WO2022032584A1 - Solid solution multiferroic thin film and preparation method, and electronic device applied to 5g storage technology - Google Patents

Abstract

The present application relates to a solid solution multiferroic thin film and a preparation method, and an electronic device comprising the multiferroic thin film and applied to a 5G storage technology. The thin film is a complex oxide solid solution having a pseudo perovskite structure, and the chemical formula of the thin film is: (1-x1-x2)LM(1-y)/2FeyN(1- y)/2O3x1Rx2Q, wherein y is equal to 0-1, x1 is equal to 0-1, x2 is equal to 0-1, and x1+x2≤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 and N are respectively selected from Mg, Ti, Hf, Co, Mn, Ni or Zr, and can be the same or different; R is LFeO3; Q is an oxide of L, M, and N; and the thin film is a rhombohedral phase and orthorhombic phase solid solution and is polycrystal. The thin film has higher room-temperature electric polarization intensity and lower room-temperature leakage current density.

Description

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

The present application relates to the field of multiferroic thin film materials, and more particularly, to a solid solution multiferroic thin film, a preparation method, an electronic device comprising the multiferroic thin film, and an electronic device comprising the multiferroic thin film and applied to 5G storage technology.

Background technique

At present, 5G communication technology has become increasingly mature. 5G technology can not only improve people's mobile experience, but also change the way many industries outside the communication realm operate. 5G processes data 10 to 100 times faster than 4G, making data generation 10 to 100 times faster. At the same time, with the exponential growth of data volume, the demand for server storage capacity has also increased significantly, and the storage used for backup has also doubled accordingly. Therefore, the emergence of 5G has spawned massive storage requirements. In the 5G environment, although the current memory can operate normally, it cannot keep up with the demand for data and bandwidth in the system. Therefore, it is necessary to develop and apply a new generation of memory as soon as possible.

New multiferroic materials promise better information storage. A multiferroic material refers to a material with two or more ferrous properties (including ferroelectricity, ferromagnetism or ferroelasticity) at the same time. A variety of ferrous inter-coupling multiferroic materials have broad application prospects in electrical, optical, magnetic field sensors, random access memory, photovoltaic, photoelectric rectification and so on. Among them, multiferroic materials with magnetoelectric coupling effect can induce magnetic moments by external electric fields or be polarized by magnetic fields, so they are the technical core of many electronic devices and sensors, such as magnetic field sensors, magnetoelectric MRAM (ME-MRAM) and Microwave devices, especially the technical core of 5G information storage devices.

Current multiferroic materials include composite multiferroic materials and unidirectional multiferroic materials. Among them, composite materials have the advantage of large magnetoelectric coupling coefficient, but are not easy to integrate due to interface problems.

Ferroelectricity and ferromagnetism (or antiferromagnetism) have different electronic structures and therefore do not usually coexist in single-phase materials. The conventional mechanism of ferroelectricity involves closed ^- shell do or s cations, whereas the ferromagnetic order requires an open ^- shell ^dn configuration with unpaired electrons. This fundamental distinction makes it difficult to combine the long-range order of the two dipoles to simultaneously break the space-inversion and time-reversal symmetry at room temperature.

These two ordered design routes can be produced in single-phase materials such as ABO _{3 perovskite} bismuth ferrite (BiFeO ₃ , BFO for short), which is the only perovskite bismuth ferrite that simultaneously possesses iron at room temperature. Electrical and antiferromagnetic single-phase multiferroic materials with the largest remanent polarization, high ferroelectric Curie temperature T _C =1100K, and relatively high antiferromagnetic Nell temperature T _N =643K , and smaller forbidden band width, so it has received extensive attention at home and abroad. Although bismuth ferrite has a high remanent polarization in theory, due to the easy volatilization of bismuth and the transformation of part of Fe ³⁺ to Fe ²⁺ during the preparation process, more oxygen vacancies are generated, which makes its leakage current larger. , it is difficult to polarize, so it is difficult to prepare samples with high remanent polarization. _In addition, BiFeO3 suppresses weak ferromagnetism and linear magnetoelectric coupling due to trochoidal magnetic ordering, so its commercial application is greatly limited.

SUMMARY OF THE INVENTION

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

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

The third object of the present application is to provide an electronic device, which has the advantages of better performance and lighter weight.

The fourth objective of the present application is to provide an electronic device applied to the 5G storage technology, the electronic device applied to the 5G storage technology has the advantages of better performance and lighter weight.

In order to achieve the above-mentioned first purpose, the application provides the following technical solutions: a solid solution multiferroic thin film, which is a complex oxide solid solution of pseudoperovskite structure, and has the following chemical formula: (1-x ₁ -x ₂ )LM _{( 1-y)/2} Fe _y N _(1-y)/2 O ₃ x ₁ Rx ₂ Q;

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 selected from From Mg, Ti, Hf, Co, Mn, Ni or Zr, which may be the same or different; and R is _LFeO3 ; 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 above technical scheme, bismuth ferrite is doped to form a pseudo-perovskite structure, and a complex oxide solid solution is obtained, which has low leakage characteristics, good hysteresis loop at room temperature, and great electric polarization Strength, showing excellent ferroelectric properties, while improving its ferromagnetism, with strong magnetoelectric coupling performance, and stable dielectric constant and low dielectric loss, which can better meet the requirements of 5G technology memory. Require. Further, in the case of polycrystalline thin films, the structure and properties are more stable.

Replacing Bi or part of Bi with lanthanides and Y can improve the content of Bi vacancies and oxygen vacancies, and the doped ions will also distort the oxygen octahedron and improve the ferroelectric properties of the film; rare earth elements have certain magnetic properties at low temperature, The ferromagnetism of the film can be improved. Mg, Ti, Hf, Co, Mn, Ni, and Zr can also optimize the ferromagnetism of the films and suppress the generation of oxygen vacancies to improve the ferroelectricity of the films.

In a preferred solution, the multiferroic thin film has the following chemical formula: (1-x ₁ -x ₂ )BiTi _(1-y)/2 Fe _y Mg _{(1- y)/2} O ₃ x ₁ LaFeO ₃ x ₂ La ₂ MgTiO ₆ , wherein y=0 to 0.9, x ₁ =0 to 1, x ₂ =0 to 1, and x ₁ +x ₂ ≤1.

The multiferroic thin film can further reduce leakage characteristics and have stronger magnetoelectric coupling performance.

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

By adopting the above technical solution, within the thickness range of 10-100 nm, it can be better applied to some microelectronic devices, so as to facilitate the manufacture of thinner electronic devices. The crystal grains of the film are smaller and uniform, on the one hand, it is convenient to make the film monolayer thinner, and the film quality is more stable and the multiferroic performance is better.

Further, the multiferroic film has a pseudo-perovskite structure co-modified by A-site and 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 above technical scheme, the A site and the B site are jointly modified, so that the leakage characteristic of the film can be further reduced, so that the film has stronger magnetoelectric coupling performance.

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

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

In order to achieve the above-mentioned second purpose, the application provides the following technical solutions: the preparation method of the above-mentioned solid solution multiferroic thin film, comprising the following steps:

Step 1, using a sol-gel method to prepare a precursor solution of a complex oxide solid solution, wherein the concentration of the precursor solution is 0.1-0.5 mol/L;

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

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

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

Step 5. The film obtained in step 4 is annealed in an oxygen atmosphere to obtain a solid solution thin film.

Optionally, steps 3-4 may be repeated multiple times according to the actual needs of the thickness of the solid solution film to obtain solid solution films with different thicknesses.

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

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

By adopting the above technical solutions, the thickness and quality of the film can be better controlled.

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

The above-mentioned solvent components and proportions can better control the precursor solution to form a colloid, and citric acid plays a good role in accelerating coagulation.

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

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

Further, step 3 includes: coating the precursor sol obtained in step 2 on the substrate, and the substrate is spin-coated at 3000-6000 r/min for 10-60 s to obtain a uniform wet film. In one embodiment, the substrate is selected from the group consisting of Pt(111)/Ti/ _SiO2 /Si, Pt(111)/Ti/substrate, _SiO2 /Si substrate, _SrTiO3 substrate, MgO substrate, LaAlO ₃ substrate or mica substrate.

Further, step 4 includes: placing the uniform wet film in step 3 in the air, heating the temperature from 180° C. to 300-400° C. on a heating table, and maintaining the temperature for 5-30 minutes to obtain a solid solution precursor film.

Further, step 5 includes: placing the precursor film obtained in step 4 in an oxygen atmosphere with an oxygen flow rate of 1 L/min, heating it to 500-800° C. at a speed of 5-100° C./min, and maintaining the temperature for 15-120 min to obtain solid solution films.

The present application adopts the sol-gel and chemical solution method to prepare the bismuth ferrite solid solution thin film. Moreover, the thin film prepared by the present application has a relatively large room temperature electric polarization strength, a relatively low room temperature leakage current density, no holes, a dense and uniform structure, and a uniform thickness.

Bi ³⁺ ions are volatile in high temperature synthesis, and the addition amount of bismuth nitrate exceeds 10% according to the theoretical value. By rationally selecting suitable metal salts, coordinating solvents, and adding citric acid, a precursor sol with uniform distribution of each component can be obtained, which is very important for the preparation of ultra-thin multiferroic films. By controlling the spin coating speed and The time wet film is more uniform; the temperature setting of the heating table, the ambient atmosphere, the subsequent heating rate, and the holding time are also crucial to the formation of the film. The above parameter settings can better ensure that the film has no holes and is less likely to appear. The impurity phase can better ensure the quality of the film.

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

In order to achieve the above third purpose, the present application provides the following technical solutions: an electronic device comprising the solid solution multiferroic thin film described in the above solution, wherein the electronic device is selected from a memory, an energy collector, a tunnel junction, a magnetoelectric Sensors, transmitters, and receivers, including the solid solution multiferroic thin film described in the above scheme.

Since the aforementioned multiferroic thin films have better magnetoelectric coupling properties, smaller leakage current and higher remanent polarization, the electronic devices incorporating the aforementioned multiferroic thin films have correspondingly better performances. The multiferroic film is thinner and can better meet the requirements of thin and light electronics.

In order to achieve the above fourth purpose, the present application provides the following technical solution: an electronic device applied to 5G storage technology, comprising the solid solution multiferroic thin film described in the above solution.

The above-mentioned electronic devices applied to 5G storage technology have better multi-ferrous performance to keep up with the data and bandwidth demands in the system.

To sum up, at least one beneficial technical effect of the present application is:

1. The oxide solid solution multiferroic thin film prepared in this application has a larger room temperature electric polarization strength, a lower room temperature leakage current density, and a remanent polarization of 3.92-8.55 μC/cm ² ; the remanent magnetization of the ternary film is 0.02emu /cm ³ , the residual magnetization of the binary film is 0.06emu/cm ³ , the leakage current density is up to 10 ^-3 A/cm ² , stable dielectric constant and low dielectric loss, no holes, dense and uniform structure , the thickness is uniform.

2. By doping bismuth ferrite to form a pseudo-perovskite structure, a complex oxide solid solution is obtained, which has low leakage characteristics, good hysteresis loop at room temperature, and great electric polarization strength, showing Excellent ferroelectric properties, while improving its ferromagnetism, with strong magnetoelectric coupling properties. Since the film is a polycrystalline film, the structure and performance are more stable.

3. The joint modification of the A site and the B site can further reduce the leakage characteristics of the film, and the film has stronger magnetoelectric coupling properties.

4. The thickness of the single layer of the film is only 10-100nm, which can be better applied to some microelectronic devices, and can better meet the needs of thinner electronic devices. The crystal grains of the film are smaller and uniform, on the one hand, it is convenient to make the film monolayer thinner, and the film quality 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, precise control of the stoichiometric ratio of raw materials, less equipment and low cost, and can realize industrial production and meet commercial application. By rationally selecting suitable metal salts, coordinating solvents, and adding citric acid, a precursor sol with uniform distribution of components can be obtained, which is very important for the preparation of ultra-thin multiferroic films. By controlling the spin coating speed and The time wet film is more uniform; the temperature setting of the heating table, the ambient atmosphere, the subsequent heating rate, and the holding time are also crucial to the formation of the film. The above parameter settings can better ensure that the film has no holes and is less likely to appear. The impurity phase can better ensure the quality of the film.

Description of drawings

Figure 1(a) is a scanning electron micrograph of the cross section of a 0.72BiTi _0.27 Fe _0.46 Mg _0.27 -0.28LaFeO ₃ solid solution thin film;

Figure 1(b) is the scanning electron micrograph of the surface of the 0.72BiTi _0.27 Fe _0.46 Mg _0.27 -0.28LaFeO ₃ solid solution thin film;

Figure 2 shows the XRD patterns of bismuth ferrite (BiFeO ₃ ) thin film and 0.5BFMO-0.5LFO and 0.625BTFM-0.25LFO-0.125LMT solid solution thin films; wherein, the symbols in the figure are BFO, 0.5BFMO-0.5LFO and 0.625BTFM-0.25LFO -0.125LMT represents BiFeO ₃ film, 0.5BiTi _0.27 Fe _0.46 Mg _0.27 O ₃ -0.5LaFeO ₃ film and 0.625BiTi _0.27 Fe _0.46 Mg _0.27 O ₃ -0.25LaFeO ₃ -0.125La ₂ MgTiO ₆ film respectively; ” represents the peak of the substrate;

Figure 3 shows the XRD patterns of 0.72BiMg _0.27 Fe _0.46 Ti _0.27 -0.28LaFeO ₃ solid solution thin films annealed on SrTiO ₃ substrates under different conditions; among them, the labels are STO, 700°C for 2h, 700°C for 15min, 750°C for 15min and 800°C °C for 15min represent untreated SrTiO3 substrates, annealed at 700 °C for ₂ hours in a tube furnace, annealed at 700 °C for 15 minutes in an infrared annealing furnace, annealed at 750 °C for 15 minutes in an infrared annealing furnace, and annealed at 750 °C in an infrared annealing furnace. Annealing at 800℃ for 15 minutes;

Figure 4 shows the AFM morphology of 0.72BiMg _0.27 Fe _0.46 Ti _0.27 -0.28LaFeO ₃ solid solution thin films annealed on SrTiO ₃ substrates under different conditions; the annealing temperature of Figure 4(a), (b), (c) is 600 ℃, 700℃, 800℃; Figure 4(d) shows the relationship between the surface roughness of the film and the annealing temperature;

Figure 5 is a Raman scattering diagram of a 0.72BiMg _0.27 Fe _0.46 Ti _0.27 -0.28LaFeO ₃ solid solution thin film and a 0.625BiTi _0.27 Fe _0.46 Mg _0.27 O ₃ -0.25LaFeO ₃ -0.125La ₂ MgTiO ₆ solid solution thin film; iron is shown respectively The diffraction peaks of E(TO2), A1(TO3), E(TO3), E(TO5), E(TO7), E(TO9) modes of bismuth acid and the diffraction peaks of STO single crystal;

Figure 6 shows the hysteresis loops of 0.72BiMg _0.27 Fe _0.46 Ti _0.27 -0.28LaFeO ₃ solid solution thin film and 0.625BiTi _0.27 Fe _0.46 Mg _0.27 O ₃ -0.25LaFeO ₃ -0.125La ₂ MgTiO ₆ solid solution thin film; The curve represents the hysteresis loop of the 0.72BiMg _0.27 Fe _0.46 Ti _0.27 -0.28LaFeO ₃ solid solution thin film, and the BTFM-LFO-LMT curve represents the 0.625BiTi _0.27 Fe _0.46 Mg _0.27 O ₃ -0.25LaFeO ₃ -0.125La ₂ MgTiO ₆ solid solution thin film. Hysteresis loop;

Fig. 7(a) and Fig. 7(b) are the electro-optics of 0.72BiMg _0.27 Fe _0.46 Ti _0.27 -0.28LaFeO ₃ solid solution thin film and 0.625BiTi _0.27 Fe _0.46 Mg _0.27 O ₃ -0.25LaFeO ₃ -0.125La ₂ MgTiO ₆ solid solution thin film, respectively. hysteresis line;

Figure 8(a) and Figure 8(b) are the inversion curve and butterfly curve measured by PFM of 0.72BiMg _0.27 Fe _0.46 Ti _0.27 -0.28LaFeO ₃ solid solution thin film, respectively;

Fig. 9 is the leakage current curve of 0.72BiMg _0.27 Fe _0.46 Ti _0.27 -0.28LaFeO ₃ thin film and 0.625BiTi _0.27 Fe _0.46 Mg _0.27 O ₃ -0.25LaFeO ₃ -0.125La ₂ MgTiO ₆ thin film at 0-20V voltage; The BTFM-LFO curve represents a 0.72BiMg _0.27 Fe _0.46 Ti _0.27 -0.28LaFeO ₃ film, and the BTFM-LFO-LMT curve represents a 0.625BiTi _0.27 Fe _0.46 Mg _0.27 O ₃ -0.25LaFeO ₃ -0.125La ₂ MgTiO ₆ film;

Figure 10 shows the curve of the dielectric constant of 0.72BiMg _0.27 Fe _0.46 Ti _0.27 -0.28LaFeO ₃ film and 0.625BiTi _0.27 Fe _0.46 Mg _0.27 O ₃ -0.25LaFeO ₃ - 0.125La ₂ MgTiO ₆ film as a function of frequency; The LFO curve represents 0.72BiMg _0.27 Fe _0.46 Ti _0.27 -0.28LaFeO ₃ film, and the BTFM-LFO-LMT curve represents 0.625BiTi _0.27 Fe _0.46 Mg _0.27 O ₃ -0.25LaFeO ₃ -0.125La ₂ MgTiO ₆ film;

Figure 11 shows the dielectric loss versus frequency curves of 0.72BiMg _0.27 Fe _0.46 Ti _0.27 -0.28LaFeO ₃ thin films and 0.625BiTi _0.27 Fe _0.46 Mg _0.27 O ₃ -0.25LaFeO ₃ -0.125La ₂ MgTiO ₆ thin films. The BTFM-LFO curve in the figure represents a 0.72BiMg _0.27 Fe _0.46 Ti _0.27 -0.28LaFeO ₃ film, and the BTFM-LFO-LMT curve represents a 0.625BiTi _0.27 Fe _0.46 Mg _0.27 O ₃ -0.25LaFeO ₃ -0.125La ₂ MgTiO ₆ film.

detailed description

Definition of Terms

A solid solution refers to an alloy phase in which solute atoms dissolve into the solvent lattice while remaining solvent-type. According to the different positions of solute atoms in the crystal lattice, they can be divided into substitutional solid solutions and interstitial solid solutions.

Substitutional solid solution: A solid solution formed by solute atoms occupying node positions in the solvent lattice is called a substitutional solid solution.

Interstitial solid solution: A solid solution formed by the distribution of solute atoms in the interstitial space of the solvent lattice is called an interstitial solid solution.

For a better understanding of 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. Obviously, the described embodiments are only a part of the embodiments of the present application, but not all of the embodiments. Based on the embodiments in the present application, other embodiments obtained by those of ordinary skill in the art on the premise of understanding the inventive concept of the present application all fall within the protection scope of the present application.

The chemical formula of the oxide solid solution multiferroic thin film prepared in this application is (1-x ₁ -x ₂ )LM _(1-y)/2 Fe _y N _(1-y)/2 O ₃ x ₁ Rx ₂ Q, p-ferric acid Bismuth is doped to form a pseudo-perovskite structure. Using lanthanides and Y to replace Bi or replace part of Bi can improve the content of Bi vacancies and oxygen vacancies. The doped ions will also distort the oxygen octahedron and improve the ferroelectricity of the film. properties; Mg, Ti, Hf, Co, Mn, Ni and Zr can also optimize the ferromagnetism of the films and suppress the generation of oxygen vacancies to improve the ferroelectricity of the films.

The multiferroic film is a complex oxide solid solution of rhombohedral phase and orthorhombic phase. In the case of polycrystalline film, the structure and performance are more stable, with greater room temperature electric polarization strength, lower room temperature leakage current density, residual electrode It is 3.92-8.55μC/cm ² ; the residual magnetization of the ternary film is 0.02emu/cm ³ , the remanent magnetization of the binary film is 0.06emu/cm ³ , the leakage current density is 10 ^-3 A/cm ² , stable High dielectric constant and low dielectric loss, no holes, dense and uniform structure and uniform thickness.

The joint modification of the A site and the B site can further reduce the leakage characteristics of the film, and the film has stronger magnetoelectric coupling properties. The thickness of the single layer of the film is only 10-100nm, which can be better applied to some microelectronic devices, and can better fit the needs of thinner electronic devices. The crystal grains of the film are smaller and uniform, on the one hand, it is convenient to make the film monolayer thinner, and the film quality is more stable and the multiferroic performance is better.

The preparation method is simple, the stoichiometric ratio of raw materials can be precisely controlled, the equipment is few, the cost is low, industrial production can be realized, and commercial application can be met. By rationally selecting suitable metal salts, coordinating solvents, and adding citric acid, a precursor sol with uniform distribution of components can be obtained, which is very important for the preparation of ultra-thin multiferroic films. By controlling the spin coating speed and The time wet film is more uniform; the temperature setting of the heating table, the ambient atmosphere, the subsequent heating rate, and the holding time are also crucial to the formation of the film. The above parameter settings can better ensure that the film has no holes and is less likely to appear. The impurity phase can better ensure the quality of the film.

In order to make it easier to understand 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 will be described in further detail below, but not as the protection scope limited by the present application.

Example 1

The method for preparing 0.5BiFe _0.63 Mg _0.37 0.5LaFeO ₃ solid solution thin film by chemical solution deposition includes the following steps:

S1. Prepare a precursor solution: weigh bismuth nitrate pentahydrate, lanthanum nitrate hexahydrate, magnesium nitrate hexahydrate, and ferric nitrate nonahydrate according to the molar ratio of 1:1:0.37:1.63, and add the volume ratio of 15:3:2 The mixed solution of ethylene glycol methyl ether, glacial acetic acid and propionic anhydride was stirred at room temperature until dissolved to obtain a titanium-free precursor solution, and the concentration of the precursor solution was 0.2 mol/L.

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

S3. Preparation of the precursor film: The precursor sol obtained in S2 is coated on the Pt(111)/Ti/SiO ₂ /Si substrate, and the substrate is spin-coated at a low speed of 700r/min for 6s, and at a high speed of 5000r/min. A uniform wet film was obtained after a total of 15s;

S4. The uniform wet film in S3 is placed in the air, heated from 180°C to 380°C on a heating table, kept for 30 minutes, and then cooled in a furnace to obtain a solid solution precursor film;

S5. Preparation of solid solution thin film: The precursor thin film obtained in S4 is placed in a heating furnace in an oxygen atmosphere, heated to 600 ℃ at a rate of 100 ℃/min, and kept for 15 minutes to obtain a BiFe _0.63 Mg _0.37 0.5LaFeO ₃ solid solution thin film, referred to as 0.5BFMO-LFO.

Example 2

A method for preparing 0.5BiFe _0.63 Ti _0.37 -0.5LaFeO ₃ solid solution thin film by chemical solution deposition, comprising the following steps:

S1. Prepare a precursor solution: weigh bismuth nitrate pentahydrate, lanthanum nitrate hexahydrate, ferric nitrate nonahydrate, and tetrabutyl titanate in a molar ratio of 1:1:1.63:0.37, and add a volume ratio of 15:3: 2 in the mixed solution of ethylene glycol methyl ether, glacial acetic acid and propionic anhydride, stir at room temperature until dissolved to obtain a magnesium-free precursor solution, and the concentration of the precursor solution is 0.3 mol/L.

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

S3. Preparation of the precursor film: The precursor sol obtained in S2 is coated on the Pt(111)/Ti/SiO ₂ /Si substrate, and the substrate is spin-coated at a low speed of 700r/min for 6s, and at a high speed of 5000r/min. A uniform wet film was obtained after a total of 15s;

S4. The uniform wet film in S3 is placed in the air, heated from 180°C to 380°C on a heating table, kept for 30 minutes, and then cooled in a furnace to obtain a solid solution precursor film;

S5. Preparation of solid solution film: The precursor film obtained in S4 is placed in a heating furnace in an oxygen atmosphere, heated to 600°C at a rate of 100°C/min, and maintained for 15 minutes to obtain a solid solution film.

Example 3

A method for preparing 0.5BiTi _0.27 Fe _0.46 Mg _0.27 -0.5LaFeO ₃ solid solution thin film by chemical solution deposition, comprising the following steps:

S1. Prepare the precursor solution: weigh bismuth nitrate pentahydrate, lanthanum nitrate hexahydrate, ferric nitrate nonahydrate, tetrabutyl titanate, and magnesium nitrate hexahydrate according to the molar ratio of 1:1:1.46:0.27:0.27, add In the mixed solution of ethylene glycol methyl ether, glacial acetic acid and propionic anhydride with a volume ratio of 15:3:2, stir at room temperature until dissolved to obtain a magnesium-free precursor solution, and the concentration of the precursor solution is 0.4mol/L .

S2, preparing the precursor sol: adding citric acid to the precursor solution obtained in S1, the concentration of 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 the precursor sol;

S3. Preparation of the precursor film: apply the precursor sol obtained in S2 to the SrTiO ₃ substrate, spin the substrate at a low speed of 700r/min for 6s, and spin at a high speed of 5000r/min for a total of 15s to obtain a uniform wet film;

S4. The uniform wet film in S3 is placed in the air, heated from 180°C to 380°C on a heating table, kept for 30 minutes, and then cooled in a furnace to obtain a solid solution precursor film;

S5. Preparation of solid solution film: The precursor film obtained in S4 is placed in a heating furnace in an oxygen atmosphere, heated to 800°C at a rate of 100°C/min, and maintained for 15 minutes to obtain a solid solution film.

Example 4

A method for preparing 0.72BiMg _0.27 Fe _0.46 Ti _0.27 -0.28LaFeO ₃ solid solution thin film by chemical solution deposition, comprising the following steps:

S1. Prepare a precursor solution: weigh 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, add In the mixed solution of ethylene glycol methyl ether, glacial acetic acid and propionic anhydride with a volume ratio of 15:3:2, stir at room temperature until dissolved to obtain a magnesium-free precursor solution, and the concentration of the precursor solution is 0.3mol/L .

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

S3. Preparation of the precursor thin film: apply the precursor sol obtained in S2 to the SrTiO ₃ substrate, spin the substrate at a low speed of 700r/min for 6s, and spin at a high speed of 6000r/min for a total of 15s to obtain a uniform wet film;

S4. The uniform wet film in S3 is placed in the air, heated from 180°C to 380°C on a heating table, kept for 30 minutes, and then cooled in a furnace to obtain a solid solution precursor film;

S5. Preparation of solid solution film: The precursor film obtained in S4 is placed in a heating furnace in an oxygen atmosphere, heated to 800°C at a rate of 5°C/min, and kept for 2 hours to obtain a solid solution film.

Example 5

A method for preparing 0.625BiTi _0.27 Fe _0.46 Mg _0.27 O ₃ 0.25LaFeO ₃ -0.125La ₂ MgTiO ₆ solid solution thin film by chemical solution deposition, comprising the following steps:

S1. Prepare a precursor solution: weigh 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, add In the mixed solution of ethylene glycol methyl ether, glacial acetic acid and propionic anhydride with a volume ratio of 15:3:2, stir at room temperature until dissolved to obtain a magnesium-free precursor solution, and the concentration of the precursor solution is 0.3mol/L .

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

S3. Preparation of the precursor film: apply the precursor sol obtained in S2 to the SrTiO ₃ substrate, spin the substrate at a low speed of 700r/min for 6s, and spin at a high speed of 5000r/min for a total of 15s to obtain a uniform wet film;

S4. The uniform wet film in S3 is placed in the air, heated from 180°C to 380°C on a heating table, kept for 30 minutes, and then cooled in a furnace to obtain a solid solution precursor film;

S5. Preparation of solid solution film: The precursor film obtained in S4 is placed in a heating furnace in an oxygen atmosphere, heated to 700°C at a rate of 100°C/min, and maintained for 15 minutes to obtain a solid solution film.

Example 6

A method for preparing 0.625BiTi _0.27 Fe _0.46 Mg _0.27 O ₃ 0.25LaFeO ₃ -0.125La ₂ MgTiO ₆ solid solution thin film by chemical solution deposition, comprising the following steps:

S1. Prepare a precursor solution: weigh 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, add In the mixed solution of ethylene glycol methyl ether, glacial acetic acid and propionic anhydride with a volume ratio of 15:3:2, stir at room temperature until dissolved to obtain a magnesium-free precursor solution, and the concentration of the precursor solution is 0.3mol/L .

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

S3. Preparation of the precursor film: apply the precursor sol obtained in S2 to the SrTiO ₃ substrate, spin the substrate at a low speed of 700r/min for 6s, and spin at a high speed of 5000r/min for a total of 15s to obtain a uniform wet film;

S4. The uniform wet film in S3 is placed in the air, heated from 180°C to 380°C on a heating table, kept for 30 minutes, and then cooled in a furnace to obtain a solid solution precursor film;

S5. Preparation of solid solution film: The precursor film obtained in S4 is placed in a heating furnace in an oxygen atmosphere, heated to 700°C at a rate of 5°C/min, and maintained for 2 hours to obtain a solid solution film.

Performance Testing

In order to see the thickness and surface condition of the thin film more intuitively, the application has made 0.72BiTi _0.27 Fe _0.46 Mg _0.27 0.28LaFeO ₃ solid solution thin film cross-section and scanning electron micrographs of the surface. It can be seen from Figure 1(a) that the thickness of the film is basically 30 nm and the thickness is uniform. It can be seen from Figure 1(b) that the thin film sample is very dense, without visible voids, and the grain size is in the range of 10-100 nm.

It can be clearly seen from Figure 2 that the 0.5BFMO-0.5LFO and 0.625BTFM-0.25LFO-0.125LMT solid solution films are polycrystalline films, and the crystal structure is basically the same as that of rhombohedral BFO, and the space group is R3c. It can also be clearly seen from the XRD pattern that the thin film sample is very pure and has no impurity peaks.

It can be clearly seen from Figure 3 that the films obtained at the annealing temperature of 700-800°C are polycrystalline films, with obvious peaks appearing around 32°, the direction is the (110) direction, and with the increase of the annealing temperature The crystallinity of the film increases gradually.

From Figure 4(a), (b), (c), it can be seen more intuitively that the 0.72BiMg _0.27 Fe _0.46 Ti _0.27 -0.28LaFeO ₃ solid solution thin film has a dense structure, uniform grain size, and approximately circular grains. Figure 4(d) uses AFM to calculate the surface roughness of the film at different temperatures. It can be clearly seen from Figure 4(d) that the surface roughness increases from less than 1 nm to more than 30 nm with the increase of annealing temperature. Other films with different ratios have similar rules. The surface roughness of the thin film can be flexibly controlled according to the requirements of different electronic devices, which can better meet the requirements of 5G memory devices.

As shown in Figure 5, due to the La substitution on Bi sites and the random substitution of Ti and Mg on Fe sites, disorder is introduced at atomic sites, resulting in very low peak intensity and spectrum diffusion, so only A few major Raman modes can be clearly distinguished.

For better testing, the number of layers of the film is set to 6, and the thickness of the film is estimated to be 180 nm according to the thickness of each layer of 30 nm; the area of the film is all 1 cm ² . As shown in Fig. 6, the thin film exhibits weak ferromagnetism, and the remanent magnetization of the ternary thin film, namely 0.625BiTi _0.27 Fe _0.46 Mg _0.27 O ₃ -0.25LaFeO ₃ -0.125La ₂ MgTiO ₆ solid solution thin film, is estimated to be 0.29emu/cm ³ , the binary thin film, that is, the remanent magnetization of the 0.72BiMg _0.27 Fe _0.46 Ti _0.27 -0.28LaFeO ₃ solid solution thin film is 0.62 emu/cm ³ .

As shown in Fig. 7(a) and Fig. 7(b), the saturation polarization of the 0.72BiMg _0.27 Fe _0.46 Ti _0.27 -0.28LaFeO ₃ film is 11.9 μC/cm ² and the remanent polarization is 8.55 μC/cm ² ; 0.625 The saturation polarization of the BiTi _0.27 Fe _0.46 Mg _0.27 O ₃ -0.25LaFeO ₃ -0.125La ₂ MgTiO ₆ film was 9.71 μC/cm ² and the remanent polarization was 3.92 μC/cm ² . The remanent polarization of the multiferroic film is greatly improved, which can better meet the requirements of electronic devices.

As shown in Fig. 8(a) and Fig. 8(b), the piezoelectric response and phase versus voltage curve of the 0.72BiMg _0.27 Fe _0.46 Ti _0.27 -0.28LaFeO ₃ solid solution thin film measured under PFM, namely the flip curve and butterfly curve. The highest bias voltage is 15V, it can be clearly seen that the film achieves a 180° polarization reversal under the condition of applying a DC bias voltage; at the same time, the film has a typical butterfly curve of piezoelectric materials, which proves the piezoelectric properties of the film .

As shown in FIG. 9 , when the voltage is 20V, the leakage current density reaches 10 ^-3 A/cm ² . The leakage current is also lower, which achieves lower room temperature leakage current and higher room temperature residual polarization, which is beneficial to practical production and application.

As shown in Figure 10, as a whole, in the frequency range of 100 to 1 MHz, the relative permittivity of the thin film of 0.72BiMg _0.27 Fe _0.46 Ti _0.27 -0.28LaFeO ₃ remained in the range of 100 to 130; 0.625BiTi _0.27 The relative permittivity of the Fe _0.46 Mg _0.27 O ₃ -0.25LaFeO ₃ -0.125La ₂ MgTiO ₆ thin film was maintained in the range of 110-140. The dielectric constants of the two films are not much different, and both have good frequency stability, which further proves the excellent and stable multiferroic properties of the series of products of the application, and also proves that the preparation process of the application can be better. Ensure the stability of various products and better meet the requirements of electronic devices used in 5G storage technology.

As shown in Figure 11, in the frequency range of 100-1MHz, the dielectric loss of the thin film of 0.72BiMg _0.27 Fe _0.46 Ti _0.27 -0.28LaFeO ₃ is basically below 0.1, while that of 0.625BiTi _0.27 Fe _0.46 Mg _0.27 O ₃ -0.25LaFeO ₃ The dielectric loss of the -0.125La ₂ MgTiO ₆ film is in the range of 0.02 to 0.05, with lower dielectric loss and more stable than the former.

To sum up, the oxide solid solution thin film prepared in this application has a polycrystalline structure and is co-doped with A site and B site. And low dielectric loss, no holes, dense and uniform structure, uniform thickness, can be more widely used in various electronic devices; especially in the application of 5G memory devices has great potential, can better meet the needs of 5G memory devices The preparation process of the present application is simple, the stoichiometric ratio of the raw materials can be precisely controlled, the equipment is less, and the cost is low, and the industrial production can be realized, and the commercial application can be met.

This specific embodiment is only an explanation of the application, and it does not limit the application. Those skilled in the art can make modifications to the embodiment without creative contribution as needed after reading this specification, but as long as the rights of the application are All claims are protected by patent law.

Claims (10)

A solid solution multiferroic thin film is characterized in that it is a complex oxide solid solution of pseudoperovskite structure, and has the following chemical formula: (1-x ₁ -x ₂ )LM _(1-y)/2 Fe _y N _{(1 -y)/2} O ₃ x ₁ Rx ₂ Q; Wherein, 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 selected from from Mg, Ti, Hf, Co, Mn, Ni or Zr, which may be the same or different; and R is _LFeO3 ; and Q is an oxide of L, M, N; The multiferroic thin film is a solid solution of a rhombohedral phase and an orthorhombic phase, and is a polycrystalline thin film. The solid solution multiferroic thin film according to claim 1, wherein the multiferroic thin film has the following chemical formula: (1-x ₁ -x ₂ )BiTi _(1-y)/2 Fe _y Mg _{(1-y) /2} O ₃ -x ₁ LaFeO ₃ x ₂ La ₂ MgTiO ₆ , wherein y=0˜0.9, x ₁ =0˜1, x ₂ =0˜1, and x ₁ +x ₂ ≦1. The solid solution multiferroic thin film according to claim 2, wherein the monolayer thickness of the multiferroic thin film is 10- 100nm, the grain size of the film is 10-100nm. The solid solution multiferroic thin film according to any one of claims 1-3, wherein the multiferroic thin film has a pseudoperovskite structure modified by A site and B site, wherein the A site of the perovskite structure is in a pseudoperovskite structure. La is introduced, and Mg and Ti are introduced at the B site; preferably, the preparation method of the solid solution multiferroic thin film is chemical solution deposition method, sol-gel method or metal organic thermal decomposition method. The preparation method of the solid solution multiferroic thin film according to any one of claims 1-4, characterized in that, comprising the following steps: Step 1, using a sol-gel method to prepare a complex oxide solid solution precursor solution, wherein the concentration of the precursor solution is 0.1-0.5 mol/L; Step 2, adding a chelating agent to the precursor solution of step 1 and standing to obtain a precursor sol; Step 3, spin coating the precursor sol obtained in step 2 on the substrate to obtain a uniform wet film; Step 4, drying and pyrolyzing the uniform wet film obtained in step 3 in the air; Step 5, annealing the film obtained in step 4 in an oxygen atmosphere to obtain a solid solution thin film; Optionally, steps 3-4 may be repeated multiple times according to the actual needs of the thickness of the solid solution film to obtain solid solution films with different thicknesses. The method for preparing a 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 step 2 is 0.2-0.4 mol/L L. The preparation method of the described solid solution multiferroic film of claim 6, is characterized in that, described chelating agent is citric acid, and the solvent of precursor solution is ethylene glycol methyl ether, glacial acetic acid and propionic anhydride, and its volume ratio is 15: 3:2. The preparation method of the solid solution multiferroic thin film according to any one of claims 5-7, characterized in that it comprises the following steps: in step 1, one or more nitrates and organic titanium are weighed in a molar ratio, and ethylene glycol is added. In the mixed solution of methyl alcohol ether, glacial acetic acid and propionic anhydride, stir at room temperature until dissolved to obtain a precursor solution; the addition amount of bismuth nitrate is 10% excess according to the theoretical value; preferably, the nitrate is selected from bismuth nitrate, nitric acid Lanthanum, magnesium nitrate, ferric nitrate; the organic titanium is tetrabutyl titanate; Preferably, step 2 includes: adding a chelating agent to the precursor solution obtained in step 1, stirring at room temperature for more than 12 hours, and standing for 24 hours to obtain a precursor sol; preferably, the chelating agent is citric acid; Preferably, step 3 includes: coating the precursor sol obtained in step 2 on a substrate, and the substrate is spin-coated at 3000-6000r/min for 10-60s to obtain a uniform wet film; preferably, the substrate is selected from Pt ( 111)/Ti/ _SiO2 /Si, Pt(111)/Ti/substrate, _SiO2 /Si substrate, SrTiO3 substrate, MgO substrate, _LaAlO3 substrate or mica substrate _; Further, step 4 includes: placing the uniform wet film in step 3 in the air, heating the temperature from 180°C to 300-400°C on a heating table, and maintaining the temperature for 5-30min to obtain a solid solution precursor film; Further, step 5 includes: placing the precursor film obtained in step 4 in an oxygen atmosphere with an oxygen flow rate of 1 L/min, heating to 500-800° C. at a rate of 5-100° C./min, and maintaining the temperature for 15-120 min to obtain solid solution films. An electronic device, characterized in that the electronic device is a memory device, an energy harvester, a tunnel junction, a magnetoelectric sensor, a transmitter, and a receiver, including the solid solution multiferroic thin film of any one of claims 1-5. An electronic device applied to 5G storage technology, characterized by comprising the solid solution multiferroic thin film according to any one of claims 1-4.

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