Synthesis and ethanol sensing characteristics of nanostructured MoO3:Zn thin films

Abstract

In this research, gas sensing characteristics of undoped and zinc-doped molybdenum trioxide (MoO3) thin films toward ethanol vapor were investigated. Thin films were deposited using low cost and simple technique of spray pyrolysis on top of glass substrates at 450°C. Effects of addition of Zn, as an impurity, on the surface morphology, structural and optical properties of MoO3 thin films were also investigated. X-ray diffraction (XRD) pattern analysis showed that by increasing the amount of impurity, crystal structure changes from orthorhombic α-MoO3 to two new phases of monoclinic β-ZnMoO4 and Mo5O14 reduced phase. Field emission scanning electron microscope (FESEM) images showed that by increasing the amount of impurity up to 5at.%, grain sizes decrease to about 60nm. UV-Vis analysis showed that by increasing the percentage of impurity the band gap of thin films increases. Gas sensing properties of samples were studied at three temperatures of 200°C, 250°C and 300°C toward different concentrations of ethanol vapor. Gas response of 5at.% Zn-doped MoO3 thin film reached the maximum value of ∼84% when it exposed to 1000ppm of ethanol vapor. Response and recovery times for all samples were reported at different temperatures.