Nanomechanical resonators based on atomic layers of tungsten diselenide (WSe2) offer intriguing prospects for enabling novel sensing and signal processing functions. The frequency scaling law of such resonant devices is critical for designing and realizing these high-frequency circuit components. Here, we elucidate the frequency scaling law for WSe2 nanomechanical resonators by studying devices of one-, two-, three-, to more than 100-layer thicknesses and different diameters. We observe resonant responses in both mechanical limits and clear elastic transition in between, revealing intrinsic material properties and devices parameters such as Young’s modulus and pretension. We further demonstrate a broad frequency tuning range (up to 230%) with a high tuning efficiency (up to 23% V–1). Such tuning efficiency is among the highest in resonators based on two-dimensional (2D) layered materials. Our findings can offer important guidelines for designing high-frequency WSe2 resonant devices.

In‐plane anisotropy in 2D rhenium disulfide (ReS2) offers intriguing opportunities for designing future electronic and optical devices, and toward such applications, it is crucial to identify the crystal orientation in such 2D anisotropic materials. Existing spectroscopy or electron microscopy methods for determining the crystalline orientation often require complicated sample preparing procedures and specialized equipment, which could sometimes limit their application. In this work, a dichromatic polarized reflectance method is demonstrated, which can quickly and accurately resolve the crystal orientation (Re–Re chain) in 2D ReS2 crystals with different thicknesses. Furthermore, it can be readily extended to multi‐chromatic schemes to achieve greater measurement capability and can be easily tailored to work for different 2D materials. The method offers a simple and effective approach for studying anisotropy in 2D materials.

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 Ti3C2T 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/Hz1/2, and a fundamental-mode frequency-quality factor product up to f 0 × Q ≈ 6.85 × 109 Hz. By combining experimental results with theoretical calculations, we independently derive the Young’s modulus of 2D Ti3C2T 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.

With the development of multi-polarization in the world, the UN Security Council plays an increasingly important role in maintaining international peace and promoting international cooperation, which has attracted much attention from the academic and industrial circles. However, the current structure of five permanent and ten non-permanent members of the Council does not maximize efficiency and legitimacy, making it more difficult to resolve international conflicts on time. This article first has carried on the extensive search for relevant theories and finishing, and on this basis, using the survey method, literature research, interdisciplinary research method, qualitative analysis method, and other research methods. The goal is to balance the efficiency and the legitimacy of the UNSC, especially improving the council’s legitimacy. This paper draws the following conclusions: 1. Increase the number of seats on the Council by twenty-four (five permanent members, eight four-year renewable seats, and 11 non-permanent members) 2. It is impossible to abolish the veto completely, but permanent members should be urged to reduce the use of the veto through legislation. Given the political conflicts of interest and the complexity of revising the UN Charter, governments of all countries should promote internal negotiations as soon as possible, conduct in-depth dialogue and consultation on core major issues, clarify the principles and methods of reform, and determine practical solutions.

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