Device based on spin-orbit torque and preparation method thereof

Abstract

The spin-orbit torque-based device comprises a microwave transmission layer and a microwave absorption layer, and the microwave absorption layer is arranged on the upper surface of the microwave transmission layer; the microwave transmission layer is a CPW coplanar waveguide, and the microwave absorption layer is a ferromagnetic layer / strong spin coupling layer heterojunction. Through the heavy metal / ferromagnetic layer heterojunction, spin-orbit torque is generated by the spin Hall effect in the heavy metal layer to influence the magnetic property of the ferromagnetic layer, the current is directly used as a regulation and control mode, an electromagnet or coil current does not need to be additionally arranged outside the device, and the problem of large size is solved. Meanwhile, the spin-orbit torque is actually regulated and controlled by the current density, microwave tuning of milliampere-level current is achieved by controlling the size of a device, the advantage of low power consumption is achieved, and meanwhile the potential of constructing a device with extremely low power consumption is achieved. And the functional layer can be realized only by the coplanar waveguide and the double-layer film heterojunction, so that the structure is simple and clear.

Description

Technical Field

[0001] The present invention belongs to the technical field of tunable filters, and particularly relates to a device based on spin-orbit torque and a preparation method thereof. Background Art

[0002] Tunable filters play a very important role in realizing the full utilization of diverse spectrum resources in modern communication technologies. In the field of high-frequency tuning, in order to obtain a large tuning range, a magnetic field tuning method is usually adopted to construct the tunable component of the filter.

[0003] The above-mentioned magnetic field tuning changes the magnetic properties of a specified material by applying an external magnetic field generated by an electromagnet or coil current. To achieve large-range tuning, it is inevitable to require a large-volume external magnet or increase the coil current, so there are problems of large volume and high power consumption; at the same time, since the magnetic field magnitude needs to be regulated first and then the change in the magnetic properties of the material is realized, this type of method has the problem of slow response speed. Summary of the Invention

[0004] The purpose of the present invention is to provide a device based on spin-orbit torque and a preparation method thereof to solve the above problems.

[0005] To achieve the above purpose, the present invention adopts the following technical solutions: A device based on spin-orbit torque, comprising: a microwave transmission layer and a microwave absorption layer, and the microwave absorption layer is disposed on the upper surface of the microwave transmission layer; The microwave transmission layer is a CPW coplanar waveguide, and the microwave absorption layer is a ferromagnetic layer / strong spin-coupling layer heterojunction.

[0006] Further, the CPW coplanar waveguide includes an insulating layer, a microwave transmission line, a substrate, and a ground layer; the microwave transmission line is disposed on the substrate, the insulating layer covers the microwave transmission line, and the ground layer is disposed at the bottom of the substrate.

[0007] Further, the microwave transmission line is two parallel S-shaped copper wires; the insulating layer is a polyimide insulating layer.

[0008] Further, the ferromagnetic layer / strong spin-coupling layer heterojunction includes a CoFeB thin film and a Pt thin film. The CoFeB thin film is disposed on a single-crystalline silicon substrate, and the Pt thin film covers the CoFeB thin film; the CoFeB thin film is a ferromagnetic layer, and the Pt thin film is a strong spin-coupling layer.

[0009] Further, a wire is led out from the surface of the Pt thin film.

[0010] A preparation method of a device based on spin-orbit torque, comprising the following steps: Clean the single-crystalline silicon substrate and air-dry the cleaned silicon substrate; A ferromagnetic layer / strong spin-coupling layer heterojunction is prepared on a silicon substrate after air drying. The ferromagnetic layer has ferromagnetism and a resistivity greater than that of the strong spin-coupling layer, and the strong spin-coupling layer has a large spin Hall angle. A wire is led out from the surface of the strong spin-coupling layer for applying a current. A coplanar waveguide is prepared, and the ferromagnetic layer / strong spin-coupling layer heterojunction is placed in the center of the coplanar waveguide.

[0011] Furthermore, the cleaning of the single-crystalline silicon substrate and the air drying of the cleaned silicon substrate include: A double-sided polished single-crystalline silicon with a crystal orientation of <100> is used as the substrate. The silicon substrate is successively soaked in 40 ml to 60 ml of deionized water, acetone, and ethanol solution, and the surface of the silicon wafer is cleaned by ultrasonic waves. The ultrasonic cleaning time is 5 min to 15 min, and the ultrasonic cleaning power is 50 w to 100 w. After cleaning, the edge of the cleaned silicon substrate is clamped and dried in a nitrogen atmosphere until the surface is bright and there is no solution residue.

[0012] Furthermore, the preparation of the ferromagnetic layer / strong spin-coupling layer heterojunction on the air-dried silicon substrate includes: on a clean single-crystalline silicon substrate, a CoFeB thin film is grown as the ferromagnetic layer by direct current magnetron sputtering technology, and the base pressure in the vacuum chamber is less than 1×10-7 Torr; on the deposited CoFeB layer, a Pt thin film is continuously grown by direct current magnetron sputtering technology, and oxygen doping is achieved by controlling the growth atmosphere. The Pt thin film forms a heavy metal / ferromagnetic layer heterojunction with the CoFeB thin film as the heavy metal layer.

[0013] Furthermore, a wire is led out from the surface of the Pt thin film by an ultrasonic bonder.

[0014] Furthermore, the preparation of the coplanar waveguide and the placement of the ferromagnetic layer / strong spin-coupling layer heterojunction in the center of the coplanar waveguide include: Two parallel S-shaped copper wires are arranged on an insulating dielectric substrate to form a microwave transmission line, and a polyimide insulating layer is covered on the surface. The sample film surface is placed face down in the center of the coplanar waveguide.

[0015] Compared with the prior art, the present invention has the following technical effects: The purpose of the present invention is to provide a tunable magnetic filter that does not rely on an external electromagnet and can directly regulate the microwave absorption frequency band of materials by current, thereby getting rid of the huge volume of the external magnet, and at the same time having the advantages of low power consumption, fast response, and easy integration.

[0016] In the present invention, through a heavy metal / ferromagnetic layer heterojunction, the spin Hall effect in the heavy metal layer is utilized to generate a spin-orbit torque that affects the magnetic properties of the ferromagnetic layer. The current is directly used as the regulation method, eliminating the need to attach an electromagnet or coil current outside the device, thus overcoming the problem of large volume. At the same time, the magnitude of the spin-orbit torque is actually regulated by the current density. By controlling the device size, microwave tuning of milliampere-level currents is achieved, which has the advantages of low power consumption and the potential to construct devices with extremely low power consumption. Moreover, the functional layer of the present invention can be realized only by a coplanar waveguide and a bilayer film heterojunction, with a simple and clear structure. Brief Description of the Drawings

[0017] Figure 1 It is a schematic diagram of the device structure of the present invention; Figure 2 It is a schematic diagram of the current regulation principle in the present invention; Figure 3 It is a diagram of the results of the current regulation of the ferromagnetic resonance frequency under oxygen doping. Detailed Embodiments

[0018] The present invention is further described below with reference to the accompanying drawings: Example 1. Refer to Figure 1 , the present invention provides a device based on spin-orbit torque, including: a microwave transmission layer and a microwave absorption layer, and the microwave absorption layer is disposed on the upper surface of the microwave transmission layer; The microwave transmission layer is a CPW coplanar waveguide, and the microwave absorption layer is a ferromagnetic layer / strong spin-coupling layer heterojunction.

[0019] Through the design of the ferromagnetic layer / strong spin-coupling layer heterojunction, a tuning mechanism based on spin-orbit torque is provided for the filter, which is the key to realizing current regulation of the microwave absorption frequency band.

[0020] Example 2. The present invention provides a device based on spin-orbit torque, specifically including: A device based on spin-orbit torque, characterized in that it includes: a microwave transmission layer and a microwave absorption layer, and the microwave absorption layer is disposed on the upper surface of the microwave transmission layer; The microwave transmission layer is a CPW coplanar waveguide, and the microwave absorption layer is a ferromagnetic layer / strong spin-coupling layer heterojunction.

[0021] The CPW coplanar waveguide includes an insulating layer, a microwave transmission line, a substrate, and a ground layer; the microwave transmission line is disposed on the substrate, the insulating layer covers the microwave transmission line, and the ground layer is disposed at the bottom of the substrate.

[0022] The microwave transmission line is two parallel S-shaped copper wires; the insulating layer is a polyimide insulating layer.

[0023] The ferromagnetic layer / strong spin-coupling layer heterojunction includes a CoFeB thin film and a Pt thin film. The CoFeB thin film is disposed on a single-crystalline silicon substrate, and the Pt thin film covers the CoFeB thin film. The CoFeB thin film is the ferromagnetic layer, and the Pt thin film is the strong spin-coupling layer.

[0024] A wire is led out from the surface of the Pt thin film.

[0025] The microwave transmission line is designed as two parallel S-shaped copper wires, which helps to optimize the microwave transmission efficiency and the performance of the filter.

[0026] The insulating layer uses a polyimide material, which has good insulation performance and heat resistance, ensuring the stability and reliability of the filter.

[0027] Spin-orbit torque is generated through the spin Hall effect in the heavy metal (Pt) layer, which affects the magnetic properties of the ferromagnetic layer (CoFeB), realizing the function of current-controlled microwave absorption frequency band. It overcomes the problem of the large volume of traditional filters that require external magnets or coil currents, and has the advantages of low power consumption, fast response, and easy integration.

[0028] Example 3, the present invention provides a method for preparing a device based on spin-orbit torque, including: Step 1: Clean the single-crystalline silicon substrate.

[0029] The specific process is as follows: Use a double-sided polished single-crystalline silicon with a crystal orientation of <100> as the substrate, soak the silicon substrate in deionized water, acetone, and ethanol solutions with volumes of 40 ml to 60 ml successively, and use ultrasonic waves to clean the surface of the silicon wafer. The ultrasonic cleaning time is 5 min to 15 min, and the ultrasonic cleaning power is 50 w to 100 w.

[0030] Step 2: Air-dry the cleaned silicon substrate.

[0031] The specific process: Use tweezers to clamp the edge of the cleaned silicon substrate and dry it in a nitrogen atmosphere until the surface is bright and there is no residue of excess solution.

[0032] Step 3: Prepare the ferromagnetic layer / strong spin-coupling layer heterojunction. The ferromagnetic layer only needs to have ferromagnetism and a resistivity much greater than that of the strong spin-coupling layer, and the strong spin-coupling layer is required to have a large spin Hall angle and a resistivity much smaller than that of the ferromagnetic layer (Pt, Bi2Se3, or even a bilayer structure of Sn / Ag is acceptable).

[0033] The specific process is as follows: On a clean single-crystalline silicon substrate, a CoFeB thin film is grown as the ferromagnetic layer through DC magnetron sputtering technology. The base pressure in the vacuum chamber is less than 1×10-7 Torr, the sputtering power is 50 W, the working pressure of Ar is 5 mTorr, the deposition rate is 0.0071 nm / s, and the thickness of the CoFeB layer is 4 nm. On the deposited CoFeB layer, a Pt thin film is continuously grown through DC magnetron sputtering technology, and oxygen doping is achieved by controlling the growth atmosphere. The Pt thin film forms a heavy metal / ferromagnetic layer heterojunction with the CoFeB thin film as the heavy metal layer. The background vacuum of the sputtering chamber is less than 1×10-7 Torr, the sputtering power is 30 W, the working pressure of Ar is 10 mTorr. When depositing, the gas path connecting oxygen in the vacuum chamber is opened, and the flow rate is controlled so that oxygen accounts for 3% of the total gas volume during sputtering. The deposition rate is 0.0363 nm / s, and the thickness of the Pt layer is 6 nm.

[0034] Step 4: Lead out wires on the surface of the Pt thin film through ultrasonic bonding technology for applying current.

[0035] Step 5: Fabricate a coplanar waveguide and conduct filter current tuning tests.

[0036] The specific process is as follows: The coplanar waveguide consists of an insulating dielectric substrate and two parallel S-shaped microwave transmission lines composed of copper wires, which are fabricated by PCB, with a length of 50 mm and a width of 20 mm. The surface of the coplanar waveguide is covered with a polyimide insulating layer. The size of the thin film sample is 5×5 mm, and the sample film surface is placed face down in the center of the coplanar waveguide, as shown in Figure 1 Figure. Relevant tests are carried out on the Si / CoFeB / Pt tunable filter prepared by the above implementation method, with an applied current of -50~+100 mA, and the test results are as shown in Figure 3 Figure.

[0037] See Figure 2 Figure, in the device microwave absorption structure of the present invention, it is a heavy metal / ferromagnetic heterojunction (Pt / CoFeB), and the absorption of a specific microwave frequency band is achieved through the ferromagnetic resonance effect of the CoFeB layer. The magnetic moment state of the CoFeB layer in the present invention is regulated by the spin Hall effect of the Pt layer under an applied current. A DC current is applied to the Pt layer in the present invention. Due to the spin Hall effect in the Pt layer, part of the charge current is converted into a spin current, and the vertical spin current forms a spin accumulation at the interlayer interface, thereby generating a spin-orbit torque acting on the magnetic moment of the CoFeB layer and changing the magnetic state of the CoFeB layer. When a positive current is applied, the spin polarization direction of the Pt layer is along P2, the magnetic moment of the CoFeB layer deviates from the effective field, and the ferromagnetic resonance frequency of the device decreases, and the microwave absorption frequency shifts to the low frequency; when a reverse current is applied, the spin polarization direction of the Pt layer is along P1, and the microwave absorption frequency shifts to the high frequency.

[0038] During the preparation of the heavy metal layer, its spin Hall angle can be increased by doping to improve the regulation efficiency. In Example 1, oxygen doping causes certain impurity scattering in the Pt layer, enhancing the spin Hall effect in the Pt layer. Under the same conditions, the charge current is more likely to be converted into the spin current, that is, the spin Hall angle increases, so that a larger regulation range can be achieved under the same current.

Claims

1. A device based on spin-orbit torque, characterized in that: include: A microwave transmission layer and a microwave absorption layer, wherein the microwave absorption layer is arranged on the upper surface of the microwave transmission layer; The microwave transmission layer is a CPW coplanar waveguide, and the microwave absorption layer is a ferromagnetic layer / strong spin coupling layer heterojunction.

2. A device based on spin-orbit torque according to claim 1, characterized in that: The CPW coplanar waveguide includes an insulating layer, a microwave transmission line, a substrate and a ground layer; the microwave transmission line is arranged on the substrate, the insulating layer covers the microwave transmission line, and the ground layer is arranged at the bottom of the substrate.

3. A device based on spin-orbit torque according to claim 2, characterized in that: The microwave transmission line is two parallel S-shaped copper conductors; the insulation layer is a polyimide insulation layer.

4. The device based on spin-orbit torque according to claim 1, characterized in that: The ferromagnetic layer / strong spin coupling layer heterojunction includes a CoFeB film and a Pt film. The CoFeB film is arranged on a single crystal silicon substrate, and the Pt film covers the CoFeB film. The CoFeB film is a ferromagnetic layer, and the Pt film is a strong spin coupling layer.

5. A device based on spin-orbit torque according to claim 4, characterized in that: There are wires extending from the surface of the Pt film.

6. A method for preparing a device based on spin-orbit torque, characterized in that: A device based on spin-orbit torque according to any one of claims 1 to 5, comprising the following steps: Cleaning the single crystal silicon substrate and air drying the cleaned silicon substrate; A ferromagnetic layer / strong spin coupling layer heterojunction is prepared on an air-dried silicon substrate, wherein the ferromagnetic layer has ferromagnetism and a resistivity greater than that of the strong spin coupling layer, and the strong spin coupling layer has a large spin Hall angle; Leading out a wire on the surface of the strong spin coupling layer for applying current; A coplanar waveguide is prepared, and a ferromagnetic layer / strong spin coupling layer heterojunction is placed in the center of the coplanar waveguide.

7. The method for preparing a device based on spin-orbit torque according to claim 6, characterized in that: The method of cleaning the single crystal silicon substrate and air-drying the cleaned silicon substrate comprises: The crystal orientation is <100> The double-sided polished single crystal silicon in the direction is used as the substrate, and the silicon substrate is soaked in 40 ml~60 ml of deionized water, acetone, and ethanol solution successively, and the surface of the silicon wafer is cleaned by ultrasonic wave, the ultrasonic cleaning time is 5min~15min, and the ultrasonic cleaning power is 50w~100w; After cleaning, the edge of the cleaned silicon substrate is clamped and blown dry in a nitrogen atmosphere until the surface is bright and no solution remains.

8. The method for preparing a device based on spin-orbit torque according to claim 6, characterized in that: The method of preparing a ferromagnetic layer / strong spin coupling layer heterojunction on an air-dried silicon substrate comprises: growing a CoFeB film as a ferromagnetic layer on a clean single crystal silicon substrate by direct current magnetron sputtering technology, wherein the base pressure in a vacuum chamber is less than 1×10-7 Torr; and continuing to grow a Pt film on the deposited CoFeB layer by direct current magnetron sputtering technology, and achieving oxygen doping by controlling the growth atmosphere, wherein the Pt film serves as a heavy metal layer and forms a heavy metal / ferromagnetic layer heterojunction with the CoFeB film.

9. The method for preparing a device based on spin-orbit torque according to claim 6, characterized in that: Lead wires are connected to the surface of the Pt film by ultrasonic bonding machine.

10. The method for preparing a device based on spin-orbit torque according to claim 6, characterized in that: The method of preparing a coplanar waveguide and placing a ferromagnetic layer / strong spin coupling layer heterojunction in the center of the coplanar waveguide comprises: Two parallel S-shaped copper wires are arranged on an insulating dielectric substrate to form a microwave transmission line, the surface is covered with a polyimide insulating layer, and the sample film is placed facing downward in the center of the coplanar waveguide.

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