Optical Absorption and Reflectivity of Four 2D Materials: MoS2, MoP2, NbS2, and NbP2

E Garcés,L F Magaña,O Salas

doi:10.3389/fmats.2021.720768

Abstract

We calculated the energy band structure and the optical absorption and reflectivity for each of the ultrathin 2D hexagonal materials MoS2, MoP2, NbS2, and NbP2. Our simulations included density functional theory, generalized gradient approximation (GGA), and the Quantum Espresso code. Other researchers already synthesized the first three materials. We obtained that NbP2 should be another hexagonal 2D material. In all cases in the infrared and visible ranges, the absorptions present much larger concerning graphene. However, the absorptions for MoP2, NbP2, and NbS2, are far more prominent concerning MoS2. In the ultraviolet region, the absorptions are like each other and differ from graphene. In all cases, the reflectivities are similar to each other and vary from graphene.

Highlights

Graphite is a layered material with strong bonds between atoms of the same layer and a much weaker interaction between particles of different layers, basically Van der Waals type interactions among layers
The experimental obtention of a graphite monolayer was only theoretical speculation since 1968 when Mermin (1968) proved that one and twodimensional materials could within the harmonic approximation not exist naturally
We performed our simulations with density functional theory to optimize the geometry of graphene and four ultra-thin 2D materials for comparison

Summary

Introduction

Graphite is a layered material with strong bonds between atoms of the same layer and a much weaker interaction between particles of different layers, basically Van der Waals type interactions among layers. In 2004 Novoselov and Geim isolated the first 2D material, graphene (Novoselov et al, 2004). They deserved the Nobel Prize in 2010. We must say that the careful investigation of graphene shows the presence of ruffles, ripples (Fasolino et al, 2007; Meyer et al, 2007) that make graphene strictly a 3D material. In this way, the theoretical theorem about 2D materials holds still

Methods

Results

Conclusion