Physical properties and structure of carbon-rich a-SiC:H films prepared by r.f. glow discharge decomposition

Abstract

Carbon-rich a-SiC:H films were prepared by glow discharge decomposition from SiH 4 and CH 4. The deposition rate, hydrogen content, optical band gap and microhardness were investigated for various carbon contents. In particular, carbon atom coordination was investigated by solid-state 13C magic angle spinning nuclear magnetic resonance measurements of the sp 2 and sp 3 bonding sites. Unsaturated character (sp 2 carbon) appears clearly in the film of composition a-Si 0.25C 0.75 at about 130 ppm. Film hardness and optical band gap correlate with both the hydrogen content and the fraction of tetrahedral(sp 3) vs. graphitic(sp 2) bonding. It was also observed from annealing treatment experiments that a change of network structure takes place, from high density to low density, at a carbon content of about 0.63.