Abstract
Large unit cells of dimer-adatom-stacking-fault structure and related 2 × 2 and c(4 × 2) reconstructions have been prepared by low-temperature solid-phase epitaxy and observed by scanning tunneling microscopy. The size-different unit cells of the DAS structure are considered to be a structure evolution in which more electron charge transfers in a larger unit cell from the adatom dangling bonds to the rest-atom dangling bonds. In some cases the DAS structure can degenerate into triangular 2 × 2 domains and bundlinke c(4 × 2) domains. The rest atoms are always fully filled by electrons due to the charge transfer. The adatom dangling bonds are partially filled in a c(4 × 2) symmetry and essentially empty in a 2 × 2 symmetry. As a result, the rest atoms in 2 × 2 domains can be imaged without the adatom protrusions while in the c(4 × 2) domains the protrusions of the adatoms and the rest atoms appear in zigzag chains, when the sample is negatively biased.
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