CHARACTERIZATION OF POROUS AL2O3 SIO2/SI SENSOR FOR LOW AND MEDIUM HUMIDITY RANGES

We present the preliminary a.c, electrical characterization of a humidity sensor based on a thin Al2O3 porous layer grown on an SiO2/Si substrate. The sensor is prepared by sputter deposition of a thin film of At, followed by its anodic oxidation in a sulphuric acid solution. A gold electrode is deposited on the substrate tilted at a grazing angle with respect to the substrate plane. The electrical a.c. measurements are made in the range 100 Hz-15 MHz and in a small chamber where either the relative humidity or the temperature could be easily changed. The sensor response is not influenced by interfering gases like CO, CO2, NO2, CH4, C2H6 and H-2. The experimental results of the impedance spectroscopy are compared with the frequency responses of different equivalent circuits of the sensor.