Understanding the Si 7x 7: Energetics, Topology, and Stress
Several experiments [1-4] strongly support the “dimer adatom stacking-fault” (OAS) model of TAKAYANAGI et al. as being the correct structural model for the Si 7×7. Attention is now shifting towards attempts to understand the reasons for the formation of this structure. McRAE  has suggested that relief of a strong compressive surface stress  is the driving force for the reconstruction. QIAN and CHAOI  and NORTHRUP  have emohasized danglinqbond reduction and adatom formation as the driving mechanisms. A successful theory should discriminate among these possibilities, identify the factors which determine the DAS periodicity, elucidate the relationship of the Si 7×7 to the Gé c2×8, and explain experiments showing a strain-dependence of the surface reconstruction pattern [9-13].
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