DLC-SiOx nanocomposite films deposited from CH4 : SiH4 : O2 gas mixtures

Abstract Nanocomposite DLC-SiO x films were deposited by PECVD from CH 4  : SiH 4  : O 2 gas mixtures. The effects of gas mixture composition and self-bias voltage on the optical and mechanical properties of these films were investigated. Results show that high optical gap (∼3 eV) coatings can be obtained at low oxygen contents in the gas mixture (∼5 vol.%). At low self-bias voltages, oxygen incorporation increases the deposition rate of the films. On the other hand, at bias voltages larger than 200 V oxygen incorporation decreases the deposition rate revealing that etching of the films is dominant. Nevertheless, oxygen is incorporated into the films mainly as SiO x , competing with the formation of the DLC phase. Residual internal stress of the films are reduced to about 1 GPa, while hardness is approximately constant in the range from 13 to 14 GPa. All investigated DLC-SiO x nanocomposite films turned out to be more hydrophilic than pure DLC as determined by contact angle measurements.