Oxidation of TaSi2 thin films on polycrystalline Si

XPS and UPS have been used for studying the oxidation of TaSi2 films formed by annealing, under ultrahigh-vacuum, of Ta deposits (≈70A) on polycrystalline Si. Oxidation has been carried out at room-temperature and at 700°C with an oxygen pressure of 2×10-5 mbar. Both Ta and Si react with oxygen. At room-temperature, O chemisorbs on the surface giving a mixed phase of Si suboxides and Ta oxides (TaO, TaO2 and Ta2O5). At 700°C, a very thin Ta2O5 layer (