A transfer method for preparing two-dimensional homogeneous / heterogeneous structures with clean interfaces

Abstract

The present invention provides a method for transferring two-dimensional homogeneous / heterogeneous structures with a clean interface, comprising: step S1, peeling different two-dimensional materials onto a substrate; step S2, preparing a pick-up sample slide and a flip sample slide; step S3, using the pick-up sample slide to sequentially pick up different two-dimensional materials, so that the two-dimensional materials form a two-dimensional homogeneous / heterogeneous structure; step S4, heating the flip sample slide after attaching it to the pick-up sample slide, so that the picked-up two-dimensional homogeneous / heterogeneous structure is transferred to the flip sample slide; step S5, heating the flip sample slide, transferring the picked-up two-dimensional homogeneous / heterogeneous material to the substrate, and completing the transfer. Through the above design, the present application can achieve the transfer of two-dimensional homogeneous / heterogeneous structures with a large area and a clean interface.

Description

Technical Field

[0001] The present invention belongs to the field of two-dimensional material stacking, and in particular relates to a transfer method for preparing a two-dimensional homogeneous / heterogeneous structure with a clean interface. Background Art

[0002] In recent years, the emergence of mechanical exfoliation and stacking techniques for two-dimensional layered materials (such as graphene, transition metal sulfides, and hexagonal boron nitride) has made it possible to manipulate these materials at the atomic level. Quantum confinement due to the thickness of the atomic layer leads to the emergence of additional properties, and detailed characterization of their stacking interfaces is crucial for explaining these new phenomena. Currently, mainstream characterization methods include various modes of atomic force microscopy and scanning electron microscopy. All of these characterization methods require extremely clean interfaces in the prepared samples, but existing stacking technologies struggle to guarantee this.

[0003] At present, the transfer methods for preparing homojunction / heterojunction structures mainly include wet transfer method and dry transfer method. Among them, the wet transfer method is to dissolve the thin film of the pickup material with water or N-methylpyrrolidone solution after the stacking is completed to expose the sample surface; the dry transfer method is to use external force to remove the thin film with the sample from the polydimethylsiloxane slide, and then directly place it on the corresponding substrate to expose the surface. However, the existing technology has the following defects: 1. Due to the injection of chemical reagents, the wet transfer method has many high points in its morphology and large surface roughness, and the surface cannot guarantee atomic-level cleanliness; 2. Although the dry transfer method with large external force intervention can ensure cleanliness, it will generate large external stress due to mechanical tearing, which is not conducive to the preparation of large-area two-dimensional material homojunction / heterojunction samples, and at the same time reduces the success rate of preparation. Summary of the Invention

[0004] In order to avoid the influence of chemical residues on surface cleanliness and the destruction of structural integrity by large external forces during the preparation process, and to improve the success rate of the preparation process, the present invention designs a two-dimensional homogeneous / heterogeneous structure transfer method in order to realize the preparation of two-dimensional homogeneous / heterogeneous structures with large areas and clean interfaces.

[0005] A method for transferring two-dimensional homogeneous / heterogeneous structures to prepare a clean interface comprises the following steps:

[0006] Step S1, peeling different two-dimensional materials onto a substrate;

[0007] Step S2, preparing a sample slide and flipping the sample slide;

[0008] Step S3: using a sample picking slide to sequentially pick up different two-dimensional materials, so that the two-dimensional materials form a two-dimensional homogeneous / heterogeneous structure;

[0009] Step S4, flipping the sample slide, attaching it to the picked-up sample slide, and then heating it to transfer the picked-up two-dimensional homogeneous / heterogeneous structure to the flipped sample slide;

[0010] Step S5: Heat and flip the sample slide to transfer the picked-up two-dimensional homogeneous / heterogeneous structure to the substrate to complete the transfer.

[0011] Preferably, the substrate is a silicon dioxide substrate.

[0012] Preferably, the two-dimensional material includes few-layer hexagonal boron nitride, thin-layer graphene, and thin-layer transition metal sulfide.

[0013] Preferably, the pickup sample slide is a polydimethylsiloxane slide covered with a polypropylene carbonate film and containing a heat-release adhesive tape, and the flip sample slide is a polydimethylsiloxane slide with holes.

[0014] Preferably, before step S3, an atomic force microscope is used to assist in cutting the thin layer of two-dimensional material.

[0015] Preferably, the heating temperature in step S4 is 130-135 degrees.

[0016] Preferably, in step S5, the temperature for heating and flipping the sample slide is 160-165 degrees.

[0017] Preferably, the sample picking slide comprises a glass slide, dimethylsiloxane, double-sided tape, heat release tape, and polypropylene carbonate film;

[0018] The dimethylsiloxane is placed on a glass slide;

[0019] Double-sided tape is placed on the glass slide around the dimethylsiloxane;

[0020] A heat-release tape is placed on the double-sided tape;

[0021] The polypropylene carbonate film was placed on top of the thermal release tape and dimethyl silicone.

[0022] Preferably, the flip sample slide comprises a slide, porous dimethylsiloxane, and double-sided tape;

[0023] The porous dimethylsiloxane is placed on a glass slide.

[0024] The double-sided tape is placed on a glass slide surrounded by porous dimethylsiloxane.

[0025] The advantages and effects of this application are as follows:

[0026] 1. The present application designs a transfer method for preparing a two-dimensional homogeneous / heterogeneous structure with a clean interface. Compared with the existing technology, it is a dry transfer technology for exposed surfaces with high cleanliness and low external stress. It can ensure the high quality of the stacking interface after the two-dimensional material is transferred; the sample surface after transfer is smoother and cleaner than the wet transfer method; and the interface structure within the sample area is very complete.

[0027] 2. The present application designs a transfer method for preparing a two-dimensional homogeneous / heterogeneous structure with a clean interface, which is a transfer method using a polypropylene carbonate film. Many existing methods use a wet transfer method in which a polyvinyl alcohol film or a polymethyl methacrylate film is dissolved by pure water or N-methylpyrrolidone. The present application does not require the injection of chemical reagents and can obtain a cleaner surface.

[0028] 3. The present application designs a transfer method for preparing a two-dimensional homogeneous / heterogeneous structure with a clean interface, which is a transfer technology without the intervention of large external forces. The existing technology generally separates the polypropylene carbonate film from the polydimethylsiloxane by directly using external force, which will cause the polypropylene carbonate film to have a large deformation. The present application uses a porous polydimethylsiloxane slide for flipping the polypropylene carbonate film, and utilizes the high-temperature detackification of the heat release tape to transfer the film from the sample pickup slide to the flip sample slide. At the same time, an optical microscope is used to ensure that the sample on the film is in the pores of the polydimethylsiloxane, while reducing the influence of external stress and ensuring the success rate of transfer.

[0029] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application so that it can be implemented in accordance with the contents of the specification, and to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the following is a detailed description of the preferred embodiment of the present application in conjunction with the accompanying drawings.

[0030] Based on the detailed description of the specific embodiments of the present application in conjunction with the accompanying drawings below, those skilled in the art will become more aware of the above and other objects, advantages and features of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following will briefly introduce the drawings required for the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present application. For those of ordinary skill in the art, other drawings can also be obtained based on these drawings without inventive work. In all drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, the elements or parts are not necessarily drawn according to the actual scale.

[0032] Figure 1A flow chart of a method for transferring two-dimensional homogeneous / heterogeneous structures to prepare a clean interface provided in this application;

[0033] Figure 2 Optical microscope images of the samples provided for this application after preparation;

[0034] Figure 3 Atomic force microscope topography of the sample provided for this application;

[0035] Figure 4 This is the piezoelectric atomic force microscope result of large-area twisted graphene provided in this application;

[0036] Figure 5 The piezoelectric force atomic microscope results provided for this application;

[0037] Figure 6 The conductive force atomic force microscope results provided for this application;

[0038] Figure numerals: 1. glass slide; 2. double-sided tape; 3. thermal release tape; 4. polypropylene carbonate film; 5. non-porous dimethylsiloxane; 6. few-layer hexagonal boron nitride; 7. single-layer graphene; 8. porous dimethylsiloxane; 9. separated polypropylene carbonate film. DETAILED DESCRIPTION

[0039] In order to make the purpose, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all of the embodiments. In the following description, specific details such as specific configurations and components are provided only to help fully understand the embodiments of the present application. Therefore, it should be clear to those skilled in the art that various changes and modifications can be made to the embodiments described herein without departing from the scope and spirit of the present application. In addition, for clarity and brevity, the description of known functions and structures has been omitted in the embodiments.

[0040] It should be understood that references throughout this specification to "one embodiment" or "this embodiment" mean that a particular feature, structure, or characteristic associated with the embodiment is included in at least one embodiment of the present application. Therefore, the appearance of "one embodiment" or "this embodiment" throughout this specification does not necessarily refer to the same embodiment. Furthermore, these particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

[0041] In addition, the present application may repeat reference numerals and / or letters in different examples. This repetition is for the purpose of simplicity and clarity and does not in itself indicate the relationship between the various embodiments and / or settings discussed.

[0042] The term "and / or" in this article is only a description of the association relationship of associated objects, indicating that three relationships can exist. For example, A and / or B can mean: A exists alone, B exists alone, and A and B exist at the same time. The term " / and" in this article describes another type of association object relationship, indicating that two relationships can exist. For example, A / and B can mean: A exists alone, and A and B exist alone. In addition, the character " / " in this article generally indicates that the previous and subsequent associated objects are in an "or" relationship.

[0043] The term "at least one" in this article is merely a description of the association relationship between associated objects, indicating that three relationships may exist. For example, at least one of A and B can mean: A exists alone, A and B exist at the same time, and B exists alone.

[0044] It should also be noted that, in this document, relational terms such as first and second are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "include," "comprises," or any other variations thereof are intended to cover non-exclusive inclusion.

[0045] Example 1

[0046] Please refer to Figure 1 , Figure 1 The present application provides a method for transferring two-dimensional homogeneous / heterogeneous structures to prepare a clean interface, characterized by comprising the following steps:

[0047] Step S1, peeling different two-dimensional materials onto a substrate;

[0048] Step S2, preparing a sample slide and flipping the sample slide;

[0049] Step S3: using a sample picking slide to sequentially pick up different two-dimensional materials, so that the two-dimensional materials form a two-dimensional homogeneous / heterogeneous structure;

[0050] Step S4: Laminating the flipped sample slide with the picked-up sample slide and heating the slide to transfer the picked-up two-dimensional homogeneous / heterogeneous structure to the flipped sample slide;

[0051] Step S5: Heat and flip the sample slide to transfer the picked-up two-dimensional homogeneous / heterogeneous structure to the substrate to complete the transfer.

[0052] Furthermore, the substrate is a silicon dioxide substrate.

[0053] Furthermore, the two-dimensional material includes a few-layer hexagonal boron nitride, a thin-layer graphene, and a thin-layer transition metal sulfide.

[0054] Furthermore, the pick-up sample slide is a polydimethylsiloxane slide with a heat-release tape covered with a polypropylene carbonate film, and the flip sample slide is a polydimethylsiloxane slide with a hole;

[0055] Furthermore, before step S3, an atomic force microscope is used to assist in cutting the thin layer of two-dimensional material.

[0056] Furthermore, the turning heating temperature in step S4 is 130-135 degrees.

[0057] Furthermore, in step S5, the temperature for heating and flipping the sample slide is 160-165 degrees.

[0058] Furthermore, the sample picking slide includes a slide, dimethylsiloxane, double-sided tape, heat release tape, and polypropylene carbonate film;

[0059] The dimethylsiloxane is placed on a glass slide;

[0060] Double-sided tape is placed on the glass slide around the dimethylsiloxane;

[0061] A heat-release tape is placed on the double-sided tape;

[0062] The polypropylene carbonate film was placed on top of the thermal release tape and dimethyl silicone.

[0063] Furthermore, the flip sample slide includes a slide, porous dimethylsiloxane, and double-sided tape;

[0064] The porous dimethylsiloxane is placed on a glass slide.

[0065] The double-sided tape is placed on a glass slide surrounded by porous dimethylsiloxane.

[0066] Furthermore, the film can be changed to a polymethyl methacrylate film.

[0067] The present application designs a transfer method for preparing two-dimensional homogeneous / heterogeneous structures with clean interfaces. Compared with the existing technology, it is a dry transfer technology for exposed surfaces with high cleanliness and low external stress. It can ensure the high quality of the stacking interface after the two-dimensional material is transferred; the sample surface after transfer is smoother and cleaner than the wet transfer method; and the interface structure within the sample area is very complete.

[0068] Example 2

[0069] Based on the above-mentioned Example 1, this example mainly introduces a first design of a transfer method for preparing a two-dimensional homogeneous / heterogeneous structure with a clean interface, including the following steps:

[0070] Step S1: using tape to peel off the graphite crystal and the hexagonal boron nitride crystal to obtain a single-layer graphene 7 and a few-layer hexagonal boron nitride 6;

[0071] Step S2: Using a mold, make two circular polydimethylsiloxanes, one of which is hollowed out. These are placed on two clean glass slides, one of which is made of non-porous polydimethylsiloxane (5) and the other one is used as the pickup sample slide. The perforated polydimethylsiloxane (8) serves as the flip sample slide. To the pickup sample slide, attach double-sided tape (2) and heat-release tape (3) with pre-punched holes larger than the polydimethylsiloxane, centered around the circular polydimethylsiloxane. Finally, cover the polydimethylsiloxane with polypropylene carbonate film (4). For the flip sample slide, attach double-sided tape with a larger hole, centered around the circular polydimethylsiloxane.

[0072] Step S3: Using an atomic force microscope probe, a high-frequency AC voltage is applied to catalyze a chemical reaction between the graphene and water, thereby etching the graphene. Subsequently, using a micromanipulator, the sample slide is clamped onto a cantilever fixture, and a few layers of hexagonal boron nitride, a single layer of graphene, and a single layer of graphene are sequentially picked up. The micromanipulator is heated at a constant temperature of 80-85°C.

[0073] Step S4, after all the two-dimensional materials are picked up, the sample slide is taken out of the cantilever clamp, placed on the heating stage of the microscope operation table, and then the flip sample slide is clamped on the cantilever clamp. Lower the height of the cantilever clamp until the porous polydimethylsiloxane on the flip sample slide is firmly in contact with the polydimethylsiloxane on the picked-up sample slide. After the above operations are completed, the temperature of the heating stage is raised to the release temperature of the thermal release tape, and the thermal release tape completely loses its stickiness, and the polypropylene carbonate film above it is separated from the thermal release tape; at this time, only tweezers are needed to pick up the separated polypropylene carbonate film 9 and make close contact with the double-sided tape on the flip sample slide. After the above steps are completed, the film is transferred from the picked-up sample slide to the flip sample slide, achieving the purpose of flipping the homo / heterojunction and exposing the surface.

[0074] Step S5: Remove the heating platform and pick up the sample slide, place the silicon dioxide substrate, and melt the organic film on the flipped sample slide onto the silicon wafer at a melting temperature of 160-165 degrees. The homojunction is transferred to the silicon dioxide substrate, and the transfer process is completed.

[0075] Please refer to Figure 1 , Figure 1 This is a schematic diagram of the steps of the transfer method described in Example 1 of the present invention. Figure 1Figure Ⅰ shows the use of a pick-up slide to pick up a few-layer hexagonal boron nitride on a silica substrate; Ⅱ shows the schematic diagram of picking up the first portion of a single-layer graphene etched by an atomic force microscope; Ⅲ shows the schematic diagram of picking up the second portion of a single-layer graphene; Ⅳ shows the placement of the pick-up slide on a heating stage, followed by the pressing of a flip-up slide onto the pick-up slide, ensuring that the sample remains within the dimethylsiloxane pores of the flip-up slide. Once the heating temperature reaches the release temperature of the thermal release tape, the polypropylene carbonate film is separated from the pick-up slide; Ⅴ shows the pressing of the separated polypropylene carbonate film onto the double-sided tape of the pick-up slide; Ⅵ shows the melting of the polypropylene carbonate film. At this point, the structures on the silica substrate, from bottom to top, are polypropylene carbonate film, few-layer hexagonal boron nitride, and single-monolayer graphene.

[0076] The present invention is a transfer method using a polypropylene carbonate film. Many existing methods use a wet transfer method in which a polyvinyl alcohol film or a polymethyl methacrylate film is dissolved by pure water or N-methylpyrrolidone. The present invention does not require the injection of chemical reagents and can obtain a cleaner surface.

[0077] The present invention is a transfer technology that eliminates the need for significant external force. Existing techniques for separating polypropylene carbonate films from polydimethylsiloxane typically utilize direct external force, which can significantly deform the polypropylene carbonate film. The present invention utilizes a porous polydimethylsiloxane slide for flipping the polypropylene carbonate film and exploits the high-temperature detackification properties of thermal release tape to transfer the film from the sample pickup slide to the flipping sample slide. Simultaneously, an optical microscope is used to ensure that the sample on the film is within the pores of the polydimethylsiloxane. This method reduces the influence of external stress and ensures a high transfer success rate.

[0078] The present invention is a high-precision two-dimensional material transfer method with good universality for various two-dimensional materials. Combined with electrode preparation technology, it can prepare micro-nanoscale electrical devices with excellent scalability.

[0079] Example 3

[0080] Based on the above-mentioned embodiment 2, this embodiment mainly introduces a second design of a transfer method for preparing a two-dimensional homogeneous / heterogeneous structure with a clean interface.

[0081] Step 1: Using adhesive tape, peel off the molybdenum disulfide crystal, molybdenum diselenide crystal and hexagonal boron nitride crystal on the silicon dioxide substrate to obtain a few-layer hexagonal boron nitride, a single-layer molybdenum disulfide and a single-layer molybdenum diselenide;

[0082] Step 2: The film is changed to polymethyl methacrylate film, the sample picking temperature is 50 degrees, and a few layers of hexagonal boron nitride, a single layer of molybdenum disulfide, a single layer of molybdenum diselenide, and a few layers of hexagonal boron nitride are picked up in sequence. Other operations are the same as steps S4 to S5 in Example 1;

[0083] Step 3: Use electron beam lithography to carve the required electrode channels on the polymethyl methacrylate;

[0084] Step 4: Use thermal evaporation to plate 7nm / 70nm chromium / gold (Cr / Au) on the electrode trench.

[0085] Compared with the existing technology, this invention is a surface-exposed dry transfer technology with high cleanliness and low external stress, which can ensure the high quality of the stacking interface after the transfer of two-dimensional materials. Figure 2 This is the optical image of the sample after transfer. We found that the surface is smoother than that of the wet transfer method by atomic force microscopy. Figure 3 This shows that the transfer technology of the present invention can obtain a cleaner surface. Figure 4 , within the sample area, the interface structure is very complete. Similarly, this technology can be used to prepare other high-quality samples and has wide applicability, see Figure 5 By combining the existing electrode picking technology or electron beam etching and thermal evaporation technology, electrical devices can be prepared. Using conductive atomic force microscopy, the current map of the interface can be obtained, see Figure 6 , indicating that the technology has good scalability. Therefore, the present application has a wide range of adaptability, and the homogeneous / heterogeneous structures prepared therefrom have atomic-level flatness and a wide range of complete interface structures.

[0086] The foregoing description is merely a preferred embodiment of the present invention and does not limit the scope of protection of the present invention. Those skilled in the art will readily appreciate that the present invention is susceptible to various modifications and variations. Any variation, modification, replacement, integration, or parameter change to these embodiments, which is within the spirit and principles of the present invention and which achieves the same functionality through conventional substitutions, without departing from the principles and spirit of the present invention, falls within the scope of protection of the present invention.

Claims

1. A method for preparing a two-dimensional homogeneous / heterogeneous structure transfer with a clean interface, characterized in that: The following steps are involved: Step S1, peeling different two-dimensional materials onto a substrate; Step S2, preparing a sample slide and flipping the sample slide; Step S3: using a sample picking slide to sequentially pick up different two-dimensional materials, so that the two-dimensional materials form a two-dimensional homogeneous / heterogeneous structure; Step S4, flipping the sample slide, attaching it to the picked-up sample slide, and then heating it to transfer the picked-up two-dimensional homogeneous / heterogeneous structure to the flipped sample slide; Step S5: heating and flipping the sample slide to transfer the picked-up two-dimensional homogeneous / heterogeneous structure to the substrate to complete the transfer; In step S2, two circular polydimethylsiloxanes are made using a mold, one of which is hollowed out in the middle, and are placed on two clean glass slides, respectively. The glass slide containing the non-porous polydimethylsiloxane is used as the pickup sample slide, and the glass slide containing the perforated polydimethylsiloxane is used as the flip sample slide. Double-sided tape and heat-release tape with pre-punched holes larger than the polydimethylsiloxane are sequentially attached to the pickup sample slide, with the circular polydimethylsiloxane as the center. Finally, a polypropylene carbonate film is covered on the polydimethylsiloxane. Double-sided tape with a hole larger than the polydimethylsiloxane is attached to the flip sample slide, with the polydimethylsiloxane as the center.

2. A method for transferring two-dimensional homogeneous / heterogeneous structures for preparing a clean interface according to claim 1, characterized in that: The substrate is a silicon dioxide substrate.

3. The method for transferring two-dimensional homogeneous / heterogeneous structures to prepare a clean interface according to claim 1, characterized in that: The two-dimensional materials include few-layer hexagonal boron nitride, thin-layer graphene, and thin-layer transition metal sulfide.

4. The method for transferring two-dimensional homogeneous / heterogeneous structures for preparing a clean interface according to claim 1, characterized in that: Before step S3, an atomic force microscope is required to assist in cutting the thin layer of two-dimensional material.

5. The method for transferring two-dimensional homogeneous / heterogeneous structures for preparing a clean interface according to claim 1, characterized in that: The heating temperature in step S4 is 130-135 degrees.

6. The method for transferring two-dimensional homogeneous / heterogeneous structures for preparing a clean interface according to claim 1, characterized in that: In step S5, the temperature for heating and flipping the sample slide is 160-165 degrees.

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