1. [1] J. R. Engstrom, D. J. Bonser, M. M. Nelson, and T. Engel, Surf. Sci. 256, 317 (1991).
2. [2] S. Ogawa and Y. Takakuwa, Jpn. J. Appl. Phys. 44, L1051 (2005).
3. [3] S. Ogawa and Y. Takakuwa, Surf. Sci. 601, 3838 (2007).
4. [4] Y. Takakuwa, F. Ishida, and T. Kawawa, Appl. Surf. Sci. 190, 20 (2002).
5. [5] Y. Takakuwa, F. Ishida, and T. Kawawa, Appl. Surf. Sci. 216, 133 (2003).