Molecular orientations and interfacial structure of C 60 on Pt(111)

Molecular orientations and assembled structures of C 60 molecules on Pt(111) have been characterized by low-temperature scanning tunneling microscopy for coverage between 0.1 ML and 1.5 ML. At room temperature, C 60 molecules preferentially decorate the steps and nucleate into single layer islands (SLIs) with hexagonal close-packed structures upon increasing coverage. C 60 islands comprise two differently oriented C 60 /Pt(111)-(√13×√13) R13.9° phases, in which five types of molecular orientation of C 60 carbon cage configurations are clearly identified by the high-resolution scanning tunneling microscopy image. Further annealing treatment leads to more uniform molecular orientation without apparent aggregation of C 60 SLIs. As coverage increases above 1 ML, domains corresponding to (2√3×2√3) R30° superstructure appear. To explain the above transformation, an interfacial reconstruction model is proposed according to the detailed study of the molecular adsorption structures in different domains.