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Nano Lett. 2019 Jan 9;19(1):90-99. doi: 10.1021/acs.nanolett.8b03386. Epub 2018 Dec 4.

Evidence of Pure Spin-Current Generated by Spin Pumping in Interface-Localized States in Hybrid Metal-Silicon-Metal Vertical Structures.

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Unité Mixte de Physique, CNRS, Thales, Université Paris-Sud, Université Paris-Saclay , 91767 , Palaiseau , France.
Laboratoire des Solides Irradiés, École Polytechnique, CNRS, CEA , Université Paris-Saclay , 91128 Palaiseau , France.
Université de Lorraine , CNRS, Institut Jean Lamour, UMR 7198, campus ARTEM , 2 Allée André Guinier , 54011 Nancy , France.
Beijing National Laboratory of Condensed Matter Physics , Institute of Physics, University of Chinese Academy of Sciences , Beijing 100190 , PR China.
Univ RennesCNRS, IPR (Institut de Physique de Rennes) - UMR 6251 , F-35000 Rennes , France.
State Key Laboratory on Integrated Optoelectronics, Institute of Semiconductors, Center of Materials Science and Optoelectronics Engineering , University of Chinese Academy of Sciences Chinese Academy of Sciences , Beijing 100083 , PR China.


Due to the difficulty of growing high-quality semiconductors on ferromagnetic metals, the study of spin diffusion transport in Si was limited to lateral geometry devices. In this work, by using an ultrahigh-vacuum wafer-bonding technique, we have successfully fabricated metal-semiconductor-metal CoFeB/MgO/Si/Pt vertical structures. We hereby demonstrate pure spin-current injection and transport in the perpendicular current flow geometry over a distance larger than 2 μm in n-type Si at room temperature. In those experiments, a pure propagating spin current is generated via ferromagnetic resonance spin pumping and converted into a measurable voltage by using the inverse spin Hall effect occurring in the top Pt layer. A systematic study varying both Si and MgO thicknesses reveals the important role played by the localized states at the MgO-Si interface for the spin-current generation. Proximity effects involving indirect exchange interactions between the ferromagnet and the MgO-Si interface states appears to be a prerequisite to establishing the necessary out-of-equilibrium spin population in Si under the spin-pumping action.


Spin pumping; inverse spin Hall effect; localized electronic states; spin current; wafer bonding

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