Method for transferring a two-dimensional material and two-dimensional material and applications thereof

Abstract

A method for transferring two-dimensional materials, the resulting two-dimensional materials, and their applications are provided. According to one embodiment, the transfer method includes the following steps: placing one side of a substrate carrying the two-dimensional material opposite another two-dimensional material / substrate, heating each side to a specified temperature, then bringing them into contact and applying pressure to the two substrates. After applying pressure for a certain time, the pressure is released, thereby achieving the transfer and stacking of the two-dimensional materials. This transfer method eliminates the need for substrate etching, avoiding contamination of the two-dimensional material during the transfer process. Furthermore, this method avoids wrinkles, bubbles, and impurities that frequently occur during transfer. This method can achieve the transfer and stacking of large-area two-dimensional materials, obtaining clean, multilayered stacked two-dimensional materials.

Description

Technical Field

[0001] This application relates to the field of semiconductor materials technology, and more specifically, to a dry transfer method for two-dimensional materials, two-dimensional materials, and their specific applications. Background Technology

[0002] Two-dimensional materials (2D materials) refer to materials in which electrons can move freely only in two dimensions at the nanoscale (1-100 nm), such as nanofilms, superlattices, and quantum wells. Due to their excellent electrical, thermal, and magnetic properties, 2D materials have promising applications in integrated circuits and optoelectronic devices. However, for subsequent device fabrication, it is necessary to transfer the fabricated 2D materials onto other substrates. Furthermore, van der Waals homojunctions and heterojunctions formed from 2D materials are also attractive for enriching device performance. Therefore, the large-area, intact, and non-destructive transfer of 2D materials from one growth substrate to another is a crucial task.

[0003] Currently, methods for transferring two-dimensional materials generally require the use of etchants (such as potassium hydroxide, ferric chloride, ammonium sulfate solution, etc.) to detach them from the original substrate. This method necessitates organic adhesives as transfer carriers for the two-dimensional materials, such as polycarbonate (PC), polymethyl methacrylate (PMMA), and polystyrene (PS). These organic adhesives then need to be removed with organic solvents (such as acetone, chloroform, or chlorobenzene). These organic reagents cause chemical corrosion, and residual reagents can damage and contaminate the two-dimensional materials, affecting their performance. Summary of the Invention

[0004] Therefore, one of the objectives of this invention is to provide a method for transferring and stacking two-dimensional materials, which can achieve the transfer of two-dimensional materials with clean interfaces and large-area non-destructive processes, so as to solve at least one of the problems existing in the prior art in the two-dimensional material transfer process, such as polymer residue, easy damage to two-dimensional materials, contamination, and cracking.

[0005] Another object of the present invention is to provide a two-dimensional material obtained by the transfer method described above, which has a cleaner interface and higher interlayer coupling.

[0006] One aspect of the present invention provides a method for transferring two-dimensional materials, the method comprising the following steps:

[0007] The first substrate and the second substrate are heated to a predetermined temperature, wherein the first substrate carries a first two-dimensional material;

[0008] The first substrate is brought into contact with the second substrate, such that the side carrying the first two-dimensional material is in contact with the second substrate;

[0009] Pressure is applied to the first and second substrates and maintained for a predetermined time; and

[0010] The pressure is relieved, and the first substrate and the second substrate are separated to transfer the first two-dimensional material from the first substrate to the second substrate.

[0011] In some examples, a second two-dimensional material is carried on the second substrate, and contacting the first substrate with the second substrate includes contacting the first two-dimensional material with the second two-dimensional material face to face.

[0012] In some examples, the first two-dimensional material and / or the second two-dimensional material are grown on the first substrate and / or the second substrate by deposition, epitaxy, or precipitation. Alternatively, the first two-dimensional material and / or the second two-dimensional material are attached to the first substrate and / or the second substrate by transfer.

[0013] In some examples, the equivalent surface diameter of the first two-dimensional material and / or the second two-dimensional material is greater than 1 mm.

[0014] In some examples, the predetermined temperature is between 50°C and 300°C, preferably between 90°C and 200°C.

[0015] In some examples, the pressure applied is 0.5 MPa or more, preferably 1-100 MPa, more preferably 2-60 MPa; and / or, the predetermined time for applying pressure is 1 min or more, preferably 2-20 min, more preferably 3-5 min.

[0016] In some examples, the environment in which the two-dimensional material is transferred is an atmospheric or vacuum environment, preferably a vacuum environment.

[0017] In some examples, the transfer method further includes cooling the first substrate and the second substrate after the pressure is released. Preferably, the first substrate and the second substrate are cooled to 30-180°C after the pressure is released, and more preferably, to 70-90°C.

[0018] In some examples, the first substrate may be the same as or different from the second substrate. Preferably, the first substrate is at least one of silicon, silicon dioxide, sapphire, copper foil or mica, and the second substrate is at least one of a noble metal, silicon, silicon dioxide, sapphire, copper foil or mica.

[0019] Another aspect of the present invention provides a two-dimensional material prepared by the above-described two-dimensional material transfer and stacking method. By using a stacking transfer method on the surface of the two-dimensional material located on the initial substrate or on the surface of the target substrate, the transfer of multi-layer two-dimensional materials or the transfer of a single-layer two-dimensional material from the initial substrate to the target substrate can be realized. For example, van der Waals homojunctions or heterojunctions composed of multi-layer two-dimensional materials can be stacked to prepare the material.

[0020] Another aspect of the present invention provides the application of the two-dimensional materials described above in integrated circuits, solar cells or optical devices.

[0021] This invention employs a heating and pressurizing method, utilizing the difference in adhesion between two-dimensional materials (2D materials) and different substrates under heating conditions, to transfer 2D materials from an initial substrate to a target substrate, achieving dry transfer and / or stacking of 2D materials. This transfer method eliminates the need for substrate etching and the use of transfer media such as organic matter or water as in existing technologies, avoiding surface contamination of the 2D materials. Furthermore, the transfer process is convenient, avoiding common issues such as wrinkles, bubbles, and impurities. The resulting multilayer 2D material structure exhibits clean interfaces and large-area flatness without damage, ensuring the integrity of the thin film and enabling applications in integrated circuits, solar cells, and optical devices. Attached Figure Description

[0022] To more clearly illustrate the technical solutions and advantages of the specific embodiments of the present invention, the accompanying drawings used will be briefly described below.

[0023] Figure 1 A schematic diagram of a two-dimensional material transfer method according to an exemplary embodiment of this application is shown.

[0024] Figure 2 shows the optical micrograph, Raman spectrum, and fluorescence spectrum of the bilayer molybdenum disulfide corner homojunction prepared by the transfer method of an exemplary embodiment of this application.

[0025] Figure 3 The image shows a localized atomic force microscopy characterization of a bilayer molybdenum disulfide corner homojunction prepared by the transfer method of an exemplary embodiment of this application.

[0026] Figure 4 This illustration shows a schematic diagram of the bonding force between a two-dimensional material and a substrate as a function of temperature, according to an exemplary embodiment of this application.

[0027] Figure 5 shows an optical micrograph, Raman spectrum, and fluorescence spectrum of a molybdenum disulfide and molybdenum diselenide heterojunction prepared by the transfer method of an exemplary embodiment of this application.

[0028] Figure 6 shows an optically illuminated photograph and the corresponding Raman spectrum of a molybdenum disulfide and graphene heterojunction prepared by the transfer method of an exemplary embodiment of this application.

[0029] Figure 7 Photographs of two-dimensional materials obtained by the transfer method of this application are shown in proportion.

[0030] Figure 8 Photographs of two-dimensional materials obtained by another comparative transfer method of this application are shown. Detailed Implementation

[0031] Exemplary embodiments of this application will now be described in detail with reference to the accompanying drawings. It is obvious that the described embodiments are merely a part of the embodiments of this application, and not all of them, and it should be understood that this application is not limited to the exemplary embodiments described herein. Unless otherwise specified, the technical terms used herein have the meanings commonly understood by those skilled in the art.

[0032] Figure 1 A schematic diagram of a two-dimensional material transfer method according to an exemplary embodiment of this application is shown. Figure 1 As shown, the method may first involve a heating step, heating a first substrate 10 (e.g., an initial substrate) and a second substrate 12 (e.g., a target substrate) to a predetermined temperature, wherein a first two-dimensional material 14 is supported on the first substrate 10. Although the figure shows a second two-dimensional material 16 supported on the second substrate 12, as described below, the second substrate 12 may also not support two-dimensional material, meaning that the method of the present invention can also transfer single-layer or multi-layer two-dimensional material 14 from the initial substrate 10 to the target substrate 12.

[0033] The first two-dimensional material 14 and the second two-dimensional material 16 may be, for example, including but not limited to, two-dimensional materials such as molybdenum disulfide, molybdenum diselenide, tungsten disulfide, graphene, or boron nitride. The first two-dimensional material 14 and the second two-dimensional material 16 can be grown / transferred onto the first substrate 10 and the second substrate 12 by processes such as deposition, epitaxy, precipitation, and transfer. For example, two-dimensional materials can be grown on the substrate by methods such as chemical vapor deposition, evaporation deposition, molecular beam epitaxy, and dissolution-precipitation, and can be single-layer or multi-layer two-dimensional materials. Specifically, two-dimensional transition metal chalcogenides (MoS2, MoSe2, MoTe2, WS2, WSe2, etc.) can be prepared by the above methods, and graphene can be prepared on metal substrates (Pt, Ru, Cu, Ni, etc.) by methods such as metal-catalyzed epitaxial growth and chemical vapor deposition. Alternatively, the first two-dimensional material 14 and the second two-dimensional material 16 can also be multilayer homogeneous or heterogeneous two-dimensional materials obtained by a transfer / stacking method. For example, as described below, the multilayer two-dimensional materials can first be stacked and transferred to the first substrate by the method of this application, and then the two-dimensional materials on the first substrate can be transferred / stacking to the second substrate by repeating the method of this application.

[0034] In one embodiment, the first two-dimensional material 14 and the second two-dimensional material 16 can be the same. In this case, a two-dimensional homojunction can be prepared by the transfer method of the present invention. In another embodiment, the first two-dimensional material 14 and the second two-dimensional material 16 can also be different. In this case, a two-dimensional heterojunction can be prepared by the transfer method of the present invention.

[0035] A suitable substrate can be selected based on the two-dimensional material being grown and the growth process. In one embodiment, the first substrate 10 and the second substrate 12 can be the same; for example, to prepare a homojunction of two-dimensional materials, two-dimensional materials are generally deposited on substrates of the same material. In another embodiment, the first substrate 10 and the second substrate 12 can be different; for example, to prepare a heterojunction of two-dimensional materials, different two-dimensional materials can be deposited and grown on different substrates. Specifically, the first substrate 10 and / or the second substrate 12 can be selected from silicon, silicon dioxide, sapphire, copper foil, or mica. In another embodiment, for the case where two-dimensional material 14 is transferred from the first substrate 10 to the second substrate 12 (without two-dimensional material), the second substrate 12 can be selected as a noble metal substrate such as Au, and the first substrate 10 can be selected from silicon, silicon dioxide, sapphire, copper foil, or mica.

[0036] The inventors of this invention have discovered that the interlayer bonding force between two-dimensional (2D) materials can be enhanced by heating and pressurizing, while the bonding force between the 2D material and the growth substrate can be weakened, thereby enabling the stacking of the same or different 2D materials or the transfer of a single layer of 2D material. Due to the atomically flat nature of 2D materials, the contact area between two layers of 2D materials can reach a large size, thus enhancing their interlayer bonding force. When this enhanced interlayer bonding force, or the bonding force between the 2D material and the target substrate, is greater than the bonding force between the 2D material and the initial substrate, the 2D material can be stacked / transferred from the initial substrate to the target substrate. In this way, this invention can achieve large-area transfer and stacking of 2D materials, with an equivalent surface diameter of 1 mm or more, and especially wafer-scale transfer, with an equivalent surface diameter of 2 inches or more. This method can significantly improve the success rate of large-area transfer of 2D materials and reduce contamination and damage to the 2D materials during the transfer process.

[0037] The heating temperature is crucial in this invention. If the temperature is too low, the integrity of the two-dimensional material cannot be guaranteed; if the temperature is too high, thermal oxidation of the two-dimensional material will occur, leading to a deterioration in its quality. In one embodiment, the predetermined heating temperature for the first substrate 10 and the second substrate 12 is between 50 and 300°C. When the temperature is below 50°C, the transferred two-dimensional material is incomplete and cracks. If the temperature is within the above-mentioned temperature range, the transferred two-dimensional material has better integrity. Preferably, the heating temperature can be between 90°C and 200°C, for example, 120-180°C; more preferably, the heating temperature can be selected as 150-170°C.

[0038] The bonding force between the two-dimensional material and the substrate varies at different temperatures. In one embodiment, the heating programs of the first substrate 10 and the second substrate 12 can be controlled separately. For example, the first substrate 10 can be heated to a first temperature and the second substrate 12 can be heated to a second temperature. The first temperature may be different from the second temperature. For example, the first temperature may be controlled to be higher than the second temperature, thereby weakening the bonding force between the first two-dimensional material and the first substrate to a greater extent. For example, the bonding force between the first two-dimensional material 14 and the first substrate 10 may be less than the bonding force between the second two-dimensional material 16 and the second substrate 12, thereby realizing the transfer of the first two-dimensional material from the first substrate to the second substrate.

[0039] In another embodiment, the heating processes of the first substrate 10 and the second substrate 12 can also be controlled simultaneously. For example, the first temperature and the second temperature can be controlled to be the same so that the first substrate and the second substrate are heated at the same temperature. Generally, the first two-dimensional material 14 and the second two-dimensional material 16 are obtained through different production processes. For example, by setting different process parameters such as precursor, growth temperature, gas flow, and substrate annealing conditions, the first two-dimensional material 14 and the second two-dimensional material 16 are prepared on the first substrate 10 and the second substrate 12, respectively. The two-dimensional materials on the two substrates will have different bonding forces. Therefore, when, for example, the bonding force between the first two-dimensional material 14 and the first substrate 10 is less than the bonding force between the second two-dimensional material 16 and the second substrate 12, the method of the present invention can also realize the transfer of two-dimensional materials from the first substrate to the second substrate.

[0040] This application does not impose specific limitations on the heating time, but it is preferred to be 10 minutes or more. In one embodiment, the heating and holding time of the substrate can be 10 minutes to 60 minutes, for example, the substrate can be held for 12-45 minutes, such as about 15-20 minutes, so that the bonding force between the two-dimensional material and the substrate is relatively uniform across the entire bonding interface.

[0041] After heating and holding the two substrates on which the two-dimensional material has been grown for a predetermined time, the first substrate 10 and the second substrate 12 can be brought into contact, such that the side on which the first two-dimensional material 14 has been grown is in contact with the second substrate 12, for example, as shown in the example. Figure 1 As shown, the first substrate 10 can be placed above the second substrate 12, and the first two-dimensional material 14 and the second two-dimensional material 16 on the second substrate are arranged opposite to each other, so that the first two-dimensional material 14 and the second two-dimensional material 16 are in face-to-face contact with each other.

[0042] like Figure 1 As shown, to enhance the interlayer bonding force between the two-dimensional materials, pressure is applied to the first substrate 10 and the second substrate 12 after the two substrates come into contact and maintained for a predetermined time. The complete transfer of the two-dimensional materials can be achieved by adjusting the pressure. If the pressure is too low, the interlayer bonding force between the two-dimensional materials is insufficient to achieve large-area lossless transfer; if the pressure is too high, it may cause substrate damage. To improve the interlayer bonding force between the contacting two-dimensional materials, a higher pressure can be selected for the pressurization operation under permissible equipment conditions. In one embodiment, the pressurized pressure is 0.5 MPa or higher, preferably 1-100 MPa, for example 2-60 MPa, preferably 2-30 MPa, and more preferably 3-15 MPa. In one embodiment, the pressure can be maintained for 1 minute or more, for example 1-20 minutes, preferably 3-5 minutes.

[0043] In one embodiment, a machine with a hot-pressing function can be used to apply vertical pressure to the two substrates, thereby maintaining the heating temperature of the first substrate 10 and the second substrate 12 during the pressurization process, thus weakening the bonding force between the first two-dimensional material 14 and the first substrate 10. For example, the pressurizing device used includes at least one of a constant temperature hot press, a pulse hot press, a dual-station hot press or a dual-head pulse hot press, a vacuum hot press, and a wafer bonding machine.

[0044] Continue to refer to Figure 1 After the pressurization operation is completed, the pressure can be released and the first substrate 10 and the second substrate 12 can be separated, thereby realizing the transfer of the first two-dimensional material 14 from the first substrate 10 to the second substrate 12.

[0045] As previously described, after the heating and pressurization process, the bonding force between the first two-dimensional material 14 and the second two-dimensional material 16 will be greater than the bonding force between the first two-dimensional material 14 and the initial substrate 10. Therefore, when the pressure is released and the two substrates are separated, the first two-dimensional material 14 will peel off the initial substrate 10 and stack onto the second two-dimensional material 16. Although not shown, it can be understood that in the case where no two-dimensional material is grown on the second substrate, when the two substrates are separated, the first two-dimensional material 14 will peel off the initial substrate 10 and transfer onto the second substrate.

[0046] Pressure can be released gradually. In one embodiment, the first substrate 10 and the second substrate 12 can be cooled after pressure is removed. For example, after pressure is released, the first substrate 10 and the second substrate 12 can be cooled to 30-180°C, preferably to 70-90°C. This can improve the success rate of large-area transfer of two-dimensional materials and prevent oxidation of the two-dimensional materials when they come into contact with the atmospheric environment, thus preventing quality deterioration. Specifically, for hard substrates such as silicon, silicon dioxide, sapphire, mica, and precious metals, the substrates separate simultaneously with pressure release, so they can be cooled after the first substrate 10 and the second substrate 12 are separated. For soft substrates such as copper foil, i.e., when the first substrate 10 and / or the second substrate 12 are copper foil, the two substrates may not separate after pressure is released. In this case, the substrates can be cooled after pressure is released but before separation, and then the substrates can be separated manually to transfer the first two-dimensional material onto the second substrate.

[0047] The transfer method of the present invention can be performed in an atmospheric or vacuum environment. To achieve clean interfaces and large-area, non-destructive stacking transfer of two-dimensional materials, the present invention is preferably performed under vacuum conditions. For example, the transfer operation chamber can be evacuated first to remove adsorbed impurities from the substrate and the surface of the two-dimensional materials, thereby obtaining a clean bonding interface and improving interlayer coupling between the two-dimensional materials. For example, in one embodiment, a method of first evacuating and then heating and pressurizing can be used to peel off the two-dimensional material on the initial substrate and transfer it to another substrate.

[0048] To improve the transfer quality of two-dimensional materials, the first and second substrates can be cleaned before transfer to remove particulate matter from the surface of the two-dimensional materials. For example, ultrasonic cleaning can be performed on both substrates to remove surface particles. The ultrasonic medium can be alcohol, acetone, isopropanol, etc. Afterward, the substrates are dried to obtain clean substrates, which helps to improve the success rate of two-dimensional material transfer.

[0049] This exemplary embodiment achieves the transfer of two-dimensional materials from an initial substrate to a target substrate through the above method. No chemical reaction occurs between the two-dimensional material and the initial substrate. The transfer process does not require the use of transfer media such as water or organic solvents, and no wrinkles, bubbles or impurities will occur, thereby obtaining clean multilayer stacked two-dimensional materials.

[0050] Another embodiment of the present invention provides a two-dimensional material and its application. For example, multilayer two-dimensional materials can be prepared by the stacking transfer method described above. Two-dimensional materials with the same or different properties can be stacked to form two-dimensional material homogeneous or heterogeneous junctions, which can be combined to form more complex devices. By utilizing their excellent physical and chemical properties, the application of two-dimensional materials in integrated circuits, solar cells or optical devices can be expanded.

[0051] The transfer method of the present invention and the obtained two-dimensional material will be further explained below with reference to specific examples, comparative examples and accompanying drawings.

[0052] Example 1

[0053] A monolayer of molybdenum disulfide (MoD2) grown on a sapphire surface was transferred to another monolayer of MoD2 on a sapphire substrate, resulting in a bilayer of MoD2 on the sapphire substrate. The two sapphire substrates with their MoD2 grown sides placed face-to-face were heated to a specified temperature and held for a period of time. Then, pressure was applied to the two substrates in contact, and after maintaining the pressure for a period, the pressure was released, simultaneously separating the substrates. The substrates were then cooled to achieve the transfer of MoD2 to MoD2, resulting in a homojunction of bilayer MoD2.

[0054] The substrate was heated to 50 degrees Celsius for 60 minutes, subjected to 60 MPa pressure for 5 minutes, and then cooled to 30 degrees Celsius after the pressure was released.

[0055] Figure 2 shows the optical imaging, Raman spectrum, and fluorescence spectrum of the bilayer molybdenum disulfide corner homojunction obtained by the above method. As shown in Figure 2, the bilayer molybdenum disulfide homojunction can be obtained by the above method. The molybdenum disulfide coupling interface is tight, and the transferred two-dimensional material has good integrity.

[0056] Figure 3 The following are atomic force microscopy images of the bilayer molybdenum disulfide turn homojunction prepared by the above method: Figure 3 As shown, the surface of the molybdenum disulfide homojunction obtained through the above steps is smooth.

[0057] Example 2

[0058] A monolayer of molybdenum disulfide (MoD2) grown on a sapphire surface was transferred to another monolayer of MoD2 on a sapphire substrate, resulting in a bilayer of MoD2 on the sapphire substrate. The MoD2 grown surfaces of the two sapphire substrates were placed face-to-face. The two substrates were heated to a specified temperature and held for a period of time. Then, pressure was applied to the two contacting substrates, and after maintaining the pressure for a period, the substrates were released, simultaneously separating them. The substrates were then cooled to achieve the transfer of MoD2 to MoD2, resulting in a homojunction of bilayer MoD2.

[0059] The sapphire substrate located above is heated to a temperature of 90 degrees Celsius, and the sapphire substrate located below is heated to a temperature of 50 degrees Celsius. All other conditions are the same as in Example 1.

[0060] Figure 4 A schematic diagram illustrating the change in bonding strength between the two-dimensional material and the substrate as a function of temperature is shown. This figure illustrates the change in lateral force over time during the scratching of the two-dimensional material (molybdenum disulfide grown on a sapphire substrate), which was measured using a nanoindenter. Figure 4 As shown, a sudden change in lateral force occurs around 10 seconds. This change is positively correlated with the substrate bonding strength of the two-dimensional material. It can be seen that the bonding strength between molybdenum disulfide and the sapphire substrate decreases with increasing temperature. That is, in this example, the bonding strength between the upper sapphire substrate and molybdenum disulfide is less than that between the lower sapphire substrate and molybdenum disulfide, thus facilitating the transfer of molybdenum disulfide from the upper substrate to the lower substrate, resulting in a more complete bilayer molybdenum disulfide homojunction.

[0061] Example 3

[0062] A monolayer of molybdenum diselenide (covering the entire surface of the substrate) grown on a 2-inch diameter sapphire substrate was transferred to a monolayer of molybdenum disulfide on another sapphire substrate, resulting in a heterojunction of molybdenum diselenide and molybdenum disulfide on the sapphire substrate. Two sapphire substrates with the two-dimensional materials grown on them were placed face to face. The two substrates were first heated to a specified temperature and held for a period of time. Then, pressure was applied to the two substrates in contact, and after maintaining the pressure for a period of time, the pressure was released, simultaneously separating the substrates. The substrates were then cooled to achieve the transfer of molybdenum diselenide to molybdenum disulfide, resulting in a heterojunction of molybdenum diselenide and molybdenum disulfide.

[0063] The substrate was heated to 120 degrees Celsius for 30 minutes, subjected to 4 MPa pressure for 1 minute, and then cooled to 80 degrees Celsius after the pressure was released.

[0064] Figure 5 shows the optical imaging, Raman spectrum, and fluorescence spectrum of the molybdenum diselenide / molybdenum disulfide heterojunction obtained by the above method. As shown in Figure 5, the heterojunction can be obtained by the above method, with a flat and tight coupling interface, and the transferred two-dimensional material has good integrity.

[0065] Example 4

[0066] The double layer of molybdenum disulfide obtained by the transfer method of this application is transferred to a gold substrate to obtain a double layer of molybdenum disulfide on gold. Specifically, the double layer of molybdenum disulfide on the sapphire substrate prepared in Example 1 is placed with one side facing up under a gold substrate (a gold thin film deposited on a silicon wafer by electron beam evaporation). The two substrates are first heated to a specified temperature and held for a period of time, then pressure is applied and maintained for a period of time. After that, the pressure is released and the substrates are separated. Then the substrates are cooled to transfer the double layer of molybdenum disulfide from the sapphire substrate to the gold substrate.

[0067] The substrate was heated to 180 degrees Celsius for 15 minutes, subjected to 20 MPa pressure for 3 minutes, and then cooled to 90 degrees Celsius after the pressure was released.

[0068] That is, by repeatedly performing the transfer method of the present invention, the same or different two-dimensional materials can be stacked to form multilayer more complex devices and transferred to a suitable substrate.

[0069] Example 5

[0070] Monolayer graphene grown on copper foil was transferred to molybdenum disulfide grown on a sapphire substrate, resulting in a graphene / molybdenum disulfide heterojunction on a sapphire substrate. The sapphire substrate with the molybdenum disulfide side facing up and the copper foil with the graphene side facing down were placed opposite each other. The two substrates were first heated to a specified temperature and held for a period of time. Then, pressure was applied to the two substrates in contact, and after maintaining the pressure for a period of time, the pressure was released. After the substrates were cooled, the two substrates were manually separated, achieving the transfer of graphene to molybdenum disulfide.

[0071] The substrate was heated to 180 degrees Celsius for 20 minutes, subjected to 1 MPa pressure for 10 minutes, and then cooled to 90 degrees Celsius after the pressure was released.

[0072] Figure 6 shows the optical imaging and corresponding Raman spectrum of the graphene / molybdenum disulfide heterojunction obtained by the above method. As shown in Figure 6, two-dimensional materials with different properties can be stacked to form a heterojunction by the above method.

[0073] Example 6

[0074] A monolayer of tungsten disulfide grown on a sapphire surface was transferred to a monolayer of molybdenum disulfide grown on another sapphire substrate, resulting in a heterojunction of tungsten disulfide and molybdenum disulfide on the sapphire substrate. The two sapphire substrates with their two-dimensional material surfaces were placed face-to-face. The substrates were first heated to a specified temperature and held for a period of time, then pressure was applied and maintained for a further period before the pressure was released, thus achieving the transfer of tungsten disulfide to molybdenum disulfide.

[0075] The substrate was heated to 300 degrees Celsius for 10 minutes, and the pressure was 50 MPa for 4 minutes.

[0076] Comparative Example 1

[0077] Two sapphire substrates with molybdenum disulfide grown on their surfaces are placed face to face. The two substrates are first heated to a specified temperature and held for a period of time. Then, pressure is applied and maintained for a period of time before the pressure is released, thus achieving the transfer of molybdenum disulfide to molybdenum disulfide.

[0078] The substrate was kept at ambient temperature, the pressure was 60 MPa, and the pressure was applied for 5 minutes.

[0079] Unlike Example 1, this comparative example does not involve heating the substrate, which is outside the scope of protection of this invention. Figure 7 The image shows a photoluminescence of the two-dimensional material obtained by the comparative transfer method. It can be seen that the interface of the two-dimensional material is uneven, and the integrity of the two-dimensional material after transfer is worse than that of Example 1.

[0080] Comparative Example 2

[0081] Two sapphire substrates with molybdenum disulfide grown on their surfaces are placed face to face. The two substrates are first heated to a specified temperature and held for a period of time. Then, pressure is applied and maintained for a period of time before the pressure is released, thus achieving the transfer of molybdenum disulfide to molybdenum disulfide.

[0082] The substrate was heated to 90 degrees Celsius for 60 minutes, with a pressure of 0.1 MPa and a pressure application time of 20 minutes.

[0083] Unlike Example 1, the pressure applied to the substrate in this comparative example is 0.1 MPa, which is outside the scope of protection of this invention. Figure 8 The image shows a photoluminescence of the two-dimensional material obtained by the comparative transfer method. It can be seen that the interface of the two-dimensional material is uneven, and the integrity of the two-dimensional material after transfer is worse than that of Example 1.

[0084] In this text, words such as “including,” “contains,” and “has” are open-ended terms meaning “including but not limited to,” and are used interchangeably. The words “or” and “and” as used herein refer to the words “and / or” and are used interchangeably unless the context explicitly indicates otherwise. The word “such as” as used herein refers to the phrase “such as but not limited to,” and is used interchangeably.

[0085] Although terms such as "first" or "second" may be used to describe different components or features, these components or features are not limited to these terms. Using these terms, only one component is distinguished from another, without emphasizing order, positional relationship, importance, or tier. For example, without departing from the scope of this application, a first component may be referred to as a second component; and a second component may also be referred to as a first component. Thus, "first substrate" may be referred to as "second substrate," "first two-dimensional material" may be referred to as "second two-dimensional material," and vice versa; that is, modifiers such as "first" and "second" without quantifiers are interchangeable.

[0086] The basic principles of this application have been described above with reference to specific embodiments. However, it should be noted that the advantages, benefits, and effects mentioned in this application are merely examples and not limitations, and should not be considered as essential features of each embodiment of this application. Furthermore, the specific details disclosed above are for illustrative and facilitative purposes only, and are not limitations. These details do not limit the application to the necessity of employing the aforementioned specific details for implementation.

[0087] The above description has been given for purposes of illustration and description. Furthermore, this description is not intended to limit the embodiments of this application to the forms disclosed herein. Although several exemplary aspects and embodiments have been discussed above, those skilled in the art will recognize that many modifications and variations in detail and form can be made without departing from the spirit and scope of the invention. The scope of the invention is defined by the claims and their equivalents.

Claims

1. A method for transferring two-dimensional materials, comprising the following steps: heating the first substrate and the second substrate to a predetermined temperature, wherein The first substrate carries a first two-dimensional material, and the predetermined temperature is between 50°C and 300°C. After heating and holding the first substrate and the second substrate for a predetermined time, the first substrate is brought into contact with the second substrate carrying the second two-dimensional material, so that the first two-dimensional material and the second two-dimensional material are in face-to-face contact, wherein the first two-dimensional material and the second two-dimensional material are different. Applying vertical pressure to the first and second substrates to apply pressure and maintaining it for a predetermined time; and The pressure is relieved, and the first and second substrates are separated, thereby transferring the first two-dimensional material from the first substrate to the second substrate. The first two-dimensional material and / or the second two-dimensional material are grown on the first substrate and / or the second substrate by deposition, epitaxy, or precipitation methods, or the first two-dimensional material and / or the second two-dimensional material are attached to the first substrate and / or the second substrate by transfer methods. The pressure applied is 0.5-100 MPa.

2. The method of claim 1, wherein, The equivalent surface diameter of the first two-dimensional material and / or the second two-dimensional material is greater than 1 mm.

3. The method according to claim 1, wherein, The predetermined temperature is between 90°C and 200°C.

4. The method according to claim 1 or 2, wherein, The predetermined pressurization time is 1-20 minutes.

5. The method of claim 4, wherein, The pressurization pressure is 2-60 MPa, and the predetermined time is 3-5 minutes.

6. The method of claim 1 or 2, wherein, The method further includes: After the pressure is released, the first and second substrates are cooled.

7. The method of claim 6, wherein, After the pressure is released, the first and second substrates are cooled to 30-180°C.

8. The method of claim 7, wherein, After the pressure is released, the first and second substrates are cooled to 70-90°C.

9. The method of claim 1 or 2, wherein, The first substrate may be the same as or different from the second substrate.

10. The method of claim 9, wherein, The first substrate is at least one of silicon, silicon dioxide, sapphire, copper foil or mica, and the second substrate is at least one of noble metal, silicon, silicon dioxide, sapphire, copper foil or mica.

11. A two-dimensional material obtained by the two-dimensional material transfer method according to any one of claims 1-10.

12. The application of the two-dimensional material of claim 11 in integrated circuits, solar cells or optical devices.

Images