A non-layered two-dimensional molybdenum dioxide material, its preparation, and its application in magnetic devices

Abstract

The present invention belongs to the field of two-dimensional magnetic materials, and specifically relates to a method for preparing a MoO2 non-layered two-dimensional material. MoO3 powder is heated to volatilize, and then chemically deposited on a substrate surface with hydrogen in a hydrogen-containing carrier gas to form the MoO2 non-layered two-dimensional material. The volatilization temperature of the MoO3 powder is greater than or equal to 700°C; the surface of the substrate is silicon dioxide or TMDs; and the chemical deposition temperature is 540-590°C. The present invention also includes materials prepared by the preparation method and their magnetic applications. The preparation method described in the present invention can successfully prepare MoO2 non-layered two-dimensional materials, and the materials prepared by the preparation method unexpectedly exhibit linear magnetoresistance behavior and possess superior magnetic properties.

Description

Technical Field

[0001] The present invention belongs to the field of nanomaterials, and specifically relates to the preparation of non-layered two-dimensional molybdenum dioxide materials and the characterization of their magnetic properties. Technical Background

[0002] Two-dimensional (2D) materials have broad application prospects in electronics, optoelectronics, spintronics, valleytronics, sensors, catalysis and other fields. 1-8 , especially ferromagnetism in two-dimensional materials is expected to promote the development of new spintronic devices, information storage devices and memory devices 9-11 Some two-dimensional materials with intrinsic ferromagnetism have been verified, including Fe3GeTe2 12 -14 、Cr2Ge2Te6 15 、CrI3 16 、CrTe 10 and CrSe2 11 Since the number of intrinsic ferromagnetic materials is limited, magnetic doping and defect engineering methods can be used to introduce magnetic properties into non-ferromagnetic materials. 17-20 In addition, intrinsic defects can also introduce magnetic 21-22 , surface states and surface resonance states also play a vital role in the magnetic process 23-24 Therefore, it is interesting to explore the ferromagnetism introduced by defects that are not present in the original material. Improving the sensitivity of magnetic storage or sensor devices has always encouraged the discovery and exploration of materials with large magnetoresistance (MR). 25-28 In general, large linear magnetoresistance (LMR) describes the linear relationship between resistance and applied magnetic field, with non-saturation characteristics over a wide range of magnetic field strengths. 29 Large LMRs have been observed in zero-bandgap semiconductors and semimetallic topological phases. 30-31 Typically, the magnetoresistance of ferromagnetic materials is small and negative due to spin disorder scattering. 32 The topology of the Fermi surface of magnetic topological semimetals can be controlled by applying an external electromagnetic field, which has potential applications in topological spin electronics research. 29 Large magnetoresistance is an important prerequisite for manipulating many spintronic devices, including the desired control of spin states by electrical signals. 33 .

[0003] Two-dimensional magnetic materials are mainly obtained through mechanical exfoliation, chemical vapor transport and molecular beam epitaxy (MBE). The thickness of the samples obtained by mechanical exfoliation is random and poorly controllable. At the same time, for non-layered crystals, due to the existence of covalent bonds between layers, it is impossible to obtain a few-layer sample by mechanical exfoliation; MBE requires strict lattice matching, so it can only grow on a specific substrate, which is incompatible with the traditional silicon industry. Chemical vapor deposition (CVD), as a simple and industrially compatible method, has been widely used in the growth of two-dimensional materials and the construction of their heterostructures. However, since the research on the growth mechanism of two-dimensional magnetic materials and the characterization of their magnetic properties is still not comprehensive, it is still a huge challenge to grow high-quality and thickness-controllable two-dimensional magnetic materials and explore thickness-related magnetism.

[0004] Monoclinic MoO2 (space group P21 / c) is a non-layered material 34 Bulk MoO2 has been widely used as an electrode material for lithium-ion batteries, as a substrate for surface-enhanced Raman spectroscopy and as a catalyst for hydrogen evolution. 35-37 Theoretical studies predict that it is a nodal semimetal when spin-orbit coupling (SOC) is neglected. 38 However, the thickness-controlled synthesis and thickness-dependent magnetotransport properties of two-dimensional MoO2 nanosheets have not been reported.

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[0043] In view of the problems that MoO2 non-layered materials are difficult to prepare and the research on magnetic properties is still blank, the first purpose of the present invention is to provide a method for epitaxial growth of non-layered materials on a silicon wafer substrate and successfully prepare MoO2 nanosheets with controllable thickness and high crystallinity (also referred to as MoO2 non-layered two-dimensional materials in the present invention), aiming to successfully prepare MoO2 non-layered two-dimensional materials with linear magnetoresistance behavior and excellent magnetoresistance properties.

[0044] The second object of the present invention is to provide a MoO2 two-dimensional material with controllable thickness obtained by the preparation method.

[0045] The third object of the present invention is to provide applications of MoO2 nanosheets of different thicknesses obtained by the preparation method, and to explore the magnetic properties related to MoO2 thickness.

[0046] A method for preparing a MoO2 non-layered two-dimensional material comprises heating MoO3 powder to volatilize it, and chemically depositing it on a substrate surface with hydrogen in a hydrogen-containing carrier gas to form the MoO2 non-layered two-dimensional material;

[0047] The volatilization temperature of the MoO3 powder is greater than or equal to 700°C;

[0048] The surface of the substrate is silicon dioxide or TMDs;

[0049] The temperature of the chemical deposition is 540-590°C.

[0050] MoO2 does not inherently have magnetic behavior, so magnetic research on this material is still an industry-wide gap. However, the present invention's research found that by innovatively chemically vapor depositing MoO3 powder and hydrogen, and further coordinating with the joint control of the substrate and deposition temperature, it can unexpectedly successfully solve the problems faced by chemical deposition in the preparation of MoO2, such as unsatisfactory crystal phase and crystallinity, easy vertical growth and difficulty in epitaxial growth to obtain MoO2 non-layered two-dimensional materials, and can successfully prepare MoO2 non-layered two-dimensional materials with high crystallinity, high phase purity, excellent morphology and cleanliness. Not only that, the prepared material can also exhibit special linear magnetoresistance behavior, which can improve magnetoresistance and improve its response sensitivity in magnetic devices.

[0051] In the present invention, the vapor phase chemical deposition method of MoO3 powder and hydrogen and the joint control of the substrate and deposition temperature are the key to the successful synergistic preparation of the MoO2 non-layered two-dimensional material and its excellent linear magnetoresistance behavior.

[0052] In the present invention, MoO3 powder is heated and volatilized and then chemically deposited on the substrate surface under the influence of hydrogen gas, activation, and chemical reaction. Preferably, the volatilization temperature of the MoO3 powder is 740-790°C, more preferably 750-770°C.

[0053] Preferably, the hydrogen-containing carrier gas is hydrogen or a mixture of hydrogen and protective gas;

[0054] Preferably, the protective gas is at least one of nitrogen and inert gas;

[0055] Preferably, the hydrogen content in the hydrogen-containing carrier gas is 5-45v%, more preferably 20-35v%.

[0056] Preferably, the flow rate of the hydrogen-containing carrier gas is 20 to 200 sccm, and more preferably 100 to 120 sccm.

[0057] The substrate is a SiO2 / Si substrate, a glass substrate or a substrate with a two-dimensional material deposited on the surface.

[0058] In the present invention, the temperature of the chemical deposition is the temperature of the substrate. The deposition temperature of the present invention can be controlled by an independent temperature control device, or can be controlled by the temperature of the MoO3 powder source and / or the distance between the source and the substrate.

[0059] Preferably, the temperature of the chemical deposition is 560-590° C. In the present invention, this preferred range is conducive to further obtaining high-quality, thickness-controllable ultrathin MoO2 nanosheets, and not only that, it is also conducive to improving its linear magnetoresistance behavior.

[0060] Preferably, the chemical deposition time is 10 to 20 minutes.

[0061] In the present invention, the deposition apparatus for implementing the preparation method includes a sealed quartz tube, one end of which is provided with an inlet for inputting a hydrogen-containing carrier gas into the quartz tube chamber, and the other end is provided with an outlet for outputting the gas from the quartz tube chamber. The chamber of the quartz tube is divided into an upstream high-temperature constant temperature zone and a downstream low-temperature variable temperature zone according to the direction of the hydrogen-containing carrier gas flow. The high-temperature constant temperature zone is provided with a heating device, a porcelain boat containing MoO3 powder is placed in the upstream high-temperature constant temperature zone, and a porcelain boat containing a substrate is placed in the downstream low-temperature variable temperature zone.

[0062] During the preparation process, MoO3 powder is heated to the volatilization temperature, so that the volatilized MoO3 raw material and the hydrogen therein are chemically deposited on the surface of the substrate under the action of the hydrogen-containing carrier gas, and MoO2 non-layered two-dimensional material is grown on the substrate.

[0063] The present invention also provides a MoO2 non-layered two-dimensional material prepared by the preparation method. The MoO2 non-layered two-dimensional material has (100), (110), (-112), (220) and (300) crystal planes, a P21 / c space group and a rhombohedral morphology, and grows along the crystal axis

[201] .

[0064] Preferably, the thickness of the MoO2 non-layered two-dimensional material is 7-60 nm, preferably 20-60 nm;

[0065] Preferably, the planar size of the MoO2 non-layered two-dimensional material is 2-40 μm.

[0066] The present invention also provides an application of the MoO2 non-layered two-dimensional material obtained by the preparation method, which is used to prepare magnetic devices; preferably, the magnetic device is a Hall device.

[0067] In the present invention, the non-layered two-dimensional MoO2 material described herein can be used to produce desired magnetic devices based on existing methods. For example, the method of the present invention can be used to prepare high-quality MoO2 nanosheets, and Hall effect devices with nanosheets of varying thicknesses can be fabricated using electron beam lithography. The magnetic properties of the resulting MoO2 nanosheets can then be tested using a comprehensive physical property measurement system (PPMS).

[0068] The present invention also provides a Hall device, which is made from the MoO2 non-layered two-dimensional material prepared by the preparation method.

[0069] Beneficial effects

[0070] 1. In response to the problems of CVD-synthesized MoO2 non-layered two-dimensional materials being easy to grow vertically but difficult to grow epitaxially, and having unsatisfactory crystallinity, phase and surface cleanliness, this paper innovatively uses the chemical vapor deposition method of MoO3 powder and hydrogen to further cooperate with the joint control of the substrate and deposition temperature to solve the many preparation problems faced by CVD-synthesized MoO2 non-layered two-dimensional materials. Not only that, it can also unexpectedly obtain materials with linear magnetoresistance behavior and excellent magnetoresistance properties.

[0071] 2. The material prepared by the preparation method of the present invention can unexpectedly exhibit linear magnetoresistance behavior and can unexpectedly exhibit excellent magnetic properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0072] Figure 1 Schematic diagram of the atmospheric pressure chemical vapor deposition apparatus for preparing MoO2 nanosheets;

[0073] Figure 2 is the XRD pattern of MoO2 nanosheets prepared in Example 1;

[0074] Figure 3 This is the EDS image of the MoO2 nanosheets prepared in Example 1;

[0075] Figure 4 This is the STEMHRTEM image of the MoO2 nanosheets prepared in Example 1;

[0076] Figure 5 This is an optical microscope image of the MoO2 nanosheets obtained in Example 1.

[0077] Figure 6 Optical microscope image of MoO2 nanosheets obtained in Example 2

[0078] Figure 7 This is an optical microscope image of the MoO2 nanosheets obtained in Comparative Example 1.

[0079] Figure 8 This is an optical microscope image of the MoO2 nanosheets obtained in Comparative Example 2.

[0080] Figure 9 This is an optical microscope image of the MoO2 nanosheets obtained in Example 3;

[0081] Figure 10 This is an optical microscope image of the MoO2 nanosheets obtained in Example 4;

[0082] Figure 11 , Figure 12 and Figure 13 Schematic diagram of optical photographs, linear magnetoresistance images, and anomalous Hall effect images of the MoO2 Hall device prepared in Example 5;

[0083] Figure 14 These are pictures of the magnetoresistance performance of MoO2 nanosheet devices with different thicknesses in Example 6. Specific implementation methods

[0084] The present invention is further described below by way of examples, but the present invention is not limited to the following examples.

[0085] Schematic diagram of the vapor deposition device for preparing MoO2 nanosheets is shown in Figure 1 The device comprises a quartz tube 1; an upstream constant temperature zone 2, loaded with a porcelain boat containing MoO3 powder; and a downstream variable temperature zone 3, loaded with silicon wafers (SiO2 / Si) with the polished surface facing upward. The device is also equipped with a heating device for heating the high-temperature constant temperature zone (upstream constant temperature zone). The quartz tube 1 is provided with air holes at both ends. The air hole at the left end (upstream of the carrier gas) serves as the air inlet, and the air hole at the right end serves as the air outlet.

[0086] The present invention has no special requirements on the particle size of the raw materials. Unless otherwise stated, the raw materials used in the following examples and comparative examples are:

[0087] MoO3 was provided by MacLean with a purity of 99.99%.

[0088] Example 1

[0089] Preparation of MoO2 nanosheets:

[0090] Place a porcelain boat containing MoO3 powder (1g in this embodiment) in the upstream constant temperature zone (temperature zone 2) of the tube furnace, and place a porcelain boat containing a substrate (285nmSiO2 / Si in this embodiment) in the downstream variable temperature zone (temperature zone 3). Before heating, use a large flow of argon gas of 655sccm to exhaust the air in the quartz tube. Then heat the constant temperature zone 2 to 760℃ (MoO3 volatilization temperature, marked as T1), the deposition temperature of the substrate area to 560℃ (deposition temperature, marked as T2), and the flow rate of argon-hydrogen mixed gas is 80 / 10sccm, and constant temperature deposition is carried out for 15 minutes. Single crystal MoO2 nanosheets will be generated on the substrate. The experimental device of MoO2 nanosheets is shown in the figure below. Figure 1 As shown in the figure, the XRD, EDS, STEM and optical photos of the prepared MoO2 nanosheets are shown in the figure. Figure 2 ,3,4 and 5 as shown.

[0091] Figure 2 The XRD pattern of the prepared MoO2 nanosheets shows that the four peaks correspond to the (100), (110), (-112), (220) and (300) planes on the PDF#04-005-4546 card of MoO2. The sharp peaks prove that the MoO2 nanosheets have good crystallinity. Figure 3EDS showed that the MoO2 nanosheets we synthesized contained only two elements, Mo and O, and the ratio was 1:2. Figure 4 In the figure, the high-resolution image of the synthesized MoO2 nanosheets shows that the nanosheets are of P21 / c space group and contain only two elements, Mo and O. Figure 5 This is an optical schematic diagram of the prepared MoO2 nanosheets. The SiO2 / Si substrate is light red, and the purple-red diamonds represent MoO2 nanosheets with uniform thickness distribution. The MoO2 nanosheets obtained under this condition have good crystallinity, a thickness of 15-20nm, and a size of 5-30μm.

[0092] Example 2

[0093] Compared with Example 1, the only difference is that the distance between molybdenum trioxide and the substrate remains unchanged, and the deposition temperature (T2) is changed by changing the temperature of T1, which is respectively:

[0094] Experimental group 2a: T2 is 590℃;

[0095] Experimental group 2b: T2 is 580℃;

[0096] Experimental group 2c: T2 is 570°C;

[0097] Experimental group 2d: T2 was 550°C;

[0098] Other operations and parameters are the same as in Example 1.

[0099] Figure 6 This is an optical schematic diagram of the prepared MoO2 nanosheets. The SiO2 / Si substrate is light red, and the gold, white or light red diamonds are MoO2. When the substrate temperature is 590°C, the thickness of the obtained nanosheets is mainly distributed (the proportion is greater than 50%) between 36 and 60 nm; when the substrate temperature is 580°C, the thickness of the obtained nanosheets is mainly distributed between 30 and 40 nm; when the substrate temperature is 570°C, the thickness of the obtained nanosheets is mainly distributed between 20 and 30 nm; when the substrate temperature is 550°C, the thickness of the obtained nanosheets is mainly distributed between 8 and 16 nm. Figure 6 The scale bar in the figure is 10 μm.

[0100] Comparative Example 1

[0101] Compared with Example 1, the only difference is that the deposition temperature T2 is changed to 530° C., and other operations and parameters are the same as Example 1.

[0102] Figure 7 Optical schematic diagram of the prepared MoO2 nanosheets. The SiO2 / Si substrate is light red and the pink ellipse is MoO2. The nanosheets are difficult to grow epitaxially and the crystal quality is average.

[0103] Comparative Example 2

[0104] Compared with Example 1, the only difference is that the deposition temperature T2 is changed to 600° C., and other operations and parameters are the same as Example 1.

[0105] Figure 8 This is an optical schematic diagram of the prepared MoO2 nanosheets. The SiO2 / Si substrate is light red, and the black or gold diamonds are MoO2, indicating that the test nanosheets are thicker and contain more impurities.

[0106] Example 3

[0107] Compared with Example 1, the only difference is that the carrier gas and flow rate are changed. The experimental groups are:

[0108] Group A: Carrier gas and flow rate: Ar / H2: 80 / 0 sccm (Optical diagram see Figure 9 a);

[0109] Group B: Carrier gas and flow rate: Ar / H2: 80 / 20 sccm (Optical image see Figure 9 b);

[0110] Group C: Carrier gas and flow rate: Ar / H2: 80 / 40 sccm (Optical diagram see Figure 9 c);

[0111] Other operations and parameters are the same as in Example 1.

[0112] Figure 9 This is an optical schematic diagram of the prepared MoO2 nanosheets. The SiO2 / Si substrate is light red. When the hydrogen content is zero, there are only green irregular substances on the substrate, indicating that no MoO2 nanosheets are generated under this condition. When the hydrogen content in the carrier gas gradually increases, the nanosheets on the silicon wafer are dense but small in size, indicating that when the hydrogen content is too high, the activation energy of the reaction is high, so that a large amount of raw material MoO3 is reduced to MoO2, and the nucleation density is high. Figure 9 The scale bar in the figure is 50 μm.

[0113] Example 4

[0114] Compared with Example 1, the only difference is that the substrate is changed. The experimental groups are:

[0115] Group A: substrate is glass;

[0116] Group B: The substrate is a SiO2 / Si substrate with WS2 deposited on the surface;

[0117] Comparative group A: The substrate is pure silicon wafer (Si);

[0118] Other operations and parameters are the same as in Example 1.

[0119] Figure 10 This is an optical schematic diagram of the prepared MoO2 nanosheets. On the pure silicon substrate, there are fewer diamond-shaped two-dimensional MoO2 nanosheets, which are golden in color, and most of them are black impurities. On the glass substrate, the two-dimensional MoO2 nanosheets are mainly golden and white diamonds, with a large number of deposits and high crystallinity. On the WS2 substrate, the two-dimensional MoO2 nanosheets are mainly purple diamonds, indicating that they are thinner.

[0120] Example 5

[0121] The magnetic properties of the MoO2 non-layered two-dimensional material prepared in Example 1 were tested.

[0122] The device fabrication method involves spin-coating two layers of PMMA polymer onto a substrate. Then, using two electron beam exposures, the Hall effect device pattern is carved onto a specific nanosheet. Next, 10nm of metallic In and 50nm of metallic Au are deposited onto the Hall effect device pattern via thermal evaporation. Finally, the remaining In / Au layers on the substrate are stripped in acetone. This creates a MoO2 nanosheet Hall effect device.

[0123] Figure 11 This is an optical microscope image of the prepared MoO2 nanosheet Hall device. The SiO2 / Si substrate is light red, the gold is the evaporated 10nm / 50nmIn / Au electrode, and the purple diamond is MoO2.

[0124] Figure 12 The magnetoresistance curve (thickness of 17.5 nm) tested for the MoO2 Hall device proves that the MoO2 nanosheets prepared in the present invention have large linear magnetoresistance.

[0125] Figure 13 The hysteresis loops of MoO2 nanosheets at different temperatures within 3-300K (thickness is 17.5nm). The hysteresis phenomenon disappears at around 50K, indicating that the Curie temperature of MoO2 nanosheets is around 50K.

[0126] Example 6

[0127] The MoO2 of different thicknesses in Examples 1 and 2 were prepared, wherein the thickness of the nanosheets was 17.5 nm in Example 1, the nanosheets were 39.2 nm in Example 2a, the nanosheets were 35.1 nm in Example 2b, the nanosheets were 25.8 nm in Example 2c, and the nanosheets were 14.6 nm and 9.0 nm in Example 2d (respectively). Figure 14 A Hall effect device (purple and green curves) was fabricated. Aluminum was spot-welded between the electrodes and the sample stage as connecting wires. The device was placed in the sample chamber of a PPMS instrument, evacuated, set to the test temperature, and subjected to current and magnetic field. The magnetic field deflected the carriers in the sample, yielding a magnetoresistance curve.

[0128] Figure 14 The MR-μ0H diagram of the Hall device of nanosheets of different thicknesses prepared in Example 1 and Example 2 changes with the magnetic field. The magnetoresistance data of nanosheets of different thicknesses can be obtained through this diagram. It is found that the linear magnetoresistance value of the nanosheet increases with the increase of the thickness of the nanosheet, and the linear magnetoresistance value is very large, which shows that the two-dimensional MoO2 nanosheets we prepared have important application prospects in high-tech fields such as magnetic sensors and magnetic recording.

[0129] In summary, the innovative method of preparing MoO2 two-dimensional materials by chemical deposition of MoO3 and hydrogen, and further based on the joint control of substrate and deposition temperature parameters, can unexpectedly prepare two-dimensional materials of different thicknesses. Not only that, the materials prepared by the preparation method unexpectedly have thickness-dependent linear magnetoresistance behavior and have excellent magnetic properties.

Claims

1. A method for preparing a MoO2 non-layered two-dimensional material, characterized in that: MoO3 powder is heated and volatilized, and then chemically deposited on the substrate surface with hydrogen in a hydrogen-containing carrier gas to form a MoO2 non-layered two-dimensional material; The volatilization temperature of the MoO3 powder is greater than or equal to 700°C; The surface of the substrate is silicon dioxide or TMDs; The temperature of the chemical deposition is 540-590°C; The deposition apparatus for implementing the preparation method includes a sealed quartz tube, one end of which is provided with an inlet for inputting a hydrogen-containing carrier gas into the quartz tube chamber, and the other end is provided with an outlet for outputting the gas from the quartz tube chamber. The chamber of the quartz tube is divided into an upstream high-temperature constant temperature zone and a downstream low-temperature variable temperature zone according to the direction of the hydrogen-containing carrier gas flow. The high-temperature constant temperature zone is provided with a heating device, a porcelain boat containing MoO3 powder is placed in the upstream high-temperature constant temperature zone, and a porcelain boat containing a substrate is placed in the downstream low-temperature variable temperature zone. During the preparation process, MoO3 powder is heated to the volatilization temperature, so that the volatilized MoO3 raw material and the hydrogen therein are chemically deposited on the surface of the substrate under the action of the hydrogen-containing carrier gas, and MoO2 non-layered two-dimensional material is grown on the substrate.

2. The method for preparing the MoO2 non-layered two-dimensional material according to claim 1, wherein: The volatilization temperature of MoO3 powder is 740~790 ℃.

3. The method for preparing the MoO2 non-layered two-dimensional material according to claim 2, wherein: The volatilization temperature of MoO3 powder is 750~770 ℃.

4. The method for preparing the MoO2 non-layered two-dimensional material according to claim 1, wherein: The hydrogen-containing carrier gas is hydrogen or a mixture of hydrogen and protective gas.

5. The method for preparing the MoO2 non-layered two-dimensional material according to claim 4, wherein: The protective gas is at least one of nitrogen and inert gas.

6. The method for preparing the MoO2 non-layered two-dimensional material according to claim 4, wherein: The hydrogen content in the hydrogen-containing carrier gas is 5-45v%.

7. The method for preparing the MoO2 non-layered two-dimensional material according to claim 4, wherein: The flow rate of hydrogen-containing carrier gas is 20~200 sccm.

8. The method for preparing the MoO2 non-layered two-dimensional material according to claim 7, wherein: The flow rate of hydrogen-containing carrier gas is 100~120 sccm.

9. The method for preparing the MoO2 non-layered two-dimensional material according to claim 1, wherein: The substrate is a SiO2 / Si substrate, a glass substrate or a substrate with a two-dimensional material deposited on the surface.

10. The method for preparing the MoO2 non-layered two-dimensional material according to claim 1, wherein: The temperature of the chemical deposition is the temperature of the substrate.

11. The method for preparing a MoO2 non-layered two-dimensional material according to claim 1, wherein: The temperature of the chemical deposition is 560-590°C.

12. The method for preparing a MoO2 non-layered two-dimensional material according to claim 1, wherein: The chemical deposition time is 10~20 min.

13. A MoO2 non-layered two-dimensional material obtained by the preparation method according to any one of claims 1 to 12, characterized in that: MoO2 is a non-layered two-dimensional material with (100), (110), (-112), (220) and (300) crystal planes, P21 / c space group and rhombohedral morphology, growing along the crystal axis [201].

14. The MoO2 non-layered two-dimensional material according to claim 13, wherein The MoO2 non-layered two-dimensional material has a thickness of 7-60 nm and a plane size of 2-40 μm.

15. An application of a MoO2 non-layered two-dimensional material obtained by the preparation method according to any one of claims 1 to 12, characterized in that: It is used to prepare magnetic devices.

16. The use according to claim 15, characterized in that: The magnetic device is a Hall device.

17. A Hall device, characterized in that: The MoO2 non-layered two-dimensional material is prepared by the preparation method according to any one of claims 1 to 12.

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