Role of hetero-junctions in oxide semiconductor gas sensors

A new design concept of semiconductor gas sensors, which introduces a foreign antenna material to a gas in problem, is described for the detection of dilute odorous gases such as HN3 and H2S. The antenna material, dispersed on the surface of a semiconducting oxide, interacts with the gas sensitively and selectively, and the resulting change in its chemical state induces a change in semiconducting properties of the underlying oxide through hetero-junctions. Typical examples of such sensors include NH3 sensors using Au and Pt WO3 and an H2S sensor using CuO--SnO2.