KR20200006512A - Meta-material including core-shell particles - Google Patents

Abstract

The present invention relates to a meta-material comprising a plurality of core-shell particles arranged in a host material and an application thereof. A conductive material is used as the shell component, thereby controlling a capacitive effect between two particles.

Description

Meta-materials containing core-shell particles {META-MATERIAL INCLUDING CORE-SHELL PARTICLES}

The present application relates to metamaterials and applications thereof comprising a plurality of core-shell particles arranged in a host material.

Metamaterials have unusual optical properties that are not present in nature. These unusual optical properties include very high refractive indices, zero indices, and even negative indices. In addition, the meta-material is capable of polarization control through amplitude and phase control of electromagnetic waves. These properties can be obtained from the periodic arrangement of the unit cell, which is called metaatom (~ λ / 10), which is much smaller than the wavelength. Metaatoms have an artificially structured design and the geometrical parameters that form the unit cell provide various effective properties.

High refractive index metamaterials have a large real number of complex refractive indices, and the refractive indices of natural materials are very limited, so if you develop metamaterials with high refractive index over a wide frequency range, they are highly applicable and have high resolution imaging, waveguide, It can be used for grating or small form factor antennas.

In many studies, the mechanism by which the effective properties of metamaterials are adjusted is to use electromagnetic resonance between metaatoms. Controlling electromagnetic resonance involves changing the size and shape of the cavity, which is described by John B. Pendry [Pendry, JB, Holden, AJ, Robbins, DJ & Stewart, WJ "Magnetism from conductors and enhanced nonlinear phenomena ". IEEE Trans. Microwave Theory Tech. 47, 2075-2084 (1999) and the like use a metal wire or ring resonator. The methods can be used to artificially generate strong electrical interactions and strong magnetic interactions near the resonance frequency, thus generating near zero or negative or high effective permittivity (or effective permeability), and also anisotropic electromagnetic properties, which It is the physical origin of the aforementioned unnatural optical properties.

However, there are disadvantages to metamaterials based on resonant structures, one of which is the band width. Improvements in electrical or magnetic properties occur only near certain frequencies, and schemes using non-resonant structures have been studied to overcome this limitation. Metamaterials with resonance structures exhibit this kind of behavior near the resonance frequency.

Another drawback is the manufacturing process, since metaatoms must be less than one tenth of the wavelength, or even smaller than the wavelength, because multiple repeated photo-lithography and etching processes produce structures such as cubic, wire and rings. It is very difficult to obtain area metamaterials (or metasurfaces). In particular, metamaterials that operate optically in the infrared region must be able to be processed into structures of several tens of nanometers in size, even with current nanotechnology such as block copolymer self-assembly or nano-imprint. Thus, a manufacturing-friendly structure is needed to create large scale metamaterial applications.

The present application relates to metamaterials and applications thereof comprising a plurality of core-shell particles arranged in a host material.

However, the problem to be solved by the present application is not limited to the above-mentioned problem, and other problems not mentioned will be clearly understood by those skilled in the art from the following description.

A first aspect of the present disclosure is directed to a host material comprising: a host material; And a plurality of core-shell particles each spaced apart from within the host material.

A second aspect of the present application provides a device comprising a meta material according to the first aspect.

The meta-material according to the embodiments of the present invention includes particles of a core-shell structure, and the conductive material as the shell component may be used to control the capacitive effect between the two particles, and thus may be very effective. It is possible to achieve a high effective permeability by achieving a high effective permittivity and at the same time suppressing the diamagnetic effect.

Since the metamaterial according to the embodiments of the present invention does not use the electromagnetic resonance between the metaatoms of the prior art, but uses the electrostatic effect between particles, with the advantage that the operating bandwidth is wideband (10 GHz to 100 GHz), Since it is not manufactured using burn photo-lithography, there is an advantage that a large area can be manufactured by a simple process.

The metamaterial according to the embodiments of the present invention is free to independently adjust the effective permittivity and the effective permeability by controlling each material in the core-shell structure, the thickness of the shell, the width gap between the particles, and / or the unit lattice size. There is a characteristic that can reach a high refractive index. In addition, it is possible to achieve high refractive index, so it can be applied to small factor antennas, efficient absorbers, and high resolution imaging devices, and with the recent rapid development of 5G technology, there is an advantage that it can be applied at microwave frequencies.

1 is a schematic diagram showing the structure of dielectric core-conductive shell particles in one embodiment of the present application.
FIG. 2 is a schematic diagram showing unit lattice of core-shell particle arrays arranged in a hexagonal array in one embodiment of the present disclosure.
3 is a schematic diagram illustrating placement of ports and simulated metamaterials in one embodiment of the present application.
4A-4D, in one embodiment of the present application, show magnetic induction of a cylindrical conductor with a radius of 4,500 nm (a), magnetic induction profile of a cylindrical conductor with a radius of 3,000 nm and 4,500 nm, and a radius of 4,500 nm. , Magnetic induction profile (c) of cylindrical conductor shell with shell thickness of 250 nm, magnetic induction profile (d) of cylindrical conductor shell with radius of 3,000 nm to 4,500 nm and shell thickness of 250 nm.
5 is a graph showing the real part of the effective permeability of the cylindrical conductor and the cylindrical conductor shell in one embodiment of the present application.
6A-6C illustrate magnetic field distribution (a), gap width of a metamaterial comprising core-shell particles having a shell thickness of 40 nm, a gap width of 50 nm, and a unit lattice size of 5 μm, in one embodiment of the present disclosure. Simple spherical magnetic field distribution (comparative) with 50 nm and unit cell size 5 μm (b), meta-material comprising core-shell particles with shell thickness 40 nm, gap width 50 nm and unit cell size 5 μm It is a graph which shows the electric field distribution (c).
7A to 7C illustrate an effective dielectric constant (a) of a metamaterial according to a gap width, an effective permeability (b) of a metamaterial according to a shell thickness at a gap width of 15 nm, and a gap width 15 according to an embodiment of the present disclosure. It is a graph showing the effective refractive index (c) of the metamaterial according to the shell thickness at nm.
FIG. 8 is a graph showing effective refractive indices of a meta-material including core-shell particles and a simple metal particle array (comparative example) according to one embodiment of the present application; ) Denotes 24 GHz, 27 GHz and 30 GHz, respectively.
9A and 9B are graphs showing the effective permeability (a) and the effective refractive index (b) of metamaterials having a gap width of 15 nm and a shell thickness of 5 nm in one embodiment of the present application.
10A-10C illustrate, in one embodiment of the present application, a cubic core-shell metamaterial having a cubic unit lattice arrangement with a gap width of 60 nm and a unit lattice size of 2 μm to 6 μm, and simple metal particles. It is a graph which shows the dielectric constant (a), permeability (b), and refractive index (c) of an array (comparative example), respectively.
11A to 11C are dielectric constants (a), permeability (b), and refractive index according to the frequency of a multilayer metamaterial having a gap width of 20 nm, shell thickness of 40 nm, and unit cell size of 6 μm in one embodiment of the present application; c) is a graph showing each.
12A to 12C, in one embodiment of the present application, the effective permeability of the meta-material according to the radius and the shell thickness of the core-shell particles of the core-shell particles including the SiO ₂ core and the Au shell, respectively, 10 GHz, The graphs were checked at 50 GHz and 100 GHz.

Throughout this specification, when a part is said to be "connected" to another part, it includes not only "directly connected" but also "electrically connected" with another element in between. do.

Throughout this specification, when a member is located “on” another member, this includes not only when one member is in contact with another member but also when another member exists between the two members.

Throughout this specification, when a part is said to "include" a certain component, it means that it can further include other components, without excluding the other components unless specifically stated otherwise. As used throughout this specification, the terms “about”, “substantially”, and the like, are used at, or in close proximity to, numerical values when manufacturing and material tolerances inherent in the meanings indicated are provided, and an understanding of the present application may occur. Accurate or absolute figures are used to assist in the prevention of unfair use by unscrupulous infringers.

As used throughout this specification, the term “step of” or “step of” does not mean “step for”.

Throughout this specification, the term “combination (s) thereof” included in the expression of a makushi form refers to one or more mixtures or combinations selected from the group consisting of the components described in the expression of makushi form, It means to include one or more selected from the group consisting of the above components.

Throughout this specification, the description of “A and / or B” means “A or B, or A and B”.

Throughout this specification, the term "meta material" is a material made of an array of meta atoms designed from metals or dielectric materials made to a size much smaller than the wavelength of light, which natural materials have. It means the artificially designed and made to have tough optical properties.

Throughout this specification, the term "refractive index" refers to the rate of velocity of waves traveling in two media as light travels from one medium to another. The refractive index varies with wavelength, and at the interface of the media with different refractive indices, the light bends according to Snell's law and some reflects according to the angle of incidence. The refractive index may be expressed as the square root of the product of relative permittivity and relative permeability with respect to Equation 1 below, and as the refractive index value increases, the resolution, which is an ability to distinguish two objects from each other in an optical device, is improved. Because the resolution increases:

[Equation 1]

;

;

Where n _complex = Refractive index, ε = relative permittivity, μ = relative permeability, the refractive index is a complex value, the real part n of the refractive index determines the phase velocity of the EM wave in the material, and the imaginary part k of the refractive index is attenuated ( attenuation).

Throughout this specification, the term "unit lattice of a plurality of core-shell particle arrays" includes a gap width between core-shell particles and particles, wherein the size of the unit lattice is the size of the core-shell particles and the particles. It is length that sums gap width of liver.

Hereinafter, with reference to the accompanying drawings will be described in detail the embodiments and embodiments of the present application. However, the present disclosure may not be limited to these embodiments, examples, and drawings.

A first aspect of the present disclosure is directed to a host material comprising: a host material; And a plurality of core-shell particles each spaced apart from within the host material.

In one embodiment of the present disclosure, the core of the core-shell particles may include a dielectric material, and the shell of the core-shell particles may include a conductive material, but is not limited thereto. Specifically, when the conductive material is located in a magnetic field that changes with time, current is induced into the conductive material, and the induced current weakens the magnetic field in the conductive material. Because of this diamagnetic effect, the magnetic permeability of the metamaterial based on the conductive material is lower than one. In order to suppress the diamagnetic effects described above, instead of a particle composed of only a conductive material, a core-shell structured particle formed of a shell of a thin conductive material and a core of a dielectric material is produced, and an array of a plurality of core-shell particles is used as a unit lattice. It was.

In one embodiment of the present application, the host material is SiO ₂ , ZnO, Al ₂ O ₃ , ITO, TiO ₂ , ZrO ₂ , SnO ₃ , Si ₃ N ₄ , AlGaN, SiC, polymethyl methacrylate (poly ( methyl methacrylate), PMMA), polydimethylsiloxane (PDMS), polyethylene (PE, PE), and combinations thereof, but may be selected from the group consisting of, but is not limited thereto.

In one embodiment of the present application, the dielectric material is SiO ₂ , ZnO, Al ₂ O ₃ , ITO, TiO ₂ , ZrO ₂ , SnO ₃ , Si ₃ N ₄ , AlGaN, SiC, polymethyl methacrylate (PMMA) , Polydimethylsiloxane (PDMS), polyethylene (PE) and combinations thereof may be included, but is not limited thereto.

In one embodiment of the present disclosure, the conductive material includes one selected from the group consisting of gold, silver, aluminum, copper, nickel, platinum, chromium, palladium, iron, brass, zinc, bronze, and combinations thereof. It may be, but is not limited thereto.

In one embodiment of the present application, the unit lattice of the plurality of core-shell particle array may be to form a single layer or multiple layers arranged in a hexagonal system, but is not limited thereto.

1 and 2, meta-material in accordance with one embodiment of the present application is SiO _2, as a core material may comprise gold as SiO ₂ and the shell material, the plurality of cores as a host material, - the unit cell of the shell particles Can be arranged in a hexagonal array (hexagonal array), which can be composed of a multilayer as well as a single layer. In addition, as shown in FIG. 1, one more layer of the dielectric material may be present at the outermost portion of the dielectric core-conductive shell structure according to the exemplary embodiment of the present application. The outermost dielectric shell may be added for ease of fabrication process as an optional element that functions as a spacer to facilitate fabrication of densely arranged core-shell particles at uniform intervals.

In one embodiment of the present application, by controlling the capacitive effect (capacitive effect) between the plurality of core-shell particles may be to control the dielectric constant and / or permeability. Specifically, an inhomogeneous metamaterial in which a metal and a dielectric material are mixed, such as the metamaterial according to the present application, must be calculated as an effective medium theory, and an effective permittivity and an effective permeability, in particular, the conductive material constitute the particles. The effect of electrostatics should be taken into account, which is expressed as:

[Equation 2]

;

;

[Equation 3]

, (여기서, Z_eff = 유효 임피던스, n_eff = 유효 굴절률, ε_eff = 유효 유전율, μ_eff = 유효 투자율임). 본원의 일 구현예에 따른 메타 물질의 유효 유전율 및 유효 투자율은 갭(gap) 폭과 상기 쉘 두께를 각각 조절함으로써 제어될 수 있다. 또한, 상기 유전율은 편광률 (polarizability)에 의해 결정되며, 이것은 단위 격자당 커패시턴스와 직접적으로 관련이 있다. 평행판 캐패시터의 커패시턴스는 간단히 하기와 같다:

(Where Z _eff = effective impedance, n _eff = effective refractive index, ε _eff = effective dielectric constant, μ _eff = effective permeability). The effective dielectric constant and effective permeability of the meta material according to one embodiment of the present application can be controlled by adjusting the gap width and the shell thickness, respectively. In addition, the dielectric constant is determined by polarizability, which is directly related to the capacitance per unit lattice. The capacitance of a parallel plate capacitor is simply as follows:

[Equation 4]

, (여기서, C = 커패시턴스, ε₀ = 진공의 유전율, ε_r = 상대 유전율, A = 도체판 하나의 넓이, d = 도체판 사이의 거리임). 따라서, 두 개의 판들 사이의 거리가 감소하면 전기적 커패시턴스는 증가한다. 메타 물질의 단위 격자당 커패시턴스가 유사하므로 전도성 입자들 사이의 거리가 유효 유전율을 결정한다. 특히, 큐빅 입자로 형성된 메타 물질의 유전율은 적절한 근사법을 사용함으로써 페쇄형으로 표현될 수 있다. 따라서 유효 유전율은 하기 식의 기하학적 파라미터로 결정될 수 있다:

(Where C = capacitance, ε ₀ = dielectric constant of vacuum, ε _r = relative permittivity, A = width of one conductor plate, d = distance between conductor plates). Thus, as the distance between the two plates decreases, the electrical capacitance increases. Since the capacitance per unit lattice of the metamaterial is similar, the distance between the conductive particles determines the effective dielectric constant. In particular, the permittivity of metamaterials formed from cubic particles can be expressed in closed form by using an appropriate approximation method. The effective permittivity can thus be determined by the geometric parameter of the formula:

[Equation 5]

, (여기서, a = 단위 격자의 크기, b = 입자의 크기, g = 갭 폭이며, a = b + g임). 즉, 전도성 입자들 사이의 갭 폭이 짧을수록 상기 갭 내의 전기장이 강하게 집중되며, 이것은 상기 메타 물질의 편광률을 증가시킴으로써 유효 유전율이 증가하게 되는 것이므로, 코어-쉘 입자 간의 갭 폭으로써 유효 유전율을 제어할 수 있다.

, Where a = size of the unit cell, b = particle size, g = gap width, and a = b + g. That is, the shorter the gap width between the conductive particles, the stronger the electric field in the gap is, which increases the effective permittivity by increasing the polarization rate of the metamaterial, thus increasing the effective permittivity as the gap width between core-shell particles. Can be controlled.

The effective permeability increases as more magnetic fields penetrate into the metamaterial, and the conductive material attenuates the magnetic field, so when the core is a dielectric material and the shell is a conductive material, As it penetrates better inside, the metamaterial according to one embodiment of the present application can increase the permeability to around 1. Specifically, referring to FIGS. 6A and 6B, the magnetic field distribution of the core-shell particles (FIG. 6A) is larger than the magnetic field inside and outside the simple spherical metal particles (FIG. 6B). can confirm.

In one embodiment of the present disclosure, a gap width between the plurality of core-shell particles may be about 50 nm or less, but is not limited thereto. Specifically, a gap width between the plurality of core-shell particles may be about 50 nm or less, about 50 nm or less, about 45 nm or less, about 40 nm or less, about 35 nm or less, about 30 nm or less, about 25 nm or less, about 20 nm or less, about 5 nm to about 50 nm, about 5 nm to about 50 nm, about 5 nm to about 45 nm, about 5 nm to about 40 nm, about 5 nm to about 35 nm, about 5 nm to about 30 nm, about 5 nm to about 25 nm, about 5 nm to about 20 nm, about 10 nm to about 50 nm, about 10 nm to about 45 nm, about 10 nm to about 40 nm, about 10 nm to About 35 nm, about 10 nm to about 30 nm, about 10 nm to about 25 nm, about 10 nm to about 20 nm, about 15 nm to about 50 nm, about 15 nm to about 45 nm, about 15 nm to about 40 nm, about 15 nm to about 35 nm, about 15 nm to about 30 nm, about 15 nm to about 25 nm or about 15 nm to about 20 nm.

In one embodiment of the present application, the thickness of the shell of the plurality of core-shell particles may be about 100 nm or less, but is not limited thereto. Specifically, the thickness of the shell of the plurality of core-shell particles is about 100 nm or less, about 90 nm or less, about 80 nm or less, about 70 nm or less, about 60 nm or less, about 50 nm or less, about 40 nm or less, About 30 nm or less, about 20 nm or less, about 10 nm or less, about 5 nm or less, about 5 nm to about 100 nm, about 5 nm to about 90 nm, about 5 nm to about 80 nm, about 5 nm to about 70 nm, about 5 nm to about 60 nm, about 5 nm to about 50 nm, about 5 nm to about 40 nm, about 5 nm to about 30 nm, about 5 nm to about 25 nm, about 5 nm to about 20 nm or About 5 nm to about 10 nm.

In one embodiment of the present application, the unit lattice of the plurality of core-shell particle array may be about 2 μm to about 14 μm, but is not limited thereto. Specifically, the unit lattice of the plurality of core-shell particle arrays has a size of about 2 μm to about 14 μm, about 2 μm to about 12 μm, about 2 μm to about 10 μm, about 2 μm to about 8 μm, about 2 μm to about 6 μm, about 4 μm to about 14 μm, about 4 μm to about 12 μm, about 4 μm to about 10 μm, about 4 μm to about 8 μm, about 6 μm to about 14 μm, about 6 μm To about 10 μm or about 6 μm to about 8 μm.

Referring to FIG. 7A, due to the electrostatic effect between core-shell particles included in the meta material, it can be seen that the electric field is focused on the upper and lower ends of the core-shell particles. As a result, the effective dielectric constant decreases as the spacing between particles decreases. It can be seen that this is increased. In addition, it can be seen that the effective dielectric constant increases as the size of the core-shell particles increases. Referring to FIG. 7B, as the thickness of the metal shell decreases, a large amount of magnetic field may penetrate into the particle, so the effective permeability is maintained at about 1. In addition, as opposed to the effective dielectric constant, the effective permeability decreases as the size of the core-shell particles increases. That is, the size of the core-shell particles are opposite in the effective dielectric constant and effective permeability, so it is important to properly control the size of the core-shell particles.

Referring to FIG. 7C, when the thickness of the metal shell is 5 nm, as the size of the unit lattice of the array of core-shell particles increases, the effective refractive index is maintained because the effective permeability is maintained and the effective dielectric constant is increased. On the other hand, since the formation of a thin film of several nm level can be practically difficult, it was confirmed that the thicker metal shell has a maximum refractive index when the size of the unit lattice is about 6 μm to 10 μm.

In one embodiment of the present application, the ratio of unit lattice size of the plurality of core-shell particles array: gap width between the plurality of core-shell particles may be about 280: 1 or less, but is not limited thereto. Specifically, the unit lattice size of the plurality of core-shell particles arrays: the ratio of the gap width between the plurality of core-shell particles is about 280: 1 or less, about 260: 1 or less, about 240: 1 or less, about 220: 1 or less, about 200: 1 or less, about 180: 1 or less, about 160: 1 or less, about 140: 1 or less, about 120: 1 or less, or about 100: 1 or less.

In one embodiment of the present application, the operating bandwidth of the metamaterial may be from about 10 GHz to about 100 GHz, but is not limited thereto. Specifically, the operating bandwidth of the metamaterial is about 10 GHz to about 100 GHz, about 10 GHz to about 90 GHz, about 10 GHz to about 80 GHz, about 10 GHz to about 70 GHz, about 10 GHz to about 60 GHz, About 10 GHz to about 50 GHz, about 15 GHz to about 50 GHz, about 20 GHz to about 50 GHz, about 25 GHz to about 50 GHz, about 30 GHz to about 50 GHz, about 10 GHz to about 45 GHz, about 10 GHz to about 40 GHz, about 10 GHz to about 35 GHz, about 10 GHz to about 30 GHz, or about 15 GHz to about 30 GHz. Referring to FIG. 8, the core-shell particles of the meta-material according to the present invention exhibit high refractive index at broadband because the effective refractive index remains high at almost 24 GHz, 27 GHz and 30 GHz even though the unit lattice size is increased. It can be seen.

In one embodiment of the present invention, the core-shell particles are tetrahedral, hexahedral, octahedral, dodecahedral, tetrahedral, icosahedron, rod, concave tetrahedral, tetrahedral, such as tetrahedral, hexagonal It may include, but is not limited to, twin, spherical, ellipsoidal, cylindrical, such as plate-shaped, triangular plate-shaped, circular pentagonal twin.

Hereinafter, the embodiments of the present application will be described in detail. However, the present application may not be limited thereto.

[ Example ]

1. Experimental Design

1-1. Finite element method

The finite element method is a numerical analysis tool that interprets a physical object as a finite element. In theory, the finite element method can be applied to any physical problem. To get the solution, FEM software is able to divide a given object into finite elements, set the relationship between each element using governing equations, and solve it to obtain a numerical analysis. The software used herein solves the following governing equations:

[Equation 5]

.

.

1-2. Simulation setup

3 shows a simulated structure for measuring the transmitted and reflected wavelengths. Port 1 excites the y-polarized electromagnetic waves, and port 1 and port 2 measure the reflected and transmitted wavelengths, respectively. The unit cell of metamaterials is located in the middle of the two ports. The role of the additional vacuum gap between the meta material and the port is to prevent unwanted higher order scattering waves. Periodic boundary conditions were applied to create an infinite array of unit cells in the x and y directions.

1-3. Substance parameters

In order to analyze the metamaterial structure using finite element analysis, material property information must be entered. The material parameters required for the simulation are electrical permittivity, magnetic permeability and conductivity. The electrical permittivity of the metal is as follows:

[Equation 6]

.

.

However, since the microwave frequency is smaller than the impingement frequency, the imaginary part is larger than the real part, and thus the electrical permittivity may be reduced:

[Equation 7]

.

.

Experimentally measured DC conductivity of very thin metals was used. Table 1 below shows the material parameters used in the simulation.

Relative permittivity Relative permeability Conductivity (S / m) vacuum One One 0 SiO ₂ 3.9 One 0 aluminum 1.14 X (10 ¹⁸ / ω) One 1.25 X 10 ⁷ gold 3.95 X (10 ¹⁸ / ω) One 3.5 X 10 ⁷ silver 6.21 X (10 ¹⁸ / ω) One 5.5 X 10 ⁷ Copper 5.65 X (10 ¹⁸ / ω) One 5 X 10 ⁷

2. Magnetic response of cylindrical conductor

The cylindrical conductor or cylindrical conductor shell of the time-harmonic magnetic field has a magnetic field in the form of a Bessel function. 4A to 4D show magnetic induction according to radius and magnetic field distribution. The magnetic field is attenuated very fast near the surface, so the permeability of the cylindrical shell arrangement does not differ significantly from the permeability of the cylinder unless the shell is thin.

5 shows the effective permeability of a cylindrical conductor and a cylindrical shell conductor. When the shell thicknesses are the same, the permeability decreases with increasing radius. Thus, the effective permeability of such a collection of cylindrical shells, 3-D core-shell structure, can be expected to be similar.

3. Core-shell Meta  Electromagnetic properties of matter

3-1. fault Meta  Effective properties of the substance

Field distributions and investigated characteristics are shown in FIGS. 6A-8. Simulations were performed for unit cell sizes of 2 μm to 15 μm, metal shell thicknesses of 5 nm to 25 nm, and gap widths of 15 nm to 35 nm. Meta-materials containing core-shell particles were monolayered and filled with a hexagonal packed structure. It was found that the electric field was strongly concentrated in the gap between adjacent particles, and the magnetic field was reduced in the structure. More magnetic fields penetrated the core-shell structure of the present application as compared to FIG. 6b, which is a simple metal particle arrangement (comparative example) rather than the core-shell structure, which confirmed higher permeability.

Higher permeability can be obtained at smaller gaps, which can yield about 1 permeability in thinner metal shells. As a result, it was confirmed that a high refractive index of about 8 can be achieved for the monolayer. In addition, it was confirmed that high refractive index characteristics appeared in the wideband frequency range (24 GHz to 30 GHz), and the refractive index was significantly improved in the core-shell structure of the present application compared with the simple metal particle arrangement (comparative example) of FIG. 8.

3-2. Meta  Material Effects on Substances

The magnetic field, which changes over time, creates a current inside the metal. The induced current determines the effective permeability of the metamaterials. Therefore, the smaller the resistance, the more induced current is generated. Conductivity affects the magnetic field of the conductor, and the higher the conductivity, the faster the magnetic field decays in the cylindrical conductor. Clearly, this results in an increase in the imaginary part of the magnetic permeability. For Al, the permeability of about 1 can be obtained for larger unit cell sizes. As a result, it was found that core-shell metamaterials using low conductivity metals had a higher effective refractive index. (FIGS. 9A and 9B).

3-3. Meta  Particle Shape Effects on Materials

The cubic structure metamaterial was simulated here. In this case, a very large dielectric constant was obtained because very large refractive indices can be obtained even if the unit cell and gap ratio are less than 200: 1. The results confirmed that the unit cells do not have to be perfectly spherical in the manufacture of the actual application, and even large refractive indices can be obtained even when using different shaped unit cells (FIGS. 10A-10C).

3-4. Including a multilayer core-shell array Meta  Effective properties of the substance

The multilayer structure was also simulated. If the structure of the metamaterials is symmetrical along the propagation axis, they can be separated into surface and bulk portions. Both monolayers and multilayers have two surface portions, while multilayers have thicker bulk portions. The field between the spherical particles is larger in bulk than near the surface. Therefore, it was confirmed that the effective dielectric constant and refractive index of the obtained multilayer structure may be higher than that of the single layer structure (FIGS. 11A to 11C).

12A to 12C, effective permeability may be confirmed by approximating a spherical particle in a cylindrical shape in a core-shell particle including an SiO ₂ core and an Au shell. Specifically, as a result of confirming the effective permeability of the meta-material according to the radius of the core-shell particles and the shell thickness, which is the outer radius of the cylinder, even if the thickness of Au decreases to about 100 nm or less at 10 GHz, regardless of the outer radius, It was found to have a high effective permeability of 0.8 or more (FIG. 12A). In addition, as a result of confirming the effective permeability by setting the frequency domain 50 GHz, it was confirmed that the permeability of more than 1 (2.987) at an outer radius of 8 μm, Au thickness 50 nm. As a result of confirming the effective permeability by setting the frequency range to 100 GHz, it was confirmed that the Au thickness should fall below 50 nm for high permeability. As a result, the effective permeability increases as the frequency decreases, and the effective permeability increases as the outer radius decreases and the thickness of Au decreases in common at all frequencies.

Taken together, the proposed core-shell structured meta-materials were simulated using finite element method, freely showing material selection and broadband high refractive index characteristics, and the smaller the gap between two adjacent particles, the higher the electrical permittivity was obtained. Also, the larger the radius of the particles, the lower magnetic permeability could be obtained. Therefore, as the unit cell size increases in the fixed gap, the effective permittivity increases but the effective permeability decreases.

The structure proposed here is free to select metals and it was particularly easier to control the magnetic permeability for Al having a relatively low resistance. In addition, it was confirmed that the advantage of the core-shell structure is that a high refractive index can be obtained even if the shape or size of the particles is not uniform.

Metamaterials, including core-shell metamaterials, can be applied to a wide range of applications. For example, small factor antennas, efficient absorbers, high resolution imaging devices may be possible. With the recent rapid development of 5G technology, it is very likely that the high refractive index metamaterials of the present application will be applied at microwave frequencies.

The above description of the present application is intended for illustration, and it will be understood by those skilled in the art that the present invention may be easily modified in other specific forms without changing the technical spirit or essential features of the present application. Therefore, it should be understood that the embodiments described above are exemplary in all respects and not restrictive. For example, each component described as a single type may be implemented in a distributed manner, and similarly, components described as distributed may be implemented in a combined form.

The scope of the present application is indicated by the following claims rather than the above detailed description, and all changes or modifications derived from the meaning and scope of the claims and their equivalents should be construed as being included in the scope of the present application.

Claims (13)

Host material; And
A plurality of core-shell particles arranged spaced apart from each other within the host material
Including, meta-materials.
The method of claim 1,
The core of the core-shell particle comprises a dielectric material,
The shell of core-shell particles comprises a conductive material.
The method of claim 1,
The unit material lattice of the plurality of core-shell particle arrangements form a single layer or a multi-layer arranged in a hexagonal system, meta-material.
The method of claim 1,
Meta material and / or permeability to control electrostatic effects between the plurality of core-shell particles.
The method of claim 1,
The gap width between the plurality of core-shell particles is 50 nm or less.
The method of claim 1,
The thickness of the shell of the plurality of core-shell particles is less than 100 nm, meta material.
The method of claim 1,
Meta unit material of the plurality of core-shell particle array of the size of the unit lattice 2 μm to 14 μm.
The method of claim 1,
The unit material size of the plurality of core-shell particles array: the ratio of the gap width between the plurality of core-shell particles is 280: 1 or less, the meta-material.
The method of claim 1,
The host material is SiO ₂ , ZnO, Al ₂ O ₃ , ITO, TiO ₂ , ZrO ₂ , SnO ₃ , Si ₃ N ₄ , AlGaN, SiC, polymethyl methacrylate (PMMA), polydimethylsiloxane (PDMS), Meta material comprising one selected from the group consisting of polyethylene (PE) and combinations thereof.
The method of claim 2,
The dielectric material may be SiO ₂ , ZnO, Al ₂ O ₃ , ITO, TiO ₂ , ZrO ₂ , SnO ₃ , Si ₃ N ₄ , AlGaN, SiC, polymethyl methacrylate (PMMA), polydimethylsiloxane (PDMS), Meta material comprising one selected from the group consisting of polyethylene (PE) and combinations thereof.
The method of claim 2,
Wherein the conductive material comprises one selected from the group consisting of gold, silver, aluminum, copper, nickel, platinum, chromium, palladium, iron, brass, zinc, bronze, and combinations thereof.
The method of claim 1,
The operating bandwidth of the metamaterial is from 10 GHz to 100 GHz.
A device comprising the meta-material according to any of the preceding claims.

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