ANISOTROPIC STRAIN EFFECT ON MORPHOLOGY AND ATOMIC-STRUCTURE OF VICINAL SI(001) SURFACE

On vicinal Si(001) surfaces, dependence of growth morphology on the ap plied strain direction and formation of vacancy lines from Ag-induced missing dimer vacancies are studied. Both phenomena are intimately rel ated to the anisotropic nature of the strain field which originates fr om the surface dimerization. Strain relief mechanism, reflecting on th e surface morphology, is shown to be different in two orthogonal direc tions. Normal to the steps, step-pair bunching and waving lead to form ation of hillocks and pits. Along the step direction, bending of step pairs forms a cusp which later develops into a deep groove. Toward the atomic scale, the formation of the vacancy lines is driven by the sho rt-range attractive interaction between the vacancies in adjacent dime r rows and the long-range repulsive interaction between them in the sa me dimer row. A full form and magnitudes of the interactions are deriv ed from the thermally-excited wandering of the vacancy lines formed by a nominal amount of Ag depositing onto the surface.