Resonant micro/nanoelectromechanical systems (MEMS/NEMS) exhibits rich nonlinear responses because of their relatively small size and high vibration amplitude [1]. In this work, we provide experimental results and a quantitative study of nonlinear dynamics in atomically-thin nanomechanical resonators made of single-layer, bi-layer, and tri-layer (1L, 2L, and 3L) molybdenum disulfide (MoS₂) vibrating drumheads. For these two-dimensional (2D) MoS₂ resonators operating in the very high-frequency band, a synergistic study with calibrated measurements and analytical modeling on the observed nonlinear responses have resulted in nonlinear damping and cubic and quintic order nonlinear stiffness. We find that the quintic force can be ~20% of the Duffing force at larger amplitudes, and thus it generally cannot be ignored in a nonlinear dynamics analysis. Though the nonlinear stiffness of 2D NEMS has been studied in literature, to date, there has been no experimental demonstration and investigation of nonlinear damping in 2D semiconductor NEMS resonators. This study provides the first quantification of nonlinear damping and frequency detuning characteristics in 2D semiconductor nanomechanical resonators and elucidates their origins and dependency on engineerable parameters, setting a foundation for future exploration and utilization of the rich nonlinear dynamics in 2D nanomechanical systems.

[1] Cross, M.C.; Lifshitz, R. In Review of Nonlinear Dynamics and Complexity; Schuster, H., Ed.; Wiley: New York, 2008; Chapter 1.