Composite amorphous carbon film pressure-sensitive material and preparation method therefor

Abstract

The present invention provides a composite amorphous carbon film pressure-sensitive material and a preparation method therefor. The composite amorphous carbon film pressure-sensitive material comprises an amorphous carbon film layer and a metal micro-nano particle layer, which are arranged on a surface of an insulating rigid matrix from top to bottom, wherein the metal micro-nano particle layer is prepared by subjecting a metal film layer to an annealing treatment. The thickness of the metal film layer is 10-100 nm, and the particle density of the metal micro-nano particle layer is 150 / mm2-15000 / mm2; and the thickness of the amorphous carbon film layer is 50-400 nm. The present invention further provides a preparation method for the composite amorphous carbon film pressure-sensitive material. Compared with the prior art, the present invention can improve the sensitivity of amorphous carbon by adjusting and controlling the density of metal micro-nano particles on the basis that good protection performance of amorphous carbon is maintained, and the piezoresistive coefficient can reach 36.9; and the amorphous structure determines that same has isotropy, and the sensitivity in all directions is the same, which is conducive to wide application in an MEMS system.

Description

Composite amorphous carbon film pressure-sensitive material and preparation method thereof Technical Field

[0001] The present invention belongs to the technical field of thin film sensors, and in particular relates to a composite amorphous carbon thin film pressure-sensitive material and a preparation method thereof. Background Art

[0002] With the rapid development of piezoresistive micro-electro-mechanical systems (MEMS) in recent years, piezoresistive pressure sensors have become increasingly widely used in automotive, biomedical, and consumer electronics applications. The performance of piezoresistive pressure sensors depends largely on the pressure-sensitive material. The piezoresistive factor (GF), the ratio of the material's resistivity change to strain, reflects the sensitivity of the pressure-sensitive material.

[0003] Currently, the pressure-sensitive materials used in piezoresistive sensors are primarily single-crystal silicon or polycrystalline silicon. However, single-crystal silicon is expensive to produce and exhibits anisotropy. While polycrystalline silicon is cheaper to produce and can facilitate miniaturization and integration, it has a lower piezoresistive coefficient (GF-10) and is highly sensitive to temperature. With the rapid development of high-tech industries, pressure-sensitive materials such as single-crystal silicon and polycrystalline silicon struggle to meet the requirements for stable sensing under harsh operating conditions such as high temperatures, corrosion, and scratches. Consequently, the development of new pressure-sensitive materials has become an urgent need.

[0004] Amorphous carbon film is called Amorphous Carbon, abbreviated as aC, which is composed of sp 2 and sp 3 A large class of materials formed by mixing, which may contain a certain amount of H and metal and non-metal elements. The carbon atoms are mainly connected by sp 2 Covalent bonds and sp 3 Covalent bonds form an irregular spatial network structure, presenting an amorphous state. Therefore, unlike the anisotropy of crystalline materials, amorphous carbon appears isotropic. Compared to silicon, amorphous carbon has advantages such as excellent mechanical properties and corrosion resistance, and a high piezoresistive coefficient (GF can be as high as 1200).

[0005] However, currently, high-GF amorphous carbon typically exhibits extremely high resistance and temperature coefficient of resistance (TCR), which restricts its application in piezoresistive sensors. At home and abroad, the reduction of resistance and TCR has been achieved by introducing metal elements into amorphous carbon using a sputtering metal target. However, due to the inability to actively design the metal size, distribution, and conductivity, the GF is relatively low (generally less than 1-10). Furthermore, high metal doping levels can impair the protective properties of amorphous carbon, while low metal content control can easily lead to problems such as metal "target poisoning." Therefore, breakthroughs are needed in the controllable preparation of high-performance composite amorphous carbon thin film piezoresistive materials.

[0006] Summary of the Invention

[0007] The purpose of the present invention is to provide a composite amorphous carbon thin film piezoresistive material. By introducing metal micro-nano structures with adjustable size and distribution into amorphous carbon, a new conductive path can be formed, which is a new idea for developing high-performance amorphous carbon piezoresistive materials.

[0008] To achieve the above-mentioned purpose, the technical solution adopted by the present invention is: a composite amorphous carbon film pressure-sensitive material, including an amorphous carbon film layer and a metal micro-nano particle layer arranged from top to bottom on the surface of an insulating rigid substrate, wherein the metal micro-nano particle layer is prepared by annealing a metal film layer, the thickness of the metal film layer is 10-100nm, and the particle density of the metal micro-nano particle layer is 150 / mm 2 -15000 / mm 2 , the thickness of the amorphous carbon thin film layer is 50-400nm.

[0009] In the present invention, the metal micro-nano particle layer is formed by dewetting the metal film on the surface of the insulating rigid substrate by annealing. By changing the thickness of the metal film before dewetting and adjusting the corresponding annealing process parameters, the size and density of the micro-nano particles after the metal film is dewetted can be actively controlled. Based on the aC piezoresistive characteristic "Thick Film Resistor Model" (Thick Film Resistor, TFR), aC can be regarded as a conductive sp 2 Cluster distribution and insulating sp 3 The structure of the matrix, under stress / strain, the carriers are in sp 2 Changes in inter-cluster transition behavior lead to changes in resistance, which manifests as a piezoresistive effect.

[0010] Preferably, the piezoresistive coefficient of the composite amorphous carbon thin film pressure-sensitive material is 12.45-36.9.

[0011] Preferably, the metal element in the metal film layer is selected from one of Cu, Al, Ni, Ag, Au and Pt. Another object of the present invention is to provide a method for preparing a composite amorphous carbon film pressure-sensitive material, the preparation method specifically comprising the following steps:

[0012] S1. Placing an insulating rigid substrate in an ion beam composite magnetron sputtering deposition system, and then using argon ions to etch the surface of the metal rigid substrate after vacuuming.

[0013] S2, depositing a metal thin film layer on the surface of the insulating rigid substrate etched in step S1 by a magnetron sputtering method; S3, annealing the metal thin film layer to obtain a metal micro-nano particle layer;

[0014] S4. A composite amorphous carbon thin film pressure-sensitive material is obtained by depositing an amorphous carbon film on the surface of the metal micro-nano particle layer using a magnetron sputtering method.

[0015] Electron transport is controlled by sp 2 The hopping mechanism between conductive clusters is controlled, and electron transport is controlled by sp 2 The distance between conductive clusters and the size of clusters are controlled. The present invention introduces metal micro-nano particles into the amorphous carbon film to make the sp 2 、sp 3 The distribution of clusters changes, effectively changing the transport direction of electrons and forming new conductive channels. By adjusting the thickness of the metal film layer in step S2, the size and density of the micro-nano particles formed after annealing the metal film in step S3 can be actively regulated, thereby affecting the sp 2 、sp 3 The distribution of clusters can be controlled to adjust the piezoresistance coefficient of amorphous carbon films.

[0016] Preferably, in step S1, the specific parameters of etching are as follows: 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. The present invention etches the substrate before depositing the metal layer, which can effectively remove impurities and loose layers on the substrate surface, improve the film-substrate bonding strength, and reduce the probability of peeling during subsequent metal film plating.

[0017] Preferably, in step S2, the element of the metal film layer is Cu, the magnetron sputtering method is DC magnetron sputtering, and the deposition parameters of the DC magnetron sputtering are as follows: the Cu magnetron target current is 1A, the gas pressure in the chamber is 4.4-4.6mTorr, the applied bias voltage is -100V, the deposition time is 1-4 minutes, and the thickness of the Cu metal film layer is 13-54mm. Within the above parameter range, the present invention can change the thickness of the film by regulating the deposition time in step S2, thereby regulating the surface morphology of the metal micro-nano particle layer after annealing.

[0018] Furthermore, in step S3, the annealing parameters are as follows: an annealing temperature of 400-800°C and an annealing time of 1 hour. The present invention prepares metal micro-nanoparticle layers of varying morphologies by annealing metal film layers of varying thicknesses at appropriate annealing temperatures and times. Excessively low annealing temperatures and times may prevent the metal film from being completely dehumidified. Excessively high temperatures and times may cause the metal micro-nanoparticles formed after complete dehumidification to further reduce surface energy, causing them to aggregate and merge, hindering control of the resulting surface morphology.

[0019] Preferably, in step S2, the element of the metal thin film layer is Al, the magnetron sputtering method is DC magnetron sputtering, and the deposition parameters of the DC magnetron sputtering are as follows: Al magnetron target current is 0.2A, the gas pressure in the chamber is 1.4-1.5mTorr, the applied bias voltage is -200V, the deposition time is 14-27min, and the thickness of the Al metal thin film layer is 20-100mm. Within the above parameter range, the present invention can change the film thickness by adjusting the deposition time in step S2, thereby adjusting the surface morphology of the metal micro-nano particle layer after annealing.

[0020] Furthermore, in step S3, the annealing parameters are as follows: an annealing temperature of 600-650°C and an annealing time of 3 hours. The present invention prepares metal micro-nanoparticle layers of varying morphologies by annealing metal film layers of varying thicknesses at appropriate annealing temperatures and times. Excessively low annealing temperatures and times may prevent the metal film from being completely dehumidified. Excessively high temperatures and times may cause the metal micro-nanoparticles formed after complete dehumidification to further reduce surface energy, causing them to aggregate and merge, hindering control of the resulting surface morphology.

[0021] Preferably, in step S4, the magnetron sputtering method is high-power pulse magnetron sputtering, and the deposition parameters of the high-power pulse magnetron sputtering are as follows: the target material is graphite, the pulse power supply voltage is 660-670V, the power is 500W, the pulse duty cycle is 10%, the gas pressure in the chamber is 8mTorr, the applied bias voltage is -200V, and the deposition time is 160min. The present invention adopts the method of high-power pulse magnetron sputtering to prepare amorphous carbon. Due to its higher ionization rate, it can achieve a wide range of ion energy regulation, which is conducive to regulating the sp 2 -C / sp 3 -C ratio, under the above deposition conditions, a high sp 3 The amorphous carbon film with a high content of carbon fiber has excellent piezoresistive properties.

[0022] Compared with the prior art, the present invention has the following advantages:

[0023] Compared with single-crystal silicon, which has a high sensitivity coefficient but is anisotropic, and polycrystalline silicon, which has isotropic but low sensitivity coefficient, the composite amorphous carbon thin film pressure-sensitive material of the present invention can have a high sensitivity coefficient by regulating the density of metal micro-nanoparticles. Its piezoresistive coefficient can reach 36.9, and its amorphous structure determines that it is isotropic, with the same sensitivity in all directions, which is conducive to its wide application in MEMS systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] FIG1 is a surface morphology of an Al metal thin film layer after annealing according to Example 1 of the present invention;

[0025] FIG2 is a statistical diagram of surface particle size of the Al metal film layer after annealing in Example 1 of the present invention;

[0026] FIG3 is a surface morphology of the Al metal film layer after annealing in Example 2 of the present invention;

[0027] FIG4 is a statistical diagram of surface particle size of the Al metal film layer after annealing in Example 2 of the present invention;

[0028] FIG5 is a diagram of the marking sites of a TEM sample prepared in Example 2 of the present invention;

[0029] Figure 6 shows the EELS results at different positions in Figure 5;

[0030] Figure 7 shows the sp after fitting calculation at different positions in Figure 5 2 and sp 3 Content map;

[0031] FIG8 is a surface morphology of the Cu metal film layer after annealing according to Example 3 of the present invention;

[0032] FIG9 is a statistical diagram of surface particle size of the Cu metal film layer after annealing in Example 3 of the present invention;

[0033] FIG10 is a surface morphology of the Cu metal film layer after annealing according to Example 4 of the present invention;

[0034] FIG11 is a statistical diagram of the surface particle size of the Cu metal thin film layer after annealing in Example 4 of the present invention.

[0035] Implementation Method

[0036] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0037] It should be understood that the terms described herein are intended only to describe particular embodiments and are not intended to limit the present invention. In addition, for numerical ranges herein, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each smaller range between any intermediate value within a stated value or stated range and any other stated value or intermediate value within the stated range is also encompassed by the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded within the scope.

[0038] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments described herein without departing from the scope or spirit of the invention. Other embodiments will be apparent to those skilled in the art from the description of the invention. The present description and examples are intended to be illustrative only.

[0039] The embodiment of the present invention provides a composite amorphous carbon film pressure-sensitive material, including an amorphous carbon film layer and a metal micro-nano particle layer arranged from top to bottom on the surface of an insulating rigid substrate, the metal micro-nano particle layer is prepared by annealing the metal film layer, the thickness of the metal film layer is 10-100nm, and the particle density of the metal micro-nano particle layer is 150 / mm 2 -15000 / mm 2 The thickness of the amorphous carbon film layer is 50-400 nm, the piezoresistive coefficient of the composite amorphous carbon film pressure-sensitive material is 12.45-36.9, and the metal element in the metal film layer is selected from one of Cu, Al, Ni, Ag, Au and Pt.

[0040] In a specific embodiment, the metal element in the metal film layer is Cu or Al. Since Al and Cu have excellent electrical conductivity, introducing these conductive metals into amorphous carbon can effectively improve the film's piezoresistive properties. Furthermore, Al and Cu have low melting points, requiring a lower annealing temperature for dewetting. This makes it easier to produce the desired metal micro-nanoparticles through annealing in practical applications.

[0041] This embodiment also provides a method for preparing the composite amorphous carbon thin film pressure-sensitive material, which specifically includes the following steps:

[0042] S1. Place the insulating rigid substrate in an ion beam composite magnetron sputtering deposition system. After vacuuming, use argon ions to etch the surface of the metal rigid substrate. The specific etching parameters are as follows: vacuum degree <2×10 -5 Torr, the applied bias voltage was -200 V, the anode layer ion source current was 0.2 A, and the etching time was 20 min;

[0043] S2, depositing a metal thin film layer on the surface of the insulating rigid substrate etched in step S1 by a magnetron sputtering method;

[0044] S3, annealing the metal film layer to obtain a metal micro-nano particle layer;

[0045] S4. A composite amorphous carbon thin film pressure-sensitive material is obtained by depositing an amorphous carbon film on the surface of the metal micro-nano particle layer using a magnetron sputtering method. The magnetron sputtering method is high-power pulsed magnetron sputtering, and the deposition parameters of the high-power pulsed magnetron sputtering are as follows: the target material is graphite, the pulse power supply voltage is 660-670V, the power is 500W, the pulse duty cycle is 10%, the gas pressure in the cavity is 8mTorr, the applied bias voltage is -200V, and the deposition time is 160min.

[0046] In a specific embodiment, in step S1, the insulating rigid substrate is selected from one of Al2O3, AlN, ZrO2, SiO2, and Si3N4. The present invention adopts one of the above substrates because these materials are commonly used in current MEMS devices. In order to combine the actual situation of industrial production and application, the above substrate is adopted.

[0047] In a specific embodiment, in step S2, if the element of the metal film layer is Cu, the magnetron sputtering method is DC magnetron sputtering, and the deposition parameters of the DC magnetron sputtering are as follows: the Cu magnetron target current is 1A, the gas pressure in the chamber is 4.4-4.6mTorr, the applied bias voltage is -100V, the deposition time is 1-4min, and the thickness of the Cu metal film layer is 13-54mm. In step S3, the parameters of the annealing treatment are as follows: the annealing temperature is 400-800℃, and the annealing time is 1h.

[0048] In a specific embodiment, in step S2, if the element of the metal thin film layer is Al, the magnetron sputtering method is DC magnetron sputtering, and the deposition parameters of the DC magnetron sputtering are as follows: Al magnetron target current is 0.2A, the gas pressure in the chamber is 1.4-1.5mTorr, the applied bias voltage is -200V, the deposition time is 14-27 minutes, and the thickness of the Al metal thin film layer is 20-100mm. In step S3, the annealing treatment parameters are as follows: annealing temperature is 600-650°C, and annealing time is 3 hours. The technical effects of the present invention are described below with reference to specific embodiments.

[0049] Example 1

[0050] This embodiment provides a composite amorphous carbon thin film pressure-sensitive material, the base material of which is silicon dioxide. The composite amorphous carbon thin film pressure-sensitive material is prepared on the base material, as follows:

[0051] Step 1: The substrate was ultrasonically cleaned with acetone, dried, and placed in a vacuum chamber, which was evacuated to 2×10 -5 Torr, argon gas is introduced into the coating chamber through the anode layer ion source to maintain the gas pressure at 2.4mTorr, a bias voltage of -200V is applied to the substrate, the anode layer ion source is turned on, the current is 0.2A, and the substrate surface is etched by ionized argon ions. This process lasts for 20 minutes;

[0052] Step 2: Turn on the magnetron sputtering source, introduce Ar gas, and sputter the aluminum target. Maintain the chamber pressure at 1.4 mTorr, the sputtering target current at 0.2 A, and the bias voltage applied to the substrate at -200 V. This process lasts for 14 minutes to produce an Al metal film layer with a thickness of approximately 40 nm.

[0053] Step 3: Place the Al metal film layer prepared in step 2 in a vacuum annealing furnace and evacuate to 2×10 -3 Pa, annealing temperature was maintained at 600 °C for 3 h, and then furnace cooled to room temperature;

[0054] The Al metal film layer after annealing was observed and tested, and the results are shown in Figures 1 and 2. Figure 1 is a surface morphology diagram of the Al metal film layer after annealing, and Figure 2 is a statistical diagram of the surface particle size of the Al metal film layer after annealing in Example 1 of the present invention.

[0055] Step 4: placing the sample obtained in step 3 in a vacuum chamber, using high-power pulsed magnetron sputtering technology, selecting a high-purity graphite target, sputtering carbon atoms from the high-purity graphite target by ionized argon gas, and depositing an amorphous carbon film on the surface of the substrate treated in step 3, controlling the pressure in the vacuum coating chamber to 8 mTorr, the high-power pulse power supply voltage to 670 V, the power to 500 W, the pulse duty cycle to 10%, and the bias voltage applied to the substrate to -200 V. This process is maintained for 2 hours and 40 minutes, and an amorphous carbon film layer with a thickness of about 200 nm is prepared to obtain a composite amorphous carbon film pressure-sensitive material;

[0056] The piezoresistive effect test of the pressure-sensitive material prepared above was conducted, that is, a vertical force was applied to the center of the pressure-sensitive material to deform the pressure-sensitive material and observe the change in its resistance. A three-point piezoresistive coefficient tester was used to apply a force to the sample, causing the sample to bend downward by 0.2 mm, and the change in the sample resistance R before and after bending was observed. The following formula was used: Where R0 is the initial resistance of the film, R is the resistance of the film after deformation, t is the sample thickness, l is the sample length, and ΔY is the displacement. Calculations using this formula show that, given that the majority of the introduced metal micro-nanoparticles are approximately 1 to 2 μm in size and have a low density, the resulting composite amorphous carbon film pressure-sensitive material has a piezoresistive coefficient of 12.45.

[0057] Example 2

[0058] The only difference from Example 1 is that in step 2 of this embodiment, the maintenance time of magnetron sputtering is 20 minutes, the thickness of the obtained Al metal film layer is 70 nm, and in step 3, the annealing temperature is 650°C. The rest is the same as in Example 1 and will not be repeated here.

[0059] The Al metal film layer after annealing was observed and tested, and the results are shown in Figures 3 and 4. Figure 3 is a surface morphology of the Al metal film layer after annealing, and Figure 4 is a statistical diagram of the surface particle size of the Al metal film layer after annealing.

[0060] The piezoresistive effect test of the pressure-sensitive material prepared above was conducted, that is, a vertical force was applied to the center of the pressure-sensitive material to deform the pressure-sensitive material and observe the change in its resistance. A three-point piezoresistive coefficient tester was used to apply a force to the sample, causing the sample to bend downward by 0.2 mm, and the change in the sample resistance R before and after bending was observed. The following formula was used: Where R0 is the initial resistance of the film, R is the resistance of the film after deformation, t is the sample thickness, l is the sample length, and ΔY is the displacement. Calculations using this formula show that, given that the majority of the introduced metal micro-nanoparticles are approximately 2 to 3 μm in size and have a high density, the resulting composite amorphous carbon film pressure-sensitive material has a piezoresistive coefficient of 36.9.

[0061] In order to study the evolution of the microstructure inside the amorphous carbon film after adding the metal film layer, as shown in FIG5 , 9 points were marked at different positions in the TEM sample prepared by this embodiment, namely the flat surface (marked as 1 and 2), the bottom of the spherical surface (marked as 3 and 9), the middle of the spherical surface (marked as 4 and 8), the upper part of the spherical surface (marked as 5 and 7) and the top of the spherical surface (marked as 6), and electron energy loss spectroscopy (EELS) analysis was performed on the 9 different positions. EELS is to determine the chemical composition and structure of the material by measuring the energy loss caused by the inelastic electron-electron collision of electrons passing through the sample. For amorphous carbon materials, the content of sp2 and sp3 in the amorphous carbon film can be confirmed by the CK edge spectrum in the range of 280-305eV. The carbon spectrum is partially decomposed into π * and σ * Characteristics, and according to the fitting requirements of the double window method, the π * The peak is fitted with a Gaussian function, and σ * The peak is integrated in a small energy window between 290 and 305 eV using the following formula: You can calculate sp 2 The ratio of carbon atoms in the bond. * / σ * ) film and (π * / σ * ) std are the π of the sample to be tested and the reference sample respectively. * Peak and σ * The integrated area ratio of the peak. The reference sample is composed of 100% sp2 evaporated carbon. Figures 6 and 7 are the EELS results at different positions and the sp 2 and sp 3 The content diagram shows that the sp 2 The content is about 49%, and the sp 2 The content is generally in the range of 52% to 56%, which is significantly higher than that of sp in the smooth surface. 2 The results show that the addition of Al balls induces local graphitization of the amorphous carbon film.

[0062] Example 3

[0063] In this embodiment, the substrate is the same as that in Example 1, and a composite amorphous carbon thin film pressure-sensitive material is prepared on the substrate, specifically as follows:

[0064] Step 1: The substrate was ultrasonically cleaned with acetone, dried, and placed in a vacuum chamber, which was evacuated to 2×10 -5 Torr, argon gas is introduced into the coating chamber through the anode layer ion source to maintain the gas pressure at 2.4mTorr, a bias voltage of -100V is applied to the substrate, the anode layer ion source is turned on, the current is 0.2A, and the substrate surface is etched by ionized argon ions. This process lasts for 10 minutes;

[0065] Step 2: Turn on the magnetron sputtering source, introduce Ar gas, and sputter the Cu target; maintain the chamber pressure at 3.5 mTorr, the sputtering target current at 1 A, and the bias voltage applied to the substrate at -100 V. This process lasts for 1 minute, and a Cu metal film layer with a thickness of about 13 nm is prepared;

[0066] Step 3: Place the Cu metal film layer prepared in step 2 in a vacuum annealing furnace and evacuate to 2×10 -3 Pa, annealing temperature of 800 °C for 1 h, followed by furnace cooling to room temperature;

[0067] The annealed Cu metal film layer was observed and tested, and the results are shown in Figures 5 and 6. Figure 5 is a surface morphology of the Cu metal film layer after annealing, and Figure 6 is a statistical diagram of the particle size on the surface of the Cu metal film layer after annealing.

[0068] Step 4: basically the same as step 4 in Example 1, except that this process is maintained for 4 hours and the thickness is about 300 nm;

[0069] The piezoresistive effect test of the pressure-sensitive material prepared above was conducted, that is, a vertical force was applied to the center of the pressure-sensitive material to deform the pressure-sensitive material and observe the change in its resistance. A three-point piezoresistive coefficient tester was used to apply a force to the sample, causing the sample to bend downward by 0.2 mm, and the change in the sample resistance R before and after bending was observed. The following formula was used: Where R0 is the initial resistance of the film, R is the resistance of the film after deformation, t is the sample thickness, l is the sample length, and ΔY is the displacement. Calculations using this formula show that, given that the majority of the introduced metal micro-nanoparticles are approximately 100-200 nm in size and have a high density, the resulting composite amorphous carbon film pressure-sensitive material has a piezoresistive coefficient of 26.4.

[0070] Example 4

[0071] The only difference from Example 3 is that in step 2 of this embodiment, the maintenance time of magnetron sputtering is 2 minutes, and the thickness of the obtained Cu metal film layer is 27 nm. The rest is the same as Example 3 and will not be repeated here.

[0072] The annealed Cu metal film layer was observed and tested, and the results are shown in Figures 7 and 8. Figure 7 is a surface morphology diagram of the Cu metal film layer after annealing, and Figure 8 is a statistical diagram of the surface particle size of the Cu metal film layer after annealing.

[0073] The piezoresistive effect test of the pressure-sensitive material prepared above was conducted, that is, a vertical force was applied to the center of the pressure-sensitive material to deform the pressure-sensitive material and observe the change in its resistance. A three-point piezoresistive coefficient tester was used to apply a force to the sample, causing the sample to bend downward by 0.2 mm, and the change in the sample resistance R before and after bending was observed. The following formula was used: Where R0 is the initial resistance of the film, R is the resistance of the film after deformation, t is the sample thickness, l is the sample length, and ΔY is the displacement. Calculations using this formula show that, when the majority of the introduced metal micro-nanoparticles are approximately 200 to 600 nm in size and have a moderate density, the resulting composite amorphous carbon film material has a piezoresistive coefficient of 20.

[0074] Combining the preparation processes of Examples 1 to 4, it can be seen that the present invention can obtain a composite amorphous carbon thin film material with a high high-voltage resistivity by regulating the size of the introduced metal micro-nano particles.

[0075] Example 5

[0076] In this embodiment, the substrate is the same as that in Example 1, and a composite amorphous carbon thin film pressure-sensitive material is prepared on the substrate, specifically as follows:

[0077] Step 1: The substrate was ultrasonically cleaned with acetone, dried, and placed in a vacuum chamber, which was evacuated to 2×10 -5 Torr, argon gas is introduced into the coating chamber through the anode layer ion source to maintain the gas pressure at 2.4mTorr, a bias voltage of -100V is applied to the substrate, the anode layer ion source is turned on, the current is 0.2A, and the substrate surface is etched by ionized argon ions. This process lasts for 10 minutes;

[0078] Step 2: Turn on the magnetron sputtering source, introduce Ar gas, and sputter the Ni target; maintain the chamber pressure at 3.5 mTorr, the sputtering target current at 1 A, and the bias voltage applied to the substrate at -100 V. This process lasts for 1 minute, and a Ni metal film layer with a thickness of about 13 nm is prepared;

[0079] Step 3: Place the Ni metal film layer prepared in step 2 in a vacuum annealing furnace and evacuate to 2×10 -3Pa, annealing temperature of 800 °C for 1 h, followed by furnace cooling to room temperature;

[0080] Step 4: basically the same as step 4 in Example 1, except that this process is maintained for 4 hours and the thickness is about 300 nm;

[0081] The piezoresistive effect test of the pressure-sensitive material prepared above was conducted, that is, a vertical force was applied to the center of the pressure-sensitive material to deform the pressure-sensitive material and observe the change in its resistance. A three-point piezoresistive coefficient tester was used to apply a force to the sample, causing the sample to bend downward by 0.2 mm, and the change in the sample resistance R before and after bending was observed. The following formula was used: Where R0 is the initial resistance of the film, R is the resistance of the film after deformation, t is the sample thickness, l is the sample length, and ΔY is the displacement. Calculations using this formula show that, given that the majority of the introduced metal micro-nanoparticles are approximately 100-200 nm in size and have a high density, the resulting composite amorphous carbon film pressure-sensitive material has a piezoresistive coefficient of 18.7.

[0082] Example 6

[0083] In this embodiment, the substrate is the same as that in Example 1, and a composite amorphous carbon thin film pressure-sensitive material is prepared on the substrate, specifically as follows:

[0084] Step 1: The substrate was ultrasonically cleaned with acetone, dried, and placed in a vacuum chamber, which was evacuated to 2×10 -5 Torr, argon gas is introduced into the coating chamber through the anode layer ion source to maintain the gas pressure at 2.4mTorr, a bias voltage of -100V is applied to the substrate, the anode layer ion source is turned on, the current is 0.2A, and the substrate surface is etched by ionized argon ions. This process lasts for 10 minutes;

[0085] Step 2: Turn on the magnetron sputtering source, introduce Ar gas, and sputter the Ag target; maintain the chamber pressure at 3.5 mTorr, the sputtering target current at 1 A, and the bias voltage applied to the substrate at -100 V. This process lasts for 1 minute, and a Ag metal film layer with a thickness of about 13 nm is prepared;

[0086] Step 3: Place the Ag metal film layer prepared in step 2 in a vacuum annealing furnace and evacuate to 2×10 -3 Pa, annealing temperature of 800 °C for 1 h, followed by furnace cooling to room temperature;

[0087] Step 4: basically the same as step 4 in Example 1, except that this process is maintained for 4 hours and the thickness is about 300 nm;

[0088] The piezoresistive effect test of the pressure-sensitive material prepared above was conducted, that is, a vertical force was applied to the center of the pressure-sensitive material to deform the pressure-sensitive material and observe the change in its resistance. A three-point piezoresistive coefficient tester was used to apply a force to the sample, causing the sample to bend downward by 0.2 mm, and the change in the sample resistance R before and after bending was observed. The following formula was used: Where R0 is the initial resistance of the film, R is the resistance of the film after deformation, t is the sample thickness, l is the sample length, and ΔY is the displacement. Calculations using this formula show that, given that the majority of the introduced metal micro-nanoparticles are approximately 100-200 nm in size and have a high density, the resulting composite amorphous carbon film pressure-sensitive material has a piezoresistive coefficient of 17.45.

[0089] Example 7

[0090] In this embodiment, the substrate is the same as that in Example 1, and a composite amorphous carbon thin film pressure-sensitive material is prepared on the substrate, specifically as follows:

[0091] Step 1: The substrate was ultrasonically cleaned with acetone, dried, and placed in a vacuum chamber, which was evacuated to 2×10 -5 Torr, argon gas is introduced into the coating chamber through the anode layer ion source to maintain the gas pressure at 2.4mTorr, a bias voltage of -100V is applied to the substrate, the anode layer ion source is turned on, the current is 0.2A, and the substrate surface is etched by ionized argon ions. This process lasts for 10 minutes;

[0092] Step 2: Turn on the magnetron sputtering source, introduce Ar gas, and sputter the Cu target; maintain the chamber pressure at 3.5mTorr, the sputtering target current at 1A, and the bias voltage applied to the substrate at -100V. This process lasts for 1 minute to prepare an Au metal film layer with a thickness of about 13nm;

[0093] Step 3: Place the Au metal film layer prepared in step 2 in a vacuum annealing furnace and evacuate to 2×10 -3 Pa, annealing temperature of 800 °C for 1 h, followed by furnace cooling to room temperature;

[0094] Step 4: basically the same as step 4 in Example 1, except that this process is maintained for 4 hours and the thickness is about 300 nm;

[0095] The piezoresistive effect test of the pressure-sensitive material prepared above was conducted, that is, a vertical force was applied to the center of the pressure-sensitive material to deform the pressure-sensitive material and observe the change in its resistance. A three-point piezoresistive coefficient tester was used to apply a force to the sample, causing the sample to bend downward by 0.2 mm, and the change in the sample resistance R before and after bending was observed. The following formula was used: Where R0 is the initial resistance of the film, R is the resistance of the film after deformation, t is the sample thickness, l is the sample length, and ΔY is the displacement. Calculations using this formula show that, given that the majority of the introduced metal micro-nanoparticles are approximately 100-200 nm in size and have a high density, the resulting composite amorphous carbon film pressure-sensitive material has a piezoresistive coefficient of 19.25.

[0096] Example 8

[0097] In this embodiment, the substrate is the same as that in Example 1, and a composite amorphous carbon thin film pressure-sensitive material is prepared on the substrate, specifically as follows:

[0098] Step 1: The substrate was ultrasonically cleaned with acetone, dried, and placed in a vacuum chamber, which was evacuated to 2×10 -5 Torr, argon gas is introduced into the coating chamber through the anode layer ion source to maintain the gas pressure at 2.4mTorr, a bias voltage of -100V is applied to the substrate, the anode layer ion source is turned on, the current is 0.2A, and the substrate surface is etched by ionized argon ions. This process lasts for 10 minutes;

[0099] Step 2: Turn on the magnetron sputtering source, introduce Ar gas, and sputter the Pt target; maintain the chamber pressure at 3.5 mTorr, the sputtering target current at 1 A, and the bias voltage applied to the substrate at -100 V. This process lasts for 1 minute, and a Pt metal film layer with a thickness of approximately 13 nm is prepared;

[0100] Step 3: Place the Pt metal film layer prepared in step 2 in a vacuum annealing furnace and evacuate to 2×10 -3 Pa, annealing temperature of 800 °C for 1 h, followed by furnace cooling to room temperature;

[0101] Step 4: basically the same as step 4 in Example 1, except that this process is maintained for 4 hours and the thickness is about 300 nm;

[0102] The piezoresistive effect test of the pressure-sensitive material prepared above was conducted, that is, a vertical force was applied to the center of the pressure-sensitive material to deform the pressure-sensitive material and observe the change in its resistance. A three-point piezoresistive coefficient tester was used to apply a force to the sample, causing the sample to bend downward by 0.2 mm, and the change in the sample resistance R before and after bending was observed. The following formula was used: Where R0 is the initial resistance of the film, R is the resistance of the film after deformation, t is the sample thickness, l is the sample length, and ΔY is the displacement. Calculations using this formula show that, given that the majority of the introduced metal micro-nanoparticles are approximately 100 to 200 nm in size and have a high density, the resulting composite amorphous carbon film pressure-sensitive material has a piezoresistive coefficient of 16.98.

[0103] Comparative Example 1

[0104] In the pressure-sensitive material of this comparative example, the base material is silicon dioxide, and a layer of pure amorphous carbon film is prepared on the base, as follows:

[0105] Step 1: The substrate was ultrasonically cleaned with acetone, dried, and placed in a vacuum chamber, which was evacuated to 2×10 -5 Torr, argon gas is introduced into the coating chamber through the anode layer ion source to maintain the gas pressure at 2.4mTorr, a bias voltage of -200V is applied to the substrate, the anode layer ion source is turned on, the current is 0.2A, and the substrate surface is etched by ionized argon ions. This process lasts for 20 minutes;

[0106] Step 2: The sample obtained in step 1 is placed in a vacuum chamber, and a high-power pulsed magnetron sputtering technique is used. A high-purity graphite target is selected, and carbon atoms are sputtered from the high-purity graphite target by ionized argon gas. An amorphous carbon film is deposited on the surface of the substrate treated in step 1. The pressure in the vacuum coating chamber is controlled at 8 mTorr, the high-power pulse power supply voltage is 670 V, the power is 500 W, the pulse duty cycle is 10%, and the bias voltage applied to the substrate is -200 V. This process is maintained for 2 hours and 40 minutes to prepare an amorphous carbon film with a thickness of approximately 200 nm.

[0107] The piezoresistive effect test of the pressure-sensitive material prepared above was conducted, that is, a vertical force was applied to the center of the pressure-sensitive material to deform the pressure-sensitive material and observe the change in its resistance. A three-point piezoresistive coefficient tester was used to apply a force to the sample, causing the sample to bend downward by 0.2 mm, and the change in the sample resistance R before and after bending was observed. The following formula was used: Where R0 is the initial resistance of the film, R is the resistance of the film after deformation, t is the thickness of the sample, l is the length of the sample, and ΔY is the displacement. The formula shows that without the introduction of metal micro-nanoparticles, the piezoresistive coefficient of the obtained pressure-sensitive material is 8.2. The results of Example 1 and Comparative Example 1 show that the present invention, by introducing a metal film layer and then annealing it to obtain a metal micro-nanoparticle layer, can enable the obtained composite pressure-sensitive material to have a high piezoresistive coefficient.

[0108] Comparative Example 2

[0109] The only difference from Example 2 is that in step 4 of this comparative example, the magnetron sputtering is maintained for 6 hours and 40 minutes, and the thickness of the prepared amorphous carbon film layer is 500 nm. The rest is the same as Example 2 and will not be repeated here.

[0110] The piezoresistive effect test of the pressure-sensitive material prepared above was conducted, that is, a vertical force was applied to the center of the pressure-sensitive material to deform the pressure-sensitive material and observe the change in its resistance. A three-point piezoresistive coefficient tester was used to apply a force to the sample, causing the sample to bend downward by 0.2 mm, and the change in the sample resistance R before and after bending was observed. The following formula was used: Where R0 is the initial resistance of the film, R is the resistance of the film after deformation, t is the thickness of the sample, l is the length of the sample, and ΔY is the displacement. Calculated by the formula, when the thickness of the amorphous carbon film layer exceeds 400 nm, the piezoresistive coefficient of the resulting pressure-sensitive material is 5.62. The results of Example 2 and Comparative Example 2 show that by adopting the thickness of the amorphous carbon layer given in the present invention, a composite pressure-sensitive material with a high piezoresistive coefficient can be obtained.

[0111] In summary, the composite amorphous carbon thin film pressure-sensitive material of the present invention can have a high sensitivity coefficient by regulating the density of metal micro-nanoparticles and coordinating with other key process parameters. Its piezoresistive coefficient can reach 36.9, and its amorphous structure determines that it is isotropic and has the same sensitivity in all directions, which is conducive to its wide application in MEMS systems.

[0112] Although the present disclosure is disclosed as above, the protection scope of the present disclosure is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present disclosure, and these changes and modifications will fall within the protection scope of the present invention.

Claims

1. A composite amorphous carbon film pressure-sensitive material, characterized in that: The invention comprises an amorphous carbon film layer and a metal micro-nano particle layer arranged from top to bottom on the surface of an insulating rigid substrate, wherein the metal micro-nano particle layer is prepared by annealing the metal film layer, the thickness of the metal film layer is 10-100nm, and the particle density of the metal micro-nano particle layer is 150 / mm 2 -15000 / mm 2 The thickness of the amorphous carbon film layer is 50-400 nm, and the metal element in the metal film layer is selected from one of Cu, Al, Ni, Ag, Au and Pt.

2. The composite amorphous carbon thin film pressure-sensitive material according to claim 1, characterized in that: The piezoresistance coefficient of the composite amorphous carbon film pressure-sensitive material is 12.45-36.

9.

3. A method for preparing a composite amorphous carbon thin film pressure-sensitive material according to any one of claims 1 to 2, characterized in that: The preparation method specifically comprises the following steps: S1, placing an insulating rigid substrate in an ion beam composite magnetron sputtering deposition system, and using argon ions to etch the surface of the insulating rigid substrate after vacuuming; S2, depositing a metal film layer on the surface of the insulating rigid substrate etched in step S1 by a magnetron sputtering method; S3, annealing the metal film layer to obtain a metal micro-nano particle layer; S4. A composite amorphous carbon thin film varistor is obtained by depositing an amorphous carbon film on the surface of the metal micro-nano particle layer using a magnetron sputtering method.

4. The method for preparing the composite amorphous carbon thin film pressure-sensitive material according to claim 3, characterized in that: In step S1, the specific parameters of etching are as follows: 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.

5. The method for preparing the composite amorphous carbon thin film pressure-sensitive material according to claim 3, characterized in that: In the step S2, the element of the metal film layer is Cu, the magnetron sputtering method is DC magnetron sputtering, and the deposition parameters of the DC magnetron sputtering are as follows: the Cu magnetron target current is 1A, the gas pressure in the chamber is 4.4-4.6mTorr, the applied bias voltage is -100V, the deposition time is 1-4min, and the thickness of the Cu metal film layer is 13-54mm.

6. The method for preparing the composite amorphous carbon thin film pressure-sensitive material according to claim 5, characterized in that: In step S3, the parameters of the annealing treatment are as follows: the annealing temperature is 400-800° C., and the annealing time is 1 hour.

7. The method for preparing the composite amorphous carbon thin film pressure-sensitive material according to claim 3, characterized in that: In the step S2, the element of the metal film layer is Al, the magnetron sputtering method is DC magnetron sputtering, and the deposition parameters of the DC magnetron sputtering are as follows: the Al magnetron target current is 0.2A, the gas pressure in the chamber is 1.4-1.5mTorr, the applied bias voltage is -200V, the deposition time is 14-27min, and the thickness of the Al metal film layer is 20-100mm.

8. The method for preparing the composite amorphous carbon thin film pressure-sensitive material according to claim 7, characterized in that: In step S3, the parameters of the annealing treatment are as follows: the annealing temperature is 600-650° C., and the annealing time is 3 hours.

9. The method for preparing the composite amorphous carbon thin film pressure-sensitive material according to claim 3, characterized in that: In step S4, the magnetron sputtering method is high-power pulsed magnetron sputtering, and the deposition parameters of the high-power pulsed magnetron sputtering are as follows: the target material is graphite, the pulse power supply voltage is 660-670V, the power is 500W, the pulse duty cycle is 10%, the gas pressure in the chamber is 8mTorr, the applied bias voltage is -200V, and the deposition time is 160min.

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