Depth profiling of thin films of binary metal oxides

Our previous results on the XPS depth profiling of binary metal oxides are compared with the new experimental data obtained for the films of Sn-W, Mo-Ti and Mo-Sn oxides. The samples have been prepared by sol-gel and magnetron sputtering techniques. XPS depth profiling of the samples has been carried out by using cyclic Ar+ sputtering at the energies of 0.5-2.0 keV. In order to compare the chemical states of constituent elements at different sampling depths, angle-resolved XPS depth profiling has been performed on selected samples. Starting from the stoichiometric oxides on the surface and going deeper into the volume of the films, the depth profiling revealed there the presence of reduced Mo and W ions. The amount of reduced species and their distribution in depth was found to be independent of the sputtering energy and photoelectron collection angle. These metal ions in lower oxidation states were attributed to the sample preparation processes rather than to the detrimental effect of ion sputtering, dominating at higher ion energies. Copyright (C) 2004 John Wiley Sons, Ltd.