Effect of microwave irradiation on the gas sensing properties of SnO2 thin films

Several studies clearly show that the gas sensing activity of metal oxides especially SnO2 is governed by the nature of surfaces exposed to ambient gas. Consequently, control over film morphology, the size and shape of faces in crystallites, defects etc. are required for the development of better chemical gas sensors with increased sensitivity and selectivity. In the formation of nanoparticles, homogenous fast heating is desired and thereupon microwaves exposure is looked upon as supportive to play a fabulous role in the growth and structure of materials. In this work, microwave treated (0.5-4 min.) SnO2 based precursor sol is used to prepare nanoparticulate thin film by spray pyrolysis, and the morphology, as well as the grain characteristics, are modified to enrich the surface physico-chemical, electrical transport and gas sensing properties. The structural characterization via XRD shows the formation of consistent films with tetragonal cassiterite structure accompanied with some local defects. The crystallite size lies in the nano regime (28-36 nm). The texture coefficient of prominent planes shows marked variation upon energy irradiation. The improvement in the gas sensing properties of as prepared films is investigated. The film made from 1 min. irradiated precursor sol shows LPG response of 98.5% and the mechanism of gas sensing has been explained on the basis of structural investigations and morphological aspects. Field Emission Scanning Electron Micrograph (FESEM) and UV characterization confirm that microwave assisted preparation technique helps to modify the gas-sensing properties by tuning the amount of surface defects which is an overriding factor in the gas-sensing process and influences the gas molecule adsorption and catalytic reaction at the surface. (C) 2019 Elsevier Ltd. All rights reserved.