The model of gradient distributed oxygen vacancies was extensionally investigated. Based on the dynamics of oxygen vacancies under diffusion and exclusion effects in cooling process, the steady state and non-steady state solutions of the diffusion equation of the vacancies were solved. The transient distribution of oxygen vacancies was revealed during the idealized cooling process. It was concluded that the exclusion effect dominates the density distribution of oxygen vacancies throughout the crystallite. The time-dependent expressions of potential barrier [qV(x,t)], film resistance and response to reducing gases were formulated on the basis of Schottky model and Poisson's equation. The simulated gas sensing characteristics were in good correlation with experimental results. The constants and variables were estimated according to the correlation. Presumptions and reservations of the present expressions were also considered.

Time-Dependent Oxygen Vacancy Distribution and Gas Sensing Characteristics of Tin Oxide Gas Sensitive Thin Films. J.Liu, S.Gong, Q.Fu, Y.Wang, L.Quan, Z.Deng, B.Chen, D.Zhou: Sensors and Actuators B, 2010, 150[1], 330-8