CN114791449B - A kind of gas sensor and its preparation method and application - Google Patents

Abstract

The invention relates to a gas sensor, a preparation method and application thereof, and relates to the technical field of gas sensors. The gas sensor of the present invention comprises a substrate, the surface of the substrate is also provided with a GeTeO _x thin film and an element-co-doped CuO thin film; the middle part of the GeTeO _x thin film and the element-co-doped CuO thin film overlaps to form a heterogeneous structure, the GeTeO _x thin film and the element-co-doped CuO thin film partly extend to the substrate, and the end of the GeTeO _x thin film and the element-co-doped CuO thin film is provided with a conductive metal thin film, wherein 0<x≤4. The gas sensor of the invention has high sensitivity and lower detection limit for H ₂ S, NH ₃ and NO ₂ . The higher the test temperature, the lower the detection limit and the higher the sensitivity. The invention has simple and convenient operation, simple and convenient reaction conditions, and the magnetron sputtering method has low price and uniform film formation, can be used for large-scale preparation of container sensor components, and is suitable for industrial production.

Description

A kind of gas sensor and its preparation method and application

technical field

The invention relates to the technical field of gas sensors, in particular to a gas sensor and its preparation method and application.

Background technique

Gas sensors are components used to detect gas composition and content. It is generally believed that a gas sensor is a converter that converts a certain gas volume fraction into a corresponding electrical signal.

With the development of science and technology, people gradually pay attention to environmental safety issues, and pay more and more attention to air pollution and other issues. In order to ensure personal safety and prevent accidents, it is necessary to monitor the air quality in various places in life in real time and detect the concentration of toxic and harmful gases. At present, the monitoring and detection of various gases have been widely used in various fields such as medical and health care, mine safety, pollution source investigation, environmental monitoring, and industrial production. For example, ethanol gas involved in drunk driving in traffic safety, formaldehyde gas emitted from interior decoration materials, nitrogen oxides in automobile exhaust emissions, methane gas, ammonia gas and hydrogen sulfide gas in oil and coal mines, etc. If a sensor is designed to detect several or more gases at the same time, it will undoubtedly be very competitive in the market. At present, most commercial gas sensors are selective for a single gas, or form a sensor array through multiple single-component sensors, which will greatly increase the cost and cannot meet the needs of testing multiple mixed components.

Generally, the ideal gas sensor should have the following characteristics: (1) Fast response speed, and usually requires that the response speed is less than 50s (including two processes of gas adsorption and adsorption); (2) high sensitivity, only high sensitivity can be sensitive to small amounts of gas concentration; (3) high selectivity, only a specific gas sensitivity, not sensitive other gas; (4) Reverseness can repeat sensitivity, that is, it is not a one -time sensitivity and can be used for a long time; (5) The service life is long, and it is generally required for half a year or one year;

A physical interface between two different materials is often called a heterojunction, and a material that combines these two different components has a heterostructure. The conductivity type on both sides of the junction is controlled by doping. The same type of doping is called homo-heterojunction (n-n, p-p), and the type of doping is called hetero-heterojunction (n-p, p-n). Among them, the homotype heterojunction is a majority carrier device, which has a higher speed than the minority carrier device, and is suitable for gas sensors. Most of the existing gas sensors of the same kind can only detect a single specific gas, and cannot realize the specific detection of multiple gases at the same time with one chip, and the existing heterogeneous structure gas sensors cannot simultaneously satisfy the switching between the independent test of a single component and the test of forming a heterojunction, and the function is single and the cost is high.

Contents of the invention

Therefore, the technical problem to be solved by the present invention is to overcome the problems in the prior art that a single chip cannot specifically detect multiple gases at the same time and that the traditional heterogeneous structure gas sensor cannot simultaneously satisfy the switching between the independent test of a single component and the test of forming a heterojunction, single function, and high cost.

In order to solve the above technical problems, the present invention provides a gas sensor and its preparation method and application. Based on a single chip using MEMS processing technology, a multi-functional patterned multi-layer thin film heterogeneous structure is designed. Through the switching of the output electrode, the specific detection of multiple gases can be realized at the same time, and it has high sensitivity.

The first object of the present invention is to provide a gas sensor, comprising a substrate, the surface of the substrate is also provided with a GeTeO _{x film and an element-codoped CuO film; the middle part of the GeTeO x film} and the element-co-doped CuO film overlaps to form a heterogeneous structure, the GeTeO _x film and the element-co-doped CuO film partly extend to the substrate, and the end of the GeTeO _x film and the element-co-doped CuO film is provided with a conductive metal film, wherein 0<x≤4.

In one embodiment of the present invention, 0-2 conductive metal films are arranged on both ends of the GeTeO _x film and the element-co-doped CuO film, and at least one conductive metal film is provided on the GeTeO _x film and the element-co-doped CuO film.

In one embodiment of the present invention, the overlapping portion of the GeTeO _x thin film and the element-codoped CuO thin film has an interdigitated structure.

In one embodiment of the present invention, the material of the base body is Si.

In one embodiment of the present invention, the elements doped in the CuO film are two or more of Y, W, Sn, Al, In and Ni.

In one embodiment of the present invention, the conductive metal is one or more of Au, Ag, Cr, Pt, Pd, Ti, Al, W.

In one embodiment of the present invention, the gas sensor can meet the requirements of highly sensitive and highly selective gas detection by optimizing relevant parameters such as material composition and film thickness.

In one embodiment of the present invention, the patterned interdigitated structure in the gas sensor can continue to drip sensitive materials, easily realize the construction of new heterostructures, and detect more gases.

In one embodiment of the present invention, the gas sensor is arranged in an interdigitated structure.

In an embodiment of the present invention, zinc oxide nanomaterials can also be introduced to form a pn heterostructure to detect _H2 gas.

The second object of the present invention is to provide a method for preparing a gas sensor, comprising the following steps,

S1. Etching an electrode channel on the surface of the pretreated substrate, and sputtering a conductive metal film on the electrode channel;

S2. Sputtering a GeTeO _x film on the surface of the substrate, the sputtering gas is a mixed gas of argon and oxygen, where 0<x≤4;

S3. Sputtering an element-co-doped CuO film on the surface of the GeTeO _x film, the element-co-doped CuO film extends to the surface of the substrate, and the sputtering gas is argon;

S4. Sputtering a conductive metal film on the surface of the non-overlapping portion of the GeTeO _x film and the CuO film co-doped with the elements to obtain the gas sensor.

In one embodiment of the present invention, in step S1, the pretreatment is ultrasonic cleaning with acetone, ethanol and deionized water in sequence.

In one embodiment of the present invention, in the step S1, the etching is to first prepare a specific electrode pattern by using a glue coating-photolithography-development process, and then make a shallow electrode channel by a reactive ion etching machine.

In one embodiment of the present invention, the sputtering adopts a vapor phase deposition method, and the degree of vacuum is less than 1.0×10 ^{−3 Pa} .

In one embodiment of the present invention, the sputtering power is 5-200W, and the sputtering time is 1-30min.

In one embodiment of the present invention, the flow rate of the gas is 1-50 sccm, and the sputtering pressure of the gas is 0.5-10 Pa.

The third object of the present invention is to provide an application of the gas sensor in detecting H ₂ S, NH ₃ or NO ₂ .

In one embodiment of the present invention, the temperature detected in the application is 50-300° C., and the gas concentration is 1-200 ppm.

In one embodiment of the present invention, the switch between the independent test of a single component and the test of forming a heterojunction can be simultaneously satisfied through structural optimization design, realizing multi-functionality and greatly reducing costs.

Compared with the prior art, the technical solution of the present invention has the following advantages:

(1) GeTeO in the gas sensor of the present invention_xThe film itself reacts to H₂S has good selectivity and sensitivity, element co-doped CuO thin film has a good effect on NO₂With good selectivity and sensitivity, GeTeO_xIt can form a heterogeneous structure with element-doped CuO thin films, and form a built-in electric field at the interface of the two thin film materials, which can promote the separation of carriers. At the same time, the active adsorption sites formed at the interface junction are higher than other positions. Gas molecules tend to interact with the material at the interface junction, resulting in electron exchange, increasing the electrons or holes of the material, and promoting the transport of carriers under the action of the built-in electric field. The heterojunction interface for NH₃exhibited good selectivity and sensitivity.

(2) The multifunctional patterned multilayer thin film heterostructure chip in the gas sensor of the present invention can specifically detect various gases by connecting different electrode points, and the multifunctional patterned multilayer thin film heterostructure chip can be further used as an interdigital electrode to form a new heterogeneous structure by dropping or sputtering sensitive materials, thereby realizing the specific detection of more gases.

(3) The gas sensor of the present invention has high sensitivity and low detection limit for H ₂ S, NH ₃ , and NO ₂ . The higher the test temperature, the lower the detection limit and the higher the sensitivity. In addition, the thin-film electrode product adopts the hard template method to form an interdigitated electrode structure, which can further perform drop samples of other gas-sensing materials, and can flexibly introduce new gas-sensing materials to construct new heterogeneous structures, making the functions of the device more diversified. The invention has simple and convenient operation, simple and convenient reaction conditions, and the magnetron sputtering method has low price and uniform film formation, can be used for large-scale preparation of container sensor components, and is suitable for industrial production.

Description of drawings

In order to make the content of the present invention more easily understood, the present invention will be described in further detail below according to specific embodiments of the present invention in conjunction with the accompanying drawings, wherein:

Fig. 1 is a flow chart of the preparation of the gas sensor in the embodiment of the present invention.

FIG. 2 is a physical diagram of the gas sensor in Embodiment 1 of the present invention.

3-8 are response-recovery curves of different gas sensors to different gases in the test examples of the present invention.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, so that those skilled in the art can better understand the present invention and implement it, but the examples given are not intended to limit the present invention.

Example 1

Referring to Fig. 1, a gas sensor and its preparation method specifically include the following steps:

S1. Etching electrode channels on the surface of the Si substrate after ultrasonic cleaning with acetone, ethanol, and deionized water in sequence;

S2. Sputtering an Al thin film on the electrode channel by vapor deposition method; the vacuum degree of the chamber is 8.0×10 ^-4 Pa; the sputtering power is 20W, and the sputtering time is 3min;

S3, sputtering a GeTeO _x (1≤x≤3) film on the surface of the substrate by vapor deposition, the sputtering gas is a mixed gas of 15sccm argon and 10sccm oxygen; the sputtering power is 50W and 100W; the sputtering pressure is 1.0Pa; the sputtering time is 5min;

S4. Sputtering a CuO film co-doped with Y and W on the surface of the GeTeO _x film by vapor deposition, and extending to the surface of the substrate, the sputtering gas is 30 sccm argon; the sputtering power is 10W, 20W, 40W respectively; the sputtering pressure is 1.0Pa; the sputtering time is 3min;

S5. Sputtering an Al film on the surface of the non-overlapping part of the GeTeO _x film and the CuO film co-doped with Y and W by vapor deposition method; the sputtering power is 20W, and the sputtering time is 3min to obtain the gas sensor shown in FIG. 2 .

Example 2

A gas sensor and a preparation method thereof, specifically comprising the following steps:

S1. Etching electrode channels on the surface of the Si substrate after ultrasonic cleaning with acetone, ethanol, and deionized water in sequence;

S2. Au thin film is sputtered on the electrode channel by vapor deposition method; the vacuum degree of the chamber is 8.0×10 ^-4 Pa; the sputtering power is 20W, and the sputtering time is 3min;

S3, sputtering a GeTeO _x (2≤x≤4) film on the surface of the substrate by vapor deposition, the sputtering gas is a mixed gas of 10sccm argon and 20sccm oxygen; the sputtering power is 50W and 100W; the sputtering time is 5min;

S4. Sputtering a CuO film co-doped with Y and W on the surface of the GeTeO _x film by vapor deposition, and extending to the surface of the substrate, the sputtering gas is 30 sccm argon; the sputtering power is 10W, 20W, 40W; the sputtering time is 3min;

S5. Sputtering an Au film on the surface of the non-overlapping part of the GeTeO _x film and the CuO film co-doped with Y and W by vapor deposition method; the sputtering power is 20W, and the sputtering time is 3min.

Example 3

A gas sensor and a preparation method thereof, specifically comprising the following steps:

S1. Etching electrode channels on the surface of the Si substrate after ultrasonic cleaning with acetone, ethanol, and deionized water in sequence;

S2. Sputtering a Pt film on the electrode channel by vapor deposition method; the vacuum degree of the chamber is 8.0×10 ^-4 Pa; the sputtering power is 20W, and the sputtering time is 3min;

S3. Sputtering a GeTeO _x (1≤x≤3) film on the surface of the substrate by vapor deposition, the sputtering gas is a mixed gas of 10sccm argon and 15sccm oxygen; the sputtering power is 50W and 100W; the sputtering time is 5min;

S4. Sputtering an Al and In co-doped CuO film on the surface of the GeTeO _x film by vapor deposition, and extending to the surface of the substrate, the sputtering gas is 30 sccm argon; the sputtering power is 20W, 20W, 40W; the sputtering time is 3min;

S5. Sputtering a Pd film on the surface of the non-overlapping part of the GeTeO _x film and the Al, In co-doped CuO film by vapor deposition method; the sputtering power is 20W, and the sputtering time is 3min.

Comparative example 1

S1. Etching electrode channels on the surface of the Si substrate after ultrasonic cleaning with acetone, ethanol, and deionized water in sequence;

S2. Au thin film is sputtered on the electrode channel by vapor deposition method; the vacuum degree of the chamber is 8.0×10 ^-4 Pa, the sputtering power is 20W, and the sputtering time is 3min;

S3. Sputtering a GeTeO _x (1≤x≤3) film on the surface of the substrate by vapor deposition, the sputtering gas is a mixed gas of 5 sccm argon and 25 sccm oxygen; the sputtering power is 50W and 100W; the sputtering time is 2min;

S4. Sputtering a CuO film co-doped with Y and W on the surface of the GeTeO _x film by vapor deposition, and extending to the surface of the substrate, the sputtering gas is 30 sccm argon; the sputtering power is 10W, 20W, 40W; the sputtering time is 3min;

S5. Sputtering an Au film on the surface of the non-overlapping part of the GeTeO _x film and the Y, W co-doped CuO film by vapor deposition method; the sputtering power is 20W, and the sputtering time is 3min.

Comparative example 2

S1. Etching electrode channels on the surface of the Si substrate after ultrasonic cleaning with acetone, ethanol, and deionized water in sequence;

S2. Au thin film is sputtered on the electrode channel by vapor deposition method; the vacuum degree of the chamber is 8.0×10 ^-4 Pa, the sputtering power is 20W, and the sputtering time is 3min;

S3. Sputtering a GeTeO _x (1≤x≤3) film on the surface of the substrate by vapor deposition, the sputtering gas is a mixed gas of 10sccm argon and 15sccm oxygen; the sputtering power is 50W and 100W; the sputtering time is 5min;

S4. Sputtering a CuO film co-doped with Y and W on the surface of the GeTeO _x film by vapor deposition, and extending to the surface of the substrate, the sputtering gas is a mixed gas of 20 sccm oxygen and 10 sccm argon; the sputtering power is 10W, 20W, 40W respectively; the sputtering time is 3min;

S5. Sputtering an Au film on the surface of the non-overlapping part of the GeTeO _x film and the CuO film co-doped with Y and W by vapor deposition method; the sputtering power is 20W, and the sputtering time is 3min.

Comparative example 3

S1. Etching electrode channels on the surface of the Si substrate after ultrasonic cleaning with acetone, ethanol, and deionized water in sequence;

S2. Au thin film is sputtered on the electrode channel by vapor deposition method; the vacuum degree of the chamber is 8.0×10 ^-4 Pa, the sputtering power is 20W, and the sputtering time is 3min;

S3. Sputtering a GeTeO _x (1≤x≤3) film on the surface of the substrate by vapor deposition, the sputtering gas is a mixed gas of 10sccm argon and 15sccm oxygen; the sputtering power is 50W and 100W; the sputtering time is 5min;

S4. Sputtering a CuO film co-doped with Y and W on the surface of the GeTeO _x film by vapor deposition, and extending to the surface of the substrate, the sputtering gas is 30 sccm of argon; the sputtering power is 10W, 10W, 40W; the sputtering time is 3min;

S5. Sputtering an Au film on the surface of the non-overlapping portion of the GeTeO _x film and the CuO film co-doped with Y and W by vapor deposition method; the sputtering power is 20W, and the sputtering time is 3min.

test case 1

将实施例1中所得器件(实物图见图2)，如图1(4)所示，将传感器件的4、5电极接入动态气体测试系统，测试电压设置为1V，干燥空气作为背景气和稀释气体，通入目标气体(待测气体)前用干燥空气吹扫器件并将器件加热至200℃，同时持续测试记录其电流-时间变化曲线，当基线跑平时，将浓度为10ppm的NO ₂气体通入测试腔60s后用干燥空气吹扫600s，重复该过程6次，得到该4、5电极对应的气敏材料对10ppmNO ₂气体的响应-恢复曲线，通过响应公式S＝(|I _t -I ₀ |)/I ₀计算其响应，其中S为响应值，I _t为器件在目标气体中的电流值，I ₀为干燥空气中器件的电流值，得到如图3所示的响应-时间曲线。 Figure 3 shows the response-recovery curves of the YW-co-doped CuO film for 6 repetitions of 10ppm NO ₂ gas. The response sensitivity is high, about 5.0, and the recovery performance is good.

test case 2

将对比例1中所得器件，如图1(4)所示，将传感器件的2、3电极接入动态气体测试系统，测试电压设置为1V，干燥空气作为背景气和稀释气体，通入目标气体(待测气体)前用干燥空气吹扫器件并将器件加热至200℃，同时持续测试记录其电流-时间变化曲线，当基线跑平时，将浓度为10ppm的NO ₂气体通入测试腔60s后用干燥空气吹扫600s，重复该过程4次，得到该2、3电极对应的气敏材料对10ppm NO ₂气体的响应-恢复曲线，通过响应公式S＝(|I _t -I ₀ |)/I ₀计算其响应，其中S为响应值，I _t为器件在目标气体中的电流值，I ₀为干燥空气中器件的电流值，得到如图4所示的响应-时间曲线。 Figure 4 shows the response-recovery curves of the GeTeO _x thin film to 10ppmNO ₂ gas for 4 repetitions. The response sensitivity is very poor, about 0.03. Due to the poor recovery performance, the baseline drifts upward.

Test case 3

将对比例2中所得器件，如图1(4)所示，将传感器件的4、5电极接入动态气体测试系统，测试电压设置为1V，干燥空气作为背景气和稀释气体，通入目标气体(待测气体)前用干燥空气吹扫器件并将器件加热至200℃，同时持续测试记录其电流-时间变化曲线，当基线跑平时，将浓度为10ppm的H ₂ S气体通入测试腔60s后用干燥空气吹扫600s，得到该4、5电极对应的气敏材料对10ppm H ₂ S气体的响应-恢复曲线，通过响应公式S＝(|I _t -I ₀ |)/I ₀计算其响应，其中S为响应值，I _t为器件在目标气体中的电流值，I ₀为干燥空气中器件的电流值，得到如图5所示的响应-时间曲线。 Figure 5 shows the response-recovery curve of the YW-co-doped CuO film to 10ppm H ₂ S gas, the response sensitivity is poor, about 0.75, and the recovery performance is poor.

Test case 4

将实施例1中所得器件，如图1(4)所示，将传感器件的2、3电极接入动态气体测试系统，测试电压设置为1V，干燥空气作为背景气和稀释气体，通入目标气体(待测气体)前用干燥空气吹扫器件并将器件加热至200℃，同时持续测试记录其电流-时间变化曲线，当基线跑平时，将浓度为10-50ppm的H ₂ S气体依次通入测试腔60s后用干燥空气吹扫600s，得到该2、3电极对应的气敏材料对10ppm H ₂ S气体的响应-恢复曲线，通过响应公式S＝(|I _t -I ₀ |)/I ₀计算其响应，其中S为响应值，I _t为器件在目标气体中的电流值，I ₀为干燥空气中器件的电流值，得到如图6所示的响应-时间曲线。 Figure 6 shows the response-recovery curve of the GeTeO _x film to 10-50ppm H ₂ S gas, the response sensitivity is good, the recovery performance is excellent, and the baseline does not drift upward.

Test case 5

将实施例2中所得器件，如图1(4)所示，将传感器件的2、3电极接入动态气体测试系统，测试电压设置为1V，干燥空气作为背景气和稀释气体，通入目标气体(待测气体)前用干燥空气吹扫器件并将器件加热至200℃，同时持续测试记录其电流-时间变化曲线，当基线跑平时，将浓度为10-40ppm的H ₂ S气体通入测试腔60s后用干燥空气吹扫600s，得到该2、3电极对应的气敏材料对10-40ppm H ₂ S气体的响应-恢复曲线，通过响应公式S＝(|I _t -I ₀ |)/I ₀计算其响应，其中S为响应值，I _t为器件在目标气体中的电流值，I ₀为干燥空气中器件的电流值，得到如图7所示的响应-时间曲线。 Figure 7 shows the response-recovery curve of the GeTeO _x thin film to 10-40ppm H ₂ S gas, which has high response sensitivity and good recovery performance.

Test case 6

将实施例1中所得器件，如图1(4)所示，将传感器件的2、6或4、7电极接入动态气体测试系统，测试电压设置为1V，干燥空气作为背景气和稀释气体，通入目标气体(待测气体)前用干燥空气吹扫器件并将器件加热至200℃，同时持续测试记录其电流-时间变化曲线，当基线跑平时，将浓度为10-50ppm的NH ₃气体通入测试腔60s后用干燥空气吹扫600s，得到该2、6或4、7电极对应的气敏材料对10-50ppm NH ₃气体的响应-恢复曲线，通过响应公式S＝(|I _t -I ₀ |)/I ₀计算其响应，其中S为响应值，I _t为器件在目标气体中的电流值，I ₀为干燥空气中器件的电流值，得到如图8所示的响应-时间曲线。 Figure 8 shows the response-recovery curve of the GeTeO _x @YW-co-doped CuO heterojunction film to 10-50ppm NH ₃ gas, which has high response sensitivity and good recovery performance.

Apparently, the above-mentioned embodiments are only examples for clear description, and are not intended to limit the implementation. For those of ordinary skill in the art, on the basis of the above description, other changes or changes in various forms can also be made. It is not necessary and impossible to exhaustively list all the implementation manners here. However, the obvious changes or changes derived therefrom are still within the scope of protection of the present invention.

Claims (10)

1. A gas sensor, comprising a base body, characterized in that the surface of the base body is also provided with a GeTeO _x thin film and an element-codoped CuO film; the middle part of the GeTeO _x film and the element co-doped CuO film overlaps and forms a heterogeneous structure, the GeTeO _x film and the element co-doped CuO film part all extend to the substrate, and the end of the GeTeO _x film and the element co-doped CuO film is provided with a conductive metal film, wherein 0<x≤4. 2 . The gas sensor according to claim 1 , characterized in that 0-2 conductive metal films are respectively provided at both ends of the GeTeO _x film and the CuO film co-doped with the elements. 3 . The gas sensor according to claim 1 , characterized in that, the overlapping portion of the GeTeO _x thin film and the CuO thin film co-doped with the elements has an interdigitated structure. 4 . 4. The gas sensor according to claim 1, wherein the material of the base is Si. 5 . The gas sensor according to claim 1 , wherein the element doped in the CuO film is two or more of Y, W, Sn, Al, In and Ni. 6. The gas sensor according to claim 1, wherein the conductive metal is one or more of Au, Ag, Cr, Pt, Pd, Ti, Al, W. 7. A method for preparing a gas sensor, comprising the following steps, S1. Etching an electrode channel on the surface of the pretreated substrate, and sputtering a conductive metal film on the electrode channel; S2. Sputtering a GeTeO _x film on the surface of the substrate, the sputtering gas is a mixed gas of argon and oxygen, wherein 0<x≤4; S3. Sputtering an element-co-doped CuO film on the surface of the GeTeO _x film, the element-co-doped CuO film extends to the surface of the substrate, and the sputtering gas is argon; S4. Sputtering a conductive metal film on the surface of the non-overlapping portion of the GeTeO _x film and the CuO film co-doped with the elements to obtain the gas sensor. 8 . The method for preparing the gas sensor according to claim 7 , wherein the power of the sputtering is 5-200 W, and the sputtering time is 1-30 min. 9 . The method for preparing a gas sensor according to claim 7 , wherein the flow rate of the gas is 1-50 sccm, and the sputtering pressure of the gas is 0.5-10 Pa. 10. The application of the gas sensor according to any one of claims 1-6 in detecting H ₂ S, NH ₃ or NO ₂ , characterized in that the temperature detected in the application is 50-300° C., and the gas concentration is 1-200 ppm.