NO2 monitoring with a novel p-type material: TiO

A simple and reliable method to produce nano-sized oxides was recently accomplished: magnetron radio frequency sputtering of a W/Ti composite target under oxidising environment followed by annealing. Depending on the temperature at which annealing was carried out, the resulting thin films were either WO3/TiO or W-doped TiO and the semiconductor behaviour changed from n- to p-type, respectively. The films were structurally characterized by microscopy techniques. Electrical characterisation was executed over the samples. In particular, it was observed that the films responded with high sensitivity to NO2, a gas of increasing importance for environmental monitoring. We describe the features of the sensing layers with particular focus to the role of TiO — a novel p-type material in the field of gas sensing. The films exhibited a considerable detection capability towards 0.5 ppm of NO2.