Diamond

Abstract

A diamond in which the content of 14C based on the number of atoms is 0.3 ppt to 3.0 ppt.

Description

diamond

[0001] The present disclosure relates to diamonds. This application claims priority to Japanese Patent Application No. 2023-204540, filed on December 4, 2023. The entire contents of the Japanese patent application are incorporated herein by reference.

[0002] Diamonds used in industrial products and jewelry are classified into natural diamonds and synthetic diamonds. Natural diamonds are made from carbon derived from ancient organisms and plants that exist deep underground. Synthetic diamonds are generally produced from fossil fuels such as graphite (see, for example, Patent Document 1).

[0003] Japanese Unexamined Patent Publication No. 2-17934

[0004] The diamond of the present disclosure is １４ The diamond has a C content based on the number of atoms of 0.3 ppt or more and 3.0 ppt or less.

[0005] FIG. 1 is a schematic cross-sectional view showing an example of a sample chamber configuration used in producing diamond according to an embodiment of the present disclosure.

[0006] [Problem to be Solved by the Present Disclosure] In recent years, from the viewpoint of improving the global environment, various efforts have been made to achieve carbon neutrality, which means reducing the total amount of greenhouse gas emissions such as carbon dioxide to zero. There is a demand for technologies that can contribute to the realization of carbon neutrality in diamonds as well.

[0007] Therefore, an object of the present disclosure is to provide a diamond that can contribute to realizing carbon neutrality.

[0008] [Effects of the Present Disclosure] According to the present disclosure, it is possible to provide a diamond that can contribute to realizing carbon neutrality.

[0009] [Description of the embodiments of the present disclosure] First, the embodiments of the present disclosure will be listed and described. (1) The diamond of the present disclosure is １４ The diamond has a C content based on the number of atoms of 0.3 ppt or more and 3.0 ppt or less.

[0010] According to the present disclosure, it is possible to provide diamonds that can contribute to realizing carbon neutrality.

[0011] (2) In the above (1), １４ The carbon content based on the number of atoms may be 0.6 ppt or more and 1.5 ppt or less. This proves that the diamond is a diamond that has fixed carbon that has circulated from the atmosphere in recent years. Compared to carbon directly recovered from the atmosphere, plant-derived carbon also contains carbon that has been transferred via the earth. １４ The C concentration is slightly lower.

[0012] (3) In the above (1) or (2), １３ The content of C based on the number of atoms may be 0.8% or more and 1.5% or less. This indirectly and supplementarily proves that the diamond is a diamond in which carbon circulated from the atmosphere in recent years has been fixed.

[0013] (4) In the above (3), １３ The content of C based on the number of atoms may be 1.0% or more and 1.2% or less, which further proves that the diamond is a diamond in which carbon circulated from the atmosphere in recent years has been fixed.

[0014] (5) In any of (1) to (4) above, the diamond may contain at least one element selected from the group consisting of phosphorus, potassium, and calcium, and the total content of phosphorus, potassium, and calcium in the diamond based on the number of atoms may be 1 ppb or more.

[0015] Phosphorus, potassium and calcium are found in plants that grow on land, so if a diamond contains phosphorus, potassium and calcium, it is clear that the diamond was made using plants that grow on land as its raw material.

[0016] (6) In any of the above (1) to (5), the diamond may have a maximum diameter of 1 mm or more, which makes it easier to use the diamond for various purposes.

[0017] (7) In any of the above (1) to (6), the half-width of the X-ray diffraction rocking curve of the diamond may be 15 seconds or less. The half-width of the X-ray diffraction rocking curve is measured by X-ray diffraction using a double crystal method, using a diamond crystal as the first crystal, with the (004) plane parallel to the crystal, and CuKα radiation.

[0018] This shows that the diamond has high crystallinity, reduced crystal defects and distortion, making it a highly useful diamond.

[0019] (8) In any of the above (1) to (7), the number of defects confirmed in the X-ray topography image of the diamond is 100 / cm ２ This shows that the diamond has reduced crystal defects and strain, making it a more valuable diamond.

[0020] (9) In any of the above (1) to (8), the average phase difference per unit thickness of the diamond may be 10 nm / mm or less. This means that the diamond has reduced crystal defects and distortion, making it a diamond with higher utility value.

[0021] (10) In any one of the above (1) to (9), the Raman shift of the Raman spectrum of the diamond is 1332 cm －１ 1333cm or more －１ The half-width of the following peaks is 3.0 cm －１ This shows that diamond can have high crystallinity and is a diamond with high utility value.

[0022] (11) In any of the above (1) to (10), the transmittance of the diamond at a wavelength of 270 nm may be 70% or more. This increases the value of diamond as a heat dissipation material that requires thermal conductivity, a window material that requires transparency, and jewelry, and increases the amount of diamond used, reducing atmospheric CO ２ This contributes to reducing

[0023] (12) In any of the above (1) to (11), the photoluminescence spectrum of the diamond may have a maximum emission peak within a wavelength range of 490 nm to 510 nm. This increases the value of diamond as a heat dissipation material that requires thermal conductivity, a window material that requires transparency, and jewelry, and increases the amount of diamond used, reducing atmospheric CO ２ This contributes to reducing

[0024] (13) In any of the above (1) to (12), the diamond may contain two or more different growth sectors. The presence of two or more different growth sectors in a diamond indicates that the diamond grains are fully utilized and that a diamond larger than the seed crystal has been successfully synthesized, proving that more carbon can be fixed.

[0025] (14) In any of the above (1) to (13), the diamond may be free of inclusions. Inclusions have the property of impairing the heat dissipation, optical properties, and appearance of a diamond-based product. Therefore, if the diamond is free of inclusions, the value of the product increases.

[0026] [Details of the embodiment of the present disclosure] Specific examples of the diamond of the present disclosure will be described below with reference to the drawings. In the drawings of the present disclosure, the same reference numerals represent the same or equivalent parts. Furthermore, dimensional relationships such as length, width, thickness, and depth have been appropriately changed for the sake of clarity and simplification of the drawings, and do not necessarily represent actual dimensional relationships.

[0027] In this specification, the expression "A to B" means the upper and lower limits of a range (i.e., A or more and B or less), and when no unit is specified for A and a unit is specified only for B, the unit of A and the unit of B are the same.

[0028] The present inventors have investigated the raw materials for synthetic diamonds in order to provide diamonds that can contribute to the realization of carbon neutrality. Generally, carbon derived from fossil fuels, such as graphite, is used as the raw material for synthetic diamonds. Fossil fuel-derived carbon can be highly purified, making it easy to synthesize diamonds stably; however, producing diamonds from fossil fuel-derived carbon does not contribute to reducing atmospheric carbon dioxide. Meanwhile, the carbon that currently constitutes plants growing on Earth is derived from atmospheric carbon dioxide. Therefore, these carbon sources are not highly pure or dense, making it generally difficult to synthesize diamonds stably. However, if diamonds could be produced using plants growing on Earth, it would be possible to reduce atmospheric carbon dioxide, thereby contributing to the realization of carbon neutrality. After extensive research, the present inventors have discovered a technology for producing diamonds using plants growing on Earth, and have completed the diamond disclosed herein. The diamond disclosed herein will be described below.

[0029] [Embodiment 1: Diamond] A diamond according to one embodiment of the present disclosure (hereinafter also referred to as "Embodiment 1") is １４ The diamond has a C content based on the number of atoms of 0.3 ppt or more and 3.0 ppt or less.

[0030] In nature １２ C. １３ C and １４ There are three carbon isotopes of C. １４ C is radioactive carbon with a half-life of 5730 years. １４ The C content is the carbon content of fossil fuels. １４ Specifically, during the normal solar activity, the carbon dioxide in the atmosphere is １４ The carbon content of the organic matter in the soil is about 0.9 ppt or more. １４ C content, trees up to 7000 years old (such as Jomon cedars), and carbon from plants that grew using carbon dioxide in the atmosphere. １４The carbon content is about 0.3 ppt or more, although it may grow during solar minimums. １４ The C content is less than about 0.1 ppt. １４ Based on the content of C based on the atomic number, it is possible to determine whether the raw material of the diamond contains carbon derived from carbon dioxide in the atmosphere.

[0031] The diamond of embodiment 1 is １４ The content of C based on the number of atoms (hereinafter referred to as " １４ The carbon content of diamond is between 0.3 ppt and 3.0 ppt. １４ The C content of 0.3 ppt or more and 3.0 ppt or less indicates that the raw material of the diamond contains carbon derived from atmospheric carbon dioxide, and that the diamond is made by fixing carbon circulated from the atmosphere in recent years. Therefore, the diamond of embodiment 1 can contribute to the realization of carbon neutrality.

[0032] < １４ C content> of the diamond of embodiment 1 １４ The content of C based on the number of atoms is 0.3 ppt or more and 3.0 ppt or less, or may be 0.30 ppt or more and 3.0 ppt or less, 0.6 ppt or more and 2.0 ppt or less, or may be 0.9 ppt or more and 1.5 ppt or less.

[0033] In this disclosure, diamond １４ The content of C based on the atomic number is measured using accelerator mass spectrometry (AMS), which is a known dating method using carbon isotopes.

[0034] < １３ C content> of the diamond of embodiment 1 １３ The content of C based on the number of atoms may be 0.8% or more and 1.5% or less, 0.9% or more and 1.3% or less, or 1.0% or more and 1.2% or less.

[0035] In this disclosure, diamond １３The content of C based on the atomic number is measured by secondary ion mass spectrometry (SIMS).

[0036] <Phosphorus, Potassium, and Calcium> The diamond of embodiment 1 may contain at least one element selected from the group consisting of phosphorus, potassium, and calcium.

[0037] The total content of phosphorus, potassium and calcium in the diamond of embodiment 1 based on the number of atoms may be 1 ppb or more, 1 ppb or more to 2000 ppb or less, 10 ppb or more to 1500 ppb or less, or 100 ppb or more to 1000 ppb or less.

[0038] In the present disclosure, the total content of phosphorus, potassium and calcium in diamond based on the atomic number is measured as follows: It is measured by secondary ion mass spectrometry (SIMS).

[0039] <Maximum Diameter> The maximum diameter of the diamond of embodiment 1 may be 1 mm or more, 1 mm or more and 50 mm or less, 2 mm or more and 50 mm or less, or 3 mm or more and 50 mm or less.

[0040] In this disclosure, the maximum diameter of a diamond refers to the maximum length of a straight line connecting two different points on the surface of the diamond, as measured using an optical microscope equipped with a length measurement function.

[0041] <Fulfillment at half maximum of X-ray diffraction rocking curve> The smaller the fill factor at half maximum of the X-ray diffraction rocking curve of a diamond, the higher the crystallinity of the diamond and the more reduced the crystal defects and strain.

[0042] The half-width of the X-ray diffraction rocking curve of the diamond of embodiment 1 may be 15 seconds or less, 4 seconds or more and 15 seconds or less, 4 seconds or more and 10 seconds or less, 4 seconds or more and 8 seconds or less, or 4 seconds or more and 6 seconds or less.

[0043] The half-width of the X-ray diffraction rocking curve of diamond is measured in the X-ray diffraction by double crystal method using a diamond crystal as the first crystal, with the (004) plane parallel arrangement, using CuKα radiation. This measures the half-width of the X-ray diffraction rocking curve of the (001) plane of the diamond. In the double crystal method, the first and second crystals are diamond crystals cut from the diamond to be measured. The first crystal acts as a monochromator. The half-width of the rocking curve reflects the crystallinity of both the first and second crystals. Therefore, when both the first and second crystals are diamond crystals cut from the diamond to be measured, the half-width of the rocking curve is a value that sensitively reflects the crystalline quality of the sample.

[0044] The half-width of the X-ray diffraction rocking curve of diamond may be measured using an apparatus using four Ge crystals. In this case, since the half-width of the four Ge crystals is included, this half-width must be subtracted by separating the Gaussian distribution, and the half-width of the diamond alone must be calculated, and then multiplied by √2 to correspond to the result of two diamond crystals.

[0045] It has been confirmed that there is no variation in the results when the above measurements are carried out in different regions of the diamond of embodiment 1.

[0046] <Number of defects> The defects contained in diamond include point defects such as vacancies, linear needle-like defects, impurities, stacking faults, strain, etc.Among these defects, linear defects and stacking faults can be confirmed in X-ray topography images.These defects have higher X-ray reflection intensity than other parts of crystal (parts with fewer defects, i.e., parts with high crystallinity), so in X-ray topography images, their presence is shown as dark areas in positive images and bright areas in negative images.In this disclosure, the number of defects is an index that indicates the amount of defects derived from the number of linear defects in diamond.

[0047] The number of defects in the diamond of embodiment 1 is 100 / cm ２ It may be less than 0 pieces / cm ２ More than 100 pieces / cm ２It may be less than 0 pieces / cm ２ More than 10 pieces / cm ２ It may be less than or equal to 0 pieces / cm ２ That's fine too.

[0048] The X-ray topography image of the diamond is measured by transmitting X-rays of 0.71 Å wavelength through the diamond using (220) diffraction at 2θ=32.9°.

[0049] <Phase Difference> Diamond is an isotropic crystal, so it usually has an isotropic refractive index (dielectric constant). However, when defects and distortions exist in diamond, diamond exhibits birefringence. When circularly polarized light is irradiated onto a defect in diamond, a phase difference occurs between the light polarized along the slow and fast axes, resulting in the light being emitted as elliptically polarized light (including linear polarization). If the refractive index is not isotropic due to defects or distortions in the diamond crystal, the slowest polarization direction (slow axis) and the fastest polarization direction (fast axis) will be generated. On the other hand, when circularly polarized light is irradiated onto a part of the diamond that maintains an isotropic refractive index, no phase difference occurs, and the light is emitted as circularly polarized light. The optical axis and phase difference can be determined by calculating the orientation of the major and minor axes of the ellipse and the ratio of the lengths of the major and minor axes. In addition, by combining lenses and microscopes, information on local phase differences in fine areas can be obtained. Furthermore, by placing an integrated polarizer in front of the pixels of a digital detector, information on each pixel (i.e., information on the local position of the sample) can be obtained two-dimensionally.

[0050] The phase difference measured at each local position is a value integrated in the thickness direction of the substrate. Therefore, samples of the same thickness are compared, or the values ​​are normalized by thickness. When normalized by thickness, the phase difference is expressed as a value converted to a 1 mm thickness (unit: nm / mm). For example, to convert to a 1 mm thickness, a value measured at a 0.1 mm thickness is multiplied by 10, a value measured at a 0.2 mm thickness is multiplied by 5, and a value measured at a 0.5 mm thickness is multiplied by 2.

[0051] The two-dimensional retardation value indicates the distribution within the substrate surface. A reasonable method for expressing the characteristics of a substrate is to represent it by the average value of the retardation within any given surface of the substrate. The average value of the retardation of a substrate refers to the average value of the retardation within the effective area of ​​the substrate. Here, the effective area refers to the area excluding the edge of the substrate, since the retardation value cannot be accurately measured at the edge of the substrate. More precisely, when the distance from the center of gravity of the main surface of the substrate to the edge is taken as 100%, it is defined as the area within a distance of 90% from the center of gravity. Here, the average value of the retardation within the effective area does not mean the retardation per area, but rather the value obtained by averaging the retardation of each local portion across the surface, i.e., the average frequency distribution of the retardation within the surface. Therefore, the average value of the retardation is also expressed in units of nm / mm.

[0052] Even if the amount of crystal defects is constant, the thicker the substrate, the greater the accumulated phase difference. Also, the larger the area of ​​the substrate, the greater the effect of defects on the entire surface, resulting in a larger phase difference. For this reason, the smaller the phase difference converted to unit thickness and / or the smaller the average phase difference of the in-plane power distribution, the better the quality of the diamond. Also, even with the same phase difference, the larger the substrate, the better the quality of the diamond. This is because when cut into small pieces, stress is relieved and the phase difference becomes smaller. The magnitude of the phase difference and the size of the substrate affect the quality of distortion.

[0053] The value of the phase difference shows a positive correlation with the amount of defects and the magnitude of strain in the diamond. The average phase difference per unit thickness of the diamond of embodiment 1 is 10 nm / mm or less, and may be 0 nm / mm or more and 10 nm / mm or less, 0.01 nm / mm or more and 5 nm / mm or less, or 0.01 nm / mm or more and 2 nm / mm or less.

[0054] The phase difference per unit thickness of diamond is measured using the following procedure. First, the diamond is processed into a plate shape with a thickness of 0.1 to 5 mm. Processing methods that can be used include laser processing, polishing, plasma etching, ion etching, or a combination of these. The value converted into a diamond thickness of 1 mm is the phase difference per unit thickness.

[0055] Next, the phase difference of the diamond is measured using a birefringence distribution measurement device (Photonic Lattice, Inc., "WPA-micro" (trademark) or "WPA-100" (trademark)). Generally, it is difficult to distinguish a phase difference exceeding 90 degrees (1 / 4 of the wavelength). However, the birefringence distribution measurement device described above uses an integrated waveplate system instead of an integrated polarizer system, and the measurement range is expanded to a phase difference of 180 degrees (1 / 2 of the wavelength). It has been experimentally verified that when three wavelengths (one central wavelength and two wavelengths close to it) are used, the measurement range can be expanded to 5 to 6 times the wavelength. The measured values ​​obtained by the birefringence distribution measurement device described above are processed using software (Photonic Lattice, Inc., "PA-View" (trademark)) to determine the average phase difference per unit thickness.

[0056] For the same diamond, the above-mentioned measuring device measures the surface distribution and calculates the average within the surface, so it is not affected by the measurement placement, etc. It has been confirmed that there is no variation in the measurement results even if the setting location of the above-mentioned measurement area is arbitrarily changed.

[0057] <Raman Spectroscopy> Raman shift of 1332 cm in the Raman spectroscopic spectrum of diamond －１ 1333cm or more －１ The sharper the diamond phonon peak that appears below and the smaller the half-width, the higher the crystallinity of the diamond.

[0058] The Raman shift of the Raman spectrum of the diamond of embodiment 1 is 1332 cm －１ 1333cm or more －１ The half-width of the following peak (hereinafter also referred to as "half-width of the peak of the Raman spectroscopy spectrum") is 3.0 cm －１It may be less than 1.6 cm －１ 2.0cm or more －１ It may be less than 1.6 cm －１ Over 1.8cm －１ It may be less than 1.6 cm －１ 1.7cm or more －１ The following is also acceptable.

[0059] In this disclosure, the half-width of the peak in a Raman spectrum is measured by the following procedure. First, the surface of the (001) plane of a diamond, which is the measurement sample, is polished with a metal-bonded grinding wheel so that the surface roughness Ra is 20 nm or less. The measurement sample is preferably mainly square or close to octagonal. A laser is irradiated onto the polished surface under the following conditions, and scattered Raman rays are detected.

[0060] <<Measurement conditions>> Measurement device: LabRAM HR-800 (manufactured by HORIBA JOBIN YVON) Laser wavelength: 532 nm Measurement temperature: room temperature (20°C or higher and 25°C or lower) Wavenumber resolution: 0.5 cm －１ The half-width of the peak in the Raman spectrum of the diamond of embodiment 1 is a value measured under the following conditions: －１ If the half-width of the laser beam used as the excitation light is measured, the half-width due to the light source and the device can be determined. －１ Super 3.0cm －１ If the value is less than 3.0 cm, the square of the measured value of the half-width is subtracted from the square of the half-width due to the light source and the device, and the square root of this value is used to convert it into the half-width inherent to the diamond. －１A value greater than this is not preferable because it reduces accuracy. Laser irradiation direction: perpendicular incidence when the (001) face of the diamond is cut out. Laser irradiation position (measurement area): Raman lines are detected at the following five locations (i) to (v). (i) Raman lines are detected at the center of the polished surface of the measurement sample (the center of gravity position on a two-dimensional plane). (ii) A line is drawn from the center to the edge of the polished surface, and the position P where the length of the line is longest is identified. If the distance from the center to P is D1, Raman lines are detected on the line segment from the center to P at a distance of (3 / 4)D1 from the center. (iii) A line is drawn from the center in the opposite direction to P, and the intersection Q of the line and the edge of the polished surface is identified. In other words, P, the center, and Q are on the same straight line L1. If the distance from the center to Q is D2, Raman lines are detected on the line segment from the center to Q at a distance of (3 / 4)D2 from the center. (iv) Draw a line L2 that passes through the central portion and is perpendicular to the line L1 that passes through P, the central portion, and Q, and identify the intersections R and S of the line L2 with the edge of the polished surface. If the distance from the central portion to R is D3, Raman rays are detected on the line segment from the central portion to R at a position that is (3 / 4)D3 away from the central portion. (v) If the distance from the central portion to S is D4, Raman rays are detected on the line segment from the central portion to S at a position that is (3 / 4)D4 away from the central portion.

[0061] Spectral analysis was performed on the Raman lines detected at each of the five locations, and the Raman shift was 1332 cm －１ 1333cm or more －１ The diamond phonon peak that appears below is identified. A Lorentzian function is fitted to the diamond phonon peak by the least squares method, and a Raman shift of 1332 cm －１ 1333cm or more －１ The half-width of the peak at each of the five points described above is determined as follows: The half-width of the peak at each of the five points is averaged. In the present disclosure, this average value corresponds to the half-width of the peak in the Raman spectroscopy spectrum.

[0062] By setting the five measurement areas and calculating the average for the same diamond, the crystallinity of the sample, such as distortion, can be uniquely evaluated and compared between samples.

[0063] <Transmittance of light with a wavelength of 270 nm> The transmittance of light with a wavelength of 270 nm of the diamond of embodiment 1 may be 70% or more, 85% or more, or 95% or more. Transmittance is measured by an ultraviolet-visible transmittance spectrophotometer. This transmittance means the net transmittance of the substrate excluding reflectance. Generally, the reflectance of diamond is about 28%, and the transmittance of an ideal substrate without absorption is about 72%. This transmittance means the transmittance relative to the ideal value excluding reflectance.

[0064] <Photoluminescence spectrum> In the photoluminescence spectrum of the diamond of embodiment 1, the maximum emission peak may be present in the wavelength range of 490 nm or more and 510 nm or less. The photoluminescence spectrum of diamond is measured using a fluorescence spectrometer or a Raman spectrometer. The maximum peak refers to the peak with the greatest peak intensity in the spectrum that produces light emission. The excitation wavelength must be shorter than 490 nm, and excitation light with a wavelength of 340 nm ± 20 nm is preferred. For example, when irradiated with 325 nm excitation laser light, it is confirmed that the maximum peak wavelength (PL peak) of photoluminescence in the wavelength range of 400 nm to 700 nm is present in the wavelength range of 490 nm or more and 510 nm or less. The irradiation direction of the excitation light is perpendicular incidence when the (001) face of the diamond is cut out.

[0065] <Growth Sectors> The diamond of embodiment 1 may include two or more different growth sectors. Whether the diamond includes two or more different growth sectors can be confirmed by observing a fluorescent image using a two-dimensional fluorescence distribution evaluation device or a fluorescence microscope (for example, Diamond View (trademark) manufactured by Diamond Trading Company).

[0066] <Inclusions> The diamond of embodiment 1 may not contain inclusions. Inclusions refer to graphite that appears as black lumps under an optical microscope or inclusions made of non-diamond components including Fe, Co, Si, and other elements. Inclusions with a diameter of 10 μm or more observed under a low-magnification optical microscope may not be included, as they particularly affect the identification of the diamond.

[0067] When a diamond is observed under an optical microscope at 40x magnification, if no black dots are observed, the diamond is determined to be free of inclusions.

[0068] <Type of Crystal> The diamond of embodiment 1 may be a single crystal diamond, which has high heat dissipation properties, high transmittance, and few inclusions.

[0069] The diamond of the first embodiment may be a polycrystalline diamond, which allows for a large diamond size to be obtained and allows for more carbon to be immobilized.

[0070] <Nitrogen> The diamond of embodiment 1 may contain nitrogen. The nitrogen content of the diamond may be 0.0001 ppm or more and 200 ppm or less, 0.001 ppm or more and 10 ppm or less, or 0.005 ppm or more and 1 ppm or less.

[0071] The nitrogen content of diamond is measured by secondary ion mass spectrometry (SIMS), or ESR.

[0072] <Applications> The diamond of embodiment 1 can be used in the same applications as conventional diamonds, such as tools, jewelry, optical components, semiconductor substrates, and heat dissipation components.

[0073] [Embodiment 2: Method for manufacturing diamond] An example of a method for manufacturing diamond according to embodiment 1 will be described below. The diamond according to embodiment 1 can be manufactured by a temperature difference method using, for example, a sample chamber having the configuration shown in Figure 1.

[0074] As shown in Figure 1, in the sample chamber 10 used for producing diamond in the first embodiment, an insulator 2, a carbon source 3, a solvent metal 4, and a seed crystal 5 are arranged in a space surrounded by a graphite heater 7, and a pressure medium 6 is arranged outside the graphite heater 7. The temperature difference method is a method in which a vertical temperature gradient is provided inside the sample chamber 10, and a high temperature part (T ｈｉｇｈ ) carbon source 3, low temperature part (T ｌｏｗ In this synthesis method, a diamond seed crystal 5 is placed in a carbon source 3, a solvent metal 4 is placed between the carbon source 3 and the seed crystal 5, and the diamond is grown on the seed crystal 5 under conditions that are higher than the temperature at which the solvent metal 4 dissolves and higher than the pressure at which the diamond becomes thermally stable.

[0075] Carbon source 3 is binchotan charcoal made from plants less than 7,000 years old. A carbon source made from binchotan charcoal is produced using the following procedure: First, raw wood dried at room temperature is prepared. The raw wood is slowly steamed in a furnace at low temperature for at least five days to thoroughly remove moisture. Then, while a mixed gas of inert gas and a small amount of oxygen is flowed into the furnace, the raw wood is quickly baked at 1,200-1,300°C to carbonize it and obtain charcoal. The charcoal is then immediately removed from the furnace and covered with finely crushed dry ice to rapidly lower the charcoal temperature. The charcoal is then sealed in a vacuum in a dry pump for 24 hours and returned to atmospheric pressure with an inert gas such as Ar. This produces the raw binchotan charcoal. The binchotan charcoal is then pulverized in a ball mill to produce powder. This powder is then pressed and solidified to form the carbon source.

[0076] The density of the carbon source prepared by the above method is 1.8 g / cm ３ The density of the carbon source is 1.8 g / cm or more, and the volumetric porosity is 20% or less. ３ If it is less than this, the pressure during diamond synthesis will not be stable, causing problems with synthesis.

[0077] By using the binchotan charcoal produced by the above method as a carbon source, １４ It is possible to produce the diamond of embodiment 1 in which the C content based on the number of atoms is 0.3 ppt or more and 3.0 ppt or less.

[0078] Iron (Fe) and cobalt (Co) can be used as the solvent metal 4. The compounding ratio of iron to cobalt is Fe / Co=10 / 90 to 90 / 10.

[0079] Titanium (Ti) or aluminum (Al) may be added to the solvent metal as a nitrogen getter.The content of titanium or aluminum in the solvent metal can be 1.5 mass% or more and 3 mass% or less.By adding nitrogen getter to the solvent metal, the nitrogen content of diamond can be reduced.If no nitrogen getter is used, the nitrogen content of diamond becomes the same as that of type Ib diamond.

[0080] The conditions for the high-temperature, high-pressure method are as follows: The temperature gradient is adjusted so that the temperature difference between the high-temperature section where the carbon source 3 is placed and the low-temperature section where the seed crystal 5 is placed is 10°C or more and 25°C or less, and the pressure is maintained at 5.0 GPa or more and 5.8 GPa or less, and the temperature of the low-temperature section is maintained at 1300°C or more and 1600°C or less for 80 hours or more and 250 hours or less. The temperature change during this maintenance is controlled to within ±3°C. This allows a single-crystal diamond to grow on the seed crystal.

[0081] If the temperature difference between the carbon source 3 and the seed crystal 5 exceeds 25°C, crystal growth becomes disrupted and the desired diamond cannot be obtained. If the temperature difference is less than 10°C, it takes a long time to grow a crystal of the desired size, and only small diamonds can be synthesized. If the temperature change is greater than ±3°C, crystal growth becomes unstable, resulting in crystal defects, distortion, and inclusions, reducing the crystallinity of the diamond.

[0082] If carbon source contains a large amount of elements other than carbon (for example, minerals, etc.), it becomes difficult to synthesize single crystal diamond itself, and it becomes difficult to produce single crystal diamond with narrow half-width of X-ray diffraction rocking curve, or with few defects confirmed in X-ray topography image, or with small phase difference, or with small Raman half-width, or with low transmittance at 270 nm wavelength.For this reason, the porosity of the carbon source that is compacted by pressing powder is preferably 20% or less.

[0083] The present embodiment will be described in more detail with reference to examples, although the present embodiment is not limited to these examples.

[0084] [Preparation of Diamond] Diamond samples were synthesized by the temperature difference method using a solvent metal, using a sample chamber having the configuration shown in FIG.

[0085] The carbon sources used were binchotan charcoal, high-purity graphite manufactured by Toyo Tanso, and ordinary charcoal. The type of carbon source used for each sample is shown in the "Carbon Source" column in Table 1.

[0086] The carbon source made from Binchotan charcoal was produced using the following procedure. Dried logs were prepared. The logs were heated in a furnace at 200°C for five days to thoroughly evaporate the moisture. Then, while a mixed gas of Ar gas and oxygen was flowing into the furnace, the logs were quickly baked at 1200-1300°C to carbonize them and obtain charcoal. The oxygen content of the mixed gas was 1% by volume.

[0087] The charcoal was then immediately removed from the furnace and covered with finely crushed dry ice to rapidly lower the charcoal temperature. The charcoal was then confined in a vacuum using a dry pump for 24 hours, and the pressure was returned to atmospheric pressure using an inert gas such as Ar to produce binchotan charcoal. The binchotan charcoal was then crushed into powder in a ball mill, and the powder was pressed and solidified to form a carbon source.

[0088] High-purity graphite powder manufactured by Toyo Tanso was pressed and used as the carbon source. Regular charcoal was used as the carbon source.

[0089] The density of the carbon source used in each sample is shown in the "Carbon source density" column of Table 1.

[0090] Next, a solvent metal was prepared. Iron (Fe) powder, cobalt (Co) powder, and titanium (Ti) powder were prepared in a mass ratio of Fe:Co:Ti = 58:39:3 and mixed in a mixer for about an hour to obtain a mixed powder. The mixed powder was pelletized using a press to produce a pellet-shaped solvent metal. The solvent metal was heated in a vacuum at 1000°C for 30 minutes to degas. Then, the solvent metal and a carbon source were placed in a container. The carbon source was placed in the high-temperature section of the sample chamber.

[0091] The temperature inside the sample chamber was adjusted with a graphite heater so that the temperature difference between the high-temperature section where the carbon source was placed and the low-temperature section where the seed crystal was placed was 20°C. Using an ultra-high pressure generator, the sample chamber was maintained at 5.4 GPa and the low-temperature section was maintained at 1340°C for 150 hours, and diamond was grown on the seed crystal. The diamond was a single crystal diamond.

[0092]

[0093] [Diamond Measurement] For each sample diamond, １４ C atomic number content, １３ The content of C based on the number of atoms, the content of phosphorus (P) based on the number of atoms, the content of potassium (K) based on the number of atoms, the content of calcium (Ca) based on the number of atoms, the maximum diameter, the half width of the X-ray diffraction rocking curve (shown as "Xrc" in Table 2), the number of defects confirmed in the X-ray topography image, the average phase difference per unit thickness (shown as "phase difference" in Table 2), and the Raman shift of 1332 cm in the Raman spectroscopy spectrum. －１ 1333cm or more －１ The following peak half-widths (shown as "Raman half-widths" in Table 2), transmittance of light with a wavelength of 270 nm (shown as "270 nm transmittance" in Table 2), maximum peak wavelength of photoluminescence in the wavelength range of 400 nm to 700 nm when irradiated with excitation laser light of 325 nm (shown as "PL peak" in Table 2), presence or absence of two or more different growth sectors, and presence or absence of inclusions were measured or confirmed. Specific measurement and confirmation methods are as described in embodiment 1. The results are shown in Tables 1 and 2.

[0094]

[0095] The diamonds of Samples 1 to 3 correspond to the examples. １４ The carbon content based on the number of atoms is between 0.3 ppt and 3.0 ppt, and the diamond contains carbon that has been circulated from the atmosphere in recent years, making it possible to contribute to the realization of carbon neutrality.

[0096] The diamonds of Samples 101 and 102 were produced using a carbon source produced from fossil fuels and correspond to comparative examples.

[0097] Sample 103 was made from ordinary charcoal, and the density of the carbon raw material was 1.6 g / cm ３ At this density, the pressure in the synthesis environment was not stable, and diamond could not be produced.

[0098] Although the embodiments and examples of the present disclosure have been described above, it is intended from the beginning that the configurations of the above-described embodiments and examples may be appropriately combined or modified in various ways. The embodiments and examples disclosed herein are illustrative in all respects and should not be considered limiting. The scope of the present invention is defined by the claims, not by the above-described embodiments and examples, and is intended to include meanings equivalent to the claims and all modifications within the scope of the claims.

[0099] 1 Diamond, 2 Insulator, 3 Carbon source, 4 Solvent metal, 5 Seed crystal, 6 Pressure medium, 7 Graphite heater, 10 Sample chamber

Claims

1. １４ A diamond having a C content based on the atomic number of 0.3 ppt or more and 3.0 ppt or less.

2. The foregoing １４ 2. The diamond according to claim 1, wherein the C content based on the number of atoms is 0.6 ppt or more and 1.5 ppt or less.

3. １３ 3. Diamond according to claim 1 or claim 2, wherein the C content based on the atomic number is 0.8% or more and 1.5% or less.

4. The foregoing １３ 4. The diamond according to claim 3, wherein the C content based on the atomic number is 1.0% or more and 1.2% or less.

5. A diamond according to any one of claims 1 to 4, wherein the diamond contains at least one type selected from the group consisting of phosphorus, potassium and calcium, and the total content of the phosphorus, potassium and calcium in the diamond based on the atomic number is 1 ppb or more.

6. A diamond according to any one of claims 1 to 5, wherein the maximum diameter of the diamond is 1 mm or more.

7. A diamond according to any one of claims 1 to 6, wherein the half-width of the X-ray diffraction rocking curve of the diamond is 15 arcseconds or less, and the half-width of the X-ray diffraction rocking curve is measured in X-ray diffraction by a double crystal method, using a diamond crystal as the first crystal and in a (004) plane parallel arrangement with CuKα radiation.

8. The number of defects identified in the X-ray topography image of the diamond is 100 / cm ２ 8. A diamond according to any one of claims 1 to 7, wherein:

9. A diamond according to any one of claims 1 to 8, wherein the average phase difference per unit thickness of the diamond is 10 nm / mm or less.

10. The Raman shift of the Raman spectrum of the diamond is 1332 cm －１ 1333cm or more －１ The half-width of the following peaks is 3.0 cm －１ 10. A diamond according to any one of claims 1 to 9, which is as follows:

11. A diamond according to any one of claims 1 to 10, wherein the transmittance of the diamond to light with a wavelength of 270 nm is 70% or more.

12. A diamond according to any one of claims 1 to 11, in which the photoluminescence spectrum of the diamond has a maximum emission peak within the wavelength range of 490 nm or more and 510 nm or less.

13. A diamond according to any one of claims 1 to 12, wherein the diamond comprises two or more distinct growth sectors.

14. A diamond according to any one of claims 1 to 13, wherein the diamond is free of inclusions.

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