Microstructural characterization of sol-gel derived Ga2O3-TiO2 thin films for gas sensing

Binary TiO₂-Ga₂O₃ thin films were prepared from the sol-gel process. Titanium butoxide and gallium isopropoxide were used as precursor materials. The mixed solution was spun onto the sapphire and silicon substrates at 2500 rpm for 30 s to prepare thin films. The X-Ray Diffraction (XRD) results revealed that the films annealed at a temperature of 500°C for 1 hr is γ-Ga₂O₃ structure. Scanning Electronic Microscope (SEM) images revealed that the film surface is smooth with grains in a nanometer scale. The film showed good responses to 100 ppm, 1000 ppm and 1% O₂ at an operating temperature of 470°C. The resistance of Ga-doped TiO₂ film is between the resistances of pure TiO₂ and Ga₂O₃ films. The response of Ga-doped TiO₂ thin film is sensitive, fast and stable to oxygen gas.