Large Spin‐to‐Charge Conversion at Room Temperature in Extended Epitaxial Sb₂Te₃ Topological Insulator Chemically Grown on Silicon

Abstract

Spin-charge interconversion phenomena at the interface between magnetic materials and topological insulators (TIs) are attracting enormous interest in the research effort toward the development of fast and ultra-low power devices for future information and communication technology. A large spin-to-charge (S2C) conversion efficiency in Au/Co/Au/Sb 2 Te 3 /Si(111) heterostructures based on Sb 2 Te 3 TIs grown by metal-organic chemical vapor deposition on 4″ Si(111) substrates is reported. By conducting room temperature spin pumping ferromagnetic resonance, a 250% enhanced charge current due to spin pumping in the Sb 2 Te 3containing system is measured when compared to the reference Au/Co/Au/ Si(111). The corresponding inverse Edelstein effect length λ IEE ranges from 0.28 to 0.61 nm, depending on the adopted methodological analysis, with the upper value being so far the largest observed for the second generation of 3D chalcogenide-based TIs. These results open the path toward the use of chemical methods to produce TIs on large area Si substrates and characterized by highly performing S2C conversion, thus marking a milestone toward future technology-transfer.

Spin‐Charge Conversion in Fe/Au/Sb2Te3 Heterostructures as Probed By Spin Pumping Ferromagnetic Resonance

“…The two-magnon scattering (TMS) cannot be fully accounted for with the subtraction method, and it can generate an over-or under-estimation of g eff . [4,35] On the other hand, our extracted g eff value for both PRE ANN and POST ANN samples is g eff = 2.2 • 10 19 m 2 , being very well in accordance with those reported for similar heterostructures, [25][26][27][28][29][30][31][32][33][34][35][36][37][38][39] thus suggesting a negligible contribution of TMS at the Fe/Sb 2 Te 3 interfaces.…”

“…By interpreting the S2C conversion with the inverse Edelstein effect (IEE), a conversion efficiency of λ IEE ≈ 0.27 nm is obtained, in good agreement with that previously observed in Co/Sb 2 Te 3 systems. [4] Our results point to the conclusion that the observed S2C, as detected by SP-FMR in Fe/Au/Sb 2 Te 3 , originates from the topologically protected surface states (TSS) of Sb 2 Te 3 , which are likely detrimentally affected when depositing Fe in direct contact with Sb 2 Te 3 .…”

“…In order to investigate the relationship between the measured g eff in the POST ANN sample and the occurrence of S2C, and to estimate the SP efficiency, we refer to the procedure described in ref. [4]. In particular, SP-FMR is conducted on the POST ANN sample, and the results are depicted in Figure 4c.…”

“…where V sym and V asym are the symmetric and anti-symmetric components, respectively due to SP and rectification effects. [4] The symmetric contribution can also arise from the thermal Seebeck effect. Being such a thermal contribution independent from the H res direction, [40] it can be eliminated by considering the effective SP signal (V SP ), as extracted by the following Equation ( 5).…”

“…[1] Clarifying the role played in S2C by the specific chemical bonds and/or the presence of magnetically dead-layers and/or intentionally-grown interlayers at the interface between TI and ferromagnetic (FM) layers is highly demanding. [2][3][4] Additionally, in ANN heterostructures, the only difference is in the Sb 2 Te 3 preparation (see Experimental Section). [5] The evaporated Fe and Au layers are polycrystalline, see Figure S1 in the Supporting Information.…”