Adsorption of pure C70 and its mixture with C60 on the Cu(111)1×1 surface was investigated by using scanning tunneling microscopy. The pure C70 monolayer was found to form the 4×4-commensurate superlattice, similar to the case of pure C60, after a brief annealing at approximately 320°C. The individual C70 molecules take the upright position with the long axis perpendicular to the surface. Introducing C60s in the C70 layer allows some of the C70 molecules to take the lying-down position with the long axis parallel to the 110 direction of the surface. By comparing with theoretical simulations, we propose that C70 molecules in the C70-C60 mixture cease their internal rotation and are ratcheted with one of the hexagonal rings around the equator facing down the Cu(111) surface.
ASJC Scopus subject areas
- Condensed Matter Physics