Synthesis of Bi₂Te₃ Single Crystals with Lateral Size up to Tens of Micrometers by Vapor Transport and Its Potential for Thermoelectric Applications

Abstract

Bismuth telluride (Bi 2 Te 3 ) has recently attracted significant attention owing to its unique physical properties as a three-dimensional topological insulator and excellent properties as a thermoelectric material. Meanwhile, it is important to develop a synthesis process yielding high-quality single crystals over a large area to study the inherent physical properties and device applications of twodimensional materials. However, the maturity of Bi 2 Te 3 vapor-phase synthesis is not good, compared to those of other semiconductor twodimensional crystals. In this study, therefore, we report the synthesis of relatively large-area Bi 2 Te 3 crystals by vapor transport method, and we investigated the key process parameters for a synthesis of relatively thin and large-area Bi 2 Te 3 crystals. The most important factor determining the crystal synthesis was the temperature of the substrate. A Bi 2 Te 3 device exhibited a considerable photocurrent when the laser was irradiated inside the electrode area. This indicated that the photo-thermoelectric effect was the main mechanism of generation of photocurrent. The estimated Seebeck coefficient of the device was ∼196 μV/K, which is comparable to the previously reported high Seebeck coefficient of Bi 2 Te 3 . This synthesis method can guide the development and applications of various types of layered crystals with the space group of R3̅ m.

Two-Dimensional Materials in Large-Areas: Synthesis, Properties and Applications

“…8 b) [ 109 ]. However, several critical 2D compounds of Bi including chalcogenides have not been realised with lateral sizes larger than 100 µm by CVD methods [ 112 ]. Sub-millimetre single crystals of Bi 2 O 2 Se have been synthesised by low-pressure CVD (LPCVD) with ultra-high mobility of 29,000 cm 2 V −1 s −1 at 1.9 K and 450 cm 2 V −1 s −1 in RT [ 45 ].…”

Two‐Dimensional Van Der Waals Topological Materials: Preparation, Properties, and Device Applications

“…CVD is a promising and readily accessible method for the controllable growth of high‐quality 2D vdW materials and heterostructures, [ 152,153 ] which is undoubtedly suitable for the growth of 2D vdW TMs (e.g., TI, [ 55,154–157 ] WSM, [ 158–162 ] and DSM [ 125,163–166 ] ) ( Table 3 ). Typical schematic of CVD for growing various 2D vdW TMs is presented in Figure a–d.…”

“…Since most vdW TMs have a high melting point and decompose when heated to high temperature (e.g., MoTe 2 , WTe 2, and NiTe 2 ), this type of CVD is usually used for the synthesis of 2D vdW TMs nanosheets with low melting points, like Bi 2 Te 3. [ 155 ] Tunable thickness and lateral sizes of 2D vdW TMs will be realized by careful tuning the grown parameters like suitable substrate, adjusting gas flow and substrate temperature (Figure 4e).…”

Low Thermal Conductivity and Magneto-suppressed Thermal Transport in a Highly Oriented FeSb2 Single Crystal

“…The thermoelectric material, which can realize the interconversion between waste heat and electricity directly, has attracted widespread attention due to the promising applications for power generators and cryogenic cooling devices. − The thermoelectric efficiency mainly depends on the dimensionless thermoelectric figure of merit: ZT = S 2 σ T /κ, where S , σ, and T refer to the Seebeck coefficient, electrical conductivity, and the absolute temperature, respectively. , S 2 σ is defined as the power factor . κ is the thermal conductivity, which mainly includes the lattice thermal conductivity κ L and the carrier thermal conductivity κ c . , The high-performance thermoelectric materials should possess a high power factor and low thermal conductivity at a specific temperature .…”