Adlayers of Fullerene Monomer and [2 + 2]-Type Dimer on Au(111) in Aqueous Solution Studied by in Situ Scanning Tunneling Microscopy

In situ scanning tunneling microscopy (STM) revealed that highly ordered adlayers of fullerene monomer (C 60 ) and [2 + 2]-type dimer (C 120 ) were formed on Au(111) by immersing the surface in benzene solution containing C 60 or C 120 molecules. High-resolution STM images allowed us to determine packing arrangements of C 60 and C 120 on a Au(111) surface in an aqueous HClO 4 solution. The (2√3 × 2√3)R30° and the so-called in-phase structures of the C 60 adlayer were found on the Au(111) surface, whereas the (2√3 × 4√3)R30° and (2√3 × 5√3)R30° structures were observed for the C 120 dimer. Each C 120 dimer was imaged in a dumbbell shape by in situ STM.