A diamond spin quantum sensor and a preparation method thereof

Abstract

This invention belongs to the field of quantum sensors and discloses a diamond spin quantum sensor and its fabrication method. The fabrication method includes: cleaning and polishing a single-crystal diamond substrate; and preparing a nitrogen-vacancy color center with a density greater than 10 on the single-crystal diamond substrate using microwave plasma chemical vapor deposition. 16 cm ‑3 A diamond spin quantum sensor was obtained by fabricating an antiferromagnetic NiO thin film on a diamond film using radio frequency magnetron sputtering. This invention comprises a diamond thin film with a high concentration of nitrogen-vacancy centers. Nitrogen-vacancy center measurements exhibit extremely high spatial resolution and can detect nanoscale magnetic field changes. The diamond spin quantum sensor is applied to the precise measurement of the magnetic moment of antiferromagnetic thin films and the magnetic coupling effect at the interface of antiferromagnetic / ferromagnetic heterojunctions. Furthermore, its fabrication method is simple and economical, providing a possibility for the application of diamond nitrogen-vacancy center materials in the field of quantum magnetic sensors.

Description

Technical Field

[0001] This invention relates to the field of quantum sensor technology, and in particular to a diamond spin quantum sensor and its fabrication method. Background Technology

[0002] The magnetic moment of antiferromagnetic thin films is usually small and localized, making it difficult to accurately measure using traditional magnetic measurement methods.

[0003] Diamond nitrogen-vacancy color centers possess nanoscale spatial resolution and extremely high magnetic field sensitivity, enabling the detection of these minute magnetic moments. The magnetic structure of antiferromagnetic thin films can be reconstructed by analyzing changes in optically detected magnetic resonance (ODMR) spectral lines. Firstly, diamond nitrogen-vacancy color centers can achieve direct imaging of antiferromagnetic domains, revealing their size, shape, and distribution. Secondly, by measuring temperature-dependent ODMR spectral lines, the magnetic order phase transition process of antiferromagnetic materials can be studied. Furthermore, spin waves in antiferromagnetic materials can be detected, allowing for the study of spin wave propagation characteristics. Finally, they can be used to investigate interfacial magnetic coupling effects in antiferromagnetic / ferromagnetic heterostructures, providing an important experimental foundation for the development of novel spintronic devices. Based on these technological advancements, providing highly sensitive and precise magnetic field measurement methods and devices remains a challenge that needs to be addressed.

[0004] Therefore, existing technologies still need to be improved and developed. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the purpose of this invention is to provide a diamond spin quantum sensor and its preparation method, which aims to solve the problem that traditional magnetic measurement methods are difficult to accurately measure antiferromagnetic thin films.

[0006] The technical solution of the present invention is as follows:

[0007] A first aspect of the present invention provides a method for fabricating a diamond spin quantum sensor, comprising the steps of:

[0008] S10. Clean and polish the Ib-type (111) single-crystal diamond substrate.

[0009] S20. A nitrogen-doped diamond film is prepared on the single-crystal diamond substrate treated in step S10 using microwave plasma chemical vapor deposition (MPCVD). The nitrogen-vacancy center density of the diamond film is greater than 10. 16 cm-3 ;

[0010] S30. An antiferromagnetic NiO film is prepared on the nitrogen-doped diamond film using radio frequency magnetron sputtering to obtain the diamond spin quantum sensor.

[0011] Optionally, step S10, the step of cleaning and polishing the single-crystal diamond substrate, includes:

[0012] The Ib type (111) single crystal diamond substrate was boiled in a mixed solution of 95% concentrated sulfuric acid and 30% hydrogen peroxide with a volume ratio of 3:1. Then, the single crystal diamond substrate was repeatedly cleaned with acetone, ethanol and deionized water. After being dried with nitrogen, the surface of the single crystal diamond substrate was polished along the

[112] direction at an offset angle of 2°.

[0013] Optionally, in step S20, the microwave plasma chemical vapor deposition method uses CH4 as the source gas, H2 as the carrier gas, and N2 as the nitrogen source to deposit on the single-crystal diamond substrate.

[0014] Optionally, CH4 accounts for 4% of the flow in H2; N2 accounts for 0.002% to 0.04% of the flow in H2.

[0015] Optionally, during the deposition process, the pressure range is 140–160 Torr, and the microwave power is 4.5–5.0 kW.

[0016] Optionally, during the deposition process, the temperature of the single-crystal diamond substrate is 1000–1100°C, and the plasma temperature is 5000K.

[0017] Optionally, in step S20, the thickness of the nitrogen-doped diamond film is 120–150 μm.

[0018] Optionally, in step S30, the step of preparing an antiferromagnetic NiO film on a diamond film using radio frequency magnetron sputtering includes: [the process is described in the original text, but the provided text is incomplete and requires further context to translate accurately.] -8 Under mTorr conditions, using Ar as the working gas and a NiO ceramic target as the target material, the antiferromagnetic NiO thin film was prepared by magnetron sputtering on the diamond thin film for 40-60 minutes.

[0019] Optionally, the thickness of the antiferromagnetic NiO thin film is 20–30 nm.

[0020] In a second aspect, the present invention provides a diamond spin quantum sensor, which is prepared by the method described above.

[0021] Beneficial effects:

[0022] This invention provides a diamond spin quantum sensor and its fabrication method. A high-concentration nitrogen-vacancy center (NCC) diamond thin film was prepared using microwave plasma chemical vapor deposition (IPCVD), and a diamond spin quantum sensor was further fabricated. Compared to traditional techniques, NCC measurement offers extremely high spatial resolution, enabling the detection of nanoscale magnetic field changes and exhibiting high sensitivity to weak magnetic fields. It can also indirectly measure the magnetic properties of antiferromagnetic materials. Utilizing the ability of NCC to detect magnetic fields is crucial for studying the spin transport mechanism of antiferromagnetic materials and is essential for designing efficient spintronic devices. The diamond spin quantum sensor of this invention can be applied to the precise measurement of the magnetic moment of antiferromagnetic thin films and the magnetic coupling effect at the interface of antiferromagnetic / ferromagnetic heterojunctions, enabling the measurement of weak magnetic moments. Furthermore, its fabrication method is simple, economical, and suitable for industrial production, thus opening up possibilities for the application of diamond NCC materials in the field of quantum magnetic sensors. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the fabrication process of the diamond spin quantum sensor described in this embodiment of the invention.

[0024] Figure 2 This is a schematic diagram of the structure of the diamond spin quantum sensor described in an embodiment of the present invention. Detailed Implementation

[0025] This invention provides a diamond spin quantum sensor and its fabrication method. To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the invention is further described in detail below. It should be understood that the specific embodiments described herein are only for explaining the invention and are not intended to limit the invention.

[0026] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0027] This invention provides a method for fabricating a diamond spin quantum sensor, such as... Figure 1 As shown, the steps include:

[0028] S10. Clean and polish the Ib-type (111) single-crystal diamond substrate.

[0029] S20. A nitrogen-doped diamond film is prepared on the single-crystal diamond substrate treated in step S10 using microwave plasma chemical vapor deposition. The nitrogen-vacancy center density of the diamond film is greater than 10. 16 cm -3 ;

[0030] S30. An antiferromagnetic NiO film is prepared on the nitrogen-doped diamond film using radio frequency magnetron sputtering to obtain the diamond spin quantum sensor.

[0031] In some embodiments, step S10, the step of cleaning and polishing the single-crystal diamond substrate, includes:

[0032] The Ib type (111) single crystal diamond substrate was boiled in a mixed solution of 95% concentrated sulfuric acid and 30% hydrogen peroxide with a volume ratio of 3:1. Then, the single crystal diamond substrate was repeatedly cleaned with acetone, ethanol and deionized water. After being dried with nitrogen, the surface of the single crystal diamond substrate was polished along the

[112] direction at an offset angle of 2°.

[0033] This invention selects a (111) oriented single-crystal diamond substrate, ensuring that the diamond nitrogen-vacancy color centers prepared by microwave plasma chemical vapor deposition form a perfect alignment along the

[111] direction, achieving a theoretical maximum contrast of approximately 30%. The purpose of polishing the surface of the single-crystal diamond substrate along the

[112] direction at an offset angle of approximately 2° is to achieve stepped flow growth, increasing the concentration of diamond nitrogen-vacancy color centers and thus improving the magnetic detection sensitivity of the diamond spin quantum sensor. This is because the magnetic detection sensitivity (η) of the diamond spin quantum sensor can be expressed as… Where C is the contrast ratio and N is the nitrogen-vacancy color center density. Here, V represents the spin decoherence time, and V is the volume of the laser-excited diamond film. Therefore, under the same conditions, increasing the nitrogen-vacancy center density can improve the magnetic detection sensitivity of the diamond spin quantum sensor. Conversely, without polishing under these conditions, the grown diamond film has a lower nitrogen-vacancy center concentration.

[0034] In some embodiments, in step S20, the microwave plasma chemical vapor deposition method uses CH4 as the source gas, H2 as the carrier gas, and N2 as the nitrogen source to deposit on the single-crystal diamond substrate.

[0035] In some specific implementations, CH4 accounts for 4% of the flow rate in H2; N2 accounts for 0.002% to 0.04% of the flow rate in H2.

[0036] In some specific implementations, the pressure range during deposition is 140–160 Torr, and the microwave power is 4.5–5.0 kW.

[0037] In some specific embodiments, during the deposition process, the temperature of the single-crystal diamond substrate is 1000–1100°C, and the plasma temperature is 5000 K. Within this temperature range, a nitrogen-vacancy center density greater than 10 can be obtained. 16 cm-3 Diamond film.

[0038] This invention achieves the preparation of nitrogen-doped diamond films with high concentration and high uniformity by incorporating a controllable amount of N2 to change the proportion of N2 in H2 and by controlling the plasma temperature and microwave power to optimize the arrangement and concentration of nitrogen-vacancy color centers in diamond films.

[0039] In some embodiments, in step S20, the thickness of the nitrogen-doped diamond film is 120–150 μm. The required diamond film thickness can be obtained by controlling the deposition time; within a certain range, a longer deposition time results in a thicker diamond film.

[0040] In some embodiments, step S30, which involves preparing an antiferromagnetic NiO film on a diamond film using radio frequency magnetron sputtering, includes: operating under a vacuum level less than 5 x 10⁻⁶. -8 Under mTorr conditions, using Ar as the working gas and a NiO ceramic target as the target material, the antiferromagnetic NiO thin film was prepared by magnetron sputtering on the diamond thin film for 40-60 minutes.

[0041] In some specific embodiments, the thickness of the antiferromagnetic NiO film is 20–30 nm.

[0042] This invention provides a diamond spin quantum sensor, fabricated using the method described above. A microwave antenna is used to apply a uniformly varying microwave signal to a diamond / antiferromagnetic thin-film heterojunction via a microwave signal generator. Specifically, a planar antenna is used when applying the microwave signal. Compared to linear or helical copper wires, planar antennas can achieve a wide-range, high-intensity, and large-area uniform microwave magnetic field. This allows for the acquisition of a graph showing the relationship between the characteristic peak corresponding to the nitrogen-vacancy color center in the PL spectrum and the microwave signal. Combined with relevant computer software, the data can be acquired. The diamond spin quantum sensor provided by this invention can measure weak magnetic moments.

[0043] The following detailed description uses specific examples.

[0044] Example 1

[0045] The specific steps for preparing the diamond spin quantum sensor in this embodiment are as follows: Microwave plasma chemical vapor deposition equipment was used, with CH4 as the source gas, H2 as the carrier gas, and N2 as the nitrogen source. Ib-type HPHT(111) diamond was used as the substrate for epitaxial growth. The substrate size was 1mm × 1mm × 0.3mm. The Ib-type (111) diamond substrate was immersed in a mixed solution of 95% concentrated sulfuric acid and 30% hydrogen peroxide (volume ratio 3:1) for acid boiling to remove impurities from the diamond surface. The diamond was then repeatedly cleaned with acetone, ethanol, and deionized water, and dried with nitrogen gas for later use. Subsequently, polishing was performed along the

[112] direction at an offset angle of approximately 2° to achieve stepped flow growth. A controllable amount of N2 was incorporated, with the N2 content as the variable factor. The proportion of CH4 in H2 was 4%, and the proportion of N2 in H2 was 0.04%. The substrate temperature was 1000℃, the plasma temperature was 5000K, and the deposition time was 4 hours, resulting in a film thickness of 130μm. An antiferromagnetic NiO film was prepared on a diamond film using radio frequency magnetron sputtering with a vacuum degree less than 5 x 10⁻⁶. -8 A NiO thin film with a thickness of 30 nm was fabricated using an mTorr sputtering method, a substrate temperature of room temperature, an Ar gas flow rate of 32 sccm, and a sputtering time of 60 min. Finally, a diamond spin quantum sensor was obtained, the structure of which is shown in the schematic diagram below. Figure 2 As shown.

[0046] A sample of the aforementioned diamond spin quantum sensor was placed on a microwave antenna, and a uniformly varying microwave signal was applied to it using a microwave signal generator. This demonstrated that the diamond spin quantum sensor can measure weak magnetic moments. When applying the microwave signal, a planar antenna was used. Compared to straight or spiral copper wires, planar antennas can achieve a wide-range, high-intensity, and large-area uniform microwave magnetic field.

[0047] The proportion of CH4 in H2 is 4%, and the proportion of N2 in H2 is 0.002% to 0.04%. The film thickness is 130 μm.

[0048] In summary, this invention prepared a high-concentration nitrogen-vacancy center diamond film using microwave plasma chemical vapor deposition and further fabricated a diamond spin quantum sensor. The high-concentration nitrogen-vacancy center measurement exhibits extremely high spatial resolution, enabling the detection of nanoscale magnetic field changes and demonstrating high sensitivity to weak magnetic fields, thus allowing for the indirect measurement of the magnetic properties of antiferromagnetic materials. This invention's diamond spin quantum sensor enables the measurement of weak magnetic moments, opening up possibilities for the application of diamond nitrogen-vacancy center materials in the field of quantum magnetic sensors.

[0049] It should be understood that the application of the present invention is not limited to the examples above. Those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A method for fabricating a diamond spin quantum sensor, characterized in that, Including the following steps: S10. Clean and polish the Ib-type (111) single-crystal diamond substrate. S20. A nitrogen-doped diamond film is prepared on the single-crystal diamond substrate treated in step S10 using microwave plasma chemical vapor deposition. The nitrogen-vacancy center density of the diamond film is greater than 10. 16 cm -3 ; S30. An antiferromagnetic NiO film is prepared on the nitrogen-doped diamond film using radio frequency magnetron sputtering to obtain the diamond spin quantum sensor.

2. The method for fabricating a diamond spin quantum sensor according to claim 1, characterized in that, Step S10, the steps of cleaning and polishing the Ib-type (111) single-crystal diamond substrate, include: The Ib type (111) single crystal diamond substrate was boiled in a mixed solution of 95% concentrated sulfuric acid and 30% hydrogen peroxide with a volume ratio of 3:

1. Then, the single crystal diamond substrate was repeatedly cleaned with acetone, ethanol and deionized water. After being dried with nitrogen, the surface of the single crystal diamond substrate was polished along the [112] direction at an offset angle of 2°.

3. The method for fabricating a diamond spin quantum sensor according to claim 1, characterized in that, In step S20, the microwave plasma chemical vapor deposition method uses CH4 as the source gas, H2 as the carrier gas, and N2 as the nitrogen source to deposit on the single-crystal diamond substrate.

4. The method for fabricating a diamond spin quantum sensor according to claim 3, characterized in that, CH4 accounts for 4% of the H2 flow; N2 accounts for 0.002% to 0.04% of the H2 flow.

5. The method for fabricating a diamond spin quantum sensor according to claim 3, characterized in that, During the deposition process, the pressure range is 140–160 Torr, and the microwave power is 4.5–5.0 kW.

6. The method for fabricating a diamond spin quantum sensor according to claim 3, characterized in that, During the deposition process, the temperature of the single-crystal diamond substrate is 1000–1100℃, and the plasma temperature is 5000K.

7. The method for fabricating a diamond spin quantum sensor according to claim 1, characterized in that, In step S20, the thickness of the nitrogen-doped diamond film is 120–150 μm.

8. The method for fabricating a diamond spin quantum sensor according to claim 1, characterized in that, Step S30, the step of preparing an antiferromagnetic NiO film on a diamond film using radio frequency magnetron sputtering, includes: [the process is described in the original text, but the provided text is incomplete and requires further context to translate accurately.] -8 Under mTorr conditions, using Ar as the working gas and a NiO ceramic target as the target material, the antiferromagnetic NiO thin film was prepared by magnetron sputtering on the diamond thin film for 40-60 minutes.

9. The method for fabricating a diamond spin quantum sensor according to claim 8, characterized in that, The thickness of the antiferromagnetic NiO thin film is 20–30 nm.

10. A diamond spin quantum sensor, characterized in that, It is prepared by the method for preparing the diamond spin quantum sensor as described in claims 1-9.

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