  We measure the resistance and frequency-dependent gate capacitance of carbon
nanotube (CNT) thin films in ambient, vacuum, and under low-pressure (10E-6
torr) analyte environments. We model the CNT film as an RC transmission line
and show 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.
