JP2014016221A - Optical field amplifying device and method of manufacturing the same - Google Patents

Abstract

A photoelectric field enhancement device with excellent durability capable of detecting Raman scattered light with high sensitivity is obtained.
A thin film 20 made of a first metal or an oxide thereof is formed on a resin substrate 11, and the thin film 20 formed on the resin substrate 11 is hydrothermally reacted to oxidize the first metal. By forming a fine concavo-convex structure layer 22 made of a hydrate of a product, forming a metal fine concavo-convex structure layer 24 made of a second metal on the surface of the fine concavo-convex structure layer 22, and shrinking the resin substrate 11 by heating Then, a crack 30 is generated on the surface of the metal fine concavo-convex structure layer 24.
[Selection] Figure 1A

Description

  The present invention relates to a photoelectric field enhancement device having a fine metal concavo-convex structure capable of inducing localized plasmons and a method for manufacturing the same.

  There are known electric field enhancement devices such as a sensor device and a Raman spectroscopic device using an electric field enhancement effect by a localized plasmon resonance phenomenon on a metal surface. Raman spectroscopy is a method of obtaining a spectrum of Raman scattered light (Raman spectrum) by dispersing scattered light obtained by irradiating a substance with single wavelength light, and is used for identification of substances.

  In Raman spectroscopy, in order to enhance weak Raman scattered light, there is Raman spectroscopy using surface-enhanced Raman scattering (SERS: Surface Enhanced Raman Scattering), which uses a photoelectric field enhanced by localized plasmon resonance ( Non-patent document 1). This is because, when light is applied to a metal body, particularly a metal body having nano-order irregularities on the surface, the photoelectric field is enhanced by localized plasmon resonance, and the Raman of the sample in contact with the surface of the metal body is generated. This utilizes the principle that the scattered light intensity is enhanced. Surface-enhanced Raman spectroscopy can be carried out by using a substrate having a metal concavo-convex structure on the surface as a carrier (substrate) for supporting an object.

  As a substrate having a metal fine concavo-convex structure on its surface, a substrate in which concavo-convex is provided on the surface of an Si substrate and a metal film is formed on the concavo-convex surface is mainly used (see Patent Documents 1 to 3).

In addition, the surface of the Al substrate is anodized to form a part of the metal oxide layer (Al ₂ O ₃ ), which is naturally formed inside the metal oxide layer during the anodic oxidation process, and is opened on the surface of the metal oxide layer. A substrate in which a plurality of fine holes are filled with metal has also been proposed (see Patent Document 4).

  Furthermore, a device having a transparent fine concavo-convex structure made of boehmite on the surface of a transparent substrate, a metal film formed thereon, and a fine concavo-convex structure of metal has also been proposed (Patent Document 5, 6).

  On the other hand, in Non-Patent Document 2, a nanoporous film made of an alloy of silver and gold is formed by a dealloying reaction, and the film is placed on a polystyrene film and heated and shrunk, whereby a wrinkled structure larger than the nanoporous structure is formed. Is making. The nanoporous film alone has a large Raman enhancement effect, and the wrinkle-like structure enables further enhancement of the Raman signal intensity to increase the surface area and the number of hot spots.

JP-T-2006-514286 Japanese Patent No. 4347801 JP 2006-145230 A JP 2005-172569 A JP 2012-63293 A JP 2012-63294 A

Optics Express Vol.17, No.21 18556 Scientific Reports, 1: 112, DOI: 10.1038 / srep00112

  However, as described in Non-Patent Document 2, in a method in which a metal nanostructure (nanoporous film) is prepared separately from a substrate and then the structure is arranged on a substrate made of polystyrene film, the metal nanostructure is brittle. It is very difficult to arrange the device on the substrate, and in particular, it becomes difficult to manufacture a device having a large area. In addition, since the adhesion between the substrate and the metal nanostructure is poor, the nanostructure becomes wrinkled due to the shrinkage of the substrate, and it is easy to peel off from the wrinkled floating portion, and the durability is very low. is there.

  The present invention has been made in view of the above circumstances, and provides a method for producing a photoelectric field enhancement device having high durability and high strength at low cost.

The photoelectric field enhancement device of the present invention comprises a resin substrate,
A fine concavo-convex structure layer having a fine concavo-convex structure formed on a resin substrate and made of a hydrate of a metal oxide on the surface;
A metal fine concavo-convex structure layer formed on the surface of the fine concavo-convex structure layer and having a fine concavo-convex structure on the surface;
The metal fine concavo-convex structure layer has a crack.

  Here, the metal fine concavo-convex structure layer has a fine concavo-convex structure that can generate localized plasmons when irradiated with excitation light. Note that the fine concavo-convex structure capable of generating localized plasmons is generally a concavo-convex structure in which the average size and average pitch of the convex portions and concave portions forming the concavo-convex structure are smaller than the wavelength of the excitation light.

  In particular, the average pitch (period) of the fine uneven structure of the metal fine uneven structure layer is desirably 200 nm or less.

  Moreover, it is preferable that the distance (depth) between the vertex of a part and the bottom part of a recessed part is 200 nm or less.

  The average pitch of the unevenness is obtained by taking a surface image of the fine unevenness structure with an SEM (scanning electron microscope), binarizing it by image processing, and obtaining it by statistical processing.

  The average depth of the unevenness is determined by statistical processing by measuring the surface shape with an AFM (Atomic Force Microscope).

  Here, the crack means that the continuity of the metal fine concavo-convex structure layer is broken and the metal fine concavo-convex structure layer is partially divided. The crack (gap) of the crack is usually in the range of 1 nm to 100 μm (hereinafter referred to as 1 nm or more and 100 μm or less in this manner), and many differ depending on the location. The interval between cracks is preferably in the range of 1 nm to 10 μm, more preferably in the range of 1 nm to 1 μm, and most preferably in a state where a large number of portions of 1 nm to 10 nm are partially present or continuously present. There may be one such crack, but a larger number is preferable. In addition, the metal fine concavo-convex structure layer in which the continuity is divided by the crack may partially overlap at the crack portion (see FIG. 6B).

  The metal oxide hydrate is preferably boehmite or Bayerlite.

  The metal fine concavo-convex structure layer may be any material that can generate localized plasmons upon irradiation with excitation light, but is particularly preferably made of gold, silver, copper, aluminum, or platinum.

In the method for producing a photoelectric field enhancing device of the present invention, a first metal is formed by forming a thin film made of a first metal or an oxide of the first metal on a resin substrate and subjecting the thin film to hydrothermal reaction. Forming a fine concavo-convex structure layer having a fine concavo-convex structure made of an oxide hydrate of
On the surface of the fine uneven structure layer, a metal fine uneven structure layer having a fine uneven structure on the surface made of the second metal is formed,
Thereafter, the substrate is contracted to cause cracks in the metal fine concavo-convex structure layer.

  As in the case of the above photoelectric field enhancement device, the metal fine concavo-convex structure layer has a fine concavo-convex structure that can generate localized plasmons upon irradiation with excitation light, and the average of the convex and concave portions forming the concavo-convex structure. It is a concavo-convex structure in which the average size and the average pitch are smaller than the wavelength of the excitation light.

  In particular, the average pitch (period) of the fine uneven structure of the metal fine uneven structure layer is desirably 200 nm or less.

  In the above, the resin substrate can be contracted by heating the resin substrate.

The measuring apparatus of the present invention comprises the photoelectric field enhancing device of the present invention,
An excitation light irradiation unit for irradiating the photoelectric field enhancement device with excitation light;
And a light detection unit that detects light generated by the irradiation of excitation light.

  The photoelectric field enhancement device of the present invention can effectively induce localized plasmons on the surface of a metal fine concavo-convex structure when light is irradiated onto a cracked metal fine concavo-convex structure. An enhancement effect can be produced. At this time, since the metal fine concavo-convex structure layer has cracks, it is possible to generate a high-intensity photoelectric field as compared with the case of only the metal fine concavo-convex structure layer.

  In addition, by placing a subject on this photoelectric field enhancement device and irradiating the region where the subject is placed with light, the light generated from the subject is enhanced by the photoelectric field enhancement effect. It becomes possible to detect light with sensitivity. It can be suitably used as a surface-enhanced Raman substrate, the Raman signal can be effectively enhanced, and high sensitivity can be achieved.

  According to the method for manufacturing a photoelectric field enhancing device of the present invention, a metal fine concavo-convex structure layer is cracked by a simple method of providing a fine concavo-convex structure layer and a metal fine concavo-convex structure layer on a resin substrate and shrinking the resin substrate. Photoelectric field enhancement devices that can be generated and produce a very high intensity photoelectric field can be produced.

  Also, since the fine uneven structure layer is formed directly on the resin substrate, and further the metal fine uneven structure layer is formed, compared with the case where the nanostructure is formed in advance and then placed on the substrate to shrink the substrate And since it is excellent in adhesiveness, its durability is high.

Since the photoelectric field enhancement device can be obtained by such a very simple process, the manufacturing cost can be suppressed.
In addition, each step in the manufacturing method can be applied to a substrate having a relatively large area or a substrate having an arbitrary shape, and a photoelectric field enhancing device having a large area and an arbitrary shape can be manufactured.

The perspective view which shows the photoelectric field enhancement board | substrate 1 which concerns on 1st Embodiment of a photoelectric field enhancement device. Enlarged view of a part IB of the side surface of the photoelectric field enhancement substrate 1 shown in FIG. 1A Sectional drawing which shows the manufacturing process of a photoelectric field enhancement board | substrate Schematic diagram showing the configuration of an enhanced Raman spectroscopic device provided with a photoelectric field enhancing substrate 1 Schematic showing an example of design change of an enhanced Raman spectrometer SEM image of boehmite layer surface SEM image of the surface of the metal fine relief structure layer SEM image of the enlarged part of Fig. 6A Graph showing Raman spectrum distribution obtained using a cracked and crack-free substrate

  Hereinafter, an embodiment of a method for producing a photoelectric field enhancement device of the present invention will be described with reference to the drawings. In addition, for easy visual recognition, the scale of each component in the drawings is appropriately changed from the actual one.

  FIG. 1A is a perspective view showing a photoelectric field enhancement substrate 1 according to an embodiment of the photoelectric field enhancement device of the present invention, and FIG. 1B is an enlarged view of a part IB of a side surface of the photoelectric field enhancement substrate 1 shown in FIG. 1A. FIG.

  As shown in FIG. 1A and FIG. 1B, the photoelectric field enhancement substrate 1 includes a transparent resin substrate 10, a fine concavo-convex structure layer 22 having fine undulations on the surface, and the fine concavo-convex structure formed on the resin substrate 10. It has a metal fine concavo-convex structure layer 24 formed on the surface of the structure layer 22 and having fine concavo-convex on the surface, and further has a crack 30 penetrating from the surface of the metal fine concavo-convex structure layer 24 through the fine concavo-convex structure layer 23. ing. The formation period of the cracks 30 is larger than the fine uneven period of the metal fine uneven structure layer 24 or the like, and is specifically on the order of tens of μm. The crack (gap) of the crack 30 is several nanometers to several hundred micrometers, and it is particularly preferable that a part of 10 nm or less is included in part. The crack formation period is the average pitch between cracks in a predetermined direction in the plane of the substrate.

  Although the manufacturing method of the photoelectric field enhancing substrate will be described later, the crack 30 is generated by shrinking the resin substrate after forming the metal fine concavo-convex structure layer on the resin substrate. Has arisen in the rules.

  In this photoelectric field enhancing substrate 1, localized plasmon resonance is induced by light (hereinafter referred to as excitation light) irradiated on the surface of the metal fine concavo-convex structure layer 24. An enhanced photoelectric field is generated on the surface of the concavo-convex structure layer 24, and when excitation light is irradiated to the crack 30 of several nm formed in the metal fine concavo-convex structure layer 24, it is called a hot spot. It produces a more enhanced photoelectric field. Even if the crack is on the order of μm, the photoelectric field enhancement effect can be obtained.

  The resin substrate 1 preferably has a large volume shrinkage due to heating. In particular, a transparent plastic substrate such as polystyrene is preferable.

The fine concavo-convex structure layer 22 is made of a metal oxide hydrate (metal or metal oxide hydroxide). Specific examples include alumina hydrate. More specifically, alumina monohydrate boehmite (expressed as Al ₂ O ₃ .H ₂ O or AlOOH), alumina trihydrate ( Bayerlite (expressed as Al ₂ O ₃ .3H ₂ O or Al (OH) ₃ ), which is aluminum hydroxide).

  The fine concavo-convex structure layer 22 made of a metal oxide hydrate such as a boehmite layer is transparent, and as shown in FIG. 1B, although the size (vertical angle size) and direction are various, it is generally sawtooth. Has a cross-section. The fine unevenness of the fine uneven structure layer 22 is not limited as long as the period (average pitch) and depth are shorter than the wavelength of the excitation light, and the metal fine uneven structure layer 24 described later can be formed thereon. As the excitation light, visible light is usually used. Here, in the transparent fine concavo-convex structure 23, the pitch is the distance between the vertices of the nearest adjacent convex portions across the concave portion, and the depth is the distance from the convex vertex to the bottom of the adjacent concave portion.

  The fine unevenness on the surface of the metal fine unevenness structure layer 24 is a structure that can generate localized plasmons on the surface upon irradiation with excitation light, and the period (average pitch) and the depth should be shorter than the wavelength of the excitation light. . The period of the fine irregularities is on the order of several tens of nm to several hundreds of nm. In particular, the average depth from the apex of the convex part to the bottom of the adjacent concave part is 200 nm or less, and the average pitch between the apexes of the re-adjacent convex parts across the concave part Is preferably 200 nm or less. Furthermore, it is preferable that it is a magnitude | size which produces the enhanced electric field efficiently, and it is especially preferable that it is 10-150 nm.

  The metal constituting the metal fine concavo-convex structure layer 24 may be any metal that generates localized plasmons when irradiated with excitation light. Gold (Au), silver (Ag), copper (Cu), aluminum (Al) Platinum (Pt) or an alloy containing these as a main component is preferable. In particular, Au or Ag is more preferable.

  The metal fine concavo-convex structure layer 24 may be formed in substantially the same shape along the fine concavo-convex structure of the fine concavo-convex structure layer 22 serving as the base, or in a shape different from the fine concavo-convex structure of the fine concavo-convex structure layer 22. There may be. The period and depth do not have to coincide with each other.

A method for producing the photoelectric field enhancement substrate 1 according to this embodiment will be described with reference to FIG.
FIG. 2 is a cross-sectional view for each process, illustrating a process for manufacturing a photoelectric field enhancement substrate according to an embodiment of the photoelectric field enhancement device of the present invention.

  A plate-like resin substrate 10 is prepared and washed with ethanol. Thereafter, the aluminum 20 is deposited on the surface of the resin substrate 10 as a first metal by several tens to several hundreds of nanometers by EB (Electric Beam) vapor deposition. Thereafter, the substrate 10 with aluminum 20 is immersed in boiling pure water, and is taken out after several minutes to 1 hour. By this boiling treatment (boehmite treatment), the aluminum 20 becomes transparent and becomes a boehmite layer 22 constituting a transparent fine uneven structure. Next, a metal fine concavo-convex structure layer 24 is further formed on the boehmite layer 22 by depositing a second metal on the boehmite layer 22. Next, the substrate 10 is heated and contracted to cause cracks 30 in the boehmite layer 22 and the metal fine concavo-convex structure layer 24. In general, when a resin substrate is used, the resin substrate contracts by heating the resin substrate. The crack 30 is generated when the metal fine concavo-convex structure layer 24 is compressed as the resin substrate contracts.

  By the above process, the photoelectric field enhancing substrate 1 in which the fine uneven structure layer 22 and the metal fine uneven structure 24 are formed on the resin substrate 10 can be manufactured.

  In the above description, a plate-shaped substrate is used as the substrate. However, the present invention can be applied to a substrate having an arbitrary shape.

The first metal to be hydrothermally reacted in the fine concavo-convex structure layer manufacturing step includes aluminum, but a metal oxide such as alumina (Al ₂ O ₃ ) may be used instead. Aluminum and alumina form a fine concavo-convex structure with a complex triangular pyramid structure consisting of either buyer light (Al (OH) ₃ ) or boehmite (AlOOH) or both by hydrothermal reaction on the substrate. can do.

In the manufacturing process, as the first metal, in addition to aluminum, a metal that forms a fine uneven structure by a hydrothermal reaction, such as titanium (Ti), can be used. Alternatively, a first metal oxide (eg, Al ₂ O ₃ ) may be formed instead of the first metal.

Further, the method for forming the first metal or its metal oxide on the substrate 10 is not limited to the sputtering method, and a heating vapor deposition method or a sol-gel method may be used.
The hydrothermal reaction is not limited to boiling treatment, and the substrate on which the first metal is formed may be exposed to high-temperature water vapor so that the first metal reacts with high-temperature water vapor.

  The second metal constituting the metal fine concavo-convex structure layer 24 may be any metal that can generate localized plasmons when irradiated with excitation light. For example, gold (Au), silver (Ag), copper (Cu ), Aluminum (Al), platinum (Pt), or an alloy containing these as a main component. In particular, Au or Ag is preferable.

  The photoelectric field enhancing device of the present embodiment uses a transparent resin substrate such as plastic as the resin substrate 10 and includes a transparent fine uneven structure layer 22 such as a buyer light layer or a boehmite layer. Even if excitation light is incident, a light enhancement field can be generated on the surface of the metal fine concavo-convex structure layer 24, and signal light such as Raman signal light can be detected from either the front or back of the substrate. Here, the term “transparent” means that the transmittance is 50% or more with respect to the irradiated light and the light generated from the subject by the light. Note that the transmittance of these lights is preferably 75% or more, and more preferably 90% or more.

In the above embodiment, the second metal is only one layer, but two or more kinds of metals may be laminated. A dielectric may be laminated on the second metal.
Thus, by laminating two or more kinds of metals or laminating a dielectric on the second metal, it is possible to provide an interference effect and an antioxidant effect. That is, when the thickness of the layer structure matches the phase with light due to the effect of optical interference, the light is confined in the layer structure, and a further photoelectric field enhancement effect can be generated. Further, for example, by providing a silver layer as the second metal and laminating a gold layer thereon, oxidation of silver can be suppressed.
In addition, when laminating | stacking a dielectric material on the metal fine concavo-convex structure layer which consists of a 2nd metal, it is desirable that the film thickness of a dielectric material shall be 50 nm or less. For example, 10 nm of SiO ₂ is laminated on the metal microstructure layer.

(Raman spectroscopy and Raman spectrometer)
Below, a Raman spectroscopy and a Raman spectroscopy apparatus are demonstrated as an example of the measuring method using the above-mentioned photoelectric field enhancement board | substrate 1 of this invention.

  FIG. 3 is a schematic diagram showing a configuration of an enhanced Raman spectroscopic device including the photoelectric field enhancing substrate 1 according to the above-described embodiment.

  As shown in FIG. 3, the Raman spectroscopic device 100 includes the above-described photoelectric field enhancement substrate 1, the excitation light irradiation unit 140 that irradiates the photoelectric field enhancement substrate 1 with the excitation light L1, and the photoelectric field enhancement emitted from the subject S. And a light detection unit 150 for detecting Raman scattered light L2 enhanced by the action of the substrate.

  The excitation light irradiation unit 140 includes a semiconductor laser 141 that emits the excitation light L1, a mirror 142 that reflects the light L1 emitted from the semiconductor laser 141 toward the substrate 1, and the excitation light L1 reflected by the mirror 142. Transmitted through the half mirror 144 and the half mirror 144 that reflects light from the substrate 1 side including the enhanced Raman scattered light L2 generated from the subject S by irradiation of the excitation light L1 to the light detection unit 150 side And a lens 146 that condenses the excitation light L1 in a region of the photoelectric field enhancement substrate 1 on which the subject S is placed.

  The light detection unit 150 absorbs the excitation light L1 out of the light reflected by the half mirror 144 and transmits the other light, and a pin provided with a pinhole 152 for removing noise light. A lens 154 for condensing the enhanced Raman scattered light L2 emitted from the Hall plate 153, the subject S, and transmitted through the lens 146 and the notch filter 151 to the pinhole 152, and the Raman scattered light passing through the pinhole 152 Is provided with a lens 156 for collimating light and a spectroscope 158 for detecting enhanced Raman scattered light.

  A Raman spectroscopy method for measuring the Raman spectrum of the subject S using the above-described Raman spectrometer 100 will be described.

  Excitation light L1 is emitted from the semiconductor laser 141 of the light irradiation unit 140, the excitation light L1 is reflected to the substrate 1 side by the mirror 142, passes through the half mirror 144 and is collected by the lens 146, and the photoelectric field enhancement substrate 1 Irradiated on top.

  Irradiation with the excitation light L1 induces localized plasmon resonance in the metal fine concavo-convex structure layer 24 of the photoelectric field enhancing substrate 1, and an enhanced photoelectric field is generated on the surface of the metal fine concavo-convex structure layer 24. The Raman scattered light L2 emitted from the subject S enhanced by the enhanced photoelectric field passes through the lens 146 and is reflected by the half mirror 144 toward the spectroscope 158 side. At this time, the excitation light L1 reflected by the photoelectric field enhancement substrate 1 is also reflected by the half mirror 144 and reflected to the spectroscope 158 side, but the excitation light L1 is cut by the notch filter 151. On the other hand, light having a wavelength different from that of the excitation light passes through the notch filter 151, is condensed by the lens 154, passes through the pinhole 152, is collimated again by the lens 156, and enters the spectroscope 158. In the Raman spectroscopic device, the wavelength of Rayleigh scattered light (or Mie scattered light) is the same as that of the excitation light L 1, so that it is cut by the notch filter 151 and does not enter the spectroscope 158. The Raman scattered light L2 enters the spectroscope 158 and is subjected to Raman spectrum measurement.

  The Raman spectroscopic device 100 of the present embodiment is configured using the photoelectric field enhancement substrate 1 of the above embodiment, and since the Raman enhancement is effectively performed, the data reliability is high and the data reproducibility is high. Good high-precision Raman spectroscopic measurement can be performed. Since the in-plane uniformity of the surface concavo-convex structure of the photoelectric field enhancing substrate 1 is high, data with good reproducibility can be obtained even if the same sample is measured by changing the light irradiation location. Therefore, it is possible to take a plurality of data by changing the light irradiation location for the same sample, and to improve the reliability of the data.

  As in the Raman spectroscopic device 100 of the present embodiment, the configuration in which detection is performed from the back surface of the photoelectric field enhancement substrate 1 allows the metal fine concavo-convex structure layer and the subject to be detected when the subject is a large sample such as a cell. Can be detected from the back side of the transparent substrate without being shielded by the subject itself. In addition, if the metal fine concavo-convex structure layer has a certain thickness, enhanced Raman scattered light can be sufficiently detected from the back side of the transparent substrate.

  The Raman spectroscopic apparatus 100 according to the above-described embodiment is configured so that excitation light is incident from the side opposite to the sample holding surface (front surface) of the photoelectric field enhancing device 1 (back surface of the device) and Raman scattered light is detected. However, as shown in FIG. 4 showing a Raman spectroscopic device 110 of a design change example, the excitation light L1 is incident from the surface side (sample holding surface) of the metal fine concavo-convex structure layer 24 and Raman scattering is performed as in the conventional device. You may comprise so that the light L2 may be detected.

  Furthermore, it is good also as a structure which arrange | positions any one of an excitation light irradiation part and a light detection part in the surface side of the metal fine concavo-convex structure layer 24, and arrange | positions the other in the back surface side of the board | substrate 1. FIG.

  Thus, since the photoelectric field enhancement device of the present invention uses a transparent substrate, light can be irradiated from either the surface side of the metal fine concavo-convex structure layer or the back side of the transparent substrate, Light generated from the sample by this light irradiation can also be detected from either the surface side of the metal fine concavo-convex structure layer or the back side of the transparent substrate. Therefore, depending on the type, size, etc. of the subject, irradiation of excitation light and detection of detection light can be performed from either the front surface side of the metal fine concavo-convex structure layer or the back surface side of the transparent substrate. The degree is high, and it is possible to detect with a higher S / N.

  As described above, the photoelectric field enhancement device of the present invention can be applied to a plasmon enhanced fluorescence detection apparatus. Even in such a case, the subject may be placed on the metal fine concavo-convex structure layer of the photoelectric field enhancing device, and excitation light may be irradiated from the subject side to detect the enhanced fluorescence from the subject side. The excitation light may be irradiated from the back side of the transparent substrate, and the fluorescence may be detected from the back side. Or you may irradiate excitation light from the subject side, and you may comprise so that fluorescence may be detected from the transparent substrate back surface side.

  Hereinafter, the result of having performed the Raman spectroscopic measurement using the specific example of the photoelectric field enhancement board | substrate 1 which is embodiment of the photoelectric field enhancement device of this invention, and the sample for a measurement is demonstrated.

"Optical field enhancement substrate"
After 100 nm of aluminum was EB-deposited on a substrate (ZEONEX (registered trademark) 330R), 50 nm of Au was deposited on a substrate provided with a boehmite layer formed by boiling for 1 hour. FIG. 5 is an SEM image obtained by photographing the substrate surface with an SEM (Hitachi S4100). In FIG. 5, convex portions are observed in white, and concave portions are observed in gray. Although the uneven pattern is irregular, it is uniformly formed on the entire surface, and the in-plane uniformity of the fine uneven structure made of boehmite and Au is high.

  Further, the substrate was heated at 140 ° C. for 10 minutes using a hot plate. 6A is an SEM image obtained by photographing the heated Au surface with an SEM, and FIG. 6B is an SEM image obtained by enlarging a crack portion on the Au surface.

  As shown in FIG. 6A, the Au surface has a plurality of cracks due to substrate shrinkage. When the crack portion is enlarged, it can be seen that the fine concavo-convex structure made of metal is close as shown in FIG. 6B. The crack is caused by the compressive stress applied when the substrate is heated and contracted. In the vicinity of the crack, a part of the metal microstructure is floated by the compression, and one of them overlaps the other with the crack interposed therebetween. Due to this crack, many hot spots are formed, and a larger signal can be obtained than in the case of only the metal fine concavo-convex structure.

"Raman spectroscopy measurement using measurement samples"
A substrate having a crack (with cracks) in the metal concavo-convex structure layer produced in the production process and a substrate having no crack (no crack) in the metal concavo-convex structure layer before heating the substrate in the production process, A sample obtained by dropping 40 μL of a 100 μM rhodamine 6G ethanol solution onto a substrate and drying the sample was measured with a Raman microscope (manufactured by Nanophoton: Raman5).

FIG. 7 shows the Raman shift spectrum distribution obtained for two measurement samples. The excitation wavelength is 785 nm, and a 20 × objective lens is used. Integration time is 10 seconds and averaging is performed twice.
From this data, the Raman signal can be obtained three times as much as the case where there is a crack compared to the case where there is no crack, demonstrating the electric field enhancement effect of forming a crack.

1 Photoelectric field enhancement substrate (photoelectric field enhancement device)
DESCRIPTION OF SYMBOLS 11 Transparent substrate 20 Aluminum 22 Fine uneven structure layer 24 Metal fine uneven structure layer 30 Crack 100 Raman spectroscopic device 140 Excitation light irradiation part 150 Photodetection part

Claims (8)

A resin substrate;
A fine concavo-convex structure layer having a fine concavo-convex structure formed on the surface of the resin substrate and made of a metal oxide hydrate;
A metal fine concavo-convex structure layer formed on the fine concavo-convex structure layer and having a fine concavo-convex structure on the surface,
A photoelectric field enhancement device, wherein the metal fine concavo-convex structure layer has a crack.   The photoelectric field enhancement device according to claim 1, wherein a period of the fine uneven structure of the metal fine uneven structure layer is 200 nm or less.   The photoelectric field enhancement device according to claim 1 or 2, wherein the metal oxide hydrate is boehmite or Bayerlite.   The method for producing a photoelectric field enhancement device according to any one of claims 1 to 3, wherein the metal fine concavo-convex structure layer is made of gold, silver, copper, aluminum, or platinum. A thin film made of the first metal or the oxide of the first metal is formed on the resin substrate, and the thin film is hydrothermally reacted to thereby form a fine film made of the hydrate of the first metal oxide. Forming a fine concavo-convex structure layer having a concavo-convex structure on its surface;
On the surface of the fine uneven structure layer, a metal fine uneven structure layer having a fine uneven structure on the surface made of the second metal is formed,
Thereafter, the resin substrate is contracted to cause cracks in the metal fine concavo-convex structure layer.   6. The method of manufacturing a photoelectric field enhancement device according to claim 5, wherein a period of the fine uneven structure of the metal fine uneven structure layer is 200 nm or less.   The method of manufacturing a photoelectric field enhancement device according to claim 5 or 6, wherein the resin substrate is contracted by heating the resin substrate. The photoelectric field enhancement device according to any one of claims 1 to 4,
An excitation light irradiation unit for irradiating the photoelectric field enhancement device with excitation light;
A measurement apparatus comprising: a light detection unit that detects light generated by the irradiation of the excitation light.