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CPP: Chemische Physik und Polymerphysik
CPP 23: POSTER Functional Organic Thin Films
CPP 23.9: Poster
Donnerstag, 30. März 2006, 17:00–19:00, P2
Electronic Properties of DNA Base Layers on H-passivated Si(111)(7x7) — •Stefan Seifert1, Gianina Gavrila1, Walter Braun2, and Dietrich R.T. Zahn1 — 1Chemnitz University of Technology, Semiconductor Physics, D-09107 Chemnitz, Germany — 2BESSY GmbH, Albert-Einstein-Straße 15, Berlin, D-12489, Germany
Despite of the increasing interest in the charge transport properties of DNA base stacks and poly DNA strands, reliable data on the electronic properties of DNA bases in the condensed phase is rare if at all available. Therefore, an extensive photoelectron spectroscopy study of layers of adenine, cytosine, and guanine is presented in comparison with density functional theory (DFT) calculations for single molecules. The layers were prepared under ultra high vacuum conditions by organic molecular beam deposition onto H-passivated Si(111)(7x7). The valence band photoemission (VB-PE) spectra of these layers were obtained with 55eV and 150eV excitation energy at the synchrotron facility BESSY. The determined ionization energies for the bio-organic layers are considerably smaller than those of free molecules. The adenine and cytosine layers show formation of an interface dipole with the substrate while the interface between guanine layers and H-Si(111)(7x7) displays nearly vacuum level alignment. The comparison of the VB-PE spectra to DFT/B3LYP calculations for single molecules (with 6-311+G(p,d) basis sets) reveals clear signs of band formation in cytosine and guanine layers.