Development of a Feedback Controlled Carbon Nanotube-Based Nanoelectromechanical DeviceChanghong Ke, Ph.D., Northwestern University, 2006.
Major Professor: Dr. Horacio D. Espinosa.
This dissertation presents the development of a feedback controlled carbon nanotube based nanoelectromechanical device. The device consists of a cantilevered multi-walled carbon nanotube (MWNT) clamped to a top electrode and actuated by a bottom electrode. The actuation circuit also includes a source and a feedback resistor. The pull-in/pull-out and tunneling characteristics (I-V) of the system are investigated by means of electromechanical analysis and in-situ scanning electron microscopy (SEM) measurement. The electromechanical model takes into account various aspects of mesoscopic interactions including the effects of concentration of electrical charges, at the end of the nanocantilever, finite kinematics, van der Waals force and tunneling contact when the free end of the nanocantilever touches the bottom electrode. Based on the energy method, a close-form formula to predict the pull-in voltage of the device is derived and verified by in-situ SEM measurement. Both experiments and modeling show that the device has two well-defined stable equilibrium positions and the pull-in/pull-out processes together with these two stable equilibrium positions form a hysteretic loop.
The fabrication of individual devices has been demonstrated by the means of the nanomanipulation of individual carbon nanotubes, together with MEMS micro-fabrication. Fabrication of massively parallel device array based on directed self-assembly approach is also discussed.
The unique bistability behavior and tunneling gap of the device offer tremendous opportunities in the fields of nanoelectronics and sensors. The potential application of the device includes NEMS switches and random access memory elements, logic devices, sensor for ultrasonic wave detection and gap sensing.