A four-function terahertz metasurface absorber with electric / thermal dual control and its preparation method

Abstract

The present invention discloses a four-function terahertz metasurface absorber with dual electrical / thermal control and a preparation method thereof. The absorber utilizes a novel structural design of graphene layers and vanadium dioxide layers. The surface comprises an outer square graphene ring, four graphene trapezoids, and an inner square graphene structure, effectively increasing the absorption bandwidth. The absorber also utilizes a dual-control design of graphene voltage and vanadium dioxide temperature. By independently regulating the voltages of the inner and outer graphene patterns, switching between a single-frequency absorption mode and a broadband absorption mode is achieved. Adjusting the temperature of the vanadium dioxide layer allows the absorber to switch between a low-frequency absorption band and a high-frequency absorption band, making the absorber a four-function terahertz metasurface absorber with dual electrical / thermal control. The present invention effectively addresses the current problem of absorbers being unable to regulate absorption bands and absorption modes, opening up a new path for device design in the field of terahertz absorption.

Description

Technical Field

[0001] The present invention relates to the field of electromagnetic wave absorption and regulation, and in particular to an electric / thermal dual-controlled multifunctional terahertz absorber and a preparation method thereof. Background Art

[0002] Terahertz waves are electromagnetic waves between infrared and microwaves (frequency 0.1-10 THz). Due to their high magnetic permeability and high imaging resolution, terahertz waves are widely used in military search, wireless communications, security inspections, and other fields. Perfect absorption of terahertz waves is crucial for terahertz detectors, sensors, and stealth, making efficient absorption a research hotspot. However, traditional terahertz absorbing materials with only a single function, such as MXene, transition metal sulfides, metal oxides, metal powders, and carbon-based nanomaterials, are no longer sufficient for complex operational scenarios.

[0003] Since Landy et al. proposed the first perfect absorber based on metasurface, metasurfaces have been considered one of the best choices for perfect electromagnetic wave absorption. Combining the tunable properties of vanadium dioxide and graphene, Zheng et al. designed a vanadium dioxide-based absorber that can flexibly switch between narrowband absorption mode and broadband absorption mode by adjusting the temperature of vanadium dioxide. Liu et al. proposed a metasurface absorber based on vanadium dioxide and graphene to achieve dual broadband absorption characteristics (low-frequency absorption mode and high-frequency absorption mode) that can be freely switched in the terahertz state. Most of the work mentioned above focuses on absorption frequency or frequency band switching. However, in order to further realize the integration of absorbers, it is necessary to integrate functions such as absorption mode and absorption band switching into a single metasurface absorber.

[0004] Combining the electrical tunability of graphene with the thermal phase transition properties of vanadium dioxide, this paper designs a voltage- and heat-controlled quadrifunctional metasurface absorber for the terahertz band. By electrically controlling the graphene layer, the proposed absorber can switch between narrowband and broadband absorption modes, while utilizing the phase transition of vanadium dioxide to achieve switching between low- and high-frequency absorption modes. This proposed absorber has the potential for applications in various terahertz band applications, including sensing, modulation, switching devices, and energy harvesting. Summary of the Invention

[0005] To achieve multifunctional, controllable absorption of terahertz waves, this paper proposes a voltage- and temperature-controlled, quadruple-function metasurface absorber for the terahertz band. This structure switches between different absorption modes under voltage and temperature control, enabling four absorption modes: low-frequency single-band absorption, high-frequency single-band absorption, low-frequency broadband absorption, and high-frequency broadband absorption. This effectively addresses the current problem of terahertz absorbers' inability to selectively absorb incident waves.

[0006] The present invention proposes a voltage / heat dual-control four-function metasurface absorber in the terahertz band, which includes, from top to bottom: a graphene layer 1 for absorbing terahertz waves and completing the regulation of the absorption mode; a first dielectric layer 2 for absorbing terahertz waves; a vanadium dioxide layer 3 for regulating the absorption band; a second dielectric layer 4 for absorbing terahertz waves; a metal substrate 5 for total reflection of terahertz waves so that the incident wave cannot penetrate the absorber; a first external bias voltage regulation circuit 6 for achieving the regulation of the chemical potential of the internal square graphene; a second external bias voltage regulation circuit 7 for achieving the regulation of the chemical potential of the external square graphene ring and four graphene trapezoids; and an external temperature controller 8 for achieving the regulation of the temperature of the vanadium dioxide.

[0007] The absorber structural unit of the present invention has a period of 20 μm, a thickness of the first dielectric layer of 11 μm, a thickness of the second dielectric layer of 5 μm, a thickness of the vanadium dioxide layer of 1 μm, and a thickness of the metal substrate of 1 μm.

[0008] The graphene layer 1 of the absorber described in the present invention adopts a structural design of a square graphene ring and four graphene trapezoids on the outside and a square graphene on the inside, wherein the four trapezoidal graphenes are evenly distributed outside the four sides of the square graphene ring, and the upper base of the trapezoid is close to the square graphene ring, and the lower base is far away from the square graphene ring. The center of the upper base is on the same horizontal line as the center of the square graphene ring edge. The inner square graphene is located in the middle of the square graphene ring, and the centers of the two coincide. The square graphene ring and the trapezoidal graphene are connected by a slender strip of graphene to ensure electrical continuity between the square graphene ring and the trapezoidal graphene.

[0009] The side length of the square graphene is 5μm, the inner and outer side lengths of the square graphene ring are 7μm and 11μm respectively, the upper and lower base lengths of the trapezoidal graphene are 12μm and 14μm respectively, the height of the trapezoidal graphene is 4μm, and the width of the slender graphene strip used to connect the square graphene ring and the trapezoidal graphene is 0.2μm.

[0010] The vanadium dioxide layer 3 adopts a non-patterned design.

[0011] The first dielectric layer 2 and the second dielectric layer 4 of the absorber of the present invention are made of cycloolefin copolymer (TOPAS) with a refractive index of 1.53.

[0012] The metal substrate 5 of the absorber of the present invention is made of gold (Au), which has an electrical conductivity of 4.56×10 7 S / m, and the thickness was set to 1 μm.

[0013] The internal and external graphene patterns of the graphene layer 1 of the absorber of the present invention are respectively connected to an external first external bias voltage adjustment circuit 6 and a second external bias voltage adjustment circuit 7, wherein the positive and negative poles of the first external bias voltage adjustment circuit 6 are respectively connected to the internal square graphene and the metal substrate 5, and the positive and negative poles of the second external bias voltage adjustment circuit 7 are respectively connected to the external square graphene ring and the trapezoidal graphene and the metal substrate 5. By controlling the external bias voltage (0-18V), the absorption mode of the absorber can be regulated. The temperature of the vanadium dioxide can be changed (60℃-70℃) by an external temperature controller 8 to switch the absorption band.

[0014] With respect to the above-mentioned four-function terahertz metasurface absorber with dual electrical and thermal control, the present invention also proposes a preparation method thereof, comprising the following steps:

[0015] S1 deposits 1 μm thick gold by electron beam evaporation to form the metal substrate (5);

[0016] S2: Spin-coating TOPAS on the gold surface and baking to form the 5 μm thick second dielectric layer (4);

[0017] S3 depositing vanadium dioxide with a thickness of 1 μm by electron beam evaporation to form the vanadium dioxide layer (3);

[0018] S4: Spin-coating TOPAS on the vanadium dioxide layer and baking to form the 11 μm thick first dielectric layer (2);

[0019] S5 transfers the graphene layer onto the first dielectric layer;

[0020] S6 sputters zinc onto the uppermost graphene layer, selectively removing a portion of the graphene from the graphene layer to form a graphene layer (1) of the structural unit pattern.

[0021] Beneficial effects of the present invention:

[0022] 1. The absorber of the present invention solves the problem of uncontrollable absorption mode of the current terahertz absorber and achieves controllable absorption mode.

[0023] 2. The absorber of the present invention solves the problem that the absorption band of the current terahertz absorber cannot be adjusted, and achieves controllable absorption band.

[0024] 3. The absorber of the present invention solves the problem that the current terahertz absorber cannot realize multifunctional regulation, and achieves multifunctional regulation of the absorber. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1This is a schematic diagram of a terahertz band voltage / heat dual-control four-function metasurface absorber structural unit proposed by the present invention.

[0026] The meanings of the accompanying figures are as follows: 1. graphene layer; 2. first dielectric layer; 3. vanadium dioxide layer; 4. second dielectric layer; 5. metal substrate; 6. first external bias voltage adjustment circuit; 7. second external bias voltage adjustment circuit; 8. external temperature controller.

[0027] Figure 2 This is a top view of a terahertz-band voltage / heat dual-control four-function metasurface absorber structural unit proposed by the present invention.

[0028] Figure 3 This is a side view of a voltage / heat dual-control four-function metasurface absorber in the terahertz band proposed by the present invention.

[0029] Figure 4 This is a graph showing the variation of the absorption rate of a terahertz band voltage / heat dual-control four-function metasurface absorber proposed by the present invention with frequency. DETAILED DESCRIPTION

[0030] The present invention proposes a four-function terahertz metasurface absorber with dual electrical and thermal control and a method for preparing the same. This device utilizes a novel structural design of graphene layers and vanadium dioxide layers. The surface features an outer square graphene ring, four graphene trapezoids, and an inner square graphene structure, effectively increasing the absorption bandwidth. The design also employs a dual-control design combining graphene voltage with vanadium dioxide temperature. By independently regulating the voltages of the inner and outer graphene patterns, switching between single-frequency and broadband absorption modes is achieved. Adjusting the temperature of the vanadium dioxide layer switches the absorber between low-frequency and high-frequency absorption bands, resulting in a four-function terahertz metasurface absorber with dual electrical and thermal control. This invention effectively addresses the current problem of absorbers being unable to regulate absorption bands and modes, opening a new path for device design in the field of terahertz absorption.

[0031] The implementation of the present invention will be further described below with reference to the accompanying drawings.

[0032] Figure 1 The figure shows a schematic diagram of a voltage / heat dual-control four-function metasurface absorber in the terahertz band, including a top graphene layer 1, a first dielectric layer 2, a vanadium dioxide layer 3, a second dielectric layer 4, a metal substrate 5, a first external bias voltage adjustment circuit 6, a second external bias voltage adjustment circuit 7 and an external temperature controller 8.

[0033] Among them, the graphene layer 1 is designed as an outer square graphene ring, four graphene trapezoids and an inner square graphene. The middle vanadium dioxide layer 3 is selected as a structure design without pattern. The material of the first dielectric layer 2 and the second dielectric layer 4 is TOPAS; the material of the metal substrate 5 is gold. 6 and 7 are external bias voltage adjustment circuits, which can realize independent regulation of the chemical potential of the internal pattern graphene and the external pattern graphene of the graphene layer 1. 8 is an external temperature controller, which can realize temperature regulation of the vanadium dioxide layer 3.

[0034] Set the temperature of the external temperature controller 8 to 70°C (greater than 68°C), the voltage of the first external bias voltage regulating circuit 6 to 6V, and the voltage of the second external bias voltage regulating circuit 7 to 0V. At this time, the absorber is in the low-frequency single-frequency absorption mode. Adjust the temperature of the external temperature controller 8 to 60°C (less than 68°C). At this time, the absorber switches to the high-frequency single-frequency absorption mode. Set the temperature of the external temperature controller 8 to 70°C, the voltage of the first external bias voltage regulating circuit 6 to 0V, and the voltage of the second external bias voltage regulating circuit 7 to 18V. At this time, the absorber is in the high-frequency broadband absorption mode. Adjust the temperature of the external temperature controller 8 to 60°C. At this time, the absorber switches to the low-frequency broadband absorption mode.

[0035] like Figure 2 The figure shows a top view of a voltage / heat dual-control four-function metasurface absorber structure unit in the terahertz band proposed by the present invention, wherein the period P of the structure unit is x =P y =20μm, the side length of the inner square graphene is d1 = 5μm, the inner and outer sides of the outer square graphene ring are d2 = 7μm and d3 = 11μm respectively, the upper and lower bases of the trapezoidal graphene are d4 = 12μm and d5 = 14μm respectively, the height of the trapezoidal graphene is d6 = 4μm, the width of the thin graphene strip connecting the square graphene ring and the trapezoidal graphene is r = 0.2μm, and the gap between the upper base of the trapezoid and the square ring is 0.5μm. The graphene thickness is about 0.3nm.

[0036] Figure 3 As shown, this is a side view of a voltage / heat dual-control four-function metasurface absorber in the terahertz band proposed by the present invention, wherein the thickness of the first dielectric layer 2 is t1 = 11 μm, the thickness of the vanadium dioxide layer 3 is t2 = 1 μm, the thickness of the second dielectric layer 4 is t3 = 5 μm, and the thickness of the metal substrate 5 is t4 = 1 μm.

[0037] Figure 4As shown, this is a graph showing the absorption rate variation with frequency of a voltage / heat dual-control four-function metasurface absorber in the terahertz band proposed by the present invention. The temperature of the external temperature controller 8 is set to 70°C (greater than 68°C), the voltage of the first external bias voltage adjustment circuit 6 is set to 6V, and the voltage of the second external bias voltage adjustment circuit 7 is set to 0V. At this time, the absorber is in a low-frequency single-frequency absorption mode. The temperature of the external temperature controller 8 is adjusted to 60°C (less than 68°C), and the absorber switches to a high-frequency single-frequency absorption mode. The temperature of the external temperature controller 8 is set to 70°C, the voltage of the first external bias voltage adjustment circuit 6 is set to 0V, and the voltage of the second external bias voltage adjustment circuit 7 is set to 18V. At this time, the absorber is in a high-frequency broadband absorption mode. The temperature of the external temperature controller 8 is adjusted to 60°C, and the absorber switches to a low-frequency broadband absorption mode.

[0038] The preparation method of the above-mentioned voltage / heat dual-control four-function metasurface absorber in the terahertz band is completed by the following steps:

[0039] (1) depositing gold with a thickness of 1 μm by electron beam evaporation to form the metal substrate 5;

[0040] (2) Spin-coating TOPAS on the gold surface and baking to form the second dielectric layer 4;

[0041] (3) depositing vanadium dioxide with a thickness of 1 μm by electron beam evaporation to form the vanadium dioxide layer 3;

[0042] (4) Spin-coating TOPAS on the vanadium dioxide layer and baking to form the first dielectric layer 2;

[0043] (5) transferring the graphene layer onto the first dielectric layer;

[0044] (6) Sputtering zinc onto the topmost graphene layer to selectively remove graphene from these areas to form Figure 2 The first graphene layer 1 with a specific pattern is shown. Thus, the preparation of the terahertz absorber is completed.

[0045] The series of detailed descriptions listed above are only specific descriptions of feasible implementation methods of the present invention. They are not intended to limit the scope of protection of the present invention. Any equivalent methods or changes that do not deviate from the technology of the present invention should be included in the scope of protection of the present invention.

Claims

1. A four-function terahertz metasurface absorber with electrical / thermal dual control, characterized in that: From top to bottom, it includes: a graphene layer (1), used for absorbing terahertz waves and completing the regulation of the absorption mode; a first dielectric layer (2), used for absorbing terahertz waves; a vanadium dioxide layer (3), used for regulating the absorption band; a second dielectric layer (4), used for absorbing terahertz waves; a metal substrate (5), used for total reflection of terahertz waves, so that the incident wave cannot penetrate the absorber; an external bias voltage regulation circuit, used for achieving chemical potential regulation of the graphene layer (1); and an external temperature controller (8), used for achieving temperature regulation of the vanadium dioxide. The graphene layer (1) is patterned, and the structural unit of the pattern adopts a structural design with a square graphene ring and four trapezoidal graphene on the outside and a square graphene on the inside; wherein the four trapezoidal graphenes are evenly distributed outside the four sides of the square graphene ring, and the upper base of the trapezoid is close to the square graphene ring, and the lower base is far away from the square graphene ring, the center of the upper base and the center of the square graphene ring are on the same horizontal line, the inner square graphene is located in the middle of the square graphene ring, and the centers of the two coincide, and the square graphene ring and the trapezoidal graphene are connected by a thin strip of graphene to ensure electrical continuity between the square graphene ring and the trapezoidal graphene; The external bias voltage regulating circuit comprises a first external bias voltage regulating circuit (6) and a second external bias voltage regulating circuit (7); the first external bias voltage regulating circuit (6) is used to realize the regulation of the chemical potential of the square graphene inside the structural unit; the second external bias voltage regulating circuit (7) is used to realize the regulation of the chemical potential of the external square graphene ring and four graphene trapezoids of the structural unit; by regulating the external bias voltage, the absorption mode of the absorber can be regulated, and by regulating the external temperature, the temperature of the vanadium dioxide can be changed to realize the regulation of the absorption band.

2. The four-function terahertz metasurface absorber with electrical / thermal dual control according to claim 1, characterized in that: The side length of the inner square graphene is 5μm, the inner and outer side lengths of the outer square graphene ring are 7μm and 11μm respectively, the upper and lower base lengths of the trapezoidal graphene are 12μm and 14μm respectively, the height of the trapezoidal graphene is 4μm, the width of the slender graphene strip used to connect the square graphene ring and the trapezoidal graphene is 0.2μm, and the gap between the upper base of the trapezoid and the square ring is 0.5um.

3. The four-function terahertz metasurface absorber with electrical / thermal dual control according to claim 2, characterized in that: The entire graphene layer is composed of the structural units arranged periodically at intervals of 20 μm.

4. The four-function terahertz metasurface absorber with electrical / thermal dual control according to claim 1, characterized in that: The vanadium dioxide layer (3) adopts a non-patterned design.

5. The four-function terahertz metasurface absorber with electrical / thermal dual control according to claim 1, characterized in that: The thickness of the first dielectric layer (2) is 11 μm, the thickness of the second dielectric layer (4) is 5 μm, the thickness of the vanadium dioxide layer (3) is 1 μm, and the thickness of the metal substrate (5) is 1 μm.

6. The four-function terahertz metasurface absorber with electrical / thermal dual control according to claim 1, characterized in that: The temperature of the external temperature controller (8) is set to be higher than 68°C, the voltage of the first external bias voltage regulating circuit (6) is set to 6V, and the voltage of the second external bias voltage regulating circuit (7) is set to 0V. At this time, the absorber is in a low-frequency single-frequency absorption mode. The temperature of the external temperature controller (8) is adjusted to be lower than 68°C, and the absorber is switched to a high-frequency single-frequency absorption mode. The temperature of the external temperature controller (8) is set to be higher than 68°C, the voltage of the first external bias voltage regulating circuit (6) is set to 0V, and the voltage of the second external bias voltage regulating circuit (7) is set to 18V. At this time, the absorber is in a high-frequency broadband absorption mode. The temperature of the external temperature controller (8) is adjusted to be lower than 68°C, and the absorber is switched to a low-frequency broadband absorption mode.

7. The four-function terahertz metasurface absorber with electrical / thermal dual control according to claim 1, characterized in that: The first dielectric layer (2) and the second dielectric layer (4) are made of cyclic olefin copolymer (TOPAS) with a refractive index of 1.53; the metal substrate (5) is made of gold (Au) with a conductivity of 4.56×10 7 S / m.

8. A method for preparing a four-function terahertz metasurface absorber with electrical / thermal dual control, characterized in that: The steps include: S1 deposits 1 μm thick gold by electron beam evaporation to form a metal substrate (5); S2 spin-coats TOPAS on the gold surface and bakes it to form a 5 μm thick second dielectric layer (4); S3 deposits vanadium dioxide with a thickness of 1 μm by electron beam evaporation to form a vanadium dioxide layer (3); S4: Spin-coating TOPAS on the vanadium dioxide layer and baking to form a first dielectric layer (2) with a thickness of 11 μm; S5 transfers the graphene layer onto the first dielectric layer; S6: sputtering zinc onto the uppermost graphene layer, selectively removing part of the graphene from the graphene layer, so as to form a graphene layer (1) having a pattern as described in any one of claims 1, 2, and 3.

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