We have investigated the influence of the duty ratio 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 pulse duty ratio. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy analyses revealed that Si-C, Si-H-n, and C-H-n bonds in the Si-DLC films increased with decreasing duty ratio. The internal stress decreased as the duty ratio decreased, which is probably due to the increase in Si-C, Si-H-n, and C-H-n bonds in the films. The Si-DLC films deposited using pulsed bias had higher adhesion strength than the dc-biased Si-DLC film because of the further reduction of internal stress. At higher duty ratios, although the Si fractions of the pulse-biased Si-DLC films were higher than that of the dc-biased Si-DLC film, the wear rates of the former were less than that of the latter. (C) 2013 Elsevier B.V. All rights reserved.