CHARACTERIZATION OF THE CATALYST-SEMICONDUCTOR INTERACTION MECHANISM IN METAL-OXIDE GAS SENSORS

Catalysts may affect the iutergranular contact regions in polycrystall ine metal-oxide films with two mechanisms: spillover and Fermi energy control. In this work, a simple experimental method is proposed consis ting of monitoring sensor resistance as a function of oxygen partial p ressure, in order to distinguish which of these mechanisms is dominant in certain catalyst-metal oxide interfaces. Interpretation of experim ental results, using the theoretical background for these two mechanis ms in the case of InOx sensors with palladium and platinum catalysts, indicates that the electronic interaction of Fermi energy control domi nates in the case of palladium, while the chemical interaction of spil lover dominates in the case of platinum. These results are also confir med by Monte Carlo simulation of the spillover process. (C) 1997 Elsev ier Science S.A.