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, and chronoamperometry. 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 of more than 0.35 V down to 0.15 V. Below this potential, 2D Ni phase formation sets in and a complete monolayer grows over a period of ∼800 s. In the overpotential (OPD) range, different morphologies of Ni nanoclusters 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, large nearly spherical (∼10 nm diameter) Ni clusters first nucleate at the step edges of the Au(111) substrate and spread with time all over the surface. In this case, a progressive nucleation and growth mechanism with diffusion control is found. A distinct and interesting morphology is obtained, if first a complete monolayer of Ni is deposited at UPD conditions and then the potential is directly decreased to OPD values near −0.18 V. Elongated Ni clusters with a diameter of ∼10 nm and an aspect ratio of ∼2 nucleate and grow instantaneously. Most interestingly, they are all oriented in one direction which is indicative of a magnetic interaction between the Ni clusters.

The nanoscale electrocrystallization of pure Sb and the compound semiconductor AlSb on Au(111) has been studied by in situ scanning probe techniques (STM and STS) employing an ionic liquid electrolyte, {AlCl3-[C4mim]+Cl-} (1:1) containing SbCl3. The characteristic changes of the electronic structures with varying potentials have been probed for the first time by normalized differential conductance spectra, (dI/dU)/(I/U). In the underpotential deposition range of Sb the formation of two layers is observed. For the first monolayer a (square root 3 x square root 3)R30 degrees structure is determined from atomically resolved STM images. During the deposition and dissolution of the Sb monolayers characteristic wormlike or spinodal structures appear indicating surface alloying of antimony with the gold substrate. Under overpotential conditions two different Sb structures have been observed. If the deposition potential is continuously stepped to -0.1 V, Sb nanostripes form. On the other hand, randomly dispersed small clusters occur if the potential is jumped from 0.0 to -0.3 V vs Al/Al(III). Both modifications exhibit typical semimetallic behavior as shown by the STS spectra. At -1.1 V the cyclic voltammogram shows a clear reduction wave that is assigned to AlSb compound formation. Deposits in this potential range are characterized by a homogeneous distribution of clusters with diameters of approximately 20 nm. Conductance spectra of these clusters exhibit the main features of the electronic structure of the bulk semiconductor AlSb, with a band gap of 2.0 +/- 0.2 eV. Electrodeposition experiments on both sides of the compound deposition potential show a strong doping effect that is manifest in the corresponding conductance spectra.

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