Title : Near room temperature LPG sensing by nanoparticulate tin oxide thin films formed by pyrolysis of microwave irradiated SnCl4-based precursors
Development of room temperature sensor is a vital aspect in the field of gas sensors. Herein, we report the near room temperature LPG sensing by polycrystalline nanoparticulate tin dioxide (SnO2) thin films formed by pyrolysis of microwave irradiated (MwI) precursor. The gas sensing properties of the films without any post annealing procedure displayed an enhancement along with quick response to LPG compared with un-irradiated precursor formed SnO2 films. In comparison with un-irradiated films, investigations are carried out with irradiated precursor grown films to study the LPG sensing ability in evaluation with the phase composition, microstructure, morphology, and charge transport properties. Evidenced by XPS, EDS and FTIR analysis, the sensing process could be assigned to the adsorption interaction between the charged oxygen species and the test gas molecules that originates largely from oxygen vacancies. The agglomeration of nanoparticles in grains and the crystallinity variation is evaluated from HRTEM and SAED patterns, respectively. The photoluminescence and dielectric properties significantly reveal the aspects responsible for the improvement in response in the microwave administered films. The LPG sensing of the films display considerable advancement in lowering the response temperature down to 50 °C for 50 ppm, in addition to good selectivity to NH3, CO2 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 at 250 °C. Ageing characterizations showed that the sensing capacity of as-prepared films could be retained at 90% even after 2 years ageing period at a humidity value of 60, which is clearly superior. From the results of the impedance study, the role of interface states endorsed by defects in microstructure on the gas sensing of the 1 min SnO2 films are evaluated. The density of OVs along with Sn4+ and Sn2+ ions decide the distribution of long and short-range conduction and these in tandem with charged surface oxygen and lattice stress determine the gas sensing attributes. Thus, the facile approach using microwaves represents a promising way towards the inexpensive, fast and scalable deposition of nanocrystalline SnO2 films suitable for gas sensors.
Audience take away:
• Near room temperature LPG sensors of nanoparticulate SnO2 thin films can be grown by Microwave- irradiated precursor pyrolysis.
• The films demonstrate good lower temperature LPG sensing properties which are crucial for applications.
• Different studies elucidate the features of the formed films and the gas sensing abilities.
• This method can be developed for the enhanced detection of other gases and better gas adsorption in different materials.
• The technique can be perfected to improve the LPG sensing at room temperature and certainly provide a solution for the energy-efficient gas sensing.