ESCA INVESTIGATION OF SNOX FILMS USED AS GAS SENSORS

The electronic properties of amorphous and ion-implanted polycrystalline SnO2 films have been studied using x-ray photoemission spectromicroscopy. First, we analysed the degree of oxidation and the homogeneity of as-deposited films. The SnO and SnO2 phases were identified from their valence band spectra rather than from the Sn 3d core level spectra. Then we studied the damage effects due to the implantation of Pd+ and Ga+ ions in polycrystalline films. The ion bombardment of SnO2 films results in drastic changes of valence-band spectra which is correlated to compositional changes. Annealing in air at 600-degrees-C for 4 leads to complete recovery of radiation damage. However, after such thermal annealings, the film surface still contains a relatively high amount of SnO (5-10%).