Fabrication and Characterisation of TiO2 Thin Film Methanol Vapor Sensor

In this study, titanium dioxide (TiO₂) thin film with a thickness of approximately 250 nm was deposited on silicon dioxide (SiO₂) substrate using the pulsed DC sputtering technique to investigate gas sensing performance of methanol vapor detection. The structural, morphological, and vibrational characteristics of the film was analysed using X-ray diffraction (XRD), scanning electron microscopy (SEM), and micro-Raman spectroscopy, respectively. UV–Vis spectrophotometry was used to analyse the optical properties, including light absorption behaviour, and to determine the band gap of the sensing material. For sensor measurements under methanol vapor ambient, aluminium interdigitated electrodes (IDEs) ohmic contacts were fabricated on the surface of the TiO₂ film using DC sputtering. The sensor was subsequently exposed to various concentrations of methanol vapor (up to 1900 ppm) at three different operating temperatures: 150 °C, 200 °C, and 250 °C. The dynamic gas sensing performance, including response and recovery times, was systematically monitored under each condition. The highest response was recorded at 250 °C, where the sensor exhibited a Ra/Rg value of 6.3 upon exposure to 1900 ppm methanol, along with the shortest response and recovery times. In contrast, at lower operating temperatures (150 °C and 200 °C), the sensor response decreased, and both the response and recovery times were significantly prolonged