Atomic details of step flow growth on Si(001)

Growth at step edges by the addition of single adatoms has been studied using scanning tunneling microscopy ~STM!. It is shown that the use of empty-state instead of filled-state STM images enables the assessment of the binding sites of single adatoms at step edges. We describe all different step edge configurations obtained by subsequently sticking adatoms to these step edges. Adatom diffusion along step edges as well as the dimerization of adatoms at a step edge are also demonstrated. Finally, the creation of single dimer vacancies at step edges is discussed. @S0163-1829~97!01412-4# Step edges form the crucial growth template during epitaxial growth. In the step-flow growth mode the mobility is high enough for all growth units to reach the step edges and stick there before a new growth center is nucleated. These step edges either originate from a macroscopic misalignment of the surface relative to the crystallographic plane or from dislocations terminating at the surface. In case the mobility of the growth units is insufficient to reach existing steps, islands nucleate on the terraces. The majority of the growth