Diffusion and chemical composition of TiNxOy thin films studied by Rutherford Backscattering Spectroscopy

Thickness and chemical composition of the TiNxOy thin films deposited by reactive magnetron sputtering from Ti target at controllable oxygen flow rate were determined by Rutherford Backscattering Spectroscopy (RBS) using 2 MeV He+ ions. The films were deposited on carbon foils and amorphous silica (a-SiO2) substrates at 25 °C and 250 °C. The estimated film thickness is of 75-100 nm. The O/Ti atomic ratio in the films increases up to 1.5 with increasing oxygen flow rate, while that of N/Ti decreases from about 1.1 for TiN to 0.4 at the highest oxygen flow rate. Substantial out-diffusion of carbon from the substrate is observed which is independent of the substrate temperature. Films grown onto a-SiO2 substrates can be treated as homogeneous single layers without interdiffusion. It is more difficult to determine the nitrogen and oxygen content due to superposition of RBS signals arising from film and substrate. RBS analysis of the depth profile indicates that for the investigated films the carbon diffusion and oxidation not only at the topmost surface layers but over the bulk of the films were found. Comparison with XPS results indicates substantial oxygen adsorption at the surface of TiNx thin films obtained at zero oxygen flow rate.