Metallic Glass Hemispherical Shell Resonators

By utilizing bulk metallic glasses' (BMGs) unique combination of amorphous structure, material properties, and fabrication opportunities, ultrasmooth and symmetric 3-D metallic glass resonators that are complimentary metal oxide semiconductor (CMOS) post-processing compatible are fabricated. Surface roughness to size ratio fabrication precision in the order of 100 parts per billion is demonstrated with a 3-mm diameter Pt57.5Cu14.7Ni5.3P22.5 BMG hemispherical shell with a thickness variation <;100 nm and a surface roughness of <;1 nm Ra. The resonator exhibits a resonant frequency of 13.9440 kHz ± 0.1 Hz with 0.035% frequency mismatch between degenerate N = 2 wineglass modes with a quality factor of 6200. This performance was obtained in the asmolded state without any device tuning or trimming. Another resonator with N = 2 resonant modes at 9.393 and 9.401 kHz, and quality factors of 7800 and 6500 was mounted into an integrated electrode system. Electrical readout by capacitive sensing in both time and frequency domains showed a resonance shift to 9.461 and 9.483 kHz, respectively. The quality factor was reduced to 5400 and 5300, respectively. This investigation demonstrates that BMG resonators may serve as a basis for robust microelectromechanical systems resonator devices with increased performance and low-cost fabrication techniques that exploits the atomic structure, unique softening behavior, strength, formability, and toughness of metallic glasses.