Measurement method and structure

Abstract

To provide a measurement method and a structure capable of easily visualizing plasmon waves.SOLUTION: The measurement method includes a preparation step and a measurement step. In the preparation step, a structure 30 is prepared by applying a light-emitting material 22 to a substrate 10. The substrate 10 includes an interface between a metal layer 14 and a dielectric layer 12. In the measurement step, a plasmon wave is generated in the substrate 10 of the structure 30, and light output from the light-emitting material 22 of the structure 30 is measured in response to the generation of plasmon wave. The light-emitting material 22 is a light-emitting particle such as a quantum dot.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a measurement method and structure. [Background technology]

[0002] Attempts are being made to utilize plasmon waves in electronic and communication devices. In the development of such devices, it is important to understand the state of plasmon waves. However, since the propagation of plasmon waves is a phenomenon that does not involve radiation, it cannot be seen as it is. Technology is needed to visualize the propagation state of plasmon waves.

[0003] Non-Patent Document 1 describes that the propagation of plasmon waves was visualized by photoelectron microscopy and the wave characteristics were evaluated.

[0004] Non-Patent Document 2 describes that a resin layer containing a dye was formed on silver, and the fluorescence generated from the dye in association with the propagation of plasmon waves was observed with an optical microscope. [Prior art documents] [Non-patent literature]

[0005] [Non-Patent Document 1] Atsushi Kubo et al., "Visualization of Surface Plasmon Waves by Femtosecond Laser Excitation Photoelectron Microscopy," Surface Science, Japan Surface Science Society, Vol. 33, No. 4, 2012, pp. 235-241 [Non-Patent Document 2] Tatsumi Hattori and 4 others, "Femtosecond Laser-Excited Two-Photon Fluorescence Microscopy of Surface Plasmon Polariton", Japanese Journal of Applied Physics, The Japan Society of Applied Physics, 2012, Vol. 51, 04DG03 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the technique of Non-Patent Document 1 requires the use of a photoelectron microscope, so that the measurement target must be placed under ultra-high vacuum, limiting the measurement target. In addition, it requires special and advanced experimental techniques. In addition, the technique of Non-Patent Document 2 requires the inclusion of a dye in the dielectric layer, limiting the measurement target.

[0007] The present invention provides a measurement method and structure that can easily visualize plasmon waves. [Means for solving the problem]

[0008] According to one aspect of the present invention, the following measurement method and structure are provided.

[0009] 1. preparing a structure by applying a light emitting material to a substrate including an interface between a metal layer and a dielectric layer; generating a plasmon wave on the substrate in the structure, and measuring light output from the light-emitting material of the structure in response to the generation of the plasmon wave. Measurement method. 2. In the measurement method described in 1., the substrate has a laminated region in which the metal layer and the dielectric layer are laminated in contact with each other, In the structure, the dielectric layer is located between the metal layer in the laminated region and the light-emitting material. Measurement method. 3. In the measurement method according to 1. or 2., In the measuring step, light output from a measurement surface which is at least one surface of the structure is measured; The structure includes, in at least a part of the region, the light emitting material, the dielectric layer, and the metal layer in this order from the measurement surface side. Measurement method. 4. In the measurement method according to any one of 1. to 3., the base has a first surface on the dielectric layer side and a second surface on the metal layer side opposite to the first surface, In the structure, the light-emitting material is applied to at least a partial area of ​​the first surface of the base at a coverage rate of 30% or more and 100% or less. Measurement method. 5. In the measurement method according to any one of 1. to 4., In the step of preparing the structure, a light-emitting layer including the light-emitting material is formed on the base. Measurement method. 6. In the measurement method according to 5., The light-emitting layer includes an alternating laminate of light-emitting particles as the light-emitting material and a polymer. Measurement method. 7. In the measurement method according to 6., In the step of preparing the structure, the substrate is immersed in a first liquid containing the light-emitting particles and a second liquid containing the polymer in that order to form the light-emitting layer. Measurement method. 8. In the measurement method according to any one of 1. to 7., The method further includes removing the luminescent material from the structure after the measuring step. Measurement method. 9. In the measurement method according to 8., In the removing step, the light-emitting material is washed away from the structure with water. Measurement method. 10. In the measurement method according to any one of 1. to 9., In the measuring step, light output from the light emitting material of the structure is measured using an optical microscope. Measurement method. 11. In the measurement method according to any one of 1. to 10., The substrate is at least a part of a waveguide, a solar cell, a photosensor, or a communication circuit. Measurement method. 12. A substrate including an interface between a metal layer and a dielectric layer; a luminescent material applied to the substrate; The dielectric layer is located between the metal layer and the light-emitting material in at least a portion of the region. structure. 13. The structure according to 12., the substrate has a laminated region in which the metal layer and the dielectric layer are laminated in contact with each other, The dielectric layer is located between the metal layer and the light emitting material in the laminated region. structure. 14. The structure according to 12. or 13., the base has a first surface on the dielectric layer side and a second surface on the metal layer side opposite to the first surface, The light-emitting material is applied to at least a partial area of ​​the first surface of the base body at a coverage rate of 30% or more and 100% or less. structure. 15. The structure according to any one of 12. to 14., The structure includes a light-emitting layer that includes the light-emitting material. structure. 16. The structure according to 15., The light-emitting layer includes an alternating laminate of light-emitting particles as the light-emitting material and a polymer. structure. 17. The structure according to any one of claims 12 to 16, The substrate is at least a part of a waveguide, a solar cell, a photosensor, or a communication circuit. structure. Effect of the Invention

[0010] According to the present invention, it is possible to provide a measurement method and a structure that can easily visualize plasmon waves. [Brief description of the drawings]

[0011] [Figure 1] FIG. 2 is a diagram showing an overview of a measurement process according to the embodiment. [Diagram 2] FIG. 2 is a diagram illustrating a configuration of a base body according to an embodiment. [Diagram 3]1A to 1C are diagrams illustrating the configuration of a structure according to an embodiment. [Figure 4] FIG. 13 is a diagram showing a first modified example of a structure. [Diagram 5] FIG. 11 is a diagram showing a second modified example of the structure. [Figure 6] This is an electron microscope image of a part of a sample in which a gold film with slits is formed on a glass substrate. [Figure 7] FIG. 13 is a diagram showing measurement results according to an embodiment. [Figure 8] FIG. 13 is a diagram showing measurement results according to an embodiment. [Figure 9] 8 is a schematic diagram showing a cross section of the structure A in the measurement range of FIG. 7. FIG. [Figure 10] The images were obtained with excitation light wavelengths of 780 nm, 820 nm, and 860 nm, respectively. [Figure 11] 1 is a graph showing light intensity profiles obtained at each of several excitation wavelengths. [Figure 12] 12 is a graph showing the relationship between the beat wavelength λ beat calculated based on FIG. 11 and the pump wavelength, and the relationship between k′SPP and the pump wavelength. [Figure 13] 1 is a graph showing the relationship between k′SPP and the angular frequency ω of the plasmon wave. [Figure 14] 1 is a graph showing the relationship between the number of layers of a CdTe quantum dot film and the wave number of a plasmon wave. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In all the drawings, the same components are given the same reference numerals and the description will be omitted as appropriate.

[0013] FIG. 1 is a diagram showing an overview of a measurement process according to an embodiment. The measurement method according to this embodiment includes a preparation process and a measurement process. In the preparation process, a light emitting material 22 is attached to a substrate 10 to prepare a structure 30. The substrate 10 includes an interface between a metal layer 14 and a dielectric layer 12. In the measurement process, a plasmon wave is generated in the substrate 10 in the structure 30, and light output from the light emitting material 22 of the structure 30 in response to the generation of the plasmon wave is measured. The measurement method according to this embodiment will be described in detail below.

[0014] The measurement method according to the present embodiment is not limited to the example shown in Fig. 1. In addition, applying the luminescent material 22 to the base 10 includes not only applying the luminescent material 22 directly to the base 10, but also applying the luminescent material 22 to the base 10 via another layer or the like.

[0015] Plasmon waves, also known as propagating surface plasmon polaritons (SPPs), are known as collective oscillations of free electrons propagating at the interface between metals and dielectrics. It is expected that new electronic devices, communication devices, optical elements, solar cells, etc. will be developed using plasmon waves. In developing such devices, it is important to understand the generation and propagation conditions of plasmon waves, as well as the wave characteristics. In other words, it is necessary to understand what kind of plasmon waves are generated, where they are generated, and how they are propagating in the device structure. However, since the propagation of plasmon waves does not involve radiation, some kind of visualization technique is necessary to understand the generation and propagation conditions of plasmon waves and their wave characteristics.

[0016] Examples of visualization techniques for plasmon waves include a method using a scanning near-field optical microscope and a method using a photoelectron microscope. However, the scanning near-field optical microscope has problems such as the time required for imaging, low time resolution, and the need for advanced operation techniques. In addition, the photoelectron microscope has problems such as the need to place the measurement target under ultra-high vacuum, limiting the measurement target, and requiring special and advanced operation techniques. There is also a method using an optical (fluorescence) microscope, but there are problems such as low detection sensitivity and the need to incorporate dye into the structure to be measured in the method shown in Non-Patent Document 2.

[0017] In contrast, in the measurement method according to the present embodiment, the electromagnetic energy generated by the plasmon wave is converted into light and measured, so that the propagation pattern and wave physical characteristics can be easily evaluated. This light measurement can be performed, for example, by a general-purpose optical microscope, and does not require skilled techniques. In addition, there is no need to prepare a sample specifically for the measurement by changing the material, and the measurement can be performed by attaching the light-emitting material 22 to any measurement object.

[0018] Furthermore, as will be described in detail later, by uniformly applying the luminescent material 22 to the substrate 10, it is possible to perform evaluation with high resolution and high accuracy. When the luminescent material 22 is applied to the substrate 10 so as to be removable later, the original substrate 10 can be obtained by removing the luminescent material 22 from the substrate 10 after the measurement process.

[0019] FIG. 2 is a diagram illustrating the configuration of the base 10 according to the present embodiment. FIG. 3 is a diagram illustrating the configuration of the structure 30 according to the present embodiment. The structure 30 in FIG. 3 is obtained by applying a light-emitting material 22 to the base 10 in FIG. 2. Note that the base 10 and the structure 30 according to the present embodiment are not limited to the examples shown in these figures. The base 10 and the structure 30 according to the present embodiment will be described in detail below with reference to FIG. 2 and FIG. 3.

[0020] The structure 30 includes a substrate 10 and a light-emitting material 22 applied to the substrate 10. The substrate 10 includes an interface between a metal layer 14 and a dielectric layer 12. In the example of Fig. 3, the dielectric layer 12 is located between the metal layer 14 and the light-emitting material 22 in at least a partial region of the structure 30.

[0021] The substrate 10 may be a part of a device having some function, or may be a structure having no particular function. The substrate 10 is not particularly limited, but may be at least a part of a waveguide, a solar cell, an optical sensor, or a communication circuit, for example.

[0022] There is no particular limitation on the metal layer 14 as long as it is capable of generating plasmon waves. The metal constituting the metal layer 14 may be, for example, gold, silver, or aluminum, or may be an alloy containing one or more selected from gold, silver, and aluminum. The metal layer 14 may also have a multi-layer structure made up of layers of different metals.

[0023] The thickness of the metal layer 14 is preferably 100 nm or more. The thickness of the metal layer 14 may be 200 nm or more. The thickness of the metal layer 14 is not particularly limited, but is, for example, 10 mm or less.

[0024] The material constituting the dielectric layer 12 may be an inorganic material or an organic material, so long as it is a dielectric material. When the dielectric layer 12 is an organic material, the dielectric layer 12 includes at least one selected from, for example, a resin and an organic molecular film. The dielectric layer 12 may function, for example, as a carrier activation layer, a protective film, or the like in a device. In the measurement step according to this embodiment, since light emission from the light-emitting material 22 is measured, the dielectric layer 12 may or may not have optical transparency. In addition, the dielectric layer 12 may have a multilayer structure consisting of layers of different materials. The dielectric layer 12 according to this embodiment may not include a light-emitting material, etc.

[0025] The thickness of the dielectric layer 12 is not particularly limited as long as it exceeds 0 nm, but is preferably 1 nm or more, more preferably 100 nm or more, and even more preferably 300 nm or more. The thickness of the dielectric layer 12 is, for example, 1000 nm or less, and preferably 800 nm or less.

[0026] The substrate 10 has a laminated region 18 in which the metal layer 14 and the dielectric layer 12 are laminated in contact with each other. In the example of FIG. 2, the substrate 10 is entirely the laminated region 18. In the substrate 10, the plasmon wave propagates through the interface between the dielectric layer 12 and the metal layer 14. The substrate 10 only needs to include the interface between the dielectric layer 12 and the metal layer 14 in at least a portion thereof, and may have a region in which another layer is interposed between the dielectric layer 12 and the metal layer 14. The substrate 10 also has an origin structure 16 that can be a origin of the propagation of the plasmon wave. The origin structure 16 can be, for example, at least one of a slit, a groove, a beam, a hole, an edge, a step, and a convex portion. However, the origin structure 16 can be not only an intentionally formed structure, but also an unintentionally generated structure such as a defect or dust. In the example of FIG. 2, the origin structure 16 is a step.

[0027] The base 10 may further include a layer such as a glass substrate. However, it is preferable that at least a part of the first surface 101, which is the surface of the base 10 facing the dielectric layer 12, is made of the dielectric layer 12.

[0028] The substrate 10 can be produced using existing techniques, such as a dry process such as deposition, a wet process such as a coating method, cutting of metals, various types of lithography, and microfabrication using a focused ion beam.

[0029] In the preparation step, the structure 30 is obtained by applying the luminescent material 22 to the base 10. The method of applying the luminescent material 22 to the base 10 will be described in detail later.

[0030] As described above, the substrate 10 has a laminated region 18 in which the metal layer 14 and the dielectric layer 12 are laminated in contact with each other. In the structure 30, the dielectric layer 12 is located between the metal layer 14 in the laminated region 18 and the light emitting material 22. In addition, the structure 30 includes the light emitting material 22, the dielectric layer 12, and the metal layer 14 in this order from the measurement surface 301 side in at least a part of the region. In other words, in at least any cross section perpendicular to the measurement surface 301, the structure 30 has a region in which the light emitting material 22, the dielectric layer 12, and the metal layer 14 are laminated in this order. The measurement surface 301 is at least any surface of the structure 30, and in the measurement process, the light output from the measurement surface 301 is measured.

[0031] As described above, the base 10 has a first surface 101 which is the surface on the dielectric layer 12 side. The base 10 also has a second surface 102 which is the surface opposite to the first surface 101 and is the surface on the metal layer 14 side. In the preparation step, the light emitting material 22 is applied to the first surface 101 of the base 10.

[0032] FIG. 4 is a diagram showing a first modified example of the structure 30. The light emitting material 22 may be applied to the entire first surface 101, or may be applied selectively to a partial region of the first surface 101. FIG. 3 shows an example in which the light emitting material 22 is applied to the entire first surface 101, and FIG. 4 shows an example in which the light emitting material 22 is applied selectively to a partial region of the first surface 101. For example, by performing masking when applying the light emitting material 22 to the base 10, the light emitting material 22 can be applied selectively to a partial region of the first surface 101. The light emitting material 22 is applied to the base 10 so as to cover at least a region where a plasmon wave can be generated.

[0033] The light emitting material 22 may be attached not only to the first surface 101 of the base 10 but also to the second surface 102 and other side surfaces.

[0034] In this manner, in the structure 30, the luminescent material 22 is applied to at least a partial region of the first surface 101 of the base 10. In the structure 30, the luminescent material 22 may be applied to at least a partial region of the first surface 101 of the base 10 with a coverage of 100% or less than 100%. In the structure 30, the luminescent material 22 is preferably applied to at least a partial region of the first surface 101 of the base 10 with a coverage of 30% or more.

[0035] The light-emitting material 22 is, for example, a fluorescent material. The light-emitting material 22 may be a low molecular weight material or a high molecular weight material. Alternatively, the light-emitting material 22 may be a light-emitting particle such as a quantum dot. An example of the light-emitting particle is a nanoparticle. The particle size of the light-emitting particle is, for example, 1 nm or more and 10 nm or less. The light-emitting particle is, for example, one or more selected from the group consisting of CdS quantum dots, CdSe quantum dots, ZnTe quantum dots, CdTe quantum dots, HgSe quantum dots, HgTe quantum dots, HgS quantum dots, ZnS quantum dots, ZnSe quantum dots, CuInSe quantum dots, CuInS quantum dots, PbS quantum dots, PbSe quantum dots, InP quantum dots, InAs quantum dots, GaP quantum dots, and GaAs quantum dots. The surface of the quantum dot may have a ligand. The shape of the light-emitting particle may be spherical or non-spherical. The luminescent particles may also have a core-shell structure combining two or more components selected from the group consisting of CdS, CdSe, ZnTe, CdTe, HgSe, HgTe, HgS, ZnS, ZnSe, CuInSe, CuInS, PbS, PbSe, InP, InAs, GaP, and GaAs.

[0036] In the example of Fig. 3, the structure 30 includes a light-emitting layer 20 including a light-emitting material 22. That is, in the preparation step, the light-emitting layer 20 including the light-emitting material 22 may be formed on the base 10. When the light-emitting material 22 is light-emitting particles, the light-emitting layer 20 is, for example, a monoparticle film of the light-emitting particles or a deposited film of the light-emitting particles. As another example, the light-emitting layer 20 may include a resin binder or the like in addition to the light-emitting material 22.

[0037] The thickness of the light-emitting layer 20 is not particularly limited, but is, for example, 2 nm or more, preferably 3 nm or more, and more preferably 5 nm or more. The thickness of the light-emitting layer 20 is not particularly limited, but is, for example, 50 nm or less, preferably 30 nm or less, and more preferably 20 nm or less.

[0038] Fig. 5 is a diagram showing a second modified example of the structure 30. In the example of Fig. 5, the light-emitting layer 20 includes an alternating laminate of light-emitting particles as the light-emitting material 22 and a polymer 24. In the example of Fig. 5, the structure 30 further includes an underlayer 35 between the light-emitting layer 20 and the base 10. The underlayer 35 is, for example, a polymer layer. Additionally, in the example of Fig. 5, the structure 30 includes a substrate 15, on which a metal layer 14 and a dielectric layer 12 are laminated. The substrate 15 is, for example, a glass substrate.

[0039] When the light-emitting layer 20 includes a layer of the light-emitting material 22, the number of layers of the light-emitting material 22 in the light-emitting layer 20 is not particularly limited, and may be, for example, 1 to 10 layers, preferably 1 to 5 layers, and more preferably 1 to 3 layers. As described above, the light-emitting material 22 attached to the base 10 may be less than one layer. In the above-mentioned alternate laminate, the outermost surface of the light-emitting layer 20 may be a layer of the light-emitting material 22 or a layer of the polymer 24. The more layers there are, the higher the intensity of the light measured in the measurement step can be. On the other hand, in order to suppress the influence on the physical phenomenon in the base 10, it is preferable that the number of layers is small.

[0040] In the example of Fig. 5, the laminated region 18 is a part of the base 10. Also in the example of Fig. 5, the starting structure 16 is a step. The first surface 101 of the base 10 may be flat (for example, Fig. 5) or may have projections and recesses (for example, Fig. 3).

[0041] An example of a method for applying the luminescent material 22 to the substrate 10 is described in detail below.

[0042] It is preferable that the light emitting material 22 is applied uniformly to the substrate 10. By doing so, it is possible to measure light that more accurately reflects the state of the plasmon wave, and as a result, it is possible to measure the state of the plasmon wave with high accuracy.

[0043] In the preparation step, for example, a Layer-by-Layer method (LBL method) that utilizes electrostatic interaction can be used to form the light-emitting layer 20. In the LBL method, the base 10 is immersed in a first liquid containing light-emitting particles and a second liquid containing polymers 24, in that order, to form the light-emitting layer 20.

[0044] The first liquid contains water and luminescent particles. The luminescent particles are attached with ligands. In the first liquid, luminescent particles with ligands are dispersed in water. In the first liquid, the ligands are negatively charged. On the other hand, the second liquid contains water and polymers 24. The second liquid may also contain a pH adjuster. The pH adjuster is, for example, sodium hydroxide. In the second liquid, the polymers 24 are dispersed in water. In the second liquid, the polymers 24 are positively charged. By immersing the substrate 10 in the first liquid and the second liquid in turn, a uniform laminate of the luminescent particles and the polymers 24 is obtained by electrostatic interaction. In particular, by immersing the substrate 10 alternately in the first liquid and the second liquid, a uniform alternating laminate of the luminescent particles and the polymers 24 is obtained by electrostatic interaction. That is, when the substrate 10 having a layer of polymers 24 formed on its surface is immersed in the first liquid, the negatively charged light-emitting particles adhere to the positively charged polymers 24, forming a layer of light-emitting particles. When the substrate 10 having a layer of light-emitting particles formed on its surface is immersed in the second liquid, the positively charged polymers 24 adhere to the layer of negatively charged light-emitting particles, forming a layer of polymers 24.

[0045] For example, the ligand of the quantum dot is one or more selected from the group consisting of N-acetyl-L-cysteine ​​(NAC), thioglycolic acid, cysteine, ethyl 2-mercaptopropionate, glutathione, and 3-mercaptopropionic acid. The polymer 24 is, for example, a cationic polymer. For example, the polymer 24 is one or more selected from the group consisting of polydiallyldimethylammonium (PDDA), polyethyleneimine, and polystyrenesulfonic acid.

[0046] The structural formula of N-acetyl-L-cysteine ​​is as shown in the following formula (1). The structural formula of polydiallyldimethylammonium is as shown in the following formula (2). In formula (2), n is not particularly limited, but is, for example, 100 or more and 2000 or less.

[0047] [ka] [ka]

[0048] Optical density (OD) of quantum dots in the first liquid Q is, for example, 0.1 or more and 1.0 or less. Here, the optical density OD Q is the optical density measured at the light absorption peak wavelength of the quantum dot. The concentration of the quantum dots in the first liquid is, for example, 10 16 pcs / liter or more 10 20 The time T during which the substrate 10 is immersed in the first liquid can be set to 1 / L or less. Q The time T is, for example, 5 minutes or more and 30 minutes or less per one time. Q By adjusting the density of quantum dots in each layer, D Q In addition, the quantum dots do not stack in multiple layers during one immersion, but rather have a density D Q saturates to a certain value.

[0049] The concentration of the polymer 24 in the second liquid is, for example, 0.1 wt % or more and 5 wt % or less. P For example, each session lasts for more than 5 minutes and less than 30 minutes.

[0050] It is preferable to perform an etching treatment on the substrate 10 before forming the laminate of the light-emitting particles and the polymer 24. The etching treatment is, for example, at least one of etching with a piranha solution, etching with an acid, and ion etching.

[0051] In addition, it is preferable to form the underlayer 35 before forming the alternate laminate. By forming the underlayer 35, a more uniform light-emitting layer 20 can be formed. The underlayer 35 can be, for example, a polymer layer. For example, the underlayer 35 can be a laminated film of polyacrylic acid (PAA) and PDDA. The substrate 10 after the etching process is immersed in the above-mentioned second liquid containing PDDA, thereby forming a PDDA layer on the first surface 101 of the substrate 10. Next, the substrate 10 is immersed in a third liquid containing PAA, thereby forming a PAA layer on the PDDA layer. Furthermore, the substrate 10 is immersed in the second liquid, thereby forming a PDDA layer on the PAA layer. In this way, by alternately immersing the substrate 10 in the second liquid and the third liquid, a film in which the PDDA layer and the PAA layer are alternately laminated is obtained as the underlayer 35. The uppermost layer of the underlayer 35 is a PDDA layer. The underlayer 35 is, for example, 1 nm or more and 3 nm or less. By immersing the substrate 10 on which the underlayer 35 has been formed in a first liquid containing quantum dots, a layer of quantum dots can be formed on the underlayer 35. Furthermore, by immersing the substrate 10 alternately in the second liquid and the first liquid, an alternating laminate of quantum dots and polymers can be formed as the light-emitting layer 20. Note that the structure 30 may be obtained by forming only one layer of quantum dots on the underlayer 35.

[0052] By forming the light-emitting layer 20 using the LBL method, it is possible to form a uniform light-emitting layer 20 and measure the plasmon wave with high accuracy. In addition, since the light-emitting layer 20 can be easily washed off the substrate 10 with water, the substrate 10 can be returned to its original state after the measurement process.

[0053] The configuration and method of forming the underlayer 35 are not limited to the above example.

[0054] The method of applying the light-emitting material 22 to the base 10 is not limited to the above example. For example, a film of the light-emitting material 22 may be formed on the first surface 101 of the base 10 by the Langmuir-Blodgett method (LB method). Alternatively, the light-emitting layer 20 may be formed by applying a mixture of a resin binder and the light-emitting material 22 to the first surface 101 of the base 10.

[0055] The measurement step will be further described with reference to Fig. 1. In the measurement step, plasmon waves are generated in the base 10 of the structure 30. Specifically, by irradiating the starting structure 16 with excitation light, plasmon waves can be generated and propagated starting from the starting structure 16. The excitation light is, for example, a pulsed laser beam.

[0056] The electromagnetic energy of the plasmon wave is converted into light by the luminescent material 22. The luminescent material 22 receives the electromagnetic energy of the plasmon wave and emits fluorescence.

[0057] In the measurement step, the light output from the light emitting material 22 of the structure 30 can be measured using an optical microscope 40. The optical microscope 40 includes, for example, an objective lens 42, a filter 44, and a sensor 46. The light emitted from the light emitting material 22 is incident on the objective lens 42. Of the light incident on the objective lens 42, a component in a predetermined wavelength band passes through the filter 44 and is incident on the sensor 46. The filter 44 is configured to transmit the fluorescence emitted from the light emitting material 22. Of the light incident on the objective lens 42, components other than the predetermined wavelength band are not transmitted through the filter 44. For example, the filter 44 is configured to not transmit the excitation light reflected by the substrate 10, but to transmit the fluorescence emitted from the light emitting material 22. The sensor 46 is an image sensor, for example a CMOS sensor. The sensor 46 outputs the intensity distribution of the light incident on the light receiving surface of the sensor 46 as an image. The optical microscope 40 may further include other lenses, filters, etc. The area measured by the optical microscope 40 preferably includes at least the origin structure 16 and the surroundings of the origin structure 16 .

[0058] The principle of the measurement will be explained in more detail. The plasmon wave propagates at the interface between the dielectric layer 12 and the metal layer 14. The complex wave vector k SPP is expressed by equation (3), where k' SPP k SPP is the real part of k'' SPP k SPP , i is the imaginary unit, ω is the angular frequency of the plasmon wave, c is the speed of light, and ε m is the complex dielectric constant of the metal layer 14, and ε d is the complex dielectric constant of the dielectric layer 12.

[0059]

number

[0060] On the other hand, when the propagation path is also irradiated with excitation light, the plasmon wave and the excitation light interfere with each other in the propagation path, generating a beat. The wave number k of the x-axis component of the excitation light irradiated at an incidence angle θ is x K x = k0 sin θ. Here, the x-axis direction is parallel to the measurement surface 301, and is the direction in which the incident direction of the excitation light is projected onto the measurement surface 301. The incident angle θ is the angle between the incident direction and the measurement surface 301. k0 is the wave number of the excitation light. And the wave number k of the generated "beat" is beat is k beat =k' SPP -k x k0 is also conserved inside the dielectric layer 12 according to Snell's law.

[0061] In the image obtained by the optical microscope 40, this "beat" is observed in a striped pattern. By analyzing the beat, the propagation state of the plasmon wave can be understood. In other words, it can be said that the measurement method according to the present embodiment can measure the propagation state of the plasmon wave.

[0062] The wavelength of the excitation light is preferably determined according to the type of metal in the metal layer 14. When the metal layer 14 is gold, the wavelength of the excitation light is preferably 600 nm or more and 2500 nm or less. When the metal layer 14 is silver, the wavelength of the excitation light is preferably 400 nm or more and 2500 nm or less. When the metal layer 14 is aluminum, the wavelength of the excitation light is preferably 200 nm or more and 2500 nm or less.

[0063] The light-emitting material 22 is preferably selected according to the wavelength of the excitation light. When the wavelength of the excitation light is 500 nm or more and 700 nm or less, the light-emitting material 22 is preferably one or more selected from the group consisting of CdS quantum dots, ZnTe quantum dots, ZnSe quantum dots, and ZnS quantum dots. When the wavelength of the excitation light is 700 nm or more and 1200 nm or less, the light-emitting material 22 is preferably one or more selected from the group consisting of CdTe quantum dots, CdSe quantum dots, GaAs quantum dots, and InP quantum dots. When the wavelength of the excitation light is 1200 nm or more and 2500 nm or less, the light-emitting material 22 is preferably one or more selected from the group consisting of HgTe quantum dots, HgSe quantum dots, HgS quantum dots, PbS quantum dots, PbSe quantum dots, InAs quantum dots, CuInS quantum dots, and CuInSe quantum dots.

[0064] The measurement step may use a pump-probe method. That is, probe light is irradiated onto the measurement surface 301 in addition to the excitation light (pump light). The pump light is irradiated onto the measurement surface 301 at time t1, and the probe light is irradiated onto the measurement surface 301 at time t2=t1+Δt, where Δt is a predetermined delay time. The pump light is irradiated onto the origin structure 16. Meanwhile, the probe light is irradiated onto an area away from the origin structure 16 within the propagation area of ​​the plasmon wave. The optical microscope 40 measures the light from the light-emitting material 22 in the area irradiated with the probe light. Time-resolved measurement is possible by performing multiple measurements while changing the delay time Δt.

[0065] The measurement method according to the present embodiment may further include, after the measurement step, a removal step of removing the luminescent material 22 from the structure 30. The luminescent material 22 is preferably water-soluble. Alternatively, the luminescent layer 20 is preferably water-soluble. In that case, in the removal step, the luminescent material 22 can be washed away from the structure 30 with water.

[0066] Next, the action and effect of this embodiment will be described. According to this embodiment, the light emitting material 22 of the substrate 10 is attached, and the light output from the light emitting material 22 of the structure 30 in response to the generation of the plasmon wave is measured. Therefore, it is possible to provide a measurement method and a structure that can easily visualize the plasmon wave. EXAMPLES

[0067] The present embodiment will be described in detail below with reference to examples. However, the present embodiment is not limited to the description of these examples.

[0068] Example 1 In Example 1, the plasmon wave was measured by the method described in the embodiment.

[0069] <Base material> After a gold film having a thickness of 250 nm was laminated on a glass substrate, etching was performed using a piranha solution, and then a part of the gold was removed using a focused ion beam to form a slit. FIG. 6 is a scanning ion microscope image of a part of a sample in which a gold film having a slit was formed on a glass substrate. In this sample, the gold was removed in the slit to expose the glass substrate. A dielectric layer (corresponding to the dielectric layer 12 in the embodiment) made of a resin (polymethylmethacrylate) having a thickness of 500 nm was laminated on this sample to obtain a substrate A according to this example.

[0070] For substrate A, an underlayer was formed on the dielectric layer. The underlayer was an alternating laminate of PDDA and PAA films. Of the underlayers, the layer in contact with the dielectric layer and the top layer were PDDA films. The overall thickness of the underlayer was 2.5 nm.

[0071] The PDDA film was formed by immersing substrate A in a PDDA solution. The PDDA solution was prepared by dissolving 700 μl of PDDA in 40 ml of water. The concentration of PDDA in the PDDA solution was 0.34 wt%. Substrate A was immersed in the PDDA solution for 10 minutes each time. The PAA film was formed by immersing substrate A in a PAA solution. The PAA solution was prepared by dissolving 25 g of PAA in 500 ml of water. Substrate A was immersed in the PAA solution for 10 minutes each time.

[0072] A light-emitting layer was formed on the underlayer to obtain a structure A according to this embodiment. As the light-emitting layer, an alternating laminate of a CdTe quantum dot film and a PDDA film was formed. First, a CdTe quantum dot film, a PDDA film, a CdTe quantum dot film, a PDDA film, and a CdTe quantum dot film were laminated in this order on the PDDA film, which was the top layer of the underlayer. That is, the number of layers of the CdTe quantum dot film in the light-emitting layer was set to 5 layers.

[0073] The PDDA film in the light-emitting layer was formed in the same manner as the PDDA film in the underlayer. The CdTe quantum dot film was formed by immersing the substrate A in a quantum dot solution. The quantum dot solution was prepared by diluting the stock solution in which quantum dots were synthesized with water until the optical density (OD) at the light absorption peak wavelength was 0.5. The substrate was immersed in the quantum dot solution for 20 minutes each time.

[0074] Structure A was irradiated with excitation light, causing the propagation of plasmon waves originating from the right edge of the slit indicated by the black arrow in Figure 6, and the light output from Structure A was measured with an optical microscope. The peak wavelength of the fluorescence emitted from the CdTe quantum dots was 560 nm, and the light that entered the sensor via a filter that transmits light in the wavelength range of 300 nm to 700 nm was detected with the optical microscope. An image showing the intensity distribution of the light detected by the sensor, i.e., the light output from the quantum dots, was obtained from the optical microscope.

[0075] 7 and 8 are diagrams showing the measurement results according to the embodiment. Images obtained by an optical microscope when the wavelength of the excitation light is 800 nm are shown in FIG. 7 and FIG. 8. In FIG. 7 and FIG. 8, the irradiation direction of the excitation light was from the left side to the right side of each figure. FIG. 9 is a schematic diagram showing a cross section of the structure A in the measurement range of FIG. 7. In FIG. 6, the right edge of the slit is indicated by an arrow. And the position of the edge indicated by the arrow in FIG. 6 is also indicated by an arrow in FIG. 7 and FIG. 9. In the image of FIG. 7, stripes appear in the area to the right of the edge of the slit. This stripe corresponds to the "beat" described above in the embodiment. That is, the propagation of the plasmon wave with the edge of the slit as the starting structure was confirmed. Also, in FIG. 8, stripes appear starting from the dot-shaped convex portion unintentionally generated on the gold film. That is, the propagation of the plasmon wave with the convex portion as the starting structure was confirmed.

[0076] Three images obtained in the same manner as in FIG. 7 are further shown in FIG. 10. However, in these three images, the wavelengths of the excitation light were 780 nm, 820 nm, and 860 nm, respectively. In each image shown in FIG. 10, the direction of the excitation light was from the left side to the right side of the figure. The position of the edge indicated by the arrow in FIG. 6 is also indicated by an arrow in FIG. 10. Propagation of the plasmon wave was also confirmed in each image in FIG. 10.

[0077] FIG. 11 is a graph showing the light intensity profile obtained for each of a number of excitation wavelengths (i.e., wavelengths of excitation light). In the graph of FIG. 11, the horizontal axis represents the distance in the x-axis direction, and the vertical axis represents normalized light intensity. Each profile was obtained by integrating the brightness of each x coordinate in each image in the y-axis direction. FIG. 12 shows the beat wavelength λ calculated based on FIG. 11. beat and the excitation wavelength, and k' SPP FIG. 13 is a graph showing the relationship between k' and excitation wavelength. SPP13 is a graph showing the relationship between the group velocity v obtained by dω / dk and the angular frequency ω of the plasmon wave. FIG. 13 further shows a straight line showing ω=ck sinθ and a straight line showing ω=ck. c is the speed of light, and k is the wave number of the excitation light or the plasmon wave. From these results, the group velocity v obtained by dω / dk g is 1.97 x 10 8 This was calculated to be 0.66c, or m / s.

[0078] As described above, we were able to easily visualize plasmon waves and analyze the propagation phenomenon of plasmon waves.

[0079] Example 2 In Example 2, Structure B, Structure C, and Structure D were prepared, and plasmon waves were measured. Structure B is the same as Structure A according to Example 1, except that the number of layers of the CdTe quantum dot film in the light-emitting layer is two. Structure C is the same as Structure A according to Example 1, except that the number of layers of the CdTe quantum dot film in the light-emitting layer is seven. Structure D is the same as Structure A according to Example 1, except that the number of layers of the CdTe quantum dot film in the light-emitting layer is ten. In Example 2, the measurement of plasmon waves was performed in the same manner as in Example 1. The wavelength of the excitation light was 800 nm.

[0080] Figure 14 is a graph showing the relationship between the number of layers of the CdTe quantum dot film and the wavenumber of the plasmon wave, obtained from the measurement results of the plasmon wave in structures A to D. The wavenumber of the plasmon wave was obtained by analyzing the "beat" in each measurement result. As shown in Figure 14, the greater the number of layers, the greater the wavenumber. This is thought to be because the plasmon characteristics are modulated by the effect of the quantum dots. On the other hand, when the number of layers is small, the change in wavenumber is small. By extrapolating the curve in the graph in Figure 14, the wavenumber at the "0 layer" could be obtained. The wavenumber at the "0 layer" obtained here was calculated based on the plasmon characteristics of the interface between gold and polymethyl methacrylate (PMMA) (8.7 μm -1) showed very good agreement. From the above results, it was confirmed that in order to suppress the influence on the physical phenomenon in the base 10, it is preferable to have a smaller number of quantum dot (light-emitting material) layers than a larger number.

[0081] Although the embodiments of the present invention have been described above with reference to the drawings, these are merely examples of the present invention, and various configurations other than those described above can also be adopted. [Explanation of symbols]

[0082] 10 Base 12 Dielectric layer 14 Metal layer 15 Substrate 16 Origin structure 18 Lamination area 20 Light-emitting layer 22 Luminous material 24 Polymer 30 Structure 35 Base layer 40 Optical Microscope 42 Objective Lens 44 Filters 46 Sensors 101 Page 1 102 Side 2 301 Measurement surface

Claims

1. providing a structure by applying a light emitting material to a substrate including an interface between a metal layer and a dielectric layer; generating a plasmon wave on the substrate in the structure, and measuring light output from the light-emitting material of the structure in response to the generation of the plasmon wave. Measurement method.

2. 2. The method according to claim 1 , the substrate has a laminated region in which the metal layer and the dielectric layer are laminated in contact with each other, In the structure, the dielectric layer is located between the metal layer in the laminated region and the light-emitting material. Measurement method.

3. The method according to claim 1 or 2, In the measuring step, light output from a measurement surface which is at least one surface of the structure is measured; The structure includes, in at least a part of the region, the light emitting material, the dielectric layer, and the metal layer in this order from the measurement surface side. Measurement method.

4. The measurement method according to any one of claims 1 to 3, the substrate has a first surface on the dielectric layer side and a second surface on the metal layer side opposite to the first surface, In the structure, the light-emitting material is applied to at least a partial area of ​​the first surface of the base at a coverage rate of 30% or more and 100% or less. Measurement method.

5. The measurement method according to any one of claims 1 to 4, In the step of preparing the structure, a light-emitting layer including the light-emitting material is formed on the base. Measurement method.

6. The measurement method according to claim 5, The light-emitting layer includes an alternating laminate of light-emitting particles as the light-emitting material and a polymer. Measurement method.

7. 7. The method according to claim 6, In the step of preparing the structure, the substrate is immersed in a first liquid containing the light-emitting particles and a second liquid containing the polymer in that order to form the light-emitting layer. Measurement method.

8. The measurement method according to any one of claims 1 to 7, The method further includes removing the luminescent material from the structure after the measuring step. Measurement method.

9. The measurement method according to claim 8, In the removing step, the light-emitting material is washed away from the structure with water. Measurement method.

10. The method according to any one of claims 1 to 9, In the measuring step, light output from the light emitting material of the structure is measured using an optical microscope. Measurement method.

11. The measurement method according to any one of claims 1 to 10, The substrate is at least a part of a waveguide, a solar cell, a photosensor, or a communication circuit. Measurement method.

12. a substrate including an interface between a metal layer and a dielectric layer; a luminescent material applied to the substrate; The dielectric layer is located between the metal layer and the light-emitting material in at least a portion of the region. structure.

13. 13. The structure of claim 12, the substrate has a laminated region in which the metal layer and the dielectric layer are laminated in contact with each other, The dielectric layer is located between the metal layer and the light emitting material in the laminated region. structure.

14. 14. The structure according to claim 12 or 13, the substrate has a first surface on the dielectric layer side and a second surface on the metal layer side opposite to the first surface, The light-emitting material is applied to at least a portion of the first surface of the substrate at a coverage rate of 30% or more and 100% or less. structure.

15. 15. The structure according to any one of claims 12 to 14, The structure includes a light-emitting layer that includes the light-emitting material. structure.

16. 16. The structure of claim 15, The light-emitting layer includes an alternating laminate of light-emitting particles as the light-emitting material and a polymer. structure.

17. 17. The structure according to any one of claims 12 to 16, The substrate is at least a part of a waveguide, a solar cell, a photosensor, or a communication circuit. structure.

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