Dimers of the (100) surface, which had previously been observed at 120 to 140K and which had appeared to be symmetrical, were frozen at 6K and an atomically resolved structural change between c(4x2) and p(2x2) arrangements of the (100) surface were observed for the first time by means of scanning tunnelling microscopy. The observed change was attributed to the fluctuations of phase defects of a new type on dimer rows. These had a structure which was similar to that of the type-C defect. Dimer flip-flop motion at the phase boundary, which caused the apparent phase transition, and the creation and annihilation of antiphase domains were clearly observed.

H.Shigekawa, K.Miyake, M.Ishida, K.Hata, H.Oigawa, Y.Nannichi, R.Yoshizaki, A.Kawazu, T.Abe, T.Ozawa, T.Nagamura: Japanese Journal of Applied Physics, 1996, 35[2-8B], L1081-4