Phase transition between c(4x2) and p(2x2) structures of the Si(100) surface at 6K caused by the fluctuation of phase defects on dimer rows due to dimer flip-flop motion

Dimers of the Si(100) surface previously observed at 120-140 K, which partially appeared to be symmetric, were frozen at 6 K, and an atomically resolved structural change between c(4 x 2) and p(2 x 2) arrangements of the Si(100) surface was observed for the first time by scanning tunneling microscopy. The observed change was due to the fluctuation of phase defects of a new type on dimer rows, which have a structure similar to that of the type-C defect. Dimer flip-flop motion at the phase boundary which induces the apparent phase transition; and creation and annihilation of the anti-phase domain were clearly observed.