| Autor: |
Fecher, G.H., Grünewald, Ch., Merkel, M., Ostertag, Ch., Oelsner, A., Schönhense, G., Jentzsch, Th., Jüpner, H.J. |
| Zdroj: |
Thin Solid Films; July 1997, Vol. 303 Issue: 1-2 p58-65, 8p |
| Abstrakt: |
Polycrystalline C60 and Pentacene films grown on W(110) and Pt(111) have been studied in valence band photoemission using circularly polarised synchrotron radiation from BESSY with special emphasis on circular dichroism in photoemission. For thin films of C60, dichroic asymmetries of about 10% occur independent of the temperature and the substrate hinting that the rotation of the topmost layer is hindered even at room temperature. For Pentacene we found asymmetries up to 50% in the region of the σ-electrons. Moreover, we found for this molecule a dichroic asymmetry in normal emission, that is a forbidden geometry. This hints on adsorption with the molecules perpendicularly oriented at the surface. Doping the films with rubidium causes a filling of unoccupied electronic states in both molecules. In Pentacene all valence level binding energies are shifted depending on the amount of exposed Rb. For the Rb-doped C60 and C22H14 films a dichroism in emission from the Rb 4p signal occurs that is much stronger than in the case of pure, disordered Rb films at Pt(111) where the asymmetry almost vanishes. This hints on a high correlation of the Rb p-electrons in both materials that may not be neglected in investigations of the electronic structure. |
| Databáze: |
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