Carbon occupancy of interstitial sites in vanadium carbide films deposited by direct current reactive magnetron sputtering

Vanadium carbide thin films were deposited on Si substrates by direct current reactive magnetron sputtering from a V target in Ar/CH4 plasma, varying the Ar/CH4 partial pressure ratio and substrate temperature. The films were characterized by glancing angle X-ray diffraction and Rutherford backscattering spectrometry. Well defined crystalline structures were obtained for CH4 content higher than 13%. The increase of substrate temperature during deposition diminishes the film thickness slightly while diminishing substantially the C/V atomic ratio. The intensity ratio of the Bragg peaks (111)/(200) decreases for increasing substrate temperature. This result is discussed in terms of a proposed mechanism for interstitial diffusion of carbon atoms in vanadium carbide thin films with fcc-like crystalline structure and the temperature dependence of carbon occupancy of tetrahedral or octahedral interstitial sites.