Structure and dynamics of fullerenes adsorbed on the Au(111) surface

摘要

Scanning tunneling microscopy was used to characterize the structure of partial monolayers of C_(60) and C_(70) on the Au(1 11) surface. Both 2 3~(1/2) x 2 3~(1/2) R30° and 7 x 7 lattice symmetries were observed for C_(60) monolayers, in accordance with previous results. For C_(70) monolayers, structures are observed with rotation angles of 0°, 30°, and 14° with respect to the underlying substrate; we propose a previously unreported (13)~(1/2) x (13)~(1/2) R13.9° lattice structure to explain this last observation. Time sequences of STM images show that while fullerene monolayers are largely stable, molecular motion can be observed on the timescale of minutes or hours. For C_(60), thermal diffusion is the predominant cause of this motion, and STM perturbation of the sample is negligible. In contrast, C_(70) is observed to diffuse far more slowly; under normal scanning conditions, tip-induced motion is the major effect.