Depth profiling of W, O and H in tungsten trioxide thin films using RBS and ERDA techniques

Tungsten trioxide thin films obtained by vacuum evaporation of tungsten oxide powder of high purity were analyzed using Rutherford backscattering spectroscopy (RBS) and elastic recoil detection analysis (ERDA) with 4He+ ions of 2.85 MeV for W, O and H profiling. The films have been deposited onto either C or Si substrates. It has been found that the film stoichiometry depends on the pressure in the vacuum chamber before and during the evaporation process. The films contain water molecules which can be removed easily by heating the samples up to 180°C in vacuum. Most of the water is then weakly bound to the oxide. It has also been shown that the films mostly adsorb oxygen-containing species during storage in air.