Engineering edge structure and electronic properties of graphene nanoislands

Abstract

The possible applications of graphene at the nanoscale require a precise control of its structural and electronic properties. The interfacial interaction between graphene and the underlying substrate can control the morphology and edge atomic structure of the nanostructure, dope the Dirac cones and induce band gaps or spin-polarization. In this work, we show by using Scanning Tunneling Microscopy and Spectroscopy how this interfacial interaction can be effectively tuned by metal intercalation and used to engineer the properties of graphene nanoislands (GNI). On the catalytic Ni(111) where we grow the GNIs, the strong interaction determines favorable stacking configurations that lead to a selection of shape and edge structures (Fig.1a). The Dirac cone, strongly affected by the substrate, turns into gapped spin-polarized graphene bands. After intercalation of Au, GNIs are found on top of the Au overlayer or embedded in it (Fig. 1b). The effective chemical and electronic decoupling is evidenced by tip-induced displacement of the islands and by electron interference patterns that are related to the semimetallic Dirac cone. Interestingly, spectroscopic measurements reveal split states localized at the edge, compatible with the onedimensional spin-split states predicted for zigzag edges in free-standing graphene nanostructures.