Direct Evidence Of Porosity In Carbon-rich Hydrogenated Amorphous Silicon Carbide Films

Infrared absorption spectroscopy was used to study the oxidation of hydrogenated amorphous silicon carbide (a-Si:C:H) films prepared by the glow-discharge decomposition of gaseous mixtures of silane and methane. It has been found that carbon-rich samples incorporate oxygen when exposed to air, as detected by an increased absorption of the Si-O-Si stretching vibration band. The analysis of the infrared spectra of samples annealed in air at room temperature and at 200 °C indicates that, except for their oxidation rate, no appreciable difference exists in the mechanisms of oxygen incorporation in the films at the two temperatures. The oxidation kinetics suggests an open porous structure for these carbon-rich films. On the contrary, samples having a low carbon content appear to oxidize on the surface only, in a way similar to amorphous silicon.6694544454