Dresden 2009 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 52: Metal substrates: Adsorption of organic / bio molecules VII
O 52.1: Vortrag
Donnerstag, 26. März 2009, 15:00–15:15, SCH A118
Understanding the electronic transport across single phthalocyanine molecules — •Annika Bork1, Albert F. Takács1,2, Florian Witt1, Stefan Schmaus1,2, Timofey Balashov1, Martin Bowen3, Eric Beaurepaire3, and Wulf Wulfhekel1,2 — 1Physikalisches Institut, Universität Karlsruhe (TH) — 2CFN-DFG Centrum für Funktionelle Nanostrukturen — 3Institut de Physique et Chimie des Matériaux de Strasbourg
Regarding the increasing miniaturization of electronic devices, molecular electronics is a field of growing interest. Here, we present STM and STS results on hydrogen (H2Pc), cobalt (CoPc) and manganese (MnPc) phthalocyanines deposited on a clean Cu(111) surface as well as on bilayer cobalt islands on Cu(111). By laterally positioning the STM tip over a single molecule and approaching the tip towards the surface we were able to investigate the conductance of the molecules. Our results show that the molecules tend to lift from the surface and jump into contact with the STM tip. On Cu(111) we found that the conductance through H2Pc, CoPc and MnPc is about 0.1 G0 whereas the conductance of H2Pc and CoPc on the cobalt islands is about 3 times higher. By performing STS measurements the orbitals of the H2Pc and CoPc can be obtained. In both cases we can observe a shift of the HOMO to the Fermi edge, which explains the increased conductance on the cobalt islands. Further, inelastic STS revealed a soft phonon excitation located on the sidegroups, that is the underlying mechanism of the jump into contact.