magnetic detector

Abstract

A magnetic detector (1) comprises: a diamond substrate (10) having an NV center (11); a transparent first substrate (13) on which the diamond substrate is disposed; a radiating body (24) provided on a surface of the first substrate (13) or on the surface of the diamond substrate (10) that is opposite from the surface on which the NV center (11) is provided; and a second substrate (15) which has an opening (16) and on which the first substrate (13) is disposed. The diamond substrate (10) is at least partially exposed through the opening (16).

Description

[Technical Field]

[0001] The present disclosure relates to magnetic detectors. [Background technology]

[0002] Patent Document 1 discloses a sensor for measuring a magnetic field, which includes a diamond having an NV center and an antenna made of a loop-shaped conductor formed on the surface of the diamond. In the technology described in Patent Document 1, excitation light and its fluorescence are input and output to the NV center from the surface of the sensor opposite to the antenna-forming surface. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-165670 Summary of the Invention

[0004] A magnetic detector according to one embodiment comprises a diamond substrate having an NV center, a transparent first substrate on which the diamond substrate is disposed, an emitter formed on a surface of the first substrate or on a surface of the diamond substrate facing opposite to the surface on which the NV center is formed, and a second substrate having an opening and on which the first substrate is disposed, wherein at least a portion of the diamond substrate is exposed from the opening. [Brief explanation of the drawings]

[0005] [Figure 1] FIG. 1 is a schematic diagram illustrating an example of a magnetic detector according to the first embodiment. [Figure 2] FIG. 2 is a schematic diagram illustrating an example of a substrate on which a magnetic detector is arranged. [Figure 3-1] FIG. 3-1 is a schematic diagram illustrating an example of a radiator. [Figure 3-2] Figure 3-2 is an enlarged partial view of the radiator. [Figure 4]FIG. 4 is a diagram showing the S11 reflection characteristic of the loop antenna. [Figure 5] FIG. 5 is a schematic diagram illustrating an example of a magnetic detector according to the second embodiment. [Figure 6] FIG. 6 is a schematic diagram illustrating an example of a magnetic detector according to the third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0006] A magnetic detector according to an embodiment will be described below. The magnetic detector 1 is for detecting magnetism generated in a measured sample 100. Fig. 1 is a schematic diagram for explaining an example of a magnetic detector according to a first embodiment.

[0007] [First embodiment] (sample to be measured) The sample 100 to be measured is an object to be detected by the magnetic detector 1, in other words, a specimen. A magnetic field is generated in the sample 100 to be measured when a current flows through a circuit. The magnetic field generated in the sample 100 to be measured is detected by the magnetic detector 1.

[0008] (magnetic detector) The magnetic detector 1 is disposed between an objective lens of a microscope (not shown) and a sample 100 to be measured. The magnetic detector 1 includes a diamond substrate 10, a first substrate 13, a radiator 24, and a second substrate 15.

[0009] The diamond substrate 10 is a so-called diamond sensor. The diamond substrate 10 has an NV center 11 formed in a diamond crystal.

[0010] The diamond crystal has an NV center 11. The diamond crystal has a side length of, for example, 2 mm. The diamond crystal has a thickness of, for example, 300 μm.

[0011] The NV center 11 may be arranged singly or in multiple locations on one surface of the diamond crystal. The NV center 11 may be oriented in one direction. The NV center 11 may also be a crystal with multiple different orientations. The NV center 11 is formed on the extreme surface of the surface 11b by, for example, a CVD (Chemical Vapor Deposition) method or an ion implantation method.

[0012] NV centers 11 are complex defects in diamond crystals where carbon would normally be present, replaced by nitrogen, with a vacancy at the adjacent position. NV centers 11 are missing some of the degenerate shared electron pairs. In zero magnetic field, NV centers 11 have electrons with spin angular momentum at two levels, m=0 and m=±1. Because the m=±1 electrons have a magnetic moment, they are affected by an external magnetic field, and the degeneracy of m=±1 is broken, resulting in two more energy levels. The strength of an external magnetic field can be detected by detecting the electron spin resonance caused by these using light waves and microwaves.

[0013] The electrons in the NV center 11 are excited by light with a wavelength of 532 nm and emit fluorescence with a wavelength of 638 nm during the relaxation process. This fluorescence process is unlikely to occur at the electron spin resonance frequency. Therefore, by utilizing this property, the state of the m = ±1 electrons can be observed. The electron spin resonance frequency of the NV center 11 in a diamond crystal is known to be approximately 2.87 GHz in zero magnetic field. When microwaves with the frequency of this resonance point (resonance frequency) are irradiated, the fluorescence with a wavelength of 638 nm is quenched. Furthermore, the resonant frequency of the microwave changes due to changes in the state of the m = ±1 electrons depending on the strength of the external magnetic field, etc. Then, by capturing this change as a frequency change in the fluorescence intensity, magnetic fields and currents can be detected.

[0014] At least a portion of the surface 10a of the diamond substrate 10 is exposed from the opening 16 of the second substrate 15, which will be described later. In this embodiment, the entire surface of the surface 10a of the diamond substrate 10 is exposed from the opening 16. Microwaves and green light enter from the portion of the diamond substrate 10 exposed from the opening 16. Red light exits from the portion of the diamond substrate 10 exposed from the opening 16. In FIG. 1, the incident direction of the green light is indicated by arrow LG. The exit direction of the red light is indicated by arrow LR. The incident direction of the microwave is indicated by arrow LM.

[0015] The surface 10b of the diamond substrate 10 is a magnetic detection surface. A first substrate 13 is disposed on the surface 10a side of the diamond substrate 10.

[0016] The first substrate 13 is an antenna substrate. The first substrate 13 is a transparent substrate. The first substrate 13 is a substrate that is transmissive to green light, red light, and microwaves. A diamond substrate 10 is arranged on a surface 13b of the first substrate 13. A second substrate 15 and a radiator 24 are arranged on a surface 13a of the first substrate 13. The first substrate 13 has an outer shape that is larger than the opening 16 of the second substrate 15. The diamond substrate 10 is bonded to the central portion of the first substrate 13, which is exposed from the opening 16. The outer edge of the first substrate 13 and the inner edge of the surface 15b of the second substrate 15 are bonded to each other.

[0017] The first substrate 13 is provided with an opening 16 and holds the diamond substrate 10 in place of the second substrate 15 which cannot directly hold the diamond substrate 10 .

[0018] Second substrate 15 is a PCB (Printed Circuit Board). Second substrate 15 has an opening 16 in the center. First substrate 13 is disposed in the center of second substrate 15. The outer edge of first substrate 13 is joined to the inner edge of surface 15b of second substrate 15.

[0019] When viewed from above, a gap S exists between the peripheral edge 16a of the opening 16 and the diamond substrate 10 in the radial direction.

[0020] The top view is a view in a direction along the incident direction of the green light. The top view is a view of the magnetic detector 1 from the side opposite to the magnetic detection surface.

[0021] The relationship between the aperture 16 in the second substrate 15 and the field of view V of the objective lens will now be described. In FIG. 1, the dashed line indicates the field of view V of the objective lens, i.e., the NA (Numerical Aperture) and working distance. If the aperture 16 in the second substrate 15 is narrower than the field of view V, part of the excitation light incident from the objective lens is blocked by the second substrate 15, reducing the amount of light and the detection sensitivity. Therefore, the size of the aperture 16 in the second substrate 15 is set so that the excitation light incident from the objective lens is not blocked, in other words, so that the field of view A is not blocked. This allows the excitation light and microwaves to be appropriately incident from the surface 10a of the diamond substrate 10 through the aperture 16 in the second substrate 15 and act on the NV centers 11 on the surface 10b, which is the magnetic detection surface.

[0022] Second substrate 15 is provided with a high-frequency transmission line that supplies microwaves to radiator 24. The high-frequency transmission line will be described later.

[0023] In the magnetic detector 1 configured in this manner, when measuring the magnetic field of the sample 100 to be measured, the diamond substrate 10, the first substrate 13, and the second substrate 15 are stacked in this order in order from the substrate closest to the sample 100 to the substrate closest to the sample 100 to be measured.

[0024] (Microwave power supply system) The microwave power supply system supplies microwaves in the magnetic detector 1. The microwave power supply system is a radiator 24. The radiator 24 is provided on the surface 13a of the first substrate 13. The radiator 24 applies microwaves to the NV centers 11 of the diamond substrate 10. The radiator 24 transmits microwaves to be irradiated to the NV centers 11 of the diamond substrate 10. The radiator 24 transmits microwaves from a microwave source (not shown). A high-frequency transmission line provided on the second substrate 15 is connected to the radiator 24, and microwaves are supplied from the outside.

[0025] The radiator 24 is, for example, a small loop antenna. The radiator 24 has, for example, a frequency of 2.8 GHz or more and 2.9 GHz or less. The radiator 24 has, for example, an input power of -20 dBm or more and +20 dBm or less.

[0026] The radiator 24 may be provided in a comb-like shape as shown in Fig. 3-2. The comb-tooth portion forms a capacitance. By adjusting the line and space and number of pairs of the electrode elements, the comb-tooth portion can reduce the reflection of microwaves of a specific frequency that are incident on the radiator 24.

[0027] (optical system) The optical system detects the magnetism of the sample 100 to be measured in the magnetic detector 1. The optical system includes a light-emitting element and a light-receiving element, not shown. The light-emitting element and the light-receiving element are arranged, for example, on an objective lens arranged facing the diamond substrate 10. The light-emitting element and the light-receiving element are focused on the NV center 11 provided in the diamond substrate 10.

[0028] The light-emitting element irradiates the diamond substrate 10 with green light. The light-emitting element emits excitation light that irradiates the diamond crystal. The light-emitting element is, for example, a laser diode. The light-emitting element emits laser light with a wavelength of, for example, 527 nm. The light-emitting element emits green excitation light. As the light-emitting element, for example, a green light-emitting diode (LED: Light Emitting Diode), a green surface-emitting laser diode (VCSEL: Vertical Cavity Surface Emitting Laser), a green edge-emitting laser diode (LD: Laser Diode), etc. can be used.

[0029] The light receiving element receives red light generated by inputting green light into the diamond substrate 10. The light receiving element detects fluorescence from the diamond substrate 10. The light receiving element is a photodiode. The light receiving element receives fluorescence emitted from the diamond crystal in response to excitation light. For example, a Si-PIN photodiode (PD: Photo Diode) or an InGaAs-PIN photodiode can be used as the light receiving element.

[0030] (substrate) FIG. 2 is a schematic diagram illustrating an example of a substrate on which a magnetic detector is arranged. FIG. 3-1 is a schematic diagram illustrating an example of a radiator. FIG. 3-2 is a partially enlarged view of the radiator. The magnetic detector 1 configured in this manner is arranged on a substrate 50. The substrate 50 is a PCB. In this embodiment, the second substrate 15 of the magnetic detector 1 and the substrate 50 may be a single substrate or may be separate substrates.

[0031] A microwave power supply system including a high-frequency connector 51, a high-frequency transmission line 52, a high-frequency transmission line 53, a high-frequency transmission line 54, and a high-frequency transmission line 55 is arranged on the substrate 50. The width of the end 54a of the high-frequency transmission line 54 gradually tapers toward the connection portion with the second substrate 15.

[0032] (Magnetic field detection method and action) The following describes a method for detecting the magnetic field of the sample 100 to be measured in the magnetic detector 1. When detecting a magnetic field, the sample 100 to be measured is placed close to or in close contact with the surface 10b of the diamond substrate 10 of the magnetic detector 1, which is the magnetic field acting surface.

[0033] The microwaves generated by the microwave source propagate to the radiator 24 via the high-frequency connector 51, high-frequency transmission line 52, high-frequency transmission line 53, high-frequency transmission line 54, and high-frequency transmission line 55. The microwaves are then radiated from the radiator 24. The microwaves radiated from the radiator 24 then act on the NV centers 11 in the diamond substrate 10, causing electron spin resonance. Spatial changes in the direction or magnitude of the magnetic field generated in the sample 100 to be measured act on the NV centers 11 of the diamond crystals in the diamond substrate 10 of the magnetic detector 1.

[0034] The green excitation light from the light-emitting element is incident on the diamond crystal, and the green excitation light that has entered the diamond crystal diffuses widely within the diamond crystal, irradiating and exciting the NV centers 11.

[0035] The excited NV centers 11 generate red fluorescence, which enters the diamond crystal, then diffuses widely within the diamond crystal, and enters the light-receiving surface of the light-receiving element.

[0036] The light receiving element receives, as fluorescence, an electron spin resonance signal of the NV center 11 excited by the excitation light from the diamond crystal.

[0037] Figure 4 shows the S of the loop antenna. 11 4 shows the reflection characteristics of the magnetic detector 1 when it is realized as a diamond quantum sensor head. 11 4 is a graph showing the results of measuring the reflection characteristics. As shown in FIG. 4, at an input frequency of 2.9 GHz, 11 =-25dB, and good characteristics were confirmed.

[0038] (effect) As described above, in this embodiment, at least a portion of the diamond substrate 10 is exposed through the opening 16 of the second substrate 15. The radiator 24 is provided on a surface of the first substrate 13 or on the surface of the diamond substrate 10 facing away from the magnetic detection surface. In this embodiment, even if the diamond substrate 10 is small, the optical field can be secured by the opening 16 of the second substrate 15. In this embodiment, no optical system or microwave power supply system is arranged on the side of the surface 10b, which is the magnetic detection surface, of the diamond substrate 10. In this embodiment, power can be supplied to the radiator 24 from the surface 10a, which is the opposite side of the surface 10b, which is the magnetic detection surface, via the second substrate 15. In this embodiment, samples 100 to be measured of various shapes can be brought close to the surface 10b, which is the magnetic detection surface. In this way, this embodiment enables highly sensitive magnetic field detection.

[0039] According to this embodiment, when the magnetic detector 1 is applied to a microscope, the field of view of the objective lens is sufficiently secured, making it easy to optically bring the NV center 11 into the field of view. This embodiment can be used for observing the magnetic field of a flat microcircuit, for example.

[0040] In this embodiment, when viewed from above, a gap S exists between the peripheral edge 16a of the opening 16 in the second substrate 15 and the diamond substrate 10. According to this embodiment, when viewed from above, the entire diamond substrate 10 can be exposed from the opening 16 in the second substrate 15. According to this embodiment, the optical field of view can be efficiently secured.

[0041] In this embodiment, the diamond substrate 10, the first substrate 13, and the second substrate 15 are stacked in this order, starting from the substrate closest to the sample 100. According to this embodiment, samples 100 to be measured having various shapes can be placed close to the surface 10b, which is the magnetic detection surface. In this embodiment, the diamond substrate 10 can be placed without any restrictions on thickness.

[0042] In this embodiment, the radiator 24 is disposed on the first substrate 13. In this embodiment, the antenna formation surface can be disposed along the surface of the second substrate 15. According to this embodiment, there is no need to provide a through-hole or the like in the second substrate 15, and therefore the configuration can be easily performed.

[0043] In contrast, in the technology described in Patent Document 1, the antenna-forming surface is the magnetic detection surface. As a result, the wiring that supplies power to the antenna from outside the diamond forms a convex portion on the magnetic detection surface. This can make it difficult to bring the sample to be measured close to the magnetic detection surface. If the sample to be measured cannot be brought close enough to the magnetic detection surface, the magnetic field detection sensitivity decreases.

[0044] [Second embodiment] 5 is a schematic diagram illustrating an example of a magnetic detector according to the second embodiment. In this embodiment, a diamond substrate 10, a first substrate 13, and a second substrate 15 are different from those in the first embodiment.

[0045] The diamond substrate 10 and the second substrate 15 are disposed on the surface 13b of the first substrate 13. The diamond substrate 10 is disposed inside the opening 16 of the second substrate 15.

[0046] The diamond substrate 10 may protrude from the surface 13 b of the first substrate 13 .

[0047] The emitter 24 is disposed between the diamond substrate 10 and the first substrate 13. More specifically, the emitter 24 is provided on the surface 13b of the first substrate 13 or the surface 10a of the diamond substrate 10.

[0048] (effect) As described above, in this embodiment, the diamond substrate 10 and the second substrate 15 are arranged on the surface 13b of the first substrate 13. In this embodiment, the diamond substrate 10 is arranged inside the opening 16 of the second substrate 15. In this embodiment, the thickness of the magnetic detector 1 can be made thinner than in the first embodiment. According to this embodiment, the objective lens can be brought closer to the NV center 11 of the diamond substrate 10.

[0049] In this embodiment, the radiator 24 is disposed between the diamond substrate 10 and the first substrate 13. In this embodiment, power can be supplied to the radiator 24 from the surface 10a opposite to the surface 10b, which is the magnetic detection surface.

[0050] In this embodiment, when the diamond substrate 10 protrudes from the surface 13b of the first substrate 13, the sample 100 to be measured can be brought close to or in close contact with the surface 10b, which is the magnetic field acting surface of the diamond substrate 10 of the magnetic detector 1. This embodiment allows samples 100 to be measured of various shapes to be brought close to the surface 10b, which is the magnetic detection surface. In this way, this embodiment allows magnetic fields to be detected with high sensitivity.

[0051] [Third embodiment] 6 is a schematic diagram illustrating an example of a magnetic detector according to a third embodiment. In this embodiment, the magnetic detector 1 is different from the first embodiment in that it includes a magnet 30.

[0052] The magnet 30 applies a static magnetic field to the NV center 11 of the diamond substrate 10. The magnet 30 is disposed on the first substrate 13 or the second substrate 15. The magnet 30 is adjusted so that the direction AM of the magnetic field is perpendicular to the direction AD of the NV center 11.

[0053] (effect) As described above, in this embodiment, the magnet 30 can be fixed onto the surface 13b of the first substrate 13. According to this embodiment, double resonance can be generated stably and accurately by the magnet 30. This embodiment can measure the magnetic field more accurately.

[0054] The embodiments disclosed in the present application can be modified without departing from the spirit and scope of the invention. Furthermore, the embodiments disclosed in the present application and their modifications can be combined as appropriate.

[0055] Although specific embodiments have been described to fully and clearly disclose the claimed technology, the appended claims should not be limited to the above-described embodiments, but should be construed to embody all modifications and alternative arrangements that may be made by those skilled in the art within the scope of the basic concept presented herein. [Explanation of symbols]

[0056] 1 Magnetic detector 10 Diamond substrate 11 NV Center 13 First board 15 Second board 16 Aperture 24 Radiator 50 boards 51 High Frequency Connector 52 High-frequency transmission line 53 High-frequency transmission line 54 High-frequency transmission line 54a end 55 High-frequency transmission line 100 samples to be measured

Claims

1. a diamond substrate having an NV center; a transparent first substrate on which the diamond substrate is disposed; a radiator provided on a surface of the first substrate or on a surface of the diamond substrate facing opposite to a surface on which the NV center is provided; a second substrate having an opening and on which the first substrate is disposed; Equipped with At least a portion of the diamond substrate is exposed through the opening. Magnetic detector.

2. When viewed from above, there is a gap between the peripheral edge of the opening and the diamond substrate. The magnetic detector according to claim 1 .

3. The diamond substrate, the first substrate, and the second substrate are stacked in this order in order of proximity to a sample to be measured for magnetic detection. The magnetic detector according to claim 1 .

4. The radiator is disposed on the first substrate. The magnetic detector according to claim 3 .

5. the diamond substrate and the second substrate are disposed on a surface of the first substrate; the diamond substrate is disposed inside the opening of the second substrate; The magnetic detector according to claim 1 .

6. the emitter is disposed between the diamond substrate and the first substrate; The magnetic detector according to claim 5 .

7. a magnet disposed on the first substrate or the second substrate; Equipped with The magnetic field is adjusted to be oriented perpendicular to the direction of the NV center. The magnetic detector according to claim 1 .

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