Quantum diamond with high magnetic resonance contrast ratio and preparation method and application thereof

Abstract

The invention relates to the technical field of diamond preparation, in particular to a quantum diamond with high magnetic resonance contrast and a preparation method and application thereof. In the process of preparing the diamond (quantum diamond) containing the NV-color center by adopting an electron irradiation and annealing method, cutting is carried out along a diamond {111} surface; in the irradiation process, the included angle between the irradiation electron beam and the diamond cutting face is limited to be larger than or equal to 45 degrees, and therefore the quantum diamond with the high magnetic resonance contrast ratio is prepared. The prepared quantum diamond is high in magnetic resonance contrast ratio, the magnetic resonance contrast ratio can be increased by more than two times, and the influence of other harmful fluorescence noise on the test sensitivity is avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of diamond preparation, and more particularly to a quantum diamond with high magnetic resonance contrast, a preparation method thereof, and applications thereof. Background Art

[0002] Quantum sensors are devices that utilize the principles of quantum mechanics to perform measurements, boasting extremely high sensitivity and precision. They exploit the properties of quantum states, such as superposition and entanglement, for measurement. There are many types of quantum sensors, including atomic clocks, quantum magnetometers, quantum accelerometers, and quantum thermometers.

[0003] Diamond NV - A color center is a point defect formed by nitrogen atoms replacing carbon atoms in the diamond structure and combining with adjacent vacancies. Quantum diamonds are diamonds that have quantum properties by doping with nitrogen, vacancies and other defects. - Color-centered diamond is a type of quantum diamond.

[0004] When NV - 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. The magnetic resonance contrast of quantum 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 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 a change in the magnetic field.

[0005] Based on nitrogen-vacancy (NV - The sensitivity of a quantum sensor based on a diamond (quantum diamond) containing a color center is closely related to the magnetic resonance contrast between the quantum diamond and the object. The greater the magnetic resonance contrast of the quantum diamond, the higher the sensitivity of the quantum sensor based on the quantum diamond.

[0006] Currently, including NV - The typical method for preparing color-center diamonds involves electron irradiation and vacuum annealing of initially synthesized nitrogen-containing diamonds. However, the resulting quantum diamonds exhibit low magnetic resonance contrast, making them difficult to meet the development needs of quantum sensors. Summary of the Invention

[0007] In order to solve the problem of low magnetic resonance contrast of existing quantum diamonds, the present invention provides a quantum diamond with high magnetic resonance contrast, a preparation method and application thereof.

[0008] In the preparation of NV-containing - In 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 arbitrary. The magnetic resonance contrast of the quantum diamonds produced is generally low. Research has 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 during irradiation is greater than or equal to 45°, the magnetic resonance contrast of the quantum diamonds produced is higher. Therefore, the present invention produces quantum diamonds with high magnetic resonance contrast by cutting the diamond in a specific manner while limiting the angle between the irradiating electron beam and the cut diamond surface.

[0009] One of the objects of the present invention is to provide a quantum diamond with high magnetic resonance contrast.

[0010] The magnetic resonance contrast of the quantum diamond is greater than or equal to 3%. The magnetic resonance contrast is greater than or equal to 3% means that the magnetic resonance contrast parameter C is greater than or equal to 3%.

[0011] In the magnetic resonance study of quantum diamond, the parameter C usually refers to a quantitative index of 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.

[0012] A second object of the present invention is to provide a method for preparing quantum diamond with high magnetic resonance contrast as described in the first object of the invention.

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

[0014] Before irradiation, the diamond is cut along the {111} crystal plane; during irradiation, the angle between the irradiating electron beam and the diamond cutting surface is greater than or equal to 45°, such as 45°, 60°, 75°, 90°, preferably 60-90°, and more preferably 70-85°.

[0015] Compared with existing methods for preparing quantum diamonds, the method of the present invention cuts diamonds in a specific manner while limiting the angle between the irradiated electron beam and the diamond cutting surface, thereby preparing quantum diamonds with high magnetic resonance contrast.

[0016] When the angle between the irradiated electron beam and the diamond cutting surface is greater than or equal to 45 degrees, the magnetic resonance contrast parameter C of the prepared quantum diamond is greater than or equal to 3%;

[0017] When the angle between the irradiated electron beam and the diamond cutting surface is greater than or equal to 70 degrees, the magnetic resonance contrast parameter C of the prepared quantum diamond is greater than or equal to 4.5%;

[0018] When the angle between the irradiated electron beam and the diamond cutting surface is equal to 90 degrees, the magnetic resonance contrast parameter C of the prepared quantum diamond is greater than or equal to 5%.

[0019] The diamond is nitrogen-containing diamond, and the nitrogen content of the nitrogen-containing diamond is 1-800 ppm, such as 5 ppm, 30 ppm, 100 ppm, 300 ppm, 800 ppm, preferably 30-300 ppm.

[0020] The nitrogen-containing diamond can be prepared by any existing method; for example, chemical vapor deposition or high temperature and high pressure methods. As an alternative, the nitrogen-containing diamond with a nitrogen content of 30-300 ppm is prepared by the following method:

[0021] 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.

[0022] The irradiation dose can be a conventional irradiation dose in the art. As a preferred embodiment, the irradiation dose is 0.5×10 19 cm -2 ~20×10 19 cm -2 , preferably 1×10 19 cm -2 ~6×10 19 cm -2 .

[0023] The irradiation energy may be conventional irradiation energy in the art, for example, 0.2-10 MeV. The irradiation energy is selected according to the thickness of the diamond: preferably 1.5-5 MeV for a thickness of 1 mm, and preferably 3-10 MeV for a thickness of 2 mm.

[0024] The irradiation current can be conventional in the art, for example, 1-10 mA. The irradiation current and irradiation time are selected based on the nitrogen content of the diamond: for diamonds with a nitrogen content of 30-100 ppm, the irradiation current is preferably 1-5 mA. The irradiation time is calculated and determined based on the irradiation dose and equipment parameters.

[0025] The irradiation temperature can be conventional in the art, such as room temperature (20°C). However, when the irradiation temperature is raised to 190-1100°C, the resulting quantum diamond exhibits not only high magnetic resonance contrast but also high transparency. Therefore, as a preferred embodiment, the irradiation temperature is 20°C or higher, for example, 20-1100°C. More preferably, a high-temperature irradiation method is employed: the irradiation temperature is 190-1100°C. The irradiation temperature refers to the temperature at which the diamond is heated during irradiation; the temperature at which the diamond is heated is the irradiation temperature.

[0026] The annealing pressure can be 0GP-15GPa. Compared with vacuum annealing (0GPa), when the annealing temperature is 3-6GPa, the NV of the prepared quantum diamond is - The color center density is further improved. Therefore, as a preferred solution, a high-pressure annealing method is adopted: the annealing pressure is 3-6 GPa, preferably 5.0 GPa.

[0027] The annealing temperature can be conventional in the art, such as around 600°C. When the annealing temperature is increased to 1200-1900°C, the quantum diamond produced also exhibits a long coherence time. Therefore, as a preferred approach, high-temperature annealing is employed: the annealing temperature is 1200-1900°C.

[0028] The annealing time can be a conventional annealing time in the art. As a solution, the annealing time is 0.1-6 hours, preferably 0.5-6 hours.

[0029] A third object of the present invention is to provide a quantum diamond with high magnetic resonance contrast as described in the first object of the invention or a quantum diamond with high magnetic resonance contrast prepared by the preparation method as described in the second object of the invention for use in the field of quantum sensing.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] The problem of low magnetic resonance contrast is common in quantum diamonds, which leads to other harmful fluorescence noises that reduce the test sensitivity. -During the process of producing diamonds with color centers (quantum diamonds), the diamond is cut along the {111} planes. During the irradiation process, the angle between the irradiating electron beam and the cut diamond surface is limited to 45° or greater, thereby producing quantum diamonds with high magnetic resonance contrast. The quantum diamonds produced by this method have high magnetic resonance contrast, which can be increased by more than two times, eliminating the impact of other harmful fluorescence noise on test sensitivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a continuous wave optical probe magnetic resonance (CW-ODMR) image of the quantum diamond prepared in Example 6;

[0033] Figure 2 This is the continuous wave optical detection magnetic resonance (CW-ODMR) image of the quantum diamond prepared in Comparative Example 1. DETAILED DESCRIPTION

[0034] 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.

[0035] The reagents used in the following examples and comparative examples are all commercially available products.

[0036] Example 1

[0037] (1) Preparation of nitrogen-containing diamond using high temperature and high pressure method:

[0038] 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 5 ppm, 30 ppm, 100 ppm, 300 ppm, and 800 ppm were synthesized under high temperature and high pressure (20 GPa, 1500°C) for 60 hours.

[0039] (2) Preparation of ultra-high NV - Color center density in quantum diamond:

[0040] Diamonds with a particle size of 3 mm and a nitrogen content of 5 ppm prepared in step (1) were selected and cut along the {111} face of the diamond to obtain 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 1.5 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 exit and the diamond cut surface was 45°. The irradiated diamond was annealed at 600°C, atmospheric pressure, and for 0.1 hour to obtain quantum diamond.

[0041] Example 2

[0042] Diamonds with a particle size of 3 mm and a nitrogen content of 30 ppm prepared in Example 1 were selected and cut along the {111} face of the diamond to obtain a sample with a thickness of 1 mm. The sample was wrapped in 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 exit and the diamond cut surface was 60°. The irradiated diamond was annealed at 600°C, atmospheric pressure, and for 0.1 hour to obtain quantum diamond.

[0043] Example 3

[0044] Diamonds with a particle size of 3 mm and a nitrogen content of 30 ppm prepared in Example 1 were selected and cut along the {111} face of the diamond to obtain a sample with a thickness of 1 mm. The sample was wrapped in 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 exit and the diamond cut surface was 70°. The irradiated diamond was annealed at 600°C, atmospheric pressure, and for 0.1 hour to obtain quantum diamond.

[0045] Example 4

[0046] Diamonds with a particle size of 3 mm and a nitrogen content of 30 ppm prepared in Example 1 were selected and cut along the {111} face of the diamond to obtain a sample with a thickness of 1 mm. The sample was wrapped in 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 -2During irradiation, the angle between the electron beam exit and the diamond cut surface was 75°. The irradiated diamond was annealed at 600°C, atmospheric pressure, and for 0.1 hour to obtain quantum diamond.

[0047] Example 5

[0048] Diamonds with a particle size of 3 mm and a nitrogen content of 30 ppm prepared in Example 1 were selected and cut along the {111} face of the diamond to obtain a sample with a thickness of 1 mm. The sample was wrapped in 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 outlet and the diamond cut surface was 90°. The irradiated diamond was annealed at 600°C, atmospheric pressure, and for 0.1 hour to obtain quantum diamond.

[0049] Example 6

[0050] Diamonds with a particle size of 3 mm and a nitrogen content of 100 ppm prepared in Example 1 were cut along the {111} plane to obtain samples with a thickness of 2 mm. The samples were wrapped in aluminum foil. The samples were irradiated at room temperature with an irradiation energy of 10 MeV, an irradiation current of 5 mA, and an irradiation 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 600°C, atmospheric pressure, and for 0.1 hour to obtain quantum diamond.

[0051] The CW-ODMR image of the quantum diamond prepared in this example is as follows: Figure 1 The horizontal axis reflects the relationship between microwave radiation and NV - The resonance conditions between the electron spin energy levels in the color center. When the microwave frequency matches the energy level splitting frequency, the system undergoes a magnetic resonance transition, resulting in a significant change in the fluorescence signal (ordinate). Each data point on the abscissa corresponds to a state of microwave-spin interaction. The position of the resonance peak (the extreme point on the abscissa) directly reflects the zero-field splitting (ZFS) or other energy level parameters, and is a key basis for analyzing the characteristics of quantum systems. The ordinate is the fluorescence contrast. When the microwave frequency resonates with the spin energy level (that is, the abscissa corresponds to the resonance point), the spin state undergoes a transition, resulting in a significant decrease in fluorescence intensity, forming a resonance valley. 1 minus the fluorescence intensity corresponding to the resonance valley is the magnetic resonance intensity (C, %), which is 5.4.

[0052] Example 7

[0053] Diamonds with a particle size of 3 mm and a nitrogen content of 100 ppm prepared in Example 1 were cut along the {111} plane to obtain samples with a thickness of 2 mm. The samples were wrapped in aluminum foil. The samples were irradiated at room temperature with an irradiation energy of 10 MeV, an irradiation current of 5 mA, and an irradiation 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 600°C, atmospheric pressure, and for 0.1 hour to obtain quantum diamond.

[0054] Example 8

[0055] Diamonds with a particle size of 3 mm and a nitrogen content of 800 ppm prepared in Example 1 were selected and cut along the {111} face of the diamond to obtain 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 5 mA, and an irradiation 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 600°C, atmospheric pressure, and for 0.1 hour to obtain quantum diamond.

[0056] Example 9

[0057] Diamonds with a particle size of 3 mm and a nitrogen content of 100 ppm prepared in Example 1 were selected and cut along the {111} face of the diamond to obtain 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 5 mA, and an irradiation dose of 6 × 10 19 cm -2 During irradiation, the angle between the electron beam exit and the diamond cut surface was 90°. The irradiated diamond was annealed at 600°C, 3 GPa, and 0.1 h to obtain quantum diamond.

[0058] Example 10

[0059] Diamonds with a particle size of 3 mm and a nitrogen content of 100 ppm prepared in Example 1 were selected and cut along the {111} face of the diamond to obtain 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 5 mA, and an irradiation dose of 6 × 10 19 cm -2During irradiation, the angle between the electron beam exit and the diamond cut surface was 90°. The irradiated diamond was annealed at 600°C, 6 GPa, and 0.1 h to obtain quantum diamond.

[0060] Example 11

[0061] Diamonds with a particle size of 3 mm and a nitrogen content of 100 ppm prepared in Example 1 were cut along the {111} plane to obtain samples with a thickness of 2 mm. The samples were wrapped in aluminum foil. The samples were irradiated at room temperature with an irradiation energy of 10 MeV, an irradiation current of 5 mA, and an irradiation 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 1200°C, atmospheric pressure, and for 0.1 hour to obtain quantum diamond.

[0062] Example 12

[0063] Diamonds with a particle size of 3 mm and a nitrogen content of 100 ppm prepared in Example 1 were cut along the {111} plane to obtain samples with a thickness of 2 mm. The samples were wrapped in aluminum foil. The samples were irradiated at room temperature with an irradiation energy of 10 MeV, an irradiation current of 5 mA, and an irradiation dose of 6 × 10 19 cm -2 During irradiation, the angle between the electron beam exit and the diamond cut surface was 90°. The irradiated diamond was annealed at 1900°C, atmospheric pressure, and for 0.1 hour to obtain quantum diamond.

[0064] Example 13

[0065] Diamonds with a particle size of 3 mm and a nitrogen content of 100 ppm, prepared in Example 1, were selected and cut along the {111} plane to obtain samples with a thickness of 2 mm. The samples were placed on top of the insulating boron nitride layer and wrapped with aluminum foil. The samples were irradiated at a temperature of 190°C, an energy of 10 MeV, a current of 5 mA, and a dose of 6 × 10 19 cm -2 During the irradiation process, the angle between the electron beam outlet and the diamond cut surface was 90°. The irradiated diamond was annealed at 600°C, atmospheric pressure, and for 0.1 hour to obtain quantum diamond.

[0066] Example 14

[0067] Diamonds with a particle size of 3 mm and a nitrogen content of 100 ppm, prepared in Example 1, were selected and cut along the {111} plane to obtain 2 mm thick samples. The samples were placed on top of the insulating boron nitride layer and wrapped with aluminum foil. The samples were irradiated at a temperature of 1100°C, an energy of 10 MeV, a current of 5 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 600°C, atmospheric pressure, and for 0.1 hour to obtain quantum diamond.

[0068] Comparative Example 1

[0069] Diamonds with a particle size of 3 mm and a nitrogen content of 5 ppm prepared in Example 1 were selected and cut along the {111} face of the diamond to obtain a sample with a thickness of 1 mm. The sample was wrapped in 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 exit and the diamond cut surface was 15°. The irradiated diamond was annealed at 600°C, atmospheric pressure, and for 0.1 hour to obtain quantum diamond.

[0070] The CW-ODMR image of the quantum diamond prepared in this comparative example is as follows: Figure 1 The horizontal axis reflects the relationship between microwave radiation and NV - The resonance conditions between the electron spin energy levels in the color center. When the microwave frequency matches the energy level splitting frequency, the system undergoes a magnetic resonance transition, resulting in a significant change in the fluorescence signal (ordinate). Each data point on the abscissa corresponds to a state of microwave-spin interaction. The position of the resonance peak (the extreme point on the abscissa) directly reflects the zero-field splitting (ZFS) or other energy level parameters, and is a key basis for analyzing the characteristics of quantum systems. The ordinate is the fluorescence contrast. When the microwave frequency resonates with the spin energy level (that is, the abscissa corresponds to the resonance point), the spin state undergoes a transition, resulting in a significant decrease in fluorescence intensity, forming a resonance valley. 1 minus the fluorescence intensity corresponding to the resonance valley is the magnetic resonance intensity (C, %) value of 2.1.

[0071] Performance Testing

[0072] The quantum diamonds prepared in Examples 1-14 and Comparative Example 1 were tested.

[0073] 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 - Fluorescence count rate measurement verification of color centers 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.

[0074] The transparency of quantum diamonds is typically characterized by spectral transmittance. Transparency can be assessed by measuring the transmittance of diamond at different wavelengths. Transmittance is tested using ultraviolet-visible (UV-Vis) absorption spectroscopy. UV-Vis absorption spectra are measured in transmission mode at room temperature using a custom 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 nm.

[0075] Coherence time test method: NV is measured using standard free induction decay (FID) and Hahn echo sequence. - The spin coherence time of the color center (coherence time T2, decoherence 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.

[0076] The calculation method of magnetic resonance contrast (C) is: C = I max -I min / I max +I min Among them, Imax is when there is no microwave excitation, NV - 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.

[0077] The test results of the above tests are shown in Table 1.

[0078] Table 1

[0079]

[0080] The data in Table 1 show that the magnetic resonance contrast (C) of Comparative Example 1 is 2.1%, while that of Examples 1-14 is 3.1-5.4%. Compared with Comparative Example 1, the magnetic resonance contrast (C) of Examples 1-14 is improved by 48-157%. In Comparative Example 1 and Examples 1-14, diamond {111} planes were cut before irradiation. During irradiation, the angle between the electron beam outlet and the cut diamond surface was 15° in Comparative Example 1, while the angle between the electron beam outlet and the cut diamond surface was 45°-90° in Examples 1-14. This indicates that limiting the angle between the electron beam outlet and the cut diamond surface to 45°-90°, compared to a 15° angle, can improve the magnetic resonance contrast of quantum diamond. Cutting along the diamond {111} planes and limiting the angle between the irradiating electron beam and the cut diamond surface to greater than 45° can produce quantum diamonds with high magnetic resonance contrast.

[0081] Compared with Example 1-10, which adopts conventional annealing temperature (600°C), Example 11-12 adopts high temperature annealing (1200-1900°C). Compared with Example 1-10, the coherence time (T2, T2 * ) is significantly extended. This shows that compared with conventional annealing, high temperature annealing can further extend the coherence time of high quantum diamond.

[0082] In contrast to Examples 1-10, in which the diamond was not heated during the irradiation process (room temperature irradiation), Examples 13-14 all heated the diamond to 190-1100°C during the irradiation process (high temperature irradiation). Compared to Examples 1-10, the transmittance of Examples 13-14 was significantly improved. This indicates that high temperature irradiation can significantly improve the transparency of the prepared quantum diamond compared to room temperature irradiation.

[0083] Compared with Example 7, which adopts atmospheric pressure vacuum annealing, Examples 9-10 adopt 3-6 GPa high pressure annealing. Compared with Example 7, the NV of quantum diamond prepared in Examples 9-10 is - The color center density is significantly improved. It can be seen that compared with normal pressure vacuum annealing, high pressure annealing can further improve the NV of quantum diamond. - Color center density.

Claims

1. A quantum diamond with high magnetic resonance contrast, characterized in that The magnetic resonance contrast of the quantum diamond is greater than or equal to 3%.

2. A method for preparing quantum diamond according to claim 1, characterized in that: The preparation method comprises sequentially irradiating and annealing the diamond; 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 45°, preferably 60-90°.

3. The method for preparing quantum diamond according to claim 2, wherein: The nitrogen content of the diamond is 1-800 ppm, preferably 30-300 ppm.

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 irradiation dose was 0.5×10 19 cm -2 ~20×10 19 cm -2 , preferably 1×10 19 cm -2 ~6×10 19 cm -2 .

6. The method for preparing quantum diamond according to claim 2, wherein: Irradiation energy is 0.2-10 MeV; or / and, The irradiation current is 1-5mA.

7. The method for preparing quantum diamond according to claim 2, wherein: The annealing pressure is 0-15 GPa, preferably 3-6 GPa.

8. The method for preparing quantum diamond according to claim 2, wherein: The annealing temperature is 600-1900°C, preferably 1200-1900°C.

9. The method for preparing quantum diamond according to claim 2, wherein: The annealing time is 0.1-6 hours, preferably 0.5-6 hours.

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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