Development of commercial nanoporous trace moisture sensor following sol–gel thin film technique

A simple laboratory technique for the routine preparation of γ-alumina (Al 2O 3) thin films on gold electrodes coated on an α-alumina substrate (10 mm × 20 mm × 1 mm) is described here. Prepared thin films and porous electrodes are dried at 100 °C and sintered at 400–550 °C for 4 h to achieve the γ-Al 2O 3 phase. Further the temperature is shifted to 950 °C for 1.5 h for curing the electrodes. Microstructure of the films are analysed by means of atomic force microscopy (AFM) and scanning electron microscopy (SEM). The studies suggested that doubly coated γ-Al 2O 3 led to an increase in the surface roughness of the deposited film which provided a unique sensor sensitive to trace moisture on a ppm level by volume (ppm v).