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Electron states of mono- and bilayer graphene on SiC probed by scanning-tunneling microscopy

2007; American Physical Society; Volume: 76; Issue: 4 Linguagem: Inglês

10.1103/physrevb.76.041403

1550-235X

Pierre Mallet, F. Varchon, Cécile Naud, L. Magaud, Claire Berger, Jean-Yves Veuillen,

Diamond and Carbon-based Materials Research

We present a scanning-tunneling microscopy (STM) study of a gently graphitized $6H\text{\ensuremath{-}}\mathrm{Si}\mathrm{C}(0001)$ surface in ultrahigh vacuum. From an analysis of atomic scale images, we identify two different kinds of terraces, which we attribute to mono- and bilayer graphene capping a C-rich interface. At low temperature, both terraces show $(\sqrt{3}\ifmmode\times\else\texttimes\fi{}\sqrt{3})$ quantum interferences generated by static impurities. Such interferences are a fingerprint of $\ensuremath{\pi}$-like states close to the Fermi level. We conclude that the metallic states of the first graphene layer are almost unperturbed by the underlying interface, in agreement with recent photoemission experiments [Bostwick et al., Nat. Phys. 3, 36 (2007)].