Infrared absorption and bonding in amorphous hydrogenated silicon-carbon alloys

Abstract

Films of a-Si_1-xC_x:H were prepared by DC magnetron glow discharge decomposition of silane-methane-gas mixtures. The infrared absorption coefficient was studied using a reflection method in the range 650-4000 cm^-1 as a function of the fraction of methane in the gas mixture and as a function of substrate temperature. The results enabled assignments of the hydrogen-related absorption features to be made. At a substrate temperature of 478 degrees C the silicon-hydrogen stretching mode split into three bands. The silicon-carbon stretching mode was used to estimate the degree of heteronuclear bonding. It was shown that heteronuclear bonding increased with substrate temperature and was accompanied by useful increases in the photoconductivity of the films.