The surface science of graphene: Metal interfaces, CVD synthesis, nanoribbons, chemical modifications, and defects

Graphene, a single atomic layer of sp² hybridized carbon, exhibits a zero-band gap with linear band dispersion at the Fermi-level, forming a Dirac-cone at the $K$-points of its Brillouin zone. In this review, we focus on basic materials science issues of this intriguing material. The scope of this work is further narrowed by concentrating on graphene grown at transition metal surfaces, mostly under vacuum conditions, and neglecting other graphene synthesis approaches, namely growth on SiC or by graphene oxide reduction. Thus one large section of this review focuses on metal/graphene interfaces. We summarize recent surface science studies on the structure, interaction, and the growth of graphene on various metals. Metal supported graphene is a recurring theme throughout this review as it provides model-systems for studying adsorption and graphene modifications on well-defined, large area samples, and thus is ideal for employing surface science techniques. Other aspects of graphene are also reviewed. Approaches for creating and characterizing graphene nanostructures, in particular graphene nanoribbons, are discussed. Graphene nanoribbons play an important role for potential electronic applications because the lateral electron confinement in the ribbons opens a band-gap in graphene. Materials issues of nanoribbons, like formation of well-defined edges are introduced. Atomic-scale defect-structures in graphene are another topic. The known defect structures in graphene are categorized and atomic scale characterization of these defects by scanning tunneling microscopy (stocktickerSTM) and high resolution transmission electron microscopy (TEM) is illustrated. Important for applications of graphene is our ability of modifying its properties. Therefore, studies of substitutional doping of graphene with nitrogen or boron, hydrogenation or fluorination of graphene, and the adsorption of molecules with strong electron affinity are included in this review. This review is restricted to a summary of surface science studies on well-ordered systems. Other important graphene research areas such as transport measurements on pure and modified graphene are not included. The goal of this review is to give a concise overview of the materials science of graphene from the surface science perspective.