Effect of small concentrations of oxygen and nitrogen on the structure and mechanical properties of sputtered titanium films

The results of a study of small additions of oxygen and nitrogen on the structure and mechanical properties of nanocrystalline titanium films obtained by magnetron sputtering are presented.The hardness and elastic modulus were determined by nanoindentaion technique. The film composition and structure were investigated by OES, SEM, XRD. Hardness and elastic modulus of the nanocrystalline films with small content of oxygen (≤ 2 at.%) and nitrogen (≤ 1 at.%) remained approximately the same as for nanocrystalline films deposited in pure Ar. Significant growth of hardness from ~ 4 to ~ 10 GPa was observed at the increase of oxygen/nitrogen content up to ~ 6 at.%. It was accompanied by reducing grain size from ~ 85 to ~ 20 nm and growth of compressive stress. The obtained results are explained by changing of the film structure and composition.

► Non-monotonous dependence of mechanical properties at very low content of impurities.
► Small oxygen or nitrogen content increases both hardness and modulus of α-Ti films.
► Increase of oxygen content leads to reduction of grain size.