Chemisorption of azafullerene on silicon: isolating C59N monomers

We find that C59N exists as a monomer on Si(111) and Si(100) surfaces, in c ontrast to the dimerised state ((C59N)(2)) it adopts in the bulk azafullere ne solid. A combination of scanning tunnelling microscopy, photoelectron sp ectroscopy and X-ray absorption measurements indicates that, as for C-60, t he chemical bond between C59N and the Si(111)-(7 x 7) surface involves the formation of covalent Si-C bonds. We argue that the strong C59N-surface int eraction 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 tunnelli ng microscope-based molecular manipulation experiments. (C) 2000 Elsevier S cience S.A. All rights reserved.