Sensitivity and stability of porous polycrystalline silicon gas sensor

Porous silicon (PS) used as a sensing material for micro-sensors has attracted a lot of attention in recent years. Owing to the large surface area (similar to 200 m(2) cm(-3)) and high chemical activity, porous silicon would be a good choice for gas sensor applications. In this paper, a resistivity sensor using porous polycrystalline silicon (PPS) thin films was fabricated by anodization and standard lithographic technique. Analytical measurements on the sample reveal that these sensing porous poly-Si films consist of many pores with a diameter of similar to 100 nm. A high sensitivity to ambient pressure and ethanol vapor was observed. The sensitivity and stability of PPS gas sensor have been characterized and analyzed as a function of gas concentration and storing duration. In particular, we will discuss the mechanism of the interaction between the surface state of PPS and ambient gases in detail. Suggestions to further improve the sensor stability will also be proposed. (C) 2001 Elsevier Science B.V. All rights reserved.