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O: Oberflächenphysik

O 24: Postersitzung (Epitaxie und Wachstum, Oxide und Isolatoren, Elektronische Struktur, Oberfl
ächenreaktionen, Adsorption an Oberfl
ächen, Organische Dünnschichten)

O 24.27: Poster

Wednesday, March 26, 2003, 14:30–17:30, P1

Evidence of strongly localised states at the Fermi Level at the Si(111)(7×7) surface — •Richard Schillinger, C. Bromberger, O. Kühlert, H. J. Jänsch, C. Weindel, and D. Fick — Philipps Universität Fachbereich Physik and Zeuntrum für Materialwissenschaften, 35032 Marburg

The Si(111)(7×7) surface is well described by the Dimer Adatom Stacking fault Model (DAS). Investigations using EELS [1] and PES [2] yielded contradictory results for the density of states (DOS) at the Fermi Level. The electronic structure of the surface at the Fermi Level is mainly derived from the adatom dimers and rings. Local density approximation calculations [3] show sharp features in the DOS at the Fermi Level due to localisation effects. β-NMR measurements of the longitudinal relaxation time T₁ of ⁸Li probe atoms adsorbed at extremely low coverage of 10⁻⁵ of a monolayer show a temperature dependence qualitatively in accordance with the latter [3] predictions. A localised state as narrow as a few meV is found at the Fermi Level.

Supported by the Deutsche Forschungsgemeinschaft Bonn.

[1] B. N. J. Persson and J. E. Demuth, Phys. Rev. B 30,(10),5960 (1984)

[2] R.Losio, K. N. Altmann and F. Himpsel, Phys. Rev. B 61,(16),10845 (2000)

[3] J. Ortega et. al, Phys. Rev. B 58,(8),4584 (1998)