Quality Factor in Polycrystalline Diamond Micromechanical Flexural Resonators

This paper reports an investigation into the various dissipation mechanisms that can affect polycrystalline diamond micromechanical resonators. Double-ended tuning fork and cantilever resonators were fabricated from 1-5-μm thick microcrystalline diamond films. It is shown that the quality factor of the low frequency (<;500 kHz) resonators is limited by surface loss, whereas the thermoelastic damping limits the quality factor of the higher frequency resonators. In resonators where surface loss is the dominant effect, the dependence of quality factor on resonator thickness is demonstrated. The addition of a lossy surface layer of Al₂O₃ deposited via atomic layer deposition is shown to degrade quality factor, and an experiment that further demonstrates the effect of surface dissipation and results in a reduction in quality factor that scales with the thickness of the Al₂O₃ layer. Heat treatment of cantilever resonators in N₂ for various times up to 660 min is used to modify the resonator surface and is shown to result in a threefold increase in quality factor up to 365 000 at 26.6 kHz.