A method for preparing ultra-thin two-dimensional transition metal nitride by a template method

Abstract

The application relates to the field of two-dimensional transition metal nitrides and a chemical vapor deposition method, in particular to a method for preparing an ultrathin two-dimensional transition metal nitride by a template method. The preparation method mainly comprises the following steps: growing MA2N4 material on a copper / transition metal laminated substrate by a chemical vapor deposition method at a high temperature; growing a two-dimensional ultrathin transition metal nitride by cooling; etching a copper layer after spin-coating a polymer protective layer; transferring the sample to a required substrate; washing away the polymer protective layer; and obtaining a clean ultrathin two-dimensional transition metal nitride and a MA2N4 thin film. The application uses MA2N4 material which is similar to the structure of the transition metal nitride as a growth substrate to prepare an ultrathin two-dimensional transition metal nitride thin film. The MA2N4 material is a van der Waals material with an atomically smooth surface, and the characteristic of being capped with a nitride makes it more conducive to the horizontal growth of the transition metal nitride on the surface.

Description

Technical Field

[0001] This invention relates to the field of two-dimensional transition metal nitrides and their preparation by chemical vapor deposition, specifically a template method for preparing ultrathin two-dimensional transition metal nitrides, which is suitable for preparing large-area, high-quality, uniform-thickness ultrathin two-dimensional transition metal nitride films and doping them. Background Technology

[0002] Since the discovery of two-dimensional materials, two-dimensional ultrathin transition metal nitrides (Mo2N, WN, CrN, TaN, etc.), possessing both excellent stability and mechanical properties, have attracted widespread attention. As non-layered materials, transition metal nitrides cannot be fabricated in large areas using a top-down mechanical exfoliation method. Furthermore, the crystal structure of transition metal nitrides during chemical vapor deposition dictates that they tend to grow in an "island-like" pattern to reduce surface energy. Therefore, obtaining ultrathin and uniformly thick transition metal nitride films remains challenging, and the synthesis of high-quality single-crystal two-dimensional ultrathin transition metal nitrides with micrometer-scale or larger dimensions is rarely reported, necessitating the development of effective preparation strategies.

[0003] The MA2N4 family, a newly discovered nitrogen-terminated layered material in 2020, possesses an atomically smooth surface and a structure similar to transition metal nitrides. Therefore, using this type of material as an epitaxial template in chemical vapor deposition (CVD) to prepare ultrathin two-dimensional transition metal nitrides is feasible. This approach is characterized by process compatibility, high efficiency, and high feasibility. Combined with magnetron sputtering to construct transition metal alloys, it also allows for the doping of transition metal nitrides, expanding the properties of this type of material. The key to this process lies in controlling the growth sequence of the two thin films and the supply rate of the transition metal source. The realization of this process provides a new approach for the preparation of large-area non-layered ultrathin two-dimensional material films, laying the foundation for the expansion of the two-dimensional material family and its applications in various fields. Summary of the Invention

[0004] The purpose of this invention is to provide a template method for preparing ultrathin two-dimensional transition metal nitrides. The template method is used to prepare ultrathin two-dimensional transition metal nitrides on copper / transition metal composite substrates. The preparation process is simple, efficient, does not require vacuum, can be realized in an atmospheric pressure chemical vapor deposition system, the equipment is simple and low cost, and the obtained ultrathin two-dimensional transition metal nitrides have good crystal quality and thickness uniformity.

[0005] The technical solution of this invention is:

[0006] A template method for preparing ultrathin two-dimensional transition metal nitrides uses MA2N4 family materials with atomically smooth texture and similar structure to transition metal nitrides as growth substrates to promote horizontal growth and weaken the "island" growth in non-layered materials. By selecting different MA2N4 family materials, different transition metal nitrides can be prepared.

[0007] The template method for preparing ultrathin two-dimensional transition metal nitrides utilizes magnetron sputtering to dope the nitrides and expand their physical properties.

[0008] The template method for preparing ultrathin two-dimensional transition metal nitrides uses a copper / transition metal multilayer composite substrate as the growth substrate. Copper serves as the matrix for growing MA2N4 and as the diffusion channel for the transition metal, located on the surface of the transition metal multilayer substrate.

[0009] The method for preparing ultrathin two-dimensional transition metal nitrides using the template method, wherein the selection of the lower transition metal substrate depends on the type of transition metal in the target growth material, has diffusion capability in copper, and can form stable nitrides.

[0010] The method for preparing ultrathin two-dimensional transition metal nitrides using the template method, wherein the transition metal includes, but is not limited to, one or more alloys of molybdenum, tungsten, chromium, vanadium, niobium, and tantalum, with a purity greater than 99.95 wt% and a thickness of not less than 50 micrometers.

[0011] The method for preparing ultrathin two-dimensional transition metal nitrides using the template method employs a chemical vapor deposition system. A pre-selected copper / transition metal stacked substrate is used as the growth substrate and placed in the center of the heating zone of a horizontal tube furnace. The temperature is raised above the melting point of copper and held for 0-60 min to allow the lower transition metal atoms to diffuse to the copper surface. Subsequently, the temperature is lowered to 1030-1050 °C and held. A solid, liquid, or gaseous nitrogen source is introduced in a reducing atmosphere with a flow rate of 100-500 sccm to grow MA2N4 material.

[0012] The method for preparing ultrathin two-dimensional transition metal nitrides using the template method involves lowering the furnace temperature of the chemical vapor deposition system tube furnace to 800~1010 ℃ and holding it at that temperature after the MA2N4 material has grown. A solid or gaseous nitrogen source is introduced under a reducing atmosphere with a flow rate of 100~500 sccm, and the ultrathin two-dimensional transition metal nitride material is grown using MA2N4 as a substrate.

[0013] The method for preparing ultrathin two-dimensional transition metal nitrides using the template method, in the chemical vapor deposition process, uses a nitrogen source of one or more of ammonia, nitrogen dioxide, nitrogen, urea, and nitrate, and an auxiliary carrier gas of one or a mixture of hydrogen and argon, with a flow rate of 100-500 sccm; in the MA2N4 material, the element represented by M is a transition metal element, including but not limited to molybdenum, tungsten, titanium, zirconium, hafnium, vanadium, niobium, tantalum, or chromium; the element represented by A is a Group IV element, including but not limited to silicon or germanium, supplied by silicon dioxide, silane, germanium particles, germanium dioxide, or germanium iodide as a precursor.

[0014] The method for preparing ultrathin two-dimensional transition metal nitrides using the template method involves the following steps: After the transition metal nitride is epitaxially grown on MA2N4 material, it is rapidly removed from the heating zone of a tube furnace in a chemical vapor deposition system for cooling. After cooling to room temperature, it is removed and a polymer is spin-coated onto its surface, followed by heating and curing to form a polymer protective layer. The substrate covered with the protective layer is then immersed in a 0.05~0.2 mol / L ammonium persulfate solution for etching. During the etching process, the etching solution is selectively heated at a temperature of 30~70 ℃. After etching, a film completely covered with the polymer protective layer is obtained and transferred to the desired substrate. The polymer protective layer is then removed using an organic solvent.

[0015] The method for preparing ultrathin two-dimensional transition metal nitrides using the template method is described in which the polymer is one or more of polyethylene, polypropylene, polystyrene, and polymethyl methacrylate, and the organic solvent for cleaning the protective layer of the polymer is one or more of alcohols, ketones, aromatics, and halogenated hydrocarbons.

[0016] The design concept of this invention is:

[0017] This invention provides a method for preparing ultrathin two-dimensional transition metal nitride materials with uniform thickness using chemical vapor deposition (CVD) with a layered two-dimensional material lacking surface dangling bonds and having a structure similar to transition metal nitrides as an epitaxial template. The material selected as the template is from the MA2N4 family, grown under high temperature and low ammonia source conditions, followed by the growth of uniformly thick ultrathin two-dimensional transition metal nitrides under low temperature and high ammonia source conditions. This method offers advantages such as high efficiency, good controllability, and high sample quality, and can serve as a method for preparing uniformly thick non-layered two-dimensional material films.

[0018] The advantages and beneficial effects of this invention are:

[0019] 1. This invention proposes a template method for preparing ultrathin two-dimensional transition metal nitrides. The method uses MA2N4 family materials without surface dangling bonds and nitrogen-capped as epitaxial templates. By utilizing the structural similarity between MA2N4 and transition metal nitrides, the transition metal nitrides are epitaxially grown on the templates, promoting their growth in the horizontal direction and inhibiting their "island-like" growth. This solves the problems of uneven thickness and small size of non-layered two-dimensional materials in traditional methods, and realizes the controllable preparation of ultrathin two-dimensional transition metal nitrides.

[0020] 2. This invention develops a method for preparing non-layered two-dimensional materials. By replacing the transition metal element in the copper / transition metal stack substrate, the growth of different two-dimensional transition metal nitrides can be achieved, which has a certain degree of universality and expands the feasibility of chemical vapor deposition in the preparation of various types of two-dimensional materials.

[0021] 3. The ultrathin two-dimensional transition metal nitrides prepared by this invention have high crystallinity, which lays the foundation for the application of transition metal nitrides in nanoelectronic devices, spintronic devices, energy storage and other fields.

[0022] 4. The invention has a simple manufacturing process, low cost, can be grown under normal pressure, saves energy, and has the potential for large-scale production. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the process for preparing ultrathin two-dimensional transition metal nitrides using the van der Waals template method of this invention.

[0024] Figure 2 This is a schematic diagram of the chemical vapor deposition system used in the annealing and chemical vapor deposition process of this invention. In the diagram, 21 is the growth substrate, 22 is the tube furnace, 23 is the quartz tube, 24 is the gas inlet, and 25 is the gas outlet.

[0025] Figure 3 This is a schematic diagram of the apparatus used in the magnetron sputtering technology of this invention. In the diagram, 31 represents the growth substrate, 32 represents the magnetron sputtering cathode, and a high-purity target is placed thereon.

[0026] Figure 4 Optical microscope images of ultrathin two-dimensional transition metal nitrides with uniform thickness prepared for this invention.

[0027] Figure 5 Cross-sectional scanning transmission electron microscope images of ultrathin two-dimensional transition metal nitrides prepared for this invention. Detailed Implementation

[0028] In its specific implementation, this invention provides a template method for preparing ultrathin two-dimensional transition metal nitrides. A copper / transition metal bimetallic layer is selected as the growth substrate. Copper serves as the substrate for growing MA2N4 and is located on the upper surface of the transition metal bimetallic substrate. The choice of the lower transition metal substrate depends on the type of transition metal in the target growth material. It must possess a certain diffusion capacity in copper and be able to form stable nitrides. This includes, but is not limited to, one or more alloys of molybdenum, tungsten, chromium, vanadium, niobium, and tantalum, with a purity greater than 99.95 wt% and a thickness of not less than 50 micrometers. The atomically smooth surface, nitrogen-sealed end surface, and crystal structure similar to transition metal nitrides without dangling bonds of MA2N4 family materials are used as growth templates for ultrathin transition metal nitrides, promoting their horizontal growth and weakening the "island" growth mode of non-layered materials during chemical vapor deposition. By selecting different MA2N4 family materials, the growth temperature and time of MA2N4 materials, the growth temperature of transition metal nitrides, the concentration of ammonia source, and the type of transition metal substrate can be controlled. At the same time, magnetron sputtering can be used to dope the nitrides. The growth quality and types of transition metal nitride materials can be controlled by the type of transition metal material introduced by magnetron sputtering, thus expanding their physical properties.

[0029] like Figure 2 As shown, the chemical vapor deposition system of the present invention mainly includes: a growth substrate 21 located in the central heating zone of a horizontal tube furnace, a tube furnace 22, a quartz tube 23, a gas inlet 24, a gas outlet 25, and a gas mass flow controller (MFC). The quartz tube 23 is horizontally inserted into the tube furnace 22, and the growth substrate 21 is provided in the quartz tube 23 corresponding to the central heating zone of the tube furnace 22. Under the action of the gas mass flow controller (MFC), the carrier gas enters the quartz tube 23 of the tube furnace 22 from the gas inlet 24 and is discharged from the gas outlet 25.

[0030] The preparation method for MA2N4 template material growth adopts Chinese patent application (publication number: CN113718227A), invention title: A type of two-dimensional layered ternary compound and its preparation method. The MA2N4 template material prepared by this method has good film-forming quality.

[0031] A pre-selected copper / transition metal multilayer substrate was used as the growth substrate and placed in the center of the heating zone of a horizontal tube furnace. The temperature was raised above the melting point of copper and held for 0–60 min to allow the lower transition metal atoms to diffuse to the copper surface. The temperature was then lowered to 1030–1050 °C and held. A solid, liquid, or gaseous nitrogen source was introduced under a reducing atmosphere (including but not limited to H2, CO, etc.) at a flow rate of 100–500 sccm to grow MA2N4 material. After the MA2N4 material growth was complete, the furnace temperature was lowered to 800–1010 °C and held. A solid or gaseous nitrogen source was introduced under a reducing atmosphere (including but not limited to H2, CO, etc.) at a flow rate of 100–500 sccm to grow ultrathin two-dimensional transition metal nitride material with a thickness of ~3 nm using MA2N4 as the substrate.

[0032] In chemical vapor deposition, the nitrogen source selected is one or more of the following: gaseous or solid ammonia, nitrogen dioxide, nitrogen, urea, and nitrate. The auxiliary carrier gas is one of hydrogen, argon, or a mixture of both, with a flow rate of 100-500 sccm. In MA2N4 material, the element M represents a transition metal element, including but not limited to molybdenum, tungsten, titanium, zirconium, hafnium, vanadium, niobium, tantalum, or chromium; the element A represents a Group IV element, including but not limited to silicon or germanium, supplied through precursors such as silicon dioxide, silane, germanium particles, germanium dioxide, and germanium iodide.

[0033] After the transition metal nitride is epitaxially grown on MA2N4 material, it is rapidly removed from the furnace heating zone and quickly cooled. Once cooled to room temperature, it is removed and a polymer is spin-coated onto its surface, followed by heating and curing to form a polymer protective layer. The substrate covered with the protective layer is then immersed in a 0.05–0.2 mol / L ammonium persulfate aqueous solution for etching. During etching, the etching solution can be selectively heated at a temperature of 30–70°C. After etching, a complete polymer protective layer film is obtained and can be transferred to the desired substrate. The polymer protective layer can be removed using an organic solvent; the polymer is one or more of polyethylene, polypropylene, polystyrene, and polymethyl methacrylate, and the organic solvent for cleaning the polymer protective layer is one or more of alcohols, ketones, aromatics, and halogenated hydrocarbons.

[0034] The present invention will be further described in detail below through embodiments.

[0035] Example 1

[0036] like Figure 1 As shown, the method for preparing ultrathin two-dimensional transition metal nitrides using the template method in this embodiment includes the following steps:

[0037] S1: Pretreatment of copper and transition metal molybdenum substrates used in chemical vapor deposition processes.

[0038] The metal substrates (copper foil, 12.5 μm thick, 5 mm long, 5 mm wide; molybdenum foil, 100 μm thick, 5 mm long, 5 mm wide; purity 99.95 wt%) required for chemical vapor deposition were ultrasonically cleaned sequentially with deionized water, ethanol, and acetone for 1 h, and then dried with a nitrogen gun. The cleaned metal substrates were then placed... Figure 2 Annealing is performed in the central heating zone of the tube furnace within the sealed quartz tube 23 of the chemical vapor deposition system shown. The furnace body of the tube furnace 22 is heated to 1000°C and held at that temperature for 5 hours under a hydrogen atmosphere with a flow rate of 500 sccm. The purpose of this step is to remove as much residual organic matter and surface oxide layer as possible from the surface of the metal substrate.

[0039] S2: MA2N4 family materials for growing ultrathin two-dimensional transition metal nitride epitaxial templates.

[0040] Copper sheets are stacked on top of molybdenum sheets to form a growth substrate 21. Figure 2 The chemical vapor deposition system shown is located in the central heating zone of the tubular furnace within the sealed quartz tube 23. Argon gas at a flow rate of 1000 sccm is introduced and held for 5 min to purge the growth system. The argon gas is then turned off, and hydrogen gas at a flow rate of 200 sccm is introduced and held. The heating program is set as follows: heating to 1100℃ at a rate of 30℃ / min, at which point copper melts on the molybdenum substrate. This temperature is then held for 5 min to allow time for the lower molybdenum atoms to diffuse to the copper surface. The temperature is then allowed to naturally cool to 1030℃, and ammonia gas at a flow rate of 4 sccm is introduced. Simultaneously, the ammonia gas etches the silicon dioxide in the quartz tube, providing a silicon source. The temperature is held for 3 h to grow MoSi₂N₄ material, which serves as the epitaxial template for subsequent growth of ultrathin two-dimensional transition metal nitrides.

[0041] S3: Growth of ultrathin two-dimensional transition metal nitrides.

[0042] After the MoSi2N4 material growth was completed, the furnace temperature was lowered to 950℃, the ammonia flow rate was increased to 6 sccm, and the furnace was held at this temperature for 8 h. The remaining molybdenum atoms diffused from S2 to the copper surface reacted with the ammonia to grow Mo2N on the MoSi2N4 surface, with a thickness of ~3 nm. After the growth process was completed, the ammonia and hydrogen gases were turned off, and the argon gas was turned on. The argon flow rate was adjusted to 500 s·ccm, and the grown substrate was removed from the furnace to allow it to cool rapidly under the protective atmosphere of argon, protecting the sample from etching by argon and hydrogen.

[0043] S4: Non-destructive transfer of ultrathin two-dimensional transition metal nitrides and their templates

[0044] After the sample cooled to room temperature, it was removed from the quartz tube. A 4 wt% polymethyl methacrylate (PMMA) ethyl lactate solution was then spin-coated onto the sample surface at 4500 rpm. The sample was then baked at 120°C for 10 min to solidify the spin-coated polymer film, forming a protective layer with a thickness of ~180 nm. The sample with the polymer protective layer was then immersed in a 0.1 mol / L ammonium persulfate aqueous solution at 70°C. After the copper layer surface was etched, the sample with the polymer protective layer naturally detached from the substrate. The sample was retrieved using the desired substrate (silicon wafer, gold, etc.) and dried. Subsequently, the polymer protective layer was cleaned with acetone and isopropanol to obtain clean Mo2N crystals grown on the surface of MoSi2N4 material.

[0045] Example 2

[0046] like Figure 1 As shown, the method for preparing ultrathin two-dimensional transition metal nitrides using the template method in this embodiment includes the following steps:

[0047] S1: Pretreatment of copper and transition metal molybdenum substrates used in chemical vapor deposition processes.

[0048] The metal substrates (copper foil, 12.5 μm thick, 5 mm long, 5 mm wide; molybdenum foil, 100 μm thick, 5 mm long, 5 mm wide; purity 99.95 wt%) required for chemical vapor deposition were ultrasonically cleaned sequentially with deionized water, ethanol, and acetone for 1 h, and then dried with a nitrogen gun. The cleaned metal substrates were then placed... Figure 2 Annealing is performed in the central heating zone of the tube furnace within the sealed quartz tube 23 of the chemical vapor deposition system shown. The furnace body of the tube furnace 22 is heated to 1000°C and held at that temperature for 5 hours under a hydrogen atmosphere with a flow rate of 500 sccm. The purpose of this step is to remove as much residual organic matter and surface oxide layer as possible from the surface of the metal substrate.

[0049] S2: MA2N4 family materials for growing ultrathin two-dimensional transition metal nitride epitaxial templates.

[0050] Copper sheets are stacked on top of molybdenum sheets to form a growth substrate 21. Figure 2The central heating zone of the tubular furnace within the sealed quartz tube 23 of the chemical vapor deposition system is shown. Argon gas at a flow rate of 1000 sccm is introduced and held for 5 minutes to clean the growth system. The argon gas is then turned off, and hydrogen gas at a flow rate of 200 sccm is introduced and held. The heating program is set as follows: heating to 1100°C at a rate of 30°C / min, at which point copper melts on the molybdenum substrate. This temperature is then held for 5 minutes to allow time for the lower molybdenum atoms to diffuse to the copper surface. Unlike Example 1, the temperature is then allowed to naturally cool to 1020°C, and ammonia gas at a flow rate of 4 sccm is introduced. Simultaneously, the ammonia gas etches the silicon dioxide in the quartz tube to provide a silicon source. The temperature is held for 5 hours to grow MoSi2N4 material, which serves as the epitaxial template for subsequent growth of ultrathin two-dimensional transition metal nitrides.

[0051] S3: Growth of ultrathin two-dimensional transition metal nitrides.

[0052] Unlike Example 1, after the MoSi2N4 material growth was completed, the furnace temperature was lowered to 980°C, the ammonia flow rate was increased to 8 sccm, and the furnace was held at this temperature for 8 hours. The remaining molybdenum atoms diffused to the copper surface in S2 reacted with the ammonia to grow Mo2N on the MoSi2N4 material surface, with a thickness of ~5 nm. After the growth process was completed, the ammonia and hydrogen gases were turned off, and the argon gas was turned on. The argon flow rate was adjusted to 500 sccm, and the grown substrate was pushed out of the furnace to allow it to cool rapidly under the protective atmosphere of argon, protecting the sample from etching by argon and hydrogen.

[0053] S4: Non-destructive transfer of ultrathin two-dimensional transition metal nitrides and their templates

[0054] After the sample cooled to room temperature, it was removed from the quartz tube. A 4 wt% polymethyl methacrylate (PMMA) ethyl lactate solution was then spin-coated onto the sample surface at 4500 rpm. The sample was then baked at 120°C for 10 min to solidify the spin-coated polymer film, forming a protective layer with a thickness of ~180 nm. The sample with the polymer protective layer was then placed in a 0.1 mol / L ammonium persulfate aqueous solution at 70°C. After the copper layer surface was etched, the sample with the polymer protective layer naturally detached from the substrate. The sample was retrieved using the desired substrate (silicon wafer, gold, etc.) and dried. Subsequently, the polymer protective layer was cleaned with acetone and isopropanol to obtain clean Mo2N crystals grown on the surface of MoSi2N4 material.

[0055] Example 3

[0056] like Figure 1 As shown, the method for preparing ultrathin two-dimensional transition metal nitrides using the template method in this embodiment includes the following steps:

[0057] S1: Pretreatment of copper and transition metal molybdenum substrates used in chemical vapor deposition processes.

[0058] The metal substrates (copper foil, 12.5 μm thick, 5 mm long, and 5 mm wide; tungsten foil, 100 μm thick, 5 mm long, and 5 mm wide, with a purity of 99.95 wt%) required for chemical vapor deposition were ultrasonically cleaned sequentially with deionized water, ethanol, and acetone for 1 hour, and then dried with a nitrogen gun. The cleaned metal substrates were then placed... Figure 2 Annealing is performed in the central heating zone of the tube furnace within the sealed quartz tube 23 of the chemical vapor deposition system shown. The furnace body of the tube furnace 22 is heated to 1000°C and held at that temperature for 5 hours under a hydrogen atmosphere with a flow rate of 500 sccm. The purpose of this step is to remove as much residual organic matter and surface oxide layer as possible from the surface of the metal substrate.

[0059] S2: MA2N4 family materials for growing ultrathin two-dimensional transition metal nitride epitaxial templates.

[0060] Copper sheets are stacked on top of tungsten sheets to form a growth substrate 21, which is placed as follows: Figure 2 In the central heating zone of the tubular furnace within the sealed quartz tube 23 of the chemical vapor deposition system shown, argon gas at a flow rate of 1000 sccm is introduced and maintained for 5 min to purge the growth system. The argon gas is then turned off, and hydrogen gas at a flow rate of 200 sccm is introduced and maintained. Unlike Example 1, the heating program is set as follows: heating to 1030°C at a rate of 30°C / min, introducing ammonia gas at a flow rate of 4 sccm, while simultaneously etching the silicon dioxide in the quartz tube with ammonia gas to provide a silicon source, holding at this temperature for 10 h to grow WSi₂N₄ material, which serves as the epitaxial template for subsequent growth of ultrathin two-dimensional transition metal nitrides.

[0061] S3: Growth of ultrathin two-dimensional transition metal nitrides.

[0062] Unlike Example 1, after the WSi2N4 material growth was completed, the furnace temperature was lowered to 900°C, the ammonia flow rate was increased to 6 sccm, and the furnace was held at this temperature for 10 h. The remaining tungsten atoms diffused to the copper surface from S2 reacted with the ammonia to grow WN on the MoSi2N4 material surface, with a thickness of ~3 nm. After the growth process was completed, the ammonia and hydrogen were turned off, and the argon gas was turned on. The argon flow rate was adjusted to 500 sccm, and the grown substrate was pushed out of the furnace to allow it to cool rapidly under the protective atmosphere of argon, protecting the sample from etching by argon and hydrogen.

[0063] S4: Non-destructive transfer of ultrathin two-dimensional transition metal nitrides and their templates

[0064] After the sample cooled to room temperature, it was removed from the quartz tube. A 4 wt% polymethyl methacrylate (PMMA) ethyl lactate solution was then spin-coated onto the sample surface at 4500 rpm. The sample was then baked at 120°C for 10 min to solidify the spin-coated polymer film, forming a protective layer with a thickness of ~180 nm. The sample with the polymer protective layer was then placed in a 0.1 mol / L ammonium persulfate aqueous solution at 70°C. After the copper layer surface was etched, the sample with the polymer protective layer naturally detached from the substrate. The sample was retrieved using the desired substrate (silicon wafer, gold, etc.) and dried. Subsequently, the polymer protective layer was cleaned with acetone and isopropanol to obtain clean WN crystals grown on the surface of WSi2N4 material.

[0065] Example 4

[0066] like Figure 1 As shown, the method for preparing ultrathin two-dimensional transition metal nitrides using the template method in this embodiment includes the following steps:

[0067] S1: Pretreatment of copper and transition metal molybdenum substrates used in chemical vapor deposition processes.

[0068] The metal substrates (copper foil, 12.5 μm thick, 5 mm long, 5 mm wide; molybdenum foil, 100 μm thick, 5 mm long, 5 mm wide; purity 99.95 wt%) required for chemical vapor deposition were ultrasonically cleaned sequentially with deionized water, ethanol, and acetone for 1 h, and then dried with a nitrogen gun. The cleaned metal substrates were then placed... Figure 2 Annealing is performed in the central heating zone of the tube furnace within the sealed quartz tube 23 of the chemical vapor deposition system shown. The furnace body of the tube furnace 22 is heated to 1000°C and held at that temperature for 5 hours under a hydrogen atmosphere with a flow rate of 500 sccm. The purpose of this step is to remove as much residual organic matter and surface oxide layer as possible from the surface of the metal substrate.

[0069] S2: MA2N4 family materials for growing ultrathin two-dimensional transition metal nitride epitaxial templates.

[0070] Unlike Example 1, as Figure 3 As shown, magnetron sputtering was used to introduce chromium into the growth substrate and achieve doping of transition metal nitrides with this element. The growth substrate 31 (molybdenum sheet) was fixed on the magnetron sputtering sample stage, and the sample disk was rotated at a speed of 30 rpm. After loading a chromium target with a purity of 99.999 wt% at the magnetron sputtering cathode 32, the vacuum level of the magnetron sputtering cavity was evacuated to 10. -5 The pressure was on the order of mbar, followed by the introduction of argon gas at a flow rate of 50 sccm to maintain a stable working pressure of 10. -2mbar. The sputtering process used a DC power supply with a sputtering voltage of 600 V, a sputtering power of 25 W, and a sputtering rate of 0.2 Å / s to sputter a 0.5 nm thick chromium film on a molybdenum substrate.

[0071] Copper sheets are stacked on a molybdenum-chromium composite substrate to form a growth substrate 21. Figure 2 The central heating zone of the tubular furnace within the sealed quartz tube 23 of the chemical vapor deposition system is shown. Argon gas at a flow rate of 1000 sccm is introduced and held for 5 minutes to clean the growth system. The argon gas is then turned off, and hydrogen gas at a flow rate of 200 sccm is introduced and held. The heating program is set as follows: heating to 1100℃ at a rate of 30℃ / min, at which point copper melts on the molybdenum-chromium composite substrate. Unlike Example 1, this temperature is then held for 30 minutes to allow time for the lower molybdenum and chromium atoms to diffuse to the copper surface. The temperature is then allowed to naturally cool to 1030℃, and ammonia gas at a flow rate of 4 sccm is introduced. Simultaneously, the ammonia gas etches the silicon dioxide in the quartz tube, providing a silicon source. The temperature is held for 3 hours to grow MoSi2N4 material, which serves as the epitaxial template for subsequent growth of ultrathin two-dimensional transition metal nitrides.

[0072] S3: Growth and preparation of ultrathin two-dimensional transition metal nitrides and their doped phases.

[0073] After the MoSi2N4 material growth was completed, the furnace temperature was lowered to 950℃, the ammonia flow rate was increased to 6 sccm, and the furnace was held at this temperature for 8 h. The remaining molybdenum atoms diffused from S2 to the copper surface were used to react with the ammonia to grow chromium-doped Mo2N on the MoSi2N4 material surface. The thickness of the chromium doping was ~3 nm, and the chromium doping concentration was 12.5 at%. After the growth process was completed, the ammonia and hydrogen were turned off, and the argon gas was turned on. The argon flow rate was adjusted to 500 sccm, and the grown substrate was pushed out of the furnace to allow it to cool rapidly under the protective atmosphere of argon, protecting the sample from etching by argon and hydrogen.

[0074] After the sample cooled to room temperature, it was removed from the quartz tube. A 4 wt% polymethyl methacrylate (PMMA) ethyl lactate solution was then spin-coated onto the sample surface at 4500 rpm. The sample was then baked at 120°C for 10 min to solidify the spin-coated polymer film, forming a protective layer with a thickness of ~180 nm. The sample with the polymer protective layer was then placed in a 0.1 mol / L ammonium persulfate aqueous solution at 70°C. After the copper layer surface was etched, the sample with the polymer protective layer naturally detached from the substrate. The sample was retrieved using the desired substrate (silicon wafer, gold, etc.) and dried. Subsequently, the polymer protective layer was cleaned with acetone and isopropanol to obtain a clean chromium-doped Mo2N crystal grown on the surface of MoSi2N4 material.

[0075] Example 5

[0076] like Figure 1 As shown, the method for preparing ultrathin two-dimensional transition metal nitrides using the template method in this embodiment includes the following steps:

[0077] S1: Pretreatment of copper and transition metal molybdenum substrates used in chemical vapor deposition processes.

[0078] The metal substrates (copper foil, 12.5 μm thick, 5 mm long, 5 mm wide; molybdenum foil, 100 μm thick, 5 mm long, 5 mm wide; purity 99.95 wt%) required for chemical vapor deposition were ultrasonically cleaned sequentially with deionized water, ethanol, and acetone for 1 h, and then dried with a nitrogen gun. The cleaned metal substrates were then placed... Figure 2 Annealing is performed in the central heating zone of the tube furnace within the sealed quartz tube 23 of the chemical vapor deposition system shown. The furnace body of the tube furnace 22 is heated to 1000°C and held at that temperature for 5 hours under a hydrogen atmosphere with a flow rate of 500 sccm. The purpose of this step is to remove as much residual organic matter and surface oxide layer as possible from the surface of the metal substrate.

[0079] S2: MA2N4 family materials for growing ultrathin two-dimensional transition metal nitride epitaxial templates.

[0080] like Figure 3 As shown, magnetron sputtering was used to introduce chromium into the growth substrate and achieve doping of transition metal nitrides with this element. The growth substrate 31 (molybdenum sheet) was fixed on the magnetron sputtering sample stage, and the sample disk was rotated at a speed of 30 rpm. After loading a chromium target with a purity of 99.999 wt% at the magnetron sputtering cathode 32, the vacuum level of the magnetron sputtering cavity was evacuated to 10. -5 The pressure was on the order of mbar, followed by the introduction of argon gas at a flow rate of 50 sccm to maintain a stable working pressure of 10. -2 mbar. The sputtering process used a DC power supply with a sputtering voltage of 600 V, a sputtering power of 25 W, and a sputtering rate of 0.2 Å / s. Unlike Example 4, a 3 nm thick chromium film was sputtered on a molybdenum sheet.

[0081] Copper sheets are stacked on a molybdenum-chromium composite substrate to form a growth substrate 21. Figure 2In the central heating zone of the tubular furnace within the sealed quartz tube 23 of the chemical vapor deposition system shown, argon gas at a flow rate of 1000 sccm is introduced and maintained for 5 min to purge the growth system. The argon gas is then turned off, and hydrogen gas at a flow rate of 200 sccm is introduced and maintained. The heating program is set as follows: heating to 1100℃ at a rate of 30℃ / min, at which point copper melts on the molybdenum-chromium composite substrate. Unlike Example 4, cooling to 1030℃ is immediately initiated. After cooling, ammonia gas at a flow rate of 4 sccm is introduced, simultaneously etching the silicon dioxide in the quartz tube to provide a silicon source. The temperature is maintained for 3 h to grow MoSi2N4 material, which serves as the epitaxial template for subsequent growth of ultrathin two-dimensional transition metal nitrides.

[0082] S3: Growth and preparation of ultrathin two-dimensional transition metal nitrides and their doped phases.

[0083] After the MoSi2N4 material growth was completed, unlike in Example 4, the furnace temperature was lowered to 900°C, the ammonia flow rate was increased to 6 sccm, and the furnace was held at this temperature for 8 hours. The remaining molybdenum atoms diffused to the copper surface in S2 reacted with the ammonia to grow chromium-doped Mo2N on the MoSi2N4 material surface. The thickness of the chromium doping was ~3 nm, and the chromium doping concentration was 12.5 at%. After the growth process was completed, the ammonia and hydrogen were turned off, and the argon gas was turned on. The argon flow rate was adjusted to 500 sccm, and the grown substrate was pushed out of the furnace to cool rapidly under the protective atmosphere of argon, protecting the sample from etching by argon and hydrogen.

[0084] After the sample cooled to room temperature, it was removed from the quartz tube. A 4 wt% polymethyl methacrylate (PMMA) ethyl lactate solution was then spin-coated onto the sample surface at 4500 rpm. The sample was then baked at 120°C for 10 min to solidify the spin-coated polymer film, forming a protective layer with a thickness of ~180 nm. The sample with the polymer protective layer was then placed in a 0.1 mol / L ammonium persulfate aqueous solution at 70°C. After the copper layer surface was etched, the sample with the polymer protective layer naturally detached from the substrate. The sample was retrieved using the desired substrate (silicon wafer, gold, etc.) and dried. Subsequently, the polymer protective layer was cleaned with acetone and isopropanol to obtain a clean chromium-doped Mo2N crystal grown on the surface of MoSi2N4 material.

[0085] Example 6

[0086] like Figure 1 As shown, the method for preparing ultrathin two-dimensional transition metal nitrides using the template method in this embodiment includes the following steps:

[0087] S1: Pretreatment of copper and transition metal molybdenum substrates used in chemical vapor deposition processes.

[0088] The metal substrates required for chemical vapor deposition (different from Example 4, the copper foil was 25 μm thick, 5 mm long, and 5 mm wide; the molybdenum sheet was 100 μm thick, 5 mm long, and 5 mm wide; purity 99.95 wt%) were ultrasonically cleaned sequentially with deionized water, ethanol, and acetone for 1 h, and then dried with a nitrogen gun. The cleaned metal substrates were then placed... Figure 2 Annealing is performed in the central heating zone of the tube furnace within the sealed quartz tube 23 of the chemical vapor deposition system shown. The furnace body of the tube furnace 22 is heated to 1000°C and held at that temperature for 5 hours under a hydrogen atmosphere with a flow rate of 500 sccm. The purpose of this step is to remove as much residual organic matter and surface oxide layer as possible from the surface of the metal substrate.

[0089] S2: MA2N4 family materials for growing ultrathin two-dimensional transition metal nitride epitaxial templates.

[0090] like Figure 3 As shown, magnetron sputtering was used to introduce chromium into the growth substrate and achieve doping of transition metal nitrides with this element. The growth substrate 31 (molybdenum sheet) was fixed on the magnetron sputtering sample stage, and the sample disk was rotated at a speed of 30 rpm. After loading a chromium target with a purity of 99.999 wt% at the magnetron sputtering cathode 32, the vacuum level of the magnetron sputtering cavity was evacuated to 10. -5 The pressure was on the order of mbar, followed by the introduction of argon gas at a flow rate of 50 sccm to maintain a stable working pressure of 10. -2 mbar. The sputtering process used a DC power supply with a sputtering voltage of 600 V, a sputtering power of 25 W, and a sputtering rate of 0.2 Å / s to sputter a 0.5 nm thick chromium film on a molybdenum substrate.

[0091] Copper sheets are stacked on a molybdenum-chromium composite substrate to form a growth substrate 21. Figure 2 In the central heating zone of the tubular furnace within the sealed quartz tube 23 of the chemical vapor deposition system shown, argon gas at a flow rate of 1000 sccm is introduced and maintained for 5 min to purge the growth system. The argon gas is then turned off, and hydrogen gas at a flow rate of 200 sccm is introduced and maintained. The heating program is set as follows: heating to 1100℃ at a rate of 30℃ / min, at which point copper melts onto the molybdenum-chromium composite substrate. Unlike Example 4, after holding at this temperature for 20 min, the temperature is allowed to naturally cool to 1030℃. Ammonia gas at a flow rate of 4 sccm is then introduced, simultaneously etching the silicon dioxide in the quartz tube to provide a silicon source. The temperature is maintained for 3 h to grow MoSi2N4 material, which serves as the epitaxial template for subsequent growth of ultrathin two-dimensional transition metal nitrides.

[0092] S3: Growth and preparation of ultrathin two-dimensional transition metal nitrides and their doped phases.

[0093] Unlike Example 4, after the MoSi2N4 material growth was completed, the furnace temperature was lowered to 1010°C, the ammonia flow rate was increased to 6 sccm, and the furnace was held at this temperature for 8 hours. The remaining molybdenum atoms diffused to the copper surface in S2 reacted with the ammonia to grow chromium-doped Mo2N on the MoSi2N4 material surface. The thickness of this layer was ~3 nm, and the chromium doping concentration was 12.5 at%. After the growth process was completed, the ammonia and hydrogen gases were turned off, and the argon gas was turned on. The argon flow rate was adjusted to 500 sccm, and the grown substrate was pushed out of the furnace to allow it to cool rapidly under the protective atmosphere of argon, protecting the sample from etching by argon and hydrogen.

[0094] After the sample cooled to room temperature, it was removed from the quartz tube. A 4 wt% polymethyl methacrylate (PMMA) ethyl lactate solution was then spin-coated onto the sample surface at 4500 rpm. The sample was then baked at 120°C for 10 min to solidify the spin-coated polymer film, forming a protective layer with a thickness of ~180 nm. The sample with the polymer protective layer was then placed in a 0.1 mol / L ammonium persulfate aqueous solution at 70°C. After the copper layer surface was etched, the sample with the polymer protective layer naturally detached from the substrate. The sample was retrieved using the desired substrate (silicon wafer, gold, etc.) and dried. Subsequently, the polymer protective layer was cleaned with acetone and isopropanol to obtain a clean chromium-doped Mo2N crystal grown on the surface of MoSi2N4 material.

[0095] Example 7

[0096] like Figure 1 As shown, the method for preparing ultrathin two-dimensional transition metal nitrides using the template method in this embodiment includes the following steps:

[0097] S1: Pretreatment of copper and transition metal tungsten substrates used in chemical vapor deposition processes.

[0098] The metal substrates (copper foil, 12.5 μm thick, 5 mm long, and 5 mm wide; tungsten foil, 100 μm thick, 5 mm long, and 5 mm wide, with a purity of 99.95 wt%) required for chemical vapor deposition were ultrasonically cleaned sequentially with deionized water, ethanol, and acetone for 1 hour, and then dried with a nitrogen gun. The cleaned metal substrates were then placed... Figure 2Annealing is performed in the central heating zone of the tube furnace within the sealed quartz tube 23 of the chemical vapor deposition system shown. The furnace body of the tube furnace 22 is heated to 1000°C and held at that temperature for 5 hours under a hydrogen atmosphere with a flow rate of 500 sccm. The purpose of this step is to remove as much residual organic matter and surface oxide layer as possible from the surface of the metal substrate.

[0099] S2: MA2N4 family materials for growing ultrathin two-dimensional transition metal nitride epitaxial templates.

[0100] like Figure 3 As shown, chromium was introduced into the growth substrate using magnetron sputtering, and this element was used to dope transition metal nitrides. The growth substrate 31 (tungsten sheet) was fixed on the magnetron sputtering sample stage, and the sample disk was rotated at a speed of 30 rpm. After loading a chromium target with a purity of 99.999 wt% at the magnetron sputtering cathode 32, the vacuum level of the magnetron sputtering cavity was evacuated to 10. -5 The pressure was on the order of mbar, followed by the introduction of argon gas at a flow rate of 50 sccm to maintain a stable working pressure of 10. -2 mbar. The sputtering process uses a DC power supply with a sputtering voltage of 600 V, a sputtering power of 25 W, and a sputtering rate of 0.2 Å / s to sputter a 0.5 nm thick chromium film on a tungsten sheet.

[0101] Copper sheets are stacked on a tungsten-chromium composite substrate to form a growth substrate 21, which is then placed as follows: Figure 2 The central heating zone of the tubular furnace within the sealed quartz tube 23 of the chemical vapor deposition system is shown. Argon gas at a flow rate of 1000 sccm is introduced and maintained for 5 min to purge the growth system. The argon gas is then turned off, and hydrogen gas at a flow rate of 200 sccm is introduced and maintained. Unlike Example 4, the heating program is set as follows: heating to 1030°C at a rate of 30°C / min, introducing ammonia gas at a flow rate of 4 sccm, while simultaneously etching the silicon dioxide in the quartz tube with ammonia gas to provide a silicon source, holding at this temperature for 10 h to grow WSi2N4 material, which serves as the epitaxial template for subsequent growth of ultrathin two-dimensional transition metal nitrides.

[0102] S3: Growth and preparation of ultrathin two-dimensional transition metal nitrides and their doped phases.

[0103] Unlike Example 4, after the WSi2N4 material growth was completed, the furnace temperature was lowered to 1000°C, the ammonia flow rate was increased to 6 sccm, and the furnace was held at this temperature for 8 hours. The remaining tungsten atoms diffused to the copper surface in S2 reacted with the ammonia to grow chromium-doped WN on the WSi2N4 material surface. The thickness of the WN was ~4 nm, and the chromium doping concentration was 12.5 at%. After the growth process was completed, the ammonia and hydrogen were turned off, and the argon gas was turned on. The argon flow rate was adjusted to 500 sccm, and the grown substrate was pushed out of the furnace to allow it to cool rapidly under the protective atmosphere of argon, protecting the sample from etching by argon and hydrogen.

[0104] After the sample cooled to room temperature, it was removed from the quartz tube. A 4 wt% polymethyl methacrylate (PMMA) ethyl lactate solution was then spin-coated onto the sample surface at 4500 rpm. The sample was then baked at 120°C for 10 min to solidify the spin-coated polymer film, forming a protective layer with a thickness of ~180 nm. The sample with the polymer protective layer was then placed in a 0.1 mol / L ammonium persulfate aqueous solution at 70°C. After the copper layer surface was etched, the sample with the polymer protective layer naturally detached from the substrate. The sample was retrieved using the desired substrate (silicon wafer, gold, etc.) and dried. Subsequently, the polymer protective layer was cleaned with acetone and isopropanol to obtain a clean chromium-doped WN crystal grown on the surface of WSi2N4 material.

[0105] Example 8

[0106] like Figure 1 As shown, the method for preparing ultrathin two-dimensional transition metal nitrides using the template method in this embodiment includes the following steps:

[0107] S1: Pretreatment of copper and transition metal tungsten substrates used in chemical vapor deposition processes.

[0108] The metal substrates (copper foil, 12.5 μm thick, 5 mm long, 5 mm wide; tungsten foil, 100 μm thick, 5 mm long, 5 mm wide; purity 99.95 wt%) required for chemical vapor deposition were ultrasonically cleaned sequentially with deionized water, ethanol, and acetone for 1 h, and then dried with a nitrogen gun. The cleaned metal substrates were then placed... Figure 2 Annealing is performed in the central heating zone of the tube furnace within the sealed quartz tube 23 of the chemical vapor deposition system shown. The furnace body of the tube furnace 22 is heated to 1000 °C and held at that temperature for 5 hours under a hydrogen atmosphere with a flow rate of 500 sccm. The purpose of this step is to remove as much residual organic matter and surface oxide layer as possible from the surface of the metal substrate.

[0109] S2: MA2N4 family materials for growing ultrathin two-dimensional transition metal nitride epitaxial templates.

[0110] like Figure 3 As shown, chromium was introduced into the growth substrate using magnetron sputtering, and this element was used to dope transition metal nitrides. The growth substrate 31 (tungsten sheet) was fixed on the magnetron sputtering sample stage, and the sample disk was rotated at a speed of 30 rpm. After loading a chromium target with a purity of 99.999 wt% at the magnetron sputtering cathode 32, the vacuum level of the magnetron sputtering cavity was evacuated to 10. -5 The pressure was on the order of mbar, followed by the introduction of argon gas at a flow rate of 50 sccm to maintain a stable working pressure of 10. -2 mbar. The sputtering process used a DC power supply with a sputtering voltage of 600 V, a sputtering power of 25 W, and a sputtering rate of 0.2 Å / s. Unlike Example 7, a 3 nm thick chromium film was sputtered on a tungsten sheet.

[0111] Copper sheets are stacked on a tungsten-chromium composite substrate to form a growth substrate 21, which is then placed as follows: Figure 2 The chemical vapor deposition system shown is located in the central heating zone of the tubular furnace within the sealed quartz tube 23. Argon gas at a flow rate of 1000 sccm is introduced and maintained for 5 min to purge the growth system. The argon gas is then turned off, and hydrogen gas at a flow rate of 200 sccm is introduced and maintained. The heating program is set as follows: heating to 1030℃ at a rate of 30℃ / min, introducing ammonia gas at a flow rate of 4 sccm, simultaneously etching the silicon dioxide in the quartz tube with ammonia gas to provide a silicon source, holding at this temperature for 10 h to grow WSi₂N₄ material, which will serve as the epitaxial template for subsequent growth of ultrathin two-dimensional transition metal nitrides.

[0112] S3: Growth and preparation of ultrathin two-dimensional transition metal nitrides and their doped phases.

[0113] Unlike Example 7, after the WSi2N4 material growth was completed, the furnace temperature was lowered to 950°C, the ammonia flow rate was increased to 6 sccm, and the furnace was held at this temperature for 8 hours. The remaining tungsten atoms diffused to the copper surface in S2 and the chromium atoms introduced by magnetron sputtering reacted with the ammonia to grow chromium-doped WN on the WSi2N4 material surface. The thickness of the WN was ~4 nm, and the chromium doping concentration was ~12.5 at%. After the growth process was completed, the ammonia and hydrogen were turned off, and the argon gas was turned on. The argon flow rate was adjusted to 500 sccm, and the grown substrate was pushed out of the furnace to cool rapidly under the protective atmosphere of argon, protecting the sample from etching by argon and hydrogen.

[0114] After the sample cooled to room temperature, it was removed from the quartz tube. A 4 wt% polymethyl methacrylate (PMMA) ethyl lactate solution was then spin-coated onto the sample surface at 4500 rpm. The sample was then baked at 120°C for 10 min to solidify the spin-coated polymer film, forming a protective layer with a thickness of ~180 nm. The sample with the polymer protective layer was then placed in a 0.1 mol / L ammonium persulfate aqueous solution at 70°C. After the copper layer surface was etched, the sample with the polymer protective layer naturally detached from the substrate. The sample was retrieved using the desired substrate (silicon wafer, gold, etc.) and dried. Subsequently, the polymer protective layer was cleaned with acetone and isopropanol to obtain a clean chromium-doped WN crystal grown on the surface of WSi2N4 material.

[0115] like Figure 4 As shown in the optical microscope images of the uniformly thick ultrathin two-dimensional transition metal nitrides prepared by this invention, the sample size is greater than 20 micrometers and the thickness is uniform, indicating good growth quality.

[0116] like Figure 5 As shown in the cross-sectional scanning transmission electron microscope image of the ultrathin two-dimensional transition metal nitride prepared by this invention, the atomic images of the sample are clearly visible, and the Fourier transform results (upper right inset) are consistent with the selected area electron diffraction results of the sample, which all indicate that the sample has extremely high crystallinity.

[0117] The results show that this invention utilizes MA2N4, a material with a structure similar to transition metal nitrides, as a growth substrate to prepare ultrathin two-dimensional transition metal nitride films. MA2N4, as a van der Waals material, possesses an atomically smooth surface, and its nitride-terminated characteristics make it more conducive to the horizontal growth of transition metal nitrides on its surface. This invention can obtain large-area, uniformly thick ultrathin two-dimensional transition metal nitride films, laying the foundation for expanding the family of two-dimensional materials, exploring their properties, and developing applications of two-dimensional materials.

Claims

1. A method for preparing ultrathin two-dimensional transition metal nitrides using a template method, characterized in that, MA2N4 family materials, which have atomic-level smoothness and similar structures to transition metal nitrides, are used as growth substrates to promote horizontal growth and weaken the "island" growth in non-layered materials. Different transition metal nitrides are prepared by selecting different MA2N4 family materials. A copper / transition metal multilayer composite substrate was selected as the growth substrate. Copper served as the matrix for growing MA2N4 and as the diffusion channel for the transition metal, and was located on the surface of the transition metal multilayer substrate. A chemical vapor deposition system was used, with a pre-selected copper / transition metal stacked substrate as the growth substrate, placed in the center of the heating zone of a horizontal tube furnace. The temperature was raised above the melting point of copper and held for 0-60 min to allow the lower transition metal atoms to diffuse to the copper surface. The temperature was then lowered to 1030-1050 °C and held. A solid, liquid, or gaseous nitrogen source was introduced in a reducing atmosphere with a flow rate of 100-500 sccm to grow MA2N4 material. After the MA2N4 material is grown, the furnace temperature of the tube furnace in the chemical vapor deposition system is reduced to 800~1010 ℃ and kept at that temperature. A solid or gaseous nitrogen source is introduced under a reducing atmosphere with a flow rate of 100~500 sccm. Using MA2N4 as the substrate, ultrathin two-dimensional transition metal nitride materials are grown. In the chemical vapor deposition process, the nitrogen source is one or more of ammonia, nitrogen dioxide, nitrogen, urea, and nitrate, and the auxiliary carrier gas is one of hydrogen, argon, or a mixture of the two, with a flow rate of 100~500 sccm; in the MA2N4 material, the element M represents a transition metal element, including molybdenum, tungsten, titanium, zirconium, hafnium, vanadium, niobium, tantalum, or chromium; the element A represents a Group IV element, including silicon or germanium, which is supplied as a precursor through silicon dioxide, silane, germanium particles, germanium dioxide, or germanium iodide.

2. The method for preparing ultrathin two-dimensional transition metal nitrides by template method according to claim 1, characterized in that, Magnetron sputtering is used to dope nitrides and expand their physical properties.

3. The method for preparing ultrathin two-dimensional transition metal nitrides using the template method according to claim 1, characterized in that, The choice of the underlying transition metal matrix depends on the type of transition metal in the target growth material. In copper, it has diffusion capability and can form stable nitrides.

4. The method for preparing ultrathin two-dimensional transition metal nitrides by template method according to claim 3, characterized in that, Transition metals include one or more of molybdenum, tungsten, chromium, vanadium, niobium, and tantalum, with a purity greater than 99.95 wt% and a thickness of not less than 50 micrometers.

5. The method for preparing ultrathin two-dimensional transition metal nitrides by template method according to claim 1, characterized in that, After the transition metal nitride is epitaxially grown on MA2N4 material, it is rapidly removed from the heating zone of the tube furnace in the chemical vapor deposition system for cooling. After cooling to room temperature, it is taken out and a polymer is coated onto its surface using spin coating and then heated and cured to form a polymer protective layer. The substrate covered with the protective layer is then immersed in a 0.05~0.2 mol / L ammonium persulfate solution for etching. During the etching process, the etching solution is heated to a temperature of 30~70 ℃. After etching, a thin film with a complete polymer protective layer is obtained and transferred to the desired substrate. The polymer protective layer is then removed using an organic solvent.

6. The method for preparing ultrathin two-dimensional transition metal nitrides by template method according to claim 5, characterized in that, The polymer is one or more of polyethylene, polypropylene, polystyrene, and polymethyl methacrylate, and the organic solvent for cleaning the protective layer of the polymer is one or more of alcohols, ketones, aromatics, and halogenated hydrocarbons.

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