Berlin 2008 – wissenschaftliches Programm
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SYSA: Symposium Tayloring Organic Interfaces: Molecular Structures and Applications
SYSA 1: Bandalignment in Organic Materials
SYSA 1.4: Vortrag
Dienstag, 26. Februar 2008, 10:30–10:45, H 0105
Intramolecular band structure and disorder effects in monolayers of linear molecules — •M. Häming1, J. Ziroff1, M. Wießner1, O. Seitz2, E. Salomon3, A. Kahn3, D. Cahen2, A. Schöll1, F. Reinert1, and E. Umbach1 — 1Universität Würzburg, Experimentelle Physik II, D-97074 Würzburg — 2Weizmann Institute of Science, Department of Materials and Interfaces, Israel — 3Princeton University, Department of Electrical Engineering, USA
For a detailed understanding of charge transport on a molecular level a comprehensive understanding of the molecular electronic structure is mandatory. Self assembled alkyl monolayers (SAM) are appropriate model systems due to interesting charge transport properties and their relatively simple molecular structure. We have investigated the intramolecular band structure of alkyl/Si(111) SAMs with high resolution photoemission spectroscopy (HR-PES) using variable photon energy. There are significant changes in the valence band spectra for photon energies between 30 eV and 190 eV indeed, but the electronic dispersion is blurred due to a strong DOS effect. This is very unlikely a property of the intramolecular band structure, but rather the consequence of disorder in the molecular layer. In reverse, this effect can provide structural information. A comparison between the PES data and projections of the total DOS onto the free electron final state for different distributions of alkyl orientations allows to estimate the spread in the molecular orientation angle and thus the degree of disorder. Consequently, this needs to be taken into account for a proper description of the intramolecular electronic structure.