Infrared sensing device and variable resistance film used therein

Abstract

The present disclosure provides an infrared sensing device that can detect an infrared ray with a simple structure. A device 300 comprises a resistance-variable part 13 of which the electrical resistance changes in response to the infrared ray and a detection unit that detects a change in the electrical resistance of the resistance-variable part. The resistance-variable part satisfies at least one of i) including a material that can absorb the infrared ray through local surface plasmon resonance and ii) including the material and receiving, from a carrier supply unit, carriers that are electrons and / or holes generated by irradiating the carrier supply unit 23 in contact with the resistance-variable part with the infrared ray.

Description

[Technical Field]

[0001] This invention relates to a device for detecting infrared radiation and a variable-resistivity film used therein. [Background technology]

[0002] With the advancement of smart societies, demand for various sensing devices continues to expand. Infrared sensing devices, in particular, are becoming increasingly important in a wide range of fields, including information communication, temperature measurement, and biometric detection.

[0003] Infrared sensing devices that utilize materials whose electrical resistance increases with temperature rise due to infrared irradiation are known. In this type of device, metals such as platinum, titanium, and copper, or oxide semiconductors such as vanadium oxide, are typically used as resistance-changing materials. Infrared sensing devices using these materials are called bolometers, and development is progressing particularly for use in image forming apparatuses (for example, Patent Document 1). [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2001-13010 [Overview of the project] [Problems that the invention aims to solve]

[0005] However, as described in Patent Document 1, bolometers have the problem of having a complex structure because they require a reference resistor along with a heat-sensitive resistor to detect infrared radiation in order to counteract the influence of heat from the surrounding environment. The present invention aims to provide a new infrared sensing device that can detect infrared radiation even with a simple structure. [Means for solving the problem]

[0006] The inventors have discovered that the electrical resistance of a material capable of absorbing infrared radiation by localized surface plasmon resonance (LSPR) (hereinafter sometimes referred to as "LSPR-IR absorbing material") can change rapidly upon irradiation with infrared radiation, and that if electrons and / or holes generated in the LSPR-IR absorbing material by infrared radiation are supplied to a portion to which a voltage can be applied, the electrical resistance of that portion can change rapidly. Based on these findings, the inventors have completed the present invention. These changes in electrical resistance can occur even at a constant temperature.

[0007] In other words, the present invention is An infrared sensing device, The infrared sensing device comprises a variable resistance unit whose electrical resistance changes upon irradiation with infrared light, and a detection unit that detects the change in electrical resistance of the variable resistance unit. The aforementioned variable resistance section is i) A material that can absorb infrared radiation by local surface plasmon resonance, ii) Receiving from the carrier supply unit a carrier supply unit containing the material and in contact with the variable resistance unit carriers which are electrons and / or holes generated by irradiation of the carrier supply unit with infrared radiation, the carrier supply unit satisfies at least one selected from the group consisting of the above, We provide infrared sensing devices.

[0008] Furthermore, the present invention is It contains a material that can absorb infrared radiation through local surface plasmon resonance, When applying voltage and starting infrared irradiation, and then stopping the irradiation, The electrical resistance increases in response to the start of the irradiation, and decreases in response to the cessation of the irradiation, or The electrical resistance decreases when the irradiation starts, and increases when the irradiation stops. We provide a variable resistance film. This resistive film is particularly useful for infrared sensing devices.

[0009] Further, the present invention provides an infrared transmittance measuring device, comprising an infrared sensing device according to the present invention and a light source that irradiates light including infrared rays to the infrared sensing device, wherein infrared rays irradiated from the light source to a measurement sample and transmitted through the measurement sample are detected by the infrared sensing device.

Advantages of the Invention

[0010] According to the present invention, it is possible to provide an infrared sensing device capable of rapidly detecting infrared rays with a simple structure. The device according to the present invention is most valuable in the field of infrared detection, but as shown in the examples described later, it can also be used as an optical sensing device capable of detecting light with shorter wavelengths, for example, light in the visible and ultraviolet regions.

Brief Description of the Drawings

[0011] [Figure 1] It is a diagram showing an outline of the configuration of one form of the device of the present invention. [Figure 2] It is a diagram showing an outline of the configuration of another form of the device of the present invention. [Figure 3] It is an example of the result of measuring the relaxation time from local surface plasmon excitation by the time-resolved transient absorption spectroscopy method. [Figure 4] It is a diagram showing the ON / OFF pattern of the light irradiation performed in the examples. [Figure 5] It is data of the change in electrical resistance (change in current value) obtained from Example 1. [Figure 6] It is data of the change in electrical resistance (change in current value) obtained from Example 2. [Figure 7] It is data of the change in electrical resistance (change in current value) obtained from Example 3. [Figure 8] It is data of the change in electrical resistance (change in current value) obtained from Example 4. [Figure 9] It is data of the change in electrical resistance (change in current value) obtained from Example 5. [Figure 10] Data of the change in electrical resistance (change in current value) obtained from Example 6. [Figure 11] Data of the change in electrical resistance (change in current value) obtained from Example 7. [Figure 12] Data of the spectral transmittance of the resistance change film obtained from Example 4. [Figure 13] It is a cross-sectional view showing a part of another form of the device of the present invention. [Figure 14] It is a cross-sectional view showing a part of another form of the device of the present invention. [Figure 15] It is a cross-sectional view showing a part of another form of the device of the present invention. [Figure 16] It is a cross-sectional view showing a part of another form of the device of the present invention. [Figure 17] It is a cross-sectional view showing a part of another form of the device of the present invention. [Figure 18] It is a diagram showing an outline of one form of the infrared transmittance measuring device of the present invention.

Mode for Carrying Out the Invention

[0012] In this specification, "infrared ray" means an electromagnetic wave having a wavelength of 0.7 to 1000 μm. "Semiconductor" is used in a meaning that includes not only ordinary semiconductors but also doped semiconductors, semimetals, and degenerate semiconductors. "Semimetal" is a substance having a band structure in which the lower part of the conduction band and the upper part of the valence band slightly overlap across the Fermi level due to distortion of the crystal structure, interaction between crystal layers, etc. "Degenerate semiconductor" is a substance having a band structure in which the conduction band or valence band overlaps with the Fermi level. "Nanoparticle" means a particle whose minimum diameter is less than 1 μm, for example, in the range of 0.1 nm or more and less than 1 μm. Nanoparticles typically mean particles whose maximum size is 5 μm or less, and further in the range of 3 nm to 2 μm. Note that the "minimum diameter" is determined by the minimum dimension passing through the center of gravity of the particle, and the "maximum size" is determined by the longest line segment that can be set within the particle. "Functional group" is used as a term including halogen atoms.

[0013] The device according to the present invention may include a group of electrodes that apply a voltage to the variable resistance section. The electrode group may include a first electrode electrically connected to the positive electrode of a power supply and a second electrode electrically connected to the negative electrode of a power supply. Both the first electrode and the second electrode may be in direct contact with the variable resistance section and / or the carrier supply section. Even in a configuration that includes a carrier supply section, both the first electrode and the second electrode can be in direct contact with the variable resistance section.

[0014] The device according to the present invention may further include a power supply that supplies voltage to the electrodes. However, the voltage may be supplied from an external power supply.

[0015] In one embodiment of the present invention, when a voltage is applied to the variable resistance portion from a group of electrodes that apply a voltage to the variable resistance portion, infrared irradiation of the variable resistance portion is started, and then the irradiation is stopped, the electrical resistance increases in accordance with the start of irradiation and decreases in accordance with the stop of irradiation. In this embodiment, the variable resistance portion may also include an infrared absorbing film that is a single layer film containing the above-mentioned material. Furthermore, the variable resistance portion may contain a compound containing copper and a chalcogen element excluding oxygen as the above-mentioned material. This compound is copper sulfide, copper selenide, etc. The variable resistance portion may contain, for example, nanoparticles of copper sulfide.

[0016] In another embodiment of the present invention, when a voltage is applied to the variable resistance from a group of electrodes that apply a voltage to the variable resistance, infrared irradiation of the variable resistance is started and then stopped, the electrical resistance decreases in accordance with the start of irradiation and increases in accordance with the stop of irradiation. In this embodiment, the infrared sensing device includes a carrier supply unit, and the carrier supply unit and the variable resistance unit may constitute a laminated structure. The carrier supply unit and the variable resistance unit may also be composed of different semiconductor materials. The variable resistance unit may also contain cesium-doped tungsten oxide (cesium-doped tungsten oxide) as the material mentioned above. The variable resistance unit may contain, for example, nanoparticles of cesium-doped tungsten oxide.

[0017] In one embodiment of the present invention, the variable resistance portion includes a semiconductor material that receives carriers, which are electrons and / or holes, generated by irradiation of the carrier supply portion with infrared light, which includes semiconductor nanoparticles.

[0018] The relaxation time from local surface plasmon excitation is tens of femtoseconds to hundreds of picoseconds for many LSPR-IR absorbing materials (infrared photoresponsive LSPR materials), but in materials such as copper sulfide and cesium-doped tungsten oxide, this relaxation time includes long-lived components of 1 ns or more. LSPR-IR absorbing materials that can have such long relaxation times are thought to exhibit transient transitions in their electronic states upon irradiation with infrared light, which contribute to an increase or decrease in electrical resistance. That is, in one embodiment of the present invention, the LSPR-IR absorbing material is a material in which a relaxation time of 1 ns or more from local surface plasmon excitation can be measured. In embodiments using such materials, the use of the second material described later is not essential.

[0019] When using an LSPR-IR absorbing material whose relaxation time is not as long as described above, carrier transfer between materials may be utilized. That is, in one embodiment of the present invention, the resistivity variable part includes a first material which is an LSPR-IR absorbing material, and a second material which receives carriers, which are electrons and / or holes, generated by irradiation of the first material with infrared light.

[0020] In one embodiment of the present invention, both the first and second materials are transparent conductive oxides. This embodiment is suitable for providing a device that is translucent in the visible range. However, as will be described later, good translucency in the visible range can also be achieved in an embodiment using copper sulfide nanoparticles.

[0021] In one embodiment of the present invention, the resistivity variable portion is a resistivity variable film, and more particularly, a single-layer film. However, the resistivity variable film may be a multilayer film containing two or more layers, for example, the resistivity variable portion and the carrier supply portion may constitute a multilayer film. Here, even if the film formation involves the supply of raw materials multiple times, a film observed as a single layer will be treated as a "single-layer film".

[0022] In a form comprising a first material and a second material, the second material may be included as nanoparticles. In addition, the first material may also be included as nanoparticles. Furthermore, the present invention is not limited to this form, and a material capable of absorbing infrared radiation by local surface plasmon resonance may be included as nanoparticles.

[0023] The first and second materials may be semiconductor materials. The second material is not particularly limited, but a semiconductor with a higher electrical resistivity than the first material is preferred. Furthermore, the first and second materials may be the same type of semiconductor material or different types of semiconductor materials.

[0024] In one embodiment of the present invention, the resistance variable portion does not contain graphite and carbon nanotubes. The resistance variable portion does not require a conductive carbon material and may not contain conductive materials such as conductive carbon materials or metallic materials.

[0025] The variable resistance section may be a part in which the electrical resistance increases or decreases before the temperature rise of the variable resistance section due to the start of infrared irradiation substantially begins. To avoid changes in electrical resistance due to temperature rise, the device according to the present invention may be connected to a component designed as a heat sink or capable of functioning as a heat sink, or to a temperature controller having a cooling function, and the heat sink or a component performing the same function, or a temperature controller may be further provided as a heat dissipation section that releases heat from the variable resistance section to the outside. A component capable of functioning as a heat sink is, for example, a substrate for forming a film including the variable resistance section. A temperature controller having a cooling function is, for example, a Peltier element. The above specific examples of heat dissipation sections are illustrative, and the heat dissipation section is not limited to these.

[0026] In one embodiment of the present invention, the infrared sensing device is further provided with a cover portion that transmits at least a portion of the infrared radiation irradiated onto it. The cover portion may include a substrate and at least one selected from the group consisting of an optical filter portion and a sample placement portion, which is supported by the substrate. The cover portion may also shield a portion of the infrared radiation irradiated onto the device. The cover portion can shield infrared radiation in a certain area or in a certain wavelength range.

[0027] In one embodiment of the present invention, the resistivity variable portion may have high transmittance in the visible range with wavelengths of 400 to 800 nm. The transmittance in the visible range is, for example, 65% or more, 70% or more, even more specifically 75% or more, and particularly 80% or more.

[0028] The embodiments of the present invention will be described below with reference to the drawings as appropriate, but the following description is not intended to limit the present invention to any particular embodiment. In addition, the same reference numerals are used for the same members and parts in each drawing, and redundant explanations are omitted.

[0029] (Device configuration) The infrared sensing device 100 shown in Figure 1 comprises a variable resistance unit 11 and a first electrode 1 and a second electrode 2 that apply voltage to the variable resistance unit 11. Voltage is supplied to electrodes 1 and 2 from a power supply 5. The power supply 5 is, for example, a DC power supply. A measurement unit 7 is provided in the electrical circuit including the variable resistance unit 11, electrodes 1 and 2, and power supply 5. Although not shown, the device 100 may also include switching elements and other electronic components, a memory unit for storing measurement results, a display unit for displaying measurement results, a control unit responsible for controlling each part and component, etc. In this configuration, changes in electrical resistance in the variable resistance unit 11 are detected using electrodes 1 and 2 and the measurement unit 7. In other words, the detection unit for detecting changes in electrical resistance comprises an electrode group consisting of electrodes 1 and 2 and the measurement unit 7.

[0030] The variable resistance unit 11 is positioned to receive infrared (IR) light. Infrared light (IR) is incident on the infrared light receiving surface 40 of the variable resistance unit 11. As infrared (IR) irradiation begins, the electrical resistance of the variable resistance unit 11 changes, and this change is detected by the measuring unit 7. The measuring unit 7 detects infrared (IR) irradiation, for example, by the current flowing through the circuit or by a change in the potential at the location where the measuring unit 7 is installed. Changes associated with the cessation of infrared (IR) irradiation are also detected by the measuring unit 7. In this way, the measuring unit 7 detects the irradiation and / or non-irradiation of infrared (IR). Known electronic equipment, circuits, and other components can be used as the measuring unit 7 without any particular limitations. The detection of infrared light by the measuring unit 7 is basically performed while a voltage is supplied from the power supply 5 to the variable resistance unit 11 via electrodes 1 and 2.

[0031] The device 100 may further include a calculation unit that calculates values ​​such as the intensity of infrared radiation (IR) and the temperature of the light source or heat source emitting the infrared radiation, based on the change in potential measured by the measurement unit 7. In particular, if the device 100 is designed to allow a measurement sample that absorbs a portion of the infrared radiation (IR) from the light source to be placed therein, the calculation unit may also include a function to measure the infrared absorption rate of the measurement sample, the content of infrared components in the measurement sample, etc. The calculation unit can be configured by appropriately combining an MPU (Micro-processing unit), memory, etc. The measurement sample may be non-living, living organism, or more specifically, a part of living organism.

[0032] The variable resistance section 11 may be formed as a variable resistance film. The variable resistance film may be formed on a substrate (not shown) together with electrodes 1 and 2. The variable resistance film can be formed by a method that does not require a reduced pressure atmosphere, as shown in the embodiments described later, specifically by a liquid-phase film formation method such as coating, dipping, or spraying. The substrate is preferably an insulating substrate made of glass, resin, ceramic, etc. The substrate may be made of a material that can transmit infrared rays in the band to be detected, specifically a glass plate, a resin plate, etc. If heat dissipation to the substrate alone is insufficient to avoid fluctuations in the electrical resistance of the variable resistance section due to temperature changes, an additional heat dissipation section such as a heat sink may be connected to the substrate, or a temperature controller such as a Peltier element or a blower may be used as an additional heat dissipation section to promote heat dissipation from the variable resistance section.

[0033] The substrate may be made of at least one material selected from the group consisting of woven fabrics, nonwoven fabrics, felt, knitted fabrics, paper, and film. These materials are lightweight and flexible, making them suitable for portable or wearable devices. The substrate is not limited to the above materials and may be made of a semiconductor, such as silicon, or it may be a metal plate that functions as a heat sink with an insulating coating formed on its surface. The semiconductor substrate may have control circuits and other components of device 100 formed on it.

[0034] In bolometers, where resistance changes in response to temperature, adiabatic structures using MEMS technology, such as beam structures, are sometimes introduced into the substrate to improve response speed. However, a sufficiently fast response speed can be obtained from device 100 without introducing a complex adiabatic structure.

[0035] In device 100, the first electrode 1 and the second electrode 2 are in direct contact with the variable resistance section 11. The variable resistance section 11 and electrode 1, and the variable resistance section 11 and electrode 2 do not have to be in direct contact, as long as a voltage can be applied to the variable resistance section 11 using electrodes 1 and 2, thereby allowing current to flow through the variable resistance section 11. However, unlike photovoltaic devices, light-emitting devices, etc., in device 100, there does not have to be a layer acting as a carrier injection layer or carrier transport layer between the variable resistance section 11 and electrodes 1 and 2.

[0036] The variable resistance section 11 includes an LSPR-IR absorbing material. When the variable resistance section 11 includes an LSPR-IR absorbing material whose relaxation time from local surface plasmon excitation is 1 ns or more, more specifically 10 ns or more, and particularly 100 ns or more, the electrical resistance of the variable resistance section 11 increases or decreases to a sufficiently detectable extent due to the transient transition of the electronic state of the LSPR-IR absorbing material caused by infrared irradiation.

[0037] If the variable resistance section 11 does not contain an LSPR-IR absorbing material that can achieve a relaxation time from local surface plasmon excitation to the extent described above, it is desirable that the variable resistance section 11 further includes a second material that receives carriers, which are electrons and / or holes, generated by irradiation of the LSPR-IR absorbing material (first material) with infrared light.

[0038] In the infrared sensing device 300 shown in Figure 2, the carrier supply unit 23 is positioned in contact with the variable resistance unit 13 but not in contact with electrodes 1 and 2. In device 300, electrodes 1 and 2 are in direct contact with the variable resistance unit 13. The variable resistance unit 13 and the carrier supply unit 23 may be a laminated film formed to be in contact with each other.

[0039] Preferably, the carrier supply unit 23 includes an LSPR-IR absorbing material (first material), and the resistance variable unit 13 includes a second material. In device 300, when infrared irradiation of the carrier supply unit 23 is initiated, the carriers, which are electrons and / or holes, generated in the first material are supplied to the second material of the resistance variable unit 13, causing the electrical resistance of the resistance variable unit 13 to increase or decrease.

[0040] The electrical resistance of the variable resistance unit 13 decreases as the major carriers increase in response to the start of infrared irradiation, provided that the major carriers of the variable resistance unit 13 and the carriers supplied from the carrier supply unit 23 are of the same type, i.e., both are electrons or both are holes. The electrical resistance of the variable resistance unit 13 increases as the major carriers recombine in response to the start of infrared irradiation, provided that the major carriers of the variable resistance unit 13 and the carriers supplied from the carrier supply unit 23 are of different types, i.e., one of the carriers is an electron and the other is a hole.

[0041] When infrared irradiation is stopped, the electrical resistance of the variable resistance section 13 basically returns to the state when infrared irradiation is not occurring. However, due to the effects of temperature rise, etc., it may not return to the same resistance value as before infrared irradiation. Even if the electrical resistance does not return to the state before irradiation, it can still be used as a sensing device. Changes associated with the cessation of infrared irradiation will be measured as an increase in electrical resistance if the electrical resistance decreased in response to the start of infrared irradiation, and as a decrease in electrical resistance if the electrical resistance increased in response to the start of infrared irradiation. The above changes in electrical resistance can also occur similarly in the device 100 shown in Figure 1.

[0042] Due to the high responsiveness of the LSPR-IR absorbing material, devices 100 and 300 can detect the increase or decrease in electrical resistance associated with the start or stop of infrared irradiation sufficiently quickly. If a material with a long relaxation time from local surface plasmon excitation is used in the variable resistance section 11, it may take a slightly longer time for device 100 to detect the stop of infrared irradiation. However, even in this case, detection is possible on the order of microseconds or less. Furthermore, in device 300, by appropriately controlling the band alignment between the material in the variable resistance section 13 and the material in the carrier supply section 23, the detection time can be further accelerated even when the variable resistance section 13 contains a material with a long relaxation time. The devices according to this embodiment can also detect the start or stop of infrared irradiation in, for example, on the order of ps or less.

[0043] The device according to this embodiment can operate in the atmosphere at room temperature. Bolometers, which are so-called thermal sensing devices, can operate at room temperature, but as is clear from their operating principle, they are inherently disadvantageous in terms of response speed. On the other hand, some so-called quantum sensing devices respond quickly, but are practically unusable unless cooled to low temperatures. The device according to this embodiment, which utilizes LSPR-IR absorbing materials, is highly practical in that it combines a fast response speed with a wide range of operating environments. The device according to this embodiment may have wavelength selectivity, exhibiting relatively high sensitivity to near-infrared irradiation up to a wavelength of 2.5 μm, and relatively low sensitivity to infrared radiation with longer wavelengths. Such wavelength selectivity is an advantageous feature from the viewpoint of suppressing noise due to thermal conduction.

[0044] Furthermore, if the electrical resistance of the variable resistance section 13 is too low, the aforementioned increase or decrease in electrical resistance, in other words, the increase or decrease in electrical resistance due to photodoping, will not be clearly apparent. From this viewpoint, the second material is preferably a non-metallic material, specifically a semiconductor material.

[0045] In Figure 2, electrodes 1 and 2, which constitute the electrode group, are not in contact with the carrier supply unit 23, but are in contact with the variable resistance unit 13. However, the arrangement of the electrode group, variable resistance unit, and carrier supply unit is not limited to the configuration shown in Figure 2, as long as carriers, which are electrons and / or holes, generated by the start of infrared irradiation of the carrier supply unit, can be supplied to the variable resistance unit.

[0046] The variable resistor section 13 and the carrier supply section 23 may contain the same type of semiconductor material or different types of semiconductor materials. In other words, it is sufficient that the carriers generated in the carrier supply section 23 are transmitted to the variable resistor section 13, so the required configuration differs from that of solar cells, which require a pn coupling or Schottky junction.

[0047] As shown in Figures 13 and 14, the infrared sensing device may further include a cover portion 30 positioned to allow infrared light IR incident on its interior to pass through. The cover portion 30 may transmit at least a portion of the infrared light IR and may also block at least a portion of the infrared light IR. In the device 101 shown in Figure 13, the cover portion 30 is positioned to cover at least a portion of the infrared light receiving surface 40 of the variable resistor portion 11. In the device 301 shown in Figure 14, the cover portion 30 is positioned to cover at least a portion of the infrared light receiving surface 40 of the carrier supply portion 23.

[0048] As shown in Figures 13 and 14, the variable resistance section 11, or the variable resistance section 13 and the carrier supply section 23, may be supported on the substrate 10 as a single layer or a multilayer film. The substrate 10 and the variable resistance section 11, or the variable resistance section 13 and the carrier supply section 23 constitute the variable resistance unit 50. In the variable resistance unit 50, the variable resistance sections 11 and 13 and the carrier supply section 23 all have the form of a film. The variable resistance unit 50 may also include films that function other than the variable resistance section or the carrier supply section, such as a protective film, a base film, an electrode film, etc. By using a flexible substrate 10, flexibility can be given to the variable resistance unit 50. The variable resistance unit 50 may be flexible enough to be wrapped around the outer circumference of a cylinder with a diameter of 10 cm without damage. It is also possible to make the entire combination of the cover section 30 and the variable resistance unit 50 as flexible as described above.

[0049] In Figures 13 and 14, the cover portion 30 is positioned such that a gap 60 is formed between it and the light-receiving surface 40 of the variable resistance unit 11 or the light-receiving surface 40 of the carrier supply unit 23, with a portion of it separated from the variable resistance unit 50. However, the presence of the gap 60 is not essential, and the cover portion 30 may be positioned so as to be in close contact with the infrared light-receiving surface 40. The cover portion 30 may also be detachably installed on the variable resistance unit 50.

[0050] The infrared sensing device can also be used as an absorptive rate measuring device, when combined with a light source, to measure the infrared absorptive rate of a sample based on the change in infrared absorptive rate due to the arrangement of the sample. It is also possible to measure the content of infrared absorbing components contained in the sample based on the change in infrared absorptive rate. In the configuration for measuring the infrared absorptive rate of a sample, it is desirable that the cover portion 30 transmits at least a portion of the infrared IR. In this case, the cover portion 30 may transmit only a portion of the infrared IR, or it may transmit substantially all of it.

[0051] The material constituting the cover portion 30 is not particularly limited, but examples include fibrous materials such as woven fabrics and nonwoven fabrics, and plastic materials such as films and resin plates. The cover portion 30 may also be equipped with an optical filter function, such as a bandpass function that transmits light in a predetermined wavelength range including at least a part of the infrared region.

[0052] The surface of the cover portion 30 can be used as a surface for positioning the measurement sample or as an opposing surface 80. Surface 80 is typically a positioning surface that contacts and supports the measurement sample. However, depending on the shape and type of the measurement sample, the measurement sample may be held above surface 80 in a non-contact state. In this case, surface 80 can be understood as an opposing surface that faces the measurement sample held above it.

[0053] The arrangement or opposing surface 80 is not particularly limited in its form, as long as the sample to be measured can be placed on or above it. Surface 80 may be a surface suitable for fixing the sample to be measured, or it may be a surface that constitutes a flow path through which the sample to be measured passes. Surface 80 may be a surface that preferentially binds to a predetermined component contained in the sample to be measured, and is suitable for fixing only that component. There are no particular restrictions on the form of the sample to be measured that comes into contact with surface 80, and it may be a solid, liquid, or gas.

[0054] As shown in Figures 15 and 16, the cover portion 30 may comprise a base material 31 and a sample placement portion 32. The sample placement portion 32 is supported by the base material 31. In the device 102 shown in Figure 15, the sample placement portion 32 is positioned to cover at least a portion of the infrared light receiving surface 40 of the variable resistance portion 11. In the device 103 shown in Figure 16, the sample contact portion 32 is positioned to cover at least a portion of the infrared light receiving surface 40 of the carrier supply portion 23. Typically, at least a portion of the surface of the sample placement portion 32 functions as a placement surface 80 that supports the sample to be measured. The sample placement portion 32 may also be positioned on the side of the base material 31 opposite to the infrared light incident surface, facing the void 60.

[0055] The sample placement section 32 is not particularly limited, but examples include hydrophobic or hydrophilic films, biocompatible films, antigen-modified films, antibody-modified films, adhesive films, etc. The sample contact section 32 is selected according to the characteristics of the sample to be measured. The sample placement section 32 itself is made of a material that transmits at least a portion of infrared (IR) light.

[0056] The sample placement section may be placed as part of the variable resistor unit 50, rather than as part of the cover section 30. In the device 103 shown in Figure 17, the sample placement section 32 is placed on the surface of the substrate 10 opposite to the surface on which the variable resistor unit 11 is placed. In this example, the substrate 10 is made of a material that transmits at least a portion of infrared IR. In Figure 17, the exposed surface of the substrate 10 may be used as the placement or opposing surface 80 without providing the sample placement section 32.

[0057] The cover portion 30 may include an optical filter portion instead of, or together with, the sample placement portion 32. The optical filter portion may have the optical filter function described above, that is, a bandpass function that transmits light in a predetermined wavelength range including at least a part of the infrared region. The cover portion 30 may be provided with the optical filter portion and the sample placement portion in this order from the substrate side, and may have a portion that combines the optical filter function and the sample placement function. Thus, the cover portion 30 may include a substrate 31 and a portion 32 supported by the substrate 31 that functions as an optical filter portion and / or a sample placement portion.

[0058] Each of the infrared sensing devices described above, together with a light source, can constitute an infrared transmittance measuring device for a sample. The infrared transmittance measuring device 500 illustrated in Figure 18 comprises an infrared sensing device 200 and a light source 400. The infrared sensing device 200 can be any of the sensing devices described above. As the light source 400, a light source that emits light including infrared light, in other words, a light source capable of emitting light in a wavelength range including the infrared region, should be used. The light emitted from the light source 400 does not need to cover the entire infrared region; it is sufficient that it contains infrared light that the sample can absorb. Furthermore, this light may include ultraviolet light and visible light, or it may be so-called laser light that contains only infrared light of almost a single wavelength.

[0059] In the apparatus 500 shown in Figure 18, the sample to be measured is placed in the sample holding space 600 between the device 200 and the light source 400. The sample to be measured may be placed in contact with the device 200 or at a distance from the device 200. In this state, infrared IR irradiated from the light source 400 passes through the sample to be measured and enters the device 200, and the incident infrared IR is measured by the measurement unit of the device 200. Subsequently, for example, the infrared transmittance T1 of the sample to be measured is measured by the calculation unit of the device 200. The infrared absorptance of the sample to be measured is calculated by the difference T1-T2 between the infrared transmittance T2, which is similarly measured and calculated without the sample to be measured, and the infrared absorptance of the sample to be measured. The calculation unit may also calculate the content of infrared absorbing components contained in the sample to be measured based on T1-T2.

[0060] In one example of measurement, the sample to be measured is blood, and the infrared-absorbing component is glucose. In this example, the sample to be measured may also be a part of a living organism, such as a fingertip or earlobe. In this example, the blood glucose level can be calculated based on the absorption rate by the living organism of infrared light around 1500 nm, which is permeable to living organisms and is characteristically absorbed by glucose. In other words, the infrared transmittance measuring device 500 can be used as a blood glucose measuring device. This blood glucose measuring device is a so-called non-invasive sensor, and it is a sensor that takes advantage of the features of device 200, which can respond to molecules whose concentration and concentration distribution in the body change rapidly. This device can also be easily made into a wearable sensor by taking advantage of the flexibility of the variable resistance unit 50.

[0061] (LSPR-IR absorbing material) The presence of LSPR in an LSPR-IR absorbing material can be confirmed, for example, by demonstrating the linearity of the wavelength change of the absorption peak when the refractive index of the surrounding medium is changed. The LSPR-IR absorbing material may also be a semiconductor.

[0062] The LSPR-IR absorbing material may contain at least one selected from the group consisting of oxides, phosphides, sulfides, selenides, and tellurides, or it may contain at least one selected from the group consisting of sulfides, selenides, and tellurides. However, for applications where durability such as heat resistance is required, materials containing oxides are generally suitable. Furthermore, the LSPR-IR absorbing material is preferably doped, and the doping is preferably carried out by doping with heterogeneous elements, self-doping, defect doping, etc.

[0063] The LSPR-IR absorbing material may contain a transparent conductive oxide. Examples of the transparent conductive oxide include indium tin oxide, aluminum-doped indium oxide, cerium-doped indium oxide, aluminum-doped zinc oxide, gallium-doped zinc oxide, indium-doped zinc oxide, indium-doped cadmium oxide, fluorine indium-doped cadmium oxide, fluorine-doped cadmium oxide, chlorine-doped cadmium oxide, bromine-doped cadmium oxide, cesium-doped molybdenum oxide, antimony-doped tin oxide, fluorine-doped tin oxide, and titanium oxide.

[0064] The LSPR-IR absorbing material may contain at least one selected from the group consisting of copper sulfide, copper phosphide, copper telluride, copper selenide, ruthenium oxide, rhenium oxide, molybdenum oxide, tungsten oxide, tungsten bronzes, and delafossite-type copper oxides, and may contain copper sulfide and / or tungsten oxide. When using these materials, it is advantageous because there is no need to use highly toxic semiconductors such as InGaAs, InSb, or PbS that are commonly used in infrared sensor devices.

[0065] Examples of copper sulfide include those represented by CuS or Cu 2-x S(0 < x < 1). Similarly, examples of copper phosphide include those represented by Cu 3-x P(0 < x < 1) or CuP, examples of copper telluride include those represented by CuTe or Cu 2-x Te(0 < x < 1), and examples of copper selenide include those represented by CuSe or Cu 2-x Se(0 < x < 1), respectively.

[0066] Examples of ruthenium oxide include those represented by RuO2 or RuO 2-x (0 < x < 1). Similarly, examples of rhenium oxide include those represented by ReO2 or ReO 2-x ((0 < x < 1), examples of molybdenum oxide include those represented by MoO3 or MoO 3-x (0 < x < 1), and examples of tungsten oxide include those represented by WO3 or WO3-x Those represented by (0 < x < 1) can be exemplified respectively.

[0067] Tungsten bronze is a non-stoichiometric compound in which alkali metals and other metal atoms penetrate into tungsten oxide in a non-stoichiometric ratio. Specifically, Cs x WO3 (0 < x < 1), LiWO3, LiCsWO3, LiRbWO3, and LiKWO3 can be exemplified. As delafossite-type copper oxides, CuAlO2, CuGaO2, and CuCrO2 can be exemplified.

[0068] As the LSPR-IR absorption material, a material in which the relaxation time from local surface plasmon excitation can be 1 ns or more is suitable. A material having this property is, for example, at least one selected from the group consisting of copper sulfide, copper selenide, and cesium-doped tungsten oxide. However, not limited to these materials, the relaxation time from local surface plasmon excitation can be measured by the time-resolved transient absorption spectrum method, and appropriate materials can be selected.

[0069] Fig. 3 shows an example of the result of measuring the relaxation time from local surface plasmon excitation by the time-resolved transient absorption spectrum method. Fig. 3 shows absorption spectra after 2.5 nanoseconds (ns), 6 ns, and 12.5 ns after local surface plasmon excitation. In the absorption spectra shown in Fig. 3, a bleach (negative signal) due to local surface plasmon excitation can be confirmed in the near-infrared region. In the example shown in Fig. 3, the negative signal has not disappeared even after 2.5 ns, 6 ns, and further 12.5 ns, so the relaxation time is at least 10 ns or more. A material that can show a relaxation time of active carriers as long as this after the excitation of LSPR regardless of the wavelength and intensity of the pump light is suitable as the LSPR-IR absorption material. The time-resolved transient absorption spectrum method may apply a direct method that directly measures the entire time of the phenomenon. <000029​Figure 3 shows the measurement results for copper sulfide. This measurement was performed using a pump-probe method, employing a chloroform solution of copper sulfide as the sample, a picosecond laser with a wavelength of 1064 nm as the pump light, and a supercontinuum light source as the probe light. Details of the laser and probe light are as follows. • Picosecond laser (EKSPLA PL2210A, repetition rate 1kHz, pulse width 25ps, pulse energy 0.9mJ (wavelength 1064nm)) • Supercontinuum light source (Fianium SC450, repetition frequency 20MHz, pulse width 50-100ps) However, this condition is just one example, and appropriate conditions can be set depending on the material being measured for measuring relaxation time from local surface plasmon excitation.

[0071] The following are examples of desirable combinations of the first and second materials described above. When the first material is copper sulfide, a desirable second material is, for example, cadmium sulfide. When the first material is cesium-doped tungsten oxide, a desirable second material is, for example, zinc oxide, titanium oxide, tin oxide, or gallium oxide.

[0072] The LSPR-IR absorbing material may be nanoparticles. The nanoparticles may be semiconductor nanoparticles, and specifically may contain the compounds exemplified above. The resistivity portion preferably further contains a binder along with the nanoparticles. The binder can be interposed between the nanoparticles to impart desirable properties such as flexibility to the film.

[0073] The binder may contain at least one functional group that can bind to nanoparticles, for example, selected from fluorine (F), chlorine (Cl), bromine (Br), iodine (I), cyanide (CN), thiocyanate (SCN), isothiocyanate (NCS), hydroxide (OH), mercapto (SH), carbonyl (CO), amino (NR3), nitrosyl (NO), nitrite (NO2), phosphan (PR3), carbene (R2C), and pyridine (NC5H5). The functional group may be an anion, i.e., for example, F - These may be anionic functional groups that bind to nanoparticles, for example. Here, R is independently any organic group or hydrogen atom. As can be seen from the above examples, functional groups that can bind to nanoparticles may also be other functional groups that can function as ligands to metal atoms or anions.

[0074] The binder may be an inorganic compound or an organic compound. The binder may be an ion containing or consisting of the functional groups exemplified above, or a salt composed of such an ion and its counterion. The binder may also be a compound having multiple of the above-mentioned functional groups, such as hydrazine (H2NNH2), ethylenediamine (H2NCH2CH2NH2), 1,2-ethanedithiol (HSCH2CH2SH, EDT), mercaptopropionic acid (HSCH2CH2COOH), acetylacetonate (H3CCOCHCOCH3), and aminobenzonitrile (NH2C6H4CN).

[0075] The molecular weight of the binder is, for example, 280 or less, more preferably 250 or less, more preferably 200 or less, more preferably 100 or less, even more preferably 80 or less, and in some cases less than 65. The lower limit of the molecular weight is not particularly limited, but for example, 20 or more, and more preferably 30 or more. Using a binder with a molecular weight that is not too large is suitable for controlling the spacing between nanoparticles to be narrow, and for controlling the electrical resistance, infrared absorption characteristics, and other properties of the variable resistance section to an appropriate range.

[0076] The amount of binder can be adjusted as appropriate depending on the type, but it can be expressed as the ratio of the mass of the binder to the total amount of nanoparticles and binder, for example, 1% or more, more preferably 2% or more, especially 3% or more, and in some cases 5% or more, and preferably 8% or more. There is no particular upper limit to this content, but it should be 30% or less, and more preferably 20% or less.

[0077] The binder described above is suitable for coordination or adhesion to nanoparticles. The binder may be made of a material other than such adhesive compounds. Examples of such compounds include various resins, specifically polyvinyl alcohol, polyvinyl acetal, polyvinylpyrrolidone, carboxymethylcellulose, acrylic resin, polyvinyl acetate, polyethylene terephthalate, polystyrene, polyethylene, etc. In addition, depending on the requirements for film formation and application, organic solvents, conductive polymers, conductive particles, pH adjusters, colorants, thickeners, surfactants, etc., may also be used.

[0078] When the LSPR-IR absorbing material is nanoparticles, the variable resistance section 13 or carrier supply section 23 can be fabricated by coating, spraying, dipping, etc. (hereinafter referred to as coating, etc.) using the binder, etc. In this case, the binder may be coordinated to the nanoparticles by ligand exchange. When the variable resistance section 13 or carrier supply section 23 is fabricated as a coated film in this way, it can be fabricated easily and inexpensively by coating, etc., compared to infrared sensing devices using bulk semiconductors, so that infrared sensing devices can be manufactured inexpensively and the size of the infrared sensing device can be easily increased. Furthermore, unlike infrared sensing devices using bulk semiconductors, a flexible infrared sensing device can be fabricated by coating, etc., on a flexible material.

[0079] Infrared sensing devices can also be used in optical sensors, optical switching devices, and memory devices. These infrared sensing devices can be used in infrared communication. Furthermore, infrared sensing devices can be used in thermal sensors, motion sensors, infrared cameras, thermal imaging devices, and more.

[0080] The present invention will be further described below with reference to examples, but the following description is not intended to limit the present invention to any particular example.

[0081] (Example 1) 1.891 g of copper acetate, 1.13 g of 1,3-dibutyl-2-thiourea, and 10 ml of oleylamine were placed in a three-pronged flask, and nitrogen purging was performed while stirring. Next, the liquid temperature was raised to 80°C using a mantle heater and maintained for 1 hour. After the liquid temperature had dropped to 40°C, 40 ml of chloroform was gradually added to the three-pronged flask to dissolve the solids.

[0082] The contents of the three-pronged flask were transferred to a centrifuge tube, and after confirming that the solids were completely dissolved in the centrifuge tube, 40 ml of ethanol was added. Further centrifugation was performed at 2000 rpm (revolutions / minute) for 10 minutes, and the supernatant was immediately discarded. Subsequently, the precipitate was dissolved in 5 ml of octane, and then 30 ml of ethanol was added again. Centrifugation was performed again at a rotation speed of 2000 rpm for 5 minutes, and the precipitate was collected. The mass of the precipitate was measured, and based on this, octane was added to a concentration of 200 mg / ml to disperse copper sulfide nanoparticles and obtain the first ink.

[0083] The first ink contains copper sulfide nanoparticles along with oleylamine, a compound that can coordinate to the copper sulfide nanoparticles. Thermogravimetric analysis (TGA) of the precipitate revealed that the ratio of oleylamine mass to the total mass of copper sulfide nanoparticles and oleylamine was 10%. This ratio remained the same in subsequent examples.

[0084] A coating film was obtained by applying 50 μl of the first ink to a glass plate on which comb-shaped electrodes had been pre-formed using a spin coater. The concentration of the first ink was adjusted to 50 mg / ml during coating. The glass plate on which the comb-shaped electrodes were formed was a commercially available product (Drop Sens, G-IDEU5) with an electrode width and electrode spacing of 5 μm or 10 μm, a number of pairs of electrodes of 250 (for an electrode width of 5 μm) or 125 (for an electrode width of 10 μm), and a length of 6760 μm.

[0085] A 200 μl solution containing aminobenzonitrile (second ink) was applied to the coated film using a spin coater to obtain a thin film that functions as an infrared response sensor. The solvent in this solution was octane, and the concentration of aminobenzonitrile was 0.3% by mass. Upon contact with the second ink, at least a portion of the compound coordinating to the copper sulfide nanoparticles was replaced from oleylamine (first compound) to aminobenzonitrile (second compound, binder).

[0086] An additional coating film was formed on this coating film by the same film formation method as described above using the first ink, and then compound substitution was carried out using the second ink in the same manner as described above. In this way, a thick-film variable-resistivity film was obtained.

[0087] A comb-shaped electrode on a glass plate with a variable resistance film was connected to a Keithley 2450 source meter (serving as the measurement unit) and a 1V DC power supply. Under atmospheric pressure and room temperature, the variable resistance film was irradiated with light from an Eagle Engineering xenon lamp light source, and the change in current value was measured using the source meter. The light from the light source was passed through a bandpass filter, and the irradiated light was infrared light with a wavelength of 800 nm or longer. The light irradiation was switched ON / OFF every 20 seconds using a shutter. The ON / OFF pattern is shown in Figure 4.

[0088] The measured current value changes are shown in Figure 5. Figure 5 also shows the current value changes when the irradiation light is ultraviolet light with a wavelength of 450 nm or less.

[0089] (Examples 2-6) A resistive film was formed in the same manner as in Example 1, except that the second compound in the second ink was changed from aminobenzonitrile to one of the compounds shown in Table 1. The change in current value was measured while irradiating the resistive film with infrared (IR) or ultraviolet (UV) light. The results are shown in Figures 6 to 10.

[0090] (Example 7) (1) A coating film was obtained by coating a glass plate on which the comb-shaped electrode used in Example 1 was formed with 50 μl of cadmium sulfide nanoparticle ink using a spin coater. The concentration of the cadmium sulfide nanoparticle ink was adjusted to 50 mg / ml with octane before coating. (2) A 200 μl solution containing 1,2-ethanedithiol (EDT, binder) was applied to the coated film using a spin coater to obtain a cadmium sulfide nanoparticle thin film. The solvent of this solution was acetonitrile, and the concentration of EDT was 0.03% by mass. (3) Then, by repeating operations (1) and (2), a cadmium sulfide nanoparticle film (variable resistance film) with a thickness of 110 nm was formed as a variable resistance film. (4) A coated film was obtained by coating a cadmium sulfide nanoparticle film with 50 μl of copper sulfide nanoparticle ink using a spin coater. The concentration of the copper sulfide nanoparticle ink was adjusted to 100 mg / ml before coating. (5) A 200 μl solution containing 1,2-ethanedithiol (EDT) was applied to the coated film obtained in (4) using a spin coater to obtain a copper sulfide nanoparticle thin film. The solvent of this solution was acetonitrile, and the concentration of EDT was 0.03% by mass. (6) Then, by repeating steps (4) and (5), a copper sulfide nanoparticle film with a thickness of 30 nm was formed on the resistivity film as a carrier supply layer (carrier supply film). Cadmium sulfide nanoparticles are generally n-type semiconductor materials, and copper sulfide nanoparticles are generally p-type semiconductor materials.

[0091] The results of Examples 1 to 7 are summarized in Table 1. Table 1 also shows the resistance values ​​of the variable resistance section in the non-light-irradiated state.

[0092] [Table 1]

[0093] It should be noted that in some of the above embodiments, the measured resistance change was slight (for example, Figure 11). However, the small amount of change itself can be overcome by amplification using known means as needed, and does not hinder its use as a sensing device.

[0094] The spectral transmission spectrum of the resistance-changing film in Example 4 was measured. The results are shown in Figure 12. From Figure 12, it can be confirmed that there is an absorption region in the near-infrared region and that a transmittance of 80% or more is achieved in the visible region with wavelengths of 400 to 800 nm.

Claims

1. An infrared sensing device, The infrared sensing device comprises a variable resistance unit whose electrical resistance changes upon irradiation with infrared light, and a detection unit that detects the change in electrical resistance of the variable resistance unit. The aforementioned variable resistance section is The material includes a material capable of absorbing infrared radiation by local surface plasmon resonance, and the electrical resistance increases or decreases when the carrier supply unit, which is in contact with the variable resistance portion, receives carriers, which are electrons and / or holes, generated by irradiation of the carrier supply unit with infrared radiation. Infrared sensing device. However, the aforementioned material is Multiple metal chalcogenide nanocrystals coated with multiple organic ligands and multiple inorganic ligands, The metal is selected from Hg, Pb, Sn, Cd, Bi, Sb, or mixtures thereof; the chalcogen is selected from S, Se, Te, or mixtures thereof; where the plurality of inorganic ligands is S 2- HS - Se 2- Te 2- OH - BF 4 - PF 6 - Cl - Br - I - As 2 Se 3 Sb 2 S 3 Sb 2 Te 3 Sb 2 Se 3 As 2 S 3 and includes at least one inorganic ligand selected from these or a mixture thereof Excluding materials containing multiple metal chalcogenide nanocrystals.

2. The detection unit includes a group of electrodes that apply a voltage to the variable resistance unit. The electrode group includes a first electrode electrically connected to the positive electrode of the power supply and a second electrode electrically connected to the negative electrode of the power supply. The device according to claim 1, wherein both the first electrode and the second electrode are in direct contact with the variable resistance portion.

3. The detection unit includes a group of electrodes that apply a voltage to the variable resistance unit. When a voltage is applied from the electrode to the variable resistance portion, and infrared radiation is started onto the variable resistance portion, and then the irradiation is stopped, The device according to claim 1, wherein the electrical resistance decreases in response to the start of irradiation and increases in response to the cessation of irradiation.

4. The carrier supply unit is provided, The device according to claim 3, wherein the carrier supply unit and the variable resistance unit constitute a laminated structure.

5. The device according to claim 4, wherein the carrier supply unit and the variable resistance unit are made of different semiconductor materials.

6. The device according to any one of claims 3 to 5, wherein the variable resistance portion includes nanoparticles of cesium-doped tungsten oxide as the material.

7. The device according to any one of claims 1 to 6, wherein the material capable of absorbing infrared radiation by local surface plasmon resonance is a material from which the relaxation time of active carriers from local surface plasmon excitation can be measured to be 1 ns or more.

8. The device according to any one of claims 1 to 7, wherein the variable resistance portion does not contain a conductive carbon material.

9. The device according to any one of claims 1 to 8, further comprising a heat dissipation section for releasing heat from the variable resistance section to the outside.

10. The device according to any one of claims 1 to 9, further comprising a cover portion that transmits at least a portion of the infrared light irradiated onto the infrared sensing device.

11. The device according to claim 10, wherein the cover portion includes a substrate and at least one selected from the group consisting of an optical filter portion and a sample placement portion, which is supported by the substrate.

12. An infrared sensing device according to any one of claims 1 to 11, and a light source that irradiates the infrared sensing device with light including infrared light, An infrared transmittance measuring device in which infrared rays irradiated from the light source onto a sample to be measured and transmitted through the sample to be measured are detected by the infrared sensing device.

Images