NV color center diamond MEMS magnetic field detection device and method under constant microwave frequency

Abstract

The invention discloses an NV color center diamond MEMS magnetic field detection device and method under a constant microwave frequency, and aims to solve the problems that an existing diamond MEMS magnetic sensor enables an NV color center electronic ground state energy level to resonate with a microwave frequency based on microwave frequency sweeping, and the microwave frequency sweeping is unstable. The magnetic field detection method comprises the steps that 1, a laser device is adopted to emit laser to irradiate the NV color center diamond cantilever beam MEMS magnetic sensor, when electrons fall back to a ground state from an excited state, the NV color center radiates red fluorescence, and the energy range determined by fluorescence spectrums of the excited light and the red fluorescence is the zero field splitting energy level; 2, determining the microwave energy to be Emw according to the constant microwave frequency, wherein the magnetic sensor is arranged in an external magnetic field environment; and 3, applying external stress to the diamond cantilever beam through a stress applying device, and when the electron energy level and the microwave frequency reach a resonance state, calculating to obtain the magnetic field energy. The external magnetic field is detected under the constant microwave frequency, and control over microwave conditions is simplified.

Description

Technical Field

[0001] The present invention belongs to the field of MEMS magnetic sensors, and particularly relates to an NV - center diamond MEMS magnetic field detection device and method under a constant microwave frequency. Background Art

[0002] The applications of magnetic materials in artificial manufacturing and research have increased significantly. The importance of magnetic measurement and testing applications will continue to rise, along with corresponding technological trends, such as new energy vehicles, robotics, miniaturization and automation technologies, and promising magnetic materials (e.g., polymer - bonded magnets and magnetic shape - memory alloys). Meanwhile, the growing demand for sensors for static and dynamic magnetic measurement applications has pushed existing sensor technologies to their limits. Magnetic sensor technology provides a new perspective for the field of magnetic measurement and testing. At the same time, the development of MEMS technology has made it possible to fabricate microstructures on chips, while reducing the cost of micro - electromechanical systems and enabling many tasks that cannot be accomplished by large - scale electromechanical systems, thus promoting the development of magnetic field sensors. MEMS magnetic field sensors have advantages that cannot be compared with traditional sensors, such as small size, light weight, low power consumption, low cost, high reliability, excellent performance, and powerful functions.

[0003] Current diamond MEMS magnetic sensors often rely on microwave frequency sweeping to resonate the electronic ground - state energy level of the NV center with the microwave frequency, thereby changing the electronic energy level, and further causing Zeeman splitting under the action of an external magnetic field. However, for a constant microwave with a fixed frequency, the above - mentioned process cannot be used to measure the external magnetic field. Due to its mature process and comprehensive performance, silicon - based is the most commonly used material for MEMS cantilever beam structures. However, silicon - based materials have various defects: elemental Si has poor mechanical properties, Si3N4 has high internal stress and complex deposition processes, and SiC has high manufacturing costs and may have thermal mismatch problems with other materials.

[0004] Diamond has extremely excellent physical properties, such as ultra - high mechanical strength, high thermal conductivity, and low thermal expansion coefficient, etc., which makes diamond an excellent material for fabricating high - performance MEMS devices. During the past nearly decade, significant achievements have been made in the fields of polycrystalline diamond, nanocrystalline diamond, and single - crystal diamond (SCD). However, grain boundaries and sp2 contained in polycrystalline diamond limit the final performance and reliability of MEMS devices. To achieve MEMS resonators with ultra - high Q - factors, single - crystal diamond is an ideal material. Aiming at the deficiencies of the above - mentioned existing technologies, it is urgent to develop a diamond MEMS magnetic field detection device and method that can be used for constant microwave frequencies, is simple to manufacture, and has fast operation. Summary of the Invention

[0005] The object of the present invention is to solve the problem that in the existing diamond MEMS magnetic sensors, the microwave frequency is swept to make the electron ground state energy level of the NV color center resonate with the microwave frequency, and the microwave frequency sweeping is unstable, and to provide an NV color center diamond MEMS magnetic field detection device and method under a constant microwave frequency.

[0006] The NV color center diamond MEMS magnetic field detection method based on a constant microwave frequency according to the present invention is realized according to the following steps:

[0007] First, a laser is used to emit laser light to irradiate the NV color center diamond cantilever beam MEMS magnetic sensor. After the NV color centers in the diamond cantilever beam of the diamond cantilever beam MEMS magnetic sensor are irradiated by the laser light, the internal electrons are pumped from the ground state to the excited state. When the electrons fall back from the excited state to the ground state, the NV color centers emit red fluorescence. The energy level difference between the ground state and the excited state, that is, the zero-field splitting energy level E, is determined by the fluorescence spectra of the excitation light and the red fluorescence. D ;

[0008] Second, a constant microwave is input to the NV color center diamond cantilever beam MEMS magnetic sensor through a microwave generating device. The energy of the microwave is determined to be E by the frequency of the constant microwave, and then the NV color center diamond cantilever beam MEMS magnetic sensor is arranged in an external magnetic field environment. mw

[0009] Third, an external stress is applied to the diamond cantilever beam of the NV color center diamond cantilever beam MEMS magnetic sensor through a stress applying device, and the magnitude of the external stress is adjusted. When the fluorescence intensity received by the fluorescence receiving device becomes weaker, the electron energy level and the microwave frequency reach the resonance state. At this time, the relationship between the energies satisfies formula (1):

[0010] E D + E B + E σ = E mw (1)

[0011] Then, the magnitude of the external stress is converted into the energy difference E, and the magnetic field energy E is obtained from formula (1), thereby obtaining the magnitude of the magnetic field in the external magnetic field environment. σ B

[0012] The NV - center diamond MEMS magnetic field detection device based on a constant microwave frequency of the present invention includes an NV - center diamond cantilever beam MEMS magnetic sensor, a laser emission and fluorescence reception device, a microwave generation device, and a stress application device. The laser emission and fluorescence reception device emits a laser to irradiate the NV - center diamond cantilever beam MEMS magnetic sensor, and the fluorescence radiated by the NV - centers in the NV - center diamond cantilever beam is received by the laser emission and fluorescence reception device again. After receiving the fluorescence signal, the microwave generation device inputs a constant microwave to the NV - center diamond cantilever beam MEMS magnetic sensor, and at the same time, the stress application device applies an external stress to the diamond cantilever beam in the NV - center diamond cantilever beam MEMS magnetic sensor.

[0013] The diamond MEMS magnetic field detection device and method under a constant microwave frequency of the present invention have the following beneficial effects:

[0014] 1. Using diamond material as the main material of the MEMS cantilever beam structure, compared with traditional silicon - based materials, it has excellent mechanical properties, thermal conductivity, and excellent chemical inertness.

[0015] 2. Utilizing the characteristic that the electron spin energy levels of diamond NV - centers change under stress, the measurement of the external magnetic field is realized under the combined action of a constant microwave frequency and stress regulation.

[0016] 3. The method for detecting the external magnetic field with a constant microwave frequency in the present invention detects the external magnetic field at a constant microwave frequency. Compared with the existing method of making the electron ground - state energy level of the NV - center resonate with the microwave frequency by microwave frequency sweeping, it simplifies the control of microwave conditions and avoids the instability of microwave frequency sweeping. Description of the Drawings

[0017] Figure 1 It is a schematic structural diagram of the NV - center diamond MEMS magnetic field detection device based on a constant microwave frequency of the present invention for detecting the magnetic field;

[0018] Figure 2 It is a schematic diagram of the change of electron energy levels in the NV - center during the magnetic field measurement process;

[0019] Figure 3 It is a schematic diagram of applying stress to the cantilever beam in the NV - center diamond cantilever beam MEMS magnetic sensor in the embodiment. Detailed Embodiments

[0020] Detailed Embodiment 1: The NV - center diamond MEMS magnetic field detection method based on a constant microwave frequency of the present embodiment is implemented according to the following steps:

[0021] 1. Use a laser to emit laser light to irradiate an NV - color - center diamond cantilever MEMS magnetic sensor. After the NV - color - centers in the diamond cantilever of the diamond cantilever MEMS magnetic sensor are irradiated by the laser, the internal electrons are pumped from the ground state to the excited state. When the electrons fall back from the excited state to the ground state, the NV - color - centers emit red fluorescence. The energy level difference between the ground state and the excited state, which is the zero - field splitting energy level E, is determined from the fluorescence spectra of the excitation light and the red fluorescence. D ;

[0022] 2. Input a constant microwave to the NV - color - center diamond cantilever MEMS magnetic sensor through a microwave generating device. Determine the energy of the microwave as E mw from the frequency of the constant microwave, and then set the NV - color - center diamond cantilever MEMS magnetic sensor in an external magnetic field environment;

[0023] 3. Apply an external stress to the diamond cantilever of the NV - color - center diamond cantilever MEMS magnetic sensor through a stress applying device and regulate the magnitude of the external stress. When the fluorescence intensity received by the fluorescence receiving device becomes weaker, the electron energy level and the microwave frequency reach the resonance state. At this time, the relationship between the energies satisfies formula (1):

[0024] E D +E B +E σ =E mw (1)

[0025] Then convert the magnitude of the external stress into the energy difference E σ , and obtain the magnetic field energy E B from formula (1), so as to obtain the magnitude of the magnetic field in the external magnetic field environment.

[0026] In this embodiment, the cantilever in the diamond cantilever MEMS magnetic sensor is a diamond containing NV - color - centers.

[0027] Specific embodiment two: The difference between this embodiment and specific embodiment one is that the wavelength of the laser emitted by the laser in step one is 532 nm.

[0028] Specific embodiment three: The difference between this embodiment and specific embodiment one or two is that in step one, the fluorescence receiving device is used to obtain the fluorescence spectrum of the red fluorescence.

[0029] Specific embodiment four: The difference between this embodiment and one of specific embodiments one to three is that in step two, the energy of the microwave is determined as E mw from the constant microwave frequency, and the calculation formula for the microwave energy E mw is as follows:

[0030] E mw =hν (2)

[0031] Among them, ν is the frequency of the constant microwave, and h is the Planck constant.

[0032] Specific Embodiment 5: The difference between this embodiment and any one of Embodiments 1 to 4 is that in Step 3, an external stress is applied to the diamond cantilever of the NV - color - center diamond cantilever beam MEMS magnetic sensor through a stress - applying device, and the direction of the external stress is vertically downward.

[0033] Specific Embodiment 6: The difference between this embodiment and any one of Embodiments 1 to 5 is that in Step 3, the magnitude of the external stress is converted into an energy difference E σ The calculation formula is:

[0034]

[0035] Among them, σ is the magnitude of the external stress, ε is the strain generated by the external stress, and V is the volume of the cantilever beam.

[0036] In this embodiment, the calculation formula of E σ can also be written as:

[0037]

[0038] Among them, M z is the torque in the z - axis (perpendicular to the cantilever beam) direction, I z is the moment of inertia about the z - axis direction, E is the Young's modulus of the NV - color - center diamond cantilever beam, and ε represents the strain.

[0039] Specific Embodiment 7: The difference between this embodiment and Embodiment 6 is that the external strain ε generated by the stress is obtained by detection with a strain gauge.

[0040] Specific Embodiment 8: The difference between this embodiment and any one of Embodiments 1 to 7 is that in Step 3, the calculation relationship between the magnetic - field energy E B and the magnetic - induction intensity B is:

[0041]

[0042] Among them, H is the direct magnetic - field intensity, and V is the volume of the cantilever beam.

[0043] Specific Embodiment Nine: The NV - color - center diamond MEMS magnetic field detection device based on a constant microwave frequency includes an NV - color - center diamond cantilever beam MEMS magnetic sensor, a laser emission and fluorescence reception device, a microwave generation device, and a stress application device. The laser emission and fluorescence reception device emits a laser to irradiate the NV - color - center diamond cantilever beam MEMS magnetic sensor. The fluorescence radiated by the NV - color centers in the NV - color - center diamond cantilever beam is then received by the laser emission and fluorescence reception device. After receiving the fluorescence signal, the microwave generation device inputs a constant microwave to the NV - color - center diamond cantilever beam MEMS magnetic sensor, and at the same time, the stress application device applies an external stress to the diamond cantilever beam in the NV - color - center diamond cantilever beam MEMS magnetic sensor.

[0044] Example: The NV - color - center diamond MEMS magnetic field detection method based on a constant microwave frequency is implemented according to the following steps:

[0045] 1. Use a laser to emit green laser light with a wavelength of 532 nm to irradiate the NV - color - center diamond cantilever beam MEMS magnetic sensor. After the NV - color centers in the diamond cantilever beam of the diamond cantilever beam MEMS magnetic sensor are irradiated by the laser, the internal electrons are pumped from the ground state to the excited state. When the electrons fall back from the excited state to the ground state, the NV - color centers radiate red fluorescence. The fluorescence reception device acquires the fluorescence spectrum, and from the fluorescence spectra of the excitation light and the red fluorescence, the energy difference between the ground state and the excited state, which is the zero - field splitting energy level E D , and the zero - field splitting energy level can be expressed as E D = D×h, where D = 2.87 GHz and h is the Planck constant;

[0046] 2. The microwave generation device inputs a constant microwave to the NV - color - center diamond cantilever beam MEMS magnetic sensor. Determine the energy of the microwave as E mw from the frequency of the constant microwave. Since the microwave frequency is fixed, the magnitude of E mw is fixed during the experiment. Place the NV - color - center diamond cantilever beam MEMS magnetic sensor in an external magnetic field environment. The electrons in the NV - color centers undergo Zeeman splitting, and the energy difference generated in this process is the magnetic field energy level E B ;

[0047] 3. Apply an external stress to the NV - color - center diamond cantilever beam MEMS magnetic sensor through the stress application device, and adjust the magnitude of the external stress to make the electron energy level resonate with the microwave frequency. That is, when the fluorescence intensity received by the fluorescence reception device becomes weaker, the relationship between the energies at this time satisfies formula (1):

[0048] E D + E B + E σ = E mw (1)

[0049] Then, the magnitude of the external stress is converted into the energy difference E σ , and the magnetic field energy E is obtained from formula (1) B , thereby obtaining the magnitude of the magnetic field in the external magnetic field environment. The change in the electron energy level in the NV color center during this process is as shown in Figure 2 .

[0050] The NV color center diamond MEMS magnetic field detection device based on a constant microwave frequency in this embodiment includes an NV color center diamond cantilever beam MEMS magnetic sensor, a laser emission and fluorescence reception device, a microwave generation device, a stress application device, and a control and processing device. The laser emission and fluorescence reception device emits laser light to irradiate the NV color center diamond cantilever beam MEMS magnetic sensor, and the fluorescence emitted by the NV color center of the NV color center diamond cantilever beam MEMS magnetic sensor is received by the laser emission and fluorescence reception device again. After receiving the fluorescence signal, the control and processing device sends working signals to the microwave generation device and the stress application device. The microwave generation device inputs a constant microwave to the NV color center diamond cantilever beam MEMS magnetic sensor, and at the same time, the stress application device applies stress to the NV color center diamond cantilever beam MEMS magnetic sensor. The cantilever beam in the cantilever beam MEMS magnetic sensor is a single-crystal diamond material containing NV color centers, and the stress can change the electron energy level of the NV color centers in the single-crystal diamond. The NV color center diamond cantilever beam MEMS magnetic sensor is a YESENSE-YIS106 model MEMS magnetic sensor, and the cantilever beam is made of NV color center diamond.

[0051] The structural schematic diagram of the NV color center diamond cantilever beam MEMS magnetic sensor in this embodiment is as shown in Figure 3 . When a microwave frequency is applied, an equivalent electrostatic force acts between the MEMS cantilever beam and the signal line, and the MEMS cantilever beam bends and deforms under the traction of the force. The deformation of the structure causes a change in the energy level of the NV color center. By adjusting the magnitude of the applied stress, resonance between the NV color center energy level and the microwave frequency is achieved under the coupling action of stress and magnetic field.

[0052] The laser emission and fluorescence detection device in this embodiment is used to emit laser light to the cantilever beam MEMS magnetic sensor, detect the fluorescence emitted by the NV color center, and transmit the fluorescence intensity signal to the control and processing device and the stress application device.

[0053] The microwave generation device is used to generate a constant microwave. After receiving the control signal transmitted by the collection and processing device, it transmits the constant microwave to the cantilever beam MEMS magnetic sensor.

[0054] After receiving the fluorescence signal transmitted by the laser emission and fluorescence detection device and the constant microwave transmitted by the microwave generation device simultaneously, the stress application device starts to apply stress with a controllable change rate to the cantilever beam MEMS magnetic sensor, achieving resonance with the electronic ground state energy level of the NV color center at a constant microwave frequency and changing the electron spin energy level.

[0055] The control and processing device is used to receive, process, and analyze the fluorescence signal transmitted by the laser emission and fluorescence detection device, and send a control signal to the microwave generation device.

[0056] The laser emission and fluorescence detection device consists of a laser source, a laser switch, a dichroic mirror, a filter, and a fluorescence receiver. The green laser with a wavelength of 532 nm is emitted by the laser source, reflected by the dichroic mirror, and received by the NV color center in the cantilever beam MEMS magnetic sensor. The NV color center emits red fluorescence, which is filtered by the dichroic mirror and the filter in sequence and then collected by the fluorescence receiving device.

[0057] The microwave generation device consists of a microwave source, a signal receiver, and a microwave amplifier. When the signal receiver receives the microwave activation signal from the control and processing device, the microwave source starts to emit microwaves, which act on the cantilever beam MEMS magnetic sensor after being strengthened by the microwave amplifier.

[0058] The stress application device consists of a stress needle and a stress regulator. After the fluorescence intensity presented by the cantilever beam MEMS magnetic sensor shows a trough, the stress needle starts to apply an external stress to the cantilever beam MEMS magnetic sensor, and continuously adjusts the stress magnitude through the stress regulator.

[0059] The control and processing device includes a fluorescence signal receiver and a microwave signal transmitter. After the fluorescence radiated by the cantilever beam MEMS magnetic sensor is received by the fluorescence signal receiver, the control and processing device transmits the microwave activation signal to the microwave generation device via the microwave signal transmitter.

[0060] This embodiment provides a magnetic field measurement device and method at a constant microwave frequency based on an NV - center diamond cantilever beam MEMS magnetic sensor. Among them, the magnetic field measurement device includes: a cantilever beam MEMS magnetic sensor, a laser emission and fluorescence detection device, a constant microwave generation device, a data collection and processing device, and a prestress application device. The microwave emission device radiates constant microwaves to the detection area. At the same time, the prestress application device applies a constant stress to the cantilever beam MEMS magnetic sensor. Under the action of the stress, the NV energy level of the cantilever beam MEMS magnetic sensor changes. Under the action of an external magnetic field, the constant stress is adjusted to achieve resonance with the microwave frequency, and then the magnitude of the external magnetic field is obtained. This method only needs to adjust the magnitude of the constant stress to change the NV energy level of the cantilever beam MEMS magnetic sensor, and then the magnitude of the external magnetic field at a constant microwave frequency can be measured. The operation is simple and fast, and based on the quantum precision measurement technology of diamond NV centers, it has the advantages of high accuracy and high spatial resolution.

Claims

1. A method for detecting magnetic fields using NV - color - center diamond MEMS at a constant microwave frequency, characterized in that The NV - color - center diamond MEMS magnetic field detection method based on a constant microwave frequency is implemented according to the following steps:

1. Use a laser to emit laser light to irradiate the NV - center diamond cantilever MEMS magnetic sensor. After the NV - centers in the diamond cantilever of the diamond cantilever MEMS magnetic sensor are irradiated by the laser, the internal electrons are pumped from the ground state to the excited state. When the electrons fall back from the excited state to the ground state, the NV - centers emit red fluorescence. The energy level difference between the ground state and the excited state, which is the zero - field splitting energy level E, is determined by the fluorescence spectra of the excitation light and the red fluorescence D ; II. Input a constant microwave into the NV - center diamond cantilever beam MEMS magnetic sensor through a microwave generating device, and determine that the energy of the microwave is E according to the frequency of the constant microwave mw , and then set the NV - center diamond cantilever beam MEMS magnetic sensor in an external magnetic field environment; 3. Apply an external stress to the diamond cantilever of the NV - color - center diamond cantilever MEMS magnetic sensor through a stress application device, and regulate the magnitude of the external stress. When the electron energy level and the microwave frequency reach the resonance state, the relationship between the energies at this time satisfies formula (1): E D +E B +E σ =E mw (1) Then, the magnitude of the external stress is converted into an energy difference E σ , and the magnetic field energy E is obtained from formula (1) B , thereby obtaining the magnitude of the magnetic field in the external magnetic field environment.

2. The NV - center diamond MEMS magnetic field detection method based on a constant microwave frequency according to claim 1, wherein In step 1, the laser wavelength emitted by the laser is 532 nm.

3. The NV - center diamond MEMS magnetic field detection method based on a constant microwave frequency according to claim 1, wherein In step 1, the fluorescence spectrum of the red fluorescence is obtained by the fluorescence receiving device.

4. The NV - center diamond MEMS magnetic field detection method based on a constant microwave frequency according to claim 1, wherein In Step 2, the energy of the microwave is determined to be E by the constant microwave frequency mw , the microwave energy E mw has the following calculation formula: E mw = hν (2) Among them, ν is the frequency of the constant microwave, and h is Planck's constant.

5. The NV - center diamond MEMS magnetic field detection method based on a constant microwave frequency according to claim 1, wherein In step 3, an external stress is applied to the diamond cantilever of the NV - color - center diamond cantilever MEMS magnetic sensor through a stress application device, and the direction of the external stress is vertically downward.

6. The NV - center diamond MEMS magnetic field detection method based on a constant microwave frequency according to claim 1, wherein In Step 3, the magnitude of the external stress is converted into an energy difference E σ The calculation formula is as follows: Among them, σ is the magnitude of the external stress, ε is the strain generated by the external stress, and V is the volume of the cantilever.

7. The NV - center diamond MEMS magnetic field detection method based on a constant microwave frequency according to claim 6, wherein The strain ε generated by the external stress is detected by a strain gauge.

8. The NV - center diamond MEMS magnetic field detection method based on a constant microwave frequency according to claim 1, wherein In step 3, the calculation relationship between the magnetic field energy E B and the magnetic induction intensity B is as follows: Among them, H is the direct magnetic field strength, and V is the volume of the cantilever.

9. The NV - center diamond MEMS magnetic field detection device based on a constant microwave frequency, referring to the claims of the detection method, is characterized in that The NV - color - center diamond MEMS magnetic field detection device based on a constant microwave frequency includes an NV - color - center diamond cantilever MEMS magnetic sensor, a laser emission and fluorescence receiving device, a microwave generating device, and a stress application device. The laser emission and fluorescence receiving device emits laser light to irradiate the NV - color - center diamond cantilever MEMS magnetic sensor, and the fluorescence radiated by the NV - centers in the NV - color - center diamond cantilever is received by the laser emission and fluorescence receiving device again. After receiving the fluorescence signal, the microwave generating device inputs a constant microwave to the NV - color - center diamond cantilever MEMS magnetic sensor, and at the same time, the stress application device applies an external stress to the diamond cantilever in the NV - color - center diamond cantilever MEMS magnetic sensor.

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