A preparation method of an optical dielectric microsphere array / single layer of tungsten diselenide composite structure applied to improve valley polarization degree

Abstract

The application discloses a preparation method of an optical dielectric microsphere array / single layer of tungsten diselenide composite structure applied to improve valley polarization, and the optical dielectric microsphere dispersion liquid is dropped on the single layer of tungsten diselenide to obtain the optical dielectric microsphere array / single layer of tungsten diselenide composite structure through a self-assembly method. The optical dielectric microsphere array / single layer of tungsten diselenide composite structure obtained by the application has excellent valley polarization photoelectric performance, and provides a new scheme for design, manufacture and application of valley electronic devices.

Description

Technical Field

[0001] This invention relates to the field of valley electronic devices and provides a method for preparing an optical dielectric microsphere array / monolayer tungsten diselenide composite structure for improving valley polarization. Background Technology

[0002] With the rapid development of science and technology, electronic degrees of freedom are becoming increasingly important in information processing and related electronic device manufacturing. Exploring and studying electronic degrees of freedom and applying them to the design of electronic devices is a core issue in condensed matter physics today. Transition metal dihalogen compounds, as representatives of next-generation optoelectronic devices, exhibit excellent optical properties. They possess a band structure composed of two degenerate but unequal valley "states," which is usually related to the occupancy of spin electrons (holes) near the band extrema. The spin and valley degrees of freedom of these materials provide an important platform for discovering new quantum phenomena and have been developed for various applications in spintronic devices and valley-selective light emitters. However, due to the strong phonon-assisted inter-valley scattering and long-range electron-hole exchange interactions in transition metal dihalogen compounds, it is difficult to distinguish valley polarization at room temperature, limiting their practical applications. Monolayer tungsten diselenide, with a direct band gap of ~1.64 eV, is a candidate two-dimensional material for nanophotonics, quantum optics, and valleytronic devices. Controlling and improving the valley polarization of monolayer tungsten diselenide to increase the practical application temperature of valleytronic devices is crucial for future research.

[0003] Currently, various methods have been developed to control the valley polarization degree of transition metal dihalogen compounds, including chiral plasmonic nanostructures and optical resonators. Chiral plasmonic nanostructures, whose mirror images cannot be superimposed on themselves, have been widely studied to enhance the chiral response of molecules, thereby improving the valley polarization degree of transition metal dihalogen compounds. Chiral plasmonic nanostructures leverage the strong optical chirality of metallic chiral structures and enhance light-matter interactions through localized surface plasmon resonance modes, thus achieving control over valley polarization degree. However, due to the complex and costly fabrication process and significant errors involved, chiral plasmonic nanostructures have not yet yielded satisfactory results in practical applications.

[0004] Recent studies have shown that the coupling between optical resonators and valley spins holds great promise for overcoming low-temperature limitations and achieving room-temperature control of valley dynamics. Specifically, the strong coupling between excitons and optical resonators to form exciton-polarizer pairs can prevent the complete disappearance of valley polarization due to inter-valley scattering, making the modulation of valley polarization by optical resonators a key research focus. However, strong coupling requires precise spatial and spectral overlap between excitons and the optical cavity. This limitation challenges the flexible and active adjustment of valley polarization in monolayer transition metal dihalogen compounds at room temperature, hindering the development of valley-electron devices. Optical dielectric microsphere arrays are simple to fabricate, small in size, and inexpensive, facilitating their application in valley-electron devices. By using successfully fabricated optical dielectric microsphere arrays with optimized parameters to improve the valley polarization of monolayer tungsten diselenide, room-temperature improvement of tungsten diselenide's valley polarization has been successfully achieved, demonstrating significant scientific research value and potential application potential. However, no methods for fabricating optical dielectric microsphere array / monolayer tungsten diselenide composite structures for improving valley polarization have been reported. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing an optical dielectric microsphere array / monolayer tungsten diselenide composite structure for improving valley polarization by utilizing the controllability of optical dielectric microspheres. By combining the self-assembly of optical dielectric microspheres with monolayer tungsten diselenide, a composite structure with improved valley polarization of monolayer tungsten diselenide can be obtained.

[0006] Another objective of this invention is to provide an optical dielectric microsphere array / monolayer tungsten diselenide composite structure.

[0007] The technical solution adopted to achieve the purpose of this invention is:

[0008] A method for fabricating an optical dielectric microsphere array / monolayer tungsten diselenide composite structure for improving valley polarization includes the following steps:

[0009] Step 1: Clean the surface of the single-layer tungsten diselenide with a bulb syringe to ensure that the surface is thoroughly clean and dry;

[0010] Step 2: Disperse and dilute the optical dielectric microsphere solution with deionized water;

[0011] Step 3: Thoroughly mix the diluted optical dielectric microsphere suspension using an ultrasonic method;

[0012] Step 4: Using a dropper, a portion of the optical dielectric microsphere dispersion is drawn up and suspended above the monolayer tungsten diselenide, then dripped onto the surface of the monolayer tungsten diselenide.

[0013] Step 5: Transfer the monolayer tungsten diselenide with the optical dielectric microsphere dispersion to a sealed box with a 5-10° tilting stage to reduce the impact of external airflow on the fabrication of the microsphere array.

[0014] In the above technical solution, in step 2, the diameter of the optical dielectric microspheres is 3.98-6.10 μm, and their material is silicon dioxide. Further, the formula for calculating the optical whispering-gallery mode spacing (FSR) caused by the microsphere cavity is: FSR = λ 2 / nπD, where n is the refractive index of the microsphere, λ is the PL spectral peak position, and D is the diameter of the microsphere. Microspheres of different diameters have different free spectral paths and whispering-gallery mode wavelengths. When the whispering-gallery mode wavelength of the microsphere matches the PL emission wavelength of the material, the whispering-gallery mode enhancement effect of the microsphere reaches its maximum value.

[0015] In the above technical solution, in step 3, the equipment used in the ultrasonic method is an ultrasonic cleaner, and the working time of the ultrasonic cleaner is set to 30-60 seconds. Furthermore, this is to ensure that the optical dielectric microsphere suspension and deionized water are fully mixed.

[0016] In the above technical solution, in step 4, the droplet is suspended 1-2 cm above the monolayer tungsten diselenide to ensure a rounded droplet shape. Furthermore, this helps the microsphere droplets form a uniform hexagonal array.

[0017] In the above technical solution, in step 5, the composite structure is transferred to a sealed box with a 5-10° tilting stage in order to ensure that the hexagonal microsphere array formed by self-assembly in the composite structure is closely arranged.

[0018] In the above technical solution, the valley polarization degree of the optical dielectric microsphere array / monolayer tungsten diselenide composite structure at 300K is 0.06-0.09.

[0019] Compared with the prior art, the beneficial effects of the present invention are:

[0020] 1) The optical dielectric microsphere array / monolayer tungsten diselenide composite structure provided by the present invention for improving valley polarization degree has a simple preparation method and high stability.

[0021] 2) The optical dielectric microsphere array / monolayer tungsten diselenide composite structure provided by the present invention for improving valley polarization can prepare optical dielectric microsphere array / monolayer tungsten diselenide composite structures with different diameters according to different emission wavelengths, and ultimately achieve the improvement of valley polarization.

[0022] 3) The optical dielectric microsphere array / monolayer tungsten diselenide composite structure provided by this invention for improving valley polarization has excellent comprehensive performance and has important application value in the field of valley electronic devices. Attached Figure Description

[0023] Figure 1 The diagram shows the fabrication process of the optical dielectric microsphere array / monolayer tungsten diselenide composite structure.

[0024] Figure 2 The image shown is a scanning electron microscope image of an optical dielectric microsphere array.

[0025] Figure 3 The image shown is a scanning electron microscope image of an optical dielectric microsphere array.

[0026] Figure 4 The image shows the polarization PL spectrum and DoP of the optical dielectric microsphere array / monolayer tungsten diselenide composite structure. Detailed Implementation

[0027] The present invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0028] Implementation Case 1

[0029] A method for fabricating an optical dielectric microsphere array / monolayer tungsten diselenide composite structure for improving valley polarization includes the following steps:

[0030] Step 1: Clean the surface of the single-layer tungsten diselenide with a bulb syringe to ensure that the surface is thoroughly clean and dry;

[0031] Step 2: Disperse and dilute the 4.86 μm optical dielectric microsphere solution with deionized water;

[0032] Step 3: The diluted 4.86μm optical dielectric microsphere suspension is thoroughly mixed by ultrasonication for 60 seconds;

[0033] Step 4: Take a portion of the 4.86μm optical dielectric microsphere dispersion using a dropper, suspend it 1cm above the monolayer tungsten diselenide, and then drop it onto the surface of the monolayer tungsten diselenide.

[0034] Step 5: Transfer the monolayer tungsten diselenide coated with optical dielectric microsphere dispersion to a sealed box with a 10° tilting stage to reduce the impact of external airflow on the fabrication of the microsphere array.

[0035] The enhancement effect of the obtained 4.86 μm optical dielectric microsphere array / monolayer tungsten diselenide composite structure on valley polarization fluorescence emission was measured by spectrometer, and the valley polarization degree at 300 K was increased to 0.09.

[0036] Implementation Case 2

[0037] A method for fabricating an optical dielectric microsphere array / monolayer tungsten diselenide composite structure for improving valley polarization includes the following steps:

[0038] Step 1: Clean the surface of the single-layer tungsten diselenide with a bulb syringe to ensure that the surface is thoroughly clean and dry;

[0039] Step 2: Disperse and dilute the 3.98 μm optical dielectric microsphere solution with deionized water;

[0040] Step 3: The diluted 3.98μm optical dielectric microsphere suspension is thoroughly mixed by ultrasonication for 40 seconds;

[0041] Step 4: Take a portion of the 3.98μm optical dielectric microsphere dispersion using a dropper, suspend it 1.5cm above the monolayer tungsten diselenide, and then drop it onto the surface of the monolayer tungsten diselenide.

[0042] Step 5: Transfer the monolayer tungsten diselenide coated with optical dielectric microsphere dispersion to a sealed box with a 5° tilting stage to reduce the impact of external airflow on the fabrication of the microsphere array.

[0043] The enhancement effect of the 3.98 μm optical dielectric microsphere array / monolayer tungsten diselenide composite structure obtained above on valley polarization fluorescence emission was measured by spectrometer, and the valley polarization degree at 300 K was increased to 0.07.

[0044] Implementation Case 3

[0045] A method for fabricating an optical dielectric microsphere array / monolayer tungsten diselenide composite structure for improving valley polarization includes the following steps:

[0046] Step 1: Clean the surface of the single-layer tungsten diselenide with a bulb syringe to ensure that the surface is thoroughly clean and dry;

[0047] Step 2: Disperse and dilute the 6.10 μm optical dielectric microsphere solution with deionized water;

[0048] Step 3: The diluted 6.10 μm optical dielectric microsphere suspension is thoroughly mixed by ultrasonication for 30 seconds;

[0049] Step 4: Take a portion of the 6.10μm optical dielectric microsphere dispersion using a dropper, suspend it 2cm above the monolayer tungsten diselenide, and then drop it onto the surface of the monolayer tungsten diselenide.

[0050] Step 5: Transfer the monolayer tungsten diselenide coated with optical dielectric microsphere dispersion to a sealed box with an 8° tilting stage to reduce the impact of external airflow on the fabrication of the microsphere array.

[0051] The enhancement effect of the 6.10 μm optical dielectric microsphere array / monolayer tungsten diselenide composite structure obtained above on valley polarization fluorescence emission was measured by a spectrometer. The valley polarization degree was increased to 0.06 at 300 K.

[0052] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is impossible to exhaustively list all embodiments here. All obvious variations or modifications derived from the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. A method for preparing an optical dielectric microsphere array / monolayer tungsten diselenide composite structure for improving valley polarization, characterized in that, Includes the following steps: Step 1: Clean the surface of the single-layer tungsten diselenide with a bulb syringe to ensure that the surface is thoroughly clean and dry; Step 2: Disperse and dilute the optical dielectric microsphere solution with deionized water; the optical dielectric microspheres have a diameter of 3.98-6.10 μm and are made of silicon dioxide; Step 3: Thoroughly mix the diluted optical dielectric microsphere suspension using an ultrasonic method; Step 4: Using a dropper, a portion of the optical dielectric microsphere dispersion is drawn up and suspended and dripped onto the surface of a monolayer of tungsten diselenide; the suspension is 1-2 cm above the monolayer of tungsten diselenide. Step 5: Transfer the monolayer tungsten diselenide coated with optical dielectric microsphere dispersion to a sealed box.

2. The preparation method according to claim 1, characterized in that, In step 3, the equipment used in the ultrasonic method is an ultrasonic cleaner, and the working time of the ultrasonic cleaner is set to 30-60 seconds.

3. The preparation method according to claim 1, characterized in that, In step 5, the contents are transferred to a sealed box with a 5-10° tilting platform.

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