Publications

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In this work, we demonstrated engineered modification of propagation of thermal phonons, i.e. at THz frequencies, using phononic crystals. This work combined theoretical work at Sandia National Laboratories, the University of New Mexico, the University of Colorado Boulder, and Carnegie Mellon University; the MESA fabrication facilities at Sandia; and the microfabrication facilities at UNM to produce world-leading control of phonon propagation in silicon at frequencies up to 3 THz. These efforts culminated in a dramatic reduction in the thermal conductivity of silicon using phononic crystals by a factor of almost 30 as compared with the bulk value, and about 6 as compared with an unpatterned slab of the same thickness.

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Frequency tuning of aluminum nitride (AlN) micromechanical resonators has been demonstrated by reactance manipulation via termination with variable capacitors. Shunting one electrode with a variable capacitor in a 13 MHz fourth overtone length-extensional mode resonator effected resonator stiffening to yield a ∼600 ppm frequency shift. Tunability could be further increased by dedicating two electrodes for tuning doubling the frequency tuning range to ∼1500 ppm. A tunable bandwidth balun filter has been constructed by parallel coupling of independently tunable resonators demonstrating almost three-fold increase in the bandwidth from 12 kHz to 33 kHz. Also a voltage-controlled frequency tuning printed circuit board (PCB) was implemented. © 2011 IEEE.

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