Grating-insulation-metal three-layer structured visible light perfect absorber and processing method
阅读说明：本技术 一种光栅-绝缘-金属三层结构的可见光完美吸收器及加工方法 (Grating-insulation-metal three-layer structured visible light perfect absorber and processing method ) 是由 陈煦 吴九汇 于 2020-07-30 设计创作，主要内容包括：本发明涉及一种光栅-绝缘-金属三层结构的可见光完美吸收器及其加工方法。完美吸收器由三层结构组成,最上层为圆形孔状光栅层,中间层为均匀介质层,最下层为金属层,所述结构的金属材料为锰,介质材料为Al<Sub>2</Sub>O<Sub>3</Sub>。通过参数优化,该结构的厚度仅为150nm,在可见光范围可实现宽带、大角度、偏振无关的近完美吸收,平均吸收率可达95％。本发明所述的加工方法为首先通过磁控溅射完成均匀金属和电介质薄膜的制造,然后利用湿法刻蚀完成上层光栅结构的加工,在显影后结合磁控溅射和剥离工艺完成最上层孔状光栅结构的制造加工。本结构在精密位移检测、太阳能电池和光学隐身等领域具有潜在的应用前景。(The invention relates to a visible light perfect absorber with a grating-insulation-metal three-layer structure and a processing method thereof. The perfect absorber is composed of three layers, wherein the uppermost layer is a circular porous grating layer, the middle layer is a uniform medium layer, the lowermost layer is a metal layer, the metal material of the structure is manganese, and the medium material is Al 2 O 3 . Through parameter optimization, the thickness of the structure is only 150nm, near-perfect absorption with broadband, large angle and polarization independence can be realized in a visible light range, and the average absorption rate can reach 95%. The processing method comprises the steps of firstly completing the manufacture of uniform metal and dielectric films through magnetron sputtering, then completing the processing of the upper grating structure through wet etching, and completing the manufacture and processing of the uppermost layer of porous grating structure through combining magnetron sputtering and stripping processes after development. The structure has potential application prospect in the fields of precision displacement detection, solar cells, optical stealth and the like.)
1. The visible light perfect absorber with the grating-insulation-metal three-layer structure is characterized in that a main body is a three-layer micro-nano structure which is closely in contact and stacked, the upper layer is a grating layer (1), the middle layer is a uniform dielectric layer (2), the lower layer is a metal layer (3), and the grating layer (1) is a periodic micro-nano structure.
2. The visible light perfect absorber with a grating-insulation-metal three-layer structure as claimed in claim 1, wherein the grating structure of the grating layer (1) is a cylindrical periodic structure with a plurality of longitudinally penetrating circular holes, the main material of the grating layer (1) is manganese, the medium material in the circular holes is air, and the period of the grating structure is in micron order.
3. The visible light perfect absorber of the grating-insulator-metal three-layer structure as claimed in claim 2, wherein the uniform dielectric layer (2) is coated on the metal layer (3), the dielectric material is a passive non-magnetic material, and the material of the metal layer (3) is manganese.
4. The visible light perfect absorber with grating-insulator-metal three-layer structure as claimed in claim 3, wherein the passive non-magnetic material is Al2O3Or TiO2。
5. The visible light perfect absorber of the grating-insulator-metal three-layer structure as claimed in claim 4, wherein the metal layer (3) is coated on a flexible or hard substrate with a thickness greater than the skin depth of its metal material.
6. The perfect absorber of visible light of the grating-insulator-metal tri-layer structure of any of claims 1-4, wherein the thickness of the grating layer (1) is 10nm, the diameter of the circular hole is 30 μm, the lattice constant is 50 μm, the thickness of the uniform dielectric layer (2) is 70nm, and the thickness of the metal layer (3) is 70 nm.
7. The visible light perfect absorber with the grating-insulation-metal three-layer structure as claimed in claim 6, wherein the perfect absorber has a working wavelength range of 375nm to 640nm, an absorption rate of the whole wavelength range is greater than 0.9, a maximum absorption rate is 0.99, an average absorption rate is 0.96, and an absorption rate of the structure is greater than 0.8 in a wavelength range of 350nm to 760nm, and covers the visible light wavelength range.
8. The perfect visible light absorber of the grating-insulator-metal three-layer structure as claimed in claim 6, wherein the absorption rate of normal incidence is the maximum and is 99.6% when the wavelength of the incident wave is 500nm, the absorption rate of the structure is slowly reduced and is reduced from 99.6% to 90% when the incident angle is gradually increased to 53 °, and the absorption rate is reduced to 80% when the incident angle is further increased to 67 °; the rate of decrease of the absorption of the structure increases significantly after an angle of incidence exceeding 67 deg..
9. The perfect absorber of visible light of the grating-insulation-metal three-layer structure as claimed in claim 3, wherein the thickness of the grating layer (1) is as thin as possible, so that more incident electromagnetic waves can enter the model structure by optimizing the material and structure parameters of the grating structure, and the possibility of increasing the absorption rate is improved; the uniform dielectric layer (2) captures incident electromagnetic waves by adjusting materials and thickness, so that the electromagnetic waves are transmitted and dissipated back and forth between an upper layer and a lower layer to realize perfect absorption, wherein the refractive index of the materials determines the resonant frequency of the cavity, the thickness of the materials determines the dissipation degree of the captured light waves in the middle layer, and the absorption wave band is freely regulated and controlled by selecting the materials and the thickness of the middle layer; the metal layer (3) is required to be thicker than the skin depth of the selected metal to ensure that the transmissivity of the overall absorber structure is minimized, and finally near perfect absorption of electromagnetic waves is achieved.
10. The method for producing a perfect absorber of visible light of a grating-insulator-metal three-layer structure as described in claim 1, comprising the steps of:
step 1: uniformly depositing a metal layer (3) and a uniform dielectric layer (2) on the surface of the substrate by a magnetron sputtering method;
step 2: utilizing wet etching to complete a grating structure with preset parameters on the photoresist, and obtaining the photoresist structure containing porous particles after exposure and development;
and step 3: depositing an ultrathin metal layer on the surface of the photoresist by a magnetron sputtering method;
and 4, step 4: and stripping the photoresist particles and the metal coated on the photoresist to obtain a grating layer (1) and obtain a grating-insulation-metal three-layer absorber structure.
Technical Field
The invention belongs to the technical field of artificial electromagnetic materials, and particularly relates to a visible light perfect absorber with a grating-insulation-metal three-layer structure and a processing method thereof.
Background
The perfect absorber is widely applied to the fields of solar cells, light stealth, thermal imaging sensors, photoelectric detection and the like.
Originally, the design concept of the conventional absorber is to realize the absorption of electromagnetic waves by using a thick high-loss material, so that the frequency band tunable characteristic cannot be realized except that the absorption device is difficult to meet the requirements of integration and miniaturization. With the emergence of artificial electromagnetic metamaterials, the perfect absorption of electromagnetic waves by designing a metal micro-nano structure rapidly draws wide attention, different resonance modes can be obtained when the relative impedance of the material and a free space is matched, the complete absorption of the electromagnetic waves in multiple bands is realized, and the absorption efficiency is effectively improved. In order to further widen the absorption frequency band, a method of overlapping multiple resonance modes is also proposed, and broadband absorption is completed by using a combination of different metal/dielectric materials.
The existing absorber structure needs to be overlapped with more than 4 layers to realize perfect broadband absorption, so that the whole thickness is thicker, the structure is more complex, the social requirements of miniaturization and portability are difficult to meet, and the preparation method and the processing technology are also greatly limited. In the aspect of material selection, noble metal materials such as gold and silver are also used, so that the cost is high, and the noble metal materials are easily oxidized at high temperature or under strong laser irradiation, so that the structure and the performance are influenced to different degrees. Therefore, in time, it is becoming urgent to take into consideration other materials and find suitable materials.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention aims to provide a visible light perfect absorber with a grating-insulation-metal three-layer structure and a processing method thereof, wherein a proper material is selected to reduce the thickness of the whole structure, reduce the processing difficulty and realize an ideal absorber structure which has excellent performance and is suitable for popularization.
In order to achieve the purpose, the invention adopts the technical scheme that:
a visible light perfect absorber with a grating-insulation-metal three-layer structure is characterized in that a main body is a three-layer periodic micro-nano structure which is closely in contact and stacked arrangement, the upper layer is a
Preferably, the grating structure of the
Preferably, the uniform dielectric layer 2 covers the metal layer 3, and the dielectric material is Al2O3Or TiO2And the metal layer 3 is made of manganese and is coated on the flexible or hard substrate, and the thickness of the metal layer is larger than the skin depth of the metal material.
Preferably, the thickness of the
The invention also provides a processing method of the visible light perfect absorber with the grating-insulation-metal three-layer structure, which comprises the following steps:
step 1: uniformly depositing a metal layer 3 and a uniform dielectric layer 2 on the surface of the substrate by a magnetron sputtering method;
step 2: utilizing wet etching to complete a grating structure with preset parameters on the photoresist, and obtaining the photoresist structure containing porous particles after exposure and development;
and step 3: depositing an ultrathin metal layer on the surface of the photoresist by a magnetron sputtering method;
and 4, step 4: and stripping the photoresist particles and the metal coated on the photoresist to obtain a
Compared with the prior art, the grating-insulation-metal perfect absorber can obtain near perfect absorption irrelevant to broadband polarization, greatly reduces the whole thickness and the structural complexity on the premise of similar absorption efficiency of the traditional absorption structure, completely meets the processing requirement, and can easily change the working frequency band of the perfect absorber by adjusting the material and the thickness of the middle layer. The processing mode related to the invention has the advantages of simple process, convenient operation and the like for the grating-insulation-metal multilayer structure, and the processing precision of the grating layer and the intermediate layer can be ensured. In conclusion, the invention can be used in the fields of precision displacement detection, solar cells, optical stealth and the like.
Drawings
Fig. 1 is a schematic diagram of the structure of a perfect absorber of the grating-insulator-metal structure of the present invention.
FIG. 2 is an absorption spectrum of the absorber of the present invention in the range of 0.2 μm to 0.8. mu.m.
Fig. 3 is an absorption spectrum of the absorber of the present invention in the visible range at the incidence of TM and TE waves.
Fig. 4 shows the absorption of the structure at different angles of incidence for a fixed wavelength of 500 nm.
Figure 5 is a schematic view of the overall process for making a three-layer absorbent structure according to the present invention.
Fig. 6 is a schematic diagram of a structural sample processed according to the present invention, in which (a) is a multi-layer micro-nano structure in which a grating layer is circular, (b) is a multi-layer micro-nano structure in which a grating layer is square, (c) is a multi-layer micro-nano structure in which a grating layer is rectangular, and (d) is a concrete object diagram.
Detailed Description
The embodiments of the present invention will be described in detail below with reference to the drawings and examples.
As shown in fig. 1, the visible light perfect absorber with a grating-insulation-metal three-layer structure of the invention has a three-layer periodic micro-nano structure with a main body in close contact stacking arrangement and no air in the middle, wherein:
the upper layer is a
The middle insulating layer is a uniform dielectric layer 2 which is also of a flat structure and covers the metal layer 3, and the dielectric material is Al2O3Or TiO2Etc. passive non-magnetic materials.
The lowest layer is a metal layer 3 which is covered on a flexible or hard substrate, the material can be selected from conventional metal materials, such as manganese, and the thickness is larger than the skin depth of the metal material.
The design idea of the visible light perfect absorber is as follows: the thickness of the
The perfect absorber for visible light can obtain the absorption of large-angle electromagnetic waves irrelevant to polarization, the whole structure only consists of a simple cylindrical periodic grating structure and two uniform material layers, the application requirements of simple processing mode and easy popularization are met, the whole thickness of the perfect absorber is in the nanometer level, and the requirements of miniaturization, portability and integration can be met.
In a specific embodiment of the present invention, a plurality of longitudinally penetrating circular holes are distributed on the
As shown in FIG. 2, the working wavelength band of the perfect absorber of the present invention is 375 nm-640 nm, the absorbance of the whole wavelength band is greater than 0.9, the maximum absorbance is 0.99, and the average absorbance is 0.96. In the wave band range of 350 nm-760 nm, the absorptivity of the structure is greater than 0.8, and the structure covers the visible light wave band.
As shown in FIG. 3, the perfect absorber of the present invention is insensitive to the polarization direction of the incident electromagnetic wave, and can achieve perfect absorption of visible light in any polarization state, wherein the absorption effect is better when TM is polarized.
As shown in fig. 4, the perfect absorber of the present invention can realize ultra-wideband perfect absorption at a large incident angle, and when the wavelength of the incident wave is 500nm, the absorption rate is the largest at normal incidence, which is about 99.6%; when the incident angle is gradually increased to 53 degrees, the absorptivity of the structure is slowly reduced from 99.6% to about 90%; when the incident angle is further increased to 67 °, the absorption rate is reduced to 80%; the rate of decrease of the absorption of the structure increases significantly after an angle of incidence exceeding 67 deg..
The invention provides a processing method of a perfect absorber, and a specific flow is shown in figure 5, and the processing method comprises the following steps:
step 1: firstly, depositing a layer of metal manganese with the thickness of 70nm on a substrate by a magnetron sputtering process to be used as a bottom metal layer;
step 2: depositing a layer of Al with the thickness of 70nm on the manganese metal by a magnetron sputtering process2O3As an intermediate insulating layer;
and step 3: processing a hole-shaped structure in the grating structure at the uppermost layer by wet etching, and developing to obtain cylindrical photoresist particles, wherein the photoresist in the example is AZ 5214;
and 4, step 4: and continuously depositing a layer of metal manganese with the thickness of 10nm on the photoresist particles by a magnetron sputtering process, and removing the photoresist and the metal manganese coated on the photoresist by a stripping process to obtain the uppermost layer of the metal grating structure.
SEM images of the perfect absorber sample produced by the above processing method are shown in fig. 6 (a) to (c), and a concrete figure is shown in fig. 6 (d). Fig. 6 shows that the grating layer is a multi-layer micro-nano structure with the shape of circle, square, rectangle and the like, and the multi-layer micro-nano structure can be processed by the method.
The processing method is simple to operate, convenient to process and convenient to regulate and control in the processing process, the influence of the processing mode and process of the grating layer on the intermediate medium layer can be avoided to the greatest extent, and the regular periodic structure can be obtained.
In conclusion, the perfect absorber provided by the invention effectively reduces the reflectivity of the whole structure by using the local plasmon resonance mode generated when the incident wave is coupled with the metal grating structure, on the basis, the matched FP cavity resonance mode is constructed by selecting materials and structural parameters, the captured electromagnetic wave is stored and dissipated in the structure of the perfect absorber, and the near perfect absorption unrelated to wide-frequency large-angle polarization is realized by the synergistic effect of the two resonance modes. By introducing manganese metal, the simple structure can meet the dual requirements of absorption efficiency in the visible light band and convenience in processing and manufacturing under the condition of smaller thickness. The processing technology is suitable for processing and manufacturing the grating layer-insulating layer-metal layer structure, simple in technology, portable in operation and capable of being properly regulated and controlled in the processing process.
It should be understood that the technical solutions and the design concepts of the present invention may be equally replaced or changed by those skilled in the art, and those changes or substitutions should also fall into the protection scope of the appended claims.
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