JP2013028497A - Polycrystalline diamond and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide polycrystalline nanodiamond utilizable to magnetic sensing, and to provide a production method thereof.SOLUTION: This polycrystalline nanodiamond 1 is composed of carbon with ≥99.9 mass% purity ofC carbon isotope, and a plurality of impurities other than carbon, where the concentration of the plurality of impurities is each 0.01 mass% or less, and the crystal grain diameter is 500 nm or less. This polycrystalline nanodiamond 1 has ≥99.9 mass% purity ofC carbon isotope, and can be produced by pyrolyzing hydrocarbon gas with ≥99 mass% chemical purity to obtain graphite, and applying heat treatment to the obtained graphite in a high temperature, high pressure press machine to convert the graphite into diamond.

Description

  The present invention relates to polycrystalline diamond and a method for producing the same, and more particularly to polycrystalline diamond having nano-sized crystal grains (hereinafter referred to as “nanopolycrystalline diamond”) and a method for producing the same. .

  It is known that magnetic sensing can be performed by using an NV (Nitrogen-Vacancy) center inside a diamond. For example, J. et al. R. Maze et al. , “Nanoscale magnetic sensing with an individual electrical spin in diamond”, Nature vol. 455, p. 644-647 (2008) reports on magnetic sensing using individual electron spins in diamond.

J. et al. R. Maze et al. , “Nanoscale magnetic sensing with an individual electrical spin in diamond”, Nature vol. 455, p. 644-647 (2008)

  However, the presence of many impurities in the diamond adversely affects the fluorescence intensity of the NV center and also widens the resonance line width that determines the sensitivity, resulting in a decrease in the accuracy of magnetic sensing. There is concern about making it happen.

  By the way, in the conventional synthesis process of polycrystalline diamond, many impurities such as hydrogen, nitrogen, silicon and boron are mixed in the diamond. For example, nano-polycrystalline diamond can be produced by directly converting graphite into diamond, but since commercially available graphite is produced from coke and pitch, it is difficult to avoid the incorporation of impurities into the graphite. . Therefore, impurities are also taken into the polycrystalline diamond synthesized by the method. Moreover, even if the graphite is highly purified, it is difficult to remove impurities mixed in during the production of graphite with the current technology. The impurities that could not be removed segregate at the grain boundaries of the synthesized diamond crystal.

  Thus, since polycrystalline diamond contains many impurities, it has been considered difficult to produce a substrate suitable for magnetic sensing using polycrystalline diamond. In particular, nano-polycrystalline diamond having small nano-sized crystal grains has been considered to be highly difficult.

  Then, an object of this invention is to provide the nano polycrystalline diamond which can be utilized for magnetic sensing, and its manufacturing method.

The polycrystalline diamond according to the present invention is substantially composed of a specific carbon isotope, and is a diamond that can be used for magnetic sensing while being polycrystalline. Specifically, the polycrystalline diamond is composed of carbon having a carbon isotope ¹² C purity of 99.9% by mass or more and a plurality of impurities other than carbon. The concentration of the plurality of impurities is 0.01% by mass or less, and the crystal grain size (maximum length) is 500 nm or less.

The polycrystalline diamond has a small crystal grain size, includes a high purity carbon isotope ¹² C, and has an extremely low impurity concentration throughout. The polycrystalline diamond of the present invention shows no segregation of impurities as in the prior art, and the impurity concentration in any part is extremely low. Therefore, the impurity concentration at the crystal grain boundary is also about 0.01% by mass or less. Thus, since the impurity concentration is extremely low and the crystal grain size is small, the Knoop hardness of the polycrystalline diamond is also high. For example, the Knoop hardness is 150 GPa or more.

Examples of the plurality of impurities include hydrogen, oxygen, nitrogen, silicon, and boron. The concentration of hydrogen in the polycrystalline diamond is, for example, about 2 × 10 ¹⁸ / cm ³ or less, the concentration of oxygen is, for example, about 2 × 10 ¹⁷ / cm ³ or less, and the concentration of nitrogen is, for example, 4 × 10 10 ¹⁶ / cm ³ on the order or less, the concentration of silicon is for example, about 1 × ^{10 16} / cm ³ or less, the concentration of boron is, for example, about 2 × ^{10 15} / cm ³ or less.

The polycrystalline diamond is produced by sintering graphite (graphite) obtained by pyrolyzing a hydrocarbon having a carbon isotope ¹² C purity of 99.9% by mass or more at a temperature of 1500 ° C. or higher. Is possible.

The method for producing polycrystalline diamond according to the present invention comprises a graphite obtained by pyrolyzing a hydrocarbon gas having a carbon isotope ¹² C purity of 99.9% by mass or more and a chemical purity of 99% by mass or more. A step of preparing, and a step of heat-treating the graphite in a high-temperature and high-pressure press to convert the graphite into diamond.

In the step of converting the graphite into diamond, it is preferable to heat-treat the graphite under high pressure without adding a sintering aid or a catalyst. The step of preparing the graphite may include a step of thermally decomposing the hydrocarbon gas introduced into the vacuum chamber at a temperature of preferably 1500 ° C. or higher to form graphite on the substrate. . In the step of converting graphite to diamond, the graphite formed on the substrate may be subjected to a heat treatment at 1500 ° C. or higher under a high pressure of 7 GPa or higher. The bulk density in the graphite is preferably 1.4 g / cm ³ or more.

In the polycrystalline diamond of the present invention, the concentration of carbon isotope ¹² C in carbon is as high as 99.9% by mass or more, and the concentration of each impurity in diamond is 0.01% by mass or less. Since it is extremely low in comparison, magnetic sensing using the NV center can be performed.

In the method for producing polycrystalline diamond according to the present invention, a carbon isotope is obtained by thermally decomposing a hydrocarbon gas having a carbon isotope ¹² C purity of 99.9% by mass or more and a chemical purity of 99% by mass or more. ^A graphite (solid carbon) having a purity of ¹² C of 99.9% by mass or more and a chemical purity of 99% by mass or more is prepared, and the graphite is subjected to heat treatment to be converted into diamond. Polycrystalline diamond containing the body ¹² C and having a very low impurity concentration can be produced. That is, a polycrystalline diamond capable of magnetic sensing using the NV center can be produced.

It is a perspective view which shows a mode that the nano polycrystal diamond in one embodiment of this invention is produced from the graphite formed on the base material.

Hereinafter, an embodiment of the present invention will be described with reference to FIG.
The nano-polycrystalline diamond in the present embodiment is substantially composed of the carbon isotope ¹² C and has an extremely small amount of impurities. Here, “impurities” in this specification refer to elements other than carbon. Typically, nanopolycrystalline diamond contains a plurality of inevitable impurities. In nanopolycrystalline diamond in the present embodiment, the concentration of each impurity is 0.01% by mass or less.

As shown in FIG. 1, nanopolycrystalline diamond 1 of the present embodiment is formed on a substrate 2. The nano-polycrystalline diamond 1 can be produced by subjecting graphite (graphite) 10 formed on the base material 2 and substantially composed of high-purity carbon isotope ¹² C to heat treatment.

  In the nano-polycrystalline diamond 1 of the present embodiment, the impurity concentration is extremely low as a whole, no conventional segregation of impurities is observed, and the impurity concentration in any part is extremely low. For this reason, the concentration of impurities at the crystal grain boundaries of nano-polycrystalline diamond is also about 0.01% by mass or less.

  Thus, in the nano-polycrystalline diamond 1 of the present embodiment, the concentration of each impurity in the diamond is extremely low at 0.01% by mass or less, so that the impurities are the fluorescence intensity of the NV center inside the diamond, It is possible to effectively suppress adverse effects on the resonance line width that determines the sensitivity. As a result, magnetic sensing using the NV center can be performed by the nanopolycrystalline diamond of the present embodiment.

Further, the carbon isotope ¹² C is concentrated to be highly purified to 99.9 mass% or more (when the carbon isotope ¹³ C is contained, the concentration of the carbon isotope ¹³ C is 0.1 mass% or less). Thus, unnecessary nuclear spins and electron spins can be effectively suppressed. Furthermore, in the diamond crystal composed of the mixed state of the carbon isotope ¹² C and the carbon isotope ¹³ C, the influence of the nuclear spin is further improved by setting the concentration of the carbon isotope ¹³ C to 0.1 mass% or less. It can be effectively reduced.

  The distance between adjacent spins is preferably about several tens of nm or more. Further, it is desirable that the electron spin having a spin magnetic moment 1000 times the nuclear spin is 1/1000, that is, 0.001% or less.

  The magnetic measurement may use the fluorescence of the NV center and the change in fluorescence due to the magnetic response. For example, magnetic measurement is performed by utilizing the fact that 638 nm or 1042 nm light emission generated by absorbing light having a wavelength of 400 to 550 nm shows intensity change with respect to an external magnetic field under specific microwave irradiation conditions. be able to.

When the nanopolycrystalline diamond of the present embodiment contains, for example, hydrogen, oxygen, nitrogen, silicon, and boron as impurities, the concentration of hydrogen in the nanopolycrystalline diamond is about 2 × 10 ¹⁸ / cm ³ or less. The concentration of oxygen is about 2 × 10 ¹⁷ / cm ³ or less, the concentration of nitrogen is about 4 × 10 ¹⁶ / cm ³ or less, the concentration of silicon is about 1 × 10 ¹⁶ / cm ³ or less, boron The concentration of is about 2 × 10 ¹⁵ / cm ³ or less. Preferably, the hydrogen concentration in the nano-polycrystalline diamond is about 5 × 10 ¹⁷ / cm ³ or less, the oxygen concentration is about 1 × 10 ¹⁷ / cm ³ or less, and the nitrogen concentration is 1 × 10 ¹⁶ / cm ³ or less. cm ³ on the order less, the concentration of silicon is on the order 5 × ^{10 15} / cm ³ or less, the concentration of boron is much 7 × ^{10 14} / cm ³ or less.

  In the nano-polycrystalline diamond of the present embodiment, as described above, the impurity concentration at the crystal grain boundary is also extremely low, so that the slip of the crystal grain at the crystal grain boundary can be suppressed. As a result, the bonding between crystal grains can be strengthened as compared with polycrystalline diamond produced by a conventional CVD method.

  Further, the nanopolycrystalline diamond of the present embodiment has a small anisotropy compared to other diamonds such as single crystal diamond. Therefore, it can be used in various shapes. For example, it can be needle-shaped so that it can be directly inserted into the inspection object. In this case, it becomes possible to inspect hard materials. Further, the nano-polycrystalline diamond of the present embodiment can be formed into a thin plate shape, and a sample can be placed thereon for inspection. Even in this case, since nano-polycrystalline diamond is difficult to break because cleaving is unlikely to occur, it is possible to observe the magnetic response of substances and cells under pressure.

  In addition, the high purity of carbon isotopes not only makes it more difficult for crystals to slip at the grain boundaries of nano-polycrystalline diamond, but also reduces carbon isotope heterogeneity due to enrichment of carbon isotopes. Can also be eliminated. For this reason, all the crystal grains in nano-polycrystalline diamond are combined like a single crystal, and even at the crystal grain boundary, the molecule is in a state closer to a single crystal than the crystal grain boundary of normal diamond polycrystal. They can be joined together. By these synergistic effects, the Knoop hardness of the nano-polycrystalline diamond of this embodiment can be increased to about 150 GPa or more. In addition, it has less thermal wear due to higher thermal conductivity and less isotope heterogeneity compared to those with high purity. An additional effect was obtained that the wear resistance in the range of 800 ° C. was about three times higher than that of the enriched isotope.

  In addition to the above, abnormal growth of crystal grains during the synthesis of diamond can be effectively suppressed, and variation in crystal grain size can also be reduced. Specifically, the crystal grain size (maximum length) of the nanopolycrystalline diamond of the present embodiment is 500 nm or less. More specifically, the crystal grain size (maximum length) of nano-polycrystalline diamond is about 10 to 100 nm.

  Next, graphite that can be used when producing the nano-polycrystalline diamond of the present embodiment will be described.

  The graphite is an integral solid carbon and includes a crystallized portion. In the example of FIG. 1, the polycrystalline diamond 1 and the graphite 10 have a flat plate shape, but can have any shape and thickness. In addition, components such as impurity concentration in the graphite 10 are basically inherited by the nano-polycrystalline diamond 1.

  The crystal grain size (maximum length of crystal grains) in the crystallized portion of graphite is not particularly limited. Regardless of whether it is polycrystalline or single crystal, the concentration of impurities and isotopes in this embodiment is essential, and the crystal grains of polycrystalline diamond are caused by non-martensitic transformation of graphite. Can be nano-sized. At this time, a small amount of impurities has a good effect of preventing excessive growth of crystal grains, and a particle size of 100 nm or less can be easily obtained.

The bulk density of graphite may be, for example, 0.8 g / cm ³ or more. Preferably, the bulk density of graphite is 1.4 g / cm ³ or more. By setting the density to such a level, volume change due to compression during the high-temperature and high-pressure process can be suppressed to be small, and not only temperature control is facilitated, but also the yield can be improved.

  Examples of impurities mixed in graphite include nitrogen, hydrogen, oxygen, boron, silicon, and transition metals that promote the growth of crystal grains. As described above, nitrogen has a large amount of precipitation at the crystal grain boundary, and the concentration at the crystal grain boundary usually reaches several hundred ppm in the conventional example. This makes the crystal grains slip easily at the crystal grain boundaries. Hydrogen is stabilized by sp2 bonds at the grain boundaries, and as a result, the hardness of graphite is lowered. In a diamond sintered body produced using conventional graphite, since the raw material of graphite is coke or pitch as described above, hydrogen of an amount of about several hundred ppm is always used despite high purification treatment. Is mixed into graphite. Oxygen easily reacts with carbon and forms an oxide with boron to promote local crystal grain growth. Nitrogen and boron also cause slipping of crystal grains at the crystal grain boundary, which is an obstacle to increasing the hardness to an essential limit hardness.

  In the graphite used for producing the nano-polycrystalline diamond of the present embodiment, the amount of impurities such as nitrogen, hydrogen, oxygen, boron, silicon, and transition metal is 0.01% by mass or less. That is, the impurity concentration in the graphite is about the detection limit or less in SIMS (Secondary Ion Mass Spectrometry) analysis. Moreover, about the transition metal, the density | concentration in graphite is below the detection limit in ICP (Inductively Coupled Plasma) analysis or SIMS analysis.

  In this way, by reducing the amount of impurities in graphite to a detection limit level in SIMS analysis or ICP analysis, when diamond is produced using the graphite, extremely high purity and high hardness diamond is produced. be able to. Even when graphite containing impurities slightly higher than the detection limit in SIMS analysis or ICP analysis is used, a diamond having a remarkably superior characteristic can be obtained as compared with the conventional case.

Next, a method for producing nano-polycrystalline diamond in the present embodiment will be described.
Nano polycrystalline diamond according to the present embodiment, the purity of the carbon isotope ^{12 C} is not less than 99.9% by weight (if it contains carbon isotope ^{13 C} is 0 the concentration of carbon isotope ^{13 C.} 1% by mass or less) and graphite obtained by pyrolyzing a hydrocarbon gas having a chemical purity of 99% by mass or more can be produced by subjecting it to heat treatment in a high-temperature and high-pressure press to convert it into diamond. In other words, the nano-polycrystalline diamond according to the present embodiment can be manufactured by subjecting solid-phase carbon that is substantially composed of the high-purity carbon isotope ¹² C and has a very low impurity concentration to heat treatment in a vacuum atmosphere. it can.

  The graphite may be produced in a vacuum chamber before the nano-polycrystalline diamond is produced, or graphite previously formed on a substrate or the like may be separately prepared and stored.

The graphite is introduced into a vacuum chamber, and a hydrocarbon gas having a carbon isotope ¹² C purity of 99.9% by mass or more and a chemical purity of 99% by mass or more is heated to a temperature of about 1500 ° C. to 3000 ° C. And can be formed on a substrate by pyrolysis. At this time, the degree of vacuum in the vacuum chamber may be about 20 to 100 Torr. As a result, solid-state graphite that is an integral crystalline or polycrystalline structure can be formed directly from the gas phase hydrocarbons on the substrate. In addition, graphite with an extremely small amount of impurities can be produced on a substrate. Note that methane gas is preferably used as the hydrocarbon gas.

  When producing graphite on a base material, the base material installed in the vacuum chamber is heated to a temperature of 1500 ° C. or higher. A well-known method can be adopted as the heating method. For example, it is conceivable to install a heater in the vacuum chamber that can directly or indirectly heat the substrate to a temperature of 1500 ° C. or higher.

  As a base material for producing graphite, any solid phase material may be used as long as it can withstand a temperature of about 1500 ° C. to 3000 ° C. Specifically, a metal, an inorganic ceramic material, or a carbon material can be used as a base material. From the viewpoint of suppressing impurities from being mixed into graphite, it is preferable that the substrate is made of carbon. Examples of the solid-state carbon material include diamond and graphite. When using graphite as a base material, it is conceivable to use graphite with an extremely small amount of impurities prepared by the above-mentioned method as a base material. When a carbon material such as diamond or graphite is used as the material for the base material, at least the surface of the base material may be composed of the carbon material. For example, only the surface of the substrate may be composed of a carbon material, the remaining portion of the substrate may be composed of a material other than the carbon material, and the entire substrate may be composed of a carbon material.

  In the step of converting the graphite into diamond, it is preferable to heat-treat the graphite in a high-temperature and high-pressure press without adding a sintering aid or a catalyst. As diamond synthesis conditions, the temperature may be about 1200 ° C. to 2500 ° C., and the pressure may be about 7 GPa to 25 GPa. Preferably, the synthesis temperature is 1900 ° C. or higher and the synthesis pressure is 12 GPa or higher.

  For synthesis of diamond, uniaxial pressure may be applied or isotropic pressure may be applied. However, synthesis under hydrostatic pressure is preferred from the viewpoint of aligning the crystal grain size and the degree of crystal anisotropy with isotropic pressure.

  Next, examples of the present invention will be described.

In a vacuum chamber, a diamond substrate heated to 1900 ° C. through a porous titanium heated to 600 ° C. with methane gas having a carbon isotope ¹² C purity of 99.9% by mass and a chemical purity of 99% by mass Sprayed on top. At this time, the degree of vacuum in the vacuum chamber was set to 20 to 30 Torr. Then, graphite (graphite) was deposited on the diamond substrate. The bulk density of graphite was 2.0 g / cm ³ .

  The above graphite was directly converted to polycrystalline diamond under conditions of a temperature of 2300 ° C. and a pressure of 15 GPa. Each polycrystalline diamond had a crystal grain size of about 10 to 100 nm. According to SIMS analysis, the content of nitrogen, hydrogen, oxygen, boron and silicon in the polycrystalline diamond was below the detection limit. Further, from the X-ray diffraction pattern of the polycrystalline diamond, no components other than diamond were found in the polycrystalline diamond.

The nano-polycrystalline diamond was irradiated with nitrogen at an acceleration energy of 300 keV for about 10 ¹⁰ / cm ² and subjected to a heat treatment at 900 ° C., and then the fluorescence intensity at 637 nm by the NV-center formed by the process was measured. As a result, when a 532 nm laser was irradiated as excitation light under microwave irradiation with a diameter of 0.5 cm, a circular coil with a frequency of 2.87 GHz, 5 turns, and an output of 0.5 W, a maximum of 1% fluorescence was obtained depending on the presence or absence of a magnetic field. A change in intensity was observed. The Knoop hardness of this polycrystalline diamond was 190 GPa.

In a vacuum chamber, a diamond substrate in which methane gas having a carbon isotope ¹² C purity of 99.999 mass% and a chemical purity of 99 mass% is heated to 1900 ° C. through porous titanium heated to 600 ° C. Sprayed on top. At this time, the degree of vacuum in the vacuum chamber was set to 20 to 30 Torr. Then, graphite was deposited on the diamond substrate. The bulk density of graphite was 2.0 g / cm ³ .

  The above graphite was directly converted to polycrystalline diamond under conditions of a temperature of 2300 ° C. and a pressure of 15 GPa. Each polycrystalline diamond had a crystal grain size of about 10 to 100 nm. According to SIMS analysis, the content of nitrogen, hydrogen, oxygen, boron and silicon in the polycrystalline diamond was below the detection limit. Further, from the X-ray diffraction pattern of the polycrystalline diamond, no components other than diamond were found in the polycrystalline diamond.

The nano-polycrystalline diamond was irradiated with nitrogen at an acceleration energy of 300 keV for about 10 ¹⁰ / cm ² and subjected to a heat treatment at 900 ° C., and then the fluorescence intensity at 637 nm by the NV-center formed by the process was measured. As a result, when a 532 nm laser was irradiated as excitation light under microwave irradiation with a diameter of 0.5 cm, a circular coil with a frequency of 2.87 GHz, 5 turns, and an output of 0.5 W, a maximum of 3% fluorescence depending on the presence or absence of a magnetic field. A change in intensity was observed. The Knoop hardness of this polycrystalline diamond was 190 GPa.

In a vacuum chamber, a diamond substrate in which methane gas having a carbon isotope ¹² C purity of 99.999 mass% and a chemical purity of 99 mass% is heated to 1900 ° C. through porous titanium heated to 600 ° C. Sprayed on top. At this time, the degree of vacuum in the vacuum chamber was set to 20 to 30 Torr. Then, graphite was deposited on the diamond substrate. The bulk density of graphite was 2.0 g / cm ³ .

  The above graphite was directly converted to polycrystalline diamond under conditions of a temperature of 2400 ° C. and a pressure of 15 GPa. Each polycrystalline diamond had a crystal grain size of about 10 to 100 nm. According to SIMS analysis, the content of nitrogen, hydrogen, oxygen, boron and silicon in the polycrystalline diamond was below the detection limit. Further, from the X-ray diffraction pattern of the polycrystalline diamond, no components other than diamond were found in the polycrystalline diamond.

The nano-polycrystalline diamond was irradiated with nitrogen at an acceleration energy of 300 keV for about 10 ¹⁰ / cm ² and subjected to a heat treatment at 900 ° C., and then the fluorescence intensity at 637 nm by the NV-center formed by the process was measured. As a result, when a 532 nm laser was irradiated as excitation light under microwave irradiation with a diameter of 0.5 cm, a circular coil with a frequency of 2.87 GHz, 5 turns, and an output of 0.5 W, a maximum of 3% fluorescence depending on the presence or absence of a magnetic field. A change in intensity was observed. The Knoop hardness of this polycrystalline diamond was 190 GPa.

In a vacuum chamber, a diamond substrate in which methane gas having a carbon isotope ¹² C purity of 99.999 mass% and a chemical purity of 99 mass% is heated to 1900 ° C. through porous titanium heated to 600 ° C. Sprayed on top. At this time, the degree of vacuum in the vacuum chamber was set to 20 to 30 Torr. Then, graphite was deposited on the diamond substrate. The bulk density of graphite was 2.0 g / cm ³ .

  The above graphite was directly converted to polycrystalline diamond under the conditions of a temperature of 2500 ° C. and a pressure of 15 GPa. Each polycrystalline diamond had a crystal grain size of about 10 to 100 nm. According to SIMS analysis, the content of nitrogen, hydrogen, oxygen, boron and silicon in the polycrystalline diamond was below the detection limit. Further, from the X-ray diffraction pattern of the polycrystalline diamond, no components other than diamond were found in the polycrystalline diamond.

The nano-polycrystalline diamond was irradiated with nitrogen at an acceleration energy of 300 keV for about 10 ¹⁰ / cm ² and subjected to a heat treatment at 900 ° C., and then the fluorescence intensity at 637 nm by the NV-center formed by the process was measured. As a result, when a 532 nm laser was irradiated as excitation light under microwave irradiation with a diameter of 0.5 cm, a circular coil with a frequency of 2.87 GHz, 5 turns, and an output of 0.5 W, a maximum of 3% fluorescence depending on the presence or absence of a magnetic field. A change in intensity was observed. The Knoop hardness of this polycrystalline diamond was 190 GPa.

In a vacuum chamber, a diamond substrate in which methane gas having a carbon isotope ¹² C purity of 99.999 mass% and a chemical purity of 99 mass% is heated to 1900 ° C. through porous titanium heated to 600 ° C. Sprayed on top. At this time, the degree of vacuum in the vacuum chamber was set to 20 to 30 Torr. Then, graphite was deposited on the diamond substrate. The bulk density of graphite was 2.0 g / cm ³ .

  The above graphite was directly converted to polycrystalline diamond under the conditions of a temperature of 2000 ° C. and a pressure of 16 GPa. Each polycrystalline diamond had a crystal grain size of about 10 to 100 nm. According to SIMS analysis, the content of nitrogen, hydrogen, oxygen, boron and silicon in the polycrystalline diamond was below the detection limit. Further, from the X-ray diffraction pattern of the polycrystalline diamond, no components other than diamond were found in the polycrystalline diamond.

The nano-polycrystalline diamond was irradiated with nitrogen at an acceleration energy of 300 keV for about 10 ¹⁰ / cm ² and subjected to a heat treatment at 900 ° C., and then the fluorescence intensity at 637 nm by the NV-center formed by the process was measured. As a result, when a 532 nm laser was irradiated as excitation light under microwave irradiation with a diameter of 0.5 cm, a circular coil with a frequency of 2.87 GHz, 5 turns, and an output of 0.5 W, a maximum of 3% fluorescence depending on the presence or absence of a magnetic field. A change in intensity was observed. The Knoop hardness of this polycrystalline diamond was 190 GPa.

In a vacuum chamber, a diamond substrate in which methane gas having a carbon isotope ¹² C purity of 99.999 mass% and a chemical purity of 99 mass% is heated to 1900 ° C. through porous titanium heated to 600 ° C. Sprayed on top. At this time, the degree of vacuum in the vacuum chamber was set to 20 to 30 Torr. Then, graphite was deposited on the diamond substrate. The bulk density of graphite was 2.0 g / cm ³ .

  The above graphite was directly converted to polycrystalline diamond under the conditions of a temperature of 2100 ° C. and a pressure of 16 GPa. Each polycrystalline diamond had a crystal grain size of about 10 to 100 nm. According to SIMS analysis, the content of nitrogen, hydrogen, oxygen, boron and silicon in the polycrystalline diamond was below the detection limit. Further, from the X-ray diffraction pattern of the polycrystalline diamond, no components other than diamond were found in the polycrystalline diamond.

The nano-polycrystalline diamond was irradiated with nitrogen at an acceleration energy of 300 keV for about 10 ¹⁰ / cm ² and subjected to a heat treatment at 900 ° C., and then the fluorescence intensity at 637 nm by the NV-center formed by the process was measured. As a result, when a 532 nm laser was irradiated as excitation light under microwave irradiation with a diameter of 0.5 cm, a circular coil with a frequency of 2.87 GHz, 5 turns, and an output of 0.5 W, a maximum of 3% fluorescence depending on the presence or absence of a magnetic field. A change in intensity was observed. The Knoop hardness of this polycrystalline diamond was 190 GPa.

In a vacuum chamber, a diamond substrate in which methane gas having a carbon isotope ¹² C purity of 99.999 mass% and a chemical purity of 99 mass% is heated to 1900 ° C. through porous titanium heated to 600 ° C. Sprayed on top. At this time, the degree of vacuum in the vacuum chamber was set to 20 to 30 Torr. Then, graphite was deposited on the diamond substrate. The bulk density of graphite was 2.0 g / cm ³ .

  The above graphite was directly converted to polycrystalline diamond under conditions of a temperature of 2200 ° C. and a pressure of 16 GPa. Each polycrystalline diamond had a crystal grain size of about 10 to 100 nm. According to SIMS analysis, the content of nitrogen, hydrogen, oxygen, boron and silicon in the polycrystalline diamond was below the detection limit. Further, from the X-ray diffraction pattern of the polycrystalline diamond, no components other than diamond were found in the polycrystalline diamond.

The nano-polycrystalline diamond was irradiated with nitrogen at an acceleration energy of 300 keV for about 10 ¹⁰ / cm ² and subjected to a heat treatment at 900 ° C., and then the fluorescence intensity at 637 nm by the NV-center formed by the process was measured. As a result, when a 532 nm laser was irradiated as excitation light under microwave irradiation with a diameter of 0.5 cm, a circular coil with a frequency of 2.87 GHz, 5 turns, and an output of 0.5 W, a maximum of 3% fluorescence depending on the presence or absence of a magnetic field. A change in intensity was observed. The Knoop hardness of this polycrystalline diamond was 190 GPa.

In a vacuum chamber, a diamond substrate in which methane gas having a carbon isotope ¹² C purity of 99.999 mass% and a chemical purity of 99 mass% is heated to 1500 ° C. through porous titanium heated to 600 ° C. Sprayed on top. At this time, the degree of vacuum in the vacuum chamber was set to 20 to 30 Torr. Then, graphite was deposited on the diamond substrate. The bulk density of graphite was 1.6 g / cm ³ .

  The above graphite was directly converted to polycrystalline diamond under conditions of a temperature of 2200 ° C. and a pressure of 15 GPa. Each polycrystalline diamond had a crystal grain size of about 10 to 100 nm. According to SIMS analysis, the content of nitrogen, hydrogen, oxygen, boron and silicon in the polycrystalline diamond was below the detection limit. Further, from the X-ray diffraction pattern of the polycrystalline diamond, no components other than diamond were found in the polycrystalline diamond.

The nano-polycrystalline diamond was irradiated with nitrogen at an acceleration energy of 300 keV for about 10 ¹⁰ / cm ² and subjected to a heat treatment at 900 ° C., and then the fluorescence intensity at 637 nm by the NV-center formed by the process was measured. As a result, when a 532 nm laser was irradiated as excitation light under microwave irradiation with a diameter of 0.5 cm, a circular coil with a frequency of 2.87 GHz, 5 turns, and an output of 0.5 W, a maximum of 3% fluorescence depending on the presence or absence of a magnetic field. A change in intensity was observed. Further, the Knoop hardness of this polycrystalline diamond was 150 GPa.

In a vacuum chamber, a diamond substrate in which methane gas having a carbon isotope ¹² C purity of 99.999 mass% and a chemical purity of 99 mass% is heated to 1500 ° C. through porous titanium heated to 600 ° C. Sprayed on top. At this time, the degree of vacuum in the vacuum chamber was set to 20 to 30 Torr. Then, graphite was deposited on the diamond substrate. The bulk density of graphite was 1.6 g / cm ³ .

  The above graphite was directly converted to polycrystalline diamond under conditions of a temperature of 2300 ° C. and a pressure of 15 GPa. Each polycrystalline diamond had a crystal grain size of about 10 to 100 nm. According to SIMS analysis, the content of nitrogen, hydrogen, oxygen, boron and silicon in the polycrystalline diamond was below the detection limit. Further, from the X-ray diffraction pattern of the polycrystalline diamond, no components other than diamond were found in the polycrystalline diamond.

The nano-polycrystalline diamond was irradiated with nitrogen at an acceleration energy of 300 keV for about 10 ¹⁰ / cm ² and subjected to a heat treatment at 900 ° C., and then the fluorescence intensity at 637 nm by the NV-center formed by the process was measured. As a result, when a 532 nm laser was irradiated as excitation light under microwave irradiation with a diameter of 0.5 cm, a circular coil with a frequency of 2.87 GHz, 5 turns, and an output of 0.5 W, a maximum of 3% fluorescence depending on the presence or absence of a magnetic field. A change in intensity was observed. Further, the Knoop hardness of this polycrystalline diamond was 150 GPa.

In a vacuum chamber, a diamond substrate in which methane gas having a carbon isotope ¹² C purity of 99.999 mass% and a chemical purity of 99 mass% is heated to 1500 ° C. through porous titanium heated to 600 ° C. Sprayed on top. At this time, the degree of vacuum in the vacuum chamber was set to 20 to 30 Torr. Then, graphite was deposited on the diamond substrate. The bulk density of graphite was 1.6 g / cm ³ .

  The above graphite was directly converted to polycrystalline diamond under conditions of a temperature of 2400 ° C. and a pressure of 15 GPa. Each polycrystalline diamond had a crystal grain size of about 10 to 100 nm. According to SIMS analysis, the content of nitrogen, hydrogen, oxygen, boron and silicon in the polycrystalline diamond was below the detection limit. Further, from the X-ray diffraction pattern of the polycrystalline diamond, no components other than diamond were found in the polycrystalline diamond.

The nano-polycrystalline diamond was irradiated with nitrogen at an acceleration energy of 300 keV for about 10 ¹⁰ / cm ² and subjected to a heat treatment at 900 ° C., and then the fluorescence intensity at 637 nm by the NV-center formed by the process was measured. As a result, when a 532 nm laser was irradiated as excitation light under microwave irradiation with a diameter of 0.5 cm, a circular coil with a frequency of 2.87 GHz, 5 turns, and an output of 0.5 W, a maximum of 3% fluorescence depending on the presence or absence of a magnetic field. A change in intensity was observed. Further, the Knoop hardness of this polycrystalline diamond was 150 GPa.

In a vacuum chamber, a diamond substrate in which methane gas having a carbon isotope ¹² C purity of 99.999 mass% and a chemical purity of 99 mass% is heated to 1500 ° C. through porous titanium heated to 600 ° C. Sprayed on top. At this time, the degree of vacuum in the vacuum chamber was set to 20 to 30 Torr. Then, graphite was deposited on the diamond substrate. The bulk density of graphite was 1.6 g / cm ³ .

  The above graphite was directly converted to polycrystalline diamond under the conditions of a temperature of 2500 ° C. and a pressure of 15 GPa. Each polycrystalline diamond had a crystal grain size of about 10 to 100 nm. According to SIMS analysis, the content of nitrogen, hydrogen, oxygen, boron and silicon in the polycrystalline diamond was below the detection limit. Further, from the X-ray diffraction pattern of the polycrystalline diamond, no components other than diamond were found in the polycrystalline diamond.

The nano-polycrystalline diamond was irradiated with nitrogen at an acceleration energy of 300 keV for about 10 ¹⁰ / cm ² and subjected to a heat treatment at 900 ° C., and then the fluorescence intensity at 637 nm by the NV-center formed by the process was measured. As a result, when a 532 nm laser was irradiated as excitation light under microwave irradiation with a diameter of 0.5 cm, a circular coil with a frequency of 2.87 GHz, 5 turns, and an output of 0.5 W, a maximum of 3% fluorescence depending on the presence or absence of a magnetic field. A change in intensity was observed. Further, the Knoop hardness of this polycrystalline diamond was 150 GPa.

In a vacuum chamber, a diamond substrate in which methane gas having a carbon isotope ¹² C purity of 99.999 mass% and a chemical purity of 99 mass% is heated to 1500 ° C. through porous titanium heated to 600 ° C. Sprayed on top. At this time, the degree of vacuum in the vacuum chamber was set to 20 to 30 Torr. Then, graphite was deposited on the diamond substrate. The bulk density of graphite was 1.6 g / cm ³ .

  The above graphite was directly converted to polycrystalline diamond under the conditions of a temperature of 2000 ° C. and a pressure of 16 GPa. Each polycrystalline diamond had a crystal grain size of about 10 to 100 nm. According to SIMS analysis, the content of nitrogen, hydrogen, oxygen, boron and silicon in the polycrystalline diamond was below the detection limit. Further, from the X-ray diffraction pattern of the polycrystalline diamond, no components other than diamond were found in the polycrystalline diamond.

The nano-polycrystalline diamond was irradiated with nitrogen at an acceleration energy of 300 keV for about 10 ¹⁰ / cm ² and subjected to a heat treatment at 900 ° C., and then the fluorescence intensity at 637 nm by the NV-center formed by the process was measured. As a result, when a 532 nm laser was irradiated as excitation light under microwave irradiation with a diameter of 0.5 cm, a circular coil with a frequency of 2.87 GHz, 5 turns, and an output of 0.5 W, a maximum of 3% fluorescence depending on the presence or absence of a magnetic field. A change in intensity was observed. Further, the Knoop hardness of this polycrystalline diamond was 150 GPa.

In a vacuum chamber, a diamond substrate in which methane gas having a carbon isotope ¹² C purity of 99.999 mass% and a chemical purity of 99 mass% is heated to 1500 ° C. through porous titanium heated to 600 ° C. Sprayed on top. At this time, the degree of vacuum in the vacuum chamber was set to 20 to 30 Torr. Then, graphite was deposited on the diamond substrate. The bulk density of graphite was 1.6 g / cm ³ .

  The above graphite was directly converted to polycrystalline diamond under the conditions of a temperature of 2100 ° C. and a pressure of 16 GPa. Each polycrystalline diamond had a crystal grain size of about 10 to 100 nm. According to SIMS analysis, the content of nitrogen, hydrogen, oxygen, boron and silicon in the polycrystalline diamond was below the detection limit. Further, from the X-ray diffraction pattern of the polycrystalline diamond, no components other than diamond were found in the polycrystalline diamond.

The nano-polycrystalline diamond was irradiated with nitrogen at an acceleration energy of 300 keV for about 10 ¹⁰ / cm ² and subjected to a heat treatment at 900 ° C., and then the fluorescence intensity at 637 nm by the NV-center formed by the process was measured. As a result, when a 532 nm laser was irradiated as excitation light under microwave irradiation with a diameter of 0.5 cm, a circular coil with a frequency of 2.87 GHz, 5 turns, and an output of 0.5 W, a maximum of 3% fluorescence depending on the presence or absence of a magnetic field. A change in intensity was observed. Further, the Knoop hardness of this polycrystalline diamond was 150 GPa.

In a vacuum chamber, a diamond substrate in which methane gas having a carbon isotope ¹² C purity of 99.999 mass% and a chemical purity of 99 mass% is heated to 1500 ° C. through porous titanium heated to 600 ° C. Sprayed on top. At this time, the degree of vacuum in the vacuum chamber was set to 20 to 30 Torr. Then, graphite was deposited on the diamond substrate. The bulk density of graphite was 1.6 g / cm ³ .

  The above graphite was directly converted to polycrystalline diamond under conditions of a temperature of 2200 ° C. and a pressure of 16 GPa. Each polycrystalline diamond had a crystal grain size of about 10 to 100 nm. According to SIMS analysis, the content of nitrogen, hydrogen, oxygen, boron and silicon in the polycrystalline diamond was below the detection limit. Further, from the X-ray diffraction pattern of the polycrystalline diamond, no components other than diamond were found in the polycrystalline diamond.

The nano-polycrystalline diamond was irradiated with nitrogen at an acceleration energy of 300 keV for about 10 ¹⁰ / cm ² and subjected to a heat treatment at 900 ° C., and then the fluorescence intensity at 637 nm by the NV-center formed by the process was measured. As a result, when a 532 nm laser was irradiated as excitation light under microwave irradiation with a diameter of 0.5 cm, a circular coil with a frequency of 2.87 GHz, 5 turns, and an output of 0.5 W, a maximum of 3% fluorescence depending on the presence or absence of a magnetic field. A change in intensity was observed. Further, the Knoop hardness of this polycrystalline diamond was 170 GPa.

In a vacuum chamber, methane gas having a carbon isotope ¹² C purity of 99.999 mass% and a chemical purity of 99.999 mass% was heated to 1900 ° C. through porous titanium heated to 600 ° C. Sprayed onto a diamond substrate. At this time, the degree of vacuum in the vacuum chamber was set to 20 to 30 Torr. Then, graphite was deposited on the diamond substrate. The bulk density of graphite was 2.0 g / cm ³ .

  The above graphite was directly converted to polycrystalline diamond under conditions of a temperature of 2200 ° C. and a pressure of 15 GPa. Each polycrystalline diamond had a crystal grain size of about 10 to 100 nm. According to SIMS analysis, the content of nitrogen, hydrogen, oxygen, boron and silicon in the polycrystalline diamond was below the detection limit. Further, from the X-ray diffraction pattern of the polycrystalline diamond, no components other than diamond were found in the polycrystalline diamond.

The nano-polycrystalline diamond was irradiated with nitrogen at an acceleration energy of 300 keV for about 10 ¹⁰ / cm ² and subjected to a heat treatment at 900 ° C., and then the fluorescence intensity at 637 nm by the NV-center formed by the process was measured. As a result, when a 532 nm laser was irradiated as excitation light under microwave irradiation with a diameter of 0.5 cm, a circular coil with a frequency of 2.87 GHz, 5 turns, and an output of 0.5 W, a maximum of 3% fluorescence depending on the presence or absence of a magnetic field. A change in intensity was observed. The polycrystalline diamond had a Knoop hardness of 205 GPa.

In a vacuum chamber, methane gas having a carbon isotope ¹² C purity of 99.999 mass% and a chemical purity of 99.999 mass% was heated to 1900 ° C. through porous titanium heated to 600 ° C. Sprayed onto a diamond substrate. At this time, the degree of vacuum in the vacuum chamber was set to 20 to 30 Torr. Then, graphite was deposited on the diamond substrate. The bulk density of graphite was 2.0 g / cm ³ .

  The above graphite was directly converted to polycrystalline diamond under conditions of a temperature of 2300 ° C. and a pressure of 15 GPa. Each polycrystalline diamond had a crystal grain size of about 10 to 100 nm. According to SIMS analysis, the content of nitrogen, hydrogen, oxygen, boron and silicon in the polycrystalline diamond was below the detection limit. Further, from the X-ray diffraction pattern of the polycrystalline diamond, no components other than diamond were found in the polycrystalline diamond.

The nano-polycrystalline diamond was irradiated with nitrogen at an acceleration energy of 300 keV for about 10 ¹⁰ / cm ² and subjected to a heat treatment at 900 ° C., and then the fluorescence intensity at 637 nm by the NV-center formed by the process was measured. As a result, when a 532 nm laser was irradiated as excitation light under microwave irradiation with a diameter of 0.5 cm, a circular coil with a frequency of 2.87 GHz, 5 turns, and an output of 0.5 W, a maximum of 3% fluorescence depending on the presence or absence of a magnetic field. A change in intensity was observed. Further, the Knoop hardness of this polycrystalline diamond was 200 GPa.

In a vacuum chamber, methane gas having a carbon isotope ¹² C purity of 99.999 mass% and a chemical purity of 99.999 mass% was heated to 1900 ° C. through porous titanium heated to 600 ° C. Sprayed onto a diamond substrate. At this time, the degree of vacuum in the vacuum chamber was set to 20 to 30 Torr. Then, graphite was deposited on the diamond substrate. The bulk density of graphite was 2.0 g / cm ³ .

  The above graphite was directly converted to polycrystalline diamond under conditions of a temperature of 2400 ° C. and a pressure of 15 GPa. Each polycrystalline diamond had a crystal grain size of about 10 to 100 nm. According to SIMS analysis, the content of nitrogen, hydrogen, oxygen, boron and silicon in the polycrystalline diamond was below the detection limit. Further, from the X-ray diffraction pattern of the polycrystalline diamond, no components other than diamond were found in the polycrystalline diamond.

The nano-polycrystalline diamond was irradiated with nitrogen at an acceleration energy of 300 keV for about 10 ¹⁰ / cm ² and subjected to a heat treatment at 900 ° C., and then the fluorescence intensity at 637 nm by the NV-center formed by the process was measured. As a result, when a 532 nm laser was irradiated as excitation light under microwave irradiation with a diameter of 0.5 cm, a circular coil with a frequency of 2.87 GHz, 5 turns, and an output of 0.5 W, a maximum of 3% fluorescence depending on the presence or absence of a magnetic field. A change in intensity was observed. Further, the Knoop hardness of this polycrystalline diamond was 200 GPa.

In a vacuum chamber, methane gas having a carbon isotope ¹² C purity of 99.999 mass% and a chemical purity of 99.999 mass% was heated to 1900 ° C. through porous titanium heated to 600 ° C. Sprayed onto a diamond substrate. At this time, the degree of vacuum in the vacuum chamber was set to 20 to 30 Torr. Then, graphite was deposited on the diamond substrate. The bulk density of graphite was 2.0 g / cm ³ .

  The above graphite was directly converted to polycrystalline diamond under the conditions of a temperature of 2500 ° C. and a pressure of 15 GPa. Each polycrystalline diamond had a crystal grain size of about 10 to 100 nm. According to SIMS analysis, the content of nitrogen, hydrogen, oxygen, boron and silicon in the polycrystalline diamond was below the detection limit. Further, from the X-ray diffraction pattern of the polycrystalline diamond, no components other than diamond were found in the polycrystalline diamond.

The nano-polycrystalline diamond was irradiated with nitrogen at an acceleration energy of 300 keV for about 10 ¹⁰ / cm ² and subjected to a heat treatment at 900 ° C., and then the fluorescence intensity at 637 nm by the NV-center formed by the process was measured. As a result, when a 532 nm laser was irradiated as excitation light under microwave irradiation with a diameter of 0.5 cm, a circular coil with a frequency of 2.87 GHz, 5 turns, and an output of 0.5 W, a maximum of 3% fluorescence depending on the presence or absence of a magnetic field. A change in intensity was observed. The polycrystalline diamond had a Knoop hardness of 205 GPa.

In a vacuum chamber, methane gas having a carbon isotope ¹² C purity of 99.999 mass% and a chemical purity of 99.999 mass% was heated to 1900 ° C. through porous titanium heated to 600 ° C. Sprayed onto a diamond substrate. At this time, the degree of vacuum in the vacuum chamber was set to 20 to 30 Torr. Then, graphite was deposited on the diamond substrate. The bulk density of graphite was 2.0 g / cm ³ .

  The above graphite was directly converted to polycrystalline diamond under the conditions of a temperature of 2000 ° C. and a pressure of 16 GPa. Each polycrystalline diamond had a crystal grain size of about 10 to 100 nm. According to SIMS analysis, the content of nitrogen, hydrogen, oxygen, boron and silicon in the polycrystalline diamond was below the detection limit. Further, from the X-ray diffraction pattern of the polycrystalline diamond, no components other than diamond were found in the polycrystalline diamond.

The nano-polycrystalline diamond was irradiated with nitrogen at an acceleration energy of 300 keV for about 10 ¹⁰ / cm ² and subjected to a heat treatment at 900 ° C., and then the fluorescence intensity at 637 nm by the NV-center formed by the process was measured. As a result, when a 532 nm laser was irradiated as excitation light under microwave irradiation with a diameter of 0.5 cm, a circular coil with a frequency of 2.87 GHz, 5 turns, and an output of 0.5 W, a maximum of 3% fluorescence depending on the presence or absence of a magnetic field. A change in intensity was observed. The polycrystalline diamond had a Knoop hardness of 205 GPa.

In a vacuum chamber, methane gas having a carbon isotope ¹² C purity of 99.999 mass% and a chemical purity of 99.999 mass% was heated to 1900 ° C. through porous titanium heated to 600 ° C. Sprayed onto a diamond substrate. At this time, the degree of vacuum in the vacuum chamber was set to 20 to 30 Torr. Then, graphite was deposited on the diamond substrate. The bulk density of graphite was 2.0 g / cm ³ .

  The above graphite was directly converted to polycrystalline diamond under the conditions of a temperature of 2100 ° C. and a pressure of 16 GPa. Each polycrystalline diamond had a crystal grain size of about 10 to 100 nm. According to SIMS analysis, the content of nitrogen, hydrogen, oxygen, boron and silicon in the polycrystalline diamond was below the detection limit. Further, from the X-ray diffraction pattern of the polycrystalline diamond, no components other than diamond were found in the polycrystalline diamond.

The nano-polycrystalline diamond was irradiated with nitrogen at an acceleration energy of 300 keV for about 10 ¹⁰ / cm ² and subjected to a heat treatment at 900 ° C., and then the fluorescence intensity at 637 nm by the NV-center formed by the process was measured. As a result, when a 532 nm laser was irradiated as excitation light under microwave irradiation with a diameter of 0.5 cm, a circular coil with a frequency of 2.87 GHz, 5 turns, and an output of 0.5 W, a maximum of 3% fluorescence depending on the presence or absence of a magnetic field. A change in intensity was observed. The Knoop hardness of this polycrystalline diamond was 190 GPa.

In a vacuum chamber, methane gas having a carbon isotope ¹² C purity of 99.999 mass% and a chemical purity of 99.999 mass% was heated to 1900 ° C. through porous titanium heated to 600 ° C. Sprayed onto a diamond substrate. At this time, the degree of vacuum in the vacuum chamber was set to 20 to 30 Torr. Then, graphite was deposited on the diamond substrate. The bulk density of graphite was 2.0 g / cm ³ .

  The above graphite was directly converted to polycrystalline diamond under conditions of a temperature of 2200 ° C. and a pressure of 16 GPa. Each polycrystalline diamond had a crystal grain size of about 10 to 100 nm. According to SIMS analysis, the content of nitrogen, hydrogen, oxygen, boron and silicon in the polycrystalline diamond was below the detection limit. Further, from the X-ray diffraction pattern of the polycrystalline diamond, no components other than diamond were found in the polycrystalline diamond.

The nano-polycrystalline diamond was irradiated with nitrogen at an acceleration energy of 300 keV for about 10 ¹⁰ / cm ² and subjected to a heat treatment at 900 ° C., and then the fluorescence intensity at 637 nm by the NV-center formed by the process was measured. As a result, when a 532 nm laser was irradiated as excitation light under microwave irradiation with a diameter of 0.5 cm, a circular coil with a frequency of 2.87 GHz, 5 turns, and an output of 0.5 W, a maximum of 3% fluorescence depending on the presence or absence of a magnetic field. A change in intensity was observed. The polycrystalline diamond had a Knoop hardness of 198 GPa.

In a vacuum chamber, methane gas having a carbon isotope ¹² C purity of 99.999 mass% and chemical purity of 99.999 mass% was heated to 1500 ° C. through porous titanium heated to 600 ° C. Sprayed onto a diamond substrate. At this time, the degree of vacuum in the vacuum chamber was set to 20 to 30 Torr. Then, graphite was deposited on the diamond substrate. The bulk density of graphite was 1.6 g / cm ³ .

  The above graphite was directly converted to polycrystalline diamond under conditions of a temperature of 2300 ° C. and a pressure of 15 GPa. Each polycrystalline diamond had a crystal grain size of about 10 to 100 nm. According to SIMS analysis, the content of nitrogen, hydrogen, oxygen, boron and silicon in the polycrystalline diamond was below the detection limit. Further, from the X-ray diffraction pattern of the polycrystalline diamond, no components other than diamond were found in the polycrystalline diamond.

The nano-polycrystalline diamond was irradiated with nitrogen at an acceleration energy of 300 keV for about 10 ¹⁰ / cm ² and subjected to a heat treatment at 900 ° C., and then the fluorescence intensity at 637 nm by the NV-center formed by the process was measured. As a result, when a 532 nm laser was irradiated as excitation light under microwave irradiation with a diameter of 0.5 cm, a circular coil with a frequency of 2.87 GHz, 5 turns, and an output of 0.5 W, a maximum of 3% fluorescence depending on the presence or absence of a magnetic field. A change in intensity was observed. Further, the Knoop hardness of this polycrystalline diamond was 160 GPa.

In a vacuum chamber, a diamond substrate in which methane gas having a carbon isotope ¹² C purity of 99.999 mass% and a chemical purity of 99 mass% is heated to 1500 ° C. through porous titanium heated to 600 ° C. Sprayed on top. At this time, the degree of vacuum in the vacuum chamber was set to 20 to 30 Torr. Then, graphite was deposited on the diamond substrate. The bulk density of graphite was 1.6 g / cm ³ .

  The above graphite was directly converted to polycrystalline diamond under conditions of a temperature of 2300 ° C. and a pressure of 15 GPa. Each polycrystalline diamond had a crystal grain size of about 10 to 100 nm. According to SIMS analysis, the content of nitrogen, hydrogen, oxygen, boron and silicon in the polycrystalline diamond was below the detection limit. Further, from the X-ray diffraction pattern of the polycrystalline diamond, no components other than diamond were found in the polycrystalline diamond.

The nano-polycrystalline diamond was irradiated with nitrogen at an acceleration energy of 300 keV for about 10 ¹⁰ / cm ² and subjected to a heat treatment at 900 ° C., and then the fluorescence intensity at 637 nm by the NV-center formed by the process was measured. As a result, when a 532 nm laser was irradiated as excitation light under microwave irradiation with a diameter of 0.5 cm, a circular coil with a frequency of 2.87 GHz, 5 turns, and an output of 0.5 W, a maximum of 3% fluorescence depending on the presence or absence of a magnetic field. A change in intensity was observed. Further, the Knoop hardness of this polycrystalline diamond was 160 GPa.

In a vacuum chamber, methane gas having a carbon isotope ¹² C purity of 99.999 mass% and chemical purity of 99.999 mass% was heated to 1500 ° C. through porous titanium heated to 600 ° C. Sprayed onto a diamond substrate. At this time, the degree of vacuum in the vacuum chamber was set to 20 to 30 Torr. Then, graphite was deposited on the diamond substrate. The bulk density of graphite was 1.6 g / cm ³ .

  The above graphite was directly converted to polycrystalline diamond under conditions of a temperature of 2400 ° C. and a pressure of 15 GPa. Each polycrystalline diamond had a crystal grain size of about 10 to 100 nm. According to SIMS analysis, the content of nitrogen, hydrogen, oxygen, boron and silicon in the polycrystalline diamond was below the detection limit. Further, from the X-ray diffraction pattern of the polycrystalline diamond, no components other than diamond were found in the polycrystalline diamond.

The nano-polycrystalline diamond was irradiated with nitrogen at an acceleration energy of 300 keV for about 10 ¹⁰ / cm ² and subjected to a heat treatment at 900 ° C., and then the fluorescence intensity at 637 nm by the NV-center formed by the process was measured. As a result, when a 532 nm laser was irradiated as excitation light under microwave irradiation with a diameter of 0.5 cm, a circular coil with a frequency of 2.87 GHz, 5 turns, and an output of 0.5 W, a maximum of 3% fluorescence depending on the presence or absence of a magnetic field. A change in intensity was observed. Further, the Knoop hardness of this polycrystalline diamond was 160 GPa.

In a vacuum chamber, methane gas having a carbon isotope ¹² C purity of 99.999 mass% and chemical purity of 99.999 mass% was heated to 1500 ° C. through porous titanium heated to 600 ° C. Sprayed onto a diamond substrate. At this time, the degree of vacuum in the vacuum chamber was set to 20 to 30 Torr. Then, graphite was deposited on the diamond substrate. The bulk density of graphite was 1.6 g / cm ³ .

  The above graphite was directly converted to polycrystalline diamond under the conditions of a temperature of 2500 ° C. and a pressure of 15 GPa. Each polycrystalline diamond had a crystal grain size of about 10 to 100 nm. According to SIMS analysis, the content of nitrogen, hydrogen, oxygen, boron and silicon in the polycrystalline diamond was below the detection limit. Further, from the X-ray diffraction pattern of the polycrystalline diamond, no components other than diamond were found in the polycrystalline diamond.

The nano-polycrystalline diamond was irradiated with nitrogen at an acceleration energy of 300 keV for about 10 ¹⁰ / cm ² and subjected to a heat treatment at 900 ° C., and then the fluorescence intensity at 637 nm by the NV-center formed by the process was measured. As a result, when a 532 nm laser was irradiated as excitation light under microwave irradiation with a diameter of 0.5 cm, a circular coil with a frequency of 2.87 GHz, 5 turns, and an output of 0.5 W, a maximum of 3% fluorescence depending on the presence or absence of a magnetic field. A change in intensity was observed. Further, the Knoop hardness of this polycrystalline diamond was 160 GPa.

In a vacuum chamber, methane gas having a carbon isotope ¹² C purity of 99.999 mass% and chemical purity of 99.999 mass% was heated to 1500 ° C. through porous titanium heated to 600 ° C. Sprayed onto a diamond substrate. At this time, the degree of vacuum in the vacuum chamber was set to 20 to 30 Torr. Then, graphite was deposited on the diamond substrate. The bulk density of graphite was 1.6 g / cm ³ .

  The above graphite was directly converted to polycrystalline diamond under the conditions of a temperature of 2000 ° C. and a pressure of 16 GPa. Each polycrystalline diamond had a crystal grain size of about 10 to 100 nm. According to SIMS analysis, the content of nitrogen, hydrogen, oxygen, boron and silicon in the polycrystalline diamond was below the detection limit. Further, from the X-ray diffraction pattern of the polycrystalline diamond, no components other than diamond were found in the polycrystalline diamond.

The nano-polycrystalline diamond was irradiated with nitrogen at an acceleration energy of 300 keV for about 10 ¹⁰ / cm ² and subjected to a heat treatment at 900 ° C., and then the fluorescence intensity at 637 nm by the NV-center formed by the process was measured. As a result, when a 532 nm laser was irradiated as excitation light under microwave irradiation with a diameter of 0.5 cm, a circular coil with a frequency of 2.87 GHz, 5 turns, and an output of 0.5 W, a maximum of 3% fluorescence depending on the presence or absence of a magnetic field. A change in intensity was observed. Further, the Knoop hardness of this polycrystalline diamond was 160 GPa.

In a vacuum chamber, methane gas having a carbon isotope ¹² C purity of 99.999 mass% and chemical purity of 99.999 mass% was heated to 1500 ° C. through porous titanium heated to 600 ° C. Sprayed onto a diamond substrate. At this time, the degree of vacuum in the vacuum chamber was set to 20 to 30 Torr. Then, graphite was deposited on the diamond substrate. The bulk density of graphite was 1.6 g / cm ³ .

  The above graphite was directly converted to polycrystalline diamond under the conditions of a temperature of 2100 ° C. and a pressure of 16 GPa. Each polycrystalline diamond had a crystal grain size of about 10 to 100 nm. According to SIMS analysis, the content of nitrogen, hydrogen, oxygen, boron and silicon in the polycrystalline diamond was below the detection limit. Further, from the X-ray diffraction pattern of the polycrystalline diamond, no components other than diamond were found in the polycrystalline diamond.

The nano-polycrystalline diamond was irradiated with nitrogen at an acceleration energy of 300 keV for about 10 ¹⁰ / cm ² and subjected to a heat treatment at 900 ° C., and then the fluorescence intensity at 637 nm by the NV-center formed by the process was measured. As a result, when a 532 nm laser was irradiated as excitation light under microwave irradiation with a diameter of 0.5 cm, a circular coil with a frequency of 2.87 GHz, 5 turns, and an output of 0.5 W, a maximum of 3% fluorescence depending on the presence or absence of a magnetic field. A change in intensity was observed. Further, the Knoop hardness of this polycrystalline diamond was 160 GPa.

In a vacuum chamber, methane gas having a carbon isotope ¹² C purity of 99.999 mass% and chemical purity of 99.999 mass% was heated to 1500 ° C. through porous titanium heated to 600 ° C. Sprayed onto a diamond substrate. At this time, the degree of vacuum in the vacuum chamber was set to 20 to 30 Torr. Then, graphite was deposited on the diamond substrate. The bulk density of graphite was 1.6 g / cm ³ .

  The above graphite was directly converted to polycrystalline diamond under conditions of a temperature of 2200 ° C. and a pressure of 16 GPa. Each polycrystalline diamond had a crystal grain size of about 10 to 100 nm. According to SIMS analysis, the content of nitrogen, hydrogen, oxygen, boron and silicon in the polycrystalline diamond was below the detection limit. Further, from the X-ray diffraction pattern of the polycrystalline diamond, no components other than diamond were found in the polycrystalline diamond.

The nano-polycrystalline diamond was irradiated with nitrogen at an acceleration energy of 300 keV for about 10 ¹⁰ / cm ² and subjected to a heat treatment at 900 ° C., and then the fluorescence intensity at 637 nm by the NV-center formed by the process was measured. As a result, when a 532 nm laser was irradiated as excitation light under microwave irradiation with a diameter of 0.5 cm, a circular coil with a frequency of 2.87 GHz, 5 turns, and an output of 0.5 W, a maximum of 3% fluorescence depending on the presence or absence of a magnetic field. A change in intensity was observed. Further, the Knoop hardness of this polycrystalline diamond was 160 GPa.

In a vacuum chamber, a diamond substrate in which methane gas having a carbon isotope ¹² C purity of 99.999 mass% and a chemical purity of 99 mass% is heated to 1900 ° C. through porous titanium heated to 600 ° C. Sprayed on top. At this time, the degree of vacuum in the vacuum chamber was 90 to 100 Torr. Then, graphite was deposited on the diamond substrate. The bulk density of graphite was 2.0 g / cm ³ .

  The above graphite was directly converted to polycrystalline diamond under conditions of a temperature of 2200 ° C. and a pressure of 15 GPa. Each polycrystalline diamond had a crystal grain size of about 10 to 100 nm. According to SIMS analysis, the content of nitrogen, hydrogen, oxygen, boron and silicon in the polycrystalline diamond was below the detection limit. Further, from the X-ray diffraction pattern of the polycrystalline diamond, no components other than diamond were found in the polycrystalline diamond.

The nano-polycrystalline diamond was irradiated with nitrogen at an acceleration energy of 300 keV for about 10 ¹⁰ / cm ² and subjected to a heat treatment at 900 ° C., and then the fluorescence intensity at 637 nm by the NV-center formed by the process was measured. As a result, when a 532 nm laser was irradiated as excitation light under microwave irradiation with a diameter of 0.5 cm, a circular coil with a frequency of 2.87 GHz, 5 turns, and an output of 0.5 W, a maximum of 3% fluorescence depending on the presence or absence of a magnetic field. A change in intensity was observed. The Knoop hardness of this polycrystalline diamond was 190 GPa.

In a vacuum chamber, a diamond substrate in which methane gas having a carbon isotope ¹² C purity of 99.999 mass% and a chemical purity of 99 mass% is heated to 1900 ° C. through porous titanium heated to 600 ° C. Sprayed on top. At this time, the degree of vacuum in the vacuum chamber was 90 to 100 Torr. Then, graphite was deposited on the diamond substrate. The bulk density of graphite was 2.0 g / cm ³ .

  The above graphite was directly converted to polycrystalline diamond under conditions of a temperature of 2300 ° C. and a pressure of 15 GPa. Each polycrystalline diamond had a crystal grain size of about 10 to 100 nm. According to SIMS analysis, the content of nitrogen, hydrogen, oxygen, boron and silicon in the polycrystalline diamond was below the detection limit. Further, from the X-ray diffraction pattern of the polycrystalline diamond, no components other than diamond were found in the polycrystalline diamond.

The nano-polycrystalline diamond was irradiated with nitrogen at an acceleration energy of 300 keV for about 10 ¹⁰ / cm ² and subjected to a heat treatment at 900 ° C., and then the fluorescence intensity at 637 nm by the NV-center formed by the process was measured. As a result, when a 532 nm laser was irradiated as excitation light under microwave irradiation with a diameter of 0.5 cm, a circular coil with a frequency of 2.87 GHz, 5 turns, and an output of 0.5 W, a maximum of 3% fluorescence depending on the presence or absence of a magnetic field. A change in intensity was observed. The Knoop hardness of this polycrystalline diamond was 190 GPa.

In a vacuum chamber, a diamond substrate in which methane gas having a carbon isotope ¹² C purity of 99.999 mass% and a chemical purity of 99 mass% is heated to 1900 ° C. through porous titanium heated to 600 ° C. Sprayed on top. At this time, the degree of vacuum in the vacuum chamber was 90 to 100 Torr. Then, graphite was deposited on the diamond substrate. The bulk density of graphite was 2.0 g / cm ³ .

  The above graphite was directly converted to polycrystalline diamond under conditions of a temperature of 2400 ° C. and a pressure of 15 GPa. Each polycrystalline diamond had a crystal grain size of about 10 to 100 nm. According to SIMS analysis, the content of nitrogen, hydrogen, oxygen, boron and silicon in the polycrystalline diamond was below the detection limit. Further, from the X-ray diffraction pattern of the polycrystalline diamond, no components other than diamond were found in the polycrystalline diamond.

The nano-polycrystalline diamond was irradiated with nitrogen at an acceleration energy of 300 keV for about 10 ¹⁰ / cm ² and subjected to a heat treatment at 900 ° C., and then the fluorescence intensity at 637 nm by the NV-center formed by the process was measured. As a result, when a 532 nm laser was irradiated as excitation light under microwave irradiation with a diameter of 0.5 cm, a circular coil with a frequency of 2.87 GHz, 5 turns, and an output of 0.5 W, a maximum of 3% fluorescence depending on the presence or absence of a magnetic field. A change in intensity was observed. The Knoop hardness of this polycrystalline diamond was 190 GPa.

In a vacuum chamber, a diamond substrate in which methane gas having a carbon isotope ¹² C purity of 99.999 mass% and a chemical purity of 99 mass% is heated to 1900 ° C. through porous titanium heated to 600 ° C. Sprayed on top. At this time, the degree of vacuum in the vacuum chamber was 90 to 100 Torr. Then, graphite was deposited on the diamond substrate. The bulk density of graphite was 2.0 g / cm ³ .

  The above graphite was directly converted to polycrystalline diamond under the conditions of a temperature of 2500 ° C. and a pressure of 15 GPa. Each polycrystalline diamond had a crystal grain size of about 10 to 100 nm. According to SIMS analysis, the content of nitrogen, hydrogen, oxygen, boron and silicon in the polycrystalline diamond was below the detection limit. Further, from the X-ray diffraction pattern of the polycrystalline diamond, no components other than diamond were found in the polycrystalline diamond.

The nano-polycrystalline diamond was irradiated with nitrogen at an acceleration energy of 300 keV for about 10 ¹⁰ / cm ² and subjected to a heat treatment at 900 ° C., and then the fluorescence intensity at 637 nm by the NV-center formed by the process was measured. As a result, when a 532 nm laser was irradiated as excitation light under microwave irradiation with a diameter of 0.5 cm, a circular coil with a frequency of 2.87 GHz, 5 turns, and an output of 0.5 W, a maximum of 3% fluorescence depending on the presence or absence of a magnetic field. A change in intensity was observed. The Knoop hardness of this polycrystalline diamond was 190 GPa.

In a vacuum chamber, a diamond substrate in which methane gas having a carbon isotope ¹² C purity of 99.999 mass% and a chemical purity of 99 mass% is heated to 1900 ° C. through porous titanium heated to 600 ° C. Sprayed on top. At this time, the degree of vacuum in the vacuum chamber was 90 to 100 Torr. Then, graphite was deposited on the diamond substrate. The bulk density of graphite was 2.0 g / cm ³ .

  The above graphite was directly converted to polycrystalline diamond under the conditions of a temperature of 2000 ° C. and a pressure of 16 GPa. Each polycrystalline diamond had a crystal grain size of about 10 to 100 nm. According to SIMS analysis, the content of nitrogen, hydrogen, oxygen, boron and silicon in the polycrystalline diamond was below the detection limit. Further, from the X-ray diffraction pattern of the polycrystalline diamond, no components other than diamond were found in the polycrystalline diamond.

The nano-polycrystalline diamond was irradiated with nitrogen at an acceleration energy of 300 keV for about 10 ¹⁰ / cm ² and subjected to a heat treatment at 900 ° C., and then the fluorescence intensity at 637 nm by the NV-center formed by the process was measured. As a result, when a 532 nm laser was irradiated as excitation light under microwave irradiation with a diameter of 0.5 cm, a circular coil with a frequency of 2.87 GHz, 5 turns, and an output of 0.5 W, a maximum of 3% fluorescence depending on the presence or absence of a magnetic field. A change in intensity was observed. The Knoop hardness of this polycrystalline diamond was 190 GPa.

In a vacuum chamber, a diamond substrate in which methane gas having a carbon isotope ¹² C purity of 99.999 mass% and a chemical purity of 99 mass% is heated to 1900 ° C. through porous titanium heated to 600 ° C. Sprayed on top. At this time, the degree of vacuum in the vacuum chamber was 90 to 100 Torr. Then, graphite was deposited on the diamond substrate. The bulk density of graphite was 2.0 g / cm ³ .

  The above graphite was directly converted to polycrystalline diamond under the conditions of a temperature of 2100 ° C. and a pressure of 16 GPa. Each polycrystalline diamond had a crystal grain size of about 10 to 100 nm. According to SIMS analysis, the content of nitrogen, hydrogen, oxygen, boron and silicon in the polycrystalline diamond was below the detection limit. Further, from the X-ray diffraction pattern of the polycrystalline diamond, no components other than diamond were found in the polycrystalline diamond.

The nano-polycrystalline diamond was irradiated with nitrogen at an acceleration energy of 300 keV for about 10 ¹⁰ / cm ² and subjected to a heat treatment at 900 ° C., and then the fluorescence intensity at 637 nm by the NV-center formed by the process was measured. As a result, when a 532 nm laser was irradiated as excitation light under microwave irradiation with a diameter of 0.5 cm, a circular coil with a frequency of 2.87 GHz, 5 turns, and an output of 0.5 W, a maximum of 3% fluorescence depending on the presence or absence of a magnetic field. A change in intensity was observed. The Knoop hardness of this polycrystalline diamond was 190 GPa.

In a vacuum chamber, a diamond substrate in which methane gas having a carbon isotope ¹² C purity of 99.999 mass% and a chemical purity of 99 mass% is heated to 1900 ° C. through porous titanium heated to 600 ° C. Sprayed on top. At this time, the degree of vacuum in the vacuum chamber was 90 to 100 Torr. Then, graphite was deposited on the diamond substrate. The bulk density of graphite was 2.0 g / cm ³ .

  The above graphite was directly converted to polycrystalline diamond under conditions of a temperature of 2200 ° C. and a pressure of 16 GPa. Each polycrystalline diamond had a crystal grain size of about 10 to 100 nm. According to SIMS analysis, the content of nitrogen, hydrogen, oxygen, boron and silicon in the polycrystalline diamond was below the detection limit. Further, from the X-ray diffraction pattern of the polycrystalline diamond, no components other than diamond were found in the polycrystalline diamond.

The nano-polycrystalline diamond was irradiated with nitrogen at an acceleration energy of 300 keV for about 10 ¹⁰ / cm ² and subjected to a heat treatment at 900 ° C., and then the fluorescence intensity at 637 nm by the NV-center formed by the process was measured. As a result, when a 532 nm laser was irradiated as excitation light under microwave irradiation with a diameter of 0.5 cm, a circular coil with a frequency of 2.87 GHz, 5 turns, and an output of 0.5 W, a maximum of 3% fluorescence depending on the presence or absence of a magnetic field. A change in intensity was observed. The Knoop hardness of this polycrystalline diamond was 190 GPa.

In a vacuum chamber, a diamond substrate in which methane gas having a carbon isotope ¹² C purity of 99.999 mass% and a chemical purity of 99 mass% is heated to 1500 ° C. through porous titanium heated to 600 ° C. Sprayed on top. At this time, the degree of vacuum in the vacuum chamber was 90 to 100 Torr. Then, graphite was deposited on the diamond substrate. The bulk density of graphite was 1.6 g / cm ³ .

  The above graphite was directly converted to polycrystalline diamond under conditions of 2200 ° C. and a pressure of 15 GPa. Each polycrystalline diamond had a crystal grain size of about 10 to 100 nm. According to SIMS analysis, the content of nitrogen, hydrogen, oxygen, boron and silicon in the polycrystalline diamond was below the detection limit. Further, from the X-ray diffraction pattern of the polycrystalline diamond, no components other than diamond were found in the polycrystalline diamond.

The nano-polycrystalline diamond was irradiated with nitrogen at an acceleration energy of 300 keV for about 10 ¹⁰ / cm ² and subjected to a heat treatment at 900 ° C., and then the fluorescence intensity at 637 nm by the NV-center formed by the process was measured. As a result, when a 532 nm laser was irradiated as excitation light under microwave irradiation with a diameter of 0.5 cm, a circular coil with a frequency of 2.87 GHz, 5 turns, and an output of 0.5 W, a maximum of 3% fluorescence depending on the presence or absence of a magnetic field. A change in intensity was observed. Further, the Knoop hardness of this polycrystalline diamond was 150 GPa.

In a vacuum chamber, a diamond substrate in which methane gas having a carbon isotope ¹² C purity of 99.999 mass% and a chemical purity of 99 mass% is heated to 1500 ° C. through porous titanium heated to 600 ° C. Sprayed on top. At this time, the degree of vacuum in the vacuum chamber was 90 to 100 Torr. Then, graphite was deposited on the diamond substrate. The bulk density of graphite was 1.6 g / cm ³ .

  The above graphite was directly converted to polycrystalline diamond under conditions of a temperature of 2300 ° C. and a pressure of 15 GPa. Each polycrystalline diamond had a crystal grain size of about 10 to 100 nm. According to SIMS analysis, the content of nitrogen, hydrogen, oxygen, boron and silicon in the polycrystalline diamond was below the detection limit. Further, from the X-ray diffraction pattern of the polycrystalline diamond, no components other than diamond were found in the polycrystalline diamond.

The nano-polycrystalline diamond was irradiated with nitrogen at an acceleration energy of 300 keV for about 10 ¹⁰ / cm ² and subjected to a heat treatment at 900 ° C., and then the fluorescence intensity at 637 nm by the NV-center formed by the process was measured. As a result, when a 532 nm laser was irradiated as excitation light under microwave irradiation with a diameter of 0.5 cm, a circular coil with a frequency of 2.87 GHz, 5 turns, and an output of 0.5 W, a maximum of 3% fluorescence depending on the presence or absence of a magnetic field. A change in intensity was observed. Further, the Knoop hardness of this polycrystalline diamond was 150 GPa.

In a vacuum chamber, a diamond substrate in which methane gas having a carbon isotope ¹² C purity of 99.999 mass% and a chemical purity of 99 mass% is heated to 1500 ° C. through porous titanium heated to 600 ° C. Sprayed on top. At this time, the degree of vacuum in the vacuum chamber was 90 to 100 Torr. Then, graphite was deposited on the diamond substrate. The bulk density of graphite was 1.6 g / cm ³ .

  The above graphite was directly converted to polycrystalline diamond under conditions of a temperature of 2400 ° C. and a pressure of 15 GPa. Each polycrystalline diamond had a crystal grain size of about 10 to 100 nm. According to SIMS analysis, the content of nitrogen, hydrogen, oxygen, boron and silicon in the polycrystalline diamond was below the detection limit. Further, from the X-ray diffraction pattern of the polycrystalline diamond, no components other than diamond were found in the polycrystalline diamond.

The nano-polycrystalline diamond was irradiated with nitrogen at an acceleration energy of 300 keV for about 10 ¹⁰ / cm ² and subjected to a heat treatment at 900 ° C., and then the fluorescence intensity at 637 nm by the NV-center formed by the process was measured. As a result, when a 532 nm laser was irradiated as excitation light under microwave irradiation with a diameter of 0.5 cm, a circular coil with a frequency of 2.87 GHz, 5 turns, and an output of 0.5 W, a maximum of 3% fluorescence depending on the presence or absence of a magnetic field. A change in intensity was observed. Further, the Knoop hardness of this polycrystalline diamond was 150 GPa.

In a vacuum chamber, a diamond substrate in which methane gas having a carbon isotope ¹² C purity of 99.999 mass% and a chemical purity of 99 mass% is heated to 1500 ° C. through porous titanium heated to 600 ° C. Sprayed on top. At this time, the degree of vacuum in the vacuum chamber was 90 to 100 Torr. Then, graphite was deposited on the diamond substrate. The bulk density of graphite was 1.6 g / cm ³ .

  The above graphite was directly converted to polycrystalline diamond under the conditions of a temperature of 2500 ° C. and a pressure of 15 GPa. Each polycrystalline diamond had a crystal grain size of about 10 to 100 nm. According to SIMS analysis, the content of nitrogen, hydrogen, oxygen, boron and silicon in the polycrystalline diamond was below the detection limit. Further, from the X-ray diffraction pattern of the polycrystalline diamond, no components other than diamond were found in the polycrystalline diamond.

The nano-polycrystalline diamond was irradiated with nitrogen at an acceleration energy of 300 keV for about 10 ¹⁰ / cm ² and subjected to a heat treatment at 900 ° C., and then the fluorescence intensity at 637 nm by the NV-center formed by the process was measured. As a result, when a 532 nm laser was irradiated as excitation light under microwave irradiation with a diameter of 0.5 cm, a circular coil with a frequency of 2.87 GHz, 5 turns, and an output of 0.5 W, a maximum of 3% fluorescence depending on the presence or absence of a magnetic field. A change in intensity was observed. Further, the Knoop hardness of this polycrystalline diamond was 150 GPa.

In a vacuum chamber, a diamond substrate in which methane gas having a carbon isotope ¹² C purity of 99.999 mass% and a chemical purity of 99 mass% is heated to 1500 ° C. through porous titanium heated to 600 ° C. Sprayed on top. At this time, the degree of vacuum in the vacuum chamber was 90 to 100 Torr. Then, graphite was deposited on the diamond substrate. The bulk density of graphite was 1.6 g / cm ³ .

  The above graphite was directly converted to polycrystalline diamond under the conditions of a temperature of 2000 ° C. and a pressure of 16 GPa. Each polycrystalline diamond had a crystal grain size of about 10 to 100 nm. According to SIMS analysis, the content of nitrogen, hydrogen, oxygen, boron and silicon in the polycrystalline diamond was below the detection limit. Further, from the X-ray diffraction pattern of the polycrystalline diamond, no components other than diamond were found in the polycrystalline diamond.

The nano-polycrystalline diamond was irradiated with nitrogen at an acceleration energy of 300 keV for about 10 ¹⁰ / cm ² and subjected to a heat treatment at 900 ° C., and then the fluorescence intensity at 637 nm by the NV-center formed by the process was measured. As a result, when a 532 nm laser was irradiated as excitation light under microwave irradiation with a diameter of 0.5 cm, a circular coil with a frequency of 2.87 GHz, 5 turns, and an output of 0.5 W, a maximum of 3% fluorescence depending on the presence or absence of a magnetic field. A change in intensity was observed. Further, the Knoop hardness of this polycrystalline diamond was 150 GPa.

In a vacuum chamber, a diamond substrate having a carbon isotope ¹² C purity of 99.999 mass% and chemical purity of 99 mass% is heated to 1500 ° C. through porous titanium heated to 600 ° C. Sprayed on top. At this time, the degree of vacuum in the vacuum chamber was 90 to 100 Torr. Then, graphite was deposited on the diamond substrate. The bulk density of graphite was 1.6 g / cm ³ .

  The above graphite was directly converted to polycrystalline diamond under the conditions of a temperature of 2100 ° C. and a pressure of 16 GPa. Each polycrystalline diamond had a crystal grain size of about 10 to 100 nm. According to SIMS analysis, the content of nitrogen, hydrogen, oxygen, boron and silicon in the polycrystalline diamond was below the detection limit. Further, from the X-ray diffraction pattern of the polycrystalline diamond, no components other than diamond were found in the polycrystalline diamond.

The nano-polycrystalline diamond was irradiated with nitrogen at an acceleration energy of 300 keV for about 10 ¹⁰ / cm ² and subjected to a heat treatment at 900 ° C., and then the fluorescence intensity at 637 nm by the NV-center formed by the process was measured. As a result, when a 532 nm laser was irradiated as excitation light under microwave irradiation with a diameter of 0.5 cm, a circular coil with a frequency of 2.87 GHz, 5 turns, and an output of 0.5 W, a maximum of 3% fluorescence depending on the presence or absence of a magnetic field. A change in intensity was observed. Further, the Knoop hardness of this polycrystalline diamond was 150 GPa.

In a vacuum chamber, a diamond substrate in which methane gas having a carbon isotope ¹² C purity of 99.999 mass% and a chemical purity of 99 mass% is heated to 1500 ° C. through porous titanium heated to 600 ° C. Sprayed on top. At this time, the degree of vacuum in the vacuum chamber was 90 to 100 Torr. Then, graphite was deposited on the diamond substrate. The bulk density of graphite was 1.6 g / cm ³ .

  The above graphite was directly converted to polycrystalline diamond under conditions of a temperature of 2200 ° C. and a pressure of 16 GPa. Each polycrystalline diamond had a crystal grain size of about 10 to 100 nm. According to SIMS analysis, the content of nitrogen, hydrogen, oxygen, boron and silicon in the polycrystalline diamond was below the detection limit. Further, from the X-ray diffraction pattern of the polycrystalline diamond, no components other than diamond were found in the polycrystalline diamond.

The nano-polycrystalline diamond was irradiated with nitrogen at an acceleration energy of 300 keV for about 10 ¹⁰ / cm ² and subjected to a heat treatment at 900 ° C., and then the fluorescence intensity at 637 nm by the NV-center formed by the process was measured. As a result, when a 532 nm laser was irradiated as excitation light under microwave irradiation with a diameter of 0.5 cm, a circular coil with a frequency of 2.87 GHz, 5 turns, and an output of 0.5 W, a maximum of 3% fluorescence depending on the presence or absence of a magnetic field. A change in intensity was observed. Further, the Knoop hardness of this polycrystalline diamond was 170 GPa.

In a vacuum chamber, methane gas having a carbon isotope ¹² C purity of 99.999 mass% and a chemical purity of 99.999 mass% was heated to 1900 ° C. through porous titanium heated to 600 ° C. Sprayed onto a diamond substrate. At this time, the degree of vacuum in the vacuum chamber was 90 to 100 Torr. Then, graphite was deposited on the diamond substrate. The bulk density of graphite was 2.0 g / cm ³ .

  The above graphite was directly converted to polycrystalline diamond under conditions of a temperature of 2200 ° C. and a pressure of 15 GPa. Each polycrystalline diamond had a crystal grain size of about 10 to 100 nm. According to SIMS analysis, the content of nitrogen, hydrogen, oxygen, boron and silicon in the polycrystalline diamond was below the detection limit. Further, from the X-ray diffraction pattern of the polycrystalline diamond, no components other than diamond were found in the polycrystalline diamond.

The nano-polycrystalline diamond was irradiated with nitrogen at an acceleration energy of 300 keV for about 10 ¹⁰ / cm ² and subjected to a heat treatment at 900 ° C., and then the fluorescence intensity at 637 nm by the NV-center formed by the process was measured. As a result, when a 532 nm laser was irradiated as excitation light under microwave irradiation with a diameter of 0.5 cm, a circular coil with a frequency of 2.87 GHz, 5 turns, and an output of 0.5 W, a maximum of 4% fluorescence depending on the presence or absence of a magnetic field. A change in intensity was observed. Further, the Knoop hardness of this polycrystalline diamond was 200 GPa.

In a vacuum chamber, methane gas having a carbon isotope ¹² C purity of 99.999 mass% and a chemical purity of 99.999 mass% was heated to 1900 ° C. through porous titanium heated to 600 ° C. Sprayed onto a diamond substrate. At this time, the degree of vacuum in the vacuum chamber was 90 to 100 Torr. Then, graphite was deposited on the diamond substrate. The bulk density of graphite was 2.0 g / cm ³ .

  The above graphite was directly converted to polycrystalline diamond under conditions of a temperature of 2300 ° C. and a pressure of 15 GPa. Each polycrystalline diamond had a crystal grain size of about 10 to 100 nm. According to SIMS analysis, the content of nitrogen, hydrogen, oxygen, boron and silicon in the polycrystalline diamond was below the detection limit. Further, from the X-ray diffraction pattern of the polycrystalline diamond, no components other than diamond were found in the polycrystalline diamond.

The nano-polycrystalline diamond was irradiated with nitrogen at an acceleration energy of 300 keV for about 10 ¹⁰ / cm ² and subjected to a heat treatment at 900 ° C., and then the fluorescence intensity at 637 nm by the NV-center formed by the process was measured. As a result, when a 532 nm laser was irradiated as excitation light under microwave irradiation with a diameter of 0.5 cm, a circular coil with a frequency of 2.87 GHz, 5 turns, and an output of 0.5 W, a maximum of 4% fluorescence depending on the presence or absence of a magnetic field. A change in intensity was observed. Further, the Knoop hardness of this polycrystalline diamond was 200 GPa.

In a vacuum chamber, methane gas having a carbon isotope ¹² C purity of 99.999 mass% and a chemical purity of 99.999 mass% was heated to 1900 ° C. through porous titanium heated to 600 ° C. Sprayed onto a diamond substrate. At this time, the degree of vacuum in the vacuum chamber was 90 to 100 Torr. Then, graphite was deposited on the diamond substrate. The bulk density of graphite was 2.0 g / cm ³ .

  The above graphite was directly converted to polycrystalline diamond under conditions of a temperature of 2400 ° C. and a pressure of 15 GPa. Each polycrystalline diamond had a crystal grain size of about 10 to 100 nm. According to SIMS analysis, the content of nitrogen, hydrogen, oxygen, boron and silicon in the polycrystalline diamond was below the detection limit. Further, from the X-ray diffraction pattern of the polycrystalline diamond, no components other than diamond were found in the polycrystalline diamond.

The nano-polycrystalline diamond was irradiated with nitrogen at an acceleration energy of 300 keV for about 10 ¹⁰ / cm ² and subjected to a heat treatment at 900 ° C., and then the fluorescence intensity at 637 nm by the NV-center formed by the process was measured. As a result, when a 532 nm laser was irradiated as excitation light under microwave irradiation with a diameter of 0.5 cm, a circular coil with a frequency of 2.87 GHz, 5 turns, and an output of 0.5 W, a maximum of 4% fluorescence depending on the presence or absence of a magnetic field. A change in intensity was observed. Further, the Knoop hardness of this polycrystalline diamond was 200 GPa.

In a vacuum chamber, methane gas having a carbon isotope ¹² C purity of 99.999 mass% and a chemical purity of 99.999 mass% was heated to 1900 ° C. through porous titanium heated to 600 ° C. Sprayed onto a diamond substrate. At this time, the degree of vacuum in the vacuum chamber was 90 to 100 Torr. Then, graphite was deposited on the diamond substrate. The bulk density of graphite was 2.0 g / cm ³ .

  The above graphite was directly converted to polycrystalline diamond under the conditions of a temperature of 2500 ° C. and a pressure of 15 GPa. Each polycrystalline diamond had a crystal grain size of about 10 to 100 nm. According to SIMS analysis, the content of nitrogen, hydrogen, oxygen, boron and silicon in the polycrystalline diamond was below the detection limit. Further, from the X-ray diffraction pattern of the polycrystalline diamond, no components other than diamond were found in the polycrystalline diamond.

The nano-polycrystalline diamond was irradiated with nitrogen at an acceleration energy of 300 keV for about 10 ¹⁰ / cm ² and subjected to a heat treatment at 900 ° C., and then the fluorescence intensity at 637 nm by the NV-center formed by the process was measured. As a result, when a 532 nm laser was irradiated as excitation light under microwave irradiation with a diameter of 0.5 cm, a circular coil with a frequency of 2.87 GHz, 5 turns, and an output of 0.5 W, a maximum of 4% fluorescence depending on the presence or absence of a magnetic field. A change in intensity was observed. Further, the Knoop hardness of this polycrystalline diamond was 200 GPa.

In a vacuum chamber, methane gas having a carbon isotope ¹² C purity of 99.999 mass% and a chemical purity of 99.999 mass% was heated to 1900 ° C. through porous titanium heated to 600 ° C. Sprayed onto a diamond substrate. At this time, the degree of vacuum in the vacuum chamber was 90 to 100 Torr. Then, graphite was deposited on the diamond substrate. The bulk density of graphite was 2.0 g / cm ³ .

  The above graphite was directly converted to polycrystalline diamond under the conditions of a temperature of 2000 ° C. and a pressure of 16 GPa. Each polycrystalline diamond had a crystal grain size of about 10 to 100 nm. According to SIMS analysis, the content of nitrogen, hydrogen, oxygen, boron and silicon in the polycrystalline diamond was below the detection limit. Further, from the X-ray diffraction pattern of the polycrystalline diamond, no components other than diamond were found in the polycrystalline diamond.

The nano-polycrystalline diamond was irradiated with nitrogen at an acceleration energy of 300 keV for about 10 ¹⁰ / cm ² and subjected to a heat treatment at 900 ° C., and then the fluorescence intensity at 637 nm by the NV-center formed by the process was measured. As a result, when a 532 nm laser was irradiated as excitation light under microwave irradiation with a diameter of 0.5 cm, a circular coil with a frequency of 2.87 GHz, 5 turns, and an output of 0.5 W, a maximum of 3% fluorescence depending on the presence or absence of a magnetic field. A change in intensity was observed. The polycrystalline diamond had a Knoop hardness of 210 GPa.

In a vacuum chamber, methane gas having a carbon isotope ¹² C purity of 99.999 mass% and a chemical purity of 99.999 mass% was heated to 1900 ° C. through porous titanium heated to 600 ° C. Sprayed onto a diamond substrate. At this time, the degree of vacuum in the vacuum chamber was 90 to 100 Torr. Then, graphite was deposited on the diamond substrate. The bulk density of graphite was 2.0 g / cm ³ .

  The above graphite was directly converted to polycrystalline diamond under the conditions of a temperature of 2100 ° C. and a pressure of 16 GPa. Each polycrystalline diamond had a crystal grain size of about 10 to 100 nm. According to SIMS analysis, the content of nitrogen, hydrogen, oxygen, boron and silicon in the polycrystalline diamond was below the detection limit. Further, from the X-ray diffraction pattern of the polycrystalline diamond, no components other than diamond were found in the polycrystalline diamond.

The nano-polycrystalline diamond was irradiated with nitrogen at an acceleration energy of 300 keV for about 10 ¹⁰ / cm ² and subjected to a heat treatment at 900 ° C., and then the fluorescence intensity at 637 nm by the NV-center formed by the process was measured. As a result, when a 532 nm laser was irradiated as excitation light under microwave irradiation with a diameter of 0.5 cm, a circular coil with a frequency of 2.87 GHz, 5 turns, and an output of 0.5 W, a maximum of 4% fluorescence depending on the presence or absence of a magnetic field. A change in intensity was observed. The Knoop hardness of this polycrystalline diamond was 190 GPa.

In a vacuum chamber, methane gas having a carbon isotope ¹² C purity of 99.999 mass% and a chemical purity of 99.999 mass% was heated to 1900 ° C. through porous titanium heated to 600 ° C. Sprayed onto a diamond substrate. At this time, the degree of vacuum in the vacuum chamber was 90 to 100 Torr. Then, graphite was deposited on the diamond substrate. The bulk density of graphite was 2.0 g / cm ³ .

  The above graphite was directly converted to polycrystalline diamond under conditions of a temperature of 2200 ° C. and a pressure of 16 GPa. Each polycrystalline diamond had a crystal grain size of about 10 to 100 nm. According to SIMS analysis, the content of nitrogen, hydrogen, oxygen, boron and silicon in the polycrystalline diamond was below the detection limit. Further, from the X-ray diffraction pattern of the polycrystalline diamond, no components other than diamond were found in the polycrystalline diamond.

The nano-polycrystalline diamond was irradiated with nitrogen at an acceleration energy of 300 keV for about 10 ¹⁰ / cm ² and subjected to a heat treatment at 900 ° C., and then the fluorescence intensity at 637 nm by the NV-center formed by the process was measured. As a result, when a 532 nm laser was irradiated as excitation light under microwave irradiation with a diameter of 0.5 cm, a circular coil with a frequency of 2.87 GHz, 5 turns, and an output of 0.5 W, a maximum of 3% fluorescence depending on the presence or absence of a magnetic field. A change in intensity was observed. The polycrystalline diamond had a Knoop hardness of 198 GPa.

In a vacuum chamber, methane gas having a carbon isotope ¹² C purity of 99.999 mass% and chemical purity of 99.999 mass% was heated to 1500 ° C. through porous titanium heated to 600 ° C. Sprayed onto a diamond substrate. At this time, the degree of vacuum in the vacuum chamber was 90 to 100 Torr. Then, graphite was deposited on the diamond substrate. The bulk density of graphite was 1.6 g / cm ³ .

  The above graphite was directly converted to polycrystalline diamond under conditions of a temperature of 2300 ° C. and a pressure of 15 GPa. Each polycrystalline diamond had a crystal grain size of about 10 to 100 nm. According to SIMS analysis, the content of nitrogen, hydrogen, oxygen, boron and silicon in the polycrystalline diamond was below the detection limit. Further, from the X-ray diffraction pattern of the polycrystalline diamond, no components other than diamond were found in the polycrystalline diamond.

The nano-polycrystalline diamond was irradiated with nitrogen at an acceleration energy of 300 keV for about 10 ¹⁰ / cm ² and subjected to a heat treatment at 900 ° C., and then the fluorescence intensity at 637 nm by the NV-center formed by the process was measured. As a result, when a 532 nm laser was irradiated as excitation light under microwave irradiation with a diameter of 0.5 cm, a circular coil with a frequency of 2.87 GHz, 5 turns, and an output of 0.5 W, a maximum of 4% fluorescence depending on the presence or absence of a magnetic field. A change in intensity was observed. Further, the Knoop hardness of this polycrystalline diamond was 180 GPa.

In the above example, the carbon isotope ¹² C is produced by pyrolyzing a hydrocarbon gas having a purity of 99.9% by mass or more and a chemical purity of 99% by mass or more. It can be used for magnetic sensing by performing a heat treatment at a temperature of about 2000 ° C. to 2500 ° C. and a pressure of about 15 to 16 GPa on extremely high purity graphite of about / cm ³ to 2.0 g / cm ³ , It was confirmed that high-purity nanopolycrystalline diamond having a Knoop hardness of about 150 GPa to 205 GPa can be produced. However, it is considered that nanopolycrystalline diamond having equivalent characteristics can be produced even under conditions other than this within the range described in the claims of the present application.
Although the embodiments and examples of the present invention have been described above, various modifications can be made to the above-described embodiments and examples. Further, the scope of the present invention is not limited to the above-described embodiments and examples. The scope of the present invention is defined by the terms of the claims, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  1 nano-polycrystalline diamond, 2 substrate, 10 graphite.

Claims (10)

Carbon whose carbon isotope ¹² C has a purity of 99.9% by mass or more;
Composed of a plurality of impurities other than carbon,
Polycrystalline diamond, wherein the concentration of the plurality of impurities is 0.01% by mass or less and the crystal grain size is 500 nm or less.   2. The polycrystalline diamond according to claim 1, wherein the concentration of the impurity at a grain boundary of the polycrystalline diamond is 0.01% by mass or less.   The polycrystalline diamond according to claim 1 or 2, wherein the Knoop hardness is 150 GPa or more. The plurality of impurities include hydrogen, oxygen, nitrogen, silicon and boron,
The hydrogen concentration is 2 × 10 ¹⁸ / cm ³ or less,
The oxygen concentration is 2 × 10 ¹⁷ / cm ³ or less,
The nitrogen concentration is 4 × 10 ¹⁶ / cm ³ or less,
The silicon concentration is 1 × 10 ¹⁶ / cm ³ or less,
The polycrystalline diamond according to any one of claims 1 to 3, wherein the boron concentration is 2 x 10 ¹⁵ / cm ³ or less. The polycrystalline diamond is produced by sintering graphite obtained by pyrolyzing a hydrocarbon having a carbon isotope ¹² C purity of 99.9% by mass or more at a temperature of 1500 ° C. or higher. The polycrystalline diamond according to any one of claims 1 to 4. A step of preparing graphite obtained by pyrolyzing a hydrocarbon gas having a carbon isotope ¹² C purity of 99.9% by mass or more and a chemical purity of 99% by mass or more;
Converting the graphite into diamond by heat-treating the graphite in a high-temperature and high-pressure press apparatus;
A method for producing polycrystalline diamond, comprising:   The method for producing polycrystalline diamond according to claim 6, wherein in the step of converting the graphite into diamond, the graphite is subjected to heat treatment under high pressure without adding a sintering aid or a catalyst.   The step of preparing the graphite includes a step of thermally decomposing the hydrocarbon gas introduced into the vacuum chamber at a temperature of 1500 ° C. or more to form graphite on a substrate. The manufacturing method of the polycrystalline diamond of description.   The method for producing polycrystalline diamond according to claim 8, wherein in the step of converting the graphite into diamond, the graphite formed on the base material is subjected to a heat treatment at 1500 ° C or higher under a high pressure of 7 GPa or higher. The method for producing polycrystalline diamond according to any one of claims 6 to 9, wherein the bulk density of the graphite is 1.4 g / cm ³ or more.

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