Orientational configurations of the C₆₀ molecules in the (2×2) superlattice on a solid C₆₀ (111) surface at low temperature

The orientational configurations of C₆₀ molecules on the surface of a multilayer C₆₀ island with a (111)-terminating plane were studied at 78 K by using a scanning tunneling microscope. A 2×2 superlattice, which resulted from the orientational ordering of the C₆₀ molecules, was observed. In each unit cell of the superlattice, one C₆₀ molecule with a three-lobe intramolecular pattern, and three C₆₀ molecules with dumbbell-like intramolecular patterns, were clearly resolved. In combination with the theoretical analysis and simulation, the orientational configurations of the C₆₀ molecules were determined.