Potentiostatic deposition of Cu2O films as p-type transparent conductors at room temperature

Abstract

Single phase Cu2O films have been prepared via an electrodeposition technique onto ITO glass substrates at room temperature. Likewise, Cu2O films were deposited using a potentiostatic process from an alkaline electrolyte containing copper (II) nitrate and 1M sodium citrate. Single phase Cu2O films were electrodeposited at a cathodic deposition potential of 500mV for a reaction period of 90min, and pH of 12 to yield a film thickness of 0.49μm. The mechanism for nucleation of Cu2O films was found to vary with deposition potential. Applying the Scharifker and Hills model at −500 and −600mV to describe the mechanism of nucleation for the electrochemical reaction, the nucleation mechanism consisted of a mix between instantaneous and progressive growth mechanisms at −500mV, while above −600mV the growth mechanism was instantaneous. Using deposition times from 30 to 90min at −500mV deposition potential, pure Cu2O films with different microstructures were electrodeposited. Changing the deposition time from 30 to 90min varied the microstructure from cubic to more complex polyhedra. The transmittance of electrodeposited Cu2O films ranged from 20 to 70% in visible range, and samples exhibited a 2.4eV band gap. The electrical resistivity for electrodeposited Cu2O films was found to decrease with increasing deposition time from 0.854×105Ω-cm at 30min to 0.221×105Ω-cm at 90min without any thermal treatment following the electrodeposition process.