XPS study of thin films of binary metal oxides for gas sensing applications

The chemical composition of the thin films of mixed metal oxides (Sn-W, Mo-Sn and Mo-Ti), prepared by magnetron sputtering and by sol-gel, were investigated by standard and angle-resolved XPS depth profiling techniques. Starting from the stoichiometric compounds on the surface and going deeper into the volume of the films, the depth profiles revealed there the presence of reduced metal ions. The possible contribution of sputtering-induced reduction of the oxides, interchange redox reactions between two metal ions in these compounds, influence of sputtering ion energy and photoelectron collection angle are discussed on the basis of obtained experimental results.