The atomic structures, at monatomic-height SB steps on clean (001) surfaces and Ni-contaminated (001) surfaces, were investigated by using high-resolution scanning tunnelling microscopy at room temperature. It was found that re-bonded SB steps predominated on clean (001) surfaces. On the other hand, non re-bonded SB steps with split-off dimers were favored on the Ni-contaminated (001) surfaces, and in the vicinity of dimer vacancies on clean (001) surfaces. Non re-bonded steps with split-off dimers were generated by the strain that was caused by dimer vacancies. A buckled dimer was observed, in the vicinity of a kink of SB step edges, on a clean (001) surface.

J.Y.Koo, J.Y.Yi, C.Hwang, D.H.Kim, S.Lee, J.Cho: Physical Review B, 1996, 54[15], 10308-11