Influence of metallic impurities on response kinetics in metal oxide thin film gas sensors

The kinetics of the resistance response to a steep change in gas composition is experimentally and theoretically investigated in SnO2-based thin film sensors modified by different catalytic metals. H-2 and CO gases were used in the tests. Based on the phenomenological model, the transients of the resistance response are described by a combination of the characteristics of both the layer and the surface chemical reaction. The time constants are introduced for characterisation of the response kinetics and are defined by the phenomenology using the rates of the reaction. An influence of the type and density of metallic impurities on the time constants and the rates of the surface processes is discussed. (C) 2004 Elsevier B.V. All rights reserved.