High dose carbon implantation into silicon to form a beta-SiC buried layer has been performed by using a metal vapor vacuum arc ion source. The implantation energy and dose are 65 keV and I X 10(18) ions cm(-2), respectively. Post-implantation thermal annealing was carried out at 1250 degreesC for various time intervals in Ar ambient. The composition depth profile, chemical state of C and Si atoms, microstructure and optical properties of the samples have been studied using X-ray photoelectron spectroscopy, Fourier transform IR spectroscopy, cross-section transmission electron microscopy and spectroscopic ellipsometry. For the as-implanted sample, the carbon depth profile shows a Gaussian shape-like distribution with a maximum concentration exceeding the stoichiometric ratio. A clear redistribution of the implanted carbon from the Gaussian shape-like distribution to the two sides is observed during annealing. After annealing at 1250 degreesC for 10 h, a stoichiometric SiC buried layer of approximately 150 nm is formed. Results show the annealed sample is a multi-layered structure of SiO2 surface layer/Si top layer/damaged Si layer/upper interface layer/beta-SiC buried layer/lower interface layer on Si substrate. The optical constants of the beta-SiC buried layer formed by ion beam synthesis are determined from simulation of the measured ellipsometric spectra (2.3-5.0 eV) using an appropriate multi-layered model and the Bruggeman effective medium approximation.