Fig. 4.

Evolution of step morphology at σ ≈ 0.1 at the beginning of an experiment (A) Initial configuration step. (B) Two newly formed mounds, indicated with a black arrowhead and a white square (shown enlarged in Inset). (Inset) Mound depth d is defined. (B and C) The lower mound in B produces multiple kinks indicated with a black arrowhead in C. Multiple kinks generated above the field of view cover molecular rows generated by mounds in B. (D) At 430 s, the step straightens out again. (D–F) The spreading of a multiple kink generated out of the viewfield is monitored between 430 and 608 s. White arrowheads in F point to two defects in the outermost row of molecules. Black arrows indicate scan directions. Times after the first image are marked on the frames; a shift of the viewfield to follow the step took 10 s between D and E. Black lines mark step location on the current image, and white lines mark step location in the preceding image.