CN101135674B - Method for improving sonic surface wave gas sensors temperature stability - Google Patents
Method for improving sonic surface wave gas sensors temperature stability Download PDFInfo
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- CN101135674B CN101135674B CN2007100502243A CN200710050224A CN101135674B CN 101135674 B CN101135674 B CN 101135674B CN 2007100502243 A CN2007100502243 A CN 2007100502243A CN 200710050224 A CN200710050224 A CN 200710050224A CN 101135674 B CN101135674 B CN 101135674B
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Abstract
The invention comprises: an acoustic surface wave filter and a gas sensor composed of a sensitive film. Said acoustic surface wave filter comprises a piezoelectric substrate, an electrode and a wave guide layer; said sensitive film is located on the surface of the acoustic surface wave filter. It features the following: changing the piezoelectric materials in order to change the tangential of the piezoelectric materials; changing the thickness of waveguide film or changing the thickness of the sensitive film to make the frequency temperature coefficient of the said gas sensor become a negative value.
Description
Technical field
The present invention relates to the gas sensor technical field, be specifically related to a kind of method that improves sonic surface wave gas sensors temperature stability.
Background technology
Sonic surface wave gas sensors is a kind of high-sensitive sensitive element, but it is subject to the influence of environment temperature etc.In order to overcome Temperature Influence, the measure of adopting at present mainly contains:
1) adopting frequency-temperature coefficient (TCF) is zero device;
Mainly by piezoelectric crystal and tangential decision thereof, the thickness of sensitive membrane only has small size influence to TCF to the TCF of sound table device, and for the Love wave device, the thickness of ducting layer also can change the TCF of device to a great extent.The device of TCF ≈ 0 commonly used is that AT cuts quartz.
2) adopt channel structure.
Conventional channel structure is to apply sensitive thin film on a sound passage, and does not apply sensitive thin film on another passage, and the difference on the frequency by adopting two passages can reduce Temperature Influence more than 10 times as signal of sensor.But because two channel temperature characteristics and inconsistent, the interference of temperature can not be eliminated fully.For this reason, U.S. Pat 6378370B1 discloses a kind of improved binary channels scheme: at responsive passage, cover passivation layer earlier, back coating sensitive membrane; At reference channel, apply sensitive membrane earlier, the back covers passivation layer.Structure is further similar each other to make binary channels like this, and its TCF is also further approaching, and Temperature Influence further reduces.
Temperature is divided into two aspects to the influence of sonic surface wave gas sensors: on the one hand, temperature will cause the fundamental frequency drift of SAW device; On the other hand, the temperature effect sensitive membrane causes the variable quantity of frequency to reduce to the adsorbance of gas.People have only considered the influence of first aspect usually, and have ignored the influence of second aspect.Therefore, the said temperature indemnifying measure is incomplete in principle.And the 1st measure limited piezoelectric and tangential selecting for use thereof, sacrificed peak response; Article 2, measure has increased the complicacy of system.In addition, also can adopt thermostat to reduce Temperature Influence, but also be to be cost to increase system complexity.And the SAW gas sensor all is array structure usually, how to ensure that the temperature consistance of array elements region also has very big difficulty technically.
Summary of the invention
Technical matters to be solved by this invention is how a kind of method that improves sonic surface wave gas sensors temperature stability is provided, and this method advantages of simple on the basis of the structure that does not change gas sensor, has realized the self compensation of temperature.
Technical matters proposed by the invention is to solve like this: a kind of method that improves sonic surface wave gas sensors temperature stability is provided, described sonic surface wave gas sensors is the gas sensor that is made of SAW (Surface Acoustic Wave) device and sensitive thin film, SAW (Surface Acoustic Wave) device comprises piezoelectric substrate, electrode and ducting layer constitute, described sensitive thin film is arranged on the SAW (Surface Acoustic Wave) device surface, it is characterized in that, by changing piezoelectric, change the tangential of piezoelectric, it is negative value that the thickness of the thickness of change waveguide film or change sensitive thin film makes the frequency-temperature coefficient of described gas sensor.
Method according to raising sonic surface wave gas sensors temperature stability provided by the present invention, it is characterized in that SAW (Surface Acoustic Wave) device is a kind of in R wave device (Rayleigh), Love wave device (Love), surface transverse wave device (STW), lamb wave devic (lamb) and the horizontal shear Lamb wave device (SH-APM).
Method according to raising sonic surface wave gas sensors temperature stability provided by the present invention, it is characterized in that, for R wave, surface transverse wave device, Lamb wave, horizontal shear plate device, one or more in the following method are adopted in the adjusting of the frequency-temperature coefficient of gas sensor (TCF): 1. change piezoelectric; 2. change the tangential of piezoelectric; 3. change the thickness of sensitive thin film.
Method according to raising sonic surface wave gas sensors temperature stability provided by the present invention, it is characterized in that, for the Love wave device, one or more in the following method are adopted in the adjusting of the frequency-temperature coefficient of gas sensor (TCF): 1. change piezoelectric; 2. change the tangential of piezoelectric; 3. change the thickness of waveguide film; 4. change the thickness of sensitive thin film.
Key of the present invention is to adopt the SAW (Surface Acoustic Wave) device of negative TCF, and this is in order to offset environment temperature and to change, and sensitive membrane is to the change of object gas adsorbance, thereby reduces the drift of sensor frequency with temperature, reaches the purpose of temperature compensation.The sensitive membrane adsorbance with the change of temperature remove have with properties of materials outside the Pass, mainly by the thickness decision of sensitive membrane.Therefore, for reaching better temperature compensation function, need carry out matching to the TCF of device and thickness and regulate, method is to regulate one of them or regulate both simultaneously, wherein, and the TCF of fixed sound table device and regulate the way that sensitive membrane thickness is the easiest realization.
The present invention can be easily realizes comprising on various types of SAW (Surface Acoustic Wave) device of Love wave, this method only just can realize the self compensation of temperature on a sound passage, simple in structure, preparation easily, have the advantages that effect temperature compensation is good, reliability is high, precision is high, can be applicable to various types of SAW gas sensors.
Description of drawings
Fig. 1 is the love wave gas sensor structural representation with temperature self-compensation function.
Wherein, 1 is piezoelectric substrate; 2 is interdigital electrode; 3 is ducting layer; 4 is sensitive thin film.
Embodiment
The present invention is further illustrated below in conjunction with accompanying drawing and embodiment.
As shown in Figure 1, this has the love wave gas sensor of temperature self-compensation function, and it comprises: piezoelectric substrate 1, interdigital electrode 2, ducting layer 3, sensitive thin film 4.The structure of sensor, the circuit all love wave sensor with routine are the same, and difference only is that the TCF of sensor is a negative value.The TCF by regulating sensor and the thickness of sensitive membrane improve the temperature stability of sensor.Principle of work of the present invention is as follows:
If f
t,
The frequency of sensor when representing no gas under a certain temperature respectively and gas being arranged then for any two temperature, has:
Δ f in the formula
tRepresent the change of the sensor frequency that gas causes under a certain temperature.The temperature stability of sensor is meant that the oscillation frequency of surface acoustic wave does not change with temperature, or variable quantity is very little, can be expressed as:
Suppose t
2＞t
1Because along with the rising of temperature, sensitive membrane reduces the adsorbance of gas, then
So,
When
, i.e. TCF＜0 of sound table device o'clock, the effect of two aspects will be cancelled out each other, and sensor will have better temperature stability.
The preparation method of love wave gas sensor (see figure 1) provided by the present invention following (example):
Piezoelectric substrate 1 is selected the ST-quartz for use, thickness 0.5mm; Interdigital electrode 2 makes through photoetching process for the Al film of evaporation, and the cycle is 40 μ m; Ducting layer 3 adopts PMMA, utilizes the spin coating proceeding preparation; Sensitive thin film 4 adopts poly--(methyl-phenyl siloxane), utilizes the spraying coating process preparation.Be the temperature stability of more different love wave sensors, prepared following three kinds of sensors:
1) thickness of ducting layer 3 is 1.6 μ m, and the thickness of sensitive thin film 4 is 72nm.
2) thickness of ducting layer 3 is 1.8 μ m, and the thickness of sensitive thin film 4 is 42nm.
3) thickness of ducting layer 3 is 1.8 μ m, and the thickness of sensitive thin film 4 is 68nm.
When the thickness of ducting layer 3 is respectively 1.6 μ m and 1.8 μ m, at 5-40 ℃ N
2Under the atmosphere TCF of test Love wave device be about 0 and-20ppm/ ℃, after the sensitive membrane that has applied tens nanometer, the TCF of sensor does not change.When the dimethyl methyl phosphonate (DMMP) and the high-purity N that in test chamber, feed 10ppm
2During the mixed gas of gas, the frequency drift of three kinds of sensors under 5 ℃ and 40 ℃ is respectively: 8.7KHz, 5.6KHz, 1.2KHz.As seen, adopt method of the present invention can reduce Temperature Influence effectively.
Claims (4)
1. method that improves sonic surface wave gas sensors temperature stability, described sonic surface wave gas sensors is the gas sensor that is made of SAW (Surface Acoustic Wave) device and sensitive thin film, SAW (Surface Acoustic Wave) device comprises that piezoelectric substrate, electrode and ducting layer constitute, described sensitive thin film is arranged on the SAW (Surface Acoustic Wave) device surface, it is characterized in that making the frequency-temperature coefficient of described gas sensor by the thickness tangential or the change waveguide film that changes piezoelectric, change piezoelectric is negative value.
2. according to the method for the described raising sonic surface wave gas sensors temperature stability of claim 1, it is characterized in that SAW (Surface Acoustic Wave) device is a kind of in R wave device, Love wave device, surface transverse wave device, lamb wave devic and the horizontal shear Lamb wave device.
3. the method for raising sonic surface wave gas sensors temperature stability according to claim 1 and 2, it is characterized in that, for R wave, surface transverse wave device, Lamb wave, horizontal shear plate device, one or more in the following method are adopted in the adjusting of the frequency-temperature coefficient of gas sensor: 1. change piezoelectric; 2. change the tangential of piezoelectric.
4. the method for raising sonic surface wave gas sensors temperature stability according to claim 1 and 2, it is characterized in that, for the Love wave device, one or more in the following method are adopted in the adjusting of the frequency-temperature coefficient of gas sensor: 1. change piezoelectric; 2. change the tangential of piezoelectric; 3. change the thickness of waveguide film.
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| CN101135674B true CN101135674B (en) | 2011-09-21 |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN103177717B (en) * | 2013-02-05 | 2015-06-17 | 长安大学 | Dual-mode wave generating device for Rayleigh waves and Love waves |
| CN103336053B (en) * | 2013-06-18 | 2015-11-04 | 电子科技大学 | A kind of surface acoustic wave gas sensors array of private reference |
| CN104280343B (en) * | 2013-07-09 | 2018-03-02 | 青岛中一监测有限公司 | A kind of gas sensor and environment monitoring sensor for environment monitoring sensor |
| CN103512950B (en) * | 2013-10-25 | 2015-12-30 | 中国电子科技集团公司第三十八研究所 | A kind of surface acoustic wave formaldehyde gas sensor utilizing water to absorb formaldehyde |
| CN103604864B (en) * | 2013-10-25 | 2016-02-10 | 中国电子科技集团公司第三十八研究所 | A kind of surface acoustic wave formaldehyde gas sensor based on electric conduction composite sensitive material |
| CN105934667B (en) * | 2014-09-30 | 2019-09-24 | 京瓷株式会社 | Sensor device |
| CN106168603B (en) * | 2016-07-05 | 2019-04-23 | 中国飞机强度研究所 | A kind of temperature-compensation method in Lamb wave monitoring structural health conditions |
| CN109187737B (en) * | 2018-08-03 | 2023-09-01 | 山东鑫利达安防科技有限公司 | Carbon monoxide sensor based on SAW device and concentration calculation method thereof |
| CN111751444A (en) * | 2020-07-08 | 2020-10-09 | 中国科学院声学研究所 | Surface acoustic wave sensor and equipment |
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| CN1647756A (en) * | 2005-01-26 | 2005-08-03 | 浙江大学 | Respiration detecting method and its device for diagnosing early lung cancer |
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| CN1647756A (en) * | 2005-01-26 | 2005-08-03 | 浙江大学 | Respiration detecting method and its device for diagnosing early lung cancer |
Non-Patent Citations (2)
| Title |
|---|
| Felicidade Moreira etal.Numerical development of ZnO/Quartz love wave structurefor gas contamination detection.IEEE SENSORS JOURNAL7 3.2007,7(3),336，338. |
| Felicidade Moreira etal.Numerical development of ZnO/Quartz love wave structurefor gas contamination detection.IEEE SENSORS JOURNAL7 3.2007,7(3),336,338. * |
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