Deactivation mechanisms of gas sensors based on semiconducting oxides

The present paper summarizes an approach based on surface science for the s tudy and the characterization of the properties of solid state gas sensors using semiconducting oxides for hydrocarbon detection. In these sensors the detection mechanism relies on the conductivity changes induced by the cata lytic reaction of gaseous species on the oxide surface. Devices based on th ese oxides can be sensitive to better than one ppm of hydrocarbons in the a tmosphere. Surface science techniques based, for instance, on electron or i on spectroscopy can be used to determine surface parameters suck as the deg ree of oxidation, the stoichiometry of the topmost layers in the sensing el ement, the presence of impurities and/or dopants, and the mechanisms of rea ction and deactivation on the surface. These data can be of fundamental imp ortance in the design of new, more selective and more sensitive sensors. So me examples are reported in the present paper for a study on SnO2 based sen sors for hydrocarbon detection.