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 ROWSDUE 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 atomica lly resolved structural change between c(4 x 2) and p(2 x 2) arrangeme nts 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 s imilar to that of the type-C defect. Dimer flip-flop motion at the pha se boundary which induces the apparent phase transition; and creation and annihilation of the anti-phase domain were clearly observed.