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Adatoms on Si(111) and Ge(111) surfaces

Adatoms on Si(111) and Ge(111) surfaces First-principles calculations of energy and stress are performed on adatom-covered Si(111) and Ge(111) surfaces. The presence of adatoms is found to lower the surface energy and cause a large change in surface stress. While the 1×1 surfaces are under a weak compressive stress, the √3×√3 and 2×2 adatom-covered surfaces are under a strong tensile stress. Calculations at high plane-wave cutoff unambiguously identify the 2×2 top-site geometry as the energetically preferred adatom configuration. Relaxed geometries are presented and compared with x-ray structural measurements of adatoms in the Si(111)- 7×7 structure. Vibrational mode frequencies and eigenvectors of the adatom unit are determined from a comprehensive set of frozen-phonon calculations for the Si 2×2 surface; we find two symmetric modes that are strongly localized at the surface, in agreement with electron-energy-loss – spectroscopy measurements. It is found that the 2×2 adatom-covered surfaces have three surface bands, and the dispersion relations are calculated along symmetry directions in the surface Brillouin zone. The surface band structures are in good agreement with angle-resolved photoelectron-spectroscopy data for the 7×7 -Si(111) surface. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Physical Review B American Physical Society (APS)

Adatoms on Si(111) and Ge(111) surfaces

Meade, Robert D; Vanderbilt, David D
Physical Review B , Volume 40 (6) – Aug 15, 1989
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Publisher
American Physical Society (APS)
Copyright
Copyright © 1989 The American Physical Society
ISSN
1095-3795
DOI
10.1103/PhysRevB.40.3905
Publisher site
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Abstract

First-principles calculations of energy and stress are performed on adatom-covered Si(111) and Ge(111) surfaces. The presence of adatoms is found to lower the surface energy and cause a large change in surface stress. While the 1×1 surfaces are under a weak compressive stress, the √3×√3 and 2×2 adatom-covered surfaces are under a strong tensile stress. Calculations at high plane-wave cutoff unambiguously identify the 2×2 top-site geometry as the energetically preferred adatom configuration. Relaxed geometries are presented and compared with x-ray structural measurements of adatoms in the Si(111)- 7×7 structure. Vibrational mode frequencies and eigenvectors of the adatom unit are determined from a comprehensive set of frozen-phonon calculations for the Si 2×2 surface; we find two symmetric modes that are strongly localized at the surface, in agreement with electron-energy-loss – spectroscopy measurements. It is found that the 2×2 adatom-covered surfaces have three surface bands, and the dispersion relations are calculated along symmetry directions in the surface Brillouin zone. The surface band structures are in good agreement with angle-resolved photoelectron-spectroscopy data for the 7×7 -Si(111) surface.

Journal

Physical Review B – American Physical Society (APS)

Published: Aug 15, 1989

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