Graphene film, preparation method thereof and electronic device

Abstract

The invention provides a graphene film and a preparation method thereof, and an electronic device, the preparation method comprises the following steps: forming a patterned second substrate on a first surface of a first substrate, the carbon solubility of the first substrate being less than the carbon solubility of the second substrate at the same temperature; a graphene film is formed on the second surface of the first substrate, and the second surface and the first surface are located on the two opposite sides of the first substrate respectively; the graphene film comprises a first graphene film and a second graphene film, and the layer number of the first graphene film is larger than that of the second graphene film; the first graphene film is distributed in a first area of the second surface, the second graphene film is distributed in a second area of the second surface, the second area is an orthographic projection area formed by the second substrate on the second surface, and the first area is a remaining area, except the orthographic projection area, on the second surface. The preparation method provided by the invention can realize controlled growth of the graphene film.

Description

Technical Field

[0001] The present application relates to the field of semiconductor material technology, and in particular to a graphene film and a preparation method thereof, and an electronic device. Background Art

[0002] Graphene is a two-dimensional material formed by carbon atoms arranged in a honeycomb lattice. Due to its excellent physical and chemical properties, such as extremely high carrier mobility, excellent light transmittance and strong mechanical properties, it has always been a hot topic in the field of scientific research. It has a wide range of potential applications in electronic devices, sensors, energy storage (such as supercapacitors) and flexible electronics. Due to its excellent conductivity and high carrier mobility, graphene is considered to be a candidate for the next generation of semiconductor materials. So far, researchers have developed a variety of graphene preparation techniques, such as mechanical exfoliation, silicon carbide epitaxy, liquid phase exfoliation, redox method, chemical vapor deposition and bottom-up synthesis methods. These methods have their own characteristics and advantages for different application scenarios. In particular, chemical vapor deposition on copper foil has become an attractive method with its high-quality graphene growth ability and suitability for large-scale production.

[0003] However, during large-scale preparation, it is often difficult to achieve precise control of the number of graphene layers during the patterned growth process, while the number of graphene layers directly affects device performance. Specifically, single-layer graphene (SLG) has the highest carrier mobility and unique quantum Hall effect, and is suitable for high-frequency electronic devices and transparent conductive films. Double-layer graphene (BLG) can adjust its band gap through an external field and is suitable for field effect transistors (FETs). Multilayer graphene (MLG) has higher mechanical strength and is suitable for shielding materials or composite reinforcement materials. Therefore, precise control of the number of graphene layers is crucial to improving device performance. Summary of the invention

[0004] The present application provides a graphene film and a preparation method thereof, and an electronic device, which can achieve controlled growth of a graphene film (number of layers).

[0005] The first aspect of the present application provides a method for preparing a graphene film, comprising:

[0006] forming a patterned second substrate on a first surface of a first substrate, wherein the carbon solubility of the first substrate is less than the carbon solubility of the second substrate at the same temperature;

[0007] forming a graphene film on a second surface of the first substrate, wherein the second surface and the first surface are respectively located on two opposite sides of the first substrate;

[0008] The graphene film includes a first graphene film and a second graphene film, and the number of layers of the first graphene film is greater than the number of layers of the second graphene film;

[0009] The first graphene film is distributed in a first area of ​​the second surface, the second graphene film is distributed in a second area of ​​the second surface, the second area is an orthographic projection area formed by the second substrate on the second surface, and the first area is a remaining area on the second surface outside the orthographic projection area.

[0010] In some embodiments of the present application, there are multiple second substrates and multiple second graphene films, a gap exists between two adjacent second substrates, and the first graphene film is distributed in the area between two adjacent second graphene films.

[0011] In some embodiments of the present application, one or more of the following conditions are met:

[0012] (1) The material of the first substrate includes one or more of copper, nickel, tungsten, molybdenum, iron, cobalt, iridium, osmium, palladium, rhodium, platinum and gold, and copper may be selected;

[0013] (2) the material of the second substrate includes one or more of copper, nickel, tungsten, molybdenum, iron, cobalt, iridium, osmium, palladium, rhodium, platinum and gold, and the solubility of the second substrate material in carbon is greater than the solubility of the first substrate material in carbon at the same temperature;

[0014] Optionally, the material of the second substrate is tungsten and / or nickel;

[0015] (3) The thickness of the first substrate is 10 μm to 100 μm;

[0016] (4) The thickness of the second substrate is 20 nm to 50 μm;

[0017] (5) The number of layers of the first graphene film is greater than or equal to 2, and the number of layers of the second graphene film is 1.

[0018] In some embodiments of the present application, the step of forming a patterned second substrate on the first surface of the first substrate includes:

[0019] Attaching the patterned second substrate on the first surface; or forming the patterned second substrate on the first surface by plating;

[0020] Optionally, the attaching method includes printing and / or heat pressing.

[0021] In some embodiments of the present application, the step of forming the patterned second substrate on the first surface by plating includes:

[0022] Using a patterned photoresist or a patterned mask to cover the first surface, and forming the second substrate on the first surface by a patterned coating technology;

[0023] Optionally, the patterned coating technology includes one or more of photolithography, mask coating, spray coating, and self-assembly, and can further be mask coating;

[0024] Optionally, the coating method in the mask coating includes one or more of electroplating, chemical plating, magnetron sputtering, evaporation, chemical vapor deposition, thermal spraying and hot dip coating, and magnetron sputtering may be further selected.

[0025] In some embodiments of the present application, the method for forming the first graphene film and the second graphene film includes one of a chemical vapor deposition method and a plasma enhanced chemical vapor deposition method;

[0026] Optionally, the formation process of the first graphene film and the second graphene film includes:

[0027] The second substrate formed with the first substrate is placed in a chemical vapor deposition device or a plasma enhanced chemical vapor deposition device, a carbon source is introduced and heated in a protective atmosphere, so that carbon atoms are deposited on the first substrate, and after cooling, they grow into the first graphene film and the second graphene film respectively.

[0028] In some embodiments of the present application, before the step of forming a patterned second substrate on the first surface of the first substrate, the method further includes:

[0029] Pre-treating the first substrate to remove impurities on the surface of the first substrate;

[0030] Optionally, the preprocessing step includes one or more of the following:

[0031] (1) cleaning the first substrate in a volatile organic solvent for 1 min to 10 min;

[0032] Optionally, the volatile organic solvent includes one or more of ethanol, acetone and isopropanol;

[0033] (2) washing the first substrate in deionized water for 1 min to 10 min;

[0034] (3) cleaning the first substrate in an acidic solvent for 1 min to 10 min;

[0035] Optionally, the acidic solvent includes one or more of phosphoric acid, acetic acid, hydrochloric acid and nitric acid.

[0036] The second aspect of the present application provides a graphene film, which is prepared by the preparation method described in the first aspect of the present application.

[0037] In some embodiments of the present application, the graphene film includes a first graphene film and a second graphene film, the first graphene film and the second graphene film are alternately distributed, and the number of layers of the first graphene film is greater than the number of layers of the second graphene film;

[0038] Optionally, the number of layers of the first graphene film is greater than or equal to 2, and the number of layers of the second graphene film is equal to 1.

[0039] The third aspect of the present application provides an electronic device, comprising the graphene film described in the second aspect of the present application.

[0040] The preparation method provided in the present application, by setting a second substrate on the back side (i.e., the first surface) of the first substrate, can simultaneously grow graphene films of different numbers of layers in different regions, thereby realizing the patterned growth of graphene films of different numbers of layers. Through the patterned growth of graphene films of different numbers of layers, the integration of multifunctional devices (such as sensing + conduction + shielding) on ​​a single substrate is realized, which is of vital importance for improving the application and promotion of graphene films in high-end electronic devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 This is a schematic diagram of the preparation process of a graphene film according to one embodiment of the present application.

[0042] Figure 2 A schematic diagram of a graphene film according to an embodiment of the present application.

[0043] Figure 3 This is a Raman test spectrum of the graphene film grown on the front side of the first substrate directly opposite to the tungsten film on the second substrate in Example 1.

[0044] Figure 4 This is the Raman test spectrum of the graphene film grown on the first substrate copper foil in Example 1.

[0045] Reference numerals: 11 first substrate; 12 second substrate; 30 first graphene film; 20 second graphene film. DETAILED DESCRIPTION

[0046] In order to facilitate understanding of the present application, the present application will be described more comprehensively below. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present application more thorough and comprehensive.

[0047] For simplicity, this application only explicitly discloses some numerical ranges. However, any lower limit can be combined with any upper limit to form an unclearly recorded range; and any lower limit can be combined with other lower limits to form an unclearly recorded range, and any upper limit can be combined with any other upper limit to form an unclearly recorded range. In addition, although not clearly recorded, each point or single value between the range endpoints is included in the range. Thus, each point or single value can be combined with any other point or single value as its own lower limit or upper limit or with other lower limits or upper limits to form an unclearly recorded range.

[0048] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are for the purpose of describing specific embodiments only and are not intended to limit this application. It should be noted that, unless otherwise specified, the term "and / or" used herein includes any and all combinations of one or more related listed items, and "above" and "below" are inclusive of the number, and the meaning of "multiple" in "one or more" is more than two.

[0049] Herein, when it comes to a numerical interval (i.e., a numerical range), unless otherwise specified, the distribution of the optional numerical values ​​within the numerical interval is considered to be continuous and includes the two numerical endpoints (i.e., the minimum and maximum values) of the numerical interval, and each numerical value between the two numerical endpoints. Unless otherwise specified, when a numerical interval only refers to integers within the numerical interval, including the two endpoint integers of the numerical range, and each integer between the two endpoints, is equivalent to directly listing each integer. When multiple numerical ranges are provided to describe features or characteristics, these numerical ranges can be combined. In other words, unless otherwise specified, the numerical ranges disclosed herein should be understood to include any and all sub-ranges included therein. The "numerical value" in the numerical interval can be any quantitative value, such as a number, a percentage, a ratio, etc. "Numerical interval" allows broadly including numerical interval types such as percentage intervals, ratio intervals, and ratio intervals.

[0050] In this article, if there are multiple steps involved in the method flow, unless there is a clear different description in this article, there is no strict order restriction for the execution of these steps, and they can be executed in other orders than described. Moreover, any step can include multiple sub-steps or multiple stages, and these sub-steps or stages are not necessarily executed at the same time, but can be executed at different times, and their execution order is not necessarily sequential, but can be executed in turn, alternating or simultaneously with other steps or parts of sub-steps or stages of other steps.

[0051] The above application content of the present application is not intended to describe each disclosed embodiment or each implementation in the present application. The following description more specifically illustrates exemplary embodiments. In many places throughout the application, guidance is provided by a series of examples, which can be used in various combinations. In each example, enumeration is only used as a representative group and should not be interpreted as exhaustive.

[0052] At present, with the increasing integration of electronic devices, higher requirements are placed on the performance of graphene films; in view of the different performance requirements of graphene for different functional devices and the different physical properties of graphene with different numbers of layers, it is particularly important to achieve regional selective growth of graphene with different numbers of layers for the application of graphene in multifunctional electronic devices; however, the current traditional graphene growth process is difficult to achieve precise control of the number of graphene layers, and it is also difficult to achieve regional selective growth of graphene with different numbers of layers. Based on this, the present application proposes the following technical solution.

[0053] In a first aspect, the present application provides a method for preparing a graphene film, which may include the following steps:

[0054] S1: See Figure 1 , forming a patterned second substrate 12 on a first surface of a first substrate 11, wherein the carbon solubility of the first substrate 11 is less than the carbon solubility of the second substrate 12 at the same temperature;

[0055] S2: See Figure 2 , forming a graphene film on a second surface of the first substrate 11, wherein the second surface and the first surface are respectively located on two opposite sides of the first substrate;

[0056] The graphene film includes a first graphene film 30 and a second graphene film 20, wherein the number of layers of the first graphene film 30 is greater than the number of layers of the second graphene film 20;

[0057] The first graphene film 30 is distributed in a first area of ​​the second surface, and the second graphene film 20 is distributed in a second area of ​​the second surface. The second area is an orthographic projection area formed by the second substrate on the second surface, and the first area is a remaining area on the second surface outside the orthographic projection area.

[0058] In the above preparation method provided by the present application, after forming the second substrate on the first surface of the first substrate (also referred to as the back side of the first substrate) in step S1, in the process of forming the graphene film in step S2, since the carbon solubility of the second substrate is greater than that of the first substrate at the same temperature, the second substrate on the back side of the first substrate has a higher carbon solubility capacity than the first substrate portion (i.e., the first substrate portion in the second region) on the second surface (also referred to as the front side of the first substrate) that is opposite to the second substrate; then in the process of forming the graphene film, compared with the first substrate portion in the second region on the front side, the carbon active substance will be more preferentially combined with the second substrate on the back side, and will be mainly distributed on the second substrate, so that after being affected by the second substrate, the second region on the front side of the first substrate has relatively less active carbon substances participating in the growth of graphene, fewer graphene nucleation points and a lower graphene growth rate, and ultimately it is easier to form a single-layer graphene film in this region. The first region on the front side of the first substrate (i.e., the first substrate portion within the first region) is less affected by the second substrate during the graphene formation process because there is no second substrate on the opposite back side, and is therefore easier to form double-layer or multi-layer graphene. Through such a setting, the number of layers of the first graphene film can ultimately be made greater than the number of layers of the second graphene film, thereby achieving controlled growth of graphene films with different numbers of layers in the same film, laying the foundation for its application in high-end integration.

[0059] In this way, the above preparation method provided in the present application can realize the patterned growth of graphene films with different numbers of layers. Through the patterned growth of graphene films with different numbers of layers, the integration of multifunctional devices on a single substrate (such as sensing + conduction + shielding) can be realized, which is of vital importance to improving the application and promotion of graphene films in high-end electronic devices.

[0060] It can be understood that the “carbon solubility” mentioned in the present application refers to the solubility of carbon in different substrates at the same temperature.

[0061] In some embodiments, the second substrate and the second graphene film are each multiple, a gap exists between two adjacent second substrates, and the first graphene film is distributed in the region between two adjacent second graphene films. This is more conducive to the controlled growth of graphene films with different numbers of layers.

[0062] In some embodiments, the material of the first substrate includes one or more of copper, nickel, tungsten, molybdenum, iron, cobalt, iridium, osmium, palladium, rhodium, platinum and gold, and copper may be selected.

[0063] In some embodiments, the material of the second substrate includes one or more of copper, nickel, tungsten, molybdenum, iron, cobalt, iridium, osmium, palladium, rhodium, platinum and gold, and the solubility of the material of the second substrate in carbon is greater than the solubility of the material of the first substrate in carbon at the same temperature; optionally, the material of the second substrate is tungsten and / or nickel.

[0064] It can be understood that the regulation of the carbon solubility of the first substrate or the second substrate can be achieved by regulating the content of metal contained in the material of the first substrate or the second substrate; for example, the material of the second substrate includes copper and nickel, then the carbon solubility of the second substrate can be regulated by regulating the relative content of copper and nickel in the second substrate.

[0065] In some embodiments, the thickness of the first substrate is 10 μm to 100 μm. For example, the thickness of the first substrate can be 10 μm, 30 μm, 50 μm, 70 μm, 90 μm, 100 μm, or any range thereof.

[0066] In some embodiments, the thickness of the second substrate is 20 nm to 50 μm. For example, the thickness of the second substrate can be 20 nm, 50 nm, 80 nm, 100 nm, 500 nm, 1 μm, 5 μm, 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, or within a range consisting of any of the above values.

[0067] In some embodiments, the number of layers of the first graphene film is greater than or equal to 2, and the number of layers of the second graphene film is 1.

[0068] In some embodiments, the step of forming a patterned second substrate on the first surface of the first substrate may include:

[0069] The patterned second substrate is attached to the first surface; or, the patterned second substrate is formed on the first surface by plating.

[0070] In some implementations, the attaching method includes printing and / or heat pressing.

[0071] In some embodiments, the step of forming the patterned second substrate on the first surface by plating may include:

[0072] The first surface is shielded by using a patterned photoresist or a patterned mask, and the second substrate is formed on the first surface by using a patterned coating technology.

[0073] In some embodiments, the patterned coating technology includes one or more of photolithography, mask coating, spray coating, and self-assembly, and mask coating may be further selected.

[0074] In some embodiments, the coating method in the mask coating includes one or more of electroplating, chemical plating, magnetron sputtering, evaporation, chemical vapor deposition, thermal spraying and hot dip coating, and magnetron sputtering can be selected.

[0075] In some embodiments, a method of forming the first graphene film and the second graphene film includes one of a chemical vapor deposition method (CVD) and a plasma enhanced chemical vapor deposition method (PECVD).

[0076] In some embodiments, the formation process of the first graphene film and the second graphene film may include the following steps:

[0077] The second substrate formed with the first substrate is placed in a chemical vapor deposition device or a plasma enhanced chemical vapor deposition device, a carbon source is introduced and heated in a protective atmosphere, so that carbon atoms are deposited on the first substrate, and after cooling, they grow into the first graphene film and the second graphene film respectively.

[0078] In the above process of preparing graphene film by CVD method or PECVD method, the second substrate on the back side of the first substrate has a higher carbon solubility ability than the first substrate part (i.e., the first substrate part in the second region) on the second surface (also called the front side of the first substrate) that is opposite to the second substrate. Then, in the formation process of the graphene film, compared with the first substrate part in the second region on the front side, the carbon active substance will be more preferentially combined by the second substrate on the back side, and will be mainly distributed on the second substrate. In this way, after being affected by the second substrate, the second region on the front side of the first substrate has relatively less active carbon substances participating in the growth of graphene, fewer graphene nucleation points and a lower graphene growth rate. Finally, the carbon in this part of the region is easier to form a single-layer graphene film after precipitation during the cooling process. The first area on the front side of the first substrate (i.e., the first substrate portion within the first area) is less affected by the second substrate during the graphene formation process because the second substrate is not arranged on the opposite back side. Therefore, carbon is more easily precipitated after cooling to form double-layer or multi-layer graphene. Through such a setting, the number of layers of the first graphene film can eventually be made greater than the number of layers of the second graphene film, thereby achieving controlled growth of graphene films with different numbers of layers in the same film, laying the foundation for its application in high-end integration.

[0079] In some embodiments, before the step of forming a patterned second substrate on the first surface of the first substrate, the method may further include:

[0080] The first substrate is pretreated to remove impurities on the surface of the first substrate.

[0081] In some embodiments, the preprocessing step may include one or more of the following:

[0082] (1) cleaning the first substrate in a volatile organic solvent for 1 min to 10 min;

[0083] (2) washing the first substrate in deionized water for 1 min to 10 min;

[0084] (3) Cleaning the first substrate in an acidic solvent for 1 min to 10 min.

[0085] It is understood that the order of the above steps (1) to (3) is not limited and can be adjusted according to actual needs.

[0086] The above steps (1) to (3) can remove most of the impurities on the surface of the first substrate by combining cleaning and acidic solvent micro-etching.

[0087] In some embodiments, the volatile organic solvent includes one or more of ethanol, acetone, and isopropanol.

[0088] In some embodiments, the acidic solvent includes one or more of phosphoric acid, acetic acid, hydrochloric acid, and nitric acid.

[0089] The second aspect of the present application provides a graphene film, which can be prepared by the preparation method described in the first aspect of the present application.

[0090] In some embodiments, see Figure 2 The graphene film includes a first graphene film 30 and a second graphene film 20 , the first graphene film 30 and the second graphene film 20 are alternately distributed, and the number of layers of the first graphene film 30 is greater than the number of layers of the second graphene film 20 .

[0091] In some embodiments, the number of layers of the first graphene film is greater than or equal to 2, and the number of layers of the second graphene film is equal to 1.

[0092] The third aspect of the present application provides an electronic device, comprising the graphene film described in the second aspect of the present application.

[0093] Example

[0094] The following are specific examples, which more specifically describe the contents disclosed in this application, and these examples are only for illustrative purposes, because it is obvious to those skilled in the art that various modifications and variations are made within the scope of the disclosure of this application. Unless otherwise stated, all parts, percentages, and ratios reported in the following examples are based on weight, and all reagents used in the examples are commercially available or synthesized according to conventional methods and can be used directly without further processing, and the instruments used in the examples are commercially available.

[0095] Example 1

[0096] Step 1: Clean the surface of the first base copper foil:

[0097] 1.1. Ultrasonic clean the 25 μm thick copper foil in acetone solution for 5 minutes;

[0098] 1.2. Then ultrasonically clean in water and acetic acid for 5 minutes each, and blow dry with nitrogen.

[0099] Step 2: Compounding the back surface of the first substrate with the second substrate

[0100] 2.1. The cleaned and dried copper foil was sputtered with a patterned tungsten film on the back of the copper foil substrate by magnetron sputtering. A pure tungsten target (99.95%) was used, and the patterned mask was placed between the copper foil and the target. The conditions for magnetron sputtering were: the sputtering pressure was 1×10 -2 mbar, Ar gas was used as the sputtering gas, and the thickness of the second substrate tungsten film after sputtering was 50 nm.

[0101] Step 3: Use CVD technology to grow patterned graphene film:

[0102] 3.1. Place the copper foil in a CVD furnace, introduce Ar and H2 gas at a flow rate of 500 sccm, raise the temperature to 1050°C and perform annealing for 30 minutes at atmospheric pressure.

[0103] 3.2. After annealing, a (CH4+Ar) mixed gas with a volume concentration of 0.5% is introduced at a flow rate of 5 sccm. The reaction time is 20 min. After the growth of the graphene film on the front side of the first substrate is completed, the temperature is rapidly cooled and the patterned graphene film is taken out of the CVD device.

[0104] Example 2

[0105] Step 1: Clean the surface of the first base copper foil:

[0106] 1.1. Ultrasonic clean the 25 μm thick copper foil in acetone solution for 5 minutes;

[0107] 1.2. Then ultrasonically clean in water and acetic acid for 5 minutes each, and blow dry with nitrogen.

[0108] Step 2: Compounding the back surface of the first substrate with the second substrate

[0109] 2.1. The cleaned and dried copper foil was sputtered with a patterned nickel film on the back of the copper foil substrate by magnetron sputtering. A pure nickel target (99.95%) was used, and the patterned mask was placed between the copper foil and the target. The conditions for magnetron sputtering were: the sputtering pressure was 1×10 -2 mbar, Ar gas was used as the sputtering gas, and the thickness of the second substrate nickel film after sputtering was 50 nm.

[0110] Step 3: Use CVD technology to grow patterned graphene film:

[0111] 3.1. Place the copper foil in a CVD furnace, introduce Ar and H2 gas at a flow rate of 500 sccm, raise the temperature to 1050°C and perform annealing for 30 minutes at atmospheric pressure.

[0112] 3.2. After annealing, a (CH4+Ar) mixed gas with a volume concentration of 0.5% is introduced at a flow rate of 5 sccm. The reaction time is 20 min. After the growth of the graphene film on the front side of the first substrate is completed, the temperature is rapidly cooled and the patterned graphene film is taken out of the CVD device.

[0113] The graphene obtained in Example 1 was transferred to the surface of a silicon wafer using a wet etching method and Raman characterization was performed. The test results are as follows: Figure 3~4 shown.

[0114] from Figure 3~4 It can be seen that on the front side of the first substrate facing the tungsten film of the second substrate, the I2D / IG of the graphene film grown is about 2, indicating that the graphene film grown in this area is mainly a single layer; while the I2D / IG of the graphene film grown in other areas on the front side of the copper foil of the first substrate is about 1, indicating that the graphene film grown in this area is mainly a double layer.

[0115] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described 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.

[0116] The above-mentioned embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the attached claims.

Claims

1. A method for preparing a graphene film, characterized in that: include: forming a patterned second substrate on a first surface of a first substrate, wherein the carbon solubility of the first substrate is less than the carbon solubility of the second substrate at the same temperature; forming a graphene film on a second surface of the first substrate, wherein the second surface and the first surface are respectively located on two opposite sides of the first substrate; The graphene film includes a first graphene film and a second graphene film, and the number of layers of the first graphene film is greater than the number of layers of the second graphene film; The first graphene film is distributed in a first area of ​​the second surface, the second graphene film is distributed in a second area of ​​the second surface, the second area is an orthographic projection area formed by the second substrate on the second surface, and the first area is a remaining area on the second surface outside the orthographic projection area.

2. The preparation method according to claim 1, characterized in that: There are a plurality of the second substrates and a plurality of the second graphene films, and there is a gap between two adjacent second substrates. The first graphene film is distributed in the region between two adjacent second graphene films.

3. The preparation method according to claim 1 or 2, characterized in that: One or more of the following conditions are met: (1) The material of the first substrate includes one or more of copper, nickel, tungsten, molybdenum, iron, cobalt, iridium, osmium, palladium, rhodium, platinum and gold, and copper may be selected; (2) the material of the second substrate includes one or more of copper, nickel, tungsten, molybdenum, iron, cobalt, iridium, osmium, palladium, rhodium, platinum and gold, and the solubility of the second substrate material in carbon is greater than the solubility of the first substrate material in carbon at the same temperature; Optionally, the material of the second substrate is tungsten and / or nickel; (3) The thickness of the first substrate is 10 μm to 100 μm; (4) The thickness of the second substrate is 20 nm to 50 μm; (5) The number of layers of the first graphene film is greater than or equal to 2, and the number of layers of the second graphene film is 1.

4. The preparation method according to claim 1 or 2, characterized in that: The step of forming a patterned second substrate on the first surface of the first substrate comprises: Attaching the patterned second substrate on the first surface; or forming the patterned second substrate on the first surface by plating; Optionally, the attaching method includes printing and / or heat pressing.

5. The preparation method according to claim 4, characterized in that: The step of forming the patterned second substrate by plating on the first surface comprises: Using a patterned photoresist or a patterned mask to cover the first surface, and forming the second substrate on the first surface by a patterned coating technology; Optionally, the patterned coating technology includes one or more of photolithography, mask coating, spray coating, and self-assembly, and can further be mask coating; Optionally, the coating method in the mask coating includes one or more of electroplating, chemical plating, magnetron sputtering, evaporation, chemical vapor deposition, thermal spraying and hot dip coating, and magnetron sputtering may be further selected.

6. The preparation method according to claim 1 or 2, characterized in that: The forming method of the first graphene film and the second graphene film comprises one of a chemical vapor deposition method and a plasma enhanced chemical vapor deposition method; Optionally, the formation process of the first graphene film and the second graphene film includes: The second substrate formed with the first substrate is placed in a chemical vapor deposition device or a plasma enhanced chemical vapor deposition device, a carbon source is introduced and heated in a protective atmosphere, so that carbon atoms are deposited on the first substrate, and after cooling, they grow into the first graphene film and the second graphene film respectively.

7. The preparation method according to claim 1 or 2, characterized in that: Before the step of forming a patterned second substrate on the first surface of the first substrate, the method further includes: Pre-treating the first substrate to remove impurities on the surface of the first substrate; Optionally, the preprocessing step includes one or more of the following: (1) cleaning the first substrate in a volatile organic solvent for 1 min to 10 min; Optionally, the volatile organic solvent includes one or more of ethanol, acetone and isopropanol; (2) washing the first substrate in deionized water for 1 min to 10 min; (3) cleaning the first substrate in an acidic solvent for 1 min to 10 min; Optionally, the acidic solvent includes one or more of phosphoric acid, acetic acid, hydrochloric acid and nitric acid.

8. A graphene film, characterized in that: It is prepared by the preparation method according to any one of claims 1 to 7.

9. The graphene film according to claim 8, characterized in that: The graphene film includes a first graphene film and a second graphene film, the first graphene film and the second graphene film are alternately distributed, and the number of layers of the first graphene film is greater than the number of layers of the second graphene film; Optionally, the number of layers of the first graphene film is greater than or equal to 2, and the number of layers of the second graphene film is equal to 1.

10. An electronic device, characterized in that: Comprising the graphene film as described in claim 8 or 9.

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