CN102570049A - Graphene-based electromagnetic absorber - Google Patents

Abstract

A graphene-based electromagnetic wave absorber, comprising: a laminated silicon substrate and a silicon dioxide substrate, a stepped circular hole is provided on the silicon substrate, and a step A step-shaped protrusion matching the round hole, and the step-shaped protrusion is embedded in the step-shaped round hole, and a graphene layer is arranged on the silicon dioxide substrate. One pole of the bias voltage source is added to the silicon substrate, and the other pole is added to the graphene. By designing the thickness of different regions of the silicon substrate and suitable bias voltage, the invention can realize the capture and absorption of electromagnetic waves at multiple frequency points. The invention is simple in structure, light in weight, easy to integrate, and can be used for multiple purposes such as energy collection and local heating.

Description

Graphene-based electromagnetic wave absorber

technical field

The invention relates to an electromagnetic wave absorber realized by using graphene, in particular to an electromagnetic wave absorber whose dielectric constant based on graphene can be realized by regulating this characteristic through gate voltage. By designing a suitable structure, the absorber can absorb electromagnetic waves into a specific area and generate heat.

Background technique

In 2009, Professor Cui Tiejun and Professor Chen Qiang of Southeast University in China put the theory of Narimano and Kirdishevi into practice, and designed and manufactured a "black hole" ("An omnidirectional electromagnetic absorber made of metamaterials," New J. Phys. 12, 063006 2010). Electromagnetic black holes have a wide range of applications and extremely important research value.

Since the discovery of graphene in 2004, it has aroused intense research interest. Professor G.W. Hanson proposed that the conductivity of graphene can be expressed by the Kubo formula ("Dyadic Green's functions and guided surface waves for a surface conductivity model of graphene," J.Appl.Phys.103(6), 064302, 2008).

为普朗克常数，f_d(ε)＝1/(1+exp[(ε-μ_c)/(k_BT)])是费米狄拉克分布，k_B为波尔兹曼常数，ω为角频率，μ_c为化学势，Γ表示散射率，T表示温度。由上述公式可知，石墨烯的电导率是随着化学势的变化而变化的。不同的电导率又对应着不同的介电常数，它们的对应关系为：Re(ε_g，eq)＝-σ_g，i/ωΔ+ε₀≈-σ_g，i/ωΔ，Im(ε_g，eq)＝σ_g，r/ωΔ，石墨烯的损耗为|Im(ε_g，eq)/Re(ε_g，eq)|。所以，我们可以通过改变石墨烯的化学势来得到我们想要的介电常数，从而可以得到不同的折射率。基于以上所述，石墨烯是一种可以用来制作电磁波吸收器的理想材料。石墨烯化学势与门电压的关系为：Where -e is the electron quantity,

is Planck’s constant, f _d (ε)=1/(1+exp[(ε-μ _c )/(k _B T)]) is Fermi Dirac distribution, k _B is Boltzmann’s constant, ω is the angular frequency, μ _c is the chemical potential, Γ is the scattering rate, and T is the temperature. It can be seen from the above formula that the conductivity of graphene changes with the change of chemical potential. Different electrical conductivities correspond to different dielectric constants, and their corresponding relationship is: Re(ε _{g, eq} )=-σ _{g, i} /ωΔ+ε ₀ ≈-σ _{g, i} /ωΔ, Im(ε _{g , eq} )=σ _{g, r} /ωΔ, the loss of graphene is |Im(ε _{g, eq} )/Re(ε _{g, eq} )|. Therefore, we can get the dielectric constant we want by changing the chemical potential of graphene, so that we can get different refractive indices. Based on the above, graphene is an ideal material that can be used to make electromagnetic wave absorbers. The relationship between graphene chemical potential and gate voltage is:

Among them, ε ₀ and ε _r represent the permittivity of air and sio ₂ respectively, and t is the thickness of sio ₂ , so we can change the chemical potential of graphene by changing the gate voltage to change the permittivity of graphene. So far, no one has used graphene to design electromagnetic wave absorbers.

Contents of the invention

Technical problem: The present invention provides a graphene-based electromagnetic wave absorber. When an incident electromagnetic wave encounters the device of the present invention, the electromagnetic wave will be captured by the device, then guided into the central core, absorbed by the central core, and the electromagnetic wave will no longer Coming out of the central core, the light will be converted to heat energy at the central core.

The present invention adopts following technical scheme:

A graphene-based electromagnetic wave absorber, comprising: a laminated silicon substrate and a silicon dioxide substrate, a stepped circular hole is provided on the silicon substrate, and a step A step-shaped protrusion matching the round hole, and the step-shaped protrusion is embedded in the step-shaped round hole, and a graphene layer is arranged on the silicon dioxide substrate.

The bottom of the present invention is a silicon substrate, a silicon dioxide substrate is laid on the silicon substrate, a graphene layer is laid on the silicon dioxide substrate, one pole of the bias voltage source is added on the silicon substrate, and the other pole added to graphene. The thickness of the silicon substrate in different regions is different, and different thicknesses of the silicon substrate lead to different thicknesses of silicon dioxide, so that under the same bias voltage, the chemical potentials induced by graphene in different regions are different. Therefore, graphene on different regions has different dielectric constants. When the permittivity of these regions satisfies a certain relationship, the capture and absorption of electromagnetic waves can be realized.

Compared with the prior art, the present invention has the following advantages:

1. The invention realizes the graphene-based electromagnetic wave absorber for the first time

2. This graphene-based electromagnetic wave absorber can work at multiple frequency points by designing the thickness of different regions of the silicon substrate and suitable bias voltage.

3. This graphene-based electromagnetic wave absorber has a simple structure, light weight, and is easy to integrate. It can be used for energy collection, local heating and other purposes.

Description of drawings:

Fig. 1 is a schematic diagram of the present invention, graphene comprises central core 5 regions and shell 6 regions, central core 5 regions are graphene regions corresponding to silicon substrate 7, and shell 6 regions are graphene regions corresponding to silicon substrate 8 area. When the dielectric constants in the area of the central core 5 and the area of the shell 6 satisfy the following relationship (I), the capture and absorption of electromagnetic waves can be realized.

$\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; r</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\left\{\begin{array}{c}{\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; r</span>}<span\; class="notranslate">\; ></span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}\\ {\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}<span\; class="notranslate">\; \&times;</span>{<span\; class="notranslate">\; (</span>\frac{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}}{\mathrm{<span\; class="notranslate">\; r</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}\\ {\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; i\&gamma;</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; r</span>}<span\; class="notranslate">\; <</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}\end{array},<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; \&le;</span>\mathrm{<span\; class="notranslate">\; r</span>}<span\; class="notranslate">\; \&le;</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}<span\; class="notranslate">\; ,</span>\right.<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

FIG. 2 is a schematic structural diagram of the present invention, which includes a silicon substrate 1 , a silicon dioxide substrate 2 and graphene 3 . One pole of the bias voltage source 4 is added on the silicon substrate, and the other pole is added on the graphene.

Fig. 3 is the top view of silicon substrate 1, and silicon substrate has been etched the step-shaped round hole of different thickness, to satisfy the dielectric constant of the corresponding graphene on the silicon substrate region 7 has the center that satisfies relational formula (I) In the core 5 area, the dielectric constant of the corresponding graphene on the silicon substrate area 8 has the shell 6 area satisfying the relational formula (1), and the loss in the central core 5 area is very large.

Figure 4 is a point source simulation result diagram. It can be seen from the figure that when the spherical wave excited by the point source passes through the shell 6, it is guided into the central core 5 and absorbed by the central core 5, and the electromagnetic wave will no longer pass through the central core 5. come out.

Fig. 5 is a simulation result diagram of a beam of light at the central position. It can be seen from the figure that when a beam of light at the central position is incident on the shell 6, it will be guided into the central core 5 and absorbed by the central core 5, and the electromagnetic waves will no longer Come out of central core 5.

Fig. 6 is a simulation result diagram of a beam of light at the lower side of the center. It can be seen from the figure that when a beam of light at the lower side of the center is incident on the housing 6, it will be guided into the central core 5 and absorbed by the central core 5. Electromagnetic waves will no longer come out from the central core 5.

Detailed ways:

A graphene-based electromagnetic wave absorber, comprising: a silicon substrate 1 and a silicon dioxide substrate 2 stacked together, a stepped circular hole is provided on the silicon substrate 1, and on the silicon dioxide substrate 2 A stepped protrusion matching the stepped circular hole is provided, and the stepped protrusion is embedded in the stepped circular hole, and a graphene layer 3 is provided on the silicon dioxide substrate 2 .

One pole of the bias voltage source 4 is added on the graphene, and the other pole is added on the silicon substrate. Different thicknesses are etched in different regions of the silicon substrate, so that the silicon dioxide substrate laid on the silicon substrate has different thicknesses in corresponding regions. According to the formula:

And the formula of graphene gate voltage and silicon dioxide thickness:

We just can by designing the thickness of silicon substrate and suitable bias voltage, make the dielectric constant of graphene central core area and shell area satisfy relation (I), and the loss of graphene central core area is very big. According to the above, the invention of the graphene-based electromagnetic wave absorber can be realized.

Claims (2)

1. A graphene-based electromagnetic wave absorber, characterized in that it comprises: a silicon substrate (1) and a silicon dioxide substrate (2) laminated together, and a step is provided on the silicon substrate (1) shaped round hole, on the silicon dioxide substrate (2) there is a stepped protrusion matching the stepped round hole, and the stepped protrusion is embedded in the stepped round hole, on the silicon dioxide substrate (2) A graphene layer (3) is provided on it. 2. A graphene-based electromagnetic wave absorber according to claim 1, characterized in that the thickness of each region of the silicon substrate and the size of the bias voltage can be adjusted to change the frequency point of electromagnetic wave absorption.

Images