Amorphous TiO2 in LP-OMCVD TiNxOy thin films revealed by XPS

TiN(O)–TiO2 thin films were prepared on Si(1 0 0) by the low pressure organo metallic chemical vapor deposition (LP-OMCVD) method, using ammonia and titanium isopropoxide as precursors. In order to complete previous characterizations, an Ar+ bombardment/XPS coupled study was carried out. This method is based on the fact that the behavior of a compound towards an ion bombardment is a function of its composition. In particular, Ar+ bombardment of TiO2 (whatever its form) leads to a preferential sputtering of oxygen atoms with subsequent reduction of titanium and formation of Ti3+ and Ti2+ easily detectable by XPS from a significant broadening of the Ti 2p lines. In the opposite, no broadening of the Ti 2p lines is observed for an Ar+ bombardment of TiN. Then, with this method, we succeed in showing that films obtained at high temperature (≥700°C) contain only a TiNxOy phase which is isomorphic to TiN. In the coatings, synthesized at low temperatures (≤650°C) amorphous TiO2 has been evidenced.