Continuous wave (cw) and equivalently powered, pulsed radio frequency plasmas are used to deposit a-Si1-xCx:H films. Films produced from SiH4/CH4 and SiH4/CH4/H2 gas mixtures were analyzed with Fourier-transform infrared, x-ray photoelectron spectroscopy, scanning electron microscopy, and profilometery. Gas-phase plasma species were identified using optical emission spectroscopy. The effects of biasing (±1000 V) and grounding the substrates, pulse peak power, pulse on time and off time, and duty cycle on film composition were examined. Films deposited with cw plasmas show an increase in hydrogen incorporation compared to films deposited in the pulsed systems. In the pulsed plasmas, deposition rates depend on both the on time and off time of the plasma pulse cycle, while grounding the substrate causes a significant reduction in oxidation rates for films deposited under all conditions. © 1999 American Vacuum Society.