Gas sensing of Au/n-SnO2/p-PSi/c-Si heterojunction devices prepared by rapid thermal oxidation

Transparent and conducting SnO2 thin film has been produced on (quartz, ITO, silicon and porous silicon) substrates using rapid photothermal oxidation of pure Sn in air at 600 degrees C oxidation temperature and different oxidation time. The structural, optical, electrical properties, scan electron microscope and atomic force microscope of the prepared films were studied. The transmittance T in the visible and NIR was investigated; the allowed direct energy gap was determined to be 3.18 eV at optimum condition of 600 degrees C and 90 s. The dependence of the resistivity on the film thickness and oxidation time has been studied. The optimum thickness of high transmittance and lowest resistivity is about 150 nm for SnO2, where rho = 1.7 x 10(-3) Omega cm and T = 88 %. The sensitivity behaviors of the n-SnO2/p-PSi/c-Si-based gas sensor to H-2 and CO2 gas were investigated. The film sensitivity dependence on the temperature and test gas concentration was tested and the optimum operation temperature was determined at around 250 and 300 degrees C with an applied voltage was constant at 2.5 V.