Oxidation of vanadium nitride and titanium nitride coatings

The oxidation of vanadium nitride (VN) and titanium nitride (TiN) coatings in ultra-high vacuum has been investigated in situ by X-ray photoelectron spectroscopy. On the VN coatings mixed oxide layers containing V3+ and V4+ species form at elevated temperatures (⩾600°C) and at high oxygen exposures, which cover completely the VN surface. Under similar oxidation conditions the TiN surface oxidises partially to a mixture of TiO2 and Ti oxynitride (TiOxNy) phases. This oxidation behaviour has been correlated to the tribological properties of the VN and TiN coatings investigated recently.