Substrate, analysis method, device, and manufacturing method

Abstract

To improve the intensity of Raman light.SOLUTION: A substrate comprises a plurality of convex parts including metal. A first metal part including metal having at least one of gold, silver, platinum, copper, and palladium is provided on a first convex part of the plurality of convex parts. A second metal part including metal having at least one of gold, silver, platinum, copper, and palladium is provided on a second convex part different from the first convex part of the plurality of convex parts. A dielectric part is provided between the first convex part and the first metal part and between the second convex part and the second metal part. A surface of the dielectric part on the opposite side of the plurality of convex parts has a shape along the convex part. A gap is provided between the first metal part and the second metal part, and the distance between the first metal part and the second metal part is 50 nm or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a substrate. [Background technology]

[0002] When light hits a metal, plasma resonance occurs on the metal surface, and this resonance produces an electric field enhancement effect (localized plasmon resonance phenomenon). Development of electric field enhancement devices, such as sensor devices and Raman spectroscopy devices, that utilize the electric field enhancement effect is progressing. A known Raman spectroscopy method uses the optical electric field enhanced by localized plasmon resonance to enhance the Raman scattered light obtained by Raman spectroscopy.

[0003] For example, Patent Document 1 discloses a configuration comprising a boehmite layer that constitutes a fine uneven structure and a metal film formed on the surface of the fine uneven structure. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-63293 Summary of the Invention [Problem to be solved by the invention]

[0005] In the embodiment of Patent Document 1, there is a risk that the light may not be scattered well depending on the specimen, resulting in weak Raman light. Therefore, an object of the present invention is to improve the intensity of Raman light. [Means for solving the problem]

[0006] A first means for solving the above problem is a substrate having a plurality of convex portions containing a metal, wherein a first metal portion containing a metal having at least one of gold, silver, platinum, copper, and palladium is provided on a first convex portion of the plurality of convex portions, and a second metal portion containing a metal having at least one of gold, silver, platinum, copper, and palladium is provided on a second convex portion of the plurality of convex portions that is different from the first convex portion, and a dielectric portion is provided between the first convex portion and the first metal portion, and between the second convex portion and the second metal portion, and the surface of the dielectric portion opposite the plurality of convex portions is shaped to conform to the convex portions, a gap is provided between the first metal portion and the second metal portion, and the distance between the first metal portion and the second metal portion is 50 nm or less.

[0007] A second means for solving the above problem includes the steps of: forming a dielectric part having a first uneven structure on a surface; forming a metal-containing structure having a second uneven structure onto which the first uneven structure is transferred, on the first uneven structure; removing a part of the dielectric part so that the dielectric part covers the convex parts of the second uneven structure; and removing a part of the dielectric part so that the distance from the surface of the dielectric part opposite the structure to the concave parts of the second uneven structure is smaller than the difference in height between the convex parts and the concave parts of the structure adjacent to the convex parts. and forming a first metal portion containing a metal having at least one of gold, silver, platinum, copper, and palladium on a first convex portion of the convex portions on the side of the dielectric portion opposite the structure, and a second metal portion containing a metal having at least one of gold, silver, platinum, copper, and palladium on a second convex portion of the convex portions different from the first convex portion, wherein a gap is provided between the first metal portion and the second metal portion, and the distance between the first metal portion and the second metal portion is 50 nm or less. [Effects of the Invention]

[0008] To provide a technique that is advantageous in improving the intensity of Raman light. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 2 is a schematic diagram of a substrate according to the embodiment. [Figure 2] 5A to 5C are schematic diagrams illustrating a method for manufacturing a substrate according to the present embodiment. [Figure 3] FIG. 1 is a schematic diagram showing an example of an apparatus equipped with a substrate according to the present embodiment. [Figure 4] FIG. 6 is a schematic view of a substrate according to a second embodiment. [Figure 5] SEM image of the substrate surface. [Figure 6] Graph showing Raman spectroscopy results. [Figure 7] 1 is a graph showing the Raman signal intensity ratio versus gold film thickness. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, a description will be given of an embodiment of the present invention with reference to the drawings. However, the embodiment described below is one embodiment of the invention and is not limited to this. Common configurations will be described with mutual reference to multiple drawings, and descriptions of configurations with common reference numerals will be omitted as appropriate. Items with the same name but different functions can be distinguished by adding "0", such as "first item" and "second item".

[0011] First Embodiment A substrate 10 according to this embodiment will be described with reference to Figure 1. The substrate 10 includes a structure 1, a dielectric portion 3 provided on the surface of the structure 1, and a metal portion 2 that forms an interface with the dielectric portion 3. The structure 1 has a concave-convex structure, and the metal portion 2 and the dielectric portion 3 are each provided on a plurality of convex portions 4 including convex portions 41 and 42 of the concave-convex structure. The dielectric portion 3 is provided between the structure 1 and the metal portion 2, and preferably has a structure that forms an interface with both the structure 1 and the metal portion 2.

[0012] A gap 9 is provided between the metal portion 21 and the metal portion 22 adjacent to the metal portion 21, and the distance D between the metal portion 21 and the metal portion 22 is greater than 0 and not greater than 50 nm. The distance D between the metal portion 21 and the metal portion 22 is more preferably greater than 0 and not greater than 10 nm. The distance D is the shortest distance between the metal portion 21 and the metal portion 22. Although the distance D is preferably the distance between the metal portion 21 and the metal portion 22, it may also be the distance between the metal portions 21 and 22 when multiple metal portions 21 are provided on the same convex portion 41. Furthermore, the distance D may be the distance between the metal portion 2 provided on a different convex portion 4, rather than between the convex portion 42 adjacent to the convex portion 41. Providing the gap 9 makes it possible to further strengthen the optical electric field, thereby improving the intensity of Raman light in the substrate 10. The metal portion 21 and the metal portion 22 may be connected at a portion other than the gap 9 provided therebetween, but is preferably discontinuous.

[0013] In FIG. 1(a), the metal portion 2 has a horsetail-like shape, but as shown in FIG. 1(b), the metal portion 2 may be shaped to fit the dielectric portion 3, and the shape of the metal portion 2 is not limited. As shown in FIG. 1(b), the dielectric portion 3 may be provided on a recess 43, and the dielectric portion 3 may be connected to the dielectric portion 3 on the protrusions 41 and 42. The metal of the protrusions 41 and 42 may be discontinuous. It is preferable that the metal portion 2 does not cover the recess 43, and that the dielectric portion 3 is exposed in the space above the recess 43.

[0014] The uneven structure is preferably provided on only one surface of the structure 1, and the distance between the convex portions 41 and the concave portions 43, i.e., the height difference of the uneven structure, is preferably 100 nm or more and 1000 nm or less, more preferably 100 nm or more and 500 nm or less. The height difference is preferably the average height difference of the uneven structure. The height difference may be the linear distance from the convex portion 41 to the concave portion 43, or the vertical distance from the convex portion 41 to the concave portion 43. The height difference can be determined by observing the cross section of the substrate 10 using a scanning electron microscope or the like. The convex portions 41 and 42 are preferably connected via the concave portion 43, but may be separated. In the structure 1, the convex portions 4 are metal, but the concave portions 43 do not have to be metal and may be non-metallic, such as ceramics or resin.

[0015] The material of the structure 1 is preferably a highly conductive material, such as gold, silver, copper, aluminum, magnesium, tungsten, cobalt, zinc, nickel, or chromium, with nickel, zinc, or chromium being preferred, and nickel being particularly preferred.

[0016] The material of the metal portion 2 includes any one metal selected from gold, silver, platinum, copper, and palladium, with gold or silver being particularly preferred. There are no particular restrictions on the thickness of the metal portion 2 as long as it is thick enough to maintain the uneven structure that can generate localized plasmons when irradiated with excitation light, but a thickness of 5 nm to 50 nm is preferred.

[0017] The material of the dielectric portion 3 is preferably a metal oxide. While the material of the metal oxide is not particularly limited, it is preferably alumina-based, and more preferably contains alumina-based plate crystals. The alumina-based plate crystals are formed from plate crystals primarily composed of aluminum oxide, hydroxide, or hydrates thereof, with boehmite being a particularly preferred crystal. Here, the alumina-based plate crystals may be plate crystals composed solely of alumina, or may be alumina plate crystals containing trace amounts of zirconium, silicon, titanium, zinc, or the like. In the case of a plate structure of alumina-based plate crystals, it is preferable that the alumina-based plate crystals are arranged perpendicular to the surface direction of the structure 1, and that their spatial occupancy rate continuously changes. The metal oxide may also contain an amorphous alumina gel. The dielectric portion 3 is preferably formed in a shape that follows the uneven structure or protrusions 4 of the structure 1, as shown in FIG. 1(b). The thickness of the dielectric portion 3 is preferably 30 nm or more and 200 nm or less.

[0018] The substrate 10 according to this embodiment preferably has a specific surface area Sr of 1.0 or more and 3.0 or less. The specific surface area Sr can be calculated by the following formula. Sr=S / S0 formula (1)

[0019] In equation (1), S0 is the surface area when the measurement surface is assumed to be ideally flat, and S is the surface area of ​​the actual measurement surface. The specific surface area can be determined by observing a surface with an uneven structure using a scanning probe microscope or the like.

[0020] The metal elements in the structure 1 and the metal oxides in the dielectric portion 3 can be detected by energy dispersive X-ray analysis (EDX) when observing the surface or cross section using a scanning electron microscope (SEM) or a transmission electron microscope (TEM). They can also be detected by X-ray photoelectron spectroscopy (XPS). In the direction perpendicular to the surface direction of the structure 1, the proportion of metal oxides decreases relatively from the dielectric portion 3 toward the structure 1, and the proportion of metal elements constituting the structure 1 increases, until finally only the metal elements are detected.

[0021] The substrate 10 has a base material 5 on the surface of the structure 1 opposite to the side on which the concave-convex structure is provided. The base material 5 is attached to the structure 1 via an adhesive layer 6, although the adhesive layer 6 can be omitted. The base material 5 may have any shape suitable for its intended use, including, but not limited to, a flat plate, a film, or a sheet. Materials for the base material 5 include, but are not limited to, metal, glass, ceramics, wood, paper, and resin. Examples of resins include polyester, triacetyl cellulose, cellulose acetate, polyethylene terephthalate, polypropylene, polystyrene, polycarbonate, polymethyl methacrylate, and ABS resin. Other examples include films and molded products of thermoplastic resins such as polyphenylene oxide, polyurethane, polyethylene, and polyvinyl chloride; and thermosetting resins such as unsaturated polyester resin, phenolic resin, crosslinked polyurethane, crosslinked acrylic resin, and crosslinked saturated polyester resin. The adhesive layer 6 may be any layer capable of adhering the base material 5 to the structure 1, including, for example, a layer made of a cured adhesive resin (e.g., epoxy resin) and double-sided tape.

[0022] Next, a method for manufacturing the substrate 10 will be described with reference to Fig. 2. The manufacturing method according to this embodiment includes a step of forming the structure 1, a step of forming the dielectric portion 3, and a step of forming the metal portion 2.

[0023] The process of forming the dielectric portion 3 will be described using Figures 2(a) and 2(b). Here, the dielectric portion 3 contains a metal oxide having alumina. An aluminum compound, and optionally other compounds, stabilizers, and water-soluble organic polymer compounds, are dissolved or suspended in an organic solvent to prepare a sol-gel coating liquid. This sol-gel coating liquid is applied to a base substrate 8 and dried to form an alumina gel film as an aluminum film 7 containing aluminum. Alternatively, an alumina gel film containing metallic aluminum as the aluminum film 7 is formed on the base substrate 8 by dry film formation such as vacuum deposition or sputtering.

[0024] Next, the aluminum film 7 is immersed in warm water to form an alumina texture. Immersing the aluminum film 7 in warm water causes the surface of the aluminum film 7 to undergo peptization, dissolving some of the components. However, due to differences in the solubility of various hydroxides in warm water, plate-like crystals primarily composed of alumina precipitate and grow on the surface of the aluminum film 7, thereby forming the texture of the dielectric portion 3. Furthermore, if a film containing metallic aluminum is used instead of the aluminum film 7, the aluminum reacts with the warm water and is oxidized to alumina, and then the texture of the dielectric portion 3 is formed, similar to when the aluminum film 7 is used. Therefore, if the material of the base substrate 8 primarily contains aluminum or alumina, the formation of the aluminum film 7 on the base substrate 8 can be omitted. The temperature of the warm water is preferably 40°C or higher and lower than 100°C. The immersion time is preferably approximately 5 minutes to 24 hours. In the immersion treatment of the aluminum film 7 containing compounds other than the alumina component, the difference in solubility of each component in hot water is utilized to crystallize the alumina plate crystals. Therefore, unlike the immersion treatment of the aluminum film 7 containing only alumina, the size of the plate crystals can be controlled over a wide range by changing the composition of the inorganic component. In addition, the height of the alumina unevenness can be adjusted by adjusting the film thickness of the aluminum film 7. The average height of the uneven structure of the dielectric portion 3 is preferably 100 nm or more and 1000 nm or less, more preferably 100 nm or more and 500 nm or less. The thickness of the dielectric portion 3 is preferably 30 nm or more and 200 nm or less. As a result, it is possible to control the unevenness formed by the plate crystals over a wide range.

[0025] The material of the base substrate 8 is not particularly limited, and various materials such as glass, plastic, and metal can be used. When forming the aluminum film 7 using a sol-gel coating solution that does not contain a stabilizer, the coating atmosphere is preferably an inert gas atmosphere such as dry air or dry nitrogen. The relative humidity of the dry atmosphere is preferably 30% or less. Known coating methods, such as dipping, spin coating, spraying, printing, flow coating, and combinations thereof, can be appropriately used to apply the solution to form the aluminum film 7. The film thickness can be controlled by changing the lifting speed in the dipping method, the substrate rotation speed in the spin coating method, and the concentration of the sol-gel coating solution. Drying can be performed at room temperature for approximately 30 minutes. Furthermore, drying or heat treatment at higher temperatures can be performed as needed. The higher the heat treatment temperature, the more stable the uneven structure of the dielectric portion 3 can be formed by the immersion treatment described below. The suitable film thickness of the aluminum film 7 is 100 nm or more and 600 nm or less, preferably 100 nm or more and 300 nm or less, and more preferably 100 nm or more and 200 nm or less.

[0026] Next, the process of forming the structure 1 will be described with reference to FIG. 2(c). A metal-containing structure 1 is formed on the uneven structure of the dielectric portion 3 described in FIG. 2(b). Metal plating, and even more preferably electroless plating, is preferred as a method for forming the structure 1. In electroless plating, activation is performed by applying an aqueous solution containing a palladium compound such as palladium chloride, a gold compound such as gold chloride, a silver compound such as silver chloride, or a tin compound such as tin chloride to the uneven structure of the dielectric portion 3. Activation may also be performed by immersing the uneven structure of the dielectric portion 3 together with the base substrate 8 in an aqueous solution containing a palladium compound. Then, the structure 1 is deposited on the uneven structure of the dielectric portion 3 using an electroless plating solution. The metal ions in the electroless plating solution correspond to the structure 1 of the substrate 10 of this embodiment. An electroless plating solution containing nickel ions, chromium ions, and zinc ions is preferred, with a nickel plating solution containing nickel ions being particularly preferred. The nickel plating solution may contain phosphorus or boron components in addition to nickel. The temperature of the plating solution in the electroless plating process is preferably 30°C or higher and 98°C or lower, and more preferably 50°C or higher and 90°C or lower. The time for the electroless plating process can be adjusted depending on the thickness of the structure 1 to be formed, and is usually 30 seconds to 1 hour. In this way, the structure 1 is formed so as to fill the gaps in the uneven structure, and a structure 1 having an uneven structure to which the uneven structure of the dielectric portion 3 is transferred is formed. It is preferable to perform the electroless plating process so that the thickness of the structure 1 having an uneven structure is 200 nm or higher and 15,000 nm or lower. Furthermore, the average height difference of the uneven structure corresponds to the average height difference of the uneven structure of the dielectric portion 3, and is 100 nm or higher and 1,000 nm or lower.

[0027] After the electroless plating process described above, electroplating may be performed on the surface of the structure 1 opposite the surface on which the concave-convex structure is formed to increase its thickness. A known electroplating solution can be used for the electroplating process, such as an electroplating solution containing nickel ions, iron ions, copper ions, or the like as metal ions. When electroplating is performed using the same metal as the metal of the structure 1, the thickness of the structure 1 can be increased by the electroplating process. When electroplating is performed using a metal different from the metal of the structure 1, the metal formed by the electroplating process serves as the base material. In addition to inorganic salts serving as raw materials for the metal ions, the electroplating solution may also contain, as needed, conductive salts, salts for adjusting counterions, carboxylic acid additives for improving the uniformity of the plating film, brighteners, and the like. Furthermore, the desired thickness of the structure 1 can be achieved by adjusting the temperature, current density, and plating time of the electroplating solution during the electroplating process. If necessary, prior to the electroplating process, activation treatment of the surface of the structure 1 opposite the surface on which the concave-convex structure is formed may be performed using an aqueous solution containing, for example, an acid. Furthermore, in order to improve the quality of the film formed by the electroplating process, in addition to stirring the electroplating solution during the electroplating process, a step of removing foreign matter from the electroplating solution may also be provided.

[0028] Next, the step of adhering the substrate 5 to the structure 1 will be described with reference to FIG. 2(d). When the material of the substrate 5 is metal, a metal that will become the substrate 5 may be further laminated on the surface of the structure 1 opposite to the surface on which the concave-convex structure is provided. The metal may be laminated by the electroplating process described above, or by physical vapor deposition such as sputtering. When the material of the substrate 5 is resin, the substrate 5 may be provided by depositing a resin that will become the substrate 5 on the surface of the structure 1 opposite to the concave-convex structure and then curing the resin. The substrate 5 may be adhered to the structure 1 by an adhesive layer 6. The adhesive used for the adhesive layer 6 is preferably a resin, but is not particularly limited, as long as it is a material that can adhere the substrate 5 and the structure 1.

[0029] Next, the etching process for the base substrate 8, the aluminum film 7, and a portion of the dielectric portion 3 will be described using Figures 2(e), 2(f), and 2(g). Figure 2(e) is a diagram obtained by inverting Figure 2(d). First, the base substrate 8 is removed as shown in Figure 2(f). If the aluminum film 7 is an alumina gel film, it can function as part of the dielectric portion 3 of the substrate 10. The aluminum film 7 may also be partially removed by etching. A preferred etching method is wet etching, which dissolves aluminum-containing films using an acid or alkaline solution. Examples of acids include hydrochloric acid, nitric acid, and sulfuric acid. Examples of alkalis include sodium hydroxide and potassium hydroxide. From the perspective of work efficiency, an etching method using an alkaline solution is more preferred. The etching concentration is preferably in the range of several percent to several tens of percent, and the etching time is preferably in the range of several hours to several days. The remaining metal oxides, such as alumina, after etching can be detected by EDX or XPS measurements during surface or cross-sectional observation using SEM or TEM. In this step, the dielectric portion 3 is removed so that the distance H1 to the recesses of the uneven structure of the transferred structure 1 is smaller than the height difference H2 between the protrusions and the recesses of the structure 1 adjacent to the protrusions. The distance H1 may be 0, and the dielectric portion 3 in the recesses may be entirely etched. At this time, the protrusions of the uneven structure of the structure 1 are covered with the dielectric portion 3. The dielectric portion 3 is removed so that the surface of the dielectric portion 3 opposite the structure 1 has a shape that matches the uneven structure transferred to the structure 1. Before performing the bonding step of the substrate 5, the etching step of this step may be performed and then the substrate 5 may be bonded.

[0030] Next, the process of forming the metal part 2 will be described with reference to Fig. 2(h). The metal part 2 containing any one selected from gold, silver, platinum, copper, and palladium is formed on the member obtained after etching by dry film formation such as vacuum deposition or sputtering.

[0031] The manufacturing method of the substrate 10 according to this embodiment thus obtained can obtain high in-plane uniformity on the same sample, thereby enabling data with good reproducibility in measurements and enabling highly reliable and effective measurements. Furthermore, because the manufacturing method is very simple, production costs can be reduced compared to conventional devices.

[0032] In addition to surface-enhanced Raman scattering spectroscopy, the substrate 10 of this embodiment can also be used as a fluorescence enhancement device in fluorescence detection. The substrate 10 of this embodiment can be used not only to detect Raman scattered light and fluorescence, but also to detect Rayleigh scattered light, Mie scattered light, second harmonics, and the like generated from a specimen irradiated with excitation light. The substrate 10 of this embodiment can enhance Raman light by the enhanced optical field associated with localized plasmon resonance.

[0033] Various adhesives can be used when attaching the substrate 10 of this embodiment to the surface of a member or an article. Therefore, the substrate 10 of this embodiment can be attached to the surface of a member or an article depending on the intended use, and the surface of the member or article is not limited to being smooth, but may also be a two-dimensional or three-dimensional curved surface.

[0034] Next, a Raman spectrometer will be described with reference to FIG. 3 as an example of an apparatus 100 capable of mounting the substrate 10 according to this embodiment.

[0035] The device 100 includes a substrate 10, a light irradiating section 140 that irradiates the substrate 10 with light L1, and a light detecting section 150 that detects Raman scattered light L2 scattered by the specimen S.

[0036] The light irradiation unit 140 has a laser 141 that emits light L1, a mirror 142 that reflects the light L1 emitted from the laser 141 toward the substrate 10, a half mirror 144, and a lens 146. The light L1 reflected by the mirror 142 passes through the half mirror 144, and is focused by the lens 146 onto an area of ​​the substrate 10 where the specimen S is placed. The half mirror 144 reflects light from the substrate 10 side, including Raman scattered light L2 scattered by the specimen S due to irradiation with the light L1, toward the light detection unit 150.

[0037] The light detection unit 150 includes a notch filter 151, a pinhole plate 153 with a pinhole 152, a lens 154, a lens 156, a spectrometer 158, and a detector 159. The notch filter 151 absorbs light of the same wavelength as light L1 among the light reflected by the half mirror 144 and transmits other light. The pinhole plate 153 with the pinhole 152 removes noise light from the light that has passed through the notch filter 151. The lens 154 focuses the Raman scattered light L2 that has passed through the lens 146 and the notch filter 151 onto the pinhole 152, and the lens 156 collimates the Raman scattered light L2 that has passed through the pinhole 152. The spectrometer 158 disperses the Raman scattered light L2 that has been collimated by the lens 156, and the detector 159 detects the dispersed light.

[0038] Irradiation with light L1 induces localized plasmon resonance in the uneven structure of substrate 10, generating an enhanced optical electric field on the surface of metal portion 2. Raman scattered light L2 emitted from specimen S, enhanced by this enhanced optical electric field, passes through lens 146 and is reflected by half mirror 144 toward spectrometer 158. At this time, light L1 reflected by substrate 10 is also reflected by half mirror 144 toward spectrometer 158, but light L1 is cut by notch filter 151. On the other hand, light having a wavelength different from that of light L1 passes through notch filter 151, is collected by lens 154, passes through pinhole 152, is collimated by lens 156, enters spectrometer 158, and is detected by detector 159. In the Raman spectroscopy device, Rayleigh scattered light (or Mie scattered light) and the like have the same wavelength as light L1, so they are cut by notch filter 151 and do not enter spectrometer 158. The Raman scattered light L2 is incident on the detector 159, where the Raman spectrum is measured and analyzed.

[0039] The wavelength of the light irradiated from the laser 141 to the specimen S can be set to any value depending on the measurement environment, and can range from ultraviolet to visible and near-infrared. However, depending on the wavelength, the quantum efficiency of the detector 159 may decrease or the specimen S may emit fluorescence, so the wavelength of the light irradiated to the specimen S is preferably between 400 nm and 850 nm.

[0040] Here, a Raman spectrometer has been described as an example of the device 100, but the device is not limited to a Raman spectrometer, and can also be used in a microscopic Raman spectrometer, a fluorescence detector, or the like.

[0041] Second Embodiment Next, the substrate 10 according to this embodiment will be described with reference to FIG.

[0042] The substrate 10 according to this embodiment differs from the first embodiment in that the structure 1 has a hierarchical structure. The hierarchical structure is composed of at least two types of structures with different structural sizes, and refers to a structure that combines, for example, a first structure having a structural size on the order of microns and a second structure having a structural size on the order of submicrons. The height difference of the first structure having a structural size on the order of microns is, for example, 1 μm or more and 10 μm or less.

[0043] The structure 1 has a base 11 provided on an adhesive layer 6 and a concave-convex structure 12 provided on the base 11, and the concave-convex structure 12 is composed of a first concave-convex structure 121 and a second concave-convex structure 122 that is smaller in scale than the first concave-convex structure 121. The second concave-convex structure 122 is provided on the first concave-convex structure 121, and the first concave-convex structure 121 and the second concave-convex structure 122 have a plurality of convex portions and concave portions provided between the plurality of convex portions.

[0044] Furthermore, similar to the first embodiment, a metal portion 2 is provided on the second uneven structure 122, and a dielectric portion 3 is provided between the structure 1 and the metal portion 2. By providing gaps between the metal portions 2 provided on the convex portions of the second uneven structure 122, it is possible to further strengthen the optical electric field, and the intensity of Raman light in the substrate 10 can be improved.

[0045] The first uneven structure 121 and the second uneven structure 122 are preferably formed from the same material, and the base 11 is also preferably made from the same material. The distance between the convex and concave portions of the second uneven structure 122, i.e., the height difference of the uneven structure, is preferably 100 nm or more and 1000 nm or less, and more preferably 100 nm or more and 500 nm or less.

[0046] When forming a concave-convex structure on a hierarchical structure as in this embodiment, the substrate 5 used may be any substrate having a micro-order concave-convex structure on the surface thereof, such as, but not limited to, ground glass roughened with an abrasive or an etching solution such as acid or alkali, or a substrate processed with an electron beam.

[0047] Although FIG. 4 shows a horsetail-like layered structure as shown in FIG. 1(a), it may also be possible to use a structure in which the metal portion 2 fits along the recessed portion as shown in FIG. 1(b).

[0048] <Example> Examples will be described below, but the present invention is not limited to the following examples.

[0049] Example 1 An alumina sol solution was prepared by dissolving aluminum sec-butoxide (Al(O-sec-Bu)3) and ethyl acetoacetate (EtOAcAc) in 2-propanol (IPA) and stirring for approximately 3 hours at room temperature. The molar ratio of each component in the alumina sol solution was Al(O-sec-Bu)3: EtOAcAc: IPA = 1:1:20. A 0.01 M dilute hydrochloric acid solution was added to the alumina sol solution so that the molar ratio of hydrochloric acid added was twice that of Al(O-sec-Bu)3, and the mixture was refluxed for approximately 6 hours to prepare a sol-gel coating solution. The sol-gel coating solution was applied to a mirror-polished quartz glass substrate as a base substrate by spin coating to form a coating film. The coating film was then heat-treated at 100°C for 1 hour to obtain a transparent alumina gel film. Next, the alumina gel film was immersed in warm water at 80° C. for 30 minutes, and then dried at 100° C. for 10 minutes to form an alumina layer as the dielectric portion 3 having an uneven structure.

[0050] A palladium chloride aqueous solution was applied onto the alumina layer with the uneven structure by spin coating, and then dried at 100° C. Thereafter, the substrate was immersed in a nickel-phosphorus plating solution (phosphorus content: approximately 1 to 2 wt%) set at 80° C. for 40 minutes to form the uneven structure and a nickel layer as Structure 1.

[0051] After peeling off the metal portion with the alumina layer from the quartz glass substrate, an etching process was performed using a 3M aqueous sodium hydroxide solution at room temperature for 50 hours. SEM observation and XPS measurements revealed that a nickel uneven structure was formed on the nickel layer, which was the metal layer, and alumina remained on top of the uneven structure as the dielectric portion 3. The average height difference of the uneven structure was 272 nm, the average surface roughness Ra' was 3.8 nm, and the specific surface area was 1.1.

[0052] Furthermore, a gold magnetron sputtering device (Quick Coater SC-701HMCII manufactured by Sanyu Electronics Co., Ltd.) was used to form a gold film on the surface of the obtained member. Three gold film thicknesses were used: 5 nm, 10 nm, and 15 nm. In this manner, the substrate 10 was obtained. The observation was carried out using a scanning electron microscope (product name: ULTRA55, manufactured by Carl Zeiss). The observation conditions were an acceleration voltage of 1 kV and no vapor deposition. Figure 4 shows an SEM image of the surface of the substrate 10 with a gold film thickness of 15 nm. The surface SEM image shown in Figure 4 reveals that a gold film was formed on the uneven structure.

[0053] (Raman spectroscopy measurement) A 100 μM aqueous solution of the dye rhodamine 6G (R6G) was dropped onto the surface of the substrate 10 as a sample, and Raman spectroscopy was performed. The measurement conditions were as follows: The measurement device used was a Tokyo Instruments Nanofinder 30 three-dimensional microscopic laser Raman spectroscopy system. The excitation light source was a He-Ne laser (wavelength 633 nm), the laser intensity was 120 μW (ND 2.0), the objective lens was 20x (NA 0.45), the pinhole diameter was 100 μm, the diffraction grating was 300 gr / mm (measurement range approximately 0 to 3000 cm-1), the exposure time was 10 s, and the number of integrations was 1. Figure 5 shows the Raman spectroscopy results. The Raman signal of R6G was detected at all gold film thicknesses, confirming that the substrate 10 described in this example has a SERS effect. Figure 6 also shows the Raman signal intensity as a function of gold film thickness. The Raman peak around 1647 cm (stretching mode of the C-C bond in the aromatic ring) was taken as the Raman signal intensity of R6G, and the peak between 1700 and 1750 cm -1The SERS enhancement effect was evaluated using the average intensity of the R6G signal as the background intensity. It was found that the signal intensity ratio to the background was high (good S / N) for all gold film thicknesses. Table 1 shows the Raman evaluation results for the substrate 10 produced in Example 1. Detected SERS signal intensity is indicated by ◯, and undetected SERS signal intensity is indicated by ×. In addition, high R6G Raman signal intensity ratio to the background (good S / N) is indicated by ◯, and low R6G signal intensity ratio to the background (poor S / N) is indicated by ×.

[0054] Example 2 In Example 2, substrates 10 were manufactured by varying the etching conditions for the alumina used as the dielectric portion 3 and the thickness of the gold used as the structure 1. Substrates 10 were manufactured in the same manner as in Example 1, except for varying the etching time. The etching times were 8 hours, 24 hours, 122 hours, 194 hours, 226 hours, and 338 hours. For each sample with varying etching times, three gold film thicknesses (5 nm, 10 nm, and 15 nm) were used, and a total of 18 samples were evaluated. Table 1 shows the Raman evaluation results for the substrates 10 manufactured in Example 2. Raman spectroscopy measurements were performed on all substrates 10, and R6G Raman signals were detected, confirming that the substrates 10 had a SERS effect. Furthermore, it was found that the signal intensity ratio to the background was high (good S / N). Furthermore, for samples that were not etched, the SERS effect was confirmed for those with a gold film thickness of 5 nm.

[0055] Example 3 Substrates 10 were manufactured in the same manner as in Example 1, except that the base substrate 8 was changed to a quartz glass substrate having a ground surface. For the base substrate 8, #1200, #600, #400, #240, and #120 quartz glass substrates having a ground surface were used.

[0056] For each sample in which the base substrate 8 was changed, the gold film thickness was set to three levels: 5 nm, 10 nm, and 15 nm, and a total of 15 samples were evaluated. Table 2 shows the Raman evaluation results for the substrates 10 manufactured in Example 3. When Raman spectroscopy measurements were performed on all of the substrates 10, Raman signals of R6G were detected, confirming that the substrates 10 had a SERS effect. It was also found that the signal intensity ratio to the background was high (good S / N).

[0057] (Comparative Example 1) Similar to Example 1, three gold film thicknesses of 5 nm, 10 nm, and 15 nm were formed on samples with only an alumina layer having a textured structure that had not undergone a plating process, and Raman spectroscopy measurements were performed. Figure 6 shows the Raman signal intensity ratio versus gold film thickness. Although a Raman signal was detected, it was found that the Raman signal intensity ratio to the background was lower (poor S / N) compared to the optical field enhancement device shown in the Examples. Furthermore, for samples that had not undergone etching, with gold film thicknesses of 10 nm and 15 nm, no Raman signal was detected, as shown in Table 1, and the SERS effect could not be confirmed.

[0058] [Table 1]

[0059] [Table 2]

[0060] The disclosure of the present invention is shown below.

[0061] (Structure 1) A substrate having a plurality of convex portions containing a metal, wherein a first metal portion containing a metal having at least one of gold, silver, platinum, copper, and palladium is provided on a first convex portion of the plurality of convex portions, and a second metal portion containing a metal having at least one of gold, silver, platinum, copper, and palladium is provided on a second convex portion of the plurality of convex portions different from the first convex portion, and the substrate is provided with a dielectric portion between the first convex portion and the first metal portion, and between the second convex portion and the second metal portion, and the surface of the dielectric portion opposite the plurality of convex portions is shaped to conform to the convex portions, and a gap is provided between the first metal portion and the second metal portion, and the distance between the first metal portion and the second metal portion is 50 nm or less.

[0062] (Configuration 2) The substrate according to configuration 1, wherein the distance between the first metal portion and the second metal portion is 10 nm or less.

[0063] (Configuration 3) The substrate according to configuration 1 or 2, wherein the dielectric portion forms an interface with the first metal portion and the second metal portion.

[0064] (Configuration 4) The substrate according to any one of configurations 1 to 3, wherein the dielectric portion contains alumina.

[0065] (Configuration 5) The substrate according to any one of configurations 1 to 4, wherein the second convex portion is a convex portion adjacent to the first convex portion among the plurality of convex portions.

[0066] (Configuration 6) The substrate according to any one of configurations 1 to 5, wherein the first metal portion and the second metal portion are discontinuous.

[0067] (Configuration 7) The substrate according to any one of configurations 1 to 6, wherein each of the plurality of protrusions includes a metal having at least one of nickel, chromium, and zinc.

[0068] (Structure 8) The substrate according to any one of Structures 1 to 7, characterized in that it has a concave-convex structure including the plurality of convex portions and concave portions between the plurality of convex portions, and the height difference of the concave-convex structure is 100 nm or more and 1000 nm or less.

[0069] (Configuration 9) The substrate according to configuration 8, wherein the dielectric portion is provided in the recess.

[0070] (Configuration 10) The substrate according to configuration 8 or 9, wherein the dielectric portion is exposed in the space above the recess.

[0071] (Configuration 11) The substrate according to any one of configurations 1 to 10, wherein the dielectric portion forms an interface with the first convex portion.

[0072] (Configuration 12) The substrate according to any one of configurations 1 to 11, wherein the thickness of the first metal portion or the second metal portion is 5 nm or more and 50 nm or less.

[0073] (Configuration 13) The substrate according to any one of configurations 1 to 12, wherein the thickness of the dielectric portion is 30 nm or more and 200 nm or less.

[0074] (Structure 14) A substrate having a plurality of convex portions containing a metal, wherein a first metal portion containing a metal having at least one of gold, silver, platinum, copper, and palladium is provided on a first convex portion of the plurality of convex portions, and a second metal portion containing a metal having at least one of gold, silver, platinum, copper, and palladium is provided on a second convex portion of the plurality of convex portions different from the first convex portion, and the substrate is provided with a dielectric portion between the first convex portion and the first metal portion, and between the second convex portion and the second metal portion, and the thickness of the dielectric portion is 40 nm or more and 200 nm or less, a gap is provided between the first metal portion and the second metal portion, and the distance between the first metal portion and the second metal portion is 50 nm or less.

[0075] (Configuration 15) The substrate according to configuration 14, wherein the surface of the dielectric portion opposite to the plurality of convex portions has a shape that conforms to the convex portions.

[0076] (Configuration 16) The substrate according to any one of configurations 1 to 15, which enhances Raman light.

[0077] (Analysis method 1) An analysis method comprising placing a specimen on the substrate according to any one of configurations 1 to 15 and irradiating the specimen with light.

[0078] (Analysis Method 2) The analysis method according to Analysis Method 1, wherein the wavelength of the light is 400 nm or more and 850 nm or less.

[0079] (Apparatus 1) An apparatus comprising a light source for irradiating light and a substrate according to configuration 1 or 14, characterized in that the light source is configured to irradiate light onto a specimen placed on the substrate.

[0080] (Apparatus 2) The apparatus according to Apparatus 1, characterized in that it comprises a spectrometer that disperses the Raman light scattered by the sample.

[0081] (Manufacturing method 1) A step of forming a dielectric part having a first uneven structure on a surface thereof; a step of forming a metal-containing structure having a second uneven structure to which the first uneven structure is transferred on the first uneven structure; a step of removing a portion of the dielectric portion so that the dielectric portion covers the convex portions of the second uneven structure, and a step of removing a portion of the dielectric portion so that the distance from the surface of the dielectric portion opposite the structure to the concave portions of the second uneven structure is smaller than the difference in height between the convex portions and the concave portions of the structure adjacent to the convex portions; and a step of forming a first metal portion on the side of the dielectric portion opposite the structure, the first metal portion containing a metal having at least one of gold, silver, platinum, copper, and palladium on first convex portions of the convex portions, and a second metal portion containing a metal having at least one of gold, silver, platinum, copper, and palladium on second convex portions of the convex portions different from the first convex portions, wherein a gap is provided between the first metal portion and the second metal portion, and the distance between the first metal portion and the second metal portion is 50 nm or less.

[0082] (Manufacturing Method 2) A method for manufacturing a substrate according to Manufacturing Method 1, characterized in that the dielectric portion is removed so that the surface of the dielectric portion opposite the structure has a shape that conforms to the uneven structure transferred to the structure.

[0083] (Manufacturing Method 3) A manufacturing method according to Manufacturing Method 1 or 2, characterized in that the distance between the first metal portion and the second metal portion is a gap of 10 nm or less.

[0084] (Manufacturing Method 4) A manufacturing method according to any one of Manufacturing Methods 1 to 3, wherein the first metal portion and the second metal portion form an interface with the dielectric portion.

[0085] The above-described embodiments can be modified as appropriate without departing from the spirit and scope of the present invention. For example, multiple embodiments can be combined. Furthermore, some details of at least one embodiment can be deleted or replaced.

[0086] Furthermore, new matters may be added to at least one embodiment. The disclosure of this specification includes not only what is explicitly described in this specification, but also all matters that can be understood from this specification and the drawings attached hereto.

[0087] Furthermore, the disclosure of this specification includes the complement of each individual concept described in this specification. In other words, if this specification contains a statement that "A is greater than B," for example, it can be said that this specification discloses "A is not greater than B," even if it omits the statement that "A is not greater than B." This is because when a statement that "A is greater than B" is made, it is assumed that the case in which "A is not greater than B" is taken into consideration. [Explanation of symbols]

[0088] 3 Dielectric part 4 Convex part 9 Gap 10 Substrate 11 First protrusion 12 Second convex part 21 1st metal part 22 Second metal part D distance

Claims

1. A substrate having a plurality of protrusions containing metal, a first metal portion including a metal having at least one of gold, silver, platinum, copper, and palladium is provided on a first convex portion of the plurality of convex portions; a second metal portion including a metal having at least one of gold, silver, platinum, copper, and palladium is provided on a second convex portion of the plurality of convex portions that is different from the first convex portion; a dielectric portion is provided between the first convex portion and the first metal portion and between the second convex portion and the second metal portion; a surface of the dielectric portion opposite to the plurality of protrusions has a shape that conforms to the protrusions, A substrate characterized in that a gap is provided between the first metal portion and the second metal portion, and the distance between the first metal portion and the second metal portion is 50 nm or less.

2. 2. The substrate according to claim 1, wherein the distance between the first metal portion and the second metal portion is 10 nm or less.

3. The substrate according to claim 1 , wherein the dielectric portion forms an interface with the first metal portion and the second metal portion.

4. 3. The substrate according to claim 1, wherein the dielectric portion contains alumina.

5. The substrate according to claim 1 or 2, wherein the second convex portion is a convex portion adjacent to the first convex portion among the plurality of convex portions.

6. The substrate according to claim 1 or 2, wherein the first metal portion and the second metal portion are discontinuous.

7. 3. The substrate according to claim 1, wherein each of the plurality of protrusions includes a metal containing at least one of nickel, chromium, and zinc.

8. 3. The substrate according to claim 1, further comprising a concave-convex structure including the plurality of convex portions and concave portions between the plurality of convex portions, wherein the height difference of the concave-convex structure is 100 nm or more and 1000 nm or less.

9. The substrate according to claim 8 , wherein the dielectric portion is provided in the recess.

10. The substrate according to claim 8 , wherein the dielectric portion is exposed in the space above the recess.

11. The substrate according to claim 1 , wherein the dielectric portion forms an interface with the first convex portion.

12. 3. The substrate according to claim 1, wherein the thickness of the first metal portion or the second metal portion is 5 nm or more and 50 nm or less.

13. 3. The substrate according to claim 1, wherein the thickness of the dielectric portion is 30 nm or more and 200 nm or less.

14. A substrate having a plurality of protrusions containing metal, a first metal portion including a metal having at least one of gold, silver, platinum, copper, and palladium is provided on a first convex portion of the plurality of convex portions; a second metal portion including a metal having at least one of gold, silver, platinum, copper, and palladium is provided on a second convex portion of the plurality of convex portions that is different from the first convex portion; a dielectric portion is provided between the first convex portion and the first metal portion and between the second convex portion and the second metal portion; the thickness of the dielectric portion is 40 nm or more and 200 nm or less, A substrate characterized in that a gap is provided between the first metal portion and the second metal portion, and the distance between the first metal portion and the second metal portion is 50 nm or less.

15. The substrate according to claim 14 , wherein the surface of the dielectric portion opposite to the plurality of protrusions has a shape that conforms to the protrusions.

16. 15. The substrate of claim 1 or 14, which enhances Raman light.

17. 15. An analytical method comprising placing a specimen on the substrate according to claim 1 and irradiating the specimen with light.

18. 18. The analytical method according to claim 17, wherein the wavelength of the light is 400 nm or more and 850 nm or less.

19. An apparatus comprising a light source that irradiates light and the substrate according to claim 1 or 14, The apparatus, wherein the light source is configured to irradiate light onto a specimen placed on the substrate.

20. The apparatus according to claim 19, further comprising a spectrometer for dispersing the Raman light scattered by the specimen.

21. forming a dielectric portion having a first uneven structure on a surface thereof; forming a metal-containing structure having a second uneven structure on the first uneven structure, to which the first uneven structure has been transferred; a step of removing a part of the dielectric portion so that the dielectric portion covers the convex portions of the second uneven structure, and a step of removing a part of the dielectric portion so that a distance from a surface of the dielectric portion opposite the structure to a concave portion of the second uneven structure is smaller than a difference in height between the convex portions and a concave portion of the structure adjacent to the convex portions; forming a first metal part containing a metal having at least one of gold, silver, platinum, copper, and palladium on a first convex part of the convex parts, the first metal part being on the side of the dielectric part opposite to the structure, and a second metal part containing a metal having at least one of gold, silver, platinum, copper, and palladium on a second convex part of the convex parts different from the first convex part, A method for manufacturing a substrate, characterized in that a gap is provided between the first metal portion and the second metal portion, and the distance between the first metal portion and the second metal portion is 50 nm or less.

22. 22. The method for manufacturing a substrate according to claim 21, wherein the dielectric portion is removed so that the surface of the dielectric portion opposite the structure has a shape that conforms to the uneven structure transferred to the structure.

23. 23. The manufacturing method according to claim 21, wherein the distance between the first metal portion and the second metal portion is a gap of 10 nm or less.

24. 23. The manufacturing method according to claim 21, wherein the first metal portion and the second metal portion form an interface with the dielectric portion.

25. Further having a hierarchical structure, the plurality of convex portions constitute a second concave-convex structure included in the hierarchical structure, and a height difference in the concave-convex structure including the plurality of convex portions and the concave portions between the plurality of convex portions is 100 nm or more and 1000 nm or less; the second concavo-convex structure is provided on a first concavo-convex structure included in the hierarchical structure, The substrate described in claim 1, characterized in that the height difference in the uneven structure including the convex portions of the first uneven structure and the concave portions between the convex portions of the first uneven structure is 1 μm or more and 10 μm or less.

Images