Field-effect-induced gas sensitivity changes in metal oxides

The sensitivity of micromachined gas sensor elements with respect to CO, NO, NO2, CH4, H2O and oxygen partial pressure changes was investigated. The microsensors consisted of thin films of RGTO-SnO2 deposited on top of resistively heated Si3N4 membranes. The electrical insulation between the Pt heater and SnO2 sensing layer circuits was provided by a thin dielectric layer. Applying a bias voltage across this layer, field-effect-induced changes in the gas sensing properties could be studied. We find that bias voltage changes can be used to systematically modify the cross-sensitivity of identically prepared sensor elements. These results are relevant for the realisation of monolithically integrated gas sensor arrays. (C) 1997 Elsevier Science S.A.