Single-Domain and Atomically Flat Surface of κ-Ga2O3 Thin Films on FZ-Grown ε-GaFeO3 Substrates via Step-Flow Growth Mode

Herein, single-domain κ-Ga 2 O 3 thin films were grown on FZ-grown ε-GaFeO 3 substrates via a step-flow growth mode. The ε-GaFeO 3 possessing the same crystal structure and similar lattice parameters as those of the orthorhombic κ-Ga 2 O 3 facilitated the growth of κ-Ga 2 O 3 thin films, as observed by the X-ray diffraction (XRD) analysis. Furthermore, the surface morphologies of the κ-Ga 2 O 3 thin films exhibited a step-terrace and atomically flat structure. XRD φ-scan and transmission electron microscopy with selected area electron diffraction revealed that there is no occurrence of in-plane rotational domains in the κ-Ga 2 O 3 thin films on ε-GaFeO 3 substrates and that the κ-Ga 2 O 3 thin film comprised a single domain. TEM analysis revealed that there were no clear dislocations in the observation area. Moreover, high-resolution TEM observation showed that the atomic arrangements of the film and the substrate were continuous without the presence of an intermediate layer along the growth direction and were well-aligned in the in-plane direction.