Fabrication, motion detection and amplification techniques in radio-frequency nanoelectromechanical systems (NEMS)

The theme of this work is to address problems that pose roadblocks to the success of Nanoelectromechanical Systems (NEMS). The anticipated NEMS applications range from ultrasensitive bio-chemical sensing, to force detection, to signal processing and time-keeping. Yet, several critical technological problems prevent NEMS from achieving their full potential. For the fabrication of NEMS, electron-beam lithography is employed, but low throughput makes batch device fabrication quite impractical. In NEMS operation, the miniscule mechanical displacement amplitudes necessitate ultrasensitive motion/displacement detection techniques. Widely-used optical and magnetomotive detection techniques require complex measurement set-ups, which can only be used in the research laboratory environment. This research is targeted to provide novel approaches to the fabrication and operation of NEMS for more efficient and wider use of these devices.; We have developed a nanoimprint lithography based technique for the fabrication of NEMS. The technique involves imprinting the pattern-to-be-suspended upon an existing anchor structure, metallizing the pattern, and finally removing the excess material. This approach potentially possesses all the desirable aspects of nanoimprint lithography, which is required for mass nanofabrication.; We propose two capacitive techniques to sense the motion of NEMS devices. The main challenge here stems from the fact that the motional modulation of the NEMS capacitance becomes extremely small as a device is scaled-down. In this limit, parasitic capacitances on the chip dominate the measured signal. The first approach presented here relies upon simple impedance transformation. The second approach is based on canceling the parasitic capacitance using a matching inductor and performing a transmission measurement.; We also present a capacitive technique to parametrically amplify the NEMS motion. Here, a capacitive pump signal, which modulates the spring constant at twice the NEMS resonance frequency, results in phase dependent amplification of the displacement. By choosing the phase properly, one can amplify the motional response of the NEMS and improve the sensitivity. Using the same approach, thermomechanical noise amplification and squeezing in a narrow-band and the full resonance sideband are also experimentally demonstrated.