Preparation method of mixed multi-stage full-spectrum high-efficiency absorber based on phase separation technology

Abstract

The application provides a method for preparing a mixed multi-stage plasmonic resonant cavity based on a phase separation technology, and comprises the following steps: cleaning a substrate, electron beam evaporation of a reflection layer on a substrate surface, spin coating of a polymer layer and a silicon dioxide layer, subsequent coating of a phase separation blend film, and then selective etching by a reactive ion etching technology to transfer to an underlying structure; with etching of oxygen, PPSQ columns are exposed, a small amount of small droplets are wrapped in a high-concentration blend, with an increase in etching time, a residual layer forms a film with nanometer holes, small columns are etched out, a mixed multi-stage multi-size structure is obtained, and then a gold layer is evaporated on the above-mentioned template by an electron beam evaporation technology to obtain a mixed multi-stage multi-size plasmonic resonant cavity. The mixed multi-stage resonant cavity provided by the application has high sunlight absorption, and has the advantages of a simple preparation method, stable performance, large-area production, and the like, and can be combined with a photocatalyst to improve photocatalytic hydrogen production performance, provide more catalytic sites, and improve sunlight utilization. The application of the multi-stage broadband plasmonic resonant cavity in the research of solar photocatalytic hydrogen production has very important significance.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of spectral absorption, and relates to a method for preparing a mixed multi-level plasmonic resonant cavity based on a phase separation technique, and in particular to a method for preparing a plasmonic resonant cavity for full-spectrum solar light high-efficiency absorption based on a phase separation technique. BACKGROUND

[0002] In modern energy technology, solar energy, as a clean and renewable energy, is widely used in photocatalysis, photothermal conversion and other fields. Therefore, broadening the solar light absorption has attracted widespread attention in recent years. In order to improve the utilization efficiency of solar energy, researchers have devoted to developing solar energy absorption materials with high spectral absorption capacity. Traditional solar energy absorbers can only absorb light energy in a limited wavelength range, which limits the overall efficiency.

[0003] As a new type of optical structure, plasmonic resonant cavity can produce strong local electromagnetic field enhancement effect in a specific wavelength range, thereby improving the absorption efficiency of solar energy, and is widely used in photocatalysis, photothermal conversion and other fields. However, a single plasmonic resonant cavity is limited by the size of the structure, which is not conducive to wide-band and full-spectrum absorption. At present, through diversified regulation mechanisms, spectral regulation can be realized to achieve wide-spectrum and high-efficiency light absorption. For example, by combining plasmonic resonant cavity with other optical hierarchical structures [ACS Photonics, 2019, 6(1), 139-147]; preparing a multi-mode optical resonant cavity composite plasmonic surface (patent CN116165733A) can realize enhanced light absorption effect in a wide spectral range. Plasmonic resonance effect can significantly enhance the local electromagnetic field on the surface of the material, so that it can absorb more light energy at a specific wavelength.

[0004] Mixed multi-level plasmonic resonant cavity can combine the advantages of different materials and structures to achieve a wider absorption spectral range and higher absorption efficiency. At the same time, by reasonably designing and optimizing the structural parameters of the plasmonic resonant cavity, the spectral response range can be further improved, and the overall energy conversion efficiency is also improved, providing a new way for the efficient use of solar energy. However, the more scales the structure has, the more complex the design is, which increases the difficulty of preparation. Therefore, it is necessary to design a mixed multi-level structure with a simple preparation method and good compatibility with conventional micro-nano processes from the aspects of structural performance, process convenience and the like. SUMMARY

[0005] The purpose of the present application is to solve the above technical problems, and a method for preparing a mixed multi-level plasmonic resonant cavity based on a phase separation technique is provided.

[0006] The technical scheme of the present application is a method for preparing a mixed multi-stage plasmonic resonant cavity based on phase separation technology, and the specific steps are as follows:

[0007] a) substrate cleaning: the glass substrate is placed in an ethanol solution for ultrasonic cleaning, and finally cleaned with deionized water, dried with nitrogen, and dried on a hot plate;

[0008] b) depositing a metal layer: using electron beam evaporation or resistance evaporation technology to deposit a reflective metal layer on the substrate;

[0009] c) spin coating an organic solution of a silicon-free high molecular weight polymer on the surface of the deposited reflective metal layer, and obtaining a silicon-free high molecular weight polymer layer after curing;

[0010] d) depositing a layer of SiO2 film on the silicon-free high molecular weight polymer layer;

[0011] e) dissolving polystyrene and silicon-containing polymer in an organic solvent, stirring to form a phase separation solution;

[0012] f) spin coating the phase separation solution on the substrate prepared in step d) to obtain a phase separation blend film;

[0013] g) using reactive ion etching technology to selectively etch the phase separation blend film to form a discontinuous mixed multi-stage structure template on the surface of the substrate;

[0014] h) using electron beam evaporation technology to evaporate a layer of gold on the surface of the template.

[0015] Preferably, the substrate in step a) is silicon, quartz or glass.

[0016] Preferably, the metal layer in step b) is gold, silver or aluminum; the thickness is 50-100 nm.

[0017] Preferably, the silicon-free high molecular weight organic solution in step c) is a chlorobenzene solution of polymethyl methacrylate with a mass concentration of 1% to 5%; the thickness of the silicon-free high molecular weight layer is 100-500 nm; the spin coating speed is 1000-4000 rpm, and the spin coating time is 40-60 s.

[0018] Preferably, the curing temperature in step c) is 80-85°C, and the curing time is 1-3 min.

[0019] Preferably, the method for depositing the SiO2 layer in step d) is plasma enhanced chemical vapor deposition technology (OXFORD P80 PECVD); the thickness of the deposited SiO2 layer is 15-40 nm.

[0020] Preferably, the organic solvent in step e) is toluene or chlorobenzene; the silicon-containing polymer is a polyphenylsilsesquioxane; the mass ratio of polystyrene to the silicon-containing polymer is (1-5) : 1; and the total mass concentration of the phase separation solution is 2-10%.

[0021] Preferably, the rotation speed in step f) is 2000-4000 rpm, and the spin-coating time is 40-60 s.

[0022] Preferably, the reaction ion etching instrument in step g) is a ULVAC ICPRIE etching machine; the selective etching process is as follows: first, O2 plasma etching is used to remove part of the continuous phase of polystyrene to form a polyphenylsilsesquioxane dispersed phase of nanocolumns, and the etching time is 250-500 s; then, O2 / CHF3 mixed gas is used to partially remove the polyphenylsilsesquioxane adhered together at the bottom of the nanocolumns, and the etching time is 20-250 s; and then, CF4 / CHF3 mixed gas is used to continue etching the SiO2 layer downward as a mask, and the etching time is 90-210 s; and then, O2 plasma is used to etch the non-silicon polymer layer downward, and the etching time is 50-250 s; and the plasma flow is 10-30 sccm, and the power is 35-40 W.

[0023] Preferably, the electron beam evaporation process in step h) is as follows: the inside of the film plating instrument is degassed to break the vacuum state, the above-mentioned template is clamped on the sample table, and metal nickel evaporation material is added to the lower tungsten crucible, vacuum is drawn until the vacuum degree is 1-5*10 -3 Pa, a high-pressure electron beam is opened, a 10-20 nm metal gold layer is evaporated, the film plating rate is

[0024] Beneficial effects:

[0025] The application provides a mixed multi-level disordered plasmonic resonant cavity prepared based on a phase separation technology, the prepared resonant cavity can respond in a full spectrum range, has strong light absorption, and can generate hot electrons and enhance electric field intensity, and after being combined with a photocatalyst, can effectively promote separation of photo-generated electrons and holes, thereby promoting photocatalytic hydrogen production performance and improving solar light utilization rate; in addition, the preparation process of the application is simple, is suitable for large-area preparation, and has wide application prospects. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 is a structural schematic diagram of the mixed multi-level plasmonic resonant cavity.

[0027] Figure 2 is an SEM diagram of the mixed multi-level resonant cavity of Example 1 of the application.

[0028] Figure 3SEM image of the cross section of the mixed multi-level resonant cavity of Example 1 of the present application.

[0029] Figure 4 Absorption spectrum of the mixed multi-level resonant cavity prepared by the phase separation technique of Example 1 of the present application in the range of 200-2500 nm.

[0030] Figure 5 SEM image of the mixed multi-level resonant cavity of Example 2 of the present application.

[0031] Figure 6 Absorption spectrum of the mixed multi-level resonant cavity prepared by the phase separation technique of Example 2 of the present application in the range of 200-2500 nm. DETAILED DESCRIPTION

[0032] The specific embodiments of the present application will be described below with reference to the drawings, obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments.

[0033] The structural schematic diagram of the mixed multi-level plasmonic resonant cavity of Examples 1-5 of the present application is shown in Figure 1

[0034] In the following examples, the substrate cleaning is as follows: the glass substrate is placed in an ethanol solution for ultrasonic cleaning, finally cleaned with deionized water, dried with nitrogen, and dried on a hot plate;

[0035] In the following examples, the electron beam evaporation process involved in step h) is as follows: the film coater is placed in a vacuum, the vacuum state is broken, the above-mentioned template is clamped on the sample table, and the metal nickel evaporation material is added to the lower tungsten crucible, vacuum is drawn until the vacuum degree is 1-5*10 -3 Pa, the high-pressure electron beam is turned on, and a 10-20 nm gold metal layer is evaporated at a coating rate of

[0036] In the following examples, when testing the photochemical performance, the prepared multi-level plasmonic resonant cavity is used to deposit a thin film of a photocatalyst by chemical bath deposition or electrostatic adsorption. The photocatalytic thin film is cadmium sulfide, and the deposition time is 10-30 min.

[0037] Example 1

[0038] Deposition of metal layer: a 50 nm gold metal layer is deposited on the glass substrate by electron beam evaporation technology;

[0039] Preparation of a polymethyl methacrylate polymer layer on the surface of the glass substrate: a 3% polymethyl methacrylate solution by mass fraction is prepared with chlorobenzene as the solvent, and is spin-coated on the glass substrate with the deposited gold metal layer at a rotation speed of 2000 revolutions per minute for 45 seconds. Heat treatment at 85°C for 3 minutes completes solidification, and the thickness of the polymethyl methacrylate is 200 nm; ​

[0040] Deposition of SiO2 layer: SiO2 layer with thickness of 20 nm is deposited on the polymer layer by chemical vapor deposition technology;

[0041] Preparation of phase separation structure film: polystyrene and polyphenylsilsesquioxane blended polymer solution is spin-coated on the above substrate, the mass ratio of polystyrene and polyphenylsilsesquioxane is 1:1, the total solution concentration is 6%, the solvent is toluene, the spin-coating rate of the blended polymer solution is 3000 rpm, and the spin-coating time is 45 s;

[0042] Selective etching: polystyrene continuous phase is removed by O2 plasma (30 sccm, 35 W) etching for 400 s, then polyphenylsilsesquioxane partially remaining on the bottom of the nanocolumn and adhering together is partially removed by O2 / CHF3 mixed gas (20 sccm / 20 sccm, 40 W) etching for 120 s, a film with nanoholes is formed on the glass substrate, accompanied by the appearance of residual layer small pillars, and then the film with nanoholes is used as a mask to continue etching downward by CF4 / CHF3 mixed gas for 130 s to remove the SiO2 layer in the holes, and then O2 plasma (10 sccm, 35 W) is used to etch downward for 100 s to remove the polymethyl methacrylate polymer layer below the holes, to obtain a nanohole phase separation template;

[0043] Coating: a 15 nm metal gold film is coated on the above substrate by electron beam evaporation technology to prepare a multi-stage plasmonic resonance cavity; wherein the coating rate is 1*10 -3 Pa; the SEM image of the mixed multi-stage resonance cavity is shown in Figure 2 , the corresponding cross-sectional electron microscope image is shown in Figure 3 , the ultraviolet absorption spectrum of the plasmonic resonance cavity is tested as shown in Figure 4 , which shows that the multi-stage plasmonic resonance cavity has high absorption efficiency in the range of 200-2500 nm;

[0044] CdS is deposited by chemical bath deposition method to uniformly load a photocatalyst film on the surface of the multi-stage structure, the deposition time is 20 min, and a uniform mixed multi-stage resonance cavity photocatalyst film is obtained; the above sample is placed in a 200 mg / mL glucose solution for photocatalytic hydrogen production experiment. The photocatalytic water decomposition hydrogen production test is carried out by using an online sampling system connected with a gas chromatograph (7890B, Agilent, using argon as the carrier gas), in which a thermal conductivity detector (TCD) is used, under the irradiation of a 300 W xenon lamp, the system is deoxygenated by blowing argon gas for 1 h to remove air in the reactor, then the hydrogen production amount is recorded every 30 min, and the test is carried out for 2 h, and the photocatalytic yield can reach 8.94 μmol.

[0045] Example 2

[0046] Depositing a metal layer: a 100 nm gold layer was deposited on the glass substrate by electron beam evaporation;

[0047] Preparing a polymethyl methacrylate polymer layer on the surface of the glass substrate: a 3% polymethyl methacrylate solution was prepared using chlorobenzene as a solvent, and was spin-coated on the glass substrate with the deposited metal layer at a rotation speed of 2000 rpm for 50 s, and was then heat-treated at 85°C for 2 min to complete solidification, and the thickness of the polymethyl methacrylate layer was 200 nm;

[0048] Depositing a SiO2 layer: a 20 nm thick SiO2 layer was deposited on the polymer layer by chemical vapor deposition;

[0049] Preparing a phase separation structure film: a polystyrene and polyphenylsilsesquioxane blended polymer solution was spin-coated on the above substrate, the mass ratio of polystyrene to polyphenylsilsesquioxane was 1:1, the total solution concentration was 10%, the solvent was toluene, and the spin-coating rate of the blended polymer solution was 3000 rpm for 50 s;

[0050] Selective etching: polystyrene continuous phase was removed by O2 plasma (10 sccm, 35 W) etching for 500 s, and then polyphenylsilsesquioxane remaining on the bottom of the nanocolumns was partially removed by O2 / CHF3 mixed gas (20 sccm / 20 sccm, 40 W) etching for 250 s, to form a film with nanoholes on the substrate of the glass substrate, accompanied by the appearance of residual layer nanocolumns, and then the film was used as a mask to continue etching down the SiO2 layer in the holes by CF4 / CHF3 mixed gas for 130 s, and then the polymethyl methacrylate polymer layer below the holes was removed by O2 plasma (10 sccm, 35 W) etching for 100 s, to obtain a nanohole phase separation template;

[0051] Coating: a 10 nm gold film was coated on the above substrate by electron beam evaporation to prepare a multistage plasmonic resonant cavity; the coating rate was 2*10 -3 Pa; the SEM image of the mixed multistage resonant cavity is shown in Figure 5 , and the ultraviolet absorption spectrum of the plasmonic resonant cavity is shown in Figure 6 , which shows that the multistage plasmonic resonant cavity can well absorb sunlight in the range of 200-2500 nm;

[0052] CdS was deposited on the surface of the hierarchical structure by chemical bath deposition to uniformly load the photocatalyst film, and a uniform mixed hierarchical resonant cavity photocatalytic film was obtained after 30 min of deposition. The sample was placed in a 200 mg / mL glucose solution for photocatalytic hydrogen production experiments. The photocatalytic decomposition of water to produce hydrogen was tested using an online sampling system connected to a gas chromatograph (7890B, Agilent, with argon as the carrier gas). A thermal conductivity detector (TCD) was used under the irradiation of a 300 W xenon lamp. The system was deoxygenated by blowing argon for 1 h to remove the air in the reactor. The hydrogen production was then recorded every 30 min, and the test was performed for 2 h. The photocatalytic yield reached 8.54 μmol.

[0053] Example 3

[0054] Deposition of metal layer: A 50 nm silver metal layer was deposited on the silicon wafer using electron beam evaporation technology;

[0055] Preparation of a polymethyl methacrylate polymer layer on the surface of the silicon wafer: A 1% polymethyl methacrylate solution was prepared using chlorobenzene as the solvent. The solution was spin-coated on the silicon substrate with the deposited silver metal layer at a speed of 2000 rpm for 40 s. The polymethyl methacrylate layer was then cured by heat treatment at 85°C for 2 min. The thickness of the polymethyl methacrylate layer was 100 nm.

[0056] Deposition of a SiO2 layer: A 40 nm thick SiO2 layer was deposited on the polymer layer using chemical vapor deposition technology.

[0057] Preparation of a phase separation structure film: A solution of a blend of polystyrene and polyphenylsilsesquioxane polymers was spin-coated on the above substrate. The mass ratio of polystyrene to polyphenylsilsesquioxane was 3:1, and the total solution concentration was 2%. Chlorobenzene was used as the solvent, and the spin-coating rate of the blend polymer solution was 4000 rpm for 60 s.

[0058] Selective etching: The polystyrene continuous phase was removed by O2 plasma etching (10 sccm, 35 W) for 250 s. Then, the polyphenylsilsesquioxane that was partially adhered together at the bottom of the nanocolumns was partially removed by O2 / CHF3 mixed gas etching (20 sccm / 20 sccm, 40 W) for 20 s to form a film with nanoholes on the silicon substrate, exposing the upper small-sized columns. The film was then used as a mask for further etching. CF4 / CHF3 mixed gas was used to etch downward for 210 s to remove the SiO2 layer in the holes. O2 plasma (30 sccm, 35 W) was then used to etch downward for 50 s to remove the polymethyl methacrylate polymer layer below the holes, obtaining a hierarchical multi-sized phase separation template.

[0059] Coating: A 15 nm gold metal film was coated on the above substrate using electron beam evaporation technology to prepare a hierarchical plasmonic resonant cavity. The coating rate was The vacuum degree during coating is 5*10 -3 Pa; the multi-stage plasmonic resonance cavity has high absorption efficiency in 200-2500nm.

[0060] CdS was deposited by chemical bath deposition method to uniformly load the photocatalyst film on the surface of the multi-stage structure, the deposition time was 20min, and a uniform mixed multi-stage resonance cavity photocatalyst film was obtained; the above sample was placed in a 200mg / mL glucose solution for photocatalytic hydrogen production experiment. The photocatalytic decomposition of water to produce hydrogen test was carried out by using an online sampling system connected with a gas chromatograph (7890B, Agilent, using argon as the carrier gas), in which a thermal conductivity detector (TCD) was used under the irradiation of a 300W xenon lamp, the system was deoxygenated by blowing argon for 1h to remove the air in the reactor, and then the hydrogen production was recorded every 30min, and the test was carried out for 2h, and the photocatalytic yield was up to 6.91μmol.

[0061] Example 4

[0062] Deposition of metal layer: a metal layer of gold 50nm was deposited on the silicon wafer by electron beam evaporation technology;

[0063] Preparation of polymer layer on the surface of silicon wafer: a polymethyl methacrylate solution with a mass fraction of 5% was prepared with chlorobenzene as the solvent, and was spin-coated on the silicon substrate with deposited metal layer at a rotation speed of 1200r / min for 60s, and then was heat-treated at 80℃ for 1min for solidification, and the thickness of the polymethyl methacrylate was 500nm;

[0064] Deposition of SiO2 layer: a SiO2 layer was deposited on the polymer layer by chemical vapor deposition technology, and the thickness was 15nm;

[0065] Preparation of phase separation structure film: a solution of polystyrene and polysilsesquioxane blend polymer was spin-coated on the above substrate, in which the mass ratio of polystyrene to polysilsesquioxane was 5:1, the total solution concentration was 6%, the solvent was toluene, and the spin-coating rate of the blend polymer solution was 2000r / min for 40s;

[0066] Selective etching: O2 plasma (10sccm, 35W) was used for etching for 400s to remove the polystyrene continuous phase, then O2 / CHF3 mixed gas (20sccm / 20sccm, 40W) was used for etching for 250s to remove the polysilsesquioxane remaining at the bottom of the nanorod and sticking together, a nanorod film was formed on the silicon wafer substrate, and then CF4 / CHF3 mixed gas was used for further etching downward for 90s to remove the SiO2 layer in the hole, and then O2 plasma (10sccm, 35W) was used for etching downward for 250s to remove the polymethyl methacrylate polymer layer below the hole, and a nanohole phase separation template was obtained;

[0067] Coating: 20 nm of gold thin film is coated on the substrate by using electron beam evaporation technology to prepare a multi-stage plasmonic resonant cavity; wherein the coating rate is 0.2 nm / s The vacuum degree during coating is 2*10 -3 Pa; the multi-stage plasmonic resonant cavity has high absorption efficiency in the range of 200-2500 nm.

[0068] Composite photocatalyst: cadmium sulfide is deposited on the multi-stage structure surface by using chemical bath deposition method to uniformly load a photocatalyst thin film, the deposition time is 30 min, and a uniform mixed multi-stage resonant cavity photocatalyst thin film is obtained; the above sample is placed in a 200 mg / mL glucose solution for photocatalytic hydrogen production experiment. The photocatalytic hydrogen production test is carried out by using an online sampling system connected with a gas chromatograph (7890B, Agilent, using argon as the carrier gas), wherein a thermal conductivity detector (TCD) is used, under the irradiation of a 300 W xenon lamp, the system is deoxygenated by blowing argon gas for 1 h, then the hydrogen production amount is recorded every 30 min, and the test is carried out for 2 h, and the photocatalytic yield can reach 7.74 μmol.

[0069] Example 5

[0070] Depositing a metal layer: a metal layer of aluminum 100 nm is deposited on a glass substrate by using electron beam evaporation technology;

[0071] Preparing a polymethyl methacrylate polymer layer on the surface of the glass substrate: a polymethyl methacrylate solution with a mass fraction of 3% is prepared with chlorobenzene as the solvent, and is spin-coated on the glass substrate with the deposited aluminum metal layer at a rotation speed of 4000 revolutions / minute, the spin-coating time is 45 s, and the thickness of the polymethyl methacrylate is 200 nm after heat treatment at 85°C for 3 min for solidification;

[0072] Depositing a SiO2 layer: a SiO2 layer is deposited on the polymer layer by using chemical vapor deposition technology, and the thickness is 30 nm;

[0073] Preparing a phase separation structure thin film: a polystyrene and polyphenylsilsesquioxane blended polymer solution is spin-coated on the above substrate, wherein the mass ratio of polystyrene to polyphenylsilsesquioxane is 1:1, the total solution concentration is 6%, the solvent is toluene, and the spin-coating rate of the blended polymer solution is 2000 revolutions / minute, and the spin-coating time is 40 s;

[0074] Selective etching: 400s of O2 plasma (10sccm, 35W) was used to remove the polystyrene continuous phase, and then 120s of O2 / CHF3 mixed gas (20sccm / 20sccm, 40W) was used to remove the residual polystyrene silsesquioxane adhered together at the bottom of the nanopillar, forming a nanoporous film on the glass substrate, accompanied by the appearance of smaller pillars with the increase of etching time, and then using it as a mask, 180s of CF4 / CHF3 mixed gas was used to etch down to remove the SiO2 layer in the hole, and then 100s of O2 plasma (30sccm, 35W) was used to etch down to remove the polymethyl methacrylate polymer layer below the hole, obtaining a nanoporous phase separation template;

[0075] Coating: 10nm of metal gold film was coated on the above substrate by using electron beam evaporation technology to prepare a multi-stage plasmonic resonant cavity; wherein the coating rate is The vacuum degree during coating is 3*10 -3 Pa; the multi-stage plasmonic resonant cavity has high absorption efficiency in 200-2500nm;

[0076] CdS was deposited on the surface of the multi-stage structure by chemical bath deposition to uniformly load a photocatalyst film, the deposition time was 20min, and a uniform mixed multi-stage resonant cavity photocatalyst film was obtained; the above sample was placed in a 200mg / mL glucose solution for photocatalytic hydrogen production experiment. The photocatalytic water decomposition hydrogen production test was carried out by using an online sampling system connected with a gas chromatograph (7890B, Agilent, using argon as the carrier gas), in which a thermal conductivity detector (TCD) was used, under the irradiation of a 300W xenon lamp, the system was deoxidized by blowing argon for 1h to remove the air in the reactor, and then the hydrogen production was recorded every 30min, and the test was carried out for 2h, and the photocatalytic yield was 8.71μmol.

Claims

1. A method for preparing a mixed multi-level plasmonic resonant cavity based on phase separation technology, comprising the following steps: a) substrate cleaning: placing a glass substrate in an ethanol solution for ultrasonic cleaning, then cleaning with deionized water, blowing dry with nitrogen, and drying on a hot plate; b) depositing a metal layer on the substrate, wherein the metal layer is gold, silver or aluminum, and the thickness of the metal layer is 50-100 nm; c) spin-coating an organic solution of a silicon-free high polymer on the surface of the deposited metal layer, and obtaining a silicon-free high polymer layer after curing, wherein the organic solution of the silicon-free high polymer in step c) is a chlorobenzene solution of polymethyl methacrylate with a mass concentration of 1-5%, and the thickness of the silicon-free high polymer layer is 100-500 nm; d) depositing a SiO2 film on the silicon-free high polymer layer, wherein the thickness of the deposited SiO2 layer is 15-40 nm; e) dissolving polystyrene and a silicon-containing polymer in an organic solvent to form a blended phase separation solution, wherein the organic solvent in step e) is toluene or chlorobenzene, the silicon-containing polymer is a polyphenylsilsesquioxane, the mass ratio of polystyrene to the silicon-containing polymer is (1-5):1, and the total mass concentration of the blended phase separation solution is 2-10%; f) spin-coating the blended phase separation solution on the substrate prepared in step d) to obtain a phase separation blended film; g) performing selective etching on the phase separation blended film by using a reactive ion etching technology to form a discontinuous mixed multi-level structure template on the surface of the substrate; and h) evaporating a layer of gold on the surface of the template by using an electron beam evaporation technology. The substrate in step a) is silicon, quartz or glass. b) depositing a metal layer: depositing a reflective metal layer on the substrate using electron beam evaporation or resistive evaporation techniques; wherein, The spin-coating speed in step c) is 1000-4000 rpm, and the spin-coating time is 40-60 s. The curing temperature in step c) is 80-85°C, and the curing time is 1-3 min. The method for depositing the SiO2 layer in step d) is plasma-enhanced chemical vapor deposition technology. The spin-coating speed in step f) is 2000-4000 rpm, and the spin-coating time is 40-60 s. The instrument for the reactive ion etching technology in step g) is a ULVAC ICPRIE etching machine, and the selective etching process comprises the following steps: first, etching part of the continuous phase of polystyrene by using O2 plasma to form a polyphenylsilsesquioxane dispersed phase of nanocolumns, and the etching time is 250-500 s; then, etching part of the polyphenylsilsesquioxane remaining and adhered together at the bottom of the nanocolumns by using O2 / CHF3 mixed gas, and the etching time is 20-250 s; and finally, continuing to etch the SiO2 layer downward by using CF4 / CHF3 mixed gas as a mask, and the etching time is 90-210 s, and etching the silicon-free high polymer layer downward by using O2 plasma, and the etching time is 50-250 s; the plasma flow is 10-30 sccm, and the power is 35-40 W. ​ ​ 2. The method of claim 1, wherein, ​ 3. The method of claim 1, wherein, ​ 4. The method of claim 1, wherein, ​ 5. The method of claim 1, wherein, ​ 6. The method of claim 1, wherein, ​ 7. The method of claim 1, wherein, ​ 8. The method of claim 1, wherein, The electron beam evaporation process in step h) is as follows: the film coater is degassed to break the vacuum state, the above-mentioned template is clamped on the sample table, and the metal nickel evaporation material is added to the lower tungsten crucible, vacuum is drawn until the vacuum degree is 1-5*10 -3 Pa, the high-pressure electron beam is turned on, a 10-20 nm metal gold layer is evaporated, and the film coating rate is 0.8-1.2 Å / s.

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