Band gap control of hydrogenated amorphous silicon carbide films prepared by hot-wire chemical vapor deposition

Hydrogenated amorphous silicon carbide thin films were prepared by hot-wire chemical vapor deposition using methane as a carbon source and the effect of the methane gas flow rate on the film structure and properties was investigated. In the case of 4 Torr pressure, the optical band gap increased from ∼1.9 to ∼2.3 eV with increasing the methane gas flow rate from 2 to 8 sccm and remained unchanged with a further increase in the methane gas flow rate up to 20 sccm. On the other hand, in the case of 2 Torr pressure, the optical band gap increased monotonically from ∼1.8 to ∼2.0 eV with increase in methane gas flow rate from 4 to 20 sccm. Infrared absorption spectra showed that the Si–C bonds increased with increasing the methane gas flow rate. It was found that methane gas flow rate at a low gas pressure has a smaller influence on film structure and properties than that at higher gas pressure.