A single crystal of tantalum diselenide and a method for growing and applications thereof

Abstract

This invention belongs to the field of quantum functional materials and nanoelectronic devices, specifically relating to a tantalum diselenide single crystal, its growth method, and its applications. The chemical formula of the tantalum diselenide single crystal is 2H-TaSe2. Its growth method involves mixing Ta and Se raw materials at a molar ratio of 1:2.1~2.5 and sintering to obtain a polycrystalline material. This polycrystalline material is then sealed in a quartz tube with an iodine transport agent and subjected to a gas-phase transport reaction at dual temperatures of 940℃~960℃ and 840℃~860℃. After cooling, a millimeter-sized, smooth-surfaced, and easily peelable tantalum diselenide single crystal is obtained. The superconducting transition temperature of this single crystal is... T c With a charge density wave transition temperature of approximately 90 K and a K ≥ 2.0 K, two-dimensional sheet materials can be prepared by cleaving along the (001) plane, and the resulting sheets retain the properties of the material. T c With superconductivity and charge density wave characteristics of ≥1.8 K, this invention has important application value in the fabrication of low-dimensional quantum devices such as ultrafast optically controlled switches and single-photon detectors.

Description

Technical Field

[0001] This invention belongs to the field of quantum functional materials and nanoelectronic devices, specifically relating to a tantalum diselenide single crystal, its growth method, and its applications. Background Technology

[0002] In today's semiconductor technology, the switching speed and energy consumption of silicon-based transistors are gradually approaching physical limits. In order to seek breakthroughs, researchers have turned their attention to new low-dimensional materials with unique quantum properties. Tantalum diselenide (TaSe2), as a typical transition metal chalcogenide, has attracted much attention for its potential in ultrafast switching applications. Its scientific background is mainly based on the following effects: (1) Charge density wave and Mott phase transition: TaSe2 enters the charge density wave (CDW) state at low temperatures, and its electron density exhibits periodic modulation. Stronger electron correlation effects can even drive it to undergo a Mott phase transition, changing from a metallic state to an insulating state. The huge difference in resistance between these two states provides a basis for realizing the switching function. (2) Ultrafast external modulation: Studies have shown that by applying external excitation, TaSe2 can be induced to switch between different electronic phases (such as CDW state and normal metallic state) extremely quickly. This switching may be achieved by electrical pulses or laser pulses, and the process can be as fast as picoseconds, far exceeding the switching speed of traditional silicon-based transistors. (3) Structural advantages of two-dimensional materials: TaSe2 can be prepared into two-dimensional thin films with atomic layer thickness. This extreme thickness is conducive to effectively controlling its electronic state through external fields such as electric field and light field. It also makes it easy to integrate with other materials to construct novel van der Waals heterostructures, providing an ideal platform for developing compact and high-speed nanoelectronic devices.

[0003] Although bulk 2H-TaSe2 exhibits abundant quantum order, its application in nanoelectronics is limited by three-dimensional bulk phase effects. Currently, TaSe2 thin layers obtained by mechanical or liquid-phase exfoliation can retain or even control its CDW and superconducting coexistence states, and are more easily subjected to ultrafast phase transitions through gate voltage and optical fields. However, existing TaSe2 single crystals prepared using chemical vapor transport (CVT) generally suffer from surface roughness and high defect density, resulting in low exfoliation yields, small two-dimensional flake sizes, and severe property degradation. Therefore, there is an urgent need to develop a TaSe2 single crystal growth method that can simultaneously achieve high crystal quality, large size, and easy cleavage, laying the foundation for subsequent single-crystal two-dimensionalization and device integration. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides a tantalum diselenide single crystal, its growth method, and its applications. The tantalum diselenide (2H-TaSe2) single crystal material is large in size, has a smooth surface, and is easily exfoliated. It exhibits enhanced superconducting transition temperature and stable charge density wave phase transition. The two-dimensional flakes obtained through controlled exfoliation still retain [the characteristics of the material]. Tc The superconductivity and charge density wave characteristics at ≥1.8 K can be further used to fabricate low-dimensional quantum devices such as ultrafast optically controlled switches and single-photon detectors.

[0005] To achieve the above objectives, the specific technical solution of the present invention is as follows: The first aspect of this invention provides a method for growing tantalum diselenide single crystals, comprising the following steps: Ta and Se raw materials are mixed at a molar ratio of 1:2.1~2.5 and sintered to obtain polycrystalline tantalum diselenide; Tantalum diselenide polycrystalline material and gaseous transport agent are placed in a quartz tube, and the tube is evacuated to ≤0.1 mbar and then sealed. The temperature of the reaction end containing the raw materials was set at 940℃~960℃ and the heating rate was 94℃ / h~96℃ / h. The temperature of the crystallization zone at the other end was set at 840℃~860℃ and the heating rate was 84℃ / h~86℃ / h. After holding at this temperature for 7~10 days, the temperature was lowered to room temperature to obtain tantalum diselenide single crystals.

[0006] This invention achieves synergistic control over the crystal phase, morphology, and defects through precise regulation of raw material ratios, temperature field, and transport kinetics. First, using selenium-enriched raw materials (Ta:Se = 1:2.1~2.5) compensates for selenium volatilization losses at high temperatures, ensuring the stability of the stoichiometry in the reaction system. Setting a relatively high temperature (940℃~960℃) at the reaction end significantly improves the vapor pressure and thermal stability of the gaseous complexes (TaSe2 and I2), thereby ensuring sufficient concentration of gaseous species transported to the crystallization region, providing a material basis for crystal growth. Simultaneously, the crystallization region temperature (840℃~860℃) is selected based on the tantalum diselenide polymorphic phase diagram, placing it within the thermodynamically stable range of the target phase (2H-TaSe2), avoiding unnecessary phase transitions during growth. Maintaining a temperature difference of approximately 100℃ between the reaction end and the crystallization region creates a high degree of supersaturation in the growth region, effectively reducing the nucleation barrier, promoting efficient and controllable crystal precipitation, and improving experimental reproducibility. Furthermore, the 7-day isothermal growth process, by suppressing the crystallization rate, allows atoms to diffuse fully and arrange themselves in an orderly manner, ultimately yielding 2H-TaSe2 single crystals with a smooth surface, metallic luster, low defect density, and large size. This synergistic condition of temperature difference and time is crucial for achieving crystal phase purification, morphological optimization, and structural integrity.

[0007] Further, the gas-phase transport agent is iodine; the addition amount of the gas-phase transport agent is 5 mg / cm³. 3 .

[0008] Furthermore, the iodine is iodine tablets. Iodine tablets typically have high purity and a dense texture. Compared to powdered iodine, iodine tablets volatilize more slowly at room temperature, making them easier to weigh accurately and control the amount filled into the quartz tube. If iodine particles are too fine, they may be carried away by the gas flow during vacuuming, or the reaction may be too vigorous in the initial heating stage, affecting the nucleation process.

[0009] Furthermore, the tantalum diselenide polycrystalline material is synthesized by the following steps: Ta and Se raw materials are mixed at a molar ratio of 1:2.1~2.5, pressed into shape, transferred to a quartz tube, vacuumed to ≤0.1 mbar, sealed, and fired at 940℃~960℃ for 3 days to obtain tantalum diselenide polycrystalline material. Pressing avoids the uneven agglomeration or adhesion of loose powder to the quartz tube wall. The polycrystalline material obtained by pressing typically has a dense structure, good strength, is easy to remove from the quartz tube, and facilitates subsequent grinding. Pre-firing the polycrystalline material improves the chemical homogeneity, phase purity, and reactivity of the raw materials, thereby greatly improving the controllability of the chemical vapor transport process and the quality of the final single crystal.

[0010] Furthermore, the Ta raw material is Ta powder with a purity ≥99.999% and a particle size ≤0.3mm; the Se raw material is Se powder with a purity ≥99.999% and a particle size ≤0.3mm.

[0011] The particle size of Ta and Se raw materials is ≤0.3mm, which can promote solid-phase reaction: in the first step of polycrystalline synthesis, the increased contact area allows Ta and Se to react fully, resulting in pure and homogeneous TaSe2 polycrystalline material; on the other hand, it optimizes gas-phase transport: grinding the polycrystalline material into fine powder greatly increases the contact surface area with the iodine transport agent, which is beneficial for the formation of gaseous TaSe2-I. x Complexes make the transport process more efficient and uniform, which is a key pretreatment step for obtaining high-quality single crystals.

[0012] Furthermore, the pressure of the compression is 8 MPa.

[0013] A second aspect of the present invention provides a tantalum diselenide single crystal prepared according to the growth method described above.

[0014] The tantalum diselenide single crystal has the following characteristics: (1) Superconducting transition temperature T c ≥ 2.0 K; (2) The charge density wave transition temperature is 90K~110K; (3) Crystal size ≥ 0.2 mm × 0.3 mm, thickness 30 μm ~ 1000 μm; (4) Solution along the (001) plane.

[0015] A third aspect of this invention provides a two-dimensional tantalum diselenide sheet, which is obtained by exfoliation of a tantalum diselenide single crystal. The tantalum diselenide single crystal exhibits weak van der Waals interlayer interaction along the c-axis, allowing for the exfoliation of a two-dimensional tantalum diselenide sheet with the following characteristics:

[0016] (1) Thickness ≤ 1 μm; (2) Superconducting transition temperature T c ≥1.8 K; (3) Charge density wave transition temperature range: 80 K~110 K.

[0017] Furthermore, the stripping is mechanical stripping or liquid phase stripping.

[0018] Further, the mechanical peeling is as follows: the surface of the tantalum diselenide single crystal is repeatedly adhered to and peeled off with polymer tape 10 to 50 times, the tape with the thin layer of product is pressed and transferred to the target substrate, and then the tape is peeled off by heating or solvent treatment. After cleaning to remove the adhesive and drying, a two-dimensional tantalum diselenide sheet is obtained on the target substrate.

[0019] Furthermore, the polymer tape is 3M Scotch tape.

[0020] Further, the liquid phase exfoliation is performed by grinding tantalum diselenide single crystals and dispersing them in isopropanol at a final concentration of 0.1 mg / mL to 5 mg / mL, followed by ultrasonication in an ice-water bath, centrifugation, and drying of the supernatant.

[0021] Furthermore, the power of the ultrasound is 50W, and the duration of the ultrasound is 25-30 minutes.

[0022] Furthermore, the centrifugation speed is 500 rpm to 1000 rpm, and the centrifugation time is 5 min to 10 min.

[0023] The fourth aspect of the present invention provides an application of the aforementioned tantalum diselenide two-dimensional thin film in the fabrication of ultrafast optically controlled switches, neuromorphic computing elements, superconducting single-photon detectors, or guided quantum interference devices.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention provides a tantalum diselenide material, its growth method, and its applications. The chemical formula of tantalum diselenide single crystal is 2H-TaSe2. Its growth method involves mixing Ta and Se raw materials at a molar ratio of 1:2.1~2.5 and sintering to obtain a polycrystalline material. This polycrystalline material is then sealed in a quartz tube with an iodine transport agent and subjected to a gas-phase transport reaction at dual temperatures of 940℃~960℃ and 840℃~860℃. After cooling, a tantalum diselenide single crystal is obtained. The tantalum diselenide material growth method disclosed in this invention significantly improves the superconducting transition temperature of tantalum diselenide single crystals, and the CDW phase transition can be effectively controlled. Tantalum diselenide single crystals have a size ≥ 0.2 mm × 0.3 mm and a thickness of 30 μm to 1000 μm. They have the following characteristics: smooth surface and easy to peel off; superconducting transition temperature Tc ≥ 2.0 K, with an optimal value of 2.4 K (significantly higher than the literature value -Tc≈0.14 K); charge density wave (CDW) transition temperature of 90 K to 110 K, showing strong competition and coexistence between the CDW and SC quantum orders; and can be cleaved along the (001) plane.

[0025] Tantalum diselenide single crystals exhibit weak van der Waals interactions along the c-axis, allowing for the fabrication of two-dimensional tantalum diselenide sheet materials with a thickness ≤1 μm via mechanical or liquid-phase exfoliation, while retaining... T c With superconductivity ≥1.8 K and charge density wave (80 K ~ 110 K) characteristics, tantalum diselenide two-dimensional thin films can be used to further participate in the fabrication of ultrafast optically controlled switches, neuromorphic computing elements, superconducting single-photon detectors or guided quantum interference devices. This invention lays the foundation for subsequent single-crystal two-dimensionalization and device integration. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 This is a physical image of tantalum diselenide single crystal 2H-TaSe2.

[0028] Figure 2 This is the EDS diagram of tantalum diselenide single crystal 2H-TaSe2. Figure 2 In the diagram, A represents the distribution of Ta and Se elements, showing the characteristic peaks of Ta and Se. Figure 2 B in the text represents the specific analysis point. Figure 2 C in the diagram corresponds to the EDS energy spectrum at the marked point in B.

[0029] Figure 3The image shows the EDS (Electronic Data Selenide) plot of a single crystal tantalum triselenide (TaSe3). Figure 3 In the diagram, A represents the distribution of Ta and Se elements, showing the characteristic peaks of Ta and Se. Figure 3 B in the text represents the specific analysis point. Figure 3 C in the diagram corresponds to the EDS energy spectrum at the marked point in B.

[0030] Figure 4 This is a temperature-resistivity curve of tantalum diselenide single crystal 2H-TaSe2. Figure 4 In the figure, A represents the temperature-resistivity curve of tantalum diselenide single crystal 2H-TaSe2. Figure 4 B in the image is an enlarged view of the area within the box in A.

[0031] Figure 5 This is a temperature-resistance curve of tantalum triselenide single crystal TaSe3.

[0032] Figure 6 The temperature-resistance curve of the two-dimensional tantalum diselenide sheet prepared in Example 4 of the present invention is shown.

[0033] Figure 7 Temperature-resistance curve of tantalum diselenide two-dimensional thin film prepared in Example 5 of the present invention. Detailed Implementation

[0034] The specific embodiments of the present invention are described in detail below, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Unless otherwise specified, the experimental methods described in the embodiments of the present invention are conventional methods, and the materials and reagents used in the following embodiments are commercially available unless otherwise specified.

[0035] Example 1: A method for growing tantalum diselenide material (chemical formula TaSe2), comprising the following steps: (1) Weigh out 0.5339g of Ta powder and 0.4871g of Se powder respectively. The purity of both Ta powder and Se powder is 99.999%. (2) The weighed Ta powder and Se powder are mixed (the molar ratio of Ta to Se is 1:2.1) and then ground into powder with a particle size of 0.3 mm. Then, it is placed in a tableting mold and a pressure of 8 MPa is applied to fix it into shape. Then, it is wrapped with quartz wool and placed in a quartz tube. A high vacuum is drawn and sealed. Finally, the quartz tube is fired at a high temperature of 950°C for 3 days to synthesize tantalum diselenide polycrystalline. (3) Grind 1g of the obtained tantalum diselenide polycrystalline material into powder with a particle size of 0.3mm, place it in a quartz tube, add iodine at the same time, evacuate to a high vacuum and seal the tube. The added mass of iodine is 5 mg / cm³. 3 One end of the quartz tube is heated to a high temperature of 950°C at a heating rate of 95°C / h, while the other end is kept at a low temperature of 850°C at a heating rate of 85°C / h. After sintering for 7 days, the gaseous material cools and deposits in the low-temperature region, forming tantalum diselenide single crystals.

[0036] Example 2: A method for growing tantalum diselenide material (chemical formula TaSe2), comprising the following steps: (1) Weigh out 0.5339g of Ta powder and 0.512g of Se powder respectively. The purity of both Ta powder and Se powder is 99.999%. (2) The weighed Ta powder and Se powder are mixed (the molar ratio of Ta to Se is 1:2.5) and then ground into powder with a particle size of 0.3 mm. Then, it is placed in a tableting mold and a pressure of 8 MPa is applied to fix it into shape. Then, it is wrapped with quartz wool and placed in a quartz tube. A high vacuum is drawn and sealed. Finally, the quartz tube is fired at a high temperature of 940°C for 3 days to synthesize tantalum diselenide polycrystalline. (3) Grind 1g of the obtained tantalum diselenide polycrystalline material into powder with a particle size of 0.3mm, place it in a quartz tube, add iodine at the same time, evacuate to a high vacuum and seal the tube. The added mass of iodine is 5 mg / cm³. 3 One end of the quartz tube was heated to a high temperature of 940°C at a heating rate of 94°C / h, while the other end was kept at a low temperature of 840°C at a heating rate of 84°C / h. After sintering for 7 days, the gaseous material cooled and deposited in the low-temperature region, forming tantalum diselenide single crystals.

[0037] Example 3: A method for growing tantalum diselenide (chemical formula TaSe2), comprising the following steps: (1) Weigh out 0.5339g of Ta powder and 0.5799g of Se powder respectively. The purity of both Ta powder and Se powder is 99.999%. (2) The weighed Ta powder and Se powder are mixed (the molar ratio of Ta to Se is 1:2.5) and then ground into powder with a particle size of 0.3 mm. Then, it is placed in a tableting mold and a pressure of 8 MPa is applied to fix it into shape. Then, it is wrapped with quartz wool and placed in a quartz tube. A high vacuum is drawn and sealed. Finally, the quartz tube is fired at a high temperature of 960°C for 3 days to synthesize tantalum diselenide polycrystalline. (3) Grind 1g of the obtained tantalum diselenide polycrystalline material into powder with a particle size of 0.3mm, place it in a quartz tube, add iodine at the same time, evacuate to a high vacuum and seal the tube. The added mass of iodine is 5 mg / cm³. 3One end of the quartz tube was heated to a high temperature of 960°C at a heating rate of 96°C / h, while the other end was kept at a low temperature of 860°C at a heating rate of 86°C / h. After sintering for 7 days, the gaseous material cooled and deposited in the low-temperature region, forming tantalum diselenide single crystals.

[0038] Comparative Example 1: A method for growing tantalum triselenide (chemical formula TaSe3), comprising the following steps: (1) Weigh out 0.4330g of Ta powder and 0.5670g of Se powder respectively. The purity of both Ta powder and Se powder is 99.999%. (2) The weighed Ta powder and Se powder are mixed (the molar ratio of Ta to Se is 1:3) and then ground into powder with a particle size of 0.3 mm. Then, it is placed in a tableting mold and a pressure of 8 MPa is applied to fix it into shape. Then, it is wrapped with quartz wool and placed in a quartz tube. A high vacuum is drawn and sealed. Finally, the quartz tube is fired at a high temperature of 950°C for 3 days to synthesize tantalum triselenide polycrystalline. (3) Grind 1g of the obtained tantalum triselenide polycrystalline powder into a particle size of 0.3mm, place it in a quartz tube, add iodine at the same time, evacuate to a high vacuum and seal, the added mass of iodine is 5 mg / cm³. 3 One end of the quartz tube is heated to a high temperature of 950°C at a heating rate of 95°C / h, while the other end is kept at a low temperature of 850°C at a heating rate of 85°C / h. After sintering for 7 days, the gaseous material cools and deposits in the low-temperature region, forming high-quality tantalum triselenide single crystal material.

[0039] Examples 1-3 have similar effects. For ease of subsequent discussion and reference, the experimental results of Example 1 will be used as an example. The following are the experimental results of Example 1.

[0040] 1. Characterization and performance determination of single crystals The tantalum diselenide single crystal prepared in Example 1 has a physical size of approximately 0.3 mm × 0.3 mm and a thickness of 30 μm. Figure 1 SEM-EDS analysis revealed that tantalum diselenide single crystals contain only Ta and Se elements, with a Ta to Se ratio of approximately 1:2. Figure 2 Tantalum triselenide single crystals contain only Ta and Se elements, with a Ta to Se ratio of approximately 1:3. Figure 3 ).

[0041] The temperature-resistance curve shows that the resistance of tantalum diselenide single crystal undergoes a charge density wave transition near 90 K and a superconducting transition near 2.2 K. Figure 4 However, the resistance-temperature curves of tantalum triselenide single crystals did not reveal either a charge density wave transition or a superconducting transition. Figure 5 ).

[0042] Example 4: Preparation and Characterization of a Two-Dimensional Tantalum Diselenide Thin Film The TaSe2 single crystal obtained in Example 1 was placed on a clean SiO2 / Si substrate and repeatedly adhered and peeled 10 times with 3M Scotch tape to transfer it to the target substrate. The tape was then removed by heat treatment, and after cleaning and drying, a two-dimensional tantalum diselenide sheet was obtained on the target substrate.

[0043] Electron microscopy measurements showed that typical slices had a thickness of 500 nm, a lateral dimension of 200 μm, and a CDW ≈ 80 K. Figure 6 As shown, the resistivity versus temperature curve shows a charge density wave transition near 80 K and a superconducting transition near 2.1 K.

[0044] Example 5: Preparation and Characterization of a Two-Dimensional Tantalum Diselenide Thin Film The TaSe2 single crystal obtained in Example 1 was placed on a clean SiO2 / Si substrate and transferred to the target substrate by repeatedly sticking and peeling 3M Scotch tape 50 times. The tape was then removed by heat treatment, and after cleaning and drying, a two-dimensional tantalum diselenide sheet was obtained on the target substrate.

[0045] Electron microscopy measurements showed that typical sections had a thickness of 1 μm, a lateral dimension of 200 μm, and a CDW ≈ 110 K. Figure 7 As shown, the resistivity-temperature curve shows a charge density wave transition near 110 K and a superconducting transition near 2 K.

[0046] Example 6: A two-dimensional tantalum diselenide sheet obtained by liquid phase exfoliation The TaSe2 single crystal obtained in Example 1 was ground into powder and then dispersed in isopropanol at a final concentration of 0.1 mg / m. The powder was ultrasonically treated in an ice-water bath at 50 W for 25 min to obtain a dispersion. Subsequently, the dispersion was centrifuged at 500 rpm for 5 min, and the supernatant after centrifugation was dried to obtain a two-dimensional tantalum diselenide sheet.

[0047] Example 7: A two-dimensional tantalum diselenide sheet obtained by liquid phase exfoliation The TaSe2 single crystal obtained in Example 1 was ground into powder and then dispersed in isopropanol at a final concentration of 2.5 mg / mL. The powder was ultrasonically treated in an ice-water bath at 50 W for 28 min to obtain a dispersion. Subsequently, the dispersion was centrifuged at 800 rpm for 8 min, and the supernatant after centrifugation was dried to obtain a two-dimensional tantalum diselenide sheet.

[0048] Example 8: A two-dimensional tantalum diselenide sheet obtained by liquid phase exfoliation The TaSe2 single crystal obtained in Example 1 was ground into powder and then dispersed in isopropanol at a final concentration of 5 mg / mL. The powder was ultrasonically treated in an ice-water bath at 50 W for 30 min to obtain a dispersion. Subsequently, the dispersion was centrifuged at 1000 rpm for 10 min, and the supernatant after centrifugation was dried to obtain a two-dimensional tantalum diselenide sheet.

[0049] It should be noted that when numerical ranges are involved in this invention, it should be understood that both endpoints of each numerical range and any value between the two endpoints can be selected. Since the steps and methods used are the same as in the embodiments, preferred embodiments are described here to avoid redundancy. Although preferred embodiments of the invention have been described, those skilled in the art, once they understand the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this invention.

[0050] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for growing tantalum diselenide single crystals, characterized in that, Includes the following steps: Ta and Se raw materials are mixed at a molar ratio of 1:2.1~2.5 and sintered to obtain polycrystalline tantalum diselenide; Tantalum diselenide polycrystalline material and a gaseous transport agent are placed inside a quartz tube, which is then evacuated and sealed. The temperature of the reaction end containing the raw materials was set at 940℃~960℃ and the heating rate was 94℃ / h~96℃ / h. The temperature of the crystallization zone at the other end was set at 840℃~860℃ and the heating rate was 84℃ / h~86℃ / h. After holding at this temperature for 7~10 days, the temperature was lowered to room temperature to obtain tantalum diselenide single crystals.

2. The growth method according to claim 1, characterized in that, The gas-phase transport agent is iodine; based on the volume of the quartz tube, the amount of the gas-phase transport agent added is 5 mg to 10 mg per cubic centimeter of quartz tube.

3. The growth method according to claim 1, characterized in that, The tantalum diselenide polycrystalline material is synthesized through the following steps: Ta and Se raw materials are mixed at a molar ratio of 1:2.1~2.5, pressed into shape, transferred into a quartz tube, vacuumed and sealed, and fired at 940℃~960℃ for 3 days to obtain tantalum diselenide polycrystalline.

4. The growth method according to claim 3, characterized in that, The purity of the Ta raw material is ≥99.999% and the particle size is ≤0.3mm; the purity of the Se raw material is ≥99.999% and the particle size is ≤0.3mm.

5. The growth method according to claim 2, characterized in that, The iodine mentioned is iodine tablets.

6. A tantalum diselenide single crystal grown by the growth method according to any one of claims 1 to 5, characterized in that, The tantalum diselenide single crystal has the following characteristics: (1) Superconducting transition temperature ≥ 2.0 K; (2) The charge density wave transition temperature is 90K~110K; (3) Crystal size ≥ 0.2 mm × 0.3 mm, thickness 30 μm ~ 1000 μm; (4) Solution along the (001) plane.

7. A two-dimensional tantalum diselenide sheet, characterized in that, The two-dimensional tantalum diselenide sheet is obtained by peeling off the tantalum diselenide single crystal as described in claim 6.

8. The two-dimensional tantalum diselenide sheet according to claim 7, characterized in that, The peeling is either mechanical peeling or liquid phase peeling.

9. The two-dimensional tantalum diselenide sheet according to claim 8, characterized in that, The tantalum diselenide single crystal is repeatedly adhered and peeled off with polymer tape 10 to 50 times. The peeled product is transferred to the target substrate, peeled off, de-adhesive removed, and dried to obtain a two-dimensional tantalum diselenide sheet.

10. The application of the two-dimensional tantalum diselenide sheet of claim 7 in the fabrication of an ultrafast optically controlled switch, a neuromorphic computing element, or a superconducting single-photon detector.

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