Microwave-enhanced pyrolysis grown nanostructured SnO2 thin films for near room temperature LPG detection and the impedance analysis

Abstract Near room temperature LPG sensing ability of polycrystalline nanoparticulate SnO2 thin films prepared by pyrolysis of microwave irradiated (MwI) precursor is investigated without any post annealing process. This technique facilitates to produce homogeneous nano-structured thin films in just 15 minutes. The phase composition, morphology, and microstructure of the films obtained by pyrolysis of different duration MwI precursors are examined by XRD, FT-IR, TEM and HRTEM. The gas sensing properties of the films display a significant advancement in lowering LPG and CO2 sensing temperature in addition to sensitivity in comparison with the films from unirradiated precursor. The LPG sensors have shown considerable response down from 50 ppm at a lower operating temperature of 50 °C and for CO2 from ∼150 °C, along with high selectivity to NH3 and NO2. The 1 min irradiated films exhibit an excellent LPG response of −98.4% in 500 ppm with a resistance ratio Ra/Rg of 78, whereas for 3 min irradiated, the CO2 response is +77.9% in 500 ppm of gas. The photoluminescence and dielectric properties are investigated to elucidate the factors responsible for the enhancement in response of the microwave processed films. From the results of the impedance investigation, the role of interface states promoted by defects in microstructure on the gas sensing of SnO2 films is discussed.