title: Direct observation of epitaxial organic film growth: temperature-dependent growth mechanisms and metastability.
abstract: The growth of the first ten layers of organic thin films on a smooth metallic substrate has been investigated in real-time using the model system PTCDA on Ag(111). The complex behaviour is comprehensively studied by electron microscopy, spectroscopy and diffraction in a combined PEEM/LEEM instrument revealing several new phenomena and yielding a consistent picture of this layer growth. PTCDA grows above room temperature in a Stranski-Krastanov mode, forming three-dimensional islands on a stable bi-layer, in competition with metastable 3rd and 4th layers. Around room temperature this growth mode changes into a quasi layer-by-layer growth, while at temperatures below about 250 K a Vollmer-Weber-like behaviour is observed. By means of laterally resolved soft X-ray absorption spectroscopy the orientation of all adsorbed molecules is found to be homogeneously flat lying on the surface, even during the growth process. The films grow epitaxially, showing long-range order with rotational domains. For the monolayer these domains could be directly analysed, showing an average size of several micrometers extending over substrate steps.
authors.affiliation: Fritz-Haber-Institut der Max-Planck-Gesellschaft, Chemische Physik, 14195 Berlin, Germany. schmidtt@fhi-berlin.mpg.de and ELMITEC Elektronenmikroskopie GmbH, Albrecht-von-Groddeck-Str.3, 38678 Clausthal-Zellerfeld, Germany.
authors.forename: Helder
authors.initials: H
authors.lastname: Marchetto
authors.affiliation: Fritz-Haber-Institut der Max-Planck-Gesellschaft, Chemische Physik, 14195 Berlin, Germany. schmidtt@fhi-berlin.mpg.de and Universität Würzburg, Experimentelle Physik, Am Hubland, 97074 Würzburg, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Schmidt
authors.affiliation: Universität Würzburg, Experimentelle Physik, Am Hubland, 97074 Würzburg, Germany.
authors.forename: Ullrich
authors.initials: U
authors.lastname: Groh
authors.affiliation: Universität Würzburg, Experimentelle Physik, Am Hubland, 97074 Würzburg, Germany and Forschungszentrum Jülich GmbH, IEK-5 Photovoltaik, 52425 Jülich, Germany.
authors.forename: Florian C
authors.initials: FC
authors.lastname: Maier
authors.affiliation: Fritz-Haber-Institut der Max-Planck-Gesellschaft, Chemische Physik, 14195 Berlin, Germany. schmidtt@fhi-berlin.mpg.de and Université de Montréal, Département de Chimie, Montréal, Québec H3C 3J7, Canada.
authors.forename: Pierre L
authors.initials: PL
authors.lastname: Lévesque
authors.affiliation: Friedrich-Alexander-Universität Erlangen-Nürnberg, Department Chemie und Pharmazie, 91058 Erlangen, Germany.
authors.forename: Rainer H
authors.initials: RH
authors.lastname: Fink
authors.affiliation: Fritz-Haber-Institut der Max-Planck-Gesellschaft, Chemische Physik, 14195 Berlin, Germany. schmidtt@fhi-berlin.mpg.de.
authors.forename: Hans-Joachim
authors.initials: HJ
authors.lastname: Freund
authors.affiliation: Fritz-Haber-Institut der Max-Planck-Gesellschaft, Chemische Physik, 14195 Berlin, Germany. schmidtt@fhi-berlin.mpg.de and Universität Würzburg, Experimentelle Physik, Am Hubland, 97074 Würzburg, Germany.
authors.forename: Eberhard
authors.initials: E
authors.lastname: Umbach