Fractal aggregation growth and the surrounding diffusion field

Silver metal trees grow and form a forest at the edge of a Cu plate in the AgNO3 water solution in a two-dimensional (d = 2) cell. The local structure of the forest is similar to that of the diffusion-limited aggregation (DLA), but the whole pattern approaches a uniform structure. Its growth dynamics is characterized by the fractal dimension Df of DLA. Time-dependence of the tip height is found to satisfy the scaling relation with the solute concentration c, and the asymptotic growth velocity V is consistent with the power law V similar to c1/(d-Df) expected from the theory. The thickness zetac of the diffusion boundary layer is measured by the Michelson interferometry, and the scaling relation is also confirmed. (c) 2005 Elsevier B.V. All rights reserved.