Dielectric properties of graphene/ MoS2 heterostructures from ab initio calculations and electron energy-loss experiments

Abstract

High-energy electronic excitations of graphene and MoS 2 heterostructures are investigated by momentumresolved electron energy-loss spectroscopy in the range of 1 to 35 eV. The interplay of excitations on different sheets is understood in terms of long-range Coulomb interactions and is simulated using a combination of ab initio and dielectric model calculations. In particular, the layered electron-gas model is extended to thick layers by including the spatial dependence of the dielectric response in the direction perpendicular to the sheets. We apply this model to the case of graphene/MoS 2 /graphene heterostructures and discuss the possibility of extracting the dielectric properties of an encapsulated monolayer from measurements of the entire stack.

Plasmons in MoS2 studied via experimental and theoretical correlation of energy loss spectra

“…It is possible that the peak at 14 eV in their spectra which they described as having plasmonic character could have been indirect transitions due to their large convergence and collection angles similar to this work. Mohn et al [44] conducted similar momentum resolved measurements on MoS2 in the Γ → M direction.…”

Compton profile of few-layer graphene investigated by electron energy-loss spectroscopy

“…In general, understanding the many fascinating properties of graphene requires a detailed knowledge of its electronic structure. Although sufficient work is available regarding the structural, electronic and optical properties of graphene, the experiment and theoretical electron momentum density of graphene still remains unexplored 16–21 .…”

Electron energy loss spectroscopy of thin slabs with supercell calculations

“…When dealing with 1D or 2D isolated objects, one loses the periodicity, in at least one direction. A way to treat this situation is to use a mixed-space formalism: for example in the 2D case, the reciprocal space in the plane and the real space out-of-plane (z) 11,13,16,17 . It is nevertheless computationally very demanding, since it requires small integration steps along the z axis 1,18 . The remaining periodicity justies the use of 3Dreciprocal space codes.…”