Electrically Tunable MXene Nanomechanical Resonators Vibrating at Very High Frequencies.

As an emerging class of two-dimensional (2D) layered nanomaterial, MXene exhibits a number of intriguing properties, such as good electrical conductivity and high elastic modulus, and has witnessed continued growth in related device research. However, nanoscale MXene devices which leverage both the intrinsic electrical and mechanical properties of these 2D crystals have not been experimentally studied. Here we demonstrate nanoelectromechanical resonators based on 2D MXene crystals, where Ti 3 C 2 T x drumheads with a wide range of thickness, from more than 50 layers all the way down to a monolayer, exhibit robust nanomechanical vibrations with fundamental-mode frequency f 0 up to >70 MHz in the very high frequency (VHF) band, a displacement noise density down to 52 fm/Hz 1/2 , and a fundamental-mode frequency-quality factor product up to f 0 × Q ≈ 6.85 × 10 9 Hz. By combining experimental results with theoretical calculations, we independently derive the Young's modulus of 2D Ti 3 C 2 T x crystals to be 270-360 GPa, in excellent agreement with nanoindentation measurements, based on which we elucidate frequency scaling pathways toward microwave frequencies. We further demonstrate electrical tuning of resonance frequency in MXene resonators and frequency-shift-based MXene vacuum gauges with responsivity of 736%/Torr and detection range down to 10 -4 Torr. Our study can lead to the design and creation of nanoscale vibratory devices that exploit the intrinsic electrical and mechanical properties in 2D MXene crystals.