Impact of Ag on the Limit of Detection towards NH3-Sensing in Spray-Coated WO3 Thin-Films

Ag-doped WO₃ (Ag–WO₃) films were deposited on a soda-lime glass substrate via a facile spray pyrolysis technique. The surface roughness of the films varied between 0.6 nm and 4.3 nm, as verified by the Atomic Force Microscopy (AFM) studies. Ammonia (NH₃)-sensing measurements of the films were performed for various concentrations at an optimum sensor working temperature of 200 °C. Enrichment of oxygen vacancies confirmed by X-ray Photoelectron Spectroscopy (XPS) in 1% Ag–WO₃ enhanced the sensor response from 1.06 to 3.29, approximately 3 times higher than that of undoped WO₃. Limit of detection (LOD) up to 500 ppb is achieved for 1% Ag–WO₃, substantiating the role of Ag in improving sensor performance.