WO2018230736A1

WO2018230736A1 - Sensor and method for manufacturing sensor

Info

Publication number: WO2018230736A1
Application number: PCT/JP2018/023039
Authority: WO
Inventors: 大雅清水
Original assignee: 国立大学法人東京農工大学
Priority date: 2017-06-15
Filing date: 2018-06-15
Publication date: 2018-12-20
Also published as: JP7210027B2; JPWO2018230736A1

Abstract

In order to provide a sensor using a surface plasmon polariton excitation structure, the present invention provides a sensor which is provided with: a substrate; a ferromagnetic layer provided on the substrate; a low refractive index layer that is provided on the ferromagnetic layer and that includes a space through which a substance to be measured flows; and a high refractive index layer that is provided on the low refractive index layer and that has a higher refractive index than the low refractive index layer. In addition, the present invention provides a method for manufacturing the sensor, the method including: preparing a substrate; providing a ferromagnetic layer on the substrate; providing, on the ferromagnetic layer, a low refractive index layer that includes a space through which a substance to be measured flows; and providing, on the low refractive index layer, a high refractive index layer that has a higher refractive index than the low refractive index layer.

Description

Sensor and sensor manufacturing method

The present invention relates to a sensor and a method for manufacturing the sensor.

Conventionally, a sensor using a surface plasmon polariton excitation structure is known (see, for example, Patent Document 1).
Patent Document 1 International Publication No. 2011/142118

Challenges to be solved

There is a need for a more sensitive sensor that uses a surface plasmon polariton excitation structure.

General disclosure

In the first aspect of the present invention, a substrate, a ferromagnetic layer provided above the substrate, and a low refractive index layer provided above the ferromagnetic layer and including a space for flowing a measurement target substance And a high refractive index layer that is provided above the low refractive index layer and has a higher refractive index than the low refractive index layer.

In the second aspect of the present invention, a substrate is prepared, a ferromagnetic layer is provided above the substrate, and a low refractive index layer including a space for flowing a measurement target substance is provided above the ferromagnetic layer. Provided is a sensor manufacturing method in which a high refractive index layer having a refractive index larger than that of the low refractive index layer is provided above the low refractive index layer.

Note that the above summary of the invention does not enumerate all the features of the present invention. In addition, a sub-combination of these feature groups can also be an invention.

1 shows an exemplary configuration of a sensor 100 according to a first embodiment. An example of the structure of the sensor 100 is shown. An example of the manufacturing method of the sensor 100 is shown. In the sensor configuration of FIG. 1, the surface plasmon polariton light wave is in a laminated structure comprising the substrate 10, the metal layer 12, the ferromagnetic layer 14, the metal layer 16, the low refractive index layer 20, the high refractive index layer 22, and the prism 24. An example of a state of distribution is shown. The wavelength dependence of the index ΔR _p / R _p of the sensor 100 is shown. The dependence of the index ΔR _p / R _p of the sensor 100 on the incident angle θ is shown. An example of the structure of the sensor 100 which concerns on Example 2 is shown. An example of the structure of the sensor 100 which concerns on Example 3 is shown. An example of the structure of the sensor 100 which concerns on Example 4 is shown. The structure of the sensor 500 concerning the comparative example 1 is shown. The sensitivity of the sensor 100 which concerns on Example 2, and the sensitivity of the sensor 500 which concerns on the comparative example 1 are shown. A specific incident angle θ dependency of the index ΔR _p / R _p of the sensor 100 is shown. The specific incident angle θ dependency of the index R _p of the sensor 500 is shown. Shows a specific incident angle θ dependency of index sensor 100 according to Example _{_{4 (ΔR p / R p)}} '. An example of an application example of the sensor device 200 will be described. An example of a structure of the sensor apparatus 200 is shown. The relationship between the magnetic field applied to the ferromagnetic layer 14 and the magneto-optic effect is shown.

Hereinafter, the present invention will be described through embodiments of the invention. However, the following embodiments do not limit the invention according to the claims. In addition, not all the combinations of features described in the embodiments are essential for the solving means of the invention.

[Example 1]
FIG. 1 illustrates an exemplary configuration of a sensor 100 according to the first embodiment. The sensor 100 of this example includes a substrate 10, a metal layer 12, a ferromagnetic layer 14, a metal layer 16, a low refractive index layer 20, a high refractive index layer 22, a prism 24, and a molecular recognition element 32. With. The sensor 100 measures the refractive index of the measurement target substance 30.

The substrate 10 may be a substrate of any material such as a glass substrate or a semiconductor substrate. The material of the substrate 10 is a material on which an oxide such as silicon oxide (SiO ₂ ) or magnesium oxide (MgO) or a metal such as iron (Fe) such as silicon, silver (Ag), or gold (Au) can be formed. It is preferable.

The metal layer 12 is provided above the substrate 10. The metal layer 12 in this example is provided between the substrate 10 and the metal layer 16. The materials of the metal layer 12 and the metal layer 16 are materials having higher conductivity at the measurement wavelength than the ferromagnetic layer 14. The metal layer 12 may be a noble metal such as Ag or Au, or an alloy of two or more materials selected from these. The metal layer 12 is an example of a second metal layer.

The ferromagnetic layer 14 includes a magnetic material having a magnetic moment aligned in a predetermined direction. In one example, the direction of the magnetic moment of the ferromagnetic layer 14 is controlled by applying an external magnetic field. By changing the magnitude of the external magnetic field applied to the ferromagnetic layer 14, the detection sensitivity of the sensor 100 changes. For example, the material of the ferromagnetic layer 14 includes a ferromagnetic material such as cobalt, iron, nickel, or an alloy of two or more kinds of materials selected from these.

The metal layer 16 is provided on the upper surface of the ferromagnetic layer 14. The metal layer 16 of this example is provided between the ferromagnetic layer 14 and the low refractive index layer 20. The material of the metal layer 16 is a material having a higher conductivity than the ferromagnetic layer 14. The metal layer 16 may be a noble metal such as Ag or Au, or an alloy of two or more materials selected from these. The metal layer 12, the ferromagnetic layer 14, and the metal layer 16 constitute a composite metal thin film having a laminated structure of a ferromagnetic metal and a noble metal. By using a noble metal as the metal layer 12 and the metal layer 16, the loss in the composite metal thin film can be reduced and the ATR curve described later can be made steep. The film thickness of the metal layer 16 in this example is smaller than the film thickness of the metal layer 12. The metal layer 16 is an example of a first metal layer.

The low refractive index layer 20 is provided above the ferromagnetic layer 14. The low refractive index layer 20 of this example is provided on the upper surface of the metal layer 16. The low refractive index layer 20 has a space for flowing the measurement target substance 30 having a predetermined refractive index. The low refractive index layer 20 has a predetermined layer thickness t. In one example, the layer thickness t of the low refractive index layer 20 may be 15000 nm or less, 3000 nm or less, 1500 nm or less, or 500 nm or less. The refractive index of the low refractive index layer 20 is determined according to the substance to be measured. When the layer thickness t of the low refractive index layer 20 is changed with respect to a combination of a metal layer containing a ferromagnetic metal and a dielectric for a predetermined refractive index, a radiation mode (that is, a mode represented by −M) The refractive index of the high refractive index layer 22 is determined so that the confinement mode (that is, the mode represented by + M) can be switched by the magnetization reversal of the ferromagnetic metal. End portions of the low refractive index layer 20 are supported by a plurality of support layers 21. The support layers 21 of this example are provided at the four corners of the substrate 10 when the planar shape of the substrate 10 is a rectangle. The plurality of support layers 21 may form an inflow port for flowing in the measurement target substance 30 and an outflow port for flowing out the measurement target substance 30. However, the method for supporting the space between the metal layer 16 and the high refractive index layer 22 is not particularly limited as long as a space into which the low refractive index layer 20 flows can be secured.

Further, the upper surface and the lower surface of the low refractive index layer 20 are not limited to flat surfaces, and may have curved surfaces, irregularities, or the like as long as the sensor 100 can operate. Furthermore, in order to make the layer adjacent to the low refractive index layer 20 disposable, members such as the metal layer 16 and the high refractive index layer 22 may be exchangeable.

The measurement target substance 30 is a substance whose characteristics are to be detected by the sensor 100. The measurement target substance 30 is not particularly limited as long as it can be introduced into the space of the low refractive index layer 20. The measurement target substance 30 in this example is a liquid or a gas. The sensor 100 measures the physical properties of the measurement target substance 30. In one example, the sensor 100 acquires information on the measurement target substance 30 in advance, thereby measuring the type, composition, concentration, binding / dissociation of the analyte and the antibody, and the like from the change in refractive index. . For example, when the measurement target substance 30 is a gas, the sensor 100 functions as a gas sensor.

The molecular recognition element 32 adsorbs the measurement target substance 30. In one example, the molecular recognition element 32 is an antibody corresponding to the measurement target substance 30. The molecular recognition element 32 is provided in the space of the low refractive index layer 20. The molecular recognition element 32 of this example is provided on the upper surface of the metal layer 16. That is, the molecular recognition element 32 is provided on the bottom surface side of the low refractive index layer 20. However, the molecular recognition element 32 may be provided on the upper surface side of the low refractive index layer 20 or may be provided in the center. The sensor 100 can measure a plurality of measurement target substances 30 by providing a plurality of molecular recognition elements 32.

The high refractive index layer 22 is provided above the low refractive index layer 20. The high refractive index layer 22 is a layer having a higher refractive index than the low refractive index layer 20. In one example, the refractive index difference between the low refractive index layer 20 and the high refractive index layer 22 is determined as follows. The refractive index of the low refractive index layer 20 is determined with respect to the refractive index of the measurement target substance 30. When the layer thickness t of the low-refractive index layer 20 is changed for a combination of a metal layer containing a ferromagnetic metal and a dielectric for a predetermined refractive index, a radiation mode (mode represented by −M) and a confinement mode The refractive index of the high-refractive index layer 22 is determined so that (the mode represented by + M) can be switched by the magnetization reversal of the ferromagnetic metal.

In another example, the refractive index difference between the low refractive index layer 20 and the high refractive index layer 22 is determined as follows. The refractive index of the low refractive index layer 20 is determined with respect to the refractive index of the measurement target substance 30. When the layer thickness t of the low refractive index layer 20 is changed for a combination of a metal layer containing a ferromagnetic metal and a dielectric for a predetermined refractive index, the radiation mode and the confinement mode are changed to the layer of the low refractive index layer 20. The refractive index of the high refractive index layer 22 is determined so that it can be switched depending on the thickness t. The refractive index difference is determined so as to satisfy the following conditions for a certain wavelength, the layer thickness t of the low refractive index layer 20, and the combination of the ferromagnetic metal and the noble metal. For example, when the refractive index of the low refractive index layer 20 is 1.02, the material of the high refractive index layer 22 can be SiO ₂ .

The prism 24 is provided on the high refractive index layer 22. Incident light 110 having a predetermined wave number is incident on the prism 24. The incident light 110 is incident on the prism 24 at a predetermined incident angle θ. Incident light 110 includes at least p-polarized light. The wave number and incident angle θ of the incident light 110 may be changed according to the plasmon excited by the sensor 100, the material constituting the low refractive index layer 20 and the high refractive index layer 22, or the like. In one example, the prism 24 is made of the same material as the high refractive index layer 22. The material of the prism 24 in this example is SiO ₂ .

The sensor 100 of this example measures the reflectance of the incident light 110 and detects the difference in the refractive index of the measurement target substance 30 from the difference in the measured reflectance. The total reflection attenuation method (ATR method) is used to measure the reflectance of the incident light 110. For example, the sensor 100 measures the dependence of the reflectance on the incident angle θ when the magnetization of the ferromagnetic metal is positive and negative, and the change in reflectance when the magnetization is reversed (ΔR _p / R _p ). Alternatively, the change in refractive index is detected using the reflectance (R _p ) as an index. Thereby, the sensor 100 measures the physical property of the measurement target substance 30.

Here, surface plasmons are excited at the interface of the ferromagnetic layer 14 on the low refractive index layer 20 side. The excitation condition and excitation state of the surface plasmon are determined by the incident angle θ and the wave number of the incident light 110 incident from the prism 24. For example, the surface plasmon is excited through an evanescent wave when light incident from the high refractive index layer 22 side is totally reflected at the interface between the high refractive index layer 22 and the low refractive index layer 20. The excited state of the surface plasmon changes as the refractive index of the measurement target substance 30 occupying the space of the low refractive index layer 20 changes. By designing the layer thickness t of the low refractive index layer 20 so that the Z-direction component of the wave number on the high refractive index layer 22 side matches the wave number on the surface plasmon side, the reflectance of the incident light 110 is made zero, or Can approach zero.

Of the indices of the sensor 100, the change in reflectivity (ΔR _p / R _p ) at the time of magnetization reversal is expressed by the following equation (1). For example, when the index (ΔR _p / R _p ) of the sensor 100 changes by δ (ΔR _p / R _p ) with respect to the change in refractive index δn, δ (ΔR _p / R _p ) / δn Corresponds to sensitivity. The index in this example is obtained by normalizing the difference in reflectance at the time of magnetization reversal by the sum of reflectances, and takes a value between −1 and +1.

ΔR _p indicates a change in reflectance (that is, a difference in reflectance) at the time of magnetization reversal measured at a certain incident angle θ. The magnetization reversal means a case where a predetermined external magnetic field (+ M) is applied to the ferromagnetic layer 14 and an external magnetic field (−M) obtained by reversing the external magnetic field (+ M) is applied to the ferromagnetic layer 14. Point to. R _p is the reflectance R _p (+ M), R _p (−M) obtained under the external magnetic field (+ M) and the external magnetic field (−M) when the reflectance is measured at a certain incident angle θ. ). Sensor 100 detects a change in the refractive index from the index [Delta] R _p / _{R p} is the ratio between the [Delta] R _p and _{R p.} Equation (1) is an example of an index ΔR _p / R _p when the sensor 100 is used, and is not limited to using a difference in reflectance or a sum of reflectances. For example, it is possible to use an average value of the reflectance as R _p.

Note that the change in reflectivity (ΔR _p / R _p ) at the time of magnetization reversal with respect to the change in refractive index is larger than the change in reflectivity with respect to the change in refractive index. That is, the change δ (ΔR _p / R _p ) / δn of the change in reflectance at the time of magnetization reversal is larger than the change δR _p / δn of the reflectivity with respect to the refractive index. Sensor 100, by the index and [Delta] R _p / _{R p,} is enhanced sensitivity than if an index _{R p.} In one example, the sensor 100 of this example can detect a refractive index difference of 10 to the sixth power.

As another index of the sensor 100, the reflectances R _p (t1) and R _p (t2) at two points (t1, t2) having different layer thicknesses t of the low refractive index layer 20 are measured, and the reflectances at different positions are measured. Change (ΔR _p / R _p ) ′. When (ΔR _p / R _p ) ′ changes by δ (ΔR _p / R _p ) ′ with respect to the refractive index change δn, δ (ΔR _p / R _p ) ′ / δn corresponds to the sensitivity of the sensor 100. To do. The index in this example is obtained by normalizing the difference in reflectance at different positions by the sum of reflectances, and takes a value between −1 and +1. The magnetization state of the ferromagnetic metal may be arbitrary.

ΔR _p ′ indicates a change in reflectance (that is, a difference in reflectance) at two points where the layer thickness t of the low refractive index layer 20 is different, which is measured at a certain incident angle θ. R _p ′ represents the sum of the reflectances R _p (t1) and R _p (t2) at two points with different layer thicknesses t of the low refractive index layer 20 measured at a certain incident angle θ. The sensor 100 detects a change in refractive index from an index ΔR _p ′ / R _p ′, which is a ratio between ΔR _p ′ and R _p ′. The equation (2) is an example of an index (ΔR _p / R _p ) ′ when the sensor 100 is used, and is not limited to using a difference in reflectance or a sum of reflectances. For example, an average value of reflectance may be used as R _p ′.

The sensor 100 of this example is configured by an otto arrangement having a three-layer structure of a high refractive index layer 22, a low refractive index layer 20 including a measurement target substance 30, and a metal. In the Otto arrangement, the Z-direction component of the wave number on the high refractive index layer side and the wave number of the surface plasmon can be perfectly matched, and the reflectance is theoretically zero. Thereby, the sensitivity of the sensor 100 improves. In the sensor 100 of this example, in the otto configuration, the indices are ΔR _p / R _p and (ΔR _p / R _p ) ′, but even when R _p is used as the index, the low refractive index layer By selecting and measuring the layer thickness t of 20 with respect to the analyte and the measurement wavelength, the sensitivity can be improved as compared with the Kretschmann arrangement.

As described above, the sensor 100 reduces the reflectivity to zero and combines the ferromagnetic metal and the noble metal to change the reflectivity at the time of magnetization reversal (ΔR _p / R with respect to the change in the refractive index of the measurement target substance 30. _p ) to make the change steep. The sensor 100 makes the reflectance change (ΔR _p / R _p ) at the time of magnetization reversal, which is an index, close to 1 (that is, 100%) by setting the reflectance to zero. In addition, since the measurement target substance 30 generally has a wavelength dependency on the refractive index, a large sensitivity can be realized by selecting an appropriate wavelength. For example, the sensor 100 is designed in accordance with a wavelength at which the measurement target substance 30 exhibits the largest refractive index change.

FIG. 2 shows an example of the configuration of the sensor 100. The sensor 100 of this example further includes a magnetic field application unit 40. In FIG. 2, although the detailed structure of the sensor 100 is omitted, the sensor 100 may have the same structure as the sensor 100 shown in FIG.

The magnetic field application unit 40 applies a magnetic field to the ferromagnetic layer 14. In one example, the magnetic field application unit 40 applies either the first magnetic field or a second magnetic field different from the first magnetic field to the ferromagnetic layer 14. For example, the magnetic field application unit 40 applies a saturation magnetic field to the ferromagnetic layer 14 as the first magnetic field, and applies a reverse magnetic field of the saturation magnetic field to the ferromagnetic layer 14 as the second magnetic field. However, the magnetic field applied to the ferromagnetic layer 14 is not limited to the reversal magnetic field, and may be a magnetic field having the same polarity. The magnetic field application unit 40 stabilizes the signal by setting the external magnetic field applied to the ferromagnetic layer 14 as the saturation magnetic field of the ferromagnetic layer 14. However, the magnetic field applied to the ferromagnetic layer 14 is not limited to the saturation magnetic field.

The low refractive index layer 20 is connected to the inflow portion 26 and the outflow portion 28 at both ends. The inflow portion 26 and the outflow portion 28 are connected to the space of the low refractive index layer 20. The inflow portion 26 allows the measurement target substance 30 to flow into the low refractive index layer 20 from the outside. The outflow part 28 causes the measurement target substance 30 to flow out from the inside of the low refractive index layer 20 to the outside.

The sensor 100 of this example changes the direction of the magnetic field applied to the ferromagnetic layer 14 and measures the physical property of the measurement target substance 30 using the index ΔR _p / R _p . The sensor 100 realizes high sensitivity by adding a magnetic action to the surface plasmon.

FIG. 3 shows an example of a method for manufacturing the sensor 100. This example is an example of the manufacturing method of the sensor 100, and the sensor 100 may be manufactured using another manufacturing method.

In manufacturing the sensor 100, the substrate 10 is prepared. A ferromagnetic layer 14 is provided above the substrate 10. In this example, a metal layer 12, a ferromagnetic layer 14, and a metal layer 16 are stacked on the upper surface of the substrate 10. A low refractive index layer 20 and a high refractive index layer 22 are laminated on the upper surface of the metal layer 16. In one example, an adhesive is applied to the upper surface of the ferromagnetic layer 14, and the high refractive index layer 22 is laminated above the ferromagnetic layer 14 via the adhesive. When the sensor 100 has the metal layer 16, the adhesive is applied to the upper surface of the metal layer 16. The laminated structure of the ferromagnetic layer 14, the low refractive index layer 20, and the high refractive index layer 22 is formed by laminating the high refractive index layer 22 above the ferromagnetic layer 14 with an adhesive. It is formed by heating the layer 14, the adhesive, and the high refractive index layer 22.

The high refractive index layer 22 is laminated on the upper surface of the metal layer 16 via the support layer 21. That is, the adhesive is cured by heating to become the support layer 21. For example, after providing indium on the metal layer 16 as the material of the support layer 21, the high refractive index layer 22 is laminated and heated in a nitrogen atmosphere. Thus, the high refractive index layer 22 is formed above the metal layer 16 in the manner of solder. Thereby, the low refractive index layer 20 is provided between the high refractive index layer 22 and the metal layer 16.

The space of the low refractive index layer 20 may be formed using a technique such as an etching process. For example, when the high refractive index layer 22 is SiO ₂ , the flow path is formed by providing a groove on the SiO ₂ substrate. The low refractive index layer 20 may be formed between the high refractive index layer 22 and the metal layer 16 by bonding the side on which the flow path of the SiO ₂ substrate is formed to the metal layer 16 side. The prism 24 may be bonded to the upper surface of the high refractive index layer 22 with matching oil or the like.

FIG. 4 shows an example of a state in which light waves of surface plasmon polariton are distributed in a sensor structure mainly composed of a laminated structure. The figure shows a simplified structure of the sensor 100 and an ATR curve of the sensor 100. The vertical axis of the ATR curve indicates the intensity of the plasmon wave, and the horizontal axis indicates the coordinates of the sensor 100 in the depth direction. The coordinates are such that the interface between the low refractive index layer 20 and the high refractive index layer 22 is the origin, the low refractive index layer 20 side is the positive direction, and the high refractive index layer 22 side is the negative direction. The solid line in the graph corresponds to the intensity distribution of the plasmon wave when the magnetic field application unit 40 applies the magnetic field (−M), and the broken line indicates the plasmon when the magnetic field application unit 40 applies the magnetic field (+ M). Corresponds to the wave intensity distribution.

The plasmon wave is mainly generated near the interface between the ferromagnetic layer 14 and the low refractive index layer 20. The intensity of the plasmon wave is particularly high at the interface between the ferromagnetic layer 14 and the low refractive index layer 20. The characteristics of the plasmon wave are changed by changing the direction of the magnetic field applied by the magnetic field applying unit 40 between the magnetic field (+ M) and the magnetic field (−M). The plasmon wave has an approximately constant intensity in the high refractive index layer 22. That is, the graph of this example shows the intensity distribution of the plasmon wave at the time of cutoff.

The cut-off refers to a state in which the light intensity on the high refractive index layer 22 side is constant and the wave number of the plasmon wave becomes a real number, and coincides with the z direction component of the wave number of light incident from the high refractive index layer 22 side. By doing so, the reflectance becomes zero. In the cutoff, the surface plasmon is excited, but is confined at the interface between the ferromagnetic layer 14 and the low refractive index layer 20 and the intensity converges to zero at the point where the coordinate is −∞ shown in FIG. 4 (plasmon) Corresponding to the boundary between the ferromagnetic layer 14 and the low refractive index layer 20 not coupled by the evanescent wave, the wave number of the plasmon wave becomes a real number. Actually, the thicknesses of the high refractive index layer 22 and the prism 24 are finite, but they are sufficiently thicker than the layer thickness t of the low refractive index layer 20, and the point where the coordinate is −∞ is the upper end of the high refractive index layer 22. Even if it is regarded as the edge of the semicircle of the prism 24, there is no problem in using the sensor. For example, in the case of cutoff when a magnetic field is applied in a certain direction and the + M state is realized, R _p (+ M) is 0 in Equation (1), so the index is 1. When the magnitude of the applied magnetic field changes, the plasmon wave number changes, so the conditions such as the wavelength of the incident light 110 that causes the cutoff also change. The sensor 100 of the present example can realize a cut-off state by optimally selecting the structure constituted by the otto arrangement and the incident light 110.

FIG. 5 shows the wavelength dependence of the index ΔR _p / R _p of the sensor 100. The vertical axis represents the index ΔR _p / R _p , and the horizontal axis represents the wavelength λ [nm] of the incident light 110. Each graph shows a case where the incident angle θ of the incident light 110 is θ = 55 °, θ = 55.3 °, θ = 55.4 °, θ = 56 °, and θ = 56.5 °. In the graph, the triangle indicates the case of θ = 55 °, the black circle indicates the case of θ = 55.3 °, the white circle indicates the case of θ = 55.4 °, and the diamond indicates the case of θ = 56 ° The case where the square is θ = 56.5 ° is shown.

In this example, the index [Delta] R p _/ R _p is found to behave differently depending on the incident angle theta. It can also be seen that the incident angle θ has a different wavelength λ dependency. For example, when the incident angle θ is 55.3 °, the figure of merit ΔR _p / R _p approaches +1.0 and −1.0. Further, the incident light 110 has a wavelength at which ΔR _p / R _p greatly changes with respect to a change in wavelength between two wavelengths λ when ΔR _p / R _p approaches +1.0 and −1.0. It is preferable. Thereby, the sensitivity of the sensor 100 improves. For example, the sensor 100 may have a figure of merit ΔR _p / R _p of −1.0 or more and −0.9 or less, −0.9 or more and +0.9 or less, +0.9 or more, It may be designed to satisfy +1.0 or less.

FIG. 6 shows the dependence of the index ΔR _p / R _p of the sensor 100 on the incident angle θ. The vertical axis represents the index ΔR _p / R _p , and the horizontal axis represents the incident angle θ [°] of the incident light 110. In the sensor 100 of this example, the low refractive index layer 20 has a laminated structure including a vacuum (n = 1) and a SiO ₂ protective layer, the high refractive index layer 22 is made of SiO ₂ , the ferromagnetic layer 14 is made of Fe, a metal The layer 12 is made of Ag which is a noble metal.

The index ΔR _p / R _{p in} this example approaches +1.0 and −1.0 when the incident angle θ is around 46.1 °. Further, when the incident angle θ is around 46.1 °, the change of the index ΔR _p / R _p becomes steep. That is, when the incident angle θ is around 46.1 °, the maximum signal (index) change is obtained with respect to the change in the refractive index of the measurement target substance 30, so the measurement conditions of the sensor are set.

As described above, the sensor 100 of this example can realize the index ΔR _p / R _p = 1. In addition, the sensor 100 makes the change (inclination) of the index steep by combining Fe and Ag which is a noble metal. Thereby, the sensitivity of the sensor 100 improves. The sensor 100 can adjust the measurement wavelength according to the measurement target substance 30 by changing the thickness of the low refractive index layer 20.

[Example 2]
FIG. 7 illustrates an exemplary configuration of the sensor 100 according to the second embodiment. The sensor 100 of this example includes a propagation constant adjustment layer 18.

The propagation constant adjusting layer 18 is provided on the upper surface of the ferromagnetic layer 14. The propagation constant adjusting layer 18 of this example is provided between the ferromagnetic layer 14 and the low refractive index layer 20. The refractive index of the propagation constant adjusting layer 18 is greater than 1. The film thickness of the propagation constant adjusting layer 18 is smaller than the layer thickness of the low refractive index layer 20. For example, the material of the propagation constant adjusting layer 18 is SiO ₂ . The film thickness of the propagation constant adjusting layer 18 is equal to or less than the layer thickness of the low refractive index layer 20. In this example, the propagation constant adjustment layer 18 is provided instead of the metal layer 16. However, the sensor 100 includes the metal layer 16 and the propagation constant adjustment layer between the ferromagnetic layer 14 and the low refractive index layer 20. 18 may be provided. The propagation constant adjustment layer 18 may have a refractive index adjusted according to the measurement target substance 30 so that the sensitivity of the sensor 100 is improved.

[Example 3]
FIG. 8 illustrates an example of a configuration of the sensor 100 according to the third embodiment. The sensor 100 of this example includes a wedge-shaped low refractive index layer 20.

The low refractive index layer 20 includes a support layer 21 having a predetermined layer thickness t1 and a support layer 21 having a layer thickness t2 different from the layer thickness t1. Since the low refractive index layer 20 includes the support layers 21 having different layer thicknesses t1 and t2, the cross-sectional area of the low refractive index layer 20 changes depending on the position. The low refractive index layer 20 of this example has a wedge-shaped structure in which the layer thickness gradually changes from the layer thickness t1 to the layer thickness t2. Therefore, in the sensor 100, the layer thickness of the measurement target substance 30 varies depending on the position where the incident light 110 is incident, and the wavelength λ for measuring the measurement target substance 30 also differs. For example, when the support layers 21 having different layer thicknesses are formed of solder, solders having different layer thicknesses are provided on the metal layer 16. In the case of forming by providing grooves supporting layer 21 of different thickness to the SiO ₂ substrate, such that the space layer thickness of SiO ₂ substrate surface are different, polished by inclining the SiO ₂ substrate slightly. As a result, the low refractive index layer 20 is formed with the support layers 21 having different layer thicknesses t1 and t2.

Since the sensor 100 of the present example includes the wedge-shaped low refractive index layer 20, reflection at substantially different incident angles θ without changing the incident angle θ by selecting the incident position and wavelength of the incident light 110. The rate (measurement result corresponding to FIG. 6) can be detected. In addition, the sensor 100 of this example may select the optimum incident position (layer thickness t) corresponding to the measurement target substance 30 and the wavelength of the incident light 110 according to the refractive index of the low refractive index layer 20.

FIG. 9 shows an example of the configuration of the sensor 100 according to the fourth embodiment. Similar to the sensor 100 according to the third embodiment, the sensor 100 of the present example has different layer thicknesses t1 and t2 of the low refractive index layer 20. In the present example, differences from the third embodiment will be particularly described.

The sensor 100 can acquire the incident light 110 reflected at different reflectances R _p (t ₁ ) and R _p (t ₂ ) by changing the position where the incident light 110 is incident. Incident light 110 reflected at different reflectances may be received by different photodiodes. The sensor 100 of this example can measure the measurement target substance 30 without changing the applied magnetic field by using the low refractive index layer 20 having different layer thicknesses t1 and t2. In this example, the case where two different layer thicknesses are used has been described, but three or more different layer thicknesses may be used.

[Comparative Example 1]
FIG. 10 shows a configuration of a sensor 500 according to the comparative example. The sensor 500 includes a dielectric layer 520 containing a measurement target substance, a noble metal layer 522, and a prism 524. The sensor 500 includes a molecular recognition element 532 on the side of the dielectric layer 520 containing the measurement target substance.

The dielectric layer 520 containing the measurement target substance is air. The noble metal layer 522 is formed on the prism 524. The noble metal layer 522 in this example is Au. A noble metal layer 522 is formed on the prism 524. The prism 524 of this example is SiO ₂ , and an evanescent wave generated when the light incident from the prism 524 is totally reflected by the noble metal layer 522 is generated at the interface between the noble metal layer 522 and the dielectric layer 520 containing the measurement target substance. A sensor is realized using excited plasmon waves. That is, the sensor 500 has a Kretschmann arrangement.

Incident light 510 enters the prism 524 at an incident angle θ. R _p is the intensity of the incident p-polarized reflected light. The plasmon wave is formed between the dielectric layer 520 containing the measurement target substance and the noble metal layer 522.

Here, the sensitivity of the sensor 500 is determined by the slope of the ATR curve indicating the angle dependency of the reflectance. The sensitivity is determined by the steep slope of the ATR curve or the narrow half-value width of the reflectance valley.

For example, as the sensitivity of the SPR sensor of the sensor 500, the following index represented by Equation (3) is used. A represents the reflectance of light incident on the sensor 100.

The sensor 500 of this example is configured in a Kretschmann arrangement, and the wavelength of the incident light 510 used in the sensor 500 is determined according to the incident angle θ, the type and thickness of the dielectric and metal containing the measurement target substance, and the like. . In the sensor 500, since the incident angle θ suitable for measurement is determined when the measurement wavelength is determined, when the measurement wavelength is adjusted to the optimum wavelength at which the measurement target substance of the sensor 500 exhibits a large refractive index, it is necessary to greatly change the incident angle. Depending on the optimum wavelength, it may be difficult to adjust the incident angle between 0 ° and 90 °. Further, in the sensor 500, it is necessary to set the layer thickness of the noble metal layer 522 in order to completely match the Z-direction component (real number) of the wave number of light incident from the prism 524 side with the wave number (complex number) of the plasmon wave. There is. The setting accuracy of the thickness of the metal layer needs to be higher than the setting accuracy of the layer thickness of the low refractive index layer 20 in the sensor 100. Accordingly, it is difficult for the sensor 500 to achieve a sharp change by making the reflectance approach zero.

FIG. 11 shows the sensitivity of the sensor 100 according to the second embodiment and the sensitivity of the sensor 500 according to the first comparative example. This figure shows the ATR curve of the sensor and the change of the index with respect to the change of the refractive index. The vertical axis indicates the indices ΔR _p / R _p and R _p , and the horizontal axis indicates the incident angle θ and time of the incident light 110. The ratio of the change of the index ΔR _p / R _p to the change n of the refractive index indicates the sensitivity of the sensor 100 according to the embodiment. The index R _p indicates the sensitivity of the sensor 500 according to Comparative Example 1. In the sensor 100, θ _SPR is an incident angle θ at the time of cutoff when a magnetic field is applied in a certain direction to realize a + M state. In the sensor 500, θ _C corresponds to the incident angle at which the index R _p shows the largest change with respect to the change in the incident angle θ.

The index ΔR _p / R _p of the sensor 100 changes more rapidly than the index R _{p of the} sensor 500. Therefore, when the refractive index changes from n _d to n _d + δn, the change δ (ΔR _p / R _p ) of the index of the sensor 100 becomes larger than the change δ (R _p ) of the performance index of the sensor 500. Therefore, the sensor 100 is more sensitive to a change in refractive index than the sensor 500.

FIG. 12A shows the specific dependence of the index ΔR _p / R _p of the sensor 100 on the incident angle θ. FIG. 12B shows the specific incident angle θ dependency of the index R _p of the sensor 500. The vertical axis represents the index ΔR _p / R _p and the index R _p , and the horizontal axis represents the incident angle θ.

A solid line indicates a case where the refractive index is n = 1. A one-dot chain line indicates a case where the refractive index is n = 1.0001. A broken line indicates a difference in index when n = 1 and n = 1.0001. When the refractive index changes, the sensitivity is better when the index difference is larger. In the case of the sensor 100, when the refractive index changes between n = 1 and n = 1.0001, the magnitude of change of δ (ΔR _p / R _p ) is about 1. On the other hand, in the case of the sensor 500, when the refractive index changes between n = 1 and n = 1.0001, the magnitude of change of δ (R _p ) is about 0.003. That is, the sensor 100 has a sensitivity 1 / 0.003≈3 × 10 ² times that of the sensor 500.

The specific dependence on the incident angle θ of ΔR _p / R _{p in} FIG. 12A is obtained by measuring at an appropriate incident angle θ interval. For example, when there is an experimental apparatus that can measure the incident angle θ at intervals of 0.01 degrees, ΔR _p / R _p is 0.02 degrees when n = 1, that is, with respect to a change in the incident angle θ at three points. It changes from -1 to 1. That is, the refractive index cannot be measured unless there is a resolution of the incident angle θ that can measure the change in ΔR _p / R _p at least at three points. A method for obtaining a sufficient resolution of the incident angle θ, here 0.001 degree, will be described below.

When generating FIG. 12A by simulation, data is generated with an angular resolution of 0.001 degrees. On the other hand, the left data is generated at 0.01 degrees. Since there are ten ways of taking the angle, ten pieces of low-angle resolution data are generated. By obtaining a correspondence between a simulation result with a fine angular resolution and a coarse simulation result, and based on the measurement results of the reflectance R _p and ΔR _p / R _p obtained with the coarse angular resolution, the fine measurement with the angular resolution is performed. Estimate the result. Based on the estimated measurement result, the change in ΔR _p / R _p is read more accurately, and the refractive index is measured. Thus, the sensor 100 of this example acquires a high angular resolution by reconstructing a 10-fold high-definition image. Therefore, the sensor 100 can obtain the super-resolution exceeding the resolution of the incident angle by image analysis (that is, super-resolution), and can accurately measure the angle dependency of the figure of merit.

FIG. 13 shows specific incident angle θ dependence of the index (ΔR _p / R _p ) ′ of the sensor 100 according to the fourth embodiment. The vertical axis indicates the index (ΔR _p / R _p ) ′, and the horizontal axis indicates the incident angle θ.

A solid line indicates a case where the refractive index is n = 1. A one-dot chain line indicates a case where the refractive index is n = 1.0001. A broken line indicates a difference in index when n = 1 and n = 1.0001. When the refractive index changes, the sensitivity is better when the index difference is larger. In the case of the sensor 100 of this example, when the refractive index changes between n = 1 and n = 1.0001, the magnitude of the change of δ (ΔR _p / R _p ) ′ is about 1.7. Therefore, the sensor 100 according to the fourth embodiment has further excellent sensitivity.

FIG. 14 shows an example of an application example of the sensor device 200. The sensor device 200 includes a sensor 100, a light source 120, and a light receiving unit 130.

The sensor 100 detects a derivative substance of a plant hormone as the measurement target substance 30. Derivative substances of plant hormones are volatile organic compounds such as methyl salicylate and methyl jasmonate. A measurement target substance 30 containing a plant hormone derivative substance flows into the sensor 100. In one example, the measurement target substance 30 is a gas containing a derivative substance of a plant hormone. The refractive index of the low refractive index layer 20 is a refractive index corresponding to the plant hormone derivative substance which is the measurement target substance 30. Thereby, the sensor 100 detects the kind and density | concentration of the derivative substance of a plant hormone.

The light source 120 makes incident light 110 incident on the sensor 100. The light receiving unit 130 receives the reflected light of the incident light 110 incident from the light source 120. The light receiving unit 130 receives reflected light having an intensity corresponding to the characteristics of the measurement target substance 30.

The display unit 300 displays the measurement result of the sensor device 200. The display unit 300 may receive the measurement result of the sensor device 200 by wireless communication. Further, the sensor device 200 may include a display device, and the sensor device 200 itself may display the measurement result.

The processing unit 400 processes the measurement result of the sensor 100. For example, the processing unit 400 has a data table indicating the relationship between the derivative substance of plant hormone and the refractive index, and acquires the type and concentration of the derivative substance of plant hormone according to the measurement result of the sensor 100.

The sensor device 200 of the present example can detect a derivative substance of a plant hormone with an extremely high sensitivity by using the sensor 100 which is an ultrasensitive magnetic plasmon sensor. Thus, the sensor device 200 can be applied to fields such as agriculture that require highly sensitive sensing.

FIG. 15 shows an example of the configuration of the sensor device 200. The sensor device 200 of this example is an example in the case of simultaneously measuring each substance of the low refractive index layer 20 including a plurality of refractive indexes. Note that the sensor device 200 of this example may be used in combination with the sensor 100 according to other Examples 1 to 3.

The low refractive index layer 20 includes the measurement target substance 30 having various concentrations. For example, the low refractive index layer 20 holds the measurement target substance 30 by providing a molecular recognition element 32 such as an antibody corresponding to the measurement target substance 30. Thereby, the refractive index of the low refractive index layer 20 has a different refractive index depending on the concentration. The low refractive index layer 20 of this example has a refractive index of n ₁ , n ₂ , and n ₃ according to the concentrations c ₁ , c ₂ , and c ₃ , for example. In this example, the angle of incidence at which the reflectance is minimized differs depending on the difference in refractive index. Therefore, a line with low luminance is displayed at different locations on the light receiving unit 130 in FIG. 15 according to the minimum reflectance. The lines with low luminance are arranged linearly, but may be arranged two-dimensionally according to the shape of the low refractive index layer 20.

The light source 120 irradiates the low refractive index layer 20 with the incident light 110. For example, the light source 120 condenses the incident light 110 using the lens unit 125, thereby irradiating the incident light 110 on the region where the measurement target substance 30 is held.

The light receiving unit 130 receives reflected light including information on a plurality of refractive indexes. The light receiving unit 130 may receive the reflected light by using the lens unit 135 as a parallel beam. For example, the light receiving unit 130 includes an optical sensor array in which photodiodes are arranged. Thereby, when the density | concentration of the measuring object substance 30 changes, the light-receiving part 130 can acquire the measurement result corresponding to each from the output signal of an optical sensor array.

Note that the measurement target substance 30 for measurement is supplied from the supply source 140 to the chamber 160 via the supply amount control unit 145. The chamber 160 may be connected to a pump 150 for sucking the measurement target substance 30.

The sensor 100 of this example is provided by bonding the high refractive index layer 22 to the substrate 10. For example, the space of the low refractive index layer 20 is provided by providing irregularities on the upper surface of the substrate 10 and bonding a bonding member functioning as the high refractive index layer 22 to the upper surface of the substrate 10. The sensor 100 includes a metal layer 12 made of Au or Fe, a ferromagnetic layer 14, and a metal layer 16 below the low refractive index layer 20 as in the other embodiments.

FIG. 16 shows the relationship between the magnetic field applied to the ferromagnetic layer 14 and the magneto-optic effect. The ferromagnetic layer 14 of this example is an iron thin film as an example. The vertical axis represents the magneto-optical effect [a. u. The horizontal axis represents the applied magnetic field [Oe]. The magneto-optical effect is a physical quantity proportional to the magnetization. The applied magnetic field is a magnetic field applied to the ferromagnetic layer 14.

The magnetic field applied to the ferromagnetic layer 14 by the magnetic field application unit 40 is not limited to a magnitude that maximizes or minimizes the magneto-optic effect. For example, the applied magnetic field of the ferromagnetic material layer 14 may be a magnetic field in which the magneto-optical effect is 1/3 or 2/3 of the maximum (absolute value). Further, the two types of magnetic fields applied by the magnetic field application unit 40 to the ferromagnetic layer 14 need not be inverted magnetic fields, and may be magnetic fields having the same polarity. The sensor 100 may set the applied magnetic field of the magnetic field applying unit 40 to an appropriate magnitude according to the relationship with the layer thickness t of the low refractive index layer 20 and the like.

Since the sensor 100 of this example has excellent sensitivity, it realizes high resolution, label-free, real-time and in-situ observation, and can measure mass changes and time transitions. The sensor 100 can be applied in a wide range of fields such as medical diagnosis and environmental monitoring. For example, the sensor 100 is used for life science, environmental gas measurement, medical diagnosis, and the like. The sensor 100 can also be applied to drug detection, landmine sensors, and the like.

As mentioned above, although this invention was demonstrated using embodiment, the technical scope of this invention is not limited to the range as described in the said embodiment. It will be apparent to those skilled in the art that various modifications or improvements can be added to the above-described embodiment. It is apparent from the scope of the claims that the embodiments added with such changes or improvements can be included in the technical scope of the present invention.

The execution order of each process such as operations, procedures, steps, and stages in the apparatus, system, program, and method shown in the claims, the description, and the drawings is particularly “before” or “prior”. It should be noted that they can be implemented in any order unless the output of the previous process is used in the subsequent process. Regarding the operation flow in the claims, the description, and the drawings, even if it is described using “first”, “next”, etc. for the sake of convenience, it means that it is essential to carry out in this order. is not.

DESCRIPTION OF SYMBOLS 10 ... Board | substrate, 12 ... Metal layer, 14 ... Ferromagnetic material layer, 16 ... Metal layer, 18 ... Propagation constant adjustment layer, 20 ... Low refractive index layer, 21 ... Support layer, 22 ... high refractive index layer, 24 ... prism, 26 ... inflow part, 28 ... outflow part, 30 ... substance to be measured, 32 ... molecular recognition element, 40 ... Magnetic field application unit, 100 ... Sensor, 110 ... Incident light, 120 ... Light source, 125 ... Lens unit, 130 ... Light receiving unit, 135 ... Lens unit, 140 ... -Supply source, 145 ... Supply amount control unit, 150 ... Pump, 160 ... Chamber, 200 ... Sensor device, 300 ... Display unit, 400 ... Processing unit, 500 ... Sensor, 510... Incident light, 520... Dielectric layer containing measurement target substance, 522. 4 ... prism, 532 ... molecular recognition element

Claims

A substrate,
A ferromagnetic layer provided above the substrate;
A low refractive index layer provided above the ferromagnetic layer and including a space for flowing a measurement target substance;
A high refractive index layer provided above the low refractive index layer and having a higher refractive index than the low refractive index layer.
The sensor according to claim 1, further comprising: a magnetic field application unit configured to apply either the first magnetic field or a second magnetic field different from the first magnetic field to the ferromagnetic layer.
The magnetic field application unit applies a saturation magnetic field to the ferromagnetic layer as the first magnetic field, and applies an inverted magnetic field of the saturation magnetic field to the ferromagnetic layer as the second magnetic field. Sensor.
The low refractive index layer is
An inflow portion for flowing the measurement target substance into the low refractive index layer;
The sensor according to any one of claims 1 to 3, further comprising: an outflow portion that causes the measurement target substance to flow out from the low refractive index layer.
The sensor according to any one of claims 1 to 4, wherein a layer thickness of the low refractive index layer is 15000 nm or less.
The sensor according to any one of claims 1 to 5, wherein the low refractive index layer has a predetermined first layer thickness and a second layer thickness different from the first layer thickness.
The sensor according to claim 6, wherein the low refractive index layer has a wedge-shaped structure in which the layer thickness gradually changes from the first layer thickness to the second layer thickness.
The sensor according to any one of claims 1 to 7, further comprising a propagation constant adjusting layer having a refractive index larger than 1, which is provided between the ferromagnetic layer and the low refractive index layer.
The sensor according to claim 8, wherein a film thickness of the propagation constant adjusting layer is thinner than a layer thickness of the low refractive index layer.
The sensor according to any one of claims 1 to 9, further comprising a first metal layer having a higher conductivity than the ferromagnetic layer between the low refractive index layer and the ferromagnetic layer.
The sensor according to claim 10, further comprising a second metal layer having a higher conductivity at a measurement wavelength than the ferromagnetic layer between the substrate and the ferromagnetic layer.
The sensor according to claim 11, wherein a film thickness of the first metal layer is thinner than a film thickness of the second metal layer.
When the reflectance change at the time of magnetization reversal measured at a certain incident angle θ is ΔR p and the reflectance is measured at a certain incident angle θ, the external magnetic field (+ M) and the external magnetic field (−M) Where R p is the sum of the reflectances obtained in
The sensor according to any one of claims 1 to 12, wherein the figure of merit ΔR p / R p satisfies −1.0 or more and −0.9 or less, or +0.9 or more and +1.0 or less.
When the reflectance change at two points (t1, t2) having different layer thicknesses t of the low refractive index layer measured at a certain incident angle θ is ΔR p ′, and the reflectance is measured at a certain incident angle θ, the sum of the reflectivity which the layer thickness t was obtained under t1, t2 when the R p,
Merit (ΔR p / R p) 'is -1.0 or more, -0.9 or less, or, + 0.9 or more, the sensor according to any one of claims 1 to 12 satisfying + 1.0 .
15. The sensor according to claim 13, wherein the sensor has a super-resolution exceeding the resolution of the incident angle when measuring the dependency of the reflection index R p and the figure of merit on the incident angle.
Prepare the board,
Providing a ferromagnetic layer above the substrate;
Provided above the ferromagnetic layer is a low refractive index layer including a space for flowing the measurement target substance,
A method for manufacturing a sensor, wherein a high refractive index layer having a refractive index larger than that of the low refractive index layer is provided above the low refractive index layer.
The laminated structure of the ferromagnetic layer, the low refractive index layer, and the high refractive index layer is:
A support layer is provided on the upper surface of the ferromagnetic layer,
The method for manufacturing a sensor according to claim 16, wherein the sensor is formed by laminating the high refractive index layer above the ferromagnetic layer via the support layer.
The laminated structure of the ferromagnetic layer, the low refractive index layer, and the high refractive index layer is:
Further preparing a substrate including the high refractive index layer,
Forming a groove in the substrate including the high refractive index layer;
The method for manufacturing a sensor according to claim 16, wherein the sensor is formed by bonding a surface of the substrate including the high refractive index layer on which the groove is formed to the ferromagnetic layer.
When the reflectance change at the time of magnetization reversal measured at a certain incident angle θ is ΔR p and the reflectance is measured at a certain incident angle θ, the external magnetic field (+ M) and the external magnetic field (−M) Where R p is the reflectance obtained in
19. The method for manufacturing a sensor according to claim 16, wherein the figure of merit ΔR p / R p satisfies −1.0 or more and −0.9 or less, or +0.9 or more and +1.0 or less. .
When the reflectance change at two points (t1, t2) having different layer thicknesses t of the low refractive index layer measured at a certain incident angle θ is ΔR p ′, and the reflectance is measured at a certain incident angle θ, the sum of the reflectivity which the layer thickness t was obtained under t1, t2 when the R p,
Merit (ΔR p / R p) 'is -1.0 or more, -0.9 or less, or, the sensor according to any one of claims 16 18 + 0.9 or more, satisfying the + 1.0 Manufacturing method.