7.3.4 Thin-Film Gas Sensors Operating in a Perpendicular Current Mode

Abstract

Thin-film gas sensors operating in a perpendicular current mode are presented. To achieve this mode, a mesh-like top electrode is deposited on a sensing film instead of an electrode that is normally deposited on a substrate. The sensor current flows perpendicularly to the surface of the thin film and thus is not blocked by the cracks that are generated by an annealing process after deposition and by the difference of the thermal expansion coefficients between the sensing film and the substrate. The sensor is expected to work for a longer period of time without possible deterioration caused by cracks. Moreover, the mesh-like top electrode enhances the sensitivity to hydrogen by acting as a catalyst when Pt is used for the top electrode.