Ultrawide Frequency Tuning of Atomic Layer van der Waals Heterostructure Electromechanical Resonators

Abstract

We report on the experimental demonstration of atomically thin molybdenum disulfide (MoS2)graphene van der Waals (vdW) heterostructure nanoelectromechanical resonators with ultrawide frequency tuning. With direct electrostatic gate tuning, these vdW resonators exhibit exceptional tunability, in general, Δf/f0 >200%, for continuously tuning the same device and the same mode (e.g., from ~23 to ~107MHz), up to Δf/f0370%, the largest fractional tuning range in such resonators to date. This remarkable electromechanical resonance tuning is investigated by two different analytical models and finite element simulations. Further, we carefully perform clear control experiments and simulations to elucidate the difference in frequency tuning between heterostructure and single-material resonators. At a given initial strain level, the tuning range depends on the two-dimensional (2D) Young's moduli of the constitutive crystals; devices built on materials with lower 2D moduli show wider tuning ranges. This study exemplifies that vdW heterostructure resonators can retain unconventionally broad, continuous tuning, which is promising for voltage-controlled, tunable nanosystems.

Nanomechanical Resonators: Toward Atomic Scale

“…In one example, the frequency of a MoS2/graphene heterostructure could be tuned up to 370% with a gate voltage (Figure 7.4g). 179 In other examples, 180,181 the resonance frequencies of MoS2 and graphene resonators have been tuned by -32-temperature, and the direction of frequency tuning depends on the device structure and thermal expansion coefficient of the materials. A thermal hysteresis effect has also been exploited to realize frequency-reconfigurable resonators (Figure 7.4d).…”

Frequency Scaling, Elastic Transition, and Broad-Range Frequency Tuning in WSe2 Nanomechanical Resonators

“…Figure shows the experimental results for electrically driven, optothermally driven, and thermomechanical resonances of this device. The NEMS resonator exhibits clear and consistent gate tuning of frequency under all measurement schemes and shows an excellent tuning range Δ f/f 0 reaching 230% (from 2.78 to 9.21 MHz for the fundamental mode), comparable to the best performance found in 2D NEMS resonators ,− (see Table S2 for details), far exceeding those found in NEMS resonators based on convensional semiconductors such as Si and GaAs (e.g., less than 10%). − Furthermore, such broad tuning is achieved with just 10 V of gate voltage, suggesting a very high gate tuning efficiency of device tension and thus resonance frequency. Here, we use a very simple metric (Δ f/f 0 ) / Δ V g (relative frequency shift per volt) to benchmark such tuning efficiency across different 2D resonators.…”

Dynamics of Interfacial Bubble Controls Adhesion Mechanics in Van der Waals Heterostructure

“…Such large tuning of resonance frequency has been recently reported in clean MoS 2 /graphene heterostruc-ture as well. 18 We see two strong modes in drums D1 and D2, and only one in drum D3 in the measurement window. Though both the modes in D1 and the upper mode in D2 show usual gate dispersion, 4 some unusual features show up in the lowest mode of D2 and D3.…”

“…Mechanical properties of 2D material interfaces have been studied using NEMS devices, − STEM imaging, , AFM-based techniques, blister tests, , use of stochastic and defect nucleated bubbles. , These experiments provide important information about the interface and its adhesion properties at the nanoscale; however, they are quasi-static in nature. Combining NEMS and vdWH allows probing dynamic properties of interfacial interaction.…”