Berlin 2012 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 13: Polymeric biomolecular films

O 13.1: Vortrag

Montag, 26. März 2012, 16:00–16:15, MA 005

Photoelectron Diffraction on SnPc/Ag(111) — •Michael Greif, Luca Castiglioni, Jürg Osterwalder, and Matthias Hengsberger — Physik Institut, University of Zurich, Winterthurerstrasse 190, 8057 Zurich

Photoelectron diffraction is a method to monitor the atomic structure of surfaces. From the emitter site in the sample the photoelectron propagates as wave that is then coherently scattered by the neighboring atoms. The directly emitted and the scattered waves create interference fringes in the detector plane. By scanning all emission directions on top of the sample with the detector, a 2-D data set is recorded that gives structural information about the examined system.

In the presented work we investigated Tin-Phthalocyanine molecules (SnPc) on a Ag(111) surface with X-Ray photoelectron diffraction (XPD) and UV photoelectron diffraction (UPD). SnPc shows a well ordered wetting layer growth on a Ag(111) surface. Hence core levels of the Sn-Atom in the center of the molecule serve as well defined emitter sites for photoelectron diffraction experiments.

The diffraction patterns correspond to the structural environment around the Sn-Atoms. Comparing our measurements with simulations using single scattering calculations (SSC), we see indications of the conformational change that the SnPc molecules undergo upon adsorption. Additionally our measurements show the azimuthal orientation of the molecules with respect to the Ag(111) surface. Due to a higher probability of backscattering for low energy electrons, the UPD patterns also show contributions of the substrate structure.