Chemisorption of azafullerene on silicon: isolating C59N monomers

We find that C59N exists as a monomer on Si(111) and Si(100) surfaces, in contrast to the dimerised state ((C59N)2) it adopts in the bulk azafullerene solid. A combination of scanning tunnelling microscopy, photoelectron spectroscopy and X-ray absorption measurements indicates that, as for C60, the chemical bond between C59N and the Si(111)-(7×7) surface involves the formation of covalent SiC bonds. We argue that the strong C59N-surface interaction on both Si(111) and Si(100) precludes molecular diffusion and thus prohibits the formation of dimers. The dominant role of molecule–surface, as opposed to intermolecular interactions is confirmed by scanning tunnelling microscope-based molecular manipulation experiments.