Structure transition of a C 60 monolayer on the Bi(111) surface.

The interfacial structures of C 60 molecules adsorbed on solid surfaces are essential for a wide range of scientific and technological processes in carbon-based nanodevices. Here, we report structural transitions of the C 60 monolayer on the Bi(111) surface studied via low-temperature scanning tunneling microscopy (STM). With an increase in temperature, the structure of the C 60 monolayer transforms from local-order structures to a (√93 × √93) R20° superstructure, and then to a (11 × 11) R0° superstructure. Moreover, the individual C 60 molecules in different superstructures have different orientations. C 60 molecules adopt the 6 : 6 C-C bond and 5 : 6 C-C bond facing-up, mixed orientations, and hexagon facing-up in the local-order structure, (√93 × √93) R20°, and (11 × 11) R0° superstructure, respectively. These results shed important light on the growth mechanism of C 60 molecules on solid surfaces.