Broadband wave-absorbing metamaterial based on micro-nano double-coupling gradient resonator structure and preparation method

Abstract

The invention belongs to the field of electromagnetic wave absorption, and particularly relates to a broadband wave-absorbing metamaterial of a micro-nano double-coupling gradient resonator structure and a preparation method. The metamaterial is provided with gradient resonators in two dimensions of nanometer and micrometer. The nano-dimension gradient resonator is composed of three layers of metal-medium-metal resonant cavity structures with the thickness changing in a gradient mode on the protruding structure. The micron-dimension gradient resonator is composed of a cavity between the protruding structures and metal-medium-metal resonant cavities on the two sides. The material structure comprises three layers, the upper layer is a metal thin layer, the middle layer is a dielectric layer, and the bottom layer is a metal reflecting layer. The material has wide application prospects in the fields of solar energy utilization, seawater desalination, photo-thermal deicing and the like. The wave-absorbing material has the advantages of small thickness, high absorption, low cost, easiness in regulation and control, simple manufacturing process, high temperature resistance and the like, and is an efficient wave-absorbing material.

Description

Technical Field

[0001] The invention belongs to the field of electromagnetic wave absorption, and specifically relates to a broadband wave absorbing metamaterial based on a micro-nano dual-coupled gradient resonator structure and a preparation method thereof. Background Art

[0002] Perfect electromagnetic wave absorbers, also known as black body absorbers, can achieve near-perfect absorption of omnidirectional and non-polarized incident electromagnetic waves in a specific band, and have important application value in the fields of solar energy collection systems, thermal emitters, infrared imaging, sensors and photodetectors. To achieve perfect absorption of electromagnetic waves, it is necessary to effectively adjust the spectral characteristics and electromagnetic response mode of the absorber. Metamaterials, as an artificial subwavelength structure, can achieve customized optical response and are considered to be perfect candidates in the design of absorbing materials. Metamaterials usually adopt a sandwich structure, including a metal pattern layer, a dielectric spacer layer and a metal reflective layer. Due to the characteristics of the periodic arrangement structure, metamaterials often show a perfect response to electromagnetic waves at a single frequency point. Traditional electromagnetic wave absorbing metamaterials usually use resonator units with different absorption frequencies superimposed in the plane direction or vertical direction to achieve the broadening of the electromagnetic response site and the superposition of absorption peaks. However, the number of superimposed resonators per unit area is limited, and as the number of resonators increases, the response intensity of a single resonator will decrease and the absorption peak will be discontinuous, which will have an adverse effect on the overall performance. In addition, the superposition of resonators of different structures poses a huge challenge to preparation, and the cost increases exponentially. Summary of the invention

[0003] In view of the problems in the prior art, the present invention proposes a broadband absorbing metamaterial based on a micro-nano dual-coupled gradient resonator structure and a preparation method. By constructing a gradient resonator structure, the limitation on the number of different resonance units in the metamaterial design is broken, and the "resonance point" is converted into a "resonance band", realizing the continuous response of the resonance frequency of the resonance unit. The material has broad application prospects in the fields of solar energy utilization, seawater desalination, photothermal deicing, etc. It has the advantages of thin thickness, high absorption, low cost, easy control, simple manufacturing process, and high temperature resistance, and is a highly efficient absorbing material.

[0004] The technical solution of the present invention is: A method for preparing a broadband wave absorbing metamaterial based on a micro-nano dual-coupled gradient resonator structure comprises the following steps: Step 1: preparing a protruding structure substrate by nanoimprinting technology; Step 2: depositing a bottom metal reflective layer, an intermediate dielectric layer and an upper metal thin layer on the substrate in sequence by means of a coating technique, and forming a gradient resonator structure by means of a shadow effect to obtain the metamaterial; During the preparation process, the protruding structures are arranged periodically, and the top of the protruding structures shield the material particles emitted from the deposition source, so that the thickness gradient changes are naturally achieved on the protruding structures. The incident angle of the deposited material will affect the shadow effect. If the deposition angle is too large or too small, some areas will be over-deposited and other areas will be under-deposited. The deposition angle is preferably 30°~80°.

[0005] In order to avoid additional errors caused by angles, the uniform area of ​​the test equipment needs to be tested so that it is mainly affected by geometric occlusions. In addition, during the preparation process, the sample stage rotates at a constant speed, which can effectively avoid the influence of angles. Deposition rates that are too high or too low may aggravate the shadow effect. Too high a deposition rate may cause material to accumulate near the obstruction, while too low a deposition rate may not be able to fill the obstruction area fast enough. Therefore, a suitable protrusion structure is selected to avoid the influence of the deposition angle, and it is preferred to use the shadow effect to realize the preparation of the gradient resonator at a rate of 1nm / min~20nm / min.

[0006] Furthermore, the above-mentioned method for preparing a broadband absorbing metamaterial based on a micro-nano dual-coupled gradient resonator structure can optimize and adjust the electromagnetic wave absorption performance by adjusting structural parameters such as the type, size, shape, spacing of the upper metal thin layer, the type and thickness of the intermediate dielectric layer, and the type and thickness of the bottom metal reflective layer, so that the absorption range is optional, thereby achieving broadband perfect absorption for different bands.

[0007] A broadband wave-absorbing metamaterial based on a micro-nano dual-coupled gradient resonator structure, wherein the material structure is a metal-dielectric-metal resonant cavity structure, wherein the upper layer is a metal thin layer, the middle layer is a dielectric layer, and the bottom layer is a metal reflective layer, and the total thickness ranges from 50 nm to 2300 nm.

[0008] Furthermore, the above-mentioned broadband wave absorbing metamaterial based on a micro-nano dual-coupled gradient resonator structure has gradient resonators in both nanometer and micrometer dimensions.

[0009] Furthermore, in the above-mentioned broadband wave-absorbing metamaterial based on a micro-nano dual-coupled gradient resonator structure, the nano-dimensional gradient resonator is composed of a metal-medium-metal resonant cavity structure with three layers of thickness gradient changes on a protruding structure, and the thickness of the metal-medium-metal resonant cavity on the top of the protruding structure is h t The thickness of the metal-dielectric-metal resonant cavity at the bottom of the protruding structure h b Gradually decreases, that is h t > h b .

[0010] Furthermore, in the above-mentioned broadband absorbing metamaterial based on a micro-nano dual-coupled gradient resonator structure, the micron-dimensional gradient resonator is composed of a cavity between the protruding structures and a metal-medium-metal resonance cavity on both sides, and the size of the cavity between the protruding structures decreases gradually from top to bottom.

[0011] Furthermore, in the above-mentioned broadband wave-absorbing metamaterial based on a micro-nano dual-coupled gradient resonator structure, the protrusion structure can be periodically densely packed or randomly densely packed.

[0012] Furthermore, in the above-mentioned broadband wave absorbing metamaterial based on the micro-nano dual-coupled gradient resonator structure, the thickness of the upper metal thin layer is recorded as h 1 , the size range is 3 nm~20 nm, and the metal type is one metal or an alloy of multiple metals such as Al, Ti, Au, Ag, Cu, Mo, and W.

[0013] Furthermore, in the above-mentioned broadband absorbing metamaterial based on a micro-nano dual-coupled gradient resonator structure, the thickness of the intermediate dielectric layer is recorded as h 2 , the size range is 20~200 nm, the medium is oxide, nitride, carbide, sulfide, semiconductor or organic matter, specifically including SiO2, SiO, Al3O2, TiO2, Si3N4, ZnS or polyvinyl chloride, etc.

[0014] Furthermore, in the above-mentioned broadband absorbing metamaterial based on a micro-nano dual-coupled gradient resonator structure, the bottom metal reflective layer is composed of metal, including but not limited to one metal or an alloy composed of multiple metals selected from the group consisting of Al, Ti, Au, Ag, Cu, Mo, W, etc., and the thickness is recorded as h 3 , the size range is 30nm~2000 nm.

[0015] Furthermore, in the above-mentioned broadband wave-absorbing metamaterial based on a micro-nano dual-coupled gradient resonator structure, the nano-dimensional gradient resonator is formed by vapor deposition through shadowing.

[0016] Furthermore, in the above-mentioned broadband wave-absorbing metamaterial based on a micro-nano dual-coupled gradient resonator structure, the micron-dimensional gradient resonator is formed by using a protruding structure as a template.

[0017] Furthermore, the above-mentioned broadband absorbing metamaterial based on a micro-nano dual-coupled gradient resonator structure has an absorption rate of 93% in the 0.2~5 μm band.

[0018] The key point of the present invention is that by having a gradient resonant cavity of two dimensions, each resonant cavity has a continuous resonant site, breaking through the limitation on the number of different resonant units in the metamaterial design, converting the "resonance point" into a "resonance band", and realizing the continuous response of the resonant frequency of the resonant unit. Through this gradient structured design, the 200 nm thick material has an average absorption rate of up to 93% in the 0.2~5μm band and an average absorption rate of up to 70% in the 0.2~10 μm band, showing excellent broadband wave absorbing performance. Due to its central symmetry and strong side scattering mechanism, the material achieves polarization insensitivity and wide incident angle absorption. The material has broad application prospects in the fields of solar energy utilization, seawater desalination, photothermal deicing, etc. It has the advantages of thin thickness, high absorption, low cost, easy control, simple manufacturing process, and high temperature resistance, and is a high-efficiency wave absorbing material.

[0019] Advantages and beneficial effects of the present invention: The present invention proposes a broadband absorbing metamaterial based on a micro-nano dual-coupled gradient resonator structure. The structure has a gradient resonance cavity of two dimensions, each of which has a continuous resonance site, breaking through the limitation on the number of different resonance units in the metamaterial design, converting the "resonance point" into a "resonance band", and realizing the continuous response of the resonance frequency of the resonance unit. It has the advantages of thin thickness, high absorption, low cost, easy control, simple manufacturing process, and high temperature resistance, and is a highly efficient absorbing material.

[0020] Patent CN202210142662.7 discloses a metamaterial near-infrared broadband absorber and a preparation method thereof, wherein the metamaterial near-infrared broadband absorber comprises a substrate and a metal bottom layer, a middle dielectric layer, a metal microstructure layer and a top dielectric layer sequentially covered on the substrate from bottom to top, wherein the metal microstructure layer is composed of a plurality of metal microstructures arranged in a periodic array, and a metal-medium-metal structure is formed by combining the metal bottom layer and the middle dielectric layer, and a localized surface plasma resonance is formed on the surface of the metal pattern, and a magnetic resonance is formed between the metal bottom layer and the middle dielectric layer, and under the action of resonant coupling, an average absorption rate of 90% is achieved in the band of 1000 to 3000nm. Compared with this invention, the present invention can achieve an average absorption rate of up to 93% in the band of 200 to 5000nm, a wider material absorption band, a thinner thickness, and can absorb electromagnetic waves more effectively.

[0021] Patent CN202410467490.X discloses an ultra-wideband high-absorption solar absorber based on a MIM resonant structure. The absorber structure uses metal tungsten (W) as the substrate, and the multi-layer stacked disks on the substrate are composed of metal titanium (Ti), amorphous Ge2Sb2Te5 (A-GST) or gallium arsenide (GaAs), forming a three-layer MIM continuous interlayer plasma strong resonator with a total thickness of 0.66 μm, achieving ultra-wideband and efficient solar absorption. Compared with this invention, the thinnest thickness of the present invention is only 50 nm, with the advantages of thinner material thickness and simpler material structure. It has the advantages of simple preparation process and low production cost in the process of large-scale production, and has better application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a structural schematic diagram of the present invention; Figure 2 It is a schematic diagram of the structure of the nano-gradient resonator and the micron-gradient resonator of the present invention; Figure 3 is a graph of the absorptivity of the metamaterial with different thicknesses of the upper metal thin layer of the present invention; Figure 4 This is a graph of the absorption rate of the metamaterial with different dielectric layer thicknesses of the present invention. DETAILED DESCRIPTION

[0023] The specific implementation modes of the present invention are further described in detail below in conjunction with the accompanying drawings and specific embodiments. The following embodiments are used to illustrate the present invention but cannot be used to limit the scope of the present invention. Example 1

[0024] A broadband absorbing metamaterial based on a micro-nano dual-coupled gradient resonator structure, such as Figure 1 and 2 As shown, the convex structure as a whole presents a close-packed hexagonal structure. d =3.0 μm, bottom diameter a =2.7 μm, average height h =1.7 μm. The upper layer is a thin Ti metal layer with a thickness of h 1 The middle layer is a dielectric layer composed of a non-metallic SiO2 dielectric layer with a thickness of 10 nm. h 2 The bottom metal reflective layer is composed of metal Ti with a thickness of 100 nm. h 3The preparation method is to prepare a periodically densely packed convex structure substrate by nanoimprinting technology, and deposit the bottom Ti layer, the middle SiO2 dielectric layer and the upper Ti metal thin layer on the substrate in sequence by coating technology; because the geometric shape of the convex structure blocks, a shadow effect is caused during the magnetron sputtering process, and the preparation of a broadband absorbing metamaterial with a gradient resonator structure is realized. The nano-dimensional gradient resonator is composed of a metal-dielectric-metal resonant cavity structure with three layers of thickness gradient changes on the convex structure. The thickness of the metal-dielectric-metal resonant cavity on the top of the convex structure is h t The thickness of the metal-dielectric-metal resonant cavity at the bottom of the protruding structure h b Gradually decreases, that is h t > h b ; Thickness of top h t 210 nm, 146 nm at the waist and 146 nm at the bottom h b The thickness of the film deposition between the structures is 95 nm, and the thickness of the gap film deposition between the structures is 201 nm. The micron-dimensional gradient resonator is composed of the cavity between the raised structures and the metal-medium-metal resonant cavity on both sides. The size of the cavity between the raised structures decreases from top to bottom, and the gap between the two microstructures from bottom to top ranges from 0.3 μm to 3 μm.

[0025] The performance analysis of the materials described in Example 1 is as follows: 1. Analysis of the influence of the upper metal reflective layer on the microwave absorption performance Comsol electromagnetic simulation software analysis found that the upper metal reflective layer also has a certain influence on the electromagnetic wave absorption performance of the metamaterial, as shown in the schematic diagram. Figure 3 Through simulation, when the thickness of the upper metal reflective layer is 10 nm, the absorption peak is higher, and when the thickness is 20 nm, the absorption peak decreases to a certain extent.

[0026] 2. Analysis of the influence of dielectric layer thickness on microwave absorption performance Comsol electromagnetic simulation software analysis found that the thickness of the intermediate dielectric layer also has a certain influence on the solar absorption performance of the metamaterial. The results are as follows: Figure 4 As shown in Figure 2, as the thickness of the dielectric layer increases, there is a certain red shift in the visible absorption peak.

Claims

1. A method for preparing a broadband wave-absorbing metamaterial based on a micro-nano dual-coupled gradient resonator structure, characterized in that: The following steps are involved: Step 1: preparing a protruding structure substrate by nanoimprinting technology; Step 2: depositing a bottom metal reflective layer, an intermediate dielectric layer and an upper metal thin layer on the substrate in sequence by using a coating technology, and utilizing a shadow effect to form a gradient resonator structure to obtain the metamaterial.

2. A broadband wave absorbing metamaterial based on a micro-nano dual-coupled gradient resonator structure according to claim 1, characterized in that: The material structure is a metal-dielectric-metal resonant cavity structure, with an upper layer of a metal thin layer, a middle layer of a dielectric layer, and a bottom layer of a metal reflective layer. The total thickness ranges from 50 nm to 2300 nm. The metamaterial has gradient resonators in both nanometer and micrometer dimensions.

3. The broadband wave absorbing metamaterial based on a micro-nano dual-coupled gradient resonator structure according to claim 2, characterized in that: The nano-dimensional gradient resonator is composed of a three-layer metal-dielectric-metal resonant cavity structure with a gradient thickness on a protruding structure. The thickness of the metal-dielectric-metal resonant cavity on the top of the protruding structure is h t The thickness of the metal-dielectric-metal resonant cavity at the bottom of the protruding structure h b Gradually decreases, that is h t > h b .

4. The broadband absorbing metamaterial based on a micro-nano dual-coupled gradient resonator structure according to claim 2, characterized in that: The micron-dimensional gradient resonator is composed of a cavity between protruding structures and metal-dielectric-metal resonant cavities on both sides. The size of the cavity between the protruding structures decreases gradually from top to bottom.

5. The broadband wave absorbing metamaterial based on a micro-nano dual-coupled gradient resonator structure according to claim 2, 3 or 4, characterized in that: The protrusion structure is periodically densely packed or randomly densely packed.

6. The broadband wave absorbing metamaterial based on a micro-nano dual-coupled gradient resonator structure according to claim 2, characterized in that: The upper metal thin layer is an alloy composed of one or more metals selected from Al, Ti, Au, Ag, Cu, Mo, and W.

7. The broadband wave absorbing metamaterial based on a micro-nano dual-coupled gradient resonator structure according to claim 2, characterized in that: The intermediate dielectric layer is oxide, nitride, carbide, sulfide, semiconductor or organic matter, specifically including SiO2, SiO, Al3O2, TiO2, Si3N4, ZnS or polyvinyl chloride.

8. The broadband wave absorbing metamaterial based on a micro-nano dual-coupled gradient resonator structure according to claim 2, characterized in that: The bottom metal reflective layer is made of metal, including but not limited to an alloy consisting of one or more metals selected from Al, Ti, Au, Ag, Cu, Mo, and W.

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