Scanning tunneling microscopy of C-60/Al(111)-6x6: Inequivalent molecular sites and electronic structures

We present a scanning tunneling microscopy and spectroscopy (STM/S) study of a thermally stable, annealed monolayer of C-60 On Al(111). The C-60 molecules are arranged into a close-packed hexagonal layer of 2 root 3 x 2 root 3 periodicity with the symmetry reduced to 6 x 6 as a result of a substrate reconstruction which raises one third of the fullerenes. Molecularly resolved tunnelling spectroscopy provides experimental evidence for the geometrical displacement in height and shows dramatic differences between the electronic structure of the fullerenes in the two inequivalent adsorption sites.