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 (root 93 x root 93) R20 degrees superstructure, and then to a (11 x 11) R0 degrees 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, (root 93 x root 93) R20 degrees, and (11 x 11) R0 degrees superstructure, respectively. These results shed important light on the growth mechanism of C-60 molecules on solid surfaces.