Raman Signatures of Surface and Interface Effects in Two-Dimensional Layered Materials: Theoretical Insights

Abstract

Raman spectroscopy is a non-destructive and versatile method of identifying materials through their Raman “fingerprints”. To this end, first principles calculations are essential to predict the Raman spectra of different materials. First principles calculations, together with parametrized models, can also give atomic scale insights into the origins of Raman shifts and Raman intensities, thus providing a guide to experiments. In this chapter, we will discuss some insights we have gained through our theoretical modeling of Raman spectra in 2D materials and their heterostructures. In particular, we show that surface and interface effects in 2D materials can give rise to observable changes in the Raman spectra. For example, we show that the formation of a surface in the 2D material leads to larger interatomic force constants at the surface, which results in experimentally observed anomalous frequency trends of the \\( {E}_{2g}^1 \\) mode in MoS2, and the \\( {E}_{2g}^1 \\) and \\( {B}_{2g}^1 \\) modes in WSe2. We further show that the Raman intensities of the interlayer shear modes in 2D layered materials can be simply predicted based on the stacking sequence.