Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
742756 | Sensors and Actuators B: Chemical | 2012 | 8 Pages |
Receptor function of oxide semiconductor gas sensors to oxygen and an oxidizing or reducing gas was extended successfully to include two types of adsorbed oxygen, O− and O2−. The receptor function relying on O2− ions is featured by linear dependence of resistance on PO21/4 (PO2PO2, partial pressure of oxygen), while that relying O− shows linear dependence on PO21/2. As a result, the resistance can be brought to a high value at small PO2PO2 when O2− ions are formed. The drastic increase of resistance in air under desiccated condition can be accounted for as a result of the formation of O2− ions which is blocked by water vapor in humid conditions. On the response to an oxidizing gas (NO2) in air, O2− ions exert an adverse effect; those increase the gross resistance of the device in air, thus reducing the conventionally defined response to the gas. Those influence on the response to a reducing gas (H2) in a particular way. Owing to a kinetic reason, O2− ions are almost distinguished at steady state under exposure to the gas, rendering only O− ions to be responsible for the response to the gas, and thus contributing to amplify the conventionally defined response.