Identifying, Resolving, and Quantifying Anisotropy in ReS2 Nanomechanical Resonators

• Published in: Small (Weinheim an der Bergstrasse, Germany) Germany), 2023-06, Vol.19 (24), p.e2300631-n/a
• Main Authors: Xu, Bo, Zhu, Jiankai, Xiao, Fei, Jiao, Chenyin, Liang, Yachun, Wen, Ting, Wu, Song, Zhang, Zejuan, Lin, Lin, Pei, Shenghai, Jia, Hao, Chen, Ying, Ren, Ziming, Wei, Xueyong, Huang, Wen, Xia, Juan, Wang, Zenghui
• Format: Article
• Language: English
• Subjects: Anisotropy; Crystals; Dynamic response; Mechanical properties; Modal analysis; mode shapes; Modulus of elasticity; nanomechanical resonator; Nanotechnology; Nanotechnology devices; Numerical models; Optical properties; ReS 2; Resonators; Rhenium; Thermodynamic properties
• ISSN: 1613-6810; 1613-6829
• DOI: 10.1002/smll.202300631

As an emerging two‐dimensional semiconductor, rhenium disulfide (ReS2) is renowned for its strong in‐plane anisotropy in electrical, optical, and thermal properties. In contrast to the electrical, optical, optoelectrical, and thermal anisotropies that are extensively studied in ReS2, experimental characterization of mechanical properties has largely remained elusive. Here, it is demonstrated that the dynamic response in ReS2 nanomechanical resonators can be leveraged to unambiguously resolve such disputes. Using anisotropic modal analysis, the parameter space for ReS2 resonators in which mechanical anisotropy is best manifested in resonant responses is determined. By measuring their dynamic response in both spectral and spatial domains using resonant nanomechanical spectromicroscopy, it is clearly shown that ReS2 crystal is mechanically anisotropic. Through fitting numerical models to experimental results, it is quantitatively determined that the in‐plane Young's moduli are 127 and 201 GPa along the two orthogonal mechanical axes. In combination with polarized reflectance measurements, it is shown that the mechanical soft axis aligns with the Re‐Re chain in the ReS2 crystal. These results demonstrate that dynamic responses in nanomechanical devices can offer important insights into intrinsic properties in 2D crystals and provide design guidelines for future nanodevices with anisotropic resonant responses. Dynamic response in ReS2 nanomechanical resonators is leveraged to unambiguously resolve the mechanical anisotropy in 2D ReS2 crystal. Using resonant nanomechanical spectromicroscopy, the in‐plane Young's moduli of 2D ReS2 are found to be 127 and 201 GPa along the two orthogonal mechanical axes, with the mechanical soft axis aligns with the Re‐Re chain in the ReS2 crystal.