Solvent-removing lossless accurate transfer method for two-dimensional material

Abstract

The invention discloses a solvent-removing lossless precise transfer method for a two-dimensional material. The method comprises the following steps: carrying out surface functionalization on a silicon wafer by using HMDS (hexamethyldisilazane); carrying out spin coating on the functionalized silicon wafer by adopting a PMMA anisole solution, and drying to form a PMMA supporting film; picking up the PMMA support film by using a heat release adhesive PDMS; pDMS / PMMA is transferred to the surface of a two-dimensional material / first substrate needing to be transferred, PDMS and PMMA are separated after heating, and PMMA covers the surface of the two-dimensional material; the PMMA / two-dimensional material is separated from the first substrate through etching of the etching solution; fishing up the PMMA / two-dimensional material separated from the first substrate by using PDMS; transferring the PMMA / two-dimensional material to a second substrate; and washing away PMMA with acetone, and blow-drying with nitrogen to obtain the product. The two-dimensional material can be cleanly, efficiently and accurately transferred, and the intolerance of the two-dimensional material to an organic solvent and the pollution of the organic solvent can be avoided.

Description

Technical Field

[0001] The present invention belongs to the field of two-dimensional material preparation, and specifically relates to a method for desolvation-free and precise transfer of two-dimensional materials. Background Art

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

[0003] The effective use of two-dimensional materials requires transfer from the growth substrate to different target substrates, for example: transfer to a copper mesh for transmission electron microscopy characterization, transfer to a new two-dimensional material to prepare a homojunction or heterojunction, or transfer to different substrates to adapt to different application scenarios.

[0004] Currently, wet transfer is the most commonly used transfer technology for two-dimensional materials. This method involves spin-coating a polymethyl methacrylate (PMMA) or polycarbonate (PPC) solution on the surface of the two-dimensional material, then baking it on a hot plate to form a solidified support layer, then etching the two-dimensional material in the middle layer, and using a new substrate to pick up the two-dimensional material, and finally cleaning it with acetone to complete the transfer.

[0005] However, the solvents in PMMA or PPC solutions may cause chemical corrosion to two-dimensional materials, so they are not suitable for two-dimensional materials that are not resistant to such solvents. The process of spin coating PMMA or PPC may cause some damage to the two-dimensional materials, resulting in wrinkles, breakage or loss of the materials. In addition, there are still challenges in the process of picking up the two-dimensional materials with a support layer and accurately transferring them to the target material or substrate surface, which seriously limits the use scenarios of two-dimensional materials. Summary of the invention

[0006] The purpose of the present invention is to overcome the defects of the prior art and provide a method for the lossless 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 non-destructive and precise transfer of two-dimensional materials by solvent removal, comprising the following steps:

[0009] (1) Cleaning the silicon wafer;

[0010] (2) placing the cleaned silicon wafer in step (1) into a closed reaction vessel filled with HMDS for heat treatment to obtain an HMDS-functionalized silicon wafer;

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

[0012] (4) picking up the PMMA support film obtained in step (3) with a thermal release adhesive PDMS, and transferring the PMMA support film to the surface of the two-dimensional material on the first substrate, and then tearing off the thermal release adhesive PDMS after heat treatment to obtain PMMA / two-dimensional material / first substrate;

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

[0014] (6) using PDMS to transfer the PMMA / two-dimensional material separated from the first substrate to the cleaned second substrate, and then naturally drying to obtain PMMA / two-dimensional material / second substrate;

[0015] (7) Soak the PMMA / two-dimensional material / second substrate obtained in step (6) in acetone to remove PMMA, take it out and blow it dry with nitrogen to obtain the two-dimensional material located on the second substrate, thereby completing the desolvation and lossless and precise transfer of the two-dimensional material located on the first substrate to the second substrate.

[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] Further 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 substrates containing another two-dimensional material.

[0020] Further 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 PMMA support film has a thickness of 0.5-3 μm.

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

[0025] The beneficial effects of the present invention are:

[0026] 1. The HDMS functionalized silicon wafer spin-coated with a PMMA support film in the present invention can be placed for a long time and is less affected by the environment. The size and shape of the PMMA support film can be prefabricated according to the usage scenario, and quantitative and selective transfer can be performed. This is different from the cumbersome process of the PMMA wet transfer method in the prior art, which requires spin coating and curing before each transfer.

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

[0028] 3. The present invention uses thermal release adhesive PDMS to transfer two-dimensional materials, which can accurately transfer two-dimensional materials to the surfaces of various substrates and has extremely high universality.

[0029] 4. The present invention provides a more convenient, clean and pollution-free transfer method for two-dimensional materials, provides more possibilities for the research of high-quality two-dimensional materials and heterojunctions, and is conducive to the research and development of the next generation of two-dimensional material multifunctional devices and integrated circuits. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a schematic diagram of the process of Example 1 of the present invention.

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

[0034] Figure 5 1 and 2 are the Raman spectrum and fluorescence spectrum of MoS2 / SiO2 in Example 1 of the present invention.

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

[0036] Figure 7 2. Raman spectrum and fluorescence spectrum of WSe2 / SiO2 in Example 2 of the present invention.

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

[0038] Fig. 9 These are the Raman spectrum and fluorescence spectrum of MoS2 / WSe2 / SiO2 in Example 2 of the present invention. DETAILED DESCRIPTION

[0039] The technical solution of the present invention is further illustrated and described below through specific implementation modes in combination with the accompanying drawings.

[0040] It should be noted that the transfer method of the present invention can be applied 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 examples, the SiO2 substrate is a SiO2 / Si substrate having a SiO2 layer with a thickness of 300 nm, the Al2O3 substrate is an Al2O3 / Si substrate having an Al2O3 layer with a thickness of 300 nm, and other materials and reagents used can be obtained from commercial sources. The experimental methods used are conventional methods unless otherwise specified.

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

[0043] The process of this embodiment is as follows Figure 1 As shown, the following steps are included:

[0044] (1) Acetone, isopropanol, ethanol and ultrapure water were used to ultrasonically clean silicon wafers (SiO2 substrates) and Al2O3 / Si substrates with a surface roughness of ±0.5 nm, and each ultrasonic cleaning time was 30 min;

[0045] (2) placing the silicon wafer ultrasonically cleaned in step (1) into a stainless steel hydrothermal reactor with a polytetrafluoroethylene liner filled with HMDS (hexamethyldisilazane) for heat treatment at 80° C. for 10 min to obtain an HMDS-functionalized silicon wafer;

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

[0047] (4) Pick up the PMMA support film with a thermal release adhesive PDMS, and transfer the PMMA support film 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 stage, remove the thermal release adhesive PDMS to obtain PMMA / MoS2 / SiO2, wherein the MoS2 / SiO2 is as follows: Figure 2 , Figure 4 and Figure 5 shown.

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

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

[0050] (7) Use the thermal release adhesive PDMS adhered to the glass slide to pick up the PMMA / MoS2 obtained in step (6), so that one side of PMMA adheres to PDMS, to obtain glass slide / PDMS / PMMA / MoS2.

[0051] (8) On a transfer table, align the glass slide / PDMS / PMMA / MoS2 obtained in step (7) with the marked position of the Al2O3 / Si substrate and stick them on the marked position, then heat treat them at 100°C on the transfer table for 20 min and lift up the glass slide / PDMS to obtain PMMA / MoS2 / Al2O3 / Si.

[0052] (9) Soak the PMMA / MoS2 / Al2O3 / Si obtained in step (7) in acetone for 30 min to remove PMMA, take it out and blow dry it with nitrogen to obtain the Al2O3 / Si substrate at the marked position. Figure 2 and Figure 3 As shown in the figure, the desolvation-free and precise transfer of the two-dimensional material MoS2 on the SiO2 substrate to the Al2O3 / Si substrate is completed.

[0053] Example 2: MoS2 / SiO2 is transferred to the WSe2 surface.

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

[0055] (8) Place the glass slide / PDMS / PMMA / MoS2 obtained in step (7) on a transfer table and place the WSe2 (WSe2 / SiO2, such as Figure 6 and Figure 7 As shown in the figure, the glass slide / PDMS was aligned and attached to the WSe2, and then heat treated at 100°C for 20 min on a transfer table and then lifted up to obtain PMMA / MoS2 / WSe2 / SiO2.

[0056] (9) The PMMA / MoS2 / WSe2 / SiO2 obtained in step (8) was soaked in acetone for 30 min to remove PMMA, and then taken out and dried with nitrogen to obtain MoS2 / WSe2 / SiO2 (such as Figure 8 and Fig. 9 As shown in the figure, the desolvation-free and precise transfer of the two-dimensional material MoS2 on the SiO2 substrate to the WSe2 surface is completed.

[0057] The above description is only a preferred embodiment of the present invention, and therefore cannot be used to limit the scope of the present invention. That is, equivalent changes and modifications made according to the patent scope of the present invention and the contents of the specification should still fall within the scope of the present invention.

Claims

1. A method for non-destructive and precise transfer of two-dimensional materials by solvent removal, characterized in that: The steps include: (1) Cleaning the silicon wafer; (2) placing the cleaned silicon wafer in step (1) into a closed reaction vessel filled with HMDS for heat treatment to obtain an HMDS-functionalized silicon wafer; (3) spin coating and drying the HMDS functionalized silicon wafer obtained in step (2) with a PMMA anisole solution to form a PMMA support film on the HMDS functionalized silicon wafer; (4) picking up the PMMA support film with a thermal release adhesive PDMS, and transferring the PMMA support film to the surface of the two-dimensional material on the first substrate, and then tearing off the thermal release adhesive PDMS after heat treatment to obtain PMMA / two-dimensional material / first substrate; (5) separating the PMMA / two-dimensional material in the PMMA / two-dimensional material / first substrate obtained in step (4) from the first substrate by etching with an etching solution; (6) using PDMS to transfer the PMMA / two-dimensional material separated from the first substrate to the cleaned second substrate, and then naturally drying to obtain PMMA / two-dimensional material / second substrate; (7) Soak the PMMA / two-dimensional material / second substrate obtained in step (6) in acetone to remove PMMA, take it out and blow it dry with nitrogen to obtain the two-dimensional material located on the second substrate, thereby completing the desolvation and lossless and precise transfer of the two-dimensional material located on the first substrate to the second substrate.

2. The method for lossless and precise transfer by solvent removal according to claim 1, characterized in that: The two-dimensional materials include transition metal chalcogenides, hexagonal boron nitride, oxides, phosphorene, silicene, graphene and MXene.

3. The method for non-destructive and precise transfer by solvent removal according to claim 2, characterized in that: The two-dimensional material is MoS2.

4. The method for lossless and precise transfer by solvent removal according to claim 1, characterized in that: The first substrate is a SiO2 / Si substrate, an Al2O3 / Si substrate or a sapphire substrate.

5. The method for lossless and precise transfer by solvent removal according to claim 1, characterized in that: The second substrate is a silicon wafer, an ITO substrate, a sapphire substrate, a SiO2 / Si substrate, an Al2O3 / Si substrate or the above substrates containing another two-dimensional material.

6. The method for lossless and precise transfer by solvent removal according to claim 5, characterized in that: The other two-dimensional material is WSe2.

7. The method for lossless and precise transfer by solvent removal according to claim 1, characterized in that: The etching solution is selected from NaOH solution, KOH solution and HF solution.

8. The method for lossless and precise transfer by solvent removal according to claim 1, characterized in that: The concentration of the PMMA anisole solution is 6-18 wt %.

9. The method for lossless and precise transfer by solvent removal according to claim 1, characterized in that: The thickness of the PMMA support film is 0.5-3 μm.

10. The method for non-destructive and precise transfer by solvent removal according to any one of claims 1 to 9, characterized in that: The sealed container is a stainless steel hydrothermal kettle with a polytetrafluoroethylene liner.

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