The oxygen controlled chemoresistance of tin oxide based gas sensors was investigated in the temperature range from 20 to 320 °C. Polycrystalline thin film gas sensors were fabricated by the reactive dc-magnetron sputtering. The parameters of the sensors were also modified by additional Pt or Sb doping. The effect of surface oxygen species on the chemoresistance was studied by x-ray photoelectron spectroscopic (XPS) analysis of the surface chemical composition before and after different sample treatments. The oxygen peak at a binding energy 531.8 eV in the XPS core level spectrum was found to be related to the chemisorbed molecular oxygen O−2. The variation of an amount of the O−2 species is found to be the main cause of gas sensitivity of tin oxide films at temperatures from 20 to 230 °C.
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Kačiulis et al. (1996) studied this question.