Preparation method of thin-layer two-dimensional material island

Abstract

The embodiment of the invention discloses a preparation method of a thin-layer two-dimensional material island. The preparation method comprises the following steps: cleaving a two-dimensional material plate for more than one time through a heat release adhesive tape until a two-dimensional material sheet adhered to the heat release adhesive tape is obtained; the heat release adhesive tape is heated, so that the heat release adhesive tape loses viscosity and is separated from the two-dimensional material sheet; and flatly attaching the two-dimensional material sheet which is separated from the heat release adhesive tape to a substrate sheet. Wherein the two-dimensional material plate can be thinned to obtain the thin two-dimensional material sheet through the viscosity and the heat release property of the heat release adhesive tape, and meanwhile, the original smooth stacking property between material layers can be effectively ensured to be well kept on the surface of the stripped two-dimensional material sheet, namely, the thickness of the two-dimensional material sheet is reduced; and the section of the two-dimensional material generated by stripping is flat and large in size from the source level. In addition, the adhesive force between the two-dimensional material sheet and the substrate sheet is increased, surface wrinkles of the two-dimensional material sheet can be further reduced and avoided, and the actual utilization rate and the application value of the two-dimensional material island made of the two-dimensional material sheet are improved.

Description

Technical Field

[0001] The embodiments of the present application relate to the field of material technology, and in particular to a method for preparing thin-layer two-dimensional material islands. Background Art

[0002] Two-dimensional materials such as single-crystal graphite and molybdenum disulfide, whose electrons can only move freely (planar motion) in two dimensions at the non-nanoscale (1-100nm), have many unique physical and chemical properties, such as high conductivity, high strength, low friction coefficient and heat resistance, which have attracted widespread attention in basic research and applications in various fields.

[0003] Taking graphite as an example, in the field of ultra-slippery materials, in order to obtain sufficiently thin graphite flakes, in the existing process, lasers or chemical reagents are often used to directly peel off graphite flakes from graphite of a certain thickness. However, the surface of the graphite flakes peeled off in this way is mostly uneven, and a large number of wrinkles are easily generated during the transfer process, which affects its electrical and mechanical properties and reduces the subsequent practical application value of graphite flakes made into graphite islands. Summary of the invention

[0004] The embodiment of the present application provides a method for preparing a thin layer of two-dimensional material island, which is used to easily prepare a thin two-dimensional material island with few wrinkles on the surface, thereby improving the practical application value of the material sheet with high quality.

[0005] A first aspect of an embodiment of the present application provides a method for preparing a thin layer of two-dimensional material island, comprising:

[0006] Cleavage the two-dimensional material sheet more than once using a thermal release tape until a two-dimensional material sheet adhered to the thermal release tape is obtained; the thickness of the two-dimensional material sheet is 1 to 20 microns;

[0007] heating the heat release tape to which the two-dimensional material sheet is adhered, so that the heat release tape loses its stickiness and separates from the two-dimensional material sheet;

[0008] Transferring the two-dimensional material sheet after being separated from the heat release tape to a base sheet, and increasing the adhesion between the two-dimensional material sheet and the base sheet, so as to obtain the two-dimensional material sheet flatly attached to the base sheet;

[0009] The two-dimensional material sheet is used to prepare at least one two-dimensional material island;

[0010] The surface of the area of ​​the base sheet used to adhere to the two-dimensional material sheet is flat and free of impurities.

[0011] Optionally, transferring the two-dimensional material sheet after being separated from the heat release tape to a base sheet and increasing the adhesion between the two-dimensional material sheet and the base sheet comprises:

[0012] Transferring the two-dimensional material sheet after being separated from the thermal release tape to a substrate sheet dripped with pure water;

[0013] The purified water is dried to increase the adhesion, thereby obtaining the two-dimensional material sheet that is evenly attached to the base sheet.

[0014] Optionally, transferring the two-dimensional material sheet after being separated from the heat release tape to a base sheet and increasing the adhesion between the two-dimensional material sheet and the base sheet comprises:

[0015] transferring the two-dimensional material sheet after being separated from the heat release tape to the base sheet;

[0016] stacking a press tool on the two-dimensional material sheet, wherein the roughness of the press tool is greater than the roughness of the base sheet;

[0017] An external force is applied to the press to increase the adhesion force, so that the two-dimensional material sheet is flatly attached to the base sheet.

[0018] Optionally, when the pressing tool is a roller structure, applying external force to the pressing tool includes:

[0019] The roller structure is rolled back and forth on top of the two-dimensional material sheet by external force.

[0020] Optionally, after stacking a press on the two-dimensional material sheet, the method further comprises:

[0021] The two-dimensional material sheet on which the press is placed is heated to increase the surface flatness of the two-dimensional material sheet.

[0022] Optionally, the heating temperature of the two-dimensional material sheet on which the press is placed is 100 to 150 degrees Celsius.

[0023] Optionally, after transferring the two-dimensional material sheet after being separated from the heat release tape to a base sheet and increasing the adhesion between the two-dimensional material sheet and the base sheet, the method further comprises:

[0024] Performing film coating, gluing, exposure and development processing on the two-dimensional material sheet attached to the substrate sheet, so that a desired pattern appears on the two-dimensional material sheet;

[0025] The material above the developed two-dimensional material slice is etched to obtain a two-dimensional material island arranged based on the expected pattern.

[0026] Optionally, etching the material above the developed two-dimensional material slice to obtain two-dimensional material islands arranged based on the expected pattern includes:

[0027] The developed upper material is dry-etched according to a preset etching selectivity to obtain two-dimensional material islands arranged according to the expected pattern; the etching selectivity refers to the etching rate ratio between the photoresist exposed above the two-dimensional material slice and the coating material under the same etching conditions.

[0028] Optionally, the etching selectivity ratio is determined based on the coverage thickness and / or coverage area between the photoresist and the coating material.

[0029] Optionally, when the dry etching is performed using oxygen plasma, the etching time is 1 to 3 minutes.

[0030] Optionally, the heating temperature of the heat release tape with the two-dimensional material sheet adhered thereto is 100 to 200 degrees Celsius.

[0031] It can be seen from the above technical solutions that the embodiments of the present application have at least the following advantages:

[0032] The embodiment of the present application can thin the two-dimensional material plate to obtain a thin layer of two-dimensional material flakes through the adhesiveness and heat release of the heat release tape. At the same time, it can effectively ensure that the surface of the peeled two-dimensional material flakes well maintains the original flat stacking between the material layers, that is, the cross-section of the two-dimensional material produced by peeling is flat and large in size from the source level. In addition, the surface wrinkles of the two-dimensional material flakes can be further reduced by flatly attaching the two-dimensional material flakes to the substrate sheet, thereby improving the actual utilization rate and application value of the two-dimensional material islands made of the two-dimensional material flakes. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present application. For ordinary technicians in this field, other drawings can also be obtained based on these drawings.

[0034] It should be noted that, although the steps in the process diagrams (if any) involved in the embodiments are drawn in sequence as indicated by the arrows, unless otherwise specified herein, there is no strict order restriction on the execution of these steps, and these steps can be executed in other orders. Moreover, at least a portion of the steps in the flowcharts involved in the embodiments may include multiple steps or multiple stages, and these steps or stages are not necessarily executed at the same time, but can be executed at different times, and the execution order of these steps or stages is not necessarily sequential, but can be executed in turn or alternately with other steps or at least a portion of the steps or stages in other steps.

[0035] Figure 1 A schematic diagram of a process for preparing a thin layer of two-dimensional material island according to an embodiment of the present application;

[0036] Figure 2 A schematic diagram of a dry etching process for preparing a thin layer of two-dimensional material island according to an embodiment of the present application;

[0037] Figure 3 Schematic diagram of the lift-off process of the method for preparing a thin layer of two-dimensional material island according to an embodiment of the present application. DETAILED DESCRIPTION

[0038] In order to make the purpose, technical solutions and advantages of the present application clearer, the present application will be further described in detail below in conjunction with the accompanying drawings. The described embodiments should not be regarded as limiting the present application. All other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of this application.

[0039] The terms "first", "second", "third", "fourth", etc. (if any) in the specification and claims and drawings of the present application are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchangeable where appropriate, so that the embodiments described herein can be implemented in an order other than that illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0040] In the following description, similar expressions such as "a specific implementation" or "a specific example" are involved, which describe a subset of all possible embodiments, but it can be understood that "a specific implementation" or "a specific example" can be the same subset or different subsets of all possible embodiments, and can be combined with each other without conflict. In the following description, the term multiple refers to at least two. In some specific examples, the numerical value mentioned in this application reaches the threshold value (if any), which may include the case where the former is greater than the latter of the threshold value; if similar expressions such as "any" or "at least one" are mentioned, it can specifically refer to any one of the listed examples or any combination of these examples.

[0041] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein are only for the purpose of describing the embodiments of this application and are not intended to limit this application.

[0042] The method of the present application will be described in further detail below.

[0043] See also Figure 1 In a first aspect, the present application provides a specific embodiment of a method for preparing a thin layer of two-dimensional material island, which comprises the following steps:

[0044] Step S11, cleaving the two-dimensional material plate more than once by using the thermal release tape until a two-dimensional material sheet adhered to the thermal release tape is obtained;

[0045] The above-mentioned two-dimensional material can specifically be a two-dimensional material such as graphite or molybdenum disulfide, and the graphite can be highly oriented pyrolytic graphite (HOPG) or natural graphite. For ease of description and understanding, the embodiments of the present application mainly use HOPG (obtained by stacking multiple graphite layers) as a two-dimensional material for exemplary description.

[0046] For example, the thermal release tape can be adhered to a complete HOPG surface with a size of 12mm*12mm*(thickness)2mm, such as the thermal release tape is evenly adhered to the upper surface of the HOPG; thereafter, by peeling off the thermal release tape, the graphite layer (the number of layers is uncertain) on the upper surface of the HOPG adhered to the tape can be torn off at the same time, and the graphite layer adhered to the thermal release tape is the graphite flake obtained by thinning, and the thickness of the graphite flake can be between 1 and 20 microns.

[0047] In addition, because the graphite flakes are obtained by interlayer exfoliation from the middle layer of HOPG, the cross section of the graphite flakes can maintain the original flatness and integrity of the graphite layers, that is, the cross section is smooth, free of impurities, burrs, and a large area is not fragmented, which effectively avoids the actual application value of the graphite flakes being affected by surface roughness and fragmentation.

[0048] Step S12, heating the thermal release tape to which the two-dimensional material sheet is adhered, so that the thermal release tape loses its stickiness and separates from the two-dimensional material sheet;

[0049] For example, the thermal release tape can be placed on a hot plate and heated to make it lose its stickiness and separate from the two-dimensional material sheet. Still taking HOPG as an example, in some examples, the loss of stickiness of the thermal release tape here may peel off part of the graphite layer, that is, further thinning the above-mentioned two-dimensional material sheet; of course, whether to peel off part of the graphite layer or several layers of graphite layers can be determined by at least one of the stickiness of the thermal release tape, the heating temperature and the heating time, which are not limited here. In some examples, the temperature for heating the thermal release tape can be between 100 and 200 degrees Celsius, which can be determined by the actual situation and is not limited here.

[0050] Step S13, transferring the two-dimensional material sheet after being separated from the heat release tape to the base sheet, and increasing the adhesion between the two-dimensional material sheet and the base sheet, so as to obtain the two-dimensional material sheet flatly attached to the base sheet;

[0051] The two-dimensional material sheet can be used to prepare at least one two-dimensional material island; the surface of the area of ​​the substrate sheet used to bond the two-dimensional material sheet is flat and free of impurities, and this limitation can avoid increasing the surface roughness of the graphite bonded thereto and contaminating the HOPG ultra-thin sheet. According to the operation of step S13, the HOPG ultra-thin sheet can be fixed on the substrate with few wrinkles, so as to perform subsequent micro-processing operations such as coating, gluing, exposure and development, so as to obtain a graphite island of the required thickness.

[0052] In summary, the embodiment of the present application can thin the two-dimensional material plate to obtain a thin layer of two-dimensional material flakes through the viscosity and heat release of the heat release tape, and at the same time, it can effectively ensure that the surface of the peeled two-dimensional material flakes well maintains the original flat stacking between the material layers, that is, the cross-section of the two-dimensional material produced by peeling is flat and large in size from the source level. In addition, increasing the adhesion between the two-dimensional material flakes and the substrate can further reduce the surface wrinkles of the two-dimensional material flakes, and improve the actual utilization rate and application value of the two-dimensional material islands made of the two-dimensional material flakes.

[0053] See also Figure 2Based on the above example descriptions, some specific possible implementation examples will be provided below. In actual applications, the implementation contents between these examples can be combined or implemented separately as needed according to the corresponding functional principles and application logic. If implemented in combination, the execution order between the combined examples can be determined according to their respective processing logics, which can be determined by the actual scenario.

[0054] based on Figure 1 In some specific examples, the cleavage process of step S11 can be implemented in combination with polymer fiber tape (such as 3M brand tape), thermal release tape, etc. For example, 3M brand tape and thermal release tape can be respectively attached to the upper and lower surfaces of graphite, and by peeling off one or both of the tapes, the graphite can be peeled off from each other, thereby obtaining a gradually thinned graphite sheet.

[0055] As a possible implementation, the specific operation process of the above step S13 may include (Scheme 1): transferring the two-dimensional material sheet after being separated from the heat release tape to a base sheet dripped with pure water; drying the pure water to increase adhesion, thereby obtaining a two-dimensional material sheet that is flatly attached to the base sheet.

[0056] like Figure 2 As shown, a substrate hydrophilic infiltration method can be used: pure water is dropped on a clean hydrophilic substrate for wetting, and then the HOPG ultra-thin sheet obtained in step S12 is transferred to the substrate, and the moisture is slowly heated and dried, thereby increasing the adhesion between the two-dimensional material sheet and the substrate sheet, making the fit between the two-dimensional material sheet and the substrate sheet tighter.

[0057] The above-mentioned base sheet can be a substrate such as a silicon (Si) sheet, a sapphire sheet or a glass sheet. This substrate is generally required to have a flat and clean surface and can have good van der Waals force with the two-dimensional material.

[0058] As another possible implementation, the specific operation process of the above step S13 may include (Scheme 2): transferring the two-dimensional material sheet after being separated from the heat release tape to the base sheet; stacking a press on top of the two-dimensional material sheet, wherein the roughness of the press is greater than the roughness of the base sheet; applying external force to the press to increase adhesion, so that the two-dimensional material sheet is smoothly attached to the base sheet.

[0059] like Figure 2 As shown, a pressurization method can be used: the HOPG ultra-thin sheet is transferred to the substrate, and a rough sheet (i.e., a press) is placed on top of the HOPG ultra-thin sheet; generally, the roughness of the rough sheet needs to be greater than the surface roughness of the underlying substrate sheet. This design can prevent the HOPG ultra-thin sheet from adhering to the rough sheet above (because it should normally adhere to the surface of the underlying substrate sheet), thereby affecting the surface flatness of the HOPG ultra-thin sheet.

[0060] In some specific examples, after the above-mentioned “stacking a press on top of the two-dimensional material sheet”, the method of the embodiment of the present application may also include: heating the two-dimensional material sheet with the press to increase the surface flatness of the two-dimensional material sheet.

[0061] Based on the above description of the second scheme, the above step S13 can be implemented by heating and pressing: when applying external force to the rough sheet, the current environment of the HOPG ultra-thin sheet can also be heated, so as to iron out the wrinkles that may exist in the HOPG ultra-thin sheet, and ensure that the surface of the HOPG ultra-thin sheet is flat and has few wrinkles. Experiments have shown that the heating temperature here can generally be within 100 to 150°C, because too high a temperature can easily oxidize graphite.

[0062] As another possible implementation, the pressing tool may be a roller structure, so the specific operation process of the step S13 may include (Scheme 3): rolling the roller structure back and forth above the two-dimensional material sheet by external force.

[0063] Option 3 can be considered as a derivative of Option 2, such as Figure 2 As shown, the HOPG ultra-thin sheet can be transferred to the substrate, and a roller is placed on the HOPG ultra-thin sheet to roll back and forth to increase the adhesion between the two-dimensional material sheet and the substrate sheet. At the same time, rolling helps to flatten the wrinkles that may exist on the HOPG ultra-thin sheet. Similarly, heating operation can be combined in scheme three to further ensure that the surface of the HOPG ultra-thin sheet is flat and has few wrinkles.

[0064] In summary, the above three schemes can all facilitate the HOPG ultra-thin sheet to be attached to the substrate with few wrinkles, that is, to obtain a HOPG ultra-thin sheet sample that is firmly flattened on the substrate.

[0065] Taking Si wafer as an example, the substrate is based on Figure 1 In some specific examples, the bonding surface of the Si sheet with a flat surface and no impurities (the surface for bonding the two-dimensional material sheet) can be treated with argon Ar plasma sputtering, so that the bonding surface is bombarded into a nanometer (nm) or picometer (pm) level microporous surface, that is, a concave-convex structure is formed to increase the roughness of the bonding surface. Plasma sputtering treatment of the Si sheet here can expose the chemical bonds in the Si sheet, so that its bonding surface presents a tiny roughness at the ion level, that is, the bonding surface of the Si sheet is not uneven, and it can still be regarded as a flat surface, but the presence of this rough surface can make the graphite and the Si sheet fit more tightly. Because compared with the smooth surface, the above-mentioned concave-convex structure can use its own microporous gaps in the future to enhance the adhesion between the substrate and the graphite layer.

[0066] In some examples, the presence of the above-mentioned concave-convex structure also facilitates the subsequent combination with the viscosity of the tape to allow the graphite to separate from the layers through dual effects of upper and lower effects, thereby further thinning the graphite sheet to obtain a thinner one adhered to the Si sheet to meet the demand for thinner graphite sheets.

[0067] Of course, in some examples, plasma sputtering treatment can be performed with an inert gas other than Ar, or with oxygen. The above plasma sputtering treatment mainly uses Ar because the applicant has found through multiple experiments that the inert gas Ar plasma, due to its high ionization rate, can easily form a surface microstructure when treating the substrate, and combined with vacuum negative pressure exhaust, it can increase the physical adsorption force between graphite and the substrate. In addition, in comparison, the use of Ar plasma + vacuum negative pressure treatment currently has a better effect, while the effect and success rate of stripping large-area and flat graphite using oxygen or nitrogen plasma treatment are much worse.

[0068] The above mainly describes the cleavage or thinning process of the two-dimensional material slice. The following will mainly describe how to micro-process the two-dimensional material slice obtained by cleavage to prepare two-dimensional material islands.

[0069] based on Figure 1 According to the example content, in some specific examples, after step S13, the method of the embodiment of the present application may also include (micro-machining the two-dimensional material sheet obtained by cleavage): coating, gluing, exposing and developing the two-dimensional material sheet attached to the substrate sheet so that the expected pattern appears above the two-dimensional material sheet; etching the material above the developed two-dimensional material sheet to obtain two-dimensional material islands arranged based on the expected pattern.

[0070] In practical applications, the etching process in this micro-machining process can be implemented in different ways such as wet etching or dry etching. The wet etching process can refer to a lift-off process, which mainly uses the chemical reaction of the solution to strip (or etch) the photoresist layer; while the dry etching process refers to a waterless stripping process that does not use a solution to strip the photoresist layer. In addition, what is different is that for the coating process (such as metal film) in micro-machining, the coating process is executed after the glue coating when the lift-off process is used, and before the glue coating when the dry etching process is used; for this reason, the same HOPG sample is processed through the lift-off process or the dry etching process, and the position and size of the graphite islands finally formed on the substrate are different relative to the HOPG sample as a whole. For details, please see the following text description, Figure 2 , Figure 3 .

[0071] 1. Dry etching process is used to strip the photoresist layer in micromachining

[0072] As a possible implementation, the above-mentioned micro-machining process may specifically include: coating the two-dimensional material slice on the substrate to obtain a mask layer; coating, exposing and developing the mask layer so that the expected pattern covered by the photoresist layer appears above the two-dimensional material slice; dry etching the upper material after development (i.e., the photoresist layer and the mask layer) according to a preset etching selectivity to obtain two-dimensional material islands arranged according to the expected pattern; the etching selectivity refers to the etching rate ratio between the photoresist exposed above the two-dimensional material slice and the coating material under the same etching conditions.

[0073] Specifically, Figure 2 As shown, the HOPG flakes attached to the substrate can be coated (such as (metal film or other dielectric film), and the coating process can be specifically electron beam evaporation or magnetron sputtering process; then, the HOPG flakes can be coated, exposed, and developed to design the expected pattern covered by the photoresist layer, that is, surface patterning design is performed; using gas plasma such as oxygen or argon, the developed HOPG flakes are dry-etched to dissolve the top layer of material (because etching is from top to bottom), such as dissolving all the photoresist and the exposed part of the metal film on the top, and retaining the metal film originally covered and protected by the photoresist. Of course, in order to achieve such an ideal product effect with both deletion and retention, it is necessary to control the etching selectivity between the photoresist and the metal film, which is crucial for accurately controlling the size and shape of the graphite island forming pattern; the remaining metal film can be used as the graphite island cover, and finally, the metal island cover mask can be etched away to complete the preparation of the graphite island.

[0074] Exemplarily, the calculation formula of the above etching selectivity ratio can be recorded as: Etching selectivity ratio = etching rate of masking layer material (such as photoresist) / etching rate of etched material (such as metal), such as Figure 3 As shown, selecting a low selectivity (i.e., the denominator is greater than the numerator) here means that during the etching process, the photoresist on the metal film is as small as possible, and the metal layer that is not covered and protected by the photoresist (i.e., exposed) is etched away as much as possible. Because etching is generally from top to bottom, the selectivity is small or even non-existent, so the etching selectivity in this formula can be between 1:5 and 1:10. Of course, in practical applications, the value of the above etching selectivity can be comprehensively determined according to at least one factor such as the thickness and distribution size of the covered photoresist and the metal film, and is not specifically limited.

[0075] In some specific examples, when the above dry etching is performed using oxygen plasma, the etching time is 1 to 3 minutes. Of course, a gas other than oxygen (such as argon) plasma can also be used here to etch for a certain length of time, which can be determined according to actual conditions and is not limited here.

[0076] It should be noted that the above-mentioned process flow for preparing ultra-thin HOPG graphite islands, especially the dry etching process, reduces the immersion time of the ultra-thin HOPG sheet in the solution, and can reduce the risk of ultra-thin HOPG detaching from the substrate during micro-machining. Because the use of the dry etching process does not use a solution, but uses a gas reaction for etching; of course, in some cases or requirements, the following lift-off process can also be used.

[0077] In general, the ultra-thin HOPG obtained by cleaving according to the method of the embodiment of the present application can be of the order of um in thickness (ultra-thin) and of the order of cm in size (large size), and can avoid the ultra-thin HOPG from introducing a large number of wrinkles, effectively preventing the actual utilization rate of the ultra-thin HOPG from being affected. In addition, the ultra-thin HOPG obtained by cleaving according to the embodiment of the present application can be used for the preparation of graphite islands, and the ultra-thin HOPG sheet is flattened on the substrate and optimized for a variety of bonding schemes to achieve wrinkle-free bonding between the ultra-thin HOPG sheet and the substrate, which has the advantage of controlling the cost to within one-tenth of the original cost, and promoting the mass production of ultra-smooth products.

[0078] 2. Lift-off process is used to remove the photoresist layer in micromachining

[0079] As a possible implementation mode, the above-mentioned micro-machining process may specifically include: coating, exposing and developing the sample flakes on the substrate so that the upper surface of the sample flakes shows the expected pattern not covered by the photoresist layer; coating the photoresist layer and the expected pattern, and using a lift-off process to peel off the photoresist layer to obtain a mask directly deposited on the upper surface and forming the expected pattern; etching the sample flakes according to the deposition position of the mask to obtain two-dimensional material islands arranged in the expected pattern.

[0080] Specifically, Figure 3 As shown, the HOPG flakes on the silicon wafer can be coated with glue (such as photoresist), exposed, and developed to obtain a photoresist pattern not covered by the photoresist layer; then, a metal film can be plated on the surface of the photoresist layer and the upper surface of the exposed HOPG flakes through electron beam evaporation or magnetron sputtering, and then the unnecessary photoresist can be dissolved away using a remover of the lift-off process to retain the required metal pattern mask; finally, the HOPG flakes can be etched using oxygen plasma with reference to the distribution position of the metal pattern mask to form pieces of graphite islands.

[0081] In summary, the method of the embodiment of the present application can peel off a flat graphite flake of ten microns or less. Experiments have also shown that this graphite flake can obtain an extremely low friction coefficient in friction and wear tests with three-dimensional materials (spherical surfaces) and two-dimensional materials (graphite islands), and can maintain a high surface flatness and no defects during the transfer process; this graphite flake and the substrate can be in rigid contact and tightly adhered, which has a wide range of use value for the transfer of specific devices.

[0082] In short, the method of the embodiment of the present application realizes the large-area, thin-layer, pollution-free, adhesive-free transfer and tight fitting of two-dimensional super-slippery materials (graphite, molybdenum disulfide, etc.) on a flat substrate, providing a feasible reference solution for the high-quality transfer of super-slippery materials with a scale of ten microns or less in related devices.

[0083] Compared to Figure 1 The examples shown illustrate that the above-mentioned additional or detailed example contents or possible implementation methods do not necessarily have to be executed during the specific implementation. If more than two examples or possible implementation methods are added, these examples or possible implementation methods can be implemented in combination or separately. If implemented in combination, the execution order between the combined examples can be determined according to their respective processing logic, which can be determined according to the actual scenario.

[0084] The above embodiments are only used to illustrate the technical solution of the present application, but not to limit it.

Claims

1. A method for preparing a thin layer of two-dimensional material island, characterized in that: include: Cleavage the two-dimensional material sheet more than once using a thermal release tape until a two-dimensional material sheet adhered to the thermal release tape is obtained; the thickness of the two-dimensional material sheet is 1 to 20 microns; heating the heat release tape to which the two-dimensional material sheet is adhered, so that the heat release tape loses its stickiness and separates from the two-dimensional material sheet; Transferring the two-dimensional material sheet after being separated from the heat release tape to a base sheet, and increasing the adhesion between the two-dimensional material sheet and the base sheet, so as to obtain the two-dimensional material sheet flatly attached to the base sheet; The two-dimensional material sheet is used to prepare at least one two-dimensional material island; The surface of the area of ​​the base sheet used to adhere to the two-dimensional material sheet is flat and free of impurities.

2. The method for preparing a thin layer of two-dimensional material island according to claim 1, characterized in that: The method of transferring the two-dimensional material sheet after being separated from the thermal release tape to a substrate sheet and increasing the adhesion between the two-dimensional material sheet and the substrate sheet comprises: Transferring the two-dimensional material sheet after being separated from the thermal release tape to a substrate sheet dripped with pure water; The purified water is dried to increase the adhesion, thereby obtaining the two-dimensional material sheet that is evenly attached to the base sheet.

3. The method for preparing a thin layer of two-dimensional material island according to claim 1, characterized in that: The step of transferring the two-dimensional material sheet after being separated from the heat release tape to a base sheet and increasing the adhesion between the two-dimensional material sheet and the base sheet comprises: transferring the two-dimensional material sheet after being separated from the heat release tape to the base sheet; stacking a press tool on the two-dimensional material sheet, wherein the roughness of the press tool is greater than the roughness of the base sheet; An external force is applied to the press to increase the adhesion force, so that the two-dimensional material sheet is flatly attached to the base sheet.

4. The method for preparing a thin layer of two-dimensional material island according to claim 3, characterized in that: When the pressing tool is a roller structure, applying external force to the pressing tool includes: The roller structure is rolled back and forth on top of the two-dimensional material sheet by external force.

5. The method for preparing a thin layer of two-dimensional material island according to claim 3, characterized in that: After stacking a press on top of the two-dimensional material sheet, the method further includes: The two-dimensional material sheet on which the press is placed is heated to increase the surface flatness of the two-dimensional material sheet.

6. The method for preparing a thin layer of two-dimensional material island according to claim 5, characterized in that: The heating temperature of the two-dimensional material sheet on which the press is placed is 100 to 150 degrees Celsius.

7. The method for preparing a thin layer of two-dimensional material island according to claim 1, characterized in that: After transferring the two-dimensional material sheet after being separated from the heat release tape to a base sheet and increasing the adhesion between the two-dimensional material sheet and the base sheet, the method further includes: Performing film coating, gluing, exposure and development processing on the two-dimensional material sheet attached to the substrate sheet, so that a desired pattern appears on the two-dimensional material sheet; The material above the developed two-dimensional material slice is etched to obtain a two-dimensional material island arranged based on the expected pattern.

8. The method for preparing a thin layer of two-dimensional material island according to claim 7, characterized in that: The etching of the upper material of the developed two-dimensional material slice to obtain two-dimensional material islands arranged based on the expected pattern includes: The developed upper material is dry-etched according to a preset etching selectivity to obtain two-dimensional material islands arranged according to the expected pattern; the etching selectivity refers to the etching rate ratio between the photoresist exposed above the two-dimensional material slice and the coating material under the same etching conditions.

9. The method for preparing a thin layer of two-dimensional material island according to claim 8, characterized in that: The etching selectivity ratio is determined based on the coverage thickness and / or coverage area between the photoresist and the coating material.

10. The method for preparing a thin layer of two-dimensional material island according to claim 8, characterized in that: When the dry etching is performed using oxygen plasma, the etching time is comprised between 1 and 3 minutes.

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