Single-crystal diamond substrate

Abstract

Provided is a single crystal diamond substrate comprising a first main surface and a second main surface opposite from the first main surface. The first main surface and the second main surface each include a continuous single growth sector having a surface area of 0.25 mm2 or greater. The average value c1 of the content ratio of nitrogen in the growth sector in terms of the number of atoms is 0.01-50 ppm.

Description

Single crystal diamond substrate

[0001] This disclosure relates to a single-crystal diamond substrate. This application claims priority to Japanese Application No. 2024-054171, filed on March 28, 2024, and incorporates by reference all of the contents of said Japanese application.

[0002] In recent years, a new application of diamond has been attracting attention: the use of diamond in magnetic sensors. Diamond for magnetic sensors is doped with nitrogen by substitution (Patent Document 1). Diamond for magnetic sensors is fabricated, for example, from a single-crystal diamond substrate.

[0003] International Publication No. 2022 / 210566

[0004] The single crystal diamond substrate of the present disclosure includes a first major surface and a second major surface opposite the first major surface. Each of the first and second major surfaces has an area of ​​0.25 mm ２ The growth sectors include a single continuous growth sector having the above structure, and the average nitrogen atom number content c1 of the growth sectors is 0.01 ppm or more and 50 ppm or less.

[0005] FIG. 1 is an example of a side view of a single crystal diamond substrate according to embodiment 1. FIG. 2 is an example of a top view of a single crystal diamond substrate according to embodiment 1. FIG. 3 is a diagram showing a single crystal diamond grown from a single crystal diamond seed substrate. FIG. 4 is a diagram showing a first main surface 1a of a single crystal diamond substrate cut out at a position indicated by symbol P1 from the single crystal diamond shown in FIG. 3. FIG. 5 is a diagram showing a second main surface 1b of a single crystal diamond substrate cut out at a position indicated by symbol P1 from the single crystal diamond shown in FIG. 3. FIG. 6 is a diagram for explaining a method for measuring the nitrogen content of a single crystal diamond substrate. FIG. 7 is a cross-sectional view of a single crystal diamond seed substrate used in embodiment 2. FIG. 8 is a diagram schematically showing the configuration of a sample chamber used in a temperature difference method under high temperature and high pressure. FIG. 9 is a diagram for explaining the relationship between the cutting position of a single crystal diamond substrate and the plane orientation of the main surface. FIG. 10 is a diagram for explaining the relationship between the cutting position of a single crystal diamond substrate and the plane orientation of the main surface. FIG. 11 is a diagram for explaining the cutting position of a single crystal diamond substrate.

[0006] A single crystal diamond substrate can be cut from a single crystal diamond formed on a single crystal diamond seed substrate (hereinafter also referred to as "seed substrate"). In the synthesis of single crystal diamond, the seed substrate has a significant effect on the crystallinity of the single crystal diamond grown thereon. For example, cracks occur inside the single crystal diamond that grows from the corners of the seed substrate. If a single crystal diamond substrate is cut from a single crystal diamond containing a crack, the crack will cause the single crystal diamond substrate to break. Even if the single crystal diamond substrate does not break, the cracks present inside the single crystal diamond substrate will divide the growth sector, and the single growth sector area will be 0.25 mm ２ It will be less than.

[0007] An object of the present disclosure is to provide a single crystal diamond substrate that can produce diamonds for high-sensitivity magnetic sensors of uniform quality at a high yield.

[0008] From the single crystal diamond substrate of the present disclosure, diamonds for high-sensitivity magnetic sensors of the same quality can be obtained with a high yield.

[0009] First, embodiments of the present disclosure will be listed and described.

[0010] (1) A single crystal diamond substrate according to an embodiment of the present disclosure is a single crystal diamond substrate including a first main surface and a second main surface opposite to the first main surface, wherein each of the first main surface and the second main surface has an area of ​​0.25 mm ２ The growth sectors include the above-mentioned continuous single growth sectors, and the average nitrogen atom number content c1 of the growth sectors is 0.01 ppm or more and 50 ppm or less.

[0011] The single crystal diamond substrate of the present disclosure has a large area of ​​a single continuous growth sector on its main surface, and this growth sector has a nitrogen concentration suitable for high-sensitivity magnetic sensors. As a result, diamonds for high-sensitivity magnetic sensors of the same quality can be obtained from the single crystal diamond substrate of the present disclosure with a high yield.

[0012] (2) In the above (1), the area of ​​the growth sector is 5 mm ２ This allows diamond for high-sensitivity magnetic sensors of the same quality to be obtained from the single crystal diamond substrate with a higher yield.

[0013] (3) In the above (1) or (2), the plane orientation of the first main surface and the second main surface may be an (lmn) plane that satisfies l + m + n ≦ 8. This allows the flat growth surface (the surface that appears as an idiomorph) formed by the temperature difference method under high temperature and high pressure in the single crystal diamond substrate, the crystal axis that makes it easy to determine the sensing orientation, and the plane orientation for realizing high-sensitivity sensing to be determined, and therefore, in a magnetic sensor that uses diamond for a magnetic sensor from a single crystal diamond substrate, it is possible to cover all the magnetic orientations required for sensing.

[0014] (4) In any of the above (1) to (3), the plane orientation of the first main surface and the second main surface may be the (111) plane. This makes it easier to align the magnetic orientation to be sensed with <111> in a magnetic sensor using a diamond for a magnetic sensor made from a single crystal diamond substrate, thereby increasing the magnetic sensitivity to be detected.

[0015] (5) In any of the above (1) to (3), the plane orientation of the first main surface and the second main surface may be the (100) plane. This makes it easier to align the magnetic orientation to be sensed with <100> in a magnetic sensor using a diamond for a magnetic sensor made from a single crystal diamond substrate, thereby increasing the magnetic sensitivity to be detected.

[0016] (6) In any of the above (1) to (3), the plane orientation of the first main surface and the second main surface may be the (110) plane. This makes it easier to align the magnetic orientation to be sensed with <110> in a magnetic sensor using a diamond for a magnetic sensor made from a single crystal diamond substrate, thereby increasing the magnetic sensitivity to be detected.

[0017] (7) In any of the above (1) to (6), the total atomic content of the impurity elements excluding nitrogen in the growth sector may be lower than the atomic content of nitrogen, and may be 0.01 ppb or more and 5 ppm or less. This reduces magnetic sensitivity noise caused by impurities in a magnetic sensor using diamond for a magnetic sensor from a single crystal diamond substrate, thereby increasing magnetic sensitivity.

[0018] (8) In any of (1) to (7) above, in the growth sector, the percentage of the difference between the maximum value c2 of the nitrogen content based on the number of atoms and the average value c1 of the nitrogen content based on the number of atoms, {(c2-c1) / c1} x 100, relative to the average value c1 of the nitrogen content based on the number of atoms, may be 50% or less, and the percentage of the difference between the average value c1 and the minimum value c3 of the nitrogen content based on the number of atoms, {(c1-c3) / c1} x 100, relative to the average value c1, may be 50% or less.

[0019] Variation in the nitrogen atomic number content within a growth sector is a factor that causes noise in the magnetic sensitivity of a magnetic sensor. When the average value c1, maximum value c2, and minimum value c3 of the nitrogen atomic number content satisfy the above conditions, magnetic sensitivity noise can be reduced and magnetic sensitivity can be increased in a magnetic sensor using a diamond for a magnetic sensor from a single crystal diamond substrate.

[0020] [Details of the Embodiments of the Present Disclosure] Details of the embodiments of the present disclosure will be described below with reference to the drawings. In the following drawings, 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 clarity and simplification of the drawings, and do not necessarily represent actual dimensional relationships.

[0021] 1 and 2, a single crystal diamond substrate 1 according to one embodiment of the present disclosure (hereinafter also referred to as "embodiment 1") includes a first main surface 1a and a second main surface 1b opposite to the first main surface 1a. Each of the first main surface 1a and the second main surface 1b has an area of ​​0.25 mm ２ The average nitrogen atom number content c1 of the continuous single growth sectors is 0.01 ppm or more and 50 ppm or less.

[0022] The single crystal diamond substrate 1 of Embodiment 1 has a large area of ​​a single continuous growth sector on its main surface, and this growth sector has a nitrogen concentration suitable for high-sensitivity magnetic sensors. Therefore, it is possible to obtain diamonds for high-sensitivity magnetic sensors of the same quality from the single crystal diamond substrate 1 of Embodiment 1 with a high yield.

[0023] <Area of ​​a continuous single growth sector> The single crystal diamond substrate 1 of embodiment 1 of the present disclosure is made from a single crystal diamond grown on a single crystal diamond seed substrate (hereinafter also referred to as "seed substrate"). The single crystal diamond includes growth sectors grown from a crystal plane of a specific plane orientation of the seed substrate. The growth sector grown from the (abc) plane (crystal plane) of the seed substrate is referred to as the (abc) sector. Growth sectors included in single crystal diamond include a (100) sector, a (111) sector, a (113) sector, and a (115) sector. For example, the single crystal diamond 2 shown in FIG. 3 includes a (100) sector grown from the (100) plane of the seed substrate 5 and a (111) sector grown from the (111) plane of the seed substrate 5.

[0024] FIG. 4 is a diagram showing the first main surface 1a of a single crystal diamond substrate cut at the position indicated by symbol P1 from the single crystal diamond 2 shown in FIG. 3. FIG. 5 is a diagram showing the second main surface 1b of a single crystal diamond substrate cut at the position indicated by symbol P1 from the single crystal diamond 2 shown in FIG. 3. As shown in FIG. 4, the first main surface 1a consists of only a continuous (100) sector. As shown in FIG. 5, the second main surface 1b consists of a continuous (100) sector and four (111) sectors. Because the four (111) sectors of the second main surface 1b grow from four different crystal planes of the seed substrate, as shown in FIG. 5, there are boundaries 20 between the (111) sectors. Therefore, the four (111) sectors of the second main surface 1b are not continuous. Thus, even if a main surface contains multiple growth sectors of the same type adjacent to each other, if there is a boundary separating them, these multiple growth sectors do not constitute a single continuous growth sector.

[0025] Each of the first and second main surfaces of the single crystal diamond substrate of embodiment 1 has an area of ​​0.25 mm ２ This method includes the above-mentioned continuous single growth sector. This improves the uniformity of the quality of the single crystal diamond substrate, making it possible to obtain diamond for magnetic sensors of the same quality from the single crystal diamond substrate with a high yield.

[0026] The area of ​​a single continuous growth sector on each of the first and second major surfaces of the single crystal diamond substrate is 0.25 mm ２ Over 400mm ２ It may be less than 5 mm ２ More than 300 mm ２ Less than 7mm is also acceptable ２ More than 200 mm ２ It may be less than 10 mm ２ More than 100 mm ２ The following is also acceptable.

[0027] Growth sectors growing from different crystal planes of the seed substrate have different impurity concentrations and therefore different fluorescence intensities. The fluorescence distribution on the main surface of the single-crystal diamond substrate can be observed using photoluminescence (PL) or cathodoluminescence (CL). Observation of the fluorescence distribution allows the boundaries of growth sectors growing from different crystal planes of the seed substrate to be identified. The boundaries of different growth sectors on each of the first and second main surfaces are identified using PL or CL, and the areas of single, continuous growth sectors on each of the first and second main surfaces are measured.

[0028] PL is performed by adjusting the excitation light intensity so that the boundaries of the growth sectors can be clearly observed, for example, using excitation light with a wavelength of 350 nm or less.CL is performed by detecting the light emitted when an electron beam is irradiated onto a single-crystal diamond substrate under conditions of an acceleration voltage of 20 kV and a specimen current of 20 nA.

[0029] <Nitrogen content of a continuous single growth sector> <Average value c1 of nitrogen content> In the single crystal diamond substrate of embodiment 1, the average value c1 of the nitrogen content based on the number of atoms of a continuous single growth sector (hereinafter also referred to as "nitrogen content") is 0.01 ppm or more and 50 ppm or less. When the average value c1 of nitrogen content is 0.01 ppm or more, the diamond for magnetic sensors from the single crystal diamond substrate is suitable for high-sensitivity magnetic sensors. When the average value c1 of nitrogen content is 50 ppm or less, the occurrence of crystal defects and distortion that may be caused by nitrogen in the single crystal diamond substrate can be suppressed. The average value c1 of nitrogen content may be 0.1 ppm or more and 20 ppm or less, 0.3 ppm or more and 10 ppm or less, or 0.5 ppm or more and 3 ppm or less.

[0030] The average value c1 of the nitrogen content of a single continuous growth sector is measured and calculated by secondary ion mass spectrometry (SIMS). The analysis conditions are as follows: <Analysis conditions> Primary ion species: Cs+ Primary acceleration voltage: 15 kV Measurement spot diameter: φ30 mm

[0031] The measurement points for the nitrogen content of a single continuous growth sector will be explained using Figure 6. In Figure 6, the reference symbols 3a, 3b, 3c, 3d, and 3e indicate measurement points, which are set as follows: 3a is the center of the maximum inscribed circle C1 of a single continuous growth sector on the first main surface 1a of the single crystal diamond substrate 1. The points dividing the circumference of the maximum inscribed circle C1 into four are designated as 3b, 3c, 3d, and 3e, respectively.

[0032] The nitrogen content is measured by SIMS at the five measurement points 3a, 3b, 3c, 3d, and 3e, and the average value is calculated. In the present disclosure, this average value corresponds to the average nitrogen content c1 of a single continuous growth sector.

[0033] It has been confirmed that even when the nitrogen content is measured by changing the measurement points 3b, 3c, 3d, and 3e on the circumference of the largest inscribed circle C1 of the same single crystal diamond substrate, the nitrogen content obtained is almost the same. Furthermore, in the above, the nitrogen content of a single continuous growth sector is measured at the measurement points provided on the first main surface. As with the first main surface, even when the nitrogen content is measured by providing measurement points on the second main surface, it has been confirmed that the nitrogen content obtained on the second main surface is almost the same as that on the first main surface.

[0034] <<Variation in Nitrogen Content>> In a single continuous growth sector of the single crystal diamond substrate of embodiment 1, the percentage of the difference between the maximum nitrogen content c2 and the average nitrogen content c1, relative to the average nitrogen content c1, {(c2-c1) / c1} x 100, is 50% or less, and the percentage of the difference between the average nitrogen content c1 and the minimum nitrogen content c3, relative to the average nitrogen content c1, {(c1-c3) / c1} x 100, may be 50% or less.

[0035] The percentage {(c2-c1) / c1} x 100 may be 30% or less, and the percentage {(c1-c3) / c1} x 100 may be 30% or less. The percentage {(c2-c1) / c1} x 100 may be 15% or less, and the percentage {(c1-c3) / c1} x 100 may be 15% or less. The percentage {(c2-c1) / c1} x 100 may be 5% or less, and the percentage {(c1-c3) / c1} x 100 may be 5% or less. The lower limits of the percentage {(c2-c1) / c1} x 100 and the percentage {(c1-c3) / c1} x 100 are not particularly limited and may be 0% or more.

[0036] The maximum value c2 and minimum value c3 of the nitrogen content correspond to the maximum and minimum values ​​of the nitrogen content at the measurement points 3a, 3b, 3c, 3d, and 3e set in measuring the average nitrogen content value c1, respectively.

[0037] <Maximum Length> The maximum length of each of the first and second main surfaces of the single crystal diamond substrate of embodiment 1 may be 4 mm or more, 4 mm or more and 30 mm or less, 5 mm or more and 30 mm or less, 6 mm or more and 30 mm or less, or 7 mm or more and 30 mm or less.

[0038] In the present disclosure, the maximum length refers to the maximum length of a straight line connecting two points on the outer edge of the main surface. The maximum lengths of the first and second main surfaces of the single-crystal diamond substrate are measured using an optical microscope with a length measurement function.

[0039] <Plane Orientation> The plane orientation of the first and second main faces of the single crystal diamond substrate of embodiment 1 may be an (lmn) plane that satisfies l + m + n ≤ 8, where both m and n are integers of 0 or greater.

[0040] The first and second main surfaces of the single crystal diamond substrate of embodiment 1 may have a (111) plane orientation.

[0041] The first and second main surfaces of the single crystal diamond substrate of embodiment 1 may have a plane orientation of (100).

[0042] The first and second main surfaces of the single crystal diamond substrate of embodiment 1 may have a (110) plane orientation.

[0043] <Impurity content excluding nitrogen in a continuous single growth sector> The total content of impurity elements excluding nitrogen in a continuous single growth sector of the single crystal diamond substrate of embodiment 1 based on the atomic number (hereinafter also referred to as "impurity element content") may be lower than the nitrogen content and may be 0.01 ppb or more and 5 ppm or less. The impurity element content of a continuous single growth sector may be 0.01 ppb or more and 4 ppm or less, or 0.01 ppb or more and 3 ppm or less.

[0044] Examples of impurity elements excluding nitrogen include boron (B), aluminum (Al), silicon (Si), iron (Fe), nickel (Ni), chromium (Cr), cobalt (Co), manganese (Mn), titanium (Ti), zirconium (Zr), hafnium (Hf), gallium (Ga), and magnesium (Mg). When two or more types of impurity elements are contained, the impurity element content means the total content of all the impurity elements.

[0045] The impurity element content in a single continuous growth sector is measured by SIMS under the same analytical conditions and at the same locations as those used for measuring the nitrogen content in a single continuous growth sector.

[0046] <Applications> The single crystal diamond substrate of embodiment 1 can be suitably used for highly sensitive magnetic sensors. The single crystal diamond substrate of embodiment 1 can also be used for infrared optical components (e.g., laser window materials, pressure cells, prisms), laser windows, spectroscopic crystals, monochromators, anvils for ultra-high pressure generators, semiconductor diamond substrates, precision cutting tools, etc.

[0047] <Embodiment 2: Method for manufacturing a single crystal diamond substrate> The single crystal diamond substrate of embodiment 1 can be obtained by synthesizing a single crystal diamond on a seed substrate by a temperature difference method under high temperature and high pressure, and then cutting out a substrate from the single crystal diamond.

[0048] <Step of Preparing a Single-Crystal Diamond Seed Substrate> First, a seed substrate is prepared. Figure 7 is a cross-sectional view of the seed substrate 5 used in embodiment 2. The seed substrate 5 has a third main surface 5a on which the single-crystal diamond grows, an inclined surface 5c inclined from the edge portion 5b of the third main surface 5a to the third main surface 5a, a fourth main surface 5e opposite the third main surface 5a, and a side surface 5f connecting the inclined surface 5c and the fourth main surface 5e. The edge portion 5b of the third main surface 5a and the inclined surface 5c form a chamfered portion 5d. The angles α1 and α2 between the third main surface 5a and the inclined surface 5c are greater than 90 degrees. The angles α3 and α4 between the side surface 5f and the inclined surface 5c are greater than 90 degrees. The size of seed substrate 5 may be 0.5 mm or more, 0.5 mm to 20 mm, 1.5 mm to 20 mm, 2 mm to 20 mm, 2.5 mm to 20 mm, or 3 mm to 20 mm.

[0049] The nitrogen content of the seed substrate may be 50 ppm or less, 40 ppm or less, 30 ppm or less, or 20 ppm or less.

[0050] <Step of Growing Single Crystal Diamond> Next, single crystal diamond is grown on the seed substrate using a temperature gradient method under high temperature and high pressure. The temperature gradient method under high temperature and high pressure is performed using a sample chamber having the configuration shown in Figure 8, for example.

[0051] As shown in Figure 8, in the sample chamber 10 used for producing the single crystal diamond 2, an insulator 52, a carbon source 53, a solvent metal 54, and a seed substrate 5 are arranged in a space surrounded by a graphite heater 57, and a pressure medium 56 is arranged outside the graphite heater 57. The temperature difference method under high temperature and high pressure 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 53, low temperature part (T ｌｏｗ ) and a solvent metal 54 is placed between the carbon source 53 and the seed substrate 5, and the temperature is maintained at or above the temperature at which the solvent metal 54 dissolves and at or above the pressure at which the diamond becomes thermally stable, thereby growing a single crystal diamond 2 on the seed substrate 5.

[0052] In the second embodiment, a seed substrate including a chamfered portion 5d as shown in Fig. 7 is used as the seed substrate 5. This suppresses the occurrence of cracks inside the single crystal diamond that originate from the corners of the seed substrate.

[0053] Diamond powder is preferably used as the carbon source 53. Graphite or pyrolytic carbon may also be used as the carbon source 53. The solvent metal 54 may be one or more metals selected from iron (Fe), cobalt (Co), nickel (Ni), manganese (Mn), etc., or an alloy containing these metals.

[0054] At least one nitrogen getter selected from the group consisting of titanium (Ti), zirconium (Zr), hafnium (Hf), gallium (Ga), aluminum (Al) and magnesium (Mg) is added to the solvent metal 54 at a total concentration of 0.1% by mass to 20% by mass, thereby making it possible to keep the nitrogen content in the grown single crystal diamond at 50 ppm or less.

[0055] <Step of Obtaining Single Crystal Diamond Substrate> Next, a single crystal diamond substrate is cut out from the single crystal diamond. For example, a water-guard laser processing machine may be used for cutting. By adjusting the cutting position and direction, the area of ​​the continuous single growth sector on the main surface of the single crystal diamond substrate and the plane orientation of the main surface can be adjusted. For example, as shown below.

[0056] When a single crystal diamond substrate is cut out at the position indicated by symbol P5 of the single crystal diamond 2 shown in Figure 9, the plane orientation of the first main surface 1a and the second main surface 1b of the obtained single crystal diamond substrate becomes the (100) plane. Also, when a single crystal diamond substrate is cut out at the position indicated by symbol P6, the plane orientation of the first main surface 1a and the second main surface 1b of the obtained single crystal diamond substrate becomes the (110) plane. Both the first main surface and the second main surface of the obtained single crystal diamond substrate have a (100) sector as a continuous single growth sector, which is 0.25 mm apart. ２ Includes the above.

[0057] When a single crystal diamond substrate is cut out at the position indicated by symbol P7 of the single crystal diamond 2 shown in Figure 10, the plane orientation of the first main surface 1a and the second main surface 1b of the obtained single crystal diamond substrate becomes the (111) plane. Also, when a single crystal diamond substrate is cut out at the position indicated by symbol P8, the plane orientation of the first main surface 1a and the second main surface 1b of the obtained single crystal diamond substrate becomes the (110) plane. Both the first main surface and the second main surface of the obtained single crystal diamond substrate have a (111) sector as a continuous single growth sector, which is 0.25 mm apart. ２ Includes the above.

[0058] [Supplementary Note 1] A method for manufacturing a single crystal diamond substrate according to a second embodiment of the present disclosure is the method for manufacturing a single crystal diamond substrate according to the first embodiment, comprising the steps of: preparing a single crystal diamond seed substrate including a third main surface and a fourth main surface opposite the third main surface; growing a single crystal diamond on the third main surface using a temperature difference method under high temperature and high pressure; and cutting out a single crystal diamond substrate from the single crystal diamond, wherein the single crystal diamond seed substrate includes an inclined surface that is inclined from an edge portion of the third main surface toward the third main surface, and a side surface that connects the inclined surface and the fourth main surface, and the angle between the third main surface and the inclined surface is greater than 90 degrees, and the angle between the inclined surface and the side surface is also greater than 90 degrees.

[0059] [Supplementary Note 2] The method for producing a single crystal diamond substrate according to Supplementary Note 1, wherein the diameter of the inscribed circle of the third main surface is 0.5 mm or more.

[0060] [Appendix 3] A method for producing a single crystal diamond substrate as described in Appendix 1 or Appendix 2, wherein at least one selected from the group consisting of titanium, zirconium, hafnium, gallium, aluminum, and magnesium is added to the solvent metal in a concentration of 0.1 mass % or more and 20 mass % or less in total in the step of growing the single crystal diamond.

[0061] The present embodiment will be described in more detail with reference to examples, although the present embodiment is not limited to these examples.

[0062] [Fabrication of Single Crystal Diamond Substrates] For Samples 1 to 6, seed substrates including chamfered portions were prepared as shown in Figure 7. In each substrate, the angles α1 and α2 between the third main surface and the inclined surface of the chamfered portion were greater than 90 degrees. The angles α3 and α4 between the inclined surface and the side surface of the chamfered portion were also greater than 90 degrees.

[0063] For sample 7, a seed substrate not including a chamfered portion was prepared.

[0064] In all samples, the plane orientation of the third principal plane on which the single crystal diamond grows was the (100) plane. The nitrogen content of the seed substrate used in each sample and the diameter of the inscribed circle of the third principal plane on which the single crystal diamond grows are as shown in the "Nitrogen content" and "Seed substrate size" columns in Table 1.

[0065]

[0066] Next, using a sample chamber having the configuration shown in FIG. 8, single crystal diamond was grown on the seed substrate by the temperature difference method under high temperature and high pressure to obtain single crystal diamond for each sample.

[0067] Diamond powder was used as the carbon source. The solvent metal composition was Fe / Co = 60 / 40 (mass ratio). Approximately 4 mass% of carbon was added to the solvent to prevent dissolution of the seed substrate. Furthermore, 1 mass% of Ti was added to the solvent as a nitrogen getter.

[0068] The carbon source and the seed substrate were placed in a graphite heater so that there was a temperature difference of about 30°C between them. This was then held at a pressure of 5.5 GPa and a temperature of 1300°C for 100 hours using an ultra-high pressure generator, allowing a single crystal diamond to grow on the seed substrate. Thereafter, the temperature was first lowered to room temperature, then the pressure was reduced, and the grown single crystal diamond was removed.

[0069] Single crystal diamond substrates for each sample were cut out from the extracted single crystal diamond 2 at the position indicated by symbol P9 in Figure 11. In all samples, the plane orientation of the first main surface 1a and the second main surface 1b was the (100) plane. In sample 7, a crack had occurred inside the single crystal diamond, causing the cut single crystal diamond substrate to break. For this reason, in sample 7, the area of ​​the largest continuous single growth sector containing no cracks in the broken single crystal diamond substrate was measured as described below.

[0070] <Area of ​​a Single Continuous Growth Sector> The area of ​​a single continuous growth sector on the first and second main surfaces of the single crystal diamond substrate of each sample was measured by the method described in embodiment 1. The results are shown in Table 2. When the area of ​​the single continuous growth sector on the first and second main surfaces differed, the smaller area was shown in Table 2.

[0071] <Measurement of nitrogen content> In the single crystal diamond substrate of each sample, the average nitrogen content c1, maximum nitrogen content c2, and minimum nitrogen content c3 of a single continuous growth sector were measured by the method described in embodiment 1. Based on the obtained values, {(c2-c1) / c1} x 100 and {(c1-c3) / c1} x 100 were calculated. The results are shown in Table 3.

[0072] <Maximum Length> For each sample of single crystal diamond substrate, the maximum length of each of the first and second main faces was measured using the method described in embodiment 1. The results are shown in Table 2. When the maximum lengths of the first and second main faces differ, Table 2 shows the smaller maximum length.

[0073] <Impurity content excluding nitrogen in a single growth sector> In a single continuous growth sector of the single crystal diamond substrate of each sample, the impurity element content was measured by the method described in embodiment 1. The results are shown in the "Impurity element content" column of Table 3.

[0074] <Number of 0.5 mm square diamond samples produced> For each sample, 0.5 mm square diamond samples were cut from a single continuous growth sector of the single crystal diamond substrate, and the number of diamond samples obtained was counted. The results are shown in the "Number of NV diamonds" column in Table 3.

[0075]

[0076]

[0077] [Discussion] The single crystal diamond substrates of Samples 1 to 5 correspond to Examples. The single crystal diamond substrates of Samples 6 and 7 correspond to Comparative Examples. The single crystal diamond substrates of the Examples were capable of producing more 0.5 mm square diamond samples of the same quality than the single crystal diamond substrates of the Comparative Examples. This is because the single crystal diamond substrates of the Examples have a large area of ​​a single continuous growth sector on the main surface, and this growth sector has a nitrogen concentration suitable for high-sensitivity magnetic sensors, so diamonds for high-sensitivity magnetic sensors of the same quality can be obtained with a high yield.

[0078] 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 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 above-described embodiments and examples, and is intended to include meanings equivalent to the claims and all modifications within the scope of the claims.

[0079] REFERENCE SIGNS LIST 1 Single crystal diamond substrate 1a First main surface 1b Second main surface 2 Single crystal diamond 5 Single crystal diamond seed substrate 5a Third main surface 5b Edge portion 5c Inclined surface 5d Chamfered portion 5e Fourth main surface 5f Side surface 10 Sample chamber 52 Insulator 53 Carbon source 54 Solvent metal 56 Pressure medium 57 Graphite heater 70 Polishing device 71 Sample holder 72 Metal bonded diamond grinding wheel 20 Boundary 3a, 3b, 3c, 3d, 3e Measurement point C1 Maximum inscribed circle P1, P5, P6, P7, P8, P9 Cutting position

Claims

1. A single crystal diamond substrate including a first major surface and a second major surface opposite the first major surface, wherein each of the first major surface and the second major surface has an area of ​​0.25 mm ２ a single crystal diamond substrate comprising the above continuous growth sectors, wherein an average nitrogen content c1 based on the number of atoms in the growth sectors is 0.01 ppm or more and 50 ppm or less.

2. The area of ​​the growth sector is 5 mm ２ The single crystal diamond substrate according to claim 1 .

3. A single crystal diamond substrate according to claim 1 or 2, wherein the plane orientations of the first and second principal surfaces are (lmn) planes that satisfy l+m+n≦8.

4. A single crystal diamond substrate according to any one of claims 1 to 3, wherein the first main surface and the second main surface have a (111) plane orientation.

5. A single crystal diamond substrate according to any one of claims 1 to 3, wherein the first main surface and the second main surface have a (100) plane orientation.

6. A single crystal diamond substrate according to any one of claims 1 to 3, wherein the first main surface and the second main surface have a (110) plane orientation.

7. A single crystal diamond substrate described in any one of claims 1 to 6, wherein the total atomic content of impurity elements excluding nitrogen in the growth sector is lower than the atomic content of nitrogen and is 0.01 ppb or more and 5 ppm or less.

8. A single-crystal diamond substrate according to any one of claims 1 to 7, wherein in the growth sector, the percentage difference between the maximum nitrogen content rate c2 based on the number of atoms and the average nitrogen content rate c1, relative to the average nitrogen content rate c1 based on the number of atoms {(c2-c1) / c1} x 100, is 50% or less, and the percentage difference between the average nitrogen content rate c1 and the minimum nitrogen content rate c3 based on the number of atoms, relative to the average nitrogen content rate c1, {(c1-c3) / c1} x 100, is 50% or less.

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