calculated from the electrical contact resist-ance. The obtained results indicated that the stearic acid-LB films act as an efficient lubri-cant, having a high contact resistance and a low frictional coefficient.