Surface X-Ray Diffraction: The Atomic Geometry of the Ge(111)7×7-Sn and Ge(111)5×5-Sn Reconstructions
The Ge(111) surface exhibits 7×7 and 5×5 reconstructions after deposition of submonolayer coverages of Sn and subsequent annealing. We have examined these structures by surface x-ray diffraction and collected 90 non-equivalent fractional-order reflections for the 7×7 structure, and 115 for the 5×5. The diffraction pattern for both structures show considerable similarity with the pattern for Si(111)7×7, and it is shown that the DAS (Dimer Adatom Stacking fault) model for Si(111)7×7 is also applicable to the Sn-induced Ge(111)7×7 and 5×5 structures. Furthermore, we have identified the adatoms to be Sn. For the 5×5 structure a partial substitution of Ge with Sn was found at the dimer positions closest to the corner vacancies.
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