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O: Fachverband Oberflächenphysik

O 5: Adsorption on semiconductors, oxides and insulators I

O 5.10: Talk

Monday, March 26, 2012, 12:45–13:00, MA 042

Reflectance anisotropy spectroscopy of clean and adsorbate-covered Si(111) surfaces: comparison of experiment and hybrid density functional theory — Soumya Banerjee, Sofia Giorgi, John F. McGilp, and •Charles H. Patterson — School of Physics, Trinity College Dublin, Dublin 2, Ireland.

Reflectance anisotropy (RA) at surfaces of cubic semiconductors provides a means of probing the electronic structure and optical transitions of their outermost atomic layers. We present experimental data and hybrid density functional theory (DFT) calculations for RA spectra of the clean Si(111)-2x1, Si(111)-3x1-Ag and Si(111)-5x2-Au surfaces. We test several structural models for the metal adsorbate covered surfaces as their exact structures are not known. Models which consist of linear regions of pi-bonded Si in honeycombs, which are separated by metal-rich rows give good agreement with experimental RA data. The exchange functional in these hybrid DFT calculations is adjusted so that the bulk Si band gap agrees with the experimental band gap. There is no need for a 'scissors' shift of the conduction band in these calculations.