Real-time scanning tunnelling microscopic evidence was presented for spontaneous roughening on Cl-terminated Si(100)-2x1 surfaces. Dimer vacancy strings were shown to dissociate into individual single-atom vacancy strings. These strings could be separated by single or double rows of Si dimers, producing regions with local 3x2 and 5x2 structures, respectively. The dynamical rearrangements reported here were driven by the reduction in steric interactions on the roughened surface. For Cl, the driving force was small and these local rearrangements were often reversible. However, certain vacancy configurations pinned the rearrangement so as to yield stable surface structures.

Spontaneous Roughening and Vacancy Dynamics on Si(100)-2x1:Cl. D.Chen, J.J.Boland: Surface Science, 2002, 518[3], L583-7