Low-Dissipation Nanomechanical Devices from Monocrystalline Silicon Carbide.

The applications of nanomechanical resonators range from biomolecule mass sensing to hybrid quantum interfaces. Their performance is often limited by internal material damping, which can be greatly reduced by using crystalline materials. Crystalline silicon carbide is appealing due to its exquisite mechanical, electrical, and optical properties, but has suffered from high internal damping due to material defects. Here we resolve this by developing nanomechanical resonators fabricated from bulk monocrystalline 4H-silicon carbide. This allows us to achieve damping as low as 2.7 mHz, more than an order-of-magnitude lower than any previous crystalline silicon carbide resonator and corresponding to a quality factor as high as 20 million at room temperature. The volumetric dissipation of our devices reaches the material limit for silicon carbide for the first time. This provides a path to greatly increase the performance of silicon carbide nanomechanical resonators.