A diamond piezoresistive material and its pressure sensing applications

Abstract

The application discloses a diamond piezoresistive material and a pressure sensing application thereof, in particular to a piezoresistive material based on boron-doped diamond and a sensor application method thereof. 6 The application adopts a gradient doping structure and a hetero-layer design to construct the diamond piezoresistive material with high sensitivity, high linearity, temperature stability, corrosion resistance and radiation resistance; through optimization of a CVD process and a pattern etching structure, stable piezoresistive response in an environment of-60 DEG C to 250 DEG C is realized, and the cycle life is more than 10 6 times, and the application is suitable for high-reliability sensor devices under extreme working conditions such as aerospace engines, deep-sea exploration equipment and nuclear reactors.

Description

Technical Field

[0001] This invention belongs to the field of materials and applications, and relates to a diamond piezoresistive material and its pressure sensing application. Background Technology

[0002] As high-end equipment in aerospace, deep-sea exploration, and nuclear safety monitoring moves towards extreme environmental conditions, higher demands are being placed on the performance of core sensor materials. Especially in the field of pressure sensing, materials must maintain long-term stable operation in high-temperature, high-pressure, high-radiation, and even highly corrosive media. Piezoresistive pressure sensors are widely used in industrial fields due to their simple structure, high sensitivity, and suitability for miniaturization and integration. However, in extreme environments, the limitations of traditional piezoresistive materials become increasingly prominent, severely restricting the expansion of sensor performance.

[0003] Currently, widely used piezoresistive materials mainly include silicon (Si), polycrystalline silicon (Poly-Si), and silicon carbide (SiC). Among them, silicon-based materials are widely deployed in room temperature and medium temperature sensors due to their mature CMOS compatibility and excellent piezoresistive coefficient. However, their intrinsic band gap is relatively small (approximately 1.1 eV), and the thermal excitation effect of charge carriers is significantly enhanced when the temperature exceeds 200–300°C, leading to increased output drift and rapid performance degradation. Therefore, silicon-based piezoresistors are difficult to meet the requirements of environments above 600°C in aero-engines, high-temperature combustion chambers, or nuclear reactors.

[0004] To overcome the thermal stability defects of silicon, wide-bandgap materials such as SiC have been proposed for use in high-temperature piezoresistive devices. SiC has a bandgap of approximately 3.2 eV and exhibits significantly better thermal stability than silicon. Pressure sensors made from SiC maintain good performance even at operating temperatures of 500–600°C, and some military engines (such as the GE90) have already incorporated SiC pressure sensors into their air intake or exhaust nozzle structures. However, SiC piezoresistive materials have significant drawbacks, including: a relatively low rate of change of resistance per unit strain (i.e., piezoresistive coefficient), resulting in limited sensitivity; lattice defects at high temperatures easily causing fluctuations in carrier mobility; furthermore, the patterning of SiC at the micro / nano scale is complex, limiting the processing resolution and restricting its application potential in next-generation high-precision integrated sensors.

[0005] Besides silicon and SiC, some researchers have also attempted to develop oxide or nitride material systems such as ZnO and GaN for piezoresistive sensing. However, these materials suffer from problems such as nonlinear piezoresistive response, poor environmental stability, and low electrode contact consistency. Furthermore, their manufacturing processes are still immature, and reliability verification cycles are long, making it difficult to meet the needs of high-end engineering applications. In addition, some novel two-dimensional materials such as graphene and black phosphorus have also been explored for use in flexible piezoresistive devices, but their intrinsic thermal stability is insufficient, and their resistance to oxidation and radiation is weak, making them unsuitable for deployment in harsh environments such as aerospace or nuclear energy systems.

[0006] On the other hand, some recent studies have pointed out that diamond materials theoretically possess good potential for piezoresistive effects, especially boron-doped diamond (BDD) which has gradually attracted attention due to its semiconductor properties and extremely high thermal and chemical stability. However, the application of BDD materials in practical piezoresistive sensors still faces several core problems. First, the crystal growth process of existing BDD films is prone to anisotropy, making the piezoresistive response directionally dependent and reducing device consistency. Second, the boron doping process is difficult to precisely control the spatial distribution, especially in the film thickness direction. Insufficient gradient control leads to uneven charge carrier concentration in the strain response layer, resulting in nonlinear output characteristics. Third, the poor contact consistency between the diamond surface and the metal electrode leads to large changes in contact resistance at high temperatures, making the device signal prone to fluctuation. In addition, most existing BDD devices adopt simple film layer structures, lacking micro-nano structure design optimization, and cannot effectively utilize stress concentration regions or enhance directional selective response, making it difficult to balance sensitivity and linearity.

[0007] In summary, traditional piezoresistive materials each have shortcomings in terms of sensitivity, temperature drift suppression, processing compatibility, and high-temperature stability, making it difficult to achieve long-term reliable operation in extreme application scenarios. While boron-doped diamond, as a potential high-performance piezoresistive material, possesses significant theoretical advantages, it is still limited by key issues such as insufficient anisotropy control, low gradient doping precision, and difficulty in controlling the contact interface, thus lacking a stable and reproducible engineering preparation route. Therefore, there is an urgent need to develop a novel boron-doped diamond piezoresistive material with controllable structure, tunable process, and balanced performance, and to establish a systematic preparation and integration scheme to meet the practical needs of pressure monitoring under high-temperature, high-pressure, and high-radiation environments. Summary of the Invention

[0008] To address the shortcomings of existing technologies, this invention provides a diamond piezoresistive material and its pressure sensing application.

[0009] To achieve the above objectives, the present invention adopts the following technical solution:

[0010] A method for preparing a diamond piezoresistive material includes the following steps:

[0011] 1) Substrate pretreatment: Prepare a substrate and perform surface treatment on the substrate to enhance the diamond nucleation density. The substrate is a Si<111> wafer, alumina Al2O3, or silicon carbide SiC.

[0012] 2) Gradient doping deposition: Boron-doped diamond films are deposited on the substrate in stages by chemical vapor deposition (CVD). Boron source gas is introduced in stages during the growth process to form a concentration gradient doping structure along the thickness direction. The film includes a highly doped bottom layer, a medium-doped intermediate layer, and a lightly doped top layer. The boron source gas is B2H6 or BF3.

[0013] 3) Introduction of heterostructure: A heterostructure layer is introduced on the top or bottom surface of the gradient-doped diamond film. The heterostructure layer is a diamond-like carbon (DLC) layer or a silicon carbide (SiC) layer.

[0014] 4) Piezoresistive sensitive pattern construction: Micro-nano pattern etching is performed on boron-doped diamond films to construct piezoresistive response regions with stress concentration function;

[0015] 5) Electrode deposition and device packaging: Deposit a metal electrode in the piezoresistive response region. The metal electrode has a double-layer structure. Introduce a multi-layer packaging system around the device to complete the packaging and obtain diamond piezoresistive material.

[0016] By adopting the above technical solution, diamond particles are uniformly impacted and adhered to the substrate surface under ultrasonic excitation, forming a large number of "nucleation centers". The introduction of heterostructure can improve structural stability and environmental tolerance, and can suppress lattice mismatch and stress fluctuation, thereby homogenizing surface stress. The resulting diamond piezoresistive material has high sensitivity, high linearity, temperature stability, acid corrosion resistance and radiation resistance.

[0017] Preferably, in step 1), the surface treatment includes ultrasonic seeding with diamond particles with a particle size of 5-10 nm, followed by high-temperature hydrogen or oxygen plasma treatment to enhance nucleophilicity.

[0018] Preferably, the CVD deposition process in step 2) lasts for 2-6 hours and includes three stages:

[0019] The boron doping concentration of the bottom layer is 5×10 20 ~1×10 21 cm⁻³;

[0020] The intermediate layer is a highly doped layer with a concentration of 1×10⁻⁶. 21 ~5×10 21 cm⁻³;

[0021] The top layer is a lightly doped layer, with a concentration controlled at 1×10⁻⁶. 19 ~5×10 20 cm⁻³.

[0022] By adopting the above technical solution, the gradient can be precisely controlled in stages by adjusting the B2H6 flow rate and CVD time, so as to achieve a continuous and smooth gradient structure.

[0023] Preferably, the CVD deposition temperature is controlled at 750℃~950℃, the volume ratio of CH4 to H2 in the reaction gas is 1:100~5:100, and the concentration of B2H6 is 1000~5000 ppm.

[0024] Preferably, the heterostructure layer is located on the upper surface of the diamond layer or between the interface with the substrate; its thickness is 20~100 nm, and it is deposited using plasma-enhanced CVD or atomic layer deposition (ALD) methods.

[0025] Preferably, the micro-nano pattern etching is performed using electron beam lithography and plasma etching (RIE) techniques, with a pattern width of 2~10 μm and a piezoresistive structure of asymmetric dog bone structure, slit bridge structure, or cross groove structure.

[0026] Preferably, the metal electrode adopts a titanium / platinum (Ti / Pt) or chromium / gold (Pt / Au) bilayer structure, with a non-noble metal layer thickness of 20~50 nm and a noble metal layer thickness of 100~200 nm. The contact area is subjected to oxidation treatment or hydrogen passivation treatment before deposition to improve the consistency of ohmic contact. The encapsulation layer is made of polyimide or polyetheretherketone material.

[0027] By adopting the above technical solutions, the long-term stability of the device can be improved in high-temperature, highly corrosive and radiation environments.

[0028] This invention also provides an application of diamond piezoresistive material in pressure sensors. The diamond piezoresistive material is prepared by the aforementioned method and serves as a core sensing element connected in a strain gauge bridge structure to construct a pressure sensor. It can be applied in aerospace engines, deep-sea exploration equipment, or nuclear reactors. It can be used in high-temperature, high-pressure, highly corrosive, and highly radioactive environments to achieve highly reliable in-situ pressure detection.

[0029] Preferably, the diamond piezoresistive material is configured as a sensitive resistor element in a piezoresistive bridge structure, or constructed as a two-dimensional array piezoresistive unit, integrated in a flexible package or rigid housing, for real-time sensing of environmental pressure changes.

[0030] Furthermore, the pressure sensor has a piezoresistive sensitivity factor ranging from 80 to 160, an output signal linearity better than 0.2% of full scale, and a temperature coefficient less than 0.01%.

[0031] Adopting the above technical solution, its sensitivity is not less than 80, its linearity is better than 99%, and it can work stably for a long time in an environment of -60℃ to 250℃, possessing more than 10 6 Cyclic stress response life.

[0032] The beneficial effects of this invention are:

[0033] 1) By introducing a boron-doped structure with a gradient along the thickness direction, the carrier density and stress distribution are synergistically controlled, so that the piezoresistive effect forms a gradient response region between the highly doped layer and the lowly doped layer, which greatly improves the sensitivity factor and satisfies both high piezoresistive sensitivity and linearity.

[0034] 2) By introducing asymmetric dog-bone type, slit bridge type and other micro-nano piezoresistive patterns, the anisotropic response caused by crystal orientation of traditional diamond is effectively avoided, the directional consistency and repeatability of strain response are improved, and the material strain is more uniform.

[0035] 3) By introducing surface pretreatment, such as oxidation or hydrogen passivation and a double-layer metal electrode structure, low contact resistance and long-term stability between the metal and the piezoresistive material are ensured.

[0036] 4) The device adopts PI or PEEK packaging, which has excellent radiation resistance, waterproof and pressure resistance, and can support flexible or rigid integrated layout to meet the stress detection needs in complex structural environments.

[0037] In summary, this invention improves diamond piezoresistive materials to obtain a piezoresistive material that can withstand harsh environments such as high temperature, strong acid and alkali and nuclear radiation. The prepared boron-doped diamond piezoresistive material can work stably in high temperature environments above 800℃, far exceeding the temperature limit of existing Si and SiC-based piezoresistive materials, and meets the stringent application requirements of aero-engines, deep-sea exploration, nuclear facility monitoring and other applications. Attached Figure Description

[0038] Figure 1 This is a magnified microscopic schematic diagram of the structure of the piezoresistive material;

[0039] Figure 2 This is a schematic diagram of the piezoresistive response pattern, showing micro / nano structures such as asymmetric dog bone type, slit bridge type, and cross groove;

[0040] Figure 3 A graph showing the number of cycles versus the change in resistance;

[0041] Figure 4 SEM image of the Ti / Pt electrode-BDD interface;

[0042] Figure 5 This is a schematic diagram of the temperature-resistance drift curve of a heterostructure.

[0043] Figure 6 This is the curve showing the change in impedance under pressure. Detailed Implementation

[0044] The present invention will be further described below through specific embodiments. To make the inventive objectives, technical solutions, and beneficial technical effects of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments. It should be understood that the embodiments described in this specification are merely for explaining the present invention and are not intended to limit the present invention.

[0045] Unless otherwise stated, all films and reagents used in the examples are commercially available or synthesized using conventional methods and can be used directly without further processing, as are the instruments used in the examples.

[0046] Experimental methods

[0047] The properties of the prepared boron-doped diamond (BDD) piezoresistive material were tested, including its piezoresistive sensitivity factor (GF), linearity, temperature coefficient, and cyclic stability. The experimental setup included a micro-loading platform, a laser interferometer, a resistance strain gauge, and a high-temperature isothermal cavity.

[0048] Example 1:

[0049] 1) Substrate and pretreatment: Al2O3 wafers were selected as substrates. The substrate surface was ultrasonically treated with 10 nm diamond particles for 10 min and hydrogen plasma treated for 10 min at 800℃ to enhance the nucleation density.

[0050] 2) CVD gradient doping deposition: A hot-filament CVD system was used, with a reaction temperature of 750℃, a CH4:H2 volume ratio of 1:100, and a boron source B2H6 concentration of 1000 ppm; the deposition time was 2 hours.

[0051] Highly doped substrate (30 min): 5 × 10² 0 cm⁻³;

[0052] Intermediate layer (45 min): 1×10²¹ cm⁻³;

[0053] Top layer (45 min): 1×10¹ 9 cm⁻³; the film thickness is approximately 1.5 μm, clearly showing a doping gradient transition structure;

[0054] 3) Introduction of heterostructure: A 20 nm thick SiC heterolayer was deposited on the top surface using the ALD method;

[0055] 4) Piezoresistive pattern construction: Electron beam lithography + RIE etching form a slit bridge structure with a pattern width of 3 μm and a depth of 200 nm;

[0056] 5) Electrode and encapsulation: Deposit Cr (20 nm) / Au (100 nm) double-layer electrode; the diamond surface is pretreated with oxygen plasma to improve contact consistency; the encapsulation layer is made of 25 μm thick polyimide (PI) material.

[0057] Example 2:

[0058] 1) Substrate and pretreatment: Si<111> wafers were used, and 5 nm diamond particles were ultrasonically seeded for 20 min, followed by hydrogen plasma treatment at 950℃ for 15 min.

[0059] 2) CVD gradient doping deposition: hot-filament CVD reaction temperature was 850℃, CH4:H2 ratio was 3:100, B2H6 concentration was 3000ppm, and deposition time was 4 hours.

[0060] Bottom layer (1h): 1×10²¹ cm⁻³;

[0061] Intermediate layer (1h): 5×10² 0 cm⁻³;

[0062] Top floor (2h): 5×10² 0 cm⁻³; Total membrane thickness approximately 3 μm;

[0063] 3) Heterogeneous structure: A DLC layer with a thickness of 50 nm was deposited using hydrogen plasma CVD;

[0064] 4) Micro-nano pattern etching: Photolithography forms an asymmetric dog bone structure with a minimum width of 4 μm, an edge width of 10 μm, and an etching depth of approximately 400 nm.

[0065] 5) Electrode and packaging: Evaporated Ti (30 nm) / Pt (150 nm) electrodes, with hydrogen passivation pretreatment of the contact interface; the packaging material is a 50 μm thick PI film.

[0066] Example 3:

[0067] 1) Substrate and pretreatment: SiC wafers were selected as substrates, and 10 nm diamond particles were ultrasonically seeded for 30 min, followed by oxygen plasma treatment at 950℃ for 20 min.

[0068] 2) CVD deposition conditions: reaction temperature 950℃, CH4:H2 volume ratio 5:100, B2H6 concentration 5000 ppm, total deposition time 6 hours.

[0069] Bottom layer (1.5 h): 1×10²¹ cm⁻³;

[0070] Intermediate layer (2 h): 5 × 10²¹ cm⁻³;

[0071] Top floor (2.5 h): 5 × 10² 0 cm⁻³. The film thickness is approximately 4.5 μm, with a clear interface;

[0072] 3) Heterogeneous layer: A 100 nm thick SiC heterolayer is introduced by atomic layer deposition to improve thermal interface stability;

[0073] 4) Pattern construction: A cross-groove structure is adopted, with a pattern width of 10 μm and a depth of 600 nm, to maximize stress concentration and multiaxial sensitivity;

[0074] 5) Electrode structure and packaging: Evaporation of Cr (50 nm) / Au (200 nm) structure, and passivation of the contact area by oxygen plasma for 10 min; the outer packaging uses 100 μm thick polyether ether ketone (PEEK) material and is covered with a thin aluminum layer.

[0075] Example 4:

[0076] Replace step 3) of Example 1 with the atomic layer deposition method by introducing an 80 nm thick SiC heterolayer, and keep the rest unchanged.

[0077] Example 5:

[0078] The plasma CVD deposited DLC layer in Example 2 was replaced with a layer of 60 nm thickness, while the rest remained unchanged.

[0079] Example 6:

[0080] Replace step 1) in Example 2 with oxygen plasma treatment, and leave the rest unchanged.

[0081] Comparative Example 1:

[0082] Step 3) in Example 1 is omitted from the atomic layer deposition method, while the rest remains unchanged.

[0083] Comparative Example 2:

[0084] The plasma treatment will be omitted in step 1) of Example 2, while the rest remains unchanged.

[0085] The piezoresistive materials obtained in Examples 1-6 and Comparative Examples 1-2 were subjected to performance tests, and the test results are as follows:

[0086] ① Sensitivity, piezoresistive sensitivity factor (GF) test

[0087] The sample was fabricated into a standard strain bridge structure, and static stress within the range of 0~50 MPa was applied. The ratio of the rate of change of resistance ΔR / R0 to the strain ε was measured.

[0088] Example 1 Low-doping gradient (lightly doped top layer) 81.2 Example 2 Gradient structure 112.7 Example 3 Highly doped gradient structure 153.9

[0089] ② Output linearity test (error within full scale): constant stress loading (0~100 MPa) is used to record the goodness of fit between the output resistance change and the theoretical linear curve.

[0090] Example 1 0.19% 0.991 Example 2 0.13% 0.995 Example 3 0.09% 0.998

[0091] ③ Temperature coefficient test: Apply constant stress (30 MPa) within the temperature range of -60℃ to 250℃ and test the rate of change of resistance with temperature (% / ℃).

[0092] Example 1 0.0076 Example 2 0.0062 Example 3 0.0053

[0093] ④ Cyclic stress fatigue test: The sample is placed under a cyclic loading of 200 MPa stress at a frequency of 10 Hz, and the resistance drift is recorded.

[0094] Example 1 1.2% no Example 2 0.9% no Example 3 0.5% no

[0095] ⑤ Under the same CVD deposition parameters and pattern structure, two sets of samples with and without heterolayer were constructed, and their output voltage stability (temperature drift) and sensitivity factor changes at high temperature were tested.

[0096] Comparative Example 1 No heterolayer 25~250℃ 88 0.034 Example 4 SiC 80 nm 25~250℃ 91 0.012 Example 5 DLC 60 nm 25~250℃ 93 0.014

[0097] ⑥ Contact resistance comparison test design: using Ti / Pt double-layer electrodes, the contact resistance with BDD is tested under the following three treatment methods;

[0098] Comparative Example 2 No pretreatment <![CDATA[8×10⁻ 4 ]]> Example 6 Oxygen plasma treatment <![CDATA[2.5×10⁻ 5 ]]> Example 2 Hydrogen plasma treatment <![CDATA[2×10⁻ 6 ]]>

[0099] As can be seen from the above examples and the data in the table: the sensitivity factor increases significantly with increasing boron doping concentration and structural complexity, verifying that multilayer gradient doping and micro / nano patterning help improve response sensitivity; linearity and temperature coefficient both improve with structural optimization. Example 1 belongs to the low parameter group and is preferred for sensor construction in economically feasible experiments or under moderate operating conditions; Example 2 belongs to the parameter matching group and is preferred for the large-scale fabrication of conventional high-performance sensors, with excellent overall performance; Example 3 exhibits the best resistance to temperature drift and high linearity, belonging to the high parameter group, and is particularly suitable for nuclear power plants, aerospace engines, or deep-sea high-pressure extreme environments; compared with Examples 1-2, although the top layer doping concentration is higher, the ultra-high doping of the middle layer (5×10²¹ cm⁻³) significantly reduces the bulk resistance, and the strain concentration effect of the micro / nano patterning, together with the strain concentration effect, improves the overall GF; and the thermal expansion coefficient of PEEK encapsulation is more compatible with diamond, and the aluminum thin layer further suppresses thermal radiation interference, jointly reducing temperature drift;

[0100] Compared with Comparative Example 1, Examples 4 and 5 show that the temperature drift coefficient of the device is reduced by about 65% after the introduction of the SiC heterolayer; the DLC layer also significantly reduces temperature drift and improves output linearity; the heterostructure effectively blocks thermal diffusion stress and improves interface electrical and structural stability; indicating that this layer plays a key role in the long-term stability of the device in high-temperature environments.

[0101] Compared with Comparative Example 2, Examples 2 and 6 show that after plasma passivation treatment, the contact resistance of the contact area is reduced to 2×10⁻. 6 Ω·cm² (25℃); Improved ohmic contact consistency and significantly reduced output noise; Passivation can remove the surface amorphous layer and form H-terminal surfaces, which helps to form stable metal-semiconductor contacts.

[0102] Although there are slight differences in performance between the various embodiments, overall, all samples in the embodiments perform well within 10... 6 No failure occurred during the next cycle, and the resistor response remained stable (see attached). Figure 3 The invention demonstrates that the material can be used for extended periods in complex stress fields with a temperature drift coefficient of less than 0.01%, exhibiting excellent high-temperature stability and suitability for high-temperature environments. In other words, this invention provides a piezoresistive material that can meet the requirements of extreme environments such as aerospace, nuclear power plants, and deep-sea exploration. Its application in pressure sensors can meet the stress detection needs in complex structural environments.

[0103] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a diamond piezoresistive material, characterized in that, Includes the following steps: Step 1) Substrate pretreatment: Prepare the substrate and perform surface treatment on the substrate to enhance the diamond nucleation density. The substrate is a Si<111> wafer, alumina Al2O3, or silicon carbide SiC. Step 2) Gradient doping deposition: Boron-doped diamond films are deposited in stages on the substrate by chemical vapor deposition (CVD). Boron source gas is introduced in stages during the growth process to form a concentration gradient doping structure along the thickness direction. The film includes a highly doped bottom layer, a medium-doped intermediate layer, and a lightly doped top layer. The boron source gas is B2H6 or BF3. Step 3) Introduction of heterostructure: A heterostructure layer is introduced on the top or bottom surface of the gradient-doped diamond film. The heterostructure layer is a diamond-like carbon (DLC) layer or a silicon carbide (SiC) layer. Step 4) Piezoresistive sensitive pattern construction: Micro-nano pattern etching is performed on the boron-doped diamond film to construct a piezoresistive response region with stress concentration function; Step 5) Electrode deposition and device packaging: Deposit a metal electrode in the piezoresistive response region. The metal electrode has a double-layer structure. Introduce a multi-layer packaging system around the device to complete the packaging and obtain diamond piezoresistive material. The CVD deposition process in step 2) lasts for 2-6 hours and includes three stages: The boron doping concentration of the bottom layer is 5×10 20 ~1×10 21 cm -3 ; The intermediate layer is a highly doped layer with a concentration of 1×10⁻⁶. 21 ~5×10 21 cm -3 ; The top layer is a lightly doped layer with a concentration of 1×10⁻⁶. 19 ~5×10 20 cm -3 ; The micro-nano pattern etching described in step 4) is performed using electron beam lithography and plasma etching (RIE) techniques. The pattern width is 2~10μm, and the piezoresistive structure is an asymmetric dog bone structure, a slit bridge structure, or a cross groove structure. The metal electrode described in step 5) adopts a titanium / platinum or chromium / gold bilayer structure, with a non-noble metal layer thickness of 20~50 nm and a noble metal layer thickness of 100~200 nm. Before deposition, the contact area is subjected to oxidation treatment or hydrogen passivation treatment to improve the consistency of ohmic contact. The encapsulation layer is made of polyimide or polyetheretherketone material.

2. The method for preparing a diamond piezoresistive material according to claim 1, characterized in that, In step 1), the surface treatment includes ultrasonic seeding with diamond particles with a particle size of 5-10 nm, followed by high-temperature hydrogen or oxygen plasma treatment to enhance nucleophilicity.

3. The method for preparing a diamond piezoresistive material according to claim 1, characterized in that, The CVD deposition temperature is controlled at 750℃~950℃, the volume ratio of CH4 to H2 in the reaction gas is 1:100~5:100, and the concentration of B2H6 is 1000~5000 ppm.

4. The method for preparing a diamond piezoresistive material according to claim 1, characterized in that, The thickness of the heterostructure layer described in step 3) is 20~100 nm, and it is deposited using plasma-enhanced CVD or atomic layer deposition (ALD) methods.

5. An application of a diamond piezoresistive material in a pressure sensor, characterized in that, The diamond piezoresistive material is prepared by the preparation method described in any one of claims 1-4. The diamond piezoresistive material is connected as a core sensitive element to form a strain bridge structure to construct a pressure sensor device; it is applied in aerospace engines, deep-sea exploration equipment or nuclear reactors.

6. The application according to claim 5, characterized in that, The diamond piezoresistive material is configured as a sensitive resistor element in a piezoresistive bridge structure, or constructed as a two-dimensional array of piezoresistive units, integrated in a flexible package or rigid housing, for real-time sensing of environmental pressure changes.

7. The application according to claim 6, characterized in that, The pressure sensor has a piezoresistive sensitivity factor ranging from 80 to 160, an output signal linearity better than 0.2% of full scale, and a temperature coefficient less than 0.01%.

Images