Symmetry, structure, and step induced ordering of the Si(001)-(2 × 3)Ag surface

The formation of the Si(001)-(2 × 3)Ag structure has been studied by low energy electron microscopy. The lack of mirror symmetry within the (2 × 3) unit cell in the period doubled direction gives rise to the formation of two overlayer domain types on each terrace, which dynamically order with respect to step edges. We show that an anisotropic step-domain interaction energy explains the observations. Based on a quantitative determination of the number of Ag and Si atoms in the unit cell a structure model is suggested. © 1994 The American Physical Society.