CN113248248A

CN113248248A - Solid solution multiferroic film, preparation method and electronic device applied to 5G storage technology

Info

Publication number: CN113248248A
Application number: CN202010814984.2A
Authority: CN
Inventors: 贾婷婷; 胡芳; 方伟; 于淑会; 孙蓉
Original assignee: Shenzhen Institute of Advanced Technology of CAS
Current assignee: Shenzhen Institute of Advanced Technology of CAS
Priority date: 2020-08-13
Filing date: 2020-08-13
Publication date: 2021-08-13

Abstract

The application relates to a solid solution multiferroic film, a preparation method and an electronic device comprising the multiferroic film and applied to a 5G storage technology. The film is a complex oxide solid solution with a pseudo perovskite structure, and the chemical formula is as follows:(1‑x ₁‑x ₂)LM_y(1‑)/2Fe_yN_y(1‑)/ ₂O₃ x ₁Rx ₂q; wherein the content of the first and second substances,y=0~1，x ₁=0~1，x ₂=0~1，x ₁+x ₂less than or equal to 1; l is selected from one or more of Bi, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu or Y; m, N are selected from Mg, Ti, Hf, Co, Mn, Ni or Zr, which may be the same or different; r is LFeO₃(ii) a Q is an oxide of L, M, N; the film is a solid solution of rhombohedral phase and orthorhombic phase, and is polycrystalline. The film has larger room temperature electric polarization intensity and lower room temperature leakage current density.

Description

Solid solution multiferroic film, preparation method and electronic device applied to 5G storage technology

Technical Field

The application relates to the field of multiferroic thin film materials, in particular to a solid solution multiferroic thin film, a preparation method, an electronic device containing the multiferroic thin film and applied to a 5G storage technology.

Background

Currently, 5G communication technology is becoming mature. The 5G technology can not only improve the mobile experience of people, but also change the operation modes of many industries outside the communication field. 5G processes data 10 to hundred times faster than 4G, making data generation 10 to hundred times faster. Meanwhile, along with the exponential increase of the data volume, the storage capacity requirement of the server is correspondingly greatly increased, and the storage for backup is doubled, so that the 5G generation of the mass storage requirement is promoted. In the 5G large environment, although the current memory can work normally, the current memory cannot keep up with the requirements of data and bandwidth in the system, so that it is necessary to develop and apply a new generation of memory as soon as possible.

The novel multiferroic material is expected to realize better information storage. A multiferroic material is a material that has two or more ferroicity (including ferroelectricity, ferromagnetism, or ferroelasticity) simultaneously in the material. The multiferroic material with various ferrosexes mutually coupled has wide application prospect in the aspects of electric, optical and magnetic field inductors, random access memories, photovoltaics, photoelectric rectification and the like. Among them, multiferroic materials having a magnetoelectric coupling effect can induce a magnetic moment by an external electric field or be polarized by a magnetic field, and thus are the technical core of many electronic devices and sensors, such as magnetic field sensors, magnetoelectric MRAM (ME-MRAM) and microwave devices, especially applied to 5G information storage devices.

Current multiferroic materials include composite multiferroic materials and unidirectional multiferroic materials. Among them, the composite material has an advantage of a large magnetoelectric coupling coefficient, but is not easy to integrate due to an interface problem.

Ferroelectricity and ferromagnetism (or antiferromagnetism) have different electronic structures and thus do not generally coexist in a single phase material. The conventional mechanism of ferroelectricity involves a closed shell d⁰Or s²Cationic, while ferromagnetic order requires an open shell d with unpaired electronsⁿConfiguration. This fundamental difference makes it difficult to combine the long-range order of the two dipoles to break the space-inversion and time-inversion symmetries simultaneously at room temperature.

Single phase materials such as ABO₃Perovskite bismuth ferrite (BiFeO)₃Abbreviated BFO) can be generated with these two ordered design routes, ABO₃The perovskite bismuth ferrite is the only single-phase multiferroic material with ferroelectricity and antiferromagnetism at room temperature, and has the maximum residual polarization intensity and high ferroelectric Curie temperature T at present_C1100K, relatively high antiferromagnetic Neel temperature T_N643K and a smaller forbidden band width, so the device is widely concerned at home and abroad. Although bismuth ferrite theoretically has higher remanent polarization, bismuth element is easy to volatilize and part of Fe is generated in the preparation process³⁺To Fe²⁺And more oxygen vacancies are generated, so that the leakage current is larger, and the polarization is difficult, and therefore, a sample with higher remanent polarization is difficult to prepare. In addition, BiFeO₃Commercial applications are greatly limited due to the inhibition of weak ferromagnetism and linear magnetoelectric coupling due to cycloidal magnetic ordering.

Disclosure of Invention

Aiming at the problems of large leakage current and low remanent polarization of multiferroic materials in the prior art, a first object of the present application is to provide a solid solution multiferroic thin film with small leakage current and high remanent polarization.

A second object of the present application is to provide a method for preparing a solid solution multiferroic thin film, which has the advantages of simple preparation method and easy mass production.

A third object of the present application is to provide an electronic device having advantages of more excellent performance and being more lightweight and thinner.

A fourth object of the present application is to provide an electronic device applied to 5G storage technology, which has the advantages of more excellent performance and being thinner and lighter.

In order to achieve the first object, the present application provides the following technical solutions: a solid solution multiferroic thin film is a complex oxide solid solution with a pseudo perovskite structure and has the following chemical formula:(1-x ₁-x ₂)LM_y(1-)/2Fe_yN_y(1-)/2O₃ x ₁Rx ₂Q；

wherein, in the chemical formula,y=0~1，x ₁=0~1，x ₂=0~1，x ₁+ x ₂≤1；

l is selected from one or more of Bi, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu or Y; m, N are respectively selected from Mg, Ti, Hf, Co, Mn, Ni or Zr, which may be the same or different; and R is LFeO₃(ii) a And Q is an oxide of L, M, N.

In one embodiment, the multiferroic thin film is a solid solution of rhombohedral and orthorhombic phases, and in another embodiment, the multiferroic thin film is a polycrystalline thin film.

By adopting the technical scheme, bismuth ferrite is doped to form a pseudo perovskite structure, so that a complex oxide solid solution is obtained, the complex oxide solid solution has low electric leakage characteristic, has good electric hysteresis loop at room temperature, has great electric polarization strength, shows excellent ferroelectric property, improves ferromagnetism, has strong magnetoelectric coupling property, stably has a fixed dielectric constant and lower dielectric loss, and can better meet the requirement of being applied to a 5G technical memory. Further, in the case of a polycrystalline thin film, the structure and performance are more stable.

The lanthanide and Y are used for replacing Bi or replacing part of Bi, so that the content of Bi vacancy and oxygen vacancy can be improved, the doped ions can also distort oxygen octahedron, and the ferroelectric property of the film is improved; the rare earth elements have certain magnetism at low temperature, and can improve the ferromagnetism of the film. Mg, Ti, Hf, Co, Mn, Ni and Zr can also optimize the ferromagnetism of the film, inhibit the generation of oxygen vacancies and improve the ferroelectricity of the film.

In a preferred embodiment, the multiferroic thin film has the following chemical formula: (1-x ₁-x ₂)BiTi_y(1-)/ ₂Fe_yMg_y(1-)/2O₃ x ₁LaFeO₃ x ₂La₂MgTiO₆Wherein, in the step (A),y=0~0.9，x ₁=0~1，x ₂=0~1，x ₁+ x ₂≤1。

the multiferroic film can further reduce the leakage characteristic and has stronger magnetoelectric coupling performance.

Furthermore, the thickness of the single layer of the multiferroic film is 10-100nm, and the grain size of the film is 10-100 nm.

By adopting the technical scheme, the method can be better suitable for some microelectronic devices within the thickness range of 10-100nm, so as to be beneficial to manufacturing electronic devices with thinner thickness. The crystal grains of the film are smaller and uniform, so that the film is thinner in a single layer, the quality of the film is more stable, and the multiferroic performance is better.

Further, the multiferroic thin film has a pseudo perovskite structure with a modified A site and a modified B site, wherein La is introduced into the A site of the perovskite structure, and Mg and Ti are introduced into the B site.

By adopting the technical scheme, the A site and the B site are jointly modified, so that the electric leakage characteristic of the film can be further reduced, and the film has stronger magnetoelectric coupling performance.

Further, the preparation method of the multiferroic film is a chemical solution deposition method, a sol-gel method or a metal organic thermal decomposition method.

Compared with other preparation methods, the sol-gel and chemical solution deposition methods can produce and prepare films in a large area at lower cost, and are easier for industrial production.

In order to achieve the second object, the present application provides the following technical solutions: the preparation method of the solid solution multiferroic film comprises the following steps:

step 1, preparing a precursor solution of a complex oxide solid solution by adopting a sol-gel method, wherein the concentration of the precursor solution is 0.1-0.5 mol/L;

step 2, adding a chelating agent in the step 1 and standing to obtain precursor sol;

step 3, spin-coating the precursor sol obtained in the step 2 on a substrate to obtain a uniform wet film;

step 4, drying and pyrolyzing the uniform wet film prepared in the step 3 in the air;

and 5, annealing the film obtained in the step 4 in an oxygen atmosphere to obtain a solid solution film.

Optionally, steps 3-4 may be repeated as many times as is practical depending on the thickness of the solid solution film to obtain solid solution films having different thicknesses.

The multiferroic solid solution film prepared by the preparation method has stable performance, higher yield, simple preparation method and easy industrial production.

Further, the concentration of the precursor solution in the step 1 is 0.2-0.4 mol/L; the concentration of the chelating agent in the step 2 is 0.2-0.4 mol/L.

Through adopting above-mentioned technical scheme, thickness and the quality of control film that can be better.

Further, the chelating agent is citric acid, and the solvent of the precursor solution is ethylene glycol monomethyl ether, glacial acetic acid and propionic anhydride, and the volume ratio of the chelating agent to the glacial acetic acid to the propionic anhydride is 15:3: 2.

The solvent components and the proportion can better control the precursor solution to form colloid, and the citric acid has good coagulation promoting effect.

Further, step 1, one or more nitrates and organic titanium are weighed according to a molar ratio, added into a mixed solution of ethylene glycol monomethyl ether, glacial acetic acid and propionic anhydride, and stirred at room temperature until dissolved to obtain a precursor solution; the bismuth nitrate is added in an amount of 10% excess from the theoretical value. In one embodiment, the nitrate is selected from bismuth nitrate, lanthanum nitrate, magnesium nitrate, iron nitrate. In another embodiment, the organotitanium is tetrabutyl titanate.

Further, step 2 comprises: and (3) adding a chelating agent into the precursor solution obtained in the step (1), stirring at room temperature for more than 12 hours, and standing for 24 hours to obtain precursor sol. In one embodiment, the chelating agent is citric acid.

Further, step 3 comprises: and (3) coating the precursor sol obtained in the step (2) on a substrate, and spin-coating the substrate at 3000-6000 r/min for 10-60 s to obtain a uniform wet film. In one embodiment, the substrate is selected from Pt (111)/Ti/SiO₂(ii)/Si, Pt (111)/Ti/substrate, SiO₂Si substrate, SrTiO₃Substrate, MgO substrate, LaAlO₃A substrate or a mica substrate.

Further, step 4 comprises: and (3) placing the uniform wet film in the step (3) in the air, heating the uniform wet film to 400 ℃ from 180 ℃ on a heating table, and preserving the heat for 5-30 min to obtain the solid solution precursor film.

Further, step 5 comprises: and (4) placing the precursor film obtained in the step (4) in an oxygen atmosphere with the oxygen flow of 1L/min, heating to 500-800 ℃ at the speed of 5-100 ℃/min, and preserving the heat for 15-120 min to obtain the solid solution film.

The bismuth ferrite solid solution film is prepared by adopting a sol-gel method and a chemical solution method, the preparation process is simple, the stoichiometric ratio of raw materials can be accurately controlled, the equipment is few, the cost is low, the industrial production can be realized, and the commercialization requirement is met. Moreover, the film prepared by the method has the advantages of high room-temperature electric polarization strength, low room-temperature leakage current density, no hole, compact and uniform structure and uniform thickness.

Bi³⁺Ions are easy to volatilize in high-temperature synthesis, and the addition amount of bismuth nitrate is excessive by 10 percent according to a theoretical value. By reasonably selecting appropriate metal salt, matching with a solvent and adding citric acid, a precursor sol with uniformly distributed components can be obtained, which is important for preparing an ultrathin multiferroic film, and the wet film is more uniform by controlling the spin coating speed and time; temperature setting of heating stage, ambient atmosphere and postThe heating speed and the heat preservation time of the surface are also very important for the formation of the film, and through the parameter setting, the film can be better ensured to have no holes, the impurities are less prone to occurring, and the quality of the film can be better ensured.

The selection of the substrate can control the crystal form of the film according to actual needs, so that the film can better adapt to the requirements of electronic devices.

In order to achieve the third object, the present application provides the following technical solutions: an electronic device comprising the solid solution multiferroic thin film described in the above aspect, wherein the electronic device is selected from the group consisting of a memory, an energy concentrator, a tunnel junction, a magnetoelectric sensor, a transmitter, and a receiver, comprising the solid solution multiferroic thin film described in the above aspect.

Because the multiferroic film has better magnetoelectric coupling performance, smaller leakage current and higher remanent polarization, an electronic device introduced with the multiferroic film correspondingly has more excellent performance. The multiferroic film is thinner, and can better meet the requirement of lightness and thinness of the electronic product.

In order to achieve the fourth object, the present application provides the following technical solutions: an electronic device applied to 5G storage technology comprises the solid solution multiferroic thin film.

The electronic device applied to the 5G storage technology has better multi-iron performance and keeps up with the requirements of data and bandwidth in the system.

In summary, at least one beneficial technical effect of the present application is:

1. the oxide solid solution multiferroic thin film prepared by the method has higher room-temperature electric polarization strength and lower room-temperature leakage current density, and the residual polarization is 3.92-8.55 mu C/cm²(ii) a The residual magnetization of the ternary film was 0.02emu/cm³The residual magnetization of the binary film was 0.06 emu/cm³The leakage current density reaches 10^-3A/cm²Stable dielectric constant, low dielectric loss, no holes, compact and uniform structure and uniform thickness.

2. The bismuth ferrite is doped to form a pseudo perovskite structure, so that a complex oxide solid solution is obtained, the complex oxide solid solution has low electric leakage characteristic, good electric hysteresis loop at room temperature and extremely high electric polarization strength, shows excellent ferroelectric property, improves ferromagnetism and has strong magnetoelectric coupling property. Because the film is a polycrystalline film, the structure and the performance are more stable.

3. The A site and the B site are modified together, so that the electric leakage characteristic of the film can be further reduced, and the film has stronger magnetoelectric coupling performance.

4. The single-layer thickness of the film is only 10-100nm, so that the film can be better suitable for some microelectronic devices and can be more suitable for the thinner requirement of electronic devices. The crystal grains of the film are smaller and uniform, so that the film is thinner in a single layer, the quality of the film is more stable, and the multiferroic performance is better.

5. The multiferroic solid solution film prepared by the preparation method has stable performance, higher yield, simple preparation method, precisely controllable stoichiometric ratio of raw materials, less equipment and low cost, can realize industrial production, and meets the requirements of commercial application. By reasonably selecting appropriate metal salt, matching with a solvent and adding citric acid, a precursor sol with uniformly distributed components can be obtained, which is important for preparing an ultrathin multiferroic film, and the wet film is more uniform by controlling the spin coating speed and time; the temperature setting of the heating table, the ambient atmosphere, the subsequent heating speed and the subsequent heat preservation time are also of great importance for the formation of the film, and through the parameter setting, the film can be better ensured to have no holes, the impurities are less prone to occurring, and the quality of the film can be better ensured.

Drawings

FIG. 1(a) shows 0.72BiTi_0.27Fe_0.46Mg_0.27-0.28LaFeO₃Scanning electron micrographs of solid solution film sections;

FIG. 1(b) is 0.72BiTi_0.27Fe_0.46Mg_0.27-0.28LaFeO₃Scanning electron micrographs of the surface of the solid solution film;

FIG. 2 shows bismuth ferrite (BiFeO)₃) XRD patterns of the film and 0.5BFMO-0.5LFO and 0.625BTFM-0.25LFO-0.125LMT solid solution film; wherein, the labels in the figure are BFO and 0.5BFMO-0.5LFO and 0.625BTFM-0.25LFO-0.125LMT respectively represent BiFeO₃Film, 0.5BiTi_0.27Fe_0.46Mg_0.27O₃-0.5LaFeO₃Film and 0.625BiTi_0.27Fe_0.46Mg_0.27O₃-0.25LaFeO₃-0.125La₂MgTiO₆A film; wherein "# represents a peak of the basal slice;

FIG. 3 is 0.72BiMg_0.27Fe_0.46Ti_0.27-0.28LaFeO₃Solid solution film on SrTiO₃XRD patterns annealed at different conditions on the substrate; wherein the reference numbers STO, 700 ℃ for 2 h, 700 ℃ for 15 min, 750 ℃ for 15 min and 800 ℃ for 15 min represent untreated SrTiO respectively₃A substrate is annealed for 2 hours at 700 ℃ in a tube furnace, for 15 minutes at 700 ℃ in an infrared annealing furnace, for 15 minutes at 750 ℃ in the infrared annealing furnace and for 15 minutes at 800 ℃ in the infrared annealing furnace;

FIG. 4 is 0.72BiMg_0.27Fe_0.46Ti_0.27-0.28LaFeO₃Solid solution film on SrTiO₃AFM topography maps annealed at different conditions on a substrate; the annealing temperatures in FIGS. 4(a), (b), and (c) are 600 deg.C, 700 deg.C, and 800 deg.C, respectively; FIG. 4(d) is a graph of film surface roughness versus annealing temperature;

FIG. 5 is 0.72BiMg_0.27Fe_0.46Ti_0.27-0.28LaFeO₃Film of solid solution and 0.625BiTi_0.27Fe_0.46Mg_0.27O₃-0.25LaFeO₃-0.125La₂MgTiO₆Raman scattering patterns of solid solution films; wherein diffraction peaks of the E (TO2), a1(TO3), E (TO3), E (TO5), E (TO7), E (TO9) modes and STO single crystal of bismuth ferrite are shown, respectively;

FIG. 6 is 0.72BiMg_0.27Fe_0.46Ti_0.27-0.28LaFeO₃Film of solid solution and 0.625BiTi_0.27Fe_0.46Mg_0.27O₃- 0.25LaFeO₃-0.125La₂MgTiO₆A hysteresis loop of the solid solution film; wherein the BTFM-LFO curve in the graph represents 0.72BiMg_0.27Fe_0.46Ti_0.27-0.28LaFeO₃Hysteresis loop of solid solution film, BTFM-LFO-LMT curve represents 0.625BiTi_0.27Fe_0.46Mg_0.27O₃- 0.25LaFeO₃-0.125La₂MgTiO₆A hysteresis loop of the solid solution film;

FIG. 7(a) and FIG. 7(b) each show 0.72BiMg_0.27Fe_0.46Ti_0.27-0.28LaFeO₃Film of solid solution and 0.625BiTi_0.27Fe_0.46Mg_0.27O₃-0.25LaFeO₃-0.125La₂MgTiO₆The electric hysteresis loop of the solid solution film;

FIG. 8(a) and FIG. 8(b) each represent 0.72BiMg_0.27Fe_0.46Ti_0.27-0.28LaFeO₃The turning curve and the butterfly curve of the solid solution film are measured under PFM;

FIG. 9 is 0.72BiMg_0.27Fe_0.46Ti_0.27-0.28LaFeO₃Film and 0.625BiTi_0.27Fe_0.46Mg_0.27O₃-0.25LaFeO₃-0.125La₂MgTiO₆A leakage current curve of the film under the voltage of 0-20V; wherein the BTFM-LFO curve in the graph represents 0.72BiMg_0.27Fe_0.46Ti_0.27-0.28LaFeO₃Film, BTFM-LFO-LMT curve representing 0.625BiTi_0.27Fe_0.46Mg_0.27O₃-0.25LaFeO₃-0.125La₂MgTiO₆A film;

FIG. 10 is 0.72BiMg_0.27Fe_0.46Ti_0.27-0.28LaFeO₃Film and 0.625BiTi_0.27Fe_0.46Mg_0.27O₃-0.25LaFeO₃-0.125La₂MgTiO₆The dielectric constant of the film varies with frequency; wherein the BTFM-LFO curve in the graph represents 0.72BiMg_0.27Fe_0.46Ti_0.27-0.28LaFeO₃Film, BTFM-LFO-LMT curve representing 0.625BiTi_0.27Fe_0.46Mg_0.27O₃-0.25LaFeO₃-0.125La₂MgTiO₆A film;

FIG. 11 is 0.72BiMg_0.27Fe_0.46Ti_0.27-0.28LaFeO₃And 0.625BiTi_0.27Fe_0.46Mg_0.27O₃-0.25LaFeO₃-0.125La₂MgTiO₆Dielectric loss versus frequency curve for thin films. Wherein the BTFM-LFO curve in the graph represents 0.72BiMg_0.27Fe_0.46Ti_0.27-0.28LaFeO₃Film, BTFM-LFO-LMT curve representing 0.625BiTi_0.27Fe_0.46Mg_0.27O₃-0.25LaFeO₃-0.125La₂MgTiO₆A film.

Detailed Description

Definition of terms

Solid solution refers to an alloy phase in which solute atoms dissolve into the solvent lattice while still maintaining the solvent type. Substitutional solid solutions and interstitial solid solutions can be classified according to the position of solute atoms in the crystal lattice.

Substitutional solid solution: solid solutions formed by solute atoms occupying nodal positions in the solvent lattice are called substitutional solid solutions.

Interstitial solid solution: solid solutions formed by the distribution of solute atoms in the interstitial spaces of a solvent lattice are called interstitial solid solutions.

In order to better understand the present invention, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the tables in the embodiments of the present application. It is to be understood that the described embodiments are merely a few embodiments of the present application and not all embodiments. Based on the embodiments in the present application, other embodiments obtained by persons of ordinary skill in the art with the understanding of the inventive concepts in the present application are within the scope of the present application.

The chemical formula of the oxide solid solution multiferroic film prepared by the method is(1-x ₁-x ₂)LM_y(1-)/2Fe_yN_y(1-)/ ₂O₃ x ₁Rx ₂Q, doping bismuth ferrite to form a pseudo perovskite structure, replacing Bi or replacing part of Bi with lanthanide and Y, improving the content of Bi vacancies and oxygen vacancies, and twisting oxygen octahedrons by doped ions to improve the ferroelectric property of the film; mg, Ti, Hf, Co, Mn, Ni and Zr can also optimize the ferromagnetism of the film, inhibit the generation of oxygen vacancies and improve the ferroelectricity of the film.

The multiferroic film is a complex oxide solid solution of rhombohedral phase and orthorhombic phase, has more stable structure and performance, higher room-temperature electric polarization strength and lower room-temperature leakage current density under the condition of polycrystalline film, and the residual polarization is 3.92-8.55 mu C/cm²(ii) a The residual magnetization of the ternary film was 0.02emu/cm³The residual magnetization of the binary film was 0.06 emu/cm³The leakage current density reaches 10^-3A/cm²Stable dielectric constant, low dielectric loss, no holes, compact and uniform structure and uniform thickness.

The A site and the B site are modified together, so that the electric leakage characteristic of the film can be further reduced, and the film has stronger magnetoelectric coupling performance. The single-layer thickness of the film is only 10-100nm, so that the film can be better suitable for some microelectronic devices and can be more suitable for the thinner requirement of electronic devices. The crystal grains of the film are smaller and uniform, so that the film is thinner in a single layer, the quality of the film is more stable, and the multiferroic performance is better.

The preparation method is simple, the stoichiometric ratio of the raw materials can be accurately controlled, the equipment is less, the cost is low, the industrial production can be realized, and the commercial application is met. By reasonably selecting appropriate metal salt, matching with a solvent and adding citric acid, a precursor sol with uniformly distributed components can be obtained, which is important for preparing an ultrathin multiferroic film, and the wet film is more uniform by controlling the spin coating speed and time; the temperature setting of the heating table, the ambient atmosphere, the subsequent heating speed and the subsequent heat preservation time are also of great importance for the formation of the film, and through the parameter setting, the film can be better ensured to have no holes, the impurities are less prone to occurring, and the quality of the film can be better ensured.

In order to facilitate understanding of the technical solutions of the present application, the multiferroic thin film, the preparation method and the electronic device comprising the multiferroic thin film of the present application are described in further detail below, but are not intended to limit the scope of the present application.

Example 1

Preparation of 0.5BiFe by chemical solution deposition_0.63Mg_0.370.5LaFeO₃A method of solid solution thin film comprising the steps of:

s1, preparing a precursor solution: weighing bismuth nitrate pentahydrate, lanthanum nitrate hexahydrate, magnesium nitrate hexahydrate and ferric nitrate nonahydrate according to a molar ratio of 1:1:0.37:1.63, adding into a mixed solution of ethylene glycol monomethyl ether, glacial acetic acid and propionic anhydride with a volume ratio of 15:3:2, and stirring at room temperature until the mixed solution is dissolved to obtain a precursor solution without titanium, wherein the concentration of the precursor solution is 0.2 mol/L.

S2, preparing precursor sol: adding citric acid into the precursor solution obtained in the step S1, wherein the concentration of the citric acid in the solution is 0.2 mol/L, stirring at room temperature for more than 12 hours, and standing for 24 hours to obtain precursor sol;

s3, preparing a precursor film: the precursor sol obtained in S2 was coated on Pt (111)/Ti/SiO₂On a/Si substrate, spin-coating the substrate at a low speed of 700r/min for 6s and at a high speed of 5000r/min for 15s to obtain a uniform wet film;

s4, placing the uniform wet film in the step S3 in the air, heating the film on a heating table from 180 ℃ to 380 ℃, preserving the heat for 30min, and then cooling the film along with the furnace to obtain a solid solution precursor film;

s5, preparing a solid solution film: placing the precursor film obtained in the step S4 in a heating furnace in an oxygen atmosphere, heating to 600 ℃ at the speed of 100 ℃/min, and preserving heat for 15 minutes to obtain BiFe_0.63Mg_0.370.5LaFeO₃Solid solution film, 0.5BFMO-LFO for short.

Example 2

Preparation of 0.5BiFe by chemical solution deposition method_0.63Ti_0.37-0.5LaFeO₃A method of solid solution thin film comprising the steps of:

s1, preparing a precursor solution: weighing bismuth nitrate pentahydrate, lanthanum nitrate hexahydrate, ferric nitrate nonahydrate and tetrabutyl titanate according to a molar ratio of 1:1:1.63:0.37, adding into a mixed solution of ethylene glycol monomethyl ether, glacial acetic acid and propionic anhydride in a volume ratio of 15:3:2, and stirring at room temperature until the mixed solution is dissolved to obtain a magnesium-free precursor solution, wherein the concentration of the precursor solution is 0.3 mol/L.

S2, preparing precursor sol: adding citric acid into the precursor solution obtained in the step S1, wherein the concentration of the citric acid in the solution is 0.3 mol/L, stirring at room temperature for more than 12 hours, and standing for 24 hours to obtain precursor sol;

s5, preparing a solid solution film: and (3) placing the precursor film obtained in the step (S4) in a heating furnace in an oxygen atmosphere, heating to 600 ℃ at the speed of 100 ℃/min, and preserving the temperature for 15 minutes to obtain the solid solution film.

Example 3

Preparation of 0.5BiTi by chemical solution deposition method_0.27Fe_0.46Mg_0.27-0.5LaFeO₃A method of solid solution thin film comprising the steps of:

s1, preparing a precursor solution: weighing bismuth nitrate pentahydrate, lanthanum nitrate hexahydrate, ferric nitrate nonahydrate, tetrabutyl titanate and magnesium nitrate hexahydrate according to a molar ratio of 1:1:1.46:0.27:0.27, adding the weighed materials into a mixed solution of ethylene glycol monomethyl ether, glacial acetic acid and propionic anhydride with a volume ratio of 15:3:2, and stirring the mixed solution at room temperature until the mixed solution is dissolved to obtain a precursor solution without magnesium, wherein the concentration of the precursor solution is 0.4 mol/L.

S2, preparing precursor sol: adding citric acid into the precursor solution obtained in the step S1, wherein the concentration of the citric acid in the solution is 0.4mol/L, stirring at room temperature for more than 12 hours, and standing for 24 hours to obtain precursor sol;

s3, preparing a precursor film: coating the precursor sol obtained in S2 on SrTiO₃On the substrate, spin-coating the substrate at a low speed of 700r/min for 6s and at a high speed of 5000r/min for 15s to obtain a uniform wet film;

s5, preparing a solid solution film: and (3) placing the precursor film obtained in the step (S4) in a heating furnace in an oxygen atmosphere, heating to 800 ℃ at the speed of 100 ℃/min, and preserving the temperature for 15 minutes to obtain the solid solution film.

Example 4

Method for preparing 0.72BiMg by chemical solution deposition method_0.27Fe_0.46Ti_0.27-0.28LaFeO₃A method of solid solution thin film comprising the steps of:

s1, preparing a precursor solution: weighing bismuth nitrate pentahydrate, lanthanum nitrate hexahydrate, ferric nitrate nonahydrate, tetrabutyl titanate and magnesium nitrate hexahydrate according to the molar ratio of 0.72:0.28:0.6112:0.1944:0.1944, adding the weighed materials into a mixed solution of ethylene glycol monomethyl ether, glacial acetic acid and propionic anhydride in the volume ratio of 15:3:2, and stirring the mixed solution at room temperature until the mixed solution is dissolved to obtain a precursor solution without magnesium, wherein the concentration of the precursor solution is 0.3 mol/L.

s3, preparing a precursor film: coating the precursor sol obtained in S2 on SrTiO₃On the substrate, spin-coating the substrate at a low speed of 700r/min for 6s and at a high speed of 6000 r/min for 15s to obtain a uniform wet film;

s5, preparing a solid solution film: and (3) placing the precursor film obtained in the step (S4) in a heating furnace in an oxygen atmosphere, heating to 800 ℃ at the speed of 5 ℃/min, and preserving heat for 2 hours to obtain the solid solution film.

Example 5

Method for preparing 0.625BiTi by chemical solution deposition method_0.27Fe_0.46Mg_0.27O₃0.25LaFeO₃-0.125La₂MgTiO₆A method of forming a thin film of a solid solution comprisingThe following steps:

s1, preparing a precursor solution: weighing bismuth nitrate pentahydrate, lanthanum nitrate hexahydrate, ferric nitrate nonahydrate, tetrabutyl titanate and magnesium nitrate hexahydrate according to the molar ratio of 0.625:0.5:0.5375:0.29375:0.29375, adding the weighed materials into a mixed solution of ethylene glycol monomethyl ether, glacial acetic acid and propionic anhydride in the volume ratio of 15:3:2, and stirring the mixed solution at room temperature until the mixed solution is dissolved to obtain a precursor solution without magnesium, wherein the concentration of the precursor solution is 0.3 mol/L.

s5, preparing a solid solution film: and (3) placing the precursor film obtained in the step (S4) in a heating furnace in an oxygen atmosphere, heating to 700 ℃ at the speed of 100 ℃/min, and preserving the temperature for 15 minutes to obtain the solid solution film.

Example 6

Method for preparing 0.625BiTi by chemical solution deposition method_0.27Fe_0.46Mg_0.27O₃0.25LaFeO₃-0.125La₂MgTiO₆A method of solid solution thin film comprising the steps of:

s5, preparing a solid solution film: and (3) placing the precursor film obtained in the step (S4) in a heating furnace in an oxygen atmosphere, heating to 700 ℃ at the speed of 5 ℃/min, and preserving heat for 2 hours to obtain the solid solution film.

Performance testing

In order to visually see the thickness and the surface condition of the film, 0.72BiTi is made_0.27Fe_0.46Mg_0.270.28LaFeO₃Scanning electron micrographs of the cross section and surface of the solid solution film. As can be seen from FIG. 1(a), the film had a thickness of substantially 30nm and was uniform. As can be seen from FIG. 1(b), the film sample was very dense with no visible voids and a grain size in the range of 10 to 100 nm.

From FIG. 2, it is clear that the film of 0.5BFMO-0.5LFO and 0.625BTFM-0.25LFO-0.125LMT solid solution is a polycrystalline film, and the crystal structure is substantially consistent with that of rhombohedral phase BFO, and the space group is R3c, and from the XRD pattern, it is clear that the film sample is very pure and free of peaks.

As is clear from FIG. 3, the film obtained at the annealing temperature of 700-800 ℃ is a polycrystalline film, and has a distinct peak at about 32 ℃ in the (110) direction, and the crystallinity of the film gradually increases with the increase of the annealing temperature.

As can be seen more intuitively from FIGS. 4(a), (b), and (c), 0.72BiMg_0.27Fe_0.46Ti_0.27-0.28LaFeO₃The solid solution film has compact structure, uniform grain size and approximately circular grains. FIG. 4(d) usesAFM counted the roughness of the film surface at different temperatures, and it is clear from FIG. 4(d) that the surface roughness increased from within 1nm to over 30nm as the annealing temperature increased. Other films with different ratios have similar rules. The surface roughness of the film can be flexibly controlled according to the requirements of different electronic devices, and the requirements of being applied to a 5G storage device can be better met.

As shown in fig. 5, the film has La substitution at Bi sites, random substitution of Ti and Mg at Fe sites, and disorder introduced at atomic sites, resulting in low peak intensity and spectrum diffusion, so that only a few main raman modes can be clearly distinguished.

For better testing, the number of layers of the film was set to 6, and the thickness of the film was estimated to be 180 nm from the thickness of each layer of 30 nm; the area of the film is 1 cm². As shown in FIG. 6, the film exhibited weak ferromagnetism, and a ternary film, i.e., 0.625BiTi, was estimated_0.27Fe_0.46Mg_0.27O₃- 0.25LaFeO₃-0.125La₂MgTiO₆The residual magnetization of the solid solution film was 0.29emu/cm³Binary films, i.e. 0.72BiMg_0.27Fe_0.46Ti_0.27-0.28LaFeO₃The residual magnetization of the solid solution film was 0.62 emu/cm³。

As shown in FIGS. 7(a) and 7(b), 0.72BiMg_0.27Fe_0.46Ti_0.27-0.28LaFeO₃The saturation polarization of the film was 11.9. mu.C/cm²The residual polarization is 8.55 mu C/cm²；0.625BiTi_0.27Fe_0.46Mg_0.27O₃-0.25LaFeO₃-0.125La₂MgTiO₆The saturation polarization of the film is 9.71 mu C/cm²The residual polarization is 3.92 mu C/cm². The remanent polarization of the multiferroic film is greatly improved, and the requirements of electronic devices can be better met.

As shown in FIGS. 8(a) and 8(b), 0.72BiMg_0.27Fe_0.46Ti_0.27-0.28LaFeO₃Piezoelectric response and phase variation curve with voltage measured by solid solution film under PFM, i.e. turning curve and butterfly curveA wire. The highest applied bias voltage is 15V, and the film can be clearly seen to realize 180-degree polarization reversal under the condition of applying direct-current bias voltage; meanwhile, the film has a butterfly curve typical of piezoelectric materials, and the piezoelectric property of the film is proved.

As shown in FIG. 9, when the voltage is 20V, the leakage current density reaches 10^-3A/cm². The leakage current is lower, the lower room temperature leakage current and the higher room temperature residual polarization intensity are realized, and the practical production popularization and application are facilitated.

As shown in FIG. 10, 0.72BiMg is observed in the frequency range of 100 to 1MHz as a whole_0.27Fe_0.46Ti_0.27-0.28LaFeO₃The relative dielectric constant of the film (2) is kept within the range of 100-130; 0.625BiTi_0.27Fe_0.46Mg_0.27O₃-0.25LaFeO₃-0.125La₂MgTiO₆The relative dielectric constant of the film is kept within the range of 110 to 140. The dielectric constants of the two films have little difference and have good frequency stability, a series of excellent and stable multiferroic properties of the product are further proved, and meanwhile, the preparation process can better ensure the stability of various products and can better meet the requirements of electronic devices applied to the 5G storage technology.

As shown in FIG. 11, 0.72BiMg at 100-1 MHz_0.27Fe_0.46Ti_0.27-0.28LaFeO₃The dielectric loss of the film of (2) is substantially 0.1 or less, and 0.625BiTi_0.27Fe_0.46Mg_0.27O₃-0.25LaFeO₃-0.125La₂MgTiO₆The dielectric loss of the film is in the range of 0.02-0.05, has lower dielectric loss, and is more stable than the former.

In conclusion, the oxide solid solution film prepared by the method is of a polycrystalline structure, is doped at the A site and the B site together, has higher room-temperature electric polarization strength, lower room-temperature leakage current density, stable dielectric constant and lower dielectric loss, is free of holes, compact and uniform in structure and uniform in thickness, and can be widely applied to various electronic devices; particularly, the method has great potential in the application of 5G memory devices, and can better meet the requirements of the 5G memory devices; the preparation method has the advantages of simple preparation process, accurate control of the stoichiometric ratio of the raw materials, less equipment and low cost, can realize industrial production, and meets the requirements of commercial application.

The present embodiment is only for explaining the present application, and it is not limited to the present application, and those skilled in the art can make modifications of the present embodiment without inventive contribution as needed after reading the present specification, but all of them are protected by patent law within the scope of the claims of the present application.

Claims

1. A solid solution multiferroic thin film is characterized in that the film is a complex oxide solid solution with a pseudo perovskite structure and has the following chemical formula:(1-x ₁-x ₂)LM_y(1-)/2Fe_yN_y(1-)/2O₃ x ₁Rx ₂Q；

wherein the content of the first and second substances,y=0~1，x ₁=0~1，x ₂=0~1，x ₁+ x ₂≤1；

l is selected from one or more of Bi, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu or Y; m, N are respectively selected from Mg, Ti, Hf, Co, Mn, Ni or Zr, which may be the same or different; and R is LFeO₃(ii) a And Q is an oxide of L, M, N;

the multiferroic thin film is a solid solution of rhombohedral phases and orthorhombic phases and is a polycrystalline thin film.

2. The solid solution multiferroic film of claim 1, wherein said multiferroic film has the following chemical formula: (1-x ₁-x ₂)BiTi_y(1-)/2Fe_yMg_y(1-)/2O₃- x ₁LaFeO₃ x ₂La₂MgTiO₆Wherein, in the step (A),y=0~0.9，x ₁=0~1，x ₂=0~1，x ₁+ x ₂≤1。

3. the solid solution multiferroic film of claim 2, wherein the multiferroic film has a monolayer thickness of 10-100nm and a film grain size of 10-100 nm.

4. The solid solution multiferroic thin film according to any one of claims 1 to3, wherein the multiferroic thin film has a pseudo-perovskite structure with both A-site and B-site modified, wherein La is introduced at the A-site of the perovskite structure, and Mg and Ti are introduced at the B-site;

preferably, the preparation method of the solid solution multiferroic film is a chemical solution deposition method, a sol-gel method or a metal organic thermal decomposition method.

5. The method for preparing a solid solution multiferroic thin film according to any one of claims 1 to 4, comprising the steps of:

step 1, preparing a complex oxide solid solution precursor solution by adopting a sol-gel method, wherein the concentration of the precursor solution is 0.1-0.5 mol/L;

step 2, adding a chelating agent into the precursor solution obtained in the step 1 and standing to obtain precursor sol;

step 5, annealing the film obtained in the step 4 in an oxygen atmosphere; obtaining a solid solution film;

6. The method for preparing the solid solution multiferroic thin film according to claim 5, wherein the concentration of the precursor solution in step 1 is 0.2-0.4 mol/L; the concentration of the chelating agent in the solution in the step 2 is 0.2-0.4 mol/L.

7. The method for preparing the solid solution multiferroic film according to claim 6, wherein the chelating agent is citric acid, and the solvent of the precursor solution is ethylene glycol monomethyl ether, glacial acetic acid and propionic anhydride, and the volume ratio of the solvents is 15:3: 2.

8. The method for preparing a solid solution multiferroic thin film according to any one of claims 5 to7, comprising the steps of: step 1, weighing one or more nitrates and organic titanium according to a molar ratio, adding the weighed nitrates and organic titanium into a mixed solution of ethylene glycol monomethyl ether, glacial acetic acid and propionic anhydride, and stirring the mixed solution at room temperature until the mixed solution is dissolved to obtain a precursor solution; the addition amount of bismuth nitrate is 10% excess according to a theoretical value;

preferably, the nitrate is selected from bismuth nitrate, lanthanum nitrate, magnesium nitrate, ferric nitrate; the organic titanium is tetrabutyl titanate;

preferably, step 2 comprises: adding a chelating agent into the precursor solution obtained in the step (1), stirring at room temperature for more than 12 hours, and standing for 24 hours to obtain precursor sol; preferably, the chelating agent is citric acid;

preferably, step 3 comprises: coating the precursor sol obtained in the step (2) on a substrate, and spin-coating the substrate at 3000-6000 r/min for 10-60 s to obtain a uniform wet film; preferably, the substrate is selected from Pt (111)/Ti/SiO₂(ii)/Si, Pt (111)/Ti/substrate, SiO₂Si substrate, SrTiO₃Substrate, MgO substrate, LaAlO₃A substrate or a mica substrate;

further, step 4 comprises: placing the uniform wet film in the step 3 in the air, heating the uniform wet film on a heating table from 180 ℃ to 300-400 ℃, and preserving the heat for 5-30 min to obtain a solid solution precursor film;

9. An electronic device, wherein the electronic device is a memory device, an energy harvester, a tunnel junction, a magnetoelectric sensor, a transmitter, a receiver, comprising the solid solution multiferroic thin film of any one of claims 1-5.

10. An electronic device for use in 5G memory technology, comprising the solid solution multiferroic thin film of any of claims 1-4.