Influence of the electrode potential on the Ehrlich-Schwoebel barrier

Abstract

Using the surface-embedded-atom-model, recently modified to describe atomic interactions at the electrolyte-metal interface, we calculate the variation of terrace-diffusion and Ehrlich-Schwoebel (ES) barriers for Ag adatoms migrating on Ag surfaces with variations of the electrode potential. We consider both hopping and exchange diffusion. We find that whereas the terrace diffusion barrier on the flat (unstepped) (111) surface is relatively insensitive to the potential, the ES barrier is extremely sensitive, undergoing a rapid increase at potentials positive of the potential of zero charge (PZC) with an increase of the order of 1 eV between 0.5 and 1 V positive of the PZC. This sensitivity arises from changes in the position of step-edge atoms brought about by the changes in the surface stress and vertical relaxation caused by the potential changes. On the Ag(100) surface, however, both terrace diffusion and ES barriers are sensitive to changes in the potential, but the situation is complicated by the different effect of the potential on exchange and hopping diffusion resulting in the switchover from one to the other mechanism being dominant. We also assess the effect of the electrode potential on the ES barriers for Ag adatoms migrating on overlayers of Ag on Au(111) and its role on the observed Stranski-Krastanov growth observed for Ag electrodeposited on Au(111).