Ag-mediated step-bunching instability on vicinal Si(100)

Silver-mediated multistep formation on vicinal Si(100)-(2x1) is investigated by spot profile-analysing-low-energy electron diffraction and scanning tunnelling microscopy. The employed 4 degrees-miscut of the sample towards [110] leads to a single domain substrate with smooth and equidistant double steps. Surface reconstruction and step structure of the vicinal are altered drastically upon submonolayer adsorption of Ag at similar to 700 K: a (3 x 2) superstructure is formed which is characterised by an anisotropic interaction with steps, thus preserving the single domain character of the surface. Furthermore, pronounced step-bunching leads to the formation of a regular array of multiple double steps with preference For sixfold step height. It is supposed that the attempt to lower surface stress is the driving force for this step-bunching instability. As a general feature of the restructured step topography, the long-range order of lateral step positions is not affected, i.e. the vicinal remains Bat with respect to the macroscopic surface orientation. Finally, the experimental results are verified by comparative numerical simulations of the diffracted intensity I(k(perpendicular to), k(parallel to)). (C) 1997 Elsevier Science B.V.