Orientationally ordered island growth of higher fullerenes onAg/Si(111)−(3×3)R30°

The adsorption of the higher endohedral and empty fullerenes ${\mathrm{La}\mathrm{@}\mathrm{C}}_{82}$ and ${\mathrm{C}}_{84}$ on $\mathrm{A}\mathrm{g}/\mathrm{S}\mathrm{i}\mathrm{}\left(111\right)-(\sqrt{3}\times \sqrt{3})R30\mathrm{}°$ has been investigated using ultrahigh-vacuum scanning tunneling microscopy. At low coverage these molecules form single-layer islands with orientational order, a consequence of the commensurability between the intermolecular separation for each species and the surface lattice constant. The preferred adsorption site for the molecules is above an Ag trimer. Several other domains are observed at higher coverage which may be understood using a simple model. Following annealing, domains with a single orientation remain and the possibilities for epitaxial and heteroepitaxial growth are discussed.