Karl Franzens University Graz
Graz University of Technology
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Karl Franzens University Graz | Graz University of Technology | |
Epitaxial graphene on Ir(111): Growth, electronic structure and active template Through pyrolysis of hydrocarbons on noble metal surfaces monolayer graphite – graphene – is readily formed. On Ir(111) graphene of exceptional quality grows. Using scanning tunneling microscopy (STM) and low energy electron microscopy (LEEM) we investigate the temperature dependent growth and the nature of point and line defects in the graphene layer. We identify heptagon-pentagon pairs of carbon atom rings to accommodate for slight misalignments of graphene domains and wrinkles in the graphene layer for the mismatch in thermal expansion of graphene and Ir. Angle resolved photo emission finds graphene on Ir(111) to be only marginally doped and to display the characteristic Dirac cone at the K-point of the graphene Brillouin zone. The moiré resulting from the incommensurate epitaxy of graphene on Ir(111) gives rise to a large graphene supercell. In the graphene electronic structure it is reflected in the opening of minigaps at the boundaries of the induced mini-Brillouin zone. The graphene moiré is an active template allowing one to grow a lattice of Ir clusters, spatially and thermally stable below 500 K. Based on STM and density functional theory calculations it is proposed that at geometrically defined locations within the supercell the graphene rehybridizes form sp2 graphitelike to sp3 diamondlike bonding in between the substrate and the cluster deposit. This binding mechanism is likely to apply also to other substrate deposit combination, with ensuing potential applications in electrochemistry, catalysis or data storage. For the graphene moiré on Ir(111) we show for example that ordered cluster lattices of Au, Fe, Pt, Re and W may be grown, either directly or by seeding with Ir. |