SENSITIVITY TO REDUCING GAS AS A FUNCTION OF ENERGY BARRIER IN SNO2 THICK-FILM GAS SENSOR

A characterization of screen-printed tin oxide gas sensors as a function of the thickness is presented: on a few samples a concentration of Pd has been deposited by CVD for comparison. While it generally appears possible to link the electronic structure of the bulk and the chemical state of the surface by the energy-barrier model, the difference between the minimum and the maximum of the barrier energy DELTA-E is quite different depending on the thickness and the catalyst. The curves of the energy barrier as a function of temperature are obtained by temperature-stimulated conductance measurements. The aim of this work is to illustrate the correlation between DELTA-E and the sensitivity to reducing gas particularly to methane. It seems important to highlight that for the case of no catalyst, the sensitivity to reducing gas has a minimum thickness threshold of approximately 20-mu-m. The morphology and the microstructure of the samples have been analysed bv TEM and SEM observations.