Preparation method of monatomic layer two-dimensional metal nitride

Abstract

The invention discloses a preparation method of a monatomic layer two-dimensional metal nitride. The preparation method comprises the following steps: providing a metal single crystal substrate; carrying out surface treatment on the metal single crystal substrate; and preparing the monatomic layer two-dimensional metal nitride on the metal single crystal substrate by using a molecular beam epitaxy process. According to the method, the molecular beam epitaxy technology is used for preparing the monatomic layer two-dimensional metal nitride on the surface of the metal single crystal substrate with atomic-scale flatness, and the prepared monatomic layer two-dimensional metal nitride is high in purity and few in lattice defects.

Description

Technical Field

[0001] The present invention belongs to the technical field of semiconductor materials, and particularly relates to a method for preparing single-atomic-layer two-dimensional metal nitrides. Background Art

[0002] Nitride semiconductors are an important part of the third-generation semiconductor family. They have an ultra-wide bandgap, high temperature resistance, and excellent radiation resistance, and are suitable for high-frequency and high-power devices. With the in-depth research on single-atomic-layer two-dimensional nitrides, compared with traditional bulk nitrides, single-atomic-layer two-dimensional nitrides have more excellent properties: a wider bandgap, excellent mechanical strain ability, extremely strong optical transparency, and ultra-low thermal conductivity, etc.

[0003] Gallium nitride (GaN) is an important wide-bandgap semiconductor material. As the most characteristic material in nitride semiconductors, it has a wide range of applications in the fields of optoelectronics and microelectronics due to its unique optoelectronic properties. Gallium nitride has a direct wide bandgap of 3.4 eV, which makes it have application prospects in fields such as light-emitting diodes (LEDs), laser diodes, and high-performance ultraviolet detectors. Secondly, gallium nitride exhibits the characteristics of high carrier concentration and high breakdown electric field, which makes it perform well in high-frequency and high-power electronic devices. In addition, the high thermal conductivity and good chemical stability of gallium nitride make it an ideal material for high electron mobility transistors (HEMTs), high-frequency microwave communication, and terahertz detectors operating at high temperatures. These properties make gallium nitride a key material in fields such as optoelectronic devices and high-frequency and high-power power electronic devices.

[0004] In traditional preparation processes, gallium nitride materials are often prepared by the method of bulk single-crystal growth. However, due to the high melting point and saturated vapor pressure of gallium nitride, it cannot exist in the form of single crystals in nature, and it is difficult to prepare two-dimensional gallium nitride thin films by traditional bulk single-crystal growth methods. With the in-depth research on gallium nitride materials, their optoelectronic properties in different dimensions and structures are being continuously explored and optimized to meet the growing application requirements, so new preparation methods need to be sought.

[0005] In the prior art, two-dimensional gallium nitride thin films can be grown through metal-organic chemical vapor deposition (MOCVD) technology and hydride vapor phase epitaxy (HVPE) technology. However, the two-dimensional GaN film grown by MOCVD needs to be annealed after growth, and the final film may have cracks, affecting product quality. HVPE usually requires the use of a heterogeneous substrate for the growth of two-dimensional gallium nitride thin films. The mismatch between the lattice constant and the thermal expansion coefficient will cause strong stress in the epitaxial layer, which in turn causes cracks and high defect density. At the same time, the growth conditions of HVPE are relatively harsh and the growth window is narrow, resulting in poor process repeatability. In addition, liquid metal gallium is transferred to the surface of copper foil, and a tube furnace is used to keep the mixture at 900°C for 10 hours to obtain a copper-gallium alloy. Then, the copper-gallium alloy is used to prepare a two-dimensional gallium nitride / copper foil composite by chemical vapor deposition. Then, the two-dimensional gallium nitride in the two-dimensional gallium nitride / copper foil composite is transferred to a carrier sheet by PMMA transfer method or bubbling transfer method to obtain a two-dimensional gallium nitride film. This method realizes the growth of two-dimensional gallium nitride through the surface-restricted nitration reaction of chemical vapor deposition. The prepared two-dimensional gallium nitride does not require epitaxial two-dimensional materials to restrict the growth of the three-dimensional structure. The obtained two-dimensional gallium nitride film can be directly transferred, and a thinner two-dimensional gallium nitride film can be prepared. However, although this method obtains a thinner two-dimensional gallium nitride film, the obtained two-dimensional gallium nitride is still a wurtzite crystal structure, and a single atomic layer of two-dimensional gallium nitride cannot be prepared.

[0006] Therefore, in order to solve the above technical problems, it is necessary to provide a method for preparing a single atomic layer of two-dimensional metal nitride. Summary of the invention

[0007] The object of the present invention is to provide a method for preparing a single atomic layer of two-dimensional metal nitride, which can achieve controllable growth of the single atomic layer of two-dimensional metal nitride.

[0008] In order to achieve the above purpose, the technical solution provided by an embodiment of the present invention is as follows:

[0009] A method for preparing a single atomic layer two-dimensional metal nitride, the preparation method comprising the following steps:

[0010] Providing a metal single crystal substrate;

[0011] Surface treatment of a metal single crystal substrate;

[0012] Single atomic layer two-dimensional metal nitride is prepared on a metal single crystal substrate using molecular beam epitaxy.

[0013] In one embodiment, the single atomic layer two-dimensional metal nitride is prepared by using a molecular beam epitaxy device, and the molecular beam epitaxy device includes a first chamber and a second chamber, the vacuum degree of the second chamber is higher than the vacuum degree of the first chamber, and the second chamber is provided with a metal source, a nitrogen source and a liquid nitrogen cold trap.

[0014] In one embodiment, preparing a single atomic layer of two-dimensional metal nitride on a metal single crystal substrate using a molecular beam epitaxy process includes the following steps:

[0015] Placing the metal single crystal substrate in the second chamber, and raising the temperature of the metal single crystal substrate to 350° C. to 800° C. at a heating rate of 0.1° C. / s to 10° C. / s;

[0016] A metal source beam and a nitrogen plasma source beam are obtained respectively through a metal source and a nitrogen source, so as to prepare a single atomic layer of two-dimensional metal nitride on a metal single crystal substrate;

[0017] The prepared single atomic layer two-dimensional metal nitride is cooled to room temperature at a cooling rate of 1°C / min to 30°C / min.

[0018] In one embodiment, the metal source beam is obtained by heating the metal source to 500° C. to 800° C., and the flow rate of the metal source beam is and / or,

[0019] The nitrogen source is nitrogen gas, the flow rate of the nitrogen gas is 0.5 sccm to 5 sccm, the nitrogen plasma source beam is obtained by radio frequency cracking of the nitrogen gas, and the power of the radio frequency cracking of the nitrogen gas is 100W to 350W.

[0020] In one embodiment, surface treatment of a metal single crystal substrate comprises the following steps:

[0021] Performing degassing and annealing treatment on the metal single crystal substrate in the first chamber;

[0022] The metal single crystal substrate is subjected to argon etching and annealing treatment for several times in the second chamber.

[0023] In one embodiment, the vacuum degree of the first chamber is 1×10 -8 ~1×10 -9 mbar, the vacuum degree of the second chamber is not less than 1×10 -10 mbar.

[0024] In one embodiment, the purity of the metal source is greater than or equal to 99.9999%, and the purity of the nitrogen source is greater than or equal to 99.9999%.

[0025] In one embodiment, after the metal single crystal substrate is surface treated, the height of the atomic-level steps on the surface of the metal single crystal substrate is 0.1 nm to 0.5 nm.

[0026] In one embodiment, the metal in the single atomic layer two-dimensional metal nitride is a combination of one or more of gallium, aluminum, and indium.

[0027] In one embodiment, the metal single crystal substrate is a gold single crystal substrate, a silver single crystal substrate or a copper single crystal substrate.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] The present invention uses molecular beam epitaxy technology to prepare a single atomic layer of two-dimensional gallium nitride on the surface of a metal single crystal substrate with atomic-level flatness;

[0030] The entire preparation process of the present invention is carried out in a high vacuum environment, which can effectively avoid contamination by impurities and control the doping amount to prepare high-purity, high-quality single-atomic-layer two-dimensional gallium nitride;

[0031] The present invention can control the growth rate of the single atomic layer two-dimensional gallium nitride, thereby realizing the control of the thickness and composition of the single atomic layer two-dimensional gallium nitride on the atomic scale. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0033] Figure 1 Schematic diagram of the process of preparing a single atomic layer two-dimensional metal nitride in Example 1 of the present invention;

[0034] Figure 2 This is an STM image of a single atomic layer of two-dimensional gallium nitride in Example 1 of the present invention;

[0035] Figure 3 This is a local STM image of a single atomic layer of two-dimensional gallium nitride in Example 1 of the present invention;

[0036] Figure 4 NC-AFM image and crystal structure schematic diagram of a single atomic layer of two-dimensional gallium nitride in Example 1 of the present invention. DETAILED DESCRIPTION

[0037] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0038] The present invention discloses a method for preparing a single atomic layer two-dimensional metal nitride, characterized in that the preparation method comprises the following steps:

[0039] Providing a metal single crystal substrate;

[0040] Surface treatment of a metal single crystal substrate;

[0041] Single atomic layer two-dimensional metal nitride is prepared on a metal single crystal substrate using molecular beam epitaxy.

[0042] Molecular beam epitaxy is a physical deposition process for compound semiconductor multilayer films. Its basic principle is to heat the elements that make up the film in their own molecular beam furnaces under ultra-high vacuum conditions into directional molecular beams that are incident on the heated substrate to grow the film.

[0043] The molecular beam epitaxy device used in the present invention includes a first chamber and a second chamber, the first chamber and the second chamber are connected to facilitate the transfer of samples between the first chamber and the second chamber, and a baffle is provided between the first chamber and the second chamber to isolate the first chamber and the second chamber so that the first chamber and the second chamber can work independently. When the first chamber and the second chamber are evacuated to the vacuum state required for work, the vacuum degree of the second chamber is higher than the vacuum degree of the first chamber.

[0044] Specifically, the first chamber is the front chamber of the molecular beam epitaxy equipment, which is evacuated by mechanical pumps and molecular pumps. The second chamber is the growth chamber of the molecular beam epitaxy equipment, which has a higher vacuum degree. Under normal circumstances, the growth chamber always maintains a vacuum state. The sample introduction process is to first enter the front chamber from the atmosphere, evacuate the front chamber to the vacuum degree that meets the requirements, and then enter the growth chamber; the sample removal process is to first transfer the sample from the growth chamber to the front chamber, close the growth chamber, and then break the vacuum of the front chamber. When the vacuum degree of the front chamber is close to the atmospheric environment, the sample is taken out.

[0045] The present invention is further described below with reference to specific examples.

[0046] Comparative Example 1:

[0047] The preparation method of the metal nitride in this comparative example comprises:

[0048] providing a substrate;

[0049] Metal nitrides are grown on substrates using molecular beam epitaxy.

[0050] The substrate is a silicon substrate, a silicon carbide substrate or a sapphire substrate, and the metal nitride is any one of AlN, AlGaN, AlInGaN and GaN.

[0051] In this comparative example, metal nitrides were prepared in conventional substrates of semiconductor devices using molecular beam epitaxy. However, such metal nitrides are only ordinary single crystal metal nitrides with stable structure. However, their photoelectric properties are significantly different from those of single atomic layer two-dimensional metal nitrides. With the development of optoelectronic devices and electronic power devices, such metal nitrides can no longer meet the demand.

[0052] Embodiment 1:

[0053] Ginseng Figure 1 As shown, the method for preparing a single atomic layer two-dimensional metal nitride in this embodiment includes the following steps:

[0054] S1. Provide a metal single crystal substrate.

[0055] The metal single crystal substrate includes but is not limited to a gold single crystal substrate, a silver single crystal substrate or a copper single crystal substrate. The metal single crystal substrate used in this embodiment is a gold single crystal substrate with a (111) crystal plane. In other embodiments, gold single crystal substrates with different crystal planes such as (110) can also be selected.

[0056] S2. Surface treatment is performed on the metal single crystal substrate.

[0057] Illustratively, in this embodiment, the metal single crystal substrate is surface treated in a molecular beam epitaxy device.

[0058] Specifically, this step includes:

[0059] 1. Degassing and annealing the metal single crystal substrate in the first chamber.

[0060] First, the gold single crystal substrate is introduced from the atmosphere into the first chamber of the molecular beam epitaxy equipment, and the first chamber is evacuated until the vacuum degree of the first chamber reaches 1×10 -8 ~1×10 -9 mbar level, the gold single crystal substrate is subjected to low-temperature annealing and degassing treatment. The temperature is set to 200°C and the treatment time is 2h to 48h to remove water molecules and other impurities adsorbed on the surface of the gold single crystal substrate.

[0061] 2. Performing argon etching and annealing treatments on the metal single crystal substrate several times in the second chamber.

[0062] Using argon etching to process metal single crystal substrates has the following beneficial effects:

[0063] (1) During the argon etching process, argon ions are used to bombard the surface of the metal single crystal substrate, which can peel off the atoms and impurity atoms on the surface of the metal single crystal substrate, remove the impurities and oxide layer on the surface, and obtain a clean surface;

[0064] (2) Argon etching can help optimize the surface structure of metal single crystal substrates so that they can achieve the atomic-level flatness and specific surface state required for subsequent preparation processes.

[0065] Annealing after argon etching has the following beneficial effects:

[0066] (1) During the growth and processing of the metal single crystal substrate, various stresses will be introduced into the material. Annealing the metal single crystal substrate after argon etching can rearrange the crystal lattice of the metal single crystal substrate and release the stress, thereby preventing the metal single crystal substrate from being deformed or broken during subsequent processing or use;

[0067] (2) The argon etching process will cause lattice damage to the surface or interior of the metal single crystal substrate. Annealing treatment can cause atoms to rearrange, repair these defects, and make the crystal structure of the metal single crystal substrate more complete.

[0068] By combining argon etching and annealing to treat the surface of the metal single crystal substrate, the surface of the metal single crystal substrate can be made smoother, irregular structures and defects on the surface can be eliminated, and large-area atomic-level steps can be formed on the surface. The height of the atomic-level steps is 0.1nm to 0.5nm, preferably 0.1nm.

[0069] Specifically, after the degassing and annealing treatments are completed, the first chamber is further evacuated until the vacuum degree of the first chamber is not less than 1×10 -10 mbar level, the baffle is opened to transfer the gold single crystal substrate in this embodiment to the second chamber of the molecular beam epitaxy equipment, and the gold single crystal substrate is subjected to several rounds of argon etching and annealing. Argon etching is used to remove impurities on the surface of the gold single crystal, and annealing can rearrange the gold single crystal lattice. The combination of argon etching and annealing can form an atomically flat surface on the gold single crystal substrate.

[0070] It is worth noting that after each round of argon etching and annealing treatment on the metal single crystal substrate, the treated metal single crystal substrate will be transferred to the scanning probe microscope (SPM) chamber, and the surface morphology of the gold single crystal substrate will be obtained using an ultra-high vacuum scanning tunneling microscope (STM) to confirm whether a clean atomic-level flat surface is obtained. If so, it will be transferred back to the second chamber for the growth process of a single atomic layer of two-dimensional metal nitride; if not, it will be transferred back to the second chamber for argon etching and annealing again until an atomic-level flat surface is obtained. Among them, the vacuum degree of the SPM chamber must be no less than 1×10 -11 mbar.

[0071] S3. Prepare a single atomic layer of two-dimensional metal nitride on a metal single crystal substrate using a molecular beam epitaxy process.

[0072] The metal in the single atomic layer two-dimensional metal nitride is a combination of one or more of gallium, aluminum, and indium. The single atomic layer two-dimensional metal nitride in this embodiment is a single atomic layer two-dimensional gallium nitride.

[0073] This step is carried out in a molecular beam epitaxy device having corresponding metal sources and nitrogen sources. The metal source and nitrogen source can be controlled respectively by an electron beam thermal evaporation source and a gas radio frequency cracking source in the molecular beam epitaxy device, specifically including:

[0074] 1. Obtain a metal source beam and a nitrogen plasma source beam through a metal source and a nitrogen source respectively.

[0075] The metal source beam is obtained by heating the metal source to 500°C to 800°C, and the flow rate of the metal source beam is controlled at The purity of the metal source is greater than or equal to 99.9999%. The metal source in this embodiment is a gallium source, and the metal source beam is a gallium source beam.

[0076] The nitrogen source in this embodiment is nitrogen gas, and the purity of the nitrogen source is greater than or equal to 99.9999%. Nitrogen gas is introduced into the molecular beam epitaxy equipment with a flow rate of 0.5 sccm to 5 sccm. The nitrogen plasma source beam is obtained by radio frequency cracking of the nitrogen gas, and the power of the radio frequency cracking of the nitrogen gas is 100W to 350W.

[0077] 2. Place the metal single crystal substrate in the second chamber, and increase the temperature of the metal single crystal substrate to 350° C. to 800° C. at a heating rate of 0.1° C. / s to 10° C. / s.

[0078] Specifically, the growth of a single atomic layer of two-dimensional gallium nitride is carried out in the second chamber of the molecular beam epitaxy equipment, a surface-treated gold single crystal substrate is placed on a growth table in the second chamber, and the metal single crystal substrate is heated by electron beam heating.

[0079] 3. Prepare single atomic layer two-dimensional metal nitride on metal single crystal substrate.

[0080] Specifically, in this embodiment, the gallium source beam and the nitrogen plasma source beam are aligned with a gold single crystal substrate placed on a growth platform to prepare a single atomic layer of two-dimensional gallium nitride on the gold single crystal substrate.

[0081] It is worth noting that the beam ports of the metal source beam and the nitrogen plasma source beam in the molecular beam epitaxy equipment are provided with mechanical baffles, and the growth time of the single atomic layer two-dimensional metal nitride is controlled by the time when the mechanical baffles are opened.

[0082] 4. Cool the prepared single atomic layer two-dimensional metal nitride to room temperature at a cooling rate of 1°C / min to 30°C / min.

[0083] It should be understood that the surface treatment of metal single crystal substrates, the preparation and characterization of single atomic layer two-dimensional metal nitrides must all be carried out in an ultra-high vacuum environment. The quality of the vacuum environment is crucial to whether high-quality single atomic layer two-dimensional metal nitrides can be grown, which is mainly reflected in the following aspects:

[0084] (1) Reduce impurity contamination: In an ultra-high vacuum environment, impurities in the air, such as oxygen, water vapor, and dust, are significantly reduced, thereby preventing these impurities from forming defects on the surface or interface of the single atomic layer of two-dimensional metal nitride;

[0085] (2) Keep the surface clean: After being treated, the surface of the metal single crystal substrate can be kept clean in an ultra-high vacuum environment, thus avoiding the problem of contamination during the subsequent growth of the single atomic layer of two-dimensional metal nitride;

[0086] (3) Precise control of the purity of the metal source and nitrogen source: The vacuum environment eliminates the interference of oxygen and other impurities in the air, allowing the preparation of single-atomic-layer two-dimensional metal nitrides under pure conditions;

[0087] (4) Controlling the growth rate and uniformity: In a vacuum, the transmission process of the metal source beam from the metal source to the metal single crystal substrate is not disturbed by air molecules, ensuring uniform material deposition, so that the deposition rate and uniformity of MBE can be better controlled;

[0088] (5) Optimizing the structure and crystal quality of single-atomic-layer two-dimensional metal nitrides: The vacuum environment provides a stable deposition condition, allowing single-atomic-layer two-dimensional metal nitrides to grow with an ideal crystal structure and uniformity, which is very important for the formation of high-quality single-atomic-layer two-dimensional metal nitrides;

[0089] (6) Improved surface and interface properties: In a vacuum, a single atomic layer of two-dimensional metal nitride can be uniformly deposited on the surface of a non-polluting metal single crystal substrate, and the resulting single atomic layer of two-dimensional metal nitride has a smooth and defect-free surface. At the same time, the vacuum environment can reduce chemical reactions and contamination at the interface, and improve the purity and stability of the interface;

[0090] (7) Atomic layer-by-layer deposition: Under ultra-high vacuum conditions, MBE can achieve true atomic layer-by-layer deposition and atomic mutation interfaces between layers. This precise control is crucial for the preparation of single-atomic-layer two-dimensional metal nitride films with specific structures and functions.

[0091] In addition, a liquid nitrogen cold trap is provided in the second chamber of the molecular beam epitaxy device in the present embodiment, and the liquid nitrogen cold trap can adsorb impurity gases in the growth chamber, such as water vapor, oxygen, etc. These gases condense on the surface of the cold trap at low temperatures, thereby reducing the residual gas in the second chamber and improving the vacuum degree of the second chamber. At the same time, through adsorption, the liquid nitrogen cold trap reduces the density of gas molecules in the second chamber, so that the molecular beam will not collide during the transmission process, ensuring the purity and stability of the molecular beam. In addition, the liquid nitrogen cold trap can also absorb and shield the thermal radiation generated by the source furnace and other high-temperature components to prevent these heats from adversely affecting the sample and other equipment in the second chamber. By lowering the temperature in the second chamber, the liquid nitrogen cold trap helps to maintain a stable growth environment, thereby avoiding the interference of temperature fluctuations on the growth process.

[0092] Compared with traditional vapor phase epitaxy technology, the growth temperature required for preparing single atomic layer two-dimensional metal nitride using molecular beam epitaxy technology in this embodiment is lower, and the growth temperature ranges from 500°C to 700°C, which helps to reduce lattice defects caused by differences in thermal expansion coefficients during the growth process.

[0093] Ginseng Figure 2 and Figure 3 Shown are STM images of the single atomic layer two-dimensional gallium nitride prepared in this embodiment at different magnifications. Figure 2 It shows that the prepared two-dimensional gallium nitride is distributed on a gold single crystal substrate with a (111) crystal plane, and forms regular triangular two-dimensional islands, and the three sides of the two-dimensional islands are parallel to the lattice direction of the gold single crystal substrate. Figure 3The sample has a fishbone structure. The fishbone structure on the left corresponds to the atomic reconstruction of the surface of the (111) crystal plane gold single crystal substrate, while the fishbone structure on the right is a hexagonal lattice with a period of about 3nm in the two-dimensional island. This structure originates from the moiré effect between the two-dimensional gallium nitride and the (111) crystal plane gold single crystal substrate lattice. The average height of the two-dimensional island is only 0.03nm, and a single atomic layer of two-dimensional gallium nitride has been successfully prepared on the surface.

[0094] Ginseng Figure 4 As shown, the atomic resolution image obtained on the two-dimensional island in a liquid nitrogen environment using non-contact atomic force microscopy (NC-AFM) in constant height mode is observed, and the atoms are arranged in a hexagonal structure with a period of 0.32nm, which is highly consistent with the theoretical model of gallium nitride (as shown in the ball-and-stick model in the figure). This result further verifies the successful preparation of a single atomic layer of two-dimensional gallium nitride.

[0095] It can be seen from the above technical solution that the present invention has the following beneficial effects:

[0096] The present invention uses molecular beam epitaxy technology to prepare a single atomic layer of two-dimensional gallium nitride on the surface of a metal single crystal substrate with atomic-level flatness;

[0097] The entire preparation process of the present invention is carried out in a high vacuum environment, which can effectively avoid contamination by impurities and control the doping amount to prepare high-purity, high-quality single-atomic-layer two-dimensional gallium nitride;

[0098] The present invention can control the growth rate of the single atomic layer two-dimensional gallium nitride, thereby realizing the control of the thickness and composition of the single atomic layer two-dimensional gallium nitride on the atomic scale.

[0099] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

[0100] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A method for preparing a single atomic layer two-dimensional metal nitride, characterized in that: The preparation method comprises the following steps: Providing a metal single crystal substrate; Surface treatment of a metal single crystal substrate; Single atomic layer two-dimensional metal nitride is prepared on a metal single crystal substrate using molecular beam epitaxy.

2. The method for preparing a single atomic layer two-dimensional metal nitride according to claim 1, characterized in that: The single atomic layer two-dimensional metal nitride is prepared by using a molecular beam epitaxy device, which includes a first chamber and a second chamber. The vacuum degree of the second chamber is higher than that of the first chamber. The second chamber is provided with a metal source, a nitrogen source and a liquid nitrogen cold trap.

3. The method for preparing a single atomic layer two-dimensional metal nitride according to claim 2, characterized in that: The preparation of a single atomic layer of two-dimensional metal nitride on a metal single crystal substrate using a molecular beam epitaxy process includes the following steps: Placing the metal single crystal substrate in the second chamber, and raising the temperature of the metal single crystal substrate to 350° C. to 800° C. at a heating rate of 0.1° C. / s to 10° C. / s; A metal source beam and a nitrogen plasma source beam are obtained respectively through a metal source and a nitrogen source, and a single atomic layer of two-dimensional metal nitride is prepared on a metal single crystal substrate; The prepared single atomic layer two-dimensional metal nitride is cooled to room temperature at a cooling rate of 1°C / min to 30°C / min.

4. The method for preparing a single atomic layer two-dimensional metal nitride according to claim 3, characterized in that: The metal source beam is obtained by heating the metal source to 500°C to 800°C, and the flow rate of the metal source beam is and / or, The nitrogen source is nitrogen gas, the flow rate of the nitrogen gas is 0.5 sccm to 5 sccm, the nitrogen plasma source beam is obtained by radio frequency cracking of the nitrogen gas, and the power of the radio frequency cracking of the nitrogen gas is 100W to 350W.

5. The method for preparing a single atomic layer two-dimensional metal nitride according to claim 2, characterized in that: The surface treatment of the metal single crystal substrate includes the following steps: Performing degassing and annealing treatment on the metal single crystal substrate in the first chamber; The metal single crystal substrate is subjected to argon etching and annealing treatment for several times in the second chamber.

6. The method for preparing a single atomic layer two-dimensional metal nitride according to claim 2, characterized in that: The vacuum degree of the first chamber is 1×10 -8 ~1×10 -9 mbar, the vacuum degree of the second chamber is not less than 1×10 -10 mbar.

7. The method for preparing a single atomic layer two-dimensional metal nitride according to claim 2, characterized in that: The purity of the metal source is greater than or equal to 99.9999%, and the purity of the nitrogen source is greater than or equal to 99.9999%.

8. The method for preparing a single atomic layer two-dimensional metal nitride according to claim 1, characterized in that: After the metal single crystal substrate is surface treated, the height of the atomic-level steps on the surface of the metal single crystal substrate is 0.1 nm to 0.5 nm.

9. The method for preparing a single atomic layer two-dimensional metal nitride according to claim 1, characterized in that: The metal in the single atomic layer two-dimensional metal nitride is a combination of one or more of gallium, aluminum and indium.

10. The method for preparing a single atomic layer two-dimensional metal nitride according to claim 1, characterized in that: The metal single crystal substrate is a gold single crystal substrate, a silver single crystal substrate or a copper single crystal substrate.

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