Room-temperature layer-by-layer epitaxial growth and characteristics of Fe3O4 ultrathin films

Fe3O4 films with thicknesses of 2?200 unit cells were epitaxially grown on ?-Al2O3(0?0?0?1) substrates by laser molecular beam epitaxy at room temperature. The fine streaky pattern and clear intensity oscillations were observed by in situ reflection high-energy electron diffraction, indicating that the films are perfect two-dimensional layer-by-layer epitaxial growth. X-ray diffraction and atomic force microscope measurements reveal that the Fe3O4 films have high-pure crystal phase and atom-level-smooth surface. The experimental results demonstrate that the structural, electrical and magnetic properties of the room-temperature epitaxial Fe3O4 films strongly depend on the film thickness.