A method for producing a diamond microstructure

Abstract

This invention proposes a method for preparing diamond microstructures, comprising the following steps: ultrafast laser modification: focusing an ultrafast laser onto a designated area on or inside the diamond surface for scanning and direct writing modification, transforming the diamond in the modified area into a graphite phase; when preparing diamond surface microstructures, the ultrafast laser parameters are: wavelength 1030 nm, pulse width 100-500 fs, frequency 10-800 kHz, and power 0.001-0.5 W; when preparing diamond internal microchannels, the ultrafast laser parameters are: wavelength 1030 nm or 515 nm, pulse width 100-600 fs, frequency 50-800 kHz, and power 0.001-1 W; the internal microchannels have inlets and outlets, both located on the end face in the thickness direction of the diamond. This invention achieves highly selective etching of the laser-modified graphitized region, with significantly higher corrosion selectivity than conventional strong mixed acid systems, and the complexing protection effect of concentrated phosphoric acid effectively avoids corrosion of the diamond matrix.

Description

Technical Field

[0001] This invention relates to the field of diamond micro / nano fabrication technology, and more particularly to a method for preparing diamond microstructures. Background Technology

[0002] Diamond, with its ultra-high hardness, high thermal conductivity, excellent optical transparency, good biocompatibility, and chemical inertness, has become an ideal material for fabricating micro and nanostructures. These microstructures have significant applications in fields such as optical photonics, microelectronic heat dissipation, biomedical sensing, and tribology. Ultrafast lasers, due to their high peak power and short pulse duration, have become the core method for processing diamond microstructures. Currently, there are two main processing methods: Direct femtosecond laser ablation: This method directly etches microstructures on the surface of diamond by controlling the laser energy density, or focuses on the interior to achieve three-dimensional engraving. However, this method has the drawbacks of low processing efficiency and high surface roughness of microstructures, making it difficult to meet the requirements for the preparation of high-precision microstructures. Selective etching for graphitization: Diamond is first locally modified into graphite using an ultrafast laser, then the graphitized areas are etched with a strong oxidizing acid, leaving the unmodified diamond areas intact. This method can obtain microstructures with high aspect ratios, but conventional strong mixed acid etching systems have low selectivity between modified and unmodified areas, resulting in limited etching depth of the microstructures. Furthermore, there are currently no reports on laser-modified etching techniques for preparing microchannels within diamond. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to overcome the defects of the existing technology. The present invention proposes a method for preparing diamond microstructures.

[0004] To address the shortcomings of direct femtosecond laser ablation (which suffers from low processing efficiency and high surface roughness of microstructures, making it difficult to meet the requirements for high-precision microstructure fabrication) and graphitization selective etching (which can obtain high aspect ratio microstructures, but suffers from low selectivity between modified and unmodified regions in conventional strong mixed acid etching systems, resulting in limited etching depth), and the lack of reported laser-modified etching techniques for diamond internal microchannels, the technical solution adopted in this invention is: A method for preparing diamond microstructures includes the following steps: Ultrafast laser modification: An ultrafast laser is focused on a designated area on the surface or inside of a diamond to perform scanning and direct writing modification, which transforms the diamond in the modified area into the graphite phase; When preparing microstructures on the surface of diamond, the ultrafast laser parameters are: wavelength 1030nm, pulse width 100-500fs, frequency 10-800KHz, and power 0.001-0.5W. When preparing the internal microchannels of diamond, the ultrafast laser parameters are: wavelength 1030nm or 515nm, pulse width 100-600fs, frequency 50-800KHz, and power 0.001-1W; the internal microchannels are provided with inlet and outlet, and both the inlet and outlet are located on the end face in the thickness direction of the diamond. Alkaline pre-etching: The diamond modified by ultrafast laser is placed in an alkaline etching solution and is etched at a constant temperature of 90-120℃; the etching time for the surface microstructure is 10-30h, and the etching time for the internal microchannels is 30-60h. Acidic secondary corrosion: The diamond, after alkaline pre-corrosion, is placed in an acidic etching solution and subjected to constant temperature corrosion at 100-200℃; the corrosion time for the surface microstructure is 20-40 hours, and the corrosion time for the internal microchannels is 40-80 hours. Post-processing: The diamonds that have undergone secondary acid etching are sequentially cleaned and dried to obtain the diamond microstructure.

[0005] Preferably, the alkaline corrosive solution is an aqueous solution of potassium hydroxide, potassium perchlorate, and potassium fluoride, wherein, by weight ratio, potassium hydroxide is 20%-40%, potassium perchlorate is 30%-50%, and potassium fluoride is 20%-40%. The acidic corrosive solution is composed of concentrated sulfuric acid, concentrated phosphoric acid, and perchloric acid, with the following weight ratios: concentrated sulfuric acid 20%-40%, concentrated phosphoric acid 10%-30%, and perchloric acid 10%-60%.

[0006] Preferably, the alkaline corrosive solution is prepared by weighing potassium hydroxide, potassium perchlorate, and potassium fluoride according to the weight ratio, adding deionized water, and stirring until completely dissolved to obtain a uniform and transparent alkaline corrosive solution.

[0007] Preferably, the concentrated sulfuric acid has a mass fraction of 98%, the concentrated phosphoric acid has a mass fraction of 85%, and the perchloric acid has a mass fraction of 70%.

[0008] Preferably, the diamond is a single-crystal diamond, more preferably a type IIa single-crystal diamond, and the diamond substrate is a clean substrate after polishing.

[0009] Preferably, the isothermal corrosion is carried out in a sealed corrosion-resistant reactor, and magnetic stirring is used during the corrosion process at a stirring rate of 200-500 r / min.

[0010] Preferably, the cleaning is performed by ultrasonic cleaning with deionized water 3-5 times, with each ultrasonic cleaning lasting 5-10 minutes; the drying is performed by vacuum drying at 60-80°C for 2-4 hours.

[0011] Preferably, the ultrafast laser is a fiber femtosecond laser, with a focal defocus of 0-50 μm and a scanning speed of 100-1000 mm / s for direct laser scanning.

[0012] Preferably, the width of the microchannels inside the diamond is 5-50 μm, the depth is 10-100 μm, and the inlet and outlet apertures are 10-80 μm.

[0013] Preferably, the prepared diamond microstructure includes surface micropits, microgrooves, microlens arrays, nano-wave structures, and internal microchannels, microcavities, and optical waveguides.

[0014] Compared with the prior art, the beneficial effects of the present invention are: This invention designs a composite alkaline etching solution of potassium hydroxide-potassium perchlorate-potassium fluoride and a composite acidic etching solution of concentrated sulfuric acid-concentrated phosphoric acid-perchloric acid, and adopts a two-step process of alkaline pre-etching + acid secondary etching to achieve highly selective etching of laser-modified graphitized regions. The corrosion selectivity (etching rate of graphitized region / etching rate of diamond body) is significantly higher than that of conventional strong mixed acid systems, and the complexing protection effect of concentrated phosphoric acid effectively avoids the corrosion of diamond body. This invention precisely defines the modification parameters of ultrafast lasers, and designs suitable laser parameters for the microstructure on the diamond surface and the internal microchannels respectively, avoiding uneven modification areas caused by thermal diffusion and ensuring the forming accuracy of the microstructure. At the same time, it is the first to realize the laser modification and etching preparation of the internal microchannels of diamond. The end face design of the inlet and outlet of the microchannel ensures the flow of the etching liquid and the porosity. The prepared microchannels are unblocked and have smooth inner walls. Attached Figure Description

[0015] The disclosure of this invention is illustrated with reference to the accompanying drawings. It should be understood that the drawings are for illustrative purposes only and are not intended to limit the scope of protection of this invention. In the drawings, the same reference numerals are used to refer to the same parts. Wherein: Figure 1 This is a flowchart of the preparation method of the present invention; Figure 2 Image 1 of the microstructure of the diamond surface prepared according to the present invention; Figure 3 Photograph 2 of the diamond surface microstructure prepared for this invention; Figure 4 Schematic diagram of the three-dimensional structure of the internal microchannels of diamond prepared according to the present invention. Figure 1 ; Figure 5 Schematic diagram of the three-dimensional structure of the internal microchannels of diamond prepared according to the present invention. Figure 2 . Detailed Implementation

[0016] It is readily understood that, based on the technical solution of this invention, those skilled in the art can propose various interchangeable structural methods and implementations without altering the essential spirit of the invention. Therefore, the following detailed embodiments and accompanying drawings are merely illustrative examples of the technical solution of this invention and should not be considered as the entirety of the invention or as limitations or restrictions on the technical solution of this invention.

[0017] Specific embodiments of the present invention are described below with reference to the accompanying drawings.

[0018] Please see Figures 1-5 A method for preparing diamond microstructures includes four steps: ultrafast laser modification, alkaline pre-etching, acidic secondary etching, and post-treatment, as detailed below: 1. Ultrafast laser modification A diamond substrate is fixed on a precision displacement platform. A fiber femtosecond laser is used as the light source, and the ultrafast laser is focused onto a designated area on the surface or inside of the diamond. The laser scanning and direct-writing modification is achieved by moving the precision displacement platform, transforming the diamond in the modified area... Hybrid carbon transforms into the graphite phase Hybrid carbon provides the basis for subsequent selective corrosion; The ultrafast laser scanning direct writing has a focal defocus of 0-50μm and a scanning speed of 100-1000mm / s. The scanning spacing and number of scans can be adjusted according to the design size of the microstructure.

[0019] When preparing diamond surface microstructures, the laser parameters are precisely limited to: wavelength 1030nm, pulse width 100-500fs, frequency 10-800KHz, and power 0.001-0.5W. This parameter range can avoid graphitization of unmodified areas caused by thermal diffusion and ensure the uniformity of modified areas. When preparing microchannels inside diamond, the laser parameters are: wavelength 1030nm or 515nm, pulse width 100-600fs, frequency 50-800KHz, and power 0.001-1W. The inlet and outlet of the microchannel are both set on the end face in the thickness direction of the diamond to facilitate the entry of subsequent etching solution and the discharge of products, thus ensuring the porosity of the microchannel.

[0020] 2. Alkaline pre-corrosion The diamond modified by ultrafast laser was placed in a sealed polytetrafluoroethylene corrosion-resistant reactor, and a prepared alkaline etching solution was added. The reactor was then placed in a constant temperature heating device and etched at a constant temperature of 90-120℃. During the etching process, magnetic stirring was used at a stirring rate of 200-500 r / min to ensure the uniformity of the etching solution and avoid differences in etching effect caused by uneven local concentration.

[0021] The alkaline etching solution is a composite aqueous solution of potassium hydroxide, potassium perchlorate, and potassium fluoride, with a weight ratio of 20%-40% potassium hydroxide, 30%-50% potassium perchlorate, and 20%-40% potassium fluoride. Potassium hydroxide provides a strongly alkaline environment, promoting the dissolution of corrosion products; potassium perchlorate acts as an oxidant, accelerating the graphitization process. Oxidation reaction of hybrid carbon; potassium fluoride provides The carbon atoms in the graphite layer form easily soluble fluorinated carbon, achieving initial etching of the graphitized region. The synergistic effect of the three can achieve selective pre-etching of the graphitized region without damaging the unmodified diamond region.

[0022] The etching time is adjusted according to the type of microstructure prepared: the etching time for surface microstructures is 10-30h, and the etching time for internal microchannels is 30-60h; the purpose of pre-etching is to remove the loose carbon layer in the graphitized area and provide a uniform reaction interface for subsequent acidic secondary etching.

[0023] 3. Acidic secondary corrosion After alkaline pre-etching, the diamond is removed from the reactor, drained, and placed back into the corrosion-resistant reactor. An acidic etching solution is added, and the diamond is subjected to constant-temperature magnetic stirring etching at 100-200℃ with a stirring rate of 200-500 r / min. The acidic etching solution achieves deep etching of the graphitized region, further improving the aspect ratio of the microstructure.

[0024] The acidic etching solution is composed of concentrated sulfuric acid, concentrated phosphoric acid, and perchloric acid. By weight ratio, the concentrations are 20%-40% concentrated sulfuric acid, 10%-30% concentrated phosphoric acid, and 10%-60% perchloric acid; the mass fractions of concentrated sulfuric acid are 98%, concentrated phosphoric acid is 85%, and perchloric acid is 70%. Among them, concentrated sulfuric acid and perchloric acid are strong oxidants that continuously oxidize carbon atoms in the graphitized regions. Concentrated phosphoric acid has a complexing and protective effect, forming a dense complex film in the unmodified areas of diamond, inhibiting the corrosion of diamond by the acid solution, and significantly improving the corrosion selectivity.

[0025] The etching time is adjusted according to the type of microstructure: the etching time for surface microstructures is 20-40 hours, and the etching time for internal microchannels is 40-80 hours. This time range can ensure that the graphitized area is thoroughly etched, while avoiding microstructure collapse caused by excessive etching.

[0026] 4. Post-processing After the diamond has undergone secondary acid etching, it is removed and ultrasonically cleaned with deionized water 3-5 times, 5-10 minutes each time, to thoroughly remove the residual etching solution and etching products on the surface. After cleaning, the diamond is placed in a vacuum drying oven and dried at 60-80℃ for 2-4 hours to obtain a diamond microstructure with high forming accuracy and good sidewall quality.

[0027] The diamond substrate used in this invention is type IIa single-crystal diamond, and it is a clean substrate after polishing. The preferred diamond crystal orientation is... <100> or <111> Crystal orientation and a substrate surface free of impurities and scratches ensure uniformity of laser modification and etching.

[0028] The alkaline corrosive solution is prepared as follows: Weigh potassium hydroxide, potassium perchlorate, and potassium fluoride according to the weight ratio, add deionized water, and stir magnetically at room temperature until completely dissolved to obtain a homogeneous and transparent aqueous solution. Prepare and use immediately to avoid component failure.

[0029] The diamond microstructures prepared by this invention include surface micropits, microgrooves, microlens arrays, nano-wave structures, and internal microchannels, microcavities, optical waveguides, etc., wherein the width of the internal microchannels is 5-50 μm, the depth is 10-100 μm, and the aperture of the inlet and outlet is 10-80 μm. The size and shape of the microstructure can be adjusted according to the actual application requirements.

[0030] This invention also protects the application of the diamond microstructures prepared by the above method in the fields of optical photonics, microelectronics and heat dissipation, biomedicine and sensing, tribology and tools: In the field of optical photonics: fabrication of diamond microlens arrays, Fresnel lenses, anti-reflective nanowave structures, optical waveguides and optical resonators with integrated photonic circuits; Microelectronics and heat dissipation: fabrication of microstructures for diamond MEMS / NEMS devices and diamond / gallium nitride heterojunction heat dissipation substrates; Biomedical and sensing fields: fabrication of microfluidic chips, biomolecule immobilization substrates, and nitrogen-vacancy center quantum sensor arrays; In the field of tribology and tools: preparation of anti-friction microtextures for diamond cutting tools and drawing die surfaces.

[0031] The diamond substrates used in the embodiments of this invention are all type IIa single-crystal diamonds, which have been polished and have their crystal orientation... <100> The substrate size was 10mm×10mm×0.5mm; all ultrafast lasers were fiber femtosecond lasers; both alkaline and acidic etching solutions were prepared and used immediately; constant temperature etching was carried out in a polytetrafluoroethylene sealed reactor with a magnetic stirring rate of 300r / min; post-treatment involved ultrasonic cleaning with deionized water four times for 8 minutes each time, followed by vacuum drying at 70℃ for 3 hours; and the microstructure-related performance indicators in each embodiment were detected by scanning electron microscopy (SEM), atomic force microscopy (AFM), profilometer, and micro-CT.

[0032] Example 1: Fabrication of a diamond surface microlens array Ultrafast laser modification: A laser is focused on the diamond surface and scanned to directly write the modified area of ​​the microlens array. The laser parameters are: wavelength 1030nm, pulse width 100fs, frequency 800KHz, power 0.001W, scanning speed 500mm / s, focal defocus 0μm, and scanning spacing 2μm. Alkaline pre-corrosion: Prepare an alkaline etching solution by weight of 20% potassium hydroxide, 50% potassium perchlorate, and 30% potassium fluoride, and add deionized water and stir until completely dissolved; completely immerse the diamond in the etching solution and etch at a constant temperature of 90°C for 30 hours. Acidic secondary corrosion: Prepare an acidic corrosion solution by weight ratio of 20% concentrated sulfuric acid, 30% concentrated phosphoric acid, and 50% perchloric acid (98% concentrated sulfuric acid, 85% concentrated phosphoric acid, and 70% perchloric acid by mass); completely immerse the diamond in the corrosion solution and corrode at a constant temperature of 100°C for 40 hours. Post-processing: After cleaning and drying according to the above unified process, a diamond surface microlens array is obtained.

[0033] Testing revealed that the microlens array had a microstructure aspect ratio of 12:1, a maximum etching depth of 58 μm, a surface roughness Ra≤40 nm, a corrosion selectivity (corrosion rate in the graphitized region / corrosion rate in the diamond body) of 60:1, no obvious corrosion damage in the unmodified diamond region, and a microlens array forming accuracy deviation ≤±1 μm.

[0034] Example 2: Preparation of nano-ripple structure on diamond surface Ultrafast laser modification: A laser is focused on the surface of diamond and the nano-wave structure modification region is prepared by scanning and direct writing. The laser parameters are: wavelength 1030nm, pulse width 500fs, frequency 10KHz, power 0.5W, scanning speed 300mm / s, focal defocus 20μm, and scanning spacing 1μm. Alkaline pre-corrosion: Prepare an alkaline etching solution by weight of 40% potassium hydroxide, 40% potassium perchlorate, and 20% potassium fluoride, and add deionized water and stir until completely dissolved; completely immerse the diamond in the etching solution and etch at a constant temperature of 120℃ for 10 hours. Acidic secondary corrosion: Prepare an acidic corrosion solution with the following weight ratios: 30% concentrated sulfuric acid, 10% concentrated phosphoric acid, and 60% perchloric acid; completely immerse the diamond in the corrosion solution and corrode at a constant temperature of 200℃ for 20 hours. Post-processing: After cleaning and drying according to the above unified process, a nano-ripple structure is obtained on the diamond surface.

[0035] Testing revealed that the nano-corrugated structure has a microstructure depth of 60 μm, a period of 500 nm, a sidewall roughness Ra≤50 nm, a corrosion selectivity of 55:1, no significant change in surface smoothness in the unmodified diamond area, and no collapse or deformation of the corrugated structure.

[0036] Example 3: Fabrication of microchannels inside diamond (1030nm laser) Ultrafast laser modification: A laser is focused at a depth of 200 μm inside the diamond, and a microchannel modification region is prepared by scanning and direct writing. The microchannel is designed with a width of 10 μm, a depth of 20 μm, and a length of 5 mm. The inlet and outlet apertures are both 20 μm and are located on the end face of the diamond in the thickness direction. The laser parameters are: wavelength 1030 nm, pulse width 100 fs, frequency 800 kHz, power 0.01 W, scanning speed 400 mm / s, focal defocus 10 μm, and scanning interval 1 μm. Alkaline pre-corrosion: Prepare an alkaline etching solution by weight of 20% potassium hydroxide, 50% potassium perchlorate, and 30% potassium fluoride, and add deionized water and stir until completely dissolved; completely immerse the diamond in the etching solution and etch at a constant temperature of 90°C for 30 hours. Acidic secondary corrosion: Prepare an acidic corrosion solution with the following weight ratios: 20% concentrated sulfuric acid, 20% concentrated phosphoric acid, and 60% perchloric acid; completely immerse the diamond in the corrosion solution and corrode at a constant temperature of 100°C for 80 hours. Post-processing: After cleaning and drying according to the above unified process, the internal microchannels of the diamond are obtained.

[0037] Testing revealed that the internal microchannels had a 100% porosity, with no blockages or cracks. The actual formed dimensions were 10.2 μm in width, 19.8 μm in depth, and 4.99 mm in length, with a dimensional deviation of ≤ ±1 μm. The inner wall roughness of the channel was Ra ≤ 80 nm, and the diamond body showed no signs of corrosion, perforation, or deformation.

[0038] Example 4: Fabrication of microchannels inside diamond (515nm laser) Ultrafast laser modification: A laser is focused at a depth of 300 μm inside the diamond, and a microchannel modification region is prepared by scanning and direct writing. The microchannel is designed with a width of 30 μm, a depth of 50 μm, and a length of 8 mm. The inlet and outlet apertures are both 50 μm and located on the end face of the diamond in the thickness direction. The laser parameters are: wavelength 515 nm, pulse width 600 fs, frequency 50 kHz, power 1 W, scanning speed 200 mm / s, focal defocusing amount 30 μm, and scanning interval 2 μm. Alkaline pre-corrosion: Prepare an alkaline etching solution by weight of 40% potassium hydroxide, 40% potassium perchlorate, and 20% potassium fluoride, and add deionized water and stir until completely dissolved; completely immerse the diamond in the etching solution and etch at a constant temperature of 120℃ for 60 hours. Acidic secondary corrosion: Prepare an acidic corrosion solution with the following weight ratios: 40% concentrated sulfuric acid, 30% concentrated phosphoric acid, and 30% perchloric acid; completely immerse the diamond in the corrosion solution and corrode at a constant temperature of 200°C for 40 hours. Post-processing: After cleaning and drying according to the above unified process, the internal microchannels of the diamond are obtained.

[0039] Testing revealed that the internal microchannels had a 100% porosity, with no blockages or cracks. The actual formed dimensions were 30.4 μm in width, 49.8 μm in depth, and 7.98 mm in length, with a dimensional deviation of ≤ ±2 μm. The inner wall roughness of the channel was Ra ≤ 90 nm, and the diamond body showed no signs of corrosion, perforation, or deformation.

[0040] Comparative test To verify the superiority of the preparation method of the present invention, three sets of comparative experiments were set up, all using the same diamond substrate (type IIa single crystal diamond) as in Example 1 of the present invention. <100> Crystal orientation, 10mm×10mm×0.5mm polished substrate, ultrafast laser modification parameters (wavelength 1030nm, pulse width 100fs, frequency 800KHz, power 0.001W, scanning speed 500mm / s, focal defocus 0μm, scanning spacing 2μm) and post-treatment process (deionized water ultrasonic cleaning 4 times, 8min each time, vacuum drying at 70℃ for 3h), only the etching solution system and etching process were changed. The etching process was carried out in a polytetrafluoroethylene sealed reactor with a magnetic stirring rate of 300r / min. The microstructure performance index detection method was the same as in the example. The specific experimental scheme and test results are as follows: Comparative Experiment 1: Conventional strong mixed acid single corrosion process (current mainstream technology) Etching solution: The solution used is a mixture of concentrated nitric acid and concentrated sulfuric acid, which is commonly used in the etching of diamond graphitization regions in existing technologies. The concentrated nitric acid (68% by mass) and concentrated sulfuric acid (98% by mass) are mixed at a volume ratio of 3:1 and stirred evenly at room temperature. Corrosion process: The diamond modified by the same ultrafast laser was completely immersed in the above mixed acid solution and constant temperature corrosion was carried out at 150°C using the conventional corrosion temperature of the prior art for 30 hours (compared with the total corrosion time of 70 hours of alkali + acid in Example 1 of this invention, the optimal effective corrosion time of the prior art was selected). Post-processing: Same as in Embodiment 1 of the present invention.

[0041] Test results: The corrosion selectivity was only 8:1, the aspect ratio of the microlens array microstructure was 2.5:1, the maximum etching depth was only 8μm, the unmodified diamond area showed obvious corrosion damage, and the surface roughness increased from the original Ra≤5nm to Ra≥200nm; the microlens array forming accuracy deviation was ≥±8μm, and some microlens structures collapsed and had edge defects, which could not meet the requirements of practical applications.

[0042] Comparative Experiment 2: Corrosion Process of the Single Alkaline Corrosive Solution of the Present Invention The etching solution used was the same alkaline etching solution as in Example 1 of this invention (an aqueous solution of 20% potassium hydroxide, 50% potassium perchlorate, and 30% potassium fluoride by weight). Etching process: The diamond, after being modified by the same ultrafast laser, was completely immersed in the above-mentioned alkaline etching solution and etched at a constant temperature of 90°C for 70 hours (consistent with the total alkali + acid etching time in Example 1 of this invention). Post-processing: Same as in Embodiment 1 of the present invention.

[0043] Test results: The corrosion selectivity was 35:1, the maximum etching depth of the microlens array microstructure was 22μm, the aspect ratio was 4.2:1, and the surface roughness Ra≤60nm; there was no obvious corrosion damage in the unmodified diamond area, but the etching in the graphitized area was incomplete, and there was a large amount of unetched graphite residue at the bottom of the microlens array, the microstructure outline was blurred, and a complete lens surface could not be formed.

[0044] Comparative Experiment 3: Corrosion Process of the Single Acidic Corrosive Solution of the Present Invention Etching solution: The acidic etching solution used is exactly the same as that used in Example 1 of this invention (a mixture of 20% concentrated sulfuric acid, 30% concentrated phosphoric acid, and 50% perchloric acid by weight, with the concentration of each acid solution being the same as in Example 1). Etching process: The diamond, after being modified by the same ultrafast laser, was completely immersed in the above-mentioned acidic etching solution and etched at a constant temperature of 100°C for 70 hours (consistent with the total alkali + acid etching time in Example 1 of this invention). Post-processing: Same as in Embodiment 1 of the present invention.

[0045] Test results: The corrosion selectivity was 15:1, the maximum etching depth of the microlens array microstructure was 30 μm, the aspect ratio was 5.8:1, and the surface roughness Ra≤70nm; slight corrosion damage was observed in the unmodified diamond area, and the surface roughness increased to Ra≥50nm; local corrosion pits appeared on the sidewall of the microlens array, the forming accuracy deviation was ≥±5μm, and a sharp drop in corrosion rate occurred in the later stage of etching, making it impossible to achieve deep etching.

[0046] Summary of comparative experiments The results of the above three sets of comparative experiments show that: The conventional strong mixed acid single etching process in the existing technology has defects such as extremely low corrosion selectivity, shallow etching depth of microstructure, severe corrosion of diamond body and poor forming accuracy, and cannot prepare high-precision diamond microstructures with high aspect ratio. Although the alkaline etching solution of the present invention alone does not cause significant damage to the diamond body and has better corrosion selectivity than conventional mixed acid, it has problems such as incomplete etching of graphitized areas, slow etching rate, inability to achieve deep etching, and difficulty in forming a complete microstructure outline. When using the acidic etching solution of this invention alone, the etching depth is better than that of a single alkaline solution and conventional mixed acid, but the corrosion selectivity is greatly reduced, the diamond body is corroded and damaged, and the corrosion rate drops sharply in the later stage, making it impossible to balance etching depth and microstructure forming quality. The two-step process of alkaline pre-etching + acid secondary etching of the present invention realizes the synergistic effect of alkaline and acid etching solutions. It not only solves the problem of incomplete etching by alkaline solution alone, but also optimizes the etching interface of acid solution by using the base effect of alkaline pre-etching. At the same time, it avoids the corrosion of diamond body by relying on the complexation protection effect of concentrated phosphoric acid in acid solution. Finally, it realizes the preparation of diamond microstructure with high corrosion selectivity, high aspect ratio, high forming accuracy and low roughness. All performance indicators are significantly better than existing technologies and single etching solution processes.

[0047] Industrial application The diamond microstructure fabrication method of this invention features controllable processes, readily available raw materials, and conventional equipment, requiring no specialized customized equipment. It enables high-precision and highly selective fabrication of diamond surface microstructures (micropits, microgrooves, microlens arrays, nano-wave structures, etc.) and internal microchannels (microchannels, microcavities, etc.). The fabricated microstructures exhibit high forming precision, good sidewall quality, and a large aspect ratio, while the diamond body shows no significant corrosion damage. The diamond microstructures prepared by this invention can be widely applied in fields such as optics and photonics, microelectronics and heat dissipation, biomedicine and sensing, tribology and tools, including diamond microlenses for high-power laser systems, optical waveguides for on-chip quantum information processing, microfluidic channels for biochips, and friction-reducing microtextures for diamond cutting tools. It has significant industrial application value and practical significance.

[0048] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing diamond microstructures, characterized in that, Includes the following steps: Ultrafast laser modification: An ultrafast laser is focused on a designated area on the surface or inside of a diamond to perform scanning and direct writing modification, which transforms the diamond in the modified area into the graphite phase; When preparing microstructures on the surface of diamond, the ultrafast laser parameters are: wavelength 1030nm, pulse width 100-500fs, frequency 10-800KHz, and power 0.001-0.5W. When preparing the internal microchannels of diamond, the ultrafast laser parameters are: wavelength 1030nm or 515nm, pulse width 100-600fs, frequency 50-800KHz, and power 0.001-1W; the internal microchannels are provided with inlet and outlet, and both the inlet and outlet are located on the end face in the thickness direction of the diamond. Alkaline pre-etching: The diamond modified by ultrafast laser is placed in an alkaline etching solution and is etched at a constant temperature of 90-120℃; the etching time for the surface microstructure is 10-30h, and the etching time for the internal microchannels is 30-60h. Acidic secondary corrosion: The diamond, after alkaline pre-corrosion, is placed in an acidic etching solution and subjected to constant temperature corrosion at 100-200℃; the corrosion time for the surface microstructure is 20-40 hours, and the corrosion time for the internal microchannels is 40-80 hours. Post-processing: The diamonds that have undergone secondary acid etching are sequentially cleaned and dried to obtain the diamond microstructure.

2. The method for preparing diamond microstructures according to claim 1, characterized in that, The alkaline corrosive solution is an aqueous solution of potassium hydroxide, potassium perchlorate, and potassium fluoride, with the following weight ratios: potassium hydroxide 20%-40%, potassium perchlorate 30%-50%, and potassium fluoride 20%-40%. The acidic corrosive solution is composed of concentrated sulfuric acid, concentrated phosphoric acid, and perchloric acid, with the following weight ratios: concentrated sulfuric acid 20%-40%, concentrated phosphoric acid 10%-30%, and perchloric acid 10%-60%.

3. The method for preparing diamond microstructures according to claim 2, characterized in that, The alkaline corrosive solution is prepared by weighing potassium hydroxide, potassium perchlorate, and potassium fluoride according to the weight ratio, adding deionized water, and stirring until completely dissolved to obtain a homogeneous and transparent alkaline corrosive solution.

4. The method for preparing diamond microstructures according to claim 2, characterized in that, The concentrated sulfuric acid has a mass fraction of 98%, the concentrated phosphoric acid has a mass fraction of 85%, and the perchloric acid has a mass fraction of 70%.

5. The method for preparing diamond microstructures according to claim 1, characterized in that, The diamond is a single-crystal diamond, preferably a type IIa single-crystal diamond, and the diamond substrate is a clean substrate after polishing.

6. The method for preparing diamond microstructures according to claim 1, characterized in that, All the isothermal corrosion was carried out in a sealed corrosion-resistant reactor, and magnetic stirring was used during the corrosion process at a stirring rate of 200-500 r / min.

7. The method for preparing diamond microstructures according to claim 1, characterized in that, The cleaning process involves ultrasonic cleaning with deionized water 3-5 times, with each ultrasonic cleaning lasting 5-10 minutes; the drying process involves vacuum drying at 60-80℃ for 2-4 hours.

8. The method for preparing diamond microstructures according to claim 1, characterized in that, The ultrafast laser is a fiber femtosecond laser, with a focal defocus of 0-50 μm and a scanning speed of 100-1000 mm / s for direct laser scanning.

9. The method for preparing diamond microstructures according to claim 1, characterized in that, The width of the microchannels inside the diamond is 5-50 μm, the depth is 10-100 μm, and the diameter of the inlet and outlet is 10-80 μm.

10. The method for preparing diamond microstructures according to any one of claims 1-9, characterized in that, The prepared diamond microstructures include surface micropits, microgrooves, microlens arrays, nano-wave structures, and internal microchannels, microcavities, and optical waveguides.

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