Defect-induced localized lattice distortions in Sn/Ge(111)

Abstract

The gradual $(\sqrt{3}\ifmmode\times\else\texttimes\fi{}\sqrt{3})$ to $(3\ifmmode\times\else\texttimes\fi{}3)$ phase transition of the Sn/Ge(111) system nucleates at substitutional Ge defects in the Sn layer, as observed by scanning tunneling microscopy (STM). We offer an interpretation of the STM images in terms of frozen defect-induced localized phonon modes, resulting in local lattice distortions with $(3\ifmmode\times\else\texttimes\fi{}3)$ symmetry. Furthermore, we speculate on the nature of the phase transition.