Plasma assisted molecular beam epitaxy of Cu2O on MgO(001): Influence of copper flux on epitaxial orientation

• Epitaxial Cu2O thin films were grown by PAMBE on MgO(001).
• Enhancement of cube-on-cube growth MgO(001) substrates.
• This correlates with the appearance of a (3√2×√2)R45° reconstruction.
• Thin films exhibit distinct excitonic features in absorption and photoluminescence.

We report on the growth of cuprous oxide on MgO(001) by plasma-assisted molecular beam epitaxy. An increased copper to oxygen ratio enhances the cube-on-cube growth of the Cu2O crystallites compared to the Cu2O(110)||MgO(100) oriented crystallites. This correlates with the occurrence of a (3√2×√2)R45° surface reconstruction observed during growth. This reconstruction is known to be unstable under oxygen-rich conditions and stabilizes the Cu2O(001) surface compared to the Cu2O(110) surface for higher copper to oxygen ratios enhancing cube-on-cube growth.High resolution X-ray diffraction analysis of the resulting cube-on-cube Cu2O layers indicates partial relaxation by 39.7%. Investigations of the optical absorption and photoluminescence properties of the films reveal excitonic contributions comparable to those of single crystals.