Method for regulating electroluminescent wavelength by magnetic field based on two-dimensional semiconductor CrSBr

Abstract

The invention discloses a method for regulating electroluminescent wavelength by a magnetic field based on a two-dimensional semiconductor CrSBr, and belongs to the field of spintronics and optoelectronic devices. The method comprises the following steps: firstly, preparing an electroluminescent device based on a CrSBr material; then bias voltage is applied to the electroluminescent device, and when the applied bias voltage exceeds threshold voltage, the electroluminescent device generates electroluminescence; under the voltage with the maximum luminous intensity, a magnetic field is applied to the electroluminescent device in the c-axis direction of the CrSBr crystal, along with increase of the magnetic field, the interlayer magnetic sequence of the CrSBr material of the electroluminescent device is converted from an antiferromagnetic state to a ferromagnetic state through a spin tilt process, and tuning of the electroluminescent wavelength of the electroluminescent device is achieved. Based on the magnetic sequence-exciton coupling characteristic of the two-dimensional material CrSBr, fine regulation and control of the electroluminescent wavelength are realized through magnetic field regulation and control.

Description

Technical Field

[0001] The present invention provides a method for realizing magnetic field regulation of electroluminescence based on a two-dimensional van der Waals heterojunction, and specifically relates to a method for realizing magnetic field regulation of electroluminescence wavelength based on a two-dimensional semiconductor CrSBr, belonging to the field of spin electronics and optoelectronic devices. Background Art

[0002] Wavelength-tunable electroluminescent devices are core components for realizing advanced functions such as multicolor display and spectral encoding, and have important application value in fields such as lighting, optical communications, and biosensing. The rapid development of information technology has placed higher demands on the high resolution, low power consumption, and dynamic tunability of electroluminescent devices. Traditional devices mainly achieve wavelength regulation through semiconductor bandgap engineering or exciton state regulation. Although electric field regulation can achieve discrete switching of luminescence peaks, it cannot achieve continuous and fine tuning of the spectrum. Its wavelength resolution is limited by the energy difference between exciton states, making it difficult to meet the needs of high-precision spectral control.

[0003] In recent years, two-dimensional materials, with their atomic-scale thickness, van der Waals interfaces without dangling bonds, and tunable electronic band structures, have provided new ideas for breaking through these bottlenecks. The novel two-dimensional magnetic semiconductor CrSBr exhibits unique magnetic order-exciton coupling properties: its intrinsic A-type antiferromagnetic order (intralayer ferromagnetic coupling and interlayer antiferromagnetic coupling) can induce interlayer magnetic order reconstruction through spin tilt under the action of an external magnetic field, thereby affecting the interlayer electronic coupling strength and exciton transition energy. The magnetic order-exciton coupling properties of CrSBr provide new ideas for wavelength control of electroluminescent devices, and are expected to break through the limitations of traditional light-emitting devices that rely on discrete switching of exciton states, and achieve fine control of the radiation energy of the same exciton state. Summary of the Invention

[0004] In response to the problems existing in the prior art, the present invention provides a method for realizing magnetic field-regulated electroluminescence based on the two-dimensional magnetic semiconductor CrSBr. By utilizing the characteristics of CrSBr magnetic order-exciton coupling, the electroluminescence wavelength can be finely tuned by controlling the magnetic field.

[0005] The present invention provides the following technical solutions:

[0006] A method for realizing magnetic field regulation of electroluminescence wavelength based on two-dimensional semiconductor CrSBr, comprising the following steps:

[0007] 1) preparing an inelastic tunneling structure, impact ionization excitation structure, metal-insulator-semiconductor structure or quantum well structure based on CrSBr material, and placing the above structure on a Si / SiO2 substrate with a prefabricated electrode to obtain an electroluminescent device;

[0008] 2) applying a bias voltage to the electroluminescent device, wherein when the applied bias voltage exceeds a threshold voltage, the electroluminescent device generates electroluminescence, and applying a magnetic field to the electroluminescent device along the c-axis direction of the CrSBr crystal at a voltage at which the luminescence intensity is maximum. As the magnetic field increases, the interlayer magnetic order of the CrSBr material of the electroluminescent device transforms from an antiferromagnetic state to a ferromagnetic state through a spin tilt process, thereby achieving tuning of the electroluminescence wavelength of the electroluminescent device.

[0009] Furthermore, the step length of the magnetic field is 0.1T, and the range of the magnetic field increase is 0 to 2.5T.

[0010] Furthermore, the inelastic tunneling structure is composed of a CrSBr material layer, a single-layer graphene, an insulating layer and a few-layer graphene stacked in sequence from top to bottom; the impact ionization excitation structure is composed of a CrSBr material layer and source and drain electrodes at both ends of the CrSBr material layer; the metal-insulator-semiconductor structure is composed of a metal, an insulating layer and a CrSBr material layer stacked in sequence from top to bottom; and the quantum well structure is composed of a metal layer, an insulating layer, CrSBr, an insulating layer and a metal layer stacked in sequence from top to bottom.

[0011] Furthermore, the thickness of the CrSBr is in the range of 2 to 15 nm.

[0012] Furthermore, the threshold voltage ranges from 1.34V to 2.5V, and the tunneling current ranges from 0.5μA to 2μA.

[0013] Furthermore, the voltage range at which the luminous intensity is maximum is 2.1V to 3.1V, and the tunneling current is 10μA to 16μA.

[0014] The technical effects of the present invention are as follows:

[0015] This invention leverages the universality of magnetic order-exciton coupling in the two-dimensional material CrSBr. By manipulating the interlayer magnetic order and exciton peak energy of CrSBr using a magnetic field, it achieves precise control of the electroluminescence wavelength. This invention is adaptable to a variety of device structures, meeting the needs of applications such as flexible electronics, high-density optoelectronic integration, and quantum light sources. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 Shown is a schematic diagram of the electroluminescent structure of the inelastic tunneling structure according to a specific embodiment of the present invention.

[0017] Figure 2 Shown are optical photographs and spatially dependent electroluminescence imaging of an electroluminescent device according to a specific embodiment of the present invention.

[0018] Figure 3 Shown are the electroluminescence spectra of the electroluminescent device under different DC bias voltages in a specific embodiment of the present invention.

[0019] Figure 4 Shown are the results of magnetic field-controlled electroluminescence spectra and Lorentz peak position fitting in a specific embodiment of the present invention.

[0020] Figure 5 The structure of an electroluminescent device to which the present invention is applicable is shown. DETAILED DESCRIPTION

[0021] The present invention will be further described below through specific embodiments in conjunction with the accompanying drawings.

[0022] First, prepare the device. Taking the inelastic tunneling structure as a specific embodiment, the present invention obtains a few-layer graphene (FLG) with a thickness of less than 10nm, a CrSBr with a thickness of 2nm to 15nm, a hexagonal boron nitride (h-BN) with a thickness of 1.5nm to 2.5nm, and a single-layer graphene (graphene) by mechanical exfoliation. Through dry transfer, CrSBr, graphene, h-BN, and FLG are lifted layer by layer using a polycarbonate (PC) film and placed on a Si / SiO2 substrate with prefabricated electrodes by electron beam exposure and electron beam evaporation. After cleaning the residual PC with chloroform, acetone, and isopropanol, a device based on Figure 1 The electroluminescent device shown in Figure 1 is a 15nm thick CrSBr electroluminescent device. Hexagonal boron nitride serves as a tunneling barrier layer, few-layer graphene and single-layer graphene serve as source and drain electrodes, respectively, and CrSBr serves as a light-emitting layer. The inelastic tunneling process excites excitons in the CrSBr layer through energy transfer, and electrons and holes emit photons through radiative recombination. The optical photograph of the electroluminescent device with a 15nm thick CrSBr electroluminescent layer is shown in Figure 11. Figure 2 As shown in (a), the spatially dependent electroluminescence spectrum of the electroluminescent device is as follows Figure 2 As shown in (b), Figure 2 The overlapping area of ​​the heterojunction is the light-emitting area.

[0023] Under zero magnetic field, a bias voltage (0V to 3.1V) is applied to the device with a thickness of 4nm of CrSBr. The electroluminescence spectra under different bias voltages are as follows: Figure 3 As shown. When the bias voltage exceeds the threshold voltage of 2.5V, the device shows a clear luminescence peak; when the bias voltage is 3.1V, the intensity of the luminescence peak reaches the maximum. Comparing the PL spectrum, the EL exciton peak (X peak) near 1.34eV corresponds to the CrSBr exciton transition, and the high energy peak (X peak) near 1.36eV ​​corresponds to the CrSBr exciton transition. * The peak is attributed to the conduction band splitting caused by the dielectric asymmetry. The electroluminescence (EL) spectrum of the device of the present invention is highly consistent with the photoluminescence (PL) spectrum, confirming that the luminescence originates from the intrinsic exciton transition of CrSBr.

[0024] A bias voltage of 3.1 V was applied to the device with a thickness of 4 nm of CrSBr, and a magnetic field along the c-axis of the CrSBr crystal was gradually applied with a step size of 0.1 T. Figure 4As shown in (a), after the magnetic field stabilizes, the electroluminescence spectra under various magnetic fields (0T~2.5T) are collected. Among them, as the magnetic field increases (0T~2.3T), the X peak energy shows a quadratic dependence on the magnetic field, and the energy continuously redshifts by about 8meV. When the saturation magnetic field is reached (2.3T~2.5T), the X peak energy remains basically unchanged. The quadratic dependence of the X peak energy (E) on the magnetic field (B) originates from the change in the interlayer electron coupling strength during the spin tilt process. When the magnetic field is along the c-axis, the magnetization vector of CrSBr gradually tilts, resulting in a continuous change in the spin angle θ between adjacent layers. According to perturbation theory, the X peak energy is related to the interlayer hopping integral (t h ) is proportional to the square of , satisfying: The electroluminescence spectra under different magnetic field strengths were subjected to Lorentz fitting analysis, such as Figure 4 As shown in (b), the X-peak energy shows a quadratic dependence on the magnetic field. As the magnetic field increases, the interlayer magnetic order of CrSBr transforms from an antiferromagnetic (AFM) state to a ferromagnetic (FM) state through a spin tilting process, resulting in a continuous redshift of the exciton peak by approximately 8 meV, enabling fine tuning of the electroluminescence wavelength from 928 nm to 933 nm.

[0025] The magnetic order-exciton coupling characteristics of CrSBr of the present invention are universal and are not limited to electroluminescent devices with inelastic tunneling structures. Figure 5 As shown, Figure 5 The impact ionization excitation structure shown in (a) consists of a CrSBr material layer and source and drain electrodes at both ends, where the source and drain electrodes can be Au electrodes; Figure 5 The metal-insulator-semiconductor structure shown in (b) consists of a metal, an insulating layer, and a CrSBr light-emitting layer stacked in sequence from top to bottom, where the metal can be Au and the insulator is an h-BN material layer; Figure 5 The quantum well structure shown in (c) consists of a stacked metal layer, an insulating layer, CrSBr, an insulating layer, and a metal layer. For example, a single-layer graphene layer, an h-BN insulating layer, a CrSBr material, an h-BN insulating layer, and a single-layer graphene layer can be stacked. This structure can still achieve magnetic field control of the electroluminescence wavelength.

[0026] Finally, it should be noted that the purpose of disclosing the embodiments is to facilitate a further understanding of the present invention. However, those skilled in the art will appreciate that various substitutions and modifications are possible without departing from the spirit and scope of the present invention and the appended claims. Therefore, the present invention should not be limited to the contents disclosed in the embodiments; the scope of protection claimed by the present invention shall be determined by the scope defined in the claims.

Claims

1. A method for realizing magnetic field regulation of electroluminescence wavelength based on two-dimensional semiconductor CrSBr, comprising the following steps: 1) preparing an inelastic tunneling structure, impact ionization excitation structure, metal-insulator-semiconductor structure or quantum well structure based on CrSBr material, and placing the above structure on a Si / SiO2 substrate with a prefabricated electrode to obtain an electroluminescent device; 2) applying a bias voltage to the electroluminescent device, wherein when the applied bias voltage exceeds a threshold voltage, the electroluminescent device generates electroluminescence, and applying a magnetic field to the electroluminescent device along the c-axis direction of the CrSBr crystal at a voltage at which the luminescence intensity is maximum. As the magnetic field increases, the interlayer magnetic order of the CrSBr material of the electroluminescent device transforms from an antiferromagnetic state to a ferromagnetic state through a spin tilt process, thereby achieving tuning of the electroluminescence wavelength of the electroluminescent device.

2. The method for realizing magnetic field regulation of electroluminescence wavelength based on two-dimensional semiconductor CrSBr according to claim 1, characterized in that: The step size of the magnetic field is 0.1T, and the range of the magnetic field increase is 0-2.5T.

3. The method for realizing magnetic field regulation of electroluminescence wavelength based on two-dimensional semiconductor CrSBr according to claim 1, characterized in that: The inelastic tunneling structure is composed of a CrSBr material layer, a single-layer graphene, an insulating layer and a few-layer graphene stacked in sequence from top to bottom.

4. The method for realizing magnetic field regulation of electroluminescence wavelength based on two-dimensional semiconductor CrSBr according to claim 1, characterized in that: The impact ionization excitation structure is composed of a CrSBr material layer and source and drain electrodes at both ends thereof.

5. The method for realizing magnetic field regulation of electroluminescence wavelength based on two-dimensional semiconductor CrSBr according to claim 1, characterized in that: The metal-insulator-semiconductor structure is composed of a metal layer, an insulating layer and a CrSBr light-emitting layer stacked in sequence from top to bottom.

6. The method for realizing magnetic field regulation of electroluminescence wavelength based on two-dimensional semiconductor CrSBr according to claim 1, characterized in that: The quantum well structure is composed of a metal layer, an insulating layer, CrSBr, an insulating layer and a metal layer stacked in sequence from top to bottom.

7. The method for realizing magnetic field regulation of electroluminescence wavelength based on two-dimensional semiconductor CrSBr according to claim 3, 4, 5 or 6, characterized in that: The thickness of the CrSBr is in the range of 2 to 15 nm.

8. The method for realizing magnetic field regulation of electroluminescence wavelength based on two-dimensional semiconductor CrSBr according to claim 1, characterized in that: The threshold voltage ranges from 1.34V to 2.5V, and the tunneling current ranges from 0.5μA to 2μA.

9. The method for realizing magnetic field regulation of electroluminescence wavelength based on two-dimensional semiconductor CrSBr according to claim 1, characterized in that: The voltage range of the maximum luminous intensity is 2.1V to 3.1V, and the tunneling current is 10μA to 16μA.

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