Epitaxial Fe3Si/Ge/Fe3Si thin film multilayers grown on GaAs(001)

We demonstrate Fe3Si/Ge/Fe3Si/GaAs(001) structures grown by molecular-beam epitaxy and characterized by transmission electron microscopy, electron backscattered diffraction, and X-ray diffraction. The bottom Fe3Si epitaxial film on GaAs is always single crystalline. The structural properties of the Ge film and the top Fe3Si layer depend on the substrate temperature during Ge deposition. Different orientation distributions of the grains in the Ge and the upper Fe3Si film were found. The low substrate temperature Ts of 150 °C during Ge deposition ensures sharp interfaces, however, results in predominantly amorphous films. We find that the intermediate Ts (225 °C) leads to a largely [111] oriented upper Fe3Si layer and polycrystal films. The high Ts of 325 °C stabilizes the [001] oriented epitaxial layer structure, i.e., delivers smooth interfaces and single crystal films over as much as 80% of the surface area.