Ethanol gas sensing performance of spinel Mn: Co3O4 nanostructure thin film prepared by spray pyrolysis

Abstract

In this present, the effect of Mn doping was investigated on the structural, surface morphology, and optical properties of Co3O4 and Mn: Co3O4 thin films prepared by spray pyrolysis on a glass substrate. X-ray diffraction patterns of these films show the spinel cubic structure with no secondary phases corresponding to the impurity or other Mn oxides. The grain size of these electrodes was determined about 25 nm. Scanning electron microscopy images show that the Mn changed the Co3O4 surface structure. The optical property was studied by UV–vis spectroscopy in 400–1100 nm and the band gap was determined by two different methods. The UV–vis spectra shows the Mn: Co3O4 thin films have two absorption edges with two direct and indirect band gaps at ∼2.2 and 1.5 eV. The energy dispersive spectroscopy (EDS) analysis confirmed that the Mn doping has been done successfully. The resistance of films was measured at about 103 Ω/□, and decreased by increasing Mn concentration. Then the characteristics of the Mn: Co3O4 gas sensors such as sensitivity, response time, recovery time, and operating temperature were investigated under 100 ppm ethanol as a reducing gas. The operation temperature in this research was 250 C. The response time and operating temperature were investigated under 100 ppm ethanol.