Dresden 2009 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 36: Particles and clusters
O 36.5: Vortrag
Mittwoch, 25. März 2009, 16:00–16:15, SCH A01
Non-IPR isomers of C60 on HOPG — •Daniel Löffler1, Noelia Bajales1, Patrick Weis1, Sergei Lebedkin1, Angela Bihlmeier2, Wim Klopper2, Artur Böttcher1, and Manfred Kappes1 — 1Institut für physikalische Chemie, Universität Karlsruhe — 2Institut für theoretische Chemie, Universität Karlsruhe
Thin monodisperse films consisting of exclusively non-IPR C60 molecules have been generated by depositing vibronically excited C60 cations onto HOPG followed by sublimation of the more volatile C60(Ih) isomers. A beam of C60 cations was generated by the electron-impact mediated heating and ionization of C70. The associated excitation and fragmentation leads to the formation of C60+ cages with non-IPR sites (in addition to the dominant C60(Ih) derived cation). The fabrication of pure C60 (non-IPR) films has been achieved simply by heating the film grown up to 600 K which results in the thermal removal of all IPR cages, C60(Ih). The topography of the resulting films, is governed by the aggregation of the C60 (non-IPR) cages, which is in turn driven by intercage bonds constituted by non-IPR sites (e.g. pairs of adjacent pentagonal rings). These covalent intercage bonds are responsible for the high stability of the C60 (non-IPR) films as mirrored by a sublimation temperature of 1100 K - significantly higher than for pure C60(Ih). The valence band of the C60 (non-IPR) films exhibits a triplet with a well distinguishable additional peak at a binding energy of 2.6 eV. The C60 (non-IPR) films exhibit a narrower HOMO-LUMO gap than that found for C60(Ih) films.