DOUBLE DOMAIN ORDERING AND SELECTIVE REMOVAL OF C-60 ON AG SI(111)-(ROOT-3X-ROOT-3)R30-DEGREES/

We have used ultra-high-vacuum scanning tunneling microscopy to invest igate the interaction of C-60 with the Ag/Si(111)-(root 3 x root 3)R30 degrees surface. C-60 molecules bond preferentially at defect sites a nd step edges and form double domain islands that are ordered relative to the bulk Si in exactly the same positions as previously observed f or Si(111)-7x7. We discuss the dependence of molecular packing on surf ace geometry and reactivity and show that the islands are removed by a nnealing leaving Si(111) terraces coexisting with a network of strongl y bound C-60 molecules adsorbed at step edges.