Carbon Nanotube (CNT) resonators are comprised of a CNT clamped between source and drain electrodes on a silicon substate. The midsection of the nanotube is free to vibrate above a trench containing a gate electrode. The gap between the source and drain was 300-1000 nm and the gap between the CNT and the gate was 200-500 nm.
The resonator is actuated by applying an RF signal at the gate. A carrier signal (which is a slightly different in frequency than the actuation signal) is applied at the drain and the source is monitored using a lock-in amplifier. The CNTs were operated both bare and after being coated with metals such as indium. The researchers we also able to determine the quantity and mobility of excess charge that can build up on the CNT by employing two different methods for measuring the resonant properties of the NEMS.
According to Nickolay Lavrik, a nanotechnology and sensor specialist at Oak Ridge National Laboratory in the US, the Berkeley resonators represent an important step towards the development of these sensors. Lavrik told PhysicsWeb that CNTs show great promise for the development of ultra sensitive mass detectors because they can be self-assembled into very small structures down to the molecular scale. Indeed, Lavrik believes that CNTs have a good chance at achieving zeptogram (10-21g) sensitivity.
http://physicsweb.org/articles/news/10/8/21/1
Nano tubes circuits for GHz oscillator- ORNL
