In this work, a reactive DC magnetron sputtering technique was used to prepare TiO2 thin films. The variation in argon and oxygen gases mixing ratios (4:1, 2:1, 1:1, 1:2, 1:4) was used to achieve optimal properties for gas sensing. In addition, an analysis of the optical XRD properties of TiO2 thin films is presented. High-quality and uniform nanocrystalline films were obtained at a working gas pressure of 0.25 mbar and 1:4 (Ar/O2) gas mixture. The optical properties showed a transparent thin film with uniform adherence to the substrate. The average transmission of the TiO2 films deposited on the glass substrates was higher than 95% over the range of 400 to 800 nm. The optical band gap varied from 3.84 eV to 3.93 eV as a function of oxygen/argon ratios. The XRD pattern showed that the films have an amorphous structure, which is shifted to polycrystalline with increasing oxygen to argon ratio. The sensitivity, response time, and recovery time were measured for TiO2 thin films using NO2 oxidizing gas.
