Seed-based film plating method for growing diamond under high pressure and high temperature

Abstract

The application discloses a high-temperature and high-pressure synthesis method for cultivating diamond based on seed coating, and particularly relates to the following steps: pretreating the seed; using a magnetron sputtering coating technology to prepare a catalyst layer and a nitrogen removal layer on the surface of the pretreated seed; the catalyst layer is prepared by using a pre-alloyed target material, fixing the seed in a sputtering furnace, and sputtering a catalyst layer on the surface of the seed; the nitrogen removal layer is prepared by using an alloy target material, fixing the seed coated with the catalyst layer in a sputtering furnace, and sputtering a nitrogen removal layer on the surface of the seed. The coated seed is assembled after being seeded and is synthesized under high temperature and high pressure to obtain cultivated diamond with high purity and high qualified rate. The method can precisely control the catalyst composition and the content of the nitrogen removal agent by preparing the catalyst layer and the nitrogen removal layer on the surface of the seed, and thus the color (stabilized to D color and above), the purity (reached VS and above), and the crystal integrity of the cultivated diamond are improved, and the yield of the finished product is increased to more than 80%.

Description

Technical Field

[0001] This invention belongs to the field of lab-grown diamond synthesis technology, specifically relating to a high-temperature, high-pressure synthesis method for lab-grown diamonds based on seed crystal coating. Background Technology

[0002] High-temperature and high-pressure (HTHP) synthesis, as one of the mainstream technologies for lab-grown diamonds, has achieved mass production of lab-grown diamonds ranging from industrial-grade to gem-quality due to its advantages such as high process maturity, short synthesis cycle, and strong crystal growth stability. Currently, the core process of HTHP synthesis for lab-grown diamonds is as follows: using industrial diamond as a seed crystal, under high temperature (1200-1800℃) and high pressure (5-8GPa) conditions, nitrogen is removed through a denitrification layer, and a catalyst material catalyzes the conversion of graphite carbon source into diamond crystals, ultimately forming lab-grown diamonds that meet specifications.

[0003] Currently, the requirements for color and clarity of gem-quality lab-grown diamonds are becoming increasingly stringent. However, in traditional synthesis processes, it is often difficult to achieve precise quantitative and uniform distribution of catalysts and denitrifying agents, becoming a core bottleneck restricting the improvement of lab-grown diamond quality. The main problems are as follows: First, quality issues caused by uncontrolled catalyst content: Excessive concentration leads to uneven crystal growth, resulting in irregularly shaped crystals (such as tabular or dendritic crystals); insufficient concentration reduces carbon source conversion efficiency, making the crystals prone to defects such as vacancies and dislocations, thus lowering clarity and mechanical strength. Second, unstable denitrification affects color: Nitrogen impurities in lab-grown diamonds are the main cause of yellow and brown hues, requiring denitrifying agents (such as Al and Ti) to combine with nitrogen to form stable compounds (such as AlN and TiN) to reduce nitrogen content. However, in traditional processes, the nitrogen removal agent is not mixed evenly with the carbon source and catalyst, which can easily lead to "nitrogen removal dead zones". This results in large color differences in the same batch of diamonds (such as fluctuations from D color to J color), and the yield rate is only 40%-50%. Third, the bonding between the seed crystal and the carbon source is poor: the surface of traditional seed crystals has no functional modification, and the interfacial bonding force with the carbon source is weak under high temperature and high pressure. This can easily lead to crystal growth breakage, resulting in a decrease in the integrity of the finished diamond and an increase in the loss rate of subsequent cutting and processing.

[0004] In summary, the existing high-temperature and high-pressure synthetic lab-grown diamond technology lacks functional and precise design in the treatment of the seed nitrogen removal layer and catalyst layer, which cannot meet the mass production requirements of high-color and high-clarity lab-grown diamonds. There is an urgent need for a seed treatment method that can achieve precise control of the amount of catalyst and nitrogen removal agent and improve the stability of crystal growth. Summary of the Invention

[0005] The purpose of this invention is to provide a high-temperature and high-pressure synthesis method for lab-grown diamonds based on seed coating, which solves the problems of uneven distribution and difficulty in controlling the content of catalysts and denitrifying agents in existing high-temperature and high-pressure synthesis technologies for lab-grown diamonds.

[0006] The technical solution adopted in this invention is a high-temperature and high-pressure synthesis method for cultured diamonds based on seed coating, which is implemented according to the following steps:

[0007] Step 1: Pre-treat the seed crystals; Step 2: Using magnetron sputtering coating technology, a catalyst layer and a denitrification layer are sequentially prepared on the pretreated seed crystal surface. The preparation process of the catalyst layer is as follows: using a pre-alloyed target, the seed crystal is fixed in the sputtering furnace, and a catalyst layer is sputtered on its surface. The preparation process of the denitrification layer is as follows: using an alloy target, the seed crystal covered with the catalyst layer is fixed in the sputtering furnace, and a denitrification layer is sputtered on its surface. Step 3: After the coated seed crystals are planted, they are assembled and heat-insulated to obtain cultured diamonds with high clarity and a high pass rate.

[0008] The invention is further characterized in that, Step 1 specifically involves: selecting diamond with a particle size of 200-500 μm as seed crystals; sequentially placing the seed crystals in ethanol and acetone solutions for ultrasonic cleaning; then rinsing with deionized water 3-5 times, and drying in a vacuum drying oven to obtain a clean seed crystal surface. The ultrasonic power is 300-500 W, and the cleaning time is 20-60 min; the vacuum drying temperature is 100-150℃, the vacuum drying time is 2-4 h, and the vacuum degree is ≤10 Pa.

[0009] In step 2, the catalyst layer is prepared as follows: using a pre-alloyed target with a purity ≥99.99%, the seed crystal is fixed in the sputtering furnace, and the vacuum level in the vacuum chamber is reduced to ≤5×10⁻⁶. -4 Argon gas is introduced at a constant flow rate of 40-60 sccm during sputtering deposition. The sputtering power is 300-400 W, the deposition temperature is 200-400℃, and the deposition time is 50-100 min. A catalyst layer is finally sputtered onto the surface. The catalyst layer thickness is 300-500 nm. The pre-alloyed target material is specifically Fe-Ni, Fe-Ni-Co, or Ni-Mn-Co target.

[0010] In step 2, the preparation process of the denitrification layer is as follows: using an alloy target with a purity ≥99.99%, the seed crystals coated with the catalyst layer are fixed in the sputtering furnace, and the vacuum degree of the vacuum chamber is reduced to ≤5×10 -4 Argon gas is introduced at a constant flow rate of 30-50 sccm during sputtering deposition. The sputtering power is 150-250 W, the deposition temperature is 100-200℃, and the deposition time is 20-60 min. Finally, a denitrification layer is sputtered onto the surface. The thickness of the denitrification layer is 50-200 nm. The alloy target is an Al-Ti alloy target or a Cu-Zr alloy target with an alloy ratio of 1:1-3.

[0011] Step 3 specifically involves: arranging the coated seed crystals, assembling them, and holding them at 1400-1600℃ and 5-7GPa for 240-480 hours to obtain cultured diamonds with high clarity and a high pass rate.

[0012] Another technical solution adopted in this invention is a cultured diamond synthesized by a high-temperature and high-pressure synthesis method based on seed coating.

[0013] The beneficial effects of this invention are: (1) Significantly improves the color of lab-grown diamonds: Al, Ti and other elements in the nitrogen layer can be efficiently combined with nitrogen impurities, reducing the nitrogen content of lab-grown diamonds from 50-100ppm in traditional processes to 5-15ppm, stabilizing the color at DF color, and increasing the proportion of colorless diamonds from 53% to over 79%. (2) Improve clarity and crystal integrity: The directional catalysis of the catalyst layer can reduce crystal growth defects (such as dislocations and inclusions), and the proportion of crystals with clarity of VS or above increases from 57% to 82%; (3) Improve the yield and production efficiency: The method of this invention increases the yield of lab-grown diamonds (meeting the requirements for color and clarity) from the traditional 63% to over 80%, and due to the improved uniformity of crystal growth, the loss rate of subsequent cutting and processing is reduced from 28% to 16%, significantly reducing production costs. Attached Figure Description

[0014] Figure 1 is a schematic diagram of the seed crystal layered coating structure of the present invention; Figure 2 This is a quality comparison chart of the untreated diamond seed sample (left) and the diamond seed sample prepared in Example 1 (right); Figure 3 This is a quality comparison chart of the untreated diamond seed sample (left) and the diamond seed sample prepared in Example 2 (right); Figure 4 This is a quality comparison chart of the untreated diamond seed sample (left) and the diamond seed sample prepared in Example 3 (right). Detailed Implementation

[0015] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0016] This invention relates to a high-temperature, high-pressure synthesis method for cultured diamonds based on seed coating, which is implemented according to the following steps: Step 1: Pre-treat the seed crystals; Diamond with a particle size of 200-500μm was selected as seed crystals; the seed crystals were placed in ethanol and acetone solutions for ultrasonic cleaning to remove surface oil and impurities; then rinsed with deionized water 3-5 times and dried in a vacuum drying oven to obtain a clean seed crystal surface. The ultrasonic power is 300-500W, and the cleaning time is 20-60 minutes; The vacuum drying temperature is 100-150℃, the vacuum drying time is 2-4h, and the vacuum degree is ≤10Pa; Step 2: Using magnetron sputtering coating technology, a catalyst layer and a denitrification layer are sequentially prepared on the pretreated seed crystal surface; The catalyst layer is prepared as follows: a pre-alloyed target material with a purity ≥99.99% (carbon content 1%-3%) is used to fix the seed crystal in the sputtering furnace, and the vacuum degree of the vacuum chamber is reduced to ≤5×10 -4 Pa, argon gas is introduced, and the argon gas flow rate is kept constant during sputtering deposition. The argon gas flow rate is 40-60 sccm, the sputtering power is 300-400W, the deposition temperature is 200-400℃, and a catalyst layer is finally sputtered on the surface. The deposition time is 50-100 min, and the catalyst layer thickness is 300-500 nm. The pre-alloyed target material is specifically Fe-Ni (mass ratio 3:1) target material, Fe-Ni-Co (mass ratio 5:3:1) target material, or Ni-Mn-Co (mass ratio 5:3:1) target material; The role of the catalyst layer is to catalyze the conversion of carbon source (graphite) into diamond crystals and guide crystal growth in a directional manner; the carbon content can reduce the diffusion resistance of carbon source at high temperatures and improve growth uniformity. The process for preparing the nitrogen removal layer is as follows: using an alloy target with a purity ≥99.99%, the seed crystals coated with the catalyst layer are fixed in the sputtering furnace, and the vacuum level in the vacuum chamber is reduced to ≤5×10⁻⁶. -4 Pa, argon gas is introduced, and the argon gas flow rate is kept constant during sputtering deposition. The argon gas flow rate is 30-50 sccm, the sputtering power is 150-250W, and the deposition temperature is 100-200℃. Finally, a denitrification layer is sputtered on its surface. The deposition time is 20-60 min and the thickness of the denitrification layer is 50-200 nm. The alloy target material is either an Al-Ti alloy target material or a Cu-Zr alloy target material, with an alloy ratio of 1:1-3; The function of the denitrification layer is to combine with nitrogen impurities during the synthesis process to form stable nitrides (such as AlN and TiN), preventing nitrogen from entering the diamond lattice; the alloy system can improve the denitrification efficiency (20%-30% higher than that of the element). The coating process uses a barrel coating device (rotation speed of 10-20 r / min) to ensure the consistency of coating thickness on the seed crystal surface and achieve precise control of composition and thickness.

[0017] Step 3: After the coated seed crystals are planted, they are assembled and kept at 1400-1600℃ and 5-7GPa for 240-480 hours to obtain cultured diamonds with high clarity and high pass rate.

[0018] The method of this invention achieves precise control of catalyst composition and denitrifier content by preparing a catalyst layer and a denitrification layer on the surface of the seed crystal, thereby improving the color (stabilizing to D color and above), clarity (reaching VS and above), and crystal integrity of lab-grown diamonds, and increasing the yield to over 80%.

[0019] Figure 1 The diagram shows the layered coating structure of the seed crystal of the present invention. It can be seen that the surface of the diamond seed crystal is coated with a denitrification layer and a catalyst layer. The denitrification layer can effectively isolate and remove nitrogen impurities mixed in during the growth of grown diamond crystals, thereby improving the purity and color of the crystal growth. The catalyst layer on the seed side can effectively improve the fusion co-diffusion effect and efficiency.

[0020] Example 1 This invention relates to a high-temperature, high-pressure synthesis method for cultured diamonds based on seed coating, which is implemented according to the following steps: Step 1: Pre-treat the seed crystals; Diamond with a particle size of 200 μm was selected as seed crystal; the seed crystal was placed in ethanol and acetone solutions for ultrasonic cleaning to remove surface oil and impurities; then it was rinsed 4 times with deionized water and dried in a vacuum drying oven to obtain a clean seed crystal surface; The ultrasonic power is 300W, and the cleaning time is 20 minutes. The vacuum drying temperature was 100℃, the vacuum drying time was 2h, and the vacuum degree was 8Pa. Step 2: Using magnetron sputtering coating technology, a denitrification layer and a catalyst layer are sequentially prepared on the pretreated seed crystal surface; The catalyst layer is prepared as follows: using a pre-alloyed target with a purity ≥99.99%, the seed crystal is fixed in the sputtering furnace, and the vacuum level in the vacuum chamber is reduced to 4×10⁻⁶. -4 Pa, argon gas was introduced, and the argon gas flow rate was kept constant during the sputtering deposition process. The argon gas flow rate was 40 sccm, the sputtering power was 300 W, and the deposition temperature was 200℃. Finally, a catalyst layer was sputtered on the surface of the denitrification layer. The deposition time was 50 min and the thickness of the catalyst layer was 300 nm. The pre-alloyed target material is specifically an Fe-Ni target material (mass ratio 2:1); The process for preparing the nitrogen removal layer is as follows: using an alloy target with a purity ≥99.99%, the pretreated seed crystals are fixed in the sputtering furnace, and the vacuum level in the vacuum chamber is reduced to 5×10⁻⁶. -4 Pa, argon gas was introduced, and the argon gas flow rate was kept constant during the sputtering deposition process. The argon gas flow rate was 30 sccm, the sputtering power was 150 W, and the deposition temperature was 100 °C. Finally, a denitrification layer was sputtered on its surface; the deposition time was 20 min, and the thickness of the denitrification layer was 50 nm. The alloy target material is an Al-Ti alloy target material with an alloy ratio of 1:1; The coating process uses a barrel coating machine (rotation speed of 10 r / min).

[0021] The catalyst layer serves to catalyze the conversion of carbon source (graphite) into diamond crystals and guide crystal growth in a directional manner; the carbon content can reduce the diffusion resistance of carbon source at high temperatures and improve growth uniformity. Step 3: After the coated seed crystals are planted, they are assembled and kept at 1450℃ and 5.5GPa for 240 hours to obtain cultured diamonds with high clarity and high pass rate.

[0022] Figure 2 shows a comparison of lab-grown diamond quality. The figure clearly shows that the crystals produced from pretreated seeds have high internal cleanliness and a high yield. Untreated crystals, on the other hand, have significantly higher impurity content, directly resulting in a lower yield. Because the catalyst layer and denitrification layer are at their lowest values, the pretreated samples also contain small amounts of yellow and pale yellow impurities, but the overall quality is significantly improved compared to the untreated samples. Seed pretreatment can effectively reduce the internal impurity content during diamond crystal growth and increase the yield.

[0023] Example 2 This invention relates to a high-temperature, high-pressure synthesis method for cultured diamonds based on seed coating, which is implemented according to the following steps: Step 1: Pre-treat the seed crystals; Diamond with a particle size of 350μm was selected as seed crystal; the seed crystal was placed in ethanol and acetone solutions for ultrasonic cleaning to remove surface oil and impurities; then it was rinsed 4 times with deionized water and dried in a vacuum drying oven to obtain a clean seed crystal surface; The ultrasonic power is 400W, and the cleaning time is 40 minutes. The vacuum drying temperature was 125℃, the vacuum drying time was 3 hours, and the vacuum degree was 8 Pa. Step 2: Using magnetron sputtering coating technology, a denitrification layer and a catalyst layer are sequentially prepared on the pretreated seed crystal surface; The catalyst layer is prepared as follows: using a pre-alloyed target with a purity ≥99.99%, the seed crystal is fixed in the sputtering furnace, and the vacuum level in the vacuum chamber is reduced to 4×10⁻⁶. -4 Pa, argon gas was introduced, and the argon gas flow rate was kept constant during the sputtering deposition process. The argon gas flow rate was 50 sccm, the sputtering power was 350 W, and the deposition temperature was 300℃. Finally, a catalyst layer was sputtered on the surface of the denitrification layer. The deposition time was 70 min and the thickness of the catalyst layer was 400 nm. The pre-alloyed target material is specifically Fe-Ni-Co (mass ratio 5:3:1); The process for preparing the nitrogen removal layer is as follows: using an alloy target with a purity ≥99.99%, the pretreated seed crystals are fixed in the sputtering furnace, and the vacuum level in the vacuum chamber is reduced to 5×10⁻⁶.-4 Pa, argon gas was introduced, and the argon gas flow rate was kept constant during the sputtering deposition process. The argon gas flow rate was 40 sccm, the sputtering power was 200 W, and the deposition temperature was 150 °C. Finally, a denitrification layer was sputtered on its surface; the deposition time was 40 min and the thickness of the denitrification layer was 100 nm. The alloy target material is an Al-Ti alloy target material with an alloy ratio of 1:2; The coating process uses a barrel coating equipment (rotation speed of 15 r / min).

[0024] The catalyst layer serves to catalyze the conversion of carbon source (graphite) into diamond crystals and guide crystal growth in a directional manner; the carbon content can reduce the diffusion resistance of carbon source at high temperatures and improve growth uniformity. Step 3: After the coated seed crystals are planted and assembled, they are kept at 1450℃ and 5.5GPa for 360 hours to obtain cultured diamonds with high clarity and a high pass rate. See [link to article]. Figure 3 .

[0025] Figure 3 is a comparison of the quality of lab-grown diamonds in Example 2. As can be seen from the figure, the comparison sample is yellowish in color and contains some dark particles. The main reason is that the catalyst layer and denitrification layer are both thin and uneven in thickness, resulting in poor denitrification effect and overall seed seed coverage during growth. In Example 2, the thickness of the catalyst layer and denitrification layer is increased, and the denitrification and catalyst coverage effects are better. Therefore, the produced crystals have high internal cleanliness and no yellow particles.

[0026] Example 3 This invention relates to a high-temperature, high-pressure synthesis method for cultured diamonds based on seed coating, which is implemented according to the following steps: Step 1: Pre-treat the seed crystals; Diamond with a particle size of 500 μm was selected as seed crystal; the seed crystal was placed in ethanol and acetone solutions for ultrasonic cleaning to remove surface oil and impurities; then it was rinsed 4 times with deionized water and dried in a vacuum drying oven to obtain a clean seed crystal surface. The ultrasonic power is 500W, and the cleaning time is 60 minutes. The vacuum drying temperature was 150℃, the vacuum drying time was 4 hours, and the vacuum degree was 8 Pa. Step 2: Using magnetron sputtering coating technology, a denitrification layer and a catalyst layer are sequentially prepared on the pretreated seed crystal surface; The catalyst layer is prepared as follows: using a pre-alloyed target with a purity ≥99.99%, the seed crystal is fixed in the sputtering furnace, and the vacuum level in the vacuum chamber is reduced to 4×10⁻⁶. -4Pa, argon gas was introduced, and the argon gas flow rate was kept constant during the sputtering deposition process. The argon gas flow rate was 60 sccm, the sputtering power was 400 W, and the deposition temperature was 400℃. Finally, a catalyst layer was sputtered on the surface of the denitrification layer. The deposition time was 100 min and the thickness of the catalyst layer was 500 nm. The pre-alloyed target material is specifically a Ni-Mn-Co target material (mass ratio 5:3:1); The process for preparing the nitrogen removal layer is as follows: using an alloy target with a purity ≥99.99%, the pretreated seed crystals are fixed in the sputtering furnace, and the vacuum level in the vacuum chamber is reduced to 5×10⁻⁶. -4 Pa, argon gas was introduced, and the argon gas flow rate was kept constant during the sputtering deposition process. The argon gas flow rate was 60 sccm, the sputtering power was 250 W, the deposition temperature was 200 ℃, and finally a denitrification layer was sputtered on its surface; the deposition time was 460 min, and the thickness of the denitrification layer was 200 nm. The alloy target material is an Al-Ti alloy target material with an alloy ratio of 1:3; The coating process uses a barrel coating equipment (rotation speed of 20 r / min).

[0027] The catalyst layer serves to catalyze the conversion of carbon source (graphite) into diamond crystals and guide crystal growth in a directional manner; the carbon content can reduce the diffusion resistance of carbon source at high temperatures and improve growth uniformity. Step 3: After the coated seed crystals are planted and assembled, they are kept at 1450℃ and 5.5GPa for 480 hours to obtain cultured diamonds with high clarity and a high pass rate. See [link to article]. Figure 4 .

[0028] Figure 4 is a comparison chart of coarse-grained products. As can be seen from the figure, the particle size increases with the extension of time. The thickness of the catalyst layer and denitrification layer of the diamond seed crystal in Example 3 increases, resulting in better coating and denitrification effects during long-term synthesis. Therefore, the color, clarity and yield of the sample in Example 3 are higher than those of the conventional sample.

[0029] Example 4 This invention relates to a high-temperature, high-pressure synthesis method for cultured diamonds based on seed coating, which is implemented according to the following steps: Step 1: Pre-treat the seed crystals; Diamond with a particle size of 300μm was selected as seed crystal; the seed crystal was placed in ethanol and acetone solutions for ultrasonic cleaning to remove surface oil and impurities; then it was rinsed 5 times with deionized water and dried in a vacuum drying oven to obtain a clean seed crystal surface; The ultrasonic power is 300W, and the cleaning time is 20 minutes. The vacuum drying temperature was 150℃, the vacuum drying time was 2.5h, and the vacuum degree was 8.5Pa. Step 2: Using magnetron sputtering coating technology, a catalyst layer and a denitrification layer are sequentially prepared on the pretreated seed crystal surface; The catalyst layer is prepared as follows: a pre-alloyed target material with a purity ≥99.99% (containing 1% carbon) is used to fix the seed crystal in the sputtering furnace, and the vacuum level in the vacuum chamber is reduced to ≤5×10⁻⁶. -4 Pa, argon gas is introduced, and the argon gas flow rate is kept constant during sputtering deposition. The argon gas flow rate is 40-60 sccm, the sputtering power is 300W, the deposition temperature is 350℃, and a catalyst layer is finally sputtered on the surface. The deposition time is 60min, and the catalyst layer thickness is 300nm. The pre-alloyed target material is specifically an Fe-Ni-Co target material (mass ratio 5:3:1); The process for preparing the nitrogen removal layer is as follows: using an alloy target with a purity ≥99.99%, the seed crystals coated with the catalyst layer are fixed in the sputtering furnace, and the vacuum level in the vacuum chamber is reduced to ≤5×10⁻⁶. -4 Pa, argon gas was introduced, and the argon gas flow rate was kept constant during the sputtering deposition process. The argon gas flow rate was 30 sccm, the sputtering power was 200 W, and the deposition temperature was 180℃. Finally, a denitrification layer was sputtered on its surface; the deposition time was 30 min, and the thickness of the denitrification layer was 100 nm. The alloy target material is an Al-Ti alloy target material with an alloy ratio of 1:1; Step 3: After the coated seed crystals are planted, they are assembled and kept at 1400℃ and 5GPa for 300h to obtain cultured diamonds with high clarity and high pass rate.

[0030] Example 5 This invention relates to a high-temperature, high-pressure synthesis method for cultured diamonds based on seed coating, which is implemented according to the following steps: Step 1: Pre-treat the seed crystals; Diamond with a particle size of 400μm was selected as seed crystal; the seed crystal was placed in ethanol and acetone solutions for ultrasonic cleaning to remove surface oil and impurities; then it was rinsed three times with deionized water and dried in a vacuum drying oven to obtain a clean seed crystal surface; The ultrasonic power is 400W, and the cleaning time is 30 minutes. The vacuum drying temperature was 100℃, the vacuum drying time was 4h, and the vacuum degree was 7Pa. Step 2: Using magnetron sputtering coating technology, a catalyst layer and a denitrification layer are sequentially prepared on the pretreated seed crystal surface; The catalyst layer is prepared as follows: a pre-alloyed target material with a purity ≥99.99% (containing 2% carbon) is used to fix the seed crystal in the sputtering furnace, and the vacuum level in the vacuum chamber is reduced to ≤5×10⁻⁶. -4Pa, argon gas is introduced, and the argon gas flow rate is kept constant during sputtering deposition. The argon gas flow rate is 60 sccm, the sputtering power is 300 W, the deposition temperature is 200 ℃, and a catalyst layer is finally sputtered on the surface. The deposition time is 50 min and the catalyst layer thickness is 300 nm. The pre-alloyed target material is specifically an Fe-Ni target material (mass ratio 3:1); The process for preparing the nitrogen removal layer is as follows: using an alloy target with a purity ≥99.99%, the seed crystals coated with the catalyst layer are fixed in the sputtering furnace, and the vacuum level in the vacuum chamber is reduced to ≤5×10⁻⁶. -4 Pa, argon gas was introduced, and the argon gas flow rate was kept constant during the sputtering deposition process. The argon gas flow rate was 30 sccm, the sputtering power was 200 W, and the deposition temperature was 200 °C. Finally, a denitrification layer was sputtered on its surface; the deposition time was 50 min, and the thickness of the denitrification layer was 150 nm. The alloy target material is a Cu-Zr alloy target material with an alloy ratio of 1:3; Step 3: After the coated seed crystals are planted, they are assembled and kept at 1600℃ and 7GPa for 400h to obtain cultured diamonds with high clarity and high pass rate.

[0031] Example 6 This invention relates to a high-temperature, high-pressure synthesis method for cultured diamonds based on seed coating, which is implemented according to the following steps: Step 1: Pre-treat the seed crystals; Diamond with a particle size of 200μm was selected as seed crystal; the seed crystal was placed in ethanol and acetone solutions for ultrasonic cleaning to remove surface oil and impurities; then it was rinsed 5 times with deionized water and dried in a vacuum drying oven to obtain a clean seed crystal surface; The ultrasonic power is 500W, and the cleaning time is 20 minutes. The vacuum drying temperature was 150℃, the vacuum drying time was 4 hours, and the vacuum degree was 9 Pa. Step 2: Using magnetron sputtering coating technology, a catalyst layer and a denitrification layer are sequentially prepared on the pretreated seed crystal surface; The catalyst layer is prepared as follows: a pre-alloyed target material with a purity ≥99.99% (containing 3% carbon) is used to fix the seed crystal in the sputtering furnace, and the vacuum degree of the vacuum chamber is reduced to ≤5×10 -4 Pa, argon gas was introduced, and the argon gas flow rate was kept constant during the sputtering deposition process. The argon gas flow rate was 60 sccm, the sputtering power was 300W, the deposition temperature was 300℃, and a catalyst layer was finally sputtered on the surface. The deposition time was 100 min, and the thickness of the catalyst layer was 400 nm. The pre-alloyed target material is specifically an Fe-Ni target material (mass ratio 3:1); The process for preparing the nitrogen removal layer is as follows: using an alloy target with a purity ≥99.99%, the seed crystals coated with the catalyst layer are fixed in the sputtering furnace, and the vacuum level in the vacuum chamber is reduced to ≤5×10⁻⁶. -4 Pa, argon gas was introduced, and the argon gas flow rate was kept constant during the sputtering deposition process. The argon gas flow rate was 50 sccm, the sputtering power was 250 W, and the deposition temperature was 100℃. Finally, a denitrification layer was sputtered on its surface. The deposition time was 60 min and the thickness of the denitrification layer was 180 nm. The alloy target material is a Cu-Zr alloy target material with an alloy ratio of 1:1; Step 3: After the coated seed crystals are planted, they are assembled and kept at 1600℃ and 5GPa for 300h to obtain cultured diamonds with high clarity and high pass rate.

[0032] This invention aims to overcome the shortcomings of uneven distribution and difficulty in controlling the content of catalysts and denitrifying agents in existing high-temperature and high-pressure synthetic lab-grown diamond technology. It provides a high-temperature and high-pressure synthesis method for lab-grown diamonds based on seed coating. By preparing a catalyst layer and a denitrifying layer in layers on the seed surface, the catalyst composition and denitrifying agent content can be precisely controlled, thereby improving the color (stabilizing to D color and above), clarity (reaching VS and above), and crystal integrity of lab-grown diamonds, and increasing the yield to over 80%.

Claims

1. A high-temperature, high-pressure synthesis method for lab-grown diamonds based on seed crystal coating, characterized in that, The specific steps are as follows: Step 1: Pre-treat the seed crystals; Step 2: Using magnetron sputtering coating technology, a catalyst layer and a denitrification layer are sequentially prepared on the pretreated seed crystal surface. The preparation process of the catalyst layer is as follows: using a pre-alloyed target, the seed crystal is fixed in the sputtering furnace, and a catalyst layer is sputtered on its surface. The preparation process of the denitrification layer is as follows: using an alloy target, the seed crystal covered with the catalyst layer is fixed in the sputtering furnace, and a denitrification layer is sputtered on its surface. Step 3: After the coated seed crystals are planted, they are assembled and heat-insulated to obtain cultured diamonds with high clarity and a high pass rate.

2. The high-temperature, high-pressure synthesis method for lab-grown diamonds based on seed film coating as described in claim 1, characterized in that, In step 1, specifically: Diamond with a particle size of 200-500μm was selected as seed crystals; the seed crystals were placed in ethanol and acetone solutions for ultrasonic cleaning in sequence; then rinsed with deionized water 3-5 times and dried in a vacuum drying oven to obtain a clean seed crystal surface.

3. The high-temperature, high-pressure synthesis method for lab-grown diamonds based on seed film coating as described in claim 2, characterized in that, The ultrasonic power is 300-500W, and the cleaning time is 20-60 minutes; The vacuum drying temperature is 100-150℃, the vacuum drying time is 2-4h, and the vacuum degree is ≤10Pa.

4. The high-temperature, high-pressure synthesis method for lab-grown diamonds based on seed film coating as described in claim 1, characterized in that, In step 2, the catalyst layer is prepared as follows: using a pre-alloyed target with a purity ≥99.99%, the seed crystal is fixed in the sputtering furnace, and the vacuum level in the vacuum chamber is reduced to ≤5×10⁻⁶. -4 Pa, argon gas is introduced, and the argon gas flow rate is kept constant during sputtering deposition. The argon gas flow rate is 40-60 sccm, the sputtering power is 300-400W, the deposition temperature is 200-400℃, and the deposition time is 50-100min. Finally, a catalyst layer is sputtered on the surface.

5. The high-temperature, high-pressure synthesis method for lab-grown diamonds based on seed film coating as described in claim 4, characterized in that, The catalyst layer thickness is 300-500 nm; the pre-alloyed target material is specifically Fe-Ni target material, Fe-Ni-Co target material or Ni-Mn-Co target material.

6. The high-temperature, high-pressure synthesis method for lab-grown diamonds based on seed film coating as described in claim 4, characterized in that, In step 2, the preparation process of the denitrification layer is as follows: using an alloy target with a purity ≥99.99%, the seed crystals coated with the catalyst layer are fixed in the sputtering furnace, and the vacuum degree of the vacuum chamber is reduced to ≤5×10⁻⁶. -4 Pa, argon gas is introduced, and the argon gas flow rate is kept constant during the sputtering deposition process. The argon gas flow rate is 30-50 sccm, the sputtering power is 150-250W, the deposition temperature is 100-200℃, and the deposition time is 20-60min. Finally, a nitrogen-removing layer is sputtered on its surface.

7. The high-temperature, high-pressure synthesis method for lab-grown diamonds based on seed film coating as described in claim 6, characterized in that, The thickness of the denitrification layer is 50-200nm; the alloy target is an Al-Ti alloy target or a Cu-Zr alloy target, with an alloy ratio of 1:1-3.

8. The high-temperature, high-pressure synthesis method for lab-grown diamonds based on seed film coating as described in claim 1, characterized in that, In step 3, the specific steps are as follows: after the coated seed crystals are planted, they are assembled and kept at 1400-1600℃ and 5-7GPa for 240-480h to obtain cultured diamonds with high clarity and high qualification rate.

9. The cultured diamond synthesized by the high-temperature and high-pressure synthesis method based on seed coating as described in any one of claims 1-8.

Images