Effects of γ-ray radiation on two-dimensional molybdenum disulfide (MoS2) nanomechanical resonators

Abstract

We report on experimental investigation and analysis of γ-ray radiation effects on two-dimensional molybdenum disulfide (MoS2) drumhead nanomechanical resonators vibrating at megahertz frequencies. Given calibrated dosages of γ-ray radiation of ∼5000 photons with energy at 662 keV, upon exposure over 24 or 12 h, all the MoS2 resonators exhibit ∼0.5–2.1% resonance frequency upshifts due to the ionizing γ-ray induced charges and their interactions. The devices show γ-ray photon responsivity of ∼30–82 Hz/photon, with an intrinsic γ-ray sensitivity (limit of detection) estimated to approach ∼0.02–0.05 photon. After exposure expires, resonance frequencies return to an ordinary tendency where the frequency variations are dominated by long-term drift. These γ-ray radiation induced frequency shifts are distinctive from those due to pressure variation or surface adsorption mechanisms. The measurements and analyses show that MoS2 resonators are robust yet sensitive to very low dosage γ-ray, demonstrating a potential for ultrasensitive detection and early alarm of radiation in the very low dosage regime.

Hexagonal boron nitride nanomechanical resonators with spatially visualized motion

“…4), semiconducting MoS 2 (Refs. 3,5-7), and black phosphorus 8,9 , which opens a wide spectrum of emerging applications, such as sensing 10,11 and signal processing with ultralow power and broad tunability 12,13 . Although atomic layer crystals with bandgaps ranging from 0 to 2 eV have been studied in earlier explorations (such as 0 eV graphene 1,2,12 , 0.3-1.5 eV black phosphorus 8,9 , 1.2-1.9 eV MoS 2 (Refs.…”

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

“…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].…”

“…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.…”