Deposition Temperature as a Crucial Process Parameter in Tuning the CO2 Sensing Properties of Spary-Pyrolyzed SnO2 Thin Film

Abstract

SnO2 thin films are deposited on 76 × 26 × 12 mm glass substrates by spray pyrolysis technique from an aqueous solution of SnCl4.5H2O at various deposition temperatures in the range 250 °C–330 °C and their Carbon Dioxide (CO2) sensing properties are studied. Crystallographic measurements performed on the samples reveal the tetragonal cassiterite structure with a P42/mnm space group. The micro-strain, crystallite size and the texture of prominent planes vary with deposition temperature. The effect of deposition temperature on the surface topography is closely examined by Field Emission Scanning Electron Microscopy (FESEM). The CO2 sensing properties reveals that the sample prepared at 310 °C shows better response to CO2. The presence of tin interstitials oxygen vacancies and excitons is confirmed by PL spectra. Raman spectra depict the formation of sub-stoichiometric phases in the sample. It is found that the deposition temperature is crucial in controlling the dislocations, surface defects, and crystalline orientation that play an important role in enhancing the CO2 sensing performance. To investigate the conduction mechanism prevailing in the sample, AC conductivity measurements of the SnO2 thin films are carried out using Agilent 4294 A precision impedance analyzer and the results are correlated with their CO2 sensing properties.