A nitrogen vacancy color center sensor and preparation method thereof

Abstract

The present invention provides a nitrogen vacancy color center sensor, comprising: a circuit board; electrodes are arranged on the circuit board; a tuning fork device; the end of the tuning fork device is electrically connected to the electrodes of the circuit board; a transfer beam; the transfer beam is arranged at the front end of the tuning fork device; the transfer beam can transmit the fluorescence emitted by the nitrogen vacancy color center and the laser that excites the nitrogen vacancy color center; a diamond substrate; one side of the diamond substrate is connected to the transfer beam; a diamond nanocolumn waveguide array is arranged on the opposite side; a nitrogen vacancy color center is arranged on the diamond nanocolumn waveguide. Compared with the prior art, the sensor provided by the present invention is provided with a diamond nanocolumn waveguide array to form a plurality of probes containing nitrogen vacancy color centers, thereby improving the efficiency and service life of the nitrogen vacancy color center sensor; and it is arranged on the diamond substrate and connected by the transfer beam to enhance the rigidity of the probe; and its sensitivity is further improved by setting the shape of the diamond nanocolumn waveguide.

Description

Technical Field

[0001] The invention belongs to the technical field of scanning sensors, and in particular relates to a nitrogen vacancy color center sensor and a preparation method thereof. Background Art

[0002] The nitrogen vacancy center (NV center) is a solid point defect in diamond, consisting of a nitrogen atom and an adjacent vacancy, and is a three-level structure system with a spin of 1. The quantum state of the nitrogen vacancy center can be initialized by laser, quantum manipulated by microwaves, and read out by fluorescence. The NV center can be used as a molecular-scale sensitive sensor to measure physical quantities such as magnetic field, temperature, and electric field in the environment. These physical quantities will cause changes in the electron spin energy level of the NV center, and the size of these physical quantities can be inferred by testing the disturbance of the NV energy level. The NV center in the diamond is made into a scanning sensor, and combined with the atomic force microscope scanning system, it can realize nanoscale scanning imaging of the target to be measured, and obtain images of the target's magnetic field, electric field, temperature, etc.

[0003] This type of NV color center-based scanning sensor currently mainly uses a single diamond nanoparticle or a single diamond nanorod as a scanning probe.

[0004] There are two main ways to use diamond nanoparticles as probes. The first is to sprinkle diamond nanoparticles on the sample to be tested. Nanoparticles with a size of about 10nm allow the NV color center to detect signals within 10nm of the sample surface. However, the yield of diamond nanoparticles containing a single NV color center is low, and the way the diamond particles are scattered on the sample surface is relatively random, and the nanoparticles can only detect nearby sample signals, making it difficult to image a large range of sample signals. The second method is to use an optical fiber head to pick up diamond nanoparticles. The movement of the optical fiber head can drive the diamond nanoparticles to move and image the sample surface signal. However, since the optical fiber head and the sample are distributed on both sides of the diamond nanoparticle, the objective lens for collecting fluorescence signals can only be placed on one side of the sample, and only transparent samples can be measured, which causes limitations.

[0005] A single nano-column probe is a nano-column optical waveguide on a ten-micron diamond substrate. The NV color center is within 10nm from the front end of the nano-column, and the sample can be directly scanned and imaged in combination with the AFM system. However, the yield of a single nano-column probe is low, the process is complicated, and when a single NV color center is damaged, the scanning can only be interrupted and the probe replaced, and continuous and uninterrupted measurement cannot be achieved.

[0006] In summary, the existing NV color center scanning sensor solutions mainly have problems such as poor NV color center quality, low sensitivity, low probe manufacturing yield, and short probe life. Summary of the invention

[0007] In view of this, the technical problem to be solved by the present invention is to provide a nitrogen vacancy color center sensor with greater rigidity and higher sensitivity and a preparation method thereof.

[0008] The present invention provides a nitrogen vacancy color center sensor, comprising:

[0009] A circuit board; electrodes are arranged on the circuit board;

[0010] A tuning fork device; the end of the tuning fork device is electrically connected to an electrode of a circuit board;

[0011] A transfer beam; the transfer beam is disposed at the front end of the tuning fork device; the transfer beam can transmit the fluorescence emitted by the nitrogen vacancy color center and the laser that excites the nitrogen vacancy color center;

[0012] A diamond substrate; one side of the diamond substrate is connected to a transfer beam; the opposite side is provided with a diamond nanocolumn waveguide array; and the diamond nanocolumn waveguide is provided with a nitrogen vacancy color center.

[0013] Preferably, the diamond nanorod waveguide is in the shape of a truncated cone.

[0014] Preferably, the diameter of the upper surface of the truncated cone is 200-800 nm; the edge tilt angle is 5°-30°; and the height is 0.3-2 μm.

[0015] Preferably, the nitrogen vacancy color center on the diamond nanorod waveguide has a depth of 3 to 50 nm from the surface.

[0016] Preferably, the circuit board has a length of 1 to 50 mm, a width of 1 to 50 mm, and a thickness of 0.5 to 5 mm; the transfer beam has a length of 0.1 to 3 mm, a width of 0.01 to 1 mm, and a thickness of 30 to 500 μm; the diamond substrate has a length of 50 to 300 μm, a width of 50 to 300 μm, and a thickness of 10 to 80 μm.

[0017] Preferably, the transfer beam is a glass transfer beam and / or a silicon cantilever beam.

[0018] Preferably, one surface of the diamond substrate and the adapter beam is a precision polished surface, and the polishing roughness thereof reaches an rms of less than 1 nm.

[0019] Preferably, it also includes an atomic force microscope system; the electrodes of the circuit board are connected to a scanning imaging feedback system of the atomic force microscope system.

[0020] The present invention also provides a method for preparing a nitrogen vacancy color center sensor, comprising:

[0021] S1) nitrogen ion implantation is performed on diamond as a substrate, and diamond containing nitrogen vacancy color centers is obtained after annealing;

[0022] S2) preparing a patterned mask on the diamond surface containing nitrogen vacancy color centers, and performing etching to obtain a diamond substrate;

[0023] S3) The end of the tuning fork device is electrically connected to the electrode of the circuit board, and then the adapter beam is connected to the front end of the tuning fork device, and then the side of the diamond substrate without the nitrogen vacancy color center is connected to the tuning fork device to obtain a nitrogen vacancy color center sensor.

[0024] Preferably, the energy of the nitrogen ion implantation is 2.5-20 keV; the implantation ion dose is 10 10 ~10 12 atom / cm 2 .

[0025] The present invention provides a nitrogen vacancy color center sensor, comprising: a circuit board; electrodes are arranged on the circuit board; a tuning fork device; the end of the tuning fork device is electrically connected to the electrodes of the circuit board; a transfer beam; the transfer beam is arranged at the front end of the tuning fork device; the transfer beam can transmit the fluorescence emitted by the nitrogen vacancy color center and the laser that excites the nitrogen vacancy color center; a diamond substrate; one side of the diamond substrate is connected to the transfer beam; a diamond nanocolumn waveguide array is arranged on the opposite side; a nitrogen vacancy color center is arranged on the diamond nanocolumn waveguide. Compared with the prior art, the sensor provided by the present invention is provided with a diamond nanocolumn waveguide array to form a plurality of probes containing nitrogen vacancy color centers, thereby improving the efficiency and service life of the nitrogen vacancy color center sensor; and the diamond nanocolumn waveguide array is arranged on the diamond substrate and connected by the transfer beam to enhance the rigidity of the probe; and the sensitivity is further improved by setting the shape of the diamond nanocolumn waveguide. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 A schematic diagram of the structure of the nitrogen vacancy color center sensor provided by the present invention;

[0027] Figure 2 A schematic diagram of the shape structure of the diamond nanocolumn waveguide in the nitrogen vacancy color center sensor provided by the present invention;

[0028] Figure 3 A schematic diagram of the principle of the nitrogen vacancy color center sensor provided by the present invention;

[0029] Figure 4 This is a photograph of the nitrogen vacancy color center sensor prepared in Example 1 of the present invention;

[0030] Figure 5 This is a scanning electron beam microscope photograph of the nitrogen vacancy color center sensor prepared in Example 1 of the present invention;

[0031] Figure 6This is a fluorescence image of the nitrogen vacancy color center in the nitrogen vacancy color center sensor prepared in Example 1 of the present invention;

[0032] Figure 7 A curve showing a change in fluorescence count of one of the nitrogen vacancy color centers in the nitrogen vacancy color center sensor prepared in Example 1 of the present invention as a function of laser power;

[0033] Figure 8 This is an electron paramagnetic resonance spectrum of one of the nitrogen vacancy color centers in the nitrogen vacancy color center sensor prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0034] The following will be combined with the accompanying drawings of the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0035] The present invention provides a nitrogen vacancy color center sensor, comprising:

[0036] A circuit board; electrodes are arranged on the circuit board;

[0037] A tuning fork device; the end of the tuning fork device is electrically connected to an electrode of a circuit board;

[0038] A transfer beam; the transfer beam is disposed at the front end of the tuning fork device; the transfer beam can transmit the fluorescence emitted by the nitrogen vacancy color center and the laser that excites the nitrogen vacancy color center;

[0039] A diamond substrate; one side of the diamond substrate is connected to a transfer beam; the opposite side is provided with a diamond nanocolumn waveguide array; and the diamond nanocolumn waveguide is provided with a nitrogen vacancy color center.

[0040] See also Figure 1 , Figure 1 This is a schematic structural diagram of the nitrogen vacancy color center sensor provided by the present invention.

[0041] The nitrogen vacancy color center sensor provided by the present invention comprises a circuit board; the circuit board is preferably a printed circuit board; electrodes are arranged on the circuit board, preferably metal electrodes are arranged, and more preferably metal electrodes are symmetrically arranged on both sides of the same surface, and the two symmetrical metal electrodes have no electrical connection; the circuit board is used to connect the sensor to an atomic force microscope scanning imaging feedback system; the length of the circuit board is preferably 1 to 50 mm; the width is preferably 1 to 50 mm; and the thickness is preferably 0.5 to 5 mm.

[0042] The electrodes of the circuit board are provided with a tuning fork device, and the end of the tuning fork device is electrically connected to the electrodes of the circuit board for contact force feedback of an atomic force microscope; the tuning fork device is preferably a quartz tuning fork device. In the present invention, a tuning fork device is used as a carrier of the sensor probe. When the sensor waveguide probe (diamond substrate) is close enough to the surface of the material to be measured, due to the extremely weak repulsive force between the atoms at the tip of the probe and the atoms on the surface of the sample, the resonance frequency of the tuning fork crystal oscillator will change. The piezoelectric signal of the tuning fork device is monitored to obtain the change of the resonance frequency of the tuning fork crystal oscillator, and a feedback loop is formed with the piezoelectric ceramic that controls the height of the sensor to ensure that the distance between the probe and the material to be measured is maintained at the nanometer size. At the same time, the NV color center optical detection magnetic resonance signal is detected to obtain physical quantity information such as magnetic field, temperature, and electric field in the environment.

[0043] A transfer beam is provided at the front end of the tuning fork device; the transfer beam can transmit the fluorescence emitted by the nitrogen vacancy color center and the laser that excites the nitrogen vacancy color center, and preferably can transmit light with a wavelength of 532 to 800 nm; the transfer beam is preferably a glass transfer beam and / or a silicon cantilever beam, and more preferably a silicon cantilever beam, a thin quartz glass tube or an ultra-thin quartz glass; the length of the transfer beam is preferably 0.1 to 3 mm, more preferably 0.5 to 2 mm, and more preferably 1 to 2 mm; the width is preferably 0.01 to 1 mm, more preferably 0.05 to 0.8 mm, more preferably 0.1 to 0.5 mm, and most preferably 0.2 to 0.5 mm; the thickness is preferably 30 to 500 μm, more preferably 50 to 400 μm, more preferably 100 to 200 μm, and most preferably 150 to 170 μm; the length of the portion of the transfer beam exposed from the tuning fork device is preferably at least 400 μm to ensure that the fluorescence of the nitrogen vacancy color center is not blocked by the tuning fork.

[0044] A diamond substrate is arranged on the transfer beam; the length of the diamond substrate is preferably 50-300 μm; the width is preferably 50-300 μm; the thickness is preferably 10-80 μm, more preferably 30-80 μm, more preferably 40-60 μm, and most preferably 50 μm; one side of the diamond substrate is connected to the transfer beam, and the surface is preferably a precision polished surface; its polishing roughness is preferably less than 1 nm in rms; the diamond substrate and the transfer beam are preferably rigidly fixed by a light-transmitting resin; the light-transmitting resin is preferably a light-transmitting epoxy resin; a diamond nanocolumn waveguide array is arranged on the side opposite to the connection surface of the transfer beam; the number of diamond nanocolumn waveguides in the array is preferably greater than or equal to 2×2, more preferably 2×2-20×20, more preferably 5×5-15×15, and most preferably 7×7-10×10; the diamond nanocolumn waveguide is preferably in the shape of a truncated cone; see Figure 2 , Figure 2It is a schematic diagram of the structure of a diamond nanocolumn waveguide shape; the diameter of the upper surface of the truncated cone shape is preferably 200-800nm, more preferably 300-600nm, and more preferably 400-500nm; the edge tilt angle is preferably 5°-30°, more preferably 10°-25°, more preferably 10°-20°, and most preferably 15°; the height is preferably 0.3-2μm, more preferably 1-2μm; a nitrogen vacancy color center is provided on the diamond nanocolumn waveguide; the depth of the nitrogen vacancy color center from the surface is preferably 3-50nm, more preferably 5-50nm, more preferably 10-40nm, more preferably 20-40nm, and most preferably 30nm. The present invention adjusts the upper surface diameter D1, the edge tilt angle θ, the truncated cone height H and the position of the color center of the diamond nanocolumn waveguide truncated cone, and uses the finite difference time domain method to simulate the light intensity distribution of the fluorescence emitted by the NV color center after it is emitted from the bottom of the truncated cone along each divergence angle. s , η p According to the obtained light intensity distribution information, the fluorescence emission efficiency within the lens collection angle range when the fluorescence passes through the lower surface of the diamond can be calculated by integrating the solid angle in accordance with geometric optics and Fresnel's law of reflection and refraction.

[0045]

[0046] T s , T p are the coefficients of the S and P polarization components passing through the diamond and air interface, respectively, obtained from the Fresnel law of reflection and refraction. s , η p The fluorescence emission efficiencies are respectively the S and P polarization components. Finally, the various parameters corresponding to the better fluorescence collection efficiency can be obtained by simulation, so that the fluorescence emission efficiency of the NV color center that meets the morphology is greater than 30%. The nitrogen vacancy is a six-electron system, three electrons come from the carbon atoms adjacent to the vacancy, two electrons come from the nitrogen atoms adjacent to the vacancy, and one electron is captured from the lattice, so the NV is a three-level system, and its electron paramagnetic resonance spectrum can reflect the magnetic field, electric field and temperature information near the NV. The sensor provided by the present invention is provided with a plurality of isolated probes containing a single NV color center, which is used to realize nanoscale, high-sensitivity measurement and scanning imaging of magnetic field, spin magnetic resonance, and electric field. Due to the presence of a plurality of isolated probes, the used probe can be replaced immediately after being damaged, and continuous measurement can be achieved without replacing the entire sensor, thereby solving the shortcomings of low production efficiency, easy loss and high cost of the previous scanning NV color center sensor.

[0047] According to the present invention, it is preferred that an atomic force microscope system is also included; the electrodes of the circuit board are connected to a scanning imaging feedback system of the atomic force microscope system.

[0048] The nitrogen vacancy color center sensor provided by the present invention can be used for nanoscale scanning imaging. The circuit board carrying the tuning fork device, the adapter beam and the diamond substrate also provides a mechanical interface to be fixedly connected to the experimental platform. The high-frequency signal that drives the tuning fork device is connected to the tuning fork device and the diamond substrate through the electrodes on the circuit board. The high-frequency signal fed back by the diamond substrate as a probe is conducted out through another electrode on the circuit board, and the phase-locked amplifier controls the displacement stage to realize the movement of the diamond substrate, that is, the probe, relative to the sample. When the probe approaches or moves away from the surface, the damping felt by the tuning fork device changes, the tuning fork amplitude changes, and the high-frequency signal fed back by the tuning fork is amplified and transmitted to the phase-locked amplifier. By adjusting the PID parameters of the phase-locked amplifier, the movement of the Z-direction displacement stage where the probe system is located can be feedback-controlled to perform non-destructive scanning and imaging of the sample surface. See Figure 3 , Figure 3 This is a schematic diagram of the principle of the nitrogen vacancy color center sensor provided by the present invention.

[0049] The sensor provided by the present invention is provided with a diamond nanocolumn waveguide array to form a plurality of probes containing nitrogen vacancy color centers, thereby improving the efficiency and service life of the nitrogen vacancy color center sensor; and the diamond nanocolumn waveguide array is arranged on a diamond substrate and connected by a transfer beam to enhance the rigidity of the probe; and further, the sensitivity is improved by setting the shape of the diamond nanocolumn waveguide.

[0050] The present invention also provides a method for preparing a nitrogen vacancy color center sensor, comprising: S1) performing nitrogen ion implantation on a diamond substrate, and obtaining diamond containing nitrogen vacancy color centers after annealing; S2) preparing a patterned mask on the surface of the diamond containing the nitrogen vacancy color centers, and performing etching to obtain a diamond substrate; S3) electrically connecting the end of a tuning fork device to an electrode of a circuit board, and then connecting a transfer beam to the front end of the tuning fork device, and then connecting a side of the diamond substrate without a nitrogen vacancy color center to the tuning fork device to obtain a nitrogen vacancy color center sensor.

[0051] The present invention uses ion implantation and annealing processes to prepare near-surface NV color centers, implements doping of nitrogen and vacancies on the diamond surface through ion implantation technology, and implements the combination of vacancies and nitrogen to produce NV color centers through ultra-high vacuum high-temperature annealing process. Diamond is used as a substrate for nitrogen ion implantation; the thickness of the diamond is 10 to 80 μm, more preferably 30 to 80 μm, more preferably 40 to 60 μm, and most preferably 50 μm; the diamond is electronic grade purity single crystal diamond; the nitrogen ion implantation selects N + 、N 2+ The nitrogen-containing ions are implanted; the energy of the ion implantation is preferably 2.5 to 20 keV; the implantation ion dose is preferably 10 10 ~10 12atom / cm 2 , more preferably 10 11 atom / cm 2 ; The substrate after ion implantation is annealed to obtain diamond containing nitrogen vacancy color centers; the temperature of the annealing treatment is preferably 600°C to 1200°C, more preferably 700°C to 1100°C, and more preferably 800°C to 1000°C; the time of the annealing treatment is preferably two hours or more; the annealing treatment is preferably carried out in a vacuum degree of better than 10 -4 Pa or filled with inert gas to protect the diamond to ensure that it is not graphitized.

[0052] A patterned mask is prepared on the surface of a diamond containing nitrogen vacancy color centers, and the mask pattern is transferred to the diamond surface by a diamond etching process to achieve the preparation of a waveguide with high fluorescence collection efficiency. The material used for the patterned mask is preferably metal, metal oxide, SiO2, HSQ electron beam photoresist; after the patterned mask is prepared, etching is performed, preferably using oxygen or oxygen-containing gas as etching gas, and the diamond containing nitrogen vacancy color centers is etched by reactive plasma etching to obtain a diamond substrate containing a diamond nanocolumn waveguide array.

[0053] Taking the metal material Ti as a mask as an example, it is preferably carried out in the following manner:

[0054] Preparation of PMMA small hole array on diamond surface was achieved by electron beam lithography.

[0055] PMMA coating: Spin-coat electron beam exposed positive PMMA 950k on diamond at 7000 rpm for 1 min. Bake on a hot plate at 130°C for 15 min. The PMMA coating thickness reaches 160-240 nm.

[0056] Spin coating the conductive layer: Spin coating the conductive adhesive SX AR-PC 5000 / 90.2 on the PMMA surface at a speed of 4000 rpm, and bake on a hot plate at 90° C. for 2 minutes to evaporate the solvent.

[0057] Electron beam exposure: electron beam energy 10KeV, exposure dose 170uC / cm 2 , exposure pattern of circular arrays of different diameters. In order to make the stripping process smoother, use a lower energy 10KeV electron energy exposure system, or use double-layer adhesive stripping.

[0058] Development: The diamond was placed in deionized water for 2 minutes to wash off the conductive glue, and then dried with nitrogen. After that, it was developed in developer (MIBK:IPA, 1:3) for 110 seconds, and then fixed in fixer (IPA) for 100 seconds. Finally, it was dried with nitrogen.

[0059] The surface mask is prepared by coating and stripping.

[0060] Electron beam evaporation coating: Use electron evaporation coating to coat titanium metal 80 to 120 nm perpendicular to the diamond surface.

[0061] Dissolution and stripping: Place the diamond in acetone or degumming agent, soak for more than 10 minutes, and rinse the diamond surface to remove the photoresist on the surface.

[0062] Pure oxygen is introduced into an inductively coupled reactive plasma etcher for etching, and the frustum structure is etched using the physical facet phenomenon.

[0063] The etching parameters of the inductively coupled reactive plasma etcher used in the present invention are preferably as follows: RF power: 40W, ICP power: 800W, O2 flow rate: 30scmm, pressure: 20mTorr.

[0064] Due to the excessive consumption of the mask by ion sputtering during the etching process, the mask thickness decreases as the etching depth increases. The shape of the mask also deforms with the sputtering of the ion beam, because the mask at the sharp corners is always consumed first and fastest. The sidewalls of the etched structure under the mask also have an inclination, eventually forming a waveguide shape with high fluorescence collection efficiency.

[0065] The mask on the remaining waveguide end face is removed by wet method.

[0066] Wet etch in mixed acid solution (HClO4:H2SO4:HNO3=1:1:1) at 200℃ for 1 hour. Rinse with deionized water.

[0067] Since electronic grade purity single crystal diamond is used as the substrate, the size of the single crystal needs to be greater than 1mm×1mm. Therefore, the diamond is preferably cut after etching to obtain a diamond substrate. The cutting is preferably performed using a laser scribing device and then further cleaned by a wet method. Chemical wet cleaning can remove residual contaminants in the micro-nano processing process, improve the quality of nitrogen vacancy color centers, and thus improve sensitivity.

[0068] The end of the tuning fork device is electrically connected to the electrode of the circuit board; in the present invention, preferably, an electric soldering iron is used to heat the soldering to complete the electrical connection between the tuning fork device and the electrode.

[0069] Then the adapter beam is connected to the front end of the tuning fork device, preferably under a microscope, the adapter beam is bonded to the front end of the tuning fork device by resin; the resin is preferably epoxy resin.

[0070] Then, the side of the diamond substrate without the nitrogen vacancy color center is connected to the tuning fork device, preferably, the side of the diamond substrate without the nitrogen vacancy color center is connected to the tuning fork device through a resin to obtain a nitrogen vacancy color center sensor; the resin is preferably epoxy resin.

[0071] The present invention provides a micro-nano processing method for a diamond nanocolumn waveguide array on a diamond substrate, which is used to improve the collection efficiency of NV color center fluorescence and improve the signal strength; and uses direct laser cutting to miniaturize the diamond substrate, and further cleans it, and then bonds and assembles it at the micron scale, ensuring that the surface of the sensor is clean after production, further ensuring the quality of the sensor.

[0072] In order to further illustrate the present invention, a nitrogen vacancy color center sensor and a preparation method thereof provided by the present invention are described in detail below in conjunction with embodiments.

[0073] The reagents used in the following examples are all commercially available.

[0074] Example 1

[0075] The nitrogen vacancy color center sensor provided in this embodiment includes a printed circuit board, a quartz tuning fork, a transfer beam and a diamond substrate; the length of the printed circuit board can be 50mm, the width is 50mm, and the thickness is 0.5mm. Among them, the length of the transfer beam is 1mm, the width is 0.2mm, and the thickness is 170μm; the printed circuit board includes a printed circuit board connected to the tuning fork, and the metal electrodes are symmetrically plated on both sides of the upper surface, and the front end of the electrode is connected to the quartz tuning fork electrode. The quartz tuning fork includes a quartz tuning fork located on the upper surface of the printed circuit board, the quartz tuning fork is located in the middle of the end of the printed circuit board electrode, the root of the quartz tuning fork is connected to the printed circuit board, and the quartz tuning fork electrode is connected to the corresponding electrode of the printed circuit board. The transfer beam can transmit light with a wavelength of 532 to 800nm ​​and is located at one end of the quartz tuning fork. The diamond substrate is composed of a diamond substrate and an array of truncated cone-shaped nanowaveguides located in the center. The smooth side of the diamond substrate is connected to the lower surface of the glass beam through a light-transmitting epoxy resin. This surface is a precision polished surface with a polishing roughness of rms<1nm. The other side is a nano-truncated cone array, with a number of 7 x 7 nano-truncated cones. The root of the nano-waveguide column is connected to the diamond substrate, and the end face of the nano-waveguide column contains a NV color center with a depth of about 30nm near the surface. The waveguide morphology is a truncated cone shape (the upper surface diameter is 400nm, the edge tilt angle is 15°, and the truncated cone height is 2μm), which meets the NV color center fluorescence emission efficiency of more than 30%.

[0076] Making diamond substrate:

[0077] (a) Preparation of NV color centers

[0078] Use electronic grade purity single crystal diamond with a surface polishing thickness of 50μm as the substrate. The single crystal size must be larger than 1mm×1mm. Select N + 、N 2+ The nitrogen-containing ions are used as implanted ions; the implanted energy range is 20keV; the implanted ion dose is 10 11 atom / cm 2 Annealing process: annealing temperature range 800 degrees Celsius, annealing time 2 hours, vacuum degree during annealing better than 10 - 4 Pa is used for protection to ensure that the diamond is not graphitized.

[0079] (b) Waveguide preparation with high fluorescence collection efficiency

[0080] A patterned mask is prepared on the diamond surface processed in (a), and the mask pattern is transferred to the diamond surface through a diamond etching process to achieve the preparation of a waveguide with high fluorescence collection efficiency. The mask material can be selected from metals, metal oxides, SiO2, HSQ electron beam photoresist, etc.

[0081] Taking the metal material Ti as a mask as an example, the specific implementation scheme is as follows:

[0082] Preparation of PMMA small hole array on diamond surface was achieved by electron beam lithography.

[0083] PMMA coating: Spin-coat electron beam exposed positive PMMA 950k on diamond at 7000 rpm for 1 min. Bake on a hot plate at 130°C for 15 min. The PMMA coating thickness reaches 160-240 nm.

[0084] Spin coating the conductive layer: Spin coating the conductive adhesive SX AR-PC 5000 / 90.2 on the PMMA surface at a speed of 4000 rpm, and bake on a hot plate at 90° C. for 2 minutes to evaporate the solvent.

[0085] Electron beam exposure: electron beam energy 10KeV, exposure dose 170uC / cm 2 , exposure pattern of circular arrays of different diameters. In order to make the stripping process smoother, use a lower energy 10KeV electron energy exposure system, or use double-layer adhesive stripping.

[0086] Development: The diamond was placed in deionized water for 2 minutes to wash off the conductive glue, and then dried with nitrogen. After that, it was developed in developer (MIBK:IPA, 1:3) for 110 seconds, and then fixed in fixer (IPA) for 100 seconds. Finally, it was dried with nitrogen.

[0087] Surface mask preparation by coating and stripping

[0088] Electron beam evaporation coating: Use electron evaporation coating to coat titanium metal 80 to 120 nm perpendicular to the diamond surface.

[0089] Dissolution and stripping: Place the diamond in acetone or degumming agent, soak for more than 10 minutes, and rinse the diamond surface to remove the photoresist on the surface.

[0090] Pure oxygen is introduced into an inductively coupled reactive plasma etcher for etching, and the frustum structure is etched using the physical facet phenomenon.

[0091] The inductively coupled reactive plasma etcher used in this production scheme has the following preferred etching parameters: RF power: 40 W, ICP power: 800 W, O2 flow rate: 30 scmm, pressure: 20 mTorr; etching time: 10 min.

[0092] Due to the excessive consumption of the mask by ion sputtering during the etching process, the mask thickness decreases as the etching depth increases. The shape of the mask also deforms with the sputtering of the ion beam, because the mask at the sharp corners is always consumed first and fastest. The sidewalls of the etched structure under the mask also have an inclination, eventually forming a waveguide shape with high fluorescence collection efficiency.

[0093] Wet removal of the mask of the residual waveguide end face

[0094] Wet etch in mixed acid solution (HClO4:H2SO4:HNO3=1:1:1) at 200℃ for 1 hour. Rinse with deionized water.

[0095] (c) Laser cutting and dissociation of sensor substrate

[0096] This scheme uses laser scribing to cut diamonds. The diamonds processed in this section (b) are cut into small-sized diamond substrates using laser scribing equipment. The size of the substrates after cutting ranges from 50μm×50μm to 300μm×300μm, and the graphite produced by cutting is cleaned by wet method. The specific implementation scheme is as follows: Bond the diamond sheet waveguide surface upward to the transparent quartz substrate through epoxy resin glue, and use high-power ultraviolet laser cutting equipment to scribing the diamond along the reserved cutting path. Put the cut diamond sheet and the quartz substrate into a glass container, add triacid (HClO4:HNO3:H2SO4=1:1:1) to submerge the material, and heat it at 200 degrees Celsius for more than 5 hours. In this way, the graphite produced by ultraviolet cutting is removed, and the quartz and diamond are debonded. Finally, deionized water is used to dilute and replace the triacid in the container. Take out the quartz substrate from the container, pour the deionized water in the container together with the diamond sheet onto the flat and solidified polydimethylsiloxane (PDMS) surface, and evaporate the deionized water in an oven. Find the diamond sheet under a microscope, and use a micro-nano manipulator to flip the diamond sheet with the waveguide facing up so that the waveguide side faces down, in preparation for assembly and bonding of the sensor.

[0097] Sensor assembly bonding

[0098] (a) Bonding of fixture and quartz tuning fork crystal

[0099] The quartz tuning fork crystal will be fixed on the fixture. In order to obtain the piezoelectric signal of the quartz tuning fork crystal, the electrodes on the quartz tuning fork need to be connected to the electrodes on the fixture. Specific implementation plan: Use the tuning fork crystal electronic component, remove its shell, pins and glass valve to get the central quartz tuning fork, weld the tail of the tuning fork to the fixture, and connect the electrodes on the tuning fork to the electrodes on the fixture through wire bonding.

[0100] (b) Bonding of sensor substrate and tuning fork crystal

[0101] The tuning fork crystal oscillator and the sensor substrate can be connected through small-sized items such as silicon cantilever beams, thin quartz glass tubes, and ultra-thin quartz glass. Taking ultra-thin quartz glass as an example, the specific implementation plan is: select a quartz glass sheet with a thickness of 170μm, cut it into strips with a length of 700mm and a width of 400μm. The smaller-sized quartz beam helps the tuning fork crystal oscillator to have a better vibration quality factor. Bond one end of the glass beam to one of the legs of the tuning fork through epoxy resin, and the quartz beam exposes at least 400μm of the tuning fork to ensure that the fluorescence of the NV color center is not blocked by the tuning fork.

[0102] A small amount of epoxy resin glue with good light transmittance and UV curing is applied on the quartz beam. Through the micro-operation platform, the quartz beam is aligned and contacted with the sensor substrate with the waveguide facing downward on the PDMS under an optical microscope. The epoxy resin glue is cured by UV irradiation, completing the bonding of the sensor substrate and the quartz beam.

[0103] Figure 4 This is a photograph of the nitrogen vacancy color center sensor prepared in Example 1.

[0104] The nitrogen vacancy color center sensor prepared in Example 1 was analyzed using a scanning electron beam microscope to obtain a scanning electron beam microscope photograph thereof. Figure 5 shown.

[0105] On a light detection magnetic resonance platform using a 532 nm laser, fluorescence imaging of the nitrogen vacancy color center in the nitrogen vacancy color center sensor prepared in Example 1 was performed, and the fluorescence image thereof was obtained as follows: Figure 6 shown.

[0106] The relationship between the magnetic detection sensitivity δB of the sensor and the fluorescence count N of the nitrogen vacancy color center can be expressed as It can be seen that the higher the fluorescence count, the higher the magnetic detection sensitivity. Figure 7 The fluorescence saturation curve of a nitrogen vacancy color center in Example 1 is shown, and the fluorescence count obtained by fitting can reach 500kcounts / s, which is much larger than that of a single nanocolumn probe.

[0107] Example 1: On a 532nm laser light detection magnetic resonance platform, the electron paramagnetic resonance spectrum of one of the nitrogen vacancy color centers of the prepared nitrogen vacancy color center scanning sensor was experimentally measured as follows: Figure 8 shown.

Claims

1. A nitrogen vacancy color center sensor, characterized in that: include: A circuit board; electrodes are arranged on the circuit board; A tuning fork device; the end of the tuning fork device is electrically connected to an electrode of a circuit board; Transfer beam; The transfer beam is disposed at the front end of the tuning fork device; the transfer beam can transmit the fluorescence emitted by the nitrogen vacancy color center and the laser that excites the nitrogen vacancy color center; A diamond substrate; one side of the diamond substrate is connected to a transfer beam; the opposite side is provided with a diamond nanocolumn waveguide array; a nitrogen vacancy color center is provided on the diamond nanocolumn waveguide; the nitrogen vacancy color center on the diamond nanocolumn waveguide has a depth of 3 to 50 nm from the surface; The diamond nanocolumn waveguide is in the shape of a truncated cone; The upper surface diameter of the truncated cone is 200-800 nm; the edge tilt angle is 5°-30°; and the height is 0.3-2 μm; The transfer beam is a glass transfer beam; the length of the portion of the transfer beam exposed from the tuning fork device is at least 400 μm; The diamond substrate has a length of 50 to 300 μm, a width of 50 to 300 μm, and a thickness of 10 to 80 μm; One side of the diamond substrate and the transfer beam is a precision polished surface, and the polishing roughness reaches an rms of less than 1nm; The diamond substrate and the transfer beam are rigidly fixed by light-transmitting resin.

2. The nitrogen vacancy color center sensor according to claim 1, characterized in that: The circuit board has a length of 1 to 50 mm, a width of 1 to 50 mm, and a thickness of 0.5 to 5 mm; the transfer beam has a length of 0.1 to 3 mm, a width of 0.01 to 1 mm, and a thickness of 30 to 500 μm.

3. The nitrogen vacancy color center sensor according to claim 1, characterized in that: The number of diamond nano-pillar waveguides in the diamond nano-pillar waveguide array is greater than or equal to 2×2.

4. The nitrogen vacancy color center sensor according to claim 1, characterized in that: It also includes an atomic force microscope system; the electrodes of the circuit board are connected to a scanning imaging feedback system of the atomic force microscope system.

5. A method for preparing the nitrogen vacancy color center sensor according to claim 1, characterized in that: include: S1) nitrogen ion implantation is performed on diamond as a substrate, and diamond containing nitrogen vacancy color centers is obtained after annealing; S2) preparing a patterned mask on the diamond surface containing nitrogen vacancy color centers, and performing etching to obtain a diamond substrate; S3) The end of the tuning fork device is electrically connected to the electrode of the circuit board, and then the adapter beam is connected to the front end of the tuning fork device, and then the side of the diamond substrate without the nitrogen vacancy color center is connected to the tuning fork device to obtain a nitrogen vacancy color center sensor.

6. The preparation method according to claim 5, characterized in that: The energy of the nitrogen ion implantation is 2.5-20 keV; the implantation ion dose is 10 10 ~10 12 atom / cm 2 .

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