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O: Fachverband Oberflächenphysik

O 6: Organic/bio Molecules on Metal Surfaces I

O 6.4: Talk

Monday, March 11, 2013, 11:15–11:30, H38

Identification of two different charge transfer mechanisms at Phthalocyanines/Ag interfaces — •Eric Salomon and Thierry Angot — Aix-Marseille university, Marseille, France

As the performance of organic molecule based electronic devices depends critically on the electrode-organic interfaces it appears crucial to have thorough understanding of the fundamental processes governing the metal-molecule interactions.

The vibrational properties of several M-phthalocyanines (here with M=H2, Zn, Cu, Co, Fe) adsorbed on Ag surfaces have been carefully investigated using high resolution electron energy loss spectroscopy (HREELS). In the monolayer range, a wide loss feature ranging from 200 up to 800 meV is commonly observed that displays a positive quadratic dispersion. It is interpreted as a surface-plasmon resulting from a space-charge region arising from an electron-vibration coupling at the interface between the organic monolayer and the metallic substrate. Nevertheless, significant differences are observed depending on the metal atom M. In most cases, while Infra Red active modes dominate, some vibrational motions of the adsorbate are damped by energy transfer to the metal substrate leading to Raman active modes with Fano line shape. However, this is not the case for Co- and Fe-Pc, in which systems no Fano line shape mode is observed. This demonstrates that electron-phonon coupling strongly depends on the property of the central metal atom. This is further confirm by photoemission spectroscopy measurements demonstrating that the alteration of the valence band upon adsorption depends of the central atom.