Chemical vapor deposition method

Abstract

The invention discloses a chemical vapor deposition method which comprises the following steps: coating a conductive film on the surface of an insulating substrate to obtain a conductive composite material; a conductive composite material is adopted as a growth substrate, so that the growth substrate is electrified to be self-heated to a growth temperature, and a guest material is deposited and grown. According to the method, the surface of the insulating substrate is coated with the conductive film, so that the insulating substrate has conductive performance, and subsequent power-on spontaneous heating is realized. Furthermore, the substrate is heated in situ, so that only the surface temperature of the substrate is high, the pollution of a precursor (such as a carbon source) cracking byproduct can be reduced, the quality of the guest material can be improved, meanwhile, higher heating rate (400-1400 DEG C / s) and growth temperature (greater than 1100 DEG C) in a quartz tube can be realized, and the growth rate and the crystallization quality of the guest material can be improved. According to the method, the substrate is directly heated, so that uneven heating caused by indirect heating is avoided, and the crystallization quality of a guest material is remarkably improved.

Description

Technical Field

[0001] The invention belongs to the field of graphene preparation, and in particular relates to a method for growing a guest material by chemical vapor deposition on an insulating substrate and a composite structure prepared by the method. Background Art

[0002] As a material with excellent physical and chemical properties, achieving high-quality uniform growth with adjustable thickness is a prerequisite for its large-scale application. Chemical vapor deposition (CVD) is one of the main methods for preparing high-quality continuous graphene films. The CVD method usually grows graphene films on metal substrates represented by copper and nickel. The prepared graphene has a fast growth rate and good crystallization quality, but it is often necessary to transfer the graphene from the metal substrate to the target substrate through a transfer and peeling process. The transfer and peeling process of atomically thick graphene is undoubtedly another major challenge. Therefore, directly growing graphene on the target substrate, usually an insulating substrate, is an important technical route for realizing graphene applications. Unlike the preparation of graphene on a metal substrate, insulating substrates often lack catalytic activity, resulting in problems such as high graphene nucleation density, small domain size, poor growth quality, and slow growth rate.

[0003] The existing chemical vapor deposition of graphene is usually carried out in a hot wall CVD system consisting of a quartz tube and a tube furnace or a cold wall CVD system consisting of an electromagnetic induction coil and a graphite disk. In order to increase the growth rate and crystal quality of graphene, a higher temperature is generally selected.

[0004] However, for the hot wall CVD system, the melting point of the quartz tube limits the maximum temperature of graphene growth to 1100°C, and the tubular furnace limits the heating rate of the quartz tube to no more than 20°C / min. Higher temperatures can help improve the crystallization quality of graphene, and faster heating rates can save the time required to prepare graphene. In addition, the heat transfer method of the existing device is from the furnace to the sample, so the entire growth environment is hot, and the carbon source will be cracked in large quantities in the gas phase, and further react to generate by-products that are adsorbed on the sample, further reducing the quality of graphene.

[0005] For the cold wall CVD system, the coil is wound around the outer circumference of the quartz tube to generate a magnetic field. The graphite disk generates heat under the action of the magnetic field to heat the growth substrate. This heating method is indirect heating, and there must be interface thermal resistance, resulting in low heating efficiency and uneven heating, which affects the preparation efficiency and preparation quality.

[0006] Therefore, achieving high-quality and uniform growth of graphene on an insulating substrate has become an urgent problem to be solved in large-area applications of graphene. Summary of the invention

[0007] In order to solve the problems of uneven heat conduction during chemical vapor deposition of an insulating substrate and the growth temperature being limited by the melting point of a quartz tube, the present invention provides a chemical vapor deposition method and a composite structure prepared by the method.

[0008] The invention provides a chemical vapor deposition method, which coats a conductive film on the surface of an insulating substrate to obtain a conductive composite material; the conductive composite material is used as a growth substrate, the growth substrate is energized to self-heat to a growth temperature, and a growth guest material is deposited.

[0009] According to an embodiment of the present invention, during the guest material growth stage, the temperature gradient between the growth substrate and its surroundings is greater than or equal to 500° C. / cm.

[0010] According to another embodiment of the present invention, the growth substrate is graphene composite fiber fabric, graphene composite fiber felt or graphene composite fiber, and the insulating substrate is insulating fiber fabric, insulating fiber felt or insulating fiber; preferably, the growth substrate is graphene composite fiber fabric.

[0011] According to another embodiment of the present invention, the graphene composite fiber fabric is obtained by depositing graphene on an insulating fiber fabric, or by coating a graphene slurry on the surface of an insulating fiber fabric, or by reducing a graphene oxide slurry on the surface of an insulating fiber fabric; the graphene composite fiber felt is obtained by depositing graphene on an insulating fiber felt, or by coating a graphene slurry on the surface of an insulating fiber felt, or by reducing a graphene oxide slurry on the surface of an insulating fiber felt; the graphene composite fiber is obtained by depositing graphene on an insulating fiber, or by coating a graphene slurry on the surface of an insulating fiber, or by reducing a graphene oxide slurry on the surface of an insulating fiber; preferably, the graphene composite fiber fabric, the graphene composite fiber felt or the graphene composite fiber is obtained by chemical vapor deposition of graphene on the surface of an insulating fiber fabric, an insulating fiber felt or an insulating fiber.

[0012] According to another embodiment of the present invention, the insulating fiber fabric is one or more of glass fiber fabric, alumina fiber fabric, silicon carbide fiber fabric, and basalt fiber fabric; the insulating fiber felt is one or more of glass fiber felt, alumina fiber felt, silicon carbide fiber felt, and basalt fiber felt; the insulating fiber is one or more of glass fiber, alumina fiber, silicon carbide fiber, and basalt fiber.

[0013] According to another embodiment of the present invention, the guest material is graphene, carbon nanotubes, or semiconductor materials; preferably, the guest material is graphene.

[0014] According to another embodiment of the present invention, the temperature is increased to the growth temperature at a heating rate of 400-1400° C. / s.

[0015] According to another embodiment of the present invention, the growth temperature is 900-1500°C; preferably, the growth temperature is 1100-1500°C.

[0016] According to another embodiment of the present invention, a constant power density is applied to the growth substrate during the growth phase.

[0017] The invention also provides a composite structure prepared by the method.

[0018] The method of the present invention coats the surface of an insulating substrate with a conductive film to make it conductive, thereby achieving subsequent self-heating when powered on. Furthermore, by heating the substrate in situ so that only the surface temperature of the substrate is high, the contamination of the byproducts of the cracking of the precursor (such as a carbon source) can be reduced to improve the quality of the guest material. At the same time, a higher heating rate (400-1400°C / s) and growth temperature (greater than 1100°C) can be achieved in the quartz tube, thereby improving the growth rate and crystallization quality of the guest material. The method of the present invention directly heats the substrate to avoid uneven heating caused by indirect heating, and significantly improves the crystallization quality of the guest material. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic flow chart of a method for growing graphene by vapor deposition according to one embodiment of the present invention.

[0020] Figure 2 It is a transmission electron microscope photograph of the composite structure prepared in Example 1 and Comparative Examples 1-2 of the present invention.

[0021] Figure 3 It is the Raman spectra of the graphene grown in Example 1 and Comparative Examples 1-2 of the present invention. DETAILED DESCRIPTION

[0022] The present invention is described in detail below in conjunction with specific implementation modes.

[0023] The chemical vapor deposition method of the present invention coats a conductive film on the surface of an insulating substrate to obtain a conductive composite material; the conductive composite material is used as a growth substrate, the growth substrate is energized to self-heat to a growth temperature, and a growth guest material is deposited.

[0024] The "growth stage" in this patent refers to the period of time from when the growth substrate reaches the growth temperature to when it stops maintaining at the growth temperature.

[0025] The method of the present invention first coats a conductive film on the surface of an insulating substrate to obtain a conductive composite material; further, the conductive composite material is used as a growth substrate, and the growth substrate is electrically connected. The growth substrate is self-heated so that only the surface temperature of the substrate is high, which can reduce the gas phase reaction and reduce the pollution of the precursor (such as carbon source) cracking byproducts, improve the quality of the guest material, and reduce energy consumption. At the same time, it can break through the limitation of the melting point of the quartz tube wall and achieve a higher growth temperature (greater than 1100°C) in the quartz tube to improve the crystallization quality of the guest material. The method of the present invention directly heats the substrate, so that the heating of the substrate is more uniform, avoiding the uneven heating caused by indirect heating, and significantly improving the quality of the guest material. The method of the present invention is suitable for the growth of any material that can be obtained by a vapor deposition method, such as but not limited to graphene, carbon nanotubes, semiconductor materials, etc.

[0026] The specific heating method of energizing the growth substrate can be to energize the growth substrate by setting electrodes with opposite polarities at both ends of the growth substrate and applying voltage to the electrodes. Electrodes can be set in the reaction chamber of a conventional chemical vapor deposition device, and the growth substrate can be energized to generate self-heat by applying voltage to the growth substrate. Compared with the indirect heating method, this heating method makes only the surface temperature of the growth substrate high, and the temperature gradient between the growth substrate and its surroundings is large, which effectively reduces the pollution of cracking by-products.

[0027] In an optional embodiment, the temperature gradient between the growth substrate and its surroundings during the growth stage of the guest material is greater than or equal to 500°C / cm. In this patent, the "temperature gradient between the growth substrate and its surroundings" refers to the temperature change starting from the surface of the growth substrate in an outward direction.

[0028] In an optional embodiment, the growth substrate is a graphene composite fiber fabric, a graphene composite fiber felt or a graphene composite fiber. Preferably, it is a graphene composite fiber fabric. The insulating substrate is an insulating fiber fabric, an insulating fiber felt or an insulating fiber. By coating the surface of the insulating substrate with graphene, a graphene composite material is obtained as a growth substrate. Since graphene has excellent electrical conductivity, a high electric heating temperature rise rate can be effectively guaranteed.

[0029] In an optional embodiment, the graphene composite fiber fabric is obtained by depositing graphene on an insulating fiber fabric, or by coating a graphene slurry on the surface of the insulating fiber fabric, or by reducing the surface of the insulating fiber fabric after coating a graphene oxide slurry. The graphene composite fiber felt is obtained by depositing graphene on an insulating fiber felt, or by coating a graphene slurry on the surface of the insulating fiber felt, or by reducing the surface of the insulating fiber felt after coating a graphene oxide slurry. The graphene composite fiber is obtained by depositing graphene on an insulating fiber, or by coating a graphene slurry on the surface of the insulating fiber, or by reducing the surface of the insulating fiber after coating a graphene oxide slurry. Preferably, the graphene composite fiber fabric, the graphene composite fiber felt or the graphene composite fiber is obtained by chemically vapor depositing graphene on the surface of the insulating fiber fabric, the insulating fiber felt or the insulating fiber. The insulating fiber fabric can be one or more of a glass fiber fabric, an alumina fiber fabric, a silicon carbide fiber fabric and a basalt fiber fabric. The insulating fiber mat can be one or more of glass fiber mat, alumina fiber mat, silicon carbide fiber mat, and basalt fiber mat. The insulating fiber can be one or more of glass fiber, alumina fiber, silicon carbide fiber, and basalt fiber.

[0030] In an optional embodiment, the temperature is increased to the growth temperature at a heating rate of 400-1400°C / s, and the growth temperature is 900-1500°C. Preferably, the growth temperature is 1100-1500°C. Graphene has excellent electrical conductivity, and its electric heating heating rate is much higher than hot wall CVD heating, reaching 400-1400°C / s; by high-speed heating, it can be ensured that only the local high temperature of the growth substrate is achieved, which can effectively avoid the generation of carbon source by-products and improve the quality of graphene. At the same time, high-speed heating can shorten the preparation time of graphene and improve production efficiency. According to the resistance of the growth substrate, the expected heating rate and the growth temperature, the appropriate voltage and current can be selected, for example but not limited to a voltage of 10-1000V and a current of 1-50A.

[0031] In an optional embodiment, a constant power density is applied to the growth substrate during the growth phase. The growth temperature is controlled to remain unchanged by a constant power mode. In the growth phase, when the guest material is graphene, the resistance decreases after the graphene is deposited. By adopting a constant power mode, the growth temperature can be effectively kept constant, thereby improving the uniformity of graphene growth.

[0032] Figure 1 A schematic diagram of a process for growing graphene by chemical vapor deposition according to an embodiment of the present invention is shown. A person skilled in the art will appreciate that the present invention is not limited to Figure 1 The process shown, Figure 1The method shown is only an example for understanding the present invention. An electrode is set in the reaction chamber of the chemical vapor deposition device to heat the growth substrate by electricity. After the temperature is stabilized, a carbon source is introduced so that the carbon source is cracked near the heated growth substrate, thereby depositing and growing graphene on the growth substrate. The power density of the growth substrate can be maintained constant by changing the voltage and current introduced, thereby controlling the temperature of the growth substrate to remain constant. By controlling the growth time, the number of layers of the grown graphene layer can be controlled to obtain a graphene layer of a desired thickness.

[0033] The present invention is further described below by specific examples. However, these examples are merely exemplary and do not constitute any limitation to the scope of the present invention. In the following examples and comparative examples, the reagents, materials and instruments used are all commercially available unless otherwise specified.

[0034] Example 1

[0035] Provide a glass fiber fabric as a substrate and place it in the heating zone of a quartz tube furnace. Introduce 100 sccm argon as a protective gas, increase the temperature from room temperature to 1100°C at a rate of 20°C / min, and stabilize for 10 minutes. After the temperature stabilizes, turn off the argon gas, turn on 10 sccm ethylene gas and 200 sccm hydrogen gas, and keep the temperature constant for 2 hours. Turn off the 10 sccm ethylene gas, turn on 100 sccm argon gas, turn off the heating, and cool naturally to room temperature to obtain graphene glass fiber fabric.

[0036] The graphene glass fiber fabric prepared as above is used as a growth substrate and sandwiched between positive and negative electrode blocks to form a conductive path, thereby achieving further chemical vapor deposition of graphene on the graphene glass fiber fabric.

[0037] A voltage was applied to the electrode block in an argon atmosphere with a flow rate of 100 sccm, so that the temperature of the graphene glass fiber fabric increased by 1200°C, and the heating rate was ∼1300°C / s.

[0038] After the fabric temperature reaches the growth temperature of 1200°C (the temperature is measured by an infrared camera, the temperature is measured at the entire graphene fabric, the temperature of the glass outer tube is ~500°C, and the temperature gradient between the fabric and the surrounding is about 500°C / cm), the growth temperature is kept constant at constant power, 3sccm ethylene gas and 80sccm hydrogen gas are introduced, and the growth time is 10min.

[0039] After the growth is completed, the introduction of ethylene gas is stopped, 50 sccm of hydrogen gas and 100 sccm of argon gas are introduced, and the power is turned off to obtain the graphene glass fiber fabric.

[0040] Comparative Example 1

[0041] The growth substrate is the same as that in Example 1. The vapor deposition furnace uses a corundum tube.

[0042] The chemical vapor deposition furnace was heated in an argon atmosphere with a flow rate of 100 sccm at a heating rate of 20°C / min.

[0043] After the fabric temperature reaches the growth temperature of 1200°C (temperature is measured using an infrared camera over the entire graphene fabric), 3 sccm ethylene gas and 80 sccm hydrogen gas are introduced, and the growth time is 10 min.

[0044] After the growth is completed, the introduction of ethylene gas is stopped, 50 sccm of hydrogen gas and 100 sccm of argon gas are introduced, and the chemical vapor deposition furnace is cooled down to obtain the graphene glass fiber fabric.

[0045] Comparative Example 2

[0046] The growth substrate is the same as that in Example 1. The substrate is placed on the carbon felt sandwiched between the positive and negative electrode blocks, and the carbon felt is energized to generate heat and transfer heat to the graphene glass fiber fabric, thereby achieving further chemical vapor deposition of graphene on the graphene glass fiber fabric.

[0047] A voltage was applied to the carbon felt in an argon atmosphere with a flow rate of 100 sccm to generate heat at a heating rate of ∼1300°C / s.

[0048] After the fabric temperature reaches the growth temperature of 1200°C (temperature is measured using an infrared camera over the entire graphene fabric), 3 sccm ethylene gas and 80 sccm hydrogen gas are introduced, and the growth time is 10 min.

[0049] After the growth is completed, the introduction of ethylene gas is stopped, 50 sccm of hydrogen gas and 100 sccm of argon gas are introduced, and the power is turned off to obtain the graphene glass fiber fabric.

[0050] The monene glass fibers prepared in Example 1 and Comparative Examples 1-2 were sliced ​​and cross-sectional transmission electron microscopy (HRTEM) images were taken to observe the stacking structure of graphene. Figure 2 shown. Figure 2 From left to right in the figure are transmission electron microscope photos of slices of monene glass fiber of Example 1, Comparative Example 1 and Comparative Example 2. By comparison, it can be seen that the graphene in Example 1 is stacked in layers according to the two-dimensional material, while the non-layered stacking forms appear in Comparative Examples 1 and 2, which destroys the two-dimensional structure of graphene on the surface of monene glass fiber and reduces the electrical and thermal properties of graphene. It shows that the quality of graphene prepared in Example 1 is better than that of Comparative Examples 1 and 2.

[0051] The quality of the graphene layer is characterized by Raman mapping, such as Figure 3 As shown. It can be seen that the graphene layer prepared in Example 1 has the best quality, and the graphene layer prepared in Comparative Example 1 has the worst quality. This is because Comparative Example 1 uses a conventional tubular furnace for heating, the heating source is located outside the quartz tube, and the heat transfer method is from the furnace to the sample, so the entire growth environment is hot, and the carbon source will be cracked in large quantities in the gas phase, and further react to generate by-products that are adsorbed on the sample, further reducing the quality of graphene. Comparative Example 2 uses carbon felt for electrical heating and transfers heat to the growth substrate, which reduces the cracking of useless carbon sources to a certain extent, but because the heat transfer is not completely uniform, the temperature of the growth substrate will be uneven, so the quality of the graphene layer is slightly worse than that of Example 1.

[0052] The preferred embodiments of the present invention disclosed above are only used to help illustrate the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to the specific implementation methods described. Obviously, many modifications and changes can be made according to the content of this specification. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A chemical vapor deposition method, characterized in that: Coating a conductive film on the surface of an insulating substrate to obtain a conductive composite material; A conductive composite material is used as a growth substrate, and the growth substrate is made to self-heat to a growth temperature when powered on, so as to deposit a growth guest material.

2. The method according to claim 1, characterized in that: During the guest material growth stage, the temperature gradient between the growth substrate and its surroundings is greater than or equal to 500° C. / cm.

3. The method according to claim 1, characterized in that The growth substrate is graphene composite fiber fabric, graphene composite fiber felt or graphene composite fiber, and the insulating substrate is insulating fiber fabric, insulating fiber felt or insulating fiber; preferably, the growth substrate is graphene composite fiber fabric.

4. The method according to claim 3, characterized in that The graphene composite fiber fabric is obtained by depositing graphene on an insulating fiber fabric, or by coating a graphene slurry on the surface of the insulating fiber fabric, or by coating an oxide graphene slurry on the surface of the insulating fiber fabric and then reducing the slurry; The graphene composite fiber felt is obtained by depositing graphene on an insulating fiber felt, or by coating a graphene slurry on the surface of the insulating fiber felt, or by coating an oxide graphene slurry on the surface of the insulating fiber felt and then reducing the slurry; The graphene composite fiber is obtained by depositing graphene on insulating fiber, or by coating graphene slurry on the surface of insulating fiber, or by coating graphene oxide slurry on the surface of insulating fiber and then reducing it; Preferably, the graphene composite fiber fabric, graphene composite fiber felt or the graphene composite fiber is obtained by chemical vapor deposition of graphene on the surface of the insulating fiber fabric, insulating fiber felt or insulating fiber.

5. The method according to claim 4, characterized in that The insulating fiber fabric is one or more of glass fiber fabric, alumina fiber fabric, silicon carbide fiber fabric, and basalt fiber fabric; The insulating fiber felt is one or more of glass fiber felt, alumina fiber felt, silicon carbide fiber felt, and basalt fiber felt; The insulating fiber is one or more of glass fiber, alumina fiber, silicon carbide fiber and basalt fiber.

6. The method according to any one of claims 1 to 5, characterized in that: The guest material is graphene, carbon nanotubes, or semiconductor materials; preferably, the guest material is graphene.

7. The method according to claim 1, characterized in that The temperature is raised to the growth temperature at a heating rate of 400-1400°C / s.

8. The method according to claim 1, characterized in that The growth temperature is 900-1500°C; preferably, the growth temperature is 1100-1500°C.

9. The method according to claim 1, characterized in that: A constant power density is applied to the growth substrate during the growth phase.

10. A composite structure, characterized in that Prepared by the chemical vapor deposition method according to any one of claims 1 to 9.

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