Thursday, June 28, 2007, 9:30 am — Chemistry Bldg. Third Floor Conf. Rm. 300
Gokhan Esen
University of Maryland @ College Park
Transmission line Impedance of carbon nanotube thin films for chemical sensing"
Single-walled carbon nanotubes (CNTs) have a number of favorable properties for chemical sensors and there has been an ongoing interest in research community in using them as transducer elements for chemical sensing devices Chemical sensing in CNT may take place through a number of different mechanisms that are hard to sort independently. In order to understand the sensing mechanism in CNT thin film sensors, we have measured the resistance and frequency-dependent gate capacitance in ambient, vacuum, and under low pressure (10^-6 Torr) analyte environments. We modeled the CNT film as a RC transmission line and showed that changes in the measured capacitance as a function of gate bias and analyte pressure are consistent with changes in the transmission line impedance due to changes in the CNT film resistivity alone; the electrostatic gate capacitance of the CNT film does not depend on gate voltage or chemical analyte adsorption. However, the CNT film resistance is enormously sensitive to low pressure analyte exposure.
Hosted by: Peter Sutter
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