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O: Fachverband Oberflächenphysik

O 51: Metal Substrates: Adsorption of Organic/Bio Molecules III

O 51.11: Vortrag

Mittwoch, 27. Februar 2008, 17:45–18:00, MA 041

Local and Long Range Structure of Ferrocene on Au(111) Surfaces — •Gerhard Pirug¹, Michel Kazempoor¹, Josef Mysliveček², and Bert Voigtländer¹ — ¹Institut für Bio- und Nanosysteme (IBN3), Forschungszentrum Jülich GmbH, Germany — ²Dept. of Surface and Plasma Science, Faculty of Mathematics and Physics, Charles University Prague, Czech Republic

The adsorption of ferrocene (Fe(C₅H₅)₂) on Au(111) surfaces has been studied spectroscopically applying HREELS and structurally by means of LEED and STM. The vibrational modes observed by HREELS indicate reversible molecular adsorption at temperatures of about 110 K. The corresponding frequencies are not significantly shifted with respect to IR or Raman data for solid ferrocene, indicating a weak adsorbate - substrate interaction. Multilayer adsorption can be distinguished from the physisorbed first layer based on relative intensity changes of vibrational modes. In the monolayer regime vibrational modes with a perpendicular dipole moment from more or less upright standing ferrocene molecules dominate. Dissociation into cyclopentadienyl radicals (C₅H₅) can be excluded. Molecular self assembly yields well ordered surface structures. A commensurate (3×√3)rect (p2mg) structure has been identified from topographical STM images and LEED pattern, consistently. In addition a compressed incommensurate structure develops. Both structures are at variance with recent findings by Braun et al.¹ but can be related to the crystallographic structure of crystalline ferrocene. (¹K.F. Braun V. Iancu, N. Pertaya, K.H. Rieder and S.-W. Hla, Phys. Rev. Lett. 96, 246102 (2006))