A THIN-FILM SNO2 GAS SENSOR SELECTIVE TO ULTRA-LOW NO2 CONCENTRATIONSIN AIR

Thin film nanocrystalline SnO2, sensors, prepared by reactive sputteri ng, showed high sensitivity to ultra-low concentrations of NO2 in the parts per billion (ppb) range. The gas sensitivity shown by these sens ors was compared with that measured by conventional methods currently in use to monitor air pollution. These sensors were insensitive to O-3 , and only slightly sensitive to NO in dry air, CO could be detected o nly al high temperatures. The only gas that masked the response to NO2 was water vapour. The NO2 responses were found to be very high and qu ite reversible, while the response times were fast and the reproducibi lity was satisfactory. The responses to low: NO2 concentrations of the se sensors have been compared with theoretical results obtained using a multispecies adsorption model. The experimental results showed good agreement with theory. (C) 1997 Elsevier Science S.A.