Structural and morphological analyses of tungsten oxide nanophasic thin films obtained by MOCVD

Nanophasic tungsten oxide thin films were deposited at 500 °C on quartz and glass substrates starting from W(CO)6 using the metal organic chemical vapour deposition technique. The films were analysed by X-ray diffraction, X-ray photoelectron spectroscopy and scanning electron microscopy. By using an O2 + H2O atmosphere, the fully oxidized tungsten yellow compound was obtained (tetragonal WO3) with a morphology characterized by pyramidal-shaped grains. The average crystallite size resulted of 75 nm. Conversely, under a N2 + H2 atmosphere, a polycrystalline blue deposit was obtained, corresponding mainly to a mixture of oxides in the composition range between WO2.7 and WO3. The crystallites have an average size of 50 nm and the morphology revealed a packed structure, with grains in a singular wool skein shape.