Abstract
The spin–orbit interaction in a solid couples the spin of an electron to its momentum. This coupling gives rise to mutual conversion between spin and charge currents: the direct and inverse spin Hall effects. The spin Hall effects have been observed in metals and semiconductors. However, the spin/charge conversion has not been realized in one of the most fundamental semiconductors, silicon, where accessing the spin Hall effects has been believed to be difficult because of its very weak spin–orbit interaction. Here we report observation of the inverse spin Hall effect in silicon at room temperature. The spin/charge current conversion efficiency, the spin Hall angle, is obtained as 0.0001 for a ptype silicon film. In spite of the small spin Hall angle, we found a clear electric voltage due to the inverse spin Hall effect in the pSi film, demonstrating that silicon can be used as a spincurrent detector.
Introduction
Silicon is a group IV semiconductor having the diamond structure. This material has had a crucial role in exploring the physics of semiconductors. Silicon has been broadly viewed as an ideal host also for spintronics owing to its low atomic mass, crystal inversion symmetry, and near lack of nuclear spin, resulting in the exceptionally long spin lifetime^{1,2,3}.
Along with long spin lifetimes, key elements for spintronics are generation and detection of spin currents^{4,5,6,7,8,9,10,11}. A promising method is the utilization of the direct and inverse spin Hall effects (DSHE/ISHE), which convert a charge current into a spin current and vice versa^{12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30}. However, the underlying origin of the spin Hall effects is the spin–orbit interaction and, thus, it is natural to expect that the spin Hall effects are not accessible in a material that shows long spin lifetimes, such as silicon. Generation of spin currents from an electric field through the spin–orbit interaction, the DSHE, was first observed in gallium arsenide (GaAs) using optical detection techniques, a Kerrmicroscopy and a twodimensional lightemitting diode^{17,18}. Although these optical techniques have had a crucial role for investigating the physics of the DSHE^{17,18,19,21,28}, the application range of the techniques is limited to direct bandgap semiconductors with strong spin–orbit interaction; the indirect bandgap of silicon precludes using these techniques, making it difficult to explore the DSHE in silicon along with its very weak spin–orbit interaction.
The spin–orbit interaction responsible for the DSHE also causes the conversion of a spin current into an electric field, the ISHE^{25,26,27}, which could offer a way to circumvent the above obstacle in exploring the spin Hall effects. The ISHE enables the electric measurement of the spin/charge conversion through the spin–orbit interaction, as demonstrated, for example, in platinum and gallium arsenide^{22,25,26,29}. The electric field E_{ISHE} generated by the ISHE from a spin current j_{s} with the spinpolarization vector σ is described as^{25}
where is the spin Hall angle, σ_{SHE} and σ_{N} are the spin Hall conductivity and electric conductivity, respectively, and ρ_{N} is the electric resistivity. Equation (1) shows that the magnitude of the electric field due to the ISHE is proportional to the resistivity ρ_{N} of the material, indicating that the ISHE enables sensitive detection of spin currents especially in highresistivity materials, such as semiconductors.
Although spin injection efficiency into semiconductors is drastically limited by the impedance mismatch problem^{31}, recent advances revealed that efficient spin injection is possible using hotelectron injection^{32}, tunnel barriers^{33,34}, and spin pumping^{35}. In particular, the generation of spin currents from magnetization precession^{36,37}, a recently discovered method utilizing spin pumping, enables highdensity spin current injection into a macroscopic area^{35}, which is difficult to achieve by other methods. This is beneficial for enhancing the electric voltage due to the ISHE; V_{ISHE} is proportional both to the spin current density j_{s} and length w_{F} of the sample along E_{ISHE}. The combination of the spin pumping and ISHE has been observed and is a wellestablished technique in metallic systems^{38}. This has also been applied to semiconductors with strong spin–orbit interaction, enabling the observation of the ISHE in heavily doped n and ptype GaAs^{35}. In this work, we experimentally demonstrate that the combination of the ISHE and spin pumping provides a route for exploring the spin/charge current conversion in highresistivity materials with weak spin–orbit interaction by showing successful measurement of the ISHE in silicon at room temperature.
Results
Detection of inverse spin Hall effect in silicon
Figure 1a shows a schematic illustration of the sample used in this study. The sample is a Ni_{81}Fe_{19}/Bdoped Si (Ni_{81}Fe_{19}/pSi) film with a doping concentration of N_{A}=2×10^{19} cm^{−3} (see Methods). Two ohmic contacts were attached on the pSi layer (Fig. 1a,b). Here the currentvoltage characteristic shown in Figure 1c shows an almost ohmic behaviour at the Ni_{81}Fe_{19}/pSi interface, suggesting strong dynamical exchange interaction J_{ex} between the magnetization in the Ni_{81}Fe_{19} layer and carrier spins in the pSi layer^{35}.
We measured the ferromagnetic resonance (FMR) signal and electricpotential difference V between the electrodes attached to the pSi layer to detect the ISHE^{35}; in the FMR condition, the spin pumping driven by the dynamical exchange interaction injects pure spin currents into the pSi layer. This spin current gives rise to an electric voltage V_{ISHE} through the ISHE in the pSi layer. During the measurements, the Ni_{81}Fe_{19}/pSi sample was placed at the centre of a TE_{011} microwave cavity with the frequency of f=9.45 GHz, where the microwave magnetic field was applied along the y direction (Fig. 1a). An external static magnetic field H was applied along the film plane as shown in Figure 1a. All of the measurements were performed at room temperature.
Figure 2a,b shows the DC electromotive force signals measured for the Ni_{81}Fe_{19}/pSi film at various microwave excitation power, when the external magnetic field H is applied along the film plane at θ=0 and θ=180° (see the insets), respectively. Here θ is the outofplane angle of H. In the V spectra, clear electromotive force signals are observed around the ferromagnetic resonance field H_{FMR} (compare the V spectra with the FMR spectra shown in Fig. 2c,d). Figure 2c,d shows that the microwave absorption intensity I is identical for θ=0 and 180°. In contrast, importantly, the magnitude of the electromotive force V is clearly changed by reversing the magnetic field direction as shown in Figure 2a,b; this distinctive behaviour of V is the key feature of the ISHE induced by the spin pumping^{35}.
The electromotive force observed here is the combination of the ISHE in the pSi layer, the ordinary Hall effect (OHE) in the pSi layer, the anomalous Hall effect (AHE) in the Ni_{81}Fe_{19} layer, and heating effects. The direct contribution from the ISHE in the pSi layer can be extracted as follows (see Methods). The OHE and AHE voltages can be ruled out from the observed electromotive force by fitting the V spectra using a combination of symmetric (absorption shape) and asymmetric (dispersion shape) functions^{25}, , where H_{FMR} is the resonance field. Figure 2e,f is the fitting result for the V spectra at 200 mW for θ=0 and θ=180°, respectively, showing that the observed V spectra are well reproduced with V_{s}=3.50 μV and V_{as}=−0.41 μV for θ=0 and V_{s}=1.76 μV and V_{as}=0.41 μV for θ=180°. What is notable is that the Hall voltage due to rectification changes its sign across H_{FMR} as shown in Figure 2g (ref. 25). In contrast, the electromotive force due to the ISHE is proportional to the microwave absorption intensity^{38}. Here V_{s} is attributed to both the ISHE in the pSi layer and heating effects^{35}. To eliminate the heating effects arising from the microwave absorption from the V spectra, we define , as the ISHE voltage due to the spin pumping changes its sign by reversing H whereas the electromotive force due to the heating effects is independent on the H direction. In Figure 2h, we show the microwave power P_{MW} dependence of ΔV_{s}. ΔV_{s} increases linearly with P_{MW}, as expected for the ISHE induced by the spin pumping^{38}. ΔV_{s} signal disappears when an inplane magnetic field is applied parallel to the direction across the electrodes, supporting that ΔV_{s} is attributed to the ISHE in the pSi layer because of equation (1).
Spin precession and inverse spin Hall effect
To further buttress the above result, we measured the outofplane magnetic field angle θ dependence of ΔV_{s}, which provides further evidence that the observed ΔV_{s} signals are attributed to the ISHE induced by the spin injection in the pSi layer. Here the outofplane magnetic field angle θ is defined in Figure 3a. As shown in Figure 3a, when H is applied oblique to the film plane, the magnetization precession axis is not parallel to H because of the demagnetization field in the Ni_{81}Fe_{19} layer. The relation between the external magnetic field angle θ and the angle of magnetization–precession axis φ can be obtained using the Landau–Lifshitz–Gilbert equation with the measured values of the resonance field H_{FMR} shown in Figure 3b (ref. 38). The θ dependence of φ for the Ni_{81}Fe_{19}/pSi film is shown in Figure 3c. In Figure 3d,e, we show the dI/dH and V_{s}(H) signals for the Ni_{81}Fe_{19}/pSi film at different θ. As shown in Figure 3e, ΔV_{s} disappears when the external magnetic field is applied perpendicular to the film plane; the θ dependence of ΔV_{s} shows the drastic variation of ΔV_{s} around θ=90° (Fig. 3f). Here the spinpolarization vector σ of the spin current injected into the pSi layer is parallel to the magnetization–precession axis. Therefore, the spins of the spin current precess around the axis parallel to H, as shown in Figure 3a. This is described in the Bloch equation with spin diffusion and precession in the pSi layer:
where m(x, t) is the magnetization of carriers in the pSi layer; γ_{c} and τ_{sf} are the gyromagnetic ratio and spin relaxation time of carriers in the pSi layer, respectively; D_{N} is the diffusion constant in the pSi layer; e_{x} and e_{z} are the unit vector parallel to the x and z axes, respectively (Fig. 3a); δ(x) is the delta function and is the spin current density with the spin orientation direction p and flow direction q at the interface x=0. Thus and , where the spin current density j_{s} generated by the spin pumping at the interface in the FMR condition is given by^{38},
Here is the spin mixing conductance, γ and M_{s} are the gyromagnetic ratio and saturation value of the magnetization M, respectively; α is the Gilbert damping constant; h is the microwave magnetic field; and ω=2πf is the angular frequency of the magnetization precession. By solving equation (2) for the equilibrium condition (∂m/∂t=0), we obtain
where and ; is the spin diffusion length of the Si layer; and are the real and imaginary part of , respectively. Because the spin current flows along the x direction, the electric field induced by the ISHE, E_{ISHE}(x), is proportional to . As shown in Figure 4a, decays because of the spin relaxation in the pSi layer; the charge current density j_{c}(x) generated by the ISHE also depends on x, which induces short circuit currents in the Ni_{81}Fe_{19} and pSi layers^{38}. Equivalent circuit models of the Ni_{81}Fe_{19}/pSi film are shown in Figure 4b,c (see Methods). Therefore, we obtain the angular dependence of the ISHE signal V_{ISHE} in the presence of spin precession as^{35}
where d_{N} is the thickness of the pSi layer. From equation (5), the electromotive force without taking into account spin precession () is given by , which is valid for materials where the spin relaxation time is very fast, such as Pt (ref. 38). Here, calculated θ dependence of ΔV_{s} is shown in the inset of Figure 3f for (the black curve), τ_{sf}=10 ps (the blue curve), and τ_{sf}=20 ps (the red curve) with 4πM_{s}=0.852 T. As τ_{sf} increases, spin precession reduces the electromotive force; the drastic variation of ΔV_{s} around θ=80° for becomes gentle for τ_{sf}=10 ps and τ_{sf}=20 ps owing to spin precession. The experimentally measured θ dependence of ΔV_{s} is well reproduced using equation (5) with τ_{sf}=9±3 ps as shown in Figure 3f, where ΔV_{s} is obtained from Figure 3e. This is the direct evidence of the observation of the ISHE in the pSi layer; the ΔV_{s} signal cannot be attributed to the ISHE in the Ni_{81}Fe_{19} layer, as the spin relaxation time in Ni_{81}Fe_{19}, τ_{sf}=9 fs, is so fast that is satisfied (see the dashed curve in Fig. 3f), where τ_{sf} is obtained from the spin diffusion length^{39} λ_{F}=3 nm and diffusion constant^{40} D_{F}=10 cm^{2} s^{−1}. This result also supports that magnetogalvanic effects, that is, the OHE and AHE, and heating effects are irrelevant to ΔV_{s}.
Discussion
The above experimental results allow estimation of the spin Hall conductivity of the pSi layer. In the FMR condition, when the magnetic field is applied along the film plane, the magnitude of the ISHE signal V_{ISHE} is obtained from equation (3) with the equivalent circuit model of the spinpumpinginduced ISHE where shortcircuit currents in the Ni_{81}Fe_{19} layer are taken into account^{38}: . Here w_{F}, d_{F} and σ_{F} are the length defined as in Figure 1b, thickness and electric conductivity of the Ni_{81}Fe_{19} layer, respectively. Using the parameters for the Ni_{81}Fe_{19}/pSi film, w_{F}=2.0 mm, D_{N}=3.23 cm^{2} s^{−1}, d_{N}=4 μm, d_{F}=10 nm, σ_{N}=2×10^{2} Ω^{−1} cm^{−1}, σ_{F}=1.5×10^{4} Ω^{−1} cm^{−1}, 4πM_{s}=0.852T, α=0.0088, h=0.16 mT, τ_{sf}=9 ps, and ΔV_{s}=0.87 μV, we find m^{−2}. Here the spin mixing conductance can be obtained from the enhancement of the FMR spectral width due to the spin pumping^{41}. The spin mixing conductance of the Ni_{81}Fe_{19}/pSi film is estimated from the FMR spectral width for the Ni_{81}Fe_{19}/pSi film and a Ni_{81}Fe_{19}/SiO_{2} film as m^{−2}. Thus we obtain the spin Hall angle for the pSi layer θ_{SHE}≈1×10^{−4}, which corresponds to the spin Hall conductivity σ_{SHE}≈2×10^{−2} Ω^{−1} cm^{−1}. These values are much smaller than those for doped GaAs^{28}, showing that this approach enables highly sensitive electric measurement of the ISHE. The successful measurement of the ISHE in silicon is attributed to its high electric resistivity, which is essential for large voltage generation due to the ISHE, and the highdensity spin injection into macroscopic area by the spin pumping.
Although spin injection into ntype Si has been reported by several groups^{33,34,42,43}, there is only one report of roomtemperature spin injection into ptype Si, using tunnel contacts^{34}. The successful observation of the ISHE in the Ni_{81}Fe_{19}/pSi film now confirms this by a different approach, namely dynamical spin injection. The present experiment shows that the spin relaxation time in the pSi layer is τ_{sf}=9 ps. Here in the direct Ni_{81}Fe_{19}/pSi contact, the spin relaxation time near the interface may be reduced because of the coupling of the spins in the pSi layer to the Ni_{81}Fe_{19} layer^{44}. The spin relaxation time obtained using the electrical spin injection is τ_{sf}=270 ps for pSi with the doping concentration of N_{A}=4.8×10^{18} cm^{−3} (ref. 34). Therefore, the spin relaxation time in pSi obtained by both the electrical and dynamical spin injection is much longer than the momentum relaxation time ~5 fs in the pSi layer^{45}; understanding the hole spin relaxation in ptype Si remains a challenge.
We showed that silicon has the potential to be used not only as a spincurrenttransmission path^{43,46} but also as a spincurrent detector in spite of its weak spin–orbit interaction. Although the spin/charge current conversion efficiency is not large in the pSi layer, the spin Hall effects in silicon can now be further explored; the combination of the spin pumping and ISHE paves the only way for quantitative exploration of the spin–orbit coupling effect in silicon for different doping density and dopant type. This approach provides also a way to extract the spin relaxation time τ_{sf}; as shown in Figure 4d, the magnitude of the electromotive force due to the ISHE is strongly dependent on τ_{sf} under the oblique magnetic field, especially when τ_{sf} is of the order of 10 ps. Furthermore, the approach presented here, thanks to the highdensity spin injection, opens the way for exploring the spin Hall effects in a wide range of materials, including highresistivity materials with weak spin–orbit interaction. This extends the range of potential materials for spincurrent detector without magnetic materials.
Methods
Sample preparation
The sample used in this study is a Ni_{81}Fe_{19}/Bdoped Si (Ni_{81}Fe_{19}/pSi) film with a doping concentration of N_{A}=2×10^{19} cm^{−3}. Two 30nmthick AuPd electrodes were sputtered on a silicononinsulator substrate (Fig. 1a) in an Ar atmosphere. After the sputtering, the silicononinsulator substrate was annealed at 400 °C for 10 min in a high vacuum, which yields ohmic contacts to the pSi layer (Fig. 1b). The 10nmthick Ni_{81}Fe_{19} layer was then deposited on the pSi layer by electronbeam evaporation in a high vacuum. Immediately before the evaporation, the surface of the pSi layer was cleaned by Arion etching. The surface of the Ni_{81}Fe_{19} layer and AuPd contact is of a 1.0×2.0mm^{2} rectangular shape and of a 1×0.5mm^{2} rectangular shape, respectively. The distance from the AuPd contact to the Ni_{81}Fe_{19} layer is ~300 μm.
Electric voltage due to inverse spin Hall effect
The observed electromotive force in the Ni_{81}Fe_{19}/pSi film is the combination of the ISHE in the pSi layer, the OHE in the pSi layer, the AHE in the Ni_{81}Fe_{19} layer, and heating effects. The direct contribution from the ISHE in the pSi layer can be extracted as follows: the OHE in the pSi layer induces a DC electromotive force from an AC charge current due to a microwave electric field and an AC stray field due to precessing magnetization. This rectified voltage changes its sign across the resonance field, that is, the sign of the electromotive force when H<H_{FMR} is opposite to that when H>H_{FMR}, as the phase of magnetization precession shifts by π at resonance. Therefore, the shape of the electromotive force due to the OHE is asymmetric as shown in Figure 2g. Here a microwave magnetic field cannot create a detectable DC OHE voltage, since the direction of the microwave magnetic field is parallel to the direction across the electrodes (the y direction; Fig. 1a). Furthermore, the microwave magnetic field is independent of the FMR. The shape of the electromotive force due to the AHE is also asymmetric, because it is a rectified voltage induced by the combination of a charge current due to a microwave electric field and precessing magnetization^{38}. In contrast to the rectified voltage due to the OHE and AHE, the electromotive force due to the ISHE is proportional to the intensity of microwave absorption^{47}. This indicates that the shape of the electromotive force due to the ISHE is symmetric as shown in Figure 2g, and, thus, the electromotive force due to the OHE and AHE can be eliminated from the observed electromotive force. The electromotive force due to the sample heating is induced by the Seebeck effect, which is independent on the magnetic field direction. The Seebeck effect in the Ni_{81}Fe_{19}/pSi film is induced by a lateral temperature gradient along the film plane due to small but finite misalignment of the position of the Ni_{81}Fe_{19} layer with respect to the substrate. In fact, the magnitude of the symmetric component of V that does not change the sign with reversal of H depends strongly on samples. A longitudinal temperature gradient, that is, a temperature gradient perpendicular to the film plane, may induce a voltage through the Nernst effect. Although the Nernst effect induces a Hdependent voltage, Figure 3f clearly shows that this effect is irrelevant to the ΔV_{s} signals; the variation of ΔV_{s} cannot be reproduced by the cross product of a longitudinal temperature gradient and the external magnetic field. The θ dependence of ΔV_{s} is well reproduced using equation (5) with the spin relaxation time τ_{sf}=9 ps for P_{MW}=100, 150 and 200 mW. All errors and error bars represent the 90% confidence interval.
Equivalent circuit model
As shown in Figure 4a, decays because of the spin relaxation in the pSi layer; the charge current density j_{c}(x) generated by the ISHE also depends on x, which induces short circuit currents in the Ni_{81}Fe_{19} and pSi layers^{38}. Here a total charge current generated by the ISHE is , where d_{N} is the thickness of the pSi layer. By dividing the pSi layer into n layers, an equivalent circuit of the Ni_{81}Fe_{19}/pSi film is obtained as shown in Figure 4b, where R_{F} is the electrical resistance of the Ni_{81}Fe_{19} layer. The electrical resistance and the charge current generated by the ISHE of the ith layer satisfy and , where R_{N} is the electrical resistance of the pSi layer. It is straightforward to convert the circuit shown in Figure 4b into that shown in Figure 4c. Thus, the electromotive force due to the ISHE is obtained as . This result shows that V_{ISHE} is proportional to the total charge current I_{N} generated by the ISHE; the electromotive force due to the ISHE in the Ni_{81}Fe_{19} layer is negligibly small because of the extremely short spin diffusion length^{39} and small spin Hall angle^{48}.
Additional information
How to cite this article: Ando, K. & Saitoh, E. et al. Observation of the inverse spin Hall effect in silicon. Nat. Commun. 3:629 doi: 10.1038/ncomms1640 (2012).
References
 1
Žutić, I., Fabian, J. & Das Sarma, S. Spintronics: fundamentals and applications. Rev. Mod. Phys. 76, 323–410 (2004).
 2
Fabian, J., MatosAbiague, A., Ertler, C., Stano, P. & Žutić, I. Semiconductor spintronics. Acta Phys. Slov. 57, 565–907 (2007).
 3
Cheng, J. L., Wu, M. W. & Fabian, J. Theory of the spin relaxation of conduction electrons in silicon. Phys. Rev. Lett. 104, 016601 (2010).
 4
Wolf, S. A. et al. Spintronics: a spinbased electronics vision for the future. Science 294, 1488–1495 (2001).
 5
Johnson, M. & Silsbee, R. H. Interfacial chargespin coupling: injection and detection of spin magnetization in metals. Phys. Rev. Lett. 55, 1790–1793 (1985).
 6
Jedema, F. J., Filip, A. T. & van Wees, B. J. Electrical spin injection and accumulation at room temperature in an allmetal mesoscopic spin valve. Nature 410, 345–348 (2001).
 7
Lou, X. et al. Electrical detection of spin transport in lateral ferromagnetsemiconductor devices. Nature Phys. 3, 197–202 (2007).
 8
Crooker, S. A. et al. Imaging spin transport in lateral ferromagnet/semiconductor structures. Science 309, 2191–2195 (2005).
 9
Lou, X. et al. Electrical detection of spin accumulation at a ferromagnetsemiconductor interface. Phys. Rev. Lett. 96, 176603 (2006).
 10
Tran, M. et al. Enhancement of the spin accumulation at the interface between a spinpolarized tunnel junction and a semiconductor. Phys. Rev. Lett. 102, 036601 (2009).
 11
Zhu, H. J. et al. Roomtemperature spin injection from Fe into GaAs. Phys. Rev. Lett. 87, 016601 (2001).
 12
Bakun, A. A., Zakharchenya, B. P., Rogachev, A. A., Tkachuk, M. N. & Fleisher, V. G. Observation of a surface photocurrent caused by optical orientation of electrons in a semiconductor. JETP Lett. 40, 1293–1295 (1984).
 13
Dyakonov, M. I. & Perel, V. I. Currentinduced spin orientation of electrons in semiconductors. Phys. Lett. 35A, 459–460 (1971).
 14
Hirsch, J. E. Spin Hall effect. Phys. Rev. Lett. 83, 1834–1837 (1999).
 15
Murakami, S., Nagaosa, N. & Zhang, S. C. Dissipationless quantum spin current at room temperature. Science 301, 1348–1351 (2003).
 16
Sinova, J. et al. Universal intrinsic spin Hall effect. Phys. Rev. Lett. 92, 126603 (2004).
 17
Kato, Y. K., Myers, R. C., Gossard, A. C. & Awschalom, D. D. Observation of the spin Hall effect in semiconductors. Science 306, 1910–1913 (2004).
 18
Wunderlich, J., Kaestner, B., Sinova, J. & Jungwirth, T. Experimental observation of the spinHall effect in a twodimensional spinorbit coupled semiconductor system. Phys. Rev. Lett. 94, 047204 (2005).
 19
Sih, V. et al. Spatial imaging of the spin Hall effect and currentinduced polarization in twodimensional electron gases. Nature Phys. 1, 31–35 (2005).
 20
Stern, N. P. et al. Currentinduced polarization and the spin Hall effect at room temperature. Phys. Rev. Lett. 97, 126603 (2006).
 21
Stern, N. P., Steuermann, D. W., Mack, S., Gossard, A. C. & Awschalom, D. D. Timeresolved dynamics of the spin Hall effect. Nature Phys. 4, 843–846 (2008).
 22
Wunderlich, J. et al. Spin Hall effect transistor. Science 330, 1801–1804 (2010).
 23
Tse, W. K. & Das Sarma, S. Spin Hall effect in doped semiconductor structures. Phys. Rev. Lett. 96, 056601 (2006).
 24
Engel, H. A., Halperin, B. I. & Rashba, E. I. Theory of spin Hall conductivity in ndoped GaAs. Phys. Rev. Lett. 95, 166605 (2005).
 25
Saitoh, E., Ueda, M., Miyajima, H. & Tatara, G. Conversion of spin current into charge current at room temperature: inverse spinHall effect. Appl. Phys. Lett. 88, 182509 (2006).
 26
Kimura, T., Otani, Y., Sato, T., Takahashi, S. & Maekawa, S. Roomtemperature reversible spin Hall effect. Phys. Rev. Lett. 98, 156601 (2007).
 27
Valenzuela, S. O. & Tinkham, M. Direct electronic measurement of the spin Hall effect. Nature 442, 176–179 (2006).
 28
Matsuzaka, S., Ohno, Y. & Ohno, H. Electron density dependence of the spin Hall effect in GaAs probed by scanning Kerr rotation microscopy. Phys. Rev. B 80, 241305(R) (2009).
 29
Garlid, E. S., Hu, Q. O., Chan, M. K., Palmstrøm, C. J. & Crowell, P. A. Electrical measurement of the direct spin Hall effect in Fe/InxGa1−xAs Heterostructures. Phys. Rev. Lett. 105, 156602 (2010).
 30
Brüne, C. et al. Evidence for the ballistic intrinsic spin Hall effect in HgTe nanostructures. Nature Phys. 6, 448–454 (2010).
 31
Schmidt, G., Ferrand, D., Molenkamp, L. W., Filip, A. T. & van Wees, B. J. Fundamental obstacle for electrical spin injection from a ferromagnetic metal into a diffusive semiconductor. Phys. Rev. B 62, R4790–R4793 (2000).
 32
Appelbaum, I., Huang, B. & Monsma, D. J. Electronic measurement and control of spin transport in silicon. Nature 447, 295–298 (2007).
 33
Jonker, B. T., Kioseoglou, G., Hanbicki, A. T., Li, C. H. & Thompson, P. E. Electrical spininjection into silicon from a ferromagnetic metal/tunnel barrier contact. Nature Phys. 3, 542–546 (2007).
 34
Dash, S. P., Sharma, S., Patel, R. S., de Jong, M. P. & Jansen, R. Electrical creation of spin polarization in silicon at room temperature. Nature 462, 491–494 (2009).
 35
Ando, K. et al. Electrically tunable spin injector free from the impedance mismatch problem. Nature Mater. 10, 655–569 (2011).
 36
Tserkovnyak, Y., Brataas, A. & Bauer, G. E. W. Enhanced Gilbert damping in thin ferromagnetic films. Phys. Rev. Lett. 88, 117601 (2002).
 37
Brataas, A., Tserkovnyak, Y., Bauer, G. E. W. & Halperin, B. I. Spin battery operated by ferromagnetic resonance. Phys. Rev. B 66, 060404(R) (2002).
 38
Ando, K. et al. Inverse spinHall effect induced by spin pumping in metallic system. J. Appl. Phys. 109, 103913 (2011).
 39
Bass, J. & Pratt Jr., W. P. Spindiffusion lengths in metals and alloys, and spinflipping at metal/metal interfaces: an experimentalist’s critical review. J. Phys. Condens. Matter 19, 183201 (2007).
 40
GarciaCervera, C. J. & Wang, X. P. Advances in numerical micromagnetics: spinpolarized transport. Bol. Soc. Esp. Mat. Apl. 34, 217–221 (2006).
 41
Tserkovnyak, Y., Brataas, A., Bauer, G. E. W. & Halperin, B. I. Nonlocal magnetization dynamics in ferromagnetic heterostructures. Rev. Mod. Phys. 77, 1375 (2005).
 42
Ando, Y. et al. Electrical injection and detection of spinpolarized electrons in silicon through an Fe3Si/Si Schottky tunnel barrier. Appl. Phys. Lett. 94, 182105 (2009).
 43
Suzuki, T. et al. Roomtemperature electron spin transport in a highly doped Si channel. Appl. Phys. Exp. 4, 023003 (2011).
 44
Dash, S. P. et al. Spin precession and inverted Hanle effect in a semiconductor near a finiteroughness ferromagnetic interface. Phys. Rev. B 84, 054410 (2011).
 45
Ray, S. K. et al. Characteristics of THz waves and carrier scattering in borondoped epitaxial Si and Si1−xGex films. J. Appl. Phys. 95, 5301–5304 (2004).
 46
Dery, H., Song, Y., Li, P. & Žutić, I. Silicon spin communication. Appl. Phys. Lett. 99, 082502 (2011).
 47
Ando, K. et al. Electric detection of spin wave resonance using inverse spinHall effect. Appl. Phys. Lett. 94, 262505 (2009).
 48
Tanaka, T., Kobayashi, I., Takahashi, M. & Wakiyama, T. Anisotropic magnetoresistance and Hall effects for NiFeM alloy thin films. IEEE Trans. Magn. 26, 2418 (1990).
Acknowledgements
We thank S. Takahashi and R. Takahashi for valuable discussions. This work was supported by the Cabinet Office, Government of Japan through its 'Funding Program for Next Generation WorldLeading Researchers,' the Asahi Glass Foundation, the Casio Foundation, the Kurata Foundation, and JSTCREST 'Creation of Nanosystems with Novel Functions through Process Integration'.
Author information
Affiliations
Contributions
K.A. designed the experiment, collected all the data, performed analysis of the data, and wrote the manuscript. E.S. supervised the study. Both the authors discussed the results and commented on the manuscript.
Corresponding author
Correspondence to Kazuya Ando.
Ethics declarations
Competing interests
The authors declare no competing financial interests.
Rights and permissions
This work is licensed under a Creative Commons AttributionNonCommercialNo Derivative Works 3.0 Unported License. To view a copy of this license, visit http://creativecommons.org/licenses/byncnd/3.0/
About this article
Cite this article
Ando, K., Saitoh, E. Observation of the inverse spin Hall effect in silicon. Nat Commun 3, 629 (2012). https://doi.org/10.1038/ncomms1640
Received:
Accepted:
Published:
Further reading

Spin imbalance of charge carriers induced by an electric current
Journal of Magnetism and Magnetic Materials (2020)

Observation of long spin lifetime in MAPbBr3 single crystals at room temperature
Journal of Physics: Materials (2020)

Variable spincharge conversion across metalinsulator transition
Nature Communications (2020)

Electrically Switchable and Tunable RashbaType Spin Splitting in Covalent Perovskite Oxides
Physical Review Letters (2019)

Direct detection of induced magnetic moment and efficient spintocharge conversion in graphene/ferromagnetic structures
Physical Review B (2019)
Comments
By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.