A two-dimensional material-liquid field effect two-dimensional material transfer method

Abstract

This invention relates to the field of two-dimensional material preparation technology, specifically to a two-dimensional material-liquid field effect method for transferring two-dimensional materials, comprising: Step 1, placing a target substrate on a two-dimensional material, wherein the two-dimensional material is grown on a growth substrate, and drying the target substrate; Step 2, cutting the target substrate to expose the interface between the target substrate and the two-dimensional material; Step 3, continuously dripping liquid into the interface between the target substrate and the two-dimensional material. This invention does not introduce chemical contamination during the transfer process; it can significantly improve the ability of two-dimensional materials to transfer to a target substrate; it can self-drive the improvement of two-dimensional material transfer capability without the need for external electric field assistance; it does not involve high-temperature annealing or other methods, has low requirements for environmental humidity and cleanliness, and is widely applicable to various two-dimensional materials; it is simple to operate and low in cost. Considering the above advantages, this invention has good application prospects in the field of two-dimensional material application technology.

Description

Technical Field

[0001] This invention relates to the field of two-dimensional material application technology, and specifically to a two-dimensional material transfer method based on a two-dimensional material-liquid field effect. Background Technology

[0002] Two-dimensional materials, with their nanoscale thickness and excellent optoelectronic properties, have attracted much attention in the energy field and can be widely used in logic devices, catalysis, and solar cells. Currently, most two-dimensional materials require growth on specific substrates, which limits their further application due to the challenge of transferring them from the original substrate to the target substrate. Existing transfer methods can be mainly divided into three categories: dry transfer, wet transfer, and liquid bridge transfer (ACS nano, 2010, 4(2): 1108-1114, ACS nano, 2015, 9(5): 4726-4733). Dry transfer typically uses adhesive polymers, taking advantage of the strong adhesion between the adhesive polymer and the two-dimensional material to bond the two-dimensional material from the original substrate to the adhesive polymer. Then, the adhesive polymer and the two-dimensional material are bonded together to the target substrate, and finally, the adhesive polymer is peeled off to complete the transfer. Dry transfer involves mechanical extrusion during the transfer process, which can easily damage the two-dimensional material. It also introduces residual adhesive onto the target substrate during the transfer process, affecting material properties. Wet transfer typically involves spin-coating a polymer support layer (e.g., polymethyl methacrylate) onto the original substrate, then using chemical etching to remove the growth substrate, leaving the polymer and two-dimensional material. This is then retrieved using the target substrate, and the polymer support layer is removed using chemical reagents (e.g., acetone) to finally complete the material transfer. However, wet transfer involves toxic chemical reagents during the transfer process, requiring a high-quality experimental environment. Furthermore, the etching process and the removal of the polymer support layer inevitably introduce chemical residues that can affect the properties of the two-dimensional material.

[0003] Liquid bridge transfer involves spin-coating a hydrophobic polymer onto a hydrophilic substrate, then immersing it at a specific angle in deionized water. Water molecules penetrate the interface between the hydrophilic substrate and the hydrophobic polymer, reducing the adhesion between the substrate and the two-dimensional material (2D material). The polymer then separates from the substrate, and the 2D material detaches along with the polymer during this process. However, liquid bridge transfer requires effective interaction between the substrate, the 2D material, and water, limiting its applicability. Relying solely on water interaction for transfer is time-consuming, and its transfer efficiency is lower than dry and wet transfer methods. These limitations hinder the widespread application of 2D materials. Therefore, achieving high-quality, efficient, and complete transfer of 2D materials from the original substrate to the target substrate is of great significance. Summary of the Invention

[0004] To address the above problems, this invention provides a two-dimensional material transfer method based on a two-dimensional material-liquid field effect, comprising the following steps:

[0005] Step 1: Place the target substrate on the two-dimensional material, which is grown on the growth substrate, and dry the target substrate;

[0006] Step 2: Cut open the target substrate to expose the interface between the target substrate and the two-dimensional material;

[0007] Step 3: Continuously drip the liquid into the interface between the target substrate and the two-dimensional material.

[0008] Furthermore, after step 2, a first electrode and a second electrode are respectively disposed on the other side of the target substrate and the growth substrate, and the first electrode and the second electrode are connected in an external circuit; the liquid also comes into contact with the first electrode and the second electrode.

[0009] Furthermore, the two-dimensional material is molybdenum disulfide, and the growth substrate is sapphire.

[0010] Furthermore, in step 2, a scalpel is used to cut open the target base and the area around the target base is cut open.

[0011] Furthermore, after step 2, plasma cleaning is also included.

[0012] Furthermore, in step 3, the liquid is deionized water, methanol, ethanol, or liquid metal.

[0013] Furthermore, in step 3, the target substrate and the growth substrate are tilted.

[0014] Furthermore, the target substrate is prepared from PDMS and a curing agent.

[0015] Furthermore, in step 1, the method for setting the target substrate is spin coating.

[0016] Furthermore, the number of swirls is 3.

[0017] The beneficial effects of this invention are:

[0018] The working principle of this invention is as follows: Polymer materials have high electronegativity and a strong ability to attract electrons, while two-dimensional materials easily lose electrons, creating an electrostatic field at their interface. When the initially falling water droplet reaches the edge of the air gap between the two, driven by capillary wetting force, water continuously penetrates into the air gap between the polymer material layer and the two-dimensional material layer, forming a liquid layer. The liquid layer and the interface between the two materials acquire opposite charges, forming two electrostatic fields. As subsequent water droplets rub against the two-dimensional material, a voltage is generated and accumulated between the electrostatic fields of the two-dimensional material and the liquid layer through a circuit. Due to the extremely thin thickness of the two-dimensional material, the charge gap between the double layer of the liquid layer and the two-dimensional material is extremely small, which can be equivalent to a microcapacitor. The entire system can be equivalent to a dynamic charging and discharging process of the equivalent capacitance between the polymer material, the liquid layer, and the two-dimensional material layer. A momentary high voltage will be generated at the equivalent capacitance interface between the liquid layer and the two-dimensional material. This voltage will cause the two-dimensional material to tend to detach from the original substrate and adsorb onto the droplet, thereby enhancing the transfer capability. The beneficial effects of this invention are as follows: (1) This invention can realize the transfer of most two-dimensional materials to the target substrate, and has high versatility; (2) No chemical pollution is introduced during the transfer process; (3) It can significantly improve the ability of two-dimensional materials to be transferred to the target substrate; (4) It can self-drive the improvement of the transfer ability of two-dimensional materials without the need for external electric field assistance; (5) It does not involve high-temperature annealing or other methods, has low requirements for environmental humidity and cleanliness, and is widely applicable to various two-dimensional materials; (6) It is simple to operate and low in cost. During the transfer, the triboelectricity between the two-dimensional material and the water droplet can be measured, which can expand the research on the electrical properties of two-dimensional materials. In summary, this invention has good application prospects in the field of two-dimensional material application technology.

[0019] The present invention will now be described in further detail with reference to the accompanying drawings. Attached Figure Description

[0020] Figure 1 The potential difference induced at the interface between the two-dimensional material and the liquid layer (a) and the induced charge at the interface between the two-dimensional material and the liquid layer (b) are when the droplet falls only on the two-dimensional material.

[0021] Figure 2 This is a schematic diagram of a two-dimensional material transfer mechanism based on the two-dimensional material / liquid field effect.

[0022] Figure 3 The potential difference induced at the interface of the two-dimensional material / liquid layer (a) and the induced charge at the interface of the two-dimensional material / liquid layer (b) are as follows: when the liquid drips not only onto the two-dimensional material, but also onto the first electrode and the second electrode.

[0023] Figure 4 These are photos before and after the transfer of molybdenum disulfide: (a) before transfer, (b) after transfer.

[0024] In the figure: 1. Two-dimensional material; 2. Growth substrate; 3. Target substrate; 4. First electrode; 5. Second electrode; 6. Liquid layer. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided with reference to the accompanying drawings and embodiments.

[0026] This invention provides a two-dimensional material transfer method based on the two-dimensional material-liquid field effect, comprising: Step 1, placing a target substrate on a two-dimensional material, wherein the two-dimensional material is grown on a growth substrate, and drying the target substrate; Step 2, cutting the target substrate to expose the interface between the target substrate and the two-dimensional material; Step 3, continuously dripping liquid into the interface between the target substrate and the two-dimensional material. For clarity, each step is described below:

[0027] Step 1: The two-dimensional material is molybdenum disulfide, grown on a sapphire substrate. The target substrate is prepared from PDMS (polydimethylsiloxane) and a curing agent: PDMS and curing agent are mixed in a 10:1 ratio (10 mL PDMS, 1 mL curing agent) and stirred for 3-5 minutes. The mixture is then spin-coated three times onto the two-dimensional material at 2000 rpm for 1 minute. Comparing three spin-coations (small amounts multiple times) with one spin-coation, the PDMS is more evenly covered on the two-dimensional material, allowing for better control of the PDMS thickness and facilitating the removal of the PDMS film in the final step with improved transfer efficiency. The material is then dried at 90℃-110℃ for 180 minutes. Preferably, after stirring, the material is ultrasonically cleaned for 2 minutes to remove air bubbles from the PDMS and curing agent mixture, resulting in more uniform spin-coating and better transfer of the two-dimensional material.

[0028] Step 2: Use a scalpel to cut open the target substrate, exposing the interface between the target substrate and the two-dimensional material. Furthermore, use the scalpel to cut open the target substrate, including its perimeter, to maximize the contact area between the two-dimensional material and the target substrate while ensuring the droplet can enter the gap. Specifically, the scalpel cut width is 1 mm from the edge of the growth substrate. After cutting the target substrate, place the entire sample in a plasma cleaner for 10 minutes to facilitate easier droplet entry into the gap between the target substrate and the two-dimensional material.

[0029] Step 3: Liquid, deionized water, is continuously dripped into the interface between the target substrate and the two-dimensional material. During this process, both the target substrate and the growth substrate are tilted to facilitate liquid flow between them. Friction between the deionized water and the two-dimensional material generates electrical charge. A liquid layer with a high dielectric constant is formed between the target substrate and the two-dimensional material, applying a triboelectric field to the surface of the two-dimensional material. In this step, the target substrate is tilted at a 30° angle to ensure better contact between the droplet and the electrode, maximizing the triboelectric voltage generated by friction with the two-dimensional material. Finally, the target substrate is peeled off to obtain the transferred molybdenum disulfide.

[0030] In this invention, deionized water generates an electric charge through friction with the two-dimensional material, forming an electric field between the two-dimensional material and the deionized water. This electric field overcomes the adsorption between the two-dimensional material and the growth substrate, causing the two-dimensional material to detach from the growth substrate and complete the transfer of the two-dimensional material.

[0031] Traditional transfer methods often fail to simultaneously achieve both high transfer efficiency and the absence of chemical residues. This invention proposes a two-dimensional material transfer method based on the two-dimensional material / liquid field effect. This invention uses water as a medium between the two-dimensional material and the target substrate. The interface between the water droplet and the two-dimensional material / target substrate acquires opposite charges and generates an electrostatic field. The voltage generated by friction between the water droplet and the two-dimensional material (Small, 2023:2304988) further enhances the electrostatic field strength between the two-dimensional material and the water droplet, thereby strengthening the transfer efficiency. This method effectively balances the characteristics of no chemical residues and high transfer efficiency in two-dimensional material transfer.

[0032] In the experiment, the liquid used in this invention was deionized water, and the two-dimensional material was molybdenum disulfide. Upon contact between deionized water and molybdenum disulfide, an electric field was formed at the interface between the two materials. Two electrodes were placed at opposite ends of the two-dimensional material, and the voltage and transferred charge between the electrodes were measured. Figure 1 As shown. From Figure 1 (a) It can be seen that the two-dimensional material / liquid layer interface induces a potential difference of approximately 0.4-0.7V; from Figure 1 (b) It can be seen that there are indeed a large number of induced charges at the interface between the two-dimensional material and the liquid layer.

[0033] In practical applications, the two-dimensional materials can be molybdenum disulfide, tungsten disulfide, molybdenum diselenide, tungsten diselenide, graphene, or boron nitride, and the liquids can be methanol, ethanol, or liquid metals. When these liquids flow over the surface of the aforementioned two-dimensional materials, their high dielectric constant and high conductivity properties facilitate the increase of induced charge density and the generation and transfer of triboelectric charge, thus generating triboelectricity and achieving the effects of this invention.

[0034] In this invention, PDMS in the target substrate readily gains electrons, thus becoming negatively charged, and adsorbs cations from the liquid layer, forming an electric field at the interface between the target substrate and the liquid layer. The two-dimensional material acts as a friction material for the droplets, generating a voltage.

[0035] Furthermore, after step 2, the method further includes setting a first electrode 4 and a second electrode 5 on the other side of the target substrate and the growth substrate, respectively, and connecting the first electrode 4 and the second electrode 5 in an external circuit; the material of the first electrode 4 and the second electrode 5 is copper; the liquid also comes into contact with the first electrode 4 and the second electrode 5, and the related device and mechanism are as follows: Figure 2 As shown. The first electrode 4 and the second electrode 5 are made of copper, so that the system can accurately measure the accumulated voltage generated by friction.

[0036] Due to the presence of the liquid layer 6, and the fact that the liquid also drips onto the first electrode 4 and the second electrode 5, the entire device forms a conductive loop even though the target substrate 3 and the growth substrate 2 are insulating materials. The current flows through the first electrode 4, the droplet on the first electrode 4, the liquid layer 6, the two-dimensional material 1, the droplet on the second electrode 5, the second electrode 5, and the first electrode 4. The first electrode 4 and the second electrode 5 form a loop, causing the triboelectric charge generated between the two-dimensional material 1 and the droplet to act on the target substrate 3 / liquid layer 6 / two-dimensional material 1, creating a directional local electric field. The charge continuously accumulates at this solid / liquid / solid interface, generating a high voltage to enhance the transfer capability of the two-dimensional material 1. As the droplet continues to drip across the entire device, triboelectric charge is generated and accumulates at the solid-liquid-solid interface, forming a strong electric field between the two-dimensional material 1 and the liquid layer 6. This electric field overcomes the van der Waals force between the two-dimensional material 1 and the growth substrate 2, enhancing the ability of the two-dimensional material 1 to transfer to the target substrate 3.

[0037] In this invention, the negative charge of the target substrate 3 induces a positive charge in the upper part of the liquid layer 6, while the positive charge of the two-dimensional material 1 induces a negative charge in the lower part of the liquid layer 6, forming two symmetrical double-layer electric fields, correspondingly generating two equivalent capacitors C1 and C2. Additionally, an equivalent capacitor C3 is formed between the first and second electrodes. The principle behind enhanced two-dimensional material transfer is as follows: when a falling water droplet contacts the electrodes, the first and second electrodes form a closed loop. Due to electrostatic coupling, the system continuously injects and accumulates induced charges at the liquid-solid interface of the liquid layer / two-dimensional material, effectively charging the two ends of capacitor C2, thereby generating a high voltage. The electric field generated by this voltage promotes the exfoliation of the two-dimensional material, thus enhancing the transfer capability.

[0038] Figure 3When an external liquid continuously drips onto the two-dimensional material 1, and the droplets also drip onto the first electrode 4 and the second electrode 5, meaning the droplets are in contact with both electrodes, the voltage between the first electrode 4 and the second electrode 5 and the charge transfer at the interface between the liquid layer 6 and the two-dimensional material 1 are considered. Figure 3 It can be seen that the system generates a voltage as high as 48V and a transfer charge of 17nC, indicating that this mechanism can provide an additional electric field at the interface between the two-dimensional material 1 and the growth substrate 2, thereby improving the transfer effect of the two-dimensional material 1. Accordingly, Figure 4 (a) is a photograph of molybdenum disulfide before transfer; Figure 4 (b) is a photograph of molybdenum disulfide after transfer. By comparing the images before and after transfer, it can be seen that the molybdenum disulfide grains were not damaged or missing, and were transferred relatively intact from the growth substrate to the target substrate, achieving a high transfer effect.

[0039] Furthermore, the growth substrate 2 and the target substrate 3 are fixed on a vibration table, and the vibration table vibrates along the plane of the growth substrate 2, which generates a stronger impact force between the droplet and the two-dimensional material 1, resulting in a stronger friction effect and allowing the two-dimensional material 1 to be peeled off better.

[0040] In summary, this invention provides a two-dimensional material transfer method based on a liquid field effect, comprising: step 1, placing a target substrate on a two-dimensional material grown on a growth substrate, and drying the target substrate; step 2, cutting the target substrate to expose the interface between the target substrate and the two-dimensional material; and step 3, continuously dripping liquid into the interface between the target substrate and the two-dimensional material. This invention does not introduce chemical contamination during the transfer process; it can significantly improve the ability of two-dimensional materials to transfer to a target substrate; it can self-drive the improvement of two-dimensional material transfer capability without the need for external electric field assistance; it does not involve high-temperature annealing or other methods, has low requirements for environmental humidity and cleanliness, and is widely applicable to various two-dimensional materials; it is simple to operate and low in cost. Considering the above advantages, this invention has good application prospects in the field of two-dimensional material application technology.

[0041] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A two-dimensional material transfer method based on a two-dimensional material-liquid field effect, characterized in that, Includes the following steps: Step 1: Place the target substrate on the two-dimensional material, which is grown on the growth substrate, and dry the target substrate; Step 2: Cut open the target substrate to expose the interface between the target substrate and the two-dimensional material; Step 3: Continuously drip liquid into the interface between the target substrate and the two-dimensional material. The liquid penetrates the air gap between the target substrate and the two-dimensional material, forming a liquid layer. The liquid and the two-dimensional material generate electrical charges through friction, creating an electric field between the liquid and the two-dimensional material. This electric field overcomes the adsorption between the two-dimensional material and the growth substrate, causing the two-dimensional material to detach from the growth substrate, thus completing the transfer of the two-dimensional material. The liquid layer has a high dielectric constant. The two-dimensional material is molybdenum disulfide, tungsten disulfide, molybdenum diselenide, tungsten diselenide, graphene, or boron nitride. The growth substrate is sapphire. The liquid is deionized water, methanol, or ethanol.

2. The two-dimensional material transfer method based on the two-dimensional material-liquid field effect as described in claim 1, characterized in that: After step 2, a first electrode and a second electrode are respectively disposed on the other side of the target substrate and the growth substrate, and the first electrode and the second electrode are connected in an external circuit; the liquid also comes into contact with the first electrode and the second electrode.

3. The two-dimensional material transfer method based on the two-dimensional material-liquid field effect as described in claim 1, characterized in that: In step 2, a scalpel is used to cut open the target base and the area around the target base.

4. The two-dimensional material transfer method based on the two-dimensional material-liquid field effect as described in claim 3, characterized in that: Step 2 is followed by plasma cleaning.

5. The two-dimensional material transfer method based on the two-dimensional material-liquid field effect as described in claim 1, characterized in that: In step 3, the target substrate and the growth substrate are tilted.

6. The two-dimensional material transfer method based on the two-dimensional material-liquid field effect as described in any one of claims 1-5, characterized in that: The target substrate is prepared from PDMS and a curing agent.

7. The two-dimensional material transfer method based on the two-dimensional material-liquid field effect as described in claim 6, characterized in that: In step 1, the method for setting the target substrate is spin coating.

8. The two-dimensional material transfer method based on the two-dimensional material-liquid field effect as described in claim 7, characterized in that: The number of times to coat is 3.

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