INFLUENCE OF SURFACE OXYGEN ON CHEMORESISTANCE OF TIN OXIDE FILM

The oxygen controlled chemoresistance of tin oxide based gas sensors w as investigated in the temperature range from 20 to 320 degrees C. Pol ycrystalline 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 o n the chemoresistance was studied by x-ray photoelectron spectroscopic (XPS) analysis of the surface chemical composition before and after d ifferent 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 chemi sorbed 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 oxi de films at temperatures from 20 to 230 degrees C. (C) 1996 American V acuum Society.