Theoretical study of the gas sensitivity and response time of metal oxide thin films

In this paper, based on the gas sensitive mechanism of metal oxide semiconductor thin film, the law of gas diffusion, first order aerodynamics and the relative assumption, we present a simple model for the simulation of the steady state gas sensitivity of metal oxide thin film. Our model provides a general mathematical relationship between the steady state sensitivity and the film thickness. The metal oxide semiconductor thin film is supposed to be formed with a finite number of independent layers. Each layer consists of ideally spherical grains with close-packed structure. The target gas is assumed to affect the inner layers either by penetrating through the grain boundaries or by direct interacting with each layer surface. Besides we propose a model to analyze the thickness dependence of the response time for metal oxide gas-sensing film.