Influence of surface resistance on the response of planar capacitive humidity sensors

The influence of surface conductivity on the response of a surface-type humidity sensor is shown. The measurements are compared with results from a theoretical model, based on distributed RC-transmission lines. Interdigital capacitors were covered with a sputtered aluminiumoxide and a thin (1nm-6nm) gold layer of variable thickness as a humidity sensitive layer. The results are showing clearly the dependence of the humidity sensitivity on the surface resistance of the thin gold film. (IFT)