Preparation method of corner combined magnetoelectric single crystal heterojunction and magnetoelectric heterojunction

Abstract

A preparation method of a corner combined magnetoelectric single crystal heterojunction and a magnetoelectric heterojunction, comprising: sequentially epitaxially growing a single crystal sacrificial layer and a ferromagnetic single crystal layer on a substrate to obtain a single crystal thin film; bonding the single crystal thin film on a piezoelectric single crystal substrate with electrodes, measuring the included angle between the edge of the epitaxial substrate and the edge of the piezoelectric single crystal substrate, and twisting the thin film to the required angle; dissolving the single crystal sacrificial layer with deionized water to separate the epitaxial substrate from the target thin film to obtain a corner magnetoelectric heterojunction. The application provides a preparation process of a corner magnetoelectric single crystal heterojunction, which can prepare a novel oxide heterolayer composite structure through steps of epitaxial growth, thin film corner combination and sacrificial layer dissolution, so as to realize the regulation of the target thin film magnetic performance by an editable stress mode.

Description

Technical Field

[0001] This invention belongs to the field of magnetoelectric coupling devices, and particularly relates to a method for preparing a corner-connected magnetoelectric single-crystal heterojunction and the magnetoelectric heterojunction itself. Background Technology

[0002] Functional oxide thin films, due to their excellent properties, are widely used in core electronic devices in many key fields such as information, medical, military, and aerospace, including sensors, memories, logic gates, and microwave devices. Stress-controlled material properties in functional oxide magnetoelectric heterostructures are fundamental to realizing these various functional devices. However, due to the intrinsic characteristics of epitaxial growth, the crystal orientation of the target material is fixed by the epitaxial substrate, limiting the magnitude and mode of applied stress. Therefore, how to freely apply stress to induce changes in the crystal structure of functional oxides, thereby manipulating their key properties and achieving specific functions, is a crucial problem that urgently needs to be solved. Summary of the Invention

[0003] The purpose of this invention is to provide a method for preparing a corner-joined magnetoelectric single-crystal heterojunction and a magnetoelectric heterojunction, so as to solve the problem that the crystal orientation of the target material is fixed by the epitaxial substrate, which limits the magnitude and mode of the applied stress.

[0004] To achieve the above objectives, the present invention adopts the following technical solution:

[0005] A method for fabricating a corner-joined magnetoelectric single-crystal heterojunction, comprising:

[0006] A single-crystal thin film is obtained by epitaxially growing a single-crystal sacrificial layer and a ferromagnetic single-crystal layer sequentially on a substrate.

[0007] A single-crystal thin film is bonded to a piezoelectric single-crystal substrate with electrodes. The angle between the edge of the epitaxial substrate and the edge of the piezoelectric single-crystal substrate is measured, and the thin film is twisted to adjust it to the required angle.

[0008] Deionized water was used to dissolve the single-crystal sacrificial layer to separate the epitaxial substrate from the target thin film, resulting in a corner magnetoelectric heterojunction.

[0009] Furthermore, a single-crystal sacrificial layer and a ferromagnetic single-crystal layer are epitaxially grown sequentially on the substrate:

[0010] The hot stage was placed in the pulsed laser deposition system and the following steps were performed in sequence: vacuuming, heating, oxygen supply, pre-sputtering, deposition growth, and in-situ annealing. The sacrificial layer Sr3Al2O6 and the target ferromagnetic oxide film were epitaxially grown sequentially.

[0011] Further, substrate preparation: The single crystal substrate was ultrasonically cleaned with acetone and ethanol in sequence, the residual liquid was dried with nitrogen, the substrate was attached to the hot stage surface of the pulsed laser deposition system with silver paste, and dried at 120°C for 5 minutes.

[0012] Furthermore, the single-crystal substrate is either strontium titanate (SrTiO3) or lanthanum strontium aluminum tantalum (LSAT).

[0013] Furthermore, the single-crystal thin film is bonded to a piezoelectric single-crystal substrate with electrodes:

[0014] A high Young's modulus resin adhesive is applied to the surface of a piezoelectric substrate on which electrodes are deposited. The target film grown epitaxially is then directly attached to the surface of the piezoelectric substrate. After curing, the angle between the edge of the epitaxial substrate and the edge of the piezoelectric substrate is measured, and the film is twisted to adjust it to the required angle.

[0015] Further, piezoelectric substrate electrode preparation: The piezoelectric substrate is placed in a sample tray and then placed in a magnetron sputtering system to perform vacuuming and sputtering deposition steps in sequence, and electrodes are deposited on its upper and lower surfaces.

[0016] Furthermore, the piezoelectric single crystal substrate is selected from PMN-PT, PZN-PT or PZT, with a tangential orientation of 001, 011 or 111. Various piezoelectric single crystal materials have different piezoelectric coefficients, and different tangential orientations have different piezoelectric strain modes.

[0017] Furthermore, after curing, deionized water is used to dissolve the single-crystal sacrificial layer to separate the epitaxial substrate from the target thin film:

[0018] Remove the mold from the solidified sample and dissolve it in deionized water for 3-6 hours. Once the sacrificial layer is completely dissolved, remove the sample and dry the surface with nitrogen to obtain a corner magnetoelectric heterojunction.

[0019] Further, the resin adhesive is cured: pressure is applied to the upper and lower surfaces of the bonded structure using a mold, and the structure is heated at 100-120℃ for 10-30 minutes to allow the resin adhesive to fully cure; the thickness of the resin adhesive is between 1-10 μm.

[0020] Furthermore, a magnetoelectric heterojunction is fabricated based on a method for preparing a corner-bonded magnetoelectric single-crystal heterojunction.

[0021] Compared with the prior art, the present invention has the following technical effects:

[0022] This invention provides a fabrication process for a corner magnetoelectric single-crystal heterostructure, which can prepare a novel oxide heterolayer composite structure through steps such as epitaxial growth, thin film corner bonding and sacrificial layer dissolution, so as to achieve the control of the magnetic properties of the target thin film by editable stress modes.

[0023] Furthermore, with the transfer method provided by this invention, the orientation of the ferromagnetic single crystal thin film can be arbitrarily selected, and the material and tangential of the piezoelectric single crystal substrate can also be freely selected, greatly expanding the range of material selection and tunable physical effects.

[0024] Furthermore, the ferromagnetic single-crystal thin film and the piezoelectric substrate can be twisted arbitrarily during the bonding process, which can change the piezoelectric strain mode of the target thin film, thereby changing the magnetoelectric coupling effect of the heterojunction. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the preparation method of the present invention;

[0026] Figure 2 These are XRD comparison images of the ferromagnetic single crystal thin film before and after transfer in this invention (using 60nm epitaxial La). 0.67 Sr 0.33 (For example, MnO3);

[0027] Figure 3 This is a photograph of the actual magnetoelectric heterostructure in this invention;

[0028] Figure 4 These are the TEM images and selected area electron diffraction images of the cross-section of the magnetoelectric heterostructure (with 60nm epitaxial La). 0.67 Sr 0.33 (For example, MnO3);

[0029] Figure 5 The above magnetoelectric heterojunction exhibits magnetoelectric coupling performance (based on 60nm epitaxial La). 0.67 Sr 0.33 (For example, MnO3);

[0030] Figure 6 In the diagram, a is the magnetization curve of the easy and difficult axis of a single-crystal magnetoelectric heterojunction with a 0-degree turn, and b is the magnetization curve of the easy and difficult axis of a single-crystal magnetoelectric heterojunction with a 45-degree turn (based on a 60nm epitaxial La). 0.67 Sr 0.33 (MnO3 as an example). Detailed Implementation

[0031] The invention is further described below with reference to the accompanying drawings. The invention is described in detail below with reference to specific exemplary embodiments. However, it should be understood that various modifications and variations can be made without departing from the scope of the invention as defined by the appended claims. The detailed description and drawings should be considered illustrative only and not restrictive, and any such modifications and variations will fall within the scope of the invention described herein.

[0032] This invention provides a fabrication process for a corner magnetoelectric single-crystal heterostructure, which can prepare a novel oxide heterolayer composite structure through steps such as epitaxial growth, thin film corner bonding and sacrificial layer dissolution, so as to achieve a controllable magnetoelectric coupling effect.

[0033] To further explain, the fabrication process of the corner magnetoelectric single-crystal heterostructure described in this invention includes the following steps for preparing the ferromagnetic single-crystal thin film:

[0034] A single-crystal thin film is obtained by epitaxially growing a single-crystal sacrificial layer and a ferromagnetic single-crystal layer sequentially on a substrate.

[0035] A single-crystal thin film is bonded to a piezoelectric single-crystal substrate with electrodes. The angle between the edge of the epitaxial substrate and the edge of the piezoelectric single-crystal substrate is measured, and the thin film is twisted to adjust it to the required angle.

[0036] Deionized water was used to dissolve the single-crystal sacrificial layer to separate the epitaxial substrate from the target thin film, resulting in a corner magnetoelectric heterojunction.

[0037] Specifically:

[0038] Step (1) Substrate preparation: The single crystal substrate is ultrasonically cleaned with acetone and ethanol in sequence, the residual liquid is dried with nitrogen, the substrate is pasted onto the hot stage surface of the pulsed laser deposition system with silver paste, and dried at 120°C for 5 minutes.

[0039] Furthermore, in step (1), the single crystal substrate can be strontium titanate (SrTiO3), lanthanum strontium aluminum tantalum (LSAT), etc., and the substrate orientation can be selected according to the desired target ferromagnetic thin film orientation.

[0040] Step (2) Epitaxial growth of thin film: The hot stage is placed in the pulsed laser deposition system and the steps of vacuuming, heating, oxygen supply, pre-sputtering, deposition growth and in-situ annealing are performed in sequence to epitaxially grow the sacrificial layer Sr3Al2O6 and the target ferromagnetic oxide thin film in sequence.

[0041] Step (3) Preparation of piezoelectric substrate electrodes: Place the piezoelectric substrate in the sample tray and put it into the magnetron sputtering system to perform vacuuming and sputtering deposition steps in sequence, and deposit electrodes on its upper and lower surfaces;

[0042] Furthermore, in step (3), the piezoelectric single crystal substrate can be PMN-PT, PZN-PT, or PZT, and the tangential direction can be (001), (011), or (111). Among them, various piezoelectric single crystal materials have different piezoelectric coefficients, and different tangential directions have different piezoelectric strain modes.

[0043] Step (4) Corner bonding: Apply high Young's modulus resin adhesive to the surface of the piezoelectric substrate on which the electrodes are deposited, directly bond the epitaxially grown target film to the surface of the piezoelectric substrate, measure the angle between the edge of the epitaxial substrate and the edge of the piezoelectric substrate, and twist the film to adjust it to the required angle.

[0044] Furthermore, the angle between the ferromagnetic single crystal thin film and the piezoelectric single crystal substrate in step (4) can be arbitrarily selected.

[0045] Step (5) Resin adhesive curing: Apply pressure to the upper and lower surfaces of the bonded structure using a mold, and place the structure in an environment of 100-120℃ for 10-30 minutes to allow the resin adhesive to fully cure.

[0046] Furthermore, in step (5), the thickness of the resin adhesive varies depending on the applied pressure, ranging from 1 to 10 μm.

[0047] Step (6) Sacrificial layer dissolution: Remove the mold from the solidified sample and place it in deionized water to dissolve for 3-6 hours. After the sacrificial layer is completely dissolved, remove it and blow the surface dry with nitrogen to obtain a corner magnetoelectric heterojunction.

[0048] Specifically:

[0049] 1) A 3mm × 3mm × 0.5mm SrTiO3(001) substrate was ultrasonically cleaned with acetone and ethanol for 5 minutes each, then dried with nitrogen to remove residual liquid. The substrate was then attached to the hot stage of the pulsed laser deposition system using silver paste and dried at 120°C for 5 minutes. 2) The hot stage was placed in the pulsed laser deposition system, and a mechanical pump and a molecular pump were used to evacuate the system. When the vacuum level was below 1 × 10⁻⁶, the vacuum level was adjusted to 1 × 10⁻⁶. -5 The heating module is turned on when pa is reached, and the heating rate is 20℃ / min.

[0050] 2) When the temperature reaches 800℃, turn off the molecular pump and open the oxygen valve, open the mechanical pump valve, and adjust the oxygen pressure to 20 Pa.

[0051] 3) Adjust the laser path, turn on the target rotation, and pre-sputter the Sr3Al2O6 target at a frequency of 5Hz for 5 minutes. The laser power is 1.4W / cm². 2 ;

[0052] 4) Open the baffle and start the epitaxial growth of Sr3Al2O6. The laser frequency is 2Hz and the growth time is 10min.

[0053] 5) Adjust the oxygen pressure to 30 Pa, close the baffle, and apply oxygen to La at a frequency of 5 Hz. 0.67 Sr 0.33 MnO3 target pre-sputtering was performed for 5 minutes at a laser power of 1.4 W / cm². 2 ;

[0054] 6) Open the baffle and begin epitaxial growth of La. 0.67 Sr 0.33 MnO3, laser frequency of 2Hz, growth time of 20min;

[0055] 7) After growth, maintain oxygen pressure and anneal in situ for 10 min; then cool to 500℃ at a rate of 10℃ / min; then allow to cool naturally. The thickness of the ferromagnetic single crystal film grown under the above conditions is 60 nm.

[0056] For further explanation, please refer to the appendix. Figure 1 The present invention discloses a fabrication process for a corner magnetoelectric single-crystal heterojunction structure, the fabrication of which includes the following steps:

[0057] 1) The PMN-PT(011) piezoelectric substrate was placed in the sample tray and then placed in the magnetron sputtering system for vacuuming and sputtering deposition steps, with 50nm Pt electrodes deposited on the upper and lower surfaces; further, under the applied electric field, the PMN-PT substrate with (011) tangential orientation was provided with compressive strain and tensile strain along the two crystal orientations

[100] and [01-1] of the substrate edge, respectively, and their typical piezoelectric coefficients were d 100 = -1800pC / N,d 01-1 =900pC / N, piezoelectric strain exhibits uniaxial anisotropy.

[0058] 2) Apply approximately 0.01 ml of high Young's modulus resin adhesive to the surface of the PMN-PT piezoelectric substrate with deposited Pt electrodes. The amount of resin adhesive should not be excessive; just enough to avoid overflowing the edges of the ferromagnetic film is optimal. Then apply the epitaxially grown La... 0.67 Sr 0.33 The MnO3 thin film is directly attached to the substrate surface. The angle between the edge of the epitaxial substrate and the edge of the piezoelectric substrate is measured using a protractor to determine the required rotation angle.

[0059] 3) Apply pressure to the upper and lower surfaces of the adhesive structure using a mold, and heat the structure at 100-120℃ for 10-30 minutes to allow the resin to fully cure, with a resin thickness of 1µm. 4) Remove the mold from the cured sample, place it in deionized water for 6 hours to dissolve, and remove it after the sacrificial layer has completely dissolved. Dry the surface with nitrogen gas to obtain the corner La. 0.67 Sr 0.33 MnO3 / PMN-PT magnetoelectric heterojunction.

[0060] To further explain, the La prepared in the above steps 0.67 Sr 0.33 In the MnO3(001) / PMN-PT(011) heterostructure, the ferromagnetic single crystal film and the piezoelectric single crystal have different orientations, which is impossible to achieve by epitaxial growth to construct heterojunctions. The separation of the film from the epitaxial substrate allows the heterostructure components to be freely combined.

[0061] For further explanation, please refer to the appendix. Figure 1 The present invention also includes changing La 0.67 Sr 0.33 The torsion angle of MnO3 single crystal thin film and PMN-PT piezoelectric single crystal, edited to the effect of an electric field on La. 0.67 Sr 0.33The strain magnitude and mode of MnO3 single-crystal thin films induce different magnetoelectric coupling effects. This method can achieve significant inverse magnetoelectric coupling effects and greatly broadens the research scope of functional magnetic oxides through stress modulation. The invention is described in detail below with reference to specific exemplary embodiments.

[0062] Example 1

[0063] The epitaxial La used in this embodiment 0.67 Sr 0.33 The MnO3 thin film was grown according to the above-described ferromagnetic single crystal thin film preparation steps, with a thickness of 60 nm. (See attached diagram.) Figure 2 It exhibits good single crystallinity and leaves no sacrificial layer residue after transfer. Referring to the heterojunction preparation steps described above in this invention, La was selected. 0.67 Sr 0.33 A magnetoelectric heterojunction was prepared by bonding a MnO3(001) single crystal thin film with a PMN-PT(011) single crystal piezoelectric substrate at an angle of 0°.

[0064] Example 2

[0065] The basic content of this embodiment is the same as that of embodiment 1, except that La is selected. 0.67 Sr 0.33 A magnetoelectric heterojunction was prepared by bonding a MnO3(001) single crystal thin film and a PMN-PT(011) single crystal piezoelectric substrate at an angle of 45°.

[0066] See attached document Figure 3-4 The rotation angle La prepared in Examples 1 and 2 of the present invention 0.67 Sr 0.33 MnO3(001) / PMN-PT(011) magnetoelectric heterostructure with La 0.67 Sr 0.33 The MnO3 thin film exhibits high integrity and appears relatively smooth under an optical microscope. Furthermore, the epitaxial La in the examples described in this invention... 0.67 Sr 0.33 The rotation angles of the MnO3 thin film and the PMN-PT piezoelectric substrate are given by optical photographs, and the relationship between their layered composite structure and crystal orientation is confirmed by cross-sectional TEM photographs and electron diffraction images.

[0067] Comparing Example 1 and Example 2

[0068] See attached document Figure 5 In Embodiments 1 and 2 of the present invention, the turning angle La 0.67 Sr 0.33 Both MnO3(001) / PMN-PT(011) heterostructures can achieve good stress transfer. For samples with 0° and 45° rotation angles, the magnetoelectric coupling coefficients are 20.07 Oe·cm / kV and 26.18 Oe·cm / kV, respectively.

[0069] See attached document Figure 6 In Embodiments 1 and 2 of the present invention, the turning angle La 0.67 Sr 0.33 The magnetization curves induced by the electric field in the MnO3(001) / PMN-PT(011) heterostructure exhibit different anisotropy. This confirms that the rotation angle alters the magnetization curves acting on La. 0.67 Sr 0.33 The magnitude and mode of piezoelectric strain in MnO3 single-crystal thin films can be used to manipulate the magnetoelectric coupling effect.

[0070] Further explanation: The La selected in Examples 1 and 2 0.67 Sr 0.33 The MnO3(001) thin films grown under the same conditions exhibit the same intrinsic magnetic anisotropy. The only difference lies in the torsion angle, thus confirming the effectiveness of the preparation method described in this invention.

[0071] This invention provides a simple and effective method for fabricating a twist-coupled magnetoelectric single-crystal heterojunction. This method alters the strain mode acting on the ferromagnetic single-crystal thin film by manipulating the twist angle between the epitaxial thin film and the piezoelectric substrate, thereby achieving free control over the stress mode applied to the ferromagnetic single-crystal thin film. This significantly broadens the research scope of stress-controlled functional magnetic oxides and enables significant inverse magnetoelectric coupling effects, possessing potential application value in the development of novel magnetoelectric sensors, tunable microwave devices, and logic devices.

[0072] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a corner-joined magnetoelectric single-crystal heterojunction, characterized in that, include: A single-crystal thin film is obtained by epitaxially growing a single-crystal sacrificial layer and a ferromagnetic single-crystal layer sequentially on a substrate. The single-crystal thin film is bonded to a piezoelectric single-crystal substrate with electrodes, the angle between the edge of the epitaxial substrate and the edge of the piezoelectric single-crystal substrate is measured, and the thin film is twisted to adjust to the required angle. The single-crystal sacrificial layer was dissolved using deionized water to separate the epitaxial substrate from the target thin film, resulting in a corner magnetoelectric heterojunction. The single-crystal thin film is bonded to a piezoelectric single-crystal substrate with electrodes: A high Young's modulus resin adhesive is applied to the surface of a piezoelectric substrate on which electrodes are deposited. The target film grown epitaxially is then directly attached to the surface of the piezoelectric substrate. After curing, the angle between the edge of the epitaxial substrate and the edge of the piezoelectric substrate is measured, and the film is twisted to adjust it to the required angle.

2. The method for preparing a twist-bonded magnetoelectric single-crystal heterojunction according to claim 1, characterized in that, A single-crystal sacrificial layer and a ferromagnetic single-crystal layer are epitaxially grown sequentially on the substrate: The hot stage was placed in the pulsed laser deposition system and the following steps were performed in sequence: vacuuming, heating, oxygen supply, pre-sputtering, deposition growth, and in-situ annealing. The sacrificial layer Sr3Al2O6 and the target ferromagnetic oxide film were epitaxially grown sequentially.

3. The method for preparing a twist-bonded magnetoelectric single-crystal heterojunction according to claim 2, characterized in that, Substrate preparation: The single crystal substrate was ultrasonically cleaned with acetone and ethanol in sequence, the residual liquid was dried with nitrogen, the substrate was attached to the hot stage surface of the pulsed laser deposition system with silver paste, and dried at 120°C for 5 minutes.

4. The method for preparing a twist-bonded magnetoelectric single-crystal heterojunction according to claim 3, characterized in that, The single-crystal substrate is either strontium titanate (SrTiO3) or lanthanum strontium aluminum tantalum (LSAT).

5. The method for preparing a twist-bonded magnetoelectric single-crystal heterojunction according to claim 1, characterized in that, Piezoelectric substrate electrode preparation: The piezoelectric substrate is placed in the sample tray and put into the magnetron sputtering system to perform vacuuming and sputtering deposition steps in sequence, and electrodes are deposited on its upper and lower surfaces.

6. The method for preparing a twist-bonded magnetoelectric single-crystal heterojunction according to claim 5, characterized in that, The piezoelectric single crystal substrate is selected from PMN-PT, PZN-PT or PZT, with tangential orientations of 001, 011 or 111. Various piezoelectric single crystal materials have different piezoelectric coefficients, and different tangential orientations have different piezoelectric strain modes.

7. The method for preparing a twist-bonded magnetoelectric single-crystal heterojunction according to claim 1, characterized in that, After curing, deionized water is used to dissolve the single-crystal sacrificial layer to separate the epitaxial substrate from the target thin film. Remove the mold from the solidified sample and dissolve it in deionized water for 3-6 hours. Once the sacrificial layer is completely dissolved, remove the sample and dry the surface with nitrogen to obtain a corner magnetoelectric heterojunction.

8. The method for preparing a twist-bonded magnetoelectric single-crystal heterojunction according to claim 7, characterized in that, Resin adhesive curing: Apply pressure to the upper and lower surfaces of the bonded structure using a mold, and heat the structure at 100-120℃ for 10-30 minutes to allow the resin adhesive to fully cure; the resin adhesive thickness is between 1-10µm.

9. A magnetoelectric heterojunction, characterized in that, It is made based on the method according to any one of claims 1 to 8.

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