Titanium silicides (TiSi2) films grown on Si(1 0 0) substrate were investigated by ex situ XPS depth profiling after athermal ion beam induced oxidation (IBO) at 12 keV O-2(+) incident energy and normal incidence. The composition and stoichiometry of these films were quantitatively determined as chemical state relative concentrations versus sputter time. "In depth" silicon and titanium oxidation states have been obtained after spectra deconvolution, showing a mixture of silicon dioxide, titanium dioxide, titanium suboxides, elemental titanium and residual traces of titanium nitride. Thermochemical data based on the corresponding enthalpies of formation of the oxides cannot explain our experimental results as in the case of low energy IBO, an oxygen defective altered layer is formed, presenting features of a reduced TiOx phase. (c) 2006 Elsevier B.V. All rights reserved.