Observation of anisotropic interlayer Raman modes in few-layer ReS2

TL;DR

This study investigates the layer-dependent Raman modes of ReS₂, revealing anisotropic interlayer vibrations and their polarization dependence, which enhances understanding of its unique in-plane anisotropic properties.

Contribution

It provides the first detailed layer-dependent Raman analysis of ReS₂, highlighting anisotropic interlayer modes and their polarization behavior.

Findings

Layer breathing and shear modes are identified across different layer numbers.

Polarization dependence reveals in-plane anisotropy in shear modes.

An energetic shift in shear mode indicates anisotropic shear modulus.

Abstract

ReS$_2$ has recently emerged as a new member in the rapidly growing family of two-dimensional materials. Unlike MoS$_2$ or WSe$_2$, the optical and electrical properties of ReS$_2$ are not isotropic due to the reduced symmetry of the crystal. Here, we present layer-dependent Raman measurements of ReS$_2$ samples ranging from monolayers to ten layers in the ultralow frequency regime. We observe layer breathing and shear modes which allow for easy assignment of the number of layers. Polarization-dependent measurements give further insight into the crystal structure and reveal an energetic shift of the shear mode which stems from the in-plane anisotropy of the shear modulus in this material.