Dresden 2017 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 45: Organic-Inorganic Hybrid Systems and Organic Films

O 45.14: Poster

Dienstag, 21. März 2017, 18:30–20:30, P1A

The initial stages and local configurations of ultrathin TiOPc layers on Ag(111) — •Sebastian Thussing, Laura Fernandez, Alexander Mänz, Gregor Witte, and Peter Jakob — Fachbereich Physik, Philipps-Universität Marburg, 35032 Marburg, Germany

The evolution of titanyl-phthalocyanine (TiOPc) thin films grown on Ag(111) has been investigated using IRAS, SPA-LEED, TDS and STM. In the (sub)monolayer regime a 2D-gas, a commensurate (c) and a point-on-line (POL) phase can be observed, thereby the non-planar TiOPc molecule is adsorbed in an oxygen-up configuration with the molecular backbone oriented parallel to the surface. The c-phase contains two molecules at inequivalent adsorption sites within the unit cell displaying different azimuthal orientations with respect to the Ag(111) substrate. Approaching full saturation (POL-phase) Pauli repulsion leads to a further azimuthal reorientation that enables a higher packing density. By monitoring the prominent Ti=O stretching mode in IRAS and identifying local molecular packing configurations in STM, a microscopic model for the growth of TiOPc bilayers on Ag(111) is suggested and defect structures within these bilayers are identified. The TiOPc bilayer displays a high thermal stability up to 500 K, which is attributed to hydrogen bonds between oxygen of the titanyl unit and the hydrogen rim of phthalocyanines in the second layer, in addition to contributions arising from the oppositely oriented axial dipole moments and the ubiquitous van der Waals interactions.