Evidence and analysis of parallel growth mechanisms in Cu sub(2)O films prepared by Cu anodization

• Published in: Electrochimica acta Vol. 55; no. 14; pp. 4353 - 4358
• Main Authors: Caballero-Briones, F, Palacios-Padros, A, Calzadilla, O, Sanz, Fausto
• Format: Journal Article
• Language: English
• Published: 30.05.2010
• Subjects: ANODES; ANODIZING; Copper; COPPER OXIDE; CUPROUS OXIDE; DISSOLUTION; ELECTRODES; Film thickness; MORPHOLOGY; NUCLEATION; Reflectance
• ISSN: 0013-4686
• DOI: 10.1016/j.electacta.2009.10.031

We have studied the preparation of Cu sub(2)O films by copper anodization in a 0.1 M NaOH electrolyte. We identified the potential range at which Cu super(+) dissolution takes place then we prepared films with different times of exposure to this potential. The morphology, crystalline structure, band gap, Urbach energy and thickness of the films were studied. Films prepared with the electrode unexposed to the dissolution potential have a pyramidal growth typical of potential driven processes, while samples prepared at increasing exposure times to dissolution potential present continuous nucleation, growth and grain coalescence. We observed a discrepancy in the respective film thicknesses calculated by coulometry, atomic force microscopy and optical reflectance. We propose that anodic Cu sub(2)O film formation involves three parallel mechanisms (i) Cu sub(2)O nucleation at the surface, (ii) Cu super(+) dissolution followed by heterogeneous nucleation and (iii) Cu super(+) and OH super(-) diffusion through the forming oxide and subsequent reaction in the solid state.