Preferentially oriented thin-film growth of CuO(1 1 1) and Cu2O(0 0 1) on MgO(0 0 1) substrate by reactive dc-magnetron sputtering

Copper oxide films deposited on MgO(0 0 1) substrates by reactive magnetron sputtering under the metal-mode condition were studied by X-ray diffraction (XRD) and reflection high-energy electron diffraction (RHEED) analyses for structural analysis, and X-ray-excited Auger electron spectroscopy (XAES) for chemical bonding analysis. CuO(1 1 1) thin films grew from their initial growth stage maintaining the same crystallinity on MgO(0 0 1) substrates at 400°C. When the substrate temperature was increased to 600 °C, the as-sputtered films comprise Cu(0 0 1), amorphous Cu2O phase, and Cu2O(0 0 1) phase. The Cu(0 0 1) phase was observed at initial growth stage. This is probably because O2 gas molecules could not sufficiently stick to the MgO substrate at 600 °C. Single phase of Cu2O(0 0 1) was obtained by the cooling of the as-sputtered films in O2 atmosphere. The growth of single phase Cu2O(0 0 1) is considered as a solid-phase heteroepitaxial growth on MgO(0 0 1) surface, which was caused by incorporating O2 gas into the as-sputtered films.