Magnetite epitaxial growth on Ag(001): Selected orientation, seed layer, and interface sharpness
Résumé
Epitaxial iron oxide layers with different orientations were grown on Ag(001) surface by choosing the appropriate preparation conditions. A film with a hexagonal surface mesh interpreted as (111)-oriented magnetite was formed by reactive deposition of iron in molecular oxygen at room temperature (RT), followed by annealing in UHV. Instead, highly ordered epitaxial layers with P4m symmetry were obtained by a three-step process, optimized through in situ experiments. Following this method, an ultrathin Fe layer was first grown in coherent epitaxy on the substrate and then dosed twice with O2, first at RT and next during annealing. A structural analysis combining low-energy electron diffraction, scanning tunneling microscopy, and accurate surface x-ray diffraction measurements confirmed that these films consist of (001)-oriented magnetite, although with a slight tetragonal distortion induced by the substrate constraints. Both its surface and interface are atomically sharp, an essential requirement for its integration into spintronic based devices.