Turn-angle graphene-tungsten disulfide heterojunction material based on ultrafast light response regulation and preparation method thereof

Abstract

The invention relates to a corner graphene-tungsten disulfide heterojunction material based on ultrafast light response regulation and a preparation method of the corner graphene-tungsten disulfide heterojunction material. The preparation method comprises the following steps: SA, pasting a tungsten disulfide layer on a graphene layer at a preset angle to obtain a corner graphene-tungsten disulfide heterojunction with the preset angle; the preset angle is changed, the step SA is repeated for multiple times, and a plurality of corner graphene-tungsten disulfide heterojunctions with different preset angles are obtained; and SB, measuring the ultrafast light response performance of the plurality of corner graphene-tungsten disulfide heterojunctions with different preset angles, and screening out the corner graphene-tungsten disulfide heterojunction with the optimal preset angle and the optimal ultrafast light response performance. The invention studies the relationship between the large torsion angle and the ultrafast light response of the graphene-tungsten disulfide heterojunction material, and provides a method for rapidly screening the optimal torsion angle with the optimal ultrafast light response performance and efficiently preparing the corner graphene-tungsten disulfide heterojunction material with the optimal torsion angle.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor optoelectronic devices, and particularly to a twisted graphene-tungsten disulfide heterojunction material based on ultrafast optical response regulation and a preparation method thereof. Background Art

[0002] Optoelectronic devices refer to devices that can convert optical signals and electrical signals. The ultrafast optical response of optoelectronic devices refers to the response of optoelectronic materials to optical pulse signals on a femtosecond or smaller time scale. The ultrafast optical response performance of optoelectronic devices has an important impact on the applications of optoelectronic devices in fields such as high-speed communication, high-speed imaging, and ultrafast optical computing.

[0003] The graphene-tungsten disulfide heterojunction is a semiconductor optoelectronic device composed of two two-dimensional materials, graphene and tungsten disulfide. Graphene and tungsten disulfide are combined by weak van der Waals forces, which enables them to form a stable heterojunction structure while maintaining their respective unique electronic properties. Charge transfer occurs in the graphene-tungsten disulfide heterojunction: negative charges accumulate near tungsten disulfide, and positive charges accumulate near graphene, thereby forming a built-in electric field at the interface between the two materials. This phenomenon endows the graphene-tungsten disulfide heterojunction with optoelectronic properties.

[0004] However, the prior art lacks research on the ultrafast optical response of graphene-tungsten disulfide heterojunction materials, which limits the further popularization and application of graphene-tungsten disulfide heterojunction materials. Summary of the Invention

[0005] Based on this, the object of the present invention is to provide a twisted graphene-tungsten disulfide heterojunction material based on ultrafast optical response regulation and a preparation method thereof.

[0006] The present invention provides a preparation method of a twisted graphene-tungsten disulfide heterojunction material, which includes the steps: SA, pasting a tungsten disulfide layer onto a graphene layer at a preset angle to obtain a twisted graphene-tungsten disulfide heterojunction at the preset angle; changing the preset angle and repeating step SA several times to obtain several twisted graphene-tungsten disulfide heterojunctions with different preset angles; SB, measuring the ultrafast optical response performance of several twisted graphene-tungsten disulfide heterojunctions with different preset angles, and screening out the twisted graphene-tungsten disulfide heterojunction at the optimal preset angle with the best ultrafast optical response performance.

[0007] The present invention studies the relationship between the large twist angle and the ultrafast optical response of graphene-tungsten disulfide heterojunction materials, and provides a method for quickly screening out the optimal twist angle with the best ultrafast optical response performance and efficiently preparing the twisted graphene-tungsten disulfide heterojunction material with the optimal twist angle. The present invention does not rely on atomic force microscopy or electron microscopy and has the possibility of large-scale industrial preparation, which is conducive to the further popularization and application of graphene-tungsten disulfide heterojunction materials in the fields of high-speed communication, high-speed imaging, ultrafast optical computing, etc.

[0008] Further, the range of the preset angle is: 0° to 30°.

[0009] Further, the preset angles include: 0°, 10°, 20° and 30°.

[0010] Further, step SB specifically includes: SB1, measuring the transient absorption spectra of the twisted graphene-tungsten disulfide heterojunctions with several different preset angles by transient absorption spectroscopy technology; SB2, extracting the characteristics of the transient absorption spectra to obtain characteristic values; SB3, evaluating the ultrafast optical response performance of the twisted graphene-tungsten disulfide heterojunctions with several different preset angles according to the characteristic values; SB4, screening out the twisted graphene-tungsten disulfide heterojunction with the optimal preset angle having the best ultrafast optical response performance.

[0011] Further, step SB2 specifically includes: identifying the main absorption peak of the transient absorption spectrum and measuring the peak intensity ΔA of the main absorption peak; performing time-resolved analysis on the transient absorption spectrum and fitting to obtain the decay time constant τ; step SB3 specifically includes: calculating the ultrafast optical response performance score according to the peak intensity and the decay time constant; the calculation formula of the ultrafast optical response performance score is: In the formula, Score represents the ultrafast optical response performance score, ΔA represents the peak intensity, α represents the first weighting coefficient corresponding to the peak intensity, τ represents the decay time constant, and β represents the second weighting coefficient corresponding to the decay time constant.

[0012] Further, the graphene layer is prepared by the following steps: SA1, growing graphene domains on a copper substrate by chemical vapor deposition to obtain a graphene-copper composite material; SA2, immersing the graphene-copper composite material in an ammonium persulfate solution and etching the copper substrate with the ammonium persulfate solution to obtain a graphene layer.

[0013] Further, the tungsten disulfide layer is prepared by the following steps: SA3, growing tungsten disulfide domains on a sapphire substrate by chemical vapor deposition to obtain a tungsten disulfide-sapphire composite material; SA4, immersing the tungsten disulfide-sapphire composite material in a sodium hydroxide solution and separating it by using the difference in hydrophilicity and hydrophobicity to obtain a tungsten disulfide layer.

[0014] Further, in step SA, the tungsten disulfide layer is pasted onto the graphene layer at a preset angle, which specifically includes: SA5, moving the tungsten disulfide layer above the graphene layer using a fixed-point transfer platform, and observing the angle formed between the tungsten disulfide layer and the graphene layer through an optical microscope; after adjusting the angle formed between the tungsten disulfide layer and the graphene layer to the preset angle, the tungsten disulfide layer is bonded to the graphene layer.

[0015] Based on the same inventive concept, the present invention also provides a corner graphene-tungsten disulfide heterojunction material prepared by the above method, which includes: a graphene layer, and a tungsten disulfide layer disposed on the graphene layer at an optimal preset angle; the optimal preset angle is the preset angle at which the ultrafast light response performance is optimal.

[0016] Further, the optimal preset angle is 30°.

[0017] For better understanding and implementation, the present invention will be described in detail below with reference to the accompanying drawings. Description of the Drawings

[0018] Figure 1 It is a schematic flow chart of the preparation method of the corner graphene-tungsten disulfide heterojunction material based on ultrafast light response regulation of the present invention;

[0019] Figure 2 It is a schematic structural diagram of the corner graphene-tungsten disulfide heterojunction material with preset angles of 0°, 10°, 20°, and 30° respectively in an embodiment of the present invention;

[0020] Figure 3 It is an optical microscope image of the corner graphene-tungsten disulfide heterojunction material with preset angles of 0°, 10°, 20°, and 30° respectively in an embodiment of the present invention;

[0021] Figure 4 It is a schematic diagram of the change of the transient absorption spectrum with wavelength of the corner graphene-tungsten disulfide heterojunction material with preset angles of 0°, 10°, 20°, and 30° respectively in an embodiment of the present invention;

[0022] Figure 5 It is a schematic diagram of the change of the transient absorption spectrum with time delay of the corner graphene-tungsten disulfide heterojunction material with preset angles of 0° and 30° respectively in an embodiment of the present invention. Detailed Embodiments

[0023] It should be clear that the described embodiments are only a part of the embodiments of this application, rather than all embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope protected by the embodiments of this application. The terms used in the embodiments of this application are only for the purpose of describing specific embodiments, and are not intended to limit the embodiments of this application. The singular forms of "a", "the" and "said" used in the embodiments of this application and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise. In addition, in the description of this application, unless otherwise specified, "a plurality of" and "several" mean two or more. It should be understood that the embodiments of this application are not limited to the exact structures already described and shown in the drawings, and various modifications and changes can be made without departing from its scope. The scope of the embodiments of this application is only limited by the appended claims.

[0024] The prior art research on improving the optical properties of graphene-tungsten disulfide heterojunction materials mainly focuses on aspects such as element doping, strain engineering, and nanotechnology. These existing studies are either costly and difficult to promote and apply on a large scale, or have little effect on improving the ultrafast optical response performance of the materials. By studying the relevant literature of other types of heterojunction materials, the inventor noticed that: by regulating the stacking and twisting angle of the two-dimensional material heterojunction, a certain performance parameter of the heterojunction material can be regulated. For example, the technical solution of patent document number CN112781736A makes the thermal sensor composed of bilayer graphene have an ultra-low electron heat capacity by adjusting the twisting angle between the bilayer graphene to be around 1°. Therefore, the inventor conjectured that by changing the twisting angle between the graphene layer and the tungsten disulfide layer in the graphene-tungsten disulfide heterojunction material, perhaps the graphene-tungsten disulfide heterojunction material can obtain better ultrafast optical response. For this reason, the present invention uses transient absorption spectroscopy technology to study the relationship between the large twisting angle and the ultrafast optical response of the graphene-tungsten disulfide heterojunction material. After multiple experiments, a method for quickly screening out the optimal twisting angle with the best ultrafast optical response performance and efficiently preparing the twisted-angle graphene-tungsten disulfide heterojunction material with the optimal twisting angle is obtained. The preparation method of the present invention does not need to rely on atomic force microscopy or electron microscopy, and has the possibility of large-scale industrial preparation.

[0025] Please refer to Figure 1 , Figure 1 which is a schematic flow chart of the preparation method of the twisted-angle graphene-tungsten disulfide heterojunction material based on ultrafast optical response regulation of the present invention. The twisted-angle graphene-tungsten disulfide heterojunction material based on ultrafast optical response regulation of the present invention is prepared by the following method:

[0026] SA, paste the tungsten disulfide layer onto the graphene layer at a preset angle to obtain a twisted graphene-tungsten disulfide heterojunction with a preset angle. The preset angle is the twist angle formed between the graphene layer and the tungsten disulfide layer.

[0027] Specifically, step SA includes:

[0028] SA1, grow graphene domains on a copper substrate by chemical vapor deposition (CVD) to obtain a graphene-copper composite material.

[0029] SA2, immerse the graphene-copper composite material in an ammonium persulfate solution, and let the ammonium persulfate solution etch the copper substrate to obtain a graphene layer.

[0030] SA3, grow tungsten disulfide domains on a sapphire substrate by chemical vapor deposition to obtain a tungsten disulfide-sapphire composite material.

[0031] SA4, immerse the tungsten disulfide-sapphire composite material in a sodium hydroxide solution, and separate it by using the difference in hydrophilicity and hydrophobicity to obtain a tungsten disulfide layer.

[0032] SA5, paste the graphene layer onto a target substrate; then use a fixed-point transfer platform to move the tungsten disulfide layer above the graphene layer, and observe the angle formed between the tungsten disulfide layer and the graphene layer through an optical microscope; after adjusting the angle formed between the tungsten disulfide layer and the graphene layer to the preset angle by using the fixed-point transfer platform, bond the tungsten disulfide layer to the graphene layer to obtain a twisted graphene-tungsten disulfide heterojunction with a preset angle. The fixed-point transfer platform is a high-resolution electric two-dimensional material transfer platform dedicated to the preparation of two-dimensional material heterojunctions.

[0033] Change the preset angle, and repeat step SA several times to obtain several twisted graphene-tungsten disulfide heterojunctions with different preset angles.

[0034] Due to the symmetry of the lattice structures of graphene and tungsten disulfide, the twist angle formed between the graphene layer and the tungsten disulfide layer can cover all independent orientation angles between 0° and 30°. A twist angle greater than 30° can be converted into an equivalent twist angle between 0° and 30° through symmetry. Therefore, the value range of the preset angle is 0° to 30°.

[0035] Please refer to Figure 2-3 , Figure 2 which is a schematic structural diagram of a twisted graphene-tungsten disulfide heterojunction material with preset angles of 0°, 10°, 20°, and 30° respectively in an embodiment of the present invention. Figure 3Optical microscope images of twisted graphene - tungsten disulfide heterojunction materials with preset angles of 0°, 10°, 20°, and 30° respectively in an embodiment of the present invention. To study the trend of the ultrafast optical response performance of the heterojunction material changing with the twist angle, in this embodiment, the number of times of repeating step SA is 4, and the preset angles each time are 0°, 10°, 20°, and 30°, that is, the specific values of the preset angle include: 0°, 10°, 20°, and 30°.

[0036] SB. Measure the ultrafast optical response performance of twisted graphene - tungsten disulfide heterojunctions with several different preset angles, and screen out the twisted graphene - tungsten disulfide heterojunction with the optimal preset angle having the best ultrafast optical response performance.

[0037] Specifically, step SB includes:

[0038] SB1. Through transient absorption spectroscopy technology, measure the transient absorption spectra of twisted graphene - tungsten disulfide heterojunctions with several different preset angles.

[0039] Transient absorption spectroscopy technology is an ultrafast laser spectroscopy technology used to study the excited state process of substances. Its working principle is as follows: The laser emits a pump pulse to the sample, exciting the sample from the ground state to the excited state; after waiting for a preset time delay Δt, the laser emits a probe pulse with a preset wavelength λ to the sample, and the spectrometer detects the absorption of the sample to the probe pulse, obtaining the transient absorption spectrum intensity at the preset time delay Δt and the preset wavelength λ; by adjusting the specific values of the preset time delay Δt / preset wavelength λ, the change of the transient absorption spectrum intensity with the time delay Δt / wavelength λ can be obtained, thereby obtaining the transient absorption spectrum. Since the time scale of the pump pulse emitted by the laser is on the femtosecond or smaller time scale, the relaxation process of the sample returning from the excited state to the ground state reflected by the transient absorption spectrum is directly related to the ultrafast optical response of the sample.

[0040] SB2. Extract the features of the transient absorption spectrum to obtain feature values. In this embodiment, the feature values include: peak intensity ΔA and decay time constant τ, that is, step SB2 specifically includes: identifying the main absorption peak of the transient absorption spectrum, measuring the peak intensity ΔA of the main absorption peak; performing time - resolved analysis on the transient absorption spectrum and fitting to obtain the decay time constant τ.

[0041] SB3. According to the feature values, evaluate the ultrafast optical response performance of twisted graphene - tungsten disulfide heterojunctions with several different preset angles. In this embodiment, step SB3 is specifically: According to the peak intensity and the decay time constant, calculate the ultrafast optical response performance score; the calculation formula of the ultrafast optical response performance score is: Where Score represents the score of the ultrafast optical response performance, ΔA represents the peak intensity, α represents the first weighting coefficient corresponding to the peak intensity, τ represents the decay time constant, and β represents the second weighting coefficient corresponding to the decay time constant.

[0042] A higher peak intensity ΔA indicates a higher carrier concentration or a higher carrier excitation efficiency, and a smaller decay time constant τ indicates a faster carrier recombination rate, that is, a faster optical response speed. Therefore, under the same excitation conditions, the higher the peak intensity ΔA and the smaller the decay time constant τ, the more excellent the ultrafast optical response performance of the material. Based on the above principle, in this embodiment, the ultrafast optical response performance score Score is positively correlated with the peak intensity ΔA and negatively correlated with the decay time constant τ. Those skilled in the art can independently adjust the values of the first weighting coefficient α and the second weighting coefficient β according to needs, so as to adjust the weights of the two indicators in the process of calculating the ultrafast optical response performance score Score, and thus comprehensively consider the two indicators to evaluate the ultrafast optical response performance of the material.

[0043] SB4, to screen out the twist graphene-tungsten disulfide heterojunction with the optimal preset angle and the best ultrafast optical response performance. In this embodiment, the higher the ultrafast optical response performance score Score, the more excellent the ultrafast optical response performance. Therefore, step SB4 is specifically: screening out the twist graphene-tungsten disulfide heterojunction with the optimal preset angle and the highest ultrafast optical response performance score Score.

[0044] Please refer to Figure 4 , Figure 4 which is a schematic diagram of the change of the transient absorption spectrum with wavelength of the twist graphene-tungsten disulfide heterojunction material with preset angles of 0°, 10°, 20° and 30° in an embodiment of the present invention. Figure 4 The independent variable on the horizontal axis in Figure 4 represents the wavelength λ of the probe pulse, the dependent variable on the vertical axis represents the transient absorption spectrum intensity, and the curves of 4 colors respectively represent the twist graphene-tungsten disulfide heterojunction materials with preset angles of 0°, 10°, 20° and 30°. It can be seen from

[0045] Please refer to Figure 5 , Figure 5 which is a schematic diagram of the change of the transient absorption spectrum with time delay of the twist graphene-tungsten disulfide heterojunction materials with preset angles of 0° and 30° in an embodiment of the present invention. Figure 5The independent variable on the horizontal axis represents the time delay Δt of the probe pulse, and the dependent variable on the vertical axis represents the transient absorption spectrum intensity. The curves of the two colors respectively represent the graphene-tungsten disulfide heterojunction materials with rotation angles of 0° and 30°. From Figure 5 It can be seen that the peak value of the transient absorption spectrum intensity of the graphene-tungsten disulfide heterojunction material with a rotation angle of 30° is significantly greater than that of the graphene-tungsten disulfide heterojunction material with a rotation angle of 0°, and the rate at which the transient absorption spectrum intensity decreases with time (i.e., the decay time constant τ) is significantly lower than that of the graphene-tungsten disulfide heterojunction material with a rotation angle of 0°. It can be seen that the interfacial charge transfer lifetime of the graphene-tungsten disulfide heterojunction material with a rotation angle of 30° is greater than that of the graphene-tungsten disulfide heterojunction materials with other preset angles.

[0046] Since the photo-generated carrier concentration of the graphene-tungsten disulfide heterojunction material with a rotation angle of 30° is larger, the charge separation efficiency is higher, and the interfacial charge transfer lifetime is longer, therefore, in this embodiment, the ultrafast optical response performance of the graphene-tungsten disulfide heterojunction material with a rotation angle of 30° is the best, and the corresponding preset angle of 30° is the optimal preset angle.

[0047] The present invention has the following technical effects: The prior art focuses on the research of the twist angle of two-dimensional material heterostructures at small twist angles. For example, the twist angle of magic angle bilayer graphene is about 1°. This research on small twist angles relies on atomic force microscopes or electron microscopes, which is costly and difficult for large-scale industrial preparation; and the objects of the existing research are usually the electrical properties (such as conductivity) or thermal response characteristics of materials, without involving ultrafast optical response performance. The present invention for the first time uses transient absorption spectroscopy technology to study the relationship between the large twist angle and ultrafast optical response of graphene-tungsten disulfide heterojunction materials, provides a method for quickly screening out the optimal twist angle with the best ultrafast optical response performance, and efficiently preparing the graphene-tungsten disulfide heterojunction material with the optimal twist angle. The present invention only needs an optical microscope to prepare the graphene-tungsten disulfide heterojunction material with the best ultrafast optical response performance, without relying on atomic force microscopes or electron microscopes, and has the possibility of large-scale industrial preparation.

[0048] The above embodiments only represent several implementation manners of the present invention, and the description thereof is relatively specific and detailed, but it should not be construed as a limitation on the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and the present invention also intends to include these modifications and improvements.

Claims

1. A method for preparing a twisted graphene-tungsten disulfide heterojunction material, characterized in that: Includes steps: SA, pasting the tungsten disulfide layer onto the graphene layer at a preset angle to obtain a rotated graphene-tungsten disulfide heterojunction at a preset angle; Changing the preset angle, repeating step SA several times, and obtaining several angled graphene-tungsten disulfide heterojunctions with different preset angles; SB, measures the ultrafast light response performance of several twisted graphene-tungsten disulfide heterojunctions with different preset angles, and screens out the twisted graphene-tungsten disulfide heterojunction with the optimal preset angle with the best ultrafast light response performance.

2. The method for preparing the twisted graphene-tungsten disulfide heterojunction material according to claim 1, characterized in that: The preset angle ranges from 0° to 30°.

3. The method for preparing the twisted graphene-tungsten disulfide heterojunction material according to claim 2, characterized in that: The preset angles include: 0°, 10°, 20° and 30°.

4. The method for preparing the twisted graphene-tungsten disulfide heterojunction material according to claim 3, characterized in that: Step SB specifically includes: SB1, using transient absorption spectroscopy, measures the transient absorption spectra of several different preset angles of the twisted graphene-tungsten disulfide heterojunctions; SB2, extracting features from the transient absorption spectrum to obtain feature values; SB3, evaluating the ultrafast light response performance of the angled graphene-tungsten disulfide heterojunctions at several different preset angles according to the characteristic values; SB4, screens out the optimal preset angle of the corner graphene-tungsten disulfide heterojunction with the best ultrafast light response performance.

5. The method for preparing the twisted graphene-tungsten disulfide heterojunction material according to claim 4, characterized in that: Step SB2 specifically includes: Identifying a main absorption peak of the transient absorption spectrum, and measuring a peak intensity ΔA of the main absorption peak; Performing time-resolved analysis on the transient absorption spectrum and fitting to obtain a decay time constant τ; Step SB3 specifically includes: The ultrafast light response performance score is calculated according to the peak intensity and the decay time constant; the calculation formula of the ultrafast light response performance score is: Wherein Score represents the ultrafast light response performance score, ΔA represents the peak intensity, α represents the first weighting coefficient corresponding to the peak intensity, τ represents the decay time constant, and β represents the second weighting coefficient corresponding to the decay time constant.

6. The method for preparing the twisted graphene-tungsten disulfide heterojunction material according to claim 1, characterized in that: The graphene layer is prepared by the following steps: SA1, graphene domains are grown on a copper substrate by chemical vapor deposition to obtain a graphene-copper composite material; SA2, immersing the graphene-copper composite material into an ammonium persulfate solution, allowing the ammonium persulfate solution to etch the copper substrate to obtain a graphene layer.

7. The method for preparing the twisted graphene-tungsten disulfide heterojunction material according to claim 6, characterized in that: The tungsten disulfide layer is prepared by the following steps: SA3, growing tungsten disulfide domains on a sapphire substrate by chemical vapor deposition to obtain a tungsten disulfide-sapphire composite material; SA4, immersing the tungsten disulfide-sapphire composite material in a sodium hydroxide solution, and separating the tungsten disulfide layer by utilizing the difference in hydrophilicity and hydrophobicity.

8. The method for preparing the twisted graphene-tungsten disulfide heterojunction material according to claim 7, characterized in that: In step SA, the tungsten disulfide layer is attached to the graphene layer at a preset angle, which specifically includes: SA5, use a fixed-point transfer platform to move the tungsten disulfide layer to the top of the graphene layer, and observe the angle formed by the tungsten disulfide layer and the graphene layer through an optical microscope; after adjusting the angle formed by the tungsten disulfide layer and the graphene layer to a preset angle, the tungsten disulfide layer is attached to the graphene layer.

9. A twisted graphene-tungsten disulfide heterojunction material prepared by the method of claim 1, characterized in that: include: A graphene layer, and a tungsten disulfide layer disposed on the graphene layer at an optimal preset angle; The optimal preset angle is a preset angle with the best ultrafast light response performance.

10. The twisted graphene-tungsten disulfide heterojunction material according to claim 9, characterized in that: The optimal preset angle is 30°.

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