JP2019192910A - Switching element and thermoelectric conversion element - Google Patents

Abstract

To provide a switching element that utilizes local heat generated at a metamaterial complete absorption structure.SOLUTION: A switching element 100 includes a metamaterial complete absorption structure 10 composed of a conductive microstructure 1, a metal thin film 2, and a thermal phase transition material layer 3 sandwiched therebetween.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a switching element and a thermoelectric conversion element.

A metamaterial is an artificial material consisting of a structure smaller than the wavelength of light, and if a metamaterial with a negative refractive index can be realized in 2000, a paper says that infinitely small objects can be observed with visible light. It was announced and attracted attention.
Later, various metamaterial structures were reported. One of them is a metamaterial complete absorption structure in which a thin film is sandwiched between a metal nanostructure and a metal flat plate.

N. I. Landy, S. Sajuyigbe, J. J. Mock, D. R. Smith, W. J. Padilla, Phys. Rev. Lett. 2008, 100, 207402. S. Lysenko, A. J. Rua, V. Vikhnin, J. Jimenez, F. Fernandez, H. Liu, Appl. Surf. Sci. 2006, 252, 5512. Appavoo, B. Wang, N. F. Brady, M. Seo, J. Nag, R. P. Prasankumar, D. J. Hilton, S. T. Pantelides and R. F. Haglund, Nano Lett., 2014, 14, 112. A. J. Green, A. A. Alaulamie, S. Baral and H. H. Richardson, Nano Lett., 2013, 13, 4142. A. Rasoul, A. Mohammad and R. Carsten, J. Phys. D: Appl. Phys., 2017, 50, 503002 M. L. Brongersma, N. J. Halas and P. Nordlander, Nat Nano, 2015, 10, 25.

  Conventionally, most of the literature on the metamaterial complete absorption structure has widely used a material that does not interact with electromagnetic waves, such as a metal oxide, as a material for the thin film (see Non-Patent Document 1).

The inventor has conducted intensive research on the metamaterial by using a novel switching element and a thermoelectric conversion element having a structure in which a material layer (for example, vanadium dioxide (VO ₂ ) thin film) having a thermal response property is inserted into the metamaterial complete absorption structure. A novel switching element and thermoelectric conversion element utilizing local heat generated in a complete absorption structure have been conceived.

It has been reported that a phase transition can be induced by light irradiation of a vanadium dioxide (VO ₂ ) thin film (see Non-Patent Document 2). The light intensity per pulse of femtosecond laser light required for non-patent document 2 to induce the phase transition is 140 GW / cm ² , and the switching element having a VO ₂ thin film only by light irradiation is very powerful. The light was needed.

  An object of this invention is to provide the switching element and thermoelectric conversion element which utilize the local heat produced | generated in a metamaterial perfect absorption structure.

  The present invention provides the following means in order to solve the above problems.

(1) The switching element according to the first aspect of the present invention includes a fully absorbing metamaterial structure including a conductive microstructure, a metal thin film, and a thermal phase transition material layer sandwiched between them.

(2) In the above aspect, a plurality of the conductive microstructures may be provided.

(3) In the above aspect, the plurality of conductive microstructures may be configured to exhibit the same plasmon resonance wavelength.

(4) In the above aspect, the plurality of conductive microstructures may include those having different plasmon resonance wavelengths.

(5) In the above aspect, the plurality of conductive microstructures may be randomly arranged.

(6) In the above aspect, the plurality of conductive microstructures may be regularly arranged.

(7) In the above aspect, the conductive microstructure may have an anisotropic shape.

(8) The thermoelectric conversion element which concerns on the 2nd aspect of this invention is equipped with the perfect absorption metamaterial structure which consists of an electroconductive microstructure, a metal thin film, and the thermoelectric conversion layer pinched | interposed among them.

(9) In the above aspect, the conductive microstructure may be disposed inside or on a part of the thermoelectric conversion film.

(10) In the above aspect, a plurality of the conductive microstructures may be provided.

(11) In the above aspect, the plurality of conductive microstructures may be ones exhibiting the same plasmon resonance wavelength.

(12) In the above aspect, the plurality of conductive microstructures may include ones exhibiting different plasmon resonance wavelengths.

(13) In the above aspect, the plurality of conductive microstructures may be randomly arranged.

(14) In the above aspect, the plurality of conductive microstructures may be regularly arranged.

(15) In the above aspect, the conductive microstructure may have an anisotropic shape.

According to the switching element of the present invention, it is possible to provide a switching element that utilizes local heat generated in the metamaterial complete absorption structure.
According to the thermoelectric conversion element of the present invention, it is possible to provide a thermoelectric conversion element that uses local heat generated in the metamaterial complete absorption structure.

It is sectional drawing which showed typically the switching element concerning one Embodiment of this invention. It is a graph showing a change characteristic of the electrical resistivity with respect to temperature of the vanadium dioxide (VO _2). It is a figure for demonstrating the drive method of the switching element of this invention, (a) is a cross-sectional schematic diagram of a switching element, (b) controls on / off of an electric current by light on / off control. It is a drive timing chart which shows doing. It is a schematic diagram which illustrates the shape of an electroconductive microstructure. (A) is a metal plate electrode on the substrate, a structure formed VO ₂ thin film, a metal nanostructure in order, cross-sectional view schematically showing the case of performing light irradiation from the side of forming the metamaterial complete absorption structure of the substrate FIG. 2B is a schematic cross-sectional view showing a structure in which a metal nanostructure, a VO ₂ thin film, and a metal flat plate electrode are sequentially formed on a substrate, and light irradiation is performed from below the substrate. It is sectional drawing shown typically for demonstrating the manufacturing method of the switching element of this invention, (a) is the process of forming a metal thin film on a board | substrate, (b) is a thermal phase change material layer on a metal thin film. (C) shows a step of forming a conductive microstructure and an electrode portion on the thermal phase transition material layer. It is a perspective schematic diagram of the switching element which can be manufactured with the manufacturing method 2 of the switching element of this invention. It is sectional drawing which showed typically an example of the switching element concerning one Embodiment of this invention. It is sectional drawing which showed typically the other example of the switching element concerning one Embodiment of this invention. It is sectional drawing which showed typically the other example of the switching element concerning one Embodiment of this invention, (a) is an example which arrange | positions several strip | belt-shaped electroconductive microstructures at irregular intervals. (B) is an example in which a plurality of dot-like conductive microstructures are arranged at irregular intervals. It is a perspective schematic view showing a configuration used in measuring the electrical resistivity of the VO ₂ thin film. Is a graph showing the results of measuring the electrical resistivity of the VO ₂ thin film is irradiated with monochromatic light polarized in the short axis direction. Under irradiation with monochromatic light of 650nm polarized in the short axis direction and the major axis of the silver nanorod is a graph showing the results of measuring the electrical resistivity of the VO ₂ thin film by elevating the temperature. 2D electromagnetic field calculation was performed, a model view of a metal plate electrode / VO ₂ thin film / metal nanostructure electrode structure. FIG. 11B is a graph showing an absorption spectrum when the period is 100 nm to 300 nm in the model diagram shown in FIG. 11A. FIG. 11B is an electric field distribution diagram of an absorption peak near a wavelength of 1.7 micrometers in the model diagram shown in FIG. It is sectional drawing which showed typically the thermoelectric conversion element 200 concerning one Embodiment of this invention. It is a conceptual diagram of the thermoelectric conversion element of this invention which has a metamaterial perfect absorption structure in one end. The example of arrangement | positioning (arrangement | positioning) of the some electroconductive microstructure of the thermoelectric conversion element concerning one Embodiment of this invention is shown. (A) is the structure which formed the metal plate electrode, the thermoelectric conversion film, and the metal nanostructure in order on the board | substrate, and is a cross-sectional schematic which shows the case where light irradiation is performed from the side which formed the metamaterial perfect absorption structure of the board | substrate. It is a figure, (b) is a structure which formed the metal nanostructure, the thermoelectric conversion film, and the metal flat plate electrode in order on the board | substrate, and is a cross-sectional schematic diagram which shows the case where light irradiation is performed from the downward direction of a board | substrate. It is a cross-sectional schematic diagram which shows notionally the utilization method of the thermoelectric conversion element concerning one Embodiment of this invention.

  Hereinafter, the present embodiment will be described in detail with appropriate reference to the drawings. In the drawings used in the following description, in order to make the characteristics of the present invention easier to understand, there are cases where the characteristic parts are enlarged for the sake of convenience, and the dimensional ratios of the respective components are different from actual ones. is there. The materials, dimensions, and the like exemplified in the following description are merely examples, and the present invention is not limited to these, and can be implemented with appropriate modifications within the scope of the effects of the present invention.

(Switching element)
FIG. 1 is a cross-sectional view schematically showing a switching element 100 according to an embodiment of the present invention.
The switching element 100 includes a metamaterial complete absorption structure 10 including a conductive microstructure 1, a metal thin film 2, and a thermal phase transition material layer 3 sandwiched between them.
The conductive microstructure 1 and the metal thin film 2 can also be used as electrodes.

  In this specification, complete absorption means having light absorption characteristics of 80% or more. The metamaterial complete absorption structure is capable of confining 80% or more of incident light.

<Thermal phase transition material layer>
As the material constituting the thermal phase transition material layer 3, any material can be used as long as its electrical resistivity changes significantly by heat (a material having high resistance and low resistance). For example, vanadium dioxide (VO ₂ ), trivanadium oxide (V ₂ O ₃ ), vanadium monoxide (VO), germanium antimony tellurium (GeSbTe) and the like can be exemplified.

  The thickness of the thermal phase transition material layer 3 is not particularly limited, but a guideline is exemplified by several nm or more and several hundred nm or less, preferably 10 nm or more and 100 nm or less.

FIG. 2 is a graph showing a change characteristic of electric resistivity with respect to temperature of vanadium dioxide (VO ₂ ).
As shown in FIG. 2, a high-resistance dielectric phase is shown at room temperature, and a low-resistance metal phase is shown above the phase transition temperature (around 68 ° C.). That is, a metal-insulator (dielectric) phase transition occurs around the phase transition temperature. Since the electrical resistivity difference between the dielectric phase and the metal phase is, for example, 3 to 4 digits, the current on / off control can be performed by switching the dielectric phase and the metal phase of the vanadium dioxide thin film by phase transition. .

If the metamaterial complete absorption structure is irradiated with light, the metamaterial complete absorption structure can confine light and generate high heat in the thermal phase change material layer. If the thermal phase transition material undergoes phase transition due to this local heat, the electrical resistivity of the thermal phase transition material layer decreases, and a current flows between the conductive microstructure 1 and the metal thin film 2. If the light irradiation is stopped, the heat in the metamaterial complete absorption structure decreases and the thermal phase transition material returns to the high-resistance dielectric phase, so that no current flows.
For this reason, as shown in FIG. 3, it functions as an optical switching device capable of turning on / off the current flowing between the conductive microstructure electrode 1 and the metal plate electrode 2 by light on / off control.

More specifically, the phase transition in the thermal phase transition material layer sandwiched between the metamaterial complete absorption structures is considered to proceed by the following two processes.
(1) Phase transition due to local heat confined in the dielectric layer of the metamaterial complete absorption structure The metamaterial complete absorption structure excites a plasmon quadrupole mode having a particularly high Q value. The quadrupole mode is known to have a long life in a narrow band and high generation efficiency of thermoelectrons that are the source of local heat. Since the thermoelectrons become local heat through a relaxation mechanism, the local heat is given to the thermal phase transition material layer, and the phase transition of the thermal phase transition material proceeds.
(2) Phase transition by injection of thermoelectrons generated in metamaterial complete absorption structure Metamaterial complete absorption structure is known for its high generation efficiency of thermoelectrons. It is known that when a gold nanostructure and vanadium dioxide come into contact, thermoelectrons are injected from the metal nanostructure into the conduction band of the vanadium dioxide thin film, and a phase transition of vanadium dioxide is induced (see Non-Patent Document 3). . The time when the phase transition of vanadium dioxide occurs by thermionic injection is reported to be in the picosecond range. If the phase transition by thermionic injection is the main process in the vanadium dioxide phase transition by the metamaterial complete absorption structure, the optical switching element of the present invention is a high-speed switching element capable of switching current in picosecond order.

<Metal thin film>
Although it does not specifically limit as a material of the metal thin film 2, Metals, such as gold | metal | money, silver, copper, platinum, aluminum, can be mentioned.
When the metal thin film 2 is also used as an electrode, it may be referred to as a metal flat plate electrode.

  The metal thin film 2 is preferably a flat film or a flat surface, but is not limited thereto as long as a metamaterial complete absorption structure can be formed.

  Although it does not specifically limit as a film thickness of the metal thin film 2, If a standard is illustrated, it will be several nm-several hundred nm.

<Conductive microstructure>
As a material that can be used as the material of the conductive microstructure 1, a known material that exhibits plasmon resonance can be used.
Specific examples include metals such as gold, silver, copper, platinum, and aluminum, and metal oxides such as indium tin oxide.

In addition, the structure that can be used as the structure of the conductive microstructure 1 is required to have a shape in which the surface facing the metal thin film 2 is parallel. Furthermore, the structure needs to exhibit plasmon resonance.
Specifically, as shown in part in FIG. 4, a sphere, a disk, an elliptical cylinder, an elliptical rectangular parallelepiped, a cube, a patch (thin plate), a cylinder, a hollow cylinder, a bowtie (bow tie) type, two Examples thereof include n-mers such as a monomer, trimer, tetramer, and pentamer, a star, a grating, and a metal thin film in which minute holes are randomly or regularly arranged. A material having anisotropy in shape, for example, a rectangular parallelepiped has polarization response.
A known method can be used as a method for forming these shapes, and for example, an electron beam drawing method, a light exposure method, a vacuum deposition method, a sputtering method, a synthesis method, a self-integration method, and the like can be used.

In the switching element 100 shown in FIG. 1, one conductive microstructure is provided, but a plurality of conductive microstructures may be provided.
In this specification, unless otherwise specified, the “conductive microstructure” includes a single conductive microstructure as well as a plurality of conductive microstructures (in this case, “conductive microstructures”). In the case of “group of bodies”). In addition, in FIG. 1, a configuration including a plurality of conductive microstructures is illustrated, but is illustrated only as an example, and the present embodiment includes one conductive microstructure. Similarly, in the following drawings, even when a plurality of conductive microstructures are shown, the embodiment includes one conductive microstructure, and similarly, there is one conductive microstructure. Even if only shown, embodiments include a plurality of conductive microstructures.

  Since the metamaterial complete absorption structure 10 is a metamaterial complete absorption structure using plasmon resonance, the plasmon resonance wavelength is determined by the type, size, shape, number, density, and the like of the conductive microstructure. Therefore, by appropriately controlling the mode of the conductive microstructure, it is possible to control characteristics such as a wavelength region that is driven by the switching element. For example, a conductive microstructure having an arbitrary plasmon resonance wavelength such as visible light or far infrared light can be formed.

  In the switching element of the present invention, local heat generated is increased by providing a plurality of conductive microstructures having the same plasmon resonance wavelength. For example, in the case where the switching element cannot be driven by local heat generated by a single conductive microstructure, a plurality of the same plasmons are generated so as to generate sufficient local heat to drive the switching element. A conductive microstructure exhibiting a resonance wavelength may be provided. By adopting a configuration including a plurality of conductive microstructures having the same plasmon resonance wavelength, the narrow band response can be improved.

In the switching element of the present invention, the configuration including a plurality of conductive microstructures (conductive microstructure groups) may include a configuration including conductive microstructures exhibiting different plasmon resonance wavelengths.
In this configuration, wideband response is improved when different plasmon resonance wavelengths are relatively close. Alternatively, a switching element that responds to light having a plurality of specific wavelengths may be provided by including a group of conductive microstructures having different plasmon resonance wavelengths that absorb light having a desired wavelength that is not near.
By selecting a conductive microstructure exhibiting a different plasmon resonance wavelength, a switching element having an arbitrarily designed plasmon resonance wavelength spectrum can be obtained.

In the switching element of the present invention, a conductive microstructure having an anisotropic shape may be used.
For example, a rectangular parallelepiped conductive microstructure has a shape having a predetermined aspect ratio. The rectangular parallelepiped conductive microstructure has two different plasmon resonance wavelengths derived from the short axis and the long axis. That is, it has a resonance mode derived from free electron vibration in each axial direction. A switching element having a rectangular parallelepiped conductive microstructure absorbs light whose polarization direction coincides with either the short axis or the long axis, and thus has polarization response.
Also, a plurality of conductive microstructures having the same anisotropic shape may be arranged in a predetermined plurality of orientation directions to form a pattern.

In the switching element of the present invention, a plurality of conductive microstructures may be randomly arranged. Randomly arranged conductive microstructures can be easily formed.
“Randomly arranged” means an arrangement other than “regularly arranged” described later. Examples of the random arrangement method include a method in which a plurality of conductive microstructures are mixed in an organic thermoelectric material solution and a thermoelectric conversion material is formed by spin coating, or an inorganic thermoelectric material is formed by sputtering or vapor deposition. A method of forming a thermoelectric conversion material by confining the conductive microstructure in the thermoelectric conversion film by simultaneously sputtering and vapor-depositing the material of the conductive microstructure when forming the film is mentioned.

  In the switching element of the present invention, a plurality of conductive microstructures may be regularly arranged. Examples of the regular arrangement method include regular arrangement patterning by photolithography. The regularly arranged conductive microstructures have response characteristics unique to their regularity (for example, periodicity).

Taking a rectangular parallelepiped shape as an example of the size of the conductive microstructure, the length may be 1 to 10,000 nm, the width may be 1 to 10,000 nm, and the height may be 1 to 10,000 nm. .
When the conductive microstructure is of a nanometer scale, it may be referred to as a conductive nanostructure. In addition, when a material is a metal and a nanometer size is used, it may be a metal nanostructure.

In the switching element according to the present invention, in a configuration including a plurality of conductive microstructures, two dimers, three trids, four deciphers, etc., each having n elements in close proximity to each other, a trimer It can be set as a conductive microstructure group composed of n-mers such as a body and a tetramer.
In the n-mer, heat tends to accumulate, so that the generated local heat can be used efficiently.
For example, when using plasmon resonance absorption of visible light, the distance between adjacent conductive microstructures that interact is preferably greater than 0 nm and less than or equal to 40 nm, and more preferably less than or equal to 10 nm. In the case of using plasmon resonance absorption of infrared light, the distance between adjacent conductive microstructures that interact with each other is preferably 1 nm or more and 40 nm or less, and more preferably 1 nm or more and 20 nm or less. preferable.

<Board>
In the switching element of the present invention, a substrate is not essential, but when the switching element of the present invention is fabricated on a substrate, for example, soda lime glass can be used as the substrate.
Although a substrate can be selected according to the application, when it is desired to make the substrate flexible as a whole, for example, polyethylene terephthalate, cycloolefin polymer, or the like can be used as the flexible substrate. On the contrary, when it is desired to make the substrate rigid as a whole, for example, a sapphire substrate, a quartz substrate, a silicon substrate, or the like can be used.

  In the optical switching element of the present invention having a metamaterial complete absorption structure, the response wavelength region and the polarization dependency are determined depending on the material of the conductive microstructure (for example, the metal species constituting the metal nanostructure (gold, silver, The metal that induces plasmon, such as copper, platinum, and aluminum))) and its size and shape can be arbitrarily controlled. Therefore, the driving wavelength can be selected from a wide range of wavelengths (for example, from the ultraviolet region to the infrared region).

It is known that the metamaterial perfect absorption structure that induces the plasmon quadrupole mode has a much higher thermoelectron generation efficiency than simple plasmonic structures such as metal nanoparticles. High thermoelectron generation efficiency means that the amount of local heat generated by thermal electron relaxation is also large. Therefore, compared with the laser light-induced phase transition that requires about 1 kW / cm ^2, the optical switching element of the present invention using the metamaterial complete absorption structure is a thermal phase transition material with weak light that is a few orders of magnitude lower ( For example, switching of VO ₂ ) is enabled.

5, on the substrate, the metamaterial metallic nanostructures -VO ₂ thin film as an example of a complete absorbent structure of the present invention - showing the structure of a metal plate electrode structure is disposed.
FIG. 5A shows a configuration in which a metal plate electrode, a VO ₂ thin film, and a metal nanostructure are sequentially formed on a substrate, and shows a case where light irradiation is performed from the side where the metamaterial complete absorption structure of the substrate is formed. FIG. 5B is a schematic cross-sectional view showing a configuration in which a metal nanostructure, a VO ₂ thin film, and a metal flat plate electrode are sequentially formed on a substrate, and shows a case where light irradiation is performed from below the substrate. FIG. In the case of FIG. 5B, it is preferable to use a highly transparent substrate.
It is conceivable that a metal nanostructure is produced on a substrate and light is irradiated from the bottom of the substrate. Since the metal nanostructure determines the response wavelength, light irradiation is always performed from the metal nanostructure side.

  Since the local heat of the metamaterial complete absorption structure is generated between the conductive microstructure (for example, metal nanostructure) and the metal thin film (for example, metal plate electrode), a thermal phase transition material layer is inserted at the generation site. This is a feature of the present invention.

By appropriately designing the size and shape of the conductive microstructure (eg, metal nanostructure), the response wavelength can be selected from a wide wavelength range from the ultraviolet to the infrared range. Since the plasmon quadrupole mode has a narrow band response with a very high Q value, it can be expected to be used as a narrow band optical switching element. In principle, since only one metal nanostructure exhibits wavelength response, a high-resolution image sensor with a pixel size on the order of nm can be realized.
The switching element of the present invention can also be used for a photodetector.

(Manufacturing method of switching element)
FIG. 6 is a cross-sectional view schematically illustrating a method for manufacturing a switching element according to an embodiment of the present invention. Below, three examples of the manufacturing method of a switching element are demonstrated.

<Manufacturing method 1 of a switching element>
(1) A metal thin film is formed on a substrate (a method such as a vapor deposition method, a sputtering method, or an electrolytic (electroless) plating method can be used) (FIG. 6A).
(2) Next, a thermal phase transition material layer is formed on the metal thin film (a method such as sputtering, vapor deposition, or chemical synthesis can be used) (FIG. 6B).
(3) Next, a conductive microstructure and an electrode portion for taking out current are formed. (For microfabrication, a technique such as an optical lithography method or an electron beam lithography method can be used. Methods such as vapor deposition, sputtering, and electrolysis (electroless) plating can be used) (FIG. 6C).

<Manufacturing method 2 of a switching element>
(1) A metal thin film is formed on a substrate (a method such as a vapor deposition method, a sputtering method, or an electrolytic (electroless) plating method can be used) (FIG. 6A).
(2) Next, a thermal phase transition material layer is formed on the metal thin film (a method such as sputtering, vapor deposition, or chemical synthesis can be used) (FIG. 6B).
(3) Next, a conductive microstructure is formed (for microfabrication, techniques such as photolithography and electron beam lithography can be used. For metal formation, vapor deposition, sputtering, electrolysis ( Techniques such as electroless plating may be used).
(4) A transparent electrode for taking out an electric current is formed (a method such as a chemical forming method such as sputtering, vapor deposition or sol-gel method can be used) (see FIG. 7).

<Manufacturing method 3 of a switching element>
(1) A conductive microstructure is formed on a substrate (for microfabrication, techniques such as photolithography and electron beam lithography can be used. For metal formation, vapor deposition, sputtering, electrolysis ( Techniques such as electroless plating may be used).
(2) Next, a thermal phase transition material layer is formed on the substrate and the conductive microstructure (a method such as sputtering, vapor deposition, or chemical synthesis can be used).
(3) Next, a metal plate electrode is formed on the thermal phase transition material layer (a method such as a vapor deposition method, a sputtering method, an electrolytic (electroless) plating method can be used for forming the metal).

FIG. 8 is a cross-sectional view schematically showing an example of a switching element according to an embodiment of the present invention.
The switching element 110 shown in FIG. 8 is sandwiched between a plurality of conductive microstructures 1Aa, regularly (more specifically, periodically) spaced apart at equal intervals, and the metal thin film 2. And a metamaterial complete absorption structure comprising the thermal phase transition material layer 3.
In the switching element 110 shown in FIG. 8, a plurality of strip-like conductive microstructures 1Aa and the common portion 1Ab connected to them constitute a conductive microstructure electrode 1A.
The switching element 110 shown in FIG. 8 is an optical switching device capable of turning on / off the current flowing between the conductive microstructure electrode 1A and the metal thin film (metal plate electrode) 2 by light on / off control. Function.
The period of the plurality of conductive microstructures 1Aa is determined by the response wavelength of the fully absorbing metamaterial structure. The period is, for example, several tens of nm to several hundreds of μm.
The switching element 110 illustrated in FIG. 8 is a switching element exhibiting narrow bandwidth because the plurality of conductive microstructures 1Aa are arranged at the same period.

FIG. 9 is a cross-sectional view schematically showing another example of the switching element according to the embodiment of the present invention.
The switching element 120 shown in FIG. 9 is sandwiched between a plurality of strip-like conductive microstructures 1Ba arranged at intervals that change stepwise from a narrow interval to a wide interval, a metal thin film 2, and the like. A metamaterial complete absorption structure including the thermal phase transition material layer 3 is provided.
In the switching element 120 shown in FIG. 9, the plurality of conductive microstructures 1Ba constitutes a conductive microstructure electrode 1B together with the common portion 1Bb connected to them.
The switching element 120 shown in FIG. 9 is an optical switching device that can turn on / off the current flowing between the conductive microstructure electrode 1B and the metal thin film (metal plate electrode) 2 by light on / off control. Function.
Each interval between the plurality of conductive microstructures 1Ba is determined by the response wavelength of the fully absorbing metamaterial structure. Each interval is, for example, several tens of nm to several hundreds of μm.
The switching element 120 shown in FIG. 9 is a switching element having a wide bandwidth because the plurality of conductive microstructures 1Ba are arranged at intervals that change stepwise from a narrow interval to a wide interval.

  FIGS. 10A and 10B are cross-sectional views schematically showing another example of the switching element according to the embodiment of the present invention.

The switching element 130 shown in FIG. 10A includes a plurality of strip-like conductive microstructures 1Ca arranged at irregular (random) intervals, a metal thin film 2, and a thermal phase sandwiched between them. A metamaterial complete absorption structure including the transition material layer 3 is provided.
In the switching element 130 shown in FIG. 10A, a plurality of conductive microstructures 1Ca constitute a conductive microstructure electrode 1C together with a common portion 1Cb connected to them.
In the switching element 130 shown in FIG. 10A, light that can turn on / off the current flowing between the conductive microstructure electrode 1 </ b> C and the metal thin film (metal plate electrode) 2 by light on / off control. Functions as a switching device.
The switching element 130 shown in FIG. 10A is a switching element exhibiting broadband characteristics when the irregular (random) intervals of the plurality of conductive microstructures 1Ca have a predetermined distribution.

The switching element 140 shown in FIG. 10B includes a plurality of dot-like conductive microstructures 1Da that are spaced apart at irregular (random) intervals, the metal thin film 2, and the heat sandwiched between them. A metamaterial complete absorption structure including the phase change material layer 3 is provided.
In the switching element 140 shown in FIG. 10B, the plurality of conductive microstructures 1Da constitute the conductive microstructure electrode 1D together with the transparent electrode 1Db disposed on the thermal phase transition material layer 3 so as to cover them. ing.
In the switching element 140 shown in FIG. 10B, light that can be turned on / off between the conductive microstructure electrode 1D and the metal thin film (metal plate electrode) 2 by light on / off control. Functions as a switching device.
The switching element 140 shown in FIG. 10B is a switching element exhibiting broadband characteristics when the irregular (random) intervals of the plurality of conductive microstructures 1Da have a predetermined distribution.

<Measurement of electrical resistivity of VO ₂ thin film>
As shown in FIG. 11, a VO ₂ thin film with a thickness of 250 nm is formed on a glass substrate, and a silver nanorod array (approximately 36 million silver nanorods with a length of 60 nm × width 150 nm × height 40 nm) is formed on the VO ₂ thin film. did. Furthermore, silver having a width of 2 mm was deposited on both ends of the VO ₂ thin film to a thickness of 100 nm and separated by 3 mm to form silver electrodes.

Next, the monochromatic light polarized in the minor axis direction was irradiated, and the electrical resistivity of the VO ₂ thin film at that time was measured. The result is shown in FIG.
In the graph of FIG. 12, the horizontal axis represents the wavelength (nm), the left vertical axis represents the transmittance of the silver nanorod array, and the right vertical axis represents the electrical resistivity (Ωcm).
The electrical resistivity was obtained by irradiating each monochromatic light (black circle in FIG. 9) with a monochromatic light having a light intensity of 10 mW / cm ² and measuring the current flowing through the VO ₂ thin film. Is.

The Figure 12, the electrical resistivity of the VO ₂ thin film in the plasmon resonance wavelength (650 nm) is decreased, the heat generated in the silver nanorod array by plasmon resonance propagates to the VO ₂ thin film, progression phase transition VO ₂ thin film As a result, the electrical resistivity of the VO ₂ thin film is lowered.

FIG. 13 shows that the temperature of the VO ₂ thin film is increased from 20 ° C. to 100 ° C. and then decreased from 100 ° C. to 20 ° C. under irradiation of monochromatic light of 650 nm polarized in the short axis direction and the long axis direction of the silver nanorods. Te is a graph showing the results of measuring the electrical resistivity of the VO ₂ thin film.
According to FIG. 12, 650 nm monochromatic light has a plasmon resonance wavelength in the minor axis direction of the silver nanorods. Therefore, irradiation with 650 nm monochromatic light polarized in the minor axis direction is accompanied by plasmon excitation, and irradiation with 650 nm monochromatic light polarized in the major axis direction is not accompanied by plasmon excitation. Hereinafter, the former case may be referred to as plasmon-excited polarized light irradiation, and the latter case may be referred to as plasmon non-excited polarized light irradiation.

Comparing the measurement under plasmon excitation polarized light irradiation and the measurement under plasmon unpolarized polarized light irradiation, the temperature of the VO ₂ thin film is 68 ° C., and it is 0 in the case of plasmon excited polarized light irradiation than in the case of plasmon unpolarized polarized light irradiation. The electrical resistivity of the VO ₂ thin film of 0.05 [Ωcm] was lowered. 0.05 [Ωcm] corresponds to 0.7 ° C. This heat generated on the silver nanorods by plasmon resonance propagates to the VO ₂ thin film, the results of phase transition of the VO ₂ thin film is progressed.
The intensity of the irradiated monochromatic light is 10 mW / cm ² . Since heat generated during plasmon resonance increases linearly according to the intensity of irradiated light, silver nanorods generate heat corresponding to 7 ° C. when irradiated with monochromatic light having a light intensity of 100 mW / cm ² , and the electrical properties of the VO ₂ thin film It can be predicted that the resistivity decreases from the 10 [Ωcm] to the 10 ⁻³ [Ωcm] level and a three-digit electrical resistivity change is obtained.

In the case of Non-Patent Document 2 in which VO ₂ is switched by simply irradiating femtosecond laser light, a light intensity of at least about 140 GW / cm ² is required, but in the case of VO ₂ switching with a fully absorbing metamaterial structure It is considered that switching is possible even with a light intensity of 10 mW / cm ² or less.

<Expectation of heat generated by fully absorbing metamaterial structure>
(1) The two-dimensional electromagnetic field calculation of the metal plate electrode / VO ₂ thin film / metal nanostructure electrode structure shown in FIG. 14A was performed.
As a result, a complete absorption characteristic having an absorption rate of 80% or more was confirmed (FIG. 14B). “Pitch” in FIG. 14B is “Pitch” shown in FIG. 14A, and indicates the repetition period (pitch) of the same structure. In FIG. 14B, the horizontal axis represents the wavelength, and the vertical axis represents the light absorption rate when the incident light is 1.
In particular, when the electric field distribution of the absorption peak near 1.7 micrometers was calculated (FIG. 14C), the electric field distribution derived from the complete absorption characteristics was confirmed, and high absorption characteristics of 80% or more were brought about by the complete absorption structure. It was confirmed by calculation.

(2) Estimation of the amount of heat generated by the fully absorbing metamaterial structure The heat generated by plasmon resonance can be calculated mainly by the following equation (see Non-Patent Document 4).

For fully absorbing structures, the structure factor (R _eq , Since it is difficult to obtain β), it is difficult to calculate the actual calorific value. The heat generated by the fully absorbing metamaterial structure was predicted from experimental findings and related research reports.
As shown in FIG. 13, even when simple silver nanorods were irradiated with light of 10 mW / cm ² , heat generation of about 1 ° C. was experimentally observed.
Since the absorption rate / absorption cross-sectional area of the fully absorbing metamaterial structure is 10 times higher than that of the silver nanorods, the calculation results show that when the 10 mW / cm ² resonant light is irradiated, The degree of heat generation is estimated to be at least 10 ° C. (see Non-Patent Document 5).

It is known that a metamaterial perfect absorption structure that induces a plasmon quadrupole mode has a much higher thermoelectron generation efficiency than a simple plasmonic structure such as metal nanoparticles (see Non-Patent Document 6). High thermoelectron generation efficiency means that the amount of local heat generated by thermal electron relaxation is also large. Therefore, compared with the laser light-induced phase transition that requires about 1 kW / cm ^2, the optical switching element of the present invention using the metamaterial complete absorption structure is a thermal phase transition material with weak light that is a few orders of magnitude lower ( For example, switching of VO ₂ ) is enabled.

In addition, for example, when a VO ₂ thin film is used, it has already been reported that when VO ₂ and a plasmon structure are in contact, thermoelectrons generated in the plasmon structure are injected into the VO ₂ conduction band to promote phase transition. It has been reported that the phase transition phenomenon induced by thermionic injection is on the order of picoseconds (10 ⁻¹² ) (see Non-Patent Document 3).
Therefore, when the fully absorbing metamaterial structure with high thermoelectron generation efficiency promotes the phase transition of VO ₂ by the thermoelectron injection mechanism, the response speed is on the order of picoseconds, which is the response speed of a switching element such as an existing MOSFET. A response speed much faster than nanoseconds is obtained.

(Thermoelectric conversion element)
FIG. 15 is a cross-sectional view schematically showing a thermoelectric conversion element 200 according to an embodiment of the present invention.
The thermoelectric conversion element 200 includes a metamaterial complete absorption structure 200 including the conductive microstructure 11, the metal thin film 12, and the thermoelectric conversion layer 13 sandwiched between them.

The thermoelectric conversion element of the present invention is different from the switching element of the present invention in that the thermal phase transition material layer is changed to a thermoelectric conversion layer, but is common in that a metamaterial complete absorption structure is used.
Moreover, since the thing of the same structure can be used about a conductive microstructure and a metal thin film, although a different point is mainly demonstrated, description may be abbreviate | omitted about a common point.

Also in the thermoelectric conversion element of the present invention, the metamaterial complete absorption structure can confine incident light nearly 100%, and high heat is generated between the conductive microstructure 11 and the metal thin film 12.
Therefore, one end of the thermoelectric conversion film sandwiched between the conductive microstructure 11 and the metal thin film 12 is heated to generate a temperature difference, and an electromotive force is generated between both ends of the thermoelectric conversion element due to the Seebeck effect.
The thermoelectric conversion element of the present invention is a thermoelectric conversion element that functions using local heat generated during plasmon resonance of a conductive microstructure as a power source.
The thermoelectric conversion element of the present invention does not require a high-temperature part or a low-temperature part, a high-temperature heat source, or a low-temperature heat source provided in a conventional thermoelectric conversion element or thermoelectric conversion module in actual use.

<Conductive microstructure>
The conductive microstructure 11 may be disposed inside or on a part of the thermoelectric conversion layer 13.
The conductive microstructure is provided “only in part” of the thermoelectric conversion film. This is because it is necessary to provide a temperature difference in the thermoelectric conversion film (making a high-temperature part and a low-temperature part). It cannot be provided over the entire membrane. This “part” may be one end of the thermoelectric conversion film. In this case, the one end part becomes a high temperature part, and the other part becomes a low temperature part. The electrode for taking out the current or voltage may be provided near the high temperature part and somewhere in the low temperature part. For example, when the thermoelectric conversion film has a shape extending in one direction, the electrode of the low temperature part may be provided on the other end opposite to the “one end” in the longitudinal direction.

<Thermoelectric conversion membrane>
As the material of the thermoelectric conversion film 13, a known organic thermoelectric conversion material or inorganic thermoelectric conversion material can be used.
Specifically, as an organic thermoelectric conversion material, PEDOT: PSS (3,4-ethylenedioxythiophene: poly (4-styrenesulfonate)), P3HT (3-hexylthiophene), poniphenylenevinylene, etc. And carbon materials such as carbon nanotubes. Examples of the inorganic thermoelectric conversion material include metal oxides, tellurium compounds, silicon compounds, and antimony compounds.

  Although it does not limit as a film thickness of the thermoelectric conversion film | membrane 13, if a standard is illustrated, it can be set to 10 nm-10000 nm.

  As a method for forming the thermoelectric conversion film, a known method can be used. For example, coating, spin coating, dip coating, spray coating, vapor deposition, sputtering, or the like can be used. All of the exemplified methods can be used for the formation of the thermoelectric conversion film with the inorganic thermoelectric conversion material, and all the methods other than the sputtering method are used for the formation of the thermoelectric conversion film with the organic thermoelectric conversion material. be able to.

  Since the metal thin film having a metamaterial complete absorption structure also functions as an electrode, it is not necessary to newly form an electrode on the thermoelectric conversion element.

In FIG. 16, the conceptual diagram of the thermoelectric conversion element of this invention which has a metamaterial perfect absorption structure in one end is shown.
Light irradiation is performed on the surface of the conductive microstructure of the metamaterial complete absorption structure. Excitation of the complete absorption characteristic confines incident light between the metal thin film (metal plate electrode) of the metamaterial complete absorption structure and the conductive microstructure, and generates high heat. A temperature difference occurs at both ends of the thermoelectric conversion element, and an electromotive force is generated between the electrodes disposed at both ends.

In the thermoelectric conversion element of the present invention, a substrate is not essential, but a substrate similar to the switching element of the present invention can be used.
For example, a thermoelectric conversion element as shown in FIG. 16 can be formed using a flexible substrate (the substrate is not shown in the drawing).

  The metamaterial complete absorption structure excites a plasmon quadrupole mode having a particularly high Q value. The quadrupole mode is known to have a long life in a narrow band and high generation efficiency of thermoelectrons that are the source of local heat. Therefore, compared to other simple plasmonic structures, a larger amount of local heat is generated and the efficiency of the thermoelectron injection mechanism into the thermoelectric conversion film is increased, so that a metal thin film that excites the quadrupole mode ( It is important that a thermoelectric conversion film is inserted between the metal flat plate electrode) and the conductive microstructure. This is because the quadrupole mode efficiently injects thermoelectrons and propagates local heat to the thermoelectric element.

  FIG. 17 shows an example of the arrangement (arrangement) of a plurality of conductive microstructures of a thermoelectric conversion element according to an embodiment of the present invention, and (a) to (d) are shown in FIG. The same arrangement as that of the plurality of conductive microstructures 1Aa included in the switching element 110, the same arrangement as that of the plurality of conductive microstructures 1Ba included in the switching element 120 illustrated in FIG. 9, and illustrated in FIG. An example of the same arrangement as the plurality of conductive microstructures 1Ca included in the switching element 130 and the same arrangement as the plurality of conductive microstructures 1Da included in the switching element 140 illustrated in FIG. is there.

  For example, in the thermoelectric conversion element 200 shown in FIG. 16, the plurality of conductive microstructures 11 are replaced with the plurality of conductive microstructures in the arrangement examples shown in FIGS. 17 (a) to 17 (d). The element is a thermoelectric conversion element exhibiting a narrow band characteristic or a wide band characteristic corresponding to each of FIGS.

FIG. 18 shows a configuration in which a metal nanostructure-thermoelectric conversion film-metal plate electrode structure is disposed on a substrate as an example of the metamaterial complete absorption structure of the present invention.
FIG. 18A shows a configuration in which a metal plate electrode, a thermoelectric conversion film, and a metal nanostructure are sequentially formed on a substrate, and shows a case where light irradiation is performed from the side where the metamaterial complete absorption structure of the substrate is formed. FIG. 4B is a schematic cross-sectional view showing a configuration in which a metal nanostructure, a thermoelectric conversion film, and a metal flat plate electrode are sequentially formed on a substrate, and shows a case where light irradiation is performed from below the substrate. FIG. In the case of FIG. 18B, it is preferable to use a highly transparent substrate.
It is conceivable that a metal nanostructure is produced on a substrate and light is irradiated from the bottom of the substrate. Since the metal nanostructure determines the response wavelength, light irradiation is always performed from the metal nanostructure side.

By appropriately designing the size and shape of the conductive microstructure (eg, metal nanostructure), the response wavelength can be selected from a wide wavelength range from the ultraviolet to the infrared range. Since the plasmon quadrupole mode has a narrow band response with a very high Q value, it can be expected to be used as a narrow band optical switching element. In principle, since only one metal nanostructure exhibits wavelength response, a high-resolution image sensor having a pixel size in the order of nm can be realized.
The switching element of the present invention can also be used for a photodetector.

<Surface protective film>
In the thermoelectric conversion element of the present invention, when the conductive microstructure is formed on the surface of the thermoelectric conversion film, a surface protective film may be formed. As the material for the surface protective film, any known material used as a surface protective film for an electronic device or the like can be used as long as it is a material that transmits a plasmon resonance wavelength.
Such a surface protective film has an opening so that the conductive microstructure is exposed from the thermoelectric conversion film in the region where the conductive microstructure is formed in a configuration in which the conductive microstructure is buried inside the thermoelectric conversion film. It may be formed and provided to protect the opening.

  The embodiments of the present invention have been described in detail with reference to the drawings, but the configurations and combinations of the embodiments in the embodiments are examples, and within the scope of the effects of the present invention, the addition, omission of configurations, Substitutions and other changes are possible.

(Method for manufacturing thermoelectric conversion element)
An example of the manufacturing method of the thermoelectric conversion element of this invention is demonstrated below.
<The manufacturing method 1 of a thermoelectric conversion element>
(1) A metal thin film is formed on a substrate (a method such as a vapor deposition method, a sputtering method, or an electrolytic (electroless) plating method can be used) (see FIG. 6A).
(2) Next, a thermoelectric conversion layer is formed on the metal thin film (application, spin coating, dip coating, spray coating, vapor deposition, sputtering, etc. can be used) (see FIG. 6B) .
(3) Next, a conductive microstructure and an electrode portion for taking out an electric current are formed on the thermoelectric conversion layer (a method such as a photolithographic method or an electron beam lithography method can be used for microfabrication). For metal formation, techniques such as vapor deposition, sputtering, and electrolytic (electroless) plating can be used (see FIG. 6C).
In the thermoelectric conversion element manufactured by this manufacturing method, the conductive microstructure is disposed on the surface of the thermoelectric conversion film.

<The manufacturing method 2 of a thermoelectric conversion element>
(1) A metal thin film is formed on a substrate (a method such as a vapor deposition method, a sputtering method, an electrolytic (electroless) plating method, or the like can be used) (see FIG. 6A).
(2) Next, a thermoelectric conversion layer is formed on the metal thin film (application, spin coating, dip coating, spray coating, vapor deposition, sputtering, etc. can be used) (see FIG. 6B) .
(3) Next, a conductive microstructure is formed on the thermoelectric conversion layer (a method such as a photolithographic method or an electron beam lithography method can be used for microfabrication. Techniques such as sputtering and electrolysis (electroless) plating can be used).
(4) Next, a second thermoelectric conversion layer is formed on the thermoelectric conversion layer and the conductive microstructure (using techniques such as coating, spin coating, dip coating, spray coating, vapor deposition, and sputtering). it can).
In the thermoelectric conversion element manufactured by this manufacturing method, the conductive microstructure is disposed inside a part of the thermoelectric conversion film.

<Method 3 for producing thermoelectric conversion element (see FIG. 18B)>
(1) A conductive microstructure is formed on a substrate (for microfabrication, a technique such as an optical lithography method or an electron beam lithography method can be used. For metal formation, a vapor deposition method, a sputtering method, an electrolysis ( Techniques such as electroless plating may be used).
(2) Next, a thermoelectric conversion layer is formed on the substrate and the conductive microstructure (a method such as coating, spin coating, dip coating, spray coating, vapor deposition, or sputtering can be used).
(3) Next, a metal plate electrode is formed on the thermoelectric conversion layer (a method such as a vapor deposition method, a sputtering method, an electrolytic (electroless) plating method can be used for forming the metal).

(Use of waste heat (waste heat))
An electromotive force can be generated using the thermoelectric conversion element of the present invention using exhaust heat (waste heat) of a heating element such as various electronic devices, various industrial equipment, and various automobiles as a heat source.

In FIG. 19, the conceptual sectional drawing which showed typically the thermoelectric conversion element 210 concerning one Embodiment of this invention is shown.
A thermoelectric conversion element 210 illustrated in FIG. 19 is a thermoelectric conversion element including a fully absorbing metamaterial structure including the conductive microstructure 11, the metal thin film 12A, and the thermoelectric conversion layer 13 sandwiched therebetween.
By installing the thermoelectric conversion element 210 so that the conductive microstructure 11 is disposed close to the heating element 50, an electromotive force can be generated using heat generated from the heating element 50. In the thermoelectric conversion element 210, the generated electromotive force or current can be taken out from the metal thin film 12A that also functions as one electrode and the other electrode 12B that is spaced apart from the metal thin film 12A.

For example, when the heating element is an LSI, and the LSI is at a temperature of about 100 ° C., the thermoelectric conversion layer 210 absorbs the radiation (infrared rays) emitted from the LSI by the fully absorbing metamaterial structure of the thermoelectric conversion element 210. Since the vicinity of the metal thin film 12A is a high temperature portion and the electrode 12B is a low temperature (room temperature) portion, voltage or current can be taken out by the metal thin film 12A and the electrode 12B.
The electromagnetic wave generated by the heating element at about 100 ° C. is infrared light centered on 6 μm, and the spectral emission luminance (W / cm ² .μm), which is the infrared intensity when separated from the heating element by 100 nm, is 1 × 10 ^{− 1} (W / cm ² · μm). Thermoelectric conversion element with a fully absorbing metamaterial structure with a photothermoelectric conversion efficiency of 1.2% installed 100 nm away from the heating element (when using a thermoelectric conversion material with Seebeck coefficient of 76 μV / K and conductivity of 142000 S / m) Was confirmed by simulation calculation to absorb electromagnetic waves radiated from a heating element of about 100 ° C. and generate a current of at least about 108 nA.

  When the thermoelectric conversion element of the present invention is configured to be flexible as shown in FIG. 16, for example, a heating element having a curved surface such as a tube can be wound around the curved surface.

  The distance at which the completely absorbing metamaterial structure is brought close to the heating element depends on the type of the heating element, but can be, for example, larger than zero and about several μm.

  The thermoelectric conversion element of the present invention can be produced by a thin film. Normal heat sink (for example, an element made of metal material such as aluminum, iron, copper, etc. with high thermal conductivity for the purpose of heat dissipation, fin type or sword mountain type, bellows so that the surface area becomes large The thermoelectric conversion element having a fully absorbing metamaterial structure (hereinafter sometimes referred to as a fully absorbing thermoelectric conversion element) is a thin film having a maximum thickness of 300 to 1000 nm. be able to. When compared with the same film thickness, the exhaust heat efficiency of the complete absorption thermoelectric conversion element is higher than that of the heat sink.

By appropriately designing the metal nanostructure that is a component of the fully absorbing metamaterial structure, it is possible to absorb the broadband radiation spectrum generated from the heating element without leakage. In addition, since only the portion where the metal nanostructure is formed absorbs the radiation spectrum, the temperature gradient of the complete absorption thermoelectric conversion element is maintained, and the thermoelectric conversion mechanism works.
In the first place, a thin-film thermoelectric conversion element has a low infrared absorptivity in the first place, and cannot generate power by absorbing the radiant infrared rays of a similar heating element.

(Exhaust heat (waste heat) function)
Heat generated by heating elements of various electronic devices, various industrial equipment, various automobiles, and the like can be converted into electricity using the thermoelectric conversion element of the present invention, and the heating elements can be exhausted.

DESCRIPTION OF SYMBOLS 1 Conductive microstructure 2 Metal thin film 3 Thermal phase transition material layer 10 Metamaterial complete absorption structure 11 Conductive microstructure 12 Metal thin film 13 Thermoelectric conversion film 20 Metamaterial complete absorption structure 100 Switching element 200, 210 Thermoelectric conversion element

Claims (15)

  A switching element having a fully absorbing metamaterial structure comprising a conductive microstructure, a metal thin film, and a thermal phase transition material layer sandwiched between them.   The switching element according to claim 1, wherein a plurality of the conductive microstructures are provided.   The switching element according to claim 2, wherein the plurality of conductive microstructures have the same plasmon resonance wavelength.   The switching element according to claim 2, wherein the plurality of conductive microstructures include those having different plasmon resonance wavelengths.   The switching element according to any one of claims 1 to 4, wherein the plurality of conductive microstructures are randomly arranged.   The switching element according to claim 1, wherein the plurality of conductive microstructures are regularly arranged.   The switching element according to claim 1, wherein the conductive microstructure has an anisotropic shape.   A thermoelectric conversion element comprising a fully absorbing metamaterial structure comprising a conductive microstructure, a metal thin film, and a thermoelectric conversion layer sandwiched between them.   The thermoelectric conversion element according to claim 8, wherein the conductive microstructure is disposed inside or on a part of the thermoelectric conversion film.   The thermoelectric conversion element according to claim 8, wherein a plurality of the conductive microstructures are provided.   The thermoelectric conversion element as described in any one of Claims 8-10 which consists of what a some electroconductive microstructure shows the same plasmon resonance wavelength.   The thermoelectric conversion element as described in any one of Claims 8-10 in which what shows a different plasmon resonance wavelength is contained in several electroconductive microstructures.   The thermoelectric conversion element according to any one of claims 8 to 12, wherein the plurality of conductive microstructures are randomly arranged.   The thermoelectric conversion element according to any one of claims 8 to 12, wherein the plurality of conductive microstructures are regularly arranged.   The thermoelectric conversion element according to claim 8, wherein the conductive microstructure has an anisotropic shape.