Strain two-dimensional magnetic tunnel junction device and preparation method thereof

Abstract

The invention relates to a strain two-dimensional magnetic tunnel junction device and a preparation method thereof, and the device comprises a strain substrate located at the bottom, a two-dimensional ferromagnetic free layer located on the substrate, a bottom metal electrode located at one side of the upper part of the two-dimensional ferromagnetic free layer, and a bottom metal electrode located at the other side of the upper part of the two-dimensional ferromagnetic free layer. The device comprises a two-dimensional ferromagnetic free layer, a two-dimensional insulating tunneling layer located on the other side above the two-dimensional ferromagnetic free layer, a two-dimensional ferromagnetic pinning layer located on the two-dimensional insulating tunneling layer, an antiferromagnetic thin film layer located on the two-dimensional ferromagnetic pinning layer, and a top metal electrode located on the antiferromagnetic thin film layer. Controllable local lattice distortion is introduced into the two-dimensional magnetic crystal by using the nano patterned substrate, so that the spin-orbit coupling effect of the material is enhanced, the tunneling magnetoresistance of the device is remarkably improved, and the driving current density is reduced. Compared with the prior art, the method has more excellent controllability, universality and expandability, and lays a foundation for a new-generation high-performance spinning electronic device and the realization of functions such as logical operation and the like thereof.

Description

Technical Field

[0001] The present invention relates to the technical field of magnetic storage devices, and in particular to a strained two-dimensional magnetic tunnel junction device and a preparation method thereof. Background Art

[0002] With the rapid development of the information age, emerging technologies such as big data, artificial intelligence, and the Internet of Things have placed exponentially increasing demands on the performance of storage and sensing devices. Traditional semiconductor technology is facing increasingly prominent bottlenecks in power consumption, speed, and integration. Spintronics, a new discipline that has emerged in the field of condensed matter physics in recent years, uses electron spin states as information carriers. By effectively controlling the electron spin degrees of freedom, spintronic devices achieve near-zero power consumption for multifunctional applications such as data storage, logical operations, and quantum computing. This breaks through the limitations of traditional electronics that rely solely on charge control, opens up new avenues for the development of new functional devices with higher performance and lower power consumption, and is expected to become one of the core technologies of the next-generation quantum information industry.

[0003] The magnetic tunnel junction is one of the main structural units of spintronic devices. Its functionality is achieved through the tunneling magnetoresistance effect, and it has shown irreplaceable application potential in non-volatile storage, high-sensitivity sensing, and high-frequency microwave devices. In recent years, the introduction of two-dimensional magnetic materials has further expanded the performance boundaries of magnetic tunnel junction devices, bringing new opportunities for the development of magnetic tunnel junction devices. Compared with three-dimensional bulk materials, the atomic-level thickness of two-dimensional materials represents the physical limit of device size. Their flat, dangling bond-free surface allows heterogeneous stacking to be unrestricted by lattice mismatch and without the involvement of chemical bonds, which facilitates the design and construction of heterostructures and functional devices for different application scenarios. It is expected to achieve a breakthrough improvement in the performance of magnetic tunnel junction devices, bringing new possibilities for their application in ultra-high frequency devices (such as terahertz oscillators) and flexible electronics.

[0004] However, most of the two-dimensional magnetic materials reported so far generally face difficulties such as poor air stability, low critical temperature, lack of large-area synthesis technology, and poor compatibility with silicon-based semiconductor processes. Their development is also limited by the inherent defects of the material system and regulation methods, which restricts the practical application of materials and devices.

[0005] The magnetic tunnel junction memory cell mentioned in the comparative document CN110931633A introduces a phase change layer between the ferromagnetic reference layer and the ferromagnetic pinned layer, and uses external temperature or light changes to change the magnetization direction. However, this structure still has problems such as limited write speed, difficulty in further improving storage density, and limited reduction in power consumption. In particular, the introduction of phase change materials, although enhancing the functionality of the device to a certain extent, also leads to increased complexity of the device structure, increased difficulty in the preparation process, and the stability and reliability of the phase change materials still need to be improved.

[0006] On the other hand, the antiferromagnetic tunnel junction proposed in the comparative document CN116056551A uses non-collinear antiferromagnetic material layers as the reference layer and free layer, which has the advantages of fast write speed and high storage density. However, the preparation process of this device is relatively complicated and requires annealing in a magnetic field vacuum annealing furnace to enhance the exchange interaction between the pinned layer and the reference layer. In addition, the selection range of non-collinear antiferromagnetic materials is relatively narrow, and the preparation process requires extremely high precision, which to a certain extent limits its feasibility of large-scale production and practical application.

[0007] Therefore, there is an urgent need to provide a strained two-dimensional magnetic tunnel junction device and a preparation method thereof, so as to achieve a significant improvement in tunneling magnetoresistance, an effective reduction in driving current density, and simplify the preparation process and reduce costs. Summary of the Invention

[0008] The purpose of the present invention is to overcome the defects of the above-mentioned prior art and provide a strained two-dimensional magnetic tunnel junction device and its preparation method, which uses a patterned substrate to introduce controllable local lattice distortion in the two-dimensional magnetic crystal, enhance the spin-orbit coupling effect of the material, thereby significantly improving the tunneling magnetoresistance of the device and reducing the driving current density, and has better controllability, universality, scalability, and low process cost.

[0009] During the development of this invention, it was determined that the key to achieving diversified applications of two-dimensional magnetic tunnel junction devices lies in developing effective exogenous control technologies applicable to two-dimensional systems, enabling controllable modulation of the intrinsic quantum properties of the material without compromising the stability of the intrinsic magnetic order. Strain control technology, with its atomic-level control of the two-dimensional lattice, can effectively enhance magnetic anisotropy and optimize spin-polarized transport channels, providing a new approach to regulating the intrinsic magnetic transport properties of two-dimensional magnetic tunnel junction devices. This is expected to lead to breakthroughs in room-temperature stability, signal contrast, and integration density of two-dimensional magnetic tunnel junction devices.

[0010] The purpose of the present invention can be achieved by the following technical solutions:

[0011] The first aspect of the present invention provides a strained two-dimensional magnetic tunnel junction device, comprising: a patterned substrate, a two-dimensional ferromagnetic free layer, a bottom metal electrode, a two-dimensional insulating tunnel layer, a two-dimensional ferromagnetic pinning layer, an antiferromagnetic thin film layer, and a top metal electrode, wherein specifically:

[0012] A two-dimensional ferromagnetic free layer is provided on the patterned substrate;

[0013] A bottom metal electrode is provided on one side above the two-dimensional ferromagnetic free layer;

[0014] A two-dimensional insulating tunneling layer is provided on the other side of the two-dimensional ferromagnetic free layer;

[0015] A two-dimensional ferromagnetic pinning layer is provided on the two-dimensional insulating tunneling layer;

[0016] The antiferromagnetic film layer is provided on the two-dimensional ferromagnetic pinned layer;

[0017] A top metal electrode is located on the antiferromagnetic film layer;

[0018] The patterned substrate generates local lattice distortion in the two-dimensional ferromagnetic free layer through surface nanoscale patterns, thereby enhancing the spin-orbit coupling effect of the two-dimensional ferromagnetic free layer.

[0019] Furthermore, the surface nanoscale pattern of the patterned substrate includes a hole-shaped and / or strip-shaped ordered structure, the hole depth / strip height is 10-150nm, the hole diameter / strip width is 100-500nm, the hole diameter / strip spacing is 50-350nm, and the two-dimensional ferromagnetic free layer covers the surface of the ordered structure to produce local lattice distortion.

[0020] Furthermore, the material of the patterned substrate is selected from any one of silicon nitride / silicon, silicon oxide / silicon, hafnium oxide / silicon, and aluminum oxide / silicon;

[0021] The “ / ” above indicates a composite structure formed by two materials, that is, one material is deposited or grown on another material to form a substrate with specific functional and structural characteristics. For example, a “silicon nitride / silicon” substrate refers to a silicon material, on the basis of which a silicon nitride film is formed on the silicon surface through a certain process (such as chemical vapor deposition, physical vapor deposition, etc.). A “silicon oxide / silicon” substrate is a silicon oxide film grown or deposited on a silicon substrate. The silicon oxide film usually has excellent dielectric properties and thermal stability, can be used as an insulating layer or passivation layer, and can cooperate with the silicon substrate during the patterning process to achieve support for the upper material and performance regulation.

[0022] The two-dimensional ferromagnetic free layer is selected from any one of iron-germanium-tellurium compounds, chromium-germanium-tellurium compounds, manganese-bismuth-tellurium compounds, and cobalt-iron-boron compounds.

[0023] Furthermore, the bottom metal electrode is selected from any one or more of chromium, titanium, gold, nickel, tungsten, platinum, and palladium;

[0024] The two-dimensional insulating tunneling layer is selected from any one of hexagonal boron nitride, molybdenum oxide, and magnesium oxide.

[0025] Furthermore, the two-dimensional ferromagnetic pinning layer is selected from any one of iron-germanium-tellurium compounds, chromium-germanium-tellurium compounds, manganese-bismuth-tellurium compounds, and cobalt-iron-boron compounds;

[0026] The antiferromagnetic film layer is selected from any one of iridium-manganese alloy and chromium oxide;

[0027] The top metal electrode is selected from any one or more of chromium, titanium, gold, nickel, tungsten, platinum or palladium.

[0028] A second aspect of the present invention provides a method for preparing the strained two-dimensional magnetic tunnel junction device as described above, comprising the following steps:

[0029] S1, preparing an initial flat substrate into a patterned substrate using a mask etching process;

[0030] S2, preparing a two-dimensional ferromagnetic free layer on the patterned substrate in step S1;

[0031] S3, using a mask layer to define a bottom metal electrode region on one side above the two-dimensional ferromagnetic free layer in step S2, and performing metal deposition, and preparing a bottom metal electrode using a lift-off process;

[0032] S4, preparing a two-dimensional insulating tunneling layer on the other side of the two-dimensional ferromagnetic free layer in step S2;

[0033] S5, preparing a two-dimensional ferromagnetic pinning layer on the two-dimensional insulating tunneling layer in step S4;

[0034] S6, preparing an antiferromagnetic thin film layer on the two-dimensional ferromagnetic pinned layer in step S5;

[0035] S7. Using a mask layer, define a top metal electrode region on the antiferromagnetic film layer in step S6, perform metal deposition, and prepare a top metal electrode using a lift-off process.

[0036] Furthermore, in S1, the mask etching process specifically includes the following steps:

[0037] Depositing a carbon film on an initially flat substrate, and spin-coating a block copolymer and its solvent on the carbon film, heating to volatilize the solvent, and causing the block copolymer to self-assemble to form a regular nanopattern, wherein the block copolymer is selected from any one of polystyrene-polydimethylsiloxane, polystyrene-polybutadiene, and polystyrene-polybutadiene-polystyrene, and the solvent is selected from any one of toluene, chloroform, or tetrahydrofuran;

[0038] Using the obtained block copolymer nanopattern as a first mask layer, obtaining a carbon film pattern by oxygen reactive ion etching, using the obtained carbon film pattern as a second mask layer, and using methane reactive ion etching to etch the initial flat substrate to obtain a patterned substrate;

[0039] Oxygen reactive ion etching is further performed to remove the residual carbon film, hydrofluoric acid etching is used to remove the residual substrate impurities, and the substrate is further cleaned using piranha solution.

[0040] Furthermore, the preparation process of the two-dimensional ferromagnetic free layer is selected from any one of mechanical exfoliation, chemical vapor deposition, molecular beam epitaxy, electron beam deposition, atomic layer deposition, and magnetron sputtering;

[0041] In step S3, the mask layer is a photoresist;

[0042] In step S3, the process defined by the mask layer is to pattern the mask layer by electron beam exposure or photolithography, through exposure and development means;

[0043] In step S3, the metal deposition process is selected from any one of thermal evaporation, electron beam evaporation, and magnetron sputtering.

[0044] Furthermore, the preparation process of the two-dimensional insulating tunneling layer is selected from any one of mechanical exfoliation, chemical vapor deposition, molecular beam epitaxy, electron beam deposition, atomic layer deposition, and magnetron sputtering;

[0045] In step S5, the preparation process of the two-dimensional ferromagnetic pinned layer is selected from any one of mechanical exfoliation, chemical vapor deposition, molecular beam epitaxy, electron beam deposition, atomic layer deposition, and magnetron sputtering.

[0046] Furthermore, the preparation process of the antiferromagnetic thin film layer is selected from any one of mechanical exfoliation, chemical vapor deposition, molecular beam epitaxy, electron beam deposition, atomic layer deposition or magnetron sputtering;

[0047] In step S7, the mask layer is a photoresist;

[0048] In step S7, the process defined by the mask layer is to pattern the mask layer by electron beam exposure or photolithography, through exposure and development means;

[0049] In step S7, the metal deposition process is selected from any one of thermal evaporation, electron beam evaporation, and magnetron sputtering.

[0050] After an in-depth analysis of the development needs of two-dimensional magnetic tunnel junction devices, the present invention proposes an innovative solution based on strain control technology. Traditional two-dimensional magnetic tunnel junction devices are limited by the difficulty of controlling the intrinsic properties of the material, making it difficult to achieve breakthroughs in room temperature stability, signal contrast, and integration density. The present invention recognizes that the key lies in the development of effective exogenous control technology applicable to two-dimensional systems, and this technology must achieve precise modulation of its quantum properties without destroying the stability of the material's intrinsic magnetic order. Strain control technology, with its ability to finely control the two-dimensional lattice at the atomic level, can effectively enhance the magnetic anisotropy of the material, optimize the spin-polarized transport channel, and provide a new path to improve device performance. By introducing controllable local lattice distortion into two-dimensional magnetic crystals, the present invention not only enhances the spin-orbit coupling effect and improves the tunneling magnetoresistance, but also significantly reduces the driving current density, thereby fundamentally promoting breakthroughs in key performance indicators such as room temperature stability, signal contrast, and integration density of two-dimensional magnetic tunnel junction devices, and opening up a new technical direction for the development of high-performance spintronic devices.

[0051] Compared with the prior art, the present invention has the following beneficial effects:

[0052] (1) This invention introduces controllable local lattice distortion through a patterned substrate, achieving precise modulation of the spin-orbit coupling effect and magnetic anisotropy of two-dimensional magnetic materials. This effectively optimizes the spin-polarized transport properties of the tunneling interface, reduces spin scattering, and enhances the tunneling magnetoresistance effect. At the same time, by enhancing magnetic anisotropy, the driving current density is significantly reduced, breaking through the limitations of performance control methods for two-dimensional magnetic tunnel junction devices and providing core technical support for the research and development of functional devices such as high-sensitivity magnetic sensors and high-density non-volatile magnetic memories.

[0053] (2) The present invention achieves precise design of substrate morphology through fine micro-nano processing technologies such as electron beam exposure and reactive ion etching, which combines controllability, universality and process scalability, has low process cost, and is compatible with silicon-based semiconductor process technology. It supports scalable preparation from single-function devices to high-density array structures, and provides a key technical path for the large-scale production, integrated regulation, and diversified applications of spintronic devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 Schematic diagram of the preparation process of the patterned substrate of the present invention.

[0055] Figure 2 Schematic diagram of a two-dimensional ferromagnetic free layer fabricated on a patterned substrate.

[0056] Figure 3 Schematic diagram after preparing the bottom metal electrode.

[0057] Figure 4Schematic diagram of the preparation of a two-dimensional insulating tunneling layer.

[0058] Figure 5 Schematic diagram of the preparation of a two-dimensional ferromagnetic pinning layer.

[0059] Figure 6 Schematic diagram of the preparation of antiferromagnetic thin film layer.

[0060] Figure 7 Schematic diagram after preparing the top metal electrode.

[0061] Figure 8 To regulate the spin-orbit coupling effect, tunneling magnetoresistance and driving current density of two-dimensional magnetic tunnel junction devices under strain.

[0062] Figure 9 Schematic diagram of the process for preparing strained two-dimensional magnetic tunnel junction devices.

[0063] The following are marked in the figure:

[0064] 1001 is a patterned substrate, 2001 is a two-dimensional ferromagnetic free layer, 3001 is a bottom metal electrode, 4001 is a two-dimensional insulating tunneling layer, 5001 is a two-dimensional ferromagnetic pinned layer, 6001 is an antiferromagnetic thin film layer, and 7001 is a top metal electrode. DETAILED DESCRIPTION

[0065] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. Any features such as preparation methods, materials, structures or composition ratios not explicitly described in this technical solution are considered to be common technical features disclosed in the prior art.

[0066] Examples of embodiments of the present invention are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar materials or methods having the same or similar functions.

[0067] The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and are not to be construed as limiting the present invention. In order to simplify disclosure of the present invention, the materials and methods of specific examples are described below. Of course, they are merely examples, and purpose is not intended to limit the present invention. In addition, the present invention provides various specific processes and examples of materials, but those of ordinary skill in the art will appreciate the applicability of other processes and / or the use of other materials.

[0068] Hereinafter, an example of a strained two-dimensional magnetic tunnel junction device and a method for manufacturing the same according to the present invention will be described with reference to the accompanying drawings.

[0069] Example 1:

[0070] This embodiment provides a strained two-dimensional magnetic tunnel junction device and a method for preparing the same. Figure 1 is a schematic diagram of the preparation process of the patterned substrate, which includes the following steps: depositing a carbon film on an initially flat silicon oxide / silicon substrate, and using toluene as a solvent to spin-coat a polystyrene-polydimethylsiloxane block copolymer on the carbon film, heating to evaporate the solvent, causing the block copolymer to self-assemble and form a regular nanopattern; using the obtained block copolymer nanopattern as the first mask layer, obtaining a carbon film pattern by oxygen reactive ion etching; using the obtained carbon film pattern as the second mask layer, using methane reactive ion etching to obtain a patterned substrate; using oxygen reactive ion etching to remove the residual carbon film, using hydrofluoric acid etching to remove residual substrate impurities, and using piranha solution to further clean the substrate.

[0071] exist Figure 2 , a two-dimensional ferromagnetic free layer prepared on a patterned substrate is shown, comprising a patterned substrate 1001 and a two-dimensional ferromagnetic free layer 2001; Figure 3 Schematic diagram after preparing the bottom metal electrode is shown in FIG, including a patterned substrate 1001, a two-dimensional ferromagnetic free layer 2001, and a bottom metal electrode 3001; Figure 4 , which shows a schematic diagram of preparing a two-dimensional insulating tunneling layer, including a patterned substrate 1001, a two-dimensional ferromagnetic free layer 2001, a bottom metal electrode 3001, and a two-dimensional insulating tunneling layer 4001; Figure 5 , which shows a schematic diagram of preparing a two-dimensional ferromagnetic pinned layer, including a patterned substrate 1001, a two-dimensional ferromagnetic free layer 2001, a bottom metal electrode 3001, a two-dimensional insulating tunneling layer 4001, and a two-dimensional ferromagnetic pinned layer 5001; Figure 6 Schematic diagram of preparing antiferromagnetic thin film layer is shown in FIG, including patterned substrate 1001, two-dimensional ferromagnetic free layer 2001, bottom metal electrode 3001, two-dimensional insulating tunneling layer 4001, two-dimensional ferromagnetic pinning layer 5001, antiferromagnetic thin film layer 6001; Figure 7 Schematic diagram after preparing the top metal electrode is shown in FIG, including a patterned substrate 1001, a two-dimensional ferromagnetic free layer 2001, a bottom metal electrode 3001, a two-dimensional insulating tunneling layer 4001, a two-dimensional ferromagnetic pinning layer 5001, an antiferromagnetic film layer 6001, and a top metal electrode 7001; Figure 8 The regulation of strain on the spin-orbit coupling effect, tunneling magnetoresistance, and driving current density of two-dimensional magnetic tunnel junction devices is shown in Figure 9 A schematic diagram of the process for preparing strained two-dimensional magnetic tunnel junction devices is shown in FIG.

[0072] The following is in accordance with Figure 9 The steps for preparing strained two-dimensional magnetic tunnel junction devices are shown in Figures 1 to 8 , a specific example is given below.

[0073] In step S1, use Figure 1 The fabrication process shown yields a nano-patterned substrate 1001 (silicon oxide / silicon).

[0074] Specifically, the preparation process of the patterned substrate is a key starting step in achieving performance improvements in strained two-dimensional magnetic tunnel junction devices. Specifically, a carbon film is first deposited on an initially flat silicon oxide / silicon substrate 1001. The carbon film, as a key intermediate layer, can act as a temporary mask in the subsequent etching process. Then, using toluene as a solvent, a polystyrene-polydimethylsiloxane block copolymer is spin-coated on the carbon film. After heating to evaporate the solvent, the block copolymer self-assembles to form a regular nanopattern. This self-assembly behavior is based on the microphase separation phenomenon between the block copolymer molecular chains, and nanoscale patterns with specific sizes (hole depth / strip height 10-150nm, hole diameter / strip width 100-500nm) and spacing (50-350nm) can be obtained, such as holes, strips or other ordered structures.

[0075] Specifically, the block copolymer nanopattern is used as the first mask layer, and the pattern is transferred to the carbon film by oxygen reactive ion etching (RIE) to form a carbon film pattern. During the oxygen reactive ion etching process, charged ions are accelerated to impact the surface of the mask layer under the action of the electric field, and oxygen reacts chemically with the bombarded material to generate volatile products, thereby achieving patterned etching of the carbon film. Using the carbon film pattern as the second mask layer, methane reactive ion etching is used to initially flatten the substrate. Methane reactive ion etching etches the substrate by generating highly reactive free radicals and ions, which react chemically with the substrate material. The pattern of the carbon film is accurately transferred to the silicon oxide / silicon substrate to form a nano-patterned substrate 1001.

[0076] In step S2, a mechanical exfoliation process is used to prepare a two-dimensional ferromagnetic free layer 2001 (iron germanium telluride compound) on the nano-patterned substrate 1001 (silicon oxide / silicon). The schematic diagram of the prepared structure is shown in FIG. Figure 2 shown.

[0077] Specifically, the step of preparing the two-dimensional ferromagnetic free layer 2001 on the patterned substrate adopts a mechanical stripping process. Mechanical stripping utilizes the weak van der Waals force between the two-dimensional material and the substrate to separate the two-dimensional material from its bulk material layer by layer through a physical stripping method. In this embodiment, an iron-germanium-tellurium compound is used as the two-dimensional ferromagnetic free layer material. The iron-germanium-tellurium compound is placed on a stripping medium such as a tape, and by repeatedly folding and stretching the tape, a two-dimensional ferromagnetic free layer with a thickness of a single layer or a few layers is stripped out layer by layer. This mechanical stripping method can obtain high-quality, defect-free two-dimensional materials, ensuring the integrity of their magnetic properties and crystal structure.

[0078] Specifically, the exfoliated two-dimensional ferromagnetic free layer 2001 is placed on a nano-patterned substrate 1001. The nanostructure of the patterned substrate then induces localized strain modulation on the lattice of the two-dimensional ferromagnetic free layer. This strain modulation, by altering the lattice parameters, influences the energy level distribution and motion trajectory of electrons in the two-dimensional ferromagnetic free layer, thereby enhancing the spin-orbit coupling effect. This enhanced spin-orbit coupling effect improves the degree and stability of electron spin polarization, laying the foundation for the subsequent realization of the tunneling magnetoresistance effect.

[0079] In step S3, photoresist is used as a mask layer, and electron beam exposure technology is used to define the bottom metal electrode area on the side above the two-dimensional ferromagnetic free layer 2001 (iron germanium telluride compound) described in step S2, and chromium and gold stacked metals are successively evaporated using electron beam evaporation, where the thickness of chromium and gold are 5nm and 50nm respectively, and then the bottom metal electrode 3001 is peeled off using acetone solution. Figure 3 A schematic diagram of the structure after preparing the bottom metal electrode is shown.

[0080] Specifically, electron beam exposure forms a precise pattern on the photoresist by controlling the electron beam's scanning path and dosage. After exposure and development, the photoresist exposes the patterned area for the bottom metal electrode. Chromium and gold are then sequentially deposited using electron beam evaporation, with the chromium layer having a thickness of 5nm and the gold layer having a thickness of 50nm. Chromium, as the bottom metal, provides excellent adhesion and contact with the two-dimensional material; gold, as the top metal, has excellent conductivity and chemical stability. The photoresist is then stripped using an acetone solution, yielding the bottom metal electrode 3001. The ohmic contact between the metal electrode and the two-dimensional ferromagnetic free layer enables efficient injection of electrical signals. The geometry and positional accuracy of the metal electrode significantly influence the device's electrical performance and magnetic field response characteristics.

[0081] In step S4, a two-dimensional insulating tunneling layer 4001 (hexagonal boron nitride) is formed using polydimethylsiloxane (PDMS)-assisted dry transfer. The hexagonal boron nitride is deposited on the PDMS substrate using a mechanical lift-off process and then transferred to the other side of the two-dimensional ferromagnetic free layer 2001 (iron germanium telluride) described in step S2 using a self-aligned transfer platform. Figure 4 A schematic diagram of the structure for preparing a two-dimensional insulating tunneling layer is shown.

[0082] Specifically, a two-dimensional insulating tunneling layer 4001 is prepared using polydimethylsiloxane-assisted dry transfer. First, hexagonal boron nitride (hBN) is peeled from its bulk material using a mechanical exfoliation process and placed on a polydimethylsiloxane (PDMS) substrate. Then, a self-aligned transfer platform is used to precisely transfer the hBN to the other side above the two-dimensional ferromagnetic free layer 2001. This transfer process ensures good contact and alignment between the hBN and the two-dimensional ferromagnetic free layer by precisely controlling the transfer angle and pressure, forming a high-quality tunneling barrier. As a two-dimensional insulating tunneling layer, hBN has an atomically flat surface and a highly ordered crystal structure, which can effectively block direct conduction of electrons and promote electron transmission through the tunneling effect, which is a key factor in achieving the tunneling magnetoresistance (TMR) effect.

[0083] In step S5 , the method for preparing the two-dimensional ferromagnetic pinning layer 5001 (iron germanium telluride compound) is the same as the method for preparing the two-dimensional insulating tunneling layer 4001 (hexagonal boron nitride). Figure 5 A schematic diagram of the structure for preparing a two-dimensional ferromagnetic pinning layer is shown.

[0084] Specifically, the method for preparing the two-dimensional ferromagnetic pinning layer 5001 is the same as the method for preparing the two-dimensional insulating tunneling layer 4001, and also uses mechanically stripped iron-germanium-tellurium compound and places it on the two-dimensional insulating tunneling layer 4001 using a self-aligned transfer platform. A parallel magnetic coupling structure is formed between the two-dimensional ferromagnetic pinning layer 5001 and the two-dimensional ferromagnetic free layer 2001 through the two-dimensional insulating tunneling layer 4001. In step S6, a magnetron sputtering process is used to prepare an antiferromagnetic thin film layer 6001 (iridium-manganese alloy) on the two-dimensional ferromagnetic pinning layer 5001 (iron-germanium-tellurium compound) described in step S5. The schematic diagram of the prepared structure is shown as follows: Figure 6 shown.

[0085] Specifically, in step S6, an antiferromagnetic thin film layer 6001 is formed on the two-dimensional ferromagnetic pinned layer 5001 using a magnetron sputtering process. Magnetron sputtering bombards an iridium-manganese alloy target with high-energy ions, causing target atoms to sputter out and deposit on the surface of the two-dimensional ferromagnetic pinned layer. The iridium-manganese alloy has strong antiferromagnetism and forms an exchange bias coupling with the two-dimensional ferromagnetic pinned layer at the interface. This coupling can firmly pin the magnetization direction of the two-dimensional ferromagnetic pinned layer to a fixed direction, making it difficult to change the magnetization direction under the action of an external magnetic field, thereby achieving stable control of the magnetization direction.

[0086] In step S7, using photoresist as a mask layer, electron beam exposure technology is used to define the top metal electrode area on the antiferromagnetic film layer 6001 described in step S6, and chromium and gold stacked metals are successively evaporated using electron beam evaporation, where the thickness of chromium and gold are 5nm and 50nm respectively. Subsequently, the top metal electrode 7001 is peeled off using acetone solution. Figure 7 A schematic diagram is shown after preparing the top metal electrode.

[0087] Using electron beam exposure and electron beam evaporation processes similar to those in step S3, a top metal electrode 7001 is defined and deposited on the antiferromagnetic film layer 6001. This top metal electrode 7001 forms symmetrical electrical contact with the bottom metal electrode 3001, enabling voltage application and tunneling current detection. The entire device fabrication process achieves high-performance construction of a strained two-dimensional magnetic tunnel junction device by precisely controlling the fabrication process of each material layer and the interface quality between them. This process begins with the preparation of a patterned substrate and continues with the sequential construction of each functional layer.

[0088] The strain strength of the strained two-dimensional magnetic tunnel junction device in the present invention is determined by the structural dimensions of the obtained patterned substrate. Figure 8 As shown in Figure 2, when the strain intensity increases from 0% to 4%, the spin-orbit coupling strength of the device increases by nearly 60%, the tunneling magnetoresistance increases from 13.5% to 46.2%, and the driving current density decreases to 10 5 Acm -2 the following.

[0089] The method of the present invention has better controllability, universality and scalability, and lays the foundation for the realization of a new generation of high-performance spintronic devices and their logical operations and other functions. Specifically, the present invention effectively simplifies the preparation process of two-dimensional magnetic tunnel junction devices and reduces costs by introducing controllable local lattice distortion through patterned substrates. In traditional preparation processes, the regulation of the magnetic properties of two-dimensional materials often requires complex epitaxial growth, multi-layer structure stacking or chemical doping. These methods are not only cumbersome, but may also lead to increased material defects and increased costs. The present invention uses strain control technology and only needs to perform patterning on the initial substrate to produce local lattice distortion in the two-dimensional magnetic crystal, thereby achieving the regulation of the spin-orbit coupling effect and magnetic anisotropy of the material. The preparation of the patterned substrate adopts a mask etching process, combined with the nano-pattern formed by self-assembly of block copolymers, which avoids the complex mask production and multiple exposure etching steps in the traditional photolithography process, reducing the process flow and equipment requirements. Furthermore, subsequent steps such as 2D material preparation and electrode deposition utilize mature physical deposition techniques, such as mechanical exfoliation and electron beam evaporation. These techniques are relatively simple to operate, highly compatible, and amenable to large-scale integration. The entire preparation process does not require high temperatures or specialized crystal growth environments, significantly reducing reliance on expensive equipment and complex processes, thereby simplifying the preparation process and effectively controlling costs.

[0090] The above describes in detail a strained two-dimensional magnetic tunnel junction device and its fabrication method according to the present invention. However, the present invention is not limited to the above examples. Various modifications and variations are possible without departing from the spirit and scope of the present invention, and the general principles described herein can be applied to other embodiments without requiring inventive effort. Therefore, the present invention is not limited to the above-described embodiments. Improvements and modifications made by those skilled in the art based on the present invention's teachings without departing from the scope of the present invention should be within the scope of protection of the present invention.

Claims

1. A strained two-dimensional magnetic tunnel junction device, characterized in that: include: a patterned substrate (1001); A two-dimensional ferromagnetic free layer (2001) is provided on the patterned substrate (1001); A bottom metal electrode (3001) is provided on one side above the two-dimensional ferromagnetic free layer (2001); A two-dimensional insulating tunneling layer (4001) is provided on the other side above the two-dimensional ferromagnetic free layer (2001); A two-dimensional ferromagnetic pinning layer (5001) is provided on the two-dimensional insulating tunneling layer (4001); an antiferromagnetic film layer (6001), provided on the two-dimensional ferromagnetic pinned layer (5001); A top metal electrode (7001) is located on the antiferromagnetic film layer (6001); The patterned substrate (1001) generates local lattice distortion in the two-dimensional ferromagnetic free layer (2001) through surface nanoscale patterns, thereby enhancing the spin-orbit coupling effect of the two-dimensional ferromagnetic free layer (2001).

2. The strained two-dimensional magnetic tunnel junction device according to claim 1, characterized in that: The surface nanoscale pattern of the patterned substrate (1001) includes a hole-shaped and / or strip-shaped ordered structure, wherein the hole depth / strip height is 10-150nm, the hole diameter / strip width is 100-500nm, and the hole diameter / strip spacing is 50-350nm. The two-dimensional ferromagnetic free layer (2001) covers the surface of the ordered structure to produce local lattice distortion.

3. The strained two-dimensional magnetic tunnel junction device according to claim 1, characterized in that: The material of the patterned substrate (1001) is selected from any one of silicon nitride / silicon, silicon oxide / silicon, hafnium oxide / silicon, and aluminum oxide / silicon; The two-dimensional ferromagnetic free layer (2001) is selected from any one of iron-germanium-tellurium compounds, chromium-germanium-tellurium compounds, manganese-bismuth-tellurium compounds, and cobalt-iron-boron compounds.

4. The strained two-dimensional magnetic tunnel junction device according to claim 1, characterized in that: The bottom metal electrode (3001) is selected from any one or more of chromium, titanium, gold, nickel, tungsten, platinum, and palladium; The two-dimensional insulating tunneling layer (4001) is selected from any one of hexagonal boron nitride, molybdenum oxide, and magnesium oxide.

5. The strained two-dimensional magnetic tunnel junction device according to claim 1, characterized in that: The two-dimensional ferromagnetic pinning layer (5001) is selected from any one of iron-germanium-tellurium compounds, chromium-germanium-tellurium compounds, manganese-bismuth-tellurium compounds, and cobalt-iron-boron compounds; The antiferromagnetic film layer (6001) is selected from any one of iridium-manganese alloy and chromium oxide; The top metal electrode (7001) is selected from any one or more of chromium, titanium, gold, nickel, tungsten, platinum or palladium.

6. A method for preparing a strained two-dimensional magnetic tunnel junction device according to any one of claims 1 to 5, characterized in that: The following steps are involved: S1, using a mask etching process to prepare an initial flat substrate into a patterned substrate (1001); S2, preparing a two-dimensional ferromagnetic free layer (2001) on the patterned substrate (1001) in step S1; S3, using a mask layer to define a bottom metal electrode region on one side above the two-dimensional ferromagnetic free layer (2001) in step S2, and performing metal deposition, and preparing a bottom metal electrode (3001) using a lift-off process; S4, preparing a two-dimensional insulating tunneling layer (4001) on the other side above the two-dimensional ferromagnetic free layer (2001) in step S2; S5, preparing a two-dimensional ferromagnetic pinning layer (5001) on the two-dimensional insulating tunneling layer (4001) in step S4; S6, preparing an antiferromagnetic thin film layer (6001) on the two-dimensional ferromagnetic pinned layer (5001) in step S5; S7. Using a mask layer, define a top metal electrode region on the antiferromagnetic film layer (6001) described in step S6, perform metal deposition, and prepare a top metal electrode (7001) using a lift-off process.

7. The method for preparing a strained two-dimensional magnetic tunnel junction device according to claim 6, characterized in that: In S1, the mask etching process specifically includes the following steps: Depositing a carbon film on an initially flat substrate, and spin-coating a block copolymer and its solvent on the carbon film, heating to volatilize the solvent, and causing the block copolymer to self-assemble to form a regular nanopattern, wherein the block copolymer is selected from any one of polystyrene-polydimethylsiloxane, polystyrene-polybutadiene, and polystyrene-polybutadiene-polystyrene, and the solvent is selected from any one of toluene, chloroform, or tetrahydrofuran; Using the obtained block copolymer nanopattern as a first mask layer, obtaining a carbon film pattern by oxygen reactive ion etching, using the obtained carbon film pattern as a second mask layer, and using methane reactive ion etching to etch the initial flat substrate to obtain a patterned substrate (1001); Oxygen reactive ion etching is further performed to remove the residual carbon film, hydrofluoric acid etching is used to remove the residual substrate impurities, and the substrate is further cleaned using piranha solution.

8. The method for preparing a strained two-dimensional magnetic tunnel junction device according to claim 6, characterized in that: In step S2, the preparation process of the two-dimensional ferromagnetic free layer (2001) is selected from any one of mechanical exfoliation, chemical vapor deposition, molecular beam epitaxy, electron beam deposition, atomic layer deposition, and magnetron sputtering; In step S3, the mask layer is a photoresist; In step S3, the process defined by the mask layer is to pattern the mask layer by electron beam exposure or photolithography, through exposure and development means; In step S3, the metal deposition process is selected from any one of thermal evaporation, electron beam evaporation, and magnetron sputtering.

9. The method for preparing a strained two-dimensional magnetic tunnel junction device according to claim 6, characterized in that: In step S4, the preparation process of the two-dimensional insulating tunneling layer (4001) is selected from any one of mechanical stripping, chemical vapor deposition, molecular beam epitaxy, electron beam deposition, atomic layer deposition, and magnetron sputtering; In step S5, the preparation process of the two-dimensional ferromagnetic pinned layer (5001) is selected from any one of mechanical stripping, chemical vapor deposition, molecular beam epitaxy, electron beam deposition, atomic layer deposition, and magnetron sputtering.

10. The method for preparing a strained two-dimensional magnetic tunnel junction device according to claim 6, characterized in that: The preparation process of the antiferromagnetic thin film layer (6001) is selected from any one of mechanical exfoliation, chemical vapor deposition, molecular beam epitaxy, electron beam deposition, atomic layer deposition or magnetron sputtering; In step S7, the mask layer is a photoresist; In step S7, the process defined by the mask layer is to pattern the mask layer by electron beam exposure or photolithography, through exposure and development means; In step S7, the metal deposition process is selected from any one of thermal evaporation, electron beam evaporation, and magnetron sputtering.

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