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Spin Injection Behavior of CoFe/MgO/Si Tunnel Contacts: Effects of Radical Oxygen Annealing

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Abstract

Spin injection phenomena of CoFe/MgO/Si tunnel contacts are demonstrated, the MgO tunnel barrier of which is fabricated using radical oxidation (ROX) at room temperature and successive radical oxygen annealing (ROA). The effects of the ROA processing on spin accumulation behavior in the Si channel are analyzed using Hanle-effect signals measured using a three-terminal spin-accumulation technique. The ROA condition is optimized through the spin injection efficiency obtained from the Hanle-effect signal analysis. The Hanle-effect signals can be decomposed into a non-Lorentz-shaped signal due to spin accumulation in the Si channel and a Lorentz-shaped signal due to other phenomena. The intensity ratio of the channel spin signal component to the total signal intensity significantly changes depending on the ROA condition. Also, the ratio increases with decreasing bias voltage for the Hanle-effect measurement. For the optimum ROA condition, the channel spin component becomes almost dominant for lower bias voltages (<~ 100 mV), i.e., high spin intensity ratios can be achieved for near-zero bias measurements. These phenomena can be attributed to the energy-dependent trap-density distribution of the MgO barrier and/or its interfaces, which have been analyzed from the direct tunneling current through the barrier. The fabrication technique using the ROX and ROA processing is promising for MgO-based spin injectors with high spin injection efficiency.

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Acknowledgment

The authors acknowledge Research Hub for Advanced Nano Characterization, The University of Tokyo.

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  1. Taiju Akushichi

    Present address: TDK Corporation, Chiba, Japan

Authors and Affiliations

  1. Laboratory for Future Interdisciplinary Research of Science and Technology, Tokyo Institute of Technology, Yokohama, Japan

    Taiju Akushichi, Yusaku Shiotsu, Shuu’ichirou Yamamoto & Satoshi Sugahara

  2. Department of Electrical and Electronic Engineering, Tokyo Institute of Technology, Tokyo, Japan

    Yota Takamura

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  1. Taiju Akushichi
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  2. Yota Takamura
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Akushichi, T., Takamura, Y., Shiotsu, Y. et al. Spin Injection Behavior of CoFe/MgO/Si Tunnel Contacts: Effects of Radical Oxygen Annealing. J. Electron. Mater. 52, 6902–6910 (2023). https://doi.org/10.1007/s11664-023-10606-4

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