Copper electrodeposition can create periodic self-assembled structures with randomly distributed Cu/Cu2O nanograins and spontaneously periodic variations of cell voltage in the presence of an ultrathin layer of concentrated CuSO4 electrolyte. The experiment was performed at -4.85 degreesC and cell currents of 30 muA. We suggest that the observed self-assembled structures and periodic variations of cell voltage are caused by a change in the cathode over-potential and the standard electrode potential for Cu2O and Cu in front of the growing interface. The mechanism of the self-assembled structure and the spontaneously periodic variations of cell voltage is discussed. (C) 2004 Elsevier Ltd. All rights reserved.