IMPEDANCE SPECTROSCOPY OF RAMIFIED ELECTRODEPOSITS

Electrodeposition of copper from CuSO4 solutions under high electric f ield gives rise to ramified deposits. We report on impedance measureme nts on these deposits as a function of their size. The transfer impeda nce of the interface of the deposits is markedly reduced compared to t he original electrode and exhibits a CPA behaviour. This behaviour is related to the large increase of the deposit surface area. The impedan ce spectra of the obtained deposits vary in time, evidencing deposit r eorganization and/or dissolution, and homogenization of the solution. For the largest deposits that we have studied, the impedance diagrams do not depend on the cathodic polarization time, ie on the deposit siz e. Our cathodic potential measurements at the early stages of the grow th permit to give a qualitative description of the onset of ramified e lectrodeposition.