Fabrication of Er-doped WO3 thin films as a potential candidate for the detection of ammonia at room temperature

Abstract

In this work, we report on pure and Er-doped (1, 2, 3, 4, and 5 wt.%) WO₃ thin films prepared via the nebulizer spray pyrolysis technique. The microcrystalline structure, surface morphology, optical properties, and gas-sensing characteristics of the films were studied. XRD analysis revealed that the prepared samples exhibited hexagonal crystal structures, with an increase in grain size from 48 to 63 nm for the WO₃:Er2% thin film. FESEM analysis showed a nanofibrous network morphology, with increased porosity and reduced nanofiber size observed in the WO₃:Er2% film. Photoluminescence (PL) spectra demonstrated six emission peaks at 360, 400, 420, 445, 475, and 520 nm for both the pristine and WO₃:Er films, with maximum PL emission noted for the 2% Er doped sample. Optical measurements indicated a decrease in transmission spectra from pure to WO₃:Er2%, with the optical bandgap decreasing from 3.2 eV to 2.9 eV for the WO₃:Er2% film. Key gas-sensing parameters, including gas responsivity, response and recovery time, were measured as 368, 5.2 s, and 6.7 s, respectively, for the WO₃:Er2% thin film, confirming its strong gas-sensing capabilities. This study demonstrates that WO₃:Er2% thin film is an efficient, fast-responding gas sensor, developed using the simple and cost-effective nebulizer spray pyrolysis method.