A new family of gaseous sensors utilizing catalyst-adsorptive oxide-semiconductor MIS structure

A new family of gaseous sensors utilizing catalyst-adsorptive oxide-semiconductor MIS structures fabricated on silicon has been developed for gas detection. Devices with Pd, Pt, or Ag as catalyst layer deposited on highly sensitive SnO/sub x/ or ZnO adsorptive oxide incorporated in the MIS capacitor have been studied for the detection of O/sub 2/, H/sub 2/, and CO gases. The operating principle of the devices is based on the change in ionic charge density and/or charge redistribution in the adsorptive oxide, SnO/sub x/, or ZnO of the MIS capacitor upon gas adsorption. This leads to a shift in the flatband voltage of the device. The mechanism of O/sub 2/ detection is attributed to the dissociation of O/sub 2/ molecules on the metal catalyst and the subsequent chemisorption at extrinsic surface states in the adsorptive oxide as negatively charged ions. The detection of H/sub 2/ and CO in air ambient is through a reaction with the extrinsic states associated with the chemisorbed oxygen ions.