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

Abstract

The invention provides an amorphous carbon film deep sea piezoresistive sensing element and a preparation method thereof. The amorphous carbon film deep sea piezoresistive sensing element comprises an insulating substrate layer; the two metal electrode layers are cushioned at the top end of the insulating substrate layer and located at the two ends in the length direction of the insulating substrate layer so as to be connected with electrode leads, and the two metal electrode layers are made of metal films; the first piezoresistive sensing layer is cushioned at the top end of the insulating substrate layer and is positioned between the two metal electrode layers; the second piezoresistive sensing layer is stacked at the top end of the first piezoresistive sensing layer, the length of the second piezoresistive sensing layer is larger than that of the first piezoresistive sensing layer, and the first piezoresistive sensing layer and the second piezoresistive sensing layer are made of trace metal doped amorphous carbon films; and the protective layer is stacked at the top end of the second piezoresistive sensing layer, the length of the protective layer is the same as that of the second piezoresistive sensing layer, and the protective layer adopts a hydrogen-containing amorphous carbon film. The invention has the beneficial effects of simplifying the process, improving the sensitivity, improving the structural stability and reducing the environmental influence.

Description

Technical Field

[0001] The present invention relates to the technical field of pressure sensor devices, and in particular to an amorphous carbon film deep-sea piezoresistive sensor element and a preparation method thereof. Background Art

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

[0003] The sensitive materials of the pressure sensors currently used are mainly single crystal silicon or polycrystalline silicon, which are difficult to meet the stable sensing requirements under harsh working conditions such as corrosion and scratching in complex working conditions of marine engineering equipment. They usually require complex packaging processes for processing. For deep-sea pressure sensors that need to work continuously for a long time in a marine corrosion environment, this will cause serious drift in the test results, and then produce cumulative data errors, which will seriously affect the accuracy of detection such as seawater depth.

[0004] Existing technical solutions usually adopt packaging and protection of sensing materials to solve the problem that sensing performance is easily affected by the environment. For example, in patent CN200420055437.7, an insulating partition is introduced to prevent sensor deformation, but the response speed is affected; the high-pressure resistant temperature sensor prepared by patent CN201020107919.8 uses a thermal conductive medium to fill the thermistor inside the temperature measuring probe, but reduces the temperature sensitivity and response speed.

[0005] Secondly, highly stable sensitive materials such as diamond and SiC are used for sensing. For example, in patent CN201910053826.7, a SiC pressure sensor with a leadless package is used, which can work in harsh environments and maintain good stability. In addition, sensors with a highly sensitive functional layer and a composite surface protective layer also have certain improvement effects. For example, in patent CN202311787094.7, a carbon-based film with a high resistivity is composited with silicon oxide to solve the electrical failure of the sensor in a corrosive environment and realize sensing in a corrosive medium environment; in patent CN202210366465.3, a carbon-based piezoresistive film sensor with a wear-resistant layer, a sensing layer, an insulating layer and an electrode layer structure is prepared, which realizes wear-resistant protection and sensing in one, and the component sensitivity is 4.2 to 7.4.

[0006] However, the above methods still cannot solve the problems of complex and high-cost preparation or packaging processes of existing sensor elements, poor interface matching between heterogeneous functions and protective layer structures, easy peeling and failure, and difficulty in coordinating strong protection and high sensitivity. They cannot meet the needs of long-term observation in corrosive environments such as seawater. Summary of the invention

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

[0008] The present invention provides an amorphous carbon film deep-sea piezoresistive sensing element, comprising: an insulating base layer; Two metal electrode layers are stacked on the top of the insulating base layer and located at both ends along the length direction of the insulating base layer for connecting electrode leads, and the two metal electrode layers are made of metal films; A first piezoresistive sensing layer, which is deposited on the top of the insulating base layer and located between the two metal electrode layers; a second piezoresistive sensing layer, which is padded on the top of the first piezoresistive sensing layer and has a length greater than that of the first piezoresistive sensing layer, and the first piezoresistive sensing layer and the second piezoresistive sensing layer are made of amorphous carbon films doped with trace metals; A protective layer is deposited on the top of the second piezoresistive sensing layer and has the same length as the second piezoresistive sensing layer. The protective layer is made of a hydrogenated amorphous carbon film.

[0009] Compared with the prior art, the amorphous carbon film deep-sea piezoresistive sensor element of the present application has the following advantages: In the present invention, a trace metal-doped amorphous carbon film is used as the piezoresistive sensitive layer of the seawater piezoresistive sensor element, and a hydrogen-containing amorphous carbon film is used as the protective layer of the seawater piezoresistive sensor element. The piezoresistive sensing layer adopts trace metal-doped amorphous carbon and has high piezoresistive sensitivity. At the same time, both the piezoresistive sensing layer and the protective layer are carbon-based thin film materials, and the bonding between the thin film interfaces is better and more stable, which is suitable for corrosion and high-pressure environments, and has the characteristics of simple preparation process, small size, high sensitivity, and little external influence on measurement.

[0010] In a possible implementation manner, the surface of the insulating base layer is etched using plasma.

[0011] In a possible implementation, the metal film is made of one of Cr, Cu, Al, Ag, Au, and Pt.

[0012] In a possible implementation manner, the doping range of the metal in the first piezoresistive sensing layer and the second piezoresistive sensing layer is 0.1-5.0 at.%.

[0013] In a possible implementation manner, the piezoresistive coefficients of the first piezoresistive sensing layer and the second piezoresistive sensing layer are 1.58-46.7.

[0014] In a possible implementation manner, the thickness of the first piezoresistive sensing layer and the second piezoresistive sensing layer is 100-300 nm.

[0015] In a possible implementation manner, the thickness of the protective layer is 100-500 nm.

[0016] The present invention also provides a method for preparing an amorphous carbon film deep-sea piezoresistive sensor element, comprising the following steps: Step S1, placing the insulating base layer in a deposition device, evacuating the device, and then etching the surface of the insulating base layer using plasma; Step S2, using magnetron sputtering technology to deposit the two metal electrode layers on top of the insulating base layer through a mask plate; Step S3, using the mask plate to reserve lead positions, and using magnetron sputtering technology to deposit the first piezoresistive sensing layer and the second piezoresistive sensing layer; Step S4, introducing acetylene or methane gas into the coating chamber, ionizing it through the anode layer ion source, and then depositing the protective layer on the second piezoresistive sensing layer to obtain an amorphous carbon thin film piezoresistive sensing element.

[0017] In a possible implementation manner, in step S1, the specific parameters of plasma etching are as follows: the vacuum degree is 2×10 -5 Torr, the applied bias voltage is -200 V, the anode layer ion source current is 0.2 A, and the etching time is 20 min.

[0018] In a possible implementation manner, in the step S3 , a metal-doped amorphous carbon film is deposited as the first piezoresistive sensing layer and the second piezoresistive sensing layer, and in the step S4 , a hydrogenated amorphous carbon film is deposited as the protective layer.

[0019] Compared with the prior art, the method for preparing an amorphous carbon film deep-sea piezoresistive sensor element in the present application has the following advantages: The metal electrode layer of the seawater piezoresistive sensor element in the present invention is a metal film prepared by magnetron sputtering technology, which serves as the metal electrode layer connecting the piezoresistive sensor layer and the lead; the amorphous carbon piezoresistive sensor layer is a pressure-sensitive layer made of a metal-doped amorphous carbon film with a piezoresistive effect, which measures the change in pressure by reacting to changes in resistance; the hydrogen-containing amorphous carbon protective layer is a protective layer deposited on the surface of the piezoresistive sensor layer, which prevents the metal-doped amorphous carbon piezoresistive sensor layer from being affected by the external corrosive environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of the overall structure of the amorphous carbon film deep-sea piezoresistive sensor element of the present invention; Figure 2 is a flow chart of the steps of the preparation method of the present invention; Figure 3 The following is a process flow chart of the preparation of the amorphous carbon film deep-sea piezoresistive sensor element of the present invention; Figure 4 Graph showing the piezoresistance coefficients of Examples 1, 2, 3 and Comparative Examples 1 and 2 of the present invention; Figure 5 This is a graph of piezoresistance coefficients of Examples 1, 2, 3 of the present invention and Comparative Examples 1 and 2 after being immersed in a simulated deep-sea high-pressure environment for 4 days; Figure 6 This is a graph of piezoresistive coefficients of Example 4 of the present invention and Comparative Example 3 after serving in a simulated deep-sea high-pressure environment for 7 days; Explanation of the reference numerals: 1. insulating base layer; 2. metal electrode layer; 3. first piezoresistive sensing layer; 4. second piezoresistive sensing layer; 5. protective layer; 6. mask plate. DETAILED DESCRIPTION

[0021] First, those skilled in the art should understand that these implementations are only used to explain the technical principles of the embodiments of the present application, and are not intended to limit the protection scope of the embodiments of the present application. Those skilled in the art can make adjustments to them as needed to adapt to specific application scenarios.

[0022] The present application is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0023] See also Figure 1 , the embodiment of the present application discloses an amorphous carbon thin film deep-sea piezoresistive sensor element. Compared with Ag, Cu and Cr, Cr with high bonding force with the amorphous carbon film is preferably selected as the metal electrode layer 2, including a Cr metal electrode layer, a Cr-doped amorphous carbon piezoresistive sensor layer and a hydrogen-containing amorphous carbon protective layer arranged on the surface of an insulating base layer 1. The thickness of the metal electrode layer 2 is about 100nm, the thickness of the Cr-doped amorphous carbon piezoresistive sensor layer is about 120nm and 180nm, the thickness of the hydrogen-containing amorphous carbon protective layer is about 220nm and 280nm, and the piezoresistive coefficient of the amorphous carbon thin film piezoresistive sensor element is 1.58-46.7.

[0024] Continue to see Figure 1The structure of the amorphous carbon film deep-sea piezoresistive sensor element includes an insulating base layer 1, two metal electrode layers 2, a first piezoresistive sensing layer 3, a second piezoresistive sensing layer 4 and a protective layer 5, wherein the two metal electrode layers 2 are padded on the top of the insulating base layer 1 and are located at both ends along the length direction of the insulating base layer 1, and the two metal electrode layers 2 are made of metal films; the first piezoresistive sensing layer 3 is padded on the top of the insulating base layer 1 and is located between the two metal electrode layers 2; the second piezoresistive sensing layer 4 is padded on the top of the first piezoresistive sensing layer 3 and the length of the second piezoresistive sensing layer 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 trace metal-doped amorphous carbon film; the protective layer 5 is padded on the 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, and the protective layer 5 is made of hydrogen-containing amorphous carbon film.

[0025] Continue to see Figure 1 , the "Thick Film Resistor" model based on the amorphous carbon piezoresistive effect adopts trace / low content metal doping, which is conducive to introducing conductive metal or metal carbide into the amorphous carbon grid, optimizing the transition distance of carriers between conductive phases, improving the piezoresistance coefficient of the sensitive layer, and realizing high pressure sensitivity of the component. At the same time, trace / low content metal is conducive to reducing film stress and improving component stability. Too high metal content leads to too small transition distance between conductive phases of the film, and the piezoresistance coefficient decreases. At the same time, cluster structure is prone to occur, causing loose functional layer and decreased corrosion resistance. Hydrogenated amorphous carbon has the characteristics of high hardness, wear resistance, high density, corrosion resistance, and high insulation. As a surface protective layer 5, it is suitable for functional layer protection in harsh environments such as seawater and acid-base corrosion. At the same time, hydrogenated amorphous carbon is similar to the functional layer component, which is conducive to achieving strong interface bonding and improving component stability. In addition, regulating the thickness ratio of the functional layer to the protective layer 5 is conducive to achieving strong interface bonding and high sensitivity to pressure, improving the working stability and life of the device.

[0026] See also Figure 2 and Figure 3 The method for preparing the amorphous carbon film deep-sea piezoresistive sensor element comprises the following steps: Step S1, placing the insulating base layer 1 in a deposition device, evacuating the device, and then etching the surface of the insulating base layer 1 with plasma; Step S2, using magnetron sputtering technology to deposit two metal electrode layers 2 on the top of the insulating base layer 1 through a mask plate 6; Step S3, using a mask plate 6 to reserve lead positions, and using magnetron sputtering technology to deposit the first piezoresistive sensing layer 3 and the second piezoresistive sensing layer 4; Step S4, introducing acetylene or methane gas into the coating chamber, ionizing it through the anode layer ion source, and then depositing the protective layer 5 on the second piezoresistive sensing layer 4 to obtain an amorphous carbon thin film piezoresistive sensing element.

[0027] Example 1 This embodiment provides a seawater piezoresistive sensor element based on an amorphous carbon film. The base material is silicon dioxide. A metal electrode layer 2, a piezoresistive sensing layer and a protective layer 5 are sequentially prepared on the base. The specific steps are as follows: S1. Cleaning the substrate: ultrasonically clean it with ethanol, dry it, place it in a vacuum chamber, and evacuate it to 2×10 -5 Torr, introduce argon gas into the coating chamber to maintain the gas pressure at 2.4mTorr, apply a bias voltage of -200V on the substrate, turn on the anode layer ion source, the current is 0.2A, and use ionized argon ions to etch the substrate surface. This process lasts for 20 minutes; S2. Preparation of Cr electrode: Turn on the magnetron sputtering source, introduce Ar gas, sputter the Cr target, maintain the chamber pressure at 2.2mTorr, the sputtering target current at 4A, and the bias voltage applied to the substrate at -200V. This process is maintained for 3.5min, and a Cr metal electrode layer with a thickness of about 100nm is prepared at both ends of the substrate; S3. Preparation of sensing layer: Take the sample obtained in S2, remove the middle mask plate, cover the two ends of the substrate with mask plates and stick them 35 cm away from the top of the base frame, then place it in a vacuum chamber, use magnetron sputtering technology to sputter C and Cr spliced ​​targets, deposit Cr-doped amorphous carbon piezoresistive sensing layer, control the gas pressure in the vacuum coating chamber to 8mTorr, the magnetron sputtering power supply voltage is 630V, the power is 500W, the pulse duty cycle is 10%, and the bias voltage applied to the substrate is -200V. This process is 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; S4. Preparation of hydrogen-containing amorphous carbon protective layer: Place the sample obtained in S3 in a vacuum chamber, introduce acetylene gas into the chamber through the anode layer ion source to deposit a hydrogen-containing amorphous carbon protective layer, maintain the gas pressure in the vacuum coating chamber at 2.5mTorr, the current at 0.2A, the substrate bias at -100V, and this process is maintained for 16.5min to prepare a hydrogen-containing amorphous carbon protective layer with a thickness of about 220nm.

[0028] S5. Prepare electrode leads: Connect Cu wires at both ends of the piezoresistive sensor element with conductive silver glue, dry in an oven for 90 minutes, and set the temperature to 120℃.

[0029] The piezoresistive effect test was performed on the piezoresistive sensor element prepared above, that is, a vertical force was applied to the center of the piezoresistive sensor element to deform the piezoresistive sensor element and observe its resistance change. A three-point piezoresistive coefficient tester was used to apply a force to the sample to bend the sample downward by 0.2 mm, and the change in the sample resistance R before and after bending was observed. The following formula was used: GF= , where R0 is the initial resistance of the piezoresistive sensor element, R is the resistance value of the piezoresistive sensor element after the sample is deformed, and t is the thickness of the sample. is the sample length, is the displacement, and through the formula, it can be calculated that the piezoresistance coefficient of the prepared composite amorphous carbon film varistor material is 9.4.

[0030] Example 2 The difference from Example 1 is that in step S3 of this embodiment, the sample is placed 28 cm from the top of the base frame, the sputtering is maintained for 2 h 40 min, the Cr doping content of the obtained piezoresistive sensing layer is 1.38 at.%, and the thickness is about 180 nm. The rest is the same as Example 1 and will not be repeated here.

[0031] The piezoresistive effect test was performed on the piezoresistive sensor element prepared above, that is, a vertical force was applied to the center of the piezoresistive sensor element to deform the piezoresistive sensor element and observe its resistance change. A three-point piezoresistive coefficient tester was used to apply a force to the sample to bend the sample downward by 0.2 mm, and the change in the sample resistance R before and after bending was observed. The following formula was used: GF= , where R0 is the initial resistance of the piezoresistive sensor element, R is the resistance value of the piezoresistive sensor element after the sample is deformed, and t is the thickness of the sample. is the sample length, is the displacement, and through the formula, it can be calculated that the piezoresistance coefficient of the prepared composite amorphous carbon film varistor material is 22.8.

[0032] Example 3 The difference from Example 1 is that in step S3 of this embodiment, the sample is placed at 21 cm from the top of the base frame, the sputtering is maintained for 2 h, and the Cr doping content of the obtained piezoresistive sensing layer is 4.27 at.%, and the thickness is about 180 nm. The rest is the same as Example 1 and will not be repeated here.

[0033] The piezoresistive effect test was performed on the piezoresistive sensor element prepared above, that is, a vertical force was applied to the center of the piezoresistive sensor element to deform the piezoresistive sensor element and observe its resistance change. A three-point piezoresistive coefficient tester was used to apply a force to the sample to bend the sample downward by 0.2 mm, and the change in the sample resistance R before and after bending was observed. The following formula was used: GF= , where R0 is the initial resistance of the piezoresistive sensor element, R is the resistance value of the piezoresistive sensor element after the sample is deformed, and t is the thickness of the sample. is the sample length, is the displacement, and through the formula, it can be calculated that the piezoresistance coefficient of the prepared composite amorphous carbon film varistor material is 16.2.

[0034] Example 4 The difference from Example 1 is that in step S3 of this embodiment, the sample is placed at 28 cm from the top of the base frame, the sputtering is maintained for 1 h 33 min, and the Cr doping content of the obtained piezoresistive sensing layer is 1.38 at.%, and the thickness is about 120 nm.

[0035] S4. Preparation of a 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 anode layer ion source to deposit a 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 is -100 V. This process is maintained for 21 minutes to prepare a hydrogen-containing amorphous carbon protective layer with a thickness of about 280 nm. The thickness ratio of the sensing layer to the protective layer is adjusted. The rest is the same as in Example 1 and will not be repeated here.

[0036] The piezoresistive effect test was performed on the piezoresistive sensor element prepared above, that is, a vertical force was applied to the center of the piezoresistive sensor element to deform the piezoresistive sensor element and observe its resistance change. A three-point piezoresistive coefficient tester was used to apply a force to the sample to bend the sample downward by 0.2 mm, and the change in the sample resistance R before and after bending was observed. The following formula was used: GF= , where R0 is the initial resistance of the piezoresistive sensor element, R is the resistance value of the piezoresistive sensor element after the sample is deformed, and t is the thickness of the sample. is the sample length, is the displacement, and through the formula, it can be calculated that the piezoresistance coefficient of the prepared composite amorphous carbon film varistor material is 37.2.

[0037] Comparative Example 1 The difference from Example 1 is that in step S3 of this comparative example, the sample is placed 14 cm from the top of the base frame, the sputtering is maintained for 2 h, the Cr doping content of the prepared piezoresistive sensing layer is 11.05 at.%, and the thickness is about 180 nm. The rest is the same as Example 1 and will not be repeated here.

[0038] The piezoresistive effect test was performed on the piezoresistive sensor element prepared above, that is, a vertical force was applied to the center of the piezoresistive sensor element to deform the piezoresistive sensor element and observe its resistance change. A three-point piezoresistive coefficient tester was used to apply a force to the sample to bend the sample downward by 0.2 mm, and the change in the sample resistance R before and after bending was observed. The following formula was used: GF= , where R0 is the initial resistance of the piezoresistive sensor element, R is the resistance value of the piezoresistive sensor element after the sample is deformed, and t is the thickness of the sample. is the sample length, is the displacement, and through the formula, it can be calculated that the piezoresistance coefficient of the prepared composite amorphous carbon film varistor material is 1.9.

[0039] Comparative Example 2 The difference from Example 1 is that in step S3 of this comparative example, the sample is placed 7 cm from the top of the base frame, the sputtering is maintained for 2 h, and the Cr doping content of the obtained piezoresistive sensing layer is 23.17 at.%, and the thickness is about 180 nm. The rest is the same as Example 1 and will not be repeated here.

[0040] The piezoresistive effect test was performed on the piezoresistive sensor element prepared above, that is, a vertical force was applied to the center of the piezoresistive sensor element to deform the piezoresistive sensor element and observe its resistance change. A three-point piezoresistive coefficient tester was used to apply a force to the sample to bend the sample downward by 0.2 mm, and the change in the sample resistance R before and after bending was observed. The following formula was used: GF= , where R0 is the initial resistance of the piezoresistive sensor element, R is the resistance value of the piezoresistive sensor element after the sample is deformed, and t is the thickness of the sample. is the sample length, is the displacement, and through the formula, it can be calculated that the piezoresistance coefficient of the prepared composite amorphous carbon film varistor material is 1.6.

[0041] Comparative Example 3 The difference from Example 1 is that in step S3 of this comparative example, the sample is placed at 28 cm from the top of the base frame, the sputtering is maintained for 1 h 33 min, and the Cr doping content of the obtained piezoresistive sensing layer is 1.38 at.%, and the thickness is about 120 nm. Only the sensing layer is prepared, and no protective layer is prepared. The rest is the same as Example 1 and will not be repeated here.

[0042] The piezoresistive effect test was performed on the piezoresistive sensor element prepared above, that is, a vertical force was applied to the center of the piezoresistive sensor element to deform the piezoresistive sensor element and observe its resistance change. A three-point piezoresistive coefficient tester was used to apply a force to the sample to bend the sample downward by 0.2 mm, and the change in the sample resistance R before and after bending was observed. The following formula was used: GF= , where R0 is the initial resistance of the piezoresistive sensor element, R is the resistance value of the piezoresistive sensor element after the sample is deformed, and t is the thickness of the sample. is the sample length, is the displacement, and through the formula, it can be calculated that the piezoresistance coefficient of the prepared composite amorphous carbon film varistor material is 46.7.

[0043] The piezoresistive sensor elements of the above embodiments and comparative examples were subjected to deep sea simulated service tests, and the specific test methods are as follows: (1) Autoclave immersion: The deep sea environment is simulated by autoclave, and the service effect of the piezoresistive sensor element in the deep sea environment is simulated. The immersion solution in the autoclave is 3.5wt.% NaCl solution, and the pressure in the autoclave is maintained at 20MPa and the temperature is 25°C. Examples 1, 2, 3 and Comparative Examples 1 and 2 are immersed for 4 days, and Example 4 and Comparative Example 3 are immersed for 7 days;

[0044] (2) Piezoresistive effect test: The piezoresistive effect test was performed on the piezoresistive sensor elements of Examples 1, 2, 3, 4 and Comparative Examples 1, 2, 3 after simulated deep-sea service using a three-point piezoresistive coefficient tester. That is, a vertical force was applied to the center of the piezoresistive sensor element to deform the piezoresistive sensor element and observe the change in resistance. A three-point piezoresistive coefficient tester was used to apply a force to the sample to bend the sample downward by 0.2 mm, and the change in the resistance R of the sample before and after bending was observed. The following formula was used: GF = , where R0 is the initial resistance of the piezoresistive sensor element, R is the resistance value of the piezoresistive sensor element after the sample is deformed, and t is the thickness of the sample. is the sample length, is the displacement, and the test results are as follows Figure 3 As shown, it can be concluded that after immersion in a simulated deep-sea environment, the piezoresistance coefficients of the piezoresistive sensor elements of Examples 1, 2, 3 and Comparative Examples 1 and 2 tend to decrease, the piezoresistive coefficient of Example 1 is 7.2, the piezoresistive coefficient of Example 2 is 16.3, the piezoresistive coefficient of Example 3 is 9.8, the piezoresistive coefficient of Comparative Example 1 is 2.3, and the piezoresistive coefficient of Comparative Example 2 is 2.1. The piezoresistive coefficient of Example 2 still maintains a relatively high level after high-pressure immersion in seawater.

[0045] 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 piezoresistance coefficient of Example 4 decreases from 37.2 to 32.8, and the piezoresistance coefficient of Comparative Example 3 decreases from 46.7 to 28.1. The piezoresistance coefficient of Example 3 is more stable, and seawater has little effect on the piezoresistance coefficient of the piezoresistive sensing layer, indicating that the protective layer 5 has an excellent protective effect on the piezoresistive sensing layer.

[0046] In the description of the present application, the description with reference to the terms "one embodiment", "some embodiments", "in the present embodiment", "specific example", or "some examples" etc. means that the specific features, mechanisms, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, mechanisms, materials or characteristics described may be combined in a suitable manner in any one or more embodiments or examples. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0047] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application shall be based on the protection scope of the claims.

Claims

1. An amorphous carbon film deep-sea piezoresistive sensor element, characterized in that: include: an insulating base layer (1); Two metal electrode layers (2) are stacked on the top of the insulating base layer (1) and located at both ends along the length direction of the insulating base layer (1) for connecting electrode leads, and the two metal electrode layers (2) are made of metal thin films; a first piezoresistive sensing layer (3), which is deposited on the top of the insulating base layer (1) and is located between the two metal electrode layers (2); a second piezoresistive sensing layer (4), which is padded on the top of the first piezoresistive sensing layer (3), and the length of the second piezoresistive sensing layer is greater than the length of the first piezoresistive sensing layer (3), and the first piezoresistive sensing layer (3) and the second piezoresistive sensing layer (4) are made of amorphous carbon films doped with trace amounts of metal; A protective layer (5) is deposited on the 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 a hydrogen-containing amorphous carbon film.

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

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

4. The amorphous carbon film deep-sea piezoresistive sensor element according to claim 1, characterized in that: The metal doping range in the first piezoresistive sensing layer (3) and the second piezoresistive sensing layer (4) is 0.1-5.0 at.%.

5. The amorphous carbon film deep-sea piezoresistive sensor 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.

6. The amorphous carbon film deep-sea piezoresistive sensor 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.

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

8. A method for preparing an amorphous carbon film deep-sea piezoresistive sensor element, characterized in that: The amorphous carbon film deep-sea piezoresistive sensor element as claimed in any one of claims 1 to 7 comprises the following steps: Step S1, placing the insulating base layer (1) in a deposition device, evacuating the device, and then etching the surface of the insulating base layer (1) using plasma; Step S2, using magnetron sputtering technology to deposit the two metal electrode layers (2) on top of the insulating base layer (1) through a mask plate (6); Step S3, using the mask plate (6) to reserve lead positions, and using magnetron sputtering technology to deposit the first piezoresistive sensing layer (3) and the second piezoresistive sensing layer (4); Step S4, introducing acetylene or methane gas into the coating chamber, ionizing it through the anode layer ion source, and then depositing the protective layer (5) on the second piezoresistive sensing layer (4), thereby obtaining an amorphous carbon thin film piezoresistive sensing element.

9. The method for preparing an amorphous carbon film deep-sea piezoresistive sensor element according to claim 8, characterized in that: In step S1, the specific parameters of plasma etching are as follows: the vacuum degree is 2×10 -5 Torr, the applied bias voltage is -200 V, the anode layer ion source current is 0.2 A, and the etching time is 20 min.

10. The method for preparing an amorphous carbon film deep-sea piezoresistive sensor element according to claim 8, characterized in that: In the step S3, a metal-doped amorphous carbon film is deposited as the first piezoresistive sensing layer (3) and the second piezoresistive sensing layer (4), and in the step S4, a hydrogen-containing amorphous carbon film is deposited as the protective layer (5).

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