The mobility and bonding of C60 on a (110) Pd surface were characterized by means of variable-temperature scanning tunnelling microscopy. After adsorption at 435 to 485K, the motion of single molecules could be directly monitored, and the corresponding tracer diffusion barrier was deduced to be 1.4eV. Upon annealing at up to about 700K, the molecules underwent an irreversible bonding transition which resulted in a second, more strongly bound C60 species, having different imaging characteristics. This was attributed to a local surface reconstruction, where C60 sank into the microscopic pits which were formed. These results demonstrated that substrate restructuring might account for the coexistence of distinct C60 species at surfaces.

Mobility and Bonding Transition of C60 on Pd(110). J.Weckesser, J.V.Barth, K.Kern: Physical Review B, 2001, 64[16], 161403 (4pp)