Influence of mass transfer on the steady-state response of catalytic-metal-gate gas sensors

A mathematical model for the steady-state transport of analyte to a catalytic-metal-gate gas sensor directly exposed to a laminar gas flow in a duct is derived. The model is utilized in order to examine under what conditions problems with mass-transfer-limited response will occur for a measurement situation commonly encountered when catalytic-metal-gate semiconductor devices are used as gas sensors. Quantitative predictions for the lowering of the measured analyte concentration as compared to the nominal one are made for different total flows, sensor areas and reactive sticking coefficients. It is found that for square catalytic surfaces larger than 0.25 mm(2) and reactive sticking coefficients higher than 10(-4), the measured analyte concentration is significantly lower than the nominal concentration. (C) 1997 Elsevier Science S.A.