Method for catalytic preparation of a single crystal material of a wurtzite semimetal from noble metals

Abstract

The application relates to a method for preparing a Wolfram half-metal single crystal material through noble metal catalysis, wherein a bulk metal niobium foil or a tantalum foil is mixed with powdery arsenic and iodine to obtain a first mixture; a noble metal material is added into the first mixture as a catalyst to obtain a second mixture; the second mixture is added into a quartz tube as a reaction raw material; the quartz tube is sealed after being vacuumized; the sealed quartz tube is vertically placed in a vertical growth furnace, is heated to 450-550 DEG C and is kept for 20-40 min; the temperature is continuously increased to 1000-1100 DEG C and is kept for 20-40 days; after the keeping is finished, the temperature is slowly cooled to 450-550 DEG C, the reaction is stopped and the temperature is cooled to room temperature. In the method, the noble metal can be used as a catalyst for the growth of the Wolfram half-metal crystal, the reaction barrier of the crystal growth is reduced, and the reaction rate of the intermediate product is accelerated.

Description

Technical Field

[0001] This invention belongs to the field of new material preparation, specifically involving a process for large-size Weyl semimetal single crystals. Background Technology

[0002] In 1829, German physicist Weyl discovered a massless solution to the Dirac equation, which was thought to be a new particle—the Weyl fermion. However, this particle was not confirmed until more than 80 years later and was observed in materials such as tantalum arsenide and niobium arsenide. Scientists discovered that fermions in Weyl halfmetals exist in pairs and possess chiral anomalous properties; that is, Weyl fermions are divided into left-handed and right-handed types. Those with momentum parallel to the spin direction are called right-handed, and vice versa. This gives Weyl halfmetals negative magnetoresistance, anomalous Hall effect, and chiral magnetism, among other properties.

[0003] Therefore, Weyl semimetals are expected to have extremely high mobility, which is of great significance for the development of new consumables, miniaturized and multifunctional electronic devices; at the same time, their stable chirality can also be used to carry quantum information, so they are expected to be used to design new quantum computing platforms to realize highly fault-tolerant topological quantum information.

[0004] Currently, the main publicly available process for preparing Weyl half-metal crystals is the chemical vapor transport method. However, this method produces a large number of crystal nuclei and has a long reaction cycle, resulting in low growth efficiency. Consequently, the products are small-sized grains, making it difficult to obtain large-scale, high-quality single crystals. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a method for preparing Weyl semimetal single crystal materials by noble metal catalysis. This method can shorten the growth cycle, accelerate the crystal growth rate, and obtain large-size, high-quality Weyl semimetal crystals.

[0006] To solve the above technical problems, the technical solution adopted by this invention is: a method for preparing Weyl semimetal single crystal materials by noble metal catalysis, comprising the following steps: Step 1: Mix bulk niobium foil or tantalum foil with powdered arsenic and iodine to obtain a first mixture; Step two: A precious metal material is added to the first mixture as a catalyst to obtain a second mixture; Step 3: Add the second mixture as a reaction raw material into the quartz tube, evacuate the quartz tube and seal it; Step 4: Place the sealed quartz tube vertically in a vertical growth furnace, heat it to 450-550 ℃ and hold it for 20-40 minutes; continue heating to 1000-1100 ℃ and hold it for 20-40 days; after the holding period, slowly cool it to 450-550 ℃, stop the reaction and cool it to room temperature.

[0007] Further, in step one, the molar ratio of niobium foil or tantalum foil: arsenic powder: iodine powder is 1.00: (1.02-1.05): (0.02-0.05).

[0008] Furthermore, in step one, the blocky tantalum foil or niobium foil is a small-sized fragment that has been finely crushed, with a thickness of 0.015-0.025 mm and a size of (1.5-2.5) × (1.5-2.5) mm. 2 .

[0009] Furthermore, in step one, the thickness of the block tantalum foil or niobium foil is 0.02 mm, and its size is 2×2 mm. 2 .

[0010] Furthermore, in step two, the catalyst is a filamentous or sheet-like precious metal material such as platinum or gold.

[0011] Furthermore, in step two, the catalyst to niobium foil or tantalum foil is in a molar ratio of (0.005-0.015):1.000.

[0012] Furthermore, in step three, the quartz tube is placed in an acetone solution with dry ice throughout the sealing process.

[0013] Furthermore, in the third stage, the quartz tube was evacuated to 10... -5 -10 -4 After pa, seal it.

[0014] Furthermore, in step four, the temperature is increased to 500 ℃ at a rate of 2 ℃ / min.

[0015] Furthermore, in step four, the temperature is increased to 1050 ℃ at a rate of 5 ℃ / min.

[0016] This invention addresses the shortcomings of previously disclosed processes for preparing Weyl semimetal single crystals by proposing a method for noble metal-catalyzed growth of Weyl semimetal crystals. This method incorporates a noble metal as a catalyst into the traditional chemical vapor transport process. First, the intermediate products tantalum iodide (TaI5) and arsenic iodide (AsI3) dissolve into the noble metal surface. During cooling, tantalum iodide and arsenic iodide decompose and tantalum and arsenic ions nucleate on the noble metal surface, growing tantalum arsenide. In this reaction, the noble metal not only acts as a catalyst, lowering the reaction barrier, but also transforms the dissolved tantalum iodide and tantalum arsenide from the gas phase to the liquid phase, significantly increasing the reaction rate. Therefore, these two factors combined accelerate crystal growth and shorten the reaction cycle, demonstrating that the presence of a noble metal is crucial for obtaining large-size, high-quality crystals.

[0017] In this invention, niobium (Nb) foil or tantalum (Ta) foil and arsenic (As) powder, after being finely crushed, are selected as raw materials. The crushed niobium and tantalum foils will produce fewer defects and a larger specific surface area during crystal growth. In addition, a small amount of elemental iodine (I2) powder is added to play a role in atmosphere transport and catalysis.

[0018] Unlike the previous two-step CVT process, which involves first obtaining small-sized grains and then performing secondary growth to obtain larger-sized crystals, the process of this invention only requires one step.

[0019] The process of this invention is simple, highly reproducible, and has high reaction efficiency. It has a certain degree of universality. The single-dimensional size of the prepared Weyl semimetal single crystal reached 8 mm. The rocking curve and STEM data also proved that the niobium arsenide crystal prepared by this method has the characteristics of uniform crystal quality and high crystal quality. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the crystal structure of the Weyl semimetal niobium arsenide (NbAs) single crystal material obtained in Example 1.

[0021] Figure 2 This is an optical image of the niobium arsenide (NbAs) single crystal material obtained in Example 1.

[0022] Figure 3 The image shows the XRD diffraction pattern of the niobium arsenide material obtained in Example 1.

[0023] Figure 4 The image shows the Raman spectrum of the niobium arsenide single crystal material obtained in Example 1.

[0024] Figure 5 The image shows the rocking curve of the XRD pattern of the niobium arsenide single crystal obtained in Example 1.

[0025] Figure 6This is a STEM image of the niobium arsenide single crystal material obtained in Example 1.

[0026] Figure 7 The image shows the EDS spectrum of the niobium arsenide single crystal material obtained in Example 1.

[0027] Figure 8 This is an optical image of the platinum wire, a precious metal added in Example 1, after its reaction.

[0028] Figure 9 The image shows the Raman spectrum of the platinum wire added in Example 1 after the reaction. Detailed Implementation

[0029] A typical embodiment of the present invention provides a method for preparing Weyl semimetal single crystal materials using noble metal catalysis, comprising the following steps: Step 1: Mix bulk niobium or tantalum foil with powdered arsenic and iodine to obtain a first mixture.

[0030] Wherein, in molar ratio, niobium foil or tantalum foil: arsenic powder: iodine powder = 1.00: (1.02-1.05): (0.02-0.05). Preferably, niobium foil or tantalum foil: arsenic powder: iodine powder = 1.00: 1.05: 0.05.

[0031] The blocky tantalum foil or niobium foil consists of small fragments that have been finely crushed, with a thickness of 0.015-0.025 mm and a size of (1.5-2.5) × (1.5-2.5) mm. 2 Preferably, the block-shaped tantalum foil or niobium foil has a thickness of 0.02 mm and a size of 2 × 2 mm. 2 Using finely crushed niobium and tantalum foils will result in fewer defects and a larger specific surface area during the preparation of Weyl semimetal single crystal materials, which will help improve reaction efficiency and obtain larger-sized single crystal materials.

[0032] Step two: a precious metal material is added to the first mixture as a catalyst to obtain a second mixture.

[0033] The catalyst mentioned in step two is preferably a precious metal material such as platinum or gold in filament or sheet form. The molar ratio of catalyst to niobium foil or tantalum foil is (0.005-0.015):1.000.

[0034] In this step, a noble metal is added as a catalyst, which lowers the reaction barrier and accelerates the reaction rate of intermediate products. Therefore, adding a noble metal as a catalyst is key to growing large-size, high-quality Weyl semimetal single crystals.

[0035] Step three: Add the second mixture as a reactant into the quartz tube, then evacuate and seal the quartz tube. Preferably, the quartz tube is evacuated to 10... -5 -10 -4 After pa, seal it.

[0036] During the sealing process, the quartz tube is immersed in an acetone solution containing dry ice throughout. The sealing process must be carried out in a low-temperature solution to prevent the volatilization of iodine. The combined pressure of the arsenic powder and iodine powder must not exceed the pressure that the quartz tube can withstand after sealing.

[0037] Step 4: Place the sealed quartz tube vertically in a vertical growth furnace, heat it to 450-550 ℃ and hold it for 20-40 minutes; continue heating to 1000-1100 ℃ and hold it for 20-40 days; after the holding period, slowly cool it to 450-550 ℃, stop the reaction and cool it to room temperature.

[0038] Specifically, the temperature is increased to 450-550℃ at a rate of 2℃ / min, preferably to 500℃ at a rate of 2℃ / min.

[0039] Specifically, the temperature is increased to 1000-1100℃ at a rate of 5℃ / min, preferably to 1050℃ at a rate of 5℃ / min.

[0040] Specifically, the temperature is reduced to 450-550℃ at a rate of 5℃ / min, preferably to 500℃ at a rate of 5℃ / min.

[0041] The technical solutions claimed in this invention will be further described below through some embodiments. However, the embodiments are for explaining the implementation of the present invention and do not exceed the scope of the subject matter of the present invention. The scope of protection of the present invention is not limited by the embodiments. Unless otherwise specified, the materials and reagents used in this invention can be obtained from commercially available products in the art.

[0042] Example 1 Niobium foil, arsenic powder, iodine powder, and platinum wire in a molar ratio of 1:1.05:0.05:0.01 were selected as raw materials. Specifically, 0.279 g of niobium foil, 0.236 g of arsenic powder, 0.038 g of iodine powder, and 0.006 g of platinum wire were selected, mixed evenly, and added to a quartz tube. This process had to be carried out in a glove box.

[0043] Evacuate the quartz tube to 4×10⁻⁶. -4 The tube must be sealed immediately after Pa, and the process requires placing the quartz tube in a low-temperature solution.

[0044] The quartz tube was placed in a vertical growth furnace, and the program was set to heat to 500 ℃ at 2 ℃ / min and hold for 30 min; then heat to 1050 ℃ at 5 ℃ / min and hold for 30 days; after the holding period, the temperature was cooled to 500 ℃ at 5 ℃ / min and the reaction was stopped and cooled to room temperature.

[0045] Through the above experimental steps, centimeter-sized Weyl semimetal niobium arsenide single crystals were successfully prepared.

[0046] The crystal structure of the niobium arsenide single crystal material prepared in this example is as follows: Figure 1 As shown, its structure is a body-centered tetragonal structure.

[0047] The optical image of the niobium arsenide single crystal material prepared in this example is as follows: Figure 2 As shown, the single crystal size is approximately 8 mm.

[0048] The XRD pattern of the niobium arsenide single crystal material prepared in this example is as follows: Figure 3 As shown, the diffraction peaks of the pulverized crystal are consistent with those on the PDF card, and the diffraction peaks of the crystal prove that the exposed surface (001) is oriented.

[0049] The Raman spectrum of the niobium arsenide single crystal material prepared in this example is as follows: Figure 4 As shown, the three Raman displacements in the figure are consistent with those reported in the literature.

[0050] The XRD rocking curve of the niobium arsenide single crystal material prepared in this example is shown in the figure. Figure 5 As shown, rocking curve tests were performed at three different locations on the (004) crystal plane of the crystal. The rocking curve data of the test points and the surrounding area were recorded, which proved that the crystal has uniform quality and high crystallization quality.

[0051] The STEM image of the niobium arsenide single crystal material prepared in this example is as follows: Figure 6 As shown, the (010) and (100) orientations of the crystal are marked in Figure (a), and their interplanar spacing matches the data in the crystal structure. The schematic diagrams of the (110) and (001) crystal planes of the crystal shown in Figures (b) and (c) correspond to the FFT images in the inset of Figure (a).

[0052] The EDS image of the niobium arsenide single crystal material prepared in this example is as follows: Figure 7 As shown in the image, the crystal exhibits a uniform elemental distribution and high crystal quality.

[0053] The optical image of the precious metal platinum wire used in this example is as follows: Figure 8 As shown in the image, it can be clearly observed that the smooth crystal faces on the surface of the platinum wire are formed by the reaction of trace amounts of arsenic-containing elements with platinum.

[0054] The Raman spectrum of the precious metal platinum wire used in this example is as follows: Figure 9 As shown in the figure, the Raman shift is completely consistent with the Raman shift of platinum diarsenide reported in the literature. This confirms that the noble metal platinum wire plays a catalytic role in the growth of Weyl semimetal single crystals.

[0055] Example 2 Tantalum foil, arsenic powder, iodine powder, and platinum wire in a molar ratio of 1:1.05:0.05:0.01 were selected as raw materials. Specifically, 0.541 g of niobium foil, 0.236 g of arsenic powder, 0.038 g of iodine powder, and 0.006 g of platinum wire were selected, mixed evenly, and added to a quartz tube. This process had to be carried out in a glove box.

[0056] Evacuate the quartz tube to 4×10⁻⁶. -4 The tube must be sealed immediately after Pa, and the process requires placing the quartz tube in a low-temperature solution.

[0057] The quartz tube was placed in a vertical growth furnace, and the program was set to heat to 500 ℃ at 2 ℃ / min and hold for 30 min; then heat to 1030 ℃ at 5 ℃ / min and hold for 30 days; after the holding period, the temperature was cooled to 500 ℃ at 5 ℃ / min and the reaction was stopped and cooled to room temperature.

[0058] Through the above experimental steps, centimeter-sized Weyl semimetal tantalum arsenide single crystals were successfully prepared.

[0059] Example 3 Niobium foil, arsenic powder, iodine powder, and gold foil were selected as raw materials in a molar ratio of 1:1.02:0.05:0.01. Specifically, 0.279 g of niobium foil, 0.229 g of arsenic powder, 0.038 g of iodine powder, and 0.006 g of gold foil were selected, mixed evenly, and added to a quartz tube. This process had to be carried out in a glove box.

[0060] Evacuate the quartz tube to 4×10⁻⁶. -4 The tube must be sealed immediately after Pa, and the process requires placing the quartz tube in a low-temperature solution.

[0061] The quartz tube was placed in a vertical growth furnace, and the program was set to heat to 500 ℃ at 2 ℃ / min and hold for 30 min; then heat to 1050 ℃ at 5 ℃ / min and hold for 30 days; after the holding period, the temperature was cooled to 500 ℃ at 5 ℃ / min and the reaction was stopped and cooled to room temperature.

[0062] Through the above experimental steps, centimeter-sized Weyl semimetal niobium arsenide single crystals were successfully prepared.

[0063] Example 4 Niobium foil, arsenic powder, iodine powder, and platinum wire in a molar ratio of 1:1.02:0.02:0.005 were selected as raw materials. Specifically, 0.279 g of niobium foil, 0.229 g of arsenic powder, 0.015 g of iodine powder, and 0.003 g of platinum wire were selected, mixed evenly, and added to a quartz tube. This process had to be carried out in a glove box.

[0064] Evacuate the quartz tube to 10. -4 The tube must be sealed immediately after Pa, and the process requires placing the quartz tube in a low-temperature solution.

[0065] The quartz tube was placed in a vertical growth furnace, and the program was set to heat to 450 ℃ at 2 ℃ / min and hold for 40 min; then heat to 1000 ℃ at 5 ℃ / min and hold for 40 days; after the holding period, cool to 550 ℃ at 5 ℃ / min and then stop the reaction and cool to room temperature.

[0066] Through the above experimental steps, centimeter-sized Weyl semimetal niobium arsenide single crystals were successfully prepared.

[0067] Example 5 Niobium foil, arsenic powder, iodine powder, and platinum sheet were selected as raw materials in a molar ratio of 1:1.02:0.05:0.015. Specifically, 0.279 g of niobium foil, 0.229 g of arsenic powder, 0.038 g of iodine powder, and 0.009 g of platinum sheet were selected, mixed evenly, and added to a quartz tube. This process had to be carried out in a glove box.

[0068] Evacuate the quartz tube to 10. -5 The tube must be sealed immediately after Pa, and the process requires placing the quartz tube in a low-temperature solution.

[0069] The quartz tube was placed in a vertical growth furnace, and the program was set to heat to 550 ℃ at 2 ℃ / min and hold for 20 min; then heat to 1100 ℃ at 5 ℃ / min and hold for 20 days; after the holding period, the temperature was cooled to 450 ℃ at 5 ℃ / min and the reaction was stopped and cooled to room temperature.

[0070] Through the above experimental steps, centimeter-sized Weyl semimetal niobium arsenide single crystals were successfully prepared.

[0071] The above embodiments are used to explain the implementation schemes of the present invention and do not exceed the scope of the subject matter of the present invention. The protection scope of the present invention is not limited by the described embodiments. Unless otherwise specified, the materials and reagents used in the present invention can be obtained from commercially available products in the art.

Claims

1. A method for preparing Weyl semimetal single crystal materials using noble metal catalysis, characterized in that, Including the following steps: Step 1: Mix bulk niobium foil or tantalum foil with powdered arsenic and iodine to obtain a first mixture; In molar ratio, niobium foil or tantalum foil: arsenic powder: iodine powder = 1.00: (1.02-1.05): (0.02-0.05); The blocky tantalum or niobium foil is a small fragment after fine crushing, with a thickness of 0.015-0.025 mm and a size of (1.5-2.5) × (1.5-2.5) mm. 2 ; Step two: A precious metal material is added to the first mixture as a catalyst to obtain a second mixture; The catalyst is platinum or gold in filament or sheet form; Step 3: Add the second mixture as a reaction raw material into the quartz tube, evacuate the quartz tube and seal it; Step 4: Place the sealed quartz tube vertically in a vertical growth furnace, heat it to 450-550 ℃ and hold it for 20-40 minutes; continue heating to 1000-1100 ℃ and hold it for 20-40 days; after the holding period, slowly cool it to 450-550 ℃, stop the reaction and cool it to room temperature.

2. The method according to claim 1, characterized in that: In step one, the thickness of the bulk tantalum or niobium foil is 0.02 mm, and the size is 2 × 2 mm. 2 .

3. The method according to claim 2, characterized in that: In step two, the catalyst to niobium foil or tantalum foil ratio is (0.005-0.015):1.000, based on a molar ratio.

4. The method according to claim 1 or 3, characterized in that: In step three, the quartz tube is kept in an acetone solution with dry ice throughout the sealing process.

5. The method according to claim 4, characterized in that: In step three, the quartz tube is evacuated to 10... -5 -10 -4 After pa, seal it.

6. The method according to claim 1 or 5, characterized in that: In step four, the temperature is increased to 500℃ at a rate of 2℃ / min.

7. The method according to claim 6, characterized in that: In step four, the temperature is increased to 1050℃ at a rate of 5℃ / min.

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