Crystallinity Control of the Topological-Insulator Surface 
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 via Interfacial Engineering for Enhanced Spin-Orbit Torque

Poh, H. Y.; Ang, Calvin Ching Ian; Lim, Gerard Joseph; Jin, Tianli; Lee, S. H.; Koh, Eng Kang; Poh, F.; Lew, Wen Siang

doi:10.1103/physrevapplied.19.034012

Cited by 4 publications

(3 citation statements)

References 41 publications

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“…Smooth MBE films with good crystalline quality were obtained on GaMnAs-buffered GaAs (001) substrates . Moreover, the difficult integration of a buried MRAM stacking before TI growth motivated the search for different substrates and growth strategies. , In previous studies, we reported the 2D MBE growth of BiSb films with TSS on GaAs (111)A and (001). , Room-temperature Hall measurements revealed a semiconducting behavior of the bulk, transiting to a metallic one below 100 K. Typical hole Hall mobilities at 20 K are 1430 and 7620 cm 2 /(V·s) for 450 nm and 1 μm thick films, respectively. , For the integration of such material in future low-energy consumption spintronic devices, two essential points need to be considered: the TI films’ uniformity and surface smoothness need to be optimized for magnetic material deposition and preserved topological surface states are required.…”

Section: Introductionmentioning

confidence: 99%

“…22 Moreover, the difficult integration of a buried MRAM stacking before TI growth motivated the search for different substrates and growth strategies. 23,24 In previous studies, we reported the 2D MBE growth of BiSb films with TSS on GaAs (111)A and (001). 25,26 Roomtemperature Hall measurements revealed a semiconducting behavior of the bulk, transiting to a metallic one below 100 K. Typical hole Hall mobilities at 20 K are 1430 and 7620 cm 2 / (V•s) for 450 nm and 1 μm thick films, respectively.…”

Section: ■ Introductionmentioning

confidence: 99%

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Large-Scale Epitaxial Integration of Single-Crystalline BiSb Topological Insulator on GaAs (111)A

Khaled,

Cancellara,

Fekraoui

et al. 2024

ACS Appl. Electron. Mater.

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Topological insulators (TIs) are promising materials for future spintronics applications, and their epitaxial integration would allow the realization of hybrid interfaces. As the first materials studied, bismuth antimony alloys (Bi 1−x Sb x ) show great potential due to their tunable electronic band structure and efficient charge-to-spin conversion. Here, we report the growth of Bi 1−x Sb x thin films on GaAs (111)A substrates following two different protocols. For the conventional epitaxy process, the grown films show excellent crystallinity and twin domains corresponding to an in-plane 180°rotation of the crystalline structure. Domain walls are found to be composition-dependent and have a lower density for antimony-rich films. For the optimized process, depositing an antimony bilayer prior to BiSb growth allows for the achievement of single crystallinity of the TI films. The topologically protected surface states are evidenced by ex situ ARPES measurements for domain-free and conventional films. To the best of our knowledge, this work presents the first large-scale epitaxial integration of single-crystalline Bi 1−x Sb x thin films on industrial substrates.

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Section: Introductionmentioning

confidence: 99%

Section: ■ Introductionmentioning

confidence: 99%

Large-Scale Epitaxial Integration of Single-Crystalline BiSb Topological Insulator on GaAs (111)A

Khaled,

Cancellara,

Fekraoui

et al. 2024

ACS Appl. Electron. Mater.

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“…BiSb typically crystallizes in a rhombohedral A7 crystal structure with a specific ordered arrangement of Bi and Sb atoms, as shown in Figure a. However, the low melting point of the BiSb alloy raises concerns about Bi/Sb diffusion and phase separation, which could compromise SOT efficiency during annealing and even room-temperature (RT) aging. , Also, the TSS of BiSb thin films was reported to be significantly affected by the selection of adjacent layers. ,− To date, it still remains a critical aspect requiring further investigation of the phenomenon of interdiffusion in the BiSb alloy with neighboring layers and interface chemistry to fully exploit the potential of BiSb-based heterostructures for spintronic applications.…”

Section: Introductionmentioning

confidence: 99%

Spin–Orbit Torque Modulated by Interface Chemistry in Topological BiSb/NiFe Bilayers with Titanium Insertion

Manoj,

Wen,

Uzuhashi

et al. 2024

ACS Appl. Electron. Mater.

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Topological insulators are intriguing materials in the field of spintronics because they exhibit unique electronic properties that hold great promise for device applications. BiSb has attracted more research interest among topological materials due to its remarkably high spin−orbit torque (SOT) efficiency. However, due to the low melting point of the alloy, high diffusivities of Bi/Sb tend to degrade the SOT efficiency with temperature and aging. In this work, we utilize interfacial chemistry driven by a titanium (Ti) spacer between BiSb and NiFe bilayers to improve the SOT efficiency. We investigated the effect of the Ti insertion layer on the SOT efficiency under as-deposited, room-temperature aging, and annealing conditions. The SOT efficiency, estimated from the spin-torque ferromagnetic resonance response, revealed that the samples with the Ti layer had shown a multifold increase in the SOT efficiency compared to those without Ti insertion. Atomic resolution microstructural analyses provided a clear understanding of the interfacial chemistry where Ti successfully hindered the interdiffusion of Ni and Sb. The interfacial chemistry in the vicinity of Ti contributed significantly to the improvement of the SOT efficiency. These results highlight the importance of the Ti insertion layer in the BiSb-based topological material/ferromagnet bilayer systems for SOT applications in spintronics.

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Recent progress in strong spin-orbit coupling van der Waals materials and their heterostructures for spintronic applications

Shi,

Wang,

Zhao

et al. 2023

Materials Today Electronics

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Crystallinity Control of the Topological-Insulator Surface Bi85Sb15(012) via Interfacial Engineering for Enhanced Spin-Orbit Torque

Cited by 4 publications

References 41 publications

Large-Scale Epitaxial Integration of Single-Crystalline BiSb Topological Insulator on GaAs (111)A

Large-Scale Epitaxial Integration of Single-Crystalline BiSb Topological Insulator on GaAs (111)A

Spin–Orbit Torque Modulated by Interface Chemistry in Topological BiSb/NiFe Bilayers with Titanium Insertion

Recent progress in strong spin-orbit coupling van der Waals materials and their heterostructures for spintronic applications

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