SENSING MECHANISM OF A CARBON-MONOXIDE SENSOR-BASED ON ANATASE TITANIA

This paper reports results on a TiO2 (anatase)-based CO sensor and pro poses a possible surface-controlled sensing mechanism. The complex pla ne analysis of the ac electrical data provides quantitative evidence s upporting the mechanism. The grain-boundary capacitance and conductanc e, extracted from the impedance plane, were observed to increase with the CO concentration. This effect is attributed to a change in the dep letion region thickness and barrier height at the TiO2 intergranular c ontact. The analysis of the electrical data combined with x-ray diffra ction and x-ray photoelectron spectroscopy observations support the pr oposed sensing mechanism involving CO adsorption and ionization on the titania surface, and not an oxidation-reduction type reaction as obse rved in most oxide-based sensors.