title: Complex Stoichiometry-Dependent Reordering of 3,4,9,10-Perylenetetracarboxylic Dianhydride on Ag(111) upon K Intercalation.
abstract: Alkali metal atoms are frequently used for simple yet efficient n-type doping of organic semiconductors and as an ingredient of the recently discovered polycyclic aromatic hydrocarbon superconductors. However, the incorporation of dopants from the gas phase into molecular crystal structures needs to be controlled and well understood in order to optimize the electronic properties (charge carrier density and mobility) of the target material. Here, we report that potassium intercalation into the pristine 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) monolayer domains on a Ag(111) substrate induces distinct stoichiometry-dependent structural reordering processes, resulting in highly ordered and large KxPTCDA domains. The emerging structures are analyzed by low-temperature scanning tunneling microscopy, scanning tunneling hydrogen microscopy (ST[H]M), and low-energy electron diffraction as a function of the stoichiometry. The analysis of the measurements is corroborated by density functional theory calculations. These turn out to be essential for a correct interpretation of the experimental ST[H]M data. The epitaxy types for all intercalated stages are determined as point-on-line. The K atoms adsorb in the vicinity of the oxygen atoms of the PTCDA molecules, and their positions are determined with sub-Ångström precision. This is a crucial prerequisite for the prospective assessment of the electronic properties of such composite films, as they depend rather sensitively on the mutual alignment between donor atoms and acceptor molecules. Our results demonstrate that only the combination of experimental and theoretical approaches allows for an unambiguous explanation of the pronounced reordering of KxPTCDA/Ag(111) upon changing the K content.
authors.affiliation: Institute of Solid State Physics, Friedrich Schiller University Jena , Helmholtzweg 5, 07743 Jena, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Zwick
authors.affiliation: Institute of Solid State Physics, NAWI Graz, Graz University of Technology , Petersgasse 16, 8010 Graz, Austria.|Department of Materials Science, University of Milano-Bicocca , Via R. Cozzi 55, 20125 Milano, Italy.
authors.forename: Anu
authors.initials: A
authors.lastname: Baby
authors.affiliation: Institute of Solid State Physics, Friedrich Schiller University Jena , Helmholtzweg 5, 07743 Jena, Germany.
authors.forename: Marco
authors.initials: M
authors.lastname: Gruenewald
authors.affiliation: Institute of Solid State Physics, NAWI Graz, Graz University of Technology , Petersgasse 16, 8010 Graz, Austria.
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Verwüster
authors.affiliation: Institute of Solid State Physics, NAWI Graz, Graz University of Technology , Petersgasse 16, 8010 Graz, Austria.
authors.forename: Oliver T
authors.initials: OT
authors.lastname: Hofmann
authors.affiliation: Institute of Solid State Physics, Friedrich Schiller University Jena , Helmholtzweg 5, 07743 Jena, Germany.
authors.forename: Roman
authors.initials: R
authors.lastname: Forker
authors.affiliation: Department of Materials Science, University of Milano-Bicocca , Via R. Cozzi 55, 20125 Milano, Italy.|Dipartimento di Fisica, Università degli Studi di Milano , Via Celoria 16, 20133 Milano, Italy.
authors.forename: Guido
authors.initials: G
authors.lastname: Fratesi
authors.affiliation: Department of Materials Science, University of Milano-Bicocca , Via R. Cozzi 55, 20125 Milano, Italy.
authors.forename: Gian Paolo
authors.initials: GP
authors.lastname: Brivio
authors.affiliation: Institute of Solid State Physics, NAWI Graz, Graz University of Technology , Petersgasse 16, 8010 Graz, Austria.
authors.forename: Egbert
authors.initials: E
authors.lastname: Zojer
authors.affiliation: Institute of Solid State Physics, Friedrich Schiller University Jena , Helmholtzweg 5, 07743 Jena, Germany.|Graduate School of Science and Institute for Academic Initiatives, Department of Chemistry, Osaka University , 1-1 Machikaneyama, Toyonaka 560-0043, Osaka, Japan.
authors.forename: Torsten
authors.initials: T
authors.lastname: Fritz
keywords: density functional theory (DFT); low-energy electron diffraction (LEED); low-temperature scanning tunneling microscopy (LT-STM); potassium intercalation; scanning tunneling hydrogen microscopy (STHM); self-assembled nanostructures