Mechanical characterisation of titanium nitride films formed by low-energy ion beam assisted deposition

Ion beam assisted deposition of thin films has gained widespread acceptance in industrial applications. In this work, fine crystalline titanium nitride films on steel were examined with respect to their mechanical properties. Nanohardness was determined by nanoindentation experiments. The influence of ion current density during the IBAD process on hardness was investigated. Additionally, samples produced by reactive evaporation (RE) and photon assisted deposition (PHAD) were examined. The nanohardness of all the titanium nitride films decreased with increasing indentation depth and ion current density, and increased with exposure time to air. It was found that the nanohardness of TiN films correlates directly with the oxygen content of the films. Therefore, high oxygen concentration in the near-surface region results in a higher hardness.