Quantifying electronic band interactions in van der Waals materials using angle-resolved reflected-electron spectroscopy

Abstract

High electron mobility is one of graphene's key properties, exploited for applications and fundamental research alike. Highest mobility values are found in heterostructures of graphene and hexagonal boron nitride, which consequently are widely used. However, surprisingly little is known about the interaction between the electronic states of these layered systems. Rather pragmatically, it is assumed that these do not couple significantly. Here we study the unoccupied band structure of graphite, boron nitride and their heterostructures using angle-resolved reflected-electron spectroscopy. We demonstrate that graphene and boron nitride bands do not interact over a wide energy range, despite their very similar dispersions. The method we use can be generally applied to study interactions in van der Waals systems, that is, artificial stacks of layered materials. With this we can quantitatively understand the ‘chemistry of layers' by which novel materials are created via electronic coupling between the layers they are composed of.

Intrinsic stacking domains in graphene on silicon carbide: A pathway for intercalation

“…1f,i). The tilted incidence yields an in-plane k-vector, which influences the reflectivity spectrum 32,37 . This is taken into account in our calculations, but needs to be considered when comparing to other LEEM and LEED data.…”

Nonuniversal Transverse Electron Mean Free Path through Few-layer Graphene

“…Figure 1(b) shows the results of such an Angle-Resolved Reflected Electron Spectroscopy (ARRES) experiment on bulk graphite reproduced from Ref. [7]. Reflectivity is plotted as function of energy and in-plane momentum k .…”

“…For other, more complex materials this simple toy model does not yield valid predictions. Already for other layered crystals such as hexagonal boron nitride [7] or transition metal dichalcogenides [31,32] only the full ab initio theory can describe the reflectivity spectra correctly. This indicates that the MFPs in these materials are also strongly affected by the band structure effects discussed here.…”

Measuring the Local Twist Angle and Layer Arrangement in Van der Waals Heterostructures

“…The quality and properties of these heterostacks, however, are not only influenced by defects, but also critically depend on other factors such as the substrate, the crystallographic polytype of the layers, and their relative orientation with respect to each other. In particular, atomically flat substrates that do not perturb the electronic structure of the VdW stacks are desired, and consequently hexagonal boron nitride is widely used . The polytype of the different flakes, that is, the different crystallographic configurations of the layers with respect to each other, determines many of the properties of VdW heterostacks.…”