Two-dimensional materials and heterostructures on intermediate polymer transfer layers

Abstract

The present disclosure relates to a method for producing a water-soluble transfer stack comprising a multilayer two-dimensional material, the method comprising: i. providing a growth stack comprising a growth substrate and a two-dimensional material layer; ii. applying an intercalation solution to the growth stack; iii. applying a transfer layer comprising a water-soluble polymer film to the growth stack; iv. peeling the water-soluble polymer film together with the two-dimensional material layer from the growth substrate to obtain a peeled film; and v. repeating steps i.-iv. a number of times, wherein the peeled film is used as a transfer layer, thereby producing a water-soluble transfer stack comprising the multilayer two-dimensional material.

Description

[Technical Field]

[0001] The present disclosure relates to a method for making a water-soluble transfer layer that includes multiple layers of a two-dimensional material. Additionally, the present disclosure relates to water-soluble transfer layers, uses of water-soluble transfer layers, and multi-layer two-dimensional materials. [Background technology]

[0002] Two-dimensional materials such as graphene are crystalline materials consisting of a single layer of atoms. These materials have proven to be extremely useful in areas such as photovoltaics, semiconductors, electrodes, and water purification.

[0003] Graphene is a crystalline allotrope of carbon in the form of one-atom-thick sheets that are nearly transparent (to visible light). Graphene is a highly promising two-dimensional (2D) nanomaterial with extraordinary properties, including the highest known thermal and electrical conductivity, and strength hundreds of times greater by weight than most steels.

[0004] Typically, the assembly of graphene-based products occurs remotely from the production of the graphene layers, requiring the graphene to be transferred from its growth site to the target substrate location. This is typically done by applying a supporting polymethyl methacrylate (PMMA) film to the graphene, followed by chemical etching of the metal substrate or electrochemically peeling the graphene from the growth substrate.

[0005] Using this method, a layer of PMMA is spin-coated onto graphene to act as a support. An etchant is then used to remove the metal catalyst, after which the PMMA / graphene stack can be transferred to the target substrate location. A solvent is then used to remove the PMMA, completing the graphene transfer.

[0006] However, graphene transfer using the PMMA method is not a simple procedure and requires advanced knowledge, including wet chemistry. A further problem is the high cost, as the catalyst accounts for a significant portion of the graphene production cost.

[0007] Other methods, such as electrochemical exfoliation, have been developed that allow for catalyst reuse, but throughput is severely limited because the exfoliation rate must be kept low to prevent excessive foaming, which can damage the graphene film.

[0008] Another drawback of prior art transfer methods is that they are not suitable for use in transferring multi-layer graphene or other two-dimensional materials where a specific number of layers must be controlled. Multi-layer graphene has excellent properties, such as high electrical and thermal conductivity and current-carrying ability, making it highly suitable for a wide range of applications, including high-performance transparent conductors, low-resistance wiring, and heat spreaders. Depending on the intended use of multi-layer graphene, a specific number of layers may be required.

[0009] However, producing single- or multi-layer graphene via a simple, efficient, cost-effective, and scalable route remains a major challenge in materials science. Some early efforts have been made to produce multi-layer graphene by methods that build on aspects of single-graphene layer production methods. However, no method remains that can provide a scalable, non-toxic, and simple approach to producing high-quality multi-layer two-dimensional materials.

[0010] Therefore, there is a strong need for a simple and versatile method that allows the transfer of two-dimensional materials or multilayers, where the application of the transfer layer can be performed without the use of specialized equipment or harsh chemicals, and is highly amenable to high throughput. Summary of the Invention

[0011] The inventors have recognized that water-soluble polymer films can be advantageously used for the continuous transfer of multilayer two-dimensional materials in a highly scalable manner that allows for the reuse of growth substrates and does not rely on the use of sophisticated equipment, highly trained personnel, or hazardous chemicals. Indeed, certain embodiments of the presently disclosed method rely on the use of water as an intercalation solution to separate the two-dimensional layers from the growth substrate. This results in a method in which water is the only solvent used.

[0012] Accordingly, the present disclosure relates in a first aspect to a method of manufacturing a water-soluble transfer stack comprising a plurality of layers of two-dimensional material, the method comprising: i. providing a growth stack comprising a growth substrate and a two-dimensional material layer; ii. applying an intercalation solution to the growth stack; iii. applying a transfer layer comprising a water-soluble polymer film to the growth stack; iv. peeling the water-soluble polymer film together with the two-dimensional material layer from the growth substrate, thereby obtaining a peeled film; and v. Repeating steps i. through iv. multiple times, with the most recently obtained peeled film being used as the transfer layer for each repetition; thereby producing a water-soluble transfer stack comprising multiple layers of two-dimensional material.

[0013] The highly versatile method, based on the sequential transfer of two-dimensional layers to form a transfer stack, advantageously allows the production of transfer layers containing any number of two-dimensional layers, and even two-dimensional layers of different types. The resulting transfer layers can be easily transported to the end user for application onto product-specific target substrates, eliminating the need to transport the target substrates to and from the growth facility. At the same time, this method allows the production of high-quality two-dimensional layers with specific properties, such as for the production of two-dimensional material layers with significant roughness.

[0014] Chen, W. et al., (2018). Two-Dimensional Materials Wrinkling: Methods, Properties and Applications. As further described in Nanoscale Horizons, rough and wrinkled two-dimensional materials have been shown to be highly useful in a wide range of applications, including electrodes, chemical detectors, mechanical sensors, and controllable patterns.

[0015] In a preferred embodiment of the present disclosure, the method is configured such that at least a portion of the method is repeated, whereby additional two-dimensional material layers are added to the transfer stack, with each repetition of that portion of the method adding an additional two-dimensional material layer to the transfer stack, whereby by repeating this process an appropriate number of times a transfer stack having a desired number of two-dimensional material layers can be produced.

[0016] In addition to the fact that the method for fabricating the transfer layer is simple to implement, the final product, the transfer layer itself, can be applied to the target substrate by simple means. Furthermore, neither the fabrication of the transfer layer nor its application to the target substrate may require hazardous chemicals, highly trained personnel, or expensive equipment.

[0017] This method is highly versatile and may allow the use of any conventional growth substrate. The growth substrate may even be provided as a metal foil, allowing for increased throughput, for example by integrating the method into a roll-to-roll process. A key advantage of the presently disclosed method compared to prior art methods is that it allows for the reuse of the growth substrate. Since the growth substrate represents a large portion of the costs associated with the production of two-dimensional materials, a reusable growth substrate could lead to a significant reduction in costs and expand the number of applications.

[0018] In addition to the versatility in the selection of two-dimensional material layers, the methods disclosed herein enable the fabrication of a water-soluble transfer layer comprising any number of two-dimensional material layers, for example, at least two, and more preferably at least 20. By repeating at least a portion of the method, such as steps i.-iv., an appropriate number of times, a water-soluble transfer stack comprising a corresponding number of two-dimensional material layers is produced.

[0019] It should be noted that the methods disclosed herein are not limited to any particular material for the two-dimensional material layer. Instead, the methods disclosed herein can be used to form water-soluble transfer stacks that include two-dimensional layers of different materials, thereby enabling the fabrication of heterostructures in a process that is easy to implement.

[0020] It is an object of the present disclosure to provide a method that is at least partially compatible with high-throughput processing methods. For example, the method is compatible with roll-to-roll processing, e.g., by using metal foil as the growth substrate, while the application of the transfer layer to the growth stack can be performed, e.g., by using a hot roll laminator. Process scalability is an important aspect of the presently disclosed method.

[0021] In preferred embodiments of the presently disclosed method, application of the transfer layer to the growth stack is carried out in a single step while applying heat and pressure, such as at least 140° C. and at least 2 bar. Such increased temperature and pressure eliminates the need for a post-bake step, further simplifying the method and increasing throughput.

[0022] In a further aspect, the present disclosure relates to a water-soluble transfer stack comprising a plurality of two-dimensional material layers, the water-soluble transfer stack being manufactured by a method comprising: i. providing a growth stack comprising a growth substrate and a two-dimensional material layer; ii. applying an intercalation solution to the growth stack; iii. applying a transfer layer comprising a water-soluble polymer film to the growth stack; iv. peeling the water-soluble polymer film together with the two-dimensional material layer from the growth substrate, thereby obtaining a peeled film; and v. Repeating steps i. through iv. a number of times, with the most recently obtained peeled film being used as the transfer layer for each repetition.

[0023] In a further aspect, the present disclosure relates to the use of a water-soluble transfer stack for producing multiple two-dimensional material layers on a target substrate, the use comprising: i. obtaining a water-soluble transfer stack comprising a multi-layer two-dimensional material, as disclosed elsewhere herein; and ii. applying the water-soluble transfer stack to a target substrate; thereby producing a plurality of two-dimensional material layers on the target substrate.

[0024] In a further aspect, the present disclosure relates to multiple layers of two-dimensional materials. An objective of the presently disclosed embodiments is to provide multi-layer two-dimensional materials with low surface roughness, such as a maximum roughness height average (RzISO) of less than 50 nm. Preferably, the two-dimensional materials are at least 1 cm thick. 2 It has a surface area (installation area) of [Brief explanation of the drawings]

[0025] [Figure 1] 1 shows a schematic overview of a method for manufacturing a water-soluble transfer stack according to certain embodiments of the present disclosure. [Figure 2] 1 shows four samples of tri-layer graphene on water-soluble PVA foil, according to certain embodiments of the present disclosure. [Figure 3] 10A-10C illustrate multi-layer graphene transferred onto different target substrates according to certain embodiments of the present disclosure. [Figure 4] 1 shows a photograph of sunlight transmitted through three-layer graphene and the optical transmittance of visible light through graphene with different numbers of layers, according to certain embodiments of the present disclosure. [Figure 5]1 shows multi-layer graphene on a 90 nm SiO2 / Si substrate, according to certain embodiments of the present disclosure. [Figure 6] 1 shows a scanning electron microscope (SEM) image of three-layer graphene on a water-soluble PVA film, according to certain embodiments of the present disclosure. [Figure 7] 1 shows atomic force microscope (AFM) scans of three different samples of tri-layer graphene transferred to SiO2 / Si substrates, according to certain embodiments of the present disclosure. [Figure 8] 1 shows Raman point spectra obtained for three different samples of tri-layer graphene transferred onto SiO2 / Si substrates, according to certain embodiments of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0026] definition As used herein, the term "two-dimensional material" refers to a crystalline material consisting of a single or a few atomic layers. Typically, materials such as graphene are a single layer of atoms, while materials such as MXene are only a few atoms thick. This is sometimes referred to as a single-layer material. Combining multiple, typically 2-100, layers of two-dimensional material results in a stack comprising a "multilayer two-dimensional material," also referred to herein as "multiple two-dimensional material layers."

[0027] As used herein, the term "growth substrate" refers to a substrate for the growth of two-dimensional materials. Typically, the substrate is planar and made of a material selected from transition metals such as copper, nickel, or gold. The substrate is usually selected based on the lattice mismatch and the strength of the interface between the substrate and the two-dimensional material.

[0028] The term "transfer stack" is used interchangeably herein with the term "transfer layer" and refers to a stack that includes a water-soluble polymer layer attached to at least one two-dimensional material layer. Repeating at least a portion of the method of the present disclosure adds two-dimensional material layers to the transfer stack / transfer layer. The different layers of the transfer layer at least partially overlap, and preferably the layers are the same size and / or aligned.

[0029] As used herein, the term "intercalation solution" refers to the reversible encapsulation or insertion of molecules (or ions) into a material having a layered structure. In a preferred embodiment of the present disclosure, water is used as the intercalation solution, in which water molecules are intercalated between the growth substrate and the two-dimensional material. The intercalation solution is thereby preferably configured to at least partially intercalate between the growth substrate and the two-dimensional material layer of the growth stack. The intercalation preferably leads to separation, allowing the two-dimensional material layer to adhere more strongly to a second layer, such as a transfer layer.

[0030] As used herein, the term "water-soluble polymer film" refers to any film comprising a polymer that is at least partially water-soluble. Typical water-soluble polymer films are those having the ideal formula [CHCH(OH)] n It is a film of poly(vinyl alcohol) (PVOH, PVA, or PVAl).

[0031] As used herein, the term "vacuum" refers to a pressure well below atmospheric pressure (i.e., well below 1 atm). In particular, vacuum refers to low, medium, and / or high vacuum conditions (i.e., 9.87×10 -13 atm~3×10 -2 This refers to a vacuum in the range of 1000 to 2000 atm.

[0032] As used herein, the term "vacuum deposition" refers to a set of processes used to deposit layers of material atom by atom or molecule on a solid surface, such as a growth substrate. These processes operate at pressures well below atmospheric pressure (i.e., vacuum). The deposited layers range in thickness from one atom to several millimeters and form free-standing structures. Multiple layers of different materials can be used to form, for example, optical coatings. Processes can be qualified based on the source of the vapor: physical vapor deposition uses a liquid or solid source, while chemical vapor deposition uses a chemical vapor.

[0033] In a first aspect, the present disclosure relates to a method for producing a water-soluble transfer stack. The water-soluble transfer stack comprises at least two layers of one or more two-dimensional materials, i.e., the water-soluble transfer stack comprises multiple two-dimensional layers, the layers being of the same and / or different materials. A preferred embodiment of the present disclosure relates to the layer-by-layer formation of a transfer layer comprising multiple two-dimensional materials.

[0034] In an embodiment of the present disclosure, at least some iterations of the method (step v) are performed such that the method includes: i. providing a growth stack comprising a growth substrate and a two-dimensional material layer; ii. applying an intercalation solution to the growth stack; iii. applying a transfer layer comprising a water-soluble polymer film to the growth stack; iv. peeling the water-soluble polymer film together with the two-dimensional material layer from the growth substrate, thereby obtaining a water-soluble transfer stack; and v. Repeating the process with additional growth stacks by doing at least one of the following: a. providing a further growth stack comprising a further layer of two-dimensional material and the same or a further growth substrate; b. applying an intercalation solution to the further growth stack; c. applying the resulting aqueous transfer stack to a further growth stack; d. peeling the water-soluble transfer stack together with the additional growth stack from the same or additional growth substrate, thereby obtaining an additional water-soluble transfer stack (i.e., a water-soluble transfer stack comprising an additional layer of two-dimensional material); However, with each iteration, an additional layer of two-dimensional material is added to the water-soluble transfer stack, thereby producing a water-soluble transfer stack that includes multiple layers of two-dimensional material.

[0035] An objective of the present disclosure is to provide a water-soluble transfer stack that is easy to handle and work with, for example, typically for application to a target substrate on a final product. Precision manufacturing of two-dimensional materials, such as high-quality graphene, is a resource-intensive and expensive process, especially for high throughput. Therefore, the method is preferably adapted so that the transfer stack is manufactured at one location, typically the site of the two-dimensional material manufacturer, and then transported to a second location, typically the site of a custom product manufacturer, where the two-dimensional material is applied to the target substrate. Therefore, it is highly desirable for the transfer layer to be easy to handle and transport. Furthermore, it may be highly desirable for the transfer layer to be configured so that the custom product manufacturer can easily apply the two-dimensional material layer of the transfer layer to the target substrate of the product. The use of a water-soluble polymer film, such as a polyvinyl alcohol film, eliminates the need for harsh chemicals that are otherwise required, allowing for the reuse of growth substrates while simultaneously simplifying the process of applying the layer to the target substrate.

[0036] In an embodiment of the present disclosure, the method includes providing a growth stack including a growth substrate and a two-dimensional material layer grown on the growth substrate by a vacuum deposition method, such as chemical vapor deposition. However, one skilled in the art will appreciate that there are other routes for forming two-dimensional layers that may be suitable for providing the two-dimensional layer in the presently disclosed method. Finally, the presently disclosed method is not limited to any exemplary processes mentioned herein.

[0037] In embodiments of the present disclosure, the intercalation solution and / or application conditions of the intercalation solution are configured such that at least a portion of the intercalation solution intercalates the growth stack, such as between the growth substrate and the two-dimensional material. As used herein, intercalation preferably refers to the reversible encapsulation or insertion of molecules (or ions) into a material having a layered structure. Thus, the intercalation solution can include moieties, such as molecules, that intercalate between the growth substrate and the two-dimensional layer.

[0038] In a further embodiment of the present disclosure, the method includes applying a transfer layer to the growth stack, the transfer layer including a water-soluble polymer film. Consequently, the transfer layer can consist of a single water-soluble polymer film layer. Typically, the method is configured to be at least partially repeated. The step of applying a transfer layer to the growth stack typically involves the use of a transfer layer consisting of a water-soluble polymer film the first time the step is performed. However, each time the step is repeated, the transfer layer includes an additional two-dimensional material layer. Thus, the first time the step is repeated, the transfer layer can consist of a water-soluble polymer film and a two-dimensional material layer. Each repetition of the step can include the use of a transfer layer having n layers of two-dimensional material layers, where n refers to the number of times the step is repeated.

[0039] In further embodiments of the present disclosure, the method includes a peeling step. Typically, the step includes peeling the water-soluble polymer film together with the two-dimensional material layers from the growth substrate, resulting in a peeled film. The peeling step preferably includes peeling the water-soluble polymer film together with each two-dimensional material layer. Since the previous step preferably includes applying a transfer layer to the growth stack, the peeling typically includes peeling the transfer layer together with the two-dimensional layers of the growth stack from the growth substrate. Typically, the peeling step is configured so that the two-dimensional layers of the growth stack adhere more strongly to the transfer layer than to the growth substrate, such as the exposed two-dimensional material layer of the transfer layer. In embodiments of the present disclosure, the peeling consists of or includes mechanical peeling.

[0040] In further embodiments of the present disclosure, at least a portion of the method is repeated, preferably one or more steps including any of the following are repeated: providing a growth stack, applying an intercalation solution to the growth stack, applying a transfer layer to the growth stack, and / or peeling the water-soluble polymer film together with the two-dimensional material layer from the growth substrate. In preferred embodiments of the present disclosure, all of the following are repeated: providing a growth stack, applying an intercalation solution to the growth stack, applying a transfer layer to the growth stack, and / or peeling the water-soluble polymer film together with the two-dimensional material layer from the growth substrate.

[0041] In a further embodiment of the present disclosure, the method is configured to produce a water-soluble transfer stack comprising a multilayer two-dimensional material, where the multilayer two-dimensional material can comprise any number of layers greater than one. As disclosed elsewhere herein, the two-dimensional material layers of the water-soluble transfer stack can comprise different materials, i.e., the two-dimensional material layer can comprise layers of different materials. This allows the two-dimensional material layer to be a heterostructure.

[0042] Growth Stack In further embodiments of the present disclosure, the growth substrate comprises or consists of a metal substrate, such as a transition metal. In embodiments of the present disclosure, the material of the growth substrate is iron, copper, nickel, gold, aluminum, silicon, gallium, tin, or any of their oxides or alloys. In further embodiments of the present disclosure, the growth substrate is provided as a metal foil. The use of a metal foil can increase process throughput by enabling roll-to-roll processing. Furthermore, the metal foil can be rolled up during the intercalation step to reduce the space it occupies.

[0043] In a further embodiment of the present disclosure, the step of providing a growth stack comprises growing two-dimensional material layers on a growth substrate, such as by chemical vapor deposition.

[0044] In further embodiments of the present disclosure, the growth stack can comprise a growth substrate having a plurality of two-dimensional materials. For example, two-dimensional material layers can be grown on two opposing sides of the growth substrate, e.g., on each side of a metal foil, thereby doubling throughput. Thus, in further embodiments of the present disclosure, providing the growth stack comprises growing two-dimensional material layers on two opposing sides of the growth substrate, such as by chemical vapor deposition.

[0045] In further embodiments of the present disclosure, the method is reused multiple times, such as by repeating at least a portion of the method to apply additional two-dimensional layers to the growth stack, such that the growth substrate adds additional two-dimensional material layers. Unlike methods that rely on the use of corrosive materials to remove two-dimensional layers from the growth substrate, the presently disclosed method is preferably configured to allow the growth substrate to be reused, thereby significantly reducing costs. The growth substrate can be reused, for example, to form additional two-dimensional material layers of the same material. This allows for an additional growth substrate to be provided for each additional material in the two-dimensional material layer.

[0046] In further embodiments of the present disclosure, the material of the two-dimensional material layer is either graphene, hexagonal boron nitride, and / or a transition metal dichalcogenide such as molybdenum disulfide, hafnium disulfide, or tungsten diselenide, and / or MXene. The transfer stack may comprise a mixture of two-dimensional material layers of different materials. Thereby, in further embodiments of the present disclosure, the water-soluble transfer stack comprises a plurality of two-dimensional material layers, each comprising a layer of a different two-dimensional material.

[0047] The presently disclosed method allows for the fabrication of water-soluble transfer stacks comprising large area two-dimensional material layers. Thus, in embodiments of the presently disclosed invention, the two-dimensional material layers each have an area of ​​at least 1 cm 2 , more preferably at least 10 cm each 2 , most preferably at least 100 cm each 2 (i.e., the surface area of ​​one side of any one of the two-dimensional material layers).

[0048] Intercalation In further embodiments of the present disclosure, the intercalation solution comprises or consists of water, an alcohol solution (EtOH or IPA), a salt solution such as sodium chloride, potassium chloride, etc., up to 1 M.

[0049] In a further embodiment of the present disclosure, the step of applying the intercalation solution is adapted to intercalate the intercalation solution between the growth substrate and the two-dimensional material layer. For example, the process occurs by intercalation of water between the two-dimensional material layer and the growth substrate, followed by electrical coupling between the more noble two-dimensional material layer (e.g., graphene film) and the growth substrate (e.g., copper surface), which promotes oxidation, leading to corrosion of the surface and subsequent separation of the two-dimensional material layer (e.g., graphene film) from the growth substrate (e.g., copper surface). Those skilled in the art know that intercalation can be performed by using different types of substances and different methods for achieving intercalation and ultimately separation of the layer. Intercalation can be achieved, for example, by electrochemical intercalation instead of or in addition to immersion in the intercalation solution. However, in a preferred embodiment of the present disclosure, the intercalation solution comprises or consists of water. It is highly preferred that the method is configured so as not to rely on any harsh chemicals. Thereby, the method can include intercalation in a step solely by application of water, and similarly, the transfer stack can be applied to the target substrate by dissolving the water-soluble material with water.

[0050] In further embodiments of the present disclosure, the intercalation solution is applied to the growth stack for less than 48 hours, preferably less than 24 hours, more preferably less than 12 hours, and most preferably less than 8 hours. Concurrently, the intercalation solution is applied to the growth stack for at least 30 minutes, more preferably at least 3 hours, and most preferably at least 6 hours. In embodiments of the present disclosure, the intercalation solution is applied to the growth stack for a period of 30 minutes to 12 hours, more preferably 3 to 8 hours. In further embodiments of the present disclosure, the intercalation solution is applied to the growth stack at a temperature of at least 20°C, more preferably at least 30°C, even more preferably at least 45°C, and even more preferably at least 60°C. Increasing the temperature during the intercalation step may accelerate the intercalation process, thereby allowing for a reduction in the length of the step.

[0051] Applicable Following intercalation of the intercalation solution, a transfer layer is preferably applied to the growth substrate. Preferably, the step of applying the transfer layer to the growth stack is configured to increase adhesion between the two-dimensional layers of the growth stack and the transfer layer, i.e., the water-soluble polymer film or exposed two-dimensional material layer, surpassing the adhesion between the two-dimensional material layer of the growth stack and the growth substrate. In a preferred embodiment of the present disclosure, the step of applying the transfer layer to the growth stack includes applying heat and / or pressure. The transfer layer, e.g., the water-soluble polymer film, can be applied by using a laminator. In a preferred embodiment of the present disclosure, the transfer layer and the growth stack (preferably the intercalated growth stack) are laminated or hot-pressed at a temperature of 100°C to 180°C and a pressure of between 2 bar and 5 bar. While the step of applying the transfer layer to the growth stack, i.e., the lamination step, can be performed at ambient pressure, in a preferred embodiment of the present disclosure, the step of applying the transfer layer to the growth stack is performed under reduced pressure, preferably under low, medium, or high vacuum conditions.

[0052] In preferred embodiments of the present disclosure, the temperature during the step of applying the transfer layer to the growth stack is at least 80°C, more preferably at least 100°C, even more preferably at least 120°C, even more preferably at least 140°C, and most preferably about 150°C, and / or preferably, the temperature during the step of applying the transfer layer to the growth stack is applied for at least 1 second, more preferably at least 5 seconds, and even more preferably at least 10 seconds. In preferred embodiments of the present disclosure, the temperature during the step of applying the transfer layer to the growth stack is at least 80°C, more preferably at least 100°C, even more preferably at least 120°C, even more preferably at least 140°C, and most preferably about 150°C, and / or preferably, the temperature during the step of applying the transfer layer to the growth stack is applied for 1 second to 20 seconds, more preferably at least 2 seconds to 10 seconds, and even more preferably at least 3 seconds to 7 seconds.

[0053] In further embodiments of the present disclosure, the step of applying the transfer layer to the growth stack further comprises a post-bake step carried out at at least 80°C, more preferably at least 100°C, even more preferably at least 120°C, and most preferably at least 140°C, e.g., for at least 30 seconds. The post-bake step can include the application of heat, e.g., by placing the transfer layer and growth stack on a hotplate. Generally, the post-bake step does not include the application of pressure to the transfer layer and growth stack. Certain embodiments of the present disclosure may not require or even benefit from a post-bake step. For example, a higher temperature, such as at least 130°C, during the step of applying the transfer layer to the growth stack can eliminate the need for a post-bake step.

[0054] It should be noted that the transfer layer may initially consist of a water-soluble polymer film, such as before repeating at least a portion of the method. After repeating at least a portion of the method, the transfer layer typically comprises a water-soluble polymer film and at least one two-dimensional material layer. Thus, in further embodiments of the present disclosure, applying heat and / or pressure comprises or consists of applying said heat and / or pressure to: i. the water-soluble polymer film and the growth stack, and / or ii. the peeled film and the further growth stack.

[0055] In a further embodiment of the present disclosure, the transfer layer is applied to the growth stack by a roll laminator, such as a hot roll laminator, a roll-to-roll press, and / or a hot press, preferably configured to apply heat and / or pressure to the transfer layer and the growth stack to increase their adhesion, preferably stronger than the adhesion between the growth substrate and the two-dimensional material layer of the growth stack.

[0056] polymer film In a further embodiment of the present disclosure, the water-soluble polymer film material is polyvinyl alcohol. Polyvinyl alcohol, or PVOH, is a transparent, water-soluble thermoplastic derived from polyvinyl acetate by partial or complete hydroxylation. PVOH is highly hydrophilic, resulting in high solubility in water and high resistance to hydrocarbons, mineral oil, and many organic solvents, such as ethers, esters, and ketones. Films made from polyvinyl alcohol have excellent heat-sealing properties and excellent adhesion to cellulose and other hydrophilic surfaces.

[0057] Preferably, the water-soluble polymer film is provided at a thickness that provides sufficient bending stiffness to facilitate handling. In certain embodiments, the film is provided at a thickness that is thin enough to form a rolled-up transfer stack, for example, when the method is carried out in a roll-to-roll process. In a preferred embodiment of the present disclosure, the water-soluble polymer film has a thickness of 100 nm to 100 μm.

[0058] Peeling In further embodiments of the present disclosure, the step of delaminating comprises or consists of mechanically separating the water-soluble transfer layer and the two-dimensional layers of the growth stack from the growth substrate, typically to form a transfer layer that includes additional two-dimensional layers.

[0059] In a further embodiment of the present disclosure, the method is configured such that each time the steps are repeated, an additional layer of two-dimensional material is added to the water-soluble transfer stack, which may be the same material and / or a different material.

[0060] In a further embodiment of the present disclosure, the method is repeated by applying a peeled film, i.e., a stack comprising a water-soluble polymer film and at least one two-dimensional material layer, to a two-dimensional material layer, e.g., a two-dimensional material layer of a growth stack. Preferably, the peeled film is applied to a growth stack that has been exposed to an intercalation solution, preferably such that the intercalation solution is at least partially intercalated between the two-dimensional layer of the growth stack and the growth substrate.

[0061] In a further embodiment of the present disclosure, the method is adapted to be performed in a roll-to-roll process.

[0062] In embodiments of the present disclosure, the multilayer two-dimensional material has an electrical resistance of at most 10 kΩ / sq, preferably less than 1 kΩ / sq. In certain embodiments of the present disclosure, the water contact angle is between 30° and 90°. In further embodiments of the present disclosure, the surface hardness is at most about 10,000 N / mm, as measured by nanoindentation techniques. 2 is.

[0063] Water-soluble transfer stack In a further aspect, the present disclosure relates to a water-soluble transfer stack comprising a multilayer two-dimensional material.

[0064] In an embodiment of the present disclosure, the water-soluble transfer stack is manufactured according to the method of manufacturing a water-soluble transfer stack comprising a multilayer two-dimensional material, as disclosed elsewhere herein.

[0065] In yet another aspect, the present disclosure relates to a method for fabricating a multi-layer two-dimensional material on a target substrate, the method comprising: a) producing a water-soluble transfer stack comprising a multi-layer two-dimensional material, comprising: i. providing a growth stack comprising a growth substrate and a two-dimensional material layer; ii. applying an intercalation solution to the growth stack; iii. applying a transfer layer comprising a water-soluble polymer film to the growth stack; iv. peeling the water-soluble polymer film together with the two-dimensional material layer from the growth substrate, thereby obtaining a peeled film; and v. Repeating steps i to iv a number of times, the peeled film being used as a transfer layer; b) applying the transfer stack to a target substrate;

[0066] In an embodiment of the present disclosure, the water-soluble transfer stack is manufactured according to the method of manufacturing a water-soluble transfer stack comprising a multilayer two-dimensional material, as disclosed elsewhere herein.

[0067] Use of a water-soluble transfer stack In a further aspect, the present disclosure relates to the use of a water-soluble transfer stack comprising a multi-layer two-dimensional material for producing a multi-layer two-dimensional material on a target substrate, the use comprising: a) obtaining a water-soluble transcription stack comprising: i. providing a growth stack comprising a growth substrate and a two-dimensional material layer; ii. applying an intercalation solution to the growth stack; iii. applying a transfer layer comprising a water-soluble polymer film to the growth stack; iv. peeling the water-soluble polymer film together with the two-dimensional material layer from the growth substrate, thereby obtaining a peeled film; and v. Repeating steps i to iv a number of times, the peeled film being used as a transfer layer; b) applying the water-soluble transfer stack to a target substrate. This allows for the fabrication of multi-layer two-dimensional materials on a target substrate.

[0068] In an embodiment of the present disclosure, the water-soluble transfer stack is manufactured according to the method of manufacturing a water-soluble transfer stack comprising a multilayer two-dimensional material, as disclosed elsewhere herein.

[0069] In an embodiment of the present disclosure, the multilayer two-dimensional material has a surface roughness (Ra) of less than 3 nm, preferably less than 2.5 nm, for example, between 1 nm and 2.5 nm. In another embodiment of the present disclosure, the multilayer two-dimensional material has a maximum roughness height (R) of less than 50 nm, more preferably less than 30 nm, and even more preferably less than 15 nm. z In a preferred embodiment, the multilayer two-dimensional material has three layers of one or more two-dimensional materials. In an embodiment of the present disclosure, the multilayer two-dimensional material is a heterostructure.

[0070] Preferably, the transfer stack is applied to the target substrate before exposing the transfer stack to water. In a preferred embodiment of the present disclosure, applying the transfer stack to the target substrate includes applying heat and / or pressure. The transfer stack can be applied, for example, using a laminator. In a preferred embodiment of the present disclosure, the transfer stack and the target substrate (preferably the intercalated target substrate) are laminated or hot-pressed at a temperature between 100°C and 180°C and / or while applying a pressure between 2 bar and 5 bar. While the step of applying the transfer stack to the target substrate, i.e., the lamination step, can be performed at ambient pressure, in a preferred embodiment of the present disclosure, applying the target substrate to the transfer stack is performed under reduced pressure, preferably under low, medium, or high vacuum conditions.

[0071] In a preferred embodiment of the present disclosure, the temperature during the step of applying the transfer stack to the target substrate is at least 80°C, more preferably at least 100°C, even more preferably at least 120°C, even more preferably at least 140°C, and most preferably about 150°C, for example for at least 3 seconds, more preferably at least 10 seconds.

[0072] In a further embodiment of the present disclosure, the step of applying the transfer layer to the target substrate further comprises a post-bake step carried out at at least 80°C, more preferably at least 100°C, even more preferably at least 120°C, and most preferably at least 140°C, for example, for at least 30 seconds. The post-bake step can include the application of heat, for example, by placing the transfer stack and target substrate on a hotplate. Generally, the post-bake step does not include the application of pressure to the transfer stack and target substrate.

[0073] In a further embodiment of the present disclosure, the transfer stack is applied to the target substrate by a roll laminator, such as a hot roll laminator, a roll-to-roll press, and / or a hot press, preferably configured to apply heat and / or pressure to the transfer stack and the target substrate to increase their adhesion, preferably stronger than the adhesion between the growth substrate and the two-dimensional material layer of the target substrate.

[0074] multilayer two-dimensional material In yet another aspect, the present disclosure relates to a multilayer two-dimensional material. In an embodiment of the present disclosure, the multilayer two-dimensional material has a surface roughness (Ra) of less than 3 nm, preferably less than 2.5 nm, for example, between 1 nm and 2.5 nm. In another embodiment of the present disclosure, the multilayer two-dimensional material has a maximum average roughness height (R) of less than 50 nm, more preferably less than 30 nm, and even more preferably less than 15 nm. z In a preferred embodiment, the multilayer two-dimensional material has three layers of one or more two-dimensional materials. In an embodiment of the present disclosure, the multilayer two-dimensional material is a heterostructure.

[0075] In embodiments of the present disclosure, the material of the two-dimensional material layer is either graphene, hexagonal boron nitride, and / or transition metal dichalcogenides such as molybdenum disulfide, hafnium disulfide, and tungsten diselenide, or MXene.

[0076] In an embodiment of the present disclosure, the two-dimensional material layer is composed of multiple layers of different materials selected from, for example, graphene, hexagonal boron nitride, and / or transition metal dichalcogenides such as molybdenum disulfide, hafnium disulfide, and tungsten diselenide, or MXene.

[0077] In an embodiment of the present disclosure, the surface area of ​​each layer of the multi-layer two-dimensional material is at least 1 cm 2 is.

[0078] In an embodiment of the present disclosure, the multilayer two-dimensional material is applied to a target substrate, such as SiO2, such that the multilayer two-dimensional material covers a portion of the target substrate.

[0079] In embodiments of the present disclosure, the 2D / G ratio is greater than 1. For example, a multilayer two-dimensional material may include three layers, such as three graphene layers, and have a 2D / G ratio greater than 1.

[0080] In embodiments of the present disclosure, the multilayer two-dimensional material has an electrical resistance of at most 10 kΩ / sq, preferably less than 1 kΩ / sq. In certain embodiments of the present disclosure, the water contact angle is between 30° and 90°. In further embodiments of the present disclosure, the surface hardness is at most about 10,000 N / mm, as measured by nanoindentation techniques. 2 is.

[0081] Detailed Description of the Drawings The present invention will now be described in more detail with reference to the accompanying drawings, which are illustrative and intended to illustrate some of the features of the presently disclosed methods of making water-soluble transfer stacks, water-soluble transfer stacks, multi-layer two-dimensional materials, and uses thereof, and should not be construed as limiting the presently disclosed invention.

[0082] FIG. 1 shows a schematic overview of a method for fabricating a water-soluble transfer stack containing a multilayer two-dimensional material according to certain embodiments of the present disclosure. (i-ii) A growth stack (8) is provided, including a growth substrate (3) and a grown two-dimensional material layer (2). An intercalation solution, such as water, is applied to the growth stack (8) to facilitate separation of the two-dimensional material layer, for example, by immersing the growth stack in the intercalation solution. A water-soluble polymer film (1) is then contacted with the grown two-dimensional material layer (2) provided on the growth substrate (3). The resulting stack is laminated or hot-pressed at a temperature of 100°C to 180°C and a pressure of 2 to 5 bar. The pressure should be understood as a pressure mechanically applied to an object, such as a mechanical lamination pressure. Note that the pressure can be applied with various air pressures, for example, vacuum pressure. In certain examples, the stack is also subjected to a post-bake step. (iii) The polymer / graphene laminate (i.e., the water-soluble polymer film and the two-dimensional material layer(s)) is then mechanically peeled off from the growth substrate (3) to form an exfoliated film (4).

[0083] (iv) The process is then repeated multiple times, including providing additional growth stacks (9) containing additional two-dimensional material layers (10) and additional growth substrates (11), or the same growth substrates if reused. The additional two-dimensional layers can be the same as or different (i.e., different materials) from the two-dimensional layers of the exfoliated film. The additional growth stacks (9) are typically exposed to the intercalation solution by immersing the additional growth stacks in the solution. (v) The two-dimensional material layer (2) of the exfoliated film (4) is then contacted with the additional two-dimensional layer (10) of the additional growth stack (9), and the resulting stacks are laminated or hot-pressed as in (i-ii). (vi) The polymer / graphene / graphene stack is mechanically peeled from the growth substrate to produce a water-soluble transfer stack containing two two-dimensional material layers.

[0084] This process can be repeated any number of times to produce a transfer stack containing many more two-dimensional material layers, including two-dimensional material layers of different materials (to form heterostructures). Repeating this process is shown in steps vii-ix of Figure 1 and involves providing an additional growth stack, applying an intercalation solution to the additional growth stack, and laminating or hot-pressing a two-dimensional layer of the water-soluble transfer stack containing multiple (e.g., two) two-dimensional material layers onto additional two-dimensional materials of the additional growth stack. Repeating is shown in steps vii-ix and involves providing an additional two-dimensional material layer (12), resulting in a water-soluble transfer stack (5) containing three graphene layers on a water-soluble polymer (e.g., PVA layer). While a method for producing a water-soluble transfer stack containing three two-dimensional material layers is shown, this step can be repeated any number of times to produce n layers of two-dimensional material on a water-soluble polymer film. The transfer stack may contain 10, 20, or even more two-dimensional layers, such as graphene and / or other two-dimensional material layers. In some examples, the transfer stack comprises a heterostructure comprising multiple layers of different two-dimensional materials.

[0085] The water-soluble transfer stack is preferably configured for easy transport to another location, and typically the multilayer 2D material is applied to a custom target substrate. This is shown in Figures x-xi, where the transfer stack is contacted with the target substrate (6) and hot-pressed or laminated. The water-soluble polymer film is then dissolved in water (xi), leaving behind the multilayer 2D material (7) on the target substrate (6).

[0086] Figure 2 shows (A) four samples of three-layer graphene on water-soluble PVA foil with a white PET-based support, with a centimeter dimension scale included for reference, and (B) different numbers of graphene layers on PVA foil with a support. The numbers indicate the number of graphene layers.

[0087] Figure 3 shows multilayer graphene transferred onto different target substrates. (A) Trilayer graphene transferred onto an acrylic substrate. (B) Trilayer graphene transferred onto a 90 nm thermally grown silicon oxide layer on top of a silicon substrate (centimeter ruler included for reference). (C) Graphene with different layer counts on a quartz target substrate. The number of layers for each column of samples is indicated in the figure.

[0088] Figure 4 shows (A) a photograph of sunlight transmitted through three-layer graphene transferred onto a glass target substrate, and (B) the optical transmittance of visible light transmitted through graphene with different numbers of layers, as plotted.

[0089] Figure 5 shows multilayer graphene on a 90 nm SiO2 / Si substrate: (A) 3-layer graphene with the monolayer, 2-layer, and 3-layer regions appropriately marked; (B) 15-layer graphene; and (C) 3-layer graphene, where the layers of graphene crystals are visible, as well as the top-layer holes through the second and first layers.

[0090] Figure 6 shows scanning electron microscope (SEM) images of trilayer graphene on a water-soluble PVA film. The SEM images were taken with a Zeiss Supra 40VP operating at 5 keV in (a) SE mode and (b) in-lens detection mode. In Figure 6A, the white area in the lower left corner indicates the bare PVA film, while the dark area indicates the PVA film covered with trilayer graphene. Figure 6B shows a higher magnification image of the trilayer graphene. The top layer has cracks and holes through which the second and first graphene layers are visible.

[0091] Figure 7 shows atomic force microscope (AFM) scans of three different samples of trilayer graphene transferred to SiO2 / Si substrates, with the corresponding line scan profile shown below each respective scan. AFM was performed on a Bruker AFM Dimension Icon in tapping mode. The measurement results are summarized in Table 1 below. [Table 1]

[0092] Figure 8 shows Raman point spectra acquired for three different samples of trilayer graphene transferred onto SiO2 / Si substrates, in which the 2D, G, and reference silicon peaks are labeled. Typically, the G peak is significantly larger than the 2D peak, but in some samples and regions the 2D peak can be larger, indicating the degree of variation visible in the spectra between samples depending on the stacking order of the graphene layers. -1 The nearby Raman peaks are due to instrument artifacts and should be ignored. Raman spectroscopy was performed on a Thermo Fisher DXR microscope equipped with a 455 nm laser, 5 mW incident power, a 10x objective, and three acquisitions with 10 s exposure times.

[0093] Further Details of the Disclosure 1. A method for making a water-soluble transfer stack comprising multiple two-dimensional material layers, comprising: i. providing a growth stack comprising a growth substrate and a two-dimensional material layer; ii. applying an intercalation solution to the growth stack; iii. applying a transfer layer comprising a water-soluble polymer film to the growth stack; iv. peeling the water-soluble polymer film together with the two-dimensional material layer from the growth substrate to obtain a peeled film; and v. repeating steps i. through iv. a number of times, with each repetition using the most recently obtained peeled film as the transfer layer; thereby producing a water-soluble transfer stack comprising a multi-layer two-dimensional material.

[0094] 2. The method of claim 1, wherein the growth substrate comprises or consists of a metal substrate such as a metal foil comprising or consisting of iron, copper, nickel, cobalt, gold, aluminum, silicon, gallium, tin, or oxides thereof.

[0095] 3. The method of any one of the preceding items, wherein the step of providing a growth stack comprises growing the two-dimensional material layers on the growth substrate, such as by chemical vapor deposition.

[0096] 4. The method of any one of the preceding items, wherein the growth substrate is reused multiple times for the formation of further two-dimensional material layers when repeating the steps.

[0097] 5. The method of any one of the preceding items, wherein the material of any of the two-dimensional material layers is any of graphene, hexagonal boron nitride, and / or transition metal dichalcogenides such as molybdenum disulfide, hafnium disulfide, and tungsten diselenide, and / or MXene.

[0098] 6. The method of any one of the preceding items, wherein the water-soluble transfer stack comprising multiple layers of two-dimensional material comprises layers of different two-dimensional materials.

[0099] 7. The surface area of ​​each layer of the multilayer two-dimensional material is at least 1 cm 2 Item 10. The method of any one of the preceding items, wherein:

[0100] 8. The method of any one of the preceding items, wherein the intercalation solution comprises or consists of water, an alcohol solution (EtOH or IPA), a salt solution such as sodium chloride or potassium chloride, for example up to 1 M.

[0101] 9. The method of any one of the preceding items, wherein the step of applying the intercalation solution is adapted to intercalate between the growth substrate and the two-dimensional material layer, such as by oxidizing the growth substrate.

[0102] 10. The method of any one of the preceding items, wherein the intercalation solution comprises or consists of water.

[0103] 11. The method of any one of the preceding items, wherein the intercalation solution is applied to the growth substrate for less than 48 hours, preferably less than 24 hours, more preferably less than 16 hours, even more preferably less than 12 hours, even more preferably less than 8 hours, and most preferably less than 4 hours.

[0104] 12. The method of any one of the preceding items, wherein the intercalation solution is applied to the growth substrate at a temperature of at least 40°C.

[0105] 13. The method of any one of the preceding items, wherein the step of applying the transfer layer to the growth stack comprises applying a vacuum, such as a low or medium vacuum.

[0106] 14. The method of any one of the preceding items, wherein the step of applying the transfer layer to the growth stack comprises applying heat and / or pressure.

[0107] 15. The method of claim 14, wherein said applying heat and / or pressure comprises or consists of applying said heat and / or pressure to i. the water-soluble polymer film and the growth stack, and / or ii. the peeled film and a further growth stack.

[0108] 16. The method according to any one of items 14 to 15, wherein the temperature when applying the transfer layer to the growth stack is at least 80°C, more preferably at least 100°C, even more preferably at least 120°C, even more preferably at least 140°C, and most preferably about 150°C.

[0109] 17. The method according to any one of items 14 to 16, wherein the step of applying the transfer layer to the growth stack comprises a post-bake step carried out at at least 80°C, more preferably at least 100°C, even more preferably at least 120°C, and most preferably at least 140°C, e.g. for at least 30 seconds.

[0110] 18. The method of any one of the preceding items, wherein the transfer layer is applied to the growth stack by any of a roll laminator, a hot roll laminator, a roll-to-roll press, and / or a hot press.

[0111] 19. The method of any one of the preceding items, wherein the material of the water-soluble polymer film is polyvinyl alcohol.

[0112] 20. The method of any one of the preceding items, wherein the thickness of the water-soluble polymer film is between 100 nm and 100 μm.

[0113] 21. The method of any one of the preceding items, wherein the step of peeling comprises or consists of mechanically separating the water-soluble transfer stack and the two-dimensional layer from the growth substrate.

[0114] 22. The method of any one of the preceding items, wherein steps i. to iv. are repeated, each time adding an additional two-dimensional layer to the aqueous transfer stack.

[0115] 23. The method of any one of the preceding items, wherein at least a portion of the method is repeated by applying the peeled film to a further two-dimensional material layer, such as an exposed two-dimensional material layer of the further growth stack.

[0116] 24. The method of any one of the preceding items, carried out in a roll-to-roll process.

[0117] 25. A water-soluble transfer stack comprising a multilayer two-dimensional material layer manufactured according to any one of items 1 to 24.

[0118] 26. A method for producing a multi-layer two-dimensional material on a target substrate, comprising: a) obtaining a water-soluble transfer stack comprising a multi-layer two-dimensional material, i. providing a growth stack comprising a growth substrate and a two-dimensional material layer; ii. applying an intercalation solution to the growth stack; iii. applying a transfer layer comprising a water-soluble polymer film to the growth stack; iv. peeling the water-soluble polymer film together with the two-dimensional material layer from the growth substrate to obtain a peeled film; and v. repeating steps i. to iv. a number of times, wherein the peeled film is used as the transfer layer; obtaining the water-soluble transfer stack, b) applying the transfer stack to the target substrate; The method comprising:

[0119] 27. The method according to item 26, wherein the water-soluble transcription stack is obtained according to any one of items 1 to 24.

[0120] 28. Use of a water-soluble transfer stack comprising a multi-layer two-dimensional material for producing a multi-layer two-dimensional material on a target substrate, comprising: a) obtaining a water-soluble transcription stack, i. providing a growth stack comprising a growth substrate and a two-dimensional material layer; ii. applying an intercalation solution to the growth stack; iii. applying a transfer layer comprising a water-soluble polymer film to the growth stack; iv. peeling the water-soluble polymer film together with the two-dimensional material layer from the growth substrate to obtain a peeled film; and v. repeating steps i. to iv. a number of times, wherein the peeled film is used as the transfer layer; obtaining the water-soluble transfer stack, b) applying the water-soluble transfer stack to the target substrate; Including, Use of the water-soluble transfer stack thereby fabricating the multi-layer two-dimensional material on the target substrate.

[0121] 29. The use according to item 28, wherein the water-soluble transcription stack is obtained according to any one of items 1 to 24.

[0122] 30. A multilayer two-dimensional material comprising multiple layers of two-dimensional material, the average maximum roughness height being less than 50 nm.

[0123] 31. The multilayer two-dimensional material according to item 30, wherein the material of the two-dimensional material layer is graphene, hexagonal boron nitride, and / or a transition metal dichalcogenide such as molybdenum disulfide, hafnium disulfide, tungsten diselenide, or MXene, or a mixture thereof.

[0124] 32. The multilayer two-dimensional material has a surface area of ​​at least 1 cm 2 32. The multilayer two-dimensional material according to any one of items 30 to 31, wherein

[0125] 33. The multilayer two-dimensional material according to any one of items 30 to 32, wherein the multilayer two-dimensional material is applied to a target substrate such as SiO2.

Claims

1. 1. A method for making a water-soluble transfer stack including multiple layers of two-dimensional material, comprising: i. providing a growth stack comprising a growth substrate and a two-dimensional material layer; ii. applying an intercalation solution to the growth stack; iii. applying a transfer layer comprising a water-soluble polymer film to the growth stack; iv. peeling the water-soluble polymer film together with the two-dimensional material layer from the growth substrate to obtain a peeled film; and v. Repeating steps i. through iv. a number of times, with each repetition using the most recently obtained peeled film as the transfer layer; thereby producing a water-soluble transfer stack comprising a plurality of layers of two-dimensional material.

2. the two-dimensional material is graphene; and / or 10. The method of claim 1, wherein the multiple two-dimensional material layers of the transfer stack include layers of different materials selected from any of graphene, hexagonal boron nitride, transition metal dichalcogenides, and / or MXene.

3. The surface area of ​​each two-dimensional material in the transfer stack is at least 1 cm ２ The method of claim 1, wherein

4. the step of providing the growth stack includes growing the two-dimensional material layers on the growth substrate, such as by chemical vapor deposition; 10. The method of claim 1 , wherein steps i.-iv. are repeated, with the growth substrate being reused to form each additional layer of two-dimensional material.

5. 10. The method of claim 1, wherein the intercalation solution comprises or consists of either water, an alcohol solution (EtOH or IPA), and / or a salt solution such as sodium chloride or potassium chloride.

6. 10. The method of claim 1, wherein the step of applying the intercalation solution is adapted to intercalate between the growth substrate and the two-dimensional material layer, such as by oxidizing the growth substrate.

7. The method according to any one of claims 1 to 6, wherein the intercalation solution is applied to the growth substrate at a temperature of at least 40°C, for example between 40°C and 80°C.

8. The method of claim 1 , wherein applying the transfer layer to the growth stack comprises applying a vacuum, such as a low or medium vacuum.

9. 10. The method of claim 1, wherein applying the transfer layer to the growth stack comprises applying heat at a temperature between 100° C. and 180° C. and pressure, such as a mechanical lamination pressure between 2 and 5 bar.

10. 2. The method of claim 1 , wherein the step of applying the transfer layer to the growth stack comprises a post-bake step carried out at at least 80° C., more preferably at least 100° C., even more preferably at least 120° C., and most preferably at least 140° C., e.g. for at least 30 seconds.

11. The method of claim 1 , wherein the transfer layer is applied to the growth stack by one of a roll laminator, a hot roll laminator, a roll-to-roll press, and / or a hot press.

12. The method of claim 1 , wherein the water-soluble polymeric film material is polyvinyl alcohol.

13. The method of claim 1, wherein the water-soluble polymer film has a thickness between 100 nm and 100 μm.

14. 10. The method of claim 1, wherein steps i.-iv. are repeated each time an additional two-dimensional layer is added to the water-soluble transfer stack.

15. The method of claim 1 , wherein the peeling step comprises or consists of mechanically separating the water-soluble transfer stack and the two-dimensional layer from the growth substrate.

16. 10. The method of claim 1, wherein at least a portion of the method is repeated by applying the peeled film to an additional two-dimensional material layer, such as an exposed two-dimensional material layer of a further growth stack.

17. The method described in claim 1, further comprising a step of applying the transfer stack to a target substrate.

18. A water-soluble polymer film, and Multiple 2D material layers A water-soluble transfer stack comprising:

19. The average maximum roughness height is less than 50 nm, and / or The water soluble transfer stack of claim 18 , wherein the material of the two-dimensional material layer is graphene.

20. The surface area of ​​each layer of the multi-layered two-dimensional material is at least 1 cm ２ 20. The water soluble transfer stack of claim 18,

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