Surface-Dominated Conduction in a 6 nm thick Bi<sub>2</sub>Se<sub>3</sub> Thin Film

He, Liang; Xiu, Faxian; Yu, Xinxin; Teague, M. L.; Jiang, Wanjun; Fan, Yabin; Kou, Xufeng; Lang, Murong; Wang, Yong; Huang, Guan‐Hua; Yeh, N.-C.; Wang, Kang L.

doi:10.1021/nl204234j

Cited by 170 publications

(150 citation statements)

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“…103,104,108,170,171,184,[229][230][231] Since it is important to clarify this confusion, let us discuss this issue in some detail. In solids, the resistivity tensor is an inverse of the conductivity tensor, and in the isotropic case their relation is …”

Section: Quantum Oscillationsmentioning

confidence: 99%

Topological Insulator Materials

2013

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Topological insulators represent a new quantum state of matter which is characterized by peculiar edge or surface states that show up due to a topological character of the bulk wave functions. This review presents a pedagogical account on topological insulator materials with an emphasis on basic theory and materials properties. After presenting a historical perspective and basic theories of topological insulators, it discusses all the topological insulator materials discovered as of May 2013, with some illustrative descriptions of the developments in materials discoveries in which the author was involved. A summary is given for possible ways to confirm the topological nature in a candidate material. Various synthesis techniques as well as the defect chemistry that are important for realizing bulk-insulating samples are discussed. Characteristic properties of topological insulators are discussed with an emphasis on transport properties. In particular, the Dirac fermion physics and the resulting peculiar quantum oscillation patterns are discussed in detail. It is emphasized that proper analyses of quantum oscillations make it possible to unambiguously identify surface Dirac fermions through transport measurements. The prospects of topological insulator materials for elucidating novel quantum phenomena that await discovery conclude the review.

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Section: Quantum Oscillationsmentioning

confidence: 99%

Topological Insulator Materials

2013

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“…This is called Van der Waals epitaxy [40,41], which relaxes the lattice-matching condition required for most common epitaxial growth of covalent semiconductors and their heterostructures. Because of this, a variety of substrates have been chosen for the growth of TIs, despite the large lattice mismatch between the films and the substrates, and relatively good epitaxial films have been achieved from various reports [11,[22][23][24][25][26][27][28][42][43][44][45][46][47][48][49]. Their lattice constants and their mismatches to different TIs are shown in Fig.…”

Section: Substrate Selectionmentioning

confidence: 99%

“…Of course, those numbers also highly depend on the growth temperature and rate, which will be discussed later. Although it is difficult to gain a quantitatively assessment on the growth on different substrates at this time, it should be pointed out that in spite of the Van der Waals nature of growth, the lattice-matched substrates do give a better surface morphology, as in the case of Bi 2 Se 3 grown on CdS (-0.24%) [11,28] and InP (0.24%) [50] and Bi 2 Te 3 grown on BaF 2 (0.05%) [42]. This result seems to indicate that the strain caused by the lattice mismatch still affects the film quality to some extent.…”

Section: Substrate Selectionmentioning

confidence: 99%

“…Electronically, detecting the signal of surface state conduction has been hindered for a long time, mostly due to the overwhelming bulk conduction from the imperfect materials. Only very recently did workers start to distinguish the surface state, by applying an electrical field to deplete the bulk carriers [9], by counterdoping to lower the bulk carrier density [10], by the use of thin films to eliminate the bulk contribution [11,12], and by constantly improving material synthesis techniques. However, continued improving material quality remains the key issue and the stumbling block for further exploring new properties and physics as well as applications for the Dirac fermions on the surface states.…”

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Review of 3D topological insulator thin‐film growth by molecular beam epitaxy and potential applications

Kou

Wang

2013

Physica Rapid Research Ltrs

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Abstractmagnified imageThin films of V–VI compound semiconductors (Bi2Se3, Bi2Te3 and Sb2Te3) have been synthesized recently as three‐dimensional topological insulators (TIs). Although these materials have been used as thermoelectric materials for many years, for future studies and applications of the topological surface states, a major bottleneck remains the lack of high‐quality bulk materials that have very few defects and the Fermi level can be moved to inside the bulk bandgap. In this paper, we review the use of molecular beam epitaxy (MBE) technique to achieve high‐quality TI materials. Furthermore, the use of layered growth in MBE affords us the fabrication of heterostructures, such as quantum wells and superlattices. Thus, it may further enable additional studies and applications, similar to those of conventional semiconductor heterostructures but with the novel properties of TI. We explore the growth mechanism, providing a detail discussion on the growth parameters of thin‐film synthesis by MBE. Then we discuss more complex cases, such as functional doping, heterostructures and superlattices. Potential new properties in such quantum structures are discussed. Finally, we give an outlook on this material system for both fundamental studies and applications. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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“…Overall, the spin signal amplitude decreases as the temperature increases, 30 suggesting that the effective spin polarization of the total current decreases. This could be attributed to the fact that with the temperature increasing: (1) the bulk conduction increases due to thermally activated bulk dopants, so that the relative contribution from the spin-polarized surface states conduction decreases; 48 (2) inelastic scatterings such as phonon scatterings increase so that the spin polarization of surface states conduction also decreases. To explain the temperature dependence of the surface states conduction more clearly, standard magneto-transport measurements were performed on the Hall bar structure patterned on the same (Bi 0.53 Sb 0.47 ) 2 Te 3 film (see Figure 1d for the device structure and dimension).…”

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Electrical Detection of Spin-Polarized Surface States Conduction in (Bi_0.53Sb_0.47)₂Te₃ Topological Insulator

et al. 2014

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Strong spin−orbit interaction and time-reversal symmetry in topological insulators enable the spin-momentum locking for the helical surface states. To date, however, there has been little report of direct electrical spin injection/ detection in topological insulator. In this Letter, we report the electrical detection of spin-polarized surface states conduction using a Co/Al 2 O 3 ferromagnetic tunneling contact in which the compound topological insulator (Bi 0.53 Sb 0.47 ) 2 Te 3 was used to achieve low bulk carrier density. Resistance (voltage) hysteresis with the amplitude up to about 10 Ω was observed when sweeping the magnetic field to change the relative orientation between the Co electrode magnetization and the spin polarization of surface states. The two resistance states were reversible by changing the electric current direction, affirming the spin-momentum locking in the topological surface states. Angle-dependent measurement was also performed to further confirm that the abrupt change in the voltage (resistance) was associated with the magnetization switching of the Co electrode. The spin voltage amplitude was quantitatively analyzed to yield an effective spin polarization of 1.02% for the surface states conduction in (Bi 0.53 Sb 0.47 ) 2 Te 3 . Our results show a direct evidence of spin polarization in the topological surface states conduction. It might open up great opportunities to explore energy-efficient spintronic devices based on topological insulators. KEYWORDS: Topological insulator, spin polarization, surface states, spin-momentum locking, spin detection S ince the discovery of two-dimensional (2D) and threedimensional (3D) topological insulators (TIs), 1−5 they have attracted extensive research interest for their exotic physical properties that could lead to dissipationless transport in the quantum spin Hall state. 6−9 Recent studies have shown a giant spin−orbit torque in TI originating from the strong spin− orbit interaction, 10,11 which enabled the current-induced magnetization switching through spin-transfer torque with a low current density. The unique feature of 3D TI, for instance, is that it has both insulating bulk and gapless Dirac surface states. 8,9 Ternary TI compounds, such as (Bi x Sb 1−x ) 2 Te 3 , have been widely investigated for their tunability to achieve low bulk carrier density and manifest topological surface states conduction. 12,13 The presence of surface states is supported by extensive angle-resolved photoemission spectroscopy (ARPES) measurements and transport studies, 14−20 such as Shubnikov-de Haas (SdH) and Aharonov Bohm (AB) quantum oscillations. Because of the strong spin−orbital interaction in TI, direct back scatterings from nonmagnetic impurities are prohibited by the time-reversal symmetry. 8,9 More importantly, the spin-momentum locking naturally leads to a currentinduced spin polarization in surface states; 21 the surface states conduction is spin-polarized once an electric current is passed through a TI film, and this spin polarization can be...

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Surface-Dominated Conduction in a 6 nm thick Bi₂Se₃ Thin Film

Cited by 170 publications

References 34 publications

Topological Insulator Materials

Topological Insulator Materials

Review of 3D topological insulator thin‐film growth by molecular beam epitaxy and potential applications

Electrical Detection of Spin-Polarized Surface States Conduction in (Bi_0.53Sb_0.47)₂Te₃ Topological Insulator

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Surface-Dominated Conduction in a 6 nm thick Bi2Se3 Thin Film

Cited by 170 publications

References 34 publications

Topological Insulator Materials

Topological Insulator Materials

Review of 3D topological insulator thin‐film growth by molecular beam epitaxy and potential applications

Electrical Detection of Spin-Polarized Surface States Conduction in (Bi0.53Sb0.47)2Te3 Topological Insulator

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Surface-Dominated Conduction in a 6 nm thick Bi₂Se₃ Thin Film

Electrical Detection of Spin-Polarized Surface States Conduction in (Bi_0.53Sb_0.47)₂Te₃ Topological Insulator