533. Investigation of grain radius dependence of sensitivity for porous thin film semiconducting …

Fig. 1 A simplified model for a porous thin film semiconducting metal oxide gas sensor.

Fig. 2 Model of gas reaction process with absorbed oxygen on the surface.

Table 1 Parameters in model.

Zhenyu Yuan, et al, IEEE Sen J. 20, 4275 (2019)
https://doi.org/10.1109/JSEN.2019.2961388

(1) The gas diffusion in the porous thin film follows Fick law including surface diffusion in micropore (pore radius r < 1 nm), Knudsen diffusion in mesopore (1 nm < r < 50 nm) and molecular diffusion in macropore (r > 50 nm).
(2) Gas concentration profile is a result of competition between gas diffusion in the gas phase and
gas reaction on the surfaces.
(3) For the porous thin film medium gas sensor, the grain radius d not only affects the gas diffusion coefficient kD, but also determines the saturated amounts of the surface coverage mq and the velocity constant mk.
(4) The gas sensitivity decreases monotonously with the increasing grain radius d under the steady stage of the gas concentration.