Achieving selectivity from the synergistic effect of Cr and Pt activated SnO2 thin film gas sensors

The enhanced selectivity due to the synergistic effect of Cr and Pt co-doping on gas sensing properties of SnO2 thin films, is reported. The undoped and Cr/Pt co-doped SnO2 thin films are deposited on the glass substrates by Ultrasonic Nebulized Spray Pyrolysis of Aqueous Combustion Mixture (UNSPACM). The as-deposited films are nanocrystalline in nature with crystallite size similar to 3 nm, as seen from x-ray diffraction and transmission electron microscopy (TEM). The chemical state of dopants is investigated using x-ray photoelectron spectroscopy. Further, the presence of separate Pt additives in SnO2 film is also confirmed using TEM studies. The gas sensing properties show that although Pt addition enhances the overall sensitivity, it does not improve the selectivity of the sensor. Nonetheless, Cr and Pt co-doped SnO2 films exhibit greater selectivity towards CO gas, while only Cr doped film exhibits selectivity towards NO2 gas at 275 degrees C. The improved selectivity is attributed to the change in carrier concentration, oxygen stoichiometry and specific catalytic effect of the dopant ions. (C) 2016 Elsevier B.V. All rights reserved.