Epitaxial graphene on metal surfaces

Epitaxial graphene can be grown by catalytic decomposition of hydrocarbons on Ir(111). Scanning tunneling microscopy reveals that C/Ir(111) has a high degree of structural quality (¿m-sized domains, coherent overgrowth of surface defects). The system is characterized by weak metal-graphene bonding and shows a pronounced moire¿ superstructure. The growth process can be tuned to yield different morphologies ranging from compact, nm-sized flakes to uniform sample coverage on the mm-scale. The Dirac cone in the electronic structure of free graphene (i. e. the linear dispersion relation for electrons close to the Fermi energy) is preserved in this system. The substrate induces slight p-doping and the superstructure leads to the opening of additional mini-gaps. The localized, possibly spin-polarized electronic edge state predicted for zigzag edges in free graphene can be observed for nanoflakes on Ir(111). C/Ir(111) is a template for the growth of metal cluster lattices showing a narrow size distribution and exceptional thermal stability. The clusters bind strongly via a rehybridization of C from sp² to sp³ leading to the formation of covalent carbon-metal bonds. This effect is rather general and has been observed for a range of cluster materials.