An investigation was made, by means of ab initio calculations, of the influence of graphitic monoatomic steps upon the diffusion of Au adatoms and small clusters. It was found that the presence of dangling bonds dramatically affected the adsorbate behavior. Thus, graphite steps attracted atoms and clusters which were diffusing on the upper terrace, so as to create a so-called negative step barrier. However, if the step dangling bonds were passivated by H atoms, these defects reverted to a behavior similar to that of metallic steps; showing a repulsive barrier.

Step Barrier for Gold Adatoms and Small Clusters Diffusing on Graphite - an ab initio Study. P.Jensen, X.Blasé: Physical Review B, 2004, 70[16], 165402 (5pp)