Two-dimensional material continuous conformal transfer method based on composite impression

Abstract

The invention relates to a two-dimensional material continuous conformal transfer method based on a composite impression, and belongs to the technical field of two-dimensional material transfer. The method comprises the steps that a composite impression is provided and comprises a hard substrate, a first thermoplastic polymer layer, a second thermoplastic polymer layer and a first two-dimensional material layer which are sequentially stacked, and the melting point of the first thermoplastic polymer layer is lower than that of the second thermoplastic polymer layer; providing a base body to be transferred, wherein the base body comprises a sacrificial substrate and a second two-dimensional material layer arranged on the surface of the sacrificial substrate; pressing one side, provided with the first two-dimensional material layer, of the composite impression to the second two-dimensional material layer, heating until the first thermoplastic polymer layer is softened and deformed, preserving heat for a period of time, then cooling, separating the second two-dimensional material layer from the sacrificial substrate, and repeating for multiple times until a preset number of second two-dimensional material layers are formed on the surface of the composite impression; and removing the hard substrate, the first thermoplastic polymer layer and the second thermoplastic polymer layer to obtain the two-dimensional laminated structure.

Description

Technical Field

[0001] The present application relates to the technical field of two-dimensional material transfer, and in particular to a method for continuous conformal transfer of two-dimensional materials based on a composite mold. Background Art

[0002] Two-dimensional materials, due to their excellent properties such as sub-nanometer thickness, fast charge transfer, high carrier mobility and intrinsic spin-valley coupling, show broad application prospects in the fields of next-generation electronics, optoelectronics and spintronics. Today, the preparation technology of large-area two-dimensional materials has become mature. To further integrate them with existing silicon-based technologies or expand their applications in flexible electronics and deformable optoelectronics, reliable large-area transfer technology is crucial. In addition, by stacking two-dimensional materials into homogeneous or heterogeneous structures with high interface quality, their applications in photodetectors, photocatalysts, lasers and light-emitting diodes can be broadened. However, traditional transfer technology will inevitably introduce impurities or defects at the interface, reducing the quality of the material. The existing improved conformal transfer technology can only achieve high-quality transfer of single-layer two-dimensional materials, and cannot complete stable and continuous stacking, which makes it difficult to meet the demand for stacked two-dimensional materials in the rapidly developing corner electronics and moiré electronics. Summary of the Invention

[0003] To solve the above problems, the purpose of the embodiments of the present application includes providing a method for continuous conformal transfer of two-dimensional materials based on a composite mold, which can realize continuous conformal transfer of two-dimensional materials and complete the controllable preparation of multi-layer homogeneous or heterogeneous structures of large-area two-dimensional materials.

[0004] The present invention provides a method for continuous conformal transfer of two-dimensional materials based on a composite stamp, comprising the following steps:

[0005] Providing a composite stamp, the composite stamp comprising a hard substrate, a first thermoplastic polymer layer, a second thermoplastic polymer layer, and a first two-dimensional material layer stacked in sequence along a thickness direction; wherein the melting point of the first thermoplastic polymer layer is lower than the melting point of the second thermoplastic polymer layer;

[0006] Providing a substrate to be transferred, wherein the substrate to be transferred includes a sacrificial substrate and a second two-dimensional material layer provided on a surface of the sacrificial substrate;

[0007] Pressing the side of the composite stamp provided with the first two-dimensional material layer against the second two-dimensional material layer, heating the first thermoplastic polymer layer until it softens and deforms, maintaining the temperature for a period of time to allow the first two-dimensional material layer and the second two-dimensional material layer to conformally contact, cooling the second two-dimensional material layer overlapping the composite stamp from the sacrificial substrate, and repeating the process multiple times until a predetermined number of second two-dimensional material layers are formed on the surface of the composite stamp;

[0008] The rigid substrate, the first thermoplastic polymer layer, and the second thermoplastic polymer layer are removed to obtain a two-dimensional laminate structure.

[0009] In the above technical solution, by designing a first thermoplastic polymer layer with a relatively low melting point and a second thermoplastic polymer layer with a relatively high melting point in the composite mold, during the transfer of the two-dimensional material, heating the first thermoplastic polymer layer to near its melting point, causing it to soften and deform, can drive the deformation of the first two-dimensional material layer to match the surface roughness of the second two-dimensional material layer to be transferred, thereby achieving close conformal contact. The resulting consistency and enhanced adhesion enable the transferred second two-dimensional material layer to be directly peeled from the sacrificial substrate, thereby achieving high-quality, stable, and continuous stacking of large-area two-dimensional materials. Furthermore, during the continuous conformal transfer process, only the first two-dimensional material layer contacts the polymer, avoiding the introduction of defects in the two-dimensional stacked structure, thereby achieving high-quality, stable, and continuous stacking and the controllable preparation of two or more homogeneous or heterogeneous structures of large-area two-dimensional materials. During this process, the second thermoplastic polymer layer with a relatively high melting point maintains structural stability, separates the first thermoplastic polymer layer from the first two-dimensional material layer, and prevents the melting and deformation of the first thermoplastic polymer layer from causing the first two-dimensional material layer to tear. At the same time, there is a sufficiently strong force between the second thermoplastic polymer layer with a relatively high melting point and the first two-dimensional material layer to prevent the first two-dimensional material layer from falling off.

[0010] In some embodiments of the present application, the material of the first thermoplastic polymer layer is polypropylene carbonate, and the material of the second thermoplastic polymer layer is polymethyl methacrylate;

[0011] Alternatively, the material of the first thermoplastic polymer layer is polymethyl methacrylate, and the material of the second thermoplastic polymer layer is polycarbonate.

[0012] In the above technical solution, by selecting a specific polymer, the polymer can be subsequently simply removed by soaking in an organic solvent.

[0013] In some embodiments of the present application, the thickness of the first thermoplastic polymer layer is 200-1000 μm, and the thickness of the second thermoplastic polymer layer is 10-50 μm.

[0014] In the above technical solution, the first thermoplastic polymer layer is set to have a larger thickness, so as to ensure that it can be subsequently melted and deformed multiple times to guide multiple conformal contacts, thereby completing the continuous and stable stacking of multiple layers of two-dimensional materials.

[0015] In some embodiments of the present application, the materials of the first two-dimensional material layer and the second two-dimensional material layer are independently selected from one of molybdenum sulfide, tungsten sulfide, molybdenum selenide, tungsten selenide, graphene or boron nitride.

[0016] In the above technical solution, the materials of the first two-dimensional material layer and the second two-dimensional material layer can be the same or different, so that homogeneous or heterogeneous structures can be prepared accordingly.

[0017] In some embodiments of the present application, the hard substrate is selected from one of an aluminum oxide wafer, a fused quartz wafer, or a magnesium oxide wafer. Optionally, the area of ​​the hard substrate is 0.25 mm 2 ~1cm 2 .

[0018] In some embodiments of the present application, before removing the hard substrate, the first thermoplastic polymer layer and the second thermoplastic polymer layer, the method further includes: providing a target substrate on a surface of the second two-dimensional material layer facing away from the first two-dimensional material layer.

[0019] In some embodiments of the present application, the step of removing the hard substrate, the first thermoplastic polymer layer, and the second thermoplastic polymer layer includes: soaking the composite stamp with the second two-dimensional material layer in an organic solvent that is soluble in the polymer.

[0020] In some embodiments of the present application, the method for preparing the composite stamp includes the following steps:

[0021] Providing a first substrate, the first substrate comprising a hard substrate and a first thermoplastic polymer layer disposed on a surface of the hard substrate;

[0022] Providing a second substrate, the second substrate comprising a growth substrate and a first two-dimensional material layer and a second thermoplastic polymer layer sequentially stacked on a surface of the growth substrate;

[0023] Pressing the side of the first substrate provided with the first thermoplastic polymer layer onto the surface of the second thermoplastic polymer layer, heating the substrate until the first thermoplastic polymer layer is completely melted, maintaining the temperature for a period of time, and then cooling the substrate to bring the first thermoplastic polymer layer into conformal contact with the second thermoplastic polymer layer;

[0024] The second thermoplastic polymer layer and the first two-dimensional material layer overlapping the first thermoplastic polymer layer are separated from the growth substrate to obtain a composite stamp consisting of a hard substrate, a first thermoplastic polymer layer, a second thermoplastic polymer layer and a first two-dimensional material layer stacked in sequence along the thickness direction.

[0025] In the above technical solution, by controlling the melting points of the first thermoplastic polymer layer and the second thermoplastic polymer layer, the first thermoplastic polymer layer can be heated to completely melt and diffuse to achieve close conformal contact with the second thermoplastic polymer layer. The preparation method is simple and reliable.

[0026] In some embodiments of the present application, the method for preparing the first substrate includes: coating a first thermoplastic polymer solution on a surface of a hard substrate, and drying the solution to form a first thermoplastic polymer layer to obtain the first substrate.

[0027] In some embodiments of the present application, a method for preparing the second substrate includes: providing a growth substrate with a first two-dimensional material layer;

[0028] A second thermoplastic polymer solution is coated on the surface of the first two-dimensional material layer, and after drying, a second thermoplastic polymer layer is formed to obtain a second substrate.

[0029] In the above technical solution, the thickness and uniformity of the first thermoplastic polymer layer and the second thermoplastic polymer layer can be simply controlled by coating. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without creative work.

[0031] Figure 1 A schematic structural diagram of a first substrate provided in an embodiment of the present application;

[0032] Figure 2 A schematic structural diagram of the second substrate provided in an embodiment of the present application;

[0033] Figure 3 For the general Figure 1 The first matrix shown and Figure 2 A schematic diagram of the composite structure after the second substrate is bonded is shown;

[0034] Figure 4 A schematic structural diagram of the composite stamp provided in an embodiment of the present application;

[0035] Figure 5 For the general Figure 4 The composite structure schematic diagram shown is a composite stamp placed on a third substrate;

[0036] Figure 6 For the general Figure 5 A schematic structural diagram of a second two-dimensional material layer formed after a portion of the second two-dimensional material layer is peeled off from a sacrificial substrate;

[0037] Figure 7 For the general Figures 5 and 6 Schematic diagram of the structure of the intermediate obtained by repeating the steps shown multiple times;

[0038] Figure 8 for Figure 7 A schematic diagram of the three-dimensional structure of the steps shown;

[0039] Figure 9 For the general Figure 7 The schematic diagram of the structure in which the intermediate is placed on the target substrate;

[0040] Figure 10 A schematic structural diagram of a two-dimensional stacked structure provided in an embodiment of the present application;

[0041] Figure 11 This is an optical image of the MoS2 stacked structure provided in Example 1 of the present application;

[0042] Figure 12 A scanning transmission electron microscope cross-sectional image of the MoS2 stacked structure provided in Example 1 of the present application;

[0043] Figure 13 This is an optical image of the first substrate prepared on a glass slide in Example 2 of the present application;

[0044] Figure 14 A physical diagram of a partial structure of the two-dimensional material transfer platform in Example 2 of the present application;

[0045] Figure 15 This is an optical image of the WS2 / WSe2 heterojunction prepared in Example 2 of the present application.

[0046] Description of the accompanying drawings:

[0047]

[0048] DETAILED DESCRIPTION

[0049] Figures 1-10 This is a schematic diagram of the structure of the method for continuous conformal transfer of two-dimensional materials based on a composite stamp provided in an embodiment of the present application. Figures 1 to 10 The present application provides a method for continuous conformal transfer of two-dimensional materials based on a composite stamp, comprising the following steps:

[0050] S1, see Figure 4 A composite stamp 100 is provided. The composite stamp 100 includes a hard substrate 11, a first thermoplastic polymer layer 12, a second thermoplastic polymer layer 23, and a first two-dimensional material layer 22, which are sequentially stacked along the thickness direction. The melting point of the first thermoplastic polymer layer 12 is lower than the melting point of the second thermoplastic polymer layer 23.

[0051] By way of example, the first thermoplastic polymer layer 12 can be made of polypropylene carbonate, and the second thermoplastic polymer layer 23 can be made of polymethyl methacrylate. Alternatively, the first thermoplastic polymer layer 12 can be made of polymethyl methacrylate, and the second thermoplastic polymer layer 23 can be made of polycarbonate. It is understood that the first thermoplastic polymer layer 12 and the second thermoplastic polymer layer 23 can also be made of other thermoplastic polymers, as long as the melting point of the first thermoplastic polymer layer 12 is lower than that of the second thermoplastic polymer layer 23. When the first thermoplastic polymer layer 12 softens and deforms at its melting point, the second thermoplastic polymer layer 23 can maintain structural stability.

[0052] Preferably, the thickness of the first thermoplastic polymer layer 12 is greater than the thickness of the second thermoplastic polymer layer 23. The thickness of the first thermoplastic polymer layer 12 may be 200-1000 μm, and the thickness of the second thermoplastic polymer layer 23 may be 10-50 μm.

[0053] The materials of the first two-dimensional material layer 22 and the second two-dimensional material layer 32 can be independently selected from one of molybdenum sulfide, tungsten sulfide, molybdenum selenide, tungsten selenide, graphene or boron nitride.

[0054] The hard substrate 11 can be selected from one of an alumina wafer, a fused quartz wafer or a magnesium oxide wafer. The size of the hard substrate 11 determines the size of the entire composite stamp 100 and can be customized according to needs. The area can be 0.25mm 2 ~1cm 2 In the embodiment of the present application, the hard substrate 11 is substantially square, and its width may be 500 μm-10 mm.

[0055] See also Figures 1 to 4 The method for preparing the composite stamp 100 may include the following steps:

[0056] S10, see Figure 1 , providing a first substrate 10, the first substrate 10 includes a hard base 11 and a first thermoplastic polymer layer 12 provided on the surface of the hard base 11 along a thickness direction A.

[0057] The preparation method of the first substrate 10 may include the following steps:

[0058] The first thermoplastic polymer solution is coated on the surface of the hard substrate 11 and dried to form the first thermoplastic polymer layer 12 , thereby obtaining the first base 10 .

[0059] Specifically, a drop coating method is used to coat an organic solution of a first thermoplastic polymer onto a hard substrate 11, which is then heated and dried. The solution is then placed on a high-temperature resistant plate and placed in a tube furnace. The temperature is raised to a temperature above its melting point at a controlled rate under low pressure. The temperature is then maintained for 60 minutes to remove any residual organic solvent. This forms a first thermoplastic polymer layer 12 on the surface of the hard substrate 11, thereby obtaining the first base 10. The high-temperature resistant plate may include a quartz plate, a corundum plate, or the like.

[0060] As an example, the organic solution of the first thermoplastic polymer may be an anisole solution of polypropylene carbonate.

[0061] The drop coating method can be used to obtain a first thermoplastic polymer layer 12 with a relatively large thickness, so as to facilitate subsequent multiple melt deformations to guide multiple conformal contacts.

[0062] S11, see Figure 2 , providing a second substrate 20 , the second substrate 20 includes a growth substrate 21 and a first two-dimensional material layer 22 and a second thermoplastic polymer layer 23 sequentially stacked on the surface of the growth substrate 21 .

[0063] The preparation method of the second substrate 20 may include the following steps:

[0064] A growth substrate 21 with a first two-dimensional material layer 22 is provided, and a second thermoplastic polymer solution is coated on the surface of the first two-dimensional material layer 22 . After drying, a second thermoplastic polymer layer 23 is formed to obtain a second base body 20 .

[0065] Specifically, an organic solution of a second thermoplastic polymer is spin-coated on the surface of the growth substrate 21 provided with the first two-dimensional material layer 22, and then heated and dried at a temperature close to the melting point of the second thermoplastic polymer to form a second thermoplastic polymer layer 23 on the surface of the first two-dimensional material layer 22, thereby obtaining the second substrate 20. For example, the organic solution of the second thermoplastic polymer can be an anisole solution of polymethyl methacrylate.

[0066] The first two-dimensional material layer 22 on the surface of the growth substrate 21 can be prepared by chemical vapor deposition (for molybdenum sulfide, tungsten sulfide, molybdenum selenide, tungsten selenide) or transfer method (for graphene, boron nitride).

[0067] S12, see Figure 3 and Figure 4, press the side of the first substrate 10 provided with the first thermoplastic polymer layer 12 to the surface of the second substrate 20 provided with the second thermoplastic polymer layer 23, heat until the first thermoplastic polymer layer 12 is completely melted and becomes fluid, and diffuses and conformally contacts with the second thermoplastic polymer layer 23, then cool down, and peel off the part of the first two-dimensional material layer 22 and the second thermoplastic polymer layer 23 corresponding to the first thermoplastic polymer layer 12 from the growth substrate 21 to obtain a composite stamp 100 which is composed of the hard substrate 11, the first thermoplastic polymer layer 12, the second thermoplastic polymer layer 23, and the first two-dimensional material layer 22 in the thickness direction A.

[0068] Among them, the stripping method can be water-assisted direct stripping (for molybdenum sulfide, tungsten sulfide, molybdenum selenide, tungsten selenide, etc.) or etching stripping (for graphene, boron nitride, etc.).

[0069] S2, see Figure 5 and Figure 6 A third substrate 30 is provided, comprising a sacrificial substrate 31 and a second two-dimensional material layer 32 disposed on the surface of the sacrificial substrate 31. The side of the composite stamp 100 prepared above, on which the first two-dimensional material layer 22 is disposed, is pressed against the surface of the second two-dimensional material layer 32 along the thickness direction A. The temperature is raised until the first thermoplastic polymer layer 12 softens and deforms. The temperature is maintained for a period of time such that the first two-dimensional material layer 22 and the second two-dimensional material layer 32 are in conformal contact. The temperature is then lowered to room temperature, and the portion of the second two-dimensional material layer 32 overlapping with the composite stamp 100 is peeled off from the sacrificial substrate 31, thereby obtaining the second two-dimensional material layer 32 on the surface of the first two-dimensional material layer 22.

[0070] The materials of the first two-dimensional material layer 22 and the second two-dimensional material layer 32 may be the same or different, thereby forming a two-dimensional homogeneous structure or a two-dimensional heterogeneous structure.

[0071] In this step, by heating the first thermoplastic polymer layer 12 until it softens and deforms, the second thermoplastic polymer layer 23 and the first two-dimensional material layer 22 are deformed. This allows the roughness of the first two-dimensional material layer 22 and the second two-dimensional material layer 32 to match, enhancing consistency and adhesion. This allows for conformal contact and high-quality conformal transfer. If pressure alone is used without conformal contact, the loose contact between the two two-dimensional material layers can introduce defects such as cracks, wrinkles, and voids during the peeling process.

[0072] Understandably, in step S12, the first thermoplastic polymer layer 12 must fully diffuse to the upper and lower interfaces to connect and secure the first thermoplastic polymer layer 12 and the second thermoplastic polymer layer 23. Therefore, heating to a temperature above its melting point is necessary to completely melt it. In step S2, however, only softening and deforming the first thermoplastic polymer layer 12 is necessary to guide conformal formation. Therefore, heating to a temperature close to its melting point is sufficient.

[0073] S3, see Figure 7 and Figure 8 , repeat step S2 multiple times to form a predetermined number of second two-dimensional material layers 32 on the surface of the first two-dimensional material layer 22 to obtain the intermediate 200 .

[0074] The size of the sacrificial substrate 31 and the surface second two-dimensional material layer 32 may be larger than that of the composite stamp 100 , so that multiple continuous conformal transfers can be completed on the same surface of the second two-dimensional material layer 32 .

[0075] In the process of repeating twice or more, only the first two-dimensional material layer 22 is in contact with the polymer, thereby reducing interlayer contamination and improving the quality of the two-dimensional stacked structure.

[0076] S4, see Figure 9 and Figure 10 , the hard substrate 11 , the first thermoplastic polymer layer 12 , and the second thermoplastic polymer layer 23 are removed to obtain a two-dimensional laminated structure 300 .

[0077] In some embodiments, before removing the hard substrate 11, the first thermoplastic polymer layer 12, and the second thermoplastic polymer layer 23, the method further includes:

[0078] The side of the intermediate 200 provided with the second two-dimensional material layer 32 is pressed against the target substrate 40, and the temperature is raised until the first thermoplastic polymer layer 12 softens and deforms. The temperature is kept for a period of time so that the second two-dimensional material layer 32 is in conformal contact with the target substrate 40, and then cooled to room temperature.

[0079] The target substrate 40 may be a silicon oxide / silicon wafer, a fused quartz wafer, or the like.

[0080] The removal method may be: immersing the intermediate 200 in an organic solvent soluble in the polymer and drying it. The organic solvent may be acetone.

[0081] In some embodiments, after soaking, the method further includes: annealing treatment to fully remove the polymer remaining on the surface of the first two-dimensional material layer 22 .

[0082] Specifically, the removal step includes placing the intermediate 200 and the target substrate 40 in a polymer-soluble organic solvent for 3 hours, drying at room temperature, and then placing them in a tube furnace. After evacuating the furnace until the pressure is below 0.1 Pa, a protective gas is introduced, maintaining the pressure at 50-300 Pa, and the temperature is raised to 400-420°C for 240 minutes. The protective gas can be argon or nitrogen, which can also serve as a carrier gas to remove the volatilized polymer.

[0083] In the above method, by designing a first thermoplastic polymer layer 12 with a relatively low melting point and a second thermoplastic polymer layer 23 with a relatively high melting point in the composite mold, during the two-dimensional material transfer, the first thermoplastic polymer layer 12 is heated to its melting point to soften and deform, thereby causing the first two-dimensional material layer 22 to deform, matching the surface roughness of the second two-dimensional material layer 32 to be transferred, thereby achieving close conformal contact. The resulting consistency and enhanced adhesion enable the second two-dimensional material layer 32 to be transferred to be directly peeled from the sacrificial substrate 31, thereby achieving high-quality, stable, and continuous stacking of large-area two-dimensional materials. Furthermore, during the continuous conformal transfer process, only the first two-dimensional material layer 22 contacts the polymer, which can avoid the introduction of defects in the two-dimensional stacked structure 300, thereby achieving high-quality, stable, and continuous stacking, and realizing the controllable preparation of two or more layers of homogeneous or heterogeneous structures of large-area two-dimensional materials. During this process, the second thermoplastic polymer layer 23 maintains structural stability, separating the first thermoplastic polymer layer 12 from the first two-dimensional material layer 22, and preventing the first two-dimensional material layer 22 from tearing due to melting and deformation of the first thermoplastic polymer layer 12. Furthermore, the relatively high-melting-point second thermoplastic polymer layer 23 exerts a sufficiently strong force on the first two-dimensional material layer 22 to prevent the first two-dimensional material layer 22 from falling off.

[0084] The continuous conformal transfer method of two-dimensional materials based on a composite mold provided in this application can be used in conjunction with a two-dimensional material angle-controlled transfer platform, thereby promoting the development of stacked two-dimensional materials in the fields of corner electronics and moiré electronics.

[0085] To make the purpose, technical solutions and advantages of the examples of the present application clearer, the technical solutions in the examples of the present application will be described clearly and completely below. Where specific conditions are not specified in the examples, conventional conditions or conditions recommended by the manufacturer are used. Where the manufacturer of the reagents or instruments is not specified, they are all conventional products that can be purchased commercially.

[0086] Example 1

[0087] This embodiment provides a 1cm 2 The continuous conformal transfer preparation method of an eight-layer MoS2 stacked structure comprises the following steps:

[0088] (1) Preparation of composite impression

[0089] S10: 1cm 2 A double-sided polished alumina substrate was used as a hard substrate. 4 g of polypropylene carbonate was weighed and dissolved in 16 g of anisole. The polypropylene carbonate / anisole solution was drop-coated onto the first surface of the alumina substrate. The substrate was then dried on a 50°C heating table for 2 hours. The substrate was then placed in a tube furnace and heated at a controlled rate of 10°C / min to 160°C under low pressure. The temperature was then maintained for 60 minutes to form a polypropylene carbonate layer on the double-sided polished alumina substrate, yielding the first substrate.

[0090] S11: 1cm 2 A single layer of MoS2 grown on an alumina substrate served as the first two-dimensional material layer. A polymethyl methacrylate (PMMA) solution in anisole was evenly spin-coated onto the surface of the MoS2 monolayer, which was then dried on a 120°C heating platform to form a PMMA layer, creating the second substrate.

[0091] S12: Align and press the side of the hard substrate with the polypropylene carbonate layer onto the surface of the polymethyl methacrylate layer, and place it on a 150°C heating table for heating to melt the polypropylene carbonate layer and diffuse it to the entire interface. Then cool it to room temperature, and peel the single-layer MoS2 from the alumina substrate in water to obtain a composite mold consisting of double-sided polished alumina, polypropylene carbonate layer, polymethyl methacrylate layer and single-layer MoS2 bonded to each other from top to bottom.

[0092] (2) Preparation of MoS2 laminated structure

[0093] S20: providing a third substrate, wherein the third substrate comprises a silicon oxide / silicon wafer substrate and a single layer of MoS2 grown on the substrate.

[0094] S21: Press the above composite stamp onto the surface of the MoS2 layer and heat it to 90°C, then keep it warm for 1-2 minutes, and then cool it to 30°C. Then, directly peel the composite stamp and the MoS2 underneath from the silicon oxide / silicon wafer in air. Repeat six times until eight layers of MoS2 are obtained on the composite stamp.

[0095] S21: Press the composite stamp with eight layers of MoS2 onto the target substrate silicon oxide / silicon wafer, and heat it to 90°C, then keep it warm for 1-2 minutes, and then cool it to 30°C.

[0096] S22: Place the composite stamp together with the target substrate in acetone and soak for 3 hours. After drying at room temperature, place it in a tube furnace and evacuate until the pressure inside the tube furnace is less than 0.1 Pa. Then, introduce protective gas and maintain the pressure inside the tube at 50 Pa. Control the heating rate at 10 ° C / min to increase the temperature to 400-420 ° C and anneal for 240 minutes. After the annealing is completed, turn off the heating power supply, maintain the Ar flow rate unchanged, and cool to room temperature to obtain 1 cm 2 Eight-layer MoS2 stacked structure.

[0097] Figure 11 This is an optical photo of the MoS2 stacked structure prepared in this embodiment. It can be seen from the figure that this embodiment can achieve centimeter-level eight-layer MoS2 transfer stacking that is uniform and flawless.

[0098] The prepared eight-layer MoS2 stacked structure was characterized by scanning transmission electron microscopy (STEM atomic phase), testing instrument: FEI Titan Themis G2 300, acceleration voltage: 300kV.

[0099] Figure 12 This is the STEM atomic phase image of an eight-layer MoS2 stacked sample. It can be clearly seen from the figure that the distance between MoS2 layers is uniform, about The interface is free of contamination and defects, demonstrating that the eight-layer MoS2 stacked sample has intrinsic high clean quality.

[0100] Example 2

[0101] This embodiment uses Figure 14 The two-dimensional material transfer platform (angular resolution 0.1°) shown provides a method for transferring and preparing a high-quality WS2-WSe2 heterojunction with an interlayer rotation angle of 0°, including the following steps:

[0102] (1) Preparation of composite impression

[0103] S10: 1cm 2 Double-sided polished alumina substrate was used as a hard substrate. 4 g of polypropylene carbonate was weighed and dissolved in 16 g of anisole. The anisole solution of polypropylene carbonate was dripped onto the first surface of the double-sided polished alumina substrate by a drop coating method. The substrate was placed on a 50°C heating table for drying for 2 hours. The substrate was then placed in a tube furnace. The heating rate was controlled at 10°C / min under low pressure. The temperature was raised to 160°C, and then kept warm for 60 minutes to obtain a thick layer of polypropylene carbonate on the double-sided polished alumina substrate. In addition, a UV curing adhesive was used to stick the double-sided polished alumina substrate to a glass slide from the second surface. The UV curing adhesive was irradiated with UV light for 30 minutes to induce the UV curing adhesive to cure, and the following was obtained: Figure 13 Double polished aluminum oxide covered with a polypropylene carbonate layer on a glass slide is shown, i.e. the first substrate.

[0104] S11: WS2 grown on an alumina substrate is used as the first two-dimensional material layer, and an anisole solution of polymethyl methacrylate is evenly spin-coated on the WS2 layer by a spin coating method, and then placed on a 120°C heating table for drying to obtain a second substrate.

[0105] S12: Align and press the side of the hard substrate with the polypropylene carbonate layer onto the surface of the polymethyl methacrylate layer, and place it on a 150°C heating table for heating to allow the polypropylene carbonate to diffuse to the entire interface. Then cool it to room temperature and peel the WS2 layer from the alumina substrate in water to obtain a composite mold consisting of a glass slide, double-sided polished alumina, polypropylene carbonate layer, polymethyl methacrylate layer, and a single layer of WS2 bonded to each other from top to bottom.

[0106] (2) Preparation of WS2-WSe2 heterojunction

[0107] S20: Provide a third substrate, the third substrate including an aluminum oxide substrate and a WSe2 layer grown on the aluminum oxide substrate, and fix the third substrate on a Figure 14 On the heating table shown.

[0108] S21: Fix the composite stamp prepared in step (1) on a transfer device and place it above the heating table using a glass slide, and align the WS2 layer on the composite stamp with the WSe2 layer on the third substrate using a microscope. Rotate the third substrate using a rotating table until the angle between the WS2 layer and the WSe2 layer is 0°. Press down the composite stamp 100 using a transfer device to fit the WS2 layer and the WSe2 layer. Heat to 90°C using a heating table and keep warm for 1-2 minutes. After cooling to 30°C, peel off the WSe2 layer from the alumina substrate in water to obtain a WS2-WSe2 heterojunction with an interlayer angle of 0° on the composite stamp.

[0109] S22: Press the composite stamp with the WS2-WSe2 heterojunction having an interlayer rotation angle of 0° onto the target silicon oxide / silicon wafer, heat it to 90°C, keep it warm for 1-2 minutes, and then cool it to 30°C.

[0110] S23: Place the composite stamp and target substrate in acetone and soak for 3 hours. After drying at room temperature, place it in a tube furnace and evacuate until the pressure inside the tube furnace is less than 0.1 Pa. Then, introduce protective gas, maintain the pressure inside the tube at 50 Pa, and control the heating rate to increase to 400-420°C at a controlled rate of 10°C / min. Anneal at this temperature for 240 minutes. After annealing, turn off the heating power supply, maintain the Ar flow constant, and cool to room temperature to obtain a WS2-WSe2 heterojunction sample with an interlayer angle of 0° on the silicon oxide / silicon substrate.

[0111] Figure 15This is an optical image of the WS2 / WSe2 heterojunction prepared in this embodiment. It can be seen from the figure that the angle of the heterojunction prepared in this embodiment is precisely controllable and has no defects such as wrinkles and contamination.

[0112] The embodiments described above are part of the embodiments of the present application, rather than all of the embodiments. The detailed description of the embodiments of the present application is not intended to limit the scope of the present application for protection, but merely represents selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

Claims

1. A method for continuous conformal transfer of two-dimensional materials based on a composite stamp, characterized in that: The following steps are involved: Providing a composite stamp, the composite stamp comprising a hard substrate, a first thermoplastic polymer layer, a second thermoplastic polymer layer, and a first two-dimensional material layer stacked in sequence along a thickness direction; wherein the melting point of the first thermoplastic polymer layer is lower than the melting point of the second thermoplastic polymer layer; Providing a substrate to be transferred, wherein the substrate to be transferred includes a sacrificial substrate and a second two-dimensional material layer provided on a surface of the sacrificial substrate; Pressing the side of the composite stamp provided with the first two-dimensional material layer against the second two-dimensional material layer, heating the first thermoplastic polymer layer until it softens and deforms, maintaining the temperature for a period of time to allow the first two-dimensional material layer and the second two-dimensional material layer to conformally contact, cooling the second two-dimensional material layer overlapping the composite stamp from the sacrificial substrate, and repeating the process multiple times until a predetermined number of second two-dimensional material layers are formed on the surface of the composite stamp; The rigid substrate, the first thermoplastic polymer layer, and the second thermoplastic polymer layer are removed to obtain a two-dimensional laminate structure.

2. The method for continuous conformal transfer of two-dimensional materials according to claim 1, characterized in that: The material of the first thermoplastic polymer layer is polypropylene carbonate, and the material of the second thermoplastic polymer layer is polymethyl methacrylate; Alternatively, the first thermoplastic polymer layer is made of polymethyl methacrylate, and the second thermoplastic polymer layer is made of polycarbonate.

3. The method for continuous conformal transfer of two-dimensional materials according to any one of claims 1 to 2, characterized in that: The thickness of the first thermoplastic polymer layer is 200-1000 μm; the thickness of the second thermoplastic polymer layer is 10-50 μm.

4. The method for continuous conformal transfer of two-dimensional materials according to claim 1, wherein: The materials of the first two-dimensional material layer and the second two-dimensional material layer are independently selected from one of molybdenum sulfide, tungsten sulfide, molybdenum selenide, tungsten selenide, graphene or boron nitride.

5. The method for continuous conformal transfer of two-dimensional materials according to claim 1, wherein: The hard substrate is selected from one of an alumina wafer, a fused quartz wafer or a magnesium oxide wafer; Optionally, the area of ​​the hard substrate is 0.25 mm 2 ~1cm 2 .

6. The method for continuous conformal transfer of two-dimensional materials according to claim 1, characterized in that: Before removing the hard substrate, the first thermoplastic polymer layer and the second thermoplastic polymer layer, the method further includes: providing a target substrate on a surface of the second two-dimensional material layer that is away from the first two-dimensional material layer.

7. The method for continuous conformal transfer of two-dimensional materials according to claim 1, wherein: The step of removing the hard substrate, the first thermoplastic polymer layer and the second thermoplastic polymer layer comprises: soaking the composite stamp with the second two-dimensional material layer in an organic solvent that is soluble in polymers.

8. The method for continuous conformal transfer of two-dimensional materials according to any one of claims 1 to 7, characterized in that: The preparation method of the composite stamp comprises the following steps: Providing a first substrate, wherein the first substrate comprises the hard substrate and the first thermoplastic polymer layer disposed on a surface of the hard substrate; Providing a second substrate, the second substrate comprising a growth substrate and a first two-dimensional material layer and a second thermoplastic polymer layer sequentially stacked on a surface of the growth substrate; Pressing the side of the first substrate provided with the first thermoplastic polymer layer against the surface of the second thermoplastic polymer layer, heating the substrate until the first thermoplastic polymer layer is completely melted, maintaining the temperature for a period of time, and then cooling the substrate so that the first thermoplastic polymer layer and the second thermoplastic polymer layer are in conformal contact; The second thermoplastic polymer layer and the first two-dimensional material layer overlapping with the first thermoplastic polymer layer are separated from the growth substrate to obtain a composite stamp consisting of the hard substrate, the first thermoplastic polymer layer, the second thermoplastic polymer layer and the first two-dimensional material layer stacked in sequence along the thickness direction.

9. The method for continuous conformal transfer of two-dimensional materials according to claim 8, characterized in that: The preparation method of the first matrix comprises: A first thermoplastic polymer solution is coated on the surface of the hard substrate and dried to form the first thermoplastic polymer layer, thereby obtaining the first matrix.

10. The method for continuous conformal transfer of two-dimensional materials according to claim 8, characterized in that: The preparation method of the second matrix comprises: providing the growth substrate with the first two-dimensional material layer; A second thermoplastic polymer solution is coated on the surface of the first two-dimensional material layer, and dried to form the second thermoplastic polymer layer, thereby obtaining the second substrate.

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