Method for synthesizing Van der Waals miscoordinate layered compound based on solid-state high temperature and application of Van der Waals miscoordinate layered compound

Abstract

The invention provides a method for synthesizing a Van der Waals miscoordinate layered compound based on solid high temperature and application, and belongs to the technical field of functional devices, the compound is composed of at least two Van der Waals material sub-layers; according to the preparation method, a structure existing under the thermodynamic stable condition is synthesized through high-temperature sintering, and alternate self-assembly growth of a heterostructure is achieved; in the aspect of application, a functional device application regulation and control system is constructed, and the application of the compound in the fields of transverse ferroelectric metal memristors, vertical piezoelectric devices, superconducting ferroelectric memristors and the like is realized. According to the invention, the problems of complex process, low efficiency and high cost of traditional preparation of Van der Waals miscoordinate layered compounds are solved, a functional device application regulation and control system is constructed, wide application in multiple fields is realized, and a brand new direction is provided for future scientific and technological development.

Description

Technical Field

[0001] The present invention relates to the technical field of functional devices, and in particular to a method and application of solid-state high-temperature synthesis of van der Waals mismatched layered compounds. Background Art

[0002] Van der Waals (vdW) materials and mismatched layered compounds have attracted much attention in the field of materials research in recent years. Van der Waals materials are layered materials connected by van der Waals forces. Their unique layered structure gives them many excellent properties, such as high flexibility and adjustable electrical properties. Mismatched layered compounds are composed of two-dimensional components with different lattice constants. Mismatched layered compounds based on two-dimensional vdW materials have weak interlayer van der Waals forces, and each component can retain its intrinsic properties, realizing the fusion of multiple properties, which has great development potential in the field of future functional devices.

[0003] The emergence of two-dimensional vdW layered ferroelectric materials has opened up a new direction for the design of future all-two-dimensional material heterostructure non-volatile devices. This type of material not only has the stable spontaneous polarization and strong nonlinear properties of traditional ferroelectric materials, but also has unique advantages. Its band gap range is adjustable, which is of great significance in optoelectronic devices. It can flexibly control the absorption and emission of light of different wavelengths; at the same time, it also has extraordinary quantum topological properties, providing new material options for research in cutting-edge fields such as quantum computing and quantum communication. Therefore, the new vdW ferroelectric is regarded as a highly potential candidate material for electronic and optoelectronic devices in the post-Moore era, and shows broad application prospects in many fields such as high-density integrated ferroelectric storage, neuromorphic computing, optoelectronic sensing and storage chips, nanogenerators, photovoltaic devices, etc.

[0004] However, the current research on vdW materials is uneven. Although a lot of research results have been achieved in terms of optical and electrical properties, and researchers have a deeper understanding of their optical absorption, emission mechanisms, and electrical conduction properties, the exploration of ferroelectricity is still in a relatively early stage. Many questions about the basic properties of vdW ferroelectric materials, ferroelectric phase transition mechanisms, and coupling relationships with other physical properties have not been fully studied and clearly answered, which to a certain extent limits the optimization design and performance improvement of vdW ferroelectric materials in related devices.

[0005] In terms of material preparation technology, traditional heterogeneous superlattice crystal preparation mostly adopts a layer-by-layer preparation process. This process forms crystals by stacking materials layer by layer, which exposes many disadvantages in the actual operation process. The low deposition rate leads to low production efficiency, which is difficult to meet the needs of large-scale industrial production; poor scalability makes it difficult to prepare large-sized or complex structure crystals; poor stability and easy interference from external environmental factors lead to uneven crystal quality; and the material selection is limited, and only specific matching materials can be selected for layer-by-layer stacking, which greatly limits the development and application potential of new material systems and makes it difficult to meet the growing demand for high-performance and multifunctional materials. Summary of the invention

[0006] In order to overcome the shortcomings of the prior art, the present invention provides a method and application based on solid-state high-temperature synthesis of van der Waals misfit layered compounds, which solves the problems of complex process, low efficiency and high cost in the traditional preparation of van der Waals misfit layered compounds, constructs a functional device application regulation system, realizes its wide application in multiple fields, and provides a new direction for future scientific and technological development.

[0007] To achieve the above object, the present invention provides the following solutions: The first object of the present invention is to provide a van der Waals mismatched layered compound based on solid-state high-temperature synthesis. The van der Waals mismatched layered compound is prepared by a solid-state high-temperature synthesis method and is composed of at least two van der Waals material sublayers, one of the van der Waals material sublayers is a compound layer containing a Group IV or Group V transition metal, and the other of the van der Waals material sublayers is a compound layer containing tin, lead, bismuth, antimony or a rare earth metal element, and the atoms of the two van der Waals material sublayers are connected by van der Waals forces.

[0008] Preferably, the general chemical formula of the van der Waals mismatched layered compound is ([MX] 1+δ ) m (TX2) n ; Wherein, M is any one of tin, lead, bismuth, antimony or rare earth metal elements, T is a transition metal element of Group IV or Group V, X is sulfur or selenium, the parameter δ is the in-plane area ratio of the two components, m is the stoichiometric number of the MX layer, and n is the stoichiometric number of the TX2 layer.

[0009] Preferably, the two van der Waals material sublayers are tetragonal phase layer A and hexagonal phase layer B, respectively, forming a heterogeneous superlattice according to the stacking mode of ABAB and AAB; the crystal structure of the van der Waals mismatch layered compound is jointly characterized by Raman spectroscopy and scanning transmission electron microscopy-high-angle annular dark field, comprising two two-dimensional components with different lattice constants, and presenting a staggered arrangement to form a mismatch layered structure.

[0010] The second object of the present invention is to provide a method for preparing the above-mentioned van der Waals mismatched layered compound based on solid-state high temperature synthesis, comprising the following steps: According to the chemical formula of the target compound, weigh the single substance powders of each element as starting materials, and mix them evenly to obtain a mixed powder; The mixed powder and the transfer agent are encapsulated together in a vacuum-sealed quartz tube; The packaged quartz tube is placed in a dual-temperature zone furnace, and the temperature of the precursor mixture source end and the crystal growth end is set, and the mixed powder is reacted and crystallized in a gas phase environment by using a chemical vapor transport method; After the reaction is completed, the quartz tube is taken out from the double-temperature zone furnace and quenched to cool the crystal in the quartz tube from the reaction temperature to room temperature, fix the crystal structure, and obtain a single crystal of a van der Waals mismatched layered compound, that is, a van der Waals mismatched layered compound.

[0011] Preferably, the transfer agent is a stannous halide compound, and the stannous halide compound is one of stannous chloride and stannous bromide.

[0012] Preferably, the temperature range of the precursor mixture source end is 800-900° C.; the temperature range of the crystal growth end is 750-850° C.; the crystal growth is carried out by chemical vapor transport method, and the growth time is 7-14 days.

[0013] The third object of the present invention is to provide an application of the above-mentioned van der Waals misfit layered compound, which is applied to a variety of functional devices based on the electrical properties of the van der Waals misfit layered compound, specifically including: lateral ferroelectric metal memristor, vertical piezoelectric, and superconducting ferroelectric memristor devices.

[0014] Preferably, the hysteresis current-voltage hysteresis curve of the in-plane ferroelectric tunnel junction of the van der Waals misfit layered compound has the characteristic of low threshold voltage, and thus can be applied to lateral ferroelectric metal memristors with low energy consumption.

[0015] Preferably, the crystal structure of the van der Waals mismatched layered compound has the characteristic of broken out-of-plane symmetry due to the mismatch between the two groups of sub-layer lattices, and deforms along the direction of the electric field under the action of the electric field, and is applied to vertical piezoelectric devices with efficient electromechanical conversion performance.

[0016] Preferably, the van der Waals misfit layered compound is an Ising superconductor, which has the characteristics of a high upper critical field, and thus can maintain a stable superconducting state in a strong magnetic field environment, and can be applied to superconducting ferroelectric memristor devices with high stability.

[0017] According to the specific embodiments provided by the present invention, the present invention discloses the following technical effects: (1) The present invention provides a preparation method of van der Waals misfit layered compounds based on solid-state high-temperature synthesis. By precisely controlling the stoichiometric ratio of each element, selecting a suitable transport agent, and sintering the grown compound in a high-temperature zone by means of chemical vapor transport, and using a quenching process at the reaction temperature to stabilize its structure and properties, the traditional preparation process is simplified, the cumbersomeness of the layer-by-layer preparation process is overcome, the preparation efficiency and stability are improved, and the method has a higher potential for industrial application. It can achieve large-scale production at a lower cost, laying a solid foundation for the extensive research and application of the compound.

[0018] (2) The van der Waals misfit layered compound provided by the present invention has great application potential in the field of functional devices, especially in cutting-edge science and technology fields such as artificial intelligence. The compound can be used to construct non-volatile electronic devices, which provides the possibility of realizing a brain-like architecture with integrated storage and computing. Specifically, by constructing lateral ferroelectric metal memristors, vertical piezoelectric devices, superconducting ferroelectric memristor devices, etc., it meets the needs of brain-like computing and neural networks for high-performance devices, promotes the development of artificial intelligence hardware, and provides a new direction for future technological innovation. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0020] Figure 1 This is a flow chart of a preparation method of a van der Waals mismatched layered compound based on solid-state high-temperature synthesis of the present invention; Figure 2 (SnSe) provided in Example 1 of the present invention 1.16 X-ray diffraction spectrum of (NbSe2) crystal; Figure 3 (SnSe) provided in Example 1 of the present invention 1.16 STEM-HAADF image of (NbSe2) crystal; Figure 4 (SnSe) obtained by using transverse piezoelectric force microscopy provided in Example 1 of the present invention 1.16 (NbSe2) crystal ferroelectric properties diagram; where, Figure 4 (a) is the local electrical switching polarization spectrum. Figure 4 (b) is the phase diagram in the U-shaped plane. Figure 4 (c) is the amplitude domain diagram; Figure 5The (SnSe) obtained by vertical piezoelectric force microscopy provided in Example 1 of the present invention 1.16 (NbSe2) crystal piezoelectric effect diagram; Figure 6 (SnSe) obtained by angle-resolved photoelectron spectroscopy provided in Example 1 of the present invention 1.16 (NbSe2) crystal electronic structure diagram; where: Figure 6 (a) is under 45eV excitation (SnSe) 1.16 Binding Energy and In-Plane Wave Vector of (NbSe2) Crystal k / / The relationship diagram, Figure 6 (b) is under 40eV excitation (SnSe) 1.16 Binding Energy and In-Plane Wave Vector of (NbSe2) Crystal k / / The relationship diagram, Figure 6 (c) is under 35eV excitation (SnSe) 1.16 Binding Energy and In-Plane Wave Vector of (NbSe2) Crystal k / / The relationship diagram, Figure 6 (d) is under 30eV excitation (SnSe) 1.16 Binding Energy and In-Plane Wave Vector of (NbSe2) Crystal k / / The relationship diagram, Figure 6 (e) in the figure is under 25eV excitation (SnSe) 1.16 Binding Energy and In-Plane Wave Vector of (NbSe2) Crystal k / / Relationship diagram; Figure 7 The structure diagram of the in-plane ferroelectric tunnel junction device provided by Example 4 of the present invention; wherein, Figure 7 (a) is a schematic diagram of the overall structure of the in-plane ferroelectric tunnel junction device. Figure 7 (b) is a physical picture of the in-plane ferroelectric tunnel junction device; Figure 8 The in-plane ferroelectric tunnel junction performance diagram provided by Example 4 of the present invention; wherein, Figure 8 (a) is the IV hysteresis curve. Figure 8 (b) is the asymmetric current switching diagram; Fig. 9 The piezoelectric device structure and performance test diagram provided in Example 4 of the present invention; wherein, Fig. 9 (a) is the structural principle diagram of the piezoelectric device. Fig. 9 (b) in the figure is the piezoelectric performance diagram of the piezoelectric device. DETAILED DESCRIPTION

[0021] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0022] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0023] like Figure 1 As shown, the present invention provides a method for preparing a van der Waals mismatched layered compound based on solid-state high temperature synthesis, comprising the following steps: Step 100: According to the chemical formula of the target compound, weigh out the single substance powders of each element as starting materials, and mix them evenly to obtain a mixed powder; Step 200: Encapsulating the mixed powder and the transmission agent in a vacuum-sealed quartz tube; Step 300: placing the packaged quartz tube in a dual-temperature zone furnace, setting the temperature of the precursor mixture source end and the crystal growth end, and using chemical vapor transport to make the mixed powder react and crystallize in a gas phase environment; Step 400: After the reaction is completed, the quartz tube is taken out from the dual-temperature zone furnace and quenched to cool the crystal in the quartz tube from the reaction temperature to room temperature, fix the crystal structure, and obtain a single crystal of a van der Waals mismatched layered compound, that is, a van der Waals mismatched layered compound.

[0024] In the above steps, the transport agent is a stannous halide compound, and the stannous halide compound is selected from one of stannous chloride and stannous bromide. The temperature range of the precursor mixture source end is 800-900°C; the temperature range of the crystal growth end is 750-850°C; the crystal is grown by chemical vapor transport method, and the growth time is 7-14 days.

[0025] The obtained van der Waals mismatch layered compound is prepared by a solid-state high-temperature synthesis method, and is composed of at least two van der Waals material sublayers, one of which is a compound layer containing a transition metal of Group IV or Group V, and the other of which is a compound layer containing tin, lead, bismuth, antimony or a rare earth metal element, and the atoms of the two van der Waals material sublayers are connected by van der Waals forces. The two van der Waals material sublayers are tetragonal phase layer A and hexagonal phase layer B, respectively, and form a heterogeneous superlattice according to the stacking mode of ABAB and AAB; the crystal structure of the van der Waals mismatch layered compound is jointly characterized by Raman spectroscopy and scanning transmission electron microscopy-high-angle annular dark field, and contains two two-dimensional components with different lattice constants, and is staggered to form a mismatch layered structure.

[0026] In addition, the general chemical formula of the van der Waals mismatched layered compound is ([MX] 1+δ ) m (TX2) n ; Wherein, M is any one of tin, lead, bismuth, antimony or rare earth metal elements, T is a transition metal element of Group IV or Group V, X is sulfur or selenium, the parameter δ is the in-plane area ratio of the two components, m is the stoichiometric number of the MX layer, and n is the stoichiometric number of the TX2 layer.

[0027] According to the above content, the electrical properties of van der Waals misfit layered compounds are applied to a variety of functional devices, including: lateral ferroelectric metal memristors, vertical piezoelectrics, and superconducting ferroelectric memristor devices.

[0028] Among them, the hysteresis current-voltage hysteresis curve of the in-plane ferroelectric tunnel junction of the van der Waals misfit layered compound has the characteristics of low threshold voltage, and is thus applied to lateral ferroelectric metal memristors with low energy consumption. The crystal structure of the van der Waals misfit layered compound has a special crystal structure, specifically: due to the mismatch of the two sets of sub-layer lattices, the crystal structure has the characteristics of out-of-plane symmetry breaking, and deforms along the direction of the electric field under the action of the electric field, and is applied to vertical piezoelectrics with efficient electromechanical conversion performance. The van der Waals misfit layered compound is an Ising superconductor with the characteristics of a high upper critical field, and thus maintains a stable superconducting state in a strong magnetic field environment, and is applied to superconducting ferroelectric memristor devices with high stability.

[0029] The above contents will be further verified by listing specific implementation methods below.

[0030] Example 1 In this example, a van der Waals mismatched layered compound (SnSe) was prepared. 1.16 (NbSe2), comprising the following steps: (1) Weigh tin (Sn, purity 99.99%), niobium (Nb, purity 99.99%) and selenium (Se, purity 99.99%) powders as starting materials, mix them evenly in a ratio of 1.16:1:3.16 to obtain a mixed powder, and the mass of the mixed powder is about 1.5 g; (2) Using 150 mg of stannous chloride (SnCl2, purity 99.99%) as a transfer agent, the mixed powder and the transfer agent are packaged together in a vacuum-sealed quartz tube; (3) placing the packaged quartz tube in a dual-temperature zone furnace, setting the temperature of the precursor mixture source end to 900°C and the temperature of the crystal growth end to 850°C, and growing the tube by chemical vapor transport for 7 days to allow the mixed powder to react and crystallize in a gas phase environment; (4) After the reaction is completed, the quartz tube is taken out of the dual-temperature zone furnace and quenched to cool the crystals in the quartz tube from the reaction temperature to room temperature, fixing the crystal structure and obtaining a millimeter-sized and bright black flaky van der Waals mismatched layered compound (SnSe). 1.16 (NbSe2) single crystal.

[0031] The van der Waals mismatched layered compound (SnSe) obtained in Example 1 is as follows: 1.16 (NbSe2) was jointly tested and characterized: The crystal structure of the material obtained in Example 1 was characterized by X-ray diffraction (XRD). Figure 2 As shown. The XRD spectrum shows that all diffractions are (001) peaks, the diffraction angle range is 5 to 65 degrees, with a common (002) peak and a small half-height width, indicating that the grown (SnSe) 1.16 (NbSe2) single crystal samples are of high quality and good crystallinity.

[0032] The crystal structure of the material obtained in Example 1 was characterized by scanning transmission electron microscopy-high angle annular dark field (STEM-HAADF). Figure 3 As shown. Through the STEM-HAADF image, this vdW mismatch superlattice (SnSe) can be clearly seen 1.16 The microscopic crystal structure of NbSe2 and the local atomic structure show alternating stacked SnSe and NbSe2 heterogeneous layers and different features of the two planes. The high contrast produced by heavy atoms (such as Nb) provides detailed atomic arrangement information, showing the regular arrangement and distribution of different material layers. And the large range is also highly ordered alternating heterogeneous superlattice stacking arrangement, indicating that it has long-period order.

[0033] The ferroelectric properties of the material obtained in Example 1 were characterized by lateral piezoelectric force microscopy (LPFM). Figure 4As shown. At the resonant frequency of 750kHz, Figure 4 (a) shows the local electrically switched polarization spectrum (SS-PFM) in the voltage range of -6V to 6V, showing an amplitude butterfly curve and a phase cycle curve with a phase difference of 180°, indicating that the material obtained in Example 1 has a hysteresis behavior of in-plane ferroelectric switching, proving that (SnSe) 1.16 There is an electrically switchable bistable antiparallel polarization state in (NbSe2), with polarization switching voltages of approximately -0.7V and +0.6V. Figure 4 (b) and Figure 4 (c) in the figure shows the U-shaped in-plane phase and amplitude domain diagrams of the material obtained in Example 1 after tip bias polarization at +5V and -5V, respectively, showing an antiparallel remnant polarization with a phase contrast of nearly 180°. Transverse piezoelectric force microscopy technology shows that (SnSe) 1.16 (NbSe2) has in-plane ferroelectricity, which is the basis for its use in lateral ferroelectric metal memristor devices.

[0034] The piezoelectric effect of the material obtained in Example 1 was characterized by vertical piezoelectric force microscopy (VPFM). Figure 5 As shown. For 3×3μm 2 -5V voltage was applied to the region and (SnSe) was observed 1.16 The height of the (NbSe2) crystal surface decreases, and then at its center 1×1μm 2 The area is polarized by applying +5V voltage, and the crystal surface height is raised. The height of the electro-shrinking area is 1.3nm lower than that of the intrinsic area, while the height of the electro-stretching area is 4.7nm higher. Vertical piezoelectric force microscopy shows that (SnSe) 1.16 (NbSe2) has piezoelectric effect, which is the basis for its use in vertical piezoelectric devices.

[0035] Angle-resolved photoelectron spectroscopy (ARPES) was used to characterize the electronic structure of the material obtained in Example 1. The results obtained are as follows: Figure 6 See Figure 6 In (e), (d), (c), (b) and (a), the band dispersion along the Γ-M direction remains basically unchanged when the photon energy changes from 25eV to 45eV, indicating that (SnSe) 1.16 (NbSe2) has quasi-two-dimensional electronic properties.

[0036] Example 2 In this example, a van der Waals mismatched layered compound (SnSe) was prepared. 1.16 (NbSe2)2, comprising the following steps: (1) Weigh tin (Sn, purity 99.99%), niobium (Nb, purity 99.99%) and selenium (Se, purity 99.99%) powders as starting materials, mix them in a ratio of 1.16:2:5.16 to obtain a mixed powder with a mass of about 1.6 g; (2) Using 200 mg of stannous bromide (SnBr2, purity 99.99%) as a transfer agent, the mixed powder and the transfer agent are encapsulated together in a vacuum-sealed quartz tube; (3) placing the packaged quartz tube in a dual-temperature zone furnace, setting the temperature of the precursor mixture source end to 900°C and the temperature of the crystal growth end to 850°C, and growing the tube by chemical vapor transport for 7 days to allow the mixed powder to react and crystallize in a gas phase environment; (4) After the reaction is completed, the quartz tube is taken out of the dual-temperature zone furnace and quenched to cool the crystals in the quartz tube from the reaction temperature to room temperature, fixing the crystal structure and obtaining a van der Waals mismatched layered compound (SnSe) with a size of 2 mm and a thickness of 0.04-0.1 mm. 1.16 (NbSe2)2 single crystal.

[0037] Example 3 In this example, a van der Waals mismatched layered compound (SnSe) was prepared. 1.17 (NbSe2), comprising the following steps: (1) Weigh tin (Sn, purity 99.99%), niobium (Nb, purity 99.99%) and sulfur (S, purity 99.99%) powders as starting materials, mix them evenly in a ratio of 1.17:2:3.17 to obtain a mixed powder, and the mass of the mixed powder is about 1.6 g; (2) Using 200 mg of stannous chloride (SnCl2, purity 99.99%) as a transfer agent, the mixed powder and the transfer agent are packaged together in a vacuum-sealed quartz tube; (3) placing the packaged quartz tube in a dual-temperature zone furnace, setting the temperature of the precursor mixture source end to 850°C and the temperature of the crystal growth end to 770°C, and growing the tube by chemical vapor transport for 14 days to allow the mixed powder to react and crystallize in a gas phase environment; (4) After the reaction is completed, the quartz tube is taken out of the dual-temperature zone furnace and quenched to cool the crystals in the quartz tube from the reaction temperature to room temperature, fix the crystal structure, and obtain a van der Waals mismatched layered compound (SnSe) with a size of 5 mm. 1.17 (NbSe2) single crystal.

[0038] Example 4 like Figure 7 (a) and Figure 7As shown in (b), the van der Waals mismatched layered compound (SnSe) obtained in Example 1 1.16 (NbSe2) is prepared into an in-plane ferroelectric tunnel junction (FTJ) device. Figure 8 As shown in (a) in the figure, the IV hysteresis curve is obtained by scanning at different bias voltages, which intuitively presents the volt-ampere characteristic behavior of the memristor. Figure 8 As shown in (b), under a bias of ±0.3 V, an asymmetric current switch was measured, showing repeated reversible behavior between the ON and OFF states, proving that the polarization direction can be effectively adjusted by a small driving voltage, indicating that (SnSe) 1.16 (NbSe2) ferroelectric metal memristor has the advantage of low power consumption.

[0039] Reference Fig. 9 As shown in (a), the van der Waals mismatched layered compound (SnSe) obtained in Example 1 1.16 (NbSe2) is prepared into a piezoelectric device. When the external electric field is in the opposite direction to the polarization field of the piezoelectric device material itself, the piezoelectric device material is stretched, and when the external electric field is in the same direction as the polarization field of the piezoelectric device material itself, the piezoelectric device material is compressed. Fig. 9 As shown in (b), when alternating current of different amplitudes is applied, the piezoelectric amplitude of the piezoelectric device increases linearly with the amplitude of the alternating current.

[0040] Therefore, the above-mentioned method and application of solid-state high-temperature synthesis of van der Waals misfit layered compounds solves the problems of complex process, low efficiency and high cost in the traditional preparation of van der Waals misfit layered compounds, constructs a functional device application regulation system, realizes its wide application in multiple fields, and provides a new direction for future scientific and technological development.

[0041] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0042] The principles and implementation methods of the present invention are described in this article using specific examples. The description of the above embodiments is only used to help understand the method and core idea of ​​the present invention. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A van der Waals mismatched layered compound based on solid-state high temperature synthesis, characterized in that: The van der Waals mismatched layered compound is prepared by a solid-state high-temperature synthesis method and is composed of at least two van der Waals material sublayers, one of the van der Waals material sublayers is a compound layer containing a transition metal of Group IV or Group V, and the other of the van der Waals material sublayers is a compound layer containing tin, lead, bismuth, antimony or a rare earth metal element, and the atoms of the two van der Waals material sublayers are connected by van der Waals forces.

2. The van der Waals mismatched layered compound based on solid-state high temperature synthesis according to claim 1, characterized in that: The general chemical formula of the van der Waals mismatched layered compound is ([MX] 1+δ ) m (TX2) n ; Wherein, M is any one of tin, lead, bismuth, antimony or rare earth metal elements, T is a transition metal element of Group IV or Group V, X is sulfur or selenium, the parameter δ is the in-plane area ratio of the two components, m is the stoichiometric number of the MX layer, and n is the stoichiometric number of the TX2 layer.

3. The van der Waals mismatched layered compound based on solid-state high temperature synthesis according to claim 1, characterized in that: The two van der Waals material sublayers are tetragonal phase layer A and hexagonal phase layer B, respectively, which form a heterogeneous superlattice according to the stacking mode of ABAB and AAB; the crystal structure of the van der Waals mismatch layered compound is jointly characterized by Raman spectroscopy and scanning transmission electron microscopy-high-angle annular dark field, and contains two two-dimensional components with different lattice constants, which are arranged in an interlaced manner to form a mismatch layered structure.

4. A method for preparing a van der Waals mismatched layered compound based on solid-state high-temperature synthesis according to any one of claims 1 to 3, characterized in that: The following steps are involved: According to the chemical formula of the target compound, weigh the single substance powders of each element as starting materials, and mix them evenly to obtain a mixed powder; The mixed powder and the transfer agent are encapsulated together in a vacuum-sealed quartz tube; The packaged quartz tube is placed in a dual-temperature zone furnace, and the temperature of the precursor mixture source end and the crystal growth end is set, and the mixed powder is reacted and crystallized in a gas phase environment by using a chemical vapor transport method; After the reaction is completed, the quartz tube is taken out from the double-temperature zone furnace and quenched to cool the crystal in the quartz tube from the reaction temperature to room temperature, fix the crystal structure, and obtain a single crystal of a van der Waals mismatched layered compound, that is, a van der Waals mismatched layered compound.

5. The method for preparing a van der Waals mismatched layered compound based on solid-state high-temperature synthesis according to claim 4, characterized in that: The transfer agent is a stannous halide compound, and the stannous halide compound is one of stannous chloride and stannous bromide.

6. The method for preparing a van der Waals mismatched layered compound based on solid-state high-temperature synthesis according to claim 4, characterized in that: The temperature range of the precursor mixture source end is 800-900° C.; the temperature range of the crystal growth end is 750-850° C.; the crystal growth is carried out by chemical vapor transport method, and the growth time is 7-14 days.

7. An application of the van der Waals mismatched layered compound based on solid-state high temperature synthesis according to any one of claims 1 to 3, characterized in that: The electrical properties of the van der Waals misfit layered compound are applied to a variety of functional devices, including: lateral ferroelectric metal memristors, vertical piezoelectrics, and superconducting ferroelectric memristor devices.

8. The use of a van der Waals mismatched layered compound based on solid-state high-temperature synthesis according to claim 7, characterized in that: The hysteresis current-voltage hysteresis curve of the in-plane ferroelectric tunnel junction of the van der Waals mismatched layered compound has the characteristic of low threshold voltage, and is therefore applied to lateral ferroelectric metal memristors with low energy consumption.

9. The use of a van der Waals mismatched layered compound based on solid-state high-temperature synthesis according to claim 7, characterized in that: The crystal structure of the van der Waals mismatched layered compound has the characteristic of broken out-of-plane symmetry due to the mismatch between the two groups of sub-layer lattices, and deforms along the direction of the electric field under the action of the electric field, and is applied to vertical piezoelectric devices with efficient electromechanical conversion performance.

10. The use of a van der Waals mismatched layered compound based on solid-state high-temperature synthesis according to claim 7, characterized in that: The van der Waals misfit layered compound is an Ising superconductor, has the characteristics of a high upper critical field, and thus can maintain a stable superconducting state in a strong magnetic field environment, and can be applied to superconducting ferroelectric memristor devices with high stability.

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