Effect of doping on the structural, optical and electrical properties of TiO₂ thin films for gas sensor

In this research, we investigated the structural, electrical, and sensing characteristics of undoped and doped TiO₂ thin films prepared through the spray pyrolysis technique, using titanium tetrachloride as the precursor material. The thin films were deposited on quartz and silicon substrates, maintaining a substrate temperature of 350 ºC, and subjected to annealing at 550 ºC for 120 min. X-ray diffraction (XRD) analysis revealed the polycrystalline nature of the films, and the crystallite size was calculated using Scherrer's formula. Nickel-doped titanium oxide thin films were also fabricated, varying the doping concentrations (Ni/Ti = 0%, 1%, 2%, 3%, 4%, and 5%), deposited on quartz substrates via the spray pyrolysis technique. The impact of doping on the structural and optical properties was explored, with X-ray diffraction indicating polycrystalline thin films exhibiting an anatase phase structure. Optical analysis demonstrated a reduction in the optical band gap with increasing doping concentration in TiO₂ thin films.