High-Performance Polycrystalline Diamond Micro- and Nanoresonators

Cantilever type MEMS resonators were fabricated using boron-doped (~5 times 10
¹⁹
cm
^-3
) and undoped polycrystalline diamond (poly-C) films that were grown at 600degC or 780degC. The resonator dimensions ranged from 500 mum long, 10 mum wide, and 0.7 mum thick to 40 mum long, 100 nm wide, and 0.6 mum thick. Resonance frequencies and quality factors Qs were measured in vacuum, 10 5 torr, over the temperature range of 23degC-400degC. The measured values of the temperature coefficient of the resonance frequency were in the range of -7.2- -25.6 ppm. degC
^-1
and seemed to be related to changes in the Young's modulus with temperature. Undoped poly-C cantilevers exhibit Qs as high as 116 000, the highest value reported for a cantilever resonator fabricated from a polycrystalline film. A thermally activated relaxation process seems to limit the measured Q -values for the highly doped poly-C samples.