Electric field regulation and control two-dimensional magnetic tunnel junction and preparation method and application thereof

Abstract

The invention provides an electric field regulation and control two-dimensional magnetic tunnel junction and a preparation method and application thereof, and belongs to the technical field of spinning electronic devices. The two-dimensional magnetic tunnel junction comprises a bottom electrode, a two-dimensional ferromagnetic material layer I, a two-dimensional ferroelectric material layer, a two-dimensional ferromagnetic material layer II and a protective layer which are stacked in sequence, the two-dimensional ferroelectric material layer adopts CuInP2S6, and migration of Cu ions is regulated and controlled through external voltage. The device can be applied to a high-density magnetic random access memory (MRAM), a high-sensitivity magnetic sensor and a low-power-consumption spin logic device, and has an industrialization prospect.

Description

Technical Field

[0001] The present invention belongs to the technical field of spin electronic devices, and in particular relates to an electric field-controlled two-dimensional magnetic tunnel junction and a preparation method and application thereof. Background Art

[0002] The application of tunnel magnetoresistance (TMR) in magnetic tunnel junctions (MTJs) has had a huge impact on the development of magnetic electronic devices, including magnetoresistive random access memory (MRAM), radio frequency sensors, microwave generators, etc. Most magnetic tunnel junctions use repeated tunneling of current to write or read, which places great demands on the durability of the material. The emergence of two-dimensional (2D) van der Waals materials has provided more process possibilities for magnetic tunnel junctions, especially two-dimensional materials with high spin polarization are expected to be used in the next generation of nanoscale devices.

[0003] Existing devices require repeated writing and reading of current, which consumes a lot of energy and generates a lot of heat. It will have a certain impact on adjacent structures, making it difficult to break through the limitations of size and precision, and requires extremely high durability of materials. Some even require the influence of an external magnetic field, which is difficult to avoid affecting other devices. Each write causes strong material loss, and the repeatability is not good enough. The coupling effect between in-plane materials makes it difficult to solve the problem of high-density integration. Summary of the invention

[0004] In view of this, the present invention aims to propose an electric field-regulated two-dimensional magnetic tunnel junction and its preparation method and application, which changes the overall resistance state of the magnetic tunnel junction by regulating CuInP2S6 through an external electric field, reduces the process of passing large current into the tunnel junction, thereby protecting the magnetic tunnel junction material itself and improving its durability.

[0005] To achieve the above object, the technical solution of the present invention is achieved as follows: An electric field-regulated two-dimensional magnetic tunnel junction comprises a substrate, a bottom electrode, a two-dimensional ferromagnetic material layer I, a two-dimensional ferroelectric material layer, a two-dimensional ferromagnetic material layer II and a protective layer arranged in sequence from bottom to top. The material of the two-dimensional ferroelectric material layer is CuInP2S6, and an electric field is applied to the left and right ends of the two-dimensional ferroelectric material layer.

[0006] A magnetic tunnel junction is a device formed by sandwiching an extremely thin insulating layer with a thickness of nanometers between two ferromagnetic sheets. The extremely thin insulating layer used in the present invention is a two-dimensional ferroelectric material layer CuInP2S6.

[0007] The traditional ferromagnetic layer (free layer) flipping requires the use of electric current to generate a magnetic field to change the magnetocrystalline anisotropy. This process has high heat loss. In addition, the traditional three-dimensional ferroelectric material has a large leakage current, or basically has no ferroelectricity below 50nm, making it difficult to make its size sub-nanometer limit. General ferroelectric materials have fatigue characteristics, and it is difficult to restore their intrinsic characteristics after multiple ferroelectric flips. The Cu ions in CuInP2S6 can migrate repeatedly within the layer with good repeatability. When the Cu ions migrate to the middle of the two ferromagnetic material layers, it is equivalent to raising the barrier layer. In addition, the Cu ions may have a shielding effect on the electric field of the tunneling electrons, reducing the effective tunneling ability of the electrons, thereby increasing the difficulty of tunneling, and thus increasing its resistance. On the contrary, the Cu ions migrate in the opposite direction, reducing the resistance.

[0008] Using CuInP2S6 and applying an electric field can avoid the thermal effects of current on the device, and migrate back and forth within the layer, improving the cycle stability performance and achieving the purpose of using a two-dimensional magnetic tunnel junction as a storage medium.

[0009] Furthermore, the dimensions of the substrate, the bottom electrode, the two-dimensional ferromagnetic material layer I, the two-dimensional ferromagnetic material layer II and the protective layer are all the same, and the length of the two-dimensional ferroelectric material layer is greater than the length of the two-dimensional ferromagnetic material layer I and the two-dimensional ferromagnetic material layer II, so that the left end or the right end or both ends of the two-dimensional ferroelectric material layer protrude.

[0010] The length of the protrusions was 2-6 μm.

[0011] The two-dimensional ferroelectric material layer has a bulge because CuInP2S6 can withstand relatively large voltages, while the two-dimensional ferromagnetic material of a few nanometers to more than 10 nanometers can be easily broken down or burned, causing device failure. The bulge makes the voltage basically applied to the two-dimensional ferroelectric material layer, and the voltage distributed to the two-dimensional ferromagnetic material is almost 0, which can protect the two-dimensional ferromagnetic material. Another function is to move the Cu ions out of the same position of the three-layer structure (two-dimensional ferromagnetic material layer I, two-dimensional ferroelectric material layer, two-dimensional ferromagnetic material layer II).

[0012] Furthermore, the materials of the two-dimensional ferromagnetic material layer I and the two-dimensional ferromagnetic material layer II are the same or different, specifically Fe 3+ x Any one of GaTe2, CrI3 or Cr2Ga2Te6, where x = 0-2. The ferromagnetic material must satisfy different perpendicular magnetic anisotropy.

[0013] Preferably, the two-dimensional ferromagnetic material layer I and the two-dimensional ferromagnetic material layer II are both Fe3GaTe2.

[0014] The strong magnetism of Fe3GaTe2 has a high spin polarization rate, which enhances the tunnel magnetoresistance effect (TMR). A high TMR ratio means a greater resistance change, which improves the signal detection sensitivity of the MTJ device and makes the reading speed of storage units (such as MRAM) faster and energy-saving. Fe3GaTe2 has a high Curie temperature (Tc), which can maintain a stable ferromagnetic state in a high temperature environment and avoid magnetization reversal caused by thermal disturbance. This is crucial for high-temperature application scenarios such as automotive electronics and industrial equipment to ensure the reliability of data storage. Fe3GaTe2 has good interface properties (such as low defect density and lattice matching with other functional layers), which can reduce interface scattering in the tunnel junction and improve electron tunneling efficiency. This is crucial to improving TMR and device durability.

[0015] Further, the thickness of the two-dimensional ferromagnetic material layer I is 1-10 nm, and the thickness of the two-dimensional ferromagnetic material layer II is 10-20 nm; Alternatively, the thickness of the two-dimensional ferromagnetic material layer I is 10-20 nm, and the thickness of the two-dimensional ferromagnetic material layer II is 1-10 nm.

[0016] The thickness of the two-dimensional ferromagnetic material layer I and the two-dimensional ferromagnetic material layer needs to be different. The thicker layer is used as a reference layer and can be named as a ferromagnetic reference layer. The thinner layer is used as a free layer and can be named as a ferromagnetic free layer. The ferromagnetic reference layer or the ferromagnetic free layer can be above or below. The reference layer (fixed layer (thicker layer)) needs to maintain a stable magnetization direction and is usually designed to be thicker to enhance its magnetocrystalline anisotropy to resist external interference (such as thermal disturbance or stray magnetic field) and ensure the reliability of data storage. The free layer (thinner layer) needs a smaller magnetic anisotropy so that the magnetization direction can be quickly switched by an external magnetic field or current. The thinner thickness can reduce its stability threshold, making it easier to flip.

[0017] Furthermore, the thickness of the two-dimensional ferroelectric material layer is 1nm-10nm.

[0018] Furthermore, the electric field has a magnitude of 0.1-10 kV / cm.

[0019] Furthermore, the thickness of the substrate is 0.2-5 mm, the thickness of the bottom electrode is 15-60 nm, the thickness of the protective layer is 1-200 nm; and the material of the protective layer is h-BN.

[0020] The present invention also provides a method for preparing the electric field controlled two-dimensional magnetic tunnel junction as described above, the method comprising the following steps: (1) Fabricating a bottom electrode on a substrate by combining photolithography and magnetron sputtering processes; (2) sequentially preparing a two-dimensional ferromagnetic material layer I, a two-dimensional ferroelectric material layer, a two-dimensional ferromagnetic material layer II and a protective layer on the bottom electrode; (3) The left and right ends of the two-dimensional ferroelectric material layer are in contact with the electric field electrodes respectively.

[0021] Furthermore, the method for preparing the two-dimensional ferromagnetic material layer I, the two-dimensional ferroelectric material layer, the two-dimensional ferromagnetic material layer II and the protective layer is any one of molecular beam epitaxy, pulsed laser deposition, physical vapor deposition, chemical vapor deposition, and mechanical stripping.

[0022] The present invention also provides an application of the electric field controlled two-dimensional magnetic tunnel junction as described above in a magnetoelectronic device.

[0023] Compared with the prior art, the electric field controlled two-dimensional magnetic tunnel junction and its preparation method and application described in the present invention have the following advantages: (1) The electric field-controlled two-dimensional magnetic tunnel junction described in the present invention changes the conductivity of the two-dimensional ferroelectric CuInP2S6 by electric field control, thereby changing the resistance state of the overall device. Compared with the traditional magnetic tunnel junction, the present invention does not have a large write current, and can reduce energy consumption and heat generation, thereby providing better protection for the device itself and greatly improving the durability of the device.

[0024] (2) The electric field-controlled two-dimensional magnetic tunnel junction described in the present invention uses the two-dimensional magnetic material Fe3GaTe2, which has a high Curie temperature and exhibits good perpendicular magnetic anisotropy at room temperature, which can greatly reduce the size of the device and improve its integration.

[0025] (3) The preparation process of the electric field-controlled two-dimensional magnetic tunnel junction described in the present invention is relatively simple, and the perpendicular magnetic structure of the two-dimensional ferromagnetic material layer I and the two-dimensional ferromagnetic material layer II has little effect on adjacent components, resulting in a better yield rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the accompanying drawings: Figure 1 A schematic diagram of the structure of the electric field controlled two-dimensional magnetic tunnel junction according to the present invention; Figure 2 is the in-plane IV curve of CuInP2S6; Figure 3 The data diagram of applying electric field to the two-dimensional ferroelectric material layer; (a) is the top view of the KPFM mode of atomic force, and (b) is the measured potential distribution corresponding to the white line in (a); Figure 4 The resistance-voltage diagram measured for Comparative Example 1; Figure 5 This is the resistance-voltage diagram measured in Comparative Example 2.

[0027] Description of reference numerals: 1. Substrate; 2. Bottom electrode; 3. Two-dimensional ferromagnetic material layer I; 4. Two-dimensional ferroelectric material layer; 5. Two-dimensional ferromagnetic material layer II; 6. h-BN layer. DETAILED DESCRIPTION

[0028] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0029] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and the like are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, features defined as "first", "second", and the like may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0030] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood by specific circumstances.

[0031] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] Example 1

[0033] An electric field-regulated two-dimensional magnetic tunnel junction comprises a SiO2 / Si substrate 1, a Ti+Pt bottom electrode 2, a two-dimensional ferromagnetic material layer Ⅰ 3, a two-dimensional ferroelectric material layer 4, a two-dimensional ferromagnetic material layer Ⅱ 5 and an h-BN layer 6 arranged in sequence from bottom to top, wherein the material of the two-dimensional ferroelectric material layer 4 is CuInP2S6, an electric field is applied to the left and right ends of the two-dimensional ferroelectric material layer 4, and the electric field magnitude is 0.1 kV / cm, and the materials of the two-dimensional ferromagnetic material layer Ⅰ 3 and the two-dimensional ferromagnetic material layer Ⅱ 5 are the same, both are Fe3GaTe2.

[0034] The thickness of the substrate 1 is 0.5 mm, the thickness of the Ti+Pt bottom electrode 2 is 5+15 nm, and the thickness of the h-BN layer 6 is 30 nm; the thickness of the two-dimensional ferromagnetic material layer Ⅰ 3 is 9 nm, the thickness of the two-dimensional ferromagnetic material layer Ⅱ 5 is 15 nm, and the thickness of the two-dimensional ferroelectric material layer 4 is 5 nm.

[0035] The substrate 1, the bottom electrode 2, the two-dimensional ferromagnetic material layer I 3, the two-dimensional ferromagnetic material layer II 5 and the h-BN layer 6 are all of the same size, and the length of the two-dimensional ferroelectric material layer 4 is greater than the length of the two-dimensional ferromagnetic material layer I 3 and the two-dimensional ferromagnetic material layer II 5, so that the left end or the right end of the two-dimensional ferroelectric material layer 4 protrudes. Figure 1 As shown, the left end of the two-dimensional ferroelectric material layer 4 protrudes, and the protrusion length is 3 μm.

[0036] The preparation method of the above-mentioned electric field controlled two-dimensional magnetic tunnel junction is as follows: (1) Cleaning SiO2 / Si substrate The substrate was ultrasonically treated in acetone, ethanol and deionized water for 15 min in sequence and then dried with a nitrogen air gun.

[0037] (2) Preparation of bottom electrode Ti+Pt By combining photolithography and magnetron sputtering processes, the electrode pattern is used for exposure and development, and the bottom electrode Ti+Pt (room temperature) with a thickness of 5+15 nm is obtained by magnetron sputtering.

[0038] (3) Preparation of two-dimensional ferromagnetic material layer I The solid material Fe3GaTe2 is directly peeled off onto the surface of polydimethylsiloxane (PDMS) to form a Fe3GaTe2 / PDMS assembly; the Fe3GaTe2 in the obtained Fe3GaTe2 / PDMS assembly is brought into contact with the bottom electrode obtained in step (2), so that the Fe3GaTe2 is separated from the PDMS, and the Fe3GaTe2 is spread flat on the bottom electrode and forms a good contact with the bottom electrode, thereby forming a two-dimensional ferromagnetic material layer I.

[0039] (4) Preparation of two-dimensional ferroelectric material layer Similar to step (3), the two-dimensional ferroelectric material CuInP2S6 is peeled off using PDMS by mechanical peeling to form a CuInP2S6 / PDMS composite, and the CuInP2S6 in the composite is brought into contact with the two-dimensional ferromagnetic material layer I to form a two-dimensional ferroelectric material layer; and the left and right ends of the two-dimensional ferroelectric material layer are respectively brought into contact with the electric field electrodes.

[0040] (5) Preparation of two-dimensional ferromagnetic material layer II Similar to step (3), a Fe3GaTe2 / PDMS composite is obtained, and a two-dimensional ferromagnetic material layer II is formed on the two-dimensional ferroelectric material layer.

[0041] (6) Preparation of h-BN protective layer Similarly, the mechanical stripping method is adopted to use PDMS to obtain a BN film of a certain thickness, to obtain a BN / PDMS combination, and to cover the surface of the entire magnetic tunnel junction with BN, and finally to obtain a complete magnetic tunnel junction device.

[0042] The current and voltage between the bottom electrode, the two-dimensional ferromagnetic material layer I, the two-dimensional ferroelectric material layer, and the two-dimensional ferromagnetic material layer II are measured by an ammeter and a voltmeter.

[0043] Figure 2 This is the in-plane IV curve of CuInP2S6 material, which reflects the migration characteristics of Cu ions.

[0044] Figure 3 The bright part in (a) is where the Cu ions gather, which has a high potential. The darker part in the figure has a low potential, so electrons can tunnel more easily and have low resistance. It is non-volatile after power failure.

[0045] The tunnel junction changes the conductivity of the two-dimensional ferroelectric CuInP2S6 by regulating the electric field, thereby changing the resistance state of the overall device. Compared with the traditional magnetic tunnel junction, the present invention does not have a large write current, and can reduce energy consumption and heat generation, which provides better protection for the device itself and greatly improves the durability of the device.

[0046] In this embodiment, the bottom electrode is first made, and then the device is made by mechanical stripping. The electrode only needs to be made once. Compared with the traditional production process of the upper and lower electrodes of the magnetic tunnel junction, the fault tolerance of the work is greatly increased, and the two-dimensional material is better protected. In addition, the preparation of the device of this embodiment is carried out in a glove box, and mechanical stripping can be performed under protective gas to prevent oxidation.

[0047] Comparative Example 1 The difference from the above-mentioned embodiment 1 is that the thickness of the two-dimensional ferromagnetic material layer I and the two-dimensional ferromagnetic material layer II are the same, both of which are 15 nm.

[0048] An electric field is applied across the ferroelectric material, and the current and voltage between the bottom electrode, two-dimensional ferromagnetic material layer I, two-dimensional ferroelectric material layer, and two-dimensional ferromagnetic material layer II are measured using an ammeter and a voltmeter to measure the resistance.

[0049] The results are as follows Figure 4 As shown, when the thickness is the same, the resistance changes very little when the voltage is changed, and basically remains consistent, indicating that the structure has no tunneling effect and is just an ordinary ohmic resistor.

[0050] Comparative Example 2 The difference from the above-mentioned embodiment 1 is that the thickness of the two-dimensional ferroelectric material layer 4 is 30 nm.

[0051] An electric field is applied across the ferroelectric material, and the current and voltage between the bottom electrode, two-dimensional ferromagnetic material layer I, two-dimensional ferroelectric material layer, and two-dimensional ferromagnetic material layer II are measured using an ammeter and a voltmeter to measure the resistance.

[0052] The results are as follows Figure 5 As shown, when the two-dimensional ferroelectric material layer becomes thicker and the voltage is changed, its resistance changes very little and remains basically consistent, indicating that the structure has no tunneling effect and is just an ordinary ohmic resistor.

[0053] From the above conclusions, it can be seen that when the thickness of the two-dimensional ferroelectric material layer is changed or there is no thickness difference between the two-dimensional ferromagnetic material layer I and the two-dimensional ferromagnetic material layer II, a magnetic tunnel junction structure cannot be formed. Only when it meets the setting requirements of the present invention can a magnetic tunnel junction with good effect be prepared.

[0054] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. An electric field controlled two-dimensional magnetic tunnel junction, characterized in that: It includes a substrate, a bottom electrode, a two-dimensional ferromagnetic material layer I, a two-dimensional ferroelectric material layer, a two-dimensional ferromagnetic material layer II and a protective layer arranged in sequence from bottom to top, the material of the two-dimensional ferroelectric material layer is CuInP2S6, and an electric field is applied to the left and right ends of the two-dimensional ferroelectric material layer; Wherein, the thickness of the two-dimensional ferromagnetic material layer I is 1-10 nm, and the thickness of the two-dimensional ferromagnetic material layer II is 10-20 nm; Or the thickness of the two-dimensional ferromagnetic material layer I is 10-20 nm, and the thickness of the two-dimensional ferromagnetic material layer II is 1-10 nm; The thickness of the two-dimensional ferroelectric material layer is 1nm-10nm.

2. The electric field controlled two-dimensional magnetic tunnel junction according to claim 1, characterized in that: The dimensions of the substrate, bottom electrode, two-dimensional ferromagnetic material layer I, two-dimensional ferromagnetic material layer II and protective layer are the same. The length of the two-dimensional ferroelectric material layer is greater than the length of the two-dimensional ferromagnetic material layer I and the two-dimensional ferromagnetic material layer II, so that the left end or the right end or both ends of the two-dimensional ferroelectric material layer protrude.

3. The electric field controlled two-dimensional magnetic tunnel junction according to claim 1, characterized in that: The materials of the two-dimensional ferromagnetic material layer I and the two-dimensional ferromagnetic material layer II are the same or different, specifically Fe 3+x Any of GaTe2, CrI3 or Cr2Ga2Te6, where x=0-2.

4. The electric field controlled two-dimensional magnetic tunnel junction according to claim 1, characterized in that: The electric field strength is 0.1-10 kV / cm.

5. The electric field controlled two-dimensional magnetic tunnel junction according to claim 1, characterized in that: The thickness of the substrate is 0.2-5 mm, the thickness of the bottom electrode is 15-60 nm, the thickness of the protective layer is 1-200 nm; the material of the protective layer is h-BN.

6. A method for preparing an electric field controlled two-dimensional magnetic tunnel junction according to any one of claims 1 to 5, characterized in that: The method comprises the following steps: (1) Fabricating a bottom electrode on a substrate by combining photolithography and magnetron sputtering processes; (2) sequentially preparing a two-dimensional ferromagnetic material layer I, a two-dimensional ferroelectric material layer, a two-dimensional ferromagnetic material layer II and a protective layer on the bottom electrode; (3) The left and right ends of the two-dimensional ferroelectric material layer are in contact with the electric field electrodes respectively.

7. The method for preparing an electric field-controlled two-dimensional magnetic tunnel junction according to claim 6, characterized in that: The method for preparing the two-dimensional ferromagnetic material layer I, the two-dimensional ferroelectric material layer, the two-dimensional ferromagnetic material layer II and the protective layer is any one of molecular beam epitaxy, pulsed laser deposition, physical vapor deposition, chemical vapor deposition and mechanical stripping.

8. An application of the electric field controlled two-dimensional magnetic tunnel junction as described in any one of claims 1 to 5 in a magnetoelectronic device.

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