Quantum diamond with ultrahigh NV-color center density and preparation method and application thereof

Abstract

The invention relates to the technical field of diamond preparation, in particular to a quantum diamond with an ultrahigh-density NV-color center and a preparation method and application of the quantum diamond. At present, the preparation of the quantum diamond generally adopts an electron irradiation and vacuum annealing method, and the quantum diamond prepared by the method is difficult to obtain the ultra-high density characteristic; therefore, the ultra-high-density quantum diamond is difficult to prepare at present. The quantum diamond with the NV-color center density larger than or equal to 15 ppm is prepared by greatly improving the irradiation dose, adjusting the annealing pressure and other technological conditions. The problem that ultra-high-density quantum diamond cannot be prepared in a common method is solved; and a favorable condition is provided for wide application.

Description

Technical Field

[0001] The present invention relates to the technical field of diamond preparation, and more particularly to a method for preparing a diamond having an ultra-high density NV - Quantum diamond with color center, preparation method and application thereof. Background Art

[0002] Diamond has high hardness, ultra-wide bandgap, outstanding carrier mobility and excellent thermal conductivity. It is the most promising semiconductor material after Si, SiC and GaN, and is also regarded as the ultimate material for the next generation of power electronic devices.

[0003] Natively Charged Nitrogen-Vacancy (NV) - ) Color center is a point defect formed by nitrogen atoms replacing carbon atoms in the diamond structure and combining with adjacent vacancies. Contains high-quality NV - Diamonds with color centers have shown great potential in quantum computing, sensing, communications, biomedicine and basic scientific research, and are called quantum diamonds.

[0004] NV - Color centers are highly sensitive to magnetic fields, electric fields, etc. High density can improve the sensitivity of the sensor. - Color centers can be used as quantum repeaters in quantum communication. High density helps improve communication efficiency and distance. High density can enhance signal strength, improve signal-to-noise ratio, and improve measurement accuracy. In summary, the pursuit of high NV - Color center density is of great significance to the development and application of quantum technology.

[0005] Currently, including NV - The preparation method of color center diamond is usually: on the basis of the preliminary synthesized diamond, the diamond is further subjected to electron irradiation and atmospheric pressure vacuum annealing. - Color centers are mainly based on a series of processes such as migration and recombination of nitrogen atoms and vacancies inside diamonds under specific conditions. During the vacuum annealing stage, the diamond with vacancies generated by irradiation is placed in a vacuum environment and heated to a certain temperature. The vacuum environment can prevent adverse reactions such as oxidation of the diamond surface, while providing a relatively "clean" environment for the migration of atoms. Heating allows the atoms inside the diamond to obtain enough energy to become active, and the migration ability of nitrogen atoms and vacancies is enhanced. When nitrogen atoms migrate to a position adjacent to the vacancy, NV is formed. - The basic structure of the color center. Afterwards, the electron distribution in the system will be adjusted, and an electron may be captured around this nitrogen-vacancy complex, thus forming a stable negatively charged NV -However, during vacuum annealing, the migration and reaction of atoms mainly depend on the energy provided by heating, and the atomic activity is relatively limited. - The formation efficiency of color centers is low, the adjustable parameters are limited, and it is difficult to precisely control the internal structure of diamond and the defect formation process. - The color center density is low. Summary of the Invention

[0006] In order to solve the NV problem of existing quantum diamonds - To solve the problem of low color center density, the present invention provides a method with ultra-high NV - Color center density quantum diamond and its preparation method and application.

[0007] At present, quantum diamonds are generally prepared by electron irradiation and vacuum annealing. It is difficult for quantum diamonds prepared in this way to obtain ultra-high density characteristics; so it is difficult to prepare quantum diamonds with ultra-high density. This invention prepares a NV by significantly increasing the irradiation dose and adjusting the annealing pressure and other process conditions. - Quantum diamonds with a color center density of 15 ppm or more.

[0008] One of the purposes of the present invention is to provide a device having ultra-high NV as described in one of the purposes of the invention. - Color center density in quantum diamond.

[0009] The NV of quantum diamond - The color center density is greater than or equal to 15 ppm, preferably 15 ppm-46 ppm.

[0010] NV - Color center (Nitrogen-Vacancy Center) is a point defect in diamond crystal formed by nitrogen atoms (N) replacing carbon atoms and combining with adjacent vacancies (V). Its density refers to the NV per unit volume. - The number of color centers, usually expressed in "ppm".

[0011] NV of existing quantum diamonds - The color center density is usually less than 10ppm. - The color center density is greater than or equal to 15ppm, which is much higher than the NV of existing quantum diamonds. - Color center density.

[0012] The second object of the present invention is to provide a device with ultra-high NV as described in one of the invention objects. - Preparation method of quantum diamond with high color center density.

[0013] The preparation method comprises sequentially irradiating and annealing the diamond;

[0014] The diamond is nitrogen-containing diamond, and its nitrogen content is 50ppm-800ppm, preferably 100ppm-800ppm, more preferably 100ppm-300ppm;

[0015] The irradiation dose was 0.5×10 19 cm -2 -20×10 19 cm -2 , preferably the irradiation dose is 1×10 19 cm -2 -6×10 19 cm -2 ;

[0016] The annealing pressure is 4.5 Pa-15 GPa, preferably the annealing pressure is 4.5 GPa-6 GPa.

[0017] Compared with the existing preparation method of quantum diamond, the present invention uses nitrogen-containing diamond with a nitrogen content of 50ppm-800ppm. High nitrogen content is used to obtain high NV - Color center density provides the possibility.

[0018] Compared with the existing preparation method of quantum diamond, the present invention only requires one annealing, the irradiation dose is greatly increased, and the annealing pressure is 4.5GPa-15GPa; thereby improving the NV of the prepared quantum diamond. - Color center density.

[0019] The nitrogen-containing diamond with a nitrogen content of 50ppm-800ppm can be prepared by any existing method; for example, by chemical vapor deposition or high temperature and high pressure. As an alternative, the nitrogen-containing diamond with a nitrogen content of 50ppm-800ppm is prepared by the following method:

[0020] Type Ib diamond was selected as the seed, high-purity graphite powder (purity 99.9 wt%) as the carbon source, and Fe-Ni alloy as the catalyst for diamond growth; nitride (NaN3 / Ba(N3)2) was used as the nitrogen source to control the nitrogen content in the growth medium, and aluminum powder or titanium powder was used as the nitrogen absorber; the temperature was kept at high temperature and high pressure for 60 h; the Fe-Ni alloy was preferably Fe 70 Ni 30 The nitride is preferably NaN3 / Ba(N3)2, and the high temperature and high pressure are 1500°C and 20 GPa. Theoretically, any mass ratio of type Ib diamond, high-purity graphite powder, Fe-Ni alloy, nitride, and nitrogen absorber can be used. However, in practice, the ratio can be selected based on different nitrogen concentrations.

[0021] The annealing temperature can be a conventional annealing temperature in the art, such as about 550°C. Compared with the conventional annealing temperature of about 550°C, when the annealing temperature is increased to 1200°C-1900°C, the prepared quantum diamond has high NV. - The color center density also has the characteristic of a long coherence time. Therefore, as a preferred solution, the annealing temperature is greater than or equal to 550°C, for example, 550°C-1900°C; more preferably, a high temperature annealing method is used: the annealing temperature is 1200°C-1900°C.

[0022] Coherence time is usually expressed as T2 and T2 * T2 is the time that the quantum bit maintains phase coherence, and T2* refers to the overall decoherence time of the quantum bit. * Is a measure of NV - The ability of the color center electron spin to maintain a quantum coherent state, while T2 is a more comprehensive parameter that describes the NV - The actual time scale of decoherence of color center spin states. In practical applications, such as quantum sensing and quantum information processing, it is usually desirable to have T2 * and T2 as long as possible to enable more complex quantum operations and more precise measurements. T2, T2 * NV was detected by Hahn echo sequence and standard free induction decay (FID). - The spin coherence of the color center is quantified.

[0023] The coherence of quantum diamond refers to the ability of its quantum state to maintain phase consistency in time or space. - The color center of diamond is mainly reflected in the nitrogen-vacancy (NV - ) center's spin state coherence. Coherence time is an important parameter for measuring the coherence of a quantum system. Long coherence time helps realize more complex quantum algorithms.

[0024] The annealing time may be a conventional annealing time in the art, for example, 0.1 h to 20 h, preferably 1 to 20 h.

[0025] The irradiation energy may be conventional irradiation energy in the art, for example, 0.2 MeV to 10 MeV. The irradiation energy is selected according to the thickness of the diamond: preferably 1.5 MeV to 5 MeV for a thickness of 1 mm, and preferably 5 MeV to 10 MeV for a thickness of 2 mm.

[0026] The irradiation current can be conventional in the art, for example, 1 mA to 16 mA. The irradiation current is selected based on the diamond's nitrogen content: when the diamond nitrogen content is 50 ppm to 100 ppm, the irradiation current is preferably 1 ppm to 5 mA; when the diamond nitrogen content is 100 ppm to 2000 ppm, the irradiation current is preferably 5 mA to 16 mA. The irradiation time is calculated and determined based on the irradiation dose and equipment parameters.

[0027] The irradiation temperature can be a conventional irradiation temperature in the art, such as room temperature 20°C. Compared with room temperature irradiation, when the irradiation temperature is increased to 190°C-1100°C, the prepared quantum diamond has high NV - The color center density also has the characteristic of high transparency. Therefore, as a preferred embodiment, the irradiation temperature is greater than or equal to 20°C, for example, the irradiation temperature is 20°C-1100°C. More preferably, a high-temperature irradiation method is used: the irradiation temperature is 190°C-1100°C. The irradiation temperature refers to the temperature of the diamond after heating during irradiation.

[0028] In the preparation of NV-containing - During the process of producing diamonds with color centers (quantum diamonds), the diamond is irradiated without further treatment, and the angle between the irradiating electron beam and the diamond can be any angle. The magnetic resonance contrast of the resulting quantum diamonds is generally low. Studies have found that when the diamond is cut along the {111} crystal plane and the angle between the irradiating electron beam and the cut diamond surface is greater than or equal to 50° during irradiation, the magnetic resonance contrast of the resulting quantum diamonds is higher. Therefore, as a more preferred embodiment, the angle between the irradiating electron beam and the cut diamond surface is greater than or equal to 50°, and more preferably, it is between 75° and 90°.

[0029] The magnetic resonance contrast of diamond refers to the NV in diamond - When the color center is measured by magnetic resonance, the degree of signal intensity change, that is, under different magnetic field conditions, NV - The relative change in the intensity of the fluorescence signal generated by the color center. This magnetic resonance contrast is a measure of the NV - The amount of change in the intensity of the optical signal (usually fluorescence) caused by the change in the electron spin state of the color center under the change of the magnetic field. - When the electron spin state of the color center interacts with the external magnetic field, its energy level will split, resulting in different intensities of the fluorescence signal under different magnetic fields.

[0030] In the magnetic resonance research of quantum diamond, the parameter C usually refers to a quantitative index of magnetic resonance contrast, which describes the NV caused by the change of external magnetic field in the magnetic resonance experiment. -The degree of change in the fluorescence signal intensity of the color center. The higher the value of parameter C, the higher the magnetic resonance contrast.

[0031] A third object of the present invention is to provide an application of the quantum diamond described in the first object of the invention or the quantum diamond prepared by the preparation method described in the second object of the invention in the field of quantum sensing.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] This invention prepared for the first time a high NV - Color center density (NV - Quantum diamonds with a color center density higher than 15ppm solve the problem that commonly used methods cannot produce ultra-high-density quantum diamonds.

[0034] The ultra-high NV prepared by the present invention - Color center density of quantum diamond NV - The color center density can be as high as 46ppm; greatly improving the NV of quantum diamond - Color center density provides favorable conditions for its wide application. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is the fluorescence intensity distribution diagram of the quantum diamond prepared in Example 10. DETAILED DESCRIPTION

[0036] The present invention will be described in detail below with reference to specific drawings and embodiments. It is necessary to point out that the following embodiments are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art to the present invention based on the contents of the present invention still fall within the scope of protection of the present invention.

[0037] The reagents used in the examples and comparative examples are all commercially available products.

[0038] Example 1

[0039] (1) Preparation of nitrogen-containing diamond using high temperature and high pressure method:

[0040] Type Ib diamond with a particle size of 0.4 mm was selected as the seed crystal, high-purity graphite powder (purity 99.9 wt%) was selected as the carbon source, and Fe-Ni (Fe 70 Ni 30) alloy as a catalyst for diamond growth. Nitrides (NaN3 / Ba(N3)2) were used as nitrogen sources to control the nitrogen content in the growth medium, with aluminum powder or titanium powder acting as nitrogen absorbers. Diamonds with nitrogen contents of 50 ppm, 100 ppm, 300 ppm, 600 ppm, and 800 ppm were synthesized under high temperature and high pressure (20 GPa, 1500°C) for 60 hours.

[0041] (2) Preparation of ultra-high NV - Color center density in quantum diamond:

[0042] The diamond prepared in step (1) with a particle size of 3 mm and a nitrogen content of 50 ppm was selected and prepared into a sample with a thickness of 0.5 mm. The sample was wrapped with aluminum foil. The sample was irradiated at room temperature with an irradiation energy of 1 MeV, an irradiation current of 1 mA, and an irradiation dose of 1×10 19 cm -2 During irradiation, the angle between the electron beam and the diamond surface was 50 degrees. The irradiated diamond was annealed at a temperature of 550°C, a pressure of 4.5 GPa, and a time of 0.1 hour to obtain quantum diamond.

[0043] Example 2

[0044] Diamond with a nitrogen content of 100 ppm and a particle size of 3 mm prepared in Example 1 was selected and prepared into a sample with a thickness of 2 mm. The sample was wrapped with aluminum foil. The sample was irradiated at room temperature with an irradiation energy of 10 MeV, an irradiation current of 10 mA, and an irradiation dose of 6 × 10 19 cm -2 During irradiation, the angle between the electron beam outlet and the diamond surface was 50°. The irradiated diamond was annealed at a temperature of 550°C, a pressure of 5 GPa, and a time of 0.1 h to obtain quantum diamond.

[0045] Example 3

[0046] Diamond with a nitrogen content of 300 ppm and a particle size of 3 mm prepared in Example 1 was selected and prepared into a sample with a thickness of 2 mm. The sample was wrapped with aluminum foil. The sample was irradiated at room temperature with an irradiation energy of 10 MeV, an irradiation current of 10 mA, and an irradiation dose of 6 × 10 19 cm -2 During irradiation, the angle between the electron beam outlet and the diamond surface was 50°. The irradiated diamond was annealed at a temperature of 550°C, a pressure of 5 GPa, and a time of 0.1 h to obtain quantum diamond.

[0047] Example 4

[0048] Diamond with a nitrogen content of 600 ppm and a particle size of 3 mm prepared in Example 1 was selected and prepared into a sample with a thickness of 2 mm. The sample was wrapped with aluminum foil. The sample was irradiated at room temperature with an irradiation energy of 10 MeV, an irradiation current of 10 mA, and an irradiation dose of 6 × 10 19 cm -2 During irradiation, the angle between the electron beam outlet and the diamond surface was 50°. The irradiated diamond was annealed at a temperature of 550°C, a pressure of 5 GPa, and a time of 0.1 h to obtain quantum diamond.

[0049] Example 5

[0050] Diamond with a nitrogen content of 800 ppm and a particle size of 3 mm prepared in Example 1 was selected and prepared into a sample with a thickness of 2 mm. The sample was wrapped with aluminum foil. The sample was irradiated at room temperature with an irradiation energy of 10 MeV, an irradiation current of 10 mA, and an irradiation dose of 6 × 10 19 cm -2 During irradiation, the angle between the electron beam outlet and the diamond surface was 50°. The irradiated diamond was annealed at a temperature of 550°C, a pressure of 5 GPa, and a time of 0.1 h to obtain quantum diamond.

[0051] Example 6

[0052] Diamond with a nitrogen content of 100 ppm and a particle size of 3 mm prepared in Example 1 was selected to prepare a sample with a thickness of 2 mm. The sample was wrapped in aluminum foil. The sample was irradiated at room temperature with an irradiation energy of 10 MeV, an irradiation current of 10 mA, and an irradiation dose of 6 × 10 19 cm -2 During irradiation, the angle between the electron beam outlet and the diamond surface was 50°. The irradiated diamond was annealed at a temperature of 550°C, a pressure of 6 GPa, and a time of 0.1 h to obtain quantum diamond.

[0053] Example 7

[0054] Diamond with a nitrogen content of 100 ppm and a particle size of 3 mm, prepared in Example 1, was prepared into a 2 mm thick sample. The sample was placed on top of a thermally insulating boron nitride layer and wrapped with aluminum foil. The sample was irradiated at a temperature of 190°C, an energy of 10 MeV, a current of 10 mA, and a dose of 6 × 10 19 cm -2During irradiation, the angle between the electron beam outlet and the diamond surface was 50°. The irradiated diamond was annealed at a temperature of 550°C, a pressure of 5 GPa, and a time of 0.1 h to obtain quantum diamond.

[0055] Example 8

[0056] Diamond with a nitrogen content of 100 ppm and a particle size of 3 mm, prepared in Example 1, was prepared into a 2 mm thick sample. The sample was placed on top of a thermally insulating boron nitride layer and wrapped with aluminum foil. The sample was irradiated at a temperature of 1100°C, an energy of 10 MeV, a current of 10 mA, and a dose of 6 × 10 19 cm -2 During irradiation, the angle between the electron beam outlet and the diamond surface was 50°. The irradiated diamond was annealed at a temperature of 550°C, a pressure of 5 GPa, and a duration of 6 hours to obtain quantum diamond.

[0057] Example 9

[0058] Diamond with a nitrogen content of 100 ppm and a particle size of 3 mm, prepared in Example 1, was prepared into a 2 mm thick sample. The sample was placed on top of a thermally insulating boron nitride layer and wrapped with aluminum foil. The sample was irradiated at a temperature of 1100°C, an energy of 10 MeV, a current of 10 mA, and a dose of 6 × 10 19 cm -2 During irradiation, the angle between the electron beam outlet and the diamond surface was 50 degrees. The irradiated diamond was annealed at a temperature of 1900°C, a pressure of 5 GPa, and a time of 0.1 hour to obtain quantum diamond.

[0059] Example 10

[0060] Diamond with a nitrogen content of 100 ppm and a particle size of 3 mm, prepared in Example 1, was prepared into a 2 mm thick sample. The sample was placed on top of a thermally insulating boron nitride layer and wrapped with aluminum foil. The sample was irradiated at a temperature of 1100°C, an energy of 10 MeV, a current of 10 mA, and a dose of 6 × 10 19 cm -2 During irradiation, the angle between the electron beam outlet and the diamond surface was 50 degrees. The irradiated diamond was annealed at a temperature of 1200°C, a pressure of 5 GPa, and a time of 0.1 hour to obtain quantum diamond.

[0061] Example 11

[0062] Diamond with a nitrogen content of 100 ppm and a particle size of 3 mm, prepared in Example 1, was selected and 2 mm thick along the {111} diamond crystal plane. The sample was placed on top of a thermally insulating boron nitride layer and wrapped with aluminum foil. The sample was irradiated at a temperature of 1100°C, an energy of 10 MeV, a current of 10 mA, and a dose of 6 × 10 19 cm -2 During irradiation, the angle between the electron beam outlet and the diamond cut surface was 50°. The irradiated diamond was annealed at a temperature of 550°C, a pressure of 5 GPa, and a time of 0.1 h to obtain quantum diamond.

[0063] Example 12

[0064] Diamond with a nitrogen content of 100 ppm and a particle size of 3 mm, prepared in Example 1, was selected and 2 mm thick along the {111} diamond crystal plane. The sample was placed on top of a thermally insulating boron nitride layer and wrapped with aluminum foil. The sample was irradiated at a temperature of 1100°C, an energy of 10 MeV, a current of 10 mA, and a dose of 6 × 10 19 cm -2 During irradiation, the angle between the electron beam outlet and the diamond cut surface was 90°. The irradiated diamond was annealed at a temperature of 550°C, a pressure of 5 GPa, and a time of 0.1 h to obtain quantum diamond.

[0065] Comparative Example 1

[0066] Diamond with a nitrogen content of 50 ppm and a particle size of 3 mm prepared in Example 1 was selected and prepared into a sample with a thickness of 1 mm. The sample was wrapped with aluminum foil. The sample was irradiated at room temperature with an irradiation energy of 1 MeV, an irradiation current of 1 mA, and an irradiation dose of 0.1 × 10 19 cm -2 During irradiation, the angle between the electron beam outlet and the diamond surface was 50°. The irradiated diamond was then annealed in a vacuum at 550°C for 0.1 h to obtain quantum diamond.

[0067] Performance Testing

[0068] The quantum diamonds prepared in Examples 1-12 and Comparative Example 1 were tested.

[0069] NV was obtained by quantitative analysis of nitrogen vacancy concentration -Color center density. The quantitative analysis process of nitrogen vacancy concentration is as follows: Under the same experimental conditions (laser power 7mW), the fluorescence count rate of the sample to be tested is compared with that of the standard sample to complete the calibration. The validity of the standard sample is verified by a single NV - The fluorescence count rate measurement verification of the color center under the same experimental conditions. All fluorescence count rate data are calibrated based on the dead time correction factor of the single photon counting module. For example, the fluorescence intensity map (mapping, fluorescence count) of the quantum diamond prepared in Example 10 is as follows Figure 1 As shown. Figure 1 The photon number of the sample (quantum diamond prepared in Example 10) is obtained. The NV of the sample is calculated according to the calculation formula - Color center density. The calculation formula is: number of standard sample photons (measured) / standard sample concentration (known) = number of sample photons (measured) / sample concentration (calculated). The transparency of quantum diamond is usually characterized by spectral transmittance. By measuring the transmittance of diamond at different wavelengths, its transparency can be evaluated. The transmittance is tested using ultraviolet-visible (UV-Vis) absorption spectroscopy. The ultraviolet-visible (UV-Vis) absorption spectrum is measured in transmission mode at room temperature using a customized system equipped with a xenon lamp light source, a 10x objective lens, an adjustable sample holder and a fiber optic spectrometer (FX2000) with a detection range of 400-800 nanometers.

[0070] Coherence time test method: The spin coherence time of NV- color center (coherence time T 2、 Coherence time T2 * ) was quantified. In the experiment, an external magnetic field of 80 Gauss was applied to eliminate the degeneracy of the |m_S=±1> state and the NV - The energy level mixing caused by the four crystal directions of the color center. T2 is a quantum bit (such as NV - The time that the electron spin of the color center remains phase coherent, and T2* refers to the overall decoherence time of the quantum bit.

[0071] The calculation method of magnetic resonance contrast (C) is: C = Imax-Imin / Imax+Imin. Where Imax is the value of NV when there is no microwave excitation. - The maximum intensity of the color center fluorescence signal; Imin is the microwave frequency and NV - The minimum intensity of the fluorescence signal when the color center spin resonance frequency matches. Imax and Imin are obtained through detection.

[0072] The test results of the above tests are shown in Table 1.

[0073] Table 1

[0074]

[0075] The data in Table 1 show that the NV - The color center density is 1.1ppm, and the NV of Examples 1-12 - The color center density is 15.4-46.1ppm. Compared with Comparative Example 1, the NV - The color center density is increased by 1300-4090%. Comparative Example 1 adopts atmospheric vacuum annealing, and Examples 1-12 adopt 4.5-5.5GPa high pressure annealing. This shows that compared with atmospheric vacuum annealing, the high pressure annealing of the present invention improves the NV of quantum diamond. - Color center density; NV was prepared - Ultra-high-density quantum diamond with a color center density greater than 15ppm.

[0076] In contrast to Examples 1-6, in which the diamond was not heated during the irradiation process (room temperature irradiation), Examples 7-12 all heated the diamond to 190°C-1100°C (high temperature irradiation). Compared to Examples 1-6, the transmittance of Examples 7-12 was significantly improved. This indicates that high temperature irradiation can significantly improve the transparency of the prepared quantum diamond compared to room temperature irradiation.

[0077] Compared with the conventional annealing temperature (550°C) used in Examples 1-8, the high temperature (1200-1900°C) annealing was used in Examples 9-10. 2、 T2 * ) were significantly prolonged. This shows that compared with conventional annealing, high temperature annealing can further extend the coherence time of high quantum diamond.

[0078] Compared with Examples 1-10, Examples 11-12 have the same <111> The diamond was cut along a surface perpendicular to the crystal direction; during the irradiation process, the angles between the electron beam outlet and the diamond cutting surface were 50° and 90°. Compared with Examples 1-10, the magnetic resonance contrast of Examples 11-12 was significantly improved. <111> Cutting the surface perpendicular to the crystal direction and limiting the angle between the irradiated electron beam and the cutting surface to be greater than or equal to 50° can further improve the magnetic resonance contrast of quantum diamond.

Claims

1. A type with ultra-high NV - Color center density quantum diamond, characterized by The NV of quantum diamond - The color center density is greater than or equal to 15 ppm, preferably 15 ppm-46 ppm.

2. The method for preparing quantum diamond according to claim 1, wherein: The preparation method comprises sequentially irradiating and annealing the diamond; The diamond is nitrogen-containing diamond, and its nitrogen content is 50ppm-800ppm; The irradiation dose was 0.5×10 19 cm -2 -20×10 19 cm -2 ; The annealing pressure is 4.5 GPa-15 GPa.

3. The method for preparing quantum diamond according to claim 2, wherein: The nitrogen content of the diamond is 100ppm-800ppm; or / and, The irradiation dose was 1×10 19 cm -2 -6×10 19 cm -2 ; or / and, The annealing pressure is 4.5GPa-6GPa.

4. The method for preparing quantum diamond according to claim 2, wherein: The diamond is prepared by a chemical vapor deposition method or a high temperature and high pressure method.

5. The method for preparing quantum diamond according to claim 2, wherein: The annealing temperature is 550℃-1900℃.

6. The method for preparing quantum diamond according to claim 2, wherein: The annealing time is 0.1h-20h, preferably 1h-20h.

7. The method for preparing quantum diamond according to claim 2, wherein: Irradiation energy is 0.2MeV-10MeV; or, The irradiation current is 1mA-16mA.

8. The method for preparing quantum diamond according to claim 2, wherein: The irradiation temperature is 20℃-1100℃.

9. The method for preparing quantum diamond according to claim 2, wherein: Before irradiation, the diamond is cut along the {111} crystal plane; during the irradiation process, the angle between the irradiating electron beam and the diamond cutting surface is greater than or equal to 50 degrees.

10. Use of the quantum diamond according to claim 1 or the quantum diamond prepared by the preparation method according to any one of claims 2 to 9 in the field of quantum sensing.

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