Diaphragm material, preparation method and acoustic wave sensor

Abstract

The present invention provides a diaphragm material, a preparation method, and an acoustic wave sensor. The diaphragm material comprises a silicon film and a graphene film. The graphene film is grown on the silicon film by van der Waals forces to form a graphene-silicon van der Waals heterojunction. The silicon film has a thickness between 200 nanometers and 100 micrometers. The surface roughness of the silicon film is between 0.0001 micrometers and 0.01 micrometers. The number of graphene layers contained in the graphene film is less than or equal to 10.

Description

Technical Field

[0001] The present invention relates to the field of materials, and in particular to a diaphragm material, a preparation method and an acoustic wave sensor. Background Art

[0002] Acoustic wave sensors are used in a variety of fields, including the energy sector (such as oil and gas extraction), medical devices (such as magnetic resonance and ultrasound imaging), underwater communications, seismic research (such as underwater measurement), nondestructive testing (such as large-scale structural monitoring), and military applications (such as air, ground, and underwater surveillance). The performance requirements for acoustic wave sensors vary greatly across these fields, but they are generally expected to have a very low minimum detectable pressure, a wide bandwidth (from a few hertz to tens of thousands of hertz), and a high dynamic range (170 dB pressure is common). These sensors can be used in environments with high temperatures, high pressures, strong corrosion, and strong radiation, where traditional electroacoustic sensors struggle.

[0003] The development of acoustic wave sensors is closely linked to the research of lightweight diaphragm materials. The development of traditional diaphragm materials has reached a bottleneck, unable to meet the practical needs of acoustic wave detection in harsh environments such as industry, military, and aerospace, requiring high sensitivity, high sound pressure levels, and wide spectrum response.

[0004] Silicon is one of the most important semiconductor materials, boasting a low coefficient of thermal expansion, strong chemical resistance, and the ability to maintain excellent vibration performance without prestressing. Currently, large-scale ultra-thin silicon films, typically 20-30μm thick, can only be obtained through conventional thinning processes. Compared to traditional metal and polymer thin films, single-crystal silicon is formed by covalent bonds and has a very high elastic modulus. Silicon films are prone to in-plane fracture and interfacial delamination, making them vulnerable to damage during many conventional manufacturing processes used in acoustic device construction. Consequently, their low-frequency response and sensitivity remain significantly limited. Using thinner, less flexurally stiff film materials to construct the diaphragm structure of a pickup could improve the sensitivity and frequency response range of acoustic wave sensors. Summary of the Invention

[0005] In view of the above problems, the present invention aims to overcome the defects of existing silicon film materials that are prone to in-plane fracture and interface delamination.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] The present invention provides a diaphragm material, comprising a silicon film and a graphene film; wherein the graphene film is grown on the silicon film by van der Waals force to form a graphene-silicon van der Waals heterojunction;

[0008] The thickness of the silicon film is between 200 nanometers and 100 micrometers; the surface roughness of the silicon film is between 0.0001 micrometers and 0.01 micrometers;

[0009] The number of graphene layers included in the graphene film is less than or equal to 10.

[0010] The present invention also provides a method for preparing a diaphragm material, which comprises:

[0011] Growing a graphene film on the surface of the silicon film to form a graphene-silicon van der Waals heterojunction;

[0012] The thickness of the silicon film in the graphene-silicon van der Waals heterojunction is reduced to a first preset value, and the surface roughness of the silicon film is reduced to a second preset value to obtain a diaphragm material.

[0013] In the above technical solution, the step of reducing the thickness of the silicon film in the graphene-silicon van der Waals heterojunction to a first preset value and reducing the surface roughness of the silicon film to a second preset value to obtain the diaphragm material includes:

[0014] Determining an etching rate and an etching time according to an original thickness of the silicon film and a first preset value;

[0015] Determining the etching solution and etching temperature according to the etching rate; wherein the etching solution contains an active agent with low interfacial tension;

[0016] At a determined etching temperature, the silicon film in the graphene-silicon van der Waals heterojunction is etched by an etching solution within the etching time until the thickness of the silicon film is reduced to a first preset value and the surface roughness of the silicon film is reduced to a second preset value, thereby obtaining a diaphragm material.

[0017] In the above technical solution, the etching solution is an alkaline solution.

[0018] In the above technical solution, the etching solution is a KOH solution, and the mass fraction of the KOH solution is between 1% and 80%.

[0019] In the above technical solution, the etching temperature is between 20°C and 100°C.

[0020] In the above technical solution, the step of growing a graphene film on the surface of a silicon film to form a graphene-silicon van der Waals heterojunction comprises:

[0021] The silicon film is placed in a high-temperature tube furnace, and the temperature in the reaction chamber of the high-temperature tube furnace is set to 300°C to 1500°C;

[0022] The reaction chamber is evacuated to ensure that the atmospheric pressure in the reaction furnace is within a preset range;

[0023] A mixed gas comprising a protective gas and a reducing gas is introduced into the reaction chamber, and after the flow of the mixed gas becomes stable, carbon source steam is introduced into the reaction chamber;

[0024] After a preset time period, the carbon source steam is turned off and the mixed steam is continued to be introduced. After the temperature in the reaction furnace reaches room temperature, the mixed gas is turned off.

[0025] The present invention also provides an acoustic wave sensor, which adopts the diaphragm material described in the above technical solution.

[0026] The present invention has the following advantages due to the adoption of the above technical solution:

[0027] The diaphragm material of the present invention directly grows a graphene film on a silicon-based surface to form a graphene-silicon van der Waals heterojunction. Under the multi-level interactions of van der Waals forces and covalent bonds at the interface between the two, stress is effectively dispersed and transmitted, thereby improving the sound propagation speed and tension bearing capacity of the diaphragm. This solves the problem that the reliable suspension distance of general graphene thin diaphragm materials does not exceed 10μm, greatly improves the mechanical properties of the material, and enables the preparation and application of large-scale diaphragm materials. At the same time, by leveraging the chemical stability of graphene in harsh environments such as strong acids and strong alkalis, a submicron silicon film thinning process is developed. Through the dual optimization of diaphragm materials and structural parameters, high-quality responses of diaphragm materials in the infrasound, audible and ultrasonic bands are achieved, providing a technical basis for the preparation of high-sensitivity, broadband response acoustic wave sensor devices.

[0028] In addition, since silicon is doped with graphene, the overall conductivity is improved. Therefore, when the silicon film containing the graphene film is used as the diaphragm material, there is no need to evaporate the electrode separately, which reduces the complexity of the preparation. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions in the present invention or the prior art, a brief introduction is given below to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0030] Figure 1 It is a schematic structural diagram of the diaphragm material of the present invention;

[0031] Figure 2 is a flow chart of a method for preparing a diaphragm material of the present invention;

[0032] Figure 3(a) shows the Raman spectra of silicon-based graphene grown at different times;

[0033] FIG3( b ) is a graph showing the transmittance spectra and corresponding resistance changes of silicon-based graphene with different growth times;

[0034] Figure 4(a) is a physical picture of graphene growing on the surface of a silicon film;

[0035] Figure 4(b) is a low-magnification TEM image of graphene grown on the surface of a silicon film;

[0036] Figure 4(c) is a high-magnification TEM image of graphene grown on the surface of the silicon film;.

[0037] Figure 5 This is a physical picture of the thinned graphene-silicon van der Waals heterojunction diaphragm material;

[0038] Figure 6 The figure is a frequency response curve of an acoustic wave sensor using the diaphragm material of the present invention. DETAILED DESCRIPTION

[0039] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0040] Silicon membranes are currently used as diaphragm materials in acoustic wave sensors. However, these membranes, composed of covalently bonded single-crystal silicon, exhibit a high Young's modulus but are susceptible to in-plane fracture and interfacial delamination. They are also susceptible to damage during conventional manufacturing processes during acoustic device construction. Consequently, acoustic sensors using these membranes are significantly limited in their low-frequency response and sensitivity.

[0041] Based on the above problems in the prior art, the present invention provides a diaphragm material. Figure 1 Schematic diagram of the structure of the diaphragm material of the present invention. Figure 1 As shown, the diaphragm material includes a silicon film and a graphene film, and the graphene film grows on the silicon film through van der Waals force to form a graphene-silicon van der Waals heterojunction.

[0042] The thickness of the silicon film is between 200 nanometers and 100 micrometers; the surface roughness of the silicon film is between 0.0001 and 0.01 micrometers.

[0043] The number of graphene layers included in the graphene film is less than or equal to 10.

[0044] In the diaphragm material of the present invention, the graphene film and the silicon film form a graphene-silicon van der Waals heterojunction through van der Waals forces. This van der Waals heterojunction forms the graphene film and the silicon film into a whole, thereby being able to utilize the ultra-thin performance, excellent mechanical properties and extreme flexibility of graphene to improve the conductivity, sound propagation speed, Young's modulus, loss factor (internal damping) and other physical indicators of the silicon film, thereby improving the sensitivity and frequency response range of the entire diaphragm material and obtaining lower distortion. In addition, since the silicon is doped with graphene, the overall conductivity is improved. Therefore, when the silicon film containing the graphene film is used as the diaphragm material, there is no need to evaporate the electrode separately, which reduces the complexity of the preparation.

[0045] The present invention also provides a method for preparing the aforementioned diaphragm material. Figure 2 is a flow chart of the preparation method of the diaphragm material, such as Figure 2 As shown, the preparation method of the diaphragm material of the present invention includes:

[0046] Step 1: growing a graphene film on the surface of the silicon film to generate a graphene-silicon van der Waals heterojunction.

[0047] In this embodiment, a graphene film is grown on the surface of a silicon film using chemical vapor deposition. Specifically, the process includes the following steps:

[0048] The silicon film is placed in a high-temperature tube furnace, and the temperature in the reaction chamber of the high-temperature tube furnace is set to 300°C to 1500°C;

[0049] The reaction chamber is evacuated to ensure that the atmospheric pressure in the reaction furnace is within a preset range;

[0050] A mixed gas comprising a protective gas and a reducing gas is introduced into the reaction chamber, and after the flow of the mixed gas becomes stable, carbon source steam is introduced into the reaction chamber;

[0051] After a preset time period, the carbon source steam is turned off and the mixed steam is continued to be introduced. After the temperature in the reaction furnace reaches room temperature, the mixed gas is turned off.

[0052] In this embodiment, the preset range of the atmospheric pressure in the reaction furnace may be between 1 Pa and 100 Pa.

[0053] In this embodiment, the protective gas introduced into the reaction chamber may be argon, and the reducing gas may be hydrogen. The carbon source vapor introduced into the reaction chamber may be at least one of a gaseous carbon source (methane, ethylene, acetylene), a solid carbon source (polyaniline, polystyrene, etc.), or a liquid carbon source (toluene, benzoic acid, chlorobenzene, ethanol, acetonitrile, etc.).

[0054] When the silicon film reacts in a high-temperature tube furnace, the reaction temperature, gas flow rates, and reaction time can be adjusted according to process requirements, specifically following the following principles:

[0055] (1) The higher the reaction temperature, the faster the graphene grows and the larger the domain area;

[0056] (2) The higher the proportion of carbon source gas, the faster the graphene grows;

[0057] (3) The longer the growth time, the thicker the graphene layer.

[0058] In this embodiment, the reaction temperature of the silicon film in the high-temperature tube furnace is 1050 degrees Celsius; the gas flow rate is Ar / H2 1000 / 1000 sccm; and the reaction time is 30 minutes.

[0059] Figure 3(a) shows the Raman spectra of silicon-based graphene grown at different growth times, and Figure 3(b) shows the transmittance spectra and corresponding resistance changes of silicon-based graphene grown at different growth times. Figure 3(a) shows that the 2D peak in Figure 3(a) gradually broadens with time, indicating that the number of graphene layers increases with increasing growth time. In other words, the number of graphene layers can be controlled by controlling the growth time. The changes in transmittance and resistance shown in Figure 3(b) also indicate that the number of graphene layers increases with increasing growth time.

[0060] Through the above reaction, the silicon film and the graphene film are combined together by van der Waals forces to form a graphene-silicon van der Waals heterojunction.

[0061] Step 2: reducing the thickness of the silicon film in the graphene-silicon van der Waals heterojunction to a first preset value, and reducing the surface roughness of the silicon film to a second preset value to obtain a diaphragm material.

[0062] Generally, commercially available silicon membranes are several hundred microns thick. If used as a diaphragm material in acoustic sensors, the required thickness is less than or equal to 100 microns. Therefore, based on the graphene-silicon van der Waals heterojunction obtained in step 1, the thickness of the silicon membrane needs to be reduced.

[0063] Various techniques are currently available for reducing silicon film thickness, including grinding, polishing, dry polishing, electrochemical etching, wet etching, plasma-assisted chemical etching, and atmospheric pressure plasma etching. However, these existing techniques fail to address the issue of precisely controlling silicon film thickness. Furthermore, the surface roughness of the silicon film directly affects the sensitivity of the diaphragm material. Therefore, while etching the silicon film, it is also necessary to reduce its surface roughness.

[0064] In this embodiment, this step specifically includes:

[0065] Determining an etching rate and an etching time according to an original thickness of the silicon film and a first preset value;

[0066] Determining the etching solution and etching temperature according to the etching rate; wherein the etching solution contains an active agent with low interfacial tension;

[0067] At a determined etching temperature, the silicon film in the graphene-silicon van der Waals heterojunction is etched by an etching solution within the etching time until the thickness of the silicon film is reduced to a first preset value and the surface roughness of the silicon film is reduced to a second preset value, thereby obtaining a diaphragm material.

[0068] In this embodiment, the first preset value is the target thickness of the silicon film, such as a value between 200 nanometers and 100 microns; the second preset value is the target value of the surface roughness of the silicon film, such as a value between 0.0001 microns and 0.01 microns.

[0069] The etching solution is an aqueous solution of an alkali metal hydroxide. In this embodiment, the etching solution is a KOH solution, and the mass fraction of the KOH solution is between 1% and 80%. In other embodiments, the composition of the etching solution may also vary, such as using an alkaline aqueous solution with a pH value of 12 or above containing an alkali metal hydroxide, hydroxylamine, and an inorganic carbonate compound. The etching solution may also be an acidic solution, such as a mixture of nitric acid with a volume percentage greater than 0 vol% and less than or equal to 80 vol%, hydrofluoric acid with a volume percentage greater than 0 vol% and less than or equal to 20 vol%, and acetic acid with a volume percentage greater than 0 vol% and less than or equal to 50 vol%.

[0070] The etching temperature can be controlled between 20°C and 100°C.

[0071] The rate at which the etching solution etches the silicon film is related to both the etching temperature and the etching solution concentration. Within the aforementioned range, the higher the etching temperature, the higher the etching rate; and the higher the etching solution concentration, the higher the etching rate.

[0072] For example, using a 40 wt% KOH etchant at 80°C, the etching rate of the silicon film can be controlled to 1.01 μm / min. Furthermore, if the original thickness of the silicon film is 90 μm, the etching time using the above etchant is controlled to 10 minutes, resulting in a silicon film with a thickness of approximately 80 μm.

[0073] In this embodiment, a low interfacial tension surfactant is added to the etching solution to reduce the tension on the silicon surface, thereby improving the wettability of the silicon surface and reducing the surface roughness of the silicon film. The low interfacial tension surfactant can be FM-31 low interfacial tension surfactant (non-ionic) or FC-116 low interfacial tension surfactant (anionic) from Hangzhou Renshan Technology Co., Ltd.

[0074] The present invention uses chemical vapor deposition to directly grow a high-quality graphene film on a silicon-based surface, forming a graphene-silicon van der Waals heterojunction. Under the multi-level interactions of van der Waals forces and covalent bonds at the interface between the two, stress is effectively dispersed and transmitted, thereby improving the sound propagation speed and tension bearing capacity of the diaphragm. This solves the problem that the reliable suspension distance of general graphene thin diaphragm materials does not exceed 10μm, greatly improves the mechanical properties of the material, and enables the preparation and application of large-size diaphragm materials. At the same time, by leveraging the chemical stability of graphene in harsh environments such as strong acids and strong alkalis, a submicron silicon film thinning process is developed. Through the dual optimization of diaphragm materials and structural parameters, high-quality responses of diaphragm materials in the infrasound, audible sound and ultrasonic bands are achieved, providing a technical basis for the preparation of high-sensitivity, broadband response acoustic wave sensor devices.

[0075] The present invention also provides an acoustic wave sensor, which uses the aforementioned diaphragm material.

[0076] The diaphragm material provided by the present invention is a graphene-silicon van der Waals heterojunction, which can utilize the ultra-thin performance, excellent mechanical properties and extreme flexibility of graphene to improve the conductivity, sound propagation speed, Young's modulus, loss factor (internal damping) and other physical indicators of the silicon membrane, so that the entire diaphragm material has higher sensitivity, frequency response range, and lower distortion, thereby making the acoustic wave sensor using the above-mentioned diaphragm material have higher sensitivity, frequency response range, and lower distortion.

[0077] The present invention will be described in detail below with reference to the accompanying drawings and embodiments.

[0078] Example 1

[0079] The silicon wafer was ultrasonically cleaned in cyclohexane, ethanol, and deionized water for 10 minutes, followed by drying with nitrogen. The cleaned silicon wafer was placed in a high-temperature tube furnace at 1100°C. The atmospheric pressure in the reaction chamber was evacuated to 10 Pa using an oil-free vortex vacuum pump. Ar / H₂ (1000 / 1000 sccm) was introduced. Once the flow stabilized, the methane gas valve was opened and the methane gas flow rate was controlled to 1000 sccm. Upon entering the reaction chamber, methane vapor rapidly decomposed into activated carbon species, which were then adsorbed onto the silicon wafer surface, where they migrated and collided, promoting the nucleation and growth of microcrystalline graphite. The graphene growth process was set to 120 minutes. After the growth period was complete, the methane valve was quickly closed, and the Ar / H₂ ratio was set to 300 / 300 sccm, initiating a cooling process. Once the reaction chamber temperature dropped to room temperature, the Ar / H₂ ratio was turned off, and the chamber was opened to remove the sample.

[0080] A 40% KOH etching solution was prepared, and 3% FM-31 low interfacial tension surfactant (non-ionic) from Hangzhou Renshan Technology Co., Ltd. was added. The etching temperature was controlled at 80°C. The prepared silicon-based graphene material was immersed in a reaction tank containing the etching solution for 6 minutes. After removal, it was rinsed with deionized water and dried for characterization.

[0081] Analysis of experimental results: Graphene on the silicon surface was characterized using transmission electron microscopy. Figure 4(a) shows a photo of graphene grown on the silicon film surface, Figure 4(b) shows a low-magnification TEM image of graphene grown on the silicon film surface, and Figure 4(c) shows a high-magnification TEM image of graphene grown on the silicon film surface. These images demonstrate that graphene growth is achieved on the silicon film surface.

[0082] Figure 5 This is a schematic diagram of the thinned graphene-silicon van der Waals heterojunction diaphragm material. It can be seen from the figure that the ultra-thin and ultra-flexible diaphragm material is obtained by the above method. Further SEM testing shows that its surface roughness Ra is 0.001μm.

[0083] Based on the existing 1 / 4-inch acoustic wave sensor on the market, the original diaphragm is replaced by a graphene-silicon van der Waals heterojunction diaphragm. The frequency response curve of the diaphragm is tested on an acoustic test platform. Figure 6 As shown in the figure, it can be seen that the frequency response range of the diaphragm can reach 10Hz~100kHz, and the frequency response curve is relatively flat, with a sensitivity of -30dB.

[0084] Example 2

[0085] The silicon wafer was ultrasonically cleaned in cyclohexane, ethanol, and deionized water for 10 minutes, followed by drying with nitrogen. The cleaned silicon wafer was placed in a high-temperature tube furnace at 1500°C. The atmospheric pressure in the reaction chamber was evacuated to 1 Pa using an oil-free scroll vacuum pump. Ar / H₂ (1000 / 1000 sccm) was introduced. Once the flow stabilized, the polyaniline gas valve was opened. The polyaniline gas flow rate was controlled to 1000 sccm. Upon entering the reaction chamber, the polyaniline vapor rapidly decomposed into activated carbon species. These activated carbon species adsorbed onto the silicon wafer surface, where they migrated and collided, leading to the nucleation and growth of microcrystalline graphite. The graphene growth process was set to 30 minutes. After the growth period was complete, the polyaniline gas valve was quickly closed, and the Ar / H₂ flow rate was set to 300 / 300 sccm, initiating a cooling process. Once the reaction chamber temperature dropped to room temperature, the Ar / H₂ was turned off, and the sample was removed from the chamber.

[0086] Prepare an 80% KOH etching solution and add 3% FC-116 low interfacial tension surfactant (anionic type) from Hangzhou Renshan Technology Co., Ltd. The etching temperature is controlled at 20°C. The prepared silicon-based graphene material is immersed in a reaction tank containing the etching solution for 6 minutes. After removal, it is rinsed with deionized water and dried for characterization.

[0087] Example 3

[0088] The silicon wafer was ultrasonically cleaned in cyclohexane, ethanol, and deionized water for 10 minutes, followed by drying with nitrogen. The cleaned silicon wafer was placed in a high-temperature tube furnace at 300°C. The atmospheric pressure in the reaction chamber was evacuated to 100 Pa using an oil-free scroll vacuum pump. Ar / H₂ (1000 / 1000 sccm) was introduced. Once the flow stabilized, the ethanol gas valve was opened and ethanol gas was introduced at a controlled flow rate of 1000 sccm. Upon entering the reaction chamber, the ethanol gas rapidly decomposed into activated carbon species, which then adsorbed onto the silicon wafer surface, where they migrated and collided, promoting the nucleation and growth of microcrystalline graphite. The graphene growth process was set to 30 minutes. After the growth period was complete, the ethanol gas valve was quickly closed, and the Ar / H₂ ratio was set to 300 / 300 sccm, initiating a cooling process. Once the reaction chamber temperature dropped to room temperature, the Ar / H₂ ratio was turned off, and the sample was removed.

[0089] A 1% KOH etching solution was prepared, and 3% FC-116 low interfacial tension surfactant (anionic type) from Hangzhou Renshan Technology Co., Ltd. was added. The etching temperature was controlled at 100°C. The prepared silicon-based graphene material was immersed in a reaction tank containing the etching solution for 30 minutes. After removal, it was rinsed with deionized water and dried for characterization.

[0090] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A diaphragm material, characterized in that: The invention comprises a silicon film and a graphene film; wherein the graphene film is grown on the silicon film by van der Waals force to form a graphene-silicon van der Waals heterojunction; The thickness of the silicon film is between 200 nanometers and 100 micrometers; the surface roughness of the silicon film is between 0.0001 micrometers and 0.01 micrometers; The number of graphene layers included in the graphene film is less than or equal to 10.

2. A method for preparing a diaphragm material, for preparing the diaphragm material according to claim 1, characterized in that: include: Growing a graphene film on the surface of the silicon film to form a graphene-silicon van der Waals heterojunction; The thickness of the silicon film in the graphene-silicon van der Waals heterojunction is reduced to a first preset value, and the surface roughness of the silicon film is reduced to a second preset value to obtain a diaphragm material.

3. The method for preparing a diaphragm material according to claim 2, wherein: The step of reducing the thickness of the silicon film in the graphene-silicon van der Waals heterojunction to a first preset value and reducing the surface roughness of the silicon film to a second preset value to obtain a diaphragm material comprises: Determining an etching rate and an etching time according to an original thickness of the silicon film and a first preset value; Determining the etching solution and etching temperature according to the etching rate; wherein the etching solution contains an active agent with low interfacial tension; At a determined etching temperature, the silicon film in the graphene-silicon van der Waals heterojunction is etched by an etching solution within the etching time until the thickness of the silicon film is reduced to a first preset value and the surface roughness of the silicon film is reduced to a second preset value, thereby obtaining a diaphragm material.

4. The method for preparing a diaphragm material according to claim 3, wherein: The etching solution is an aqueous solution of alkali metal hydroxide.

5. The method for preparing a diaphragm material according to claim 4, characterized in that: The etching solution is a KOH solution, and the mass fraction of the KOH solution is between 1% and 80%.

6. The method for preparing a diaphragm material according to claim 3, wherein: The etching temperature is between 20°C and 100°C.

7. The method for preparing a diaphragm material according to claim 2, wherein: The step of growing a graphene film on the surface of the silicon film to generate a graphene-silicon van der Waals heterojunction comprises: The silicon film is placed in a high-temperature tube furnace, and the temperature in the reaction chamber of the high-temperature tube furnace is set to 300°C to 1500°C; Evacuating the reaction chamber so that the atmospheric pressure in the high-temperature tube furnace is within a preset range; A mixed gas comprising a protective gas and a reducing gas is introduced into the reaction chamber, and after the flow of the mixed gas becomes stable, carbon source steam is introduced into the reaction chamber; After a preset time period, the carbon source steam is turned off and the mixed steam is continued to be introduced. After the temperature in the high-temperature tube furnace reaches room temperature, the mixed gas is turned off.

8. An acoustic wave sensor, characterized in that: The acoustic wave sensor adopts the diaphragm material according to claim 1.

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