WO2019146692A1 - Analysis substrate - Google Patents

Abstract

This analysis substrate (10) comprises: a substrate (1) having at least a first surface (1a) that comprises a dielectric or a conductor and having a two-dimensional lattice structure that has a plurality of recessed sections or protruding sections periodically arranged two dimensionally on the first surface (1a); a metal membrane (3) provided upon the first surface (1a) of the substrate (1) and having a surface sheet resistance at 25°C of no more than 5,000 Ω/□; and a plurality of metal nanoparticles (5) arranged dispersed upon the metal membrane (3) and having an average primary particle diameter of 5–100 nm.

Description

Analytical substrate

The present invention relates to a substrate for analysis.
Priority is claimed on Japanese Patent Application No. 2018-010683, filed January 25, 2018, the content of which is incorporated herein by reference.

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

For example, the followings have been proposed as analytical substrates utilizing electric field enhancement by surface plasmon resonance.
(1) A substrate having a nanoperiodic structure in which a plurality of depressions or a plurality of projections are arranged in a lattice at a predetermined specific lattice spacing to generate surface plasmon resonance, and formed on the surface of the nanoperiodic structure The signal amplification apparatus for Raman spectroscopy analysis provided with 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 It has a periodic arrangement capable of exciting propagating surface plasmons propagating through the interface between the metal layer and the dielectric layer, and the propagating surface plasmons and localized surface plasmons excited by the metal particles are electromagnetic. Interact with each other, and the resonance wavelength of each surface plasmon is different, and in the spectrum of the reflected light when the electric field enhancing element is irradiated with white light, the half bandwidths of the first absorption region and the second absorption region satisfy a specific relationship. An electric field enhancing element in which the wavelength of excitation light of the electric field enhancing element is included in the range of the second absorption region (Patent Document 2).

JP, 2015-232526, A JP, 2015-212626, A

However, the analysis substrates of (1) to (2) may not have sufficient sensitivity.
The device of Patent Document 1 utilizes propagating surface plasmons, and thus has the advantage that the variation of the electric field distribution on the nano-periodic structure is small, but the enhancement effect is due to the electric field enhancement solely by the propagating surface plasmons. Has the disadvantage of being low.
On the other hand, in the electric field enhancing element of Patent Document 2, the propagating surface plasmon and the localized surface plasmon are combined, the electric field distribution is homogenized by the propagating surface plasmon, and the localized electric surface plasmon is enhanced. By doing this, 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, due to the presence of the dielectric layer between the metal layer and the metal particles, there is a disadvantage that the molecule to be measured of the sample can not approach the metal film surface with the highest electric field enhancing effect of the propagating surface plasmon. In addition, since the metal particles are arranged in the arrangement necessary for exciting the propagating surface plasmon, the distance between the particles is required to utilize the electric field enhancement utilizing the gap between the metal particles having a large effect as the localized surface plasmon. Too large is also mentioned as a disadvantage.

An object of the present invention is to provide a substrate for analysis which can carry out optical analysis with high sensitivity utilizing electric field enhancement by surface plasmon resonance.

The present invention has the following aspects.
[1] A substrate having a two-dimensional lattice structure in which at least a first surface is made of a dielectric or a semiconductor, and a plurality of recesses or projections are periodically arranged in two dimensions on the first surface,
A metal film provided on the first surface of the substrate and having a surface sheet resistance at 25 ° C. of 5000 Ω / □ or less;
A plurality of metal nanoparticles dispersed on the metal film and having an average primary particle diameter of 5 to 100 nm;
An analytical substrate comprising:
[2] The analytical substrate of [1], wherein the two-dimensional lattice structure is a triangular lattice structure or a square lattice structure.
[3] A plurality of the metal films are provided in the form of island-like gaps having a length of 1 μm or less in the major axis direction in the metal film, and a plurality of metal is not present and the first surface of the substrate is exposed The analytical substrate of [1] or [2], which has a non-film formation region of

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

It is a sectional view showing typically the substrate for analysis of one embodiment of the present invention. It is an upper side figure which shows typically the board | substrate for analysis which concerns on an example of embodiment shown in FIG. 1 (however, illustration of the metal nanoparticle was abbreviate | omitted). It is a perspective view of the substrate for analysis shown in FIG. It is an enlarged top view which shows typically the surface by the side of the metal film of the board | substrate for analysis which concerns on an example of embodiment shown in FIG. 1 (however, illustration of a metal nanoparticle was abbreviate | omitted). FIG. 5 is a partial cross-sectional view schematically showing a IV-IV cross-section in FIG. 4 (however, illustration of metal nanoparticles is omitted). It is a scanning electron microscope image of the board | substrate for analysis obtained in Example 1. FIG. 7 is a scanning electron microscope image of the analysis substrate obtained in Example 2.

Hereinafter, an analysis substrate of the present invention will be described by showing an embodiment with reference to the attached drawings.
FIG. 1 is a cross-sectional view schematically showing an analysis substrate according to a 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, the illustration of the metal nanoparticles is omitted in FIGS.
The analysis substrate 10 of the present embodiment includes a substrate 1, a metal film 3 provided on the first surface 1 a of the substrate 1, and a plurality of metal nanoparticles 5 dispersed 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 of the conductor layer, the dielectric layer, and the semiconductor layer may be stacked such that the first surface is a dielectric or a semiconductor. It may be a multilayer substrate. The dielectric or semiconductor is not particularly limited, and may be a known material in applications such as a substrate for analysis.
Typically, a substrate made of only a dielectric or a semiconductor is used as the substrate 1 and, for example, a quartz substrate, various glass substrates such as alkali glass and non-alkali glass, sapphire substrate, silicon (Si) substrate, silicon carbide Examples include substrates made of inorganic substances such as SiC), and substrates made of organic substances such as polymethyl methacrylate, polycarbonate, polystyrene, polyolefin resin, and 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 measurement method established in JIS B7507.

The two-dimensional lattice structure of the first surface 1 a is for providing a two-dimensional lattice structure on the surface of the metal film 3, and is set according to the 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 electric field enhancement by surface plasmon resonance, and examples thereof include gold, silver, aluminum, copper, platinum, alloys of two or more of these, and the like.

The sheet resistance of the surface of the metal film 3 at 25 ° C. (hereinafter, “sheet resistance of the surface at 25 ° C.” may simply be referred to as “sheet resistance of the surface”) is 5000 Ω / □ or less, and 3 to 5000 Ω. / □ is preferable, 3 to 500 Ω / □ is more preferable, and 3 to 300 Ω / □ is the most preferable. The sheet resistance of the surface of the metal film 3 being equal to or less than the upper limit value indicates that the metal film 3 is a continuous film. When the sheet resistance of the surface of the metal film 3 is within this range, the metal film 3 is not completely divided even though it has nanogaps due to the non-film formation region G described later. When the metal film 3 has the non-film formation region G, the sheet resistance of the surface of the metal film 3 is less than or equal to the above upper limit value because the distance between the metal surfaces 3 a facing each other via the non-film formation region G is In 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 does not become 5000 Ω / □ or less. Even if the metal film 3 partially has the non-film formation region G, the metal film 3 can induce propagation type surface plasmons, which will be described later, because the film is a continuous film as a whole. It becomes easy to obtain the nonlinear optical effect by superposition.
The sheet resistance (Ω / □) of the surface of the metal film 3 is a value at 25 ° C. Specifically, the sheet resistance is the electrical resistance (Ω) when current flows from one end to the opposite end of a square area of any size on the surface of the metal film 3 under the condition of 25 ° C. . The details are as shown in Examples described later.

The metal film 3 has a two-dimensional lattice structure that follows the first surface 1 a of the substrate 1.
Here, “follow” 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 1 a of the substrate 1 Indicates that.

When the surface of the metal film 3 which is a continuous film has a two-dimensional lattice structure, electric field enhancement can be generated on the surface of the metal film 3 by propagating surface plasmon resonance.
Here, the “two-dimensional lattice structure” is a periodic uneven structure in which a plurality of convex portions or concave portions are periodically arranged in two dimensions. Two-dimensionally arranged indicates that the plurality of convex portions or concave portions are arranged in two or more directions.
Note that a periodic uneven structure in which a plurality of projections or depressions are periodically arranged in one dimension is also referred to as a one-dimensional lattice structure. The arrangement in one dimension indicates that the arrangement direction of the plurality of projections or depressions is one direction.
The propagation type surface plasmon of the metal surface is a surface electromagnetic field accompanied by a compressional wave of free electrons generated by light (excitation light such as a laser used in Raman spectroscopy) incident on the metal surface. When the metal surface is flat, propagating surface plasmon resonance is not induced because the dispersion curve of the surface plasmon present on the metal surface does not cross the dispersion line of light. When a periodic uneven structure exists on the metal surface, the dispersion straight line of light (diffracted light) diffracted by this periodic uneven structure intersects with the dispersion curve of the surface plasmon, and the propagating surface plasmon resonance is induced .
As the arrangement direction of the plurality of convex portions or concave portions in the periodic concavo-convex structure is larger, there are more conditions under which diffracted light can be obtained, and propagation surface plasmon resonance can be induced with high efficiency. By having a two-dimensional lattice structure as a 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 (concave portions) or convex lines (convex portions) are arranged in parallel). Optical analysis using electric field enhancement by surface plasmon resonance can be performed more sensitively than in some cases.

As a preferable two-dimensional lattice structure, a tetragonal lattice structure in which the arrangement direction is two directions and the crossing angle is 90 °, and the arrangement direction is three directions and the crossing angle is 60 ° (also referred to as a hexagonal lattice). And the like. 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 sine wave 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, a shape obtained by inverting the shape of the convex portion mentioned above.
As a two-dimensional lattice structure, a triangular lattice structure is preferable because it can induce propagating surface plasmon resonance with higher efficiency.

The two-dimensional lattice structure of the surface of the metal film 3 according to an example of the present embodiment is a triangular lattice structure constituted of a plurality of truncated cone-shaped convex portions 3c as shown in FIGS.
The height of the convex portion 3c is preferably 15 to 150 nm, and more preferably 30 to 80 nm. If the height of the convex portion 3c is equal to or more than the lower limit value 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. If the height of the convex portion 3c is equal to or less than the upper limit value of the above range, the metal film 3 tends to be a continuous film.
Also in the case where 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 recesses, the preferred depth of the recesses is approximately the same as the preferred height of the protrusions 3c. Precisely, the optimum value of the height of the convex portion 3c is determined by the volume fraction and the dielectric constant of the convex portion 3c which interacts with the electromagnetic field by the surface plasmon.

The height of the convex portion 3c is the distance in the vertical direction to the average value of the top surfaces of the truncated cones of the three convex portions starting from the central point equidistant from the adjacent three convex portions as AFM (atomic force microscope Measured by) etc. For measurement, five two-dimensional lattice structure surfaces separated by 100 μm or more are used. AFM images of 5 μm × 5 μm are acquired for these five measurement regions, and the above-mentioned three-point center depths of nine locations randomly measured for each AFM image are measured. Since the AFM probe may generate anisotropy in the image depending on the scan direction, as shown in Fig. 2, the length measurement is performed by creating profile images in three directions D _M1 to D _M3 and in each direction Perform at three measurement points, for a total of nine measurement points. The average value of the measured values obtained at the nine measurement points is taken as the measured value of one measurement area, the measured values of the five measurement areas are similarly determined, and the average of the measured values of the five measurement areas is calculated. The height of the projection 3c is obtained.
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 portions 3 c on the main surface of the metal film 3 (Because the actual lattice arrangement has some distortion, Not necessarily orthogonal).
The heights of the projections of the other shapes and the depths of the recesses are also measured by the same measurement method.

The pitch Λ of the convex portions 3c in the arrangement direction of the convex portions 3c is designed to correspond to the wavelength λ _i of the incident light (excitation light). Assuming that the wave number of the incident light is k _i (k _i = 2π / λ _i ), the real part of the relative dielectric constant of metal at k _i is ε ₁ , and the real part of the relative dielectric constant of the specimen is ε ₂ . The wavenumber k _spp is given by the following equation 1:
_{k spp = k i ((ε} 1 × ε 2) / (ε 1 + ε 2)) 0.5 ( Equation 1)
Can be obtained schematically. Since the wavelength λ _{spp of the} surface plasmon is an inverse number of k _spp and the convex portions 3 c have a triangular lattice arrangement, the pitch Λ of the convex portions 3 c is expressed by the following equation 2:
Λ = (2 / √3) × λ _spp (Expression 2)
Determined by Formula 1 and Formula 2 are general.
According to the above calculation method, for example, when the wavelength λ _{i of} incident light is 785 nm, the metal constituting the convex portion 3c is gold (Au), and the sample is an aqueous solution (ε ₂ 1.31.33),
k _spp = 11.8 μm ⁻¹ , Λ = 655 nm
It becomes. Similarly, for example, when the wavelength λ _{i of} incident light is 633 nm, the metal forming the convex portion 3c is gold (Au), and the sample is a dried organic substance (ε ₂ 2.22.25),
k _spp = 16.6 μm ⁻¹ , Λ = 438 nm
It is. When a laser is used for incident light, its wavelength distribution is extremely narrow, and therefore, the convex portions 3c may be fabricated as close as possible to the pitch Λ. When the two-dimensional lattice arrangement is a square lattice or one-dimensional lattice arrangement (line and 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 ones corresponding to various wavelengths such as 785, 633, 532, 515, 488, and 470 nm. Generally, it is preferable to use gold (Au) for a light source larger than the wavelength of about 500 nm, and a light source smaller than the wavelength about 500 nm or so as a metal species constituting the sea-island structure, metal nanoparticles and periodic uneven structure. It is preferable to use silver (Ag), but metal enhanced species other than gold (Au) and silver (Ag) may be able to obtain the surface enhanced Raman scattering effect, which is not necessarily limited to the above.
The preferred pitch is the same as in the case where the projections 3c have other shapes. When the two-dimensional lattice structure of 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 protrusions 3c.

The pitch of the convex portions 3c is obtained by measuring the horizontal distance between the center points of two adjacent truncated conical projections by AFM (atomic force microscope) or the like. For measurement, five two-dimensional lattice structure surfaces separated by 100 μm or more are used. AFM images of 5 μm × 5 μm are acquired for these five measurement regions, and the distance between the two points of nine locations randomly extracted for each AFM image is measured. Since the AFM probe may cause anisotropy in the image depending on the scan direction, as shown in Fig. 2, the profile image is created in three directions E _M1 to E _M3 as shown in FIG. Perform at 9 points in total. The average value of the measurement values obtained at the nine measurement points is taken as the measurement value of one measurement area, and the average of the measurement values of the five measurement areas is determined to obtain the pitch of the convex 3c.
The pitches of convex portions of other shapes and the pitches of concave portions are also measured by the same measurement method.

As a preferred embodiment of the metal film 3, the following embodiment A or embodiment B can be mentioned.
Aspect A: A plurality of non-film-forming areas provided as an island-like gap shape having a length of 1 μm or less in the major axis direction in the metal film and the first surface 1a of the substrate 1 is exposed without metal Metal film with.
Aspect B: a metal film not having the non-film formation region.

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

The metal film 3A will be described in more detail with reference to FIGS. FIG. 4 is an enlarged top view schematically showing the surface on the metal film 3 side of the analysis substrate 10 when the metal film 3 is the metal film 3A, and FIG. 5 is an IV in FIG. 4 of this analysis substrate. FIG. 4 is a partial cross-sectional view schematically showing a cross-section of FIG. However, in FIGS. 4 to 5, the illustration of the metal nanoparticles is omitted.
The metal film 3A has a plurality of non-film formation regions G. The plurality of non-film formation regions G are dispersedly provided in the metal film 3A as an island-like gap shape whose length in the long axis direction is 1 μm or less. A region other than the non-film formation region G of the metal film 3 is a film formation region.
The non-film formation region G is a region in which the first surface 1 a is exposed without the presence of metal. That is, it is a gap (gap) penetrating the metal film 3A in the thickness direction. A region (for example, a region S in FIG. 5) which is not a void penetrating the metal film 3A even if metal does not exist in a part in the thickness direction does not correspond to the non-film formation region G. It is a film formation area.

The non-film formation area G is an island-shaped gap in a top view, and the plurality of non-film formation areas G may be independent of one another or may be several in number. Absent. Therefore, as shown in FIG. 5, the non-film formation area G is surrounded by the metal surface 3a, and the metal surfaces 3a face each other through the non-film formation area G. The distance between the metal surfaces facing each other through the non-film formation area G, that is, the width of the non-film formation area 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-film formation region G is one digit nanometer, extremely strong electric field enhancement is obtained.

The distance between the metal surfaces 3a facing each other through the non-film formation region G is preferably 1 to 20 nm, more preferably 1 to 10 nm, and still more preferably 1 to 5 nm. If the distance between the metal surfaces 3a is within the above range, the electric field enhancing effect by localized surface plasmon resonance is more excellent.
When the metal surface surrounding the non-film formation 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 distribution exists in the distance between the metal surfaces 3a, it is preferable that the maximum value of the distance between the metal surfaces 3a is below the said preferable upper limit. Moreover, it is preferable that the minimum value of the distance between the metal surfaces 3a is more than the said preferable lower limit.
The distance between the metal surfaces 3a is measured by the method described in the examples to be 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-film formation region G, ie, the film formation region. If the thickness of the metal film 3A is within the above range, the non-film formation region G is provided, and the distance between the metal surfaces opposed via the non-film formation region G, the non-film formation region with respect to the total area of the metal film 3A It tends to become the metal film 3A in which the ratio of the area of G is within the above preferable range. If the thickness of the metal film 3A is equal to or more than the lower limit value, the sheet resistance of the surface of the metal film 3A is likely to be equal to or less than the upper limit value.

The thickness of the metal film 3A (average thickness of the film formation region) is a value calculated from the film formation rate obtained by the following method. First, a flat substrate such as a single crystal silicon substrate or the like and having a center line average roughness Ra of 1 nm or less obtained by atomic force microscope (AFM) is prepared, and is masked with a tape etc. After forming a film for a fixed time of about several tens of nm and removing the mask, the film thickness is measured by AFM. From the above information, the deposition rate (deposition thickness per unit time (nm / min)) is determined. Once the film formation rate is determined, the thickness of the metal film 3A can be calculated from the film formation rate and the film formation time for forming the metal film 3A.
In the above method, for convenience, the thickness of the film may be measured using a stylus type profilometer instead of AFM. In this case, similar results can be obtained, but in the case where the measurement values by the AFM and the stylus type profilometer differ, in the present invention, the measurement values by the AFM are adopted.
For the thickness of the metal film 3A, for convenience, a microscopic image of a cross-sectional sample of the substrate including the metal film 3A is acquired using a transmission electron microscope (TEM), and the thickness of the metal film 3A is measured in the image. It may be measured by a method. Similar results are obtained in this case as well. Since this method does not need to measure information such as the film formation rate in advance, this method is an effective means for samples whose manufacturing conditions and the like are unknown.
As another method to know the thickness of the metal film 3A of the sample whose film forming rate is unknown, an extremely thin 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 method of lengthening is effective. Since the metal film 3A is extremely thin, it is possible to form a scratch in which the substrate is exposed 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. If the thickness of the metal film 3B is equal to or more than the above lower limit value, it tends to be a metal film having no non-film formation region. If the thickness of the metal film 3BA is within the above range, the sheet resistance of the surface of the metal film 3A is likely 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 as long as it can generate electric field enhancement by surface plasmon resonance, and examples thereof include gold, silver, aluminum, copper, platinum, alloys of two or more of these, and the like.
The shape of the metal nanoparticles 5 is not particularly limited, and may be, for example, spherical, needle-like (rod-like), flake-like, polyhedral-like, ring-like, hollow (in the center part, a cavity or a dielectric exists), dendritic crystals, Other irregular shapes are also included.
At least a part of the plurality of metal nanoparticles 5 may be aggregated to form a secondary particle.

The average primary particle diameter of the metal nanoparticles 5 is 5 to 100 nm, preferably 5 to 80 nm, and more preferably 5 to 40 nm. If the average primary particle diameter of the metal nanoparticles 5 is within the above range, the electric field enhancing effect by 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 by a scanning electron microscope (SEM) and obtaining an average value thereof. In this case, in order to know an 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 are obtained in this case as well.
The average primary particle size of the metal nanoparticles 5 may be conveniently measured by a particle size distribution analyzer by a dynamic light scattering method. In this case, when secondary particles (aggregates in which primary particles are aggregated) are present, a plurality of peaks are generated in the particle size distribution curve, and therefore the peak with the smallest particle diameter is the target particle diameter. Also in this method, the same result as the measurement method using the above SEM can be obtained.
A measuring method using a microscopic means such as SEM is useful when analyzing the surface of a substrate for analysis as a product later, and a measuring method by dynamic light scattering method is useful for producing an analytical substrate .

The shortest distance between two adjacent metal nanoparticles 5 arranged on the metal film 3 at a distance is preferably 1 to 20 nm, more preferably 1 to 10 nm, and still more preferably 1 to 5 nm. If the shortest distance is within the above range, electric field enhancement occurs by localized surface plasmon resonance between the metal nanoparticles 5, and high sensitivity Raman spectroscopy of the measurement target molecules adsorbed between the metal nanoparticles 5 Analysis is possible. In addition, even if the metal nanoparticles 5 are grounded to the metal film 3, minute gaps between the metal film 3 and the metal nanoparticles 5 are generated in the vicinity of the contact points, so here also by localized surface plasmon resonance. Electric field enhancement occurs to enable highly sensitive Raman spectroscopy.
The said shortest distance acquires the microscopic image of the surface sample of the board | substrate containing two adjacent metal nanoparticles using a scanning electron microscope (SEM), and measures the gap of two adjacent metal nanoparticles in the image. Measured by the method. This method requires a magnification of at least 100,000, preferably at least a million. Since the shortest distance between two adjacent metal nanoparticles 5 is locally different and not uniform, measurement of n = 20 or more is performed to obtain a distribution of distances.
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 are obtained in this case as well.
However, what is most effectively contributed to the surface enhanced Raman scattering effect is said to be a nanogap of about 1 nm, and the average value of the distribution of distances does not necessarily have a meaning.

(Manufacturing method of substrate for analysis)
Examples of the method for producing the analysis substrate 10 include the following production method (I).
Production method (I):
And 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”).
And a step of applying a metal nanoparticle dispersion liquid containing a plurality of metal nanoparticles 5 and a dispersion medium on the metal film 3 and drying it (hereinafter, also referred to as “step I-2”). Manufacturing method.
In step I-1, a plurality of regions where metal is not deposited remain on the first surface 1a as island-like gaps having a length of 1 μm or less in the long axis direction, and sheet resistance on the surface of the metal film When deposition of metal on the first surface 1a is completed in a state of 5000 Ω / □ or less, the metal film 3A is obtained. If the deposition of metal is continued without completion, the non-film formation region G disappears, and the unevenness of the film surface becomes small, and the metal film 3B having a flat surface is formed.

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

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 original plate does not have a predetermined two-dimensional lattice structure on the surface.
As a method of forming a two-dimensional lattice structure on the surface of the original plate, for example, dry etching (colloidal lithography) using a single particle film as an etching mask, electron beam lithography, mechanical cutting, laser thermal lithography, Nanoimprint method from a transfer master having a two-dimensional lattice structure on the surface, which is manufactured by the interference exposure method, more specifically, the two-beam interference exposure method, the reduction exposure method, the anodic oxidation method of alumina, and any of them. Etc.

As a method of forming a two-dimensional lattice structure, various methods can be applied, such as a photolithography method combining electron beam drawing and dry etching, a nanoporous alumina anodic oxidation method, or a nanoimprint method using a master obtained therefrom. However, a dry etching method (colloidal lithography method) using a single particle film as an etching mask is preferable in that a microstructure can be produced with a large area and low cost. In addition, the colloidal lithography method can easily produce a plurality of structures with different pitches, and has an advantage that structure optimization and functional verification can be performed quickly.
More specifically, in the production of the substrate 1 by the colloidal lithography method, a step of disposing a single particle film on an original plate (a substrate before forming a two-dimensional lattice structure on the surface) (a single particle film disposing step); It can carry out by the manufacturing method including the process (dry etching process) which dry-etches a single particle film and the said original plate.
The monoparticulate 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 dry methods such as vapor deposition, and wet methods 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 deposition methods, and various chemical vapor deposition methods (CVD).

When metal film deposition (metal deposition) is performed on the first surface 1a by a dry method, first, a plurality of metal particles adhere to the entire first surface 1a, and the metal particles are joined by growth to form fine particles. Plural island-shaped metal films are formed. As film formation proceeds, adjacent metal films form larger clusters, and the area and thickness of the metal films increase. Along with this, the region where the metal is not deposited on the first surface 1a becomes narrower. The film formation is completed in a state in which the area where the metal is not deposited remains like an island and the value of the surface sheet resistance of the formed metal film falls within the above range (the metal film becomes a continuous film). Thus, the aforementioned metal film 3A is obtained. An area in which the island remains and in which the metal is not deposited is a non-film formation area G. If the deposition of metal is continued without completion, the non-film formation region G disappears and it becomes the metal film 3B.

When a catalyst is dispersedly disposed on the first surface 1a in advance and a metal film is formed by electroless plating in that state, first, metal adheres to the periphery of the catalyst, and a plurality of fine island-shaped metal films are formed. 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 which the metal is not deposited on the first surface 1a is narrowed. The above-described metal film 3A is obtained by completing the film formation in a state where the region where metal is not deposited remains in an island shape and the surface sheet resistance value of the formed metal film is in the above range. An area in which the island remains and in which the metal is not deposited is a non-film formation area G. If the deposition of metal is continued without completion, the non-film formation region G disappears and it becomes the metal film 3B.

As a method of depositing a metal on the first surface 1a, a sputtering method is preferable from the viewpoint that adhesion of impurities is difficult to occur, adhesion strength of a metal film to a substrate is high, and control of sea-island structure is easily performed. That is, the metal film 3 is preferably a film formed by sputtering.
The fact that a plurality of regions where metal is not deposited remains in the form of islands on the first surface 1a is 100,000 times as large as with a high magnification microscope such as atomic force microscope (AFM) or scanning electron microscope (SEM) This can be confirmed by surface observation of the degree.
The sheet resistance of the surface of the metal film 3 at the end of the deposition is preferably 3 to 500 Ω / □, and most preferably 3 to 300 Ω / □.

<Step I-2>
The dispersion medium of the metal nanoparticle dispersion liquid may be any one as long as the metal nanoparticles 5 can be dispersed, 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 mass%.
The metal nanoparticle dispersion may further contain citric acid, various inorganic salts, and the like as a dispersion stabilizer, as needed, as long as the effects of the invention are not impaired.

It does not specifically limit as a coating method of a metal nanoparticle dispersion liquid, For example, it can select suitably from well-known coating methods, such as a spray method, a drop cast method, a dip coating method, a spin coat method, an inkjet printing method. The spray method or the inkjet printing method is preferable in that metal nanoparticles can be densely and uniformly arranged on the substrate surface by metal nanoparticle dispersion.

After step I-1 or after step I-2, when stored for a long time under normal environment (in air), contaminants in the air adhere to the metal structure on the substrate surface, and the effect of the present invention It may decrease. Therefore, storage is preferably performed in a vacuum vessel or an inert gas such as nitrogen or argon. If the effect of the present invention is reduced due to contaminants in the air, the substrate may be subjected to surface treatment such as ultraviolet (UV) / ozone to restore its function, if necessary. Good.

<Single particle film>
The “single particle film” is a single layer film in which a plurality of particles are two-dimensionally arranged.
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 polymethyl methacrylate (PMMA); thermosetting resins such as phenol resin and epoxy resin; and the like.
Examples of the inorganic material include carbon allotropes, inorganic carbides, inorganic oxides, inorganic nitrides, inorganic borides, inorganic sulfides, inorganic selenides and the like. Examples of the carbon allotrope include diamond, graphite, fullerenes and the like. Examples of inorganic carbides include silicon carbide and boron carbide. 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, boron nitride and the like. Examples of inorganic borides include ZrB ₂ and CrB ₂ . Examples of inorganic sulfides include zinc sulfide, calcium sulfide, cadmium sulfide, strontium sulfide and the like. Examples of inorganic selenides include zinc selenide and cadmium selenide.
The material constituting the particles may be one kind or two or more kinds.

The average particle diameter of the particles constituting the single particle film corresponds to the pitch of the periodic uneven structure calculated by the above-mentioned method in accordance with the excitation wavelength used for the spectral analysis. If the average particle diameter of the particles is the above calculated value, propagation surface plasmons are easily induced.
The average particle diameter of the particles in a slurry state not constituting the single particle film can be determined by a conventional method from the peak obtained by fitting the particle size distribution determined 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 (the value obtained by dividing the standard deviation by the average value) of the particle diameter of the particles constituting the single particle film is preferably 20% or less 10% or less is more preferable, and 5% or less is more preferable. As described above, when particles having a small variation coefficient of particle diameter, that is, small variation of particle diameter, are used, it becomes difficult to form a defect location where particles do not exist in the formed single particle film, and misalignment D of the arrangement of particles is 10%. It is possible to obtain a highly accurate single particle film which is as follows. In a single particle film in which the misalignment D is 10% or less, each particle is two-dimensionally close-packed, the particle spacing is controlled, and the accuracy of the alignment is high. Therefore, if such a single particle film is disposed 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 composed of particles having a large variation coefficient of particle diameter. For example, a single particle film may be configured 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 formula (1).
D [%] = | B-A | × 100 / A (1)
In Formula (1), A is an average particle diameter of particles constituting a single particle film, and B is an average pitch between particles in the single particle film. Also, | B−A | 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 apexes of two adjacent particles, and the average pitch is the average of these. If the particles are spherical, the distance between the apexes of 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 determined as follows.
First, an atomic force microscope image or a scanning electron microscope image is obtained for a square region of 30 to 40 wavelengths of repeating units of a fine structure in a randomly selected region of a single particle film. For example, in the case of a single particle film using particles of 300 nm in particle diameter, an image of a region of 9 μm × 9 μm to 12 μm × 12 μm is obtained. Then, this image is waveform separated by two-dimensional Fourier transform to obtain an FFT image (fast Fourier transform image). Next, the distance from the zero-order peak to the first-order peak in the profile of the FFT image is determined. Thus the inverse of the calculated distance is the average pitch B ₁ in this region. Such processing is similarly performed on randomly selected areas of 25 areas or more having the same area in total, and average pitches B ₁ to B ₂₅ in each area are determined. The average value of the average pitches B ₁ to B ₂₅ in the region of 25 or more places thus obtained is the average pitch B in the equation (1). In this case, the respective regions are preferably selected to be separated by at least 1 mm, and more preferably selected to be separated by 5 mm to 1 cm.
At this time, it is also possible to evaluate, for each image, the variation in pitch among 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 disposing step is preferably performed by the Langmuir-Blodgett method (LB method). This method combines the accuracy of single-layering, the simplicity of operation, the response to an increase in area, the reproducibility, etc., for example, the liquid thin film described in Nature, Vol. 361, 7 January, 26 (1993), etc. It is extremely superior to the so-called particle adsorption method described in U.S. Pat.

In the single particle film disposing step by LB method, for example, a water tank (trough) containing water as a liquid (hereinafter sometimes referred to as a lower layer liquid) for developing particles on the liquid surface is prepared, and the liquid Step of dropping a dispersion in which particles are dispersed in an organic solvent having a smaller specific gravity than water on a surface (dropping step) and step of forming a single particle film composed of particles by volatilizing the organic solvent (single particle A film formation process can be implemented by the method including the process (transfer process) which transfers the formed single particle film to a negative | original plate. After the transfer step, a step (fixing step) of fixing the single particle film transferred to the substrate to the substrate may be performed.
At this time, particles having a hydrophobic surface are used as the particles so that the particles do not dip below the surface of the hydrophilic lower layer liquid. Also, as the organic solvent, a hydrophobic solvent is selected so that when the dispersion is dropped onto the liquid surface of the lower layer liquid, the dispersion will expand to the air-liquid interface of the air and the lower layer liquid without mixing with the lower layer liquid. Be done.
In this example, the particles having a hydrophobic surface and the organic solvent having a hydrophobic surface are selected, and the lower layer liquid is hydrophilic, but the particles having a hydrophilic surface and an organic solvent are used. A hydrophilic solvent may be selected, and a hydrophobic liquid may be used as the lower layer liquid.
The dispersion to be used and each step will be specifically described below.

"Dispersion liquid"
The organic solvent used for the dispersion is a hydrophobic one having a smaller specific gravity than water. It is also important that the organic solvent have high volatility. Examples of organic solvents having a specific gravity smaller than water and being hydrophobic and having high volatility include chloroform, methanol (used as a material for mixing), ethanol (used as a material for mixing), isopropanol (used as a material for mixing), acetone (Used as a material for mixing) Volatile organic solvents comprising one or more kinds of methyl ethyl ketone, diethyl ketone, toluene, hexane, cyclohexane, ethyl acetate, butyl acetate and the like.

Among the particles exemplified above, particles having an organic material such as polystyrene and having an originally hydrophobic surface may be used as the particles having a hydrophobic surface, and the particles having a hydrophilic surface are treated with a hydrophobicizing agent. You may use what was made hydrophobic.
As the hydrophobizing agent, for example, surfactants, metal alkoxides and the like can be used.
The method of using a surfactant as a hydrophobizing agent is effective for hydrophobization of 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 inorganic oxide particles, the present invention can be applied to particles having a hydroxyl group on the surface.

As the surfactant, cationic surfactants such as hexadecyltrimethylammonium bromide and decyltrimethylammonium bromide, and anionic surfactants such as sodium dodecyl sulfate and sodium 4-octylbenzene sulfonate can be suitably used. Also, alkanethiols, disulfide compounds, tetradecanoic acid, octadecanoic acid and the like can be used.

As a metal alkoxide, an alkoxysilane is mentioned, for example.
As the alkoxysilane, monomethyltrimethoxysilane, monomethyltriethoxysilane, dimethyldiethoxysilane, phenyltriethoxysilane, hexyltrimethoxysilane, decyltrimethoxysilane, vinyltrichlorosilane, vinyltrimethoxysilane, vinyltriethoxysilane, 2 -(3,4-Epoxycyclohexyl) ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltriethoxysilane, p-styryltrimethoxysilane Silane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxy Ropyltriethoxysilane, 3-acryloxypropyltrimethoxysilane, N-2 (aminoethyl) 3-aminopropylmethyldimethoxysilane, N-2 (aminoethyl) 3-aminopropyltrimethoxysilane, N-2 (amino Ethyl) 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, 3-ureidopropyltriethoxysilane, 3-chloropropyl Examples thereof include trimethoxysilane, 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-isocyanatopropyltriethoxysilane and the like.

The hydrophobization treatment using a surfactant may be carried out by dispersing particles in a liquid such as an organic solvent or water, and may be carried out on particles in a dry state.
When it is carried out in a liquid, for example, particles to be hydrophobized may be added and dispersed in the above-mentioned volatile organic solvent, and then the surfactant may be mixed and dispersion may be continued. By dispersing particles in this manner and then adding a surfactant, the surface can be made more uniformly hydrophobic. The dispersion after such hydrophobization treatment can be used as it is as a dispersion for dropping onto the liquid surface of the lower layer liquid in the dropping step.
When the particles to be hydrophobized are in the form of an aqueous dispersion, a surfactant is added to the aqueous dispersion to perform hydrophobization on the particle surface in the aqueous phase, and then an organic solvent is added to hydrophobize. The method of oil phase extraction of the finished particles is also effective. The dispersion (dispersion in which the particles are dispersed in the organic solvent) thus obtained can be used as it is as a dispersion to be dropped onto the liquid surface of the lower layer liquid in the dropping step.
In order to increase the particle dispersibility of the dispersion, it is preferable to appropriately select and combine the type of organic solvent and the type of surfactant. By using a dispersion having high particle dispersibility, it is possible to suppress aggregation of particles in the form of clusters, and it becomes easier to obtain a single particle film in which each particle is densely packed in two dimensions. For example, when chloroform is selected as the organic solvent, it is preferable to use decyltrimethylammonium bromide as the surfactant. Besides, a combination of ethanol and sodium dodecyl sulfate, a combination of methanol and sodium 4-octylbenzene sulfonate, a combination of methyl ethyl ketone and octadecanoic acid, and the like can be preferably exemplified.
The ratio of the particles to be hydrophobized to the surfactant is preferably such that the mass of the surfactant is 1/3 to 1/15 times the mass of the particles to be hydrophobized.
In the case of such hydrophobization treatment, it is also effective to stir the dispersion during treatment or to irradiate the dispersion with ultrasonic waves in terms of improvement of the 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 form 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 dehydrating condensation of the generated hydroxyl groups with hydroxyl groups on the particle surface. Therefore, it is preferable to carry out the hydrophobization treatment using a metal alkoxide in water. When the hydrophobization treatment is carried out in water as described above, it is preferable to stabilize the dispersion state of the particles before hydrophobization by using, for example, a dispersing agent such as a surfactant, depending on the kind of the dispersing agent. Since the hydrophobization effect of the metal alkoxide may be reduced, the combination of the dispersant and the metal alkoxide is appropriately selected.

As a specific method of hydrophobizing particles with metal alkoxide, first, the particles are dispersed in water, and this is mixed with a metal alkoxide-containing aqueous solution (an aqueous solution containing a hydrolyzate of metal alkoxide), The reaction is carried out for a predetermined time, preferably 6 to 12 hours, with appropriate stirring in the range of ° C. By conducting the reaction under such conditions, the reaction proceeds moderately, and a dispersion liquid of sufficiently hydrophobized particles can be obtained. When the reaction proceeds excessively, the silanol groups react with each other to combine the particles with each other, the particle dispersibility of the dispersion decreases, and in the obtained single particle film, the particles partially aggregate in a cluster 2 It is easy to become more than a layer. On the other hand, if the reaction is insufficient, the hydrophobicization of the particle surface also becomes insufficient, and in the operation of developing the particles to be described later on the water surface, problems occur that the particles settle in water, or the strength of the obtained single particle film decreases. It is not preferable because wrinkle-like defects occur.
Among the above-mentioned alkoxysilanes, since the alkoxysilanes other than amine based hydrolyze under acidic or alkaline conditions, it is necessary to adjust the pH of the dispersion to be acidic or alkaline during the reaction. There is no limitation on the method of adjusting the pH, but according to the method of adding an aqueous acetic acid solution having a concentration of 0.1 to 2.0% by mass, in addition to the promotion of hydrolysis, the effect of stabilizing the silanol group is also obtained. .
The ratio of the particles to be hydrophobized to the metal alkoxide is preferably such that the mass of the metal alkoxide is 1/3 to 1/100 times 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 oil-phase extracted particles made hydrophobic in water. At this time, the volume of the organic solvent to be added is preferably 0.3 to 3 times the volume of the dispersion before addition of the organic solvent. The dispersion (dispersion in which the particles are dispersed in the organic solvent) thus obtained can be used as it is as a dispersion to be dropped onto the liquid surface of the lower layer liquid in the dropping step.
In such hydrophobization treatment, in order to enhance the particle dispersibility of the dispersion during treatment, it is preferable to carry out stirring, ultrasonic irradiation and the like. By enhancing the particle dispersibility of the dispersion, it is possible to suppress aggregation of the particles in the form of clusters, and it becomes easier to obtain a single particle film in which each particle is two-dimensionally dense.

"Dropping process"
In the dropping step, the above dispersion liquid is dropped onto the liquid surface of the lower layer liquid.
The concentration of particles in the dispersion to be dropped to the lower layer solution is preferably 1 to 10% by mass. In addition, the dropping speed of the dispersion is preferably 0.001 to 0.01 mL / sec. When the concentration of particles in the dispersion and the dropping amount of the dispersion are in such a range, the particles partially aggregate in a cluster shape to form two or more layers, causing a defect location where no particles exist, interparticle The tendency of the pitch to spread is suppressed, and a single particle film in which each particle is densely packed in two dimensions is more easily obtained.

In order to further enhance the accuracy of the single particle membrane to be formed, the dispersion before dropping onto the liquid surface is precision filtered with a membrane filter or the like, and aggregated particles (secondary particles consisting of a plurality of primary particles) present in the dispersion Is preferred to be removed. Thus, if precision filtration is performed in advance, it is hard to produce the location which became two or more layers partially, the defect location which particle | grains do not exist, and it is easy to obtain a highly accurate single particle film. Assuming that a defect portion having a size of several to several tens of μm exists in the formed single particle film, a surface pressure sensor that measures the surface pressure of the single particle film in the transition step described in detail later; Even if an LB trough apparatus provided with a movable barrier that compresses a single particle film in the liquid surface direction is used, such a defect is not detected as a difference in surface pressure, and a high accuracy single particle film can be obtained. It becomes difficult.

"Single particle film formation process"
When the dispersion liquid is dropped onto the liquid surface of the lower layer liquid in the dropping step, the solvent as the dispersion medium is volatilized, and the particles are spread in a single layer on the liquid surface of the lower liquid layer, and the particles are two-dimensionally dense 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 are concentrated, surface tension acts due to the dispersion medium present between the particles, and as a result, the particles are not separated from each other, but are concentrated on the liquid surface of the lower layer liquid Automatically forms a single layer structure. In other words, the formation of a single layer structure by such surface tension can be said to be mutual adsorption of particles due to the lateral capillary force. For example, when three spherical particles of the same particle size float and gather on the water surface and contact each other, surface tension acts to minimize the total length of the waterline of the particle group, and the three particles are based on an equilateral triangle. Stabilize in place. If the waterline is at the top of the particle group, that is, if the particle dives below the liquid surface, such self-organization does not occur and a monoparticle film is not formed. Therefore, it is important to make the particles and the lower layer liquid hydrophilic if one is hydrophobic so that the particle group does not dip below the liquid surface.
As the lower layer liquid, it is preferable to use water as described above, and when water is used, relatively large surface free energy acts to form a dense single layer structure of particles once generated on the liquid surface. It becomes stable and easy to sustain.

The single particle film forming step is preferably performed under ultrasonic irradiation conditions. When the single particle film forming step is performed while irradiating ultrasonic waves from the lower layer solution to the water surface, mutual adsorption of particles is promoted, and a single particle film in which each particle is densely packed in two dimensions 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 ultrasonic waves 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 that water vapor or water droplets rise from the water surface occurs, which is not preferable for the LB method. If the frequency is too low, the cavitation radius in the lower layer solution will be large, and bubbles will be generated in the water and will rise toward the water surface. When such bubbles accumulate under the monoparticle film, the flatness of the water surface is lost, which is disadvantageous for the LB method.
When ultrasonic waves are applied, standing waves are generated on the water surface. If the output is too high at any frequency, or if the wave height of the water surface is too high due to the tuning conditions of the ultrasonic transducer and the transmitter, the single particle film is broken by the water wave, so care must be taken.

If the frequency of ultrasonic waves is set appropriately in consideration of the above, it is possible to effectively promote the concentration of particles without destroying the monoparticle film being formed. In order to perform effective ultrasonic wave irradiation, it is good to use the natural frequency calculated from the particle diameter of particles as a standard. However, when the particle size is small, for example, 100 nm or less, the natural frequency becomes very high, and it becomes difficult to give ultrasonic vibration as calculated. In such a case, it is possible to reduce the necessary frequency to a realistic range by performing calculations assuming that the natural vibration corresponding to the mass from the particle dimer to about 20 mer is given. . Even when ultrasonic vibration corresponding to the natural frequency of the aggregate of particles is given, the effect of improving the packing ratio of particles is exhibited. The irradiation time of the ultrasonic waves may be sufficient to complete the rearrangement of the particles, and the required time changes depending on the particle diameter, the frequency of the ultrasonic waves, the water temperature, and the like. However, under normal preparation conditions, it is preferably performed for 10 seconds to 60 minutes, more preferably for 3 minutes to 30 minutes.
The advantages obtained by the ultrasonic irradiation include the effect of destroying the soft agglomerates of particles that are easily generated during preparation of the nanoparticle dispersion, point defects, line defects, or crystals that are easily generated during preparation of the nanoparticle dispersion, in addition to high-density packing of particles. There is an effect of repairing the metastasis etc. to some extent.

"Migration process"
In the transfer step, the single particle film formed on the liquid surface in the single particle film forming step is transferred onto the original plate in a single layer state.
The original plate is the same as the substrate 1 except that the two-dimensional lattice structure is not formed on the surface.
There is no particular limitation on the specific method of transferring the monoparticle film onto the original plate, and for example, the hydrophobic original plate is lowered from above while being kept substantially parallel to the single particle membrane to form a single particle membrane. Method of adsorbing and transferring the single particle film to the original plate by contact and affinity between the single particle film and the original plate both being hydrophobic; transferring the original plate in advance to the lower layer liquid of the water tank before forming the single particle film There is a method of transferring the single particle film onto the original plate by arranging the particles in the horizontal direction and forming the single particle film on the liquid surface and then gradually lowering the liquid surface.
According to these methods, the single particle film can be transferred onto the original plate without using a special device, but even with a larger area single particle film, a plurality of particles are densely packed in two dimensions. It is preferable to adopt the so-called LB trough method in that it is easily transferred onto 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, Vol. 12, 3268 (2002), etc.).

In the LB trough method, an original plate is dipped in a substantially vertical direction in a lower layer solution in a water tank in advance, and the dropping step and the single particle film forming step described above are performed in this state 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 in the single particle film forming step, the temperature condition of the transfer step (the temperature of the lower layer liquid) and the pulling speed of the original plate are somewhat Even if it fluctuates, there is no fear that the single particle film collapses and becomes multilayered in the transfer step. The temperature of the lower layer liquid is usually about 3 to 30 ° C., depending on the environmental temperature which fluctuates depending on the season and the weather.
At this time, an LB trough apparatus including a surface pressure sensor based on a Wilhelmy plate or the like for measuring the surface pressure of a single particle film as a water tank and a movable barrier for compressing the single particle film in the direction along the liquid surface. Can be used to more stably transfer a large-area single particle membrane onto the original plate. According to such an apparatus, 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 at a constant speed toward the substrate. . Therefore, the transition from the liquid surface of the single particle membrane to the original plate smoothly proceeds, and troubles such as only the small particle single particle membrane of the small area can be transferred onto the original plate hardly 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 two-dimensionally. The speed of pulling up the original plate is preferably 0.5 to 20 mm / min. The LB trough apparatus can be obtained as a commercial product.

"Fixing process"
By performing the fixing step of fixing the single particle film transferred onto the original plate in the transfer step to the original plate, the particles constituting the single particle film move on the surface of the original plate during the dry etching step described later. Can be suppressed, and the original plate can be etched more stably and accurately.
As a method of a fixing process, the method of using a binder, and the sintering method are mentioned.
In the method of using a binder, a binder solution is supplied to the surface of the original plate on which the single particle film is formed, and is made to permeate between the particles constituting the single particle film and the original plate.
As the binder, the metal alkoxide exemplified as the hydrophobizing agent, a general organic binder, an inorganic binder and the like can be used.
The amount of binder used is preferably 0.001 to 0.02 mass times the mass of the single particle film. In such a range, the particles can be sufficiently fixed without causing a problem that the binder is too much and the binder is clogged between particles, which adversely affects the accuracy of the single particle film. If a large amount of binder solution has been supplied, the binder solution may be removed by using a spin coater or tilting the original plate after the binder solution has penetrated.
After the binder solution has penetrated, heat treatment may be appropriately performed according to the type of the binder. When a metal alkoxide is used as a binder, heat treatment is preferably performed at 40 to 80 ° C. for 3 to 60 minutes.

In the case of employing the sintering method, the original plate on which the single particle film is formed may be heated to fuse the particles 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 diameter of 1 μm or less, the interfacial reaction is initiated at a temperature lower than the melting point inherent to the material constituting the particles, so sintering is completed at a relatively low temperature side. When 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 be changed, which may affect the accuracy.
When the heating is performed in air, depending on the material, the original plate and the particles may be oxidized. For example, when a silicon substrate is used as an original plate and this is sintered at 1100 ° C., a thermally oxidized layer is formed on the surface of this 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 process, 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 manner, each particle constituting the single particle film is etched, the particle diameter of each particle gradually decreases, and a gap is also formed in a portion where the particles are in contact with each other before dry etching. The particles are formed, and the particles are not in contact with each other. Further, the etching gas passes through the gaps between the particles to reach the surface of the original plate, and the surface of the original plate located below the gaps is etched to form a recess. The part covered with particles remains unetched, and this part becomes the convex 3c. Thereby, the substrate 1 is obtained.
Before dry etching the original plate, the particles may be dry etched under conditions that the original plate is not substantially etched.

By adjusting 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 surface layer: filling factor), convex portion 3c Height (the depth of the recess) etc. can be adjusted.

The etching gas can be appropriately selected from known etching gases according to the material of the particles, the substrate, etc., 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, CBrF ₃ , _{HCl, CH 4, NH 3,} O 2, H 2, N 2, CO, and CO ₂ and the like can be used.
When the original plate is quartz and the particles are silica, Ar or CF ₄ can be used.
When the original plate is sapphire and the particles are silica, Cl ₂ , BCl ₃ , SiCl ₄ , HBr, HI, HCl, etc. can be used.
The etching gas may be used alone or in combination of two or more. Adjustment of etching conditions is facilitated by the mixing ratio of two or more 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 larger than in the horizontal direction of the original plate. As a usable etching apparatus, it is possible to use anisotropic etching such as a reactive ion etching apparatus, an ion beam etching apparatus, etc., and generate a bias electric field of about 20 W at the minimum, it is possible to generate plasma There are no particular limitations on specifications such as the method, the structure of the electrode, the structure of the chamber, and the frequency of the high frequency power source.

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

The dry etching of the original plate may be ended when the particles constituting the single particle film disappear, or may be ended 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 method for removing particles include a chemical removal method using an etchant which is etchable to particles and etch resistant to the substrate 1, and a physical removal method using a brush roll cleaner or the like.

The original plate is obtained as described above.
The transferred product of the original plate is obtained by transferring the two-dimensional lattice structure of the original plate surface to another original plate one or more times. When the number of times of transfer is an odd number, a transfer product having a two-dimensional lattice structure in which the two-dimensional lattice structure of the original plate surface is inverted is obtained. When the number of times of transfer is an even number, a transfer product having a two-dimensional lattice structure similar in shape to the two-dimensional lattice structure of the original plate surface is obtained.
For example, the two-dimensional lattice structure of the original plate surface is transferred to a mold (a mold or a stamper) (first transfer), and then the two-dimensional lattice structure of the mold is transferred (second transfer). A transfer product having a two-dimensional lattice structure of the same shape as the two-dimensional lattice structure is obtained.
As a method of transferring the two-dimensional lattice structure of the original plate to a mold (a mold or a stamper), for example, an electroforming method as disclosed in JP 2009-158478 A is preferable.
Examples of a method for transferring a two-dimensional lattice structure of a mold include a nanoimprinting method, a heat pressing method, an injection molding method, a UV embossing method, and the like as disclosed in JP-A-2009-158478. Above all, the nanoimprint method is suitable for the transfer of a fine two-dimensional lattice structure.

(Action effect)
In the analysis substrate 10 of the present embodiment, when this is used for spectrometry, localization due to incident light between the metal film 3 and the metal nanoparticles 5 and between the adjacent metal nanoparticles 5 is made. Type surface plasmon resonance is generated, and it is possible to obtain a non-linear optical electric field enhancing effect by superposition of 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 propagation type surface plasmon resonance. The combination of localized surface plasmon resonance in two or three types of metal gaps and propagation type surface plasmon resonance in one type of metal lattice structure enables highly sensitive optical analysis utilizing an electric field enhancement effect.
In particular, when the metal film 3 is the metal film 3A of the aspect A, even in the non-film formation region G of the metal film 3, electric field enhancement can be generated by localized surface plasmon resonance, and optical using the electric field enhancement Analysis can be performed with higher sensitivity.
The analysis substrate 10 is also excellent in productivity. For example, as shown in the manufacturing method (I), metal can be deposited on the substrate 1B, and further, the metal nanoparticle dispersion can be coated and dried. In addition, it is not necessary to use a large amount of metal in order to form a structure capable of generating an electric field enhancement by localized surface plasmon resonance, and the raw material cost can be suppressed.
Since the above effect is exhibited, the analytical substrate 10 is useful for optical analysis utilizing electric field enhancement by surface plasmon resonance. As such an optical analysis method, the same as described above can be mentioned.

Since the above effect is exhibited, the analysis substrate 10 is useful for optical analysis utilizing an electric field enhancement effect by surface plasmon resonance.
Examples of such optical analysis include Raman spectroscopy, infrared spectroscopy, and fluorescence analysis. Among these, Raman spectroscopy is preferable.
The Raman spectroscopy is an analysis means for observing the Raman scattering shifted by the vibrational energy of the molecule with respect to the incident light when the sample is irradiated with light, and analyzing the structure at the molecular level. Similar to the infrared spectrum obtained by infrared spectroscopy, the obtained Raman spectrum is a vibration spectrum based on the vibration of the molecule, the vertical axis is the scattering intensity (Intensity), and the horizontal axis is the Raman shift (cm ⁻¹ ) Is represented by The vibration mode of the same functional group is detected in the same wave number in the Raman spectroscopy and the infrared spectroscopy, but unlike the infrared spectroscopy, the Raman spectroscopy can measure the aqueous sample, so the living body It has the advantage of not requiring pretreatment of the sample in analysis of the sample, food sample, etc. However, conventional Raman spectroscopy without surface electric field enhancement has the disadvantage that the intensity of the Raman scattered light is very low.
Surface enhanced Raman spectroscopy is Raman spectroscopy 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 significantly enhanced by the SERS effect, which enables high sensitivity spectral analysis. . In fact, even in the case of a dilute trace sample, it is possible to detect a spectrum unique to a substance, which is useful for environmental measurement, measurement of a trace biomarker, detection of a biological or chemical weapon, and the like.

Although the present invention has been described with the embodiments shown above, the present invention is not limited to these embodiments. The configurations and combinations thereof in the above embodiment are merely examples, and additions, omissions, substitutions, and other modifications of the configurations 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-film formation region G in a top view is a band shape, but the shape of the non-film formation region G in a top view is not limited thereto. For example, it may have a circular shape, a rectangular shape, a tree shape, or an irregular shape.
Although the shape, size, and distribution of each of the plurality of non-film formation regions G are random (not constant), the shape and size of each of the plurality of non-film formation regions G may be constant. The plurality of non-film formation regions G may be regularly arranged.
Although FIG. 5 shows an example in which the metal surface 3 a surrounding the non-film formation region G is an inclined surface, the metal surface 3 a may be a non-inclined surface. 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 the substrate (sputtering method, vacuum evaporation method, etc.), the metal surface surrounding the non-film formation region G is locally inclined In many cases, it is an irregular surface.

EXAMPLES The present invention will be described in more detail using the following examples, but the present invention is not limited to these examples.
The measuring method used in each case is shown below. In addition, the measuring method of the height and pitch of the convex part of a periodic uneven structure is as above-mentioned.

(Sheet resistance of metal film surface at 25 ° C)
The sheet resistance was measured at 25 ° C. with a resistivity meter (Loresta AX MCP-T370) used in a general continuity test. Since the metal film that composes the metal structure is very thin, the probe of the resistivity meter uses 1.5 mm between the pins of the PSP option probe (MCP-TP06P) pin for thin film measurement, with an average value of n = 5 or more The measured value (Ω / □) was obtained.

(Distance between opposing metal surfaces through non-film formation area G)
The metal film 3 is formed of an island (a gap in the non-film formation region G) with respect to a sea-island structure (sea-island structure sea (metal = film formation region)) composed of the metal film and the non-film formation region G dispersed in the metal film. And the distance between the metal surfaces 3a was measured by the following measurement method.
That is, SEM images of an area of 0.6 μm × 0.45 μm are obtained at a magnification of 200,000 and five points separated by 100 μm or more from each other on the surface of the metal film 3 and measurement of the non-film formation area G in each SEM image Do the length. Since the SEM image at this magnification may blur the outline, use Adobe Photoshop or similar image processing software after the SEM image acquisition to enhance the contrast of the image or Make it easy to measure by digitizing. Here, the gap in the minor axis direction of the non-film formation region G 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 intersects each non-film formation region G. Specifically, a point P which is a half of the intersection distance formed by the diagonal with the non-film formation region G is defined. 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 taken 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 formation region) was measured by the above-mentioned method. That is, a very thin scratch (scratch) is made with a sharp knife tip to the metal film 3 deposited on the substrate, and the area including the scratch is measured by a stylus-type step meter (fine shape measuring machine ET4000A The average thickness of the metal film 3 was measured by a method of measuring the average height difference between the bottom surface of the flaw (where the substrate is exposed) and the surface of the metal film 3 by the Kosaka Research Institute, Ltd. .
In the embodiment, a stylus type step system is used, but an atomic force microscope (AFM) image is obtained to similarly average the difference in height between the exposed portion of the substrate and the surface of the metal film 3 The same result can be obtained even if it is determined.

(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, the surface of the substrate for analysis is observed at a magnification of 200,000 using SEM, the primary particle diameter of the metal nanoparticles is measured, the average value of n = 20 is calculated, and the value is the average primary particle diameter. And

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

(Measurement of Raman scattering intensity)
Add 5 μL of 100 μM 4, 4'-bipyridyl aqueous solution to the surface of the analysis substrate (surface provided with metal film, metal nanoparticles etc.), and use a Raman spectrophotometer (Almega XR, Thermo Fisher Scientific Co., Ltd.) The Raman spectrum was measured using each. A laser with an excitation wavelength of 780 nm and an output of 10 mW was used as a light source, and each measured value was compared at an intensity (Intensity) of a detection peak of 1607 cm ⁻¹ . The Raman conditions were 100% laser output, a pinhole with a diameter of 100 μm, and 64 exposures.

Example 1
A substrate for analysis having the same configuration as the substrate for analysis 10 shown in FIG. 1 and in which the metal film 3 is the metal film 3A of the embodiment A was manufactured in the following procedure.
Colloidal silica particles having an average particle diameter of 600 nm were single-layer coated on a quartz substrate by the LB method described below. First, N-phenyl-3-aminopropyltrimethoxysilane as a hydrophobizing agent was added to the silica particle slurry, and hydrophobization was performed at a reaction temperature of 40.degree. Thereafter, the hydrophobized silica particles were subjected to oil layer extraction using a mixed solvent of ethanol: chloroform = 30: 70. Next, the above-mentioned hydrophobized particle slurry was dropped onto the water surface of the lower layer water of pH 7.2 at 21 ° C. to form a particle monolayer film on the water surface. Furthermore, while compressing the particle monolayer film with the barrier, the clean flat quartz substrate previously 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 The After that, dry etching is performed under the conditions of 1.2 Pa, 2000/1800 W, Cl ₂ = 80 sccm, 100 sec using a dry etching apparatus (ME510I manufactured by Tokyo Electron Ltd.), and the structure period (pitch) 600 nm, structure height ( Vertical distance from the center point of the three particles to the top of the structure) 52 nm periodic relief structure was obtained. Furthermore, using a sputtering apparatus (ion sputtering apparatus E-1030, Hitachi High-Technologies), the Au thin film was pressured on the periodic uneven structure at a pressure of 6 to 8 Pa, a current value of 15 mA, and a deposition rate of 11.6 nm / min. The film was formed to a thickness of 8 nm. Finally, the step of spray coating an Au nanoparticle dispersion (average primary particle diameter: 20.7 nm) on an Au thin film and drying was repeated three times to disperse and arrange Au nanoparticles on the substrate.
FIG. 6 shows an SEM image of the obtained analysis substrate.

(Example 2)
A substrate for analysis having the same configuration as the substrate for analysis 10 shown in FIG. 1 and in which the metal film 3 is the metal film 3B of the embodiment B was manufactured in the following procedure.
Colloidal silica particles having an average particle diameter of 600 nm were single-layer coated on a quartz substrate by the LB method described below. First, N-phenyl-3-aminopropyltrimethoxysilane as a hydrophobizing agent was added to the silica particle slurry, and hydrophobization was performed at a reaction temperature of 40.degree. Thereafter, the hydrophobized silica particles were subjected to oil layer extraction using a mixed solvent of ethanol: chloroform = 30: 70. Next, the above-mentioned hydrophobized particle slurry was dropped onto the water surface of the lower layer water of pH 7.2 at 21 ° C. to form a particle monolayer film on the water surface. Furthermore, while compressing the particle monolayer film with the barrier, the clean flat quartz substrate previously 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 The After that, dry etching is performed under the conditions of 1.2 Pa, 2000/1800 W, Cl ₂ = 80 sccm, 100 sec using a dry etching apparatus (ME510I manufactured by Tokyo Electron Ltd.), and the structure period (pitch) 600 nm, structure height ( Vertical distance from the center point of the three particles to the top of the structure) 52 nm periodic relief structure was obtained. Furthermore, using a sputtering apparatus (ion sputtering apparatus E-1030, Hitachi High-Technologies Corporation), an Au thin film was pressured on the periodic uneven structure at a pressure of 6 to 8 Pa, a current value of 15 mA, and a deposition rate of 11.6 nm / min. The film was formed to a thickness of 0 nm. Finally, the step of spray coating an Au nanoparticle dispersion (average primary particle diameter: 20.7 nm) on an Au thin film and drying was repeated three times to disperse and arrange Au nanoparticles on the substrate.
FIG. 7 shows an SEM image of the obtained analysis substrate.

(Comparative example 1)
A flat quartz substrate was prepared with a clean surface with no metal film or metal particles applied and nothing attached to the surface.

(Comparative example 2)
A flat quartz substrate was prepared with a clean surface with no metal film or metal particles applied and nothing attached to the surface. Thereafter, the step of spray-coating the Au nanoparticle dispersion (average primary particle diameter 20.7 nm) on the substrate and drying the same is repeated three times to obtain the Au nanoparticles at the same dispersion density as in Examples 1 and 2 Distributed on the top.

(Comparative example 3)
Colloidal silica particles having an average particle diameter of 600 nm were single-layer coated on a quartz substrate by the LB method described below. First, N-phenyl-3-aminopropyltrimethoxysilane as a hydrophobizing agent was added to the silica particle slurry, and hydrophobization was performed at a reaction temperature of 40.degree. Thereafter, the hydrophobized silica particles were subjected to oil layer extraction using a mixed solvent of ethanol: chloroform = 30: 70. Next, the above-mentioned hydrophobized particle slurry was dropped onto the water surface of the lower layer water of pH 7.2 at 21 ° C. to form a particle monolayer film on the water surface. Furthermore, while compressing the particle monolayer film with the barrier, the clean flat quartz substrate previously 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 The After that, dry etching is performed under the conditions of 1.2 Pa, 2000/1800 W, Cl ₂ = 80 sccm, 100 sec using a dry etching apparatus (ME510I manufactured by Tokyo Electron Ltd.), and the structure period (pitch) 600 nm, structure height ( Vertical distance from the center point of the three particles to the top of the structure) 52 nm periodic relief structure was obtained. Furthermore, using a sputtering apparatus (ion sputtering apparatus E-1030, Hitachi High-Technologies), on the periodic uneven structure, an Au thin film is formed at a pressure of 6 to 8 Pa, a current value of 15 mA, and a deposition rate of 11.6 nm / min. The film was formed to a thickness of 2 nm.

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

 

The analysis substrates of Comparative Example 1 and Comparative Example 2 could not detect Raman scattering. In addition, although the Raman scattering could be detected in the substrate for analysis of Comparative Example 3, its intensity was lower than the intensities of all the examples.
On the other hand, in the analysis substrates of Examples 1 and 2, Raman scattering at a sample concentration of 100 μM was obtained at high intensity, and Raman scattering could be detected even at a sample concentration as low as 1 nM.

1 substrate 1a first surface 3, 3A metal film 5 metal nanoparticle 10 substrate for analysis G non-deposited area

Claims (3)

1. A substrate having a two-dimensional lattice structure in which at least a first surface is made of a dielectric or a semiconductor, and a plurality of recesses or projections are periodically arranged in two dimensions on the first surface;
   A metal film provided on the first surface of the substrate and having a surface sheet resistance at 25 ° C. of 5000 Ω / □ or less;
   A plurality of metal nanoparticles dispersed on the metal film and having an average primary particle diameter of 5 to 100 nm;
   An analytical substrate comprising:
2. The analytical substrate according to claim 1, wherein the two-dimensional lattice structure is a triangular lattice structure or a square lattice structure.
3. The metal film is provided as an island-like gap shape having a length of 1 μm or less in the major axis direction in the metal film, and a plurality of non-formed metal in which the first surface of the substrate is exposed without metal The analysis substrate according to claim 1, which has a membrane region.

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