In situ observations using interference contrast microscopy have carried out in an electrochemical deposition system of a ZnSO4 solution film. Concentration oscillation around a growing dendrite tip, which is illustrated by local contrast oscillation, has been found to correspond to sidebranching of the dendrite. A model concerning the competition between diffusion of cations and growth of dendrites has been used to explain this oscillation phenomenon. It appears that this concentration field oscillation in front of the dendrite tip plays an important role in sidebranching.

In situ observations technique is evmloyed to study the freatctal growth in a thin isothermal aqueous-soulution film of Ba(NO3)2. The micromorphology and the growing process of the fractals have been investigated. The experimental findings provide direct evidence that the fractals are formed by random successive nucleation. A nucleation-limited-aggregation (NLA) model is proposed to describe the fractal growth in our system. A computer simuation using the NLA model is also presented.

Straight copper wire arrays are electrochemically deposited on a silicon substrate without utilizing additives or templates. To suppress the influence of the factors which arouse the ramification of the copper electrodeposit, an ultrathin electrochemical deposition system and an initially homogeneous electric field are used. The width of the copper wires may vary from about 200nm to about 1.5μm depending on the control parameters. The microstructure of the copper wires and their electric resistance after vacuum-annealing at 200℃ are studied. We suggest that this self-organized copper electrodeposition is helpful in gaining an understanding of the formation of dense-branching morphology. It also implies the potential application in microelectronics.

In this Letter we report a unique fractal aggregation behavior of NH4Cl crystallites grown in agarose gel. The fractal branches consist of faceted crystallites with remarkable correlations in their crystallographic orientations, which are formed by successive heterogeneous nucleations. Unlike the conventional fractal growth, this aggregation process occurs at a low growth driving force with strong crystallographic anisotropy, which leads to the ordering in the fractal branches. [S0031-9007 (98) 05675-0]