Magnetoresistive device and preparation method and application thereof

Abstract

The invention provides a magnetic resistance device and a preparation method and application thereof, the magnetic resistance device comprises a substrate, a multi-wall carbon tube film and a metal electrode, the multi-wall carbon tube film is combined on the surface of the substrate, and the multi-wall carbon tube film comprises a plurality of multi-wall carbon tubes distributed in parallel; the metal electrode is combined on the multi-wall carbon tube film, and an opening is formed in the combination position of the multi-wall carbon tube film and the metal electrode. The magnetic resistance device containing the multi-wall carbon tube film is constructed, the metal electrode is combined on the multi-wall carbon tube film, the opening is formed in the combination position of the multi-wall carbon tube film and the metal electrode, the multi-wall carbon tube with part of the opening is in metal contact with the electrode, the spin-orbit coupling effect at the interface is higher, and the magnetic resistance is improved. A part of the opening of the multi-walled carbon tube can generate a carbon source in contact with the metal electrode, so that the carbon-based ferromagnetism is easier to realize, and the application of the multi-walled carbon tube in a magnetoresistive device is expanded.

Description

Technical Field

[0001] The present application belongs to the technical field of microelectronic devices, and more specifically, to a magnetoresistive device and a preparation method and application thereof. Background Art

[0002] Magnetic reluctance refers to a parameter in a magnetic circuit containing a permanent magnet. Changes in magnetic flux will cause changes in the resistance of a magnetic device, so changes in device reluctance are an important tool for determining the magnetic properties of a material. Therefore, the construction and measurement of reluctance devices are important tools for magnetic materials.

[0003] 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. Summary of the invention

[0004] Based on this, the present application provides a magnetoresistive device and a preparation method and application thereof to solve the technical problem that there is no magnetoresistive device made of multi-walled carbon nanotubes in the prior art.

[0005] To achieve the above purpose, the technical solution adopted in this application is:

[0006] In the first aspect, a magnetoresistive device is provided, comprising a substrate, a multi-walled carbon tube film and a metal electrode, wherein the multi-walled carbon tube film is bonded to the surface of the substrate, and the multi-walled carbon tube film comprises 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.

[0007] Optionally, a direct current is passed through the magnetoresistive device, and in an environment with a temperature less than 6K, the magnetoresistive device exhibits a positive magnetoresistive to the applied magnetic field; in an environment with a temperature greater than or equal to 6K, the magnetoresistive device exhibits a negative magnetoresistive to the applied magnetic field.

[0008] Optionally, the DC current is 10nA-10mA.

[0009] Optionally, the length of the multi-walled carbon tube is 200 μm-300 μm; and / or,

[0010] The diameter of multi-walled carbon tubes is less than or equal to 100nm.

[0011] 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.

[0012] Optionally, the angle θ is 0°-90°; and / or,

[0013] For the same multi-walled carbon tube film and metal electrode, the resistance of the magnetoresistive device decreases as the angle θ decreases.

[0014] 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,

[0015] 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.

[0016] In a second aspect, a method for preparing the above magnetoresistive device is provided, comprising the following steps:

[0017] 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;

[0018] 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;

[0019] The metal mask is removed, and the redundant multi-walled carbon tube film is bombarded by plasma etching to obtain a magnetoresistive device.

[0020] Optionally, before depositing the metal on the surface of the multi-walled carbon tube film by magnetron sputtering evaporation, the method further comprises:

[0021] 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,

[0022] The preparation method meets at least one of the following conditions:

[0023] Before growing multi-walled carbon tubes on the surface of the substrate by chemical vapor deposition, the substrate is subjected to hydrophilic treatment;

[0024] The magnetron sputtering evaporation was in DC mode with a power of 300W;

[0025] The thickness of the metal electrode is 100nm-300nm;

[0026] 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.

[0027] Thirdly, the application of magnetoresistive devices in spintronics is also provided.

[0028] The beneficial effects of this application are:

[0029] The present application constructs a magnetoresistive device containing a multi-walled carbon tube film, wherein a 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. The opening means that the hexagonal carbon atom grid structure on the tube wall of the multi-walled carbon tube is destroyed, and a gap is formed on the tube wall. The partially opened multi-walled carbon tube is in contact with 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 realize carbon-based ferromagnetism, and expanding the application of the multi-walled carbon tube in magnetoresistive devices.

[0030] The preparation method of the present application uses a mask plate method to set the pattern of the metal electrode according to the material characteristics, and the metal electrode with the preset pattern is combined with the surface of the multi-walled carbon tube film, without the need for traditional processes such as coating and photolithography, which simplifies the preparation process and avoids the problem of residual glue in the device.

[0031] The magnetoresistive device provided by the present application, in which the multi-walled carbon tubes are combined with the metal electrodes to exhibit magnetism, provides the possibility of application in spintronic devices and expands the diversity of spintronic devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The present invention will be further described below in conjunction with the accompanying drawings and embodiments, in which:

[0033] Figure 1 A schematic diagram of the structure of a magnetoresistive device according to an embodiment of the present application;

[0034] Figure 2 is a cross-sectional schematic diagram of a magnetoresistive device according to an embodiment of the present application;

[0035] Figure 3 A schematic diagram of a structure in which a junction between a multi-walled carbon tube film and a metal electrode in a magnetoresistive device according to an embodiment of the present application has an opening;

[0036] Figure 4 This is a schematic structural diagram of a magnetoresistive device according to Embodiment 1 of the present application;

[0037] Figure 5 This is a flow chart of a method for preparing a magnetoresistive device according to Example 1 of the present application;

[0038] Figure 6 This is a schematic structural diagram of a magnetoresistive device according to Embodiment 2 of the present application;

[0039] Figure 7 (a) is an optical photograph of the aligned multi-walled carbon tube film of Example 3 of the present application; Figure 7 (b) is an optical photograph of the thinned aligned multi-walled carbon tube film of Example 3; Figure 7 (c) is an optical photograph of the metal mask of Example 3; Figure 7(d) is a schematic diagram of the multi-walled carbon tube film seen through the hollow structure of the metal mask in Example 3; Figure 7 (e) is the magnetoresistive device of Example 3; Figure 7 (f) is an enlarged schematic diagram of the structure of the multi-walled carbon tube parallel to the molybdenum metal strip in Example 3;

[0040] Figure 8 A curve diagram showing the change in resistance of the magnetoresistive device according to Example 1 of the present application as the temperature changes;

[0041] Fig. 9 This is a curve diagram of the resistance change of the magnetoresistive device of Example 1 of the present application at a temperature of 2K as the magnetic field changes;

[0042] Fig.10 This is a curve diagram of the resistance change of the magnetoresistive device of Example 1 of the present application at a temperature of 10K as the magnetic field changes;

[0043] Fig.11 This is a curve diagram of the resistance change of the magnetoresistive device of Example 1 of the present application at a temperature of 100K as the magnetic field changes;

[0044] Fig.12 This is a curve diagram of the resistance change of the magnetoresistive device of Example 1 of the present application at a temperature of 200K as the magnetic field changes;

[0045] Fig.13 This is a curve diagram of the resistance change of the magnetoresistive device of Example 1 of the present application at a temperature of 300K as the magnetic field changes;

[0046] Fig.14 A curve diagram showing the change in resistance of the magnetoresistive device according to Example 2 of the present application as the temperature changes;

[0047] Fig.15 This is a curve diagram of the resistance change of the magnetoresistive device of Example 2 of the present application at a temperature of 2K as the magnetic field changes;

[0048] Fig.16 This is a curve diagram of the resistance change of the magnetoresistive device of Example 2 of the present application at a temperature of 100K as the magnetic field changes;

[0049] Fig.17 This is a curve diagram of the resistance change of the magnetoresistive device of Example 2 of the present application at a temperature of 200K as the magnetic field changes.

[0050] Description of reference numerals:

[0051] 10. Magnetoresistive device; 11. Substrate; 12. Multi-walled carbon tube film; 13. Metal electrode. DETAILED DESCRIPTION

[0052] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0053] The present application embodiment provides a magnetoresistive device 10, such as Figure 1 and Figure 2 As shown, 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.

[0054] The embodiment of the present application 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, and an opening is provided at the junction of the multi-walled carbon tube film 12 and the metal electrode 13. The opening means that the hexagonal carbon atom grid structure on the tube wall of the multi-walled carbon tube is destroyed, and a gap is formed on the tube wall. Figure 3 As shown, a carbon-metal chemical bond is formed between part of the multi-walled carbon tube and the metal electrode 13, and the multi-walled carbon tube with a part of the opening is in contact with the metal electrode 13, and the spin-orbit coupling effect at the interface is stronger. The opening of the multi-walled carbon tube can produce 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 tube combined with the metal electrode 13 exhibits magnetism, which expands the application of the multi-walled carbon tube in the magnetoresistive device 10.

[0055] 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 to the applied magnetic field; in an environment with a temperature greater than or equal to 6K, the magnetoresistive device 10 exhibits a negative magnetoresistive to the applied magnetic field. In particular, when the temperature is less than 3K, the magnetoresistive device 10 exhibits an obvious positive magnetoresistive to the applied magnetic field; when the temperature is greater than or equal to 10K, the magnetoresistive device 10 exhibits an obvious negative magnetoresistive to the 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, etc.

[0056] 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. The magnetoresistive performance of the magnetoresistive device can be observed.

[0057] In some embodiments, the DC current passed through the magnetoresistance device 10 is 10nA-10mA. If the DC current is too large, for example, greater than 10mA, the magnetoresistance device 10 generates greater energy consumption and heat, which may cause the magnetoresistance device 10 to burn out; if the DC current is too small, for example, less than 10nA, the magnetoresistance exhibited may be too small to be detected.

[0058] Generally, most multi-walled carbon tubes used in electronic devices have a length of 10 μm-40 μm, which is less than 50 μm. The short length is not conducive to regular distribution. The irregular distribution of multi-walled carbon tubes may affect the combination of multi-walled carbon tubes and metal electrodes, and affect the magnetism generated by the combination of the two.

[0059] 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, and can be oriented and distributed as needed. The orientation distribution is flexible, easy to arrange, and not messy. 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 is beneficial to increase the toughness and service life of the multi-walled carbon tube film 12.

[0060] The super-aligned arrangement in the embodiments of the present application means that the multi-walled carbon tubes have highly consistent orientations and uniform diameters and can be directly drawn into films.

[0061] In some embodiments, the diameter of the multi-walled carbon tube is less than or equal to 100 nm, with a typical value of 3 nm-100 nm, forming a multi-walled carbon nanotube.

[0062] 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 certain subgroup).

[0063] 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.

[0064] In some embodiments, the central axis of the metal electrode 13 and the extension direction of the multi-walled carbon tube have an angle θ. In particular, when the length of the multi-walled carbon tube is relatively long, for example, the length of the multi-walled carbon tube is 200 μm-300 μm, most 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, which is conducive to designing the angle between the metal electrode 13 and the multi-walled carbon tube, thereby regulating the resistance of the magnetoresistive device 10.

[0065] 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°.

[0066] According to experiments, for the same multi-walled carbon tube film 12 and metal electrode 13, the resistance of the magnetoresistive device 10 will decrease as the angle θ decreases. That is, when the multi-walled carbon tube film 12 and the metal electrode 13 are the same, the angle θ in the first embodiment is 1 For example, the angle θ in the second embodiment is 10°. 2 For example, if the angle is 20°, the resistance of the magnetoresistive device 10 of the first embodiment will be smaller than that of the magnetoresistive device 10 of the second embodiment.

[0067] 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 tube 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 tube.

[0068] According to 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 tube. It can be understood that a magnetoresistive device 10 may contain metal electrodes 13 and multi-walled carbon tubes with multiple angles θ, and the resistance of the magnetoresistive device 10 will present a superposition of multiple resistance properties of the corresponding series or parallel circuits according to the series or parallel circuits of the metal electrodes 13 with multiple angles θ.

[0069] In some embodiments, the structure of the metal electrode 13 is at least one of a strip, dumbbell, cross, tic-tac-toe and Hall bar. The strip 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, tic-tac-toe shape and Hall bar type all have horizontal lines and straight lines. The horizontal lines and vertical lines of the metal electrodes 13 of these shapes can form at least two 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 vertically 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 13 and the multi-walled carbon tubes being parallel to each other can also be measured.

[0070] When applied, 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 be able to exhibit the properties produced by the metal electrodes 13 with two or more shapes and structures.

[0071] In some embodiments, along the central axis direction of the metal electrode 13 , the minimum width of the metal electrode 13 is 28 μm-35 μm.

[0072] 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 magnetoresistive devices.

[0073] 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 embodiment of the present application proposes a possible mechanism for the magnetoresistance effect of the magnetoresistance device 10 containing the multi-walled carbon tube film 12, that is, high-energy metal atoms such as molybdenum atoms or gold atoms generated by magnetron sputtering react with the multi-walled carbon tubes in a solid-solid reaction, so that the multi-walled carbon tubes produce a radially open structure, which has a magnetic moment.

[0074] The present application also provides a method for preparing the above magnetoresistive device, comprising the following steps:

[0075] 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.

[0076] 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.

[0077] In some embodiments, before growing multi-walled carbon tubes on the surface of the substrate by chemical vapor deposition, the substrate is subjected to a hydrophilic treatment.

[0078] Optionally, the hydrophilic treatment comprises the following steps:

[0079] The substrate is placed in an acetone solution and subjected to a first ultrasonic cleaning. After the cleaning is completed, the substrate is transferred to an isopropanol solution and subjected to a second ultrasonic cleaning.

[0080] After cleaning, take out the substrate and blow dry it with a nitrogen gun;

[0081] The cleaned substrate is then bombarded with oxygen plasma to increase the surface hydrophilicity of the substrate. Optionally, the power of the first ultrasonic cleaning and the second ultrasonic cleaning are both about 100W, and the cleaning time is about 5 minutes. The cleaning time can be selected according to actual conditions.

[0082] The power of oxygen plasma bombardment is set to 100 W, and the time is set to 5 min, which can be selected according to actual conditions.

[0083] In some embodiments, the carbon source is selected from benzene, toluene or alkane, and the temperature of vapor deposition is 650°C-800°C.

[0084] 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.

[0085] 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, developing, and stripping, thereby improving production efficiency.

[0086] In the process of preparing molybdenum or gold covered multi-walled carbon tube films by 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-area solid-solid reaction with the multi-walled carbon nanotubes, thereby forming a local radial opening structure of the carbon nanotubes.

[0087] In some embodiments, the magnetron sputtering evaporation is in direct current mode with a power of 300W.

[0088] Optionally, the thickness of the metal electrode is 100nm-300nm.

[0089] 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:

[0090] The multi-walled carbon tube film of the first-stage product is bombarded with plasma etching to obtain a multi-walled carbon tube film with a preset thickness.

[0091] 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.

[0092] S3: removing the metal mask and bombarding the excess multi-walled carbon tube film with plasma etching to obtain a magnetoresistive device.

[0093] 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.

[0094] The preparation method of the embodiment of the present application sets the pattern of the metal electrode by a mask method according to the material properties, and combines the metal electrode of the preset pattern with 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.

[0095] The magnetoresistive device provided in the embodiment of the present application, the multi-walled carbon tube combined with the metal electrode exhibits magnetism and ferromagnetism, provides the possibility of application in spin electronic devices, and expands the diversity of spin electronic devices.

[0096] The following is illustrated by multiple embodiments.

[0097] Example 1

[0098] The magnetoresistive device 10 of this embodiment is as follows: Figure 4 As shown, it 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 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, and the molybdenum metal electrode 13 is bonded to the surface of the multi-walled carbon tube film.

[0099] The multi-walled carbon tubes in the multi-walled carbon tube film are parallel to each other, the length of the multi-walled carbon tube 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.

[0100] The molybdenum metal electrode 13 is in a barbell shape, the central axis of the molybdenum metal electrode 13 is parallel to the extension direction of the multi-walled carbon tube, and the thickness of the molybdenum metal electrode 13 is 150 nm.

[0101] The preparation method of the above magnetoresistive device is as follows: Figure 5 As shown, the following steps are included:

[0102] S1: providing a substrate, placing the substrate in an acetone solution, and performing a first ultrasonic cleaning at a power of 100 W for 5 minutes; after the cleaning is completed, transferring the substrate to an isopropanol solution, and performing a second ultrasonic cleaning at a power of 100 W for 5 minutes;

[0103] After cleaning, take out the substrate and blow dry it with a nitrogen gun;

[0104] The cleaned substrate is 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 hydrophilically treated substrate.

[0105] 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 750°C to form a multi-walled carbon tube film to obtain a first-stage product.

[0106] S3: The multi-walled carbon tube film of the first-stage product is bombarded with plasma etching, the etching gas is argon, the flow rate of argon is 20 sccm, and the power is 200 W, so as to obtain a multi-walled carbon tube film with a thickness of 60 nm.

[0107] 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 by magnetron sputtering evaporation. The magnetron sputtering evaporation is a DC current mode with a power of 300W to obtain a second-stage product. The thickness of the molybdenum metal electrode is 150nm.

[0108] S5: removing the metal mask, bombarding the excess multi-walled carbon tube film with plasma etching, and obtaining a magnetoresistive device.

[0109] Example 2

[0110] The magnetoresistive device 10 of this embodiment is as follows: Figure 6 As shown, it 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 300nm 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.

[0111] The multi-walled carbon tubes in the multi-walled carbon tube film are parallel to each other, the length of the multi-walled carbon tube 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.

[0112] The molybdenum metal electrode 13 is in a barbell shape, 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.

[0113] The method for preparing the magnetoresistive device comprises the following steps:

[0114] S1: providing a substrate, placing the substrate in an acetone solution, and performing a first ultrasonic cleaning at a power of 100 W for 6 minutes; after the cleaning is completed, transferring the substrate to an isopropanol solution, and performing a second ultrasonic cleaning at a power of 100 W for 6 minutes;

[0115] After cleaning, take out the substrate and blow dry it with a nitrogen gun;

[0116] The cleaned substrate is 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 hydrophilically treated substrate.

[0117] 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.

[0118] S3: The multi-walled carbon tube film of the first-stage product is bombarded with plasma etching, the etching gas is argon, the flow rate of argon is 20 sccm, and the power is 200 W, so as to obtain a multi-walled carbon tube film with a thickness of 60 nm.

[0119] 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 by magnetron sputtering evaporation. The magnetron sputtering evaporation is a DC current mode with a power of 300W to obtain a second-stage product. The thickness of the molybdenum metal electrode is 150nm.

[0120] S5: removing the metal mask, bombarding the excess multi-walled carbon tube film with plasma etching, and obtaining a magnetoresistive device.

[0121] Example 3

[0122] 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, and the molybdenum metal electrode is bonded to the surface of the multi-walled carbon tube film.

[0123] 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.

[0124] 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 200nm.

[0125] The method for preparing the magnetoresistive device comprises the following steps:

[0126] S1: providing a substrate, placing the substrate in an acetone solution, and performing a first ultrasonic cleaning at a power of 100 W for 6 minutes; after the cleaning is completed, transferring the substrate to an isopropanol solution, and performing a second ultrasonic cleaning at a power of 100 W for 6 minutes;

[0127] After cleaning, take out the substrate and blow dry it with a nitrogen gun;

[0128] The cleaned substrate is 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 hydrophilically treated substrate.

[0129] S2: Place the substrate in a vapor deposition device, introduce carbon source benzene, toluene or alkane, and use chemical vapor deposition to grow multi-walled carbon tubes on the surface of the substrate at a temperature of 750°C to form a multi-walled carbon tube film to obtain the first-stage product, such as Figure 7 (a) in .

[0130] S3: The first-stage product is subjected to plasma etching to bombard the multi-walled carbon tube film, the etching gas is argon, the flow rate of argon is 20sccm, and the power is 200W, so as to obtain a multi-walled carbon tube film with a thickness of 60nm. Figure 7 (b) in .

[0131] S4: Covering the surface of the multi-walled carbon tube film with a metal mask having a preset pattern, the metal mask such as Figure 7 In (c), 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 300 W to obtain a second-order product, and the thickness of the molybdenum metal electrode is 200 nm.

[0132] S5: Remove the metal mask and bombard the excess multi-walled carbon tube film with plasma etching to obtain a magnetoresistive device, such as Figure 7 (e) in .

[0133] Figure 7 (a) is an optical photograph of the aligned multi-walled carbon tube film. It can be seen that the multi-walled carbon tubes are evenly arranged in the same direction and have good continuity within the range of 300μm. However, some multi-walled carbon tubes are entangled with each other to form tube bundles. Some tube bundles have a thicker diameter of 100nm-200nm, which has an adverse effect on subsequent device processing.

[0134] Therefore, in order to facilitate the subsequent device processing and form a molybdenum-covered multi-walled carbon tube film, argon plasma etching was used to thin the aligned multi-walled carbon tube film. The optical photograph of the treated multi-walled carbon tube film is shown in FIG. Figure 7 As shown in (b), it can be seen that the tube bundle is significantly thinned, indicating that the effect of using argon plasma etching on thinning the multi-walled carbon tube film is obvious.

[0135] picture Figure 7 (c) is an optical photo of the metal mask, which has two hollow dumbbell shapes that are perpendicular to each other and evenly distributed. At this point, the metal mask has covered the surface of the multi-walled carbon tube film, and the thinned multi-walled carbon tube film (CNT) can be seen through the hollow structure on the metal mask, as shown in Figure 2. Figure 7 (d) in.

[0136] Since the orientation of our aligned multi-walled carbon tube film is the same, there will be two structures of magnetoresistive devices after evaporating molybdenum metal, one is that the multi-walled carbon tube is parallel to the molybdenum metal strip (CNT∥Mo bar), and the other is that the multi-walled carbon tube is perpendicular to the molybdenum metal strip (CNT⊥Mo bar). Figure 7 As shown in (e), Figure 7 (f) is an enlarged schematic diagram of the structure of a multi-walled carbon tube parallel to a molybdenum metal bar (CNT∥Mo bar).

[0137] The magnetoresistive devices made 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.

[0138] Among them, Figure 8 As shown in the figure, as the temperature increases, the resistance of the magnetoresistive device of Example 1 gradually increases. When the temperature is 2K, 10K, 100K, 200K, and 300K, a magnetic field is applied to the device, and the magnitude of the magnetic field is reduced from 5T to -5T, and then from -5T back to 5T. A DC current of 5μA is passed through the magnetoresistive device, and the resistance of the device is recorded every time the magnetic field changes by 0.5T. The test results are shown in the figure below. Figures 9 to 13 , the magnetoresistance device exhibits positive magnetoresistance when the temperature is 2K, and the resistance of the device increases with the increase of the magnetic field. When the temperature is 10K, 100K, 200K, and 300K, the device exhibits negative magnetoresistance, and the resistance of the device decreases with the increase of the magnetic field.

[0139] like Fig.14 As shown in the figure, as the temperature increases, the resistance of the magnetoresistive device of Example 2 gradually increases. When the temperature is 2K, 100K, and 200K, a magnetic field is applied to the magnetoresistive device, and the magnitude of the magnetic field is reduced from 5T to -5T, and then from -5T back to 5T. A DC current of 5μA is passed through the magnetoresistive device, and the resistance of the device is recorded every time the magnetic field changes by 0.5T. The test results are shown in the figure below. Figures 15 to 17 When the temperature is 2K, the magnetoresistance device exhibits positive magnetoresistance. As the magnetic field increases, the resistance of the device increases. When the temperature is 100K or 200K, the device exhibits negative magnetoresistance. As the magnetic field increases, the resistance of the device decreases.

[0140] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application should be included in the protection scope 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 direct current is 10nA-10mA.

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.

Images