XPS study of reactively sputtered Ti-B-N hard coatings

Thin films (500 nm) of Ti-B-N have been produced by d.c. magnetron sputtering from a TiB₂ target in various Ar+N₂ gas mixtures. The atomic concentration of nitrogen in the films varies between 0 and 38 at.%. The ratio of boron to titanium in the films is fixed by the relative concentration of these two elements in the TiB₂ sputtering target. Bonds of B-N, B-Ti, Ti-N and Ti-B are observed in the B 1s and the Ti 2p spectra. The change of shape observed in the N 1s spectra led to the conclusion that at low nitrogen concentration the nitrogen atoms are preferentially bonded with titanium atoms, in good agreement with thermodynamical data. By using quantitative information from the B 1s, Ti 2p and N is curve fittings, the formation of a film containing three separate phases (TiN, BN and TiB₂) is discussed.