Three-dimensional structure deformation induced ferroelectric topological domain structure construction method

Abstract

The invention discloses a three-dimensional structure deformation induced ferroelectric topological domain structure construction method, which comprises the following steps of providing a self-supporting ferroelectric film which is made of an ultrathin oxide material; applying three-dimensional structure deformation to the self-supporting ferroelectric film; inducing a non-uniform strain field or a strain gradient field in the thin film through the deformation of the three-dimensional structure; and based on the non-uniform strain field or the strain gradient field, reconstructing ferroelectric polarization distribution, and forming a polarity topological domain structure with an adjustable transverse size. According to the invention, the dimension limitation of traditional plane strain regulation and control is broken through, the directional design of a novel topological domain structure is supported, and a controllable and low-power-consumption micro-nano domain engineering platform is provided for novel electronic devices such as integrated photonic devices (such as light field modulators), photoelectric couplers, flexible electronic devices, high-density nonvolatile memories and the like.

Description

Technical Field

[0001] The present invention belongs to the technical field of preparation and characterization of micro-nano ferroelectric materials, and particularly relates to a method for regulating ferroelectric topological domain structures based on three-dimensional structural deformation, which is particularly applicable to the functional micro-nano domain engineering of flexible electronics, integrated photon devices, and high-density non-volatile memories. Background Art

[0002] Due to the spontaneous polarization and the characteristic of electric-field controllable flipping, ferroelectric materials have attracted much attention in information storage, sensors, and optoelectronic devices. In addition, by precisely regulating parameters such as the boundary conditions, size, and dimension of ferroelectric materials, a series of novel non-trivial polar topological domain structures have been successively discovered through the mutual competition and balance within a small difference among the elastic energy (strain), electrostatic energy, and gradient energy in the system, including flux-closed domains, vortex domains, polar "bubble" domains, polar skyrmions, halfons, etc. These nano-scale polar topological structures exhibit novel physical properties significantly different from those of bulk materials, such as enhanced conductivity, negative capacitance, and enhanced electromechanical response, etc., and have great application potential in the development of high-density, high-speed, and low-power consumption information storage devices.

[0003] In recent years, with the progress of micro-nano processing technology, precise regulation of the polarization domain structure (such as polar vortices, skyrmions) of ferroelectric materials through strain engineering has become a research hotspot. Traditional strain regulation means (such as epitaxial lattice mismatch, interface stress engineering) change the domain wall energy barrier by introducing in-plane biaxial strain (the strain amplitude is usually <3%), and realize the directional arrangement and optimization of the flipping dynamics of ferroelectric domains. However, this kind of method is limited by the rigid substrate coupling effect and is difficult to break through the dimensional limitation of two-dimensional plane strain regulation, which severely restricts the in-depth research and functional development of ferroelectric topological domains in integrated photon devices, optoelectronic coupling devices, flexible electronic devices, etc. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for constructing a ferroelectric topological domain structure induced by three-dimensional structural deformation to achieve cross-dimensional ferroelectric polarization reconstruction and controllable construction of polar topological domains.

[0005] To achieve the above purpose, the present invention adopts the following technical solutions:

[0006] The first purpose of the present invention is to provide a method for constructing a ferroelectric topological domain structure induced by three-dimensional structural deformation.

[0007] A method for constructing a ferroelectric topological domain structure induced by three-dimensional structural deformation includes the following steps:

[0008] Step 1, providing a self-supporting ferroelectric thin film with super-soft characteristics, and the self-supporting ferroelectric thin film is composed of an ultra-thin oxide material;

[0009] Step 2: Apply a three-dimensional structural deformation to the self-supporting ferroelectric thin film, where the three-dimensional structural deformation includes at least one of bending, bulging, or twisting;

[0010] Step 3: Induce a non-uniform strain field or strain gradient field in the thin film through the three-dimensional structural deformation;

[0011] Step 4: Based on the non-uniform strain field or strain gradient field, reconstruct the ferroelectric polarization distribution to form a polar topological domain structure with adjustable lateral dimensions, where the polar topological domain structure includes at least one of polar vortices, skyrmions, or central-type polar topological domains.

[0012] Preferably, the self-supporting ferroelectric thin film has super-soft characteristics.

[0013] Preferably, in Step 1, the thickness of the self-supporting ferroelectric thin film is 1 nm to 100 μm.

[0014] Preferably, in Step 1, the material of the self-supporting ferroelectric thin film is a ferroelectric oxide, more preferably a perovskite-type ferroelectric oxide, including but not limited to barium titanate (BaTiO), lead titanate (PbTiO), bismuth ferrite (BiFeO), lithium niobate (LiNbO), lead zirconate titanate (PZT), potassium niobate (KNbO), or one or more of perovskite-type ferroelectric thin films doped with rare earth elements.

[0015] In some preferred embodiments, in Step 1, the preparation method of the self-supporting ferroelectric thin film is as follows:

[0016] (1) Epitaxially grow a sacrificial layer on a single crystal substrate;

[0017] (2) Deposit a ferroelectric layer on the sacrificial layer;

[0018] (3) Remove the sacrificial layer by chemical stripping or mechanical stripping to obtain a self-supporting ferroelectric thin film.

[0019] In some preferred embodiments, the growth method of the ferroelectric layer is one or more of molecular beam epitaxy, pulsed laser deposition, atomic layer deposition, metal-organic chemical vapor deposition, or sol-gel method;

[0020] In some preferred embodiments, the sacrificial layer is one or more of an acid-corrosive sacrificial layer, an alkali-corrosive sacrificial layer, a water-soluble sacrificial layer, or graphene.

[0021] In some preferred embodiments, the chemical stripping method is one of acid-corroding the sacrificial layer, alkali-corroding the sacrificial layer, or water-soluble sacrificial layer.

[0022] In some preferred embodiments, the mechanical stripping method is remote epitaxy.

[0023] Preferably, in step 2, the realization method of the three-dimensional structure deformation is one of the following:

[0024] (a) Construct a bilayer homogeneous or heterogeneous structure in the self-supporting ferroelectric thin film. There is a strain mismatch between the lattice parameters of the bilayer structure, and the lattice mismatch degree is 0.1%-8%. When the bilayer structure is released from the constraint of the substrate, a dome-shaped three-dimensional morphology is spontaneously formed due to strain relaxation, and its size is controlled within the range of sub-microns to hundreds of microns by adjusting the thickness of the bilayer structure and the lattice mismatch degree;

[0025] (b) Transfer the self-supporting ferroelectric thin film to a preformed three-dimensional curved substrate with a radius of curvature of 1 nm - 10 mm, and use the curvature of the three-dimensional curved substrate to drive the film to generate bending or bulging deformation, where the substrate material is a flexible polymer material or a hard oxide. In some preferred embodiments, the flexible polymer material is PDMS and the hard oxide is Al2O3.

[0026] In some preferred embodiments, in step 2, during the three-dimensional structure deformation, a bending, bulging or twisting deformation is applied using a fixture or a nanoindenter.

[0027] In some preferred embodiments, the radius of curvature of the bending is 1 nm - 10 mm.

[0028] In some preferred embodiments, the height of the bulge is 1 nm - 10 mm.

[0029] In some preferred embodiments, the angle of twist is 5° - 30°.

[0030] Preferably, in step 3, the strain gradient field generates a corresponding flexoelectric field through the flexoelectric effect.

[0031] Preferably, in step 4, the three-dimensional deformation-induced non-uniform strain field or strain gradient field regulates the topological domains in the following manner:

[0032] Reduce the nucleation energy barrier of the topological domains through the flexoelectric effect, and at the same time compete with the ferroelectric domain wall energy, elastic energy and electrostatic energy to determine the size and topological number of the topological domains.

[0033] Preferably, in step 4, the lateral dimension of the polar topological domain structure is regulated within the range of 1 nm to 10 mm, and the domain structure regulation with sub-micron precision is achieved by adjusting the radius of curvature or the twist angle of the three-dimensional deformation.

[0034] Preferably, the method further includes characterizing the ferroelectric topological domain structure.

[0035] In some preferred embodiments, the characterization method is one or more of atomic force microscopy (AFM), scanning probe microscopy (SPM) and transmission electron microscopy (TEM).

[0036] The second object of the invention is to provide a micro-nano ferroelectric device.

[0037] A micro-nano ferroelectric device is prepared by the method for constructing a ferroelectric topological domain structure induced by the deformation of the three-dimensional structure, and the micro-nano ferroelectric device is any one of the following categories:

[0038] (a) Integrated photon devices: including a light field modulator or an optical vortex generator, and realizing the dynamic modulation of the beam phase and polarization state through the electric field regulation of the polar vortex domain;

[0039] (b) Photoelectric coupling devices: utilizing the coupling effect of the strain gradient field and photo-generated carriers to improve the photoelectric signal conversion efficiency;

[0040] (c) Flexible electronic devices: based on the ultra-flexible characteristics of the self-supporting film, maintaining the topological domain stability when the bending radius of curvature ≥ 1 mm, and being applicable to wearable sensors or flexible memories;

[0041] (d) High-density non-volatile memories: using a periodic conductive domain wall array as a storage unit.

[0042] Beneficial effects: Compared with the prior art, the innovative method for regulating the ferroelectric topological domain structure by the deformation of the three-dimensional structure of the present invention has significant advantages: by combining the three-dimensional structure deformation with the ultra-flexible film, the core problems in the traditional ferroelectric topological domain regulation technology, such as limited dimension, insufficient precision, and complex process, are solved, realizing the full-chain innovation from basic materials to functional devices, and providing a new material design paradigm for new electronic devices such as optoelectronics, flexible electronics, and quantum information technology.

[0043] The innovation points of the present invention are mainly reflected in:

[0044] Cross-dimensional regulation ability: breaking through the two-dimensional plane limitation, realizing the leap from two-dimensional plane strain to three-dimensional strain gradient for the first time, and solving the problem that it is difficult to construct an out-of-plane strain field by traditional methods;

[0045] Regulation range and efficiency: realizing the wide-range regulation of the lateral size of the topological domain (1 nm - 10 mm) by adjusting the three-dimensional deformation parameters (curvature radius 1 nm - 10 mm);

[0046] Process compatibility and scalability: combining epitaxial growth and chemical exfoliation (such as water-soluble Sr3Al2O6 sacrificial layer), the process is simple and there is no substrate constraint; traditional topological domains are mainly for non-volatile memories (such as FeRAM), with single functions and limited performance. The present invention can expand the application of ferroelectric topological domains to integrated photon devices: regulating the light field phase by the chiral polarization of the vortex domain; flexible electronic devices: maintaining the domain stability when the bending radius of curvature ≥ 10 mm, and being applicable to wearable sensors; high-density memories: storing data using a periodic conductive domain wall array. Description of the Drawings

[0047] Figure 1 Schematic diagram of lattice deformation and induced flexoelectric field in a three-dimensional dome-shaped microstructure;

[0048] Figure 2 Schematic diagram of the experimental design of the bilayer structure (including layer 1: relaxation layer and layer 2: strain layer) required for the dome-shaped microstructure;

[0049] Figure 3 Schematic diagram of the growth - water dissolution - transfer of ferroelectric thin films;

[0050] Figure 4 Corner LPFM characterization of a centrally converging ferroelectric topological domain structure;

[0051] Figure 5 Thickness dependence of a centrally converging ferroelectric topological domain structure;

[0052] Figure 6 Ferroelectric topological domain structures induced by other bilayer structures;

[0053] Figure 7 Schematic diagram of the process flow for constructing a ferroelectric topological domain structure induced by three-dimensional structure deformation. Detailed Implementation Manner

[0054] A method for constructing a ferroelectric topological domain structure induced by three-dimensional structure deformation according to the present invention utilizes the ultra-flexible characteristics of a self-supporting thin film, breaks through the physical limitations of traditional two-dimensional strain engineering, directly induces a non-uniform strain field and a flexoelectric field through three-dimensional structure deformation (bending, bulging, or twisting), realizes cross-dimensional ferroelectric polarization reconstruction and controllable construction of polar topological domains, and provides a new solution for the development of multifunctional devices.

[0055] A method for constructing a ferroelectric topological domain structure induced by three-dimensional structure deformation according to the present invention includes the following steps:

[0056] Step 1: Provide a self-supporting ferroelectric thin film, which is composed of an ultra-thin oxide material;

[0057] Among them, the self-supporting ferroelectric thin film has ultra-flexible characteristics.

[0058] Among them, the thickness of the self-supporting ferroelectric thin film is 1 nm to 100 μm.

[0059] Among them, the material of the self-supporting ferroelectric thin film is a ferroelectric oxide, preferably a perovskite-type ferroelectric oxide, including but not limited to one or more of barium titanate (BaTiO), lead titanate (PbTiO), bismuth ferrite (BiFeO), lithium niobate (LiNbO), lead zirconate titanate (PZT), potassium niobate (KNbO), or a perovskite-type ferroelectric thin film doped with rare earth elements.

[0060] The preparation method of the self-supporting ferroelectric thin film is as follows:

[0061] (1) Epitaxially grow a sacrificial layer on a single-crystal substrate;

[0062] (2) Deposit a ferroelectric layer on the sacrificial layer;

[0063] (3) Remove the sacrificial layer by chemical stripping or mechanical stripping to obtain a self-supporting ferroelectric thin film;

[0064] The growth method of the ferroelectric layer is one or more of molecular beam epitaxy, pulsed laser deposition, atomic layer deposition, metal-organic chemical vapor deposition, or sol-gel method;

[0065] The sacrificial layer is one or more of an acid-corrosive sacrificial layer, an alkali-corrosive sacrificial layer, a water-soluble sacrificial layer, or graphene.

[0066] The chemical stripping method is one of an acid-corrosive sacrificial layer, an alkali-corrosive sacrificial layer, or a water-soluble sacrificial layer.

[0067] The mechanical stripping method is the remote epitaxy method.

[0068] Step 2: Apply a three-dimensional structural deformation to the self-supporting ferroelectric thin film. The three-dimensional structural deformation includes at least one of bending, bulging, or twisting;

[0069] The implementation method of the three-dimensional structural deformation is one of the following:

[0070] (a) Construct a bilayer homogeneous or heterogeneous structure in the self-supporting ferroelectric thin film. There is a strain mismatch between the lattice parameters of the bilayer structure, and the lattice mismatch degree is 0.1%-8%. When the bilayer structure is released from the constraint of the substrate, a dome-shaped three-dimensional morphology is spontaneously formed due to strain relaxation, and its size is controlled between sub-microns and hundreds of microns by adjusting the thickness of the bilayer structure and the lattice mismatch degree;

[0071] (b) Transfer the self-supporting ferroelectric thin film to a preformed three-dimensional curved substrate with a radius of curvature of 1 nm - 10 mm, and use the curvature of the three-dimensional curved substrate to drive the film to generate bending or bulging deformation, where the substrate material is a flexible polymer material or a hard oxide. The flexible polymer material is preferably PDMS, and the hard oxide is preferably Al2O3.

[0072] In the three-dimensional structural deformation, a bending, bulging or twisting deformation is applied using a fixture or a nano-indentation instrument. Among them: the radius of curvature of the bending is 1 nm - 10 mm, the height of the bulge is 1 nm - 10 mm, and the angle of twist is 5° - 30°.

[0073] Step 3, inducing a non-uniform strain field or a strain gradient field in the thin film through the three-dimensional structural deformation, wherein the strain gradient field generates a corresponding flexoelectric field through the flexoelectric effect;

[0074] Step 4, based on the non-uniform strain field or the strain gradient field, reconstructing the ferroelectric polarization distribution to form a polar topological domain structure with an adjustable lateral size, and the polar topological domain structure includes at least one of a polar vortex, a skyrmion or a central-type polar topological domain;

[0075] Among them, the non-uniform strain field or the strain gradient field induced by the three-dimensional deformation regulates the topological domain in the following way:

[0076] The flexoelectric effect is used to reduce the nucleation energy barrier of the topological domain, and at the same time, it competes with the ferroelectric domain wall energy, the elastic energy and the electrostatic energy to determine the size and the topological number of the topological domain.

[0077] Among them, the regulation range of the lateral size of the polar topological domain structure is from 1 nm to 10 mm, and the domain structure regulation with sub-micron accuracy is realized by adjusting the radius of curvature or the twist angle of the three-dimensional deformation.

[0078] Step 5, characterizing the ferroelectric topological domain structure, and the characterization methods are one or more of an atomic force microscope (AFM), a scanning probe microscope (SPM) and a transmission electron microscope (TEM).

[0079] Through the above method for constructing a ferroelectric topological domain structure induced by three-dimensional structural deformation, a micro-nano ferroelectric device can be obtained, which is any one of the following categories:

[0080] (a) Integrated photon devices: including a light field modulator or an optical vortex generator, and realizing the dynamic modulation of the beam phase and the polarization state through the electric field regulation of the polar vortex domain;

[0081] (b) Optoelectronic coupling devices: utilizing the coupling effect between the strain gradient field and the photo-generated carriers to improve the optoelectronic signal conversion efficiency;

[0082] (c) Flexible electronic devices: based on the ultra-flexible characteristics of the self-supporting thin film, maintaining the topological domain stability when the bending radius of curvature ≥ 1 mm, and being applicable to wearable sensors or flexible memories;

[0083] (d) High-density non-volatile memories: using a periodic conductive domain wall array as a storage unit.

[0084] To illustrate the present application more clearly, the present application will be further described below in conjunction with preferred embodiments and the accompanying drawings. It should be noted that this embodiment is only used to exemplarily display the technical solution of the present invention, and those skilled in the art can adjust the material selection, process parameters or structural design according to actual needs, and these variations should be regarded as falling within the protection scope of the present invention.

[0085] Embodiment

[0086] In this embodiment, a generation method of three-dimensional structural deformation and the lattice distortion generated by this structure are as Figure 1 shown. By using the strain mismatch in the bilayer structure, a dome-shaped microstructure (bulge) is spontaneously formed during strain relaxation in the free state, as Figure 1 shown in A. The three-dimensional strain distribution induced by this structure includes: tensile strain distributed along the radial direction and compressive strain distributed perpendicular to the radial direction ( Figure 1 B). Combining the microscopic lattice distortion in Figure 1 C and the flexoelectric field generated by it, it can be seen that the introduction of the dome-shaped microstructure leads to anisotropic distortion of the lattice, generating a radially distributed flexoelectric field, which in turn drives the dipole to be oriented, forming a centrally converging polar topological microdomain. It should be noted that the dome-shaped morphology shows a form of three-dimensional deformation, and any geometric configuration that can generate an equivalent strain gradient field (such as helical deformation, wrinkled structure) belongs to the protection scope of the present invention.

[0087] A growth and transfer process of the self-supporting ferroelectric thin film in this embodiment is as Figure 2 shown. In this embodiment, the ferroelectric oxide thin film is grown by oxide molecular beam epitaxy (MBE) technology. The MBE growth process is only an example. On the premise of ensuring the crystallization quality of the thin film, alternative processes such as pulsed laser deposition, metal oxide chemical vapor deposition or sol-gel method can also be used. The epitaxial substrate material is selected as SrTiO3 (STO), and the water-soluble sacrificial layer is Sr3Al2O6 (SAO). The growth sequence is SAO and BTO in turn. In the preferred embodiment, the thickness of the SAO thin film is 10 nm, and the thickness of the BTO thin film is 16 nm. The transfer method is to invert this three-layer structure onto functional substrates such as sapphire, ITO and Si wafers, and transfer the flat self-supporting thin film by applying an external pressure as described in the Chinese invention patent (application number: CN202110830705.6). Those skilled in the art can understand that the BTO thin film used in the embodiment can be replaced by other perovskite oxides with similar ferroelectric properties.

[0088] In this embodiment, by using the lattice mismatch (~2.3%) between the strontium titanate substrate and the epitaxial BTO thin film, strain relaxation is induced during the growth process, generating a bilayer structure ( Figure 3) After the water-soluble release of the substrate, a dome-shaped microstructure is spontaneously formed in the bilayer structure due to strain relaxation. Its radius of curvature (R) can be estimated by the formula: R≈T / x%, where T is the total thickness of the film and x% is the lattice mismatch rate of the bilayer structure. For example, when T = 20 nm and x% = 1%, R≈2 μm. Further, by controlling the thickness of the bilayer structure (1 nm - 100 μm) and the lattice mismatch degree (0.1% - 8%), a wide range of control over the dome diameter can be achieved, and thus the size of the ferroelectric topological domain (1 nm - 100 mm) can be regulated.

[0089] In this embodiment, in order to accurately characterize the ferroelectric domain structure, the present invention adopts the following sample preparation process: First, transfer the free-standing ferroelectric film onto a rigid target substrate such as sapphire (Al2O3) or silicon substrate, and then completely remove the residual moisture at the interface through an optimized drying process (including nitrogen purging and vacuum baking at 60 - 80 °C). This process can ensure that the film and the substrate form an atomically flat contact interface (surface roughness <0.5 nm RMS), thereby effectively eliminating the interference of topography fluctuations on the piezoresponse force microscopy (PFM) characterization, controlling the proportion of non-intrinsic signals below 5%, and significantly improving the accuracy of domain structure characterization.

[0090] The piezoresponse force microscopy (PFM) technique is used to systematically characterize the topological domain structure in the free-standing ferroelectric film. The experimental results reveal the existence of a central-type topological microdomain structure ( Figure 4 ). The rotating-angle lateral piezoresponse (LPFM) test shows that the BTO film has significant in-plane multi-domain polarization characteristics ( Figure 4 A), while the out-of-plane polarization is weak; several domain wall-like regions with weakened piezoresponse amplitudes are detected, and these regions remain stable in position during the rotating-angle test, indicating that they are regions with weaker polarization intensity. The formation of these domain wall-like regions can be attributed to the reduction of lattice distortion during the transformation of the film from a dome-shaped morphology to a flat structure; this lattice relaxation mechanism is the key factor for the retention of three-dimensional topological patterns. Further statistical analysis of the polarization orientation of the central-type topological microdomain structure ( Figure 4 C) shows that the polarization orientation in the BTO film is mainly distributed along the high-symmetry directions, presenting a typical Maltese cross-shaped contrast, which is due to the constraint of the anisotropic elastic energy by the BTO tetragonal lattice symmetry during the formation of the topological texture.

[0091] By precisely controlling the thickness parameters of the free-standing ferroelectric film, the size-controllable preparation of the ferroelectric topological domain structure is achieved. Specifically, by adjusting the thickness of the free-standing ferroelectric film, that is, changing the thickness ratio of the strained layer (layer 1) to the relaxed layer (layer 2), precise control over the size of the ferroelectric topological domain can be realized. As Figure 5As shown, by changing the thickness of the BTO thin film from 40 layers to 160 layers, the size of the ferroelectric topological domain structure generated by the three-dimensional structural deformation shows a significant increasing trend. Under the condition of keeping the interlayer strain difference (Δx%) constant, the increase in the total thickness (T) of the thin film will inevitably lead to the increase in the topological domain size (R).

[0092] In addition, by introducing a bilayer structure into the self-supporting ferroelectric thin film in the present invention, not only can the strain difference be generated by using the strain relaxation during the growth process in the homogeneous material, but also a self-supporting thin film can be prepared by selecting a heterostructure with lattice mismatch (such as BTO / STO or other similar structures), so as to achieve a similar dome-shaped microstructure deformation. As Figure 6 shown, in this heterostructure, the ferroelectric topological domain structure formed by introducing the three-dimensional dome-shaped structure deformation can exhibit a similar regulation effect to that of a single BTO self-supporting thin film.

[0093] In summary, a method for constructing a ferroelectric topological domain structure induced by three-dimensional structural deformation proposed in the present invention directly induces a non-uniform strain field and a flexoelectric field by introducing three-dimensional structural deformation (bending, bulging or twisting), realizes cross-dimensional ferroelectric polarization reconstruction and controllable construction of polar topological domains, solves the core problems such as limited strain dimension and uncontrollable domain structure in traditional ferroelectric materials, and establishes a collaborative design paradigm of "three-dimensional structural deformation - super-flexible self-supporting thin film - dynamic domain engineering", providing an efficient regulation means for functional micro-nano domains for a new generation of optoelectronics, flexible electronics and quantum communication technologies.

[0094] The above are only the preferred embodiments of the present invention. It should be pointed out that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for constructing a ferroelectric topological domain structure induced by three-dimensional structural deformation, characterized in that: It includes the following steps: Step 1: Provide a self-supporting ferroelectric thin film, which is composed of an ultra-thin oxide material; Step 2: Apply a three-dimensional structural deformation to the self-supporting ferroelectric thin film, and the three-dimensional structural deformation includes at least one of bending, bulging or twisting; Step 3: Induce a non-uniform strain field or strain gradient field in the thin film through the three-dimensional structural deformation; Step 4: Based on the non-uniform strain field or strain gradient field, reconstruct the ferroelectric polarization distribution to form a polar topological domain structure with adjustable lateral size, and the polar topological domain structure includes at least one of polar vortices, skyrmions or central-type polar topological domains.

2. The method according to claim 1, wherein: In Step 1, the thickness of the self-supporting ferroelectric thin film is 1 nm to 100 μm, and the material is a ferroelectric oxide, which is one or more of barium titanate, lead titanate, bismuth ferrite, lithium niobate, lead zirconate titanate, potassium niobate or a perovskite-type ferroelectric thin film doped with rare earth elements.

3. The method according to claim 1, wherein: In Step 1, the preparation method of the self-supporting ferroelectric thin film is as follows: (1) Epitaxially grow a sacrificial layer on a single crystal substrate; (2) Deposit a ferroelectric layer on the sacrificial layer, and the growth method of the ferroelectric layer is one or more of molecular beam epitaxy, pulsed laser deposition, atomic layer deposition, metal oxide chemical vapor deposition or sol-gel method; (3) Remove the sacrificial layer by chemical peeling or mechanical peeling to obtain a self-supporting ferroelectric thin film; the sacrificial layer is one or more of an acid-corrosive sacrificial layer, an alkali-corrosive sacrificial layer, a water-soluble sacrificial layer or graphene; the chemical peeling method is one of acid-corroding the sacrificial layer, alkali-corroding the sacrificial layer or water-soluble sacrificial layer, and the mechanical peeling method is remote epitaxy.

4. The method according to claim 1, characterized in that: In Step 2, the implementation method of the three-dimensional structural deformation is one of the following: (a) Construct a bilayer homogeneous or heterogeneous structure in the self-supporting ferroelectric thin film. There is a strain mismatch between the lattice parameters of the bilayer structure, and the lattice mismatch degree is 0.1%-8%. When the bilayer structure is released from the restraint of the substrate, a dome-shaped three-dimensional morphology is spontaneously formed due to strain relaxation, and its size is controlled within the range of sub-microns to hundreds of microns by adjusting the thickness of the bilayer structure and the lattice mismatch degree; (b) Transfer the self-supporting ferroelectric thin film to a preformed three-dimensional curved substrate with a curvature radius of 1 nm - 10 mm, and use the curvature of the three-dimensional curved substrate to drive the film to generate bending or bulging deformation, where the substrate material is a flexible polymer or a hard oxide.

5. The method according to claim 1, wherein: In Step 3, the strain gradient field generates a corresponding flexoelectric field through the flexoelectric effect.

6. The method according to claim 1, characterized in that: In Step 4, the non-uniform strain field or strain gradient field induced by the three-dimensional deformation regulates the topological domains in the following way: Reduce the nucleation energy barrier of the topological domains through the flexoelectric effect, and at the same time compete with the ferroelectric domain wall energy, elastic energy and electrostatic energy to determine the size and topological number of the topological domains.

7. The method according to claim 1, characterized in that: The lateral size regulation range of the polar topological domain structure is 1 nm to 10 mm, and the domain structure regulation with sub-micron accuracy is realized by adjusting the curvature radius or torsion angle of the three-dimensional deformation.

8. The method according to claim 1, characterized in that: It also includes characterizing the ferroelectric topological domain structure, and the characterization method is one or more of atomic force microscopy (AFM), scanning probe microscopy (SPM), and transmission electron microscopy (TEM).

9. A micro-nano ferroelectric device prepared by the method according to any one of claims 1-8, characterized in that, The micro-nano ferroelectric device is any one of the following categories: (a) Integrated photon device: including a light field modulator or an optical vortex generator, and realizing dynamic modulation of the beam phase and polarization state through the electric field control of the polar vortex domain; (b) Photoelectric coupling device: utilizing the coupling effect between the strain gradient field and the photo-generated carriers to improve the photoelectric signal conversion efficiency; (c) Flexible electronic device: based on the ultra-flexible characteristics of the self-supporting film, maintaining the topological domain stability when the bending radius of curvature ≥ 1 mm, and applicable to wearable sensors or flexible memories; (d) High-density non-volatile memory: using a periodic conductive domain wall array as a storage unit.

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