Biatomic Layer-High Steps on Si(001)2×1 Surface

Abstract
Clean Si(001) surfaces with the 2×1 reconstruction are investigated by transmission electron diffraction (TED) and microscopy (TEM). TED patterns from (1̄1l) vicinal surfaces of off-angles of 2-5° indicate the formation of a single oriented 2×1 structure. The 2×1 superlattice reflection spots in the TED patterns indicate first that the surface has bilayer-high steps and dimers are parallel to the steps. Secondly, the 2×1 unit cell displaces across the bilayer-high step by + [110]/2 ( - [110]/2) on the vicinal surface were the mean direction of the steps rotated positively (negatively) from the [110]. Up to about 20 degrees of the rotation, the single 2×1 domain persists.