SOLID IONIC CONDUCTOR SEMICONDUCTOR JUNCTIONS FOR CHEMICAL SENSORS

The potential drop at solid ionic conductor/semiconductor contacts responds to partial pressure changes of gases since the Fermi level of the semiconductor depends on the adsorbed species and equilibrates with that of the ionic conductor. In an alternative consideration, the semiconductor acts as a catalyst for the reaction of the mobile ions of the solid ionic conductor with the adsorbed species. The junction is employed as a chemical sensor for the detection of CO2 by using NASICON as solid electrolyte and doped SnO2 as semiconductor. The device is applicable even at room temperature with fast response time. Mechanisms of the response of the junction to gases are discussed in detail. The principle of employing solid ionic conductor/semiconductor junctions for sensors is in general applicable for many gases.