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The unusual transport properties of graphene are the direct consequence of a peculiar band structure near the Dirac point. We determine the shape of the bands and their characteristic splitting, and find the transition from two-dimensional to bulk character for 1 to 4 layers of graphene by angle-resolved photoemission. By detailed measurements of the bands we derive the stacking order, layer-dependent electron potential, screening length, and strength of interlayer interaction by comparison with tight binding calculations, yielding a comprehensive description of multilayer graphene's electronic structure. DOI: 10.1103/PhysRevLett.98.206802 PACS numbers: 73.21.ÿb, 73.22.ÿf, 73.90.+f, 79.60.ÿi Much recent attention has been given to the electronic structure of multilayer films of graphene, the honeycomb carbon sheet which is the building block of graphite, carbon nanotubes, C 60 , and other mesoscopic forms of carbon [1]. Recent progress in synthesizing or isolating multilayer graphene films [2 -4] has provided access to their physical properties, and revealed many interesting transport phenomena, including an anomalous quantum Hall effect [5,6], ballistic electron transport at room temperature [7], micronscale coherence length [7,8], and novel many-body couplings [9].These effects originate from the effectively massless Dirac fermion character of the carriers derived from graphene's valence bands, which exhibit a linear dispersion degenerate near the so-called Dirac point energy E D [10].These unconventional properties of graphene offer a new route to room temperature, molecular-scale electronics capable of quantum computing [6,7]. For example, a possible switching function in bilayer graphene has been suggested by reversibly lifting the band degeneracy at the Fermi level (E F ) upon application of an electric field [11,12]. This effect is due to a unique sensitivity of the band structure to the charge distribution brought about by the interplay between strong interlayer hopping and weak interlayer screening, neither of which is currently well understood [13,14].In order to evaluate the interlayer screening, stacking order,and interlayer coupling, we have systematically studied the evolution of the band structure of one to four layers of graphene using angle-resolved photoemission spectroscopy (ARPES). We demonstrate experimentally that the interaction between layers and the stacking sequence affect the topology of the bands, the former inducing an electronic transition from 2D to 3D (bulk) character when going from one layer to multilayer graphene. The interlayer hopping integral and screening length are determined as a function of the number of graphene layers by exploiting the sensitivity of states to the Coulomb potential, and the layer-dependent carrier concentration is estimated.The films were synthesized on n-type (nitrogen, 1 10 18 cm ÿ3 ) 6H-SiC(0001) substrates (SiCrystal AG) that were etched in hydrogen at 1550 C. Annealing in a vacuum first removes the resulting silicate adlayer and then causes t...

A combination of angle-resolved photoemission and scanning tunneling microscopy is used to explore the possibilities for tailoring the electronic structure of gold atom chains on silicon surfaces. It is shown that the interchain coupling and the band filling can be adjusted systematically by varying the step spacing via the tilt angle from Si͑111͒. Planes with odd Miller indices are stabilized by chains of gold atoms. Metallic bands and Fermi surfaces are observed. These findings suggest that atomic chains at stepped semiconductor substrates make a highly flexible class of solids approaching the one-dimensional limit.

We have studied friction and dissipation in single and bilayer graphene films grown epitaxially on SiC. The friction on SiC is greatly reduced by a single layer of graphene and reduced by another factor of 2 on bilayer graphene. The friction contrast between single and bilayer graphene arises from a dramatic difference in electron-phonon coupling, which we discovered by means of angle-resolved photoemission spectroscopy. Bilayer graphene as a lubricant outperforms even graphite due to reduced adhesion.