Sm cluster superlattice on graphene/Ir(111)

We report on the first example of a self-assembled rare earth cluster superlattice.As a template, we use the moiré pattern formed by graphene on Ir(111); its lattice constant of 2.52nm defines the interparticle distance.The samarium cluster superlattice forms for substrate temperatures during deposition ranging from 80 to 110K, and it is stable upon annealing to 140K.By varying the samarium coverage, the mean cluster size can be increased up to 50 atoms, without affecting the longrange order.The spatial order and the width of the cluster size distribution match the best examples of metal cluster superlattices grown by atomic beam epitaxy on template surfaces.