A method of oxide cleavage two-dimensional material

Abstract

The application discloses a kind of based on oxide cleavage two-dimensional material method;The specific steps of the method are as follows: (1) the block crystal material to be cleaved is closely attached together with vacuum tape, and a layer of insulating oxide film is covered on the surface of the crystal material;(2) heat release tape is heated in advance and released onto the substrate, forming a layer of heat release tape residual layer;(3) the side of the crystal mother tape covered with oxide film is pressed onto the substrate;(4) tear the vacuum tape, as the heat release tape residual layer has adhesion, it will stick the oxide film together with the crystal on the substrate, the crystal surface is exposed;(5) use traditional cleavage tape to continuously thin the crystal to complete the cleavage of the crystal.The application has fewer transfer steps and high cleavage efficiency;The application avoids direct heating of the crystal material sample, which can ensure the stability of the crystal material, and is especially suitable for cleavage of unstable crystal materials.

Description

Technical Field

[0001] This invention belongs to the field of metal cleavage technology, specifically, it relates to a method based on oxide cleavage of two-dimensional materials. Background Technology

[0002] Two-dimensional materials exhibit many unique properties, making them widely used in fields such as field-effect transistors, optoelectronic devices, and thermoelectric devices. Currently, mechanical cleavage is one of the commonly used methods for obtaining high-quality two-dimensional materials. In our previous Chinese invention patent application (application number 201811138228.1), entitled "Method for Cleavage of Two-Dimensional Materials," we proposed a mechanical cleavage method that utilizes inert oxides to cleave crystalline materials and transfers them using a stamp material. This method can obtain large-area, high-quality two-dimensional materials, expanding the two-dimensional material library. However, in this cleavage method, to separate the sample from the heat-releasing tape, the sample needs to be directly heated to a temperature of 115-125℃. This significantly limits the application of this method in some thermally unstable crystalline materials. Furthermore, this method requires a stamp material to transfer the obtained two-dimensional material onto a substrate, requiring multiple transfer steps. During this process, some cleaved two-dimensional material is inevitably lost, which is detrimental to improving the yield of two-dimensional materials. Summary of the Invention

[0003] To address the shortcomings of the prior art, the present invention aims to provide a method for cleaving two-dimensional materials based on oxides; this method has fewer transfer steps, higher cleavage efficiency, and is particularly suitable for cleaving crystalline materials with poor thermal stability.

[0004] The technical solution of the present invention is described in detail below.

[0005] This invention provides a method for cleaving two-dimensional materials based on oxides. The method primarily utilizes the adhesion force between the oxide deposited or sputtered onto the surface of the two-dimensional material and the two-dimensional material to achieve cleavage. The method includes the following steps: (1) The bulk crystal to be cleaved is attached to vacuum tape and a layer of insulating oxide film is covered on the surface of the crystal; (2) Prepare the substrate, attach the heat release tape tightly to the substrate, heat the heat release tape to release it onto the substrate, and separate the heat release tape from the substrate while it is hot, so that a layer of tape residue is formed on the surface of the substrate. (3) Place the tape with the insulating oxide film in step (1) face down on the tape residue layer on the substrate and press it firmly to make it adhere evenly. (4) Tear off the tape. The bulk crystal material and insulating oxide film remain on the substrate, and the oxide film surface is close to the substrate surface, exposing the crystal surface. (5) The crystal plane obtained in step (4) is repeatedly pasted with traditional cleavage tape to reduce its thickness and complete the cleavage.

[0006] In this invention, in step (1), an insulating oxide film is coated on the crystal surface by vapor deposition or sputtering.

[0007] In this invention, in step (1), the insulating oxide is aluminum oxide or magnesium oxide, and the thickness of the insulating oxide film layer is between 50-100 nm.

[0008] In this invention, in step (1), the bulk crystal is selected from any one of MoS2, TaS2, Fe3GeTe2, MnBi2Te4, VSe2, FeSe, CrI3, Cr2Ge2Te6, WSe2, single WS2, WTe2 or black phosphorus.

[0009] In this invention, in step (1), the bulk crystal is selected from any one of Fe3GeTe2, MnBi2Te4, VSe2, FeSe, CrI3, Cr2Ge2Te6 or black phosphorus.

[0010] In this invention, in step (2), the substrate is selected from any one of quartz, sapphire, indium tin oxide (ITO) or strontium titanate (STO).

[0011] In this invention, depending on the different applications of the device, the substrate is specially selected and processed in step (2). If the number of layers needs to be determined, a transparent substrate is selected; if a back gate voltage needs to be applied, a transparent electrode and a transparent gate dielectric layer need to be pre-deposited.

[0012] In this invention, in step (2), the heat treatment temperature is 100-120℃. At this temperature, the heat release tape loses its adhesiveness.

[0013] In this invention, in step (1), the main components of the vacuum tape are polyimide film and silicone adhesive; in step (5), the main component of the traditional cleavage tape is acrylic resin.

[0014] In this invention, the adhesion between the vacuum tape and the crystal is greater than the adhesion between the tape residue and the oxide, which is greater than the adhesion between the oxide and the two-dimensional material, which is greater than the adhesion between the conventional cleavage tape and the crystal.

[0015] Compared with the previously proposed mechanical cleavage method, the advantages of this invention are as follows: (1) It can avoid direct heating of crystal material samples and ensure the stability of crystal materials. It is especially suitable for cleavage of a series of crystal materials that are unstable when heated (such as Fe3GeTe2, MnBi2Te4, VSe2, FeSe, CrI3, Cr2Ge2Te6 or black phosphorus, etc.). (2) Fewer transfer steps, avoiding the loss of two-dimensional material during repeated transfers, greatly improving the cleavage efficiency and yield of two-dimensional materials; (3) The thin layer material obtained by cleavage no longer comes into contact with any organic matter, which can ensure that the surface of the obtained two-dimensional material is cleaner and is conducive to improving device performance. Attached Figure Description

[0016] Figure 1 Schematic diagram of vacuum tape.

[0017] Figure 2 A schematic diagram of the master tape obtained by bonding the material to be cleaved with vacuum tape.

[0018] Figure 3 A schematic diagram of covering a bulk crystalline material with a thin film of insulating oxide.

[0019] Figure 4 Schematic diagram of the substrate.

[0020] Figure 5 A schematic diagram showing the heat-release tape being tightly bonded to the substrate.

[0021] Figure 6 A schematic diagram showing the heat treatment and separation of the heat-release tape from the substrate, with residual adhesive from the heat-release tape adhering to the substrate.

[0022] Figure 7 A schematic diagram showing the master tape coated with an oxide film being tightly bonded to the substrate.

[0023] Figure 8 A schematic diagram showing partial cleavage of the crystalline material when the vacuum tape is peeled off.

[0024] Figure 9 A schematic diagram of cleaving a crystalline material on a substrate using traditional cleaving tape.

[0025] Labels in the diagram: 1-Vacuum tape, 2-Blocking material to be cleaved, 3-Insulating oxide film, 4-Substrate, 5-Heat-releasing tape, 6-Residual adhesive with a certain degree of stickiness, 7-Traditional cleaving tape, 2 a 2 b - Thin layers of material after partial cleavage of a bulk material. Detailed Implementation

[0026] The technical solution of the present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0027] This invention provides a method for two-dimensional materials based on oxide dissociation, the specific implementation steps of which are as follows: S1: The bulk crystal to be cleaved is attached to a vacuum tape, and an insulating oxide film is covered on the crystal surface. The oxide film can be formed by vapor deposition or sputtering. The formation process of the insulating oxide can be a chemical reaction process or a physical process. S2: Prepare the substrate. For example, if the number of layers needs to be determined, select a transparent substrate; if a back gate voltage needs to be applied, transparent electrodes and a transparent gate dielectric layer need to be pre-deposited. S3: Heat the heat release tape and release it onto the substrate of S2, so that a layer of tape residue is formed on the surface of the substrate; S4: Place the adhesive tape from S1 with the oxide film side down firmly onto the substrate formed in S3, and press it firmly to make it adhere evenly. S5: Tear off the vacuum tape. Bulk crystal material and oxide film remain on the substrate, with the oxide film side close to the substrate side and the crystal side exposed. S6: The crystal obtained in S5 is repeatedly glued together using traditional cleavage tape to reduce its thickness and complete the cleavage process; S7: If it is necessary to determine the number of layers, a transparent substrate can be used, and the number of layers can be determined by using different contrasts in the transmission mode of the microscope.

[0028] Example 1

[0029] In this embodiment, the insulating oxide is alumina, the crystal material is MoS2, the substrate is a transparent quartz single crystal wafer, the vacuum tape is named Kapton tape, the main components are polyimide film and silicone adhesive, it does not release gas in a vacuum, and is a commonly used vacuum tape; the thermal release tape is named Nitto thermal release tape, the main components are made of special polymers or resins, and it loses its adhesiveness when heated to about 120°C; the traditional cleavage tape is named Scotchmagic tape, a commonly used transparent tape, the main component of which is acrylic resin; the specific process is as follows: S1: The crystal to be cleaved is attached to a vacuum tape, and an oxide film is deposited on the surface of the crystal by vapor deposition. The oxygen partial pressure is controlled at 1E-4 mbar during the vapor deposition. S2: Prepare the substrate by pre-depositing transparent electrode ITO on a quartz single crystal substrate, and then growing aluminum oxide of appropriate thickness as a transparent gate dielectric layer by atomic layer deposition. S3: Heat the heat release tape and release it onto the substrate of S2, so that a layer of tape residue is formed on the surface of the substrate; S4: Place the adhesive tape from S1 with the oxide film side down firmly onto the substrate and press it down firmly to make it adhere evenly; S5: Tear off the tape; crystals and oxide films remain on the substrate. S6: The crystals obtained in S5 are repeatedly glued together with traditional tape to reduce their thickness; S7: While repeating step S6, continuously determine the number of layers using different contrasts in transmission mode of the microscope. Select suitable thin layers to fabricate the device.

Claims

1. A method based on oxide cleavage two-dimensional materials, characterized in that, Includes the following steps: (1) The bulk crystal to be cleaved is attached to vacuum tape and a layer of insulating oxide film is covered on the surface of the crystal; (2) Prepare the substrate, attach the heat release tape tightly to the substrate, heat the heat release tape to release it onto the substrate, and separate the heat release tape from the substrate while it is hot, so that a layer of tape residue is formed on the surface of the substrate. (3) Place the tape with the insulating oxide film in step (1) face down on the tape residue layer on the substrate and press it firmly to make it adhere evenly. (4) Tear off the tape. The bulk crystal material and insulating oxide film remain on the substrate, and the oxide film surface is close to the substrate surface, exposing the crystal surface. (5) The crystal plane obtained in step (4) is repeatedly pasted with traditional cleavage tape to reduce its thickness and complete the cleavage; wherein: In step (1), the main components of the vacuum tape are polyimide film and silicone adhesive; an insulating oxide film is coated on the crystal surface by vapor deposition or sputtering, and the insulating oxide is aluminum oxide or magnesium oxide; In step (5), the main component of the traditional cleavage tape is acrylic resin; The adhesion between vacuum tape and crystal > the adhesion between tape residue and oxide > the adhesion between oxide and two-dimensional material > the adhesion between traditional cleavage tape and crystal.

2. The method based on oxide cleavage two-dimensional materials according to claim 1, characterized in that, In step (1), the thickness of the insulating oxide thin film layer is between 50-100 nm.

3. The method based on oxide cleavage two-dimensional materials according to claim 1, characterized in that, In step (1), the bulk crystals are selected from any one of MoS2, TaS2, Fe3GeTe2, MnBi2Te4, VSe2, FeSe, CrI3, Cr2Ge2Te6, WSe2, single WS2, WTe2 or black phosphorus.

4. The method based on oxide cleavage two-dimensional materials according to claim 1, characterized in that, In step (1), the bulk crystals are selected from any one of Fe3GeTe2, MnBi2Te4, VSe2, FeSe, CrI3, Cr2Ge2Te6 or black phosphorus.

5. The method based on oxide cleavage two-dimensional materials according to claim 1, characterized in that, In step (2), the substrate is selected from any one of quartz, sapphire, indium tin oxide (ITO) or strontium titanate (STO).

6. The method based on oxide cleavage two-dimensional materials according to claim 1, characterized in that, In step (2), the heat treatment temperature is 100-120℃. At this temperature, the heat release tape loses its stickiness.

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