Berlin 2012 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 68: Focussed session: Functional molecules at surfaces III

O 68.3: Topical Talk

Donnerstag, 29. März 2012, 11:30–12:00, A 053

Charge transfer dynamics in assemblies of functional molecules — •Michael Zharnikov — Angewandte Physikalische Chemie, Universität Heidelberg, 69120 Heidelberg, Germany

Development of future technologies such as molecular electronics and sustained progress in organic electronics and photovoltaics rely on reliable information about the charge transport (CT) through individual molecular units (or loosely "molecular wires") which serve as important building blocks of a variety of potential devices. In this context, femtosecond CT dynamics in a series of self-assembled monolayers with different backbones, which are prototypes of potential molecule wires, was addressed by resonant Auger electron spectroscopy using the core hole clock approach. The CT pathway was unambiguously defined by resonant excitation of a special marker group attached to the backbone. The length of the backbone was varied to monitor the respective dependence of the CT time. Similar to the static conductance, this dependence can be coarsely described by an exponential function. The respective attenuation factors and CT time associated with the anchoring to the substrate were determined. These factors and characteristic CT times through molecular frameworks are found to depend strongly on the character of the molecular orbital which mediates the CT process. Thus, the efficiency of tunnelling in molecular wires can be significantly affected by controlling the specific orbitals into which charge carriers are injected. This can be a valuable input for theory and an important consideration for molecular electronics devices where improvements in conductance can have significant technological impact.