Comparison of surface oxidation of titanium nitride and chromium nitride films studied by x-ray absorption and photoelectron spectroscopy

Surface oxidation mechanisms of TiN and CrN films were studied by means of x-ray photoelectron (XPS) and absorption spectroscopy (XAS). In the N 1s XPS spectra of both the oxidized TiN and CrN films, a feature assigned to molecular nitrogen was observed in addition to a feature assigned to nitride. The assignment was confirmed by the N K-edge XAS spectra of the TiN and CrN films which exhibited a sharp feature at 401.4 eV. Besides these features, the N 1s XPS spectra of the oxidized TiN films showed a third feature, which was assigned to NX–Ti–OY like structures taking into account the change in the Ti 2p XPS spectra. However, no evident feature assigned to NX–Ti–OY like structures was observed in the XAS spectra because of the overlapping with the nitride features. The above results indicated that the CrN films directly changed to Cr2O3 with the formation of molecular nitrogen in the interstitial positions of the surface oxide layers, while the TiN films were oxidized to TiO2 through the formation of NX–Ti–OY like structures. The formation of the NX–Ti–OY like structures may allow the rapid diffusion of oxygen and hence lower the oxidation resistance of TiN films.