阅读说明：本技术 一种自支撑的磁电纳米复合结构及其制备方法 (Self-supporting magnetoelectric nano composite structure and preparation method thereof ) 是由 刘明 王志广 胡忠强 周子尧 杜琴 于 2020-03-19 设计创作，主要内容包括：一种自支撑的磁电纳米复合结构及其制备方法,包括钛酸锶衬底、铝酸锶牺牲层和铁酸铋/铁酸钴磁电复合薄膜；钛酸锶衬底、铝酸锶牺牲层和铁酸铋/铁酸钴磁电复合薄膜自下而上依次设置,形成自支撑的磁电纳米复合结构；铁酸铋/铁酸钴磁电复合薄膜中铁酸铋为网格状结构,铁酸钴填充在网格结构内。本发明有利于提高磁电耦合性能,在能量存储与转换,磁存储及磁传感等方面有潜在的应用价值。(A self-supporting magnetoelectric nano composite structure and a preparation method thereof comprise a strontium titanate substrate, a strontium aluminate sacrificial layer and a bismuth ferrite/cobalt ferrite magnetoelectric composite film; the strontium titanate substrate, the strontium aluminate sacrificial layer and the bismuth ferrite/cobalt ferrite magnetoelectric composite film are sequentially arranged from bottom to top to form a self-supporting magnetoelectric nano composite structure; bismuth ferrite in the bismuth ferrite/cobalt ferrite magnetoelectric composite film is in a grid structure, and cobalt ferrite is filled in the grid structure. The invention is beneficial to improving the magnetoelectric coupling performance and has potential application value in the aspects of energy storage and conversion, magnetic storage, magnetic sensing and the like.)

1. A self-supporting magnetoelectric nano composite structure is characterized by comprising a strontium titanate substrate, a strontium aluminate sacrificial layer and a bismuth ferrite/cobalt ferrite magnetoelectric composite film; the strontium titanate substrate, the strontium aluminate sacrificial layer and the bismuth ferrite/cobalt ferrite magnetoelectric composite film are sequentially arranged from bottom to top to form a self-supporting magnetoelectric nano composite structure; bismuth ferrite in the bismuth ferrite/cobalt ferrite magnetoelectric composite film is in a grid structure, and cobalt ferrite is filled in the grid structure.

2. The self-supporting magnetoelectric nanocomposite structure according to claim 1, wherein the strontium aluminate sacrificial layer is cubic phase with a strontium aluminate lattice constant of cubic phase ofThe strontium titanate substrate is a cubic junction,the lattice constants of strontium aluminate and strontium titanate are in a multiple relationship.

3. The self-supporting magnetoelectric nanocomposite structure according to claim 1, wherein the thickness of the strontium aluminate sacrificial layer is 20 to 50 nm; the thickness of the bismuth ferrite/cobalt ferrite magnetoelectric composite film is 300-500 nm.

4. A self-supporting magnetoelectronics nanocomposite structure according to claim 1, wherein the strontium titanate substrate comprises three strontium titanate single crystals having crystal plane orientations of 001, 110, and 111 directions.

5. A method for preparing a self-supporting magnetoelectric nanocomposite structure, which is based on the self-supporting magnetoelectric nanocomposite structure of any one of claims 1 to 4, comprising the steps of:

step 1, taking strontium aluminate as a target material, and performing first-layer deposition on the surface of a strontium titanate substrate by adopting a pulse laser deposition method to form a strontium aluminate sacrificial layer;

step 2, performing secondary deposition on the surface of the strontium aluminate sacrificial layer by using the composite bismuth ferrite/cobalt ferrite as a target material and adopting a pulse laser deposition method;

step 3, etching the annealed bismuth ferrite/cobalt ferrite in 50% dilute hydrochloric acid for 1 hour at room temperature to obtain a surface texture;

and 4, covering PMMA on the upper surface of the grown bismuth ferrite/cobalt ferrite self-assembled film, then soaking the film in deionized water to ensure that the strontium aluminate sacrificial layer is completely dissolved by the deionized water at room temperature, and stripping the flexible self-supporting bismuth ferrite/cobalt ferrite self-assembled film.

6. The method for preparing a self-supporting magnetoelectric nanocomposite structure according to claim 5, wherein the temperature of the strontium titanate substrate in the first deposition process is 800 ℃; the deposition oxygen pressure is 20 Pa; the laser energy is 1.04W; the frequency is 3 Hz; the deposition time is 15-20 min;

the growth temperature in the second deposition process is 700 ℃, the oxygen pressure in the oxygen atmosphere is 20Pa, the deposition rate is 10Hz, and the laser energy density is 3J/cm²The target base distance is 6 cm.

7. The method for preparing a self-supporting magnetoelectric nanocomposite structure according to claim 5, wherein the substrate material can be any one of polyethylene terephthalate, polydimethylsiloxane, polyethylene and polypropylene; the PMMA substrate and the substrate need to be cleaned by ultrasonic for 10 minutes by using de-acetone, ethanol and ionized water in advance.

8. The method for preparing a self-supporting magnetoelectric nanocomposite structure according to claim 5, wherein the target in step 2 is a bismuth ferrite composite 0.65/cobalt ferrite composite 0.35.

Technical Field

The invention belongs to the technical field of magnetoelectric nano composite structures, and particularly relates to a self-supporting magnetoelectric nano composite structure and a preparation method thereof.

Background

With the development of new device miniaturization technologies, there is an increasing interest in combining electricity and magnetism into multifunctional thin film materials for potential applications. The magnetoelectric material can show induced polarization/magnetization under an external magnetic field/electric field, and has wide application prospect in novel multifunctional devices. Compared with a single-phase magnetoelectric material, the magnetoelectric composite material consisting of a piezoelectric phase and a magnetostrictive phase has attracted much attention because of stronger magnetoelectric coupling and higher use temperature. For such composite materials, the magnetoelectric coupling effect is the product of the piezoelectric and magnetostrictive coefficients of the corresponding functional phases. The interconnected structure of magnetoelectric composite films, which has been widely studied at present, on a microscopic or nano scale, includes: (0-3) type particle composite material, (2-2) type laminate composite material and (1-3) type. However, (2-2) the effective magnetoelectric coupling performance of the thin film connection is limited by the clamping effect of the thin film and the substrate, while (0-3) the structure easily generates a dielectric leakage current path due to the randomness of the distribution of the magnetic particles in the ferroelectric phase, and the magnetoelectric coupling effect thereof strongly depends on the magnetic bias and the magnetic field frequency. (1-3) the structure vertically arranges the nano composite material film that grows, wherein two-phase material can self-assemble and epitaxial growth, have offered a powerful method for vertical interface coupling and microstructure adjustment, the structure has reduced the clamping effect of the film in the vertical structure, in addition can produce the effective magnetoelectric coupling because of the larger specific surface area of interface. However, the morphology of the component phases in thin films varies significantly with substrate orientation and changes in phase composition, and the design and control of such heterostructures is still a challenge today.

Disclosure of Invention

The present invention aims at providing a self-supporting magnetoelectric nanocomposite structure and a preparation method thereof to solve the above problems.

In order to achieve the purpose, the invention adopts the following technical scheme:

a self-supporting magnetoelectric nano composite structure comprises a strontium titanate substrate, a strontium aluminate sacrificial layer and a bismuth ferrite/cobalt ferrite magnetoelectric composite film; the strontium titanate substrate, the strontium aluminate sacrificial layer and the bismuth ferrite/cobalt ferrite magnetoelectric composite film are sequentially arranged from bottom to top to form a self-supporting magnetoelectric nano composite structure; bismuth ferrite in the bismuth ferrite/cobalt ferrite magnetoelectric composite film is in a grid structure, and cobalt ferrite is filled in the grid structure.

Further, the strontium aluminate sacrificial layer is cubic phase with a cubic phase strontium aluminate lattice constant ofThe strontium titanate substrate is a cubic junction,the lattice constants of strontium aluminate and strontium titanate are in a multiple relationship.

Further, the thickness of the strontium aluminate sacrificial layer is 20-50 nm; the thickness of the bismuth ferrite/cobalt ferrite magnetoelectric composite film is 300-500 nm.

Further, the strontium titanate substrate includes three strontium titanate single crystals having crystal plane orientations of 001, 110 and 111 directions.

Further, a preparation method of the self-supporting magnetoelectric nano composite structure comprises the following steps:

step 1, taking strontium aluminate as a target material, and performing first-layer deposition on the surface of a strontium titanate substrate by adopting a pulse laser deposition method to form a strontium aluminate sacrificial layer;

step 2, performing secondary deposition on the surface of the strontium aluminate sacrificial layer by using the composite bismuth ferrite/cobalt ferrite as a target material and adopting a pulse laser deposition method;

step 3, etching the annealed bismuth ferrite/cobalt ferrite in 50% dilute hydrochloric acid for 1 hour at room temperature to obtain a surface texture;

and 4, covering PMMA on the upper surface of the grown bismuth ferrite/cobalt ferrite self-assembled film, then soaking the film in deionized water to ensure that the strontium aluminate sacrificial layer is completely dissolved by the deionized water at room temperature, and stripping the flexible self-supporting bismuth ferrite/cobalt ferrite self-assembled film.

Further, the temperature of the strontium titanate substrate in the first deposition process is 800 ℃; the deposition oxygen pressure is 20 Pa; the laser energy is 1.04W; the frequency is 3 Hz; the deposition time is 15-20 min;

the growth temperature in the second deposition process is 700 ℃, the oxygen pressure in the oxygen atmosphere is 20Pa, the deposition rate is 10Hz, and the laser energy density is 3J/cm²The target base distance is 6 cm.

Further, the substrate material can be any one of polyethylene terephthalate, polydimethylsiloxane, polyethylene and polypropylene; the PMMA substrate and the substrate need to be cleaned by ultrasonic for 10 minutes by using de-acetone, ethanol and ionized water in advance.

Further, the target material in the step 2 is a target material of 0.65 composite bismuth ferrite/0.35 cobalt ferrite.

Compared with the prior art, the invention has the following technical effects:

the invention designs a new strategy to prepare a self-supporting nano composite heterostructure so as to overcome the problems that the existing magnetoelectric composite film magnetoelectric coupling effect and the practical application environment are influenced and limited by the restriction of a substrate. By dissolving water-soluble strontium aluminate (Sr)₃Al₂O₆SAO for short) sacrificial layer growth (1-3) type BiFeO₃/CoFe₂O₄And (BFO/CFO) magnetoelectric composite film, then covering a layer of flexible PMMA on the magnetoelectric composite film, soaking the magnetoelectric composite film in water for a period of time, and removing the substrate to obtain the self-supporting flexible BFO/CFO self-assembly magnetoelectric composite film. The new hetero-epitaxial film has excellent connectivity between piezoelectric and magnetostriction phases, and the self-supporting magnetoelectric composite film structure provided by the invention overcomes the constraint effect of a substrate, is favorable for improving magnetoelectric coupling performance, has potential application values in the aspects of energy storage and conversion, magnetic storage, magnetic sensing and the like, has the flexibility characteristic, can be further applied to related flexible devices, and develops the application of the magnetoelectric film in micro devicesA new way is provided.

Drawings

FIG. 1 is a schematic structural diagram of a BFO/CFO self-assembled film provided by the present invention;

FIG. 2 is a schematic flow chart of a method for preparing a self-supporting BFO/CFO self-assembled film provided by the present invention;

FIGS. 3a-d are schematic diagrams of peeling of flexible self-supporting BFO/CFO self-assembled thin film structures;

FIG. 4 is an SEM image of an epitaxially grown BFO/CFO self-assembled film on a <001> STO substrate.

Detailed Description

The invention is further described below with reference to the accompanying drawings:

referring to fig. 1 to 4, a self-supporting magnetoelectric nanocomposite structure includes a strontium titanate substrate, a strontium aluminate sacrificial layer, and a bismuth ferrite/cobalt ferrite magnetoelectric composite film; the strontium titanate substrate, the strontium aluminate sacrificial layer and the bismuth ferrite/cobalt ferrite magnetoelectric composite film are sequentially arranged from bottom to top to form a self-supporting magnetoelectric nano composite structure; bismuth ferrite in the bismuth ferrite/cobalt ferrite magnetoelectric composite film is in a grid structure, and cobalt ferrite is filled in the grid structure. Comprises strontium titanate (SrTiO) from bottom to top in sequence₃STO substrate, strontium aluminate (Sr)₃Al₂O₆SAO for short), bismuth ferrite/cobalt ferrite (BiFeO)₃/CoFe₂O₄BFO/CFO) magnetoelectric composite film

The strontium aluminate sacrificial layer is cubic phase with a cubic phase strontium aluminate lattice constant ofThe strontium titanate substrate is a cubic junction,the lattice constants of strontium aluminate and strontium titanate are in a multiple relation, so that the strontium aluminate and the strontium titanate can be epitaxially grown.

The thickness of the strontium aluminate sacrificial layer is 20-50 nm; the SAO as a sacrificial layer can be completely dissolved by deionized water at room temperature, so that the upper BFO/CFO composite film is completely released. The thickness of the bismuth ferrite/cobalt ferrite magnetoelectric composite film is 300-500 nm.

The strontium titanate substrate includes three strontium titanate single crystals having crystal plane orientations of 001, 110 and 111 directions. And epitaxially growing BFO/CFO self-assembled nano-structures with different structures.

The BFO has a diamond R3c structure and can be described as a pseudo-cubeAnd CFO is a ferromagnetic spinel structure having a cubic Fm3m structureIts magnetic easy axis edge<100>And (4) direction. The BFO/CFO self-assembled heterostructure has vertically aligned interfaces due to lattice mismatch of BFO and CFO (8.39)>3.96 x 2) to create compressive strain between the CFO nanocrystals. As the CFO particle size decreases to the micron level, the shape anisotropy energy will dominate. Therefore, adjusting the shape and aspect ratio of CFO nanoarrays is an effective means to control the magnetic performance.

A preparation method of a self-supporting magnetoelectric nano composite structure comprises the following steps:

step 1, taking strontium aluminate as a target material, and performing first-layer deposition on the surface of a strontium titanate substrate by adopting a pulse laser deposition method to form a strontium aluminate sacrificial layer;

step 2, performing secondary deposition on the surface of the strontium aluminate sacrificial layer by using the composite bismuth ferrite/cobalt ferrite as a target material and adopting a pulse laser deposition method;

step 3, etching the annealed bismuth ferrite/cobalt ferrite in 50% dilute hydrochloric acid for 1 hour at room temperature to obtain a surface texture;

and 4, covering PMMA on the upper surface of the grown bismuth ferrite/cobalt ferrite self-assembled film, then soaking the film in deionized water to ensure that the strontium aluminate sacrificial layer is completely dissolved by the deionized water at room temperature, and stripping the flexible self-supporting bismuth ferrite/cobalt ferrite self-assembled film.

The temperature of the strontium titanate substrate in the first deposition process is 800 ℃; the deposition oxygen pressure is 20 Pa; the laser energy is 1.04W; the frequency is 3 Hz; the deposition time is 15-20 min;

the growth temperature in the second deposition process is 700 ℃, the oxygen pressure in the oxygen atmosphere is 20Pa, the deposition rate is 10Hz, and the laser energy density is 3J/cm²The target base distance is 6 cm.

The substrate material can also be any one of polyethylene terephthalate, polydimethylsiloxane, polyethylene and polypropylene; the PMMA substrate and the substrate need to be cleaned by ultrasonic for 10 minutes by using de-acetone, ethanol and ionized water in advance. Facilitating the deposition and growth of the subsequent ferroelectric film.

The target material in the step 2 is a target material of 0.65 composite bismuth ferrite/0.35 cobalt ferrite.

In the invention, the morphology of the grown BFO/CFO self-assembly nanostructure can be effectively regulated and controlled by changing the conditions such as the orientation of the STO substrate, and FIG. 4 is an SEM image of the BFO/CFO grown on the STO substrate with the orientation of <001 >;

in the present invention, the flexible substrate material for supporting the film transfer may be any one of polyethylene terephthalate, polydimethylsiloxane, polyethylene, and polypropylene, but is not limited thereto. The PMMA substrate needs to be cleaned by using acetone, ethanol and ionized water in advance for 10 minutes in an ultrasonic mode to remove organic matters, metal ions and impurity microparticles adhered to the surface of the substrate, so that the adsorption of the organic ferroelectric film and the subsequent material structure and physical property test are facilitated.

In the invention, the obtained BFO/CFO self-assembled film can directly adopt the supporting layer as a flexible functional layer, and can also be transferred and applied to a specific working environment by removing the supporting layer.