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Capacitance Measurements of a Single Carbon Nanotube

One of the most important quantities determining the properties of carbon nanotube transistors is the capacitance between a nanotube and the “gate” electrode that turns the transistor on and off. However, direct measurements of this capacitance are difficult due to the very small size of the nanotube. CNS investigators have now for the first time directly measured this capacitance using an ultrasensitive measurement technique. The overall magnitude of the capacitance is in good agreement with theoretical calculations. Furthermore, the investigators observed the effects of the so called quantum capacitance. This quantum correction arises from the density of current-carrying electron states in a nanotube. These measurements provide for the first time a direct electronic probe of the filling of the one-dimensional electron channels of a nanotube as a function of the electrical bias resulting from a voltage being applied to the gate electrode. .


Schematic of the device geometry: The capacitance between the top gate and the nanotube (dark blue) is measured as a function of the gate voltage applied to the top gate.

[Lead CNS Investigator: P. McEuen]

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