Preparation and micro-structural characterization of nanosized thin film of TiO2-WO3 compound as a novel material with high-performance gas sensing

WO3-TiO2 thin films were prepared by r.f. reactive sputtering from a Ti0.1---W0.9 target. Annealing in synthetic air-flow of the initial W-Ti-O deposited compound results in layers with different features, depending on the temperature at which the annealing is being carried out. Morphological and structural characteristics of the thin films have been studied through X-ray diffraction, electron microscopy and Raman techniques. After annealing at 600°C, a polycrystalline thin film isostructural to WO3 is achieved. This layer is capable of detecting concentrations of NO2 lower than 1 ppm. Annealing of the film at 800°C results in a nanosized structurally stable TiO2-anatase layer. This layer can detect a few ppm of NO2 in dry air even at as high a temperature as 800°C.