Electric field enhancement element and raman spectroscopic device

Abstract

To provide an electric filed enhancement element capable of improving detection sensitivity.SOLUTION: An electric filed enhancement element has: a substrate; a plurality of fine structures provided in the substrate and having conductivity; and a transparent layer for covering the plurality of fine structures and the substrate. An enhanced electric field generated by the plurality of fine structures has a maximum at a position spaced from the plurality of fine structures on a side opposed to the substrate of the plurality of fine structures in a perpendicular direction of the substrate.SELECTED DRAWING: Figure 9

Description

[Technical field]

[0001] The present invention relates to an electric field enhancing element and a Raman spectroscopy device. [Background technology]

[0002] In recent years, Raman spectroscopy using Localized Surface Plasmon Resonance (LSPR) has become known as one of the spectroscopic techniques for detecting low-concentration sample molecules. In such Raman spectroscopy, an enhanced electric field is formed by an electric field enhancing element with a nanometer-scale uneven structure, and Surface Enhanced Raman Scattering (SERS) occurs, in which the Raman scattered light is enhanced.

[0003] For example, Patent Document 1 describes an optical device including a substrate, a metal microstructure made of a plurality of metal particles formed on the surface of the substrate, and an organic molecular film formed on the metal microstructure. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2013-96939 A Summary of the Invention [Problem to be solved by the invention]

[0005] In the above optical devices, it is desirable to improve the detection sensitivity. [Means for solving the problem]

[0006] One aspect of the electric field enhancing element according to the present invention is A substrate; A plurality of microstructures provided on the substrate and having electrical conductivity; a transparent layer covering the plurality of microstructures and the substrate; having The enhanced electric field generated by the plurality of microstructures has a maximum at a position spaced apart from the plurality of microstructures, on the opposite side of the plurality of microstructures from the substrate in a direction perpendicular to the substrate.

[0007] One aspect of the Raman spectroscopy apparatus according to the present invention is An embodiment of the electric field enhancing element; a light source that irradiates the electric field enhancing element with light; a detector for detecting light from the electric field enhancing element; has. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a cross-sectional view showing a schematic diagram of an electric field enhancing element according to an embodiment of the present invention. [Diagram 2] FIG. 1 is a plan view showing a schematic diagram of an electric field enhancing element according to an embodiment of the present invention. [Diagram 3] FIG. 1 is a plan view showing a schematic diagram of an electric field enhancing element according to an embodiment of the present invention. [Figure 4] FIG. 1 is a plan view showing a schematic diagram of an electric field enhancing element according to an embodiment of the present invention. [Diagram 5] FIG. 1 is a plan view showing a schematic diagram of an electric field enhancing element according to an embodiment of the present invention. [Figure 6] FIG. 1 is a plan view showing a schematic diagram of an electric field enhancing element according to an embodiment of the present invention. [Figure 7] 4A and 4B are diagrams for explaining plasmon resonance in the electric field enhancing element according to the embodiment. [Figure 8] 4A and 4B are diagrams for explaining plasmon resonance in the electric field enhancing element according to the embodiment. [Figure 9] 4A and 4B are diagrams for explaining an enhanced electric field generated by a plurality of microstructures of the electric field enhancing element according to the embodiment. [Figure 10] FIG. 11 is a cross-sectional view showing a schematic diagram of an electric field enhancing element according to a modified example of the embodiment. [Figure 11] FIG. 1 is a cross-sectional view showing a schematic diagram of a Raman spectroscopic apparatus according to an embodiment of the present invention. [Figure 12] FIG. 1 is a diagram for explaining the principle of Raman scattering spectroscopy. [Figure 13] FIG. 2 is a schematic diagram showing an example of a Raman spectrum obtained by Raman scattering spectroscopy. [Figure 14] FIG. 2 is an XZ cross-sectional view showing a schematic diagram of the model used in the simulation. [Figure 15] FIG. 2 is an XY cross-sectional view showing a schematic diagram of the model used in the simulation. [Figure 16] FIG. 2 is an XY cross-sectional view showing a schematic diagram of the model used in the simulation. [Figure 17] FIG. 2 is an XZ cross-sectional view showing a schematic diagram of the model used in the simulation. [Figure 18] 1 is a table showing dimensions and main parameters that were changed in Examples 1 to 16 and Comparative Example 1. [Figure 19] Simulation results of Example 1. [Figure 20] Simulation results of Example 2. [Figure 21] Simulation results of Example 3. [Figure 22] Simulation results of Example 4. [Figure 23] Simulation results of Example 5. [Figure 24] Simulation results for Example 6. [Diagram 25] Simulation results for Example 7. [Figure 26] Simulation results for Example 8. [Figure 27] Simulation results for Example 9. [Figure 28] Simulation results for Example 10. [Figure 29] Simulation results for Example 11. [Diagram 30] Simulation results for Example 12. [Diagram 31] Simulation results for Example 13. [Diagram 32] Simulation results for Example 14. [Diagram 33] Simulation results for Example 15. [Diagram 34]Simulation results for Example 16. [Diagram 35] Simulation results for Comparative Example 1. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Preferred embodiments of the present invention will be described in detail below with reference to the drawings. Note that 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 necessarily essential components of the present invention.

[0010] 1. Electric field enhancing element Configuration 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 that shows a typical electric field enhancing element 100 according to the present embodiment. Fig. 2 is a plan view that shows a typical electric field enhancing element 100 according to the present embodiment. Fig. 1 is a cross-sectional view taken along line II in Fig. 2. Figs. 1 and 2 show an X-axis, a Y-axis, and a Z-axis as three mutually orthogonal axes.

[0011] 1 and 2, the electric field enhancing element 100 includes a substrate 10, a dielectric layer 20, a microstructure 30, and a transparent layer 40. For convenience, the transparent layer 40 is not shown in FIG.

[0012] The substrate 10 supports the microstructure 30 via the dielectric layer 20. When light from a light source (not shown in Figs. 1 and 2 ) used for Raman scattering is incident from the substrate 10 side, the substrate 10 transmits the light. When light from the light source is incident from the transparent layer 40 side, the substrate 10 may reflect the light toward the transparent layer 40 side.

[0013] The substrate 10 is, for example, a glass substrate or a silicon substrate. The material of the substrate 10 is, for example, SiO2 or Si. The substrate 10 has a perpendicular line Q. The perpendicular line Q is a perpendicular line to the upper surface of the substrate 10. In the illustrated example, the perpendicular line Q is parallel to the Z axis, and the direction of the perpendicular line Q is the Z axis direction.

[0014] The dielectric layer 20 is provided on the substrate 10 as shown in Fig. 1. The dielectric layer 20 is provided between the substrate 10 and the microstructure 30. The thickness of the dielectric layer 20 is, for example, 1 nm or more and 2000 nm or less, and preferably 10 nm or more and 1000 nm or less. The dielectric layer 20 does not necessarily have to be provided.

[0015] The dielectric layer 20 is transparent to light from the light source. The material of the dielectric layer 20 is, for example, Al2O3, TiO2, MgO, LiNbO3, HfO2, Ta2O5, SiON, Si3N4, etc. The dielectric layer 20 may be composed of multiple layers. In this case, the materials of the multiple layers may be different.

[0016] The microstructure 30 is provided on the dielectric layer 20. The microstructure 30 is provided on the substrate 10 via the dielectric layer 20. The microstructure 30 is provided between the dielectric layer 20 and the transparent layer 40. The shape of the microstructure 30 is, for example, a cylinder. The diameter of the microstructure 30 is, for example, 1 nm or more and 1000 nm or less, preferably 5 nm or more and 500 nm or less, and more preferably 10 nm or more and 400 nm or less.

[0017] Note that the "diameter of the microstructure 30" refers to the diameter when the planar shape of the microstructure 30 is a circle, and refers to the diameter of the smallest including circle when the planar shape of the microstructure 30 is not a circle. For example, when the planar shape of the microstructure 30 is a polygon, the diameter of the microstructure 30 refers to the diameter of the smallest circle that includes the polygon, and when the planar shape of the microstructure 30 is an ellipse, the diameter of the smallest circle that includes the ellipse.

[0018] A plurality of microstructures 30 are provided. The plurality of microstructures 30 are spaced apart from each other. A transparent layer 40 is provided between adjacent microstructures 30. The distance between adjacent microstructures 30 is, for example, 20 nm or more and 1000 nm or less, and preferably 100 nm or more and 900 nm or less. The plurality of microstructures 30 are arranged at a predetermined pitch in a predetermined direction as viewed from the Z-axis direction. The plurality of microstructures 30 are provided periodically. In the example shown in FIG. 2, the plurality of microstructures 30 are arranged in a square lattice pattern.

[0019] The "pitch of the microstructures 30" refers to the distance between the centers of adjacent microstructures 30 in a given direction. When the planar shape of the microstructures 30 is a circle, the "center of the microstructures 30" refers to the center of the circle, and when the planar shape of the microstructures 30 is a shape other than a circle, the center of the smallest inclusive circle. For example, when the planar shape of the microstructures 30 is a polygon, the center of the microstructures 30 refers to the center of the smallest circle that contains the polygon, and when the planar shape of the microstructures 30 is an ellipse, the center of the microstructures 30 refers to the center of the smallest circle that contains the ellipse.

[0020] 3, the microscopic structures 30 may be arranged in a triangular lattice shape as viewed from the Z-axis direction. Although not shown, the periodicity of the microscopic structures 30 may expand and contract at a certain ratio, and the microscopic structures may include a fractal structure.

[0021] In addition, the planar shape of the microstructure 30 is not limited to a circle. The planar shape may be an ellipse as shown in Fig. 4 or a rectangle as shown in Fig. 5. The microstructure 30 may have various planar shapes such as granular, polygonal, ring-shaped, linear, etc. as shown in Fig. 6. Furthermore, multiple microstructures 30 with different shapes may be combined. This allows the strength and distribution of the enhanced electric field generated by the multiple microstructures 30 to be controlled in the in-plane direction perpendicular to the direction of the normal Q.

[0022] Although not shown, a plurality of recesses may be formed on the upper surface of the dielectric layer 20, and the microstructures 30 may be provided in the recesses.

[0023] The microstructure 30 has electrical conductivity. The material of the microstructure 30 is, for example, a metal such as Al, Au, Ag, Cu, Pt, Pd, or Ni. The material of the microstructure 30 may be an alloy of these metals. The microstructure 30 may be metal particles. The material of the microstructure 30 is not particularly limited as long as it has a plasma frequency with respect to the light from the light source, and may be a transparent electrode such as ITO (Indium Tin Oxide) or a carbon nanotube.

[0024] The transparent layer 40 is provided on the microstructure 30 and the substrate 10. The transparent layer 40 covers the microstructure 30 and the substrate 10. The transparent layer 40 has a thickness of, for example, 10 nm or more and 2000 nm or less, and preferably 20 nm or more and 1000 nm or less.

[0025] The transparent layer 40 is transparent to the light from the light source. The material of the transparent layer 40 is a dielectric material such as Al2O3, TiO2, MgO, LiNbO3, HfO2, Ta2O5, SiON, or Si3N4. The material of the transparent layer 40 may be polystyrene. The transparent layer 40 may be composed of a plurality of layers. In this case, the materials of the plurality of layers may be different. The refractive index of the transparent layer 40 may be the same as that of the dielectric layer 20. If the refractive index of the transparent layer 40 is the same as that of the dielectric layer 20, it is easy to generate the Rayleigh anomaly described later. The refractive index of the transparent layer 40 may be higher than that of the substrate 10.

[0026] The transparent layer 40 has an upper surface 42. The upper surface 42 constitutes, for example, an interface between the transparent layer 40 and an air layer. In the illustrated example, the upper surface 42 is a flat surface. A target substance to be detected comes into contact with the upper surface 42, for example.

[0027] 1.2. Enhanced electric field 7 and 8 are diagrams for explaining plasmon resonance in the electric field enhancing element 100. FIG 9 is a diagram for explaining the enhanced electric field E generated by the multiple microstructures 30 of the electric field enhancing element 100.

[0028] 7 and 8, light is incident on the multiple microstructures 30 from the substrate 10 side. The light incident on the microstructures 30 has a wavelength capable of generating plasmon resonance in the multiple microstructures 30. The wavelength of the light incident on the microstructures 30 is, for example, not less than 350 nm and not more than 650 nm.

[0029] 7, when light from a light source is incident on the microstructure 30, LSPR is induced. Furthermore, 90° diffraction by the multiple microstructures 30, that is, Rayleigh anomaly, occurs. The combination of this Rayleigh anomaly and LSPR induces SLR (Surface Lattice Resonance).

[0030] 8, the light is guided in the transparent layer 40. When the guided mode in the transparent layer 40 and the LSPR are combined, a quasi guided mode (QGM) is induced.

[0031] Then, the SLR and the QGM are combined and cooperate with each other, and cooperative plasmon polaritons are induced in the multiple microstructures 30. As shown in FIG. 9, the combined SLR and the QGM induce an enhanced electric field E generated by the multiple microstructures 30, which has not only a first enhanced field Ea generated at the end of the microstructure 30 due to LSPR, but also a second enhanced field Eb generated above the microstructure 30 due to SLR and QGM. The enhanced electric field E enhances the Raman scattered light and generates SERS. The enhanced electric field E has a maximum at a position S1, which is on the opposite side of the multiple microstructures 30 from the substrate 10 in the Z-axis direction and is separated from the multiple microstructures 30, due to the second enhanced field Eb. The fact that the enhanced electric field E has a maximum at the position S1 can be said to be a characteristic of the cooperative plasmon polariton phenomenon. In the illustrated example, the position S1 is located in the +Z-axis direction from the multiple microstructures 30. The second enhanced field Eb may be separated from the first enhanced field Ea, or may be continuous with the first enhanced field Ea.

[0032] 9, the second enhanced field Eb exists at a position S2 that is a distance L away from the microstructures 30 in the Z-axis direction. The distance L may be 100 nm or 200 nm. In the illustrated example, the distance between the position S1 and the microstructures 30 in the Z-axis direction is smaller than the distance L, but may be equal to or greater than the distance L. The second enhanced field Eb exists across the upper surface 42 of the transparent layer 40, for example.

[0033] 1.3. Effects The electric field enhancing element 100 comprises a substrate 10, a plurality of conductive microstructures 30 provided on the substrate 10, and a transparent layer 40 covering the plurality of microstructures 30 and the substrate 10. The enhanced electric field E generated by the plurality of microstructures 30 has a maximum at a position S1 spaced apart from the plurality of microstructures 30, on the opposite side of the plurality of microstructures 30 to the substrate 10, in the direction of a perpendicular line Q to the substrate 10.

[0034] Therefore, the electric field enhancing element 100 can improve the detection sensitivity. For example, when the enhanced electric field E occurs only at the end of the microstructure due to LSPR, the effect of the electric field enhancement cannot be obtained unless the target substance is positioned very close to the microstructure. In general, the probability that the target substance is positioned near the microstructure varies, so when the enhanced electric field E occurs only at the end of the microstructure, the detection sensitivity is likely to decrease. In addition, the reproducibility of the detection is also deteriorated. Furthermore, if the size of the target substance is large, the target substance cannot enter between the adjacent microstructures, and it may be difficult to position the target substance near the microstructure.

[0035] As described above, in the electric field enhancing element 100, the enhanced electric field E generated by the multiple microstructures 30 has a maximum at a position S1 that is on the opposite side of the multiple microstructures 30 from the substrate 10 in the direction of the perpendicular line Q and is spaced apart from the multiple microstructures 30, so that the detection signal caused by the target substance can be enhanced even if the target substance is not positioned very close to the microstructures 30. As a result, the detection sensitivity can be improved. In addition, the target substance, such as a virus or a bacterium, can be freely selected.

[0036] Furthermore, in the electric field enhancing element 100, since the target substance does not need to be located in the immediate vicinity of the microstructure 30 as described above, the transparent layer 40 that covers the microstructure 30 can be provided. This makes it possible to suppress changes in the chemical properties of the microstructure 30, such as oxidation and sulfurization. In particular, Ag is prone to deterioration and deformation due to oxidation, sulfurization, migration, and the like. In the electric field enhancing element 100, even if Ag is used as the microstructure 30, such deterioration and deformation can be suppressed. As a result, durability and reliability can be improved.

[0037] Furthermore, in the electric field enhancing element 100, the transparent layer 40 can reduce unevenness caused by the multiple microstructures 30. This can improve the flatness of the surface that comes into contact with the target substance. This can reduce the variation in the detection signal caused by the target substance in the in-plane direction.

[0038] In the electric field enhancing element 100, a transparent layer 40 is provided between adjacent microstructures 30 among the multiple microstructures 30, and the refractive index of the transparent layer 40 is higher than that of the substrate 10. Therefore, in the electric field enhancing element 100, light is more easily collected at the position of the multiple microstructures 30 in the direction of the perpendicular line Q than in a case where the refractive index of the transparent layer is lower than that of the substrate. This makes it easier to induce QGM.

[0039] In the electric field enhancing element 100, an enhanced electric field E exists at a position S2 that is 100 nm away from the multiple microstructures 30 on the opposite side to the substrate 10 in the direction of the perpendicular line Q. Therefore, in the electric field enhancing element 100, even if the target substance is not positioned in the immediate vicinity of the microstructures 30, the detection signal caused by the target substance can be enhanced.

[0040] In the electric field enhancing element 100, an enhanced electric field E exists at a position S2 that is 200 nm away from the multiple microstructures 30 on the opposite side to the substrate 10 in the direction of the perpendicular line Q. Therefore, in the electric field enhancing element 100, even if the target substance is not positioned in the immediate vicinity of the microstructures 30, the detection signal caused by the target substance can be enhanced.

[0041] In the electric field enhancing element 100, the microstructures 30 are periodically arranged. Therefore, in the electric field enhancing element 100, the variation in the intensity of the enhanced electric field E in the in-plane direction can be reduced. When the microstructures are randomly arranged, only the microstructures having a pitch and a diameter that match the wavelength of the light from the light source induce LSPR, and the intensity of the enhanced electric field E varies in the in-plane direction. Furthermore, in the electric field enhancing element 100, the microstructures 30 are periodically arranged, so that SLR can be easily induced.

[0042] 2. Manufacturing method of electric field enhancing element Next, a method for manufacturing the electric field enhancing element 100 according to this embodiment will be described with reference to the drawings.

[0043] 1, a dielectric layer 20 is formed on a substrate 10. The dielectric layer 20 is formed by, for example, a deposition method, a sputtering method, a CVD (Chemical Vapor Deposition) method, or an ALD (Atomic Layer Deposition) method.

[0044] Next, a plurality of microstructures 30 are formed on the dielectric layer 20. The microstructures 30 are formed, for example, by forming a thin film by a vacuum deposition method, a sputtering method, or the like, and then patterning the thin film. Examples of patterning include photolithography and etching, a microcontact printing method, and a nanoimprinting method.

[0045] Next, the transparent layer 40 is formed on the dielectric layer 20 and the microstructure 30. The transparent layer 40 is formed by, for example, a vapor deposition method, a sputtering method, a CVD method, or an ALD method.

[0046] Through the above steps, the electric field enhancing element 100 can be manufactured.

[0047] 3. Modifications of the electric field enhancing element Next, an electric field enhancing element according to a modified example of this embodiment will be described with reference to the drawings. Fig. 10 is a cross-sectional view showing a schematic diagram of an electric field enhancing element 200 according to a modified example of this embodiment. Hereinafter, in the electric field enhancing element 200 according to the modified example of this embodiment, the same reference numerals are used for components having the same functions as those of the electric field enhancing element 100 according to the above-described embodiment, and detailed description thereof will be omitted.

[0048] As shown in FIG. 10, the electric field enhancing element 200 differs from the above-described electric field enhancing element 100 in that it has a molecular trapping layer 50 .

[0049] The molecular capture layer 50 is provided on the transparent layer 40. The molecular capture layer 50 is in contact with the transparent layer 40. The molecular capture layer 50 is an organic molecular film. The molecular capture layer 50 is, for example, a SAM (Self-Assembled Monolayers). The thickness of the molecular capture layer 50 is, for example, 0.1 nm or more and 1 nm or less, and preferably 0.4 nm or less. The molecular capture layer 50 has a function of capturing a target substance. The molecular capture layer 50 is appropriately selected depending on the type of the target substance, and examples of the molecular capture layer 50 include an alkanethiol film and a silane coupling agent. The molecular capture layer 50 is formed, for example, by a liquid immersion method, a vacuum deposition method, a MVD (Molecular Vapor Deposition) method, or a CVD method.

[0050] In the electric field enhancing element 200, the molecular trapping layer 50 is provided on the transparent layer 40, which can reduce unevenness in the deposition of the molecular trapping layer 50. For example, if a transparent layer is not provided and the molecular trapping layer is deposited directly on the microstructure and the substrate, uneven deposition of the molecular trapping layer may occur due to the different physical and chemical conditions of the surface of the microstructure and the surface of the substrate.

[0051] Furthermore, in the electric field enhancing element 200, as described above, the target substance does not need to be located in the immediate vicinity of the microstructure 30, which broadens the options for the molecular chain length of the molecular capture layer 50. Although not shown, a primer layer may be provided between the transparent layer 40 and the molecular capture layer 50 to improve adhesion between them.

[0052] In the illustrated example, the shape of the microstructure 30 is a semicircle. The cross-sectional shape of the microstructure 30 is not particularly limited, and may be, for example, a trapezoid, a circle, an inverse tapered shape, a spherical tip, etc. The shape of the microstructure 30 may be a square truncated shape or a cone.

[0053] 4. Raman Spectroscopy Equipment Configuration Next, the Raman spectroscopic device according to this embodiment will be described with reference to the drawings. Fig. 11 is a diagram showing a schematic diagram of a Raman spectroscopic device 300 according to this embodiment.

[0054] 11, the Raman spectroscopic device 300 includes, for example, an electric field enhancing element 100, a light source 310, a collimator lens 320, a polarization control element 330, a dichroic mirror 340, an objective lens 350, a condenser lens 360, and a detector 370. For convenience, the electric field enhancing element 100 is illustrated in a simplified form in FIG.

[0055] The target material is carried into the Raman spectroscopic device 300 from the direction C1 and is discharged in the direction C2. For example, by controlling the driving of a fan (not shown), the target material is introduced into the transport section from the inlet and discharged to the outside of the transport section from the outlet.

[0056] The light source 310 irradiates light onto the electric field enhancing element 100. The light emitted from the light source 310 has a wavelength that induces SLR and QGM in the electric field enhancing element 100. For example, a laser or an LED (Light Emitting Diode) is used as the light source 310. For example, a laser may be a VCSEL (Vertical Cavity Surface Emitting Laser) or a PCSEL (Photonic Crystal Surface Emitting Laser).

[0057] Light emitted from the light source 310 is, for example, collimated by a collimator lens 320, passes through a polarization control element 330, and is guided toward the electric field enhancing element 100 by a dichroic mirror 340. The light heading toward the electric field enhancing element 100 is collected by an objective lens 350 and enters the electric field enhancing element 100. At this time, a target substance is in contact with the transparent layer 40 of the electric field enhancing element 100.

[0058] When light is incident on the electric field enhancing element 100, an enhanced electric field E is generated by the multiple microstructures 30. When a target substance is positioned in the enhanced electric field E, SERS light is generated therefrom. The SERS light passes through the objective lens 350 and is guided by the dichroic mirror 340 toward the detector 370. The SERS light heading toward the detector 370 is focused by the focusing lens 360 and enters the detector 370.

[0059] The detector 370 detects the SERS light from the electric field enhancing element 100. The detector 370 is, for example, a diffraction grating type spectrometer. In the Raman spectroscopy device 300, the detector 370 performs spectral resolution of the SERS light to obtain spectral information. The detector 370 may be a Fabry-Perot etalon spectrometer.

[0060] 4.2. Principle FIG. 12 is a diagram for explaining the principle of Raman scattering spectroscopy.

[0061] As shown in Figure 12, for example, when light of wavelength Lin is irradiated onto target substance X, in addition to Rayleigh scattered light Ray with the same wavelength λ1 as the wavelength λin of the incident light Lin, Raman scattered light Ram with a wavelength λ2 different from λ1 is generated in the scattered light. The energy difference between this Raman scattered light Ram and the incident light Lin corresponds to the energy of the vibrational level, rotational level, and electronic level of target substance X. Target substance X has a unique vibrational energy according to its structure, so target substance X can be identified by using light of wavelength Lin.

[0062] Fig. 13 is a schematic diagram showing an example of a Raman spectrum obtained by Raman scattering spectroscopy. In Fig. 13, the horizontal axis represents the Raman shift. The Raman shift is the difference between the wave number (frequency) of the Raman scattered light Ram and the wave number of the incident light Lin, and takes a value specific to the molecular bonding state of the target substance X.

[0063] As shown in FIG. 13, when comparing the scattering intensity of the Raman scattered light Ram shown in K1 with the scattering intensity of the Rayleigh scattered light Ray shown in K2, it can be seen that the Raman scattered light Ram is weaker. Thus, while Raman scattering spectroscopy has excellent ability to identify the target substance X, it is a measurement method with low sensitivity for detecting the target substance X. For this reason, the Raman spectroscopic device 300 uses SERS to achieve high sensitivity.

[0064] 4.3. Effects The Raman spectroscopy device 300 includes an electric field enhancing element 100, a light source 310 that irradiates the electric field enhancing element 100 with light, and a detector 370 that detects the light from the electric field enhancing element 100. As described above, the electric field enhancing element 100 can improve the detection sensitivity. Therefore, the Raman spectroscopy device 300 has high detection sensitivity.

[0065] 5. Experimental Example Model <Example 1> Fig. 14 is an XZ sectional view that shows a model M used in the simulation. Fig. 15 is an XY sectional view that shows a model M used in the simulation.

[0066] In model M, the material of the substrate was SiO2, as shown in Figure 14. Light was incident on model M from the substrate side. The wavelength of the incident light was 578 nm.

[0067] The material of the dielectric layer was Al2O3, and the thickness A of the dielectric layer was 20 nm.

[0068] The material of the microstructures was Al. As shown in Fig. 15, the arrangement of the microstructures was a square lattice. The shape of the microstructures was a cylinder. The pitch P of the microstructures was 391 nm, the diameter D was 156 nm, and the thickness H was 20 nm.

[0069] The material of the transparent layer was Al2O3. The thickness B of the transparent layer was 360 nm. An air layer was placed on the transparent layer.

[0070] <Example 2> Example 2 is similar to Example 1, except that the thickness H of the microstructure is 200 nm, and the wavelength of the incident light is 432 nm.

[0071] <Example 3> Example 3 is similar to Example 1, except that the diameter D of the microstructure is 39 nm, the thickness H of the microstructure is 60 nm, and the wavelength of the incident light is 410 nm.

[0072] <Example 4> Example 4 is similar to Example 1, except that the diameter D of the microstructure is 352 nm, the thickness H of the microstructure is 60 nm, and the wavelength of the incident light is 571 nm.

[0073] <Example 5> Example 5 is similar to Example 1, except that the thickness A of the dielectric layer is zero, i.e., no dielectric layer is provided, the diameter D of the microstructure is 39 nm, the thickness H of the microstructure is 60 nm, and the wavelength of the incident light is 408 nm.

[0074] <Example 6> Example 6 is similar to Example 1, except that the thickness A of the dielectric layer is 1000 nm, the diameter D of the microstructure is 39 nm, the thickness H of the microstructure is 60 nm, and the wavelength of the incident light is 576 nm.

[0075] <Example 7> Example 7 is similar to Example 1, except that the thickness H of the microstructure is 19 nm, the thickness B of the transparent layer is 20 nm, and the wavelength of the incident light is 412 nm.

[0076] <Example 8> Example 8 is similar to Example 1, except that the thickness H of the microstructure is 19 nm, the thickness B of the transparent layer is 1000 nm, and the wavelength of the incident light is 404 nm.

[0077] <Example 9> Example 9 is similar to Example 1, except that the pitch P of the microstructure is 278 nm, the material of the dielectric layer is TiO2, the diameter D of the microstructure is 111 nm, the thickness H of the microstructure is 60 nm, and the wavelength of the incident light is 426 nm.

[0078] <Example 10> Example 10 is the same as Example 1, except that the pitch P of the microstructure is 365 nm, the material of the dielectric layer is MgO, the diameter D of the microstructure is 146 nm, the thickness H of the microstructure is 60 nm, and the wavelength of the incident light is 568 nm.

[0079] <Example 11> In Example 11, the material of the microstructure was Au, the diameter D of the microstructure was 196 nm, the thickness H of the microstructure was 60 nm, and the wavelength of the incident light was 583 nm. Same as Example 1.

[0080] <Example 12> Example 12 is similar to Example 1, except that the material of the microstructure is ITO, the diameter D of the microstructure is 235 nm, the thickness H of the microstructure is 60 nm, and the wavelength of the incident light is 413 nm.

[0081] <Example 13> Example 13 is similar to Example 1, except that the pitch P of the microstructures is 246 nm, the diameter D of the microstructures is 98 nm, the thickness H of the microstructures is 60 nm, and the wavelength of the incident light is 386 nm.

[0082] <Example 14> Example 14 is similar to Example 1, except that the pitch P of the microstructures is 829 nm, the diameter D of the microstructures is 332 nm, the thickness H of the microstructures is 60 nm, and the wavelength of the incident light is 638 nm.

[0083] <Example 15> Example 15 is similar to Example 1, except that the microstructures are arranged in a triangular lattice pattern as shown in FIG. 16, the thickness H of the microstructures is 60 nm, and the wavelength of the incident light is 505 nm.

[0084] <Example 16> Example 16 is similar to Example 1, except that the shape of the microstructure is a cone as shown in FIG. 17, the thickness H of the microstructure is 60 nm, and the wavelength of the incident light is 576 nm.

[0085] <Comparative Example 1> Comparative Example 1 is the same as Example 1, except that the thickness A of the dielectric layer is zero, i.e., no dielectric layer is provided, the thickness B of the transparent layer is zero, i.e., no transparent layer is provided, the material of the microstructure is Ag, the pitch P of the microstructure is 250 nm, the diameter D of the microstructure is 50 nm, the thickness H of the microstructure is 25 nm, and the wavelength of the incident light is 464 nm.

[0086] FIG. 18 is a table showing the dimensions and the main parameters that were changed in the above Examples 1 to 16 and Comparative Example 1.

[0087] 5.2. Simulation results A simulation was performed on the distribution of the enhanced electric field in the above-mentioned Examples 1 to 16 and Comparative Example 1. The simulation was performed using the finite difference time domain (FDTD) method.

[0088] 19 to 35 respectively show the simulation results of Examples 1 to 16 and Comparative Example 1. In Fig. 19 to Fig. 35, the distribution of the normalized enhanced electric field is shown.

[0089] In FIG. 19 to FIG. 35, α indicates the distribution of the enhanced electric field in the XZ cross section. Specifically, α is defined as (Ex 2 +Ez 2 ), that is, √(Ex 2 +Ez 219 to 34, "air interface" refers to the interface between the transparent layer and the air layer. In Fig. 35, "substrate / air interface" refers to the interface between the substrate and the air layer.

[0090] In FIG. 19 to FIG. 35, β indicates the distribution of the enhanced electric field in the XY cross section. In practice, β is (Ex 2 +Ez 2 ), that is, √(Ex 2 +Ez 2 ) in Fig. 19 to Fig. 34, β indicates an XY cross section at a position 1 nm in the +Z axis direction from the "air interface" indicated by α. In Fig. 35, β1 indicates an XY cross section at a position 1 nm in the +Z axis direction from the "air interface" indicated by α, and β2 indicates an XY cross section at a position 100 nm in the +Z axis direction from the "substrate / air interface" indicated by α.

[0091] As shown in β of Figures 19 to 34, in Examples 1 to 16, a predetermined pattern was confirmed at a position 1 nm above the air interface. This is because the enhanced electric field is located above the air interface due to SLR and QGM induced by the microstructure. As shown in Figures 19 to 34, it was found that the enhanced electric field exists at a position 100 nm above the microstructure and even at a position 200 nm above the microstructure.

[0092] On the other hand, as shown by β2 in FIG. 35, in Comparative Example 1, no pattern was observed at a position 100 nm above the substrate / air interface, and no enhanced electric field was present.

[0093] The above-described embodiment and modifications are merely examples, and the present invention is not limited to these. For example, the embodiments and modifications can be appropriately combined.

[0094] The present invention includes configurations that are substantially the same as the configurations described in the embodiments, for example, configurations with the same functions, methods, and results, or configurations with the same purpose and effect. The present invention also includes configurations in which non-essential parts of the configurations described in the embodiments are replaced. The present invention also includes configurations that achieve the same effects as the configurations described in the embodiments, or configurations that can achieve the same purpose. The present invention also includes configurations in which publicly known technology is added to the configurations described in the embodiments.

[0095] The following can be derived from the above-described embodiment and modifications.

[0096] One embodiment of the electric field enhancing element is A substrate; A plurality of microstructures provided on the substrate and having electrical conductivity; a transparent layer covering the plurality of microstructures and the substrate; having The enhanced electric field generated by the plurality of microstructures has a maximum at a position spaced apart from the plurality of microstructures, on the opposite side of the plurality of microstructures from the substrate in a direction perpendicular to the substrate.

[0097] This electric field enhancing element can improve detection sensitivity.

[0098] In one embodiment of the electric field enhancing element, the transparent layer is provided between adjacent microstructures among the plurality of microstructures, The refractive index of the transparent layer is higher than the refractive index of the substrate.

[0099] This electric field enhancing element makes it easy to focus light at the positions of the multiple microstructures in the direction perpendicular to the substrate.

[0100] In one embodiment of the electric field enhancing element, The enhanced electric field may be present at a position 100 nm or more away from the plurality of microstructures in the perpendicular direction.

[0101] This electric field enhancing element can enhance the detection signal caused by the target substance even if the target substance is not located in the immediate vicinity of the microstructure.

[0102] In one embodiment of the electric field enhancing element, The enhanced electric field may be present at a position 200 nm or more away from the plurality of microstructures in the perpendicular direction.

[0103] This electric field enhancing element can enhance the detection signal caused by the target substance even if the target substance is not located in the immediate vicinity of the microstructure.

[0104] In one embodiment of the electric field enhancing element, The plurality of microscopic structures may be arranged periodically.

[0105] This electric field enhancing element can reduce variations in the intensity of the enhanced electric field in an in-plane direction perpendicular to the normal direction of the substrate.

[0106] In one embodiment of the electric field enhancing element, The material of each of the plurality of microstructures may be a metal.

[0107] In one embodiment of the electric field enhancing element, The transparent layer may be made of a dielectric material.

[0108] One aspect of the Raman spectroscopy apparatus is An embodiment of the electric field enhancing element; a light source that irradiates the electric field enhancing element with light; a detector for detecting light from the electric field enhancing element; has.

[0109] This Raman spectrometer has high detection sensitivity. [Explanation of symbols]

[0110] 10...substrate, 20...dielectric layer, 30...microstructure, 40...transparent layer, 42...upper surface, 50...molecular capture layer, 100, 200...electric field enhancing element, 300...Raman spectroscopic device, 310...light source, 320...collimator lens, 330...polarization control element, 340...dichroic mirror, 350...objective lens, 360...condenser lens, 370...detector

Claims

1. A substrate; A plurality of microstructures provided on the substrate and having electrical conductivity; a transparent layer covering the plurality of microstructures and the substrate; having An electric field enhancing element, wherein an enhanced electric field generated by the plurality of microstructures has a maximum at a position spaced apart from the plurality of microstructures, on the opposite side of the substrate from the plurality of microstructures in a direction perpendicular to the substrate.

2. In claim 1, the transparent layer is provided between adjacent microstructures among the plurality of microstructures, The refractive index of the transparent layer is higher than the refractive index of the substrate.

3. In claim 1, An electric field enhancing element, wherein the enhanced electric field is present at a position 100 nm or more away from the plurality of microstructures in the perpendicular direction.

4. In claim 1, An electric field enhancing element, wherein the enhanced electric field is present at a position 200 nm or more away from the plurality of microstructures in the perpendicular direction.

5. In claim 1, An electric field enhancing element, wherein the plurality of microstructures are periodically arranged.

6. In claim 1, The electric field enhancing element, wherein each of the plurality of microstructures is made of a metal.

7. In claim 1, The electric field enhancing element, wherein the transparent layer is made of a dielectric material.

8. An electric field enhancing element according to any one of claims 1 to 7; a light source that irradiates the electric field enhancing element with light; a detector for detecting light from the electric field enhancing element; A Raman spectroscopic apparatus comprising:

Images