High-throughput investigation of electroepitaxial growth of Cu2O on Cu substrates

Abstract

The present study investigates epitaxial growth of Cu₂O on Cu through electrochemical deposition using a high-throughput method. It used a combinatorial substrate approach involving polycrystalline Cu substrates followed by verification tests involving single-crystal substrates to clarify the effects of electrolyte composition, pH, current density, and substrate orientation on the electroepitaxy of Cu₂O. The electron backscatter diffraction technique was used to analyze both the orientation and crystallinity of Cu₂O. The results reveal that electrolyte pH, current density, and substrate orientation are all critical factors governing Cu₂O electroepitaxy. Two reported epitaxial orientation relationships (ORs), (001)_Cu2O//(001)_Cu, [010]_Cu2O//[010]_Cu and (111)_Cu2O//(111)_Cu, [1–10]_Cu2O//[0–11]_Cu, were associated with a new OR of (111)_Cu2O//(001)_Cu, [1–10]_Cu2O//[1–10]_Cu. Epilayers with (111) and (110) orientations, free of twin variants and secondary orientations, were obtained in two electrolytes at 0.25 mA/cm² in accordance with the established OR maps. Among these, the (110) Cu₂O epilayers exhibited the highest crystallinity, with a rocking curve FWHM of 0.97–1.05°, surpassing all previously reported electrochemically deposited epilayers. Furthermore, the correlation established between EBSD-derived average orientation spread and XRD rocking curve FWHM demonstrates that EBSD can assess not only the orientations of the substrate and epilayer but also their crystallinity.