Nanometer-to-micron sized cuprous oxide (Cu2O) single crystals were fabricated on Au/Pd sputter-coated silicon wafer and stainless steel cathode substrates by electrodeposition in CuSO4 at pH 4.0 at room temperature (25 degrees C) with no additives. The Cu2O crystals were generally of an octahedral shape with sizes ranging from 100 nm to 400 nm on Si wafer, and 1 mu m to 3 mu m on stainless steel substrates respectively. Very small crystals of a spherical shape were also observed under low applied voltage. Transient crystal shapes observed on the cathode near the electrolyte surface suggest that growth slows down once {1 1 1} free surfaces are formed, and this explains the robust observation of the octahedral crystal shape. The effect of electrodeposition parameters such as deposition voltage and deposition time on the size of the crystals and their coverage on the substrates was investigated. Apart from the cathode, similar octahedral Cu2O nanocrystals were also found to deposit on the Cu anode used. This work provides a method to fabricate Cu2O crystals on both electrodes in a single step. (C) 2011 Elsevier Ltd. All rights reserved.