Complete determination of crystallographic orientation of ReX2 (X=S, Se) by polarized Raman spectroscopy

Abstract

Polarized Raman spectroscopy on few-layer ReS2 and ReSe2 was carried out to determine the crystallographic orientations. Since monolayer ReX2 (X=S or Se) has a distorted trigonal structure with only an inversion center, there is in-plane anisotropy and the two faces of a monolayer crystal are not equivalent. Since many physical properties vary sensitively depending on the crystallographic orientation, it is important to develop a reliable method to determine the crystal axes of ReX2. By comparing the relative polarization dependences of some representative Raman modes measured with three different excitation laser energies with high-resolution scanning transmission electron microscopy, we established a reliable procedure to determine the all three principal directions of few-layer ReX2 including a way to distinguish the two types of faces: a 2.41-eV laser for ReS2 or a 1.96-eV laser for ReSe2 should be chosen as the excitation source of polarized Raman measurements; then the relative directions of the maximum intensity polarization of the Raman modes at 151 and 212 cm-1 (124 and 161 cm-1) of ReS2 (ReSe2) can be used to determine the face types and the Re-chain direction unambiguously.

22 pages, 4 figures, supplementary information 9 pages

References in corpus (3)

• Uniaxial Strain in Graphene by Raman Spectroscopy: G peak splitting, Gruneisen Parameters and Sample Orientation
• Cleavage Tendency of Anisotropic Two Dimensional Materials: ReX2 (X=S, Se) and WTe2
• Determination of the thickness and orientation of few-layer tungsten ditelluride using polarized Raman spectroscopy

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• Crystallographic Reconstruction Driven Modified Mechanical Properties in Anisotropic Rhenium Disulfides