Exploiting the Close-to-Dirac Point Shift of the Fermi Level in the Sb2Te3/Bi2Te3 Topological Insulator Heterostructure for Spin-Charge Conversion

Emanuele Longo; Lorenzo Locatelli; Polychronis Tsipas; Akylas Lintzeris; Athanasios Dimoulas; Marco Fanciulli; Massimo Longo; Roberto Mantovan

doi:10.1021/acsami.3c08830

Exploiting the Close-to-Dirac Point Shift of the Fermi Level in the Sb₂Te₃/Bi₂Te₃ Topological Insulator Heterostructure for Spin-Charge Conversion

ACS Appl Mater Interfaces. 2023 Nov 1;15(43):50237-50245. doi: 10.1021/acsami.3c08830. Epub 2023 Oct 20.

Authors

Emanuele Longo¹, Lorenzo Locatelli¹, Polychronis Tsipas², Akylas Lintzeris^{2

3}, Athanasios Dimoulas², Marco Fanciulli⁴, Massimo Longo^{1

5}, Roberto Mantovan¹

Affiliations

¹ CNR-IMM, Unit of Agrate Brianza, Via C. Olivetti 2, Agrate Brianza 20864, Italy.
² National Centre for Scientific Research "Demokritos", Institute of Nanoscience and Nanotechnology, Agia Paraskevi 15341, Athens, Greece.
³ Department of Physics, School of Applied Mathematical and Physical Sciences, National Technical University of Athens, Athens 10682, Greece.
⁴ Department of Material Science, University of Milano Bicocca, Via R. Cozzi 55, Milan 20125, Italy.
⁵ Department of Chemical Science and Technologies, University of Rome Tor Vergata, Via della Ricerca Scientifica, Rome 100133, Italy.

Abstract

Properly tuning the Fermi level position in topological insulators is of vital importance to tailor their spin-polarized electronic transport and to improve the efficiency of any functional device based on them. Here, we report the full in situ metal organic chemical vapor deposition (MOCVD) and study of a highly crystalline Bi₂Te₃/Sb₂Te₃ topological insulator heterostructure on top of large area (4″) Si(111) substrates. The bottom Sb₂Te₃ layer serves as an ideal seed layer for the growth of highly crystalline Bi₂Te₃ on top, also inducing a remarkable shift of the Fermi level to place it very close to the Dirac point, as visualized by angle-resolved photoemission spectroscopy. To exploit such ideal topologically protected surface states, we fabricate the simple spin-charge converter Si(111)/Sb₂Te₃/Bi₂Te₃/Au/Co/Au and probe the spin-charge conversion (SCC) by spin pumping ferromagnetic resonance. A large SCC is measured at room temperature and is interpreted within the inverse Edelstein effect, thus resulting in a conversion efficiency of λ_IEEE ∼ 0.44 nm. Our results demonstrate the successful tuning of the surface Fermi level of Bi₂Te₃ when grown on top of Sb₂Te₃ with a full in situ MOCVD process, which is highly interesting in view of its future technology transfer.

Keywords: Fermi level engineering; MOCVD; spin pumping; spin-charge conversion; spintronics; topological insulators.