PHYSICAL REVIEW B, cilt.69, sa.12, 2004 (SCI-Expanded)
We have used scanning tunneling microscopy to study the faceting of <010> oriented steps on Si(001) and Ge(001) surfaces. The <010> oriented steps on Si(001) tend to facet into local S-A and S-B step segments, whereas <010> oriented steps on Ge(001) meander along the mean <010> direction. We show that the step faceting behavior of the Si and Ge(001) surfaces is fully governed by the next-nearest-neighbor (NNN) interaction between the substrate dimers. Only in the case of a repulsive NNN interaction, as for Si(001), faceting occurs.