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Journal of Sensors
Volume 2012 (2012), Article ID 496546, 7 pages
http://dx.doi.org/10.1155/2012/496546
Research Article

Single-Walled Carbon Nanotube Network Field Effect Transistor as a Humidity Sensor

1NanoMaterials Group, Department of Applied Physics, Aalto University, P.O. Box 15100, 00076 Aalto, Finland
2IACQER Center for Research and Development on Nanotechnology, Malla Reddy Engineering College, Secunderabad 500014, India
3Microsystems and Nanoelectronics, VTT Technical Research Centre of Finland, P.O. Box 1000, 02044 VTT, Finland
4Nokia Research Centre, Helsinki, Finland
5VTT Technical research centre of Finland, Tietotie 3, 02044 Espoo, Finland
6Canatu Oy, Konalankuja 5, 00390 Helsinki, Finland
7Department of Materials Science and Technology, Aalto University, P.O. Box 13500, 00076 Aalto, Finland

Received 10 January 2012; Accepted 19 March 2012

Academic Editor: Andrea Cusano

Copyright © 2012 Prasantha R. Mudimela et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Single-walled carbon nanotube network field effect transistors were fabricated and studied as humidity sensors. Sensing responses were altered by changing the gate voltage. At the open channel state (negative gate voltage), humidity pulse resulted in the decrease of the source-drain current, and, vice versa, the increase in the source-drain current was observed at the positive gate voltage. This effect was explained by the electron-donating nature of water molecules. The operation speed and signal intensity was found to be dependent on the gate voltage polarity. The positive or negative change in current with humidity pulse at zero-gate voltage was found to depend on the previous state of the gate electrode (positive or negative voltage, respectively). Those characteristics were explained by the charge traps in the gate dielectric altering the effective gate voltage, which influenced the operation of field effect transistor.