Spontaneous oscillations in gold electrodeposition

We report the appearance of spontaneous oscillations during the electrodeposition of gold along the surface of aqueous hydrogen tetrachloroaurate solutions coated by a positively charged dimethyldioctadecylammonium monolayer, when a current ramp with a rate comprised between 1 and 1.5 nA s^-1 is applied to the working electrode. Alternating sequences of two-dimensional (2D) growth and three-dimensional (3D) thickening of the deposits leading to gold films with a well-de.ned terraced structure are observed. Such a phenomenon appears to be produced by the competition between two mechanisms controlling the current density J₁: one is the current ramp which tends to increase J₁ and the other one is the growing of the gold deposit which induces a decrease of J₁.