New Submission

Unlike other rocksalt-structure metal monoxides (e.g., MgO, NiO, CoO, etc.), iron (II) monoxide (FeO), or wustite, is thermodynamically unstable at standard ambient conditions, making thin-film production particularly difficult. To date, there are very few reports of high-quality thin films, and only a maximum of 8 nm as-grown thickness has been achieved (although nearly 20 nm with post-deposition reductive annealing is reported); thicker films decompose into the more thermodynamically stable metallic Fe and magnetite Fe3O4. We report here on work toward the growth of epitaxially-stabilized FeO thin films on small-mismatch 4H-SiC substrates using molecular beam epitaxy (MBE). Pure wustite films of up to nearly 200 nm have been achieved, ~22× thicker than any previously reported, with no post-processing required. The as-grown thin films exhibit a small, consistent rhombohedral distortion, with lattice parameters that remain unchanged, regardless of thickness. Preliminary Superconductive Quantum Interference Device (SQUID) magnetometry measurements confirm the characteristic antiferromagnetic behavior, but with a potential small shift in Neel temperature. Magnetic measurements, as well as other optical/electronic/magnetic properties, are currently being conducted against a wider range of film thicknesses and growth conditions and will be discussed at the conference.