CN110632687B - Metamaterial crystal structure capable of regulating and controlling electromagnetic wave absorption and preparation method thereof - Google Patents
Metamaterial crystal structure capable of regulating and controlling electromagnetic wave absorption and preparation method thereof Download PDFInfo
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Abstract
The invention provides a metamaterial crystal structure capable of regulating and controlling electromagnetic wave absorption and a preparation method thereof, wherein the preparation method comprises the following steps: providing a blazed grating substrate, wherein a periodically arranged sawtooth array structure is formed on the surface of the blazed grating substrate and comprises a first groove surface with a first inclination angle and a second groove surface with a second inclination angle; forming an alternative multilayer film structure on a blazed grating substrate, wherein the alternative multilayer film structure comprises a plurality of metamaterial structure units, a plurality of metamaterial structure units and a plurality of grating structure units, the metamaterial structure units comprise a first equivalent dielectric constant unit and a second equivalent dielectric constant unit, and an electromagnetic wave absorption interface is formed between the first equivalent dielectric constant unit and the second equivalent dielectric constant unit; the absorption coefficient of the electromagnetic wave can be effectively regulated and controlled by regulating and controlling the period P of the metamaterial crystal structure, namely the grating constant, and the metamaterial crystal structure does not need to be redesigned aiming at the absorption regulation and control of the electromagnetic wave of different frequency bands.
Description
Technical Field
The invention belongs to the technical field of electromagnetic metamaterials, and particularly relates to a metamaterial crystal structure capable of regulating and controlling electromagnetic wave absorption and a preparation method thereof.
Background
At present, with the rapid development of micro-nano processing technology, novel artificial microstructures are continuously emerging, wherein the electromagnetic metamaterial is an artificial microstructure formed by an electromagnetic response unit array with sub-wavelength or deep sub-wavelength. Compared with the traditional electromagnetic material, the electromagnetic metamaterial can control transmission of electromagnetic waves and interaction of the electromagnetic waves and substances more flexibly. For example, the dielectric constant and the magnetic permeability of the specially designed metamaterial can be negative at the same time, so that negative refraction transmission of electromagnetic waves is realized, which is a characteristic that natural materials do not have; meanwhile, the metamaterial regulates the interaction of electromagnetic waves and substances, so that novel electromagnetic devices such as invisible clothes, super lenses, artificial black holes (wave absorbers) and the like can be realized. Therefore, the electromagnetic metamaterial greatly expands an electromagnetic material library and realizes more flexible electromagnetic wave control.
Among them, the regulation of the electromagnetic wave absorption characteristic is particularly important for an electro-optical device, an electromagnetic wave detector, and the like. At present, the regulation and control of electromagnetic wave absorption characteristics mainly utilize the intrinsic absorption of natural materials to electromagnetic waves, and the average effect of artificial microstructure unit arrays or metamaterials to electromagnetic wave absorption. Compared with natural materials, the artificial microstructure or metamaterial has richer electromagnetic properties, but the artificial microstructure or metamaterial with a specific structure is usually only effective on electromagnetic waves with specific frequency (section) and has no universality; therefore, for electromagnetic waves of different frequencies (bands), artificial microstructures or metamaterial structures with different structures are often required to be designed.
Therefore, how to provide a metamaterial crystal structure for regulating and controlling electromagnetic wave absorption to realize the characteristics of wide spectrum absorption and the like and play application potential in the aspect of photoelectric devices such as high-efficiency solar cells and the like is really necessary.
Disclosure of Invention
In view of the above-mentioned shortcomings of the prior art, an object of the present invention is to provide a metamaterial crystal structure capable of regulating and controlling electromagnetic wave absorption and a method for manufacturing the same, which are used to solve the problems that in the prior art, an artificial microstructure or a metamaterial is often only effective for electromagnetic waves of a specific frequency (band) and cannot flexibly regulate and control the electromagnetic wave absorption characteristics of each frequency band.
In order to achieve the above objects and other related objects, the present invention provides a method for preparing a metamaterial crystal structure capable of regulating and controlling electromagnetic wave absorption, comprising the steps of:
1) providing a blazed grating substrate, wherein a sawtooth array structure which is periodically arranged is formed on the surface of the blazed grating substrate, and a single sawtooth array structure period comprises a first groove surface with a first inclination angle and a second groove surface which is connected with the first groove surface and has a second inclination angle; and
2) forming an alternating multilayer film structure on the blazed grating substrate, wherein the alternating multilayer film structure comprises a plurality of metamaterial structure units corresponding to a single sawtooth-shaped array structure period, and the metamaterial structure units comprise first equivalent dielectric constant units located on the first groove surface and second equivalent dielectric constant units located on the second groove surface;
the equivalent dielectric constant of the first equivalent dielectric constant unit is different from the equivalent dielectric constant of the second equivalent dielectric constant unit, so that an electromagnetic wave absorption interface is formed between the first equivalent dielectric constant unit and the second equivalent dielectric constant unit, and the metamaterial crystal structure capable of regulating and controlling electromagnetic wave absorption is formed.
In a preferable embodiment of the present invention, in step 2), the thickness of the single-layer film layer in the alternating multilayer film structure is less than 1/10 of the wavelength of the incident wave.
As a preferable mode of the present invention, in the step 2), an absorption coefficient of the electromagnetic wave is adjusted according to a size of a single period of the zigzag array structure, wherein the absorption coefficient of the electromagnetic wave increases as the single period of the zigzag array structure decreases.
As a preferable scheme of the present invention, in step 2), the alternating multilayer film structure is formed by alternately stacking at least two film layer units made of different materials, and the material of the film layer unit corresponds to the frequency band of the electromagnetic wave to be regulated.
As a preferable aspect of the present invention, the alternating multilayer film structure includes a first film unit and a second film unit, the first film unit and the second film unit are alternately stacked, and a thickness ratio of the first film unit to the second film unit is set according to a desired equivalent dielectric constant of the alternating multilayer film structure.
As a preferable mode of the present invention, in step 1), the blazed grating substrate includes a single crystal material substrate.
As a preferable aspect of the present invention, in step 1), in a single period of the zigzag array structure, the arrangement manner of the first groove surface and the second groove surface includes any one of a symmetrical arrangement and an asymmetrical arrangement.
As a preferable scheme of the present invention, in step 1), the mode of forming the periodically arranged zigzag array structure on the surface of the blazed grating substrate is selected from any one of low-energy ion irradiation, anisotropic etching, high-temperature annealing, imprint technology, and semiconductor heteroepitaxy technology.
As a preferable embodiment of the present invention, the performing of the low-energy ion irradiation further includes: and simultaneously heating the blazed grating substrate, wherein the temperature for heating is between the recrystallization temperature of the blazed grating substrate material and the Ehrlich-Schwoebel barrier failure temperature of the material surface step.
As a preferable aspect of the present invention, the characteristic absorption peak of the electromagnetic wave is adjusted by adjusting any one of the first tilt angle, the second tilt angle, the material of the alternating multilayer film structure, and the thickness ratio between the single-layer film layers in the alternating multilayer film structure.
The invention also provides a metamaterial crystal structure capable of regulating and controlling electromagnetic wave absorption, which comprises:
the blazed grating comprises a blazed grating substrate, wherein a sawtooth array structure is formed on the surface of the blazed grating substrate in periodic arrangement, wherein the period of a single sawtooth array structure comprises a first groove surface with a first inclination angle and a second groove surface with a second inclination angle, and the second groove surface is connected with the first groove surface; and
the alternating multilayer film structure is positioned on the blazed grating substrate and comprises a plurality of metamaterial structure units corresponding to a single sawtooth-shaped array structure period, and the metamaterial structure units comprise first equivalent dielectric constant units positioned on the first groove surface and second equivalent dielectric constant units positioned on the second groove surface;
the equivalent dielectric constant of the first equivalent dielectric constant unit is different from the equivalent dielectric constant of the second equivalent dielectric constant unit, so that an electromagnetic wave absorption interface is formed between the first equivalent dielectric constant unit and the second equivalent dielectric constant unit.
As a preferable mode of the present invention, the absorption coefficient of the electromagnetic wave is adjusted according to the size of the period of the single sawtooth-shaped array structure, and the absorption coefficient of the electromagnetic wave increases with the decrease of the period of the single sawtooth-shaped array structure; and adjusting the characteristic absorption peak of the electromagnetic wave by adjusting any one of the first inclination angle, the second inclination angle, the material of the single-layer film layers in the alternating multilayer film structure and the thickness ratio between the single-layer film layers in the alternating multilayer film structure.
As a preferable scheme of the present invention, the alternating multilayer film structure is formed by alternately stacking film layer units made of at least two different materials, and the material of the film layer units corresponds to the frequency band of the electromagnetic wave to be regulated; the blazed grating substrate comprises a single crystal material substrate.
In a preferred embodiment of the present invention, the thickness of the single-layer film layer in the alternating multilayer film structure is less than 1/10 of the wavelength of the incident wave.
As described above, the metamaterial crystal structure capable of regulating and controlling electromagnetic wave absorption and the preparation method thereof of the present invention have the following beneficial effects: the metamaterial crystal structure capable of regulating and controlling electromagnetic wave absorption provided by the invention can regulate and control the absorption of electromagnetic waves as required, and can accurately regulate and control the characteristic absorption peak of electromagnetic waves by regulating and controlling the interface wave vector supported by the metamaterial crystal structure, the material parameters of the multilayer film and the blaze angle of the grating; the absorption coefficient of the electromagnetic wave can be effectively regulated and controlled by regulating and controlling the period P of the metamaterial crystal structure, namely the grating constant. Meanwhile, the metamaterial crystal structure provided by the invention is effective in regulating and controlling the absorption characteristics of electromagnetic waves of various frequency bands, and the metamaterial crystal structure does not need to be redesigned aiming at the absorption regulation and control of the electromagnetic waves of different frequency bands.
Drawings
FIG. 1 shows a flow chart of a process for preparing a crystalline structure of a metamaterial according to the present invention.
Fig. 2 shows a schematic structural diagram of a blazed grating substrate provided in the preparation of the metamaterial crystal structure provided by the present invention.
FIG. 3 is a schematic diagram illustrating the formation of an alternating multilayer film structure in the preparation of a crystalline structure of a metamaterial according to the present invention.
Fig. 4 shows an absorption curve of a metamaterial crystal structure provided in an example of the present invention and a conventional flat multilayer film.
Fig. 5 shows the absorption profile of the metamaterial crystal structure provided in an example of the invention as a function of the grating period.
Fig. 6 shows the absorption curve of the metamaterial crystal structure provided in the examples of the present invention as a function of the blaze angle of the grating.
FIG. 7 is a schematic view of an alternate multilayer film structure having different tilt angles.
Description of the element reference numerals
100 blazed grating substrate
101 zigzag array structure
101a first groove surface
101b second groove surface
200 alternating multilayer film structure
201 metamaterial unit structure
200a first film layer unit
200b second film layer unit
201a first equivalent permittivity unit
201b second equivalent permittivity unit
S1-S2 steps 1) -2)
Detailed Description
The embodiments of the present invention are described below with reference to specific embodiments, and other advantages and effects of the present invention will be easily understood by those skilled in the art from the disclosure of the present specification. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention.
Please refer to fig. 1 to 7. It should be noted that the drawings provided in the present embodiment are only schematic and illustrate the basic idea of the present invention, and although the drawings only show the components related to the present invention and are not drawn according to the number, shape and size of the components in actual implementation, the form, quantity and proportion of the components in actual implementation may be changed arbitrarily, and the layout of the components may be more complicated.
As shown in fig. 1 to 3, the present invention provides a method for preparing a metamaterial crystal structure capable of regulating electromagnetic wave absorption, comprising the following steps:
1) providing a blazed grating substrate, wherein a sawtooth array structure which is periodically arranged is formed on the surface of the blazed grating substrate, and a single sawtooth array structure period comprises a first groove surface with a first inclination angle and a second groove surface which is connected with the first groove surface and has a second inclination angle; and
2) forming an alternating multilayer film structure on the blazed grating substrate, wherein the alternating multilayer film structure comprises a plurality of metamaterial structure units corresponding to a single sawtooth-shaped array structure period, and the metamaterial structure units comprise first equivalent dielectric constant units located on the first groove surface and second equivalent dielectric constant units located on the second groove surface;
the equivalent dielectric constant of the first equivalent dielectric constant unit is different from the equivalent dielectric constant of the second equivalent dielectric constant unit, so that an electromagnetic wave absorption interface is formed between the first equivalent dielectric constant unit and the second equivalent dielectric constant unit, and the metamaterial crystal structure capable of regulating and controlling electromagnetic wave absorption is formed.
The metamaterial crystal structure capable of regulating electromagnetic wave absorption and the preparation thereof according to the present invention will be described in detail with reference to the accompanying drawings.
First, as shown in S1 in fig. 1 and fig. 2, step 1) is performed to provide a blazed grating substrate 100, and a periodic zigzag array structure 101 is formed on a surface of the blazed grating substrate 100, wherein a single period P of the zigzag array structure includes a first groove surface 101a having a first inclination angle θ 1 and a second groove surface 101b connected to the first groove surface 101a and having a second inclination angle θ 2.
As an example, in step 1), the blazed grating substrate 100 comprises a single crystal material substrate.
Specifically, a blazed grating substrate 100 is first provided to provide a structural foundation for the subsequent formation of the alternating multilayer film structure 200, wherein preferably, the material of the blazed grating substrate 100 is preferably a single crystal material or a non-single crystal metal material to facilitate the formation of a stable sawtooth type blazed grating structure, i.e., the periodically arranged sawtooth array structure 101, and in a preferred embodiment, the single crystal substrate has lattice symmetry and is suitable for preparing a grating substrate by using its own symmetry, such as low energy ion irradiation, anisotropic etching and high temperature annealing, and the material of the blazed grating substrate 100 may be gallium arsenide (GaAs), indium arsenide (InAs), silicon (Si), copper (Cu), Al (Al), or a combination thereof2O3And the like, but is not limited to, a single crystal semiconductor or metallic material, and as in other examples, may also be a non-single crystal material substrate, such as may be produced using "imprinting" techniques.
For example, in step 1), in a single period P of the zigzag array structure, the first groove surface 101a and the second groove surface 101b are disposed in a symmetrical manner or an asymmetrical manner.
Specifically, in this example, the arrangement of the zigzag array structure is provided, and a symmetrical and an asymmetrical groove surface design is performed, and the design is performed according to the different dispersion relations of the electromagnetic wave absorption cross sections, so that the control of the electromagnetic wave absorption is facilitated.
As an example, in step 1), the manner of forming the periodically arranged zigzag array structures 101 on the surface of the blazed grating substrate 100 is selected from any one of low-energy ion irradiation, anisotropic etching, high-temperature annealing, imprinting technology, and semiconductor hetero-epitaxy technology.
As an example, the low-energy ion irradiation process further includes a step of simultaneously performing a heating process on the blazed grating substrate 100, wherein the temperature for performing the heating process is between the recrystallization temperature of the blazed grating substrate material and the Ehrlich-Schwoebel barrier failure temperature of the material surface step.
Specifically, the mode of forming the periodically arranged zigzag array structures 101 on the surface of the blazed grating substrate 100 is selected from any one of low-energy ion irradiation, anisotropic etching and high-temperature annealing, wherein the temperature of the high-temperature annealing is different according to the used materials, for example, aluminum oxide is annealed at 1400 ℃ to form a grating structure, and the anisotropic etching process includes anisotropic wet etching.
In addition, in a preferred embodiment, the ion beam irradiation is selected to be low-energy ion irradiation, the ion beam can be used for normally and vertically irradiating the surface of the substrate, and other adjustable incident angles can also be used+，Ne+，Ar+，Kr+，Xe+Inert gases, or other gas sources, e.g. N+，O+Plasma ion, ion sputtering, requires vacuum conditions, e.g. in a vacuum chamber at a pressure of 10 deg.f-3The ion energy is below 50 eV-10 keV, and the beam density and the ion flux density of the ion beam are 0-1017cm-2s-1Preferably between 1014cm-2s-1To 1017cm-2s-1Ion dose of 1016cm-2and 1020cm-2, the ion irradiation time depends on the specific process conditions and is generally between 10 minutes and 200 minutes. In order to make the substrate surface irradiated under the same condition, the ion beam can adopt a wide beam with a large cross section, and when the ion beam is irradiated, the size of the wide beam covers the whole area of the blazed grating substrate 100, which needs to prepare the sawtooth-shaped array structure 200, so that the sawtooth-shaped array structure 2 with a large area can be formed by one-step irradiation00。
Preferably, when the sawtooth array structure 101 is prepared on the surface of the single crystal blazed grating substrate 100, the substrate is heated, and meanwhile, the single crystal substrate is heated by ion irradiation sputtering, so that the preparation of the sawtooth array structure on the surface is realized. For blazed grating substrate materials, such as InAs and GaAs, although the surface layer of the material may generate heat due to the input of ion energy during the ion irradiation process, additional heating is required during the nano-patterning process to achieve the optimal conditions for the preparation of the nano-patterning. In particular, crystal defects due to ions can be effectively annealed under certain temperature conditions. In addition, increasing the heat input to the sample surface by increasing the ion beam current also generally increases the lattice defects of the crystal, which affects the crystal quality of the prepared nanostructure. Therefore, the nano-patterned sample can be heated by an additional heat source such as a heating plate which is irrelevant to the self-heating effect of the ion beam, so as to achieve the optimal condition for preparing the single crystal and regular zigzag array structure array in the invention. The surface of the nano-prepared material faces to the surface of the material layer at the normal incidence of the ion beam. According to an embodiment, the material to be structured is heated from the rear side during the production of the structure. For example, one can use as heating means an element (for example a hot plate) in contact with the back of the layer of material to be structured. Generally, the energy of the ions in the ion beam is high enough to cause a large number of defects on the irradiated surface or to cause amorphization of the surface, but in the present invention, when ion irradiation sputtering is performed, the irradiated substrate surface is heated to a high enough temperature so that defects such as Frenkel defects, vacancies and interstitial atoms are created on the substrate surface, and the surface created vacancies can diffuse and redistribute and aggregate into a void structure of reactive crystal symmetry. The diffusion constant of surface vacancies is affected by temperature, increasing with increasing temperature. According to the embodiment, the diffusion of the vacancy is completed on the surface of the irradiated material, the single crystal characteristic and the regularity of the prepared zigzag array structure are greatly improved, and the prepared zigzag nano structure has complete single crystal characteristic. The substrate material is heated during the ion irradiation process, preferably to a temperature above the recrystallization temperature of the material itself, the maximum temperatureThe degree does not exceed the Ehrlich-Schwoebel barrier failure temperature of the material, so that defects introduced on the surface of the material by ion irradiation can be effectively repaired by annealing. For the diffusion of vacancies or atoms at the crystal surface, there is a barrier at the edge of the crystal surface step that constrains the diffusion of atoms or vacancies, which is commonly referred to as the Ehrlich-Schwoebel barrier (also known as ES barrier), where the Ehrlich-Schwoebel barrier has an energy EESCorresponding temperature, i.e. activation temperature TESSatisfies equation EES＝kTES(k is Boltzmann constant). Thus, when the structuring temperature is at its highest, the thermal energy of the atoms in the material at this temperature is just equal to the Ehrlich-Schwoebel barrier energy.
Then, as shown in S2 in fig. 1 and fig. 3, step 2) is performed to form an alternating multilayer film structure 200 on the blazed grating substrate 100, where the alternating multilayer film structure 200 includes a plurality of metamaterial structural units 201 corresponding to a single period of the zigzag array structure, and the metamaterial structural units include a first equivalent dielectric constant unit 201a on the first groove surface 101a and a second equivalent dielectric constant unit 201b on the second groove surface 101 b;
the equivalent dielectric constant of the first equivalent dielectric constant unit 201a is different from the equivalent dielectric constant of the second equivalent dielectric constant unit 201b, so that an electromagnetic wave absorption interface is formed between the first equivalent dielectric constant unit and the second equivalent dielectric constant unit to form the metamaterial crystal structure capable of regulating and controlling electromagnetic wave absorption.
As an example, in step 2), the alternating multilayer film structure 200 is formed by alternately stacking at least two film layer units made of different materials, and the material of the film layer unit corresponds to the frequency band of the electromagnetic wave to be regulated.
Specifically, in this step, the alternating multilayer film structure 200 is prepared on the blazed grating substrate 100, wherein the method for preparing the alternating multilayer film structure 200 may be conventional processes such as electron beam evaporation, sputtering, or thermal evaporation, and details are not repeated here. At least two different film layers of the alternating multilayer film structure 200 are formed by periodic alternation, the material of the film layer unit corresponds to the frequency band of the electromagnetic wave to be regulated, the dielectric constants of different materials are different, the equivalent dielectric constant converted by the equivalent dielectric constant theory is naturally different, and the different dielectric constants naturally correspond to different electromagnetic wave responses. For example, if the periodic multilayer film is composed of A, B two film layers, the alternating multilayer film structure may be A, B, A, B, A, B … periodic stacked structure; if the alternating multilayer film structure is composed of A, B, C three film layers, the alternating multilayer film structure may be A, B, C, A, B, C, A, B, C … periodic stacked structures, and so on.
As an example, in step 2), the thickness of the single-layer film layer in the alternating multilayer film structure 200 is smaller than the incident wave wavelength. As an example, in step 2), the thickness of the single-layer film layers in the alternating multilayer film structure 200 is less than 1/10 of the wavelength of the incident wave.
Specifically, in this example, the thickness of the single-layer film layer in the alternating multilayer film structure 200 is selected to be smaller than 1/10 of the incident wave wavelength, preferably the thickness of the single-layer film layer is smaller than 1/20 of the incident wave wavelength, and further preferably smaller than 1/30 of the incident wave wavelength, so that the alternating multilayer film structure can be conveniently described by using an equivalent medium theory, which is further beneficial to regulation and control of electromagnetic wave absorption by the metamaterial structure of the present invention.
As an example, the alternating multilayer film structure includes a first film layer unit 200a and a second film layer unit 200b, wherein the first film layer unit 200a and the second film layer unit 200b are alternately stacked, and a thickness ratio of the first film layer unit 200a to the second film layer unit 200b is set according to a desired equivalent dielectric constant of the alternating multilayer film structure.
As an example, in step 2), the size of the period P of a single sawtooth-shaped array structure 101 is adjusted, wherein the absorption coefficient of the electromagnetic wave increases as the period of the single sawtooth-shaped array structure decreases.
As an example, the characteristic absorption peak of the electromagnetic wave is adjusted by adjusting any one of the first inclination angle θ 1, the second inclination angle θ 2, the material of the single-layer film layers in the alternating multilayer film structure, and the thickness ratio between the single-layer film layers in the alternating multilayer film structure.
In particular, in the metamaterial crystal structure provided by the invention, the appearance of the sawtooth-shaped array structure of the blazed grating substrate is repeatedly engraved by the alternating multilayer film structure, in the invention, the electromagnetic wave absorption interface is introduced, i.e., the interface formed between the first equivalent permittivity unit 201a and the second equivalent permittivity unit 201b, introduces additional absorption, the meta-material to which the present application relates, the absorption of the electromagnetic wave is concentrated on the electromagnetic wave absorption interface, but not on the surface, the response to the electromagnetic wave with different frequencies can be regulated and controlled by regulating and controlling the dispersion relation of the interface, the size of the period P of the sawtooth-shaped array structure is controlled, i.e., the grating constant, i.e., the size of the metamaterial unit 201, wherein the smaller the period P, the larger the number of interfaces per unit length, the more energy is absorbed, and thus the absorption coefficient of the electromagnetic wave increases. In addition, by adjusting the interface wave vector supported by the metamaterial crystal structure, that is, the material parameter (dielectric constant) of the multilayer film and the blaze angle of the blazed grating substrate, for example, adjusting the first tilt angle and the second tilt angle, the thickness ratio between the single-layer film layers in the alternating multilayer film structure, the selection of the material, and the like, these parameters affect the equivalent dielectric constant, the characteristic absorption peak of the electromagnetic wave can be accurately adjusted and controlled, and the absorption of the electromagnetic wave of different wave bands can be flexibly controlled as required.
In addition, it should be noted that the thickness ratio of the first film layer unit 200a to the second film layer unit 200b is set according to the required equivalent dielectric constant of the alternating multilayer film structure, wherein an equivalent Medium (Effective Medium) and a conversion Medium (Transformation Medium) can be described as follows: as shown in FIG. 7, which is a schematic view showing the structure of the alternating multilayer film having different tilt angles (+ α), FIG. 7(a) shows dielectric constants εdAnd εmA, B, the normal line of which is along the u direction; FIG. b shows an alternating multilayer film structure with an inclination angle- α; figure c shows an alternating multilayer film structure with an inclination angle + alpha.
For the structure shown in fig. 7(a), the equivalent dielectric constant can be obtained from the equivalent dielectric theory:
wherein epsilonu＝[fεB -1+(1-f)εA -1]-1,εv＝fεB+(1-f)εAAnd f is the fill ratio of material B (equivalent here to the percentage of the thickness of material B to the sum of the thicknesses of materials a and B, i.e., the ratio of the thicknesses of the first film-layer unit 200a and the second film-layer unit 200B). In combination with the theory of the conversion medium, for an alternating multilayer film structure with an inclination angle θ, the equivalent dielectric constant can be expressed as:
the equivalent dielectric constant corresponding to the structure shown in fig. 7 (b) is:
the equivalent dielectric constant corresponding to the structure shown in fig. 7 (c) is:
wherein the content of the first and second substances,
and
similarly, only epsilonxyThe terms are opposite numbers.
The invention also provides a metamaterial crystal structure capable of regulating and controlling electromagnetic wave absorption, which comprises:
the blazed grating comprises a blazed grating substrate 100, wherein a sawtooth array structure 101 which is periodically arranged is formed on the surface of the blazed grating substrate 100, and the period P of a single sawtooth array structure 101 comprises a first groove surface 101a with a first inclination angle theta 1 and a second groove surface 101b which is connected with the first groove surface 101a and has a second inclination angle theta 2;
an alternating multilayer film structure 200 on the blazed grating substrate 100, wherein the alternating multilayer film structure 200 comprises a plurality of metamaterial structure units 201 corresponding to a single period of the zigzag array structure, and the metamaterial structure units comprise first equivalent dielectric constant units 201a on the first groove surface 101a and second equivalent dielectric constant units 202b on the second groove surface 101 b;
the equivalent dielectric constant of the first equivalent dielectric constant unit 201a is different from the equivalent dielectric constant of the second equivalent dielectric constant unit 201b, so that an electromagnetic wave absorption interface is formed between the first equivalent dielectric constant unit and the second equivalent dielectric constant unit.
As an example, the blazed grating substrate 100 comprises a single crystal material substrate.
For example, in the period P of the single zigzag array structure 101, the arrangement manner of the first groove surface 101a and the second groove surface 101b includes any one of a symmetrical arrangement and an asymmetrical arrangement
Specifically, in a preferred embodiment, the material of the blazed grating substrate 100 is preferably a single crystal material or a non-single crystal metal material, so as to form a stable sawtooth type blazed grating structure, that is, the periodically arranged sawtooth array structure 101, and the material of the blazed grating substrate 100 may be gallium arsenide (GaAs), indium arsenide (InAs), silicon (Si), copper (Cu), Al, or a combination thereof2O3And the like, a single crystal semiconductor or a metal material, but is not limited thereto. In addition, the arrangement mode of the sawtooth array structure is designed by symmetrical and asymmetrical groove surfaces according to different dispersion relations of the electromagnetic wave absorption cross section, so that the regulation and control of the electromagnetic wave absorption are favorably controlled.
As an example, the absorption coefficient of the electromagnetic wave is adjusted according to the size of the single period of the zigzag array structure 101, and the absorption coefficient of the electromagnetic wave increases with the decrease of the single period of the zigzag array structure.
As an example, the characteristic absorption peak of the electromagnetic wave is adjusted by adjusting any one of the first inclination angle θ 1, the second inclination angle θ 2, the material of the single-layer film layers in the alternating multilayer film structure 200, and the thickness ratio between the single-layer film layers in the alternating multilayer film structure.
As an example, the alternating multilayer film structure 200 is formed by alternately stacking at least two film layer units made of different materials, and the material of the film layer units corresponds to the frequency band of the electromagnetic wave to be controlled.
In particular, in the metamaterial crystal structure provided by the invention, the appearance of the sawtooth-shaped array structure of the blazed grating substrate is repeatedly engraved by the alternating multilayer film structure, in the invention, the electromagnetic wave absorption interface is introduced, i.e., the interface formed between the first equivalent permittivity unit 201a and the second equivalent permittivity unit 201b, introduces additional absorption, the meta-material to which the present application relates, the absorption of the electromagnetic wave is concentrated on the electromagnetic wave absorption interface, but not on the surface, the response to the electromagnetic wave with different frequencies can be regulated and controlled by regulating and controlling the dispersion relation of the interface, the size of the period P of the sawtooth-shaped array structure is controlled, i.e., the grating constant, i.e., the size of the metamaterial unit 201, wherein the smaller the period P, the larger the number of interfaces per unit length, the more energy is absorbed, and thus the absorption coefficient of the electromagnetic wave increases. In addition, by regulating and controlling the interface wave vector supported by the metamaterial crystal structure, namely the material parameter (dielectric constant) of the multilayer film and the blazed angle of the blazed grating substrate, for example, by regulating the first inclination angle and the second inclination angle, the two parameters affect the equivalent dielectric constant, the characteristic absorption peak of the electromagnetic wave can be accurately regulated and controlled, and the absorption of the electromagnetic wave with different wave bands can be flexibly controlled according to the requirements.
As an example, the alternating multilayer film structure includes a first film layer unit 200a and a second film layer unit 200b, wherein the first film layer unit 200a and the second film layer unit 200b are alternately stacked, and a thickness ratio of the first film layer unit 200a to the second film layer unit 200b is set according to a desired equivalent dielectric constant of the alternating multilayer film structure.
As an example, the thickness of the single film layers in the alternating multilayer film structure is less than 1/10 of the wavelength of the incident wave.
Specifically, in this example, the thickness of the single-layer film layer in the alternating multilayer film structure 200 is selected to be smaller than 1/10 of the incident wave wavelength, preferably the thickness of the single-layer film layer is smaller than 1/20 of the incident wave wavelength, and further preferably smaller than 1/30 of the incident wave wavelength, so that the alternating multilayer film structure can be conveniently described by using an equivalent medium theory, which is further beneficial to regulation and control of electromagnetic wave absorption by the metamaterial structure of the present invention.
In addition, in order to illustrate the beneficial effects of the metamaterial crystal structure capable of regulating and controlling electromagnetic wave absorption and the preparation thereof, the invention also provides a specific example: a metamaterial crystal structure capable of regulating and controlling electromagnetic wave absorption comprises a blazed grating substrate with a period (grating constant) of 50nm and symmetrical groove surfaces, and a silver (Ag) and silicon (Si) alternating multilayer film structure above the blazed grating substrate. The blazed grating substrate is made of gallium arsenide (GaAs) single crystals, and the symmetrical groove surface blazed grating substrate with the period of 50nm is formed on the GaAs single crystal substrate through low-energy argon ion bombardment under the condition of specific window temperature; the blazed angle of the blazed grating is 18 degrees; and (3) alternately plating Ag and Si films with the thickness of 5nm on the blazed grating substrate for 5 periods by a magnetron sputtering process to form the alternating multilayer film structure.
Wherein fig. 4 is an absorption curve of the metamaterial crystal structure in the example, comparing the absorption curves of the flat multilayer film structure and the metamaterial crystal structure can find that: the metamaterial crystal structure regulates and controls the electromagnetic wave absorption of a 400-800 nm frequency band; the absorption regulation of the metamaterial crystal structure has wide incidence angle adaptability. FIG. 5 is a graph of the absorption rate curve of the metamaterial crystal in the example along with the grating period P, and the smaller the period P is observed, the larger the electromagnetic wave absorption coefficient is; the larger the period P, the smaller the electromagnetic wave absorption coefficient. FIG. 6 shows the variation of the absorption rate curve of the metamaterial crystal in the example along with the blaze angle of the grating, and the characteristic absorption peak of the electromagnetic wave can be adjusted along with the adjustment of the blaze angle through observation.
In summary, the present invention provides a method for preparing a metamaterial crystal structure capable of regulating electromagnetic wave absorption, comprising the following steps: 1) providing a blazed grating substrate, wherein a sawtooth array structure which is periodically arranged is formed on the surface of the blazed grating substrate, and a single sawtooth array structure period comprises a first groove surface with a first inclination angle and a second groove surface which is connected with the first groove surface and has a second inclination angle; and 2) forming an alternating multilayer film structure on the blazed grating substrate, wherein the alternating multilayer film structure comprises a plurality of metamaterial structure units corresponding to a single sawtooth-shaped array structure period, and the metamaterial structure units comprise a first equivalent dielectric constant unit positioned on the first groove surface and a second equivalent dielectric constant unit positioned on the second groove surface; according to the scheme, the metamaterial crystal structure capable of regulating and controlling electromagnetic wave absorption can regulate and control the absorption of electromagnetic waves as required, and characteristic absorption peaks of the electromagnetic waves can be accurately regulated and controlled by regulating and controlling interface wave vectors supported by the metamaterial crystal structure, material parameters of the multilayer film and a blaze angle of a grating; the absorption coefficient of the electromagnetic wave can be effectively regulated and controlled by regulating and controlling the period P of the metamaterial crystal structure, namely the grating constant. Meanwhile, the metamaterial crystal structure provided by the invention is effective in regulating and controlling the absorption characteristics of electromagnetic waves of various frequency bands, and the metamaterial crystal structure does not need to be redesigned aiming at the absorption regulation and control of the electromagnetic waves of different frequency bands. Therefore, the invention effectively overcomes various defects in the prior art and has high industrial utilization value.
The foregoing embodiments are merely illustrative of the principles and utilities of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or change the above-mentioned embodiments without departing from the spirit and scope of the present invention. Accordingly, it is intended that all equivalent modifications or changes which can be made by those skilled in the art without departing from the spirit and technical spirit of the present invention be covered by the claims of the present invention.
Claims (13)
1. A preparation method of a metamaterial crystal structure capable of regulating and controlling electromagnetic wave absorption is characterized by comprising the following steps:
1) providing a blazed grating substrate, wherein a sawtooth array structure which is periodically arranged is formed on the surface of the blazed grating substrate, and a single sawtooth array structure period comprises a first groove surface with a first inclination angle and a second groove surface which is connected with the first groove surface and has a second inclination angle; and
2) forming an alternating multilayer film structure on the blazed grating substrate, wherein the alternating multilayer film structure comprises a plurality of metamaterial structure units corresponding to a single sawtooth-shaped array structure period, and the metamaterial structure units comprise first equivalent dielectric constant units located on the first groove surface and second equivalent dielectric constant units located on the second groove surface;
the equivalent dielectric constant of the first equivalent dielectric constant unit is different from that of the second equivalent dielectric constant unit, so that an electromagnetic wave absorption interface is formed between the first equivalent dielectric constant unit and the second equivalent dielectric constant unit; and adjusting the equivalent dielectric constant of the first equivalent dielectric constant unit and the equivalent dielectric constant of the second equivalent dielectric constant unit by adjusting any one of the first inclination angle, the second inclination angle, the material of the single-layer film layers in the alternating multilayer film structure and the thickness ratio of the single-layer film layers in the alternating multilayer film structure, so as to adjust the characteristic absorption peak of the electromagnetic wave and realize the metamaterial crystal structure capable of adjusting and controlling the absorption of the electromagnetic wave.
2. The method for preparing a metamaterial crystal structure capable of regulating and controlling electromagnetic wave absorption as claimed in claim 1, wherein in the step 2), the thickness of the single-layer film layer in the alternating multilayer film structure is less than 1/10 of the wavelength of the incident wave.
3. The method as claimed in claim 1, wherein in step 2), the absorption coefficient of the electromagnetic wave is adjusted according to the period of the single sawtooth-shaped array structure, wherein the absorption coefficient of the electromagnetic wave increases as the period of the single sawtooth-shaped array structure decreases.
4. The method for preparing a metamaterial crystal structure capable of regulating electromagnetic wave absorption as claimed in claim 1, wherein in step 2), the alternating multilayer film structure is formed by alternately stacking film units made of at least two different materials, and the material of the film units corresponds to the frequency band of the electromagnetic wave to be regulated.
5. The method according to claim 4, wherein the alternating multilayer film structure comprises a first film unit and a second film unit, and wherein the first film unit and the second film unit are alternately stacked.
6. The method for preparing a metamaterial crystal structure capable of regulating electromagnetic wave absorption as claimed in claim 1, wherein in step 1), the blazed grating substrate comprises a single crystal material substrate.
7. The method as claimed in claim 1, wherein in step 1), the first groove surface and the second groove surface are disposed in a symmetrical or asymmetrical manner during a single period of the zigzag array structure.
8. The method for preparing a metamaterial crystal structure capable of regulating electromagnetic wave absorption as claimed in claim 1, wherein in the step 1), the mode of forming the zigzag array structure on the surface of the blazed grating substrate is selected from any one of low energy ion irradiation, anisotropic etching, high temperature annealing, imprinting technology and semiconductor heteroepitaxy technology.
9. The method for preparing a crystalline structure of metamaterial with controllable electromagnetic wave absorption as claimed in claim 8, wherein the performing of the low energy ion irradiation further comprises: and simultaneously heating the blazed grating substrate, wherein the temperature for heating is between the recrystallization temperature of the blazed grating substrate material and the Ehrlich-Schwoebel barrier failure temperature of the material surface step.
10. A metamaterial crystal structure capable of modulating electromagnetic wave absorption, comprising:
the blazed grating comprises a blazed grating substrate, wherein a sawtooth array structure is formed on the surface of the blazed grating substrate in periodic arrangement, wherein the period of a single sawtooth array structure comprises a first groove surface with a first inclination angle and a second groove surface with a second inclination angle, and the second groove surface is connected with the first groove surface; and
the alternating multilayer film structure is positioned on the blazed grating substrate and comprises a plurality of metamaterial structure units corresponding to a single sawtooth-shaped array structure period, and the metamaterial structure units comprise first equivalent dielectric constant units positioned on the first groove surface and second equivalent dielectric constant units positioned on the second groove surface;
the equivalent dielectric constant of the first equivalent dielectric constant unit is different from that of the second equivalent dielectric constant unit, so that an electromagnetic wave absorption interface is formed between the first equivalent dielectric constant unit and the second equivalent dielectric constant unit; and adjusting the equivalent dielectric constant of the first equivalent dielectric constant unit and the equivalent dielectric constant of the second equivalent dielectric constant unit by adjusting any one of the first inclination angle, the second inclination angle, the material of the single-layer film layers in the alternating multilayer film structure and the thickness ratio of the single-layer film layers in the alternating multilayer film structure, so as to adjust the characteristic absorption peak of the electromagnetic wave and realize the metamaterial crystal structure capable of adjusting and controlling the absorption of the electromagnetic wave.
11. The metamaterial crystal structure for controlling absorption of electromagnetic waves as claimed in claim 10, wherein the absorption coefficient of the electromagnetic waves is adjusted according to the period of the single sawtooth-shaped array structure, and the absorption coefficient of the electromagnetic waves increases with the period of the single sawtooth-shaped array structure.
12. The metamaterial crystal structure for controlling electromagnetic wave absorption of claim 10, wherein the alternating multilayer film structure is formed by alternately stacking film units made of at least two different materials, and the material of the film units corresponds to the frequency band of the electromagnetic wave to be controlled; the blazed grating substrate comprises a single crystal material substrate.
13. The metamaterial crystal structure for regulating electromagnetic wave absorption according to any one of claims 10-12, wherein the thickness of the single-layer film layers in the alternating multilayer film structure is less than 1/10 of the wavelength of the incident wave.
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