Magnetic reluctance device, manufacturing method therefor and use thereof

Abstract

A magnetic reluctance device, a manufacturing method therefor and a use thereof. The magnetic reluctance device comprises a substrate, a multi-walled carbon nanotube film and a metal electrode, wherein the multi-walled carbon nanotube film is bonded to the surface of the substrate, and the multi-walled carbon nanotube film comprises a plurality of multi-walled carbon nanotubes distributed in parallel; the metal electrode is bonded onto the multi-walled carbon nanotube film; and an opening is formed in the joint of the multi-walled carbon nanotube film and the metal electrode. The partially opened multi-walled carbon nanotubes are in contact with electrode metal, the spin-orbit coupling effect at the interface is stronger, and the partially opened multi-walled carbon nanotubes can produce a carbon source in contact with the metal electrode, facilitating achieving the carbon-based ferromagnetic property, and expanding the use of the multi-walled carbon nanotubes in the magnetic reluctance device.

Description

Magnetoresistive device and its preparation method and application

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on July 19, 2023, with application number 202310893811.8 and invention name “Magnetoresistive device, preparation method and application thereof”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application belongs to the field of microelectronic device technology, and more specifically, relates to magnetoresistive devices and their preparation methods and applications. Background Art

[0003] Magnetic reluctance refers to a parameter in a magnetic circuit containing a permanent magnet. Changes in magnetic flux cause changes in the resistance of a magnetic device. Therefore, changes in device reluctance are an important tool for determining the material's inherent magnetic properties. Therefore, the construction and measurement of magnetoresistive devices are crucial tools for magnetic materials.

[0004] In the prior art, there is no magnetoresistive device made of multi-walled carbon nanotubes, which limits the application of multi-walled carbon nanotubes in magnetoresistive devices. Technical issues

[0005] Based on this, the present application provides a magnetoresistive device and a preparation method and application thereof to solve the technical problem in the prior art that there is no magnetoresistive device made of multi-walled carbon nanotubes. Technical Solutions

[0006] To achieve the above objectives, the technical solution adopted in this application is:

[0007] In a first aspect, a magnetoresistive device is provided, comprising a substrate, a multi-walled carbon tube film, and a metal electrode. The multi-walled carbon tube film is bonded to the surface of the substrate, and the multi-walled carbon tube film includes a plurality of multi-walled carbon tubes distributed in parallel. The metal electrode is bonded to the multi-walled carbon tube film, and an opening is provided at the junction of the multi-walled carbon tube film and the metal electrode.

[0008] Optionally, a direct current is passed through the magnetoresistive device, and in an environment with a temperature less than 6K, the magnetoresistive device exhibits positive magnetoresistive resistance to the applied magnetic field; in an environment with a temperature greater than or equal to 6K, the magnetoresistive device exhibits negative magnetoresistive resistance to the applied magnetic field.

[0009] Optionally, the DC current is 10 nA-10 mA.

[0010] Optionally, the length of the multi-walled carbon tube is 200 μm-300 μm; and / or,

[0011] The diameter of multi-walled carbon tubes is less than or equal to 100nm.

[0012] Optionally, the plurality of multi-walled carbon tubes are parallel to each other, and an angle θ is formed between a central axis of the metal electrode and an extending direction of the multi-walled carbon tubes.

[0013] Optionally, the angle θ is 0°-90°; and / or,

[0014] For the same multi-walled carbon tube film and metal electrodes, the resistance of the magnetoresistive device decreases as the angle θ decreases.

[0015] Optionally, the resistance of the magnetoresistive device when the central axis of the metal electrode is perpendicular to the extension direction of the multi-walled carbon tube is greater than the resistance of the magnetoresistive device when the central axis of the metal electrode is parallel to the extension direction of the multi-walled carbon tube; and / or,

[0016] The structure of the metal electrode is at least one of a strip shape, a dumbbell shape, a cross shape, a tic-tac-toe shape and a Hall bar shape.

[0017] In a second aspect, a method for preparing the above-mentioned magnetoresistive device is provided, comprising the following steps:

[0018] Providing a substrate, growing multi-walled carbon tubes on the surface of the substrate by chemical vapor deposition to form a multi-walled carbon tube film, and obtaining a first-stage product;

[0019] Covering the surface of the multi-walled carbon tube film with a metal mask having a preset pattern, and depositing metal on the surface of the multi-walled carbon tube film by magnetron sputtering evaporation to obtain a second-stage product;

[0020] The metal mask is removed, and the redundant multi-walled carbon tube film is bombarded by plasma etching to obtain a magnetoresistive device.

[0021] Optionally, before depositing the metal on the surface of the multi-walled carbon tube film by magnetron sputtering evaporation, the method further comprises:

[0022] Bombarding the multi-walled carbon tube film of the first-stage product with plasma etching to obtain a multi-walled carbon tube film of a preset thickness; and / or,

[0023] The preparation method satisfies at least one of the following conditions:

[0024] Before growing multi-walled carbon tubes on the surface of the substrate by chemical vapor deposition, the substrate is subjected to hydrophilic treatment;

[0025] The magnetron sputtering evaporation was in DC mode with a power of 300W;

[0026] The thickness of the metal electrode is 100nm-300nm;

[0027] The parameters of plasma etching bombardment are as follows: etching gas is argon, the flow rate of argon is 20 sccm, the power is 200 W, and the bombardment time is 1 min.

[0028] Thirdly, the application of magnetoresistive devices in spintronics is also provided. Beneficial effects

[0029] The beneficial effects of this application are:

[0030] The present application constructs a magnetoresistive device containing a multi-walled carbon tube film. A metal electrode is bonded to the multi-walled carbon tube film. The junction between the multi-walled carbon tube film and the metal electrode has an opening. The opening refers to the destruction of the hexagonal carbon atom grid structure on the tube wall of the multi-walled carbon tube, forming a gap in the tube wall. The partially opened multi-walled carbon tube contacts the electrode metal, and the spin-orbit coupling effect at the interface is stronger. The partially opened multi-walled carbon tube can generate a carbon source in contact with the metal electrode, thereby making it easier to achieve carbon-based ferromagnetism and expanding the application of multi-walled carbon tubes in magnetoresistive devices.

[0031] The preparation method of the present application uses a mask method to set the pattern of the metal electrode according to the material characteristics, and the metal electrode with the preset pattern is bonded to the surface of the multi-walled carbon tube film. It does not require traditional processes such as coating and photolithography, which simplifies the preparation process and avoids the problem of residual adhesive in the device.

[0032] The magnetoresistive device provided by the present application, in which the multi-walled carbon tubes are combined with metal electrodes to exhibit magnetism, provides the possibility of application in spintronics and expands the diversity of spintronics. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The present invention will be further described below with reference to the accompanying drawings and embodiments, in which:

[0034] FIG1 is a schematic structural diagram of a magnetoresistive device according to an embodiment of the present application;

[0035] FIG2 is a schematic cross-sectional view of a magnetoresistive device according to an embodiment of the present application;

[0036] FIG3 is a schematic structural diagram of a magnetoresistive device according to an embodiment of the present application, wherein the junction between the multi-walled carbon tube film and the metal electrode has an opening;

[0037] FIG4 is a schematic structural diagram of a magnetoresistive device according to Example 1 of the present application;

[0038] FIG5 is a flow chart of a method for preparing a magnetoresistive device according to Example 1 of the present application;

[0039] FIG6 is a schematic structural diagram of a magnetoresistive device according to Example 2 of the present application;

[0040] FIG7 (a) is an optical photograph of the aligned multi-walled carbon tube film of Example 3 of the present application; FIG7 (b) is an optical photograph of the aligned multi-walled carbon tube film after thinning of Example 3; FIG7 (c) is an optical photograph of the metal mask of Example 3; FIG7 (d) is a schematic diagram of the multi-walled carbon tube film of Example 3 seen through the hollow structure of the metal mask; FIG7 (e) is a magnetoresistive device of Example 3; FIG7 (f) is an enlarged schematic diagram of the multi-walled carbon tube structure parallel to the molybdenum metal strip in Example 3;

[0041] FIG8 is a graph showing the change in resistance of the magnetoresistive device according to Example 1 of the present application as the temperature changes;

[0042] FIG9 is a graph showing the change in resistance of the magnetoresistive device of Example 1 of the present application at a temperature of 2K as the magnetic field changes;

[0043] FIG10 is a graph showing the change in resistance of the magnetoresistive device of Example 1 of the present application at a temperature of 10K as the magnetic field changes;

[0044] FIG11 is a graph showing the change in resistance of the magnetoresistive device according to Example 1 of the present application at a temperature of 100K as the magnetic field changes;

[0045] FIG12 is a graph showing the change in resistance of the magnetoresistive device according to Example 1 of the present application at a temperature of 200K as the magnetic field changes;

[0046] FIG13 is a graph showing the change in resistance of the magnetoresistive device according to Example 1 of the present application at a temperature of 300K as the magnetic field changes;

[0047] FIG14 is a graph showing the change in resistance of the magnetoresistive device according to Example 2 of the present application as the temperature changes;

[0048] FIG15 is a graph showing the change in resistance of the magnetoresistive device according to Example 2 of the present application at a temperature of 2K as the magnetic field changes;

[0049] FIG16 is a graph showing the change in resistance of the magnetoresistive device according to Example 2 of the present application at a temperature of 100K as the magnetic field changes;

[0050] FIG17 is a curve diagram showing the change in resistance of the magnetoresistive device according to Example 2 of the present application at a temperature of 200K as the magnetic field changes.

[0051] Description of reference numerals:

[0052] 10. Magnetoresistive device; 11. Substrate; 12. Multi-walled carbon tube film; 13. Metal electrode. Modes for Carrying Out the Invention

[0053] In order to make the technical problems, technical solutions and beneficial effects to be solved by this application more clearly understood, this application is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit this application.

[0054] An embodiment of the present application provides a magnetoresistive device 10, as shown in Figures 1 and 2. The magnetoresistive device 10 includes a substrate 11, a multi-walled carbon tube film 12, and a metal electrode 13. The multi-walled carbon tube film 12 is bonded to the surface of the substrate 11, and the multi-walled carbon tube film 12 includes a plurality of multi-walled carbon tubes distributed in parallel; the metal electrode 13 is bonded to the multi-walled carbon tube film 12, and the junction between the multi-walled carbon tube film 12 and the metal electrode 13 has an opening.

[0055] The present embodiment of the present invention constructs a magnetoresistive device 10 containing a multi-walled carbon tube film 12. A metal electrode 13 is bonded to the multi-walled carbon tube film 12. The junction between the multi-walled carbon tube film 12 and the metal electrode 13 has an opening. The opening refers to the destruction of the hexagonal carbon atom grid structure on the tube wall of the multi-walled carbon tube, forming a gap in the tube wall. As shown in Figure 3, carbon-metal chemical bonds are formed between some multi-walled carbon tubes and the metal electrode 13. The partially opened multi-walled carbon tubes are in contact with the metal electrode 13, and the spin-orbit coupling effect at their interface is stronger. The partially opened multi-walled carbon tubes can generate a carbon source in contact with the metal electrode 13, thereby making it easier to achieve carbon-based ferromagnetism. After measuring the magnetoresistive device 10, it was verified that the multi-walled carbon tubes exhibit magnetism when combined with the metal electrode 13, which expands the application of multi-walled carbon tubes in magnetoresistive devices 10.

[0056] According to experiments, in some embodiments, when a direct current is passed through the magnetoresistive device 10, in an environment with a temperature less than 6K, the magnetoresistive device 10 exhibits a positive magnetoresistive response to an applied magnetic field; in an environment with a temperature greater than or equal to 6K, the magnetoresistive device 10 exhibits a negative magnetoresistive response to an applied magnetic field. In particular, when the temperature is less than 3K, the magnetoresistive device 10 exhibits a significant positive magnetoresistive response to an applied magnetic field; and when the temperature is greater than or equal to 10K, the magnetoresistive device 10 exhibits a significant negative magnetoresistive response to an applied magnetic field. The magnetoresistive device 10 exhibits positive and negative magnetoresistive properties in different temperature ranges, and based on this property, the magnetoresistive device 10 can be used to monitor temperature changes, for example.

[0057] It can be understood that the magnetic field of the magnetoresistive device 10 can be selected according to the situation to be observed. In some embodiments, the magnetic field can be selected to be 5T to -5T. At a specific temperature, the size and direction of the magnetic field are changed, for example, the magnetic field is reduced from 5T to -5T, and then increased from -5T to 5T, and the magnetoresistive performance of the magnetoresistive device can be observed.

[0058] In some embodiments, the DC current passed through the magnetoresistive device 10 is 10nA-10mA. If the DC current is too large, for example, greater than 10mA, the magnetoresistive device 10 generates large energy consumption and heat, which may cause the magnetoresistive device 10 to burn out; if the DC current is too small, for example, less than 10nA, the magnetoresistive device 10 may be unable to be detected because the displayed magnetic resistance is too small.

[0059] Generally, most multi-walled carbon tubes used in electronic devices are 10μm-40μm long, less than 50μm. This short length is not conducive to regular distribution. The irregular distribution of multi-walled carbon tubes may affect the bonding between the multi-walled carbon tubes and the metal electrodes, and affect the magnetism generated by the bonding between the two.

[0060] The length of the multi-walled carbon tubes in the embodiment of the present application can be selected to be 200μm-300μm, and can be super-aligned and highly oriented. The orientation distribution can be flexible, easy to arrange, not messy, and a regular array distribution helps to regularize the combination of the multi-walled carbon tubes and the metal electrode 13, reduce multi-anisotropic interference, and help increase the toughness and service life of the multi-walled carbon tube film 12.

[0061] The super-aligned arrangement in the embodiment of the present application means that the orientation of the multi-walled carbon tubes is highly consistent, the diameter is uniform, and they can be directly drawn into a film.

[0062] In some embodiments, the diameter of the multi-walled carbon tubes is less than or equal to 100 nm, typically 3 nm to 100 nm, forming multi-walled carbon nanotubes.

[0063] The typical value of the embodiments of the present application refers to the average value or normal value of a certain performance of the product, which is a representative parameter that can characterize the characteristics of a group (or the characteristics of a subgroup).

[0064] Optionally, the thickness of the multi-walled carbon tube film 12 is 55nm-70nm, which is sufficient to combine with the metal electrode 13 and does not waste raw materials. Of course, in application, the appropriate thickness of the multi-walled carbon tube film 12 can be selected according to actual needs.

[0065] In some embodiments, the central axis of the metal electrode 13 forms an angle θ with the extension direction of the multi-walled carbon tubes. In particular, when the multi-walled carbon tubes are relatively long, for example, 200 μm to 300 μm in length, the majority of the multi-walled carbon tubes in the multi-walled carbon tube film 12 are parallel to each other, forming a regular multi-walled carbon tube array. This facilitates designing the angle between the metal electrode 13 and the multi-walled carbon tubes, thereby regulating the resistance of the magnetoresistive device 10.

[0066] It can be understood that the metal electrode 13 can be distributed perpendicular to the multi-walled carbon tubes or parallel to the multi-walled carbon tubes, or a specific angle is formed between the central axis of the metal electrode 13 and the extension direction of the multi-walled carbon tubes, that is, the angle θ between the central axis of the metal electrode 13 and the extension direction of the multi-walled carbon tubes ranges from 0° to 90°.

[0067] According to experiments, for identical multi-walled carbon tube films 12 and metal electrodes 13, the resistance of the magnetoresistive device 10 decreases as the angle θ decreases. That is, when the multi-walled carbon tube films 12 and metal electrodes 13 are identical, the angle θ1 in the first embodiment is, for example, 10°, and the angle θ2 in the second embodiment is, for example, 20°, the resistance of the magnetoresistive device 10 in the first embodiment will be smaller than that of the magnetoresistive device 10 in the second embodiment.

[0068] It can be understood that the resistance of the magnetoresistive device 10 when the central axis of the metal electrode 13 is perpendicular to the extension direction of the multi-walled carbon tubes is greater than the resistance of the magnetoresistive device 10 when the central axis of the metal electrode 13 is parallel to the extension direction of the multi-walled carbon tubes.

[0069] Based on the above properties, the resistance of the magnetoresistive device 10 can be adjusted by adjusting the angle θ between the metal electrode 13 and the multi-walled carbon tubes. It can be understood that a magnetoresistive device 10 can contain metal electrodes 13 and multi-walled carbon tubes with multiple angles θ. According to the resistance of the magnetoresistive device 10, according to the series or parallel circuits of the metal electrodes 13 with multiple angles θ, a superposition of multiple resistance properties corresponding to the series or parallel circuits will be presented.

[0070] In some embodiments, the structure of the metal electrode 13 is at least one of a strip shape, a dumbbell shape, a cross shape, a well shape and a Hall bar shape. The strip-shaped and dumbbell-shaped metal electrodes 13 are basically distributed along a straight line, and the angle θ between them and the multi-walled carbon tubes is an angle. The cross shape, the well shape and the Hall bar shape all have horizontal lines and straight lines. The horizontal lines and vertical lines of the metal electrodes 13 of these shape structures can form at least two angles of different angles with the multi-walled carbon tubes. For example, the vertical lines of a cross-shaped metal electrode 13 can be perpendicular to the extension direction of the multi-walled carbon tubes, and the horizontal lines are parallel to the extension direction of the multi-walled carbon tubes. Then, a cross-shaped metal electrode 13 can have electrical properties generated perpendicularly and parallelly at the same time, and the electrical properties generated by the metal electrode 13 and the multi-walled carbon tubes being perpendicular to each other can be measured, and the electrical properties generated by the metal electrode and the multi-walled carbon tubes being parallel to each other can also be measured.

[0071] During application, a metal electrode 13 with a suitable shape and structure can be selected as needed. When a magnetoresistive device 10 contains metal electrodes 13 with two or more shapes and structures, the magnetoresistive device 10 will exhibit the properties produced by the metal electrodes 13 with two or more shapes and structures.

[0072] In some embodiments, along the central axis of the metal electrode 13 , the minimum width of the metal electrode 13 is 28 μm-35 μm.

[0073] Optionally, the substrate 11 is a P-type heavily doped silicon wafer with a silicon dioxide insulating layer. The silicon wafer is a semiconductor material with good electrical properties and is not prone to problems such as warping, fragmentation, and oxygen precipitation, which is beneficial to improving the yield of the magnetoresistive device.

[0074] In some embodiments, the metal of the metal electrode 13 is deposited on the surface of the multi-walled carbon tube film by magnetron sputtering, and the metal electrode 13 includes molybdenum and / or gold. The embodiments of the present application propose a possible mechanism for the magnetoresistance effect of the magnetoresistive device 10 containing the multi-walled carbon tube film 12, namely, high-energy metal atoms generated by magnetron sputtering, such as molybdenum atoms or gold atoms, undergo a solid-solid reaction with the multi-walled carbon tubes, causing the multi-walled carbon tubes to produce a radially open structure, which has a magnetic moment.

[0075] The present invention also provides a method for preparing the magnetoresistive device, comprising the following steps:

[0076] S1: providing a substrate, and growing multi-walled carbon tubes on the surface of the substrate by chemical vapor deposition to form a multi-walled carbon tube film, thereby obtaining a first-stage product.

[0077] The substrate is placed in a vapor deposition device, a carbon source is introduced, the carbon source is cracked at high temperature, and then multi-walled carbon tubes are grown on the surface of the substrate, and multiple multi-walled carbon tubes form a multi-walled carbon tube film.

[0078] In some embodiments, before growing multi-walled carbon nanotubes on the surface of the substrate using chemical vapor deposition, the substrate is subjected to a hydrophilic treatment.

[0079] Optionally, the hydrophilic treatment comprises the following steps:

[0080] The substrate is placed in an acetone solution and ultrasonically cleaned for the first time. After the cleaning is completed, the substrate is transferred to an isopropyl alcohol solution and ultrasonically cleaned for the second time.

[0081] After cleaning, take out the substrate and blow dry it with a nitrogen gun;

[0082] The cleaned substrate is then bombarded with oxygen plasma to increase the hydrophilicity of the substrate surface. Optionally, the power of the first ultrasonic cleaning and the second ultrasonic cleaning are both about 100 W, and the cleaning time is about 5 minutes. The cleaning time can be selected according to actual conditions.

[0083] The power of oxygen plasma bombardment was set to 100 W, and the time was set to 5 min, which can be selected according to actual conditions.

[0084] In some embodiments, the carbon source is selected from benzene, toluene or alkanes, and the temperature of vapor deposition is 650°C-800°C.

[0085] S2: Covering the surface of the multi-walled carbon tube film with a metal mask having a preset pattern, and depositing metal on the surface of the multi-walled carbon tube film by magnetron sputtering evaporation to obtain a second-stage product.

[0086] A preset pattern is set on a metal mask plate, and the metal mask plate is used to cover the surface of the multi-walled carbon tube film, so that metal vapor can be deposited according to the preset pattern, eliminating multiple processes such as coating, development, and stripping, thereby improving production efficiency.

[0087] In the process of preparing molybdenum or gold-covered multi-walled carbon tube films using magnetron sputtering, sufficiently strong magnetron sputtering power can make the sputtered Mo atoms or Au atoms have relatively high initial energy (more than a dozen electron volts), which can undergo micro-region solid-solid reaction with multi-walled carbon nanotubes, thereby forming a local radial opening structure of the carbon nanotubes.

[0088] In some embodiments, the magnetron sputtering evaporation is performed in a direct current mode with a power of 300W.

[0089] Optionally, the thickness of the metal electrode is 100 nm-300 nm.

[0090] In some embodiments, before depositing the metal on the surface of the multi-walled carbon tube film by magnetron sputtering evaporation, the method further comprises:

[0091] The first-stage product is bombarded with a multi-walled carbon tube film by plasma etching to obtain a multi-walled carbon tube film with a preset thickness.

[0092] Optionally, the parameter conditions of plasma etching bombardment are: etching gas is argon, the flow rate of argon is 20 sccm, the power is 200 W, and the bombardment time is 1 min.

[0093] S3: removing the metal mask and bombarding the excess multi-walled carbon tube film with plasma etching to obtain a magnetoresistive device.

[0094] After removing the metal mask, plasma bombardment removes the multi-walled carbon tube film outside the area corresponding to the metal electrode to obtain a magnetoresistive device.

[0095] The preparation method of the embodiment of the present application sets the pattern of the metal electrode using a mask plate method according to the material properties, and combines the metal electrode with the preset pattern on the surface of the multi-walled carbon tube film. It does not require traditional processes such as coating and photolithography, simplifies the preparation process, and avoids the problem of residual glue in the device.

[0096] The magnetoresistive device provided in the embodiment of the present application, in which the multi-walled carbon tubes are combined with the metal electrodes, exhibits magnetism and ferromagnetism, providing the possibility of application in spintronics and expanding the diversity of spintronics.

[0097] The following is illustrated by multiple embodiments.

[0098] Example 1

[0099] The magnetoresistive device 10 of this embodiment, as shown in FIG4 , includes a P-type heavily doped silicon wafer 11, a multi-walled carbon tube film, and a molybdenum metal electrode 13. The P-type heavily doped silicon wafer 11 has a 300 nm thick silicon dioxide insulating layer, the multi-walled carbon tube film is bonded to the surface of the P-type heavily doped silicon wafer, and the molybdenum metal electrode 13 is bonded to the surface of the multi-walled carbon tube film.

[0100] The multi-walled carbon tubes in the multi-walled carbon tube film are parallel to each other, the length of the multi-walled carbon tubes is 200 μm-300 μm, the tube diameter is 3 nm-100 nm, and the thickness of the multi-walled carbon tube film is 60 nm.

[0101] The molybdenum metal electrode 13 is barbell-shaped, the central axis of the molybdenum metal electrode 13 is parallel to the extension direction of the multi-walled carbon tubes, and the thickness of the molybdenum metal electrode 13 is 150 nm.

[0102] The method for preparing the magnetoresistive device, as shown in FIG5 , comprises the following steps:

[0103] S1: Provide a substrate, place the substrate in an acetone solution, and perform a first ultrasonic cleaning at a power of 100 W for 5 minutes. After the cleaning is completed, transfer the substrate to an isopropanol solution and perform a second ultrasonic cleaning at a power of 100 W for 5 minutes.

[0104] After cleaning, take out the substrate and blow dry it with a nitrogen gun;

[0105] The cleaned substrate was then bombarded with oxygen plasma with a power of 100 W and a time of 5 min to increase the surface hydrophilicity of the substrate, thereby obtaining a hydrophilic-treated substrate.

[0106] S2: Place the substrate in a vapor deposition device, introduce a carbon source such as benzene, toluene or alkane, and grow multi-walled carbon tubes on the surface of the substrate by chemical vapor deposition at a temperature of 750°C to form a multi-walled carbon tube film to obtain the first-stage product.

[0107] S3: The first-stage product is subjected to plasma etching to bombard the multi-walled carbon tube film. The etching gas is argon gas with a flow rate of 20 sccm and a power of 200 W to obtain a multi-walled carbon tube film with a thickness of 60 nm.

[0108] S4: Cover the surface of the multi-walled carbon tube film with a metal mask plate with a preset pattern, and deposit metal molybdenum on the surface of the multi-walled carbon tube film using magnetron sputtering evaporation. The magnetron sputtering evaporation is in DC current mode with a power of 300W to obtain the second-stage product. The thickness of the molybdenum metal electrode is 150nm.

[0109] S5: removing the metal mask and bombarding the excess multi-walled carbon tube film with plasma etching to obtain a magnetoresistive device.

[0110] Example 2

[0111] As shown in FIG6 , the magnetoresistive device 10 of this embodiment includes a heavily P-type doped silicon wafer 11, a multi-walled carbon tube film, and a molybdenum metal electrode 13. The heavily P-type doped silicon wafer 11 has a 300nm silicon dioxide insulating layer, the multi-walled carbon tube film is bonded to the surface of the heavily P-type doped silicon wafer, and the molybdenum metal electrode 13 is bonded to the surface of the multi-walled carbon tube film.

[0112] The multi-walled carbon tubes in the multi-walled carbon tube film are parallel to each other, the length of the multi-walled carbon tubes is 200 μm-300 μm, the tube diameter is 5 nm-100 nm, and the thickness of the multi-walled carbon tube film is 60 nm.

[0113] The molybdenum metal electrode 13 is barbell-shaped, the central axis of the molybdenum metal electrode 13 is perpendicular to the extension direction of the multi-walled carbon tube, and the thickness of the molybdenum metal electrode 13 is 200 nm.

[0114] The method for preparing the magnetoresistive device comprises the following steps:

[0115] S1: Provide a substrate, place the substrate in an acetone solution, and perform a first ultrasonic cleaning at a power of 100 W for 6 minutes. After the cleaning is completed, transfer the substrate to an isopropanol solution and perform a second ultrasonic cleaning at a power of 100 W for 6 minutes.

[0116] After cleaning, take out the substrate and blow dry it with a nitrogen gun;

[0117] The cleaned substrate was then bombarded with oxygen plasma with a power of 100 W and a time of 5 min to increase the surface hydrophilicity of the substrate, thereby obtaining a hydrophilic-treated substrate.

[0118] S2: placing the substrate in a vapor deposition device, introducing a carbon source such as benzene, toluene or alkane, and growing multi-walled carbon tubes on the surface of the substrate by chemical vapor deposition at a temperature of 800°C to form a multi-walled carbon tube film to obtain a first-stage product.

[0119] S3: The first-stage product is subjected to plasma etching to bombard the multi-walled carbon tube film. The etching gas is argon gas with a flow rate of 20 sccm and a power of 200 W to obtain a multi-walled carbon tube film with a thickness of 60 nm.

[0120] S4: Cover the surface of the multi-walled carbon tube film with a metal mask plate with a preset pattern, and deposit metal molybdenum on the surface of the multi-walled carbon tube film using magnetron sputtering evaporation. The magnetron sputtering evaporation is in DC current mode with a power of 300W to obtain the second-stage product. The thickness of the molybdenum metal electrode is 150nm.

[0121] S5: removing the metal mask and bombarding the excess multi-walled carbon tube film with plasma etching to obtain a magnetoresistive device.

[0122] Example 3

[0123] The magnetoresistive device of this embodiment includes a P-type heavily doped silicon wafer, a multi-walled carbon tube film, and a molybdenum metal electrode. The P-type heavily doped silicon wafer has a 300nm thick silicon dioxide insulating layer. The multi-walled carbon tube film is bonded to the surface of the P-type heavily doped silicon wafer. The molybdenum metal electrode is bonded to the surface of the multi-walled carbon tube film.

[0124] The multi-walled carbon tubes in the multi-walled carbon tube film are parallel to each other, the length of the multi-walled carbon tubes is 200 μm-300 μm, the diameter of a small number of multi-walled carbon tubes is 5 nm-100 nm, and the thickness of the multi-walled carbon tube film is 60 nm.

[0125] The molybdenum metal electrode has a dumbbell structure, the central axis of some molybdenum metal electrodes is perpendicular to the extension direction of the multi-walled carbon tubes, and the central axis of some molybdenum metal electrodes is parallel to the extension direction of the multi-walled carbon tubes. The thickness of the molybdenum metal electrode is 200 nm.

[0126] The method for preparing the magnetoresistive device comprises the following steps:

[0127] S1: Provide a substrate, place the substrate in an acetone solution, and perform a first ultrasonic cleaning at a power of 100 W for 6 minutes. After the cleaning is completed, transfer the substrate to an isopropanol solution and perform a second ultrasonic cleaning at a power of 100 W for 6 minutes.

[0128] After cleaning, take out the substrate and blow dry it with a nitrogen gun;

[0129] The cleaned substrate was then bombarded with oxygen plasma with a power of 100 W and a time of 5 min to increase the surface hydrophilicity of the substrate, thereby obtaining a hydrophilic-treated substrate.

[0130] S2: Place the substrate in a vapor deposition device, introduce a carbon source such as benzene, toluene or alkane, and grow multi-walled carbon tubes on the surface of the substrate by chemical vapor deposition at a temperature of 750°C to form a multi-walled carbon tube film, thereby obtaining the first-stage product, as shown in (a) in Figure 7.

[0131] S3: The first-stage product is subjected to plasma etching to bombard the multi-walled carbon tube film. The etching gas is argon gas with a flow rate of 20 sccm and a power of 200 W to obtain a multi-walled carbon tube film with a thickness of 60 nm, as shown in FIG7 (b).

[0132] S4: Cover the surface of the multi-walled carbon tube film with a metal mask plate with a preset pattern. The metal mask plate is shown in (c) of Figure 7. Metal molybdenum is deposited on the surface of the multi-walled carbon tube film by magnetron sputtering evaporation. The magnetron sputtering evaporation is in DC current mode with a power of 300W to obtain the second-stage product. The thickness of the molybdenum metal electrode is 200nm.

[0133] S5: removing the metal mask and bombarding the excess multi-walled carbon tube film with plasma etching to obtain a magnetoresistive device, as shown in (e) in FIG7 .

[0134] (a) in Figure 7 is an optical photograph of the aligned MWCNT film. It can be seen that the MWCNTs are evenly arranged in the same direction and have good continuity within the range of 300 μm. However, some MWCNTs are entangled with each other to form bundles. Some bundles have a relatively thick diameter of 100 nm-200 nm, which has an adverse effect on subsequent device processing.

[0135] Therefore, in order to facilitate subsequent device processing and the formation of molybdenum-covered multi-walled carbon tube films, argon plasma etching was used to thin the in-line multi-walled carbon tube film. The optical photograph of the multi-walled carbon tube film after treatment is shown in (b) of Figure 7. It can be seen that the tube bundle is significantly thinner, indicating that the use of argon plasma etching to thin the multi-walled carbon tube film is effective.

[0136] Figure 7(c) shows an optical photograph of a metal mask, which features two hollowed-out dumbbell-shaped sections, perpendicular and evenly spaced. At this point, the metal mask has covered the surface of the multi-walled carbon tube film. Through the hollowed-out sections, the thinned multi-walled carbon tube (CNT) film can be seen, as shown in Figure 7(d).

[0137] Since the orientation of our aligned multi-walled carbon tube films is the same, there will be two structures of magnetoresistive devices after evaporating molybdenum metal. One is that the multi-walled carbon tubes are parallel to the molybdenum metal strips (CNT∥Mo bar), and the other is that the multi-walled carbon tubes are perpendicular to the molybdenum metal strips (CNT⊥Mo bar), as shown in (e) in Figure 7. (f) in Figure 7 is an enlarged schematic diagram of the structure of multi-walled carbon tubes parallel to the molybdenum metal strips (CNT∥Mo bar).

[0138] The magnetoresistive devices manufactured in Example 1 and Example 2 were tested to observe the resistance of the magnetoresistive devices at different temperatures, and the magnetoresistive performance of the magnetoresistive devices when the magnitude of the magnetic field was changed at a specific temperature.

[0139] As shown in Figure 8, the resistance of the magnetoresistive device of Example 1 gradually increases with increasing temperature. A magnetic field was applied to the device at temperatures of 2K, 10K, 100K, 200K, and 300K, with the magnitude of the magnetic field decreasing from 5T to -5T and then returning from -5T to 5T. A DC current of 5μA was passed through the magnetoresistive device, and the resistance of the device was recorded every time the magnetic field changed by 0.5T. The test results are shown in Figures 9 to 13, respectively. The magnetoresistive device exhibits positive magnetoresistive resistance at 2K, and the resistance of the device increases with increasing magnetic field. When the temperature is 10K, 100K, 200K, and 300K, the device exhibits negative magnetoresistive resistance, and the resistance of the device decreases with increasing magnetic field.

[0140] As shown in Figure 14, the resistance of the magnetoresistive device of Example 2 gradually increases with increasing temperature. A magnetic field was applied to the magnetoresistive device at temperatures of 2K, 100K, and 200K, decreasing from 5T to -5T and then back to 5T. A DC current of 5μA was passed through the device, and the resistance of the device was recorded every time the magnetic field changed by 0.5T. The test results are shown in Figures 15 to 17, respectively. The magnetoresistive device exhibits positive magnetoresistive resistance at 2K, increasing its resistance as the magnetic field increases. At temperatures of 100K and 200K, the device exhibits negative magnetoresistive resistance, decreasing its resistance as the magnetic field increases.

[0141] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present application should be included in the scope of protection of the present application.

Claims

1. A magnetoresistive device, characterized in that: It includes a substrate, a multi-walled carbon tube film and a metal electrode. The multi-walled carbon tube film is bonded to the surface of the substrate and includes a plurality of multi-walled carbon tubes distributed in parallel. The metal electrode is bonded to the multi-walled carbon tube film, and an opening is provided at the junction of the multi-walled carbon tube film and the metal electrode.

2. The magnetoresistive device according to claim 1, wherein: A direct current is passed through the magnetoresistive device. In an environment with a temperature less than 6K, the magnetoresistive device exhibits a positive magnetoresistive property to the applied magnetic field; in an environment with a temperature greater than or equal to 6K, the magnetoresistive device exhibits a negative magnetoresistive property to the applied magnetic field.

3. The magnetoresistive device according to claim 2, wherein: The DC current is 10 nA-10 mA.

4. The magnetoresistive device according to claim 1, wherein: The length of the multi-walled carbon tube is 200 μm-300 μm; and / or, The diameter of the multi-walled carbon tube is less than or equal to 100 nm.

5. The magnetoresistive device according to any one of claims 1 to 4, characterized in that: An angle θ is formed between the central axis of the metal electrode and the extending direction of the multi-walled carbon tube.

6. The magnetoresistive device according to claim 5, characterized in that: The angle θ is 0°-90°; and / or, With the same multi-walled carbon tube film and the same metal electrode, the resistance of the magnetoresistive device decreases as the angle θ decreases.

7. The magnetoresistive device according to claim 5, characterized in that: The resistance of the magnetoresistive device when the central axis of the metal electrode is perpendicular to the extension direction of the multi-walled carbon tube is greater than the resistance of the magnetoresistive device when the central axis of the metal electrode is parallel to the extension direction of the multi-walled carbon tube; and / or, The structure of the metal electrode is at least one of a strip shape, a dumbbell shape, a cross shape, a tic-tac-toe shape and a Hall bar shape.

8. A method for preparing a magnetoresistive device, for preparing the magnetoresistive device according to any one of claims 1 to 7, characterized in that: The preparation method comprises the following steps: Providing a substrate, growing multi-walled carbon tubes on the surface of the substrate by chemical vapor deposition to form a multi-walled carbon tube film, and obtaining a first-stage product; Covering the surface of the multi-walled carbon tube film with a metal mask having a preset pattern, and depositing metal on the surface of the multi-walled carbon tube film by magnetron sputtering evaporation to obtain a second-stage product; The metal mask is removed, and the redundant multi-walled carbon tube film is bombarded by plasma etching to obtain a magnetoresistive device.

9. The method for preparing a magnetoresistive device according to claim 8, characterized in that: Before depositing metal on the surface of the multi-walled carbon tube film by magnetron sputtering evaporation, the method further comprises: The first-stage product is subjected to plasma etching to bombard the multi-walled carbon tube film to obtain the multi-walled carbon tube film with a preset thickness; and / or, The preparation method meets at least one of the following conditions: Before growing multi-walled carbon tubes on the surface of the substrate by chemical vapor deposition, the substrate is subjected to hydrophilic treatment; The magnetron sputtering evaporation is in direct current mode with a power of 300W; The parameters of the plasma etching bombardment are as follows: the etching gas is argon, the flow rate of argon is 20 sccm, the power is 200 W, and the bombardment time is 1 min.

10. Use of the magnetoresistive device according to any one of claims 1 to 7 in a spintronic device.

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