A composite thin film and ferroelectric memory based on polar topological domain structure and a preparation method thereof

Abstract

The application discloses a composite film based on a polar topological domain structure, a ferroelectric memory and a preparation method thereof, and belongs to the technical field of ferroelectric materials. The composite film comprises a dielectric layer and a ferroelectric layer, the dielectric layer comprises a dielectric material, the ferroelectric layer comprises a ferroelectric material, and the ferroelectric layer is arranged in parallel on the surface of the dielectric layer; one of the dielectric layer and the ferroelectric layer is grown on the surface of the other layer; the thickness of the dielectric layer is X times the thickness of a single unit cell layer of the dielectric material, the thickness of the ferroelectric layer is Y times the thickness of a single unit cell layer of the ferroelectric material, 0.5 < Y / X < 10, and the thickness of the composite film is not more than 30 nm. The application can realize the preparation of a single-layer polar Sgmin-like topological nanodomain in an ultrathin composite film, and can prepare a ferroelectric memory with high density, high response speed and low energy consumption.

Description

Technical Field

[0001] This invention belongs to the field of ferroelectric materials technology, and more specifically, relates to a composite thin film based on a polar topological domain structure and a ferroelectric memory, as well as a method for preparing the same. Background Technology

[0002] In the context of the big data era, the size of traditional semiconductor chips has approached the quantum limit, making further development difficult. This has driven the exploration of new semiconductor electronic material systems for memory to meet real-world needs. The usual approach to reducing the dimensionality of ferroelectric materials starts with bulk materials and gradually reduces their size. However, as the size decreases, ferroelectric materials encounter the bottleneck of "dead layers," making it difficult to break through the nanometer scale. Recently, a novel approach has been proposed to utilize topological structures to achieve the reduction of dimensionality in ferroelectric materials.

[0003] In 2013, Nobel laureate in Physics Professor Fert and others proposed using magnetic topological defects (such as magnetic skyrmions) with topological protection properties as information storage units to record binary data, enabling contactless reading and writing. However, the experimentally observed magnetic topological structures are all larger than 20 nm. Since the size of ferroelectric domains is usually smaller than that of magnetic domains, researchers hope to find smaller spontaneous polar topological structures similar to those in magnetic materials within ferroelectric materials. Naumov et al. used first-principles calculations to predict the possible existence of bistable polar vortex domain structures as small as 3.2 nm in ferroelectric nanodots, and theoretically speculated that information storage units based on such polar topological structures could achieve an areal density exceeding 60 Tbit / in. 2 Ultra-high density memory. Subsequent research has shown that, under the influence of size effects, interface coupling and their interactions, and epitaxial strain, spontaneous non-trivial polar topological domain structures can also appear in ferroelectric materials, including flux-closed domains, vortices, polar "magnetic bubble" domains, polar skyrmions, and semions. These polar topological domain structures also exhibit rich physical properties. Exploring low-dimensional ferroelectric materials with polar topological domain structures in low-dimensional ferroelectric systems presents entirely new opportunities for future high-density memory devices.

[0004] Despite their potential applications, the integration of these polar topological domain structures into conventional silicon memory technologies remains challenging due to the lack of compatibility between perovskite oxide systems and current mature complementary metal-oxide-semiconductor (CMOS) processes. Furthermore, research on vortex-like topological domains is conducted in bottom-electrode-less or multilayer systems. The design of such material structures allows for the generation of toroidal / cycloidal topologies through precise manipulation of the depolarization field in the thin film. However, in practical information storage, a metal bottom electrode is required to apply an electric field to manipulate individual memory cells. Due to interlayer interactions, flipping topological domains in such multilayer / superlattice structures may require higher energy consumption. In addition, the overlap of multiple topological domain structural units in the thickness direction leads to signal overlap, hindering read and write operations.

[0005] To address the compatibility issues between perovskite oxides and semiconductor materials, researchers have attempted to fabricate high-quality self-supporting crystalline films by oxidizing transition metals, and then combining and transferring these independent functional units onto semiconductor substrates to achieve functional integration. Despite years of effort, significant progress has been slow. A breakthrough was achieved in this area in 2016 when Professor Harold Hwang and colleagues at Stanford University used pulsed laser deposition to grow perovskite films on a water-soluble intermediate layer, Sr3Al2O6, obtaining self-supporting perovskite films by dissolving the transition layer. Borrowing from this method, using the water-soluble Sr3Al2O6 film as a transition sacrificial layer, the applicant successfully prepared and transferred two-dimensional SrTiO3 and BiFeO3 self-supporting films with high lattice quality and near-single-cell thickness using oxide molecular beam epitaxy. Notably, when the thickness of the BiFeO3 self-supporting film approached the two-dimensional limit, a tetragonal phase and significant ferroelectric polarization were generated within the film. The successful fabrication of self-supporting two-dimensional oxide ferroelectric materials has inspired further exploration of the mechanisms and device applications of novel oxide-based ferroelectric and multiferroic two-dimensional materials. Summary of the Invention

[0006] 1. The problem to be solved

[0007] To address the challenges of low-dimensional development of traditional ferroelectric memories and the high energy consumption and read / write difficulties of existing topological domain-based memories, this paper provides a composite thin film based on a polar topological domain structure, a ferroelectric memory, and its fabrication method. This method produces a high-density ferroelectric impedance memory based on polar skyrmions that can be integrated with silicon semiconductors, thereby effectively solving the problems of high energy consumption and read / write difficulties in existing ferroelectric memories.

[0008] 2. Technical Solution

[0009] To solve the above problems, the technical solution adopted by the present invention is as follows:

[0010] This invention discloses a composite thin film based on a polar topological domain structure, comprising a dielectric layer and a ferroelectric layer. The dielectric layer comprises a dielectric material, and the ferroelectric layer comprises a ferroelectric material, wherein the ferroelectric layer is disposed parallel to the surface of the dielectric layer. In the dielectric and ferroelectric layers, one layer is grown on the surface of the other. The thickness of the dielectric layer is X times the thickness of a single cell layer of the dielectric material, and the thickness of the ferroelectric layer is Y times the thickness of a single cell layer of the ferroelectric material, where 0.5 < Y / X < 10, and the thickness of the composite thin film does not exceed 30 nm. The ferroelectric layer can be manipulated to generate diode conduction characteristics through the polar topological domain structure, and the diode conduction characteristics can be modulated by changes in the polar topological domain structure. This invention achieves the preparation of a single-layer polar skyrmion-like topological nanodomain in the ferroelectric layer by growing the dielectric or ferroelectric layer using physical or chemical methods, and by controlling the thickness of the dielectric and ferroelectric layers, thus solving the problems of high energy consumption and difficult reading / writing of flipped topological domains in multilayer / superlattice structures in the prior art.

[0011] Preferably, both the dielectric layer and the ferroelectric layer are single-crystal thin film layers, and both the ferroelectric material and the dielectric material are oxide materials.

[0012] Preferably, X = 5 to 16, the thickness of the composite film does not exceed 20 nm, and 1.6 < Y / X < 5; more preferably, Y / X = 1.8 to 2.2.

[0013] Preferably, the dielectric material includes one or more of SrTiO3, CaTiO3, LaAlO3, SiO2, and HfO2; the ferroelectric material includes one or more of BiFeO3, PbTiO3, BaTiO3, PZT, and PMN-PT.

[0014] Preferably, the growth method includes epitaxial growth; the epitaxial growth method includes one or more of molecular beam epitaxy, pulsed laser deposition, electron beam deposition, atomic beam deposition, electrophoretic deposition, chemical vapor deposition, and liquid phase epitaxy.

[0015] This invention discloses a method for preparing a composite thin film, wherein the composite thin film is a composite thin film based on a polar topological domain structure as described in this invention. First, a sacrificial layer is epitaxially grown on a single-crystal substrate. Then, a dielectric layer and a ferroelectric layer are sequentially epitaxially grown on the surface of the sacrificial layer. Finally, the sacrificial layer is dissolved in water to obtain the composite thin film. The sacrificial layer includes an acid-etched sacrificial layer, an alkali-etched sacrificial layer, or a water-soluble sacrificial layer. The acid-etched sacrificial layer can be etched with an acid solution to peel the composite thin film off the substrate; similarly, the alkali-etched sacrificial layer or the water-soluble sacrificial layer can be dissolved with an alkali solution or water, respectively.

[0016] Preferably, the specific steps are as follows:

[0017] (1) A water-soluble sacrificial layer is deposited on a single crystal substrate as a transition layer using oxide molecular beam epitaxy, wherein the material of the water-soluble sacrificial layer includes Sr3Al2O6;

[0018] (2) An SrTiO3 thin film was deposited on the transition layer using oxide molecular beam epitaxy;

[0019] (3) A PbTiO3 thin film was deposited on the SrTiO3 layer described in (2) by oxide molecular beam epitaxy;

[0020] (4) The water-soluble sacrificial layer is dissolved and removed with deionized water, so that the PbTiO3 / SrTiO3 bilayer structure is separated from the substrate, and PbTiO3 / SrTiO3 composite film is obtained.

[0021] The present invention discloses a ferroelectric memory comprising a conductive substrate and a composite thin film, wherein the conductive substrate and the composite thin film are arranged in parallel and connected, and the composite thin film is a composite thin film based on a polar topological domain structure as described in the present invention. The ferroelectric memory stores information by modulating the diode conduction characteristics of the composite thin film.

[0022] Preferably, the method for preparing the ferroelectric memory is as follows: the composite film is transferred onto a platinum-plated silicon substrate, and the dielectric layer is in contact with the silicon substrate.

[0023] Preferably, the method for modulating the conduction characteristics of the diode is as follows: an external electric field E is applied across the ferroelectric memory, and modulation is achieved by changing the magnitude or direction of the external electric field; the maximum absolute value of the external electric field E is |E|. m , |E| m ≥0.083V / nm.

[0024] Preferably, the |E| m ≥0.25V / nm.

[0025] 3. Beneficial effects

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0027] (1) The composite thin film based on the polar topological domain structure of the present invention has only a single layer of polar skyrmions instead of multiple layers of interacting polar skyrmions, so it is easier to switch each independent polar skyrmion by an external electric field, allowing for efficient “writing” operations; in addition, since there is no interference between multiple layers of skyrmions, it can also be tested directly by PFM, which is actually a non-destructive “read” operation, thereby enabling faster and more efficient reading and writing of data.

[0028] (2) The present invention provides a composite thin film based on a polar topological domain structure, based on a single layer of polar skyrmions in the ferroelectric layer, making the entire composite thin enough, and the change in the conductivity of the polar skyrmions can effectively adjust the resistance state of the double film near the nanodomain core.

[0029] (3) A ferroelectric memory of the present invention is obtained by integrating the composite thin film of the present invention onto a conductive substrate such as a silicon wafer. By applying an external electric field of different magnitudes or directions to the ferroelectric memory, the conversion between the central divergent domains in the high conductivity state and the central convergent domains in the low conductivity state can be achieved, thereby using this controllable conductivity difference for data storage. The ferroelectric memory of the present invention has advantages such as high density, high response speed and low energy consumption control, which is conducive to the development of non-volatile memories utilizing oxide topological polarity structures. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the growth and peeling process of the ferroelectric / dielectric composite film of the present invention;

[0031] Figure 2 Schematic diagrams of single-layer polar skyrmion-like nanodomain structures: (a) Schematic diagram of high-density polar skyrmions in a self-supporting composite film, (b) Schematic diagram of ferroelectric domain structures of centrally divergent and (c) centrally convergent polar skyrmions, (d) Schematic diagram of a cross-section of a self-supporting ferroelectric / dielectric bilayer structure film, and (e) Schematic diagram of a cross-section of a self-supporting energy-saving / ferroelectric / dielectric bilayer structure film.

[0032] Figure 3 PFM characterization of polar skyrmions: (a) morphology, VPFM amplitude, VPFM phase, LPFM amplitude and LPFM phase diagrams of self-supporting bilayer films; (b) magnified PFM images of centrally divergent and (d) centrally convergent nanodomains.

[0033] Figure 4 Vector PFM characterization of polar skyrmions: (a) topography, VPFM and LPFM of four different cantilever beam rotation directions (α = 0°, 30°, 60°, 90°, where α is the angle between the cantilever beam and the

[010] axis), (b) polarization distribution map of the same region in (a);

[0034] Figure 5 4D-STEM characterization of polar skyrmions: (a, b) 4D-STEM polarization distribution diagrams;

[0035] Figure 6 CAFM characterization of polar skyrmions: (a) Morphology, VPFM / LPFM and CAFM images collected in the same region after +5V i) and -5V ii) scans;

[0036] Figure 7 The reversible flipping of polar skyrmions under an external electric field: (a) Schematic diagram of topological nanodomain flipping under an applied electric field, (bd) VPFM phase, VPFM amplitude, LPFM phase and LPFM amplitude diagrams corresponding to the three cases in the schematic diagram;

[0037] Figure 8 The flipping process of a single polar skyrmion under the action of an external electric field: (a) VPFM amplitude (top left), VPFM phase (bottom left), LPFM amplitude (top right) and LPFM phase (bottom right) after applying external electric fields of 0V, -1V, -4V, -2V, +1V and +4V in sequence; (b) the flipping hysteresis loop of the polarized skyrmion;

[0038] Figure 9 The different impedance characteristics (E) of the two polar skyrmions F Fermi level; E c Conductor band; E v Price band; E g (band gap);

[0039] Figure 10 For self-supporting PTO n / STO 10 (n=12,16,20) Dependence of domain structure on n in composite thin films: (a) Morphology, LPFM amplitude and LPFM phase diagram when n=20, (b) n=16, (c) n=12;

[0040] Figure 11 The following diagram illustrates the stability of a single-layer polar skyrmion-like structure after conventional electron beam lithography: (a) Schematic diagram of the electron beam lithography process; (b) Periodic square patterns formed by electron beam lithography on a PTO / STO bilayer film transferred onto a P-doped silicon substrate (the inset shows the AFM morphology of a single square region); (c) PTO transferred onto a P-type doped silicon substrate. 20 / STO 10 VPFM amplitude, VPFM phase, LPFM amplitude and LPFM phase diagrams of the bilayer film. Detailed Implementation

[0041] The following detailed description of exemplary embodiments of the invention refers to the accompanying drawings, which form part of the description, illustrating exemplary embodiments in which the invention may be practiced, wherein features of the invention are identified by reference numerals. The more detailed description of embodiments of the invention below is not intended to limit the scope of the claimed invention, but is merely illustrative and not to limit the description of the features and characteristics of the invention, to suggest the best mode for carrying out the invention, and is sufficient to enable those skilled in the art to practice the invention. However, it should be understood that various modifications and variations can be made without departing from the scope of the invention as defined by the appended claims. The detailed description and drawings should be considered illustrative only and not restrictive, and any such modifications and variations will fall within the scope of the invention described herein. Furthermore, the background art is intended to illustrate the current state of research and development and significance of the technology, and is not intended to limit the invention or the application field of the invention.

[0042] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains; the terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to limit the invention.

[0043] It should be noted that when an element is referred to as being "set on" another element, it can be directly on the other element or it can be an intervening element; the terms "a layer," "another layer," "one end," and similar expressions used herein are for illustrative purposes only. The invention will be further described below with reference to specific embodiments.

[0044] Example 1

[0045] This embodiment provides a composite thin film based on a polar topological domain structure, comprising a dielectric layer and a ferroelectric layer. The dielectric layer is made of SrTiO3, and the ferroelectric layer is made of PbTiO3. The ferroelectric layer is disposed parallel to the surface of the dielectric layer and is formed by epitaxial growth on the surface of the dielectric layer. This embodiment uses oxide molecular beam epitaxy (MBE), but this is not limiting. In other embodiments, the ferroelectric layer can be grown using pulsed laser deposition, electron beam deposition, atomic beam deposition, electrophoretic deposition, chemical vapor deposition, liquid phase epitaxy, or other epitaxial growth methods, or physical or chemical thin film preparation methods suitable for oxide growth, such as sol-gel methods.

[0046] In this embodiment, the thickness of the dielectric layer is X times the thickness of a single cell layer of the dielectric material, and the thickness of the ferroelectric layer is Y times the thickness of a single cell layer of the ferroelectric material, where X = 10 and Y = 20, therefore Y / X = 2. The thickness of the composite film is approximately 12 nm. In this invention, the composite film is represented as PbTiO3(20 u.c.) / SrTiO3(10 u.c.) or PTO. 20 / STO 10 The specific preparation method is as follows:

[0047] (1) A water-soluble sacrificial layer of SAO (Sr3Al2O6) was deposited as a transition layer on a STO (SrTiO3) single crystal substrate in the (001) direction using oxide molecular beam epitaxy. Figure 1 It should be noted that the transition layer is not limited to a water-soluble sacrificial layer. In other embodiments, it can also be an acid-etched sacrificial layer or an alkaline-etched sacrificial layer, which can be removed by acid solution or alkaline solution, respectively.

[0048] (2) A thin film with a thickness of 10 STO (SrTiO3) unit cells was deposited on the SAO transition layer using oxide molecular beam epitaxy. Figure 1 );

[0049] (3) A thin film with a thickness of 20 PTO (PbTiO3) cells was deposited on the STO layer described in (2) using oxide molecular beam epitaxy. Figure 1 );

[0050] (4) The SAO water-soluble sacrificial layer was dissolved and removed with deionized water, so that the PTO / STO bilayer structure was separated from the substrate, and PTO was obtained. 20 / STO 10 (Ferroelectric / Dielectric) Composite Thin Film.

[0051] This embodiment prepares self-supporting PTO by adjusting the thickness of the PTO and STO layers using oxide molecular beam epitaxy and a water-soluble method. 20 / STO 10 Composite film, ultimately in PTO 20 / STO 10 The fabrication of monolayer polar skyrmion-like topological nanodomains was achieved in the structure, such as Figure 3 and Figure 7 As shown, these polar skyrmions have high density and are independent of each other.

[0052] This invention employs conductive atomic force microscopy (CAFM) to characterize the conductivity of samples and vector piezoelectric microscopy (vector PFM) to detect nanodomain types, analyzing the correlation between domain structure evolution and conductivity levels. For example... Figures 3-5As shown, characterization using piezoelectric microscopy (PFM) and scanning / transmission electron microscopy (S / TEM) reveals polar skyrmion-like topological nanodomains with both central divergent and central convergent types in the composite film. Conductive atomic force microscopy (CAFM) can characterize the different impedance information of these two types of topological nanodomains. Figure 6 CAFM images show that the centrally divergent nanodomains are in a high conductivity state, while the centrally convergent nanodomains are in a low conductivity state.

[0053] Furthermore, in this embodiment, the aforementioned composite thin film is transferred onto a Si substrate with Pt deposited on its surface. Figure 2 ), used as a ferroelectric memory. From Figure 7 The study observed two spontaneous states of nanodomains in the composite film (i). Applying an external electric field of +5V flipped all the nanodomains into center-divergent topological domains (ii), and applying -5V further flipped all the nanodomains into center-convergent topological domains (iii). This indicates that center-divergent and center-convergent nanodomains can be converted into each other by applying an external electric field and have different resistive behaviors.

[0054] Therefore, in this embodiment, when a positive bias voltage (e.g., +5V) is applied across the ferroelectric memory (i.e., the end of the ferroelectric layer away from the Si substrate and the end of the Si substrate away from the composite film), the centrally divergent nanodomains formed by polarization cause the charge carriers in the composite film to exhibit forward-conducting diode characteristics. Conversely, when a negative bias voltage (e.g., -5V) is applied across the ferroelectric memory, the centrally converging nanodomains formed by polarization cause the charge carriers in the composite film to exhibit negative-conducting diode characteristics. After positive and negative polarization operations, when the same voltage is applied across the ferroelectric memory, different currents can be read, and this current information can be used as stored information. For example... Figure 9 As shown in (a), when the bias voltage is +5V as the read voltage, the forward polarized current is approximately 0.5 × 10⁻⁶. 2 pA can be defined as storage state "1" (low resistance state), while the current generated by negative polarization after biasing -5V is approximately zero, which can be defined as storage state "0" (high resistance state). Applying +5V and -5V bias voltages can realize reversible switching between divergent nanodomains in the high conductivity state and convergent nanodomains in the low conductivity state, thus enabling information reading and writing. Figure 9 (b) shows a schematic diagram of the energy bands for two different types of topologies: the polar skyrmion type diverges from the center, and hole carriers are injected into the central region of the nanodomains, moving the Fermi level below the valence band. As a result, the barrier width narrows, leading to a high conductivity state (i); in contrast, the centrally convergent nanodomains remain in a low conductivity state due to their smaller divergence (ii).

[0055] It should be noted that the read / write voltage of ferroelectric memory is not limited to ±5V. Those skilled in the art can select the read / write voltage based on factors such as the current ratio under high and low resistance conditions and read power consumption. Figure 8 As shown, in this embodiment, the ferroelectric memory operates when the bias voltage exceeds 1V (in this embodiment, |E|). m Approximately 0.083V / nm) can cause a deflection in the polarization direction of skyrmions, thereby changing the resistance state of the ferroelectric memory and enabling information reading and writing; furthermore, when the bias voltage reaches 3V (in this embodiment, |E| m =0.25V / nm), which can achieve a maximum angle deflection of 180° in the polarization direction of the skyrmion. Therefore, in practical applications, the read / write voltage can be reasonably selected according to the required current ratio of high and low resistance states.

[0056] Furthermore, the aforementioned single-layer polar skyrmions are compatible with the silicon-based semiconductor industry, such as... Figure 11 As shown, a self-supporting composite film was transferred onto a p-doped silicon substrate, and the film was etched into a periodically arranged square pattern using electron beam lithography. The topological nanodomains remained intact and were reversible. This indicates that the independent film and the polar skyrmions within it can be integrated with silicon and can withstand damage during the process to some extent.

[0057] Comparative Example 1

[0058] This comparative example provides a composite film whose structure and preparation method are basically the same as those in Example 1, with the main difference being:

[0059] 1) In this comparative example, X = 10 and Y = 16, therefore Y / X = 1.6, and the thickness of the composite film is approximately 10 nm. The composite film is referred to as PTO in this invention. 16 / STO 10 .

[0060] Final characterization of PTO 16 / STO 10 The morphology, LPFM amplitude, and LPFM phase diagram of the composite thin film are summarized with the characterization results of Example 1. Figure 10 middle.

[0061] Comparative Example 2

[0062] This comparative example provides a composite film whose structure and preparation method are basically the same as those in Example 1, with the main difference being:

[0063] 1) In this comparative example, X = 10 and Y = 12, therefore Y / X = 1.2, and the thickness of the composite film is approximately 9 nm. The composite film is referred to as PTO in this invention. 12 / STO 10 .

[0064] Final characterization of PTO 12 / STO 10 The morphology, LPFM amplitude, and LPFM phase diagram of the composite thin film are summarized with the characterization results of Example 1. Figure 10 middle.

[0065] Example 2

[0066] This embodiment provides a composite thin film and ferroelectric memory based on a polar topological domain structure. Its structure and preparation method are basically the same as those in Embodiment 1, with the main difference being:

[0067] 1) In this comparative example, X = 12 and Y = 21, therefore Y / X = 1.75, and the thickness of the composite film is approximately 13 nm. The composite film is referred to as PTO in this invention. 21 / STO 12 .

[0068] Final characterization of PTO 21 / STO 12 LPFM amplitude and LPFM phase diagram of composite thin film and Figure 10 The result (a) is similar.

[0069] Example 3

[0070] This embodiment provides a composite thin film and ferroelectric memory based on a polar topological domain structure. Its structure and preparation method are basically the same as those in Embodiment 1, with the main difference being:

[0071] 1) In this comparative example, X = 8 and Y = 18, therefore Y / X = 2.25, and the thickness of the composite film is approximately 10 nm. The composite film is referred to as PTO in this invention. 18 / STO8.

[0072] Final characterization of PTO 18 LPFM amplitude and LPFM phase diagram of / STO8 composite film and Figure 10 The result (a) is similar.

[0073] Example 4

[0074] This embodiment provides a composite thin film and ferroelectric memory based on a polar topological domain structure. Its structure and preparation method are basically the same as those in Embodiment 1, with the main difference being:

[0075] 1) In this comparative example, X = 15 and Y = 27, therefore Y / X = 1.8, and the thickness of the composite film is approximately 17 nm. The composite film is referred to as PTO in this invention. 27 / STO 15 .

[0076] Final characterization of PTO27 / STO 15 LPFM amplitude and LPFM phase diagram of composite thin film and Figure 10 The result (a) is similar.

[0077] Example 5

[0078] This embodiment provides a composite thin film and ferroelectric memory based on a polar topological domain structure. Its structure and preparation method are basically the same as those in Embodiment 1, with the main difference being:

[0079] 1) In this comparative example, X = 5 and Y = 11, therefore Y / X = 2.2, and the thickness of the composite film is approximately 6 nm. The composite film is referred to as PTO in this invention. 11 / STO5.

[0080] Final characterization of PTO 11 LPFM amplitude and LPFM phase diagram of / STO5 composite film and Figure 10 The result (a) is similar.

[0081] like Figure 10 As shown, comparing Examples 1-5 with Comparative Examples 1-2, it can be seen that the presence of monolayer polar skyrmion-like nanodomain structures cannot be observed in the composite films of Comparative Examples 1 and 2. This indicates that the ratio and thickness of the ferroelectric layer and dielectric layer in the composite film play a key role in the preparation of polar topological domain structures. Only within the preferred range can monolayer polar skyrmions be prepared in the composite film.

[0082] Example 6

[0083] This embodiment provides a composite thin film and ferroelectric memory based on a polar topological domain structure. Its structure and preparation method are basically the same as those in Embodiment 1, with the main difference being:

[0084] 1) The material of the ferroelectric layer was replaced with BiFeO3 to prepare BFO. 20 / STO 10 Composite film.

[0085] Final characterization of BFO 20 / STO 10 LPFM amplitude and LPFM phase diagram of composite thin film and Figure 10 The result (a) is similar.

[0086] Example 7

[0087] This embodiment provides a composite thin film and ferroelectric memory based on a polar topological domain structure. Its structure and preparation method are basically the same as those in Embodiment 1, with the main difference being:

[0088] 1) The dielectric layer material was replaced with CaTiO3 to prepare PTO. 20 / CTO 10 Composite film.

[0089] Final characterization of PTO 20 / CTO 10 LPFM amplitude and LPFM phase diagram of composite thin film and Figure 10 The result (a) is similar.

[0090] Example 8

[0091] This embodiment provides a composite thin film and ferroelectric memory based on a polar topological domain structure. Its structure and preparation method are basically the same as those in Embodiment 1, with the main difference being:

[0092] 1) In PTO 20 / STO 10 A thin film with a thickness of 10 STO unit cells is then deposited on the PTO surface of the composite film, such as... Figure 2 As shown, STO is obtained. 10 / PTO 20 / STO 10 Three-layer composite thin film.

[0093] Final characterization of STO 10 / PTO 20 / STO 10 LPFM amplitude and LPFM phase diagram of three-layer composite thin film Figure 10 The result (a) is similar.

[0094] It should be noted that in other embodiments, the ferroelectric layer material can also be BaTiO3, PZT, PMN-PT, and the dielectric layer material can also be LaAlO3, SiO2, HfO2. This invention is only an example of several common materials and cannot exhaustively list dielectric oxide materials and ferroelectric oxide materials. This is not a limitation on the types of dielectric oxide materials and ferroelectric oxide materials. On the contrary, this invention has universal applicability to the preparation of composite thin films based on polar topological domain structures using a wide range of dielectric oxide materials and ferroelectric oxide materials.

[0095] The present invention has been described in detail above with reference to specific exemplary embodiments. However, it should be understood that various modifications and variations can be made without departing from the scope of the invention as defined by the appended claims. The detailed description and drawings should be considered illustrative only and not restrictive, and any such modifications and variations shall fall within the scope of the invention described herein. Furthermore, the background art is intended to illustrate the current state of development and significance of the technology and is not intended to limit the present invention or the scope of application of the present application.

[0096] More specifically, although exemplary embodiments of the invention have been described herein, the invention is not limited to these embodiments, but includes any and all embodiments modified, omitted, such as combinations between various embodiments, adaptive changes, and / or substitutions, as would be apparent to those skilled in the art from the foregoing detailed description. The limitations in the claims are to be interpreted broadly as used in the language of the claims and are not limited to the examples described in the foregoing detailed description or during the implementation of this application, which should be considered non-exclusive. Any step listed in any method or process claim may be performed in any order and is not limited to the order set forth in the claims. Therefore, the scope of the invention should be determined solely by the appended claims and their legal equivalents, and not by the description and examples given above.

[0097] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. In case of conflict, the definitions in this specification shall prevail. When thickness, electric field strength, or other values ​​or parameters are expressed as ranges, preferred ranges, or a series of upper and lower preferred values, this shall be understood as specifically disclosing all ranges formed by any pair of any upper or preferred value with any lower or preferred value, regardless of whether such range is disclosed individually. For example, the range 1-50 should be understood to include any number, combination of numbers, or subrange selected from 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, or 50, as well as all decimal values ​​between the integers mentioned above, such as 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, and 1.9. Regarding subranges, specifically consider "nested subranges" extending from any endpoint of the range. For example, nested sub-ranges of the exemplary range 1-50 may include 1-10, 1-20, 1-30 and 1-40 in one direction, or 50-40, 50-30, 50-20 and 50-10 in another direction.

Claims

1. A ferroelectric memory comprising a composite thin film based on a polar topological domain structure, characterized in that, It includes a conductive substrate and a composite thin film, wherein the conductive substrate and the composite thin film are arranged in parallel and connected to each other; The conductive substrate is a platinum-plated silicon substrate; The composite film is a self-supporting composite film that realizes a single layer of polar skyrmion-like topological nanodomains; The composite film includes a dielectric layer and a ferroelectric layer, wherein the dielectric layer includes a dielectric material and the ferroelectric layer includes a ferroelectric material. Both the dielectric layer and the ferroelectric layer are single-crystal thin film layers, and both the ferroelectric material and the dielectric material are oxide materials; The ferroelectric layer is disposed parallel to the surface of the dielectric layer; in the dielectric layer and the ferroelectric layer, one layer is grown on the surface of the other layer; the thickness of the dielectric layer is X times the thickness of a single cell layer of its dielectric material, the thickness of the ferroelectric layer is Y times the thickness of a single cell layer of its ferroelectric material, 0.5 < Y / X < 10, and the thickness of the composite film does not exceed 30 nm. The composite film is transferred onto a platinum-plated silicon substrate, with the dielectric layer in contact with the silicon substrate; The ferroelectric layer can be operably configured to generate diode conduction characteristics through a polar topological domain structure, and the diode conduction characteristics can be operably modulated by changes in the polar topological domain structure. The ferroelectric memory stores information by modulating the diode conduction characteristics of the composite thin film.

2. The ferroelectric memory comprising a composite thin film based on a polar topological domain structure according to claim 1, characterized in that, The method for modulating the conduction characteristics of a diode is as follows: an external electric field E is applied across the terminals of the ferroelectric memory, and modulation is achieved by changing the magnitude or direction of the external electric field; the maximum absolute value of the external electric field E is |E|. m , |E| m ≥0.083V / nm.

3. The ferroelectric memory comprising a composite thin film based on a polar topological domain structure according to claim 2, characterized in that, The |E| m ≥0.25V / nm.

4. The ferroelectric memory comprising a composite thin film based on a polar topological domain structure according to claim 1, characterized in that, X = 5 to 16, the thickness of the composite film does not exceed 20 nm, and 1.6 < Y / X < 5.

5. The ferroelectric memory comprising a composite thin film based on a polar topological domain structure according to claim 1, characterized in that, The dielectric material includes one or more of SrTiO3, CaTiO3, and LaAlO3; the ferroelectric material includes one or more of BiFeO3, PbTiO3, BaTiO3, PZT, and PMN-PT.

6. The ferroelectric memory comprising a composite thin film based on a polar topological domain structure according to claim 1, characterized in that, The growth method includes epitaxial growth; the epitaxial growth method includes one or more of molecular beam epitaxy, pulsed laser deposition, electron beam deposition, atomic beam deposition, electrophoretic deposition, chemical vapor deposition, and liquid phase epitaxy.

7. A method for fabricating a ferroelectric memory comprising a composite thin film based on a polar topological domain structure as described in any one of claims 1 to 6, characterized in that, First, a sacrificial layer is epitaxially grown on a single-crystal substrate. Then, a dielectric layer and a ferroelectric layer are epitaxially grown sequentially on the surface of the sacrificial layer. Finally, the sacrificial layer is dissolved in water to obtain the composite film. The sacrificial layer includes an acid-etched sacrificial layer, an alkali-etched sacrificial layer, or a water-soluble sacrificial layer. The composite film is transferred to a platinum-plated silicon substrate, and the dielectric layer is in contact with the silicon substrate.

8. The preparation method according to claim 7, characterized in that, The specific steps are as follows: (1) A water-soluble sacrificial layer is deposited on a single crystal substrate as a transition layer using oxide molecular beam epitaxy, wherein the material of the water-soluble sacrificial layer includes Sr3Al2O6; (2) An SrTiO3 thin film was deposited on the transition layer using oxide molecular beam epitaxy; (3) A PbTiO3 thin film was deposited on the SrTiO3 layer described in (2) by oxide molecular beam epitaxy; (4) The water-soluble sacrificial layer is dissolved and removed with deionized water, so that the PbTiO3 / SrTiO3 bilayer structure is separated from the substrate, and PbTiO3 / SrTiO3 composite film is obtained.

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