Diamond substrate and method of manufacturing the same, and sensor

Abstract

This invention provides a method for manufacturing a diamond substrate, which involves forming diamond crystals on a substrate using a CVD method. In this method, to form an NVC-containing diamond crystal layer in at least a portion of the diamond crystals, the feed gas is configured as follows: hydrocarbon gas: 0.005 vol% or more and 7.000 vol% or less; hydrogen gas: 85.000 vol% or more and less than 99.995 vol%; nitrogen gas or nitride gas: 5.0 × 10⁻⁶. ‑5 Volume percentage above 8.000% and volume percentage below 8.000% will 12 C-concentrated hydrocarbon gas is used as a hydrocarbon gas in the feed gas. 12 C Concentrated hydrocarbon gas 12 The proportion of carbon in hydrocarbon gases is higher than that in natural hydrocarbon gases. 12 The ratio of C to hydrocarbon gases. Thus, a method for manufacturing a diamond substrate can be provided, which can form a diamond crystal with a highly oriented NV axis (e.g., [111] highly oriented) and having a single spin and a high density of nitrogen-vacancy centers (NVC) by performing CVD on a substrate under specified conditions.

Description

Technical Field

[0001] This invention relates to a diamond substrate, a method for manufacturing the same, and a sensor. 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 possesses an exceptionally high dielectric breakdown strength of 10 MV / cm and can operate at high voltages. Furthermore, it exhibits excellent heat dissipation due to its highest known thermal conductivity. Additionally, its extremely high carrier mobility and saturation drift velocity make it suitable for high-speed devices.

[0004] Therefore, even compared to semiconductors such as silicon carbide and gallium nitride, diamond displays show the highest Johnson performance index as high-frequency / high-power devices, making them arguably the ultimate semiconductor.

[0005] Furthermore, diamond exhibits nitrogen-vacancy centers (NVCs) within its crystal structure and possesses the characteristic of being able to operate at room temperature and detect single spins, allowing for imaging of its state via photodetector magnetic resonance. By fully utilizing this characteristic, applications in a wide range of fields can be expected as highly sensitive sensors for magnetic fields, electric fields, temperature, pressure, and other parameters. Existing technical documents Patent documents

[0006] Patent Document 1: US2013 / 0143022A1 Non-patent literature

[0007] Non-patent literature 1: M. Hatano et al., OYOBUTURI 85, 311 (2016) Non-patent literature 2: T. Fukui, et al., APEX 7, 055201 (2014) Non-patent literature 3: H. Ozawa, et al., NDF Dia. Symp. 29, 16 (2015) Summary of the Invention (a) Technical problems to be solved

[0008] As described above, diamond is expected to be practically used as a semiconductor material and a material for electronic / magnetic devices, and it is anticipated that it will provide large-area, high-quality diamond substrates. For example, Patent Document 1 reports a technique for forming diamond (111) crystals by heteroepitaxial growth via chemical vapor deposition. Furthermore, especially in NVC devices, which are important applications of diamond, the nitrogen-vacancy axis (NV axis) must be highly oriented, so it is desirable that the diamond surface be a (111) crystal plane with the NV axis aligned in the

[111] direction (non-Patent Document 1). In addition, considering applications such as in the field of MRI for medical use, as long as the diamond substrate serving as the magnetic sensor part is large-diameter (large aperture), a device that can efficiently measure a wider area can be realized. It is also advantageous in terms of manufacturing cost.

[0009] Furthermore, when this diamond substrate is used in electronic / magnetic devices, for the sensor portion, the NV axis in the diamond crystal not only needs to be aligned in the

[111] direction, but also needs to be formed at a high density.

[0010] The fabrication of diamond crystals with high density NVC orientation

[111] as reported to date is shown below. A method for growing single-crystal diamond synthesized by high-temperature high-pressure synthesis (HPHT) as a substrate and then growing it by adding nitrogen to hydrogen-diluted methane using microwave chemical vapor deposition (CVD) was explored (Non-Patent Literature 2 and 3). However, the reported literature only uses large-sized HPHT1b (111) substrates that are difficult to obtain for practical use, and the details of the gas composition in CVD are unclear in Non-Patent Literature 2. Furthermore, it is unclear whether the CVD conditions in Non-Patent Literature 3 are optimal.

[0011] The present invention was carried out to solve the above-mentioned problems, and its object is to provide a method for manufacturing a diamond substrate, which forms a diamond crystal with a highly oriented NV axis (e.g.,

[111] highly oriented) and having a single spin and a high density of nitrogen-vacancy centers (NVCs) on a substrate by performing CVD under specified conditions. Furthermore, the present invention also aims to provide this diamond substrate. Further, the object is to provide a sensor using a diamond substrate containing this NVC. (II) Technical Solution

[0012] To achieve the above objectives, the present invention provides a method for manufacturing a diamond substrate, which is a method for manufacturing a diamond substrate by chemical vapor deposition (CVD) using a feed gas containing hydrocarbon gas and hydrogen as a dilution gas to form diamond crystals on a substrate, characterized in that... In order to form a diamond crystal layer having nitrogen vacancy centers in at least a portion of the diamond crystal formed on the substrate, nitrogen 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 to form the diamond crystal layer having nitrogen vacancy centers: The amount of hydrocarbon gas is 0.005% by volume or more and 7.000% by volume or less; The amount of hydrogen is greater than 85,000% by volume and less than 99.995% by volume; The amount of nitrogen or nitride gas is 5.0 × 10⁻⁶. -5 Volume percentage above 8.000% and below 8.000% And will 12 C-concentrated hydrocarbon gas is used as the hydrocarbon gas in the feed gas. 12 C Concentrated hydrocarbon gas contains carbon isotopes 12 The proportion of hydrocarbon gases composed of carbon is higher than that of natural hydrocarbon gases composed of carbon isotopes. 12 The ratio of hydrocarbon gases composed of carbon.

[0013] According to the diamond substrate manufacturing method under the above-described CVD conditions, a diamond substrate with a diamond crystal layer having high crystallinity, high NV axis orientation (especially

[111] high orientation), and single spin and high density NVC can be manufactured. Such diamond crystals are suitable for use in electronic / magnetic devices.

[0014] At this time, the raw material gas further contains an amount of oxygen or oxide gas of 0.010% by volume or more and 2.000% by volume or less.

[0015] This can achieve a moderate oxygen etching effect to remove non-diamond components and further improve the orientation of diamond crystals.

[0016] In addition, the hydrocarbon gas in the raw material gas can be methane gas.

[0017] If methane gas is used as described above, high-purity gas can be easily obtained at a low price, and it is also easy to operate, so it is preferred.

[0018] Furthermore, the gas pressure during the formation of the diamond crystal by CVD can be above 1.3 kPa (10 Torr) and below 50.0 kPa (376 Torr).

[0019] This gas pressure condition can more effectively suppress the growth of non-single-crystal diamonds and obtain single-crystal diamonds with high crystallinity.

[0020] Furthermore, for the aforementioned 12 C-concentrated hydrocarbon gas, this 12 C Concentrated hydrocarbon gas from12 The volume percentage of hydrocarbon gases composed of C can be above 99.950% by volume.

[0021] This allows for more efficient formation of single-spin and high-density NVC.

[0022] Furthermore, for the aforementioned 12 C-concentrated hydrocarbon gas, this 12 C Concentrated hydrocarbon gas from 13 The volume percentage of hydrocarbon gases composed of C can be less than 0.040% by volume.

[0023] This allows for more efficient formation of single-spin and high-density NVC.

[0024] In addition, the substrate can be a single-layer substrate of single-crystal diamond.

[0025] By using single-crystal diamond as a substrate as described above, the NV axis of diamond crystals containing NVC can be more effectively oriented (especially

[111] highly oriented) and formed at high density. By using the aforementioned single-crystal diamond (especially single-crystal diamond (111)) as a substrate, step flow growth is easily performed, and higher quality single-crystal diamonds with fewer growth mounds, abnormal growth particles, dislocation defects, etc. can be formed.

[0026] Furthermore, the single-layer substrate of the single-crystal diamond can be any one of high-temperature and high-pressure synthesized single-crystal diamond layer, heteroepitaxial single-crystal diamond layer, or CVD synthesized homoepitaxial diamond layer.

[0027] As the substrate in the manufacturing method of the diamond substrate of the present invention, a substrate composed of the above-mentioned single crystal diamond layer is preferably used.

[0028] Furthermore, when forming the diamond crystal by CVD, natural hydrocarbon gas can be used when forming a diamond crystal layer without nitrogen vacancy centers.

[0029] This can further reduce manufacturing costs.

[0030] Furthermore, the substrate can be a laminated structure consisting of a lower substrate and an intermediate layer on the lower substrate.

[0031] In this invention, a substrate having the above-described laminated structure may also be used.

[0032] In this case, the outermost surface of the intermediate layer can be a metal layer selected from Ir, Rh, Pd and Pt.

[0033] By forming the outermost surface of the intermediate layer with the aforementioned metal layers, after performing a nucleation process (biasing), the diamond nucleus easily becomes high-density, and a single-crystal diamond layer is easily formed on it.

[0034] Furthermore, as the CVD method, any one or more of the following methods can be used: microwave plasma CVD, direct current plasma CVD, hot filament CVD, and arc discharge plasma jet CVD.

[0035] One of the CVD methods mentioned above can be preferred, or multiple methods can be combined.

[0036] Furthermore, the present invention can also remove the substrate from a diamond substrate containing the diamond crystal layer with nitrogen vacancy centers obtained by the above-described diamond substrate manufacturing method to obtain a single-crystal diamond self-supporting substrate containing the diamond crystal layer with nitrogen vacancy centers.

[0037] Thus, a single-crystal diamond self-supporting substrate containing a diamond crystal layer with high crystallinity, high NV axis orientation (especially

[111] high orientation), and single spin and high density NVC can be obtained. It is suitable for use in electronic / magnetic devices.

[0038] In addition, the surface of the diamond crystal layer with nitrogen vacancy centers in the diamond substrate containing the diamond crystal layer with nitrogen vacancy centers obtained by the above-described diamond substrate manufacturing method can also be smoothed.

[0039] This suppresses diffuse reflection of light from the surface of the diamond crystal layer with NVC and increases the removable NV. - Central light.

[0040] The present invention also provides a diamond substrate, which is a diamond substrate comprising a diamond crystal layer having nitrogen vacancy centers, characterized in that, The diamond crystal layer with nitrogen vacancy centers is formed on a diamond crystal layer without nitrogen vacancy centers or a single-crystal diamond monolayer substrate. In the carbon atoms present in this diamond crystal layer with nitrogen vacancy centers, carbon isotopes 12 The proportion of C is higher than the proportion of natural carbon atoms. The nitrogen concentration distribution in the diamond crystal layer with nitrogen vacancy centers is steep in the interface region with the diamond crystal layer without nitrogen vacancy centers or the monolayer substrate of single-crystal diamond.

[0041] This diamond substrate is highly crystalline and has a highly oriented NV axis (especially

[111] highly oriented) and a single spin and high density NVC. Therefore, it is suitable for use in electronic / magnetic devices.

[0042] In particular, preferred method: using a secondary ion mass spectrometry analysis device with Cs + When determining the nitrogen concentration distribution in the diamond crystal layer with nitrogen vacancy centers using a primary ion type, a primary accelerating voltage of 16.0 kV, and a detection area diameter of 30 μm, the thickness of the region where the nitrogen concentration [N] decreases to 1 / e (Napier's constant) at the interface with the diamond crystal layer without nitrogen vacancy centers or the monolayer substrate of single-crystal diamond is less than 1.5 μm.

[0043] By observing the aforementioned rapid decrease in nitrogen concentration at the interface region between the layer with NVC and the layer without NVC, diamond substrates with superior properties containing NVC diamond crystals can be fabricated.

[0044] Furthermore, the hydrogen concentration [H] in the diamond crystal layer with nitrogen vacancy centers can be set to 1 × 10⁻⁶. 16 atoms / cm 3 above.

[0045] In diamond growth methods, when using the CVD method, the hydrogen concentration in the diamond crystal layer is higher than that in high temperature and high pressure diamond synthesis.

[0046] Furthermore, the nitrogen concentration [N] in the diamond crystal layer with nitrogen vacancy centers can be set to 1 × 10⁻⁶. 17 atoms / cm 3 ≤[N]≤9×10 19 atoms / cm 3 .

[0047] When the nitrogen concentration is within this range, diamond substrates with diamond crystals containing NVC can be manufactured with superior properties.

[0048] Furthermore, the average surface roughness Ra of the diamond crystal layer with nitrogen vacancy centers is preferably Ra≤260nm.

[0049] If the surface roughness is as described above, diffuse reflection of light on the surface of the diamond crystal layer with NVC can be suppressed, and the removable NV can be increased. - Central light.

[0050] Furthermore, the present invention provides a sensor using a diamond substrate as described in any of the above claims.

[0051] The sensor using the diamond substrate of the present invention exhibits excellent high sensitivity. (III) Beneficial Effects

[0052] According to the method for manufacturing a diamond substrate of the present invention, a diamond substrate having a diamond crystal layer with high crystallinity, high NV axis orientation (e.g.,

[111] high orientation), and having a single spin and high density NVC can be manufactured. Such diamond crystals are suitable for use in electronic / magnetic devices. Furthermore, the diamond substrate according to the present invention can provide a diamond substrate with high crystallinity, high NV axis orientation

[111] , and single spin and high density NVC, suitable for use in electronic / magnetic devices. Furthermore, the sensor according to the present invention can be a sensor with high sensitivity and excellent performance. Attached Figure Description

[0053] Figure 1 This is a schematic diagram illustrating an example of the diamond substrate (layer containing NVC / single-layer substrate without NVC) of the present invention. Figure 2 This is a schematic diagram illustrating an example of the diamond substrate (layer containing NVC / layer without NVC / substrate substrate with stacked structure) of the present invention. Figure 3 This is a schematic diagram illustrating an example of a diamond substrate (a layer / substrate substrate containing NVC) manufactured by the diamond substrate manufacturing method of the present invention. Figure 4 This is a schematic diagram illustrating an example of a diamond substrate (a substrate substrate with a layer / stack structure containing NVC) manufactured by the diamond substrate manufacturing method of the present invention. Figure 5 This is a schematic diagram illustrating an example of a diamond substrate (a layer containing NVC / a layer without NVC / a substrate with a stacked structure) manufactured by the diamond substrate manufacturing method of the present invention. Figure 6 This is a schematic diagram illustrating an example of a single-crystal diamond self-supporting substrate (layer with NVC / layer without NVC) obtained by the diamond substrate manufacturing method of the present invention. Figure 7 A graph showing the SIMS measurement results in Example 1. Detailed Implementation

[0054] The present invention will now be described in detail, but it is not limited thereto. As described above, the aim is to obtain a diamond substrate with a large diameter (large aperture), high crystallinity, high NV axis orientation (e.g.,

[111] high orientation) and single spin and high density NVC suitable for use in electronic / magnetic devices.

[0055] The inventors of this application have conducted in-depth research on the aforementioned technical problems and discovered that, according to the following method for manufacturing a diamond substrate, a diamond substrate with high crystallinity, high NV axis orientation (e.g.,

[111] high orientation), and single spin and high density NVC can be obtained, thus completing the present invention. The manufacturing method is as follows: in order to form a diamond substrate on a substrate by forming diamond crystals using a raw material gas containing hydrocarbon gas and hydrogen as a dilution gas via CVD, in order to form a diamond crystal layer with nitrogen vacancy centers in at least a portion of the diamond crystals formed on the substrate, nitrogen or nitride gas is mixed into the raw material gas, and the amounts of each gas contained in the raw material gas are set to the following amounts to form the diamond crystal layer with nitrogen vacancy centers: the amount of hydrocarbon gas is 0.005 vol% or more and 7.000 vol% or less; the amount of hydrogen is 85.000 vol% or more and less than 99.995 vol%; the amount of nitrogen or nitride gas is 5.0 × 10⁻⁶. -5 Volume percentage above and below 8.000% by volume, and will 12 C-concentrated hydrocarbon gas is used as the hydrocarbon gas in the feed gas. 12 C Concentrated hydrocarbon gas contains carbon isotopes 12 The proportion of hydrocarbon gases composed of carbon is higher than that of natural hydrocarbon gases composed of carbon isotopes. 12 The ratio of hydrocarbon gases composed of carbon.

[0056] Furthermore, it was discovered that the aforementioned technical problems can also be solved according to the diamond substrate described below, thereby completing the present invention. This diamond substrate is a diamond substrate comprising a diamond crystal layer having nitrogen vacancy centers. The diamond crystal layer having nitrogen vacancy centers is formed on a monolayer substrate containing a diamond crystal layer without nitrogen vacancy centers or a single-crystal diamond. In the carbon atoms present in the diamond crystal layer having nitrogen vacancy centers, carbon isotopes... 12 The presence ratio of C is higher than that of natural carbon atoms, and the nitrogen concentration distribution in the diamond crystal layer with nitrogen vacancy centers is steep in the interface region with the diamond crystal layer without nitrogen vacancy centers or the monolayer substrate of single crystal diamond.

[0057] In this specification, for the sake of simplicity, a diamond crystal layer with nitrogen vacancy centers (NVC) is sometimes referred to as a layer containing NVC, a diamond crystal layer without NVC is referred to as a layer without NVC, and a single-layer substrate of single-crystal diamond without NVC is referred to as a single-layer substrate without NVC. Furthermore, regarding the aforementioned layers and substrates, the following description will take, in particular, the case of a diamond crystal layer with a main surface of (111) and a single-layer substrate (also referred to as a single-crystal diamond (111) layer and a single-crystal diamond (111) substrate, respectively, as examples, but the present invention is not limited thereto.

[0058] (The diamond substrate and sensor of the present invention) The diamond substrate of the present invention will be described. The diamond substrate of the present invention is a diamond substrate comprising an NVC-containing layer, wherein the NVC-containing layer is formed on a single-layer substrate without NVC or on a layer without NVC.

[0059] (Option 1) Firstly, regarding the example of the former, refer to... Figure 1 Please provide an explanation. For example... Figure 1 As shown, in the diamond substrate 100 of the present invention, an NVC-containing layer 12 is formed on a single-layer substrate (single crystal diamond (111) substrate) that does not contain NVC, i.e., a substrate substrate 11. Furthermore, in the NVC-containing layer 12, among the carbon atoms present in the NVC-containing layer 12, carbon isotopes 12 The presence ratio of C is higher than that of natural carbon atoms. Furthermore, regarding the proportion of naturally occurring carbon atoms, well-known examples can be cited here. 12 C is 98.89%. 13 C is present at a rate of 1.11%. On the other hand, the substrate 11 is a single-layer substrate without NVC. 12 There are no particular restrictions on the presence ratio of C, and it can be in particular the same degree as the presence ratio of the aforementioned natural carbon atoms.

[0060] Furthermore, the nitrogen concentration distribution in the NVC-containing layer 12 is steep at the interface region with the substrate 11, and decreases rapidly from the NVC-containing layer 12 side toward the substrate 11 side. As to the specific degree of this steepness, one can cite examples such as the following: in the case of Cs using a secondary ion mass spectrometry (SIMS) device. + When determining the nitrogen concentration distribution in layer 12 containing NVC using a primary ion type, a primary acceleration voltage of 16.0 kV, and a detection area diameter of 30 μm, the thickness of the region where the nitrogen concentration [N] decreases to 1 / e (Napier constant) times in the aforementioned interface region is less than 1.5 μm. The thinner the descent region that indicates the steepness, the better. There is no particular limitation on its lower limit, but it can be, for example, 1.0 μm, more preferably 0.5 μm. In addition, examples of secondary ion mass spectrometry analysis devices include CAMECA IMS-7f (manufactured by AMETEK Co., Ltd.).

[0061] The diamond substrate 100 of the present invention described above is highly crystalline, has a high NV axis orientation of

[111] , and possesses a single spin and high density NVC. Therefore, it is suitable for use in electronic / magnetic devices.

[0062] Here, layer 12 containing NVC is transmitted through the aforementioned SIMS device CAMECA IMS-7f, with Cs + When measuring the primary ion species, the primary accelerating voltage of 16.0 kV, and the detection region diameter of 30 μm, the hydrogen concentration [H] can be 1 × 10⁻⁶. 16 atoms / cm 3 That's all. In the case of a layer formed by CVD as described below, this results in a layer with a high hydrogen concentration. Furthermore, there is no specific upper limit on the hydrogen concentration; for example, it can be 1 × 10⁻⁶. 18 atoms / cm 3 .

[0063] Furthermore, the nitrogen concentration [N] in layer 12 containing NVC is preferably 1 × 10⁻⁶. 17 atoms / cm 3 ≤[N]≤9×10 19 atoms / cm 3 With this nitrogen concentration, diamond substrates with NVC-containing layers can be fabricated to have superior properties.

[0064] Furthermore, when the average surface roughness Ra of the layer containing NVC is below 260 nm, diffuse reflection of light is suppressed, which can increase the removable NVC. - The central light source is preferred. Furthermore, due to the aforementioned diffuse reflection of light, the smaller the average surface roughness Ra, the better, so it cannot be limited; for example, it can be 200 nm. Furthermore, the following methods can be listed as examples of methods for measuring the average surface roughness Ra. (Determination Method) Measurements were performed in an 80 μm × 80 μm area using an atomic force microscopy (AFM) instrument, such as the NanoScope V / Dimension Icon manufactured by Bruker AXS, in tapping mode.

[0065] (Option 2) Next, regarding the latter example, refer to... Figure 2 Please explain. For example... Figure 2 As shown, the diamond substrate 200 of the present invention has an NVC-free layer 23 formed on a substrate 21, and an NVC-containing layer 22 formed on the NVC-free layer 23. The substrate 21 is not particularly limited and can also be used with Figure 1 The diamond substrate 100 is also a single-layer substrate without NVC, but it can also be like... Figure 2 As shown, the structure is a stacked structure consisting of a lower substrate 24 and an intermediate layer 25 above it. For example, the lower substrate 24 can be a single-crystal MgO substrate. Furthermore, the intermediate layer 25 can be a single layer or a multilayer stack. And the outermost surface of the intermediate layer 25 can be a metal layer selected from Ir, Rh, Pd and Pt. Furthermore, regarding layer 23, which does not contain NVC, the layer in this layer 12 There are no particular restrictions on the presence ratio of C; for example, it can be the same as the presence ratio of natural carbon atoms.

[0066] Furthermore, the steepness and degree of the nitrogen concentration distribution in the NVC-containing layer 22 at the interface region with the NVC-free layer 23 can be compared with the aforementioned... Figure 1 The steepness and degree of the interface region between the NVC-containing layer 12 and the substrate 11 are the same. Furthermore, the ranges of hydrogen and nitrogen concentrations in layer 22 containing NVC, and the range of its average surface roughness Ra, can also be compared with... Figure 1 The parameters mentioned above are the same in layer 12 containing NVC.

[0067] The diamond substrate 200 described above is also highly crystalline, with a high orientation of the NV axis

[111] and has a single spin and high density NVC, making it suitable for use in electronic / magnetic devices.

[0068] Furthermore, various sensors of the present invention using the diamond substrates 100 and 200 of the present invention include, for example, current, temperature, and biomagnetic sensors, each of which exhibits excellent high sensitivity.

[0069] (The method for manufacturing the diamond substrate of the present invention) Next, the method for manufacturing the diamond substrate of the present invention will be described. First, a general overview will be provided. Diamond substrates are manufactured by forming diamond crystals on a substrate using a CVD (Chemical Vapor Deposition) method with a feed gas containing hydrocarbon gas and hydrogen as a dilution gas. Examples of CVD methods include microwave plasma CVD, direct current plasma CVD, hot filament CVD, and arc discharge plasma jet CVD. Among these, diamonds obtained using microwave plasma CVD and direct current plasma CVD are high-crystallinity, with fewer growth mounds, aberrant growth particles, dislocation defects, and excellent impurity control, resulting in high-quality single-crystal diamonds. Furthermore, multiple CVD methods can be combined. For example, combining direct current plasma CVD and microwave plasma CVD allows for simultaneous diamond nucleation and film growth. Combining direct current plasma CVD and hot filament CVD allows for simultaneous diamond nucleation and large-area film growth. In addition, in order to form an NVC-containing layer in at least a portion of the diamond crystal, nitrogen or nitride gas is mixed into the raw material gas (oxygen or oxide gas may also be mixed in if necessary), and the amount of each gas (hydrocarbon gas, hydrogen, nitrogen or nitride gas (and oxygen or oxide gas)) contained in the raw material gas is limited to a specific range described later. Furthermore, 12 C-concentrated hydrocarbon gas is used as the above-mentioned hydrocarbon gas in the feed gas. 12 C Concentrated hydrocarbon gas contains carbon isotopes 12 The proportion of hydrocarbon gases composed of carbon is higher than that of natural hydrocarbon gases composed of carbon isotopes. 12 The ratio of hydrocarbon gases composed of carbon.

[0070] The following is a further detailed explanation. (First Manufacturing Plan) In order to form the NV axis with high orientation and high density

[111] , it is preferable to set the substrate as a single-layer substrate of single crystal diamond, and more preferably as an epitaxial growth of single crystal diamond (111) on the substrate. Figure 3 A diamond substrate 300 is shown with an NVC-containing layer 32 formed on a substrate 31. (See reference...) Figure 3 When describing the process, it is preferable to use a single-layer substrate of single-crystal diamond, especially single-crystal diamond (111), as the substrate 31.

[0071] Furthermore, the single-layer substrate of the single-crystal diamond used as the substrate 31 can be any one of a high-temperature high-pressure synthesized single-crystal diamond layer, a heteroepitaxial single-crystal diamond layer, or a CVD synthesized homoepitaxial diamond layer. In the manufacturing method of the present invention, the above-mentioned single-crystal diamond is preferably used as the substrate 31.

[0072] In the feed gas used to form the NVC-containing layer 32, methane, acetylene, ethylene, ethane, propane, etc. can be used as hydrocarbon gases. Methane is preferred because it is easy to obtain high-purity gas at low price and is easy to operate.

[0073] Since the etching effect of hydrogen becomes stronger when the amount of hydrocarbon gases such as methane is less than 0.005% by volume, resulting in no diamond growth, the range of hydrocarbon gas amount is set to 0.005% by volume or more, more preferably 0.01% or more, and most preferably 0.05% by volume or more. On the other hand, when the amount of hydrocarbon gas exceeds 7,000 vol%, diamond will become polycrystalline during long-term growth, so it is impossible to obtain a single crystal of excellent quality. Therefore, the range is set to 7,000 vol% or less, preferably 6.5 vol% or less, and more preferably 6.0 vol% or less.

[0074] In addition, the amount of nitrogen or nitride gas in the feed gas is less than 5.0 × 10⁻⁶. -5 At a volume percentage of 5%, the nitrogen doping content in the diamond crystal is too low, resulting in a lower NVC density. Therefore, the range for the amount of nitrogen or nitride gas is set to 5.0 × 10⁻⁶. -5 Volume percentage or higher, preferably 5.0 × 10⁻⁶ -4 Volume percentage or more, more preferably 1.0 × 10⁻⁶ -3 Volume percentage or more. On the other hand, when the amount of nitrogen gas or nitride gas exceeds 8,000% by volume, the diamond will become polycrystalline during long-term growth, making it impossible to obtain a single crystal of good quality. Therefore, the amount of nitrogen gas or nitride gas is set to 8,000% by volume or less, and more preferably 0.500% by volume or less. As a nitrogen-containing gas, ammonia, nitric oxide, nitrogen dioxide, etc. can be used. Nitrogen is preferred because it is easy to obtain high-purity gas at low cost and is easy to handle.

[0075] Furthermore, since the addition of oxygen or oxide gas removes non-diamond components and further enhances the orientation of the diamond crystal, it is preferred. When adding oxygen or oxide gas, a suitable oxygen etching effect can be obtained by setting it to 0.010 vol% or more. On the other hand, setting it to 2.000 vol% or less can effectively prevent the etching effect caused by oxygen from being too large and hindering diamond growth.

[0076] In addition, the hydrogen gas used for dilution should be set to 85.000% by volume or more and less than 99.995% by volume.

[0077] At this point, when the gas pressure during diamond crystal formation using various CVD methods is set to 1.3 kPa (10 Torr) or higher and 50.0 kPa (376 Torr) or lower, high-quality single crystals can be obtained because polymorphism of diamond can be effectively prevented. In order to effectively prevent the discharge from being difficult due to excessively low gas pressure and to prevent the plasma density from being too low to obtain high-quality single-crystal diamond, the gas pressure is set to the lower limit mentioned above, and more preferably, it can be 12.0 kPa (90 Torr) or higher. On the other hand, in order to effectively prevent problems such as difficulty in discharge due to excessively high gas pressure, or reduced crystallinity due to high temperature, which in turn leads to a smaller diamond formation range, the upper limit is set as described above, and is more preferably 33.3 kPa (250 Torr) or less.

[0078] Furthermore, hydrocarbon gases used as feedstock in CVD methods, if those derived from carbon isotope carbon-12 (… 12 C) The proportion of hydrocarbon gases composed of isotopes is higher than their proportion in natural hydrocarbon gases. 12 Concentrating hydrocarbon gases with carbon can form high-density NVC (non-volatile organic compounds). This allows for the development of highly sensitive sensors (such as magnetic sensors). Here, the ratios in natural hydrocarbon gases can be listed as follows: 12 The proportion of hydrocarbon gases composed of carbon is 98.89%, which is... 13 The proportion of hydrocarbon gases composed of carbon is 1.11% (e.g., by volume). Furthermore, by using the above ratio 12 C-concentrated hydrocarbon gas can form in crystals 12 Diamond crystals with a higher C content than those with a natural carbon content.

[0079] The 12 In C-concentrated hydrocarbon gas, if using... 12 Hydrocarbon gases composed of C with a volume percentage of 99.950% or more (less than 100% by volume) can more effectively form single-spin and high-density NVC. And by reducing the carbon isotope content, which is second only to 12 C contains more of the following: 13 Hydrocarbon gases composed of carbon can also effectively form higher-density NVC, and by... 12 C-concentrated hydrocarbon gas, especially by 13 The presence of hydrocarbon gases composed of C at a volume percentage of less than 0.040% (or more than 0% by volume) is also effective for forming single-spin and high-density NVC. 12 C Concentrated hydrocarbon gas from 12 Hydrocarbon gas composed of C or composed of13 The volume percentage of hydrocarbon gas composed of C can be adjusted, for example, by using commercially available gases of high purity.

[0080] In addition, for Figure 3 When the diamond substrate 300 is manufactured using a single-layer substrate without NVC as the substrate substrate 31, it can be manufactured to be similar to... Figure 1 The same substrate as the diamond substrate 100 shown.

[0081] This allows the fabrication of diamond substrates with highly crystalline diamond crystal layers, NV axis with high orientation

[111] , and single spin and high density NVC, making them suitable as substrates for various devices (sensor substrates).

[0082] (Second Manufacturing Plan) Furthermore, in the method for manufacturing the diamond substrate of the present invention, the substrate may also be made into a laminated structure consisting of a lower substrate and an intermediate layer on the lower substrate. Figure 4 A diamond substrate 400 with an NVC-containing layer formed on a laminated substrate is shown. That is, Figure 4 The diamond substrate 400 is a diamond substrate 400 in which a layer 42 containing NVC is formed on the substrate 41, which is a stacked structure consisting of a lower substrate 44 and an intermediate layer 45.

[0083] There are no particular restrictions on the lower substrate 44; for example, a single-crystal MgO substrate can be used. The intermediate layer 45 can be a single layer or a multilayer stack. The outermost surface of the intermediate layer 45 is preferably a metal layer selected from, for example, Ir, Rh, Pd and Pt. When using such a metal layer, it is preferred because diamond nuclei tend to become highly dense during the nucleation process (biasing process), and a single-crystal diamond layer can easily be formed on top of them.

[0084] (Third Manufacturing Plan) Furthermore, such as Figure 5 As shown, a diamond substrate 500 can also be manufactured on a substrate 51 (lower substrate 54, intermediate layer 55) with a stacked structure, wherein an undoped diamond layer (non-NVC layer) 53 (made of single crystal) and an NVC layer 52 (made of single crystal) are sequentially formed. When forming the NVC-free layer 53, it is preferable to use natural hydrocarbon gas. This is because it can further reduce manufacturing costs. In particular, as Figure 5 Diamond 500 can be manufactured with Figure 2 The same substrate as the diamond substrate 200 shown.

[0085] Furthermore, in the second and third manufacturing schemes, the conditions regarding the amounts of each gas (hydrocarbon gas, hydrogen gas, nitrogen gas, or nitride gas) during the formation of the NVC-containing layer, and " 12 C Concentrated hydrocarbon gas contains 12 The condition that "the proportion of hydrocarbon gas composed of C is greater than its proportion in natural hydrocarbon gas" is set to the same condition as in the first manufacturing scheme. Furthermore, the other conditions mentioned above, such as the use of oxygen or oxide gas and gas pressure, can also be set to the same conditions as in the first manufacturing scheme.

[0086] Furthermore, in the first to third manufacturing schemes, a process for smoothing the surface of the NVC-containing layer can also be added. Smoothing can be performed using methods such as physical polishing, chemical / physical polishing, plasma treatment, sputtering, and chemical etching. When the average surface roughness Ra of the NVC-containing layer is, for example, below 260 nm (above 0 nm), diffuse reflection of light can be suppressed, increasing the amount of NVC that can be removed. - Central light.

[0087] Furthermore, in this invention, the substrate can be removed from a diamond substrate containing an NVC-containing layer on a substrate obtained by the above-described diamond substrate manufacturing method. This results in a single-crystal diamond self-supporting substrate containing an NVC-containing layer. Consequently, the diamond substrate with an increased proportion of NVC-containing portions reduces noise factors during actual use, thus enabling the realization of highly sensitive electronic / magnetic devices. Furthermore, if the substrate is a single layer as shown in the first manufacturing scheme, the entire substrate can be removed. Also, if the substrate is composed of a lower substrate and an intermediate layer as shown in the second and third manufacturing schemes, only the lower substrate can be removed, or both the lower substrate and the intermediate layer can be removed. Furthermore, a portion of the substrate can also be removed. Moreover, the undoped nitrogen diamond layer can also be removed, thereby obtaining only the NVC-containing layer.

[0088] As an example of the manufacturing of this single-crystal diamond self-supporting substrate, Figure 6 Showing from Figure 5 In the case of removing a portion of the substrate 51 (lower substrate 54 and intermediate layer 55) from the diamond substrate 500, a diamond substrate 600 (a self-supporting structure substrate of diamond substrate) is obtained, which is composed of a layer 52 containing NVC and a diamond layer 53 without nitrogen doping (a layer without NVC).

[0089] Furthermore, there are no particular restrictions on the method for removing the substrate. Physical treatments such as grinding, optical treatments such as laser processing, wet etching, or dry etching can be appropriately selected based on the materials of the substrate, lower substrate, and intermediate layer. Furthermore, combinations of the above treatments are also possible. Example

[0090] The present invention will be illustrated in more detail below with examples, but the present invention is not limited to these examples. (Example 1) As the lower substrate in the substrate, a single-crystal MgO substrate with a diameter of 10.0 mm, a thickness of 1.0 mm, a main surface of (111) and a 4° offset angle in the crystal axis [-1-1 2] direction is prepared and polished on one side (hereinafter referred to as "single-crystal MgO (111) substrate").

[0091] Next, an intermediate layer of a single-crystal Ir film was formed on the surface of the prepared single-crystal MgO(111) substrate by RF magnetron sputtering. The single-crystal Ir film was formed by high-frequency (RF) magnetron sputtering (13.56MHz) using Ir with a diameter of 6 inches (150 mm), a thickness of 5.0 mm, and a purity of 99.9% or higher as the target. The single-crystal MgO(111) substrate, which serves as the lower substrate, was heated to 840°C, and the base pressure was confirmed to be 6 × 10⁻⁶. - 7 Torr (approximately 8.0 × 10) -5 After the pressure drops below 3 Pa, Ar gas is introduced at a rate of 50 sccm. Next, the opening of the valve leading to the exhaust system is adjusted to achieve a pressure of 3 × 10⁻⁶ Pa. -1 After applying a torque of approximately 39.9 Pa, a 1000 W RF power was applied for 15 minutes to form a film. This resulted in a single-crystal Ir film with a thickness of 1.0 μm.

[0092] The structure obtained in the above manner, in which a single-crystal Ir film is stacked on a single-crystal MgO(111) substrate, was heteroepitaxially grown along the deviation angle of the single-crystal MgO substrate. The single-crystal Ir film was analyzed by X-ray diffraction. The measuring device was RIGAKU's Smart Lab, wavelength λ=1.54Å, output 45kV, 200mA, semiconductor detector, incident optics system Ge(220) channel-cut monochromator, Soller slits input side 2.5°, light-receiving side 2.5°, slit incident side IS=1mm, long side limit 0.5mm, light-receiving side RS1=1.0mm, RS2=1.1mm, step width 0.004°, scanning speed 3° / min. The surface was (111) and had a 4° deviation angle in the direction of crystal axis [-1-1 2]. Furthermore, the full width at half maximum (FWHM) of the diffraction peak at 2θ = 40.7° belonging to Ir(111) is 0.125°. Hereinafter, this single-crystal Ir film will be referred to as the "Ir(111) film".

[0093] Next, as a pretreatment for forming diamond crystal nuclei, a nucleation treatment (bias treatment) was performed. A substrate was placed on a 25mm diameter planar electrode in the processing chamber with the Ir(111) film side facing upwards. The base pressure was confirmed to be 1×10⁻⁶. -6 Torr (approximately 1.3 × 10⁻⁶) -4 After the pressure drops below 100 Pa, hydrogen-diluted methane gas (CH4 / (CH4+H2) = 5.0 vol%) is introduced into the treatment chamber at a flow rate of 500 sccm. The opening of the valve leading to the exhaust system is adjusted to achieve a pressure of 100 Torr (approximately 1.3 × 10⁻⁶ Pa). 4 After Pa), a negative voltage is applied to the substrate side electrode and exposed to plasma for 90 seconds to bias the substrate (Ir(111) film) surface.

[0094] Diamond was heteroepitaxially grown on an Ir(111) film / single-crystal MgO(111) substrate prepared as described above using microwave plasma CVD. The biased Ir(111) film / single-crystal MgO(111) substrate was placed in the chamber of the microwave plasma CVD apparatus, and the base pressure was confirmed to be 1 × 10⁻⁶. -6 Torr (approximately 1.3 × 10⁻⁶) -4 After the pressure drops below 100 Pa, a mixture of natural methane gas (purity ≥ 99.9999% by volume) and hydrogen gas (purity ≥ 99.99999% by volume) is introduced into the chamber at a flow rate of 500 sccm at the following volume ratio. The opening of the valve leading to the exhaust system is adjusted to achieve a pressure of 120 Torr (approximately 1.6 × 10⁻⁶ Pa) within the chamber. 4 After Pa), a 3000W microwave was applied for 71 hours to form a film with a thickness of approximately 250μm (undoped nitrogen diamond layer). Methane gas 4,000% by volume Hydrogen 96,000% by volume

[0095] Next, the ingredients added as raw materials 12 C forms methane gas. 13 C constitutes 99.995% by volume of methane gas / 0.005% by volume. 12 The mixture of concentrated methane gas, hydrogen (purity ≥99.99999% by volume), and nitrogen (purity ≥99.99999% by volume) was changed to the following volume ratio and introduced into the chamber at a flow rate of 500 sccm. Pressure and microwave power remained constant. Under these conditions, film formation was carried out for 5 hours until the nitrogen-doped diamond layer reached a thickness of approximately 6 μm. 0.100% by volume of methane gas Hydrogen 99.850% by volume Nitrogen gas 0.050% by volume This allows for heteroepitaxial growth of a diamond layer on an Ir(111) film / single-crystal MgO(111) substrate, resulting in a multilayer substrate.

[0096] Subsequently, the Ir(111) film / single-crystal MgO(111) substrate was removed, and self-supporting substrate formation was performed. First, the single-crystal MgO(111) substrate was removed by wet etching, and then the Ir(111) film was removed by grinding. As a result, a single-crystal diamond(111) laminate substrate with a diameter of 10 mm was obtained, consisting of a nitrogen-doped single-crystal diamond film with a thickness of about 6 μm and an undoped single-crystal diamond(111) substrate with a thickness of about 250 μm. The surface of the diamond substrate with the laminated structure is ground and then finished.

[0097] Finally, SIMS, XRD, NVC density, and surface roughness analyses were performed on the finished laminated diamond substrate. Using a SIMS measurement device: CAMECA IMS-7f, with Cs + The nitrogen concentration [N] in diamond crystals was determined under the conditions of primary ion species, primary accelerating voltage of 16.0 kV, and detection region diameter of 30 μm. Additionally, the SIMS measurement results, including the hydrogen concentration [H] described later, are summarized as follows: Figure 7 . As a result, the nitrogen concentration at a depth of approximately 5 μm from the outermost surface of the membrane was [N] = 4.5 × 10⁻⁶. 17 atoms / cm 3 . Typically, the depth at which the nitrogen concentration [N] in a nitrogen-doped diamond film reaches 1 / e is considered the interface between the nitrogen-doped layer and the undoped layer. In this case, the distribution exhibits a steep change in thickness at approximately 1.0 μm in the interface region.

[0098] Next, the hydrogen concentration [H] in the diamond crystal was measured under the same SIMS conditions. The result showed that the hydrogen concentration from the uppermost surface to a depth of approximately 5 μm was [H] = 1.5 × 10⁻⁶. 17 atoms / cm 3 .

[0099] The crystallinity of the film was analyzed using an X-ray diffraction apparatus: RIGAKU's Smart Lab, with a wavelength of λ=1.54Å, output of 45kV and 200mA, a semiconductor detector, an incident optical system of Ge(220) channel-cut monochromator, a Soler slit with an input angle of 2.5° and a light-receiving angle of 2.5°, an incident angle of IS=1mm, a long side limit of 0.5mm, a light-receiving angle of RS1=1.0mm and RS2=1.1mm, a step size of 0.004°, and a scanning speed of 3° / min. As a result, only the diffraction intensity peak of 2θ=43.9° belonging to diamond (111) was observed, confirming that the nitrogen-doped single-crystal diamond film was epitaxially grown on the undoped single-crystal diamond (111) layer.

[0100] Furthermore, a confocal microscope (incident wavelength 532 nm) was used to perform photoluminescence measurement, confocal microscope image observation, optically detected magnetic resonance (ODMR) measurement, and Rabi vibration NVC evaluation. As a result, NVC light with a wavelength of 637 nm was detected, and the calculated NVC density based on the electron spin relaxation time T2 = 58.2 μs was 4.4 × 10⁻⁶. 16 / cm 3 . Therefore, the obtained nitrogen-doped film is a single-crystal diamond (111) crystal with high-density NVC.

[0101] In addition, the surface of the diamond substrate was measured using an atomic force microscope (NanoScope V from Bruker AXS) over an 80 μm × 80 μm area, and the average surface roughness Ra was found to be 187 nm.

[0102] In addition, the carbon isotope ratio of the nitrogen-doped layer of the NVC-containing diamond (111) substrate was measured. Measurement conditions: SIMS measurement device used: CAMECA IMS-7f, with O 2+ The carbon concentration in diamond crystals was determined under the following conditions: primary ion species, primary accelerating voltage of 11.0 kV, and detection area diameter of 30 μm. 12 C] and [ 13 C). as a result, 12 The presence rate of carbon is 99.995%, which is higher than that of natural carbon atoms. 12 The presence rate of C is 98.89%. And... 13 The presence rate of C is 0.005%.

[0103] The NVC density and other parameters in the nitrogen-doped layer of Example 1 are shown below. Nitrogen concentration: 4.5 × 10 17 atoms / cm 3 Hydrogen concentration: 1.5 × 10 17 atoms / cm 3 NVC density: 4.4 × 10 16 / cm 3 12 C and 13 The ratio of C to: 12 C is 99.995%. 13 C is 0.005% Steepness at the interface region: approximately 1.0 μm

[0104] (Example 2) As a substrate, a single-crystal diamond substrate with a diameter of 2 mm, a thickness of 200 μm, a main surface of (111), and an offset angle of 4.0° in the crystal axis [-1-1 2] direction is prepared by single-sided grinding. The manufacturing method of this single-crystal diamond substrate is as follows. First, following the same steps as in Example 1, an operation was performed to form an undoped nitrogen-coated single-crystal diamond layer, resulting in an undoped nitrogen-coated 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 form a self-supporting substrate. Specifically, after removing the single-crystal MgO(111) substrate by wet etching, the Ir(111) film was removed by grinding. Then, a 2mm square, approximately 250μm thick, undoped nitrogen-coated single-crystal diamond(111) self-supporting monolayer substrate was obtained by laser cutting. The surface of this substrate was then ground to obtain a 2mm square, approximately 200μm thick, single-crystal diamond substrate with a (111) main surface and a 4° offset angle in the crystal axis [-1-1 2] direction, which was then ground on one side.

[0105] Nitrogen-doped single-crystal diamond was epitaxially grown on a substrate prepared as described above using microwave plasma CVD. The substrate was placed in the chamber of the microwave plasma CVD apparatus, and the base pressure was confirmed to be 1 × 10⁻⁶. - 6 Torr (approximately 1.3 × 10⁻⁶) -4 After Pa) below, the additives will be used as raw materials. 12 C forms methane gas. 13 C constitutes 99.995% by volume of methane gas / 0.005% by volume. 12A mixture of concentrated methane gas, hydrogen (purity > 99.99999% by volume), and nitrogen (purity > 99.99995% by volume) is introduced into the chamber at a flow rate of 500 sccm in the following volume ratio. The opening of the valve leading to the exhaust system is adjusted to achieve a pressure of 120 Torr (approximately 1.6 × 10⁻⁶) within the chamber. 4 After Pa), a microwave power of 3500W is input for 96 hours to form a film, and the film formation is carried out until the thickness of the nitrogen-doped single crystal diamond layer reaches 218μm. 0.100% by volume of methane gas Hydrogen 99.850% by volume Nitrogen gas 0.050% by volume This results in a stacked diamond substrate consisting of a nitrogen-doped single-crystal diamond layer and an undoped single-crystal diamond (111) substrate.

[0106] Finally, SIMS and XRD analyses were performed on the finished laminated substrate. Next, the nitrogen concentration [N] and hydrogen concentration [H] in the diamond crystal were measured under the same SIMS conditions as in Example 1. The results showed that the nitrogen concentration from the uppermost surface to a depth of approximately 5 μm was [N] = 1.4 × 10⁻⁶. 18 atoms / cm 3 The hydrogen concentration is [H] = 1.5 × 10⁻⁶. 17 atoms / cm 3 . In addition, the steepness of the nitrogen concentration distribution in the nitrogen-doped layer at the interface region (the thickness of the 1 / e-folded drop region) is about 1.0 μm.

[0107] The crystallinity of the film was analyzed using an X-ray diffraction apparatus: RIGAKU's Smart Lab, with a wavelength of λ=1.54Å, output of 45kV and 200mA, a semiconductor detector, an incident optical system of Ge(220) channel-cut monochromator, a Soler slit with an input angle of 2.5° and a light-receiving angle of 2.5°, an incident angle of IS=1mm, a long side limit of 0.5mm, a light-receiving angle of RS1=1.0mm and RS2=1.1mm, a step size of 0.004°, and a scanning speed of 3° / min. As a result, only the diffraction intensity peak of 2θ=43.9° belonging to diamond (111) was observed, confirming that the nitrogen-doped single crystal diamond film was epitaxially grown on the undoped single crystal diamond (111) layer.

[0108] Furthermore, a confocal microscope (incident wavelength 532 nm) was used to perform photoluminescence measurement, confocal microscope image observation, optically detected magnetic resonance (ODMR) measurement, and Rabi vibration NVC evaluation. As a result, NVC light with a wavelength of 637 nm was detected, and the calculated NVC density based on the electron spin relaxation time T2 = 19.9 μs was 1.4 × 10⁻⁶. 17 / cm 3 . Therefore, the obtained nitrogen-doped film is a single-crystal diamond (111) crystal with high-density NVC.

[0109] In addition, the carbon isotope ratio of the nitrogen-doped layer of the NVC-containing diamond (111) substrate was determined under the same conditions as in Example 1. as a result, 12 The presence rate of C was 99.995%. 13 The presence rate of C is 0.005%.

[0110] If this diamond (111) substrate containing NVC is applied to electronic / magnetic devices, high-performance devices can be obtained. For example, a highly sensitive magnetic sensor can be obtained.

[0111] The NVC density and other parameters in the nitrogen-doped layer of Example 2 are shown below. Nitrogen concentration: 1.4 × 10 18 atoms / cm 3 Hydrogen concentration: 1.5 × 10 17 atoms / cm 3 NVC density: 1.4 × 10 17 / cm 3 12 C and 13 The ratio of C to: 12 C is 99.995%. 13 C is 0.005% Steepness at the interface region: approximately 1.0 μm

[0112] (Comparative Example 1) When growing nitrogen-doped single-crystal diamond epitaxially, natural methane gas with unconcentrated carbon isotopes (purity ≥ 99.9999% by volume) is used as the methane gas in the raw material, and the rest is prepared in the same manner as in Example 2, to obtain a stacked diamond substrate of nitrogen-doped single-crystal diamond layer / undoped single-crystal diamond (111) substrate.

[0113] The crystallinity, as determined by XRD, and the nitrogen concentration [N] and hydrogen concentration [H], as determined by SIMS, were the same as in Example 2. Other details are summarized below. Nitrogen concentration: 1.4 × 10 18 atoms / cm 3 Hydrogen concentration: 1.5 × 10 17 atoms / cm 3 NVC density: 1.2 × 10 16 / cm 3 12 C and 13 The ratio of C to: 12 C is 98.892%. 13 C is 1.108% (approximately the same as the naturally occurring concentration). Steepness at the interface: approximately 2.5 μm (significantly milder compared to Examples 1 and 2)

[0114] (Example 3) When epitaxially growing nitrogen-doped single-crystal diamond, the mixed gas used is set as follows, and the rest is carried out in the same manner as in Example 2, to obtain a stacked diamond substrate of nitrogen-doped single-crystal diamond layer / undoped single-crystal diamond (111) substrate. Methane gas 0.005% by volume 12 C forms methane gas. 13 C constitutes methane gas = 99.500% by volume / 0.500% by volume Hydrogen 99.945% by volume Nitrogen gas 0.050% by volume

[0115] The results of the various measurements are shown below. Nitrogen concentration: 1.5 × 10 18 atoms / cm 3 Hydrogen concentration: 1.5 × 10 17 atoms / cm 3 NVC density: 1.2 × 10 17 / cm 3 12 C and 13 The ratio of C to: 12 C is 99.500%. 13 C is 0.500% Steepness at the interface region: approximately 1.0 μm

[0116] (Example 4) When epitaxially growing nitrogen-doped single-crystal diamond, nitrogen-doped single-crystal diamond is added as a raw material. 12 C forms methane gas. 13 C constitutes 99.995% by volume of methane gas / 0.005% by volume. 12A mixture of concentrated methane gas, hydrogen (purity > 99.99999% by volume) and nitrogen (purity > 99.99995% by volume) was prepared in the following volume ratio, and the rest was prepared in the same manner as in Example 2 to obtain a stacked diamond substrate of a nitrogen-doped single-crystal diamond layer / undoped single-crystal diamond (111) substrate. Methane gas 7,000% by volume Hydrogen 92.950% by volume Nitrogen gas 0.050% by volume

[0117] The results of the various measurements are shown below. Nitrogen concentration: 1.0 × 10 18 atoms / cm 3 Hydrogen concentration: 1.5 × 10 17 atoms / cm 3 NVC density: 9.5 × 10 16 / cm 3 12 C and 13 The ratio of C to: 12 C is 99.995%. 13 C is 0.005% Steepness at the interface region: approximately 1.2 μm

[0118] (Comparative Example 2) When epitaxially growing nitrogen-doped single-crystal diamond, the mixed gas used was set as follows, and the rest was fabricated in the same manner as in Example 2. A stacked diamond substrate of nitrogen-doped single-crystal diamond layer / undoped single-crystal diamond (111) substrate was fabricated. 0.001% by volume of methane gas Hydrogen 99.949% by volume Nitrogen gas 0.050% by volume However, perhaps due to the low volume ratio of methane gas, nitrogen-doped single-crystal diamond was difficult to grow, and the film formation was interrupted midway.

[0119] (Comparative Example 3) When epitaxially growing nitrogen-doped single-crystal diamond, the mixed gas used was set as follows, and the rest was fabricated in the same manner as in Example 2. A stacked diamond substrate of nitrogen-doped single-crystal diamond layer / undoped single-crystal diamond (111) substrate was fabricated. Methane gas 14,000% by volume Hydrogen 85.950% by volume Nitrogen gas 0.050% by volume However, perhaps due to the excessively high volume ratio of methane gas, the nitrogen-doped diamond became polycrystalline.

[0120] (Comparative Example 4) When epitaxially growing nitrogen-doped single-crystal diamond, the mixed gas used was set as follows, and the rest was fabricated in the same manner as in Example 2. A stacked diamond substrate of nitrogen-doped single-crystal diamond layer / undoped single-crystal diamond (111) substrate was fabricated. 0.100% by volume of methane gas Hydrogen gas is approximately 99.850% by volume. Nitrogen gas 0.00001% by volume However, perhaps due to the low volume ratio of nitrogen, the NVC density is significantly lower than that of the embodiments and Comparative Example 1.

[0121] (Comparative Example 5) When epitaxially growing nitrogen-doped single-crystal diamond, the mixed gas used was set as follows, and the rest was fabricated in the same manner as in Example 2. A stacked diamond substrate of nitrogen-doped single-crystal diamond layer / undoped single-crystal diamond (111) substrate was fabricated. 0.100% by volume of methane gas Hydrogen 85.900% by volume Nitrogen 14,000% by volume However, perhaps due to the excessively high volume ratio of nitrogen, the diamond in the nitrogen-doped layer became polycrystalline.

[0122] As described above, in the cases of the products of the present invention in Examples 1-4, a high-density NVC structure can be fabricated. This allows for the fabrication of highly sensitive sensors. On the other hand, in Comparative Example 1, where the conditions of the present invention are not met, even if the nitrogen concentration and other parameters are the same as those of the products of the present invention, the NVC density is inferior to that of the products of the present invention. Furthermore, in Comparative Examples 2, 3, and 5, the growth of the nitrogen-doped single-crystal diamond layer is inherently poor. And in Comparative Example 4, the NVC density is exceptionally low.

[0123] (Example 5) Even when the formation of undoped and nitrogen-doped single-crystal diamonds in Examples 1 and 2 is carried out using DC plasma CVD, hot-wire CVD, and arc discharge plasma jet CVD respectively, and even when multiple CVD methods are combined, the resulting nitrogen-doped layers are all at a density of 4.4 × 10⁻⁶. 16 ~1.4×10 17 / cm 3 Single-crystal diamond (111) crystals formed at approximately the same NVC density. And, regarding 12 C and 13The presence of C and the steepness of the interface region, among other measurement results, are to the same extent as in the various embodiments, and are considered good values.

[0124] (Example 6, Example 7) In the epitaxial growth of nitrogen-doped single-crystal diamond, the nitrogen gas used in the mixed gas was changed to 5.0 × 10⁻⁶ compared to Example 2. -5 Volume % (Example 6) or 8.000 volume % (Example 7), and adjust the volume of hydrogen accordingly. The others were fabricated in the same manner as in Example 2 to obtain a stacked diamond substrate consisting of a nitrogen-doped single-crystal diamond layer and an undoped single-crystal diamond (111) substrate. The nitrogen-doped single-crystal diamonds were not polycrystalline, and the various measurement results were the same as those of other examples, with NVC density also being superior to that of the comparative examples.

[0125] This manual contains the following solutions. [1]: A method for manufacturing a diamond substrate, wherein a diamond substrate is manufactured by forming diamond crystals on a substrate using any of the chemical vapor deposition (CVD) methods and a feed gas containing hydrocarbon gas and hydrogen as a dilution gas, wherein... In order to form a diamond crystal layer having nitrogen vacancy centers in at least a portion of the diamond crystal formed on the substrate, nitrogen 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 to form the diamond crystal layer having nitrogen vacancy centers: The amount of hydrocarbon gas is 0.005% by volume or more and 7.000% by volume or less; The amount of hydrogen is greater than 85,000% by volume and less than 99.995% by volume; The amount of nitrogen or nitride gas is 5.0 × 10⁻⁶. -5 Volume percentage above 8.000% and below 8.000% And will 12 C-concentrated hydrocarbon gas is used as the hydrocarbon gas in the feed gas. 12 C Concentrated hydrocarbon gas contains carbon isotopes 12 The proportion of hydrocarbon gases composed of carbon is higher than that of natural hydrocarbon gases composed of carbon isotopes. 12 The ratio of hydrocarbon gases composed of carbon. [2]: The diamond substrate manufacturing method described in [1] above, wherein the raw material gas further contains an amount of oxygen or oxide gas of 0.010% by volume or more and 2.000% by volume or less. [3]: The method for manufacturing a diamond substrate according to [1] or [2] above, wherein the hydrocarbon gas in the raw material gas is methane gas. [4]: The method for manufacturing a diamond substrate according to any one of [1] to [3] above, wherein the gas pressure when forming the diamond crystal by CVD is 1.3 kPa (10 Torr) or more and 50.0 kPa (376 Torr) or less. [5]: A method for manufacturing a diamond substrate according to any one of [1] to [4] above, wherein, for the diamond substrate... 12 C-concentrated hydrocarbon gas, this 12 C Concentrated hydrocarbon gas from 12 The volume percentage of hydrocarbon gases composed of C is over 99.950% by volume. [6]: The method for manufacturing a diamond substrate according to any one of [1] to [5] above, wherein, for the 12C concentrated hydrocarbon gas, the 12 C Concentrated hydrocarbon gas from 13 The volume percentage of hydrocarbon gases composed of C is less than 0.040% by volume. [7]: The method for manufacturing a diamond substrate according to any one of [1] to [6] above, wherein the substrate is a single-layer substrate of single-crystal diamond. [8]: According to the manufacturing method of diamond substrate described in [7] above, the single-layer substrate of the single crystal diamond is any one of high temperature and high pressure synthesized single crystal diamond layer, heteroepitaxial single crystal diamond layer, and CVD synthesized homoepitaxial diamond layer. [9]: The method for manufacturing a diamond substrate according to any one of [1] to [8] above, wherein when forming the diamond crystal by CVD, a natural hydrocarbon gas is used when forming a diamond crystal layer without nitrogen vacancy centers.

[10] : The method for manufacturing a diamond substrate according to any one of [1] to [9] above, wherein the substrate is a laminated structure consisting of a lower substrate and an intermediate layer on the lower substrate.

[11] : According to the diamond substrate manufacturing method described in

[10] above, the outermost surface of the intermediate layer is a metal layer selected from Ir, Rh, Pd and Pt.

[12] : The method for manufacturing a diamond substrate according to any one of [1] to

[11] above, wherein, as the CVD method, one or more of microwave plasma CVD, DC plasma CVD, hot filament CVD and arc discharge plasma jet CVD are used.

[13] : A method for manufacturing a diamond substrate, wherein the substrate is removed from a diamond substrate containing a diamond crystal layer having nitrogen vacancy centers obtained by any one of the diamond substrate manufacturing methods described in [1] to

[12] above, thereby obtaining a single-crystal diamond self-supporting substrate containing the diamond crystal layer having nitrogen vacancy centers.

[14] : A method for manufacturing a diamond substrate, wherein the surface of the diamond crystal layer having nitrogen vacancy centers of the diamond substrate containing the diamond crystal layer having nitrogen vacancy centers obtained by any one of the diamond substrate manufacturing methods of [1] to

[13] above is smoothed.

[15] : A diamond substrate comprising a diamond crystal layer having nitrogen vacancy centers, wherein... The diamond crystal layer with nitrogen vacancy centers is formed on a diamond crystal layer without nitrogen vacancy centers or a single-crystal diamond monolayer substrate. In the carbon atoms present in this diamond crystal layer with nitrogen vacancy centers, carbon isotopes 12 The proportion of C is higher than the proportion of natural carbon atoms. The nitrogen concentration distribution in the diamond crystal layer with nitrogen vacancy centers is steep in the interface region with the diamond crystal layer without nitrogen vacancy centers or the monolayer substrate of single-crystal diamond.

[16] : According to the diamond substrate described in

[15] above, wherein, by means of a secondary ion mass spectrometry analysis device, Cs + When determining the nitrogen concentration distribution in the diamond crystal layer with nitrogen vacancy centers using a primary ion type, a primary accelerating voltage of 16.0 kV, and a detection area diameter of 30 μm, the thickness of the region where the nitrogen concentration [N] decreases to a multiple of 1 / e (Napier constant) at the interface with the diamond crystal layer without nitrogen vacancy centers or the monolayer substrate of single-crystal diamond is less than 1.5 μm.

[17] : According to the diamond substrate described in

[16] above, the hydrogen concentration [H] in the diamond crystal layer having nitrogen vacancy centers is 1 × 10⁻⁶. 16 atoms / cm 3 above.

[18] : The diamond substrate according to any one of

[15] to

[17] above, wherein the nitrogen concentration [N] in the diamond crystal layer having nitrogen vacancy centers is 1 × 10⁻⁶. 17 atoms / cm 3 ≤[N]≤9×10 19 atoms / cm 3 .

[19] : The diamond substrate according to any one of

[15] to

[18] above, wherein the average surface roughness Ra of the surface of the diamond crystal layer having nitrogen vacancy centers is Ra≤260nm.

[20] : A sensor that uses a diamond substrate of any one of

[15] to

[19] above.

[0126] Furthermore, this invention is not limited to the above-described embodiments. The above embodiments are merely illustrative, and any technical solutions having substantially the same structure and achieving the same technical effect as those described in the claims of this invention are covered within the technical scope of this invention.

Claims

1. A method for manufacturing a diamond substrate, comprising forming diamond crystals on a substrate by chemical vapor deposition (CVD) using a feed gas containing hydrocarbon gas and hydrogen as a dilution gas, characterized in that... In order to form a diamond crystal layer having nitrogen vacancy centers in at least a portion of the diamond crystal formed on the substrate, nitrogen 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 to form the diamond crystal layer having nitrogen vacancy centers: The amount of hydrocarbon gas is 0.005% by volume or more and 7.000% by volume or less; The amount of hydrogen is greater than 85,000% by volume and less than 99.995% by volume; The amount of nitrogen or nitride gas is 5.0 × 10⁻⁶. -5 Volume percentage above 8.000% and below 8.000% And will 12 C-concentrated hydrocarbon gas is used as the hydrocarbon gas in the feed gas. 12 C Concentrated hydrocarbon gas contains carbon isotopes 12 The proportion of hydrocarbon gases composed of carbon is higher than that of natural hydrocarbon gases composed of carbon isotopes. 12 The ratio of hydrocarbon gases composed of carbon.

2. The method for manufacturing a diamond substrate according to claim 1, characterized in that, The raw material gas further contains an amount of oxygen or oxide gas of 0.010% by volume or more and 2.000% by volume or less.

3. The method for manufacturing a diamond substrate according to claim 1 or 2, characterized in that, The hydrocarbon gas in the raw material gas is methane gas.

4. The method for manufacturing a diamond substrate according to claim 1 or 2, characterized in that, The gas pressure during the formation of the diamond crystal by CVD is above 1.3 kPa (10 Torr) and below 50.0 kPa (376 Torr).

5. The method for manufacturing a diamond substrate according to claim 1 or 2, characterized in that, For the above 12 C-concentrated hydrocarbon gas, this 12 C Concentrated hydrocarbon gas contains 12 The volume percentage of hydrocarbon gases composed of C is over 99.950% by volume.

6. The method for manufacturing a diamond substrate according to claim 1 or 2, characterized in that, For the above 12 C-concentrated hydrocarbon gas, this 12 C Concentrated hydrocarbon gas contains 13 The volume percentage of hydrocarbon gases composed of C is less than 0.040% by volume.

7. The method for manufacturing a diamond substrate according to claim 1 or 2, characterized in that, The substrate is a single-layer substrate of single-crystal diamond.

8. The method for manufacturing a diamond substrate according to claim 7, characterized in that, The single-layer substrate of the single-crystal diamond is any one of the following: high-temperature and high-pressure synthesized single-crystal diamond layer, heteroepitaxial single-crystal diamond layer, and CVD synthesized homoepitaxial diamond layer.

9. The method for manufacturing a diamond substrate according to claim 1 or 2, characterized in that, When forming the diamond crystal by CVD, natural hydrocarbon gas is used to form a diamond crystal layer that does not contain nitrogen vacancy centers.

10. The method for manufacturing a diamond substrate according to claim 1 or 2, characterized in that, The substrate is a laminated structure consisting of a lower substrate and an intermediate layer on the lower substrate.

11. The method for manufacturing a diamond substrate according to claim 10, characterized in that, The outermost surface of the intermediate layer is a metal layer selected from Ir, Rh, Pd and Pt.

12. The method for manufacturing a diamond substrate according to claim 1 or 2, characterized in that, As the CVD method, any one or more of the following methods are used: microwave plasma CVD, direct current plasma CVD, hot filament CVD, and arc discharge plasma jet CVD.

13. A method for manufacturing a diamond substrate, characterized in that, The substrate is removed from a diamond substrate containing a diamond crystal layer with nitrogen vacancy centers obtained by the manufacturing method of the diamond substrate according to claim 1 or 2, to obtain a single-crystal diamond self-supporting substrate containing the diamond crystal layer with nitrogen vacancy centers.

14. A method for manufacturing a diamond substrate, wherein the surface of the diamond crystal layer having nitrogen vacancy centers of the diamond substrate comprising the diamond crystal layer having nitrogen vacancy centers obtained by the method for manufacturing a diamond substrate according to claim 1 or 2 is smoothed.

15. A diamond substrate comprising a diamond crystal layer having nitrogen vacancy centers, characterized in that, The diamond crystal layer with nitrogen vacancy centers is formed on a diamond crystal layer without nitrogen vacancy centers or a single-crystal diamond monolayer substrate. In the carbon atoms present in the diamond crystal layer with nitrogen vacancy centers, carbon isotopes 12 The proportion of C is higher than the proportion of natural carbon atoms. The nitrogen concentration distribution in the diamond crystal layer with nitrogen vacancy centers is steep at the interface region with the diamond crystal layer without nitrogen vacancy centers or the monolayer substrate of single-crystal diamond.

16. The diamond substrate according to claim 15, characterized in that, Using a secondary ion mass spectrometry analysis device, Cs + When determining the nitrogen concentration distribution in the diamond crystal layer with nitrogen vacancy centers using a primary ion type, a primary accelerating voltage of 16.0 kV, and a detection area diameter of 30 μm, the thickness of the region where the nitrogen concentration [N] decreases to a multiple of 1 / e (Napier constant) at the interface with the diamond crystal layer without nitrogen vacancy centers or the monolayer substrate of single-crystal diamond is less than 1.5 μm.

17. The diamond substrate according to claim 16, characterized in that, The hydrogen concentration [H] in the diamond crystal layer with nitrogen vacancy centers is 1 × 10⁻⁶. 16 atoms / cm 3 above.

18. The diamond substrate according to any one of claims 15 to 17, characterized in that, The nitrogen concentration [N] in the diamond crystal layer with nitrogen vacancy centers is 1 × 10⁻⁶. 17 atoms / cm 3 ≤[N]≤9×10 19 atoms / cm 3 .

19. The diamond substrate according to any one of claims 15 to 17, characterized in that, The average surface roughness Ra of the diamond crystal layer with nitrogen vacancy centers is Ra≤260nm.

20. A sensor that uses a diamond substrate according to any one of claims 15 to 17.

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