Atomic structure of monatomicSBsteps on clean Si(001) and Ni-contaminated Si(001)

The atomic structure at monatomic-height ${\mathit{S}}_{\mathit{B}}$ steps on clean Si(001) and a Ni-contaminated Si(001) was investigated using high-resolution scanning tunneling microscopy at room temperature. Rebonded ${\mathit{S}}_{\mathit{B}}$ steps are dominant on clean Si(001). Nonrebonded ${\mathit{S}}_{\mathit{B}}$ steps with split-off dimers are favored on the Ni-contaminated Si(001) and in the vicinity of dimer vacancies on clean Si(001). The nonrebonded step with the split-off dimer is generated by the strain due to dimer vacancies. A buckled dimer was observed in the vicinity of a kink of ${\mathit{S}}_{\mathit{B}}$ step edges on clean Si(001). © 1996 The American Physical Society.