TRANSMISSION ELECTRON-MICROSCOPY AND VIBRATIONAL SPECTROSCOPY STUDIES OF UNDOPED AND DOPED SI,H AND SI,CH FILMS

Films of undoped and doped Si:H and Si,C:H alloys were deposited by remote plasma-enhanced chemical vapor deposition onto thermally grown silicon oxide layers at a substrate temperature of 250-degrees-C. The microstructure of the films, including the degree of crystallinity, and the distribution of carbon within the Si,C alloys films were characterized by transmission electron microscopy, Raman scattering, and infrared absorption spectroscopy. The degree of crystallinity depends on both the doping level and on the presence of carbon. For two-phase mu-c-Si or mu-c-Si,C alloy films, the results indicate that (i) the crystallites are Si, and (ii) the amorphous encapsulating materials are a-Si:H for mu-c-Si,H, and a-Si,C:H for the mu-c-Si,C:H alloys. A relationship between microstructure, doping levels, and the measured dark conductivity is discussed.