Structural color device based on refractive index gradient distribution silicon nitride super-structure surface and preparation method and application thereof

Abstract

The invention relates to a structural color device based on a refractive index gradient distribution silicon nitride metasurface and a preparation method and application thereof, and belongs to the technical field of optical elements. The invention discloses a structural color device based on a refractive index gradient distribution silicon nitride super-structure surface. The structural color device comprises a substrate and a nano-structure array arranged on the surface of the substrate, the nano-structure array comprises a plurality of nano-structure units which are periodically arranged; each nano structure unit comprises a first silicon oxide layer (the refractive index is n0), a first silicon nitride layer (the refractive index is n1), a second silicon nitride layer (the refractive index is n2), a third silicon nitride layer (the refractive index is n3), a fourth silicon nitride layer (the refractive index is n4), a fifth silicon nitride layer (the refractive index is n5) and a second silicon oxide layer (the refractive index is n6), wherein n0 = n6 < n1 = n5 < n2 = n4 < n3. The structural color device has high brightness and color purity, can cover most of visible light to realize wide color gamut display, and also has excellent stability.

Description

Technical Field

[0001] The present invention relates to the technical field of optical elements, and in particular to a structural color device based on a silicon nitride metasurface with a gradient refractive index distribution, and a preparation method and application thereof. Background Art

[0002] Structural color is an optical phenomenon produced by the interaction between incident light and micro-nanostructures. Unlike traditional chemical pigments or dyes, its color expression relies on the interference, diffraction, or scattering effects of light, offering distinct advantages such as resistance to bleaching and environmental friendliness. Classified by material, metasurface structural color primarily includes metallic metasurfaces and dielectric metasurfaces. Metallic metasurfaces utilize surface plasmon resonance to scatter and absorb light through the interaction between metallic nanostructures and light, producing structural color. However, due to the inherent properties of metal materials, they experience significant ohmic losses in the visible light range. Precious metals, such as gold and silver, in particular, exhibit significant energy absorption within the visible light range, which can easily lead to low brightness and efficiency of the structural color. Furthermore, the broad resonance peaks of metallic nanostructures result in low color saturation of the structural color. Furthermore, metallic materials are susceptible to oxidation and corrosion, resulting in poor color stability of the structural color. Unlike metal metasurfaces, dielectric metasurfaces rely on Mie resonance and high-order multipole resonance, and achieve structural color by regulating the propagation of light through the scattering and interference effects of dielectric nanostructures. Although it can effectively improve the brightness and saturation of colors, commonly used materials such as silicon and titanium dioxide have difficulties in achieving structural color in the entire color range, which limits its application in high-end display and other fields, and cannot meet the needs of high-end color printing or display applications. Summary of the Invention

[0003] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a structural color device based on a silicon nitride metasurface with a gradient refractive index distribution, and a preparation method and application thereof.

[0004] To achieve the above object, the technical solution adopted by the present invention is:

[0005] In a first aspect, the present invention provides a structural color device based on a silicon nitride metasurface with a refractive index gradient distribution, comprising a substrate and a nanostructure array provided on the surface of the substrate;

[0006] The nanostructure array includes a plurality of periodically arranged nanostructure units, each of which includes a first silicon oxide (SiO2) layer, a first silicon nitride (Si3N4) layer, a second silicon nitride (Si3N4) layer, a third silicon nitride (Si3N4) layer, a fourth silicon nitride (Si3N4) layer, a fifth silicon nitride (Si3N4) layer, and a second silicon oxide (SiO2) layer stacked in sequence;

[0007] The refractive index of the first silicon oxide layer is n0, the refractive index of the first silicon nitride layer is n1, the refractive index of the second silicon nitride layer is n2, the refractive index of the third silicon nitride layer is n3, the refractive index of the fourth silicon nitride layer is n4, the refractive index of the fifth silicon nitride layer is n5, and the refractive index of the second silicon oxide layer is n6, n0=n6<n1=n5<n2=n4<n3.

[0008] The present invention distributes silicon nitride films of different refractive indexes in a low-high-low gradient, and uses a silicon oxide film with a specific refractive index as a refractive index matching layer. The two are combined to form a nanostructure unit, which is used to regulate the scattering, interference and resonance effects of light, thereby significantly improving the high saturation, high brightness and wide color gamut of the structural color device. The chemical stability and thermal stability of silicon nitride can also be used to ensure the reliable performance of the structural color device in various complex application environments.

[0009] As a preferred embodiment of the structural color device based on the refractive index gradient distribution silicon nitride metasurface described in the present invention, n0=1.45~1.5, n1=1.85~1.9, n2=1.9~2.1, n3=2.2~2.25; preferably, n0=1.46, n1=1.87, n2=2, n3=2.23.

[0010] As a preferred embodiment of the structural color device based on the refractive index gradient distribution silicon nitride metasurface of the present invention, the thickness of the first silicon oxide layer is d1 nm, the thickness of the first silicon nitride layer is d2 nm, the thickness of the second silicon nitride layer is d3 nm, the thickness of the third silicon nitride layer is d4 nm, the thickness of the fourth silicon nitride layer is d5 nm, the thickness of the fifth silicon nitride layer is d6 nm, the thickness of the second silicon oxide layer is d7 nm, the diameter of the nanostructure unit is D nm, and the period of the nanostructure unit is P nm; d1 = 4-6, d2 = 19-21, d3 = 19-21, d4 = 148-152, d5 = 49-51, d6 = 0-1, d7 = 98-102, D = 258-262, P = 408-412; preferably, d1 = 5, d2 = 20, d3 = 20, d4 = 150, d5 = 50, d6 = 0, d7 = 100, D = 260, P = 410. By jointly regulating the values of d1, d2, d3, d4, d5, d6, d7, D, and P within the above ranges, the color of the structural color device can be made red.

[0011] As a preferred embodiment of the structural color device based on the refractive index gradient distribution silicon nitride metasurface of the present invention, d1 = 4-6, d2 = 24-26, d3 = 9-11, d4 = 148-152, d5 = 49-51, d6 = 0-1, d7 = 118-122, D = 238-242, P = 378-382; preferably, d1 = 5, d2 = 25, d3 = 10, d4 = 150, d5 = 50, d6 = 0, d7 = 120, D = 240, P = 380. By jointly controlling the values of d1, d2, d3, d4, d5, d6, d7, D, and P within the above ranges, the color of the structural color device can be made yellow.

[0012] As a preferred embodiment of the structural color device based on the refractive index gradient distribution silicon nitride metasurface of the present invention, d1 = 9-11, d2 = 34-36, d3 = 34-36, d4 = 44-46, d5 = 49-51, d6 = 74-76, d7 = 128-132, D = 228-232, P = 348-352; preferably, d1 = 10, d2 = 35, d3 = 35, d4 = 45, d5 = 50, d6 = 75, d7 = 130, D = 230, P = 350. By jointly controlling the values of d1, d2, d3, d4, d5, d6, d7, D and P within the above ranges, the color of the structural color device can be made green.

[0013] As a preferred embodiment of the structural color device based on the refractive index gradient distribution silicon nitride metasurface of the present invention, d1 = 9-11, d2 = 34-36, d3 = 34-36, d4 = 44-46, d5 = 49-51, d6 = 74-76, d7 = 128-132, D = 218-222, P = 328-332; preferably, d1 = 10, d2 = 35, d3 = 35, d4 = 45, d5 = 50, d6 = 75, d7 = 130, D = 220, P = 330. By jointly controlling the values of d1, d2, d3, d4, d5, d6, d7, D, and P within the above ranges, the color of the structural color device can be made cyan.

[0014] As a preferred embodiment of the structural color device based on the refractive index gradient distribution silicon nitride metasurface of the present invention, d1 = 9-11, d2 = 34-36, d3 = 34-36, d4 = 44-46, d5 = 49-51, d6 = 74-76, d7 = 128-132, D = 198-202, P = 303-307; preferably, d1 = 10, d2 = 35, d3 = 35, d4 = 45, d5 = 50, d6 = 75, d7 = 130, D = 200, and P = 305. By jointly controlling the values of d1, d2, d3, d4, d5, d6, d7, D, and P within the above ranges, the color of the structural color device can be made purple.

[0015] It should be noted that the shape of the nanostructure units is a cylinder or a prism, preferably a cylinder; the period of the nanostructure units refers to the distance between any two nanostructure units.

[0016] As a preferred embodiment of the structural color device based on the refractive index gradient silicon nitride metasurface of the present invention, the substrate is a silicate glass sheet with an ITO coating. The ITO coating is used to increase conductivity and its thickness can be 10nm to 15nm, specifically 10nm, 11nm, 12nm, 13nm, 14nm, 15nm, etc.

[0017] In a second aspect, the present invention provides a method for preparing the above-mentioned structural color device based on the refractive index gradient distribution silicon nitride metasurface, comprising the following steps:

[0018] S1. Depositing a first silicon oxide layer, a first silicon nitride layer, a second silicon nitride layer, a third silicon nitride layer, a fourth silicon nitride layer, a fifth silicon nitride layer, and a second silicon oxide layer in sequence on the surface of the substrate by chemical vapor deposition (preferably plasma chemical vapor deposition);

[0019] S2. Coating photoresist on the surface of the second silicon oxide layer, completing pattern transfer through exposure, and then performing development, fixing, chrome plating, stripping, and etching (preferably inductively coupled plasma etching) to obtain a structural color device based on a refractive index gradient distribution silicon nitride metasurface.

[0020] As a preferred embodiment of the method for preparing a structural color device based on a refractive index gradient distribution silicon nitride metasurface according to the present invention, the chemical gas used in the chemical vapor deposition method includes a mixture of SiH4 and Ar, and NH3; the volume proportion of SiH4 in the mixture of SiH4 and Ar is 3% to 7% (for example, the volume proportion of SiH4 can be any one of 3%, 4%, 5%, 6%, 7% or any two of them, and more preferably 5%), and the flow rate of the mixture of SiH4 and Ar is 100 sccm to 300 sccm (for example, it can be 100 sccm, 120 sccm, 150 sccm, 160 sccm, 170 sccm, 180 sccm, 200 sccm, 220 sccm, 240 sccm, 260 sccm, 270 sccm, 280 sccm, 290 sccm, 300 sccm, 310 sccm, 320 sccm, 330 sccm, 340 sccm, 360 sccm, 370 sccm, 380 sccm, 390 sccm, 400 sccm, 410 sccm, 420 sccm, 430 sccm, 440 sccm, 450 sccm, 460 sccm, 470 sccm, 480 sccm, 490 sccm, 500 sccm, 510 sccm, 510 sccm, 510 sccm, 510 sccm, 510 sccm, 510 sccm, sccm, 140sccm, 160sccm, 180sccm, 200sccm, 220sccm, 240sccm, 260sccm, 280sccm, and 300sccm) and the flow rate of NH3 is 10sccm to 20sccm (for example, it can be a range of any one of 10sccm, 11sccm, 12sccm, 13sccm, 14sccm, 15sccm, 16sccm, 17sccm, 18sccm, 19sccm, and 20sccm, or any two of the ranges).

[0021] In a third aspect, the present invention provides an application of the above-mentioned structural color device based on the refractive index gradient distribution silicon nitride metasurface in the field of optical display, decoration or sensing.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The present invention distributes silicon nitride films of different refractive indexes in a low-high-low gradient, and uses a silicon oxide film with a specific refractive index as a refractive index matching layer. The two are combined to form a nanostructure unit, which is used to regulate the scattering, interference and resonance effects of light, thereby significantly improving the high saturation, high brightness and wide color gamut of the structural color device. The chemical stability and thermal stability of silicon nitride can also be used to ensure the reliable performance of the structural color device in various complex application environments.

[0024] The preparation method of the structural color device of the present invention adopts chemical vapor deposition technology to prepare the gradient refractive index silicon nitride film layer, and combines electron beam lithography and inductively coupled plasma etching to achieve nanometer-level precision control; its process stability and repeatability are better than traditional preparation methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Schematic diagram of the structure of the structural color device based on the refractive index gradient distribution silicon nitride metasurface of the present invention;

[0026] Figure 2Schematic diagram of the process of preparing a structural color device based on a silicon nitride metasurface with a gradient refractive index distribution according to the present invention;

[0027] Figure 3 The CIE color diagram and reflection spectrum diagram of the structural color device based on the refractive index gradient distribution silicon nitride metasurface in Example 1;

[0028] Figure 4 The CIE color diagram and reflection spectrum diagram of the structural color device based on the refractive index gradient distribution silicon nitride metasurface in Example 2;

[0029] Figure 5 The CIE color diagram and reflection spectrum diagram of the structural color device based on the refractive index gradient distribution silicon nitride metasurface in Example 3;

[0030] Figure 6 The CIE color diagram and reflection spectrum diagram of the structural color device based on the refractive index gradient distribution silicon nitride metasurface in Example 4;

[0031] Figure 7 The CIE color diagram and reflection spectrum diagram of the structural color device based on the refractive index gradient distribution silicon nitride metasurface in Example 5;

[0032] Figure 8 This is an SEM image of the structural color device based on the refractive index gradient distribution silicon nitride metasurface in Example 3;

[0033] Figure 9 This is a reflection spectrum diagram of the structural color device based on the refractive index gradient distribution silicon nitride metasurface in Example 3. DETAILED DESCRIPTION

[0034] In order to better illustrate the purpose, technical solutions and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments.

[0035] Unless otherwise specified, other materials and reagents used in the examples can be obtained from commercial sources.

[0036] Example 1

[0037] A structural color device based on a refractive index gradient distribution silicon nitride metasurface (such as Figure 1The invention discloses a nanostructured substrate comprising a substrate and a nanostructure array provided on a surface of the substrate; the nanostructure array comprises a plurality of periodically arranged nanostructured units, each of which is in the shape of a cylinder with a diameter of D nm and a period of P nm; the nanostructured unit comprises a first silicon oxide layer (refractive index of 1.46, thickness d1 nm), a first silicon nitride layer (refractive index of 1.87, thickness d2 nm), a second silicon nitride layer (refractive index of 2.00, thickness d3 nm), a third silicon nitride layer (refractive index of 2.23, thickness d4 nm), a fourth silicon nitride layer (refractive index of 2.00, thickness d5 nm), a fifth silicon nitride layer (refractive index of 1.87, thickness d6 nm), and a second silicon oxide layer (refractive index of 1.46, thickness d7 nm) stacked in sequence.

[0038] The structural color device based on the refractive index gradient distribution silicon nitride metasurface can be prepared by the following preparation method (eg Figure 2 shown):

[0039] S1. Using plasma chemical vapor deposition (PECVD), a first silicon oxide layer (refractive index of 1.46), a first silicon nitride layer (refractive index of 1.87), a second silicon nitride layer (refractive index of 2.00), a third silicon nitride layer (refractive index of 2.23), a fourth silicon nitride layer (refractive index of 2.00), a fifth silicon nitride layer (refractive index of 1.87), and a second silicon oxide layer (refractive index of 1.46) are sequentially deposited on the surface of a substrate (a silicate glass sheet coated with 13 nm ITO);

[0040] The specific parameters of plasma chemical vapor deposition are as follows: base pressure of 800 mTorr, RF power of 35 W, ambient temperature of 300 ° C, flow rate of 5% SiH4 / Ar (mixture of SiH4 and Ar, SiH4 volume ratio is 5%) of 0-1000 sccm, NH3 flow rate of 0-50 sccm, N2 flow rate of 2000 sccm;

[0041] Among them, the refractive index of the silicon nitride layer is adjusted by controlling the flow rate of the gas. When the flow rate of 5% SiH4 / Ar is 300 sccm and the flow rate of NH3 is 14 sccm, the refractive index of the silicon nitride layer is 2.23; when the flow rate of 5% SiH4 / Ar is 200 sccm and the flow rate of NH3 is 14 sccm, the refractive index of the silicon nitride layer is 2.00; when the flow rate of 5% SiH4 / Ar is 100 sccm and the flow rate of NH3 is 14 sccm, the refractive index of the silicon nitride layer is 1.87.

[0042] S2. Spin-coat a PMMA photoresist with a thickness of approximately 100 nm on the surface of the second silicon oxide layer, and then bake the sample on a heating platform at 180°C for 40 min; use an electron beam lithography machine (EBL) to transfer the pattern to the photoresist; use a developer with a ratio of MIBK:IPA = 1:3 for development for 30 s, and use an IPA solution for fixing for 10 s; evaporate a layer of chromium with a thickness of 22 nm on the surface of the developed and fixed PMMA photoresist as a hard mask; soak the chromium-plated sample in a remover-PG solution for 12 to 24 hours to strip off the PMMA photoresist; use inductively coupled plasma etching (ICPEtting) to obtain a structural color device based on a refractive index gradient silicon nitride metasurface.

[0043] Example 2 to Example 5

[0044] A structural color device based on a refractive index gradient distribution silicon nitride metasurface, except that the color, d1, d2, d3, d4, d5, d6, d7, D and P of the structural color device are different from those in Example 1, the rest are the same as Example 1.

[0045] Table 1

[0046] serial number color d1 / nm d2 / nm d3 / nm d4 / nm d5 / nm d6 / nm d7 / nm D / nm P / nm Example 1 red 5 20 20 150 50 0 100 260 410 Example 2 yellow 5 25 10 150 50 0 120 240 380 Example 3 green 10 35 35 45 50 75 130 230 350 Example 4 blue 10 35 35 45 50 75 130 220 330 Example 5 Purple 10 35 35 45 50 75 130 200 305

[0047] Through COMSOL and FDTD simulation calculations (COMSOL and FDTD are simulation software), the position, reflection efficiency, and half-height peak width of different color structural color devices in the CIE color diagram are obtained. The results are as follows:

[0048] Example 1: The red color appears at (0.645, 0.329) on the CIE color diagram, with a reflection efficiency of 95% and a half-peak width of 14.83 nm (e.g. Figure 3 shown);

[0049] Example 2: Yellow appears at (0.437, 0.542) on the CIE color diagram, with a reflection efficiency of 95% and a half-peak width of 16.83 nm (e.g. Figure 4 shown);

[0050] Example 3: Green appears at (0.076, 0.777) on the CIE color diagram, with a reflection efficiency of 80% and a half-peak width of 8.67 nm (e.g. Figure 5 shown);

[0051] Example 4: The cyan color appears at (0.033, 0.539) on the CIE color diagram, with a reflection efficiency of 73% and a half-peak width of 11.46 nm (e.g. Figure 6 shown);

[0052] Example 5: Purple appears at (0.148, 0.058) on the CIE color diagram, with a reflection efficiency of 51% and a half-peak width of 13.42 nm (e.g. Figure 7 shown).

[0053] The above simulation results show that the structural color device based on the refractive index gradient distribution silicon nitride metasurface of the present invention can achieve bright and pure color display.

[0054] At the same time, the green structural color device in Example 3 was experimentally verified (the results are shown in Figure 2). Figure 8 and Figure 9 shown), according to Figure 8 From a and b in the figure, we can see that the nanostructure array on the surface of the structural color device is clear and regular. Figure 8 From the c and d in the figure, we can see that the diameter and height of the periodically arranged nanostructure units meet the design requirements. Figure 9 The reflectance spectrum of the structural color device shows a reflectivity exceeding 70%, with a half-peak width of 5.86nm. Compared to simulation results, these experimental results are generally consistent with theoretical expectations, demonstrating the excellent performance stability and repeatability of the structural color device of the present invention. Experimental verification results show that the color brightness and saturation of this structural color device exceed those of currently used structural color technologies, potentially providing superior solutions for fields such as optical displays and decoration.

[0055] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A structural color device based on a refractive index gradient silicon nitride metasurface, characterized in that: The method comprises a substrate and a nanostructure array disposed on a surface of the substrate; The nanostructure array includes a plurality of periodically arranged nanostructure units, each of which includes a first silicon oxide layer, a first silicon nitride layer, a second silicon nitride layer, a third silicon nitride layer, a fourth silicon nitride layer, a fifth silicon nitride layer, and a second silicon oxide layer stacked in sequence; The refractive index of the first silicon oxide layer is n0, the refractive index of the first silicon nitride layer is n1, the refractive index of the second silicon nitride layer is n2, the refractive index of the third silicon nitride layer is n3, the refractive index of the fourth silicon nitride layer is n4, the refractive index of the fifth silicon nitride layer is n5, and the refractive index of the second silicon oxide layer is n6, n0=n6<n1=n5<n2=n4<n3.

2. The structural color device according to claim 1, wherein n0=1.45~1.5, n1=1.85~1.9, n2=1.9~2.1, n3=2.2~2.

25.

3. The structural color device according to claim 1, wherein The thickness of the first silicon oxide layer is d1 nm, the thickness of the first silicon nitride layer is d2 nm, the thickness of the second silicon nitride layer is d3 nm, the thickness of the third silicon nitride layer is d4 nm, the thickness of the fourth silicon nitride layer is d5 nm, the thickness of the fifth silicon nitride layer is d6 nm, the thickness of the second silicon oxide layer is d7 nm, the diameter of the nanostructure unit is D nm, and the period of the nanostructure unit is P nm; d1=4~6, d2=19~21, d3=19~21, d4=148~152, d5=49~51, d6=0~1, d7=98~102, D=258~262, P=408~412.

4. The structural color device according to claim 3, wherein: d1=4~6, d2=24~26, d3=9~11, d4=148~152, d5=49~51, d6=0~1, d7=118~122, D=238~242, P=378~382.

5. The structural color device according to claim 3, wherein: d1=9~11, d2=34~36, d3=34~36, d4=44~46, d5=49~51, d6=74~76, d7=128~132, D=228~232, P=348~352.

6. The structural color device according to claim 3, wherein: d1=9~11, d2=34~36, d3=34~36, d4=44~46, d5=49~51, d6=74~76, d7=128~132, D=218~222, P=328~332.

7. The structural color device according to claim 3, wherein: d1=9~11, d2=34~36, d3=34~36, d4=44~46, d5=49~51, d6=74~76, d7=128~132, D=198~202, P=303~307.

8. The method for preparing a structural color device according to any one of claims 1 to 7, characterized in that: The following steps are involved: S1. Depositing a first silicon oxide layer, a first silicon nitride layer, a second silicon nitride layer, a third silicon nitride layer, a fourth silicon nitride layer, a fifth silicon nitride layer, and a second silicon oxide layer in sequence on the surface of the substrate by chemical vapor deposition; S2. Coating photoresist on the surface of the second silicon oxide layer, completing pattern transfer through exposure, and then performing development, fixing, chrome plating, stripping, and etching to obtain a structural color device based on a refractive index gradient distribution silicon nitride metasurface.

9. The preparation method according to claim 8, wherein the chemical gases used in the chemical vapor deposition method include a mixture of SiH4 and Ar, and NH3; the volume proportion of SiH4 in the mixture of SiH4 and Ar is 3% to 7%, the flow rate of the mixture of SiH4 and Ar is 100 sccm to 300 sccm; and the flow rate of NH3 is 10 sccm to 20 sccm.

10. Use of the structural color device according to any one of claims 1 to 7 in the field of optical display, decoration or sensing.

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