Ferromagnet/semiconductor/ferromagnet hybrid trilayers grown using solid-phase epitaxy

The direct growth of semiconductors (SC) over metals by molecular beam epitaxy is a difficult task due to the large differences in crystallization energy between these types of materials. This aspect is problematic in the context of spintronics, where coherent spin injection must proceed via ballistic transport through sharp interfacial Schottky barriers. We report the realization of single-crystalline ferromagnet/SC/ferromagnet hybrid trilayers using solid-phase epitaxy, with combinations of Fe3Si, Co2FeSi, and Ge. The slow annealing of amorphous Ge over Fe3Si results in a crystalline film identified as FeGe2. When the annealing is performed over Co2FeSi, reflected high-energy electron diffraction and x-ray diffraction indicate the creation of a different crystalline Ge(Co,Fe,Si) compound, which also preserves growth orientation. It was possible to observe independent magnetization switching of the ferromagnetic layers in a Fe3Si/FeGe2/Co2FeSi sample, thanks to the different coercive fields of the two metals and to the quality of the interfaces. This result is a step towards the implementation of vertical spin-selective transistor-like devices.