Structure-property relationship of epitaxial Van der Waals interface

Revealing and exploiting novel electronic properties in atomically thin 2D materials such as graphene and transition metal dichalcogenides have progressed dramatically in recent years. A challenge is to correlate structure and electronic properties, especially in heterostructures. Here, we focus on a prototypical Van der Waals hetero-interface of graphene and monolayer WSe₂, where both are prepared epitaxially on a SiC substrate. We present angle-resolved photoelectron spectroscopy (ARPES) and synchrotron X-ray diffraction studies, which show that WSe₂ is compressed by exactly the amount needed to realize a perfect epitaxial matching to the graphene lattice. Combined APRES and XPS directly reveal electron transfer from graphene to WSe₂.