Electrochemical self-assembly of copper/cuprous oxide layered nanostructures
"Layered nanostructures of copper metal and cuprous oxide are electrodeposited from alkaline solutions of Cu(II) lactate at room temperature. The electrode potential oscillates spontaneously during constant-current deposition. The potential oscillations are attributed to the formation and breakdown of a rectifying Cu₂O/solution interface. A thin layer of pure Cu₂O is grown during the negative-going direction in the potential oscillations and a Cu/Cu₂O composite is formed at the positive-going direction in the potential oscillations. The thicknesses of the Cu₂O layers are in the nanometer range. The phase composition of the Cu/Cu₂O films is a function of the solution pH and applied current density for the galvanostatic deposition. The coper content increases as the applied current density is increased at a given pH and decreases as the pH of the solution is increased at a given applied current density. The copper content in the Cu/Cu₂O films increases as the applied potential is more negative at a given solution pH for the potentiostatic deposition. Linear sweep voltammetry was used to study the rectifying behavior of the Cu₂O/solution junction. The Schottky-like rectifying barrier decreases as the pH of the solution is increased with a relation of -0.046 eV/pH. The barrier height of the junction is 0.61 eV for a pH 9 solution and 0.49 eV for a pH 12 solution. The optical and electrical properties of pure cuprous oxide films were also studied. The electrodeposited Cu₂O film has a direct bandgap of 2.04 eV ± 0.06eV The Cu₂O films grown at pH = 9 show a strong [100] orientation, while Cu₂O films grown at pH = 12 show [111] orientation. The Cu₂O films grown at higher pH and more positive applied potential are more conductive"--Abstract, page iii.
Missouri University of Science and Technology
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