Method for preparing torsional-angle double-layer graphene
By using oxide substrates to assist growth in chemical vapor deposition method, the problem of high-quality torsion angle bilayer graphene growth in the prior art is solved, and efficient and simple torsion angle bilayer graphene preparation is achieved, which improves crystal quality and torsion angle control.
Patent Information
- Application Number
- CN202510546109.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-28
- Publication Date
- 2025-08-08
AI Technical Summary
The prior art is difficult to efficiently prepare high-quality torsion-angle bilayer graphene in chemical vapor deposition method, especially due to the low carbon-soluble ability of liquid copper substrates, the growth of monolayer graphene, and the assembly method has problems of pollutant residues and torsion angle relaxation.
During the chemical vapor deposition process, by placing an oxide substrate above the growth substrate, the oxide substrate releases continuous, stable and trace amounts of oxygen to assist in the growth of torsional bilayer graphene, control the gap between the oxide substrate and the growth substrate and the vapor deposition parameters to achieve efficient growth.
It realizes efficient growth of high-quality torsional bilayer graphene without the need for precision equipment and harsh conditions, avoids pollutant residues and torsional angle relaxation, provides a growth mechanism assisted by a variety of oxide substrates, and improves the controllability of crystal quality and torsional angle distribution.
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Figure CN120440887A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the field of materials, and in particular to a method for preparing twisted-angle double-layer graphene. Background Art
[0002] Magic-angle bilayer graphene can transition from a metallic or Mott insulating state to a superconducting state at around 1K under gate voltage control. Since its discovery, this phenomenon has attracted increasing attention from scientists due to its simple structure and electric field tunability, ushering in a new era of artificial design and atomic manipulation in superconductivity. High-quality twisted bilayer graphene is fundamental to the study of strongly correlated phenomena such as superconductivity. In twisted bilayer graphene, adjusting the twist angle between the layers can change the rotational symmetry of the two graphene layers, thereby modifying properties such as the length of the Mohr superlattice, the band gap between the valence and conduction bands, the electronic state, and the strength of the interlayer atomic coupling. In other words, the twist angle plays a decisive role in the strongly correlated properties of tBLG. For example, a small twist angle (0° < θ < 4°) causes the tBLG lattice to relax, affecting the atomic and electronic reconfiguration at the interface between the two graphene layers. Large twist angles (5-30°) can alter the interlayer coupling strength of graphene, leading to enhanced light absorption and photocurrent. Bilayer graphene with a twist angle of 30° forms a dodecagonal quasicrystal, which facilitates the exploration of quasi-periodic ordered Dirac electron quantum states. Given the novel properties and potential applications of twisted bilayer graphene, developing a method to prepare high-quality twisted bilayer graphene with a wide range of twist angles is crucial for advancing the development of twist electronics.
[0003] Currently, methods for preparing twisted bilayer graphene can generally be divided into two categories: assembly methods and chemical vapor deposition (CVD). Assembly methods use single-layer graphene as the starting material and, using the tip of a scanning probe microscope, produce twisted bilayer graphene through techniques such as "folding," "tear-and-stack," or "cut-and-stack." These methods can precisely control the twist angle of twisted bilayer graphene, but they inevitably introduce contaminants and defects during the graphene transfer process, leading to twist angle relaxation or performance loss. These disadvantages limit research on the superior properties of twisted bilayer graphene. CVD avoids the complex assembly process and eliminates issues such as interlayer contamination, wrinkling, and twist angle relaxation, making it considered the most viable method for preparing twisted bilayer graphene. In particular, using liquid copper as the substrate for graphene production allows for control over graphene morphology and domain size. However, the low carbon solubility of liquid copper substrates predisposes them to growing single-layer graphene. The production of high-quality twisted bilayer graphene using CVD remains an urgent challenge. Summary of the Invention
[0004] The purpose of the present invention is to provide a method for preparing twisted-angle bilayer graphene, which directly releases continuous, stable and trace amounts of oxygen through an oxide substrate during chemical vapor deposition to assist the growth of twisted-angle bilayer graphene.
[0005] To solve the above technical problems, the present invention first provides a method for preparing twisted-angle bilayer graphene, comprising the following steps:
[0006] An oxide substrate is placed on the growth substrate, and a certain gap is maintained between the two, and chemical vapor deposition is performed to prepare twisted-angle double-layer graphene.
[0007] In the above method, the growth substrate and the oxide substrate are placed in parallel.
[0008] In the above method, the growth substrate is a metal / wetting substrate;
[0009] The oxide substrate is an oxide silicon wafer substrate, a quartz substrate or a sapphire substrate;
[0010] The gap between the growth substrate and the oxide substrate is 500-1000 microns, specifically 500, 600, 700, 800, 900 or 1000 microns.
[0011] In the above method, the metal / wetting substrate is a copper / tungsten substrate; the copper / tungsten substrate is obtained by stacking a copper sheet and a tungsten sheet;
[0012] Specifically, in the copper / tungsten substrate, the thickness of the copper is 50-200 microns, specifically 100 microns; the thickness of the tungsten substrate is 100-300 microns, specifically 100 microns;
[0013] The thickness of the silicon dioxide layer in the silicon oxide wafer substrate is 25-2000 nanometers, specifically 300 nanometers;
[0014] The thickness of the quartz in the quartz substrate is 300-2000 microns, specifically 1200 microns;
[0015] The thickness of the sapphire in the sapphire substrate is 300-1000 microns, specifically 500 microns.
[0016] In the above method, the pressure of the chemical vapor deposition is 0-1.01×10 5 Pa, but not 0; specifically 1.01×10 5 Pa;
[0017] The temperature of the chemical vapor deposition is 1110-1150° C., specifically 1120° C.;
[0018] The chemical vapor deposition time is 4-6 minutes;
[0019] In the chemical vapor deposition step, the flow ratio of the carbon source gas, hydrogen gas, and argon gas is 0.4:70-120:1000.
[0020] In the above method, in the chemical vapor deposition step, the flow rate of the carbon source is 0.4 sccm;
[0021] The flow rate of the hydrogen gas is 70-120 sccm, specifically 70, 80, 90, 100, 110 or 120 sccm;
[0022] The flow rate of the argon gas is 1000 sccm.
[0023] In the above method, in the chemical vapor deposition step, the carbon source is any one of methane, ethylene and ethane, specifically methane.
[0024] The above method further comprises the following steps: before the chemical vapor deposition step, heating the substrate;
[0025] Specifically, the heated atmosphere is a hydrogen atmosphere:
[0026] The flow rate of hydrogen is 70-120 sccm, specifically 100 sccm;
[0027] The heating time is 40-70 minutes, specifically 55 minutes;
[0028] The method further includes a step of cooling the system in a mixed atmosphere of argon and hydrogen after the chemical vapor deposition step; specifically, in the cooling step, the flow rate of argon is 1000 sccm; and the flow rate of hydrogen is 70-120 sccm.
[0029] In the above method, before the chemical vapor deposition step, the substrate is pretreated as follows: the growth substrate, the immersion substrate and the oxide substrate are ultrasonically cleaned in sequence with deionized water, acetone and ethanol, and then dried with nitrogen;
[0030] In the ultrasonic cleaning step, the ultrasonic time can be specifically 5-7 minutes.
[0031] In the above method, the metal in the metal / wetted substrate melts into a liquid state during the chemical vapor deposition process, and the liquid metal evenly spreads on the wetted substrate to form a surface of the liquid metal / wetted substrate.
[0032] The present invention also provides twisted-angle double-layer graphene prepared by the above method.
[0033] The present invention has the following advantages:
[0034] (1) The present invention discloses for the first time the growth of twisted-angle bilayer graphene under oxide substrate-assisted conditions in a chemical vapor deposition system;
[0035] (2) The present invention discloses for the first time that the gap between the oxide substrate and the growth substrate is a decisive factor affecting the growth of twisted-angle bilayer graphene;
[0036] (3) The present invention discloses for the first time the growth mechanism of twisted-angle bilayer graphene in a chemical vapor deposition system under oxide substrate-assisted conditions;
[0037] (4) The present invention discloses for the first time the growth of twisted-angle bilayer graphene assisted by various oxide substrates;
[0038] (5) The method of the present invention does not require the use of sophisticated equipment, harsh growth conditions, or expensive single crystal substrates, thereby achieving a more efficient and simpler method for growing twisted-angle bilayer graphene. BRIEF DESCRIPTION OF THE DRAWINGS
[0039] Figure 1 Schematic diagram of substrate placement for preparing twisted-angle bilayer graphene in Example 1;
[0040] Figure 2 Schematic diagram of the process for preparing twisted-angle bilayer graphene in Example 1;
[0041] Figure 3 This is a scanning electron microscope photograph of the twisted-angle bilayer graphene prepared in Example 1;
[0042] Figure 4 Selected area electron diffraction patterns of double-layer graphene with different twist angles prepared in Example 1;
[0043] Figure 5 This is an atomic force microscope two-dimensional image of the twisted-angle bilayer graphene prepared in Example 1;
[0044] Figure 6 Transmission electron microscopy images of double-layer graphene with different twist angles prepared in Example 1;
[0045] Figure 7 This is a scanning electron microscope photograph of the twisted-angle bilayer graphene prepared in Example 2;
[0046] Figure 8 This is the Raman spectrum of the twisted-angle bilayer graphene prepared in Example 2;
[0047] Figure 9 This is a scanning electron microscope image of the twisted-angle bilayer graphene prepared in Example 3;
[0048] Figure 10 This is the Raman spectrum of the twisted-angle bilayer graphene prepared in Example 3;
[0049] Figure 11 This is a scanning electron microscope photograph of the single-layer graphene prepared in Comparative Example 1;
[0050] Figure 12 This is a scanning electron microscope photograph of the single-layer graphene prepared in Comparative Example 2;
[0051] Figure 13 This is the Raman spectrum of the single-layer graphene prepared in Comparative Example 2. DETAILED DESCRIPTION
[0052] The present invention will be further described in detail below in conjunction with specific embodiments. The examples given are only for illustrating the present invention, not for limiting the scope of the present invention.
[0053] The experimental methods in the following examples are conventional methods unless otherwise specified.
[0054] The quantitative tests in the following examples were performed in triplicate unless otherwise specified, and the results were averaged.
[0055] Unless otherwise specified, the materials and reagents used in the following examples can be obtained from commercial sources.
[0056] The copper substrate used in the following examples was purchased from Sinopharm Chemical Reagent Co., Ltd., item number 51008360.
[0057] The tungsten substrate used in the following examples was purchased from Inotech, item number 010416.
[0058] The silicon oxide wafer substrate used in the following examples was purchased from Zhongsi Semiconductor Center in Bayuquan District, Yingkou City, with the item number O325.
[0059] The quartz substrates used in the following examples were purchased from Inokai, item number KF03111.
[0060] The sapphire substrates used in the following examples were purchased from Hefei Kejing Materials Technology Co., Ltd. <0001> / <11-20>, 10×10×0.5mm, single-side polished.
[0061] The silicon substrate used in the following comparative examples was purchased from the 46th Research Institute of China Electronics Technology Group Corporation, with the item number 20160119-4B.
[0062] Example 1: Direct growth of twisted-angle bilayer graphene by chemical vapor deposition on an oxidized silicon wafer substrate
[0063] (1) Cleaning copper, tungsten and silicon oxide substrates
[0064] The copper, tungsten, and silicon oxide wafer substrates were ultrasonically cleaned with deionized water, acetone, and ethanol for 7 minutes each, and then dried with nitrogen. The copper substrate and the tungsten substrate were stacked to obtain a copper / tungsten substrate. The thickness of the copper substrate was 100 μm, and the thickness of the tungsten substrate was 100 μm.
[0065] (2) Heating process
[0066] Place the clean substrate (a silicon oxide wafer is placed on a copper / tungsten substrate to form a gap of about 700 microns, and the thickness of the silicon dioxide layer of the silicon oxide wafer substrate is 300 nanometers) in a quartz boat, which is then placed in a quartz tube, as shown in the schematic diagram. Figure 1 As shown (quartz boat not shown). Then place the quartz tube into the tube furnace, align the copper / tungsten substrate with the thermocouple area of the tube furnace, introduce 100 sccm of hydrogen for 10 minutes, and then begin heating until the temperature in the center of the tube furnace reaches 1120°C. The heating time is 55 minutes.
[0067] (3) Growth of twisted bilayer graphene
[0068] The temperature of the quartz tube in the tubular furnace in step (2) was maintained at 1120°C, and methane with a flow rate of 0.4 sccm, hydrogen with a flow rate of 100 sccm, and argon with a flow rate of 1000 sccm was introduced. 5 After growing for 5 minutes under Pa pressure, methane was turned off and the tube furnace was cooled to room temperature under a mixed flow of 100 sccm hydrogen and 1000 sccm argon. Figure 2 shown.
[0069] The scanning electron microscope photo of the twisted double-layer graphene prepared above is shown in Figure 2. Figure 3 The prepared twisted-angle bilayer graphene sample was characterized by selected area electron diffraction, as shown in Figure 4 The twisted bilayer graphene was characterized by atomic force microscopy, as shown in Figure 5 As shown. Transmission electron microscopy was performed on double-layer graphene with different twist angles, as shown Figure 6 shown.
[0070] Depend on Figure 3-6 It can be seen that the twisted double-layer graphene prepared in this embodiment has a double-layer structure, rich twist angle distribution, and excellent crystal quality.
[0071] Example 2: Direct growth of twisted-angle bilayer graphene by chemical vapor deposition under quartz substrate-assisted conditions
[0072] The same method as in Example 1 was used, except that the oxide substrate (silicon oxide wafer) used in steps (1) and (2) was replaced with a quartz substrate (the thickness of the quartz was 1200 microns). By changing the oxide substrate, the concentration of oxygen in the system was adjusted, thereby affecting the growth of twisted angle double-layer graphene. It was found through observation that twisted angle double-layer graphene could still be grown after replacing quartz as the auxiliary substrate, as shown by scanning microscope. Figure 7 As shown. Moreover, Raman spectroscopy was performed on twisted bilayer graphene with a twist angle of 30°, as shown in Figure 8 shown.
[0073] Depend on Figure 7-8 It can be seen that after changing the oxide substrate, high-quality twisted-angle bilayer graphene can still be grown on the metal substrate, and the size of the graphene is consistent with that of the twisted-angle bilayer graphene grown under silicon oxide wafer assistance conditions.
[0074] Example 3: Direct growth of twisted-angle bilayer graphene by chemical vapor deposition on a sapphire substrate
[0075] The same method as in Example 1 was followed, except that the oxide substrate (silicon oxide wafer) used in steps (1) and (2) was replaced with a sapphire substrate (the thickness of the sapphire was 500 μm). Observations revealed that twisted-angle bilayer graphene could still be grown after replacing the sapphire substrate as the auxiliary substrate. Figure 9 As shown. Moreover, Raman spectroscopy was performed on twisted double-layer graphene with a twist angle of 5°, as shown in Figure 10 shown.
[0076] Depend on Figure 9-10 It can be seen that after changing the oxide substrate, high-quality twisted-angle bilayer graphene can still be grown on the metal substrate, and the size of the graphene is consistent with that of the twisted-angle bilayer graphene grown under silicon oxide wafer assistance conditions.
[0077] Comparative Example 1: Growth of single-layer graphene by chemical vapor deposition under non-oxide substrate auxiliary conditions
[0078] The same method as in Example 1 was followed, except that the oxide substrate (oxidized silicon wafer) used in steps (1) and (2) was replaced with a non-oxide silicon substrate. Observations revealed that only a single layer of graphene could be grown after replacing the silicon substrate as the auxiliary substrate. Figure 11 shown.
[0079] Depend on Figure 11 It can be seen that when the oxide substrate is replaced with a non-oxidized substrate while other parameters remain unchanged, twisted double-layer graphene cannot be formed and only single-layer graphene can be obtained.
[0080] Comparative Example 2: Growth of single-layer graphene by chemical vapor deposition without substrate assistance
[0081] In the same manner as in Example 1, only the oxide substrate in steps (1) and (2) is removed. Without substrate assistance, only single-layer graphene can be grown. Figure 12 The scanning electron microscope image of the substrate obtained under this condition is shown in Figure 2, and the Raman characterization of the prepared single-layer graphene is carried out, proving that the obtained graphene is a single-layer graphene. Figure 13 shown.
[0082] Depend on Figure 12-13 It can be seen that when other parameters remain unchanged, twisted-angle bilayer graphene cannot be grown without the assistance of an oxide substrate.
Claims
1. A method for preparing twisted-angle bilayer graphene, comprising the following steps: An oxide substrate is placed on the growth substrate, and a certain gap is maintained between the two, and chemical vapor deposition is performed to prepare twisted-angle double-layer graphene.
2. The method according to claim 1, wherein: The growth substrate is a metal / immersion substrate; The oxide substrate is an oxide silicon wafer substrate, a quartz substrate or a sapphire substrate; The gap between the growth substrate and the oxide substrate is 500-1000 microns.
3. The method according to claim 2, wherein: The metal / wetting substrate is a copper / tungsten substrate; specifically, in the copper / tungsten substrate, the thickness of the copper is 50-200 microns, and the thickness of the tungsten substrate is 100-300 microns; The thickness of the silicon dioxide layer in the silicon oxide wafer substrate is 25-2000 nanometers; The thickness of the quartz in the quartz substrate is 300-1000 microns; The thickness of the sapphire in the sapphire substrate is 300-1000 microns.
4. The method according to any one of claims 1 to 3, characterized in that: The pressure of the chemical vapor deposition is 0-1.01×10 5 Pa, but not 0; The temperature of the chemical vapor deposition is 1110-1150° C. The chemical vapor deposition time is 4-6 minutes; In the chemical vapor deposition step, the flow ratio of the carbon source gas, hydrogen gas, and argon gas is 0.4:70-120:1000.
5. The method according to any one of claims 1 to 4, characterized in that: In the chemical vapor deposition step, the flow rate of the carbon source is 0.4 sccm; the flow rate of the hydrogen gas is 70-120 sccm; and the flow rate of the argon gas is 1000 sccm.
6. The method according to any one of claims 1 to 5, characterized in that: In the chemical vapor deposition step, the carbon source is any one of methane, ethylene and ethane.
7. The method according to any one of claims 1 to 6, characterized in that: The method further comprises the following steps: before the chemical vapor deposition step, heating the substrate; The method further comprises, after the chemical vapor deposition step, cooling the system in a mixed atmosphere of argon and hydrogen.
8. The method according to claim 7, wherein: The heated atmosphere is a hydrogen atmosphere; The flow rate of hydrogen is 70-120 sccm; The heating time is 40-70 minutes; In the cooling step, the flow rate of argon gas is 1000 sccm; the flow rate of hydrogen gas is 70-120 sccm.
9. Twisted-angle double-layer graphene prepared by the method according to any one of claims 1 to 8.