阅读说明：本技术 一种洁净双层及少层石墨烯薄膜及其制备方法 (Clean double-layer and few-layer graphene film and preparation method thereof ) 是由 刘忠范 彭海琳 张金灿 高欣 张孟奇 刘晓婷 张月新 李广亮 于 2020-05-13 设计创作，主要内容包括：本发明提供一种洁净双层及少层石墨烯薄膜及其制备方法,该制备方法包括：将基底置于含第一氧化气体的气氛中进行退火；将退火后的所述基底置于含还原气体、碳源以及第二氧化气体的反应混合气中,升温至生长温度进行石墨烯生长,得到洁净双层及少层石墨烯薄膜,其中所述还原气体、所述碳源以及所述第二氧化气体的流量比为1～2000:0.1～20:0.1～500。本发明的制备方法快速、简便、适于制备大面积双层及少层洁净石墨烯薄膜,提高了石墨烯薄膜的质量,同时成本低廉,具有良好的工业化前景。(The invention provides a clean double-layer and few-layer graphene film and a preparation method thereof, wherein the preparation method comprises the following steps: annealing the substrate in an atmosphere comprising a first oxidizing gas; and placing the annealed substrate in a reaction mixed gas containing a reducing gas, a carbon source and a second oxidizing gas, and heating to a growth temperature to grow graphene to obtain a clean double-layer and few-layer graphene film, wherein the flow ratio of the reducing gas to the carbon source to the second oxidizing gas is 1-2000: 0.1-20: 0.1-500. The preparation method is rapid, simple and convenient, is suitable for preparing large-area double-layer and few-layer clean graphene films, improves the quality of the graphene films, and has low cost and good industrialization prospect.)

1. A method for preparing a clean double-layer and few-layer graphene film is characterized by comprising the following steps:

annealing the substrate in an atmosphere comprising a first oxidizing gas;

and placing the annealed substrate in a reaction mixed gas containing a reducing gas, a carbon source and a second oxidizing gas, and heating to a growth temperature to grow graphene to obtain a clean double-layer and few-layer graphene film, wherein the flow ratio of the reducing gas to the carbon source to the second oxidizing gas is 1-2000: 0.1-20: 0.1-500.

2. The method of claim 1, further comprising, prior to the annealing, heating the substrate to the growth temperature in an atmosphere comprising a third oxidizing gas.

3. The method of claim 2, wherein the first oxidizing gas, the second oxidizing gas, and the third oxidizing gas are each independently selected from one or more of carbon dioxide, water vapor, and oxygen.

4. The method according to claim 1, wherein the reducing gas is hydrogen or a mixture of hydrogen and argon.

5. The method of claim 1, wherein the carbon source is selected from one or more of alkanes, alkynes, nitrogen-containing organics, alcohols, and aldehydes.

6. The method according to claim 5, wherein the carbon source is one or more selected from the group consisting of methane, ethane, acetylene, acetonitrile, ethanol, formaldehyde, and pyridine.

7. The method according to claim 1, wherein the annealing time is 5 to 120min and the temperature is 800 to 1100 ℃.

8. The preparation method according to claim 1, wherein the growth temperature is 950 ℃ to 1050 ℃, and the time for the graphene to grow is 1min to 150 min.

9. A clean bilayer and few-layer graphene film, wherein said clean bilayer and few-layer graphene film is prepared by the method of any one of claims 1 to 8.

10. The clean bi-layer and few-layer graphene film according to claim 9, wherein the number of layers of the clean bi-layer and few-layer graphene film is 2-5, the area ratio of the bi-layer and few-layer graphene film is greater than 20%, and the clean area of the clean bi-layer and few-layer graphene film is greater than 90%.

Technical Field

The invention relates to the field of graphene, in particular to a double-layer and few-layer clean graphene film and a preparation method thereof.

Background

The graphene film, as a two-dimensional atomic crystal, has very excellent properties, such as ultrahigh carrier mobility, high thermal conductivity, high mechanical strength, and the like. The number of layers of the graphene film and the content of surface pollutants influence the exertion of excellent properties of the graphene film. Compared with a single-layer graphene film, the double-layer graphene film and the few-layer graphene film have higher conductivity and mechanical strength and better repairability. The method can be used for constructing electronic devices or used as a transmission electron microscope carrier net. The graphene film with a high clean area ratio has a great potential in the aspect of surface interface construction, such as being used as a buffer layer of an epitaxial growth semiconductor film, and improving the luminous efficiency of an organic light-emitting transistor.

The clean graphene film refers to a graphene product prepared by inhibiting side reactions during the high-temperature growth of the graphene film so as to avoid the generation of surface pollutants. By means of the instrument characterization of high spatial resolution such as a transmission electron microscope, an atomic force microscope and the like, the surface pollutant content of the clean graphene film can be obviously reduced greatly, namely the area ratio of the clean pollution-free graphene film area is greatly increased.

The existing method for preparing the double-layer and few-layer graphene film mainly comprises the steps of adjusting the structure of a copper foil substrate, changing the hydrogen/methane ratio, adopting a copper-nickel alloy as the substrate and the like, but the preparation methods have the defects of slow growth speed of the graphene film, high production cost, low growth quality, unsatisfactory intrinsic cleanliness of a sample, possibility of introducing impurities to be adsorbed on the wall of a reactor and difficulty in removing the impurities, and difficulty in ensuring the stable and controllable preparation of the large-area and uniform double-layer and few-layer graphene film.

It is noted that the information disclosed in the foregoing background section is only for enhancement of background understanding of the invention and therefore it may contain information that does not constitute prior art that is already known to a person of ordinary skill in the art.

Disclosure of Invention

The invention aims to overcome the defects of the prior art, and provides a preparation method of a clean double-layer and few-layer graphene film, which can simultaneously realize layer number control and surface cleanliness improvement of the graphene film.

In order to achieve the purpose, the invention adopts the following technical scheme:

a method for preparing a clean bilayer and few-layer graphene film comprises the following steps:

annealing the substrate in an atmosphere comprising a first oxidizing gas;

and placing the annealed substrate in a reaction mixed gas containing a reducing gas, a carbon source and a second oxidizing gas, and heating to a growth temperature to grow graphene to obtain a clean double-layer and few-layer graphene film, wherein the flow ratio of the reducing gas to the carbon source to the second oxidizing gas is 1-2000: 0.1-20: 0.1-500.

In some embodiments, before the annealing treatment, the method further comprises placing the substrate in an atmosphere containing a third oxidizing gas, and raising the temperature to the growth temperature.

In some embodiments, the first oxidizing gas, the second oxidizing gas, and the third oxidizing gas are each independently selected from one or more of carbon dioxide, water vapor, and oxygen.

In some embodiments, the reducing gas is hydrogen or a mixture of hydrogen and argon.

In some embodiments, the carbon source is selected from one or more of alkanes, alkynes, nitrogen-containing organics, alcohols, and aldehydes.

In some embodiments, the carbon source is selected from one or more of methane, ethane, acetylene, acetonitrile, ethanol, formaldehyde, and pyridine.

In some embodiments, the annealing time is 5min to 120min and the temperature is 800 ℃ to 1100 ℃.

In some embodiments, the growth temperature is 950 ℃ to 1050 ℃, and the time for growing the graphene is 1min to 150 min.

In another aspect, the invention further provides a clean bilayer and few-layer graphene film, which is prepared by the method.

In some embodiments, the number of layers of the clean double-layer and few-layer graphene film is 2-5, the area ratio of the double-layer and few-layer graphene film is greater than 20%, and the clean area of the clean graphene film is greater than 90%.

The preparation method is rapid, simple and convenient, is suitable for preparing large-area double-layer and few-layer clean graphene films, improves the quality of the graphene films, and has low cost and good industrialization prospect.

Drawings

Fig. 1 shows a scanning electron microscope image of double-and few-layer graphene of example 1 of the present invention.

Figure 2 shows an optical microscope image of clean bilayer and few layer graphene of example 2 of the present invention.

Figure 3 shows a transmission electron microscope image of clean bilayer and few layer graphene of example 2 of the present invention.

Fig. 4 shows a scanning electron microscope image of the surface-contaminated graphene of comparative example 1 of the present invention.

Fig. 5 shows a transmission electron microscope image of the surface-contaminated graphene of comparative example 1 of the present invention.

Figure 6 shows scanning electron microscope images before and after processing in a manner of statistical coverage of the present invention.

Detailed Description

The following presents various embodiments or examples in order to enable those skilled in the art to practice the invention with reference to the description herein. These are, of course, merely examples and are not intended to limit the invention. The endpoints of the ranges and any values disclosed in the present application are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to yield one or more new ranges of values, which ranges of values should be considered as specifically disclosed herein.

The invention provides a preparation method of a clean double-layer and few-layer graphene film, which comprises the following steps:

annealing the substrate in an atmosphere comprising a first oxidizing gas;

and placing the annealed substrate in a reaction mixed gas containing a reducing gas, a carbon source and a second oxidizing gas, and heating to a growth temperature to grow graphene to obtain a clean double-layer and few-layer graphene film, wherein the flow ratio of the reducing gas, the carbon source and the second oxidizing gas is 1-2000: 0.1-20: 0.1-500.

Before the annealing treatment, the substrate can be placed in an atmosphere containing a third oxidizing gas, the temperature is raised to the growth temperature, and then the annealing treatment is carried out.

The oxidizing gas introduced during the heating and annealing treatment is used for removing the pollutants on the surface of the substrate and flattening the surface of the substrate, and the substrate can be a foil or a thin film of a common graphene growth substrate such as copper, nickel, copper-nickel alloy, gold, platinum and the like.

In the annealing process, the substrate is placed on a carrier and placed in a high-temperature furnace, a first oxidizing gas is introduced for annealing, so that organic matters (existing forms comprise skin grease, antirust oil, lubricating oil and the like) attached to the surface of the copper foil are oxidized, decomposed or desorbed, the substrate is flattened, and the growth quality of the graphene film is improved. It should be noted that this step can also be performed by using conventional electrochemical etching, electrochemical polishing, chemical etching, mechanochemical polishing, etc. to achieve the planarization and cleaning of the substrate surface. Among them, the high temperature furnace may be a tube furnace, but the present invention is not limited thereto.

The temperature of the annealing treatment is 800 to 1100 ℃, preferably 950 to 1050 ℃. Too high a temperature increases the cost and the amount of volatilization of the copper foil substrate, and too low a temperature is liable to incomplete annealing. Generally, the annealing time is determined according to the annealing temperature, and is 5 to 120min, preferably 10 to 60 min.

In the production method of the present invention, the first oxidizing gas, the second oxidizing gas, and the third oxidizing gas may be the same or different and each is independently selected from one or more of carbon dioxide, water vapor, and oxygen. The same oxidizing gas is adopted, so that the controllability of the process can be improved, the cross contamination of the system is avoided, and meanwhile, the production efficiency is expected to be improved and the cost is reduced.

The atmosphere containing the first oxidizing gas may further include one or more of a reducing gas and an inert gas to effectively protect the substrate during the annealing process, and similarly, the atmosphere containing the third oxidizing gas may also include one or more of a reducing gas and an inert gas, and the atmosphere containing the second oxidizing gas may further include an inert gas.

And after annealing treatment, introducing reaction mixed gas containing reducing gas, a carbon source and second oxidizing gas into the reaction furnace, and heating to the growth temperature to grow graphene, so that the clean double-layer and few-layer graphene film can be obtained.

The reducing gas in the reaction mixed gas is selected from hydrogen, hydrogen-argon mixed gas and the like, the carbon source is selected from one or more of alkane, alkyne, alcohol, aldehyde and nitrogen-containing organic matter, for example, one or more of methane, ethane, acetylene, ethanol and formaldehyde, and also can be selected from nitrogen-containing liquid carbon sources such as acetonitrile, pyridine and the like or other carbon-containing solid carbon sources. By using the reducing gas, the carbon source and the second oxidizing gas as reaction mixed gas, the graphene film with the coverage degree of more than 95% can be obtained within a preset growth time.

The growth time of the graphene is not suitable to be too long or too short, and generally, the growth time can be 1min to 150min, preferably 10min to 90 min. When the time is too short, a double-layer or few-layer graphene film with high coverage can not be obtained, and when the time is too long, the time is long, so that the resource waste is caused.

The growth temperature of the graphene is 950-1050 ℃, the growth rate is slow when the temperature is too low, the efficiency is low, and the copper foil is melted when the temperature is too high.

In the graphene growth process, the total flow of the carbon source is 1sccm to 20sccm, the total flow of the inert gas is 0sccm to 2000sccm, the flow of the reducing gas is 50sccm to 2000sccm, and the total flow of the oxidizing gas is 0.1sccm to 500 sccm.

The grown clean double-layer and few-layer graphene film can be placed in one or more gas environments of reducing gas, growth gas and inert gas for cooling, and a vacuum environment can be selected, so that the compatibility is good.

In the process of reducing the temperature of the graphene, the atmosphere can be the same as the carrier gas in the growth process, or reducing gas is used for preventing the copper foil from being oxidized, the total flow of the reducing gas is 10-2000 sccm,

in the annealing, growing and cooling processes, the pressure in the reactor is 10 Pa-101.325 kPa, preferably 100 Pa-2000 Pa.

Due to the fact that reducing gas, a carbon source and second oxidizing gas are added in the growing process, due to the special etching effect of the second oxidizing gas, the graphene film with 2 layers or more can be grown under the process condition that only single-layer graphene can grow, the number of layers of the clean double-layer graphene film and the clean few-layer graphene film prepared by the method can be 2-5, the proportion of the area of the double-layer graphene film and the clean few-layer graphene film to the total area of the film is more than 20%, the area ratio of the clean area is more than 90%, even can reach 99%, and batch preparation can be achieved at the same time.

In a word, the preparation method is quick, simple and convenient, is suitable for preparing large-area double-layer and few-layer clean graphene films, improves the quality of the graphene films, and has low cost and good industrial prospect.

The invention will be further illustrated by the following examples, but is not to be construed as being limited thereto. The method is a conventional method unless otherwise specified. The starting materials are commercially available from the open literature unless otherwise specified.

Examples

Example 1

Placing ordinary commercially available copper foil (purchased from electronics, Inc. of Kunshan, Lu, Ltd.) along with a carrier into a tube furnace, introducing 500sccm CO₂Raising the temperature from room temperature to 1000 ℃ within 50min, and then annealing at the temperature for 10min to oxidize, decompose and desorb organic matters attached to the surface of the copper foil.

Introducing 1000sccm hydrogen, 10sccm methane and 35sccm carbon dioxide into the tubular furnace under the condition of keeping the temperature unchanged, adjusting the pressure to 1200Pa, growing for 20min to obtain the double-layer and few-layer graphene film with 2-5 layers, and then cooling to room temperature in a hydrogen atmosphere.

The obtained overall coverage of the sample is 20-40%, the scanning electron microscope image of the sample is shown in figure 1, the area with shallow contrast in the figure is single-layer graphene, the deeper the contrast is, the thicker the number of layers of graphene is, the coverage is calculated to be about 23.2% by the figure, the statistical mode is the area of double-layer and few-layer graphene/the total area of a single scanning electron microscope image, the specific mode of coverage statistics is shown in figure 6, the area with deep contrast is marked and dyed, and then image statistical software is used for counting the area ratio of the dyed area.

Example 2

Placing ordinary commercially available copper foil (purchased from electronics, Inc. of Kunshan, Lu, Ltd.) along with a carrier into a tube furnace, introducing 500sccm CO₂Raising the temperature from room temperature to 1000 ℃ within 50min, and then annealing at the temperature for 10min to oxidize, decompose and desorb organic matters attached to the surface of the copper foil.

And introducing 500sccm hydrogen, 10sccm methane and 55sccm carbon dioxide into the tubular furnace under the condition of keeping the temperature unchanged, adjusting the pressure to 1200Pa, growing for 20min to obtain the double-layer and few-layer graphene film with 2-5 layers, and cooling to room temperature in a hydrogen atmosphere.

Typical optical microscopy images of bi-layer and few-layer graphene films are shown in fig. 2, with both bi-layer and few-layer regions in the image.

The tem image of the bi-layer and few-layer graphene thin film is shown in fig. 3, where the regular areas are clean areas and the net-like or dot-like amorphous carbon contaminants, and the statistics of the image show that the ratio of the clean areas to the bi-layer and few-layer clean graphene thin film is 94.9%.

Example 3

Placing ordinary commercially available copper foil (purchased from electronics, Inc. of Kunshan, Lu, Ltd.) along with a carrier into a tube furnace, introducing 500sccm CO₂Raising the temperature from room temperature to 1050 ℃ within 50min, and then annealing at the temperature for 10min to oxidize, decompose and desorb organic matters attached to the surface of the copper foil.

And introducing 500sccm hydrogen, 10sccm methane and 35sccm carbon dioxide into the tubular furnace under the condition of keeping the temperature unchanged, adjusting the pressure to 1200Pa, growing for 20min to obtain the double-layer and few-layer graphene film with 2-5 layers, and cooling to room temperature in a hydrogen atmosphere.

The coverage of the bi-layer and few-layer graphene in this sample is between about 85-100%.

Example 4

Placing ordinary commercially available copper foil (purchased from electronics, Inc. of Kunshan, Lu, Ltd.) along with a carrier into a tube furnace, introducing 500sccm CO₂Raising the temperature from room temperature to 1000 ℃ within 50min, and then annealing at the temperature for 10min to oxidize, decompose and desorb organic matters attached to the surface of the copper foil.

And introducing 500sccm hydrogen, 10sccm methane and 30sccm carbon dioxide into the tubular furnace under the condition of keeping the temperature unchanged, adjusting the pressure to 10000Pa, growing for 20min to obtain the double-layer and few-layer graphene film with 2-5 layers, and cooling to room temperature in a hydrogen atmosphere.

The coverage of the bi-layer and few-layer graphene in this sample is between about 85-100%.

Comparative example 1

Common commercially available copper foil (purchased from electronics, Inc. of Kunshan, Lu, Ltd.) was used as a copper foil by electrochemical methodAfter polishing, the mixture is put into a tube furnace along with a carrier, and 500sccm H is introduced₂The temperature was raised from room temperature to 1000 ℃ within 50min, followed by annealing at this temperature for 10 min.

And introducing 500sccm hydrogen and 10sccm methane into the tubular furnace under the condition of keeping the temperature unchanged, adjusting the pressure to 1200Pa, growing for 20min to obtain the graphene film, and then cooling to room temperature in a hydrogen atmosphere.

The scanning electron microscope image of the graphene film is shown in fig. 4, from which it can be observed that the whole picture is substantially single-layer graphene.

As shown in fig. 5, the regular areas are clean areas, and the reticular or dotted amorphous carbon contaminants are counted as 30.2% clean area ratio of the graphene thin film.

It should be noted by those skilled in the art that the described embodiments of the present invention are merely exemplary and that various other substitutions, alterations, and modifications may be made within the scope of the present invention. Accordingly, the present invention is not limited to the above-described embodiments, but is only limited by the claims.