High Frequency MoS₂ Nanomechanical Resonators

Abstract

Molybdenum disulfide (MoS2), a layered semiconducting material in transition metal dichalcogenides (TMDCs), as thin as a monolayer (consisting of a hexagonal plane of Mo atoms covalently bonded and sandwiched between two planes of S atoms, in a trigonal prismatic structure), has demonstrated unique properties and strong promises for emerging two-dimensional (2D) nanodevices. Here we report on the demonstration of movable and vibrating MoS2 nanodevices, where MoS2 diaphragms as thin as 6 nm (a stack of 9 monolayers) exhibit fundamental-mode nanomechanical resonances up to f0 ~ 60 MHz in the very high frequency (VHF) band, and frequency-quality (Q) factor products up to f0 × Q ~ 2 × 10(10)Hz, all at room temperature. The experimental results from many devices with a wide range of thicknesses and lateral sizes, in combination with theoretical analysis, quantitatively elucidate the elastic transition regimes in these ultrathin MoS2 nanomechanical resonators. We further delineate a roadmap for scaling MoS2 2D resonators and transducers toward microwave frequencies. This study also opens up possibilities for new classes of vibratory devices to exploit strain- and dynamics-engineered ultrathin semiconducting 2D crystals.

Graphene versus MoS2: A short review

“…For SLMoS 2 , two recent experiments demonstrated the nanomechanical resonant behavior in SLMoS 2 [101] and few-layer MoS 2 [102]. Castellanos-Gomez et al found that the figure of merit, i.e., the frequency-Qfactor product, is f 0 × Q ≈ 2 × 10 9 Hz for SLMoS 2 [101].…”

“…Castellanos-Gomez et al found that the figure of merit, i.e., the frequency-Qfactor product, is f 0 × Q ≈ 2 × 10 9 Hz for SLMoS 2 [101]. Lee et al found that few-layer MoS 2 resonators exhibit a high figure of merit of f 0 ×Q ≈ 2×10 10 Hz [102]. The high Q-factor of SLMoS 2 could be attributed to the energy band gap in the phonon dispersion of SLMoS 2 , which protects the resonant oscillations from being scattered by thermal vibrations [47].…”

Spatial mapping of multimode Brownian motions in high-frequency silicon carbide microdisk resonators

“…The SiCon-SiO 2 technology creates novel centre-anchored circular SiC microdisks featuring a uniform gap defined by the SiO 2 thickness, which is ideal for precision optical interrogation. We have developed an ultrasensitive scanning laser interferometry scheme featuring an B1 mm spot size on device, capable of directly measuring undriven thermal motions of various devices at room temperature, with fm Hz À 1/2 -level displacement sensitivities (see Methods) 31 . In brief, thermodynamic fluctuations agitate a mechanical structure (as dictated by fluctuation-dissipation theorem and equipartition theorem) 32 such that each of the structure's eigenmodes emerges as a thermomechanical resonance in the frequency-domain noise spectrum, with a displacement noise spectral density of…”

“…We have engineered the system to achieve displacement sensitivities at pm Hz À 1/2 to fm Hz À 1/2 levels for devices in various materials and structures 31 , by further advancing the interferometry techniques developed during the last decade [53][54][55][56] . To experimentally determine the displacement sensitivity (resolution, or limit of detection for displacement), we first relate the amplitude of the thermomechanical motion to the measured noise level in the spectrum.…”

In-situ scanning electron microscopy and atomic force microscopy Young's modulus determination of indium oxide microrods for micromechanical resonator applications

“…Q-factors from few tens to 10 4 have been reported in the literature for simple resonant nano and micromechanical systems. 9,28,[30][31][32] This makes In 2 O 3 microrods a very promising material for the fabrication of resonant micromechanical devices such as sensors. Besides, the combination of high quality optical resonances, as reported recently for these In 2 O 3 rods, 17 and the mechanical resonance properties reported here, could offer the possibility to increase their response through the optomechanical coupling, as reported for other systems by Vahala et al 4,5 This recent application field will require for a more accurate measurements of In 2 O 3 mechanical properties, as those reported here.…”