Method for in-situ preparation of graphene flexible film and graphene flexible film

Abstract

This application relates to a method for in-situ preparation of flexible graphene films and the flexible graphene films themselves. The method for in-situ preparation of flexible graphene films includes the following steps: providing an alloy substrate with a solidus temperature less than or equal to 500°C; stacking the flexible substrate and the alloy substrate, heating the substrate to above its solidus temperature, and then forming a graphene film on the surface of the alloy substrate by plasma-enhanced chemical vapor deposition to obtain a graphene flexible film precursor; removing the alloy substrate from the graphene flexible film precursor to obtain a flexible graphene film. Because the alloy substrate has a low solidus temperature, the graphene film can be grown at a lower temperature, significantly reducing the preparation temperature and energy consumption of the graphene film. Furthermore, since the alloy substrate for growing the graphene film is in a molten or semi-molten state, high-quality single-crystal graphene films can be prepared.

Description

Technical Field

[0001] This invention relates to the field of semiconductor material preparation technology, and in particular to a method for in-situ preparation of graphene flexible films and the graphene flexible films themselves. Background Technology

[0002] Graphene is a two-dimensional carbon nanomaterial composed of carbon atoms arranged in a hexagonal honeycomb lattice with sp² hybrid orbitals. Graphene possesses excellent optical, electrical, and mechanical properties, and holds significant promise for applications in materials science, micro / nano fabrication, energy, biomedicine, and drug delivery, making it a revolutionary material for the future. Due to its superior electrical conductivity and high carrier mobility, graphene is considered a candidate for next-generation semiconductor materials, with broad potential applications in electronic devices, sensors, energy storage (such as supercapacitors), and flexible electronics.

[0003] Currently, the main method for preparing large-area, high-quality graphene films is chemical vapor deposition (CVD) on metal films such as copper and nickel. CVD involves introducing one or more gaseous substances into a reaction chamber to undergo a chemical reaction, depositing a film onto the substrate. However, in large-scale preparation, the commonly used polycrystalline copper foil substrate requires high temperatures, typically 1000℃, resulting in high energy consumption. Furthermore, it is difficult to prepare single-crystal graphene, limiting the size of graphene domains and hindering integration with low-temperature substrates or processes. While single-crystal copper foil can produce single-crystal graphene, its high cost severely hinders the mass production and industrialization of high-end graphene films. Summary of the Invention

[0004] Therefore, it is necessary to provide a method for in-situ preparation of flexible graphene films with low energy consumption and high quality, as well as the flexible graphene films themselves.

[0005] One aspect of the present invention provides a method for in-situ preparation of a flexible graphene film, comprising the following steps:

[0006] An alloy substrate is provided, wherein the solidus temperature of the alloy substrate is less than or equal to 500°C; a flexible substrate and the alloy substrate are stacked, and the substrate is heated to a temperature above the solidus temperature of the alloy substrate. A graphene film is then formed on the surface of the alloy substrate by plasma-enhanced chemical vapor deposition to prepare a graphene flexible film precursor; the alloy substrate in the graphene flexible film precursor is removed to prepare a graphene flexible film.

[0007] In some embodiments, the alloy substrate satisfies at least one of the following conditions:

[0008] (1) The alloy substrate is made of two or more of the following materials: copper, nickel, gallium, indium, tin, bismuth, cadmium, zinc, and lead;

[0009] (2) The alloy substrate comprises a catalyst metal and a liquid alloy metal; optionally, the catalyst metal includes any one or more of copper and nickel; optionally, the liquid alloy metal includes any one or more of gallium, indium, tin, bismuth, cadmium, zinc, and lead; optionally, the catalyst metal accounts for 5% to 40% of the mass of the alloy substrate.

[0010] In some embodiments, the alloy substrate satisfies at least one of the following conditions:

[0011] The alloy substrate is prepared by one or more of the following methods: vacuum melting, hot rolling, electric arc melting, rapid quenching, powder metallurgy, SPS sintering and electrochemical co-deposition.

[0012] The thickness of the alloy substrate is 10 μm to 100 μm;

[0013] The solidus temperature of the alloy substrate is 200℃~500℃.

[0014] In some embodiments, the flexible substrate satisfies at least one of the following conditions:

[0015] (1) The material of the flexible substrate includes any one or more of polyimide, polybenzimidazole, polyimide / alumina composite material, and MXene aerogel;

[0016] (2) The thickness of the flexible substrate is 2μm~500μm.

[0017] In some embodiments, the step of stacking a flexible substrate and the alloy substrate, and forming a graphene film on the surface of the alloy substrate by plasma-enhanced chemical vapor deposition to prepare a graphene flexible film precursor includes: stacking the flexible substrate and the alloy substrate, and then feeding them into a plasma-enhanced chemical vapor deposition apparatus, where a graphene film is grown under the action of plasma under the conditions of a protective gas and a carbon source.

[0018] Optionally, the protective gas is any one or more of argon, nitrogen, and hydrogen;

[0019] Optionally, the carbon source is one or more of methane, ethylene, acetylene, methane, ethylene, acetylene, and n-hexane;

[0020] Optionally, the power of the plasma is 10 W to 500 W;

[0021] Optionally, the temperature for growing the graphene film is 300 ℃~500 ℃, and the time is 1~60 minutes.

[0022] In some embodiments, the method for in-situ preparation of graphene flexible films includes at least one of the following features:

[0023] (1) The temperature at which the graphene film is formed on the surface of the alloy substrate is 300 ℃~500 ℃;

[0024] (2) The graphene film is a single-crystal graphene film.

[0025] In some embodiments, the graphene flexible film precursor is subjected to vapor phase modification treatment, and then the alloy substrate in the graphene flexible film precursor is removed.

[0026] Optionally, the method of vapor phase modification includes: treating the graphene flexible film precursor by introducing a vapor phase modification gas into a chemical vapor deposition apparatus or a plasma-enhanced chemical vapor deposition apparatus.

[0027] In some embodiments, the method for in-situ preparation of graphene flexible films includes any one or more of the following features:

[0028] (1) The gas-phase modification gas includes any one or more vapors of hexamethyldisilazane, trimethylsilane, perfluorooctyltrichlorosilane, carbon tetrafluoride, and phenyltrimethoxysilane;

[0029] (2) The temperature of the vapor phase modification treatment is 25℃~250℃;

[0030] (3) The time for the gas phase modification treatment is 1 min to 20 min.

[0031] In some embodiments, the method for removing the alloy substrate in the graphene flexible film precursor includes: coating the surface of the graphene flexible film precursor with polymethyl methacrylate, drying it, etching the alloy substrate with an etching solution to remove the polymethyl methacrylate coating, and obtaining the graphene flexible film.

[0032] Optionally, the etching solution is one or more of the following: ammonium persulfate solution, hydrochloric acid solution, hydrogen peroxide solution, citric acid solution, ammonia solution, ferric chloride solution, and sulfuric acid solution;

[0033] Optionally, the etching time of the alloy substrate using the etching solution is from 0.5 hours to 12 hours.

[0034] The second aspect of this application provides a graphene flexible film, which is prepared by any of the above-described in-situ preparation methods for graphene flexible films.

[0035] The aforementioned method for in-situ preparation of flexible graphene films involves heating the alloy substrate to its solidus temperature or above, allowing plasma-enhanced chemical vapor deposition (PECVD) to be performed on the substrate surface in a molten or semi-molten state. This forms a graphene film on the molten or semi-molten alloy substrate surface. Because the solidus temperature of the alloy substrate is relatively low, single-crystal graphene films can be grown at lower temperatures, significantly reducing the preparation temperature and energy consumption of single-crystal graphene films. Furthermore, since the alloy substrate for growing the graphene film is in a molten or semi-molten state, it overcomes the drawbacks of low monolayer ratio, numerous grain boundaries and defects, and poor intrinsic properties associated with plasma-enhanced chemical vapor deposition of graphene films, resulting in high-quality single-crystal graphene films. Attached Figure Description

[0036] Figure 1 This is an image of the incompletely grown graphene in the sample of Example 1 under a light microscope;

[0037] Figure 2 This is an image of a fully grown graphene film of the sample from Example 1 under a light microscope.

[0038] Figure 3 Photograph of the graphene flexible film prepared in Example 3. Detailed Implementation

[0039] To facilitate understanding of the present invention, a more complete description will be given below with reference to the accompanying drawings. Preferred embodiments of the invention are shown in the drawings. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the invention.

[0040] For simplicity, this application only explicitly discloses some numerical ranges. However, any lower limit can be combined with any upper limit to form a range not explicitly stated; and any lower limit can be combined with other lower limits to form a range not explicitly stated, just as any upper limit can be combined with any other upper limit to form a range not explicitly stated. Furthermore, although not explicitly stated, every point or individual value between the endpoints of the range is included within that range. Therefore, each point or individual value can be used as its own lower or upper limit and combined with any other point or individual value or with other lower or upper limits to form a range not explicitly stated.

[0041] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0042] In this document, when referring to numerical intervals (i.e., numerical ranges), unless otherwise specified, the distribution of selectable values ​​within a numerical interval is considered continuous, and includes the two endpoints (i.e., the minimum and maximum values) of the numerical interval, as well as every value between these two endpoints. Unless otherwise specified, when a numerical interval refers only to integers within that interval, it includes the two endpoint integers of the numerical range, as well as every integer between the two endpoints, which is equivalent to directly listing every integer. When multiple numerical ranges are provided to describe features or characteristics, these numerical ranges can be merged. In other words, unless otherwise specified, the numerical ranges disclosed herein should be understood to include any and all subranges included therein. The "numerical value" in this numerical interval can be any quantitative value, such as a number, percentage, ratio, etc. The term "numerical interval" can be broadly included to include percentage intervals, ratio intervals, proportion intervals, and other numerical interval types.

[0043] In this document, for methods involving multiple steps, unless otherwise explicitly stated herein, there is no strict order constraint on the execution of these steps; they may be executed in any order other than those described. Moreover, any step may include multiple sub-steps or multiple stages, which are not necessarily completed at the same time, but may be executed at different times, and their execution order is not necessarily sequential, but may be executed in turn, alternately, or simultaneously with other steps or parts of the sub-steps or stages of other steps.

[0044] The foregoing description of this application is not intended to describe every disclosed implementation or method. Instead, the following description provides more specific examples of exemplary embodiments. Throughout the application, guidance is provided through a series of embodiments that can be used in various combinations. The examples listed are representative only and should not be construed as exhaustive.

[0045] Currently, the growth of graphene films using commonly used substrates such as copper or nickel foil requires high temperatures, resulting in high energy consumption and making it difficult to integrate with low-temperature substrates or processes. Furthermore, the high cost of single-crystal copper foil substrates limits the domain size of graphene films prepared using ordinary polycrystalline copper foil, affecting the performance of the graphene films and making the preparation cost of single-crystal graphene films very high. Therefore, this application provides at least one method for in-situ preparation of flexible graphene films and a flexible graphene film.

[0046] According to a typical embodiment of this application, a method for in-situ preparation of a graphene flexible film is provided, comprising the following steps: providing an alloy substrate, wherein the solidus temperature of the alloy substrate is less than or equal to 500°C; stacking the flexible substrate and the alloy substrate, heating to above the solidus temperature of the alloy substrate, and then forming a graphene film on the surface of the alloy substrate by plasma-enhanced chemical vapor deposition to obtain a graphene flexible film precursor; removing the alloy substrate from the graphene flexible film precursor to obtain the graphene flexible film.

[0047] The aforementioned method for in-situ preparation of flexible graphene films involves heating the alloy substrate to its solidus temperature or above, allowing plasma-enhanced chemical vapor deposition (PECVD) to be performed on the substrate surface in a molten or semi-molten state. This forms a graphene film on the molten or semi-molten alloy substrate surface. Because the solidus temperature of the alloy substrate is relatively low, single-crystal graphene films can be grown at lower temperatures, significantly reducing the preparation temperature and energy consumption of single-crystal graphene films. Furthermore, since the alloy substrate for growing the graphene film is in a molten or semi-molten state, it overcomes the drawbacks of low monolayer ratio, numerous grain boundaries and defects, and poor intrinsic properties associated with plasma-enhanced chemical vapor deposition of graphene films, resulting in high-quality single-crystal graphene films.

[0048] Understandably, the solidus temperature of an alloy substrate refers to the temperature at which the alloy substrate begins to melt. For example, the solidus temperature of an alloy substrate can be 300 ℃, 350 ℃, 400 ℃, 450 ℃, 480 ℃, 500 ℃, etc. Optionally, the solidus temperature of the alloy substrate can be 350 ℃ to 450 ℃.

[0049] In some embodiments, the temperature at which the graphene film is formed on the surface of the alloy substrate is 300 °C to 500 °C. Non-limitingly, the temperature at which the graphene film is formed on the surface of the alloy substrate can be 300 °C, 350 °C, 400 °C, 450 °C, 480 °C, 500 °C, etc.

[0050] In some embodiments, the alloy substrate material includes two or more of the following: copper, nickel, gallium, indium, tin, bismuth, cadmium, zinc, and lead.

[0051] In some embodiments, the alloy substrate comprises a catalyst metal and a liquid alloy metal, wherein the liquid alloy metal refers to a metal whose melting temperature is lower than that of the catalyst metal and which, when mixed with the catalyst metal, can lower the melting point of the alloy substrate; by adding liquid alloy metal to the alloy substrate, the curing line temperature of the alloy substrate can be lowered, thereby enabling the growth of high-quality single-crystal graphene films at lower temperatures.

[0052] Alternatively, the catalyst metal may include any one or more of copper and nickel.

[0053] Optionally, the liquid alloy metal includes any one or more of gallium, indium, tin, bismuth, cadmium, zinc, and lead. This not only effectively reduces the curing temperature of the alloy substrate but also helps improve the quality of the graphene film grown on the surface of the alloy substrate, thus obtaining high-quality single-crystal graphene.

[0054] Optionally, the catalyst metal accounts for 5% to 40% of the mass of the alloy substrate, which is beneficial for balancing a lower curing temperature of the alloy substrate and the quality of the graphene film. Non-limitingly, the catalyst metal accounts for 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40% of the mass of the alloy substrate, etc.

[0055] Optionally, the mass of the liquid alloy metal accounts for 60% to 95% of the mass of the alloy substrate. Non-limitingly, it can be 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, etc.

[0056] In some embodiments, the alloy substrate is prepared by one or more of the following methods: vacuum melting, hot rolling, electric arc melting, rapid quenching, powder metallurgy, SPS sintering, and electrochemical co-deposition.

[0057] In some embodiments, the thickness of the alloy substrate is 10 μm to 100 μm; non-limitingly, the thickness of the alloy substrate is 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, etc. Optionally, a thickness of 20 μm to 30 μm is beneficial for preparing high-quality graphene films and facilitates etching, reducing the loss of alloy materials.

[0058] In some embodiments, the flexible substrate material includes any one or more of polyimide (PI), polybenzimidazole (PBI), polyimide / alumina composite (PI / Al2O3), and MXene aerogel, which have good high-temperature resistance and are beneficial for preparing high-quality single-crystal graphene.

[0059] In some embodiments, the thickness of the flexible substrate is 2 μm to 500 μm.

[0060] In some embodiments, the steps of stacking a flexible substrate and an alloy substrate, forming a graphene film on the surface of the alloy substrate by plasma-enhanced chemical vapor deposition, and preparing a graphene flexible film precursor include: stacking the flexible substrate and the alloy substrate, feeding them into a plasma-enhanced chemical vapor deposition apparatus, and growing a graphene film under the action of plasma under the conditions of introducing a protective gas and a carbon source.

[0061] Optionally, the protective gas is any one or more of argon, nitrogen, and hydrogen.

[0062] Optionally, the carbon source may be methane (CH4), ethylene (C2H4), acetylene (C2H2), methane (CH4), ethylene (C2H4), acetylene (C2H2), or n-hexane (n-C6H). 14 One or more of them.

[0063] Optionally, the plasma power is 10 W to 500 W. Non-limitingly, the plasma power can be 10 W, 50 W, 100 W, 150 W, 200 W, 250 W, 300 W, 350 W, 400 W, 450 W, 500 W, etc. Optionally, the plasma power is 180 W to 220 W.

[0064] Optionally, the temperature for growing the graphene film is 300℃~500℃, and non-limitingly, it can be 300℃, 350℃, 400℃, 450℃, 480℃, 500℃, etc., preferably 450℃~500℃. Further optionally, the growth time of the graphene film is 1 minute to 60 minutes, and non-limitingly, it can be 1 minute, 5 minutes, 10 minutes, 15 minutes, 20 minutes, 25 minutes, 30 minutes, 35 minutes, 40 minutes, 45 minutes, 50 minutes, 55 minutes, 60 minutes, etc.

[0065] In some embodiments, the graphene film is single-crystal graphene, that is, graphene with a perfect, continuous, grain boundary-free single-atom-layer structure at a macroscopic size (e.g., micrometers).

[0066] Considering that the graphene film needs to be transferred during the removal of the alloy substrate from the graphene flexible film precursor, and that direct separation can easily damage the graphene film due to the strong interaction between the graphene film and the alloy substrate, in some embodiments of this application, the graphene flexible film precursor is subjected to vapor phase modification treatment before the alloy substrate is removed. Through vapor phase modification treatment, the modified gas selectively permeates from the edge of the graphene to the metal interface of the underlying alloy substrate, generating active atoms that undergo covalent bonding reactions with the graphene or adhere to the graphene surface / lattice gaps. This reduces the interfacial bonding energy between the alloy substrate and the graphene, facilitating subsequent transfer and significantly reducing the breakage rate in subsequent processing.

[0067] In some embodiments, the method of vapor phase modification includes: treating the graphene flexible film precursor by introducing a vapor phase modification gas into a chemical vapor deposition apparatus or a plasma-enhanced chemical vapor deposition apparatus.

[0068] Furthermore, the gas-phase modification gas includes any one or more of the following: hexamethyldisilazane (HMDS), trimethylsilane (TMS), perfluorooctyltrichlorosilane (PFOTS), carbon tetrafluoride (CF4), and phenyltrimethoxysilane (PTMS) vapor. Optionally, the gas-phase modification gas is introduced at a rate of 150 sccm to 250 sccm.

[0069] Furthermore, the temperature for vapor phase modification is 25 ℃ to 250 ℃. Non-limitingly, the temperature for vapor phase modification can be 25 ℃, 50 ℃, 75 ℃, 100 ℃, 125 ℃, 150 ℃, 175 ℃, 200 ℃, 225 ℃, 250 ℃, etc. Optionally, the time for vapor phase modification is 1 min to 20 min. Non-limitingly, the time for vapor phase modification can be 1 min, 3 min, 5 min, 8 min, 10 min, 12 min, 15 min, 18 min, 20 min, etc.

[0070] In some embodiments, after the graphene film growth is completed, the carbon source supply is stopped and the plasma is turned off, and the temperature of the plasma-enhanced chemical vapor deposition apparatus is reduced to the temperature of the vapor phase modification treatment for vapor phase modification treatment.

[0071] In some embodiments, a method for removing the alloy substrate from a graphene flexible film precursor includes: coating the surface of the graphene flexible film precursor with polymethyl methacrylate (PMMA), drying it, etching the alloy substrate with an etching solution to remove the PMMA coating, and obtaining a graphene flexible film.

[0072] Optionally, after coating the surface of the graphene flexible film precursor with polymethyl methacrylate (PMMA), it can be left to dry.

[0073] Furthermore, the etching solution is one or more of the following: ammonium persulfate solution, hydrochloric acid solution, hydrogen peroxide solution, citric acid solution, ammonia solution, ferric chloride solution, and sulfuric acid solution. The solvent in the etching solution includes water.

[0074] Optionally, the etching solution includes ammonium persulfate, ammonia, and citric acid, which is particularly effective for removing alloy substrates. Optionally, the concentration of ammonium persulfate, ammonia, and citric acid in the etching solution is 0.1~1 mol / L.

[0075] Furthermore, the etching time for the alloy substrate using the etching solution is from 0.5 hours to 12 hours. Optionally, after etching is completed, the etched sample is cleaned with deionized water.

[0076] Furthermore, the PMMA coating can be removed by cleaning with acetone and isopropanol in sequence.

[0077] According to another typical embodiment of this application, a flexible graphene film is provided, which is prepared by any of the above-described in-situ methods for preparing flexible graphene films. The flexible graphene film prepared by the above methods has good quality and low cost.

[0078] Optionally, the above-mentioned flexible graphene film includes a graphene film and a flexible substrate; more preferably, the graphene film is single-crystal graphene.

[0079] Example

[0080] The following are specific embodiments, which describe the disclosure of this application in more detail. These embodiments are merely illustrative, as various modifications and variations within the scope of the disclosure of this application will be apparent to those skilled in the art. Unless otherwise stated, all parts, percentages, and ratios reported in the following embodiments are based on weight, and all reagents used in the embodiments are commercially available or synthesized by conventional methods and can be used directly without further processing, and the instruments used in the embodiments are commercially available.

[0081] Example 1

[0082] Step 1: Preparation of copper-liquid metal alloy substrate:

[0083] To prepare an alloy substrate of copper foil and liquid metal, copper is mixed with low-melting-point metals Ga, In, and Sn to obtain the alloy foil. The material ratio is Ga... 70 Cu 25 In4Sn1 has a solidus temperature of approximately 380°C. At 10... -3 The alloy substrate was vacuum-melted at 1200°C for 30 minutes under argon atmosphere, followed by water-cooled ingot casting. It was then hot-rolled at 320°C to a thickness of 25 micrometers to obtain the alloy substrate.

[0084] Step 2: Fabrication of single-crystal graphene films on copper-liquid metal alloy substrates:

[0085] The alloy substrate and a PI film with a thickness of 50 μm were stacked and fed into a PECVD furnace. The furnace was evacuated and 100 sccm of argon gas was introduced to heat the furnace to 480°C. The plasma was then activated at 200 W, and 10 sccm of methane was introduced to grow the graphene film at low temperature. After 10 min of growth, the carbon source supply and plasma were turned off, and the temperature was lowered to 150°C.

[0086] Step 3: Perform vapor phase modification on the graphene film:

[0087] The hexamethyldisilazane (HMDS) vapor was introduced at 200 sccm for 10 minutes, then cooled to room temperature and the grown graphene flexible film precursor was removed.

[0088] Step 4: Use in-situ etching to remove the alloy substrate and prepare a flexible graphene film:

[0089] After spin-coating PMMA onto the surface of the graphene flexible film precursor and allowing it to dry for 1 hour, an etching solution of a mixed aqueous solution of ammonium persulfate (0.5 M / L), ammonia (0.2 M / L), and citric acid (0.5 M / L) was used for etching for 4 hours. Subsequently, the film was cleaned with deionized water. After the graphene film and PI substrate were bonded, PMMA was removed by rinsing with acetone and isopropanol in sequence to form a graphene PI film.

[0090] To determine whether graphene is a single crystal, graphene films grown for 3 minutes and 10 minutes were prepared and subjected to optical microscopy. The morphologies of the graphene under the optical microscope are as follows: Figure 1 and Figure 2 As shown. Among them, the hexagonal orientation of the 3-minute sample is consistent, indicating that the graphene film grown in Example 1 is a single-crystal graphene film, and the 10-minute sample is a single-layer graphene film.

[0091] Example 2

[0092] The difference from Example 1 is that in step two, after turning off the carbon source and plasma, the temperature is lowered to room temperature and the grown graphene film is taken out; step four, using in-situ etching to remove the alloy substrate to prepare a flexible graphene film, is performed directly according to the same method as in Example 1.

[0093] The alloy substrate is difficult to peel off, resulting in severe damage to the graphene film layer in the formed flexible graphene film.

[0094] Example 3

[0095] The difference from Example 1 lies in steps one and two, as detailed below:

[0096] Step 1: Preparation of nickel-liquid metal alloy substrate:

[0097] To prepare an alloy substrate of nickel and liquid metal, an alloy foil was obtained by mixing nickel with low-melting-point metals Ga, In, and Sn, with the material ratio being Ga... 70 Ni 25 In4Sn1 has a solidus temperature of 420℃. At 10 -3 The alloy substrate was vacuum-melted at 1500°C for 30 minutes under argon atmosphere, followed by water-cooled ingot casting. Then, it was hot-rolled at 400°C to a thickness of 25 micrometers to obtain the alloy substrate.

[0098] Step 2: Fabrication of single-crystal graphene films on copper-liquid metal alloy substrates:

[0099] The alloy substrate and a PI film with a thickness of 25 μm were stacked and fed into a PECVD furnace. The furnace was evacuated and 100 sccm of argon gas was introduced to heat the furnace to 480°C. The plasma was then activated at 200 W, and 10 sccm of methane was introduced to grow the graphene film at low temperature. After 10 min of growth, the carbon source supply and plasma were turned off, and the temperature was lowered to 150°C.

[0100] The prepared graphene flexible film, such as Figure 3 As shown, the graphene film in the flexible graphene film is complete and is a single-layer single crystal.

[0101] The graphene flexible films prepared in the above embodiments were tested using a water vapor transmission rate tester and an oxygen transmission rate tester to determine their water and oxygen barrier capabilities. The test results are listed in Table 1 below:

[0102] Table 1

[0103]

[0104] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0105] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention should be determined by the appended claims, and the specification and drawings can be used to interpret the content of the claims.

Claims

1. A method for in-situ preparation of a flexible graphene film, characterized in that, The steps include the following: An alloy substrate is provided, wherein the solidus temperature of the alloy substrate is less than or equal to 500°C; A flexible substrate and the alloy substrate are stacked together and heated to above the solidus temperature of the alloy substrate. Then, a graphene film is formed on the surface of the alloy substrate by plasma-enhanced chemical vapor deposition, thus preparing a graphene flexible film precursor. The alloy substrate in the graphene flexible film precursor is removed to prepare the graphene flexible film.

2. The method for in-situ preparation of graphene flexible films according to claim 1, characterized in that, The alloy substrate satisfies at least one of the following conditions: (1) The alloy substrate is made of two or more of the following materials: copper, nickel, gallium, indium, tin, bismuth, cadmium, zinc, and lead; (2) The alloy substrate comprises a catalyst metal and a liquid alloy metal; optionally, the catalyst metal comprises any one or more of copper and nickel; optionally, the liquid alloy metal comprises any one or more of gallium, indium, tin, bismuth, cadmium, zinc, and lead; optionally, the mass of the catalyst metal accounts for 5% to 40% of the mass of the alloy substrate.

3. The method for in-situ preparation of a flexible graphene film according to claim 1, characterized in that, The alloy substrate satisfies at least one of the following conditions: The alloy substrate is prepared by one or more of the following methods: vacuum melting, hot rolling, electric arc melting, rapid quenching, powder metallurgy, SPS sintering and electrochemical co-deposition. The thickness of the alloy substrate is 10 μm to 100 μm; The solidus temperature of the alloy substrate is 200℃~500℃.

4. The method for in-situ preparation of graphene flexible films according to claim 1, characterized in that, The flexible substrate satisfies at least one of the following conditions: (1) The flexible substrate is made of any one or more of polyimide, polybenzimidazole, polyimide / alumina composite material, and MXene aerogel; (2) The thickness of the flexible substrate is 2 μm to 500 μm.

5. The method for in-situ preparation of a flexible graphene film according to any one of claims 1 to 4, characterized in that, The steps of stacking the flexible substrate and the alloy substrate, forming a graphene film on the surface of the alloy substrate by plasma-enhanced chemical vapor deposition, and preparing a graphene flexible film precursor include: stacking the flexible substrate and the alloy substrate, and then feeding them into a plasma-enhanced chemical vapor deposition apparatus, where a graphene film is grown under the action of plasma under the conditions of a protective gas and a carbon source. Optionally, the protective gas is any one or more of argon, nitrogen, and hydrogen; Optionally, the carbon source is one or more of methane, ethylene, acetylene, methane, ethylene, acetylene, and n-hexane; Optionally, the power of the plasma is 10 W to 500 W; Optionally, the temperature for growing the graphene film is 300 ℃~500 ℃, and the time is 1~60 minutes.

6. The method for in-situ preparation of a flexible graphene film according to any one of claims 1 to 4, characterized in that, Includes at least one of the following features: (1) The temperature at which the graphene film is formed on the surface of the alloy substrate is 300 ℃~500 ℃; (2) The graphene film is a single-crystal graphene film.

7. The method for in-situ preparation of a flexible graphene film according to any one of claims 1 to 4, characterized in that, After the graphene flexible film precursor is subjected to vapor phase modification treatment, the alloy substrate in the graphene flexible film precursor is removed. Optionally, the method of vapor phase modification includes: treating the graphene flexible film precursor by introducing a vapor phase modification gas into a chemical vapor deposition apparatus or a plasma-enhanced chemical vapor deposition apparatus.

8. The method for in-situ preparation of a flexible graphene film according to claim 7, characterized in that, Includes one or more of the following features: (1) The gas-phase modification gas includes any one or more vapors of hexamethyldisilazane, trimethylsilane, perfluorooctyltrichlorosilane, carbon tetrafluoride, and phenyltrimethoxysilane; (2) The temperature of the vapor phase modification treatment is 25℃~250℃; (3) The time for the gas phase modification treatment is 1 min to 20 min.

9. The method for in-situ preparation of a flexible graphene film according to any one of claims 1 to 4, characterized in that, The method for removing the alloy substrate from the graphene flexible film precursor includes: coating the surface of the graphene flexible film precursor with polymethyl methacrylate, drying it, etching the alloy substrate with an etching solution to remove the polymethyl methacrylate coating, and obtaining the graphene flexible film. Optionally, the etching solution is one or more of the following: ammonium persulfate solution, hydrochloric acid solution, hydrogen peroxide solution, citric acid solution, ammonia solution, ferric chloride solution, and sulfuric acid solution; Optionally, the etching time of the alloy substrate using the etching solution is from 0.5 hours to 12 hours.

10. A flexible graphene film, characterized in that, The graphene flexible film was prepared by the in-situ preparation method according to any one of claims 1 to 9.

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