Electrodeposition of metals for micro- and nanostructuring at interfaces between solid, liquid and gaseous conductors: Dendrites, whiskers and nanoparticles

Electrodeposition of a metal requires the reduction of metal ions by electrons and call in principle occur at any interface or in any boundary region between two electrically conducting phases with different ionic transference numbers. Here we summarize and review metal deposition at all possible five interfaces: solid/solid (short s/s), liquid/liquid (l/l), solid/liquid (s/l), solid/gas (s/g), liquid/gas (l/g), emphasizing processes at less studied interfaces. Cathodic deposition of a metal from a liquid electrolyte (s/l interface) is the most typical case and forms the basis of numerous applied galvanic processes. The equivalent deposition of a metal on a solid electrolyte (s/s interface) is much less usual, but phenomenologically identical. The deposition processes of a metal at the interface between two liquid electrolytes, or between a gaseous conductor and either a solid or a liquid conductor form three other possible situations. Examples for these five general cases (the s/l interface is only briefly treated) are reviewed and discussed with respect to the growth kinetics and the product morphology. Nano-sized memory devices, switches, electron beam induced formation of metals on solid electrolytes and plasma-cathodic metal deposition from ionic liquids, where in the first place the very low vapour pressure of ionic liquids facilitates the application of low-temperature plasmas, are discussed as possible new and unusual applications of electrochemical metal deposition.