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

Nanophasic tungsten oxide thin films were deposited at 500 degreesC 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 O-2 + 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 N-2 + H-2 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.