Single-crystal diamond and method for manufacturing the same

Abstract

Provided is a single-crystal diamond wherein: the half width of an X-ray diffraction rocking curve is 20 seconds or less, the half width of the X-ray diffraction rocking curve being measured using CuKα rays in X-ray diffraction by means of a double-crystal method in which a diamond crystal is used as a first crystal, with a (0004) plane parallel arrangement; the half width of a peak at the Raman shift of 1332 cm-1 to 1333 cm-1 in the Raman spectrum is 2.0 cm-1 or less; the etch pit density is 10000 / cm2 or less, the etch pit density being measured by means of an etching test; and the nitrogen content in terms of the number of atoms is more than 0.1 ppm and at most 50 ppm.

Description

[Technical Field]

[0001] This disclosure relates to single-crystal diamond and a method for producing the same. This application claims priority under Japanese Patent Application No. 2021-061207, filed on March 31, 2021. All contents contained in said Japanese Patent Application are incorporated herein by reference. [Background technology]

[0002] Conventionally, diamond has 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. In particular, in the fields of optical components, laser windows, spectroscopic crystals, monochromators, anvils for ultra-high pressure generators, and semiconductor diamond substrates, diamonds with fewer crystal defects and distortions have been developed to improve performance (for example, 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 [Overview of the Initiative]

[0004] This disclosure states that the full width at half maximum of the X-ray diffraction rocking curve is 20 seconds or less. The full width at half maximum of the aforementioned X-ray diffraction rocking curve was measured using the two-crystal method, with a diamond crystal as the first crystal, in a (004) plane parallel arrangement, and using CuKα rays. Raman spectroscopy spectrum with a Raman shift of 1332 cm⁻¹ -1 Over 1333cm -1The full width at half maximum (FWHM) of the peak in the following locations is 2.0 cm. -1 The following: The etch pit density is 10,000 pits / cm³. 2 The following: The aforementioned etch pit density is measured by etching tests. This is a single-crystal diamond with a nitrogen content based on the number of atoms, ranging from over 0.1 ppm to 50 ppm.

[0005] This disclosure relates to a method for manufacturing the above-mentioned single-crystal diamond, The process of preparing the seed substrate, The process includes growing a single-crystal diamond on the aforementioned seed substrate using a high-temperature, high-pressure synthesis method, The size of the main surface of the aforementioned substrate is such that the diameter of its inscribed circle is greater than 1.0 mm. The etch pit density of the main surface is 1 × 10 5 pieces / cm 2 The following: This is a method for manufacturing single-crystal diamond, wherein the main surface of the seed substrate contains two or fewer growth sectors. [Brief explanation of the drawing]

[0006] [Figure 1] Figure 1 is a diagram illustrating NV centers in single-crystal diamond. [Figure 2] Figure 2 shows an example of a diamond species substrate used in the single-crystal diamond manufacturing method according to Embodiment 2. [Figure 3] Figure 3 shows another example of a diamond species substrate used in the single-crystal diamond manufacturing method according to Embodiment 2. [Figure 4] Figure 4 is a schematic diagram showing the configuration of the sample chamber used in the single-crystal diamond manufacturing method according to Embodiment 2. [Modes for carrying out the invention]

[0007] [Issues this disclosure aims to address] To obtain single-crystal diamond with few crystal defects and distortions, it is crucial to minimize impurities such as nitrogen. In single crystals with high nitrogen content, reducing crystal defects and distortions has been difficult. In recent years, with the growing interest in new applications such as magnetic sensors, there has been a need to reduce crystal defects and distortions even in the presence of nitrogen.

[0008] In recent years, high-sensitivity magnetic sensors have attracted attention as a new application for diamond. In this application, nitrogen is added to the diamond in a substitutional manner. To improve detection sensitivity, further reduction of crystal defects and distortion in the diamond is desired. In order to use diamond as a magnetic sensor, it is necessary to form luminescent centers within the diamond. For this reason, it was necessary to add an appropriate amount of substitutional nitrogen impurity to one of the luminescent centers that has a spin that senses magnetism. Adding the appropriate amount of impurity required ingenuity, such as adding specific elements to the solvent metal or raw materials used for single-crystal diamond synthesis. This ingenuity, however, can lead to the incorporation of specific elemental raw materials into the crystal, resulting in crystal defects. Furthermore, the inclusion of impurities itself caused fluctuations in impurity inclusion during growth and differences in how impurities are incorporated between growth sectors. This was a factor in the occurrence of subtle differences in lattice spacing and distortion.

[0009] Therefore, the objective of this research is to provide single-crystal diamond with reduced crystal defects and distortions, while incorporating controlled nitrogen addition.

[0010] [Effects of this disclosure] According to this disclosure, it is possible to provide single-crystal diamond with reduced crystal defects and distortion while controlling nitrogen content is added.

[0011] [Description of Embodiments in this Disclosure] First, the embodiments of this disclosure will be listed and described. (1) This disclosure states that the full width at half maximum of the X-ray diffraction rocking curve is 20 seconds or less. The full width at half maximum of the X-ray diffraction rocking curve is measured by CuKα radiation in two-crystal X-ray diffraction with a diamond crystal as the first crystal and arranged parallel to the (004) plane. The Raman shift of the Raman spectrum is 1332 cm -1 above 1333 cm -1 ​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​ (4) The average of the phase difference is preferably 10 nm / mm or less. This further reduces crystal defects and distortion in single-crystal diamond.

[0017] (5) The single-crystal diamond contains NV centers, and the NV center content is preferably 40 ppm or less. This makes it easier to detect high-brightness fluorescence and allows for a highly sensitive magnetic sensor.

[0018] (6) The content of the NV center is preferably 25 ppm or less. This makes it easier to detect high-brightness fluorescence and allows for a more sensitive magnetic sensor.

[0019] (7) The single crystal diamond 13 The content of carbon, based on the number of atoms, is preferably 1.0% or less. This makes it easier to detect high-brightness fluorescence and allows for a more sensitive magnetic sensor.

[0020] (8) the above 13 The content of carbon (C) based on the number of atoms is preferably 0.3% or less. This makes it easier to detect high-brightness fluorescence and allows for a more sensitive magnetic sensor.

[0021] (9) Preferably, the content of boron on an atomic basis in the single-crystal diamond is less than the content of nitrogen on an atomic basis. According to this, even if the single-crystal diamond contains nitrogen impurities, the distortion of the single-crystal diamond is further reduced.

[0022] (10) Preferably, the content of boron on an atomic basis is 10% or less of the content of nitrogen on an atomic basis. According to this, even if the single crystal diamond contains nitrogen impurities, the distortion of the single crystal diamond is reduced and the fluorescence intensity required for the sensor can be increased.

[0023] (11) Preferably, the content of boron on an atomic basis is more than 10% of the content of nitrogen on an atomic basis. According to this, even if the single crystal diamond contains nitrogen impurities, the distortion of the single crystal diamond can be reduced while maintaining the minimum fluorescence intensity required for the sensor, thereby improving magnetic sensitivity.

[0024] (12) Preferably, the diameter of the inscribed circle of the main surface of the single-crystal diamond is 3 mm or more. This makes it easy to process the single-crystal diamond into a high-sensitivity magnetic sensor. In addition, it is possible to produce a large number of small sensor parts with a diameter of 0.5 mm or less, thereby reducing manufacturing costs.

[0025] (13) The diameter is preferably 5 mm or more. This makes it easier to process single-crystal diamond into a high-sensitivity magnetic sensor. In addition, it is possible to produce a larger quantity of small sensor parts with a diameter of 0.5 mm or less, which further reduces manufacturing costs.

[0026] (14) Preferably, the single sector content of the single crystal diamond is 70 volume% or more. This significantly reduces the influence of sector boundaries on the entire single crystal, which are the cause of distortion, and further reduces the distortion of the single crystal diamond.

[0027] (15) The content of the single sector is preferably 90 volume% or more. This virtually eliminates the influence of the sector boundary on the entire single crystal, which causes distortion, and further reduces the distortion of the single crystal diamond.

[0028] (16) The present disclosure relates to the method for manufacturing single-crystal diamond, The process of preparing the seed substrate, The process includes growing a single-crystal diamond on the aforementioned seed substrate using a high-temperature, high-pressure synthesis method, The size of the main surface of the aforementioned substrate is such that the diameter of its inscribed circle is greater than 1.0 mm. The etch pit density of the main surface is 1 × 10 5 pieces / cm 2 The following: This is a method for manufacturing single-crystal diamond, wherein the main surface of the seed substrate contains two or fewer growth sectors.

[0029] This disclosure makes it possible to provide single-crystal diamond with reduced crystal defects and distortion while controlling nitrogen addition. This disclosure makes it possible to obtain high-quality single-crystal diamond that can improve magnetic sensitivity.

[0030] (17) The ratio N2 / N1 of the nitrogen content of the single crystal diamond on an atomic basis to the nitrogen content N1 of the seed substrate is preferably 0.2 or more and 5 or less.

[0031] According to this method, the lattice mismatch between the seed substrate and the single-crystal diamond grown on it is eliminated, resulting in a high-quality single-crystal diamond with fewer defects and distortions, which can improve magnetic sensitivity.

[0032] [Details of the embodiments of this disclosure] A specific example of the single-crystal diamond described herein will be explained below with reference to the drawings. In the drawings of this disclosure, the same reference numerals indicate the same or equivalent part. Furthermore, dimensional relationships such as length, width, thickness, and depth have been modified as appropriate for clarity and simplification of the drawings and do not necessarily represent actual dimensional relationships.

[0033] In this specification, the notation "A~B" means an upper and lower limit of a range (i.e., greater than or equal to A and less than or equal to B). If no unit is specified for A, but a unit is specified only for B, then the units for A and B are the same.

[0034] In this specification, the term "half-width" refers to "full width at half maximum (FWHM)."

[0035] In the crystallographic descriptions herein, parentheses () indicate individual planes, and curly braces {} indicate aggregate planes.

[0036] [Embodiment 1: Single-crystal diamond] The single crystal diamond of one embodiment of this disclosure (hereinafter also referred to as "this embodiment") is The full width at half maximum of the X-ray diffraction rocking curve is less than 20 arcseconds. The above X-ray diffraction rocking curve was measured using the two-crystal method, with a diamond crystal as the first crystal, in a (004) plane parallel arrangement, and measured using CuKα rays. Raman spectroscopy spectrum with a Raman shift of 1332 cm⁻¹ -1 Over 1333cm -1 The full width at half maximum (FWHM) of the peak in the following locations is 2.0 cm. -1 The following: The etch pit density is 10,000 pits / cm³. 2 The following: The above etch pit density was measured by etching tests. The nitrogen content, based on the number of atoms, is between 0.1 ppm and 50 ppm.

[0037] (X-ray diffraction rocking curve) The smaller the full width at half maximum (FWHM) of the X-ray diffraction rocking curve of a single-crystal diamond, the higher the crystallinity of the single-crystal diamond and the reduced crystal defects and strain. The single-crystal diamond of this embodiment has a FWHM of 20 seconds or less of its X-ray diffraction rocking curve, indicating high crystallinity and reduced crystal defects and strain.

[0038] From the viewpoint of improving crystallinity, the upper limit of the full width at half maximum (FWHM) 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 a manufacturing viewpoint, the lower limit of the FWHM of the X-ray diffraction rocking curve of single-crystal diamond can be 4.2 seconds or more. The FWHM 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, even 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.

[0039] The full width at half maximum (FWHM) of the X-ray diffraction rocking curve of the above-mentioned single-crystal diamond is measured using the two-crystal method, with a diamond crystal as the first crystal, arranged parallel to the (004) plane, and measured using CuKα rays. In this two-crystal method, the first and second crystals are diamond crystals cut from the single-crystal diamond being measured. The FWHM 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 single-crystal diamond being measured, the FWHM of the rocking curve will be a value that sensitively reflects the quality of the crystallinity of the sample.

[0040] It has been confirmed that there is no variation in the results even when the above measurements are performed in different regions of the same single-crystal diamond.

[0041] (FMA of the peak in the Raman spectrum) Raman shift of 1332 cm⁻¹ in single-crystal diamond spectroscopy -1 Over 1333cm -1 The sharper the diamond phonon peak and the smaller the full width at half maximum, the higher the crystallinity of the diamond. The single-crystal diamond in this embodiment has a Raman shift of 1332 cm⁻¹ in its Raman spectrum. -1 Over 1333cm -1 The half-width of the peak in the following case (hereinafter also referred to as "half-width of the peak in the Raman spectrum") is 2.0 cm. -1 The following is true, and it has high crystallinity.

[0042] The upper limit of the full width at half maximum (FWHM) of the Raman spectrum of a single-crystal diamond is 2.0 cm. -1 The following is 1.9cm -1 The following is preferable: 1.8 cm -1 The following is more preferable: 1.7 cm -1 The following is even more preferable: From a manufacturing standpoint, the lower limit of the full width at half maximum of the peaks in the Raman spectrum of single-crystal diamond is 1.6 cm. -1 The above can be stated. The full width at half maximum of the peak in the Raman spectrum of single-crystal diamond is 1.6 cm.-1 More than 2.0cm -1 The following is preferable: 1.6 cm -1 1.9cm -1 The following is more preferable: 1.6 cm -1 1.8cm or more -1 The following is even more preferable: 1.6 cm -1 More than 1.7cm -1 The following is even more preferable.

[0043] The full width at half maximum (FWHM) of the peaks in the above Raman spectrum is measured using the following procedure. First, any surface of the single-crystal diamond sample is polished with a metal-bonded grinding wheel until the surface roughness Ra is 20 nm or less. Samples that are mainly square or close to octagonal are preferred. The polished surface is then irradiated with a laser under the following conditions, and the scattered Raman rays are detected. (Measurement conditions) Measurement device: LabRAM HR-800 (manufactured by HORIBA JOBIN YVON) Laser wavelength: 532nm Measurement temperature: Room temperature (20℃ or higher and 25℃ or lower) Wavenumber resolution: 0.5cm -1 The value measured under the following conditions is defined as the full width at half maximum (FWHM) of the peak in the Raman spectrum of the single-crystal diamond of this embodiment. The FWHM originating from the light source and apparatus is 0.5 cm². -1 The following conditions allow the measured value to be considered the diamond's inherent half-width (FWHM), regardless of the instrument's resolution: The FWHM originating from the light source and instrument can be determined by measuring the FWHM of the laser light used for excitation. Note that the FWHM originating from the light source and instrument is 0.5 cm. -1 Super 2.0cm -1 If the value is less than 2.0 cm, the diamond's inherent FWHM can be obtained by subtracting the square of the FWHM derived from the light source and equipment from the square of the measured FWHM, and then using the square root of that value. -1 If it's too high, the accuracy decreases, which is undesirable. Laser irradiation position (measurement area): Raman rays 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 centroid position in a two-dimensional plane). (ii) Draw a straight line from the central part to the edge of the polished surface and identify the position P where the length of the straight line is maximum. If the distance from the central part to P is D1, detect the Raman line on the line segment from the central part to P at a position where the distance from the central part is (3 / 4)D1. (iii) Draw a straight line from the central part in the opposite direction to P, and identify the intersection point Q between this line and the edge of the polished surface. That is, P, the central part, and Q lie on the same straight line L1. If the distance from the central part to Q is D2, detect the Raman line on the line segment from the central part to Q at a position where the distance from the central part is (3 / 4)D2. (iv) Draw a line L2 perpendicular to line L1 which passes through the central part and through P, the central part, and Q, and identify the intersection points R and S of line L2 and the edge of the polished surface. If the distance from the central part to R is D3, detect the Raman line on the line segment from the central part to R at a position where the distance from the central part is (3 / 4)D3. (v) If the distance from the central part to S is D4, a Raman line is detected on the line segment from the central part to S at a position where the distance from the central part is (3 / 4)D4.

[0044] Spectral analysis was performed on the Raman lines detected at each of the five locations mentioned above, resulting in a Raman shift of 1332 cm⁻¹. -1 Over 1333cm -1 The diamond phonon peaks appearing below are identified. The Lorentz function is fitted to these diamond phonon peaks using the least squares method, and the Raman shift is 1332 cm. -1 Over 1333cm -1 The full width at half maximum (FWHM) of each of the five peaks described below is calculated. Of the FWHMs of the five peaks described above, the FWHM of the central peak and the FWHMs of the other four peaks are weighted at a ratio of 4:1 and averaged.

[0045] By setting the five measurement areas described above and calculating their weighted average, the crystallinity of the sample, such as strain, can be uniquely evaluated and compared between samples in the same single-crystal diamond.

[0046] (Etch pit density) In this specification, etch pit density is an index indicating the amount of linear defects originating from needle-shaped defects extending linearly in single-crystal diamond, and is measured by the etching test described later. The lower the etch pit density of single-crystal diamond, the fewer defects the single-crystal diamond has and the higher its crystallinity. The single-crystal diamond of this embodiment has an etch pit density of 10,000 pits / cm³. 2 The following is true, and it has high crystallinity.

[0047] The upper limit for the etch pit density of single-crystal diamond, from the perspective of improving crystallinity, is 10,000 pits / cm². 2 The following applies: 1000 pieces / cm 2 The following is preferable: 100 pieces / cm 2 The following is more preferable: 10 pieces / cm 2 The following is even more preferable: The lower limit of the etch pit density of single-crystal diamond is 0 pits / cm². 2 The above can be achieved. The etch pit density of single-crystal diamond is 0 pits / cm³. 2 More than 10000 pieces / cm 2 The following is preferable: 0 pieces / cm 2 More than 1000 pieces / cm 2 The following is more preferable: 0 pieces / cm 2 More than 100 pieces / cm 2 The following is even more preferable: 0 pieces / cm 2 More than 10 pieces / cm 2 The following is even more preferable.

[0048] The etch pit density of the above single-crystal diamond is measured by etching tests. Specifically, it is measured using the following procedure.

[0049] A single-crystal diamond is immersed in a potassium nitrate (KNO3) molten 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 growth surface is observed with an optical microscope. The inverted pyramidal etch pits are observed, and the size of the etch pits is adjusted by the crucible temperature and processing time according to the etch pit density. To make this adjustment, the process is first carried out under conditions (crucible temperature and processing time) that produce small etch pits, and after roughly determining the etch pit density, the conditions (crucible temperature and processing time) for measurement are set.

[0050] The size of the etch pits is selected to match the etch pit density, ensuring that individual etch pits do not overlap. Since the number of etch pits remains constant during the process of increasing their size, the etch pit size is adjusted to match the size of the field of view being evaluated (etch pit density). An example of this adjustment is when the etch pit density is 5000 pits / cm². 2 When the density is higher than the above, the size of the etch pits should be approximately 5-20 μm square, and they should not overlap. Three areas with high etch pit density are selected within the growth surface, and a rectangular measurement area of ​​1 mm or less is established in each area. Within each measurement area, the area where 100 etch pits exist is measured, and based on the number of etch pits (100) and the area, the 1 cm² 2 The number of etch pits per unit area is calculated. The average of the etch pit densities of each of the three measurement areas is defined as the "etch pit density of single-crystal diamond" in this specification.

[0051] Etch pit density is 5000 pits / cm² 2 For samples where the etch pit formation conditions (crucible temperature and processing time) are changed to gradually increase the size of the etch pits so that they can be observed even at low magnification with a microscope. For samples where areas of high density cannot be identified, count the etch pits across the entire growth surface of the sample, and then count them in 1 cm increments. 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 single-crystal diamond" in this specification.

[0052] In this specification, an etch pit refers to a clearly defined inverted pyramidal depression. Etch pits of roughly the same size are distributed, allowing them to be identified as etch pits. (5000 pits / cm²) 2 For the above samples, we counted etch pits ranging from 1 / 4 of the size of the majority of etch pits (d50 size based on area) to the largest etch pit, resulting in a count of 5000 pits / cm². 2 For samples smaller than 1 / 8, count the size of the etch pits from 1 / 8 of the size of the majority (d50 size based on area) to the largest etch pit size.

[0053] In this specification, 1 cm 2 The number of etch pits per unit area (etch pit density) corresponds to the density of linear defects described above. In the same single-crystal diamond, the average number of etch pits measured using the above method is defined as the "density of dislocation defects penetrating the growth principal surface" in this embodiment.

[0054] (Nitrogen content) In single-crystal diamond, individual nitrogen atoms can cause crystal defects and distortions, so from this viewpoint, a low amount is preferable. However, since nitrogen is an element of the fluorescence intensity of the light-emitting center for magnetic sensors, a high amount is preferable from this viewpoint. Therefore, there is an optimal range. In the single-crystal diamond of this embodiment, the nitrogen content based on the number of atoms (hereinafter also referred to as "nitrogen content") is greater than 0.1 ppm and less than or equal to 50 ppm. As a result, crystal defects and distortions are reduced and fluorescence intensity is enhanced in the single-crystal diamond.

[0055] The upper limit of the nitrogen content of single-crystal diamond is 50 ppm or less, preferably 25 ppm or less, more preferably 10 ppm or less, and even more preferably 7.0 ppm or less, from the viewpoint of reducing crystal defects and strain. The lower limit of the nitrogen content of single-crystal diamond is greater than 0.1 ppm, more preferably 0.5 ppm or more, even more preferably 1.0 ppm or more, and even more preferably 2.0 ppm or more, from the viewpoint of the fluorescence detection limit in the applications of this disclosure. The nitrogen content of single-crystal diamond is greater than 0.1 ppm and 50 ppm or less, preferably 0.5 ppm or more and 25 ppm or less, more preferably 1.0 ppm or more and 10 ppm or less, and even more preferably 2.0 ppm or more and 7.0 ppm or less.

[0056] The nitrogen content in single-crystal diamond is measured by secondary ion mass spectrometry (SIMS) or ESR.

[0057] (Boron content) A single boron atom in single-crystal diamond can cause crystal defects and distortion. Furthermore, it reduces the number of luminescent centers necessary for magnetic sensors, thus hindering fluorescence intensity. In this embodiment of single-crystal diamond, the boron content (based on the number of atoms) is preferably less than the nitrogen content (based on the number of atoms). This reduces crystal defects and distortion in the single-crystal diamond, thereby enhancing fluorescence intensity.

[0058] The upper limit of the boron content of single-crystal diamond is preferably less than the nitrogen content, more preferably 10% or less of the nitrogen content, even more preferably 1% or less of the nitrogen content, and still more preferably 0.1% or less of the nitrogen content, from the viewpoint of reducing crystal defects and strain. The lower limit of the boron content of single-crystal diamond is preferably 0 ppm or more, as a lower limit is preferable from the viewpoint of increasing fluorescence intensity. The boron content of single-crystal diamond is preferably 0 ppm or more and less than the nitrogen content, more preferably 0 ppm or more and 10% or less of the nitrogen content, even more preferably 0 ppm or more and 1% or less of the nitrogen content, and still more preferably 0 ppm or more and 0.1% or less of the nitrogen content. Reducing the amount of boron to a predetermined value relative to the amount of nitrogen is preferable for increasing fluorescence intensity and miniaturizing the magnetic sensor.

[0059] On the other hand, when single-crystal diamond contains nitrogen and boron in predetermined ratios, the lengths of the bonds to carbon complement each other, becoming closer to the lengths of the bonds between carbon atoms. This tends to mitigate crystal defects and distortions caused by nitrogen and boron present individually. From this viewpoint, the boron content of single-crystal diamond is preferably 0.5% or more of the nitrogen content and less than the nitrogen content, more preferably 1% to 30% of the nitrogen content, and even more preferably 3% to 10% of the nitrogen content. Including nitrogen and boron in predetermined ratios is preferable for mitigating crystal defects and distortions while maintaining minimum fluorescence intensity and thereby increasing magnetic sensitivity.

[0060] The boron content in single-crystal diamond is measured by secondary ion mass spectrometry (SIMS).

[0061] (Number of defects) Defects found in single-crystal diamond include point defects such as vacancies, needle-like defects that extend linearly, impurities, stacking faults, and strain. Of these defects, linear defects and stacking faults can be confirmed in X-ray topography images. Because these defects have a higher X-ray reflectance intensity than other parts of the crystal (parts with fewer defects, i.e., parts with higher crystallinity), their presence is shown as dark areas in positive X-ray topography images and as bright areas in negative X-ray topography images. In this specification, the number of defects is an index indicating the amount of defects derived from the number of linear defects in single-crystal diamond.

[0062] The defect count of the single-crystal diamond in this embodiment is 1000 defects / cm². 2 The following is preferable. According to this, crystal defects and strains in single-crystal diamond are further reduced. From the viewpoint of reducing crystal defects and strains, the upper limit of the number of defects in single-crystal diamond is 1000 defects / cm². 2 The following is preferable: 100 pieces / cm 2 The following is more preferable: 10 pieces / cm 2 The following is even more preferable: 5 pieces / cm 2 The following is even more preferable: The lower limit of the number of defects in single-crystal diamond is 0 defects / cm². 2 The above is preferable. The lower limit for the number of defects in single-crystal diamond is 0 defects / cm². 2 The above can be stated. The number of defects in a single-crystal diamond is 0 per cm. 2 More than 1000 pieces / cm 2 The following is preferable: 0 pieces / cm 2 More than 100 pieces / cm 2 The following is more preferable: 0 pieces / cm 2 More than 10 pieces / cm 2 The following is even more preferable: 0 pieces / cm 2 More than 5 pieces / cm 2 The following is even more preferable.

[0063] (phase difference) Since diamond is an isotropic crystal, it normally has an isotropic refractive index (dielectric constant). However, if defects and distortions exist in the diamond, the diamond will have a birefringence. When circularly polarized light is shone on a defect in a diamond, a phase difference occurs between the light of each polarization along the slow axis and the fast axis, and the light is emitted as elliptically polarized light (including linearly polarized light). If the refractive index is not isotropic due to defects and distortions in the diamond crystal, there will be a polarization direction in which the light is slowest (slow axis) and a polarization direction in which it is fastest (fast axis). On the other hand, when circularly polarized light is shone on a part that maintains an isotropic refractive index other than the defect, no phase difference occurs, and the light is emitted as circularly polarized light. By determining the orientation of the major and minor axes of the ellipse in elliptically polarized light, and the ratio of the lengths of the major and minor axes, the optical axis and phase difference can be determined. Furthermore, by combining lenses and microscopes, information on local phase differences in minute parts can be obtained. In addition, by placing polarizers accumulated in front of the pixels of a digital detector, information at 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 location is integrated in the direction of the substrate thickness. Therefore, it is recommended to compare samples of the same thickness or to normalize by thickness before comparison. When normalizing by thickness, the phase difference (unit: nm / mm) is displayed converted to a 1 mm thickness. For example, to convert to a 1 mm thickness, multiply the value measured at 0.1 mm thickness by 10, the value measured at 0.2 mm thickness by 5, and the value measured at 0.5 mm thickness by 2.

[0065] The two-dimensional phase difference value represents the distribution within the substrate surface. A reasonable way to represent the characteristics of a substrate is to use the average value within an arbitrary surface. The average phase difference 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, as the phase difference value cannot be accurately measured at those edges. More precisely, if the distance from the centroid of the main surface of the substrate to the edge is considered 100%, the effective area is defined as the area within the range of 90% of the distance from the centroid. Here, the average value over the effective area does not mean the phase difference per unit area, but rather the average value obtained by averaging the phase differences of each local part across the surface; it represents the average of the in-plane frequency distribution of phase differences. 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 phase difference accumulates and increases with increasing substrate thickness. Furthermore, the larger the substrate area, the greater the impact of defects on the entire surface, resulting in a larger phase difference. For these reasons, a smaller phase difference per unit thickness, and / or a smaller average phase difference in the in-plane frequency distribution, indicates better diamond quality. Also, even with the same phase difference, larger substrates result in better diamond quality. This is because cutting the substrate into smaller pieces relieves stress, reducing the phase difference. The parameters of strain quality are influenced by the magnitude of the phase difference and the size of the substrate.

[0067] The above phase difference values ​​show a positive correlation with the amount of defects and the magnitude of strain in single-crystal diamond. In this embodiment, the average phase difference per unit thickness of the single-crystal diamond is preferably 30 nm / mm or less. This further reduces crystal defects and strain in the single-crystal diamond. From the viewpoint of reducing defects and strain, 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 a manufacturing viewpoint, 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 and 30 nm / mm or less, more preferably 0 nm / mm or more and 10 nm / mm or less, even more preferably 0 nm / mm or more and 5 nm / mm or less, and even more preferably 0 nm / mm or more and 2 nm / mm or less. From a manufacturing standpoint, the average phase difference per unit thickness of 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 still more preferably 0.01 nm / mm or more and 2 nm / mm or less.

[0068] The phase difference per unit thickness of 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 include polishing and etching. The value converted to a single-crystal diamond thickness of 1 mm is the phase difference per unit thickness.

[0069] Next, the phase difference of single-crystal diamond is measured using a birefringence distribution analyzer (manufactured by Photonic Lattice Co., Ltd., "WPA-micro" or "WPA-100"). Generally, phase differences exceeding 90 degrees (1 / 4 of the wavelength) are difficult to distinguish, but the above birefringence distribution analyzer uses an integrated waveplate method instead of an integrated polarizer method, extending the measurement range to a phase difference of 180 degrees (1 / 2 of the wavelength). It has been experimentally verified that using three wavelengths (one central wavelength and two wavelengths close to it) extends the measurement range to 5 to 6 times the wavelength. The measured values ​​obtained with the above birefringence distribution analyzer are processed using software (manufactured by Photonic Lattice Co., Ltd., "PA-View") to determine the average phase difference per unit thickness.

[0070] For identical single-crystal diamonds, the aforementioned measuring device measures the surface distribution and calculates the average within the surface, so it is not affected by the measurement arrangement. It has been confirmed that there is no variation in the measurement results even when the setting location of the above-mentioned measurement area is arbitrarily changed.

[0071] (NV Center) As shown in Figure 1, an NV center 100 is a composite defect in a diamond crystal consisting of a substituted nitrogen atom (N) and a vacancy (V) created by the absence of an adjacent carbon atom. The NV center is negatively charged by trapping one electron, forming a state called a spin triplet, which can sense magnetic fields, electric fields, and temperature. Even with a single spin, the state of an NV center can be sensitively detected by light. Furthermore, because diamond has strong interatomic bonds and its spins are less susceptible to disturbance, highly sensitive measurements are possible even at room temperature. For these reasons, NV centers are well-suited for use in highly sensitive magnetic sensors that can be used very easily.

[0072] The single-crystal diamond of this embodiment contains an NV center, and the content rate of the NV center is preferably 40 ppm or less. The NV center can be formed by irradiating an electron beam with an energy of 3 MeV to the single-crystal diamond, for example, at a dose amount (electron beam irradiation amount) of 3×10 17 cm -3 per 1×10 17 cm -2 of the nitrogen concentration (content rate based on the number of nitrogen atoms) in the single-crystal diamond, and then performing vacuum annealing treatment at 900 °C. Thereby, an amount of NV centers less than the nitrogen content rate can be formed. It is preferable to change the dose amount according to the nitrogen content rate of the single-crystal diamond and irradiate it without excess or deficiency. According to this, the single-crystal diamond is suitable for use as a high-sensitivity magnetic sensor. In this specification, "the single-crystal diamond contains an NV center" means that the content rate of the NV center in the single-crystal diamond is above the concentration at which fluorescence can be detected by the measurement method of the NV center. From the viewpoint of reducing crystal defects and strain and enhancing magnetic sensitivity, the upper limit of the content rate of the NV center in the single-crystal diamond is preferably 40 ppm or less, more preferably 25 ppm or less, still more preferably 20 ppm or less, further more preferably 10 ppm or less, and even further more preferably 7 ppm or less. From the viewpoint of enhancing fluorescence intensity and improving detection sensitivity, the lower limit of the content rate of the NV center in the single-crystal diamond is preferably 0.01 ppm or more, and more preferably 0.1 ppm or more. The single-crystal diamond preferably contains an NV center and the content rate of the NV center is 40 ppm or less, more preferably contains an NV center and the content rate of the NV center is 25 ppm or less, still more preferably contains an NV center and the content rate of the NV center is 20 ppm or less, further more preferably the content rate of the NV center is 0.01 ppm or more and 10 ppm or less, and even further more preferably 0.1 ppm or more and 7 ppm or less.

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

[0074] ( 13 C content rate) In the single-crystal diamond of this embodiment, 13 The content rate based on the number of C atoms is preferably 1.0% or less. According to this, the noise due to nuclear magnetism can be reduced and the magnetic sensitivity can be improved. For the single-crystal diamond 13 From the viewpoint that the upper limit of the content rate of C based on the number of atoms of the single-crystal diamond can rapidly reduce the influence from the upper limit of the noise when not controlled, it is preferably 1.0% or less, more preferably 0.3% or less, still more preferably 0.05% or less, and still more preferably 0.005% or less. For the single-crystal diamond 13 From the viewpoint of comparison with the amount of added nitrogen, the lower limit of the content rate of C based on the number of atoms is preferably 0.00001% or more. For the single-crystal diamond 13 The content rate of C based on the number of atoms of the single-crystal diamond is preferably 0.00001% or more and 1.0% or less, more preferably 0.00001% or more and 0.3% or less, still more preferably 0.00001% or more and 0.05% or less, and still more preferably 0.00001% or more and 0.005% or less. Note that the 13 C content rate of natural diamond is about 1.1%.

[0075] For the single-crystal diamond 13 The content rate of C based on the number of atoms is measured by SIMS.

[0076] It has been confirmed that even if the setting location of the above measurement region is arbitrarily changed in the same single-crystal diamond, there is no variation in the measurement results.

[0077] (Size) The diameter of the inscribed circle of the main surface of a single-crystal diamond is preferably 3 mm or more. This facilitates the processing of the single-crystal diamond into a high-sensitivity magnetic sensor. Furthermore, it reduces manufacturing costs when producing a large quantity of small sensor parts with a diameter of 0.5 mm or less. From the viewpoint of ease of processing and reduction of manufacturing costs, the lower limit of the diameter of the inscribed circle of the main surface of a 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 a manufacturing viewpoint, the upper limit of the diameter of the inscribed circle of the main surface of a single-crystal diamond can be 50 mm or less. The diameter of the inscribed circle of the main surface of a 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 even more preferably 7 mm or more and 50 mm or less.

[0078] The diameter of the inscribed circle of the principal surface of a single-crystal diamond is measured using an optical microscope with a length-measuring function.

[0079] (Single sector content) In the single-crystal diamond of this embodiment, the single-sector content is preferably 70% by volume or more. This significantly reduces the influence of sector boundaries, which cause distortion, on the entire single crystal, thus enabling the fabrication of a highly sensitive magnetic sensor. Furthermore, a large number of homogeneous, small sensor portions with a diameter of 0.5 mm or less can be produced, reducing manufacturing costs. Here, a sector is a region grown using a specific, different crystal plane as its origin (underlying substrate). Examples of sectors included in single-crystal diamond include {001} sectors, {113} sectors, {115} sectors, and {111} sectors. Each single crystal is formed by growing using the crystal plane of its respective plane orientation as the underlying substrate. Here, a {abc} sector is a region grown using the {abc} plane as its origin (underlying substrate). Of these, the single sector is preferably {100}, {111}, or {113} sector, from the viewpoint of easily forming a stable surface and forming a flat surface.

[0080] The lower limit of the single-sector content of single-crystal diamond is preferably 70 volume% or more, more preferably 80 volume% or more, even more preferably 90 volume% or more, and even more preferably 95 volume% or more. The upper limit of the single-sector content of single-crystal diamond can be 100 volume% or less. The single-sector content of single-crystal diamond is preferably 70 volume% or more and 100 volume% or less, more preferably 80 volume% or more and 100 volume% or less, even more preferably 90 volume% or more and 100 volume% or less, and even more preferably 95 volume% or more and 100 volume% or less.

[0081] The single-sector content of single-crystal diamond is measured using the following procedure. Since the growth sectors have different impurity concentrations, their fluorescence intensity varies. Therefore, the fluorescence distribution on the substrate surface is confirmed by photoluminescence (PL) or cathodoluminescence (CL), and the boundaries are clearly identified as linear. A cross-section can also be prepared in the growth direction to confirm the boundaries in the depth direction. Since the sector boundaries are approximately linear in two dimensions or approximately plane in three dimensions, the area ratio, volume ratio, and even the content of the largest sector can be determined using these linear or plane boundaries. Furthermore, the three-dimensional sector region distribution can be determined using a confocal microscope. The proportion of single sectors can also be calculated based on the area ratio exposed on the surface.

[0082] [Embodiment 2: Method for manufacturing single-crystal diamond] The single-crystal diamond of Embodiment 1 described above can be synthesized by the temperature difference method of the high-temperature, high-pressure synthesis method.

[0083] In the temperature difference method of high-temperature, high-pressure synthesis, the seed substrate significantly influences the crystallinity of the single-crystal diamond grown on it.

[0084] Conventional seed crystals (seed substrates) were less than 0.5 mm in size and had similar thicknesses. These seed crystals utilize the entire crystal. Specifically, crystal growth is carried out 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 smaller seed crystal size is preferable in order to grow single-crystal diamond with a low defect density.

[0085] On the other hand, it is known that a larger seed crystal is advantageous for growing large single-crystal diamonds. 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 larger seed crystal can result in the inclusion of five or more growth sectors. Different growth sectors have different impurity concentrations, which negatively affects the distortion of the crystal.

[0086] To obtain high-quality, large-sized single-crystal diamonds, it is important to increase the size of the seed substrate. The size of the main surface of the seed substrate is preferably such that the diameter of its inscribed circle is 1.0 mm or more, more preferably greater than 1.0 mm, even more preferably 2.0 mm or more, and still more preferably 3.0 mm or more. There is no particular upper limit to the size of the seed substrate, but from a manufacturing standpoint, it can be, for example, 50 mm or less.

[0087] In the manufacturing method of this embodiment, growth crystals from the side surface of the seed substrate are not emphasized, so a thinner 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.

[0088] As the seed substrate size increases, the growth sectors in the main plane of the grown single-crystal diamond grow larger. Depending on how the substrate is cut, it is also possible to create large substrates with single growth sectors. Furthermore, it is possible to create substrates with a high proportion of single growth sectors.

[0089] The next point to consider after the size of the seed substrate is the number of defects and the number of growing sectors on the seed substrate. The etch pit density on the main surface of the seed substrate is 1 × 10⁻⁶ 5 pieces / cm 2 The following is preferable: 5 × 10 3 pieces / cm 2 The following is more preferable: 1000 pieces / cm 2 The following is more preferable: 100 pieces / cm 2 The following is even more preferable: The lower limit of the etch pit density is not particularly limited, and is 0 pits / cm³. 2 This can be done.

[0090] A growth sector is two regions grown on different plane orientations. Because the different growth sectors have different impurity concentrations, strain accumulates near their boundaries. Therefore, the main surface of the seed substrate contains two or fewer growth sectors, preferably one. Preferably, there are one to two growth sectors.

[0091] In the manufacturing method of this embodiment, as described above, by using a single-crystal diamond with controlled etch pit density and number of growth sectors as a seed substrate, high-quality single-crystal diamond with improved magnetic sensitivity can be obtained.

[0092] The ratio N2 / N1, which is the ratio of the nitrogen content N2 of the single-crystal diamond grown on the seed substrate to the nitrogen content N1 of the seed substrate based on the number of atoms, is preferably between 0.2 and 5. This eliminates the lattice mismatch between the seed substrate and the single-crystal diamond. Therefore, a high-quality single-crystal diamond with fewer defects and distortions, and improved magnetic sensitivity, can be obtained.

[0093] The specific manufacturing method is as follows: (Preparation of seed substrate) First, prepare the diamond substrate to be used in the temperature difference method described later. The following diamond substrates A to D can be prepared.

[0094] As shown in Figures 2 and 3, single-crystal diamond materials synthesized by the temperature difference method all have multiple growth sectors. In Figures 2 and 3, 24a and 34a represent the first sector, and 24b and 34b represent the second sector. 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, respectively.

[0095] The diamond substrate A has a size (inscribed circle diameter) of 1 mm or more, preferably 5 mm or more, and the nitrogen content based on the number of atoms is 0.01 ppm or less. The etch pit density is 5 × 10⁻⁶. 3 pieces / cm 2 The following is true: Because seed substrate A has a low nitrogen content, even when it contains multiple sectors, it can minimize minute lattice mismatches caused by differences in nitrogen content between sectors, and the resulting distortion of the seed substrate itself.

[0096] The diamond substrate B has a size of 1 mm or more, preferably 5 mm or more, and its nitrogen content, based on the number of atoms, is 100 ppm to 150 ppm. The etch pit density is 1 × 10⁻¹⁶. 5 pieces / cm 2 The following applies: Seed substrate B has a large size at the expense of defects. By using a large seed substrate, the ratio of single growth sectors of the single crystal diamond grown on it can be increased, thereby reducing the strain of the grown single crystal diamond.

[0097] The diamond substrate C has a size greater than 3 mm, preferably greater than 5 mm, and its nitrogen content, based on the number of atoms, is greater than 0.1 ppm and less than or equal to 50 ppm. Furthermore, the etch pit density is 1 × 10⁻⁶. 3 pieces / cm 2 The following applies: Furthermore, the substrate is cut to consist of a single growth sector, and the main surface contains only one growth sector. The seed substrate C contains nitrogen but has few defects and consists of a single sector, thus eliminating minute lattice mismatches between the seed substrate and the grown single-crystal diamond.

[0098] The diamond substrate D has a main surface size such that the diameter of its inscribed circle is greater than 1.0 mm, and the etch pit density of the main surface is 1 × 10⁻⁶ 5 pieces / cm 2 The following conditions apply, and the number of growth sectors included in the main surface of the seed substrate is two or less.

[0099] The diamond seed substrates A to D described above can be manufactured by cutting out diamond seed substrates 22, 32a, and 32b having one or more growth sectors from single-crystal diamonds 21 and 31, as shown in Figures 2 and 3. This cutting is preferably performed using a water-guard laser processing machine. This improves processing accuracy and allows for the production of diamond seed substrates with a size of 1.0 mm or larger and a single growth sector (number of sectors: 1). The size of the diamond seed substrate is preferably 1.5 mm or larger.

[0100] (The process of growing a single-crystal diamond) Next, a single-crystal diamond is grown on the above-mentioned seed substrate using a high-temperature, high-pressure synthesis method. This allows for the production of the single-crystal diamond of Embodiment 1. In this single-crystal diamond, crystal defects and distortions are reduced.

[0101] The temperature difference method of the high-temperature, high-pressure method is performed using a sample chamber having the configuration shown in Figure 4, for example.

[0102] As shown in Figure 4, in the sample chamber 10 used for manufacturing 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 placed outside the graphite heater 57. The temperature difference method involves creating a vertical temperature gradient inside the sample chamber 10, with the high-temperature section (T high ) contains a carbon source 53, and a low-temperature section (T lowThis synthesis method involves placing a diamond seed substrate 55 on a carbon source 53 and a solvent metal 54 between the carbon source 53 and the diamond seed substrate 55, and growing a single crystal diamond 51 on the diamond seed substrate 55 under conditions above the temperature at which the solvent metal 54 dissolves and above the pressure at which the diamond becomes thermally stable.

[0103] As the carbon source 53, diamond powder is preferable. Graphite or pyrolysis carbon can also be used. As the solvent metal 54, one or more metals selected from iron (Fe), cobalt (Co), nickel (Ni), and manganese (Mn), or alloys containing these metals, can be used.

[0104] It is preferable to add titanium (Ti) as a nitrogen getter to the solvent metal 54 at a concentration of 0.2% by mass or more. This makes it possible to set the nitrogen content in the single-crystal diamond, based on the number of atoms, to 50 ppm or less.

[0105] Furthermore, it is preferable to add boron (B) to the solvent metal 54 at a concentration of 2 ppm or more. This makes it possible to achieve a boron content of 0.01 ppm or more on an atomic basis in the single-crystal diamond.

[0106] In the temperature difference method, a certain amount of titanium (Ti) can be added to the metal solvent as a nitrogen getter to intentionally retain nitrogen in the crystal. This allows for control of the nitrogen content in the crystal. This method is not used in conventional temperature difference methods.

[0107] The nitrogen content of single-crystal diamond obtained by growing on a diamond substrate is preferably 0.1 to 10 times the nitrogen content of the diamond substrate. This allows for the mitigation of defects and strains in the crystal caused by nitrogen addition.

[0108] NV centers in single-crystal diamond can be subjected to electron beams with an energy of 3 MeV, for example, when the nitrogen concentration (percentage of nitrogen atoms) in single-crystal diamond is 1 × 10⁻¹⁶.17 cm -3 Hit, 3 x 10 17 cm -2 The single-crystal diamond can be formed by irradiating it with a dose (electron beam irradiation amount) and then annealing the diamond in a vacuum at 900°C. It is preferable to increase the electron beam irradiation amount for samples with a high nitrogen content and decrease it for samples with a low nitrogen content.

[0109] [Note 1] The method for manufacturing single-crystal diamond according to this embodiment comprises the steps of preparing a seed substrate and growing a single-crystal diamond on the seed substrate using a high-temperature, high-pressure synthesis method, wherein the size of the main surface of the seed substrate is such that the diameter of its inscribed circle is greater than 1.0 mm, and the etch pit density of the main surface is 1 × 10⁻⁶ 5 pieces / cm 2 The following is a method for manufacturing single-crystal diamond, wherein the growth sectors contained in the main surface of the substrate are two or fewer. [Examples]

[0110] This embodiment will be described in more detail by reference to examples. However, this embodiment is not limited by these examples.

[0111] In the following example, the Raman shift of the Raman spectrum of single-crystal diamond is 1332 cm⁻¹. -1 Over 1333cm -1 The peak width at half maximum in the following measurements was obtained using a double monochromator Raman spectrometer with a wavenumber resolution of 0.5 cm. -1 The following measurements were taken, or using a LabRAM HR-800 (manufactured by HORIBA JOBIN YVON), and the results were obtained by converting them to the full width at half maximum of the diamond itself, taking into account the resolution of the light source and the instrument.

[0112] [Example 1: Samples 1-13, Sample 1-1, Sample 1-2] <Manufacturing of single-crystal diamonds> Diamond seed substrates A and B described in Embodiment 2 above are prepared by cutting out a diamond seed substrate containing a single growth sector or multiple sectors from a single-crystal diamond material produced by the temperature difference method. The type (A or B), size, number of growth sectors contained in the diamond seed substrate, and etch pit density of each sample are shown in the "Type," "Size," "Number of Growth Sectors," and "Etch Pit Density" columns of "Diamond Seed Substrate" in Table 1.

[0113] [Table 1]

[0114] Next, single-crystal diamonds are grown on the diamond seed substrate using the high-temperature, high-pressure temperature difference method to obtain single-crystal diamonds for each sample. The temperature difference method is performed using a sample chamber having the configuration shown in Figure 4. High-purity Fe and Co are used as the carbon source, and the solvent composition is Fe / Co = 60 / 40 (mass ratio). To prevent the seed substrate from dissolving, approximately 4 mass% of carbon is added to the solvent. Furthermore, Ti is added to the solvent as a nitrogen getter in the amount specified in the "Ti addition amount" column of the "Synthesis Conditions" in Table 1 (for example, 1.5 mass% of Ti is added for sample 1). The carbon source and seed substrate are then set in a graphite heater for heating so that there is a temperature difference of approximately 30°C. Using an ultra-high pressure generator, the pressure is maintained at 5.5 Pa and the temperature at 1300°C for the time specified in the "Synthesis Time" column of the "Synthesis Conditions" in Table 1 (for example, 120 hours for sample 1) to grow single-crystal diamonds on the seed substrate. Next, the temperature is first lowered to room temperature, then the pressure is reduced, and the grown single-crystal diamond is extracted.

[0115] For the above single-crystal diamond, an electron beam with an energy of 3 MeV was used to measure the nitrogen concentration (percentage of nitrogen atoms) in the single-crystal diamond, which was 1 × 10⁻¹⁶. 17 cm -3 Hit, 3 x 10 17 cm -2 The diamond was irradiated to a dose of [specified amount], and then the single-crystal diamond was annealed in a vacuum at 900°C to obtain single-crystal diamonds for each sample.

[0116] <Rating> For each single-crystal diamond sample before electron beam irradiation, the following parameters were measured: size, full width at half maximum of the X-ray diffraction rocking curve, full width at half maximum of the Raman spectrum peaks, etch pit density, number of defects observed in the X-ray topography image, average phase difference, nitrogen content, etc. 13 The carbon content, boron content, cut size, and single sector content were measured. For each single-crystal diamond sample after electron beam irradiation, the NV center content and the peak value and full width at half maximum of the optically detected magnetic resonance (ODMR) spectrum were measured. The specific measurement methods for each item are as described in Embodiment 1. As is generally known, the vertical axis of the ODMR spectrum is NV. - The fluorescence intensity is shown, with the horizontal axis representing the microwave frequency. When the microwave spectrum is swept, a dip-type peak is detected at the resonance frequency position (peak position), where the fluorescence intensity weakens. It is known that this peak shifts by a frequency corresponding to the magnetic field due to the Zeeman effect. Therefore, if a peak is present in the ODMR spectrum of a single-crystal diamond, it is possible to detect an external magnetic field based on the peak position, indicating that the single-crystal diamond can be applied as a magnetic sensor.

[0117] The results are shown in Table 2 in the columns for "Size," "Xrc FWHM," "Raman FWHM," "Etch Pit Density," "Number of Defects," "Average Phase Difference," "N," "13C," "B," "Cutout Size," "Single Sector," "NV," and "ODMR" for single-crystal diamond. In Table 2, the "Xrc FWHM" column shows the full width at half maximum of the X-ray diffraction rocking curve obtained by the two-crystal method. The "Raman FWHM" column shows the full width at half maximum (in-plane average) of the peaks in the Raman spectrum measured by the method described in Embodiment 1. The "Average Phase Difference" column shows the average phase difference considering the plate thickness and area described in Embodiment 1, and the "13C" column shows the carbon isotope. 13The table shows the concentration of C, the "Cut-out size" column shows the size cut from the synthesized single-crystal diamond for evaluation of the items shown in Table 2, the "Single sector" column shows the single sector content as described in Embodiment 1, and the "ODMR" column shows the full width at half maximum of the ODMR peak. The thickness of all samples evaluated in Example 1 was 0.4 mm. The single-crystal diamond size, X-ray diffraction rocking curve full width at half maximum, Raman spectrum peak full width at half maximum, etch pit density, number of defects observed in the X-ray topography image, average phase difference, nitrogen content, 13 Measurement results for carbon content, boron content, cutout size, and single sector content have been confirmed to show almost no change before and after electron beam irradiation.

[0118] [Table 2]

[0119] For example, in sample 1, the nitrogen content in the single-crystal diamond was measured by ESR and found to be 0.28 ppm. Furthermore, the boron content in the single-crystal diamond was analyzed by SIMS and found to be 0.0007 ppm. The resolution was 0.5 cm. -1 The Raman spectrum of single-crystal diamond was measured using a double monochromator Raman spectrometer, at 1332 cm⁻¹. -1 The half-width was found to be 1.60 cm. -1 Furthermore, when the polarized light transmission image of single-crystal diamond was observed using a polarized light transmission microscope and the distortion was evaluated, the average phase difference was 1 nm / mm. In addition, the full width at half maximum of the rocking curve of the X-ray diffraction at CuKα was measured using the two-crystal method with the (004) planes of diamond crystals cut from single-crystal diamonds synthesized as the first and second crystals arranged in parallel, and it was 7 seconds. Furthermore, when defects in the crystal were observed using an X-ray topograph, the number of linear dislocation defects was 9 per cm. 2 Next, the same diamond was placed in KNO3 molten salt (600-700°C) for 1 hour, and evaluated by the number of etch pits in the densely packed areas, resulting in 9 etch pits / cm². 2 That is the case.

[0120] [Example 2: Samples 21-28] Diamond seed substrates A and B described in Embodiment 2 above are prepared by cutting out a diamond seed substrate containing a single growth sector or multiple sectors from a single-crystal diamond material produced by the temperature difference method. The type (A or B), size, number of growth sectors contained in the diamond seed substrate, and etch pit density of each sample are shown in the "Type," "Size," "Number of Growth Sectors," and "Etch Pit Density" columns of "Diamond Seed Substrate" in Table 3.

[0121] [Table 3]

[0122] carbon isotopes 12 Nitrogen is removed from methane gas with a carbon concentration of 99.999% by passing it through a titanium sponge heated to over 600°C. This nitrogen-free methane gas is then blown onto a Ni-free Ta substrate heated to a high temperature of 1900°C in a vacuum chamber. This decomposes the methane gas on the Ta substrate, creating carbon isotopes with a size of 10mm x 10mm on the Ta substrate. 12 It forms graphite with a carbon concentration of 99.999% or higher. This graphite is used as a carbon source.

[0123] On the other hand, a high-purity Fe-Co-Ti alloy is prepared as a metal solvent by adding the amount of Ti listed in the "Synthesis Conditions" section of Table 3 (for example, 1.0 mass% is added for sample 21) as a nitrogen getter. In addition, carbon isotopes from the surroundings 12 To prevent contamination with carbon, the heater surface is treated with a carbon isotope concentration of 99.999% or higher. 12 Coat it with graphite having a concentration of C.

[0124] Next, a diamond synthesis system consisting of a seed substrate, a solvent, and high-purity graphite enriched with isotopes as a carbon source is placed from bottom to top, and this system is encased in a cup-shaped cell made of Fe (which does not contain carbon or Ni), with the top surface being 10 -3Seal in a vacuum of Pa or less.

[0125] Using an ultra-high pressure generator, a single-crystal diamond was grown on a seed substrate under a pressure of 5.5 Pa and a temperature of 1300°C for the time specified in the "Synthesis Time" column of the "Synthesis Conditions" in Table 3 (for example, 120 hours for Sample 1). After that, the temperature was first lowered to room temperature, and then the pressure was reduced to remove the grown single-crystal diamond.

[0126] For the above single-crystal diamond, an electron beam with an energy of 3 MeV was used to measure the nitrogen concentration (percentage of nitrogen atoms) in the single-crystal diamond, which was 1 × 10⁻¹⁶. 17 cm -3 Hit, 3 x 10 17 cm -2 The diamond was irradiated to a dose of [specified amount], and then the single-crystal diamond was annealed in a vacuum at 900°C to obtain single-crystal diamonds for each sample.

[0127] <Rating> For each single-crystal diamond sample before electron beam irradiation, the following parameters were measured: size, full width at half maximum of the X-ray diffraction rocking curve, full width at half maximum of the Raman spectrum peaks, etch pit density, number of defects observed in the X-ray topography image, average phase difference, nitrogen content, etc. 13 The carbon content, boron content, cut size, and single sector content were measured. For each single-crystal diamond sample after electron beam irradiation, the NV center content and ODMR were measured. The results are shown in Table 4 in the columns for "Size," "Xrc FWHM," "Raman Full Width at Half Max," "Etch Pit Density," "Number of Defects," "Average Phase Difference," "N," "13C," "B," "Cut Size," "Single Sector," "NV," and "ODMR" for the single-crystal diamond. The measurement methods and definitions for each measurement item are the same as in Example 1. The thickness of all samples evaluated in Example 2 was 0.4 mm. Note that the size of the single-crystal diamond, the full width at half maximum of the X-ray diffraction rocking curve, the full width at half maximum of the peaks in the Raman spectrum, the etch pit density, the number of defects observed in the X-ray topography image, the average phase difference, and the nitrogen content were also measured. 13Measurement results for carbon content, boron content, cutout size, and single sector content have been confirmed to show almost no change before and after electron beam irradiation.

[0128] [Table 4]

[0129] For example, in sample 21, the nitrogen content in the single-crystal diamond was measured by ESR and found to be 0.42 ppm, and the boron content in the single-crystal diamond was analyzed by SIMS and found to be 0.0005 ppm. 13 Analysis of the carbon content revealed it to be 0.002%. The resolution was 0.5 cm. -1 The Raman spectrum of a single-crystal diamond was measured using a double monochromator Raman spectrometer, at 1332 cm⁻¹. -1 The half-width was found to be 1.60 cm. -1 Furthermore, when the polarized light transmission image of single-crystal diamond was observed using a polarized light transmission microscope and the distortion was evaluated, the average phase difference was 1 nm / mm. In addition, the full width at half maximum of the rocking curve of the X-ray diffraction at CuKα was measured using the two-crystal method with the (004) planes of diamond crystals cut from single-crystal diamonds synthesized as the first and second crystals arranged in parallel, and it was 5 seconds. Furthermore, when defects in the crystal were observed using an X-ray topograph, the number of linear dislocation defects was 8 per cm. 2 Next, the same diamond was placed in KNO3 molten salt (600-700°C) for 1 hour, and evaluated by the number of etch pits in the densely packed areas, it was found to be 8 pits / cm². 2 That is the case.

[0130] [Example 3: Samples 31-35] <Manufacturing of single-crystal diamonds> From a single-crystal diamond material produced by the temperature difference method, a diamond seed substrate is cut out to include a single growth sector or multiple sectors, thereby preparing the diamond seed substrate C described in Embodiment 2 above. The single-crystal diamond material is one of the samples 1, 10, 13, 21, or 22 produced in Example 1 or Example 2. The type of diamond seed substrate, the sample number used for the single-crystal diamond material, the size, the number of growth sectors contained in the diamond seed substrate, and the etch pit density for each sample are shown in the "Type," "Single-crystal diamond material," "Size," "Number of growth sectors," and "Etch pit density" columns of "Diamond seed substrate" in Table 5.

[0131] [Table 5]

[0132] Next, single-crystal diamonds are grown on the diamond seed substrate using the temperature difference method to obtain single-crystal diamonds for each sample. The temperature difference method is performed using a sample chamber having the configuration shown in Figure 4. High-purity Fe and Co are used as the carbon source, and the solvent composition is Fe / Co = 60 / 40 (mass ratio). To prevent the seed substrate from dissolving, approximately 4 mass% of carbon is added to the solvent. Furthermore, Ti is added to the solvent as a nitrogen getter in the amount specified in the "Ti addition amount" column of the "Synthesis Conditions" in Table 5 (for example, 1.5 mass% is added for sample 31). The carbon source and seed substrate are then set in a graphite heater for heating so that there is a temperature difference of approximately 30°C. Using an ultra-high pressure generator, the pressure is maintained at 5.5 Pa and the temperature at 1300°C for the time specified in the "Synthesis Time" column of the "Synthesis Conditions" in Table 5 (for example, 120 hours for sample 31) to grow single-crystal diamonds on the seed substrate. Next, the temperature is first lowered to room temperature, then the pressure is reduced, and the grown single-crystal diamond is extracted.

[0133] For the above single-crystal diamond, an electron beam with an energy of 3 MeV was used to measure the nitrogen concentration (percentage of nitrogen atoms) in the single-crystal diamond, which was 1 × 10⁻¹⁶. 17 cm -3 Hit, 3 x 10 17 cm-2 The diamond was irradiated to a dose of [specified amount], and then the single-crystal diamond was annealed in a vacuum at 900°C to obtain single-crystal diamonds for each sample.

[0134] <Rating> For each single-crystal diamond sample before electron beam irradiation, the following parameters were measured: size, full width at half maximum of the X-ray diffraction rocking curve, full width at half maximum of the Raman spectrum peaks, etch pit density, number of defects observed in the X-ray topography image, average phase difference, nitrogen content, etc. 13 The carbon content, boron content, cut size, and single sector content were measured. For each single-crystal diamond sample after electron beam irradiation, the NV center content, the peak value and full width at half maximum (FWHM) of the optically detected magnetic resonance (ODMR) were measured. The results are shown in Table 6 in the columns for "Size," "Xrc FWHM," "Raman FWHM," "Etch pit density," "Number of defects," "Average phase difference," "N," "13C," "B," "Cut size," "Single sector," "NV," and "ODMR." The meaning of the columns is the same as in Example 1. The thickness of all samples evaluated in Example 3 was 0.55 mm. Note that the size of the single-crystal diamond, the FWHM of the X-ray diffraction rocking curve, the FWHM of the peaks in the Raman spectrum, the etch pit density, the number of defects observed in the X-ray topography image, the average phase difference, nitrogen content, etc. 13 Measurement results for carbon content, boron content, cutout size, and single sector content have been confirmed to show almost no change before and after electron beam irradiation.

[0135] It was confirmed that, for the production of single-crystal diamonds suitable for magnetic sensors with a nitrogen content of 0.1 ppm to 50 ppm, it is preferable to use seed substrates made from single-crystal diamonds with good crystallinity as described in Tables 2 and 4, and even more preferable to use seed substrates with a nitrogen content close to that of the single-crystal diamond to be synthesized.

[0136] [Table 6]

[0137] As described above, embodiments and examples of this disclosure have been explained, but it is also intended from the outset that the configurations of each of the above embodiments and examples may be combined as appropriate or modified in various ways. The embodiments and examples disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of the present invention is indicated by the claims rather than the embodiments and examples described above, and all modifications within the scope of the claims are intended to be included in the meaning of equivalents and within the scope. [Explanation of Symbols]

[0138] 21,31,51 Single-crystal diamond, 22,32a,32b,55 Diamond seed substrate, 5 Abrasive seed crystal, 10 Sample chamber, 24a,34a First sector, 24b,34b Second sector, 52 Insulator, 53 Carbon source, 54 Solvent metal, 56 Pressure medium, 57 Graphite heater, 100 NV center

Claims

1. The full width at half maximum of the X-ray diffraction rocking curve is less than 20 arcseconds. The full width at half maximum of the aforementioned X-ray diffraction rocking curve was measured using CuKα rays in a two-crystal X-ray diffraction method, with a diamond crystal as the first crystal and arranged parallel to the (004) plane. Raman spectroscopy spectrum with a Raman shift of 1332 cm⁻¹ －１ 1333cm or more －１ The full width at half maximum (FWHM) of the peak below is 2.0 cm. －１ The following: The etch pit density is 10,000 pits / cm³. ２ The following: The aforementioned etch pit density is measured by etching tests. The nitrogen content, based on the number of atoms, is greater than 0.1 ppm and less than or equal to 50 ppm. A single-crystal diamond in which the content of boron on an atomic basis is less than the content of nitrogen on an atomic basis.

2. The full width at half maximum of the aforementioned X-ray diffraction rocking curve is 10 seconds or less. The Raman shift of the aforementioned Raman spectroscopic spectrum is 1332 cm⁻¹. －１ 1333cm or more －１ The full width at half maximum (FMAX) of the peak in the following locations is 1.9 cm. －１ The following: The aforementioned etch pit density is 1000 pits / cm³. ２ The following: The number of defects confirmed in the X-ray topography image is 1,000 / cm ２ The single-crystal diamond according to claim 1, which is as follows.

3. The single-crystal diamond according to claim 1 or claim 2, wherein the average phase difference per unit thickness of the single-crystal diamond is 30 nm / mm or less.

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

5. The single-crystal diamond according to any one of claims 1 to 4, wherein the single-crystal diamond contains NV centers, and the content of the NV centers is 40 ppm or less.

6. The single-crystal diamond according to claim 5, wherein the content of the NV centers is 25 ppm or less.

7. The single-crystal diamond according to any one of claims 1 to 6, wherein the content of boron on an atomic basis is 10% or less of the content of nitrogen on an atomic basis.

8. The single-crystal diamond according to any one of claims 1 to 6, wherein the content of boron on an atomic basis is greater than 10% of the content of nitrogen on an atomic basis.

9. The single-crystal diamond according to any one of claims 1 to 8, wherein the diameter of the inscribed circle of the principal surface of the single-crystal diamond is 3 mm or more.

10. The single-crystal diamond according to claim 9, wherein the diameter is 5 mm or more.

11. The single-crystal diamond according to any one of claims 1 to 10, wherein the single-sector content of the single-crystal diamond is 70 volume% or more.

12. The single-crystal diamond according to claim 11, wherein the content of the single sector is 90 volume% or more.

13. A method for manufacturing a single crystal diamond according to any one of claims 1 to 12, The process of preparing the seed substrate, The process includes growing a single-crystal diamond on the aforementioned seed substrate using a high-temperature, high-pressure synthesis method, The size of the main surface of the aforementioned substrate is such that the diameter of its inscribed circle is greater than 1.0 mm. The etch pit density of the main surface is 1 × 10 ５ pieces / cm ２ The following: A method for manufacturing single-crystal diamond, wherein the main surface of the seed substrate contains two or fewer growth sectors.

14. The method for producing a single crystal diamond according to claim 13, wherein the ratio N2 / N1 of the nitrogen content N2 of the single crystal diamond to the nitrogen content N1 of the seed substrate, based on the number of atoms, is 0.2 or more and 5 or less.

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