A novel porous silicon sensor for detection of sub-ppm NO2 concentrations

We developed a new technique for the deposition of free-standing porous sil icon (PS) on alumina substrate with interdigital contacts (Italian Patent E NEA-INFM), thus removing the silicon substrate, that is inactive in gas det ection and is much more conductive than PS. The de and ac electrical measur ements in a controlled atmosphere were performed to test the sensor respons e towards NO2 (0.1-10 ppm), O-3 (200 ppb), CO (1000 ppm), benzene (20 ppm), organic vapours and humidity. The device was able to detect very low conce ntrations of nitrogen dioxide (100 ppb) with no interference from ozone, be nzene, CO and organic vapours. Indeed humidity interferes with nitrogen dio xide detection and must be kept under control. Since PS showed great respon se to NO2 at room temperature (RT), no heating of the sensor is required. ( C) 2001 Elsevier Science B.V. All rights reserved.