The orientational relationship between monoclinic β-Ga2O3 and cubic NiO

• (100) oriented β-Ga2O3 films were formed on a (100) NiO layer on a (100) MgO substrate.
• β-Ga2O3 has a 4-fold domain structure that satisfies (010) β-Ga2O3 ‖ {011} NiO.
• A γ-Ga2O3 layer was observed at the interface between β-Ga2O3 and NiO.
• An epitaxial (100) NiO film was formed on a (100) β-Ga2O3 single-crystal substrate.
• The above NiO film satisfied (011) NiO ‖ (010) β-Ga2O3.

The orientational relationship between β-Ga2O3 and NiO was studied by X-ray diffraction measurements and cross-sectional high resolution transmission electron microscopy. A β-Ga2O3 thin film was formed on a (100) NiO layer on a (100) MgO substrate by gallium evaporation in an oxygen plasma. It was found that the resulting β-Ga2O3 had a four-fold domain structure satisfying both (100) β-Ga2O3 ‖ (100) NiO and (010) β-Ga2O3 ‖ {011} NiO. A γ-Ga2O3 layer was observed at the interface between the β-Ga2O3 and the NiO. An NiO film was also formed on a (100) β-Ga2O3 single-crystal substrate by the sol–gel method. An epitaxial (100) NiO film was formed on a (100) β-Ga2O3 substrate, and satisfied (011) NiO ‖ (010) β-Ga2O3. The crystal orientations of β-Ga2O3 on (100) NiO and NiO on (100) β-Ga2O3 can be explained using atomic arrangement models of the (100) plane of NiO and the (100) plane of β-Ga2O3.