Relaxation and crystallization of amorphous silicon carbide probed by optical measurements

Optical spectroscopy in the visible (300–1100 nm) and in the infrared (400–4000cm−1) regions was used to monitor the relaxation and crystallization processes of pure amorphous silicon carbide (a-SiC) thin films upon annealing at temperatures between 200 and 1000°C. These films were obtained by ion implantation of crystalline material with 200keVkr+ at a fluence of 2 × 10 ions cm−2. The refractive index n and the absorption index k were calculated from the ultraviolet-visible transmittance and reflectance, and information on the vibration modes of the Si-C bonds was detected from infrared transmittance. Thermal treatment changes the optical properties of a-SiC; in particular, annealing at temperatures lower than 800°C resulted in a continuous variation in both the refractive index and the absorption index and in a decrease in the infrared silicon-carbon peak width. Annealing at higher temperatures produces sudden variations in the shape of the refractive index and in the infrared silicon-carbon peak. These trends allowed us to identify the occurrence of two processes: relaxation of the amorphous phase at low temperatures and crystallization at temperatures higher than 800°C.