Oxidation behavior of titanium-aluminium nitrides

Oxidation behavior of titanium-aluminium nitrides of various compositions has been explored to understand the oxidation protection mechanisms and the role of structure and composition in the oxidation behavior. Thin films of (Ti-1-x,Al-x) N have been sputter deposited on silicon substrates and the nature of oxides resulting from air oxidation at various temperatures has been evaluated using Auger electron spectroscopy. In most of the films, layered oxide structures Al2O3/TiO2 readily form on the nitride surface at about 800 degrees C and higher temperatures. At about 700 degrees C and below, the oxidation product is primarily a mixed oxide, such as Al2O3 + TiO2. Oxides forming at elevated temperatures, with a top layer of Al2O3, protect the underlying nitride from further oxidation. Thus, for low and intermediate temperature applications, the titanium-aluminium nitride films may be first treated at an elevated temperature to form a protective oxide. The role of aluminum content in the film oxidation behavior has been explored for x values ranging from 0.25 to 0.67. Despite its higher aluminum content, the (Ti-0.33,Al-0.67) N film exhibited lower oxidation resistance than other films.