KR101760212B1 - Gas sensor and method for manufacturing the same - Google Patents

Abstract

The present invention relates to a gas sensor and a method of manufacturing the same, and more particularly, to a gas sensor of a ternary compound thin film and a polymer substrate, which employs a compound semiconductor layer having high chemical stability as a ternary p-type layer, And the detection force can be improved through the heterojunction between the p-type thin film type compound semiconductor layer and the n-type compound semiconductor layer due to the dense characteristics of the p-type thin film type compound semiconductor layer, which can be applied as a technique for replacing the conventional gas sensor.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a gas sensor and a manufacturing method thereof,

The present invention relates to a gas sensor and a method of manufacturing the same, and more particularly, to an LPG gas sensor using a p-n junction capable of reducing a production cost while having excellent detection force and a method of manufacturing the same.

Gas sensors are a kind of chemical sensors that detect and quantify various gases in the atmosphere and have been continuously studied for gas sensors due to the increase of the amount of combustible gas in the atmosphere due to industrialization.

Among flammable gases, LPG (Liquefied Petroleum Gas) is widely used not only for industrial fuel such as automobile fuel, aerosol propellant, but also for home use such as fuel for gas range. However, LPG is a harmful gas to humans and the environment and can cause serious problems even in the presence of very small amounts due to high flammability. Therefore, efforts are being made to develop a gas sensor for quickly and accurately detecting LPG.

As one example, gas sensors using metal oxides such as SnO ₂ , ZnO, TiO ₂ or ZrO ₂ have been developed. The gas sensor measures the concentration and type of the gas using the reaction of the sensor generated by the adsorption and desorption of the gas to be detected. The gas sensor can be reliably operated under harsh conditions such as corrosive atmospheres or the like, and is advantageously used for improving the sensitivity and response characteristics of the gas to be detected according to a material or a manufacturing method.

In the case of a gas sensor using such a metal oxide, a high temperature operation of 200 ° C. to 600 ° C. is required in order to improve the sensitivity and response characteristics due to the reaction between the gas to be detected and the sensing element. However, such a high-temperature operation requires complicated and expensive equipment. In addition, due to the relatively dense structure of the metal oxide, the circulation of the gas is not smooth and the reaction time and recovery time are increased.

In recent years, studies on gas sensors using pn junctions have been actively conducted. [Room temperature LPG sensor based on n-CdS / p-polyaniline heterojunctions, Sensors and Actuators B 145 (2010) 205.210, Development of polyaniline / Cu ₂ ZnSnS ₄ (CZTS) thin film based heterostructure as room temperature LPG sensor, Sensors and Actuators A 193 (2013) 79. 86, Liquefied petroleum gas (LPG) sensing using spray deposited Cu ₂ ZnSnS ₄ thin film, Journal of Analytical and Applied Phyrolysis 117 (2016) 310, 316, etc.].

These prior art documents disclose a gas sensor using a p-n junction structure of a metal oxide / polyaniline or metal chalcogenide / polyaniline and a four component compound. Thus, most p-n junction gas sensors use a p-n junction of metal oxide / conductive polymer.

However, when an organic material such as a conductive polymer is used, the reaction time and the recovery time of the gas are increased through the uniformly arranged structure. Further, there are problems such as exhibiting low production yield, unstable chemical stability, and low mechanical strength. In addition, the organic material has a very high hygroscopicity, and when the organic material is used, the life of the gas sensor is shortened and its use in various places is limited. In addition, quaternary compounds are problematic in that they are not competitive because of the unstable synthesis problem and the need for four substances.

Korean Patent Publication No. 10-2010-0105023

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems of the prior art. That is, a gas sensor employing a compound semiconductor layer having ternary p-type semiconductor characteristics as a p-type layer to improve the gas detecting ability and detect the detection target gas quickly, and to reduce the production cost, and a method of manufacturing the same .

In order to solve the above-described problems, one aspect of the present invention provides a gas sensor. The gas sensor includes a substrate, a rear electrode formed on the substrate, a p-type thin film type compound semiconductor layer formed on the rear electrode, an n-type compound semiconductor layer formed on the p-type thin film type compound semiconductor layer, And a front electrode formed on the compound semiconductor layer.

The p-type thin film type compound semiconductor layer may be a ternary p-type layer.

The p-type thin film type compound semiconductor layer may contain an inorganic substance.

The p-type thin film type compound semiconductor layer may include at least one selected from Cu ₂ SnS ₃ , Cu ₂ SnSe ₃ , Cu ₄ SnS, and Cu ₂ Sn ₅ S ₇ .

The n-type compound semiconductor layer may include at least one selected from CdS, ZnOS, ZnS, ZnO, SnO ₂ , VO ₂ , TiO _2, and In ₂ O ₃ .

The p-type thin film type compound semiconductor layer includes Cu ₂ SnS ₃ , and the n-type compound semiconductor layer may include CdS.

The rear electrode may include Mo, and the front electrode may include Ag.

According to another aspect of the present invention, there is provided a method of manufacturing a gas sensor. The method of manufacturing the gas sensor includes the steps of providing a substrate on which a rear electrode is formed, forming a p-type thin film type compound semiconductor layer on the substrate, forming an n-type compound semiconductor layer on the p- And forming a front electrode on the n-type compound semiconductor layer.

The p-type thin film type compound semiconductor layer may be a ternary p-type layer.

The p-type thin film type compound semiconductor layer may include at least one selected from Cu ₂ SnS ₃ , Cu ₂ SnSe ₃ , Cu ₄ SnS, and Cu ₂ Sn ₅ S ₇ .

The step of forming the p-type thin film type compound semiconductor layer may include a step of sputtering and depositing a precursor thin film for a p-type compound semiconductor on the substrate, and a step of heat-treating the precursor thin film.

The heat treatment may be performed at 400 ° C to 800 ° C.

The step of forming the n-type compound semiconductor layer may be a step of growing an n-type compound semiconductor on the p-type thin film type compound semiconductor layer using a chemical bath deposition (CBD) method.

According to the present invention described above, a ternary p-type layer employs a compound semiconductor layer having high chemical stability and can be used at room temperature regardless of the place.

In addition, it is possible to manufacture a gas sensor having a high detection force through heterogeneous bonding with the n-type compound semiconductor layer with the dense characteristics of the p-type thin film type compound semiconductor layer.

Furthermore, it is possible to reduce the production cost as compared with the conventional quartz-based compound, thus being excellent in price competitiveness.

The technical effects of the present invention are not limited to those mentioned above, and other technical effects not mentioned can be clearly understood by those skilled in the art from the following description.

1 is a cross-sectional view showing a gas sensor according to an embodiment of the present invention.
2 is a process flow chart showing a method of manufacturing a gas sensor according to an embodiment of the present invention.
3 is an SEM image showing a cross section of a gas sensor according to an embodiment of the present invention.
4 is a JV curve showing the current density according to the gas concentration of the gas sensor according to an embodiment of the present invention.
5 is a graph showing a gas reaction rate according to a gas concentration of a gas sensor according to an embodiment of the present invention.
6 is a graph showing gas reaction rates with time of a gas sensor according to an embodiment of the present invention.
7 is a graph showing a gas reaction rate according to a date of a gas sensor according to an embodiment of the present invention.

The present invention is capable of various modifications and various forms, and specific embodiments are illustrated in the drawings and described in detail in the text. It should be understood, however, that the invention is not intended to be limited to the particular forms disclosed, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention. Like reference numerals are used for like elements in describing each drawing.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms such as those defined in commonly used dictionaries are to be interpreted as having a meaning consistent with the contextual meaning of the related art and are to be interpreted as either ideal or overly formal in the sense of the present application Do not.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. Referring to the accompanying drawings, the same or corresponding components are denoted by the same reference numerals, .

1 is a cross-sectional view showing a gas sensor according to an embodiment of the present invention.

1, a gas sensor 100 according to an exemplary embodiment of the present invention includes a substrate 110, a rear electrode 120 formed on the substrate 110, a p-type electrode 120 formed on the rear electrode 120, A thin film type compound semiconductor layer 130, an n type compound semiconductor layer 140 formed on the p type thin film type compound semiconductor layer 130 and a front electrode 150 formed on the n type compound semiconductor layer 140 .

The substrate 110 may be an insulating substrate. Further, the substrate 110 may be an oxide single crystal substrate, a ceramic substrate, or a glass substrate. For example, the substrate 110 may be made of Al ₂ O ₃ , MgO, SrTiO _3, or quartz.

A back contact 120 may be formed on the substrate 110 and the back electrode 120 may be a metal electrode. For example, the rear electrode 120 may be made of at least one selected from the group consisting of Mo, Pt, Pd, Ag, Au, Ni, Ti, Cr, Al and Cu. However, Can be used. In addition, it is preferable that the back electrode 120 has low resistivity as an electrode, and is excellent in adhesion to the substrate 110, so that a peeling phenomenon does not occur due to a difference in thermal expansion coefficient. The rear electrode 120 may be formed on the front surface of the substrate 110 as another example.

The p-type thin film type compound semiconductor layer 130 may be formed on the rear electrode 120. Further, the p-type thin film type compound semiconductor layer 130 may contain an inorganic substance having high chemical stability. For example, the p-type thin film type compound semiconductor layer 130 may be the same as a material used as a p-type layer of a solar cell. For example, the p-type thin film type compound semiconductor layer 130 may be formed of at least one selected from Cu ₂ SnS ₃ , Cu ₂ SnSe ₃ , Cu ₄ SnS, and Cu ₂ Sn ₅ S _{7. In} a preferred embodiment of the present invention The p-type thin film type compound semiconductor layer 130 may be formed of Cu ₂ SnS ₃ .

The n-type compound semiconductor layer 140 may be formed on the p-type thin film type compound semiconductor layer 130. Therefore, the n-type semiconductor layer can form a p-n junction at the interface with the p-type thin film type compound semiconductor layer 130. [

In addition, the n-type compound semiconductor layer 140 may be a metal oxide semiconductor layer having n-type semiconductor characteristics. For example, the n-type compound semiconductor layer 140 may include at least one selected from CdS, ZnOS, ZnS, ZnO, SnO ₂ , VO ₂ , TiO _2, and In ₂ O ₃ . The n-type thin film type compound semiconductor layer according to the example may be formed of CdS. That is, in the gas sensor 100 according to the preferred embodiment of the present invention, the p-type thin film type compound semiconductor layer 130 may be formed of Cu ₂ SnS ₃ and the n-type compound semiconductor layer 140 may be formed of CdS.

As described above, a gas sensor having a pn junction structure using an organic material such as a conventional four-component compound and a conductive polymer has problems in that the reaction time and recovery time of gas are increased through a uniformly aligned structure, Unstable chemical stability and low mechanical strength. However, the gas sensor according to the present invention employs a compound semiconductor layer having a high chemical stability as a ternary p-type layer and can be used at any room temperature regardless of the location. The n-type thin film type compound semiconductor layer 130 has n -Type compound semiconductor layer 140. In this case, it is possible to obtain a high detection force.

Subsequently, a front contact 150 may be formed on the n-type compound semiconductor layer 140. For example, the front electrode 150 may be made of at least one selected from the group consisting of Mo, Pt, Ag, Au, Ni, Ti, Tr, Al and Cu. However, Can be used. For example, the front electrode 150 may be formed on a part of the n-type compound semiconductor layer 140.

2 is a process flow chart showing a method of manufacturing a gas sensor according to an embodiment of the present invention.

Referring to FIG. 2, a method of manufacturing a gas sensor according to an embodiment of the present invention includes providing a substrate 110 on which a rear electrode 120 is formed (S210), forming a p-type thin film type compound A step S230 of forming an n-type compound semiconductor layer 140 on the p-type thin film type compound 130, a step S230 of forming an n-type compound semiconductor layer 140 on the n-type compound semiconductor layer 140, 150 (step S240).

The substrate 110 may be an insulating substrate and the rear electrode 120 may be a metal electrode in step S210 of providing the substrate 110 having the rear electrode 120 formed thereon. The rear electrode 120 may be formed on the front surface of the substrate 110 by thermal vapor deposition, electron beam deposition, RF sputtering, or the like.

In the step S220 of forming the p-type thin film type compound semiconductor layer 130 on the substrate 110, the p-type thin film type compound semiconductor layer 130 may contain an inorganic substance having high chemical stability. The precursor thin film for the p-type compound semiconductor formed on the substrate 110 may be a precursor thin film constituting Cu ₂ SnS ₃ , Cu ₂ SnSe ₃ , Cu ₄ SnS and Cu ₂ Sn ₅ S ₇ . The precursor thin film for the p-type compound semiconductor according to the example may be Cu ₂ SnS ₃ .

The step S220 of forming the p-type thin film type compound semiconductor layer 130 on the substrate 110 includes a step S221 of sputtering and depositing a precursor thin film for a p-type compound semiconductor on the substrate 110, And heat treating the precursor thin film (S222). That is, the p-type thin film type compound semiconductor layer 130 may be formed by sputtering and depositing a precursor thin film for a p-type compound semiconductor on the substrate 110, and heat treating the precursor thin film.

In the step of heat-treating the precursor thin film (S222), the heat treatment may be performed at 400 ° C to 800 ° C. That is, the precursor thin film for the p-type compound semiconductor can be converted into the p-type compound semiconductor layer through the heat treatment described above.

n-type compound in the step (S230) of forming the n-type compound semiconductor layer 140 on the p-type thin-film compound is CdS, ZnOS, ZnS, ZnO, SnO 2, VO 2, TiO 2 , and In ₂ O ₃ is selected from And the n-type compound according to a preferred embodiment of the present invention may be CdS. That is, in the gas sensor 100 according to the preferred embodiment of the present invention, the p-type thin film type compound semiconductor layer 130 includes Cu ₂ SnS ₃ , and the n-type compound semiconductor layer 140 includes CdS.

A chemical bath deposition (CBD) method may be used to grow CdS, which is the n-type compound semiconductor layer 140, on the p-type thin film type compound semiconductor layer 130. The CBD method can produce Cd and S ions in the solution, adjust the pH of the solution, increase the temperature of the solution, and allow the Cd and S ions to react with each other to produce a thin film.

type compound semiconductor layer 140 in the step of forming the front electrode 150 on the n-type compound semiconductor layer 140 in step S240, the front electrode 150 may be formed by thermal vapor deposition, electron beam evaporation, RF sputtering or the like can be used. The front electrode 150 may be made of any one selected from the group consisting of Mo, Pt, Ag, Au, Ni, Ti, Tr, Al and Cu. However, have.

Hereinafter, preferred examples will be given to facilitate understanding of the present invention. It should be understood, however, that the following examples are intended to aid in the understanding of the present invention and are not intended to limit the scope of the present invention.

Experimental Example

1. Manufacture of p-type CTS thin film

A precursor thin film was deposited by sputtering at room temperature, and the precursor thin film was subjected to a heat treatment by sulphide. The precursor thin film was formed of a stacked structure of glass / Mo / Sn / Cu using a Sn / Cu target on a soda lime glass substrate on which 1 μm of Mo was deposited. At this time, the RF power of Sn and Cu target was fixed to 40 W, and the working pressure was 1 mTorr. Thereafter, heat treatment was performed using 5% sulfur powder at 580 ° C for 10 minutes.

2. Synthesis of n-type CdS thin film

A CdS thin film was synthesized by CBD (Chemical Bath Deposition) on the CTS thin film prepared by the above process 1. First, Cadmium sulfate, Thiourea, and 28% NH ₃ aqueous solution are prepared as starting materials, and they are mixed and continuously stirred at a temperature of 60 degrees or more. Thereafter, the CTS thin film is vertically dipped into the solution to synthesize a CdS thin film on the CTS thin film.

3 is an SEM image showing a cross section of a gas sensor according to an embodiment of the present invention.

Referring to FIG. 3, it can be seen that the p-CTS thin film is composed of particles of micrometer (μm) size. In addition, the particles are formed in an irregular shape, and the average size of the particles is about 500 탆.

4 is a J-V curve showing the current density according to the gas concentration of the gas sensor according to an embodiment of the present invention.

Referring to FIG. 4, when a gas is supplied to the gas sensor, the forward current linearly increases to the threshold value at the p-n junction. As shown in FIG. 4, it can be seen that the forward current increases linearly with the increase of the gas concentration. It is a measure of the reactivity, and it is known that the characteristic of the diode showing the Schottky contact is apparent with the increase of the gas concentration .

5 is a graph showing a gas reaction rate according to a gas concentration of a gas sensor according to an embodiment of the present invention.

Referring to FIG. 5, it can be seen that as the gas concentration increases, the gas reaction rate increases up to a gas concentration of 800 ppm, while it decreases at a higher concentration. The increase in the gas response rate is attributed to the increase in the height of the potential barrier due to the decrease of the charge carrier by the wider depletion layer region. The decrease in the gas reaction rate at 800 ppm or more is attributed to the accumulation of gas molecules at the interface of the p-n junction, thereby reducing the effective area for the interfacial reaction. It can be seen that the gas reactivity is as high as 60% at a gas concentration of 800 ppm, indicating a very high gas detection capability.

6 is a graph showing gas reaction rates with time of a gas sensor according to an embodiment of the present invention.

Referring to FIG. 6, the gas reaction rate showed a maximum value of 50% within 50 seconds after the gas was supplied to the reaction chamber, and the reaction rate returned to 0 within 70 seconds after gas out. That is, the reaction time is about 40 seconds and the recovery time is about 70 seconds. Therefore, it can be confirmed that the gas sensor according to the embodiment of the present invention exhibits a fast reaction rate in addition to a high gas detection force.

7 is a graph showing a gas reaction rate according to a date of a gas sensor according to an embodiment of the present invention.

Referring to FIG. 7, it can be confirmed that the gas reaction rate is maintained at a maximum value of 60% for 10 days. Therefore, it can be confirmed that the gas sensor according to the embodiment of the present invention shows excellent reliability.

As described above, the gas sensor according to the present invention employs a compound semiconductor layer having high chemical stability as a ternary p-type layer as compared with the prior art, and can be used at room temperature regardless of the place. In addition, it is possible to manufacture a gas sensor having a high detection force through heterogeneous bonding with the n-type compound semiconductor layer with the dense characteristics of the p-type thin film type compound semiconductor layer.

It should be noted that the embodiments of the present invention disclosed in the present specification and drawings are only illustrative of specific examples for the purpose of understanding and are not intended to limit the scope of the present invention. It will be apparent to those skilled in the art that other modifications based on the technical idea of the present invention are possible in addition to the embodiments disclosed herein.

110: substrate 120: rear electrode
130: p-type thin film type compound semiconductor layer 140: n-type compound semiconductor layer
150: front electrode

Claims (13)

Board;
A rear electrode formed on the substrate;
A p-type thin film type compound semiconductor layer formed as a ternary p-type layer on the rear electrode;
An n-type compound semiconductor layer formed on the p-type thin film type compound semiconductor layer; And
And a front electrode formed on the n-type compound semiconductor layer,
Wherein the p-type thin film type compound semiconductor layer comprises at least one selected from Cu ₂ SnS ₃ , Cu ₂ SnSe ₃ , Cu ₄ SnS, and Cu ₂ Sn ₅ S ₇ . delete The method according to claim 1,
Wherein the p-type thin film type compound semiconductor layer contains an inorganic substance. delete The method according to claim 1,
Wherein the n-type compound semiconductor layer comprises at least one selected from the group consisting of CdS, ZnOS, ZnS, ZnO, SnO ₂ , VO ₂ , TiO ₂ and In ₂ O ₃ . The method according to claim 1,
Wherein the p-type thin film type compound semiconductor layer includes Cu ₂ SnS ₃ , and the n-type compound semiconductor layer includes CdS. The method according to claim 1,
Wherein the backside electrode comprises Mo and the front electrode comprises Ag. Providing a substrate on which a back electrode is formed;
Forming a p-type thin film type compound semiconductor layer formed as a ternary p-type layer on the substrate;
Forming an n-type compound semiconductor layer on the p-type thin film type compound; And
And forming a front electrode on the n-type compound semiconductor layer,
Wherein the p-type thin film type compound semiconductor layer comprises at least one selected from Cu ₂ SnS ₃ , Cu ₂ SnSe ₃ , Cu ₄ SnS, and Cu ₂ Sn ₅ S ₇ . delete delete 9. The method of claim 8,
The step of forming the p-type thin film type compound semiconductor layer includes:
Sputtering and depositing a precursor thin film for a p-type compound semiconductor on the substrate; And
And heat treating the precursor thin film. 12. The method of claim 11,
Wherein the heat treatment is performed at 400 ° C to 800 ° C. 9. The method of claim 8,
The step of forming the n-type compound semiconductor layer includes:
Wherein the step of growing an n-type compound semiconductor on the p-type thin film type compound semiconductor layer by using a chemical bath deposition (CBD) method.

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