Abstract
Van der Waals (vdW) heterostructures consist of isolated atomic planar structures, assembled layer-
by-layer into desired structures in a well-defined sequence. Graphene deposited on hexagonal boron
nitride (h-BN) has been first considered as a testbed system for vdW heterostructures, and many
others have been demonstrated both theoretically and experimentally, revealing many attractive
properties and phenomena. However, much less emphasis has been placed on how graphene actively
affects h-BN properties. Here, we perform local probe measurements on single-layer h-BN grown
over graphene and highlight the manifestation of a proximity effect that significantly affects the
electronic properties of h-BN due to its coupling with the underlying graphene. We find electronic
states originating from the graphene layer and the Cu substrate to be injected into the wide electronic
gap of the h-BN top layer. Such proximity effect is further confirmed in a study of the variation of
h-BN in-gap states with interlayer couplings, elucidated using a combination of topographical/
spectroscopic measurements and first-principles density functional theory calculations. The findings
of this work indicate the potential of mutually engineering electronic properties of the components of
vdW heterostructures.
