STM investigation of the initial adsorption stage of Bi on Si(100)-(2 x 1)and Ge(100)-(2 x 1) surfaces

Scanning tunneling microscopy has been used to investigate the initial adso rption stage of Bi on Si(1 0 0) and Ge(1 0 0) surfaces at room temperature. The most favorable position for a Bi ad-dimer on both surfaces is the B-co nfiguration (Bi ad-dimer positioned on-top of the substrate rows with its d imer bond aligned along the substrate dimer row direction). For Si(1 0 0) t he A-type dimers (dimer bond aligned perpendicular to the substrate dimer r ow direction) occasionally rotate back and forth to a B-configuration. The diffusion rates of B-type and A-type dimers along the substrate row and the B-A, A-B rotations on Si(1 0 0) are extracted from an analysis of many seq uences of STM images. Finally, it is shown that the presence of an attracti ve interaction between Bi ad-dimers (irrespective of their orientation) pos itioned on neighboring substrate dimer rows leads to the formation of local regions with a 2 x 2 reconstruction. (C) 2001 Published by Elsevier Scienc e B.V.