A near-field radiation filling structure and method based on hyperbolic materials

Abstract

The present invention relates to a near-field radiation filling structure and method based on hyperbolic materials. The near-field radiation filling structure based on hyperbolic materials includes an emitter, a filling layer, and a receiver connected in sequence. Among them, the material of the emitter is N-type doped silicon; the receiver is arranged parallel to the emitter, and the material of the receiver is N-type doped silicon; the emitter and the receiver are arranged parallel to each other, and the filling layer is arranged between the emitter and the receiver. The present invention can achieve the maximum excitation of the hyperbolic mode, greatly improving the heat flux. The parallel wave vector is greatly increased due to the excitation of the hyperbolic mode. Under the maximum excitation of the hyperbolic mode, more photons reach the surface of the receiving medium through the tunneling effect.

Description

Technical Field

[0001] The present invention relates to near-field radiative heat transfer materials, and particularly to a near-field radiative filling structure and method based on hyperbolic materials. Background Art

[0002] Currently, the energy issue has gradually become a resistance restricting the progress and development of human society. The main current energy source for humans is fossil energy. Due to its non-renewability and high environmental pollution, it is gradually falling behind the development of the times. Therefore, the technological breakthrough of sustainable, clean, low-carbon, safe, and efficient green energy is of crucial importance. In recent years, with the rise of micro-nano processing technology, thermophotovoltaic systems based on near-field thermal radiation have attracted much attention due to their proven high energy density and high conversion efficiency, and have great advantages in thermoelectric conversion fields such as waste heat recovery power generation.

[0003] The research on near-field thermal radiation began in the 1960s and 1970s. In 1967, Rytov first revolutionarily started from the wave perspective. Based on the stochastic Maxwell equations and the fluctuation-dissipation theorem, he regarded the energy transfer process as the emission, propagation (including scattering), and absorption of electromagnetic waves, and established the fluctuation electrodynamics for analyzing radiative heat transfer problems. This method is applicable to both far-field and near-field radiative heat transfer problems and has good generality. In 1971, D. Polder et al. first theoretically derived the near-field thermal radiation formula between two parallel plates. Due to the limitation of the micro-nano processing technology level at that time, the near-field thermal radiation phenomenon was not widely noticed. In recent years, as the component size gradually enters the micro-nano scale, the near-field thermal radiation phenomenon between objects has even become the dominant part of the total heat transfer and has received extensive attention, becoming a research hotspot in the field of thermal radiation.

[0004] Regarding the theoretical research on near-field radiative heat transfer, currently, it mainly focuses on the near-field thermal radiation between objects of different shapes and materials in a vacuum gap. The shapes include flat plates and flat plates, particles and spheres, etc., and the materials include isotropic materials, anisotropic materials, metamaterial surfaces, etc.

[0005] In 2011, Basu et al. studied the maximum near-field radiative heat transfer that can be achieved between two thin film flat plates of isotropic materials. The research shows that when the ratio D of the film thickness to the vacuum gap is equal to or less than 0.1, the maximum heat flux density is independent of D. With the rise of micro-nano processing technology, researchers have achieved breakthrough results in the field of near-field experiments, arousing great enthusiasm among near-field researchers. Currently, near-field radiative heat transfer experiments can be divided into: particle-flat plate, sphere-flat plate, flat plate-flat plate according to the system structure shape. Among them, the flat plate-flat plate experiment has received much attention because this structure is closest to the actual application scenarios, such as near-field thermophotovoltaic systems, chip heat dissipation, etc.

[0006] In 2018, Ghashami et al. developed a multifunctional near-field experimental device based on a nano-positioning platform and measured the near-field thermal radiation of a quartz sheet with a vacuum gap of nearly 200 nm. The near-field thermal radiation of the quartz sheet with a vacuum gap of nearly 200 nm.

[0007] In 2019, DeSutter developed a near-field radiative heat transfer device based on a millimeter-scale doped silicon surface, and achieved a significant enhancement of thermal radiation by using a precisely controlled vacuum gap (about 110 nm). The device separates the high-temperature emitter and the low-temperature receiver through a micro-column structure, and these micro-columns are fabricated in micron-scale deep pits, whose height is 4.5 to 45 times the nano-scale vacuum gap. Through this design, they successfully reduced the heat conduction significantly without damaging the structural integrity of the device, and achieved an enhancement of the near-field radiative heat flux about 28.5 times the blackbody radiation limit.

[0008] Great progress has been made in the experimental design of near-field radiation in the past decade. However, from the perspective of practical applications, the above three experimental methods all have their own disadvantages. For example, the locator control method requires a costly high-precision control system and needs to consider the problems of flat thermal deformation and surface roughness; the nano-column method will introduce unnecessary heat conduction and has high requirements for processing technology; the micro-electromechanical system control method has very limited application scenarios, etc. Therefore, various experimental devices developed in the current near-field research have not yet left the laboratory, and some new solutions still need to be explored.

[0009] All of the above reasons are ultimately due to the existence of the vacuum gap. Maintaining a vacuum gap at the micro-nano scale means high-precision control and processing methods. Therefore, the present invention abandons the traditional vacuum gap structure and proposes a filling structure model, which will provide a new idea for experimental design. Summary of the Invention

[0010] The present invention provides a near-field radiation filling structure based on hyperbolic materials, aiming to solve at least one of the technical problems existing in the prior art.

[0011] On the one hand, the technical solution of the present invention relates to a near-field radiation filling structure based on hyperbolic materials, and the near-field radiation filling structure based on hyperbolic materials includes an emitter, a filling layer, and a receiver connected in sequence, wherein,

[0012] The material of the emitter is N-type doped silicon; the receiver is arranged parallel to the emitter, and the material of the receiver is N-type doped silicon;

[0013] The emitter and the receiver are arranged parallel to each other, and the filling layer is arranged between the emitter and the receiver.

[0014] Further, the materials of the emitter and the receiver are made by doping nitrogen atoms into a pure silicon wafer, where the doping concentration of nitrogen atoms is 1×10 20 / cm 3 ,

[0015] In the low-frequency band , the real part of the dielectric function of the emitter and the receiver is negative, showing the characteristics of heavy metals;

[0016] In the transition frequency band , the emitter and the receiver neither behave as non-metals nor as dielectrics;

[0017] In the high-frequency band , the real part of the dielectric function of the emitter and the receiver is greater than 1, showing dielectric characteristics.

[0018] Further, the temperature of the emitter is 400K, the temperature of the receiver is 300K, and the thicknesses of the emitter and the receiver are 10 times the thickness of the filling layer.

[0019] Further, the thickness of the filling layer is 100 nm.

[0020] Further, the filling layer is made of a hyperbolic material, the hyperbolic material is an anisotropic material, and the product of the real parts in the parallel direction and the perpendicular direction of the hyperbolic material is negative.

[0021] Further, the hyperbolic material is a low-loss hyperbolic material, where

[0022] the imaginary part of the dielectric function of the low-loss hyperbolic material is:

[0023] .

[0024] Further, the hyperbolic material is hexagonal boron nitride hBN, and the optical axis of the hexagonal boron nitride hBN is perpendicular to the surfaces of the emitter and the receiver.

[0025] Further, since the hexagonal boron nitride hBN behaves as a low-loss hyperbolic material in both the first frequency band and the second frequency band , the hexagonal boron nitride hBN is set to work between the first frequency band and the second frequency band , where the first frequency band is:

[0026] ,

[0027] The second frequency band is:

[0028] .

[0029] On the other hand, the technical solution of the present invention relates to a preparation method of a near-field radiation filling structure based on hyperbolic materials, for preparing the near-field radiation filling structure based on hyperbolic materials. The preparation method of the near-field radiation filling structure based on hyperbolic materials includes:

[0030] S100. Respectively use two high-purity single-crystal silicon wafers, and sequentially remove the impurities on the surfaces of the high-purity single-crystal silicon wafers with HPM solution and DHF solution;

[0031] S200. Adopt a gas-phase diffusion method, place the cleaned single-crystal silicon wafers in a low-pressure chemical vapor deposition furnace, fill the gas-phase deposition furnace with ammonia gas and nitrogen gas, heat to 1000 °C to 1200 °C, and maintain for 5 hours to promote the diffusion of nitrogen atoms;

[0032] S300. Slowly cool the gas-phase deposition furnace to room temperature, and perform annealing treatment in a nitrogen atmosphere to obtain two pieces of uniformly doped heavy-doped silicon with a doping concentration of 1×10 20 / cm 3 ;

[0033] S400. Place the hexagonal boron nitride film between two pieces of heavy-doped silicon wafers, and make them closely connected by relying on the external mechanical pre-tightening force and the van der Waals force between atoms to form a near-field radiation filling structure based on hyperbolic materials.

[0034] On the other hand, the technical solution of the present invention relates to glass provided with the near-field radiation filling structure based on hyperbolic materials.

[0035] The beneficial effects of the present invention are as follows:

[0036] The near-field radiation filling structure and method based on hyperbolic materials of the present invention can achieve the maximum excitation of the hyperbolic mode, greatly improving the heat flux. The parallel wave vector is greatly increased due to the excitation of the hyperbolic mode. Under the maximum excitation of the hyperbolic mode, more photons reach the surface of the receiving polar medium through the tunneling effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 is a schematic diagram of the near-field radiation heat transfer model of the filling structure according to an embodiment of the present invention.

[0038] Figure 2 is a flow chart of studying the influence mechanism of near-field radiation heat transfer in the filling structure according to an embodiment of the present invention.

[0039] Figure 3 is the doping concentration according to an embodiment of the present invention Schematic diagram of the dielectric function of doped silicon

[0040] Figure 4 Spectral heat flux contrast diagram of an isotropic material filling structure according to an embodiment of the present invention

[0041] Figure 5 Spectral heat flux contrast diagram of different hyperbolic material filling structures according to an embodiment of the present invention

[0042] Figure 6 Transmission coefficient nephogram of different material fillings according to an embodiment of the present invention: (a) vacuum gap structure; (b) isotropic material filling structure; (c) hyperbolic material large imaginary part filling structure; (d) hyperbolic material small imaginary part filling structure

[0043] Figure 7 Schematic diagram of preparing a hexagonal boron nitride filled near-field thermophotovoltaic device according to an embodiment of the present invention

[0044] Figure 8 Dielectric constant diagram of hexagonal boron nitride according to an embodiment of the present invention: (a) Schematic diagram of the real part of the dielectric function varying with angular frequency in two directions; (b) Schematic diagram of the imaginary part of the dielectric function varying with angular frequency in two directions

[0045] Figure 9 Calculation results of the hexagonal boron nitride filling structure according to an embodiment of the present invention: (a) Spectral heat flux; (b) Total transmission coefficient nephogram

[0046] Figure 10 Flow chart of a preparation method of a near-field radiation filling structure based on hyperbolic materials according to an embodiment of the present invention Detailed implementation manners

[0047] The concept, specific structure and technical effects of the present invention will be clearly and completely described below in conjunction with embodiments and drawings to fully understand the purpose, solution and effects of the present invention. It should be noted that, without conflict, the embodiments in the present application and the features in the embodiments can be combined with each other

[0048] It should be noted that, unless otherwise specified, when a feature is referred to as "fixed" or "connected" to another feature, it can be directly fixed or connected to the other feature, or indirectly fixed or connected to the other feature. In addition, the up, down, left, right, top, bottom, etc. used in the present invention are only relative to the mutual positional relationship of the components of the present invention in the drawings

[0049] In addition, unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this technology belongs. The terms used in the description of this specification are only for describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any combination of one or more of the related listed items.

[0050] It should be understood that although the terms first, second, third, etc. may be used in this disclosure to describe various elements, these elements should not be limited to these terms. These terms are only used to distinguish elements of the same type from each other. For example, without departing from the scope of this disclosure, the first element may also be referred to as the second element, and similarly, the second element may also be referred to as the first element.

[0051] See Figures 1 to 10 , for the near-field radiation filling structure based on hyperbolic materials of the technical solution of the present invention, the near-field radiation filling structure based on hyperbolic materials includes an emitter, a filling layer, and a receiver connected in sequence, wherein,

[0052] the material of the emitter is N-type doped silicon; the receiver is arranged parallel to the emitter, and the material of the receiver is N-type doped silicon;

[0053] the emitter and the receiver are arranged parallel to each other, and the filling layer is arranged between the emitter and the receiver.

[0054] The beneficial effects of the present invention are as follows:

[0055] The near-field radiation filling structure and method based on hyperbolic materials of the present invention can achieve the maximum excitation of the hyperbolic mode, greatly improving the heat flux. The parallel wave vector is greatly increased due to the excitation of the hyperbolic mode. Under the maximum excitation of the hyperbolic mode, more photons reach the surface of the receiving medium through the tunneling effect.

[0056] Refer to Figure 1 , which shows the transmission paths of evanescent waves with the same wave vector (β) magnitude in different types of materials in the filling structure, Figure 1 in represents the thickness of the emitter and the receiver; represents the thickness of the filling layer; represents the wave vector, and the subscript represents the wave vector direction; represents the plane wave vector; represents the vacuum wave vector.

[0057] Refer to Figure 1 , ① indicates that when the filling layer is vacuum, at this time , the evanescent wave exponentially decays from the emitter to the receiver; ② indicates that when the filling layer is a non-hyperbolic material, there is still , the evanescent wave exponentially decays from the emitter to the receiver; ③ indicates that when the filling layer is a hyperbolic material, due to the existence of hyperbolic modes , the evanescent wave is converted into a propagating wave, extending the propagation length and effectively enhancing the radiation intensity.

[0058] Referring to Figure 2 , first, for the optical parameter changes of the filling material (such as refractive index, absorption coefficient), study its influence mechanism on near-field radiative heat transfer in the filling structure, and summarize the change trend of near-field radiative heat flux. Subsequently, by generating the transmission coefficient contour map, visually display the regulation effect of the material optical properties on the heat transfer performance and explain the internal energy transfer mechanism. Finally, taking actual materials as examples, conduct a comparative analysis with the vacuum gap model to illustrate the advantages and application potential of the filling structure.

[0059] Furthermore, the materials of the emitter and the receiver are made by doping nitrogen atoms in a pure silicon wafer, where the doping concentration of nitrogen atoms is 1×10 20 / cm 3 ,

[0060] In the low-frequency band , the real part of the dielectric function of the emitter and the receiver is negative, showing the characteristics of heavy metals;

[0061] In the transition frequency band , the emitter and the receiver neither show the characteristics of non-metals nor dielectrics;

[0062] In the high-frequency band , the real part of the dielectric function of the emitter and the receiver is greater than 1, showing the characteristics of dielectrics.

[0063] Specifically, referring to Figure 3 , for the screening of the optical parameters of the model materials, before studying the near-field radiative heat transfer mechanism of the filling structure, it is necessary to determine the optical parameters of each part of the material in the research model. First, regard the filling material as a hypothetical material and do not specify a specific thermal conductivity. Therefore, ignore the influence of heat conduction and multi-layer near-field thermal radiation, and regard it as composed of three semi-infinite parallel plates with uniform surfaces. The simplified three-layer filling flat plate structure model can be used for calculation.

[0064] Secondly, when considering the emitter and receiver materials, N-type doped silicon is selected as the parallel plate material on both sides of the emitter and receiver because it can excite broadband surface plasmon resonance and has many good properties such as adjustable optical parameters and easy preparation. The classic Drude model is used to characterize the dielectric function of doped silicon, and its expression is:

[0065]

[0066] in, is the plasma frequency of doped silicon, which is ; is the scattering rate, which is ; The contribution of band gap absorption and lattice vibration is about 11.7.

[0067] Reference Figure 3 , and the doping concentration is The dielectric function of doped silicon can be seen in the low frequency band When the real part of its dielectric function is negative, it exhibits heavy metal characteristics. The range belongs to the transition section, which neither behaves as non-metal nor as dielectric. When , the real part of its dielectric function is greater than 1, showing dielectric properties.

[0068] Furthermore, the temperature of the emitter is 400K, the temperature of the receiving electrode The temperature of the conductive layer is 300K, and the thickness of the emitter and the receiver is 10 times the thickness of the filling layer.

[0069] Specifically, in order to ensure that the two side plates are block structures rather than thin films, the temperature of the emitter Fixed to , the temperature of the receiving electrode Fixed to , and its thickness is always set to 10 times the distance between the two plates.

[0070] Furthermore, the thickness of the filling layer is 100 nm.

[0071] Furthermore, the filling layer is made of a hyperbolic material, the hyperbolic material is an anisotropic material, and the product of the real parts of the parallel direction and the vertical direction of the hyperbolic material is a negative number.

[0072] Specifically, for the selection of filling layer materials, according to the dispersion relationship, they can be divided into isotropic materials (non-hyperbolic materials) and hyperbolic materials.

[0073] according to and According to the magnitude relationship and signs, materials can be divided into four types, as shown in Table 1. Among them, dielectric materials and metallic materials can be called isotropic materials because the real and imaginary parts of the dielectric function are equal in all three directions. Hyperbolic materials belong to a special case of anisotropic materials, where the sign of the real part of the dielectric function in the parallel plane direction is opposite to that in the perpendicular plane direction.

[0074] Table 1, Material Classification Table

[0075]

[0076] First, we study non-hyperbolic materials, mainly isotropic materials as filling materials, and their optical parameters' laws and effects on near-field radiative heat transfer. Since the refractive index and extinction coefficient of isotropic materials, or rather, the real and imaginary parts of the dielectric constant, are equal in all three directions ( , ), near-field thermal radiation is only affected by two parameters and and changes accordingly.

[0077] To explore the influence of the change in the real part of the dielectric function on near-field radiation, the real values of the dielectric function of isotropic materials are selected as and ; at the same time, to explore the influence of the imaginary part of the dielectric function of isotropic materials on near-field radiation, the imaginary part of the dielectric function is reduced to . Combining them pairwise, there are a total of four material combination cases.

[0078] Referring to Figure 4 , the real and imaginary parts of the dielectric constant are introduced as variables to calculate the Fresnel reflection coefficient r. Taking the vacuum medium as the reference point, a comparison diagram of the spectral heat flux of the filled structure with four materials as the filling layer and the vacuum gap structure is plotted, showing the spectral heat flux diagram under the variation of the dielectric function of isotropic materials with the emitter temperature of 400K, the receiver temperature of 300K, the middle plate thickness of 100nm.

[0079] Referring to Figure 4 , the black curve represents the spectral heat flux curve of the traditional near-field thermal radiation model when the middle layer is vacuum, i.e., in the unfilled state. In this structure, due to the surface plasmon polaritons excited at the interface between doped silicon and vacuum, referring to Figure 4 , it can be clearly observed that there is an obvious peak in the spectral heat flux near the angular frequency , which is consistent with the calculation results of Basu et al.

[0080] The other four curves show two laws when isotropic materials with high refractive index are used as filling materials:

[0081] (1) When the real part of the dielectric constant of the filling material is equal and the imaginary part decreases, the spectral heat flux peak and the total heat slightly increase. This corresponds to or When unchanged, changing from 1 to 10 -3 When, due to the reduction of loss, it allows more wave vectors to pass through the intermediate medium to reach the acceptor, thus increasing the heat flux at each frequency.

[0082] (2) When the imaginary part of the dielectric constant of the filling material is equal and the real part increases, while the spectral heat flux peak and the total heat increase, the peak corresponding frequency point shifts to the left. This corresponds to or When unchanged, changing from 4 to 9, due to the increase of the Fresnel reflection coefficient, a stronger surface plasmon polariton is excited at the interface between the doped silicon and the filling material. This is still mainly contributed by the evanescent wave; at the same time, due to the change of the refractive index, the resonance frequency point between the media also shifts, resulting in the shift of the heat flux peak point. This means that in practical applications, such as a filled near-field thermophotovoltaic system, the optical parameters of the intermediate filling material can be adjusted to match a photovoltaic cell with a suitable bandgap, thereby improving the energy conversion efficiency of the cell.

[0083] At the same time, through Figure 4 it can be known that the near-field radiative heat flux of an isotropic material with a high refractive index and low loss as a filled structure is greatly improved compared with the traditional vacuum structure. The peak value is increased by 1 - 5 times, and the heat flux in other frequency bands is also higher than that of the traditional vacuum structure, significantly demonstrating the excellent performance and advantages of the filled structure.

[0084] The following are the near-field radiative heat transfer laws of hyperbolic materials:

[0085] Hyperbolic materials are not only anisotropic materials, but also the product of the real parts in its two directions is negative, which means that in two different directions, it can exhibit two different material characteristics. The calculation of the Fresnel reflection coefficient is more complex and is affected by four parameters, which are , , and . To facilitate observing the laws and reducing variables, the absolute values of the real parts in its parallel and perpendicular directions are set to be equal, that is ; the imaginary parts in the two directions are also set to be equal ; thus, compared with isotropic materials, only one additional real part variable in the perpendicular direction is introduced, which greatly reduces the data processing difficulty.

[0086] Refer to Figure 5, for comparison with isotropic materials, the same dielectric function value as that of the isotropic material when used as the filling material was selected, and the real part of the dielectric function of the hyperbolic material was respectively selected as and ; Similarly, in order to explore the influence of the imaginary part of the dielectric function in the hyperbolic material on near-field heat transfer, in this chapter, the imaginary part of the dielectric function was respectively set to and . Similarly, composed of four material combinations, compared with the vacuum gap structure, referring to Figure 5 , the near-field radiative heat transfer law when the filling material is a hyperbolic material is shown.

[0087] (1) Compared with the isotropic high refractive index and dielectric material, when the hyperbolic material is used as the filling material and the imaginary part is large, the spectral heat flux does not increase significantly, and there is no obvious shift in the corresponding frequency points; this corresponds to when , the real part of the dielectric function of the hyperbolic material or , its spectral heat flux is not significantly improved compared with the isotropic material with a high refractive index.

[0088] (2) When the imaginary part of the hyperbolic material is reduced by three orders of magnitude, the heat flux is greatly enhanced, and the peak value is 10 5 times that before the reduction of the imaginary part and 10 6 times that under vacuum filling. This corresponds to when the dielectric function of the hyperbolic material is or , reduced to , its heat flux is greatly enhanced.

[0089] Therefore, an important conclusion can be drawn from the above, that is, when the filling material is a low-loss hyperbolic material, the near-field radiative heat flux value can be greatly enhanced, and the lower the loss, the greater the enhancement effect.

[0090] Referring to Figure 6 , the total transmission coefficient contour maps of different structural situations are respectively shown. Through the contour maps, the contributions of the photon energies of the propagating wave and the evanescent wave in different frequency bands and different wave vector domains can be observed: Figure 6 (a) in shows that in the vacuum gap model, since there is only a single doped silicon surface SPPs excitation in the structure, its evanescent wave only contributes in the small wave vector domain and is concentrated at the Figure 6 frequency point; Similarly, Figure 6In (c), when the filling layer is a hyperbolic material with a large imaginary part, due to the coupling between the surface SPPs excitation of doped silicon and the hyperbolic modes (HMs) of the hyperbolic material, a completely different result is produced. According to the dispersion relation, in the hyperbolic mode, a parallel wave vector breaks through the vacuum wave vector limit, and the upper limit of its parallel wave vector becomes . The original evanescent wave is converted into a propagating wave that does not decay with distance, so that the photon energy has a higher contribution in the large wave vector domain. Figure 6 In (d), when the imaginary part of the hyperbolic material is small, since the photon energy is greatly reduced by the loss of the medium, more energy passes through in the large wave vector region, resulting in a huge increase in the near-field radiative heat flux.

[0091] It can be seen that the increase in the near-field radiative heat flux brought by using a low-loss hyperbolic material as the filling layer of the filling structure is huge, which means that under the filling material that satisfies the rules, the heat flux of near-field thermal radiation may be comparable to the heat flux of heat conduction. This further illustrates that the filling structure has excellent heat flux adjustable function, and at the same time greatly simplifies the difficulty of near-field radiative heat transfer experiments and large-scale applications.

[0092] Furthermore, the hyperbolic material is a low-loss hyperbolic material, and the imaginary part of the dielectric function of the low-loss hyperbolic material is:

[0093] .

[0094] In a specific embodiment, the real part of the dielectric function of the low-loss hyperbolic material is:

[0095] Or .

[0096] Furthermore, the hyperbolic material is hexagonal boron nitride hBN, and the optical axis of the hexagonal boron nitride hBN is perpendicular to the surfaces of the emitter and the receiver.

[0097] Specifically, the following is the calculation of near-field radiative heat transfer based on the hexagonal boron nitride filling structure:

[0098] Referring to Figure 7 , when the filling material is a hyperbolic material, that is, when the product of the real parts in the parallel and perpendicular directions is negative and the imaginary parts in both directions are small enough, the hyperbolic mode can be maximally excited, resulting in a great increase in the heat flux. Hexagonal boron nitride has the characteristics of being easy to prepare and stable.

[0099] Furthermore, since the hexagonal boron nitride hBN behaves as a low-loss hyperbolic material in the first frequency band and the second frequency band , the hexagonal boron nitride hBN is set to work in the first frequency band and the second frequency band therebetween, wherein the first frequency band is:[[]]

[0100] ,

[0101] the second frequency band is:[[]]

[0102] .

[0103] Referring to Figure 8 , hexagonal boron nitride is a hyperbolic material with low loss in each of and these two frequency bands. Figures 3 to 6 (a) in Figure 8 shows the curve of the real part of the dielectric constant of hexagonal boron nitride. Referring to

[0104] shows the curve of the imaginary part of the dielectric constant of hexagonal boron nitride, and the gray area represents the hyperbolic section, while the red area represents that the imaginary part in both directions is less than 0.01. In the remaining non-hyperbolic sections, it behaves as a non-hyperbolic material with a relatively high refractive index and low loss, and can also excite the SPPs effect to enhance the near-field radiative heat flux when used as a filling layer. Figure 9 Referring to

[0105] Figure 9 , when hexagonal boron nitride is used as the filling material, (a) in Figure 9 shows that its spectral heat flux in the entire frequency band is significantly improved compared with that in vacuum. Especially in the hyperbolic section, the first peak point is increased by about 100 times, and the second peak point is increased by about 1000 times, which proves the accuracy of the law.

[0106] In (b) in

[0107] , the abscissa represents the parallel wave vector normalized to the first Brillouin zone. It can be obtained from the total transmission coefficient contour map that the parallel wave vector is greatly improved due to the excitation of the hyperbolic mode, which means that more photons reach the surface of the receiving medium through the tunneling effect in this mode. Therefore, through the analysis of filling materials with different optical properties, the present invention reveals the internal heat transfer mechanism of the filling structure, and points out that at a spacing of 100 nm, the low-loss hyperbolic material can significantly extend the propagation length of the wave to the cut-off upper limit, and the heat flux intensity is increased by 5-6 orders of magnitude compared with the vacuum gap structure. And substituting hexagonal boron nitride as the filling material into the filling structure model, it is calculated that the near-field radiative heat flux of this model is 4000 times higher than that of the vacuum gap structure model under the same conditions.On the other hand, the technical solution of the present invention relates to a preparation method of a near-field radiation filling structure based on hyperbolic materials, which is used to prepare the near-field radiation filling structure based on hyperbolic materials. Referring to Figure 10 , the preparation method of the near-field radiation filling structure based on hyperbolic materials includes:

[0108] S100. Respectively use two high-purity single-crystal silicon wafers, and sequentially remove the impurities on the surfaces of the high-purity single-crystal silicon wafers with HPM solution and DHF solution;

[0109] S200. Adopt the gas-phase diffusion method, place the cleaned single-crystal silicon wafers in a low-pressure chemical vapor deposition furnace, fill the furnace with ammonia gas and nitrogen gas, heat to 1000°C to 1200°C, and maintain for 5 hours to promote the diffusion of nitrogen atoms;

[0110] S300. Slowly cool the low-pressure chemical vapor deposition furnace to room temperature, and perform annealing treatment in a nitrogen atmosphere to obtain two pieces of heavily doped silicon with a uniform doping concentration of 1×10 20 / cm 3 ;

[0111] S400. Place the hexagonal boron nitride film between the two pieces of heavily doped silicon wafers, and rely on the external mechanical pre-tightening force and the van der Waals force between atoms to make the two closely connected, forming a near-field radiation filling structure based on hyperbolic materials.

[0112] Specifically, in step S100, the thickness of the high-purity single-crystal silicon wafer is 1 micron; the component ratio of the HPM solution is HCl:H2O2:H2O = 1:1:5, and the temperature of the HPM solution is 70 - 90°C; the component ratio of the DHF solution is HF:H2O = 1:95, and the temperature of the DHF solution is 25 - 30°C.

[0113] On the other hand, the technical solution of the present invention relates to glass provided with the near-field radiation filling structure based on hyperbolic materials.

[0114] The above is only a preferred embodiment of the present invention. The present invention is not limited to the above embodiments. As long as it achieves the technical effects of the present invention by the same means, any modifications, equivalent replacements, improvements, etc., made within the spirit and principle of the present disclosure shall be included within the scope of protection of the present disclosure. All should belong to the scope of protection of the present invention. Within the scope of protection of the present invention, its technical solutions and / or implementation manners can have various different modifications and changes.

Claims

1. A near-field radiation filling structure based on hyperbolic materials, characterized in that: The near-field radiation filling structure based on hyperbolic materials comprises an emitter, a filling layer and a receiving electrode connected in sequence, wherein: The emitter is made of N-type doped silicon; the receiver is arranged in parallel with the emitter, and the receiver is made of N-type doped silicon; The emitter and the receiver are arranged in parallel, and the filling layer is arranged between the emitter and the receiver.

2. The near-field radiation filling structure based on hyperbolic material according to claim 1, characterized in that: The material of the emitter and the material of the receiver are made of pure silicon doped with nitrogen atoms, wherein the doping concentration of the nitrogen atoms is 1×10 20 / cm 3 , In the low frequency range When , the real parts of the dielectric functions of the emitter and the receiver are negative, showing heavy metal characteristics; In the transition frequency , the emitter and the receiving electrode are neither non-metallic nor dielectric; In the high frequency range When , the real part of the dielectric function of the emitter and the receiver is greater than 1, showing dielectric characteristics.

3. The near-field radiation filling structure based on hyperbolic material according to claim 1, characterized in that: The temperature of the emitter is 400K, the temperature of the receiving electrode The temperature of the conductive layer is 300K, and the thickness of the emitter and the receiver is 10 times the thickness of the filling layer.

4. The near-field radiation filling structure based on hyperbolic material according to claim 3, characterized in that: The thickness of the filling layer is 100 nm.

5. The near-field radiation filling structure based on hyperbolic material according to claim 1, characterized in that: The filling layer is made of a hyperbolic material, which is an anisotropic material, and the product of the real parts of the parallel direction and the vertical direction of the hyperbolic material is a negative number.

6. The near-field radiation filling structure based on hyperbolic material according to claim 5, characterized in that: The hyperbolic material is a low-loss hyperbolic material, wherein: The imaginary part of the dielectric function of a low-loss hyperbolic material is: 。 7. The near-field radiation filling structure based on hyperbolic material according to claim 1, characterized in that: The hyperbolic material is hexagonal boron nitride, and the optical axis of the hexagonal boron nitride is perpendicular to the surfaces of the emitter and the receiver.

8. The near-field radiation filling structure based on hyperbolic material according to claim 7, characterized in that: Since the hexagonal boron nitride is in the first frequency band and the second frequency band Both exhibit low-loss hyperbolic materials, and the hexagonal boron nitride is set to work in the first frequency band and the second frequency band between, wherein the first frequency band for: ， The second frequency band for: 。 9. A method for preparing a near-field radiation filling structure based on a hyperbolic material, used for preparing a near-field radiation filling structure based on a hyperbolic material as claimed in any one of claims 1 to 8, characterized in that: The preparation method of the near-field radiation filling structure based on hyperbolic material comprises: S100, using two high-purity single crystal silicon wafers respectively, and using HPM solution and DHF solution in turn to remove impurities on the surface of the high-purity single crystal silicon wafers; S200, using a vapor diffusion method, placing the cleaned single crystal silicon wafer in a low-pressure chemical vapor deposition furnace, filling the vapor deposition furnace with ammonia and nitrogen, heating to 1000° C. to 1200° C., and maintaining for 5 hours to promote the diffusion of nitrogen atoms; S300, slowly cool the vapor deposition furnace to room temperature and perform annealing in a nitrogen atmosphere to obtain two uniform doping concentrations of 1×10 20 / cm 3 Heavily doped silicon; S400, placing the hexagonal boron nitride film between two heavily doped silicon wafers, relying on external mechanical preload and interatomic van der Waals forces to tightly connect the two, forming a near-field radiation filling structure based on hyperbolic materials.

10. A glass, characterized in that: A near-field radiation filling structure based on a hyperbolic material as claimed in any one of claims 1 to 8 is provided.

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