Evidence for graphitic-type bonding in glow discharge hydrogenated amorphous silicon carbon alloys

Amorphous silicon carbon (a-SiC:H) films have been deposited by the glow discharge technique using SiH4 and CH4 gas mixtures. At high discharge powers and low deposition chamber pressures, evidence for graphitic-type bonding in C-deficient a-SiC:H is found and correlations are made between the appearance of this bonding with significant changes in the electronic and structural properties. This graphitic-type bonding can be minimized by significant H attachment to C via CHn (n=2, 3) bonding. This results in a-SiC:H films with low gap state densities and sharp Urbach tails.