Metal nanodot array processing method based on electrochemical anodic oxidation technology

Abstract

The invention discloses a metal nanodot array processing method based on an electrochemical anodic oxidation technology, and relates to a metal nanodot array processing method. The method aims at solving the problems that an existing machining method for an ultra-small-size metal nanodot array is low in stability, structure parameters cannot be flexibly adjusted, and cost is high. The method comprises the following steps: step 1, pretreating an aluminum sheet; 2, the pretreated aluminum sheet is impressed and oxidized, and an anodic aluminum oxide template is obtained; 3, preparing a continuous substrate aluminum cone array by using the anodic aluminum oxide template; 4, pretreating the continuous substrate aluminum cone array to obtain a sample; step 5, endowing conductivity; step 6, carrying out secondary oxidation on the sample; step 7, carrying out light transmission treatment on the sample; 8, PMMA on the surface of the sample is removed. The invention belongs to the technical field of micro-nano processing.

Description

Technical Field

[0001] The invention relates to a metal nanodot array processing method, belonging to the technical field of micro-nano processing. Background Art

[0002] Micro-nano processing technology refers to the technology of processing materials at the micron or even nanometer scale, which is widely used in semiconductors, biomedicine, optical devices and other fields. Nanoarray structures show great potential in light regulation, especially in plasmon nanoarray structures. Through precise design and preparation, efficient light regulation can be achieved, light can be localized in a small size range, and the optical diffraction limit can be broken. Therefore, how to use micro-nano processing technology to prepare plasmon nanoarray structures is a research hotspot.

[0003] Plasmons are quantized modes of collective oscillations of free electrons in metals or conductors, and they represent a special phenomenon of the interaction between electromagnetic waves and matter. When photons or external electric fields act on the surface of a metal, this oscillation can be excited to form surface plasmons. The basic theory of the plasmon phenomenon is based on Maxwell's equations and the Fermi gas model. There are a large number of freely moving electrons inside the metal, and these electrons can produce collective oscillations in response to changes in the external electric field like a liquid. When the frequency of the incident light is close to the inherent oscillation frequency of the free electrons in the metal, resonant coupling occurs between the two, resulting in a significant enhancement of the local electric field intensity. This process can not only strongly confine light on a subwavelength scale, but also greatly improve the efficiency of the interaction between light and matter.

[0004] Surface plasmons are mainly divided into propagating surface plasmons and localized surface plasmons. Propagating surface plasmons are electron density waves that propagate along the metal surface caused by the interaction between free electrons and electromagnetic fields. Propagating surface plasmons are bounded at the interface between metal and dielectric during propagation, and their field distribution decays exponentially in adjacent metals and dielectrics. The distribution depth in the metal is two orders of magnitude smaller than the wavelength of the incident light. Its electric field is perpendicular to the metal surface and has subwavelength locality. When the frequency of the incident light is close to the inherent oscillation frequency of the free electrons inside the metal nanoparticles, these electrons will oscillate collectively to form localized surface plasmons. Localized surface plasmons refer to the collective oscillation phenomenon of free electrons occurring around isolated or quasi-isolated metal nanoparticles or structures. Unlike propagating surface plasmons, localized surface plasmons are confined to a very small spatial range, usually at the nanoscale, so their energy density is very high and can strongly enhance the local electric field at subwavelength sizes. Due to the limited volume of nanoparticles, the energy of localized surface plasmons does not propagate in any direction, but is concentrated near the particles.

[0005] Metal nanodot arrays play an important role in plasmon photonics, and they can significantly enhance the interaction between light and matter. Metal nanodot array structures are an important platform for realizing the interaction between light and matter. By adjusting the morphology and structural parameters of the dot array, rich optical properties can be obtained to meet the application requirements of different fields. There are many light regulation mechanisms on the structure of metal surface plasmon arrays, which allow precise manipulation of the light field, thereby affecting the interaction between light and matter. Orderly arranged metal nanodot arrays can introduce additional photonic band gaps or waveguide effects through periodic structures to further regulate the behavior of light. For example, when the array period matches the wavelength of light, efficient light capture and guidance can be achieved. The dielectric environment surrounding the metal nanodot array also affects the properties of metal surface plasmons. Media with different refractive indices can cause the resonance frequency to redshift or blueshift, while changing the electromagnetic field distribution. Therefore, by selecting appropriate dielectric materials, the function of plasmon devices can be optimized.

[0006] At present, common methods for preparing metal dot arrays include self-assembly, template-assisted deposition, laser direct writing, etc. The self-assembly method has problems such as insufficient stability, difficulty in controlling defects, and difficulty in constructing complex structures. The template-assisted deposition method faces problems such as high template preparation cost and limited structural diversity, and the template life is usually limited. The laser direct writing method has shown significant advantages in high resolution, flexibility, and rapid prototyping. However, it also faces problems such as high equipment costs and low production efficiency. Especially for ultra-small metal nanodot arrays, it is urgent to invent a preparation method with high stability, flexible and adjustable structural parameters, and low cost. Summary of the invention

[0007] The present invention aims to solve the problems of low stability, inflexible adjustment of structural parameters and high cost in existing processing methods for ultra-small-sized metal nanodot arrays, and further proposes a metal nanodot array processing method based on electrochemical anodizing technology.

[0008] The technical solution adopted by the present invention to solve the above problems is: the steps of the present invention include:

[0009] Step 1: pre-treating the aluminum sheet;

[0010] Step 2, stamping and oxidizing the pretreated aluminum sheet to obtain an anodized aluminum template;

[0011] Step 3, preparing a continuous base aluminum cone array using an anodized aluminum template;

[0012] Step 4, pre-treating the continuous substrate aluminum cone array to obtain a sample;

[0013] Step 5, imparting conductivity;

[0014] Step 6, performing secondary oxidation on the sample;

[0015] Step 7, performing light transmittance treatment on the sample;

[0016] Step 8: Remove PMMA from the sample surface.

[0017] Furthermore, step 1 specifically includes:

[0018] Step 101, using a cutting machine to cut the high-purity aluminum coil into round aluminum sheets with a diameter of 2 cm, placing the aluminum sheets in small beakers containing ethanol, water, and ethanol in turn, ultrasonicating them in an ultrasonic machine for 7 minutes, and then taking them out and blowing them dry;

[0019] Step 102, place the aluminum sheet in a mixed solution of perchloric acid and ethanol in a volume ratio of 1:7 for electrochemical polishing, with the aluminum sheet as the anode and the lead plate as the cathode, and polish in an ice water bath with a current of 30V and 2A for about five minutes, then take out the aluminum sheet, rinse and blow dry.

[0020] Furthermore, step 2 specifically includes:

[0021] Step 201, using a tetragonal 400nm periodic lattice hard nickel film to transfer the hole array onto a smooth aluminum sheet under the pressure of an electric punch;

[0022] Step 202, the pressure used is about 5 MPa, and the duration is 2 min to initially obtain an aluminum foil having a periodic hole array;

[0023] Step 203, using a mixed solution of phosphoric acid, ethylene glycol, and water in a volume ratio of 1:200:400 as an electrolyte, using the structured side of the aluminum foil as an anode and the lead plate as a cathode for oxidation for 1 hour at a current of 160V and 0.03A to obtain an anodized aluminum template.

[0024] Furthermore, step 3 specifically includes:

[0025] The anodized aluminum template was placed in a beaker containing chromic acid and allowed to stand at room temperature for 12 hours. After being taken out, it was rinsed with ultrapure water and dried to obtain a continuous base aluminum cone array.

[0026] Furthermore, step 4 specifically includes:

[0027] Step 401, drip 450 μl of polymethyl methacrylate onto the side of the aluminum foil with the nanoarray, and spin the foil at a speed of 180 r / min for 20 s using a spin coater, and repeat the operation three times;

[0028] Step 402: Spin coat twice with 450 μl of concentrated polymethyl methacrylate using the same parameters, and remove the sample after the PMMA is dry.

[0029] Furthermore, the 450 μl of dilute polymethyl methacrylate is composed of 0.5 g of polymethyl methacrylate PMMA powder and 15 ml of dichloromethane; the 450 μl of concentrated polymethyl methacrylate is composed of 1 g of PMMA powder and 20 ml of dichloromethane.

[0030] Furthermore, step 5 specifically includes:

[0031] Cover the PMMA-coated side of the target aluminum foil with a smooth aluminum sheet, and then use copper conductive glue to connect the back area of ​​the target aluminum foil that needs to be oxidized with the smooth aluminum sheet that directly contacts the electrode, so that during the anodization process, the current can directly reach the area to be oxidized on the back of the target aluminum foil.

[0032] Furthermore, step 6 specifically includes:

[0033] Step 601, using 0.3 mol / L oxalic acid solution as an oxidizing solution, passing a current of 50 V and 0.15 A to perform secondary oxidation on the sample, and after 30 hours, the aluminum substrate of the sample is completely oxidized into aluminum oxide;

[0034] Step 602: After the oxidation of the sample is completed, the sample is rinsed with ethanol and an aqueous solution to remove the residual electrolyte on the surface.

[0035] Furthermore, step 7 specifically includes:

[0036] The sample is placed in a beaker containing chromic acid, and a portion of the alumina substrate on the back of the sample is removed with the chromic acid solution to increase the light transmittance of the sample.

[0037] Furthermore, step 8 specifically includes:

[0038] The sample was placed in an acetone solution and soaked for 30 minutes. After PMMA was completely dissolved, the sample was taken out and gently rinsed with ethanol to obtain a metal nanodot array on the alumina substrate.

[0039] The beneficial effects of the present invention are as follows: the former mainstream preparation methods of metal nanodot arrays are self-assembly method and template method. The controllability of self-assembly method is relatively poor and it is difficult to accurately control the size and shape of metal nanodot arrays. The template method has high cost and relatively complicated production process. With the development of nano devices, the technical demand for preparing large-area and large-volume two-dimensional metal nanodot arrays is increasing. The present invention uses electrochemical oxidation technology to greatly reduce the time cost and economic cost of metal nanodot arrays in the preparation process. The prepared array has a large available area and can even reach the wafer level. More importantly, the method can flexibly adjust the shape and size of the metal nanoarray according to the electrochemical anodization time. When the oxidation time is long enough, the underlying aluminum substrate becomes an aluminum oxide material, and anodization forms a short circuit. At this time, an ultra-small metal lattice structure can be obtained at the cone tip. It has broad application prospects in the fields of nano lasers, photodetectors, integrated chips, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 It is a schematic diagram of the basic preparation steps of porous anodized aluminum;

[0041] Figure 2 It is a schematic diagram of the basic morphology of a square 400nm porous anodized aluminum;

[0042] Figure 3 It is a schematic diagram of the morphology of the aluminum cone array on a square 400nm continuous metal substrate;

[0043] Figure 4 It is a schematic diagram of the conductivity imparting process after the sample is spin-coated with PMMA;

[0044] Figure 5 It is the morphology of metal nanodot array on alumina substrate;

[0045] Figure 6 This is a physical picture of the metal nanodot array. DETAILED DESCRIPTION

[0046] Specific implementation method 1: Figures 1 to 6 As shown, a method for processing a metal nanodot array based on electrochemical anodization technology comprises the following specific steps:

[0047] Step 1: pre-treating the aluminum sheet;

[0048] Step 101, using a cutting machine to cut the high-purity aluminum coil into round aluminum sheets with a diameter of 2 cm, placing the aluminum sheets in small beakers containing ethanol, water, and ethanol in turn, ultrasonicating them in an ultrasonic machine for 7 minutes, and then taking them out and blowing them dry;

[0049] Step 102, placing the aluminum sheet in a mixed solution of perchloric acid and ethanol in a volume ratio of 1:7 for electrochemical polishing, with the aluminum sheet as the anode and the lead plate as the cathode, passing a current of 30V and 2A in an ice water bath for polishing for about five minutes, then taking out the aluminum sheet, rinsing and drying it;

[0050] Step 2, stamping and oxidizing the pretreated aluminum sheet to obtain an anodized aluminum template;

[0051] Step 201, using a tetragonal 400nm periodic lattice hard nickel film to transfer the hole array onto a smooth aluminum sheet under the pressure of an electric punch;

[0052] Step 202, the pressure used is about 5 MPa, and the duration is 2 min to initially obtain an aluminum foil having a periodic hole array;

[0053] Step 203, using a mixed solution of phosphoric acid, ethylene glycol, and water in a volume ratio of 1:200:400 as an electrolyte, and using the structured side of the aluminum foil as an anode and the lead plate as a cathode for oxidation for 1 h at a current of 160 V and 0.03 A to obtain an anodized aluminum template;

[0054] Step 3, preparing a continuous base aluminum cone array using an anodized aluminum template;

[0055] The anodized aluminum template was placed in a beaker containing chromic acid and allowed to stand at room temperature for 12 hours. After being taken out, it was rinsed with ultrapure water and dried to obtain a continuous base aluminum cone array.

[0056] Step 4, pre-treating the continuous substrate aluminum cone array to obtain a sample;

[0057] Step 401, drip 450 μl of polymethyl methacrylate onto the side of the aluminum foil with the nanoarray, and spin the foil at a speed of 180 r / min for 20 s using a spin coater, and repeat the operation three times;

[0058] Step 402, spin coating twice with 450 μl of concentrated polymethyl methacrylate using the same parameters, and removing the sample after the PMMA is dry;

[0059] The 450 μl of polymethyl methacrylate is composed of 0.5 g of PMMA powder and 15 ml of dichloromethane; the 450 μl of concentrated polymethyl methacrylate is composed of 1 g of PMMA powder and 20 ml of dichloromethane;

[0060] Step 5, imparting conductivity;

[0061] Cover the PMMA-coated side of the target aluminum foil with a smooth aluminum sheet, and then use copper conductive glue to connect the back area of ​​the target aluminum foil that needs to be oxidized with the smooth aluminum sheet that directly contacts the electrode, so that the current can directly reach the area to be oxidized on the back of the target aluminum foil during the anodization process;

[0062] Step 6, performing secondary oxidation on the sample;

[0063] Step 601, using 0.3 mol / L oxalic acid solution as an oxidizing solution, passing a current of 50 V and 0.15 A to perform secondary oxidation on the sample, and after 30 hours, the aluminum substrate of the sample is completely oxidized into aluminum oxide;

[0064] Step 602: After the oxidation of the sample is completed, the sample is rinsed with ethanol and an aqueous solution to remove the electrolyte remaining on the surface;

[0065] Step 7, performing light transmittance treatment on the sample;

[0066] Place the sample in a beaker containing chromic acid, and use the chromic acid solution to remove a portion of the alumina substrate on the back of the sample to increase the light transmittance of the sample;

[0067] Step 8, removing PMMA from the sample surface;

[0068] The sample was placed in an acetone solution and soaked for 30 minutes. After PMMA was completely dissolved, the sample was taken out and gently rinsed with ethanol to obtain a metal nanodot array on the alumina substrate.

[0069] Example

[0070] Step 1: Figure 1 As shown, a high-purity aluminum coil is cut into circular aluminum sheets with a diameter of 2 cm using a sheet cutter, and the aluminum sheets are placed in small beakers containing ethanol, water, and ethanol in turn, ultrasonicated in an ultrasonic machine for 7 minutes, and then taken out and blown dry; subsequently, the aluminum sheet is placed in a mixed solution of perchloric acid and ethanol with a volume ratio of 1:7 for electrochemical polishing, with the aluminum sheet as the anode and the lead plate as the cathode, and a current of 30V, 2A is passed through the solution. After polishing in an ice water bath for about 5 minutes, the aluminum sheet is taken out, rinsed, and blown dry;

[0071] Step 2: Use a tetragonal 400nm periodic lattice hard nickel film to transfer the hole array to a smooth aluminum sheet under the pressure of an electric punch; the pressure used is about 5MPa, and the duration is 2min to initially obtain an aluminum foil with a periodic hole array; a mixed solution of phosphoric acid, ethylene glycol, and water with a volume ratio of 1:200:400 is used as an electrolyte, and at a current of 160V and 0.03A, the structured side of the aluminum foil is used as the anode, and the lead plate is used as the cathode for oxidation for 1h to obtain an anodized aluminum template, the morphology of which is as follows: Figure 2 As shown;

[0072] Step 3, preparation of continuous substrate aluminum cone array: Place the anodized aluminum template in a beaker containing chromic acid and let it stand at room temperature for about 12 hours. After taking it out, rinse it with ultrapure water and blow dry it to obtain a continuous substrate aluminum cone array. Its morphology is as follows: Figure 3 As shown;

[0073] Step 4, pretreatment of the continuous substrate aluminum cone array; 450 μl of concentrated polymethyl methacrylate (0.5 g of polymethyl methacrylate PMMA powder, 15 ml of dichloromethane) was dripped onto the side of the aluminum foil with the nanoarray, and the mixture was rotated at 180 r / min for 20 s using a spin coater, and the operation was repeated three times, and then 450 μl of concentrated polymethyl methacrylate (1 g of PMMA powder, 20 ml of dichloromethane) was spin coated twice using the same method under the same parameters, and the sample was removed after the PMMA was dried;

[0074] Step 5, imparting conductivity; Cover the side of the target aluminum foil coated with PMMA with a smooth aluminum sheet, and then use copper conductive glue to connect the back area of ​​the target aluminum foil that needs to be oxidized with the smooth aluminum sheet that directly contacts the electrode, so that during the anodization process, the current can directly reach the area to be oxidized on the back of the target aluminum foil, such as Figure 4 As shown;

[0075] Step 6, secondary oxidation; using 0.3 mol / L oxalic acid solution as the oxidizing solution, passing 50V, 0.15A current to perform secondary oxidation on the sample, and after about 30 hours, the aluminum substrate of the sample is completely oxidized into aluminum oxide; after the oxidation of the sample is completed, the sample is rinsed with ethanol and aqueous solution respectively to remove the residual electrolyte on the surface;

[0076] Step 7, sample light transmittance treatment: put the sample into a beaker containing chromic acid, and use the chromic acid solution to remove a portion of the aluminum oxide substrate on the back of the sample to increase the light transmittance of the sample;

[0077] Step 8, remove PMMA from the sample surface: place the sample in acetone solution and soak for 30 minutes. After PMMA is completely dissolved, take it out and rinse it gently with ethanol to obtain the metal nanodot array on the alumina substrate. The sample morphology diagram is shown in the figure. Figure 5 As shown in the sample picture Figure 6 shown.

[0078] The above is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technician familiar with this profession can make some changes or modify the technical contents disclosed above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent replacement and improvement made to the above embodiments without departing from the content of the technical solution of the present invention, based on the technical essence of the present invention, within the spirit and principles of the present invention, still fall within the protection scope of the technical solution of the present invention.

Claims

1. A method for processing a metal nanodot array based on electrochemical anodization technology, characterized in that: The specific steps include: Step 1: pre-treating the aluminum sheet; Step 2, stamping and oxidizing the pretreated aluminum sheet to obtain an anodized aluminum template; Step 3, preparing a continuous base aluminum cone array using an anodized aluminum template; Step 4, pre-treating the continuous substrate aluminum cone array to obtain a sample; Step 5, imparting conductivity; Step 6, performing secondary oxidation on the sample; Step 7, performing light transmittance treatment on the sample; Step 8: Remove PMMA from the sample surface.

2. The method for processing a metal nanodot array based on electrochemical anodization technology according to claim 1, characterized in that: Step 1 specifically includes: Step 101, using a cutting machine to cut the high-purity aluminum coil into round aluminum sheets with a diameter of 2 cm, placing the aluminum sheets in small beakers containing ethanol, water, and ethanol in turn, ultrasonicating them in an ultrasonic machine for 7 minutes, and then taking them out and blowing them dry; Step 102, place the aluminum sheet in a mixed solution of perchloric acid and ethanol in a volume ratio of 1:7 for electrochemical polishing, with the aluminum sheet as the anode and the lead plate as the cathode, and polish in an ice water bath with a current of 30V and 2A for about five minutes, then take out the aluminum sheet, rinse and blow dry.

3. The method for processing a metal nanodot array based on electrochemical anodization technology according to claim 1, characterized in that: Step 2 specifically includes: Step 201, using a tetragonal 400nm periodic lattice hard nickel film to transfer the hole array onto a smooth aluminum sheet under the pressure of an electric punch; Step 202, the pressure used is about 5 MPa, and the duration is 2 min to initially obtain an aluminum foil having a periodic hole array; Step 203, using a mixed solution of phosphoric acid, ethylene glycol, and water in a volume ratio of 1:200:400 as an electrolyte, using the structured side of the aluminum foil as an anode and the lead plate as a cathode for oxidation for 1 hour at a current of 160V and 0.03A to obtain an anodized aluminum template.

4. The method for processing a metal nanodot array based on electrochemical anodization technology according to claim 1, characterized in that: Step 3 specifically includes: The anodized aluminum template was placed in a beaker containing chromic acid and allowed to stand at room temperature for 12 hours. After being taken out, it was rinsed with ultrapure water and dried to obtain a continuous base aluminum cone array.

5. The method for processing a metal nanodot array based on electrochemical anodization technology according to claim 1, characterized in that: Step 4 specifically includes: Step 401, drip 450 μl of polymethyl methacrylate onto the side of the aluminum foil with the nanoarray, and spin the foil at a speed of 180 r / min for 20 s using a spin coater, and repeat the operation three times; Step 402: Spin coat twice with 450 μl of concentrated polymethyl methacrylate using the same parameters, and remove the sample after the PMMA is dry.

6. The method for processing a metal nanodot array based on electrochemical anodization technology according to claim 5, characterized in that: The 450 μl of dilute polymethyl methacrylate is composed of 0.5 g of polymethyl methacrylate PMMA powder and 15 ml of dichloromethane; the 450 μl of concentrated polymethyl methacrylate is composed of 1 g of PMMA powder and 20 ml of dichloromethane.

7. The method for processing a metal nanodot array based on electrochemical anodization technology according to claim 1, characterized in that: Step 5 specifically includes: Cover the PMMA-coated side of the target aluminum foil with a smooth aluminum sheet, and then use copper conductive glue to connect the back area of ​​the target aluminum foil that needs to be oxidized with the smooth aluminum sheet that directly contacts the electrode, so that during the anodization process, the current can directly reach the area to be oxidized on the back of the target aluminum foil.

8. The method for processing a metal nanodot array based on electrochemical anodization technology according to claim 1, characterized in that: Step 6 specifically includes: Step 601, using 0.3 mol / L oxalic acid solution as an oxidizing solution, passing a current of 50 V and 0.15 A to perform secondary oxidation on the sample, and after 30 hours, the aluminum substrate of the sample is completely oxidized into aluminum oxide; Step 602: After the oxidation of the sample is completed, the sample is rinsed with ethanol and an aqueous solution to remove the residual electrolyte on the surface.

9. The method for processing a metal nanodot array based on electrochemical anodization technology according to claim 1, characterized in that: Step 7 specifically includes: The sample is placed in a beaker containing chromic acid, and a portion of the alumina substrate on the back of the sample is removed with the chromic acid solution to increase the light transmittance of the sample.

10. The method for processing metal nanodot arrays based on electrochemical anodization technology according to claim 1, characterized in that: Step 8 specifically includes: The sample was placed in an acetone solution and soaked for 30 minutes. After PMMA was completely dissolved, the sample was taken out and gently rinsed with ethanol to obtain a metal nanodot array on the alumina substrate.

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