JP6954152B2 - Analytical substrate - Google Patents

Description

The present invention relates to an analytical substrate.

Conventionally, Raman spectroscopy has been problematic in that the intensity of Raman scattered light is very weak. It is being considered to use Surface Enhanced Raman Scattering (SERS) for the improvement. SERS is a phenomenon in which the intensity of Raman scattered light of the adsorbed molecule to be measured is remarkably enhanced by enhancing the electric field by surface plasmon resonance on the surface of a metal such as Au or Ag. The use of electric field enhancement by surface plasmon resonance is also being studied in infrared absorption spectroscopy and optical analysis methods in fluorescence spectroscopy other than Raman spectroscopy.

The following are proposed as analytical substrates that utilize the electric field enhancement by surface plasmon resonance, for example.
(1) A plurality of dents or a plurality of protrusions are arranged in a grid pattern at predetermined specific lattice intervals to form a substrate having a nano-periodic structure that causes surface plasmon resonance and a surface of the nano-periodic structure. A signal amplification device for Raman spectroscopic analysis including a metal film (Patent Document 1).
(2) An electric field enhancing element including a metal layer, a dielectric layer provided on the metal layer, and a plurality of metal particles provided on the dielectric layer, wherein the plurality of metal particles are The propagating surface plasmon having a periodic arrangement capable of exciting the propagating surface plasmon propagating at the interface between the metal layer and the dielectric layer, and the localized surface plasmon excited by the metal particles are electromagnetic. The resonance wavelengths of each surface plasmon are different, and the half-value widths of the first absorption region and the second absorption region satisfy a specific relationship in the spectrum of reflected light when the electric field enhancer is irradiated with white light. , An electric field enhancing element in which the wavelength of the excitation light of the electric field enhancing element is included in the range of the second absorption region (Patent Document 2).

Japanese Unexamined Patent Publication No. 2015-232526 JP-A-2015-212626

However, the analytical substrates of (1) and (2) may not have sufficient sensitivity.
Since the apparatus of Patent Document 1 uses a propagation type surface plasmon, it has an advantage that the variation in the electric field distribution on the nanoperiodic structure is small, but since the electric field enhancement depends only on the propagation type surface plasmon, the enhancement effect. Has the disadvantage of being low.
On the other hand, regarding the electric field enhancing element of Patent Document 2, the propagation type surface plasmon and the localized surface plasmon are combined, the electric field distribution is made uniform by the propagation type surface plasmon, and the electric field strength is enhanced by the localized surface plasmon. By doing so, it is a configuration that combines the advantages of the propagation type and the localized type, and it is possible to achieve both uniformity and strength to some extent. However, since the dielectric layer exists between the metal layer and the metal particles, the molecule to be measured in the sample cannot approach the surface of the metal film having the highest electric field enhancing effect of the propagating surface plasmon. In addition, since the metal particles are arranged in the arrangement required to excite the propagation type surface plasmon, the interparticle distance is required to utilize the electric field enhancement utilizing the gap between the metal particles, which is highly effective as a localized surface plasmon. Is too big, which is also a disadvantage.

An object of the present invention is to provide an analytical substrate capable of performing optical analysis utilizing electric field enhancement by surface plasmon resonance with high sensitivity.

The present invention has the following aspects.
[1] A substrate having a two-dimensional lattice structure in which at least the first surface is made of a dielectric or a semiconductor and a plurality of concave portions or convex portions are periodically arranged two-dimensionally on the first surface.
A metal film provided on the first surface of the substrate and having a surface sheet resistance of 5000 Ω / □ or less at 25 ° C.
A plurality of metal nanoparticles having an average primary particle size of 5 to 100 nm dispersed and arranged on the metal film, and
A substrate for analysis.
[2] The analysis substrate of [1], wherein the two-dimensional lattice structure is a triangular lattice structure or a cubic lattice structure.
[3] A plurality of the metal film provided in the metal film as an island-shaped gap having a length in the major axis direction of 1 μm or less, in which no metal is present and the first surface of the substrate is exposed. The analytical substrate of [1] or [2], which has a non-deposited region of.

According to the present invention, it is possible to provide an analytical substrate capable of performing optical analysis utilizing electric field enhancement by surface plasmon resonance with high sensitivity.
In particular, a clear difference from Patent Document 2 is that in the present invention, the molecule to be measured of the sample can approach the surface of the metal film having the highest electric field enhancing effect of the propagating surface plasmon. Due to this difference, the present invention is superior to the prior art in the effect of enhancing Raman scattered light.

It is sectional drawing which shows typically the analytical substrate of one Embodiment of this invention. It is a top view which shows typically the analytical substrate which concerns on an example of Embodiment shown in FIG. 1 (however, the illustration of metal nanoparticles was omitted). It is a perspective view of the analysis substrate shown in FIG. It is an enlarged top view which shows typically the surface on the metal film side of the analysis substrate which concerns on an example of embodiment shown in FIG. 1 (however, the illustration of metal nanoparticles was omitted). It is a partial cross-sectional view schematically showing the IV-IV cross section in FIG. 4 (however, the illustration of metal nanoparticles is omitted). It is a scanning electron microscope image of the analysis substrate obtained in Example 1. It is a scanning electron microscope image of the analysis substrate obtained in Example 2.

Hereinafter, the analytical substrate of the present invention will be described with reference to the accompanying drawings with reference to embodiments.
FIG. 1 is a cross-sectional view schematically showing an analytical substrate according to the first embodiment of the present invention. FIG. 2 is a top view schematically showing an analysis substrate according to an example of the present embodiment. FIG. 3 is a perspective view of the analysis substrate shown in FIG. However, in FIGS. 2 to 3, the illustration of metal nanoparticles is omitted.
The analytical substrate 10 of the present embodiment includes a substrate 1, a metal film 3 provided on the first surface 1a of the substrate 1, and a plurality of metal nanoparticles 5 dispersed and arranged on the metal film 3.
The first surface 1a of the substrate 1 has a two-dimensional lattice structure. The metal film 3 is formed along the first surface 1a. Therefore, the surface of the metal film 3 provided on the first surface 1a also has a two-dimensional lattice structure.
The metal film 3 and the plurality of metal nanoparticles 5 are in contact with each other.

(substrate)
At least the first surface 1a of the substrate 1 is made of a dielectric or a semiconductor.
The substrate 1 may be, for example, a substrate made of a dielectric or a semiconductor, and two or more layers of a conductor layer, a dielectric layer, and a semiconductor layer are laminated so that the first surface is a dielectric or a semiconductor. It may be a multilayer board. The dielectric or semiconductor is not particularly limited, and may be a material known in applications such as an analytical substrate.
As the substrate 1, a substrate made of only a dielectric or a semiconductor is typically used, and for example, a quartz substrate, various glass substrates such as alkaline glass and non-alkali glass, a sapphire substrate, a silicon (Si) substrate, and a silicon carbide ( Examples thereof include a substrate made of an inorganic substance such as SiC), a substrate made of an organic substance such as polymethylmethacrylate, polycarbonate, polystyrene, a polyolefin resin, and a polyester resin.
The thickness of the substrate 1 is not particularly limited and may be, for example, 0.1 to 5.0 mm.
The thickness of the substrate 1 is measured by a general caliper length measuring method defined in JIS B7507.

The two-dimensional lattice structure of the first surface 1a is for providing a two-dimensional lattice structure on the surface of the metal film 3, and is set according to a desired two-dimensional lattice structure on the surface of the metal film 3.

(Metal film)
The metal constituting the metal film 3 may be any metal that can generate an electric field enhancement due to surface plasmon resonance, and examples thereof include gold, silver, aluminum, copper, platinum, and alloys of two or more of these.

The sheet resistance of the surface of the metal film 3 is 5000 Ω / □ or less, preferably 3 to 5000 Ω / □, more preferably 3 to 500 Ω / □, and most preferably 3 to 300 Ω / □. When the sheet resistance on the surface of the metal film 3 is not more than the upper limit value, it indicates that the metal film 3 is a continuous film. When the sheet resistance on the surface of the metal film 3 is within this range, the metal film 3 is not completely divided even if it has a nanogap due to the non-deposition region G described later. Further, when the metal film 3 has the non-deposited region G, the sheet resistance of the surface of the metal film 3 is not more than the upper limit value, that is, the distance between the metal surfaces 3a facing each other via the non-deposited region G is large. This means that it falls within the range of 1 to 20 nm, more specifically in the range of 1 to 10 nm, and more specifically in the range of 1 to 5 nm. When the metal film 3 is a discontinuous film (for example, one composed of a plurality of metal films dispersed in an island shape), the sheet resistance of the surface is not 5000 Ω / □ or less. Even if the metal film 3 partially has a non-deposited region G, since it is a continuous film as a whole, the metal film 3 can induce the propagation type surface plasmon described later, and the surface electric field It becomes easy to obtain the nonlinear optical effect by superimposition.
The sheet resistance (Ω / □) on the surface of the metal film 3 is a value at 25 ° C. Specifically, the sheet resistance is the electric resistance value (Ω) when a current flows from one end to the opposite end in a square region of an arbitrary size on the surface of the metal film 3 under the condition of 25 ° C. .. Details are as shown in Examples described later.

The metal film 3 has a two-dimensional lattice structure that follows the first surface 1a of the substrate 1.
Here, "following" means that the position of the convex portion or the concave portion in the two-dimensional lattice structure on the surface of the metal film 3 substantially coincides with the position of the convex portion or the concave portion in the two-dimensional lattice structure of the first surface 1a of the substrate 1. Show that.

Since the surface of the metal film 3 which is a continuous film has a two-dimensional lattice structure, it is possible to generate an electric field enhancement by propagating surface plasmon resonance on the surface of the metal film 3.
Here, the "two-dimensional lattice structure" is a periodic uneven structure in which a plurality of convex portions or concave portions are periodically arranged two-dimensionally. The two-dimensional arrangement means that a plurality of convex or concave arrangement directions are two or more directions.
A periodic uneven structure in which a plurality of convex portions or concave portions are periodically arranged one-dimensionally is also referred to as a one-dimensional lattice structure. The one-dimensional arrangement means that the arrangement direction of the plurality of convex portions or concave portions is one direction.
In the propagation type surface plasmon on a metal surface, a sparse and dense wave of free electrons generated by light incident on the metal surface (excitation light such as a laser used in Raman spectroscopy) is accompanied by a surface electromagnetic field. When the metal surface is flat, the propagating surface plasmon resonance is not induced because the dispersion curve of the surface plasmon existing on the metal surface and the dispersion straight line of light do not intersect. When the metal surface has a periodic uneven structure, the dispersion straight line of the light (diffracted light) diffracted by this periodic uneven structure intersects the dispersion curve of the surface plasmon, and the propagation type surface plasmon resonance is induced. ..
When there are many arrangement directions of the plurality of convex portions or concave portions in the periodic concave-convex structure, there are many conditions for obtaining diffracted light, and propagation-type surface plasmon resonance can be induced with high efficiency. By having a two-dimensional lattice structure as the periodic uneven structure, the periodic uneven structure is a one-dimensional lattice structure (for example, a line-and-space structure in which a plurality of grooves (recesses) or protrusions (convex) are arranged in parallel). Compared to some cases, optical analysis using electric field enhancement by surface plasmon resonance can be performed with higher sensitivity.

Preferred two-dimensional lattice structures are a cubic lattice structure having two arrangement directions and an intersection angle of 90 °, and a triangular lattice structure having three arrangement directions and an intersection angle of 60 ° (also referred to as a hexagonal lattice). ) Structure etc. The shape of the convex portion constituting the two-dimensional lattice structure is, for example, a cylindrical shape, a conical shape, a truncated cone shape, a sinusoidal shape, a hemispherical shape, a substantially hemispherical shape, an ellipsoidal shape, or a derivative shape based on them. It may be. The shape of the concave portion constituting the two-dimensional lattice structure may be, for example, an inverted shape of the convex portion mentioned above.
As the two-dimensional lattice structure, a triangular lattice structure is preferable because it can induce propagation-type surface plasmon resonance with higher efficiency.

As shown in FIGS. 2 to 3, the two-dimensional lattice structure on the surface of the metal film 3 according to an example of the present embodiment is a triangular lattice structure composed of a plurality of truncated cone-shaped convex portions 3c.
The height of the convex portion 3c is preferably 15 to 150 nm, more preferably 30 to 80 nm. When the height of the convex portion 3c is equal to or higher than the lower limit of the above range, the two-dimensional lattice structure on the surface of the metal film 3 sufficiently functions as a diffraction grating, and propagation-type surface plasmon resonance can be induced. When the height of the convex portion 3c is equal to or less than the upper limit of the above range, the metal film 3 tends to be a continuous film.
When the convex portion 3c has another shape, the preferable height is approximately the same. When the two-dimensional lattice structure on the surface of the metal film 3 is composed of a plurality of concave portions, the preferable depth of the concave portions is approximately the same as the preferable height of the convex portion 3c. To be precise, the optimum height of the convex portion 3c is determined by the volume fraction and the dielectric constant of the convex portion 3c that interacts with the electromagnetic field due to the surface plasmon.

The height of the convex portion 3c is the vertical distance from the center point equidistant from the three adjacent convex portions to the average value of the top surfaces of the truncated cones of the three convex portions as AFM (atomic force microscope). ) Etc. to measure the length. For the length measurement, five two-dimensional lattice structure surfaces separated from each other by 100 μm or more are used. An AFM image of 5 μm × 5 μm is acquired for each of these five measurement regions, and the center depths of the nine points randomly selected for each AFM image are measured. Since the image of the AFM probe may be anisotropy depending on the scanning direction, the length measurement creates profile images in the three directions _{D M1 to} D _{M3 as shown in FIG. 2, and in each direction.} Perform at 3 points, 9 points in total. The average value of the measured values obtained at the nine measurement points is used as the measured value in one measurement area, the measured values in the five measurement areas are obtained in the same manner, and the average of the measured values in the five measurement areas is further calculated. Obtained and set the height of the convex portion 3c.
Each of D _{M1 to} D _{M3 is a direction substantially orthogonal to each of the three arrangement directions E M1 to} E _M3 of the convex portion 3c on the main surface of the metal film 3 (because the actual lattice arrangement has some distortion, be sure to be sure. Not always orthogonal).
The height of the convex portion and the depth of the concave portion of other shapes are also measured by the same measuring method.

The pitch Λ of the convex portions 3c in the arrangement direction of the convex portions 3c is designed corresponding to _{the wavelength λ i of the incident light (excitation light).} The wave number of the incident light _{k i (k i = 2π /} λ i), the real part epsilon ₁ of the dielectric constant of the metal in the k _{i, 2} the real part of the dielectric constant of the analyte _epsilon, and when, the surface plasmon The wave number k _spp is calculated by the following equation 1:
_{k spp = k i ((ε} 1 × ε 2) / (ε 1 + ε 2)) 0.5 ( Equation 1)
Can be obtained informally with. Since the wavelength λ _{spp of the} surface plasmon is _{the reciprocal of k spp} and the convex portions 3c are in a triangular lattice arrangement, the pitch Λ of the convex portions 3c is calculated by the following equation 2:
Λ = (2 / √3) × λ _spp (Equation 2)
Obtained by. Equations 1 and 2 are general.
According to the above calculation method, for example, when the wavelength of the incident light is λ _i = 785 nm, the metal constituting the convex portion 3c is gold (Au), and the sample is an aqueous solution (ε ₂ ≈ 1.33).
k _spp = 11.8 μm ^-1 , Λ = 655 nm
Will be. Similarly, for example, when the wavelength of the incident light is λ _i = 633 nm, the metal constituting the convex portion 3c is gold (Au), and the sample is a dried organic substance (ε ₂ ≈ 2.25).
k _spp = 16.6 μm ^-1 , Λ = 438 nm
Is. When a laser is used for the incident light, its wavelength distribution is extremely narrow, so that the convex portion 3c may be substantially made as close as possible to the pitch Λ. When the two-dimensional lattice array is a square lattice or the one-dimensional lattice array (line & space), the following equation 3 may be used instead of the equation 2.
Λ = λ _spp (Equation 3)
Laser light sources used as incident light include those corresponding to various wavelengths such as 785, 633, 532, 515, 488, and 470 nm. In general, it is preferable to use gold (Au) for a light source having a wavelength larger than about 500 nm as a metal species constituting a sea-island structure, metal nanoparticles, and a periodic uneven structure, and for a light source having a wavelength smaller than about 500 nm. It is preferable to use silver (Ag), but the surface-enhancing Raman scattering effect may be obtained even with a metal species other than gold (Au) and silver (Ag), and the above is not always the case.
The preferred pitch is the same when the convex portion 3c has another shape. When the two-dimensional lattice structure on the surface of the metal film 3 is composed of a plurality of recesses, the preferred pitch of the recesses in the arrangement direction of the recesses is the same as the preferred pitch of the convex portions 3c.

The pitch of the convex portion 3c is obtained by measuring the horizontal distance between the center points of the two adjacent cone protrusions with an AFM (atomic force microscope) or the like. For the length measurement, five two-dimensional lattice structure surfaces separated from each other by 100 μm or more are used. An AFM image of 5 μm × 5 μm is acquired for each of these five measurement regions, and the distance between the two points at nine randomly selected points is measured for each AFM image. Since AFM tip is that may anisotropy occurs in the image by the scan direction, length measurement, as shown in FIG. 2, to create a profile image in the three directions E _M1 to E _M3, in each direction 3 Perform at 9 measurement points in total. The average value of the measured values obtained at the nine measurement points is used as the measured value in one measurement area, and the average of the measured values in the five measurement areas is obtained and used as the pitch of the convex portion 3c.
The pitch of the convex portion and the pitch of the concave portion of other shapes are also measured by the same measuring method.

Preferred embodiments of the metal film 3 include the following aspects A or B.
Aspect A: A plurality of non-deposited regions provided in the metal film as an island-shaped gap having a length of 1 μm or less in the major axis direction, in which no metal is present and the first surface 1a of the substrate 1 is exposed. A metal film having.
Aspect B: A metal film that does not have the non-deposited region.

If the metal film 3 is the metal film of aspect A (hereinafter, also referred to as metal film 3A), the combined use of the enhanced electric field by the propagating surface plasmon and the localized surface plasmon, or the propagating surface plasmon and the localized surface. By utilizing the resonance coupling (coupling) of the enhanced electric field by the plasmon, the optical analysis can be performed with higher sensitivity. On the other hand, if the metal film 3 is the metal film of aspect B (hereinafter, also referred to as metal film 3B), the optical analysis can be performed with higher sensitivity by using the enhanced electric field by the propagation type surface plasmon.

The metal film 3A will be described in more detail with reference to FIGS. 4 to 5. FIG. 4 is an enlarged top view schematically showing the surface of the analysis substrate 10 on the metal film 3 side when the metal film 3 is the metal film 3A, and FIG. 5 is an enlarged top view schematically showing the surface of the analysis substrate 10 on the metal film 3 side. FIG. FIG. 5 is a partial cross-sectional view schematically showing a −IV cross section. However, in FIGS. 4 to 5, the illustration of metal nanoparticles is omitted.
The metal film 3A has a plurality of non-deposited regions G. The plurality of non-deposited regions G are dispersedly provided in the metal film 3A as an island-shaped gap having a length of 1 μm or less in the major axis direction. The region of the metal film 3 other than the non-deposited region G is a film-forming region.
The non-deposited region G is a region in which no metal is present and the first surface 1a is exposed. That is, it is a gap that penetrates the metal film 3A in the thickness direction. A region (for example, region S in FIG. 5) that does not form a void penetrating the metal film 3A even if the metal does not exist in a part in the thickness direction does not correspond to the non-deposition region G. This is the film formation area.

The non-deposited region G is an island-shaped gap in the top view, and the plurality of non-deposited regions G may be independent or several may be connected, but they are connected as a whole. No. Therefore, as shown in FIG. 5, the non-deposited region G is surrounded by the metal surface 3a, and the metal surfaces 3a face each other via the non-deposited region G. The distance between the metal surfaces facing each other via the non-deposited region G, that is, the width of the non-deposited region G is usually extremely small, for example, on the order of several nanometers to several tens of nanometers. Between such metal surfaces 3a, electric field enhancement can be generated by superposition of electric fields by localized surface plasmons. In particular, when the width of the non-deposited region G is a single digit nanometer, an extremely strong electric field enhancement can be obtained.

The distance between the metal surfaces 3a facing each other via the non-deposition region G is preferably 1 to 20 nm, more preferably 1 to 10 nm, and even more preferably 1 to 5 nm. When the distance between the metal surfaces 3a is within the above range, the electric field enhancing effect by the localized surface plasmon resonance is more excellent.
When the metal surface surrounding the non-deposition region G is an inclined surface inclined with respect to the thickness direction of the metal film 3 as shown in FIG. 5, there is a distribution in the distance between the metal surfaces 3a. When there is a distribution in the distance between the metal surfaces 3a, it is preferable that the maximum value of the distance between the metal surfaces 3a is equal to or less than the above-mentioned preferable upper limit value. Further, it is preferable that the minimum value of the distance between the metal surfaces 3a is equal to or more than the above-mentioned preferable lower limit value.
The distance between the metal surfaces 3a is measured by the method described in Examples described later.

The thickness of the metal film 3A is preferably 3 to 40 nm, more preferably 4 to 30 nm, and most preferably 5 to 20 nm as the average thickness of the region other than the non-deposition region G, that is, the film formation region. If the thickness of the metal film 3A is within the above range, it has a non-deposited region G, a distance between opposing metal surfaces via the non-deposited region G, and a non-deposited region with respect to the total area of the metal film 3A. The metal film 3A in which the ratio of the area of G is within the above-mentioned preferable range is likely to be obtained. When the thickness of the metal film 3A is at least the above lower limit value, the sheet resistance on the surface of the metal film 3A tends to be at least the above upper limit value.

The thickness of the metal film 3A (average thickness of the film-forming region) is a value calculated from the film-forming rate obtained by the following method. First, prepare a flat substrate such as a single crystal silicon substrate with a centerline average roughness Ra of 1 nm or less determined by an atomic force microscope (AFM), mask it with tape or the like, and then cover several metal films. A film is formed for a certain period of time of about several tens of nm, the mask is removed, and then the film thickness is measured by AFM. From the above information, the film formation rate (film thickness per unit time (nm / min)) is obtained. Once the film formation rate is obtained, the thickness of the metal film 3A can be calculated from the film formation rate and the film formation time when the metal film 3A is formed.
In the above method, for convenience, the film thickness may be measured by using a stylus type step meter instead of the AFM. The same result can be obtained in this case as well, but when the measured values by the AFM and the stylus type step meter are different, the measured values by the AFM are adopted in the present invention.
For the thickness of the metal film 3A, for convenience, a transmission electron microscope (TEM) is used to obtain a microscopic image of a cross-sectional sample of the substrate including the metal film 3A, and the thickness of the metal film 3A is actually measured in the image. It may be measured by a method. Similar results can be obtained in this case as well. Since it is not necessary to measure information such as the film formation rate in advance in this method, it is an effective means for a sample whose manufacturing conditions and the like are unknown.
As another method for knowing the thickness of the metal film 3A of a sample whose film formation rate is unknown, an extremely fine scratch is formed on the surface of the metal film 3A using a knife or the like, and the depth of the scratch is measured by AFM. The lengthening method is effective. Since the metal film 3A is extremely thin, it is possible to form scratches that expose the base material with a relatively weak force.

The thickness of the metal film 3B is more preferably 40 to 400 nm or less, further preferably 50 to 200 nm. When the thickness of the metal film 3B is at least the above lower limit value, it tends to be a metal film having no non-deposition region. Further, if the thickness of the metal film 3BA is within the above range, the sheet resistance on the surface of the metal film 3A tends to be within the range.
The thickness of the metal film 3B is measured in the same manner as the thickness of the metal film 3A.

(Metal nanoparticles)
The metal constituting the metal nanoparticles 5 may be any metal that can generate an electric field enhancement due to surface plasmon resonance, and examples thereof include gold, silver, aluminum, copper, platinum, and alloys of two or more of these.
The shape of the metal nanoparticles 5 is not particularly limited, and for example, spherical, needle-shaped (rod-shaped), flake-shaped, polyhedral-shaped, ring-shaped, hollow-shaped (hollow or dielectric is present in the center), dendritic crystal, and the like. Other examples include an indefinite shape.
At least a part of the plurality of metal nanoparticles 5 may be aggregated to form secondary particles.

The average primary particle size of the metal nanoparticles 5 is 5 to 100 nm, preferably 5 to 80 nm, and more preferably 5 to 40 nm. When the average primary particle size of the metal nanoparticles 5 is within the above range, the electric field enhancing effect by the localized surface plasmon resonance is excellent.
The average primary particle size of the metal nanoparticles 5 is measured by a method of directly measuring the primary particle size of the metal nanoparticles 5 with a scanning electron microscope (SEM) and obtaining the average value. In this case, in order to know the average state, an average value of n = 20 or more is acquired.
In the above method, for convenience, a transmission electron microscope (TEM) or an atomic force microscope (AFM) may be used instead of the SEM. Similar results can be obtained in this case as well.
For convenience, the average primary particle size of the metal nanoparticles 5 may be measured by a particle size distribution meter by a dynamic light scattering method. In this case, the presence of secondary particles (aggregates of primary particles) causes a plurality of peaks in the particle size distribution curve, so that the peak with the smallest particle size is the target particle size. With this method as well, the same result as the measurement method using the above SEM can be obtained.
The measurement method using a microscopic means such as SEM is useful when the surface of the analysis substrate as a product is analyzed later, and the measurement method by the dynamic light scattering method is useful when manufacturing the analysis substrate. ..

The shortest distance between two adjacent metal nanoparticles 5 arranged apart on the metal film 3 is preferably 1 to 20 nm, more preferably 1 to 10 nm, and even more preferably 1 to 5 nm. When the shortest distance is within the above range, electric field enhancement due to localized surface plasmon resonance occurs between the metal nanoparticles 5, and high-sensitivity Raman spectroscopy of the molecule to be measured adsorbed between the metal nanoparticles 5. Analysis is possible. Further, even if the metal nanoparticles 5 are in contact with the metal film 3, a minute gap between the metal film 3 and the metal nanoparticles 5 is generated in the vicinity of the contact point, so that the localized surface plasmon resonance also occurs here. High-sensitivity Raman spectroscopic analysis becomes possible due to the enhancement of the electric field.
For the shortest distance, a scanning electron microscope (SEM) is used to obtain a microscopic image of a surface sample of a substrate containing two adjacent metal nanoparticles, and the gap between the two adjacent metal nanoparticles in the image is actually measured. Measured by the method of This method requires a magnification of 100,000 times or more, preferably 1 million times or more. Since the shortest distance between two adjacent metal nanoparticles 5 is locally different and not uniform, a measurement of n = 20 or more is performed to obtain a distance distribution.
In the above method, for convenience, a transmission electron microscope (TEM) or an atomic force microscope (AFM) may be used instead of the SEM. Similar results can be obtained in this case as well.
However, it is said that the nanogap of about 1 nm contributes most effectively to the surface-enhanced Raman scattering effect, and the average value of the distance distribution is not necessarily a meaningful value.

(Manufacturing method of analytical substrate)
Examples of the method for manufacturing the analysis substrate 10 include the following manufacturing method (I).
Manufacturing method (I):
A step of depositing a metal on the first surface 1a of the substrate 1 to form a metal film 3 (hereinafter, also referred to as “step I-1”).
An analytical substrate comprising a step of applying a metal nanoparticle dispersion liquid containing a plurality of metal nanoparticles 5 and a dispersion medium onto the metal film 3 and drying the metal nanoparticles (hereinafter, also referred to as “step I-2”). Manufacturing method.
In step I-1, a plurality of regions where no metal is deposited remain on the first surface 1a as island-shaped gaps having a length of 1 μm or less in the major axis direction, and the sheet resistance on the surface of the metal film is increased. When the metal deposition on the first surface 1a is completed in the state of 5000Ω / □ or less, the metal film 3A is formed. If the metal deposition is continued without being completed, the non-deposited region G disappears, the unevenness of the film surface becomes smaller, and the metal film 3B has a flat surface.

<Step I-1>
As the substrate 1, an original plate having a two-dimensional lattice structure formed on its surface or a transferred product thereof can be used. As the original plate or a transferred product thereof, a product manufactured by a known production method may be used, or a commercially available product may be used.

The original plate is obtained by forming a two-dimensional lattice structure on the surface of the original plate.
The original plate is the same as the substrate 1 except that the surface does not have a predetermined two-dimensional lattice structure.
Examples of the method for forming a two-dimensional lattice structure on the surface of the original plate include a dry etching method (colloidal lithography method) using a single particle film as an etching mask, an electron beam lithography method, a mechanical cutting method, and a laser thermal lithography method. Interference exposure method, more specifically, two-beam interference exposure method, reduced exposure method, alumina anodization method, and nanoimprint method from a transfer original plate having a two-dimensional lattice structure on the surface, which is produced by any of these methods. And so on.

As a method for forming a two-dimensional lattice structure, various methods can be applied, and examples thereof include a photolithography method combining electron beam drawing and dry etching, a nanoporous alumina anodization method, and a nanoimprint method using a master based on the photolithography method. However, a dry etching method (colloidal lithography method) using a single particle film as an etching mask is preferable because a fine structure can be produced in a large area and at low cost. In addition, the colloidal lithography method has an advantage that it is possible to easily produce a plurality of types of structures having different pitches, and it is possible to quickly optimize the structure and verify the function.
More specifically, the production of the substrate 1 by the colloidal etching method includes a step of arranging a single particle film on an original plate (a substrate before forming a two-dimensional lattice structure on the surface) (single particle film arranging step) and the above-mentioned. It can be performed by a manufacturing method including a step of dry etching the single particle film and the original plate (dry etching step).
The single particle film and each step will be described in detail later.

The method of depositing the metal on the first surface 1a is not particularly limited, and examples thereof include a dry method such as a vapor deposition method and a wet method such as electrolytic plating and electroless plating. Examples of the dry method include various vacuum sputtering methods, physical vapor deposition methods (PVD) such as vacuum vapor deposition methods, and various chemical vapor deposition methods (CVD).

When a metal film is formed on the first surface 1a by a dry method (metal deposition), first, a plurality of metal particles adhere to the entire first surface 1a, and the metal particles are joined by growth and become fine. Multiple island-shaped metal films are formed. As the film formation progresses, adjacent metal films form larger clusters, and the area and thickness of the metal films increase. Along with this, the region on the first surface 1a where no metal is deposited becomes narrower. The film formation is completed when the region where the metal is not deposited remains in an island shape and the value of the surface sheet resistance of the formed metal film is within the above range (the state where the metal film is a continuous film). Then, the above-mentioned metal film 3A is obtained. The region where no metal is deposited, which remains in an island shape, is the non-deposited region G. If the metal deposition is continued without being completed, the non-deposited region G disappears and the metal film 3B is formed.

When the catalyst is dispersed and arranged in advance on the first surface 1a and a metal film is formed by electroless plating in that state, first, metal adheres around the catalyst and a plurality of fine island-shaped metal films are formed. Will be done. As the electroless plating progresses, as in the case of the dry method, the metal films form larger clusters, and the region on the first surface 1a where no metal is deposited becomes narrower. The above-mentioned metal film 3A can be obtained by completing the film formation in a state where the region where the metal is not deposited remains in an island shape and the surface sheet resistance value of the formed metal film is within the above range. The region where no metal is deposited, which remains in an island shape, is the non-deposited region G. If the metal deposition is continued without being completed, the non-deposited region G disappears and the metal film 3B is formed.

As a method of depositing the metal on the first surface 1a, the sputtering method is preferable because the adhesion of impurities is unlikely to occur, the adhesion strength of the metal film to the substrate is high, and the sea-island structure can be easily controlled. That is, it is preferable that the metal film 3 is a film formed by a sputtering method.
The fact that multiple regions where no metal is deposited remains in an island shape on the first surface 1a is 100,000 times that of high-magnification microscope means such as an atomic force microscope (AFM) and a scanning electron microscope (SEM). It can be confirmed by observing the surface of the degree.
The sheet resistance on the surface of the metal film 3 at the end of the vapor deposition is preferably 3 to 500 Ω / □, most preferably 3 to 300 Ω / □.

<Step I-2>
The dispersion medium of the metal nanoparticle dispersion liquid may be any medium as long as it can disperse the metal nanoparticles 5, and examples thereof include water, ethanol, and other organic solvents.
The content of the metal nanoparticles 5 in the metal nanoparticle dispersion may be, for example, 0.01 to 10.0 mass% with respect to the total mass of the metal nanoparticle dispersion, and further 0.1 to 1. It may be 0.0% by mass.
If necessary, the metal nanoparticle dispersion liquid may further contain citric acid as a dispersion stabilizer, various inorganic salts, and the like, as long as the effects of the invention are not impaired.

The coating method of the metal nanoparticle dispersion liquid is not particularly limited, and can be appropriately selected from known coating methods such as a spray method, a drop casting method, a dip coating method, a spin coating method, and an inkjet printing method. The spray method or the inkjet printing method is preferable because the metal nanoparticles can be uniformly arranged at high density on the surface of the substrate by spraying the metal nanoparticles.

After long-term storage in a normal environment (in air) after step I-1 or step I-2, contaminants in the air adhere to the metal structure on the surface of the substrate, and the effect of the present invention is exhibited. It may decrease. Therefore, storage is preferably performed in a vacuum container or an inert gas such as nitrogen or argon. If the effect of the present invention is reduced by pollutants in the air, the substrate may be surface-treated with ultraviolet rays (UV) / ozone, etc., if necessary, in order to restore its function. good.

<Single particle film>
A "single particle film" is a monolayer film in which a plurality of particles are arranged two-dimensionally.
The material of the particles constituting the single particle film is not particularly limited, and may be an organic material, an inorganic material, or a composite material of an organic material and an inorganic material.
Examples of the organic material include thermoplastic resins such as polystyrene and polymethylmethacrylate (PMMA); thermosetting resins such as phenol resin and epoxy resin; and the like.
Examples of the inorganic material include carbon homogenes, inorganic carbides, inorganic oxides, inorganic nitrides, inorganic borides, inorganic sulfides, and inorganic selenium compounds. Examples of carbon allotropes include diamond, graphite, fullerenes and the like. Examples of the inorganic carbide include silicon carbide, boron carbide and the like. Examples of the inorganic oxide include silicon oxide, aluminum oxide, zirconium oxide, titanium oxide, cerium oxide, zinc oxide, tin oxide, yttrium aluminum garnet (YAG) and the like. Examples of the inorganic nitride include silicon nitride, aluminum nitride, and boron nitride. Examples of the inorganic boride include ZrB ₂ , CrB _{2, and the} like. Examples of the inorganic sulfide include zinc sulfide, calcium sulfide, cadmium sulfide, and strontium sulfide. Examples of the inorganic selenium product include zinc selenide and cadmium selenide.
The material constituting the particles may be one kind or two or more kinds.

The average particle size of the particles constituting the single particle film corresponds to the pitch of the periodic uneven structure calculated by the method described in the above paragraph [0020] according to the excitation wavelength used for the spectroscopic analysis. If the average particle size of the particles is the calculated value, it is easy to induce propagation-type surface plasmons.
The average particle size of the particles in a slurry state that does not form a single particle film can be obtained by a conventional method from the peak obtained by fitting the particle size distribution obtained by the particle dynamic light scattering method to a Gaussian curve. It is the diameter.

When forming a two-dimensional lattice structure having a triangular lattice structure as shown in FIG. 2, the coefficient of variation of the particle size (value obtained by dividing the standard deviation by the average value) of the particles constituting the single particle film is preferably 20% or less. 10% or less is more preferable, and 5% or less is further preferable. When particles having a small coefficient of variation in particle size, that is, particles having a small variation in particle size are used in this way, defects in which no particles do not exist are less likely to occur in the formed single particle film, and the deviation D of the arrangement of the particles is 10%. The following high-precision single-particle film can be obtained. In a single particle film having an arrangement deviation D of 10% or less, each particle is two-dimensionally close-packed, the particle spacing is controlled, and the accuracy of the arrangement is high. Therefore, when such a single particle film is arranged on the original plate and dry etching is performed, a highly accurate two-dimensional lattice structure can be formed on the surface of the original plate.
However, the present invention is not limited to this, and a single particle film may be formed of particles having a large coefficient of variation in particle size. For example, a single particle film may be formed by using a mixture of a plurality of particle groups having different average particle sizes.

The deviation D of the arrangement of particles is defined by the following equation (1).
D [%] = | BA | × 100 / A ... (1)
In the formula (1), A is the average particle size of the particles constituting the single particle film, and B is the average pitch between the particles in the single particle film. Further, | BA | indicates the absolute value of the difference between A and B.
Here, the average particle size of the particles is as defined above.
The pitch between particles is the distance between the vertices of two adjacent particles, and the average pitch is the average of these. If the particles are spherical, the distance between the vertices of the two adjacent particles is equal to the distance between the centers of the two adjacent particles.

Specifically, the average pitch B between particles in the single particle film is obtained as follows.
First, an atomic force microscope image or a scanning electron microscope image is obtained for a square region of a repeating unit of 30 to 40 wavelengths having a fine structure on one side in a randomly selected region of a single particle membrane. For example, in the case of a single particle film using particles having a particle size of 300 nm, an image of a region of 9 μm × 9 μm to 12 μm × 12 μm is obtained. Then, this image is waveform-separated by a two-dimensional Fourier transform to obtain an FFT image (fast Fourier transform image). Then, the distance from the 0th-order peak to the 1st-order peak in the profile of the FFT image is obtained. The reciprocal of the distance thus obtained is the average pitch B ₁ in this region. Such processing is performed in the same manner for a total of 25 or more randomly selected regions of the same area, and the average pitches B _{1 to} B ₂₅ in each region are obtained. _{The average value of the average pitches B 1 to} B _{25 in} the 25 or more regions thus obtained is the average pitch B in the equation (1). At this time, the regions are preferably selected at least 1 mm apart, and more preferably 5 mm to 1 cm apart.
At this time, it is also possible to evaluate the variation in the pitch between the particles in each image from the half width of the primary peak in the profile of the FFT image.

<Single particle film placement process>
The single particle film placement step is preferably performed by the Langmuir-Bloget method (LB method). This method has the accuracy of single layering, ease of operation, support for large area, reproducibility, etc., and is described in, for example, Nature, Vol.361, 7 January, 26 (1993). It is extremely superior to the so-called particle adsorption method described in the method and Japanese Patent Application Laid-Open No. 58-120255, and can cope with the industrial production level.

In the single particle film placement step by the LB method, for example, a water tank (trough) containing water is prepared as a liquid for developing particles on the liquid surface (hereinafter, may be referred to as a lower layer liquid), and the liquid is prepared. A step of dropping a dispersion liquid in which particles are dispersed in an organic solvent having a specific gravity smaller than that of water (dropping step) and a step of forming a single particle film composed of particles by volatilizing the organic solvent (single particles). It can be carried out by a method having a film forming step) and a step of transferring the formed single particle film to the original plate (transition step). After the transition step, a step (fixing step) of fixing the single particle film transferred to the substrate to the substrate may be performed.
At this time, as the particles, particles having a hydrophobic surface are used so that the particles do not go under the surface of the hydrophilic lower layer liquid. Further, as the organic solvent, a hydrophobic one is selected so that when the dispersion liquid is dropped on the liquid surface of the lower layer liquid, the dispersion liquid does not mix with the lower layer liquid and develops at the gas-liquid interface between the air and the lower layer liquid. Will be done.
Here, an example is shown in which particles having a hydrophobic surface and an organic solvent having a hydrophobic surface are selected and a hydrophilic one is used as the underlayer liquid, but the particles have a hydrophilic surface and are organic. A hydrophilic solvent may be selected, and a hydrophobic liquid may be used as the underlayer liquid.
The dispersion liquid to be used and each step will be specifically described below.

"Dispersion"
The organic solvent used in the dispersion is hydrophobic, which has a lower specific gravity than water. It is also important that the organic solvent has high volatility. Organic solvents that have a lower specific gravity than water, are hydrophobic, and have high volatility include, for example, chloroform, methanol (used as a mixing material), ethanol (used as a mixing material), isopropanol (used as a mixing material), and acetone. (Used as a mixing material), volatile organic solvents composed of one or more of methyl ethyl ketone, ethyl ethyl ketone, toluene, hexane, cyclohexane, ethyl acetate, butyl acetate and the like can be mentioned.

As the particles having a hydrophobic surface, among the particles exemplified above, those made of an organic material such as polystyrene and having a hydrophobic surface originally may be used, and particles having a hydrophilic surface may be treated with a hydrophobic agent. Hydrophobicized ones may be used.
As the hydrophobizing agent, for example, a surfactant, a metal alkoxide or the like can be used.
The method of using a surfactant as a hydrophobizing agent is effective for hydrophobizing a wide range of materials, and is suitable when the particles are made of an inorganic oxide or the like.
The method of using a metal alkoxide as a hydrophobizing agent is effective in hydrophobizing inorganic oxide particles such as aluminum oxide, silicon oxide, and titanium oxide. In addition to the inorganic oxide particles, it can be applied to particles having a hydroxyl group on the surface.

As the surfactant, a cationic surfactant such as hexadecyltrimethylammonium bromide and decyltrimethylammonium bromide, and an anionic surfactant such as sodium dodecyl sulfate and sodium 4-octylbenzenesulfonate can be preferably used. Further, alkanethiol, disulfide compound, tetradecanoic acid, octadecanoic acid and the like can also be used.

Examples of the metal alkoxide include alkoxysilane.
Examples of alkoxysilanes include monomethyltrimethoxysilane, monomethyltriethoxysilane, dimethyldiethoxysilane, phenyltriethoxysilane, hexyltrimethoxysilane, decyltrimethoxysilane, vinyltricrolsilane, vinyltrimethoxysilane, vinyltriethoxysilane, and 2 -(3,4-epoxycyclohexyl) ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltriethoxysilane, p-styryltrimethoxy Silane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-acryloxypropyltrimethoxysilane, N- 2 (Aminoethyl) 3-Aminopropylmethyldimethoxysilane, N-2 (Aminoethyl) 3-Aminopropyltrimethoxysilane, N-2 (Aminoethyl) 3-Aminopropyltriethoxysilane, 3-Aminopropyltrimethoxysilane , 3-Aminopropyltriethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, 3-ureidopropyltriethoxysilane, 3-chloropropyltrimethoxysilane, 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropyltri Examples thereof include methoxysilane and 3-isocyanuppropyltriethoxysilane.

The hydrophobizing treatment using a surfactant may be carried out in the liquid by dispersing the particles in a liquid such as an organic solvent or water, or may be carried out on the particles in a dry state.
In the case of carrying out in a liquid, for example, particles to be hydrophobized may be added and dispersed in the above-mentioned volatile organic solvent, and then a surfactant may be mixed to continue the dispersion. By dispersing the particles in advance in this way and then adding a surfactant, the surface can be hydrophobized more uniformly. The dispersion liquid after such hydrophobization treatment can be used as it is as a dispersion liquid for dropping on the liquid surface of the lower layer liquid in the dropping step.
When the particles to be hydrophobized are in the state of an aqueous dispersion, a surfactant is added to the aqueous dispersion to hydrophobize the particle surface in the aqueous phase, and then an organic solvent is added to hydrophobize the particles. A method of extracting the oil phase of the finished particles is also effective. The dispersion liquid thus obtained (dispersion liquid in which particles are dispersed in an organic solvent) can be used as it is as a dispersion liquid for dropping onto the liquid surface of the lower layer liquid in the dropping step.
In order to enhance the particle dispersibility of the dispersion liquid, it is preferable to appropriately select and combine the type of organic solvent and the type of surfactant. By using a dispersion liquid having high particle dispersibility, it is possible to suppress the agglutination of particles in a cluster shape, and it becomes easier to obtain a single particle film in which each particle is two-dimensionally densely packed. For example, when chloroform is selected as the organic solvent, it is preferable to use decyltrimethylammonium bromide as the surfactant. In addition, a combination of ethanol and sodium dodecylsulfate, a combination of methanol and sodium 4-octylbenzenesulfonate, a combination of methyl ethyl ketone and octadecanic acid, and the like can be preferably exemplified.
The ratio of the particles to be hydrophobized to the surfactant is preferably in the range of 1/3 to 1/15 times the mass of the surfactant with respect to the mass of the particles to be hydrophobized.
At the time of such hydrophobization treatment, it is also effective to stir the dispersion liquid being treated or to irradiate the dispersion liquid with ultrasonic waves in terms of improving particle dispersibility.

In the hydrophobization treatment using a metal alkoxide, the alkoxy group bonded to the metal atom in the metal alkoxide is hydrolyzed to generate a hydroxyl group. For example, in the case of alkoxysilane, the alkoxysilyl group is hydrolyzed to form a silanol group (Si-OH). Hydrophobization is performed by dehydration condensation of the generated hydroxyl groups with the hydroxyl groups on the particle surface. Therefore, the hydrophobizing treatment using a metal alkoxide is preferably carried out in water. When the alkoxide treatment is performed in water in this way, it is preferable to use a dispersant such as a surfactant in combination to stabilize the dispersed state of the particles before the alkoxide, but depending on the type of the dispersant. Since the hydrophobizing effect of the metal alkoxide may be reduced, the combination of the dispersant and the metal alkoxide is appropriately selected.

As a specific method for making particles hydrophobic with metal alkoxide, first, the particles are dispersed in water, and this is mixed with an aqueous solution containing metal alkoxide (an aqueous solution containing a hydrolyzate of metal alkoxide) from room temperature to 40. The reaction is carried out for a predetermined time, preferably 6 to 12 hours, with appropriate stirring in the range of ° C. By reacting under such conditions, the reaction proceeds appropriately, and a dispersion of sufficiently hydrophobic particles can be obtained. If the reaction proceeds excessively, the silanol groups react with each other and the particles are bonded to each other, and the particle dispersibility of the dispersion liquid is lowered. In the obtained single particle film, the particles are partially aggregated into clusters2. It tends to be more than a layer. On the other hand, if the reaction is insufficient, the hydrophobicity of the particle surface is also insufficient, causing a problem that the particles settle in water in the operation of deploying the particles on the water surface, which will be described later, or the strength of the obtained single particle film is lowered. This is not preferable because it causes wrinkle-like defects.
Of the above-mentioned alkoxysilanes, alkoxysilanes other than amine-based are hydrolyzed under acidic or alkaline conditions, so it is necessary to adjust the pH of the dispersion to acidic or alkaline during the reaction. The method for adjusting the pH is not limited, but the method of adding an aqueous acetic acid solution having a concentration of 0.1 to 2.0% by mass is preferable because it has the effect of stabilizing the silanol group in addition to promoting hydrolysis. ..
The ratio of the particles to be hydrophobized to the metal alkoxide is preferably in the range of 1/3 to 1/100 times the mass of the metal alkoxide with respect to the mass of the particles to be hydrophobized.
After the reaction for a predetermined time, one or more of the above-mentioned volatile organic solvents are added to the dispersion, and the hydrophobicized particles in water are extracted in an oil phase. At this time, the volume of the organic solvent to be added is preferably in the range of 0.3 to 3 times that of the dispersion liquid before the addition of the organic solvent. The dispersion liquid thus obtained (dispersion liquid in which particles are dispersed in an organic solvent) can be used as it is as a dispersion liquid for dropping onto the liquid surface of the lower layer liquid in the dropping step.
In such a hydrophobizing treatment, it is preferable to carry out stirring, ultrasonic irradiation, etc. in order to enhance the particle dispersibility of the dispersion liquid during the treatment. By increasing the particle dispersibility of the dispersion liquid, it is possible to suppress the agglomeration of particles in a cluster shape, and it becomes easier to obtain a single particle film in which each particle is two-dimensionally densely packed.

"Dripping process"
In the dropping step, the above dispersion liquid is dropped on the liquid surface of the lower layer liquid.
The concentration of particles in the dispersion liquid dropped into the lower layer liquid is preferably 1 to 10% by mass. Further, it is preferable that the dropping rate of the dispersion liquid is 0.001 to 0.01 mL / sec. When the concentration of particles in the dispersion liquid and the amount of dropping of the dispersion liquid are in such a range, the particles are partially clustered to form two or more layers, and defect points where no particles do not exist occur. The tendency of widening the pitch of the particles is suppressed, and it is easier to obtain a single particle film in which each particle is densely packed in two dimensions.

In order to further improve the accuracy of the single particle film to be formed, the dispersion liquid before being dropped on the liquid surface is precisely filtered with a membrane filter or the like, and the aggregated particles (secondary particles composed of a plurality of primary particles) existing in the dispersion liquid are used. It is preferable to remove the particles). When microfiltration is performed in advance in this way, it is difficult to generate parts having two or more layers or defective parts in which particles do not exist, and it is easy to obtain a highly accurate single particle film. Assuming that the formed single particle film has a defect portion having a size of several to several tens of μm, a surface pressure sensor that measures the surface pressure of the single particle film and a surface pressure sensor that measures the surface pressure of the single particle film will be described in detail in the transition step described later. Even if an LB trough device equipped with a movable barrier that compresses the single particle film in the liquid surface direction is used, such a defective portion is not detected as a difference in surface pressure, and a highly accurate single particle film cannot be obtained. It gets harder.

"Single particle film forming process"
When the dispersion liquid is dropped on the liquid surface of the lower layer liquid in the dropping step, the solvent which is the dispersion medium is volatilized, the particles are developed as a single layer on the liquid surface of the lower layer liquid, and the particles are densely packed in two dimensions. Can be formed.

The formation of this single particle film is due to the self-organization of the particles. The principle is that when particles gather, surface tension acts due to the dispersion medium that exists between the particles, and as a result, the particles do not exist in a disjointed state, but are densely packed on the liquid surface of the underlying liquid. The single-layer structure is automatically formed. In other words, the formation of a single-layer structure by such surface tension can be said to be mutual adsorption between particles due to lateral capillary force. For example, when three spherical particles of the same particle size gather and contact while floating on the water surface, surface tension acts so as to minimize the total length of the waterline of the particle group, and the three particles are based on an equilateral triangle. Stabilize with the arrangement. If the waterline reaches the apex of the particle group, that is, if the particles go under the liquid surface, such self-organization does not occur and the single particle film is not formed. Therefore, it is important that the particles and the underlayer liquid are made hydrophilic when one is hydrophobic so that the particle group does not go under the liquid surface.
As described above, it is preferable to use water as the underlayer liquid, and when water is used, a relatively large surface free energy acts on it, and a single-layer structure in which particles once generated are densely formed is formed on the liquid surface. It becomes stable and easy to sustain.

The single particle film forming step is preferably carried out under ultrasonic irradiation conditions. When the single particle film forming step is performed while irradiating the water surface with ultrasonic waves from the lower layer liquid, mutual adsorption between the particles is promoted, and a single particle film in which each particle is densely packed in two dimensions with higher accuracy can be obtained.
At this time, the output of the ultrasonic wave is preferably 1 to 1200 W, more preferably 50 to 600 W.
The frequency of the ultrasonic wave is not particularly limited, but for example, 28 kHz to 5 MHz is preferable, and 700 kHz to 2 MHz is more preferable. If the frequency is too high, energy absorption of water molecules starts and a phenomenon of water vapor or water droplets rising from the water surface occurs, which is not preferable for the LB method. If the frequency is too low, the cavitation radius in the underlying liquid becomes large, and bubbles are generated in the water and rise toward the water surface. Accumulation of such bubbles under the single particle film is inconvenient for the LB method because the flatness of the water surface is lost.
When ultrasonic irradiation is performed, a standing wave is generated on the water surface. If the output is too high at any frequency, or if the wave height on the water surface becomes too high due to the tuning conditions of the ultrasonic transducer and transmitter, the single particle film will be destroyed by the water surface wave, so care must be taken.

If the frequency of the ultrasonic waves is appropriately set with the above in mind, it is possible to effectively promote the density of particles without destroying the single particle film that is being formed. In order to perform effective ultrasonic irradiation, it is better to use the natural frequency calculated from the particle size of the particles as a guide. However, when the particle size is as small as 100 nm or less, the natural frequency becomes very high, and it becomes difficult to apply ultrasonic vibration as the calculation result. In such a case, the required frequency can be reduced to a realistic range by performing the calculation on the assumption that the natural vibration corresponding to the mass of the dimer to the 20-mer of the particle is applied. .. Even when ultrasonic vibration corresponding to the natural frequency of the aggregate of particles is applied, the effect of improving the filling rate of particles is exhibited. The ultrasonic irradiation time may be sufficient to complete the rearrangement of the particles, and the required time varies depending on the particle size, the frequency of the ultrasonic waves, the water temperature, and the like. However, under normal production conditions, it is preferably carried out for 10 seconds to 60 minutes, more preferably 3 minutes to 30 minutes.
The advantages obtained by ultrasonic irradiation are, in addition to high-precision densification of particles, the effect of destroying soft agglomerates of particles that are likely to occur during the preparation of nanoparticle dispersions, point defects, line defects, or crystals that have occurred once. It has the effect of repairing metastasis to some extent.

"Transition process"
In the transition step, the single particle film formed on the liquid surface by the single particle film forming step is transferred onto the original plate in the single layer state.
The original plate is the same as the substrate 1 except that a two-dimensional lattice structure is not formed on the surface.
The specific method for transferring the single particle film onto the original plate is not particularly limited. For example, the hydrophobic original plate is kept substantially parallel to the single particle film and lowered from above to form the single particle film. A method of adsorbing and transferring the single particle membrane to the original plate by the affinity between the single particle membrane and the original plate, which are both hydrophobic in contact with each other; There is a method of transferring the single particle film onto the original plate by arranging the single particle film in the horizontal direction, forming the single particle film on the liquid surface, and then gradually lowering the liquid level.
According to these methods, the single particle film can be transferred onto the original plate without using a special device, but even in a single particle film having a larger area, a plurality of particles are densely packed in two dimensions. It is preferable to adopt the so-called LB trough method because it is easy to transfer to the original plate while maintaining the state of the monolayer film (Journal of Materials and Chemistry, Vol.11, 3333 (2001), Journal of Materials and Chemistry, See Vol.12, 3268 (2002), etc.).

In the LB trough method, the original plate is immersed in the lower layer liquid in the water tank in a substantially vertical direction in advance, and in that state, the above-mentioned dropping step and single particle film forming step are performed to form a single particle film. Then, after the single particle film forming step, the single particle film can be transferred onto the original plate by pulling the original plate upward.
Since the single particle film is already formed in a single layer state on the liquid surface of the lower layer liquid by the single particle film forming step, the temperature conditions (temperature of the lower layer liquid) in the transition step and the pulling speed of the original plate are somewhat different. Even if it fluctuates, there is no risk that the single particle film will collapse and become multi-layered in the transition process. The temperature of the lower layer liquid is usually about 3 to 30 ° C., depending on the environmental temperature that fluctuates depending on the season and the weather.
At this time, as a water tank, an LB trough device provided with a surface pressure sensor based on a Wilhelmy plate or the like for measuring the surface pressure of the single particle film and a movable barrier for compressing the single particle film in the direction along the liquid surface. Can be used to transfer a larger area single particle film onto the original plate more stably. According to such a device, the single particle film can be compressed to a preferable diffusion pressure (density) while measuring the surface pressure of the single particle film, and can be moved toward the substrate at a constant speed. .. Therefore, the transfer of the single particle film from the liquid surface to the original plate proceeds smoothly, and troubles such as only a small area single particle film being transferred to the original plate are unlikely to occur.
The preferred diffusion pressure is 5 to 80 mNm ^-1 , more preferably 3 to 40 mNm ^-1 . With such a diffusion pressure, it is easy to obtain a single particle film in which each particle is densely packed in two dimensions with higher accuracy. The speed at which the original plate is pulled up is preferably 0.5 to 20 mm / min. The LB trough device can be obtained as a commercially available product.

"Fixing process"
By performing a fixing step of fixing the single particle film transferred onto the original plate in the transfer step, the particles constituting the single particle film move on the surface of the original plate or the single particle film during the dry etching process described later. Can be suppressed from peeling off, and the original plate can be etched more stably and with high accuracy.
Examples of the fixing step method include a method using a binder and a sintering method.
In the method using a binder, the binder solution is supplied to the surface of the original plate on which the single particle film is formed, and permeates between the particles constituting the single particle film and the original plate.
As the binder, a metal alkoxide exemplified above as a hydrophobic agent, a general organic binder, an inorganic binder, or the like can be used.
The amount of the binder used is preferably 0.001 to 0.02 mass times the mass of the single particle film. Within such a range, the particles can be sufficiently fixed without causing a problem that the amount of the binder is too large and the binder is clogged between the particles, which adversely affects the accuracy of the single particle film. When a large amount of the binder solution has been supplied, after the binder solution has permeated, a spin coater may be used or the original plate may be tilted to remove the excess of the binder solution.
After the binder solution has permeated, heat treatment may be appropriately performed according to the type of binder. When the metal alkoxide is used as a binder, it is preferably heat-treated at 40 to 80 ° C. for 3 to 60 minutes.

When the sintering method is adopted, the original plate on which the single particle film is formed may be heated to fuse each particle constituting the single particle film to the original plate.
The heating temperature may be determined according to the material of the particles and the material of the original plate. In the case of particles having a particle size of 1 μm or less, the interfacial reaction starts at a temperature lower than the original melting point of the material constituting the particles, so that the sintering is completed on the relatively low temperature side. If the heating temperature is too high, the fused area of the particles becomes large, and as a result, the shape of the single particle film may change, which may affect the accuracy.
When heating is performed in air, the original plate and particles may be oxidized depending on the material. For example, when a silicon substrate is used as the original plate and this is sintered at 1100 ° C., a thermal oxide layer is formed on the surface of the substrate with a thickness of about 200 nm. Therefore, in the dry etching process described later, it is necessary to set the etching conditions in consideration of the possibility of such oxidation.

<Dry etching process>
In the dry etching step, for example, the original plate is dry-etched using the single particle film as an etching mask under the condition that both the particles and the original plate are substantially etched.
When dry etching is performed in this way, each particle constituting the single particle film is etched, the particle size of each particle gradually decreases, and there is a gap in the portion where the particles were in contact with each other before dry etching. It is formed and the particles are not in contact with each other. Further, the etching gas passes through the gap between the particles and reaches the surface of the original plate, and the surface of the original plate located below the gap is etched to form a recess. The portion covered with the particles remains unetched, and this portion becomes the convex portion 3c. As a result, the substrate 1 is obtained.
Before the original plate is dry-etched, the particles may be dry-etched under the condition that the original plate is not substantially etched.

By adjusting the dry etching conditions such as pressure, plasma power, bias power, etching gas type, etching gas flow rate, etching time, etc., the thickness of the convex portion 3c (occupied volume in the surface layer: filling factor), the convex portion 3c Height (depth of recess) etc. can be adjusted.

The etching gas can be appropriately selected from known etching gases according to the material of the particles and the substrate so that both the particles and the original plate can be etched.
For example, when the original plate is glass and the particles are silica (SiO ₂ ), Ar, SF ₆ , F ₂ , CF ₄ , C ₄ F ₈ , C ₅ F ₈ , C ₂ F ₆ , C ₃ F ₆ , C ₄ F ₆ , CHF ₃ , CH ₂ F ₂ , CH ₃ F, C ₃ F ₈ , Cl ₂ , CCl ₄ , SiCl ₄ , BCl ₂ , BCl ₃ , BC ₂ , Br ₂ , Br ₃ , HBr, CBr F ₃ , HCl, CH ₄ , NH ₃ , O ₂ , H ₂ , N ₂ , CO, CO _2, etc. can be used.
When the original plate S is quartz and the particles are silica, Ar, CF _4, or the like can be used.
When the original plate is sapphire and the particles are silica, Cl ₂ , BCl ₃ , SiCl ₄ , HBr, HI, HCl and the like can be used.
One type of etching gas may be used alone, or two or more types may be used in combination. The etching conditions can be easily adjusted by the mixing ratio of two or more kinds of etching gases.
The etching gas may be diluted with a gas other than the etching gas.

The dry etching is preferably performed by anisotropic etching in which the etching rate in the vertical direction is higher than that in the horizontal direction of the original plate. As the etching apparatus that can be used, if it is capable of anisotropic etching such as a reactive ion etching apparatus and an ion beam etching apparatus and can generate a bias electric field of about 20 W at the minimum, plasma generation is generated. There are no particular restrictions on the specifications such as the method, electrode structure, chamber structure, and frequency of the high-frequency power supply.

The etching selectivity (etching rate of the original plate / etching rate of the single particle film) in dry etching is not particularly limited, and each etching condition (material of particles constituting the single particle film, material of the original plate, type of etching gas, etc.) It can be adjusted by bias power, antenna power, gas flow rate, pressure, etching time, etc.).

The dry etching of the original plate may be completed when the particles constituting the single particle film disappear, or may be completed before the particles disappear.
When the dry etching of the original plate is completed before the particles disappear, the particles remaining on the formed substrate 1 are removed after the dry etching of the original plate.
Examples of the particle removing method include a chemical removing method using an etchant having etching resistance to the particles and etching resistance to the substrate 1, a physical removing method using a brush roll washing machine or the like, and the like.

The original version is obtained as described above.
The transfer product of the original plate is obtained by transferring the two-dimensional lattice structure on the surface of the original plate to another original plate at least once. When the number of transfers is an odd number, a transferred product having a two-dimensional lattice structure in which the two-dimensional lattice structure on the surface of the original plate is inverted can be obtained. When the number of transfers is an even number, a transferred product having a two-dimensional lattice structure having a shape similar to the two-dimensional lattice structure on the surface of the original plate can be obtained.
For example, when the two-dimensional lattice structure on the surface of the original plate is transferred to the mold (mold or stamper) (first transfer), and then the two-dimensional lattice structure of the mold is transferred (second transfer), the two-dimensional lattice structure on the surface of the original plate is transferred. A transferred product having a two-dimensional lattice structure having a shape similar to that of the dimensional lattice structure can be obtained.
As a method for transferring the two-dimensional lattice structure of the original plate S to a mold (mold or stamper), for example, an electroforming method as disclosed in Japanese Patent Application Laid-Open No. 2009-158478 is preferable.
Examples of the method for transferring the two-dimensional lattice structure of the mold include a nanoimprint method, a heat press method, an injection molding method, a UV embossing method and the like as disclosed in Japanese Patent Application Laid-Open No. 2009-158478. Above all, the nanoimprint method is suitable for transferring a fine two-dimensional lattice structure.

(Action effect)
In the analysis substrate 10 of the present embodiment, when it is used for spectroscopic measurement, it is localized by incident light between the metal film 3 and the metal nanoparticles 5 and between the adjacent metal nanoparticles 5. Mold surface plasmon resonance is generated, and a nonlinear optical electric field enhancement effect can be obtained by superimposing electric fields. Further, by having a two-dimensional lattice structure on the surface of the metal film 3 which is a continuous film, it is possible to obtain an electric field enhancing effect by propagating surface plasmon resonance. By combining localized surface plasmon resonance in 2 to 3 kinds of metal gaps and propagation type surface plasmon resonance by one kind of metal lattice structure, optical analysis utilizing the electric field enhancing effect can be performed with high sensitivity.
In particular, when the metal film 3 is the metal film 3A of the aspect A, the electric field enhancement due to the localized surface plasmon resonance can be generated even in the non-deposition region G of the metal film 3, and the optical field enhancement utilizing the electric field enhancement can be generated. Target analysis can be performed with higher sensitivity.
The analysis substrate 10 is also excellent in productivity. For example, as shown in the production method (I), it can be produced simply by depositing a metal on the substrate 1B, further applying a metal nanoparticle dispersion liquid, and drying. In addition, it is not necessary to use a large amount of metal to form a structure capable of generating an electric field enhancement due to localized surface plasmon resonance, and the raw material cost can be suppressed.
Since the above effects are obtained, the analysis substrate 10 is useful for optical analysis utilizing the electric field enhancement by surface plasmon resonance. Examples of such an optical analysis method include the same methods as described above.

Since the above effects are obtained, the analysis substrate 10 is useful for optical analysis utilizing the electric field enhancing effect due to surface plasmon resonance.
Examples of such an optical analysis method include Raman spectroscopy, infrared spectroscopy, fluorescence analysis and the like. Among these, Raman spectroscopy is preferable.
The Raman spectroscopic analysis method is an analytical means for analyzing the structure at the molecular level by observing Raman scattering in which the vibrational energy of the molecule is shifted with respect to the incident light when the sample is irradiated with light. The obtained Raman spectrum is a vibration spectrum based on the vibration of molecules, similar to the infrared spectrum obtained by infrared spectroscopy. The vertical axis is scattering intensity (Intensity), and the horizontal axis is Raman shift (cm ^-1 ). It is represented by. The same functional group vibration mode is detected at the same frequency in Raman spectroscopic analysis and infrared spectroscopic analysis, but unlike infrared spectroscopic analysis, Raman spectroscopic analysis can measure aqueous samples, so it is a living body. It has the advantage that pretreatment of the sample is not required in the analysis of samples, food samples, etc. However, the usual Raman spectroscopic analysis method that does not enhance the surface electric field has a drawback that the intensity of Raman scattered light is very weak.
The surface-enhanced Raman spectroscopic analysis method is a Raman spectroscopic analysis method using SERS. In the analysis substrate 10, the Raman scattering (Stokes scattering and anti-Stokes scattering) intensity of the molecules adsorbed on the surface of the analysis substrate 10 can be remarkably enhanced by the SERS effect, so that high-sensitivity spectroscopic analysis becomes possible. .. In fact, since it is possible to detect a spectrum peculiar to a substance even in a dilute trace sample, it is useful for environmental measurement, measurement of a trace amount of biomarker, detection of biological / chemical weapons, and the like.

Although the present invention has been described above with reference to embodiments, the present invention is not limited to these embodiments. Each configuration in the above embodiment and a combination thereof are examples, and the configuration can be added, omitted, replaced, and other changes are possible without departing from the spirit of the present invention.

For example, FIG. 4 shows an example in which the shape of the non-deposited region G in the top view is strip-shaped, but the shape of the non-deposited region G in the top view is not limited to this. The shape may be, for example, a circular shape, a rectangular shape, a tree shape, an indefinite shape, or the like.
Although the shape, size, and distribution of each of the plurality of non-deposited regions G are random (not constant), the shape, size, and size of each of the plurality of non-deposited regions G may be constant. A plurality of non-deposited regions G may be regularly arranged.
Although FIG. 5 shows an example in which the metal surface 3a surrounding the non-deposited region G is an inclined surface, the metal surface 3a may be an inclined surface. Further, the metal surface 3a may be a smooth surface or an uneven surface.
When the metal film is a metal film formed by a method of depositing metal on the first surface of a substrate (sputtering method, vacuum deposition method, etc.), the metal surface surrounding the non-deposited region G is locally inclined. It is a surface and is often an uneven surface.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples. Example 2 is a reference example.
The measurement method used in each example is shown below. The method for measuring the height and pitch of the convex portion of the periodic uneven structure is as described above.

(Sheet resistance on the surface of metal film)
Sheet resistance was measured with a resistivity meter (Loresta AX MCP-T370) used in a general continuity test. Since the metal film constituting the metal structure is very thin, the resistivity meter probe uses a PSP option probe (MCP-TP06P) 1.5 mm between pins for thin film measurement, and an average value of n = 5 or more is used. The measured value (Ω / □) was acquired.

(Distance between opposing metal surfaces via the non-deposition region G)
The metal film 3 is composed of a sea-island structure composed of a metal film and non-deposited regions G scattered in the metal film (islands (gap in the non-deposited region G) with respect to the sea (metal = film-formed region) of the sea-island structure). ), And the distance between the metal surfaces 3a was measured by the following measuring method.
That is, SEM images of a region of 0.6 μm × 0.45 μm at a magnification of 200,000 times are obtained from five locations on the surface of the metal film 3 separated from each other by 100 μm or more, and the non-deposited region G portion is measured in each SEM image. Do the length. Since the outline of the SEM image at this magnification may be unclear, use Adobe Photoshop or image processing software having the same function after acquiring the SEM image to enhance the contrast of the image or to increase the shade of the image by 2. Value it to facilitate length measurement. Here, the gap in the minor axis direction of the non-deposited region G portion is called a nanogap. Measurement gaps in the nanogap, first two arguments diagonal L _D in the SEM image obtained as described above, all the non-deposition region G moiety regard measuring the gap width in the minor axis direction of the diagonal lines do. The length measurement is performed at the intersection where the diagonal line intersects each non-deposited region G. Specifically, the point P which is 1/2 of the intersection distance formed by the diagonal line intersecting the non-deposited region G is defined and drawing a straight line L _G that 2 divides the non-deposition region G in the shortest distance, while as the point P, and measuring the distance I _G of the last straight line L _G passes through the non-deposition region G. The measurement of I _G performs the SEM images of 5 places above, the average value I _GAVE nanogap all non film formation region G ones determined an average value of the measured values. This average value I _GAVE is defined as the distance between the metal surfaces 3a.

(Thickness of metal film (average thickness of film formation area))
The thickness of the metal film 3 (average thickness of the film-forming region) was measured by the method described above. That is, a very fine scratch (scratch) is made on the metal film 3 formed on the substrate with the tip of a sharp knife, and the area including the scratch is covered with a stylus type step meter (fine shape measuring machine ET4000A). , Kosaka Laboratory), and the average thickness of the metal film 3 was measured by a method of determining the average height difference between the bottom surface of the scratch (the part where the substrate is exposed) and the surface of the metal film 3. ..
Although a stylus type step system was used in the examples, the average height difference between the exposed portion of the substrate and the surface of the metal film 3 was obtained by acquiring an atomic force microscope (AFM) image. The same result can be obtained even if it is obtained.

(Average primary particle size of metal nanoparticles)
The average primary particle size of the metal nanoparticles was measured by the method described above. That is, using SEM, the surface of the analysis substrate is observed at a magnification of 200,000 times, the primary particle diameter of the metal nanoparticles is measured, the average value of n = 20 is calculated, and the value is used as the average primary particle diameter. And said.

(Shortest distance between two adjacent metal nanoparticles)
The shortest distance between two adjacent metal nanoparticles was measured by the method described above. That is, using SEM, the surface of the analysis substrate is observed at a magnification of 200,000, the gap between two adjacent metal nanoparticles in the image is actually measured, the average value of n = 20 is calculated, and the value is calculated. The shortest distance was used.

(Measurement of Raman scattering intensity)
A Raman spectrophotometer (Almega XR, Thermo Fisher Scientific Co., Ltd.) was added by dropping 5 μL of a 4,4'-bipyridyl aqueous solution having a concentration of 100 μM on the surface of the analysis substrate (the surface provided with the metal film, metal nanoparticles, etc.). Raman spectra were measured using each. Using a laser with an excitation wavelength of 780 nm and an output of 10 mW as a light source, each measured value was compared with an intensity of ^{a detection peak of 1607 cm-1.} The Raman conditions were a laser output of 100%, an aperture of a pinhole with a diameter of 100 μm, and an exposure count of 64 times.

(Example 1)
An analytical substrate having the same configuration as the analytical substrate 10 shown in FIG. 1 and in which the metal film 3 is the metal film 3A of aspect A was manufactured by the following procedure.
Colloidal silica particles having a particle size of 600 nm were coated on a quartz substrate with a single layer by the LB method described below. First, N-phenyl-3-aminopropyltrimethoxysilane was added to the silica particle slurry as a hydrophobizing agent, and hydrophobization was carried out at a reaction temperature of 40 ° C. Then, the hydrophobized silica particles were extracted in an oil layer using a mixed solvent of ethanol: chloroform = 30:70. Next, the hydrophobic particle slurry was dropped onto the surface of the lower water at 21 ° C. and pH 7.2 to form a particle monolayer film on the water surface. Further, while compressing the particle monolayer film with a barrier, the clean and flat quartz substrate pre-immersed in water is gradually pulled up at 5 mm / min, and the particle monolayer film on the water surface is transferred onto the quartz substrate. rice field. Then, using a dry etching apparatus (ME510I manufactured by Tokyo Electron Limited) _{, dry etching was performed under the conditions of 1.2 Pa, 2000/1800 W, Cl 2} = 80 sccm, 100 sec, and the structural period (pitch) was 600 nm and the structural height (structure height) ( A periodic uneven structure of 52 nm (vertical distance from the center point of the three particles to the top of the structure) was obtained. Furthermore, using a sputtering device (ion sputtering device E-1030, Hitachi High-Technologies Corporation), an Au thin film was applied onto this periodic uneven structure at a pressure of 6 to 8 Pa, a current value of 15 mA, and a film formation rate of 11.6 nm / min. A film was formed to a thickness of 8 nm. Finally, Au nanoparticles were dispersed and arranged on the substrate by repeating the steps of spray-coating and drying the Au nanoparticle dispersion liquid (particle size 20 nm) on the Au thin film three times.
FIG. 6 shows an SEM image of the obtained analytical substrate.

(Example 2)
An analytical substrate having the same structure as the analytical substrate 10 shown in FIG. 1 and in which the metal film 3 is the metal film 3B of aspect B was manufactured by the following procedure.
Colloidal silica particles having a particle size of 600 nm were coated on a quartz substrate with a single layer by the LB method described below. First, N-phenyl-3-aminopropyltrimethoxysilane was added to the silica particle slurry as a hydrophobizing agent, and hydrophobization was carried out at a reaction temperature of 40 ° C. Then, the hydrophobized silica particles were extracted in an oil layer using a mixed solvent of ethanol: chloroform = 30:70. Next, the hydrophobic particle slurry was dropped onto the surface of the lower water at 21 ° C. and pH 7.2 to form a particle monolayer film on the water surface. Further, while compressing the particle monolayer film with a barrier, the clean and flat quartz substrate pre-immersed in water is gradually pulled up at 5 mm / min, and the particle monolayer film on the water surface is transferred onto the quartz substrate. rice field. Then, using a dry etching apparatus (ME510I manufactured by Tokyo Electron Limited) _{, dry etching was performed under the conditions of 1.2 Pa, 2000/1800 W, Cl 2} = 80 sccm, 100 sec, and the structural period (pitch) was 600 nm and the structural height (structure height) ( A periodic uneven structure of 52 nm (vertical distance from the center point of the three particles to the top of the structure) was obtained. Further, using a sputtering apparatus (ion sputtering apparatus E-1030, Hitachi High-Technologies Corporation), an Au thin film was applied onto this periodic uneven structure at a pressure of 6 to 8 Pa, a current value of 15 mA, and a film formation rate of 11.6 nm / min. A film was formed to a thickness of 0 nm. Finally, Au nanoparticles were dispersed and arranged on the substrate by repeating the steps of spray-coating and drying the Au nanoparticle dispersion liquid (particle size 20 nm) on the Au thin film three times.
FIG. 7 shows an SEM image of the obtained analytical substrate.

(Comparative Example 1)
A flat quartz substrate having a clean surface with no metal film or metal particles attached to the surface was prepared.

(Comparative Example 2)
A flat quartz substrate having a clean surface with no metal film or metal particles attached to the surface was prepared. Then, by repeating the process of spray-coating the Au nanoparticle dispersion liquid (particle size 20 nm) on the substrate and drying it three times, Au nanoparticles are dispersed and arranged on the substrate at the same spray density as in Examples 1 and 2. bottom.

(Comparative Example 3)
Colloidal silica particles having a particle size of 600 nm were coated on a quartz substrate with a single layer by the LB method described below. First, N-phenyl-3-aminopropyltrimethoxysilane was added to the silica particle slurry as a hydrophobizing agent, and hydrophobization was carried out at a reaction temperature of 40 ° C. Then, the hydrophobized silica particles were extracted in an oil layer using a mixed solvent of ethanol: chloroform = 30:70. Next, the hydrophobic particle slurry was dropped onto the surface of the lower water at 21 ° C. and pH 7.2 to form a particle monolayer film on the water surface. Further, while compressing the particle monolayer film with a barrier, the clean and flat quartz substrate pre-immersed in water is gradually pulled up at 5 mm / min, and the particle monolayer film on the water surface is transferred onto the quartz substrate. rice field. Then, using a dry etching apparatus (ME510I manufactured by Tokyo Electron Limited) _{, dry etching was performed under the conditions of 1.2 Pa, 2000/1800 W, Cl 2} = 80 sccm, 100 sec, and the structural period (pitch) was 600 nm and the structural height (structure height) ( A periodic uneven structure of 52 nm (vertical distance from the center point of the three particles to the top of the structure) was obtained. Furthermore, using a sputtering device (ion sputtering device E-1030, Hitachi High-Technologies Corporation), an Au thin film was applied onto this periodic uneven structure at a pressure of 6 to 8 Pa, a current value of 15 mA, and a film formation rate of 11.6 nm / min. A film was formed to a thickness of 2 nm.

The Raman scattering intensity was measured using the analytical substrates of Examples 1 and 2 and Comparative Examples 1 to 3. The results are shown in Table 1.

Raman scattering could not be detected on the analytical substrates of Comparative Example 1 and Comparative Example 2. Further, in the analytical substrate of Comparative Example 3, Raman scattering could be detected, but the intensity was lower than the intensity of all the examples.
On the other hand, in the analytical substrates of Examples 1 and 2, Raman scattering at a sample concentration of 100 μM was obtained with high intensity, and Raman scattering could be detected even in a sample having a sample concentration of 1 nM.

1 Substrate 3,3A Metal film 5 Metal nanoparticles 10 Analytical substrate G Non-deposition area

Claims (2)

A substrate having a two-dimensional lattice structure in which at least the first surface is made of a dielectric or a semiconductor and a plurality of concave portions or convex portions are periodically arranged two-dimensionally on the first surface.
A metal film provided on the first surface of the substrate and having a surface sheet resistance of 3 to 5000 Ω / □ at 25 ° C.
A plurality of metal nanoparticles having an average primary particle size of 5 to 100 nm dispersed and arranged on the metal film, and
Equipped with a,
A plurality of non-formed metal films in which the metal film is provided in the metal film as an island-shaped gap having a length of 1 μm or less in the major axis direction, in which no metal is present and the first surface of the substrate is exposed. Ru continuous film der having a membrane area substrate for analysis. The analytical substrate according to claim 1, wherein the two-dimensional lattice structure is a triangular lattice structure or a cubic lattice structure.

Images