In addition, each of the resonant structures 70 constituting the array resonator may be alternately arranged in a mutually perpendicular x-axis and y-axis direction with a spacing of 0.1 to 10 μm on the dielectric layer 30 to form the pattern portion 40. When the spacing between the resonant structures 70 is less than 0.1 μm, it may be difficult to broaden the emissivity in the non-detection band (5 to 8 μm); when the spacing between the resonant structures 70 exceeds 10 μm, it may be difficult to increase the emissivity in the non-detection band (5 to 8 μm).

The stacked resonator implemented in the stacking direction of the resonant structures 70 constituting the pattern portion 40 according to the present invention may be formed by stacking different resonator units 75 and, according to an embodiment of the present invention, the plurality of resonant structures 70 may be implemented such that the size of the cross-sectional area in the height direction decreases as it goes up to the top layer.

In more detail, the stacked resonator of the infrared selective emitter 100 according to the present invention may be implemented with at least two resonator units 75 composed of a metal layer, dielectric layer, and metal layer that are continuously stacked from the metal layer 20 of the flat portion 10 to the top layer of the resonant structure 70, as shown in FIG. 4. For example, from the top layer of the resonant structures 70 to the metal layer 20 of the flat portion 10, the first resonator unit 75a, the second resonator unit 75b, and the third resonator unit 75c may be continuously stacked, and the adjacent resonator units 75 may be stacked by sharing a metal layer 50.

That is, as shown in FIG. 4, the first resonator unit 75a and the second resonator unit 75b may be stacked by sharing a metal layer 50a, and the second resonator unit 75b and the third resonator unit 75c may be stacked by sharing a metal layer 50b.

In this case, it may be advantageous to broaden and maximize the emissivity in a specific band compared to the case where only the array resonator is used to implement the pattern portion 40. In more detail, with reference to FIG. 5, it can be observed that the emissivity increases significantly in the non-detection band when the first and second resonant structures 70a and 70b with different diameters to each include the first resonator unit 75a and the second resonator unit 75b. That is, compared to the case of using the infrared selective emitter formed with the metal pattern having a single diameter, the present invention is cable of increasing the amount of energy emission in the non-detection band, i.e., atmospheric absorption band, where the infrared detectors cannot perform detection, and improving the camouflage performance with almost no absorption and radiation due to no occurrence of resonance in the detection band, by adjusting the diameter of the resonator units constituting the array resonator, the number of the resonator units with different sizes, and the number of resonator units.

As described above, the present invention is capable of maximizing the infrared selective radiation function by broadening the emissivity in the non-detection bands with resonance phenomena between multiple resonator units at the same time as securing infrared camouflage and energy dissipation-resultant surface thermal stability by reducing the emissivity significantly in the infrared detection band and selectively dissipating energy to the non-detection bands, by using the plurality of three-dimensional resonant structures 70 implemented in the form of array resonators and stacked resonators.

That is, the infrared selective emitter 100 according to the present invention may have a maximum emissivity of 0.8 or more in the 5 to 8 μm infrared wavelength range, and the heat dissipation ratio calculated through Equation 1 may be between 45 to 70%.

Heat
⁢

dissipation
⁢

ratio
⁢

(
%
)

=

E
s

(
T
)

@
5

-

8
⁢

μ
⁢
m

E
BB

(
T
)

@
5

-

8
⁢

μ
⁢
m

Equation
⁢

1

- where E is radiant energy, T is temperature, subscript s is selective emitter, and BB is black body.

Using Equation 1, it is possible to compare the heat dissipation ratio between the conventional infrared selective emitter with a single diameter structure and the infrared selective emitter according to the present invention having a 3-dimensional resonant structure for surface temperatures ranging from 200K to 1000K. With reference to FIG. 6, it can be seen that the infrared selective emitter according to the present invention having a 3-dimensional resonant structure exhibits significantly superior heat dissipation compared to the conventional infrared selective emitter with the same temperature.

Thus, in order to secure infrared camouflage through selective energy dissipation to the non-detection band and energy dissipation-resultant surface thermal stability, and at the same time, to maximize the infrared selective radiation function by broadening the emissivity in the non-detection band using the resonance phenomenon between multiple resonator units, the multiple resonant structures 70 of the infrared selective emitter 100 according to the present invention may have diameters ranging from 0.1 to 10 and preferably from 1.2 to 1.8 μm. Here, when the diameter of the resonance structures 70 is less than 0.1 μm, it may be difficult to reduce the infrared signal of the detection band (3 to 5 μm); when the diameter of the resonance structures 70 exceeds 10 μm, it may be difficult to reduce the infrared signal of the detection band (8 to 12 μm).

In addition, the thickness of the metal layer 50 constituting the plurality of resonant structures 70 may be 10 to 500 nm, and preferably, 100 to 200 nm. Here, when the thickness of the metal layer 50 is less than 10 nm, this may cause a problem in that the infrared selective radiation phenomenon gradually disappears, making it impossible to broaden the emissivity and achieve high emissivity; when the thickness of the metal layer 50 exceeds 500 nm, this may increase the weight of the precious metal required for fabrication, leading to an increase in the weight of the overall material and production costs.

In addition, the thickness of the dielectric layer 60 of the plurality of resonant structures 70 may be 10 to 1000 nm, and preferably, 100 to 300 nm. Here, when the thickness of the dielectric layer 60 is less than 10 nm or exceeds 1000 nm, this may cause a problem in that the infrared selective radiation phenomenon gradually disappears, making it impossible to broaden the emissivity and achieve high emissivity.

Hereinafter, a description is made of the method of manufacturing the infrared selective radiator 100 according to the present invention with reference to FIG. 7. However, in order to avoid redundancy, the description of parts with the same technical concept as the above-described infrared selective radiator 100 will be omitted.

The method of manufacturing an infrared selective radiator according to the present invention includes steps of (1) stacking a metal layer and a dielectric layer alternately so that the topmost and bottommost layers are metal layers, as described above, (2) forming a mask pattern layer having a predetermined gap on the topmost metal layer, and (3) forming the pattern portion having resonant structures formed therein with the alternately stacked metal and dielectric layers, on the dielectric layer of the flat portion, in a predetermined pattern along with the flat portion formed by stacking the dielectric layer and the metal layer, by etching through the mask pattern layer.

Step (1) involves stacking the metal and dielectric layers alternately on a substrate so that the topmost and bottommost layers are metal layers.

In more detail, with reference to FIG. 8, step (1) includes depositing the metal and dielectric layers alternately on the substrate of the infrared selective radiator 100 of the present invention so that the topmost and bottommost layers are metal layers. Here, the deposition may be carried out using commonly known deposition methods suitable for the purpose of the present invention, such as physical or chemical deposition. Physical deposition or chemical deposition methods may include direct current (DC) sputtering, magnetron sputtering, electron beam evaporation, thermal evaporation, laser molecular beam epitaxy (LMBE), pulsed laser deposition (PLD), vacuum deposition, atomic layer deposition (ALD), or plasma-enhanced chemical vapor deposition (PECVD).

Next, step (2) involves forming a mask pattern layer having a predetermined gap on the topmost metal layer. The mask pattern layer may be formed by a commonly known method suitable for the purpose of the present invention, but preferably, formed by coating a photoresist (PR) on the metal layer and applying UV exposure to create a pattern of gaps spaced apart at a predetermined interval.

Next, step (3) involves forming the pattern portion having resonant structures formed therein with the alternately stacked metal and dielectric layers, on the dielectric layer of the flat portion, in a predetermined pattern along with the flat portion formed by stacking the dielectric layer and the metal layer, by etching through the mask pattern layer.

Step (3) is of removing the portion not covered by the mask pattern layer to create a resonant structure with the metal and dielectric layers below the mask pattern layer in a predetermined pattern along with the flat portion formed by stacking the metal layer and the dielectric layer. The method of removing the portion where the mask pattern layer is not formed is not specifically limited as long as it is a commonly used method in the field and does not damage the structure of the stacked insulation layer and a metal layer, and preferably, the three-dimensional resonant structures are formed in the shape of a trapezoid with increasing size from the top layer to the bottom layer by isotropic etching and stripping off the photoresist.

The following embodiments are provided to further illustrate the present invention, but are not intended to limit the scope thereof, and should be interpreted as being for the purpose of aiding in the understanding of the present invention.

Embodiment 1—Manufacturing of Infrared Selective Emitter

Metal layers of Gold (Au) with a thickness of 100 nm and dielectric layers of zinc sulfide (ZnS) with a thickness of 200 nm were deposited on a silicon wafer using an E-beam evaporator, PECVD, and E-beam evaporator, in the order as shown in FIG. 7.

Next, a mask pattern layer, on the previously manufactured layered structure, to two circular patterns with diameters of 1.3 μm and 1.5 μm.

Afterward, the stacked structure was thy-etched using an Induced Coupled Plasma (ICP) etcher in a top-down manner, using the previously formed mask pattern layer to etch the areas where the mask pattern layer was not formed; then a flat portion was formed with a metal layer of 100 nm thickness of Gold (Au) and a dielectric layer of 200 nm thickness of zinc sulfide (ZnS); the infrared selective emitter was obtained so as to include a pattern portion formed by arranging first and second resonant structures with a spacing of 3 μm on the flat portion formed by stacking the metal and dielectric layers with thicknesses of 100 nm and 200 nm, the first resonant structures including a first metal layer with a thickness of 100 nm and a diameter of 1.3 μm, a first dielectric layer with a thickness of 200 nm and a diameter of 1.2 μm, a second metal layer with a thickness of 100 nm and a diameter of 1.15 μm, a second dielectric layer with a thickness of 200 nm and a diameter of 1.05 μm, and a third metal layer with a thickness of 100 nm and a diameter of 1.0 μm, and the second resonant structures including a first metal layer with a thickness of 100 nm and a diameter of 1.5 um, a first dielectric layer with a thickness of 200 nm and a diameter of 1.4 um, a second metal layer with a thickness of 100 nm and a diameter of 1.35 um, a second dielectric layer with a thickness of 200 nm and a diameter of 1.25 um, and a third metal layer with a thickness of 100 nm and a diameter of 1.2 um.

Embodiments 2 and 3—Manufacturing of Infrared Selective Emitter

The infrared selective emitter was manufactured by following the same process as embodiment 1, but with a different number of layers in the stacked resonator.

Embodiments 4 to 11—Manufacturing of Infrared Selective Emitter

The infrared selective emitter was fabricated by following the same process as embodiment 1, but with variations in the thickness of the dielectric layer, thickness of the metal layer, and diameter of the metal layer.

Comparative Example 1—Manufacturing of Infrared Selective Emitter

The conventional infrared selective emitter was manufactured by following the same process as in embodiment 1, but with the resonant structures having a uniform diameter of 1.8 um and manufactured as a single layer.