Extremely weak magnetic Hall sensor based on two-dimensional ferromagnetic material

Abstract

The utility model discloses an extremely weak magnetic Hall sensor based on a two-dimensional ferromagnetic material, which comprises a SrTiO3 substrate with a polished single surface, a single Hall bar or a plurality of Hall bars are distributed on the polished surface of the substrate, the formed Hall bar is oriented along a z axis, and the single Hall bar comprises M periods of alternately grown single-layer SrRuO3 films and N layers of SrTiO3 films. In a specific light field, the sensitivity of the magnetic detector is greater than 11000 omega / T, and the detectable magnetic field range is greater than + / -1T. The sensitivity of response to a pT magnetic field can be realized, and a large magnetic field range can be detected. In aerospace, the method can be used for high-performance navigation equipment. And the method also has huge application potential in the aspects of medical treatment, mineral exploration, environment detection and the like.

Description

Technical Field

[0001] The utility model belongs to the technical field of magnetic sensors, in particular to an extremely weak magnetic Hall sensor based on two-dimensional ferromagnetic materials. Background Art

[0002] A magnetic detector is an instrument used to detect magnetic fields. It has a wide range of applications in defense, agriculture, ocean, resource exploration, meteorology, medical treatment, scientific research and other fields. There are many types of magnetic detectors, including Hall sensors, magnetoresistive sensors and magnetocapacitive sensors. Among them, the Hall sensor based on the Hall effect is one of the most commonly used sensors for detecting magnetic fields. The Hall effect refers to the fact that when a current in a certain direction passes through an electrical conductor, an electric field is generated in a direction perpendicular to the current. The direction of this electric field is perpendicular to the direction of the magnetic field, and its magnitude is proportional to the strength of the magnetic field. When the direction or intensity of the magnetic field changes, the magnitude of the electric field will also change, thereby generating a voltage signal output. These electrical signals can be used to accurately measure the direction and intensity of the magnetic field. At present, the most commonly used commercial Hall sensor is a Hall magnetometer based on the normal Hall effect in semiconductor materials, which has the advantages of low power consumption, high reliability and small size. However, the normal Hall effect in traditional semiconductors responds linearly to the magnetic field, and the detection accuracy is severely limited in a weak magnetic environment. Now some ferromagnetic materials can also achieve anomalous Hall resistance of tens or hundreds of Ω, thereby achieving a relatively large magnetic response. For example, the magnetic response sensitivity of thin film systems such as Cr-Doped Bi2Te3, MgO / CoFeB / X / Ta / MgO, SiO2 / Fe-Pt / SiO2 can reach 2620Ω / T, 6837Ω / T, and 12000Ω / T, respectively, but their saturation magnetic fields are only tens or even a few Oe, which means that devices based on these materials can only detect a very small magnetic field range. Utility Model Content

[0003] The utility model aims to overcome the existing material problems and provide a weak magnetic detector which has a sensitive response to pT-level weak magnetic fields and can detect magnetic fields up to 1T.

[0004] In order to solve the above technical problems, the utility model is realized by the following technical solutions:

[0005] An extremely weak magnetic Hall sensor based on two-dimensional ferromagnetic materials includes a single-side polished SrTiO3 substrate, wherein the SrTiO3 substrate is a rectangular plate structure;

[0006] The polished surface of the SrTiO3 substrate is distributed with a single Hall bar or multiple Hall bars, and the Hall bars are distributed in an array along the x-axis and y-axis corresponding to the SrTiO3 substrate, wherein the hall bar is made by using photolithography technology after the film is grown, and the formed Hall bar is oriented along the z-axis;

[0007] A single Hall bar consists of M periods of alternatingly grown single-layer SrRuO3 films and N-layer SrTiO3 films.

[0008] Furthermore, the growth orientation of the SrRuO3 film and the N-layer SrTiO3 film corresponding to a single period is z-axis orientation, and a single period consists of a SrRuO3 film with a thickness of 1 monolayer and a SrTiO3 film with N monolayers. The N corresponding to the N-layer SrTiO3 film is 1 to 5; the Hall bar is nanometer-level.

[0009] The preparation method of the extremely weak magnetic Hall sensor based on two-dimensional ferromagnetic material includes the following steps:

[0010] (1) SrTiO3 substrate cleaning: The SrTiO3 substrate is ultrasonically cleaned in acetone and anhydrous ethanol to remove surface impurities; the impurities include organic impurities, acetone used for cleaning, and other impurities;

[0011] (2) SrTiO3 substrate etching annealing: The cleaned SrTiO3 substrate is subjected to ultrasonic reaction in deionized water for about 30 minutes, then etched in BOE solution, then rinsed in deionized water and the water adsorbed on the surface is blown dry with nitrogen, and the etched substrate is subjected to high-temperature annealing to obtain a SrTiO3 substrate with a high-quality step surface and a cut-off TiO2 layer;

[0012] (3) Epitaxial growth of oxide thin films: A pulsed laser deposition system or a molecular beam epitaxy system is used for thin film growth. The SrTiO3 substrate treated in step (2) is placed in a growth chamber. The oxygen pressure, temperature, etc. are adjusted to the required conditions, wherein the oxygen pressure and temperature are 0.1 mbar and 700°C, respectively. M cycles of 1 monolayer SrRuO3 thin films and N monolayer SrTiO3 thin films are repeatedly epitaxially grown on the polished surface of the SrTiO3 substrate.

[0013] (4) Hall bar fabrication: The epitaxial film is fabricated into nanometer-sized Hall bars or arrays of Hall bars.

[0014] Furthermore, the BOE solution is an STO etching solution, and the formulation is V (49.9wt% HF solution): V (40wt% NH4F solution) = 1:6. The corresponding substrate high temperature annealing conditions in step (2) are: the etched SrTiO3 substrate is placed in a muffle furnace and subjected to high temperature annealing for 90 minutes at 950°C. In step (3), the oxygen pressure and temperature in the growth chamber are 0.1 mbar and 700°C, respectively.

[0015] Based on the application of extremely weak magnetic Hall sensor made of two-dimensional ferromagnetic materials, the transverse circuit and longitudinal circuit of the Hall bar are connected in series respectively. When in use, longitudinal current is added and the change of transverse resistance is measured.

[0016] The utility model has the following beneficial effects: the utility model can be used for detecting unknown magnetic fields, such as Figure 1 As shown, when using, place the detector on the ground to be detected, add the required light field and transverse current, lower the temperature to the required temperature, and measure the change in longitudinal resistance. Figure 2 As shown, under a specific light field, the sensitivity of the magnetic detector of the utility model is greater than 11000Ω / T, and the detectable magnetic field range is greater than ±1T. It can achieve the sensitivity of pT magnetic field response and detect a large magnetic field range. It can also be used in aerospace and national defense. With the development of wave absorbing technology, military objects can be covered with a layer of wave absorbing material to achieve invisibility, but they cannot shield the magnetic field generated by themselves. Therefore, the utility model can be used to detect hidden objects. In addition, in aerospace, it can be used for high-performance navigation equipment. In addition to the above aspects, our utility model also has great application potential in medical treatment, mineral exploration, environmental testing and other aspects. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the present utility model, the drawings required for describing the embodiments are briefly introduced below.

[0018] Figure 1 : Device schematic diagram.

[0019] Figure 2 : [(SrRuO3)1 / (SrTiO3)4] obtained in the dark and under light conditions, respectively 25 Field-dependent anomalous Hall resistivity (ρ AHE ).

[0020] In the drawings, the components represented by the reference numerals are listed as follows: SrTiO3 substrate 1, Hall bar 2. DETAILED DESCRIPTION

[0021] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments.

[0022] like Figure 1As shown: An extremely weak magnetic Hall sensor based on two-dimensional ferromagnetic materials includes a single-sided polished SrTiO3 substrate 1, which is a rectangular plate structure; the thickness corresponds to the z-axis, which is about 0.5 mm, and the length and width correspond to the x-axis and y-axis, which are about 5×5 mm. There are multiple Hall bars distributed on the polished surface of the SrTiO3 substrate, and the Hall bars are arranged in an array along the x-axis and y-axis. The Hall bars are nanometer-sized, wherein the hall bars are made using photolithography technology after the film is grown, and the molded Hall bars are oriented along the z-axis; a single Hall bar 2 includes M periods of alternatingly grown single-layer SrRuO3 films and N layers of SrTiO3 films, where N is 1 to 5.

[0023] The growth orientation of the SrRuO3 film and the N-layer SrTiO3 film corresponding to a single period is z-axis orientation, and a single period consists of a SrRuO3 film with a thickness of 1 monolayer and a SrTiO3 film with N monolayers.

[0024] Preparation method: including the following steps,

[0025] (1) SrTiO3 substrate cleaning: The SrTiO3 substrate was ultrasonically cleaned in acetone and anhydrous ethanol to remove surface impurities.

[0026] (2) SrTiO3 substrate etching annealing: The cleaned SrTiO3 substrate was ultrasonically reacted in deionized water for about 30 minutes, then etched in BOE solution, then placed in deionized water for cleaning and the water adsorbed on the surface was blown dry with nitrogen, and the etched substrate was subjected to high-temperature annealing. The high-temperature annealing conditions were: the etched SrTiO3 substrate was placed in a muffle furnace and annealed at 950°C for 90 minutes. A SrTiO3 substrate with a high-quality step surface and a TiO2 layer cutoff was obtained; the BOE solution was an STO etching solution, and the formulation was V (49.9wt% HF solution): V (40wt% NH4F solution) = 1:6.

[0027] (3) Epitaxial growth of oxide thin films: A pulsed laser deposition system or a molecular beam epitaxy system is used for thin film growth. The SrTiO3 substrate treated in step (2) is placed in a growth chamber. The oxygen pressure, temperature, etc. are adjusted to the required conditions, wherein the oxygen pressure and temperature are 0.1 mbar and 700°C, respectively. M cycles of 1 monolayer SrRuO3 thin films and N monolayer SrTiO3 thin films are repeatedly epitaxially grown on the polished surface of the SrTiO3 substrate.

[0028] (4) Hall bar fabrication: The epitaxial film is fabricated into nanometer-sized Hall bars or arrays of Hall bars.

[0029] Connect the horizontal circuit and vertical circuit of the Hall bar in series, add vertical current when using, and measure the change of horizontal resistance. Figure 2 As shown in the figure, when no light field is applied, when a certain magnetic field is applied in the z-axis direction, the saturated anomalous Hall resistivity of the film is less than 1μΩ·cm. When the energy density is 17.6nW / cm 2 When exposed to ultraviolet light, its saturated anomalous Hall resistivity can reach 11600μΩ·cm. The magnetic detection sensitivity is ≥11000Ω / T, and the detectable magnetic field range is ≥±1T. It can achieve both the sensitivity of pT magnetic field response and the detection of a large magnetic field range. The normal Hall effect in traditional semiconductors responds linearly to the magnetic field, and the detection accuracy is severely limited in a weak magnetic environment. Some of the existing materials that utilize the anomalous Hall effect can also achieve a magnetic response sensitivity of more than 10000Ω / T, but their saturation magnetic field is only a few Oe to a few hundred Oe, which cannot meet the measurement of a large range of magnetic field strength. Therefore, our utility model has great application value.

[0030] This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can better understand and utilize the present invention.

Claims

1. An extremely weak magnetic Hall sensor based on two-dimensional ferromagnetic materials, characterized in that: It comprises a single-side polished SrTiO3 substrate (1), wherein the SrTiO3 substrate (1) is a rectangular plate structure; A single Hall bar (2) or a plurality of Hall bars are distributed on the polished surface of the SrTiO3 substrate, and the Hall bars are distributed in an array along the x-axis and the y-axis corresponding to the SrTiO3 substrate (1), wherein the hallbars are formed by using photolithography technology after the film is grown, and the formed Hallbars are oriented along the z-axis; A single Hall bar (2) includes M periods of alternatingly grown single-layer SrRuO3 films and N-layer SrTiO3 films.

2. The extremely weak magnetic Hall sensor based on two-dimensional ferromagnetic material according to claim 1, characterized in that: A single period corresponds to a growth orientation of the SrRuO3 film and the N-layer SrTiO3 film in the z-axis orientation, and a single period consists of a SrRuO3 film with a thickness of 1 monolayer and a SrTiO3 film with N monolayers.

3. The extremely weak magnetic Hall sensor based on two-dimensional ferromagnetic material according to claim 1 or 2, characterized in that: N corresponding to the N-layer SrTiO3 film is 1-5.

4. The extremely weak magnetic Hall sensor based on two-dimensional ferromagnetic material according to claim 1, characterized in that: The Hall bar is nanometer-sized.

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