Enhanced methanol sensing performance of oblique deposited WO3 thin films

Methanol (CH3OH) is a colorless liquid with a mild odor. The wide ranges of applications, toxicity and clinical implications of methanol have made necessary to develop reliable and high-performance methanol sensors. In this paper, WO3 thin films were deposited on SiO2/Si substrates by e-beam evaporation technique under normal and oblique angles and then post-annealed at 500 °C with a flow of oxygen for 4h to achieve a good crystallinity. The crystalline structure of the samples was confirmed by X-ray diffraction analysis while the physical adsorption isotherm was used to measure the porosity and effective surface area. These results reveal that the deposited sample under oblique angle shows more crystallinity, and porosity relative to the sample deposited at the normal angle. The response of the samples was tested with respect to methanol vapour with different concentrations in the temperature range of 140–260 °C. Reproducibility and stability of the samples were also investigated.