Influence of the ledge orientation on the adsorption of transition atoms on stepped BCC transition metal surfaces

Abstract

The behaviours of transition adatoms on two stepped surfaces (m(110)*(110)) and (m(110)*(001)) of body-centred cubic transition metals are studied and compared using the tight-binding approximation. One finds that the most stable adsorption sites are always close to the ledge as expected. The presence of the step very slightly modifies the diffusion rate in a direction parallel to the ledge except for the path close to it in the lower terrace when the protruding edge is not close packed. On the other hand an adatom diffusing towards the edge of a terrace is reflected by a potential barrier lying near the outer edge. This study confirms the main trends found in a previous work devoted to the (m(110)*(011)) step; it also gives evidence of the role played by the specific geometry of each step edge, for instance the adatoms at the most stable adsorption sites are less strongly bound for the (m(110)*(011)) and (m(110)*(110)) steps than in the case of the more open (m(110)*(001)) ones.