Gas detector and array of gas detectors

Abstract

A gas detector (100) includes an insulating layer (3), a first electrode (2a) disposed on the insulating layer, a two-dimensional material layer (1) electrically connected to the first electrode, and a second electrode (2b) electrically connected to the first electrode via the two-dimensional material layer. The two-dimensional material layer has an exposed surface exposed to the outside. The two-dimensional material layer is configured to perform photoelectric conversion when electromagnetic waves in a wavelength region absorbed by a gas of a detection target are incident.

Description

Technical Field

[0001] This disclosure relates to gas detectors and gas detector arrays, and more particularly to gas detectors and gas detector arrays having a two-dimensional material layer. Background Technology

[0002] Japanese Patent Application Publication No. 2019-102567 (Patent Document 1) discloses a field-effect transistor (FET) having a gate and a gate insulating film made of graphene. In the FET described in Patent Document 1, the FET functions as a gas sensor that detects gas based on changes in drain current. The changes in drain current are generated based on changes in threshold voltage, which are caused by changes in the work function of the gas to be detected, such as ammonia, when it is adsorbed onto the graphene.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2019-102567 Summary of the Invention

[0006] Various gases are adsorbed onto the graphene. Therefore, in the above-described FET, the drain current changes even when gases other than the target gas are adsorbed onto the graphene. That is, in the above-described FET, it is difficult to detect or identify specific gas types in a gas mixture.

[0007] This disclosure proposes techniques for detecting or identifying specific types of gases.

[0008] A gas detector according to one embodiment of this disclosure includes: an insulating layer; at least one first electrode disposed on the insulating layer; at least one two-dimensional material layer electrically connected to the at least one first electrode; and at least one second electrode electrically connected to at least one first electrode via the at least one two-dimensional material layer. The at least one two-dimensional material layer has an exposed surface to the outside. The at least one two-dimensional material layer is configured to perform photoelectric conversion when incident with electromagnetic waves in the wavelength range absorbed by the gas being detected.

[0009] According to this disclosure, it is possible to detect or identify specific types of gases. Attached Figure Description

[0010] Figure 1 This is a top view schematic diagram of the gas detector according to Embodiment 1.

[0011] Figure 2 From Figure 1 The cross-sectional view observed by arrow II-II in the diagram.

[0012] Figure 3 This is a flowchart illustrating the manufacturing method of the gas detector according to Embodiment 1.

[0013] Figure 4 This diagram illustrates the working principle of gas detection using electromagnetic wave detection in the gas detector of Embodiment 1.

[0014] Figure 5 This is a diagram illustrating the working principle of gas detection using adsorption in the gas detector of Embodiment 1.

[0015] Figure 6 This is a cross-sectional schematic diagram of the gas detector according to Embodiment 2.

[0016] Figure 7 This is a cross-sectional schematic diagram of the gas detector according to Embodiment 3.

[0017] Figure 8 This is a cross-sectional schematic diagram of the gas detector according to Embodiment 4.

[0018] Figure 9 This is a cross-sectional schematic diagram of the gas detector according to Embodiment 5.

[0019] Figure 10 This is a cross-sectional schematic diagram of the gas detector according to Embodiment 6.

[0020] Figure 11 From Figure 10 The cross-sectional view observed by arrow XI-XI in the diagram.

[0021] Figure 12 This is a top view schematic diagram showing a first modification of the gas detector according to Embodiment 6.

[0022] Figure 13 This is a top view schematic diagram showing a second variation of the gas detector according to Embodiment 6.

[0023] Figure 14 This is a top surface view of the gas detector array in Embodiment 7.

[0024] Figure 15 This is a schematic diagram illustrating an example of a readout circuit for reading electrical signals obtained from a gas detector array according to Embodiment 7.

[0025] Figure 16 This is a top surface view showing a first modified example of the gas detector array of Embodiment 7. Detailed Implementation

[0026] Hereinafter, embodiments will be described with reference to the accompanying drawings. Furthermore, the same or equivalent parts will be referred to by the same reference numerals, and descriptions will not be repeated.

[0027] In the embodiments described below, the figures are schematic drawings, conceptually illustrating functions or structures. Furthermore, this disclosure is not limited to the embodiments described below. Except where specifically stated, the basic structure of the gas detector is common in all embodiments. Additionally, portions marked with the same symbol are considered identical or equivalent as described above. This is consistent throughout the specification.

[0028] The gas detector disclosed herein is a gas detector used to detect a gas of a target. The target gas of the gas detector of this disclosure includes any gas or any particles suspended in any gas. Examples of arbitrary particles include any liquid particles or any solid particles suspended in any gas in the form of aerosols.

[0029] The gas detector disclosed herein detects changes in the electrical properties of a two-dimensional material layer, which occur at least in the two-dimensional material layer due to photoelectric conversion when an electromagnetic wave in the wavelength range absorbed by the gas of the target being detected is incident upon it, and changes in the electrical properties of the two-dimensional material layer due to adsorption of the gas of the target being detected onto the two-dimensional material layer, as gas detection signals, and then measures each change. In this specification, gas detection based on changes in the former electrical properties is further described as gas detection using an electromagnetic wave detection method, and gas detection based on changes in the latter electrical properties is further described as gas detection using an adsorption method.

[0030] The embodiments described below illustrate the structure of a gas detector that detects visible or infrared light as electromagnetic waves in the wavelength range absorbed by the gas being detected. However, the electromagnetic waves detected by the gas detector of this disclosure are not limited to visible and infrared light. In addition to visible and infrared light, the embodiments described below are also effective as detectors for detecting, for example, X-rays, ultraviolet light, near-infrared light, terahertz (THz) waves, microwaves, and other radio waves. Furthermore, in the embodiments described below, these lights and radio waves are collectively referred to as electromagnetic waves.

[0031] The following explanation uses graphene as an example of a material for two-dimensional material layers, but the materials constituting two-dimensional material layers are not limited to graphene. For example, transition metal dichalcogenide alloys (TMD), black phosphorus, silicene (a two-dimensional honeycomb structure composed of silicon atoms), and germanene (a two-dimensional honeycomb structure composed of germanium atoms) can be used as materials for two-dimensional material layers. Examples of transition metal dichalcogenide alloys include MoS2, WS2, and WSe2.

[0032] These materials have a structure similar to graphene, meaning they are capable of arranging atoms in a single layer within a two-dimensional plane. Therefore, applying these materials to two-dimensional material layers can produce the same effect as applying graphene to two-dimensional material layers.

[0033] The two-dimensional material layer can also be composed of a single layer of two-dimensional materials (e.g., single-layer graphene). Alternatively, it can be composed of multiple layers of two-dimensional materials (e.g., multilayer graphene). In the latter case, the photoelectric conversion efficiency increases, and the sensitivity of the gas detector becomes higher. Furthermore, a band gap is formed in the latter two-dimensional material layer. As a result, the latter two-dimensional material layer can be configured to perform photoelectric conversion only when electromagnetic waves in the wavelength range absorbed by the gas of the target gas are incident on the two-dimensional material layer 1. Additionally, as the number of secondary raw material layers included in the two-dimensional material layer increases, the carrier mobility in the channel region decreases, but the two-dimensional material layer is less susceptible to carrier scattering from substrate structures such as substrates, resulting in a lower noise level. Therefore, in a gas detector equipped with a two-dimensional material layer containing multiple layers of two-dimensional materials, the detection sensitivity of electromagnetic waves can be improved. Furthermore, the orientation of the lattice vectors of the hexagonal lattice between any two graphene layers in the multiple graphene layers stacked in the two-dimensional material layer can be either consistent or inconsistent.

[0034] When a two-dimensional material layer is composed of multiple layers of graphene, it can be an AB stack as seen in graphite with its natural stacking orientation, or it can be a random stack. Random stacks are also called random layers or disordered graphene. The fabrication method for the disordered structure can be appropriately determined. For example, a disordered structure can be formed by repeatedly transferring a single layer of graphene fabricated using CVD and stacking multiple layers of graphene. Alternatively, a disordered structure can be formed by using ethanol or methane as a carbon source on graphene and then growing the graphene using CVD.

[0035] Furthermore, in the following discussion of two-dimensional material layers, terms such as p-type or n-type are sometimes used. In the following embodiments, a two-dimensional material layer with more holes than intrinsic states is referred to as p-type, and a two-dimensional material layer with more electrons than intrinsic states is referred to as n-type. The two-dimensional material layer can also be an undoped intrinsic material, or it can have either p-type or n-type conductivity.

[0036] Furthermore, regarding the materials of components in contact with two-dimensional material layers, the terms n-type or p-type are sometimes used. For example, n-type materials refer to materials that are electron-donating, while p-type materials refer to materials that are electron-withdrawing. Additionally, sometimes there is a charge shift within the molecule itself; the type dominated by electrons is called n-type, and the type dominated by holes is called p-type. These materials can be either organic or inorganic, or mixtures thereof.

[0037] Furthermore, when the two-dimensional material layer is in contact with the electrode, charge carriers are doped from the electrode into the two-dimensional material layer. For example, when gold (Au) is used as the electrode material, holes are doped into the two-dimensional material layer near the electrode based on the difference in work function between the two-dimensional material layer and Au. When the gas detector is driven in an electron conduction state in this condition, the mobility of electrons flowing through the channel region of the two-dimensional material layer decreases due to the influence of holes doped from the electrode into the two-dimensional material layer, and the contact resistance between the two-dimensional material layer and the electrode increases. Due to this increase in contact resistance, the mobility of electrons (charge carriers) in the gas detector decreases due to the electric field effect, potentially leading to a deterioration in the performance of the gas detector. In particular, when the two-dimensional material layer is composed of a single layer of graphene, the amount of charge carriers injected from the electrode is greater compared to when the two-dimensional material layer is composed of multiple layers of graphene. Therefore, when a single layer of graphene is used as the two-dimensional material layer, the aforementioned decrease in the mobility of electrons in the gas detector is particularly significant. Therefore, when the entire two-dimensional material layer is composed of a single layer of graphene, there is a possibility of a deterioration in the performance of the gas detector. Therefore, at least the contact region with the electrode in the secondary raw material layer can also be composed of multilayer graphene. In multilayer graphene, the carrier doping from the electrode is less compared to single-layer graphene. Therefore, the increase in contact resistance between the two-dimensional material layer and the electrode can be suppressed. As a result, the decrease in the aforementioned electron mobility in the gas detector can be suppressed, and the performance of the gas detector can be improved.

[0038] Furthermore, the two-dimensional material layer can also contain graphene nanoribbons (hereinafter also referred to as graphene nanoribbons). The two-dimensional material layer can be, for example, any of the following: graphene nanoribbon monomers, composites formed by stacking multiple graphene nanoribbons, or structures in which graphene nanoribbons are periodically arranged in a plane (e.g., graphene metamaterials). Plasmon resonance can occur in two-dimensional material layers configured as structures in which graphene nanoribbons are periodically arranged in a plane. As a result, the sensitivity of gas detectors can be improved.

[0039] Furthermore, in this specification, phenomena referred to as plasmonic resonance phenomena, such as surface plasmon resonance phenomena resulting from the interaction between a metal surface and light; phenomena referred to as suspected surface plasmon resonance in the sense of resonances applied to a metal surface outside the visible / near-infrared light domain; and phenomena referred to as metamaterials or plasma metamaterials in the sense of manipulating specific wavelengths through sub-wavelength structures, are not specifically distinguished by name, but are treated equivalently in terms of the effects achieved by the phenomena. In this specification, these resonances are referred to as surface plasmon resonance, plasmon resonance, or simply resonance.

[0040] In this specification, the term "insulating layer" refers to an insulating film layer having a thickness that does not generate tunneling current.

[0041] Implementation method 1.

[0042] Figure 1 This is a top view of the gas detector 100 according to Embodiment 1. Figure 2 yes Figure 1 A cross-sectional view at line segment II-II. Figure 2 The typical electrical connections of the gas detector 100 are also shown in the diagram.

[0043] Figure 1 as well as Figure 2 The gas detector 100 shown includes multiple detection units. These multiple detection units include a first detection unit 100A and a second detection unit 100B. The first detection unit 100A and the second detection unit 100B have substantially identical structures.

[0044] The first detection unit 100A and the second detection unit 100B each mainly include a two-dimensional material layer 1, a first electrode 2a, a second electrode 2b, a third electrode 2c, an insulating layer 3, and a semiconductor layer 4. For example, the first detection unit 100A and the second detection unit 100B share the third electrode 2c, the insulating layer 3, and the semiconductor layer 4. The second detection unit 100B differs from the first detection unit 100A in that it also includes a first coated film 5. From a different perspective, the gas detector 100 includes multiple two-dimensional material layers 1, multiple first electrodes 2a, multiple second electrodes 2b, an insulating layer 3, a semiconductor layer 4, and a first coated film 5.

[0045] Semiconductor layer 4 has a first surface 41 and a second surface 42 located on the side opposite to the first surface 41. A two-dimensional material layer 1, a first electrode 2a, a second electrode 2b, and an insulating layer 3 are disposed on the first surface 41 of semiconductor layer 4. A third electrode 2c is disposed on the second surface 42 of semiconductor layer 4. Hereinafter, for each of the two-dimensional material layer 1, the first electrode 2a, the second electrode 2b, and the insulating layer 3, the portion located on the side opposite to semiconductor layer 4 will be referred to as its upper portion, and the portion located on the side opposite to semiconductor layer 4 will be referred to as its lower portion.

[0046] Semiconductor layer 4 is sensitive to electromagnetic waves in the wavelength range absorbed by the gas of the object being detected. In other words, semiconductor layer 4 is configured to perform photoelectric conversion when incident electromagnetic waves in the wavelength range absorbed by the gas of the object being detected are received.

[0047] Semiconductor layer 4 is made of semiconductor materials such as silicon (Si). Specifically, a silicon substrate doped with impurities is used as semiconductor layer 4.

[0048] Here, semiconductor layer 4 can also be a multilayer structure, and pn junction photodiodes, pin photodiodes, Schottky photodiodes, or avalanche photodiodes can be used. Alternatively, phototransistors can also be used as semiconductor layer 4.

[0049] As described above, a silicon substrate has been used as an example of the semiconductor material constituting semiconductor layer 4, but other materials can also be used. For example, as the material constituting semiconductor layer 4, compound semiconductors such as germanium (Ge), III-V or II-V semiconductors, mercury cadmium tellurium (HgCdTe), indium antimony (InSb), lead selenium (PbSe), lead sulfide (PbS), cadmium sulfide (CdS), gallium nitride (GaN), silicon carbide (SiC), gallium phosphide (GaP), indium gallium arsenide (InGaAs), indium arsenide (InAs), or substrates containing quantum wells or quantum dots, type II superlattices, etc., or materials composed of these materials in single or combined forms, can also be used.

[0050] Preferably, the semiconductor layer 4 is doped with impurities in a manner that makes the resistivity of the semiconductor layer 4 below 100 Ω·cm. By doping the semiconductor layer 4 with a high concentration, the movement speed (readout speed) of charge carriers in the semiconductor layer 4 increases. As a result, the response speed of the gas detector 100 is improved.

[0051] An insulating layer 3 is disposed on the first surface 41 of the semiconductor layer 4. The lower surface of the insulating layer 3 is in contact with the first surface 41 of the semiconductor layer 4. The upper surface of the insulating layer 3 is in contact, for example, with the lower surfaces of the third portion 1c of the two-dimensional material layer 1 (described later), the first electrode 2a, and the second electrode 2b. Alternatively, a recess may be formed on the upper surface of the insulating layer 3, partially recessed relative to the lower surfaces of the first electrode 2a and the second electrode 2b. This recess may also be formed as an opening that exposes the first surface 41 of the semiconductor layer 4. In this case, the third portion 1c of the two-dimensional material layer 1 (described later) may also be disposed on the aforementioned recess of the insulating layer 3.

[0052] The material constituting the insulating layer 3 can be any material with electrical insulating properties, such as silicon oxide (SiO2). The material constituting the insulating layer 3 may include at least one selected from the group consisting of SiO2, tetraethyl orthosilicate (Si(OC2H5)4), silicon nitride (Si3N4), hafnium oxide (HfO2), aluminum oxide (Al2O3), nickel oxide (NiO), boron nitride (BN), and siloxane-based polymer materials. For example, the atomic arrangement of boron nitride is similar to that of graphene, so even if boron nitride is in contact with the two-dimensional material layer 1 composed of graphene, it will not adversely affect the charge mobility. Therefore, from the viewpoint of suppressing the properties of the two-dimensional material layer 1, such as the resistance of the insulating layer 3 to electron mobility, the material constituting the insulating layer 3 is preferably boron nitride.

[0053] A plurality of first electrodes 2a and a plurality of second electrodes 2b are arranged spaced apart from each other on the upper surface of the insulating layer 3. The plurality of first electrodes 2a and the plurality of second electrodes 2b have a first group of first electrodes 2a and second electrodes 2b included in the first detection unit 100A, and a second group of first electrodes 2a and second electrodes 2b included in the second detection unit 100B. The first electrodes 2a and second electrodes 2b of the first group are arranged spaced apart from each other. The first electrodes 2a and second electrodes 2b of the second group are arranged spaced apart from the first electrodes 2a and second electrodes 2b of the first group.

[0054] The materials constituting the first electrode 2a and the second electrode 2b can be any conductive material, for example, including at least one selected from the group consisting of gold (Au), silver (Ag), copper (Cu), aluminum (Al), nickel (Ni), chromium (Cr), and palladium (Pd). Alternatively, a bonding layer (not shown) may be formed between at least one of the first electrode 2a and the second electrode 2b and the insulating layer 3 to improve the adhesion between them. The material constituting the bonding layer is not particularly limited; for example, it may include at least one of chromium (Cr) and titanium (Ti).

[0055] like Figure 2 As shown, the first electrode 2a and the second electrode 2b are formed, for example, on the lower part of the two-dimensional material layer 1. Alternatively, the first electrode 2a and the second electrode 2b may also be formed on the upper part of the two-dimensional material layer 1.

[0056] like Figure 2 As shown, a power supply circuit for applying a bias voltage Vsd1 to the two-dimensional material layer 1 of the first detection unit 100A is electrically connected between the first electrode 2a and the second electrode 2b of the first group. A power supply circuit for applying a bias voltage Vsd2 to the two-dimensional material layer 1 of the second detection unit 100B is electrically connected between the first electrode 2a and the second electrode 2b of the second group. Each power supply circuit includes a voltage source and a galvanometer (not shown). Each voltage source applies the aforementioned bias voltage Vsd1 between the first electrode 2a and the second electrode 2b of the first group, or applies a bias voltage Vsd2 between the first electrode 2a and the second electrode 2b of the second group. Each galvanometer detects the current Isd1 flowing when the aforementioned bias voltage Vsd1 is applied between the first electrode 2a and the second electrode 2b of the first group, or the current Isd2 flowing when the bias voltage Vsd2 is applied between the first electrode 2a and the second electrode 2b of the second group.

[0057] The third electrode 2c is disposed, for example, on the entire surface of the second surface 42 of the semiconductor layer 4. Furthermore, the third electrode 2c may be in contact with at least a portion of the semiconductor layer 4. For example, the third electrode 2c may also be disposed in contact with a portion of the side surface of the semiconductor layer 4 extending in a direction intersecting the first surface 41. Such a gas detector 100 is capable of detecting electromagnetic waves incident from the second surface 42 side. Furthermore, as... Figure 2 As shown, in the case where electromagnetic waves in the wavelength range absorbed by the gas being detected are incident only from the first surface 41 side, it is preferable that the third electrode portion 2c is disposed on the entire surface of the second surface 42 of the semiconductor layer 4 in the gas detector 100. Figure 2 In the gas detector 100 shown, electromagnetic waves incident from the first surface 41 and transmitted through the semiconductor layer 4 are reflected by the second electrode 2b and reach the two-dimensional material layer 1 again, thus improving the absorption rate of electromagnetic waves in the two-dimensional material layer 1.

[0058] like Figure 2 As shown, the third electrode 2c is electrically connected to a power supply circuit that applies voltage Vg to the semiconductor layer 4.

[0059] Multiple two-dimensional material layers 1 include a first two-dimensional material layer 11 and a second two-dimensional material layer 12. The first two-dimensional material layer 11 electrically connects a first electrode 2a and a second electrode 2b of a first group. The second two-dimensional material layer 12 electrically connects a first electrode 2a and a second electrode 2b of a second group. The second two-dimensional material layer 12 is disposed at a distance from the first two-dimensional material layer 11. The first two-dimensional material layer 11 and the second two-dimensional material layer 12 have identical structures.

[0060] Each two-dimensional material layer 1 is sensitive to electromagnetic waves in the wavelength range absorbed by the gas of the object being detected. In other words, each two-dimensional material layer 1 is configured to perform photoelectric conversion when electromagnetic waves in the wavelength range absorbed by the gas of the object being detected are incident on it. Preferably, each two-dimensional material layer 1 is configured to perform photoelectric conversion only when electromagnetic waves in the wavelength range absorbed by the gas of the object being detected are incident on the two-dimensional material layer 1.

[0061] Each two-dimensional material layer 1 has an upper surface extending along its two-dimensional plane. The upper surface of the first two-dimensional material layer 11 has an adsorption area that is exposed to the outside and can adsorb the gas of the target object. The upper surface of the second two-dimensional material layer 12 is covered by the first coating 5 described later. Therefore, the upper surface of the second two-dimensional material layer 12 does not have an adsorption area for adsorbing the gas of the target object.

[0062] Each two-dimensional material layer 1 has a first portion 1a, a second portion 1b, and a third portion 1c. The first portion 1a is connected to the first electrode 2a. The second portion 1b is connected to the second electrode 2b. The third portion 1c electrically connects the first portion 1a and the second portion 1b. The lower surfaces of each of the first portion 1a, the second portion 1b, and the third portion 1c are in contact with, for example, the upper surface of the insulating layer 3. As described above, if a recess is formed on the upper surface of the insulating layer 3, the third portion 1c may also be mounted on that recess. The lower surface of the third portion 1c may also not be in contact with the upper surface of the insulating layer 3. For example, unevenness caused by the first electrode 2a and the second electrode 2b is formed on the upper surface of the two-dimensional material layer 1.

[0063] exist Figure 2 In the first two-dimensional material layer 11 shown, its entire upper surface is exposed to the outside, allowing it to adsorb the gas of the target being detected. The entire upper surface of the second two-dimensional material layer 12 is covered by the first coating film 5. Furthermore, at least the upper surface of the third portion 1c of the first two-dimensional material layer 11 is exposed to the outside, allowing it to adsorb the gas of the target being detected.

[0064] The thicknesses of the first part 1a, the second part 1b, and the third part 1c of each two-dimensional material layer 1 are, for example, equal. The thicknesses of the first part 1a, the second part 1b, and the third part 1c of each two-dimensional material layer 1 may also be different.

[0065] The first coating 5 covers the second two-dimensional material layer 12. The first coating 5 is configured to impede the transmission of the gas to be detected. Specifically, the first coating 5 is configured to prevent the gas to be detected from being adsorbed onto the second two-dimensional material layer 12. The first coating 5 is configured, for example, to not impede the transmission of electromagnetic waves in the wavelength range absorbed by the gas to be detected.

[0066] The first coating 5 covers not only the second two-dimensional material layer 12, but also the first electrode 2a and the second electrode 2b of the second group of the second detection unit 100B. The first coating 5 does not cover the first two-dimensional material layer 11.

[0067] The material constituting the first coating film 5 may include, for example, at least one selected from the group consisting of silicon oxide (SiO2), tetraethyl orthosilicate (Si(OC2H5)4), silicon nitride (Si3N4), hafnium oxide (HfO2), aluminum oxide (Al2O3), nickel oxide (NiO), boron nitride (BN), siloxane-based polymer materials, polyethylene terephthalate (PET), polyvinylidene chloride resin (PVDC), and biaxially oriented polypropylene (OPP). The material constituting the first coating film 5 may also be the same as the material constituting the insulating layer 3. Fine pores may also be formed within the first coating film 5. In this case, the first coating film 5 is preferably a dense and thick film. The density of the first coating film 5 means that its average pore size is smaller than the outer diameter of the molecules or particles of the gas being detected. The first coating film 5 may also be configured as a laminate of multiple layers composed of mutually different materials. According to such a first coating film 5, gas barrier properties can be improved compared to a first coating film 5 made of a single material with an overall thickness equal to that of the first coating film 5. From another perspective, according to the above-described first coating film 5, compared to a first coating film 5 made of a single material with equal gas barrier properties, it can be made into a thin film.

[0068] <Manufacturing Method of Gas Detector 100>

[0069] Figure 3 This is a flowchart illustrating the manufacturing method of the gas detector 100 according to Embodiment 1. (Refer to...) Figure 3 ,illustrate Figure 1 as well as Figure 2 The method for manufacturing the gas detector 100 shown.

[0070] First, a process (S1) for preparing semiconductor layer 4 is performed. In this process (S1), for example, a flat substrate made of Si or the like is prepared as semiconductor layer 4.

[0071] Second, the process of forming the third electrode 2c is performed (S2). In this process (S2), on the second surface 42 of the semiconductor layer 4 (refer to...) Figure 2 The third electrode 2c is then formed. Specifically, a protective film is first formed covering the first surface 41 of the semiconductor layer 4. The protective film is, for example, a photoresist. Next, the third electrode 2c is formed on the second surface 42 of the semiconductor layer 4. The material constituting the third electrode 2c includes, for example, at least one selected from the group consisting of gold (Au), silver (Ag), copper (Cu), aluminum (Al), nickel (Ni), and chromium (Cr).

[0072] Furthermore, in this step (S2), a bonding layer for improving the adhesion between the semiconductor layer 4 and the third electrode 2c may be formed on the second surface 42 of the semiconductor layer 4 before the formation of the third electrode 2c. The material constituting the bonding layer may include at least one of copper (Cr) and titanium (Ti). Alternatively, this step (S2) may be performed after the subsequent steps (S3 to S7), provided that the first surface 41 of the semiconductor layer 4 is protected.

[0073] Third, the process of forming the insulating layer 3 is performed (S3). In this process (S3), the insulating layer 3 is formed on the first surface 41 of the semiconductor layer 4. There are no particular limitations on the method of forming the insulating layer 3, and it can be selected arbitrarily from thermal oxidation, CVD (Chemical Vapor Deposition), and sputtering. In the case where the semiconductor layer 4 contains Si, the insulating layer 3 can also be, for example, SiO2 formed by partially thermally oxidizing the first surface 41 of the semiconductor layer 4.

[0074] Fourth, the process of forming the first electrode 2a and the second electrode 2b is carried out (S4). In this process (S4), the first electrode 2a and the second electrode 2b are formed on the insulating layer 3.

[0075] There are no particular limitations on the method for forming the first electrode 2a and the second electrode 2b, and a stripping method such as the following can be used. First, a resist mask is formed on the upper surface of the insulating layer 3 using photolithography or EB drawing. An opening is formed in the resist mask in the area where the first electrode 2a and the second electrode 2b are to be formed. Second, a conductive film that will become the first electrode 2a and the second electrode 2b is formed on the upper surface of the resist mask using vapor deposition, sputtering, or the like. The conductive film is formed such that it extends from the inside of the opening of the resist mask to the upper surface of the resist mask. Third, the resist mask and a portion of the conductive film disposed on the upper surface of the resist mask are removed together. Thus, another portion of the conductive film disposed within the opening of the resist mask remains on the surface of the insulating layer 3, becoming the first electrode 2a or the second electrode 2b. Alternatively, a bonding layer for improving the adhesion between the semiconductor layer 4 and the first electrode 2a or the second electrode 2b can be formed on the first surface 41 of the semiconductor layer 4 before forming the first electrode 2a and the second electrode 2b. Furthermore, the first electrode 2a and the second electrode 2b can also be formed by etching a mask formed on the conductive film to be the first electrode 2a and the second electrode 2b.

[0076] Fifth, the process of forming a two-dimensional material layer 1 is performed (S5). In this process (S5), for example, after the two-dimensional material layer is formed to cover the first electrode 2a, the second electrode 2b, and the insulating layer 3, the two-dimensional material layer is patterned. Thus, a two-dimensional material layer is formed. Figure 1 as well as Figure 2 The two-dimensional material layer 1 is shown.

[0077] There are no particular limitations on the method for forming the two-dimensional material layer 1. For example, the two-dimensional material layer 1 can be formed on the first electrode 2a, the insulating layer 3, and a portion of the semiconductor layer 4 by epitaxial growth or screen printing. Alternatively, the two-dimensional material layer 1 can be formed by transferring and attaching a film-like two-dimensional material layer formed on a substrate different from the semiconductor layer 4 using CVD or the like, or a film-like two-dimensional material layer peeled off from graphite or the like using mechanical peeling, onto the first electrode 2a, the insulating layer 3, and a portion of the semiconductor layer 4. There are no particular limitations on the method for patterning the two-dimensional material layer 1; photolithography or EB drawing can be used. When using a mask for patterning, the mask is removed after the two-dimensional material layer 1 is formed.

[0078] Next, the process of forming the first coated film 5 is performed (S6). In this process (S6), the first coated film 5 is formed on the upper surface of the second two-dimensional material layer 12. There are no particular limitations on the method of forming the first coated film 5. The first coated film 5 is formed by etching, for example, as follows: First, the coated film is formed by at least one of sputtering, vapor deposition, and MOD coating method (MOD: Metal Organic Composition). Second, a mask covering the area where the first coated film 5 is to be formed is formed on the upper surface of the coated film by photolithography. Third, for example, the portion of the coated film exposed from the mask is removed by dry etching. As an example of dry etching, reactive ion etching using oxygen plasma or methane tetrafluoride (CF4) plasma can be cited. Fourth, the mask is removed. Thus, a first coated film 5 is formed. Figure 1 as well as Figure 2 The coating 5 is shown.

[0079] Figure 1 as well as Figure 2 The gas detector 100 shown can be manufactured through the above processes (S1 to S6). Furthermore, in the above manufacturing method, a two-dimensional material layer 1 is formed on the first electrode 2a and the second electrode 2b, but it is also possible to form the first electrode 2a and the second electrode 2b on the two-dimensional material layer 1. However, when forming the first electrode 2a and the second electrode 2b on the two-dimensional material layer 1, care must be taken to avoid causing process damage to the two-dimensional material layer 1 during the formation of the first electrode 2a and the second electrode 2b. For example, a solution could be considered such as forming a protective film in the two-dimensional material layer 1 to protect areas where the first electrode 2a or the second electrode 2b is formed overlappingly, before forming the first electrode 2a and the second electrode 2b.

[0080] Working Principle

[0081] Next, the operating principle of the gas detector 100 will be explained. The gas detector 100 functions as a 2-to-1 field-effect transistor, in which the third portion 1c of each two-dimensional material layer 1 serves as the transistor channel, each first electrode 2a and the first portion 1a of each two-dimensional material layer 1 serve as the source, each second electrode 2b and the second portion 1b of each two-dimensional material layer 1 serve as the drain, and the third electrode 2c serves as the gate. Hereinafter, the currents Isd1 and Isd2 flowing through each two-dimensional material layer 1 will also be referred to as source-drain currents, and the voltage Vg applied to the third electrode 2c will also be referred to as the gate voltage.

[0082] The gas detector 100 is able to detect changes in the source-drain currents Isd1 and Isd2 flowing through each two-dimensional material layer 1 under various applied voltages Vg, Vds1, and Vds2.

[0083] Furthermore, the gas detector 100 can also detect changes in voltage Vds1 and voltage Vds2 when a voltage Vg is applied and constant source-drain currents Isd1 and Isd2 flow through it.

[0084] Furthermore, the gas detector 100 can also detect the frequency change of the source / drain current value in the third portion 1c of the two-dimensional material layer 1 under various applied voltages Vg, Vds1, and Vds2. The electrical resonant frequency of the third portion 1c of the two-dimensional material layer 1 depends on the total mass of the third portion 1c of the two-dimensional material layer 1. The mass of the third portion 1c of the two-dimensional material layer 1 increases when the gas to be detected is adsorbed onto the third portion 1c of the two-dimensional material layer 1. Therefore, in the gas detector 100, the concentration of the gas to be detected can also be detected by converting the change in the resonant frequency of the third portion 1c when a DC voltage is applied into the amount of electromagnetic waves irradiated onto the two-dimensional material layer 1.

[0085] As described above, the gas detector 100 can simultaneously perform gas detection using electromagnetic wave detection and gas detection using gas adsorption.

[0086] First, refer to Figure 4 This explains the working principle of gas detection using electromagnetic waves in gas detector 100.

[0087] Figure 4 This diagram illustrates the changes in electrical characteristics generated in each two-dimensional material layer 1 of the gas detector 100 when electromagnetic waves in the wavelength range absorbed by the gas being detected are incident on each two-dimensional material layer 1. Figure 4 In the graph, the solid lines show the relationship between the gate voltage Vg and the source-drain currents Isd1 and Isd2 flowing through each of the two-dimensional material layers 1 when the gas to be detected is present around the gas detector 100. The dashed lines show the relationship between the gate voltage Vg and the source-drain currents Isd1 and Isd2 flowing through each of the two-dimensional material layers 1 when the gas to be detected is not present around the gas detector 100. Furthermore, in Figure 4 The figure shows the change in gate voltage Vg (Vph) and the change in source / drain current Iph based on the presence or absence of gas.

[0088] When a voltage Vg is applied to the semiconductor layer 4 via the third electrode 2c, a depletion layer is formed at the interface between the semiconductor layer 4 and the insulating layer 3. The sign of the voltage Vg is selected according to the doping type of the semiconductor layer 4; a positive voltage is applied if it is p-type, and a negative voltage is applied if it is n-type.

[0089] Each two-dimensional material layer 1 and semiconductor layer 4 is sensitive to electromagnetic waves in the wavelength range absorbed by the gas of the target object. Therefore, when electromagnetic waves in the wavelength range absorbed by the gas of the target object are incident on each two-dimensional material layer 1 and semiconductor layer 4, photoelectric conversion occurs within each two-dimensional material layer 1 and semiconductor layer 4, generating photocarriers in each two-dimensional material layer 1 and the depletion layer. Due to the photocarriers generated in each two-dimensional material layer 1, the source-drain currents Isd1 and Isd2 change.

[0090] Furthermore, the photocarriers generated in the depletion layer provide a change in the electric field effect to the third portion 1c of each two-dimensional material layer 1 via the insulating layer 3. As a result, the gate voltage Vg applied to the third portion 1c of each two-dimensional material layer 1 changes. Based on the change in gate voltage Vg, Vph, the current flowing through the third portion 1c of each two-dimensional material layer 1 changes, and the source-drain currents Isd1 and Isd2 change. Furthermore, according to the gas detector 100, the change in source-drain currents Isd1 and Isd2, Iph, can also be detected when the electromagnetic wave incident on each two-dimensional material layer 1 and the semiconductor layer 4 in the state where the gas to be detected is not present in the optical path. By detecting this current change Iph, the change in the amount of light of the electromagnetic wave incident on the gas detector 100 caused by the absorption of the gas to be detected by the gas to be detected can be detected. By detecting this change in the amount of light, the presence or absence of the gas to be detected in the optical path of the electromagnetic wave, the concentration of the gas to be detected, and the identification of the types of gas present in the optical path of the electromagnetic wave can be performed. Hereinafter, the situation in which the change in the electrical properties of the material in contact with the two-dimensional material layer 1 provides an electric field effect to the two-dimensional material layer 1, and the change in the electrical properties of the two-dimensional material layer 1 is referred to as the optical gating effect.

[0091] Next, refer to Figure 5 This explains the working principle of gas detection using gas adsorption in gas detector 100.

[0092] Figure 5 A schematic diagram illustrates the change in electrical properties within the two-dimensional material layer 1 caused by the adsorption of gas from the object being tested onto the layer. Figure 5In the graph, the solid line shows the relationship between the gate voltage Vg and the source-drain current Isd1 flowing through the first two-dimensional material layer 11 when the gas to be detected is present around the gas detector 100. The dashed line shows the relationship between the gate voltage Vg and the source-drain current Isd1 flowing through the first two-dimensional material layer 11 when the gas to be detected is not present around the gas detector 100. Furthermore, the dashed line graph is the same as the relationship between the gate voltage Vg and the source-drain current Isd2 flowing through the second two-dimensional material layer 12 when the gas to be detected is present around the gas detector 100. Furthermore, in Figure 5 The figure shows the changes in gate voltage Vg (Vph) and source / drain current Isd1 (Iph) based on the presence or absence of gas being detected.

[0093] When the gas to be detected is physically adsorbed onto the third portion 1c of the first two-dimensional material layer 11, charge transfer occurs between the gas and the first two-dimensional material layer 11. As a result, with a gate voltage Vad applied to the third portion 1c of the first two-dimensional material layer 11, the source-drain current Isd1 flowing through the first two-dimensional material layer 11 changes. The amount of this current change Isd1 is related to the amount of gas adsorbed onto the first two-dimensional material layer 11. The amount of gas adsorbed onto the first two-dimensional material layer 11 is related to the gas concentration around the first two-dimensional material layer 11. Therefore, according to the gas detector 100, quantitative analysis of the gas present around the two-dimensional material layer 1 is possible. Hereinafter, the situation where the gas adsorbed onto the two-dimensional material layer 1 provides an electric field effect to the two-dimensional material layer 1, and the electrical characteristics of the two-dimensional material layer 1 change, is referred to as the gas adsorption gate effect.

[0094] <Effect of Gas Detector 100>

[0095] The gas detector 100 can simultaneously perform gas detection using electromagnetic wave detection and gas detection using gas adsorption. Therefore, according to the gas detector 100, it is possible to detect or identify specific gas types in mixed gases, which is difficult to achieve in conventional FETs that only perform gas detection using the aforementioned gas adsorption method. Furthermore, as described above, gas detection using electromagnetic wave detection based on the gas detector 100 can be performed using the light shutter effect. Therefore, the gas detection sensitivity of the gas detector 100 is extremely high compared to conventional gas detectors that only perform gas detection using electromagnetic wave detection.

[0096] Furthermore, in conventional FETs that only perform gas detection using the gas adsorption method described above, it is difficult to detect gases located far from the surface of the graphene. In contrast, the gas detector 100 can perform gas detection using the electromagnetic wave detection method, so as described above, as long as it is in the optical path of the electromagnetic wave, it is possible to detect whether the gas of the target object is located far from the upper surface of the two-dimensional material layer 1.

[0097] Furthermore, conventional gas detectors that only perform gas detection using electromagnetic wave detection methods provide electromagnetic waves in a specific wavelength range to a confined space (gas chamber, etc.) and measure the attenuation of these electromagnetic waves using a single element. Therefore, in such gas detectors, it is difficult to measure (map) the spatial distribution of gas concentration, especially the gas concentration distribution at locations far from the single element. In contrast, the gas detector 100 includes: a first detection unit 100A having a first two-dimensional material layer 11 with an exposed surface not covered by the coating film 5; and a second detection unit 100B having a second two-dimensional material layer 12 covered by the coating film 5 but without an exposed surface. The first detection unit 100A can simultaneously perform gas detection using electromagnetic wave detection and gas detection using gas adsorption. The second detection unit 100B can perform gas detection using only gas adsorption. Therefore, the spatial distribution of the gas to be detected can be detected based on the difference between the detection results from the two detection units; more specifically, it can be determined whether the gas to be detected exists in a region that can be adsorbed onto the two-dimensional material layer 1.

[0098] Furthermore, in the two-dimensional material layer 1, the surface-to-volume ratio is extremely high compared to other materials outside the two-dimensional material layer, and all structures exposed on the upper surface can contribute to gas adsorption. Therefore, the gas detection in the gas detector 100 utilizing the aforementioned gas adsorption grating effect has extremely high sensitivity compared to gas detection using other materials besides the two-dimensional material layer as adsorbents.

[0099] <Variation Example>

[0100] The gas detector disclosed herein may also be without the semiconductor layer 4. Even in this case, the aforementioned gas adsorption gate effect can still be generated. Furthermore, when an electromagnetic wave in the wavelength range absorbed by the gas being detected is incident on it, photocarriers are generated in the two-dimensional material layer 1, and the source-drain currents Isd1 and Isd2 change. Therefore, the gas detector 100 without the semiconductor layer 4 can simultaneously perform gas detection using electromagnetic wave detection and gas detection using gas adsorption.

[0101] The gas detector disclosed herein may also omit the second detection unit 100B. Such a gas detector can simultaneously perform gas detection using electromagnetic wave detection and gas detection using gas adsorption. Therefore, similar to the gas detector 100, it can detect specific gas types in a mixed gas, identify gas types, and determine the presence or absence of gas of a target object at a location far from the upper surface of the two-dimensional material layer 1.

[0102] In this case, the preferred gas detector 100 includes a plurality of first detection units 100A. Electromagnetic waves in the wavelength range absorbed by the gas being detected, which are transmitted through a comparison container filled with a specific comparison gas different from the gas being detected, are incident on a portion of the plurality of first detection units 100A.

[0103] The surface of the two-dimensional material layer can also be modified to bind to / capture specific gases. For example, antibodies that use the gas to be detected as an antigen can be bound to the surface of the two-dimensional material layer. This enables a gas detector capable of specific detection. The antibodies bound to the surface of the two-dimensional material layer can also include primary antibodies that bind to the gas to be detected, and secondary antibodies that are labeled with fluorescent substances or enzymes and bind to the primary antibodies. In this case, the gas detector can detect the primary antibodies that use the gas to be detected as an antigen, and investigate the distribution of fluorescent substances and enzymes on the surface of the two-dimensional material layer. In addition to the gas molecule detection described in the working principle of this invention, it can also perform detection using staining in parallel, enabling the determination of the detection accuracy and spatial concentration distribution of gas molecule types.

[0104] Antibodies bound to the surface of two-dimensional material layers can also possess reactive functional groups such as silicon, carboxyl, and amino groups that can form covalent bonds with the types of gas molecules to be detected on the surface of the two-dimensional material layer. Therefore, highly specific gas detection can be achieved by targeting specific types of gas molecules.

[0105] Alternatively, specific peptides can be coated onto the surface of the two-dimensional material layer to coat the gas molecules of the target gas. This promotes the bonding between the surface of the two-dimensional material layer 1 and the target gas, thereby improving the detection accuracy of the target gas and suppressing the degradation of detection accuracy caused by gases outside the target gas.

[0106] Hydrogels can also be applied to the surface of two-dimensional material layers. This promotes the interaction between the two-dimensional material layer and the gas molecules of the target substance, thereby improving detection accuracy.

[0107] The gas detector 100 may also be equipped with a light source that irradiates each of the multiple two-dimensional material layers 1 with electromagnetic waves in the wavelength range absorbed by the gas of the object being detected.

[0108] The gas detector 100 may also include a container, which is configured to be incident on the gas. Figure 1 as well as Figure 2 The electromagnetic wave path of the multiple detection units shown is enclosed within the gas of the target being detected. This suppresses signal quality degradation associated with false detections of gases outside the target being detected.

[0109] The gas detector 100 may also include a separation column capable of separating gas components, arranged such that the gas components separated by the separation column are supplied to the vicinity of each of the multiple detection units. The separation column may also be capable of separating multiple gas components contained in the gas to be detected. Such a gas detector 100 can detect multiple gas components separated by the separation column in succession.

[0110] The gas detector 100 may also include a gas generating device for generating the gas of the target object and supplying it to the vicinity of each of the plurality of detection units. As described above, the gas generating device may also be a heating device for generating aerosols. Such a gas detector 100 is capable of detecting particles suspended in the gas as aerosols.

[0111] The gas detector 100 may also include an optical filter that controls the wavelength range of the electromagnetic waves incident on each of the multiple detection units. The optical filter may, for example, be installed in the aforementioned container. In such a gas detector 100, if the wavelength of the electromagnetic waves irradiating the detector is controlled according to the above-described operating principle, multiple types of electromagnetic waves and even multiple types of gas molecules can be detected.

[0112] The gas detector 100 may also include a third detection unit. The gas detector 100 may also include a third group of first electrodes 2a and 2b, a third two-dimensional material layer, and a second coating covering the third two-dimensional material layer. The first electrodes 2a and 2b of the third group are arranged spaced apart from the first electrodes 2a and 2b of the first group and the first electrodes 2a and 2b of the second group. The third two-dimensional material layer is arranged spaced apart from the first two-dimensional material layer 11 and the second two-dimensional material layer 12, and the first electrodes 2a and 2b of the third group are electrically connected. The second coating is provided in a manner that blocks the transmission of electromagnetic waves in the wavelength range absorbed by the gas being detected.

[0113] Implementation method 2.

[0114] Unless otherwise specified, the gas detector in Embodiment 2 has the same structure, working principle, and effect as that in Embodiment 1. Therefore, the same reference numerals are used for structures identical to those in Embodiment 1, and the description is not repeated.

[0115] <Structure of Gas Detector 101>

[0116] like Figure 6 As shown, the gas detector 101 of Embodiment 2 includes a ferroelectric layer 6 that is in contact with at least a portion of the two-dimensional material layer 1.

[0117] The ferroelectric layer 6 is disposed, for example, between the third portion 1c of the two-dimensional material layer 1 and the insulating layer 3. Alternatively, the ferroelectric layer 6 may also be disposed on the upper surface of the third portion 1c of the two-dimensional material layer 1. Furthermore, the ferroelectric layer 6 may not be in contact with the two-dimensional material layer 1, but may be connected to the two-dimensional material layer 1 via the insulating layer 3.

[0118] The material constituting the ferroelectric layer 6 can be any material that generates polarization when electromagnetic waves in the wavelength range absorbed by the gas of the detection object are incident on the ferroelectric layer. The material constituting the ferroelectric layer 6 includes, for example, at least one of barium titanate (BaTiO3), lithium niobate (LiNbO3), lithium tantalate (LiTaO3), strontium titanate (SrTiO3), lead zirconate titanate (PZT), strontium bismuthate tantalate (SBT), bismuth ferrite (BFO), zinc oxide (ZnO), hafnium oxide (HfO2), and polyvinylidene fluoride-based ferroelectrics (PVDF, P(VDF-TrFE), P(VDF-TrFE-CTFE), etc.) as organic polymers. Alternatively, the ferroelectric layer can be formed by stacking or mixing multiple different ferroelectric materials.

[0119] The material constituting the ferroelectric layer 6 can be, for example, a material that generates polarization when electromagnetic waves in a wavelength range different from the wavelength range in which the semiconductor layer 4 has sensitivity are incident on the ferroelectric layer 6. A gas detector 101 with such a structure is suitable for detecting multiple gases.

[0120] The material of the ferroelectric layer 6 is not limited to the aforementioned materials, as long as it is a thermoelectric material that exhibits a thermoelectric effect. Specifically, the material of the ferroelectric layer can be any ferroelectric material that produces a polarization change in response to changes in the internal thermal energy of the ferroelectric layer. Furthermore, in the thermoelectric effect, electromagnetic waves only act as a heat source. Therefore, there is essentially no wavelength dependence in the thermoelectric effect. Therefore, there is essentially no wavelength dependence in the ferroelectric layer. Therefore, the ferroelectric layer is sensitive to broadband electromagnetic waves.

[0121] The gas detector 101, for example, includes a first ferroelectric layer 61 in contact with the first two-dimensional material layer 11 and a second ferroelectric layer 62 in contact with the second two-dimensional material layer 12. The second ferroelectric layer 62, for example, has the same structure as the first ferroelectric layer 61.

[0122] Working Principle

[0123] In the gas detector 101, when electromagnetic waves are irradiated onto the ferroelectric layer 6, a change in dielectric polarization occurs within the ferroelectric layer 6 due to its thermoelectric effect. This change in polarization within the ferroelectric layer 6, generated by the thermoelectric effect, provides a change in the electric field to the third portion 1c of the two-dimensional material layer 1. As a result, the gate voltage applied to the third portion 1c of the two-dimensional material layer 1 changes, and the source / drain current values ​​change. That is, in the gas detector 101, the electric field effect provided to the two-dimensional material layer 1 due to the thermoelectric effect of the ferroelectric layer 6 causes a change in the electrical characteristics of the two-dimensional material layer 1. Therefore, in the gas detector 101, for gas detection using electromagnetic wave detection, the aforementioned shutter effect obtained through the semiconductor layer 4 and the shutter effect obtained through the ferroelectric layer 6 can be utilized.

[0124] <Effect>

[0125] According to the gas detector 101, the aforementioned light shutter effect obtained through the semiconductor layer 4 and the light shutter effect obtained through the ferroelectric layer 6 can be utilized, so higher sensitivity can be achieved in comparison with the gas detector 100.

[0126] As described above, the material constituting the ferroelectric layer 6 can also be a material that generates polarization when electromagnetic waves in a wavelength domain different from the wavelength domain in which the semiconductor layer 4 has sensitivity are incident on the ferroelectric layer 6. In this case, highly sensitive gas detection utilizing the aforementioned shutter effect can be achieved in multiple electromagnetic wave wavelength domains.

[0127] <Variation Example>

[0128] Gas detector 101 can also be modified in the same way as gas detector 100.

[0129] Implementation method 3.

[0130] Unless otherwise specified, the gas detector in Embodiment 3 has the same structure, working principle, and effect as that in Embodiment 1. Therefore, the same symbols are used for structures identical to those in Embodiment 1, and the description is not repeated.

[0131] <Structure of Gas Detector 102>

[0132] like Figure 7 As shown, the gas detector 101 of Embodiment 2 has a contact layer 7 that contacts at least a portion of the two-dimensional material layer 1.

[0133] exist Figure 7 In the gas detector shown, a contact layer 7 is provided beneath the two-dimensional material layer 1. The contact layer 7 is made of a material that can supply holes or electrons to the two-dimensional material layer 1 through contact with it. Holes or electrons can be arbitrarily doped into the two-dimensional material layer 1 through the contact layer 7.

[0134] As the contact layer 7, for example, a composition containing a photosensitizer having a benzoquinone diazinol group and an ester-aldehyde resin, known as a positive photoresist, can be used. Alternatively, as a material constituting the contact layer 7, a material having a polar group can be used. For example, a material having an electron-withdrawing group, as an example of such a material, has the effect of reducing the electron density of the two-dimensional material layer 1. Conversely, a material having an electron-donating group, as an example of such a material, has the effect of increasing the electron density of the two-dimensional material layer 1. Examples of materials having an electron-withdrawing group include those having halogen, nitrile, carboxyl, or carbonyl groups. Examples of materials having an electron-donating group include those having alkyl, alcohol, amino, or hydroxyl groups. In addition to the above, materials that generate charge shifts in the molecular whole through polar groups can also be used as the material for the contact layer 7.

[0135] Furthermore, any material that generates polarity by inducing charge shifts within molecules, including organic materials, metals, semiconductors, insulators, two-dimensional materials, or mixtures of these materials, can be used as the material for contact layer 7. Here, when contact layer 7, made of an inorganic material, is in contact with two-dimensional material layer 1, the conductivity type of the doped two-dimensional material layer 1 is p-type if the work function of contact layer 7 is greater than that of two-dimensional material layer 1, and n-type if the work function of contact layer 7 is less than that of two-dimensional material layer 1. In contrast, when contact layer 7 is an organic material, the organic material constituting contact layer 7 does not have a definite work function. Therefore, regarding whether two-dimensional material layer 1 is n-type or p-type doped, it is preferable to determine the polarity of the material of contact layer 7 by the polarity of the molecules of the organic material used in contact layer 7.

[0136] For example, when a composition containing a photosensitive agent with quinone diazide groups and an ester-aldehyde resin, known as a positive photoresist, is used as the contact layer 7, the area in the two-dimensional material layer 1 where the photoresist is formed by the photolithography process becomes a p-type two-dimensional material layer area. Therefore, a mask formation process that contacts the surface of the two-dimensional material layer 1 is no longer required. As a result, process damage to the two-dimensional material layer 1 can be reduced, and the process can be simplified.

[0137] The gas detector 102, for example, has a first contact layer 71 that contacts the first two-dimensional material layer 11 and a second contact layer 72 that contacts the second two-dimensional material layer 12. The second contact layer 72, for example, has the same structure as the first contact layer 71.

[0138] As a method for manufacturing the gas detector 102, for example, a step of forming a contact layer 7 can be performed before the step of forming the two-dimensional material layer 1.

[0139] <Effect>

[0140] The gas detector 102 includes a contact layer 7 capable of supplying holes or electrons to the two-dimensional material layer 1. Therefore, in the gas detector 102, the conductivity type of the two-dimensional material layer 1 can be intentionally set to n-type or p-type. Thus, the carrier doping of the two-dimensional material layer 1 can be controlled without considering the influence of carrier doping associated with the contact between the two-dimensional material layer 1, the electrode 2, and the insulating layer 3. As a result, the performance of the gas detector 102 can be improved.

[0141] Furthermore, by forming a contact layer 7 only on either the side of the first electrode 2a or the side of the semiconductor layer 4 on the upper surface of the two-dimensional material layer 1, a charge density gradient is formed in the two-dimensional material layer 1. As a result, the mobility of charge carriers in the two-dimensional material layer 1 is improved, enabling the gas detector 102 to achieve high sensitivity.

[0142] Alternatively, multiple contact layers 7 can be formed on the two-dimensional material layer 1. The number of contact layers 7 can be more than three, and can be any number. Multiple contact layers 7 can also be formed on the two-dimensional material layer 1 located between the first electrode 2a and the semiconductor layer 4. In this case, the materials of the multiple contact layers 7 can be the same or different materials.

[0143] Furthermore, in the gas detector of this embodiment, the thickness of the contact layer 7 is preferably thin enough to enable photoelectric conversion when electromagnetic waves are irradiated onto the two-dimensional material layer 1. On the other hand, it is preferable to form the contact layer 7 with a thickness sufficient to dope the two-dimensional material layer 1 with charge carriers from the contact layer 7. Regarding the contact layer 7, it can have any structure as long as charge carriers such as molecules or electrons are introduced into the two-dimensional material layer 1. For example, it is also possible to dope the two-dimensional material layer 1 with charge carriers by immersing the two-dimensional material layer 1 in a solution and supplying charge carriers to the two-dimensional material layer 1 at the molecular level, without forming a solid contact layer 7 on the two-dimensional material layer 1.

[0144] In addition to the materials described above, materials that generate polarity reversal can also be used as the material for contact layer 7. In this case, when the contact layer 7 undergoes a polarity reversal, electrons or holes generated during the reversal are supplied to the two-dimensional material layer 1. Therefore, electron or hole doping occurs in the portion of the two-dimensional material layer 1 that is in contact with contact layer 7. Therefore, even if contact layer 7 is removed, that portion of the two-dimensional material layer 1 that is in contact with contact layer 7 remains in a state of being doped with electrons or holes. Therefore, when a material that generates polarity reversal is used as contact layer 7, contact layer 7 can be removed from the two-dimensional material layer 1 after a certain period of time. In this case, the opening area of ​​the two-dimensional material layer 1 increases compared to the case where contact layer 7 is present. Therefore, the detection sensitivity of the gas detector can be improved. Here, polarity reversal refers to phenomena such as the chemical transformation of polar groups, for example, electron-withdrawing groups changing to electron-donating groups, or electron-donating groups changing to electron-withdrawing groups, or polar groups changing to non-polar groups, or non-polar groups changing to polar groups.

[0145] Alternatively, the contact layer 7 can also be formed of a material that undergoes a polarity change upon irradiation by electromagnetic waves. In this case, by selecting a material that undergoes a polarity change at a specific wavelength of electromagnetic waves as the material of the contact layer 7, it is possible to induce a polarity change in the contact layer 7 only upon irradiation by electromagnetic waves at that specific wavelength, thereby doping the two-dimensional material layer 1. As a result, the photocurrent flowing into the two-dimensional material layer 1 can be increased.

[0146] Alternatively, a material that undergoes a redox reaction when irradiated by electromagnetic waves can be used as the material for contact layer 7. In this case, electrons or holes generated during the redox reaction can be doped into the two-dimensional material layer 1.

[0147] <Variation Example>

[0148] Gas detector 102 can also be modified in the same way as gas detector 100. In addition, the structure of the gas detector as described in this embodiment can also be applied to other embodiments.

[0149] Implementation method 4.

[0150] Unless otherwise specified, the gas detector in Embodiment 4 has the same structure, working principle, and effect as that in Embodiment 1. Therefore, the same reference numerals are used for structures identical to those in Embodiment 1, and the description is not repeated.

[0151] <Structure of Gas Detector 104>

[0152] like Figure 8 As shown, the gas detector 103 of Embodiment 4 includes at least one conductor 8 in contact with at least a portion of the two-dimensional material layer 1. Figure 8In the gas detector 103 shown, a plurality of conductors 8 are disposed on the upper surface of the third part 1c of the two-dimensional material layer 1. The plurality of conductors 8 are disposed at intervals between each other. Each conductor 8 is a floating electrode.

[0153] The material constituting the conductor 8 can be any material as long as it is a conductor. For example, metals such as gold (Au), silver (Ag), copper (Cu), aluminum (Al), nickel (Ni), chromium (Cr), or palladium (Pd) can be used as the material of the conductor 8. Here, the conductor 8 is not connected to the power supply circuit or the like and is thus floating.

[0154] Multiple conductors 8 have one-dimensional or two-dimensional periodic structures. For example, as an example of a one-dimensional periodic structure, it can be adopted in... Figure 8 The structure consists of multiple conductors 8 arranged periodically or at intervals along the horizontal or vertical direction of the paper. Alternatively, as an example of a two-dimensional periodic structure, the conductors 8 can be arranged at positions corresponding to grid nodes such as square or triangular grids when viewed from above the gas detector. Furthermore, when viewed from above the gas detector, the planar shape of each conductor 8 can be any shape, such as circular, triangular, quadrilateral, polygonal, or elliptical. Moreover, the arrangement of the conductors 8 when viewed from above is not limited to the aforementioned periodic and symmetrical arrangement; it can also be an asymmetrical arrangement when viewed from above. Here, any method can be used to form the conductors 8; for example, the same method used to manufacture the first electrode 2a and the second electrode 2b described in Embodiment 1 can be used.

[0155] The manufacturing method of the gas detector 103 may include, for example, a step of forming a conductor 8 after the step of forming the two-dimensional material layer 1 and before the step of forming the coating film 5.

[0156] <Effect of Gas Detector 103>

[0157] The gas detector 103 has a conductor 8 serving as a floating electrode on the two-dimensional material layer 1. Therefore, surface charge carriers generated in the two-dimensional material layer 1 by electromagnetic wave irradiation can travel back and forth between multiple conductors 8, resulting in a longer photocarrier lifetime. Consequently, the detection sensitivity of the gas detector 103 is improved.

[0158] Furthermore, by arranging the multiple conductors 8 in a one-dimensional periodic configuration and using a material that generates surface plasmon resonance for the conductors 8, polarization dependence is generated in the conductors 8 due to the irradiated electromagnetic waves. As a result, only electromagnetic waves with specific polarizations can be irradiated onto the semiconductor layer 4 of the gas detector 103. In this case, the gas detector 103 of this embodiment can detect only specific polarized waves.

[0159] Furthermore, by arranging the multiple conductors 8 in a two-dimensional periodic configuration and using a material that generates surface plasmon resonance for the conductors 8, it is possible to resonate electromagnetic waves of a specific wavelength using the multiple conductors 8. In this case, the gas detector 103 can detect only electromagnetic waves with a specific wavelength. In this case, the gas detector 103 of this embodiment can detect only electromagnetic waves of a specific wavelength with high sensitivity.

[0160] Furthermore, when multiple conductors 8 are formed in an asymmetrical configuration when viewed from above, similar to the case where the multiple conductors 8 are formed in a one-dimensional periodic structure, polarization dependence occurs in the conductors 8 for the irradiated electromagnetic waves. As a result, only electromagnetic waves with specific polarizations can irradiate the semiconductor layer 4. In this case, the gas detector 103 of this embodiment can improve the signal-to-noise ratio (SN ratio) of the detection signal and improve the contrast by detecting only specific polarized waves.

[0161] Alternatively, in the gas detector 103, a conductor 8 can be disposed beneath the two-dimensional material layer 1. With this structure, it is also possible to obtain... Figure 8 The gas detector 103 shown has the same effect. Furthermore, in this case, the two-dimensional material layer 1 is not damaged when the conductor 8 is formed, so the decrease in the mobility of charge carriers in the two-dimensional material layer 1 can be suppressed.

[0162] Alternatively, uneven portions can be formed in the two-dimensional material layer 1. In this case, the uneven portions of the two-dimensional material layer 1 can also be a periodic or asymmetrical structure, similar to the aforementioned plurality of conductors 8. In this case, the same effect as when forming a plurality of conductors 8 can be obtained.

[0163] <Variation Example>

[0164] Gas detector 103 can also be modified in the same way as gas detector 100. In addition, the structure of the gas detector as described in this embodiment can also be applied to other embodiments.

[0165] Implementation method 5.

[0166] Unless otherwise specified, the gas detector in Embodiment 5 has the same structure, working principle, and effect as that in Embodiment 1 described above. Therefore, the same reference numerals are used for structures identical to those in Embodiment 1, and the description is not repeated.

[0167] <Structure of Gas Detector 104>

[0168] like Figure 9As shown, in the gas detector 104 of Embodiment 4, the third portion 1c of each of the first two-dimensional material layer 11 and the second two-dimensional material layer 12 is disposed between the first portion 1a and the second portion 1b. In the insulating layer 3, a plurality of recesses 30 are formed that are recessed into the upper surface of the insulating layer 3. Each recess 30 is, for example, formed as an opening (through-hole) that exposes the first surface 41 of the semiconductor layer 4. In this case, the lower surface of the third portion 1c is arranged facing the first surface 41 of the semiconductor layer 4 at a distance from it.

[0169] Each third portion 1c of the two-dimensional material layer 1 has, for example, a pair of contact portions 1d that are in contact with the upper surface of the insulating layer 3, and a mounting portion 1e that is disposed between the pair of contact portions 1d. The mounting portion 1e is not in contact with the insulating layer 3 or the semiconductor layer 4.

[0170] Furthermore, the recess 30 of the insulating layer 3 can be configured such that even if the third part 1c bends due to its own weight, the lower surface of the third part 1c does not contact the insulating layer 3 or the semiconductor layer 4. If the recess 30 of the insulating layer 3 is formed as an opening, a second recess (not shown) can also be formed in the semiconductor layer 4, recessed relative to the first surface 41 and connected to the recess 30 of the insulating layer 3 in the vertical direction.

[0171] The gas detector 104 can be manufactured by performing a step of forming a recess 30 in the insulating layer 3 before the step of forming the two-dimensional material layer 1.

[0172] <Effect of Gas Detector 104>

[0173] In the gas detector 104, the third portion 1c of the two-dimensional material layer 1, which functions as a transistor channel, has a portion that is not in contact with other materials. Therefore, compared to the gas detector 100, the electron / hole mobility is improved. As a result, the detection sensitivity of the gas detector 104 is improved.

[0174] <Variation Example>

[0175] Gas detector 104 can also be modified in the same way as gas detector 100. In addition, the structure of the gas detector as described in this embodiment can also be applied to other embodiments.

[0176] Implementation method 6.

[0177] Unless otherwise specified, the gas detector in Embodiment 6 has the same structure, working principle, and effect as that in Embodiment 1. Therefore, the same reference numerals are used for structures identical to those in Embodiment 1, and the description is not repeated.

[0178] <Structure of Gas Detector 105>

[0179] like Figure 10 as well as Figure 11 As shown, in the gas detector 105 of Embodiment 6, at least one opening 31 is formed in the insulating layer 3, exposing a portion of the first surface of the semiconductor layer 4. Figure 10 In the gas detector 105 shown, a first opening 31A and a second opening 31B are formed at intervals. The gas detector 105, for example, has a first electrode 2a1 and a second electrode 2a2 arranged at intervals.

[0180] The gas detector 105 replaces the first two-dimensional material layer 11 and the second two-dimensional material layer 12, and includes a fourth two-dimensional material layer 13 and a fifth two-dimensional material layer 14. The fourth two-dimensional material layer 13 extends from the first opening 31A to the insulating layer 3 and electrically connects the first electrode 2a1 to the semiconductor layer 4. The fourth two-dimensional material layer 13 has an exposed surface facing outward. The fifth two-dimensional material layer 14 extends from the second opening 31B to the insulating layer 3 and electrically connects the second electrode 2a2 to the semiconductor layer 4. The fifth two-dimensional material layer 14 is covered by a coating 5 (a third coating).

[0181] The fourth two-dimensional material layer 13 and the fifth two-dimensional material layer 14 each have a first part 1a, a second part 1b and a third part 1c.

[0182] The second portion 1b of each of the fourth two-dimensional material layer 13 and the fifth two-dimensional material layer 14 contacts the aforementioned portion of the first surface 41 exposed within the opening 31 in the semiconductor layer 4. Preferably, the second portion 1b of the two-dimensional material layer 1 is Schottky connected to the semiconductor layer 4. For example, the semiconductor layer 4 is made of p-type silicon, and the two-dimensional material layer 1 is made of n-type graphene.

[0183] The second electrode 2b is disposed on the second surface 42 of the semiconductor layer 4 and is electrically connected to the two-dimensional material layer 1 via the semiconductor layer 4.

[0184] In the gas detector 105, similarly to the gas detector 100, the third portion 1c of each two-dimensional material layer 1 functions as a transistor channel, each first electrode 2a and the first portion 1a of each two-dimensional material layer 1 functions as a source, and each second electrode 2b and the second portion 1b of each two-dimensional material layer 1 functions as a drain. Furthermore, in the gas detector 105, the contact region between the second portion 1b of the two-dimensional material layer 1 and the semiconductor layer 4 functions as a Schottky barrier diode.

[0185] like Figure 11As shown, a power supply circuit for applying a voltage Vd is electrically connected between the first electrode 2a1 and the second electrode 2b, and between the second electrode 2a2 and the second electrode 2b. Preferably, the voltage Vd is set to be reverse biased relative to the Schottky junction of the two-dimensional material layer 1 and the semiconductor layer 4. By applying the voltage Vd, currents Id1 and Id2 flow in each of the two-dimensional material layers 1. The currents Id1 and Id2 are measured by a galvanometer (not shown) included in the power supply circuit.

[0186] Even in the gas detector 105, the aforementioned light shutter effect and gas adsorption grid effect can be generated.

[0187] Furthermore, in the gas detector 105, with the two-dimensional material layer 1 and the semiconductor layer 4 connected in a Schottky junction, by adjusting the voltage V to apply a reverse bias to the Schottky junction, the currents Id1 and Id2 in the state where no electromagnetic wave is incident can become zero. Additionally, by modulating the Fermi level of the two-dimensional material layer 1 using the photoelectromotive force generated when the electromagnetic wave is incident on the semiconductor layer 4, the energy barrier between the two-dimensional material layer 1 and the semiconductor layer 4 is lowered. As a result, currents Id1 and Id2 are detected only when the electromagnetic wave is irradiated, as current flows through the semiconductor layer 4. That is, an OFF operation can be performed in the gas detector of this embodiment.

[0188] The gas detector 105 in this embodiment is not limited to a structure that detects changes in current in the two-dimensional material layer 1. For example, the gas detector 105 can also detect changes in voltages Vd1 and Vd2 when a constant current flows between each of the first electrode 2a and the second electrode 2b.

[0189] Furthermore, even in the gas detector 105, it is possible to detect the frequency variation of the source / drain current value in the third part 1c of the two-dimensional material layer 1.

[0190] <Effect of Gas Detector 105>

[0191] According to the gas detector 105, an OFF operation can be performed, so a reduction in power consumption and an improvement in the signal-to-signal ratio can be expected.

[0192] <Modified example of gas detector 105>

[0193] Figure 12 as well as Figure 13 A modified example of the gas detector 105 is shown. Figure 12 The gas detector 106 shown and Figure 13 In the gas detector 107 shown, the planar shape of the second part 1b of the two-dimensional material layer 1 is similar to... Figure 10 The gas detector 105 shown is different.

[0194] The contact area between the second portion 1b of the two-dimensional material layer 1 and the semiconductor layer 4 in gas detectors 106 and 107 is smaller than the contact area between the second portion 1b and the semiconductor layer 4 in gas detector 105. In gas detectors 106 and 107, the contact area between the second portion 1b and the semiconductor layer 4 is smaller than the sum of the areas occupied by the first portion 1a and the third portion 1c when viewed from above.

[0195] The second portion 1b of each of gas detectors 106 and 107 corresponds to the portion of the second portion 1b of gas detector 105 after removing at least a plurality of regions spaced apart from each other in a direction intersecting the extension direction of the two-dimensional material layer 1 (the direction in which the first portion 1a, the third portion 1c, and the second portion 1b are arranged side by side). In gas detector 106, each of the plurality of regions has a rectangular shape. In gas detector 107, each of the plurality of regions has a regular shape.

[0196] In each of gas detectors 106 and 107, the planar shapes of the first part 1a, the second part 1b, and the third part 1c are symmetrical with respect to a straight line extending along the direction intersecting the extension direction of the two-dimensional material layer 1. Furthermore, in a cross-section passing through the center of the direction intersecting the extension direction of the two-dimensional material layer 1, gas detectors 106 and 107 have, for example, a structure equivalent to that of gas detector 105.

[0197] Figure 12 The second portion 1b of the gas detector 106 shown has a comb-shaped (ladder-shaped) planar shape. In the gas detector 106, the sum of the widths of the second portion 1b in the directions intersecting the extension direction of the two-dimensional material layer 1 is narrower than the widths of the first portion 1a and the third portion 1c in the intersecting directions. In the gas detector 106, a plurality of openings are formed to expose the semiconductor layer 4, and the plurality of openings are arranged in the aforementioned intersecting directions.

[0198] Figure 13 The second portion 1b of the gas detector 107 shown has a lattice-shaped planar shape. In the gas detector 107, multiple openings are formed in the two-dimensional material layer 1 to expose the semiconductor layer 4. These openings are arranged in various directions, including the extension direction of the two-dimensional material layer 1 and the directions intersecting it. In the gas detector 107, the minimum sum of the widths of the second portion 1b in the directions intersecting the extension direction of the two-dimensional material layer 1 is narrower than the minimum widths of the first portion 1a and the third portion 1c in those intersecting directions.

[0199] In gas detectors 106 and 107, the area of ​​the contact region between the two-dimensional material layer 1 and the semiconductor layer 4 is adjusted according to the width of the second portion 1b in the extending direction of the two-dimensional material layer 1. Therefore, in gas detectors 106 and 107, the contact resistance between the two-dimensional material layer 1 and the semiconductor layer 4, and even the resistance of the gas detector itself, can be adjusted. In gas detectors 106 and 107, the contact resistance between the two-dimensional material layer 1 and the semiconductor layer 4, and even the resistance of the gas detector, can be adjusted. Figure 10 Compared to the gas detector 105 shown, the deviation of the gas detector characteristics is reduced, and the dark current is also reduced.

[0200] Furthermore, in gas detectors 106 and 107, the sum of the areas of the end faces of part 2b is greater than [a certain value]. Figure 10 The sum of the areas of the end faces of the second part 1b of the gas detector 105 shown. The end face of the second part 1b is a face extending along the thickness direction of the two-dimensional material layer 1, in other words, orthogonal to the direction of the sheet formed by the two-dimensional arrangement of atoms in the two-dimensional material layer 1. In other words, Figure 12 as well as Figure 13 The end-face regions of the two-dimensional crystalline structures in each of Part 2b shown are compared to Figure 10 The end-face region of the two-dimensional crystalline structure shown in Part 2, 1b is increased. Therefore, in Figure 12 as well as Figure 13 In each of the two-dimensional material layers 1 shown, and with Figure 10 Compared to the two-dimensional material layer 1 shown, the proportion of unbonded hands (dangling bonds) in the two-dimensional crystalline structure increases. As a result, when charge carriers generated by electromagnetic wave irradiation in the semiconductor layer 4 are transported to each of the first electrodes 2a via the two-dimensional material layer 1, in… Figure 12 as well as Figure 13 In each of the two-dimensional material layers 1 shown, and with Figure 10 Compared to the two-dimensional material layer 1 shown, the change in carrier density is more significant, carrier mobility increases, and the change in current I is greater. As a result, Figure 12 as well as Figure 13 The gas detectors 106 and 107 shown have higher detection sensitivity than Figure 10 The sensitivity of the gas detector 105 shown.

[0201] Furthermore, in gas detectors 106 and 107, the second portion 1b of the two-dimensional material layer 1 can also be graphene nanoribbons. Graphene nanoribbons have a band gap that varies according to their width. Therefore, the wavelength range of the photoelectrically convertible electromagnetic wave in the second portion 1b can be adjusted according to the width of the aforementioned intersecting directions of the second portion 1b composed of graphene nanoribbons; for example, it can be set to be narrower than the wavelength range of the photoelectrically convertible electromagnetic wave in other regions. In this case, photocarriers generated by photoelectric conversion in the second portion 1b can be distinguished from photocarriers generated by photoelectric conversion in other regions and detected. In addition, the sensitivity of the gas detector is improved by detecting photocarriers generated by photoelectric conversion in the second portion 1b. Furthermore, in such a gas detector, the second portion 1b composed of graphene nanoribbons is connected to the Schottky junction of the semiconductor layer 4, so the dark current is reduced, and the sensitivity is improved by detecting photocarriers generated due to electromagnetic waves absorbed in the Schottky junction.

[0202] Gas detectors 105-107 may also include a third detection unit. Gas detectors 105-107 may also include a third first electrode 2a, a sixth two-dimensional material layer, and a fourth coating covering the sixth two-dimensional material layer. In gas detectors 105-107, a third opening may also be formed in the insulating layer 3, spaced apart from both the first and second openings. The first electrodes 2a and 2b of the third group are spaced apart from the first electrodes 2a and 2b of the first group and the first electrodes 2a and 2b of the second group. The sixth two-dimensional material layer extends from the third opening onto the insulating layer 3, electrically connecting the third first electrode to the semiconductor layer 4. The fourth coating is provided in a manner that blocks the transmission of electromagnetic waves in the wavelength range absorbed by the gas being detected.

[0203] The structure of the gas detector in this embodiment can also be applied to other embodiments.

[0204] <Modifications of Gas Detectors 100-107>

[0205] In each of the gas detectors 100 to 107, at least one of the materials constituting the insulating layer 3, semiconductor layer 4, ferroelectric layer 6, contact layer 7, and conductor 8 is preferably a material whose properties change due to electromagnetic wave irradiation and provides a change in potential to the two-dimensional material layer 1.

[0206] Here, materials whose properties change due to electromagnetic wave irradiation and provide a potential change to the two-dimensional material layer 1 can be, for example, quantum dots, ferroelectric materials, liquid crystal materials, fullerenes, rare earth oxides, semiconductor materials, pn junction materials, metal-semiconductor bonding materials, or metal-insulator-semiconductor bonding materials. For example, when using a ferroelectric material that has a polarization effect (thermoelectric effect) based on electromagnetic waves, a polarization change occurs in the ferroelectric material due to electromagnetic wave irradiation. As a result, a potential change can be provided to the two-dimensional material layer 1.

[0207] In the case where at least one of the materials constituting the insulating layer 3, semiconductor layer 4, ferroelectric layer 6, contact layer 7, and conductor 8 is a material whose properties change due to electromagnetic wave irradiation, the properties of at least one of the materials constituting the insulating layer 3, semiconductor layer 4, ferroelectric layer 6, contact layer 7, and conductor 8 change due to electromagnetic wave irradiation, thus providing a potential change to the two-dimensional material layer 1.

[0208] More preferably, the materials constituting the insulating layer 3, the semiconductor layer 4, the ferroelectric layer 6, the contact layer 7, and the conductor 8 are materials whose properties change due to electromagnetic wave irradiation and provide a change in potential to the two-dimensional material layer 1.

[0209] Furthermore, when the contact layer 7 is made of a material whose properties change due to electromagnetic wave irradiation and which provides a change in potential to the two-dimensional material layer 1, the contact layer 7 does not necessarily need to be in direct contact with the two-dimensional material layer 1. For example, as long as it can provide a change in potential to the two-dimensional material layer 1, the contact layer 7 can be provided on the upper or lower surface of the two-dimensional material layer 1 through an insulating film or the like.

[0210] Implementation method 7.

[0211] Figure 14 This is a top surface view of the gas detector array in Embodiment 7. Figure 15 This is a schematic diagram illustrating an example of a readout circuit for reading electrical signals obtained from a gas detector array according to Embodiment 7. Figure 16 This is a top surface view showing a first modified example of the gas detector array of Embodiment 7.

[0212] like Figure 14 As shown, the gas detector array 1000 of Embodiment 7 is an assembly of multiple gas detectors 100. The gas detector array 1000 includes multiple gas detectors 100-107, any one of Embodiments 1-6, as detection elements. For example, the gas detector array 100 includes multiple gas detectors 100 of Embodiment 1 as gas detectors.

[0213] In the gas detector array 1000, multiple gas detectors 100 each have the same detection wavelength. For example... Figure 14 As shown, in the gas detector array 1000, a plurality of gas detectors 100 are arranged in an array in a two-dimensional direction. In other words, the plurality of gas detectors 100 are arranged in a first direction and a second direction intersecting the first direction. Figure 14 In the gas detector array 1000 shown, four gas detectors 100 are arranged in a 2×2 array. However, the number of gas detectors 100 arranged is not limited to this. For example, multiple gas detectors 100 may be arranged in an array of 3 or more × 3 or more. In addition, multiple detection units included in two gas detectors 100 may be arranged in an array. For example, the two first detection units 100A, the second detection unit 100B, and the third detection unit may be arranged in a 2×2 array.

[0214] In addition, Figure 14 In the gas detector array 1000 shown, multiple gas detectors 100 are arranged periodically in two dimensions, but multiple gas detectors 100 can also be arranged periodically along one direction. In addition, the intervals between the multiple gas detectors 100 can be equal or different.

[0215] Furthermore, when multiple gas detectors 100 are arranged in an array, the first electrode 2a and the third electrode 2c can be shared electrodes as long as each gas detector 100 can be separated. By making the first electrode 2a and the third electrode 2c shared electrodes, compared with a structure where the first electrode 2a and the third electrode 2c are independent in each gas detector 100, pixel wiring can be reduced. As a result, the gas detector array can be made to have higher resolution. As a method for separating the multiple gas detectors 100, for example, an insulating layer can be provided in a manner that surrounds the outer periphery of each gas detector 100.

[0216] The gas detector array 1000, which uses multiple gas detectors 100, can also be used as an image sensor by arranging the multiple gas detectors 100 in an array.

[0217] The gas detector array 1000 may also include any one of the gas detectors described in embodiments 1 to 6 as the gas detector 100.

[0218] The gas detector array 1000 may have a gas detector of any one of the embodiments 1 to 6, or it may have a gas detector of two or more of the embodiments 1 to 6.

[0219] <Modification of Gas Detector Array 1000>

[0220] The gas detector array 1000 preferably also includes a readout circuit or a matrix selection circuit, or other detection circuit, for reading electrical signals obtained from each of the plurality of gas detectors 100. The detection circuit is preferably located on the outer side of the plurality of gas detectors 100 arranged in an array. Alternatively, the detection circuit may be located on a semiconductor chip independent of the plurality of gas detectors 100 and electrically connected to each of the plurality of gas detectors 100 using bumps or the like.

[0221] Figure 15 This is a schematic diagram illustrating an example of a gas detector array 1000 equipped with the aforementioned detection circuit. Hereinafter, each gas detector 100 (or each detection unit) constituting the gas detector array 1000 will also be referred to as a pixel. The gas detector array 1000 includes: a vertical scanning circuit 301 that scans the pixels 100 in the vertical direction; a horizontal scanning circuit 302 that scans the pixels 100 in the horizontal direction; a power supply circuit 303 that supplies bias voltage to each circuit; and an output circuit 304 that outputs the signal from the horizontal scanning circuit 302 to the outside of the gas detector array 1000.

[0222] Figure 15 The gas detector array 1000 shown is capable of detecting the response of the gas detector 100 for each pixel. Specifically, a row is selected by applying voltage to the vertical scanning circuit 301, and a column is selected by applying voltage to the horizontal scanning circuit 302, thereby reading out the response of one pixel. By fixing the row selected by the vertical scanning circuit 301 and sequentially applying voltage to the horizontal scanning circuit 302, the response of all pixels in that row is read out. Then, similarly, other rows are selected by applying voltage to the vertical scanning circuit 301, and the response of all pixels in those other rows is read out by sequentially applying voltage to the horizontal scanning circuit 302. By repeating this process, the response of all pixels can be read out.

[0223] In this embodiment, a method for reading the response for each pixel using the vertical scanning circuit 301 and the horizontal scanning circuit 302 is described, but it is not limited to this. The response can also be read for each row or each column, or other methods can be used.

[0224] <Effect>

[0225] according to Figure 15 The gas detector array 1000 shown can detect the response of each pixel and can easily perform differential detection between pixels, so it is particularly effective for, for example, the detection of multiple gases or the determination of spatial distribution.

[0226] Figure 16The gas detector array 2000 shown has the same features as... Figure 14 The gas detector array 1000 shown has essentially the same structure and achieves the same effect, but differs in that it comprises multiple gas detectors of different types 200, 201, 202, and 203. Figure 14 The gas detector arrays shown are different. That is, in Figure 16 In the gas detector array 2000 shown, gas detectors 200, 201, 202, and 203 of different types are arranged in an array (matrix) configuration.

[0227] exist Figure 16 The gas detector array 2000 shown contains gas detectors 200, 201, 202, and 203 arranged in a 2×2 matrix, but the number of gas detectors is not limited to this. Furthermore, in Figure 16 In the gas detector array 2000 shown, multiple gas detectors 200, 201, 202, and 203 are arranged periodically in a two-dimensional manner, but they can also be arranged periodically along one direction. Furthermore, the intervals between the multiple gas detectors 200, 201, 202, and 203 can be equal or different.

[0228] exist Figure 16 In the gas detector array 2000 shown, by arranging gas detectors 200, 201, 202, and 203 of any one of the embodiments 1 to 6 above in a one-dimensional or two-dimensional array, it is possible to provide the function of a gas image sensor.

[0229] Gas detectors 200, 201, 202, and 203 are, for example, gas detectors that detect wavelengths that are different from each other. Specifically, gas detectors 200, 201, 202, and 203 can also be prepared as any one of embodiments 1 to 6, and have different detection wavelength selectivity. In this case, the gas detector array can detect at least two or more different wavelengths of electromagnetic waves.

[0230] By arranging gas detectors 200, 201, 202, and 203 with different detection wavelengths in such an array, similar to image sensors used in the visible light domain, it is possible to identify the wavelength of electromagnetic waves in any wavelength domain, such as ultraviolet light, infrared light, terahertz waves, and radio waves. As a result, for example, it is possible to obtain a colorized image that represents wavelength differences as color differences.

[0231] Furthermore, the constituent material of the semiconductor layer 4 in each of the gas detectors 200, 201, 202, and 203 can also be a semiconductor material that is sensitive to different wavelength ranges. For example, semiconductor materials that detect wavelengths of visible light and those that detect wavelengths of infrared light can be used as the constituent materials. In this case, for example, when the gas detector is applied to an automotive sensor, it can be used as a visible light imaging camera during the day. Furthermore, it can be used as an infrared camera at night. Thus, it is not necessary to distinguish between cameras with image sensors based on the detection wavelength of electromagnetic waves.

[0232] Furthermore, as a gas detector for applications other than image sensors, it can be used as a gas mapping sensor capable of detecting gas concentration distribution even with a relatively small number of pixels. For example, depending on the configuration of the gas detector array, if gas detectors 200, 201, 202, and 203 with different detection wavelengths are used as described above, an image sensor that detects the intensity of electromagnetic waves of multiple wavelengths can be obtained. Thus, without using color filters conventionally required in CMOS image sensors, multiple wavelengths of electromagnetic waves can be detected, resulting in a color image.

[0233] Furthermore, a polarization recognition image sensor can be formed by arraying gas detectors 200, 201, 202, and 203 that detect different polarizations. For example, polarization imaging can be performed by treating four pixels with detected polarization angles of 0°, 90°, 45°, and 135° as a unit and configuring multiple gas detectors for each unit. With a polarization recognition image sensor, for example, it is possible to achieve the identification of man-made and natural objects, material identification, identification of objects at the same temperature in the infrared wavelength domain, identification of boundaries between objects, or equivalent improvement in resolution.

[0234] As described above, the gas detector array 2000 can detect electromagnetic waves over a wide wavelength range. Furthermore, the gas detector array 2000 can detect electromagnetic waves of different wavelengths.

[0235] The above embodiments can be appropriately modified or omitted. Furthermore, the above embodiments can be modified in various ways during implementation without departing from their essence. Additionally, the disclosures in the above embodiments, including various stages, can be extracted through appropriate combinations of the disclosed constituent elements.

[0236] The embodiments disclosed herein should be considered illustrative rather than restrictive in all respects. At least two of the embodiments disclosed herein may be combined, provided there are no contradictions. The scope of this disclosure is not defined by the foregoing description but by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims.

[0237] (Symbol Explanation)

[0238] 1: Two-dimensional material layer; 1a: Part 1; 1b: Part 2; 1c: Part 3; 1d: Contact portion; 1e: Supporting portion; 2a, 2a1, 2a2: First electrode; 2b: Second electrode; 2c: Third electrode; 3: Insulating layer; 4: Semiconductor layer; 5: Coating film; 6: Ferroelectric layer; 7: Contact layer; 8: Conductor; 11: First two-dimensional material layer; 12: Second two-dimensional material layer; 13: Fourth two-dimensional material layer; 14: Fifth two-dimensional material layer; 30: Recess; 31: Opening; 31A: First opening; 31B: ... 2. Opening; 41: First surface; 42: Second surface; 61: First ferroelectric layer; 62: Second ferroelectric layer; 71: First contact layer; 72: Second contact layer; 100, 101, 102, 103, 104, 105, 106, 107, 200, 201, 202, 203: Gas detectors; 100A: First detection unit; 100B: Second detection unit; 301: Vertical scanning circuit; 302: Horizontal scanning circuit; 303: Power supply circuit; 304: Output circuit; 1000, 2000: Gas detector array.

Claims

1. A gas detector for detecting a gas of a target object, wherein, The gas detector includes: Insulating layer; At least one first electrode is disposed on the insulating layer; At least one two-dimensional material layer is electrically connected to the at least one first electrode; as well as At least one second electrode is electrically connected to the at least one first electrode via the at least one two-dimensional material layer. The at least one two-dimensional material layer has an exposed surface that faces outwards. The at least one two-dimensional material layer is configured to perform photoelectric conversion when electromagnetic waves in the wavelength range of the gas absorbed by the object being detected are incident on it.

2. The gas detector according to claim 1, wherein, The gas detector also features: A semiconductor layer having a first surface and a second surface located on the side opposite to the first surface; and The third electrode is disposed on the second surface. The insulating layer is disposed on the first surface. The at least one second electrode is disposed on the insulating layer. The semiconductor layer is configured to perform photoelectric conversion when electromagnetic waves in the wavelength range that are incident on the gas of the object being detected are absorbed.

3. The gas detector according to claim 1 or 2, wherein, The at least one first electrode and the at least one second electrode have: a first group of first electrodes and a second electrode; and a second group of first electrodes and second electrodes, arranged at a distance from the first group of first electrodes and second electrodes. The at least one two-dimensional material layer comprises: a first two-dimensional material layer electrically connecting the first electrode and the second electrode of the first group; and a second two-dimensional material layer disposed at a distance from the first two-dimensional material layer and electrically connecting the first electrode and the second electrode of the second group. The first two-dimensional material layer has the exposed surface. The gas detector also includes a first coating that covers the second two-dimensional material layer. The first coating is configured to impede the transmission of gas from the object being detected.

4. The gas detector according to claim 3, wherein, The at least one first electrode and the at least one second electrode further include a third group of first electrodes and second electrodes, wherein the third group of first electrodes and second electrodes are arranged at intervals from each of the first group of first electrodes and second electrodes and the second group of first electrodes and second electrodes. The at least one two-dimensional material layer further comprises a third two-dimensional material layer, which is disposed spaced apart from the first two-dimensional material layer and the second two-dimensional material layer, and electrically connects the first electrode and the second electrode of the third group. The gas detector also has a second coating covering the third two-dimensional material layer. The second coating is configured to block the transmission of electromagnetic waves in the wavelength range absorbed by the gas of the object being detected.

5. The gas detector according to claim 3 or 4, wherein, The gas detector also features: The first ferroelectric layer is connected to the first two-dimensional material layer or is connected to the first two-dimensional material layer via the insulating layer; as well as The second ferroelectric layer is in contact with the second two-dimensional material layer, or connected to the second two-dimensional material layer via the insulating layer. The materials constituting the first ferroelectric layer and the second ferroelectric layer are materials that are polarized when incident with electromagnetic waves in the wavelength range absorbed by the gas of the object being detected.

6. The gas detector according to any one of claims 3 to 5, wherein, The gas detector also features: The first contact layer is in contact with the first two-dimensional material layer; as well as The second contact layer is in contact with the second two-dimensional material layer. The materials constituting the first contact layer and the second contact layer are materials capable of supplying electrons or holes to the first two-dimensional material layer or the second two-dimensional material layer.

7. The gas detector according to any one of claims 3 to 6, wherein, The gas detector also features: The first conductor is in contact with the first two-dimensional material layer; and The second conductor is in contact with the second two-dimensional material layer.

8. The gas detector according to any one of claims 3 to 7, wherein, The first two-dimensional material layer and the second two-dimensional material layer each have: a first portion and a second portion disposed at intervals on the insulating layer; and a third portion disposed between the first portion and the second portion.

9. The gas detector according to claim 1, wherein, The gas detector also includes a semiconductor layer having a first surface and a second surface located on the side opposite to the first surface. The insulating layer is disposed on the first surface. At least one opening is formed in the insulating layer to expose a portion of the first surface. The at least one two-dimensional material layer electrically connects the at least one first electrode to the semiconductor layer, and extends from the at least one opening to the insulating layer. The at least one second electrode is disposed on the second surface and is electrically connected to the at least one two-dimensional material layer via the semiconductor layer.

10. The gas detector according to claim 9, wherein, The at least one opening has a first opening and a second opening that are spaced apart from each other. The at least one first electrode has a first electrode and a second electrode arranged at intervals from each other. The at least one two-dimensional material layer has: a fourth two-dimensional material layer that extends from the first opening to the insulating layer and electrically connects the first electrode to the semiconductor layer; And a fifth two-dimensional material layer, extending from the second opening to the insulating layer and electrically connecting the second and first electrodes to the semiconductor layer. The gas detector also has a third coating that covers the fifth two-dimensional material layer. The third coating is configured to impede the transmission of gas from the object being detected.

11. The gas detector according to claim 10, wherein, The at least one opening further includes a third opening, which is disposed at a distance from each of the first and second openings. The at least one first electrode further includes a third first electrode, which is disposed at a distance from each of the first and second first electrodes. The at least one two-dimensional material layer includes a sixth two-dimensional material layer that extends from the third opening onto the insulating layer, electrically connecting the third first electrode to the semiconductor layer. The gas detector also has a fourth coating that covers the sixth two-dimensional material layer. The fourth coating is configured to block the transmission of electromagnetic waves in the wavelength range absorbed by the gas of the object being detected.

12. The gas detector according to claim 10 or 11, wherein, The portion of the fourth two-dimensional material layer disposed on the insulating layer has a first end face extending in a direction intersecting the first surface. The portion of the fourth two-dimensional material layer disposed within the first opening has a second end face extending in the direction of the intersection. The portion of the fifth two-dimensional material layer disposed on the insulating layer has a third end face extending in the direction of the intersection. The portion of the fifth two-dimensional material layer disposed within the second opening has a fourth end face extending in the direction of the intersection. The sum of the areas of the second end faces is greater than the sum of the areas of the first end faces. The total area of ​​the fourth end face is greater than the total area of ​​the third end face.

13. A gas detector array, wherein, The gas detector array includes a plurality of gas detectors as described in any one of claims 1 to 12. The plurality of gas detectors are each arranged in an array.

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