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Eguchi, G.; Kuroda, Kenta; Shirai, Kaito; Kimura, Akio; Shiraishi, Masashi

doi:10.1103/physrevb.90.201307

Cited by 31 publications

(32 citation statements)

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“…Both the surface and bulk states of Bi2Se3 have a strong tendency toward n-type due to its native n-type defects such as selenium vacancies [1][2][3][11][12][13][14][15][16][17] . In bulk crystals compensation dopants such as Ca and Mn can be used to convert the dominant carrier type from n-to p-type [18][19][20][21][22][23][24][25] . However, such a compensation doping scheme has not been successful in thin films of Bi2Se3.…”

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Solution to the Hole-Doping Problem and Tunable Quantum Hall Effect in Bi₂Se₃ Thin Films

et al. 2018

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ABSTRACT. Bi2Se3, one of the most widely studied topological insulators (TIs), is naturally electron-doped due to n-type native defects. However, many years of efforts to achieve p-type Bi2Se3 thin films have failed so far. Here, we provide a solution to this long-standing problem, showing that the main culprit has been the high density of interfacial defects. By suppressing these defects through an interfacial engineering scheme, we have successfully implemented p-type Bi2Se3 thin films down to the thinnest topological regime. On this platform, we present the first tunable quantum Hall effect (QHE) study in Bi2Se3 thin films, and reveal not only significantly asymmetric QHE signatures across the Dirac point but also the presence of competing anomalous states near the zeroth Landau level. The availability of doping tunable Bi2Se3 thin films will now make it possible to implement various topological quantum devices, previously inaccessible.KEYWORDS. Topological insulator, Bi2Se3, Doping, Interface, Quantum Hall effect 3 Hole (p) doping has been challenging in Bi2Se3 1-3 , one of the most widely studied topological insulators (TIs) [4][5][6][7][8][9][10] . Unlike conventional semiconductor materials, the problem is complicated due to the presence of both surface and bulk states in topological insulators: we have to consider the doping problem of the surface and the bulk states separately. Both the surface and bulk states of Bi2Se3 have a strong tendency toward n-type due to its native n-type defects such as selenium vacancies [1][2][3][11][12][13][14][15][16][17] . In bulk crystals compensation dopants such as Ca and Mn can be used to convert the dominant carrier type from n-to p-type [18][19][20][21][22][23][24][25] . However, such a compensation doping scheme has not been successful in thin films of Bi2Se3. More specifically, we have tried various potential p-type dopants such as Zn, Mg, Ca, Sr, and Ba as compensation dopants, but none of them have so far led to p-type Bi2Se3 thin films; no p-type Bi2Se3 thin films have been demonstrated in the literature either. Only when they were quite thick (~200 nm), we were able to achieve p-type Bi2Se3 films through a complex process 8 . This difficulty in achieving p-type Bi2Se3 thin films has been puzzling, considering the very existence of p-type Bi2Se3 bulk crystals 19,20 . It may be suspected that this discrepancy in doping efficiency between thin films and bulk crystals could be due to the different growth conditions of the two systems, such as growth temperatures, considering that films are, in general, grown at much lower temperatures than bulk crystals. However, it should be noted that even p-type Bi2Se3 bulk crystals tend to become n-type when the crystals are made into thin flakes through, say, the Scotch tape method 26 . Bi2Se3 flakes can remain p-type only if they are relatively thick (> ~150 nm) 24 . All these observations provide evidence that whether they are thin films or bulk crystals, thickness critically affects the doping efficiency of the Bi2Se3 syst...

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Solution to the Hole-Doping Problem and Tunable Quantum Hall Effect in Bi₂Se₃ Thin Films

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“…Therefore, attention has been paid to the growth and synthesis of compounds with a minimum amount of defects or impurities 6,7 . However, many topological insulators are not insulating in the bulk due to defects, impurities, or intersite defects.…”

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Quantum oscillations in metallicSb2Te2Setopological insulator

et al. 2017

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“…This problem has hindered an extraction of intrinsic Dirac-carrier properties in TlM'X 2 . Recently, an attempt has been made to achieve the bulk-insulating phase by fabricating nonstoichiometric TlBiSe 2 crystal with excess Bi and deficient Tl [27,28]. It would, however, be more useful to utilize solid solution in TlM'X 2 , to take full advantage of this system for realizing novel topological phenomena and device applications.…”

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Metal-insulator transition and tunable Dirac-cone surface state in the topological insulatorTlBi1−xSbxTe2studied by angle-resolved photoemission

et al. 2016

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We report a systematic angle-resolved photoemission spectroscopy on topological insulator (TI) TlBi1−xSbxTe2 which is bulk insulating at 0.5 x 0.9 and undergoes a metal-insulator-metal transition with the Sb content x. We found that this transition is characterized by a systematic hole doping with increasing x, which results in the Fermi-level crossings of the bulk conduction and valence bands at x ∼ 0 and x ∼ 1, respectively. The Dirac point of the topological surface state is gradually isolated from the valence-band edge, accompanied by a sign reversal of Dirac carriers. We also found that the Dirac velocity is the largest among known solid-solution TI systems. The TlBi1−xSbxTe2 system thus provides an excellent platform for Dirac-cone engineering and device applications of TIs. The three-dimensional topological insulator (3D TI) is a novel quantum state of matter with a metallic surface state and an insulating bulk. The surface state is characterized by linearly dispersive Dirac-cone band dispersion which traverses the bulk-band gap generated by the spin-orbit coupling [1][2][3]. Experimental realization of various exotic topological phenomena, such as the topological magnetoelectric effect and anomalous quantum Hall effect, [4][5][6] as well as the device applications of TIs largely rely on the dominance of surface Dirac transport and the capability to manipulate Dirac-carrier properties, whereas it is difficult to achieve highly insulating bulk in most of known the 3D TIs due primarily to the small bulk-band gap and defects in the crystal.One of the promising strategies to achieve insulating bulk is to reduce defects [7,8] and compensate defect-induced carriers by tuning chemical composition in a solid-solution system. This methodology has been successfully applied to bulk crystals of tetradymite Bi 2−x Sb x Te 3−y Se y (BSTS) where special combinations of x and y yield high resistivity [9][10][11][12]. Angle-resolved photoemission spectroscopy (ARPES) study of BSTS has revealed a sign reversal of Dirac carriers while keeping insulating bulk [13]. Discovery of the BSTS system has accelerated the engineering of Dirac carriers and device applications [11,[14][15][16][17][18][19][20][21], as highlighted by the spin injection via spin-pumping technique [17], electrical detection of spin polarization [18], and realization of quantum Hall effect at high temperature [19]. To further realize exotic quantum phenomena and device applications in TIs, it is of particular importance to explore the new materials platform of bulk-insulating TIs, since the essential characteristics of bulk and surface, such as the bulk-band gap and the Dirac velocity, strongly depend on the material.Rhombohedral III-V-VI 2 ternary chalcogenide TlM'X 2 [M = Bi and Sb; X = S, Se, and Te; see Figs. 1(a) and 1(b) for the crystal structure and Brillouin zone (BZ), respectively] [22-26] is an intriguing platform to achieve insulating TIs since its crystal structure is distinct from tetradymite due to the covalent-bonding nature and the absence o...

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Surface Shubnikov–de Haas oscillations and nonzero Berry phases of the topological hole conduction inTl1−xBi1+xSe2

Cited by 31 publications

References 19 publications

Solution to the Hole-Doping Problem and Tunable Quantum Hall Effect in Bi₂Se₃ Thin Films

Solution to the Hole-Doping Problem and Tunable Quantum Hall Effect in Bi₂Se₃ Thin Films

Quantum oscillations in metallicSb2Te2Setopological insulator

Metal-insulator transition and tunable Dirac-cone surface state in the topological insulatorTlBi1−xSbxTe2studied by angle-resolved photoemission

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Surface Shubnikov–de Haas oscillations and nonzero Berry phases of the topological hole conduction inTl1−xBi1+xSe2

Cited by 31 publications

References 19 publications

Solution to the Hole-Doping Problem and Tunable Quantum Hall Effect in Bi2Se3 Thin Films

Solution to the Hole-Doping Problem and Tunable Quantum Hall Effect in Bi2Se3 Thin Films

Quantum oscillations in metallicSb2Te2Setopological insulator

Metal-insulator transition and tunable Dirac-cone surface state in the topological insulatorTlBi1−xSbxTe2studied by angle-resolved photoemission

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Solution to the Hole-Doping Problem and Tunable Quantum Hall Effect in Bi₂Se₃ Thin Films

Solution to the Hole-Doping Problem and Tunable Quantum Hall Effect in Bi₂Se₃ Thin Films