Infrared stealth and radiation heat dissipation film based on Ge2Sb2Te5 and preparation method thereof

Abstract

The present invention belongs to the technical field of material preparation, and specifically relates to an infrared stealth and radiation heat dissipation film based on Ge2Sb2Te5 and a preparation method thereof. The infrared stealth and radiation regulation selective emission film materials of the present invention are Ni and Ge2Sb2Te5, and the substrate is a high-purity silicon wafer. The selective emission film comprises a four-layer structure of Ni / crystalline Ge2Sb2Te5 / Ni / amorphous Ge2Sb2Te5, and the middle layer of crystalline Ge2Sb2Te5 is obtained by annealing after deposition. The structure can simultaneously achieve low emission in the "atmospheric window" interval of 3‑5 and 8‑13 μm, and high emission at 5‑8 μm outside the window, while achieving the dual functional effects of stealth and heat dissipation.

Description

Technical Field

[0001] The invention belongs to the technical field of material preparation, and in particular relates to an infrared stealth and radiation heat dissipation film based on Ge2Sb2Te5 and a preparation method thereof. Background Art

[0002] With the rapid development of modern detection technology and the improvement of the accuracy of detection systems, the demand for stealth technology in modern warfare is also increasing. Objects at any temperature will radiate electromagnetic waves. Electromagnetic waves with a wavelength range of 0.78 to 1000μm are called infrared radiation. As a commonly used detection method, infrared detection and imaging device technology has been fully developed and widely used in various fields due to the spontaneity and universality of thermal radiation. At present, infrared guidance and infrared detection devices with high precision and strong anti-interference ability are widely used in modern battlefields. High-precision infrared detection devices and infrared guidance pose a great threat to ground vehicles and aircraft. In order to improve the concealment and safety of personnel and equipment in battlefield environments, it is of practical significance to develop a widely applicable infrared stealth material.

[0003] Since infrared light is affected by absorption and scattering of gas molecules and suspended particles when propagating in the atmosphere, the working bands of infrared detection systems and infrared guidance equipment are mostly concentrated in the "infrared atmospheric window" interval with wavelengths of 3-5μm and 8-13μm, so the infrared radiation generated by the target in these two bands is the reason why it is threatened. Infrared stealth technology targets the infrared radiation characteristics of the target, and uses the selection of materials and structural design to reduce the prominence of the target in the infrared radiation background, reduce the difference between the infrared radiation generated by the target and the background radiation, and reduce the probability of being discovered and locked in infrared detection and infrared guidance, thereby achieving a better infrared stealth effect. Since in practical applications, objects that need infrared stealth generally have an actual temperature higher than the background, the requirement of infrared stealth is to reduce the apparent radiation temperature of the target as much as possible, so that the target's recognizability in the environment is reduced. In general, infrared stealth or reducing the apparent radiation temperature of the object can be achieved in two ways: one is to reduce the surface temperature of the target object, which can be achieved by heat insulation, heat dissipation, or phase change heat absorption through phase change materials; the other is to reduce the surface emissivity of the target. In practical applications, both the light field and the temperature field of the target object need to be regulated to achieve the best infrared stealth effect, so the selective absorption film with the dual functions of infrared stealth and radiation heat dissipation is one of the current research hotspots.

[0004] The current mainstream methods to achieve infrared stealth include: traditional low infrared emissivity materials, photonic crystal selective emission design, metasurface selective emission design, and smart material dynamic selective emission design.

[0005] Low infrared emissivity materials can be divided into inorganic low emissivity materials, organic low emissivity materials and organic-inorganic composite low emissivity materials according to their chemical composition. Inorganic low emissivity materials are the most reported and most effective type of low infrared emissivity materials, and they dominate the field of infrared stealth materials. However, their radiation heat dissipation ability is poor, which may cause heat accumulation. The selective emission design can improve this defect. The selective emission device designed with photonic crystals combines infrared stealth with radiation heat dissipation, which has a strong application prospect. For example, a one-dimensional photonic crystal with a periodic structure of Te and ZnSe materials has a high reflectivity of 86.72% and 72.91% in the 3-5μm and 8-14μm bands, respectively, and the corresponding emissivity is 0.072 and 0.194, respectively. In the experiment, under different background temperatures, the radiation temperature of the photonic crystal is always lower than the background radiation temperature, and the maximum radiation temperature difference is 31.97℃.

[0006] The design of supersurface selective emission utilizes the plasmon absorption effect of its surface microstructure. The surface microstructure can be designed according to the specific application environment to regulate spectral selectivity and realize its ability to combine infrared stealth with radiation heat dissipation. For example, the emitter prepared by placing a hexagonal Mo disk microstructure array on an Al2O3-Mo double-layer structure can produce an ideal narrow emission peak in the range of 5-8μm and achieve a lower emissivity in other infrared bands. The design of dynamic selective emission of smart materials mostly uses electrochromic or thermochromic materials to dynamically adjust their own emissivity, reduce the radiation contrast between the target and the environment, and enhance the target's adaptability to the environment. For example, a selective emission film based on poly-o-anisidine (POA) is synthesized by cyclic voltammetry to produce an electrochromic film with variable emissivity characteristics. The film has different average emissivities in the wavelength range of 8-14μm when it is under different voltages, and the maximum value of the emissivity difference can reach 0.553, which has great application potential.

[0007] Among them, the problems existing in the prior art are:

[0008] (1) The emission in the infrared stealth range (3-5, 8-13 μm) can be further reduced;

[0009] (2) Emission in the radiation heat dissipation range (5-8μm) needs to be improved;

[0010] (3) The materials used are expensive and the preparation method is complicated, making it difficult to apply on a large scale. Summary of the invention

[0011] This design is mainly based on the fact that the optical constants of crystalline and amorphous Ge2Sb2Te5 are quite different to design a selective absorption film. The quasi-optical microcavity structure is introduced to enhance the absorption capacity of the film in a specific range. Only two materials and a relatively simple structure are used to achieve good selective emission performance.

[0012] The present invention is achieved through the following technical solutions:

[0013] An infrared stealth and radiation heat dissipation film based on Ge2Sb2Te5, wherein the film comprises a four-layer structure of Ni / crystalline Ge2Sb2Te5 / Ni / amorphous Ge2Sb2Te5.

[0014] Through extensive research, the present invention has found that the bottom Ni metal layer is used to provide reflection, and at the same time, a quasi-optical microcavity structure is formed with the crystalline Ge2Sb2Te5 and the thin Ni layer to provide a stronger peak emission capability, and the top amorphous Ge2Sb2Te5 layer provides the ability to adjust the absorption peak position. Compared with a film without such a structure, it has a stronger peak absorption and better spectral selectivity. The top amorphous Ge2Sb2Te5 can be replaced by infrared transparent materials Ge and ZnSe to achieve the same effect, and its metal layer material can also be replaced by other metals such as Cu, Al, Au, etc. that are also highly reflective in the infrared range, that is, the amorphous Ge2Sb2Te5 is replaced by other infrared transparent materials such as Ge and ZnSe, and the Ni layer is replaced by other metals such as Cu, Al, Au, etc.

[0015] As a preferred technical solution of the present invention, the thickness of each layer is respectively: Ni: 100nm±10nm; crystalline Ge2Sb2Te5: 90nm±10nm; Ni: 14nm±2nm; amorphous Ge2Sb2Te5: 320±50nm, preferably 320±20nm.

[0016] The structure was obtained through simulation optimization by Essential Macleod software. The two metal layers at the bottom and the middle and the crystalline Ge2Sb2Te5 in the middle together constitute a quasi-optical microcavity structure, which enhances the selective emission capability of the film. The enhanced absorption capability of the Ni / crystalline Ge2Sb2Te5 / Ni microcavity structure and the 320nm thick topmost amorphous Ge2Sb2Te5 achieve the best performance. The structure can simultaneously achieve low emission in the "atmospheric window" range of 3-5 and 8-13μm, and high emission outside the window of 5-8μm, while achieving the dual functional effects of stealth and heat dissipation. The present invention further provides a method for preparing the heat dissipation film:

[0017] The film materials are Ni and Ge2Sb2Te5, the substrate is a high-purity silicon wafer, the selective emission film comprises a four-layer structure of Ni / crystalline Ge2Sb2Te5 / Ni / amorphous Ge2Sb2Te5, and the middle layer of crystalline Ge2Sb2Te5 is obtained by annealing after deposition.

[0018] As a preferred technical solution of the present invention, according to the structural composition, the selective absorption film is deposited and prepared using a high vacuum multi-target magnetron sputtering system, and both Ni and Ge2Sb2Te5 are sputtered by DC sputtering, and the sputtering powers are preferably 50W and 80W, respectively. After the deposition of the intermediate Ge2Sb2Te5 film layer, a vacuum tube furnace is used to anneal at 300°C to prepare a crystalline Ge2Sb2Te5 layer, and argon is used as a protective gas. The annealing time is 40±10 minutes. Because the component Te in the Ge2Sb2Te5 material will volatilize at a high heating temperature, it is necessary to shorten the annealing time and lower the temperature as much as possible to avoid the volatilization of the Ge2Sb2Te5 component and affect the performance of the film while ensuring that the conditions for complete crystallization are met, and to pass a protective gas to prevent the film from oxidizing during the annealing process.

[0019] As a preferred technical solution of the present invention, the thickness of each layer by DC sputtering is: Ni: 100nm±10nm; crystalline Ge2Sb2Te5: 90nm±10nm; Ni: 14nm±2nm; amorphous Ge2Sb2Te5: 320±50nm, preferably 320±20nm.

[0020] The present invention proposes a selective absorption film with a quasi-optical cavity structure based on a crystalline and amorphous GST multilayer film. It has low emission in the atmospheric infrared window (ε=32.6%) and high emission outside the window (ε=67.8%), which means superior infrared camouflage and radiation heat dissipation performance, and the selective emitter has a lower contrast with the background in the infrared camera. In addition, by changing the thickness of the uppermost amorphous Ge2Sb2Te5 layer, the absorption peak of the selective absorption film can be easily changed.

[0021] The infrared stealth and radiation regulation dual-function film provided by the present invention has the following advantages:

[0022] (1) The low emissivity in the spectral range (3-5, 8-13 μm) required for infrared stealth and the high emissivity in the range (5-8 μm) required for heat dissipation achieve an excellent dual-function combination.

[0023] (2) Low cost and large-area application capability, excellent performance can be achieved using only two materials and a simple preparation process.

[0024] (3) It has the potential to adapt to different working environments, and its spectrally selective absorption performance can be adjusted by simply changing the thickness of the top film layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 .The designed infrared stealth and radiation regulation selective absorption film. (a) Schematic diagram of the film structure, simulation and experimental emission spectra. (b) Schematic diagram of the electromagnetic loss simulation of the film.

[0026] Figure 2 .(a) XRD patterns and (b) changes in optical constants n and k of crystalline and amorphous Ge2Sb2Te5 materials before and after annealing.

[0027] Figure 3 . Comparison of infrared photos of the sample (left) and silicon wafer (right) at 25, 45, 60 and 100°C.

[0028] Figure 4 .Changes in the spectral emission peak of the top amorphous Ge2Sb2Te5 layer when its thickness is 274, 320 and 366nm respectively. DETAILED DESCRIPTION

[0029] The present invention is further described below in conjunction with embodiments and drawings, but the present invention is not limited thereto:

[0030] Example 1 Preparation of infrared stealth and radiation heat dissipation film based on Ge2Sb2Te5

[0031] The infrared stealth and radiation control selective emission thin film materials are Ni and Ge2Sb2Te5, and the substrate is a high-purity silicon wafer. Figure 1 As shown, the selective emission film includes a four-layer structure of Ni / crystalline Ge2Sb2Te5 / Ni / amorphous Ge2Sb2Te5, and the middle layer of crystalline Ge2Sb2Te5 is obtained by annealing after deposition.

[0032] The selective absorption film was deposited using a high vacuum multi-target magnetron sputtering system. Both Ni and Ge2Sb2Te5 were sputtered using DC sputtering, with sputtering powers of 50 W and 80 W, respectively. After the deposition of the middle Ge2Sb2Te5 film layer, a vacuum tube furnace was used to anneal at 300°C to prepare a crystalline Ge2Sb2Te5 layer, with argon as the protective gas, and the annealing time was 40±10 minutes.

[0033] The thickness of each layer is: Ni: 100nm±10nm; crystalline Ge2Sb2Te5: 90nm±10nm; Ni: 14nm±2nm; amorphous Ge2Sb2Te5: 320±20nm.

[0034] Example 2 Performance Testing of Film

[0035] The film prepared by Example 1 was tested and found to be:

[0036] Figure 1 (a) shows the emission spectrum of the prepared film, the black curve is the reflection spectrum measured by the prepared selective absorption film sample, and the blue curve is the emission spectrum of the simulated film structure. When only considering the normal incidence, the calculation formula of its emissivity can be simplified to:

[0037]

[0038] λ is the wavelength, M bλ is the blackbody radiation intensity at temperature T; R λ is the reflectivity of the absorber in the ultraviolet-visible-infrared spectrum, which can be measured using a Fourier transform infrared spectrometer. According to the above formula, the calculation results of the performance of the selective absorption film example are: when the sample operating temperature is 90°C, the emissivity is 32.6% in the atmospheric window (3-5, 8-13μm), and the emissivity outside the window (5-8μm) is 67.8%. Figure 1 (b) shows that the film's absorption of infrared light is mainly concentrated in the middle thin metal Ni layer.

[0039] Figure 2 The figure shows that the amorphous Ge2Sb2Te5 film layer is deposited by vacuum magnetron sputtering, and the crystalline Ge2Sb2Te5 material is obtained by annealing. The difference in the optical constants n and k of the two states of Ge2Sb2Te5 materials is also shown.

[0040] Figure 3 Pictures taken with an infrared camera showed that the sample had a lower apparent temperature than the silicon wafer in the field of view of the infrared camera, proving the infrared stealth capability of the thin film structure.

[0041] Figure 4 The researchers showed that the structure can adjust the spectral emission peak position by adjusting the thickness of the top amorphous Ge2Sb2Te5 layer. The thin film structure has the potential to be designed to adapt to different working environments through simple changes.

[0042] The above contents are further detailed descriptions of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as falling within the protection scope of the present invention.

Claims

1. Infrared stealth and radiation heat dissipation film based on Ge2Sb2Te5, characterized in that: The film is a selective absorption film, and the film is a four-layer structure of Ni / crystalline Ge2Sb2Te5 / Ni / amorphous Ge2Sb2Te5; the thickness of each layer is respectively, Ni: 100nm±10nm; crystalline Ge2Sb2Te5: 90nm±10nm; Ni: 14nm±2nm; amorphous Ge2Sb2Te5: 320±50nm, and the preparation method of the film includes: The thin film materials are selected as Ni and Ge2Sb2Te5, the substrate is a high-purity silicon wafer, and the middle layer of crystalline Ge2Sb2Te5 is obtained by post-deposition annealing; The selective absorption film is deposited and prepared using a high vacuum multi-target magnetron sputtering system, and both Ni and Ge2Sb2Te5 are sputtered using direct current sputtering; By changing the thickness of the top amorphous Ge2Sb2Te5 layer, the absorption peak of the selective absorption film can be changed.

2. The film according to claim 1, characterized in that Amorphous Ge2Sb2Te5: 320±20nm.

3. The method for preparing the infrared stealth and radiation heat dissipation film based on Ge2Sb2Te5 according to any one of claims 1-2, characterized in that: The sputtering powers are 50W and 80W respectively.

4. The preparation method according to claim 3, characterized in that: The middle layer of crystalline Ge2Sb2Te5 is subjected to a post-deposition annealing process, which includes: after the middle Ge2Sb2Te5 film layer is deposited, a crystalline Ge2Sb2Te5 layer is prepared by annealing in a vacuum tube furnace.

5. The preparation method according to claim 4, characterized in that: The crystalline Ge2Sb2Te5 layer was prepared by annealing at 300°C for 40±10 min.

6. The preparation method according to claim 3, characterized in that: The annealing was performed under argon as a protective gas.

Images