In order to study mechanical, electrical and optical properties of a material, it is necessary to determine its crystallographic orientations. However, because stretching and bending deformation can lead to crystal lattice symmetry breaking, these orientations must be studied in a nondestructive way. New research demonstrates the possibility of using transverse shear microscopy (TSM) for nondestructive crystallographic orientation imaging to characterize the shear properties of two-dimensional crystals.
TSM is an application of atomic force microscopy (AFM) in which the AFM tip scans a material in the direction parallel to the cantilever. This results in a puckering of the material and twisting of the cantilever proportional to the shear force of the material.
To study shear deformation in crystal lattices, Xu et al. applied TSM techniques on a star-shaped monolayer molybdenum disulfide flake and found anisotropic deformations that depend on the crystallographic orientation of the material. This test verifies the applicability of TSM in investigating the shear properties of two-dimensional flexible materials, and the results are confirmed by density functional theory calculations.
“Our research is promising to popularize TSM as a universal technique for nondestructive determination of the crystallographic orientations of flexible two-dimensional atomic crystals,” said author Zhihai Cheng. “TSM is competitive in cases where other techniques fail.”
The authors hope to expand on their research by applying their TSM method to different types of two-dimensional materials to study more complicated physical systems. They also have plans to further enhance TSM sensitivity.
Source: “Shear anisotropy-driven crystallographic orientation imaging in flexible hexagonal two-dimensional atomic crystals,” by Kunqi Xu, Yuhao Pan, Shili Ye, Le Lei, Sabir Hussain, Qianmin Wang, Zhiyong Yang, Xinmeng Liu, Wei Ji, Rui Xu, and Zhihai Cheng, Applied Physics Letters (2019). The article can be accessed at https://doi.org/10.1063/1.5096418.