Energetics of the Si(111) and Ge(111) surfaces and the effect of strain
- School of Physics, Georgia Institute of Technology, Atlanta, Georgia 30332 (United States)
Using tight-binding models, the energies of a number of silicon and gemanium (111) surfaces are studied. These include reconstructed surfaces with dimers and stacking faults (DS), simple adatom surfaces such as 2[times]2 and [ital c](2[times]8), and more complicated cases with dimers, adatoms, and stacking faults (DAS). For reconstructed surfaces containing adatoms, it is found that a simple correction term dependent on the adatom concentration is needed in the present total-energy model to account for the unusual geometry. Similarities between the silicon and germanium reconstructions are seen and compare well with [ital ab] [ital initio] results. There are also some differences between silicon and germanium; for example, the DS surfaces are lower in energy than the relaxed (1[times]1) for silicon, but higher for germanium. Si(111) reconstructs into the DAS structure while Ge(111) goes to the simple adatom [ital c](2[times]8) surface. The [ital c](2[times]8), 7[times]7 DAS, (1[times]1), and 7[times]7 DS surface reconstructions of Ge(111) were studied with in-plane strain. For these surfaces, a strain of about 2% was sufficient to make the 7[times]7 DAS/DS surface lower in energy than the [ital c](2[times]8)/(1[times]1) surface. An analysis of the energy per atom showed that the dimer-row and associated first-layer atoms played a major part in the differing energy behavior, in agreement with an earlier proposal. An expansive strain was applied to the 2[times]2, 7[times]7 DAS, (1[times]1), and 7[times]7 DS surface reconstructions of Si(111). With a strain of about 2.5% the adatom surfaces switched relative energies, while the adatom free surfaces required only about 1.5% strain. As for germanium, the dimer-row and associated atoms were of major importance in the differing energy change.
- OSTI ID:
- 6022672
- Journal Information:
- Physical Review, B: Condensed Matter; (United States), Journal Name: Physical Review, B: Condensed Matter; (United States) Vol. 48:8; ISSN PRBMDO; ISSN 0163-1829
- Country of Publication:
- United States
- Language:
- English
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