THURSDAY, Sept. 27, 12 p.m. 11th floor Gamow Tower
Charles T. Rogers
University of Colorado, Boulder
c-axis GaN nanowires for high-quality-factor mechanical oscillators
We report on the electromechanical properties of c-axis GaN nanowires in high-quality-factor mechanical resonators and closed loop oscillators. The GaN nanowires are grown by catalyst-free molecular beam epitaxy, are single crystal, typically hexagonal in cross section, from 50 - 100 nm diameter, and 5 - 15 microns in length depending upon growth time. Such nanowires have masses in the picogram range. The nanowires display singly-clamped cantilever mechanical resonances above 1 MHz, with typical resonance full width at half maximum power of less than 100 Hz i.e., a mechanical quality factor, Q, well above 10e4. We use piezoelectric drive and scanning electron microscope detection of nanowire motion to observe closed loop GaN nanowire oscillators with Q above 10e6. We will discuss using these oscillators as sensors, demonstrating mass detection sensitivities below 10e-18 grams in a 1 second averaging time. Temperature dependences and observed noise properties will be discussed.