TRANSIENT EFFECTS OF TIN OXIDE CO SENSORS IN THE PRESENCE OF WATER-VAPOR

During the experimental study of CO sensitivity of SnO2 resistive-type gas sensors in the presence of water vapor, a transient effect was ob served which elucidates the CO sensing mechanism in tin oxide. More pr ecisely, after the removal of CO, an increase of the measured conducta nce was observed, depending on substrate temperature. An explanation o f this phenomenon is proposed, which is based on the conductance modul ation due to three different mechanisms: Formate desorption, occupatio n of lattice sites by oxygen molecules, and diffusion of lattice oxyge n vacancies to sensor's bulk.