First-Principles Study of the Optical Properties of TMDC/Graphene Heterostructures

Abstract

The transition-metal dichalcogenide (TMDC) in the family of MX2 (M=Mo,W; X=S,Se) and the graphene (Gr) monolayer are an atomically thin semiconductor and a semimetal, respectively. The monolayer MX2 has been discovered as a new class of semiconductors for electronics and optoelectronics applications. Because of the hexagonal lattice structure of both materials, MX2 and Gr are often combined with each other to generate van der Waals heterostructures. Here, the MX2/Gr heterostructures are investigated theoretically based on density functional theory (DFT). The electronic structure and the optical properties of four different MX2/Gr heterostructures are computed. We systematically compare these MX2/Gr heterostructures for their complex permittivity, absorption coefficient, reflectivity and refractive index.

Sandwich heterostructure of transition metal dichalcogenide/graphene as tunable lateral reflection shifter

“…It is found that, due to van derWaals interactions, the Dirac point in MX2/Gr hybrids opens a small gap that is minimum for WSe2/Gr. The lattice mismatch ratio of WSe2/Gr is also reported to be the smallest one at 0.01% 49 …”

“…In the MoS2/graphene heterostructure, the electron transfer from MoS2 to graphene is observed, whereas in the WSe2/graphene heterostructure, the electron transfer from graphene to WSe2 is observed. The interlayer process can also be modulated by laser intensity, which enables photo-induced doping on graphene and optically tunable electrical characteristics of graphene 49 . Meanwhile, stacking of MoS2 on graphene usually leads to a much larger shift of the graphene G band, compared with the case of graphene on MoS2 39 .…”

“…The lattice mismatch ratio of WSe2/Gr is also reported to be the smallest one at 0.01%. 49 The effect of polarization of light on spatial reflection shift of the heterostructure is shown in Fig. 10 in the Appendix.…”

“…The interlayer process can also be modulated by laser intensity, which enables photo-induced doping on graphene and optically tunable electrical characteristics of graphene. 49 Meanwhile, stacking of MoS 2 on graphene usually leads to a much larger shift of the graphene G band, compared with the case of graphene on MoS 2 . 39 The possible reason for this is that graphene becomes more sensitive when it is in contact with different bottom and top dielectric environments.…”

Effect of Introducing Defects and Doping on Different Properties of Monolayer MoS2

“…The refractive index effects are dominated by the real part of dielectric function, [ 34 ] which is observed by comparing the plots of dielectric function, as shown in Figure 5a–f, with the plots of refractive index (Figure 7a–f). The refractive index plot shows a similar behavior with the increase of photon energy as that of dielectric constant.…”