Thin silicon films produced in r.f. glow discharges fed with SiCl 4-H 2 mixtures are studied. The effect of argon addition to the feed is examined. Emission spectroscopy and laser interferometry were used to correlate some kinetic parameters, such as the deposition rate, with chemical, optical and structural properties of the deposited material. An overall film growth mechanism is suggested in which chemisorbed species and hydrogen atoms play an important role.