An X-ray diffraction study was made of the Ge(111)-c(2 x 8) surface. From the analysis of 43 in-plane, symmetry-inequivalent structure factors, a simple adatom model with sub-surface relaxation was deduced. The relaxations around the adatoms were similar to those observed in the adatom complexes on Si(111)-(7 x 7) and Sn/Ge(111)-(√3 x √3 ), -(5 x 5), and -(7 x 7), suggesting that the adatoms were located in threefold sites above the second-layer atoms (T4 sites). Significant distortions around the rest atoms were seen due to rehybridization of the dangling bonds. The diffraction peaks from the eighth-order reflections were displaced away from their nominal positions. This was explained by a model where the long-range order of the c(2 x 8) structure was disturbed by faults due to rows of 2 x 2 unit cells.

Surface Structure and Long-Range Order of the Ge(111)-c(2 x 8) Reconstruction. R.Feidenhans, J.S.Pedersen, J.Bohr, M.Nielsen, F.Grey, R.L.Johnson: Physical Review B, 1988, 38, 9715-20