阅读说明：本技术 一种二维磁性Fe3O4单晶纳米片的制备方法 (Two-dimensional magnetic Fe3O4Preparation method of single crystal nanosheet ) 是由 杨圣雪 高凡 于 2021-09-13 设计创作，主要内容包括：本发明公开了一种二维磁性Fe-(3)O-(4)单晶纳米片的制备方法,包括步骤：将Fe-(2)O-(3)粉末与助熔剂按照10：1的质量比混合作为第一前驱体,放置在水平管式炉的下游高温区,并将衬底置于前驱体正上方；将FeCl-(3)·6H-(2)O作为第二前驱体,放置在水平管式炉的上游低温区；向管式炉中通入氩氢混合气,将下游高温区加热至600-750℃,上游低温区加热至240-310℃,在氩氢混合气的氛围中保温10-20min,然后自然冷却至室温,在所述衬底上得到二维磁性Fe-(3)O-(4)单晶纳米片。该方法制备获得的Fe-(3)O4单晶纳米片空气稳定性好；利用制备的Fe-(3)O-(4)单晶纳米片制作的电学器件具有良好的导电性,可耐受较高的电场；制备的Fe-(3)O-(4)单晶纳米片具有良好的室温磁性,在信息存储器件、逻辑运算器件、霍尔传感器件等领域具有广泛的应用前景。(The invention discloses two-dimensional magnetic Fe 3 O 4 The preparation method of the single crystal nanosheet comprises the following steps: mixing Fe 2 O 3 The powder and flux were mixed in a ratio of 10: 1 as a first precursor,placing the substrate in a high-temperature area at the downstream of the horizontal tube furnace, and placing the substrate right above the precursor; FeCl is added 3 ·6H 2 O is used as a second precursor and is placed in an upstream low-temperature region of the horizontal tube furnace; introducing argon-hydrogen mixed gas into the tube furnace, heating the downstream high-temperature region to 600-750 ℃, heating the upstream low-temperature region to 240-310 ℃, preserving the heat for 10-20min in the atmosphere of the argon-hydrogen mixed gas, naturally cooling to room temperature, and obtaining two-dimensional magnetic Fe on the substrate 3 O 4 A single crystal nanosheet. The method can prepare Fe 3 The O4 single crystal nano-sheet has good air stability; using the prepared Fe 3 O 4 The electrical device made of the single crystal nanosheet has good conductivity and can resist a higher electric field; prepared Fe 3 O 4 The single crystal nano sheet has good room temperature magnetism, and has wide application prospect in the fields of information storage devices, logic operation devices, Hall sensing devices and the like.)

1. Two-dimensional magnetic Fe₃O₄The preparation method of the single crystal nanosheet is characterized by comprising the following steps:

the method comprises the following steps: mixing Fe₂O₃The powder and flux were mixed in a ratio of 10: 1 as a first precursor, placing the first precursor in a high-temperature zone at the downstream of a horizontal tube furnace, and placing a substrate right above the first precursor;

step two: FeCl is added₃·6H₂O is used as a second precursor and is placed in an upstream low-temperature region of the horizontal tube furnace;

step three: introducing argon-hydrogen mixed gas into the horizontal tube furnace, heating the downstream high-temperature region to 600-750 ℃, heating the upstream low-temperature region to 240-310 ℃, preserving the heat for 10-20min in the atmosphere of the argon-hydrogen mixed gas, naturally cooling to room temperature, and obtaining two-dimensional magnetic Fe on the substrate₃O₄A single crystal nanosheet.

2. Two-dimensional magnetic Fe according to claim 1₃O₄The preparation method of the single crystal nano sheet is characterized in that the fluxing agent is NaCl, and the substrate is sapphire or a mica sheet.

3. Two-dimensional magnetic Fe according to claim 1₃O₄The preparation method of the single crystal nanosheet is characterized in that the distance between the first precursor and the second precursor is 30-40 cm.

4. Two-dimensional magnetic Fe according to any one of claims 1 to 3₃O₄A method for preparing a single crystal nanoplate, characterized in that the Fe₃O₄The single crystal nano-sheet is in a regular triangle structure with the thickness of 10-100nm, and the side length of the triangle is 5-50 mu m.

5. A method of making an electrical device, comprising the steps of:

the method comprises the following steps: fe to be obtained by the production method according to any one of claims 1 to 4₃O₄Transferring the single crystal nano sheet to the surface of the substrate;

step two: in Fe₃O₄Designing a proper electrode pattern on the surface of the single crystal nanosheet, and performing exposure by using electron beam lithography;

step three: preparing a metal electrode of the device, and carrying out evaporation coating on the electrode by using a thermal evaporation coating method, wherein the metal electrode material is gold, and the thickness of the electrode is 30-100 nm.

6. The method for manufacturing an electrical device according to claim 5, wherein the substrate is a silicon wafer with an oxide layer of 285nm, the nanosheet transferring method is that the nanosheets are picked up from a growth substrate and transferred onto the silicon wafer by Polydimethylsiloxane (PDMS) under the assistance of water vapor, the silicon wafer is placed on a hot plate with a temperature of 120 ℃ during transferring, and the silicon wafer is naturally cooled to room temperature after transferring.

7. The method for manufacturing an electrical device according to claim 5, wherein in the second step, a layer of photoresist is spin-coated on the substrate before the electron beam lithography, the photoresist is polymethyl methacrylate (PMMA), the spin-coating speed is 2000r/min, and the spin-coating time is 60s, and then the substrate is placed on a hot plate and baked at 120 ℃ for 2 min.

8. The method for manufacturing an electrical device as claimed in claim 5, wherein in the third step, a layer of metal chromium with a thickness of 5-10nm is evaporated before the gold electrode is manufactured.

9. The preparation method of the Hall device is characterized by comprising the following steps of:

the method comprises the following steps: fe obtained by the production method according to any one of claims 1 to 4₃O₄Designing six electrode patterns on the surface of the single crystal nanosheet, and performing laser direct writing exposure;

step two: the electrode of the device is prepared by a thermal evaporation method, a layer of metal material gold is evaporated to be used as a contact electrode, and the thickness of the electrode is 30-100 nm.

10. The method for manufacturing a hall device as claimed in claim 9, wherein in the step one, the electrode is manufactured by growing Fe₃O₄Coating a layer of photoresist on a sapphire substrate of a single crystal nanosheet, designing a proper electrode pattern on the surface of the nanosheet, and preparing six electrodes separated from each other on the surface of the nanosheet by using a laser direct writing exposure technology according to the designed pattern, wherein two large electrodes and four small electrodes are in an in-plane vertical state; the photoresist is a positive photoresist S1818, the rotating speed of a spin coater is 4000r/min, the time is 1min, and the photoresist is baked for 1min in an oven at the temperature of 90 ℃ after being spin-coated; and secondly, evaporating a layer of metal chromium with the thickness of 10-20nm before preparing the gold electrode.

Technical Field

The invention belongs to the field of magnetic materials and devices, and particularly relates to two-dimensional magnetic Fe₃O₄A preparation method and application of single crystal nano-sheets.

Background

At present, the discovery of two-dimensional single crystal materials with intrinsic magnetism opens up new roads for the realization of future low-dimensional spintronic devices, including Cr₂Ge₂Te₆(Nature,2017,546(7657):265-269)、Fe₃GeTe₂(Nature,2018,563(7729):94-99)、CrI₃(Nature,2017,546(7657): 270-. Because the thickness of the two-dimensional material is very thin, the magnetic performance of the two-dimensional material can be effectively regulated and controlled by using methods such as an electric field and the like, so that a new possibility is provided for manufacturing an information storage device and a logic operation device with low power consumption and high storage density. In the research and application of magnetic materials, the stability and the Curie temperature of the materials are important. Two-dimensional magnetic Fe relative to the existing low-dimensional magnetic material₃O₄The single crystal nano sheet has the characteristics of good air stability, Curie temperature higher than room temperature and the like, meets the requirements of room temperature magnetic devices, and has good application prospect.

Existing Fe₃O₄The preparation method of the material is mainly to prepare the film material by magnetron sputtering or molecular beam epitaxy technology. Wherein, the magnetron sputtering technology has extremely high requirements on the quality of the target material and is not easy to prepare high-quality single crystal material; the molecular beam epitaxy technology has high requirements on equipment and excessive production costHigh. Recently, the chinese invention patent cn201810947517.x relates to the two-dimensional Fe deposition by chemical vapor deposition₃O₄The preparation of the single crystal material is complex, and the steps are very complicated. In addition, the Chinese patent CN202010066148.0 also carries out two-dimensional Fe by a chemical vapor deposition method₃O₄Preparation of single crystal material, but the single crystal material prepared is smaller in size: (<20 μm) limits the practical application of the material.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provide two-dimensional magnetic Fe₃O₄A preparation method of a single crystal nano sheet, a preparation method of an electrical device and a preparation method of a Hall device on the basis of the preparation method of the single crystal nano sheet. Fe prepared by the method₃O₄The raw materials for preparing the single crystal nano-sheet are easy to obtain, the preparation method is simple, and the material stability is good. The technical scheme adopted by the invention is as follows:

two-dimensional magnetic Fe₃O₄The preparation method of the single crystal nanosheet comprises the following steps:

the method comprises the following steps: mixing Fe₂O₃The powder and flux were mixed in a ratio of 10: 1 as a first precursor, placing the first precursor in a high-temperature zone at the downstream of a horizontal tube furnace, and placing a substrate right above the first precursor;

step two: FeCl is added₃·6H₂O is used as a second precursor and is placed in an upstream low-temperature region of the horizontal tube furnace;

step three: introducing argon-hydrogen mixed gas into the horizontal tube furnace, heating the downstream high-temperature region to 600-750 ℃, heating the upstream low-temperature region to 240-310 ℃, preserving the heat for 10-20min in the atmosphere of the argon-hydrogen mixed gas, naturally cooling to room temperature, and obtaining two-dimensional Fe on the substrate₃O₄A single crystal nanosheet.

The fluxing agent is NaCl, and the substrate is sapphire or a mica sheet.

The distance between the first precursor and the second precursor is 30-40 cm.

Said Fe₃O₄The single crystal nano-sheet isA regular triangle structure with the thickness of 10-100nm, and the side length of the triangle is 5-50 μm.

A method of making an electrical device comprising the steps of:

the method comprises the following steps: fe obtained by the above preparation method₃O₄Transferring the single crystal nano sheet to the surface of the substrate;

step two: in Fe₃O₄Designing a proper electrode pattern on the surface of the single crystal nanosheet, and performing exposure by using electron beam lithography;

step three: preparing a metal electrode of the device, and carrying out evaporation coating on the electrode by using a thermal evaporation coating method, wherein the metal electrode material is gold, and the thickness of the electrode is 30-100 nm.

The substrate is a silicon wafer with an oxide layer of 285nm, the nanosheet transferring method includes the steps of picking the nanosheets from the growth substrate by means of Polydimethylsiloxane (PDMS) under the assistance of water vapor and transferring the nanosheets to the silicon wafer, placing the silicon wafer on a hot plate with the temperature of 120 ℃ during transferring, and naturally cooling the silicon wafer to room temperature after transferring.

And secondly, before electron beam lithography, spin-coating a layer of photoresist on the substrate, wherein the photoresist is polymethyl methacrylate (PMMA), the spin-coating speed is 2000r/min, and the spin-coating time is 60s, then placing the substrate on a hot plate, and baking for 2min at 120 ℃.

And step three, evaporating a layer of metal chromium with the thickness of 5-10nm before preparing the gold electrode.

A preparation method of a Hall device comprises the following steps:

the method comprises the following steps: in the Fe obtained by the above preparation method₃O₄Designing six electrode patterns on the surface of the single crystal nanosheet, and performing laser direct writing exposure;

step two: the electrode of the device is prepared by a thermal evaporation method, a layer of metal material gold is evaporated to be used as a contact electrode, and the thickness of the electrode is 30-100 nm.

In the first step, the electrode is prepared by growing Fe₃O₄Coating a layer of photoresist on the sapphire substrate of the single crystal nano-sheet, and designing a proper surface of the nano-sheetPreparing six electrodes separated from each other on the surface of the nanosheet by using a laser direct writing exposure technology according to the designed pattern, wherein two large electrodes and four small electrodes are in an in-plane vertical state; the photoresist is a positive photoresist S1818, the rotating speed of a spin coater is 4000r/min, the time is 1min, and the photoresist is baked for 1min in an oven at the temperature of 90 ℃ after being spin-coated; and secondly, evaporating a layer of metal chromium with the thickness of 10-20nm before preparing the gold electrode.

Compared with the prior art, the invention has the following beneficial effects:

1. preparation of Fe₃O₄The raw materials needed by the single crystal nano-sheet are easy to obtain, and the pretreatment is not needed, so that the cost is low.

2. Preparation of Fe₃O₄The method for preparing the single crystal nano sheet has simple flow and easy operation, and the production and preparation period is shortened.

3. According to the invention, the nucleation density of the material is regulated and controlled by controlling the distance between the two precursors, and the quality and the size of the sample are obviously improved.

4. The invention realizes the control of the sample size by regulating and controlling the reaction temperature at the high temperature region, and prepares the Fe with the size of 50 mu m₃O₄The size of the sample of the single crystal nano-sheet is obviously improved.

5. Fe prepared by the invention₃O₄The single crystal nano-sheet has good air stability and can be stably stored in an air environment.

6. The invention utilizes the prepared Fe₃O₄The electric device made of the single crystal nanosheet has good conductivity, and meanwhile, the material can endure a higher electric field.

7. The invention is based on the preparation of Fe₃O₄The Hall device made of the single crystal nanosheets has obvious reaction to the change of an external magnetic field at room temperature, and has wide application prospects in the fields of information storage devices, logic operation devices, Hall sensing devices and the like.

Drawings

FIG. 1 shows two-dimensional magnetic Fe₃O₄The structural schematic diagram of the single crystal nano sheet.

FIG. 2 is Fe₃O₄Schematic diagram of a preparation device of single crystal nano-sheets.

FIG. 3 shows Fe prepared₃O₄And (3) an optical microscope top view of the nanosheet single crystal material.

FIG. 4 shows Fe prepared₃O₄Transmission electron microscopy of single crystal nanoplatelets.

FIG. 5 shows Fe prepared₃O₄And (3) a selected-area electron diffraction pattern of the single-crystal nanosheet.

FIG. 6 is Fe prepared₃O₄Optical microscopy of single crystal nanoplate electrical devices.

FIG. 7 is a current-voltage graph of an electrical device.

FIG. 8 shows Fe prepared₃O₄An optical microscopy image of a single crystal nanosheet hall device.

FIG. 9 is a graph of magnetic field vs. Hall resistance of a Hall device at 300K.

Detailed Description

The invention is described in further detail below with reference to the figures and examples.

The invention provides two-dimensional magnetic Fe₃O₄The preparation method of the single crystal nanosheet comprises the following specific steps:

the method comprises the following steps: mixing Fe₂O₃The powder and flux were mixed in a ratio of 10: 1 as a first precursor, placing the first quartz boat in a high-temperature zone downstream of the horizontal tube furnace, and placing the substrate right above the first precursor. Preferably, the fluxing agent is NaCl and is used for reducing Fe₂O₃Melting point of (2); the substrate is a sapphire or mica sheet.

Step two: FeCl is added₃·6H₂And O is used as a second precursor and is placed in a second quartz boat, and the second quartz boat loaded with the second precursor is placed in an upstream low-temperature zone of the horizontal tube furnace. Preferably, the distance between the first precursor and the second precursor is 30-40 cm.

Step three: introducing argon and hydrogen into the tube furnaceMixing gas with a gas flow of 100-200sccm, heating the downstream high-temperature region to 600-750 ℃, heating the upstream low-temperature region to 240-310 ℃, preserving the heat in the gas atmosphere for 10-20min, and naturally cooling to room temperature to obtain two-dimensional magnetic Fe on the substrate₃O₄A single crystal nanosheet.

Said Fe₃O₄The single crystal nano-sheet is in a regular triangle structure with the thickness of 10-100nm, and the side length of the triangle is 5-50 μm.

In one aspect, the present invention provides a method of using the prepared Fe₃O₄The electrical device manufactured by using the single crystal nanosheet as a material comprises the following specific steps:

the method comprises the following steps: fe to be prepared₃O₄And transferring the single crystal nanosheets to the surface of a substrate, wherein the substrate is a silicon wafer with a 285nm oxide layer. Preferably, the nanosheet transfer method is to pick up and transfer the nanosheets from the growth substrate to the silicon wafer with Polydimethylsiloxane (PDMS) under the assistance of water vapor; the silicon wafer is placed on a hot plate with the temperature of 120 ℃ during transfer, and is naturally cooled to room temperature after transfer.

Step two: if necessary in Fe₃O₄And designing a proper electrode pattern on the surface of the single crystal nanosheet, and performing exposure by using electron beam lithography. Preferably, a layer of photoresist is spin-coated on a silicon wafer before electron beam lithography, wherein the photoresist is polymethyl methacrylate (PMMA), the spin-coating speed is 2000r/min, and the spin-coating time is 60s, and then the silicon wafer is placed on a hot plate and baked at 120 ℃ for 2 min.

Step three: preparing a metal electrode of the device, and carrying out evaporation coating on the electrode by using a thermal evaporation coating method, wherein the metal electrode material is gold, and the thickness of the electrode is 30-100 nm. Preferably, a layer of metal chromium with the thickness of 5-10nm is evaporated before the gold electrode is prepared, so that the combination of the electrode and the substrate is enhanced.

In another aspect, the present invention provides a method of using the prepared Fe₃O₄The Hall device manufactured by taking the single crystal nanosheet as a material comprises the following specific steps:

the method comprises the following steps: fe produced on demand₃O₄Single crystal sodiumSix electrode patterns are designed on the surface of the rice sheet, and laser direct writing exposure is carried out. Preferably, two large electrodes and four small electrodes in the six electrodes are in an in-plane perpendicular state. Preferably, the two-dimensional Fe is grown before the laser direct writing₃O₄A layer of photoresist is coated on a sapphire substrate of the single crystal nanosheet, the photoresist is a positive photoresist S1818, the rotating speed of a spin coater is 4000r/min, the time is 1min, and the photoresist is baked for 1min in an oven at the temperature of 90 ℃ after being spin-coated.

Step two: the electrode of the device is prepared by a thermal evaporation method, a layer of metal material gold is evaporated to be used as a contact electrode, and the thickness of the electrode is 30-100 nm. Preferably, in order to enhance the adhesion of the electrode, a layer of metal chromium with the thickness of 10-20nm is evaporated before the gold electrode is prepared.

Detailed description of the preferred embodiment 1

Two-dimensional magnetic Fe provided according to the present invention₃O₄Preparation method of single crystal nano sheet by using horizontal tube furnace and Fe₂O₃200mg of powder, 20mg of NaCl powder and sapphire as a substrate, and placing the substrate in a high-temperature area, wherein the central temperature is 750 ℃; FeCl₃·6H₂500mg of O powder is placed in a low-temperature region, the central temperature is 280 ℃, and the heat preservation time is 20 min. Fe₂O₃Powder and NaCl powder mixture with FeCl₃·6H₂The distance between the O powders was 35 cm. Washing with 500sccm argon-hydrogen mixture gas for 10min before reaction, introducing 200sccm argon-hydrogen mixture gas during the reaction process, maintaining an atmospheric pressure until the reaction is finished, naturally cooling the sample to room temperature after the reaction is finished, and obtaining Fe on the sapphire substrate₃O₄Nanosheets.

FIG. 1 is a two-dimensional magnetic Fe prepared in example 1₃O₄The structural schematic diagram of the single crystal nano sheet.

FIG. 2 is Fe prepared in example 1₃O₄The device schematic diagram of the single crystal nano-sheet, and the used equipment is a horizontal tube furnace.

FIG. 3 is Fe prepared in example 1₃O₄Optical microscope top view of nanosheet single crystal material, resulting Fe₃O₄The nano-sheets are regular triangles with regular shapes.

Fe prepared in example 1 by transmission electron microscopy₃O₄The nanosheet single-crystal material is subjected to structural characterization. FIG. 4 is a High Resolution Transmission Electron Microscope (HRTEM) image of the sample with interplanar spacing measured at 0.307 nm. FIG. 5 is a selected area electron diffraction pattern of the corresponding area of FIG. 4 illustrating the Fe produced₃O₄The nano-sheet is a single crystal material.

Specific example 2

According to a method for manufacturing an electrical device, provided by the invention, Fe₃O₄The single crystal nano-sheet is prepared in the embodiment 1 and transferred to a substrate, and the substrate is a silicon wafer with an oxide layer of 285 nm. 10nm of chromium and 90nm of gold were deposited as electrodes by thermal evaporation. The conductivity of the device was measured using a micro-manipulated cryogenic probe station and a semiconductor characteristic analyzer.

FIG. 6 is an optical microscope photograph of an electrical device prepared in example 2, with two chromium/gold electrodes deposited on the Fe₃O₄And (3) the surface of the nano-sheet single crystal material.

The room temperature current-voltage (I-V) curve of the device was tested using a micro-manipulation cold probe station and a semiconductor characteristic analyzer. Fig. 7 is a current-voltage (I-V) graph of the devices tested in example 2, illustrating that the material has good conductivity.

Specific example 3

According to the preparation method of the Hall device provided by the invention, the Fe prepared in the example 1 is subjected to₃O₄Designing electrode patterns of the single crystal nanosheets, and placing six electrodes in Fe₃O₄And on the surface of the nanosheet, two large electrodes and four small electrodes are in an in-plane vertical state. Thermal evaporation was used to deposit 20nm of chromium and 80nm of gold as electrodes.

Fig. 8 is an optical microscope photograph of the hall device prepared in example 3.

Fig. 9 is a magnetic field-hall resistance curve diagram of the hall device prepared in example 3 at 300K, and the device has obvious response to external magnetic field change at room temperature, and has wide potential application values in the aspects of memory devices, logic devices, sensors and the like.

The above description is only exemplary of the present invention and should not be taken as limiting the scope of the present invention, and any modifications, equivalents, improvements and the like that are within the spirit and principle of the present invention should be included in the scope of the present invention.