Iron(II) monoxide (FeO) is thermodynamically stable in the halite (w\"ustite) structure only at elevated temperatures in a typically non-stoichiometric, Fe-deficient, Fe1−zO form that tends to phase separate and/or transform into metallic α-Fe and magnetite Fe3O4 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 w\"ustite 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.
@article{arxiv.2510.02531,
title = {Epitaxially-stabilized growth of w\"ustite FeO on 4H-SiC},
author = {Faisal Kimbugwe and Marzieh Baan and Alexandra Fonseca Montenegro and Roberto C Myers and Tyler J Grassman},
journal= {arXiv preprint arXiv:2510.02531},
year = {2026}
}