Strain-dependent damping in nanomechanical resonators from thin MoS2 crystals

Abstract

We investigate the effect of mechanical strain on the dynamics of thin MoS 2 nanodrum resonators.Using a piezoelectric crystal, compressive and tensile biaxial strain is induced in initially flat and buckled devices. In the flat device, we observe a remarkable strain-dependence of the resonance line width, while the change in the resonance frequency is relatively small. In the buckled device, the strain-dependence of the damping is less pronounced, and a clear hysteresis is observed. The experiment suggests that geometric imperfections, such as microscopic wrinkles, could play a role in the strong dissipation observed in nanoresonators fabricated from 2-D materials.

The Effect of Viscous Air Damping on an Optically Actuated Multilayer MoS2 Nanomechanical Resonator Using Fabry-Perot Interference

“…Referring to Figure 4, to detect the resonance of the MoS 2 drum, we used an optical fiber F-P interferometric method rather than the free-space optical actuation one described previously [7,9,16,17,18,19]. Resonator motion was actuated using a 1550.12-nm amplitude-modulated distributed feedback (DFB) laser S (10 dBm output power) that excited motion through photothermal expansion and contraction of the MoS 2 diaphragm via an electro optic modulator (EOM) with power amplification.…”

“…Furthermore, ultralow areal mass density of 3.3 fg/μm 2 , high elastic modulus (~0.3 TPa), and an exceptional strain limit of 10%~12% [14] make it an attractive alternative to graphene, which typically has higher energy dissipation [15], especially in air damping due to a smaller thickness per unit layer and lower mass density [7]. For these reasons, much effort has been made to characterize the resonance behaviors of NEMS devices made of single-layer, few-layer, or multilayer MoS 2 films in a vacuum chamber using electrical or optical excitation at room temperature [16,17,18,19]. Lee et al reported on the demonstration of MoS 2 nanodevices, where MoS 2 diaphragms as thin as 6 nm exhibited fundamental-mode nanomechanical resonances up to ~60 MHz in the very high frequency band, and frequency- Q factor products up to ~2 × 10 10 Hz [16].…”

“…Andres et al fabricated suspended single-layer MoS 2 resonators, which behaved with resonance frequencies in between 10 and 30 MHz and Q factors in between 16 and 109 [17]. Then, Kramer et al experimentally studied the effect of mechanical strain on the dynamics of thin 15-nm-thick MoS 2 nanodrum resonators with a diameter of 5 μm by using a piezoelectric bender to introduce strain [18]. Recently, Lee et al further investigated γ-ray radiation effects on MoS 2 nanodrum resonators with diameters of 5–6 μm by using optical interferometric resonance readout, which vibrates at megahertz frequencies [19].…”

“…However, these approaches typically involve experiments where MoS 2 flakes in adhesive contact with a substrate are mechanically exfoliated by well-controlled forces, and the motions of these resonators are detected using an optical interferometer in vacuum pressure [15,16,17,18,19]. In fact, air damping is an important dissipation mechanism when nanomechanical resonators are operated in a moderate vacuum or near ambient, and resonance characteristics in air are completely different from those in a vacuum chamber [6].…”

“…Hence, in this paper, from the viewpoint of MoS 2 device application instead of the aforementioned sample analysis, we fabricated a simple and miniature optical fiber Fabry-Perot (F-P) resonator with MoS 2 diaphragm to study the effect of viscous air damping on the F-P resonator in consideration of temperature changes, which contributes to the sensitive structural improvement and packaging design of F-P resonators. Moreover, we reported on experimental measurement of resonance behaviors of a chemically vapor deposited (CVD) MoS 2 diaphragm in air damping, which was suspendedly adhered to a zirconia (ZrO 2 ) ferrule endface with a diameter of 125 μm, much larger than several microns in previously reported resonators [7,8,9,10,15,16,17,18,19]. Then, an F-P cavity made of the transferred MoS 2 diaphragm and a fiber end was easily formed to offer photothermal excitation and motion detection by using a simple F-P interference scheme rather than the complicated free-space optical actuation scheme mentioned above.…”