Engineering edge structure and electronic properties of graphene nanoislands by Au intercalation

Abstract

The interfacial interaction between graphene and the underlying substrate can dope Dirac cones and induce electronic effects such as band gaps or spin-polarization. The same interaction also controls the growth morphology and edge atomic structure. Intercalation of metals at the graphene-substrate interface can then be an interesting method to decouple growth from final physical properties, enabling the choice of the most suitable material for each case. With graphene nanostructures, we can further explore the stabilization of different edge structures and the arousal of one dimensional edge states of different nature. In this work, we show by STM how Au intercalation can modify the characteristics of graphene nanoislands grown on Ni. On a Ni(111) surface, the choice of annealing temperature selects either triangular islands with zig-zag edges or hexagonal islands with alternated zigzag and reconstructed zz(57) edges. Gapped spin polarized bands are induced in graphene, leading to spin and edge-dependent electron scattering. After intercalation of Au, graphene nanoislands are found on top of the Au overlayer or embedded in it, possibly lying on different atomic layers. Embedded hexagonal islands now present only zig-zag edges, implying that the intercalated metal can modify the morphological properties of nanoislands. The capability of laterally displacing graphene nanoislands by using the STM tip evidences chemical decoupling from the substrate, while electronic decoupling is evidenced by the characteristic intervalley scattering patterns inside the islands.