First Principle Study for Optical Properties of TMDC/Graphene Heterostructures

The transition-metal dichalcogenide (TMDC) in the family of $\mathrm{MX}_2$ ($\mathrm{M}=\mathrm{Mo},\mathrm{W}$; $\mathrm{X}=\mathrm{S},\mathrm{Se}$) and the graphene monolayer are atomically thin semiconductors and semimetal, respectively. The monolayer $\mathrm{MX}_2$ have been discovered as a new class of semiconductors for electronics and optoelectronics applications. Because of the hexagonal lattice structure of both the materials, $\mathrm{MX}_2$ and graphene are often combined with each other to make van der Waals heterostructures. Here, the $\mathrm{MX}_2/\mathrm{Gr}$ heterostructures are investigated theoretically based on the Density Functional Theory (DFT). The electronic structure and the optical properties of four different $\mathrm{MX}_2/\mathrm{Gr}$ heterostructures are computed. We systematically compare these $\mathrm{MX}_2/\mathrm{Gr}$ heterostructures for their complex permittivity, absorption coefficient, reflectivity and refractive index.