Mechanistic investigation on tuning the conductivity type of cuprous oxide (Cu2O) thin films via deposition potential

Abstract The conductivity type of cuprous oxide (Cu 2 O) thin films is tuned by controlling the deposition potential of an electrochemical process in an acid cupric acetate solution containing sodium dodecyl sulfate. The morphology and chemical composition of the deposited Cu 2 O films are studied by SEM, XRD and XPS. The change of the conductivity type of Cu 2 O films is further studied through zero-bias photocurrent and Mott-Schottky measurements. The results indicate that the Cu 2 O films behave as n-type semiconductors when the overpotentials are low (potentials higher than −0.05 V) and p-type semiconductors when the overpotentials are high (potentials lower than −0.10 V). The transformation of conductivity from n-type to p-type comes from the competition reactions between forming Cu 2 O and forming metallic Cu from Cu 2+ . When the potential is lower than −0.10 V, most of Cu 2+ are consumed by the growth of metallic Cu at the film/solution interface, so that the Cu 2+ provided to grow Cu 2 O film are insufficient and copper vacancies form in the film, leading to the p-type conductivity.