JP4366421B2 - Sensor and manufacturing method thereof - Google Patents

Description

  The present invention relates to a sensor for detecting a substance adsorbed and desorbed on a semiconductor surface and a method for manufacturing the same. It can be applied to gas sensors and biosensors.

  Various methods have been proposed for sensors for detecting the presence and concentration of substances such as gas sensors and biosensors.

Among them, a semiconductor sensor is a sensor that detects a substance by using a metal oxide semiconductor having a property that a resistance value is changed by adsorption / desorption of the substance, and is used for a gas leak alarm or the like. As semiconductors used for gas sensors, oxide semiconductors, particularly tin oxide, are widely used. A problem of current gas sensor elements is selective detection of a gas to be detected.
JP-A-4-344450

  When a metal oxide semiconductor material is used for the gas sensor element, the width of the depletion layer present on the surface of the metal oxide changes due to adsorption / desorption of molecules adsorbed on the surface of the metal oxide, and the change in resistance value associated therewith is detected. There are many. For example, in the case of tin oxide, the adsorbed oxygen is removed from the tin oxide surface by a chemical reaction (combustion) between the gas and the adsorbed oxygen on the surface of the tin oxide, and as a result, the resistance value is reduced by reducing the depletion layer width.

Because of the operation principle as described above, when the metal oxide semiconductor is used alone, it is difficult to detect only the gas to be detected in an atmosphere in which a plurality of gas species capable of changing the depletion layer width are mixed.
Accordingly, an object of the present invention is to provide a sensor that detects a gas to be detected.

Therefore, the present invention provides
A semiconductor film having a plurality of mesopores and containing an oxide;
An electrode electrically connected to the semiconductor film,
A sensor in which at least a part of a surface in the mesopore is coated with an organic substance is provided.

The present invention also provides:
A semiconductor film having a plurality of mesopores and containing an oxide;
An electrode electrically connected to the semiconductor film,
A sensor in which at least a part of a surface in the mesopore is coated with an oxide different from the oxide is provided.

The present invention also provides:
A semiconductor film having a plurality of mesopores and containing tin oxide;
An electrode electrically connected to the semiconductor film,
The present invention provides a sensor in which inorganic particles are supported in the mesopores.

The present invention also provides:
A method for producing a sensor, comprising preparing a reaction solution containing a metal compound and a surfactant, and applying the reaction solution on a substrate;
Holding the substrate coated with the reaction solution in an atmosphere containing water vapor, and forming a film containing a metal oxide and a surfactant on the substrate;
Removing the surfactant from the film to form a film having a plurality of mesopores;
And a step of supporting inorganic particles in the mesopores.

The present invention also provides:
A method for manufacturing a sensor, comprising:
Preparing a reaction solution containing a metal compound and a surfactant, and applying the reaction solution on a substrate;
Holding the substrate coated with the reaction solution in an atmosphere containing water vapor, and forming a film containing a metal oxide and a surfactant on the substrate;
Removing the surfactant from the film to form a film having a plurality of mesopores;
And a step of coating at least a part of the surface in the mesopores with an organic substance.

The present invention also provides:
A method for manufacturing a sensor, comprising:
Preparing a reaction solution containing a metal compound and a surfactant, and applying the reaction solution on a substrate;
Holding the substrate coated with the reaction solution in an atmosphere containing water vapor, and forming a film containing a metal oxide and a surfactant on the substrate;
Removing the surfactant from the film to form a film having a plurality of mesopores;
And a step of coating at least a part of the surface of the mesopores with an inorganic oxide.

Furthermore, the present invention provides
A semiconductor film having a plurality of mesopores and containing an oxide;
An electrode electrically connected to the semiconductor film;
A layer containing a material different from the hole wall on the hole surface of the mesopores,
The present invention provides a sensor in which the low efficiency of the semiconductor film changes when a substance to be detected comes into contact with the layer.

The present invention
A semiconductor film having a plurality of mesopores and containing an oxide;
An electrode electrically connected to the semiconductor film;
A layer containing a material different from the hole wall on the surface of the mesopores,
The present invention provides a sensor in which the resistivity of the semiconductor film changes when a substance to be detected that has passed through the layer contacts the semiconductor film.

  The present invention can provide a sensor capable of performing selective detection of gas molecules.

  Details of the present invention will be described. First, the outline of the invention will be described with reference to FIGS.

  FIG. 1 is a configuration diagram as a sensor, in which an electrode 12 is formed on a substrate 13 and a porous oxide semiconductor film 11 is formed thereon as a sensitive portion. FIG. 2 is a cross-sectional view taken along A1-A2 in FIG. 1, and the electrode 12 and the porous oxide semiconductor film 11 are formed on the substrate 13. The porous oxide semiconductor film has a plurality of mesopores 14. Although the description of the meso hole will be described later, FIGS. 3 to 5 are enlarged views of the meso hole. FIG. 3 is a diagram showing that the surfaces in the mesopores are covered with the organic matter 16. FIG. 4 is a diagram showing that the surfaces in the mesopores are covered with an oxide 17 different from the oxide contained in the porous oxide semiconductor film 11. FIG. 5 is a view showing that inorganic particles 23 are supported in the mesopores. In the present invention, as shown in FIGS. 3 to 5, selective detection of gas molecules can be performed by covering the surface of the mesopores and supporting inorganic particles.

  Here, “mesopores” are based on the IUPAC classification, and pores having a pore diameter of 2 nm to 50 nm are defined as mesopores. Furthermore, those having a pore diameter of less than 2 nm are defined as micropores, and those having a pore diameter of greater than 50 nm are defined as macropores.

  In a structure having macropores having a larger pore diameter than mesopores, the specific surface area is reduced as compared with the whole structure having a plurality of mesopores. As the amount decreases, the amount of inorganic particles, organic matter, and oxides that can be supported in the pores may decrease. Moreover, there is a possibility that the amount of gas molecules to be detected decreases. On the other hand, in a structure having micropores smaller than mesopores, it may be difficult to introduce inorganic particles into the pores and to quickly adsorb and desorb gas molecules to be detected on the pore surface. .

  Therefore, a structure having mesopores is an optimal structure for detecting small molecules such as a gas sensor and a biosensor.

  The “porous oxide semiconductor film” is preferably a continuous film. There is a possibility that the utilization efficiency as a sensor is higher and the response speed as a sensor is faster than the porous oxide semiconductor film 11 is an aggregate of particles.

  When the porous oxide semiconductor film 11 is an aggregate of particles, the specific surface area is smaller than that of a structure having mesopores, so that the device utilization efficiency may not be increased and the response speed as a sensor may be slow. Because there is.

The “oxide contained in the porous oxide semiconductor film” is preferably a metal oxide that exhibits semiconductor characteristics. Metal oxides exhibiting such characteristics include tin oxide (SnO ₂ ), zinc oxide (ZnO), niobium oxide (Nb ₂ O ₅ ), and tungsten oxide (WO ₃ ). In this case, tin oxide (SnO ₂ ) is preferable.

As the “organic substance”, any substance can be basically used as long as it can selectively capture the substance to be detected and change the resistance value of the metal oxide. In particular, an organic substance containing a Lewis base is preferably used. Such an organic substance is an organic substance having the following functional groups and bonds, for example.
Example:
Functional group halogen, alcohol, amine, nitrile, nitro, sulfide, sulfoxide, sulfone, thiol, carbonyl, aldehyde, ketone, carboxylic acid, amide, carboxylic acid chloride, carboxylic acid anhydride, organic carboxylic acid bond ether bond, ester bond Amide bond

  The “oxide different from the oxide contained in the porous oxide semiconductor film 11” is an oxide that selectively separates a specific gas or an oxide that reacts with a specific gas, and the porous oxide semiconductor film Any resistance value can be used. An example is silicon oxide. Silicon oxide selectively permeates a gas having a small molecular weight. More specifically, since hydrogen selectively permeates, it can be used as a hydrogen sensor.

  As the “inorganic particles”, any substance may be used as long as it has a function of separating or decomposing the detection target from the gas or liquid containing the detection target by catalytic action. For example, palladium (Pd), platinum (Pt), ruthenium (Ru), silver (Ag), cobalt (Co), gold (Au), nickel (Ni), copper (Cu), manganese (Mn), iron (Fe) Chrome (Cr) and vanadium (V) are preferable. Particularly, for hydrogen gas, palladium (Pd) and platinum (Pt) are preferable because they exhibit excellent selectivity.

  Moreover, you may use the metal oxide particle | grains which have the same effect | action. Examples include cupric oxide (CuO), nickel oxide (NiO), and cobalt oxide (CoO). Among these, cupric oxide (CuO) exhibits excellent selectivity to hydrogen sulfide, and therefore is preferably used for a hydrogen sulfide sensor.

  The shape of the inorganic particles is not particularly limited as long as it can be introduced into the pores. For example, particles having a spherical shape, a wire shape, a rod shape, a tube shape, or the like as shown in FIG. 6 may be used.

  The inorganic particles may have any size as long as they can be supported in the pores. It is sufficient that it is not of a size that prevents the diffusion of gas into the pores. Therefore, when the shape of the inorganic particles is spherical, it is preferable to use a particle whose diameter is smaller than the pore diameter.

  The “electrode” may be a comb-type electrode as shown in FIG. 1, or a plurality of electrodes may be joined. For example, a configuration in which a plurality of electrodes are formed on the porous oxide semiconductor film as shown in FIG. 7 or a configuration in which electrodes are formed above and below the porous oxide semiconductor film as shown in FIG. . The electrode is connected to an electric circuit, and a change in the resistance value of the porous body is measured to determine whether a detection target exists.

Furthermore, the following configuration may be adopted in order to increase the sensitivity of the sensor.
1. 1. Heater 2. Mesopore (pore) arrangement and pore size Microcrystal

1. Heater A heater for heating the substrate and the porous oxide semiconductor film may be installed in order to promote the adsorption / desorption reaction of the substance to be detected. In cold places, it is convenient to set the temperature optimal for the reaction with the gas. The place to be installed is preferably arranged so as to be in contact with the porous oxide semiconductor film. However, another layer may be provided between the porous oxide semiconductor film and the heater.

2. Arrangement of Mesopores and Hole Diameter FIG. 9 shows a two-dimensional hexagonal structure. In FIG. 9, 14 is a mesopore and 15 is a pore wall. The arrangement of the pores is not limited to this, and for example, a distorted two-dimensional hexagonal structure, cubic structure, three-dimensional hexagonal structure or the like can be used. Moreover, even if the pore diameter is uniform, those having no clear periodic structure can be used.

  The porous oxide semiconductor film 11 preferably gives at least one diffraction peak in an angle region corresponding to a structural periodicity of 1 nm or more in X-ray diffraction analysis. In this case, since the arrangement of the holes in the porous oxide semiconductor film has a regular periodic structure, the mesopores are clogged with nectar and the specific surface area is increased.

  In order to evaluate the pore size distribution of the porous oxide semiconductor film 11, a method of measuring an adsorption isotherm of a gas such as nitrogen is generally used, and Berret-Joyner-Halenda (BJH) analysis is performed from the obtained isotherm adsorption line. The pore size distribution is calculated by a method or the like.

  The pores of the porous oxide semiconductor film 11 used in the present invention are determined by the BJH method from the nitrogen gas adsorption measurement, and the pore diameter distribution has a single maximum value, and the pores are 60% or more. What is contained in the range within 12 nm in diameter is preferable.

3. Microcrystal In the porous oxide semiconductor film 11 in the present invention, the pore wall preferably contains a microcrystal. For example, in the case of tin oxide, the present inventors have intensively investigated the correlation between the particle size of tin oxide and the detection sensitivity of the substance to be detected. As a result, a large sensitivity can be obtained when the crystallite diameter is 10 nm or less, particularly 6 nm or less. It has become clear.

  The crystallite diameter of the microcrystal can be controlled by the conditions of the steam treatment step and the surfactant removal step described later.

(About sensor manufacturing method)
A method for manufacturing the sensor will be described.
FIG. 10 is a process diagram showing a method for producing a porous oxide semiconductor film according to the present invention.

  In FIG. 10, step A is a step of preparing a reaction solution containing a metal compound and a surfactant and applying the reaction solution onto a substrate. Step B is a step of holding the substrate coated with the reaction solution in an atmosphere containing water vapor and forming a film containing a metal oxide and a surfactant on the substrate. Step C is a step of forming a film having a plurality of mesopores by removing the surfactant from the film. Step D1 is a step of covering at least a part of the surface of the mesopores with an organic substance or oxide, and Step D2 is a step of supporting inorganic particles in the mesopores.

  By passing through the processes A and B, the precursor of the film-form porous oxide semiconductor film which consists of the aggregate | assembly of surfactant on the said board | substrate and has the area | region used as a mesopore later is formed.

  Such a structure is formed because the surfactant self-assembles to form micelles to become a template for mesopores (pores), and further, pore walls are formed by the metal compound.

  When holding the precursor of the porous oxide semiconductor film in the water vapor atmosphere in the step B, the pore structure regularity of the precursor of the porous oxide semiconductor film to be formed becomes high and at the same time immediately after application by water vapor. Crystallization of the amorphous oxide semiconductor is induced.

  Furthermore, through Step C, the surfactant is removed, and a porous oxide semiconductor film is formed. Through the process D1 and the process D2, the film surface and the hole surface of the porous oxide semiconductor film can be modified, and inorganic particles can be supported in the holes. Thereby, the selection detection function of a to-be-detected substance can be provided.

Thereafter, an electrode for detecting a change in resistance value of the porous oxide semiconductor film may be formed. The step of forming the electrode may be performed in any step as long as the electrode can be connected to the porous oxide semiconductor film, may be performed after the step D1 or the step D2, or may be performed before the step A. good.
Hereinafter, each step will be described in detail.

(Step A: Step of preparing a reaction solution containing a metal compound and a surfactant and applying the reaction solution on a substrate)
In step A, a reaction solution containing a metal compound and a surfactant is first prepared.

(A-1: Preparation of reaction solution)
A metal compound is a material for manufacturing an oxide semiconductor, and these include, for example, tin (Sn), zinc (Zn), tungsten (W), niobium (Nb), and the like. Among these, it is particularly preferable to use a metal compound containing tin.

  Hereinafter, a tin compound will be described as an example.

Examples of the tin compound include tin chlorides such as stannous chloride (SnCl ₂ ) and stannic chloride (SnCl ₄ ), and tin alkoxides such as tin isopropoxide and tin ethoxide, but are applicable to the present invention. The tin compound is not limited to these.
The surfactant forms micelles and becomes a pore template.
A nonionic surfactant is preferably used for this surfactant.

In particular, nonionic surfactants containing ethylene oxide are suitable, and such surfactants include the following.
Example:
Triblock copolymer polyoxyethylene (10) dodecyl ether <C ₁₂ H ₂₅ <HO (CH ₂ CH ₂ O) ₂₀ (CH ₂ CH (CH ₃ ) O) ₇₀ (CH ₂ CH ₂ O) ₂₀ H> (CH ₂ CH ₂ O) ₁₀ OH>
Polyoxyethylene (10) tetradecyl ether <C ₁₄ H ₂₉ (CH ₂ CH ₂ O) ₁₀ OH>
Polyoxyethylene (10) hexadecyl ether <C ₁₆ H ₃₃ (CH ₂ CH ₂ O) ₁₀ OH>
Polyoxyethylene (10) stearyl ether <C ₁₈ H ₃₇ (CH ₂ CH ₂ O) ₁₀ OH>
Of the above surfactants, triblock copolymers are more preferably used.

As the solvent, alcohol such as methanol and ethanol is suitable, but it is not limited to this as long as it can be used in a mixed solvent such as alcohol and water and is a liquid and can dissolve the metal compound and the surfactant. . Furthermore, an acid or the like may be appropriately added as a catalyst.
The above is the preparation of the reaction solution.

(A-2: Application of reaction solution)
Next, the prepared reaction solution is applied onto the substrate.

  The substrate is preferably one that is stable to the reaction solution, that is, one that does not easily cause a chemical reaction between the reaction solution and the substrate. Illustrative examples include glass, ceramics, resin, metal and the like. Of course, a flexible film such as plastic can also be used as the substrate.

  As shown in FIGS. 1 and 2, if a substrate having an electrode formed thereon is used as the substrate, the connection between the electrode and the porous body is facilitated through the steps B and C described later. Can be done.

  Casting, dip coating, and spin coating methods are effective as methods that can be applied to the substrate easily and in a short time.

  In addition, the method is not limited to this as long as the reaction solution can be applied on the substrate, such as a spray coating method that is excellent in mass productivity.

  The above is the step of applying the reaction solution, but it is preferable to dry the reaction solution (particularly the solvent) on the substrate once after the step A and before shifting to the step B.

For example, after step A, it is preferable to perform step B after a drying step in which the solvent is dried at a humidity of 10% to 30% in the range of 25 ° C. to 50 ° C.
This step improves the uniformity of the film.

(Step B: A step of holding the substrate coated with the reaction solution in an atmosphere containing water vapor and forming a film containing a metal oxide and a surfactant on the substrate)
Next, the substrate on which the reaction solution has been applied and dried is held in an atmosphere containing water vapor to form a porous oxide semiconductor film precursor.

  The atmosphere containing water vapor in step B is preferably a humidity of 40% or more and 100% or less, and a temperature of 100 ° C. or less.

  However, even conditions outside this range can be used as long as the target porous oxide semiconductor film precursor film can be formed.

  Through this process, the continuity of the film is greatly improved, and at the same time, the uniformity of mesopores in the porous oxide semiconductor, that is, the structural regularity can be improved.

In addition, crystallization of the oxide semiconductor proceeds in the holding time in the atmosphere containing water vapor in Step B.
The steam treatment time can be appropriately determined depending on the target crystallinity and the like.

(Step C: Step of removing a surfactant from the film to form a film having a plurality of mesopores)
There are various methods for removing the surfactant. Among them, the baking treatment in which the surfactant is decomposed and removed by applying heat is a simple method, and the oxide present on the pore wall by the baking treatment. This is a preferable removal method because it has an effect of promoting crystallization of the semiconductor.

  However, when the firing temperature is high, crystallization of the oxide semiconductor proceeds, but the pore structure tends to be disturbed accordingly.

  Therefore, when the surfactant is removed by the firing treatment, the firing temperature needs to be set to an optimum temperature that maintains the pore structure.

  In addition, when the substrate material is deformed at a high temperature, for example, when a plastic substrate material is used and it is difficult to perform the baking treatment, it is possible to extract the surfactant with a supercritical fluid or a solvent. It is.

  In the extraction of the surfactant with a supercritical fluid or a solvent, the density of hydroxyl groups on the pore surface after the removal of the surfactant can be kept high, and as a result, the density of modification with organic substances can be increased.

  There are various other methods such as ultraviolet light irradiation, decomposition and removal of surfactants by oxidative decomposition with ozone, and the above method can be used as long as the pore structure of the porous oxide semiconductor film is maintained. Without being limited, any removal method can be used.

(Step D1: Step of coating at least a part of the surface in the mesopores with an organic substance or an oxide)
The pore surface and the membrane surface of the porous oxide semiconductor film are modified with a material different from that of the porous oxide semiconductor film.

  In the present invention, the substance that modifies the pore surface may be an organic substance or an inorganic oxide.

Each case will be described below.
1. When the substance that modifies the pore surface is an organic substance, any method may be used to fix the organic substance to the surface of the porous oxide semiconductor film 11 by a covalent bond, but the substance is shared by using a silane coupling agent. A method of forming a bond is preferred. This is because an organic substance can be easily bonded to the surface of the oxide semiconductor by using a silane coupling agent. Further, after forming an organic substance on the pore surface of the porous oxide semiconductor film 11 using a silane coupling agent, the functional group of the organic substance may be modified or replaced with another functional group by a chemical reaction.
2. When the substance that modifies the pore surface is silicon oxide Any method may be used for modifying the pore surface with silicon oxide as long as the formed silicon oxide does not block the pores. . It is preferable to bond a silicon compound to the surface using a silane coupling agent and then change the silicon compound to silicon oxide by heat treatment in an oxidizing atmosphere.

  This is because it is possible to coat the surface of the pores with silicon oxide relatively uniformly through such a process.

(Step D2: Step of supporting inorganic particles in the mesopores)
Inorganic particles are supported inside the pores of the porous oxide semiconductor film.

  As a method for introducing particles made of these substances into the pores, any method can be used as long as the pore structure of the porous oxide semiconductor film is significantly changed and the specific surface area is not significantly reduced. Also good.

  When supporting metal particles in the pores of the porous oxide semiconductor film, a metal compound dissolved in a solution such as an aqueous solution is introduced into the pores of the porous oxide semiconductor film, and the pores are reduced by reducing the metal compound. It is preferable to form metal particles inside.

  For example, in the case of introducing palladium, palladium particles can be formed in the pores by introducing a solution containing a palladium compound into the pores of the porous oxide semiconductor film and then performing a reduction treatment.

Palladium compounds include
Palladium acetate (Pb (CH ₃ COO) ₂ ),
Palladium (II) chloride (PdCl ₂ ),
Palladium (II) nitrate (Pd (NO ₃ ) ₂ ),
Dinitrodiammine palladium (II) ([Pd (NO ₂ ) ₂ (NH ₃ ) ₂ ]),
Dichlorodiammine palladium (II) ([Pd (NH ₃ ) ₂ Cl ₂ ]),
Tetraamminepalladium (II) dichloride ([Pd (NH ₃ ) ₄ ] Cl ₂ .nH ₂ O),
Tetraamminepalladium (II) nitrate (Pd (NH ₃ ) ₄ (NO ₃ ) ₂ ), etc.
Any material can be used as long as it can form palladium particles in the pores through the above process.

  Also, for example, when platinum is introduced, platinum particles can be formed in the pores by introducing a solution containing a platinum compound into the pores of the porous oxide semiconductor film and then performing a reduction treatment.

Platinum compounds include platinum (IV) chloride (H ₂ [PtCl ₆ ] · 6H ₂ O),
Dinitrodiammine platinum (II) ([Pt (NO ₂ ) ₂ (NH ₃ ) ₂ ]),
Tetraamminedichloroplatinum (II) ({Pt (NH ₃ ) ₄ } Cl ₂ .H ₂ O),
Hexahydroxoplatinum (IV) acid potassium (K ₂ [Pt (OH) ₆ ]),
Platinum nitrate (IV) (Pt (NO ₃ ) ₄ ), etc.
Any material can be used as long as platinum particles can be formed in the pores through the above process.

  In addition, when the oxide particles are supported in the pores of the porous oxide semiconductor film, the metal particles are first formed and then introduced into the pores of the porous oxide semiconductor film. The metal particles are preferably oxidized to form oxide particles.

  For example, in the case of copper oxide, copper (Cu) particles are formed, and then the porous semiconductor film is immersed in a solution in which the copper particles are dispersed to introduce the copper particles into the pores. Then, cupric oxide (CuO) is formed in the holes by oxidizing the copper particles.

  As described above, a porous oxide semiconductor film having mesopores with a uniform diameter, microcrystals on the pore walls, and carrying inorganic particles in the pores is formed by going through steps A to E. be able to.

  As described above, the porous oxide semiconductor film in which the pore surface is modified with an organic substance or an inorganic oxide can be formed by passing through the process A to the process D (D1, D2).

  Furthermore, a sensor can be manufactured by connecting an electrode to the porous oxide semiconductor film.

  For example, when the electrode and the porous oxide semiconductor film are connected in the configuration as shown in FIG. 2, the porous body and the electrode are good if the electrodes are first formed on the substrate and then the processes A to D are performed. Can be contacted.

  In the case of the structure shown in FIG. 7, a porous oxide semiconductor film may be formed on a substrate and an electrode may be formed thereon.

  In the case of the configuration as shown in FIG. 8, after forming an electrode on a substrate, or using a substrate made of an electrode material, a porous oxide semiconductor film is formed on the substrate, and an electrode is further formed thereon. Good.

  The step of forming the electrode may be performed before or after the steps A to D of forming the porous oxide semiconductor film.

  The electrode material is preferably a material that does not undergo chemical changes such as etching during the formation of the porous oxide semiconductor film, and specifically gold (Au) or platinum (Pt).

  However, any electrode material may be used as long as the shape change and physical, chemical, and electrical properties do not change during the formation process of the porous oxide semiconductor film.

  For forming the electrode, a general metal electrode forming method such as a vacuum deposition method, a sputtering method, or an electrodeposition method can be used.

[Example 1]
(Example in which pore surface is coated with organic substance: organic substance containing aminopropyl group)
In this example, a tin oxide porous thin film is formed on a substrate on which comb-shaped electrodes are formed to produce a gas sensor element, which is used for selective detection of carbon monoxide (CO).

  First, a platinum (Pt) comb electrode having a distance between electrodes of 20 μm and an electrode length of 370 mm was formed on a quartz substrate by photolithography.

Next, 2.9 g of anhydrous stannic chloride is added to 10 g of ethanol and stirred for 30 minutes. After stirring, the triblock copolymer P123 <HO (CH ₂ CH ₂ O) ₂₀ (CH ₂ CH (CH ₃ ) O) ₇₀ (CH ₂ CH ₂ O) ₂₀ H> 1.0 g is dissolved. Then, the mixture was further stirred for 30 minutes to obtain a precursor solution A.

Next, the precursor solution A was applied to the comb electrode portion of the substrate by a dip coating method.
Next, the substrate coated with the precursor solution A was moved into an environmental test machine and held.

The temperature and relative humidity were controlled in the environmental test machine as follows.
Hold for 10 hours at 40 ° C and 20% RH → Change in temperature and humidity over 1 hour → Hold for 5 hours at 90 ° C at 50 ° C → Change in temperature and humidity over 1 hour → 40 ° C and 20% RH
A surfactant-tin oxide mesostructured thin film was obtained by the process as described above.

  Thereafter, the substrate is taken out from the environmental testing machine and placed in a muffle furnace, heated to 300 ° C. in air at a rate of 1 ° C./min, held for 5 hours to remove the surfactant, and the mesoporous tin oxide thin film Got.

  It was confirmed by infrared spectrophotometry and the like that the organic component derived from the surfactant did not exist in the thin film after the removal of the surfactant.

When SEM observation was performed on the surface and cross section of the thin film, a tube-like structure was observed from the surface.
Further, it was confirmed from the cross section that the pores were arranged in a honeycomb shape.

  When X-ray diffraction analysis was performed, a clear diffraction peak corresponding to an interplanar spacing of 4.9 nm was observed, and a diffraction pattern suggesting a two-dimensional hexagonal structure was obtained.

  However, SEM observation of the cross section, etc. revealed that the film actually shrunk in the film thickness direction and deviated from the ideal hexagonal structure.

  When nitrogen gas adsorption measurement was performed, the pore diameter showed a single dispersion having a maximum value at 5.2 nm, and the distribution curve was in the region of 1 nm to 10 nm.

The specific surface area was about 170 m ² / g.

  Therefore, it was confirmed that the thin film is a porous thin film having substantially uniform mesopores and a large specific surface area.

  Next, when oblique incidence X-ray diffraction analysis was performed on the thin film, a clear peak attributed to Cassitete was confirmed.

Of the appearing peaks, the average crystallite diameter L is obtained from the following Scherrer equation from the half width B (rad) of the peak derived from the (211) plane in the region of 2θ = 45 ° to 58 ° and the peak position 2θ. As a result, it was 2.7 nm.
L = 0.9λ / Bcosθ
From the above, it was confirmed that a porous tin oxide thin film having a regular mesoscopic pore structure and a microcrystal on the pore wall can be formed on the electrode substrate.

  Next, 0.5 g of 3-aminopropyltrimethoxysilane, which is a silane coupling agent, was immersed in 10 g of an ethanol solution from the produced porous tin oxide thin film.

  Then, running water washing with pure water was performed, and finally, the pore surface was modified with an organic substance containing an aminopropyl group by drying at 100 ° C. for 5 hours.

  In order to confirm the modification of organic substances into the pores, a porous tin oxide thin film was prepared on the high resistance silicon substrate by the same method as above, with the pore surfaces modified with organic substances containing aminopropyl groups. And measured by an infrared absorption spectrum.

As a result, an absorption spectrum attributable to the amino group was confirmed in the vicinity of 3310 to 3500 cm ⁻¹ .

  For comparison, an FT-IR absorption spectrum of a thin film prepared by using the same modification to a tin oxide thin film having no mesopores prepared without using a surfactant was measured.

  Comparing the results, a much stronger absorption was confirmed in the one having mesopores, and it was confirmed from this result that the tin oxide thin film having mesopores had a larger amount of modification.

  Next, 7.7 mg of 3,4-dihydroxybenzoic acid was dissolved in 10 g of water, and 9.3 mg of carbodiimide was further added and stirred.

  A tin oxide thin film having mesopores whose pore surfaces were treated with the silane coupling agent was immersed in this solution for 24 hours.

  Thereafter, it was washed with running water with pure water, and finally dried at 100 ° C. for 1 hour.

In order to confirm the modification of the organic matter, the sample after the above treatment was measured with an infrared absorption spectrum. As a result, an absorption spectrum due to a hydroxyl group appeared in the vicinity of 3450 cm ⁻¹ .

  This absorption spectrum is not observed from the tin oxide thin film treated only with the silane coupling agent, and 3,4-dihydroxybenzoic acid having a hydroxyl group reacts with the silane coupling agent to form on the pore surface. It was confirmed that

  Further, the electrode substrate on which the tin oxide porous thin film was formed was connected to an electric circuit to produce a gas sensor, and the sensor characteristics with respect to the mixed gas were measured using the measuring apparatus shown in FIG. The gas sensor 18 is placed on the substrate heater 19 in the gas flow chamber 24. The heater unit is controlled by the heater control device 20. A change in the current value of the gas sensor is converted into low efficiency by the resistivity measuring device 21. The gas concentration is controlled by the gas concentration controller 22.

The mixed gas used in this measurement is a mixture of three types: a gas mixed with carbon monoxide (CO) in air, a gas mixed with methane (CH ₄ ) in air, and a gas mixed with hydrogen (H ₂ ) in air. Gas was used.

  The concentration of each mixed gas can be adjusted by the ratio of the air to be mixed and the gas to be detected. This time, the concentration of each gas was adjusted to 1000 ppm and 500 ppm and used for measurement. The measurement was performed at atmospheric pressure in a flow system.

  The measurement method is as follows.

  Let air flow for 10 minutes. → Flow a mixed gas with a concentration of 1000 ppm for 20 minutes. → Flow only air for 20 minutes. A mixed gas having a concentration of 500 ppm is allowed to flow for 20 minutes. → Use only air.

While flowing air or a mixed gas in the above procedure, a direct current of 1 V was applied between the electrodes of the sensor element, the current value was measured, and converted into a resistivity.
The temperature of the element at the time of measurement was 100 ° C.

  FIG. 12 shows a change in resistivity with respect to elapsed time in each gas when measurement is performed under the above conditions.

  From the results shown in FIG. 12, the gas sensor element having the porous tin oxide thin film in which the pore surface is modified with an organic substance according to this example has an increased resistivity only with respect to the mixed gas of CO and air, and CO is selectively used. It was confirmed to be detected.

At this time, the resistivity before introducing the CO mixed gas was Ra, the minimum value of the resistivity after introducing the mixed gas was R _CO , and the sensitivity S _CO was expressed by the following equation. In this case, S = 6 when a 1000 ppm CO mixed gas was flowed, and S = 2.5 when a 500 ppm CO mixed gas was flowed.
S _CO = R _CO / Ra
From the above results, in this example, by using a tin oxide porous thin film containing microcrystals in the pore wall and modifying the pore surface with an organic substance, it has selectivity for a specific gas, It was also confirmed that a metal oxide semiconductor gas sensor element capable of highly sensitive detection could be produced.

[Comparative Example 1]
FIG. 13 shows the result of the same measurement performed on the gas sensor manufactured by the same manufacturing method as in Example 1 except that the triblock copolymer P123 is not added.

  Although it selectively reacted to CO and air, the rate of change was smaller than that of the gas sensor element used for measurement in Example 1, and in the case of a CO mixed gas having a concentration of 1000 ppm, S = 1.1 and a concentration of 500 ppm. In the case of the CO mixed gas, S = 1.05.

Further, the change in resistivity when the H ₂ mixed gas and the CH ₄ mixed gas were introduced was smaller than that in Example 1.

[Example 2]
(Example in which pore surface is coated with organic substance: organic substance containing aminopropyl group)
Instead of using the triblock copolymer P123 (1.0 g) in the preparation of the precursor solution, the triblock copolymer F127 <HO (CH ₂ CH ₂ O) ₁₀₆ (CH ₂ CH (CH ₃ ) O) ₇₀ (CH ₂ CH ₂ O) ₁₀₆ OH> 0.7 g was used. A mesoporous tin oxide thin film was produced in the same manner as in Example 1 except that the polymer was changed.

When SEM observation was performed on the surface and cross section of the thin film, a structure in which the pores were regularly arranged from the surface and the pores were contracted in the film thickness direction was observed.
From the cross section, it was confirmed that the pores were regularly arranged.

When X-ray diffraction analysis was performed, a clear diffraction peak was observed at an interplanar spacing of 6.2 nm.
Therefore, it can be said that the tin oxide porous thin film produced this time has a cubic structure with regularity having many openings on the surface.

When nitrogen gas adsorption measurement was performed, the pore diameter showed a single dispersion having a maximum value at about 6.5 nm, and the distribution curve was in the range of 2 nm to 12 nm.
The specific surface area was about 200 m ² / g.
Therefore, it was confirmed that the thin film is a porous thin film having substantially uniform mesopores and a large specific surface area.

Next, when the average crystallite diameter L was determined from the Scherrer equation in the same manner as in Example 1, it was 2.7 nm.
As described above, it was confirmed that a porous tin oxide thin film having a regular mesoscopic pore structure and a microcrystal on the pore wall can be formed on the electrode substrate.

  Next, the pore surface of the mesoporous tin oxide thin film was modified with an organic substance in the same manner as in Example 1, and the sensor characteristics of the gas sensor in this example with respect to the mixed gas were changed using the same apparatus and method as in Example 1. Was measured. At this time, the change in resistivity with respect to the elapsed time for each gas showed almost the same behavior as in FIG.

  From the above results, the present example has selectivity for a specific gas by using a tin oxide porous thin film in which fine pores are included in the pore wall and the pore surface is modified with an organic substance. It was also confirmed that a metal oxide semiconductor gas sensor element capable of highly sensitive detection could be produced.

[Example 3]
(Example in which pore surface is coated with inorganic oxide: silicon oxide)
In this example, a tin oxide porous thin film is formed on a substrate on which comb-shaped electrodes are formed to produce a gas sensor element, which is used for selective detection of H ₂ gas.

  First, a mesoporous tin oxide thin film was formed on a substrate on which a Pt comb-shaped electrode was formed by the same method as in Example 2, and the mesoregion pore structure having regularity by the same method as in Example 1; Formation of a porous tin oxide thin film with microcrystals on the pore walls was confirmed.

  Next, the produced porous tin oxide thin film was immersed for about 10 minutes in a toluene solution having a concentration of 1 wt% of diethoxydimethylsilane (DEMS).

Thereafter, the porous tin oxide thin film subjected to the above treatment was washed with pure water and finally dried at 100 ° C. for 5 hours to modify the pore surface with an organic substance containing silicon.
Thereafter, baking was performed at 300 ° C. for 5 hours.

In order to confirm that the pore surface was modified with silicon oxide, a porous tin oxide thin film produced by the same method as the above process was produced on a high resistance silicon substrate, and TEM observation was performed.
For comparison, a TEM observation of a sample that was not immersed in the DEMS solution was also performed.

  As a result, both had regularly arranged pores, but a difference in contrast was confirmed at the pore surface, and in the vicinity of the pore surface in the sample subjected to DEMS immersion treatment by TEM-EDS measurement The presence of Si was confirmed.

  In addition, nitrogen gas adsorption measurement was performed on each sample to obtain an adsorption isotherm. Furthermore, when the pore size distribution was calculated by the Berret-Joyner-Halenda (BJH) method, it was confirmed that the pore size distribution was distributed on the lower pore size side in the sample subjected to DEMS treatment.

  From the above, it was confirmed that silicon oxide was formed in the pores of the porous tin oxide thin film while maintaining the pore structure.

Next, using the same apparatus and method as in Example 1, the sensor characteristics of the gas sensor in this example with respect to the mixed gas were measured.
The temperature of the element at the time of measurement was 150 ° C. The result is shown in FIG.

The response to the H ₂ mixed gas is large with respect to other mixed gases, the resistivity before introducing the H ₂ mixed gas is Ra, the minimum value of the resistivity after introducing the mixed gas is R _H2 , and the sensitivity S _H2 is It was expressed by the following formula. In this case, in the case of flowing of _{H 2} mixed gas concentration 1000ppm if flowed S = 300 becomes, 500 ppm _{H 2} mixed gas becomes S = 160.
S _H2 = Ra / R _H2
Further, when the sensitivity is calculated using the same equation as above for other mixed gases, S _CO = 40 in the case of a 1000 ppm concentration CO mixed gas, and S _CH4 = 3 in the case of a 1000 ppm concentration CH4 mixed gas. became.

From the above results, the present example has selectivity for H ₂ gas by using a tin oxide porous thin film containing microcrystals in the pore walls and modifying the pore surfaces with silicon oxide. It was also confirmed that a metal oxide semiconductor gas sensor element capable of highly sensitive detection could be produced.

[Comparative Example 2]
FIG. 15 shows the result of the same measurement performed on the gas sensor manufactured by the same manufacturing method as in Example 3 except that the triblock copolymer F127 is not added.

In the case of the H ₂ mixed gas having a concentration of 1000 ppm, S _H2 = 30, in the case of the CO mixed gas having a concentration of 1000 ppm, S _CO = 20, and in the case of the CH ₄ mixed gas having a concentration of 1000 ppm, S _CH4 = 1.5. The sensitivity of any of the mixed gases was smaller than that of the gas sensor element used for measurement in Example 3, and was greatly reduced particularly with respect to the H ₂ mixed gas.

[Example 4]
(Example in which inorganic particles are supported in pores: metallic palladium)
In this embodiment, a gas sensor element is produced by forming a tin oxide porous film on a substrate on which comb-shaped electrodes are formed, and is used for selective detection of hydrogen (H ₂ ) gas.

  First, a Pt comb electrode having a distance between electrodes of 20 μm and an electrode length of 370 mm was formed on a quartz substrate by photolithography.

Next, 2.9 g of anhydrous stannic chloride was added to 10 g of ethanol and stirred for 30 minutes. It was then dissolved triblock copolymer _{P123 <HO (CH 2 CH 2} O) 20 (CH 2 CH (CH 3) O) 70 (CH 2 CH 2 O) 20 H> 1.0g. Then, the mixture was further stirred for 30 minutes to obtain a precursor solution A.
Next, the precursor solution A was applied to the comb electrode portion of the substrate by a dip coating method.

  Next, the substrate coated with the precursor solution A was moved into an environmental test machine and held. The temperature and relative humidity were controlled in the environmental test machine as follows.

  First, it is dried at 40 ° C. and 20% RH for 10 hours, and then is changed to 50 ° C. and 90% RH over 1 hour, held as it is for 5 hours, and then returned to 40 ° C. and 20% RH again in 1 hour. A structure film was obtained.

  Then, the said board | substrate was taken out from the environmental test machine, it put into the muffle furnace, and it heated up to 300 degreeC in the ratio of 1 degree-C / min in the air, and hold | maintained as it was for 5 hours, and the mesoporous tin oxide film | membrane was obtained.

When the surface and cross section of the film were observed with a scanning electron microscope (SEM), a tube-like structure was observed from the surface.
Further, it was confirmed from the cross section that the holes were arranged in a honeycomb shape.

  When X-ray diffraction analysis was performed, a clear diffraction peak corresponding to an interplanar spacing of 4.9 nm was observed, and a diffraction pattern suggesting a two-dimensional hexagonal structure was obtained.

  However, SEM observation of the cross section, etc. revealed that the film actually shrunk in the film thickness direction and deviated from the ideal hexagonal structure.

When nitrogen gas adsorption measurement was performed, the pore diameter showed a single dispersion having a maximum value at 5.2 nm, and the distribution curve was in the region of 1 nm to 10 nm.
The specific surface area was about 170 m ² / g.

  Accordingly, it was confirmed that the membrane was a porous membrane having substantially uniform mesopores and a large specific surface area.

  Next, the film was subjected to oblique incidence X-ray diffraction analysis, and a clear peak attributed to Cassiterite was confirmed.

Of the appearing peaks, the average crystallite diameter L is obtained from the following Scherrer equation from the half width B (rad) of the peak derived from the (211) plane in the region of 2θ = 45 ° to 58 ° and the peak position 2θ. As a result, it was 2.7 nm.
L = 0.9λ / Bcosθ
From the above, it was confirmed that a porous tin oxide film having a regular mesoscopic pore structure and a microcrystal on the pore wall can be formed on the electrode substrate.

Next, the produced porous tin oxide film was immersed in an aqueous ammonia solution having a palladium acetate (Pd (CH3COO) ₂ ) concentration of 0.005M.

  Then, after performing a drying process, in order to obtain metal palladium particles, first, heating in a hydrogen atmosphere at 300 ° C. for 1 hour, then heating in the atmosphere at 300 ° C. for 5 hours, and again in a hydrogen atmosphere The reduction treatment was performed at 300 ° C. for 1 hour.

  In order to confirm the loading of metal palladium particles in the pores, the surface and cross-sectional structure of the porous tin oxide film were observed with a transmission electron microscope (TEM).

  As a result, it was confirmed that particles having a diameter of about 3 nm were supported in the pores. As a result of analysis using an energy dispersive X-ray analyzer (EDS) and an electron energy loss spectrometer (EELS) attached to the TEM, it was confirmed that the particles supported in the pores were metallic palladium.

  Further, in the X-ray diffraction measurement, a diffraction pattern suggesting a two-dimensional hexagonal structure was obtained, and it was confirmed that the pore structure was maintained even after palladium was supported in the pores.

Further, the specific surface area was about 180 m ₂ / g by nitrogen gas adsorption measurement, and it was confirmed that the specific surface area did not change greatly even after palladium was supported in the pores.

  Next, the electrode substrate on which the tin oxide porous film was formed was connected to an electric circuit, and the sensor characteristics of the gas sensor in this example with respect to the mixed gas were measured using the apparatus shown in FIG.

The mixed gas is a mixture of hydrogen (H ₂ ) and air (hereinafter referred to as gas A), a mixture of air and methane (CH ₄ ) (same gas B), and a mixture of nitrogen monoxide (NO) and air ( The same gas C) was prepared.

  The concentration of each gas can be changed by changing the mixing ratio of air and the gas to be detected. This time, the concentration of each gas is changed to 200 ppm, 100 ppm, and 50 ppm, and the change in resistivity against the gas concentration is measured. did.

  The measurement was performed in a flow system at atmospheric pressure. When the gas was turned on, the above-mentioned concentration of gas was introduced, and when the gas was turned off, only air was introduced.

  A DC current of 1 V was applied between the electrodes of the sensor while flowing the above gas, and the time change of the current value was measured. The temperature of the sensor at the time of measurement was 100 ° C.

  FIG. 16 shows the resistivity change obtained from the current value change with respect to the elapsed time for each gas at this time.

  As a result, the gas sensor having the tin oxide porous film according to this example selectively responded to the gas A, that is, the mixed gas of hydrogen and air, and hardly responded to the gas B and the gas C. .

In addition, in the time change of the resistivity with respect to the gas A, when the gas is turned off, that is, when the air only flows, the resistivity is R _a , and when the mixed gas of air and hydrogen flows, the resistivity is _RH in defining the sensitivity _{S H.} In this case, was _S H = 20 to hydrogen of _S H = _40,50ppm to hydrogen of _S H = _100,100ppm to hydrogen of 200 ppm.
S _H = R _a / R _H
From the above results, in this example, by using a tin oxide porous membrane containing microcrystals in the pore walls and supporting metallic palladium particles in the pores, the selectivity to a specific gas is obtained, and It was confirmed that a metal oxide semiconductor gas sensor capable of highly sensitive detection could be produced.

[Comparative Example 3]
FIG. 17 shows the result of the same measurement performed on the gas sensor manufactured by the same manufacturing method as in Example 4 except that the surfactant is not added.

  It reacted slightly to gas A, but hardly reacted to gas B and gas C.

Regarding gas A, S _H = 10 for hydrogen at a concentration of 200 ppm, S _H = 4 for hydrogen at a concentration of 100 ppm, and S _H = 1.5 for hydrogen at a concentration of 50 ppm.

[Example 5]
(Example in which inorganic particles are supported in pores: platinum)
In this example, a gas sensor element was produced by forming a tin oxide porous film on a substrate on which comb-shaped electrodes were formed, and this was used for selective detection of H ₂ gas.

First, an electrode and a porous tin oxide film were produced on a quartz substrate by the same method as in Example 4.
Next, the produced porous tin oxide film was immersed in an aqueous solution having a concentration of chloroplatinic acid (H ₂ PtCl ₆ ) of 0.005M.

  Thereafter, drying treatment was performed, and reduction treatment was performed in a hydrogen atmosphere at 170 ° C. for 2 hours in order to obtain platinum particles.

  In order to confirm the loading of platinum particles in the pores, the surface and cross-sectional structure of the porous tin oxide film were observed with a transmission electron microscope (TEM).

  As a result, it was confirmed that particles having a diameter of about 3 nm were supported in the pores.

  As a result of analysis using an energy dispersive X-ray analyzer (EDS) and an electron energy loss spectrometer (EELS) attached to the TEM, it was confirmed that the particles supported in the holes were metallic platinum.

  Further, in the X-ray diffraction measurement, a diffraction pattern suggesting a two-dimensional hexagonal structure was obtained, and it was confirmed that the pore structure was maintained after platinum was supported in the pores.

Further, the specific surface area was about 180 m ₂ / g by nitrogen gas adsorption measurement, and it was confirmed that the specific surface area did not change greatly after platinum was supported in the pores.

  Next, as a result of measuring the sensor characteristics with respect to the mixed gas of the gas sensor in this example using the same apparatus and method as in Example 4, the change in resistivity with respect to the elapsed time for each gas at this time is the same as in FIG. Showed a good behavior.

  Moreover, as a result of performing the same measurement with respect to the gas sensor produced by the same manufacturing method as in the present example except that the surfactant was not added, the same behavior as in FIG. 17 was exhibited.

  From the above results, in this example, by using a tin oxide porous membrane containing microcrystals in the pore walls and carrying platinum particles in the pores, it has selectivity for a specific gas and has high performance. It was confirmed that a metal oxide semiconductor gas sensor capable of sensitive detection could be produced.

[Example 6]
(Example in which inorganic particles are supported in the pores: cupric oxide)
In this embodiment, a gas sensor element is produced by forming a tin oxide porous film on a substrate on which comb-shaped electrodes are formed, and is used for selective detection of hydrogen sulfide (H ₂ S) gas.
First, an electrode and a porous tin oxide film were produced in the same manner as in Example 4.

  Next, the produced porous tin oxide film was immersed in an aqueous solution in which copper (Cu) particles produced by a laser ablation method were dispersed and subjected to ultrasonic treatment for about 1 hour, and then at 300 ° C. in an air atmosphere. For 1 hour to introduce cupric oxide (CuO) particles into the pores.

In order to confirm the loading of cupric oxide (CuO) particles in the pores, the surface and cross-sectional structure of the porous tin oxide film were observed with a transmission electron microscope (TEM).
As a result, it was confirmed that particles having a diameter of about 3 nm were carried in the holes.

  As a result of analysis using an energy dispersive X-ray analyzer (EDS) and an electron energy loss spectrometer (EELS) attached to the TEM, it was confirmed that the particles supported in the holes were cupric oxide. .

  Further, in the X-ray diffraction measurement, a diffraction pattern suggesting a two-dimensional hexagonal structure was obtained, and it was confirmed that the pore structure was maintained after supporting cupric oxide in the pores.

Further, the specific surface area was about 180 m ₂ / g by nitrogen gas adsorption measurement, and it was confirmed that the specific surface area did not change greatly even after cupric oxide was loaded in the pores.

  Next, as a result of measuring the sensor characteristics with respect to the mixed gas of the gas sensor in this example using the same apparatus and method as in Example 4, the change in resistivity with respect to the elapsed time for each gas at this time is the same as in FIG. Showed a good behavior.

  Moreover, as a result of performing the same measurement with respect to the gas sensor manufactured by the same manufacturing method as Example 3 except not adding surfactant, it showed the same behavior as FIG.

  From the above results, the present example has selectivity for a specific gas by using a tin oxide porous membrane containing microcrystals in the pore walls and supporting cupric oxide particles in the pores. In addition, it was confirmed that a metal oxide semiconductor gas sensor capable of highly sensitive detection can be manufactured.

  The sensor of the present invention and the manufacturing method thereof can be used for a gas sensor that selectively detects a specific gas type. The sensor of the present invention can be used for a gas sensor that detects a gas, a biosensor that detects a biological material, and the like. Can be applied.

  In addition, the sensor of the present invention and the manufacturing method thereof can be used for a gas sensor that selectively detects a specific gas type.

Schematic which shows the structure of the sensor of this invention. Sectional drawing of FIG. The enlarged view of the mesopore of FIG. The enlarged view of the mesopore of FIG. The enlarged view of the mesopore of FIG. Schematic which shows a part of particle | grains of an inorganic substance. The figure of one embodiment of a sensor section. The figure of one embodiment of a sensor section. The figure which showed the arrangement | sequence of a mesopore. Process drawing which shows an example of the process in the manufacturing method of the sensor of this invention. Schematic of the apparatus for evaluating the characteristic of the sensor of this invention. The graph which shows resistance value change at the time of detecting several gas using the sensor of this invention. The graph which shows resistance value change at the time of detecting several gas using the sensor element used as a comparative example of the sensor of this invention. The graph which shows resistance value change at the time of detecting several gas using the sensor of this invention. The graph which shows resistance value change at the time of detecting several gas using the sensor element used as a comparative example of the sensor of this invention. The graph which shows the time change of resistance value at the time of detecting several gas using the sensor of this invention. The graph which shows the time change of resistance value at the time of detecting a some gas using the sensor prepared for the comparison.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Porous oxide semiconductor film 12 Electrode 13 Substrate 14 Mesopore 15 Pore wall 16 Organic substance 17 Oxide 18 Gas sensor 19 Substrate heater 20 Heater control device 21 Resistivity measuring device 22 Gas concentration control device 23 Inorganic particle 24 Gas flow chamber

Claims (4)

A semiconductor film having a plurality of mesopores and containing tin oxide;
An electrode electrically connected to the semiconductor film,
A sensor characterized in that inorganic fine particles having an action of separating or decomposing a detection object by a catalytic action are carried in the mesopores.   The sensor according to claim 1, wherein the inorganic particles are a metal or a metal oxide.   3. The sensor according to claim 1, wherein the oxide constituting the semiconductor film contains microcrystals.   4. The semiconductor film according to claim 1, wherein the semiconductor film has a structure having one or more diffraction peaks in an angle region corresponding to a structural periodicity of 1 nm or more when X-ray diffraction measurement is performed. The sensor described.

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