MODELING AND SIMULATION OF ABNORMAL-BEHAVIOR OF THICK-FILM TIN OXIDE GAS SENSORS IN CO

A new model is proposed that takes into account oxygen vacancies in ti n oxide resistive-type gas sensors, assuming that lattice oxygen modif ies the rate of oxygen adsorption. Applying this hypothesis in a Monte Carlo simulation, effects observed in thick-film samples are explaine d, Moreover, computational techniques have been used in order to simul ate different thick-film structures, and the role of both surface cove rage and reduction in the sensing mechanism is investigated. The simul ation results are in good qualitative agreement with the experimental results obtained from our samples. In particular, phenomena like under shoot and overshoot of the sample's resistance, very long recovery tim es and poisoning of the sensor surface are discussed.