What is it about?
This study investigates why epitaxial β-Ga₂O₃ films grown on (100) diamond form a textured structure with multiple rotational domain variants instead of a single crystal. Using electron microscopy, we show that this texture originates from the pseudo-symmetry related to the oxygen sublattice and the overall low symmetry related to the monoclinic nature of β-Ga₂O₃, which together allow several nearly equivalent in-plane orientations. Domain boundaries between these variants are often highly coherent, with small lattice rotations or distortions that are likely to minimize strain and overall energy at the interfaces. In cases of higher mismatch, the boundaries change character to maintain coherence. These findings explain how symmetry, geometric factors and elastic anisotropy can govern domain formation and boundary structure in β-Ga₂O₃, and they provide insights for optimizing epitaxial growth on diamond for future high-power electronic devices.
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Why is it important?
Understanding how pseudo-symmetry and lattice geometry govern texture and domain formation in β-Ga₂O₃ films on high-symmetry substrates is key to engineering microstructure in this ultrawide-bandgap material. The findings explain why multiple domain variants form and how coherent boundaries can accommodate strain while reducing the overall energy of the system, providing a microstructural basis for optimizing epitaxial growth. These insights will guide strategies to minimize common defects and optimize the thermal and electrical performance of β-Ga₂O₃-based power electronic devices.
Perspectives
This work provides new insight into how pseudo-symmetry and elastic anisotropy govern domain formation and boundary coherency in low-symmetry oxides such as β-Ga₂O₃. The findings offer a framework for understanding how structural asymmetries manifest in the resulting microstructure and, in turn, can influence key material properties such as strain accommodation, defect distribution, and anisotropic phonon/carrier transport. Building on these results, future studies could employ interface engineering through substrate offcut, 2D-step terrace structures, among other strategies, to induce step-flow growth that can promote single-domain growth. More broadly, this approach offers a path to correlating crystallographic (pseudo-)symmetry, microstructure, and functional properties in other complex, low-symmetry materials.
Ramandeep Mandia
Northwestern University
Read the Original
This page is a summary of: (Pseudo-)symmetry-driven coherent interfaces and texture in epitaxial β-Ga
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thin films on (001) diamond, Journal of Applied Crystallography, October 2025, International Union of Crystallography,
DOI: 10.1107/s1600576725008283.
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