Single Crystal Diamonds and Tools

Abstract

A single crystal diamond having a nitrogen atom content based on the atomic number of 1 ppm or more and 2000 ppm or less, wherein the surface of the single crystal diamond includes a first region, the first region having an arithmetic mean height Sa defined in JIS B 0681-2:2018 of 3 nm or more, and the first region having a maximum height Sz defined in JIS B 0681-2:2018 of 60 nm or more.

Description

[Technical Field]

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

[0002] Single crystal diamond has very high fracture strength and excellent wear resistance, and is therefore used as a material for various tools. For example, Patent Document 1 discloses a diamond die comprising a single crystal diamond. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2017 / 014309 Summary of the Invention

[0004] The single crystal diamond of the present disclosure is A single-crystal diamond having a nitrogen atom content based on atomic number of 1 ppm or more and 2000 ppm or less, 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; The first region is a single-crystal diamond having a maximum height Sz of 60 nm or more as defined in JIS B 0681-2:2018. [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 single-crystal diamond according to an embodiment of the present disclosure. [Figure 2] FIG. 2 is a schematic cross-sectional view of a wire drawing die according to an embodiment of the present disclosure. [Figure 3] FIG. 3 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] When single crystal diamond is used as a tool material, it is common to manufacture the tool by fixing the single crystal diamond to a substrate. As a method for fixing the single crystal diamond to a substrate, for example, there is a method in which a bonding material such as alloy powder is placed between the tool substrate and the single crystal diamond, and the bonding material is sintered to fix the single crystal diamond to the substrate via the bonding material.

[0007] If the adhesion between the single crystal diamond and the bonding material is insufficient, it will be difficult to achieve stable tool performance, and there is also the possibility that the single crystal diamond will come off the substrate. For this reason, there is a demand for an improvement in the adhesion between the single crystal diamond and the bonding material.

[0008] Therefore, the present disclosure aims to provide a single crystal diamond that can improve the adhesion between the single crystal diamond and a bonding material when a tool is fabricated by fixing the single crystal diamond to a substrate via a bonding material, and a tool equipped with the single crystal diamond.

[0009] [Effects of this disclosure] According to the present disclosure, when a tool is fabricated by fixing a single crystal diamond to a substrate via a bonding material, it is possible to provide a single crystal diamond that can improve the adhesion between the single crystal diamond and a bonding material, and a tool that includes the single crystal diamond.

[0010] [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 A single-crystal diamond having a nitrogen atom content based on atomic number of 1 ppm or more and 2000 ppm or less, 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; The first region is a single-crystal diamond having a maximum height Sz of 60 nm or more as defined in JIS B 0681-2:2018.

[0011] According to the present disclosure, when a tool is fabricated by fixing a single crystal diamond to a substrate via a bonding material, it is possible to provide a single crystal diamond that can improve the adhesion between the single crystal diamond and a bonding material, and a tool that includes the single crystal diamond.

[0012] (2) In the above (1), 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 part, the energy loss amount was 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 greater than or equal to 0.15, 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.

[0013] This improves the workability of the diamond.

[0014] (3) In the above (1) or (2), 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 ) / NC is 1 to 10 5 It may be the following:

[0015] This improves the wear resistance and chipping resistance of the single crystal diamond.

[0016] (4) A tool according to the present disclosure is a tool comprising the single crystal diamond according to any one of (1) to (3) above. When the single crystal diamond is fixed to a substrate via a bonding material, the adhesive strength between the single crystal diamond and the bonding material can be improved. This allows the tool to exhibit stable tool performance and also prevents the single crystal diamond from coming off the substrate.

[0017] (5) In the above (4), the tool may be a cutting tool, a grinding tool, a wear-resistant tool, or a wire-drawing tool. These tools can exhibit stable tool performance and can prevent the single-crystal diamond from coming off the substrate.

[0018] [Details of the embodiments of the present disclosure] Specific examples of the single crystal diamond and tool of the present disclosure will be described below with reference to the drawings. In the drawings of the present disclosure, the same reference numerals represent the same or corresponding parts. In addition, the dimensional relationships of length, width, thickness, depth, etc. are appropriately changed for the sake of clarity and simplification of the drawings, and do not necessarily represent the actual dimensional relationships.

[0019] In the present disclosure, the notation in the form "A to B" means greater than or equal to A and less than or equal to B, and when no unit is specified for A and only a unit is specified for B, the unit of A and the unit of B are the same.

[0020] In this disclosure, when one or more numerical values ​​are listed as the lower limit and upper limit of a numerical range, the combination of any one numerical value listed in the lower limit and any one numerical value listed in the upper limit is also disclosed.

[0021] [Embodiment 1: Single Crystal Diamond] A single-crystal diamond according to one embodiment of the present disclosure (hereinafter also referred to as "embodiment 1") is A single-crystal diamond having a nitrogen atom content based on atomic number of 1 ppm or more and 2000 ppm or less, the surface of the single crystal diamond includes a first region; The arithmetic mean height Sa of the first region as defined in JIS B 0681-2:2018 is 3 nm or more, The first region is a single-crystal diamond having a maximum height Sz of 60 nm or more as defined in JIS B 0681-2:2018.

[0022] <Nitrogen content> The nitrogen atom content based on the atomic number of the single crystal diamond of embodiment 1 (hereinafter also referred to as "nitrogen content") is 1 ppm or more and 2000 ppm or less. If the nitrogen content is 1 ppm or more, it is easy to adjust the nitrogen content in the manufacturing process of the single crystal diamond of embodiment 1. If the nitrogen content is 2000 ppm or less, crystal defects and distortion are reduced, and a decrease in the strength of the single crystal diamond is suppressed. The nitrogen content of the single crystal diamond may be 3 ppm or more and 1400 ppm or less, 10 ppm or more and 800 ppm or less, or 30 ppm or more and 300 ppm or less.

[0023] In the present disclosure, the nitrogen atom content of a single crystal diamond based on the atomic number is measured by secondary ion mass spectrometry (SIMS). Measurement points are any five points on the single crystal diamond. In the present disclosure, the average of the five measured points corresponds to the nitrogen atom content of the single crystal diamond based on the atomic number.

[0024] <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 has 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. As a result, the surface of the single crystal diamond has appropriate irregularities, and 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.

[0025] The arithmetic mean height Sa of the first region is 3 nm or more from the viewpoint of improving the adhesion between the single crystal diamond and the bonding material. The arithmetic mean height Sa of the first region is preferably 100 nm or less from the viewpoint of ease of material installation. The arithmetic mean height Sa of the first region may be 3 nm or more and 100 nm or less, 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.

[0026] 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 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 60 nm or more and 500 nm or less, 80 nm or more and 400 nm or less, or 100 nm or more and 300 nm or less.

[0027] 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)).

[0028] In the present disclosure, whether the surface of a single crystal diamond includes a first region is confirmed by the following procedure.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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%.

[0033] <tem-eels> As shown in Figure 3, an altered region 27 may be present in the outer periphery of the single crystal diamond 21 of embodiment 1. The altered region 27 may be present in at least a part of the outer periphery of the single crystal diamond 21, or may be present in 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.

[0034] 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.

[0035] 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.

[0036] The carbon atoms having a π bond present in the altered portion 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).

[0037] In the altered portion of the single crystal diamond of embodiment 1, the percentage 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, {N1 / (N1+N2)}×100, 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 with wavelengths of 355 nm to 1064 nm, which are used in processing single crystal diamonds, compared to diamond and graphite.

[0038] 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 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 processability when laser processing the single crystal diamond.

[0039] 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.

[0040] <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:

[0041] 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.

[0042] 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 differences in contrast. When an area with a contrast different from others is identified on the surface of the single-crystal diamond, that area is deemed to be the area that corresponds to the altered area. The following measurements are performed on an area in the bright-field image that corresponds to the altered area, which is estimated to be 3 nm or more thick.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] <<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.

[0047] 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.

[0048] 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 part, and it is confirmed that the single crystal diamond being measured has an altered part.

[0049] As long as measurements are taken on the same single crystal diamond, the ratio Iπ can be measured by taking multiple bright-field images that do not overlap each other and changing the measurement point in the region corresponding to the altered part in each bright-field image. * / Iσ * It has been confirmed that there is almost no variation in the measurement results of the percentage {N1 / (N1+N2)}×100.

[0050] 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.

[0051] In the altered portion of the single crystal diamond of embodiment 1, the percentage {N1 / (N1+N2)}×100 is 90% or more, or alternatively 93% or more, 96% or more, or even 99% or more.

[0052] <Infrared absorption spectrum> In the single crystal diamond of embodiment 1, 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 or less. This makes it easier for nitrogen atoms to aggregate, or nitrogen atoms and vacancies to aggregate, or both, 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.

[0053] 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.

[0054] <<(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 can improve 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:

[0055] 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 of N, it is 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. B69 (1994) 1141. and G.S. Woods, J.A. van Wyk, A.T. Collins, Philos. Mag. B62 (1990) 589." ALL is 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 Calculate. (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)

[0056] The single crystal diamond of embodiment 1 may be a synthetic single crystal diamond.

[0057] The shape of the single crystal diamond of embodiment 1 is not particularly limited, but may be, for example, a plate, a disk, a triangular plate, a hexagonal plate, an octagonal plate, or a dodecagonal plate. 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.

[0058] <Method of manufacturing single crystal diamond> An example of the method for producing the single crystal diamond of the first embodiment will be described below.

[0059] <First step> In the first step, a diamond single crystal with a nitrogen atom content of 1 ppm to 2000 ppm (based on atomic number) is synthesized by a temperature gradient method using a solvent metal. The diamond single crystal can be produced by the temperature gradient method using, for example, a sample chamber 10 having the configuration shown in Figure 1.

[0060] As shown in Figure 1, in a sample chamber 10 used to produce a diamond single crystal 1, an insulator 2, a carbon source 3, a solvent metal 4, and a seed crystal 5 are arranged in a space surrounded by a graphite heater 7, and a pressure medium 6 is arranged outside the graphite heater 7. The temperature difference method is a method in which a vertical temperature gradient is created inside the sample chamber 10, and a high-temperature section (T high ) carbon source 3, low temperature part (T low ) and a solvent metal 4 is placed between the carbon source 3 and the seed crystal 5, and the temperature is maintained at or above the temperature at which the solvent metal 4 dissolves and at or above the pressure at which the diamond becomes thermally stable, thereby growing a diamond single crystal 1 on the seed crystal 5.

[0061] At least one selected from the group consisting of diamond powder, graphite, and pyrolytic carbon can be used as the carbon source 3. At least one metal selected from the group consisting of iron (Fe), cobalt (Co), nickel (Ni), and manganese (Mn), or an alloy containing these metals can be used as the solvent metal 4.

[0062] Nitrogen sources such as nitrides such as iron nitride (FeN, FeN), aluminum nitride (AlN), phosphorus nitride (PN), and silicon nitride (SiN) or organic nitrogen compounds such as melamine and sodium azide can be added to the carbon source 3 or solvent metal 4, either singly or as a mixture. Diamond or graphite containing a large amount of nitrogen can also be added as a nitrogen source. 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 primarily present as isolated substitutional nitrogen atoms.

[0063] The concentration of the nitrogen source in the carbon source 3 or the solvent metal 4 is adjusted so that the nitrogen atom content in the diamond single crystal synthesized is 1 ppm or more and 2000 ppm or less based on the number of atoms.For example, in the carbon source, the concentration of the nitrogen atoms derived from the nitrogen source based on the number of atoms can be 1 ppm or more and 5000 ppm or less.In addition, in the solvent metal, for example, when the solvent metal is an alloy made of iron-cobalt-nickel and the nitrogen source is Fe3N, the concentration of the nitrogen source can be 0.01% by mass or more and 10% by mass or less.

[0064] The solvent metal 4 may further contain at least one element 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).

[0065] <Second process> Next, in the second step, the diamond single crystal obtained in the first step 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.

[0066] 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 2 The 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.

[0067] <Third step> Next, in the third step, the diamond single crystal after the second step is subjected to 10 -3 A pressure of 0.2 Pa to 0.2 MPa and a temperature of 1500°C to 1800°C are applied for 10 to 1000 minutes. The temperature is increased at a rate of more than 6°C / min and not more than 10°C / min until the maximum temperature is reached. The temperature is then decreased at a rate of -0.5°C / min to -5°C / min. After cooling, the single crystal diamond is subjected to an acid treatment. The acid treatment may involve immersing the single crystal diamond in a mixed solution of concentrated sulfuric acid and concentrated nitric acid for 5 minutes or more. This allows the single crystal diamond of embodiment 1 to be obtained.

[0068] By carrying out the third step under the above conditions, irregularities are formed on at least a portion of the surface of the diamond single crystal, forming a first region with an arithmetic mean height Sa of 3 nm or more and a maximum height Sz of 60 nm or more, thereby realizing the single crystal diamond of embodiment 1. This was a new discovery made by the present inventors after extensive research.

[0069] <Features of the method for producing single crystal diamond according to this embodiment> In the manufacturing method of the single crystal diamond of this embodiment, the heating rate in the third step is more than 6 ° C / min and 10 ° C / min or less. This makes it difficult for the stress state of the surface to change, so that excessive increase in surface roughness can be suppressed. If the heating rate is faster than 10 ° C / min, the stress state of the surface changes significantly, causing fine cracks on the surface and excessive surface roughness. In the past, from the viewpoint of improving production efficiency, a heating rate of 10 ° C / min or less was not adopted.

[0070] In the manufacturing method of the single crystal diamond of this embodiment, the temperature drop rate in the third step is -5 ° C / min or slower. This makes it difficult for the stress state of the surface to change, so that excessive increase in surface roughness can be suppressed. If the temperature drop rate is faster than -5 ° C / min, the stress state of the surface changes significantly, causing fine cracks on the surface and excessive surface roughness. Conventionally, from the viewpoint of improving production efficiency, a temperature rise rate of -5 ° C / min or slower has not been adopted.

[0071] In the third step, isolated substitutional nitrogen atoms in the diamond single crystal move through the vacancies and aggregate to form aggregated nitrogen atoms.

[0072] [Embodiment 2: Tools] A tool according to one embodiment of the present disclosure (hereinafter also referred to as "Embodiment 2") is a tool comprising the single crystal diamond described in Embodiment 1. The tool of Embodiment 2 can comprise a substrate and the single crystal diamond of Embodiment 1 provided on the substrate. In the tool of Embodiment 2, the single crystal diamond is a component involved in machining and is a component that comes into contact with a workpiece during machining. In the tool of Embodiment 2, the substrate and the single crystal diamond may be fixed via a bonding material. Since the arithmetic mean height Sa of the first region of the single crystal diamond is 3 nm or more and the maximum height Sz is 60 nm or more, when the first region is arranged so as to come into contact with the bonding material, the adhesion between the single crystal diamond and the bonding material is improved.

[0073] The tool according to the second embodiment may be, for example, a wire drawing tool, a cutting tool, a grinding tool, a wear-resistant tool, or a wire drawing tool.

[0074] Examples of the wire drawing tool include a wire drawing die. Examples of the cutting tool include a drill, an end mill, an indexable cutting tip for a drill, an indexable cutting tip for an end mill, an indexable cutting tip for a milling process, an indexable cutting tip for a turning process, a metal saw, a gear cutting tool, a reamer, a tap, and a cutting tool.

[0075] Examples of the wear-resistant tools include dies, wire guides, injection molding nozzles, scribers, scribing wheels, dressers, surgical knives, etc. Examples of the grinding tools include grinding wheels, etc.

[0076] A wire drawing die 20 will be described as an example of a tool of the second embodiment. Fig. 2 is a schematic cross-sectional view of the wire drawing die 20 of the second embodiment. As shown in Fig. 2, the wire drawing die 20 includes a case member 25 having a recess 26, a single crystal diamond 21 of the first embodiment provided on a bottom surface 26a of the recess of the case member 25, and a bonding material 24 made of a metal sintered body provided between the case member 25 and the single crystal diamond 21, and the single crystal diamond 21 is fixed to the case member 25 by the metal sintered body. In the wire drawing die 20 of Fig. 2, the single crystal diamond 21 is arranged so that the surface of the single crystal diamond 21 that contacts the bonding material 24 includes the first region. This improves the adhesion between the single crystal diamond 21 and the bonding material 24.

[0077] The case member 25 can be, for example, a cylindrical stainless steel. The metal sintered body that constitutes the bonding material 24 is formed by setting the single crystal diamond 21 in the case member 25, and then filling the recess 26 with alloy powder and sintering it. A hole is formed in the single crystal diamond 21, and the top of Figure 2 is the entrance side and the bottom is the exit side. The bottom surface of the single crystal diamond 21 on the exit side contacts the bottom surface 26a of the recess, and the other surfaces of the single crystal diamond 21 contact the bonding material 24.

[0078] [Appendix 1] The tool of the present disclosure comprises: a substrate; a single crystal diamond provided on a substrate; a bonding material provided between the substrate and the single crystal diamond to fix the single crystal diamond to the substrate; At least a part of the region of the surface of the single crystal diamond that is in contact with the bonding material is a first region, The arithmetic mean height Sa of the first region as defined in JIS B 0681-2:2018 is 3 nm or more, The tool, wherein the maximum height Sz of the first region as specified in JIS B 0681-2:2018 is 60 nm or more.

[0079] [Appendix 2] The wire drawing die of the present disclosure comprises: a case member having a recess; a single crystal diamond provided on the bottom surface of the case member; a bonding material provided between the case member and the single crystal diamond to fix the single crystal diamond to the case member; At least a part of the region of the surface of the single crystal diamond that is in contact with the bonding material is a first region, The arithmetic mean height Sa of the first region as defined in JIS B 0681-2:2018 is 3 nm or more, A wire drawing die, wherein the maximum height Sz of the first region as specified in JIS B 0681-2:2018 is 60 nm or more.

[0080] [Appendix 3] The single crystal diamond of the present disclosure is A single-crystal diamond having a nitrogen atom content based on atomic number of 1 ppm or more and 2000 ppm or less, 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; The first region has a maximum height Sz defined in JIS B 0681-2:2018 of 60 nm or more, The area of ​​the first region is 100 μm 2 That's it, single crystal diamond. [Example]

[0081] The present embodiment will be described in more detail with reference to examples, although the present embodiment is not limited to these examples.

[0082] [Production of single crystal diamond] <First step> Using the sample chamber configured as shown in Figure 1, single-crystal diamond was synthesized by the temperature gradient method using a solvent metal.

[0083] 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 in the solvent metal was adjusted so that the nitrogen atom content in the single crystal diamond, based on the atomic number, was as shown in the "Nitrogen atom content" column of "Single crystal diamond" in Table 2.

[0084] Diamond powder was used as the carbon source, and approximately 0.5 mg of diamond single crystal was used as the seed crystal. The temperature in 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, the pressure was controlled to 5.5 GPa and the temperature in the low-temperature section was kept in the range of 1360°C to 1380°C for 100 hours, and diamond single crystal was synthesized on the seed crystal.

[0085] <Second process> Next, for samples marked "Yes" in the "Second step" column in Table 1, the resulting diamond single crystal was irradiated with an electron beam. The irradiation conditions were an electron beam energy of 3 MeV and a dose of 3.0 × 10 21 e / m 2 For samples with "No" in the "Presence or absence of second process" column in Table 1, the second process was not carried out.

[0086] <Third step> Next, for samples marked "Yes" in the "Whether or not third step was performed" section of Table 1, the diamond single crystal after electron beam irradiation was held at the pressure and temperature listed in the "Pressure" and "Temperature" columns for the time listed in the "Holding time" column of the "Third step" section of Table 1. The heating rate was as listed in the "Heating rate" column.

[0087] Thereafter, the samples were cooled at the rate shown in the "Cooling Rate" column in Table 1. After cooling, the single crystal diamonds were subjected to an acid treatment. For the acid treatment, the samples were immersed in a mixed solution of concentrated sulfuric acid (concentration 95% by mass) and concentrated nitric acid (concentration 60% by mass) (concentrated sulfuric acid: concentrated nitric acid = 3:1 (volume ratio)) for 30 minutes. This resulted in the production of single crystal diamonds for each sample. The single crystal diamonds for each sample were plate-shaped and had a size of 1 mm. 3 For samples with "No" in the "Whether or not the third step was performed" section of Table 1, the third step was not performed.

[0088] [Table 1]

[0089] [Evaluation of single crystal diamonds] <Nitrogen content> The nitrogen atom content of each sample of single-crystal diamond was measured by SIMS based on the atomic number. The results are shown in the "Nitrogen atom content" column in Table 2.

[0090] <Arithmetic mean height Sa and maximum height Sz> The single crystal diamond of each sample was checked to see if its surface contained a first region having an arithmetic mean height Sa of 3 nm or more and a maximum height Sz of 60 nm or more. The specific checking method is as described in embodiment 1. It was confirmed that the surfaces of the single crystal diamond of samples 3 to 5 and samples 8 to 10 were entirely composed of the first region. It was confirmed that the surfaces of the single crystal diamond of samples 1, 2, 6 and 7 did not contain the first region.

[0091] In all samples, the arithmetic mean height Sa and maximum height Sz of the surface showed almost no variation. The arithmetic mean height Sa and maximum height Sz of the entire surface of each sample are shown in the "Arithmetic mean height Sa" and "Maximum height Sz" columns in Table 2. In samples 3 to 5 and samples 8 to 10, these values ​​correspond to the "arithmetic mean height Sa" and "Maximum height Sz" of the first region.

[0092] <Affected area> The single crystal diamond of each sample was checked to see if there was an altered region on the periphery of the single crystal diamond. The specific checking method is as described in embodiment 1. It was confirmed that the single crystal diamonds of samples 3 to 5 and samples 8 to 10 had an altered region on the periphery of the single crystal diamond. It was confirmed that the single crystal diamonds of samples 1, 2, 6 and 7 did not have an altered region.

[0093] The ratio Iπ measured by the above method for checking the affected area * / Iσ * , and percentage {N1 / (N1+N2)}×100 in Table 3, "Iπ * / Iσ * " and "{N1 / (N1+N2)}×100" columns.

[0094] <Adhesion> Cu alloy powder with a particle size of 50 μm or less was placed on one bottom surface of a cylindrical SUS304 with a diameter of 30 mm and a height of 10 mm, so that the surface of the SUS304 was not exposed. 3 A single crystal diamond for each sample was placed on the bonded ...

[0095] [Table 2]

[0096] [Table 3]

[0097] [Consideration] The single crystal diamonds of Samples 3 to 5 and Samples 8 to 10 correspond to Examples. The single crystal diamonds of Samples 1, 2, 6 and 7 correspond to Comparative Examples. It was confirmed that the single crystal diamonds of Samples 3 to 5 and Samples 8 to 10 have improved adhesion to the bonding material compared to the single crystal diamonds of Samples 1, 2, 6 and 7.

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

[0099] 1 diamond single crystal, 2 insulator, 3 carbon source, 4 solvent metal, 5 seed crystal, 6 pressure medium, 7 graphite heater, 10 sample chamber, 20 wire drawing die, 21 single crystal diamond, 23 hole, 24 joining material, 25 case member, 26 recess, 26a recess bottom.

Claims

1. A single-crystal diamond having a nitrogen atom content based on the atomic number of 1 ppm or more and 2000 ppm or less, The surface of the single crystal diamond comprises a first region specified by the following method. The method for specifying the first region is as follows. The surface of the single crystal diamond is divided into a plurality of 10 μm × 10 μm rectangular unit areas, and the arithmetic mean height Sa defined in JIS B 0681-2:2018 and the maximum height Sz defined in JIS B 0681-2:2018 are measured for each of the unit areas. Of the plurality of unit regions, the unit region having the arithmetic mean height Sa of 3 nm or more and the maximum height Sz of 60 nm or more is identified as the first region.

2. an altered portion identified by the following method is present in at least a part of the outer periphery of the single crystal diamond; at least a portion of the surface of the single crystal diamond is the surface of the altered portion, 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, 2. The single-crystal diamond according to claim 1, 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. The method for identifying the altered portion is as follows. The single crystal diamond is sliced ​​using an argon ion slicer along a plane parallel to the normal direction of the surface of the single crystal diamond to obtain a measurement sample having a thickness of 3 to 100 nm. The measurement sample is observed at 50,000 to 500,000 magnifications using a transmission electron microscope to obtain a bright-field image of the single-crystal diamond. In the bright-field image, the region corresponding to the altered portion and the region other than the altered portion are distinguished by the difference in contrast. A region present in the outer periphery of the single crystal diamond and having a contrast different from the region other than the altered portion is identified as the altered portion.

3. 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 3. A single crystal diamond according to claim 1 or claim 2, wherein:

4. the arithmetic mean height Sa of the first region is 3 nm or more and 100 nm or less, 3. The single crystal diamond according to claim 1, wherein the maximum height Sz of the first region is 60 nm or more and 500 nm or less.

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

6. The tool of claim 5 , wherein the tool is a cutting tool, a grinding tool, a wear-resistant tool, or a wire-drawing tool.

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