| AVS 55th International Symposium & Exhibition | |
| Surface Science | Tuesday Sessions |
| Session SS-TuM |
| Session: | Dynamics at Surfaces |
| Presenter: | F. Komori, University of Tokyo, Japan |
| Authors: | F. Komori, University of Tokyo, Japan K. Tomatsu, University of Tokyo, Japan B. Yan, Tsinghua University, China C. Wang, Tsinghua University, China M. Yamada, University of Tokyo, Japan K. Nakatsuji, University of Tokyo, Japan G. Zhou, Tsinghua University, China W. Duan, Tsinghua University, China |
| Correspondent: | Click to Email |
Electron scattering in the transport through atomic-scale wires has attracted much interest, especially for possible application to functional devices. We have investigated this subject using a one-dimensional (1D) electronic system at surfaces, where we can study simultaneously the microscopic structure and electron scattering by observing topographic images and electronic standing waves in differential conductance (dI/dV) images with scanning tunneling microscopy (STM).1 The scattering potential can be controlled by atomic manipulation by STM. Electron scatterings by impurity Si or Sn atoms inserted in a quasi-1D system were studied on a Ge(001) surface at 80 K. On the clean surface, Ge atoms form buckled dimers, which align and form a dimer row. Among the dangling bond states of the Ge dimer, an empty π* surface electron, which localizes at the lower atoms of the Ge dimers, is quasi 1D along the dimer row. We prepared impurity dimers with Si or Sn atoms by deposition on the surface. A buckled Sn-Ge impurity dimer with Sn atom at the lower-atom position (Sn L-dimer) reflects the electrons, and a standing wave was observed in the dI/dV image. Whereas, a standing wave by a Sn-Ge dimer with Sn atom at the upper-atom position (Sn U-dimer) was too small to be observed. The standing wave amplitudes are almost the same for the Si-Ge dimers with the Si atom at the upper- and lower-atom positions (Si U-dimer and Si L-dimer). The signs of the scattering potentials by the impurity dimers were obtained by analyzing phase shift of the standing waves. The Si and Sn L-dimer, where the impurity atom is located in the conduction pathway, are potential well and barrier, respectively, for the π* electrons. Whereas, the Si U-dimer is a potential barrier. These results are qualitatively understood by the fact that the π* electrons propagate on the lower atoms of the buckled dimers. The Si and Sn U-dimer can be reversibly transformed to the Si and Sn L-dimer, respectively, by the bias voltage change for the STM observation as the Ge dimers2 on the clean surface. Consequently, by switching them between U-dimer and L-dimer, we can manipulate the scattering amplitude of the π* electrons for the Sn-Ge dimer, and the scattering phase for the Si-Ge dimer.
1 K. Tomatsu et al Science 315 1696, 2007.
2 Y. Takagi, Y. Yoshimoto, K. Nakatsuji and F. Komori, Surf. Sci. 559 1, 2004; Phys. Rev. B75 115304, 2007.