A dynamic thermal camouflage device based on electronically controlled phase-change metasurface

Abstract

The application discloses a kind of dynamic thermal camouflage devices based on electrically controlled phase change super surface, belong to thermal camouflage device technical field.It includes MIM plasmonic super surface and base layer, MIM plasmonic super surface is located at the central place above base layer, SiO2 layer is arranged between MIM plasmonic super surface and base layer, the both sides of MIM plasmonic super surface are connected with solder pad.The application uses the above-mentioned dynamic thermal camouflage device based on electrically controlled phase change super surface, MIM heat emitter has completely symmetrical structure, and the spectral emissivity of different polarization angles is almost unchanged when vertical incidence.The thermal camouflage performance and thermal stability are not sensitive to different polarization angles and a certain range of incident angles.And the application meets the basic requirements of GST amorphization.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of thermal camouflage devices, in particular to a dynamic thermal camouflage device based on an electrically controlled phase-change metasurface. BACKGROUND

[0002] Infrared thermal camouflage technology is a technology that adjusts the infrared thermal radiation characteristics of a target to make it blend in with the infrared thermal radiation characteristics of the background. Infrared thermal camouflage technology can be achieved by changing the surface temperature or emissivity of the target, where adjusting the surface emissivity is a surface feature design from the field of spectroscopy, with characteristics such as high flexibility, strong controllability, and fast manipulation speed. According to whether the emissivity is tunable, it is divided into static thermal camouflage and dynamic thermal camouflage. Traditional static thermal camouflage technologies, such as thermal infrared paint technology, thermal infrared camouflage net and camouflage technology, etc., have fixed emissivity and can only be thermally camouflaged at a specific background temperature. However, in recent years, various dynamic infrared thermal camouflage technologies have been reported, which can adjust the emissivity of the target through environmental changes, but still face some challenges in practical applications: 1) Due to its non-memory characteristics, it requires continuous external stimulation to maintain the required emissivity of the target, resulting in high power consumption, many supporting facilities, and inconvenience in installation and deployment; 2) The range of emissivity regulation is narrow, resulting in a small range of background temperature changes and poor environmental adaptability; 3) The modulation speed is slow, limiting potential applications in conditions where the background temperature changes rapidly. Therefore, in complex military environments, developing a dynamic infrared thermal camouflage device with a large dynamic range, fast switching speed, strong reversibility, high regulation efficiency, low overall power consumption, convenient installation and deployment, and memory characteristics has great research value and practical prospects in the future of national defense, military and infrared information hiding applications.

[0003] In order to overcome the regulation difficulties of existing dynamic thermal camouflage technology, in recent years, some people have proposed a metal-insulator-metal (MIM) structure based on non-volatile phase-change material (PCM). This structure has the advantages of zero static power consumption, fast modulation speed, and large adjustable range. PCM mainly refers to chalcogenide semiconductor materials represented by Ge2Sb2Te5 (GST). This type of material has very stable crystalline GST (cGST) and amorphous GST (aGST) at room temperature, with a large difference in physical properties (complex refractive index and resistivity) between the two phases. Under the excitation of heat, electricity, and light pulses, the two phases can be switched, with a repetition frequency of up to 10 12The phase transition time is in the order of nanoseconds or even sub-nanoseconds, which shows promising application prospects in optoelectronic memory, programmable waveguide devices, reconfigurable metasurfaces, brain-like computing, etc. 9 K / s quenching rate to room temperature, it is converted into aGST (quenching rate too small will recrystallize during cooling). Although some research progress has been made in dynamic infrared thermal camouflage devices based on phase change materials, this field is still in its infancy, and there are many design, simulation, experiment and dynamic control problems to be solved. 1) These reports do not study device performance from the aspects of heat conduction, temperature uniformity and cooling speed, which are necessary for the crystallization and amorphization of PCM. 2) The thick GST layer (≥240nm) will cause large internal temperature difference and slow quenching rate. 3) All experimental articles lack amorphization results due to improper device design and excitation method, such as using a thick GST layer and using a hot plate for heating. These factors cause the emissivity switch to be almost one-time, making the device unable to adapt to different environmental backgrounds. SUMMARY

[0004] The purpose of the present application is to provide a dynamic thermal camouflage device based on electrically controlled phase change metasurface, which solves the problems of lack of device performance in terms of heat conduction, temperature uniformity and cooling speed, thick GST layer (≥240nm) causing large internal temperature difference and slow quenching rate, and lack of amorphization results in existing dynamic thermal camouflage devices.

[0005] To achieve the above purpose, the present application provides a dynamic thermal camouflage device based on electrically controlled phase change metasurface, which comprises a MIM plasmonic metasurface and a base layer, the MIM plasmonic metasurface is located at the central upper part of the base layer, a SiO2 layer is arranged between the MIM plasmonic metasurface and the base layer, and the MIM plasmonic metasurface is connected with pads on both sides.

[0006] Preferably, the MIM plasmonic metasurface comprises a GST layer, the bottom of the GST layer is connected with a Pt layer, and the top of the GST layer is connected with an Au layer.

[0007] Preferably, the Au layer is a periodic cylindrical array with a height of 50nm, a diameter of 1000nm and a period of 1050nm.

[0008] Preferably, the thickness of the GST layer is 80nm, and the thickness of the Pt layer is 40nm.

[0009] Preferably, the material of the base layer is Si.

[0010] Preferably, the pads are Au material pads.

[0011] Preferably, the base layer is an oblong structure.

[0012] Therefore, the present invention adopts a dynamic thermal camouflage device based on an electrically controlled phase change metasurface with the above structure, which has the following beneficial effects:

[0013] To examine the effects of incident and polarization angles on the emission spectrum, the present invention scanned the incident angles for both s- and p-polarization modes. Although the spectral emissivity varied at different incident angles, both met the basic requirements for thermal camouflage and thermal stability. Furthermore, the MIM thermal emitter has a completely symmetrical structure, and the spectral emissivity remains virtually unchanged at vertical incidence. The thermal camouflage performance and thermal stability are insensitive to different polarization angles and incident angles within a certain range. Furthermore, the present invention meets the basic requirements for amorphization of phase change materials.

[0014] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a schematic structural diagram of a dynamic thermal camouflage device based on an electrically controlled phase-change metasurface according to the present invention;

[0016] Figure 2 Schematic diagram of the cross-sectional structure of a dynamic thermal camouflage device based on an electrically controlled phase-change metasurface according to the present invention;

[0017] Figure 3 Schematic diagram of emission spectra of MIM thermal emitters at different crystallization rates of a dynamic thermal camouflage device based on an electrically controlled phase change metasurface according to the present invention;

[0018] Figure 4 Schematic diagram of the emission spectra of an aGST-thermal emitter of a dynamic thermal camouflage device based on an electrically controlled phase change metasurface at different s-incident angles of the present invention;

[0019] Figure 5 Schematic diagram of the emission spectra of an aGST-thermal emitter of a dynamic thermal camouflage device based on an electrically controlled phase change metasurface of the present invention at different p-incident angles;

[0020] Figure 6 Schematic diagram of the emission spectra of an aGST-thermal emitter at different polarization angles of a dynamic thermal camouflage device based on an electrically controlled phase-change metasurface according to the present invention;

[0021] Figure 7 Schematic diagram of the emission spectra of a cGST-thermal emitter of a dynamic thermal camouflage device based on an electrically controlled phase change metasurface of the present invention at different s-incident angles;

[0022] Figure 8The emission spectrum diagram of a cGST-thermal emitter of a dynamic thermal camouflage device based on an electrically controlled phase change metasurface at different p-incidence angles;

[0023] Figure 9 The emission spectrum diagram of a cGST-thermal emitter of a dynamic thermal camouflage device based on an electrically controlled phase change metasurface at different polarization angles;

[0024] Figure 10 The temperature change curve diagram of a dynamic thermal camouflage device based on an electrically controlled phase change metasurface under the excitation of a 12.74V, 300ns electric pulse;

[0025] Figure 11 The temperature distribution diagram of a dynamic thermal camouflage device based on an electrically controlled phase change metasurface in the z-axis direction at the time of 300ns under the excitation of a 12.74V, 300ns electric pulse;

[0026] Figure 12 The GST top temperature distribution diagram of a dynamic thermal camouflage device based on an electrically controlled phase change metasurface;

[0027] Figure 13 The GST bottom temperature distribution diagram of a dynamic thermal camouflage device based on an electrically controlled phase change metasurface;

[0028] Figure 14 The forest background temperature diagram corresponding to different device temperatures and crystallization rates under the condition of equal radiation intensity of a dynamic thermal camouflage device based on an electrically controlled phase change metasurface;

[0029] Figure 15 The steel background temperature diagram corresponding to different device temperatures and crystallization rates under the condition of equal radiation intensity of a dynamic thermal camouflage device based on an electrically controlled phase change metasurface;

[0030] Figure 16 The base-order magnetic resonance magnetic field strength distribution diagram of a dynamic thermal camouflage device based on an electrically controlled phase change metasurface when the GST is in an amorphous state.

[0031] Reference signs

[0032] 1, MIM plasmonic metasurface, 2, base layer, 3, SiO2 layer, 4, pad, 11, Au layer, 12, GST layer, 13, Pt layer. DETAILED DESCRIPTION

[0033] The technical solutions of the present application are further described below through the drawings and examples.

[0034] Unless otherwise defined, the technical or scientific terms used in the present invention shall have the usual meanings understood by persons of ordinary skill in the field to which the present invention belongs. The words "first", "second" and similar terms used in the present invention do not indicate any order, quantity or importance, but are only used to distinguish different components. Words such as "include" or "comprise" mean that the elements or objects preceding the word include the elements or objects listed after the word and their equivalents, without excluding other elements or objects. Words such as "connect" or "connected" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the object being described changes, the relative positional relationship may also change accordingly.

[0035] Example

[0036] like Figure 1 As shown, the present invention provides a dynamic thermal camouflage device based on an electrically controlled phase change metasurface, comprising a MIM plasma metasurface 1 and a base layer 2, wherein the MIM plasma metasurface 1 is located in the center above the base layer 2, and a 145 nm thick SiO2 layer 3 is arranged between the MIM plasma metasurface 1 and the base layer 2.

[0037] The MIM plasmonic metasurface 1 consists of an upper Au layer 11, a middle GST layer 12, and a lower Pt layer 13. The Pt layer 13 is 40 nm thick and connected to pads 4 on both sides. The GST layer 12 is 80 nm thick and located centrally above the Pt layer 13. Atop the GST layer 12 is the Au layer 11. The Au layer 11 is a periodic array of cylindrical columns with a height of 50 nm, a diameter of 1000 nm, and a period of 1050 nm.

[0038] The base layer 2 is made of Si. The pad 4 is made of Au. The base layer 2 is an oblong structure.

[0039] Working principle: Figures 1-2 As shown, the device is a non-volatile thermal emitter, and its core functional component is a MIM plasma metasurface 1 composed of Pt-GST-Au. The 40nm thick Pt layer 13 at the bottom can not only block the infrared light from passing through the sample, but also serve as a heating layer to induce the GST phase change. The thickness of the middle GST layer 12 is 80nm, and the emissivity of the thermal emitter can be controlled by adjusting the peak value of the MIM plasma resonance. The top Au layer 11 is designed to be a periodic cylindrical array with a height of 50nm, a diameter of 1000nm, and a period of 1050nm. The MIM plasma metasurface has a fundamental magnetic resonance in the 8-14um band when it is in the amorphous GST state (such as Figure 16), while no obvious change in the crystalline GST, showing different emissivity of different GST phases. The MIM plasmonic metasurface 1 is on a substrate 2 (Si) with high thermal conductivity, which can quickly dissipate heat and promote amorphization. In order to improve the efficiency of electrical heating, a layer of SiO2 3 with low thermal conductivity and a thickness of 145 nm is introduced between the MIM plasmonic metasurface 1 and the substrate 2. Two Au pads are connected to the power supply, and an electrical pulse is input. The current passes through the Pt layer 13 in the middle, the Pt layer 13 generates heat, and the GST layer is heated to induce phase change.

[0040] As shown in Figure 3 , all the peaks of emissivity show a significant red shift with the increase of GST crystallization rate, and the peak intensity also decreases. This is because the effective refractive index of GST increases with the increase of crystallization rate, thereby changing the resonance mode of the MIM plasmonic metasurface 1. The emissivity difference between aGST-thermal emitter and cGST-thermal emitter is large in the wavelength range of 8-14 μm (working wavelength of commercial thermal imager), which shows that they can realize dynamic thermal camouflage in a wide range of background temperature. The higher the GST crystallization rate, the larger the dielectric constant and refractive index, resulting in a red shift of the plasmonic resonance peak.

[0041] As shown in Figures 4-9 , in order to test the influence of incident angle and polarization angle on the emission spectrum, we scanned the incident angle of s-polarization and p-polarization modes. It can be found that when the incident angle is 0-10°, the two incident modes have no effect on the spectral emissivity. When the incident angle is 10-30°, s-polarization will make the emission peak narrower, and p-polarization will make the emission peak wider. Although the spectral emissivity is different at different incident angles, it can still meet the basic requirements of thermal camouflage and thermal stability. Moreover, the MIM thermal emitter has a completely symmetrical structure, and the spectral emissivity of different polarization angles is almost unchanged when the incident angle is vertical (as shown in Figure 6 and Figure 9 ). Therefore, the performance of thermal camouflage and thermal stability is not sensitive to different polarization angles and a certain range of incident angles.

[0042] As shown in Figures 10-13 , the temperature curve of the MIM thermal emitter under the excitation of a 12.74 V, 300 ns electrical pulse is shown in Figure 10 . It can be seen that the temperature change of the top of the GST is slower than that of the bottom, and the cooling rate of the entire GST layer in the recrystallization region (560-660 K) is 1.9×10 9 ~ 3.9×10 9 K / s, which meets the basic requirements of amorphization. Figure 11 It can be seen that the temperature distribution of the GST layer in the z-axis direction is uniform at 300 ns, and the maximum temperature difference is only 42℃. Figure 12 and 13It can be seen that the temperature distribution in the center area of ​​the GST is also very uniform regardless of the top or bottom on the xy plane.

[0043] like Figures 14-15 As shown, by adjusting the device temperature (0-100℃) and the crystallization rate (0-1), the target can be integrated into the forest background of -79℃ to 28℃ (background emissivity is 0.97) and the steel background of -22℃ to 173℃ (background emissivity is 0.21).

[0044] Therefore, the present invention utilizes the aforementioned dynamic thermal camouflage device based on an electrically controlled phase-change metasurface. The MIM thermal emitter has a completely symmetrical structure, and its spectral emissivity remains virtually unchanged at different polarization angles under normal incidence. Its thermal camouflage performance and thermal stability are insensitive to different polarization angles and incident angles within a certain range. Furthermore, the present invention meets the basic requirements for amorphization.

[0045] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the same. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solutions of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A dynamic thermal camouflage device based on an electrically controlled phase-change metasurface, characterized by: It includes a MIM plasma supersurface and a base layer, wherein the MIM plasma supersurface is located in the center above the base layer, a SiO2 layer is provided between the MIM plasma supersurface and the base layer, and pads are connected to both sides of the MIM plasma supersurface; The MIM plasma supersurface includes a GST layer, a Pt layer is connected to the bottom of the GST layer, the thickness of the GST layer is 80 nm, and an Au layer is connected to the top of the GST layer; The GST layer controls the emissivity of the thermal emitter by adjusting the peak of the MIM plasmon resonance; The thickness of the Pt layer is 40 nm, and the resistivity of the Pt layer is , which is used to block infrared light from passing through the sample and also acts as a heating layer to induce GST phase transition; The Au layer is a periodic cylindrical array with a thickness of 50 nm. The diameter of the periodic cylindrical array is 1000 nm and the period is 1050 nm. The MIM plasma metasurface has a fundamental magnetic resonance in the 8-14 μm band when the amorphous GST is in the state, but not in the crystalline GST, showing different emissivities of GST in different phases. The power supply is connected to the two Au pads, an electric pulse is input, and the current passes through the middle Pt layer. The Pt layer generates heat, which heats the GST layer and causes its phase change. Under the excitation of 12.74V, 300ns electric pulse, the temperature change of the top of GST is slower than that of the bottom, making the temperature of the GST layer in the range of 560-660K. The temperature is lowered at a rate to achieve amorphous phase transition; The base layer is made of Si, and the SiO2 layer is a 145 nm SiO2 layer with low thermal conductivity.

2. The dynamic thermal camouflage device based on an electrically controlled phase change metasurface according to claim 1, characterized in that: The pad is made of Au.

3. The dynamic thermal camouflage device based on an electrically controlled phase change metasurface according to claim 1, characterized in that: The base layer is an oblong structure.

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