First principle study of processes modifying the conductivity of substoichiometric SnO2 based materials upon adsorption of CO from atmosphere

The electronic structure of tin oxide was studied with ab initio methods with an emphasis on changes induced by adsorption of CO molecules at different surface sites. Purpose of this investigation was to gain a better understanding of the processes underlying the dependence of the conductivity of SnOx based materials on the composition of atmosphere, which is the basis for their usage in gas sensing devices. It was inferred that two different mechanisms could be operating: a mechanism by which CO adsorption modifies the band structure and the order of the electronic levels and another mechanism involving the redox equilibrium between SnOx and CO/CO2 species and the dependence of SnOx, conductivity on oxygen saturation. The present results favour the first mechanism. (C) 2004 Elsevier B.V. All rights reserved.