Thin graphite overlayers: Graphene and alkali metal intercalation

Using LEED and angle resolved photoemission for characterisation we have prepared graphite overlayers with down to monolayer thickness by heating SiC crystals and monitored alkali metal intercalation for the multilayer films. The valence band structure of the monolayer is similar to that calculated for graphene though downshifted by around 0.8 eV and with a small gap at the zone corner. The shift suggests that the transport properties, which are of much present interest, are similar to that of a biased graphene sample. Upon alkali metal deposition the 3D character of the pi states is lost and the resulting band structure becomes graphene like. A comparison with data obtained for ex situ prepared intercalation compounds indicates that the graphite film has converted to the stage I compounds C8K or CgRb. Advantages with the present preparation method is that the graphite film can be recovered by desorbing small amounts of alkali metal and that the progress of compound formation can be monitored. The energy shifts measured after different deposits indicate that saturation is reached in three steps. Our interpretation is that in the first the alkali atoms are dispersed while the final steps are characterized by the formation of first one and then a second (2 x 2) ordered alkali metal layer adjacent to the uppermost carbon layer. (c) Elsevier B.V. All rights reserved

The Thinnest Carpet on the Smallest Staircase: The Growth of Graphene on Rh(533)

We here discuss the growth process and the properties of single-layer graphene on a vicinal Rh(533) surface. The structural anisotropy of the substrate leads to a moir\ue8 cell with nonequivalent lattice vectors in the directions parallel and orthogonal to the steps. Our results indicate that the high structural quality of the carbon layer, combined with the weaker interaction with the substrate and the higher thermal stability with respect to graphene on Rh(111), is strongly influenced by the presence of the surface steps, which play a fundamental role in the defect-healing mechanism first predicted by earlier theoretical calculations