title: CuPc/Au(1 1 0): Determination of the azimuthal alignment by a combination of angle-resolved photoemission and density functional theory.
abstract: Here we report on a combined experimental and theoretical study on the structural and electronic properties of a monolayer of Copper-Phthalocyanine (CuPc) on the Au(1 1 0) surface. Low-energy electron diffraction reveals a commensurate overlayer unit cell containing one adsorbate species. The azimuthal alignment of the CuPc molecule is revealed by comparing experimental constant binding energy (kxky)-maps using angle-resolved photoelectron spectroscopy with theoretical momentum maps of the free molecule's highest occupied molecular orbital (HOMO). This structural information is confirmed by total energy calculations within the framework of van-der-Waals corrected density functional theory. The electronic structure is further analyzed by computing the molecule-projected density of states, using both a semi-local and a hybrid exchange-correlation functional. In agreement with experiment, the HOMO is located about 1.2 eV below the Fermi-level, while there is no significant charge transfer into the molecule and the CuPc LUMO remains unoccupied on the Au(1 1 0) surface.
authors.affiliation: Institute of Physics, Karl-Franzens-Universität Graz, NAWI Graz, Austria.
authors.forename: Daniel
authors.initials: D
authors.lastname: Lüftner
authors.affiliation: Institute of Physics, Karl-Franzens-Universität Graz, NAWI Graz, Austria.
authors.forename: Matus
authors.initials: M
authors.lastname: Milko
authors.affiliation: Experimentelle Physik VII und Wilhelm Conrad Roentgen Research Center for Complex Material Systems, Universität Würzburg, 97074 Würzburg, Germany ; Gemeinschaftslabor für Nanoanalytik, Karlsruher Institut für Technologie KIT, 76021 Karlsruhe, Germany.
authors.forename: Sophia
authors.initials: S
authors.lastname: Huppmann
authors.affiliation: Experimentelle Physik VII und Wilhelm Conrad Roentgen Research Center for Complex Material Systems, Universität Würzburg, 97074 Würzburg, Germany ; Gemeinschaftslabor für Nanoanalytik, Karlsruher Institut für Technologie KIT, 76021 Karlsruhe, Germany.
authors.forename: Markus
authors.initials: M
authors.lastname: Scholz
authors.affiliation: Experimentelle Physik VII und Wilhelm Conrad Roentgen Research Center for Complex Material Systems, Universität Würzburg, 97074 Würzburg, Germany ; Gemeinschaftslabor für Nanoanalytik, Karlsruher Institut für Technologie KIT, 76021 Karlsruhe, Germany.
authors.forename: Nam
authors.initials: N
authors.lastname: Ngyuen
authors.affiliation: Experimentelle Physik VII und Wilhelm Conrad Roentgen Research Center for Complex Material Systems, Universität Würzburg, 97074 Würzburg, Germany ; Gemeinschaftslabor für Nanoanalytik, Karlsruher Institut für Technologie KIT, 76021 Karlsruhe, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Wießner
authors.affiliation: Experimentelle Physik VII und Wilhelm Conrad Roentgen Research Center for Complex Material Systems, Universität Würzburg, 97074 Würzburg, Germany ; Gemeinschaftslabor für Nanoanalytik, Karlsruher Institut für Technologie KIT, 76021 Karlsruhe, Germany.
authors.forename: Achim
authors.initials: A
authors.lastname: Schöll
authors.affiliation: Experimentelle Physik VII und Wilhelm Conrad Roentgen Research Center for Complex Material Systems, Universität Würzburg, 97074 Würzburg, Germany ; Gemeinschaftslabor für Nanoanalytik, Karlsruher Institut für Technologie KIT, 76021 Karlsruhe, Germany.
authors.forename: Friedrich
authors.initials: F
authors.lastname: Reinert
authors.affiliation: Institute of Physics, Karl-Franzens-Universität Graz, NAWI Graz, Austria.
authors.forename: Peter
authors.initials: P
authors.lastname: Puschnig
keywords: Angle-resolved photoemission spectroscopy; Density functional theory; Organic molecule; Organic–metal interface