Large-area nano Moire lattice and preparation method thereof

Abstract

The invention discloses a large-area nano Moire lattice and a preparation method thereof, and the method comprises the steps: 1, providing a substrate, and carrying out the cleaning and activation of the substrate; 2, spin-coating photoresist on the substrate; 3, performing primary exposure on the photoresist substrate through the holographic optical element by adopting an adjustable holographic photoetching technology and taking ultraviolet laser with the wavelength of 325nm as a light source, and rotating the substrate or the holographic optical element by a certain angle for secondary exposure; 4, developing and fixing to obtain a photoresist array with a Moire lattice pattern in morphology; and 5, depositing a material on the photoresist nano array to obtain a nano Moire lattice structure. According to the preparation method of the nanometer Moire lattice, the tunable holographic photoetching technology is utilized, large-area preparation can be completed within several minutes, and therefore the preparation method has the advantages of being low in cost, high in throughput, good in uniformity and capable of accurately controlling the rotating angle.

Description

Technical Field

[0001] The present invention belongs to the technical field of nanomanufacturing, and particularly relates to a large-area nano-Moiré lattice and a preparation method thereof. Background Art

[0002] Optical Moiré lattices can enable multifunctional optical operations. Advances in modeling, nanofabrication, and characterization tools have propelled the development of many applications of Moiré lattices: energy conversion, biomedicine, and information technology. In recent years, nanomaterials with Moiré structures have attracted great interest due to their highly tunable optical responses and high-throughput fabrication. The Moiré lattice structure can easily and precisely control the structural configuration and its optical properties by adjusting the relative lattice constant or rotating the angle between two periodic arrays. Therefore, large-scale nanostructures with highly tunable optical properties can be realized.

[0003] Currently, the preparation methods of Moiré lattice structures can be divided into two major categories: self-assembly and top-down techniques. The former is achieved through the directional assembly and arrangement of nanospheres. Although it has low cost and high throughput, it lacks large-area uniformity and has boundary defects. The top-down techniques are a general term for all lithography-based processing methods. It mainly includes the following methods: interference lithography requires multiple laser beams and multiple exposures; nanoimprint lithography largely depends on the master template and is not convenient for adjusting the structural morphology; the commercial instrument equipment of electron beam lithography and focused ion beam lithography is often very expensive, the process is extremely time-consuming and it is difficult to achieve large-area processing and preparation of the structure. Therefore, it greatly affects the popularization and application of nanostructures in various aspects such as research, development, and commercialization. Summary of the Invention

[0004] In view of the deficiencies pointed out in the above background art, the present invention provides a large-area nano-Moiré lattice and a preparation method thereof, aiming to solve the problems existing in the prior art in the above background art.

[0005] To achieve the above object, the technical solution adopted by the present invention is:

[0006] A large-area nano-Moiré lattice and a preparation method thereof, comprising the following steps:

[0007] (1) Provide a substrate, and clean and activate the substrate;

[0008] (2) Spin-coat a photoresist on the substrate to form a photoresist layer;

[0009] (3) Use an adjustable ultraviolet holographic lithography technique to perform patterned exposure on the photoresist layer at two different rotation angles. The laser wavelength of the adjustable ultraviolet holographic lithography technique is 325 nanometers, and a holographic optical element is used;

[0010] (4) After development and fixation, nitrogen gas is used to blow and remove the surface moisture, and a periodic nano-Moiré pattern array is obtained on the photoresist layer. The period of the Moiré pattern array is 0.3 - 1 μm;

[0011] (5) Using the obtained Moiré pattern as a template, material deposition is carried out to obtain a nano-Moiré lattice.

[0012] Optionally, in step (1), the substrate includes a single-crystalline silicon substrate, a glass substrate, a single-crystalline silicon substrate or a glass substrate with a metal layer grown thereon, a polydimethylsiloxane substrate, and a polystyrene substrate.

[0013] Optionally, in step (2), the thickness of the photoresist layer is 0.2 - 1 μm.

[0014] Optionally, in step (3), the rotation angle range is 0 - 360°.

[0015] Optionally, in step (5), the thickness of the material deposition is 70 - 150 nm.

[0016] Optionally, the photoresist is a positive photoresist (ALLRESIST) and a negative photoresist SU8, as well as other positive and negative photoresists with the same composition.

[0017] Optionally, the arrangement of the Moiré pattern is adjusted by changing the exposure time, adjusting the laser power, or adjusting the rotation angle.

[0018] Optionally, the configuration of the holographic optical element can be an array with three gratings arranged at 120° to each other in pairs to achieve a hexagonal arrangement, or an array with four gratings arranged at 90° to each other to achieve an orthogonal arrangement.

[0019] The present invention has the following advantages by adopting the above technologies:

[0020] 1. Using a 325 nm ultraviolet laser as the light source, nanostructures can be fabricated.

[0021] 2. By using a holographic optical element, the complexity of the optical path is greatly reduced, the stability of the system is increased, and a periodic Moiré pattern can be obtained with only two exposures.

[0022] 3. Lithography can be completed for a large area within a few minutes, and material deposition can also be carried out in large batches. Therefore, the limitations of electron beam lithography and focused ion beam etching technologies in batch processing are overcome.

[0023] 4. The method for fabricating a Moiré lattice can conveniently select the types of materials, such as metals (gold, silver, copper, aluminum, etc.) and semiconductors (silicon, silicon dioxide, etc.), which is conducive to further promoting the application of the present invention in different technical fields.

[0024] 5. The substrate of the nanomoiré lattice can be a traditional silicon-based material or glass, or flexible materials such as PDMS and PE. This can not only greatly reduce costs, but also facilitate the integration with other components. Therefore, it is of great significance for promoting the research, production and development of nano-devices and micro-nano composite devices.

[0025] 6. The prepared nanomoiré lattice not only has the characteristics of a single moiré period nanostructure, but also has the characteristics of a periodic array. For example, when depositing metals such as gold, silver, copper, and aluminum, a surface plasmon moiré lattice can be obtained. Compared with ordinary surface plasmon structures, it has richer optical modes and broadband responses. When depositing semiconductor silicon-based materials, a photonic moiré lattice can be obtained, and flat bands with highly degenerate local states will appear in real space. These properties further promote the application of nanomoiré lattices in the field of nonlinear optics. Description of the Drawings

[0026] Figure 1 is the process flow chart of the preparation of the nanomoiré lattice provided by the embodiment of the present invention.

[0027] Figure 2 is the scanning electron microscope image of the nanomoiré lattice provided by the embodiment of the present invention.

[0028] Figure 3 is the scanning electron microscope image of the nanomoiré lattice at different rotation angles provided by the embodiment of the present invention.

[0029] Figure 4 is the nanomoiré lattice with different arrangement modes obtained by using different holographic optical elements provided by the embodiment of the present invention.

[0030] Figure 5 is the electron microscope image of the nanomoiré lattice obtained under different exposure doses provided by the embodiment of the present invention, where the exposure doses of 1# - 3# gradually increase.

[0031] Figure 6 is the physical diagram of a large-area nanomoiré lattice, showing that the structure can be uniformly prepared on the scale of square centimeters.

[0032] In the figure: 1 - substrate; 2 - photoresist layer; 2' - photoresist nanoarray; 3 - deposited metal layer. Detailed Embodiments

[0033] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, and are not used to limit the present invention.

[0034] 1. The preparation process flow of a large-area nano-Moiré lattice provided by the present invention is as follows Figure 1 as shown, and the detailed steps are as follows:

[0035] (1) Use a glass sheet or a silicon wafer as the substrate 1, and clean and activate the substrate.

[0036] (2) Spin-coat a layer of negative photoresist (SU8 2000.5) uniformly on the substrate 1 to form a photoresist layer 2, and the thickness of the photoresist layer 2 is about 0.5 micrometers.

[0037] (3) Pattern-expose the photoresist layer 2 by holographic lithography. First, expose once at the initial position, and then expose again after rotating the substrate or the holographic element by a certain angle. The laser wavelength used is 325 nanometers, and a holographic optical element is used. The rotation angle and the exposure time can be determined according to the required structure.

[0038] (4) After the exposure is completed, put it into a negative photoresist developer for development. After the development is completed, put it into isopropyl alcohol for fixing, then rinse its surface with clean water, and finally blow dry the surface moisture with nitrogen to obtain a photoresist Moiré lattice nanoarray.

[0039] (5) Using the obtained photoresist nanoarray 2' as a template, perform metal deposition to obtain a surface plasmon Moiré lattice 3 with the same surface morphology as it, Figure 2 is the scanning electron microscope picture of the above structure.

[0040] In a specific embodiment, nano-Moiré lattices at different magic angles can be prepared by changing the rotation angle, as Figure 3 shown.

[0041] In a specific embodiment, nano-Moiré lattices with different arrangement patterns can be prepared by replacing the holographic optical element, as Figure 4 shown.

[0042] In a specific embodiment, the nanoscopic morphology of the prepared nano-Moiré lattice array can be changed by adjusting the exposure dose, as Figure 5 shown. It can be seen from the figure that as the exposure time increases, the morphology also keeps changing.

[0043] In a specific embodiment, the material deposited on the photoresist template is not restricted and can be selected according to the actual application. For example, precious metal materials such as gold, silver, copper, and aluminum can be selected for the preparation of the surface plasmon Moiré lattice structure. Semiconductor silicon-based materials can also be selected for the preparation of the photonic Moiré lattice.

[0044] Refer to Figure 6 , through the method of the present invention, the preparation of a large-area nano-Moiré lattice on the square centimeter scale can be realized.

[0045] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A large-area nano-Moiré lattice and a preparation method thereof, characterized in that, It includes the following steps: (1) Provide a substrate and clean and activate the substrate; (2) Spin-coat a photoresist on the substrate to form a photoresist layer; (3) Use an adjustable ultraviolet holographic lithography technique to perform patterned exposure on the photoresist layer at two different rotation angles. The laser wavelength of the adjustable ultraviolet holographic lithography technique is 325 nm, and a holographic optical element is used; (4) After development and fixation, use nitrogen purge to remove surface moisture, and obtain a nano-Moiré pattern array with two periods on the photoresist layer. The period of the Moiré pattern array is 0.3 - 1 μm; (5) Using the obtained Moiré pattern as a template, perform material deposition to obtain a nano-Moiré lattice structure.

2. The preparation method according to claim 1, characterized in that, In step (1), the substrate includes a single-crystalline silicon substrate, a glass substrate, a single-crystalline silicon substrate or a glass substrate with a metal layer grown thereon, a polydimethylsiloxane substrate, and a polystyrene substrate.

3. The preparation method according to claim 1, characterized in that, In step (2), the photoresist includes positive and negative photoresists, and the thickness of the photoresist is 0.2 - 1 μm.

4. The preparation method according to claim 1, wherein, In step (3), the rotation angle range is 0 - 360°.

5. The preparation method according to claim 1, wherein: Adjust the arrangement of the Moiré pattern by changing the exposure time or adjusting the laser power or adjusting the rotation angle.

6. The preparation method according to claim 1, characterized in that, In step (5), the deposited material is a metal or semiconductor material.

7. The preparation method according to claim 1, wherein The arrangement of the nano-Moiré pattern array is hexagonal arrangement or orthogonal arrangement.

8. A large-area nano-Moiré lattice prepared by the method according to claims 1-7, characterized in that: The nano-Moiré lattice structure includes a substrate, a photoresist layer located on the substrate, and a material layer located on the photoresist layer. An array of regularly arranged Moiré patterns is formed on the surface of the photoresist layer, and a nano-Moiré lattice structure with a period of 0.3 - 1 μm is correspondingly formed on the material layer.

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