Berlin 2005 – wissenschaftliches Programm

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O: Oberflächenphysik

O 45: Organische Dünnschichten IV

O 45.5: Vortrag

Dienstag, 8. März 2005, 16:45–17:00, TU EB301

A standing wave study of the PTCDA-precursor state on the Ag(111) surface — •A. Hauschild¹, R. Temirov², M. Sokolowski¹, and F. S. Tautz² — ¹Institut für Physikalische und Theoretische Chemie der Universität Bonn, Wegelerstr. 12, 53115 Bonn, Germany — ²International University Bremen, School of Engineering and Science, PO Box 750 561, 28725 Bremen, Germany

PTCDA deposited on Ag(111) can lead to two different adsorption states: At room temperature (RT) the commonly-known stable chemisorbed state is formed, deposition at temperatures below 160 K, however, yields a meta-stabile No-dqprecursor stateNo-dq. This state is also chemisorbed, but no long-range order exists. Photoemission spectroscopy also shows significant differences of the electronic structures of both states [1]. From an earlier normal incidence x-ray standing wave (NIXSW) study, we know that the No-dqRT stateNo-dq involves a significant distortion of the planar PTCDA molecule. The aim of the present experiment was to investigate the different bonding geometry of the precursor state in comparison to that of the RT state. A first data evaluation actually confirms the existence of differences. However, in contrast to the RT-state, the precursor also undergoes a reversible transition to a second state under exposure to the intensive x-rays, which complicated the experiments. Supported by the DFG. [1] L. Kilian, Doctoral thesis, Universität Würzburg 2002.