Single crystal diamond and tool

Abstract

Provided is a single crystal diamond in which the content of nitrogen atoms based on the number of atoms is 1 ppm to 2,000 ppm inclusive. The surface of the single crystal diamond includes a first region, the arithmetic mean height Sa, which is defined in JIS B 0681-2 (2018), of the first region is 3 nm or more, and the maximum height Sz, which is defined in JIS B 0681-2 (2018), of the first region is 60 nm or more.

Description

Single Crystal Diamonds and Tools

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

[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.

[0003] International Publication No. 2017 / 014309

[0004] The single crystal diamond of the present disclosure is 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 has an arithmetic mean height Sa defined in JIS B 0681-2:2018 of 3 nm or more, and the first region has a maximum height Sz defined in JIS B 0681-2:2018 of 60 nm or more.

[0005] Figure 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 is a schematic cross-sectional view of a wire drawing die according to an embodiment of the present disclosure. Figure 3 is a schematic cross-sectional view of a single crystal diamond according to an embodiment of the present disclosure.

[0006] [Problem to be Solved by the Present 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 an 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 the Present 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] [Explanation of embodiments of the present disclosure] First, embodiments of the present disclosure will be listed and explained. (1) The single crystal diamond of the present disclosure is 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 includes a first region, the first region has an arithmetic mean height Sa defined in JIS B 0681-2:2018 of 3 nm or more, and the first region has a maximum height Sz defined in JIS B 0681-2:2018 of 60 nm or more.

[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, and 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, and in the altered portion, a percentage {N1 / (N1+N2)}×100 of the number N1 of primary carbon atoms to a 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, N 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 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 adhesion 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 embodiment 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. Furthermore, dimensional relationships such as length, width, thickness, and depth have been appropriately changed for the sake of clarity and simplification of the drawings, and do not necessarily represent actual dimensional relationships.

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

[0020] In the present disclosure, when one or more numerical values ​​are listed as the lower limit and the upper limit of a numerical range, the combination of any one numerical value listed as the lower limit and any one numerical value listed as 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 the atomic number of 1 ppm or more and 2000 ppm or less, the surface of the single crystal diamond including 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.

[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 the decrease in 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 arithmetic mean height Sa of the first region as defined in JIS B 0681-2: 2018 is 3 nm or more, and the maximum height Sz of the first region as defined in JIS B 0681-2: 2018 is 60 nm or more. 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 facilitating 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 defined 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 defined 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 × 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 integer 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 object.

[0030] When there is a unit region 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 region. 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. Furthermore, the first region can constitute the entire surface of the single crystal diamond. The proportion of the first region to the entire surface of the single crystal diamond can be, for example, 25% or more, 50% or more, or even 100%.

[0033] 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 about 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 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, 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.

[0035] In the core electron excitation spectrum obtained by the TEM-EELS method in the altered area, the amount of energy loss 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 a peak derived from 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 exist 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 ＊ 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 ＊ and 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 of the ratio Iπ in the core electron excitation spectrum obtained by the TEM-EELS method in 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 direction of 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 region corresponding to the altered portion in the bright-field image. The region corresponding to the altered portion in the bright-field image can be identified, for example, by a difference in contrast. When a region with a contrast different from others is confirmed on the surface of the single crystal diamond, this region is deemed to be the region corresponding to the altered portion. The following measurements are carried out in the region corresponding to the altered portion in the bright-field image, which is estimated to be 3 nm or more thick.

[0043] Step A3: Starting from the surface of the region corresponding to the altered portion, a measurement point is set within a distance of 2 nm to 3 nm along the normal direction of the surface of the single crystal diamond, and an electron energy loss spectroscopy (EELS) method is applied to observe the energy loss (K edge) associated with the excitation of carbon K-shell electrons by scanning a 1 nm diameter observation spot 100 nm in a direction parallel to the surface of the single crystal diamond. In this way, a core electron excitation spectrum of around 300 eV associated with the excitation of carbon K-shell electrons at the measurement point is obtained.

[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±5 eV. ＊ 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 performed 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 portion ＊ / Iσ ＊ is judged to be 0.15 or more.

[0046] <<Measurement of percentage {N1 / (N1+N2)}×100 in the affected area>> Step B1. Next, the ratio Iπ is calculated by the above steps A1 to A4. ＊ / Iσ ＊ At each of five measurement points set in the region corresponding to the altered portion where it is determined that π is 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 result. ＊ 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 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 region corresponding to the measured altered part is determined to be 90% or more. In other words, the region corresponding to the altered part identified in step B1 is determined to be the region corresponding to the ratio Iπ in the core electron excitation spectrum obtained by the TEM-EELS method. ＊ / 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 obtained by acquiring multiple bright-field images that do not overlap each other and changing the measurement point in the region corresponding to the altered portion 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, or 96% or more, or alternatively 99% or more.

[0052] <Infrared absorption spectrum> In the single crystal diamond of embodiment 1, the atomic number N 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 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] The "C center" is a diamond crystal in which a nitrogen atom replaces a carbon atom on an atomic basis. Diamonds containing the "C center" include type Ib. Single crystal diamonds containing the C center have a wavenumber of 1130 cm in the infrared absorption spectrum measured by Fourier transform infrared spectroscopy. －１ (e.g., wave number 1130±2 cm －１ ) shows the absorption peak.

[0054] <<(N ＡＬＬ -N Ｃ ) / N Ｃ ≫ 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 This can improve the wear resistance and chipping resistance of the single crystal diamond. 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 It may be 10 or less, ３ It may be 10 or less, ２ (N ＡＬＬ -N Ｃ ) / N Ｃ is 1.5 or more 10 ４ It may be 2.0 or more and 10 ３ It may be the following:

[0055] In the present 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 performing measurements using secondary ion mass spectrometry (SIMS) under the following conditions. Ｃ and N ＡＬＬ Based on this, (N ＡＬＬ -N Ｃ ) / N Ｃ (Conditions) Measurement device: Product name (product number): "IMS-7f", manufactured by CAMECA Primary ion species: Cesium (Cs+) Primary acceleration voltage: 15 kV 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, and 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, and may be, for example, 0.1 mm ３ ~1000mm ３ may be.

[0058] <Method for Manufacturing Single Crystal Diamond> An example of a method for manufacturing a single crystal diamond according to the first embodiment will be described below.

[0059] <First step> In the first step, a diamond single crystal having a nitrogen atom content of 1 ppm to 2000 ppm based on the atomic number is synthesized by a temperature difference method using a solvent metal. The diamond single crystal can be produced by the temperature difference 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 provided 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 1 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.

[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] The carbon source 3 or the solvent metal 4 may contain, as a nitrogen source, for example, iron nitride (Fe ２ N, Fe ３ N), aluminum nitride (AlN), phosphorus nitride (P ３ N ４ ), silicon nitride (Si ３ N ４ Nitrides such as nitrite, melamine, and sodium azide can be added singly or as a mixture. Nitrogen-rich diamond or graphite can also be added as a nitrogen source. This allows nitrogen atoms to be contained in the synthesized diamond single crystal. 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 synthesized diamond single crystal 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 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, the solvent metal can be an alloy consisting of iron-cobalt-nickel, and the nitrogen source can be Fe ３ In the case of N, 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 Step> 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. Subsequently, the processed diamond single crystal is irradiated with an electron beam to introduce lattice defects into the diamond single crystal and form vacancies.

[0066] The electron beam irradiation conditions were: electron beam energy of 1.0 MeV to 10 MeV, and a dose of 1.0×10 １９ e / m ２ Above 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, the introduction of lattice defects may be insufficient. Conversely, if it exceeds the above upper limit, excessive vacancies may be generated, which may significantly reduce the crystallinity.

[0067] <Third Step> Next, in the third step, the diamond single crystal after the second step is subjected to 10 －３A 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 rate of temperature rise until the maximum temperature is reached is more than 6°C / min and not more than 10°C / min. The temperature is then lowered at a rate of -0.5°C / min to -5°C / min. After cooling, the cooled diamond single crystal is subjected to an acid treatment. For example, the acid treatment is performed by immersing the diamond single crystal 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, and a first region having an arithmetic mean height Sa of 3 nm or more and a maximum height Sz of 60 nm or more is formed, thereby realizing the single crystal diamond of embodiment 1. This was newly discovered by the present inventors as a result of extensive research.

[0069] <Features of the manufacturing method for single crystal diamond of this embodiment> In the manufacturing method for 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 it is possible to prevent the surface roughness from becoming excessively large. If the heating rate is faster than 10 ° C / min, the stress state of the surface changes significantly, causing fine cracks to occur on the surface and resulting in excessive surface roughness. In the past, from the perspective 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 it is possible to prevent the surface roughness from becoming excessively large. If the temperature drop rate is faster than -5°C / min, the stress state of the surface changes significantly, causing fine cracks to form on the surface and resulting in 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: Tool] 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 wiredrawing die 20 will be described as an example of a tool of embodiment 2. Fig. 2 is a schematic cross-sectional view of the wiredrawing die 20 of embodiment 2. As shown in Fig. 2, the wiredrawing die 20 comprises a case member 25 having a recess 26, a single crystal diamond 21 of embodiment 1 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, with the single crystal diamond 21 being fixed to the case member 25 by the metal sintered body. In the wiredrawing die 20 of Fig. 2, the single crystal diamond 21 is arranged so that the surface of the single crystal diamond 21 in contact with the bonding material 24 includes a 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 makes up 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 inlet side and the bottom is the outlet side. The bottom surface of the single crystal diamond 21 on the outlet 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] [Supplementary Note 1] The tool of the present disclosure comprises: a base; a single crystal diamond provided on the base; and a bonding material provided between the base and the single crystal diamond for fixing the single crystal diamond to the base, wherein at least a part of a region of a surface of the single crystal diamond that contacts the bonding material is a first region, and the first region has an arithmetic mean height Sa defined in JIS B 0681-2:2018 of 3 nm or more, and a maximum height Sz defined in JIS B 0681-2:2018 of 60 nm or more.

[0079] [Appendix 2] A wire drawing die according to the present disclosure comprises: a case member having a recess; a single crystal diamond provided on a bottom surface of the case member; and a bonding material provided between the case member and the single crystal diamond for fixing the single crystal diamond to the case member, wherein at least a part of a region of a surface of the single crystal diamond that contacts the bonding material is a first region, the first region has an arithmetic mean height Sa defined in JIS B 0681-2:2018 of 3 nm or more, and the first region has a maximum height Sz defined in JIS B 0681-2:2018 of 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 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, wherein 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, and the first region has an area of ​​100 μm ２ That's it, single crystal diamond.

[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] [Preparation of Single Crystal Diamond] <First Step> Using a sample chamber having the configuration shown in FIG. 1, a single crystal diamond was synthesized by the temperature difference method using a solvent metal.

[0083] An alloy consisting of iron-cobalt-nickel was prepared as a solvent metal, and iron nitride (Fe ３ The concentration of iron nitride in the solvent metal was adjusted so that the nitrogen atom content in the diamond single crystal, 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 a 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 5.5 GPa, and the temperature in the low-temperature section was controlled to be between 1360°C and 1380°C, and maintained for 100 hours, allowing the synthesis of a diamond single crystal on the seed crystal.

[0085] <Second Step> Next, for samples marked "Yes" in the "Presence or Absence of 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 in Table 1 for which "No" is written in the "Presence or absence of second step" column, the second step 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 "Third Step" in 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 the samples marked "None" in the "Whether or not the third step was performed" column in Table 1, the third step was not performed.

[0088]

[0089] [Evaluation of Single Crystal Diamond] <Nitrogen Content> The nitrogen atom content of each sample of single crystal diamond was measured by SIMS based on the number of atoms. The results are shown in the "Nitrogen Atom Content" column of Table 2.

[0090] <Arithmetic mean height Sa and maximum height Sz> It was confirmed whether the surface of the single crystal diamond of each sample 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 confirmation method is as described in embodiment 1. It was confirmed that the surfaces of the single crystal diamonds 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 diamonds 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] <Altered Region> It was confirmed whether or not an altered region was present on the outer periphery of the single crystal diamond of each sample. The specific confirmation method is as described in embodiment 1. It was confirmed that an altered region was present on the outer periphery of the single crystal diamond of samples 3 to 5 and samples 8 to 10. It was confirmed that an altered region was not present in the single crystal diamond of samples 1, 2, 6 and 7.

[0093] The ratio Iπ measured by the above-mentioned method for confirming the altered portion ＊ / Iσ ＊ , and the percentage {N1 / (N1+N2)}×100 is calculated using "Iπ ＊ / Iσ ＊ " and "{N1 / (N1+N2)}×100" columns.

[0094] <Adhesion strength> Cu alloy powder with a particle size of 50 μm or less was placed on one bottom surface of a cylindrical SUS304 plate with a diameter of 30 mm and a height of 10 mm so that the surface of the SUS304 plate was not exposed. ３A single crystal diamond of each sample was placed on the single crystal diamond. A load of 10 kg was applied from above the single crystal diamond, and the diamond and Cu alloy were sintered by holding at 850°C for 3 minutes. After cooling for 1 hour, the single crystal diamond was struck from the side with a plastic hammer, and the number of strikes with the hammer until the single crystal diamond was removed was measured. The higher the number of strikes, the better the adhesion. The relative value of the number of strikes for each sample was calculated based on the number of strikes for sample 6. In the "Adhesion" column of Table 2, a relative value of 1 to 2 is indicated as C, a value of more than 2 to 10 is indicated as B, and a value of more than 10 is indicated as A. A indicates excellent adhesion between the single crystal diamond and the bonding material.

[0095]

[0096]

[0097] [Discussion] 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 intended from the beginning that the configurations of the above-described embodiments and examples may be appropriately combined and modified in various ways. The embodiments and examples disclosed herein are illustrative in all respects and should not be considered limiting. The scope of the present invention is defined by the claims, not by the above-described embodiments and examples, and is intended to include meanings equivalent to the claims and all modifications within the scope of the claims.

[0099] REFERENCE SIGNS LIST 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 Bonding material, 25 Case member, 26 Recess, 26a Recess bottom surface.

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, wherein the surface of the single crystal diamond includes a first region, the first region has an arithmetic mean height Sa defined in JIS B 0681-2:2018 of 3 nm or more, and the first region has a maximum height Sz defined in JIS B 0681-2:2018 of 60 nm or more.

2. The single crystal diamond has an altered portion on its outer periphery, 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±5 eV. ＊ Maximum intensity of the peak Iσ ＊ The ratio 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 is 90% or more.

3. Number of nitrogen atoms in the C center, N 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. A tool comprising a single crystal diamond according to any one of claims 1 to 3.

5. The tool of claim 4, wherein the tool is a cutting tool, a grinding tool, a wear-resistant tool, or a wire-drawing tool.

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