Direct observation of interlayer hybridization and Dirac relativistic carriers in graphene/MoS2 van der Waals heterostructures.

Artificial heterostructures assembled from van der Waals materials promise to combine materials without the traditional restrictions in heterostructure-growth such as lattice matching conditions and atom interdiffusion. Simple stacking of van der Waals materials with diverse properties would thus enable the fabrication of novel materials or device structures with atomically precise interfaces. Because covalent bonding in these layered materials is limited to molecular planes and the interaction between planes are very weak, only small changes in the electronic structure are expected by stacking these materials on top of each other. Here we prepare interfaces between CVD-grown graphene and MoS2 and report the direct measurement of the electronic structure of such a van der Waals heterostructure by angle-resolved photoemission spectroscopy. While the Dirac cone of graphene remains intact and no significant charge transfer doping is detected, we observe formation of band gaps in the π-band of graphene, away from the Fermi-level, due to hybridization with states from the MoS2 substrate.