Atomic structures of kinks at double-layer steps on Si(100) surfaces

We studied the kink structures at double-layer step by scanning tunneling microscopy and catalogued the kinks into two types: complex kinks (composed of minus kinks and plus kinks) and simple kinks (only minus or plus kinks). Both of the kinks create a local A terrace. The dimers in the local A terrace are buckled. For a complex kink, the buckling of the dimers in the local A terrace is determined by the interaction of the buckled dimers propagated from minus kinks and plus kinks. For a simple kink, the buckling of the dimers in the local A terrace is determined by the buckling of the rebonded dimers at step edges. The directions of the buckled dimers are determined by the tensile stress between dimer rows. The brightness of the outermost dimers in an upper terrace is caused by the buckling of the dimers and the charge transfer between the two atoms of the dimers.