The nanocrystalline cubic SiC (nc-3C-SiC) films were deposited on quartz chips from SiH4-C2H2-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 degrees 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 degrees C and 1800 degrees C. The optical band gap of deposited films increased from 1.6 to 2.5 eV by varying the filament temperature from 1600 degrees C to 2000 degrees C. 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. (C) 2012 Elsevier B. V. All rights reserved.