C60on Al(111): Covalent bonding and surface reconstruction

Abstract

We present photoemission and C 1s photoabsorption data for an annealed monolayer ${\mathrm{C}}_{60}$/Al(111), which show that a strong covalent bond is formed between the ${\mathrm{C}}_{60}$ molecules and the substrate. Low-energy electron-diffraction and scanning tunneling microscopy data reveal a highly symmetric overlayer structure commensurate with the substrate. Al 2p photoelectron spectra show that the chemical environment at the surface is greatly modified compared to clean Al(111), and indicate that a significant fraction of the surface atoms have moved, consistent with a picture of covalent bonding to the overlayer. The strength of the interaction is such that the fullerenes are distorted more than on other metal surfaces or in compounds with alkali metals.