Sensor

Abstract

To provide a technique capable of suppressing a decrease in carrier mobility.SOLUTION: A sensor detects a target substance, and comprises a first film formed from hexagonal boron nitride, a channel region formed from graphene on the first film in one direction, a second film formed from hexagonal boron nitride on the channel region in the one direction, 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 with the second film via space in the one direction, and 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] Sensors using field-effect transistors have been proposed. For example, Patent Document 1 discloses a sensor using graphene in a gas detection layer as a channel region. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6777846 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the inventors have found that the technology described in Patent Document 1, which uses graphene, causes a decrease in carrier mobility due to the surrounding atmosphere and shape. Therefore, there is a need for a technology that can suppress the decrease in carrier mobility. [Means for solving the problem]

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

[0006] (1) According to one embodiment of the present disclosure, there is provided a sensor for detecting a target substance, comprising: a first film formed of hexagonal boron nitride; a channel region formed of graphene on the first film in one direction; a second film formed of hexagonal boron nitride on the channel region in the one direction; 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 in the one direction with a space interposed between it and the second film; and a trapping film provided on a surface of the gate electrode facing the channel region. According to this embodiment of the sensor, graphene forming the channel region is sandwiched between the first film and the second film formed of hexagonal boron nitride, thereby suppressing a decrease in carrier mobility due to the surrounding atmosphere or shape.

[0007] (2) In the sensor described in (1) above, the channel region may be covered with at least one of the first film and the second film. In this sensor, the graphene forming the channel region is covered with at least one of the first film and the second film formed of hexagonal boron nitride, which can suppress adsorption of gases and foreign matter from the surrounding atmosphere, thereby effectively suppressing a decrease in carrier mobility.

[0008] (3) In the sensor described in (1) above, the channel region may have a thickness of 0.5 nm or less. In this sensor, the channel region is formed of a single layer of graphene due to the thickness of the channel region being 0.5 nm or less, thereby maintaining high carrier mobility.

[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. 2 is a schematic diagram of a member having a channel region as viewed from the gate electrode side. 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 may be, but is not limited to, a gas such as air or exhaled breath, or a liquid such as water. The sensor 100 of this embodiment is a FET sensor including a field-effect transistor. The sensor 100 includes a first film 22, a channel region 20 formed on the first film 22, a second film 24 formed on the channel region 20, 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. In other words, the first film 22, the channel region 20, and the second film 24 overlap in one direction.

[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, antigens, 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, etc. The proteins are not particularly limited, and examples thereof include disease-related proteins and antibodies, etc. The chemical substances are not particularly limited, and examples thereof include drugs and hormones, etc. 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 second film 24 from the channel region 20, with a space between the gate electrode 50 and the second film 24. The gate electrode 50 is provided on a 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 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. Here, single layer graphene refers to graphene having a thickness of 0.5 nm or less. The thickness of the channel region 20 is not particularly limited, but is preferably 0.335 nm or more and 50 nm or less, more preferably 20 nm or less, and even more preferably less than 0.67 nm.

[0022] In this embodiment, the channel region 20 is sandwiched between a first film 22 made of hexagonal boron nitride (hBN) and a second film 24 made of hexagonal boron nitride. Specifically, in one direction, an insulating film 15 is formed on the substrate 10, and the first film 22, the channel region 20, and the second film 24 are formed on the insulating film 15 in this order.

[0023] The thickness of the first film 22 is not particularly limited, but is preferably 0.3 nm to 200 nm, more preferably 0.5 nm to 150 nm, and even more preferably 1 nm to 100 nm. By setting the thickness within the above preferred range, it is possible to suppress a decrease in carrier mobility due to unevenness of the substrate 10 or residual charges on the substrate 10.

[0024] The thickness of the second film 24 is not particularly limited, but is preferably 0.3 nm to 200 nm, more preferably 0.5 nm to 150 nm, and even more preferably 1 nm to 100 nm. By setting the thickness within the above preferred range, it is possible to suppress a decrease in carrier mobility due to the adsorption of gases and foreign matter from the surrounding atmosphere.

[0025] 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).

[0026] 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.

[0027] 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.

[0028] According to the sensor 100 of this embodiment, by providing the first film 22, the channel region 20, and the second film 24 in this order, graphene forming the channel region 20 is sandwiched between the first film 22 and the second film 24 formed of hexagonal boron nitride. The first film 22 and the second film 24 formed of hexagonal boron nitride are both electrically insulating and flat, and are bonded to the graphene by a relatively weak force, i.e., van der Waals force. Therefore, according to the sensor 100 of this embodiment, by providing the first film 22, a decrease in carrier mobility due to unevenness of the substrate 10 and residual charge on the substrate 10 can be suppressed. Furthermore, according to the sensor 100 of this embodiment, by providing the second film 24, adsorption of gases and foreign matter from the surrounding atmosphere to the channel region 20 can be suppressed. As a result, a decrease in carrier mobility due to adsorption of gases and foreign matter to the channel region 20 can be suppressed. Furthermore, the sensor 100 of this embodiment can maintain high carrier mobility, making it possible to detect an object at an extremely low concentration.

[0029] Furthermore, the channel region 20 in the sensor 100 of this embodiment is formed of a single layer of graphene, which allows the sensor 100 of this embodiment to maintain high carrier mobility.

[0030] 2 is a schematic diagram of a member having a channel region 20 as viewed from the gate electrode 50 side. As can be seen from Fig. 2, the channel region 20 is covered with a second film 24. In this embodiment, the area of ​​the second film 24 is larger than the area of ​​the channel region 20 in a plane perpendicular to the stacking direction of the channel region 20 and the second film 24.

[0031] According to the sensor 100 of this embodiment, the channel region 20 is covered with the second film 24, and therefore even if the target substance is adsorbed to the second film 24, the target substance can be prevented from coming into contact with the channel region 20. Therefore, according to the sensor 100 of this embodiment, it is possible to suppress the generation of noise and to suppress changes in the detection signal, and as a result, it is possible to accurately measure the concentration of the target substance.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] First, a substrate 10 having an insulating film 15 formed on one surface is prepared. Then, a first film 22 is formed on the insulating film 15, and a channel region 20 is formed on the first film 22, and the first film 22 and the channel region 20 are patterned into desired shapes. Then, a second film 24 is formed on the channel region 20, and the second film 24 is patterned into desired shapes. Then, films for the source electrode 30 and the drain electrode 40 are formed, and the source electrode 30 and the drain electrode 40 are patterned into desired shapes. In this way, a member including the substrate 10 can be manufactured.

[0036] 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.

[0037] B. Variations The configuration of the sensor 100 in the above embodiment is merely an example 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 be used as the trapping film 60. Furthermore, although the channel region 20 is covered with the second film 24, this is not limiting, and the channel region 20 may not be partially covered with the second film 24. Furthermore, the channel region 20 may be covered with the first film 22, or may be covered with both the first film 22 and the second film 24. In other words, the channel region 20 may be covered with at least one of the first film 22 and the second film 24.

[0038] 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]

[0039] REFERENCE SIGNS LIST 10...substrate, 15...insulating film, 20...channel region, 22...first film, 24...second film, 30...source electrode, 40...drain electrode, 50...gate electrode, 60...trapping film, 70...substrate, 72...insulating film, 100...sensor

Claims

1. A sensor for detecting a target substance, a first film formed of hexagonal boron nitride; a channel region formed of graphene on the first film in one direction; a second film formed of hexagonal boron nitride on the channel region in the one direction; 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 in the one direction with a space interposed between the gate electrode and the second film; 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 covered with at least one of the first film and the second film; A sensor characterized by:

3. 2. The sensor of claim 1, The thickness of the channel region is 0.5 nm or less. A sensor characterized by:

Images