Mechanistic Model of Diffusion and Reaction in Thin Sensor Layers — The DIRMAS-Model

A rate equation approach to the gas sensitivity of thin film metal oxide materials

“…(10). In order to obtain a simple explicit equation for N O , the assumption of a constant surface electron density n s needed to made.…”

“…The variation of the gas sensitivity with sensor operation temperature, on the other hand, has been more explicitly considered in a second group of papers, which is concerned with porous thick-film materials. In this latter group of publications [5][6][7][8][9][10] diffusion-reaction theory [11,12] is invoked to calculate temperature-dependent gas penetration profiles within a porous thick-film sensing layer. These latter models successfully reproduce the observed bell-shaped variation of the gas sensitivity with sensor operation temperature.…”

An analytic model of the dynamic response of mass-sensitive chemical sensors

“…As shown by numerical analysis in [4], the rea- son may just as well be an insufficient desorption time. This, too, is correctly predicted by our analytic model.…”

“…Fig. 5 visualizes how the analyte molecules diffuse into the sensor film, a result well known from numerical computations [4].…”

“…Hence, one must aim at predicting the steady-state response f ∞ soon after an analyte concentration change in the external phase in order to reduce the effective response time. While the governing equations are well-known -may it suffice to mention the theory of the Prandtl boundary layer for the gas transport and the reaction-diffusion equations for the diffusion and binding of molecules in the film -they can, in general, only be solved numerically [2,4].…”