Carbon Nanotube Parametric Amplifier
Alex Zettl (UCB) and Willi Mickelson (COINS)
We have designed a scheme for a parametric amplifier based on a single suspended carbon nanotube field-emitter. This novel electromechanical nanotube device acts as a phase-sensitive, variable-gain, band-pass-filtering amplifier for electronic signal processing and, at the same time, can operate as a variable-sensitivity, tunable detector and transducer of radio frequency electromagnetic waves. The amplifier can exhibit infinite gain at pumping voltages much less than 10 Volts. Additionally, the amplifier’s low overhead power consumption (10-1000 nW) makes it exceptionally attractive for ultra-low-power applications.
We expect this highly tunable carbon nanotube parametric amplifier will find many useful applications in electronics, as a filter and an amplifier, in wireless communications, as a low-power RF receiver and transmitter, and in fundamental science as a versatile NEMS device for studies in condensed matter and as a highly-sensitive RF photon detector in optics.
Prototype for a carbon nanotube parametric amplifier. (a) A false-color scanning electron micrograph of a lithographically-defined multiwalled carbon nanotube device. (b) A schematic of the device highlighting the interaction with the pump electrode and the basic electrical circuit wiring. (c) A schematic of the equivalent electromechanical system for the pump-nanotube interaction shown in (b).
Roukes developed the first silicon nanowire (SiNW) very high frequency (VHF) NEMS devices. The VHF NEMS resonators are based upon bottom-up epitaxially-grown SiNWs with well-terminated surfaces. Metallized SiNW resonators operating near 200 MHz are realized with quality factor Q=2000~2500. In collaboration with Yang, pristine SiNWs, with fundamental resonances as high as 215 MHz, are measured using a VHF readout technique that is optimized for these high resistance devices. The pristine resonators provide the highest Qâ€™s, as high as Q=13100 for an 80 MHz device. A principal advantage of the suspended SiNW resonators developed in this work is their ease of fabrication and high yield. By pushing the dimensions of the microtrenches downward and simultaneously optimizing the NW growth conditions, we expect that smaller, even molecular-size, suspended SiNWs should be achievable. These will enable scaling fundamental resonance frequencies into the extreme UHF and low microwave range. These SiNW resonators offer significant potential for applications in resonant sensing and high frequency signal processing.
Zettl constructed a fully functional, fully integrated radio receiver, orders-of-magnitude smaller than any previous radio, from a single carbon nanotube. The single nanotube serves, at once, as all major components of a radio: antenna, tuner, amplifier, and demodulator. The antenna and tuner are implemented in a radically different manner than traditional radios, receiving signals via high frequency mechanical vibrations of the nanotube rather than through traditional electrical means. The nanotube radio’s extremely small size could enable radical new applications such as radio controlled devices small enough to exist in the human bloodstream, or simply smaller, cheaper, and more efficient wireless devices such as cellular phones.