Tuning of spin-To-charge conversion in topological insulator based Sb2Te3/Ru(t)/Co60 Fe20B20/Ru heterostructures investigated by inverse spin Hall effect and spin Seebeck effect

Journal article, 2024

Owing to the robust spin-polarized topological conducting surface states, topological insulators (TIs) offer huge promise of establishing ultrafast operation and low power consumption in spin-based applications like quantum communication and magnetic memory devices. In this paper, high spin-To-charge conversion (SCC) is evidenced at room temperature in the TI/ferromagnet (FM) interface engineered Al2O3(0001)/Sb2Te3 (10 nm)/Ru(0-12 nm)/Co60Fe20B20(20 nm)/Ru (4 nm) heterostructure system (with Sb2Te3 as TI and Co60Fe20B20 as FM) grown via DC magnetron cosputtering. The generation of a significantly high charge current density is observed for a particular Ru interlayer (IL) thickness of 4 nm, above which the SCC efficiency of these heterostructures is shown to be inversely governed with the increase in the thickness of the Ru IL. The SCC efficiency in these heterostructure is quantitatively estimated through inverse spin Hall effect (ISHE) measurements, where ∼500% enhancement in the SCC is witnessed corresponding to insertion of a 4-nm-Thin Ru IL. The inverse Edelstein effect length (λIEE) for the heterostructure with the largest SCC is determined to be ∼0.19 ± 0.01 nm, which is comparable with the reported values of other TIs/FM heterostructures. Longitudinal spin Seebeck effect (LSSE) measurements, which corroborate the ISHE findings, also demonstrated the significant power-generation potential in these heterostructures. When the heterostructure is considered as a parallel load resistance model, the analysis of LSSE results disentangles the pure SSE contribution of Sb2Te3 from the anomalous Nernst effect contribution of the Co60Fe20B20 FM. Similar trends are confirmed in other test heterostructures fabricated, wherein either the TI Sb2Te3 layer is replaced with other chalcogenide TI Bi2Te3, or the Ru HM layer is replaced with Nb, thereby confirming the generalization of the approach of controlling the SCC efficiency. These results highlight the potential of TIs and interface engineering for the realization of ultralow power devices and high-current spin Seebeck thermoelectric devices for future spin-based technologies and quantum communication.