Berlin 2012 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 36: Magnetic Heusler Compounds II
MA 36.8: Vortrag
Donnerstag, 29. März 2012, 12:00–12:15, H 1012
Rare-earth oxides as interface layer for Co2FeSi/GaAs heterojunctions — •Thomas Hentschel, Jens Herfort, Oliver Bierwagen, Andre Prößdorf, and Frank Große — Paul-Drude-Institut Berlin, Hausvogteiplatz 5-7, 10117 Berlin, Germany
The ferromagnetic Heusler alloy Co2FeSi is a promising candidate for the spin-polarized injection of charge carriers into a semiconductor. Previous experiments on various GaAs and Si substrates showed a strong in-diffusion of the constituent elements of the layer and interface roughening with increasing growth temperatures TG, which favor the long-range crystal ordering.
To suppress the intermixing we evaluate rare-earth oxide (REO) layers, with a thickness of a few monolayers only, as diffusion barriers between film and substrate. REOs exhibit high melting points beyond 2000 ∘C and therefore a strong chemical bonding. We found the (GaAs-)lattice-matched La2O3 grown by molecular beam epitaxy to form hexagonal polycrystallites on GaAs(001), while epitaxial growth was observed on GaAs(111)B substrates at TG = 350 ∘C. Pronounced RHEED-oscillations for the GaAs(111)B case suggest a layer-by-layer growth mode. X-ray diffraction measurements show cubic polycrystallites for the 8%-mismatched Lu2O3 on both GaAs substrate orientations.