A study of capacitance and resistance characteristics of an Al2O3humidity sensor

In this article the fabrication of a humidity sensor employing an Au-poroue Al2O3–Al structure is described. The behaviour of the sensor in both the capacitive and the resistive mode as a function of relative humidity is studied. The effect of frequency on these characteristics is investigated. It is observed that the change in capacitance is small below 30% RH. Above this humidity the capacitance increases rapidly. The dependence of resistance of the sensor on humidity is the reverse of the capacitance dependence. An electrical equivalent circuit model of the sensor based on the structure of the device and the sensing mechanism is developed. The results are interpreted in terms of the model.