Interlayer-Mediated Stabilization of Metastable P63cm ScFeO3 on Al2O3

Abstract

The metastable P6₃cm phase of ScFeO₃ has potential for multiferroic applications not possible in the ground state if stabilization routes can be identified. This work demonstrates that the P6₃cm phase of ScFeO₃ is stabilized on (0001) Al₂O₃ by the spontaneous formation of two atomic layers of (111) Fm$\overline{3}$m FeO during pulsed laser deposition, as observed via scanning transmission electron microscopy and a shift in the Fe L-edge on approaching the interface. The matching oxygen sublattice and reduced strain of the FeO interlayer enable a ScFeO₃ [11$\overline{2}$0] || [$\overline{1}\overline{1}$2] FeO || Al₂O₃ [11$\overline{2}$0] orientation relationship despite a −17.1% lattice mismatch. Temperature-dependent X-ray diffraction further support interlayer-mediated stabilization, as FeO forms above 850 °C, preceding the formation of the P6₃cm ScFeO₃ phase at 1000 °C. The identification of the FeO interlayer provides insights into the phase stabilization mechanism of P6₃cm ScFeO₃ and presents a strategy for stabilizing other metastable materials that lack epitaxial substrates.