General mechanism for the synchronization of electrochemical oscillations and self-organized dendrite electrodeposition of metals with ordered 2D and 3D microstructures

Mechanisms for potential oscillations and synchronizing self-organized formation of ordered dendrite structures, which is an important example of morphogenesis in Laplacian fields, were studied using Sn, Zn, Cu, and Pb electrodeposition. Electron backscattering diffraction (EBSD) experiments showed that Sn latticework as a typical example of the ordered dendrite structures grew in an epitaxial mode in particular directions from the Sn electrode surface. In situ optical and phase-contrast microscopic inspection showed that the Sn latticework growth as well as the concentration profile for deposited Sn(II) ions near the growing front oscillated in synchronization with the potential oscillation, which led to formation of a highly ordered Sn latticework structure. Similar behavior was observed in other electrodeposition systems. On the basis of these results, a general mechanism for the potential oscillations and synchronized formation of the ordered dendrite structures was proposed, in which autocatalytic crystal growth, passivation in flat surfaces of dendrites, and depletion of deposited metal ions in the electrolyte near and inside the dendrites played the key roles. Numerical calculations by use of a modified coupled map lattice (CML) model confirmed the validity of the mechanism. The clarification of the general mechanism has enabled us to classify all the oscillatory dendrite growth, including reported ones by other research groups, into three types (type-I, type-II, and type-III), which will serve for preparation of designed and controlled micro- and nanostructures at solid surfaces.