Realisation of magnetically and atomically abrupt half-metal/semiconductor interface: Co 2 FeSi 0.5 Al 0.5 /Ge(111)

• Published in: Scientific reports 2016-11, Vol.6, p.37282
• Main Authors: Nedelkoski, Zlatko, Kuerbanjiang, Balati, Glover, Stephanie E, Sanchez, Ana M, Kepaptsoglou, Demie, Ghasemi, Arsham, Burrows, Christopher W, Yamada, Shinya, Hamaya, Kohei, Ramasse, Quentin M, Hasnip, Philip J, Hase, Thomas, Bell, Gavin R, Hirohata, Atsufumi, Lazarov, Vlado K
• Format: Article
• Language: English
• ISSN: 2045-2322

Halfmetal-semiconductor interfaces are crucial for hybrid spintronic devices. Atomically sharp interfaces with high spin polarisation are required for efficient spin injection. In this work we show that thin film of half-metallic full Heusler alloy Co FeSi Al with uniform thickness and B2 ordering can form structurally abrupt interface with Ge(111). Atomic resolution energy dispersive X-ray spectroscopy reveals that there is a small outdiffusion of Ge into specific atomic planes of the Co FeSi Al film, limited to a very narrow 1 nm interface region. First-principles calculations show that this selective outdiffusion along the Fe-Si/Al atomic planes does not change the magnetic moment of the film up to the very interface. Polarized neutron reflectivity, x-ray reflectivity and aberration-corrected electron microscopy confirm that this interface is both magnetically and structurally abrupt. Finally, using first-principles calculations we show that this experimentally realised interface structure, terminated by Co-Ge bonds, preserves the high spin polarization at the Co FeSi Al /Ge interface, hence can be used as a model to study spin injection from half-metals into semiconductors.