Characterization of NbCxN1-xfilms reactively sputtered in (Ar, N2, C2H4) mixtures

Niobium-Carbon-Nitrogen ternary system was prepared by reactive sputtering in a mixture of argon, nitrogen, and ethylene. ESCA study made it clear that carbon co-exists in the prepared films, combining chemically with niobium, and mol-fraction of the carbon in the films can be controlled by the intermixture amount of ethylene. Co-sputtering with ethylene brought about many effects in the properties: very slight addition of ethylene (0.1-0.2%) was sufficient to provide the films with the higher transition temperature, 15.9K, the much higher density of the electron number density, and the lower resistivity as compared with the NbN films. Chemical analyses for the surface oxidation mechanism were closely done, showing that the NbCN and NbN films have no or much thinner NbO layer than the Nb film. The decrease of the electron number density as well as the mobility with lowering temperature in the NbN and NbCN films were observed by the Hall measurement, which explains the observed negative temperature coefficient of the resistivity.