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Modelling and simulation of thin film semiconductor metal oxide gas sensor response

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2019
Atman, Berkan
Metal oxide based semiconductor gas sensors have attracted attention due to their superior properties. Over past five decades an extensive research had been conducted for understanding the true nature of the sensing mechanism, most suitable material and optimum operating conditions. SnO2 has received over years a great deal of attention as it can meet most of the necessary requirements of a gas sensor. Although commercially available gas sensors based on tin oxide are available and plenty of studies has been devoted to tin oxide based gas sensors, still there are many questions remained unanswered or have unsatisfactory explanations. In this work by developing a mathematical model with a comprehensive approach it is aimed to address some of those questions in terms of effects of diffusion, kinetic parameters, film thickness on complex dynamic behavior of the n- type semiconductor gas sensors in an environment being CO-air mixture. Furthermore, the constructed model provides an opportunity to analyze response/recovery dynamics in terms of electrical current obtained from current density distribution. The results of the simulations based on the transient model shows that increasing the thickness significantly reduces the sensitivity whereas slightly decreases the response time. The effect of diffusion on concentration profiles and current density distributions and their consequences are extensively discussed. Elevated temperature resulted in lower response and recovery times of the sensors. The temperature dependence of sensitivity was explained in terms of the competitive effect of activation energies of the surface kinetics and diffusion effect.