CO sensing with SnO2-based thick film sensors: Surface state model for conductance responses during thermal-modulation

There exists a strong interest in developing simplified models able to predict the SnO2 sensor response and aiming at a better comprehension of the mechanisms involved with sensing operation. In this paper, a simple grey-box model is proposed for predicting, with a good approximation (r.m.s. error < 10%), the behavior of some commercial SnO2-based sensors in presence of oxygen and a reducing gas (CO) during fast temperature variations. Auger electron spectroscopy (AES) permitted to highlight differences in the surface composition of the sensors after extended operation time.