Abstract
A simple moisture sensor working at room temperature has been fabricated using porous silicon (PS) coated with porous gamma-aluminium oxide (gamma - Al2O3). Porous silicon was formed by electrochemical anodization of p-type silicon. Thereafter, a porous layer of the PS was dip coated with gamma - Al2O3 film. The gamma - Al2O3 coating solution was made by a simple sol-gel method. The coated structure was sintered at 500 degrees C for 30 m to form a nano porous layer of metal oxide on the porous silicon. Sintering the gamma - Al2O3-coated PS sample improves the stability of the sensor. Two different sensors with membrane-type metal contact have been fabricated by varying electrochemical parameters of PS. The sensors were tested to detect low moisture content in the N-2 gaseous atmosphere in the range of 25 to 200 mu l. Results show that suitable pore morphology of the hybrid structure will enable one to obtain characteristics of a sensor comparable to the commercial porous alumina moisture sensor. It was further observed that the sensor output is highly reproducible and has negligible hysteresis.