Structural and optical properties of nc-3C-SiC films synthesized by hot wire chemicalvapor deposition from SiH_4-C_2H_2-H_2 mixture

摘要

The nanocrystalline cubic SiC (nc-3C-SiC) films were deposited on quartz chips from SiH_4-C_2H_2-H_2 mixture by hot wire chemical vapor deposition. During the deposition, the total gas pressure and the substrate temperature were kept at 800 Pa and 350 ℃. 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 ℃ and 1800 ℃. The optical band gap of deposited films increased from 1.6 to 2.5 eV by varying the filament temperature from 1600 ℃ to 2000 ℃. The intensities of C-H and Si-C 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.