Method for growing 1T-TaS2 single crystal by using iodine as transport agent through vapor transport method

Abstract

The invention provides a method for growing a 1T-TaS2 single crystal by using iodine as a transport agent through a vapor transport method, and belongs to the field of single crystal preparation. The method comprises the following steps: (1) preparing a TaS2 polycrystal through repeated sintering by a solid-phase reaction method, and (2) uniformly mixing the TaS2 polycrystal with a transport agent I2, and preparing the 1T-TaS2 single crystal by a chemical vapor transport method. The principle of the method is that a solid raw material reacts with a transport agent in a high-temperature region (source region) to generate a gaseous intermediate product. The gas-phase component circulates in the tube through concentration gradient to realize continuous transportation, and finally in a low-temperature region (growth region), the gaseous compound moves in a balanced manner due to temperature difference to generate reverse reaction, and target single crystals are separated out. The 1T-TaS2 single crystal grown by the method has high quality, and is suitable for further research on physical properties such as charge density wave and the like of the 1T-TaS2 single crystal.

Description

Technical Field

[0001] This invention belongs to the field of single crystal preparation, and in particular relates to a method for growing 1T-TaS2 single crystals using iodine as a transport agent via a gas-phase transport method. Background Technology

[0002] Charge density wave materials are quantum materials exhibiting spontaneous periodic electron density modulation and lattice distortion. Their extreme sensitivity to temperature, strain, and electromagnetic fields suggests significant potential applications in low-power electronics, quantum technology, sensing, and energy. TaS2 possesses a 1T, 2H, and 3R phase structure. As a transition metal sulfide, TaS2 is not only a two-dimensional material achieving interlayer coupling through weak van der Waals forces but also a typical charge density wave material. Compared to other two-dimensional materials, 1T-TaS2 possesses a higher charge density wave transition temperature, making it an ideal charge density wave material. Since charge density waves are difficult to observe in low-quality crystals, preparing high-quality 1T-TaS2 single crystals is crucial for studying charge density mechanisms. The 1T phase TaS2 exhibits three charge density wave (CDW) transitions as it cools from high to low temperatures: 550K (transition from normal metal to incommensurable charge density wave, abbreviated as ICCDW), 350K (transition from incommensurable charge density wave to near-commensurable charge density wave, abbreviated as NCCDW), and 180K (transition from near-commensurable charge density wave to fully commensurable charge density wave, abbreviated as CCDW). The preparation and study of 1T-TaS2 single crystals have contributed to a deeper understanding of the physical properties and charge density wave mechanism of two-dimensional transition metal sulfide charge density wave materials, and laid the foundation for the subsequent fabrication of charge density wave devices.

[0003] Vapor transport method is a chemical method that transports solid or liquid substances from a high-temperature end to a low-temperature end through gas-phase reactions, where they are grown into single crystals. This method utilizes the formation and decomposition of volatile intermediates to achieve the migration and purification of substances, and is widely used in materials synthesis, crystal growth, and purification. The vapor transport method can achieve atomically ordered growth in a closed system, obtaining single crystals with few defects and high lattice integrity, making it an effective method for preparing high-quality 1T-TaS2 single crystals. Summary of the Invention

[0004] The purpose of this invention is to address the high requirements for the quality of 1T-TaS2 single crystals in the study of charge density wave, which is based on the common chemical vapor deposition method for the growth of TaS2. This invention provides a method for preparing 1T-TaS2 single crystals using chemical vapor deposition with iodine as a transport agent.

[0005] Technical Solution: To achieve the above-mentioned objectives, this invention provides a method for growing 1T-TaS2 single crystals using iodine as a transport agent via a vapor-phase transport method. This method includes the following steps:

[0006] (1) Weigh tantalum powder and sulfur powder in a glove box filled with argon according to the molar ratio; after weighing, grind tantalum powder and sulfur powder with a ball mill for 15-45 minutes to mix tantalum powder and sulfur powder evenly.

[0007] (2) Place the ground powder into the tableting mold and compress for 10-15 minutes. The purpose of this step is to increase the contact area between the reactants so that the subsequent solid-phase reaction is more complete.

[0008] (3) Place the pressed sample from step (2) into the first silica tube, evacuate the inside of the first silica tube to a pressure below the preset level, and seal the tube.

[0009] (4) The first silicon dioxide tube was placed in a well furnace for solid-state reaction. It was heated from room temperature to 122°C for 1 hour and kept at that temperature for 12 hours. It was then heated to 410°C for 5 hours and kept at that temperature for 12 hours. It was then heated to 850°C for 7 hours and kept at that temperature for 5 days. Finally, it was cooled to room temperature to generate TaS2 polycrystalline material.

[0010] (5) Grind the sintered TaS2 polycrystalline material and sinter it again using the procedure in (4), repeating the sintering process more than twice;

[0011] (6) Place the repeatedly sintered TaS2 polycrystalline powder into the second silica tube for gas-phase transport; weigh elemental I2 as the transport agent, and control the density of I2 in the second silica tube for gas-phase transport to be 3-8 mg / cm³. 3 ;

[0012] (7) Vacuum the second silica tube transported in the gas phase to a pressure below the preset pressure using a tube sealing machine and seal it. Then place the second silica tube into a three-temperature zone tube furnace and heat it from room temperature for 15 hours to bring the high temperature end to 900°C and the low temperature end to 800°C. Maintain the above temperature for gas phase transport for 12-14 days. After 12-14 days, take the test tube out of the furnace and quench it in cold water below 25 degrees Celsius to ensure that the generated TaS2 single crystal is a 1T phase.

[0013] (8) Place the sample in alcohol and sonicate to remove the iodine from the surface of the single crystal sample.

[0014] Furthermore, in step (1), the tantalum powder has a purity of 99%-99.99%, and the sulfur powder has a purity of 99%-99.995%.

[0015] Furthermore, in step (1), the ratio of the amount of substance is 0.5 ± 0.1.

[0016] Furthermore, in step (3), the preset pressure of the vacuum is 4 × 10⁻⁶. 2 Pa.

[0017] Furthermore, in step (8), the preset pressure of the vacuum is 4 × 10⁻⁶. 2 Pa.

[0018] Beneficial effects: Compared with the prior art, the technical solution of the present invention has the following beneficial technical effects:

[0019] (1) The crystallinity of the product is better, the half width of the rocking curve is 0.05, and the size of the obtained sample is larger.

[0020] (2) Using iodine as a transport agent to grow TaS2 single crystals improves transport efficiency compared to using traditional TaCl3 material as a transport agent.

[0021] (3) Optimize the sintering process to improve the quality of the sample. The polycrystalline sintering temperature is controlled between the melting point and boiling point of sulfur and kept at that temperature. The polycrystalline material is repeatedly sintered to improve the quality. Attached Figure Description

[0022] Figure 1 This is the XRD pattern of the 1T-TaS2 single crystal prepared in Example 1 of this invention.

[0023] Figure 2 This is the EDS spectrum of the 1T-TaS2 single crystal prepared in Example 1 of this invention.

[0024] Figure 3 This is an overall flowchart of the method of the present invention.

[0025] Figure 4 A flowchart illustrating the preparation process of 1T-TaS2 polycrystalline material in Example 1 of this invention.

[0026] Figure 5 RT image of the 1T-TaS2 single crystal prepared in Example 1 of this invention. Detailed Implementation

[0027] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0028] Depend on Figure 3As shown, this invention provides a method for growing 1T-TaS2 single crystals using iodine as a transport agent via a vapor-phase transport method. The method includes the following steps:

[0029] (1) Weigh tantalum powder with a purity of 99%-99.99% and sulfur powder with a purity of 99%-99.995% in a glove box filled with argon gas at a molar ratio of 0.5±0.1; grind Ta powder and S powder using a ball mill for more than 30 minutes to ensure that Ta powder and S powder are mixed evenly.

[0030] (2) Place the ground powder into the tableting mold and compress for 10 minutes;

[0031] (3) Place the compressed sample into a silica tube, evacuate the inside of the silica tube to a vacuum, and seal the tube.

[0032] (4) The first silicon dioxide tube was placed in a pit furnace for solid-phase reaction. It was heated from room temperature to 122°C (10°C above the melting point of sulfur) for 1 hour and held for 12 hours. It was then heated for another 5 hours to 410°C (30°C below the boiling point of sulfur) and held for 12 hours. It was then heated for another 7 hours to 850°C and held for 5 days. Finally, it was cooled to room temperature to generate TaS2 polycrystalline material.

[0033] (5) Grind the sintered TaS2 polycrystalline material and sinter it again using the procedure in (4), repeating the sintering process more than twice;

[0034] (6) Take the sintered TaS2 polycrystal out of the test tube and put it into the second silica tube for gas phase transport; weigh I2 as the transport agent, and the density of I2 in the silica tube for gas phase transport should be 3-5 mg / cm3.

[0035] (7) Vacuum and seal the second silica tube for gas phase transport using a tube sealing machine. Place the second silica tube into a three-temperature zone tube furnace and heat it from room temperature for 15 hours to bring the high temperature end to 900°C and the low temperature end to 800°C. Maintain the above temperatures for gas phase transport for 14 days. After 14 days, take the test tube out of the furnace and quench it in cold water below 25 degrees Celsius.

[0036] (8) Place the sample in a beaker containing alcohol and sonicate for at least 10 minutes at room temperature to remove the iodine from the surface of the single crystal sample. EDS characterization of the single crystal sample yielded Table 1 below, showing that the ratio of S atoms to Ta atoms (At%) was 2:1.

[0037] Table 1

[0038] element Line type wt% wt% sigma At% S K-line system 25.59 0.11 65.99 Ta M-line system 74.41 0.11 34.01 Total 100.00 100.00

[0039] Figure 1This is the XRD pattern of the 1T-TaS2 single crystal prepared in Example 1 of this invention. Figure 1 It can be seen that the peaks are equally spaced, indicating that it is a single crystal peak. The angular positions of the four peaks are 14.92, 30.20, 46.09, and 62.98, respectively, which correspond to the (001), (002), (003), and (004) diffraction peaks of the crystal plane of 1T-TaS2. Figure 2 This is the EDS spectrum of the 1T-TaS2 single crystal prepared in Example 1 of the present invention. It can be seen that the sample contains only two elements, Ta and S, and the atomic ratio of Ta to S is 1:2. Figure 4 The process flow for preparing 1T-TaS2 polycrystalline material in Example 1 of this invention is as follows: heating from room temperature to 122°C for 1 hour and holding for 12 hours, heating to 410°C for 5 hours and holding for 12 hours, heating to 850°C for 7 hours and holding for 5 days, and finally cooling to room temperature to generate TaS2 polycrystalline material, followed by repeated sintering. Figure 5 The RT diagram of the 1T-TaS2 single crystal prepared in Example 1 of this invention shows that the resistance changes at 175K, corresponding to the transition from near commensurable charge density wave (NCCDW) to fully commensurable charge density wave (CCDW).

Claims

1. A method for growing 1T-TaS2 single crystals using iodine as a transport agent via a vapor-phase transport method, characterized in that, The method includes the following steps: (1) Polycrystalline TaS2 was prepared by repeated sintering via solid-state reaction method. (2) Mix TaS2 polycrystalline material with transport agent I2 evenly and prepare 1T-TaS2 single crystal by chemical vapor transport method.

2. The method for growing 1T-TaS2 single crystals using iodine as a transport agent via a vapor-phase transport method according to claim 1, characterized in that, In step (1), the method for preparing TaS2 polycrystalline material by repeated sintering via solid-state reaction is as follows: (1.1) Weigh tantalum powder and sulfur powder in a glove box filled with argon according to the molar ratio; after weighing, grind tantalum powder and sulfur powder with a ball mill for 15-45 minutes to mix tantalum powder and sulfur powder evenly. (1.2) Place the ground powder into the tableting mold and compress for 10-15 minutes; (1.3) Place the compressed sample into the first silica tube, evacuate the inside of the first silica tube to below the preset pressure, and seal the tube; (1.4) The first silicon dioxide tube was placed in a well furnace for solid-state reaction. It was heated from room temperature to 122°C for 1 hour and kept at that temperature for 12 hours. It was then heated to 410°C for 5 hours and kept at that temperature for 12 hours. It was then heated to 850°C for 7 hours and kept at that temperature for 5 days. Finally, it was cooled to room temperature to generate TaS2 polycrystalline material. (1.5) Grind the sintered TaS2 polycrystalline material and sinter it again using the procedure in (1.4), repeating the sintering process more than twice.

3. The method for growing 1T-TaS2 single crystals using iodine as a transport agent via a vapor-phase transport method according to claim 1, characterized in that, In step (2), the TaS2 polycrystalline material is mixed uniformly with the transport agent I2, and the 1T-TaS2 single crystal is prepared by chemical vapor phase transport as follows: (2.1) Place the repeatedly sintered TaS2 polycrystalline powder into the second silica tube for gas phase transport; weigh I2 element as transport agent, and control the density of I2 in the second silica tube for gas phase transport to be 3-8 mg / cm3. (2.2) Vacuum the second silica tube for gas-phase transport to a pressure below the preset pressure using a tube sealing machine and seal it. Then place the second silica tube into a three-temperature zone tube furnace and heat it from room temperature for 15 hours to bring the high temperature end to 900°C and the low temperature end to 800°C. Maintain the above temperatures for gas-phase transport for 12-14 days. After 12-14 days, remove the tube from the furnace and quench it in cold water below 25 degrees Celsius to ensure that the generated TaS2 single crystal is a 1T phase. (2.3) Place the sample in alcohol and sonicate to remove the iodine from the surface of the single crystal sample.

4. The method for growing 1T-TaS2 single crystals using iodine as a transport agent via a vapor-phase transport method according to claim 2, characterized in that, The tantalum powder has a purity of 99%-99.99%, and the sulfur powder has a purity of 99%-99.995%.

5. A method for growing 1T-TaS2 single crystals using iodine as a transport agent via a vapor-phase transport method according to claim 2 or 4, characterized in that, The molar ratio is 0.5 ± 0.

1.

6. A method for growing 1T-TaS2 single crystals using iodine as a transport agent via a vapor-phase transport method according to claim 2 or 4, characterized in that, In step (1.3), the preset pressure of the vacuum is 4 × 10⁻⁶. 2 Pa.

7. A method for growing 1T-TaS2 single crystals using iodine as a transport agent via a vapor-phase transport method according to claim 2 or 4, characterized in that, In step (2.2), the preset pressure of the vacuum is 4 × 10⁻⁶. 2 Pa.

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