Real time investigation of the initial stages of a-C films growth

a-C films were deposited by rf-PACVD. Their growth rate, thickness, density and roughness were derived during deposition from time dependent X-ray reflectivity (XRR) at a wavelength of 1.54 A and at a fixed incidence angle of 18. It is shown that the film density and surface roughness are not constant at the initial stages of growth. The density increases with increasing film thickness, while the surface roughness depends on the substrate roughness. The evolution of these parameters was measured also while etching the film in oxygen plasma and revealed the smoothing effect brought about by etching to the carbon surface