Effect of MoO3 addition on the NO2 sensing properties of SnO2 thin films

This paper presents the gas sensing properties of MoO3 (1, 5, 10 and 20 wt%) added SnO2 thin films prepared by a sol–gel spin coating process on float glass substrates. The sensing responses of all these deposited films towards various gases (NO2, SO2, C2H5OH and NH3) are examined. Microstructural studies have been carried out using XRD, atomic force microscopy (AFM) and transmission electron microscopy (TEM). The peculiarities of FT–IR spectra of the surface species arising from the addition of different concentrations of MoO3 are analyzed. It has been observed that with an increase in doping concentration the reflectance decreases because of an increase in roughness and a decrease in the number of free electrons. The doped films show high selectivity towards NO2 gas along with a sensor response of 360% at 170 °C to 500 ppm of gas with a 10 wt% MoO3 added SnO2 thin film.