Infrared broadband absorber and preparation method thereof

Abstract

The invention discloses an infrared broadband absorber and a preparation method thereof.The infrared broadband absorber comprises a titanium substrate, a lower loss layer, a middle composite layer and an upper dielectric layer which are sequentially arranged from bottom to top, the middle composite layer is composed of nanorods which are periodically arranged in an array, each nanorod comprises five layers, and the number of the nanorods is five. The titanium nitride layer, the ferric oxide layer, the titanium layer, the ferric oxide layer and the titanium layer are sequentially arranged from bottom to top. According to the invention, through the design of the multi-layer heterostructure and the optimization of the nanorod array, the efficient absorption of broadband infrared light is realized.

Description

Technical Field

[0001] The present invention relates to the field of optical technology, in particular to an infrared broadband absorber and a preparation method thereof. Background Art

[0002] Metamaterials are artificially designed and manufactured composite materials with periodic structures. Metamaterial absorbers are a key research area in the metamaterial field. Infrared radiation plays a crucial role in the electromagnetic spectrum. Studying the absorption properties of materials for infrared radiation can advance fields such as infrared stealth, infrared detection, infrared thermal imaging, and thermophotovoltaics.

[0003] Traditional infrared devices achieve active control based on the material's intrinsic absorption properties of infrared radiation. However, these devices have limited control over electromagnetic waves, resulting in a narrow operating band, low absorption, and difficulty in fabrication. Metamaterials, using periodic arrangements of nanostructures, can achieve electromagnetic properties not possessed by natural materials. Therefore, metamaterial-based infrared absorbers offer a new solution to these problems and have rapidly developed into a research hotspot in the field of artificial electromagnetic materials in recent years.

[0004] Currently, most metamaterial infrared absorbers utilize a sandwich structure consisting of a metal layer, an upper dielectric layer, and a metal layer to achieve perfect absorption. This three-layer structure struggles to achieve high absorption in the mid-wave infrared band. Furthermore, the metal materials used suffer from high cost (such as gold and platinum) and susceptibility to oxidation (such as silver, aluminum, and iron). These factors collectively limit the practical application potential of metamaterial infrared absorbers. Therefore, to achieve high absorption across a wide wavelength band, a metamaterial broadband infrared absorber needs to be designed. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide an infrared broadband absorber and a preparation method thereof, aiming to address the shortcomings of the above-mentioned background technology, and achieve efficient absorption of wide-band infrared light through multi-layer heterostructure design and nanocolumn array optimization.

[0006] The present invention provides an infrared broadband absorber, comprising a titanium substrate, a lower loss layer, an intermediate composite layer and an upper dielectric layer, which are arranged in sequence from bottom to top. The intermediate composite layer is composed of nanocolumns arranged in a periodic array. Each of the nanocolumns includes five layers, which are, from bottom to top, a titanium nitride layer, a ferric oxide layer, a titanium layer, a ferric oxide layer and a titanium layer.

[0007] In one embodiment, the material of the upper dielectric layer is silicon dioxide.

[0008] In one embodiment, the material of the lower lossy layer is ferric oxide.

[0009] In one embodiment, the thickness of the upper dielectric layer is h4, and the range of h4 is 140-160 nm.

[0010] In one embodiment, the thickness of each layer of the nanorods is h3, and the range of h3 is 40-60 nm.

[0011] In one embodiment, the thickness of the lower sacrificial layer is h2, and the range of h2 is 40-60 nm.

[0012] In one embodiment, the thickness of the titanium substrate is h1, and the range of h1 is 300-350 nm.

[0013] In one embodiment, the nanocolumn is a cylinder, and the diameter of the nanocolumn is a1, and the range of a1 is 300-320 nm.

[0014] In one embodiment, the distance between two adjacent nanorods is L1, and the range of L1 is 100-200 nm.

[0015] The present invention also provides a method for preparing the above-mentioned infrared broadband absorber, comprising the following steps: Titanium substrates were prepared using PECVD deposition technology; A lower sacrificial layer was prepared on a titanium substrate by PECVD deposition technology; forming an intermediate composite layer on the lower sacrificial layer by using photolithography and etching techniques; An upper dielectric layer is prepared on the middle composite layer by PECVD deposition technology.

[0016] The beneficial effects of the present invention are as follows: the infrared broadband absorber includes a titanium substrate, a lower lossy layer, an intermediate composite layer, and an upper dielectric layer, which are arranged in sequence from bottom to top. In the upper dielectric layer structure, since the energy of the evanescent wave decays rapidly in the vertical direction, the energy basically propagates in a direction parallel to the metal surface. The function of the upper dielectric layer is to facilitate the absorption of the evanescent wave energy. The intermediate composite layer is composed of nanopillars arranged in a periodic array. The nanopillars are filled with titanium (Ti), ferric oxide (Fe2O3), titanium, ferric oxide (Fe2O3), and titanium nitride (TiN) from top to bottom to form a five-layer nanopillar structure. The metal nanopillars induce a local surface plasmon resonance effect, and the nanopillars couple with it to increase the field strength and enhance the absorption effect. The lower lossy layer can gradually match the free space impedance to reduce reflection. The metal titanium substrate can prevent light from transmitting out of the bottom. The infrared broadband absorber achieves efficient absorption of broadband infrared light through a multi-layer heterostructure design and nanopillar array optimization. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0018] Figure 1 Schematic diagram of the structure of an infrared broadband absorber according to an embodiment of the present invention.

[0019] Figure 2 yes Figure 1 side view.

[0020] Figure 3 This is a spectral characteristic curve diagram of Example 1.

[0021] Figure 4 1 is a spectral characteristic curve diagram of absorbance of Example 1, Comparative Example 1 and Comparative Example 2 as a function of wavelength.

[0022] Figure 5 1 is a graph showing the absorbance-wavelength relationship of Example 1 under different polarization states. DETAILED DESCRIPTION

[0023] Specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the described embodiments are merely some, and not all, of the embodiments of the present invention. All other embodiments derived by persons of ordinary skill in the art based on the description of the present invention without inventive effort are intended to fall within the scope of protection of the present invention.

[0024] In the description of the present invention, unless otherwise specified or limited, the terms "disposed," "installed," and "connected" should be understood broadly. For example, they may refer to fixed, detachable, or integral connections; mechanical or electrical connections; and direct or indirect connections through an intermediary. Those skilled in the art will understand the specific meanings of these terms based on the specific circumstances.

[0025] The directions or positional relationships indicated by terms such as "upper", "lower", "left", "right", "front", "back", "top", "bottom", "inside" and "outside" are based on the directions or positional relationships shown in the accompanying drawings, or are the directions or positional relationships in which the inventive product is usually placed when in use. They are only for the convenience and simplification of description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operate in a specific direction. Therefore, they should not be understood as limiting the present invention.

[0026] The terms "first," "second," "third," etc. are merely used to distinguish between elements of similar nature and do not indicate or imply relative importance or a particular order.

[0027] The terms "comprises," "comprising," or any other variations thereof, are intended to cover a non-exclusive inclusion of elements other than the listed elements and may also include additional elements not specifically listed.

[0028] like Figure 1 and Figure 2 As shown, the present invention provides an infrared broadband absorber, comprising a titanium substrate 1, a lower loss layer 2, an intermediate composite layer 3 and an upper dielectric layer 4 arranged in sequence from bottom to top, wherein the intermediate composite layer 3 is composed of nanocolumns arranged periodically in an array, and each nanocolumn comprises five layers, namely, a titanium nitride layer, a ferric oxide layer, a titanium layer, a ferric oxide layer and a titanium layer, in sequence from bottom to top.

[0029] In this embodiment, the infrared broadband absorber structure includes, from bottom to top, a titanium substrate 1, a lower lossy layer 2, an intermediate composite layer 3, and an upper dielectric layer 4. In the upper dielectric layer 4, since the energy of the evanescent wave decays rapidly in the vertical direction, the energy generally propagates parallel to the metal surface. The upper dielectric layer 4 facilitates the absorption of the evanescent wave energy. The intermediate composite layer 3 is composed of nanopillars arranged in a periodic array. The nanopillars are filled with titanium, ferric oxide, titanium, ferric oxide, and titanium nitride from top to bottom, forming a five-layer nanopillar structure. The metal nanopillars induce a local surface plasmon resonance effect, which couples with the nanopillars to increase the field strength and enhance the absorption effect. The lower lossy layer 2 can gradually match the free space impedance to reduce reflection. The metal titanium substrate 1 prevents light from transmitting out of the bottom. This infrared broadband absorber achieves efficient absorption of broadband infrared light through a multi-layer heterostructure design and nanopillar array optimization.

[0030] The wide infrared absorption range of Fe2O3 material covers the near-infrared and part of the mid-infrared. Its lattice vibrations, defect states, and surface plasmon resonances effectively extend the absorption range to most of the infrared band. Furthermore, the multilayer structure of Fe2O3 and Ti can produce reflection suppression and light trapping. Specifically, the titanium metal acts as a reflective back electrode, reflecting transmitted light back into the Fe2O3 layer, increasing the optical path length (absorption rate increases by 20-30%). The designed multilayer structure (Ti / Fe2O3 / Ti / Fe2O3) selectively enhances absorption in specific wavelengths through interference effects. Furthermore, TiN, as a material with high degrees of freedom carriers, exhibits stronger resonant absorption in the infrared band. In the Fe2O3 / TiN / Fe2O3 combination, the Fe2O3 layer can be considered a dielectric layer, while the TiN layer acts as a reflective layer, forming an optical microcavity that is enhanced through multiple reflection interference. Therefore, the designed material combination exhibits superior broadband infrared absorption. Titanium substrate 1 is made of metallic titanium.

[0031] In one embodiment, the upper dielectric layer 4 is made of silicon dioxide (SiO2). It evenly covers the upper surface of the intermediate composite layer 3 (multi-layer nanopillars) and is filled with silicon dioxide. SiO2 has high transparency and chemical stability, and exhibits excellent absorption properties in the infrared band.

[0032] In one embodiment, the lower lossy layer 2 is made of ferric oxide. This lower lossy layer 2 contacts the titanium nitride layer of the intermediate composite layer 3, forming a Fe2O3 / TiN / Fe2O3 combination. The Fe2O3 layer acts as a dielectric layer, and the intermediate TiN layer acts as a reflective layer, forming an optical microcavity that is enhanced through multiple reflection interference.

[0033] As an implementation method, Figure 2 As shown, the thickness of the upper dielectric layer 4 is h4, which ranges from 140 to 160 nm. This thickness range matches the infrared wavelength and can enhance the absorption of specific wavelengths (such as evanescent waves) through interference effects.

[0034] As an implementation method, Figure 2 As shown, the thickness of each layer of the nanocolumn is h3, and the range of h3 is 40~60nm; the layer thickness is optimized to make the plasma resonance peaks of each layer overlap and broaden the absorption spectrum; ensure that each layer of material fully participates in the light-matter interaction and improves the energy conversion efficiency.

[0035] As an implementation method, Figure 2 As shown, the thickness of the lower depletion layer 2 is h2, which ranges from 40 to 60 nm. This thickness balances light absorption and carrier transport, avoiding excessive thickness that increases photogenerated carrier recombination. It also works synergistically with the nanopillars to form an optimal absorption structure.

[0036] As an implementation method, Figure 2 As shown, the titanium substrate 1 has a thickness of h1, which ranges from 300 to 350 nm. This sufficient thickness blocks light transmission, creating a reflector effect that enhances multiple reflections within the absorber and provides mechanical support to ensure device structural stability.

[0037] As an implementation method, Figure 1 and Figure 2 As shown, the nanopillars are cylindrical, with a diameter a1 ranging from 300 to 320 nm. Specifically, the nanopillars consist of five layers: titanium, ferric oxide, titanium, ferric oxide, and titanium nitride. Each layer has a circular cross-section and is uniform in size, completely overlapping when stacked. The cylindrical shape generates isotropic plasmon resonance, enhancing absorption of wide-angle incident light. The diameter matches the infrared wavelength, stimulating localized surface plasmon resonance (LSPR) and enhancing light absorption.

[0038] Among them, the absorption efficiency of the infrared broadband absorber is closely related to the shape and size of the various structures composed of its internal specific materials. Therefore, considering the influence of the shape of the absorption layer structure on the absorption spectrum, elliptical nanopillars (cross-section is elliptical) and small circular nanopillars (cross-section is small circle) are used for comparison with the present structure (large circular nanopillars, cross-section is large circle). It should be noted here that the circular nanodisk in the absorber is replaced by an elliptical nanodisk, whose major semi-axis is the disk radius parameter, the minor semi-axis is half of the disk radius, and the other parameters are the same as the disk structure, while the radius of the small disk is half of the radius of the original disk structure, and the other parameters remain unchanged. It was finally concluded that the large circular nanopillars of the present structure have a higher average absorption efficiency. (For details, see the subsequent examples and comparative examples) As an implementation method, Figure 2 As shown, the spacing between two adjacent nanopillars is L1, which ranges from 100 to 200 nm. This spacing creates strong electromagnetic coupling between the nanopillars, forming a hybrid plasma mode and broadening the absorption bandwidth, avoiding the increased processing difficulty caused by too small a spacing or the weakening of the coupling effect caused by too large a spacing. For example, the intermediate composite layer 3 is composed of sixteen groups of symmetrical circular nanopillars, each of equal size and diameter, with the bottom surface of the nanopillars in contact with the top surface of the lower lossy layer 2; in this structure, the structural period L of the infrared broadband absorber ranges from 1600 to 1700 nm.

[0039] The present invention also provides a method for preparing the above-mentioned infrared broadband absorber, comprising the following steps: A titanium substrate 1 is prepared by using PECVD deposition technology; A lower sacrificial layer 2 is prepared on a titanium substrate 1 by PECVD deposition technology; Forming an intermediate composite layer 3 on the lower sacrificial layer 2 by photolithography and etching techniques; The upper dielectric layer 4 is prepared on the middle composite layer 3 by PECVD deposition technology.

[0040] In this embodiment, the PECVD deposition technology is used to ensure the uniformity and density of each layer and improve the stability of the device; the photolithography etching process achieves nanometer-level precision and ensures the periodicity and size consistency of the nanocolumn array.

[0041] The present invention provides an infrared broadband absorber. This design mainly introduces an intermediate multi-layer column structure and selects metal and compound materials with good light absorption effects. Through simulation verification, the absorber can achieve an average absorption rate of 96.67% at a bandwidth of 3300nm in the infrared band of 700~4000nm, and the maximum absorption rate of a single absorption peak can reach up to 99.9%.

[0042] Example 1 (Big Circular Nanopillars) like Figure 1 and Figure 2 As shown, the infrared broadband absorber structure of this embodiment includes a titanium substrate 1, a lower lossy layer 2, an intermediate composite layer 3, and an upper dielectric layer 4. The upper dielectric layer 4, intermediate composite layer 3, lower lossy layer 2, and titanium substrate 1 are arranged in order from top to bottom. The lower lossy layer 2 is provided on the upper layer of the titanium substrate 1, and the lower surface of the intermediate composite layer 3 is connected to the upper surface of the lower lossy layer 2. The upper dielectric layer 4 flatly covers the upper surface of the intermediate composite layer 3. The intermediate composite layer 3 is composed of sixteen symmetrical groups of circular nanopillars, each of equal size and diameter. The lower surface of the nanopillars (titanium nitride layer) contacts the upper surface of the lower lossy layer 2, and the upper surface of the nanopillars (titanium layer) contacts the lower surface of the upper dielectric layer 4. The five layers of circular nanopillars are filled with titanium, ferric oxide, titanium, ferric oxide, and titanium nitride, in order from top to bottom.

[0043] This embodiment simulates the absorber structure by using the finite-difference time-domain method (FDTD), sets corresponding boundary conditions for simulation, measures corresponding simulation results, and demonstrates the beneficial effects of the broadband absorber structure through the simulation data.

[0044] Specifically, the incident light source is a TM-polarized plane wave, incident perpendicularly on the surface of the top nanodisk array structure. Periodic boundary conditions (PBC) are used in the x and y directions, and a perfectly matched layer (PML) boundary condition is used in the z direction.

[0045] Wherein: the period of the broadband absorber unit structure is L=1600nm; A lower lossy layer 2 is introduced on a titanium substrate 1, wherein the thickness of the titanium substrate 1 is h1 = 300 nm, and the thickness of the lower lossy layer 2 is h2 = 40 nm. The thickness of each layer of nanopillars located on the upper surface of the lower lossy layer 2 is h3 = 40 nm, the diameter a1 of the circular nanopillars is 300 nm, and the thickness of the upper dielectric layer 4 is h4 = 140 nm. The material of the upper dielectric layer 4 is silicon dioxide (SiO2); the materials of the nanocolumns of the intermediate composite layer 3 are selected from top to bottom as follows: titanium (Ti), ferric oxide (Fe2O3), titanium (Ti), ferric oxide (Fe2O3), and titanium nitride (TiN), forming a titanium layer, a ferric oxide layer, a titanium layer, a ferric oxide layer, and a titanium nitride layer; the material of the lower lossy layer 2 is ferric oxide (Fe2O3); and the material of the titanium substrate 1 is titanium (Ti); The dielectric constants of titanium, silicon dioxide, iron oxide, and titanium nitride were determined using the model of Palik (Handbook of Optical Constants of Solids I-III).

[0046] In this embodiment, a titanium substrate 1 is first prepared using PECVD deposition technology. A lower sacrificial layer 2 is then prepared on the titanium substrate 1 using PECVD deposition technology, and a filling material is formed using photolithography and etching techniques to obtain a middle multilayer nanocolumn array (middle composite layer 3). An upper dielectric layer 4 is then prepared using PECVD deposition technology. This yields the structure of an infrared broadband absorber.

[0047] Comparative Example 1 (Ellipsoid Nanopillars) The difference between Comparative Example 1 and Example 1 is that the cross-section of the nanocolumn is elliptical, the major axis is 300 nm, and the minor axis is 150 nm; except for the cross-sectional shape and size of the nanocolumn, the other structural parameters (such as the thickness of each layer, material, period, etc.) are consistent with those of Example 1.

[0048] Comparative Example 2 (Small Circular Nanopillars) The difference between Comparative Example 2 and Example 1 is that the cross section of the nanocolumn is circular with a diameter of 150 nm; except for the shape and size of the nanocolumn cross section, the other structural parameters (such as the thickness of each layer, material, period, etc.) are consistent with those of Example 1.

[0049] Through comparative analysis, we can see that: like Figure 3As shown in the absorption spectrum of Example 1 obtained by numerical simulation, absorption peaks with absorption rates exceeding 99% are obtained at 821nm and 2320nm, an absorption peak with absorption rates exceeding 97% is obtained at 3200nm, and an absorption peak with absorption rates exceeding 96% is obtained at 3620nm. It can be calculated that its average absorption rate in the 700-4000nm band is 96.67%.

[0050] like Figure 4 As shown, through the spectral characteristic curves of Example 1, Comparative Example 1 and Comparative Example 2, it is calculated that the average absorptivity of the elliptical nanopillars (Comparative Example 1) and the small circular nanopillars (Comparative Example 2) in the 700~4000nm band are 94.99% and 73.12%, respectively, both lower than the 96.67% of the large circular nanopillars (Example 1) of the present structure.

[0051] In order to verify the polarization insensitivity of the broadband absorber: Taking Example 1 as an example, the incident light source is initially set to a plane wave with TM polarization, and the incident light source is set again to a plane wave with TE polarization; according to the absorption spectrum obtained by numerical simulation, the absorption rate comparison diagram of the two light source modes is shown; Figure 5 As shown, the absorption curves under TE and TM polarizations basically coincide, confirming the polarization insensitivity of the structure and the excellence of the designed symmetric structure.

[0052] The foregoing description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications or substitutions that can be readily conceived by a person skilled in the art within the technical scope disclosed herein are intended to be encompassed within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be determined by the appended claims.

Claims

1. An infrared broadband absorber, characterized in that: The invention comprises a titanium substrate (1), a lower loss layer (2), an intermediate composite layer (3) and an upper dielectric layer (4) which are arranged in sequence from bottom to top, wherein the intermediate composite layer (3) is composed of nanocolumns arranged in a periodic array, and each of the nanocolumns comprises five layers, which are, from bottom to top, a titanium nitride layer, a ferric oxide layer, a titanium layer, a ferric oxide layer and a titanium layer.

2. The infrared broadband absorber according to claim 1, wherein The material of the upper dielectric layer (4) is silicon dioxide.

3. The infrared broadband absorber according to claim 1, wherein The material of the lower lossy layer (2) is ferric oxide.

4. The infrared broadband absorber according to claim 1, wherein The thickness of the upper dielectric layer (4) is h4, and the range of h4 is 140-160 nm.

5. The infrared broadband absorber according to claim 1, wherein The thickness of each layer of the nanocolumns is h3, and the range of h3 is 40-60 nm.

6. The infrared broadband absorber according to claim 1, wherein The thickness of the lower loss layer (2) is h2, and the range of h2 is 40-60 nm.

7. The infrared broadband absorber according to claim 1, wherein: The thickness of the titanium substrate (1) is h1, and the range of h1 is 300-350 nm.

8. The infrared broadband absorber according to claim 1, wherein: The nanocolumn is a cylinder, and the diameter of the nanocolumn is a1, and the range of a1 is 300-320 nm.

9. The infrared broadband absorber according to claim 1, wherein: The distance between two adjacent nanorods is L1, and the range of L1 is 100-200 nm.

10. A method for preparing the infrared broadband absorber according to any one of claims 1 to 9, characterized in that: The following steps are involved: The titanium substrate (1) was prepared by PECVD deposition technology; A lower sacrificial layer (2) is prepared on a titanium substrate (1) by PECVD deposition technology; forming an intermediate composite layer (3) on the lower sacrificial layer (2) by photolithography and etching techniques; An upper dielectric layer (4) is prepared on the middle composite layer (3) by PECVD deposition technology.

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