Single crystal diamond and tool including same

Abstract

Single crystal diamond has a nitrogen atom content of 1 ppm or more and 2000 ppm or less, and the number of nitrogen atoms in the C center is N C The total number of nitrogen atoms, N ALL and the number of nitrogen atoms in the C center, N C Difference from N ALL -N C Proportion (N ALL -N C ) / N C is 1 to 10 5 Below is a single crystal diamond.

Description

[Technical Field]

[0001] The present disclosure relates to single crystal diamonds and tools comprising the same. [Background technology]

[0002] Single crystal diamond is extremely hard and is therefore used industrially in a wide range of applications, including cutting tools such as precision cutting bits and woodworking cutters, as well as wear-resistant tools such as dressers for grinding wheels, wire drawing dies, scribing tools, orifices for water jets, and wire guides (Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. WO2022 / 118461 [Patent Document 2] International Publication No. WO2017 / 198662 Summary of the Invention

[0004] The single crystal diamond of the present disclosure is The atomic number content of nitrogen atoms is 1 ppm or more and 2000 ppm or less, and the atomic number N of nitrogen atoms in the C center (isolated N) is C The total number of nitrogen atoms, N ALL and the number of nitrogen atoms in the C center, N C Difference from N ALL -N C Proportion (N ALL -N C ) / N C is 1 to 10 5 The following is the result. [Brief explanation of the drawings]

[0005] [Figure 1] FIG. 1 is a schematic cross-sectional view showing an example of a sample chamber configuration used in producing a synthetic single crystal diamond according to one embodiment of the present disclosure. [Figure 2]FIG. 2 is a schematic cross-sectional view of a single crystal diamond according to one embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0006] [Problem to be solved by this disclosure] In recent years, there has been an increasing demand for improved tool life, and single-crystal diamonds that can be used in tools are required to have improved wear resistance and chipping resistance. It is known that the wear resistance and chipping resistance of single-crystal diamonds can be improved by facilitating the formation of nitrogen atom-to-atom agglomeration, nitrogen atom-to-vacancy agglomeration, or both in single-crystal diamonds (Patent Document 2). However, in the examples of Patent Documents 1 and 2, the annealing temperature (i.e., the maximum heat treatment temperature) was below 1600°C, making it difficult to sufficiently induce the formation of nitrogen atom-to-atom agglomeration, nitrogen atom-to-vacancy agglomeration, or both. Furthermore, simply increasing the annealing temperature poses the problem of facilitating the reverse phase transformation from diamond to graphite. As a result, it has sometimes been difficult to achieve both excellent wear resistance and excellent chipping resistance in single-crystal diamonds.

[0007] Therefore, an object of the present disclosure is to provide a single crystal diamond that has both excellent wear resistance and excellent chipping resistance, and a tool including the same.

[0008] [Effects of this disclosure] According to the present disclosure, it is possible to provide a single crystal diamond that has both excellent wear resistance and excellent chipping resistance, and a tool including the same.

[0009] [Description of the embodiments of the present disclosure] First, embodiments of the present disclosure will be listed and described. (1) The single crystal diamond of the present disclosure is The nitrogen atom content based on the atomic number is 1 ppm or more and 2000 ppm or less, C: Number of nitrogen atoms in the centerC The total number of nitrogen atoms, N ALL and the number of nitrogen atoms in the C center, N C Difference from N ALL -N C Proportion (N ALL -N C ) / N C is 1 to 10 5 The following is the result.

[0010] According to the present disclosure, it is possible to provide a single crystal diamond that combines excellent wear resistance and excellent chipping resistance, and a tool including the same.

[0011] (2) In the above (1), the single crystal diamond may contain an A center, thereby providing a single crystal diamond and a tool including the same that have both superior wear resistance and superior chipping resistance.

[0012] (3) In the above (1) or (2), the single crystal diamond may contain a B center, thereby providing a single crystal diamond and a tool including the same that have both superior wear resistance and superior chipping resistance.

[0013] (4) In any one of the above (1) to (3), the single crystal diamond is NV 0 The center may include a single crystal diamond, which has both superior wear resistance and superior chipping resistance, and a tool including the single crystal diamond.

[0014] (5) In any one of the above (1) to (4), the single crystal diamond is NV ― The center may include a single crystal diamond, which has both superior wear resistance and superior chipping resistance, and a tool including the single crystal diamond.

[0015] (6) In any of the above (1) to (5), the single crystal diamond may contain an H center, thereby providing a single crystal diamond and a tool including the same that have both superior wear resistance and superior chipping resistance.

[0016] (7) In any of the above (1) to (6), the single crystal diamond may contain an H3 center, thereby providing a single crystal diamond and a tool including the same that have both superior wear resistance and superior chipping resistance.

[0017] (8) In any of the above (1) to (7), the single crystal diamond may contain an N3 center, thereby providing a single crystal diamond and a tool including the same that have both superior wear resistance and superior chipping resistance.

[0018] (9) In any of (1) to (8) above, the surface of the single crystal diamond may include a first region, the first region having an arithmetic mean height Sa of 3 nm or more as defined in JIS B 0681-2: 2018, and a maximum height Sz of 60 nm or more as defined in JIS B 0681-2: 2018. This makes it possible to provide a single crystal diamond and a tool including the same that have both superior wear resistance and superior chipping resistance.

[0019] (10) In any of the above (1) to (9), an altered portion is present on the outer periphery of the single crystal diamond, and in the core electron excitation spectrum of the altered portion obtained by electron energy loss spectroscopy using a transmission electron microscope, the amount of energy loss is in the range of 285 eV ± 5 eV. * Maximum intensity of the peak Iπ * and σ in the range of energy loss 291±5eV * Maximum intensity of the peak Iσ * Ratio to Iπ * / Iσ *is 0.15 or more, and in the altered portion, the percentage of the number N1 of primary carbon atoms to the sum N1+N2 of the number N1 of primary carbon atoms constituting amorphous carbon and the number N2 of secondary carbon atoms constituting graphite, {N1 / (N1+N2)}×100, may be 90% or more. This makes it possible to provide a single crystal diamond and a tool including the same that have both superior wear resistance and superior chipping resistance.

[0020] (11) The tool of the present disclosure comprises the single crystal diamond described in (1) to (10) above.

[0021] According to the present disclosure, it is possible to provide a tool including a single crystal diamond that has both excellent wear resistance and excellent chipping resistance.

[0022] (12) In the above (11), the tool may be a cutting tool, a wear-resistant tool, or a grinding tool. This makes it possible to provide tools including single-crystal diamond that have both excellent wear resistance and excellent chipping resistance, such as wire-drawing dies, injection molding nozzles, and wire guides.

[0023] [Details of the embodiments of the present disclosure] A single crystal diamond, its manufacturing method, tool, and specific examples of the manufacturing method according to one embodiment of the present disclosure (hereinafter also referred to as "the present embodiment") will be described below with reference to the drawings. In the drawings of the present disclosure, the same reference symbols represent the same or corresponding parts. Furthermore, the dimensional relationships such as length, width, thickness, depth, etc. have been appropriately changed for the sake of clarity and simplification of the drawings, and do not necessarily represent the actual dimensional relationships.

[0024] In this disclosure, the expression "A to B" means the upper and lower limits of a range (i.e., A or more and B or less), and if 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.

[0025] In the present disclosure, when a compound or the like is represented by a chemical formula, unless the atomic ratio is particularly limited, it is intended to include any conventionally known atomic ratio, and should not necessarily be limited to only those within the stoichiometric range.

[0026] [Embodiment 1: Single Crystal Diamond] A single crystal diamond according to an embodiment of the present disclosure will be described below. One embodiment of the present disclosure (hereinafter also referred to as "the present embodiment") is The nitrogen atom content based on the atomic number is 1 ppm or more and 2000 ppm or less, C: Number of nitrogen atoms in the center C The total number of nitrogen atoms, N ALL and the number of nitrogen atoms in the C center, N C Difference from N ALL -N C Proportion (N ALL -N C ) / N C is 1 to 10 5 Below is a single crystal diamond.

[0027] According to the present disclosure, it is possible to provide a single crystal diamond that combines excellent wear resistance and excellent chipping resistance, and a tool including the same. The reasons for this are presumably as follows.

[0028] The single crystal diamond of this embodiment has a nitrogen atom content of 1 ppm or more and 2000 ppm or less based on the atomic number of nitrogen atoms, and the atomic number N of the nitrogen atoms in the C center is C The total number of nitrogen atoms, N ALL and the number of nitrogen atoms in the C center, N C Difference from N ALL -N C Proportion (N ALL -N C ) / N C is 1 to 10 5As a result, agglomeration of nitrogen atoms, agglomeration of nitrogen atoms and vacancies, or both, is likely to occur in the single crystal diamond, improving the wear resistance and chipping resistance of the single crystal diamond. As a result, it is possible to provide a single crystal diamond that has both excellent wear resistance and excellent chipping resistance, and a tool including the same.

[0029] A "C center" is a diamond crystal in which a nitrogen atom replaces a carbon atom on an atomic basis. Diamonds containing a "C center" include type Ib. Single crystal diamonds containing a C center have a wavelength of 1130 cm in the infrared absorption spectrum measured by Fourier transform infrared spectroscopy. -1 (e.g., wave number 1130±2cm -1 ) shows the absorption peak.

[0030] The "A center" described below is an aggregate consisting of two nitrogen atoms, which are covalently bonded and each nitrogen atom is substituted for a carbon atom that constitutes the diamond crystal. Diamonds containing the A center are called IaA type. Single crystal diamonds containing the A center have an infrared absorption spectrum measured by Fourier transform infrared spectroscopy at a wave number of 1282 cm -1 (e.g., wave number 1282±2 cm -1 ) shows the absorption peak.

[0031] The "B center" described below is an aggregate consisting of four nitrogen atoms and one atomic vacancy, and each nitrogen atom replaces a carbon atom that makes up the diamond crystal. Diamonds containing the B center are called IaB type. Single crystal diamonds containing the B center have an infrared absorption spectrum measured by Fourier transform infrared spectroscopy with a wavenumber of 1175 cm -1 (e.g., wave number 1175±2cm -1 ) shows the absorption peak.

[0032] The "NV" 0A "vacancy center" is a complex defect consisting of one vacancy and one nitrogen atom adjacent to the vacancy. 0 A single crystal diamond containing a center exhibits an emission peak around a fluorescence wavelength of 575 nm (for example, a fluorescence wavelength of 575±2 nm) in a fluorescence spectrum obtained by irradiating it with excitation light shorter than approximately 575 nm, for example, excitation light with a wavelength of 514 nm.

[0033] The "NV" - A "vacancy center" is a complex defect consisting of one negatively charged vacancy and one nitrogen atom adjacent to the vacancy. - A single crystal diamond containing a center exhibits an emission peak around a fluorescence wavelength of 637 nm (for example, a fluorescence wavelength of 637±2 nm) in a fluorescence spectrum obtained by irradiating it with excitation light shorter than approximately 637 nm, for example, excitation light with a wavelength of 514 nm.

[0034] The "H2 center" described below is an aggregate consisting of one negatively charged vacancy and two nitrogen atoms adjacent to the vacancy, with each nitrogen atom substituting for a carbon atom constituting the diamond crystal. Single-crystal diamonds containing H2 centers exhibit an emission peak at a fluorescence wavelength of around 986 nm (for example, a fluorescence wavelength of 986±2 nm) in the fluorescence spectrum obtained by irradiating them with excitation light shorter than approximately 986 nm, for example, excitation light with a wavelength of 830 nm.

[0035] The "H3 center" described below is an aggregate consisting of one vacancy and two nitrogen atoms adjacent to the vacancy, and each nitrogen atom substitutes for a carbon atom constituting the diamond crystal. Single crystal diamonds containing H3 centers exhibit an emission peak at a fluorescence wavelength of around 503 nm (for example, a fluorescence wavelength of 503±2 nm) in the fluorescence spectrum obtained by irradiating them with excitation light shorter than approximately 503 nm, for example, excitation light with a wavelength of 457 nm.

[0036] The "N3 center" described below is an aggregate consisting of one vacancy and three nitrogen atoms adjacent to the vacancy, and each nitrogen atom replaces a carbon atom constituting the diamond crystal. Single crystal diamond containing the N3 center shows an emission peak at either or both of a fluorescence wavelength of about 415 nm (for example, a fluorescence wavelength of 415±2 nm) and a fluorescence wavelength in the range of 420 nm to 470 nm in the fluorescence spectrum obtained by irradiating it with excitation light shorter than about 410 nm, for example, excitation light with a wavelength of 325 nm.

[0037] <<(N ALL -N C ) / N C ≫ C: Number of nitrogen atoms in the center C The total number of nitrogen atoms, N ALL and the number of nitrogen atoms in the C center, N C Difference from N ALL -N C Proportion (N ALL -N C ) / N C is 1 to 10 5 This improves the wear resistance and chipping resistance of the single crystal diamond. (N ALL -N C ) / N C The lower limit of N may be 1.5 or more, or may be 2.0 or more. ALL -N C ) / N C The upper limit is 2.0×10 4 It may be 19890 or less, or 10 4 may be less than 10 3 may be less than 10 2 (N ALL -N C ) / N C is 1.5 or more than 10 4 It may be 2.0 or more and 10 3 It may be the following:

[0038] In this disclosure, (N ALL -N C) / N C can be determined in the following way: C is the 1130 cm -1 Based on the integrated intensity of the absorption peak, the N was calculated using the method described in the literature "I. Kiflawi, A.E. Mayer, P.M. Spear, J.A. van Wyk, G.S. Woods, Philos. Mag. B 69 (1994) 1141. and G.S. Woods, J.A. van Wyk, A.T. Collins, Philos. Mag. B 62 (1990) 589." ALL was determined by carrying out measurements using secondary ion mass spectrometry (SIMS) under the following conditions. C and N ALL Based on (N ALL -N C ) / N C was calculated. (conditions) Measuring device: Product name (product number): "IMS-7f", manufactured by CAMECA Primary ion species: Cesium (Cs+) Primary accelerating voltage: 15kV Detection area: 30 (μmφ) Measurement accuracy: ±40% (2σ)

[0039] The single crystal diamond may contain an A center (2N), which can further improve the wear resistance and chipping resistance of the single crystal diamond.

[0040] In the present disclosure, "single crystal diamond contains an A center" means that the A center is present at a wavenumber of 1282 cm in an infrared absorption spectrum measured by Fourier transform infrared spectroscopy. -1 (e.g., wave number 1282±2 cm -1 ) can be identified by confirming the presence of an absorption peak.

[0041] The single crystal diamond may contain a B center (4NV), which can further improve the wear resistance and chipping resistance of the single crystal diamond.

[0042] In the present disclosure, "single crystal diamond contains a B center" means that the B center has a wavenumber of 1175 cm in the infrared absorption spectrum measured by Fourier transform infrared spectroscopy. -1 (e.g., wave number 1175±2cm -1 ) can be identified by confirming the presence of an absorption peak.

[0043] ≪NV 0 Center≫ Single crystal diamond is NV 0 The single crystal diamond may contain a center, which can further improve the wear resistance and chipping resistance of the single crystal diamond.

[0044] In this disclosure, "single crystal diamond" refers to a NV 0 "Containing a center" can be identified by confirming that an emission peak exists around a fluorescence wavelength of 575 nm (for example, a fluorescence wavelength of 575±2 nm) in the fluorescence spectrum obtained by irradiating the molecule with excitation light shorter than approximately 575 nm, for example, excitation light with a wavelength of 514 nm.

[0045] ≪NV ― Center≫ Single crystal diamond is NV ― The single crystal diamond may contain a center, which can further improve the wear resistance and chipping resistance of the single crystal diamond.

[0046] In this disclosure, "single crystal diamond" refers to a NV ― "Containing a center" can be identified by confirming that an emission peak exists around a fluorescence wavelength of 637 nm (for example, a fluorescence wavelength of 637±2 nm) in the fluorescence spectrum obtained by irradiating the molecule with excitation light shorter than approximately 637 nm, for example, excitation light with a wavelength of 514 nm.

[0047] Single crystal diamond has H2 center (2NV - ) may be contained. This can further improve the wear resistance and chipping resistance of the single crystal diamond.

[0048] In the present disclosure, whether or not a "single crystal diamond contains an H2 center" can be determined by confirming that an emission peak exists near a fluorescence wavelength of 986 nm (e.g., a fluorescence wavelength of 986±2 nm) in the fluorescence spectrum obtained by irradiating the diamond with excitation light having a wavelength shorter than approximately 986 nm, for example, excitation light having a wavelength of 830 nm.

[0049] <H3 Center> The single crystal diamond may contain an H3 center (2NV), which can further improve the wear resistance and chipping resistance of the single crystal diamond.

[0050] In the present disclosure, whether or not a "single crystal diamond contains an H3 center" can be determined by confirming that an emission peak exists around a fluorescence wavelength of 503 nm (e.g., a fluorescence wavelength of 503±2 nm) in a fluorescence spectrum obtained by irradiating the diamond with excitation light having a wavelength shorter than approximately 503 nm, for example, excitation light having a wavelength of 457 nm.

[0051] The single crystal diamond may contain an N3 center (3NV), which can further improve the wear resistance and chipping resistance of the single crystal diamond.

[0052] In the present disclosure, whether a "single crystal diamond contains an N3 center" can be determined by confirming that, in a fluorescence spectrum obtained by irradiating the diamond with excitation light shorter than approximately 410 nm, for example, excitation light with a wavelength of 325 nm, there is an emission peak at either or both a fluorescence wavelength of around 415 nm (for example, a fluorescence wavelength of 415±2 nm) and a fluorescence wavelength within the range of 420 nm or more and 470 nm or less.

[0053] <Composition of single crystal diamond> 2 is a schematic cross-sectional view of a single crystal diamond according to one aspect of the present disclosure. As shown in FIG. 2, an altered portion 27 may be present in the outer periphery of the single crystal diamond 21 of the first embodiment.

[0054] The shape of the single crystal diamond 21 is not particularly limited and can be appropriately selected depending on the application. The shape of the single crystal diamond 21 may be, for example, a flat plate, a prism, a pyramid, a truncated pyramid, or a polyhedron. The size of the single crystal diamond of embodiment 1 is not particularly limited, but may be, for example, 0.1 mm 3 ~1000mm 3 may be.

[0055] The altered regions 27 may be present in the outer periphery of the single crystal diamond 21. The altered regions 27 may be present in at least a part of the outer periphery of the single crystal diamond 21. The altered regions 27 may be present so as to cover a part of the outer periphery of the single crystal diamond 21, or may be present so as to cover the entire outer periphery of the single crystal diamond 21. A plurality of altered regions 27 may be scattered around the outer periphery of the single crystal diamond 21.

[0056] <Affected area> In the single crystal diamond of embodiment 1, in the core electron excitation spectrum obtained by electron energy loss spectroscopy (hereinafter also referred to as "TEM-EELS") using a transmission electron microscope of the altered portion, the amount of energy loss is in the range of π 285 eV±5 eV. * Maximum intensity of the peak Iπ * and σ in the range of energy loss 291±5eV * Maximum intensity of the peak Iσ * Ratio to Iπ * / Iσ * is 0.15 or more, and in the altered portion, the percentage {N1 / (N1+N2)}×100 of the number N1 of primary carbon atoms to the sum N1+N2 of the number N1 of primary carbon atoms constituting amorphous carbon and the number N2 of secondary carbon atoms constituting graphite may be 90% or more.

[0057] In the core electron excitation spectrum obtained by the TEM-EELS method for the altered part, the energy loss amount is in the range of 285 eV ± 5 eV. * The peak is derived from the π bond of carbon, and exists in the range of energy loss 291±5 eV. * The peak is due to the σ bond of carbon. * / Iσ * is 0.15 or more indicates that the ratio of carbon π bonds to carbon σ bonds is a predetermined amount or more in the altered portion of the single crystal diamond of embodiment 1.

[0058] The carbon atoms having a π bond present in the altered portion may include carbon atoms constituting amorphous carbon (also referred to as "primary carbon atoms" in the present disclosure) and carbon atoms constituting graphite (also referred to as "secondary carbon atoms" in the present disclosure).

[0059] In the altered portion of the single crystal diamond of embodiment 1, the percentage {N1 / (N1+N2)}×100 of the number of primary carbon atoms N1 relative to the sum N1+N2 of the number of primary carbon atoms N1 constituting amorphous carbon and the number of secondary carbon atoms N2 constituting graphite may be 90% or more. This indicates that 90% or more of the carbon atoms having π bonds present in the altered portion are present as amorphous carbon. Amorphous carbon has a high absorption rate for lasers. In particular, amorphous carbon has a higher absorption rate for lasers with wavelengths of 355 nm to 1064 nm, which are used in processing single crystal diamonds, than diamond and graphite.

[0060] In the core electron excitation spectrum obtained by the TEM-EELS method in the altered part of single crystal diamond, the ratio Iπ * / Iσ *When N1 / (N1+N2) is 0.15 or more and the percentage {N1 / (N1+N2)}×100 is 90% or more, the amorphous carbon with high laser absorption rate present on the surface of the single crystal diamond improves the workability of the single crystal diamond when laser processing it. Also, the wear resistance and chipping resistance of the single crystal diamond can be improved.

[0061] In the present disclosure, the presence of an altered portion in a single crystal diamond is indicated by the ratio Iπ * / Iσ * This can be confirmed by measuring the percentage {N1 / (N1+N2)}×100 in the affected area.

[0062] <Ratio Iπ in the core electron excitation spectrum obtained by TEM-EELS in the altered area * / Iσ * Measurement≫ First, the ratio Iπ in the core electron excitation spectrum obtained by the TEM-EELS method for the altered part of single crystal diamond * / Iσ * The specific measurement method is as follows:

[0063] Step A1: A single crystal diamond is sliced ​​using an argon ion slicer along a plane parallel to the normal to the surface to obtain a measurement sample with a thickness of 3 to 100 nm. The measurement sample is observed using a transmission electron microscope (TEM, JEOL Ltd. "JEM-2100F / Cs" (trademark)) at 50,000 to 500,000 magnifications to obtain a bright-field image of the single crystal diamond.

[0064] Step A2: Next, identify the area in the bright-field image that corresponds to the altered area. The area in the bright-field image that corresponds to the altered area can be identified, for example, by a difference in contrast. The following measurements are performed in the area in the bright-field image that corresponds to the altered area that is estimated to be 3 nm or more thick.

[0065] Step A3: Using electron energy loss spectroscopy (EELS), a measurement point is set within a distance of 2 to 3 nm along the normal direction of the single crystal diamond surface, starting from the surface of the region corresponding to the altered part. A 1 nm diameter observation spot is scanned 100 nm in a direction parallel to the surface of the single crystal diamond to observe the energy loss (K edge) associated with the excitation of carbon K shell electrons. This obtains a core electron excitation spectrum around 300 eV associated with the excitation of carbon K shell electrons at the measurement point.

[0066] Step A4. In the core electron excitation spectrum at the measurement point, the energy loss amount is within the range of 285 eV ± 5 eV. * Maximum intensity of the peak Iπ * and σ in the range of energy loss 291±5eV * Maximum intensity of the peak Iσ * and obtain Iπ * Iσ * By dividing by the ratio Iπ * / Iσ * Ask for.

[0067] Step A5: The above measurement is carried out at five measurement points that do not overlap each other. At all five measurement points, the ratio Iπ * / Iσ * When the ratio Iπ is 0.15 or more, the ratio Iπ in the core electron excitation spectrum obtained by the TEM-EELS method in the region corresponding to the altered part * / Iσ * is judged to be 0.15 or more.

[0068] <<Measurement of percentage {N1 / (N1+N2)}×100 in the affected area>> Step B1: Next, by the above steps A1 to A4, the ratio Iπ * / Iσ * At each of the five measurement points set in the area corresponding to the altered part where π is judged to be 0.15 or more, * The peaks are separated into peaks derived from amorphous carbon and peaks derived from graphite. The five measurement points are the same as the five measurement points set in step A5 above.

[0069] Step B2. At each measurement point, the maximum intensity Iπ is calculated based on the state separation results. * The percentage of the number of primary carbon atoms N1 to the sum N1+N2 of the number of primary carbon atoms N1 constituting amorphous carbon and the number of secondary carbon atoms N2 constituting graphite in the amount of energy loss indicated above is calculated as {N1 / (N1+N2)}×100.

[0070] If the percentage {N1 / (N1+N2)}×100 is 90% or more at all five measurement points, the percentage {N1 / (N1+N2)}×100 of the area corresponding to the measured altered part is judged to be 90% or more. In other words, the area corresponding to the altered part identified in step B1 is the area corresponding to the ratio Iπ * / Iσ * is 0.15 or more and the percentage {N1 / (N1+N2)}×100 is 90% or more, it is determined to be an altered area, and it is confirmed that an altered area exists on the outer periphery of the single crystal diamond being measured.

[0071] As long as measurements are taken on the same single crystal diamond, it has been confirmed that there is almost no variation in the measurement results even if multiple non-overlapping bright-field images are obtained and the measurement point in the region corresponding to the altered area in each bright-field image is changed.

[0072] In the altered portion of the single crystal diamond of embodiment 1, the ratio Iπ * / Iσ * is 0.15 or more, and may be 0.17 or more, or may be 0.19 or more.

[0073] In the altered portion of the single crystal diamond of embodiment 1, the percentage {N1 / (N1+N2)}×100 may be 90% or more, 93% or more, 96% or more, or 99% or more.

[0074] ≪Composition≫ <Nitrogen atom> In the single crystal diamond of this embodiment, the content of nitrogen atoms based on atomic number is 1 ppm or more and 2000 ppm or less.If this content is less than 1 ppm, the aggregation of nitrogen atoms, the aggregation of nitrogen atoms and vacancies, or both are difficult to occur, so the wear resistance and chipping resistance of the single crystal diamond tend to be insufficient.On the other hand, if this content is more than 2000 ppm, the lattice defects in the single crystal diamond tend to increase, so the wear resistance and chipping resistance of the single crystal diamond tend to be insufficient.The lower limit of this content may be 3 ppm or more, 10 ppm or more, 15 ppm or more, or 30 ppm or more.The upper limit of this content may be 1400 ppm or less, 879 ppm or less, 800 ppm or less, or 300 ppm or less. The content may be 3 ppm or more and 1400 ppm or less, 10 ppm or more and 879 ppm or less, 15 ppm or more and 800 ppm or less, or 30 ppm or more and 300 ppm or less.

[0075] In the single crystal diamond of this embodiment, the content of nitrogen atoms based on the atomic number can be measured by secondary ion mass spectrometry (SIMS).

[0076] <Arithmetic mean height Sa and maximum height Sz> The surface of the single crystal diamond of embodiment 1 includes a first region, and the first region may have an arithmetic mean height Sa of 3 nm or more as defined in JIS B 0681-2:2018, and a maximum height Sz of 60 nm or more as defined in JIS B 0681-2:2018. This can improve wear resistance and chipping resistance. Furthermore, because the surface of the single crystal diamond has appropriate irregularities, when the single crystal diamond is fixed to a substrate via a bonding material, the adhesion between the single crystal diamond and the bonding material is improved.

[0077] The lower limit of the arithmetic mean height Sa of the first region may be 3 nm or more from the viewpoint of improving the adhesion between the single crystal diamond and the bonding material. The upper limit of the arithmetic mean height Sa of the first region may be 100 nm or less from the viewpoint of facilitating material installation. The arithmetic mean height Sa of the first region may be 5 nm or more and 80 nm or less, 5 nm or more and 60 nm or less, or 5 nm or more and 40 nm or less.

[0078] The lower limit of the maximum height Sz of the first region is 60 nm or more from the viewpoint of improving the adhesion between the single crystal diamond and the bonding material. The upper limit of the maximum height Sz of the first region may be 500 nm or less from the viewpoint of ease of material installation. The maximum height Sz of the first region may be 80 nm or more and 400 nm or less, or may be 100 nm or more and 300 nm or less.

[0079] The arithmetic mean height Sa and maximum height Sz specified in JIS B 0681-2:2018 (Geometrical product specifications (GPS) - Surface texture: Areal - Part 2: Terms, definitions and surface texture parameters) correspond to the arithmetic mean height Sa and maximum height Sz specified in ISO 25178-2:2012 (Geometrical product specifications (GPS) - Surface texture: Areal - Part 2: Terms, definitions and surface texture parameters (MOD)).

[0080] In the present disclosure, whether the surface of a single crystal diamond includes a first region is confirmed by the following procedure.

[0081] The surface of the single crystal diamond is divided into rectangular unit areas of 10 μm x 10 μm, and the arithmetic mean height Sa and maximum height Sz are measured for each unit area. Depending on the shape of the surface of the single crystal diamond, it may not be possible to divide the surface into an integral number of unit areas, resulting in a remainder. In such cases, only the unit areas are measured, and the remainder areas are excluded from the measurement.

[0082] When there is a unit domain having an arithmetic mean height Sa of 3 nm or more and a maximum height Sz of 60 nm or more, it is confirmed that the surface of the single crystal diamond includes a first domain. 2 That's all.

[0083] In the present disclosure, the arithmetic mean height Sa and maximum height Sz of the first region are measured by the following procedure. On the surface of the single crystal diamond, all unit regions A having an arithmetic mean height Sa of 3 nm or more and a maximum height Sz of 60 nm or more are identified. The arithmetic mean height Sa and maximum height Sz are measured based on all unit regions A. The unit regions A may or may not be in contact with each other. In the present disclosure, the arithmetic mean height Sa measured based on all unit regions A corresponds to the arithmetic mean height Sa of the first region. In the present disclosure, the maximum height Sz measured based on all unit regions A corresponds to the maximum height Sz of the first region.

[0084] In the present disclosure, the position and size of the first region on the surface of the single crystal diamond can be appropriately set depending on the application of the single crystal diamond. For example, when the single crystal diamond is fixed to a substrate via a bonding material, the first region can constitute at least a part of the region on the surface of the single crystal diamond that contacts the bonding material. Alternatively, the first region can constitute the entire surface of the single crystal diamond. The proportion of the first region relative to the entire surface of the single crystal diamond can be, for example, 25% or more, 50% or more, or even 100%.

[0085] <Method for manufacturing single crystal diamond> The method for producing a single crystal diamond according to the present disclosure will be explained with reference to Figure 1. Figure 1 is a schematic cross-sectional view showing an example of a sample chamber configuration used in producing a synthetic single crystal diamond according to one embodiment of the present disclosure. The method for producing a single crystal diamond according to one embodiment of the present disclosure includes a step of obtaining a diamond single crystal by a temperature difference method using a solvent metal (hereinafter also referred to as the "temperature difference method step"), a step of irradiating the diamond single crystal with an electron beam (hereinafter also referred to as the "irradiation step"), a step of annealing the diamond single crystal irradiated with the electron beam (hereinafter also referred to as the "annealing step"), and a step of performing an acid treatment on the annealed diamond single crystal (hereinafter also referred to as the "acid treatment step").

[0086] <Temperature difference method process> Diamond single crystals can be produced by the temperature difference method using a sample chamber having the configuration shown in FIG.

[0087] As shown in Figure 1, in a sample chamber 10 used for producing diamond single crystals, an insulator 2, a carbon source 3, a solvent metal 4, and a seed crystal 5 are placed in a space surrounded by a graphite heater 7, and a pressure medium 6 is placed outside the graphite heater 7. 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 3, low temperature part (T low In this synthesis method, a diamond seed crystal 5 is placed in a carbon source 3, a solvent metal 4 is placed between the carbon source 3 and the seed crystal 5, and a diamond single crystal is grown on the seed crystal 5 by maintaining the temperature at which the solvent metal 4 dissolves and at a pressure at which the diamond becomes thermally stable.

[0088] Diamond powder can be used as the carbon source 3. 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.

[0089] Nitrogen sources such as iron nitride (FeN, FeN), aluminum nitride (AlN), phosphorus nitride (PN), silicon nitride (SiN), or organic nitrogen compounds such as melamine or sodium azide can be added to the carbon source 3 or solvent metal 4, either singly or as a mixture. This allows nitrogen atoms to be contained in the synthesized diamond single crystal. At this time, the nitrogen atoms in the diamond single crystal are mainly present as isolated substitutional nitrogen atoms.

[0090] The content of the nitrogen source in the carbon source 3 or the solvent metal 4 can be, for example, 1 ppm or more and 5000 ppm or less of nitrogen atoms derived from the nitrogen source in the carbon source, based on the number of atoms. In addition, in the solvent metal, for example, when the solvent metal is an alloy of iron-cobalt-nickel and the nitrogen source is FeN, the content of the nitrogen source can be 0.01% by mass or more and 10% by mass or less.

[0091] The solvent metal 4 may further contain one or more elements selected from the group consisting of titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), copper (Cu), zirconium (Zr), niobium (Nb), molybdenum (Mo), ruthenium (Ru), rhodium (Rh), hafnium (Hf), tantalum (Ta), tungsten (W), osmium (Os), iridium (Ir), and platinum (Pt).

[0092] <Irradiation process> Next, the obtained diamond single crystal is processed to a thickness of 0.1 mm to 10 mm in the case of a 10 mm square size, for example. The processed diamond single crystal is then irradiated with an electron beam to introduce lattice defects into the diamond single crystal and form vacancies.

[0093] The electron beam irradiation conditions are: electron beam energy 1.0 MeV to 10 MeV, dose 1.0 × 10 19 e / m 2 Over 1.0 x 10 23 e / m 2The range of irradiation with the electron beam is larger than the surface (region) of the diamond single crystal that is irradiated with the electron beam. If the energy or dose of the electron beam is less than the above lower limit, there is a risk that the introduction of lattice defects will be insufficient. Conversely, if it exceeds the above upper limit, there is a risk that excessive vacancies will be generated, resulting in a significant decrease in crystallinity.

[0094] <Annealing process> Next, the electron beam irradiated diamond single crystal was heated for 10 -3 Annealing is performed at a pressure of 0.2 MPa or more and 1600°C or more and 1800°C or less. The heating rate is 1°C / min or more and 3°C / min or less until the maximum temperature is reached. The temperature is then lowered at a rate of 0.5°C / min or more and 5°C / min or less. This causes isolated substitutional nitrogen atoms in the diamond single crystal to move through the vacancies, creating agglomerated nitrogen defects. The annealing time can be 10 minutes or more and 1000 minutes or less.

[0095] If the annealing temperature is less than 1600°C, the nitrogen migration speed will be slow, resulting in insufficient annealing, which is undesirable. On the other hand, if the annealing temperature is higher than 1800°C, the nitrogen migration speed will be faster, but the diamond single crystal will be graphitized under normal pressure. Therefore, when annealing at a temperature higher than 1800°C, it is necessary to perform the annealing under ultra-high pressure conditions under which diamond is thermodynamically stable, but this is undesirable from the viewpoint of increased costs and reduced productivity.

[0096] The irradiation step and the annealing step can be repeated two or more times, with each step being performed once. This can promote the movement of isolated substitutional nitrogen atoms within the diamond single crystal. By performing the irradiation step and the annealing step sufficiently, a moderately sufficient amount of agglomerated nitrogen defects are generated from the isolated substitutional nitrogen atoms in the diamond single crystal.

[0097] <Acid treatment process> Next, the annealed diamond single crystal is immersed in acid to perform an acid treatment. The acid used in the acid treatment step is a mixed solution of concentrated sulfuric acid and concentrated nitric acid. The acid treatment step lasts for 5 minutes or more. The time may be 300 minutes or less. The temperature of the acid may be from room temperature to 300°C.

[0098] <Features of the method for producing single crystal diamond according to this embodiment> In this embodiment, the single crystal diamond is produced as follows: "In the irradiation step, the electron beam irradiation conditions are: electron beam energy of 1.0 MeV or more and 10 MeV or less, and a dose of 1.0 × 10 19 e / m 2 Over 1.0 x 10 23 e / m 2 "In the annealing process, 10 -3 "The annealing step is performed at a pressure of 1600°C to 1800°C in the annealing step," "The temperature rise rate is 1°C / min to 10°C / min and the temperature fall rate is 0.5°C / min to 5°C / min in the annealing step" (in other words, the temperature is slowly raised and lowered), and "The acid treatment step is performed by immersing the material in a mixed solution of concentrated sulfuric acid and concentrated nitric acid for 5 minutes or more." By these measures, even when the nitrogen atom content is low (in other words, when the nitrogen atom content based on the atomic number is 1 ppm to 2000 ppm), "the number of nitrogen atoms in the C center, N C The total number of nitrogen atoms, N ALL and the number of nitrogen atoms in the C center, N C Difference from N ALL -N C Proportion (N ALL -N C ) / N C is 1 to 10 5 The reason for this is presumably as follows.

[0099] (i) In the method for producing a single crystal diamond according to this embodiment, "in the irradiation step, the electron beam irradiation conditions are: electron beam energy of 1.0 MeV or more and 10 MeV or less, and a dose of 1.0 × 10 19 e / m 2 Over 1.0 x 10 23 e / m 2 "In the annealing process, 10 -3 By "annealing at a pressure of 1000 Pa or more and 0.2 MPa or less" and "annealing at a temperature of 1600°C or more and 1800°C or less in the annealing step," it is possible to promote aggregation between nitrogen atoms, aggregation between nitrogen atoms and vacancies, or both. For example, in Patent Document 2, the temperature in the annealing step is less than 1600°C, making it difficult to sufficiently promote aggregation between nitrogen atoms, aggregation between nitrogen atoms and vacancies, or both.

[0100] (ii) However, "in the irradiation process, the electron beam irradiation conditions are: electron beam energy of 1.0 MeV or more and 10 MeV or less, and a dose of 1.0 × 10 19 e / m 2 Over 1.0 x 10 23 e / m 2 "In the annealing process, 10 -3 By "annealing at a pressure of 1600°C or more and 0.2MPa or less" and "annealing at a temperature of 1600°C or more and 1800°C or less in the annealing step", it is possible to promote the aggregation of nitrogen, but because the temperature of the annealing step is high, there is a tendency that the reverse phase transformation from diamond to graphite occurs easily.Therefore, in order to produce the single crystal diamond of this embodiment, it is necessary to suppress the occurrence of this reverse phase transformation.

[0101] (iii) In the method for producing a single crystal diamond according to this embodiment, "in the annealing step, the temperature rise rate is set to 1°C / min or more and 3°C / min or less, and the temperature fall rate is set to 0.5°C / min or more and 5°C / min or less" (in other words, the temperature is raised and lowered slowly), thereby making it difficult for "reverse phase transformation from diamond to graphite" to occur, which is caused by the high temperature in the annealing step. As a result, it is possible to minimize the amount of graphite that forms on the surface of the single crystal diamond.

[0102] (iv) In the method for manufacturing a single crystal diamond according to this embodiment, the graphite that forms on the surface of the single crystal diamond (in other words, the graphite that is kept to a minimum in (iii) above) can be removed by "carrying out the acid treatment process under the condition of immersing the diamond in a mixed solution of concentrated sulfuric acid and concentrated nitric acid for at least 5 minutes."

[0103] The fact that the single crystal diamond of the present disclosure can be realized by the above manufacturing method is a new discovery made by the present inventors as a result of extensive research.

[0104] [Embodiment 2: Tools] The tool according to this embodiment will be described. This embodiment is a tool comprising the single crystal diamond according to embodiment 1.

[0105] According to the present disclosure, a tool including a single crystal diamond having excellent wear resistance can be provided.

[0106] ≪Tools≫ Examples of tools according to this embodiment include wear-resistant tools such as dressers, wire-drawing dies, surgical knives, injection molding nozzles, wire guides, scribing tools, and water jet orifices, cutting tools such as precision cutting tools and woodworking cutters, and grinding tools such as grinding wheels. This makes it possible to provide wear-resistant tools, cutting tools, and grinding tools as tools equipped with single-crystal diamond having excellent wear resistance.

[0107] <Tool manufacturing method> The method for manufacturing a tool according to this embodiment can be carried out by a conventionally known method, except that the single crystal diamond according to the first embodiment is used as the material for the tool. [Example]

[0108] The present embodiment will be described in more detail with reference to examples, although the present embodiment is not limited to these examples.

[0109] <Production of single crystal diamond> Single crystal diamonds according to Samples 1 to 14 were produced as follows.

[0110] <Temperature difference method process> First, using the sample chamber configured as shown in Figure 1, single-crystal diamond was synthesized by the temperature gradient method using a solvent metal.

[0111] An alloy consisting of iron, cobalt, and nickel was prepared as the solvent metal, and iron nitride (FeN) powder was added to it as a nitrogen source. The concentration of iron nitride (FeN) in the solvent metal is shown in Table 1 under "Iron nitride concentration in solvent metal [mass%]."

[0112] Diamond powder was used as the carbon source, and a diamond single crystal with the mass listed in Table 1 was used as the seed crystal. The temperature inside the sample chamber was adjusted using a heater so that there was a temperature difference of several tens of degrees between the high-temperature section where the carbon source was located and the low-temperature section where the seed crystal was located. Using an ultra-high-pressure generator, this was held for 100 hours under conditions of a pressure of 5.5 GPa and a "low-temperature section temperature" of 1370°C ± 10°C (1360°C - 1380°C), and single crystal diamond was synthesized on the seed crystal.

[0113] <Irradiation process> Next, in cases where the "Yes" column in Table 1 states "Whether electron beam irradiation was performed" the obtained diamond single crystal was irradiated with an electron beam (electron beam energy: as listed in Table 1; electron beam dose: as listed in Table 1).

[0114] <Annealing process> Next, when "Yes" is described in the "Presence or absence of heat treatment" column of Table 2, the annealing process was carried out on the diamond single crystal after the irradiation process under normal pressure in a vacuum under the conditions described in Table 2.

[0115] <Acid treatment process> Next, the diamond single crystal after the annealing process was acid-treated with a mixed solution of concentrated sulfuric acid and concentrated nitric acid for 30 minutes to obtain single crystal diamond. In the mixed solution, the ratio of concentrated sulfuric acid (concentration 95% by mass) to concentrated nitric acid (concentration 60% by mass) was 3:1 on a volume basis.

[0116] Single crystal diamond related to Samples 1 to 14 was produced by the above procedure.

[0117] ≪Characteristic evaluation of single crystal diamond≫ <Content ratio based on the number of nitrogen atoms> For the single crystal diamond related to each sample, the content ratio based on the number of nitrogen atoms was determined by the method described in Embodiment 1. The obtained results were recorded in the column of "Nitrogen atom content [ppm]" in Table 3.

[0118] <(N ALL -N C ) / N C > For the single crystal diamond related to each sample, the ratio (N C -N ALL ) / N C of the difference N ALL -N C between the total number of nitrogen atoms N ALL -N C ) / N C and the number of nitrogen atoms N ALL -N C ) / N C of the nitrogen atoms at the C center was determined by the method described in Embodiment 1. The obtained results were recorded in the column of "(N

[0119] <Presence or absence of A center> For each single crystal diamond related to each sample, the presence or absence of A centers was determined by the method described in Embodiment 1. The obtained results are recorded in the column of "Presence or Absence of A Centers" in Table 3.

[0120] <Presence or Absence of B Centers> For each single crystal diamond related to each sample, the presence or absence of B centers was determined by the method described in Embodiment 1. The obtained results are recorded in the column of "Presence or Absence of B Centers" in Table 3.

[0121] <NV 0 Centers> For each single crystal diamond related to each sample, the presence or absence of NV 0 centers was determined by the method described in Embodiment 1. The obtained results are recorded in the column of "Presence or Absence of NV 0 Centers" in Table 3.

[0122] <NV ― Centers> For each single crystal diamond related to each sample, the presence or absence of NV ― centers was determined by the method described in Embodiment 1. The obtained results are recorded in the column of "Presence or Absence of NV ― Centers" in Table 3.

[0123] <Presence or Absence of H2 Centers> For each single crystal diamond related to each sample, the presence or absence of H2 centers was determined by the method described in Embodiment 1. The obtained results are recorded in the column of "Presence or Absence of H2 Centers" in Table 3.

[0124] <Presence or Absence of H3 Centers> For each single crystal diamond related to each sample, the presence or absence of H3 centers was determined by the method described in Embodiment 1. The obtained results are recorded in the column of "Presence or Absence of H3 Centers" in Table 3.

[0125] <Presence or Absence of N3 Centers> For each single crystal diamond related to each sample, the presence or absence of N3 centers was determined by the method described in Embodiment 1. The obtained results are recorded in the column of "Presence or Absence of N3 Centers" in Table 3.

[0126] <Wear resistance evaluation test> Using each of the single crystal diamonds of each sample, cutting tools (holder: CSRP R3225-N12, tip: SPGN120308, tool equipped with the above single crystal diamond at the cutting edge of the tip) were made, and the outer diameter of the workpiece was turned using the cutting tool under the following cutting conditions, and the cutting distance [km] until the average flank wear width of the cutting tool reached 200 μm was measured. The results obtained are shown in the "Cutting distance [km]" column in the "Wear resistance test" section of Table 4. The longer the cutting distance [km], the better the wear resistance. (Cutting conditions) Work material: Ti-6Al-4V (φ120mm×280mm) Cutting speed: 250m / min Feed rate: 0.1mm / rev Cutting depth: 0.4 mm Coolant: wet

[0127] <Chipping resistance evaluation test> Using each of the single crystal diamonds for each sample, turning inserts specified by catalog number "NF-DNMA150408" (Sumitomo Electric Industries, Ltd.) were produced. Next, the turning inserts were used to cut the workpiece under the following cutting conditions, and when the size of chipping at the cutting edge of the turning insert exceeded 0.1 mm, cutting was stopped and the time [minutes] from the start of the test to that point was measured. The results obtained are recorded in the "Time [minutes]" column in the "Chipping resistance test" section of Table 4. The longer the time [minutes], the better the chipping resistance. (Cutting conditions) Workpiece: cemented carbide (VM-40 (dimensions: diameter φ60 mm x length 100 mm), hardness: HRA88) Processing machine: lathe Cutting speed Vc: 10m / min Feed rate f: 0.05 mm / rev Depth of cut ap: 0.05mm / rev Cutting oil (coolant): None

[0128] [Table 1]

[0129] [Table 2]

[0130] [Table 3]

[0131] [Table 4]

[0132] The single crystal diamonds of Samples 7 to 14 correspond to Examples. The single crystal diamonds of Samples 1 to 6 correspond to Comparative Examples. The results in Table 1 show that the single crystal diamonds of Samples 7 to 14 have both superior wear resistance and superior chipping resistance compared to the single crystal diamonds of Samples 1 to 6.

[0133] From the above, it was found that the single crystal diamonds according to Samples 7 to 14 had both excellent wear resistance and excellent chipping resistance.

[0134] 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.

[0135] 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]

[0136] 1 Single crystal diamond, 2 Insulator, 3 Carbon source, 4 Solvent metal, 5 Seed crystal, 6 Pressure medium, 7 Graphite heater, 21 Single crystal diamond, 27 Altered area.

Claims

1. The content of nitrogen atoms based on the number of atoms is 1 ppm or more and 2000 ppm or less, Number of nitrogen atoms in the C center Ｃ The total number of nitrogen atoms, N ＡＬＬ and the number N of nitrogen atoms in the C center Ｃ Difference with N ＡＬＬ -N Ｃ The proportion of (N ＡＬＬ -N Ｃ ) / N Ｃ is 1 or more and 10 ５ is as follows: The single crystal diamond includes an H2 center.

2. The single crystal diamond according to claim 1 , wherein the single crystal diamond comprises an A center.

3. 3. The single crystal diamond according to claim 1, wherein the single crystal diamond contains a B center.

4. The single crystal diamond is NV ０ 3. The single crystal diamond according to claim 1 or claim 2, which comprises a center.

5. The single crystal diamond is NV ― 3. The single crystal diamond according to claim 1 or claim 2, which comprises a center.

6. 3. The single crystal diamond according to claim 1, wherein the single crystal diamond contains an H3 center.

7. 3. The single crystal diamond according to claim 1, wherein the single crystal diamond contains an N3 center.

8. a surface of the single crystal diamond comprising a first region; The first region has an arithmetic mean height Sa defined in JIS B 0681-2:2018 of 3 nm or more, 3. The single crystal diamond according to claim 1, wherein the first region has a maximum height Sz defined in JIS B 0681-2:2018 of 60 nm or more.

9. an altered portion is present on the outer periphery of the single crystal diamond, In the core electron excitation spectrum obtained by electron energy loss spectroscopy using a transmission electron microscope of the altered portion, the amount of energy loss is in the range of 285 eV±5 eV. ＊ Maximum intensity of the peak Iπ ＊ and σ in the range of energy loss 291±5 eV. ＊ Maximum intensity of the peak Iσ ＊ The ratio Iπ ＊ / Iσ ＊ is 0.15 or more, 3. The single-crystal diamond according to claim 1 or claim 2, wherein in the altered portion, the percentage {N1 / (N1+N2)}×100 of the number N1 of primary carbon atoms to the sum N1+N2 of the number N1 of primary carbon atoms constituting amorphous carbon and the number N2 of secondary carbon atoms constituting graphite is 90% or more.

10. A tool comprising the single crystal diamond of claim 1 or claim 2.

11. The tool of claim 10, wherein the tool is a cutting tool, a wear tool, or a grinding tool.

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