Dresden 2003 – wissenschaftliches Programm
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O: Oberflächenphysik
O 24: Postersitzung (Epitaxie und Wachstum, Oxide und Isolatoren, Elektronische Struktur, Oberfl
ächenreaktionen, Adsorption an Oberfl
ächen, Organische Dünnschichten)
O 24.79: Poster
Mittwoch, 26. März 2003, 14:30–17:30, P1
Pentacene/Ag(111): film growth via an accommodation layer — •M. Eremtchenko1, D. Bauer1, S. Döring1, T. Stolz1, J.A. Schaefer1, and F.S. Tautz2 — 1Institut für Physik und Zentrum für Mikro- und Nanotechnologien, TU Ilmenau, PF 100565, D-98684 Ilmenau — 2School of Engineering and Science, International University Bremen, PF 750561, D-28625 Bremen
In this contribution a study of pentacene growth on single crystal Ag(111) substrates is presented. LEED and STM measurements reveal the structure of molecular layers: somewhat surprisingly, an ordered structure appears in our experiments only after the completion of two molecular layers, either disordered or very sensitive to our probing technique. The existence of the intermediate layer is proved by the following observations: (1) XPS registers a change in growth rate (at constant exposition) after the first bilayer (four times larger for the bilayer than for further layers). (2) In spite of the lack of any evidence for an ordered molecular layer on the surface, the attenuation of substrate the surface plasmon in EELS indicates the existence of a compact intermediate layer between silver and pentacene crystals. (3) HREELS reveals that vibronic peaks in the first 1-3 ML shifted with respect to corresponding multilayer features at about 15 cm−1. We conclude that molecular bonding is different in the first bilayer if compared to higher layers. For the latter, STM records submolecularly resolved images of the HOMO or LUMO orbitals, depending on tunneling voltage. In conclusion, our data suggest that pentacene growth on Ag(111) proceeds via accommodation layer.