Structural and optical properties of nc-3C–SiC films synthesized by hot wire chemical vapor deposition from SiH4–C2H2–H2 mixture

Abstract

The nanocrystalline cubic SiC (nc-3C–SiC) films were deposited on quartz chips from SiH4–C2H2–H2 mixture by hot wire chemical vapor deposition. During the deposition, the total gas pressure and the substrate temperature were kept at 800Pa and 350°C. The films were characterized by X-ray diffraction, scanning electron microscopy, Raman spectroscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and UV–VIS–NIR spectroscopy. It was found that the film structure changed from microcrystalline Si to nc-3C–SiC between 1700°C and 1800°C. The optical band gap of deposited films increased from 1.6 to 2.5eV by varying the filament temperature from 1600°C to 2000°C. The intensities of CH and SiC bonds were found to be the key parameters, controlling their optical and structural properties. Furthermore, the crystallinity of SiC films was promoted with increasing the filament temperature, due to the large amount of H radicals which etches the amorphous network structure and the grain boundaries.