A method for regulating pore morphology of an anodic aluminum oxide template based on microsphere array imprinting master

Abstract

The application discloses a method for regulating hole morphology of an anodic aluminum oxide template based on microsphere array imprinting master, which comprises the following steps: after cleaning a glass substrate, a layer of PS nanosphere array is self-assembled on one side of the glass substrate; a TiN film layer is prepared on the PS nanosphere array side of the glass substrate by using a magnetron sputtering method; an aluminum sheet is electrochemically polished after cleaning, then the TiN film layer of the glass substrate is attached to the polished aluminum sheet, and the attached aluminum sheet is subjected to an imprinting treatment; finally, the imprinted aluminum sheet is subjected to two-step anodic oxidation treatment to prepare a highly ordered anodic aluminum oxide array. The application can not only make the hole morphology of the AAO template present a circular shape, but also obtain a master with low cost by using a single-layer PS microsphere array self-assembly technology; the introduction of the titanium nitride hardness promotion layer can make the PS microsphere array reusable, and the preparation of the low-cost and high-benefit AAO template is realized.

Description

A method for controlling the pore morphology of anodized aluminum template based on microsphere array imprinting master. Technical Field

[0001] This invention relates to a method for controlling the pore morphology of anodized aluminum templates based on a microsphere array imprinting master. Background Technology

[0002] Anodized aluminum oxide (AAO) templates offer advantages such as tunable structure, good insulation, and high stability, making them widely used in the fabrication of large-area patterned nanostructures. Based on AAO templates combined with electrochemical deposition, chemical vapor deposition, sol-gel, and magnetron sputtering, patterned nanostructures of polymers and metals, including nanoparticles, nanotubes, and nanowires / rods, have been successfully fabricated. The physical and chemical properties of the resulting nanostructures vary with their morphology.

[0003] Combining photolithography and nanoimprint lithography can yield AAO templates with controllable morphology. For example, Zhan et al. used a reusable nickel master to fabricate an AAO template with square nanopores and a period of 400 nm using nanoimprint lithography. The nickel master was replicated from a silicon pattern prepared by photolithography, resulting in high fabrication costs. Using a highly ordered array of polystyrene (PS) microspheres as an imprint master provides a new, economical approach to controlling the morphology of AAO templates. This invention proposes using a PS microsphere array as a master, depositing titanium nitride on top to increase hardness, and then imprinting a nano-pit array on a polished high-purity aluminum substrate using nanoimprint lithography. This replicates the circular protrusions of the PS nanosphere array. Further, a two-step anodizing process is used to prepare a nanoarray with a near-circular pore morphology. This invention differs from master fabrication based on photolithography; the master obtained by the self-assembly of a single-layer PS microsphere array is less expensive, and the resulting anodized aluminum pores naturally exhibit a near-circular morphology. In addition, the introduction of the titanium nitride hardness-enhancing layer allows the PS microsphere array to be reused, avoiding damage to the microspheres during the imprinting process. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a low-cost anodic aluminum oxide and its preparation method. This method utilizes a polystyrene microsphere array combined with nanoimprinting to achieve simple and low-cost preparation of large-pore anodic aluminum oxide templates with near-circular pore morphology.

[0005] This invention is achieved using the following technical solution:

[0006] A method for controlling the pore morphology of anodized aluminum template based on a microsphere array imprinting master includes the following steps:

[0007] S1. After cleaning the glass substrate, a layer of PS nanosphere array is self-assembled on one side of the glass substrate;

[0008] S2. Using magnetron sputtering, a TiN thin film layer was fabricated on a glass substrate PS nanosphere array surface.

[0009] S3. The cleaned aluminum sheet is electrochemically polished, and then the TiN thin film layer on the glass substrate is bonded to the polished aluminum sheet and imprinted.

[0010] S4. The imprinted aluminum sheet undergoes a two-step anodizing process to prepare a highly ordered anodized aluminum array.

[0011] Preferably, step S1 is a self-assembly method for PS nanoarrays, which involves using a PS suspension to create a PS monolayer on one side of a glass substrate, with PS nanospheres arranged in a centrally filled hexagonal close-packed structure on one side of the glass substrate.

[0012] Preferably, the diameter of the PS nanospheres is 500 nm.

[0013] Preferably, step S2 involves pre-sputtering for 10 minutes at a power of 150W, followed by formal sputtering for 20 minutes, wherein the power of formal sputtering is 150W.

[0014] Preferably, the thickness of the TiN thin film layer is 40 nm.

[0015] Preferably, the pressure during the imprinting process in step S3 is 6 kg·f / cm. 2 The imprinting process takes 3 minutes.

[0016] Preferably, the two-step anodizing process described in step S4 is as follows:

[0017] S4-1. Place the aluminum sheet and graphite electrode after imprinting vertically in the oxidation solution, with the aluminum sheet connected to the positive terminal of the power supply and the graphite connected to the negative terminal of the power supply.

[0018] S4-2. Turn on the power to perform the first anodizing. The voltage is slowly increased from 0V to 200V and then constant voltage anodizing is performed at 200V.

[0019] S4-3. After oxidation is complete, turn off the power, remove the aluminum sheet and clean and dry it.

[0020] S4-4. After drying in step S4-3, immerse the aluminum sheet in a mixed solution of 1.8wt% chromic acid and 6wt% phosphoric acid at a volume ratio of 1:1 for 11 hours at a immersion temperature of 65℃. After immersion, wash and dry the sheet for later use. S4-5. Repeat steps S4-1 to S4-3 for the second anodizing treatment of the aluminum sheet treated in step S4-4.

[0021] More preferably, the oxidation solution is a mixture of 265 mL deionized water, 130 mL ethylene glycol, 5 mL 0.3 mol / L oxalic acid aqueous solution, and 700 μL phosphoric acid.

[0022] More preferably, the first anodizing treatment lasts for 10 hours, and the second anodizing treatment lasts for 30 minutes.

[0023] The present invention also provides an anodized aluminum template (AAO template) obtained by the above method, wherein the hole morphology of the anodized aluminum template of the present invention is approximately circular.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] This invention uses a self-assembled PS nanosphere array as a nanoimprint master and combines it with a two-step anodizing method to change the micropore morphology of the anodized aluminum template.

[0026] This invention uses a PS nanosphere array as a nanoimprint template to achieve the construction of high-performance nanostructure arrays.

[0027] This invention not only enables the AAO template to have a near-circular pore morphology, but also reduces the cost of the master template obtained by the single-layer PS microsphere array self-assembly technology. The introduction of the titanium nitride hardness-enhancing layer allows the PS microsphere array to be reused, thus realizing the preparation of a low-cost and high-efficiency AAO template. Attached Figure Description

[0028] Figure 1 shows a SEM image of a self-assembled PS nanosphere array on one side of a glass substrate;

[0029] Figure 2 shows SEM images of the anodic aluminum oxide templates prepared in Example 1(a) and Comparative Document 1(b), respectively;

[0030] Figure 3 shows the SEM image of the anodic aluminum oxide template prepared in Comparative Example 2. Detailed Implementation

[0031] To make the objectives, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described in detail below. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that the disclosure of the present invention will be thorough and complete.

[0032] I. Material Preparation:

[0033] The composition of the materials is as follows: SiO2 glass substrate, TiN target, high-purity aluminum, acetone, anhydrous ethanol, deionized water, perchloric acid, oxalic acid, phosphoric acid, ethylene glycol, chromium trioxide, PS nanosphere suspension (2.5 wt% aqueous solution), and methanol. The dosage and selection criteria are as follows:

[0034] SiO2 glass substrate: 20mm×20mm×1mm;

[0035] High-purity aluminum: solid, purity 99.999%, area 20mm×20mm×3mm;

[0036] TiN target material: solid, copper backing, 99.9% purity;

[0037] Dishwashing liquid: 2±0.5mL;

[0038] Acetone: CH3COCH3 250mL±5mL;

[0039] Anhydrous ethanol: C2H5OH 500mL±5mL;

[0040] Deionized water: H2O 8000mL±50mL;

[0041] Perchloric acid: HClO4 50mL ± 5mL;

[0042] Ethylene glycol: (CH2OH)2 130mL ± 5mL;

[0043] Phosphoric acid: H3PO4 10mL±1mL;

[0044] Oxalic acid: C2H2O4, 99.5%;

[0045] Chromium trioxide: CrO3, 99%;

[0046] Sulfuric acid: H2SO4, 98%;

[0047] Hydrogen peroxide: H2O2, 3%;

[0048] PS nanosphere suspension: 500 nm in diameter, methanol as solvent, concentration 2.5 wt%;

[0049] II. Experimental Procedure

[0050] Example 1

[0051] A method for preparing anodized aluminum template, comprising the following steps:

[0052] S1. After cleaning the glass substrate, a layer of PS nanosphere array is self-assembled on one side of the glass substrate;

[0053] The cleaning of the SiO2 glass substrate includes the following steps:

[0054] First, apply detergent to the surface of the glass substrate, and repeatedly rub and clean the SiO2 glass substrate under running water until a uniform water film can be formed on the surface of the SiO2 glass substrate when rinsed with clean water.

[0055] Next, the SiO2 glass substrate was placed vertically on a beaker rack and placed in a glass beaker. Deionized water, acetone, and anhydrous ethanol were added sequentially, and the substrate was sonicated for 15 minutes each. The SiO2 glass substrate was then cleaned. The cleaned SiO2 glass substrate was placed in a beaker containing isopropanol solvent, and the mouth of the beaker was covered with aluminum foil for later use.

[0056] The method for self-assembling a layer of PS nanosphere array on one side of a glass substrate is as follows:

[0057] S1-1. Using a graduated cylinder, prepare a mixed solution of NH3(aq):H2O2:deionized water with a volume ratio of 10:10:1 in a glass beaker. Then, place the SiO2 glass substrate in the beaker and use a PS beaker holder to ensure that the substrate is in full contact with the solution. Cover the mouth of the beaker with aluminum foil and let it stand at room temperature for 10 minutes.

[0058] S1-2. Use a graduated cylinder to prepare a mixed solution of H2SO4 (98%) and H2O2 with a volume ratio of 4:1 in a glass beaker. Place the SiO2 glass substrate treated in step S201 into the beaker, use a PS beaker holder to ensure that the substrate is in full contact with the solution, cover the mouth of the beaker with aluminum foil, and let it stand at room temperature for 20 minutes.

[0059] S1-3. Mix a suspension of PS nanospheres with a diameter of 500 nm and a mass ratio of 2.5 wt% with a methanol solution (at a volume ratio of 1:2) and place it in a brown glass bottle. Sonicate the mixture in an ultrasonic cleaner for 5 minutes and then remove it for later use.

[0060] S1-4. After surface treatment, the SiO2 glass substrate is cleaned with deionized water, dried with nitrogen, placed on an inverted petri dish, and an appropriate amount of deionized water is dropped onto the substrate.

[0061] S1-5. Use a syringe to draw an appropriate amount of solution from the glass bottle, fix the syringe to the pump syringe, adjust the height of the pump syringe so that the injection head of the syringe is at the same height as the SiO2 glass substrate, set the injection rate of the pump to 0.5 mL / min, and slowly inject the prepared PS suspension into the substrate from one corner. It can be observed with the naked eye that the tension water film is pushed to the opposite corner, and the PS nanospheres preferentially self-assemble into a monolayer film at the opposite corner. As the amount of injected suspension increases, the assembled PS nanosphere array continues to expand towards the corner of the syringe. Finally, adjust the injection rate of the pump to 0.25 mL / min to reduce the amount of injected suspension, so as to ensure that the area of ​​PS nanosphere monolayer arrangement is as large as possible.

[0062] S1-6. After the entire water film is basically covered by a single layer of PS nanosphere array, place the inverted culture dish along with the sample on a 60°C hot plate and heat the sample in the air for about 2 hours. Control the evaporation and convection rates, and the water film will be completely evaporated, leaving a periodically hexagonally close-packed PS nanosphere layer on the SiO2 glass substrate.

[0063] S1-7. Remove the SiO2 glass substrate with the PS nanosphere array arranged from the hot stage and place it in a culture dish for later use.

[0064] S2. Using magnetron sputtering, a TiN thin film layer was fabricated on a glass substrate PS nanosphere array. The specific operation is as follows:

[0065] S2-1. Mount the TiN target to be sputtered onto the RF sputtering target head of the magnetron sputtering coating machine;

[0066] S2-2. Place the SiO2 glass substrate loaded with the PS nanosphere array template face down on the sample holder of the magnetron sputtering coating machine. At this time, the thin film growth surface is the side loaded with the PS nanosphere array template, and this side is facing down. Adjust the sample holder so that the SiO2 glass substrate is directly above the target.

[0067] S2-3. Close the magnetron sputtering chamber door, open and zero the vacuum gauge, and turn on the mechanical pump and pre-evacuation valve on the display screen. When the pressure drops to 30 Pa, close the pre-evacuation valve and open the gate valve and molecular pump. The chamber pressure will reach 10 Pa. -4 When the pressure is at the Pa level, turn on the argon ionization valve and the argon channel power supply;

[0068] S2-4. Open the argon magnetic control valve, mechanical valve and flow meter in sequence, select the appropriate argon flow rate, and then adjust the slide valve of the molecular pump to maintain the chamber pressure at 2Pa.

[0069] S2-5. Turn on the sputtering power supply. After ignition, further adjust the pressure through the gate valve to achieve the required sputtering rate for film formation. Perform pre-sputtering for 10 minutes at a power of 150W, followed by formal sputtering for 20 minutes at a power of 150W. When the desired film thickness is achieved, first close the large baffle, then turn off the sputtering power supply. Remove the sample from the coating chamber and place it in a petri dish for later use.

[0070] S3. The cleaned aluminum sheet is electrochemically polished, and then the TiN thin film layer on the glass substrate is bonded to the polished aluminum sheet for imprinting. The cleaning method for the aluminum sheet is as follows:

[0071] First, apply detergent to the surface of the aluminum sheet and repeatedly rub and clean the aluminum substrate under running water, ensuring the flatness of the aluminum sheet as much as possible during the cleaning process;

[0072] Next, place the aluminum sheet vertically on a beaker rack in a glass beaker, and add acetone, anhydrous ethanol, and deionized water solvent in sequence, sonicating for 15 minutes each. The aluminum sheet is now cleaned. Place the cleaned aluminum sheet in a beaker containing isopropanol solvent, and cover the mouth of the beaker with aluminum foil for later use.

[0073] Meanwhile, the electrochemical polishing method is as follows:

[0074] (1) Prepare an electrochemical polishing electrolyte in a beaker. The electrolyte is composed of a mixture of perchloric acid and anhydrous ethanol in a volume ratio of 1:7. Place the prepared electrolyte in a constant temperature bath at -4℃ to ensure that the electrolyte temperature is 0℃.

[0075] (2) Place the cleaned aluminum sheet and graphite electrode vertically into the polishing electrolyte, with the aluminum sheet connected to the positive terminal of the power supply and the graphite electrode connected to the negative terminal of the power supply.

[0076] (3) Turn on the power supply and output voltage, slowly increase the voltage from 0V to 30V, and electrochemically polish for 5 minutes at a constant voltage of 30V. Then reduce the voltage to 10V and polish at a constant voltage for 8 minutes.

[0077] (4) After polishing, turn off the power, take out the aluminum sheet, rinse its surface with deionized water to remove the residual solution, blow it dry, and place it in a petri dish for later use.

[0078] The method for bonding and imprinting the TiN thin film layer on the glass substrate with the polished aluminum sheet is as follows:

[0079] S3-1 Place the polished aluminum sheet on a flat table with the polished side facing up, and attach the TiN thin film layer of the glass substrate to the aluminum sheet;

[0080] S3-2, Apply 6 kg·f / cm 2Press the aluminum sheet under pressure for 3 minutes. After pressing, place the aluminum sheet in a petri dish for later use.

[0081] S4. The imprinted aluminum sheet undergoes a two-step anodizing process to prepare a highly ordered anodized aluminum array. The specific steps are as follows:

[0082] S4-1. Prepare the oxidizing solution in a beaker using the following ratio: 265 mL deionized water, 130 mL ethylene glycol, 5 mL 0.3 mol / L oxalic acid, and 700 μL phosphoric acid. Place the beaker in a thermostatic bath at -4°C to ensure the solution temperature remains at 0°C.

[0083] S4-2. Place the stamped aluminum sheet and the clean graphite electrode vertically opposite each other into the above-mentioned oxidation solution. Connect the high-purity aluminum sheet to the positive terminal of the power supply and the graphite electrode to the negative terminal of the power supply.

[0084] S4-3. Turn on the power supply and output voltage to perform the first anodizing. Start from 0V and slowly increase the voltage to 200V. Maintain constant voltage at 200V for 10 hours.

[0085] S4-4 After the first anodizing is completed, turn off the power, remove the oxidized aluminum sheet, rinse its surface with deionized water to remove residual solution, and carefully blow it dry.

[0086] S4-5. Prepare a 1:1 mixture of 1.8 wt% chromic acid and 6 wt% phosphoric acid in a crystallizing dish. Place the dish on a hot plate at 65°C. Place the dried aluminum sheet from step S4-4 into the crystallizing dish, ensuring the aluminum sheet is completely submerged in the solution. React for 11 hours. After the reaction is complete, remove the aluminum sheet, rinse the surface with deionized water to remove residual solution, and dry for later use.

[0087] S4-6. Prepare the oxidation solution again in the beaker, using the same ratio: 265 mL deionized water, 130 mL ethylene glycol, 5 mL of 0.3 mol / L oxalic acid, and 700 μL of phosphoric acid mixed solution. Place the beaker in a thermostat bath at -4°C to ensure the solution temperature is 0°C.

[0088] S4-7. Place the aluminum sheet and clean graphite electrode processed in step 4-5 vertically into the oxidation solution, with the aluminum sheet connected to the positive terminal of the power supply and the graphite electrode connected to the negative terminal of the power supply.

[0089] S4-8. Turn on the power supply and output voltage for the second anodizing. Start from 0V and slowly increase the voltage to 200V. Maintain constant voltage at 200V for 30 minutes.

[0090] S4-9. After the second step of oxidation is completed, turn off the power, take out the oxidized aluminum sheet, rinse its surface with deionized water to remove the residual solution, and carefully blow it dry to obtain an anodized aluminum template.

[0091] Comparative Example 1

[0092] An anodized aluminum template was prepared according to the method of Example 1, the only difference being that nanoimprinting technology was not used. Specifically, the method described in Example 1 involved cleaning an aluminum sheet, followed by electrochemical polishing, and then performing a two-step anodizing process on the polished aluminum sheet to obtain the anodized aluminum template. Electrochemical polishing and the two-step anodizing process were performed under the same conditions.

[0093] Comparative Example 2

[0094] An anodized aluminum template was prepared according to the method of Example 1. The only difference between it and Example 1 is that the aluminum sheet after the imprinting process was only subjected to the first anodizing treatment, and the operation steps S4-5 to S4-9 were not performed.

[0095] The anodic aluminum oxide templates prepared in Example 1 and Comparative Examples 1-2 were tested, analyzed, and characterized, as shown in Figures 2-3.

[0096] The AAO template prepared in Example 1 of this invention has a nanopore morphology that is closer to spherical, while the AAO template prepared by only using the two-step anodizing method (i.e., Comparative Example 1) has a hexagonal nanopore morphology. This indicates that by using a PS nanosphere array as a master template and combining nanoimprinting technology with a two-step anodizing method, it is possible to prepare AAO templates with tunable morphology at low cost and high efficiency.

[0097] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A method for controlling the pore morphology of anodized aluminum template based on a microsphere array imprinting master, characterized in that, Includes the following steps: S1. After cleaning the glass substrate, a layer of PS nanosphere array is self-assembled on one side of the glass substrate; S2. Using magnetron sputtering, a TiN thin film layer was fabricated on a glass substrate PS nanosphere array surface. S3. The cleaned aluminum sheet is electrochemically polished, and then the TiN thin film layer on the glass substrate is bonded to the polished aluminum sheet and imprinted. S4. The imprinted aluminum sheet undergoes a two-step anodizing process to prepare a highly ordered anodized aluminum array.

2. The method for controlling the pore morphology of anodized aluminum template based on a microsphere array imprinting master according to claim 1, characterized in that, Step S1 is a self-assembly method for PS nanosphere arrays. It uses PS suspension to create a single layer of PS nanospheres on one side of a glass substrate. The PS nanospheres are arranged in a centrally filled hexagonal close-packed structure on one side of the glass substrate.

3. The method for controlling the pore morphology of anodized aluminum template based on a microsphere array imprinting master according to claim 1, characterized in that, The diameter of the PS nanospheres is 500 nm.

4. The method for controlling the pore morphology of anodized aluminum template based on a microsphere array imprinting master according to claim 1, characterized in that, Step S2 involves pre-sputtering for 10 minutes at a power of 150 W, followed by formal sputtering for 20 minutes, where the power of the formal sputtering is 150 W.

5. The method for controlling the pore morphology of anodized aluminum template based on a microsphere array imprinting master according to claim 1, characterized in that, The thickness of the TiN thin film is 40 nm.

6. The method for controlling the pore morphology of anodized aluminum template based on a microsphere array imprinting master according to claim 1, characterized in that, The pressure during the imprinting process in step S3 is 6 kg∙f / cm. 2 The imprinting process takes 3 minutes.

7. The method for controlling the pore morphology of anodized aluminum template based on a microsphere array imprinting master according to claim 1, characterized in that, The two-step anodizing process described in step S4 is as follows: S4-1, The aluminum sheet and graphite electrode after imprinting are placed vertically in the oxidation solution, wherein the aluminum sheet is connected to the positive terminal of the power supply and the graphite is connected to the negative terminal of the power supply; S4-2, The power supply is turned on to perform the first anodizing, and the voltage is slowly increased from 0 V to 200 V, and constant voltage anodizing is performed at 200 V. S4-3. After oxidation is complete, turn off the power, remove the aluminum sheet and clean and dry it. S4-4. Immerse the dried aluminum sheet in a mixed solution of 1.8 wt% chromic acid and 6 wt% phosphoric acid (volume ratio 1:1) for 11 h at a temperature of 65 ℃. After immersion, wash and dry it for later use. S4-5. Repeat steps S4-1 to S4-3 for the second anodizing treatment of the aluminum sheet treated in step S4-4.

8. The method for controlling the pore morphology of anodized aluminum template based on a microsphere array imprinting master according to claim 7, characterized in that, The oxidation solution is composed of 265 mL of deionized water, 130 mL of ethylene glycol, 5 mL of 0.3 mol / L oxalic acid aqueous solution, and 700 µL of phosphoric acid.

9. The method for controlling the pore morphology of anodized aluminum template based on a microsphere array imprinting master according to claim 7, characterized in that, The first anodizing treatment lasted for 10 hours; the second anodizing treatment lasted for 30 minutes.

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