Carbon nanotubes as new materials for gas sensing applications

Carbon nanotubes (CNTs) deposited by plasma enhanced chemical vapor deposition On Si3N4/Si substrates provided with Pt electrodes have been investigated as resistive gas sensors towards NO2. The electrical response has been measured exposing the films to sub-ppm NO2 concentrations (10-100 ppb in dry air) at different operating temperatures ranging between 25 and 250 degreesC. The response to NO2 has been found to be at maximum at around 165 degreesC. Upon exposure to NO2 the electrical resistance of randomly oriented CNTs is found to decrease. The prepared films show reasonable dynamic of the electrical response and high reproducibility of the electrical properties. The resistance decrease of the CNTs when exposed to NO2 gas and the sensor response to concentrations as low as 10 ppb NO2, suggest the possibility to utilize CNTs as new sensors for air-quality monitoring. (C) 2003 Elsevier Ltd. All rights reserved.