Interconversion of α-Fe2O3 and Fe3O4 Thin Films: Mechanisms, Morphology, and Evidence for Unexpected Substrate Participation

• DOI: 10.1021/jp504020a
• Publication Date: 2014-10-01T18:50:04Z
• Authors: Francesca Genuzio; Alessandro Sala; Thomas Schmidt; Dietrich Menzel; Hans-Joachim Freund
• Keywords: Low-energy electron microscopy; Low-energy electron diffraction

The reversible transformations of thin magnetite (Fe3O4) and hematite (α-Fe2O3) films grown on Pt(111) Ag(111) single crystals as support have been investigated by a combined low energy electron microscopy (LEEM) low-energy diffraction (LEED) study. conversions were driven oxidation, annealing in ultrahigh vacuum (UHV), or Fe deposition with subsequent annealing. As expected, the oxidation Fe3O4 film yielded an α-Fe2O3 structure. Unexpectedly, UHV also led to transformation from into α-Fe2O3, but only if was used substrate. In contrast, substrate inverse reaction, slow Fe3O4, observed, expected for oxygen desorption. transformed Fe3O4. most probable explanation we propose that conversion supports proceeds cation diffusion through atom dissolution substrate, decreasing concentration within iron oxide film. This process is not possible interconversions, which best observable mixed containing domains both oxides, occurred growth one domain type well-defined boundaries rates.