Iron-intercalated Fe3Se4 non-layered two-dimensional materials, their preparation and applications in magnetic devices

Abstract

The application belongs to the technical field of two-dimensional magnetic materials, and particularly relates to a large-area ultrathin Fe3Se4 magnetic material prepared on WSe2 nanosheets, which is a Fe3Se4 non-layered two-dimensional single crystal with excellent quality. The application also provides preparation and application of the material. The novel material has special magnetic transmission behavior, and has excellent magnetic properties, especially high-temperature magnetic properties, high electrical conductivity and air stability.

Description

Technical Field

[0001] This invention belongs to the field of nanomaterials, specifically relating to the preparation of non-layered two-dimensional tetraselenide materials and the characterization of their magnetic properties. Technical Background

[0002] Since the discovery of graphene and the continued growth of the family of two-dimensional (2D) materials, researchers have made great strides in exploring the interesting properties of low-dimensional materials. [1-8] In particular, the application potential of two-dimensional magnetic materials in energy-efficient logic devices and spintronics has attracted widespread attention. [9-13] To date, the development of novel two-dimensional magnetic materials, spintronic devices, quantum and topological phases, and new phenomena has attracted widespread attention. [14-18] Exploring new materials with room-temperature magnetism and interesting properties is essential to stimulating applications by avoiding extreme temperature environments. [19-21] It is worth noting that iron-selenium systems can have different magnetic, electronic, and optical properties. [22,23] For example, 2D Fe3Se4e2 nanoplates exhibited a phase transition at 11 K.

[24] 2D Fe7Se8 nanoplates exhibit ferromagnetic behavior at room temperature.

[25] Two-dimensional Fe5Se8 nanoplates exhibit robust and stable ferromagnetism at 300 K.

[26] Bulk Fe3Se4 crystals at high Curie temperatures (T0) C (≈330K) exhibits ferromagnetic behavior

[27] Interestingly, it displays T respectively. C The following and above metal and semiconductor behaviors

[28] However, due to the lack of high-quality two-dimensional Fe3Se4 materials, the study of magnetic transport in two-dimensional Fe3Se4 nanosheets still faces considerable challenges.

[0003] Two-dimensional magnetic materials are mainly obtained through mechanical exfoliation, chemical vapor deposition (CVD), and molecular beam epitaxy (MBE). Mechanical exfoliation yields samples with random and uncontrollable thicknesses. Furthermore, for non-layered crystals, the presence of interlayer covalent bonds prevents the acquisition of few-layer samples via mechanical exfoliation. MBE requires strict lattice matching, thus limiting its growth to specific substrates and making it incompatible with traditional silicon manufacturing processes. Chemical vapor deposition (CVD), as a simple and industrially compatible method, has been widely used for the growth of two-dimensional materials and the construction of heterostructures. However, due to the incomplete understanding of the growth mechanism and magnetic properties characterizing two-dimensional magnetic materials, growing high-quality, thickness-controllable two-dimensional magnetic materials and exploring thickness-related magnetic transport properties remains a significant challenge. For example, Chinese patent document CN113764659A discloses a method for preparing iron-based selenides as a negative electrode material for sodium-ion batteries and its application. It uses Se powder Fe(CO)5 to deposit a mixed powder of FeSe2, Fe3Se4 and Fe (i.e. iron-based selenides). It can be seen that it is impossible to obtain a single pure phase Fe3Se4 two-dimensional single crystal with special magnetic properties based on the CVD method.

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[0030] 27 GCTewari,D.Srivastava,R.Pohjonen,OAJMustonen,Karttunen,J.Linden,KJKarppinen,Phys.Condens.Mat.2020,32(45),455801. Summary of the Invention

[0031] To address the problems existing in the prior art, the primary objective of this invention is to provide a non-layered two-dimensional Fe3Se4 material with iron intercalation, aiming to provide a novel material with special magnetic behavior and magnetic properties.

[0032] The second objective of this invention is to provide a method for preparing the aforementioned iron-intercalated Fe3Se4 non-layered two-dimensional material, aiming to successfully prepare the novel material that combines excellent magnetic behavior and performance.

[0033] The third objective of this invention is to provide the application of the iron-intercalated Fe3Se4 non-layered two-dimensional material in magnetic materials and the magnetic devices (such as Hall devices) formed therefrom.

[0034] A non-layered two-dimensional Fe3Se4 material with iron intercalation is a non-layered two-dimensional single crystal of Fe3Se4 with periodic iron intercalation.

[0035] This invention provides a novel material that unexpectedly exhibits unique magnetic transport behavior and possesses excellent magnetic properties, particularly at high temperatures, as well as high electrical conductivity and good air stability.

[0036] The iron-intercalated Fe3Se4 non-layered two-dimensional material of the present invention has a

[001] crystal plane orientation;

[0037] The iron-intercalated Fe3Se4 non-layered two-dimensional material of the present invention has hexagonal, trapezoidal and triangular morphologies;

[0038] The single crystal of the iron-intercalated Fe3Se4 non-layered two-dimensional material of the present invention has a planar size of 2-80 μm and a thickness of 1.1-30 nm, preferably 1.1-5.5 nm.

[0039] This invention also attempts to provide a method for preparing the aforementioned Fe3Se4 two-dimensional magnetic material using CVD. However, early research revealed that the preparation process requires overcoming several challenges, including difficulties in growing Fe3Se4 two-dimensional materials, particularly in epitaxial growth, forming a single Fe3Se4 phase, growing monolayer Fe3Se4 nanosheets, poor crystallinity, difficulty in controlling thickness, and difficulty in forming iron intercalation results. Furthermore, there are also challenges such as the prepared material lacking magnetic properties or exhibiting unsatisfactory magnetic performance and poor stability at relatively high temperatures. To address these challenges, this invention, through in-depth research, provides the following solutions:

[0040] A method for preparing the iron-intercalated Fe3Se4 non-layered two-dimensional material involves heating a selenium source to a temperature T1 to volatilize the selenium, and then preparing a FeCl2-containing material. n The mixture of xH2O (iron raw material) and additives is heated to temperature T2 to volatilize the iron raw material. The volatilized iron raw material and selenium source are chemically deposited on the surface of the substrate under the assistance of a carrier gas atmosphere to obtain the iron-intercalated Fe3Se4 non-layered two-dimensional material.

[0041] The FeCl n In xH2O, n is 2 or 3, and 0 <x<4;

[0042] The aforementioned additive is a halogen salt;

[0043] The temperature T1 is 250–500°C, and the temperature T2 and the chemical deposition temperature are 480–510°C.

[0044] The carrier gas is a composite gas of hydrogen and protective gas, wherein the flow rate of hydrogen is 5-15 sccm and the flow rate of protective gas is 5-50 sccm.

[0045] The substrate is a substrate without dangling keys.

[0046] To overcome the difficulties in preparing the novel material and achieving high-temperature magnetic properties as described in this invention, this invention has discovered an innovative method that uses modified FeCl2·xH2O, along with additives and a selenium source, to perform vapor-phase deposition on a surface without dangling bonds. Furthermore, by coordinating the control of raw material type, ratio, volatilization temperature, deposition temperature, and hydrogen-containing carrier gas during the chemical deposition stage, a synergistic effect can be achieved. This allows for the unexpected CVD growth of pure-phase Fe3Se4 single-crystal materials with excellent morphology and structure, and endows the prepared material with special properties such as electrical conductivity, magnetic transport properties, and especially magnetic properties at room temperature.

[0047] In this invention, the proportions of FeCl2·xH2O, additives, and materials, as well as the combination of the unsuspended substrate, volatilization, and deposition temperature, are key to the synergistic successful preparation of the single-phase Fe3Se4 single crystal, improving its morphology and structure, and thus endowing it with special magnetic behavior and properties.

[0048] In this invention, the combination of FeCl2·xH2O and additives helps to combine with other parameters, which is beneficial to obtaining high-performance Fe3Se4 single crystal materials with good morphology.

[0049] In this invention, the FeCl n xH2O via FeCl n • yH2O is obtained by thermal modification at a temperature T3, wherein T3 is 180–220℃, and y is 4–6. This invention demonstrates that the innovative use of this thermal modification process, combined with the control of temperature T3, helps to control FeCl₂. n The amount of x in xH2O can unexpectedly facilitate the joint control of the phase, crystallinity, morphology, and thickness of Fe3Se4 single crystals, thereby helping to endow the prepared materials with special magnetic properties.

[0050] In this invention, n is 2 and x is 4; n is 3 and x is 6.

[0051] In this invention, the temperature T3 is preferably 195-205℃.

[0052] In this invention, the heat preservation modification process is preferably carried out in a protective atmosphere, such as nitrogen or an inert gas. The flow rate of the protective atmosphere is not particularly required; for example, it can be 50–150 sccm, and more specifically, 90–110 sccm.

[0053] In this invention, the heat preservation modification time at temperature T3 is 0.3 to 1.0 h, and can be further 0.4 to 0.6 h.

[0054] In this invention, the auxiliary agent includes at least one of ammonium chloride, sodium chloride, and potassium chloride;

[0055] Preferably, the FeCl n The weight ratio of xH2O to the additive is 1:0.01-0.1, and can be further 1:0.03-0.06;

[0056] Preferably, the selenium source is selenium powder.

[0057] In this invention, the selenium source and FeCl₂ n The molar ratio of ·xH2O can be reasonably controlled according to the volatility characteristics. For example, considering the volatility of components and reaction conditions, the molar ratio of Se / Fe can be 1:3 to 6.

[0058] In this invention, the protective gas in the carrier gas includes at least one of nitrogen and an inert gas;

[0059] In the carrier gas, the flow rate of hydrogen is 8–12 sccm, and the flow rate of the protective gas is 8–20 sccm.

[0060] In this invention, the innovative use of the non-dangling bond deposition surface can be combined and synergistically with the process conditions of this invention, which can unexpectedly facilitate the preparation of the iron-intercalated Fe3Se4 non-layered two-dimensional material, and facilitate the joint optimization of the phase purity, crystallinity and morphology. More importantly, it can unexpectedly enable the prepared material to take into account special magnetic behavior and magnetic properties.

[0061] In this invention, the substrate without dangling bonds is a substrate with TMDs two-dimensional material deposited on its surface;

[0062] Preferably, the TMDs two-dimensional material is at least one of transition metal selenides and sulfides, more preferably a transition metal selenide; and more preferably a W and / or Mo selenide two-dimensional material.

[0063] The present invention also shows that the innovative use of selenide two-dimensional materials, especially selenides as the deposition surface, can be unexpectedly combined with the process of the present invention, which helps to further facilitate the joint control of the phase and morphology of the Fe3Se4 non-layered two-dimensional material with iron intercalation, and thus unexpectedly enables it to exhibit special magnetic behavior and properties.

[0064] In this invention, the TMDs two-dimensional material can be prepared based on known processes such as PVD / CVD.

[0065] In this invention, conventional CVD deposition equipment can be used to implement the present invention. For example, the present invention may optionally employ conventional dual-temperature zone deposition equipment.

[0066] An optional deposition method of the present invention involves pre-filling a magnetic boat 1 with selenium powder and placing it in temperature zone 1 of a deposition tube (temperature zone 1 is located upstream of the carrier gas), and then depositing FeCl₂... n A mixture of xH2O and additives is placed in a magnetic boat 2 and positioned in temperature zone 2 of the deposition tube (temperature zone 2 is located downstream of the carrier gas). The deposition substrate is placed in temperature zone 2 (either above the mixture or tilted on the magnetic boat 2, with the deposition surface of the substrate facing the mixture). During the synthesis process, a gas purging treatment is performed beforehand, followed by simultaneous temperature control of temperature zones 1 and 2 to allow the raw materials in each zone to volatilize and chemically deposit on the substrate.

[0067] In this invention, there are no special requirements for the temperature T1, as long as it can promote the volatilization of the selenium source. Considering the heat cost, it can be further set to 300-350°C.

[0068] Preferably, the temperature T2 and the chemical deposition temperature are 490–510°C; more preferably, they are 495–505°C.

[0069] Preferably, the chemical deposition time is 1 to 10 minutes, and more preferably 2 to 5 minutes.

[0070] The present invention also provides an application of the aforementioned iron-intercalated Fe3Se4 non-layered two-dimensional material, which is used to prepare magnetic materials, preferably magnetic transport materials, further as magnetic devices, and even further as Hall devices.

[0071] In this invention, the desired magnetic material can be prepared from the iron-intercalated Fe3Se4 non-layered two-dimensional material described in this invention using known processes.

[0072] The present invention also provides a magnetic material comprising, or made from, the iron-intercalated Fe3Se4 non-layered two-dimensional material described in the present invention.

[0073] Beneficial effects

[0074] 1. This invention provides a novel iron-intercalated Fe3Se4 non-layered two-dimensional material with unique magnetic behavior and properties, as well as high electrical conductivity.

[0075] 2. This invention innovatively employs FeCl2·xH2O and a selenium source in synergy with additives for vapor-phase deposition on a surface without dangling bonds. Furthermore, by coordinating the control of raw material type, ratio, volatilization temperature, deposition temperature, and hydrogen-containing carrier gas in the chemical deposition stage, synergistic effects can be achieved, unexpectedly enabling the CVD growth of pure-phase Fe3Se4 single-crystal materials. Moreover, the materials prepared by the aforementioned method unexpectedly possess excellent electrical conductivity and magnetic transport properties, especially magnetic properties at room temperature.

[0076] The Fe3Se4 two-dimensional materials prepared in this invention are as thin as 1.1 nm (monolayer), with a size ranging from 2 to 80 μm, exhibiting irregular hexagonal shapes, good crystallinity, and high quality. For example, the ultrathin Fe3Se4 two-dimensional materials prepared by this invention based on SiO2 / Si substrates containing large-area monolayers or few layers of WSe2 nanosheets provide a foundation for the study of their electrical and magnetic properties at the two-dimensional scale, and are expected to be applied in fields such as spintronics and nanoelectronic devices.

[0077] The preparation process of this invention does not involve complicated operation steps or expensive raw materials, and the equipment is simple, the operation is easy, and the reproducibility is good. Attached Figure Description

[0078] Figure 1 Schematic diagram of an atmospheric pressure chemical vapor deposition apparatus for preparing Fe3Se4 nanosheets;

[0079] Figure 2 The image shows the XRD pattern of the Fe3Se4 nanosheets prepared in Example 1.

[0080] Figure 3 EDS image of Fe3Se4 nanosheets prepared in Example 1;

[0081] Figure 4 STEM image of Fe3Se4 nanosheets prepared in Example 1;

[0082] Figure 5 Optical images of Fe3Se4 nanosheets grown on WSe2 obtained in Example 1, with a scale bar of 20 micrometers;

[0083] Figure 6 Optical images of Fe3Se4 nanosheets grown on WSe2 obtained in Example 2, with a scale bar of 20 micrometers;

[0084] Figure 7Optical images of Fe3Se4 nanosheets grown on WSe2 obtained in Example 3, with a scale bar of 20 micrometers;

[0085] Figure 8 Optical images of Fe3Se4 nanosheets grown on WSe2 obtained in Example 4, with a scale bar of 20 micrometers;

[0086] Figure 9 Optical images of Fe3Se4 nanosheets grown on WSe2 obtained in Example 5, with a scale bar of 20 micrometers;

[0087] Figure 10 Optical images of Fe3Se4 nanosheets grown on WSe2 obtained in Example 6, with a scale bar of 20 micrometers;

[0088] Figure 11 Optical images of the Fe3Se4 nanosheets obtained in Example 7, with a scale bar of 20 micrometers;

[0089] Figure 12 Optical images of the Fe3Se4 nanosheets obtained in Comparative Example 1, with a scale bar of 20 micrometers;

[0090] Figure 13 Optical images of the Fe3Se4 nanosheets obtained in Comparative Example 2, with a scale bar of 20 micrometers;

[0091] Figure 14 Optical images of the Fe3Se4 nanosheets obtained in Comparative Example 3, with a scale bar of 20 micrometers;

[0092] Figure 15 Optical images of the Fe3Se4 nanosheets obtained in Comparative Example 4, with a scale bar of 20 micrometers;

[0093] Figure 16 Optical images of the Fe3Se4 nanosheets obtained in Comparative Example 5, with a scale bar of 20 micrometers;

[0094] Figure 17 , Figure 18 , Figure 19 and Figure 20 The MH curve, MR curve, and magnetoresistance test curves for magnetic characterization obtained in Example 8 are shown. Specific implementation methods:

[0095] The present invention will be further illustrated by the following implementation examples, but the content of the present invention is not limited to the following content.

[0096] A schematic diagram of the vapor deposition apparatus for preparing Fe3Se4 nanosheets is shown below. Figure 1 Including quartz tube 1; upstream constant temperature zone 1 ( Figure 1The upstream isothermal zone (labeled 2) contains a ceramic boat (a) loaded with selenium powder. The downstream isothermal zone 2 (… Figure 1 The temperature zone marked 3 in the middle (downstream isothermal zone) is where FeCl3 is loaded. n The magnetic boat b and the substrate are a mixture of xH2O and additives. The substrate can be placed flat or obliquely on the magnetic boat b, with the deposition surface facing the mixture.

[0097] The vapor deposition apparatus is further equipped with a heating device for heating the high-temperature isothermal zones (upstream and downstream isothermal zones). Both ends of the quartz tube 1 are provided with air holes, wherein the air hole at the left end (upstream of the carrier gas) of the quartz tube 1 is an air inlet, and the air hole at the right end of the quartz tube 1 is an air outlet.

[0098] During the deposition process, the quartz tube was first purged with a carrier gas, and then the temperatures of temperature zone 1 and temperature zone 2 were controlled. The temperature of temperature zone 1 was marked as T1, and the temperature of temperature zone 2 was marked as T2. The selenium source volatilized in temperature zone 1 was carried by the carrier gas and deposited in temperature zone 2 with the volatilized iron source on the deposition surface of the substrate.

[0099] This invention does not have specific requirements for the particle size of the raw materials. Unless otherwise stated, the raw materials used in the following examples and comparative examples are:

[0100] The starting FeCl2·4H2O was provided by Maclean and had a purity greater than 99.99%.

[0101] The selenium powder, supplied by Shanghai Shanpu Chemical Co., Ltd., has a purity >99.99%.

[0102] In this invention, silicon wafers deposited with WSe2 nanosheets can be prepared using known processes. For example, WSe2 can be obtained by physical vapor deposition at a temperature of 1100–1300°C, with the physical vapor deposition performed in argon gas at a flow rate of, for example, 10–100 sccm. As an example, the preparation conditions are as follows: 10 g of WSe2 is placed in a magnetic boat, heated to 1200°C, and 50 sccm of argon gas is introduced, with the reaction maintained at this temperature for 5 minutes.

[0103] WS2 can be obtained by physical vapor deposition at a temperature of 1100–1300 °C, with the physical vapor deposition performed in argon gas at a flow rate of, for example, 10–100 sccm. In the following example, the preparation conditions for WS2 nanosheets are as follows: 10 g of WSe2 is placed in a magnetic boat, heated to 1200 °C, 50 sccm of argon gas is introduced, and the reaction is maintained at this temperature for 3 min.

[0104] Example 1

[0105] Preparation of Fe3Se4 nanosheets grown on WSe2:

[0106] Step (1): Pretreatment:

[0107] The pretreatment method for FeCl2·4H2O is as follows: place the FeCl2·4H2O raw material in a porcelain boat, then place the porcelain boat in a tube furnace, introduce 655 sccm of argon for 5 min to discharge the air in the tube furnace, set the heating temperature of the tube furnace to 200°C (pretreatment temperature T3), with a heating duration of 30 min and an argon gas flow of 100 sccm. Finally, pretreated FeCl2·xH2O (0<x<4) (pretreated iron raw material) is obtained under an inert atmosphere protected by argon.

[0108] Step (2): Deposition:

[0109] Place a porcelain boat a containing selenium powder in the constant temperature zone upstream of the tube furnace (temperature zone 1, temperature is 300°C, that is, volatilization temperature), place a magnetic boat b loaded with the mixture of the pretreated iron raw material obtained in step 1 and ammonium chloride in temperature zone 2, and place a silicon wafer deposited with WSe2 nanosheets (285 nm SiO2 / Si) as a substrate at the position of magnetic boat b, wherein the side of the WSe2 nanosheets faces the mixture; in the raw materials, the molar ratio of pretreated selenium powder to iron raw material (Se / Fe molar ratio) is 1:3, and the weight ratio of pretreated iron raw material to ammonium chloride is 1:0.04 to 0.05;

[0110] Before heating, purge the air in the quartz tube with 100 to 500 sccm of argon. Then heat the temperature T1 at temperature zone 1 to 300°C (selenium volatilization temperature), control the temperature T2 at temperature zone 2 at 500°C (deposition temperature, iron volatilization temperature), and perform constant temperature deposition under carrier gas, wherein the carrier gas is a mixed gas with a hydrogen-argon ratio of 1:1, the carrier gas flow rate is 20 sccm, and the constant temperature deposition time is 3 min. Single crystals are formed on the surface of the WSe2 nanosheets, and Fe3Se4 / WSe2 heterojunction nanosheets are obtained.

[0111] The XRD, EDS, STEM images and optical photographs of the prepared Fe3Se4 nanosheets are shown in Figure 2 , 3, 4 and 5 respectively.

[0112] Figure 2 For the XRD pattern of the prepared Fe3Se4 nanosheets, the main diffraction peaks at 15.9, 16.6, 32.0, 32.7, 33.1 and 33.6 in the pattern correspond to the (002, that is 001), (101), (004), (-202), (-112) and (202) planes respectively. The peaks are sharp, proving that the Fe3Se4 nanosheets have good crystallinity. Figure 3 The EDS result shows that the synthesized Fe3Se4 nanosheets only contain two elements, Fe and Se, with a ratio of 3:4. Figure 4In the high-resolution image of the synthesized Fe3Se4 nanosheets, it is shown that the nanosheets have a 1T configuration and contain only Fe and Se elements. Figure 5 The image shows an optical schematic of the prepared Fe3Se4 nanosheets. The SiO2 / Si substrate containing large-area monolayer or few-layer WSe2 nanosheets is light purple. The purplish-red trapezoids represent Fe3Se4 nanosheets with uniform thickness distribution. The Fe3Se4 nanosheets obtained under these conditions have good crystallinity, with a thickness of 1.1-30 nm and a size of 10-30 μm.

[0113] Example 2

[0114] Compared with Example 1, the only difference is that the temperature T3 of the pretreatment in step (1) was changed to 180°C and 220°C respectively. The prepared material is... Figure 6 The SiO2 / Si substrate containing large-area monolayer or few-layer WSe2 nanosheets is light purple, and the hexagonal shape is Fe3Se4, indicating that the prepared Fe3Se4 nanosheets are relatively thin. Using an iron source treated at a lower temperature of 180℃, the prepared nanosheets showed signs of etching, and the crystallinity of the sample was not as good as in Example 1. Using an iron source treated at a higher temperature of 220℃, the prepared nanosheets had good crystallinity, but the sample thickness uniformity was not as good as in Example 1.

[0115] Example 3

[0116] Compared with Example 1, the only difference is that the temperature of the deposition temperature T2 (temperature of temperature zone 2) in step (2) is changed to 490°C and 480°C respectively. Figure 7 This is an optical schematic diagram of the prepared Fe3Se4 nanosheets. The SiO2 / Si substrate containing large-area monolayer or few-layer WSe2 nanosheets is light purple. The white trapezoids represent Fe3Se4, indicating that the prepared Fe3Se4 nanosheets are very thick, while the purple trapezoids represent Fe3Se4, indicating that the prepared Fe3Se4 nanosheets are relatively thin. It can be observed that temperature has a significant regulatory effect on the thickness of the nanosheets; as the temperature increases, the thickness of the nanosheets gradually increases.

[0117] Example 4

[0118] Compared to Example 1, the only difference is that the substrate is changed to a silicon wafer with WS2 deposited on its surface. Figure 8 This is an optical schematic diagram of the prepared Fe3Se4 nanosheets. On the WS2 substrate, the Fe3Se4 nanosheets are mainly purple triangles and hexagons, indicating that the prepared nanosheets are relatively thin. It can be seen that the substrate surface without dangling bonds is conducive to the formation of thin layers of Fe3Se4 nanosheets.

[0119] Example 5

[0120] Compared to Example 1, the only difference is that the volatilization temperature of the selenium powder (T1, also known as T) is changed. se The temperatures are 300℃, 320℃, and 340℃. Figure 9 This is an optical schematic diagram of the prepared Fe3Se4 nanosheets. The SiO2 / Si substrate containing large-area monolayer or few-layer WSe2 nanosheets is light purple, and the Fe3Se4 nanosheets are purple. When the volatilization temperature of selenium powder is between 300-340℃, the thickness distribution of the prepared nanosheets ranges from 10-20 nm.

[0121] Example 6

[0122] Compared with Example 1, the only difference is that the Se:Fe molar ratio in the selenium powder and the pretreated iron raw material powder is 1:3 and 1:4, respectively. Figure 10 The image shows an optical schematic of the prepared Fe3Se4 nanosheets. The SiO2 / Si substrate containing large-area monolayer or few-layer WSe2 nanosheets is light purple. Fe3Se4 prepared under different molar ratios of iron and selenium sources is purple, with a thickness distribution of 10-30 nm.

[0123] Example 7

[0124] Compared with Example 1, the only difference is that in step (2), the flow rate of hydrogen is 8 sccm and the flow rate of Ar is 20 sccm; Figure 11 The image shows an optical schematic of the prepared Fe3Se4 nanosheets. The SiO2 / Si substrate containing large-area monolayer or few-layer WSe2 nanosheets is light purple, and the prepared Fe3Se4 is purple with a thickness distribution of 10-30 nm.

[0125] Comparative Example 1

[0126] Compared with Example 1, the only difference is that step 1 is missing, and in step (2), untreated FeCl2·4H2O is directly used as the Fe source (the total amount of iron is the same). Figure 12 The image shows an optical schematic of the prepared Fe3Se4 nanosheets. The SiO2 / Si substrate containing large-area monolayer or few-layer WSe2 nanosheets is light purple. The prepared nanosheets show obvious etching and the sample has poor crystallinity.

[0127] Comparative Example 2

[0128] Compared with Example 1, the only difference is that in step (2), the substrate is replaced with SiO2 / Si and mica substrate, while other operations and parameters are the same as in Example 1. Figure 13 This is an optical schematic diagram of the prepared nanosheets, which are essentially not formed from the target phase material.

[0129] Comparative Example 3

[0130] Compared with Example 1, the only difference is that in step (2), the temperatures (T2 temperature) of the iron source and the substrate region are 540℃ and 440℃, respectively. Figure 14 The image shows an optical schematic of the prepared Fe3Se4 nanosheets. The SiO2 / Si substrate containing large-area monolayer or few-layer WSe2 nanosheets is light purple, and the nanosheets have poor crystallinity or are deposited in a very thick layer.

[0131] Comparative Example 4

[0132] Compared with Example 1, the only difference is that in step (2), ammonium chloride powder is not added, while other operations and parameters are the same as in Example 1. Figure 15 The image shows an optical schematic of the prepared Fe3Se4 nanosheets. The SiO2 / Si substrate containing large-area monolayer or few-layer WSe2 nanosheets is light purple. The Fe3Se4 nanosheets are mainly white trapezoidal, triangular and hexagonal in shape, with small size and unsatisfactory crystallinity.

[0133] Comparative Example 5

[0134] Compared with Example 1, the only difference is that in step (2), the ratio of argon carrier gas to hydrogen is 300 sccm / 10 sccm (hydrogen content 3.2%). Figure 16 The image shows an optical schematic of the prepared Fe3Se4 nanosheets. The SiO2 / Si substrate containing large-area monolayer or few-layer WSe2 nanosheets is light purple, indicating that the Fe3Se4 nanosheets have poor crystallinity or a small number of deposits.

[0135] Example 8

[0136] The Fe3Se4 prepared in Example 1 was subjected to VSM and device testing. The VSM testing procedure was as follows: the silicon wafer carrying the sample was cut into 3mm × 3mm cubes, then adhered to a sample holder with low-temperature adhesive, and finally placed in a low-temperature property testing system for testing. The VSM testing conditions were: magnetic field range ±3T, temperature range 3-300K. The device testing procedure was as follows: first, Hall electrodes were patterned using electron beam lithography, then 10nm indium and 50nm gold were deposited as contact electrodes, and finally, the device was tested using a low-temperature property testing system. The device testing conditions were: magnetic field range ±9T, temperature range 3-300K.

[0137] Plot the magnetoresistance variation curves of nanosheets with different thicknesses.

[0138] Figure 17 The MH curve of the VSM test for Fe3Se4 proves that the Fe3Se4 nanosheets prepared in this invention are ferromagnetic at room temperature.

[0139] Figure 18The MR curves of the Fe3Se4 nanosheet Hall device reflect the change in resistance with magnetic field, and it was found that MR decreases with increasing temperature.

[0140] Figure 19 In the testing of Fe3Se4 nanosheet Hall devices, we found that at 180 K, in a low switching field Hs (defined as where MR drops sharply), we observed asymmetric hysteresis in parabolic negative magnetoresistance and the crossing of hysteresis branches in Rxy measurements.

[0141] Figure 20 In the testing of Fe3Se4 nanosheet Hall devices, a significant characteristic was found to be the hysteresis of the MR, which decreases with increasing temperature. Specifically, when the magnetic field was swept from -9T to 9T at 3K (black curve), a step size of approximately 8.4T was observed in both the Hall resistance (Rxy) and parabolic MR measurements.

[0142] Through the above embodiments and comparative examples, it was found that successfully preparing Fe3Se4 two-dimensional materials requires synergistic control of the substrate type, raw material volatilization temperature, carrier gas composition, carrier gas flow rate, and the deposition temperature of the volatilized material within the specified range. In this invention, by synergistically controlling the substrate type, deposition temperature (also known as growth temperature), and carrier gas type and flow rate, Fe3Se4 nanosheets with good morphology and controllable thickness can be prepared. The growth of Fe3Se4 non-layered materials on WSe2 provides a foundation for exploring its unique magnetic transport properties.

Claims

1. A method for preparing an iron-intercalated Fe3Se4 non-layered two-dimensional material, characterized in that, Heating the selenium source to temperature T1 causes the selenium to volatilize, releasing FeCl₂. n The mixture of xH2O and additives is heated to temperature T2 to volatilize the iron raw material, and the volatilized iron raw material and selenium source are chemically deposited on the surface of the substrate under the assistance of a carrier gas atmosphere to obtain the iron-intercalated Fe3Se4 non-layered two-dimensional material. The FeCl n In xH2O, n is 2 or 3, and 0 <x<4; The aforementioned additive is a halogen salt; The temperature T1 is 250~500℃, and the temperature T2 and the chemical deposition temperature are 480~510℃. The carrier gas is a composite gas of hydrogen and protective gas, wherein the flow rate of hydrogen is 5~15 sccm and the flow rate of protective gas is 5~50 sccm. The substrate is a substrate without dangling keys; The FeCl n xH2O via FeCl n ·yH2O was obtained by thermal modification at a temperature of T3, wherein the temperature T3 is 180~220 ℃ and the y is 4~6.

2. The method for preparing the iron-intercalated Fe3Se4 non-layered two-dimensional material as described in claim 1, characterized in that, The heat treatment time at temperature T3 is 0.3~1.0 h.

3. The method for preparing the iron-intercalated Fe3Se4 non-layered two-dimensional material as described in claim 1, characterized in that, The additives include at least one of ammonium chloride, sodium chloride, and potassium chloride.

4. The method for preparing the iron-intercalated Fe3Se4 non-layered two-dimensional material as described in claim 3, characterized in that, The FeCl n The weight ratio of xH2O to the additives is 1:0.01-0.

1.

5. The method for preparing the iron-intercalated Fe3Se4 non-layered two-dimensional material as described in claim 4, characterized in that, The FeCl n The weight ratio of xH2O to the additives is 1:0.03~0.

06.

6. The method for preparing the iron-intercalated Fe3Se4 non-layered two-dimensional material as described in claim 1, characterized in that, The selenium source is selenium powder.

7. The method for preparing the iron-intercalated Fe3Se4 non-layered two-dimensional material as described in claim 6, characterized in that, The selenium source and FeCl n The molar ratio of xH2O is 1:3~6.

8. The method for preparing the iron-intercalated Fe3Se4 non-layered two-dimensional material as described in claim 1, characterized in that, The protective gas includes at least one of nitrogen and inert gas.

9. The method for preparing the iron-intercalated Fe3Se4 non-layered two-dimensional material as described in claim 8, characterized in that, In the carrier gas, the flow rate of hydrogen is 8~12 sccm, and the flow rate of the protective gas is 8~20 sccm.

10. The method for preparing the iron-intercalated Fe3Se4 non-layered two-dimensional material as described in claim 1, characterized in that, The dangling bond-free substrate is a substrate with TMDs two-dimensional material deposited on its surface.

11. The method for preparing the iron-intercalated Fe3Se4 non-layered two-dimensional material as described in claim 10, characterized in that, The TMDs two-dimensional material is at least one of the transition metal selenides and sulfides.

12. The method for preparing the iron-intercalated Fe3Se4 non-layered two-dimensional material as described in claim 11, characterized in that, The TMDs two-dimensional material is a transition metal selenide.

13. The method for preparing the iron-intercalated Fe3Se4 non-layered two-dimensional material as described in claim 12, characterized in that, The TMDs two-dimensional materials are W or Mo selenide two-dimensional materials.

14. The method for preparing the iron-intercalated Fe3Se4 non-layered two-dimensional material according to any one of claims 1 to 13, characterized in that, Temperature T1 is 300~350℃.

15. The method for preparing the iron-intercalated Fe3Se4 non-layered two-dimensional material according to any one of claims 1 to 13, characterized in that, The temperatures T2 and the chemical deposition temperatures were 490~510℃, respectively.

16. The method for preparing the iron-intercalated Fe3Se4 non-layered two-dimensional material according to any one of claims 1 to 13, characterized in that, The chemical deposition time is 1~10 min.

17. A non-layered two-dimensional Fe3Se4 material with iron intercalation prepared by the preparation method according to any one of claims 1 to 16, characterized in that, It is a non-layered two-dimensional single crystal of Fe3Se4 with periodic iron intercalation; The Fe3Se4 non-layered two-dimensional material with iron intercalation has a [001] crystal orientation; it has a hexagonal, trapezoidal or triangular morphology; the plane size of the single crystal is 2~80 μm; and the thickness is 1.1~30 nm.

18. The application of an iron-intercalated Fe3Se4 non-layered two-dimensional material prepared by the preparation method according to any one of claims 1 to 16, characterized in that, It is used to prepare magnetic materials.

19. The application as described in claim 18, characterized in that, Magnetic materials are magnetic transport materials.

20. The application as described in claim 19, characterized in that, Magnetic transport materials are magnetic devices.

21. The application as described in claim 20, characterized in that, The magnetic device is a Hall effect device.

22. A magnetic material, characterized in that, The Fe3Se4 non-layered two-dimensional material containing iron intercalation obtained by the preparation method according to any one of claims 1 to 16.

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