AN AL2O3 SENSOR FOR LOW HUMIDITY CONTENT - CHARACTERIZATION BY IMPEDANCE SPECTROSCOPY

A sensor able to measure very low humidity concentrations and with pos sible applications for geophysical research has been developed using A l2O3 porous thin films. The sensor is obtained by anodization in sulph uric acid of an Al thin film deposited by d.c. sputtering. The electri cal properties are evaluated using impedance spectroscopy for differen t contents of water vapour in the range 20 to 200 ppmv and for tempera tures from -60 to +40 degrees C. The response of the sensor changes ac cording to the frequency of the applied voltage. These results allow u s to formulate a hypothesis on the mechanism of water absorption.