Magnetic regulation and control method of two-dimensional material

Abstract

The embodiment of the invention provides a magnetic regulation and control method for a two-dimensional material, and the method comprises the following steps: forming the two-dimensional material on a substrate, and enabling the two-dimensional material to have local magnetism; and performing post-annealing treatment on the two-dimensional material formed on the substrate to control the atom vacancy defect of the two-dimensional material so as to regulate and control the local magnetism of the two-dimensional material. According to the magnetic regulation and control method of the two-dimensional material provided by the embodiment of the invention, the atomic vacancy defect of the two-dimensional material is controlled in a post-annealing manner, so that the atomic-scale precision magnetic regulation and control of the two-dimensional material are realized.

Description

Technical Field

[0001] Embodiments of the present application relate to the technical field of two-dimensional materials, and more particularly, to a method for magnetic regulation of two-dimensional materials. Background Art

[0002] Due to their excellent electrical properties, two-dimensional materials have shown good application prospects in the field of spintronics. However, most two-dimensional materials do not have intrinsic magnetism. How to induce and precisely regulate magnetism in these materials is the key to realizing their application in spintronic devices.

[0003] To achieve magnetic regulation during sample production and preparation, common methods include introducing atomic defects, such as vacancy defects or heteroatom doping. Currently, these methods focus on achieving large-area and overall magnetic enhancement, but means for suppressing magnetism with atomic-level precision still need further research. Summary of the Invention

[0004] In view of the problems existing in the above-mentioned prior art, embodiments of the present application provide a method for magnetic regulation of two-dimensional materials, which controls the atomic vacancy defects of two-dimensional materials by post-annealing, thereby realizing magnetic regulation of two-dimensional materials with atomic-level precision.

[0005] Embodiments of the present application provide a method for magnetic regulation of two-dimensional materials, including the following steps:

[0006] Form the two-dimensional material on a substrate and make the two-dimensional material have local magnetism; and

[0007] By performing post-annealing treatment on the two-dimensional material formed on the substrate, control the atomic vacancy defects of the two-dimensional material to regulate the local magnetism of the two-dimensional material.

[0008] Further, the substrate is a double-layer substrate with a stepped structure. The forming of the two-dimensional material on the substrate includes:

[0009] Obtain the double-layer substrate; and

[0010] Form the two-dimensional material on the double-layer substrate.

[0011] Further, the substrate is a double-layer graphene substrate. Before forming the two-dimensional material on the substrate, it includes:

[0012] Perform high-temperature annealing on silicon carbide to form the double-layer graphene substrate.

[0013] Further, the two-dimensional material is niobium diselenide. The forming of the two-dimensional material on the substrate includes:

[0014] A monolayer of niobium diselenide is formed on the bilayer graphene substrate by molecular beam epitaxy, and local magnetism is distributed along the step direction of the bilayer graphene substrate in the monolayer of niobium diselenide.

[0015] Further, the high-temperature annealing of the silicon carbide to form the bilayer graphene substrate includes:

[0016] The silicon carbide is subjected to high-temperature annealing at an annealing temperature of 1250 degrees Celsius for an annealing duration of 60 minutes to form the bilayer graphene substrate.

[0017] Further, the formation of the monolayer of niobium diselenide on the bilayer graphene substrate by molecular beam epitaxy includes:

[0018] Selenium atoms and niobium atoms with a beam ratio greater than 10:1 are used to form the monolayer of niobium diselenide on the bilayer graphene substrate by molecular beam epitaxy.

[0019] Further, the post-annealing treatment of the two-dimensional material formed on the substrate to control the atomic vacancy defects of the two-dimensional material and regulate the local magnetism of the two-dimensional material includes:

[0020] The niobium diselenide formed on the bilayer graphene substrate is subjected to post-annealing at an annealing temperature of 300 degrees Celsius or higher for an annealing duration of 60 minutes (the longer the annealing time, the more atomic vacancy defects), and the atomic vacancy defects of the niobium diselenide are controlled to regulate the magnetism of the niobium diselenide.

[0021] The embodiments of the present application bring the following beneficial effects:

[0022] In the method for regulating the magnetism of two-dimensional materials provided by the embodiments of the present application, first, the two-dimensional material is formed on the substrate, and the post-annealing treatment of the two-dimensional material formed on the substrate is carried out to control the atomic vacancy defects of the two-dimensional material and regulate the magnetism of the two-dimensional material, so that the atomic-level precision magnetic regulation of the two-dimensional material can be realized. The preparation process is simple and easy to implement. At the same time, no heteroelements need to be introduced, and the elemental composition and crystal phase of the target sample can be effectively maintained. Description of the Drawings

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on the structures shown in these drawings without creative efforts.

[0024] Figure 1Schematic flowchart of the magnetic regulation method for two-dimensional materials provided by the embodiments of the present application;

[0025] Figure 2a Scanning tunneling microscope image of the substrate graphene used in the magnetic regulation method for two-dimensional materials provided by the embodiments of the present application;

[0026] Figure 2b Scanning tunneling microscope image of monolayer niobium diselenide used in the magnetic regulation method for two-dimensional materials provided by the embodiments of the present application;

[0027] Figure 3 Scanning tunneling microscope image of the magnetic strain region with a single selenium atom vacancy in monolayer niobium diselenide used in the magnetic regulation method for two-dimensional materials provided by the embodiments of the present application;

[0028] Figure 4a Differential conductance spectrum image collected along the stepped magnetic region of monolayer niobium diselenide used in the magnetic regulation method for two-dimensional materials provided by the embodiments of the present application;

[0029] Figure 4b From Figure 4a Differential conductance spectrum images of selenium vacancies and the areas without selenium vacancies on both sides extracted therefrom;

[0030] Figure 5 Differential conductance data map of the area around the selenium vacancy collected in a grid pattern of monolayer niobium diselenide used in the magnetic regulation method for two-dimensional materials provided by the embodiments of the present application.

[0031] The realization of the purpose of the present application, its functional features and advantages will be further described in conjunction with the embodiments and with reference to the accompanying drawings. Detailed implementation manners

[0032] Next, the technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art without creative efforts based on the embodiments in the present application shall fall within the protection scope of the present application.

[0033] In the description of the present application, the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present application, unless otherwise specified, "a plurality of" means two or more. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific circumstances.

[0034] Figure 1 is a flowchart of a method for magnetic regulation of two-dimensional materials according to an embodiment of the present application. As Figure 1 shown, the method for magnetic regulation of two-dimensional materials according to an embodiment of the present application includes the following steps:

[0035] S101: Form the two-dimensional material on a substrate and make the two-dimensional material have local magnetism; and

[0036] Specifically, first, a two-dimensional material with magnetism needs to be prepared, that is, the two-dimensional material needs to be formed on a substrate and the two-dimensional material is made to have magnetism or local magnetism.

[0037] S102: By performing post-annealing treatment on the two-dimensional material formed on the substrate, control the atomic vacancy defects of the two-dimensional material to regulate the local magnetism of the two-dimensional material.

[0038] Performing post-annealing treatment on the two-dimensional material on the substrate, the vacancy defects introduced by high-temperature annealing tend to be single-atom vacancies, and the generation of such vacancies causes lattice distortion at their positions and introduces unpaired electrons, which combine with the unpaired electrons causing magnetism around, thereby reducing the number of unpaired electrons and achieving the purpose of suppressing or regulating the local magnetism of the two-dimensional material.

[0039] In the method for magnetic regulation of two-dimensional materials provided by the embodiment of the present application, first, the two-dimensional material is formed on a substrate, and by performing post-annealing treatment on the two-dimensional material formed on the substrate, the atomic vacancy defects of the two-dimensional material are controlled to regulate the magnetism of the two-dimensional material, so that magnetic regulation at the atomic level of the two-dimensional material can be achieved, the preparation process is simple and easy to implement, and at the same time, no heteroelements need to be introduced, and the elemental composition and crystal phase of the target sample can be effectively maintained.

[0040] Further, in some embodiments of the present application, the substrate is a double-layer substrate with a stepped structure, and the forming the two-dimensional material on the substrate includes:

[0041] Obtain the double-layer substrate; and

[0042] Form the two-dimensional material on the double-layer substrate.

[0043] Specifically, the double-layer substrate has a stepped structure, and the two-dimensional material above the step will undergo strain. When the strain is large enough, local magnetism distributed along the step direction can be induced, which is convenient for subsequent local magnetic regulation operations of the two-dimensional material.

[0044] Further, referring to Figure 2a, in some embodiments of the present application, the substrate is a bilayer graphene substrate. Before forming the two-dimensional material on the substrate, it includes:

[0045] Perform high-temperature annealing on silicon carbide to form the bilayer graphene substrate.

[0046] Specifically, as Figure 2a shown, perform high-temperature annealing treatment on silicon carbide to prepare a substrate with steps. In a vacuum environment, perform high-temperature annealing treatment on the silicon carbide crystal to prepare a substrate covered with bilayer graphene on the surface. Due to the slight angular deviation during the cutting process, a periodic step structure will naturally form on the surface. During the high-temperature annealing process, silicon atoms preferentially sublime from the surface, and at the same time, the carbon atoms on the surface are rearranged to form graphene. The growth rate of graphene at the steps is different, further enhancing the visibility of the steps and forming a regular step distribution. As Figure 2a shown, after cooling the treated silicon carbide, perform scanning tunneling microscopy characterization, and it can be seen that the surface is already covered with bilayer graphene, and there are steps between adjacent planes.

[0047] Furthermore, referring to Figure 2b , in some embodiments of the present application, the two-dimensional material is niobium diselenide. The forming of the two-dimensional material on the substrate includes:

[0048] As Figure 2b shown, form a monolayer of niobium diselenide on the bilayer graphene substrate through molecular beam epitaxy technology, and the monolayer of niobium diselenide has local magnetism distributed along the step direction of the bilayer graphene substrate.

[0049] Specifically, molecular beam epitaxy technology is to prepare a single crystal film by spraying the components and pre-doped atoms (molecules) that make up the crystal onto the substrate from a spraying furnace at a certain thermal motion speed and in a certain proportion under ultra-high vacuum conditions similar to vacuum evaporation plating for crystal epitaxial growth. After the bilayer graphene substrate is prepared, form a monolayer of niobium diselenide on the bilayer graphene substrate through molecular beam epitaxy technology, and the monolayer of niobium diselenide has local magnetism distributed along the step direction of the bilayer graphene substrate to facilitate the subsequent regulation of the local magnetism of the two-dimensional material.

[0050] Furthermore, in some embodiments of the present application, the performing of high-temperature annealing on silicon carbide to form the bilayer graphene substrate includes:

[0051] Perform high-temperature annealing on the silicon carbide at an annealing temperature of 1250 degrees Celsius and an annealing duration of 60 minutes to form the bilayer graphene substrate.

[0052] As described above, the silicon carbide is subjected to high-temperature annealing treatment. For example, the annealing temperature is 1250 degrees Celsius and the annealing duration is 60 minutes, so as to prepare a substrate with steps. In a vacuum environment, the silicon carbide crystal is subjected to high-temperature annealing treatment to prepare a substrate covered with bilayer graphene on the surface. Due to the slight angular deviation during the cutting process, a periodic step structure will naturally form on the surface. During the high-temperature annealing process, silicon atoms preferentially sublime from the surface, and at the same time, the carbon atoms on the surface are rearranged to form graphene. The growth rate of graphene at the steps is different, which further enhances the visibility of the steps and forms a regular step distribution. After the treated silicon carbide is cooled down, scanning tunneling microscopy characterization is carried out, and it can be seen that the surface is already covered with bilayer graphene, and there are steps between adjacent planes.

[0053] Further, in some embodiments of the present application, forming niobium diselenide monolayer on the bilayer graphene substrate by molecular beam epitaxy technology includes:

[0054] Using selenium atoms and niobium atoms with a beam flux ratio greater than 10:1, forming the niobium diselenide monolayer on the bilayer graphene substrate by molecular beam epitaxy technology.

[0055] Specifically, in a vacuum environment, first, the silicon carbide is subjected to high-temperature annealing, for example, the annealing temperature is 1250 °C and the duration is about 60 min, to prepare a bilayer graphene substrate. Then, by molecular beam epitaxy technology, a niobium diselenide monolayer is prepared on the graphene surface, and the beam flux ratio of high-purity selenium atoms and niobium atoms is greater than 10:1 to provide a selenium-rich environment and reduce the generation of domain boundaries and vacancy defects during the preparation process, so as to obtain high-quality niobium diselenide monolayer. Since the silicon carbide substrate covered with graphene has steps, the niobium diselenide above the steps generates strain. When the strain is large enough, it can induce local magnetism distributed along the step direction.

[0056] Further, in some embodiments of the present application, controlling the atomic vacancy defects of the two-dimensional material by post-annealing treatment of the two-dimensional material formed on the substrate to regulate the local magnetism of the two-dimensional material includes:

[0057] Controlling the atomic vacancy defects of the niobium diselenide by post-annealing treatment of the niobium diselenide formed on the bilayer graphene substrate, the annealing temperature is above 300 degrees Celsius, and the annealing duration is 60 minutes (the longer the annealing time, the more atomic vacancy defects), so as to regulate the magnetism of the niobium diselenide.

[0058] Specifically, after the niobium diselenide monolayer is prepared, in-situ treatment is carried out by post-annealing. For example, the sample is heated to above 300 degrees Celsius by direct current and kept for about 60 min to increase the number of selenium atom vacancies in the sample. Then, as Figure 3As shown, the surface morphology of niobium diselenide was characterized by scanning tunneling microscopy to find the magnetic step strain regions with single selenium atom vacancies.

[0059] Referring to Figure 4a and Figure 4b , Figure 4a Figure 141 is the differential conductance spectrum image collected along the magnetic region of the step of monolayer niobium diselenide used in the magnetic regulation method of two-dimensional materials provided in the embodiment of the present application. Figure 4b Figure 142 is Figure 4a the differential conductance spectrum images of selenium vacancies and the areas without selenium vacancies on both sides extracted from Figure 143. The scanning tunneling microspectrum was collected in the magnetic step strain region of the selenium atom vacancy. The results showed that in the differential conductance spectrum of the region without vacancies, the peaks of the density of states showed a splitting phenomenon. Combining with the prediction of theoretical calculations, it was proved that niobium diselenide in this strain region has a local magnetic moment. The differential conductance spectrum at the vacancy showed that one of the split peaks was suppressed, proving that the local magnetic moment at the vacancy was significantly suppressed. Referring to Figure 5 Figure 144, the scanning tunneling microspectrum was collected by grid sampling in the region where a single selenium atom vacancy is located. The results showed that the selenium atom vacancy regulation region is localized around the vacancy, so that the atomic-level magnetic regulation of two-dimensional materials can be accurately realized.

[0060] The above are only the preferred embodiments of the present application, and do not limit the patent scope of the present application. Any equivalent structural transformation made using the specification and drawings of the present application under the application concept of the present application, or direct / indirect application in other related technical fields, is included in the patent protection scope of the present application.

Claims

1. A method for controlling the magnetic properties of a two-dimensional material, characterized in that: The following steps are involved: forming the two-dimensional material on a substrate, and making the two-dimensional material have local magnetism; and By performing a post-annealing treatment on the two-dimensional material formed on the substrate, the atomic vacancy defects of the two-dimensional material are controlled to adjust the local magnetism of the two-dimensional material.

2. The method according to claim 1, characterized in that The substrate is a double-layer substrate with a step structure, and the two-dimensional material is formed on the substrate, comprising: obtaining the double-layer substrate; and The two-dimensional material is formed on the double-layer substrate.

3. The method according to claim 2, characterized in that The substrate is a double-layer graphene substrate, and before forming the two-dimensional material on the substrate, the method comprises: The silicon carbide is subjected to high temperature annealing to form the double-layer graphene substrate.

4. The method according to claim 3, characterized in that: The two-dimensional material is niobium diselenide, and the two-dimensional material is formed on a substrate, comprising: A single layer of niobium diselenide is formed on the double-layer graphene substrate by molecular beam epitaxy technology, and the single layer of niobium diselenide has local magnetism distributed along the step direction of the double-layer graphene substrate.

5. The method according to claim 3, characterized in that: The step of annealing silicon carbide at high temperature to form the double-layer graphene substrate comprises: The silicon carbide is subjected to high temperature annealing at a temperature of 1250 degrees Celsius for 60 minutes to form the double-layer graphene substrate.

6. The method according to claim 4, characterized in that The method of forming a single layer of niobium diselenide on the double-layer graphene substrate by molecular beam epitaxy technology comprises: The single-layer niobium diselenide is formed on the double-layer graphene substrate by molecular beam epitaxy technology using selenium atoms and niobium atoms with a beam ratio greater than 10:

1.

7. The method according to claim 4, characterized in that The method of controlling the atomic vacancy defects of the two-dimensional material by post-annealing the two-dimensional material formed on the substrate to adjust the local magnetism of the two-dimensional material comprises: The niobium diselenide formed on the double-layer graphene substrate is post-annealed at a temperature of more than 300 degrees Celsius for 60 minutes to control the atomic vacancy defects of the niobium diselenide so as to regulate the magnetism of the niobium diselenide.

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