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arXiv · 2510.02531

Epitaxially-stabilized growth of wüstite FeO on 4H-SiC

Faisal Kimbugwe·Marzieh Baan·Alexandra Fonseca Montenegro·Roberto C Myers·Tyler J Grassman
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Abstract

Iron(II) monoxide (FeO) is thermodynamically stable in the halite (wüstite) structure only at elevated temperatures in a typically non-stoichiometric, Fe-deficient, Fe$_{1-z}$O form that tends to phase separate and/or transform into metallic $α$-Fe and magnetite Fe$_3$O$_4$ at ambient conditions. Here we report on the successful growth of up to 180 nm thick $(111)$-oriented FeO heteroepitaxial films on slightly lattice-matched 4H-SiC$(0001)$ using molecular beam epitaxy (MBE). The films have flat, terraced surfaces with tall multi-layer steps. X-ray diffraction (XRD), high-resolution scanning transmission electron microscopy (S/TEM), energy-dispersive X-ray spectroscopy (EDS), and core-level electron energy loss spectroscopy (EELS) collectively confirm the epilayer as phase-pure wüstite FeO, with atomically sharp FeO/SiC interfaces. The films are found to exhibit a slight misfit strain-induced rhombohedral distortion that does not appear to vary over the range of thicknesses examined. These results demonstrate the power of epitaxial stabilization for integrating a thermodynamically unstable, yet functionally interesting material with a commercially available and technologically important semiconductor platform.

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Faisal Kimbugwe, Marzieh Baan, Alexandra Fonseca Montenegro, Roberto C Myers, Tyler J Grassman. 2025-10-02. Epitaxially-stabilized growth of wüstite FeO on 4H-SiC. https://doi.org/10.1021/acs.cgd.5c01403

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