Microresonators with Q-factors over a million from highly stressed epitaxial silicon carbide on silicon

We utilize the excellent mechanical properties of epitaxial silicon carbide (SiC) on silicon plus the capability of tuning its residual stress within a large tensile range to fabricate microstrings with fundamental resonant frequencies (f₀) of several hundred kHz and mechanical quality factors (Q) of over a million. The fabrication of the perfect-clamped string structures proceeds through simple silicon surface micromachining processes. The resulting f $\times$  Q product in vacuum is equal or higher as compared to state-of-the-art amorphous silicon nitride microresonators. We demonstrate that as the residual epitaxial SiC stress is doubled, the f $\times$  Q product for the fundamental mode of the strings shows a four-fold increase.