Structural studies of tungsten-titanium oxide thin films

Structural studies of tungsten-titanium oxide thin films grown on alumina substrates have been performed on samples prepared by reactive magnetron sputtering of a W/Ti alloy (90% W and 10% Ti). Structural changes undergone by samples heated at 773 and 1073 K have been studied by using X-ray diffraction and X-ray photoemission techniques. The results, which have been also discussed with the aid of a structural model, indicate that the original amorphous phase transforms by annealing into a crystalline phase of tungsten oxide with a degree of order depending on the annealing temperature. The relationship between titanium and the structure of the film is discussed in terms of disorder effects induced by the Ti ions in the WO3lattice. The ordering is ascribed to the segregation of Ti ions toward the surface upon annealing at 1073 K.