A two-dimensional metal film based on liquid-gas interface segregation and a preparation method thereof

Abstract

The application discloses a two-dimensional metal film based on liquid-gas interface segregation and a preparation method thereof. The preparation method comprises the following steps: firstly, temperature rising treatment is performed to dissolve solute metal in solvent metal; and then, temperature falling treatment is performed to make the solute metal segregate to the interface between the solvent metal and a protective atmosphere, and form a two-dimensional metal film. The application aims to provide a new two-dimensional metal synthesis method. The application provides a two-dimensional metal film based on liquid-gas interface segregation and a preparation method thereof. Through the processes of temperature rising dissolution and temperature falling segregation, the solute metal segregates to the interface between the molten metal and the atmosphere, and forms a two-dimensional metal film.

Description

Technical Field

[0001] This invention relates to the field of two-dimensional materials technology, specifically to a two-dimensional metal film based on liquid-gas interface segregation and its preparation method. Background Technology

[0002] The physical and chemical properties of metals, such as hardness, conductivity, and elasticity, are closely related to their size, morphology, internal structure, and composition. In recent decades, researchers have explored precise synthesis methods for metal nanocrystals used in various applications. Especially since the discovery of graphene, researchers have conducted more extensive research on various two-dimensional materials, including but not limited to transition metal dichalcogenides (TMDs), boron nitride, black phosphorus, layered hydroxides (LDHs), silicene, metal oxides, transition metal carbides, nitrides, and carbonitrides (MXenes). Against this backdrop, ultrathin two-dimensional metallic materials have attracted increasing attention from researchers due to their unique physicochemical properties and broad potential applications in numerous fields.

[0003] These ultrathin two-dimensional metallic materials are composed of single or a few metal atoms, possessing extremely high specific surface area and relatively high surface energy. Their abundant active metal sites make them widely applicable in catalysis. Unlike traditional two-dimensional layered materials, metal atoms tend to form three-dimensional closed structures, bonded together by strong metallic bonds. While most metals have highly symmetrical crystal lattice structures, the two-dimensional morphology is not thermodynamically most stable during the growth of metal nanocrystals, thus lacking strong confinement forces to regulate the anisotropic growth of two-dimensional sheet-like structures.

[0004] Currently, common methods for synthesizing two-dimensional metals include template methods, wet chemical methods, exfoliation methods, and molecular beam epitaxy (MBE). Template methods and wet chemical methods require large amounts of organic solvents, which results in a large number of organic dangling bonds in the obtained two-dimensional metal films, thus affecting the intrinsic properties of the metal. While exfoliation can yield high-quality two-dimensional metal films, its yield and reproducibility are low. MBE can obtain atomically flat two-dimensional metal films, but the equipment is difficult to maintain and very expensive. Summary of the Invention

[0005] The present invention aims to provide a new method for synthesizing two-dimensional metals. The present invention provides a two-dimensional metal film based on liquid-gas interface segregation and its preparation method. Through the process of heating and dissolving and cooling and segregating, the solute metal will segregate to the interface between the molten metal and the atmosphere and form a two-dimensional metal film.

[0006] This invention is achieved through the following technical solution: A method for preparing a two-dimensional metal film based on liquid-gas interface segregation, comprising: First, heat the solution to dissolve the solute metal in the solvent metal. Further cooling causes the solute metal to segregate to the interface between the solvent metal and the protective atmosphere, forming a two-dimensional metal film.

[0007] The present invention provides a method for preparing the above-mentioned two-dimensional metal thin film. The method uses molten metal as a medium and the metal of the target two-dimensional metal thin film as a solute, and prepares the film by heating to dissolve and cooling to segregate.

[0008] Further optional, The solute metal has a solubility of less than 1.0% in the solvent metal; And / or, the molar ratio of solvent metal to solute metal is 100~1000; such as 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000.

[0009] And / or, the thickness of the solute metal is 50 nm to 100 nm; such as 55 nm, 60 nm, 70 nm, 80 nm, 90 nm.

[0010] In this invention, the solubility of the solute metal in the solvent metal needs to be less than 1.0%; the solute metal and the solvent metal will not react with each other, and the solute metal cannot form intermetallic compounds with the solvent metal, because once intermetallic compounds are formed, the solute metal will be difficult to segregate.

[0011] In this invention, a sufficient amount of solvent metal is required, and the amount of solute metal relative to solvent metal needs to be relatively small in order to better control the segregation process of solvent metal and ensure that the metal film formed by segregation has two-dimensional properties.

[0012] Further optionally, the solute metal includes an elemental metal and / or an alloy; the elemental metal includes at least one of titanium, molybdenum, chromium, vanadium, niobium, and tantalum; And / or, the solvent metal includes at least one of copper, nickel, and silver.

[0013] In this invention, the solute metal can be an elemental metal, an alloy, or a combination of an elemental metal and an alloy; for the elemental metal, at least one of copper, nickel, and silver can be selected. This invention can also synthesize two-dimensional binary or ternary alloy metal films by adjusting the composition of the solute metal.

[0014] In this invention, the solute metal dissolves into the solvent metal at high temperature. Since the solute metal selected usually has low solubility in the solvent metal and the two substances do not react, the solute metal will slowly segregate to the gas-liquid interface, that is, the upper surface of the solvent metal, during the cooling process, thereby forming a two-dimensional metal film.

[0015] Further optionally, the protective atmosphere includes an inert atmosphere or a reducing atmosphere.

[0016] Further optionally, the reducing atmosphere includes an argon-hydrogen mixture, and the argon-hydrogen volume ratio is 10-50; such as 15, 20, 30, 40, 45.

[0017] The background vacuum of the atmosphere furnace reaches 1×10 -3 After evacuating to a local vacuum, a protective atmosphere (e.g., an argon-hydrogen mixture (Ar:H2 = 10~50)) is filled. Preferably, the background vacuum of the atmosphere furnace reaches 1×10⁻⁶. -3 Pa is used to prevent the two-dimensional metal thin film from being oxidized during segregation.

[0018] Further, optionally, before the heating process, the following is also included: A solute metal film is deposited on an inert metal substrate using a thin film deposition method; then a solvent metal is stacked on top of the solute metal film. By using thin film deposition to deposit a layer of solute metal on an inert metal substrate, ultra-high purity solute metal films with controllable thickness can be obtained.

[0019] Thin film deposition methods include magnetron sputtering, pulsed laser beam deposition, atomic layer deposition, and plasma-enhanced chemical vapor deposition. Different thin film fabrication processes require different preparation conditions, but deposition must be performed in an inert or reducing atmosphere.

[0020] If the inert metal substrate is made of tungsten, the tungsten will support the molten solvent metal. Tungsten atoms are large and inert, and do not easily dissolve into the solvent metal, thus not interfering with the experimental results.

[0021] Before the deposition process, the inert metal substrate can be cleaned to remove impurities. For example, a tungsten metal (99.9% purity) substrate can be cleaned 3-5 times with acetone, sodium hydroxide, and deionized water.

[0022] The cleaned solvent metal is placed on the surface of the solute metal film, and then the whole thing is placed in an atmosphere furnace.

[0023] The solvent metal can be a high-purity (99.99%) bulk or foil, with the aim of forming a sufficient quantity of solvent metal. Preferably, the molar ratio of solvent metal to solute metal needs to be between 100 and 1000.

[0024] Further optional, During the heating process, the target temperature should be controlled above the melting point of the solute metal; the heating rate should be 100 ℃ / min to 150 ℃ / min. For example, heating rates of 115 ℃ / min, 120 ℃ / min, 125 ℃ / min, 130 ℃ / min, 135 ℃ / min, 140 ℃ / min, and 145 ℃ / min can be used.

[0025] This invention sets a high heating rate to minimize the impact of oxygen in the system on the prepared product.

[0026] Preferably, the target temperature is 1200 ℃~1500 ℃. After the temperature reaches the target temperature, it is held for 10 min~30 min to ensure that the solute metal is fully dissolved.

[0027] Further optional, During cooling process: First, the temperature is cooled to a temperature below the target temperature of the heating process but above the melting point of the solvent metal, so that the solute metal segregates to the interface between the solvent metal and the protective atmosphere, forming a two-dimensional metal film. It is then cooled to room temperature a second time.

[0028] The thickness of the segregated two-dimensional metal film can be controlled by controlling the cooling rate.

[0029] Further optionally, during a single cooling process, the cooling rate is 2 ℃ / min to 10 ℃ / min; for example, the cooling rate is 2 ℃ / min, 3 ℃ / min, 4 ℃ / min, 5 ℃ / min, 6 ℃ / min, 7 ℃ / min, 8 ℃ / min, 9 ℃ / min, or 10 ℃ / min. And / or, during the secondary cooling process, the cooling rate is 300℃ / min~500℃ / min; for example, the cooling rate is 350℃ / min, 400℃ / min, 450℃ / min, or 500℃ / min.

[0030] First, the temperature is controlled to decrease slowly, allowing sufficient time for the solute metal to segregate to the gas-liquid interface between the solvent metal and the atmosphere. Typically, the temperature to be reached during cooling needs to be 50°C to 100°C lower than the holding temperature, but still above the melting point of the solvent metal. The cooling rate is 2°C / min to 10°C / min. After cooling to the desired temperature, the two-dimensional metal film has segregated to the surface of the molten metal. At this point, the atmosphere furnace needs to be rapidly cooled to room temperature at a rate of 300°C / min to 500°C / min. The target temperature after the first cooling step must still be maintained above the melting point of the solvent metal. The smooth surface of the molten solvent metal is conducive to the formation of the two-dimensional metal film. If the temperature after cooling is below the melting point of the solvent metal, the solvent metal will crystallize and form numerous grain boundaries, while the solute metal will preferentially segregate at these grain boundaries, preventing the formation of a two-dimensional metal film.

[0031] This invention utilizes a process of rapid heating for dissolution and slow cooling for segregation, allowing the solute metal to better segregate to the interface between the molten metal and the atmosphere, forming a uniform two-dimensional metal film. By adjusting the composition of the solute metal, two-dimensional binary or ternary alloy metal films can also be synthesized.

[0032] A two-dimensional metal film based on liquid-gas interface segregation is prepared by the above-described method for preparing a two-dimensional metal film based on liquid-gas interface segregation.

[0033] The present invention provides a two-dimensional metal film, which is obtained by heating dissolution-cooling segregation method; the thickness of the two-dimensional metal film is 10 nm to 100 nm, preferably up to about 10 nm.

[0034] The two-dimensional metal film provided by this invention can also be used to prepare two-dimensional binary or ternary metal films by adjusting the composition (mainly referring to the composition and / or amount of solute metals) and the preparation method.

[0035] The present invention provides a method for preparing two-dimensional metal films based on liquid-gas interface segregation, which aims to improve the synthesis efficiency and quality of two-dimensional metal materials and lay the foundation for future scientific research and industrial applications.

[0036] The present invention has the following advantages and beneficial effects: 1. The present invention addresses the problem that existing two-dimensional metal thin films contain numerous dangling bonds, which degrade the intrinsic properties of the metal thin film and hinder its advanced applications. The present invention uses a high-temperature melting process to dissolve a solute metal by melting a solvent metal. During the cooling process, the dissolved solute metal is slowly released, forming a two-dimensional metal thin film on the surface of the solvent metal. The resulting metal thin film exhibits strong crystallinity and controllable thickness.

[0037] 2. This invention provides a two-dimensional metal film, which is obtained by heating dissolution-cooling segregation method; the thickness of the two-dimensional metal film is 10 nm to 100 nm. The two-dimensional metal film can also be prepared into two-dimensional binary or ternary metal thin films by adjusting the composition (mainly referring to the composition and / or amount of solute metal) and preparation method.

[0038] 3. The method for preparing two-dimensional metal films based on liquid-gas interface segregation provided by this invention aims to improve the synthesis efficiency and quality of two-dimensional metal materials, laying the foundation for future scientific research and industrial applications. The two-dimensional metal thin films provided by this invention can be further used to prepare two-dimensional metal carbides, nitrides, or directly used as conductive materials. Attached Figure Description

[0039] The accompanying drawings, which are included to provide a further understanding of embodiments of the invention and form part of this application, do not constitute a limitation thereof. In the drawings: Figure 1 The images show TOF-SIMS test images (a~f) and TEM cross-sectional images (g~j) of two-dimensional niobium (Nb) thin films. Among them, (a~c) shows the three-dimensional distribution of Nb, (d~f) shows the three-dimensional distribution of Cu, and (g~j) shows the cross-sectional TEM images of niobium thin films of different thicknesses.

[0040] Figure 2 These are planar TEM images of two-dimensional niobium thin films; in which, Figures (a-b) show the surface morphology and crystallinity of two-dimensional metallic niobium, and Figures (c-d) show the segregation process of two-dimensional metallic niobium thin films.

[0041] Figure 3 This is a schematic diagram of the preparation method of the two-dimensional metal film based on liquid-gas interface segregation according to the present invention. Detailed Implementation

[0042] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments and accompanying drawings. The illustrative embodiments and descriptions of the present invention are only used to explain the present invention and are not intended to limit the present invention. Example

[0043] This scheme provides a method for preparing two-dimensional metal films based on liquid-gas interface segregation, as detailed below: Step 1: Clean the tungsten metal substrate (99.9% purity) 3-5 times with acetone, sodium hydroxide, and deionized water. Prepare a solute metal thin film using methods such as magnetron sputtering, pulsed laser beam deposition, atomic layer deposition, or plasma-enhanced chemical vapor deposition. The thickness of the solute metal should be 50 nm to 200 nm. The preparation conditions vary depending on the thin film preparation process, but deposition must be carried out in an inert or reducing atmosphere. Suitable solute metals include copper, nickel, silver, and their alloys. The solute metal must have a solubility of less than 1.0% in the solvent metal and must not form intermetallic compounds with the solvent metal.

[0044] Step 2: The solvent metal can be a high-purity (99.99%) bulk or foil, the purpose being to form a sufficient quantity of solvent metal. Typically, the molar ratio of solvent metal to solute metal is between 100 and 1000. The cleaned solvent metal is placed on the surface of the solute metal film, and then the entire assembly is placed inside an atmosphere furnace. The background vacuum of the atmosphere furnace reaches 1 × 10⁻⁶. -3 After evacuating to local vacuum, an argon-hydrogen mixture (Ar:H2 = 10~50) is filled as a protective atmosphere. The amount of solute metal relative to solvent metal needs to be small to better control the segregation process of the solvent metal and ensure that the segregated metal film has two-dimensional properties. The background vacuum of the atmosphere furnace reaches 1×10⁻⁶. -3 Pa is used to prevent the two-dimensional metal thin film from being oxidized during segregation.

[0045] Step 3: The atmosphere furnace has a rapid heating function to minimize the impact of oxygen in the system on the prepared product. The temperature is above the melting point of the solute metal, typically 1200 ℃~1500 ℃, with a heating rate of 100 ℃ / min~150 ℃ / min. After reaching the target temperature, it is held for 10~30 min to ensure complete dissolution of the solute metal. The atmosphere furnace has rapid heating and cooling functions; in this method, the thickness of the segregated two-dimensional metal film is controlled by the cooling rate.

[0046] Step 4: Control the cooling process slowly to allow sufficient time for the solvent metal to segregate to the gas-liquid interface between the solvent metal and the atmosphere. Generally, the temperature to be reached during cooling is 50°C to 100°C lower than the holding temperature, but still higher than the melting point of the solvent metal. The cooling rate is 2°C / min to 10°C / min. After cooling to the desired temperature, the two-dimensional metal film has segregated to the surface of the molten metal. At this point, the atmosphere furnace is rapidly cooled to room temperature at a cooling rate of 300°C / min to 500°C / min. Example

[0047] This embodiment provides a two-dimensional metal film based on liquid-gas interface segregation, and the specific preparation method is as follows: Step 1: Clean the tungsten metal substrate (99.9% purity) three times with acetone, sodium hydroxide and deionized water. Deposit a niobium metal thin film as a solute metal on the tungsten metal substrate using magnetron sputtering with a thickness of 50 nm.

[0048] Step 2: High-purity copper foil (99.99%) with a thickness of 50 μm is used as the solvent metal. The cleaned copper foil is placed on a niobium metal film; then, the entire assembly is placed inside an atmosphere furnace. The background vacuum of the atmosphere furnace needs to reach 1×10⁻⁶. -3 After pumping to local vacuum, fill with an argon-hydrogen mixture (Ar:H2=10) as a protective atmosphere.

[0049] Step 3: Prepare to start heating. Set the target temperature to 1200 ℃ and the heating rate to 100 ℃ / min. After the temperature reaches the target temperature, hold it for 10 min to ensure that the niobium metal solute is fully dissolved.

[0050] Step 4: Controlled slow cooling allows sufficient time for niobium metal to segregate to the gas-liquid interface between the solvent metal and the atmosphere. The furnace is cooled to 1140 °C at a rate of 2 °C / min. After cooling to the desired temperature, the two-dimensional niobium film has segregated to the surface of the molten metal. At this point, the atmosphere furnace needs to be rapidly cooled to room temperature at a rate of 300 °C / min, resulting in a two-dimensional niobium film with a thickness of approximately 10 nm. Example

[0051] This embodiment provides a two-dimensional metal film based on liquid-gas interface segregation, and the specific preparation method is as follows: Step 1: Clean the tungsten metal substrate (99.9% purity) four times with acetone, sodium hydroxide and deionized water. Deposit a tantalum metal film as a solute metal on the tungsten metal substrate using pulsed laser deposition, with a thickness of 100 nm.

[0052] Step 2: High-purity silver foil (99.99%) with a thickness of 50 μm is used as the solvent metal. The cleaned silver foil is placed on a tantalum metal film; then, the entire assembly is placed inside an atmosphere furnace. The background vacuum of the atmosphere furnace needs to reach 1×10⁻⁶. -3 After evacuating to a local vacuum, fill with an argon-hydrogen mixture (Ar:H2=30) as a protective atmosphere.

[0053] Step 3: Prepare to start heating. Set the target temperature to 1300 ℃ and the heating rate to 130 ℃ / min. After the temperature reaches the target temperature, hold it for 20 min to ensure that the tantalum metal solute is fully dissolved.

[0054] Step 4: Controlled slow cooling allows sufficient time for tantalum metal to segregate to the gas-liquid interface between the solvent metal and the atmosphere. The furnace is cooled to 1250 °C at a rate of 5 °C / min. After cooling to the desired temperature, the two-dimensional tantalum film has segregated to the surface of the molten metal. At this point, the atmosphere furnace needs to be rapidly cooled to room temperature at a rate of 350 °C / min, resulting in a two-dimensional tantalum film with a thickness of approximately 23.6 nm. Example

[0055] Step 1: Clean the tungsten metal substrate (99.9% purity) five times with acetone, sodium hydroxide and deionized water. Deposit a vanadium metal thin film as a solute metal on the tungsten metal substrate using atomic layer deposition (ALD) with a thickness of 200 nm.

[0056] Step 2: High-purity gold foil (99.99%) with a thickness of 20 μm is used as the solvent metal. The cleaned gold foil is placed on a vanadium metal film; then, the entire assembly is placed inside an atmosphere furnace. The background vacuum of the atmosphere furnace needs to reach 1 × 10⁻⁶. -3 After evacuating to a local vacuum, fill with an argon-hydrogen mixture (Ar:H2=50) as a protective atmosphere.

[0057] Step 3: Prepare to start heating. Set the target temperature to 1500 ℃ and the heating rate to 150 ℃ / min. After the temperature reaches the target temperature, hold it for 30 min to ensure that the vanadium metal solute is fully dissolved.

[0058] Step 4: Controlled slow cooling allows sufficient time for niobium metal to segregate to the gas-liquid interface between the solvent metal and the atmosphere. The furnace is cooled to 1400 °C at a rate of 10 °C / min. After cooling to the desired temperature, the two-dimensional vanadium film has segregated to the surface of the molten metal. At this point, the atmosphere furnace needs to be rapidly cooled to room temperature at a rate of 500 °C / min, resulting in a two-dimensional vanadium film with a thickness of approximately 40.7 nm.

[0059] Comparative Example 1 This case study uses Example 1 as a control to illustrate the importance of controlling the slow cooling process in the fourth step. Without slow cooling, a two-dimensional niobium film cannot be obtained. The specific preparation method is as follows: Step 1: Clean the tungsten metal substrate (99.9% purity) three times with acetone, sodium hydroxide and deionized water. Deposit a niobium metal thin film as a solute metal on the tungsten metal substrate using magnetron sputtering with a thickness of 50 nm.

[0060] Step 2: High-purity copper foil (99.99%) with a thickness of 50 μm is used as the solvent metal. The cleaned copper foil is placed on a niobium metal film; then, the entire assembly is placed inside an atmosphere furnace. The background vacuum of the atmosphere furnace needs to reach 1×10⁻⁶. -3 After pumping to local vacuum, fill with an argon-hydrogen mixture (Ar:H2=10) as a protective atmosphere.

[0061] Step 3: Prepare to start heating. Set the target temperature to 1200 °C and the heating rate to 100 °C / min. After the temperature reaches the target temperature, hold it for 10 min to ensure that the niobium metal solute is fully dissolved.

[0062] Step 4: Rapid cooling. The cooling rate is set to 300 ℃ / min. The furnace body is directly cooled to room temperature. The niobium film dissolved in the molten copper does not have time to segregate to the gas-liquid interface and cannot form a two-dimensional metallic niobium film.

[0063] I. Structural Characterization Analysis like Figure 1 The images show TOF-SIMS images (a-f) and TEM cross-sections (g-j) of a two-dimensional niobium (Nb) thin film. (a-c) shows the three-dimensional distribution of Nb, revealing that niobium exists only on the shallow surface. Analysis of the depth distribution map indicates that the enriched region of Nb is approximately within 10.3 nm of the surface, meaning the thickness of the two-dimensional niobium thin film is 10.3 nm. (d-f) shows the three-dimensional distribution of Cu, demonstrating extremely low Cu content on the shallow surface; the same conclusion is reached from the depth distribution map. (g-j) shows cross-sectional TEM images of niobium films of different thicknesses, revealing that the thickness of the two-dimensional Nb thin film is controllable between 2.86 and 23.0 nm.

[0064] like Figure 2 The image shown is a planar TEM image of a two-dimensional niobium thin film. A small amount of methane was introduced during the niobium film segregation process to verify that the modified niobium film could be carbonized and used to prepare two-dimensional niobium carbide. The triangular area in the image represents niobium carbide, and the remaining contrasting areas represent the two-dimensional metallic niobium film. Figures c-d illustrate the segregation process of the two-dimensional metallic niobium film.

[0065] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a two-dimensional metal film based on liquid-gas interface segregation, characterized in that, include: A solute metal thin film is deposited on an inert metal substrate using a thin film deposition method. The solvent metal is then stacked on the solute metal film; then, the whole assembly is placed in an atmosphere furnace. First, heat the solution to dissolve the solute metal in the solvent metal. During the heating process, control the target temperature above the melting point of the solvent metal. The heating rate is 100℃ / min to 150℃ / min. The solute metal is then cooled to the interface between the solvent metal and the protective atmosphere, forming a two-dimensional metal film. The cooling process involves first cooling the solute metal to a temperature below the target temperature of the heating process but above the melting point of the solvent metal, causing it to segregate to the interface between the solvent metal and the protective atmosphere and form a two-dimensional metal film. Then, the solute metal is cooled to room temperature. During a single cooling process, the cooling rate is 2℃ / min to 10℃ / min; During the secondary cooling process, the cooling rate is 300℃ / min~500℃ / min; among which, The solute metal has a solubility of less than 1.0% in the solvent metal; The molar ratio of solvent metal to solute metal is 100 to 1000; The thickness of the solute metal is 50 nm to 100 nm; the solute metal includes elemental metals and / or alloys; the elemental metal includes at least one of titanium, molybdenum, chromium, vanadium, niobium, and tantalum; The solvent metal includes at least one of copper, nickel, and silver.

2. The method for preparing a two-dimensional metal film based on liquid-gas interface segregation according to claim 1, characterized in that, The protective atmosphere includes an inert atmosphere or a reducing atmosphere.

3. The method for preparing a two-dimensional metal film based on liquid-gas interface segregation according to claim 2, characterized in that, The reducing atmosphere comprises an argon-hydrogen mixture, with an argon-hydrogen volume ratio of 10 to 50.

4. A two-dimensional metal film based on liquid-gas interface segregation, characterized in that, The two-dimensional metal film was prepared using the method for preparing a liquid-gas interface segregation according to any one of claims 1 to 3.

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