Controllable Morphology and Conductivity of Electrodeposited Cu₂O Thin Film: Effect of Surfactants

Both the morphology and conductivity of Cu₂O films are controlled in a facile electrodeposition process by tuning the concentration of surfactants. With the increase of the concentration of sodium dodecyl sulfate (SDS) in the plating solution, the average size of Cu₂O crystals increases, and the electrical conductivity of Cu₂O films changes from n-type to p-type. When the concentrations of SDS are lower than 0.85 mM, the electrodeposited Cu₂O films show n-type conductivity because of the formation of oxygen vacancies or copper atoms. When the concentration of SDS is higher than 1.70 mM, the electrodeposited Cu₂O films show p-type conductivity owing to the formation of copper vacancies. The concentrations of both the donors and the acceptors increase with the concentration of SDS. The effects of surfactants on the morphology and conductivity of electrodeposited Cu₂O films are attributed to the adsorption of SDS molecules on the electrode substrate occupying the deposition sites of Cu²⁺ ions and the adsorption of SDS micelles to Cu²⁺ ions hindering the diffusion of Cu²⁺ ions to the electrode, which affect the reduction rate of Cu²⁺ ions and the formation of oxygen vacancies or copper vacancies during the electrodeposition.