JP2015212626A - Electric field enhancement element, raman spectroscopy, raman spectrometer, and electronic equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric field enhancement element capable of detecting a target substance with high sensitivity.SOLUTION: An electric field enhancement element 100 of the present invention includes a metal layer 10, a dielectric layer 20, and metal particles 30. A plurality of metal particles 30 has a periodic array capable of exciting a propagated surface plasmon that propagates on an interface between the metal layer 10 and the dielectric layer 20. The propagated surface plasmon and a localized surface plasmon excited by the metal particles 30 electromagnetically interact, while a resonance wavelength of the propagated surface plasmon is different from a resonance wavelength of the localized surface plasmon. In a reflection spectrum of reflected light when the electric field enhancement element 100 is irradiated with white light, a half-value width H1 of a first absorption region and a half-value width H2 of a second absorption region where the half-value width thereof is larger than the half-value width H1 of the first absorption region satisfy a relationship of (H2-H1)/H2×100≥40; and the wavelength of excitation light for the electric field enhancement element 100 is included in the range of the second absorption region.

Description

  The present invention relates to an electric field enhancing element, Raman spectroscopy, Raman spectroscopy apparatus, and electronic equipment.

  In recent years, demand for medical diagnosis, food inspection, and the like has been increasing, and development of a small and high-speed sensing technology has been demanded. Various types of sensors, including electrochemical techniques, have been studied. However, surface plasmon resonance (SPR) is used because it can be integrated, is low-cost, and does not choose the measurement environment. There is growing interest in sensors. For example, there is known one that detects the presence or absence of substance adsorption, such as the presence or absence of antigen adsorption in an antigen-antibody reaction, using SPR generated on a metal thin film provided on the surface of a total reflection prism. In addition, a method of detecting Raman scattered light of a substance attached to a sensor by using surface enhanced Raman scattering (SERS) and identifying the attached substance has been studied.

  For the purpose of sensing with higher sensitivity, Non-Patent Document 1 describes a hybrid mode in which both localized surface plasmon (LSP) and propagation surface plasmon (PSP) modes resonate simultaneously. As an example of a sensor having a structure for realizing the above, a sensor called GSPP (Gap type Surface Plasmon Polar) has been proposed.

Enhancing effect of SERS is, E the electric field enhancement at the wavelength lambda _i of the incident light _i, when the degree of electric field enhancement at the wavelength lambda _s of the Raman scattered light and E _s, knowledge to be proportional to E _i ² · E _s ² It has been. Non-Patent Document 1 discloses a method for increasing the enhancement of SERS by arranging metal nanoparticles in a square lattice pattern so that the wavelength λ _i and the wavelength λ _s have different peak ranges (absorption region ranges). Is disclosed.

ACSNANO, VOL. 4, no. 5, 2804-2810, 2010

However, in the electric field enhancing element disclosed in Non-Patent Document 1, when the coupling effect between LSP and PSP is the strongest (nanoparticle (gold disk) arrangement period a = 780 nm), the Raman shift is 1000 cm ^{−1 to} 1100 cm ^−. The Raman peak in the range of ¹ is enhanced, but the peak with a smaller Raman shift is not enhanced.

  As described above, in the electric field enhancing element disclosed in Non-Patent Document 1, since only a part of the peak enhanced in the hybrid mode is present, only the target substance having a specific Raman frequency has the SERS enhancing effect, The target substance that can utilize the enhancement effect may be limited. Therefore, the electric field enhancing element using the hybrid mode may not be able to detect the target substance with high sensitivity.

One of the objects according to some embodiments of the present invention is to provide an electric field enhancing element capable of detecting a target substance with high sensitivity. Another object of some embodiments of the present invention is to provide Raman spectroscopy using the electric field enhancement element. Another object of some embodiments of the present invention is to provide a Raman spectroscopic device and an electronic apparatus including the electric field enhancement.

The electric field enhancing element according to the present invention is
A metal layer,
A dielectric layer provided on the metal layer;
A plurality of metal particles provided on the dielectric layer;
An electric field enhancing element comprising:
The plurality of metal particles have a periodic array capable of exciting propagating surface plasmons propagating through an interface between the metal layer and the dielectric layer,
The propagation type surface plasmon and the localized type surface plasmon excited by the metal particle interact electromagnetically,
The resonance wavelength of the propagation surface plasmon is different from the resonance wavelength of the localized surface plasmon,
In the spectrum of reflected light when the electric field enhancing element is irradiated with white light, the half width of the first absorption region is H1, and the half width of the second absorption region is larger than the half width H1 of the first absorption region. When the price range is H2,
The H1 and the H2 are
(H2-H1) / H2 × 100 ≧ 40
Satisfy the relationship
The wavelength of the excitation light of the electric field enhancing element is included in the range of the second absorption region.

  In such an electric field enhancing element, the second absorption region has a greater contribution of localized surface plasmons and a larger half-value width than the absorption region of the reflection spectrum in the electric field enhancing device that does not satisfy the above formula. . Thereby, in such an electric field enhancing element, the wavelength of the excitation light and the wavelength of the Raman scattered light can be included in the range of the second absorption region. Furthermore, in such an electric field enhancement element, the propagation type surface plasmon excited at the interface between the metal layer and the dielectric layer and the localized type surface plasmon excited by the metal particle interact electromagnetically. Therefore, the electric field enhancement can be increased compared to the case where the localized surface plasmon alone is excited. Therefore, such an electric field enhancing element can detect a target substance with high sensitivity even for a molecule (target substance) having a small Raman shift.

In the electric field enhancing element according to the present invention,
The propagation wavelength of the propagation surface plasmon is longer than the resonance wavelength of the localized surface plasmon,
The second absorption region may be located on a shorter wavelength side than the first absorption region.

  Such an electric field enhancing element can detect the target substance with high sensitivity.

In the electric field enhancing element according to the present invention,
The propagation wavelength of the propagation surface plasmon is shorter than the resonance wavelength of the localized surface plasmon,
The second absorption region may be located on a longer wavelength side than the first absorption region.

  Such an electric field enhancing element can detect the target substance with high sensitivity.

The Raman spectroscopy according to the present invention is:
A target substance is attached to the electric field enhancement element according to the present invention, the excitation light is irradiated to the electric field enhancement element, and the Raman spectroscopy that detects the Raman scattered light emitted from the electric field enhancement element,
The wavelength of the Raman scattered light is in the range of the second absorption region.

  In such Raman spectroscopy, since the electric field enhancing element according to the present invention is used, the target substance can be detected with high sensitivity.

The Raman spectroscopic device according to the present invention is:
An electric field enhancing element according to the present invention;
A light source for irradiating the electric field enhancing element with the excitation light;
A photodetector for detecting light emitted from the electric field enhancing element;
including.

  Such a Raman spectroscopic device includes the electric field enhancing element according to the present invention, and thus can detect the target substance with high sensitivity.

The electronic device according to the present invention is
A Raman spectroscopic device according to the present invention;
A calculation unit for calculating health and medical information based on detection information from the detector;
A storage unit for storing the health care information;
A display unit for displaying the health care information;
including.

  Since such an electronic device includes the Raman spectroscopic device according to the present invention, highly accurate medical information can be provided.

Sectional drawing which shows typically the electric field enhancement element which concerns on this embodiment. The top view which shows typically the electric field enhancement element which concerns on this embodiment. The figure for demonstrating the relationship between the arrangement | sequence of a metal particle, a propagation type surface plasmon, and a localized type surface plasmon. The figure which shows typically the dispersion | distribution relationship of surface plasmon polariton. The figure for demonstrating anti-crossing. The figure for demonstrating the wavelength characteristic of a reflection spectrum and an enhancement electric field. The figure for demonstrating the wavelength characteristic of a reflection spectrum and an enhancement electric field. The figure for demonstrating the wavelength characteristic of a reflection spectrum and an enhancement electric field. The figure which shows typically the Raman spectroscopy apparatus which concerns on this embodiment. 4A and 4B are diagrams for explaining an electronic apparatus according to the embodiment. The figure for demonstrating the model used in Experimental example 1. FIG. Reflection spectrum when the diameter of Au particles is 90 nm. Reflection spectrum when the diameter of Au particles is 104 nm. Reflection spectrum when the diameter of Au particles is 140 nm. The graph which plotted the wavelength of the minimum point of two absorption regions in a reflection spectrum when changing the diameter of Au particle | grains in the range of 80 nm-150 nm. Reflection spectrum when the Au particle thickness is 15 nm. Reflection spectrum when the Au particle thickness is 25 nm. Reflection spectrum when the Au particle thickness is 40 nm. The graph which plotted the wavelength of the minimum point of two absorption regions in a reflection spectrum when changing the thickness of Au particle | grains in the range of 10 nm-40 nm. Reflection spectrum in a region where the diameter of Au particles is 90 nm and 106 nm. The figure for demonstrating how to obtain | require a half value width. The graph which shows the Raman measurement result of the area | region whose diameter of Au particle | grains is 90 nm and 106 nm.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. The embodiments described below do not unduly limit the contents of the present invention described in the claims. In addition, not all of the configurations described below are essential constituent requirements of the present invention.

1. Electric field enhancing element First, the electric field enhancing element according to the present embodiment will be described with reference to the drawings. FIG. 1 is a cross-sectional view schematically showing an electric field enhancing element 100 according to this embodiment. FIG. 2 is a plan view schematically showing the electric field enhancing element 100 according to the present embodiment. 1 is a cross-sectional view taken along the line II of FIG. 1 and 2 illustrate the X axis, the Y axis, and the Z axis as three axes orthogonal to each other.

  As shown in FIGS. 1 and 2, the electric field enhancing element 100 includes a metal layer 10, a dielectric layer 20, and metal particles 30.

1.1. Metal Layer The metal layer 10 is not particularly limited as long as it provides a metal surface that does not transmit light. For example, the metal layer 10 has a shape of a film, a plate, a layer, or a film. The metal layer 10 may be provided on the substrate 2 as shown in FIG. Although it does not specifically limit as the board | substrate 2, The thing which does not affect easily the propagation type surface plasmon (PSP) excited by the interface of the metal layer 10 and the dielectric material layer 20 is preferable. The substrate 2 is, for example, a glass substrate, a silicon substrate, or a resin substrate. The planar shape (the shape seen from the Z-axis direction) of the surface on which the metal layer 10 of the substrate 2 is provided is not particularly limited.

  The metal layer 10 is formed by a technique such as vapor deposition, sputtering, casting, or machining. The metal layer 10 may be provided on the entire surface of the substrate 2 or may be provided on a part of the surface of the substrate 2. The thickness (size in the Z-axis direction) of the metal layer 10 is not particularly limited as long as PSP is excited at the interface between the metal layer 10 and the dielectric layer 20, and is, for example, 10 nm to 1 mm, preferably 20 nm or more. It is 100 μm or less, more preferably 30 nm or more and 1 μm or less.

  The metal layer 10 is a metal having an electric field in which an electric field given by excitation light and a polarization induced by the electric field oscillate in opposite phases, that is, when a specific electric field is given, The real part has a negative value (has a negative dielectric constant), and the imaginary part has a dielectric constant that is smaller than the absolute value of the dielectric constant of the real part. Examples of the metal having such a dielectric constant include gold, silver, aluminum, copper, platinum, or alloys thereof. When light in the visible light region is used as excitation light, the metal layer 10 preferably includes a layer made of gold, silver, or copper. The surface of the metal layer 10 (a plane parallel to the XY plane in the illustrated example) may or may not be a specific crystal plane. The metal layer 10 may be composed of a plurality of metal layers.

The metal layer 10 has a function of exciting the PSP in the electric field enhancing element 100. Specifically, when light (excitation light) enters the metal layer 10, PSP is excited at the interface between the metal layer 10 and the dielectric layer 20 (near the interface). The PSP excited at the interface between the metal layer 10 and the dielectric layer 20 can electromagnetically interact (hybridize) with the localized surface plasmon (LSP) excited by the metal particles 30.

1.2. Dielectric Layer The dielectric layer 20 is provided on the metal layer 10. The dielectric layer 20 is provided in contact with the metal layer 10. The dielectric layer 20 has a film, layer, or film shape. The dielectric layer 20 can separate the metal layer 10 and the metal particles 30. The dielectric layer 20 can transmit excitation light.

  The dielectric layer 20 is formed by, for example, techniques such as vapor deposition, sputtering, CVD (Chemical Vapor Deposition), and various coatings. The dielectric layer 20 may be provided on the entire surface of the metal layer 10 or may be provided on a part of the surface of the metal layer 10.

The dielectric layer 20 only needs to have a positive dielectric constant. For example, silicon oxide (SiO ₂ ), aluminum oxide (Al ₂ O ₃ ), tantalum oxide (Ta ₂ O ₅ ), silicon nitride (Si ₃ N _4). ), Titanium oxide (TiO ₂ ), polymer such as PMMA (Polymethylmethacrylate), and ITO (Indium Tin Oxide). The dielectric layer 20 may be composed of a plurality of layers made of different materials.

  The thickness of the dielectric layer 20 is set so that the PSP excited at the interface between the metal layer 10 and the dielectric layer 20 can interact with the LSP excited by the metal particles 30. The thickness of the dielectric layer 20 is, for example, 10 nm to 1 μm, preferably 20 nm to 500 nm, and more preferably 30 nm to 100 nm.

1.3. Metal Particles The metal particles 30 are provided on the dielectric layer 20. In the illustrated example, the metal particles 30 are provided in contact with the dielectric layer 20. The shape of the metal particle 30 is not particularly limited. For example, the shape of the metal particle 30 is, for example, a cylinder, a prism, a sphere, a spheroid, an indefinite shape, or a combination thereof. In the illustrated example, the metal particle 30 has a cylindrical shape having a central axis in the thickness direction (Z-axis direction) of the dielectric layer 20.

  The thickness of the metal particle 30 is, for example, 1 nm to 100 nm, preferably 2 nm to 50 nm, more preferably 10 nm to 40 nm. The size of the metal particle 30 in the X-axis direction and the Y-axis direction (in the example shown, the diameter of the bottom surface of the cylinder) is 10 nm to 200 nm, preferably 30 nm to 180 nm, more preferably 80 nm to 150 nm. is there. The size of the metal particle 30 is smaller than the wavelength of incident light.

  The material of the metal particles 30 is not particularly limited as long as the LSP can be excited by irradiation with excitation light, but is, for example, gold, silver, aluminum, copper, platinum, or an alloy thereof.

  The metal particles 30 can be formed by, for example, a patterning method after forming a thin film by sputtering, vapor deposition, or the like, a microcontact printing method, a nanoimprinting method, or the like. Alternatively, the metal particles 30 may be formed by a colloid chemical method.

  The metal particle 30 has a function of exciting the LSP in the electric field enhancing element 100. Specifically, by irradiating the metal particles 30 with excitation light, LSP can be excited in the metal particles 30 (around the metal particles 30).

  A plurality of metal particles 30 are provided. The plurality of metal particles 30 have a periodic arrangement that can excite PSP propagating through the interface between the metal layer 10 and the dielectric layer 20. In order to excite the PSP propagating through the interface between the metal layer 10 and the dielectric layer 20, the plurality of metal particles 30 are preferably arranged at a pitch about the wavelength of the excitation light in the polarization direction of the excitation light. . However, since the PSP dispersion curve changes depending on the material and thickness of the metal layer 10 and the dielectric layer 20, the plurality of metal particles 30 are not arranged at a pitch about the wavelength of the excitation light in the polarization direction of the excitation light. It may be possible.

  The arrangement of the plurality of metal particles 30 is not particularly limited as long as PSP propagating through the interface between the metal layer 10 and the dielectric layer 20 can be excited. In the illustrated example, the plurality of metal particles 30 are arranged in a matrix in the X-axis direction and the Y-axis direction. In other words, in the illustrated example, the plurality of metal particles 30 form a row in the X-axis direction, and the row is arranged in the Y-axis direction.

  The pitch in the X-axis direction of the plurality of metal particles 30 is not particularly limited as long as PSP propagating through the interface between the metal layer 10 and the dielectric layer 20 can be excited, and is 10 nm or more and 2 μm or less, preferably 20 nm. The thickness is 1 μm or more and more preferably 400 nm or more and 700 nm or less. The pitch in the X-axis direction is the distance between the centroids of adjacent metal particles 30 in the X-axis direction. If it does in this way, anti-crossing by hybrid mode can be raised and a target substance can be detected with high sensitivity.

  The pitch in the Y-axis direction of the plurality of metal particles 30 is not particularly limited as long as PSP propagating through the interface between the metal layer 10 and the dielectric layer 20 can be excited, and is 10 nm or more and 2 μm or less, preferably 20 nm. The thickness is 1 μm or more and more preferably 400 nm or more and 700 nm or less. Note that the pitch in the Y-axis direction is the distance between the centers of gravity of adjacent metal particles 30 in the Y-axis direction. The pitch in the X-axis direction of the plurality of metal particles 30 and the pitch in the Y-axis direction of the plurality of metal particles 30 may be different, but are the same in the illustrated example.

  The distribution, intensity, and the like of LSP excited by the metal particles 30 depend on the arrangement of the plurality of metal particles 30. Therefore, the LSP that electromagnetically interacts with the PSP excited by the metal layer 10 and the dielectric layer 20 considers not only the LSP excited by the single metal particle 30 but also the arrangement of the plurality of metal particles 30. In some cases, the LSP may be included.

  Although not shown, an adhesion layer for improving the adhesion between the dielectric layer 20 and the metal particles 30 may be provided between the dielectric layer 20 and the metal particles 30. That is, the metal particle 30 may be provided on the dielectric layer 20 via the adhesion layer. Further, an adhesion layer for improving adhesion between the substrate 2 and the metal layer 10 may be provided between the substrate 2 and the metal layer 10. That is, the metal layer 10 may be provided on the substrate 2 through the adhesion layer. Thus, in this specification, for example, the expression “the member B is provided on the member A” refers to the case where the member B is provided in contact with the member A and the case where the member B is provided. And the case where the member B is provided via another member. The adhesion layer is, for example, a chromium layer or a titanium layer.

  The target substance 1 adheres (adsorbs) to the metal particles 30. The target substance 1 adheres to the metal particles 30 by bringing the electric field enhancing element 100 into contact with a gas sample containing the target substance 1. In the illustrated example, the target substance 1 is in contact with the metal particles 30 and the dielectric layer 20. The target substance 1 is a substance to be detected in the analysis using the electric field enhancing element 100. Examples of the target substance 1 include pyridine, acetic acid, acetone, methyl mercaptan, and toluene. For convenience, the target substance 1 is not shown in the example of FIG.

1.4. An array of metal particles, a propagating surface plasmon and a localized surface plasmon;
FIG. 3 shows the arrangement of metal particles and LSP (LSPR: Localized Surface).
It is a figure for demonstrating the relationship with Plasmon Resonance (PSPR) and PSP (PSPR: Propagating Surface Plasmon Resonance). In FIG. 3, (a) schematically shows a plane of the electric field enhancing element, (b) schematically shows a cross section taken along line BB of (a) of the electric field enhancing element, (c ) Schematically shows a cross-sectional view taken along the line CC of (a) of the electric field enhancing element.

  Here, the LSP generated around the metal particles (for example, the metal particles 30) includes a mode generated between adjacent metal particles (hereinafter referred to as “PPGM” (Particle-Particle Gap Mode)), and the metal particles. Two types of modes (hereinafter referred to as “PMGM” (Particle-Mirror Gap Mode)) occurring between metal layers (also having a mirror function) (for example, between metal particles 30 and metal layer 10). Is known to exist (see FIG. 3).

  Both of the two types of modes, PPGM and PMGM, are generated when the excitation light is incident on the electric field enhancement element. Among these, PPGM LSP has higher strength as the metal particles approach (the distance between the metal particles is smaller). On the other hand, the LSP in the PMGM mode is not significantly affected by the arrangement of the metal particles and the polarization direction of the excitation light as in the PPGM LSP, and is irradiated between the metal particles and the metal layer (irradiation of the metal particles). (Down). As described above, the PSP is a plasmon that propagates through the interface between the metal layer and the light-transmitting layer. When the excitation light is incident on the metal layer, the interface between the metal layer and the light-transmitting layer is isotropic. Propagate to.

  FIG. 3 schematically shows a comparison between the hybrid structure used in the following experimental example and other structures (basic structure). The polarization direction of the excitation light applied to the electric field enhancing element is indicated by an arrow in the figure. Note that the terms “basic structure” and “hybrid structure” are coined terms used to distinguish each of them in this specification, and their meanings will be described below.

  First, the basic structure is a structure in which metal particles are densely arranged on a light-transmitting layer, and the LSPR of PPGM and the LSPR of PMGM are excited by irradiation with excitation light. In this example, LSPR of PPGM is generated at both ends of the metal particles in the polarization direction of the excitation light. However, since the basic structure has a small anisotropy of the arrangement of the metal particles, the excitation light is not polarized light. Similarly, it is generated according to the electric field vector component of the excitation light. In the basic structure, as a result of the metal particles being densely arranged, the excitation light hardly reaches the metal layer, and therefore, little or no PSPR is generated. In the drawing, a schematic wavy line representing PSPR is omitted.

  The hybrid structure is a structure in which metal particles are arranged on a light-transmitting layer more sparsely than the basic structure, and the LSPR of PMGM is excited by irradiation with excitation light. In this example, the LSPR of PPGM is generated weakly as compared with the Basic structure because the metal particles are separated from each other, and is omitted in the drawing. In the hybrid structure, as a result of the metal particles being sparsely arranged, PSPR (dashed line in the figure) is generated.

  Note that FIG. 3 illustrates the case where polarized light is incident. However, in any structure, when non-polarized excitation light or circularly polarized light is incident, the component in the vibration direction of the electric field is included. In response, the SPR described above occurs.

The overall SPR strength (electric field enhancement) in each structure is related to the sum (or product) of the SPRs generated in each. If the shape and size of the metal particles are the same in each structure, the contribution of PSPR to the strength of the total SPR increases in the order of Basic structure <Hybrid structure. In addition, the contribution of LSPR (PPGM and PMGM) to the strength of the total SPR is determined in the order of Hybrid structure <Basic structure from the viewpoint of metal particle density (HSD) when the shape and size of the metal particles are the same in each structure. It grows big. Further, when paying attention to LSPR of HSD and PPGM, the contribution degree of LSPR of PPGM to the strength of all SPRs increases in the order of Hybrid structure <Basic structure.

  The Hybrid structure has the strongest PSPR intensity and the largest contribution of the PSPR to the overall enhancement compared to the Basic structure. And although the intensity | strength of LSPR of PPGM is small and the density of a metal particle is also small, LSPR and PSPR of PMGM interact strongly electromagnetically (synergistic coupling | bonding).

  The Basic structure has the strongest strength of LSPR of PPGM, and the contribution of the LSPR of PPGM to the overall enhancement is the largest. And since the intensity | strength of PSPR is small, the electromagnetic interaction of LSPR of PPGM and PSPR does not generate | occur | produce. As shown in FIG. 5 to be described later, when metal particles are arranged densely, an absorption region caused by PSPR does not occur. This can be seen from the fact that there is only one plot with an X-axis direction pitch of 300 nm as shown in FIG.

  Therefore, it can be said that the hybrid structure and the basic structure have different electric field enhancement mechanisms.

  In each structure, by changing the size of metal particles (for example, the diameter and thickness in plan view), the contribution of PSPR to the intensity of all SPR and the contribution of LSPR of PPGM to the intensity of all SPR Will change.

  The electric field enhancing element 100 according to the present embodiment has a hybrid structure or a structure in which the period of the hybrid structure in the Y-axis direction is different. As shown in FIG. It has a periodic array that can excite PSP propagating through the interface with the dielectric layer 20. The electric field enhancing element 100 is designed at the interface between the metal layer and the dielectric layer as shown in FIG. 3 by designing the thickness of the dielectric layer 20 so that the PSP and the LSP are electromagnetically coupled. The excited PSP and the LSP excited by the metal particles can be electromagnetically combined.

1.5. Resonance wavelength of propagation surface plasmon and resonance wavelength of localized surface plasmon In the electric field enhancement device 100 according to the present embodiment, the resonance wavelength of propagation surface plasmon (PSP) and the resonance wavelength of localization surface plasmon (LSP). Is different. As shown in an experimental example to be described later, for example, the resonance wavelength of the LSP can be changed by changing the size (size in plan view) or thickness (height) of the metal particles of the electric field enhancing element. . Therefore, by changing the size or thickness of the metal particle 30 in plan view, the resonance wavelength of the PSP can be made longer than the resonance wavelength of the LSP in the electric field enhancing element 100, or more than the resonance wavelength of the LSP. Can also be shortened. Hereinafter, the resonance wavelength of the PSP and the resonance wavelength of the LSP will be described in detail.

First, propagation type surface plasmon (PSP) will be described. Normally, the dispersion relation of incident light (light line of n = 1) and the dispersion relation of PSP (dispersion relation of PSP propagating through the interface between Au and air) do not have an intersection, so that no PSP occurs. However, for example, when excited using incident light (diffracted light) that has passed through a diffraction grating having a grating interval Q, as shown in FIG. 4, the dispersion relation of PSP (the PSP propagating through the interface between Au and air) (Dispersion relationship) and the dispersion relationship (light line) of incident light (diffracted light) have an intersection, and the PSP at the wavelength of the intersection is excited. FIG. 4 is a diagram schematically showing a dispersion relation of surface plasmon polariton (SPP). Here, the SPP is a quantum of vibrations in which charge vibrations near the surface of the metal layer and electromagnetic waves are combined.

The wavelength at the intersection (see FIG. 4) is called the resonance wavelength of the PSP, and the resonance wavelength λ _PSP [nm] of the _PSP can be expressed by the following formula (1). The expression (1) shows the case where the excitation light (incident light) is perpendicularly incident (the case where the excitation light is incident in parallel to the vertical line on the upper surface of the dielectric layer).

λ _PSP (n = 1) <λ _PSP <λ _PSP (n ₂ ) (1)
here,
λ _PSP (n = 1) = [1240 × SQRT {ε ₁ (λ _in ) / (ε ₁ (λ _in ) +1)}] / (4π / X _p × 100) (2)
λ _PSP (n ₂ ) = [1240 × SQRT {ε ₁ (λ _in ) × ε ₂ / (ε ₁ (λ _in ) + ε ₂ )}] / (4π / X _p × 100) (3)

In Expressions (2) and (3), X _p [nm] is the pitch (period) of the metal particles in the polarization direction of the excitation light, and ε ₁ (ω) is the dielectric constant of the metal layer. Yes, ε ₂ (ε ₂ = n ₂ ² ) is the dielectric constant of the dielectric layer, and λ _in [nm] is the wavelength of the excitation light. Further, ω is an angular frequency of excitation light incident on the electric field enhancing element, and has a relationship of λ _in [nm] = 1240 / ω (eV).

The resonant wavelength of the PSP varies with the thickness of the dielectric layer. When the thickness of the dielectric layer having a dielectric constant ε ₂ is infinite, the PSP resonance wavelength is λ _PSP (n ₂ ). When the thickness of the dielectric layer is finite, the PSP resonance wavelength is expressed by the following equation (1): the resonance wavelength of PSP generated at the interface between the metal layer and air, the metal layer, and the dielectric layer having an infinite thickness. It takes a value between the resonance wavelength of PSP generated at the interface.

For example, in Experimental Example 1 described later, if the metal layer is an Au layer, the dielectric layer is a SiO ₂ layer (n ₂ = 1.46), X _p = 600 nm, and the wavelength λ _in is 630 nm, From the formula (1), 625 nm <λ _PSP <980 nm. From the result of FDTD (Finite Difference Time Domain) calculation, λ _PSP = 700 nm.

  Next, the resonance wavelength of LSP will be described. The LSP resonance wavelength (energy) of a metal sphere placed in a uniform surrounding medium is an energy ω that satisfies the following formula (4). Note that there is a relationship of λ = 1240 / ω.

ε ₁ (ω) = − 2ε ₀ (4)

In Equation (4), the dielectric constant of the metal is ε ₁ (ω), and the dielectric constant of the surrounding medium is ε ₀ .

  The resonance wavelength of LSP depends on the dielectric constant, shape, and surrounding dielectric constant of the metal particles. In the electric field enhancing element 100 according to the present embodiment, the interaction between the metal layer 10 and the metal particles 30 (PSP excited at the interface between the metal layer 10 and the dielectric layer 20) Since there is an electromagnetic interaction with the LSP excited in the metal particle 30, the resonance wavelength of the LSP cannot be generally expressed by the equation (4).

Therefore, as in an experimental example to be described later, the asymptotic line of the resonance wavelength of PSP and the asymptotic line of the resonance wavelength of LSP were obtained by changing the diameter of the metal particles (diameter in plan view). For example,
By designing the electric field enhancement element so as to avoid the diameter of the intersection of both asymptotes (the diameter of the metal particles), the resonance wavelength of the PSP and the resonance wavelength of the LSP can be made different. The asymptote of the resonance wavelength of the PSP and the asymptote of the resonance wavelength of the LSP can be obtained by changing parameters other than the diameter of the metal particle, and the value at the intersection of both asymptotes (the value of the changed parameter) By designing the electric field enhancing element so as to avoid (), the resonance wavelength of the PSP and the resonance wavelength of the LSP can be made different.

  In the electric field enhancement element 100 according to the present embodiment, an extremely large increase in electric field can be obtained by electromagnetically coupling a propagation surface plasmon (PSP) and a localized surface plasmon (LSP). it can.

FIG. 5 is a diagram for explaining anti-crossing by a hybrid, and represents a resonance wavelength when the pitch of the metal particles 30 in the X-axis direction is changed. The metal layer 10 is an Au layer, the dielectric layer 20 is a SiO ₂ layer, the thickness is 50 nm, the metal particles 30 are Au particles, the diameter is 100 nm, the height is 30 nm, the Y-axis direction pitch = the X-axis direction pitch, and FDTD The reflection spectrum was calculated by the (Finite Difference Time Domain) method to obtain the resonance wavelength.

The resonance wavelength of PSP in this structure (resonance wavelength of PSP propagating through the interface between the Au layer and the SiO ₂ layer) can be expressed by equation (1) and is predicted to be as shown by the broken line in FIG. The resonance wavelength of the LSP is a straight line substantially parallel to the horizontal axis.

  As shown in FIG. 5, when the resonance wavelength of the PSP approaches the resonance wavelength of the LSP, the absorption region caused by the LSP and the PSP splits (anti-crossing). In particular, when the wavelengths of LSP and PSP are equal, the effect of the hybrid mode is maximized.

  The sample analysis element according to the present invention uses points other than the point where the effect of the hybrid mode is maximized. That is, this is a case where the wavelengths of LSP and PSP are different. As shown in an experimental example to be described later, for example, the resonance wavelength of the LSP can be changed by changing the size (size in plan view) or thickness (height) of the metal particles of the electric field enhancing element. .

1.6. Spectrum of Reflected Light A spectrum of reflected light when the electric field enhancing element 100 according to this embodiment is irradiated with white light will be described. Hereinafter, an example in which a reflection spectrum is used as the spectrum of reflected light when the electric field enhancing element 100 is irradiated with white light will be described.

  FIG. 6A and FIG. 7A are diagrams for explaining a reflection spectrum in the electric field enhancing element 100 according to the present embodiment. In FIG. 6A and FIG. 7A, the horizontal axis indicates the wavelength, and the vertical axis indicates the reflectance. That is, the reflection spectrum is a curve indicating the reflectance with respect to the wavelength of the irradiation light (incident light). FIG. 6B and FIG. 7B are diagrams for explaining the wavelength characteristics of the enhanced electric field in the electric field enhancing element 100 according to the present embodiment. In FIG. 6B and FIG. 7B, the horizontal axis indicates the wavelength, and the vertical axis indicates the electric field amplification.

  FIG. 6 shows the electric field enhancement element 100 in which the resonance wavelength of the PSP is longer than the resonance wavelength of the LSP. FIG. 7 shows the electric field enhancement element 100 in which the resonance wavelength of the PSP is shorter than the resonance wavelength of the LSP.

The reflection spectrum can be obtained by allowing the target substance to be adsorbed on the metal particles 30 of the electric field enhancing element 100 and then measuring the reflectance by making, for example, white light incident on the electric field enhancing element 100. In the reflection spectrum, a drop in reflectivity indicates that SPR is occurring. When SPR is generated by irradiation with excitation light (incident light), absorption due to resonance occurs and the reflectance decreases. Therefore, the intensity of the enhanced electric field of SPR can be expressed by (1-r) using the reflectance r. As shown in FIGS. 6 and 7, there is a relationship that the intensity of the enhanced electric field is stronger as the value of the reflectance r is closer to zero. Therefore, the reflectance can be used as an index of the intensity of the enhanced electric field of the SPR.

  The reflection spectrum of the electric field enhancing element 100 has a first absorption region P1 and a second absorption region P2, as shown in FIGS. 6 (a) and 7 (a). The absorption region is a region where the spectrum of reflected light changes due to light absorption due to SPR resonance, and specifically, a region where the reflectance of the reflection spectrum falls. The absorption region is, for example, a downward convex peak. Thus, the reflection spectrum has two absorption regions because the PSP excited at the interface between the metal layer 10 and the dielectric layer 20 and the LSP excited by the metal particle 30 interact electromagnetically. This is because of anti-crossing. The second absorption region P2 is an absorption region having a larger half width than the first absorption region P1. The first absorption region P1 is an absorption region where the contribution of PSP is greater than that of LSP, and the second absorption region P2 is an absorption region where the contribution of LSP is greater than that of PSP. In the reflection spectrum when the electric field enhancing element 100 is irradiated with white light, the half width of the first absorption region P1 is H1, and the half width of the second absorption region P2 is larger than the half width H1 of the first absorption region P1. When the value width is H2, the half-value width H1 and the half-value width H2 satisfy the relationship of the following formula (5).

  (H2-H1) / H2 × 100 ≧ 40 (5)

  Below, let the left side of Formula (5) be the half value width ratio HR. That is, HR = (H2−H1) / H2 × 100. In the example shown in FIG. 6A, the resonance wavelength of the PSP is longer than the resonance wavelength of the LSP, and the second absorption region P2 is located on the shorter wavelength side than the first absorption region P1. In the example shown in FIG. 7A, the resonance wavelength of the PSP is shorter than the resonance wavelength of the LSP, and the second absorption region P2 is located on the longer wavelength side than the first absorption region P1.

  The absorption regions (first absorption region P1 and second absorption region P2) in the reflection spectrum have a point at which the reflectance becomes minimum as shown in FIGS. 6 (a) and 7 (a). And the LSP are electromagnetically interacting with each other, which is a portion that is depressed more than the baseline BL. The base line BL is a straight line connecting the point Q and the point R. The point Q is, for example, closer to the short wavelength side than the minimum point (a point at which the reflectance is minimized) T1 of the first absorption region P1 and the minimum point (a point at which the reflectance is minimized) T2 of the second absorption region P2. This is a point where the reflectance is maximized. The point R is a point located on the longer wavelength side than the minimum point T1 and the minimum point T2, and is a point where the reflectance is maximized.

  In the first absorption region P1, the difference between the reflectance at the minimum point T1 and the reflectance at the intersection C1 between the straight line V1 passing through the minimum point T1 and parallel to the vertical axis and the base line BL is 0.05 or more, for example. It is. In the second absorption region P2, the difference between the reflectance of the minimum point T2 and the reflectance of the intersection C2 between the straight line V2 passing through the minimum point T2 and parallel to the vertical axis and the base line BL is, for example, 0.05 or more It is.

  Further, the half width H1 of the first absorption region P1 is a difference in wavelength at the intersections A1 and B1 between the straight line L1 and the first absorption region P1 (difference between the wavelength at the intersection A1 and the wavelength at the intersection B1). The straight line L1 is a straight line that is parallel to the base line BL and passes through a midpoint between the minimum point T1 and the intersection C1 (a point that is at an equal distance from the points T1 and C1).

The half width H2 of the second absorption region P2 is a difference in wavelength at the intersections A2 and B2 between the straight line L2 and the second absorption region P2 (difference between the wavelength at the intersection A2 and the wavelength at the intersection B2). The straight line L2 is a straight line parallel to the base line BL and passes through the midpoint between the minimum point T2 and the intersection C2 (a point at an equal distance from the points T2 and C2).

  The half width H1 of the first absorption region P1 is, for example, not less than 5 nm and not more than 50 nm, and more preferably not less than 15 nm and not more than 40 nm. The half width H2 of the second absorption region P2 is, for example, not less than 10 nm and not more than 60 nm, and more preferably not less than 25 nm and not more than 50 nm.

  In the example shown in FIG. 6A and FIG. 7A, the reflection spectrum intersects the baseline BL in the order of the intersection points Q, S, U, and R from the short wavelength side to the long wavelength side. . In the example shown in FIG. 6A, the point Q is the short wavelength side skirt of the second absorption region P2, and the point S is the long wavelength side skirt of the second absorption region P2. Further, the point U is a skirt on the short wavelength side of the first absorption region P1, and the point R is a skirt on the long wavelength side of the first absorption region P1. In the example shown in FIG. 6A, the point Q is the short wavelength side skirt of the first absorption region P1, and the point S is the long wavelength side skirt of the first absorption region P1. Further, the point U is a skirt on the short wavelength side of the second absorption region P2, and the point R is a skirt on the long wavelength side of the second absorption region P2.

Here, in surface enhanced Raman scattering (SERS) measurement, a phenomenon is used in which the intensity of Raman scattered light having a very low intensity can be dramatically increased using the electric field enhancement effect by SPR. That is, in the SERS measurement, it is required that the electric field enhancement E _{i at} the wavelength λ _i of the excitation light and the electric field enhancement E _{s at} the wavelength λ _s of the Raman scattered light are strong and the HSD is large. It is proportional to equation (6).

E _i ² × E _s ² × HSD (6)

  In Equation (6), HSD represents Hot Spot Density and is the number of hot spots per unit area.

For example, in the electric field enhancement element in which the resonance wavelength of the PSP and the resonance wavelength of the LSP are the same and does not satisfy the above formula (5), as shown in FIG. 8, the wavelength difference (reflection) between the inflection points of the two absorption regions is shown. In the case of the spectrum, the wavelength difference between the minimum points, and in the case of the wavelength characteristic of the enhanced electric field, the maximum point (wavelength difference between the points where the enhanced electric field is maximized) Δλ is, for example, about 50 nm to 70 nm. Therefore, if the difference (λ _s −λ _i ) between the wavelength λ _s and the wavelength λ _i is not less than 50 nm and not more than 70 nm, for example, the wavelength λ _s is the wavelength of the inflection point of one absorption region, and the wavelength λ _i is By setting the wavelength at the inflection point of the other absorption region, the electric field enhancement strengths E _s and E _i can be increased. However, if the difference (λ _s −λ _i ) is less than 50 nm, for example, at least one of the wavelength λ _s and the wavelength λ _i is out of the range of the absorption region, or is different from the baseline of the absorption region. And at least one of the electric field enhancement E _s and the electric field enhancement E _i is low. As a result, the SERS intensity is lowered.

On the other hand, in the electric field enhancing element 100, the resonance wavelength of the PSP and the resonance wavelength of the LSP satisfy the above formula (5), so that the second absorption region P2 having a half width larger than the two absorption regions shown in FIG. Have The wavelength λ _i of the excitation light (light for exciting the LSP and PSP) of the electric field enhancing element 100 is included in the range of the second absorption region P2. For example, the wavelength λ _i of the excitation light can be included in the range of the second absorption region P2 by adjusting the size and the like of the metal particles 30 of the electric field enhancing element 100. Since the second absorption region P2 contributes more to the LSP than the two absorption regions shown in FIG. 8, the second absorption region P2 can have a half width greater than that of the two absorption regions shown in FIG. Therefore, even if the difference (λ _s −λ _i ) is less than 50 nm, the wavelength λ _s of the Raman scattered light is different from the second absorption region P2 as shown in FIGS. 6 (a) and 7 (a). Included in the range. Therefore, in the electric field enhancing element 100, the electric field enhancement strengths E _s and E _i can be increased. Thereby, in the electric field enhancing element 100, the SERS intensity can be increased, and the target substance can be detected with high sensitivity. In the example shown in FIG. 6A and FIG. 7A, the wavelengths λ _s and λ _i are in the range of the portion where the reflectance is smaller than the points A and B of the second absorption region P2.

Note that “the wavelength λ _{i of the} excitation light is included in the range of the second absorption region” means that the second absorption region P 2 has the wavelength λ _i as shown in FIGS. 6A and 7A. and when it has become a point P _i, although not shown, for example, the second absorbent region P2 are other peaks by overlapping the (portion of depressed reflectance peak downward convex), the second absorption in the absence on the base line BL skirt region P2 is to draw extrapolation by extrapolating a second absorbing region P2 to the base line BL, including a case where the outer挿線has a point P _i.

Similarly, “the wavelength λ _s of Raman scattered light is included in the range of the second absorption region” means that the second absorption region P2 has a wavelength λ as shown in FIGS. 6A and 7A. the case has a point P _s to be _s, although not shown, for example, the second absorbent region P2 are other peaks by overlapping the (portion of depressed reflectance peak downward convex), the when hem 2 absorption region P2 is not on the base line BL is to draw extrapolation by extrapolating a second absorbing region P2 to the base line BL, including a case where the outer挿線has a point P _s.

  FIG. 8 illustrates the wavelength characteristics of the reflection spectrum and the enhanced electric field in an electric field enhancement element in which the PSP and the LSP interact electromagnetically and the resonance wavelength of the PSP and the resonance wavelength of the LSP are the same. FIG. Two absorption regions appear for anti-crossing in the hybrid mode.

  In the above, in the electric field enhancement element in which the resonance wavelength of the PSP and the resonance wavelength of the LSP are the same, the wavelength difference between the inflection points of the two absorption regions in the wavelength characteristics of the reflection spectrum and the enhancement electric field is about 50 nm to 70 nm. Although described as follows, this wavelength difference varies depending on the size and material of the members constituting the electric field enhancing element.

Raman shift wavelength difference 50nm is, 1157Cm ^-1 at a wavelength 632.8nm excitation light corresponds to 762cm ^-1 at the wavelength 785nm of excitation light. In the electric field enhancement element 100, even if the Raman shift is smaller than the above value, the target substance can be detected with high sensitivity. For example, examples of the molecule (target substance) having a Raman peak below 1157 cm ⁻¹ include pyridine, acetic acid, acetone, methyl mercaptan, and toluene as described above.

  The electric field enhancing element 100 has the following features, for example.

In the electric field enhancement element 100, the PSP excited at the interface between the metal layer 10 and the dielectric layer 20 and the LSP excited by the metal particle 30 interact electromagnetically, and the resonance wavelength of the PSP and the LSP Unlike the resonance wavelength, the reflection spectrum satisfies the above formula (5), and the wavelength λ _i of the excitation light of the electric field enhancing element 100 is included in the range of the second absorption region P2. Therefore, in the electric field enhancing element 100, the second absorption region P2 can have a greater half-value width and a greater contribution of LSP than the absorption region of the reflection spectrum in the electric field enhancing element that does not satisfy the above formula (5). . Thereby, in the electric field enhancing element 100, the wavelength λ _s of the Raman scattered light can be set to the range of the second absorption region P2. Therefore, in the electric field enhancing element 100, the wavelength λ _{i of the} excitation light and the wavelength λ _s of the Raman scattered light can be included in the range of the second absorption region P2. In the electric field enhancing element 100, for example, at least one of the wavelength λ _i and the wavelength λ _s can be included in the range of the portion where the reflectance of the second absorption region P2 is low. As described above, in the electric field enhancing element in which the resonance wavelength of the PSP is the same as that of the LSP and does not satisfy the above formula (5), at least one of the wavelength λ _i and the wavelength λ _s has an absorption region depending on the material of the target substance. Sometimes out of range. Furthermore, in the electric field enhancing element 100, the PSP excited at the interface between the metal layer 10 and the dielectric layer 20 and the LSP excited by the metal particle 30 interact electromagnetically, so that the LSP alone is The electric field enhancement can be increased as compared with the case of being excited. Therefore, the electric field enhancing element 100 can detect the target substance 1 with high sensitivity even for a molecule (target substance) having a small Raman shift.

  Specifically, the electric field enhancing element 100 can detect the target substance 1 with high sensitivity even with the target substance 1 having a small Raman shift that satisfies the following formula (7).

ν = ((1 / λ _i ) − (1 / λ _s )) × 10 ⁷ , λ _s <λ _i +50 (7)

In Expression (7), ν represents a Raman shift, λ _i represents the wavelength of excitation light (incident light), and λ _s represents the wavelength of Raman scattered light.

  For example, when it is desired to detect a molecule having a small Raman shift, the excitation wavelength may be long (for example, 623.8 nm may be 785 nm), but the pitch of the metal particles is as large as the wavelength. Therefore, the pitch of the metal particles increases, the HSD decreases, and the SERS intensity decreases. Further, if the surrounding refractive index is increased, the PSP dispersion curve is changed, so that the pitch of the metal particles can be reduced, but the target substance is limited to a liquid or a substance in a solution. In the electric field enhancement element 100, for example, the excitation wavelength does not have to be 785 nm, so that the HSD can be increased and the gaseous target substance 1 can be detected.

  In the above description, the example using the reflection spectrum as the spectrum of the reflected light when the electric field enhancing element 100 is irradiated with white light has been described. However, the spectrum of the reflected light when the electric field enhancing element 100 is irradiated with white light. For example, you may use the spectrum containing the numerical value of reflectance, such as an absorption spectrum (1-reflectance). In this case, the spectrum including the numerical value of reflectance satisfies the above formula (5).

2. Raman Spectroscopic Device Next, the Raman spectroscopic device according to the present embodiment will be described with reference to the drawings. FIG. 9 is a diagram schematically showing a Raman spectroscopic device 200 according to this embodiment.

  As shown in FIG. 9, the Raman spectroscopic device 200 includes a gas sample holding unit 110, a detection unit 120, a control unit 130, and a housing 140 that houses the detection unit 120 and the control unit 130. The gas sample holder 110 includes an electric field enhancing element according to the present invention. Hereinafter, an example including the electric field enhancing element 100 as the electric field enhancing element according to the present invention will be described.

  The gas sample holding unit 110 includes an electric field enhancing element 100, a cover 112 that covers the electric field enhancing element 100, a suction channel 114, and a discharge channel 116. The detection unit 120 includes a light source 210, lenses 122a, 122b, 122c, and 122d, a half mirror 124, and a photodetector 220. The control unit 130 includes a detection control unit 132 that processes a signal detected by the photodetector 220 and controls the photodetector 220, and a power control unit 134 that controls power and voltage of the light source 210 and the like. doing. As shown in FIG. 9, the control unit 130 may be electrically connected to a connection unit 136 for connection to the outside.

  In the Raman spectroscopic device 200, when the suction mechanism 117 provided in the discharge flow path 116 is operated, the suction flow path 114 and the discharge flow path 116 become negative pressure, and the target substance to be detected is detected from the suction port 113. The contained gas sample is aspirated. The suction port 113 is provided with a dust removal filter 115, which can remove relatively large dust, some water vapor, and the like. The gas sample passes through the suction flow path 114 and the discharge flow path 116 and is discharged from the discharge port 118. The gas sample comes into contact with the metal particles 30 of the electric field enhancing element 100 when passing through such a path.

  The shapes of the suction flow path 114 and the discharge flow path 116 are such that light from the outside does not enter the electric field enhancing element 100. Thereby, since the light which becomes noise other than a Raman scattered light does not enter, the S / N ratio of a signal can be improved. The material constituting the channels 114 and 116 is, for example, a material or a color that hardly reflects light.

  The shape of the suction channel 114 and the discharge channel 116 is such that the fluid resistance to the gas sample is reduced. Thereby, highly sensitive detection becomes possible. For example, retention of the gas sample at the corners can be eliminated by making the shapes of the channels 114 and 116 as smooth as possible by eliminating the corners. As the suction mechanism 117, for example, a fan motor or a pump having a static pressure and an air volume corresponding to the flow path resistance is used.

  In the Raman spectroscopic device 200, the light source 210 irradiates the electric field enhancing element 100 including the metal particles 30 on which the target substance is adsorbed with light (for example, laser light having a wavelength of 632.8 nm, excitation light that excites SPR). As the light source 210, for example, a semiconductor laser or a gas laser is used. The light emitted from the light source 210 is collected by the lens 122a and then enters the electric field enhancing element 100 through the half mirror 124 and the lens 122b. SERS light is emitted from the electric field enhancing element 100, and the light reaches the photodetector 220 via the lens 122b, the half mirror 124, and the lenses 122c and 122d. That is, the photodetector 220 detects the light emitted from the electric field enhancing element 100. Since the SERS light includes Rayleigh scattered light having the same wavelength as the incident wavelength from the light source 210, the Rayleigh scattered light may be removed by the filter 126 of the photodetector 220. The light from which the Rayleigh scattered light has been removed is received by the light receiving element 128 via the spectroscope 127 of the photodetector 220 as Raman scattered light. For example, a photodiode is used as the light receiving element 128.

  The spectroscope 127 of the photodetector 220 is formed of, for example, an etalon using Fabry-Perot resonance, and the pass wavelength band can be made variable. The light receiving element 128 of the light detector 220 obtains a Raman spectrum peculiar to the target substance. For example, the signal intensity of the target substance is detected by collating the obtained Raman spectrum with previously stored data. Can do.

  Note that the Raman spectroscopic device 200 includes the electric field enhancement element 100, the light source 210, and the photodetector 220. If the target substance is attached to the electric field enhancement element 100 and the Raman scattered light can be detected, the Raman scattering apparatus 200 is included in the above example. It is not limited.

  The Raman spectroscopic device 200 includes an electric field enhancing element 100. Therefore, the Raman spectroscopic device 200 can detect the target substance with high sensitivity.

3. Raman spectroscopy Next, the Raman spectroscopy according to this embodiment will be described.

  In the Raman spectroscopy according to the present embodiment, the target substance is attached to the metal particles 30 of the electric field enhancing element (for example, the electric field enhancing element 100) according to the present invention, and the electric field enhancing element 100 to which the target substance is attached is irradiated with the excitation light. Then, the Raman scattered light emitted from the electric field enhancing element 100 is detected. For example, the Raman spectroscopy according to the present embodiment is performed using the Raman spectroscopy apparatus 200 described above.

In the Raman spectroscopy according to the present embodiment, the wavelength of the excitation light and the wavelength of the Raman scattered light are within the range of the second absorption region P2 of the reflection spectrum as described above. For example, in the Raman spectroscopy according to the present embodiment, the reflectance of the electric field enhancing element 100 is measured before detecting the Raman scattered light emitted from the electric field enhancing element 100, and the wavelength of the excitation light is calculated as described above. The wavelength of the Raman scattered light may be the range of the second absorption region P2. As in an experimental example to be described later, the half width of the absorption region of the reflection spectrum is changed by changing the size (size in plan view) and the thickness of the metal particle 30 of the electric field enhancing element 100, for example. Therefore, the wavelength of the excitation light and the wavelength of the Raman scattered light may be set as the range of the second absorption region P2 by changing the size and thickness of the metal particle 30.

  Since the Raman spectroscopy according to the present embodiment uses the electric field enhancement element 100, the target substance can be detected with high sensitivity.

4). Next, an electronic device 300 according to the present embodiment will be described with reference to the drawings. FIG. 10 is a diagram schematically illustrating the electronic apparatus 300 according to the present embodiment. The electronic device 300 can include a Raman spectroscopic device according to the present invention. Hereinafter, an example including the Raman spectroscopic device 200 as the Raman spectroscopic device according to the present invention will be described.

  As shown in FIG. 10, the electronic device 300 includes a Raman spectroscopic device 200, a calculation unit 310 that calculates health and medical information based on detection information from the photodetector 220, and a storage unit 320 that stores health and medical information. A display unit 330 for displaying health and medical information.

  The calculation unit 310 is, for example, a personal computer or a personal digital assistant (PDA) and receives detection information (signals or the like) sent from the photodetector 220. The calculation unit 310 calculates health and medical information based on detection information from the photodetector 220. The calculated health and medical information is stored in the storage unit 320.

  The storage unit 320 is, for example, a semiconductor memory, a hard disk drive, or the like, and may be configured integrally with the calculation unit 310. The health care information stored in the storage unit 320 is sent to the display unit 330.

  The display unit 330 includes, for example, a display board (liquid crystal monitor or the like), a printer, a light emitter, a speaker, and the like. The display unit 330 displays or issues information based on the health and medical information calculated by the calculation unit 310 so that the user can recognize the contents.

  The health information includes the presence or amount of at least one biological substance selected from bacteria, viruses, proteins, nucleic acids, and antigens / antibodies, or at least one compound selected from inorganic molecules and organic molecules. Information about can be included.

  The electronic apparatus 300 includes a Raman spectroscopic device 200. Therefore, the electronic device 300 can provide highly accurate health care information.

5. Experimental Example An experimental example is shown below to describe the present invention more specifically. The present invention is not limited by the following experimental examples.

5.1. Experimental example 1
5.1.1. Model In Experimental Example 1, a far solution (reflection spectrum) was obtained by FDTD (Finite Difference Time Domain) simulation. FIG. 11 is a diagram for explaining the model M used in Experimental Example 1. FIG. As shown in FIG. 11, an Au layer was used as a metal layer, a SiO ₂ layer was provided as a dielectric layer on the Au layer, and cylindrical Au particles were provided as metal particles on the SiO ₂ layer to form a model M. .

In model M, the thickness of the Au layer was 150 nm. The thickness of the SiO ₂ layer was 50 nm, and the refractive index of the SiO ₂ layer was 1.46. The diameter of the Au particles in plan view (hereinafter also simply referred to as “diameter”) was changed in the range of 80 nm to 150 nm, and the thickness of the Au particles was set to 30 nm. The Au particles were provided in a matrix in the X-axis direction and the Y-axis direction, and the pitch of the Au particles in the X-axis direction and the Y-axis direction was 600 nm. The Lorenz Drude model was used for the refractive index of Au. The incident light was linearly polarized light in the X-axis direction, and the light was incident vertically on the upper surface of the SiO ₂ layer. Model M can enhance signals with an incident wavelength of 632.8 nm and a Raman shift of about 1000 cm ⁻¹ (675.5 nm).

  For the calculation, FDTD soft FullWAVE of Rsoft (currently Cybernet System Co., Ltd.) was used. The conditions for simulation of the reflection spectrum are a minimum mesh of 2 nm and a calculation time of 32 μm.

5.1.2. Calculation of reflection spectrum The reflection spectrum was calculated by changing the diameter of Au particles in the range of 80 nm to 150 nm. FIG. 12 is a reflection spectrum when the diameter of the Au particles is 90 nm. FIG. 13 is a reflection spectrum when the diameter of the Au particles is 104 nm. FIG. 14 is a reflection spectrum when the diameter of the Au particles is 140 nm.

  As shown in FIGS. 12 to 14, the reflection spectrum has two absorption regions (decrease in reflectance). FIG. 15 is a graph plotting the wavelengths of the minimum points (minimum points of reflectance) of two absorption regions in the reflection spectrum when the diameter of the Au particles is changed in the range of 80 nm to 150 nm.

As shown in FIG. 15, plots each asymptotic to two straight lines were obtained. A straight line having a constant wavelength even when the diameter of the Au particle changes indicates the resonance wavelength of the PSP. A straight line whose wavelength changes as the diameter of the Au particle changes indicates the resonance wavelength of the LSP. The diameter of the intersection IP of the straight line L _PSP indicating the resonance wavelength of the _PSP and the straight line _LLSP indicating the resonance wavelength of the _LSP is the wavelength of the minimum point of the absorption region on the short wavelength side and the wavelength of the minimum point of the absorption region on the long wavelength side It is the diameter when the difference between is the smallest. Therefore, in FIG. 15, a straight line asymptotic to the plot is drawn so that the diameter of the intersection point IP is 104 nm.

As shown in FIG. 15, when the resonance wavelength of the PSP and the resonance wavelength of the LSP approach each other, the absorption region caused by the LSP and the PSP splits (anti-crossing) away from the straight line L _PSP and the straight line L _LSP . In particular, when the wavelengths of LSP and PSP are equal, the effect of the hybrid mode is maximized. The strength of the effect of the hybrid mode can be determined by the shape of the reflection spectrum (or absorption spectrum). The stronger the effect of the hybrid mode, the more equal the half widths of the two absorption regions of the reflection spectrum. When deviating from the intersection point IP (if the resonance wavelength of the PSP and the resonance wavelength of the LSP are different), the properties of the LSP and the properties of the PSP begin to appear in the shape of the absorption region of the reflection spectrum while maintaining the hybrid mode. When the contribution degree of LSP is large, the shape of the absorption region becomes broad (half-value width is large), and when the contribution degree of PSP is large, the shape of the absorption region becomes sharp (half-value width is small).

As shown in FIG. 15, when the diameter of the Au particles is smaller than 104 nm, the resonance wavelength of the PSP becomes longer than the resonance wavelength of the LSP, and the absorption region on the shorter wavelength side than the absorption region on the longer wavelength side has a straight line L. Close to _LSP . Therefore, when the diameter of the Au particles is smaller than 104 nm, the absorption region on the short wavelength side becomes broad. Moreover, when the diameter of the Au particle is larger than 104 nm, the resonance wavelength of the PSP becomes shorter than the resonance wavelength of the LSP, and the absorption region on the long wavelength side becomes closer to the straight line L _LSP than the absorption region on the short wavelength side. I understood. Therefore, A
When the diameter of u particles becomes larger than 104 nm, the absorption region on the long wavelength side becomes broad.

  Here, the electric field enhancing element according to the present invention satisfies the above formula (5). That is, the half width ratio HR is 40% or more. If the half width ratio HR is 40% or more, the target substance can be detected with high sensitivity (for details, see Experimental Example 3 described later). In FIG. 15, a region including a plot corresponding to the absorption region (second absorption region P <b> 2) having the larger half width at which the half width ratio HR is 40% or more is indicated by hatching. In the example shown in FIG. 15, the diameter of the Au particles having a half-width ratio HR of 40% or more was 97 nm or less, or 135 nm or more. When the LSP and the PSP do not interact electromagnetically, the wavelength of the minimum point in the reflection spectrum absorption region is equal to the straight line (asymptotic line) shown in FIG.

  When the diameter of the Au particles shown in FIG. 12 was 90 nm, the half width ratio HR was 40.5%. In this case, the half value width of the absorption region on the short wavelength side is larger than the half value width of the absorption region on the long wavelength side. The absorption region on the short wavelength side has a large contribution of LSP, and the absorption region on the long wavelength side has a large contribution of PSP. When the diameter of the Au particles shown in FIG. 13 is 104 nm, the half widths of the two absorption regions are substantially equal, and the half width ratio HR is 25%. When the diameter of the Au particles shown in FIG. 14 is 140 nm, the full width at half maximum ratio HR was 49.2%. In this case, the half value width of the absorption region on the long wavelength side is larger than the half value width of the absorption region on the short wavelength side. The absorption region on the long wavelength side has a large contribution of LSP, and the absorption region on the short wavelength side has a large contribution of PSP.

As shown in FIGS. 12 and 14, when the half-width ratio HR is 40% or more, one of the two absorption regions becomes broad, and the wavelength of the excitation light and the wavelength of the Raman scattered light are broad. It can be set as the range of the absorption region (second absorption region P2). For example, in order to enhance the signal when the wavelength of the excitation light is 632.8 nm and the Raman shift is about 1000 cm ⁻¹ (675.5 nm), the wavelength of the minimum point of the broad absorption region (second absorption region P2) Is about 655 nm which is intermediate between 632.8 nm and 675.5 nm.

5.2. Experimental example 2
5.2.1. Model In Experiment Example 2, as in Experiment Example 1, the reflection spectrum was obtained by FDTD simulation. In Experimental Example 2, the reflection spectrum was obtained under the same model and the same conditions as in Experimental Example 1, except that the diameter of the metal particles was 104 nm and the thickness of the metal particles was changed in the range of 10 nm to 40 nm. .

5.2.2. Calculation of reflection spectrum The reflection spectrum was calculated by changing the thickness of Au particles in the range of 10 nm to 40 nm. FIG. 16 is a reflection spectrum when the thickness of the Au particles is 15 nm. FIG. 17 shows a reflection spectrum when the thickness of the Au particles is 25 nm. FIG. 18 is a reflection spectrum when the thickness of the Au particles is 40 nm.

  As shown in FIGS. 16 to 18, the reflection spectrum has two absorption regions (decrease in reflectivity). FIG. 19 is a graph plotting the wavelengths of the minimum points of the two absorption regions in the reflection spectrum when the thickness of the Au particles is changed in the range of 10 nm to 40 nm.

As shown in FIG. 19, plots each asymptotic to two straight lines were obtained. A straight line having a constant wavelength even when the thickness of the Au particle is changed indicates the resonance wavelength of the PSP. A straight line whose wavelength changes as the thickness of the Au particle changes indicates the resonance wavelength of the LSP. The thickness of the intersection point IP of the straight line L _PSP indicating the resonance wavelength of the _PSP and the straight line _LLSP indicating the resonance wavelength of the _LSP (the thickness of the Au particle) is the wavelength of the minimum point of the absorption region on the short wavelength side and the long wavelength side This is the thickness when the difference from the wavelength of the minimum point of the absorption region is the smallest. Therefore, in FIG. 19, a straight line asymptotic to the plot is drawn so that the diameter of the intersection point IP is 25 nm. As shown in FIG. 19, when the thickness of the Au particles is changed, the resonance wavelength of the LSP changes. When the Au particle thickness was decreased, the LSP resonance wavelength was red-shifted, and when the Au particle thickness was increased, the LSP resonance wavelength was blue-shifted.

As shown in FIG. 19, when the Au particle thickness is smaller than 25 nm, the resonance wavelength of the PSP becomes shorter than the resonance wavelength of the LSP, and the absorption region on the long wavelength side is shorter than the absorption region on the short wavelength side. It became close to L _LSP . For this reason, when the thickness of the Au particles becomes smaller than 25 nm, the absorption region on the long wavelength side becomes broad. When the Au particle thickness is greater than 25 nm, the resonance wavelength of the PSP becomes longer than the resonance wavelength of the LSP, and the absorption region on the short wavelength side is closer to the straight line L _LSP than the absorption region on the long wavelength side. It was. Therefore, when the Au particle thickness is greater than 25 nm, the absorption region on the short wavelength side becomes broad.

  In FIG. 19, a region including a plot corresponding to an absorption region (second absorption region) having a larger half width at which the half width ratio HR is 40% or more is indicated by hatching. In the example shown in FIG. 19, the thickness of the Au particles with a half-width ratio HR of 40% or more was 15 nm or less, or 35 nm or more.

  When the thickness of the Au particles shown in FIG. 16 was 15 nm, the half-value width ratio HR was 40.4%. In this case, the half value width of the absorption region on the long wavelength side is larger than the half value width of the absorption region on the short wavelength side. The absorption region on the long wavelength side has a large contribution of LSP, and the absorption region on the short wavelength side has a large contribution of PSP. When the thickness of the Au particles shown in FIG. 17 was 25 nm, the full width at half maximum ratio HR was 7.8%. When the diameter of the Au particles shown in FIG. 18 is 40 nm, the full width at half maximum ratio HR was 42.5%. In this case, the half value width of the absorption region on the short wavelength side is larger than the half value width of the absorption region on the long wavelength side. The absorption region on the short wavelength side has a large contribution of LSP, and the absorption region on the long wavelength side has a large contribution of PSP.

  In Experimental Example 2, it was found that by changing the thickness of the Au particles, the full width at half maximum ratio HR can be made 40% or more, as in Experimental Example 1.

5.3. Experimental example 3
5.3.1. Electric field enhancement element An electric field enhancement element was created and the reflectance and Raman signal were measured. A glass substrate was used as a substrate, a Cr layer as an adhesion layer was formed on the substrate by a sputtering method, and an Au layer was formed as a metal layer on the Cr layer by a sputtering method. The thickness of the Cr layer was 5 nm or less, and the thickness of the Au layer was 100 nm. Next, an Al ₂ O ₃ layer and an SiO ₂ layer were formed as a dielectric layer on the Au layer in this order by sputtering. The thickness of the Al ₂ O ₃ layer was 5 nm or less, and the thickness of the SiO ₂ layer was 50 nm.

Next, Au particles were formed as metal particles on the SiO ₂ layer. Specifically, a resist is applied on the SiO ₂ layer, a circular pattern (pattern part) is patterned by EBL (Electron Beam Lithography), and then an Au layer is formed by a vacuum deposition method. The Au layer was lifted off to form Au particles. The Au particles were formed in a matrix in the X-axis direction and the Y-axis direction, and the pitch of the Au particles in the X-axis direction and the Y-axis direction was 600 nm. The thickness of the Au particles was 30 nm.

In this experimental example, a plurality of Au particles having different diameters were formed. Specifically, Au particles having a diameter of 90 nm were formed in a matrix in the first region on the SiO ₂ layer, and Au particles having a diameter of 106 nm were formed in a matrix in the second region on the SiO ₂ layer. The Au particles having a diameter of 90 nm are Au particles according to the present invention (according to the example). The Au particles having a diameter of 106 nm are Au particles according to a comparative example. The size of each region in plan view is 100 μm × 100 μm.

Pyridine was used as a target substance to be measured. Since the Raman peak of pyridine appears at 1014 cm ⁻¹ , the Raman scattering wavelength is 676.2 nm when the incident wavelength is 632.8 nm.

5.3.2. Reflectivity measurement The electric field enhancing element formed as described above was sufficiently exposed to pyridine saturated gas, and then irradiated with a white light source to measure the reflectance. The polarization direction of incident light was the X-axis direction.

  FIG. 20 is a reflection spectrum in a region where the diameter of Au particles is 90 nm and 106 nm. In FIG. 20, the reflection spectrum in the region where the diameter of Au particles is 90 nm is indicated by a solid line, and the reflection spectrum in the region where the diameter of Au particles is 106 nm is indicated by a broken line.

  As shown in FIG. 20, three depressions (convex peaks downward) appeared in the wavelength range of 550 nm to 800 nm. Of the three depressions, the central depression D is caused by the measurement system (specifically, the objective lens of the measurement system), so the noted depression is the two depressions on both sides (short wavelength side). Absorption region on the long wavelength side).

  In the reflection spectrum of the region having a diameter of 90 nm, an absorption region on the short wavelength side appeared in the range of about 600 nm to 675 nm, and an absorption region on the long wavelength side appeared in the range of about 690 nm to 740 nm. The half value width of the absorption region on the short wavelength side was 38 nm, the half value width of the absorption region on the long wavelength side was 21 nm, and the half value width ratio HR was 45%.

  In the reflection spectrum of the region having a diameter of 106 nm, the absorption region on the short wavelength side appeared in the range of about 610 nm to 680 nm, and the absorption region on the long wavelength side appeared in the range of about 710 nm to 780 nm. The half value width of the short wavelength side absorption region was 33 nm, the half value width of the long wavelength side absorption region was 39 nm, and the half value width ratio HR was 15%.

Here, the half-value width of the absorption region on the long wavelength side of the reflection spectrum of the region having a diameter of 106 nm (hereinafter also referred to as “diameter 106 nm reflection spectrum”) is the reflection spectrum of the region having a diameter of 90 nm (hereinafter referred to as “90 nm diameter reflection”). It is larger than the half-value width of the absorption region on the short wavelength side of the spectrum. However, since the wavelength λ _{i of the} excitation light is not included in the range of the reflection spectrum with a diameter of 106 nm, the Raman signal intensity is weak in a region with a diameter of 106 nm as shown in FIG. Usually, a laser is used as a light source for irradiating excitation light, but the wavelength of a laser having a wavelength longer than the wavelength of 632.8 nm and the closest to 632.8 nm is 785 nm. Referring to FIG. 20, even if a laser having a wavelength of 785 nm is used as a light source for irradiating excitation light, it is assumed that a strong Raman signal cannot be obtained in a region having a diameter of 106 nm.

Furthermore, even if the wavelength λ _{i of the} excitation light is set to 725 nm included in the absorption region on the long wavelength side of the reflection spectrum having a diameter of 90 nm, when pyridine is used as the target substance, as described above, Since the shift is 1014 cm ⁻¹ , the wavelength λs of the Raman scattered light is 782.5 nm, and the difference (λ _s −λ _i ) is 57.5 nm. On the other hand, when the wavelength λ _{i of the} excitation light is 632.8 nm, the wavelength λs of the Raman scattered light is 676.2 nm, and the difference (λ _s −λ _i ) is 43.4 nm. Thus, when the wavelength λ _i of the excitation light is increased, the difference (λ _s −λ _i ) is increased. Therefore, it is not preferable to increase the wavelength λ _{i of the} excitation light from the viewpoint of including the wavelength λ _i and the wavelength λ _s in the range of one absorption region (including in the portion where the reflectance of one absorption region is low).

  Note that the full width at half maximum ratio HR obtained in the simulation of Experimental Example 1 is different from the full width at half maximum ratio HR obtained in the present experimental example, but this is due to differences in measurement systems, manufacturing errors, and the like.

  Further, the absolute value of the half width of the absorption region in FIG. 12, the absolute value of the half width of the absorption region in FIG. 13, and the absolute value of the half width of the absorption region in FIG. ~ Cannot be compared by reading from FIG. The same applies to the absolute value of the half width of the absorption region in FIG. 16, the absolute value of the half width of the absorption region in FIG. 17, and the absolute value of the half width of the absorption region in FIG.

  The full width at half maximum was determined as follows. FIG. 21 is a diagram for explaining how to obtain the half width. Below, the method of calculating | requiring a half value width is demonstrated using the reflection spectrum of the area | region whose diameter of the above-mentioned Au particle | grain is 106 nm.

  First, two points (points Q and R) in the reflection spectrum were determined, and a straight line connecting the points Q and R was drawn. The straight line becomes the base line BL. The point Q is a point that is located on the short wavelength side of the minimum point (minimum point of reflectance) T of the two absorption regions and has the maximum reflectance. The point R is a point that is located on the longer wavelength side than the minimum point T of the two absorption regions and has the maximum reflectance. Specifically, the point R is a point with a wavelength of 870 nm. In addition, as shown in FIG. 21, you may fit by the moving average the range (about 800 nm-870 nm range) where the noise of a reflection spectrum is large. The reason why the base line BL is not parallel to the horizontal axis is that reflected light from the Au layer is also detected.

  Next, a straight line L passing through a midpoint between the minimum point T and the point C (a point at an equal distance from the points T and C) and parallel to the base line BL was drawn. The point C is an intersection of the straight line V passing through the minimum point T and parallel to the vertical axis, and the base line BL.

  Next, the half-value width H was obtained by reading the wavelengths of the intersections A and B between the straight line L and the reflection spectrum. Specifically, the half width H is a value obtained by subtracting the wavelength of the intersection A from the wavelength of the intersection B. As described above, the half width H can be obtained.

As shown in FIG. 20, in the reflection spectrum of the region of the diameter of 90 nm, the absorption region of the short wavelength side, that wavelength is 632.8 nm (point the wavelength of the incident light) were found to have a P _i. In addition, as shown in FIG. 20, in the reflection spectrum of the 90 nm diameter region, the short wavelength side absorption region overlaps with the central depression D, but the baseline is drawn in the 90 nm diameter reflection spectrum. When an extrapolation line was drawn by extrapolating the absorption region on the wavelength side to the baseline, it was confirmed that the extrapolation line had a point at which the wavelength was 677 nm (a point at which the wavelength of Raman scattered light). Therefore, according to FIG. 20, if the half-width ratio HR is 40% or more (that is, if the above formula (5) is satisfied), the wavelength of the excitation light (incident light) and the wavelength of the Raman scattered light are absorbed by one absorption. It was found that the range of the region can be.

5.3.3. Raman measurement After sufficiently exposing a pyridine saturated gas to an electric field enhancement element similar to the electric field enhancement element for which the reflectance was measured, Raman measurement was performed by irradiating incident light with a wavelength of 632.8 nm. The polarization direction of incident light was the X-axis direction.

  FIG. 22 is a graph showing Raman measurement results in a region where the diameter of Au particles is 90 nm and 106 nm. In FIG. 22, the Raman signal intensity in a region with a diameter of 90 nm is indicated by a solid line, and the Raman signal intensity in a region with a diameter of 106 nm is indicated by a broken line.

From FIG. 22, it was found that the signal intensity of pyridine 1009 cm ⁻¹ was stronger in the 90 nm diameter region than in the 106 nm diameter region. That is, an electric field enhancing element having a half width ratio HR of 40% or more has a higher Raman signal intensity and can detect a target substance with higher sensitivity than an electric field enhancing element having a half width ratio HR smaller than 40%. I understood. From FIG. 20, in the region of 106 nm in diameter, the wavelength of the minimum point of the absorption region on the short wavelength side is 659 nm, which is approximately the wavelength of incident light (632.8 nm) and the wavelength of Raman scattered light (677 nm). Despite being in the middle (the middle is 655 nm), the Raman signal intensity of pyridine is weak. This is because the half width of the absorption region on the short wavelength side is small in the region of 106 nm in diameter. In contrast, in the region of 90 nm in diameter, as shown in FIG. 20, the half-value width of the absorption region on the short wavelength side is larger than that of the region of 106 nm in diameter, and the absorption region on the short wavelength side compared to the Raman shift of pyridine. Since the width is large, the Raman signal intensity is strong.

  The width of the absorption region on the short wavelength side refers to the wavelength of the short wavelength side of the absorption region (point Q, see FIG. 21) and the long wavelength side of the absorption region (based on the long wavelength side of the absorption region). This is the difference between the extrapolated line when extrapolated to the line BL, the base line BL, and the wavelength of the intersection).

  The above-described embodiments and modifications are merely examples, and the present invention is not limited to these. For example, it is possible to appropriately combine each embodiment and each modification.

  The present invention includes configurations that are substantially the same as the configurations described in the embodiments (for example, configurations that have the same functions, methods, and results, or configurations that have the same objects and effects). In addition, the invention includes a configuration in which a non-essential part of the configuration described in the embodiment is replaced. In addition, the present invention includes a configuration that exhibits the same operational effects as the configuration described in the embodiment or a configuration that can achieve the same object. Further, the invention includes a configuration in which a known technique is added to the configuration described in the embodiment.

DESCRIPTION OF SYMBOLS 1 ... Target substance, 2 ... Substrate, 10 ... Metal layer, 20 ... Dielectric layer, 30 ... Metal particle, 100 ... Electric field enhancement element, 110 ... Gas sample holding part, 112 ... Cover, 113 ... Suction port, 114 ... Suction Flow path, 115 ... dust removal filter, 116 ... discharge flow path, 117 ... suction mechanism, 118 ... discharge port, 120 ... detection part, 122a, 122b, 122c, 122d ... lens, 124 ... half mirror, 126 ... filter, 127 ... Spectrometer, 128 ... light receiving element, 130 ... control unit, 132 ... detection control unit, 134 ... power control unit, 136 ... connection unit, 140 ... casing, 200 ... Raman spectroscopic device, 210 ... light source, 220 ... photodetector , 300 ... electronic device, 310 ... calculation unit, 320 ... storage unit, 330 ... display unit

Claims (6)

A metal layer,
A dielectric layer provided on the metal layer;
A plurality of metal particles provided on the dielectric layer;
An electric field enhancing element comprising:
The plurality of metal particles have a periodic array capable of exciting propagating surface plasmons propagating through an interface between the metal layer and the dielectric layer,
The propagation type surface plasmon and the localized type surface plasmon excited by the metal particle interact electromagnetically,
The resonance wavelength of the propagation surface plasmon is different from the resonance wavelength of the localized surface plasmon,
In the spectrum of reflected light when the electric field enhancing element is irradiated with white light, the half width of the first absorption region is H1, and the half width of the second absorption region is larger than the half width H1 of the first absorption region. When the price range is H2,
The H1 and the H2 are
(H2-H1) / H2 × 100 ≧ 40
Satisfy the relationship
The electric field enhancing element, wherein the wavelength of the excitation light of the electric field enhancing element is included in the range of the second absorption region. In claim 1,
The propagation wavelength of the propagation surface plasmon is longer than the resonance wavelength of the localized surface plasmon,
The electric field enhancing element, wherein the second absorption region is located on a shorter wavelength side than the first absorption region. In claim 1,
The propagation wavelength of the propagation surface plasmon is shorter than the resonance wavelength of the localized surface plasmon,
The electric field enhancing element, wherein the second absorption region is located on a longer wavelength side than the first absorption region. A target substance is attached to the electric field enhancing element according to any one of claims 1 to 3, and the excitation light is applied to the electric field enhancing element to detect Raman scattered light emitted from the electric field enhancing element. Raman spectroscopy,
The wavelength of the Raman scattered light is Raman spectroscopy, which is included in the range of the second absorption region. The electric field enhancing element according to any one of claims 1 to 3,
A light source for irradiating the electric field enhancing element with the excitation light;
A photodetector for detecting light emitted from the electric field enhancing element;
Including a Raman spectroscopic apparatus. The Raman spectroscopic device according to claim 5;
A calculation unit for calculating health and medical information based on detection information from the detector;
A storage unit for storing the health care information;
A display unit for displaying the health care information;
Including electronic equipment.

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