We report a gradual transition in the deposition product from pure Cu2O to pure Cu, during electrodeposition on Au/Pd sputtercoated silicon wafer substrates in copper sulfate electrolyte with various dc potential. At voltages lower than 0.3 V, only pure Cu in a nanocrystalline form is deposited on the cathode substrate, while at voltages higher than 1.2 V, only pure Cu2O, also in a nano/microcrystalline form, is deposited. At intermediate voltages between 0.3 to 1.2 V, the deposition product comprises a mixture of both Cu and Cu2O nano/micro-crystals. The Cu2O crystals are generally of an octahedral shape with sizes ranging from 30 nm to 100 nm, while Cu nano/microcrystals are of irregular shape ranging from 100 nm to 2 mu m. This work provides a method to fabricate nanocrystalline Cu2O, Cu and Cu/Cu2O on substrates in a single step without the use of additives. (C) 2014 The Electrochemical Society. All rights reserved.