CN116008355A - Humidity sensor and preparation method thereof - Google Patents
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- CN116008355A CN116008355A CN202211546857.4A CN202211546857A CN116008355A CN 116008355 A CN116008355 A CN 116008355A CN 202211546857 A CN202211546857 A CN 202211546857A CN 116008355 A CN116008355 A CN 116008355A
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
- Y02P70/50—Manufacturing or production processes characterised by the final manufactured product
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Abstract
The invention discloses a humidity sensor and a preparation method thereof, wherein the humidity sensor comprises an insulating substrate, an electrode layer arranged on the insulating substrate, a two-dimensional transition metal sulfide layer and a two-dimensional transition metal oxide layer; the two-dimensional transition metal oxide layer is compounded on the two-dimensional transition metal sulfide layer, and the two-dimensional transition metal oxide layer and the two-dimensional transition metal sulfide layer form a composite structure; and, the two-dimensional transition metal oxide layer and the two-dimensional transition metal sulfide layer have a fermi level difference capable of causing charge transfer, thereby forming a space charge region and a potential barrier at the interface of the composite structure. The humidity sensor combines the mature humidity-sensitive characteristic of the two-dimensional transition metal oxide layer and the advantages of large specific surface area, high sensitivity, stable performance and the like of the two-dimensional transition metal sulfide layer, and the formed humidity sensor has higher sensitivity, stability and corrosion resistance, and simultaneously improves the working temperature and humidity range.
Description
Technical Field
The invention relates to the technical field of sensors, in particular to a humidity sensor and a preparation method thereof.
Background
The humidity sensor is a device or component capable of sensing the water molecules and the concentration thereof in the environment, and can convert the information related to the water molecule content in the gas into signals which can be directly read and quantized by equipment, such as electricity, light, sound and the like, so as to detect, monitor, analyze, alarm and the like. With transition metal oxide semiconductor MoO 3 、WO 3 Mature humidity sensor represented by the sameThe sensor has the advantages of high sensitivity, high response speed, economy, reliability, small volume, portability, compatibility with current electronic equipment and the like, is rapidly developed, and is one of the sensors with the largest output and the widest application in the world.
The two-dimensional transition metal sulfide has the advantages of high carrier mobility, high mechanical strength, good chemical stability, good thermal stability and the like, meanwhile, due to the thickness of molecular level and huge specific surface area, the electrical property of the two-dimensional transition metal sulfide is easily influenced by the surrounding environment and surface adsorbed water molecules, when TMDCs are directly applied to humidity sensing, the two-dimensional TMDCs material film is a humidity sensitive layer and a conductive channel, and at the moment, the influence of surface scattering on the carriers is larger and larger along with the reduction of the thickness of the two-dimensional material. The charge transfer between the two-dimensional material and the adsorption molecules not only changes the carrier concentration in the material, but also obviously reduces the mobility of the carriers by taking the adsorption molecules as scattering centers, so that the change of the resistance is difficult to truly reflect the change of humidity.
Accordingly, there is a need for improvements in humidity sensors that address the above-described issues.
Disclosure of Invention
The invention aims to solve the technical problem of providing a humidity sensor based on a two-dimensional transition metal sulfide and oxide composite structure thereof and capable of improving sensitivity and stability and a preparation method thereof.
The technical scheme adopted for solving the technical problems is as follows: providing a humidity sensor, comprising an insulating substrate, an electrode layer arranged on the insulating substrate, a two-dimensional transition metal sulfide layer and a two-dimensional transition metal oxide layer;
the two-dimensional transition metal oxide layer is compounded on the two-dimensional transition metal sulfide layer, and the two-dimensional transition metal oxide layer and the two-dimensional transition metal sulfide layer form a composite structure; and, the two-dimensional transition metal oxide layer and the two-dimensional transition metal sulfide layer have a fermi level difference capable of causing charge transfer, thereby forming a space charge region and a potential barrier at the interface of the composite structure.
Preferably, the two-dimensional transition metal oxide layer is MoO 3 The two-dimensional transition metal sulfide layer is MoS 2 。
Preferably, the two-dimensional transition metal oxide layer is WO 3 The two-dimensional transition metal sulfide layer is WS 2 。
Preferably, the two-dimensional transition metal oxide layer is WO 3 The two-dimensional transition metal sulfide layer is WSe 2 。
Preferably, the material of the insulating substrate includes at least one of glass, quartz, ceramic, and sapphire.
Preferably, the insulating substrate is a semiconductor substrate having an insulating layer; the thickness of the insulating layer is 20nm-2000nm.
Preferably, the semiconductor substrate is a semiconductor wafer; the semiconductor wafer is made of one or more of element semiconductors Si and Ge, compound semiconductors GaAs and InP.
Preferably, the material of the insulating layer comprises SiO 2 、Al 2 O 3 、HfO 2 At least one of AlN.
Preferably, the material of the electrode layer includes at least one of Au elemental metal, pt elemental metal, ni elemental metal, ti elemental metal, cr elemental metal, and an alloy of the above elemental metals.
Preferably, the material of the electrode layer includes at least one of conductive silicide, nitride and carbide.
Preferably, the thickness of the electrode layer is 20nm to 1000nm.
Preferably, the electrode layer is an interdigital electrode layer, the width of the interdigital section is 20um, and the interval between adjacent interdigital sections is 10um.
Preferably, the working temperature of the humidity sensor is 0-100 ℃, and the humidity range is 11-95%.
The invention also provides a preparation method of the humidity sensor, which comprises the following steps:
s1, providing an insulating substrate, wherein a two-dimensional transition metal sulfide layer is arranged on the surface of the insulating substrate;
s2, patterning the two-dimensional transition metal sulfide layer, and removing the two-dimensional transition metal sulfide layer part outside the target conducting channel;
s3, arranging a two-dimensional transition metal oxide layer on the two-dimensional transition metal sulfide layer, and forming a composite structure by the two-dimensional transition metal oxide layer and the two-dimensional transition metal sulfide layer;
and S4, arranging an electrode layer on the surface of the insulating substrate, wherein the electrode layer also covers the composite structure.
The invention has the beneficial effects that: the humidity sensor is based on a two-dimensional transition metal sulfide and oxide composite structure, and a space charge region and a potential barrier are generated by the two-dimensional composite structure formed by the two-dimensional transition metal sulfide and oxide and an interface thereof; when water molecules are adsorbed on the surface of the two-dimensional transition metal oxide layer, charge transfer occurs, the concentration of carriers in the two-dimensional transition metal oxide layer is caused to change, and then the space charge area and potential barrier of the composite structure are caused to change, so that the resistance of the sensor is finally changed under forward bias, and the sensing of environmental humidity is realized. The humidity sensor combines the mature humidity-sensitive characteristic of the two-dimensional transition metal oxide layer and the advantages of large specific surface area, high sensitivity, stable performance and the like of the two-dimensional transition metal sulfide layer, and the formed humidity sensor has higher sensitivity, stability and corrosion resistance, and simultaneously improves the working temperature and humidity range.
The humidity sensor is easy to integrate on a semiconductor base chip, and accords with the development trend of miniaturization, portability and intellectualization of the humidity sensor.
Drawings
The invention will be further described with reference to the accompanying drawings and examples, in which:
FIG. 1 is a schematic view showing a longitudinal sectional structure of a humidity sensor according to an embodiment of the present invention;
fig. 2 is a top view of a humidity sensor in accordance with an embodiment of the present invention.
Detailed Description
For a clearer understanding of technical features, objects and effects of the present invention, a detailed description of embodiments of the present invention will be made with reference to the accompanying drawings.
As shown in fig. 1 and 2, the humidity sensor according to an embodiment of the present invention includes an insulating substrate 100, an electrode layer 200 disposed on the insulating substrate 100, a two-dimensional transition metal sulfide layer 300, and a two-dimensional transition metal oxide layer 400.
Two-dimensional transition metal oxide layers (two-dimensional TMOs) 400 are composited on two-dimensional transition metal sulfide layers (two-dimensional TMDCs) 300, both of which form a composite structure (TMOs-TMDCs). And, there is a fermi level difference between the two-dimensional transition metal oxide layer 400 and the two-dimensional transition metal sulfide layer 300, which can cause charge transfer, thereby forming a space charge region and a potential barrier at the composite structure interface.
Specifically, the insulating substrate 100 has first and second surfaces opposite to each other, and the electrode layer 200, the two-dimensional transition metal sulfide layer 300, and the two-dimensional transition metal oxide layer 400 are all disposed on the first surface of the insulating substrate 100.
Alternatively, the insulating substrate 100 may be made of at least one of glass, quartz, ceramic, and sapphire. Since the materials are all insulating materials, the substrate made of one or more of the materials has insulating property. The insulating substrate 100 may also be a laminated structure, and the materials of the layers may be the same or different.
Alternatively, the insulating substrate 100 is a semiconductor substrate having an insulating layer. The thickness of the insulating layer is 20nm-2000nm. The material of the insulating layer comprises SiO 2 、Al 2 O 3 、HfO 2 At least one of AlN, namely the insulating layer, can be made of any one or more of the above, and can also be of a laminated structure, and the materials of the layers can be the same or different. The semiconductor substrate may preferably be a semiconductor wafer; the semiconductor wafer is made of one or more of element semiconductors Si and Ge, compound semiconductors GaAs and InP.
On the insulating substrate 100, the two-dimensional transition metal sulfide layer 300 is patterned to have a corresponding shape or orientation as a conductive channel according to a desired conductive channel. The two-dimensional transition metal oxide layer 400 is compounded on the two-dimensional transition metal sulfide layer 300 and is used as a humidity sensitive layer for contacting with water molecules, so that the two-dimensional transition metal sulfide layer 300 is protected, direct interaction between the two-dimensional transition metal sulfide layer 300 and the water molecules is avoided, and further the stability of the humidity sensor is improved. When water molecules are adsorbed on the surface of the two-dimensional transition metal oxide layer 400 to generate charge transfer, the concentration of carriers in the two-dimensional transition metal oxide layer 400 changes, and meanwhile, the width and the barrier height of a space charge region of a composite structure (TMOs-TMDCs) interface also change, so that the resistance of a conductive channel changes, and the humidity to be detected is sensed.
Two-dimensional transition metal oxide layer 400, i.e., two-dimensional TMOs, molecular formula MO 3 Wherein M is a transition metal element Mo or W. Two-dimensional transition metal sulfide layer 300, two-dimensional TMDCs, molecular formula MX 2 Wherein M is transition metal element Mo or W, and X is chalcogen element S or Se.
The two-dimensional transition metal sulfide layer 300 is MoS 2 、MoSe 2 、WS 2 、WSe 2 At least one of (a) and (b); the two-dimensional transition metal oxide layer 400 is MoO 3 、WO 3 At least one of them.
Alternatively, the two-dimensional transition metal oxide layer 400 is MoO 3 The two-dimensional transition metal sulfide layer 300 is MoS 2 . Alternatively, the two-dimensional transition metal oxide layer 400 is WO 3 The two-dimensional transition metal sulfide layer 300 is WS 2 . Alternatively, the two-dimensional transition metal oxide layer 400 is WO 3 The two-dimensional transition metal sulfide layer 300 is WSe 2 。
The thickness of the two-dimensional transition metal sulfide layer 300 may be 0.6nm-100nm, and the two-dimensional transition metal oxide layer 4001nm-2nm.
Further, the two-dimensional transition metal sulfide layer 300 may have a single-layer or multi-layer structure; the two-dimensional transition metal oxide layer 400 may have a single-layer or multi-layer structure.
On the insulating substrate 100, the electrode layer 200 is partially covered on the two-dimensional transition metal oxide layer 400, and is in conductive contact with the two-dimensional transition metal oxide layer 400. The electrode layer 200 may be at least one of Au elementary metal, pt elementary metal, ni elementary metal, ti elementary metal, cr elementary metal, or an alloy of the above elementary metals, or a mixture of the above elementary metals and metal alloys. Alternatively still, the material of the electrode layer 200 includes, i.e., is made of, at least one of conductive silicide, nitride, and carbide.
On the insulating substrate 100, the thickness of the electrode layer 200 is 20nm to 1000nm. In this embodiment, as shown in fig. 2, the electrode layer 200 is an interdigital electrode layer 200, the width of the interdigital segment is 20um, and the interval between adjacent interdigital segments is 10um.
Specifically, in the embodiment shown in fig. 2, electrode layer 200 includes two sets of interdigitated electrodes disposed opposite each other on insulating substrate 100. The body portions of the two sets of interdigital electrodes are located on the first surface of the insulating substrate 100 and are respectively located on opposite sides of the composite structure, the interdigital segments of each interdigital electrode respectively extend onto the composite structure, and the interdigital segments of the two sets of interdigital electrodes are respectively and crosswise arranged on the composite structure.
The working temperature of the humidity sensor is 0-100 ℃, and the humidity range is 11-95%.
Referring to fig. 1 and 2, the method for manufacturing the humidity sensor of the present invention may include the steps of:
s1, providing an insulating substrate 100, wherein a two-dimensional transition metal sulfide layer 300 is arranged on the surface of the insulating substrate 100.
The insulating substrate 100 is made of at least one of glass, quartz, ceramic, and sapphire. Alternatively, the insulating substrate 100 is a semiconductor substrate having an insulating layer.
Wherein the two-dimensional transition metal sulfide layer 300 is grown directly on the insulating substrate 100 or transferred to the insulating substrate 100 by micro-mechanical lift-off. Direct growth includes chemical vapor deposition methods and atomic layer deposition methods. The two-dimensional transition metal sulfide layer 300 may be preferably formed directly on the surface of the insulating substrate 100 by a chemical vapor deposition method.
The thickness of the two-dimensional transition metal sulfide layer 300 is 0.6nm to 100nm. The two-dimensional transition metal sulfide layer 300 is MoS 2 、MoSe 2 、WS 2 、WSe 2 At least one of them.
And S2, patterning the two-dimensional transition metal sulfide layer 300, and removing the two-dimensional transition metal sulfide layer 300 part outside the target conductive channel.
After patterning, the two-dimensional transition metal sulfide layer 300 has a shape or orientation corresponding to the target conductive channel to form the conductive channel of the humidity sensor.
And S3, arranging a two-dimensional transition metal oxide layer 400 on the two-dimensional transition metal sulfide layer 300, and forming a composite structure by the two-dimensional transition metal oxide layer 400.
In this step, the two-dimensional transition metal oxide layer 400 may be formed by oxidizing the surface layer of the two-dimensional transition metal sulfide layer 300 using an oxygen plasma treatment or an ozone oxidation method. The two-dimensional transition metal oxide layer 400 is specifically MoO 3 、WO 3 At least one of them. The thickness of the formed two-dimensional transition metal oxide layer 400 is 1nm to 2nm.
The two-dimensional transition metal oxide layer 400 is arranged above the two-dimensional transition metal sulfide layer 300 to serve as a humidity sensitive layer to be contacted with water molecules, and the two-dimensional transition metal sulfide layer 300 is not contacted with the water molecules, so that the stability of the humidity sensor is improved.
And S4, arranging an electrode layer 200 on the surface of the insulating substrate 100, wherein the electrode layer 200 also covers the composite structure.
Specifically, the electrode layer 200 is partially covered on the insulating substrate 100 onto the two-dimensional transition metal oxide layer 400, and is in conductive contact with the two-dimensional transition metal oxide layer 400.
On the insulating substrate 100, the thickness of the electrode layer 200 is 20nm to 1000nm.
In the embodiment shown in fig. 2, the electrode layer 200 includes two sets of interdigital electrode layers 200, the two sets of interdigital electrodes being oppositely disposed on the insulating substrate 100. The body portions of the two sets of interdigital electrodes are located on the first surface of the insulating substrate 100 and are respectively located on opposite sides of the composite structure, the interdigital segments of each interdigital electrode respectively extend onto the composite structure, and the interdigital segments of the two sets of interdigital electrodes are respectively and crosswise arranged on the composite structure.
The width of the interdigital segments of electrode layer 200 is 20um, and the pitch between adjacent interdigital segments is 10um.
The preparation method of the humidity sensor of the present invention can be operated as follows in a practical embodiment: the insulating substrate 100 has a resistivity of 0.001 Ω cmp-type resistor silicon is used as a semiconductor wafer substrate and also used as a back gate electrode layer, and 300nm thermal oxidation SiO is carried out 2 The insulating layer can be used as a back gate dielectric. Preparation of single or less layer (1-10 layers) MoS on insulating substrate 100 by mechanical lift-off 2 A thin film as the two-dimensional transition metal sulfide layer 300. The two-dimensional transition metal oxide layer 400 is directly grown or oxidized by oxygen plasma to form on the surface of the two-dimensional transition metal sulfide layer 300 so as to cover the conducting channel of the two-dimensional transition metal sulfide layer 300, and the two-dimensional transition metal oxide layer is used as a humidity sensitive layer, and the specific method is as follows:
on the one hand, a two-dimensional transition metal oxide film (namely a two-dimensional transition metal oxide layer 400) can be directly formed on the surface of the conducting channel of the two-dimensional transition metal sulfide layer 300 by adopting methods such as chemical vapor deposition, atomic layer deposition and the like; on the other hand, the two-dimensional transition metal sulfide layer 300 is oxidized by an oxygen plasma cleaning machine, and a two-dimensional transition metal oxide thin film (i.e., the two-dimensional transition metal oxide layer 400) is formed on the surface of the conductive channel of the two-dimensional transition metal sulfide layer 300.
Wherein, moO with thickness of 1-2nm is selected 3 The film acts as a humidity sensitive layer (i.e., two-dimensional transition metal oxide layer 400) because of MoO 3 The film is naturally n-type moderately doped so as to be different from MoS with different doping degree 2 A composite structure is formed between the two-dimensional transition metal sulfide layer 300 and the first layer, so that a significant space charge region is formed in the two-dimensional transition metal sulfide layer; meanwhile, the two-dimensional transition metal sulfide layer 300 is used as a conductive channel two-dimensional transition metal oxide layer 400 and is used as a humidity sensitive layer, and a thin layer (1-2 nm) MoO 3 The film is favorable for preventing the humidity sensitive layer from participating in conduction, and adverse effects in the transportation process are avoided.
When the Cr/Au metal laminate is used as the electrode layer 200, the following steps are provided:
spin-coating S1805 photoresist on the surfaces of the insulating substrate 100 and the composite structure, firstly, spin-coating for 5S at 500 rpm, then spin-coating for 60S at 4000 rpm to form a photoresist film layer with the thickness of about 500nm, and then drying for 3min at 110 ℃;
photoetching, exposing the photoresist by using a photomask with a preset layout, wherein the exposure dose is 40mJ/cm 2 Fixing in a large amount of deionized water immediately after developing for 20s, thereby forming a photoresistForming an interdigital pattern structure on the substrate;
vacuum-pumping in a thermal evaporation coating machine, and depositing 10nm Cr and 60nm Au lamination;
removing photoresist in acetone to form an electrode layer 200;
high purity N using rapid thermal annealing furnace (RTP) 2 In the atmosphere, annealing is carried out at 500 ℃ for 45min, and ohmic contact is formed between the insulating substrate 100 and the surface of the composite structure and the electrode layer 200.
The humidity sensor of the present invention operates on the principle that the fermi level difference between the two-dimensional transition metal sulfide layer 300 and the two-dimensional transition metal oxide layer 400 causes charge transfer, thereby generating a space charge region at the interface of the composite structure and forming a potential barrier. When water molecules are adsorbed on the surface of the two-dimensional transition metal oxide layer 400, charge transfer occurs, the concentration of carriers in the two-dimensional transition metal oxide layer 400 is caused to change, and further the space charge region and potential barrier of the composite structure are caused to change, so that the resistance of a conducting channel is finally changed under forward bias, and the sensing of environmental humidity is realized.
Under low humidity, water molecules are influenced by surface defects of the material of the composite structure and are decomposed into H + And OH (OH) - And H is + Electrons are acquired from the surface of the material, so that the hole potential barrier is reduced, the depletion layer is flattened, and the impedance is reduced; under high humidity, water molecules adsorb on the surface of the material of the composite structure, wherein a large amount of H is generated 3 O + And conductive ions participate in transportation in the conductive process, so that the impedance is reduced and the conductivity is improved; the change of the environmental humidity is obtained through the change of the resistance, so that the humidity sensing function is realized.
The foregoing description is only illustrative of the present invention and is not intended to limit the scope of the invention, and all equivalent structures or equivalent processes or direct or indirect application in other related technical fields are included in the scope of the present invention.
Claims (10)
1. A humidity sensor, characterized in that the humidity sensor comprises an insulating substrate, an electrode layer arranged on the insulating substrate, a two-dimensional transition metal sulfide layer and a two-dimensional transition metal oxide layer;
the two-dimensional transition metal oxide layer is compounded on the two-dimensional transition metal sulfide layer, and the two-dimensional transition metal oxide layer and the two-dimensional transition metal sulfide layer form a composite structure; and, the two-dimensional transition metal oxide layer and the two-dimensional transition metal sulfide layer have a fermi level difference capable of causing charge transfer, thereby forming a space charge region and a potential barrier at the interface of the composite structure.
2. The humidity sensor of claim 1 wherein the two-dimensional transition metal oxide layer is MoO 3 The two-dimensional transition metal sulfide layer is MoS 2 The method comprises the steps of carrying out a first treatment on the surface of the Or,
the two-dimensional transition metal oxide layer is WO 3 The two-dimensional transition metal sulfide layer is WS 2 The method comprises the steps of carrying out a first treatment on the surface of the Or,
the two-dimensional transition metal oxide layer is WO 3 The two-dimensional transition metal sulfide layer is WSe 2 。
3. The humidity sensor of claim 1 wherein the material of the insulating substrate comprises at least one of glass, quartz, ceramic, and sapphire.
4. The humidity sensor of claim 1 wherein the insulating substrate is a semiconductor substrate having an insulating layer; the thickness of the insulating layer is 20nm-2000nm.
5. The humidity sensor of claim 4 wherein the semiconductor substrate is a semiconductor wafer; the semiconductor wafer is made of one or more of element semiconductors Si and Ge, compound semiconductors GaAs and InP.
6. The humidity sensor of claim 4 wherein the material of the insulating layer comprises SiO 2 、Al 2 O 3 、HfO 2 At least one of AlN.
7. The humidity sensor of claim 1 wherein the material of the electrode layer comprises at least one of elemental Au, elemental Pt, elemental Ni, elemental Ti, elemental Cr, and alloys thereof; or,
the material of the electrode layer includes at least one of conductive silicide, nitride and carbide.
8. The humidity sensor of claim 1 wherein the electrode layer has a thickness of 20nm to 1000nm;
the electrode layer is an interdigital electrode layer, the width of the interdigital section is 20um, and the interval between the adjacent interdigital sections is 10um.
9. The humidity sensor of any one of claims 1 to 8 wherein the humidity sensor operates at a temperature of from 0 ℃ to 100 ℃ and a humidity in the range of from 11% to 95%.
10. A method of manufacturing a humidity sensor as claimed in any one of claims 1 to 9 comprising the steps of:
s1, providing an insulating substrate, wherein a two-dimensional transition metal sulfide layer is arranged on the surface of the insulating substrate;
s2, patterning the two-dimensional transition metal sulfide layer, and removing the two-dimensional transition metal sulfide layer part outside the target conducting channel;
s3, arranging a two-dimensional transition metal oxide layer on the two-dimensional transition metal sulfide layer, and forming a composite structure by the two-dimensional transition metal oxide layer and the two-dimensional transition metal sulfide layer;
and S4, arranging an electrode layer on the surface of the insulating substrate, wherein the electrode layer also covers the composite structure.
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| CN202211546857.4A CN116008355A (en) | 2022-12-05 | 2022-12-05 | Humidity sensor and preparation method thereof |
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| Country | Link |
|---|---|
| CN (1) | CN116008355A (en) |
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2022
- 2022-12-05 CN CN202211546857.4A patent/CN116008355A/en active Pending
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