Effect of Manganese Doping in SnO2 Thin Films and its NO2 Gas Sensing Performance

By using an automated nebulizer spray pyrolysis technique with varied concentrations of manganese chloride (0 - 3%) in the spray solution of tin chloride, thin films of pure and manganese-doped tin oxides (Mn-SnO2) were deposited. X-ray diffraction investigations indicated that 2% Manganese chloride concentration in the spray solution promoted development along (200) and (220) directions. The preferred growth direction in the (200) and (220) planes decreased with increasing manganese chloride doping concentration (2-3%) in the solution. The surface morphology of the films had changed as a result of adding Manganese as a dopant. Compositional analysis was carried out using EDAX. From UV-Vis spectroscopy, the optical properties of the SnO2 and Mn-SnO2 thin film were observed; the maximum optical absorbance was in the wavelength range of 300 - 400 nm. The concentration of Mn in the films affected the intensity of the photoluminescence emission peak detected at 347 and 392 nm for pure SnO2 and Mn-SnO2 films, respectively. The gas sensing performance of the films was examined by dynamic method against NO2 gas, at an operating temperature of 250 °C and 400 ppm gas concentration. Mn-SnO2 films achieved quick response and recovery times of 17 s and 34 s.