Nanostructured tungsten trioxide prepared at various growth temperatures for sensing applications

Abstract

Nanostructured tungsten trioxide (WO3) was employed as sensing materials for the preparation of gas sensors on alumina substrates. The structural studies revealed formation of monoclinic tungsten trioxide thin films. Additionally, the crystallite size density was obtained at various growth temperatures. It is evident that the crystallinity enhanced after growth temperature. The WO3 thin films had crystal clusters with a cauliflower-like shape whose cluster size and the grain boundaries increased and the structure was turned into a compact structure upon an increase in the growth temperature. Moreover, the results of X-ray photoelectron spectroscopy spectra illustrated only W6+ oxidation state and the W atoms with an oxidation state are attributed to WO3. The results of gas sensing properties exhibited the maximum sensitivity for the sensor sample which was prepared at an operating temperature of 100 °C, annealed at 600 °C, and exposed to 80 ppm of H2S. The enhancement in the crystallinity of tungsten oxide due to annealing was partially responsible for the improvement in the sensing properties of the gas sensors. This research work on gas sensors based on tungsten trioxide pave the way to produce these devices at large scale for various industrial applications.