A broadband perfect absorber based on a nanosphere array and a preparation method thereof

Abstract

The present invention belongs to the field of optoelectronic technology, and provides a broadband perfect absorber based on a nanosphere array, which is characterized in that it includes: a substrate, and a composite layer structure disposed on the substrate; the composite layer structure is sequentially arranged from the substrate upwards as: a bottom metal layer, a dielectric layer, a nanosphere array, and a top metal layer wrapped on the surface of the nanosphere array; the nanosphere array and the top metal layer form a core-shell structure, and the material of the nanosphere array is selected as polymer particles. The nanosphere array and the top metal layer in the broadband perfect absorber form a core-shell structure to generate a local surface plasmon effect, and the optical resonator formed by the bottom metal layer and the top metal layer has a light field enhancement effect, thereby achieving broadband perfect absorption for different wavelength bands.

Description

Technical Field

[0001] The present invention belongs to the field of optoelectronic technology and relates to a broadband perfect absorber and a preparation method thereof. Background Art

[0002] In recent years, with the proposal of the concept of plasmonic perfect absorbers, the development of perfect absorbers has shown a trend from single-band absorption to multi-band absorption, broadband absorption, and narrow-band absorption. Broadband perfect absorbers have broad application prospects and can be applied to solar cells, invisibility, blackbody radiation, biosensing, etc.

[0003] A surface plasmon polariton perfect absorber refers to a phenomenon where when an electromagnetic wave is incident on the absorber, both reflection and transmission are close to zero, that is, perfect absorption with A = 1 - R - T = 1 is obtained. By changing the materials and structures of each part of the absorber, the impedance of the absorber can be matched with the impedance of free space, thereby minimizing the reflectivity to the greatest extent; by using a thicker metal material at the grounding end, the transmittance can be minimized.

[0004] However, at present, in order to pursue a wider wavelength band, many absorbers adopt very complex multi-layer structures, which lead to more cumbersome manufacturing processes and higher manufacturing costs and are not suitable for large-scale production. In addition, multi-band perfect absorbers in the ultraviolet, visible, and near-infrared regions are relatively rare and have the problem of insufficient bandwidth, and the application of broadband perfect absorbers in solar cells, invisibility technology, and detection and sensing has become an urgent problem to be solved. Therefore, designing and realizing broadband perfect absorption and being able to achieve large-scale production through a simple manufacturing method have become research hotspots. Summary of the Invention

[0005] In order to solve the problem that the existing broadband absorber increases the light absorption rate by increasing the number of layer structures, resulting in a complex film layer structure and an increase in manufacturing cost, a broadband perfect absorber based on a nanosphere array is proposed.

[0006] A broadband perfect absorber based on a nanosphere array, characterized by comprising: a substrate, and a composite layer structure disposed on the substrate; the composite layer structure is sequentially disposed from the substrate upwards as: a bottom metal layer, a dielectric layer, a nanosphere array, and a top metal layer wrapped on the surface of the nanosphere array; the nanosphere array and the top metal layer form a core-shell structure, and the material of the nanosphere array is selected as polymer particles.

[0007] The working principle of the above solution is as follows: When incident light enters the absorber, a local surface plasmon resonance mode is formed between the spherical shell arrays of the top metal layer wrapped on the surface of the nanosphere array. The spherical shells of the top metal layer with nanostructures have a strong absorption effect on photon energy. The regularly arranged nanosphere array provides a periodic array structure for the top metal layer. The MIM structure absorber formed by the top metal layer, dielectric layer, and bottom metal layer with nanoarray structures forms an optical resonant cavity, which significantly improves the absorption rate by exciting electromagnetic resonance. The bottom metal layer is a metal thin film layer with a sufficient thickness to suppress transmission.

[0008] Preferably, the substrate is silica with a thickness of 200 - 500 nanometers.

[0009] The thickness of the bottom metal layer is 200 - 300 nanometers.

[0010] The thickness of the dielectric layer is 10 - 50 nanometers, and the dielectric layer material is one of alumina and titanium dioxide.

[0011] The period of the nanosphere array is 800 - 1000 nanometers. The radius of the nanosphere is 400 nanometers, and the nanosphere material is polystyrene.

[0012] The thickness of the top metal layer is 4 - 10 nanometers.

[0013] By changing parameters such as the thickness and material of the bottom metal layer, the radius of the nanosphere particles, the thickness and material of the top metal shell, the material of the metal shell, and the incident angle, the absorption band range can be effectively adjusted.

[0014] The beneficial effects of the present invention are as follows:

[0015] The present invention discloses a broadband perfect absorber based on a nanosphere array and its manufacturing method. A composite layer formed by a top metal layer, a dielectric layer, and a bottom metal layer with nanoarray structures is provided on a substrate. By utilizing the local surface plasmon resonance characteristics formed between the spherical shell arrays of the top metal layer and the optical resonant cavity formed by the MIM structure absorber formed by the top metal layer, dielectric layer, and bottom metal layer with nanoarray structures, which has a light field enhancement effect, tunable broadband perfect absorption is achieved.

[0016] The basic structure of this application is a broadband perfect absorber based on a nanosphere array, and the manufacturing method of this structure is simple and easy for large-scale manufacturing.

[0017] When the technical solution of this application is used in production, by changing parameters such as the metal material, the thickness of the metal layer, and the radius of the polymer particles, the absorption range can be made selectable, and thus broadband perfect absorption for different bands can be achieved.

[0018] The perfect absorber described in the present invention is relatively simple in structure and has the advantages of a wide absorption band, high absorption rate, and easy large-scale manufacturing. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic structural diagram of a broadband perfect absorber based on a nanosphere array;

[0020] In the figure, 1 - substrate, 2 - bottom metal layer, 3 - dielectric layer, 5 - nanosphere array, 4 - top metal layer.

[0021] Figure 2 It is a schematic cross-sectional structural diagram of a broadband perfect absorber based on a nanosphere array.

[0022] Figure 3 It is a light absorption diagram of a broadband perfect absorber based on a nanosphere array in the wavelength range of 1900 nm - 2300 nm.

[0023] Figure 4 It is a light absorption diagram of a broadband perfect absorber based on a nanosphere array in the wavelength range of 2000 nm - 2500 nm.

[0024] Figure 5 It is a light absorption diagram of a broadband perfect absorber based on a nanosphere array in the wavelength range of 400 mm - 1400 mm.

[0025] Figure 6 It is a light absorption diagram of a broadband perfect absorber based on a nanosphere array in the wavelength range of 1900 nm - 2300 nm with the change of the incident angle.

[0026] Figure 7 It is a light absorption diagram of a broadband perfect absorber based on a nanosphere array in the wavelength range of 2000 nm - 2500 nm with the change of the incident angle.

[0027] Figure 8 It is a light absorption diagram of a broadband perfect absorber based on a nanosphere array in the wavelength range of 400 mm - 1400 mm with the change of the incident angle.

[0028] Example 1

[0029] As Figure 1 and Figure 2As shown in the figure, a broadband perfect absorber based on a nanosphere array includes: a substrate 1 and a composite layer structure disposed on the substrate; the composite layer structure is sequentially disposed from the substrate upward as: a bottom metal layer 2, a dielectric layer 3, a nanosphere array 5, and a top metal layer 4 wrapped on the surface of the nanosphere array; the nanosphere array and the top metal layer form a core-shell structure, and the material of the nanosphere array is selected as polymer particles. The upper end surface of the substrate is a plane, the metal layer and the dielectric layer sequentially disposed on the upper end surface of the substrate are both planes, nanosphere particles are arranged on the surface of the dielectric layer, all the nanosphere particles form a nanosphere array, and the top metal layer wraps the surface of the nanosphere array and the upper end surface of the dielectric layer.

[0030] When incident light is incident on the absorber, a local surface plasmon resonance mode is formed between the top metal layer spherical shell arrays wrapped on the surface of the nanosphere array, and the top metal layer spherical shell with a nanostructure has a strong absorption effect on photon energy; the regularly arranged nanosphere array provides a periodic array structure for the top metal layer; the MIM structure absorber formed by the top metal layer, the dielectric layer, and the bottom metal layer with a nanoarray structure forms an optical resonant cavity, and by exciting electromagnetic resonance, the absorption rate is significantly improved; the bottom metal layer is used to suppress transmission. To increase the transmission suppression ability of the bottom metal layer, the thickness of the bottom metal layer can be increased.

[0031] The nanosphere array of this structure has a local surface plasmon effect and the optical resonant cavity formed with the top metal layer has a light field enhancement effect. By changing the top metal material, the thickness of the top metal layer, the period and diameter parameters of the nanosphere array, the absorption range is selectable, and thus broadband perfect absorption for different bands is achieved.

[0032] Example Two

[0033] A broadband perfect absorber based on a nanosphere array on the basis of Example One, the substrate is selected as silica with a thickness of 400 nanometers; the bottom metal layer is selected as gold with a thickness of 200 nanometers; the dielectric layer is selected as alumina with a thickness of 20 nanometers; the nanospheres are selected as polystyrene PS small balls with a diameter of 400 nanometers, the period of the nanosphere array is 1000 nanometers, and the thickness of the top metal layer is 5 nanometers. As Figure 3 and Figure 6 shown, in the wavelength range of 1900 nanometers - 2300 nanometers, the average absorption rate reaches 93%; the broadband perfect absorber based on the nanosphere array is insensitive to the light incident angle and can still maintain a high absorption rate at 40 degrees.

[0034] Example Three

[0035] A broadband perfect absorber based on a nanosphere array on the basis of Embodiment 1, with a silicon dioxide substrate having a thickness of 400 nm; a bottom metal layer made of silver with a thickness of 270 nm; a dielectric layer of 20 nm alumina; a top metal layer with a thickness of 4 nm and made of gold; the nanospheres are polystyrene (PS) spheres with a diameter of 400 nm, and the period of the nanosphere array is 1000 nm. Figure 4 and Figure 7 As shown, in the wavelength range of 2000 nm - 2500 nm, the average absorption rate reaches 93.5%; the broadband perfect absorber based on the nanosphere array is insensitive to the incident angle of light and can still maintain a high absorption rate at 40 degrees.

[0036] Embodiment 4

[0037] A broadband perfect absorber based on a nanosphere array on the basis of Embodiment 1, with a silicon dioxide substrate having a thickness of 400 nm; a bottom metal layer made of platinum with a thickness of 300 nm; a dielectric layer of 20 nm alumina; a top metal layer with a thickness of 10 nm and made of platinum; the nanospheres are polystyrene (PS) spheres with a diameter of 400 nm, and the period of the nanosphere array is 1000 nm. As Figure 5 and Figure 8 shown, in the wavelength range of 400 nm - 1400 nm, the average absorption rate reaches 91%; the broadband perfect absorber based on the nanosphere array is insensitive to the incident angle of light and can maintain a high absorption rate at angles up to 20 degrees.

[0038] Embodiment 5

[0039] A preparation method of a broadband perfect absorber based on a nanosphere array: deposit a bottom metal layer on the substrate by thermal evaporation, then deposit a dielectric layer on the bottom metal layer by metal organic chemical vapor deposition, and form a monolayer nanosphere array on the surface of the dielectric layer by self-assembly of nanosphere particles; then use thermal evaporation deposition to deposit a top metal layer on the surface of the dielectric layer assembled with the nanosphere array.

[0040] In one embodiment, the substrate is a planar silicon substrate, and the nanosphere particles are polystyrene spheres.

[0041] In summary, through the research on the broadband perfect absorber based on the nanosphere array, the present application provides a nanostructure for the top metal by the nanosphere array, forming a local surface plasmon resonance mode. Moreover, the optical resonator formed by the MIM structure absorber composed of the top metal layer, the dielectric layer and the bottom metal layer has a light field enhancement effect, thus obtaining a broadband perfect absorber with a relatively wide band, high absorption and angle insensitivity, which also has the advantages of simple structure and easy manufacturing. This perfect absorber has broad application prospects and can be applied to solar cells, invisibility, blackbody radiation, biosensing and other aspects.

[0042] It should be noted that in the specification, the structural schematic diagrams only illustrate the positional relationships of the respective structures, and the sizes and proportional relationships of the respective components shall not be construed as limitations of the present application. Additionally, although the present application provides examples of parameters including specific values, it should be understood that the parameters do not necessarily have to be exactly equal to the corresponding values, but may approximate the corresponding values within an acceptable error tolerance or design constraint.

[0043] The specific embodiments described above further elaborate on the purpose, technical solutions and beneficial effects of the present application. It should be understood that the above are only specific embodiments of the present application and are not intended to limit the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application shall be included within the protection scope of the present application.

Claims

1. A broadband perfect absorber based on a nanosphere array, characterized in that, It includes: a substrate, and a composite layer structure disposed on the substrate; the composite layer structure is sequentially arranged from the substrate upwards as: a bottom metal layer, a dielectric layer, a nano-sphere array, and a top metal layer wrapped on the surface of the nano-sphere array; the nano-sphere array and the top metal layer form a core-shell structure, and the material of the nano-sphere array is selected as polymer particles; when incident light is incident, a local surface plasmon resonance mode is formed between the top metal layer spherical shell arrays wrapped on the surface of the nano-sphere array, and the top metal layer spherical shell with a nano-structure has an absorption effect on photon energy; the regularly arranged nano-sphere array provides a periodic array structure for the top metal layer; the top metal layer, the dielectric layer, and the bottom metal layer with a nano-array structure form an optical resonant cavity of a MIM structure absorber, and the absorption rate is improved by exciting electromagnetic resonance; the bottom metal layer is used to suppress transmission.

2. The broadband perfect absorber based on a nanosphere array according to claim 1, characterized in that The substrate is silicon dioxide with a thickness of 200 - 500 nanometers.

3. The broadband perfect absorber based on a nanosphere array according to claim 1, characterized in that, The thickness of the bottom metal layer is 200 - 300 nanometers.

4. The broadband perfect absorber based on a nanosphere array according to claim 1, characterized in that, The thickness of the dielectric layer is 10 - 50 nanometers, and the material of the dielectric layer is one of alumina and titanium dioxide.

5. A broadband perfect absorber based on a nanosphere array according to any one of claims 1 to 4, characterized in that, The period of the nano-sphere array is 800 - 1000 nanometers; the radius of the nano-sphere is 400 nanometers, and the nano-sphere material is polystyrene.

6. The broadband perfect absorber based on a nanosphere array according to claim 5, wherein, The thickness of the top metal layer is 4 - 10 nanometers.

7. A preparation method of a broadband perfect absorber based on a nano-sphere array: deposit a bottom metal layer on the substrate by a thermal evaporation process, then deposit a dielectric layer on the bottom metal layer by a metal organic chemical vapor deposition process, and form a single-layer nano-sphere array on the surface of the dielectric layer by a self-assembly method of nano-sphere particles; then use a thermal evaporation deposition process to deposit a top metal layer on the surface of the dielectric layer assembled with the nano-sphere array.

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