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Approaching the intrinsic quality factor limit for micromechanical bulk acoustic resonators using phononic crystal tethers



Vikrant J. Gokhale, Jason J. Gorman


The goal of this work is to systematically demonstrate the effectiveness of one-dimensional phononic crystal (1-D PnC) tethers as a means to significantly reduce tether loss in micromechanical resonators to a point where the total energy loss is dominated by intrinsic mechanisms such as phonon damping. Multiple silicon resonators are designed, fabricated, and tested to provide comparisons in terms of the number of periods in the PnC and the resonance frequency, as well as a comparison with conventional straight-beam tethers. The product of resonance frequency and measured quality factor (f×Q) is the critical figure of merit, as it is inversely related to the total energy dissipation in a resonator. For a wide range of frequencies, devices with PnC tethers consistently demonstrate higher f×Q values than the best conventional straight-beam tether designs. The f×Q product improves with increasing number of PnC periods, and at a maximum value of 1.2 × 1013 Hz, approaches limiting values set by intrinsic material loss mechanisms.
Applied Physics Letters


bulk acoustic resonator, MEMS, quality factor, phononic crystal, tether
Created July 5, 2017, Updated November 10, 2018