Electrodeposition and anodic dissolution of Ni on Au(100): an in situ STM study

Results of an in situ STM study on the electrodeposition and electrochemica l dissolution of Ni on Au(100) electrodes are presented, showing pronounced differences for the nucleation and submonolayer growth on the reconstructe d and the unreconstructed surface. On perfectly reconstructed Au(100) Ni is land formation starts at overpotentials eta greater than or equal to 100 mV . Due to the simultaneous removal of the underlying Au reconstruction they contain a significant fraction of incorporated Au atoms. Deposition on the unreconstructed surface starts at eta greater than or equal to 40 mV via fo rmation of Ni monolayer islands with diameters limited to approximate to 30 Angstrom. The different growth mechanisms can be rationalized by the diffe rent surface mobility and different mechanisms of strain release in the Ni deposit. At multilayer coverages a rough morphology is found, which is inde pendent of the Au(100) surface structure. Dissolution of the Ni film indica tes an enhanced stability of the monolayer as compared to the Ni multilayer deposit.