title: Self-Limited Growth in Pentacene Thin Films.
abstract: Pentacene is one of the most studied organic semiconducting materials. While many aspects of the film formation have already been identified in very thin films, this study provides new insight into the transition from the metastable thin-film phase to bulk phase polymorphs. This study focuses on the growth behavior of pentacene within thin films as a function of film thickness ranging from 20 to 300 nm. By employing various X-ray diffraction methods, combined with supporting atomic force microscopy investigations, one crystalline orientation for the thin-film phase is observed, while three differently tilted bulk phase orientations are found. First, bulk phase crystallites grow with their 00L planes parallel to the substrate surface; second, however, crystallites tilted by 0.75° with respect to the substrate are found, which clearly dominate the former in ratio; third, a different bulk phase polymorph with crystallites tilted by 21° is found. The transition from the thin-film phase to the bulk phase is rationalized by the nucleation of the latter at crystal facets of the thin-film-phase crystallites. This leads to a self-limiting growth of the thin-film phase and explains the thickness-dependent phase behavior observed in pentacene thin films, showing that a large amount of material is present in the bulk phase much earlier during the film growth than previously thought.
authors.affiliation: Institute of Solid State Physics, NAWI Graz, Graz University of Technology , Petersgasse 16, 8010 Graz, Austria.
authors.forename: Stefan
authors.identifier: http://orcid.org/0000-0001-8276-9742
authors.initials: S
authors.lastname: Pachmajer
authors.affiliation: Institute of Solid State Physics, NAWI Graz, Graz University of Technology , Petersgasse 16, 8010 Graz, Austria.
authors.forename: Andrew O F
authors.identifier: http://orcid.org/0000-0001-9624-6643
authors.initials: AO
authors.lastname: Jones
authors.affiliation: Institute of Solid State Physics, NAWI Graz, Graz University of Technology , Petersgasse 16, 8010 Graz, Austria.
authors.forename: Magdalena
authors.initials: M
authors.lastname: Truger
authors.affiliation: Institute of Pharmaceutical Sciences, Department of Pharmaceutical Technology, University of Graz , Universitätsplatz 1, 8010 Graz, Austria.
authors.forename: Christian
authors.identifier: http://orcid.org/0000-0002-8519-9690
authors.initials: C
authors.lastname: Röthel
authors.affiliation: Department of Physics, Humboldt Universität zu Berlin , Brook-Taylor-Straße 6, 12489 Berlin, Germany.
authors.forename: Ingo
authors.initials: I
authors.lastname: Salzmann
authors.affiliation: Institute of Pharmaceutical Sciences, Department of Pharmaceutical Technology, University of Graz , Universitätsplatz 1, 8010 Graz, Austria.
authors.forename: Oliver
authors.initials: O
authors.lastname: Werzer
authors.affiliation: Institute of Solid State Physics, NAWI Graz, Graz University of Technology , Petersgasse 16, 8010 Graz, Austria.
authors.forename: Roland
authors.initials: R
authors.lastname: Resel
keywords: X-ray diffraction; organic semiconductors; organic thin film growth; pentacene; polymorphism; thin film morphology