Berlin 2012 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 54: Nanostructures at surfaces II
O 54.3: Vortrag
Mittwoch, 28. März 2012, 17:15–17:30, MA 042
Ordered Supramolecular Nanowires on a Neutral Substrate — •Roozbeh Shokri1,2, Françoise Serein-Spirau3, Jean M. Sotiropoulos4, Günter Reiter1, and Laurent Simon2 — 1Physikalisches Institut, Universität Freiburg, Germany — 2Institut de Science des Matériaux de Mulhouse (IS2M), France — 3Institut Charles Gerhardt de Montpellier, France — 4Institut Pluridisciplinaire de Recherche sur l'Environnement et les Matériaux, Pau, France
Here we present a scanning tunneling microscopy study on a well-defined organic oligomer composed of three thiophene-benzene-thiophene units deposited onto graphene. Mono-layer graphene can be considered as a neutral substrate which only weakly interacts with the molecules and thus allows observing molecular organization processes dominated by molecule-molecule interactions. Our studies exhibit well-ordered 2D domains of these molecules consisting of long supramolecular wires formed by a pi-stacking arrangement between the thiophene endgroups. The precise molecular arrangement and measurements of the HOMO-LUMO gap and spatial mapping of the electronic states reveal the possibility of transporting charges through a hoping mechanism. Scanning tunneling spectroscopy in combination with DFT calculations manifest that the electronic states of the molecules are not perturbed by the underlying graphene layer, i.e. decoupled from the substrate. Such weak interaction between molecules and graphene provides the possibility to image and "see" all molecular orbitals in detail, and to distinguish unambiguously individual molecular segments.