Identifying the Crystalline Orientation of Mechanically Exfoliated Anisotropic Layered Materials through Their Morphologies

The unique orientation‐dependent properties of in‐plane anisotropic 2D materials allow for designing novel electronic and optoelectronic devices that are hardly realized in isotropic materials. All such anisotropic studies and relevant applications require identification of the crystal orientation in advance. Although many methods have been developed to characterize the crystal orientation such as polarization‐resolved optical techniques, they usually suffer from the complex and time‐consuming process. Here, a convenient yet effective method is reported that the crystal orientation of mechanically exfoliated anisotropic 2D materials can be determined just through their morphologies. Using GeSe as an example, it is shown that the exfoliated flakes from bulk crystals naturally form long‐straight edges perpendicular to the direction with the lowest Young's modulus stemming from its in‐plane mechanical anisotropy, thus enabling the crystal orientation identification through the cleaved edges. This proposed method based on the facilely obtained anisotropic mechanical properties provides a fast, convenient, and non‐destructive approach for crystal orientation identification. The exfoliated flakes from anisotropic 2D bulk crystals naturally form long‐straight edges perpendicular to the direction with the lowest Young's modulus stemming from the in‐plane mechanical anisotropy, thus enabling the crystal orientation identification through the cleaved edges.