Supplementary Materials for

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1 advances.sciencemag.org/cgi/content/full/4/3/eaar3899/dc1 Supplementary Materials for Molecular engineering of Rashba spin-charge converter Hiroyasu Nakayama, Takashi Yamamoto, Hongyu An, Kento Tsuda, Yasuaki Einaga, Kazuya Ando This PDF file includes: Published 23 March 2018, Sci. Adv. 4, eaar3899 (2018) DOI: /sciadv.aar3899 section S1. Atomic force microscopy section S2. Infrared reflection-absorption spectroscopy section S3. Field ADMR in SAM-decorated Bi/CoFeB bilayers section S4. Field strength dependence of MR in SAM-decorated Bi/Ag/CoFeB trilayers section S5. Charge transfer at organic-inorganic interface fig. S1. AFM images of the Bi/Ag/CoFeB trilayer and SAM-decorated Bi/Ag/CoFeB trilayers. fig. S2. IRRAS spectra of SAM-decorated Bi/Ag/CoFeB trilayers and infrared absorption spectra of bulk materials. fig. S3. Field ADMR in SAM-decorated Bi/CoFeB bilayers. fig. S4. Charge transfer at organic-inorganic interface. table S1. Field strength dependence of MR.

2 section S1. Atomic force microscopy In order to investigate the surface morphology of the Bi/Ag/CoFeB trilayer and SAMdecorated Bi/Ag/CoFeB trilayers used in the present study, atomic force microscopy (AFM) measurements were carried out with a NaioAFM (Nanosurf, Switzerland) by using the dynamic force mode. As shown in figs. S1A-D, all the films exhibit continuous surfaces. In all the films, the average surface roughness, R a, is lower than 1 nm, indicating the smooth surface of the Bi/Ag/CoFeB trilayer and SAM-decorated Bi/Ag/CoFeB trilayers.

3 section S2. Infrared reflection-absorption spectroscopy We conducted the infrared reflection-absorption spectroscopy (IRRAS) for SAMs of ODT, PFDT, and AZ-SAM formed on the Bi/Ag/CoFeB trilayers. For ODT-SAM, the peak frequency of ν as (CH 2 ) was found at 2918 cm 1, which is consistent with the infrared absorption spectrum of crystalline ODT (see fig. S2A). For PFDT-SAM, we monitored the peak frequency of the asymmetric CF 2 stretching vibration. The peak frequency of ν as (CF 2 ) was found at 1242 cm 1, which is almost consistent with that of the infrared absorption spectrum of PFDT (1243 cm 1 ) (see fig. S2B). For AZ-SAM, the peak frequency of ν as (CH 2 ) was found at 2922 cm 1, which is almost consistent with that of the infrared absorption spectrum of crystalline AZ (2924 cm 1 ) (see fig. S2C). Therefore, the IRRAS results suggest that ODT-, PFDT-, and AZ-SAMs are well-packed on the Bi surface.

4 section S3. Field-angle-dependent magnetoresistance in SAM-decorated Bi/CoFeB bilayers Figures S3A-C show the change in the longitudinal resistance, R, of Bi/CoFeB bilayers during rotation of an applied magnetic field µ 0 H = 6 T in the xy, zy, and zx planes. As shown in Fig. S3A, we observed the ADMR in all three orthogonal planes for the pristine Bi/CoFeB bilayer. This result shows that the sign of R(β) in the Bi/CoFeB bilayer is opposite to that in the Bi/Ag/CoFeB trilayer, showing that the the ADMR in the Bi/CoFeB bilayer is dominated by the geometrical size effect of the AMR in the CoFeB layer (23). Figures S3A-C demonstrate that, in contrast to the ADMR in the SAM-decorated Bi/Ag/CoFeB trilayers, the ADMR in the Bi/CoFeB bilayer is not influenced by the surface decoration with ODT and PFDT. This result also supports that the observed change in the ADMR in the Bi/Ag/CoFeB trilayer originates from the modulation of the REMR induced by the molecular self-assembly.

5 section S4. Field-strength dependence of magnetoresistance in SAM-decorated Bi/Ag/CoFeB trilayers In the Bi/Ag/CoFeB trilayers, the Hanle magnetoresistance (HMR) as well as the REMR can be modulated by the SAM decoration (23). In table S1, we show MR [ R(β = 0) R(β = 90 )]/R for the Bi/Ag/CoFeB trilayers measured at different external magnetic field strengths µ 0 H. Here, the field-strength-independent component of MR arises from the REMR, whereas the field-strength-dependent component of MR arises from the HMR, because the magnetization in the CoFeB layer is saturated at µ 0 H > 2 T. The result shown in table S1 indicates that the change of MR in the Bi/Ag/CoFeB trilayer due to the SAM formation is almost independent of the magnetic field strength: (MR ODT-Bi/Ag/CoFeB MR Bi/Ag/CoFeB )/MR Bi/Ag/CoFeB = 17.5% at µ 0 H = 2 T and 17.5% at µ 0 H = 6 T, and (MR PFDT-Bi/Ag/CoFeB MR Bi/Ag/CoFeB )/MR Bi/Ag/CoFeB = 23.5% at µ 0 H = 2 T and 24.6% at µ 0 H = 6 T. This indicates that the SAM formation changes the field-independent magnetoresistance in the Bi/Ag/CoFeB trilayers. The field-independent change of MR due to the SAM formation is consistent with the fact that the HMR at µ 0 H < 6 T is an order of magnitude smaller than the REMR. These results show that the change of the magnetoresistance due to the SAM formation is dominated by the molecular tuning of the REMR.

6 section S5. Charge transfer at organic-inorganic interface In figs. S4A-C, we show schematics of the charge rearrangement in the SAM-decorated Bi/Ag/CoFeB trilayers, which is known as the cooperative molecular field effect (26). The charge rearrangement reduces the dipole-dipole repulsion within the quasi-2d layer of the dipoles, resulting the well-oriented and close-packed organic layers on the metallic heterostructures. Due to this rearrangement, the magnitude of calculated molecular dipole moments for a single molecule is different from that of the dipole moments of the SAM. If the distance between two molecules in the layer is smaller than the length of dipole, and if the size of the molecular domains is much larger than the dipole length, the system can be approximated to behave as an infinite 2D dipole layer with uniform electrostatic drop over the width of the layer (26). As shown in figs. 4B and 4C, the ODT(PFDT) formation results in the electron(hole) transfer from the molecules to the Bi layer. Thanks to the long screening length of bismuth ( 30 nm) (27), the charge transfer affects the electric potential at the Bi/Ag interface. As shown in fig. S4, the interfacial electric field at the Bi/Ag interface is enhanced(suppressed) with the formation of ODT(PFDT) due to the charge transfer. The change in the interfacial electric field results in the enhanced (suppressed) Rashba-Edelstein effect due to the formation of ODT(PFDT).

7 A Bi/Ag/CoFeB 0 20 nm B ODT-Bi/Ag/CoFeB 0 20 nm 0 0 C PFDT-Bi/Ag/CoFeB 1 µm D AZ-Bi/Ag/CoFeB 1 µm 0 20 nm 0 20 nm µm 1 µm fig. S1. AFM images of the Bi/Ag/CoFeB trilayer and SAM-decorated Bi/Ag/CoFeB trilayers. (A) The AFM image of the Bi/Ag/CoFeB trilayer, where the average surface roughness R a is 0.65 nm. (B) The AFM image of the ODT-Bi/Ag/CoFeB, where R a = 0.98 nm. (C) The AFM image of the PFDT-Bi/Ag/CoFeB, where R a = 9 nm. (D) The AFM image of the AZ-SAM-Bi/Ag/CoFeB, where R a = 0.88 nm.

8 A B C Absorbance ODT-SAM ODT-bulk Absorbance PFDT-SAM PFDT-bulk AZ-SAM Absorbance AZ-bulk wavenumber (cm -1 ) wavenumber (cm -1 ) wavenumber (cm -1 ) fig. S 2. IRRAS spectra of SAM-decorated Bi/Ag/CoFeB trilayers and infrared absorption spectra of bulk materials. (A) The IRRAS spectrum of the ODT-Bi/Ag/CoFeB and infrared absorption spectrum of ODT-bulk. (B) The IRRAS spectrum of the PFDT-Bi/Ag/CoFeB and infrared absorption spectrum of PFDT-bulk. (C) The IRRAS spectrum of the AZ-SAM- Bi/Ag/CoFeB and infrared absorption spectrum of AZ-bulk.

9 A B C R/R (%) Bi/CoFeB ODT-Bi/CoFeB PFDT-Bi/CoFeB R ( γ ) R ( α) R ( β ) α, β, γ(deg.) α, β, γ(deg.) α, β, γ(deg.) fig. S3. Field-angle-dependent magnetoresistance in SAM-decorated Bi/CoFeB bilayers. The change in the longitudinal resistance, R, of (A) the Bi(5 nm)/cofeb(2.5 nm), (B) ODT-Bi(5 nm)/cofeb(2.5 nm), and (C) PFDT-Bi(5 nm)/cofeb(2.5 nm), as a function of the rotation of the magnetic field of 6 T, where R is the longitudinal resistance at µ 0 H = 0.

10 A k y Bi Ag Interfacial electric field E0 k x CoFeB k B ODT Bi Ag CoFeB ODT Bi Ag CoFeB E(ODT) > E0 k y k x C k PFDT Bi Ag CoFeB PFDT Bi Ag CoFeB E(PFDT) < E0 k y k k x fig. S4. Charge transfer at organic-inorganic interface. (A) A schematic illustration of the Bi/Ag/CoFeB trilayer and the Fermi contours of the Bi/Ag interface under an external electric field. E 0 denotes the interfacial electric field at the Bi/Ag interface. (B) A schematic illustration of the charge rearrangement due to the ODT formation on the Bi/Ag/CoFeB trilayer. The ODT formation results in the electron transfer from the molecules to the Bi layer. Due to the charge transfer, the dipole moment of the isolated molecules (left) is different from that of the 2D dipole layer (right). The charge transfer enhances the interfacial electric field, resulting in the enhanced Rashba-Edelstein effect as shown in the Fermi contours. (C) A schematic illustration of the charge rearrangement due to the PFDT formation on the Bi/Ag/CoFeB trilayer.

11 table S 1. Field-strength dependence of magnetoresistance. The magnetoresistance ratio MR [ R(β = 0) R(β = 90 )]/R measured at different external magnetic field strengths µ 0 H for the Bi/Ag/CoFeB trilayers. MR (%) µ 0 H (T) Bi/Ag/CoFeB ODT-Bi/Ag/CoFeB PFDT-Bi/Ag/CoFeB