Formation of α-Si1−xCx:H and nc-SiC films grown by HWCVD under different process pressure

In this work, hydrogenated amorphous silicon carbide (α-Si1−xCx:H) and nanocrystalline SiC (nc-SiC) thin films were deposited by hot wire CVD (HWCVD) using SiH4/C2H2/H2 gas mixtures. It was found that the films prepared under low gas pressure were α-Si1−xCx:H and those prepared under high gas pressure were nc-3C-SiC. The α-Si1−xCx:H films showed enhanced density of C-Hn 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 Eg opt of the deposited films varied from 1.9 eV to 2.5 eV as the filament temperature increased from 1700 to 2100 °C. The deposition rate decreased rapidly from 5.74 nm/min to 0.8 nm/min with increasing TF.

► The α-Si1−xCx:H films show the monotonously enhanced density of C-Hn and Si-C bonds and the atomic carbon content increases almost linearly with increasing C2H2 fraction. ► Process gas pressure is a key parameter for the preparation of nc-SiC thin films. The increase in the gas pressure enhances the generation of various radicals. ► The generation of H radicals is the most important factor and contributes not only to the inducement of the SiC nuclei formation but also to the etching of amorphous phases.