Linear Dichroism and Nondestructive Crystalline Identification of Anisotropic Semimetal Few-Layer MoTe₂

Semimetal 1T′ MoTe₂ crystals have attracted tremendous attention owing to their anisotropic optical properties, Weyl semimetal, phase transition, and so on. However, the complex refractive indices (n-ik) of the anisotropic semimetal 1T′ MoTe₂ still are not revealed yet, which is important to applications such as polarized wide spectrum detectors, polarized surface plasmonics, and nonlinear optics. Here, the linear dichroism of as-grown trilayer 1T′ MoTe₂ single crystals is investigated. Trilayer 1T′ MoTe₂ shows obvious anisotropic optical absorption due to the intraband transition of d_z ² orbits for Mo atoms and p_x orbits for Te atoms. The anisotropic complex refractive indices of few-layer 1T′ MoTe₂ are experimentally obtained for the first time by using the Pinier equation analysis. Based on the linear dichroism of 1T′ MoTe₂, angle-resolved polarized optical microscopy is developed to visualize the grain boundary and identify the crystal orientation of 1T′ MoTe₂ crystals, which is also an excellent tool toward the investigation of the optical absorption properties in the visible range for anisotropic 2D transition metal chalcogenides. This work provides a universal and nondestructive method to identify the crystal orientation of anisotropic 2D materials, which opens up an opportunity to investigate the optical application of anisotropic semimetal 2D materials.