RELAXATION AND CRYSTALLIZATION OF AMORPHOUS-SILICON CARBIDE PROBED BYOPTICAL MEASUREMENTS

Optical spectroscopy in the visible (300-1100 MI) and in the infrared (400-4000 cm(-1)) regions was used to monitor the relaxation and cryst allization processes of pure amorphous silicon carbide (a-SiC) thin fi lms upon annealing at temperatures between 200 and 1000 degrees C. The se films were obtained by ion implantation of crystalline material wit h 200 keV Kr+ at a fluence of 2 x 10(15) ions cm(-2). The refractive i ndex n and the absorption index k were calculated from the ultraviolet -visible transmittance and reflectance, and information on the vibrati on modes of the SI-C bonds was detected from infrared transmittance. T hermal treatment changes the optical properties of a-SiC; in particula r, annealing at temperatures lower than 800 degrees C resulted in a co ntinuous variation in both the refractive index and the absorption ind ex and in a decrease in the infrared silicon-carbon peak width. Anneal ing at higher temperatures produces sudden variations in the shape of the refractive index and in the infrared silicon-carbon peak. These tr ends allowed us to identify the occurrence of two processes: relaxatio n of the amorphous phase at low temperatures and crystallization at te mperatures higher than 800 degrees C.