Gas-sensing applications of W-Ti-O-based nanosized thin films prepared by rf reactive sputtering

Thin films were obtained by r.f. reactive sputtering from a T-0.1-W-0.9 target followed by heating in dry air. Their morphological and structural characteristics were studied by means of electron-microscopy techniques. Annealing at 600 degrees C of a sample leads to a WO3 polycrystalline thin-film. A solution of Ti ions in the WO3 lattice causes the film to have higher surface-to-volume ratio and thereby higher gas-sensitivity with respect to pure WO3, sputtered thin films. This layer is highly sensitive to NO2 as concentrations lower than I ppm of NO2 are detected. Annealing the film at 800 degrees C results in a TiO2-anatase nanostructured layer which is capable to detect few ppm of NO2 in dry air within the temperature range of 350-800 degrees C. (C) 1997 Elsevier Science S.A.