Liquid petroleum gas sensor based on SnO2/Pd composite films deposited on Si/SiO2 substrates

SnO₂/Pd composite films were synthesized by d.c. sputtering of a SnO₂ target followed by thermal evaporation of a thin layer of Pd on top of it. This structure, deposited on Si wafer with 300 μm SiO₂ on the top, was subjected to rapid thermal annealing at 573 K for 5 min for the incorporation of Pd in SnO₂. The films were characterized by microstructural, optical, FTIR and Raman studies. Liquid petroleum gas (LPG) sensing measurements were carried out on these films. Sensitivity of 72% was obtained at an operating temperature of ∼573 K. The response time for these sensors was found to be ∼27 s. Sensitivity was found to increase with grain growth at higher sensing temperatures. It could be observed that the selectivity for LPG is extremely good as compared to that of methane, hydrogen, CO₂ and C₂H₅OH.