BaM single crystal film prepared through homoepitaxy and preparation method and application of BaM single crystal film

Abstract

The invention provides a BaM single crystal thin film prepared through homoepitaxy and a preparation method and application of the BaM single crystal thin film. The preparation method for preparing the BaM single crystal thin film through homogeneous epitaxy comprises the steps that 1, melt is prepared, BaCO3 and Fe2O3 serve as raw materials, K2CO3, Bi2O3 and B2O3 serve as fluxing agents, the raw materials and the fluxing agents are weighed to be mixed and melted, and the evenly-mixed melt is obtained; step 2, homoepitaxial growth of a thin film: taking a BaM seed crystal as a substrate, immersing the BaM seed crystal into the melt, and carrying out homoepitaxial growth at the temperature of 870-910 DEG C so as to form a BaM single crystal thin film on the substrate; and step 3, taking out the film: taking out the BaM single crystal film, and cleaning to obtain the cleaned BaM single crystal film. The homoepitaxial growth BaM single crystal film has the advantages of being high in crystal structure matching degree, excellent in performance, good in preparation process controllability and the like.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of single crystal preparation, in particular to a homoepitaxial BaM single crystal thin film and a preparation method and application thereof. BACKGROUND

[0002] Current microwave communication is rapidly iterating towards high frequency, miniaturization and low power consumption. The commercialization of 5G millimeter wave, 6G terahertz communication and low-orbit satellite communication puts forward more stringent performance requirements for core magnetic devices. Isolators, circulators and filters in microwave communication systems are key components for realizing one-way signal transmission and suppressing interference, and their performance directly determines the signal-to-noise ratio and stability of the communication link. Traditional magnetic materials cannot meet the high-end requirements of microwave communication due to high high-frequency loss and poor integration, and new high-performance magnetic materials are needed to break this bottleneck. Barium ferrite (BaM, chemical formula BaFe 12 O 19 ) as a hexagonal crystal material, its intrinsic performance is highly consistent with the demand of microwave communication, and it is the only candidate material that can cover high frequency, low loss and high stability. Although BaM material is suitable for microwave communication scenarios, traditional polycrystalline BaM thin films or bulk materials have obvious shortcomings: the grain boundaries in the polycrystalline structure will cause magnetic domain scattering, resulting in increased microwave frequency loss; bulk materials cannot achieve micron-level thickness control and are difficult to integrate with microwave chips. The BaM single crystal thin film solves these problems through atomic-level ordering and becomes the "core material solution" for microwave communication magnetic devices.

[0003] Although the application prospect of BaM single crystal thin film is broad, its preparation technology still faces multiple challenges. At present, radio frequency magnetron sputtering and pulsed laser deposition are the main methods for preparing BaM single crystal thin film, but these two methods have common problems: the lattice constant difference between the thin film and the substrate is large, the lattice mismatch degree is high, which leads to the easy occurrence of cracks and other defects in the thin film growth process, thereby reducing the quality and performance of the thin film and failing to meet the application requirements of actual devices. Although the introduction of a buffer layer can improve the quality and performance of the thin film, the process is complex and the cost is high, which makes it difficult to realize large-scale production. Liquid phase epitaxy is an effective technical path for preparing BaM single crystal thin film, which has obvious advantages: on the one hand, the growth temperature is relatively low, and the requirement for high temperature resistance of the equipment is more relaxed; on the other hand, the interface bonding force between the thin film and the substrate can be enhanced, thereby effectively reducing the defects of the thin film. However, the core bottleneck of this method is still focused on "substrate matching" - if the lattice mismatch degree between the substrate and BaM is high, even in a liquid phase growth environment, the thin film will still crack and the magnetic performance will be significantly degraded due to the interface stress during the thin film growth process. To address the aforementioned shortcomings, this invention proposes a method for preparing BaM single-crystal thin films via homoepitaxial growth. Compared to heteroepitaxial growth, the greatest advantage of homoepitaxial growth lies in the absence of lattice mismatch and thermal mismatch issues between the epitaxial layer and the substrate. Since the lattice structure and thermal expansion coefficient of the epitaxial layer and the substrate are completely identical, the aforementioned defects can be avoided at the source, thereby growing high-quality, low-defect single-crystal thin films that fully utilize their intrinsic excellent magnetic properties, providing a solid material foundation for the fabrication of high-performance permanent magnet devices. Summary of the Invention

[0004] This invention addresses the problems of easy cracking, high defect density, and poor magnetic properties in the preparation of barium ferrite single crystal thin films by heteroepitaxial epitaxy due to lattice mismatch and thermal mismatch. It proposes a homoepitaxial preparation method for BaM single crystal thin films, along with its application.

[0005] The technical solution adopted in this invention is as follows: A method for preparing BaM single-crystal thin films via homoepitaxial growth, comprising: Step 1: Preparation of melt: Using BaCO3 and Fe2O3 as raw materials and K2CO3, Bi2O3, and B2O3 as fluxes, weigh the above raw materials and fluxes, mix and melt them to obtain a uniformly mixed melt; Step 2, Homoepitaxial growth of thin film: BaM seed crystal is immersed in the melt as a substrate and homoepitaxial growth is carried out at a temperature of 870~910℃ to form a BaM single crystal thin film on the substrate. Step 3: Remove the film: Remove the BaM single crystal film and clean it to obtain the cleaned BaM single crystal film.

[0006] Optionally, the raw material molar ratio used in the melt is: BaCO3 1%~5%, Fe2O3 10%~14%, K2CO3 50%~65%, Bi2O3 30~50%, and B2O3 3%~7%.

[0007] Optionally, the mixing step includes: placing the raw materials and flux in a tumbler for mixing for 10-14 hours.

[0008] Optionally, the melting step includes: heating the mixed material to 1060°C to melt and stirring, with the melting time being 10~14h and the stirring time being 10~14h.

[0009] Optionally, the homoepitaxial growth step includes: lowering a fixture with a substrate to a position 10-30 mm above the melt at a speed of 10-30 mm / min at a temperature of 870-910°C, preheating for 10-15 min, and then lowering it to contact the melt surface to start growth, with a rotation speed of 50-70 rpm / min, a rotation cycle of 6-15 s, and a growth time of 15-25 h.

[0010] Optionally, the step of removing the BaM single crystal thin film includes: lifting the fixture to the furnace opening of the crystal growth furnace at a speed of 5~10 mm / min, and then removing the fixture.

[0011] Optionally, the cleaning steps include: cleaning with hot dilute nitric acid, followed by rinsing with deionized water.

[0012] Optionally, the method further includes cutting, grinding, polishing, and cleaning the BaM single crystal film.

[0013] Optionally, the grinding uses diamond polishing slurry, and the grinding disc rotates at a speed of 20~60 rpm / min; the polishing uses chemical polishing slurry, and the polishing disc rotates at a speed of 20~60 rpm / min; the cleaning uses deionized water.

[0014] The present invention also provides a method for preparing BaM single crystal thin films by homoepitaxial growth, wherein the BaM single crystal thin films prepared by homoepitaxial growth are obtained by the above-described method for preparing BaM single crystal thin films by homoepitaxial growth.

[0015] This invention also provides an application of homoepitaxial BaM single-crystal thin films in the fabrication of permanent magnet devices.

[0016] The beneficial effects of this invention are as follows: 1. The homoepitaxial growth of BaM single crystal thin films of the present invention has many advantages such as high crystal structure matching degree, excellent performance and good controllability of preparation process. Since the epitaxial layer and the substrate are the same material and have the same lattice constant, there is no lattice mismatch problem. This makes the growth process relatively simple, effectively reduces the generation of defects such as cracks, and can obtain high-quality single crystal thin films, thereby improving the stability and reliability of the thin film.

[0017] 2. The BaM single crystal thin film prepared by this invention has excellent performance and can realize the miniaturization and integration of devices.

[0018] 3. The process flow of this invention is simpler and more controllable. The equipment used does not require special customization, making it suitable for large-scale industrial production. This helps to significantly reduce the production cost of high-quality BaM single crystal thin films and promotes their widespread application. Attached Figure Description

[0019] Figure 1This is a photograph of the BaM single-crystal thin film prepared in Example 1 of the present invention.

[0020] Figure 2 This is a hysteresis loop test diagram of the BaM single crystal thin film prepared in Example 1 of the present invention. Detailed Implementation

[0021] The present invention will be further described in detail below with reference to experimental examples and specific embodiments. However, this should not be construed as limiting the scope of the above-mentioned subject matter of the present invention to the following embodiments; all technologies implemented based on the content of the present invention fall within the scope of the present invention.

[0022] This invention provides a method for preparing BaM single-crystal thin films via homoepitaxial growth, comprising: Step 1: Prepare the melt: Use BaCO3 and Fe2O3 as raw materials, and K2CO3, Bi2O3 and B2O3 as fluxes. Weigh the above raw materials and fluxes, mix and melt them to obtain a uniformly mixed melt.

[0023] In this embodiment, the molar ratio of the raw materials used in the melt is as follows: BaCO3 1%~5%, Fe2O3 10%~14%, K2CO3 50%~65%, Bi2O3 30%~45%, and B2O3 3%~7%. For example, BaCO3 is 2%, 3%, and 4%; Fe2O3 is 11%, 12%, and 13%; K2CO3 is 50%, 51%, and 52%; Bi2O3 is 39%, 40%, and 41%; and B2O3 is 4%, 5%, and 6%. This flux system (K2CO3, Bi2O3, and B2O3) of the present invention can effectively dissolve BaCO3 and Fe2O3 as solutes at a relatively low temperature, forming a supersaturated solution suitable for crystal growth.

[0024] In this embodiment, the mixing step includes: placing the raw materials and flux in a tumbler for mixing for 10-14 hours. For example, mixing for 11 hours, 12 hours, or 13 hours.

[0025] In this embodiment, the melting step includes: heating the mixed material to 1060°C to melt and stirring for 10-14 hours, for example, melting for 11, 12, or 13 hours, and stirring for 10-14 hours, for example, holding at that temperature for 11, 12, or 13 hours. This invention uses a temperature of 1060°C for melting and stirring to ensure that all components are completely melted and form a homogeneous melt, laying the foundation for subsequent high-quality epitaxial growth.

[0026] Step 2, Homoepitaxial growth of thin film: BaM seed crystal is immersed in the melt as a substrate and homoepitaxial growth is carried out at a temperature of 870~910℃ to form a BaM single crystal thin film on the substrate.

[0027] In this embodiment, the substrate and the thin film have the same structure, both being BaM seed crystals. There is no lattice mismatch between the seed crystal and the thin film, which can effectively prevent cracking during thin film growth.

[0028] In this embodiment, the method for preparing BaM seed crystals includes: Step 1, mixing and melting BaCO3, Fe2O3 and K2CO3 as flux to obtain a uniform melt; Step 2, primary growth of seed crystals: keeping the melt at a constant temperature and cooling it in stages to allow the seed crystals to spontaneously nucleate and grow, obtaining initial seed crystals; Step 3, separating and cleaning seed crystals: separating and cleaning the initial seed crystals from the solidified melt; Step 4, secondary growth of seed crystals: performing secondary growth on the cleaned initial seed crystals to obtain BaM seed crystals.

[0029] In step 1, the molar ratio of the raw materials used in the melt is: BaCO3 4%~6%, Fe2O3 6%~24%, and K2CO3 70%~90%. The mixing step includes: placing BaCO3, Fe2O3, and K2CO3 (as a flux) in a rolling mill for mixing; wherein the mixing time is 10~14 hours. The melting step includes: heating to 1150℃ for melting and stirring; wherein the melting time is 10~14 hours. In step 2, the staged cooling step includes: cooling at a rate of 0.005~5℃ / min within a temperature range of 1150~25℃. Specifically, the cooling step within the temperature range of 1150~25℃ at a cooling rate of 0.005~5℃ / min includes: a cooling rate of 2~5℃ / min within the temperature range of 1150~1125℃; a cooling rate of 0.005~0.02℃ / min within the temperature range of 1125~1020℃; a cooling rate of 0.05~1℃ / min within the temperature range of 1020~920℃; and a cooling rate of 1~5℃ / min within the temperature range of 920~25℃. The heat preservation step includes: maintaining the temperature at 1150℃ for 10~14 hours. In step 3, the cleaning step includes: using dilute nitric acid with a volume ratio of 1:1 to clean the solidified melt containing the initial seed crystal at a temperature of 60~90℃ until the initial seed crystal is completely separated from the melt. In step 4, the temperature for the secondary growth is 1080~1020℃, and the rotation speed is 50~70 rpm / min. After the secondary growth step, the process further includes cleaning, grinding, and polishing the seed crystal obtained after the secondary growth; the cleaning is performed using dilute nitric acid and deionized water, respectively, and the grinding and polishing are performed at a rotation speed of 30~50 rpm / min.

[0030] The high-quality BaM seed crystal of this invention can fundamentally solve the lattice mismatch problem and realize the high-quality and low-cost growth of BaM single crystal thin films.

[0031] In this embodiment, the homoepitaxial growth step includes: lowering a fixture with a substrate to a position 10-30 mm above the melt at a speed of 10-30 mm / min at a temperature of 870-910°C, preheating for 10-15 min, then lowering it to contact the melt surface to begin growth, with a rotation speed of 50-70 rpm, a rotation cycle of 6-15 s, and a growth time of 15-25 h. For example, the temperature can be 880°C, 890°C, or 900°C. The speed can be 15 mm / min, 20 mm / min, or 25 mm / min. The preheating time can be 12 min or 14 min. The rotation speed can be 55 rpm, 60 rpm, or 65 rpm. The rotation cycle can be 7 s, 8 s, or 9 s. The growth time can be 17 h, 20 h, or 22 h. The fixture is a platinum fixture. Here, when the temperature is lowered to 870~910℃, homoepitaxial growth is performed after the melt temperature stabilizes. The preheating step of this invention can effectively reduce the temperature difference between the substrate and the melt at the moment of contact, avoiding substrate cracking due to thermal shock.

[0032] In this embodiment, the step of removing the BaM single-crystal thin film includes: lifting the fixture to the furnace opening at a rate of 5-10 mm / min, and then removing the fixture. For example, the rate can be 7 mm / min, 8 mm / min, or 9 mm / min. This invention employs a slow, uniform lifting method of 5-10 mm / min, which effectively reduces the temperature exchange rate between the thin film and the growth environment, avoiding new interfacial stresses and microscopic defects caused by sudden temperature changes, and further ensuring the high-quality growth of the single-crystal thin film.

[0033] Step 3: Remove the film: Remove the BaM single crystal film and clean it to obtain the cleaned BaM single crystal film.

[0034] In this embodiment, the cleaning steps include: cleaning with hot dilute nitric acid, followed by rinsing with deionized water. Here, the temperature of the hot dilute nitric acid is 90~120℃.

[0035] In this embodiment, the method further includes cutting, grinding, polishing, and cleaning the BaM single-crystal thin film. Specifically, the cleaned film is first thinned to remove the substrate surface; then it is cut, ground, polished, and cleaned to obtain the BaM single-crystal thin film of the present invention. Here, diamond polishing slurry is used for grinding, and the rotation speed of the polishing disc is 20~60 rpm / min. For example, the rotation speed can be 35 rpm / min, 40 rpm / min, or 45 rpm / min. Chemical polishing slurry is used to smooth the film surface, and the rotation speed of the polishing disc is 20~60 rpm / min. For example, the rotation speed can be 35 rpm / min, 40 rpm / min, or 45 rpm / min. Deionized water is used for cleaning.

[0036] The present invention also provides a method for preparing BaM single crystal thin films by homoepitaxial growth, wherein the BaM single crystal thin films prepared by homoepitaxial growth are obtained by the above-described method for preparing BaM single crystal thin films by homoepitaxial growth.

[0037] This invention also provides an application of homoepitaxial BaM single-crystal thin films in the fabrication of permanent magnet devices.

[0038] The present invention will be described in detail below through embodiments and experimental examples. However, these are merely examples and do not limit the present invention in any way.

[0039] Example 1 This invention provides a method for preparing BaM single-crystal thin films via homoepitaxial growth, comprising the following steps: (1) Preparation of melt: Using BaCO3 and Fe2O3 as raw materials and K2CO3, Bi2O3 and B2O3 as fluxes, prepare a total mass of 5Kg of raw materials, in which the molar amount of BaCO3 is 3%, the molar amount of Fe2O3 is 10%, the molar amount of K2CO3 is 53%, the molar amount of Bi2O3 is 31%, and the molar amount of B2O3 is 3%. Calculate the mass of BaCO3, Fe2O3, K2CO3, Bi2O3 and B2O3 respectively, accurately weigh them and put them into a rolling barrel for mixing for 12h. After mixing, put them into a crucible, heat to 1060℃ to melt and stir for 12h to obtain a homogeneous melt.

[0040] (2) Homoetheographic growth of thin films: The temperature was lowered to 885℃ and held for 2 hours. After the melt stabilized, the platinum jig with the substrate was lowered to 20 mm above the melt at a rate of 20 mm / min and preheated for 15 min. Then, the platinum jig with the substrate was lowered to contact the melt (a bright halo appeared around the substrate) and the thin film growth began. The rotation speed was 60 rpm / min, the rotation cycle was 12 s, and the growth time was 20 hours.

[0041] (3) Remove the film: After the growth is completed, lift the fixture to the furnace mouth of the crystal growth furnace at a rate of 8 mm / min, then remove the fixture and clean it in hot dilute nitric acid, and finally clean it with deionized water.

[0042] (4) Thin film processing: First, the cleaned seed crystal is thinned to remove the substrate surface; then, it is cut, ground, polished and cleaned. Diamond grinding fluid is used for grinding, and the grinding wheel speed is 50 rpm / min; chemical polishing fluid is used to smooth the film surface, and the polishing wheel speed is 50 rpm / min; finally, deionized water is used to clean the seed crystal to obtain the BaM single crystal thin film of the present invention.

[0043] like Figure 1 The image shown is a physical image of the BaM single crystal thin film prepared in Example 1, with a film thickness of 630 μm.

[0044] like Figure 2 As shown, the hysteresis loop diagram of the BaM single crystal thin film prepared in Example 1 shows that the saturation magnetization and magnetocrystalline anisotropy field are almost the same as those of the bulk single crystal, indicating excellent magnetic properties.

[0045] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a BaM single crystal thin film by homoepitaxy, characterized by, The application relates to a method for preparing a BaM single crystal thin film by homogeneous epitaxy. The method comprises the following steps: 1, preparing a melt: taking BaCO3 and Fe2O3 as raw materials, K2CO3, Bi2O3 and B2O3 as fluxes, weighing the raw materials and the fluxes, mixing and melting the raw materials and the fluxes to obtain a homogeneous melt; 2, growing a thin film by homogeneous epitaxy: immersing a BaM seed crystal as a substrate into the melt, and growing a BaM single crystal thin film on the substrate by homogeneous epitaxy at a temperature of 870-910 DEG C; and 3, taking out the thin film: taking out the BaM single crystal thin film, and cleaning the BaM single crystal thin film to obtain a cleaned BaM single crystal thin film. The molar ratio of the raw materials for the melt is as follows: 1-5% of BaCO3, 10-14% of Fe2O3, 50-65% of K2CO3, 30-50% of Bi2O3 and 3-7% of B2O3. The mixing step comprises the following steps: placing the raw materials and the fluxes in a rolling barrel to mix the raw materials and the fluxes for 10-14 hours.

2. The production method according to claim 1, characterized by, The melting step comprises the following steps: heating the mixed materials to 1060 DEG C to melt and stir the mixed materials, wherein the melting time is 10-14 hours, and the stirring time is 10-14 hours.

3. The production method according to claim 1, characterized by, The homogeneous epitaxy growing step comprises the following steps: lowering a clamp with the substrate to a position 10-30 mm above the melt at a speed of 10-30 mm / min, preheating for 10-15 minutes, then lowering the clamp to contact the melt, starting to grow, rotating at a speed of 50-70 rpm / min, rotating for 6-15 seconds, and growing for 15-25 hours. The step of taking out the BaM single crystal thin film comprises the following steps: lifting the clamp to the mouth of the crystal growth furnace at a speed of 5-10 mm / min, and then taking out the clamp.

4. The method of claim 1, wherein, The cleaning step comprises the following steps: cleaning by using hot dilute nitric acid, and then cleaning by using deionized water.

5. The preparation method according to claim 4, characterized in that, The method further comprises the following steps:

6. The preparation method according to claim 4, characterized in that, Cutting, grinding, polishing and cleaning the BaM single crystal thin film.

7. The preparation method according to claim 1, characterized in that, The grinding uses a diamond grinding liquid, and the rotating speed of a grinding disc is 20-60 rpm / min. The polishing uses a chemical polishing liquid, and the rotating speed of a polishing disc is 20-60 rpm / min.

8. The preparation method according to claim 7, characterized in that, The cleaning uses deionized water. The BaM single crystal thin film prepared by homogeneous epitaxy is obtained by the method for preparing a BaM single crystal thin film by homogeneous epitaxy according to any one of claims 1-8.

10. The application of the BaM single crystal thin film prepared by homogeneous epitaxy in claim 9 in the preparation of a permanent magnet device.

9. A homoepitaxially produced BaM single crystal thin film, characterized by comprising a BaM single crystal thin film having a thickness of 1 to 1000 nm. ​ ​

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