In this work, hydrogenated amorphous silicon carbide (alpha-Si1-xCx:H) and nanocrystalline SiC (nc-SiC) thin films were deposited by hot wire CVD (HWCVD) using SiH4/C2H2/H-2 gas mixtures. It was found that the films prepared under low gas pressure were alpha-Si1-xCx:H and those prepared under high gas pressure were nc-3C-SiC. The alpha-Si1-xCx:H films showed enhanced density of C-H-n and Si-C bonds with increasing C2H2 fraction, which induced an increase in optical gap from 1.8 to 3.0 eV. For the deposition process of nc-SiC, the E-gopt of the deposited films varied from 1.9 eV to 2.5 eV as the filament temperature increased from 1700 to 2100 degrees C. The deposition rate decreased rapidly from 5.74 nm/min to 0.8 nm/min with increasing T-F. (C) 2011 Elsevier B.V. All rights reserved.