Evaluation of Zn: WO₃ Thin Films as a Sensing Layer for Detection of NH₃ Gas

Pristine WO₃ and Zn-doped WO₃ were synthesized using the spray pyrolysis technique to detect ammonia gas. The prominent orientation of the crystallites along the (200) plane was evident from X-ray diffraction (XRD) studies. Scanning Electron Microscope (SEM) morphology indicated well-defined grains upon Zn doping with a smaller grain size of 62 nm for Zn-doped WO₃ (Zn: WO₃) film. The photoluminescence (PL) emission at different wavelengths was assigned to defects such as oxygen vacancies, interstitial oxygens, localized defects, etc. X-ray Photoelectron spectroscopy (XPS) studies confirmed the formation of oxygen vacancies in the deposited films. The ammonia (NH₃) sensing analysis of the deposited films was carried out at an optimum working temperature of 250 °C. The sensor performance of Zn: WO₃ was enhanced compared to pristine WO₃ at 1 ppm NH₃ concentration, elucidating the possibility of the films in sensing applications.