CN112746263B - Method for preparing few-layer graphene film through normal-pressure chemical vapor deposition - Google Patents
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- C23C16/00—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes
- C23C16/22—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the deposition of inorganic material, other than metallic material
- C23C16/26—Deposition of carbon only
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- C23C16/00—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes
- C23C16/02—Pretreatment of the material to be coated
- C23C16/0209—Pretreatment of the material to be coated by heating
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- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C16/00—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes
- C23C16/02—Pretreatment of the material to be coated
- C23C16/0227—Pretreatment of the material to be coated by cleaning or etching
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C16/00—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes
- C23C16/44—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the method of coating
Abstract
The invention discloses a method for preparing a few-layer graphene film by normal-pressure chemical vapor deposition, which comprises the following steps: cleaning the copper foil substrate; carrying out first annealing treatment on the copper foil; carrying out nitric acid solution treatment on the copper foil subjected to the first annealing; stacking an upper layer of copper foil and a lower layer of copper foil on a quartz plate in a clearance way, and carrying out secondary annealing treatment; growing graphene on the annealed copper foil; and cooling the graphene film to complete the preparation of the graphene film. According to the method, the copper foil substrate solution is pretreated and twice annealing is combined, impurities on the copper substrate are effectively removed to obtain a clean surface, a smooth copper surface is obtained by optimizing the loading mode of the copper foil substrate, the nucleation density is effectively reduced, and the graphene domain is enlarged. Compared with other methods, the method disclosed by the invention is simple and effective in process and low in cost, and the prepared graphene film has the advantages of uniform and controllable layer number, large area, high purity, high light transmittance and the like.
Description
Technical Field
The invention relates to a method for preparing a few-layer graphene film by normal-pressure chemical vapor deposition, belonging to the technical field of graphene preparation.
Background
Graphene is a hexagonal honeycomb two-dimensional carbon nanomaterial consisting of a single layer of carbon atoms, and has been paid attention to all over the world since the first time manchester university in the uk in 2004 was made of graphite. The unique structure of graphene enables the graphene to have a series of novel physical and chemical properties, and related applications of the graphene cover high-precision fields such as composite materials, heat conduction applications, new energy sources, sensors, health medical treatment, chemical catalysis, seawater desalination, functional coatings and the like, and the graphene is known as a novel material with the highest subversion in the 21 st century, and has a wide application prospect.
The preparation method of the graphene mainly comprises a mechanical stripping method, an oxidation-reduction method, a chemical vapor deposition method, an epitaxial growth method, a thermal expansion method, a solvent intercalation method, an electrochemical method and the like. The redox method is subjected to treatment by a strong oxidant and a reducing agent, so that a large number of defects exist in a product, and meanwhile, some surface functional groups remain, and the performance and subsequent application of graphene are influenced. The mechanical method for preparing graphene has high operation difficulty in the stripping process, and the mass production of graphene is difficult to realize. Compared with other methods, the Chemical Vapor Deposition (CVD) method has the advantages of good controllability, strong operability, more complete synthesized graphene structure and the like, and is the best choice for preparing large-area and high-quality graphene films at present.
The preparation of the graphene film by the CVD method is influenced by a plurality of conditions such as a carbon source, reaction temperature, a reaction substrate, environmental pressure and the like, and the appearance and the quality of the graphene film are directly influenced by the condition of the substrate; currently, the most widely used CVD process is copper metal substrates. Since the amount of carbon dissolved in a copper substrate at high temperature is very small, a uniform graphene film having a small number of layers can be generally prepared. Most of the existing CVD methods adopt a low-pressure CVD method to prepare graphene films, so that the preparation cost is high, the operation process is complex, and potential safety hazards exist; meanwhile, the graphene prepared on the copper substrate under low pressure has self-limitation property, and most of the obtained graphene is single-layer graphene; compared with single-layer graphene, the few-layer graphene has better conductivity and is mainly used for transparent conductive films. Therefore, the preparation of the double-layer or few-layer graphene has extremely important significance in the application of the semiconductor electronic field.
The cold rolling process of the copper foil manufacturing process introduces carbon contaminants during the mechanical processing of the foil, which is a problem even with high purity copper foils, and in addition, the surface layer copper of the copper foil continues to evaporate during the reaction process at high temperatures near the melting point to form a rough surface. The growth condition of graphene is greatly influenced by the surface state of the copper foil substrate, and generally, due to the influence of carbon impurities and flatness in the copper foil substrate, the prepared graphene film is poor in uniformity and continuity and has more defects, so that the overall performance is poor.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides the method for preparing the few-layer graphene film by normal-pressure chemical vapor deposition, the prepared graphene film has the advantages of stable and controllable layer number, high light transmittance, high purity, high quality and the like, and the preparation method provided by the invention is low in cost, simple in process and applicable to large-scale production.
In order to solve the technical problem, the invention provides a method for preparing a few-layer graphene film by normal-pressure chemical vapor deposition, which comprises the following steps:
cleaning the copper foil substrate;
carrying out first annealing treatment on the copper foil;
carrying out nitric acid solution treatment on the copper foil subjected to the first annealing;
stacking an upper layer of copper foil and a lower layer of copper foil on a quartz plate in a clearance way, and carrying out secondary annealing treatment;
growing graphene on the annealed copper foil;
and cooling the graphene film to complete the preparation of the graphene film.
Preferably, the method for cleaning the copper foil is as follows: and sequentially immersing the copper foil into acetone, isopropanol or ethanol and deionized water, and ultrasonically cleaning for 5-10 minutes.
Preferably, the method of the first annealing treatment is as follows: coating copper foil on Ar, H 2 Annealing in mixed gas at 700-900 ℃ for 10-30 minutes, Ar and H 2 The volume ratio of (1) to (10: 1); the flow rate of Ar is 100-1000 sccm; the reaction chamber is in a normal pressure state in the annealing process.
Preferably, the specific method for solution processing the copper foil after the first annealing comprises: taking out the copper foil subjected to the first annealing from the reaction chamber when the temperature is reduced to below 200 ℃, treating the copper foil in a nitric acid solution for 1-10 minutes, and ultrasonically cleaning the copper foil for 3 times by using deionized water in a dipping or ultrasonic mode; the mass fraction of the nitric acid is 5-20%.
Preferably, the method for stacking the two layers of copper foils in the gap comprises the following steps: and sequentially placing the two copper foils on a quartz plate with a thin-layer groove in the center, wherein the small-size copper foil is placed in the groove of the quartz plate, the large-size copper foil covers the groove on the quartz plate, and the distance between the two copper foils is 20-50 mu m.
Preferably, the second annealing treatment method comprises the following steps: placing a sample in a reactor, vacuumizing to below 10Pa, introducing Ar to normal pressure, keeping the normal pressure state, continuously introducing Ar, starting heating to the annealing temperature of 900-1050 ℃, mixing and introducing H when the temperature is between room temperature and 600 DEG C 2 And the annealing time is 30-90 minutes.
Preferably, the flow rate of Ar is 100-1000 sccm, and Ar and H 2 The ratio of (A) to (B) is 10: 1-2: 1.
Preferably, the method for graphene growth is as follows: introducing CH after annealing 4 And Ar, H 2 Growing the graphene at 900-1050 ℃ for 10-30 minutes.
Preferably, CH is introduced 4 The flow of the gas accounts for 0.1-2% of the total gas flow, and H 2 The flow rate is 0-30% of the total, and the flow rate of Ar is 200-1000 sccm.
Preferably, the method for cooling the graphene film is as follows: and in the cooling process, the temperature is reduced in Ar atmosphere, the Ar flow is 100-500 sccm, the cooling rate is more than 20 ℃/min, and the final temperature of the temperature reduction is room temperature.
The invention achieves the following beneficial effects:
(1) the copper foil is subjected to solution treatment and two annealing treatments, so that amorphous carbon pollutants in the copper foil are effectively reduced, a clean copper substrate is obtained, and the growth defects of the graphene film are reduced;
(2) the rough surface generated by copper evaporation at high temperature is effectively avoided by the placing mode of stacking two layers of copper foils at intervals, the evaporated copper can be deposited again, the copper surface is smoother in the high-temperature process for a long time, and the smooth inner surface is beneficial to lower nucleation density and larger graphene domain, so that a continuous, uniform and high-quality graphene film is obtained by growth;
(3) the number of layers of the graphene film is controlled by adjusting the introduction of hydrogen at different temperatures and adjusting the flow parameter of methane in the second annealing stage, so that the graphene film with uniform number of layers and stable performance is obtained;
(4) the raw materials are cheap and easy to obtain, other processes are completed under normal pressure except for initial stage vacuumizing, and the preparation method is simple and effective and has low cost;
(5) the graphene is prepared by chemical vapor deposition under normal pressure, the few-layer graphene film with controllable layer number can be obtained by regulating and controlling parameters in annealing and growth stages, the conductivity is better, and the graphene film can be used in the fields of scene tubes, flexible light-transmitting films and the like;
(6) the graphene film prepared by the method has few defects, high integrity and flatness, and is beneficial to subsequent film transfer.
Drawings
FIG. 1 is a flow chart of a method for preparing a high quality few-layer graphene film by atmospheric pressure chemical vapor deposition according to the present invention;
FIG. 2 is a schematic view of the gap stacking of two copper foils according to the present invention;
FIG. 3 is a comparison of a scanning electron micrograph of a copper foil after two anneals according to the method of the present invention and a conventional annealed copper foil;
fig. 4 is a raman spectrum of a single-layer, double-layer, three-layer graphene film prepared in an example of the present invention;
FIG. 5 is a graph comparing light transmittance of single-layer, double-layer, and three-layer graphene films transferred to a quartz substrate, prepared in examples of the present invention;
FIG. 6 is a scanning electron micrograph comparing copper-based graphene films prepared in example 1 and comparative example;
fig. 7 is a graph comparing light transmittance curves of the graphene films transferred to the quartz substrate prepared in example 1 and the comparative example.
Detailed Description
The present invention will be further described with reference to the following examples. The following examples are only for illustrating the technical solutions of the present invention more clearly, and the protection scope of the present invention is not limited thereby.
The invention provides a method for preparing a graphene film by normal-pressure chemical vapor deposition, which mainly comprises the following steps as shown in figure 1:
(1) cleaning the copper foil substrate;
(2) carrying out first annealing treatment on the copper foil;
(3) carrying out nitric acid solution treatment on the copper foil subjected to the first annealing;
(4) stacking an upper layer of copper foil and a lower layer of copper foil on a quartz plate in a clearance way, and carrying out secondary annealing treatment;
(5) growing graphene on the annealed copper foil;
(6) and cooling the graphene film to complete the preparation of the graphene film.
In the step (1), the copper foil is sequentially subjected to ultrasonic cleaning for 5 minutes by using acetone, ethanol or isopropanol and deionized water so as to remove industrial residual impurities, organic matters and the like on the surface of the copper foil.
In the step (2), when the copper foil is annealed for the first time, the copper substrate is placed in Ar and H 2 Annealing in mixed gas at 700-900 ℃ for 10-20 minutes, Ar and H 2 The volume ratio of (A) to (B) is controlled to be 10: 1-1: 1; the flow rate of Ar is 100-1000 sccm; the surface oxide of the copper foil can be removed in the primary annealing process, and carbon impurities in the copper foil introduced in the rolling process are precipitated, so that the subsequent removal is facilitated.
In the step (3), the copper foil after primary annealing is treated by a dilute nitric acid solution, and a proper treatment time can be selected by adopting a soaking or ultrasonic mode and combining the concentration of nitric acid; nitric acid, as a strong reactant and oxidant relative to other solutions, can remove many different types of impurities. And in the etching process, bubbles are generated to push away impurity particles, so that impurities deposited on the Cu surface layer are effectively removed.
In the step (4), the treated copper foils are dried by inert gas and flattened, and the two copper foils are sequentially placed on a customized quartz plate with a thin-layer groove in the center, as shown in fig. 2, wherein a small-size copper foil is placed in the groove of the quartz plate, a large-size copper foil covers the groove on the quartz plate, and the distance between the two copper foils is 5-20 μm; the copper evaporated at high temperature is redeposited on the copper surface by the way that two layers of copper foils are stacked with gaps, and the copper surface is processed at high temperature for a long timeThe graphene film is smoother, and the smooth inner surface is beneficial to lower nucleation density and larger graphene domain, so that the continuous, uniform and high-quality graphene film can be grown. Placing a sample in a reactor, vacuumizing to below 10Pa, introducing Ar to restore normal pressure, keeping the normal pressure state, continuously introducing Ar and starting heating to an annealing temperature; ar with the flow rate of 100-1000 sccm is mixed and introduced with H at a specific temperature (room temperature to 600℃) 2 Ar and H 2 The ratio of the annealing time to the annealing time is 10: 1-2: 1, the annealing temperature is 900-1050 ℃, and the annealing time is set to 30-90 minutes; the second annealing is to reform the surface of the copper foil after the carbon impurities are removed, the annealing process can level the surface of the copper, enlarge the grain size of the copper, reduce the nucleation density of the graphene, and regulate and control the growth layer number of the graphene film by controlling the temperature of the introduced hydrogen; this is due to the inevitable presence of oxygen in the furnace during APCVD when H is present 2 When the current is not opened, the copper foil surface layer can be covered by a thin oxide layer, the nucleation density of graphene growth can be reduced by oxygen, the higher the oxidation degree of the copper substrate is, and the fewer graphene layers are grown subsequently.
In the step (5), in Ar, H 2 Introducing CH into the mixed gas 4 Growing graphene, wherein the growth temperature is 900-1050 ℃, and the growth time is controlled to be 10-30 minutes; CH (CH) 4 The flow rate of the gas is 0.1-2% of the total gas flow rate, and H 2 The flow accounts for 0-20% of the total; ar flow is 200-1000 sccm; CH (CH) 4 The feeding is divided into two stages, the former stage is uniformly fed with a small flow, and after a certain time, the large flow is adjusted to be uniformly fed into the rest part.
In the step (6), the temperature is reduced in Ar atmosphere, the Ar flow is 100-500 sccm, the temperature reduction rate is more than 20 ℃/min, and the final temperature of the temperature reduction is room temperature. And the opposite surfaces of the two copper foils are the obtained graphene film.
FIG. 3 is a comparison of scanning electron micrographs of copper foil after two anneals by the method of the present invention and copper foil after conventional annealing, which shows that the pretreatment and copper substrate loading method of the present invention can effectively reduce the impurities of the copper foil during the graphene growth stage, and inhibit the surface layer formed by copper evaporation from being rough, resulting in a smooth and flat copper surface;
the method of the present invention is described below with reference to specific examples so that those skilled in the art can practice the method with reference to the description, but the present invention is not limited thereto.
Example 1
Adopting a 25-micron thick metal copper foil as a growth substrate; cutting a copper foil into two pieces with the sizes of 2cm multiplied by 2cm and 2.5cm multiplied by 2.5cm, sequentially placing the two pieces in acetone, ethanol and deionized water, and respectively cleaning for 10 minutes by an ultrasonic cleaning mode; blowing the copper foil with high-purity nitrogen, rolling and flattening, firstly, horizontally placing the small-size copper foil in a groove of a quartz plate (the groove is a square with the side length of 2.1cm and the depth of 50 mu m), and horizontally placing the large-size copper foil to cover the groove (namely, the large-size copper foil covers the small-size copper foil, and the parallel distance between the small-size copper foil and the large-size copper foil is about 25 mu m); putting the sample into a tube furnace, vacuumizing to below 10Pa, and introducing Ar and H with the flow rates of 200sccm and 40sccm respectively 2 The normal pressure in the quartz tube is recovered, the gas flow rate is kept unchanged, the copper foil is heated to 900 ℃ in the mixed gas, and the annealing is kept for 10 minutes; then naturally cooling to below 200 ℃. The copper foil is taken out and is placed in a 10% nitric acid solution to be soaked for 5 minutes, and then is washed for 3 times with deionized water, and each time lasts for 5 minutes. Blowing the copper foil to dry by using nitrogen, then putting the copper foil into a tubular furnace again, introducing Ar of 200sccm under the normal pressure condition, and starting to heat; starting to introduce 20sccm of H when the temperature is raised to 300 DEG C 2 Heating the copper foil to 1000 ℃ in mixed gas, and keeping annealing for 60 minutes; after the annealing is finished, the temperature is 1000 ℃ and Ar and H 2 Under the mixed atmosphere, firstly introducing 0.4sccmCH 4 Growth for 5 min, followed by CH 4 The flow rate is adjusted to 2sccm for 15 minutes, and CH is stopped being introduced after the growth is finished 4 Naturally cooling to room temperature in Ar 200sccm atmosphere; obtaining a uniform double-layer graphene film on the opposite surfaces of the two copper foils;
example 2
The copper foil was cleaned and annealed once in the manner as in example 1; the copper foil is taken out and placed in 5 percent nitric acid solution for 5 minutes of ultrasonic treatment, and then is washed for 3 times by deionized water. After the copper foils were blown dry with nitrogen and flattened, the two copper foils were placed on a quartz plate in sequence according to the method of example 1, and then placed in a tube furnace again, and 300sccm Ar and 4 were introduced under normal pressure and room temperature0sccmH 2 And starting to heat up; heating the copper foil to 1050 ℃ in the mixed gas, and keeping annealing for 50 minutes; after the annealing is finished, the temperature is reduced to 1000 ℃, and the temperature is 1000 ℃ and Ar and H 2 Under the mixed atmosphere, firstly introducing 1sccmCH 4 Growing for 5 minutes, and introducing 2sccm CH 4 Growing for 15 minutes, stopping introducing CH after the growth is finished 4 Naturally cooling to room temperature in Ar 300sccm atmosphere; obtaining 3-4 layers of graphene films on the opposite surfaces of the two copper foils;
example 3
The copper foil was cleaned in the manner of example 1; blowing the copper foil dry by high-purity nitrogen, putting the copper foil into a tube furnace, vacuumizing the tube furnace to be less than 10Pa, and introducing Ar and H with the flow rates of 200sccm and 100sccm respectively 2 The normal pressure in the quartz tube is recovered, the gas flow rate is kept unchanged, the copper foil is heated to 800 ℃ in the mixed gas, and the annealing is kept for 20 minutes; then naturally cooling to below 200 ℃. The copper foil is taken out and is placed in a 10% nitric acid solution to be soaked for 10 minutes, and then is washed for 3 times with deionized water, and each time lasts for 5 minutes. Drying and flattening the copper foil, placing the copper foil on a specific quartz plate according to the method in the embodiment 1, placing the quartz plate into the tubular furnace again, introducing Ar of 200sccm under the normal pressure condition, and starting to heat; starting to introduce 40sccm of H when the temperature is raised to 500 DEG C 2 Heating the copper foil to 1000 ℃ in mixed gas, and keeping annealing for 60 minutes; after the annealing is finished, the temperature is 1000 ℃ and Ar and H 2 Under the mixed atmosphere, firstly introducing 0.5 sccmCH 4 Growing for 5 minutes, and introducing 1sccm CH 4 Growing for 20 minutes, stopping introducing CH after the growth is finished 4 Rapidly cooling to room temperature in Ar 200sccm atmosphere at a cooling rate of 50 ℃/min; and obtaining the uniform single-layer graphene film on the opposite surfaces of the two copper foils.
FIG. 4 is a Raman spectrum of a single-layer, double-layer, or triple-layer graphene film prepared according to examples 1-3 of the present invention; as can be seen from FIG. 4, the samples of 3 groups all appeared to be located at 1580cm -1 Near G peak and 2700cm -1 The half-height width of the 2D peak is gradually increased along with the increase of the number of the graphene layers, and I is 2D /I G The ratio will gradually decrease. According to the ratio of the intensity of the 2D peak to the intensity of the G peak (I) 2D /I G ) And 2D peak position, full width at half maximum inferable stoneThe number of layers of graphene is single layer, double layer and three layer. The defects of the graphene can be reflected on the D peak of the Raman spectrum, and 3 samples are positioned at 1350cm -1 The nearby D peak is not obvious, and the ratio of the D peak to the G peak is small, which indicates that the prepared graphene film has high quality and few extra defects are introduced into crystal lattices.
Fig. 5 is a graph comparing light transmittance of single-layer, double-layer, and triple-layer graphene films prepared in examples 1 to 3 of the present invention transferred to a quartz substrate. The light transmittance of the graphene is limited by the number of layers and the defects, and is reduced along with the increase of the number of layers and the increase of the defect degree; the light transmittance of the single-layer graphene, the double-layer graphene and the three-layer graphene at the wavelength of 550nm respectively reaches 96.8%, 95.0% and 92.7%, the light transmittance is very close to the theoretical light transmittance of the corresponding layers of graphene, and the defects of the graphene film are few, namely the prepared graphene is high in cleanliness.
Comparative example 1
The preparation method is the same as that shown in the example 1, and is characterized in that a piece of copper foil is used, and the pretreatment does not adopt a secondary annealing mode; the specific operation process is as follows: cutting a copper foil into 2cm multiplied by 2cm, sequentially placing the copper foil in acetone, ethanol and deionized water, respectively cleaning for 10 minutes by an ultrasonic cleaning mode, soaking in a 10% nitric acid solution for 5 minutes, and cleaning for 3 times by deionized water; drying the copper foil with high-purity nitrogen, rolling and flattening, and placing the copper foil in a groove of a quartz plate and a tubular furnace. The subsequent experimental procedure was the same as in example 1.
Fig. 6 is a scanning electron micrograph of the copper-based graphene film prepared in example 1 and the comparative example, and it can be seen that the graphene sample prepared by the method of comparative example 1 has poor surface flatness, pits and white impurities are present, while the sample prepared by the method of example 1 has a flat and smooth surface; as can be seen from comparison of the transmittance curves of fig. 7, the transmittance of the graphene film prepared by the comparative example method is significantly reduced; the method shows that the surface roughness of the copper foil can be effectively reduced and surface impurities can be reduced by adopting a secondary annealing combined copper foil gap stacking loading mode, so that a smooth and clean surface is obtained, and a high-quality graphene film can be prepared.
The above description is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, several modifications and variations can be made without departing from the technical principle of the present invention, and these modifications and variations should also be regarded as the protection scope of the present invention.
Claims (6)
1. A method for preparing a few-layer graphene film by atmospheric pressure chemical vapor deposition is characterized by comprising the following steps:
cleaning the copper foil substrate;
carrying out first annealing treatment on the copper foil;
carrying out nitric acid solution treatment on the copper foil subjected to the first annealing;
stacking an upper layer of copper foil and a lower layer of copper foil on a quartz plate in a clearance way, and carrying out secondary annealing treatment; the method for stacking the two layers of copper foils in the gap comprises the following steps: sequentially placing two copper foils on a quartz plate with a thin-layer groove in the center, wherein a small-size copper foil is placed in the groove of the quartz plate, a large-size copper foil covers the groove on the quartz plate, and the distance between the two copper foils is 20-50 mu m; the second annealing treatment method comprises the following steps: placing a sample in a reactor, vacuumizing to below 10Pa, introducing Ar to normal pressure, keeping the normal pressure state, continuously introducing Ar, starting heating to the annealing temperature of 900-1050 ℃, mixing and introducing H when the temperature is between room temperature and 600 DEG C 2 The annealing time is 30-90 minutes;
carrying out graphene growth on the annealed copper foil, and introducing CH after annealing is finished 4 And Ar, H 2 Growing graphene at 900-1050 ℃ for 10-30 minutes, and introducing CH 4 The flow of the gas accounts for 0.1-2% of the total gas flow, and H 2 The flow accounts for 0-30% of the total, and the Ar flow is 200-1000 sccm;
and cooling the graphene film to complete the preparation of the graphene film.
2. The method for preparing the few-layer graphene film by atmospheric pressure chemical vapor deposition according to claim 1, wherein the method for cleaning the copper foil comprises the following steps: and sequentially immersing the copper foil into acetone, isopropanol or ethanol and deionized water, and ultrasonically cleaning for 5-10 minutes.
3. According to claimThe method for preparing the few-layer graphene film by the atmospheric pressure chemical vapor deposition, which is described in claim 1, is characterized in that the first annealing treatment method comprises the following steps: coating copper foil on Ar, H 2 Annealing in mixed gas at 700-900 ℃ for 10-30 minutes, Ar and H 2 The volume ratio of (1) to (10: 1); the flow rate of Ar is 100-1000 sccm; the reaction chamber is in a normal pressure state in the annealing process.
4. The method for preparing the few-layer graphene film by atmospheric pressure chemical vapor deposition according to claim 1, wherein the specific method for solution-processing the copper foil after the first annealing comprises: taking out the copper foil subjected to the first annealing from the reaction chamber when the temperature is reduced to below 200 ℃, treating the copper foil in a nitric acid solution for 1-10 minutes, and ultrasonically cleaning the copper foil for 3 times by using deionized water in a dipping or ultrasonic mode; the mass fraction of the nitric acid is 5-20%.
5. The method of claim 1, wherein the flow rate of Ar is 100-1000 sccm, and Ar and H are mixed in the atmosphere of H 2 The ratio of (A) to (B) is 10: 1-2: 1.
6. The method for preparing the few-layer graphene film by atmospheric pressure chemical vapor deposition according to claim 1, wherein the method for cooling the graphene film comprises the following steps: and in the cooling process, the temperature is reduced in Ar atmosphere, the Ar flow is 100-500 sccm, the cooling rate is more than 20 ℃/min, and the final temperature of the temperature reduction is room temperature.
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