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Research in Nanoscale Devices


To the left is an electron microscope image of a vibrating beam (in the hourglass-shaped section), 6 microns long (~ 1 tenth the width of a human hair) and 0.2 microns wide formed in a piece of semiconductor crystal. This beam vibrates at several million times per second. On either side of it are two single electron transistors (SETs) used to measure this vibration. These devices are some of the most sensitive amplifiers in existence, and allow measurement of the vibration down to a vanishingly small level.

My research is concerned with fabricating such nanostructures with both electrical and mechanical elements. These are then cooled down to nearly absolute zero to measure their properties - specifically looking for deviations from what one would expect for a macroscopic object. This mesoscopic regime is a new laboratory for the study of quantum mechanics in human-made structures, and may lead to improved sensors and new understanding of the transition from the classical world to the quantum world.

Student Opportunities

I'm looking for 1-3 graduate students to join me in working on nanotechnology projects in the next year. Students will work on all facets of the work, including device fabrication, cryogenic measurents and laboratory equipment set-up.
Undergraduate students looking for summer positions, or for part-time work during the school year, are encouraged to contact me as well.

Research Themes

Nano-mechanics Using the techniques of lithography, etching and deposition, we can make nanometer-scale structures that can move. Their small size allows them to vibrate very fast, and respond to tiny forces. These devices can be used for force sensors, radio-frequency circuit elements, or as fascinating objects at the quantum/classical boundary themselves. Our research looks at nanomechanical systems, trying to increase the resonant frequency, and improve the readout sensitivity.

Nano-electronics Electronic devices at the nano-scale can have superior performance over more conventional devices. Fundamentally, however, they are interesting since their operation can show effects due to quantum mechanics. This quantum behaviour leads to the possibility of quantum computation - a fundamentally different type of computer. The success of quantum computation has been limited due to the effect of decoherence. The use of integrated wide-bandwidth devices will allow us to study the noise in mesoscopic electronics, looking for effects of coherence and decoherence.

Low Temperatures Measurements on mesoscopic systems must be cooled so that the quantum behaviour is evident. Samples are cooled to well below 1 Kelvin, requiring refrigeration based on Helium-3, and careful attention to the heat loads due to wiring and environmental noise.

High Frequencies Operating mesoscopic electronics at radio or microwave frequencies requires special attention in maximizing the bandwidth, matching impedances, and using sensitive preamplifiers. The benefit of such high-speed electronics is that we can try to see dynamic effects and look at how devices react in "real time", rather than averaging.

Quantum Measurement The measurement of quantities such as position is limited at its ultimate resolution by the effect the measuring device has on the measured object. This is a fundamental imposition of quantum mechanics due to the Heisenberg uncertainty principle. There are techniques to avoid this back-action, based on measuring other observables and using non-linear coupling. One facet of our research is trying to bring these techniques to nanoscale electronic and mechanical systems.

Fabrication The devices we study are fabricated using lithographic techniques, particularly electron-beam lithography. The work involves integrating nanoscale mechanical structures with electronic devices - requiring several steps of fabrication. Smaller structures often lead to novel or more robust effects in this field, so we work to improve this patterning, including the use of scanning-probe lithography and self-assembled structures.

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