Preparation method of two-dimensional ferromagnetic material and Hall device

Abstract

A preparation method of a two-dimensional ferromagnetic material and a Hall device belongs to the technical field of electronic materials, and specifically comprises the following steps: preparing single crystal Fe0. 29TaS2 through chemical vapor transport, preparing an electrode through ultraviolet lithography and magnetron sputtering, and preparing the Hall device through mechanical stripping and transferring. The preparation method of the single crystal Fe0. 29TaS2 not only has high efficiency, but also has less residual iodine and impurities on the surface of the single crystal. The prepared Hall device shows good ferromagnetism and air stability. Under the action of an external magnetic field, a huge topological Hall effect can be observed in the Hall device. It is worth noting that the topological Hall effect still exists stably even after relaxation effect measurement, and excellent stability and reliability are shown. The'robust 'chiral spin texture brought by the huge topological Hall effect has application value in the fields of magnetic storage, magnetic information transmission and the like.

Description

Technical Field

[0001] The present invention belongs to the technical field of electronic materials, and relates to a method for preparing a two-dimensional ferromagnetic material and a Hall device. Specifically, a layered two-dimensional ferromagnetic material Fe 0.29 TaS2, and the use of this material to prepare stable and reliable Hall devices. Background Art

[0002] As the miniaturization of electronic devices continues to approach physical limits, unpredictable quantum effects pose a severe challenge to device stability. The further reduction of device size not only leads to a sharp increase in cost and manufacturing difficulty, but also gives rise to an urgent need for research on new electronic devices in the post-Moore era.

[0003] Spintronic devices, which use electron spin as a carrier of information, have opened up a new dimension for information processing. With their non-volatility, extremely high computing speed and relatively low power consumption, they have become a highly promising direction in the development of the next generation of information devices.

[0004] The outstanding performance of two-dimensional materials in terms of electron spin provides new opportunities for the exploration and advancement of spintronic devices. These materials are easy to construct van der Waals heterostructures due to the absence of dangling bonds on their surfaces, which can enhance device performance by improving charge-spin conversion efficiency and optimizing heterojunction interface quality. In addition, the rich interactions and coupling relationships of two-dimensional materials provide possibilities for the discovery of novel physical phenomena and the innovation of physical property regulation mechanisms, thus showing extremely high application potential in the fields of spintronic devices and magnetic storage.

[0005] Although most known two-dimensional materials are non-magnetic in nature, they can be made magnetic by doping with magnetic impurities or by magnetic proximity effects. In recent years, some two-dimensional materials with ferromagnetism, antiferromagnetism or other magnetic orders have also been discovered, and the magnetism of these materials can be adjusted by adjusting the thickness, composition or applying external excitations (such as electric and magnetic fields).

[0006] In order to explore two-dimensional ferromagnetism, layered two-dimensional materials stand out because they can be reduced to one or two layers without damaging the ferromagnetic properties of the sample. In addition, the relatively large magnetic anisotropy makes it an ideal choice for studying two-dimensional magnetism. However, the practical application of spintronic devices still faces many challenges. For example, the two-dimensional ferromagnetic materials discovered so far (such as CrI3, Cr2Ge2Te6, Fe3GeTe2) have poor air stability, which limits their practical application prospects.

[0007] Therefore, exploring layered two-dimensional ferromagnetic materials with strong anisotropy and high air stability is crucial for the study of two-dimensional intrinsic ferromagnetism and the realization of higher density and more stable data storage technology, which has a far-reaching impact on promoting the development of next-generation spin electronic devices. Summary of the invention

[0008] The purpose of the present invention is to provide a method for preparing a two-dimensional ferromagnetic material and a Hall device, comprising preparing a single crystal Fe by chemical vapor transport. 0.29 TaS2, electrodes are prepared by UV lithography and magnetron sputtering, and Hall devices are prepared by mechanical peeling and transfer. The prepared Hall devices show excellent air stability, good magnetic properties and huge topological Hall effect.

[0009] In order to achieve the above object, the technical solution adopted by the present invention is:

[0010] First, the present invention proposes a method for preparing a two-dimensional ferromagnetic material. The prepared two-dimensional ferromagnetic material is Fe 0.29 TaS2, the preparation method specifically comprises the following steps:

[0011] 1.1): Fe, Ta and S are mixed evenly according to the molar ratio, placed at the bottom of a quartz tube, a transport agent I2 is added, the quartz tube is evacuated and sealed;

[0012] 1.2): Growth of single crystal Fe in a dual temperature zone tube furnace 0.29 TaS2, cooling after growth;

[0013] 1.3): Break the quartz tube, take out the sample, clean and dry it to obtain a single crystal sample, which is Fe 0.29 TaS2.

[0014] As a preferred technical solution of the present invention, in the method for preparing a two-dimensional ferromagnetic material:

[0015] In the step 1.1), the molar ratio of Fe, Ta and S is 0.45:1:2, and the transport agent I2 accounts for 15% of the total mass of the raw materials. The reaction zone and the growth zone of the quartz tube are necked to avoid contamination of the growth zone during the sealing process. The bottom of the quartz tube is cooled by an ice bag during the sealing process to prevent the transport agent from volatilizing.

[0016] In the step 1.2), the reaction zone is at the high temperature end and the temperature is set to 980°C; the growth zone is at the low temperature end and the temperature is set to 920°C; the heating rates of the reaction zone and the growth zone are both lower than 1°C / min, and the temperature is maintained constant for 144 hours after heating to the set temperature, and naturally cooled after the growth is completed.

[0017] In the step 1.3), the sample is cleaned 2-3 times with alcohol ultrasonic cleaning to remove residual I2 and impurities on the surface, and finally dried on a hot plate at 60° C. for 10-20 min.

[0018] Secondly, the present invention also proposes a method of utilizing Fe 0.29The method for preparing a Hall device with TaS2 specifically comprises the following steps:

[0019] 2.1): The Hall bar pattern is etched on the cleaned Si / SiO2 substrate by UV light, and the W / Pt electrode is grown by magnetron sputtering;

[0020] 2.2): Mechanically peel off and transfer the sample to the center of the Hall electrode to prepare a Hall device.

[0021] As a preferred technical solution of the present invention, in the method for preparing a Hall device:

[0022] The Hall bar pattern formed by UV lithography in step 2.1) has six electrodes, and the center is not connected, so magnetoresistance and anomalous Hall effect tests can be performed. The thickness of the W / Pt electrodes formed by magnetron sputtering is 10 nm.

[0023] During mechanical peeling in step 2.2), the sample was repeatedly folded on the tape 5-6 times and then adhered to the PDMS. The thermal release condition of the PDMS was 85° C. for 7 min.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0025] 1. The present invention uses iron (Fe), tantalum (Ta) and sulfur (S) as raw materials, mixes them in a certain molar ratio, and adds iodine (I2) as a transport agent to prepare a two-dimensional single crystal material. This preparation method is not only efficient, but also has less iodine and impurities remaining on the surface of the single crystal. In addition, the selected materials are easy to obtain, the process steps are simple, the repeatability is high, and the requirements for equipment are low.

[0026] 2. Single crystal material Fe prepared by the method of the present invention 0.29 The Hall device constructed with TaS2 exhibits good ferromagnetism and air stability. Under the action of an external magnetic field, a huge topological Hall effect can be observed in the Hall device. It is worth noting that even after the relaxation effect measurement, the topological Hall effect still exists stably, showing excellent stability and reliability. The "robust" chiral spin texture brought about by the huge topological Hall effect has application value in the fields of magnetic storage, magnetic information transmission, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 For the two-dimensional ferromagnetic material Fe 0.29 Flow chart of TaS2 growth and Hall device preparation.

[0028] Figure 2 Fe 0.29 Schematic diagram of the TaS2 Hall device measurement configuration.

[0029] Figure 3 Fe 0.29 Optical image of TaS2 Hall device.

[0030] Figure 4 Fe 0.29 EDS spectrum of TaS2.

[0031] Figure 5 Fe 0.29 XRD pattern of TaS2.

[0032] Figure 6 When the magnetic field is perpendicular to the surface of the Hall device, the magnetoresistance changes with the magnetic field.

[0033] Figure 7 When the magnetic field is perpendicular to the surface of the Hall device, the Hall resistance changes with the magnetic field.

[0034] Figure 8 The change of Hall resistance with magnetic field (squares) and the relaxation effect test fitting diagram (circles) when the value is 10K. DETAILED DESCRIPTION

[0035] The present invention is further described in detail below in conjunction with embodiments and drawings.

[0036] like Figure 1 As shown, an embodiment of the present invention provides a method for preparing a two-dimensional ferromagnetic material and a Hall device, comprising the following steps:

[0037] 1): Weigh 125.65 mg (2.25 mmol) of Fe, 904.75 mg (5 mmol) of Ta, and 320.6 mg (10 mmol) of S and mix them evenly. Use a paper trough to put the mixture into the bottom of a quartz tube, and add 202.65 mg (15% of the total mass of the raw materials) of I2 as a transport agent. Evacuate the quartz tube and seal it with a hydrogen-oxygen flame. To prevent the transport agent from volatilizing, use an ice bag to cool the bottom of the quartz tube during the sealing process.

[0038] 2): Place the quartz tube horizontally in a dual-temperature zone tube furnace (the side with the sample is placed at the high-temperature end), raise the high-temperature end (reaction zone) to 980°C, and the low-temperature end (growth zone) to 920°C. The heating time is about 16 hours, the rate is less than 1°C / min, and the growth is maintained for 144 hours before natural cooling.

[0039] 3): Break the quartz tube, take out the flake sample grown at the low-temperature end, add alcohol to ultrasonically clean it twice to remove the residual I2 and impurities on the surface, and finally dry it on a hot plate at 60°C.

[0040] 4): Photolithography of the Hall bar pattern on the cleaned Si / SiO2 substrate (such as Figure 2The Hall bar has six electrodes, which are not connected in the center. W / Pt electrodes with a thickness of 10 nm are grown by magnetron sputtering.

[0041] 5): Place the dried sheet sample on the blue tape and fold the blue tape in half 5 times. Transfer the sample on the blue tape to the PDMS, find a smooth and flat film on the PDMS, and transfer it to the center of the electrode on the two-dimensional transfer table (such as Figure 3 As shown), the heat release condition of PDMS is 85°C for 7min.

[0042] 6): Characterize the transferred six-terminal Hall device, including energy dispersive X-ray spectrometer (EDS), X-ray diffraction (XRD), and test magnetoresistance, Hall resistance, and relaxation effect in the comprehensive physical property measurement system (PPMS).

[0043] Preparation of Fe 0.29 Performance characterization of TaS2 single crystal and Hall device:

[0044] Figure 4 Fe 0.29 The results of scanning the flake sample by an energy dispersive X-ray spectrometer (EDS) of TaS2 show that the flake material synthesized by the present invention contains three elements, Fe, Ta, and S, and the ratio of the three elements is about 0.29:1:2, which conforms to the chemical formula Fe 0.29 TaS2.

[0045] Figure 5 Fe 0.29 The X-ray diffraction pattern (XRD) of TaS2 shows that the diffraction peaks are all (00l) crystal phase, without other impurities, indicating that Fe 0.29 TaS2 bulk material is a single crystal phase.

[0046] Figure 6 When the magnetic field is perpendicular to the surface of the Hall device, the magnetoresistance changes differently with the magnetic field at different temperatures, and a peak value appears at around 40K.

[0047] Figure 7 When the magnetic field is perpendicular to the surface of the Hall device, the Hall resistance changes with the magnetic field. As the temperature decreases, the Hall value first increases and then decreases. The system gradually becomes a magnetically ordered state, and the longitudinal resistance decreases with temperature.

[0048] Figure 8At 10K, the change of Hall resistance with magnetic field (square) and the relationship between the final Hall resistance and holding field extracted from the relaxation effect test (set the initial magnetic field to 2T / -2T, then change the direction of the magnetic field, and observe the change of Hall resistance with time under different holding magnetic fields until the Hall resistance tends to be stable) (circle). At 10K, a huge topological Hall effect (shaded part) can be observed in the Hall device under an external magnetic field. By fitting and extracting the final Hall resistance of the relaxation effect test, the topological Hall effect still exists.

[0049] In summary: The present invention prepares single crystal Fe by chemical vapor transport 0.29 TaS2 has simple preparation process, high preparation efficiency and few surface impurities. 0.29 The Hall device prepared from TaS2 single crystal samples exhibits excellent air stability, good magnetic properties and a huge topological Hall effect. For the first time, the relaxation effect test found that the topological Hall effect still exists. The "robust" chiral spin texture brought by the huge topological Hall effect has application value in the fields of magnetic storage and magnetic information transmission.

[0050] The above contents are merely examples and explanations of the concept of the present invention. The technicians in this technical field may make various modifications or additions to the specific embodiments described or replace them in a similar manner. As long as they do not deviate from the concept of the invention or exceed the scope defined by the claims, they should all fall within the protection scope of the present invention.

Claims

1. A method for preparing a two-dimensional ferromagnetic material, characterized in that: The prepared two-dimensional ferromagnetic material is Fe 0.29 TaS2, the preparation method specifically comprises the following steps: 1.1): Fe, Ta and S are mixed evenly according to the molar ratio, placed at the bottom of a quartz tube, a transport agent I2 is added, the quartz tube is evacuated and sealed; 1.2): Growth of single crystal Fe in a dual temperature zone tube furnace 0.29 TaS2, cooling after growth; 1.3): Break the quartz tube, take out the sample, clean and dry it to obtain a single crystal sample, which is Fe 0.29 TaS2.

2. The method for preparing a two-dimensional ferromagnetic material according to claim 1, characterized in that: In the step 1.1), the molar ratio of Fe, Ta and S is 0.45:1:

2.

3. The method for preparing a two-dimensional ferromagnetic material according to claim 1, characterized in that: In the step 1.1), the transport agent I2 accounts for 15% of the total mass of the raw materials.

4. The method for preparing a two-dimensional ferromagnetic material according to claim 1, characterized in that: In the step 1.1), the reaction zone and the growth zone of the quartz tube are necked down to avoid contamination of the growth zone during the tube sealing process. During the tube sealing process, an ice bag is used to cool the bottom of the quartz tube to prevent the transport agent from volatilizing.

5. The method for preparing a two-dimensional ferromagnetic material according to claim 1, characterized in that: In the step 1.2), the reaction zone is at the high temperature end and the temperature is set to 980°C; the growth zone is at the low temperature end and the temperature is set to 920°C; after heating to the set temperature, the constant temperature is maintained for 144 hours, and naturally cooled after the growth is completed.

6. The method for preparing a two-dimensional ferromagnetic material according to claim 2, characterized in that: In the step 1.2), the heating rates of the reaction zone and the growth zone are both lower than 1°C / min.

7. The method for preparing a two-dimensional ferromagnetic material according to claim 1, characterized in that: In the step 1.3), the sample is cleaned 2-3 times with alcohol ultrasonic cleaning to remove residual I2 and impurities on the surface, and finally dried on a hot plate at 60° C. for 10-20 min.

8. A method for preparing a Hall device by preparing a two-dimensional ferromagnetic material using the method according to any one of claims 1 to 7, characterized in that: The specific steps include: 2.1): The Hall bar pattern is etched on the cleaned Si / SiO2 substrate by UV light, and the W / Pt electrode is grown by magnetron sputtering; 2.2): Mechanically peel off and transfer the sample to the center of the Hall electrode to prepare a Hall device.

9. The method for preparing a Hall device according to claim 8, characterized in that: The Hall bar pattern formed by UV lithography in step 2.1) has six electrodes, and the center is not connected, so magnetoresistance and anomalous Hall effect tests can be performed. The thickness of the W / Pt electrodes formed by magnetron sputtering is 10 nm.

10. The method for preparing a Hall device according to claim 8, characterized in that: During mechanical peeling in step 2.2), the sample was repeatedly folded on the tape 5-6 times and then adhered to the PDMS. The thermal release condition of the PDMS was 85° C. for 7 min.

Images