Fabrication of highly (1 1 1)-oriented Cu₂O films on glass substrates by repeated chemical bath deposition

In this study, we fabricated Cu₂O films on bare glass substrates by a chemical bath deposition technique, which consists of a seeding process and a subsequent film-growth process. Dense (1 1 1)-oriented Cu₂O films were formed in an aqueous solution of copper (II) sulfate containing L-ascorbate and citrate ions at a low temperature of 80 °C. The film thickness and (1 1 1)-orientation degree (Lotgering factor) were both monotonically increased by simply repeating the film-growth process. As a result, a Cu₂O film with a high (1 1 1)-orientation degree of 0.83 and a large thickness 1440 nm was obtained. Detailed chemical and structural characterizations suggested that as-deposited Cu₂O films contained citrate ions and metallic Cu as impurities. We also found that a heat treatment at 500 °C under nitrogen flow was effective to remove these impurities.