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

We have investigated the room temperature growth of C(60) 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 C(60) depositions. For low C(60) coverages, the molecules decorate the step-edges, where also the first islands nucleate. This indicates that at room temperature the C(60) molecules are sufficiently mobile to cross the dislocation lines and to diffuse to the step-edges. For C(60) coverages of 0.4 monolayer, besides the islands nucleated at the step-edges, C(60) islands also grow in the middle of terraces. The C(60) islands typically extend over several unit cells of the dislocation network and show an unusual orientation of the hexagonally close-packed C(60) lattice as compared to that found on the bare Ag(111) surface. Whereas C(60) grows preferentially in a (2 root 3 x 2 root 3) R30 structure on Ag(111), on the Ag/ Pt(111) dislocation network the C(60) lattice adopts an orientation rotated by 30 degrees, with the close-packed C(60) 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 C(60) continues in a layer-by-layer fashion.