Tracking quintuple layer oxidation on cleaved<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi mathvariant="normal">B</mml:mi><mml:msub><mml:mi mathvariant="normal">i</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:mi mathvariant="normal">S</mml:mi><mml:msub><mml:mi mathvariant="normal">e</mml:mi><mml:mn>3</mml:mn></mml:msub></mml:mrow></mml:math>by optical second-harmonic anisotropy

An, Yongli; Green, Avery J.; Diebold, Alain C.

doi:10.1103/physrevb.93.241308

Cited by 3 publications

(1 citation statement)

References 29 publications

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“…Besides, it is widely reported that the surface degradations have a strong doping effect and can cause a large E F shift in TIs. − For example, the oxygen or water absorbed on the Bi 2 Se 3 surface was found to serve as a p-type , or an n-type dopant − and finally pin the E F in the bulk conduction band or the valence band, respectively. To address this problem, capping layers such as Al, PMMA, Se, Te, F4TCNQ, and ZnO have been used in previous studies to protect binary TIs (Bi 2 Se 3 , Bi 2 Te 3 ) or ternary TI ((Bi x Sb 1– x )Te 3 ) from degradation and charge carrier doping in the environment.…”

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Stabilizing the Fermi Level of Cr-Doped Magnetic Topological Insulators by Al Passivation

Guo

Zheng

et al. 2019

J. Phys. Chem. C

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The quantum anomalous Hall effect (QAHE) observed in magnetically doped topological insulators is not only fundamentally interesting but also has great potential applications such as quantum computation. To experimentally realize the QAHE, the Fermi level (E F) needs to be stabilized in the tiny surface-state gap. However, for topological insulators, even a very short time exposure to the atmosphere can induce a large E F shift. In this work, magnetic topological insulator Cr0.27(Bi0.43Sb0.63)1.73Te3 (CBST) thin-films are successfully prepared via magnetron sputtering, which is a more universal, efficient, and affordable method for application. Then, the evolution of the E F position has been investigated as a function of the exposure time in the air through gate-dependent transport measurements. This study reveals that the E F position can be stabilized by in situ Al passivation with carrier doping significantly reduced, and the oxidations of Bi and Te atoms can also be suppressed. The availability of wide compositions for magnetron sputtering as well as the E F position stability of the in situ Al passivation may be a key for further investigations of the topological insulator toward the achievement of the QAHE in the sputtered CBST thin-film systems.

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confidence: 99%

Stabilizing the Fermi Level of Cr-Doped Magnetic Topological Insulators by Al Passivation

Guo

Zheng

et al. 2019

J. Phys. Chem. C

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2023

Nonlinear Optics on Ferroic Materials

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Surface oxidation of the topological insulator Bi2Se3

Green¹,

Dey²,

An³

et al. 2016

Journal of Vacuum Science &Amp; Technology A: Vacuum, Surfaces, and Films

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An understanding of the aging and oxidation of the (0001) surface of Bi2Se3 is critical to a comprehensive physical picture of its topologically protected surface states. Here, the authors contribute new experimental observations about the aging and oxidation process. The authors find that surface aging in ambient conditions occurs in two major steps. Within 2 h of exfoliation, a series of ∼3.2 Å high islands are observed by atomic force microscopy over approximately 10% of the surface. Subsequently, patch growth stops, and oxidation begins after the 2 h and continues until one quintuple layer has been oxidized. X-ray photoelectron spectroscopy shows no sign of oxidation before ∼120 min of exposure to air, and the oxygen 1 s peak, as well as oxidized Se 3d and Bi 4d peaks, are clearly present after ∼190 min of ambient exposure. Variable angle spectroscopic ellipsometry indicates that the oxidation of a full quintuple layer occurs on the time scale of days. These results are in good agreement with the time dependent changes observed in the surface crystal structure by second harmonic generation. In addition to providing the ability to nondestructively measure oxide on the surface of Bi2Se3 crystals, ellipsometry can be used to identify the thickness of Bi2Se3 flakes. With these methods, the authors have constructed a consistent, experimentally based model of aging process at the surface of Bi2Se3.

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Tracking quintuple layer oxidation on cleavedBi2Se3by optical second-harmonic anisotropy

Cited by 3 publications

References 29 publications

Stabilizing the Fermi Level of Cr-Doped Magnetic Topological Insulators by Al Passivation

Stabilizing the Fermi Level of Cr-Doped Magnetic Topological Insulators by Al Passivation

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Surface oxidation of the topological insulator Bi2Se3

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