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Synthesis and characterization of 3D topological insulators: a case TlBi(S 1 − x Se x ) 2

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ABSTRACT

In this article, practical methods for synthesizing Tl-based ternary III-V-VI2 chalcogenide TlBi(SSex)2 are described in detail, along with characterization by x-ray diffraction and charge transport properties. The TlBi(SSex)2 system is interesting because it shows a topological phase transition, where a topologically nontrivial phase changes to a trivial phase without changing the crystal structure qualitatively. In addition, Dirac semimetals whose bulk band structure shows a Dirac-like dispersion are considered to exist near the topological phase transition. The technique shown here is also generally applicable for other chalcogenide topological insulators, and will be useful for studying topological insulators and related materials.

No MeSH data available.


(a) Raw materials put in a sealed quartz tube. Round black shots are selenium, round silvery shots are bismuth, and irregularly shaped pieces are thallium. The outer and inner diameters of the quartz tube are 9 mm and 7 mm, respectively. (b) Schematic of the growth, where the sealed quartz tube is put at a slightly lower position in the furnace. (c), (d) Pictures of cleaved crystals of TlBiSe2. (e) Laue diffraction pattern of TlBiSe2 on the cleaved surface.
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Figure 2: (a) Raw materials put in a sealed quartz tube. Round black shots are selenium, round silvery shots are bismuth, and irregularly shaped pieces are thallium. The outer and inner diameters of the quartz tube are 9 mm and 7 mm, respectively. (b) Schematic of the growth, where the sealed quartz tube is put at a slightly lower position in the furnace. (c), (d) Pictures of cleaved crystals of TlBiSe2. (e) Laue diffraction pattern of TlBiSe2 on the cleaved surface.

Mentions: A picture of the starting materials sealed in a quartz tube is shown in figure 2(a). The tip of the quartz tube is narrowed to restrict nucleation of the growth at the beginning. This is useful for obtaining crystals of larger domains. The purity of starting materials of Tl, Bi, Se, and S is 99.999%(5N), 99.9999%(6N), 5N, and 5N, respectively. To remove the oxidized surface of the raw materials, Tl shots are annealed in a hydrogen atmosphere at 270–300 °C and Bi shots are washed with a diluted HNO3 solution. The amount of the raw materials is carefully controlled in the glove box, and the materials are mixed into the quartz-glass tube, which is sealed after evacuating with a diffusion pump and then filled with a small amount of pure argon. The ratio of the materials is stoichiometric in the present experiment, but recently, the shifted composition of starting materials turned out to be useful for synthesizing bulk-insulating samples [38, 39]. Before the main growth procedure, the raw materials are slowly warmed up at the rate of 100 °C/h and kept at 900 °C to complete the reaction. At 900 °C, the quartz tube is shaken to homogenize the melt and eliminate bubbles.


Synthesis and characterization of 3D topological insulators: a case TlBi(S 1 − x Se x ) 2
(a) Raw materials put in a sealed quartz tube. Round black shots are selenium, round silvery shots are bismuth, and irregularly shaped pieces are thallium. The outer and inner diameters of the quartz tube are 9 mm and 7 mm, respectively. (b) Schematic of the growth, where the sealed quartz tube is put at a slightly lower position in the furnace. (c), (d) Pictures of cleaved crystals of TlBiSe2. (e) Laue diffraction pattern of TlBiSe2 on the cleaved surface.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5036500&req=5

Figure 2: (a) Raw materials put in a sealed quartz tube. Round black shots are selenium, round silvery shots are bismuth, and irregularly shaped pieces are thallium. The outer and inner diameters of the quartz tube are 9 mm and 7 mm, respectively. (b) Schematic of the growth, where the sealed quartz tube is put at a slightly lower position in the furnace. (c), (d) Pictures of cleaved crystals of TlBiSe2. (e) Laue diffraction pattern of TlBiSe2 on the cleaved surface.
Mentions: A picture of the starting materials sealed in a quartz tube is shown in figure 2(a). The tip of the quartz tube is narrowed to restrict nucleation of the growth at the beginning. This is useful for obtaining crystals of larger domains. The purity of starting materials of Tl, Bi, Se, and S is 99.999%(5N), 99.9999%(6N), 5N, and 5N, respectively. To remove the oxidized surface of the raw materials, Tl shots are annealed in a hydrogen atmosphere at 270–300 °C and Bi shots are washed with a diluted HNO3 solution. The amount of the raw materials is carefully controlled in the glove box, and the materials are mixed into the quartz-glass tube, which is sealed after evacuating with a diffusion pump and then filled with a small amount of pure argon. The ratio of the materials is stoichiometric in the present experiment, but recently, the shifted composition of starting materials turned out to be useful for synthesizing bulk-insulating samples [38, 39]. Before the main growth procedure, the raw materials are slowly warmed up at the rate of 100 °C/h and kept at 900 °C to complete the reaction. At 900 °C, the quartz tube is shaken to homogenize the melt and eliminate bubbles.

View Article: PubMed Central - PubMed

ABSTRACT

In this article, practical methods for synthesizing Tl-based ternary III-V-VI2 chalcogenide TlBi(SSex)2 are described in detail, along with characterization by x-ray diffraction and charge transport properties. The TlBi(SSex)2 system is interesting because it shows a topological phase transition, where a topologically nontrivial phase changes to a trivial phase without changing the crystal structure qualitatively. In addition, Dirac semimetals whose bulk band structure shows a Dirac-like dispersion are considered to exist near the topological phase transition. The technique shown here is also generally applicable for other chalcogenide topological insulators, and will be useful for studying topological insulators and related materials.

No MeSH data available.