Berlin 2012 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 78: Metal substrates: Adsorption of organic / bio molecules IV
O 78.3: Vortrag
Donnerstag, 29. März 2012, 16:30–16:45, A 053
Using polarized light in photoelectron emission microscopy — •Thorsten Wagner1, Zdena Druckmüllerova1,2, Daniel Roman Fritz1, and Peter Zeppenfeld1 — 1Johannes Kepler University Linz, Institute of Experimental Physics, Linz, Austria — 2Brno University of Technology, Institute of Physical Engineering, Brno, Czech Republic
Photoelectron emission microscopy (PEEM) combines a high lateral resolution with the capability to monitor processes at surfaces in real-time. For experiments in the lab, unpolarized light of a Hg lamp is commonly used to excite the photoelectrons. In this case, valuable information about the optical anisotropy of the surface under investigation is lost. On the other hand, techniques like reflectance difference spectroscopy (RDS) which are focussed on this anisotropy have proven to be useful tools to study thin adsorbate films of organic molecules. So why not combining both in a single experiment? In this presentation we will show, how polarized light can be used to study the growth of α-sexithiophene on silver and nickel oxide surfaces. As the ionization potential of the molecules is higher than the photon energy, the light of the Hg lamp only excites electrons from the metal-organic interface. In this case, no direct response of the molecules to the polarized light can be expected in the PEEM image. Nevertheless, the molecules are optical anisotropic and act as dichroic filters for the incident light. This effect can actually be used, e.g., to probe the orientation of the molecules even during growth.