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, C60 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 C60 grows preferentially in a (2 √3 x 2 √3) R300 structure on Ag(111), on the Ag/Pt(111) dislocation network the C60 lattice adopts an orientation rotated by 300, with the close-packed C60 rows aligned along the dislocations which themselves are aligned along the Ag(1-10) directions. For higher coverages in the range of 1-2 monolayers, the growth of C60 continues in a layer-by-layer fashion