| AVS 60th International Symposium and Exhibition | |
| Electronic Materials and Processing | Wednesday Sessions |
| Session EM+AS+NS+SS-WeA |
| Session: | Semiconductor Heterostructures/Heusler Alloys |
| Presenter: | S. Patel, University of California, Santa Barbara |
| Authors: | S. Patel, University of California, Santa Barbara K. Christie, University of Minnesota C. Geppert, University of Minnesota B.D. Schultz, University of California, Santa Barbara P. Crowell, University of Minnesota C.J. Palmstrøm, University of California, Santa Barbara |
| Correspondent: | Click to Email |
High spin polarization ferromagnets, including half-metallic ferromagnets, are attractive choices for use as spin injectors into semiconductors as well as other spintronic devices. Co2MnSi is predicted to be half-metallic [1], and with a lattice constant of 5.65Å, is almost perfectly lattice-matched to GaAs (0.06% mismatch), and a strong candidate for use as a spin-injector in the ferromagnet/GaAs system. We demonstrate the growth of epitaxial Co2MnSi films directly on GaAs (001) by molecular beam epitaxy (MBE) for use as a spin injector, as well as successful spin injection and detection. In addition, we observe a growth temperature dependence of spin injection/detection in three-terminal lateral transport devices on GaAs. X-ray diffraction studies verify near lattice matching of Co2MnSi films to GaAs. We employ the use of a shuttered growth technique to initiate Co2MnSi growth on GaAs. This technique allows for the initial deposition of either a full Co monolayer or a full MnSi monolayer, influencing the interfacial ordering of the ferromagnet/semiconductor interface. In order to study the effects of interfacial ordering,scanning transmission electron microscopy (STEM) and x-ray diffraction techniques, as well as electrical measurements of spin injection and transport are used. Magnetic hysteresis measurements show extremely low coercivities of grown films, as well as auniaxial anisotropy with an easy axis in the [110] direction. Co2MnSi has been grown at growth temperatures varying from 180⁰C to 320⁰C, and a layer-by-layer growth mode has been confirmed for this temperature range by the presence of intensity oscillations in reflection high energy electron diffraction (RHEED) patterns. The Co2MnSi layers have also been studied by low energy electron diffraction (LEED), scanning tunneling microscopy (STM), and scanning tunneling spectroscopy (STS). The STM and STS studies have been carried out at room temperature, and at 4.5K at which atomic resolution was obtained. STS has been performed with both a Nb tip and a W tip at room temperature and 4.5K to study the local density of states. In addition, we demonstrate a growth temperature dependence of spin injection/detection in three-terminal lateral transport devices on GaAs. These methods were used to better understand the growth mechanisms and electronic properties of the films.
This work was supported by the MRSEC Program of the National Science Foundation under Award Number DMR-0819885 and by the Semiconductor Research Corporation under award number 2011-IN-2153.
[1] S. Picozzi, A. Continenza, and A. J. Freeman. Phys. Rev. B 69 (9), 094423 (2004)