Potential-Controlled Step Flow to 3D Step Decoration Transition: Ni Electrodeposition on Ag(111)

A novel growth effect, the potential-controlled transition from 2D step-flow growth $(-0.69{\mathrm{V}}_{\mathrm{A}\mathrm{g}/\mathrm{A}\mathrm{g}\mathrm{C}\mathrm{l}})$ to (i) selective growth of 3D admetal islands at substrate steps $(-0.73\mathrm{V})$ and (ii) 3D island growth on steps and substrate terraces $(-0.85\mathrm{V})$, is demonstrated for Ni electrodeposition on Ag(111). The nucleation and growth process apparently proceeds via direct deposition from the solution at step sites and can be rationalized by a kinetically controlled multilayer growth process, where the higher layer nucleation rate increases more with overpotential than does the 2D growth rate.