Impact of Ag on the Limit of Detection towards NH 3 -Sensing in Spray-Coated WO 3 Thin-Films.

Ag-doped WO 3 (Ag-WO 3 ) 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 (NH 3 )-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-WO 3 enhanced the sensor response from 1.06 to 3.29, approximately 3 times higher than that of undoped WO 3 . Limit of detection (LOD) up to 500 ppb is achieved for 1% Ag-WO 3 , substantiating the role of Ag in improving sensor performance.