Method for preparing high-quality graphene based on bubbling transfer

Abstract

The invention relates to a method for preparing high-quality graphene based on bubbling transfer, which comprises the following steps: S1, spin-coating PMMA (Polymethyl Methacrylate) on the surface of a graphene film on a metal substrate, and attaching PDMS (Polydimethylsiloxane) to form a PDMS / PMMA / graphene / metal substrate sample; s2, respectively connecting the sample in the step S1 and the conductive material with an electrode, enabling the electrode to be in contact with a sugar / salt mixed solution, turning on a power supply to generate bubbles on the sample until graphene is separated from a metal substrate, and cleaning to obtain a PDMS / PMMA / graphene sample; s3, transferring the sample in the step S2 to a target substrate, and drying to form a PDMS / PMMA / graphene / target substrate sample; and S4, heating the sample in the step S3, stripping the PDMS, and removing the PMMA to obtain the high-quality graphene attached to the target substrate. The method provided by the invention is simple and easy to implement, has good repeatability, can improve the quality of graphene subjected to bubbling transfer, and realizes large-area graphene film transfer.

Description

Technical Field

[0001] This invention belongs to the field of two-dimensional material transfer technology, and specifically relates to a method for preparing high-quality graphene based on bubble transfer. Background Technology

[0002] In recent years, the application value of graphene in various fields has been gradually discovered, and the chemical vapor deposition (CVD) growth process for preparing high-quality graphene has also matured. However, the growth of high-quality graphene is often carried out on metal substrates, thus it cannot be directly applied in fields such as microelectronics. Instead, a transfer process is needed to transfer the graphene from the metal substrate to a target substrate suitable for the application scenario. Therefore, achieving non-destructive transfer of graphene is key to realizing the numerous application advantages of graphene in fields such as microelectronics.

[0003] Currently, graphene transfer processes are mainly divided into three types: wet etching transfer, bubble transfer, and dry transfer, each suitable for different scenarios. Wet etching transfer requires the metal substrate to be completely dissolved by the etchant, making it unsuitable for highly stable metals such as platinum and gold. Furthermore, the metal substrate cannot be reused, resulting in material waste and increased costs. Dry transfer requires a weak coupling between the graphene and the metal substrate, and is currently only achievable on a few substrates such as germanium. Compared to wet etching and dry transfer, bubble transfer is adaptable to most metal substrates and is non-destructive, allowing for substrate reuse. During bubble transfer, graphene is peeled off from the metal substrate by the mechanical action of electrochemically generated bubbles. However, the generation and movement of bubbles during bubble peeling are often quite vigorous, potentially causing mechanical damage to the graphene film, forming crystal defects, and thus reducing various properties of graphene.

[0004] Therefore, reducing or even eliminating the impact of bubbling transfer on the quality of graphene films is key to achieving complete transfer of graphene films and their application in fields such as microelectronics. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the purpose of this invention is to provide a method for preparing high-quality graphene based on bubble transfer, which solves the problem that the process of bubble peeling graphene is too violent and seriously affects the quality of graphene after transfer in the prior art.

[0006] This invention provides a method for preparing high-quality graphene based on bubble transfer, comprising the following steps:

[0007] S1. Spin-coat PMMA (polymethyl methacrylate) onto the surface of a graphene film on a metal substrate, and then attach PDMS (polydimethylsiloxane) to form a PDMS / PMMA / graphene / metal substrate sample;

[0008] S2. Connect the PDMS / PMMA / graphene / metal substrate sample and a conductive material to electrodes respectively, so that the electrodes are in contact with the sugar / salt mixed solution. Turn on the power to generate bubbles on the PDMS / PMMA / graphene / metal substrate sample until the graphene separates from the metal substrate. After cleaning, the PDMS / PMMA / graphene sample is obtained.

[0009] S3. Transfer the PDMS / PMMA / graphene sample onto the target substrate and dry it to form a PDMS / PMMA / graphene / target substrate sample;

[0010] S4. Heat the PDMS / PMMA / graphene / target substrate sample and peel off the PDMS. Use acetone to dissolve and remove the PMMA to obtain high-quality graphene attached to the target substrate.

[0011] Preferably, the graphene film in step S1 is grown by chemical vapor deposition.

[0012] Preferably, the metal substrate in step S1 is a metal thin film or a metal foil, and the material of the metal substrate includes one or a combination of platinum, gold, silver, copper, nickel, cobalt, iron, and molybdenum.

[0013] Preferably, the graphene film in step S1 comprises one or a combination of the following conditions:

[0014] The graphene film has at least one layer.

[0015] The graphene film is a continuous graphene film.

[0016] The graphene film is a discrete domain graphene film.

[0017] Preferably, the sugar solute in the sugar / salt mixed solution in step S2 includes one or a combination of glucose, fructose, and sucrose; the concentration of the sugar solute is 0.01–4 mol / L.

[0018] Preferably, in step S2, the salt solute in the sugar / salt mixed solution is any salt that can dissolve in water to form a conductive solution.

[0019] Preferably, the voltage provided by the power supply in step S2 is 0.1 to 30V.

[0020] Preferably, in step S2, the electrode connected to the PDMS / PMMA / graphene / metal substrate sample is either a positive electrode or a negative electrode, and the electrode connected to the conductive material is either a positive electrode or a negative electrode.

[0021] Preferably, the target substrate in step S3 includes, but is not limited to, one of Si substrate, SiO2 / Si substrate, quartz substrate, sapphire substrate, and mica substrate.

[0022] Preferably, the heating temperature in step S4 is 80–300°C.

[0023] Beneficial effects

[0024] The method for preparing high-quality graphene based on bubble transfer provided by this invention is simple, easy to implement, and highly reproducible. It can effectively improve the quality of graphene transferred by bubble transfer and can be used for the transfer of large-area graphene films. Furthermore, the method provided by this invention can effectively weaken the coupling strength between graphene and metal substrate through the adsorption of sugar molecules on the graphene surface, making the graphene easier to be bubble-peeled, thereby improving the quality of the transferred graphene. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the process for preparing high-quality graphene based on bubble transfer in a specific embodiment of the present invention.

[0026] Figure 2 The images shown are optical microscope photographs (a) and Raman spectra (b) of the graphene film / SiO2 / Si substrate sample prepared in Example 1 of this invention.

[0027] Figure 3 The images shown are optical microscope images (a) of the graphene film / SiO2 / Si substrate sample prepared in Example 2 of this invention, and Raman spectra of the region shown in the images, including intensity mapping of the graphene D peak (b), the graphene G peak (c), and the graphene 2D peak (d).

[0028] Figure 4 The images show an optical microscope photograph (a) and a Raman spectrum (b) of the graphene film / SiO2 / Si substrate sample prepared in Comparative Example 1 of this invention. Detailed Implementation

[0029] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0030] See Figure 1 This invention provides a method for preparing high-quality graphene based on bubble transfer, the method comprising the following steps:

[0031] S1. Spin-coat PMMA onto the graphene surface of a metal substrate, and then attach PDMS to form a PDMS / PMMA / graphene / metal substrate sample;

[0032] S2. Connect the PDMS / PMMA / graphene / metal substrate sample to one electrode, select a conductive material as the other electrode, contact the two with a sugar / salt mixed solution, turn on the power to generate bubbles on the PDMS / PMMA / graphene / metal substrate sample until the graphene separates from the metal substrate, and after cleaning, obtain the PDMS / PMMA / graphene sample.

[0033] S3. Transfer the PDMS / PMMA / graphene sample onto the target substrate and dry it to form a PDMS / PMMA / graphene / target substrate sample;

[0034] S4. Heat the PDMS / PMMA / graphene / target substrate sample and peel off the PDMS. Use acetone to dissolve and remove the PMMA to obtain high-quality graphene attached to the target substrate.

[0035] Specifically, the method for preparing high-quality graphene based on bubble transfer in the specific embodiments of the present invention is simple, easy to implement, and has good repeatability, and can effectively improve the quality of bubble-transferred graphene.

[0036] As an example, the graphene on the metal substrate described in step S1 is grown by chemical vapor deposition.

[0037] As an example, the metal substrate in step S1 is a metal thin film or a metal foil, and the composition of the metal substrate includes one or a combination of platinum, gold, silver, copper, nickel, cobalt, iron, and molybdenum.

[0038] As an example, the graphene film in step S1 has at least one layer.

[0039] As an example, the graphene film in step S1 is a continuous graphene film.

[0040] As an example, the graphene film in step S1 is a discrete domain graphene film.

[0041] As an example, in the mixed solution described in step S2, the sugar solute includes one or a combination of glucose, fructose, and sucrose, and the concentration of the sugar solute is 0.01 to 4 mol / L.

[0042] Specifically, the concentration of the sugar solute in the mixed solution can be any value within a range, such as 0.01 mol / L, 0.5 mol / L, 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L, 3 mol / L, 3.5 mol / L, or 4 mol / L, and can be adjusted according to the actual situation. If a relatively low concentration of glucose solution is used, the voltage needs to be reduced to ensure good quality graphene transfer. Experiments with too low a sugar concentration yield similar results to those without added sugar. Figure 4 When the sugar concentration is too high, the conductivity of the solution will decrease significantly, making it difficult to achieve bubbling transfer and thus the experiment cannot be completed.

[0043] As an example, in the mixed solution described in step S2, the type of salt solute is any salt that can be dissolved in water to form a conductive solution.

[0044] Specifically, the types of salt solutes in the mixed solution can include various salts such as NaOH, H2SO4, NaCl, and K2CO3. The types and concentrations of salt solutes should be sufficient to ensure that the conductivity of the mixed solution is adequate to achieve the bubbling transfer of graphene; there are no further restrictions here.

[0045] As an example, the voltage provided by the power supply in step S2 is 0.1 to 30V.

[0046] Specifically, the voltage provided by the power supply can be any value within a range such as 0.1V, 1V, 5V, 10V, 15V, 20V, 25V, or 30V, and can be adjusted according to actual needs. The voltage used needs to cause bubbles to be generated at the electrodes in the mixed solution.

[0047] As an example, the electrode connected to the sample in step S2 is either a positive or negative electrode, and correspondingly, the electrode connected to the conductive material is either a negative or positive electrode.

[0048] In a specific embodiment of the present invention, cleaning is performed by using deionized water to clean the mixed solution residue on the lower surface of the graphene film. The specific number of cleaning cycles is not excessively limited here.

[0049] As an example, the target substrate mentioned in step S3 includes one of Si substrate, Si / SiO2 substrate, quartz substrate, sapphire substrate, and mica substrate.

[0050] As an example, the heating temperature in step S4 is 80–300°C.

[0051] In a specific embodiment of the present invention, heating is used to de-stick the PDMS surface so that it can be peeled off from the PMMA.

[0052] The high quality described in this invention is reflected in the following aspects: the effect of adding sugar can, on the one hand, improve the integrity of the graphene film and reduce damage, as shown in the attached light microscope image; on the other hand, it can improve the crystallinity of graphene, as shown in the attached Raman spectrum.

[0053] To better understand the method for preparing high-quality graphene based on bubble transfer in this invention, the method is described below with reference to specific embodiments. It should be noted that these embodiments are merely descriptive and do not limit the invention in any way.

[0054] Example 1

[0055] This embodiment provides a method for preparing high-quality graphene based on bubble transfer, the method comprising the following steps:

[0056] S1. Prepare a monolayer graphene film grown by chemical vapor deposition on a Pt substrate. Use a spin coater to spin coat PMMA on the graphene surface of the Pt substrate at a speed of 2000 r / min. Then cover the PMMA surface with a 200 μm thick layer of PDMS to form a PDMS / PMMA / graphene / Pt substrate sample.

[0057] S2. Prepare a mixed solution of 0.2 mol / L glucose and 1 mol / L NaOH. Connect the PDMS / PMMA / graphene / Pt substrate sample to the positive terminal of the power supply and connect the Pt electrode to the negative terminal of the power supply. Make both the positive and negative terminals of the power supply contact the mixed solution. Turn on the power supply and set the voltage to 8V to generate bubbles on the PDMS / PMMA / graphene / Pt substrate sample until the graphene separates from the Pt substrate. Then wash the lower surface of the graphene with deionized water 5 times to obtain the PDMS / PMMA / graphene sample.

[0058] S3. Transfer the PDMS / PMMA / graphene sample onto a SiO2 / Si substrate and allow it to dry to form a PDMS / PMMA / graphene / SiO2 / Si substrate sample.

[0059] S4. The PDMS / PMMA / graphene / SiO2 / Si substrate sample was heated at 110℃ and the PDMS was peeled off. Then, the PMMA was removed by dissolving it with acetone to obtain graphene on the SiO2 / Si substrate.

[0060] See Figure 2 The images shown are optical microscope images and Raman spectroscopy results of the graphene / SiO2 / Si substrate prepared in Example 1. Figure 2 Image a is an optical microscope image (500x magnification) of a graphene film / SiO2 / Si substrate sample. Figure 2b shows the Raman spectra at three different locations on the graphene film / SiO2 / Si substrate sample. As can be seen from the figure, the graphene film obtained by this method has a complete and undamaged structure over a large area, and the D peak of the graphene Raman spectrum is not obvious, indicating that this method can effectively improve the quality of graphene.

[0061] Example 2

[0062] This embodiment provides a method for preparing high-quality graphene based on bubble transfer, the method comprising the following steps:

[0063] S1. Prepare monolayer graphene domains grown by chemical vapor deposition on a Cu substrate. Use a spin coater to spin coat PMMA onto the graphene surface on the Cu substrate at a speed of 1500 r / min. Then cover the PMMA surface with a 100 μm thick layer of PDMS to form a PDMS / PMMA / graphene / Cu substrate sample.

[0064] S2. Prepare a mixed solution of 0.4 mol / L glucose and 1.5 mol / L KOH. Connect the PDMS / PMMA / graphene / Cu substrate sample to the negative terminal of the power supply and connect the graphite electrode to the positive terminal of the power supply. Make both the positive and negative terminals of the power supply contact the mixed solution. Turn on the power supply and set the voltage to 10V to generate bubbles on the PDMS / PMMA / graphene / Cu substrate sample until the graphene separates from the Cu substrate. Then wash the lower surface of the graphene with deionized water 7 times to obtain the PDMS / PMMA / graphene sample.

[0065] S3. Transfer the PDMS / PMMA / graphene sample onto a SiO2 / Si substrate and allow it to dry to form a PDMS / PMMA / graphene / SiO2 / Si substrate sample.

[0066] S4. The PDMS / PMMA / graphene / SiO2 / Si substrate sample was heated at 140℃ and the PDMS was peeled off. Then, the PMMA was removed by dissolving it with acetone to obtain graphene on the SiO2 / Si substrate.

[0067] See Figure 3 The images shown are optical microscope images and Raman spectroscopy results of the graphene film / SiO2 / Si substrate sample prepared in Example 2 of this invention. Figure 3 Image a is an optical microscope image (1000x magnification) of a graphene film / SiO2 / Si substrate sample. Figure 3 b is Figure 3 Intensity mapping of the graphene D peak in the Raman spectrum of region a. Figure 3 c is Figure 3 Intensity mapping of the graphene G peak in the Raman spectrum of region a Figure 3 d is Figure 3 The Raman spectrum of region a shows the intensity mapping of the 2D peak of graphene. As can be seen from the figure, the graphene domain structure obtained by this method is complete and undamaged. The D peaks of the Raman spectra of the monolayer and bilayer regions in the graphene domains are not obvious. The intensities of the G peak and 2D peak are consistent with the characteristics of high-quality monolayer and bilayer graphene, indicating that this method can effectively improve the quality of graphene.

[0068] Comparative Example 1

[0069] This comparative example provides a commonly used method for bubbling transfer of graphene in the prior art, and the specific steps are as follows:

[0070] S1. Prepare a monolayer graphene film grown by chemical vapor deposition on a Pt substrate. Use a spin coater to spin coat PMMA on the graphene surface of the Pt substrate at a speed of 2000 r / min. Then cover the PMMA surface with a 200 μm thick layer of PDMS to form a PDMS / PMMA / graphene / Pt substrate sample.

[0071] S2. Prepare a 1 mol / L NaOH solution. Connect the PDMS / PMMA / graphene / Pt substrate sample to the positive terminal of the power supply and connect the Pt electrode to the negative terminal of the power supply. Contact both the positive and negative terminals of the power supply with the NaOH solution. Turn on the power supply and set the voltage to 10V to generate bubbles on the PDMS / PMMA / graphene / Pt substrate sample until the graphene separates from the Pt substrate. Then wash the lower surface of the graphene with deionized water 5 times to obtain the PDMS / PMMA / graphene sample.

[0072] S3. Transfer the PDMS / PMMA / graphene sample onto a SiO2 / Si substrate and allow it to dry to form a PDMS / PMMA / graphene / SiO2 / Si substrate sample.

[0073] S4. The PDMS / PMMA / graphene / SiO2 / Si substrate sample was heated at 120℃ and the PDMS was peeled off. Then, the PMMA was removed by dissolving it with acetone to obtain graphene on the SiO2 / Si substrate.

[0074] See Figure 4 Optical microscope images and Raman spectroscopy results of the graphene / SiO2 / Si substrate prepared in Comparative Example 1 are shown. Figure 4 Image a is an optical microscope image (500x magnification) of a graphene film / SiO2 / Si substrate sample. Figure 4 b shows the Raman spectra at three different locations on the graphene film / SiO2 / Si substrate sample. As can be seen from the figure, the graphene film obtained by this method has obvious damage, and the Raman spectrum shows a clear D peak of graphene, indicating that the quality of graphene is poor.

[0075] The optical microscope images and Raman spectra of the graphene film / SiO2 / Si substrate samples prepared in Example 1 and Comparative Example 1 show that adding sugar solutes to the electrolyte solution can effectively weaken the coupling strength between graphene and the metal substrate through the adsorption of sugar molecules on the graphene surface, making the graphene easier to peel off by bubbling, significantly reducing the damage of the graphene film, improving the crystal quality of graphene, and thus achieving the preparation of high-quality graphene.

[0076] In summary, the method for preparing high-quality graphene based on bubble transfer provided by this invention is simple, easy to implement, and highly reproducible. It can effectively improve the quality of graphene obtained through bubble transfer and can be used for the transfer of large-area graphene films. Therefore, this invention effectively overcomes the various shortcomings of existing technologies and has high industrial application value.

Claims

1. A method for preparing high-quality graphene based on bubble transfer, comprising the following steps: S1. PMMA is spin-coated onto the surface of a graphene film on a metal substrate, and then PDMS is attached to form a PDMS / PMMA / graphene / metal substrate sample; S2. Connect the PDMS / PMMA / graphene / metal substrate sample and a conductive material to electrodes respectively, so that the electrodes are in contact with the sugar / salt mixed solution. Turn on the power to generate bubbles on the PDMS / PMMA / graphene / metal substrate sample until the graphene separates from the metal substrate. After cleaning, the PDMS / PMMA / graphene sample is obtained. S3. Transfer the PDMS / PMMA / graphene sample onto the target substrate and dry it to form a PDMS / PMMA / graphene / target substrate sample; S4. Heat the PDMS / PMMA / graphene / target substrate sample and peel off the PDMS. Use acetone to dissolve and remove the PMMA to obtain high-quality graphene attached to the target substrate.

2. The method for preparing high-quality graphene based on bubble transfer according to claim 1, characterized in that, The graphene film described in step S1 is grown by chemical vapor deposition.

3. The method for preparing high-quality graphene based on bubble transfer according to claim 1, characterized in that, The metal substrate mentioned in step S1 is a metal thin film or a metal foil, and the material of the metal substrate includes one or a combination of platinum, gold, silver, copper, nickel, cobalt, iron, and molybdenum.

4. The method for preparing high-quality graphene based on bubble transfer according to claim 1, characterized in that, The graphene film described in step S1 includes one or a combination of the following conditions: The graphene film has at least one layer. The graphene film is a continuous graphene film. The graphene film is a discrete domain graphene film.

5. The method for preparing high-quality graphene based on bubble transfer according to claim 1, characterized in that, The sugar solute in the sugar / salt mixed solution in step S2 includes one or a combination of glucose, fructose, and sucrose; the concentration of the sugar solute is 0.01 to 4 mol / L.

6. The method for preparing high-quality graphene based on bubble transfer according to claim 1, characterized in that, In step S2, the salt solute in the sugar / salt mixed solution is any salt that dissolves in water to form a conductive solution.

7. The method for preparing high-quality graphene based on bubble transfer according to claim 1, characterized in that, The voltage provided by the power supply in step S2 is 0.1 to 30V.

8. The method for preparing high-quality graphene based on bubble transfer according to claim 1, characterized in that, The target substrate mentioned in step S3 includes one of the following: Si substrate, SiO2 / Si substrate, quartz substrate, sapphire substrate, and mica substrate.

9. The method for preparing high-quality graphene based on bubble transfer according to claim 1, characterized in that, The heating temperature in step S4 is 80–300°C.

Images