In this study, SnO2/TiO2 thin films are fabricated on SiO2/Si and Coming glass 1737 substrates using a R.F. magnetron sputtering process. The gas sensing properties of these films under an oxygen atmosphere with and without UV irradiation are carefully examined. The surface structure, morphology, optical transmission characteristics, and chemical compositions of the films are analyzed by atomic force microscopy, scanning electron microscopy and PL spectrometry. It is found that the oxygen sensitivity of the films deposited on Coming glass 1737 substrates is significantly lower than that of the films grown on SiO2/Si substrates. Therefore, the results suggest that SiO2/Si is an appropriate substrate material for oxygen gas sensors fabricated using thin SnO2/TiO2 films. (c) 2006 Elsevier B.V. All rights reserved.