Trivalent metal-doped TiO₂ thin films have been extensively investigated in gas sensor applications. The trivalent metal dopants are Al, Y and Gd. The trilayer fabrication of a gas sensor consists of a thin film, sputtered TiO₂ and Au nanoparticles. The characteristics of the gas sensing properties are strongly correlated with the annealing temperature, film thickness, type of doping and deposition method. The subsequent properties are presented – the crystalline structure, grain size, roughness, strain, stress and defects. Thin films have been developed with concentrations of O₂ gas up to 10 sccm. A response time for O₂ gas in milliseconds was obtained at room temperature. Al doped TiO₂ thin film have a faster response time operating at room temperature compared with other thin films. Oxygen vacancy defects also contribute to the speed of the response time for a gas sensor.
