Manganese-cobalt-zinc oxide films are deposited on graphite foils by a dry process, simpler one-step radio frequency sputtering with different substrate treatment temperatures and bias potential. The best long-term operational stability (only reduce about 7% specific capacitance at the 8000th cycle of potential cycling) and good specific capacitance are obtained at a substrate treatment temperature of 200 degrees C and without substrate bias potential. Furthermore, the lower the substrate treatment temperature, the better the stability. Moreover, the specific capacitance of the manganese-cobalt-zinc oxide electrode decreases with increasing substrate bias potential. (C) 2011 Elsevier Ltd. All rights reserved.