Nitrogen effect on the electrical properties of CNx thin films deposited by reactive magnetron sputtering

Amorphous carbon nitride (a-CNx) thin films have been synthesized by rf reactive magnetron sputtering of a graphite target in an Ar/N2 gas mixture. The total discharge pressure was 1.3 Pa and an N2 fraction in plasma was between 0 and 0.5. The electrical resistivity of films was studied as a function of temperature between 80 and 360 K. At very low nitrogen contents in films, the resistivity decreases with increasing nitrogen content, whereas there is a strong increase in ρ at nitrogen content higher than 13 at.%. Chemical composition and C-N bonds was investigated by X-ray Photoelectron Spectroscopy (XPS). The results, related to the core level C1s and N1s, show the structural change. The temperature dependence evolutions was thermally activated and suggest the presence of two types of conduction associated with two different activation energies. The conductivity variation was interpreted within the limits of the band structure model of the π electrons in a disordered carbon with the presence of localized states.