High-quality Cu2O crystals with various morphologies grown by thermal oxidation

We present an improved preparation method for, and experimental results on, high-quality crystals of cuprous oxide (${\mathrm{Cu}}_2\mathrm{O}$) grown by thermal oxidation. X-ray diffraction and low-temperature optical measurements at 2 K confirm excellent characteristics that are on par with natural-growth cuprite crystals. Synthetic ${\mathrm{Cu}}_2\mathrm{O}$ crystals were prepared in different geometries including platelets, cylindrical wires, and spheroids. Interestingly, we observed that the oxidation of Cu wires at high temperatures leads to the formation of hollow tubules of ${\mathrm{Cu}}_2\mathrm{O}$. Such unconventional structures of ${\mathrm{Cu}}_2\mathrm{O}$ could be utilized to confine excitonic matter, or serve as high-density exciton–polariton cavities.