Structure refinement and hardness enhancement of titanium nitride films by addition of copper

Titanium nitride films with a low added copper content were synthesized by ion beam-assisted sputtering deposition. The role of copper was examined with regard to the structure, hardness and elastic/plastic deformation capacity of the composite films produced. It was found that copper had significant modifying effects on the structure and property of titanium nitride films. When a very low content of Cu (<2 at.%) was added, the film showed apparent hardness enhancement. Films with low content of Cu also displayed highly elastic characteristics (91% elastic recovery under nanoindentation). On the contrary, films with >2 at.% copper were comparatively soft, up to 53% of the deformation under indentation could be plastic in this case. In addition, copper additions could also be used to tune the grain size of TiN in the range of 25–5 nm, at the same time causing a transition from a strong (111) preferred orientation to random polycrystalline morphology.