Thermochemical process occurring in PLD-derived SiC films during vacuum annealing

Compositional change on the surface of PLD-derived SiC films during vacuum (10 ^-3 Pa) annealing was investigated by using Fourier transform-infrared absorption (FT-IR) and X-ray photoelectron spectroscopy (XPS) measurements. The as-deposited film consisted of only a small amount of Si-C bonds, and was abundant in C-C component. With an increase in annealing temperature from 800 to 950°C, the amount of Si-C bond increased, and the C-C component decreased. The films were slightly oxidized by residual O ₂ at temperatures lower than 950°C. When the temperature reached 1000°C, the amount of Si-C bond dropped sharply, accompanied by production of ∼72at.% of Si-Si bonds, which was surprisingly high. A model of SiC oxidation based on the loss of C atoms and the formation of Si-Si bonds was adopted to explain the experimental results. The activation energy for Si-C formation during vacuum annealing was 22.5±2.6 kcal/mol, as calculated from the FT-IR data.