Intelligent self-adjusting method for preparing few-layer two-dimensional material film with uniform layer number and stacking mode

Abstract

The invention relates to the field of preparation of two-dimensional materials, in particular to an intelligent self-adjusting method for preparing a few-layer two-dimensional material film with uniform layer number and stacking mode, which is suitable for preparing a wafer-level high-quality few-layer two-dimensional material film with accurate layer number and stacking mode. In order to solve the problem that the number of layers and the stacking mode of few-layer two-dimensional materials are difficult to accurately control due to insufficient energy resolution in the traditional preparation method, the invention adopts a closed self-adjusting growth strategy: a liquid / solid composite substrate is constructed, and a closed system is formed after a single-layer two-dimensional material film completely covers the surface of the substrate, so that the two-dimensional material layers can be accurately grown. The non-uniform multi-layer structure is promoted to be spontaneously converted into a stable stacking multi-layer configuration by utilizing a thermodynamic driving energy minimization principle. The strategy can be expanded to two-dimensional material systems such as graphene, boron nitride and transition metal chalcogenide by adapting to different liquid / solid composite substrates and growth parameters, and a universal material preparation platform is provided for integrated circuits, quantum devices and intelligent sensors.

Description

Technical Field:

[0001] The present invention relates to the field of preparation of two-dimensional materials, and relates to a method for intelligently and self-regulating the preparation of a few-layer two-dimensional material thin film with uniform layer number and stacking mode, which is applicable to the preparation of a high-quality few-layer two-dimensional material thin film with precise layer number and stacking mode at the wafer level. Background Art:

[0002] Two-dimensional materials exhibit great application potential in the fields of next-generation integrated circuits, optoelectronic devices, etc. due to their unique physical and chemical properties. However, the layer number and stacking mode of two-dimensional materials have a great impact on their performance. Precise control of the structure of two-dimensional materials, especially the preparation of a wafer-level two-dimensional material thin film with strictly consistent layer number and stacking mode, is a key challenge for the practical application of two-dimensional materials. Currently, the synthesis strategy of two-dimensional materials is mainly based on the nucleation-dominated growth mode. This mode follows the classical growth principle, that is, the structure of two-dimensional materials is determined in the nucleation stage and remains unchanged during the subsequent growth process. However, this traditional growth method has low energy resolution and is difficult to distinguish the small differences in formation energy of two-dimensional materials with different layer numbers or stacking modes (for example, the difference in formation energy of graphene with different layer numbers is only a few meV / atom). In addition, factors such as substrate defects, impurities, and fluctuations in growth parameters during the growth process will lead to the formation of an unsatisfactory layer number and stacking mode, thus affecting the uniformity and performance of the material. For example, for few-layer graphene, despite nearly two decades of research, it is still difficult to achieve the controllable preparation of a wafer-level few-layer two-dimensional material with strictly uniform layer number and stacking mode. The mainstream chemical vapor deposition (CVD) method is difficult to avoid the formation of multi-layer graphene islands and the disorder of stacking mode, which greatly limits the large-scale application of few-layer graphene. Similarly, other two-dimensional materials (such as hexagonal boron nitride, transition metal chalcogenides, etc.) also face the same challenge. Therefore, there is an urgent need to develop a new growth method to break through the limitations of the traditional nucleation-dominated growth mode and achieve the preparation of a wafer-level two-dimensional material thin film with high energy resolution and high-precision control of the layer number and stacking mode of two-dimensional materials. Summary of the Invention:

[0003] Aiming at the problem that the traditional preparation method is difficult to precisely control the layer number and stacking mode of few-layer two-dimensional materials due to insufficient energy resolution, the purpose of the present invention is to provide a method for intelligently and self-regulating the preparation of a few-layer two-dimensional material thin film with uniform layer number and stacking mode. By utilizing the principle of energy minimization in a closed system to drive the spontaneous transformation of metastable structures, precise regulation of the structure of two-dimensional materials is achieved, and the layer number and stacking mode are precisely controlled during the growth of two-dimensional materials, obtaining a large-area, uniform, and high-quality thin film.

[0004] Technical Solution of the Present Invention:

[0005] An intelligent self - adjusting method for preparing few - layer two - dimensional material films with uniform layer number and stacking pattern, comprising the following steps:

[0006] (1) Growth stage: On a composite substrate, in an open system, through a chemical vapor deposition growth method, a two - dimensional material film with a metastable structure is grown. The metastable structure includes non - target - layer - number inhomogeneous multi - layer islands of two - dimensional materials and / or two - dimensional materials with non - target stacking patterns;

[0007] (2) Self - adjusting stage: By isolating the external precursor supply, a closed system between the two - dimensional material and the composite substrate is constructed and the internal system reaches a quasi - equilibrium state; Driven by the minimization of the system energy, with the help of the recombination process of atoms inside the composite substrate, the spontaneous adjustment of the metastable structure is realized and transformed into the target two - dimensional material with the layer number and the most stable stacking pattern, and finally a few - layer two - dimensional material film with uniform layer number and stacking pattern over a large area is obtained.

[0008] For the intelligent self - adjusting method for preparing few - layer two - dimensional material films with uniform layer number and stacking pattern, where:

[0009] a) The composite substrate includes an active material surface layer and a reservoir material bottom layer;

[0010] b) The active material surface layer is a liquid metal when the growth temperature is greater than 300 °C, with a relatively low melting point, and is used to provide a low - barrier kinetic path to promote the diffusion and migration of atoms on the surface;

[0011] c) The reservoir material bottom layer selects a metal or alloy that remains solid at a growth temperature greater than 300 °C, with a relatively high melting point, and is used to continuously supply the constituent atoms of the two - dimensional material to the active material surface layer during the growth process to maintain the concentration of active atoms on the surface layer;

[0012] d) The few - layer refers to the layer number in the range of 2 - 10 layers.

[0013] For the intelligent self - adjusting method for preparing few - layer two - dimensional material films with uniform layer number and stacking pattern, where:

[0014] a) When growing few - layer single - element two - dimensional materials such as graphene, phosphorene or silicene, the reservoir material bottom layer selects a metal foil or film that can dissolve carbon, phosphorus or silicon, including but not limited to an alloy foil or film composed of one or more of platinum, palladium, iridium, iron, nickel, with a purity greater than 99 wt% and a thickness greater than 200 nanometers;

[0015] b) When growing few-layer hexagonal boron nitride (h-BN), the bottom layer of the source material is selected as a metal foil or film that can dissolve boron or nitrogen, including but not limited to an alloy foil or film composed of one or more of the metals iron, nickel, platinum, and palladium, with a purity greater than 99 wt% and a thickness greater than 200 nm;

[0016] c) When growing few-layer transition metal compounds, the bottom layer of the source material is selected as a metal foil or film that can have a solid solubility with the transition metal, including but not limited to an alloy foil or film composed of one or more of the metals iron, nickel, platinum, and palladium, with a purity greater than 99 wt% and a thickness greater than 200 nm.

[0017] For the method of intelligently self-adjusting the preparation of few-layer two-dimensional material films with uniform layer number and stacking mode, wherein:

[0018] a) When growing few-layer graphene, phosphorene, or silicene elemental two-dimensional materials, the surface layer of the active material includes but is not limited to Pt-Si, Pd-Si, Pt-Pd-Si, Fe-Si, Ir-Si, or Ni-Si alloys, with a thickness of 50 - 1000 nm;

[0019] b) When growing few-layer hexagonal boron nitride (h-BN), the surface layer of the active material includes but is not limited to Fe-P, Fe-Si, Ni-P, Ni-Si, Pt-Si, Pt-P, Pd-Si, or Pd-P alloys, with a thickness of 50 - 1000 nm;

[0020] c) When growing few-layer transition metal compounds, the surface layer of the active material includes but is not limited to Fe-P, Fe-Si, Ni-P, Ni-Si, Pt-Si, Pt-P, Pd-Si, or Pd-P alloys, with a thickness of 50 - 1000 nm.

[0021] For the method of intelligently self-adjusting the preparation of few-layer two-dimensional material films with uniform layer number and stacking mode, the preparation method of the composite substrate is: covering a surface of a solid metal or alloy sheet used as the source material with a single element or compound containing the constituent elements of the surface layer of the active material by magnetron sputtering or electroless plating, with a thickness of 50 - 1000 nm.

[0022] For the method of intelligently self-adjusting the preparation of few-layer two-dimensional material films with uniform layer number and stacking mode, wherein:

[0023] a) When the two-dimensional material is a single two-dimensional material such as graphene, phosphorene or silicene, the growth precursor is a gaseous or liquid compound: one or more of methane, ethane, silane, ethylene, acetylene, benzene, toluene, cyclohexane, ethanol, methanol, acetone or carbon monoxide, or a solid source: one or more of amorphous carbon, phosphorus, paraffin, polymethyl methacrylate, polycarbonate, polystyrene, polyethylene, polypropylene;

[0024] b) When the two-dimensional material is hexagonal boron nitride (h-BN), the growth precursor is nitrogen, ammonia or ammonia borane;

[0025] c) When the two-dimensional material is a transition metal compound, the growth precursor in addition to the above-mentioned single substance or compound also includes one or more of sulfur, selenium, tellurium, zinc sulfide, zinc selenide, zinc telluride powder or crystal, and hydrogen sulfide gas.

[0026] The method for intelligently self-regulating the preparation of a few-layer two-dimensional material thin film with uniform layer number and stacking mode changes the total amount of the growth source for forming the two-dimensional material in the closed system by adjusting the proportion of the alloy components, the temperature in the growth stage and the growth atmosphere mode, and finally realizes the regulation of the layer number of the two-dimensional material.

[0027] The method for intelligently self-regulating the preparation of a few-layer two-dimensional material thin film with uniform layer number and stacking mode needs to maintain a stable temperature and atmosphere during the self-regulation stage to avoid etching reaction and damage to the closed system.

[0028] The method for intelligently self-regulating the preparation of a few-layer two-dimensional material thin film with uniform layer number and stacking mode controls the atomic diffusion rate and the structure transformation rate by regulating the temperature during the self-regulation stage.

[0029] The design concept of the present invention is:

[0030] The present invention proposes a closed self-regulating growth strategy: by constructing a liquid / solid composite substrate, after the single-layer two-dimensional material thin film completely covers the substrate surface, a closed system is formed, and the energy minimization principle driven by thermodynamics is used to promote the spontaneous transformation of the non-uniform multi-layer structure (such as random stacking or layer number deviation) into a stable specific stacking multi-layer configuration. This strategy can prepare various two-dimensional material systems by adapting different liquid / solid composite substrates and growth parameters, and can be extended to two-dimensional material systems such as graphene, boron nitride, and transition metal chalcogenides, providing a general material preparation platform for integrated circuits, quantum devices and intelligent sensors.

[0031] The advantages and beneficial effects of the present invention are:

[0032] 1. Intelligent self - regulation: The present invention breaks through the limitation of the prior art that relies on precise control of nucleation, introduces an intelligent self - regulation mechanism, regards non - ideal structures as controllable intermediate states, realizes atomic - level precise structure regulation, and significantly improves uniformity, repeatability, and robustness to process disturbances.

[0033] 2. Universal substrate design: The present invention breaks through the limitation of traditional single substrates, constructs an integrated substrate of "active atom reservoir - efficient diffusion channel - optimized catalytic active sites", and provides a universal solution for the growth of different types of two - dimensional materials. This design can flexibly regulate the processes of atomic supply, migration, and bonding, reduce the reaction barrier, and accelerate the self - regulation process.

[0034] 3. Quasi - equilibrium thermodynamics - driven growth: The present invention realizes the adaptive regulation of chemical potential by constructing a closed system and inhibits the formation of non - ideal structures. In the quasi - equilibrium state of the system, the chemical potential difference drives the spontaneous migration and rearrangement of atoms, and finally realizes the precise regulation of the structure of two - dimensional materials, effectively reducing the defect density and improving the material purity and crystallization quality.

[0035] 4. The method of the present invention has universality and is applicable to the growth of various two - dimensional materials, including but not limited to graphene, hexagonal boron nitride (h - BN), transition metal chalcogenides (TMDs, such as MoS2, WS2, etc.). Description of the Drawings:

[0036] Figure 1 It is a schematic diagram of the experimental device for desktop magnetron sputtering coating. In the figure, 11 is the metal substrate; 12 is the sample disk; 13 is the target; 14 is the magnetron sputtering cathode.

[0037] Figure 2 It is an experimental device for annealing in a high - temperature reducing atmosphere and growing uniform multi - layer two - dimensional materials by CVD method. In the figure, 21 is the gas inlet; 22 is the composite substrate; 23 is the reaction furnace; 24 is the gas outlet.

[0038] Figure 3 It is an experimental device for annealing in a high - temperature reducing atmosphere and growing uniform multi - layer transition metal chalcogenides by CVD method. In the figure, 31 is the gas inlet; 32 is the crucible for containing solid sources; 33 is the composite substrate; 34 is the reaction furnace; 35 is the gas outlet.

[0039] Figure 4 It is a schematic diagram of a typical intelligent self - regulation preparation method based on the liquid / solid composite substrate Pt3Si / Pt.

[0040] Figure 5 It is the scanning electron microscope (SEM) image and structure schematic diagram of graphene in the growth stage (left figure) and self - regulation stage (right figure) on the Pt3Si / Pt composite substrate.

[0041] Figure 6 Optical photograph, Raman spectrum, and high-resolution transmission electron microscope characterization of an AB-stacked bilayer graphene film prepared by the intelligent self-adjustment method. Among them, Figure a is the optical photograph, Figure b is the Raman spectrum, Figure c is the high-resolution transmission electron microscope image, Figure d is the surface scan and statistical distribution map of the G peak position, Figure e is the surface scan and statistical distribution map of the 2D peak position, and Figure f is the surface scan and statistical distribution map of the full width at half maximum of the 2D peak.

[0042] Figure 7 Optical photograph, Raman spectrum, and high-resolution transmission electron microscope characterization of an ABA-stacked trilayer graphene film prepared by the intelligent self-adjustment method. Among them, Figure a is the optical photograph, Figure b is the Raman spectrum, Figure c is the high-resolution transmission electron microscope image, Figure d is the surface scan and statistical distribution map of the G peak position, Figure e is the surface scan and statistical distribution map of the 2D peak position, and Figure f is the surface scan and statistical distribution map of the full width at half maximum of the 2D peak. Specific implementation method:

[0043] As Figure 4 and Figure 5 shown, the present invention proposes a method for intelligently self-adjusting the preparation of few-layer two-dimensional material films with uniform layer number and stacking pattern, specifically including the following steps:

[0044] 1. Growth stage (t1): Construct a metastable two-dimensional film structure

[0045] 1) Substrate design: Selecting a suitable substrate is the key to achieving self-adjusting growth. The substrate is generally a liquid / solid composite substrate structure at high temperatures. For example, a liquid Pt3Si / solid Pt composite substrate is suitable for graphene growth, a liquid Fe-P / solid Fe-B composite substrate is suitable for h-BN growth, and a liquid Ni-P / solid Ni-Mo composite substrate is suitable for MoS2 growth, etc. The liquid alloy surface layer provides a low-barrier kinetic path to promote the growth and transformation of two-dimensional materials; the solid metal / alloy serves as a reservoir to maintain the concentration of specific components in the liquid metal / alloy surface layer, such as carbon, boron, molybdenum, tungsten, etc. The design of this composite substrate structure can effectively regulate the growth kinetics of two-dimensional materials and promote the formation of metastable structures. Other substrate materials with similar properties can also be selected and optimized according to the target two-dimensional material.

[0046] 2) Adjusting growth parameters: In an open system (an open system refers to a system with material exchange with the outside world), by precisely controlling growth parameters such as temperature, precursor concentration, growth rate, carrier gas flow rate and type, pressure, etc., an initial two-dimensional material thin film mainly composed of a single layer is induced to grow on the surface of the composite substrate. At the same time, the precisely regulated growth parameters and the characteristics of the composite substrate act synergistically to promote the formation of metastable multi-layer two-dimensional material islands or regions below the single-layer two-dimensional material thin film. These metastable multi-layer structures can be stacks of different numbers of layers or different stacking modes (for example, for graphene, they can be bilayer, trilayer or more-layer graphene islands, and the stacking mode can be Bernal stacking, twisted stacking mode). These metastable structures will serve as the atomic source for the subsequent self-regulation process, and their total amount determines the number of layers of the two-dimensional material obtained.

[0047] 2. Self-regulation stage (t2): Structural evolution in a closed system

[0048] 1) Construction of a closed system: When the single-layer two-dimensional material thin film completely covers the surface of the composite substrate, it is necessary to maintain the growth atmosphere of the entire growth system to prevent the occurrence of etching reactions. Thus, a closed system is naturally formed between the two-dimensional material and the composite substrate. This closed system isolates the previously formed metastable multi-layer two-dimensional material from the external precursor, blocking the exchange of external atoms / molecules with the system and creating the necessary conditions for the system to reach a quasi-equilibrium state.

[0049] 2) Spontaneous transformation and energy minimization: In the quasi-equilibrium state of the closed system, the system tends to transform into the state with the lowest energy. Driven by this, the metastable multi-layer two-dimensional material spontaneously transforms into a more stable two-dimensional material with a specific number of layers and stacking mode. For example, in the growth of graphene, trilayer graphene islands will transform into bilayer graphene, and bilayer graphene with non-Bernal stacking will transform into bilayer graphene with Bernal stacking. This transformation process is achieved by the recombination of atoms on the active material surface layer of the composite substrate. The liquid layer provides a kinetic path with a low energy barrier, promoting the migration and rearrangement of atoms and enabling the system to reach the stable structure with the lowest energy.

[0050] 3) Kinetic regulation: Parameters such as temperature (T1) and time in the self-regulation stage need to be optimized according to the specific two-dimensional material and composite substrate to ensure complete transformation and obtain a high-quality two-dimensional material thin film. Precise kinetic regulation can effectively control the rate and direction of the transformation, and ultimately obtain the two-dimensional material with the target structure.

[0051] Next, the present invention will be further described in detail through examples and drawings.

[0052] Example 1

[0053] First, a composite substrate was prepared by magnetron sputtering. A platinum sheet (with a thickness of 250 μm, a length of 20 mm, a width of 10 mm, and a purity of 99.999 wt%) was ultrasonically cleaned in acetone, deionized water, and isopropanol for 40 min each. As Figure 1 shown, after cleaning, the metal substrate 11 (platinum sheet) was fixed on the lower surface of the sample disk 12 and rotated with the sample disk 12 at a speed of 30 revolutions per minute. A silicon target 13 with a purity of 99.999 wt% was used as the sputtering source. When the air pressure in the vacuum chamber dropped to the order of 10 -5 mbar, argon gas was introduced at a rate of 8 ml / min. The sputtering source voltage was set to 600 V and the current was set to 90 mA. Coating was carried out at a speed of 0.35 Å / s. When the thickness of the Si film reached 500 nm, the power supply was turned off and the silicon / platinum composite substrate was taken out. As Figure 2 shown, the silicon / platinum composite substrate 22 was placed in the central region of a horizontal reaction furnace 23 (with a furnace tube diameter of 22 mm and a reaction zone length of 20 mm). Hydrogen gas was introduced at a rate of 500 ml / min, and at the same time the temperature was raised to 1100 °C and maintained for 12 h. Finally, a Pt3Si / Pt composite substrate for growing bilayer graphene film was obtained.

[0054] As Figure 2 shown, in the present invention, a horizontal reaction furnace was used to grow a uniform bilayer graphene film. Gas inlets 21 and gas outlets 24 were respectively provided at both ends of the horizontal reaction furnace 23. The coating / metal matrix or the composite substrate 22 with a core-shell structure was placed in the constant temperature zone of the horizontal reaction furnace 23.

[0055] In this embodiment, the intelligent self-adjusting growth steps of the AB-stacked bilayer graphene film are as follows:

[0056] 1) Place the prepared Pt3Si / Pt composite substrate in the central region of a horizontal reaction furnace (with a furnace tube diameter of 22 mm and a reaction zone length of 20 mm); heat it to 1180 °C in a hydrogen atmosphere (during the heating process, the hydrogen flow rate is 500 ml / min and the heating rate is 20 °C / min). After the furnace temperature reaches 1180 °C, maintain it for 10 min to remove the organic residue on the substrate surface, and then introduce a mixed gas of methane and hydrogen (the gas flow rates are 2.5 ml / min for methane and 500 ml / min for hydrogen) and keep it for 360 min; after the growth is completed, quickly push the composite substrate out of the constant temperature zone, and finally obtain a 100% AB-stacked bilayer graphene film covering the surface of the composite substrate.

[0057] 2) A solution of ethyl lactate of polymethyl methacrylate (PMMA) (with PMMA accounting for 4 wt%) was dropped onto the surface of a Pt3Si / Pt composite substrate grown with bilayer graphene. A PMMA thin film was spin-coated at 2000 revolutions per minute to form a layer. After baking at 180 °C for 30 minutes, the PMMA / bilayer graphene / Pt3Si / Pt composite substrate was used as the cathode and placed in a 1 mol / L aqueous NaOH solution (electrolyte). The anode used a platinum electrode, with a constant current of 0.2 A. The PMMA / bilayer graphene film was transferred to the SiO2 / Si substrate by the electrochemical bubbling method, and then the PMMA was dissolved with acetone at room temperature, finally achieving the successful transfer of the bilayer graphene.

[0058] 3) An optical microscope, Raman spectrometer, and transmission electron microscope were used to characterize the number of layers, stacking mode, and crystallization quality of the bilayer graphene film, indicating that the obtained bilayer graphene film was 100% AB stacked and had a quality comparable to that of bilayer graphene obtained by mechanical exfoliation, as Figure 6 shown.

[0059] Example 2

[0060] First, a composite substrate was prepared by magnetron sputtering. A platinum sheet (thickness 250 μm, length 20 mm, width 10 mm, purity 99.999 wt%) was ultrasonically cleaned in acetone, deionized water, and isopropanol for 30 min respectively. As Figure 1 shown, after cleaning, the metal substrate 11 (platinum sheet) was fixed on the lower surface of the sample disk 12 and rotated at a speed of 30 revolutions per minute with the sample disk 12. Using a silicon target 13 with a purity of 99.999 wt% as the sputtering source, when the air pressure in the vacuum chamber dropped to the order of 10 -5 mbar, 8 milliliters per minute of argon was introduced, the sputtering source voltage was set to 600 V, the current was set to 90 mA, and coating was carried out at a speed of 0.35 Å / s. When the thickness of the Si film reached 500 nm, the power supply was turned off and the silicon / platinum composite substrate was taken out. As Figure 2 shown, the silicon / platinum composite substrate 22 was placed in the central region of a horizontal reaction furnace 23 (furnace tube diameter 22 mm, reaction zone length 20 mm), 500 milliliters per minute of hydrogen was introduced, and at the same time the temperature was raised to 1100 °C and maintained for 12 h, finally obtaining a Pt3Si / Pt composite substrate for growing a three-layer graphene film.

[0061] As Figure 2 shown, the present invention uses a horizontal reaction furnace to grow a uniform three-layer graphene film. Gas inlets 21 and gas outlets 24 are respectively provided at both ends of the horizontal reaction furnace 23, and the coating / metal matrix or the composite substrate 22 with a core-shell structure is placed in the constant temperature zone of the horizontal reaction furnace 23.

[0062] In this embodiment, the intelligent self-adjusting growth steps of the ABA-stacked three-layer graphene film are as follows:

[0063] 1) Place the prepared Pt3Si / Pt composite substrate in the central area of a horizontal reaction furnace (furnace tube diameter: 22 mm, reaction zone length: 20 mm); heat it to 1240 °C in a hydrogen atmosphere (during the heating process, the hydrogen flow rate is 500 mL / min, and the heating rate is 20 °C / min). After the furnace temperature reaches 1240 °C, maintain it for 10 min to remove the organic residue on the substrate surface, then introduce a mixed gas of methane and hydrogen (gas flow rates are 2 mL / min for methane and 500 mL / min for hydrogen), and keep it for 480 min; after the growth is completed, quickly push the composite substrate out of the constant temperature zone to finally obtain a 100% ABA-stacked three-layer graphene film covering the surface of the composite substrate.

[0064] 2) Drop an ethyl lactate solution of polymethyl methacrylate (PMMA) (PMMA accounts for 4 wt%) onto the surface of the Pt3Si / Pt composite substrate grown with three-layer graphene, and spin-coat it into a PMMA film at 2000 revolutions per minute. After baking at 180 °C for 30 minutes, place the PMMA / three-layer graphene / Pt3Si / Pt composite substrate as the cathode in a 1 mol / L NaOH aqueous solution (electrolyte), use a platinum electrode as the anode, with a constant current of 0.2 A, and transfer the PMMA / three-layer graphene film to the SiO2 / Si substrate by the electrochemical bubbling method, and then dissolve the PMMA with acetone at room temperature to finally achieve the successful transfer of the three-layer graphene.

[0065] 3) Characterize the number of layers, stacking mode, and crystallization quality of the three-layer graphene film using an optical microscope, Raman spectrometer, and transmission electron microscope, indicating that the obtained three-layer graphene film is 100% ABA-stacked and has a quality comparable to that of bilayer graphene obtained by mechanical exfoliation, as Figure 7 shown.

[0066] Example 3

[0067] First, prepare a composite substrate by magnetron sputtering. Place a platinum sheet (thickness: 250 μm, length: 20 mm, width: 10 mm, purity: 99.999 wt%) in acetone, deionized water, and isopropanol respectively for ultrasonic cleaning for 30 min. As Figure 1 shown, after the cleaning is completed, fix the metal substrate 11 (platinum sheet) on the lower surface of the sample disk 12 and rotate it at a speed of 30 revolutions per minute with the sample disk 12. Use a Pd target 13 with a purity of 99.999 wt% as the sputtering source. Wait until the air pressure in the vacuum chamber drops to 10 -5In the order of magnitude of mbar, argon gas is introduced at a rate of 8 mL / min, the sputtering source voltage is set to 600 V, the current is set to 120 mA, and film coating is carried out at a speed of 0.3 Å / s. When the thickness of the Pd film reaches 500 nm, the power supply is turned off, and the palladium / platinum composite substrate is taken out. As Figure 2 shown, the palladium / platinum composite substrate 22 is placed in the central area of a horizontal reaction furnace 23 (the furnace tube diameter is 22 mm, and the reaction zone length is 20 mm), hydrogen gas is introduced at a rate of 500 mL / min, and at the same time the temperature is raised to 1150 °C and maintained for 12 h, finally obtaining a Pt-Pd alloy substrate.

[0068] The obtained Pt-Pd alloy substrate is re-fixed on the lower surface of the sample disk 12 and rotated with the sample disk 12 at a speed of 30 revolutions per minute. A silicon target 13 with a purity of 99.999 wt% is used as the sputtering source. When the air pressure in the vacuum chamber drops to 10 -5 mbar order of magnitude, argon gas is introduced at a rate of 8 mL / min, the sputtering source voltage is set to 600 V, the current is set to 90 mA, and film coating is carried out at a speed of 0.35 Å / s. When the thickness of the Si film reaches 500 nm, the power supply is turned off, and the silicon / platinum-palladium composite substrate is taken out. As Figure 2 shown, the silicon / platinum-palladium composite substrate 22 is placed in the central area of a horizontal reaction furnace 23 (the furnace tube diameter is 22 mm, and the reaction zone length is 20 mm), hydrogen gas is introduced at a rate of 500 mL / min, and at the same time the temperature is raised to 1100 °C and maintained for 12 h, finally obtaining a Pd-Pt-Si / Pt-Pd composite substrate for growing a three-layer graphene film.

[0069] As Figure 2 shown, the present invention uses a horizontal reaction furnace to grow a uniform four-layer graphene film. Gas inlets 21 and gas outlets 24 are respectively arranged at both ends of the horizontal reaction furnace 23, and the coating / metal matrix or the composite substrate 22 with a core-shell structure is placed in the constant temperature zone of the horizontal reaction furnace 23.

[0070] In this embodiment, the intelligent self-adjusting growth steps of the four-layer graphene film with ABAB stacking are as follows:

[0071] Place the prepared Pd-Pt-Si / Pt-Pd composite substrate in the central area of a horizontal reaction furnace (furnace tube diameter 22 mm, reaction zone length 20 mm); heat it to 1250 °C in a hydrogen atmosphere (during the heating process, the hydrogen flow rate is 500 ml / min, and the heating rate is 20 °C / min). After the furnace temperature reaches 1250 °C, maintain it for 10 min to remove the organic residue on the substrate surface, then introduce a mixed gas of methane and hydrogen (gas flow rates are 2.5 ml / min for methane and 500 ml / min for hydrogen), and keep it for 480 min; after the growth is completed, quickly push the composite substrate out of the constant temperature zone, and finally obtain a four-layer graphene film with 100% ABAB stacking covering the surface of the composite substrate.

[0072] Example 4

[0073] First, prepare a composite substrate by magnetron sputtering. Place a palladium sheet (thickness 250 μm, length 20 mm, width 10 mm, purity 99.999 wt%) in acetone, deionized water, and isopropanol respectively for ultrasonic cleaning for 40 min. As Figure 1 shown, after the cleaning is completed, fix the metal substrate 11 (palladium sheet) on the lower surface of the sample disk 12, and rotate it at a speed of 30 revolutions per minute with the sample disk 12. Use a silicon target 13 with a purity of 99.999 wt% as the sputtering source. When the pressure in the vacuum chamber drops to the order of 10 -5 mbar, introduce 8 ml / min of argon, set the sputtering source voltage to 600 V, set the current to 90 mA, and coat the film at a speed of 0.35 Å / s. When the thickness of the Si film reaches 500 nm, turn off the power supply and take out the silicon / palladium composite substrate. As Figure 2 shown, place the silicon / palladium composite substrate 22 in the central area of a horizontal reaction furnace 23 (furnace tube diameter 22 mm, reaction zone length 20 mm), introduce 500 ml / min of hydrogen, and at the same time raise the temperature to 1100 °C and maintain it for 12 h to finally obtain a Pd5Si / Pd composite substrate for growing a five-layer graphene film.

[0074] As Figure 2 shown, the present invention uses a horizontal reaction furnace to grow a uniform five-layer graphene film. Gas inlets 21 and gas outlets 24 are respectively provided at both ends of the horizontal reaction furnace 23, and the coating / metal matrix or the composite substrate 22 with a core-shell structure is placed in the constant temperature zone of the horizontal reaction furnace 23.

[0075] In this example, the intelligent self-adjusting growth steps of the five-layer graphene film with ABABA stacking are as follows:

[0076] 1) Place the prepared Pd5Si / Pd composite substrate in the central area of a horizontal reaction furnace (furnace tube diameter: 22 mm, reaction zone length: 20 mm); heat it to 1250 °C in a hydrogen atmosphere (during the heating process, the hydrogen flow rate is 500 mL / min, and the heating rate is 20 °C / min). After the furnace temperature reaches 1250 °C, maintain it for 10 min to remove the organic residue on the substrate surface, then introduce a mixed gas of methane and hydrogen (gas flow rates are 3 mL / min for methane and 500 mL / min for hydrogen), and keep it for 600 min; after the growth is completed, quickly push the composite substrate out of the constant temperature zone, and finally obtain a five-layer graphene film with 100% ABABA stacking covering the surface of the composite substrate.

[0077] 2) Drop an ethyl lactate solution of polymethyl methacrylate (PMMA) (PMMA accounts for 4 wt%) onto the surface of the Pd5Si / Pd composite substrate grown with five-layer graphene, and spin-coat it at 2000 revolutions per minute to form a PMMA film. After baking at 180 °C for 30 minutes, place the PMMA / five-layer graphene / Pd5Si / Pd composite substrate as the cathode in a 1 mol / L NaOH aqueous solution (electrolyte), use a platinum electrode as the anode, with a constant current of 0.2 A, and transfer the PMMA / five-layer graphene film to the SiO2 / Si substrate by the electrochemical bubbling method, and then dissolve the PMMA with acetone at room temperature to finally achieve the successful transfer of the five-layer graphene.

[0078] Example 5

[0079] First, prepare a composite substrate by magnetron sputtering. Place a nickel sheet (thickness: 200 μm, length: 20 mm, width: 10 mm, purity: 99.999 wt%) in acetone, deionized water, and isopropanol respectively for ultrasonic cleaning for 40 min. As Figure 1 shown, after the cleaning is completed, fix the metal substrate 11 (nickel sheet) on the lower surface of the sample disk 12 and rotate it at a speed of 30 revolutions per minute with the sample disk 12. Use a molybdenum target 13 with a purity of 99.999 wt% as the sputtering source. When the pressure in the vacuum chamber drops to the order of 10 -5 mbar, introduce 8 mL / min of argon, set the sputtering source voltage to 600 V, set the current to 150 mA, and coat the film at a speed of 0.3 Å / s. When the thickness of the molybdenum film reaches 500 nm, turn off the power supply and take out the molybdenum / nickel composite substrate. As Figure 2 shown, place the molybdenum / nickel composite substrate 22 in the central area of a horizontal reaction furnace 23 (furnace tube diameter: 22 mm, reaction zone length: 20 mm), introduce 500 mL / min of hydrogen, and at the same time raise the temperature to 1300 °C and maintain it for 12 h to finally obtain a uniform Ni-Mo alloy substrate.

[0080] The obtained Ni-Mo alloy substrate was refixed on the lower surface of the sample disk 12 and rotated with the sample disk 12 at a speed of 30 revolutions per minute. Using a Ni3P alloy target 13 with a purity of 99.999 wt% as the sputtering source, when the air pressure in the vacuum chamber dropped to 10 -5 mbar order of magnitude, 8 milliliters per minute of argon was introduced, the sputtering source voltage was set to 600 V, the current was set to 90 mA, and coating was carried out at a speed of 0.35 Å per second. When the thickness of the Ni3P thin film reached 500 nm, the power supply was turned off, and the Ni3P / Ni-Mo composite substrate was taken out.

[0081] As Figure 3 shown, the present invention uses a horizontal reaction furnace to grow a uniformly 3R-stacked double-layer MoS2 thin film. Gas inlets 31 and gas outlets 35 are respectively provided at both ends of the horizontal reaction furnace 34. The Ni3P / Ni-Mo composite substrate 33 is placed in the constant temperature zone of the horizontal reaction furnace 34. Sulfur powder is placed in the crucible 32 containing the solid source, and its distance from the central constant temperature zone is about 10 cm.

[0082] In this embodiment, the intelligent self-adjusting growth steps of the 3R-stacked double-layer MoS2 thin film are as follows:

[0083] The prepared Ni3P / Ni-Mo composite substrate was placed in the central area of a horizontal reaction furnace (furnace tube diameter 22 mm, reaction zone length 20 mm); heated to 880 °C in a hydrogen atmosphere (during the heating process, the argon flow rate was 500 milliliters per minute, hydrogen was 5 milliliters per minute, and the heating rate was 20 °C per minute). When the furnace temperature reached 880 °C, it was maintained for 360 min; after the growth was completed, the composite substrate was quickly pushed out of the constant temperature zone, and finally a uniformly 3R-stacked double-layer MoS2 thin film covering the surface of the composite substrate was obtained.

[0084] Example 6

[0085] First, a composite substrate was prepared by magnetron sputtering. An iron sheet (thickness 200 μm, length 20 mm, width 10 mm, purity 99.999 wt%) was ultrasonically cleaned in acetone, deionized water, and isopropanol for 40 min respectively. As Figure 1 shown, after cleaning, the metal substrate 11 (iron sheet) was fixed on the lower surface of the sample disk 12 and rotated with the sample disk 12 at a speed of 30 revolutions per minute. Using a boron target 13 with a purity of 99.999 wt% as the sputtering source, when the air pressure in the vacuum chamber dropped to 10 -5 mbar order of magnitude, 8 milliliters per minute of argon was introduced, the sputtering source voltage was set to 600 V, the current was set to 150 mA, and coating was carried out at a speed of 0.3 Å per second. When the thickness of the boron thin film reached 300 nm, the power supply was turned off, and the boron / iron composite substrate was taken out. As Figure 2As shown in the figure, the boron / iron composite substrate 22 is placed in the central region of a horizontal reaction furnace 23 (furnace tube diameter: 22 mm, reaction zone length: 20 mm). Hydrogen is introduced at a rate of 500 mL / min, and at the same time, the temperature is raised to 1200 °C and maintained for 12 h, finally obtaining a uniform Fe-B alloy substrate.

[0086] The obtained Fe-B alloy substrate is re-fixed on the lower surface of the sample disk 12 and rotated with the sample disk 12 at a speed of 30 revolutions per minute. The Fe3P alloy target 13 with a purity of 99.999 wt% is used as the sputtering source. When the air pressure in the vacuum chamber drops to the order of 10 -5 mbar, argon is introduced at a rate of 8 mL / min. The sputtering source voltage is set to 600 V and the current is set to 90 mA. Coating is carried out at a speed of 0.35 Å / s. When the thickness of the Fe3P thin film reaches 500 nm, the power supply is turned off and the Fe3P / Fe-B composite substrate is taken out.

[0087] As Figure 2 shown in the figure, the present invention uses a horizontal reaction furnace to grow a uniform three-layer h-BN thin film. Gas inlets 21 and gas outlets 24 are respectively provided at both ends of the horizontal reaction furnace. The Fe3P / Fe-B composite substrate 22 is placed in the constant temperature zone of the horizontal reaction furnace 23.

[0088] In this embodiment, the intelligent self-adjusting growth steps of the three-layer h-BN thin film are as follows:

[0089] The prepared Fe3P / Fe-B composite substrate is placed in the central region of a horizontal reaction furnace (furnace tube diameter: 22 mm, reaction zone length: 20 mm); it is heated to 1060 °C in a protective atmosphere (during the heating process, the argon flow rate is 300 mL / min, the hydrogen flow rate is 50 mL / min, and the heating rate is 20 °C / min). When the furnace temperature rises to 1060 °C, nitrogen is introduced at a rate of 300 mL / min and maintained for 360 min; after the growth is completed, the composite substrate is quickly pushed out of the constant temperature zone, and finally a uniform three-layer h-BN thin film covering the surface of the composite substrate is obtained.

[0090] As Figure 1 shown in the figure, the experimental device for magnetron sputtering coating of a metal matrix in the present invention mainly includes: a metal substrate 11, a sample disk 12, a target 13, and a magnetron sputtering negative electrode 14. The metal substrates 11 are uniformly arranged along the circumference on the lower surface of the sample disk 12. The target 13 is arranged on the magnetron sputtering negative electrode 14 and corresponds to the metal substrate 11. The sample disk 12 rotates, and magnetron sputtering coating is carried out on the metal substrate 11 through the target 13.

[0091] As Figure 2As shown in the figure, the experimental device for growing high-quality uniform multi-layer graphene films with a specific stacking pattern by CVD method mainly includes: a gas inlet 21, a composite substrate 22, a reaction furnace 23, and a gas outlet 24. The composite substrate 22 is arranged in the central constant temperature area of the horizontal furnace tube of the reaction furnace 23. The solid carbon source can be directly coated or deposited on the upper surface of the composite substrate 22. The gaseous carbon source and the carrier gas enter the horizontal furnace tube of the reaction furnace 23 from the gas inlet 21, and the tail gas is discharged from the gas outlet 24.

[0092] As Figure 3 shown in the figure, the experimental device for growing high-quality uniform TMD films by CVD method mainly includes: a gas inlet 31, a crucible 32 for containing the solid source, a composite substrate 33, a reaction furnace 34, and a gas outlet 35. The crucible 32 for containing the solid source is placed upstream in the horizontal furnace tube cavity of the reaction furnace 34. The composite substrate 33 is arranged in the central constant temperature area of the horizontal furnace tube cavity of the reaction furnace 34. The solid carbon source can be directly coated or deposited on the upper surface of the composite substrate 33. The gaseous carbon source and the carrier gas enter the horizontal furnace tube of the reaction furnace 34 from the gas inlet 31, and the tail gas is discharged from the gas outlet 35.

[0093] As Figure 5 shown in the figure, from the structural schematic diagram and the corresponding SEM images, it can be seen that before and after the self-adjustment process, the graphene on the Pt3Si / Pt substrate changes from a graphene film with uneven multi-layer islands to a uniform bilayer graphene film.

[0094] As Figure 6 shown in the figure, from the results of Raman characterization and transmission electron microscopy characterization, it can be seen that the graphene film is a complete AB-stacked bilayer structure and has a quality comparable to that of bilayer graphene obtained by the mechanical exfoliation method.

[0095] As Figure 7 shown in the figure, from the results of Raman characterization and transmission electron microscopy characterization, it can be seen that the graphene film is a complete ABA-stacked trilayer structure and has a quality comparable to that of trilayer graphene obtained by the mechanical exfoliation method.

[0096] The implementation results show that the use of the present invention can realize the intelligent self-adjustable and controllable preparation of the number of layers and stacking of two-dimensional materials such as graphene, providing the possibility for the application of two-dimensional materials in integrated circuits, quantum devices, intelligent sensors, etc.

Claims

1. A method for intelligently and self - regulating the preparation of a few - layer two - dimensional material thin film with uniform layer number and stacking mode, characterized in that, It includes the following steps: (1) Growth stage: On a composite substrate, in an open system, through a chemical vapor deposition growth method, a two-dimensional material thin film with a metastable structure is grown. The metastable structure includes uneven two-dimensional material multi-layer islands with a non-target number of layers and / or two-dimensional materials with a non-target stacking pattern; (2) Self-regulation stage: By isolating the supply of external precursors, a closed system is constructed between the two-dimensional material and the composite substrate and the internal system reaches a quasi-equilibrium state; Driven by the minimization of the system energy, through the recombination process of atoms inside the composite substrate, the spontaneous regulation of the metastable structure is realized and transformed into the target two-dimensional material with the number of layers and the most stable stacking pattern. Finally, a few-layer two-dimensional material thin film with uniform number of layers and stacking pattern over a large area is obtained.

2. The method for intelligently self-regulating the preparation of a few-layer two-dimensional material thin film with uniform number of layers and stacking pattern according to claim 1, wherein: a) The composite substrate includes an active material surface layer and a reservoir material bottom layer; b) The active material surface layer is a liquid metal when the growth temperature is greater than 300 °C, having a low melting point, and is used to provide a low-barrier kinetic path to promote the diffusion and migration of atoms on the surface; c) The reservoir material bottom layer selects a metal or alloy that remains solid at a growth temperature greater than 300 °C, having a high melting point, and is used to continuously supply the constituent atoms of the two-dimensional material to the active material surface layer during growth to maintain the concentration of active atoms on the surface; d) The few-layer means that the number of layers is in the range of 2 to 10 layers.

3. The method for intelligently self-regulating the preparation of a few-layer two-dimensional material thin film with uniform number of layers and stacking pattern according to claim 2, wherein: a) When growing few-layer graphene, phosphorene or silicene elemental two-dimensional materials, the reservoir material bottom layer selects a metal foil or film that can dissolve carbon, phosphorus or silicon, including but not limited to an alloy foil or film composed of one or more of platinum, palladium, iridium, iron, nickel, with a purity greater than 99 wt% and a thickness greater than 200 nanometers; b) When growing few-layer hexagonal boron nitride (h-BN), the reservoir material bottom layer selects a metal foil or film that can dissolve boron or nitrogen, including but not limited to an alloy foil or film composed of one or more of the metals iron, nickel, platinum, palladium, with a purity greater than 99 wt% and a thickness greater than 200 nanometers; c) When growing few-layer transition metal compounds, the reservoir material bottom layer selects a metal foil or film that has a solid solubility with the transition metal, including but not limited to an alloy foil or film composed of one or more of the metals iron, nickel, platinum, palladium, with a purity greater than 99 wt% and a thickness greater than 200 nanometers.

4. The method for intelligently self-regulating the preparation of a few-layer two-dimensional material thin film with uniform number of layers and stacking pattern according to claim 2, wherein: a) When growing few-layer graphene, phosphorene or silicene elemental two-dimensional materials, the active material surface layer includes but not limited to Pt-Si, Pd-Si, Pt-Pd-Si, Fe-Si, Ir-Si or Ni-Si alloys, with a thickness of 50 to 1000 nm; b) When growing few-layer hexagonal boron nitride (h-BN), the surface layer of the active material includes, but is not limited to, Fe-P, Fe-Si, Ni-P, Ni-Si, Pt-Si, Pt-P, Pd-Si or Pd-P alloys, with a thickness of 50 to 1000 nm; c) When growing few-layer transition metal compounds, the surface layer of the active material includes, but is not limited to, Fe-P, Fe-Si, Ni-P, Ni-Si, Pt-Si, Pt-P, Pd-Si or Pd-P alloys, with a thickness of 50 to 1000 nm.

5. The method for preparing a few-layer two-dimensional material film with uniform layer number and stacking mode by intelligent self-regulation according to claim 2, wherein, The preparation method of the composite substrate is: covering a surface of a solid metal or alloy thin sheet as a source material with a single element or compound containing the constituent elements of the surface layer of the active material by magnetron sputtering or electroless plating, with a thickness of 50 to 1000 nm.

6. The method for intelligently self-regulating the preparation of a few-layer two-dimensional material thin film with uniform layer number and stacking mode according to claim 1, characterized in that: a) When the two-dimensional material is a single-element two-dimensional material such as graphene, phosphorene or silicene, the growth precursor is a gaseous or liquid compound: methane, ethane, silane, ethylene, acetylene, benzene, toluene, cyclohexane, ethanol, methanol, acetone or carbon monoxide, one or more of them, or a solid source: amorphous carbon, phosphorus, paraffin, polymethyl methacrylate, polycarbonate, polystyrene, polyethylene, polypropylene, one or more of them; b) When the two-dimensional material is hexagonal boron nitride (h-BN), the growth precursor is nitrogen, ammonia or ammonia borane; c) When the two-dimensional material is a transition metal compound, the growth precursor in addition to the above single elements or compounds also includes one or more of sulfur, selenium, tellurium, zinc sulfide, zinc selenide, zinc telluride powder or crystal, hydrogen sulfide gas.

7. The method for preparing a few-layer two-dimensional material film with uniform layer number and stacking mode by intelligent self-adjustment according to claim 1, wherein, By adjusting the proportion of the alloy components, the temperature in the growth stage and the growth atmosphere mode, the total amount of the growth source for forming the two-dimensional material in the closed system is changed, and finally the regulation of the layer number of the two-dimensional material is realized.

8. The method for preparing a few-layer two-dimensional material film with uniform prepared layer number and stacking mode according to claim 1, characterized in that, During the self-regulation stage, a stable temperature and atmosphere need to be maintained to avoid etching reactions that damage the closed system.

9. The method for preparing a few-layer two-dimensional material film with uniform layer number and stacking mode by intelligent self-adjustment according to claim 1, wherein, During the self-regulation stage, the atomic diffusion rate and the structure transformation rate are controlled by regulating the temperature.

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