A New Approach to Metal Electrodeposition at a Periodically Change Rate. Part I. The Reversing Overpotential Method

Abstract

A method of increasing the apparent deposition exchange current density value in reversing overpotential (RO) copper electrodeposition is described. In pulsating overpotential (PO) metal electrodeposition, the current density during the ‘off’ period is anodic, and proportional to the exchange current density value. The current during the ‘off’ period in PO copper electrodeposition can be increased by appropriate anodic polarization. This method is referred to as the RO method to distinguish it from the pulsating method. In order to maintain the average current density in this case, it is necessary to increase the cathodic current density during the ‘on’ period. Hence, the current density during the anodic period can be considered as proportional to the exchange current density for some other deposition process, characterized by a larger exchange current density value. The apparent deposition process exchange current density can be increased easily by using different current densities during the anodic period, and different morphologies for the same average current density can be expected. In this way, previously unknown morphologies of copper electrodeposits in the overpotential region used were obtained as spongy and needle-like forms.