| Abstract
| - Electrocrystallization of Ni nanostructures has been studied at the Au(111)/ionic liquid [AlCl3−[C4mim]+Cl-(58:42) + 5 mM Ni(II)] interface by in-situ scanning tunneling microscopy, cyclovoltammetry, andchronoamperometry. In the underpotential deposition (UPD) region, a well-defined superstructure, incommensurate c(p × 2) structure, of adsorbed AlCl4- layers is observed. It exists over a potential range ofmore than 0.35 V down to 0.15 V. Below this potential, 2D Ni phase formation sets in and a completemonolayer grows over a period of ∼800 s. In the overpotential (OPD) range, different morphologies of Ninanoclusters have been obtained depending on the parameters of the respective electrodeposition procedures.Jumping the potential from above 0.15 V (UPD) to −0.25 V, the peak potential of bulk Ni deposition, largenearly spherical (∼10 nm diameter) Ni clusters first nucleate at the step edges of the Au(111) substrate andspread with time all over the surface. In this case, a progressive nucleation and growth mechanism withdiffusion control is found. A distinct and interesting morphology is obtained, if first a complete monolayerof Ni is deposited at UPD conditions and then the potential is directly decreased to OPD values near −0.18V. Elongated Ni clusters with a diameter of ∼10 nm and an aspect ratio of ∼2 nucleate and growinstantaneously. Most interestingly, they are all oriented in one direction which is indicative of a magneticinteraction between the Ni clusters.
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