Berlin 2008 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 18: Poster Session I - MA 141/144 (Atomic Wires; Size-Selected Clusters; Nanostructures; Metal Substrates: Clean Surfaces+Adsorption of Organic / Bio Molecules+Solid-Liquid Interfaces+Adsorption of O and/or H; Surface or Interface Magnetism; Oxides and Insulators: Clean Surfaces)

O 18.23: Poster

Montag, 25. Februar 2008, 18:30–19:30, Poster F

C₆₈ deposits on Cu(111): Topography and Electronic Properties — •Albert F. Takacs^1,2, Timofey Balashov¹, Wulf Wulfhekel^1,2, Daniel Löffler³, Artur Böttcher³, and Manfred M. Kappes^2,3 — ¹Physikalisches Institut, Universität Karlsruhe, D-76131, Germany — ²CFN-DFG Centrum für Funktionelle Nanostrukturen — ³Institut für Physikalische Chemie, Universität Karlsruhe, D-76131, Germany

Non-IPR fullerenes (Isolated Pentagon Rule) have very recently attracted attention as stable building blocks for carbon-based nanotechnology. In contrast to classic fullerenes, the smaller C_n cages, n<70 and n>60, are functionalised by terminating reactive sites. We focus here on the C₆₈ species which is the largest fullerene to have only non-IPR cage isomers. Ultraviolet photoionization spectroscopy reveals the HOMO-LUMO gap of the C₆₈ layers of 1.7 eV and thermal desorption spectroscopy evidences a high intercage binding energy of ≈2 eV. We also used scanning tunnelling microscopy(STM) to determine the geometry and electronic properties of C₆₈ deposits on Cu(111). The STM images confirm that C₆₈ deposits comprise cages linked in polymeric chains as determined by the geometry of the reaction centers terminating individual cage. By proper positioning and approaching of the STM tip over an individual molecule we have investigated the conductance across the cage-substrate interface. The resulting current-voltage (I-V) and differential conductance (dI/dV) characteristics reveal two distinct trends which indicate the unique role of the non-IPR sites as responsible for the strong interactions with the substrate.