Electron beam evaporated nanostructure WO3 films for gas sensor application

In the recent years, metal oxide semiconductors such as SnO2, CuO, Fe2O3, TiO2, WO3 and ZnO were investigated for the detection of ethanol gas in the environment. Among these, WO3 is one of the best n-type semiconductor material for ethanol gas detection. In this paper, nanostructured WO3 thin films were prepared by electron beam evaporation on glass substrate and investigated their ethanol gas sensing properties. Surface morphology, structural and elemental analysis of the WO3 thin films were analysed by scanning electron microscopy (SEM), atomic microscopy (AFM), X-ray diffraction and X-ray photoelectron spectroscopy. The as deposited films exhibited nanostructure and highly influenced by the substrate temperature. From the X-ray photoelectron spectroscopy analysis, we found that substrate temperature increases the binding energy shift in lower energy regions and shows that WO3 films contain oxygen vacancies. The gas sensor sensitivities were measured for different gases with different concentrations at various operating temperatures. The obtained results show that the nanostructure WO3 films are suitable sensing material for ethanol gas. The nanostructure WO3 films deposited at substrate temperature of 100 degrees C shows best sensitivity with quick response and recovery time, which is attributed to the formation of nanorods and possess a very high surface to volume ratio.