SiC surface regular carbon nanotube and preparation method thereof

Abstract

The invention discloses a SiC surface regular carbon nanotube and a preparation method thereof, and relates to the technical field of regular preparation of low-dimensional materials. The method comprises the following steps: pretreating SiC single crystals to obtain a SiC base material; carrying out heat treatment on the SiC base material to obtain SiC pyrolytic graphene; the SiC pyrolytic graphene is activated in the metal nickel atmosphere, and activated GF / SiC is obtained; heating the metal indium source material in the evaporation source by using a molecular beam epitaxial growth technology, and growing a layer of metal indium nano film on the surface of the activated GF / SiC to obtain an InGF / SiC sheet; and placing the InGF / SiC sheet in a miniature vacuum container for high-temperature annealing treatment to prepare the SiC surface regular carbon nanotube. The regularly-oriented carbon nanotubes prepared by the method have excellent electrical, thermal and mechanical properties, and have wide application prospects in the fields of electronic devices, sensors, composite materials and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of controllable preparation of carbon nanomaterials, and particularly to a regular carbon nanotube on the SiC surface and a preparation method thereof. Background Art

[0002] Carbon nanotubes (CNTs) are a kind of nanomaterials with a tubular structure composed of carbon atoms. Since they were discovered in 1991, carbon nanotubes have become a research and application hotspot in various fields due to their unique physical and chemical properties, such as high strength, high electrical conductivity, and high thermal conductivity. The growth of carbon nanotubes mainly depends on several key methods, including arc discharge method, laser ablation method, and chemical vapor deposition method. The arc discharge method is an early method for preparing carbon nanotubes. Through the arc of the graphene electrode excited by inert gas in the reaction vessel, graphite forms carbon nanotubes during the evaporation process. Although the arc discharge method is simple, the obtained carbon nanotubes have low purity, and it is difficult to control the diameter and length of the carbon nanotubes. The laser ablation method is to irradiate a graphite target containing a catalyst with a laser, and the generated gaseous carbon grows into carbon nanotubes under the action of the catalyst. The laser ablation method can obtain high-quality carbon nanotubes, but the yield is low and the cost is also high. The chemical vapor deposition method is currently the most commonly used method for growing carbon nanotubes. Carbon-containing gases (such as methane, acetylene, etc.) decompose under the action of a catalyst (usually transition metal particles), and thus carbon nanotubes are formed on the substrate. The chemical vapor deposition method has a low synthesis temperature, which is conducive to mass production. In the chemical vapor deposition method, carbon atoms mainly nucleate and grow on the surface of metal catalyst particles. This process can be divided into four stages: dissolution, supersaturation, precipitation, and carbon nanotube growth of carbon atoms. Generally speaking, the growth of carbon nanotubes mainly has two modes: tip growth and bottom growth. In the tip growth mode, the catalyst particles are located at the tip of the carbon nanotube and drive the newly generated carbon nanotube to grow continuously under the guidance of the air flow. In the bottom growth mode, the catalyst particles remain stationary on the substrate, and new carbon nanotubes are continuously formed at the bottom. The tip growth mode has a fast growth rate and is conducive to preparing carbon nanotubes with perfect structure and macroscopic length, while the bottom growth mode is more likely to obtain a carbon nanotube array with a higher areal density.

[0003] Silicon carbide (SiC) is a wide-bandgap semiconductor material, and carbon nanotubes can also be directly grown on its surface by chemical vapor deposition or other methods. For example, Fe particles can activate the SiC surface, and the catalyst is mixed with the carrier through physical contact, and the growth of single-walled carbon nanotubes can be achieved at a relatively low temperature. The SiC-CNT composite material prepared by the direct current arc discharge technology can improve its functional characteristics. Its performance characteristics of low density, large specific surface area and low thermal conductivity make it show great potential application value in many fields such as electronic devices, composite materials, energy storage, and biomedicine. In 2007, Japanese scholars directly grew carbon nanotubes on the SiC surface by means of high-temperature heating, but the obtained carbon nanotubes grew vertically and had irregular morphologies. Therefore, it is difficult to obtain carbon nanotubes with regular orientations on the SiC surface, and relevant research and exploration are worthy of in-depth study. Summary of the Invention

[0004] The purpose of the present invention is to provide a regular carbon nanotube on the SiC surface and its preparation method to solve the problems raised in the background technology.

[0005] To achieve the above purpose, the present invention provides the following technical solutions: A preparation method of a regular carbon nanotube on the SiC surface, the specific steps are as follows: S1. Pretreat the SiC single crystal to obtain a SiC substrate; S2. Heat-treat the SiC substrate to obtain SiC pyrolytic graphene; S3. Activate the SiC pyrolytic graphene in a nickel metal atmosphere to obtain activated GF / SiC; S4. Using molecular beam epitaxy growth technology, heat and evaporate the metal indium source material in the evaporation source, and grow a layer of metal indium nanofilms on the surface of the activated GF / SiC to obtain an InGF / SiC sheet; S5. Place the InGF / SiC sheet in a micro vacuum container for high-temperature annealing treatment to prepare a regular carbon nanotube on the SiC surface.

[0006] Further, in S1, the specific operation of the pretreatment is: heat the SiC single crystal to 500°C - 600°C under vacuum conditions and keep it warm for 8 hours.

[0007] It should be noted that the pretreatment can remove the adsorbed gases and impurities on the substrate surface, such as water vapor, oxygen, etc. These impurities will affect the growth quality of graphene, so a thorough degassing treatment is required before growth. Maintain the vacuum degree of the sample preparation chamber at 2.3×10 -9Torr can effectively prevent oxygen and water vapor in the air from entering the chamber, ensure the cleanliness of the substrate surface, guarantee the purity of the graphene growth process, and provide a clean and flat surface for subsequent graphene growth.

[0008] Further, in S2, the heat treatment temperature is 1200°C - 1300°C, and the heat treatment time is 10 - 20 min.

[0009] It should be noted that high-temperature heating will cause the Si atoms on the surface of the SiC substrate to sublime, leaving carbon atoms, and the carbon atoms will self-assemble to form a graphene layer.

[0010] Further, in S3, the activation conditions are: temperature 700°C - 800°C, and activation treatment for 20 - 30 min.

[0011] It should be noted that using metal Ni as a catalyst, it reacts with pyrolytic graphene of SiC at high temperature, promotes the formation of defects on the graphene surface, increases its surface activity, raises the surface energy of graphene, makes it easier to react with other substances, and is beneficial to the subsequent deposition of indium. Activating the surface of pyrolytic graphene of SiC at high temperature can improve its surface activity, provide better attachment sites for subsequent In deposition, and improve the quality of graphene.

[0012] Further, in S4, the heating temperature is 500°C - 700°C, and the growth time is 10 - 20 min. It should be noted that depositing In on the surface of pyrolytic graphene of SiC realizes the modification of In. The subsequent annealing process is used to improve the diffusion and uniformity of In and may promote the interaction between In and graphene.

[0013] Further, in S4, the thickness of the indium metal nanofilms is 20 - 30 nm.

[0014] Further, in S5, micropores are provided in the micro vacuum container.

[0015] It should be noted that the role of the micropores is atmosphere regulation.

[0016] Further, in S5, the vacuum high-temperature annealing treatment parameters of InGF / SiC in the micro vacuum container are: vacuum degree range 1×10 -1 -5×10 -1 Torr, annealing temperature 800°C - 900°C, and annealing time 30 - 60 min.

[0017] It should be noted that the annealing process promotes the diffusion and recrystallization of In on the graphene surface, improving the uniformity of In modification. During the high-temperature annealing process, this method can inhibit and control the evaporation rate of metallic In atoms in a limited space, increasing the probability of interaction between metallic In atoms and C atoms. The pre-deposited metallic In atoms form larger crystalline grains during the high-temperature annealing process. During this process, the metallic In grains dissolve C atoms and precipitate C atoms during the cooling process. The newly precipitated C atoms form regularly oriented carbon nanotubes under the template effect of hexagonal graphene.

[0018] Furthermore, regularly oriented carbon nanotubes on the SiC surface prepared according to the preparation method.

[0019] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention grows high-quality pyrolytic graphene of SiC in situ by pre-treating and heat-treating a SiC single crystal. This graphene substrate has a clean, flat surface, good electrical conductivity, and chemical stability.

[0020] 2. The present invention introduces defects on the graphene surface through activation treatment in a nickel atmosphere, increasing its surface activity, raising the surface energy of the graphene, making it easier to react with other substances, which is beneficial for the subsequent deposition of indium metal, enabling the indium metal nanofilms to adhere more uniformly to the graphene surface and providing better attachment sites for the subsequent growth of carbon nanotubes.

[0021] 3. The present invention uses molecular beam epitaxy technology to precisely control the thickness and growth rate of indium metal nanofilms, obtaining uniform and high-quality indium metal nanofilms, providing precise structural guidance for the subsequent growth of carbon nanotubes.

[0022] 4. The present invention realizes the growth of regularly oriented carbon nanotubes through mechanisms such as the graphene template effect, the guidance of indium metal, and microporous atmosphere regulation, and improves the growth efficiency of carbon nanotubes through mechanisms such as the catalytic effect of nickel metal, high-temperature annealing, and microporous atmosphere regulation. During the high-temperature annealing process, the evaporation rate of metallic In atoms can be inhibited and controlled in a limited space, increasing the probability of interaction between metallic In atoms and C atoms. The pre-deposited metallic In atoms form larger crystalline grains during the high-temperature annealing process. During this process, the metallic In grains dissolve C atoms and precipitate C atoms during the cooling process. The newly precipitated C atoms form regularly oriented carbon nanotubes under the template effect of hexagonal graphene.

[0023] 5. The present invention details the process parameters for each step, such as temperature, time, vacuum degree, etc., which can be adjusted according to actual needs to achieve precise control over the size, structure, and properties of carbon nanotubes. The prepared regularly oriented carbon nanotubes have excellent electrical, thermal, and mechanical properties and have broad application prospects in the fields of electronic devices, sensors, composite materials, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is the main technical process flow chart in the method of the present invention.

[0025] Figure 2 It is the schematic diagram of vacuum annealing of the sample in the method of the present invention.

[0026] Figure 3 It is the schematic diagram of the formation process of regular carbon nanotubes in Example 1 of the present invention.

[0027] Figure 4 It is the large-area morphology diagram of regular carbon nanotubes on the SiC surface in Example 2 of the present invention.

[0028] Figure 5 It is the small-area morphology diagram of regular carbon nanotubes on the SiC surface in Example 3 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0029] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present invention.

[0030] Example 1: A method for preparing regular carbon nanotubes on the SiC surface, characterized in that the specific steps are as follows: S1. Pretreat the SiC single crystal: Heat the Si-terminated surface single crystal 6H-SiC(0001) substrate to 500 °C under a DC condition of 0.51 A, maintain the vacuum degree of the sample preparation chamber at 2.3×10 -9 Torr, degas and keep warm for 8 h to obtain the SiC substrate; S2. Heat-treat the SiC substrate: Heat the SiC substrate to 1250 °C with a DC current of 1.5 A and heat for 15 min, maintain the vacuum degree of the sample preparation chamber at 2.3×10 -9 Torr to obtain SiC pyrolytic graphene; S3. Activate the SiC pyrolytic graphene in a nickel atmosphere using a high-temperature furnace at an activation temperature of 700 °C for 20 min to obtain activated GF / SiC; S4. Using molecular beam epitaxy growth technology, heat the metal indium source material in the evaporation source to 500 °C with a heating current of 1.3 A for 20 min using a K-Cell evaporation device, and grow a layer of metal indium nanofilms on the surface of the activated GF / SiC to obtain InGF / SiC sheets; S5. Place the InGF / SiC sheets in a micro vacuum container with micropores, and the placement method and principle are as Figure 2 shown. Maintain the vacuum at 3.0×10 -1 Torr, heat the annealing container to 800 °C, and maintain the annealing time for 60 min to obtain regular carbon nanotubes on the SiC surface.

[0031] Example 2: A method for preparing regular carbon nanotubes on the SiC surface, characterized in that the specific steps are as follows: S1. Pretreat the SiC single crystal: Heat the Si-terminated surface single crystal 6H-SiC(0001) substrate to 500 °C under a DC condition of 0.58 A, and maintain the vacuum in the sample preparation chamber at 3.5×10 -9 Torr for 8 h of degassing and heat preservation to obtain the SiC substrate; S2. Heat-treat the SiC substrate: Heat the SiC substrate to 1250 °C with a DC current of 1.7 A for 15 min, and maintain the vacuum in the sample preparation chamber at 3.5×10 -9 Torr to obtain SiC pyrolytic graphene; S3. Activate the SiC pyrolytic graphene in a nickel atmosphere using a high-temperature furnace at an activation temperature of 690 °C for 20 min to obtain activated GF / SiC; S4. Using molecular beam epitaxy growth technology, heat the metal indium source material in the evaporation source to 550 °C with a heating current of 1.4 A for 10 min using a K-Cell evaporation device, and grow a layer of metal indium nanofilms on the surface of the activated GF / SiC to obtain InGF / SiC sheets; S5. Place the InGF / SiC sheets in a micro vacuum container with micropores, and the placement method and principle are as Figure 2 shown. Maintain the vacuum at 2.0×10 -1 Torr, heat the annealing container to 850 °C, and maintain the annealing time for 55 min to obtain regular carbon nanotubes on the SiC surface.

[0032] Example 3: A preparation method of regular carbon nanotubes on the SiC surface, characterized in that the specific steps are as follows: S1. Pretreat the SiC single crystal: Heat the Si-terminated surface single crystal 6H-SiC(0001) substrate to 630 °C under a DC condition of 0.55 A, and maintain the vacuum degree of the sample preparation chamber at 4.5×10 -9 Torr, degas and keep warm for 8 h to obtain the SiC substrate; S2. Heat-treat the SiC substrate: Heat the SiC substrate to 1310 °C with a DC current of 1.8 A and heat for 18 min, and maintain the vacuum degree of the sample preparation chamber at 4.5×10 -9 Torr to obtain SiC pyrolytic graphene; S3. Activate the SiC pyrolytic graphene in a metal nickel atmosphere through a high-temperature heating furnace. The activation temperature is 710 °C, and the activation treatment is 18 min to obtain activated GF / SiC; S4. Using molecular beam epitaxy growth technology, heat the metal indium source material in the evaporation source to 600 °C through a K-Cell evaporation device. The heating current is 1.6 A, and the growth time is 12 min. Grow a layer of metal indium nanofilms on the surface of the activated GF / SiC to obtain InGF / SiC sheets; S5. Place the InGF / SiC sheets in a micro-vacuum container provided with micropores. The placement method and principle are as Figure 2 shown. Maintain the vacuum degree at 3.0×10 -1 Torr, heat the annealing container to 900 °C, and maintain the annealing time for 50 min to prepare regular carbon nanotubes on the SiC surface.

[0033] Example 4: A preparation method of regular carbon nanotubes on the SiC surface, characterized in that the specific steps are as follows: S1. Pretreat the SiC single crystal: Heat the Si-terminated surface single crystal 6H-SiC(0001) substrate to 700 °C under a DC condition of 0.6 A, and maintain the vacuum degree of the sample preparation chamber at 4.5×10 -9 Torr, degas and keep warm for 8 h to obtain the SiC substrate; S2. Heat-treat the SiC substrate: Heat the SiC substrate to 1300 °C with a DC current of 2.0 A and heat for 13 min, and maintain the vacuum degree of the sample preparation chamber at 4.5×10 -9 Torr to obtain SiC pyrolytic graphene; S3. Activate the SiC pyrolytic graphene in a metal nickel atmosphere through a high-temperature heating furnace. The activation temperature is 750 °C, and the activation treatment is 15 min to obtain activated GF / SiC; S4. Using molecular beam epitaxy growth technology, heat the metal indium source material in the evaporation source to 700 °C through a K-Cell evaporation device, with a heating current of 1.8 A and a growth time of 10 min, to grow a layer of metal indium nanofilms on the activated GF / SiC surface, obtaining InGF / SiC sheets; S5. Place the InGF / SiC sheets in a micro-vacuum container with micropores. The placement method and principle are as Figure 2 shown. Maintain the vacuum degree at 2.0×10 -1 Torr, heat the annealing container to 850 °C, and maintain the annealing time for 55 min to obtain regular carbon nanotubes on the SiC surface.

[0034] Example 5: A preparation method of regular carbon nanotubes on the SiC surface, characterized in that the specific steps are as follows: S1. Pretreat the SiC single crystal: Heat the Si-terminated surface single crystal 6H-SiC(0001) substrate to 700 °C under a DC condition of 0.63 A, and maintain the vacuum degree of the sample preparation chamber at 1.8×10 -9 Torr, degas and keep warm for 8 h to obtain the SiC substrate; S2. Heat-treat the SiC substrate: Use a DC current of 1.9 A to heat the SiC substrate to 1280 °C and heat for 10 min, and maintain the vacuum degree of the sample preparation chamber at 1.8×10 -9 Torr to obtain SiC pyrolytic graphene; S3. Activate the SiC pyrolytic graphene in a metal nickel atmosphere through a high-temperature heating furnace. The activation temperature is 800 °C, and the activation treatment is 10 min to obtain activated GF / SiC; S4. Using molecular beam epitaxy growth technology, heat the metal indium source material in the evaporation source to 690 °C through a K-Cell evaporation device, with a heating current of 1.7 A and a growth time of 10 min, to grow a layer of metal indium nanofilms on the activated GF / SiC surface, obtaining InGF / SiC sheets; S5. Place the InGF / SiC sheets in a micro-vacuum container with micropores. The placement method and principle are as Figure 2 shown. Maintain the vacuum degree at 2.5×10 -1 Torr, heat the annealing container to 830 °C, and maintain the annealing time for 55 min to obtain regular carbon nanotubes on the SiC surface.

[0035] Test: I. Electrical properties: Use the four-probe method to test the resistivity of the regular carbon nanotubes on the SiC surface.

[0036] The carrier mobility of regular carbon nanotubes on the SiC surface was measured using a field-effect transistor method.

[0037] The test results are shown in Table 1.

[0038] Table 1

[0039] II. Mechanical properties: The tensile strength of regular carbon nanotubes on the SiC surface was measured using in-situ transmission electron microscopy tensile testing.

[0040] The Young's modulus of regular carbon nanotubes on the SiC surface was measured using atomic force microscopy tensile testing.

[0041] The test results are shown in Table 2.

[0042] Table 2

[0043] III. Thermal properties: The thermal conductivity of regular carbon nanotubes on the SiC surface was measured using the transient plane heat source method.

[0044] The thermal expansion coefficient of regular carbon nanotubes on the SiC surface was measured using an X-ray diffractometer.

[0045] The test results are shown in Table 3.

[0046] Table 3

[0047] IV. Result discussion and conclusion summary: From Table 1, it can be seen that the resistivity of regular carbon nanotubes on the SiC surface is as low as 10 -7 (Ω·cm), and the carrier mobility of regular carbon nanotubes on the SiC surface is as high as 10 3 (cm 2 / V·s). This indicates that the regular carbon nanotubes on the SiC surface have high purity, few surface impurities and defects, and regular arrangement, thus having excellent electrical properties.

[0048] From Table 2, it can be seen that the tensile strength of regular carbon nanotubes on the SiC surface can reach 23 GPa, and the Young's modulus of regular carbon nanotubes on the SiC surface can reach 178 GPa. This indicates that the regular carbon nanotubes on the SiC surface have high purity, few defects, a single and regular structure, thus having excellent mechanical properties.

[0049] From Table 3, it can be seen that the thermal conductivity of regular carbon nanotubes on the SiC surface can reach above 2200 W / m·K, and the thermal expansion coefficient of regular carbon nanotubes on the SiC surface is lower than 10 -5 (K -1), when the temperature rises, the size of the regular carbon nanotubes on the SiC surface expands at a relatively small rate. Combining its extremely high thermal conductivity, this makes the regular carbon nanotubes on the SiC surface have great application potential in the fields of thermal management, electronic devices, composite materials, etc.

[0050] In the description of the specification, the description referring to terms such as "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0051] The above content is only an example and illustration of the present invention. Those skilled in the art of the present technology make various modifications or supplements to the described specific embodiments or use similar ways to replace them. As long as they do not deviate from the invention or exceed the scope defined by the claims of the present invention, they should all belong to the protection scope of the present invention.

Claims

1. A method for preparing SiC surface regular carbon nanotubes, characterized in that: The specific steps are as follows: S1, pretreating the SiC single crystal to obtain a SiC substrate; S2, heat-treating the SiC substrate to obtain SiC pyrolytic graphene; S3, activating the SiC pyrolysis graphene in a metallic nickel atmosphere to obtain activated GF / SiC; S4, using molecular beam epitaxial growth technology, heating the metal indium source material in the evaporation source, growing a layer of metal indium nanofilm on the surface of the activated GF / SiC, and obtaining an InGF / SiC sheet; S5. Placing the InGF / SiC sheet in a micro vacuum container for high temperature annealing to obtain regular carbon nanotubes on the SiC surface.

2. The method for preparing SiC surface regular carbon nanotubes according to claim 1, characterized in that: In S1, the specific operation of the pretreatment is: heating the SiC single crystal to 500° C.-600° C. under vacuum conditions and keeping the temperature for 8 hours.

3. The method for preparing SiC surface regular carbon nanotubes according to claim 1, characterized in that: In S2, the heat treatment temperature is 1200°C-1300°C, and the heat treatment time is 10-20 minutes.

4. The method for preparing SiC surface regular carbon nanotubes according to claim 1, characterized in that: In S3, the activation conditions are: temperature 700°C-800°C, activation treatment 20-30 minutes.

5. The method for preparing SiC surface regular carbon nanotubes according to claim 1, characterized in that: In S4, the heating temperature is 500°C-700°C, and the growth time is 10-20 minutes.

6. The method for preparing SiC surface regular carbon nanotubes according to claim 1, characterized in that: In S4, the thickness of the metal indium nanofilm is 20-30 nm.

7. The method for preparing SiC surface regular carbon nanotubes according to claim 1, characterized in that: In S5, micropores are provided in the micro vacuum container.

8. The method for preparing SiC surface regular carbon nanotubes according to claim 1, characterized in that: In S5, the vacuum high temperature annealing treatment parameters of the InGF / SiC in the micro vacuum container are: vacuum range 1×10 -1 -5×10 - 1 Torr, annealing temperature 800℃-900℃, annealing time 30-60min.

9. SiC surface regular carbon nanotubes prepared according to the preparation method according to any one of claims 1 to 8.

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