Abstract: Si films were grown on SiC (111) substrate by solid-source molecular beam epitaxy (SSMBE) at different Si/C flux ratios. The structure characteristics of SiC films were investigated by reflection high energy electron diffraction (RHEED), X-ray diffraction (XRD), atomic force microscope (AFM) and Fourier transform infrared spectroscope (FTIR). For the sample grown at Si/C flux ratio (1.1:1.0), ring patterns and twin spots are observed in RHEED and the full width at half maximum (FWHM) of the rocking curve is 2.1°. For the sample grown at Si/C flux ratio(2.3:1.0), the Si spots coexist with SiC spots in the RHEED and the FWHM of the rocking curve is 1.5°. For these two Si/C flux ratios, there are voids and rough surface observed in AFM and large strain exists shown in the FTIR spectra. However, for the sample grown at the Si/C flux ratio (1.5:1.0), besides SiC streaks, a (3×3) surface reconstruction can be observed in RHEED and no SiC twin spots are observed. The results of XRD show that the FWHM of the rocking curve is just 1.1°. The AFM results indicate that the surface of the sample is even and there are no obvious voids. While the results of FTIR show that the strain in the
film is small. Therefore, the optimized Si/C flux ratio is 1.5:1.0, and the quality of the film grown at the optimized Si/C flux ratio is the best.

Key words: Si/C flux ratio, SiC, Si substrate, solid source molecular beam epitaxy