The conversion of silicon carbide surfaces into carbon upon exposure to a helium-chlorine-hydrogen gas mixture was studied. During this process, the more energetically favored reaction of Cl-2 with Si rather than C causes the selective etching of silicon from the SiC surface and leads to the formation of a carbide-derived carbon (CDC) film. Surfaces of single crystal SiC wafers as well as industrial polycrystalline alpha-SiC ceramics were treated using different gas concentrations at various temperatures. The resulting CDC films were analyzed using Xray photoelectron spectroscopy (XPS), Raman spectroscopy and scanning electron microscopy (SEM). XPS analysis of carbon C1s fundamental peak and valence band spectra revealed that the CDC films are not phase pure but consist of a mixture of sp(2) and sp(3) bonded carbon. A strong difference in the nature of the CDC process for different types of SiC materials (single crystal or industrial ceramics) was observed, which may result from the different SiC grain boundary conditions and surface morphology effects in these materials. The CDC films were also tested for suitability as seed layers for the subsequent growth of ultrananocrystallie diamond films. (C) 2004 Elsevier B.V. All rights reserved.