SYNTHESIS OF PD-DOPED SNO2 FILMS ON SILICON AND INTERACTION WITH ETHANOL AND CO

Pure and Pd-doped polycrystalline SnO2 thin films have been synthesize d by a modified chemical vapour deposition process using the pyrolysis of an aerosol generated by ultrahigh frequency spraying of a volatile precursor solution. The depositions have been carried out on oxidized [100] silicon. Growth rate, microstructure and composition of the fil ms are well-controlled by the deposition temperature (460-560-degrees- C) and the moisture of the carrier gas. Palladium particles (metal or oxide) are dispersed on SnO2 grains. At low temperature the moisture i ncreases the growth rate of tin oxide without increasing the palladium one. The influence of adsorption phenomena on the surface composition has been studied by annealing under ethanol and CO, and afterwards by analysing Sn, 0 and C contents by Auger spectroscopy. The heat treatm ents induce an increase of 0 and C concentration. The introduction of palladium in the films largely increases the gaseous adsorption, showi ng a maximum at low temperature. These results are correlated with ele ctrical conductance measurements, showing the influence of CO adsorpti on on electrical properties.