Anisotropic imaging for the highly efficient crystal orientation determination of two-dimensional materials

The remarkable in-plane anisotropy of anisotropic two-dimensional materials (ATDMs), such as black phosphorus (BP), ReS2, and ReSe2, provides a new degree of freedom for the design of novel orientation-based optical and electronic devices. Therefore, visualization of the anisotropy and determination of the crystal orientation (CO) of ATDMs is of fundamental importance. Herein, using a setup equipped with a non-polarized beam splitter, a four-dimensional anisotropic imaging technique (AIT) based on the anisotropic optical response of ATDMs was proposed, by which the COs of many different ATDMs on the same substrate could be efficiently (<30 s), easily and simultaneously discerned. These key features are rather essential for the later study of the properties and performances of ATDMs and their assembled van der Waals heterostructures. Moreover, the AIT could be used for observing the morphology and optical anisotropy of low-dimensional materials (ATDMs, such as silver nanowires, graphene and so on) with higher resolution and sensitivity than traditional optical microscopy. Via the AIT, the flexible modulation of optical and photothermal anisotropy could be achieved by fabricating orientation-controlled BP/ReS2 heterojunctions. Therefore, the AIT would significantly facilitate the further development of novel electronic, photonic and optoelectronic devices based on ATDMs.