A graphene transfer method based on electric assistance and water phase change

Abstract

A graphene transfer method based on electric assistance and water phase change utilizes ice to transfer copper-based graphene. During the transfer process, cuprous oxide intercalation is used to weaken the adhesion strength between graphene and the original substrate, and an external electric field is introduced to enhance the adhesion strength between ice and graphene, ensuring the complete transfer of graphene and enabling the transfer of graphene to any substrate. This invention achieves large-scale, pollution-free, and high-quality transfer of graphene to any substrate, which can reduce production costs and environmental pollution, while also improving the performance of transferred graphene and promoting the widespread application of graphene in various fields.

Description

Technical Field

[0001] This invention relates to the field of graphene transfer technology, specifically to a graphene transfer method based on electro-assisted and water phase change. Background Technology

[0002] Graphene plays an increasingly important role in many fields (such as environmental monitoring, biomedicine, energy, and electronic devices) due to its unique electronic, optical, mechanical, and thermal properties. However, the existing methods for large-scale, low-cost production of graphene, especially monolayer graphene films, are mainly chemical vapor deposition. The limitation of this method is that it can only use metal substrates such as copper, nickel, and platinum as the growth substrate for graphene. Therefore, this production method is greatly limited in practical applications, and graphene must be transferred from the metal substrate to the target substrate before it can be used further.

[0003] Traditional graphene transfer methods (DOI:10.1039 / C2NR31317K) typically involve etching a metal substrate and using polymers such as polymethyl methacrylate (PMMA) as transfer media. These methods are not only costly, but polymer contamination can also negatively impact the performance of two-dimensional materials, hindering large-scale application. While some methods have been proposed using clean media such as ice to transfer two-dimensional materials (DOI:10.1002 / adma.202210503), reducing contamination sources, these methods can only transfer micron-sized two-dimensional materials and are only suitable for transferring two-dimensional materials on smooth mica or silica surfaces. These surfaces have low adhesion to two-dimensional materials, making it impossible to achieve clean and intact transfer of graphene from rough metal substrates. Summary of the Invention

[0004] In order to overcome the shortcomings of the prior art, the present invention aims to provide a graphene transfer method based on electric assistance and water phase change, so as to realize the large-scale, pollution-free, and high-quality transfer of copper-based graphene to any substrate, reduce production costs and environmental pollution, and promote the widespread application of graphene in various fields.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A graphene transfer method based on electric assistance and water phase change is proposed. Ice is used as the transfer medium to transfer copper-based graphene. During the transfer process, cuprous oxide intercalation is used to weaken the adhesion strength between graphene and the original substrate. An external electric field is introduced to enhance the adhesion strength between ice and graphene, ensuring that ice and graphene can make full contact and enabling the graphene to be transferred completely.

[0007] The graphene transfer method based on electro-assisted and aqueous phase change includes the following steps:

[0008] Step 1: Prepare the sample to be transferred. The sample consists of a copper substrate 2 and graphene 1 on it. Place the graphene 1 on the copper substrate 2 on the surface of the water in a water tank 4 filled with distilled water 3 and heat for 9-11 hours. Insert cuprous oxide 5 intercalation between the graphene 1 and the copper substrate 2. The cuprous oxide 5 will grow at the interface between the graphene 1 and the copper substrate 2, generating initial cracks and reducing the adhesion between the graphene 1 and the copper substrate 2.

[0009] Step 2: Place a mold 6 on the oxidized sample to be transferred, and add distilled water 3 to the mold 6. Then place the sample to be transferred with the mold 6 and distilled water 3 in the parallel electrode plate 7, so that the sample to be transferred is in a parallel electric field environment. At the same time, use the semiconductor cooling plate 8 to lower the temperature to below -30℃, so that the distilled water 3 becomes ice column 9.

[0010] Step 3: After the distilled water 3 has completely frozen into ice column 9, the ice column 9 with graphene 1 is separated from the upper surface of the copper substrate 2 by mechanical force. At this time, the graphene 1 is adhered to the bottom of the ice column 9.

[0011] Step 4: Quickly place the ice column 9 with graphene 1 attached onto the target substrate 10. After the ice column 9 is removed, the graphene 1 is transferred to any target substrate 10.

[0012] The cooling environment in the second step is provided by the semiconductor cooling plate 8. The cooling process starts from the upper surface of graphene 1, reducing the problem of decreased bonding force at the interface between ice column 9 and graphene 1 caused by volume expansion.

[0013] The external electric field in the second step promotes the complete wetting of distilled water 3 onto graphene 1 on copper substrate 2, thereby increasing the contact force between ice column 9 and graphene 1.

[0014] The removal of ice column 9 in the third step is accomplished by freeze-drying to avoid the appearance of liquid water.

[0015] The target substrate 10 includes PDMS substrate, silicon substrate, Teflon, silicon, silicon dioxide, etc.

[0016] Compared with existing technologies, this invention has the following advantages: Because this invention uses an external electric field to enhance the bonding strength between ice and graphene, and introduces cuprous oxide intercalation to reduce the bonding strength between graphene and the copper substrate, graphene can be directly and completely peeled off from the copper substrate using ice columns. The graphene transfer method involved in this invention does not involve the introduction of any other chemical substances besides water during the transfer process. Therefore, the transferred graphene has the advantages of high quality, good continuity, and no pollution, solving the problem of clean transfer of graphene onto metal substrates. Attached Figure Description

[0017] Figure 1This is a schematic diagram of graphene 1 on the surface of the copper substrate 2 before transfer in the embodiment.

[0018] Figure 2 This is a schematic diagram illustrating the process of growing cuprous oxide on a copper substrate 2 with graphene 1 grown on it in a water tank 4 filled with distilled water 3, as an example.

[0019] Figure 3 This is a schematic diagram of graphene 1 and grown cuprous oxide 5 distributed on the surface of copper substrate 2 in an embodiment.

[0020] Figure 4 The diagram illustrates how graphene 1, mold 6, and ice column 9 are placed on semiconductor cold plate 8 and in an external electric field formed by parallel electrode plate 7.

[0021] Figure 5 This is a schematic diagram illustrating the process of peeling ice column 9 / graphene 1 from copper substrate 2 in an embodiment.

[0022] Figure 6 This is a schematic diagram of the transfer of ice column 9 / graphene 1 onto the target substrate 10 in an embodiment.

[0023] Figure 7 This is a schematic diagram showing the successful transfer of graphene 1 onto the target substrate 10 after the removal of the ice column 9 and the removal of the mold 6.

[0024] Figure 8 The transfer effect of Example 1 is shown in (a), (b), (c), and (d), where (a), (b), (c), and (d) represent the transfer effects without any assistance, with electric field assistance, with cuprous oxide assistance, and with electric field and cuprous oxide assistance, respectively.

[0025] Figure 9 This is a schematic diagram of a large-area intact graphene 1 on a copper substrate 2 in Example 2.

[0026] Figure 10 The image shows the transfer effect of Example 2, where (a) is a light microscopy image of the transferred large area of ​​graphene, (b) is a magnified view of a part, and (c) is an electron microscopy image. Detailed Implementation

[0027] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0028] Example 1: A graphene transfer method based on electro-assisted and water phase change, using a silicon substrate as the target substrate, includes the following steps:

[0029] Step 1: Prepare a patterned graphene sample to be transferred, such as... Figure 1 As shown, the sample to be transferred consists of a copper substrate 2 and graphene 1 on it; as Figure 2As shown, graphene 1 on copper substrate 2 is placed on the surface of water in tank 4 filled with distilled water 3 and heated for 10 hours, inserting a cuprous oxide intercalation layer between graphene 1 and copper substrate 2; as shown Figure 3 As shown, cuprous oxide 5 will grow at the interface between graphene 1 and copper substrate 2, generating initial cracks and reducing the adhesion between graphene 1 and copper substrate 2; otherwise, graphene 1 cannot be separated from copper substrate 2.

[0030] Step 2: As Figure 4 As shown, a mold 6 with a suitable cross-sectional size is placed on the oxidized sample to be transferred, and distilled water 3 is added to the mold 6. Then, the sample to be transferred, with the mold 6 and distilled water 3, is placed in a parallel electrode plate 7, so that the sample to be transferred is in a parallel electric field environment. At the same time, a semiconductor cooling plate 8 is used to lower the temperature to below -30°C, so that the distilled water 3 turns into ice column 9. The cooling environment is provided by the semiconductor cooling plate 8, and its cooling process starts from the upper surface of graphene 1, reducing the problem of decreased bonding force at the interface between ice column 9 and graphene 1 due to volume expansion during the process of distilled water freezing. The external electric field promotes the complete wetting of water on graphene 1 on copper substrate 2, improves the contact force between ice column 9 and graphene 1, and increases the probability of successful transfer of graphene 1.

[0031] Step 3: As Figure 5 As shown, after the distilled water 3 is completely frozen into ice column 9, the ice column 9 with graphene 1 is separated from the upper surface of the copper substrate 2 by mechanical force. At this time, the graphene 1 is adhered to the bottom of the ice column 9. The removal process of the ice column 9 is completed by freeze drying to avoid the appearance of liquid water and improve the quality of transferred graphene.

[0032] Step 4: As Figure 6 As shown, an ice column 9 with graphene 1 adhered to it is quickly placed on the target substrate 10. After the ice column 9 is removed, the graphene 1 is transferred to any target substrate 10, and the resulting product is as shown. Figure 7 As shown.

[0033] The transferred graphene was characterized using instruments such as optical microscope, scanning electron microscope, atomic force microscope, and Raman spectrometer; (Refer to...) Figure 8 The results show that (a) represents the transfer effect without an electric field or cuprous oxide intercalation, resulting in severe defects in the transferred graphene sheets; (b) and (c) represent the transfer effects with only electric field assistance and only cuprous oxide assistance, respectively. While most graphene sheets can be transferred, significant tearing occurs when only an electric field is used; with only cuprous oxide assistance, some edges are missing; and when both cuprous oxide and electric field assistance are used simultaneously, as shown in (d), the transferred graphene pattern exhibits the highest integrity. These results demonstrate that the auxiliary method proposed in this invention is crucial for the successful transfer of copper-based graphene.

[0034] Example 2: The target substrate was a PDMS substrate. A graphene transfer method based on electro-assisted and aqueous phase change was used to achieve the transfer of large-area graphene from a copper substrate to a PDMS substrate. The sample to be transferred was as follows: Figure 9 As shown in the figure, the heating time for placing the graphene 1 on the copper substrate 2 on the surface of the water in the water tank 4 filled with distilled water 3 in the first step of Example 1 was changed to 9 hours; the other steps were the same as in Example 1, and the effect of this example is as described above. Figure 10 Among them, (a) is a schematic diagram of the boundary of the transferred large-area graphene, (b) is a further magnified image, and (c) is a local SEM image, all of which show that the transferred graphene has high quality; the above results show that the transfer method proposed in this invention also has the ability to transfer large-area graphene.

[0035] Example 3: The target substrate is a Teflon substrate. A graphene transfer method based on electro-assisted and water phase change was used to realize the transfer of large-area graphene from a copper substrate to a Teflon substrate. The heating time of the graphene 1 on the copper substrate 2 placed on the water surface of the water tank 4 filled with distilled water 3 in the first step of Example 1 was changed to 11 hours. The other steps are the same as in Example 1. The effect of this example is similar to that of Example 2.

Claims

1. A graphene transfer method based on electro-assisted and aqueous phase change, characterized in that: Using ice as a transfer medium, copper-based graphene is transferred. During the transfer process, cuprous oxide intercalation is used to weaken the adhesion strength between graphene and the original substrate. An external electric field is introduced to enhance the adhesion strength between ice and graphene, ensuring that ice and graphene can make full contact and that graphene can be transferred completely. The graphene transfer method based on electro-assisted and aqueous phase change includes the following steps: Step 1: Prepare the sample to be transferred. The sample to be transferred consists of a copper substrate (2) and graphene (1) on it. Place the graphene (1) on the copper substrate (2) on the surface of the water in a water tank (4) filled with distilled water (3) and heat for 9-11 hours. Insert cuprous oxide intercalation between the graphene (1) and the copper substrate (2). Cuprous oxide (5) will grow in the interface between the graphene (1) and the copper substrate (2), generating initial cracks and reducing the adhesion between the graphene (1) and the copper substrate (2). Step 2: Place a mold (6) on the oxidized sample to be transferred, and add distilled water (3) to the mold (6). Then place the sample to be transferred with the mold (6) and distilled water (3) in the parallel electrode plate (7) so that the sample to be transferred is in a parallel electric field environment. At the same time, use a semiconductor cooling plate (8) to lower the temperature to below -30°C so that the distilled water (3) becomes an ice column (9). The cooling environment is provided by the semiconductor cooling plate (8). The cooling process starts from the upper surface of the graphene (1) to reduce the problem of decreased bonding force at the interface between the ice column (9) and the graphene (1) caused by volume expansion. Step 3: After the distilled water (3) has completely frozen into ice pillars (9), the ice pillars (9) with graphene (1) are separated from the upper surface of the copper substrate (2) by mechanical force. At this time, the graphene (1) is adhered to the bottom of the ice pillars (9). Step 4: Quickly place the ice column (9) with graphene (1) attached onto the target substrate (10). After the ice column (9) is removed, the graphene (1) is transferred to any target substrate (10). The removal process of the ice column (9) is completed by freeze drying to avoid the appearance of liquid water.

2. The method according to claim 1, characterized in that: The effect of the external electric field in the second step is to promote the complete wetting of water on the graphene (1) on the copper substrate (2), ensure that the ice column (9) is in complete contact with the graphene, and enhance the contact force between the ice column (9) and the graphene (1).

3. The method according to claim 1, characterized in that: The target substrate (10) is a PDMS substrate, a silicon substrate, or a Teflon substrate.

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