Tuning the Q-factor of nanomechanical string resonators by torsion support design

In recent years, the Q-factor of Si3N4 nanomechanical resonators has significantly been increased by soft-clamping techniques using large and complex support structures. To date, however, obtaining similar performance with smaller supports has remained a challenge. Here, we make use of torsion beam supports to tune the Q-factor of Si3N4 string resonators. By design optimization of the supports, we obtain a 50% Q-factor enhancement compared to the standard clamped–clamped string resonators. By performing experimental and numerical studies, we show that further improvement of the Q-factor is limited by a trade-off between maximizing stress and minimizing torsional support stiffness. Thus, our study also provides insight into dissipation limits of high-stress string resonators and outlines how advanced designs can be realized for reaching ultimate f0×Q product while maintaining a small footprint.