Two-dimensional (2D) materials exhibit special physical and chemical properties due to their atomically ultra-thin structure. However, making two-dimensional materials composed of single-element metal atoms remains challenging.

Recently, academician Zhang Ze of Zhejiang University and researcher Wang Jiangwei's research group, together with professor Ting Zhu of Georgia University of Technology and researcher Du Kui of Institute of Metals of Chinese Academy of Sciences, reported a technology for processing gold thin films and preparing independent two-dimensional gold (Au) films through in-situ transmission electron microscopy. Under the action of in-plane tensile strain, a large area of thinning deformation is formed in the local area of the Au film, thus forming an independent two-dimensional structure surrounded by the Au film substrate. The two-dimensional film is monatomic thick with a simple hexagonal lattice forming an atomically pointed interface with the face-centered cubic lattice of the film matrix. The diffusion and transport of surface atoms and the dynamic evolution of interface dislocations play an important role in the formation of two-dimensional Au films during mechanical thinning. These results demonstrate a top-down approach to produce freestanding 2D films and provide a feasible scheme for mechanical thinning of metal films to a single atomic layer thickness. Relevant research results are published in ACS Nano as "Free-Standing Two-Dimensional Gold Membranes Produced by Extreme Mechanical Thinning.

Original Link: https://dx.doi.org/10.1021/acsnano.0c06697

Figure: Experimental Method

Researchers Use PicoFemto®The experimental environment of mechanical thinning of gold thin film was built by in situ TEM-STM of electrical sample rod. The gold rod is fixed on the fixed end and the three-dimensional manipulation end of the sample rod respectively, and welding is realized by applying voltage after contact. Then, the sample rod is gradually stretched out of the gold two-dimensional structure by mechanical loading with sub-nanometer precision.

Figure: Electron Microscope Characterization Figure

Figure: PicoFemto used in this study®TEM-STM sample rod in situ