Enhancing approaches of NH3 gas sensing using WO3 thin film as a function of different substrates

Abstract

WO3 nanostructures thin film with thickness of 323±5 nm was deposited on different substrates, such as alumina (Al2O3) and silicon (Si) substrates, via a spray pyrolysis deposition method. The annealing process at 500°C in air for 1h was investigated. The structure properties of WO3 thin film were tested by X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), atomic force microscope (AFM), and energy dispersive X-ray (EDX). All the obtained peaks in the XRD pattern are well matched with the hexagonal phase of WO3 thin film, which prepared on silicon and alumina substrates. The grain size, roughness surface and root mean square of the thin film prepared can be estimated from the results of AFM, where, (71.31, 64.85), (9.2, 8.9) and (11.96, 11.61) respectively. FESEM analysis, showed the morphological of films prepared on the silicon and alumina substrates which showed approximately spherical-shaped particles, and uniform distributed. EDX analysis was showed that the results exhibit the characteristic peaks of W and O present in the films. Photoluminescence (PL) showed that the energy band gap was 2.78 eV for WO3/Si and 2.73 eV for WO3/Alumina and 4.69 eV for Al2O3 substrate. The film deposition on alumina was showed the sensitivity of 92.5% for NH3 gas at operating temperature of 150°C compared with silicon substrate, which exhibits the sensitivity about 82.6% at same temperature.