Motivated by the experimentally observed high mobility of gold atoms on graphene and their tendency to form nanometer-sized clusters, a density functional theory study was made of the ground-state structures of small gold clusters on graphene, their mobility and clustering. This detailed analysis of the electronic structures identified the opportunity to form strong gold-gold bonds and the graphene-mediated interaction of the pre-adsorbed fragments as the driving forces behind gold's tendency to aggregate on graphene. While clusters containing up to three gold atoms have one unambiguous ground state structure, both gas phase isomers of a cluster with four gold atoms could be found on graphene. In the gas phase the diamond-shaped Au4D cluster was the ground state structure, whereas the Y-shaped Au4Y became the actual ground state when adsorbed on graphene. As shown, both clusters could be produced on graphene via two distinct clustering processes. A detailed study was also made of the step-wise formation of a gold dimer from two pre-adsorbed adatoms, as well as the formation of Au3. All reactions were exothermic and no further activation barriers, apart from the diffusion barriers, were found. The diffusion barriers of all studied clusters range from4 to 36meV only, and were substantially exceeded by the adsorption energies of -0.1 to - 0.59eV. This explains the high mobility of Au1-4 on graphene along the C-C bonds.

Small Gold Clusters on Graphene, Their Mobility and Clustering: a DFT Study. Amft, M., Sanyal, B., Eriksson, O., Skorodumova, N.V.: Journal of Physics Condensed Matter, 2011, 23[20], 205301