Surfactant-induced layer-by-layer growth of Ag on Ag(111): origins and side effects

It has been shown that submonolayer deposits of Sb change the growth mode of Ag(111) from multilayer to layer-by-layer. Using scanning tunneling microscopy, we identify the two main origins of this behavior. (i) Sb lowers the mobility of Ag adatoms on terraces and growing islands. As a direct consequence, the additional edge barrier (barrier to descend a step minus surface diffusion barrier) is reduced. (ii) Sb lowers the mobility along step edges, inducing dendritic island shapes. Both effects favor smoother growth. Neither a lower Ag surface mobility nor heterogeneous nucleation are sufficient for a smooth growth.