Zhu Qi, Hong Youran, Cao Guang, Zhang Yin, Zhang Xiaohan, Du Kui, Zhang Ze, Zhu Ting, Wang Jiangwei
Center of Electron Microscopy and State Key Laboratory of Silicon Materials, School of Materials Science and Engineering, Zhejiang University, Hangzhou 310027, P. R. China.
Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, United States.
ACS Nano. 2020 Dec 22;14(12):17091-17099. doi: 10.1021/acsnano.0c06697. Epub 2020 Nov 5.
Two-dimensional (2D) materials exhibit exceptional physical and chemical properties owing to their atomically thin structures. However, it remains challenging to produce 2D materials consisting of pure monoelemental metallic atoms. Here free-standing 2D gold (Au) membranes were prepared transmission electron microscopy straining of Au films. The applied in-plane tensile strain induces an extensive amount of out-of-plane thinning deformation in a local region of an Au thin film, resulting in the nucleation and growth of a free-standing 2D Au membrane surrounded by its film matrix. This 2D membrane is shown to be one atom thick with a simple-hexagonal lattice, which forms an atomically sharp interface with the face-centered cubic lattice of the film matrix. Diffusive transport of surface atoms, in conjunction with the dynamic evolution of interface dislocations, plays important roles in the formation of 2D Au membranes during the mechanical thinning process. These results demonstrate a top-down approach to produce free-standing 2D membranes and provide a general understanding on extreme mechanical thinning of metallic films down to the single-atom-thick limit.
二维（2D）材料因其原子级薄的结构而展现出卓越的物理和化学性质。然而，制备由纯单元素金属原子构成的二维材料仍然具有挑战性。在此，通过对金（Au）薄膜进行透射电子显微镜拉伸，制备出了独立的二维金膜。施加的面内拉伸应变在金薄膜的局部区域引发大量面外变薄变形，导致在其薄膜基体包围下形成并生长出独立的二维金膜。该二维膜被证明为单原子厚度，具有简单六方晶格，与薄膜基体的面心立方晶格形成原子级尖锐界面。表面原子的扩散传输，连同界面位错的动态演化，在机械变薄过程中二维金膜的形成中发挥着重要作用。这些结果展示了一种制备独立二维膜的自上而下方法，并为金属薄膜直至单原子厚度极限的极端机械变薄提供了一般性认识。
