Regensburg 2007 – wissenschaftliches Programm
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DS: Fachverband Dünne Schichten
DS 2: Organic Thin Films II
DS 2.2: Vortrag
Montag, 26. März 2007, 11:30–11:45, H32
Self-assembled alkyl monolayers on Si(111) investigated by NEXAFS and HR-UPS — •M. Häming1, J. Ziroff1, S. Hame1, A. Salomon2, L. Segev2, T. Boecking3, O. Seitz2, D. Cahen2, F. Reinert1, A. Schöll1, and E. Umbach1 — 1University of Würzburg, Experimental Physics II, 97074 Würzburg — 2Weizmann Institute of Science, Department of Materials and Interfaces, Rehovot 76100 Israel — 3The University of New South Wales, Sydney, NSW 2052, Australia
The electronic structure of organic condensates is of crucial importance for the charge transport properties in these materials. Inter- and intramolecular interactions have a strong impact on the electronic system, leading to energy shifts in all levels. Moreover, for oriented chains band dispersion may occur and in the case of long range order even lateral band dispersion is possible. Self-assembled monolayers (SAMs) are ideal model systems to systematically study the intramolecular electronic band dispersion along the chains as function of chain length. In this work we investigate alkyl SAMs of various chain lengths directly bound to Si(111) substrates via Si-C bonds. Near edge x-ray absorption fine structure (NEXAFS) measurements provide information on unoccupied states and the molecular orientation with respect to the surface (∼40∘ for C14H29). Also, the influence of radiation damage is observed in the NEXAFS spectra by the formation of intra- or intermolecular π-bonds. The high resolution UV photoemission spectroscopy (HRUPS) data recorded with variable photon energy (UE112-PGM at BESSY) shows marked dispersion within the valence regime which is compatible with a tight binding model taking into account the film geometry.