METAL-DEPOSITION IN THE NANOMETER RANGE

Different nucleation and growth mechanisms (Stranski-Krastanov and Fra nk-van der Merwe) were found to operate in many cases of electrocrysta llization and thin film formation of metals Me on foreign substrates, S, in systems with underpotential deposition (upd) phenomena. Modern i n situ techniques, particularly in situ STM with lateral atomic resolu tion, have directly shown that two-dimensional upd adlayers on S act a s precursors for the subsequent nucleation and growth of three-dimensi onal Me bulk phase. This is reflected in the nucleation kinetics and e pitaxial orientation of thin film deposits. The growth mode determines the microstructure and properties of the deposit. Typical examples fo r the Stranski-Krastanov and Frank-van de Merwe growth mechanisms were observed in the systems Ag(hkl)/Pb2+ and Au(hkl)/Ag+, respectively. U ltra-thin Me-films and heterostructures (sandwich-structured Memonolay ers and surface alloys) can be deposited in the upd and opd ranges. In systems, where the Frank-van der Merwe mechanism operates, the thickn ess of a thin Me film can be varied between one monolayer and a finite number of monolayers. The thickness, structure and composition of het erostructures can be controlled by the substrate, the composition of t he electrolyte, and the experimental conditions used. The systems Ag(h kl)/Pb2+, Tl+ and Au(hkl)/Ag+, Pb2+, Tl+ are discussed as typical exam ples. The results obtained are of importance for the nanotechnology de aling with structuring and modification of metal surfaces in the nanom eter range in vertical and lateral direction.