Initial stage of C-60 thin-film growth on YB66(001) surfaces

Exposed B-156 supericosahedra on a YB66(001) surface were found align perio dically in a two-dimensional square lattice. On the YB66(001) surface, C-60 molecules were deposited at room temperature. The initial stages of C-60 t hin-film growth on the YB66(001) surface were studied using a scanning tunn eling microscope (STM). In the submonolayer regime, the C-60 molecule adsor bed strongly on the surface to show the stripe pattern due to the inner mol ecule C = C bonds. The adsorbed layer had no long-range ordering. The C-60 molecules did not favor the on-top site of the B-156 supericosahedron. We p ropose a model that the C-60 molecule adsorbs on triangular sites made up o f the B-12 icosahedra on each B-156 supericosahedron on the surface. Due to size frustration, the C-60 molecule occupies only one of two equivalent tr iangular sites. The model explains the characteristics of the adsorption si te and the arrangement of the C-60 molecules in the submonolayer regime. In the multilayer regime, the dangling bonds of the surface were passivated b y the first layer, and overlayer growth was governed by van der Waals inter action between C-60 molecules. An island, the top of which showed a hexagon al lattice, grew on the first layer. The hexagonal lattice was rotated by 1 0 degrees with respect to the underlying square lattice of the YB66(001) su rface.