Single crystal diamond and its manufacturing method

Abstract

A single crystal diamond having a half width of an x-ray diffraction rocking curve of 20 seconds or less, a half width of a peak at a Raman shift of 1332 cm-1 to 1333 cm-1 (inclusive) in a Raman spectroscopic spectrum of 2.0 cm-1 or less, an etch pit density of 10,000 / cm2 or less, a content of nitrogen based on number of atoms of 0.0001- 0.1 ppm (inclusive), and a content of 13C based on number of atoms of 0.01-1.0% (inclusive).

Description

[Technical Field]

[0001] This disclosure relates to a single crystal diamond and a method for producing the same. This application claims priority to Japanese Patent Application No. 2021-061208, filed on March 31, 2021. The entire contents of the Japanese Patent Application are incorporated herein by reference. [Background technology]

[0002] Diamond has traditionally been used in a variety of applications, including heat sinks, wire-drawing dies, precision machining tools, optical components, laser windows, spectroscopic crystals, monochromators, anvils for ultra-high pressure generators, and semiconductor diamond substrates. Among these applications, diamonds with fewer crystal defects and distortion have been developed to improve performance, particularly in the fields of optical components, laser windows, spectroscopic crystals, monochromators, anvils for ultra-high pressure generators, and semiconductor diamond substrates (e.g., Patent Documents 1 to 3). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 7-116494 [Patent Document 2] Japanese Patent Application Publication No. 7-148426 [Patent Document 3] Japanese Patent Application Publication No. 9-165295 Summary of the Invention

[0004] The present disclosure provides an X-ray diffraction rocking curve having a half-width of 20 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, in a (004) plane parallel arrangement, and CuKα radiation; Raman shift of Raman spectroscopy: 1332cm -1 Over 1333cm -1The half-width of the peak below is 2.0 cm -1 is as follows: Etch pit density is 10,000 / cm 2 is as follows: The etch pit density is measured by an etching test; The nitrogen content based on the number of atoms is 0.0001 ppm or more and 0.1 ppm or less. 13 The carbon content in terms of atomic number is 0.01% or more and 1.0% or less, and the single crystal diamond is used.

[0005] The present disclosure provides a method for producing the single crystal diamond, comprising: providing a seed substrate; growing a single crystal diamond on the seed substrate using a high-temperature, high-pressure synthesis method; The size of the primary surface of the seed substrate is such that the diameter of the inscribed circle thereof exceeds 1.0 mm, The etch pit density of the main surface is 1×10 5 pieces / cm 2 is as follows: The method for producing a single-crystal diamond includes two or less growth sectors on the primary surface of the seed substrate. [Brief explanation of the drawings]

[0006] [Figure 1] FIG. 1 is a diagram for explaining the NV center in a single crystal diamond. [Figure 2] FIG. 2 is a diagram showing another example of a diamond seed substrate used in the method for producing a single crystal diamond according to the second embodiment. [Figure 3] FIG. 3 is a diagram showing another example of a diamond seed substrate used in the method for producing a single crystal diamond according to the second embodiment. [Figure 4] FIG. 4 is a schematic diagram showing the configuration of a sample chamber used in the method for producing a single crystal diamond according to the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0007] [Problem to be solved by this disclosure] In order to obtain single-crystal diamond with few crystal defects and distortion, it is essential to reduce impurities such as nitrogen as much as possible, but it has been difficult to reduce crystal defects and distortion in single crystals with a high nitrogen content. In recent years, as new applications such as magnetic sensors have been attracting attention, it has become necessary to reduce crystal defects and distortion even when the diamond contains nitrogen.

[0008] In recent years, new applications of diamond have attracted attention, such as the use of nuclear spins in memory, such as quantum repeaters and quantum computers. Although nitrogen is added to substitutional structures in diamond for these applications to improve memory function and stability, further reduction of crystal defects and strain is desired.

[0009] Therefore, an object of the present invention is to provide a single crystal diamond containing nitrogen but with reduced crystal defects and strain.

[0010] [Effects of this disclosure] According to the present disclosure, it is possible to provide a single crystal diamond that contains nitrogen but has reduced crystal defects and strain.

[0011] [Description of the embodiments of the present disclosure] First, embodiments of the present disclosure will be listed and described. (1) The present disclosure provides an X-ray diffraction rocking curve having a half-width of 20 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, in a (004) plane parallel arrangement, and CuKα radiation; Raman shift of Raman spectroscopy: 1332cm -1 Over 1333cm -1 The half-width of the peak below is 2.0 cm -1 is as follows: Etch pit density is 10,000 / cm 2 is as follows: The etch pit density is measured by an etching test; The nitrogen content based on the number of atoms is 0.0001 ppm or more and 0.1 ppm or less. 13 The carbon content in terms of atomic number is 0.01% or more and 1.0% or less, and the single crystal diamond is used.

[0012] The single crystal diamond of the present disclosure contains nitrogen, yet has reduced crystal defects and strain, and therefore when the single crystal diamond of the present disclosure is used in applications where the nuclear spins are used as a memory, the memory function and memory stability are improved.

[0013] (2) the half-width of the X-ray diffraction rocking curve is 10 seconds or less; The Raman shift of the Raman spectrum is 1332 cm -1 Over 1333cm -1 The half-width of the peak below is 1.9 cm -1 is as follows: The etch pit density is 1000 / cm 2 is as follows: The number of defects confirmed in the X-ray topography image is 1000 / cm 2 It is preferable that:

[0014] This further reduces crystal defects and distortion in the single crystal diamond.

[0015] (3) The average phase difference per unit thickness of the single crystal diamond is preferably 30 nm / mm or less, which further reduces crystal defects and distortion in the single crystal diamond.

[0016] (4) The average phase difference is preferably 10 nm / mm or less, which further reduces crystal defects and distortion in the single crystal diamond.

[0017] (5) The single crystal diamond contains NV centers, and the NV center content is preferably 0.1 ppm or less. This allows the NV centers to exist stably as a single entity without interfering with each other's spins, and interact with stable atoms with nuclear magnetism inside the diamond, thereby providing memory functionality.

[0018] (6) The content of the NV center is preferably 0.00001 ppm or more and 0.1 ppm or less, which makes it possible to find and detect a single, isolated, stable NV center in the diamond, which interacts with stable atoms with nuclear magnetism inside the diamond, thereby providing the single crystal diamond with memory functionality.

[0019] (7) The atomic number-based boron content of the single crystal diamond is preferably equal to or less than the atomic number-based nitrogen content. - The presence of the center further reduces the distortion of the single crystal diamond.

[0020] (8) The content of the boron in terms of the number of atoms is preferably 10% or less of the content of the nitrogen in terms of the number of atoms. Boron serves as a site for capturing electrons, reducing the number of the capture sites to a certain level or less, and improving the NV of the information input / output function to the memory atoms. - It allows centers to be generated efficiently.

[0021] (9) The boron content, based on atomic number, is preferably more than 10% of the nitrogen content, based on atomic number, but less than or equal to the nitrogen content, based on atomic number. When nitrogen is substituted for carbon, the bond length between the nitrogen and carbon differs from the bond length between the carbon, resulting in strain. By increasing the amount of boron to a certain amount, the strain is alleviated, crystal defects and strain are reduced, the nuclear magnetism that serves as memory is stabilized, and the life is extended.

[0022] (10) The content of boron in terms of atomic number is preferably 1% to 10% of the content of nitrogen in terms of atomic number, which, as described above, makes it possible to reduce crystal defects and distortion while suppressing electron trapping sites caused by boron, thereby ensuring a certain amount or more of NV centers required for sensing.

[0023] (11) The diameter of the inscribed circle of the main surface of the single crystal diamond is preferably 3 mm or more. This makes it easy to process the single crystal diamond into a memory element. Furthermore, small memory elements of 0.5 mm or less can be mass-produced, reducing manufacturing costs.

[0024] (12) The diameter is preferably 5 mm or more. This makes it easier to process the single crystal diamond into a memory element. Also, it is possible to mass-produce small memory elements with a diameter of 0.5 mm or less, further reducing manufacturing costs.

[0025] (13) The single-sector content of the single-crystal diamond is preferably 70% by volume or more. This significantly reduces the influence of sector boundaries, which cause distortion, on the entire single crystal, further reducing distortion in the single-crystal diamond.

[0026] (14) The content of the single sector is preferably 90% by volume or more. This virtually eliminates the influence of the sector boundaries, which cause distortion, on the entire single crystal, further reducing distortion in the single crystal diamond.

[0027] (15) The present disclosure provides a method for producing the single crystal diamond, comprising: providing a seed substrate; growing a single crystal diamond on the seed substrate using a high-temperature, high-pressure synthesis method; The size of the primary surface of the seed substrate is such that the diameter of the inscribed circle thereof exceeds 1.0 mm, The etch pit density of the main surface is 1×10 5 pieces / cm 2is as follows: The method for producing a single-crystal diamond includes two or less growth sectors on the primary surface of the seed substrate.

[0028] According to the present disclosure, it is possible to provide a single crystal diamond that has been doped with controlled nitrogen and yet has reduced crystal defects and strain. According to the present disclosure, when used as a material for a memory element, it is possible to obtain a high-quality single crystal diamond that can improve memory function and memory stability.

[0029] [Details of the embodiments of the present disclosure] Specific examples of the single crystal 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 parts or corresponding parts.In addition, the dimensional relationships of length, width, thickness, depth, etc. are appropriately changed for the purpose of clarifying and simplifying the drawings, and do not necessarily represent the actual dimensional relationships.

[0030] 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.

[0031] In this specification, the expression "half width" means "full width at half maximum (FWHM)."

[0032] In the crystallographic depictions herein, () indicates an individual plane and {} indicates a collective plane.

[0033] [Embodiment 1: Single Crystal Diamond] The single crystal diamond of one embodiment of the present disclosure (hereinafter also referred to as "the present embodiment") is The half-width of the X-ray diffraction rocking curve is 20 seconds or less. 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. Raman shift of Raman spectroscopy: 1332cm -1 Over 1333cm -1 The half-width of the peak below is 2.0 cm -1 is as follows: Etch pit density is 10,000 / cm 2 is as follows: The etch pit density is measured by an etching test. The nitrogen content based on the number of atoms is 0.0001 ppm or more and 0.1 ppm or less. 13 The content of C based on the number of atoms is 0.01% or more and 1.0% or less.

[0034] (X-ray diffraction rocking curve) The smaller the full width at half maximum of the X-ray diffraction rocking curve of single crystal diamond, the higher the crystallinity of the single crystal diamond, and the more reduced the crystal defects and distortion.The single crystal diamond of this embodiment has a full width at half maximum of the X-ray diffraction rocking curve of 20 seconds or less, and has high crystallinity, and reduced the crystal defects and distortion.

[0035] The upper limit of the half width of the X-ray diffraction rocking curve of single crystal diamond is 20 seconds or less, preferably 10 seconds or less, more preferably 8 seconds or less, and even more preferably 6 seconds or less, from the viewpoint of improving crystallinity.The lower limit of the half width of the X-ray diffraction rocking curve of single crystal diamond can be 4.2 seconds or more, from the viewpoint of manufacturing.The half width of the X-ray diffraction rocking curve of single crystal diamond is preferably 4.2 seconds or more and 20 seconds or less, more preferably 4.2 seconds or more and 10 seconds or less, more preferably 4.2 seconds or more and 8 seconds or less, and even more preferably 4.2 seconds or more and 6 seconds or less.

[0036] The half-width of the X-ray diffraction rocking curve of the above-mentioned single crystal diamond is measured by the X-ray diffraction using the double crystal method, using a diamond crystal as the first crystal, with the (004) plane parallel arrangement, using CuKα radiation.In the double crystal method, the first crystal and the second crystal are diamond crystals cut from the single crystal diamond to be measured.The half-width of the rocking curve reflects the crystallinity of both the first crystal and the second crystal.Therefore, when both the first crystal and the second crystal are diamond crystals cut from the single crystal diamond to be measured, the half-width of the rocking curve is a value that sensitively reflects the crystalline quality of the sample.

[0037] It has been confirmed that there is no variation in the results when the above measurements are performed on different regions of the same single crystal diamond.

[0038] (Half-width of the peak in the Raman spectrum) Raman shift of 1332 cm in Raman spectroscopy of single crystal diamond -1 Over 1333cm -1 The sharper the diamond phonon peak that appears below and the smaller the half-width, the higher the crystallinity of the diamond. The single crystal diamond of this embodiment has a Raman shift of 1332 cm -1 Over 1333cm -1 The half-width of the peak in the following (hereinafter also referred to as "half-width of the peak in the Raman spectrum") is 2.0 cm -1 or less and has high crystallinity.

[0039] The upper limit of the half-width of the peak in the Raman spectrum of single-crystal diamond is 2.0 cm -1 Less than 1.9cm -1 Less than 1.8cm is preferable -1 Less than 1.7cm is preferable. -1 From the viewpoint of manufacturing, the lower limit of the half-width of the peak of the Raman spectrum of a single crystal diamond is 1.5 cm or less. -1 The half-width of the peak in the Raman spectrum of single crystal diamond can be 1.5 cm or more.-1 More than 2.0cm -1 Less than 1.5cm is preferable -1 Over 1.9cm -1 Less than 1.5cm is preferable -1 Over 1.8cm -1 Less than 1.5cm is more preferable. -1 More than 1.7cm -1 The following is even more preferred:

[0040] The half-width of the peak in the Raman spectrum is measured using the following procedure. First, any surface of the single crystal diamond to be measured is polished with a metal-bonded grinding wheel so that the surface roughness Ra is 20 nm or less. The measurement sample is preferably square or close to octagonal. A laser is irradiated onto the polished surface under the following conditions, and scattered Raman rays are detected. (Measurement conditions) Measurement device: LabRAM HR-800 (HORIBA JOBIN YVON) Laser wavelength: 532nm Measurement temperature: Room temperature (20℃ or higher and 25℃ or lower) Wavenumber resolution: 0.5cm -1 The half-width of the peak in the Raman spectrum of the single crystal diamond of this embodiment is a value measured under the following conditions: -1 If the half-width of the laser beam used as excitation light is less than 0.5cm, the measured value can be regarded as the half-width inherent to the diamond. -1 Super 2.0cm -1 If the half-width is less than 2.0 cm, it can be converted to the diamond's inherent half-width by subtracting the square of the half-width due to the light source and device from the square of the measured half-width and using the square root of that value. -1 If it exceeds this value, the accuracy will decrease, which is not preferable. Laser irradiation position (measurement area): Raman lines are detected at the following five points (i) to (v). (i) Raman lines are detected at the center of the polished surface of the measurement sample (the center of gravity on a two-dimensional plane). (ii) Draw a line from the center to the edge of the polished surface, and identify the position P where the line length is longest. If the distance from the center to P is D1, Raman rays are detected at a position on the line from the center to P that is (3 / 4)D1 away from the center. (iii) A straight line is drawn from the center in the opposite direction to P, and the intersection Q of this line with 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 rays are detected at a position on the line segment from the center to Q that is (3 / 4)D2 away from the center. (iv) Draw a line L2 that passes through the center and is perpendicular to the line L1 that passes through P, the center, and Q, and identify the intersections R and S between the line L2 and the edge of the polished surface. If the distance from the center to R is D3, then detect the Raman line on the line segment from the center to R at a distance of (3 / 4)D3 from the center. (v) If the distance from the center to S is D4, Raman lines are detected on the line segment from the center to S at a position that is (3 / 4)D4 away from the center.

[0041] Spectral analysis was performed on the Raman lines detected at each of the five locations, and the Raman shift was 1332 cm -1 Over 1333cm -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 the Raman shift of 1332 cm is obtained. -1 Over 1333cm -1 The half-width of the peak at each of the above five points is calculated as follows: Of the half-widths of the peaks at the above five points, the half-width at the center and the half-widths at the other four points are weighted and averaged at a ratio of 4:1.

[0042] For the same single crystal diamond, by setting the five measurement regions described above and calculating the weighted average, the crystallinity of the sample, such as distortion, can be uniquely evaluated and compared between samples.

[0043] (etch pit density) In this specification, the etch pit density is an index showing the amount of linear defects resulting from needle-like defects extending linearly in a single crystal diamond, and is measured by an etching test described later. The smaller the etch pit density of a single crystal diamond, the fewer defects there are in the single crystal diamond, indicating that the single crystal diamond has a higher crystallinity. The single crystal diamond of this embodiment has an etch pit density of 10,000 pieces / cm. 2 or less and has high crystallinity.

[0044] The upper limit of the etch pit density of single crystal diamond is 10,000 / cm from the viewpoint of improving crystallinity. 2 less than 1000 particles / cm 2 Preferably less than 100 pieces / cm 2 Less than 10 pieces / cm is more preferable. 2 The lower limit of the etch pit density of single crystal diamond is more preferably 0 pits / cm. 2 The etch pit density of single crystal diamond can be 0 pcs / cm or more. 2 More than 10000 pieces / cm 2 Less than 0 pieces / cm is preferable. 2 More than 1000 pieces / cm 2 Less than 0 pieces / cm is more preferable. 2 More than 100 pieces / cm 2 More preferably, 0 pieces / cm 2 More than 10 pieces / cm 2 The following is even more preferred:

[0045] The etch pit density of the single crystal diamond is measured by an etching test, specifically, by the following procedure.

[0046] A single crystal diamond is immersed in a potassium nitrate (KNO3) molten solution, which serves as an etching solution, and heated in a platinum crucible at 600-700°C for 0.5-2 hours. After slow cooling, the single crystal diamond is removed and the main growth surface is observed under an optical microscope. Inverted pyramidal etch pits are observed, and the size of the etch pits is adjusted by adjusting the crucible temperature and processing time depending on the etch pit density. To achieve this adjustment, the diamond is first processed under conditions (crucible temperature and processing time) that result in small etch pits. After roughly determining the etch pit density, the conditions for measurement (crucible temperature and processing time) are set.

[0047] The size of the etch pits is selected to match the etch pit density and prevent the individual etch pits from overlapping. In the process of enlarging the etch pits, the number of etch pits does not change, so the size of the etch pits is adjusted to match the size of the field of view to be evaluated (etch pit density). As an example of adjustment, 2 When the density is higher than this, the size of the etch pits should be about 5 to 20 μm square, and they should not overlap. Three areas with a high density of etch pits on the growth surface should be selected, and rectangular measurement areas of 1 mm or less should be set up in each area. In each measurement area, the area where 100 etch pits exist is measured, and a 1 cm measurement is made based on the number of etch pits (100) and the area. 2 The average of the etch pit densities in each of the three measurement regions is defined as the "etch pit density of the single crystal diamond" in this specification.

[0048] Etch pit density is 5000 / cm 2 For samples with a density of less than 1 / 1000, the conditions for etch pit formation (crucible temperature and treatment time) are changed to gradually enlarge the etch pits so that they can be seen even at low magnification under a microscope. For samples where the high density areas cannot be identified, the etch pits are counted over the entire sample growth surface and measured over a 1cm 2 The number of etch pits per unit area (etch pit density) is calculated. This etch pit density is referred to as the "etch pit density of the single crystal diamond" in this specification.

[0049] In this specification, etch pits refer to clear inverted pyramidal depressions. Etch pits of approximately the same size are distributed and can be determined to be etch pits. 5000 / cm 2 In the above samples, the etch pits were counted from 1 / 4 of the size of the majority etch pits (the size of d50 based on the area) to the largest size, and the number was 5000 / cm 2 For samples smaller than this size, etch pits are counted from 1 / 8 of the size of the majority of etch pits (the size of d50 based on area) to the largest size.

[0050] In this specification, 1 cm 2 The number of etch pits per unit area (etch pit density) corresponds to the density of the linear defects. For the same single crystal diamond, the average number of etch pits measured by the above measurement method is taken as the "density of dislocation defects penetrating the principal growth surface" in this embodiment.

[0051] (Nitrogen content) Since the presence of a single nitrogen atom in a single crystal diamond causes crystal defects and distortion, it is preferable to have a small amount of nitrogen. However, nitrogen is an essential luminescence center element for applications using nuclear spin as a memory, and must optimally interact with atoms having nuclear spin. Therefore, the presence of as much nitrogen as possible increases the probability of interaction, making it preferable. Therefore, there is an optimal range. In the single crystal diamond of this embodiment, the nitrogen content based on the number of atoms (also referred to as "nitrogen content" in this specification) is 0.0001 ppm or more and 0.1 ppm or less. This reduces crystal defects and distortion in the single crystal diamond, allowing nitrogen to optimally interact with atoms having nuclear spin.

[0052] From the viewpoint of single NV center, the lower limit of the nitrogen content of single crystal diamond is more than 0.0001ppm, more preferably more than 0.001ppm, more preferably more than 0.005ppm, more preferably more than 0.01ppm.The nitrogen content of single crystal diamond is more than 0.0001ppm and less than 0.1ppm, preferably more than 0.001ppm and less than 0.1ppm, more preferably more than 0.005ppm and less than 0.1ppm, more preferably more than 0.01ppm and less than 0.1ppm.

[0053] The nitrogen content in single crystal diamond is measured by secondary ion mass spectrometry (SIMS) or ESR.

[0054] (Boron content) Boron in single crystal diamond causes crystal defects and distortion. In the single crystal diamond of this embodiment, the content of boron based on the atomic number (herein, "boron content") is preferably equal to or less than the content of nitrogen based on the atomic number. This reduces crystal defects and distortion in the single crystal diamond.

[0055] The upper limit of the boron content in single-crystal diamond is set at NV center, which is essential for the insertion and removal of spins in applications where nuclear spins are used as memory. From the viewpoint of ensuring the existence and increasing the number of effective NV centers, -The boron that eliminates the center is preferably equal to or less than the nitrogen content, more preferably equal to or less than 10% of the nitrogen content, even more preferably equal to or less than 1% of the nitrogen content, and even more preferably equal to or less than 0.1% of the nitrogen content.The lower limit of the boron content of single crystal diamond is preferably 0 ppm or more, since the lower the better.The boron content of single crystal diamond is preferably 0 ppm or more and equal to or less than the nitrogen content, more preferably 0 ppm or more and equal to or less than 10% of the nitrogen content, even more preferably 0 ppm or more and equal to or less than 1% of the nitrogen content, and even more preferably 0 ppm or more and equal to or less than 0.1% of the nitrogen content.From the viewpoint of manufacturing, the lower limit of the boron content of single crystal diamond is preferably 1% or more of the nitrogen content.Therefore, the boron content of single crystal diamond is preferably 1% or more and equal to or less than 10% of the nitrogen content.

[0056] On the other hand, when single crystal diamond contains nitrogen and boron in a predetermined ratio, the crystal defects and distortion caused by nitrogen and boron tend to be alleviated.From this point of view, the boron content of single crystal diamond is preferably more than 0.5% of nitrogen content but less than nitrogen content, more preferably 1% or more and 30% or less of nitrogen content, and even more preferably 3% or more and 10% or less of nitrogen content.Boron has the effect of reducing the NV center that can be used for nuclear spin memory, but also has the effect of reducing crystal defects and distortion, preventing crystal disturbance, and creating the time allowance for nuclear spin to exchange information with electron spin.

[0057] The boron content in a single crystal diamond is measured by secondary ion mass spectrometry (SIMS).

[0058] ( 13 C content) In the single crystal diamond of this embodiment, 13 The content of C based on the number of atoms is preferably 0.01% or more and 1.0% or less. 13 C is the atom that provides the nuclear spin for memory, so a certain amount of range is required. 13When the C content is within the above range, the probability of interaction with the NV center increases. 13 The upper limit of the C content based on the number of atoms is: 13 From the viewpoint of preventing multiple overlaps of C atoms, the content is 1.0% or less, preferably 0.5% or less, more preferably 0.3% or less, and even more preferably 0.1% or less. 13 The lower limit of the C content based on the number of atoms is preferably 0.01% or more, from the viewpoint of the necessity of being adjacent to the NV center at a certain distance in order to make it a memory. 13 The content of C based on the number of atoms is 0.01% or more and 1.0% or less, preferably 0.01% or more and 0.5% or less, more preferably 0.01% or more and 0.3% or less, and even more preferably 0.01% or more and 0.1% or less. 13 The C content is approximately 1.1%.

[0059] Single crystal diamond 13 The C content based on the atomic number is measured by SIMS analysis.

[0060] It has been confirmed that there is no variation in the measurement results even if the measurement area is set at any different location for the same single crystal diamond.

[0061] (Number of defects) The defects contained in single crystal diamond include point defects such as vacancies, linear needle-like defects, impurities, stacking faults, distortions, 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 the 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 specification, the number of defects is an index that indicates the amount of defects derived from the number of linear defects in single crystal diamond.

[0062] The number of defects in the single crystal diamond of this embodiment is 1000 / cm 2It is preferable that the number of defects in the single crystal diamond is 1000 / cm or less. This further reduces crystal defects and distortion in the single crystal diamond. From the viewpoint of reducing crystal defects and distortion, the upper limit of the number of defects in the single crystal diamond is 1000 / cm. 2 Preferably less than 100 pieces / cm 2 Less than 10 pieces / cm is more preferable. 2 More preferably, 5 or less per cm 2 The lower limit of the number of defects in a single crystal diamond is more preferably 0 defects / cm. 2 The number of defects in single crystal diamond is 0 / cm. 2 More than 1000 pieces / cm 2 Less than 0 pieces / cm is preferable. 2 More than 100 pieces / cm 2 Less than 0 pieces / cm is more preferable. 2 More than 10 pieces / cm 2 More preferably, 0 pieces / cm 2 More than 5 pieces / cm 2 The following is even more preferred:

[0063] (phase difference) Diamond is an isotropic crystal, so it usually has an isotropic refractive index (dielectric constant). However, when defects and distortions exist in a diamond, the diamond exhibits birefringence. When circularly polarized light is irradiated onto a defect in a 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). When the refractive index of a diamond is not isotropic due to defects or distortions in the crystal, the slowest polarization direction (slow axis) and the fastest polarization direction (fast axis) are 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 determining the orientations of the major and minor axes of the ellipse and the ratio of the lengths of the major and minor axes. Furthermore, by combining lenses and microscopes, information on the local phase difference in a microscopic area 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.

[0064] The phase difference measured at each local position is the value integrated in the thickness direction of the substrate. Therefore, samples of the same thickness should be compared, or they should be normalized by thickness before comparison. When normalized by thickness, the phase difference is displayed as a value converted to a 1mm thickness (unit: nm / mm). For example, to convert to a 1mm thickness, a value measured at a 0.1mm thickness should be multiplied by 10, a value measured at a 0.2mm thickness by 5, and a value measured at a 0.5mm thickness by 2.

[0065] The two-dimensional retardation value indicates the distribution within the substrate surface. A reasonable way to express the characteristics of a substrate is to represent it by the average value within a given surface. The average retardation of a substrate refers to the average value over the effective area within the substrate's size. Here, the effective area refers to the area excluding the edges of the substrate, since the retardation value cannot be accurately measured at the edges. More precisely, if 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 90% of the distance from the center of gravity. Here, the average value over the effective area does not mean the retardation per area, but rather the value obtained by averaging the retardation of each local area across the surface, i.e., the average frequency distribution of the retardation within the surface. Therefore, the average value is also expressed in units of nm / mm.

[0066] Even if the amount of defects in a single crystal 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 if the phase difference is the same, 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.

[0067] The value of the phase difference shows a positive correlation with the amount of defects and the magnitude of distortion in the single crystal diamond. The average phase difference per unit thickness of the single crystal diamond of this embodiment is preferably 30 nm / mm or less. This further reduces the crystal defects and distortion of the single crystal diamond. From the viewpoint of reducing defects and distortion, the upper limit of the average phase difference per unit thickness of the single crystal diamond is preferably 30 nm / mm or less, more preferably 10 nm / mm or less, even more preferably 5 nm / mm or less, and even more preferably 2 nm / mm or less. The lower limit of the average phase difference per unit thickness of the single crystal diamond is preferably 0 nm / mm. From the viewpoint of manufacturing, the lower limit of the standard deviation of the phase difference can be, for example, 0.01 nm / mm or more. The average phase difference per unit thickness of the single crystal diamond is preferably 0 nm / mm or more to 30 nm / mm or less, more preferably 0 nm / mm or more to 10 nm / mm or less, even more preferably 0 nm / mm or more to 5 nm / mm or less, and even more preferably 0 nm / mm or more to 2 nm / mm or less. From the viewpoint of manufacturing, the average phase difference per unit thickness of the single crystal diamond is preferably 0.01 nm / mm or more and 30 nm / mm or less, more preferably 0.01 nm / mm or more and 10 nm / mm or less, even more preferably 0.01 nm / mm or more and 5 nm / mm or less, and even more preferably 0.01 nm / mm or more and 2 nm / mm or less.

[0068] The phase difference per unit thickness of a single crystal diamond is measured using the following procedure. First, the single crystal diamond is processed into a plate shape with a thickness of 0.1 to 5 mm. Processing methods that can be used include polishing and etching. The value proportional to 1 mm of the single crystal diamond thickness is the phase difference per unit thickness.

[0069] Next, the phase difference of the single-crystal diamond was measured using a birefringence distribution measurement device (Photonic Lattice, Inc., "WPA-micro" (trademark) or "WPA-100" (trademark)). Generally, phase differences exceeding 90 degrees (1 / 4 of the wavelength) are difficult to distinguish. However, the birefringence distribution measurement device uses an integrated waveplate instead of an integrated polarizer, extending the measurement range to 180 degrees (1 / 2 of the wavelength). Experiments have shown that using three wavelengths (one central wavelength and two wavelengths close to it) extends the measurement range to 5–6 times the wavelength. The measured values ​​obtained with the birefringence distribution measurement device were processed using software (Photonic Lattice, Inc., "PA-View" (trademark)) to determine the average phase difference per unit thickness.

[0070] For the same single crystal 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.

[0071] (NV Center) As shown in Figure 1, the NV center 100 is a complex defect consisting of a substitutional nitrogen atom (N) in a diamond crystal and a vacancy (V) created by the loss of the adjacent carbon atom. The NV center has captured one electron and is negatively charged, forming a state known as a spin triplet, which allows spin manipulation with light. The NV center can be detected by a single photon and is stable, making it very easy to use and suitable for applications using nuclear spin as memory.

[0072] The single crystal diamond of this embodiment contains an NV center, and the NV center content is preferably 0.1 ppm or less. The NV center can be formed, for example, by irradiating the single crystal diamond with an electron beam of 3 MeV energy followed by vacuum annealing at 900 ° C. The electron beam irradiation dose is preferably adjusted according to the nitrogen content of the single crystal diamond to achieve an adequate dose. This allows the single crystal diamond to form a single NV center without noise, making it suitable for applications using nuclear spins as memory. In this specification, "single crystal diamond contains an NV center" means that the NV center content of the single crystal diamond is at or above the concentration at which fluorescence can be detected using the NV center measurement method described below. From the viewpoint of fluorescence detection sensitivity, the lower limit of the NV center content of the single crystal diamond is preferably 0.00001 ppm or more, more preferably 0.001 ppm or more, and even more preferably 0.005 ppm or more. The single crystal diamond contains an NV center, and the NV center content is preferably 0.1 ppm or less, more preferably 0.00001 ppm or more and 0.1 ppm or less, even more preferably 0.001 ppm or more and 0.1 ppm or less, and even more preferably 0.005 ppm or more and 0.1 ppm or less.

[0073] The NV center content of single-crystal diamond is observed and calculated using electron spin resonance (ESR). In addition, for low concentrations, it can be measured by observing with a fluorescence microscope and counting single NV centers, and for high concentrations, it can be calculated from the fluorescence intensity ratio by converting the low concentration value into fluorescence intensity.

[0074] (size) The diameter of the inscribed circle of the main surface of the single crystal diamond is preferably 3 mm or more. This makes it easy to process the single crystal diamond into a memory component. Furthermore, manufacturing costs are reduced when producing a large number of small memory components with a diameter of 0.5 mm or less. From the viewpoint of ease of processing and reduced manufacturing costs, the lower limit of the diameter of the inscribed circle of the main surface of the single crystal diamond is preferably 3 mm or more, more preferably 4 mm or more, even more preferably 5 mm or more, and even more preferably 7 mm or more. From the viewpoint of manufacturing, the upper limit of the diameter of the inscribed circle of the main surface of the single crystal diamond can be 50 mm or less. The diameter of the inscribed circle of the main surface of the single crystal diamond is preferably 3 mm or more and 50 mm or less, more preferably 4 mm or more and 50 mm or less, even more preferably 5 mm or more and 50 mm or less, and even more preferably 7 mm or more and 50 mm or less.

[0075] The diameter of the inscribed circle of the main surface of the single crystal diamond is measured using an optical microscope with a length measurement function.

[0076] (single sector content) In the single crystal diamond of this embodiment, the content of the single sector is preferably 70% by volume or more. This significantly reduces the impact of sector boundaries, which cause distortion, on the entire single crystal. Furthermore, manufacturing costs are reduced compared to mass-producing small, homogeneous memory elements with a diameter of 0.5 mm or less. Here, a sector refers to a region grown from a specific, different crystal plane (base substrate). Examples of sectors contained in single crystal diamond include the {001} sector, {113} sector, {115} sector, and {111} sector. Each crystal plane of each plane orientation grows on the base substrate, forming a single crystal. Here, the {abc} sector refers to a region grown from the {abc} plane (base substrate). Of these, the single sector is preferably the {100}, {111}, or {113} sector, from the viewpoint of easily forming stable and flat surfaces.

[0077] The lower limit of the single sector content of single crystal diamond is preferably 70% by volume or more, more preferably 80% by volume or more, even more preferably 90% by volume or more, and even more preferably 95% by volume or more.The upper limit of the single sector content of single crystal diamond can be 100% by volume or less.The single sector content of single crystal diamond is preferably 70% by volume or more and 100% by volume or less, more preferably 80% by volume or more and 100% by volume or less, even more preferably 90% by volume or more and 100% by volume or less, and even more preferably 95% by volume or more and 100% by volume or less.

[0078] The single-sector content of a single-crystal diamond is measured using the following procedure. Growth sectors differ in impurity concentration, resulting in different fluorescence intensities. Therefore, photoluminescence (PL) or cathodoluminescence (CL) is used to confirm the distribution of fluorescence on the substrate surface, revealing clear linear boundaries. Furthermore, cross-sections can be made along the growth direction to confirm the depthwise boundaries. Since sector boundaries are approximately linear in two dimensions or approximately flat in three dimensions, the area ratio, volume ratio, and even the content of the largest sector can be determined using linear or flat boundaries. Furthermore, the three-dimensional sector area distribution can be determined using a confocal microscope. Furthermore, the proportion of single sectors can be calculated based on the surface area ratio.

[0079] [Embodiment 2: Method for manufacturing single crystal diamond] The single crystal diamond of the first embodiment can be synthesized by the temperature difference method of high temperature and high pressure synthesis.

[0080] When synthesizing single-crystal diamond using the temperature gradient method of high-temperature, high-pressure synthesis, the seed substrate has a significant effect on the crystallinity of the single-crystal diamond grown thereon.

[0081] Conventional seed crystals (seed substrates) are less than 0.5 mm in size, and their thickness is also comparable. This seed crystal utilizes the entire crystal. Specifically, the crystal is grown not only from the top surface of the seed crystal but also from the sides to enlarge the entire crystal. If the seed crystal itself is small, the absolute number of defects contained in the seed crystal will be small. Therefore, the defect density in the grown single crystal diamond will also be low. For this reason, a small seed crystal size is preferable to grow a single crystal diamond with a low defect density.

[0082] On the other hand, it is known that a larger seed crystal is advantageous for growing large single-crystal diamond. However, a larger seed crystal has the disadvantage of increasing the absolute number of defects and forcing the use of areas with high defect density within the single crystal. Furthermore, a large seed crystal can result in the inclusion of five or more growth sectors. Different growth sectors have different impurity concentrations, which adversely affect crystal distortion.

[0083] In order to obtain high-quality large-sized single crystal diamond, it is important to make the size of seed substrate large.The size of the main surface of seed substrate is preferably the diameter of its inscribed circle of 1.0mm or more, more preferably more than 1.0mm, more preferably 2.0mm or more, and even more preferably 3.0mm or more.The upper limit of the size of seed substrate is not particularly limited, but from the viewpoint of manufacturing, it can be, for example, 50mm or less.

[0084] In the manufacturing method of this embodiment, since the growth of crystals from the side surfaces of the seed substrate is not important, a thin substrate is preferable. From the viewpoint of suppressing the occurrence of cracks under high temperature and high pressure, the ratio of the main surface size (diameter of the inscribed circle) to the thickness (= thickness / size) is preferably 0.1 or more and 0.5 or less.

[0085] As the seed substrate size increases, the resulting single-crystal diamond will have a larger growth sector that is the same as the main surface. Depending on how the substrate is cut, it is possible to produce a large substrate with a single growth sector. It is also possible to produce a substrate with a larger proportion of a single growth sector.

[0086] The next point to consider after the size of the seed substrate is the defect amount and the number of growth sectors in the seed substrate. The etch pit density on the main surface of the seed substrate is 1×10 5 pieces / cm 2 Less than 5×10 is preferable 3 pieces / cm 2 Less than 1000 particles / cm is more preferable. 2 Less than 100 pieces / cm is more preferable. 2 The lower limit of the etch pit density is not particularly limited, and is preferably 0 pits / cm. 2 It can be more than that.

[0087] The growth sectors are two regions grown on different surface orientations. Because the different growth sectors have different impurity concentrations, strain accumulates near their boundaries. Therefore, the number of growth sectors included on the primary surface of the seed substrate is two or less, and preferably one. The number of growth sectors is preferably between one and two.

[0088] In the manufacturing method of this embodiment, as described above, a single crystal diamond with a controlled etch pit density and number of growth sectors is used as a seed substrate, thereby making it possible to obtain a high-quality single crystal diamond with few defects and distortions, which can improve memory function and memory stability when used as a material for memory components.

[0089] The ratio N2 / N1 of the nitrogen content N2 of the single crystal diamond grown on the seed substrate based on the number of atoms to the nitrogen content N1 of the seed substrate based on the number of atoms is preferably 0.2 or more and 5 or less. This eliminates the lattice mismatch between the seed substrate and the single crystal diamond. Therefore, it is possible to obtain a high-quality single crystal diamond with few defects and distortions, which can improve memory function and memory stability when used as a material for memory components.

[0090] The specific manufacturing method is as follows. (Step of Preparing Seed Substrate) A diamond seed substrate to be used in the temperature difference method described below is prepared. As the diamond seed substrate, the following diamond seed substrate A or diamond seed substrate B is prepared.

[0091] As shown in Figures 2 and 3, each single-crystal diamond material synthesized by the temperature difference method has multiple growth sectors. In Figures 2 and 3, 24a and 34a indicate first sectors, and 24b and 34b indicate second sectors. The first and second sectors are different. The first and second sectors are, for example, the {001} sector, the {113} sector, the {115} sector, or the {111} sector, etc.

[0092] The diamond seed substrate A has a size (diameter of the inscribed circle) of 1 mm or more, preferably 5 mm or more, and a nitrogen content of 0.01 ppm or less based on the number of atoms. The etch pit density is 5×10 3 pieces / cm 2 Because seed substrate A has a low nitrogen content, even if it includes multiple sectors, it is possible to reduce the minute lattice mismatch caused by the difference in nitrogen content between the sectors and the resulting strain in the seed substrate itself.

[0093] The diamond seed substrate B has a size of 1 mm or more, preferably 5 mm or more, and a nitrogen content based on the number of atoms of 100 ppm or more and 150 ppm or less. The etch pit density is 1×10 5 pieces / cm 2 Seed substrate B ensures a large seed substrate size at the expense of defects. By using a large seed substrate, the single growth sector ratio of the single crystal diamond grown thereon can be increased, thereby reducing distortion in the grown single crystal diamond.

[0094] From the diamond seed substrate A and diamond seed substrate B, diamond seed substrates 22, 32a, and 32b having single or multiple growth sectors can be cut out, as shown in Figures 2 and 3. The cutting is preferably carried out using a water-guard laser processing machine. This improves processing accuracy, and diamond seed substrates of 1 mm or more and a single growth sector (one sector) can be obtained. The size of the diamond seed substrate is preferably 1.5 mm or more.

[0095] (The process of growing single crystal diamond) Next, a single crystal diamond is grown on the seed substrate using a high-temperature, high-pressure synthesis method, thereby obtaining the single crystal diamond of embodiment 1. The single crystal diamond has reduced crystal defects and strain.

[0096] The high-temperature, high-pressure temperature difference method is carried out using a sample chamber having the configuration shown in FIG. 4, for example.

[0097] As shown in Figure 4, in the sample chamber 10 used to produce a single crystal diamond 51, an insulator 52, a carbon source 53, a solvent metal 54, and a diamond seed substrate 55 are arranged in a space surrounded by a graphite heater 57, and a pressure medium 56 is arranged outside the graphite heater 57. The temperature difference method is a method in which a vertical temperature gradient is created inside the sample chamber 10, and a high temperature section (T high ) carbon source 53, low temperature part (T low ) and a solvent metal 54 is placed between the carbon source 53 and the diamond seed substrate 55, and the temperature is maintained at or above the temperature at which the solvent metal 54 dissolves and at or above the pressure at which the diamond becomes thermally stable, thereby growing a single crystal diamond 51 on the diamond seed substrate 55.

[0098] Diamond powder is preferably used as the carbon source 53. Graphite or pyrolytic carbon can also be used. The solvent metal 4 can be one or more metals selected from iron (Fe), cobalt (Co), nickel (Ni), manganese (Mn), etc., or an alloy containing these metals.

[0099] It is preferable to add titanium (Ti) as a nitrogen getter at a concentration of 3.0 mass % or more to the solvent metal 54. This makes it possible to make the nitrogen content in the single crystal diamond 0.1 ppm or less based on the number of atoms.

[0100] It is also preferable to add boron (B) at a concentration of 0.002 to 0.2 ppm to the solvent metal 54. This allows the boron content in the single crystal diamond to be 0.00001 to 0.001 ppm based on the number of atoms.

[0101] In the temperature difference method, 13 In order to intentionally leave C in the crystal, the purity of the carbon source, graphite, is controlled. 13 The carbon content can be controlled. This method is not used in the conventional temperature difference method.

[0102] The nitrogen content, based on the atomic number, of the single crystal diamond grown on the diamond seed substrate is preferably 0.1 to 10 times the nitrogen content, based on the atomic number, of the diamond seed substrate, which makes it possible to mitigate defects and distortions in the crystal caused by the addition of nitrogen.

[0103] The NV center in a single crystal diamond is irradiated with an electron beam of 3 MeV energy at a rate of 3 × 10 per 1 ppm of nitrogen atom content in the single crystal diamond. 17 cm -2 The single crystal diamond can be formed by irradiating the electron beam at a dose (amount of electron beam irradiation) of 10 ... [Example]

[0104] The present embodiment will be described in more detail with reference to examples, although the present embodiment is not limited to these examples.

[0105] In the following examples, the Raman shift of the Raman spectrum of single crystal diamond is 1332 cm -1 Over 1333cm -1 The half-width of the following peaks was measured using a double monochromator Raman spectrometer with a wavenumber resolution of 0.5 cm. -1 The measurements were made using the following method or a LabRAM HR-800 (HORIBA JOBIN YVON) device, and the values ​​were converted into the half-width of the diamond itself, taking into consideration the light source and the resolution of the device.

[0106] <Manufacturing single crystal diamond> Diamond seed substrates containing a single growth sector or multiple sectors are cut out from single-crystal diamond materials produced by the temperature difference method to prepare diamond seed substrates A and B described in the above-mentioned embodiment 2. The type, size, number of growth sectors contained in the diamond seed substrate, and etch pit density of the diamond seed substrate for each sample are shown in the "Type," "Size," "Number of growth sectors," and "Etch pit density" columns under "Diamond seed substrate" in Table 1.

[0107] [Table 1]

[0108] For example, the size of the diamond seed substrate used in Sample 1 is 2.0 mm, and the etch pit density is 5 / cm 2 is.

[0109] Next, single-crystal diamond is grown on the diamond seed substrate using the high-temperature, high-pressure temperature gradient method to obtain the single-crystal diamond of each sample. The temperature gradient method is performed using a sample chamber with the configuration shown in Figure 4.

[0110] carbon isotopes 12Methane gas with a carbon concentration of 99.95% or more is passed through a titanium sponge heated to 600°C or higher to remove nitrogen from the methane gas. This nitrogen-removed methane gas is then sprayed onto a Ni-free Ta substrate heated to a high temperature of 1900°C in a vacuum chamber. This decomposes the methane gas onto the Ta substrate, and a 10mm x 10mm sample of carbon isotopes is formed on the Ta substrate. 12 Graphite with a carbon concentration of 99.95 to 99.99% is formed. This graphite is used as the carbon source.

[0111] The metal solvent is made of Fe and Co with a trace amount of boron added, with the solvent composition being Fe / Co = 60 / 40 (weight ratio). The boron content in the solvent was analyzed by SIMS and found to be 0.2 ppm. Furthermore, a high-purity Fe-Co-Ti alloy is prepared as the metal solvent by adding Ti in the amount shown in "Ti addition amount" under "Synthesis conditions" in Table 1 (3 mass % for sample 1) as a nitrogen getter. In addition, carbon isotopes from the surroundings are also added. 12 To prevent the inclusion of C, the heater surface is treated with carbon isotopes of 99.999% or more. 12 Coat it with graphite having a concentration of C.

[0112] Next, the diamond synthesis system, which was composed of a seed crystal, a solvent, and isotope-enriched high-purity graphite as a carbon source, was placed in order from the bottom up, and was then enclosed in a cup-shaped cell made of Fe that did not contain carbon or Ni. -3 The vacuum is sealed at 1000 kJ / cm² or less.

[0113] This is grown on the seed crystal by using an ultra-high pressure generator at a pressure of 5.5 Pa and a temperature of 1300°C for the time specified in the "Synthesis time" column under "Synthesis conditions" in Table 1 (for example, 120 hours for sample 1). After that, the temperature is first lowered to room temperature, then the pressure is reduced, and the synthesized single crystal diamond is removed.

[0114] The single crystal diamond is irradiated with an electron beam of 3 MeV energy at a rate of 3 × 10 per 1 ppm of nitrogen atom content in the single crystal diamond. 17 cm -2The single crystal diamond was then annealed in vacuum at 900° C. to obtain the single crystal diamond of each sample.

[0115] <Evaluation> Before electron beam irradiation, the single crystal diamond samples were measured for size, half-width of the X-ray diffraction rocking curve, half-width of the Raman spectrum peak, etch pit density, number of defects confirmed in the X-ray topography image, average phase difference, nitrogen content, 13 The C content, boron content, cut size, and single sector content were measured. The NV center content of each single crystal diamond sample after electron beam irradiation was measured. The specific measurement method for each item is as described in embodiment 1. The results are shown in the "Size," "FWHM of Xrc," "Raman half-width," "Etch pit density," "Number of defects," "Average phase difference," "N," "13C," "B," "Cut size," "Single sector," and "NV" columns of single crystal diamond in Table 2. The thickness of all samples evaluated in this example was 0.4 mm. The size of the single crystal diamond, the half-width of the X-ray diffraction rocking curve, the half-width of the peak of the Raman spectrum, the etch pit density, the number of defects confirmed in the X-ray topography image, the average phase difference, the nitrogen content, 13 It was confirmed that the measurement results of C content, boron content, cut size, and single sector content were almost unchanged before and after electron beam irradiation.

[0116] [Table 2]

[0117] For example, the nitrogen content in the crystal of Sample 1 was measured by ESR and found to be 0.098 ppm. The boron content in the crystal was analyzed by SIMS and found to be 0.0008 ppm. 13 The carbon content was analyzed to be 0.03%. The NV center content in the crystal was measured by ESR to be 0.05 ppm. -1The Raman spectrum was measured using a double monochromator Raman spectrometer. -1 The half-width was calculated to be 1.55 cm -1 The obtained diamond was observed with a polarized light transmission microscope to evaluate the distortion, and the average phase difference was 1 nm / mm. The half-width of the rocking curve of the X-ray diffraction by CuKα was measured using a double crystal method in which the (004) plane of a synthetic diamond crystal was arranged in parallel as the first crystal, and it was found to be 5 seconds. Furthermore, when defects in the crystal were observed by X-ray topography, it was found that the number of linear dislocation defects was 7 / cm. 2 Next, the same diamond was placed in molten KNO3 salt (600-700°C) for 1 hour, and the number of etch pits in the densely packed area was evaluated to be 7 / cm. 2 It was.

[0118] The smaller the values ​​of the single crystal diamond's "size," "Xrc FWHM," "Raman half-width," "etch pit density," "number of defects," and "average phase difference," the smaller the effect of disturbances on NV, and therefore the better the performance of memory components using that single crystal diamond. The larger the "cutting size" and "single sector" of the single crystal diamond, the more single crystal can be used for memory components, improving productivity.

[0119] Although the embodiments and examples of the present disclosure have been described above, it is originally intended 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 embodiments and examples described above, and is intended to include meanings equivalent to the claims and all modifications within the scope of the claims. [Explanation of symbols]

[0120] 21, 31 Single crystal diamond, 22, 32a, 32b, 55 Diamond seed substrate, 5 Abrasive grain seed crystal, 10 Sample chamber, 24a, 34a First sector, 24b, 34b Second sector, 51 Single crystal diamond, 52 Insulator, 53 Carbon source, 54 Solvent metal, 56 Pressure medium, 57 Graphite heater, 100 NV center

Claims

1. The half-width of the X-ray diffraction rocking curve is 20 seconds or less, The half-width of the X-ray diffraction rocking curve is measured by X-ray diffraction by a double crystal method, using a diamond crystal as the first crystal in a (004) plane parallel arrangement with CuKα radiation; Raman shift of Raman spectroscopy: 1332 cm －１ 1333cm or more －１ The half-width of the following peaks is 2.0 cm －１ is as follows: The etch pit density is 10,000 / cm ２ is as follows: The etch pit density is measured by an etching test; the nitrogen content based on the number of atoms is 0.0001 ppm or more and 0.1 ppm or less, １３ A single-crystal diamond having a C content of 0.01% or more and 1.0% or less based on the number of atoms.

2. the half-width of the X-ray diffraction rocking curve is 10 seconds or less; The Raman shift of the Raman spectrum is 1332 cm －１ 1333cm or more －１ The half-width of the peak below is 1.9 cm －１ is as follows: The etch pit density is 1000 pits / cm ２ is as follows: The number of defects confirmed in the X-ray topography image is 1000 / cm ２ 2. A single crystal diamond according to claim 1, wherein:

3. 3. The single crystal diamond according to claim 1, wherein the average phase difference per unit thickness of the single crystal diamond is 30 nm / mm or less.

4. 4. The single-crystal diamond according to claim 3, wherein the average phase difference is 10 nm / mm or less.

5. 5. The single crystal diamond according to claim 1, wherein the single crystal diamond contains an NV center, and the content of the NV center is 0.1 ppm or less.

6. 6. The single-crystal diamond according to claim 5, wherein the content of the NV center is 0.00001 ppm or more and 0.1 ppm or less.

7. 7. A single crystal diamond according to claim 1, wherein the boron content in said single crystal diamond based on the atomic number is equal to or less than the nitrogen content in said single crystal diamond based on the atomic number.

8. 8. A single-crystal diamond according to claim 7, wherein the content of boron based on atomic number is 10% or less of the content of nitrogen based on atomic number.

9. 8. The single-crystal diamond according to claim 7, wherein the content of boron on an atomic number basis is more than 10% of the content of nitrogen on an atomic number basis and is equal to or less than the content of nitrogen on an atomic number basis.

10. 8. A single-crystal diamond according to claim 7, wherein the boron content in terms of atomic number is 1% or more and 10% or less of the nitrogen content in terms of atomic number.

11. 11. A single crystal diamond according to claim 1, wherein the diameter of an inscribed circle of a major surface of the single crystal diamond is 3 mm or more.

12. 12. A single crystal diamond according to claim 11, wherein the diameter is 5 mm or greater.

13. 13. A single crystal diamond according to any one of claims 1 to 12, wherein the single sector content of the single crystal diamond is 70% by volume or more.

14. 14. A single crystal diamond according to claim 13, wherein the single sector content is 90% by volume or more.

15. A method for producing a single crystal diamond according to any one of claims 1 to 14, comprising: providing a seed substrate; growing a single crystal diamond on the seed substrate using a high-temperature, high-pressure synthesis method; the size of the primary surface of the seed substrate is such that the diameter of the inscribed circle thereof exceeds 1.0 mm; The etch pit density of the main surface is 1×10 ５ pieces / cm ２ is as follows: A method for producing a single crystal diamond, wherein the primary surface of the seed substrate includes no more than two growth sectors.

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