MECHANISM OF A MORPHOLOGY TRANSITION IN RAMIFIED ELECTROCHEMICAL GROWTH

RAMIFIED patterns are common in nature, and have been much studied in the context of non-equilibrium growth and aggregation phenomena1-4. Pr ocesses that are known to produce ramified growth may lead to a range of morphologies, depending on experimental parameters such as growth s peed. The mechanism of the transitions between different morphologies is not fully understood1-4. Electrochemical deposition of ramified dep osits5-29 is often regarded as a model system for studying two-dimensi onal pattern formation. Here we present experimental results which all ow us to propose a mechanism for the transition between fractal-like, ramified growth and rectilinear, filamentary growth of electrodeposits . We show that electroconvection of the metal ions in solution induces physical displacements of the growing branches, which results in fann ing and splitting of the tips. At sufficiently high growth speeds, bre aking of the symmetry with which this fanning occurs can lead to a cha nge in growth morphology. We suggest that mechanical motions and distu rbances may play a role in other pattern-forming systems.