Design and fabrication of enhanced room temperature NH3 sensors based on Sn-doped WO3 thin films deposited using nebulizer spray pyrolysis technique

The growing need for effective room temperature (RT) NH3 gas sensors stems from potential health risks associated with NH3 exposure. This research introduces WO3:Sn (0-5 wt%) thin films, prepared via nebulizer-assisted spray pyrolysis, as novel NH3 sensing materials. The crystallite structure analysis confirmed the hexagonal crystal structure of WO3 films, with 3 wt% Sn-doping showing increased crystallinity. The morphological study revealed a unique mesh-like porous surface morphology in Sn-doped films, conducive to gas adsorption/desorption processes. Optical analysis showed bandgap reduction in WO3 thin films up to 3 wt% doping. Photoluminescence (PL) study confirms the increase in oxygen related defect states (i.e oxygen vacancies (Ov) for the 3 wt% doping in WO3. The WO3:Sn (3wt%) sensor demonstrated superior performance, with exceptionally high gas response of 552 and low response/recovery times of 8.1 s/5.4 s to 250 ppm NH3 at room temperature. The study briefly discusses the gas sensing mechanism in n-type WO3 and compares the present results with previously reported WO3-based NH3 sensors for their suitability in the application of commercial gas sensors.