Catalyst-SnO/sub x/ MIS structure for detection of O/sub 2/, H/sub 2/ and CO

Catalyst-SnO/sub x/ MIS capacitors with palladium, platinum, or silver as catalyst and highly resistive SnO/sub x/ as the gas-adsorptive oxide have been explored for the detection of O/sub 2/, H/sub 2/, and CO gases. Device detection is based on the change in ionic charge density and/or charge redistribution in the adsorptive oxide, SnO/sub x/, of the MIS structure upon gas adsorption. The catalyst layer with a thickness of several angstroms deposited on top of SnO/sub x/ is used to enhance the gas selectivity and detectability of the device at a lower temperature range. The mechanism of oxygen detection is attributed to the dissociation of oxygen molecules on the metal catalyst and subsequent chemisorption at extrinsic surface states in SnO/sub x/ as negatively charged ions. This leads to a shift in the flatband voltage of the device to a positive gate voltage. The detection of hydrogen and carbon monoxide is through a reaction with the extrinsic states associated with the chemisorbed oxygen ions.<>