Strained Silicon Nanomechanics*

Dissipation dilution is routinely employed to suppress loss in nanomechanical resonators; however, the effect has been applied to a limited class of materials, notably the amorphous glass Si₃N₄. Crystalline thin films are an attractive alternative, due to their prospects of high intrinsic strain and lower material friction. Here, we demonstrate that single crystal strained silicon, a material developed for implementing high mobility transistors, can be used to realize mechanical resonators with extremely low dissipation, leveraging dissipation dilution and soft-clamping. High aspect ratio nanostrings support MHz mechanical modes with Q exceeding 10⁸ at room temperature and 10⁹ at 10 K, on par with state-of-the-art implementations in Si₃N₄. These observations show the value of strained silicon as a platform for implementing nanomechanical oscillators with low mass and high sensitivity.