Columnar growth and kinetic roughening in electrochemical deposition

We performed electrochemical deposition of copper at very slow rates so that local growth effects such as surface relaxation and stochastic noise can compete with the nonlocal Laplacian effects. We observed that the initial growth pattern is consistent with the conventional Mullins-Sekerka instability. This is followed by coarsening and roughening of the surface that leads to a columnar structure with deep crevices. The surface roughness for length scales below the typical column width shows a power-law behavior with an exponent α=0.55±0.06, consistent with the prediction of Kardar, Parisi, and Zhang (KPZ). However, the time dependence of the total interface width is not the ${\mathit{t}}^{1/3}$ power law predicted by KPZ.