Hamburg 2001 – wissenschaftliches Programm

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SYOF: Organische Festkörper

SYOF 2: Surfaces and Interfaces

SYOF 2.6: Vortrag

Dienstag, 27. März 2001, 12:50–13:05, S6

Characterization of thin PTCDA-layers on Ag(111) using polarization dependent Raman spectroscopy — •C. Bauer¹, M. Schneider², E. Umbach², T. Muck¹, V. Wagner¹ und J. Geurts¹ — ¹Experimentelle Physik III — ²Experimentelle Physik II, Univ. Würzburg, Am Hubland, 97074 Würzburg

We characterize thin, ordered layers of PTCDA on Ag(111)-substrate using polarized in-situ Raman measurements. The layers were grown in UHV at different substrate temperatures, which leads to a stable and a meta stable stage.
The observed Raman modes of the PTCDA film were identified on the basis of literature data and own first-principles calculations (Gaussian 98). The latter give also the eigenvectors of the modes. Another fundament of the identification is the symmetry of the modes determined experimentally using the depolarisation ratio. The assigned modes show partly a distinct Davydov splitting, whose components can be observed well separated at l-He temperature. The splitting distinctly depends on the modification of the layer (see above) and can serve as simple identification. From its analysis in consideration of the eigenvectors of the modes explicit statements can be given on the bond strength of the different molecules in the solid state.