Effects of frequency of pulsed substrate bias on structure and properties of silicon-doped diamond-like carbon films by plasma deposition

We have investigated the effects of the frequency of pulsed substrate bias on the structure and properties of Si-doped diamond-like carbon (Si-DLC) films deposited by radio-frequency plasma-enhanced chemical vapor deposition using CH4, Ar, and monomethylsilane (CH3SiH3) as the Si source. The Si/(Si + C) ratios in the Si-DLC films deposited using pulsed bias were higher than that of the dc-biased Si-DLC film, and the Si fraction increased with decreasing frequency. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy analyses revealed that Si-C, Si-Hn, and C-Hn bonds in the Si-DLC films increased with decreasing frequency. The internal stress decreased as the frequency decreased, which is probably due to the increase in Si-C, Si-Hn, and C-Hn bonds in the films. It was found that the wear rate of the pulse-biased Si-DLC film deposited at the highest frequency in this study is comparable to that of the dc-biased, undoped DLC film. Furthermore, the friction coefficient of the former is about one third of that of the latter.