Influence of adsorbate-substrate interaction on the local electronic structure of C₆₀studied by low-temperature STM

Low coverages of c₆₀on Cu(111) and K/Cu(111) have been investigated by scanning tunneling microscopy and spectroscopy at 10 K. By combining topographic imaging and mapping of the spectral intensity (dI/dV), we have analyzed the evolution of the t_1u-derived [lowest-unoccupied molecular orbital (LUMO)] electronic states resulting from the difference in adsorption geometry on Cu(111) as well as the difference in bonding when the substrate is precovered by a K monolayer. The spatial distribution and the spectral width of the LUMO-derived states are observed to be particularly sensitive to the adsorbate-substrate interaction.