Preparation method of single crystal graphene
By forming an oxide layer on the surface of the polycrystalline copper foil and using methane gas to perform chemical vapor deposition in the confined space, the problem of difficulty in large-scale preparation of high-quality single crystal graphene in the prior art is solved, and large-scale and controllable single crystal graphene growth is achieved, which simplifies the process flow and reduces costs.
Patent Information
- Application Number
- CN202510021033.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-01-07
- Publication Date
- 2025-05-02
AI Technical Summary
The prior art is difficult to prepare high-quality single crystal graphene on a large scale, and the process flow is complex and the cost is high.
By forming an oxide layer on the surface of the polycrystalline copper foil and performing chemical vapor deposition using methane gas in a confined space, the atmosphere and temperature conditions are controlled to achieve the growth of large-sized single crystal graphene.
Large-scale and controllable growth of large-sized single-crystal graphene is achieved, avoiding the high cost of single-crystal copper foil, and simplifying the process flow.
Smart Images
Figure CN119913606A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of graphene, and specifically provides a method for preparing single-crystal graphene. Background Art
[0002] Graphene is a two-dimensional material with a honeycomb structure formed by the periodic arrangement of sp2 hybridized carbon atoms. It has extremely excellent mechanical, thermal and electrical properties (Young's modulus is as high as 1060GPa, thermal conductivity is as high as 5000Wm －1 K －1 , carrier mobility up to 200000cm 2 V －1 s －1 ). There are generally three methods for preparing graphene, namely mechanical exfoliation, redox, and chemical vapor deposition. Mechanically exfoliated graphene has fewer defects and higher mobility, making it very suitable for use in the field of electronics, but this method cannot be used to prepare graphene on a large scale; the redox method can prepare graphene in batches, but graphene has many defects and can only be used in catalysis, energy storage and other fields; the chemical vapor deposition method balances the advantages and disadvantages of the above two methods, with a large output of graphene. By controlling the growth process, high-quality graphene can be prepared, and the carrier mobility value can meet the requirements of electronic devices.
[0003] In order to further improve the carrier mobility of graphene prepared by chemical vapor deposition, in addition to reducing its point defects, its grain boundaries should also be reduced because grain boundaries have a strong scattering effect on electrons. Reducing grain boundaries is to prepare single-crystalline graphene. There are two main paths: (1) growing graphene on the surface of single-crystalline copper foil. The copper atoms on the surface of single-crystalline copper foil have the same lattice orientation. When graphene grows on it, even if the nucleation density is very high, because they have the same orientation, they will eventually be perfectly spliced together without forming grain boundaries, thus preparing single-crystalline graphene; (2) suppressing the nucleation density of graphene on the surface of polycrystalline copper foil. Graphene grown on polycrystalline copper foil has multiple atomic orientations. After the nucleation points grow and meet, they have different orientations and thus form grain boundaries. Therefore, large-sized single-crystalline graphene can only be prepared by reducing the nucleation density of graphene. However, single-crystalline copper foil is relatively expensive, and the surface of polycrystalline copper foil mainly suppresses the nucleation density of graphene by increasing the partial pressure of hydrogen or oxygen. The process flow requirements are strict, and both are not suitable for large-scale preparation of single-crystalline graphene. Summary of the invention
[0004] The purpose of the present invention is to provide a simple and controllable method for preparing single-crystal graphene, which can grow large-sized single-crystal graphene at a high rate through simple oxidation and confined space formation steps.
[0005] The technical solution of the present invention is:
[0006] A method for preparing single-crystal graphene is provided, comprising the following steps:
[0007] Step 1: Oxidize the metal foil in the atmosphere to form an oxide layer on the surface of the metal foil. The number of oxygen atoms provided by the oxide layer per square millimeter is 2.5*10 14 ~5*10 15 indivual;
[0008] Step 2: placing the metal foil in a graphene growth container, and placing the graphene growth container in an atmosphere heating furnace; the graphene growth container is a closed container, and has an air inlet and an air outlet, and the atmosphere in the atmosphere heating furnace can flow through the inner cavity of the graphene growth container through the air inlet and the air outlet; the total opening area of the air inlet and the total opening area of the air outlet are both 0.0075mm 2 ~0.19mm 2 ;
[0009] Step 3, the atmosphere heating furnace is first evacuated, and then argon and hydrogen are introduced as protective gases for heating;
[0010] Step 4, after the atmosphere heating furnace is heated to a preset temperature, methane gas is introduced under the condition of maintaining argon and hydrogen as protective gases, and the methane flow rate is 0.1 sccm to 10 sccm;
[0011] Step 5: maintaining the methane gas introduction time for 30 s to 30 min, ending the heating and the introduction of methane gas, and stopping the introduction of the protective gas after naturally cooling to room temperature, thereby completing the preparation of single-crystalline graphene.
[0012] The purpose of setting up a graphene growth container is, firstly, to limit the methane in the atmosphere heating furnace from entering the inner cavity of the graphene growth container, thereby reducing the methane concentration on the surface of the metal foil, thereby inhibiting the nucleation density of graphene, which is beneficial to the growth of single-crystal graphene; secondly, to limit the speed at which oxygen atoms are extracted by the vacuum pump, so that the inner cavity of the graphene growth container maintains a high oxygen atom concentration, catalyzes the decomposition of methane, and improves the efficiency of graphene preparation. The principle of selecting the total opening area is to balance the nucleation density and growth rate of graphene. If the opening area is too small, too little methane will be introduced into the inner cavity of the graphene growth container, and the oxygen atom concentration will be too high. After the graphene nucleates, it will be difficult to grow rapidly, and it will be etched by excessive oxygen atoms, making it difficult to prepare graphene. If the opening area is too large, too much methane will be introduced into the inner cavity of the graphene growth container, and the oxygen atom concentration will be too low, resulting in too high graphene nucleation density, and polycrystalline rather than single-crystalline graphene will be prepared. Only when the opening area is appropriate and the methane and oxygen atom concentrations match, will the graphene have a lower nucleation density and grow rapidly after nucleation, and the oxygen atoms will not have a significant etching effect on the nucleated graphene, but will only be beneficial to catalyze the decomposition of methane and accelerate the growth rate of graphene.
[0013] Further, the vacuuming parameters in step 3 are: vacuuming to less than 10 ～1 Pa, introduce argon and hydrogen mixed gas as protective gas, and the gas pressure is maintained between 1Pa and normal pressure.
[0014] Furthermore, the preset temperature of heating in step 4 is 1000° C. to 1075° C. Furthermore, the heating rate of heating is 10° C. / min to 50° C. / min.
[0015] Furthermore, the introduction time of methane gas is 30s to 10min.
[0016] Furthermore, the metal foil is copper foil.
[0017] Furthermore, the heating temperature for forming the oxide layer in step 1 is 50° C. to 400° C., and the heating time is 5 min to 300 min. Furthermore, the oxide layer has a thickness of 5 nm to 100 nm.
[0018] The single crystal graphene formed by the present invention is square and has a size of 0.1 mm 2 ~100mm 2 , the growth rate is 0.01mm 2 / min~10mm 2 / min.
[0019] The advantages and beneficial effects of the present invention are:
[0020] 1. Large-sized single-crystalline graphene can be prepared using polycrystalline copper foil, avoiding the expensive problem of single-crystalline copper foil.
[0021] 2. The copper foil can be used in the experiment after being simply wiped with alcohol, avoiding tedious steps such as ultrasonic cleaning, pickling, and electrolytic polishing.
[0022] 3. The oxidation and confined space formation steps are simple to operate and have good repeatability, can stably grow single-crystalline graphene, and are easy to carry out large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS
[0023] Figure 1 This is an optical photograph of large-scale single-crystal graphene;
[0024] Figure 2 This is the Raman spectrum curve of large-size single-crystal graphene; DETAILED DESCRIPTION
[0025] The disclosed examples will be more fully described with reference to the accompanying drawings, in which some (but not all) of the disclosed examples are shown. In fact, many different examples may be described and these examples should not be construed as limited to the examples set forth herein. Instead, these examples are described so that this disclosure will be thorough and complete and will fully convey the scope of the disclosure to those skilled in the art.
[0026] Example 1
[0027] 1. The copper foil is oxidized in the atmosphere at a heating temperature of 50°C for 5 minutes. The thickness of the oxide layer is 5nm and the number of oxygen atoms provided per square millimeter is 2.5*10 14 indivual.
[0028] 2. Place the oxidized copper foil in the graphene growth container, and the total opening area of the air inlet and the total opening area of the air outlet are both 0.19mm 2 .
[0029] 3. (1) Place the graphene growth container in an atmosphere heating furnace, and evacuate the atmosphere heating furnace to a vacuum of less than 10 － 1 Pa, and then introduce a mixture of argon and hydrogen as a protective gas, and the gas pressure is maintained at 1 Pa; (2) the copper foil is heated to 1000°C, and the heating rate is 10°C / min; (3) after reaching the temperature, methane gas is introduced with a methane flow rate of 0.1sccm for 20min; (4) after the growth is completed, the heating power is turned off, the methane gas is stopped, and the copper foil is naturally cooled to room temperature, and large-sized single-crystalline graphene is grown on both sides of the copper foil.
[0030] Single crystal graphene is square and has a size of 0.2 mm 2 , the growth rate is 0.01mm 2 / min.
[0031] Example 2
[0032] 1. The copper foil is oxidized in the atmosphere at a heating temperature of 150°C for 100 minutes. The thickness of the oxide layer formed is 30nm, and the number of oxygen atoms provided per square millimeter is 1.5*10 15 indivual.
[0033] 2. Place the oxidized copper foil in the graphene growth container, and the total opening area of the air inlet and the total opening area of the air outlet are both 0.1mm 2 .
[0034] 3. (1) Place the graphene growth container in an atmosphere heating furnace, and evacuate the atmosphere heating furnace to a vacuum of less than 10 － 1Pa, and then introduce a mixture of argon and hydrogen as a protective gas, and the gas pressure is maintained at 2000 Pa; (2) heat the copper foil to 1030°C, and the heating rate is 35°C / min; (3) after reaching the temperature, introduce methane gas with a methane flow rate of 1 sccm for 30 min; (4) after the growth is completed, turn off the heating power, stop introducing methane gas, and naturally cool to room temperature, large-sized single-crystalline graphene will grow on both sides of the copper foil.
[0035] Single crystal graphene is square and measures 60mm 2 , the growth rate is 2mm 2 / min.
[0036] Example 3
[0037] 1. The copper foil is oxidized in the atmosphere at a heating temperature of 250°C for 200 minutes. The thickness of the oxide layer formed is 50nm, and the number of oxygen atoms provided per square millimeter is 2.5*10 15 indivual.
[0038] 2. Place the oxidized copper foil in the graphene growth container, and the total opening area of the air inlet and the total opening area of the air outlet are both 0.04mm 2 .
[0039] 3. (1) Place the graphene growth container in an atmosphere heating furnace, and evacuate the atmosphere heating furnace to a vacuum of less than 10 － 1 Pa, and then introduce argon and hydrogen mixed gas as protective gas, and the gas pressure is maintained at 1*10 4 Pa; (2) heating the copper foil to 1050°C at a heating rate of 20°C / min; (3) after reaching the temperature, introducing methane gas at a methane flow rate of 5 sccm for 10 min; (4) after the growth is completed, turning off the heating power supply, stopping the introduction of methane gas, and cooling naturally to room temperature, large-sized single-crystalline graphene grows on the inner surface of the copper foil.
[0040] Single crystal graphene is square and measures 100 mm 2 , the growth rate is 10mm 2 / min.
[0041] Example 4
[0042] 1. The copper foil is oxidized in the atmosphere at a heating temperature of 400°C for 300 minutes. The thickness of the oxide layer formed is 100nm, and the number of oxygen atoms provided per square millimeter is 5*10 15 indivual.
[0043] 2. Place the oxidized copper foil in the graphene growth container, and the total opening area of the air inlet and the total opening area of the air outlet are both 0.0075mm 2 .
[0044] 3. (1) Place the graphene growth container in an atmosphere heating furnace, and evacuate the atmosphere heating furnace to a vacuum of less than 10 － 1 Pa, and then introduce a mixture of argon and hydrogen as a protective gas, and the gas pressure is maintained at normal pressure; (2) the copper foil is heated to 1070°C at a heating rate of 50°C / min; (3) after reaching the temperature, methane gas is introduced with a methane flow rate of 10sccm for 2 min; (4) after the growth is completed, the heating power is turned off, the introduction of methane gas is stopped, and the copper foil is naturally cooled to room temperature, and large-sized single-crystalline graphene grows on the inner surface of the copper foil.
[0045] Single crystal graphene is square and measures 10 mm 2 , the growth rate is 5mm 2 / min.
[0046] The description of different advantageous arrangements has been presented for purposes of illustration and description, but the description is not intended to be exclusive or limited to examples of the disclosed form. Many modifications and variations will be apparent to those of ordinary skill in the art. Additionally, different advantageous examples may describe different advantages over other advantageous examples. The selected example or examples are chosen and described in order to best illustrate the principles of the examples, the practical application, and to enable those of ordinary skill in the art to understand the disclosure with various examples with various modifications suitable for the particular use contemplated.
Claims
1. A method for preparing single-crystal graphene, characterized in that: The steps include: Step 1: Oxidize the metal foil in the atmosphere to form an oxide layer on the surface of the metal foil. The number of oxygen atoms provided by the oxide layer per square millimeter is 2.5*10 14 ~5*10 15 indivual; Step 2: placing the metal foil in a graphene growth container, and placing the graphene growth container in an atmosphere heating furnace; the graphene growth container is a closed container, and has an air inlet and an air outlet, and the atmosphere in the atmosphere heating furnace can flow through the inner cavity of the graphene growth container through the air inlet and the air outlet; the total opening area of the air inlet and the total opening area of the air outlet are both 0.0075mm 2 ~0.19mm 2 ; Step 3, the atmosphere heating furnace is first evacuated, and then argon and hydrogen are introduced as protective gases for heating; Step 4, after the atmosphere heating furnace is heated to a preset temperature, methane gas is introduced under the condition of maintaining argon and hydrogen as protective gases, and the methane flow rate is 0.1 sccm to 10 sccm; Step 5: maintaining the methane gas introduction time for 30 s to 30 min, ending the heating and the introduction of methane gas, and stopping the introduction of the protective gas after naturally cooling to room temperature, thereby completing the preparation of single-crystalline graphene.
2. A method for preparing single-crystal graphene according to claim 1, characterized in that: The vacuuming parameters in step 3 are: vacuuming to less than 10 ～1 Pa, introduce argon and hydrogen mixed gas as protective gas, and the gas pressure is maintained between 1Pa and normal pressure.
3. A method for preparing single-crystal graphene according to claim 1, characterized in that: The parameters for vacuuming in step 3 are: the preset temperature for heating in step 4 is 1000°C to 1075°C.
4. A method for preparing single-crystal graphene according to claim 3, characterized in that: The parameters of the vacuuming in step 3 are: the heating rate is 10°C / min to 50°C / min.
5. The method for preparing single-crystal graphene according to claim 1, characterized in that: The parameters for vacuuming in step 3 are: the time for introducing methane gas is 30s to 10min.
6. A method for preparing single-crystal graphene according to claim 1, characterized in that: The parameters for vacuuming in step 3 are: the metal foil is copper foil.
7. A method for preparing single-crystal graphene according to claim 1, characterized in that: The parameters of the vacuuming in step 3 are as follows: the heating temperature for forming the oxide layer in step 1 is 50° C. to 400° C., and the time is 5 min to 300 min.
8. A method for preparing single-crystal graphene according to claim 7, characterized in that: The parameters of the vacuuming in step 3 are: the thickness of the oxide layer is 5nm to 100nm.