A topological semi-metallic nanostructured TaAs nanowire and preparation method thereof

Abstract

The present invention relates to a topological semimetal nanostructure TaAs nanowire and a preparation method thereof, belonging to the technical field of nanomaterials. Raw materials TaCl5 and As are weighed according to the mass ratio of TaCl5:As being 1:1.5 - 3, and are placed in the sample boat at intervals; the sample boat and the gold-plated silicon wafer are placed in a glass tube; the glass tube is placed in a dry quartz tube, sealed, and argon and hydrogen are introduced to adjust the air pressure, and then the quartz tube is placed in a tube furnace. First, it is heated from room temperature to 940 - 960 °C and kept warm for 10 - 30 min, and then cooled to 700 ± 5 °C and naturally cooled to obtain the TaAs nanowire in the quartz tube. The non-cleavable Weyl semimetal TaAs is directly grown on the silicon wafer by chemical vapor deposition to realize the synthesis of TaAs nanowires.

Description

Technical Field

[0001] The invention relates to a topological semi-metallic nanostructured TaAs nanowire and a preparation method thereof, belonging to the technical field of nanomaterials. Background Art

[0002] Topological semimetals have new topological electronic states, unique magnetic transport properties, and excellent physical properties such as extremely high carrier mobility. They are currently a hot topic and frontier in the field of quantum material research. However, due to the existence of bulk metallic states in bulk topological semimetal materials, it is extremely challenging to observe the Fermi arcs on their surfaces through common transport tests. Nanostructures have a high surface-to-volume ratio, which can minimize the contribution of the bulk state and is a powerful means to study Fermi arcs.

[0003] In 2015, Xiu Faxian's research group at Fudan University conducted relevant research on topological semimetal materials Cd3As2 nanobelts and nanowires. The experimental results showed that the material has ultra-high carrier mobility (over 32000cm 2 / Vs) and obvious SdH (Shubnikovde Haas) oscillations. In 2016, a domestic research team reported Aharonov–Bohm oscillations in single-crystalline Cd3As2 nanowires, providing another transport evidence of surface states in three-dimensional Dirac semimetals. In 2018, Wu Sanfeng et al. observed the quantum spin Hall effect (intrinsic superconductivity) in monolayer WTe2 at temperatures as high as 100K, and WTe2 can be easily combined with other 2D materials to form van der Waals heterostructures, which is a promising material system.

[0004] Research on Weyl semimetal single crystals has been progressing rapidly, but research on related device physics has been limited due to the lack of ideal material systems that can be easily integrated into nanodevices. An important reason is that most Weyl semimetals discovered so far contain heavy transition metals, which usually show low vapor pressure and are therefore difficult to grow by traditional thin film synthesis techniques such as molecular beam epitaxy and pulsed laser deposition. There are currently no reports on TaAs nanowires and their preparation methods. Summary of the invention

[0005] In view of this, the object of the present invention is to provide a topological semi-metallic nanostructure TaAs nanowire and a preparation method thereof. TaAs nanowires were successfully obtained by chemical vapor deposition (CVD) with TaCl5 powder and As block as raw materials, H2 and Ar as carrier gases, and silicon dioxide coated with a gold film as a substrate, and growth was carried out in a horizontal double-temperature zone tube furnace with vacuum.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows.

[0007] A method for preparing a topological semi-metallic nanostructured TaAs nanowire, the method comprising the following steps:

[0008] (1) Weigh raw materials TaCl5 and As according to the mass ratio of TaCl5: As of 1:1.5~3; the purity of raw materials TaCl5 and As is greater than or equal to 99.99%;

[0009] (2) Place the raw materials in a sample boat at intervals, and place the sample boat and the gold-coated silicon wafer in a glass tube;

[0010] (3) Place the glass tube in a dry quartz tube, seal it, and evacuate the quartz tube to a pressure of less than or equal to 10 -3 Torr (1Torr = 133.322Pa), followed by argon purge for 10-30min;

[0011] (4) Introduce argon and hydrogen to make the pressure in the quartz tube 190-210 Torr;

[0012] (5) Place the quartz tube in a tube furnace, first heat it from room temperature to 940~960℃, keep it warm for 10~30min, then cool it down to 700±5℃, and cool it naturally; the positions of TaCl5, As and gold-plated silicon wafer in the glass tube are arranged according to the temperature field distribution in the tube furnace, so that TaCl5 and As are distributed within 5℃ above their respective boiling points;

[0013] (6) Open the quartz tube, take out the silicon wafer, and obtain a topological semimetallic nanostructure TaAs nanowire.

[0014] Preferably, in step (2), the thickness of gold in the gold-plated silicon wafer is 20-50 nm.

[0015] Preferably, in step (3), the quartz tube is annealed at 200±10° C. for more than 2 h to obtain a dry quartz tube.

[0016] Preferably, in step (3), the argon gas flow rate is 200-450 SCCM.

[0017] Preferably, in step (4), the argon flow rate is 48-95 SCCM, and the hydrogen flow rate is 2-5 SCCM.

[0018] Preferably, in step (5), the temperature is first raised from room temperature to 940-960°C over 50-60 min, kept at that temperature for 10-30 min, and then cooled to 700±5°C within 20±5 min.

[0019] A topological semi-metallic nanostructured TaAs nanowire is prepared by the above method.

[0020] Beneficial Effects

[0021] The present invention uses chemical vapor deposition to grow the uncleavable Weyl semimetal TaAs directly on a silicon wafer, realizing the synthesis of Weyl semimetal TaAs nanostructures for the first time. The present invention also provides a material basis for subsequent research on its physical properties, such as surface state mobility.

[0022] The present invention adopts a single-temperature zone heating method of a tubular furnace, places a silicon wafer coated with a gold film and growth raw materials at appropriate positions in a high-temperature heated quartz tube, and further optimizes growth conditions (such as growth temperature, hydrogen-argon ratio, gas flow rate, raw material quality, etc.). BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is the fitting curve diagram of temperature distribution (at 950℃).

[0024] Figure 2 This is a photograph of TaAs nanowires prepared in Example 1.

[0025] Figure 3-4 This is the SEM image of the TaAs nanowires prepared in Example 1.

[0026] Figure 5 This is a photograph of TaAs nanowires prepared in Example 2.

[0027] Figure 6 This is a comparison chart of the TaAs nanowires prepared in Example 2 and the TaAs standard spectrum.

[0028] Figure 7-8 This is the SEM image of the TaAs nanowires prepared in Example 2.

[0029] Fig. 9 This is a photograph of TaAs nanowires prepared in Example 3.

[0030] Figure 10-11 This is the SEM image of TaAs nanowires prepared in Example 3.

[0031] Figure 12-13 This is the SEM image of TaAs nanowires prepared in Example 4. DETAILED DESCRIPTION

[0032] The present invention will be further described in detail below in conjunction with specific embodiments.

[0033] Example 1

[0034] Step 1. Turn on the mechanical pump and anneal in an argon atmosphere at 200 °C. Record the time. After 2 h, turn off the tube furnace and wait for natural cooling.

[0035] Step 2. While annealing, prepare the gold-plated silicon wafer. First, cut out a long silicon wafer with a silicon wafer knife, and then plate it with gold in a gold plating instrument for 10 seconds (keep the surface of the silicon wafer smooth during the operation, and use acetone solution to clean it if necessary);

[0036] Step 3. In a glove box with argon atmosphere (water and oxygen content less than 0.1PPM), weigh the raw materials TaCl5: 0.2194g, As: 0.4352g. Since the raw materials will react with moisture and oxygen in the air, we will try to minimize contact with air when taking the raw materials out of the glove box;

[0037] Step 4. Place the raw materials in the sample boat, with the distance between TaCl5 and As being about 0.5 cm. Place the sample boat and the gold-plated silicon wafer in a glass tube (60 cm long, 16 mm inner diameter, 20 mm outer diameter). The specific positions of the raw materials and the gold-plated silicon wafer (the zero scale line uses the edge of the tube furnace) are: TaCl5: 0~1.5 cm, As: 2~2.7 cm, No. 1 silicon wafer: 22.1~25.9 cm, No. 2 silicon wafer: 19.2~22.1 cm, No. 3 silicon wafer: 14.6~19.2 cm, No. 4 silicon wafer: 11~14.6 cm;

[0038] Step 5. Assemble the tube furnace, turn on the mechanical pump, and evacuate to 10 -3 Torr, followed by pure argon (flow rate 416SCCM) purge for 10 minutes. During the experiment, 95SCCM argon and 5SCCM hydrogen were passed in the subsequent process, and the gas pressure was adjusted to ensure that the gas pressure in the tube was 200Torr. The tube furnace was adjusted so that the heating program was from room temperature (25℃) to 950℃ after 60min, maintained for 20min, then cooled to 700℃ after 20min, and finally cooled naturally to room temperature;

[0039] Step 6. Open the tube furnace, take out the silicon wafers, label them, and store them in a glove box (water and oxygen content less than 0.1 PPM).

[0040] according to Figure 2 , 3 As shown in Figure 4, through SEM analysis, it can be determined that the TaAs nanowires prepared in this embodiment have good and dense morphology and are easy to collect, and belong to the category of nanowires.

[0041] Example 2

[0042] Step 1. Turn on the mechanical pump and anneal in an argon atmosphere at 200 °C. Record the time. After 2 h, turn off the tube furnace and wait for natural cooling.

[0043] Step 2. While annealing, prepare the gold-plated silicon wafer. First, cut out a long silicon wafer with a silicon wafer knife, and then plate it with gold in a gold plating instrument for 10 seconds (keep the surface of the silicon wafer smooth during the operation, and use acetone solution to clean it if necessary);

[0044] Step 3. In a glove box with argon atmosphere (water and oxygen content less than 0.1PPM), weigh enough raw materials TaCl5: 0.2267g, As: 0.3867g. Since the raw materials will react with moisture and oxygen in the air, we will try to minimize contact with air when taking the raw materials out of the glove box;

[0045] Step 4. Place the raw materials in the sample boat, with the distance between TaCl5 and As being about 0.5 cm. Place the sample boat and the gold-plated silicon wafer in a glass tube (60 cm long, 16 mm inner diameter, 20 mm outer diameter). The specific positions of the raw materials and the gold-plated silicon wafer (the zero scale line uses the edge of the tube furnace) are: TaCl5: 0~1 cm, As: 2.5~3 cm, No. 1 silicon wafer: 6.5~10.15 cm, No. 2 silicon wafer: 10.15~14.13 cm, No. 3 silicon wafer: 14.13~18.16 cm, No. 4 silicon wafer: 18.16~23.7 cm, No. 5 silicon wafer: 23.7~27.15 cm;

[0046] Step 5. Assemble the tube furnace, turn on the mechanical pump, and evacuate to 10 -3 Torr, followed by pure argon (flow rate 416SCCM) purge for 10 minutes. During the experiment, 95SCCM argon and 5SCCM hydrogen were passed in the subsequent process, and the gas pressure was adjusted to ensure that the gas pressure in the tube was 200Torr. The tube furnace was adjusted so that the heating program was from room temperature (25℃) to 950℃ after 60min, maintained for 20min, then cooled to 700℃ after 20min, and finally cooled naturally to room temperature;

[0047] Step 6. Open the tube furnace, take out the silicon wafers, label them, and store them in a glove box (water and oxygen content less than 0.1 PPM).

[0048] according to Figure 5 , 6 As shown in Figures 7 and 8, through SEM analysis, it can be determined that the TaAs nanowires prepared in this embodiment have good and dense morphology and are easy to collect, belonging to the category of nanowires; and by comparing with the TaAs standard spectrum, it can be determined that the grown nanowires are TaAs.

[0049] Example 3

[0050] Step 1. Turn on the mechanical pump and anneal in an argon atmosphere at 200 °C. Record the time. After 2 h, turn off the tube furnace and wait for natural cooling.

[0051] Step 2. While annealing, prepare the gold-plated silicon wafer. First, cut out a long silicon wafer with a silicon wafer knife, and then plate it with gold in a gold plating instrument for 10 seconds (keep the surface of the silicon wafer smooth during the operation, and use acetone solution to clean it if necessary);

[0052] Step 3. In a glove box with argon atmosphere (water and oxygen content less than 0.1PPM), weigh enough raw materials TaCl5: 0.2008g, As: 0.5190g. Since the raw materials will react with moisture and oxygen in the air, we will try to minimize contact with air when taking the raw materials out of the glove box;

[0053] Step 4. Place the raw materials in the sample boat, with the distance between TaCl5 and As being about 0.5 cm. Place the sample boat and the gold-plated silicon wafer in a glass tube (60 cm long, 16 mm inner diameter, 20 mm outer diameter). The specific positions of the raw materials and the gold-plated silicon wafer (the zero scale line uses the edge of the tube furnace) are: TaCl5: 0.5~2 cm, As: 2.5~3 cm, No. 1 silicon wafer: 21~25 cm, No. 2 silicon wafer: 17~21 cm, No. 3 silicon wafer: 13~17 cm, No. 4 silicon wafer: 10~13 cm, No. 5 silicon wafer: 5.5~10 cm;

[0054] Step 5. Assemble the tube furnace, turn on the mechanical pump, and evacuate to 10 -3 Torr, followed by pure argon (flow rate 416SCCM) purge for 10 minutes. During the experiment, 95SCCM argon and 5SCCM hydrogen were passed in the subsequent process, and the gas pressure was adjusted to ensure that the gas pressure in the tube was 200Torr. The tube furnace was adjusted so that the heating program was from room temperature (25℃) to 950℃ after 60min, maintained at 950℃ for 20min, then cooled to 700℃ after 20min, and finally cooled naturally to room temperature;

[0055] Step 6. Open the tube furnace, take out the silicon wafers, label them, and store them in a glove box (water and oxygen content less than 0.1 PPM).

[0056] according to Fig. 9 , 10 As shown in Table 1, through SEM analysis, it can be determined that the TaAs nanowires prepared in this embodiment have good and dense morphology and are easy to collect, belonging to the category of nanowires. The element distribution in this embodiment is shown in Table 1 below.

[0057] Table 1

[0058]

[0059] Example 4

[0060] Step 1. Turn on the mechanical pump and anneal in an argon atmosphere at 200 °C. Record the time. After 2 h, turn off the tube furnace and wait for natural cooling.

[0061] Step 2. While annealing, prepare the gold-plated silicon wafer. First, cut out a long silicon wafer with a silicon wafer knife, and then plate it with gold in a gold plating instrument for 10 seconds (keep the surface of the silicon wafer smooth during the operation, and use acetone solution to clean it if necessary);

[0062] Step 3. In a glove box with argon atmosphere (water and oxygen content less than 0.1PPM), weigh enough raw materials TaCl5: 0.2001g, As: 0.3880g. Since the raw materials will react with moisture and oxygen in the air, we will try to minimize contact with air when taking the raw materials out of the glove box;

[0063] Step 4. Place the raw materials in the sample boat, with the distance between TaCl5 and As being about 0.5 cm. Place the sample boat and the gold-plated silicon wafer in a glass tube (60 cm long; 16 mm inner diameter; 20 mm outer diameter). The specific positions of the raw materials and the gold-plated silicon wafer (the zero scale line uses the edge of the tube furnace) are: TaCl5: 0~2 cm, As: 2.5~3 cm, No. 1 silicon wafer: 20~23.5 cm, No. 2 silicon wafer: 15~20 cm, No. 3 silicon wafer: 10.5~15 cm, No. 4 silicon wafer: 6~10.5 cm;

[0064] Step 5. Assemble the tube furnace, turn on the mechanical pump, and evacuate to 10 -3 Torr, followed by pure argon (flow rate 416SCCM) purge for 10 minutes. During the experiment, 95SCCM argon and 5SCCM hydrogen were passed in the subsequent process, and the gas pressure was adjusted to ensure that the gas pressure in the tube was 100Torr. The tube furnace was adjusted so that the heating program was from room temperature (25℃) to 950℃ after 60 minutes, maintained at 950℃ for 20 minutes, then cooled to 700℃ after 20 minutes, and finally cooled naturally to room temperature;

[0065] Step 6. Open the tube furnace, take out the silicon wafers, label them, and store them in a glove box (water and oxygen content less than 0.1 PPM).

[0066] according to Fig.12 , 13 It can be seen that through SEM analysis, it can be determined that the TaAs nanowires prepared in this embodiment have good and dense morphology and are easy to collect, and belong to the category of nanowires.

[0067] In summary, the invention includes but is not limited to the above embodiments. Any equivalent substitution or partial improvement made under the spirit and principle of the invention shall be deemed to be within the protection scope of the invention.

Claims

1. A method for preparing a topological semi-metallic nanostructured TaAs nanowire, characterized in that: The method steps include: (1) Weigh raw materials TaCl5 and As according to the mass ratio of TaCl5: As of 1:1.5~3, and the purity of the raw materials TaCl5 and As is greater than or equal to 99.99%; (2) Place the raw materials in a sample boat at intervals; place the sample boat and the gold-coated silicon wafer in a glass tube; (3) Place the glass tube in a dry quartz tube, seal it, and evacuate the quartz tube to a pressure of less than or equal to 10 -3 Torr, followed by argon purge for 10-30 min; (4) Introduce argon and hydrogen to make the pressure in the quartz tube 190~210 Torr; the argon flow rate is 48~95 SCCM, and the hydrogen flow rate is 2~5 SCCM; (5) Place the quartz tube in a tube furnace, first heat it from room temperature to 940~960℃, keep it warm for 10~30min, then cool it down to 700±5℃, and cool it naturally; the positions of TaCl5, As and gold-plated silicon wafer in the glass tube are arranged according to the temperature field distribution in the tube furnace, so that TaCl5 and As are distributed within 5℃ above their respective boiling points; (6) Open the quartz tube, take out the silicon wafer, and obtain a topological semimetallic nanostructure TaAs nanowire.

2. The method for preparing a topological semi-metallic nanostructured TaAs nanowire according to claim 1, characterized in that: In step (2), the thickness of gold in the gold-plated silicon wafer is 20-50 nm.

3. The method for preparing a topological semi-metallic nanostructured TaAs nanowire according to claim 1, characterized in that: In step (3), the quartz tube is annealed at 200±10° C. for more than 2 hours to obtain a dry quartz tube.

4. The method for preparing a topological semi-metallic nanostructured TaAs nanowire according to claim 1, characterized in that: In step (3), the argon gas flow rate is 200-450 SCCM.

5. The method for preparing a topological semi-metallic nanostructured TaAs nanowire according to claim 1, characterized in that: In step (5), the temperature is first raised from room temperature to 940-960°C over 50-60 min, kept at that temperature for 10-30 min, and then cooled to 700±5°C within 20±5 min.

6. A topological semi-metallic nanostructured TaAs nanowire, characterized in that: It is prepared by the method according to any one of claims 1 to 5.

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