Strain-Modulated Dissipation in Two-Dimensional Molybdenum Disulfide Nanoelectromechanical Resonators

Abstract

Resonant nanoelectromechanical systems (NEMS) based on two-dimensional (2D) materials such as molybdenum disulfide (MoS2) are interesting for highly sensitive mass, force, photon, or inertial transducers, as well as for fundamental research approaching the quantum limit, by leveraging the mechanical degree of freedom in these atomically thin materials. For these mechanical resonators, the quality factor (Q) is essential, yet the mechanism and tuning methods for energy dissipation in 2D NEMS resonators have not been fully explored. Here, we demonstrate that by tuning static strain and vibration-induced strain in suspended MoS2 using gate voltages, we can effectively tune the Q in 2D MoS2 NEMS resonators. We further show that for doubly clamped resonators, the Q increases with larger DC gate voltage, while fully clamped drumhead resonators show the opposite trend. Using DC gate voltages, we can tune the Q by ΔQ/Q = 448% for fully clamped resonators, and by ΔQ/Q = 369% for doubly clamped resonators. We develop the strain-modulated dissipation model for these 2D NEMS resonators, which is verified against our measurement data for 8 fully clamped resonators and 7 doubly clamped resonators. We find that static tensile strain decreases dissipation while vibration-induced strain increases dissipation, and the actual dependence of Q on DC gate voltage depends on the competition between these two effects, which is related to the device boundary condition. Such strain dependence of Q is useful for optimizing the resonance linewidth in 2D NEMS resonators toward low-power, ultrasensitive, and frequency-selective devices for sensing and signal processing.

Nanomechanical Resonators: Toward Atomic Scale

“…63,207 Furthermore, the trend of tuning Q using a DC gate voltage is dependent on the device geometry (Figure 8.2g). 208 Increasing the AC drive voltage generally decreases the Q due to the increased vibration amplitude (Figure 8.2d). 208,101 Heterostructures can be used to enhance quality factors in 2D resonators.…”

“…208 Increasing the AC drive voltage generally decreases the Q due to the increased vibration amplitude (Figure 8.2d). 208,101 Heterostructures can be used to enhance quality factors in 2D resonators. For example, resistive loss through Joule heating can be important for NEMS resonators using electrical readout, especially at low temperatures.…”

“…The temperature dependence of the quality factor of MoS 2 resonators has been compared to models from different dissipation mechanisms (Figure c) . The Q dependence on device tension (Figure e) , and DC gate voltage has also been experimentally studied (Figure f). , Furthermore, the trend of tuning Q using a DC gate voltage is dependent on the device geometry (Figure g) . Increasing the AC drive voltage generally decreases the Q due to the increased vibration amplitude (Figure d). , …”

“…(d) Dependence of Q on DC and AC gate voltages, for 2D MoS 2 NEMS resonators. Reprinted in part with permission from ref ( 208 ). Copyright 2022 American Chemical Society.…”

Raman Spectroscopic Probe for Nonlinear MoS2 Nanoelectromechanical Resonators

“…Resonant nanoelectromechanical systems (NEMS) based on two-dimensional (2D) materials have attracted tremendous interest due to their atomic-scale thicknesses, high Young’s moduli, and ultrahigh strain limits. , Graphene NEMS resonators have been explored using detection techniques such as optical interferometry, , frequency mixing detection, , and direct radio frequency (RF) electrical readout. , Beyond graphene, semiconductor NEMS resonators in transition metal dichalcogenides (TMDCs) such as molybdenum disulfide (MoS 2 ) have also been extensively studied with optical interferometry measurements showing thermomechanical resonance frequencies up to 60 MHz in the very high frequency (VHF) band, quality ( Q ) factor up to 1050 at room temperature and 47 000 at cryogenic temperature, a frequency tuning range of 150% using strain, and a broad linear dynamic range up to 110 dB. − As a 2D semiconductor, MoS 2 also has a higher piezoresistive gauge factor than graphene, thus 2D MoS 2 NEMS resonators can exhibit strong electromechanical coupling with the channel conductance not only modulated by the displacement but also by the dynamic strain . Using such electromechanical coupling effects, all-electrical signal transduction of 2D MoS 2 NEMS resonators has been achieved. − …”