Electrically tunable microwave metamaterial absorber based on phase-change material GeTe and preparation method thereof

Abstract

This invention relates to an electrically controllable microwave metasurface absorber based on the phase change material GeTe and its fabrication method. Belonging to the field of electromagnetic wave control technology, the invention comprises a copper metal reflective substrate, a substrate, a thermal insulation layer, an electrothermal functional layer, an electrical isolation layer, a metal electrode layer, a GeTe phase change material layer, and a resonant controllable absorbing layer. Functionally, it consists of a GeTe electrically controllable switch structure and an tunable microwave metasurface absorber structure. These two structures are combined to form a metasurface absorber unit, and multiple metasurface absorber units are periodically arranged to form an electrically controllable microwave metasurface absorber. This invention maintains a controlled state without continuous power supply, providing a reliable structural foundation and technical support for the design and application of intelligent optoelectronic devices and thermal management systems. It achieves efficient absorption of specific wavelengths in the 2-12 GHz microwave band, with an absorption rate exceeding 90% at 4.5 GHz and over 95% at 11.5 GHz, meeting the performance requirements of tunable absorption bands. The system design and fabrication process are stable, demonstrating promising application prospects.

Description

Technical Field

[0001] This invention belongs to the field of electromagnetic wave control technology, and relates to an electrically controllable tunable microwave metasurface absorber based on phase change material GeTe and its preparation method. Background Technology

[0002] Adjustable microwave metasurface absorbers play an irreplaceable role in radar stealth, electromagnetic shielding, wireless communication anti-interference, and intelligent detection. They can dynamically adjust the absorption frequency, absorption intensity, and absorption bandwidth of electromagnetic waves in the microwave band. They are core components for reducing the radar cross section (RCS) of aircraft, ships, and other equipment, ensuring electromagnetic compatibility and information security, and have significant application value.

[0003] Currently, most tunable metasurface absorbers integrate active devices such as PIN diodes and varactor diodes, relying on bias voltage to control absorption performance. Feng Kuisheng et al., in their paper "Ultra-thin, Ultra-wideband Tunable Radar Absorber with Hybrid Integration of Active Devices," proposed an absorbing structure integrating varactor diodes and switching diodes, achieving tunable absorption in the 4.57–8.51 GHz range with an absorption rate exceeding 80%, and maintaining stable absorption performance within the 0° to 60° incident angle range. However, the device thickness remains relatively large, and continuous power supply is required to maintain the controlled state, resulting in high static power consumption and unsuitability for passive scenarios, failing to meet the demands of modern electronic equipment development. The paper "Phase Change Material-Driven Tunable Metasurface for Adaptive Terahertz Sensing and Communication in 6G Perceptive Networks" proposes a single-layer photoactivated phase change material GeTe tunable metasurface, achieving, for the first time, unified integration of sensing and communication functions in the 90–140 GHz Asia-Pacific Hertz band. However, it relies on laser and mask / beam scanning, making real-time control difficult, and its absorption band is located in the Asia-Pacific Hertz band with a low absorption rate. Chinese invention patent CN115122717A discloses a dual-spectrum dynamic stealth material based on a layered design, using phase-change material GeTe and graphene to achieve controlled mid-infrared (8-14μm) and microwave (2-18GHz) stealth effects, respectively. Actual measurements show that phase-change switching can vary infrared emissivity between 9% and 67%, and graphene impedance changes can reduce microwave reflectivity to below 5% in the 4-15GHz range, with a maximum suppression ratio of 15dB at key frequencies. However, its microwave functional layer has a relatively large overall thickness (the spacer layer can be up to 100mm thick), and its microwave absorption performance relies on continuously applying a gate voltage to maintain impedance. After power loss, the graphene absorption performance recovers, requiring continuous power supply.

[0004] Addressing the technical challenges of traditional tunable microwave metasurface absorbers, such as those using PIN diodes and graphene, which suffer from large structural thicknesses and require continuous power supply, this patent utilizes GeTe, a phase change material with typical non-volatile phase change characteristics. Through electrothermal effects, it can achieve rapid and reversible phase transitions between amorphous and crystalline states under electrical pulse thermal excitation. The conductivity difference before and after the phase transition can reach five orders of magnitude, and the phase state can be maintained for a long period without any external energy input after the transition, truly achieving zero static power consumption. Therefore, by using GeTe to replace traditional PIN diodes and graphene, combined with electrical pulse modulation technology, tunable microwave absorption can be achieved, possessing significant application value in fields such as stealth and electromagnetic shielding. Summary of the Invention

[0005] The main technical problem addressed by this invention is to overcome the shortcomings of existing methods. Addressing the issues of large thickness and continuous power supply requirements in microwave tunable metasurface structures, this invention proposes an electrically controlled tunable microwave metasurface absorber based on the phase change material GeTe and its fabrication method. This invention introduces the phase change material GeTe, utilizing its nanoscale thin-film substitute device to achieve static, energy-free operation through the material's non-volatility. Simultaneously, addressing the low integration density of the optical control system based on GeTe, an electrically controlled switch structure is designed. By controlling the magnitude and amplitude of the pulse voltage, the phase state of the GeTe phase change material is controlled, achieving stable electrical control adjustment. The electrically controlled drive can be integrated with the on-chip electrodes of the metasurface. The overall device thickness is only 1 mm, facilitating integration with intelligent skins and significantly reducing integration volume and engineering costs.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: An electrically controllable microwave metasurface absorber based on phase change material GeTe is disclosed, which can achieve absorption of specific wavelengths in the 2-12 GHz microwave band. Its structure includes: a copper metal reflective substrate 1, a substrate 2, a heat insulation layer 3, an electrothermal functional layer 4, an electrical isolation layer 5, a metal electrode layer 6, a phase change material GeTe layer 7, and a resonant controllable absorbing layer 8. According to function, it is divided into a phase change material GeTe electrically controllable switch structure and an adjustable microwave metasurface absorber structure. The two structures are combined to form a metasurface absorber unit. Multiple metasurface absorber units are periodically arranged and combined to form an electrically controllable microwave metasurface absorber.

[0007] The phase change material GeTe electrically controlled switch structure comprises a thermal insulation layer 3, an electrothermal functional layer 4, an electrical isolation layer 5, a metal electrode layer 6, and a phase change material GeTe layer 7. The thermal insulation layer 3 is deposited on the upper surface of the substrate 2, with a thickness ranging from 50 to 150 nm. The electrothermal functional layer 4 is disposed on the thermal insulation layer 3, located in the middle of the four sides of each metasurface absorber unit. The electrothermal functional layer 4 is designed as a dumbbell-shaped structure, including a central rod-shaped structure and head structures at both ends. The surface of the head structure is square, with a size of 15-25 μm and a thickness of 40-60 nm. It achieves rapid heating through the Joule effect, providing a heat source for the phase change material GeTe layer 7. The electrical isolation layer 5, with a thickness of 40-100 nm, covers the middle rod-shaped structure of the dumbbell-shaped structure of the electrothermal functional layer 4. The electrical isolation layer 5 prevents short circuits between the metal electrode layer 6 and the electrothermal functional layer 4. Simultaneously, the electrical isolation layer 5 also serves as a thermally conductive passivation layer between the electrothermal functional layer 4 and the phase change material GeTe layer 7, ultimately achieving electrical isolation. The metal electrode layer 6, with a thickness of 10-100 nm, is deposited on top of the head structures at both ends of the electrothermal functional layer 4, serving as electrodes to receive electrical pulse signals. The phase change material GeTe layer 7, deposited on the surface of the electrical isolation layer 5, has the same area as the electrical isolation layer 5 and a thickness of 20-80 nm. Under the action of an electrical pulse, it can achieve a reversible transition between crystalline and amorphous states: in the amorphous state, the electrical conductivity of the phase change material GeTe layer 7 is 2.7 S / m, exhibiting high-resistance insulating properties; in the crystalline state, the electrical conductivity of the phase change material GeTe layer 7 is 1.5 × 10⁻⁶. 5 With a conductivity of S / m, it exhibits high-conductivity metallic properties; the difference in conductivity before and after the phase transition exceeds five orders of magnitude, providing strong electromagnetic modulation capability for wave absorption characteristic control.

[0008] The tunable microwave metasurface absorber comprises three parts: a copper metal reflective substrate 1 at the bottom, a substrate 2 in the middle, and a resonant-tunable absorbing layer 8 at the top. The copper metal reflective substrate 1, with a thickness of 2-5 μm, is located on the reverse side of the substrate 2 and is primarily used for microwave reflection; that is, the substrate 2 is deposited on the front side of the copper metal reflective substrate 1. The resonant-tunable absorbing layer 8 consists of resonant structural units and a metal frame. The resonant structural units are a composite structure of a centrally symmetrical cross and a ring, deposited entirely on the substrate 2. The entire resonant unit is surrounded by a square metal frame, and the four ends where the cross arms intersect with the square metal frame are symmetrically integrated with a phase-change material GeTe electrically controlled switch structure. This tunable microwave metasurface absorber structure can achieve high-efficiency absorption in specific microwave bands of 2–12 GHz, with an absorption rate exceeding 90% at 4.5 GHz and exceeding 95% at 11.5 GHz.

[0009] Furthermore, the substrate 2 is made of silicon wafer or ceramic sheet, serving as the supporting base for the entire structure, with a thickness of 0.5-1.5 mm. The heat insulation layer 3 is made of silicon dioxide or hafnium dioxide. The electrothermal functional layer 4 is made of materials with good electrical conductivity, such as tungsten, indium oxide, or graphene. The electrical isolation layer 5 is made of aluminum oxide or silicon nitride thin film. The metal electrode layer 6 is made of copper, aluminum, titanium, silver, indium tin oxide, or other highly conductive alloy materials.

[0010] Furthermore, the resonant structure unit specifically comprises four orthogonally distributed metal cross arms of equal width and length that converge at the geometric center. A metal ring is embedded in the middle section of each cross arm and is connected to it. The metal ring has a tiny notch in each of the two adjacent arms of the cross arm, for a total of four tiny notches. The size of the tiny notch is 0.1-0.3mm.

[0011] Furthermore, the resonant structure unit of the resonant control absorbing layer 8 symmetrically integrates a phase change material GeTe electrically controlled switch structure at the four ends where the cross arm intersects with the square metal frame. By controlling the material phase state of the phase change material GeTe layer 7 with electrical pulses, the conductivity can be changed, thereby altering the resonant characteristics of the resonant control absorbing layer 8 and achieving electrically controlled adjustable absorption. The operating frequency band of the electrically controlled adjustable microwave metasurface absorber of this invention is 2-12 GHz; when the phase change material GeTe in the phase change material GeTe layer 7 is in an amorphous state, the highest absorption frequency is at 4.5 GHz, the peak reflection loss is about -12 dB, and the absorption rate can reach over 90%, achieving high-efficiency absorption; when the phase change material GeTe in the phase change material GeTe layer 7 is in a crystalline state, its highest absorption frequency shifts to 11.5 GHz, the peak reflection loss is about -13 dB, and the absorption rate can reach over 95%, also meeting the high-efficiency absorption standard and achieving the expected adjustable function.

[0012] A method for fabricating an electrically tunable microwave metasurface absorber based on the phase change material GeTe, employing photolithography and magnetron sputtering processes, includes the following steps: The first step involves fabricating a GeTe phase change material electrically controlled switch structure. On the front side of substrate 2, each functional layer is sequentially deposited using a thin-film deposition apparatus and patterned to form a thermal insulation layer 3, an electrothermal functional layer 4, an electrical isolation layer 5, a metal electrode layer 6, and a GeTe phase change material layer 7. Specifically: Step 1.1, Pretreatment of the back side of substrate 2. First, the back side of substrate 2 is cleaned and decontaminated; the specific steps are as follows: Substrate 2 undergoes organic cleaning. First, it is placed in an acetone solution and ultrasonically cleaned in an ultrasonic cleaner; then, substrate 2 is placed in an isopropanol solution and ultrasonically cleaned to remove surface organic residues and microparticle contamination; subsequently, it is ultrasonically cleaned again with deionized water to further remove surface impurities; after cleaning, the substrate surface is dried with high-purity nitrogen gas. The substrate is then dried using a heating stage to avoid moisture residue, obtaining a clean and smooth substrate 2 interface, providing a good adhesion base for subsequent film deposition.

[0013] Step 1.2: Perform photolithography patterning on the substrate to prepare a photoresist mask layer corresponding to the mask pattern, in order to define the positions of each layer structure in subsequent magnetron sputtering deposition. Specifically: Step 1.2.1: Spin coating. The back side of the substrate 2 after the pretreatment in step 1.1 is coated with photoresist using a spin coater. The photoresist used is the AZ1500 series. Spin coat at a low speed of 400-600 r / min for 5-15 s, and then increase to a high speed of 2000-4000 r / min for 10-30 s to obtain a smooth photoresist film.

[0014] Step 1.2.2, Pre-baking: Bake the substrate 2 coated with adhesive at 80-120℃ for 120-180s to promote the evaporation of the adhesive solvent and eliminate bubbles, thereby improving the uniformity of the adhesive film and the exposure adaptability.

[0015] Step 1.2.2, Photolithography: After the pre-baked substrate 2 is precisely aligned with the mask, perform 5-10s ultraviolet exposure.

[0016] Step 1.2.3, Development: Immerse the exposed substrate 2 in the developer for 10-30 seconds, then remove it and place it in deionized water for 5-15 seconds. Finally, use an air gun to blow away any residual liquid on the surface.

[0017] Step 1.2.4, Post-baking: The conditions are the same as the pre-baking to ensure the stability of the photoresist after development, while removing impurities at high temperature.

[0018] Step 1.3: Using a thin film deposition apparatus, a heat insulation layer 3 is deposited on substrate 2, while controlling the base vacuum of the chamber to be no greater than 5 × 10⁻⁶. -4 Pa, working gas flow rate of 20-30 sccm, sputtering power of 80-120 W, thickness of 50-150 nm, room temperature sputtering, to obtain thermal insulation layer 3.

[0019] Step 1.4: Using a photomask according to the design, the patterned area of ​​the electrothermal functional layer 4 is formed by exposure and development on the surface of the heat insulation layer 3; subsequently, the material of the electrothermal functional layer 4 is deposited in the patterned area using a thin film deposition equipment; the deposition conditions are: below 3×10 -5 Under a vacuum of Pa, the deposition temperature was room temperature, the working vacuum was 0.8-1.2 Pa, the RF power was 30-60 W, the argon flow rate was 30 sccm, the working time was 2400-3600 s, and the thickness was 40-60 nm. Finally, a photoresist removal process was performed to remove excess photoresist, obtaining the electrothermal functional layer 4.

[0020] Furthermore, the photoresist removal process is as follows: the sample with the deposited electrothermal functional layer 4 is immersed in NMP solution and left to stand for 6-12 hours until the photoresist is completely dissolved. The substrate is then immersed in alcohol and deionized water for 5-15 minutes respectively. To prevent damage to the metasurface structure, an ultrasonic cleaner is not used during the stripping and cleaning process, and the sample is then ready.

[0021] Step 1.5: Using the designed photomask, define the electrode structure region above the electrothermal functional layer 4; sequentially deposit the metal electrode layer 6 using a thin film deposition apparatus; the deposition conditions are: below 3 × 10⁻⁶. -3 Under a vacuum of Pa, the deposition temperature is room temperature, the working vacuum is 0.8-1.2 Pa, the DC power is 80-100 W, the argon flow rate is 30 sccm, the velocity is 20 nm per minute, the deposition time is 3-5 minutes, and the copper thickness is 20-80 nm. Finally, a desizing process is performed to obtain the metal electrode layer 6.

[0022] Furthermore, the photoresist removal process is as follows: the sample with the deposited metal electrode layer 6 is immersed in NMP solution and left to stand for 6-12 hours until the photoresist is completely dissolved. The substrate is then immersed in alcohol and deionized water for 5-15 minutes respectively. To prevent damage to the metasurface structure, no ultrasonic cleaning is used during the stripping and cleaning process, and the sample is then ready.

[0023] Step 1.6: Using the designed photomask, an electrically insulating layer 5 and a phase change material GeTe layer 7 are patterned on the electrothermal functional layer 4. The insulating material Al2O and the phase change material GeTe are then deposited sequentially using a thin film deposition apparatus to achieve effective electrical isolation and phase change functionality integration between the structures. The Al2O3 deposition conditions are: below 3 × 10⁻⁶. -3 The deposition conditions were: a vacuum of 1 Pa, deposition temperature of room temperature, working vacuum of 1 Pa, RF power of 100-120 W, argon flow rate of 30 sccm, deposition time of 50-60 min, and a thickness of 40-100 nm. The deposition conditions for the phase change material GeTe were: below 3 × 10⁻⁶ Pa. -3The deposition process was carried out at a vacuum level of 1 Pa, a deposition temperature of room temperature, a working vacuum level of 1 Pa, an RF power of 40-50 W, an argon flow rate of 30 sccm, a deposition time of 160-200 s, and a thickness of 20-80 nm. Finally, a desizing process was performed to obtain the target structure, namely the phase change material GeTe electronic switch structure.

[0024] Furthermore, the photoresist removal process is as follows: the sample with the deposited electrical isolation layer 5 and phase change material GeTe layer 7 is immersed in NMP solution and left to stand for 6-12 hours until the photoresist is completely dissolved. The substrate is then immersed in alcohol and deionized water for 5-15 minutes respectively. To prevent damage to the metasurface structure, an ultrasonic cleaner is not used during the stripping and cleaning process, and the sample is then ready.

[0025] The second step is to fabricate a resonant modulation absorbing layer 8 on the substrate 2 after the phase change material GeTe electrically controlled switch structure has been prepared.

[0026] Step 2.1: Perform photolithography patterning on the substrate to prepare a photoresist mask layer corresponding to the mask pattern, in order to define the positions of each layer structure in subsequent magnetron sputtering deposition. Specifically: Step 2.1.1, Spin coating: The substrate 2 after cleaning the phase change material GeTe electronic switch structure is coated with photoresist using a spin coating machine. AZ10xt series photoresist is selected. Spin coating is performed at a low speed of 500-600 r / min for 10-20 s, and then at a high speed of 2500-3500 r / min for 30-60 s to obtain a smooth photoresist film.

[0027] Step 2.1.2, Pre-baking: Bake the substrate 2 coated with adhesive at 80-120℃ for 120-180s to promote the evaporation of the adhesive solvent and eliminate bubbles, thereby improving the uniformity of the adhesive film and the exposure adaptability.

[0028] Step 2.1.3, Photolithography: After the pre-baked substrate 2 is precisely aligned with the mask, perform 5-10s ultraviolet exposure.

[0029] Step 2.1.4, Development: Immerse the exposed substrate 2 in the developer for 10-30 seconds, then remove it and place it in deionized water for 5-15 seconds. Finally, use an air gun to blow away any residual liquid on the surface.

[0030] Step 2.1.5, Post-baking: The conditions are the same as the pre-baking to ensure the stability of the photoresist after development, while removing impurities at high temperature.

[0031] Step 2.2: A copper resonant structure is grown at the corresponding location using photolithography and magnetron sputtering techniques. The copper plating conditions are: power below 3 × 10⁻⁶. -3At a vacuum level of 1 Pa, the deposition temperature is room temperature, the working vacuum is 1 Pa, the DC power is 80-100 W, the argon flow rate is 30 sccm, the velocity is 20 nm per minute, and the deposition time is 2-5 hours, with other requirements remaining unchanged. After descaling, the prepared structure can be obtained.

[0032] Furthermore, the photoresist removal process is as follows: the sample with the deposited copper resonant structure is immersed in NMP solution and left to stand for 6-12 hours until the photoresist is completely dissolved. Then, the substrate is immersed in alcohol and deionized water for 5-10 minutes respectively. To prevent damage to the metasurface structure, an ultrasonic cleaner is not used during the stripping and cleaning process, and the sample is then ready.

[0033] The innovative aspect of this invention lies in the localized surface plasmon resonance excited by the top-layer subwavelength resonant unit, which highly confines the incident wave energy and enhances the near-field, while simultaneously providing a foundation for broadband impedance matching. The copper metal reflective substrate 1 and the resonant-tuned absorbing layer 8 constitute a Fabry-Perot cavity, forming standing waves through multiple reflections, significantly extending the residence time of electromagnetic waves within the dielectric layer. The locked energy is then irreversibly converted into heat energy through metal ohmic losses, dielectric polarization losses, and lumped resistance losses. All three are indispensable and work synergistically: resonance is responsible for introducing the energy, the cavity for delaying the time, and the losses for absorbing it.

[0034] The beneficial effects of this invention are: Due to the non-volatile nature of the phase change material GeTe in this invention, the device can maintain its adjustable state without continuous power supply, and its thickness is only 1 mm. When GeTe is in its amorphous state, the highest absorption frequency is at 4.5 GHz, with a peak reflection loss of approximately -12 dB and an absorption rate of 90%, achieving highly efficient absorption. When GeTe is in its crystalline state, its highest absorption frequency shifts to 11.5 GHz, with an absorption rate of 95% and a peak reflection loss of approximately -13 dB, also meeting the high-efficiency absorption standard. The absorption frequency corresponding to the maximum absorption amplitude changes during the transition from amorphous to crystalline GeTe, and the absorption amplitude also changes before and after the phase transition at the same absorption frequency, achieving the expected adjustable function. This provides a reliable structural foundation and technical support for the design and application of intelligent optoelectronic devices and thermal management systems. This invention can achieve absorption of specific wavelengths within the 2-12 GHz microwave band, meeting performance requirements such as adjustable absorption bands. The system design and fabrication process are stable, and it has good application prospects. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the structure of the electrically controlled adjustable microwave metasurface absorber of the present invention (including the electrically controlled switch structure of the phase change material GeTe). Figure 1 (a) is a three-dimensional view of the tunable microwave metasurface absorber structure. Figure 1 (b) along Figure 1 (a) A cross-sectional view of the central black solid line AA; Figure 2 This is a three-dimensional view of the phase change material GeTe electrically controlled switch structure in this invention; Figure 3 This invention relates to a metasurface unit that possesses microwave absorption capabilities for a specific microwave band of 2-12 GHz. Figure 4 The tunable microwave metasurface absorber structure in this invention has different reflection losses in both crystalline and amorphous states. Figure 5 These are the cycle test results of the phase change material GeTe electrically controlled switch structure in this invention; In the figure: 1. Copper metal reflective substrate, 2. Substrate, 3. Thermal insulation layer, 4. Electrothermal functional layer, 5. Electrical isolation layer, 6. Metal electrode layer, 7. Phase change material GeTe layer, 8. Resonance-controlled absorbing layer. Detailed Implementation

[0036] The embodiments of the present invention are described in detail with reference to the accompanying drawings and technical solutions, illustrating the structure of the phase change material GeTe electrically controlled switch, and the structure and preparation method of the adjustable microwave metasurface absorber.

[0037] This embodiment provides an electrically controllable metasurface absorber based on the phase change material GeTe, such as... Figure 1 As shown in (a), from bottom to top, it consists of: a copper metal reflective substrate 1, a substrate 2, and a resonant-controlled absorbing layer 8. The copper metal reflective substrate 1 is 3 μm thick and is prepared by magnetron sputtering. It has a transmittance of <0.1% in the 2–12 GHz frequency band, achieving total internal reflection. The substrate 2 is made of high-resistivity silicon, 1 mm thick, and its surface is polished to ensure a flat structure. The resonant-controlled absorbing layer 8 consists of a resonant structural unit and a metal frame. The resonant unit is a centrally symmetrical cross and ring composite structure, deposited entirely on the substrate 2. The entire resonant unit is surrounded by a square metal frame. Its main body consists of four orthogonally distributed metal cross arms of equal width and length that intersect at the geometric center. A metal ring is embedded in the middle of the cross arm and connected to it. The metal ring has four tiny notches on the two arms of the cross arm, with a notch size of 2 mm. The four ends where the cross arm intersects with the square metal frame symmetrically integrate a phase change material GeTe electrically controlled switch structure. The resonant-controlled absorbing layer 8 is 3 μm thick.

[0038] Figure 2 The image shows the structure of an electrically controlled switch for GeTe phase change material. From bottom to top, the GeTe electrically controlled switch structure includes: a heat insulation layer 3, an electrothermal functional layer 4, an electrical isolation layer 5, a metal electrode layer 6, and a GeTe phase change material layer 7. It can realize the switching of GeTe phase change material by driving and controlling the phase change of GeTe using an electrical pulse signal. By controlling the magnitude and amplitude of the pulse voltage, the phase state of GeTe phase change material can be controlled.

[0039] The substrate 2 is made of silicon, which serves as the supporting base for the entire structure. It has a thickness of 1 mm and possesses excellent mechanical strength and thermal stability.

[0040] The heat insulation layer 3 is made of silicon dioxide and is deposited on the upper surface of the substrate 2 with a thickness of 100 nm. It is used to suppress the downward conduction of heat and improve the local heating efficiency.

[0041] The electrothermal functional layer 4 is made of tungsten metal and is disposed on top of the heat insulation layer 3, with a thickness of 50 nm. The electrothermal functional layer 4 is designed with a dumbbell-shaped structure, which achieves rapid heating through the Joule effect, providing a heat source for the phase change material GeTe layer.

[0042] The electrical isolation layer 5 is made of aluminum oxide and covers the middle rod of the dumbbell-shaped structure of the electrothermal functional layer 4, with a thickness of 70 nm. This layer is used to prevent short circuits between the electrode testing the electrical parameters of the phase change material GeTe and the tungsten heater. At the same time, the aluminum oxide also serves as a thermally conductive passivation layer between the tungsten heater and the phase change material GeTe layer 7, ultimately achieving electrical isolation.

[0043] The metal electrode layer 6 is made of copper and has a thickness of 50 nm. It is plated on the top of both ends of the dumbbell-shaped structure of the electrothermal functional layer 4 and serves as an electrode to receive electrical pulse signals.

[0044] The phase change material GeTe layer 7 is deposited on the surface of the electrically insulating layer 5, with a thickness of 30 nm and an area consistent with that of the electrically insulating layer 5. This phase change material can achieve a reversible transition between crystalline and amorphous states under the action of an electrical pulse, making it a key layer for realizing the electrically controlled phase change function.

[0045] Figure 3 The image shows a metasurface unit exhibiting microwave absorption in the specific microwave band of 2–12 GHz. The absorption principle is that this metasurface absorber structure achieves efficient absorption in the specific microwave band of 2–12 GHz through the synergistic effects of plasma resonance, Fabry-Perot resonator interference, and ohmic loss. Specifically: The absorption efficiency of the absorber is given by the formula A(ω)=1-R(ω)-T(ω)=1-|S 11 | 2 -|S 21 | 2 The result is obtained. Where A(ω) is the absorptivity, R(ω) is the reflectivity, T(ω) is the transmittance, and S... 21 S is the transmission coefficient. 11 The reflectance coefficient is given. Since the thickness of the copper metal reflective substrate 1 is greater than the skin depth, the transmittance is 0. Therefore, the absorber absorptivity formula can be transformed into A(ω)=1-R(ω)=1-|S 11 | 2The localized surface plasmon resonance excited by the top-layer subwavelength resonant unit highly confines the incident wave energy and enhances the near field, while providing a basis for broadband impedance matching. The copper metal reflective substrate 1 and the resonant-tuned absorbing layer 8 constitute a Fabry-Perot cavity, which forms standing waves through multiple reflections, significantly extending the residence time of electromagnetic waves within the dielectric layer. The locked energy is then irreversibly converted into heat energy through metal ohmic loss, dielectric polarization loss, and lumped resistance loss. These three elements work synergistically and are indispensable: resonance is responsible for introducing the energy, the cavity is responsible for delaying the time, and the loss is responsible for absorbing the energy.

[0046] The absorption effect of the sample in the embodiment was analyzed and tested. Absorption experiments were conducted on the phase change material GeTe in the tunable microwave metasurface absorber in both crystalline and amorphous states. The final test results are as follows: Figure 4 As shown, specifically: When the phase change material GeTe is in the amorphous state, its electrical conductivity is 2.7 S / m. This microwave structure is a narrowband absorber in the microwave frequency band. It has two resonant peaks with absorption frequencies at 4.5 GHz and 11.1 GHz, respectively. The peak reflection loss at 4.5 GHz is about -12 dB, and the absorption rate reaches 90%, achieving efficient absorption.

[0047] Its conductivity was set to 1.5 × 10⁻⁶. 5 At a current S / m, the phase change material GeTe transforms into a crystalline state. After the phase transition, the absorbing structure remains a narrowband absorber in the microwave frequency band, with its resonant peak shifting to approximately 11.5 GHz. The peak reflection loss is approximately -13 dB, and the absorption rate reaches 95%, still meeting the high-efficiency absorption standard. This demonstrates that the absorption frequency corresponding to the maximum absorption amplitude changes as the phase change material GeTe transitions from an amorphous to a crystalline state, and the absorption amplitude before and after the phase transition also changes at the same absorption frequency, achieving the expected adjustable function.

[0048] Figure 5 The cycle count test results of the GeTe phase change material electrically controlled switch structure in this invention were used to verify its cycle count. During the test, a reversible phase transition between the crystalline and amorphous states of the GeTe phase change material was achieved by applying an electrical control signal, corresponding to two operating states of the device: in the crystalline state, the highest absorption frequency of the device was stably maintained at approximately 11.5 GHz; in the amorphous state, the highest absorption frequency stably dropped back to approximately 4-5 GHz. During 20 consecutive switching cycles, both operating states of the device could be stably reproduced, with no significant drift, attenuation, or switching failure of the absorption frequency. The change in the highest absorption frequency before and after the phase transition remained stable, meeting the requirements for fabricating an tunable microwave metasurface absorber structure.

[0049] A method for fabricating an electrically tunable microwave metasurface absorber based on the phase change material GeTe, employing photolithography and magnetron sputtering processes, includes the following steps: The first step involves fabricating a GeTe phase change material electrically controlled switch structure. On the front side of substrate 2, each functional layer is sequentially deposited using a thin-film deposition apparatus and patterned to form a thermal insulation layer 3, an electrothermal functional layer 4, an electrical isolation layer 5, a metal electrode layer 6, and a GeTe phase change material layer 7. Specifically: Step 1.1, Pretreatment of the back side of substrate 2. First, the back side of substrate 2 is cleaned and decontaminated; the specific steps are as follows: Substrate 2 undergoes organic cleaning. First, it is placed in an acetone solution and ultrasonically cleaned in an ultrasonic cleaner; then, substrate 2 is placed in an isopropanol solution and ultrasonically cleaned to remove surface organic residues and microparticle contamination; subsequently, it is ultrasonically cleaned again with deionized water to further remove surface impurities; after cleaning, the substrate surface is dried with high-purity nitrogen gas. The substrate is then dried using a heating stage to avoid moisture residue, obtaining a clean and smooth substrate 2 interface, providing a good adhesion base for subsequent film deposition.

[0050] Step 1.2: Perform photolithography patterning on the substrate to prepare a photoresist mask layer corresponding to the mask pattern, in order to define the positions of each layer structure in subsequent magnetron sputtering deposition. Specifically: Step 1.2.1: Spin coating. The back side of the substrate 2 after the pretreatment in step 1.1 is coated with photoresist using a spin coater. The photoresist used is the AZ1500 series. Spin coating is performed at a low speed of 500 r / min for 10 s, and then at a high speed of 3000 r / min for 20 s to obtain a smooth photoresist film.

[0051] Step 1.2.2, Pre-baking: Bake the substrate 2 coated with adhesive at 100°C for 150 seconds to promote the evaporation of the adhesive solvent and eliminate bubbles, thereby improving the uniformity of the adhesive film and the exposure compatibility.

[0052] Step 1.2.2, Photolithography: After the pre-baked substrate 2 is precisely aligned with the mask, perform 7s ultraviolet exposure.

[0053] Step 1.2.3, Development: Immerse the exposed substrate 2 in the developer for 20 seconds, then remove it and place it in deionized water for 10 seconds. Finally, use an air gun to blow away any residual liquid on the surface.

[0054] Step 1.2.4, Post-baking: The conditions are the same as the pre-baking to ensure the stability of the photoresist after development, while removing impurities at high temperature.

[0055] Step 1.3: Using a thin film deposition apparatus, a heat insulation layer 3 is deposited on substrate 2, while controlling the base vacuum of the chamber to be no greater than 5 × 10⁻⁶. -4The working gas flow rate was 25 sccm, the sputtering power was 100 W, the thickness was 100 nm, and the sputtering was carried out at room temperature to obtain the heat insulation layer 3.

[0056] Step 1.4: Using a photomask according to the design, the patterned area of ​​the electrothermal functional layer 4 is formed by exposure and development on the surface of the heat insulation layer 3; subsequently, the material of the electrothermal functional layer 4 is deposited in the patterned area using a thin film deposition apparatus; the deposition conditions are: 3 × 10⁻⁶ m² / h². -5 Under a vacuum of 1 Pa, the deposition temperature was 25℃, the working vacuum was 1 Pa, the RF power was 50 W, the argon flow rate was 30 sccm, the working time was 3000 s, and the thickness was 50 nm. Finally, a photoresist removal process was performed to remove excess photoresist, obtaining the electrothermal functional layer 4.

[0057] Furthermore, the photoresist removal process is as follows: the sample with the deposited electrothermal functional layer 4 is immersed in NMP solution and left to stand for 8 hours until the photoresist is completely dissolved. The substrate is then immersed in alcohol and deionized water for 10 minutes each. To prevent damage to the metasurface structure, an ultrasonic cleaner is not used during the stripping and cleaning process, and the sample is then ready.

[0058] Step 1.5: Using the designed photomask, define the electrode structure region above the electrothermal functional layer 4; sequentially deposit the metal electrode layer 6 using a thin film deposition apparatus; the deposition conditions are: 3 × 10⁻⁶ -3 At a vacuum level of 1 Pa, the deposition temperature was room temperature, the working vacuum was 1 Pa, the DC power was 100 W, the argon flow rate was 30 sccm, the velocity was 20 nm per minute, and the deposition time was 4 minutes, with a copper thickness of 50 nm. Finally, a desizing process was performed to obtain the metal electrode layer 6.

[0059] In this embodiment, the photoresist removal process is as follows: The sample with the deposited metal electrode layer 6 is immersed in NMP solution and left to stand for 8 hours until the photoresist is completely dissolved. The substrate is then immersed in alcohol and deionized water for 5 minutes each. To prevent damage to the metasurface structure, no ultrasonic cleaning is used during the stripping and cleaning process, and the sample is then ready.

[0060] Step 1.6: Using the designed photomask, an electrically insulating layer 5 and a phase change material GeTe layer 7 are patterned on the electrothermal functional layer 4. The insulating material Al2O3 and the phase change material GeTe are then deposited sequentially using a thin film deposition apparatus to achieve effective electrical isolation and phase change function integration between the structures. The Al2O3 deposition conditions are: 3 × 10⁻⁶... -3 The deposition conditions were: a vacuum of 1 Pa, a deposition temperature of room temperature, a working vacuum of 1 Pa, an RF power of 120 W, an argon flow rate of 30 sccm, a deposition time of 60 min, and a thickness of 50 nm. The deposition conditions for the phase change material GeTe were: at a vacuum of 3 × 10⁻⁶ Pa. -3The deposition process was carried out at a vacuum level of 1 Pa, a deposition temperature of room temperature, a working vacuum level of 1 Pa, an RF power of 30 W, an argon flow rate of 30 sccm, a deposition time of 160-200 s, and a thickness of 50 nm. Finally, a desizing process was performed to obtain the target structure, namely the phase change material GeTe electronic switch structure.

[0061] In this embodiment, the photoresist removal process is as follows: The sample with the deposited electrical isolation layer 5 and phase change material GeTe layer 7 is immersed in NMP solution and left to stand for 12 hours until the photoresist is completely dissolved. The substrate is then immersed in alcohol and deionized water for 15 minutes each. To prevent damage to the metasurface structure, no ultrasonic cleaning is used during the stripping and cleaning process, and the sample is then ready.

[0062] The second step is to fabricate a resonant modulation absorbing layer 8 on the wafer after the phase change material GeTe electronically controlled switch structure has been prepared.

[0063] Step 2.1: Perform photolithography patterning on the substrate to prepare a photoresist mask layer corresponding to the mask pattern, in order to define the positions of each layer structure in subsequent magnetron sputtering deposition. Specifically: Step 2.1.1, Spin coating: The substrate 2 after cleaning the phase change material GeTe electronic switch structure is coated with photoresist using a spin coating machine. AZ10xt series photoresist is selected. Spin coating is performed at a low speed of 600r / min for 10s, and then at a high speed of 3000r / min for 40s to obtain a smooth photoresist film.

[0064] Step 2.1.2, Pre-baking: Bake the substrate 2 coated with adhesive at 100℃ for 150s to promote the evaporation of adhesive solvent and eliminate bubbles, thereby improving the uniformity of the adhesive film and exposure compatibility.

[0065] Step 2.1.3, Photolithography: After the pre-baked substrate 2 is precisely aligned with the mask, perform 7s ultraviolet exposure.

[0066] Step 2.1.4, Development: Immerse the exposed substrate 2 in the developer for 20 seconds, then remove it and place it in deionized water for 10 seconds. Finally, use an air gun to blow away any residual liquid on the surface.

[0067] Step 2.1.5, Post-baking: The conditions are the same as the pre-baking to ensure the stability of the photoresist after development, while removing impurities at high temperature.

[0068] Step 2.2: A copper resonant structure is grown at the corresponding location using photolithography and magnetron sputtering techniques. The copper plating conditions are: power of 3 × 10⁻⁶. -3 Under a vacuum of 1 Pa, at a deposition temperature of room temperature, a working vacuum of 1 Pa, a DC power of 100 W, an argon flow rate of 30 sccm, a velocity of 20 nm per minute, and a deposition time of 4 hours, all other requirements remain unchanged. The prepared structure is obtained after descaling.

[0069] In this embodiment, the photoresist removal process is as follows: the sample with the deposited copper resonant structure is immersed in NMP solution and left to stand for 8 hours until the photoresist is completely dissolved. Then, the substrate is immersed in alcohol and deionized water for 5 minutes each. To prevent damage to the metasurface structure, an ultrasonic cleaner is not used during the stripping and cleaning process, and the sample is then ready.

[0070] A tunable microwave metasurface absorber based on phase change material GeTe is fabricated using the above-mentioned method. It is prepared by photolithography and magnetron sputtering processes and can achieve absorption of specific wavelengths in the 2-12 GHz microwave band, meeting the performance requirements such as tunable absorption band. The system design and fabrication process are stable and have good application prospects.

[0071] In summary, the above is merely a preferred example of the present invention exhibiting absorption peaks at 3-5 GHz before modulation and 10-11 GHz after modulation at 11-12 GHz. It is not intended to limit the present invention in any way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent examples. However, any simple modifications, equivalent changes, and alterations made to the above examples based on the technical essence of the present invention without departing from the scope of the present invention's technical solution shall fall within the scope of the present invention's technical solution.

Claims

1. An electrically controllable tunable microwave metasurface absorber based on phase change material GeTe, characterized in that, The electrically controlled adjustable microwave metasurface absorber can achieve absorption of specific wavelengths in the 2-12GHz microwave band. It includes a phase change material GeTe electrically controlled switch structure and an adjustable microwave metasurface absorber structure. The two are combined to form a metasurface absorber unit with an overall square shape. Multiple metasurface absorber units are periodically arranged to form an electrically controlled adjustable microwave metasurface absorber, which can maintain the controllable state without continuous power supply. The phase change material GeTe electrically controlled switch structure comprises a heat insulation layer (3), an electrothermal functional layer (4), an electrical isolation layer (5), a metal electrode layer (6), and a phase change material GeTe layer (7); the heat insulation layer (3) is deposited on the upper surface of the substrate (2), and the electrothermal functional layer (4) is disposed on the upper surface of the heat insulation layer (3), located in the middle of the four sides of each metasurface absorber unit; the electrothermal functional layer (4) is a dumbbell-shaped structure, including a middle rod-shaped structure and head structures located at both ends; An electrical isolation layer (5) is placed over the middle rod-shaped structure to prevent short circuits and achieve electrical isolation; a metal electrode layer (6) is plated over the head structures at both ends of the electrothermal functional layer (4) to serve as electrodes to receive electrical pulse signals; a phase change material GeTe layer (7) is deposited on the surface of the electrical isolation layer (5) and can achieve reversible transition between crystalline and amorphous states under the action of electrical pulses; The adjustable microwave metasurface absorber includes a copper metal reflective substrate (1) at the bottom, a substrate (2) in the middle, and a resonant control absorbing layer (8) at the top. Specifically, the copper metal reflective substrate (1) is on the opposite side of the substrate (2) to reflect microwaves. The resonant control absorbing layer (8) is composed of a resonant structure unit and a metal frame. The resonant structure unit is a composite structure of a centrally symmetrical cross and a ring, which is deposited on the substrate (2). The entire resonant unit is surrounded by a square metal frame, and the ends of the cross arms are symmetrically integrated with a phase change material GeTe electrically controlled switch structure.

2. The electrically controlled tunable microwave metasurface absorber based on phase change material GeTe according to claim 1, characterized in that, In the phase change material GeTe electrically controlled switch structure: The thickness of the heat insulation layer (3) ranges from 50 to 150 nm; The head structure surface of the electrothermal functional layer (4) junction is square, with a size of 15-25μm and a thickness of 40-60nm, and is used to provide a heat source for the phase change material GeTe layer (7); The electrical isolation layer (5) has a thickness of 40-100nm and is used to prevent short circuits between the metal electrode layer (6) and the electrothermal functional layer (4). At the same time, the electrical isolation layer (5) also serves as a thermally conductive passivation layer between the electrothermal functional layer (4) and the phase change material GeTe layer (7), ultimately achieving electrical isolation. The thickness of the metal electrode layer (6) is 10-100 nm; The phase change material GeTe layer (7) has the same area as the electrical isolation layer (5) and a thickness of 20-80 nm. The reversible transformation is as follows: in the amorphous state, the phase change material GeTe layer (7) has a conductivity of 2.7 S / m and exhibits high resistance insulation properties; in the crystalline state, the phase change material GeTe layer (7) has a conductivity of 1.5 × 10⁻⁶. 5 With a conductivity of S / m, it exhibits high-conductivity metallic properties; the difference in conductivity before and after the phase transition exceeds five orders of magnitude, providing strong electromagnetic modulation capability for wave absorption characteristic control.

3. The electrically controlled tunable microwave metasurface absorber based on phase change material GeTe according to claim 1, characterized in that, In the electrically controllable microwave metasurface absorber: The thickness of the copper metal reflective substrate (1) is 2-5 μm; The substrate (2) is made of silicon wafer or ceramic wafer with a thickness of 0.5-1.5 mm; The insulation layer (3) is made of silicon dioxide or hafnium dioxide. The electrothermal functional layer (4) is made of materials with good electrical conductivity, such as tungsten, indium oxide, or graphene. The electrical isolation layer (5) is made of aluminum oxide or silicon nitride thin film. The metal electrode layer (6) is made of copper, aluminum, titanium, silver, indium tin oxide or other highly conductive alloy materials.

4. The electrically controlled tunable microwave metasurface absorber based on phase change material GeTe according to claim 1, characterized in that, The resonant structure unit is specifically composed of four orthogonally distributed metal cross arms of equal width and length that converge at the geometric center. A metal ring is embedded in the middle of the cross arm and connected to it. The metal ring has a tiny notch in each of the two adjacent arms of the cross arm, for a total of four tiny notches, with the size of the tiny notch being 0.1-0.3mm.

5. The electrically controlled tunable microwave metasurface absorber based on phase change material GeTe according to claim 1, characterized in that, The resonant structure unit of the resonant control absorbing layer (8) symmetrically integrates a phase change material GeTe electrically controlled switch structure at the four ends where the cross arm and the square metal frame intersect. By controlling the phase state of the phase change material GeTe layer (7) with electrical pulses, the conductivity is changed, thereby changing the resonance characteristics of the resonant control absorbing layer (8) and realizing the function of electrically controlled adjustable absorbing waves.

6. The electrically controlled tunable microwave metasurface absorber based on phase change material GeTe according to claim 1, characterized in that, The electrically adjustable microwave metasurface absorber operates in the 2-12 GHz frequency band and can achieve high-efficiency absorption in this frequency band, with high efficiency being an absorption rate of over 90% at 4.5 GHz and over 95% at 11.5 GHz.

7. The electrically controlled tunable microwave metasurface absorber based on phase change material GeTe according to claim 6, characterized in that, When the phase change material GeTe layer (7) is in an amorphous state, its highest absorption frequency is 4.5 GHz, its peak reflection loss is about -12 dB, and its absorption rate exceeds 90%, achieving high-efficiency absorption. When the phase change material GeTe layer (7) is in a crystalline state, its highest absorption frequency shifts to 11.5 GHz, its peak reflection loss is about -13 dB, and its absorption rate exceeds 95%, which also meets the high-efficiency absorption standard and achieves the expected adjustable function.

8. A method for fabricating an electrically tunable microwave metasurface absorber based on the phase change material GeTe as described in any one of claims 1-7, characterized in that, Fabricated using photolithography and magnetron sputtering processes. Includes the following steps: The first step is to prepare a phase change material GeTe electrically controlled switch structure. On the front side of the substrate (2), each functional layer is deposited sequentially using a thin-film deposition device and patterned to form a thermal insulation layer (3), an electrothermal functional layer (4), an electrical isolation layer (5), a metal electrode layer (6), and a phase change material GeTe layer (7). Specifically: Step 1.1, the back side of the substrate (2) is cleaned and decontaminated; Step 1.2 involves performing photolithography patterning on the substrate to prepare a photoresist mask layer corresponding to the mask pattern, thereby defining the positions of each layer structure in subsequent magnetron sputtering deposition. Specifically: The back side of the substrate (2) is coated with photoresist by a spin coater to obtain a flat photoresist film. Then, it is pre-baked, and after being precisely aligned with the mask, it is exposed to ultraviolet light to achieve photolithography. After development, it is post-baked. Step 1.3: Using a thin film deposition equipment, a heat insulation layer (3) is deposited on the substrate (2); Step 1.4: Using a photomask, expose and develop the pattern area of ​​the electrothermal functional layer (4) on the surface of the heat insulation layer (3); deposit the material of the electrothermal functional layer (4) in the pattern area using a thin film deposition equipment, perform a photoresist removal process to remove excess photoresist, and obtain the electrothermal functional layer (4). Step 1.5: Using a photomask, define the electrode structure region above the electrothermal functional layer (4); deposit the metal electrode layer (6) sequentially using a thin film deposition device, and perform a desizing process to obtain the metal electrode layer (6); Step 1.6: Using a mask template, an electrical isolation layer (5) and a phase change material GeTe layer (7) pattern are prepared on the electrothermal functional layer (4); the insulating material Al2O and the phase change material GeTe are deposited sequentially using a thin film deposition equipment to achieve effective electrical isolation between structures and integration of phase change functions; the adhesive is debonded to obtain the target structure, that is, the phase change material GeTe electrical control switch structure is obtained. The second step is to fabricate a resonant modulation absorbing layer (8) on the substrate (2) after the phase change material GeTe electronically controlled switch structure has been prepared; Step 2.1: Perform photolithography patterning on the substrate (2) to prepare a photoresist mask layer corresponding to the mask pattern, in order to define the positions of each layer structure in subsequent magnetron sputtering deposition. Specifically: The back side of the substrate (2) is coated with photoresist using a spin coater to obtain a flat photoresist film. Then, it is pre-baked, precisely aligned with the mask, and then subjected to UV exposure and development in sequence, followed by post-baking. Step 2.2: Copper is deposited using photolithography and magnetron sputtering techniques to grow a copper resonant structure, and finally the resist is removed to obtain the completed product.

9. The method for fabricating an electrically tunable microwave metasurface absorber based on the phase change material GeTe according to claim 8, characterized in that, In the first step: In step 1.2: the photoresist coating process is as follows: the photoresist used is the AZ1500 series; the photoresist is spin-coated at a low speed of 400-600 r / min for 5-15 s, then increased to a high speed of 2000-4000 r / min for 10-30 s; the pre-baking temperature is 80-120℃ for 120-180 s; the UV exposure time is 5-10 s; and the post-baking temperature is 80-120℃ for 120-180 s. In step 1.3: the background vacuum of the control chamber is controlled to be no greater than 5 × 10⁻ 4 Pa, working gas flow rate of 20-30 sccm, sputtering power of 80-120 W, thickness of 50-150 nm, room temperature sputtering; The deposition conditions in step 1.4 are: below 3 × 10⁻⁶. -5 Under a vacuum of Pa, the deposition temperature is room temperature, the working vacuum is 0.8-1.2 Pa, the radio frequency power is 30-60 W, the argon flow rate is 30 sccm, the working time is 2400-3600 s, and the thickness is 40-60 nm; the photoresist removal process is as follows: the sample with the electrothermal functional layer (4) deposited is immersed in NMP solution, left to stand for 6-12 h, and after the photoresist is completely dissolved, it is immersed in alcohol and deionized water for 5-15 min respectively. The deposition conditions in step 1.5 are: below 3 × 10⁻⁶. -3 Under a vacuum of Pa, the deposition temperature is room temperature, the working vacuum is 0.8-1.2 Pa, the DC power is 80-100 W, the argon flow rate is 30 sccm, the rate is 20 nm per minute, the deposition time is 3-5 min, and the copper thickness is 20-80 nm. The photoresist removal process is as follows: the sample with the deposited metal electrode layer (6) is immersed in NMP solution and left to stand for 6-12 h. After the photoresist is completely dissolved, it is immersed in alcohol and deionized water for 5-15 min respectively. The deposition conditions in step 1.6 are: below 3 × 10⁻⁶. -3 Under a vacuum of 1 Pa, the deposition temperature was room temperature, the working vacuum was 1 Pa, the RF power was 100-120 W, the argon flow rate was 30 sccm, the deposition time was 50-60 min, and the thickness was 40-100 nm; the conditions for depositing the phase change material GeTe were: below 3 × 10⁻⁶ Pa. -3 Under a vacuum of Pa, the deposition temperature is room temperature, the working vacuum is 1 Pa, the RF power is 40-50 W, the argon flow rate is 30 sccm, the deposition time is 160-200 s, and the thickness is 20-80 nm. The photoresist removal process is as follows: the sample with the deposited electrical isolation layer (5) and the phase change material GeTe layer (7) is immersed in NMP solution and left to stand for 6-12 h. After the photoresist is completely dissolved, it is immersed in alcohol and deionized water for 5-15 min respectively.

10. The method for fabricating an electrically tunable microwave metasurface absorber based on the phase change material GeTe according to claim 9, characterized in that, In the second step: In step 2.1, the coating parameters are as follows: AZ10xt series photoresist is selected, and the photoresist is spin-coated at a low speed of 500-600 r / min for 10-20 s, then increased to a high speed of 2500-3500 r / min for 30-60 s; the pre-baking temperature is 80-120℃ and the time is 120-180 s; the UV exposure time is 5-10 s; and the post-baking temperature is 80-120℃ and the time is 120-180 s. In step 2.2: the conditions for copper plating are: power consumption below 3 × 10 -3 Under a vacuum of 1 Pa, the deposition temperature is room temperature, the working vacuum is 1 Pa, the DC power is 80-100 W, the argon flow rate is 30 sccm, the velocity is 20 nm per minute, and the deposition time is 2-5 hours. Other requirements remain unchanged. The photoresist removal process is as follows: the sample with the deposited copper resonant structure is immersed in NMP solution and left to stand for 6-12 hours. After the photoresist is completely dissolved, it is immersed in alcohol and deionized water for 5-10 minutes respectively.

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