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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 sample with six welded contacts, which is mounted on a copper plate with insulation.
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Figure 5: A sample with six welded contacts, which is mounted on a copper plate with insulation.

Mentions: Measurements of transport properties are performed by the conventional six-probe method. Usually, for many chalcogenide topological insulators, electrical contacts are attached with silver paste such as 4922N by Dupont, which can be cured at room temperature. However, if Tl is included as a constituent element, then the contact resistance becomes higher than ∼15 Ω and it quickly degrades ∼1 k Ω after several hours. Indium solder can be used to make contacts with the contact resistance as low as ∼1 Ω, but the superconductivity of indium solder sometimes produces significant signals at low temperatures. To date, the spot-welding of gold wires is the best method for making electrical contacts, which become as low as ∼1 Ω and remain low for at least a few weeks. In the present experiment, 30-μm-diameter gold wires were used as lead wires (figure 5), and the typical voltage for welding the wire was 5–9 V with a capacitor of 100 μF.


Synthesis and characterization of 3D topological insulators: a case TlBi(S 1 − x Se x ) 2
A sample with six welded contacts, which is mounted on a copper plate with insulation.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 5: A sample with six welded contacts, which is mounted on a copper plate with insulation.
Mentions: Measurements of transport properties are performed by the conventional six-probe method. Usually, for many chalcogenide topological insulators, electrical contacts are attached with silver paste such as 4922N by Dupont, which can be cured at room temperature. However, if Tl is included as a constituent element, then the contact resistance becomes higher than ∼15 Ω and it quickly degrades ∼1 k Ω after several hours. Indium solder can be used to make contacts with the contact resistance as low as ∼1 Ω, but the superconductivity of indium solder sometimes produces significant signals at low temperatures. To date, the spot-welding of gold wires is the best method for making electrical contacts, which become as low as ∼1 Ω and remain low for at least a few weeks. In the present experiment, 30-μm-diameter gold wires were used as lead wires (figure 5), and the typical voltage for welding the wire was 5–9 V with a capacitor of 100 μF.

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.