Comparative Study of Carbon Monoxide Gas Sensing Mechanism for the LTPS MOS Schottky Diodes With Various Metal Oxides

The carbon monoxide (CO) gas sensing mechanism of the Au/MO/n-LTPS MOS Schottky diodes on a glass substrate has been studied with various metal oxides (MO) including SnO
₂
, ZnO, and TiO
₂
as the sensing element. Because of the deposited SnO
₂
has the highest band gap and the largest surface to volume ratio morphology, thus leading the Schottky diode with SnO
₂
to gain the highest relative sensitivity ratio of ~546% to 100 ppm CO ambient under condition of 200°C and -3 V bias. These results are better or comparable to the reported CO sensors. We propose a band gap model to interpret the related sensing mechanism in details.