High Frequency MoS<sub>2</sub> Nanomechanical Resonators

Molybdenum disulfide (MoS<sub>2</sub>), 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 MoS<sub>2</sub> nanodevices, where MoS<sub>2</sub> diaphragms as thin as 6 nm (a stack of 9 monolayers) exhibit fundamental-mode nanomechanical resonances up to <i>f</i><sub>0</sub> ∼ 60 MHz in the very high frequency (VHF) band, and frequency-quality (<i>Q</i>) factor products up to <i>f</i><sub>0</sub> × <i>Q</i> ∼ 2 × 10<sup>10</sup>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 MoS<sub>2</sub> nanomechanical resonators. We further delineate a roadmap for scaling MoS<sub>2</sub> 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.