Preparation method of terahertz wave absorbing device and terahertz wave absorbing device

Abstract

The invention relates to a preparation method of a terahertz wave absorbing device and the terahertz wave absorbing device. The method comprises the following steps: growing an absorption layer on a first temporary substrate to form a functional structure body; carrying out structured processing on the functional structure body, and forming an array structure on the absorption layer; connecting the functional structure body after the structural processing with the second temporary substrate, and stripping the first temporary substrate; forming an initial laminated structure body; connecting the functional structure body after the substrate is peeled off with the initial laminated structure body to obtain a target laminated structure body; and stripping the second temporary substrate and the third temporary substrate from the target laminated structure body to obtain the terahertz wave absorbing device. The terahertz wave absorbing device comprises a flexible substrate layer, a metal reflecting layer, a flexible coating layer and an absorbing layer. By adopting the method to construct the full-flexible laminated structure, the THz wave-absorbing device can be tightly attached to the surface of the curved surface, stable performance is kept under stretching and bending deformation, and the mechanical adaptability of the THz wave-absorbing device is improved.

Description

Technical Field

[0001] This application relates to the field of electronic device technology, and in particular to a method for fabricating a terahertz absorbing device and the terahertz absorbing device itself. Background Technology

[0002] The terahertz (THz) band (0.1THz~10THz), located between microwaves and infrared radiation, has shown great application potential in non-destructive testing, biomedical imaging, high-speed communication, and security inspection in recent years due to its unique penetrating power, non-ionizing properties, and spectral characteristics. With the rapid development of THz technology, the demand for high-performance absorbing devices is becoming increasingly urgent. THz absorbing devices can effectively suppress electromagnetic interference and improve the system's signal-to-noise ratio, making them a core component for constructing efficient THz imaging systems.

[0003] However, traditional THz absorbing devices mostly employ rigid substrates or non-deformable planar thin-film structures. Their absorptivity is fixed after fabrication, making it impossible to adjust absorption characteristics through mechanical deformation or external excitation. This results in their inability to adapt to different frequencies or dynamic environments, and they are also difficult to fit onto complex three-dimensional surfaces. Therefore, traditional THz absorbing devices still have limitations in absorption bandwidth, dynamic tunability, and mechanical adaptability, affecting their performance in practical applications. Summary of the Invention

[0004] Therefore, it is necessary to provide a method for fabricating a terahertz absorbing device and a terahertz absorbing device to address the above-mentioned technical problems, which can improve the dynamic adjustability and mechanical adaptability of the terahertz absorbing device.

[0005] In a first aspect, this application provides a method for fabricating a terahertz absorbing device, the method comprising:

[0006] An absorption layer is grown on a first temporary substrate to form a functional structure;

[0007] The functional structure is structured to form an array structure on the absorption layer. The array structure includes several periodically arranged structures.

[0008] The structured functional structure is connected to the second temporary substrate so that the first side of the absorption layer contacts and bonds with the second temporary substrate, and the first temporary substrate is peeled off to expose the second side of the absorption layer.

[0009] An initial stacked structure is formed; the initial stacked structure includes a third temporary substrate, a flexible base layer, a metal reflective layer and a flexible cladding layer stacked sequentially.

[0010] The functional structure after stripping the substrate is connected to the initial stacked structure so that the second side of the absorption layer is contacted and bonded to the flexible coating layer to obtain the target stacked structure.

[0011] The second and third temporary substrates are peeled off from the target stacked structure to obtain a terahertz absorbing device; the terahertz absorbing device includes a flexible substrate layer, a metal reflective layer, a flexible cladding layer, and an absorbing layer.

[0012] In one embodiment, the flexible substrate layer and the flexible coating layer are both made of polydimethylsiloxane, the metal reflective layer is made of copper, and the absorbent layer is made of a vertically aligned carbon nanotube array.

[0013] In one embodiment, the functional structure is structured, including:

[0014] Based on the pre-designed frustum structure, femtosecond laser processing technology is used to scan the functional structure layer by layer.

[0015] In one embodiment, before connecting the structured functional structure to the second temporary substrate, the method further includes:

[0016] The structured functional structure is annealed to weaken the interaction between the absorption layer and the first temporary substrate.

[0017] In one embodiment, the method further comprises:

[0018] A buffer layer and a catalyst are deposited on the first substrate layer to form a first temporary substrate.

[0019] In one embodiment, the second temporary substrate includes a second substrate layer and an adhesion layer; connecting the structured functional structure to the second temporary substrate includes:

[0020] The structured functional structure is connected to the second temporary substrate by hot pressing, so that the first surface of the absorption layer is bonded to the adhesion layer.

[0021] In one embodiment, the temporary substrate is peeled off by mechanical peeling or chemical peeling; the temporary substrate includes at least one of a first temporary substrate, a second temporary substrate, and a third temporary substrate.

[0022] Secondly, this application also provides a terahertz absorbing device, which includes a flexible substrate layer and a metal reflective layer, a flexible cladding layer and an absorption layer stacked sequentially on the flexible substrate layer; the absorption layer is provided with an array structure, which includes a number of periodically arranged structures.

[0023] In one embodiment, the array structure includes a frustum.

[0024] In one embodiment, the flexible substrate layer and the flexible coating layer are both made of polydimethylsiloxane, the metal reflective layer is made of copper, and the absorbent layer is made of a vertically aligned carbon nanotube array.

[0025] The above-mentioned method for fabricating a terahertz absorbing device and the terahertz absorbing device involve: growing an absorption layer on a first temporary substrate to form a functional structure; structuring the functional structure to form an array structure on the absorption layer, the array structure comprising several periodically arranged structures; connecting the structured functional structure to a second temporary substrate so that the first surface of the absorption layer contacts and bonds with the second temporary substrate, and then peeling off the first temporary substrate to expose the second surface of the absorption layer; forming an initial stacked structure; the initial stacked structure comprising a third temporary substrate, a flexible substrate layer, a metal reflective layer, and a flexible cladding layer stacked sequentially; connecting the functional structure after substrate peeling to the initial stacked structure so that the second surface of the absorption layer contacts and bonds with the flexible cladding layer to obtain a target stacked structure; and peeling off the second and third temporary substrates from the target stacked structure to obtain the terahertz absorbing device; the terahertz absorbing device comprises a flexible substrate layer, a metal reflective layer, a flexible cladding layer, and an absorption layer. A terahertz absorbing device (hereinafter referred to as a THz absorbing device) comprising a flexible substrate, a metal reflective layer, a flexible cladding layer, and an absorption layer was fabricated using the above method. Due to the elasticity and stretchability of the flexible substrate and flexible cladding layer, the spacing and curvature of the structures on the absorption layer can be changed by stretching the THz absorbing device, thereby dynamically adjusting the multiple reflection paths and local electric field distribution of the THz wave, and thus adjusting the absorption rate in real time without external energy input, improving the dynamic tunability of the THz absorbing device. By peeling off the temporary substrate to construct a fully flexible stacked structure, the THz absorbing device can closely conform to the curved surface and maintain stable performance under tensile and bending deformation, improving the mechanical adaptability of the THz absorbing device. Attached Figure Description

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present application or related technologies, the following briefly introduces the drawings required for use in the embodiments of the present application or related technical descriptions. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying any creative work.

[0027] Figure 1 This is a schematic diagram of the structure of a terahertz absorbing device in one embodiment;

[0028] Figure 2 This is a schematic diagram of the dynamic adjustment of a terahertz absorbing device in one embodiment;

[0029] Figure 3 This is a schematic diagram of the simulation results of dynamic adjustment of the absorption rate of a terahertz absorbing device in one embodiment;

[0030] Figure 4 This is a schematic flowchart of a method for fabricating a terahertz absorbing device in one embodiment;

[0031] Figure 5 This is a process flow diagram for fabricating a terahertz absorbing device in one embodiment.

[0032] Explanation of reference numerals in the attached figures:

[0033] 101: Flexible substrate; 102: Metal reflective layer; 103: Flexible cladding layer; 104: Unstructured absorption layer; 105: Structured absorption layer; 201: CNT; 301: Silicon wafer; 302: Buffer layer; 303: Catalyst; 304: VACNTs / Si functional structure; 305: Structured VACNTs / Si functional structure; 306: Non-stretchable PDMS / PET substrate; 307: Structured VACNTs / PDMS / PET stacked structure; 308: Cu / PDMS / PET composite structure; 309: PDMS / Cu / PDMS / PET composite structure; 310: VACNTs / PDMS / Cu / PDMS terahertz absorbing device. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0035] It should be noted that the terms "first," "second," etc., used in this application can be used to describe various elements, but these elements are not limited by these terms. These terms are only used to distinguish the first element from the second element. The terms "comprising" and "having," and any variations thereof, used in this application, are intended to cover non-exclusive inclusion. The term "multiple" used in this application refers to two or more. The term "and / or" used in this application refers to one of the embodiments, or any combination of multiple embodiments.

[0036] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the specification of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0037] To facilitate understanding of the embodiments provided in this application, some terms appearing in the detailed description are introduced below: THz refers to Terahertz. VACNTs refers to Vertically Aligned Carbon Nanotubes. Cu refers to copper; Si refers to silicon; Fe refers to iron; Co refers to cobalt; Al2O3 refers to aluminum oxide. CNT refers to a single carbon nanotube. PDMS refers to Polydimethylsiloxane. PET refers to polyethylene terephthalate.

[0038] Understandably, while traditional absorbing materials (such as bulk materials) can achieve high absorption rates in specific frequency bands, their absorption characteristics vary significantly with frequency, making it difficult to cover a wide THz spectrum. Furthermore, metamaterial-based resonant structure absorbing devices (also known as absorbers) achieve perfect narrowband absorption through artificially designed periodic units, but their operating bandwidth is limited by resonant characteristics, and the complex multilayer structure significantly increases the fabrication difficulty. In recent years, with the rapid development of nanomaterials, VACNTs, with their unique "forest-like" structure and material properties, can achieve perfect absorption over a wide bandwidth, and their excellent mechanical flexibility allows for integration into flexible electronic devices, thus attracting considerable attention in the THz absorbing field. However, for complex and ever-changing application scenarios, THz absorbing devices based on VACNTs still have the following problems: (1) Due to the lack of a dynamic adjustment mechanism for the absorptivity, traditional absorbing devices mostly use rigid substrates or non-deformable planar thin film structures. Their absorptivity is fixed after fabrication and cannot be adjusted by mechanical deformation or external excitation, making it difficult to adapt to the needs of different frequencies or dynamic environments; (2) Traditional absorbing devices generally use non-stretchable rigid substrates. Although they have high mechanical strength, their tensile strain capacity is insufficient, making it difficult to fit three-dimensional complex curved surfaces, which limits their application in wearable devices or curved surface detection. Therefore, while ensuring that the THz absorber can achieve flexible stretching, it is particularly important to improve its dynamic adjustable performance of absorptivity in the broadband.

[0039] To address the need for dynamically adjustable absorption rates, traditional methods typically employ optical fields, electric fields, or chemical doping to control the absorption rate. However, these methods generally suffer from drawbacks such as high power consumption, poor stability, or excessive environmental dependence. Furthermore, traditional control schemes often require external excitation sources, making effective integration with flexible devices difficult, resulting in a trade-off between achieving tunability and mechanical adaptability. Therefore, it is essential to propose a THz absorbing device design that combines broadband absorption, dynamic tunability, and flexible deformation capabilities to overcome the limitations of traditional solutions and drive the development of THz devices towards intelligence and multifunctionality.

[0040] Based on this, and to address the aforementioned problems, this application provides a method for fabricating a terahertz absorbing device and the terahertz absorbing device itself. The method fabricates a THz absorbing device comprising a flexible substrate, a metal reflective layer, a flexible cladding layer, and an absorption layer. Because the flexible substrate and flexible cladding layer are elastic and stretchable, the spacing and curvature of the structures on the absorption layer can be changed by stretching the THz absorbing device, dynamically adjusting the multiple reflection paths and local electric field distribution of the THz wave, thereby adjusting the absorption rate in real time without external energy input, thus improving the dynamic tunability of the THz absorbing device. By peeling off a temporary substrate to construct a fully flexible stacked structure, the THz absorbing device can closely conform to curved surfaces and maintain stable performance under tensile and bending deformations, improving the mechanical adaptability of the THz absorbing device.

[0041] In one exemplary embodiment, this application provides a terahertz absorbing device, which includes a flexible substrate layer and a metal reflective layer, a flexible cladding layer and an absorption layer sequentially stacked on the flexible substrate layer; the absorption layer is provided with an array structure, which includes a plurality of periodically arranged structures.

[0042] In one exemplary embodiment, the array structure includes a frustum.

[0043] In one exemplary embodiment, the flexible substrate layer and the flexible coating layer are both made of polydimethylsiloxane, the metal reflective layer is made of copper, and the absorbent layer is made of a vertically aligned carbon nanotube array.

[0044] Among them, Figure 1 As shown, the THz absorbing device includes a flexible substrate 101, a metal reflective layer 102, a flexible cladding layer 103, and absorption layers (104, 105). Optionally, the flexible substrate 101 is made of PDMS material, the metal reflective layer 102 is made of Cu thin film, the flexible cladding layer 103 is made of PDMS material, and the absorption layer is composed of VACNTs. VACNTs are primarily used as the core material, fully leveraging their unique "forest-like" vertically arranged structure: firstly, the vertical orientation of VACNTs reduces interface scattering loss; secondly, by enhancing the multipath reflection-absorption interaction between the THz wave and the carbon nanotubes, the broadband absorption efficiency is effectively improved.

[0045] like Figure 1 As shown, by combining femtosecond laser processing technology, a periodic pyramid (i.e., frustum) array 105 is constructed on the surface of VACNTs to broaden the absorption bandwidth. The inclined geometric features of the pyramid are used to guide THz waves to undergo multiple oblique reflections and interferences between adjacent units, which greatly extends the electromagnetic wave propagation path length and thus enhances energy dissipation. Furthermore, by adjusting the periodic parameters of the pyramids, the impedance matching in the low-frequency band is optimized, thereby improving the absorption rate in the range of 0.1THz to 10THz.

[0046] like Figure 1 As shown, to achieve dynamic adjustment and flexible deformation compatibility, this design employs a dual-layer PDMS flexible substrate structure: the lower PDMS layer serves as a support layer, which is composited with a Cu metal reflective layer via spin coating to form a high-reflectivity interface to suppress transmission loss; the upper PDMS layer encapsulates VACNTs absorption layers, giving the device excellent stretchability. This method enables the absorber to maintain stable performance under different environmental conditions, allowing it to adapt to complex three-dimensional curved surfaces.

[0047] like Figure 2 As shown in (a), during the stretching process, the geometric deformation of the pyramid array and the extension of the flexible substrate are highly coordinated—the pyramid spacing increases linearly with the stretching of the substrate, and the effectiveness of multiple reflection paths is maintained by dynamically adjusting the carbon nanotube density. At the same time, the curvature change at the pyramid tip redistributes the domain electric field gradient, optimizing the impedance matching characteristics. This mechanism enables the absorber to maintain stable absorption across the entire frequency band under stretching deformation, avoiding the inability of traditional methods to simultaneously achieve both flexibility and broadband absorption.

[0048] like Figure 2 As shown in (b), the unstretched VACNTs absorber has a high absorption rate and low reflection rate for THz waves. After stretching and dynamic adjustment, the size of a single CNT201 remains unchanged, and the spacing between adjacent CNT201 increases, which reduces the absorption rate of THz waves and increases the reflection rate. Through stretching deformation, the absorption rate can be dynamically adjusted.

[0049] like Figure 3 As shown, simulations were performed on the dynamic adjustment of the absorptivity of the THz absorbing device prepared using the embodiments of this application. The THz absorbing device exhibits excellent broadband absorption characteristics across the entire frequency band from 0.1THz to 10THz: in the unstretched state, the average absorptivity reaches 98.30%, which is superior to traditional absorbers. As the stretching ratio (D) increases, the absorptivity shows a gradient decreasing trend: when stretched to D=1.5, the average absorptivity is 95.54%; when stretched to D=2.0, the absorptivity decreases to 74.12%; and when stretched to D=2.5, the absorptivity further decreases to 26.07%. This result indicates that the geometric deformation of the pyramid array and the stretching of the PDMS substrate are highly synergistic. By adjusting the spacing of the VACNTs and the pyramid period, multiple reflection paths of THz waves are effectively maintained, covering the entire frequency band from 0.1THz to 10THz, thus achieving broadband absorption. On the other hand, stretching reduces the thickness of the VACNTs layer, but the pyramid slope optimizes the equivalent impedance matching by redistributing the electric field gradient, especially in the mid-to-low frequency range, thus reducing reflection loss. After stretching, the radius of curvature at the pyramid tip increases, and although the local electric field strength decreases slightly, the expansion of its coverage area can still maintain the overall energy dissipation efficiency. The absorption rate is dynamically adjustable through mechanical stretching.

[0050] Traditional rigid THz absorbing devices are prone to structural fracture under mechanical deformation, leading to a sharp drop in absorption rate. However, the flexible design of this application, through coupling between a PDMS substrate and structured VACNTs, maintains structural integrity even under 250% stretching. Unlike traditional optical / electric field modulation schemes that require additional energy input and suffer from response delay issues, the THz absorbing device of this invention, after mechanical stretching adjustment, reduces the absorption rate of THz waves and increases the reflectivity. Through stretching deformation, the absorption rate can be dynamically adjusted to meet the needs of dynamic scenarios.

[0051] In one exemplary embodiment, refer to Figure 4 A method for fabricating a terahertz absorbing device is provided, the method comprising:

[0052] Step 10: Grow an absorption layer on the first temporary substrate to form a functional structure.

[0053] In this embodiment, the temporary substrate (first temporary substrate, second temporary substrate, or third temporary substrate) refers to a platform that provides necessary mechanical support, thermal stability, and / or chemical compatibility in the early stages of the process, but is removed before the final device is completed.

[0054] The absorption layer refers to the functional layer in a THz absorbing device that absorbs THz waves. In specific implementations, the absorption layer adopts a vertically aligned carbon nanotube array (VACNTs). Specifically, VACNTs are grown on a first temporary substrate using thermochemical vapor deposition technology to form a functional structure including the first temporary substrate and the absorption layer.

[0055] In one exemplary embodiment, the method further includes depositing a buffer layer and a catalyst on a first substrate layer to form a first temporary substrate.

[0056] The first substrate layer is made of Si material, and a buffer layer and a catalyst are deposited on the Si to form a first temporary substrate. Optionally, the thickness of the Si sheet is set in the range of 200μm to 1000μm; the catalyst can be a transition metal such as Fe or Co, with a thickness of 1nm to 10nm; the buffer layer can be Al2O3, with a thickness of 1nm to 10nm.

[0057] Step 20: The functional structure is structured to form an array structure on the absorption layer. The array structure includes several periodically arranged structures.

[0058] Among them, femtosecond laser processing technology is used to structurally process the functional structure and precisely control its array structure, so that several periodically arranged structures are formed on the processed absorption layer.

[0059] In one exemplary embodiment, the structuring of the functional structure includes: scanning the functional structure layer by layer using femtosecond laser processing technology according to a preset frustum structure.

[0060] The absorption layer utilizes VACNTs. A femtosecond laser system is used to structurally process the surface of the VACNTs. The laser beam is focused onto the VACNTs surface via a galvanometer system. Based on a pre-defined periodic pattern of frustum structures across multiple two-dimensional slices, point-by-point and layer-by-layer scanning is performed on the absorption layer to ensure the uniformity of the frustum structure. In an optional implementation, the structured functional structure is stored in a nitrogen atmosphere to prevent oxidation.

[0061] In an exemplary embodiment, prior to step 20, the method further includes annealing the structured functional structure to weaken the interaction between the absorption layer and the first temporary substrate.

[0062] The structured functional components are placed in an annealing furnace for high-temperature annealing to weaken the interaction between VACNTs and the Si substrate, thus facilitating subsequent transfer operations. Optionally, the annealing temperature is between 400℃ and 800℃, and the annealing time is between 15 min and 30 min.

[0063] Step 30: Connect the structured functional structure to the second temporary substrate so that the first side of the absorption layer contacts and bonds with the second temporary substrate, and peel off the first temporary substrate to expose the second side of the absorption layer.

[0064] In this process, the annealed functional structure (VACNTs / Si) is flipped onto the surface of a second temporary substrate, allowing the surfaces of the VACNTs to bond firmly to the surface of the second temporary substrate, thus bonding the annealed functional structure to the second temporary substrate. The first temporary substrate is then peeled off, exposing the second surface of the absorber layer that was in contact with the first temporary substrate. Optionally, the second temporary substrate comprises PDMS and PET, and the functional structure after substrate peeling is a VACNTs / PDMS / PET structure.

[0065] Step 40: Form an initial stacked structure; the initial stacked structure includes a third temporary substrate, a flexible base layer, a metal reflective layer and a flexible cladding layer stacked sequentially.

[0066] In this design, the third temporary substrate can be made of PET, the flexible base layer of PDMS, the metal reflective layer of Cu, and the flexible coating layer of PDMS. In one optional implementation, a PET substrate is provided, and a PDMS layer is coated on the PET substrate to form a PDMS / PET substrate. Based on this PDMS / PET substrate, a Cu thin film is deposited on the PDMS surface using electron beam evaporation technology as the metal reflective layer. Based on the Cu / PDMS / PET substrate, a PDMS layer is coated on the Cu / PDMS / PET substrate using spin coating technology to form an initial stacked structure, namely the PDMS / Cu / PDMS / PET structure. The spin coating speed of PDMS can be set to 1000 rpm to 2000 rpm, and the spin coating time is 30 s to 90 s, with the thickness adjustable according to actual needs. The flexible base layer and flexible coating layer can also be made of other flexible, stretchable, spin-coated polymers.

[0067] Step 50: Connect the functional structure after stripping the substrate to the initial stacked structure so that the second side of the absorption layer is bonded to the flexible coating layer to obtain the target stacked structure.

[0068] The process involves flipping the VACNTs / PDMS / PET functional structure, after stripping the substrate, onto the uncured PDMS / Cu / PDMS / PET surface. A hot-pressing technique is then used to cure the structure, causing the VACNTs and PDMS to bond to each other surface-to-surface, forming a strong connection. This integrates the stripped functional structure with the initial laminated structure. The target laminated structure is a PET / PDMS / VACNTs / PDMS / Cu / PDMS / PET structure.

[0069] Step 60: Remove the second temporary substrate and the third temporary substrate from the target stacked structure to obtain the terahertz absorbing device; the terahertz absorbing device includes a flexible substrate layer, a metal reflective layer, a flexible cladding layer and an absorption layer.

[0070] After curing, the PET / PDMS substrate and the PET substrate are peeled off from the target laminated structure to form a structured, flexible, and stretchable THz absorbing device. This THz absorbing device includes a flexible substrate layer, a metal reflective layer, a flexible cladding layer, and an absorption layer. Optionally, the THz absorbing device is a VACNTs / PDMS / Cu / PDMS structure.

[0071] In this embodiment, a THz absorbing device is fabricated comprising a flexible substrate layer, a metal reflective layer, a flexible cladding layer, and an absorption layer. Due to the elasticity and stretchability of the flexible substrate layer and the flexible cladding layer, the spacing and curvature of the structures on the absorption layer can be changed by stretching the THz absorbing device, dynamically adjusting the multiple reflection paths and local electric field distribution of the THz wave, thereby adjusting the absorption rate in real time without external energy input, thus improving the dynamic adjustability of the THz absorbing device. By peeling off the temporary substrate to construct a fully flexible stacked structure, the THz absorbing device can closely conform to the curved surface and maintain stable performance under tensile and bending deformations, improving the mechanical adaptability of the THz absorbing device.

[0072] In one exemplary embodiment, the flexible substrate layer and the flexible coating layer are both made of polydimethylsiloxane, the metal reflective layer is made of copper, and the absorbent layer is made of a vertically aligned carbon nanotube array.

[0073] The THz absorbing device is a VACNTs / PDMS / Cu / PDMS structure, with PDMS as the material of the flexible substrate layer, PDMS as the material of the flexible cladding layer, Cu as the material of the metal reflective layer, and VACNTs as the material of the absorbing layer.

[0074] In an exemplary embodiment, the second temporary substrate includes a second substrate layer and an adhesive layer; connecting the structured functional structure to the second temporary substrate includes: connecting the structured functional structure to the second temporary substrate by a hot pressing process, so that the first surface of the absorber layer contacts and bonds with the adhesive layer.

[0075] The second substrate layer is made of PET material, and the adhesive layer is made of PDMS. The structured functional structure is connected to the second temporary substrate. At this time, the adhesion force between PDMS and VACNTs is greater than the interaction force between VACNTs and Si substrate, so the Si substrate can be successfully peeled off to obtain structured VACNTs / PDMS / PET.

[0076] In one alternative implementation, mechanical peeling and bonding are used, and the structure is fixed by hot pressing. The hot pressing temperature is 100℃~150℃, the pressure is 1MPa~3MPa, and the time is 20min~60min to ensure its stability and durability.

[0077] In an exemplary embodiment, the temporary substrate is peeled off using a mechanical peeling method or a chemical peeling method; the temporary substrate includes at least one of a first temporary substrate, a second temporary substrate, and a third temporary substrate.

[0078] Temporary substrates can be removed using either mechanical or chemical peeling methods. Mechanical peeling removes the substrate by using physical force (such as adhesive tape, scraping, or grinding) to detach the material from the substrate. Chemical peeling removes the substrate by using chemical reagents to react with the material or substrate, weakening or destroying the bond between the material and the substrate, thereby achieving substrate removal.

[0079] In one exemplary embodiment, refer to Figure 5 The fabrication process for terahertz absorbing devices includes the following steps:

[0080] Step 1: Select a silicon wafer 301 with a thickness of 200μm~1000μm, and ultrasonically clean it sequentially with acetone, isopropanol, and ethanol for 10 minutes to remove surface organic matter and particulate contaminants, then dry it with nitrogen. Sequentially deposit an Al2O3 buffer layer 302 and an Fe catalyst 303 on the surface of the silicon wafer 301. The thickness of the buffer layer 302 can be 1nm~10nm, and the thickness of the catalyst 303 can be 1nm~10nm, using magnetron sputtering technology. Place the silicon wafer 301 in a thermochemical vapor deposition furnace, introduce acetylene and hydrogen, and react at 750℃ and 500Pa for 60 minutes to vertically grow a VACNTs array, forming a VACNTs / Si functional structure 304.

[0081] Step 2: The surface of VACNTs is processed using a femtosecond laser system. The laser beam is focused onto the surface of VACNTs by a galvanometer system and scans point by point according to a preset pyramid period at a scanning speed of 0.5 mm / s. A nitrogen atmosphere is used to protect against oxidation, ultimately forming a periodic pyramid array.

[0082] Step 3: Place the processed VACNTs / PDMS / Si structure in an annealing furnace and anneal at 600℃ in a nitrogen atmosphere for 20 minutes to weaken the van der Waals forces between the VACNTs and the silicon substrate, making it easier for subsequent non-destructive transfer.

[0083] Step 4: Spin-coat PDMS onto the PET surface, flip and attach the structured VACNTs / Si functional structure 305 to the surface of the non-stretchable PDMS / PET substrate 306, and achieve interlayer bonding through a hot-pressing process. Subsequently, mechanically peel off the silicon substrate 301 to form a structured VACNTs / PDMS / PET stacked structure 307;

[0084] Step 5: Spin-coat a flexible substrate layer PDMS101 onto a PET substrate, deposit a Cu thin film using electron beam evaporation technology to form a metal reflective layer 102, and then coat a flexible coating layer PDMS103 onto the new Cu / PDMS / PET composite structure 308 using spin-coating technology. Cure at 80°C for 15 min to obtain a PDMS / Cu / PDMS / PET composite structure 309.

[0085] Step 6: Remove the non-stretchable PDMS / PET substrate 306 and PET substrate using a mechanical peeling method to finally obtain the flexible and stretchable VACNTs / PDMS / Cu / PDMS terahertz absorbing device 310.

[0086] Through the above steps, this embodiment successfully fabricated a high-performance THz absorbing device with dynamically tunable absorptivity. It consists of a flexible substrate layer (PDMS), a metallic reflective layer (Cu), a flexible cladding layer (PDMS), and a VACNTs absorbing layer, achieving broadband absorption and dynamic adjustment. The THz absorbing device uses PDMS as the flexible substrate, which is then coated with the Cu reflective layer and VACNTs absorbing layer to form a "VACNTs / PDMS / Cu / PDMS" stacked structure. When a THz wave is incident, the VACNTs, as the absorbing layer, interact with the THz wave first. Due to the unique "forest-like" arrangement of the VACNTs, efficient energy absorption can be achieved through multiple reflection-absorption cycles. Meanwhile, the surface impedance of VACNTs is highly matched with free space, reducing interface reflection and allowing the incident wave energy to be rapidly dissipated by the local field between VACNTs. Residual THz waves that are not fully absorbed are reflected by the Cu reflective layer and re-enter the VACNTs layer. The PDMS in the intermediate layer can encapsulate and fix the VACNTs, so the incident THz waves are absorbed again by the VACNTs after reflection by the Cu metal layer. This multiple reflection path extends the energy residence time, ultimately reducing its transmittance and improving the overall absorption rate of the device. Due to the excellent elasticity and stretchability of PDMS, it maintains stable performance even under 200% stretching and can recover its original shape after stretching and bending, enabling stable operation on complex three-dimensional surfaces and in dynamic environments. Introducing a femtosecond laser-processed pyramid array on the VACNTs surface guides the THz waves through multiple reflection paths between adjacent units via the pyramid's inclined surface, extending the electromagnetic wave propagation distance and enhancing energy dissipation. Simultaneously, the strong electric field gradient formed at the pyramid tip increases the local energy density, further promoting THz wave absorption. During stretching, the pyramid spacing increases linearly with the extension of PDMS, and the effectiveness of multiple reflection paths can be maintained by adjusting the nanotube density. Furthermore, the geometric deformation of the pyramid structure is synchronized with the stretching of the PDMS substrate, maintaining broadband absorption efficiency even under flexible deformation. The excellent elasticity of the PDMS substrate endows the absorber with the ability to conform to three-dimensional curved surfaces, and under the synergistic effect of the geometric deformation of the pyramid structure and the stretching of the PDMS substrate, high absorption efficiency can be maintained even under flexible deformation.

[0087] Compared with traditional THz absorbing devices, the THz absorbing device provided in this application has the following advantages:

[0088] (1) Traditional THz absorbing devices rely on external excitation sources such as optical fields and electric fields to adjust the absorptivity, which has the drawbacks of high power consumption and response delay. The THz absorbing device provided in this application dynamically adjusts the multiple reflection paths and local electric field distribution of THz waves by stretching a flexible substrate and simultaneously changing the spacing and curvature of the pyramid structure in VACNTs, thereby adjusting the absorptivity in real time. No external energy input is required, which improves the applicability of the device in dynamic scenarios.

[0089] (2) Traditional rigid absorbing devices are limited by the substrate material and cannot adapt to complex three-dimensional curved surfaces. This application constructs a fully flexible stacked THz absorbing device (VACNTs / PDMS / Cu / PDMS) by peeling off the non-stretchable PET substrate. Combined with the high elasticity of the PDMS substrate, the absorber can closely fit the curved surface and maintain stable performance under tension and bending deformation.

[0090] (3) Traditional carbon nanotube thin film absorbers are limited by their uniform structure and can only achieve efficient absorption in a narrow band. This application uses VACNTs as the absorption layer. Their "forest-like" vertical arrangement enhances the multiple reflection-absorption cycles of THz waves, thus broadening the effective absorption frequency band. Femtosecond laser processing technology is introduced to fabricate a pyramid array structure, which further optimizes impedance matching and suppresses reflection and transmission losses.

[0091] It should be understood that although the steps in the flowcharts of the embodiments described above are shown sequentially according to the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless explicitly stated herein, there is no strict order restriction on the execution of these steps, and they can be executed in other orders. Moreover, at least some steps in the flowcharts of the embodiments described above may include multiple steps or multiple stages. These steps or stages are not necessarily completed at the same time, but can be executed at different times. The execution order of these steps or stages is not necessarily sequential, but can be performed alternately or in turn with other steps or at least some of the steps or stages in other steps. It is understood that the steps in different embodiments can be freely combined as needed, and all non-contradictory solutions formed by such combinations are within the scope of protection of this application.

[0092] In one exemplary embodiment, this application also provides a terahertz detector, which includes the terahertz absorbing device provided in any embodiment of this application.

[0093] In the description of this specification, references to terms such as "some embodiments," "other embodiments," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative descriptions of the above terms do not necessarily refer to the same embodiments or examples.

[0094] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0095] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these modifications and improvements all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

Claims

1. A method for fabricating a terahertz absorbing device, characterized in that, The method comprises: An absorption layer is grown on a first temporary substrate to form a functional structure; The functional structure is structurally processed to form an array structure on the absorption layer, the array structure comprising a plurality of periodically arranged structures; The structured functional structure is connected to the second temporary substrate so that the first side of the absorption layer is in contact and bonded to the second temporary substrate, and the first temporary substrate is peeled off to expose the second side of the absorption layer. An initial stacked structure is formed; the initial stacked structure includes a third temporary substrate, a flexible base layer, a metal reflective layer and a flexible cladding layer stacked sequentially; The functional structure after the substrate is stripped is connected to the initial stacked structure so that the second side of the absorption layer is contacted and bonded to the flexible coating layer to obtain the target stacked structure. The second temporary substrate and the third temporary substrate are peeled off from the target stacked structure to obtain a terahertz absorbing device; the terahertz absorbing device includes a flexible substrate layer, a metal reflective layer, a flexible cladding layer and an absorption layer.

2. The method according to claim 1, characterized in that, The flexible substrate layer and the flexible coating layer are both made of polydimethylsiloxane, the metal reflective layer is made of copper, and the absorbent layer is made of vertically arranged carbon nanotube arrays.

3. The method according to claim 1, characterized in that, The structuring of the functional structure includes: Based on the preset frustum structure, femtosecond laser processing technology is used to scan the functional structure layer by layer.

4. The method according to claim 1, characterized in that, Before connecting the structured functional structure to the second temporary substrate, the method further includes: The structured functional structure is annealed to weaken the interaction between the absorption layer and the first temporary substrate.

5. The method according to claim 1, characterized in that, The method further includes: A buffer layer and a catalyst are deposited on the first substrate layer to form a first temporary substrate.

6. The method according to claim 1, characterized in that, The second temporary substrate includes a second substrate layer and an adhesion layer; the connection of the structured functional structure to the second temporary substrate includes: The structured functional structure is connected to the second temporary substrate by a hot-pressing process, so that the first surface of the absorption layer is in contact and bonded to the adhesion layer.

7. The method according to any one of claims 1 to 6, characterized in that, The temporary substrate is peeled off using mechanical or chemical methods; the temporary substrate includes at least one of the first temporary substrate, the second temporary substrate, and the third temporary substrate.

8. A terahertz absorbing device, characterized in that, The terahertz absorbing device includes a flexible substrate layer and a metal reflective layer, a flexible cladding layer, and an absorption layer stacked sequentially on the flexible substrate layer; the absorption layer is provided with an array structure, which includes a plurality of periodically arranged structures.

9. The terahertz absorbing device according to claim 8, characterized in that, The array structure includes a frustum.

10. The terahertz absorbing device according to claim 8, characterized in that, The flexible substrate layer and the flexible coating layer are both made of polydimethylsiloxane, the metal reflective layer is made of copper, and the absorbent layer is made of vertically arranged carbon nanotube arrays.

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