Nucleation and growth of C₆₀ overlayers on the Ag/Pt(111) dislocation network surface

We have investigated the room temperature growth of C₆₀ overlayers on the strainrelief dislocation network formed by two monolayers of Ag on Pt(111) by means of scanning tunneling microscopy. Extended domains of highly ordered dislocation networks with a typical superlattice parameter of 6.8 nm have been prepared, serving as templates for subsequent C₆₀ depositions. For low C₆₀ coverages, the molecules decorate the step-edges, where also the first islands nucleate. This indicates that at room temperature the C₆₀ molecules are sufficiently mobile to cross the dislocation lines and to diffuse to the step-edges. For C₆₀ coverages of 0.4 monolayer, besides the islands nucleated at the step-edges, C ₆₀ islands also grow in the middle of terraces. The C₆₀ islands typically extend over several unit cells of the dislocation network and show an unusual orientation of the hexagonally close-packed C₆₀ lattice as compared to that found on the bare Ag(111) surface. Whereas C ₆₀ grows preferentially in a (2 3 × 2 3) R30° structure on Ag(111), on the Ag/Pt(111) dislocation network the C₆₀ lattice adopts an orientation rotated by 30°, with the close-packed C₆₀ rows aligned along the dislocations which themselves are aligned along the Ag1-10 directions. For higher coverages in the range of 1-2 monolayers, the growth of C₆₀ continues in a layer-by-layer fashion.