Large-scale preparation method of double-layer two-dimensional material with controllable rotation angle

Abstract

The invention discloses a large-scale preparation method of a double-layer two-dimensional material with a controllable rotation angle. The large-scale preparation method comprises the following steps: transferring a two-dimensional material onto a substrate; patterning the two-dimensional material on the surface of the substrate to form a two-dimensional material array; dividing the two-dimensional material array into a selection area and a target area; transferring the two-dimensional material in the selected area to the composite supporting layer; and transferring the two-dimensional material on the composite support layer to the surface of the two-dimensional material in the target area (controlling the corner of the corner double-layer two-dimensional material by controlling the relative position of the two-dimensional material on the composite support layer and the two-dimensional material in the target area in the process) to form the large-scale corner double-layer two-dimensional material array. According to the preparation method provided by the invention, the large-scale corner two-dimensional material homojunction array capable of accurately controlling the interlayer torsion angle can be obtained. The preparation method has the excellent characteristics of being accurate in angle control, large in stacking area, good in universality and the like, and meanwhile the machining process is economical, efficient and extensible.

Description

Technical Field

[0001] The present invention relates to the technical field of two-dimensional semiconductor materials, and particularly to a method for large-scale preparation of bilayer two-dimensional materials with controllable twist angles. Background Art

[0002] Due to their excellent electrical, optical, and mechanical properties, two-dimensional layered materials have attracted extensive attention from researchers in multiple fields such as materials, physics, and electronics. Since the layers are bonded by relatively weak van der Waals forces, two-dimensional materials can be rotated relative to each other by a certain angle and vertically stacked together to form bilayer two-dimensional materials with twist angles, which may lead to various peculiar physical behaviors. Using atomic force microscopy or layer-by-layer transfer methods to create the desired twist angle, the sample size is limited to within ten micrometers, and angle control is difficult, which greatly hinders the development of twistronics.

[0003] Currently, various large-scale material stacking methods have been developed. However, a key challenge is that since the materials are from different samples, it is difficult to determine the grain orientation, resulting in random twist angles and difficulty in forming specific angles, lacking flexibility. In addition, the high adhesion between two-dimensional materials and the substrate leads to cracks, wrinkles, and interface contamination during the transfer process, which can affect uniformity and electronic properties. Therefore, there is an urgent need to develop a large-scale preparation technology for bilayer two-dimensional materials with controllable twist angles. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for large-scale preparation of bilayer two-dimensional materials with controllable twist angles to solve the problems existing in the above-mentioned prior art. The preparation method of the present invention has excellent characteristics such as precise angle control, large stacking area, and good universality. At the same time, the processing technology is economical, efficient, and scalable. The preparation method provided by the present invention aims to obtain a large-scale two-dimensional vdW (van der Waals interaction) homojunction with precisely controlled interlayer twist angles (i.e., twist angles).

[0005] To achieve the above purpose, the present invention provides the following solutions:

[0006] One of the technical solutions of the present invention: A method for large-scale preparation of bilayer two-dimensional materials with controllable twist angles, comprising the following steps:

[0007] Transfer two-dimensional materials onto a substrate;

[0008] Pattern the two-dimensional materials on the surface of the substrate to form a two-dimensional material array;

[0009] Divide the two-dimensional material array into a selection area and a target area;

[0010] Transfer the two-dimensional materials in the selection area (i.e., the top-layer two-dimensional materials) onto a composite support layer;

[0011] Transfer the two-dimensional material on the composite support layer to the surface of the two-dimensional material in the target area (i.e., the bottom two-dimensional material) to form a large-scale twisted bilayer two-dimensional material array (i.e., a large-scale twisted two-dimensional material homojunction array).

[0012] During the process of transferring the two-dimensional material on the composite support layer to the surface of the two-dimensional material in the target area, the twist angle of the twisted bilayer two-dimensional material is controlled by controlling the relative position of the two-dimensional material on the composite support layer and the two-dimensional material in the target area.

[0013] In the present invention, both the top layer and the bottom layer of the bilayer two-dimensional material are from the same two-dimensional material sample, and their grain orientations are the same, so that the twist angle can be controlled, which is beneficial to form a specific angle and has high flexibility. The composite support layer of the present invention can be deformed under heating to achieve controllable conformal contact, thereby realizing the large-scale transfer of the two-dimensional material array without cracks, contamination and wrinkles, providing a clean surface; moreover, when using the composite support layer for transfer, the scale of the large-scale twisted bilayer two-dimensional material array can also be controlled by controlling the contact area between the composite support layer and the two-dimensional material in the selected area, and the twist angle of the twisted bilayer two-dimensional material can be controlled by controlling the relative position of the two-dimensional material on the composite support layer and the two-dimensional material in the target area. In summary, through the preparation method of the present invention, a large-scale twisted bilayer two-dimensional material array with large scale, controllable, precisely controllable twist angle and uniform and clean surface can be obtained.

[0014] In the prior art, the stacking of bilayer two-dimensional materials is realized through the peeling process of the tape and the transfer process of viscoelastic or vitreous polymers. Such methods have limitations such as low yield, limited size, irregular sheet shape, unstable thermodynamic twist angle and inevitable interlayer contamination. In contrast, the method of the present invention can produce large-size, arrayed and uniform high-quality twisted homojunctions, with significant advantages.

[0015] Furthermore, the array size of the large-scale twisted bilayer two-dimensional material array is greater than or equal to 200×200 μm (rectangular array, with both length and width greater than or equal to 200 μm), wherein the size of each twisted bilayer two-dimensional material (i.e., a single device) is greater than or equal to 20×10 μm (rectangular, with length greater than or equal to 20 μm and width greater than or equal to 10 μm), and the array scale (i.e., the number of twisted bilayer two-dimensional materials in the array) is greater than or equal to 3×6 (in the horizontal and vertical directions, one direction is greater than or equal to 3 and the other direction is greater than or equal to 6, that is, the number of twisted bilayer two-dimensional materials in the array is greater than or equal to 18).

[0016] Furthermore, the interlayer binding force of the twisted bilayer two-dimensional material is van der Waals force.

[0017] Further, the composite support layer includes a PDMS+PMMA composite support layer, a PDMS+PPC composite support layer, a PDMS+PMMA+PPC composite support layer, or a PDMS+PMMA+PVA composite support layer.

[0018] Further, the bottom layer of the PDMS+PMMA composite support layer is PDMS (polydimethylsiloxane), and the surface layer is PMMA (polymethyl methacrylate);

[0019] Or, the bottom layer of the PDMS+PPC composite support layer is PDMS, and the surface layer is PPC (poly(ethylene carbonate));

[0020] Or, the bottom layer of the PDMS+PMMA+PPC composite support layer is PDMS, the middle layer is PMMA, and the surface layer is PPC;

[0021] Or, the bottom layer of the PDMS+PMMA+PVA composite support layer is PDMS, the middle layer is PMMA, and the surface layer is PVA (polyvinyl alcohol).

[0022] Further, the thickness of the bottom layer PDMS in the PDMS+PMMA composite support layer is 2-4 mm, and the thickness of the surface layer PMMA is 500-600 nm;

[0023] Or, the thickness of the bottom layer PDMS in the PDMS+PPC composite support layer is 2-4 mm, and the thickness of the surface layer PPC is 500 nm - 1 μm;

[0024] Or, the thickness of the bottom layer PDMS in the PDMS+PMMA+PPC composite support layer is 2-4 mm, the thickness of the middle layer PMMA is 500-600 nm, and the thickness of the surface layer PPC is 500 nm - 1 μm;

[0025] Or, the thickness of the bottom layer PDMS in the PDMS+PMMA+PVA composite support layer is 2-4 mm, the thickness of the middle layer PMMA is 500-600 nm, and the thickness of the surface layer PVA is 500 nm - 1 μm.

[0026] The composite support layer of the present invention can be deformed under heating to achieve controllable conformal contact, thereby realizing the large-scale transfer of two-dimensional material arrays without cracks, contamination, and wrinkles, providing a clean surface.

[0027] Transferring solely using PDMS will leave obvious insulating residues on the surface of two-dimensional materials. Moreover, PDMS has a relatively high mechanical hardness, and it is prone to cracks, wrinkles, and interface contamination during the transfer process, which will affect the uniformity and electrical properties of the two-dimensional materials after transfer. In the present invention, a composite layer is formed by stacking a hydroxyl-containing polymer layer (such as PVA) or small molecules such as PPC and PMMA on the surface of PDMS. On the one hand, it can ensure strong adhesion under high mechanical stress, which helps the composite support layer peel off the top-layer molybdenum disulfide nanosheets from the substrate surface; on the other hand, the glass transition temperature of this small molecule or hydroxyl-containing polymer layer will decrease when heated, weakening its molecular chains or intermolecular forces, and making it easier to deform under external pressure, resulting in conformal contact with the target substrate with different surface profiles, thereby achieving large-area transfer of two-dimensional materials without cracks, contamination, and wrinkles.

[0028] Furthermore, the transfer of the two-dimensional materials in the selected area to the composite support layer is carried out on an accurate transfer platform;

[0029] and / or, the transfer of the two-dimensional materials on the composite support layer to the surface of the two-dimensional materials in the target area is carried out on an accurate transfer platform.

[0030] Furthermore, the transfer of the two-dimensional materials in the selected area to the composite support layer includes: contacting the surface layer of the composite support layer with the two-dimensional materials in the selected area, and then performing heat treatment. After the heat treatment is completed, the composite support layer is lifted, and the two-dimensional materials in the selected area are transferred to the composite support layer.

[0031] Furthermore, the contacting of the surface layer of the composite support layer with the two-dimensional materials in the selected area includes: controlling the scale of the large-scale twist bilayer two-dimensional material array by controlling the contact area between the surface layer of the composite support layer and the two-dimensional materials in the selected area;

[0032] and / or, the temperature of the heat treatment is 40 - 70 °C, and the time is 1 - 5 min.

[0033] Furthermore, the transfer of the two-dimensional materials on the composite support layer to the surface of the two-dimensional materials in the target area includes: approaching the composite support layer with the two-dimensional materials to the two-dimensional materials in the target area until the two-dimensional materials carried on the composite support layer come into contact with the two-dimensional materials in the target area, and then performing heat treatment. After the heat treatment is completed, the bottom layer of the composite support layer is lifted to obtain a bilayer two-dimensional material with the surface layer or the surface layer + intermediate layer of the composite support layer.

[0034] Furthermore, the approaching of the composite support layer with the two-dimensional materials to the two-dimensional materials in the target area includes: controlling the twist angle of the twist bilayer two-dimensional material by controlling the relative position between the two-dimensional materials on the composite support layer and the two-dimensional materials in the target area;

[0035] And / or, the temperature of the heat treatment is 110 - 130 °C, and the time is 1 - 3 min.

[0036] Furthermore, the relative position of the two-dimensional material on the composite support layer and the two-dimensional material in the target area is realized by controlling the angle of the precise transfer platform.

[0037] Furthermore, after transferring the two-dimensional material on the composite support layer to the surface of the two-dimensional material in the target area, it further includes the operation of removing the surface layer or the surface layer + intermediate layer of the composite support layer.

[0038] Furthermore, the operation of removing the surface layer or the surface layer + intermediate layer of the composite support layer includes: soaking the double-layer two-dimensional material with the surface layer or the surface layer + intermediate layer of the composite support layer in acetone and isopropanol in sequence.

[0039] Furthermore, soaking the double-layer two-dimensional material with the surface layer or the surface layer + intermediate layer of the composite support layer in acetone and isopropanol in sequence includes: first heating and soaking in acetone for 5 - 30 min, and then soaking at room temperature in isopropanol for 3 - 5 min.

[0040] Furthermore, the temperature of the heating soak is 45 - 120 °C.

[0041] Furthermore, the two-dimensional material includes graphene, molybdenum disulfide, molybdenum diselenide, tungsten disulfide, tungsten diselenide, indium selenide, black phosphorus, tellurene or molybdenum ditelluride.

[0042] Furthermore, the substrate includes SiO2 / Si (i.e., a silicon wafer with an oxide), SiN, flexible insulating PET (polyethylene terephthalate) or sapphire.

[0043] Furthermore, the transfer method of transferring the two-dimensional material onto the substrate includes PPC-assisted transfer, PMMA-assisted transfer, PVA-assisted transfer or gold-assisted transfer.

[0044] Furthermore, patterning the two-dimensional material on the substrate surface to form a two-dimensional material array includes: first performing patterning treatment using electron beam lithography technology or ultraviolet lithography technology, and then etching the exposed area using ion etching technology or wet etching technology.

[0045] The second technical solution of the present invention: A large-scale twisted bilayer two-dimensional material array prepared according to the above preparation method.

[0046] The present invention discloses the following technical effects:

[0047] The preparation method provided by the present invention can obtain a large-scale twist-angle two-dimensional material homojunction array with precisely controlled interlayer twist angles. The preparation method of the present invention has excellent characteristics such as precise angle control, large stacking area (i.e., large area of the obtained array), and good universality. At the same time, the processing technology is economical, efficient, and scalable.

[0048] The present invention prepares a large-scale twist-angle two-dimensional material homojunction by precisely controlling the twist angle, which is expected to open up new ways for the industrial applications of twistronics and photonics. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0050] Figure 1 It is a schematic flowchart of the large-scale preparation method of the twist-angle controllable bilayer two-dimensional material of the present invention;

[0051] Figure 2 It is a topographic map of monolayer molybdenum disulfide nanosheets transferred to a SiO2 / Si substrate under an optical microscope in step (2) of Example 1;

[0052] Figure 3 It is a topographic map of the molybdenum disulfide nanosheet array obtained after patterned etching under an optical microscope in step (3) of Example 1, where the right figure is an enlarged view of a local area;

[0053] Figure 4 It is a topographic map of the large-scale twist-angle molybdenum disulfide homojunction array prepared in Example 1 under an optical microscope, where the right figure is an enlarged view of a local area;

[0054] Figure 5 It is a topographic map of a twist-angle molybdenum disulfide homojunction in the large-scale twist-angle molybdenum disulfide homojunction array prepared in Example 1 under an electron beam microscope;

[0055] Figure 6 It is a topographic map of the large-scale twist-angle molybdenum disulfide homojunction array prepared in Example 2 under an optical microscope;

[0056] Figure 7 It is an enlarged topographic map of a twist-angle molybdenum disulfide homojunction in the large-scale twist-angle molybdenum disulfide homojunction array prepared in Example 2 under an electron beam microscope;

[0057] Figure 8Figure showing the magnified morphology of a twisted molybdenum disulfide homojunction in the large-scale twisted molybdenum disulfide homojunction arrays prepared in Example 1 and Examples 3 - 5. Among them, the one with a twist angle of 0.6° is Example 1, the one with a twist angle of 1.7° is Example 3, the one with a twist angle of 3.2° is Example 4, and the one with a twist angle of 4.1° is Example 5;

[0058] Figure 9 Raman spectra of twisted molybdenum disulfide homojunctions with different twist angles prepared in Example 1 and Examples 3 - 5;

[0059] Figure 10 Morphology image of a single twisted molybdenum disulfide homojunction prepared by the prior art in Comparative Example 1 under an optical microscope;

[0060] Figure 11 Test results of the electrical properties of the twisted molybdenum disulfide homojunctions in Example 1 and Comparative Example 1. Detailed implementation manners

[0061] Now, various exemplary implementation manners of the present invention will be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, characteristics, and implementation schemes of the present invention.

[0062] It should be understood that the terms used in the present invention are only for describing specific implementation manners and are not used to limit the present invention. Additionally, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0063] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention pertains. Although the present invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein can also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the documents. In case of conflict with any incorporated document, the content of this specification shall prevail.

[0064] Without departing from the scope or spirit of the present invention, various improvements and changes can be made to the specific implementation manners of the present invention specification, which are obvious to those skilled in the art. Other implementation manners obtained from the specification of the present invention are obvious to those skilled in the art. The specification and examples of the present invention are only exemplary.

[0065] Regarding the terms "comprising", "including", "having", "containing", etc. used in this article, they are all open-ended terms, meaning including but not limited to.

[0066] It should be noted that the operations not described in detail in the present invention are all conventional operation means in the art and are not the focus of the present invention.

[0067] As a first aspect of the present invention, the present invention provides a method for large-scale preparation of a bilayer two-dimensional material with controllable twist angle, including the following steps:

[0068] Transfer the two-dimensional material onto a substrate;

[0069] Pattern the two-dimensional material on the surface of the substrate to form a two-dimensional material array;

[0070] Divide the two-dimensional material array into a selection area and a target area;

[0071] Transfer the two-dimensional material in the selection area onto a composite support layer;

[0072] Transfer the two-dimensional material on the composite support layer onto the surface of the two-dimensional material in the target area to form a large-scale twist-angle bilayer two-dimensional material array (i.e., a large-scale twist-angle two-dimensional material homojunction array);

[0073] During the process of transferring the two-dimensional material on the composite support layer onto the surface of the two-dimensional material in the target area, the twist angle of the twist-angle bilayer two-dimensional material is controlled by controlling the relative position of the two-dimensional material on the composite support layer and the two-dimensional material in the target area.

[0074] As an embodiment of the present invention, the size of the large-scale twist-angle bilayer two-dimensional material array is greater than or equal to 200×200 μm (rectangular array, with both length and width greater than or equal to 200 μm), where the size of each twist-angle bilayer two-dimensional material (i.e., a single device) is greater than or equal to 20×10 μm (rectangle, with length greater than or equal to 20 μm and width greater than or equal to 10 μm), and the array scale (i.e., the number of twist-angle bilayer two-dimensional materials in the array) is greater than or equal to 3×6 (in the horizontal and vertical directions, one direction is greater than or equal to 3 and the other direction is greater than or equal to 6, that is, the number of twist-angle bilayer two-dimensional materials in the array is greater than or equal to 18).

[0075] As an embodiment of the present invention, the interlayer binding force of the twist-angle bilayer two-dimensional material is van der Waals force.

[0076] As an embodiment of the present invention, the composite support layer includes a PDMS+PMMA composite support layer, a PDMS+PPC composite support layer, a PDMS+PMMA+PPC composite support layer, or a PDMS+PMMA+PVA composite support layer.

[0077] As an embodiment of the present invention, the bottom layer of the PDMS+PMMA composite support layer is PDMS, and the surface layer is PMMA;

[0078] Or, the bottom layer of the PDMS+PPC composite support layer is PDMS, and the surface layer is PPC;

[0079] Or, the bottom layer of the PDMS+PMMA+PPC composite support layer is PDMS, the middle layer is PMMA, and the surface layer is PPC;

[0080] Or, the bottom layer of the PDMS+PMMA+PVA composite support layer is PDMS, the middle layer is PMMA, and the surface layer is PVA.

[0081] As a preferred embodiment of the present invention, the thickness of the bottom layer PDMS in the PDMS+PMMA composite support layer is 2-4 mm, and the thickness of the surface layer PMMA is 500-600 nm;

[0082] Or, the thickness of the bottom layer PDMS in the PDMS+PPC composite support layer is 2-4 mm, and the thickness of the surface layer PPC is 500 nm-1 μm;

[0083] Or, the thickness of the bottom layer PDMS in the PDMS+PMMA+PPC composite support layer is 2-4 mm, the thickness of the middle layer PMMA is 500-600 nm, and the thickness of the surface layer PPC is 500 nm-1 μm;

[0084] Or, the thickness of the bottom layer PDMS in the PDMS+PMMA+PVA composite support layer is 2-4 mm, the thickness of the middle layer PMMA is 500-600 nm, and the thickness of the surface layer PVA is 500 nm-1 μm;

[0085] As a preferred embodiment of the present invention, the more specific steps of the method for large-scale preparation of bilayer two-dimensional materials with controllable corners include (the process schematic diagram is as Figure 1 shown, Figure 1 taking the substrate as SiO2 / Si, the two-dimensional material as MoS2, and the composite support film as PDMS+PMMA+PPC as an example):

[0086] (1) Prepare two-dimensional materials: Prepare two-dimensional materials such as graphene, molybdenum disulfide, molybdenum diselenide, tungsten disulfide, tungsten diselenide, indium selenide, black phosphorus, tellurene or molybdenum ditelluride by conventional methods for preparing two-dimensional materials in the art such as chemical vapor deposition;

[0087] (2) Transfer the two-dimensional material to the substrate: Transfer the two-dimensional material to a new substrate (SiO2 / Si, SiN, flexible insulating PET or sapphire) by PPC-assisted transfer, PMMA-assisted transfer, PVA-assisted transfer or gold-assisted transfer;

[0088] (3) Pattern the two-dimensional material on the substrate surface: First, perform patterning using an electron beam lithography process or an ultraviolet lithography process, and then etch the exposed area using an ion etching or wet etching process to obtain a two-dimensional material array, and divide the two-dimensional material array into a selected area and a target area;

[0089] (4) Prepare a composite support layer: First, prepare a bottom layer, and then spin-coat the material of the top layer on the bottom layer to obtain a composite support layer; or first prepare a bottom layer, then spin-coat the material of the intermediate layer on the bottom layer to obtain an intermediate layer, and finally spin-coat the material of the top layer on the intermediate layer to obtain a composite support layer;

[0090] (5) Transfer the two-dimensional material in the selected area to the composite support layer: On an accurate transfer platform, bring the top layer of the composite support layer into contact with the two-dimensional material in the selected area (in this process, control the scale of the top-layer molybdenum disulfide nanosheet array transferred to the composite support layer by controlling the contact area between the composite support layer and the molybdenum disulfide nanosheets in the selected area, and thus control the scale of the finally obtained bilayer two-dimensional material array), and then perform heat treatment at 40 - 70 °C for 1 - 5 min. After the heat treatment is completed, lift the composite support layer, and the two-dimensional material in the selected area is transferred to the composite support layer;

[0091] (6) Transfer the two-dimensional material on the composite support layer to the surface of the two-dimensional material in the target area: On an accurate transfer platform, bring the composite support layer with the two-dimensional material close to the two-dimensional material in the target area (in this process, control the relative position between the top-layer molybdenum disulfide nanosheets and the bottom-layer molybdenum disulfide nanosheets by controlling the angle of the transfer platform, and thus control the twist angle between the top-layer molybdenum disulfide nanosheets and the bottom-layer molybdenum disulfide nanosheets) until the two-dimensional material carried on the composite support layer comes into contact with the two-dimensional material in the target area, and then perform heat treatment at 110 - 130 °C for 1 - 3 min. After the heat treatment is completed, lift the bottom layer of the composite support layer (when lifting after the heat treatment, the top layer or the top layer + intermediate layer of the composite support layer is separated from the bottom layer), and obtain a bilayer two-dimensional material with the top layer or the top layer + intermediate layer of the composite support layer;

[0092] (7) Remove the top layer or the top layer + intermediate layer of the composite support layer: Soak the bilayer two-dimensional material with the top layer or the top layer + intermediate layer of the composite support layer in acetone at 45 - 120 °C for 5 - 30 min, then soak it in isopropanol at room temperature for 3 - 5 min, and then quickly take it out and blow it dry with nitrogen to obtain a large-scale twist-angle bilayer two-dimensional material array.

[0093] As a preferred embodiment of the present invention, the parameters of the etching include: the oxygen flow rate is 5 - 30 sccm, the SF6 flow rate is 5 - 30 sccm, the etching power is 5 - 30 W, and the etching time is 5 - 15 s.

[0094] The second technical solution of the present invention: a large-scale array of corner double-layer two-dimensional materials prepared according to the above preparation method.

[0095] The technical solution of the present invention will be further described below in conjunction with specific embodiments.

[0096] In the following embodiments, the room temperature specifically refers to 20 - 30 °C.

[0097] All raw materials used in the following embodiments are ordinary commercially available products, and all equipment used is commonly used equipment in the art.

[0098] The preparation method of the PDMS support plate used in the following embodiments is as follows: Mix the main agent and curing agent of PDMS (brand: Dow Corning, model: 184) evenly at a mass ratio of 10:1, then pour it into a round petri dish, and let it stand at 85 °C for 4 h to obtain a PDMS support plate with a thickness of 4 mm.

[0099] Example 1

[0100] A large-scale preparation method of a double-layer two-dimensional material (molybdenum disulfide homojunction) with controllable twist angle, the steps are as follows:

[0101] (1) Prepare monolayer molybdenum disulfide (MoS2) nanosheets by chemical vapor deposition: Using molybdenum trioxide powder and sulfur powder as precursors, under the conditions of a growth temperature of 850 °C and oxygen assistance, synthesize monolayer molybdenum disulfide nanosheets. The sulfur powder is placed upstream of the air inlet, and turns into sulfur vapor at 175 °C and flows to the middle reaches at a temperature of 850 °C along with the carrier gas (Ar) (here, molybdenum trioxide powder is placed, and the molybdenum trioxide powder is placed under the SiO2 substrate, and the substrate is buckled), and the reaction occurs to generate monolayer molybdenum disulfide nanosheets, and the monolayer molybdenum disulfide nanosheets adhere to the SiO2 substrate.

[0102] (2) Transfer the monolayer molybdenum disulfide nanosheets to a new substrate through PPC-assisted transfer: Weigh 3 g of PPC particles and dissolve them in 30 mL of anisole. Stir the solution at 500 rpm for 10 h under heating at 160 °C using a magnetic stirrer to obtain a PPC solution. Spin-coat the PPC solution on the surface of the monolayer molybdenum disulfide nanosheets at a speed of 1600 rpm for 30 s using a spin coater. After spin-coating, bake the sample on a hot plate at 100 °C for 10 s to form a PPC organic film. Place the sample with the spin-coated PPC organic film in an HF solution (concentration: 5 wt%) to separate the monolayer molybdenum disulfide nanosheets from the substrate by dissolving the substrate SiO2. Transfer the PPC organic film with the monolayer molybdenum disulfide nanosheets to deionized water and wash it 3 - 5 times. Then attach the PPC organic film side of the PPC organic film with the monolayer molybdenum disulfide nanosheets to a PDMS support plate and bake it on a hot plate at 100 °C for 30 s to make the PPC organic film fit seamlessly with the PDMS support plate. Then use a precise transfer platform to align the monolayer molybdenum disulfide nanosheets on the PPC organic film with the marked area on the new SiO2 / Si substrate, and heat at 100 °C for 10 min to separate the monolayer molybdenum disulfide nanosheets from the PPC organic film and transfer the monolayer molybdenum disulfide nanosheets to the new substrate (SiO2 / Si). (The morphological diagram of the monolayer molybdenum disulfide nanosheets under an optical microscope after being transferred to the SiO2 / Si substrate is as shown in Figure 2 ).

[0103] (3) Pattern etching of monolayer molybdenum disulfide nanosheets: Spin-coat a layer of PMMA colloid on the surface of the monolayer molybdenum disulfide nanosheets transferred to the new SiO2 / Si substrate and dry it at 165 °C for 1 min. Then perform patterning using electron beam lithography technology and bombard and etch using a plasma etcher in an atmosphere of SF6 and O2. The specific etching parameters are: SF6 15 sccm, O2 5 sccm, etching power 15 W, etching time 5 s. Prepare patterned molybdenum disulfide nanosheets, that is, obtain a molybdenum disulfide nanosheet array, and divide it into a selected area and a target area (as shown in Figure 3 ), where the top layer MoS2 represents the MoS2 in the selected area, and the bottom layer MoS2 represents the MoS2 in the target area).

[0104] (4) Preparation of the composite support layer: Spin-coat the PPC solution (the preparation method of the PPC solution is the same as in step (2)) on the PDMS support plate at a rotation speed of 1600 rpm and a spin-coating time of 30 s using a spin coater. After spin-coating, bake it on a hot plate at 65 °C for 60 s and then remove it to obtain a PDMS + PPC composite support layer (that is, a PDMS support plate with a PPC organic film, where the thickness of the PPC organic film is 800 nm).

[0105] (5)Precisely transfer the molybdenum disulfide nanosheets in the selected area (i.e., the top-layer molybdenum disulfide nanosheets) onto the composite support layer: Place the PDMS+PPC composite support layer at the clamping position above the precise transfer platform (with the PPC side facing down), and place the SiO2 / Si substrate with the molybdenum disulfide nanosheet array at the bottom of the precise transfer platform (with the molybdenum disulfide nanosheet side facing up). Lower the PDMS+PPC composite support layer close to the molybdenum disulfide nanosheets in the selected area, and control the lowering speed to make it slowly contact the molybdenum disulfide nanosheets (during this process, control the scale of the top-layer molybdenum disulfide nanosheet array transferred onto the composite support layer by controlling the contact area between the composite support layer and the molybdenum disulfide nanosheets in the selected area, and further control the scale of the final obtained bilayer two-dimensional material array). Then turn on the heating module, heat up to 60 °C and keep it warm for 2 min, and then slowly lift the PDMS+PPC composite support layer. At this time, the molybdenum disulfide nanosheets in the selected area have been transferred onto the PDMS+PPC composite support layer.

[0106] (6)Precisely transfer the molybdenum disulfide nanosheets on the composite support layer onto the surface of the molybdenum disulfide nanosheets in the target area (i.e., the bottom-layer molybdenum disulfide nanosheets): Lower the PDMS+PPC composite support layer with the molybdenum disulfide nanosheets slowly close to the molybdenum disulfide nanosheets in the target area (during this process, control the relative position between the top-layer molybdenum disulfide nanosheets and the bottom-layer molybdenum disulfide nanosheets by controlling the angle of the transfer platform, and further control the rotation angle between the top-layer molybdenum disulfide nanosheets and the bottom-layer molybdenum disulfide nanosheets. In this embodiment, control the rotation angle between the top-layer molybdenum disulfide nanosheets and the bottom-layer molybdenum disulfide nanosheets to be 0.6°) until the molybdenum disulfide nanosheets carried on the PDMS+PPC composite support layer contact the molybdenum disulfide nanosheets in the target area on the SiO2 / Si substrate. Then turn on the heating module, heat up to 120 °C and keep it warm for 2 min, and then slowly lift the PDMS support plate. At this time, the PPC organic film in the PDMS+PPC composite support layer is separated from the PDMS support plate, and the molybdenum disulfide nanosheets with the PPC organic film have been stacked on the molybdenum disulfide nanosheets in the target area, obtaining bilayer molybdenum disulfide nanosheets with the PPC organic film (i.e., molybdenum disulfide homojunction). Remove the SiO2 / Si substrate with the bilayer molybdenum disulfide nanosheets and the PPC organic film, and bake it on a hot plate at 110 °C for 10 min to reduce bubbles.

[0107] (7)Remove the PPC organic film: Place the SiO2 / Si substrate with the bilayer molybdenum disulfide nanosheets and the PPC organic film in acetone, bake it on a hot plate at 105 °C for 20 min to remove the PPC organic film, then soak it in isopropanol for 5 min to remove the residual acetone, quickly take it out and dry it with nitrogen to obtain a large-scale rotated molybdenum disulfide homojunction array with a rotation angle of 0.6°.

[0108] Figure 4Morphology image of the large-scale MoS₂ homojunction array prepared in this example under an optical microscope. As can be seen from Figure 4 , the MoS₂ homojunction has uniform twists and a clean surface, indicating that the method has successfully constructed a large-scale MoS₂ homojunction array. The size of the array exceeds 200×200μm, and the scale of the array is 3×6. Figure 5 The enlarged morphology image of a MoS₂ homojunction with a twist angle in the array under an electron beam microscope shows that the twist angle of the MoS₂ homojunction with a twist is 0.6°, and the size of a single MoS₂ homojunction with a twist is greater than 20×10μm.

[0109] Repeat the steps of Example 1 to prepare a large-scale MoS₂ homojunction array with an array size exceeding 200×200μm, an array scale of 3×6, a size of a single MoS₂ homojunction with a twist greater than 20×10μm, and a twist angle of 0.6° for 10 times, and the success rate is 100% (each MoS₂ homojunction with a twist in the array is complete and uniform).

[0110] Example 2

[0111] Same as Example 1, the only difference is that in step (6), the twist angle between the top MoS₂ nanosheet and the bottom MoS₂ nanosheet is controlled to be 50° by controlling the angle of the transfer platform, and finally a large-scale MoS₂ homojunction array with a twist angle of 50° is obtained.

[0112] Figure 6 Morphology image of the large-scale MoS₂ homojunction array prepared in this example under an optical microscope. As can be seen from Figure 6 , the MoS₂ homojunction has uniform twists and a clean surface, indicating that the method has successfully constructed a large-scale MoS₂ homojunction array. Figure 7 The enlarged morphology image of a MoS₂ homojunction with a twist angle in the array under an electron beam microscope shows that the twist angle of the MoS₂ homojunction with a twist is 50°.

[0113] Example 3

[0114] Same as Example 1, the only difference is that in step (6), the twist angle between the top MoS₂ nanosheet and the bottom MoS₂ nanosheet is controlled to be 1.7° by controlling the angle of the transfer platform, and finally a large-scale MoS₂ homojunction array with a twist angle of 1.7° is obtained.

[0115] Example 4

[0116] Same as Example 1, the only difference is that in step (6), the twist angle between the top MoS₂ nanosheet and the bottom MoS₂ nanosheet is controlled to be 3.2° by controlling the angle of the transfer platform, and finally a large-scale MoS₂ homojunction array with a twist angle of 3.2° is obtained.

[0117] Example 5

[0118] Same as Example 1, except that in step (6), the twist angle between the top-layer molybdenum disulfide nanosheet and the bottom-layer molybdenum disulfide nanosheet is controlled to be 4.1° by controlling the angle of the transfer platform, and finally a large-scale molybdenum disulfide homojunction twist array with a twist angle of 4.1° is obtained.

[0119] Figure 8 It is a magnified view of the morphology of a molybdenum disulfide homojunction with a twist angle in the large-scale twist-angle molybdenum disulfide homojunction arrays prepared in Example 1 and Examples 3 - 5 under an optical microscope (where the twist angle is 0.6° for Example 1, 1.7° for Example 3, 3.2° for Example 4, and 4.1° for Example 5).

[0120] Figure 9 It is the Raman spectra of molybdenum disulfide homojunctions with different twist angles prepared in Example 1 and Examples 3 - 5. It can be seen that as the twist angle changes, the Raman spectra of the molybdenum disulfide homojunctions change.

[0121] Comparative Example 1

[0122] The van der Waals force-assisted transfer method in the prior art is used to prepare a molybdenum disulfide homojunction with a twist angle. The steps are as follows:

[0123] (1) Using the chemical vapor deposition method in step (1) of Example 1, monolayer molybdenum disulfide nanosheets are respectively prepared on the surfaces of two substrates. The monolayer molybdenum disulfide nanosheet on one substrate serves as the bottom-layer molybdenum disulfide nanosheet, and the monolayer molybdenum disulfide nanosheet on the other substrate serves as the top-layer molybdenum disulfide nanosheet (both the top-layer molybdenum disulfide nanosheet and the bottom-layer molybdenum disulfide nanosheet are triangular);

[0124] (2) Spin-coat the PPC solution on the surface of the top-layer molybdenum disulfide nanosheet, and obtain a PPC organic film with the top-layer molybdenum disulfide nanosheet through wet transfer (dissolving the substrate) (the preparation method, spin-coating method, and wet transfer method of the PPC solution are the same as those in step (2) of Example 1);

[0125] (3) Place the substrate with the bottom molybdenum disulfide nanosheets (the bottom molybdenum disulfide nanosheets facing up) in the transfer platform. Bring the PPC organic film with the top molybdenum disulfide nanosheets (the top molybdenum disulfide nanosheets facing down) close to the bottom molybdenum disulfide nanosheets on the substrate, and make the top molybdenum disulfide nanosheets and the bottom molybdenum disulfide nanosheets in close contact through mechanical pressure. Use the sides of the triangular molybdenum disulfide nanosheets to judge the rotation angle. Then, remove the PPC organic film above the top molybdenum disulfide nanosheets through acetone (the same as step (7) in Example 1) to complete the transfer. The transfer was repeated 100 times, and only 50 relatively complete (realize bilayer stacking, but the surface is uneven and has holes) and the rotation angle is 0.6° homojunctions were successfully obtained.

[0126] This method directly adsorbs the top two-dimensional material onto the bottom two-dimensional material on the target substrate by using the van der Waals force between materials, without an intermediate support layer. Its transfer efficiency is low, the success rate is low, the angle randomness is large, and there may be residual pollutants.

[0127] Figure 10 Figure of the morphology of a single-rotation-angle molybdenum disulfide homojunction prepared by the prior art for Comparative Example 1 under an optical microscope. It can be seen that the surface morphology of this homojunction is significant, showing non-uniform undulating characteristics and accompanied by clearly visible hole structures. These hole defects not only damage the integrity of the molybdenum disulfide homojunction, reduce its performance, but also limit its application potential in the fields of electronic devices and optoelectronics.

[0128] Test Example 1

[0129] Use a B1500A semiconductor device parameter analyzer and a Lakeshore probe station to study and analyze the electrical characteristics of the rotation-angle molybdenum disulfide homojunction. To ensure that the electrical test results are closer to the intrinsic characteristics of the material, gold with a higher conductivity is selected as the electrode material. Based on the rotation-angle molybdenum disulfide homojunction (the homojunction part) prepared in Example 1 or Comparative Example 1, a two-dimensional transistor device is constructed for testing. At the same time, a high-vacuum environment is maintained during the test to avoid the material being affected by external environmental oxidation, doping, etc. during the test. This test example tested the current I g under different V ds and its variation with V ds , that is, the output characteristic curve. The electrical characteristic test results (output characteristic curves) of the rotation-angle molybdenum disulfide homojunctions in Example 1 and Comparative Example 1 are as Figure 11As shown, it can be seen that compared with Comparative Example 1, the molybdenum disulfide homojunction of Example 1 exhibits significant advantages: its on-state current is increased, meaning that it can conduct current more effectively in the on state; the off-state current is effectively reduced, indicating excellent current control ability and helping to reduce energy consumption; in addition, the reduction of the subthreshold swing further reflects the fast switching ability of the device between on and off states and its sensitive response to the gate voltage, which is crucial for high-performance electronic devices. In summary, the present invention has achieved outstanding advantages in optimizing the electrical properties of the twisted molybdenum disulfide homojunction.

[0130] The embodiments described above are only descriptions of the preferred embodiments of the present invention and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for large-scale preparation of double-layer two-dimensional materials with controllable rotation angle, characterized in that: The following steps are involved: transferring the two-dimensional material to a substrate; Patterning the two-dimensional material on the surface of the substrate to form a two-dimensional material array; Dividing the two-dimensional material array into a selection area and a target area; transferring the two-dimensional material of the selected area onto the composite support layer; Transferring the two-dimensional material on the composite support layer to the two-dimensional material surface of the target area to form a large-scale corner double-layer two-dimensional material array; In the process of transferring the two-dimensional material on the composite support layer to the surface of the two-dimensional material in the target area, the rotation angle of the double-layer two-dimensional material is controlled by controlling the relative position of the two-dimensional material on the composite support layer and the two-dimensional material in the target area.

2. The method for large-scale preparation of a double-layer two-dimensional material with controllable rotation angle according to claim 1, characterized in that: The composite support layer includes a PDMS+PMMA composite support layer, a PDMS+PPC composite support layer, a PDMS+PMMA+PPC composite support layer or a PDMS+PMMA+PVA composite support layer.

3. The method for large-scale preparation of a double-layer two-dimensional material with controllable rotation angle according to claim 2, characterized in that: The bottom layer of the PDMS+PMMA composite support layer is PDMS, and the surface layer is PMMA; Or, the bottom layer of the PDMS+PPC composite support layer is PDMS, and the surface layer is PPC; Or, the bottom layer of the PDMS+PMMA+PPC composite support layer is PDMS, the middle layer is PMMA, and the surface layer is PPC; Alternatively, the bottom layer of the PDMS+PMMA+PVA composite support layer is PDMS, the middle layer is PMMA, and the surface layer is PVA.

4. The method for large-scale preparation of a double-layer two-dimensional material with controllable rotation angle according to claim 3, characterized in that: The transferring of the two-dimensional material of the selected area to the composite support layer comprises: contacting the two-dimensional material of the selected area with the surface layer of the composite support layer, then heating it, and after the heating treatment, lifting the composite support layer to transfer the two-dimensional material of the selected area to the composite support layer.

5. The method for large-scale preparation of a double-layer two-dimensional material with controllable rotation angle according to claim 4, characterized in that: The contacting of the two-dimensional material of the selected area with the surface of the composite support layer comprises: controlling the scale of the large-scale corner double-layer two-dimensional material array by controlling the contact area between the surface of the composite support layer and the two-dimensional material of the selected area; And / or, the heating treatment is performed at a temperature of 40-70° C. and a time of 1-5 min.

6. The method for large-scale preparation of a double-layer two-dimensional material with controllable rotation angle according to claim 1, characterized in that: The method of transferring the two-dimensional material on the composite support layer to the surface of the two-dimensional material in the target area includes: bringing the composite support layer carrying the two-dimensional material close to the two-dimensional material in the target area until the two-dimensional material on the composite support layer contacts the two-dimensional material in the target area, and then subjecting the composite support layer to heat treatment. After the heat treatment, the bottom layer of the composite support layer is lifted to obtain a double-layer two-dimensional material with a surface layer or a surface layer + an intermediate layer.

7. The method for large-scale preparation of a double-layer two-dimensional material with controllable rotation angle according to claim 6, characterized in that: The step of bringing the composite support layer with the two-dimensional material close to the two-dimensional material in the target area comprises: controlling the rotation angle of the angled double-layer two-dimensional material by controlling the relative position of the two-dimensional material on the composite support layer and the two-dimensional material in the target area; And / or, the heating treatment is performed at a temperature of 100-130° C. and for a time of 1-3 min.

8. The method for large-scale preparation of a double-layer two-dimensional material with controllable rotation angle according to claim 6, characterized in that: After the two-dimensional material on the composite support layer is transferred to the surface of the two-dimensional material in the target area, the process also includes removing the surface layer or the surface layer + the middle layer of the composite support layer.

9. The method for large-scale preparation of a double-layer two-dimensional material with controllable rotation angle according to claim 8, characterized in that: The operation of removing the surface layer or the surface layer + the middle layer of the composite support layer comprises: soaking the double-layer two-dimensional material with the surface layer or the surface layer + the middle layer of the composite support layer in acetone and isopropanol in turn.

10. A large-scale corner double-layer two-dimensional material array prepared according to the preparation method according to any one of claims 1 to 9.

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