Reactive sputtering of vanadium nitride thin films as pseudo-capacitor electrodes for high areal capacitance and cyclic stability

Abstract

Vanadium nitride (VN) films with different thicknesses were deposited over polished silicon substrate using DC plasma reactive sputtering. These films were tested as electrodes for electrochemical capacitors in a 1 M KOH aqueous electrolyte solution. The electrodes show excellent specific capacitance with maximum areal capacitance value of 238.2 mF cm−2 at 5 mV s−1 scan rate, and 77.5% capacity retention after 2000 cycles. Moreover, the capacitance was found to increase with the VN deposit thickness. The XPS analyses of the electrodes confirm the presence of oxide and oxynitrides layers formed at the VN film surface, which could be responsible for the redox energy storage in this material. Such electrodes can compete with other pseudo-capacitive materials that deliver high energy density.