It was found that a gradual (√3 x √3)-to-(3 x 3) phase transition of the Sn/Ge(111) system nucleated at substitutional Ge defects in the Sn layer, as observed by scanning tunnelling microscopy. The scanning tunnelling microscopic images were interpreted in terms of frozen defect-induced localized phonon modes; resulting in local lattice distortions with (3 x 3) symmetry.

Defect-Induced Localized Lattice Distortions in Sn/Ge(111). L.Petersen, Ismail, E.W.Plummer: Physical Review B, 2002, 65[2], 020101 (4pp)