KR20100085321A - Gas sensor and the fabrication method thereof - Google Patents

Abstract

PURPOSE: A gas sensor and a manufacturing method thereof are provided to accelerate gas diffusion and to increase specific surface area by forming a sensing layer of a porous hemisphere structure using various sizes of colloidal templates as a sacrificial layer. CONSTITUTION: A manufacturing method of a gas sensor is as follows. A sacrificial layer(14) in which sacrificial particles are uniformly dispersed is formed on a sensor substrate(10). Using a sputtering technique, a metal oxide sensing layer(13) which contains catalyst(12) is formed on the sacrificial layer. The metal oxide sensing layer is heat-treated to eliminate the sacrificial layer. A porous metal oxide sensing layer containing catalyst is obtained. A sensor electrode(11) sensing the change of resistance to external gas exposure is formed on the sensor substrate. The average size of the sacrificial particles is in a range of 100nm-10micro.

Description

GAS SENSOR AND THE FABRICATION METHOD THEREOF

The present invention relates to a gas sensor and a method of manufacturing the same, and more particularly, to a gas sensor and a method of manufacturing the same using a thin metal oxide layer of a porous structure containing a catalyst as a sensing material.

Gas sensing of sensors using metal oxide semiconductors such as tin oxide (SnO ₂ ) and zinc oxide (ZnO) is accomplished by measuring the change in resistivity due to gas adsorption and oxidation / reduction reactions occurring on the oxide surface.

These gas sensors have the advantage of easily determining the concentration of external environmental gases (H2, O2, CO, NOx, alcohol, SOx, DMMP, phenol, acetone, formaldehyde, etc.) by changing the electrical signal (conductivity). It is widely used in leak detectors, fire alarms, alcohol detectors and engine combustion gas detectors.

Since the semiconductor gas sensor is generally operated at 200 to 500 ° C., the semiconductor gas sensor includes an electrode (Interdigitated Electrode) for detecting a change in resistance, and a heater (heating element) for increasing the temperature of the sensing element.

These gas sensors are widely used in the form of bulk and thick films, but in recent years, as the demand for miniaturization and integration increases, speed, selectivity, sensitivity, reproducibility, durability, low power consumption, integration, and arraying characteristics are further increased. It is importantly required.

In particular, in order to obtain high-sensitivity sensor characteristics, it is necessary to increase gas diffusivity and widen the gas-surface reaction area. In addition, in the case of the thin film, it is necessary to minimize the influence of the inactive layer generated at the interface between the sensing layer and the lower substrate.

In general, a gas-sensitive surface depletion layer in the gas sensing layer is formed to a thickness of 1-10 nm.

However, when the thickness of the sensor sensing layer is less than 100 nm, there is a problem that the sensor characteristics are degraded due to the interface characteristics with the lower electrode substrate.

In the case of a semiconductor gas sensor, a high sensitivity or a selectivity may be obtained by changing or combining a parent material and a catalyst in various ways.

Therefore, in order to make a sensor having a fast response time and high sensitivity, it has a microporous structure with excellent gas diffusion and greatly increases the specific surface area of the sensor sensing layer and minimizes the interfacial characteristics with the lower sensor substrate while uniformly including the metal catalyst. There is a need for the development of highly sensitive sensors made of porous thin layers.

The present invention has been made in view of the above, by using a colloidal template of various sizes as a sacrificial layer or a templating layer to form a sensing layer (sensing layer) of porous hemispherical structure It is an object of the present invention to provide a gas sensor and a method of manufacturing the same, in which gas diffusion is quick and the specific surface area is greatly increased.

In addition, another object of the present invention is to provide a gas sensor and a method for manufacturing the same, which can improve the sensitivity of the sensor by uniformly forming a catalyst inside or on the surface of the porous sensing layer.

In addition, the present invention has another object to provide a gas sensor and a method of manufacturing the same that can provide not only a high sensitivity sensor through a variety of catalyst changes but also selectivity for various gases.

The above object is a method of manufacturing a gas sensor,

Forming a sacrificial particle layer in which sacrificial particles are uniformly dispersed on the sensor substrate;

Forming a metal oxide sensing layer including a catalyst on the sacrificial particle layer using a sputtering method; And removing the sacrificial particle layer by heat-treating the metal oxide sensing layer containing the catalyst to obtain a porous metal oxide sensing layer including the catalyst.

Here, the sacrificial particle layer may be formed of a single layer or a plurality of layers.

In addition, the catalyst and the metal oxide sensing layer is preferably deposited at the same time using DC (direct current) and RF (high frequency) sputtering method.

In addition, the catalyst and the metal oxide sensing layer may be obtained by being deposited from a single target of a metal oxide containing a catalyst using a sputtering method.

In addition, the forming of the sacrificial particle layer, the forming of the metal oxide sensing layer including the catalyst, and the heat treatment may be repeated to obtain a porous metal oxide sensing layer having a multilayer structure.

On the other hand, the object is a gas sensor manufactured by the above-described method, by a gas sensor, characterized in that consisting of a sensor substrate having a sensor electrode on the upper surface, and a porous metal oxide sensing layer formed on the sensor substrate and containing a catalyst Is achieved.

Here, the porous metal oxide sensing layer containing the catalyst is characterized in that the hemispherical hollow portion (hollow hemisphere) is a microstructure arranged regularly.

In particular, the hemispherical hollow portion is characterized in that hemispherical pores having an average diameter of 100nm ~ 10㎛.

In addition, the thickness of the porous metal oxide sensing layer containing the catalyst is in the range of 5nm ~ 1 ㎛, gas reaction characteristics because the outer surface and the inner surface of the hollow hemisphere can participate in the reaction with the gas at the same time It is preferable to have the thickness of 10-20 nm corresponding to the thickness of this most excellent depletion layer.

In addition, the thin porous metal oxide layer containing the catalyst may have a multilayer structure.

In addition, the catalyst may be a metal or a metal oxide for imparting selectivity.

Accordingly, according to the gas sensor and the manufacturing method according to the present invention, there are the following advantages.

1. As the sensing layer forms a microsized porous hemispherical structure, it is possible to manufacture a gas sensor having a minimum interface property between the lower sensor substrate and the upper sensing layer.

2. By forming a porous metal oxide sensing layer containing a catalyst using a simultaneous sputtering method, it is possible to construct a gas sensor with improved selectivity and sensitivity.

3. Since it has a micro-sized hemispherical structure, the surface area is increased, and external gas can easily penetrate, and the sensitivity of the sensor can be improved.

4. By easily adjusting the thickness of the micro-sized hemispherical structure through the sputtering time, it is possible to easily produce a gas sensing layer corresponding to the thickness of the depletion layer having the best sensitivity characteristics of the gas sensor.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Gas sensor according to an embodiment of the present invention, the porous substrate including a sensor substrate 10 formed with an electrode 11 capable of measuring a change in resistance, and a catalyst 12 deposited on the sensor substrate 10 Metal oxide sensing layer 13 is included. In this case, the porous metal oxide sensing layer 13 including the catalyst 12 is obtained through a colloidal template method on the sensor substrate 10.

Platinum (Pt), gold (Au), palladium (Pd), iridium (Ir), silver (Ag), ruthenium (Ru), nickel (Ni), stainless steel (STS), and aluminum ( Al), molybdenum (Mo), chromium (Cr), copper (Cu), titanium (Ti), tungsten (W), ITO (In doped SnO ₂ ) and FTO (F doped SnO ₂ ) One kind or two or more kinds of electrodes 11 can be used.

As the sensor substrate 10, a ceramic substrate, an alumina (Al ₂ O ₃ ) substrate, a silicon (Si) substrate on which an insulating layer is deposited, a silicon oxide (SiO ₂ ) substrate, or the like may be used. In addition, the sensor substrate 10 preferably includes a substrate in which the sensor electrode 11 is patterned in the form of an interdigital electrode 11.

Looking at the manufacturing method of the gas sensor according to the present invention, at least two of the sensor substrate (10) is arranged (array), the spherical shape of the sphere by a microparticle template (microsphere template) process on the at least two sensor substrate (10) Uniformly applying the polymer nanoparticles, and depositing the catalyst 12 target and the metal oxide target by co-sputtering at a room temperature to form a metal oxide sensing layer 13 including the catalyst 12. Forming and removing spherical polymer nanoparticles through high temperature heat treatment to impart porosity to the metal oxide sensing layer 13. In this case, instead of the method of simultaneously sputtering the catalyst 12 target and the metal oxide target, a method of sputtering using a metal oxide including the catalyst 12 as a single target may be used.

According to the present invention, by controlling the porosity of the metal oxide sensing layer 13 including the catalyst 12 by controlling the size of the microparticles (hereinafter referred to as “sacrificial particles”) used as the template, the external gas Sensitivity, reaction rate, and selectivity can be adjusted. At this time, the size of the sacrificial particles is preferably 100nm ~ 10μm in diameter. Because, when it is less than 100 nm, it is difficult to uniformly disperse the micro particles, and when it exceeds 10 μm, the space between the micro particles becomes large, so that it may be difficult to apply the uniform sensing layer 13 during thin film deposition. In particular, when the thin porous sensing layer 13 is present in 10μm size, it is because the stability of the thin layer is reduced.

In addition, in the present invention, the gas diffusion is fast due to the characteristics of the porous metal oxide sensing layer 13, and the specific surface area is greatly increased compared to the general thin film layer, thereby improving sensitivity.

Hereinafter, the manufacturing method of the gas sensor of the present invention will be described in detail for each step.

1) Preparation of Sacrificial Particle Layer

In order to make the metal oxide sensing layer 13 having a porous structure on the sensor substrate 10 on which the electrode 11 is formed, first, a sacrificial particle layer 14 is formed on the sensor substrate 10, and the sacrificial particle layer 14 is formed. In order to prepare a polymer particle dispersion.

In this embodiment, polymethylmethacrylate (PMMA) of 800 nm size is used as the sacrificial particles. 2 wt% of PMMA was added to the solvent, followed by ultrasonic dispersion for 30 minutes.

As the solvent, one selected from the group consisting of ethanol, methanol, propanol, butanol, IPA, dimethylformamide (DMF), acetone, detrahydrofuran, toluene, water, and mixtures thereof may be used. However, the present invention is not limited thereto.

In the ratio of the sacrificial particles and the solvent, the polymer particles are not limited in a specific range as long as they can be uniformly dispersed in the solvent. Preferably, the sacrificial particles may prepare a dispersion solution in the range of 0.5 to 10 wt% with respect to the solvent. 2 shows a scanning electron micrograph of the PMMA sacrificial particle layer 14 uniformly dispersed on the sensor substrate 10.

The dispersion containing PMMA is dispersed on the substrate 10 on which the sensor electrode 11 is formed using an eyedropper, and dried for 24 hours to form the sacrificial particle layer 14. Formation of the sacrificial particle layer 14 can be prepared not only by the drop method of the dispersion (drop), but also by the spin coating method.

Looking at the composition and preparation method of the dispersion solution according to an embodiment of the present invention, the polystyrene particles having a size of 1-2 μm as the sacrificial particles, and the polyethylene glycol tert-octylphenyl ether t- as a surfactant to help the dispersion of the sacrificial particles It is composed of Octylphenoxypolyethoxyethanol (Triton X-100) and ethanol as a solvent, and mixed so that the weight ratio of polystyrene: Triton X-100: ethanol is 0.05 to 0.1: 0.001 to 0.001: 1, and the sacrificial particles are dispersed. Then, the polymer sacrificial particle dispersion solution was centrifuged at 2000 rpm for 15 minutes, the supernatant was removed, and ethanol particle dispersion (21 wt%) was prepared.

Then, the sacrificial particle dispersion is spin-coated into a monolayer at 2000 rpm to 4000 rpm and 20 s to 40 s. However, the content of the present invention is not limited thereto, and the sacrificial particle layer 14 may be spin-coated so as to be a multilayer.

The sacrificial particles include polystyrene (PS), polymethylmethacrylate (PMMA), polyvinyl chloride (PVC), polystyrene-co-acrylonitrile (poly (strene-co-acrylonitrile) (SAN)), latex ( latex), polyvinylidene chloride-co-vinyl chloride (poly (vinylidene chloride-co-vinyl chloride)), polybutadiene (poly (butadiene)), polyvinylidene fluoride (polyVinyl fluoride (PVDF)) Polymers can be used.

2) Preparation of Thin Metal Oxide Layer Containing Catalyst 12

Simultaneous sputtering from two or more targets on a sacrificial particle layer 14 formed by dispersing sacrificial particles such as polystyrene (PS) or polymethylmethacrylate (PMMA) or sputtering from a single target of a metal oxide containing catalyst 12 The metal oxide sensing layer 13 containing the catalyst 12 is deposited using the method.

In this case, the metal oxide includes materials such as SnO ₂ , TiO ₂ , ZnO, VO ₂ , In ₂ O ₃ , NiO, MoO ₃ , SrTiO ₃ , Fe ₂ O ₃ , WO ₃ and CuO, and the catalyst 12 is Pt , Pd, Ni, Cu and the like. However, the present invention is not limited thereto.

In this case, by adjusting the sputtering time and the RF power (W), the content of the catalyst 12 and the thickness and surface morphology of the metal oxide thin film can be controlled, and the thickness of the metal oxide sensing layer 13 is 10 nm to 1. It is preferable to adjust to the range of micrometer. This is because when the thickness of the sensing layer is less than 10 nm, the mechanical stability is lowered, and when the thickness of the sensing layer exceeds 1 μm, the sensitivity is lowered.

Since the sacrificial particles are circular polymers and have low glass transition temperature and melting temperature, the sacrificial particles layer 14 may be removed by heat treatment at 450 ° C. after the metal oxide thin film is deposited.

3) Post heat treatment step

Subsequently, the porous metal oxide sensing layer 13 including the prepared catalyst 12 is heat-treated at a temperature of 300 ° C to 800 ° C. The post sacrificial process removes the polymer sacrificial particle layer 14 and crystallizes the porous metal oxide sensing layer 13 including the catalyst 12 deposited at room temperature, thereby improving electrical conductivity.

1 is a cross-sectional view schematically showing the structure of a gas sensor consisting of a thin layer of porous metal oxide containing a catalyst 12 according to an embodiment of the present invention. (12) shows the structure applied to the surface of the porous metal oxide thin layer.

  Hereinafter, the present invention will be described in more detail based on the following examples, but the present invention is not limited by the following examples.

Example 1 Preparation of Porous ZnO Sensing Layer Containing Pt Catalyst 12

In order to prepare a sacrificial particle dispersion solution, in this embodiment, 2 wt% of a PMMA spherical polymer having a diameter of 800 nm was added to a water and ethanol mixed solution, and dispersed by sonication for 30 minutes. The PMMA sacrificial particle layer 14 was dispersed using a micropipette on the substrate 10 on which the sensor electrode 11 was formed, and dried in an air for 24 hours.

At this time, the sensor electrode 11 is composed of an IDE (Interdegitated Electrode, 16 fingers, 8 mm long and 200 μm wide, spaced 200 μm apart) structure, using a 200 nm thick Au as the electrode material, the lower Al ₂ O _A 50 nm thick Ti layer was used as the adhesive layer in order to improve the adhesiveness with the ₃ substrate 10.

In order to obtain a ZnO thin film containing the Pt catalyst 12, a simultaneous sputtering method was used in this embodiment. 3 shows an image of a simultaneous sputtering process made from a Pt target and a ZnO target. Sputtering was used for 3 inch target, and is performed at room temperature to prevent decomposition of the polymer sacrificial layer during the deposition process. The process pressure was 10 mTorr, and the RF (high frequency) power of Pt and ZnO was 50W and 110W. Ar gas was flowed at a rate of 20 sccm, and deposition was performed for 23 minutes. At this time, the content of Pt was adjusted while changing the deposition time of Pt.

After forming the Pt-containing porous ZnO sensing layer through simultaneous sputtering, the sacrificial particle layer was removed and the post-heat treatment was performed at 550 ° C. so that the Pt catalyst 12 was well distributed on the surface. 4 shows a scanning electron micrograph (x 30,000 magnification) of a thin ZnO porous layer containing Pt catalyst 12. On the surface of the porous ZnO hemisphere structure, it can be seen that the Pt catalyst 12 particles have a hexagonal structure.

FIG. 5 shows an enlarged scanning electron microscope (x 100,000 magnification) image of the ZnO porous thin layer containing the Pt catalyst 12 and shows that the Pt catalyst 12 is well distributed. The hemispherical structure produced according to the present invention provides a porous structure in micro units, thereby making it easy to penetrate external noxious gas, thereby producing a gas sensor having excellent sensitivity characteristics.

6 shows the results of X-ray diffraction analysis after post-heating the metal oxide sensing layer 13 by increasing the temperature to 750 ° C. to confirm the crystallization degree of the Pt catalyst 12 and the ZnO metal oxide. As shown in FIG. 6, the crystal peaks of Pt and ZnO are clearly observed according to the 2-theta angle, indicating that the Pt phase and the ZnO phase are well formed. At this time, the ratio (content) of each phase can be controlled by adjusting the sputtering time and the RF power.

Example 2 Preparation of Porous SnO ₂ Sensing Layer Containing Pt Catalyst 12

Through the same process as in Example 1, using a SnO ₂ target instead of ZnO to prepare a porous SnO ₂ thin layer containing a Pt catalyst 12 by the simultaneous sputtering method. FIG. 7 shows a scanning electron micrograph (x 50,000 magnification) of the SnO ₂ porous thin layer containing the Pt catalyst 12 after post-heat treatment at 550 ° C. FIG.

It can be seen that the Pt catalyst 12 is uniformly distributed on the SnO ₂ sensing layer having an empty hemispherical structure. Figure 8 shows the X-ray diffraction analysis after the post-heat treatment of the SnO ₂ sensing layer by raising the temperature to 750 ℃ to determine the crystallization degree of the Pt catalyst 12 and SnO ₂ metal oxide. The crystal peaks of Pt and SnO ₂ appear differently according to the 2-theta angle, indicating that the Pt phase and SnO ₂ phase are well formed. At this time, the ratio (content) of each phase can be controlled by adjusting the sputtering time and the RF power.

Example 3 Preparation of Porous ZnO Sensing Layer Containing NiO Catalyst 12

After the same process as in Example 1, a porous ZnO sensing layer including the NiO catalyst 12 was prepared by a simultaneous sputtering method using a NiO target instead of Pt. The porous ZnO nanoparticle sensing layer containing the NiO catalyst 12 can be prepared by dispersion of PMMA having a size of 800 nm, simultaneous sputtering deposition of NiO and ZnO, and a post-heat treatment process. 9 shows a scanning electron micrograph (x 50,000 magnification) of a thin ZnO porous layer containing NiO catalyst 12. Unlike the porous metal oxide containing the metal catalyst 12, since both NiO and ZnO are metal oxides, although the nano nanoparticles do not form a protruding structure on the surface of the porous hemisphere, the ZnO and NiO are uniformly distributed. Thus, improvement of selectivity and sensitivity characteristics can be induced.

From these results, NiO can also be utilized as catalyst 12. It is also possible to control the surface structure by manufacturing the Ni metal target as the catalyst 12 instead of the NiO ceramic target.

The hemispherical structure produced according to the present invention provides a porous structure in micro units, thereby making it easy to penetrate external noxious gas, thereby producing a gas sensor having excellent sensitivity characteristics. Figure 10 shows the X-ray diffraction analysis after the post-heat treatment of the thin layer by raising the temperature to 750 ℃ to determine the degree of crystallization of the NiO catalyst 12 and ZnO metal oxide. As shown, it can be seen that the NiO phase and the ZnO phase are well formed. At this time, the ratio (content) of each phase can be controlled by adjusting the sputtering time and the RF power.

Detection of external environmental gases (hydrogen, oxygen, CO, NOx, alcohol, SOx, DMMP, phenol, acetone, formaldehyde, etc.) using the metal oxide hemispherical structure containing the catalyst according to the present invention as the gas sensor sensing layer 13 It can be used as a gas sensor.

While the invention has been shown and described with respect to certain preferred embodiments thereof, the invention is not limited to these embodiments, and has been claimed by those of ordinary skill in the art to which the invention pertains. It includes all the various forms of embodiments that can be implemented without departing from the spirit.

1 is a manufacturing process diagram of a gas sensor according to an embodiment of the present invention;

2 is a scanning electron micrograph of a PMMA sacrificial particle layer uniformly dispersed on a sensor substrate according to the present invention;

3 is a photograph of simultaneous sputtering of a catalytic metal and a metal oxide according to an embodiment of the present invention;

Figure 4 is a surface scanning electron micrograph of a Pt-ZnO porous structure according to an embodiment of the present invention,

FIG. 5 is a surface scanning electron microscope photograph of FIG.

6 is a graph for confirming the crystallization degree of the catalyst and the metal oxide as a result of X-ray diffraction of the porous structure in FIG. 4,

7 is a surface scanning electron micrograph of a Pt-SnO ₂ porous structure according to another embodiment of the present invention,

8 is a graph for confirming the crystallization degree of the catalyst and the metal oxide as a result of X-ray diffraction of the porous structure in FIG.

9 is a surface scanning electron micrograph of the porous structure of NiO-ZnO according to another embodiment of the present invention,

10 is a graph for confirming the crystallization degree of the catalyst and the metal oxide as a result of X-ray diffraction of the porous structure in FIG. 9,

<Description of the symbols for the main parts of the drawings>

10 substrate 11 electrode

12 catalyst 13 metal oxide sensing layer

14: sacrificial particle layer

Claims (19)

In the manufacturing method of the gas sensor, Forming a sacrificial particle layer 14 in which sacrificial particles are uniformly dispersed on the sensor substrate 10; Forming a metal oxide sensing layer (13) including a catalyst (12) on the sacrificial particle layer (14) by a sputtering method; And Heat treating the metal oxide sensing layer 13 including the catalyst 12 to remove the sacrificial particle layer 14 to obtain a porous metal oxide sensing layer 13 including the catalyst 12. Method for producing a gas sensor characterized in that. The method according to claim 1, Method for manufacturing a gas sensor, characterized in that the sensor electrode (11) formed on the sensor substrate (10) to detect a change in resistance with respect to external gas exposure. The method according to claim 1 or 2, The average size of the sacrificial particles is a manufacturing method of a gas sensor, characterized in that in the range of 100nm ~ 10㎛. The method according to claim 1 or 2, The sacrificial particles are spherical polymer organic particles, characterized in that the manufacturing method of the gas sensor. The method according to claim 4, The spherical polymer organic particles may be polystyrene (PS), polymethylmethacrylate (PMMA), polyvinyl chloride (PVC), polybutadiene (poly (butadiene)), polystyrene-co-acrylonitrile (poly (strene-) co-acrylonitrile (SAN)), polyvinylidene chloride-co-vinyl chloride (poly (vinylidene chloride-co-vinyl chloride)), latex (latex), poly (vinylidene fluoride) (PVDF) Method of manufacturing a gas sensor, characterized in that any one selected. The method according to claim 1 or 2, The sacrificial particle layer (14) is a manufacturing method of a gas sensor, characterized in that formed in a single layer or multiple layers. The method according to claim 1 or 2, Method for producing a gas sensor, characterized in that the porous metal oxide sensing layer (13) containing the catalyst (12) is deposited from a plurality of targets using a sputtering method. The method according to claim 1 or 2, Method for producing a gas sensor, characterized in that the porous metal oxide sensing layer (13) containing the catalyst (12) is deposited from a single target of the metal oxide containing the catalyst (12). The method according to claim 1 or 2, Method for producing a gas sensor, characterized in that the thickness of the porous metal oxide sensing layer (13) containing the catalyst (12) obtained after the heat treatment is in the range of 10nm ~ 1㎛. The method according to claim 1 or 2, Repeating the formation of the sacrificial particle layer 14, the formation of the metal oxide sensing layer 13 including the catalyst 12, and the heat treatment step are repeated to include the metal oxide sensing layer including the catalyst 12 having a multilayer structure. (13) obtaining a gas sensor. The method according to claim 1 or 2, The heat treatment is a manufacturing method of a gas sensor, characterized in that for 10 minutes to 2 hours at 300 ~ 800 ℃. The method according to claim 1 or 2, The catalyst (12) is a method of manufacturing a gas sensor, characterized in that any one selected from Pt, Pd, Ni, Cu, Fe. The method according to claim 1 or 2, The metal oxide is at least one selected from SnO ₂ , TiO ₂ , ZnO, VO ₂ , In ₂ O ₃ , NiO, MoO ₃ , SrTiO ₃ , Fe ₂ O ₃ , WO ₃ and CuO Way. In the gas sensor, A gas sensor comprising a sensor substrate (10) having a sensor electrode (11) formed on an upper surface thereof, and a porous metal oxide sensing layer (13) formed on the sensor substrate (10) and containing a catalyst (12). The gas sensor according to claim 14, wherein the porous metal oxide sensing layer (13) including the catalyst (12) has a structure in which hollow hemispheres are regularly arranged. The method according to claim 14, The hollow hemispherical body is a gas sensor, characterized in that it comprises a hemispherical pores having an average diameter of 100nm ~ 10㎛. The method according to claim 14, Gas sensor, characterized in that the thickness of the porous metal oxide sensing layer (13) containing the catalyst (12) is in the range of 10nm ~ 1㎛. The method according to claim 14, Gas sensor, characterized in that the porous metal oxide sensing layer (13) containing the catalyst (12) has a single layer or a multilayer structure. The method according to claim 14, Gas sensor, characterized in that the catalyst (12) is uniformly dispersed inside or on the surface of the porous metal oxide sensing layer (13) containing the catalyst (12).

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