Metal island film-based structures for sensing using spectrophotometry and ellipsometry

Metal island films (MIF) are good candidates for sensors due to the strong sensitivity of the localised surface plasmon resonance to the environment refractive index. The strong near field enhancement in the vicinity of the island surface can be even higher if a metal layer (ML) is placed close to a MIF. Structures containing MIF with and without ML are prepared and sensitivities of spectrophotometric and ellipsometric features of the measurements are compared. It is shown that simple MIF is preferable for ellipsometry-based sensing and the one including ML in the case of spectrophotometric measurements

Spin-orbit torques and magnetization switching in (Bi,Sb)2Te3/Fe3GeTe2 heterostructures grown by molecular beam epitaxy

Topological insulators (TIs) hold promise for manipulating the magnetization of a ferromagnet (FM) through the spin-orbit torque (SOT) mechanism. However, integrating TIs with conventional FMs often leads to significant device-to-device variations and a broad distribution of SOT magnitudes. In this work, we present a scalable approach to grow a full van der Waals FM/TI heterostructure by molecular beam epitaxy, combining the charge-compensated TI (Bi,Sb)2Te3 with 2D FM Fe3GeTe2 (FGT). Harmonic magnetotransport measurements reveal that the SOT efficiency exhibits a non-monotonic temperature dependence and experiences a substantial enhancement with a reduction of the FGT thickness to 2 monolayers. Our study further demonstrates that the magnetization of ultrathin FGT films can be switched with a current density of Jc ∼ 1010 A/m2, with minimal device-to-device variations compared to previous investigations involving traditional FMs.This research has received funding from the European Union’s Horizon 2020 (EU H2020) research and innovation programme under grant agreement 881603 (Graphene Flagship) and was supported by the FLAG-ERA grant MNEMOSYN. ICN2 acknowledges support from the Spanish Ministry of Science and Innovation (MCIN) and Spanish Research Agency (AEI/10.13039/501100011033) under contracts PID2019-111773RB-I00, PCI2021-122035-2A, PID2022-143162OB-I00 (including FEDER funds), and Severo Ochoa CEX2021-001214-S. SPINTEC acknowledges support from the French ANR under contracts ANR-21-GRF1-0005-01 and ANR-20-CE24-0015 (ELMAX). T.G. and R.G. acknowledge support from EU H2020 programme under the Marie Skłodowska-Curie Grant Agreement Nos. 754510 and 840588 (GRISOTO, Marie Sklodowska-Curie fellowship), respectively, and JFS from MCIN/AEI/10.13039/50110001103 under contract RYC2019-028368-I.With funding from the Spanish government through the "Severo Ochoa Centre of Excellence" accreditation (CEX2021-001214-S).Peer reviewe

Metal island film-based structures for sensing using spectrophotometry and ellipsometry

Metal island films (MIF) are good candidates for sensors due to the strong sensitivity of the localised surface plasmon resonance to the environment refractive index. The strong near field enhancement in the vicinity of the island surface can be even higher if a metal layer (ML) is placed close to a MIF. Structures containing MIF with and without ML are prepared and sensitivities of spectrophotometric and ellipsometric features of the measurements are compared. It is shown that simple MIF is preferable for ellipsometry-based sensing and the one including ML in the case of spectrophotometric measurements

Spin–Orbit Torques and Magnetization Switching in (Bi,Sb)₂Te₃/Fe₃GeTe₂ Heterostructures Grown by Molecular Beam Epitaxy

Topological insulators (TIs) hold promise for manipulating the magnetization of a ferromagnet (FM) through the spin–orbit torque (SOT) mechanism. However, integrating TIs with conventional FMs often leads to significant device-to-device variations and a broad distribution of SOT magnitudes. In this work, we present a scalable approach to grow a full van der Waals FM/TI heterostructure by molecular beam epitaxy, combining the charge-compensated TI (Bi,Sb)2Te3 with 2D FM Fe3GeTe2 (FGT). Harmonic magnetotransport measurements reveal that the SOT efficiency exhibits a non-monotonic temperature dependence and experiences a substantial enhancement with a reduction of the FGT thickness to 2 monolayers. Our study further demonstrates that the magnetization of ultrathin FGT films can be switched with a current density of Jc ∼ 1010 A/m2, with minimal device-to-device variations compared to previous investigations involving traditional FMs