Amorphous carbon film deep-sea piezoresistive sensing element and preparation method thereof

Abstract

The application provides a kind of amorphous carbon film deep sea piezoresistive sensing element and its preparation method, comprising: insulating substrate layer;Two metal electrode layers, pad in the top of insulating substrate layer and located at the two ends along the length direction of insulating substrate layer, for connecting electrode lead, two metal electrode layers adopt metal film;First piezoresistive sensing layer, pad in the top of insulating substrate layer and located between two metal electrode layers;Second piezoresistive sensing layer, pad in the top of first piezoresistive sensing layer and the length of second piezoresistive sensor is greater than the length of first piezoresistive sensing layer, first piezoresistive sensing layer and second piezoresistive sensing layer adopt trace metal doped amorphous carbon film;Protective layer, pad in the top of second piezoresistive sensing layer and the length of protective layer is same with the length of second piezoresistive sensing layer, protective layer adopts hydrogen-containing amorphous carbon film.The beneficial effect is that the application can simplify process, improve sensitivity, improve structural stability and reduce environmental impact.

Description

Technical Field

[0001] This invention relates to the technical field of pressure sensor devices, and more specifically, to an amorphous carbon thin film deep-sea piezoresistive sensing element and its preparation method. Background Technology

[0002] Seawater depth is an important parameter in the field of marine exploration and development. Accurately obtaining seawater pressure and depth information is an important prerequisite and foundation for revealing the evolution law of ocean dynamic parameters. Seawater pressure sensors have been widely used in marine observation systems such as underwater moorings and underwater mobile platforms.

[0003] Currently used pressure sensors primarily use monocrystalline silicon or polycrystalline silicon as their sensitive materials, which are insufficient to meet the stable sensing requirements of marine engineering equipment under harsh conditions such as corrosion and scratching. Complex packaging processes are typically required for these sensors. For pressure sensors that require long-term continuous operation in corrosive marine environments or deep-sea applications, this can lead to severe drift in the detection results, resulting in cumulative data errors and significantly affecting the accuracy of seawater depth detection.

[0004] Existing technical solutions typically address the issue of sensor performance being susceptible to environmental influences by encapsulating and protecting the sensing material. For example, in patent CN200420055437.7, an insulating partition is introduced to prevent sensor deformation, but this affects the response speed. In patent CN201020107919.8, a high-pressure resistant temperature sensor is prepared by filling the thermistor with a thermally conductive medium inside the temperature probe, but this reduces temperature sensitivity and response speed.

[0005] Secondly, sensing is achieved using highly stable and sensitive materials such as diamond and SiC. For example, patent CN201910053826.7 uses a leadless SiC pressure sensor, which can operate in harsh environments and maintain good stability. In addition, sensors using a high-sensitivity functional layer composite surface protection layer also have certain improvement effects. For example, patent CN202311787094.7 uses a carbon-based thin film with a high resistivity composite with silicon oxide to solve the electrical failure of the sensor in corrosive environments and achieve sensing in corrosive media environments. Patent CN202210366465.3 prepares a carbon-based piezoresistive thin film sensor with a wear-resistant layer, sensing layer, insulating layer and electrode layer structure, realizing wear-resistant protection and sensing in one, with a sensitivity of 4.2 to 7.4.

[0006] However, the above methods still cannot solve the problems of complex and costly manufacturing or packaging processes of existing sensing elements, poor interface matching between heterogeneous functions and protective layer structures leading to easy peeling and failure, and difficulty in achieving strong protection and high sensitivity coordination. Therefore, they cannot meet the long-term observation needs in corrosive environments such as seawater. Summary of the Invention

[0007] The technical problem to be solved by this invention is to simplify the process, improve sensitivity, improve structural stability, and reduce the impact of the environment. In order to overcome the defects of the above-mentioned prior art (or related technology), this invention provides an amorphous carbon thin film deep-sea piezoresistive sensing element and its preparation method.

[0008] This invention provides an amorphous carbon thin-film deep-sea piezoresistive sensing element, comprising:

[0009] An insulating base layer;

[0010] Two metal electrode layers are stacked on top of the insulating substrate and located at both ends along the length of the insulating substrate for connecting electrode leads. The two metal electrode layers are made of metal thin film.

[0011] A first piezoresistive sensing layer is deposited on top of the insulating substrate and located between the two metal electrode layers;

[0012] A second piezoresistive sensing layer is stacked on top of the first piezoresistive sensing layer, and the length of the second piezoresistive sensor is greater than the length of the first piezoresistive sensing layer. The first piezoresistive sensing layer and the second piezoresistive sensing layer are made of amorphous carbon film with trace metal doping.

[0013] A protective layer is deposited on top of the second piezoresistive sensing layer, and the length of the protective layer is the same as the length of the second piezoresistive sensing layer. The protective layer is made of hydrogen-containing amorphous carbon film.

[0014] Compared with the prior art, the amorphous carbon thin film deep-sea piezoresistive sensing element disclosed in this application has the following advantages:

[0015] In this invention, a trace metal-doped amorphous carbon film is used as the piezoresistive sensitive layer of the seawater piezoresistive sensing element, and a hydrogen-containing amorphous carbon film is used as the protective layer of the seawater piezoresistive sensing element. The piezoresistive sensing layer is made of trace metal-doped amorphous carbon, which has high piezoresistive sensitivity. At the same time, both the piezoresistive sensing layer and the protective layer are carbon-based thin film materials, resulting in better and more stable bonding between the thin film interfaces. It is suitable for corrosive and high-pressure environments and has the characteristics of simple preparation process, small size, high sensitivity, and minimal influence of external factors on measurement.

[0016] In one possible implementation, the surface of the insulating substrate layer is etched using plasma etching.

[0017] In one possible implementation, the metal thin film is made of one of Cr, Cu, Al, Ag, Au, or Pt.

[0018] In one possible implementation, the doping range of the metal in the first piezoresistive sensing layer and the second piezoresistive sensing layer is 0.1-5.0 at.%.

[0019] In one possible implementation, the piezoresistive coefficients of the first piezoresistive sensing layer and the second piezoresistive sensing layer are 1.58-46.7.

[0020] In one possible implementation, the thickness of the first piezoresistive sensing layer and the second piezoresistive sensing layer is 100-300 nm.

[0021] In one possible implementation, the thickness of the protective layer is 100-500 nm.

[0022] This invention also provides a method for fabricating an amorphous carbon thin film deep-sea piezoresistive sensing element, comprising the following steps:

[0023] Step S1: Place the insulating substrate in a deposition apparatus, and after evacuation, use plasma etching to etch the surface of the insulating substrate.

[0024] Step S2: Using magnetron sputtering technology, two metal electrode layers are deposited on top of the insulating substrate layer through a mask.

[0025] Step S3: Using the pre-reserved lead positions on the mask plate, the first piezoresistive sensing layer and the second piezoresistive sensing layer are deposited using magnetron sputtering technology;

[0026] Step S4: Acetylene or methane gas is introduced into the coating chamber, and after being ionized by the anolyte ion source, the protective layer is deposited on the second piezoresistive sensing layer to obtain an amorphous carbon thin film piezoresistive sensing element.

[0027] In one possible implementation, the specific parameters for plasma etching in step S1 are as follows: vacuum degree of 2 × 10⁻⁶. -5 Torr, with a bias voltage of -200V, an ion source current of 0.2A, and an etching time of 20min.

[0028] In one possible implementation, in step S3, a metal-doped amorphous carbon film is deposited as the first piezoresistive sensing layer and the second piezoresistive sensing layer, and in step S4, a hydrogen-containing amorphous carbon film is deposited as the protective layer.

[0029] Compared with existing technologies, the method for fabricating an amorphous carbon thin film deep-sea piezoresistive sensing element disclosed in this application has the following advantages:

[0030] In this invention, the metal electrode layer of the seawater piezoresistive sensing element is a thin metal film prepared using magnetron sputtering technology, serving as the metal electrode layer connecting the piezoresistive sensing layer and the leads; the amorphous carbon piezoresistive sensing layer is a pressure-sensitive layer made of a metal-doped amorphous carbon thin film with piezoresistive effect, which measures pressure changes by responding to changes in resistance; the hydrogen-containing amorphous carbon protective layer is a protective layer deposited on the surface of the piezoresistive sensing layer to prevent the metal-doped amorphous carbon piezoresistive sensing layer from being affected by external corrosive environments. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the overall structure of the amorphous carbon thin film deep-sea piezoresistive sensing element of the present invention;

[0032] Figure 2 This is a flowchart of the preparation method of the present invention;

[0033] Figure 3 This is a process flow diagram for the fabrication of the amorphous carbon thin film deep-sea piezoresistive sensing element of the present invention;

[0034] Figure 4 The diagram shows the piezoresistive coefficients measured in Embodiments 1, 2, and 3 of the present invention and Comparative Examples 1 and 2.

[0035] Figure 5 The diagram shows the piezoresistive coefficients of Embodiments 1, 2, and 3 and Comparative Examples 1 and 2 after immersion in a simulated deep-sea high-pressure environment for 4 days.

[0036] Figure 6 The diagram shows the piezoresistive coefficients of Embodiment 4 and Comparative Example 3 after 7 days of service in a simulated deep-sea high-pressure environment.

[0037] Explanation of reference numerals in the attached figures: 1. Insulating substrate layer; 2. Metal electrode layer; 3. First piezoresistive sensing layer; 4. Second piezoresistive sensing layer; 5. Protective layer; 6. Mask plate. Detailed Implementation

[0038] First, those skilled in the art should understand that these embodiments are merely used to explain the technical principles of the embodiments of this application and are not intended to limit the scope of protection of the embodiments of this application. Those skilled in the art can make adjustments as needed to adapt to specific application scenarios.

[0039] The present application will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0040] See Figure 1This application discloses an amorphous carbon thin film deep-sea piezoresistive sensing element. Compared with Ag, Cu and Cr, Cr with high adhesion to amorphous carbon film is preferred as the metal electrode layer 2. It includes a Cr metal electrode layer, a Cr-doped amorphous carbon piezoresistive sensing layer and a hydrogen-containing amorphous carbon protective layer disposed on the surface of an insulating substrate layer 1. The thickness of the metal electrode layer 2 is about 100 nm, the thickness of the Cr-doped amorphous carbon piezoresistive sensing layer is about 120 nm and 180 nm, and the thickness of the hydrogen-containing amorphous carbon protective layer is about 220 nm and 280 nm. The piezoresistive coefficient of the amorphous carbon thin film piezoresistive sensing element is 1.58-46.7.

[0041] See also Figure 1 The structure of the amorphous carbon thin film deep-sea piezoresistive sensing element includes an insulating substrate layer 1, two metal electrode layers 2, a first piezoresistive sensing layer 3, a second piezoresistive sensing layer 4, and a protective layer 5. The two metal electrode layers 2 are stacked on top of the insulating substrate layer 1 and located at both ends along the length of the insulating substrate layer 1; the two metal electrode layers 2 are made of metal thin films. The first piezoresistive sensing layer 3 is stacked on top of the insulating substrate layer 1 and located between the two metal electrode layers 2. The second piezoresistive sensing layer 4 is stacked on top of the first piezoresistive sensing layer 3, and the length of the second piezoresistive sensing layer 4 is greater than the length of the first piezoresistive sensing layer 3; the first piezoresistive sensing layer 3 and the second piezoresistive sensing layer 4 are made of a slightly metal-doped amorphous carbon film. The protective layer 5 is stacked on top of the second piezoresistive sensing layer 4, and the length of the protective layer 5 is the same as the length of the second piezoresistive sensing layer 4; the protective layer 5 is made of hydrogen-containing amorphous carbon film.

[0042] See also Figure 1 Based on the "Thick Film Resistor" model of amorphous carbon piezoresistive effect, the use of trace / low content metal doping is beneficial for introducing conductive metals or metal carbides into the amorphous carbon mesh, optimizing the transition distance of charge carriers between conductive phases, improving the piezoresistive coefficient of the sensitive layer, and achieving high pressure sensitivity of the device. At the same time, trace / low content of metal helps to reduce film stress and improve device stability. Excessive metal content leads to too small transition distance between conductive phases in the film, resulting in a decrease in the piezoresistive coefficient. It also tends to form cluster structures, causing the functional layer to become porous and its corrosion resistance to decrease. Hydrogen-containing amorphous carbon has the characteristics of high hardness, wear resistance, high density, corrosion resistance, and high insulation. As a protective layer 5 on the surface, it is suitable for functional layer protection in harsh environments such as seawater and acid and alkali corrosion. At the same time, hydrogen-containing amorphous carbon has a similar composition to the functional layer, which is conducive to achieving strong interfacial bonding and improving device stability. In addition, adjusting the thickness ratio of the functional layer to the protective layer 5 is conducive to achieving strong interfacial bonding and high pressure sensitivity, thereby improving the operating stability and lifespan of the device.

[0043] See Figure 2 and Figure 3 The fabrication method of an amorphous carbon thin film deep-sea piezoresistive sensing element includes the following steps:

[0044] Step S1: Place the insulating substrate 1 in the deposition equipment, and after vacuuming, use plasma etching to etch the surface of the insulating substrate 1.

[0045] Step S2: Using magnetron sputtering technology, two metal electrode layers 2 are deposited on the top of the insulating substrate layer 1 through a mask plate 6;

[0046] Step S3: Using the pre-reserved lead positions on the mask plate 6, the first piezoresistive sensing layer 3 and the second piezoresistive sensing layer 4 are deposited using magnetron sputtering technology.

[0047] Step S4: Acetylene or methane gas is introduced into the coating chamber, and after ionization by the anolyte ion source, a protective layer 5 is deposited on the second piezoresistive sensing layer 4 to obtain an amorphous carbon thin film piezoresistive sensing element.

[0048] Example 1

[0049] This embodiment provides a seawater piezoresistive sensing element based on amorphous carbon thin film. The substrate material is silicon dioxide. A metal electrode layer 2, a piezoresistive sensing layer, and a protective layer 5 are sequentially fabricated on this substrate. The specific steps are as follows:

[0050] S1. Cleaning the substrate: After ultrasonic cleaning with ethanol and drying, the substrate is placed in a vacuum chamber and evacuated to a vacuum level of 2×10⁻⁶. -5 Torr, argon gas is introduced into the coating chamber to maintain the gas pressure at 2.4 mTorr, a bias voltage of -200V is applied to the substrate, the ion source of the anode layer is turned on, the current is 0.2A, and the substrate surface is etched by ionized argon ions. This process is maintained for 20 minutes.

[0051] S2. Fabrication of Cr electrodes: Turn on the magnetron sputtering source, introduce Ar gas, sputter the Cr target, maintain the chamber pressure at 2.2 mTorr, the sputtering target current at 4 A, and the bias voltage applied to the substrate at -200 V. This process is maintained for 3.5 min, and a Cr metal electrode layer with a thickness of about 100 nm is fabricated at both ends of the substrate.

[0052] S3. Preparation of the sensing layer: The sample obtained in S2 was removed, the middle mask was removed, and the mask was placed on both ends of the substrate at a distance of 35cm from the top of the base frame. Then it was placed in a vacuum chamber, and C and Cr splicing target material was spliced ​​using magnetron splicing technology to deposit a Cr-doped amorphous carbon piezoresistive sensing layer. The gas pressure in the vacuum coating chamber was controlled at 8mTorr, the magnetron splicing power supply voltage was 630V, the power was 500W, the pulse duty cycle was 10%, and the bias voltage applied to the substrate was -200V. This process was maintained for 3h to prepare a Cr-doped amorphous carbon piezoresistive sensing layer with a Cr doping content of 0.64at.% and a thickness of about 180nm.

[0053] S4. Preparation of hydrogen-containing amorphous carbon protective layer: The sample obtained in S3 is placed in a vacuum chamber, and acetylene gas is introduced into the chamber through the anolyte ion source to deposit the hydrogen-containing amorphous carbon protective layer. The gas pressure in the vacuum coating chamber is maintained at 2.5 mTorr, the current is 0.2 A, and the substrate bias voltage is -100 V. This process is maintained for 16.5 min to prepare a hydrogen-containing amorphous carbon protective layer with a thickness of about 220 nm.

[0054] S5. Preparation of electrode leads: Connect Cu wires to both ends of the piezoresistive sensing element with conductive silver paste, and dry them in an oven for 90 minutes at a temperature of 120℃.

[0055] The piezoresistive sensing element prepared above was subjected to a piezoresistive effect test. A vertical force was applied to the center of the piezoresistive sensing element, causing deformation. The change in resistance was observed. A three-point piezoresistive coefficient tester was used to apply force to the sample, bending it downwards by 0.2 mm. The change in resistance R before and after bending was observed. The resistance R was determined using the following formula: GF = Where R0 is the initial resistance of the piezoresistive sensing element, R is the resistance value of the piezoresistive sensing element after the sample is deformed, and t is the thickness of the sample. For sample length, The displacement is calculated using the formula, and the piezoresistive coefficient of the prepared composite amorphous carbon thin film piezoresistive material is 9.4.

[0056] Example 2

[0057] The difference from Example 1 is that in step S3 of this example, the sample is placed 28cm above the base, the sputtering duration is 2h40min, the piezoresistive sensing layer has a Cr doping content of 1.38at.% and a thickness of about 180nm, and the rest is the same as in Example 1, which will not be repeated here.

[0058] The piezoresistive sensing element prepared above was subjected to a piezoresistive effect test. A vertical force was applied to the center of the piezoresistive sensing element, causing deformation. The change in resistance was observed. A three-point piezoresistive coefficient tester was used to apply force to the sample, bending it downwards by 0.2 mm. The change in resistance R before and after bending was observed. The resistance R was determined using the following formula: GF = Where R0 is the initial resistance of the piezoresistive sensing element, R is the resistance value of the piezoresistive sensing element after the sample is deformed, and t is the thickness of the sample. For sample length, The displacement is calculated using the formula, and the piezoresistive coefficient of the prepared composite amorphous carbon thin film piezoresistive material is 22.8.

[0059] Example 3

[0060] The difference from Example 1 is that in step S3 of this example, the sample is placed 21 cm above the base, the sputtering duration is 2 hours, and the resulting piezoresistive sensing layer has a Cr doping content of 4.27 at.% and a thickness of approximately 180 nm. Everything else is the same as in Example 1 and will not be repeated here.

[0061] The piezoresistive sensing element prepared above was subjected to a piezoresistive effect test. A vertical force was applied to the center of the piezoresistive sensing element, causing deformation. The change in resistance was observed. A three-point piezoresistive coefficient tester was used to apply force to the sample, bending it downwards by 0.2 mm. The change in resistance R before and after bending was observed. The resistance R was determined using the following formula: GF = Where R0 is the initial resistance of the piezoresistive sensing element, R is the resistance value of the piezoresistive sensing element after the sample is deformed, and t is the thickness of the sample. For sample length, The displacement is calculated using the formula, and the piezoresistive coefficient of the prepared composite amorphous carbon thin film piezoresistive material is 16.2.

[0062] Example 4

[0063] The difference from Example 1 is that in step S3 of this example, the sample is placed 28cm above the base, the sputtering duration is 1h33min, and the piezoresistive sensing layer has a Cr doping content of 1.38at.% and a thickness of about 120nm.

[0064] S4. Preparation of hydrogen-containing amorphous carbon protective layer: The sample obtained in S3 was placed in a vacuum chamber, and acetylene gas was introduced into the chamber through the anolyte ion source to deposit the hydrogen-containing amorphous carbon protective layer. The gas pressure in the vacuum coating chamber was maintained at 2.5 mTorr, the current at 0.2 A, and the substrate bias voltage at -100 V. This process was maintained for 21 min to prepare a hydrogen-containing amorphous carbon protective layer with a thickness of approximately 280 nm. The thickness ratio of the sensing layer to the protective layer was adjusted. Other aspects were the same as in Example 1 and will not be repeated here.

[0065] The piezoresistive sensing element prepared above was subjected to a piezoresistive effect test. A vertical force was applied to the center of the piezoresistive sensing element, causing deformation. The change in resistance was observed. A three-point piezoresistive coefficient tester was used to apply force to the sample, bending it downwards by 0.2 mm. The change in resistance R before and after bending was observed. The resistance R was determined using the following formula: GF = Where R0 is the initial resistance of the piezoresistive sensing element, R is the resistance value of the piezoresistive sensing element after the sample is deformed, and t is the thickness of the sample. For sample length, The displacement is calculated using the formula, and the piezoresistive coefficient of the prepared composite amorphous carbon thin film piezoresistive material is 37.2.

[0066] Comparative Example 1

[0067] The difference from Example 1 is that in step S3 of this comparative example, the sample is placed 14cm above the base, the sputtering duration is 2h, the piezoresistive sensing layer has a Cr doping content of 11.05 at.% and a thickness of about 180nm, and the rest is the same as in Example 1, which will not be repeated here.

[0068] The piezoresistive sensing element prepared above was subjected to a piezoresistive effect test. A vertical force was applied to the center of the piezoresistive sensing element, causing deformation. The change in resistance was observed. A three-point piezoresistive coefficient tester was used to apply force to the sample, bending it downwards by 0.2 mm. The change in resistance R before and after bending was observed. The resistance R was determined using the following formula: GF = Where R0 is the initial resistance of the piezoresistive sensing element, R is the resistance value of the piezoresistive sensing element after the sample is deformed, and t is the thickness of the sample. For sample length, The displacement is calculated using the formula, and the piezoresistive coefficient of the prepared composite amorphous carbon thin film piezoresistive material is 1.9.

[0069] Comparative Example 2

[0070] The difference from Example 1 is that in step S3 of this comparative example, the sample is placed 7 cm above the base, the sputtering duration is 2 h, and the resulting piezoresistive sensing layer has a Cr doping content of 23.17 at.% and a thickness of approximately 180 nm. Everything else is the same as in Example 1 and will not be repeated here.

[0071] The piezoresistive sensing element prepared above was subjected to a piezoresistive effect test. A vertical force was applied to the center of the piezoresistive sensing element, causing deformation. The change in resistance was observed. A three-point piezoresistive coefficient tester was used to apply force to the sample, bending it downwards by 0.2 mm. The change in resistance R before and after bending was observed. The resistance R was determined using the following formula: GF = Where R0 is the initial resistance of the piezoresistive sensing element, R is the resistance value of the piezoresistive sensing element after the sample is deformed, and t is the thickness of the sample. For sample length, The displacement is calculated using the formula, and the piezoresistive coefficient of the prepared composite amorphous carbon thin film piezoresistive material is 1.6.

[0072] Comparative Example 3

[0073] The difference from Example 1 is that in step S3 of this comparative example, the sample is placed 28 cm above the base, the sputtering duration is 1 hour and 33 minutes, and the resulting piezoresistive sensing layer has a Cr doping content of 1.38 at.% and a thickness of approximately 120 nm. Only the sensing layer is prepared; the protective layer is not prepared. Everything else is the same as in Example 1 and will not be repeated here.

[0074] The piezoresistive sensing element prepared above was subjected to a piezoresistive effect test. A vertical force was applied to the center of the piezoresistive sensing element, causing deformation. The change in resistance was observed. A three-point piezoresistive coefficient tester was used to apply force to the sample, bending it downwards by 0.2 mm. The change in resistance R before and after bending was observed. The resistance R was determined using the following formula: GF = Where R0 is the initial resistance of the piezoresistive sensing element, R is the resistance value of the piezoresistive sensing element after the sample is deformed, and t is the thickness of the sample. For sample length, The displacement is calculated using the formula, and the piezoresistive coefficient of the prepared composite amorphous carbon thin film piezoresistive material is 46.7.

[0075] The piezoresistive sensing elements of the above embodiments and comparative examples were subjected to deep-sea simulated service tests. The specific test methods are as follows:

[0076] (1) Immersion in an autoclave: The deep-sea environment was simulated by using an autoclave to simulate the performance of the piezoresistive sensing element in the deep-sea environment. The immersion solution in the autoclave was a 3.5 wt.% NaCl solution, and the pressure in the autoclave was maintained at 20 MPa and the temperature at 25 °C. Examples 1, 2, and 3 and Comparative Examples 1 and 2 were immersed for 4 days, and Example 4 and Comparative Example 3 were immersed for 7 days.

[0077] (2) Piezoresistive Effect Test: The piezoresistive effect of the piezoresistive sensing elements of Examples 1, 2, 3, and 4 and Comparative Examples 1, 2, and 3 after simulated deep-sea service was tested using a three-point piezoresistive coefficient tester. A vertical force was applied to the center of the piezoresistive sensing element, causing deformation, and the change in resistance was observed. A force was applied to the sample using the three-point piezoresistive coefficient tester, causing the sample to bend downwards by 0.2 mm, and the change in resistance R before and after bending was observed. The resistance R was determined using the following formula: GF = Where R0 is the initial resistance of the piezoresistive sensing element, R is the resistance value of the piezoresistive sensing element after the sample is deformed, and t is the thickness of the sample. For sample length, The displacement is shown in the test results. Figure 3As shown, it can be concluded that although the piezoresistive coefficients of the piezoresistive sensing elements in Examples 1, 2, and 3 and Comparative Examples 1 and 2 tend to decrease after immersion in a simulated deep-sea environment, the piezoresistive coefficients of Example 1 are 7.2, Example 2 is 16.3, Example 3 is 9.8, Comparative Example 1 is 2.3, and Comparative Example 2 is 2.1. The piezoresistive coefficient of Example 2 still maintains a high level after high-pressure immersion in seawater.

[0078] For Example 4 and Comparative Example 3, the test results are as follows: Figure 4 As shown, after immersion in a simulated deep-sea environment, the piezoresistive coefficient of Example 4 decreased from 37.2 to 32.8, and the piezoresistive coefficient of Comparative Example 3 decreased from 46.7 to 28.1. The piezoresistive coefficient of Example 3 was more stable, and the seawater had little effect on the piezoresistive coefficient of the piezoresistive sensing layer, indicating that the protective layer 5 has an excellent protective effect on the piezoresistive sensing layer.

[0079] In the description of this application, the references to terms such as "an embodiment," "some embodiments," "in this embodiment," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in a suitable manner in any one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0080] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. An amorphous carbon thin-film deep-sea piezoresistive sensing element, characterized in that, include: An insulating base layer (1); Two metal electrode layers (2) are stacked on top of the insulating substrate layer (1) and located at both ends along the length of the insulating substrate layer (1) for connecting electrode leads. The two metal electrode layers (2) are made of metal thin film. A first piezoresistive sensing layer (3) is stacked on top of the insulating substrate layer (1) and located between the two metal electrode layers (2); A second piezoresistive sensing layer (4) is stacked on top of the first piezoresistive sensing layer (3), and the length of the second piezoresistive sensor is greater than the length of the first piezoresistive sensing layer (3). The first piezoresistive sensing layer (3) and the second piezoresistive sensing layer (4) are made of amorphous carbon film with trace metal doping. The doping range of the metal in the first piezoresistive sensing layer (3) and the second piezoresistive sensing layer (4) is 0.1-5.0 at.%%. A protective layer (5) is stacked on top of the second piezoresistive sensing layer (4) and the length of the protective layer (5) is the same as the length of the second piezoresistive sensing layer (4). The protective layer (5) is made of hydrogen-containing amorphous carbon film. Both the hydrogen-containing amorphous carbon film and the trace metal-doped amorphous carbon film are carbon-based thin film materials. Both the first piezoresistive sensing layer (3) and the second piezoresistive sensing layer (4) are Cr-doped amorphous carbon piezoresistive sensing layers.

2. The amorphous carbon thin-film deep-sea piezoresistive sensing element according to claim 1, characterized in that, The surface of the insulating substrate layer (1) is etched using plasma.

3. The amorphous carbon thin-film deep-sea piezoresistive sensing element according to claim 1, characterized in that, The metal thin film is made of one of the following materials: Cr, Cu, Al, Ag, Au, and Pt.

4. The amorphous carbon thin-film deep-sea piezoresistive sensing element according to claim 1, characterized in that, The piezoresistive coefficients of the first piezoresistive sensing layer (3) and the second piezoresistive sensing layer (4) are 1.58-46.

7.

5. The amorphous carbon thin-film deep-sea piezoresistive sensing element according to claim 1, characterized in that, The thickness of the first piezoresistive sensing layer (3) and the second piezoresistive sensing layer (4) is 100-300 nm.

6. The amorphous carbon thin-film deep-sea piezoresistive sensing element according to claim 1, characterized in that, The thickness of the protective layer (5) is 100-500 nm.

7. A method for fabricating an amorphous carbon thin-film deep-sea piezoresistive sensing element, characterized in that, The amorphous carbon thin-film deep-sea piezoresistive sensing element as described in any one of claims 1-6 comprises the following steps: Step S1: Place the insulating substrate (1) in a deposition apparatus, and after evacuation, use plasma to etch the surface of the insulating substrate (1); Step S2: Using magnetron sputtering technology, two metal electrode layers (2) are deposited on the top of the insulating substrate layer (1) through a mask plate (6). Step S3: Using the lead wire positions reserved in the mask plate (6), the first piezoresistive sensing layer (3) and the second piezoresistive sensing layer (4) are deposited using magnetron sputtering technology. Step S4: Acetylene or methane gas is introduced into the coating chamber and ionized by the ion source of the anode layer. The protective layer (5) is then deposited on the second piezoresistive sensing layer (4) to obtain an amorphous carbon thin film piezoresistive sensing element.

8. The method for fabricating an amorphous carbon thin-film deep-sea piezoresistive sensing element according to claim 7, characterized in that, In step S1, the specific parameters for plasma etching are as follows: vacuum degree is 2×10⁻⁶. -5 Torr, with a bias voltage of -200V, an ion source current of 0.2A, and an etching time of 20min.

9. The method for fabricating an amorphous carbon thin-film deep-sea piezoresistive sensing element according to claim 7, characterized in that, In step S3, a trace metal-doped amorphous carbon film is deposited as the first piezoresistive sensing layer (3) and the second piezoresistive sensing layer (4), and in step S4, a hydrogen-containing amorphous carbon film is deposited as the protective layer (5).

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