Diamond substrate and method for manufacturing the same

Abstract

To provide a manufacturing method of a diamond substrate capable of forming a diamond crystal having a nitrogen-vacancy center (NVC) of which the NV axis has [111] high orientation and high density by conducting CVD on a ground substrate under specified conditions.SOLUTION: A manufacturing method of a diamond substrate forms a diamond crystal layer having a nitrogen vacancy center on a ground substrate using a raw material gas containing a hydrocarbon gas and hydrogen gas in a CVD process. The raw material gas is mixed with nitrogen gas or a nitride gas to form the diamond crystal layer having the nitrogen vacancy center in at least a part of the diamond crystal. The raw material gas contains the hydrocarbon gas of 0.005 vol.% or more and 6.000 vol.% or less, the hydrogen gas of 93.500 vol.% or more and less than 99.995 vol.%, and the nitrogen gas or the nitride gas of 5.0×10-5 vol.% or more and 5.0×10-1 vol.% or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a diamond substrate and a method for manufacturing the same. [Background technology]

[0002] Diamond has a wide bandgap of 5.47 eV at room temperature and is known as a wide-bandgap semiconductor.

[0003] Among wide-bandgap semiconductors, diamond has an extremely high dielectric breakdown field strength of 10 MV / cm, enabling high-voltage operation. Furthermore, it possesses the highest thermal conductivity of any known material, resulting in excellent heat dissipation. In addition, its very high carrier mobility and saturation drift rate make it suitable for high-speed devices.

[0004] Therefore, diamond exhibits the highest Johnson figure of merit, which indicates performance as a high-frequency, high-power device, compared to semiconductors such as silicon carbide and gallium nitride, and is considered the ultimate semiconductor.

[0005] Furthermore, diamond possesses the phenomenon of nitrogen-vacancy centers (NVCs) within its crystal structure, making it possible to manipulate and detect single spins at room temperature, and to image their state using optically detected magnetic resonance (OCR). Leveraging these characteristics, diamond is expected to have a wide range of applications as a highly sensitive sensor for magnetic fields, electric fields, temperature, pressure, and other parameters. [Prior art documents] [Non-patent literature]

[0006] [Non-Patent Document 1] M.Hatano et al., OYOBUTURI 85, 311 (2016) [Non-Patent Document 2] T. Fukui, et al., APEX 7,055201(2014). [Non-Patent Document 3] H.Ozawa,et.al.,NDF Dia.Symp.29,16(2015). [Patent Documents]

[0007] [Patent Document 1] US2013 / 0143022A1 [Overview of the project] [Problems that the invention aims to solve]

[0008] As mentioned above, diamond is expected to be put into practical use as a semiconductor material and a material for electronic and magnetic devices, and there is a demand for the supply of large-area, high-quality diamond substrates. For example, Patent Document 1 reports on a technique for forming diamond (111) crystals by heteroepitaxial growth using chemical vapor deposition. In particular, for NVC device applications, which are of high importance among the applications of diamond, it is necessary for the nitrogen-vacancy axis (NV axis) to be highly oriented, and therefore it is desirable for the diamond surface to be a (111) crystal plane in which the NV axis is aligned in the

[0111] direction (Non-Patent Document 1). Furthermore, considering applications in the medical MRI field, for example, if the diamond substrate that serves as the magnetic sensor part has a large diameter (large aperture), it will be possible to realize a device that can efficiently measure a wider area. It is also advantageous in terms of manufacturing costs.

[0009] Furthermore, when using the diamond substrate in electronic and magnetic devices, the sensor portion must not only have the NV axes aligned in the

[0111] direction within the diamond crystal, but also be formed at a high density.

[0010] The following are the methods for producing high-density NVC-forming diamond crystals with

[0111] orientation that have been reported to date.

[0011] Using single-crystal diamond synthesized by high-temperature, high-pressure synthesis (HPHT) as the substrate, microwave plasmaThe chemical vapor deposition (CVD) method, which involves adding nitrogen to hydrogen-diluted methane to promote growth, is being investigated (Non-patent documents 2 and 3).

[0012] However, the reported literature only uses HPHTIb(111) as the base substrate, which is difficult to obtain in practical large sizes. Furthermore, Non-Patent Document 2 does not specify the details of the gas composition in CVD. Also, it is unclear whether the CVD conditions described in Non-Patent Document 3 are optimized.

[0013] The present invention has been made to solve the above problems and aims to provide a method for manufacturing a diamond substrate in which a diamond crystal having a highly oriented

[0111] NV axis and high density nitrogen-vacancy centers (NVCs) can be formed on a substrate by performing CVD under specified conditions. The present invention also aims to provide such a diamond substrate. [Means for solving the problem]

[0014] This invention was made to achieve the above objective, In a method for manufacturing a diamond substrate by forming diamond crystals on a substrate using a raw material gas containing hydrocarbon gas and hydrogen gas as a diluent, using one of the following CVD methods: microwave plasma CVD, DC plasma CVD, thermal filament CVD, and arc discharge plasma jet CVD, nitrogen gas or nitride gas is mixed into the raw material gas in order to form a diamond crystal layer having nitrogen vacancy centers in at least a portion of the diamond crystals formed on the substrate, and the amounts of each gas contained in the raw material gas are set as follows: hydrocarbon gas: 0.005 vol% or more, 6.000 vol% or less; hydrogen gas: 93.500 vol% or more, less than 99.995 vol%; nitrogen gas or nitride gas: 5.0 × 10 -5 5.0 × 10% or more by volume -1 The present invention provides a method for manufacturing a diamond substrate, characterized by forming a diamond crystal layer having the nitrogen vacancy centers at a volume percentage or less.

[0015] According to this CVD-based diamond substrate manufacturing method, a diamond substrate can be manufactured in which a diamond crystal layer is formed that is highly crystalline, has a highly

[0111] orientation of the NV axis, and has high density NVC. Such diamond crystals can be suitable for electronic and magnetic devices.

[0016] In this case, methane gas is used as the hydrocarbon gas, and nitrogen gas is used as the nitrogen gas or nitride gas mixed into the raw material gas, and the amounts of each gas contained in the raw material gas are set as follows: methane gas: 0.1% to 6.000% by volume, hydrogen gas: 93.500% to less than 99.900% by volume, nitrogen gas: 5.0 × 10 -5 5.0 × 10% or more by volume -1 It can be less than or equal to a volume percentage.

[0017] By using such CVD conditions for manufacturing diamond substrates, it is possible to more effectively produce diamond substrates in which a diamond crystal layer has high crystallinity, a highly oriented

[0111] NV axis, and high density NVC.

[0018] In this case, the gas pressure used in the formation of the diamond crystal by the CVD method can be set to 1.3 kPa (10 Torr) or more and 50.0 kPa (376 Torr) or less.

[0019] Furthermore, the gas pressure used in the formation of diamond crystals by the CVD method can be set to between 12.0 kPa (90 Torr) and 33.3 kPa (250 Torr).

[0020] Under these gas pressure conditions, the growth of non-single-crystal diamonds is more effectively suppressed, resulting in single-crystal diamonds with high crystallinity.

[0021] Furthermore, the discharge power density in the formation of diamond crystals by the CVD method was set to 188 W / cm². 2 More than 942W / cm 2The following is possible:

[0022] Under these discharge power density conditions, the growth of non-single-crystal diamonds is more effectively suppressed, resulting in single-crystal diamonds with high crystallinity.

[0023] Furthermore, the discharge current density in the formation of diamond crystals by the CVD method is set to 0.09 A / cm². 2 More than 0.85A / cm 2 The following is possible:

[0024] Under these discharge current density conditions, the growth of non-single-crystal diamonds is more effectively suppressed, resulting in single-crystal diamonds with high crystallinity.

[0025] Furthermore, in the method for manufacturing a diamond substrate according to the present invention, the base substrate can be a single-layer substrate made of single-crystal diamond.

[0026] By using single-crystal diamond as the substrate in this way, the NV axis of the NVC-containing diamond crystal can be formed more effectively with high orientation and high density in the

[0111] region.

[0027] In this case, it is preferable that the single-layer substrate of the single-crystal diamond is a single-crystal diamond (111) in which the main surface has an off-angle in the range of -8.0° to -0.5° or +0.5° to +8.0° with respect to the crystal plane orientation (111) in the direction of the crystal axis [-1-1 2] or in the direction of its threefold symmetry.

[0028] By using such single-crystal diamond (111) as a substrate, step-flow growth is facilitated, and high-quality single-crystal diamond with fewer hillocks, abnormally grown particles, and dislocation defects can be formed.

[0029] Furthermore, the single-layer substrate of the single-crystal diamond can be any of the following: high-temperature, high-pressure synthesized single-crystal diamond, heteroepitaxial single-crystal diamond, CVD synthesized homoepitaxial diamond, or single-crystal diamond combining these.

[0030] These single-crystal diamonds can be suitably used as the base substrate in the diamond substrate manufacturing method of the present invention.

[0031] Furthermore, in the method for manufacturing a diamond substrate according to the present invention, the base substrate can be a laminated structure consisting of a lower substrate and an intermediate layer on the lower substrate.

[0032] In the manufacturing method of the diamond substrate of the present invention, a substrate having such a laminated structure can also be used as the base substrate.

[0033] In this case, the outermost surface of the intermediate layer can be a metal layer selected from Ir, Rh, Pd, and Pt.

[0034] By forming the outermost surface of the intermediate layer with this type of metal layer, the diamond nuclei tend to become denser during nucleation treatment (bias treatment), and a single-crystal diamond layer is more easily formed on top of them.

[0035] Furthermore, the lower substrate can be a single substrate made of Si, MgO, Al2O3, SiO2, Si3N4, or SiC, or a laminate consisting of multiple layers selected from Si, MgO, Al2O3, SiO2, Si3N4, or SiC.

[0036] These materials are preferable as the base substrate material for the base substrate because, together with the intermediate layer, it is easy to set the crystal plane orientation (including the off-angle) of the main surface of the base substrate.

[0037] Furthermore, the lower substrate may be made of Si(111), or a further layer of Si(111) may be included between the lower substrate and the intermediate layer.

[0038] This configuration enables epitaxial growth, which is advantageous for increasing the surface area of ​​diamond substrates.

[0039] In this case, the Si(111) of the lower substrate or the Si(111) layer between the lower substrate and the intermediate layer may have an off-angle of -8.0° to -0.5° or +0.5° to +8.0° with respect to the crystal plane orientation (111) in the direction of the crystal axis [-1-1 2] or in the direction of its threefold symmetry.

[0040] By configuring the laminated structure of the substrate in this way, step-flow growth is facilitated, and high-quality single-crystal diamond crystals with fewer hillocks, abnormally grown particles, and dislocation defects can be formed.

[0041] Furthermore, the lower substrate may be made of MgO(111), or a further layer of MgO(111) may be included between the lower substrate and the intermediate layer.

[0042] This configuration enables epitaxial growth, which is advantageous for increasing the surface area of ​​diamond substrates.

[0043] In this case, the MgO(111) of the lower substrate or the MgO(111) layer between the lower substrate and the intermediate layer may have an off-angle of -8.0° to -0.5° or +0.5° to +8.0° with respect to the crystal plane orientation (111) in the direction of the crystal axis [-1-1 2] or in the direction of its threefold symmetry.

[0044] By configuring the laminated structure of the substrate in this way, step-flow growth is facilitated, and high-quality single-crystal diamond crystals with fewer hillocks, abnormally grown particles, and dislocation defects can be formed. Furthermore, since such MgO(111) has a lattice constant close to that of diamond, epitaxial growth of high-quality diamond crystals becomes possible.

[0045] Furthermore, in the method for manufacturing a diamond substrate as described above, the present invention makes it possible to avoid using Si-containing materials in the chamber in which the diamond crystal is formed by the CVD method.

[0046] This eliminates the inclusion of silicon in the formed diamond crystal, resulting in high sensitivity when the manufactured diamond substrate is used as an electrical or magnetic device, as there is no noise interference from silicon vacancy centers.

[0047] In this case, sapphire can be used for the viewing window of the chamber.

[0048] This makes it possible to visually observe the process during CVD without introducing Si into the diamond crystal being formed, and also allows for temperature monitoring using an infrared thermometer.

[0049] Furthermore, the present invention also allows for obtaining a single-crystal diamond self-supporting substrate containing the diamond crystal layer having nitrogen vacancy centers by removing the underlayment substrate from a diamond substrate containing the diamond crystal layer having nitrogen vacancy centers obtained by the above-described method for manufacturing a diamond substrate.

[0050] This makes it possible to obtain a single-crystal diamond self-supporting substrate containing a diamond crystal layer with high crystallinity, a highly oriented

[0111] NV axis, and high density NVC. This is applicable to electronic and magnetic devices.

[0051] Further, the present invention can also smooth the surface of the diamond crystal layer having the nitrogen vacancy center of the diamond substrate obtained by the above method for manufacturing a diamond substrate.

[0052] Thereby, the irregular reflection of light on the surface of the diamond crystal layer having NVC is suppressed, and the NV - center light that can be extracted can be increased.

[0053] Further, the present invention is a diamond substrate including a diamond crystal layer having a nitrogen vacancy center, wherein the diamond crystal layer having the nitrogen vacancy center is measured by a photoluminescence device under the conditions of an excitation light wavelength of 532 nm, an excitation light intensity of 2.0 mW, an integration time of 1 second, an integration number of 3 times, a hole diameter of 100 μm, an objective lens of 15 times, and a room temperature measurement of 298 K. When the - NV NV- center light (wavelength 637 nm) light intensity I NV- is I

[0054] ≧2800 counts, and provides a diamond substrate characterized by this.

[0055] In this case, when the diamond crystal layer having the nitrogen vacancy center is measured by the photoluminescence device under the conditions of an excitation light wavelength of 532 nm, an excitation light intensity of 2.0 mW, an integration time of 1 second, an integration number of 3 times, a hole diameter of 100 μm, an objective lens of 15 times, and a room temperature measurement of 298 K, the - NV NV- ratio I of the center light (wavelength 637 nm) light intensity I to the Raman scattered light (wavelength 573 nm) light intensity IRaman NV- / IRaman is preferably I NV- / IRaman≧0.04.

[0056] Furthermore, the nitrogen concentration [N] in the diamond crystal layer having the nitrogen vacancy center is 5 × 10 17 atoms / cm 3 ≤[N]≤9×10 19 atoms / cm 3 It is preferable that this be the case.

[0057] By possessing these physical properties, it is possible to create a diamond substrate with NVC-containing diamond crystals that have better characteristics.

[0058] Furthermore, it is preferable that the average surface roughness Ra of the diamond crystal layer having the nitrogen vacancy centers is Ra ≤ 270 nm.

[0059] With this surface roughness, diffuse reflection of light on the surface of the diamond crystal layer having NVC is suppressed, and the NV can be extracted. - The center light can be increased. [Effects of the Invention]

[0060] As described above, the diamond substrate manufacturing method of the present invention makes it possible to manufacture a diamond substrate in which a diamond crystal layer is formed that is highly crystalline, has a highly oriented

[0111] NV axis, and has high density NVC. Such diamond crystals can be suitable for electronic and magnetic devices.

[0061] Furthermore, the diamond substrate of the present invention makes it possible to provide a diamond substrate applicable to electronic and magnetic devices, which has high crystallinity, a highly oriented

[0111] NV axis, and high density NVC. [Brief explanation of the drawing]

[0062] [Figure 1] This shows an example in which NVC-containing diamond is formed on a single-layer substrate according to the present invention. [Figure 2] This shows an example in which NVC-containing diamond is formed on a laminated substrate according to the present invention. [Figure 3]This shows an example in which nitrogen-undoped diamond and NVC-containing diamond are formed on a laminated substrate according to the present invention. [Figure 4] An example of a diamond substrate retaining an NVC-containing diamond layer / nitrogen-undoped diamond layer according to the present invention is shown. [Figure 5] This is a schematic diagram illustrating the surface orientation of the substrate. [Modes for carrying out the invention]

[0063] The present invention will be described in detail below, but the present invention is not limited to these descriptions.

[0064] As described above, there was a need to obtain a diamond substrate suitable for electronic and magnetic devices, which is large in diameter, highly crystalline, has a highly oriented

[0111] NV axis, and possesses high density NVC.

[0065] As a result of diligent studies on the above problems, the present inventors have developed a method for manufacturing a diamond substrate by forming diamond crystals on a substrate using a raw material gas containing hydrocarbon gas and hydrogen gas as a diluent, using one of the following CVD methods: microwave plasma CVD, DC plasma CVD, thermal filament CVD, and arc discharge plasma jet CVD, wherein in order to form a diamond crystal layer having nitrogen vacancy centers in at least a portion of the diamond crystals formed on the substrate, nitrogen gas or nitride gas is mixed into the raw material gas, and the amounts of each gas contained in the raw material gas are set as follows: hydrocarbon gas amount of 0.005 vol% or more and 6.000 vol% or less, hydrogen gas amount of 93.500 vol% or more and less than 99.995 vol%, nitrogen gas or nitride gas amount of 5.0 × 10 -5 5.0 × 10% or more by volume -1 The present invention was completed by discovering that a diamond substrate can be obtained with high crystallinity, a highly oriented

[0111] NV axis, and high density NVC by a method for manufacturing a diamond substrate characterized by forming a diamond crystal layer having nitrogen vacancy centers at a volume of % or less.

[0066] In the raw material gas for forming a diamond crystal layer having NVC, methane gas, acetylene, ethylene, ethane, propane, etc. can be used as the hydrocarbon gas, but methane gas is preferred because high-purity methane gas is readily available at low cost and is easy to handle.

[0067] If the amount of hydrocarbon gas such as methane is less than 0.005 volume%, the etching effect by hydrogen increases, making it difficult for diamond to grow. A more preferable range for the amount of hydrocarbon gas is 0.01 volume% or more, and even more preferably 0.05 volume%. volume The amount of hydrocarbon gas should be 0% or more, most preferably 0.1 volume% or more. On the other hand, if the amount of hydrocarbon gas exceeds 6.0 volume%, the diamond will become polycrystalline if growth is carried out for a long time, making it difficult to obtain high-quality single crystals. The amount of hydrocarbon gas should more preferably be 5.5 volume% or less, and even more preferably 5.0 volume% or less.

[0068] Furthermore, in this raw material gas, the amount of nitrogen gas or nitride gas is 5.0 × 10 -5 Below a volume percent, the amount of nitrogen doping into the diamond crystal is too low, resulting in a low NVC density. A more preferable range for nitrogen gas or nitride gas is 5.0 × 10⁻⁶. -4 Volume percent or more, more preferably 1.0 × 10 -3 A volume percentage or higher is preferable. On the other hand, the amount of this nitrogen gas or nitride gas is 5.0 × 10 -1 At concentrations exceeding a certain volume percent, prolonged growth tends to result in polycrystalline diamond, making it difficult to obtain high-quality single crystals. A more preferable range for nitrogen gas or nitride gas is 1.0 × 10⁻⁶. -2 A volume percentage or less is preferable. While ammonia, nitrogen oxide, and nitrogen dioxide can be used as nitride gases, nitrogen gas is preferred because high-purity nitrogen gas is readily available at low cost and is easy to handle.

[0069] As described above, it is preferable to use methane gas as the hydrocarbon gas, and it is preferable to use nitrogen gas as the nitrogen gas or nitride gas mixed into the raw material gas. In this case, the amounts of each gas contained in the raw material gas are as follows: methane gas: 0.1 vol% or more, 6.000 vol% or less; hydrogen gas: 93.500 vol% or more, less than 99.900 vol%; nitrogen gas: 5.0 × 10 -5 5.0 × 10% or more by volume -1 It is preferable to keep it below a certain volume percentage.

[0070] In this case, when forming diamond crystals using each CVD method, it is preferable to set the gas pressure between 1.3 kPa (10 Torr) and 50.0 kPa (376 Torr) to effectively prevent polycrystallization of diamond, thereby obtaining high-quality single crystals. If the gas pressure is too low, discharge is difficult to generate, and the plasma density is too low, making it difficult to obtain high-quality single-crystal diamond. On the other hand, if the gas pressure is too high, discharge is also difficult to generate, crystallinity decreases due to high temperature, and the diamond formation area becomes smaller, among other problems. A more preferable range for gas pressure is between 12.0 kPa (90 Torr) and 33.3 kPa (250 Torr).

[0071] Furthermore, by increasing the discharge power density during diamond crystal formation using each CVD method, diamond growth can be effectively promoted, resulting in a power density of 188 W / cm². 2 More than 942W / cm 2 The following is preferable. The discharge power density is more preferably 210 W / cm². 2 The above is good. If the discharge power density is too high, polycrystallization of the diamond is likely to occur when growing for a long time, so more preferably 800 W / cm². 2 The following is good. This will allow you to obtain high-quality single crystals.

[0072] Furthermore, by increasing the discharge current density during diamond crystal formation using each CVD method, diamond growth can be effectively promoted, resulting in a discharge current of 0.09 A / cm². 2More than 0.85A / cm 2 The following is preferable. The discharge current density is more preferably 0.10 A / cm². 2 The above is good. If the discharge current density is too high, polycrystallization of the diamond is likely to occur if growth is carried out for a long time, so 0.70 A / cm is more preferable. 2 The following is good. This will allow you to obtain high-quality single crystals.

[0073] The following explanation will be given with reference to the drawings. First, the terms used in this specification will be defined.

[0074] In this specification, a crystalline layer or crystalline film whose main surface is a (111) plane is simply referred to as a "(111) layer" or "(111) film." For example, a single-crystal diamond layer whose main surface is a (111) plane is referred to as a "single-crystal diamond (111) layer."

[0075] Furthermore, the relationship of the off-angle is shown in Figure 5. Figure 5 shows the relationship of a substrate whose main surface is the (111) plane. A conceptual diagram of the [-1-1 2] direction and its three-fold symmetric directions, [-1 2-1] and [2-1-1], and the off-angle is shown. Note that in this specification,

number

[0076] (Method for manufacturing NVC-containing diamond substrates) As described above, the CVD (chemical vapor deposition) methods used in this invention to form diamond crystals on a substrate include microwave plasma CVD, DC plasma CVD, thermal filament CVD, and arc discharge plasma jet One example is the CVD method. In particular, diamonds obtained by microwave plasma CVD and DC plasma CVD are high-quality single-crystal diamonds with high crystallinity, few hillocks, abnormally grown grains, and dislocation defects, and with good impurity control.

[0077] To form the NV axis with high orientation and high density

[0111] , it is preferable to use a single-layer substrate of single-crystal diamond as the base substrate, and in particular, epitaxial growth using single-crystal diamond (111) as the base substrate is preferable. Figure 1 shows a diamond substrate 100 in which an NVC-containing diamond layer 12 is formed on a base substrate 11. Referring to Figure 1, it is preferable to use a single-layer substrate of single-crystal diamond, in particular single-crystal diamond (111), as the base substrate 11.

[0078] In this case, it is preferable that the single-crystal diamond (111) used as the substrate 11 has a main surface that has an off-angle in the range of -8.0° to -0.5° or +0.5° to +8.0° with respect to the crystal plane orientation (111) in the direction of the crystal axis [-1-1 2] or in the direction of its three-fold symmetry. By using such a single-crystal diamond (111) as the substrate 11, step flow growth is facilitated, and a high-quality single-crystal diamond with fewer hillocks, abnormally grown particles, dislocation defects, etc., can be formed.

[0079] Furthermore, the single-layer substrate of single-crystal diamond used as the base substrate 11 can be any of the following: high-temperature, high-pressure synthesized single-crystal diamond, heteroepitaxial single-crystal diamond, CVD synthesized homoepitaxial diamond, or single-crystal diamond combining these. These single-crystal diamonds can be suitably used as the base substrate 11 of the present invention.

[0080] In addition, in the method for manufacturing a diamond substrate according to the present invention, the base substrate may be a laminated structure consisting of a lower layer substrate and an intermediate layer on the lower layer substrate. Figure 2 shows a diamond substrate 200 in which an NVC-containing diamond layer is formed on a laminated base substrate. That is, the diamond substrate 200 in Figure 2 is a diamond substrate 200 in which an NVC-containing diamond layer 15 is formed on the base substrate 21, using a laminated structure consisting of a lower layer substrate 13 and an intermediate layer 14 as the base substrate 21.

[0081] The intermediate layer 14 may be a single layer or a laminate of multiple layers. The outermost surface of the intermediate layer 14 is preferably a metal layer selected from Ir, Rh, Pd, and Pt. Using such a metal film is preferable because it makes it easier for the diamond nuclei to become denser during nucleation treatment (bias treatment), and thus easier for a single-crystal diamond layer to be formed on top of them.

[0082] In this case, the lower substrate 13 may be a substrate made of a single material such as Si, MgO, Al2O3, SiO2, Si3N4, or SiC, or a laminate consisting of multiple layers selected from Si, MgO, Al2O3, SiO2, Si3N4, or SiC. Using these materials as the lower substrate 13 is preferable because, together with the intermediate layer 14, it is easy to set the crystal plane orientation (including the off-angle) of the main surface of the base substrate 21. Moreover, these materials are relatively inexpensive and readily available.

[0083] Furthermore, the lower substrate 13 may be made of Si(111), or a further layer of Si(111) may be included between the lower substrate 13 and the intermediate layer 14. By using such a lower substrate 13 made of Si(111) or a base substrate 21 having a Si(111) layer, epitaxial growth advantageous for large-area diamond substrates 200, such as substrates with a diameter of 4 inches (100 mm) or more, becomes possible.

[0084] Furthermore, in this case, it is preferable that the Si(111) of the lower substrate 13 or the Si(111) layer between the lower substrate and the intermediate layer has an off-angle in the range of -8.0° to -0.5° or +0.5° to +8.0° with respect to the crystal plane orientation (111) in the direction of the crystal axis [-1-1 2] or in the direction of its three-fold symmetry. By using a lower substrate 13 made of such Si(111) or a base substrate 21 having a Si(111) layer, step flow growth is facilitated, and high-quality single-crystal diamond crystals with fewer hillocks, abnormally grown particles, dislocation defects, etc., can be formed. In the range of off-angle greater than -0.5° or less than +0.5°, growth in the step direction is difficult, and good crystals cannot be obtained. Also, in the range of off-angle less than -8.0° or greater than +8.0°, polycrystallization occurs if growth is carried out for a long time, and good single crystals cannot be obtained.

[0085] Furthermore, as shown in Figure 2, when using a laminated substrate 21, the lower substrate 13 may be made of MgO(111), or a further layer of MgO(111) may be included between the lower substrate 13 and the intermediate layer 14. By using such a lower substrate 13 made of MgO(111) or a substrate 21 having an MgO(111) layer, epitaxial growth advantageous for large-area diamond substrates 200, such as substrates with a diameter of 4 inches (100 mm) or more, becomes possible. In addition, since such MgO(111) has a lattice constant close to that of diamond, it becomes possible to grow high-quality diamond crystals epitaxially.

[0086] Furthermore, in this case, it is preferable that the MgO(111) of the lower substrate 13 or the MgO(111) layer between the lower substrate 13 and the intermediate layer 14 has an off-angle in the range of -8.0° to -0.5° or +0.5° to +8.0° with respect to the crystal plane orientation (111) in the direction of the crystal axis [-1-1 2] or in the direction of its three-fold symmetry. By using a lower substrate 13 made of such MgO(111) or a base substrate 21 having an MgO(111) layer, step flow growth is facilitated, and high-quality single-crystal diamond crystals with fewer hillocks, abnormally grown particles, dislocation defects, etc., can be formed. If the off-angle is in the range of -0.5° or less or +0.5° or more, growth in the step direction is easily performed, making it easier to obtain good crystals. Also, if the off-angle is in the range of -8.0° or more or +8.0° or less, polycrystallization is less likely even with long-term growth, making it easier to obtain good quality single crystals.

[0087] Furthermore, in the method for manufacturing a diamond substrate according to the present invention, it is preferable not to use Si-containing materials in the chamber used to form diamond crystals by the CVD method. In conventional CVD apparatus used for diamond production, the inner wall of the chamber is made of stainless steel, the stages are made of stainless steel and molybdenum, the insulators are made of Si3N4, SiC, Al2O3, BN, etc., and the viewing window is made of SiO2. When diamond is produced using such a conventional CVD apparatus, Si is mixed into the diamond crystal, which forms silicon-vacancy centers (SiVCs) and becomes a noise source when the diamond substrate is used as an electronic or magnetic sensor. Therefore, in the present invention, it is preferable not to use Si-containing materials in the chamber components (inner wall of the chamber, stages, viewing window, etc.) used to form diamond crystals by each CVD method.

[0088] In particular, the viewing window of the CVD apparatus chamber is considered to be a source of Si contamination. Therefore, it is preferable to use sapphire for the chamber viewing window.

[0089] Furthermore, in this invention, the underlying substrate can be removed from a diamond substrate containing a diamond crystal layer with NVC obtained by the above-described method for manufacturing a diamond substrate. This makes it possible to obtain a single-crystal diamond self-supporting substrate containing a diamond crystal layer with NVC. In this way, a diamond substrate with a high proportion of NVC-containing material reduces the source of noise in actual use, thus enabling the realization of highly sensitive electronic and magnetic devices. If the underlying substrate is a single layer, the entire underlying substrate can be removed. If the underlying substrate consists of a lower layer and an intermediate layer, only the lower layer can be removed, or both the lower layer and the intermediate layer can be removed. It is also possible to remove only a portion of the underlying substrate.

[0090] Figure 3 shows a diamond substrate 300 formed on a laminated substrate 21 in the order of nitrogen-undoped diamond layer 16 (made of single crystals) and then NVC-containing diamond layer 15 (made of single crystals). Figure 4 shows a diamond substrate 400 (a self-supporting structure substrate for diamond substrates) formed by removing the portion of the substrate 21 (lower substrate 13 and intermediate layer 14) from the diamond substrate 300 in Figure 3, and consisting of the NVC-containing diamond layer 15 and the nitrogen-undoped diamond layer 16.

[0091] The method for removing the base substrates 11 and 21 is not particularly limited. Mechanical treatments such as polishing, wet or dry etching, etc., can be appropriately selected according to the materials of the base substrates 11 and 21, the lower substrate 13, and the intermediate layer 14. Furthermore, a combination of the above treatments is also possible.

[0092] Furthermore, a process to smooth the surface of the NVC-containing diamond crystal layer may be included. For smoothing, mechanical polishing, chemical-mechanical polishing, plasma treatment, sputtering, chemical etching, etc., are recommended. If the average surface roughness Ra of the NVC-containing diamond crystal layer is 270 nm or less, diffuse reflection of light is suppressed, and the amount of NVC that can be extracted is reduced. - The central light can be increased.

[0093] The diamond substrate manufacturing method of the present invention described above can be obtained as follows: A diamond substrate comprising a diamond crystal layer having NVC, wherein when the diamond crystal layer having NVC is measured using a photoluminescence apparatus under the conditions of excitation light wavelength 532 nm, excitation light intensity 2.0 mW, integration time 1 second, number of integrations 3 times, hole diameter 100 μm, objective lens 15x, and room temperature measurement at 298 K, the NV - Center light (wavelength 637nm) light intensity I NV- However, I NV- The diamond substrate has a count of ≥2800 counts. The photoluminescence device used for the above measurement can be a LabRAM-HR PL manufactured by Horiba, Ltd.

[0094] Such diamond substrates are highly crystalline, have a highly oriented

[0111] NV axis, and possess high-density NVC. Therefore, they are applicable to electronic and magnetic devices.

[0095] Here, the diamond crystal layer having the above NVC was measured using the above photoluminescence apparatus under the following conditions: excitation light wavelength 532 nm, excitation light intensity 2.0 mW, integration time 1 second, number of integrations 3 times, hole diameter 100 μm, objective lens 15x, and room temperature measurement at 298 K, and the NV - Center light (wavelength 637nm) light intensity I NV- The ratio of the light intensity I of Raman scattered light (wavelength 573 nm) to Raman I NV- / IRaman, I NV- It is preferable that / IRaman ≥ 0.04.

[0096] Furthermore, the nitrogen concentration [N] in the diamond crystal layer having the above NVC is 5 × 10 17 atoms / cm 3 ≤[N]≤9×10 19 atoms / cm 3 It is preferable that this be the case.

[0097] By possessing these physical properties, it is possible to create a diamond substrate with NVC-containing diamond crystals that have better characteristics.

[0098] Furthermore, as described above, if the average surface roughness Ra of the NVC-containing diamond crystal layer is set to 270 nm or less, diffuse reflection of light is suppressed, and the amount of NVC that can be extracted is reduced. - This is preferable because it can increase the amount of light from the center. [Examples]

[0099] The present invention will be described in detail below with reference to examples, but this is not intended to limit the present invention.

[0100] (Example 1) As a base substrate, a single-crystal MgO substrate (hereinafter referred to as "single-crystal MgO(111) substrate") was prepared, with a diameter of 20.0 mm, a thickness of 1.0 mm, a (111) plane as the main surface, and an off-angle of 2° in the crystal axis direction [-1-1 2], which had been polished on one side.

[0101] Next, an intermediate layer of single-crystal Ir film was formed on the surface of the prepared single-crystal MgO(111) substrate by RF magnetron sputtering. For the formation of the single-crystal Ir film, a high-frequency (RF) magnetron sputtering method (13.56 MHz) was used, targeting Ir with a diameter of 6 inches (150 mm), a thickness of 5.0 mm, and a purity of 99.9% or higher.

[0102] The lower layer substrate, a single-crystal MgO(111) substrate, is heated to 800°C, and the base pressure is 6 × 10⁻⁶. -7 Torr (approx. 8.0 x 10 -5 After confirming that the pressure was below Pa, Ar gas was introduced at 50 sccm. Next, the opening of the valve leading to the exhaust system was adjusted to set the pressure to 3 × 10⁻⁶. -1 After setting the Torr to approximately 39.9 Pa, a 1000 W RF power was applied and film deposition was carried out for 15 minutes. This resulted in a single-crystal Ir film with a thickness of 1.0 μm.

[0103] As described above, the single-crystal Ir film, stacked on a single-crystal MgO(111) substrate, underwent heteroepitaxial growth following the off-angle of the single-crystal MgO substrate. Analysis of this single-crystal Ir film by X-ray diffraction at a wavelength of λ=1.54 Å revealed that the surface was a (111) plane with an off-angle of 2° in the direction of the crystal axis [-1-1 2]. Furthermore, the full width at half maximum (FWHM) of the diffraction peak at 2θ=40.7°, attributed to Ir(111), was 0.187°. This single-crystal Ir film will hereafter be referred to as the "Ir(111) film".

[0104] Next, a nucleation treatment (bias treatment) was performed as a pretreatment for diamond nucleation. The substrate was placed on a 25 mm diameter flat electrode in the treatment chamber with the Ir(111) film side facing upwards. The base pressure was 1 × 10⁻¹⁰ -6 Torr (approximately 1.3 x 10 -4 After confirming that the pressure had dropped below Pa, hydrogen-diluted methane gas (CH4 / (CH4+H2)=5.0 vol%) was introduced into the treatment chamber at a flow rate of 500 sccm. The opening of the valve leading to the exhaust system was adjusted to set the pressure to 100 Torr (approximately 1.3 × 10⁻⁶). 4 After setting the temperature to Pa, a negative voltage was applied to the substrate-side electrode and the substrate (Ir(111) film) was exposed to the plasma for 90 seconds to bias-treat the substrate surface.

[0105] Diamond was heteroepitaxially grown on the Ir(111) film / single crystal MgO(111) substrate prepared as described above using DC plasma CVD. The biased Ir(111) film / single crystal MgO(111) substrate was set in the chamber of the DC plasma CVD apparatus, and the base pressure was set to 1 × 10⁻⁶ -6 Torr (approximately 1.3 x 10 -4 After confirming that the pressure is below Pa, the mixed gas of methane and hydrogen, which are the raw materials, is used. Methane gas 5,000 volume%, Hydrogen gas 95,000 volume%, The fluid was introduced into the chamber at a flow rate of 200 sccm in a volume ratio of . The opening of the valve leading to the exhaust system was adjusted to set the pressure inside the chamber to 110 Torr (approximately 1.5 × 10⁻⁶).4 After adjusting the temperature to Pa, a DC discharge current of 6.0 A was applied, and film deposition was carried out for 20 hours until the film thickness reached approximately 130 μm.

[0106] Next, a mixed gas is prepared by adding methane gas, hydrogen gas, and nitrogen gas, which are the raw materials. Methane gas 2,000 volume%, Hydrogen gas 97.995% by volume Nitrogen gas 5.0 × 10 -3 volume%, The volume ratio was changed, and the solution was introduced into the chamber at a flow rate of 200 sccm. The pressure and discharge current remained the same. Under these conditions, film deposition was carried out for 6 hours, resulting in a nitrogen-doped layer with a thickness of approximately 20 μm.

[0107] In this way, a diamond layer was heteroepitaxially grown on an Ir(111) film / single crystal MgO(111) substrate to obtain a multilayer substrate.

[0108] Next, the Ir(111) film / single-crystal MgO(111) substrate was removed to create a self-supporting substrate. First, the single-crystal MgO(111) substrate was etched off, and then the Ir(111) film was removed by polishing. As a result, a single-crystal diamond(111) multilayer substrate was obtained, consisting of a nitrogen-doped single-crystal diamond film with a diameter of 20 mm, a thickness of approximately 20 μm, and an undoped single-crystal diamond(111) substrate with a thickness of approximately 130 μm.

[0109] The surface of the diamond substrate in the laminated structure was polished to finish it.

[0110] Finally, the finished multilayer substrates were subjected to SIMS, XRD, PL, and surface roughness analyses.

[0111] The nitrogen concentration [N] in the crystal was measured using a secondary ion mass spectrometer (SIMS) (CAMECA IMS-7f). The results showed that the nitrogen concentration [N] at a depth of approximately 10 μm from the outermost surface of the film was: [N] = 8 × 10 18 atoms / cm 3 That was the case.

[0112] The crystallinity of the film surface was measured using an X-ray diffraction (XRD) instrument (RIGAKU SmartLab). As a result, only a diffraction intensity peak attributed to diamond(111) at 2θ=43.9° was observed, confirming that the nitrogen-doped single-crystal diamond film was epitaxially grown relative to the undoped single-crystal diamond(111) layer.

[0113] Furthermore, measurements were taken using a photoluminescence (PL) system (Horiba LabRAM-HR PL) under the following conditions: excitation light wavelength 532 nm, excitation light intensity 2.0 mW, integration time 1 second, number of integrations 3 times, hole diameter 100 μm, objective lens 15x, and room temperature measurement (298 K). As a result, NV - Center light (wavelength 637nm) light intensity I NV- but, I NV- = 15090 (counts) That was the case.

[0114] Also, I NV- The ratio of the light intensity I of Raman scattered light (wavelength 573 nm) to Raman I NV- / IRaman, I NV- / IRaman=1.54 That was the case.

[0115] Therefore, the resulting nitrogen-doped film was a single-crystal diamond (111) crystal with a high density of NVCs.

[0116] Furthermore, when the surface of the diamond substrate was measured in a 290 μm × 218 μm area using an optical surface roughness meter (ZYGO New View 5032), the average surface roughness Ra was found to be 147 nm.

[0117] Applying this NVC-containing diamond (111) substrate to electronic and magnetic devices can yield high-performance devices. For example, a highly sensitive magnetic sensor can be obtained.

[0118] (Example 2) As a base substrate, a single-crystal diamond substrate with a diameter of 20 mm, a thickness of 125 μm, a main surface of (111), and an off-angle of 2° in the crystal axis direction [-1-1 2] was prepared, polished on one side. The manufacturing method for this single-crystal diamond substrate is as follows. First, following the same procedure as in Example 1, a nitrogen-undoped single-crystal diamond layer was formed to obtain a nitrogen-undoped single-crystal diamond layer / Ir(111) film / single-crystal MgO(111) substrate. Next, the Ir(111) film / single-crystal MgO(111) substrate was removed to create a self-supporting substrate. Specifically, the single-crystal MgO(111) substrate was etched off, and then the Ir(111) film was removed by polishing. As a result, a nitrogen-undoped single-crystal diamond(111) self-supporting single-layer substrate with a diameter of 20 mm and a thickness of approximately 130 μm was obtained. The surface of the substrate was polished to obtain a single-crystal diamond substrate with a diameter of 20 mm, a thickness of approximately 120 μm, a main surface of (111), and an off-angle of 2° in the crystal axis direction [-1-1 2], which was polished on one side.

[0119] Nitrogen-doped single-crystal diamond was epitaxially grown on the substrate prepared as described above using DC plasma CVD. The substrate was set in the chamber of the DC plasma CVD apparatus, and the base pressure was set to 1 × 10⁻⁶. -6 Torr (approximately 1.3 x 10 -4 After confirming that the pressure was below Pa, the mixed gas, which consists of the raw materials methane gas, hydrogen gas, and nitrogen gas, was then prepared. Methane gas 0.200 volume%, Hydrogen gas 99.795% by volume Nitrogen gas 5.0 × 10 -3 volume%, The fluid was introduced into the chamber at a flow rate of 200 sccm in a volume ratio of . The opening of the valve leading to the exhaust system was adjusted to set the pressure inside the chamber to 110 Torr (approximately 1.5 × 10⁻⁶). 4 After setting the temperature to Pa, a DC discharge current of 6.0 A was applied and film deposition was carried out for 20 hours to deposit a nitrogen-doped single-crystal diamond layer to a thickness of approximately 70 μm.

[0120] In this way, a laminated diamond substrate consisting of a nitrogen-doped single-crystal diamond layer and an undoped single-crystal diamond (111) substrate was obtained.

[0121] Finally, the finished multilayer substrates were subjected to SIMS, XRD, PL, and surface roughness analyses.

[0122] The nitrogen concentration [N] in the crystal was measured using a secondary ion mass spectrometer (SIMS) (CAMECA IMS-7f). The results showed that the nitrogen concentration [N] at a depth of approximately 15 μm from the outermost surface of the film was: [N] = 8 × 10 18 atoms / cm 3 That was the case.

[0123] The crystallinity of the film surface was measured using an X-ray diffraction (XRD) instrument (RIGAKU SmartLab). As a result, only a diffraction intensity peak attributed to diamond(111) at 2θ = 43.9° was observed, confirming that the N-doped film was epitaxially grown on an undoped single-crystal diamond(111) substrate.

[0124] Furthermore, measurements were taken using a photoluminescence (PL) system (Horiba LabRAM-HR PL) under the following conditions: excitation light wavelength 532 nm, excitation light intensity 2.0 mW, integration time 1 second, number of integrations 3 times, hole diameter 100 μm, objective lens 15x, and room temperature measurement (298 K). As a result, NV - Center light (wavelength 637nm) light intensity I NV- but, I NV- = 341213 (counts) That was the case. Also, I NV- The ratio of the light intensity I of Raman scattered light (wavelength 573 nm) to Raman I NV- / IRaman, I NV- / IRaman=4.35 That was the case.

[0125] Therefore, the resulting nitrogen-doped film was a single-crystal diamond (111) crystal with a high density of NVCs.

[0126] Furthermore, when the surface of the diamond substrate was measured in a 290 μm × 218 μm area using an optical surface roughness meter (ZYGO New View 5032), the average surface roughness Ra was found to be 261 nm.

[0127] Applying this NVC-containing diamond (111) substrate to electronic and magnetic devices can yield high-performance devices. For example, a highly sensitive magnetic sensor can be obtained.

[0128] (Example 3) Nitrogen-doped single-crystal diamond was epitaxially grown on a substrate made of undoped single-crystal diamond, which was prepared in the same manner as in Example 2, with a diameter of 20 mm, a thickness of approximately 120 μm, a main surface of (111), and an off-angle of 2° in the crystal axis direction [-1-1 2], by DC plasma CVD as follows.

[0129] First, the substrate is placed inside the chamber of the DC plasma CVD apparatus, and the base pressure is set to 1 × 10 -6 Torr (approximately 1.3 x 10 -4 After confirming that the pressure was below Pa, a mixed gas was prepared by adding the raw materials acetylene (C2H2) gas, hydrogen gas, and ammonia (NH3) gas. Acetylene gas 0.500 volume%, Hydrogen gas 99.485% by volume Ammonia gas 1.5 × 10 -2 volume%, The volume ratio was changed, and the fluid was introduced into the chamber at a flow rate of 200 sccm. The opening of the valve leading to the exhaust system was adjusted to set the pressure inside the chamber to 110 Torr (approximately 1.5 × 10⁻¹⁰). 4 After setting the temperature to Pa, a DC discharge current of 6.0 A was applied, and film deposition was carried out for 5 hours to deposit a nitrogen-doped layer to a thickness of approximately 20 μm.

[0130] In this way, a single-crystal diamond (111) laminated substrate composed of a nitrogen-doped single-crystal diamond film with a diameter of 20 mm and a thickness of about 20 μm and an undoped single-crystal diamond (111) substrate with a thickness of about 120 μm was obtained.

[0131] The surface side of the diamond substrate having the laminated structure was polished and finished.

[0132] Finally, the finished laminated substrate was subjected to various analyses including SIMS, XRD, PL, and surface roughness.

[0133] The nitrogen concentration [N] in the crystal was measured with a secondary ion mass spectrometry (SIMS) apparatus (CAMECA IMS-7f). As a result, the nitrogen concentration [N] at a depth of about 10 μm from the outermost surface of the film was [N]=1×10 19 atoms / cm 3 as follows.

[0134] The crystallinity was measured from the outermost surface of the film with an X-ray diffraction (XRD) apparatus (RIGAKU SmartLab). As a result, only the diffraction intensity peak attributed to diamond (111) at 2θ = 43.9° was observed, confirming that the nitrogen-doped single-crystal diamond film had grown epitaxially with respect to the undoped single-crystal diamond (111) layer.

[0135] Furthermore, measurements were made with a photoluminescence (PL) apparatus (Horiba LabRAM-HR PL) under the conditions of an excitation light wavelength of 532 nm, an excitation light intensity of 2.0 mW, an integration time of 1 second, an integration number of 3 times, a hole diameter of 100 μm, an objective lens magnification of 15 times, and room temperature measurement (298 K). As a result, the light intensity I - of the NV NV- center light (wavelength 637 nm) was I NV- = 84290 (counts) as follows.

[0136] Also, the ratio I of I NV- to the light intensity IRaman of Raman scattered light (wavelength 573 nm)NV- / IRaman, I NV- / IRaman=2.93 That was the case.

[0137] Therefore, the resulting nitrogen-doped film was a single-crystal diamond (111) crystal with a high density of NVCs.

[0138] Furthermore, when the surface of the diamond substrate was measured in a 290 μm × 218 μm area using an optical surface roughness meter (ZYGO New View 5032), the average surface roughness Ra was found to be 12 nm.

[0139] Applying this NVC-containing diamond (111) substrate to electronic and magnetic devices can yield high-performance devices. For example, a highly sensitive magnetic sensor can be obtained.

[0140] (Example 4) As a base substrate, a single-sided polished high-temperature, high-pressure synthesized Ib-type single crystal diamond substrate (hereinafter referred to as "HPHT(111) substrate") was prepared, with a rectangular shape of 2.0 mm, a thickness of 0.5 mm, a main surface being a (111) plane, and an off-angle of 2° in the crystal axis direction [-1-1 2].

[0141] Next, diamond was epitaxially grown on a prepared HPHT(111) substrate using DC plasma CVD. The substrate was then placed in the chamber of the DC plasma CVD apparatus, and the base pressure was set to 1 × 10⁻¹⁰ -6 Torr (approximately 1.3 x 10 -4 After confirming that the pressure was below Pa, the mixed gas, which consists of the raw materials methane gas, hydrogen gas, and nitrogen gas, was then prepared. Methane gas 0.005 volume%, Hydrogen gas 99.995% by volume Nitrogen gas 5.0 × 10 -5 volume% The fluid was introduced into the chamber at a flow rate of 200 sccm in a volume ratio of . The opening of the valve leading to the exhaust system was adjusted to set the pressure inside the chamber to 110 Torr (approximately 1.5 × 10⁻⁶).4 After setting to Pa), a DC discharge current of 6.0 A was passed for 20 hours to perform film formation until the thickness reached about 3 μm.

[0142] In this way, a single-crystal diamond (111) laminated substrate composed of a square 2.0 mm, a nitrogen-doped single-crystal diamond film of about 3 μm, and an HPHT (111) substrate of the base about 0.5 mm thick was obtained.

[0143] Finally, SIMS, XRD, PL, and surface roughness analyses were performed on the finished laminated substrate.

[0144] The nitrogen concentration [N] in the crystal was measured with a secondary ion mass spectrometry (SIMS) device (CAMECA IMS-7f). As a result, the nitrogen concentration [N] at a depth of about 10 μm from the outermost surface of the film was [N]=5×10 17 atoms / cm 3 was.

[0145] The crystallinity was measured from the outermost surface of the film with an X-ray diffractometer (XRD) device (RIGAKU SmartLab). As a result, only the diffraction intensity peak attributed to diamond (111) at 2θ = 43.9° was observed, and it was confirmed that the nitrogen-doped single-crystal diamond film was epitaxially grown with respect to the undoped single-crystal diamond (111) layer.

[0146] Furthermore, it was measured with a photoluminescence (PL) device (Horiba LabRAM-HR PL) under the conditions of an excitation light wavelength of 532 nm, an excitation light intensity of 2.0 mW, an integration time of 1 second, an integration number of 3 times, a hole diameter of 100 μm, an objective lens of 15 times, and room temperature measurement (298 K). As a result, the NV - center light (wavelength 637 nm) light intensity I NV- was I NV- = 2890 (counts) was.

[0147] Also, I NV-The ratio of the light intensity I of Raman scattered light (wavelength 573 nm) to Raman I NV- / IRaman, I NV- / IRaman=0.05 That was the case.

[0148] Therefore, the resulting nitrogen-doped film was a single-crystal diamond (111) crystal with a high density of NVCs.

[0149] Furthermore, when the surface of the diamond substrate was measured in a 290 μm × 218 μm area using an optical surface roughness meter (ZYGO New View 5032), the average surface roughness Ra was found to be 40 nm.

[0150] Applying this NVC-containing diamond (111) substrate to electronic and magnetic devices can yield high-performance devices. For example, a highly sensitive magnetic sensor can be obtained.

[0151] It should be noted that the present invention is not limited to the embodiments described above. The embodiments described above are illustrative, and any configuration that is substantially identical to the technical idea described in the claims of the present invention and achieves similar effects is included within the technical scope of the present invention. [Explanation of Symbols]

[0152] 11…Underlayment substrate, 12…NVC-containing diamond layer, 13…Lower substrate, 14…Intermediate layer, 15…NVC-containing diamond layer 16...Undoped diamond layer, 21... Substrate, 100, 200, 300, 400... Diamond substrates.

Claims

1. In a method for manufacturing a diamond substrate by forming diamond crystals on a substrate using either a microwave plasma CVD method or a DC plasma CVD method, with a raw material gas containing a hydrocarbon gas and a diluent gas, hydrogen gas, (A) The base substrate is a single-layer substrate of single-crystal diamond, and the single-layer substrate of single-crystal diamond is single-crystal diamond (111), and the main surface has an off-angle in the range of -8.0° to -0.5° or +0.5° to +8.0° with respect to the crystal plane orientation (111) in the direction of the crystal axis [-1-12] or in the direction of its threefold symmetry, or (B) The base substrate has a laminated structure consisting of a lower substrate and an intermediate layer on the lower substrate, (i) The lower substrate is Si(111), or further includes a layer of Si(111) between the lower substrate and the intermediate layer, and the Si(111) of the lower substrate or the Si(111) layer between the lower substrate and the intermediate layer has an off-angle of -8.0° or more and -0.5° or more and +0.5° or more and +8.0° with respect to the crystal plane orientation (111), in the direction of the crystal axis [-1-1 2] or in the direction of its threefold symmetry, or (ii) The lower substrate is MgO(111), or further includes a layer of MgO(111) between the lower substrate and the intermediate layer, and the MgO(111) of the lower substrate or the MgO(111) layer between the lower substrate and the intermediate layer has an off-angle of -8.0° or more and -0.5° or more and +0.5° or more and +8.0° with respect to the crystal plane orientation (111), in the direction of the crystal axis [-1-1 2] or in the direction of threefold symmetry thereof, As the hydrocarbon gas, methane gas is used. In order to form a diamond crystal layer having nitrogen vacancy centers in at least a portion of the diamond crystal formed on the aforementioned substrate, nitrogen gas is mixed into the raw material gas, and the amount of each gas contained in the raw material gas is The amount of methane gas is between 0.1 volume% and 6,000 volume%. The amount of hydrogen gas is 93.500 volume% or more and less than 99.900 volume%. The amount of nitrogen gas is 5.0 × 10 －５ Volume % or more: 5.0 × 10 －１ Volume percentage or less as, Furthermore, the gas pressure in the formation of the diamond crystal by the CVD method is set to 12.0 kPa (90 Torr) or more and 33.3 kPa (250 Torr) or less. A method for manufacturing a diamond substrate, characterized by forming a diamond crystal layer having the aforementioned nitrogen vacancy centers.

2. The discharge power density in the formation of the diamond crystal by the CVD method is 188 W / cm². ２ More than 942W / cm ２ The method for manufacturing a diamond substrate according to claim 1, characterized in that it is as follows.

3. The discharge current density in the formation of the diamond crystal by the CVD method is 0.09 A / cm². ２ 0.85A / cm or more ２ The method for manufacturing a diamond substrate according to claim 1, characterized in that it is as follows.

4. The method for manufacturing a diamond substrate according to any one of claims 1 to 3, characterized in that the single-layer substrate of the single-crystal diamond is made of high-temperature, high-pressure synthesized single-crystal diamond, heteroepitaxial single-crystal diamond, CVD synthesized homoepitaxial diamond, or single-crystal diamond made by combining these.

5. The method for manufacturing a diamond substrate according to claim 1, characterized in that the outermost surface of the intermediate layer is a metal layer selected from Ir, Rh, Pd, and Pt.

6. A method for manufacturing a diamond substrate according to any one of claims 1 to 5, characterized in that no Si-containing material is used in the chamber in which the diamond crystal is formed by the CVD method.

7. The method for manufacturing a diamond substrate according to claim 6, characterized in that sapphire is used for the viewing window of the chamber.

8. A method for manufacturing a diamond substrate, characterized by removing the underlayment from a diamond substrate containing the diamond crystal layer having nitrogen vacancy centers, obtained by the method for manufacturing a diamond substrate according to any one of claims 1 to 7, to obtain a single-crystal diamond self-supporting substrate containing the diamond crystal layer having nitrogen vacancy centers.

9. A method for manufacturing a diamond substrate, characterized by smoothing the surface of the diamond crystal layer having nitrogen vacancy centers of a diamond substrate obtained by the method for manufacturing a diamond substrate according to any one of claims 1 to 8.

10. A diamond substrate including a diamond crystal layer having a nitrogen vacancy center on a lower base plate, wherein the diamond crystal layer having the nitrogen vacancy center is measured by a photoluminescence device under the conditions of an excitation light wavelength of 532 nm, an excitation light intensity of 2.0 mW, an integration time of 1 second, an integration number of 3 times, a hole diameter of 100 μm, an objective lens magnification of 15 times, and a room temperature measurement at 298 K, and the NV － center light (wavelength 637 nm) light intensity I ＮＶ－ is such that I ＮＶ－ ≧ 2800 counts, (A) The base substrate is a single-layer substrate of single-crystal diamond, and the single-layer substrate of single-crystal diamond is single-crystal diamond (111), and the main surface has an off-angle in the direction of the crystal axis [-1-12] or in the direction of its threefold symmetry with respect to the crystal plane orientation (111) in the range of -8.0° to -0.5° or +0.5° to +8.0°, or (B) The base substrate has a laminated structure consisting of a lower substrate and an intermediate layer on the lower substrate, (i) The lower substrate is Si(111), or further includes a layer of Si(111) between the lower substrate and the intermediate layer, and the Si(111) of the lower substrate or the Si(111) layer between the lower substrate and the intermediate layer has an off-angle of -8.0° or more and -0.5° or more and +0.5° or more and +8.0° with respect to the crystal plane orientation (111), in the direction of the crystal axis [-1-12] or in the direction of its threefold symmetry, or (ii) A diamond substrate characterized in that the lower substrate is MgO(111), or further includes a layer of MgO(111) between the lower substrate and the intermediate layer, and the MgO(111) of the lower substrate or the MgO(111) layer between the lower substrate and the intermediate layer has an off-angle of -8.0° to -0.5° or +0.5° to +8.0° with respect to the crystal plane orientation (111) in the direction of the crystal axis [-1-12] or in the direction of threefold symmetry thereof.

11. When the diamond crystal layer having nitrogen vacancy centers was measured using the photoluminescence apparatus under the following conditions: excitation light wavelength 532 nm, excitation light intensity 2.0 mW, integration time 1 second, number of integrations 3 times, hole diameter 100 μm, objective lens 15x, and room temperature measurement at 298 K, NV － Center light (wavelength 637 nm) light intensity I ＮＶ－ The ratio of the light intensity IR / Raman to the light intensity IR of the Raman scattered light (wavelength 573 nm) ＮＶ－ / IRaman, I ＮＶ－ The diamond substrate according to claim 10, characterized in that / IRaman ≥ 0.

04.

12. The nitrogen concentration [N] in the diamond crystal layer having the nitrogen vacancy center is 5 × 10 １７ atoms / cm ３ ≤ [N] ≤ 9 × 10 １９ atoms / cm ３ The diamond substrate according to claim 10 or 11, characterized in that it is the diamond substrate according to claim 10 or 11.

13. The diamond substrate according to any one of claims 10 to 12, characterized in that the average surface roughness Ra of the surface of the diamond crystal layer having nitrogen vacancy centers is Ra ≤ 270 nm.

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