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

Abstract

In recent years, the Q-factor of [Formula: see text] 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 [Formula: see text] 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 [Formula: see text] product while maintaining a small footprint.

Strain Engineering of Nonlinear Nanoresonators from Hardening to Softening

“…We noticed that near θ = 0, the Q-factor of our devices drops to a similar level to that of stress-free string resonators [42], whose dissipation dilution disappears with the relaxation of high tension (see Fig. 4b) [27,29]. We however note that the FE simulated Q-factor of devices close to the onset of buckling are lower than the intrinsic Q-factor Q 0 = 9864.…”

“…2a), to quantitatively capture the influence of L s and w s on k i and thus on k 3 . We particularly model the boundary springs as doubly clamped beams with pre-tension σ 0 and use their central deflection to analytically estimate k i as follows [29]:…”

“…We however note that the FE simulated Q-factor of devices close to the onset of buckling are lower than the intrinsic Q-factor Q 0 = 9864. This could be attributed to the anti-spring behavior of the buckled strings that can result in U total /U bending < 1 and thus Q < Q 0 [29,43]. Included in Fig.…”

“…Although numerous studies have already demonstrated the design optimization of resonance frequencies and Q-factor of nanomechanical resonators [24][25][26][27][28][29], the influence of geometric design on the nonlinear dynamics has been rarely investigated [11,30]. Here, we show that soft-clamping techniques that are utilized to realize high-Q nanomechanical resonators, can also be engineered to tune nonlinear dynamics.…”

High‐Strength Amorphous Silicon Carbide for Nanomechanics

“…A variety of strategies have been proposed aiming to improve the Q factors of tensile-loaded nanomechanical resonators. These include patterning 2D geometries appropriately, [9,[11][12][13]70,71] modifying mass distribution [2,72] and mode of interest (e.g., from fundamental to higher order or from flexural to torsional modes [2] ), in situ annealing for surface cleaning, [73] as well as cooling down to cryogenic temperatures. [14,74] The methods mentioned above can benefit from utilizing the LPCVD a-SiC thin film we characterized in this work, due to its high deposition film tensile stress, superior chemical resistivity, and impressive ultimate tensile strength.…”