In an attempt to obtain wustite Fe1-xO as epitaxial films on MgO(100), NO2-assisted molecular-beam epitaxy was applied. At low NO2 fluxes, the low-energy electron diffraction and reflection high-energy electron diffraction images indeed indicate the formation of a rocksaltlike structure. In addition, Mössbauer spectroscopy provides evidence for the formation of a phase that is paramagnetic at room temperature. However, the layers are not pure oxides but are well-ordered oxynitrides with composition Fe1-xO1-yNy. The nitrogen atoms occupy substitutional sites on the oxygen-anion sublattice. Similarly, at slightly higher NO2 fluxes, magnetitelike oxynitride films with composition Fe3+δ O4-yNy are obtained. By correlating x-ray photoelectron spectroscopy spectra with the intensity oscillation periods observed during reflection high-energy electron diffraction, it is possible to derive the complete stoichiometry of the films. We propose that the abrupt incorporation of nitrogen atoms only occurs if the atomic oxygen provided by the NO2 flux is insufficient to form a stoichiometric Fe3O4.
|Number of pages||11286821|
|Journal||Physical Review B - Condensed Matter and Materials Physics|
|Publication status||Published - 2001|
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics