Dresden 2003 – wissenschaftliches Programm
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O: Oberflächenphysik
O 25: Hauptvortrag Heringdorf
O 25.1: Hauptvortrag
Donnerstag, 27. März 2003, 09:30–10:15, HSZ/02
The Growth of Pentacene Thin Films for Organic Thin Film Transistors — •F.-J. Meyer zu Heringdorf1,2, M.C. Reuter1 und R.M. Tromp1 — 1IBM T.J. Watson Research Center, 1101 Kitchawan Road, Yorktown Heights, NY 10598, USA — 2present address: Universität Essen, 45117 Essen, Germany
The growth of organic thin film transistors based on pentacene has received widespread attention during the last years, due to the comparatively high transport mobilities that have been achieved in this material. To further improve pentacene-based devices, however, a fundametal understanding of the growth processes and -modes of the organic material become increasingly important. Here, we present a Low Energy Electron Microscopy (LEEM) and Photoemission Electron Microscopy (PEEM) study of the growth of pentacene thin films. On SiO2, commonly used as a substrate for organic devices, pentacene forms a polycrystalline film with high nucleation density. On clean Si substrates, after the formation of an initial wetting layer where the molecules are lying down flat, pentacene forms up to 50µ m large islands. We demonstrate how a careful chemical modification of the surface, e.g. by pre-adsorption of cycloexene, suppresses the formation of the initial layer and forces the formation of a thin film phase from the beginning of the deposition. From an analysis of island shape and nucleation density we can describe the growth mode in terms of classical nucleation theory and diffusion limited aggregation.