Role of a topological defect in the local structure transformation on clean Ge(0Â 0Â 1) surface by STM

The transformation rate of the local superstructure from c(4 × 2) to p(2 × 2) is studied on the clean Ge(0 0 1) surface at 80 K by scanning tunneling microscopy (STM). The transformation is reversible and shows hysteresis for the direction of the sample bias voltage change. The rate was found to depend on the width of the terrace. The results are explained by the mechanism that a topological defect between c(4 × 2) and p(2 × 2) structures are formed and moved by the electronic excitation from the tunneling electron to the Ge lattice. The electronic structure of the defect obtained by first-principles calculation is consistent with the bias-dependent STM images.