Transparent adjustable terahertz wave absorber based on electrochemical reversible deposition and preparation method thereof

Abstract

The invention relates to a transparent adjustable terahertz wave absorber based on electrochemical reversible deposition and a preparation method thereof, and belongs to the field of terahertz frequency band wave absorption. The wave absorber structure is an electrochemical device clamped by an upper transparent substrate and a lower transparent substrate, and sequentially comprises a first transparent substrate, a patterned transparent conductive wave absorbing functional layer, an electrochemical regulation and control layer, a transparent conductive counter electrode layer and a second transparent substrate from top to bottom, wherein the patterned transparent conductive wave-absorbing functional layer is formed by patterning a composite film composed of a transparent conductive thin film and a dielectric layer. An external voltage is applied between the patterned transparent conductive wave-absorbing functional layer and the transparent conductive counter electrode layer to drive metal ions in the electrochemical regulation and control layer to be reversibly deposited or dissolved in the edge area of the resonance unit, so that the equivalent size of the resonance unit is changed, and the dynamic regulation and control of the terahertz wave-absorbing performance are realized. The high optical transparency is maintained while the dynamic adjustability of the terahertz wave absorbing performance is considered, and the good application prospect is achieved.

Description

Technical Field

[0001] This invention belongs to the field of terahertz frequency band absorption, and specifically relates to a transparent tunable terahertz absorber based on electrochemical reversible deposition and its preparation method. Background Technology

[0002] The terahertz band (0.1–10 THz) has significant applications in wireless communication, imaging detection, information security, and electromagnetic compatibility. To effectively suppress or control the reflection and scattering of terahertz electromagnetic waves, researchers have proposed various terahertz absorber structures, among which resonant absorbers based on periodic metals or conductive microstructures are the most common. These absorbers typically achieve impedance matching and energy dissipation by introducing metal backplates, multilayer dielectric structures, or high-loss materials, thereby obtaining high absorption efficiency.

[0003] However, most of the aforementioned terahertz absorbers rely on periodically patterned conductive microstructures or thick dielectric structures of opaque metals, resulting in low visible light transmittance. This makes it difficult to meet the optical transparency requirements of applications such as transparent windows, integrated displays, and wearable devices. In existing technologies, most devices have a fixed electromagnetic response after fabrication, lacking continuous and reversible dynamic control capabilities. To achieve dynamic control of terahertz absorption performance, research has attempted to introduce two-dimensional materials and phase change materials, but these approaches typically require the introduction of additional opaque functional layers, further reducing the device's transparency.

[0004] Therefore, in existing technologies, there is often a difficult technical contradiction between the dynamic tunability of terahertz absorption performance and the overall transparency of the device: on the one hand, achieving effective dynamic control usually relies on the introduction of two-dimensional materials or phase change materials; on the other hand, improving visible light transmittance requires minimizing the use of opaque conductive layers and metal structures. How to achieve continuous and reversible control of terahertz absorption performance while maintaining high visible light transmittance remains a pressing technical problem to be solved in this field. Summary of the Invention

[0005] The purpose of this invention is to study the design of an absorber that achieves tuning while maintaining high transparency based on the size control strategy of the resonant unit using electrochemical reversible deposition, thereby achieving efficient absorption and dynamically adjustable absorption performance in the terahertz band. This invention provides a transparent tunable terahertz absorber and its fabrication method based on a patterned transparent conductive structure combined with electrochemical reversible deposition to achieve tunable terahertz absorption performance.

[0006] To achieve the above objectives, the technical solution of the present invention is: a transparent tunable terahertz absorber based on electrochemical reversible deposition, wherein the absorber structure is an electrochemical device sandwiched between two transparent substrates, and from top to bottom includes a first transparent substrate, a patterned transparent conductive absorbing functional layer, an electrochemical control layer, a transparent conductive counter electrode layer, and a second transparent substrate.

[0007] Furthermore, both the first transparent substrate and the second transparent substrate are silicon dioxide transparent substrates with a thickness of 1 mm.

[0008] Furthermore, the patterned transparent conductive absorbing functional layer is formed by patterning a composite film consisting of a transparent conductive film and a dielectric layer, and simultaneously serves as the working electrode of the absorber and the terahertz resonant absorbing unit; wherein, the transparent conductive film is indium tin oxide with a thickness of 550 nm, and the dielectric layer is a silicon dioxide layer with a thickness of 100 nm.

[0009] Furthermore, the electrochemical control layer is composed of an electrolyte solution, and its active components include silver nitrate, copper chloride, tetrabutylammonium bromide, dimethyl sulfoxide, and polyvinyl butyral.

[0010] Furthermore, the transparent conductive counter electrode layer is composed of a transparent conductive film; wherein the transparent conductive film is indium tin oxide with a thickness of 550 nm.

[0011] Furthermore, the patterned transparent conductive absorbing functional layer is formed by a periodic arrangement of micro-cross-shaped structures, with an arrangement period of p. x = p y = 250 μm, each micro cross structure includes two mutually perpendicular arms, with an arm width w1 = 50 μm, a short arm length w2 = 90 μm, and a long arm length w3 = 250 μm, and adjacent micro cross structures are connected to each other in the long arm direction.

[0012] Furthermore, the absorption capability was characterized by reflection loss. Under no applied voltage, the absorber has an absorption peak at 0.547THz, broadband absorption in the 1.2-2THz frequency range, and reflection loss is less than -10 dB.

[0013] Furthermore, through electrochemical regulation, silver metal deposition occurs at the edge of the micro-cross-shaped array of the absorber, and the center frequency of the terahertz absorption peak is reversibly tuned in the range of 0.547-0.562 THz.

[0014] Furthermore, the average transmittance of the absorber in the visible light band before and after electrochemical deposition tuning is not less than 70%.

[0015] Furthermore, the average transmittance of the absorber in the visible light band before and after electrochemical deposition tuning is 81.8% and 79.1%, respectively.

[0016] The present invention also provides a method for manufacturing an absorber as described above, comprising the following steps:

[0017] (1) A transparent conductive film is deposited on a second transparent substrate to obtain a transparent conductive counter electrode;

[0018] (2) A transparent conductive film and a dielectric layer are sequentially deposited on a first transparent substrate to obtain a working electrode;

[0019] (3) Photolithography is performed on the working electrode to form a periodic micro cross-shaped structure array, resulting in a patterned terahertz absorbing functional layer;

[0020] (4) Add 0.5 mmol silver nitrate, 0.1 mmol copper chloride, and 2.5 mmol tetrabutylammonium bromide to 10 ml of dimethyl sulfoxide, and then add 10 wt% polyvinyl butyral to obtain an electrolyte solution;

[0021] (5) Use a pad to control the spacing on the surface of the transparent conductive counter electrode, and add electrolyte solution to form an electrochemical regulation layer;

[0022] (6) The patterned terahertz absorbing functional layer is bonded to the electrochemical control layer to obtain a transparent tunable terahertz absorber.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] This invention creatively proposes a transparent tunable terahertz absorber. By utilizing the electromagnetic response between the resonant units of a patterned transparent conductive absorbing functional layer, it achieves perfect absorption of incident terahertz waves (reflection loss less than -10 dB). The absorber's tunability is achieved by applying an external voltage between the patterned transparent conductive absorbing functional layer and the transparent conductive counter electrode layer. This drives silver ions to undergo reversible electrochemical deposition or dissolution in the edge region of the micro-cross structure, thereby changing the unit size of the patterned transparent conductive absorbing functional layer, altering the device's electromagnetic resonance conditions, and achieving dynamic control of the terahertz absorption performance. All materials in the absorber are transparent, and the electrochemical deposition tuning ensures that metal is deposited only in the edge region, maintaining high visible light transmittance. This terahertz absorber combines excellent modulation performance with high visible light transparency, making it potentially valuable for applications in optically transparent fields such as transparent windows and integrated displays. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the structure of the absorber of this invention;

[0026] Figure 2 The reflection loss of this invention;

[0027] Figure 3 Electron micrographs of the micro-cross structure of this invention before and after deposition.

[0028] Figure 4 The reflection loss before and after electrochemical modulation of this invention;

[0029] Figure 5 The transmittance of this invention in the 400-800nm ​​wavelength range;

[0030] In the figure: 1-First transparent substrate; 2-Patterned transparent conductive microwave absorbing functional layer; 3-Electrochemical regulation layer; 4-Transparent conductive counter electrode; 5-Second transparent substrate; 6-Schematic diagram of the patterned transparent conductive microwave absorbing functional layer structure. Detailed Implementation

[0031] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings.

[0032] like Figure 1 As shown, this invention discloses a transparent tunable terahertz absorber based on electrochemical reversible deposition. The absorber structure is an electrochemical device sandwiched between two transparent substrates, and from top to bottom includes a first transparent substrate 1, a patterned transparent conductive absorbing functional layer 2 (e.g., ...). Figure 1 Figure 6 shows a schematic diagram of the patterned transparent conductive microwave absorbing functional layer structure, electrochemical regulation layer 3, transparent conductive counter electrode layer 4, and second transparent substrate 5.

[0033] The present invention also provides a method for manufacturing an absorber as described above, comprising the following steps:

[0034] (1) A transparent conductive film is deposited on a second transparent substrate to obtain a transparent conductive counter electrode;

[0035] (2) A transparent conductive film and a dielectric layer are sequentially deposited on a first transparent substrate to obtain a working electrode;

[0036] (3) Photolithography is performed on the working electrode to form a periodic micro cross-shaped structure array, resulting in a patterned terahertz absorbing functional layer;

[0037] (4) Add 0.5 mmol silver nitrate, 0.1 mmol copper chloride, and 2.5 mmol tetrabutylammonium bromide to 10 ml of dimethyl sulfoxide, and then add 10 wt% polyvinyl butyral to obtain an electrolyte solution;

[0038] (5) Use a pad to control the spacing on the surface of the transparent conductive counter electrode, and add electrolyte solution to form an electrochemical regulation layer;

[0039] (6) The patterned terahertz absorbing functional layer is bonded to the electrochemical control layer to obtain a transparent tunable terahertz absorber.

[0040] The present invention will be further described below with reference to specific embodiments. These embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit the scope of protection of the present invention.

[0041] Example 1: Fabrication and Performance Testing of a Transparent Adjustable Terahertz Absorber

[0042] The transparent tunable terahertz absorber described in this embodiment adopts an electrochemical device structure sandwiched between two transparent substrates, and its specific preparation process is as follows.

[0043] First, a 1 mm thick transparent silicon dioxide substrate was selected as the device substrate. A 550 nm thick indium tin oxide transparent conductive film was deposited on the surface of one of the transparent substrates using magnetron sputtering, serving as the transparent conductive counter electrode of the device.

[0044] Subsequently, on another transparent silica substrate of the same specifications, a 550 nm thick indium tin oxide transparent conductive film was deposited by magnetron sputtering, and a 100 nm thick silica dielectric layer was deposited on its surface by electron beam evaporation, thereby obtaining a composite film structure for forming the microwave absorbing unit.

[0045] The indium tin oxide / silicon dioxide composite film is photolithographically processed to form a periodic array of micro-cross-shaped structures, creating a patterned transparent conductive and microwave-absorbing functional layer. The micro-cross structures are periodically arranged along the x and y directions, with an array period of p. x = p y = 250 μm. Each micro-cross structure consists of two mutually perpendicular arms, with an arm width w1 of 50 μm, a short arm length w2 of 90 μm, and a long arm length w3 of 250 μm. Adjacent micro-cross structures are connected to each other in the long arm direction.

[0046] Subsequently, an electrochemical control layer was prepared. 0.5 mmol silver nitrate, 0.1 mmol copper chloride, and 2.5 mmol tetrabutylammonium bromide were added sequentially to 10 mL of dimethyl sulfoxide solvent as electrochemical active components, followed by the addition of 10 wt% polyvinyl butyral. After thorough stirring, a homogeneous and transparent electrolyte solution was obtained.

[0047] A pad is placed on the surface of the transparent conductive counter electrode to control the electrode spacing. The electrolyte solution is then dropped onto the surface of the transparent conductive counter electrode to form an electrochemical control layer. Subsequently, the prepared patterned transparent conductive absorbing functional layer is bonded to the electrochemical control layer, with the patterned transparent conductive absorbing functional layer and the transparent conductive counter electrode layer positioned opposite each other, thereby constituting a complete transparent tunable terahertz absorber, such as... Figure 1 As shown.

[0048] In the initial state without an applied external voltage, the device was subjected to terahertz time-domain spectroscopy, and the reflection loss of the device was obtained as follows: Figure 2 As shown in the figure. The results show that the absorber exhibits a significant absorption peak at 0.547 THz and displays broadband absorption characteristics in the 1.2–2 THz frequency band, with a reflection loss of less than −10 dB.

[0049] During device operation, by applying an external voltage between the patterned transparent conductive absorbing functional layer and the transparent conductive counter electrode layer, silver ions in the electrolyte solution are driven to undergo reversible electrochemical deposition or dissolution in the edge region of the micro-cross structure. For example... Figure 3 As shown, as the electrochemical deposition process proceeds, the effective conductive boundary of the micro-cross structure changes, thereby causing a change in the equivalent size of the resonant unit, which in turn modulates the electromagnetic resonance condition of the device.

[0050] Experimental results show that, Figure 4 As shown, through electrochemical control, the center frequency of the terahertz absorption peak of the absorber can be reversibly tuned in the range of 0.547–0.562 THz while maintaining a low level of reflection loss. Further tests show that, as Figure 5 As shown, before and after electrochemical deposition tuning, the average transmittance of the device in the visible light band is not less than 70%, indicating that the electrochemical tuning process does not significantly reduce the optical transparency of the device.

[0051] Therefore, the transparent adjustable terahertz absorber described in this embodiment achieves efficient absorption and dynamic controllability in the terahertz band while maintaining high visible light transmittance, and has good application prospects.

[0052] The above are preferred embodiments of the present invention. Any changes made to the technical solution of the present invention that do not exceed the scope of the technical solution of the present invention shall fall within the protection scope of the present invention.

Claims

1. A transparent, tunable terahertz absorber based on electrochemical reversible deposition, characterized in that, The absorber structure is an electrochemical device sandwiched between two transparent substrates. From top to bottom, it includes a first transparent substrate, a patterned transparent conductive absorber layer, an electrochemical control layer, a transparent conductive counter electrode layer, and a second transparent substrate.

2. The transparent tunable terahertz absorber based on electrochemical reversible deposition according to claim 1, characterized in that, Both the first transparent substrate and the second transparent substrate are silicon dioxide transparent substrates.

3. The transparent tunable terahertz absorber based on electrochemical reversible deposition according to claim 1, characterized in that, The patterned transparent conductive absorbing functional layer is formed by patterning a composite film consisting of a transparent conductive film and a dielectric layer, and serves as both the working electrode of the absorber and the terahertz resonant absorbing unit; wherein, the transparent conductive film is indium tin oxide with a thickness of 550 nm, and the dielectric layer is a silicon dioxide layer with a thickness of 100 nm.

4. The transparent tunable terahertz absorber based on electrochemical reversible deposition according to claim 1, characterized in that, The electrochemical control layer is composed of an electrolyte solution, and its active components include silver nitrate, copper chloride, tetrabutylammonium bromide, dimethyl sulfoxide, and polyvinyl butyral.

5. A transparent tunable terahertz absorber based on electrochemical reversible deposition according to claim 1, characterized in that, The transparent conductive counter electrode layer is composed of a transparent conductive film; wherein, the transparent conductive film is indium tin oxide with a thickness of 550 nm.

6. A transparent tunable terahertz absorber based on electrochemical reversible deposition according to claim 1, characterized in that, The patterned transparent conductive absorbing functional layer is formed by a periodic arrangement of micro-cross-shaped structures, with a period of p. x = p y = 250 μm, each micro cross structure includes two mutually perpendicular arms, with an arm width w1 = 50 μm, a short arm length w2 = 90 μm, and a long arm length w3 = 250 μm, and adjacent micro cross structures are connected to each other in the long arm direction.

7. A transparent tunable terahertz absorber based on electrochemical reversible deposition according to claim 1, characterized in that, The absorption capability was characterized by reflection loss. Under no applied voltage, the absorber has an absorption peak at 0.547THz, broadband absorption in the 1.2-2THz frequency range, and reflection loss is less than -10 dB.

8. A transparent tunable terahertz absorber based on electrochemical reversible deposition according to claim 6, characterized in that, Through electrochemical regulation, silver metal deposition occurs at the edge of the micro-cross-shaped array of the absorber, and the center frequency of the terahertz absorption peak is reversibly tuned in the range of 0.547-0.562 THz.

9. A transparent tunable terahertz absorber based on electrochemical reversible deposition according to claim 1, characterized in that, The average transmittance of the absorber in the visible light band before and after electrochemical deposition tuning is not less than 70%.

10. A method for manufacturing an absorber as described in any one of claims 1-9, characterized in that, Includes the following steps: (1) A transparent conductive film is deposited on a second transparent substrate to obtain a transparent conductive counter electrode; (2) A transparent conductive film and a dielectric layer are sequentially deposited on a first transparent substrate to obtain a working electrode; (3) Photolithography is performed on the working electrode to form a periodic micro cross-shaped structure array, resulting in a patterned terahertz absorbing functional layer; (4) Add 0.5 mmol silver nitrate, 0.1 mmol copper chloride, and 2.5 mmol tetrabutylammonium bromide to 10 ml of dimethyl sulfoxide, and then add 10 wt% polyvinyl butyral to obtain an electrolyte solution; (5) Use a pad to control the spacing on the surface of the transparent conductive counter electrode, and add electrolyte solution to form an electrochemical regulation layer; (6) The patterned terahertz absorbing functional layer is bonded to the electrochemical control layer to obtain a transparent tunable terahertz absorber.

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