High-quality epitaxial Cu2O films with (111)-terminated plateau grains obtained from single-crystal Cu (111) thin films by rapid thermal oxidation

High-quality epitaxial Cu2O (111) thin films were obtained from single-crystal Cu (111) thin films by rapid thermal oxidation at 800 °C. X-ray diffraction and electron backscattering diffraction analyses indicated that the films were pure Cu2O phase and well aligned along the [111] direction. Microscopic imaging of the films revealed a unique surface morphology in the form of a plateau grain network a few microns in size, which has never been achieved previously in this semiconductor. From the absorption coefficient and its first derivative, all of the characteristic optical transitions from the yellow to the indigo series, as well as excitonic transitions, were consistent with those observed from high-quality bulk Cu2O. The exceptional quality of our films was further verified by a very weak defect-induced photoluminescence, which typically dominates in natural-growth Cu2O crystals. We believe that our study represents a step towards the synthesis of high-quality oxide films having unusual surface morphologies.