Sensor

Abstract

To provide a technique capable of suppressing adhesion of graphene of a channel region to a board.SOLUTION: A sensor detects a target substance, and has a board, a channel region that is formed from graphene and is provided with the board via space, a source electrode connected to one end of the channel region, a drain electrode connected to the other end of the channel region, and a gate electrode that is formed in a side opposite to the board relative to the channel region and is formed with the channel region via space. The sensor also has a capturing film provided on a surface that is the surface of the gate electrode and faces the channel region.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to sensors. [Background technology]

[0002] Field-effect transistors using graphene as a channel have been proposed. For example, Patent Document 1 discloses a field-effect transistor in which a graphene layer in the channel region is suspended in mid-air. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-004718 Summary of the Invention [Problem to be solved by the invention]

[0004] The inventors of the present application have found that with the technology described in Patent Document 1, when a solution treatment is performed for cleaning after the graphene layer is formed, the graphene layer may stick to the substrate due to sticking, and the suspended state of the graphene layer may not be maintained. Therefore, there is a need for a technology that can prevent graphene in the channel region from sticking to the substrate. [Means for solving the problem]

[0005] The present disclosure can be realized in the following forms.

[0006] (1) According to one aspect of the present disclosure, there is provided a sensor for detecting a target substance. The sensor includes a substrate, a channel region formed of graphene and spaced apart from the substrate, a source electrode connected to one end of the channel region, a drain electrode connected to the other end of the channel region, and a gate electrode formed on the opposite side of the channel region from the substrate and spaced apart from the channel region, and further includes a trapping film provided on a surface of the gate electrode facing the channel region. According to this aspect of the sensor, the gate electrode is formed on the opposite side of the channel region from the substrate and spaced apart from the channel region, so that graphene attached to the substrate can be attracted by applying a voltage to the gate electrode. As a result, graphene in the channel region can be prevented from adhering to the substrate.

[0007] (2) In the sensor described in (1), the channel region may be formed of a single layer of graphene. In this sensor, the channel region is formed of a single layer of graphene, which can suppress a decrease in carrier mobility.

[0008] (3) In the sensor described in (1), the channel region may be formed of turbostratic stacked graphene. In this sensor, the channel region is formed of turbostratic stacked graphene, which can suppress a decrease in carrier mobility due to adhesion of gases or foreign matter present in the surrounding atmosphere to the graphene.

[0009] The present disclosure can be realized in various forms, for example, a method for manufacturing a sensor, a method for monitoring a target substance using a sensor, and the like. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 2 is a cross-sectional view schematically illustrating the general configuration of a sensor. [Figure 2]FIG. 10 is an explanatory diagram illustrating a schematic configuration of a sensor according to a second embodiment. [Figure 3] FIG. 10 is an explanatory diagram schematically illustrating the general configuration of a sensor according to a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] A. First embodiment FIG. 1 is a cross-sectional view illustrating a schematic configuration of a sensor 100 according to an embodiment of the present disclosure. For convenience of illustration, FIG. 1 illustrates only essential components of the sensor 100. The sensor 100 detects a target substance contained in a sample. The sample is not particularly limited, but examples thereof include gases such as air and exhaled breath, and liquids such as water. The sensor 100 of this embodiment is a FET sensor including a field-effect transistor. The sensor 100 includes a substrate 10, a channel region 20 provided with a space between the substrate 10, a source electrode 30 connected to one end of the channel region 20, a drain electrode 40 connected to the other end of the channel region 20, a gate electrode 50, and a trapping film 60 provided on a surface of the gate electrode 50 facing the channel region 20.

[0012] The capture membrane 60 of this embodiment is a membrane containing a molecularly imprinted polymer (MIP). A space for capturing a target substance is formed in this molecularly imprinted polymer. This space is formed according to the size and surface structure of the target substance by a method described below. The molecularly imprinted polymer recognizes and captures the target substance by chemically interacting with the target substance in this space. The chemical interaction is not particularly limited, but examples thereof include hydrogen bonding.

[0013] The molecularly imprinted polymer is not particularly limited, but preferably has a non-covalent functional group in the main chain or branched chain. Examples of the non-covalent functional group include, but are not particularly limited to, an OH group. Examples of the molecularly imprinted polymer include, but are not particularly limited to, polypyrrole, polyaniline, acrylic polymers, photocurable polymers, and photosolubilizable polymers. The monomer for forming the molecularly imprinted polymer is not particularly limited, but preferably has a double bond for polymerization. The double bond may be present in the molecular chain or may be a double bond of an aromatic ring. Furthermore, from the viewpoint of the polymerization reaction, a monomer having an amino group is preferred. Therefore, the monomer for forming the molecularly imprinted polymer is preferably a compound having a double bond, an OH group, and an amino group.

[0014] Although one type of monomer may be used as the monomer for forming the molecularly imprinted polymer, it is preferable to use two or more types of monomers. When two or more types of monomers are used, a monomer without a non-covalent functional group may be included. The monomer for forming the molecularly imprinted polymer may be either water-soluble or water-insoluble, but a water-soluble monomer is preferable from the viewpoint of ease of handling. Specific examples of the monomer for forming the molecularly imprinted polymer include pyrrole, aniline, ortho-phenylenediamine, acrylamide, N,N'-methylenebisacrylamide, aminophenylboronic acid, aminophenol, aminobenzoic acid, and dopamine.

[0015] The target substance is not particularly limited, and examples thereof include substances having a three-dimensional structure, chemical substances, fine particles, etc. The substances having a three-dimensional structure are not particularly limited, and examples thereof include viruses, fungi, microorganisms, proteins, etc. The fungi are not particularly limited, and examples thereof include bacteria, fungi, archaea, etc. The viruses and fungi may be pathogenic to animals such as humans. The microorganisms are not particularly limited, and examples thereof include yeast and algae. The proteins are not particularly limited, and examples thereof include disease-related proteins and antibodies. The chemical substances are not particularly limited, and examples thereof include drugs and hormones. The fine particles are not particularly limited, and examples thereof include pollen, PM2.5, yellow sand, aerosols, etc.

[0016] The target substance may be one or more types, but is preferably one type from the viewpoint of preventing a decrease in detection accuracy. In an embodiment in which two or more types of target substances are detected, two or more types of spaces are formed in the molecular imprinted polymer according to the target substances.

[0017] The gate electrode 50 is formed on the opposite side of the channel region 20 from the substrate 10, with a space between the gate electrode 50 and the channel region 20. The gate electrode 50 is provided on the substrate 70 via an insulating film 72. When a target substance is captured in the space formed in the capture film 60, the value of the current flowing through the gate electrode 50 changes, and the target substance can be detected based on this value.

[0018] The gate electrode 50 is not particularly limited as long as it is conductive, and may be formed of, for example, a metal, conductive carbon, a conductive polymer, etc. The metal is not particularly limited, and examples thereof include gold, silver, copper, aluminum, chromium, and indium tin oxide (ITO). The gate electrode 50 of this embodiment is formed of gold and chromium.

[0019] The substrate 70 is not particularly limited, but may be made of, for example, glass, ceramics, resin, etc. The resin is not particularly limited, but examples thereof include polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyether ether ketone, polycarbonate (PC), etc. The substrate 70 of this embodiment is made of silicon.

[0020] The insulating film 72 is not particularly limited, but may be formed of, for example, silica (silicon oxide), alumina (aluminum oxide), a self-assembled monolayer, polystyrene, polyvinylphenol, polyvinyl alcohol, polymethyl methacrylate, polydimethylsiloxane, polysilsesquioxane, an ionic liquid, polytetrafluoroethylene, etc. The insulating film 72 of this embodiment is formed of silica.

[0021] The channel region 20 of this embodiment is formed of graphene. The channel region 20 may be formed of a single layer of graphene, or may be formed of multiple layers of graphene. When the channel region 20 is formed of multiple layers of graphene, it may be formed of turbostratic stacked graphene. Here, turbostratic stacked graphene refers to multiple layers of graphene that do not have a specific stacking order. The channel region 20 in the sensor 100 of this embodiment is formed of a single layer of graphene. The thickness of the channel region 20 is not particularly limited, but is preferably 0.335 nm to 50 nm, more preferably 0.67 nm to 40 nm, and even more preferably 1.005 nm to 20 nm.

[0022] The channel region 20 of this embodiment is provided with a space between it and the substrate 10. In this embodiment, an insulating film 15 is provided between the source electrode 30 and the substrate 10, and an insulating film 15 is also provided between the drain electrode 40 and the substrate 10, so that a space exists between the channel region 20 and the substrate 10. The distance between the substrate 10 and the channel region 20 is not particularly limited, but is preferably 100 nm to 500 nm, more preferably 150 nm to 450 nm, and even more preferably 200 nm to 400 nm.

[0023] The substrate 10 is not particularly limited and may be formed from an inorganic material or an organic material. Examples of inorganic materials include, but are not particularly limited to, glass, ceramics, and metal. Examples of organic materials include, but are not particularly limited to, resin and paper. The member including the substrate 10 and the member including the gate electrode 50 are bonded together by an adhesive member (not shown).

[0024] The source electrode 30 and the drain electrode 40 may be formed from, but are not limited to, metals, conductive polymers, conductive carbon, conductive organic-inorganic composite materials, etc. Examples of metals include, but are not limited to, gold, silver, copper, platinum, aluminum, and chromium. Examples of conductive polymers include, but are not limited to, PEDOT and PSS. Examples of conductive carbon include, but are not limited to, conductive carbon nanotubes and graphene. The substrate 10, the gate electrode 50, the source electrode 30, and the drain electrode 40 may be surface-treated, for example, by forming a self-assembled monolayer to adjust the liquid repellency of the surface. In this embodiment, the source electrode 30 and the drain electrode 40 are both formed from gold and chromium.

[0025] The insulating film 15 is not particularly limited, but may be formed of, for example, silica (silicon oxide), alumina (aluminum oxide), a self-assembled monolayer, polystyrene, polyvinylphenol, polyvinyl alcohol, polymethyl methacrylate, polydimethylsiloxane, polysilsesquioxane, an ionic liquid, polytetrafluoroethylene, etc. The insulating film 15 of this embodiment is formed of silica.

[0026] According to the sensor 100 of this embodiment, the gate electrode 50 is formed with a space between it and the channel region 20. Therefore, even if graphene is attached to the substrate 10, the attached graphene can be separated from the substrate 10 by applying a voltage to the gate electrode 50 to attract the attached graphene. As a result, according to the sensor 100 of this embodiment, a decrease in carrier mobility due to unevenness of the substrate 10 or residual charge on the substrate 10 can be suppressed, and high carrier mobility can be maintained. Therefore, according to the sensor 100 of this embodiment, it is possible to detect a target substance at an extremely low concentration.

[0027] Furthermore, the channel region 20 in the sensor 100 of this embodiment is formed of a single layer of graphene. Therefore, the sensor 100 of this embodiment can suppress a decrease in carrier mobility.

[0028] The uses of the sensor 100 of this embodiment are not particularly limited, but may be applied to, for example, monitoring of viruses and bacteria, disease testing by measuring breath and detection of illegal drugs such as narcotics, detection of dangerous materials such as landmines and explosives, personal authentication by measuring multiple odor components, air quality monitoring, drone inspection and monitoring, food hygiene management, water quality management, and health management of humans, animals, and plants.

[0029] The method for producing a film containing the molecularly imprinted polymer of this embodiment is not particularly limited, but can be, for example, produced by the following method. Hereinafter, an example of a method for producing a molecularly imprinted polymer in the case where the target substance is Escherichia coli will be described. First, a substrate 70 on which an insulating film 72 and a gate electrode 50 are laminated in this order is washed with ethanol and ultrapure water, and then the potential is scanned from -0.7 V to +0.7 V five times in a solution containing 0.1 M LiClO4 and 50 mM pyrrole, thereby carrying out electropolymerization of pyrrole. Then, 1×10 4 After adding CFU / mL of E. coli to the electropolymerization cell, the potential is scanned for five more cycles at a scan rate of 100 mV / s to synthesize a molecularly imprinted polymer on the surface of the gate electrode 50. This is followed by ultrasonic cleaning in water for 5 minutes or 1×10 -3 A capture membrane can be produced by removing the E. coli used for template formation from the molecularly imprinted polymer by incubation in M ​​detergent.

[0030] The method for manufacturing the sensor 100 of this embodiment is not particularly limited, but it can be manufactured, for example, by the following method: An example of the method for manufacturing the sensor 100 will be described below.

[0031] First, a substrate 10 having an insulating film 15 formed on one surface is prepared. Then, a single-layer graphene film is formed on the insulating film 15, and the graphene is patterned into a desired shape. After that, a source electrode 30 and a drain electrode 40 are formed, and the source electrode 30 and the drain electrode 40 are patterned into a desired shape. Then, by sacrificial layer etching, the insulating film 15 below the graphene that forms the channel region 20 is selectively removed so as to have the desired shape. In this way, a member including the substrate 10 can be manufactured.

[0032] Next, a substrate 70 is prepared. Then, an insulating film 72 is formed on the substrate 70, and then a gate electrode 50 is formed. Then, a trapping film 60 is formed on the gate electrode 50. This allows a member including the gate electrode 50 to be manufactured. Then, the member including the substrate 10 and the member including the gate electrode 50 are joined together with a member not shown, thereby allowing the sensor 100 of this embodiment to be manufactured.

[0033] B. Second embodiment 2 is an explanatory diagram illustrating a schematic configuration of a sensor 100a according to the second embodiment. The sensor 100a according to the second embodiment is different from the sensor 100 according to the first embodiment in that it uses turbostratic stacked graphene instead of single-layer graphene, but is otherwise the same.

[0034] The manufacturing method of the sensor 100a of the second embodiment is different from the manufacturing method of the sensor 100 of the first embodiment in that the graphene film is formed multiple times, but otherwise the manufacturing method is the same. Note that in the manufacturing method of the sensor 100a of the present embodiment, the graphene film is formed three times, but it may be formed two times, or four or more times.

[0035] The channel region 20 in the sensor 100a of this embodiment is formed of turbostratic stacked graphene. Therefore, the sensor 100a of this embodiment can suppress a decrease in carrier mobility due to adhesion of gases or foreign matter present in the surrounding atmosphere to the graphene. As a result, the sensor 100a of this embodiment can detect an object at an extremely low concentration.

[0036] C. Third embodiment FIG. 3 is an explanatory diagram illustrating a schematic configuration of a sensor 100b according to a third embodiment. The sensor 100b according to the second embodiment differs from the sensor 100a according to the second embodiment in the shape of the channel region 20b and the shapes of the source electrode 30b and the drain electrode 40b, but is otherwise the same. These differences are due to the manufacturing method. Specifically, the manufacturing method of the sensor 100b according to the third embodiment differs from the manufacturing method of the sensor 100a according to the second embodiment in that the source electrode 30b and the drain electrode 40b are formed before the third layer of graphene is formed, and that after the third layer of graphene is formed, the source electrode 30b and the drain electrode 40b are further stacked to hold down the third layer of graphene, but is otherwise the same.

[0037] The channel region 20b of the sensor 100b of this embodiment is also formed of turbostratic stacked graphene. Therefore, the sensor 100b of this embodiment can suppress a decrease in carrier mobility due to adhesion of gases or foreign matter present in the surrounding atmosphere to the graphene. As a result, the sensor 100b of this embodiment can detect an object at an extremely low concentration.

[0038] D. Variations The configurations of the sensors 100, 100a, and 100b in the above embodiments are merely examples and can be modified in various ways. In this embodiment, the trapping film 60 is a film containing a molecularly imprinted polymer, but is not limited to this. For example, a metal complex such as copper phthalocyanine may also be used as the trapping film 60.

[0039] The present invention is not limited to the above-described embodiments and can be realized in various configurations without departing from the spirit of the present invention. For example, the technical features in the embodiments and examples corresponding to the technical features in each aspect described in the Summary of the Invention section can be appropriately replaced or combined to solve some or all of the above-described problems or achieve some or all of the above-described effects. Furthermore, if a technical feature is not described as essential in this specification, it can be deleted as appropriate. [Explanation of symbols]

[0040] 10...substrate, 15...insulating film, 20...channel region, 20b...channel region, 30, 30b...source electrode, 40, 40b...drain electrode, 50...gate electrode, 60...trapping film, 70...substrate, 72...insulating film, 100, 100a, 100b...sensor

Claims

1. Detecting the target substance, A substrate; a channel region formed of graphene and provided with a space between it and the substrate; a source electrode connected to one end of the channel region; a drain electrode connected to the other end of the channel region; a gate electrode formed on the opposite side of the substrate with respect to the channel region, with a space interposed between the gate electrode and the channel region; A sensor having a trapping film provided on a surface of the gate electrode facing the channel region; A sensor comprising:

2. 2. The sensor of claim 1, The channel region is formed of a single layer of graphene. A sensor characterized by:

3. 2. The sensor of claim 1, The channel region is formed of turbostratic stacked graphene. A sensor characterized by:

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