Method for epitaxial growth of single crystal diamond on a micron diamond powder substrate

Abstract

This invention relates to the field of synthetic diamond technology, and particularly to a method for epitaxial growth of single-crystal diamond on a micron-sized diamond powder substrate. It employs laser-induced graphitization anchoring technology to generate nano-graphite bonding points in situ at the micron-powder contact points, increasing the seed layer adhesion to over 18N and ensuring the stability of the seed layer during long-term MPCVD growth. A pulsed oxygen-nitrogen alternating doping strategy is used, utilizing nitrogen to promote rapid lateral expansion of the {100} crystal plane while selectively etching non-{100} crystal orientations with oxygen pulses and releasing growth stress in real time, resulting in a {100} texture of over 92% in the obtained thick film. A variable-temperature stress balance growth technology is used to rapidly cycle temperatures to cancel out thermal and growth stresses, producing single-crystal diamond with comprehensive performance close to that of HPHT, at a cost only one-fifth to one-tenth of existing technologies. This provides a new industrial solution for high-power electronic devices, optical windows, and heat sink materials.

Description

Technical Field

[0001] This invention relates to the field of synthetic diamond technology, and in particular to a method for epitaxial growth of single-crystal diamond on a micron-sized diamond powder substrate. Background Technology

[0002] Diamond is a special material possessing numerous excellent properties. It exhibits not only extremely high hardness, high thermal conductivity, and high carrier mobility, but also a large bandgap, low dielectric constant, high breakdown electric field, and excellent physical properties such as acid resistance, heat resistance, and radiation resistance, making it widely used in various industrial fields. However, natural diamond reserves are scarce and its price is high, making it difficult to meet the needs of industrial applications. Therefore, developing efficient and low-cost artificial diamond synthesis technology has long been a research hotspot and core challenge in this field.

[0003] There are two main methods for the artificial synthesis of single-crystal diamond: high-temperature high-pressure (HPHT) and chemical vapor deposition (CVD). HPHT simulates the formation conditions of diamond deep within the Earth, using graphite as a carbon source and a metal catalyst to grow diamond. This technology is relatively mature, but it requires extremely high pressure conditions, resulting in expensive equipment, high energy consumption, and severely limited growth chamber size, making it difficult to produce large-sized diamond single crystals. CVD, on the other hand, utilizes the cracking of carbon-containing gas in hydrogen plasma at lower pressures to deposit a diamond film on a substrate. Microwave plasma chemical vapor deposition (MPCVD), with its advantages of no electrode contamination, high plasma density, and good growth controllability, has become the mainstream technology for high-quality diamond epitaxial growth.

[0004] However, CVD (Chemical Vapor Deposition) employs homoepitaxial growth, where epitaxial growth is performed on a substrate of the same material. This allows for the replication of the substrate's crystal structure, resulting in high-quality crystals. However, homoepitaxial growth heavily relies on large-size single-crystal diamond substrates, which themselves require pre-fabrication via HPHT or CVD methods, resulting in extremely high costs. Furthermore, the maximum size remains limited by existing fabrication technologies, making it difficult to meet the dual requirements of size and cost in industrial applications. To reduce substrate costs and increase size, Harbin Institute of Technology developed a seed substrate vacuum brazing method for homoepitaxial growth of single-crystal diamond (application number CN201510459097.7). This method solves the problems of "unstable growth, unstable placement, and inaccurate measurement" in the diamond cultivation industry, producing diamond products with a thickness greater than 7 mm and a thermal conductivity exceeding 2400 W / (m·K). However, this technology still relies on pre-fabricated single-crystal substrates rather than building a seed layer from scratch, failing to fundamentally eliminate the dependence on large-size single-crystal substrates.

[0005] To balance large size and high quality, researchers proposed a mosaic splicing method, which involves closely arranging multiple small-sized single-crystal diamond substrates and using CVD homoepitaxial growth to create a growth layer that spans the seams between the wafers, thus achieving the fabrication of a large-area diamond epitaxial layer. This method overcomes the limitations of substrate size and has high industrial feasibility. However, the splicing growth method has the following key problems: polycrystalline, grain boundary, and dislocation-dense regions easily appear in the seam area of ​​the diamond single wafers, leading to increased crystal stress, which reduces the quality of the large-sized homoepitaxial diamond and also easily causes wafer breakage during subsequent processing. Ningbo Crystal Diamond Technology Co., Ltd. has developed a technology (application number CN202411182127.X) that describes a substrate for diamond growth and a method for splicing diamond growth using this substrate. This method achieves a large-area growth surface with small splicing seams through the design of splicing unit groups. Another patent proposes laser cutting to form V-grooves at the diamond splicing points.

[0006] Despite continuous improvements in the splicing method, its core idea remains the same: to use multiple macroscopic single-crystal diamond wafers of millimeter size or larger as splicing units, and to connect adjacent single-crystal wafers into a larger size through epitaxial growth. This approach has extremely high requirements for the crystal orientation consistency and edge flatness of the splicing units, and the defect problem at the seam is difficult to eliminate. More fundamentally, this method still cannot get rid of its dependence on pre-prepared macroscopic single-crystal substrates.

[0007] Therefore, there is an urgent need for a method for epitaxial growth of single-crystal diamond on micron-sized diamond powder substrates that can significantly reduce substrate costs and achieve near-single-crystal quality, in order to overcome the bottlenecks of existing technologies. Summary of the Invention

[0008] The purpose of this invention is to provide a method for epitaxial growth of single-crystal diamond on a micron-sized diamond powder substrate, thereby solving the problems mentioned in the background art. The specific technical solution is as follows:

[0009] The purpose of this invention is to provide a method for epitaxial growth of single-crystal diamond on a micron-sized diamond powder substrate, comprising the following steps:

[0010] S1. Centrifugal Force-Assisted Crystal Orientation: Using type Ib single-crystal diamond micro powder with a nitrogen content of 50-100ppm as raw material, its particle size is 8-15μm and the particle size distribution D90 / D10≤1.6. The single-crystal diamond micro powder is dispersed in a solvent, poured into a centrifuge mold with guide grooves, and centrifuged at 2000-5000rpm for 5-15min, so that the micro powder is aligned along the groove direction and the {100} crystal plane tends to be parallel to the surface of the molybdenum substrate.

[0011] S2. Laser-induced graphitization anchoring: A nanosecond pulsed laser is used to perform a grid-like scan on the aligned seed crystal layers, with a laser energy density of 0.5-1.0 J / cm². 2Nano-graphite is generated at the contact points between the micro-powder and the molybdenum substrate, as well as at the contact points between the micro-powders, to achieve anchoring;

[0012] S3, Crystal orientation memory induction: The seed crystal layer is treated in pure hydrogen plasma for 30-60 minutes at a temperature of 850-900℃. The surface dangling bond configuration generated by the nitrogen impurities pre-contained in the micro powder is used to make all micro powder surfaces spontaneously exhibit {100} orientation.

[0013] S4, pulsed oxygen-nitrogen alternating doping growth, until the target thickness is reached;

[0014] S5. Temperature-balanced thick film growth: When the film thickness exceeds 500 μm, switch to temperature-cycled growth, cycling between 850-950℃. The time ratio of the high-temperature segment to the low-temperature segment in each cycle is 2:1, using transient thermal stress to offset the growth stress.

[0015] S6. Post-treatment: After cooling, the molybdenum substrate is removed by electrochemical etching.

[0016] The preferred pulsed oxygen-nitrogen alternating doping growth method is as follows: with a pulse cycle of 60s, a mixed gas of H2:CH4:N2=500:5-15:0.3-0.8 is first introduced for growth for 40-55s, followed by etching with a mixed gas of H2:CH4:O2=500:1-4:0.5-1.5 for 5-20s, and the process is repeated alternately. The substrate temperature is 900-990℃; the microwave power is 2-3kW, until the target thickness is reached.

[0017] Preferably, the guide grooves of the centrifugal mold are radial, concentric, or parallel lines, with a groove depth of 50%-80% of the micro powder particle size and a groove width of 80%-120% of the micro powder particle size.

[0018] Preferably, the wavelength of the nanosecond pulsed laser is 355nm, 532nm or 1064nm, the pulse width is 1-50ns, and the repetition frequency is 5-50kHz.

[0019] Preferably, in the pulsed oxygen-nitrogen alternating doping growth, the ratio of growth time to etching time in each cycle is 4:1 to 10:1.

[0020] Preferably, in the variable temperature stress balance thick film growth, the frequency of temperature cycling is 4-8 times / hour, and the temperature change rate is ≥50℃ / min.

[0021] Preferably, the electrolyte used in the electrochemical corrosion method is a NaOH, KOH, or H2SO4 solution, and the applied voltage is 3-10V.

[0022] Preferably, the process further includes chemical mechanical polishing of the obtained diamond thick film to achieve a surface roughness Ra ≤ 0.05 μm.

[0023] The present invention provides a method for epitaxial growth of single-crystal diamond on a micron-sized diamond powder substrate, which has the following beneficial effects:

[0024] 1. This invention abandons the stringent requirements of existing technologies for high {100} exposure rate micro powders, and directly uses industrial-grade mixed crystal orientation single crystal diamond micro powders. Through centrifugal force-assisted pre-arrangement and the original crystal orientation memory effect, the particle surface spontaneously achieves {100} orientation uniformity during hydrogen plasma treatment, thereby significantly reducing raw material costs and getting rid of dependence on expensive oriented micro powders.

[0025] 2. This invention employs laser-induced graphitization anchoring technology to generate nano-graphite bonding points in situ at the micro-powder contact points, increasing the adhesion of the seed crystal layer to over 18N and ensuring the stability of the seed crystal layer during long-term MPCVD growth. A pulsed oxygen-nitrogen alternating doping strategy is used, utilizing nitrogen to promote rapid lateral expansion of the {100} crystal plane while selectively etching non-{100} crystal orientations with oxygen pulses and releasing growth stress in real time, resulting in a {100} texture of over 92% in the obtained thick film. The variable-temperature stress balance growth technology uses rapid temperature cycling to cancel out thermal and growth stresses, preparing single-crystal diamond with comprehensive performance close to HPHT, while at a cost only one-fifth to one-tenth of existing technologies. This provides a new industrialization solution for high-power electronic devices, optical windows, and heat sink materials. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0027] Figure 1 This is a flowchart of the method of the present invention. Detailed Implementation

[0028] The following detailed description, in conjunction with the accompanying drawings and specific embodiments, provides a method for epitaxial growth of single-crystal diamond on a micron-sized diamond powder substrate according to the present invention. The advantages and features of the present invention will become clearer from the following description. It should be noted that the accompanying drawings are all in a very simplified form and use non-precise proportions, and are only used to facilitate and clarify the illustration of the embodiments of the present invention.

[0029] In the description of this invention, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0030] It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Therefore, the illustrations only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the state, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0031] Example 1

[0032] S1. Centrifugal Force-Assisted Crystal Orientation: Type Ib single-crystal diamond powder was selected. The nitrogen content was determined to be 72 ppm using Fourier Transform Infrared Spectroscopy (FTIR). The purity was ≥99.99% by Inductively Coupled Plasma Mass Spectrometry (ICP-MS). Particle size was determined using a laser particle size analyzer, with the following particle size distribution: D10 = 9.2 μm, D50 = 11.8 μm, D90 = 14.1 μm, D90 / D10 = 1.53. The powder was ultrasonically dispersed in deionized water for 3 min. Random samples were observed using SEM. The proportion of particles exposed on the {100} crystal face was approximately 35%, {110} approximately 28%, {111} approximately 32%, and other low-index crystal faces approximately 5%. 5.0 g of diamond powder was weighed, added to 100 mL of anhydrous ethanol, and 0.025 g of polyvinylpyrrolidone was added. Alkyl ketone was used as a dispersant with a molecular weight of 40,000. The suspension was placed in an ultrasonic cleaner and ultrasonically dispersed for 30 minutes at an ultrasonic power of 200W. After ultrasonication, the suspension was allowed to stand for 5 minutes for observation. The suspension was uniformly gray and there were no visible precipitates or agglomerates, indicating good dispersion. The dispersed diamond micropowder was poured into a centrifuge mold with guide grooves. The centrifuge speed was set to 4000 rpm and the centrifugation time was 10 minutes. The centrifuge mold with guide grooves was a molybdenum substrate with radial grooves prepared by photolithography. The groove depth was 7.8-8.2 μm, the width was 11.5-12.3 μm, and the bottom roughness of the grooves was Ra≈0.05 μm. After centrifugation, the mold was removed, the supernatant was poured out, and the molybdenum substrate and the mold were placed in a vacuum oven at 60℃ for 2 hours to remove residual solvent. After demolding, a seed crystal layer with a good arrangement was obtained. Ten fields of view were randomly selected under a 1000x optical microscope, and the ratio of the number of microparticles falling into the trenches to the total number of trenches was counted. The arrangement density was calculated. The results showed that 93.5% of the trenches were filled with microparticles, and each trench was basically arranged with a single particle. The stacking rate was <2%. The proportion of particles with an angle ≤15° between the normal of the {100} crystal plane and the normal of the molybdenum substrate was determined by SEM orientation analysis, and the result was 78%.

[0033] S2. Laser-induced graphitization anchoring: A nanosecond pulsed laser with a wavelength of 355nm, a pulse width of 12ns, and a repetition frequency of 10kHz is used to perform a grid-like scan on the arranged seed crystal layers. Scanning parameters: laser energy density 0.8J / cm². 2 The laser spot diameter was approximately 20 μm, the scanning path was grid-like with a grid spacing of 12 μm to match the particle size of the micropowder, the scanning speed was 100 mm / s, and the number of scans was 1. The entire scanning process was carried out in an air environment for approximately 5 minutes. The laser-treated sample was observed with an optical microscope: there was no obvious change in the color of the micropowder surface. To further verify whether graphitization occurred, a control sample from the same batch of laser-treated samples was subjected to Raman spectroscopy. The results showed that D and G peaks appeared near the contact point between the micropowder and the molybdenum substrate, while there was no graphite peak at the top of the micropowder, proving that graphitization only occurred at the laser irradiation point.

[0034] S3, Crystal Orientation Memory Induction: The seed crystal layer sample prepared in S2 was placed on the molybdenum sample stage in the center of the MPCVD reaction chamber. Pure H2 was used as the gas source, with a purity ≥99.999% and a flow rate of 500 sccm. The reaction chamber pressure was 30 kPa, the substrate temperature was 880℃, the microwave power was 1.5 kW, the substrate rotation was 20 rpm, and the processing time was 45 min. During the induction process, the plasma color and stability were visually observed through the observation window on the reaction chamber. The plasma was pale purple, stably attached to the sample surface, and there was no arc or jump. The control sample from the same batch was taken out and immediately transferred to a high-energy reflection electron diffractometer for detection. The results showed that the RHEED pattern before treatment was polycrystalline ring-shaped with disordered crystal orientation. After 45 min of treatment, the RHEED pattern showed clear spots, and the spots were arranged corresponding to the {100} crystal plane, proving that the surface crystal orientation had been unified to the {100} orientation.

[0035] S4. Pulsed oxygen-nitrogen alternating doping growth: Maintaining a cavity pressure of 30 kPa and substrate rotation of 20 rpm; the pulse sequence is designed with each pulse period of 60 s, divided into two sub-stages:

[0036] During the growth pulse phase, the duration was 50 seconds. The H2 flow rate was set to 500 sccm, the CH4 flow rate to 10.0 sccm, and the N2 flow rate to 0.5 sccm. The substrate temperature was 950℃, and the microwave power was 2.5 kW.

[0037] During the oxygen etching pulse phase, the duration was 10 seconds. The H2 flow rate was set to 500 sccm, the CH4 flow rate to 2.5 sccm, and the O2 flow rate to 1.0 sccm. The O2 was diluted with 2% O2 / H2 standard gas before being introduced. The substrate temperature and microwave power remained unchanged.

[0038] Pulse switching is achieved through a gas pulse controller with a switching time of ≤100ms, ensuring that CH4 and O2 do not enter the cavity simultaneously, ultimately achieving the target thickness of 0.5mm, with a total growth time of approximately 333 hours and a growth rate of 1.5μm / h;

[0039] The substrate bending changes were recorded using an in-situ curvature monitoring system and converted into intrafilm stress. The results showed that under pulsed growth, the stress fluctuated between -120 MPa and +80 MPa, with an average stress of approximately -20 MPa, which is much lower than the stress level of traditional continuous growth.

[0040] S5. Variable Temperature Stress Balance Thick Film Growth: Variable temperature cycle design, each cycle is 15 minutes, divided into two sub-stages:

[0041] During the high-temperature growth stage, which lasted for 10 minutes, the H2 flow rate was set to 500 sccm, the CH4 flow rate to 12.5 sccm, the N2 flow rate to 0.375 sccm, and the microwave power was adjusted to 2.8 kW to bring the substrate temperature to 950°C.

[0042] During the low-temperature growth phase, the flow rates of CH4, H2, and N2 remained constant for 5 minutes. The microwave power was adjusted to 2.2 kW to bring the substrate temperature to 850°C. The temperature adjustment rate was 100°C / min.

[0043] Growing from 0.5 mm to 1.0 mm, in-situ curvature monitoring showed that the stress fluctuated between -50 MPa and +30 MPa, with an average stress of about -10 MPa, which is a further reduction compared to S4;

[0044] S6. Post-processing: Turn off CH4, N2, and O2 gases, maintain H2 flow rate at 500 sccm, and linearly reduce microwave power from 2.5 kW to 0.5 kW within 15 minutes. When the temperature drops below 100℃, turn off microwave and H2, and introduce N2 to cool to room temperature. Prepare a 10% NaOH solution, pour it into the electrolytic cell, immerse the grown sample in the solution, connect the molybdenum substrate to the positive electrode, and the stainless steel sheet to the negative electrode. Apply a DC voltage of 5V, a current density of approximately 0.1A / cm², and electrolyze for 30 minutes. After 30 minutes, the diamond film will naturally detach from the molybdenum substrate. Remove the diamond film, ultrasonically clean it in deionized water for 10 minutes to remove residual electrolyte, and peel off the intact diamond film without cracks or damage. Fix the peeled diamond film onto a ceramic carrier with wax and perform CMP polishing. After polishing, immerse it in acetone to dewax, and then ultrasonically clean it in acetone, isopropanol, and deionized water for 5 minutes each, and dry it with nitrogen.

[0045] Example 2

[0046] This embodiment seeks the optimal parameter combination by setting up comparison groups with different parameter levels;

[0047] In step S1, four centrifugation speed levels were set: 1000 rpm, 2000 rpm, 4000 rpm, and 6000 rpm. Other conditions were the same as in Example 1. Each group was repeated three times, and the average value was taken to test the effect of centrifugation speed on the arrangement density and crystal orientation parallelism.

[0048] The results are shown in Table 1:

[0049] Table 1

[0050]

[0051] As shown in Table 1, 4000 rpm is close to the optimal speed. Further increasing the speed will result in limited gains. The breakage rate at 6000 rpm is about 3%, which means that excessively high speeds may lead to micro-fragmentation.

[0052] In step S2, five laser energy density levels were set: 0.2, 0.5, 0.8, 1.2, and 1.5 J / cm², with other conditions the same as in Example 1. The results are shown in Table 2.

[0053] Table 2

[0054]

[0055] As can be seen from Table 2, if the laser energy density is below 0.5 J / cm², the anchoring is insufficient; if the laser energy density is above 1.2 J / cm², it will cause damage to the surface of the micro powder. The optimal range for laser energy density is between 0.5 and 1.0 J / cm².

[0056] In step S4, five pulse cycles are set, each pulse cycle is fixed at 60s, and the growth / etching time ratios are 60:0, 50:10, 40:20, 30:30, and 20:40, respectively. The results are shown in Table 3.

[0057] Table 3

[0058]

[0059] As can be seen from Table 3, the growth rate is negatively correlated with the etching ratio, while the crystal quality is positively correlated with the etching ratio. The growth / etching time ratio of 50:10 is the optimal overall result, with a growth rate of 1.52 μm / h and a texture degree of 93%.

[0060] Example 3

[0061] This embodiment sets up 5 control groups.

[0062] Control group C1: No centrifugal force assisted arrangement.

[0063] The difference from Example 1 is that in step S1, the single-crystal diamond micro powder is randomly spread on the flat molybdenum substrate by the "powder spreading method", and the other steps are the same as in Example 1.

[0064] Results: The density of the diamond arrangement was only about 45%, with many areas lacking seed crystal coverage; polycrystalline diamond deposition was observed on exposed molybdenum substrates during the early growth stage; the final film thickness was only 0.65 mm due to the slow growth rate in the polycrystalline regions; the {100} texture was only 58%, and the dislocation density was 2.1 × 10⁻⁶. 6 cm -2 The presence of multiple white spots on the film surface, i.e., polycrystalline regions, indicates that centrifugal force-assisted arrangement is a necessary condition for obtaining a high-density, ordered seed crystal layer.

[0065] Control group C2: No laser-induced graphitization anchoring.

[0066] The difference from Example 1 is that the laser-induced treatment in step S2 is not performed; otherwise, it is the same as Example 1.

[0067] Results: The seed crystal layer appeared normal before growth. About 10 hours after growth began, plasma disturbance was observed, and some microparticles were blown away. After 20 hours, the sample was taken out for observation, and about 35% of the microparticles had fallen off. Growth continued until 100 hours, and the area of ​​fallen particles expanded to >80%, forcing the termination of the experiment. The film thickness in the surviving area was uneven and the performance was poor. This indicates that laser graphitization anchoring can maintain the stable adhesion of the seed crystal layer during long-term growth.

[0068] Control group C3: without crystallographic memory induction.

[0069] The difference from Example 1 is that in step S3, conventional hydrogen plasma cleaning is used instead of 45 min of crystal orientation memory induction, otherwise it is the same as Example 1.

[0070] Results: In the early stage of growth in stage B, growth was normal. After 100 hours, XRD analysis showed that the final texture was only 68.5%, the polycrystalline phase accounted for about 15%, and a large number of twins appeared inside the crystal. This indicates that crystal orientation memory induction can effectively unify the {100} orientation of mixed crystal orientation seed crystals.

[0071] Control group C4: No pulsed oxygen-nitrogen alternation.

[0072] The difference from Example 1 is that in step S4, mixed gas growth is performed, but mixed gas etching is not performed; otherwise, it is the same as Example 1.

[0073] Results: The growth rate increased to 1.85 μm / h, but residual stress accumulated rapidly. In-situ curvature monitoring showed that the stress gradually increased from -50 MPa to -450 MPa. The first through crack appeared when the film thickness was 0.85 mm, and the film completely shattered when the thickness was 0.92 mm, making it impossible to obtain a complete sample. This indicates that oxygen pulses can release growth stress and prevent thick film cracking.

[0074] Control group C5: No temperature-dependent stress equilibrium.

[0075] The difference from Example 1 is that in step S5, when the film thickness exceeds 500 μm, it is grown at a constant temperature of 900°C, otherwise it is the same as Example 1.

[0076] Results: When the film grew to about 1.2 mm, in-situ curvature monitoring showed that the stress had reached -520 MPa. Microcracks appeared at 1.25 mm, and the cracks expanded into through cracks at 1.35 mm, causing the sample to break. The maximum crack-free thickness that could be obtained was about 1.2 mm, which was lower than the target of 2.0 mm. This indicates that temperature-dependent stress balance is a necessary condition for achieving crack-free growth of millimeter-thick films.

[0077] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for epitaxial growth of single-crystal diamond on a micron-sized diamond powder substrate, characterized in that, Includes the following steps: S1. Centrifugal Force-Assisted Crystal Orientation: Using type Ib single-crystal diamond micro powder with a nitrogen content of 50-100ppm as raw material, the single-crystal diamond micro powder has a particle size of 8-15μm and a particle size distribution D90 / D10≤1.

6. The single-crystal diamond micro powder is dispersed in a solvent, poured into a centrifuge mold with guide grooves, and centrifuged at 2000-5000rpm for 5-15min, so that the micro powder is aligned along the groove direction and the {100} crystal plane tends to be parallel to the surface of the molybdenum substrate. S2. Laser-induced graphitization anchoring: A nanosecond pulsed laser is used to perform a grid-like scan on the aligned seed crystal layers, with a laser energy density of 0.5-1.0 J / cm². 2 Nano-graphite is generated at the contact points between the micro-powder and the molybdenum substrate, as well as at the contact points between the micro-powders, to achieve anchoring; S3, Crystal orientation memory induction: The seed crystal layer is treated in pure hydrogen plasma for 30-60 minutes at a temperature of 850-900℃. The surface dangling bond configuration generated by the nitrogen impurities pre-contained in the micro powder is used to make all micro powder surfaces spontaneously exhibit {100} orientation. S4, pulsed oxygen-nitrogen alternating doping growth, until the target thickness is reached; S5. Temperature-balanced thick film growth: When the film thickness exceeds 500 μm, switch to temperature-cycled growth, cycling between 850-950℃. The time ratio of the high-temperature segment to the low-temperature segment in each cycle is 2:1, using transient thermal stress to offset the growth stress. S6. Post-treatment: After cooling, the molybdenum substrate is removed by electrochemical etching.

2. The method according to claim 1, characterized in that, In step S4, the pulsed oxygen-nitrogen alternating doping growth method is as follows: with a pulse cycle of 60s, a mixed gas of H2:CH4:N2=500:5-15:0.3-0.8 is first introduced for growth for 40-55s, followed by etching with a mixed gas of H2:CH4:O2=500:1-4:0.5-1.5 for 5-20s, and the process is repeated alternately. The substrate temperature is 900-990℃; the microwave power is 2-3kW, until the target thickness is reached.

3. The method according to claim 1, characterized in that, The guide grooves of the centrifugal mold are radial, concentric, or parallel lines, with a groove depth of 50%-80% of the micro powder particle size and a groove width of 80%-120% of the micro powder particle size.

4. The method according to claim 1, characterized in that, The nanosecond pulsed laser has a wavelength of 355nm, 532nm, or 1064nm, a pulse width of 1-50ns, and a repetition frequency of 5-50kHz.

5. The method according to claim 2, characterized in that, In the pulsed oxygen-nitrogen alternating doping growth, the ratio of growth time to etching time in each cycle is 4:1 to 10:

1.

6. The method according to claim 1, characterized in that, In the variable temperature stress equilibrium thick film growth process, the frequency of temperature cycling is 4-8 times / hour, and the temperature change rate is ≥50℃ / min.

7. The method according to claim 1, characterized in that, The electrochemical corrosion method uses NaOH, KOH, or H2SO4 solution as the electrolyte and applies a voltage of 3-10V.

8. The method according to claim 1, characterized in that, It also includes chemical mechanical polishing of the obtained diamond thick film to achieve a surface roughness Ra≤0.05μm.

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