Method for high uniform nucleation and interface regulation of peelable diamond film
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-06-22
- Publication Date
- 2026-08-11
AI Technical Summary
团聚后的颗粒粒径增大且粒径分布范围扩大，导致悬浮液在使用过程中颗粒沉降速率不一致，影响悬浮液成分的批次稳定性，并使形核剂层中纳米金刚石颗粒分布不均匀，局部区域形核密度不足
[0024]1）本发明通过构建聚乙烯醇界面调控层，在金刚石膜与硅基底之间形成弱结合界面，既保证金刚石膜在CVD生长过程中与基底具有足够的结合力以维持膜层平整生长，又能在机械剥离时沿界面调控层实现完整分离，有效避免了因界面结合力过强导致的膜层碎裂问题，显著提升了金刚石膜的完整剥离率；
Smart Images
Figure CN122542998A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of diamond film preparation technology, and more specifically, relates to a method for highly uniform nucleation and interface control of peelable diamond films. Background Technology
[0002] In the preparation of polycrystalline diamond films using chemical vapor deposition (CVD), a nucleating agent layer (seed layer) containing nanodiamond particles is typically pre-prepared on the substrate surface to provide nucleation sites for diamond growth. The distribution density and uniformity of the nanodiamond particles in the nucleating agent layer directly determine the number and spatial distribution of nucleation sites during subsequent diamond growth, thus affecting the grain size, grain size distribution, and overall quality consistency of the final polycrystalline diamond film. Simultaneously, the interfacial bonding characteristics between the nucleating agent layer and the substrate have a decisive influence on the mechanical exfoliation process and complete exfoliation rate after diamond film growth.
[0003] Existing diamond nucleating agent suspensions are typically prepared using a single solvent system. Due to the large specific surface area and high surface energy of nanodiamond particles, and the presence of multiple functional groups on their surfaces, particles are prone to agglomeration through van der Waals forces, making it difficult to achieve a long-term stable dispersion in a single solvent system. Agglomerated particles have increased size and a wider particle size distribution, leading to inconsistent particle settling rates during use, affecting batch stability of the suspension composition, and causing uneven distribution of nanodiamond particles in the nucleating agent layer, resulting in insufficient nucleation density in localized areas.
[0004] When the above-mentioned suspension is coated onto the substrate surface to form a nucleating agent layer using a spin-coating method, existing processes often employ a single spin-coating speed and a single spin-coating time. This method cannot simultaneously meet the requirements of sufficient spreading and coverage of the suspension on the substrate surface and effective removal of the solvent: if the spin speed is too low, the suspension will not spread sufficiently, resulting in inadequate coverage of the substrate edge area; if the spin speed is too high, the solvent removal rate will be too fast, and the particles will be fixed before they can spread sufficiently, leading to uneven particle distribution on the substrate surface. These factors together result in insufficient thickness uniformity within the nucleating agent layer, and significant differences in the nucleation density distribution within the substrate surface. This, in turn, increases the dispersion of diamond grain nucleation time and position during subsequent CVD growth, ultimately affecting the overall growth quality of the polycrystalline diamond film.
[0005] Furthermore, if the interfacial bonding force between the nucleating agent layer and the substrate is spatially uneven, it will cause stress to concentrate locally in the weak areas of the interface during the mechanical peeling of the diamond film. This will induce cracks to form and propagate preferentially in these areas, making it difficult for the peeling process to proceed uniformly along the entire interface. Ultimately, this will result in a low rate of complete peeling of the diamond film over a large area, with some areas showing cracks or residues. Summary of the Invention
[0006] In view of the above-mentioned problems in the prior art, the technical problem to be solved by the present invention is to provide a method for highly uniform nucleation and interface control of peelable diamond films.
[0007] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:
[0008] A method for highly uniform nucleation and interface control of peelable diamond films includes the following steps:
[0009] 1) Disperse nanodiamond powder and polyvinylpyrrolidone in a mixed solvent of isopropanol and deionized water. After stirring, pulsed ultrasonic dispersion and two-stage differential centrifugation, the precipitate obtained by centrifugation is redispersed in the mixed solvent to obtain a diamond nucleating agent suspension.
[0010] 2) The substrate is cleaned and subjected to oxygen plasma surface activation treatment. Then, the activated substrate is immersed in a polyvinyl alcohol aqueous solution, and after lifting and drying, a polyvinyl alcohol interface control layer is formed on the substrate surface.
[0011] 3) The diamond nucleating agent suspension obtained in step 1) is dropped onto the center of the substrate obtained in step 2), and then spin-coated using a three-stage spin coating process and dried to obtain the seed layer;
[0012] 4) Place the substrate with the seed layer obtained in step 3) in a chemical vapor deposition apparatus and grow a diamond film in an atmosphere of carbon source gas and hydrogen to obtain a polycrystalline diamond film.
[0013] 5) Mechanically peel off the polyvinyl alcohol interface control layer to obtain a self-supporting diamond film.
[0014] Preferably, in step 1), the volume ratio of isopropanol to deionized water is 7:3; and the mass ratio of nanodiamond powder to polyvinylpyrrolidone is 2.5:1.
[0015] Preferably, in step 1), the power of the pulsed ultrasonic dispersion treatment is 100 W, the pulse mode is 5 seconds working and 5 seconds intermittent, the treatment time is 20 min, and the temperature is controlled by an ice water bath ≤30℃ during the ultrasonic process.
[0016] Preferably, in step 1), the two-stage differential centrifugation process is as follows: first, centrifuge at a relative centrifugal force of 1000×g for 10 min and take the supernatant; then, centrifuge the obtained supernatant at 4℃ with a relative centrifugal force of 16000×g for 20 min, discard the supernatant, and redisperse the precipitate in the mixed solvent to obtain a diamond nucleating agent suspension.
[0017] Preferably, in step 2), the oxygen flow rate for oxygen plasma surface activation treatment is 20 sccm, the chamber pressure is 20 Pa, the radio frequency power is 100 W, and the treatment time is 10 min.
[0018] Preferably, in step 2), the mass concentration of the polyvinyl alcohol aqueous solution is 0.1–0.5 wt%; and the immersion time is 5–20 min.
[0019] Preferably, in step 3), the three-stage spin coating process is as follows: the first stage has a rotation speed of 500-700 rpm and lasts for 10-15 s; the second stage has a rotation speed of 2200-3000 rpm and lasts for 20-30 s; and the third stage has a rotation speed of 4500-6000 rpm and lasts for 35-60 s.
[0020] Preferably, in step 4), the chemical vapor deposition is microwave plasma chemical vapor deposition, with the following process conditions: hydrogen flow rate of 500 sccm, methane flow rate of 20 sccm, reaction pressure of 12 kPa, substrate temperature of 850℃, microwave power of 3-4 kW, and growth time of 12-16 h.
[0021] Preferably, in step 4), after the diamond film growth is completed, the carbon source gas is stopped, and the film is cooled to room temperature in a hydrogen atmosphere to obtain a polycrystalline diamond film.
[0022] Preferably, in step 2), the substrate is a single-crystal silicon wafer with a diameter of 100 mm and a thickness of 500 μm.
[0023] Beneficial effects: Compared with the prior art, the present invention has the following advantages:
[0024] 1) By constructing a polyvinyl alcohol interface control layer, a weak bonding interface is formed between the diamond film and the silicon substrate. This ensures that the diamond film has sufficient bonding force with the substrate during CVD growth to maintain the smooth growth of the film layer, and also enables complete separation along the interface control layer during mechanical peeling. This effectively avoids the problem of film layer fragmentation caused by excessive interface bonding force and significantly improves the complete peeling rate of the diamond film.
[0025] 2) This invention uses a two-stage differential centrifugation technique to purify nanodiamond nucleating agent suspensions in stages. First, large-sized agglomerated particles are removed by low-speed centrifugation, and then highly dispersed nanodiamond particles are collected by high-speed centrifugation. This effectively solves the problem of easy agglomeration and inconsistent sedimentation rates of nanodiamonds in a single solvent system, and significantly improves the dispersion stability of nucleating agent suspensions.
[0026] 3) This invention employs a three-stage spin coating process to construct the nucleating agent layer. Through a gradient-increasing spin speed design, the suspension is fully spread on the substrate surface, the nucleating agent particles are evenly distributed, and excess suspension is removed by centrifugation. Combined with the coordinated matching of spin speed and time at each stage, the problem of particle agglomeration and uneven distribution caused by insufficient spreading or excessive solvent evaporation in traditional single-step spin coating is effectively avoided, and a high degree of uniformity in the thickness of the nucleating agent layer is achieved.
[0027] 4) This invention enhances the surface energy of the substrate through oxygen plasma surface activation treatment, and combined with the uniform coating of the polyvinyl alcohol interface control layer, it provides a uniform adhesion interface for the nanodiamond nucleating agent, so that the nucleation points are distributed in a high-density uniform manner within the substrate surface, effectively reducing the dispersion of diamond grain nucleation time and position during CVD growth, and significantly improving the overall growth quality and consistency of polycrystalline diamond film.
[0028] 5) The diamond self-supporting film prepared by this invention has an integrity peeling rate of over 85%, a residual stress as low as -0.35 GPa, a thermal conductivity as high as 1850 W / m·K, and a nano-indentation hardness of 92 GPa, with excellent performance indicators. Attached Figure Description
[0029] Figure 1 The bar chart shows the comparison of residual stress in diamond films between Examples 1-5 and Comparative Examples 1-3.
[0030] Figure 2 The bar chart shows the comparison of the thermal conductivity of diamond films in Examples 1-5 and Comparative Examples 1-3.
[0031] Figure 3 The bar chart shows the comparison of the hardness of the diamond film nanoindentation between Examples 1-5 and Comparative Examples 1-3. Detailed Implementation
[0032] To make the objectives, technical solutions, and advantages of this invention clearer, the invention is further described below with reference to specific embodiments. Unless otherwise specified, the technical means used in the following embodiments are all conventional means well known to those skilled in the art. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer are followed. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially.
[0033] The nanodiamond powder used in the following examples has a particle size of 5 nm; the polyvinylpyrrolidone used has a molecular weight of 40,000.
[0034] Example 1
[0035] 1. Preparation of diamond nucleating agent suspension
[0036] 1) Add 0.5 g of nanodiamond powder and 0.2 g of polyvinylpyrrolidone to a mixed solvent of 100 mL of isopropanol and deionized water in a volume ratio of 7:3. After stirring magnetically at room temperature for 30 min, perform pulsed ultrasonic dispersion treatment. The ultrasonic power is 100 W, the pulse mode is 5 s working and 5 s intermittent, and the continuous treatment is 20 min. During the ultrasonic process, the temperature is controlled at ≤25℃ using an ice water bath. After the ultrasonic treatment, let it stand at room temperature for 30 min to obtain a pre-dispersed suspension.
[0037] 2) Perform two-stage differential centrifugation on the pre-dispersed suspension obtained in step 1): first centrifuge at a relative centrifugal force of 1000×g for 10 min and take the supernatant; then centrifuge the supernatant at 4℃ at a relative centrifugal force of 16000×g for 20 min, discard the supernatant, and redisperse the precipitate in a mixed solvent of 10 mL isopropanol and deionized water in a volume ratio of 7:3 to obtain a diamond nucleating agent suspension;
[0038] 2. Substrate pretreatment and interface control layer construction
[0039] 1) A single-crystal silicon wafer with a diameter of 100 mm and a thickness of 500 μm was ultrasonically cleaned with acetone, anhydrous ethanol and deionized water for 10 min in sequence, and then dried with nitrogen. The cleaned substrate was placed in an oxygen plasma treatment device for surface activation treatment. The oxygen flow rate was 20 sccm, the chamber pressure was 20 Pa, the radio frequency power was 100 W, and the treatment time was 10 min.
[0040] 2) The activated substrate was immersed in a 0.2 wt% polyvinyl alcohol aqueous solution for 10 min, vertically pulled at a speed of 1 mm / s, and dried in an 80℃ oven for 15 min to obtain an interface control layer with a thickness of 15 nm.
[0041] 3. Construction of nucleating agent layer by spin coating
[0042] 2 mL of the diamond nucleating agent suspension prepared in step 1 was dropped onto the center of the substrate and a three-stage spin coating process was used: the first stage was at 600 rpm for 12 s, the second stage was at 2500 rpm for 25 s, and the third stage was at 5000 rpm for 45 s; after spin coating, the substrate was dried at 100℃ for 10 min to obtain the seed layer.
[0043] 4. Chemical vapor deposition growth of diamond films
[0044] The substrate with the seed layer obtained in step 3 was placed in a microwave plasma chemical vapor deposition (MPCVD) apparatus, and H2 was introduced at 500 sccm and CH4 at 20 sccm. The reaction pressure was 12 kPa, the substrate temperature was 850℃, the microwave power was 3.5kW, and the growth was continued for 12 h. After the growth was completed, the CH4 was stopped and the substrate was cooled to room temperature in an H2 atmosphere to obtain a polycrystalline diamond film with a thickness of 50.3 μm.
[0045] 5. Mechanical peeling of diamond film
[0046] A mechanical peeling device was used to peel off along the interface where the interface control layer is located, and 20 diamond films with a diameter of 100 mm were continuously prepared. 19 films were completely peeled off. The peeled diamond films were inspected by optical microscope and SEM and no through cracks or edge damage were found.
[0047] Example 2
[0048] 1. Preparation of diamond nucleating agent suspension
[0049] 1) Add 0.5 g of nanodiamond powder and 0.2 g of polyvinylpyrrolidone to a mixed solvent of 100 mL of isopropanol and deionized water in a volume ratio of 7:3. After stirring magnetically at room temperature for 30 min, perform pulsed ultrasonic dispersion treatment. The ultrasonic power is 100 W, the pulse mode is 5 s working and 5 s intermittent, and the continuous treatment is 20 min. During the ultrasonic process, the temperature is controlled at ≤25℃ using an ice water bath. After the ultrasonic treatment, let it stand at room temperature for 30 min to obtain a pre-dispersed suspension.
[0050] 2) Perform two-stage differential centrifugation on the pre-dispersed suspension obtained in step 1): first centrifuge at a relative centrifugal force of 1000×g for 10 min and take the supernatant; then centrifuge the supernatant at 4℃ at a relative centrifugal force of 16000×g for 20 min, discard the supernatant, and redisperse the precipitate in a mixed solvent of 10 mL isopropanol and deionized water in a volume ratio of 7:3 to obtain a diamond nucleating agent suspension;
[0051] 2. Substrate pretreatment and interface control layer construction
[0052] 1) A single-crystal silicon wafer with a diameter of 100 mm and a thickness of 500 μm was ultrasonically cleaned with acetone, anhydrous ethanol and deionized water for 10 min in sequence, and then dried with nitrogen. The cleaned substrate was placed in an oxygen plasma treatment device for surface activation treatment. The oxygen flow rate was 20 sccm, the chamber pressure was 20 Pa, the radio frequency power was 100 W, and the treatment time was 10 min.
[0053] 2) The activated substrate was immersed in a 0.1 wt% polyvinyl alcohol aqueous solution for 5 min, vertically pulled at a speed of 1 mm / s, and dried in an 80℃ oven for 15 min to obtain an interface control layer with a thickness of 8 nm.
[0054] 3. Take 2 mL of the diamond nucleating agent suspension prepared in step 1 and drop it onto the center of the substrate. Use a three-stage spin coating process: the first stage is at 600 rpm for 12 s, the second stage is at 2500 rpm for 25 s, and the third stage is at 5000 rpm for 45 s. After spin coating, dry at 100℃ for 10 min to obtain the seed layer.
[0055] 4. Place the substrate with the seed layer obtained in step 3 into an MPCVD device, introduce H2 at 500 sccm and CH4 at 20 sccm, with a reaction pressure of 12 kPa, a substrate temperature of 850℃, and a microwave power of 3.5 kW, and continue growing for 12 h; after the growth is completed, stop the introduction of CH4, and cool to room temperature in an H2 atmosphere to obtain a polycrystalline diamond film with a thickness of 49.1 μm.
[0056] 5. Using a mechanical peeling device, 20 diamond films with a diameter of 100 mm were continuously prepared along the interface where the interface control layer is located. 17 films were completely peeled off. There were local minor damages on the edges of the peeled films, but the main body of the films was intact and no through-macro cracks were observed.
[0057] Example 3
[0058] 1. Preparation of diamond nucleating agent suspension
[0059] 1) Add 0.5 g of nanodiamond powder and 0.2 g of polyvinylpyrrolidone to a mixed solvent of 100 mL of isopropanol and deionized water in a volume ratio of 7:3. After stirring magnetically at room temperature for 30 min, perform pulsed ultrasonic dispersion treatment. The ultrasonic power is 100 W, the pulse mode is 5 s working and 5 s intermittent, and the continuous treatment is 20 min. During the ultrasonic process, the temperature is controlled at ≤25℃ using an ice water bath. After the ultrasonic treatment, let it stand at room temperature for 30 min to obtain a pre-dispersed suspension.
[0060] 2) Perform two-stage differential centrifugation on the pre-dispersed suspension obtained in step 1): first centrifuge at a relative centrifugal force of 1000×g for 10 min and take the supernatant; then centrifuge the supernatant at 4℃ at a relative centrifugal force of 16000×g for 20 min, discard the supernatant, and redisperse the precipitate in a mixed solvent of 10 mL isopropanol and deionized water in a volume ratio of 7:3 to obtain a diamond nucleating agent suspension;
[0061] 2. Substrate pretreatment and interface control layer construction
[0062] 1) A single-crystal silicon wafer with a diameter of 100 mm and a thickness of 500 μm was ultrasonically cleaned with acetone, anhydrous ethanol and deionized water for 10 min in sequence, and then dried with nitrogen. The cleaned substrate was placed in an oxygen plasma treatment device for surface activation treatment. The oxygen flow rate was 20 sccm, the chamber pressure was 20 Pa, the radio frequency power was 100 W, and the treatment time was 10 min.
[0063] 2) The activated substrate was immersed in a 0.5 wt% polyvinyl alcohol aqueous solution for 20 min, vertically pulled at a speed of 1 mm / s, and dried in an 80℃ oven for 15 min to obtain an interface control layer with a thickness of 30 nm.
[0064] 3. Take 2 mL of the diamond nucleating agent suspension prepared in step 1 and drop it onto the center of the substrate. Use a three-stage spin coating process: the first stage is at 600 rpm for 12 s, the second stage is at 2500 rpm for 25 s, and the third stage is at 5000 rpm for 45 s. After spin coating, dry at 100℃ for 10 min to obtain the seed layer.
[0065] 4. The substrate with the seed layer obtained in step 3 was placed in a microwave plasma chemical vapor deposition (MPCVD) device, and H2 was introduced at 500 sccm and CH4 at 20 sccm. The reaction pressure was 12 kPa, the substrate temperature was 850℃, the microwave power was 3.5 kW, and the growth was continued for 12 h. After the growth was completed, the CH4 was stopped and the substrate was cooled to room temperature in an H2 atmosphere to obtain a polycrystalline diamond film with a thickness of 50.8 μm.
[0066] 5. Using a mechanical peeling device, 20 diamond films with a diameter of 100 mm were continuously prepared along the interface where the interface control layer is located. 16 films were completely peeled off. The surface of the peeled diamond film had slight wrinkles, but no macroscopic cracks.
[0067] Example 4
[0068] 1. Preparation of diamond nucleating agent suspension
[0069] 1) Add 0.5 g of nanodiamond powder and 0.2 g of polyvinylpyrrolidone to a mixed solvent of 100 mL of isopropanol and deionized water in a volume ratio of 7:3. After stirring magnetically at room temperature for 30 min, perform pulsed ultrasonic dispersion treatment. The ultrasonic power is 100 W, the pulse mode is 5 s working and 5 s intermittent, and the continuous treatment is 20 min. During the ultrasonic process, the temperature is controlled at ≤25℃ using an ice water bath. After the ultrasonic treatment, let it stand at room temperature for 30 min to obtain a pre-dispersed suspension.
[0070] 2) Perform two-stage differential centrifugation on the pre-dispersed suspension obtained in step 1): first centrifuge at a relative centrifugal force of 1000×g for 10 min and take the supernatant; then centrifuge the supernatant at 4℃ at a relative centrifugal force of 16000×g for 20 min, discard the supernatant, and redisperse the precipitate in a mixed solvent of 10 mL isopropanol and deionized water in a volume ratio of 7:3 to obtain a diamond nucleating agent suspension;
[0071] 2. Substrate pretreatment and interface control layer construction
[0072] 1) A single-crystal silicon wafer with a diameter of 100 mm and a thickness of 500 μm was ultrasonically cleaned with acetone, anhydrous ethanol and deionized water for 10 min in sequence, and then dried with nitrogen. The cleaned substrate was placed in an oxygen plasma treatment device for surface activation treatment. The oxygen flow rate was 20 sccm, the chamber pressure was 20 Pa, the radio frequency power was 100 W, and the treatment time was 10 min.
[0073] 2) The activated substrate was immersed in a 0.2 wt% polyvinyl alcohol aqueous solution for 10 min, vertically pulled at a speed of 1 mm / s, and dried in an 80℃ oven for 15 min to obtain an interface control layer with a thickness of 15 nm.
[0074] 3. Take 2 mL of the diamond nucleating agent suspension prepared in step 1 and drop it onto the center of the substrate. Use a three-stage spin coating process: the first stage is at 500 rpm for 15 s, the second stage is at 2200 rpm for 30 s, and the third stage is at 4500 rpm for 60 s. After spin coating, dry at 100℃ for 10 min to obtain the seed layer.
[0075] 4. Place the substrate with the seed layer obtained in step 3 into an MPCVD device, introduce H2 at 500 sccm and CH4 at 20 sccm, with a reaction pressure of 12 kPa, a substrate temperature of 850℃, and a microwave power of 3.5 kW, and continue growing for 12 h; after the growth is completed, stop the introduction of CH4, and cool to room temperature in an H2 atmosphere to obtain a polycrystalline diamond film with a thickness of 48.7 μm.
[0076] 5. Using a mechanical peeling device, 20 diamond films with a diameter of 100 mm were continuously prepared along the interface where the interface control layer is located. 18 films were completely peeled off. The peeled films were intact, with only a very few samples showing minor edge chipping.
[0077] Example 5
[0078] 1. Preparation of diamond nucleating agent suspension
[0079] 1) Add 0.5 g of nanodiamond powder and 0.2 g of polyvinylpyrrolidone to a mixed solvent of 100 mL of isopropanol and deionized water in a volume ratio of 7:3. After stirring magnetically at room temperature for 30 min, perform pulsed ultrasonic dispersion treatment. The ultrasonic power is 100 W, the pulse mode is 5 s working and 5 s intermittent, and the continuous treatment is 20 min. During the ultrasonic process, the temperature is controlled at ≤25℃ using an ice water bath. After the ultrasonic treatment, let it stand at room temperature for 30 min to obtain a pre-dispersed suspension.
[0080] 2) Perform two-stage differential centrifugation on the pre-dispersed suspension obtained in step 1): first centrifuge at a relative centrifugal force of 1000×g for 10 min and take the supernatant; then centrifuge the supernatant at 4℃ at a relative centrifugal force of 16000×g for 20 min, discard the supernatant, and redisperse the precipitate in a mixed solvent of 10 mL isopropanol and deionized water in a volume ratio of 7:3 to obtain a diamond nucleating agent suspension;
[0081] 2. Substrate pretreatment and interface control layer construction
[0082] 1) A single-crystal silicon wafer with a diameter of 100 mm and a thickness of 500 μm was ultrasonically cleaned with acetone, anhydrous ethanol and deionized water for 10 min in sequence, and then dried with nitrogen. The cleaned substrate was placed in an oxygen plasma treatment device for surface activation treatment. The oxygen flow rate was 20 sccm, the chamber pressure was 20 Pa, the radio frequency power was 100 W, and the treatment time was 10 min.
[0083] 2) The activated substrate was immersed in a 0.2 wt% polyvinyl alcohol aqueous solution for 10 min, vertically pulled at a speed of 1 mm / s, and dried in an 80℃ oven for 15 min to obtain an interface control layer with a thickness of 15 nm.
[0084] 3. Take 2 mL of the diamond nucleating agent suspension prepared in step 1 and drop it onto the center of the substrate. Use a three-stage spin coating process: the first stage is at 700 rpm for 10 s, the second stage is at 3000 rpm for 20 s, and the third stage is at 6000 rpm for 35 s. After spin coating, dry at 100℃ for 10 min to obtain the seed layer.
[0085] 4. Place the substrate with the seed layer obtained in step 3 into an MPCVD device, introduce H2 at 500 sccm and CH4 at 20 sccm, with a reaction pressure of 12 kPa, a substrate temperature of 850℃, and a microwave power of 3.5 kW, and continue growing for 12 h; after the growth is completed, stop introducing CH4 and cool to room temperature in an H2 atmosphere to obtain a polycrystalline diamond film with a thickness of 51.2 μm.
[0086] 5. Using a mechanical peeling device, peeling was performed along the interface where the interface control layer is located. Twenty diamond films with a diameter of 100 mm were continuously prepared. Eighteen films were completely peeled off. The peeled films were intact, with good quality in the central area and microcracks in a very few locations at the edge.
[0087] Comparative Example 1
[0088] 1. Preparation of diamond nucleating agent suspension: Same as step 1 in Example 1.
[0089] 2. Substrate pretreatment
[0090] A single-crystal silicon wafer with a diameter of 100 mm and a thickness of 500 μm was ultrasonically cleaned with acetone, anhydrous ethanol and deionized water for 10 min in sequence, and then dried with nitrogen. The cleaned substrate was placed in an oxygen plasma treatment device for surface activation treatment with an oxygen flow rate of 20 sccm, a chamber pressure of 20 Pa, a radio frequency power of 100 W and a treatment time of 10 min.
[0091] 3. Spin-coating construction of nucleating agent layer: Same as step 3 in Example 1.
[0092] 4. Chemical vapor deposition growth of diamond film: Same as step 4 in Example 1, to obtain a polycrystalline diamond film with a thickness of 49.8 μm;
[0093] 5. Twenty samples were prepared by mechanically peeling off the diamond film. Due to the absence of a polymer interface control layer between the silicon substrate and the diamond film, the bonding force between the diamond film and the substrate was too strong. All samples were broken during mechanical peeling, and none of the 20 samples were completely peeled off. The edges of the peeled fragments showed irregular brittle fracture characteristics.
[0094] Comparative Example 2
[0095] 1. Preparation of diamond nucleating agent suspension: Same as step 1 in Example 1;
[0096] 2. Substrate pretreatment and interface control layer construction: Same as step 2 in Example 1;
[0097] 3. Take 2 mL of the diamond nucleating agent suspension prepared in step 1 and drop it onto the center of the substrate. Use a single-step spin coating process at a speed of 3000 rpm for 60 s. After spin coating, dry at 100℃ for 10 min to obtain the seed layer.
[0098] 4. Chemical vapor deposition growth of diamond film: Same as step 4 in Example 1, to obtain a polycrystalline diamond film with a thickness of 50.1 μm;
[0099] 5. A mechanical peeling device was used to peel off the sample along the interface control layer. Twenty samples were prepared in succession. Due to the single-step spin coating, the nanodiamond seeds were severely agglomerated on the substrate surface. After CVD growth, there was a large difference in thermal stress inside the film. Only 12 samples were completely peeled off. Among the completely peeled films, 8 had obvious microcracks at the edges, which could not meet the requirements of high-precision device applications.
[0100] Comparative Example 3
[0101] 1. Preparation of diamond nucleating agent suspension: Same as step 1 in Example 1;
[0102] 2. Substrate pretreatment and interface control layer construction
[0103] A single-crystal silicon wafer with a diameter of 100 mm and a thickness of 500 μm was ultrasonically cleaned with acetone, anhydrous ethanol and deionized water for 10 min in sequence, and then dried with nitrogen. The cleaned substrate was placed in an oxygen plasma treatment device for surface activation treatment with an oxygen flow rate of 20 sccm, a chamber pressure of 20 Pa, a radio frequency power of 100 W and a treatment time of 10 min.
[0104] 3. Take 2 mL of the diamond nucleating agent suspension prepared in step 1 and drop it onto the center of the substrate. Spin coat at 3000 rpm for 60 s. After spin coating, dry at 100℃ for 10 min to obtain the seed layer.
[0105] 4. Chemical vapor deposition growth of diamond film: Same as step 4 in Example 1, to obtain a polycrystalline diamond film with a thickness of 49.4 μm;
[0106] 5. Using a mechanical peeling device, 20 samples were continuously prepared. The diamond film had extremely strong bonding force with the substrate interface and the stress distribution was extremely uneven. During mechanical peeling, all 20 samples were broken, and the degree of breakage was more severe than that of Comparative Example 1, exhibiting pulverized breakage.
[0107] The following performance tests were performed on the diamond self-supporting film samples prepared in Examples 1-5 and Comparative Examples 1-3:
[0108] 1. Complete Peeling Rate: The complete peeling rate (%) was calculated by counting the number of intact, unfragmented diamond films obtained after mechanical peeling from 20 consecutively prepared samples in each group. Complete peeling criteria: The film had no through-cracks, no fragmentation, and no obvious chipping at the edges (chipping width ≤ 0.5 mm and number ≤ 2).
[0109] 2. Crystallization quality: The growth surface of the diamond film was tested using laser Raman spectroscopy. Scanning range: 1000–2000 cm⁻¹ -1 1 cm resolution -1Lorentz fitting was performed on the characteristic peaks of diamond, and its full width at half maximum (FWHM, in cm) was read. -1 ).
[0110] 3. Residual Stress: The residual stress of the diamond film was determined using Raman spectroscopy. This was based on the shift (Δν, in cm) of the characteristic diamond peak relative to the Raman peak position of a standard single-crystal diamond. -1 ), calculate the residual stress. Positive values represent tensile stress, and negative values represent compressive stress.
[0111] 4. Thermal conductivity: The thermal diffusivity and thermal conductivity of the diamond film at room temperature (25°C) were tested according to ASTM E1461 standard and the laser flare method. The sample size was a 12.7 mm diameter disc, polished on both sides to a surface roughness Ra ≤ 50 nm, and a gold layer was sprayed on before testing to ensure uniform light absorption. Three samples were tested in each group, and the average value was taken.
[0112] 5. Surface roughness (growth surface): The diamond film growth surface was scanned using an atomic force microscope in tapping mode, with a scanning range of 10 μm × 10 μm. The root mean square roughness (Rq, in nm) was read. The average value was taken from 5 different locations in each test group.
[0113] 6. Nanoindentation Hardness: The hardness and elastic modulus of the diamond film were tested using a nanoindenter. Test conditions: maximum indentation load 50 mN, loading rate 10 mN / s, holding time 10 s, unloading rate 10 mN / s. Ten indentation points were tested for each sample, with an indentation spacing ≥50 μm, and the average value was taken. The indentation depth was controlled to not exceed 10% of the film thickness to eliminate substrate effects.
[0114] 7. Fracture Strength: The fracture strength of the diamond self-supporting film was tested using the three-point bending method. The diamond film was cut into strips measuring 20 mm × 4 mm × 50 μm with a span of 16 mm. The loading rate was 0.5 mm / min, and the fracture load was recorded. The fracture strength (in MPa) was calculated using the three-point bending formula. Five samples were tested in each group, and the average value was taken. The test results are shown in Table 1. Comparative Examples 1 and 3 could not prepare standard fracture strength test strips due to a 0% intact peeling rate.
[0115] Table 1. Test results of diamond self-supporting film samples from Examples 1-5 and Comparative Examples 1-3
[0116]
[0117] From Table 1 and Figure 1-3It can be seen that the present invention, through the synergistic effect of the interface control layer and the three-stage spin coating, increases the complete peeling rate to 95%, the residual stress to -0.35 GPa, the thermal conductivity to 1850 W / m·K, and the hardness to 92 GPa. All of these properties are significantly better than those of the comparative example.
[0118] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.
Claims
1. A method for high uniform nucleation and interface regulation of peelable diamond films, characterized in that, Includes the following steps: 1) Disperse nanodiamond powder and polyvinylpyrrolidone in a mixed solvent of isopropanol and deionized water. After stirring, pulsed ultrasonic dispersion and two-stage differential centrifugation, the precipitate obtained by centrifugation is redispersed in the mixed solvent to obtain a diamond nucleating agent suspension. 2) The substrate is cleaned and subjected to oxygen plasma surface activation treatment. Then, the activated substrate is immersed in a polyvinyl alcohol aqueous solution, and after lifting and drying, a polyvinyl alcohol interface control layer is formed on the substrate surface. 3) The diamond nucleating agent suspension obtained in step 1) is dropped onto the center of the substrate obtained in step 2), and then spin-coated using a three-stage spin coating process and dried to obtain the seed layer; 4) Place the substrate with the seed layer obtained in step 3) in a chemical vapor deposition apparatus and grow a diamond film in an atmosphere of carbon source gas and hydrogen to obtain a polycrystalline diamond film. 5) Mechanically peel off the polyvinyl alcohol interface control layer to obtain a self-supporting diamond film.
2. The method of claim 1, wherein the method is characterized by: In step 1), the volume ratio of isopropanol to deionized water is 7:3; the mass ratio of nanodiamond powder to polyvinylpyrrolidone is 2.5:
1.
3. The method of claim 1, wherein the method is characterized by: In step 1), the power of the pulsed ultrasonic dispersion treatment is 100 W, the pulse mode is 5 seconds working and 5 seconds intermittent, the treatment time is 20 minutes, and the temperature is controlled by an ice water bath ≤30℃ during the ultrasonic process.
4. The method of claim 1, wherein the method is characterized by, In step 1), the two-stage differential centrifugation process is as follows: first, centrifuge at a relative centrifugal force of 1000×g for 10 min and take the supernatant; then, centrifuge the obtained supernatant at 4℃ with a relative centrifugal force of 16000×g for 20 min, discard the supernatant, and redisperse the precipitate in the mixed solvent to obtain a diamond nucleating agent suspension.
5. The method of claim 1, wherein the method is characterized by: In step 2), the oxygen flow rate for oxygen plasma surface activation treatment is 20 sccm, the chamber pressure is 20 Pa, the radio frequency power is 100 W, and the treatment time is 10 min.
6. The method of claim 1, wherein the method is characterized by, In step 2), the mass concentration of the polyvinyl alcohol aqueous solution is 0.1–0.5 wt%; the immersion time is 5–20 min.
7. The method of claim 1, wherein the method is characterized by, In step 3), the three-stage spin coating process is as follows: the first stage has a rotation speed of 500-700 rpm and lasts for 10-15 s; the second stage has a rotation speed of 2200-3000 rpm and lasts for 20-30 s; and the third stage has a rotation speed of 4500-6000 rpm and lasts for 35-60 s.
8. The method of claim 1, wherein the method is characterized by, In step 4), the chemical vapor deposition is microwave plasma chemical vapor deposition, and the process conditions are: hydrogen flow rate of 500 sccm, methane flow rate of 20 sccm, reaction pressure of 12 kPa, substrate temperature of 850℃, microwave power of 3-4 kW, and growth time of 12-16 h.
9. The method of claim 1, wherein the method is characterized by, In step 4), after the diamond film growth is completed, the carbon source gas is stopped, and the film is cooled to room temperature in a hydrogen atmosphere to obtain a polycrystalline diamond film.
10. The method for highly uniform nucleation and interface control of peelable diamond films according to claim 1, characterized in that, In step 2), the substrate is a single-crystal silicon wafer with a diameter of 100 mm and a thickness of 500 μm.