Enhanced response characteristics of SnO2 thin film based sensors loaded with Pd clusters for methane detection

This paper reports the response characteristics of rf-sputtered SnO2 thin films (90 nm thin) loaded with nanoscale catalytic clusters for detection of methane. Ultrathin (8 nm) metal and metal-oxide catalysts (Pt, Ag, Ni, Pd, Au, NiO, Au2O3) clusters are loaded over the surface of SnO2 thin film. The SnO2–Pd cluster structure is found to exhibit an enhanced response (97.2%) for 200 ppm of methane at a relatively low operating temperature (220 °C). The enhanced response is shown to be primarily due to the dominant roles played by both Fermi level energy control mechanism and spillover mechanism. Thickness of the Pd catalyst clusters in the nano-scale range (2–20 nm), influences significantly the sensor characteristics. Optimized performance is observed with 10 nm thick Pd catalyst clusters showing a high response (∼99.2%) at a relatively low operating temperature of 160 °C. Thickness of the Pd clusters is shown to influence the amount of adsorbed oxygen present on the uncovered SnO2 film surface and also activates the spillover mechanism. The results suggest the possibility of utilizing the sensor structure having novel dispersal of Pd catalyst clusters (10 nm thickness) on the surface of SnO2 thin film for efficient detection of methane gas.