A method for solvent-free and lossless precision transfer of two-dimensional materials

Abstract

The application discloses a kind of two-dimensional material's desolvation lossless precision transfer method, comprising: silicon wafer is functionalized with HMDS;PMMA anisole solution is used to spin coating and dry to form PMMA support film to functionalized silicon wafer;Hot release glue PDMS is used to pick up PMMA support film;PDMS / PMMA is transferred to the surface of two-dimensional material / first substrate needing to be transferred, after heating, PDMS is separated from PMMA, and PMMA covers the surface of two-dimensional material;Through etching of etching solution, PMMA / two-dimensional material is separated from first substrate;PMMA / two-dimensional material separated from first substrate is fished up with PDMS;PMMA / two-dimensional material is transferred to second substrate;Using acetone, PMMA is cleaned, and nitrogen is blown dry, namely finished.The application can realize clean, efficient and accurate transfer of two-dimensional material, and can avoid intolerance of two-dimensional material to organic solvent and pollution of organic solvent.

Description

Technical Field

[0001] This invention belongs to the field of two-dimensional material preparation, specifically relating to a method for the non-destructive and precise transfer of two-dimensional materials without solvent removal. Background Technology

[0002] Since Geim's research group at the University of Manchester in the UK successfully exfoliated single-layer graphene in 2004, single-layer or few-layer two-dimensional materials have attracted widespread attention. In recent years, two-dimensional materials such as transition metal chalcogenides, hexagonal boron nitride, oxides, phosphorene, silicene, graphene, and MXene have become research hotspots in many fields due to their unique physical and chemical properties.

[0003] Effective use of two-dimensional materials requires transfer from the growth substrate to different target substrates, such as: transfer to a copper grid for transmission electron microscopy characterization, transfer to a new two-dimensional material to prepare homojunctions or heterojunctions, or transfer to different substrates to adapt to different application scenarios.

[0004] Currently, wet transfer is the most commonly used transfer technique for two-dimensional materials. This method involves spin-coating a polymethyl methacrylate (PMMA) or polycarbonate (PPC) solution onto the surface of the two-dimensional material, then baking it on a hot plate to form a cured support layer. Next, the two-dimensional material in the intermediate layer is etched, and the two-dimensional material is retrieved using a new substrate. Finally, it is cleaned with acetone to complete the transfer.

[0005] However, the solvents in PMMA or PPC solutions can chemically corrode 2D materials, making them unsuitable for materials intolerant to such solvents. Spin-coating PMMA or PPC can also damage 2D materials, leading to wrinkles, breakage, or missing components. Furthermore, retrieving 2D materials with a support layer and precisely transferring them to the target material or substrate surface remains challenging, severely limiting the application scenarios for 2D materials. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for the non-destructive and precise transfer of two-dimensional materials by solvent removal.

[0007] The technical solution of the present invention is as follows:

[0008] A method for the non-destructive and precise transfer of two-dimensional materials after solvent removal includes the following steps:

[0009] (1) Clean the silicon wafer;

[0010] (2) The silicon wafers cleaned in step (1) are placed into a sealed reaction vessel containing HMDS for heat treatment to obtain HMDS functionalized silicon wafers.

[0011] (3) Spin-coating and drying the HMDS functionalized silicon wafer obtained in step (2) with PMMA anisole solution to form a PMMA support film on the HMDS functionalized silicon wafer.

[0012] (4) Pick up the PMMA support film obtained in step (3) with heat-release adhesive PDMS, and transfer the PMMA support film to the surface of the two-dimensional material on the first substrate. After heat treatment, peel off the heat-release adhesive PDMS to obtain PMMA / two-dimensional material / first substrate.

[0013] (5) The PMMA / two-dimensional material obtained in step (4) is removed from the first substrate by etching with an etching solution.

[0014] (6) The PMMA / two-dimensional material detached from the first substrate was transferred to the cleaned second substrate using PDMS and then naturally dried to obtain PMMA / two-dimensional material / second substrate;

[0015] (7) The PMMA / two-dimensional material / second substrate obtained in step (6) is soaked in acetone to remove PMMA. After taking it out, it is dried with nitrogen to obtain the two-dimensional material on the second substrate. The solvent-free and precise transfer of the two-dimensional material on the first substrate to the second substrate is completed.

[0016] In a preferred embodiment of the present invention, the two-dimensional material includes transition metal chalcogenides, hexagonal boron nitride, oxides, phosphorene, silicene, graphene, and MXene.

[0017] More preferably, the two-dimensional material is MoS2.

[0018] In a preferred embodiment of the present invention, the first substrate is a SiO2 / Si substrate, an Al2O3 / Si substrate, or a sapphire substrate.

[0019] In a preferred embodiment of the present invention, the second substrate is a silicon wafer, an ITO substrate, a sapphire substrate, a SiO2 / Si substrate, an Al2O3 / Si substrate, or the above-mentioned substrate containing another two-dimensional material.

[0020] More preferably, the other two-dimensional material is WSe2.

[0021] In a preferred embodiment of the present invention, the etching solution is selected from NaOH solution, KOH solution and HF solution.

[0022] In a preferred embodiment of the present invention, the concentration of the PMMA anisole solution is 6-18 wt%.

[0023] In a preferred embodiment of the present invention, the thickness of the PMMA support film is 0.5-3 μm.

[0024] In a preferred embodiment of the present invention, the sealed container is a stainless steel hydrothermal reactor with a polytetrafluoroethylene liner.

[0025] The beneficial effects of this invention are:

[0026] 1. The HDMS functionalized silicon wafers with PMMA support film spin-coated in this invention can be placed for a long time with less environmental influence. The size and shape of the PMMA support film can be pre-made according to the application scenario, and quantitative and selective transfer can be performed. This is different from the cumbersome process of spin-coating and curing required before each transfer in the PMMA wet transfer method of the prior art.

[0027] 2. The PMMA film covering method in this invention can isolate two-dimensional materials from water molecules and oxygen in the air without damaging the structure and properties of the two-dimensional materials. This is different from the PMMA wet transfer method of the prior art, which may cause damage to two-dimensional materials and corrosion introduced by organic solvents during spin coating. It has higher universality for two-dimensional materials that are not resistant to organic solvents, and at the same time has good environmental friendliness and material stability.

[0028] 3. This invention utilizes thermally release adhesive PDMS to transfer two-dimensional materials, enabling precise transfer of two-dimensional materials to the surface of various substrates, and has extremely high versatility.

[0029] 4. This invention provides a more convenient, clean, and pollution-free transfer method for two-dimensional materials, offering more possibilities for the research of high-quality two-dimensional materials and heterojunctions, and is beneficial to the research and development of next-generation two-dimensional material multifunctional devices and integrated circuits. Attached Figure Description

[0030] Figure 1 This is a flowchart illustrating Embodiment 1 of the present invention.

[0031] Figure 2 Optical photographs of MoS2 / SiO2 and labeled Al2O3 / Si substrates in Example 1 of this invention.

[0032] Figure 3 This is an optical photograph of MoS2 / Al2O3 / Si in Example 1 of the present invention.

[0033] Figure 4 This is an optical photograph of MoS2 / SiO2 in Embodiment 1 of the present invention.

[0034] Figure 5 The Raman and fluorescence spectra of MoS2 / SiO2 in Example 1 of this invention are shown.

[0035] Figure 6 This is an optical photograph of WSe2 / SiO2 in Embodiment 2 of the present invention.

[0036] Figure 7 The Raman and fluorescence spectra of WSe2 / SiO2 in Example 2 of this invention are shown.

[0037] Figure 8 This is an optical photograph of MoS2 / WSe2 / SiO2 in Embodiment 2 of the present invention.

[0038] Figure 9 The Raman and fluorescence spectra of MoS2 / WSe2 / SiO2 in Example 2 of this invention are shown. Detailed Implementation

[0039] The technical solution of the present invention will be further explained and described below with reference to specific embodiments and accompanying drawings.

[0040] It should be noted that the transfer method of the present invention is applicable to a variety of different two-dimensional materials, including transition metal chalcogenides, hexagonal boron nitride, oxides, phosphorene, silicene, graphene, and MXene.

[0041] In the following embodiments, the SiO2 substrate is a SiO2 / Si substrate with a SiO2 layer of 300 nm thickness, and the Al2O3 substrate is an Al2O3 / Si substrate with an Al2O3 layer of 300 nm thickness. All other materials and reagents used are commercially available. Unless otherwise specified, all experimental methods used are conventional methods.

[0042] Example 1: MoS2 / SiO2 transfer to Al2O3 substrate

[0043] The process in this embodiment is as follows: Figure 1 As shown, it includes the following steps:

[0044] (1) Acetone, isopropanol, ethanol and ultrapure water were used in sequence to ultrasonically clean the silicon wafer (SiO2 substrate) and Al2O3 / Si substrate with a surface roughness of ±0.5nm. The ultrasonic cleaning time was 30min each time.

[0045] (2) The silicon wafer that has been ultrasonically cleaned in step (1) is placed in a stainless steel hydrothermal reactor with a polytetrafluoroethylene liner containing HMDS (hexamethyldisilazane) and heat-treated at 80°C for 10 min to obtain HMDS functionalized silicon wafer.

[0046] (3) Spin-coating the HMDS functionalized silicon wafer obtained in step (2) with 6wt% PMMA anisole solution at 2000 rpm for 1 min, and then drying it at 100°C for 10 min to form a PMMA support film on the HMDS functionalized silicon wafer.

[0047] (4) The PMMA support film was picked up using thermally release adhesive PDMS, and the PMMA support film was transferred to the surface of the two-dimensional material MoS2 on the SiO2 substrate. After heat treatment at 100°C for 20 min on a hot plate, the thermally release adhesive PDMS was peeled off to obtain PMMA / MoS2 / SiO2, wherein the MoS2 / SiO2 is as follows: Figure 2 , Figure 4 and Figure 5 As shown.

[0048] (5) Place the PMMA / MoS2 / SiO2 obtained in step (4) on a hot plate and heat it at 150°C for 10 min. Then immerse it in a KOH solution at 80°C and a concentration of 1 mol / L for 30 min. After etching the SiO2 layer, obtain PMMA / MoS2 floating on the liquid surface.

[0049] (6) Wash the PMMA / MoS2 obtained in step (5) with ultrapure water 3 to 5 times (10 min each time).

[0050] (7) Use the heat-release adhesive PDMS adhered to the glass slide to retrieve the PMMA / MoS2 obtained in step (6), so that one side of PMMA is adhered to PDMS, to obtain glass slide / PDMS / PMMA / MoS2.

[0051] (8) On the transfer stage, align the glass slide / PDMS / PMMA / MoS2 obtained in step (7) with the marked position on the Al2O3 / Si substrate and attach it to the marked position. Then, heat-treat the glass slide / PDMS at 100°C for 20 minutes on the transfer stage and lift the glass slide / PDMS to obtain PMMA / MoS2 / Al2O3 / Si.

[0052] (9) The PMMA / MoS2 / Al2O3 / Si obtained in step (7) is soaked in acetone for 30 min to remove PMMA. After removal, it is dried with nitrogen gas to obtain the Al2O3 / Si substrate at the marked position. The above two-dimensional material MoS2 (e.g., Figure 2 and Figure 3 As shown in the figure, the solvent-free and precise transfer of two-dimensional material MoS2 on SiO2 substrate to Al2O3 / Si substrate is completed.

[0053] Example 2: MoS2 / SiO2 transfer to WSe2 surface.

[0054] Steps (1) to (7) are the same as in Example 1;

[0055] (8) On the transfer stage, transfer the glass slide / PDMS / PMMA / MoS2 obtained in step (7) to WSe2 (WSe2 / SiO2, as shown in the figure) located on the SiO2 substrate. Figure 6 and Figure 7 (As shown) Align and attach it to the WSe2, then heat treat it at 100℃ for 20 min on the transfer stage and lift the glass slide / PDMS to obtain PMMA / MoS2 / WSe2 / SiO2.

[0056] (9) The PMMA / MoS2 / WSe2 / SiO2 obtained in step (8) is soaked in acetone for 30 minutes to remove PMMA. After removal, it is dried with nitrogen gas to obtain MoS2 / WSe2 / SiO2 (e.g. Figure 8 and Figure 9 As shown, the solvent-free and precise transfer of two-dimensional material MoS2 from the SiO2 substrate to the WSe2 surface is completed.

[0057] The above description is merely a preferred embodiment of the present invention, and therefore should not be construed as limiting the scope of the present invention. All equivalent changes and modifications made in accordance with the scope of the patent and the contents of the specification should still fall within the scope of the present invention.

Claims

1. A method for the non-destructive and precise transfer of two-dimensional materials after solvent removal, characterized in that: Includes the following steps: (1) Clean the silicon wafer; (2) The silicon wafers cleaned in step (1) are placed in a sealed reaction vessel containing HMDS for heat treatment to obtain HMDS functionalized silicon wafers. (3) Spin-coating and drying the HMDS functionalized silicon wafer obtained in step (2) with PMMA anisole solution to form a PMMA support film on the HMDS functionalized silicon wafer; (4) The above PMMA support film is picked up with heat-release adhesive PDMS and transferred to the surface of the two-dimensional material on the first substrate. After heat treatment, the heat-release adhesive PDMS is peeled off to obtain PMMA / two-dimensional material / first substrate. The two-dimensional material includes transition metal chalcogenide, hexagonal boron nitride, oxide, phosphorene, silicene, graphene and MXene. The first substrate is SiO2 / Si substrate, Al2O3 / Si substrate or sapphire substrate. (5) The PMMA / two-dimensional material obtained in step (4) is removed from the first substrate by etching with an etching solution; (6) The PMMA / two-dimensional material detached from the first substrate is transferred to the cleaned second substrate using PDMS. After heat treatment, the PDMS is lifted to obtain PMMA / two-dimensional material / second substrate. The second substrate is a silicon wafer, ITO substrate, sapphire substrate, SiO2 / Si substrate, Al2O3 / Si substrate or the above-mentioned substrate containing another two-dimensional material. (7) The PMMA / two-dimensional material / second substrate obtained in step (6) is soaked in acetone to remove PMMA. After taking it out, it is dried with nitrogen to obtain the two-dimensional material on the second substrate. The solvent-free and precise transfer of the two-dimensional material on the first substrate to the second substrate is completed.

2. The solvent-free, non-destructive, and precise transfer method as described in claim 1, characterized in that: The two-dimensional material is MoS2.

3. The solvent-free, non-destructive, and precise transfer method as described in claim 1, characterized in that: The other two-dimensional material is WSe2.

4. The solvent-free, non-destructive, and precise transfer method as described in claim 1, characterized in that: The etching solution is selected from NaOH solution, KOH solution and HF solution.

5. The solvent-free, non-destructive, and precise transfer method as described in claim 1, characterized in that: The concentration of the PMMA anisole solution is 6-18 wt%.

6. The solvent-free, non-destructive, and precise transfer method as described in claim 1, characterized in that: The thickness of the PMMA support film is 0.5-3 μm.

7. The solvent-free, non-destructive, and precise transfer method according to any one of claims 1 to 6, characterized in that: The sealed reaction vessel is a stainless steel hydrothermal reactor with a polytetrafluoroethylene liner.

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