Direct identification of monolayer rhenium diselenide by an individual diffraction pattern

TL;DR

This paper demonstrates a method to identify monolayer rhenium diselenide using individual electron diffraction patterns, enabling precise characterization of low-symmetry 2D materials.

Contribution

It introduces a novel approach for unambiguously determining monolayer ReSe2 and its orientation through diffraction patterns, applicable to triclinic and monoclinic crystal systems.

Findings

Successful identification of monolayer ReSe2 using diffraction patterns

Validation of layer number with ADF-STEM imaging

Experimental results align with diffraction theory and simulations

Abstract

In the current extensive studies of transition metal dichalcogenides (TMDCs), compared to hexagonal layered materials, like graphene, hBN and MoS2, low symmetry layered 2D crystals showed great potential for applications in anisotropic devices. Rhenium diselenide (ReSe2) has the bulk space group P1 and belongs to triclinic crystal system with a deformed cadmium iodide type structure. Here we unambiguously determined monolayer and its vertical orientation of rhenium diselenide membrane with an individual electron diffraction pattern, which could be applicable to low symmetry crystal systems, including both triclinic and monoclinic lattices, as long as their third unit-cell basis vector is not perpendicular to basal plane. Atomically resolved image from probe corrected annular dark field scanning transmission electron microscope (ADF-STEM) was employed to validate layer number. Finally, experimental results were well explained by kinematical electron diffraction theory and corresponding simulations.