Matrix structure with grown diamond film and preparation method of diamond film

Abstract

The invention discloses a matrix structure with a grown diamond film and a preparation method of the diamond film, the matrix structure with the grown diamond film comprises a substrate, a buffer layer and the diamond film, and the substrate is a single-material substrate, a multi-material composite substrate or a multi-material multi-layer substrate; at least the upper surface of the substrate is provided with a buffer layer or the buffer layer wraps the outer surface of the single-material substrate, and a diamond film grows on the buffer layer; the thermal expansion coefficient of the buffer layer is smaller than that of the substrate; the buffer layer is a single crystal film or a polycrystalline film, the diamond film is a nanocrystalline diamond film and / or a micron crystal diamond film, and the surface area of the diamond film is 13mm < 2 >-465000 mm < 2 >. The matrix structure is excellent in heat conduction performance and low in thermal expansion coefficient, and the diamond film on the matrix structure is high in quality and large in surface area and has excellent heat conduction performance.

Description

Technical Field

[0001] The invention relates to the technical field of diamond materials, and in particular to a substrate structure on which a diamond film is grown and a method for preparing the diamond film. Background Art

[0002] In modern optical applications, extremely stringent requirements are placed on the optical properties and environmental stability of materials. Traditional materials, such as glass and plastic, are limited in their application in special optical environments such as high-energy lasers, high-temperature environments, and highly corrosive media due to their inherent scattering, absorption characteristics, and low chemical resistance.

[0003] Diamond stands out for its exceptional hardness, high transmittance, low scattering and excellent chemical resistance, making it one of the best materials to meet the needs of demanding optical environments.

[0004] In the traditional method, when preparing diamond film, thermal stress will occur due to uneven nucleation growth, large difference in thermal expansion coefficient between diamond and substrate, uneven substrate temperature during preparation, sudden temperature change, etc. When the internal stress accumulates to a certain extent, the film layer will break or peel off, causing the prepared diamond film to have cracks, poor optical properties, unable to achieve self-support, and poor quality. In addition, when preparing large-area diamond film, the preparation requirements are higher, and the difference between the diamond film and the substrate will be further amplified, resulting in large-area diamond film being more prone to cracking and worse performance. Summary of the invention

[0005] In view of this, the present invention proposes a substrate structure with a diamond film grown thereon and a preparation method thereof, aiming to solve the technical problem of how to prepare a large-area diamond film.

[0006] The first aspect of the present invention provides a substrate structure with a diamond film grown thereon, comprising: a substrate having a thermal conductivity greater than or equal to 20 W / mK and a thermal expansion coefficient less than 9×10 -6 / K single material substrate, multi-material composite substrate or multi-material multi-layer substrate; a buffer layer, the buffer layer is at least arranged on the upper surface of the substrate or the buffer layer wraps the outer surface of the single material substrate, and the diamond film is grown on the buffer layer; the thermal expansion coefficient of the buffer layer is less than the thermal expansion coefficient of the substrate; the buffer layer is a single crystal film or a polycrystalline film; the diamond film is a nanocrystalline diamond film and / or a micron crystal diamond film, and the upper surface area of ​​the diamond film is 13mm 2 ~465000mm 2 .

[0007] It can be seen from the above technical scheme that the substrate structure with the diamond film grown thereon proposed in the first aspect of the present invention has excellent thermal conductivity and low thermal expansion coefficient, can resist thermal expansion and thermal shock and provide excellent support, and is convenient for providing the required support foundation and rapid thermal conductivity for the subsequent growth of the diamond film; and the buffer layer located on the surface of the substrate can further reduce the difference in thermal expansion coefficient between the diamond film and the substrate, further reduce the structural difference between the diamond film and the substrate, and can protect the structure of the substrate and strengthen the structure of the substrate to a certain extent. The crystal film on the buffer layer is closer to the structure of the diamond grown thereon, and the difference in thermal expansion coefficient between the upper surface of the buffer layer and the grown diamond film is small. When the upper surface of the substrate has the above buffer layer, the heat transfer between the substrate and the buffer layer can be stabilized, and it is not easy to cause a sudden increase in thermal stress. The stress is uniform during the growth of the diamond film, and the probability of film cracking is greatly reduced. The diamond film finally prepared has high quality, large area, and excellent physical and chemical properties.

[0008] The second aspect of the present invention provides a method for preparing a diamond film, which is used to prepare a diamond film on a substrate structure on which a diamond film is grown in each of the above examples. The preparation method comprises the following steps: preparing a substrate by chemical vapor deposition or hot pressing sintering; preparing a buffer layer on the substrate by bonding, chemical vapor deposition or physical vapor deposition; cleaning the substrate with the buffer layer with a lotion; ultrasonically treating the substrate with the buffer layer in deionized water for 10 minutes to 60 minutes, and drying; treating the substrate with the buffer layer with an ozone atmosphere surface cleaner to make the surface of the buffer layer The invention relates to a method for preparing a diamond film having activity; preparing a diamond particle suspension, and ultrasonically placing the buffer layer and the substrate with the activity on the surface in the diamond particle suspension for 10 minutes to 60 minutes, so that the surface of the buffer layer is provided with diamond seeds; drying the buffer layer and the substrate with the diamond seeds, so that the surface of the buffer layer is provided with diamond seeds; placing the buffer layer and the substrate in a microwave plasma chemical vapor deposition device, introducing a mixed gas of methane, hydrogen and oxygen as a reaction gas, and depositing a diamond film on the surface of the buffer layer to form a matrix structure; and removing the substrate and the buffer layer by grinding the matrix structure and / or immersing the matrix structure in an acid solution to obtain the diamond film.

[0009] It can be seen from the above technical scheme that the method for preparing the diamond film proposed in the second aspect of the present invention has uniform nucleation and growth of the diamond film during the preparation process, uniform temperature during the film formation process and is not prone to film cracking, and the final prepared diamond film has high quality and a large film formation area.

[0010] The third aspect of the present invention provides a substrate structure with a diamond film grown thereon, comprising a substrate having a thermal conductivity greater than or equal to 20 W / mK and a thermal expansion coefficient less than 9×10 -6 / K multi-material composite substrate or multi-material multi-layer substrate; the material of the substrate is selected from at least two of graphite, graphene, carbide, nitride, silicon, titanium, molybdenum, niobium, tantalum and tungsten; the carbide and the nitride are single crystal films or polycrystalline films, and a diamond film is grown on at least the upper surface of the substrate, and the upper surface area of ​​the diamond film is 13mm 2 ~465000mm 2 .

[0011] It can be seen from the above technical scheme that the substrate structure with diamond film grown on it proposed in the third aspect of the present invention has high thermal conductivity and support performance, the selected material has a relatively small difference in thermal expansion coefficient with diamond, and has good thermal conductivity and high temperature resistance, so when the diamond film is grown on the surface of the substrate, the temperature can be evenly transferred, and there will be no sudden increase in thermal stress, and it is not easy for the surface diamond film to crack due to the influence of temperature difference. Carbides and nitrides are both single crystal films or polycrystalline films, and multi-material composite substrates or multi-material multi-layer substrates made of multiple materials have a strong affinity with diamond. When the substrate is heated, the heat is quickly transferred on the substrate, and the thermal stability is high. It is not easy to have a sudden increase in thermal stress. The difference in thermal expansion coefficient between the upper surface of the substrate and the grown diamond film is small, the stress is uniform during the growth process, and the probability of film cracking is greatly reduced. The diamond film finally prepared has high quality, large area, and excellent physical and chemical properties.

[0012] The fourth aspect of the present invention provides a method for preparing a diamond film, which is used to prepare a diamond film on the aforementioned substrate structure with a diamond film grown thereon, wherein the diamond film is a nanocrystalline diamond film and / or a micron-crystalline diamond film, and the preparation method comprises the following steps: preparing a substrate by chemical vapor deposition; cleaning the substrate with a lotion; ultrasonically treating the substrate in deionized water for 10 to 60 minutes, and drying the substrate; treating the substrate with an ozone atmosphere surface cleaner to make the substrate surface active; preparing a diamond particle suspension, and ultrasonically treating the substrate with an active surface in the diamond particle suspension for 10 to 60 minutes, so that the surface of the substrate is provided with diamond seeds; drying the substrate with diamond seeds, placing it in a microwave plasma chemical vapor deposition device, introducing a mixed gas of methane, hydrogen, and oxygen as a reaction gas, and depositing a diamond film on the surface of the substrate to form a substrate structure; and removing the substrate by grinding the substrate structure and / or soaking the substrate structure in an acid solution to obtain the diamond film.

[0013] It can be seen from the above technical scheme that the method for preparing the diamond film proposed in the fourth aspect of the present invention has a uniform nucleation and growth of the diamond film located on the multi-material composite substrate or the multi-material multi-layer substrate during the preparation process, a uniform temperature during the film formation process, and film cracking is not likely to occur. The final prepared diamond film has high quality and a large film formation area.

[0014] It should be understood that the above general description and the following detailed description are exemplary and explanatory only and are not restrictive of the disclosure of the embodiments of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained like these accompanying drawings without paying any creative work.

[0016] Figure 1 It is a schematic diagram of a base structure of a diamond film grown on a single material substrate wrapped with a buffer layer proposed in some embodiments of the present invention.

[0017] Figure 2 It is a schematic diagram of a substrate structure for growing a diamond film using a buffer layer and a multi-material composite substrate proposed in some embodiments of the present invention.

[0018] Figure 3 It is a schematic diagram of a substrate structure for growing a diamond film using a buffer layer and a multi-material composite substrate proposed in some embodiments of the present invention, and the relative content of each material in the multi-material composite substrate forms a gradient change as the height range of the substrate changes.

[0019] Figure 4 It is a schematic diagram of a substrate structure for growing a diamond film using a buffer layer and a multi-material composite substrate proposed in some embodiments of the present invention, and a schematic diagram of a gradient change formed by the relative content of each material in the multi-material composite substrate as the radius range of the substrate changes.

[0020] Figure 5 It is a schematic diagram of a substrate structure for growing a diamond film using a buffer layer and a multi-material multi-layer substrate proposed in some embodiments of the present invention, wherein the multi-material multi-layer substrate uses substrate layers of multiple materials alternately stacked.

[0021] Figure 6 is a schematic diagram of a substrate structure on which a diamond film is grown on a multi-material multi-layer substrate according to some embodiments of the invention;

[0022] Figure 7 is a schematic diagram of a substrate structure having a diamond film grown on a multi-material composite substrate according to some embodiments of the present invention;

[0023] Figure 8 It is a schematic flow chart of each step of the method for preparing diamond film according to some embodiments of the present invention.

[0024] Fig. 9It is a schematic diagram of the structure after each step of the method for preparing the diamond film in some embodiments of the present invention.

[0025] Fig.10 It is a schematic flow chart of each step of the method for preparing diamond film according to other embodiments of the present invention.

[0026] Fig.11 It is a schematic diagram of the structure after each step in the method for preparing the diamond film of other embodiments of the present invention.

[0027] Fig.12 This is a Raman spectrum data diagram of the diamond film according to Example 1 of the present invention.

[0028] Fig.13 This is the XRD spectrum of the diamond film according to Example 1 of the present invention.

[0029] Fig.14 This is a data graph of visible light to near-infrared transmittance measured by the ultraviolet-visible-near-infrared spectrophotometer according to Example 1 of the present invention.

[0030] Fig.15 It is a schematic diagram of the relationship between the thermal expansion coefficient and thermal conductivity of each material used in the present invention.

[0031] Description of reference numerals:

[0032] 100. Matrix structure;

[0033] 10. Substrate;

[0034] 11. Single material substrate;

[0035] 12. Multi-material composite substrate;

[0036] 121, first gradient layer; 122, second gradient layer; 123, third gradient layer;

[0037] 13. Multi-material and multi-layer substrates;

[0038] 20. Buffer layer;

[0039] 30. Diamond film; 31. Diamond seed. DETAILED DESCRIPTION

[0040] The following will be combined with the drawings and specific embodiments in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments in the present invention, other embodiments obtained by ordinary technicians in this field without creative work are all within the scope of protection of the present invention. In the absence of conflict, the following embodiments and features in the embodiments can be combined with each other.

[0041] like Figure 1 As shown, an embodiment of the present invention provides a base structure 100 with a diamond film 30 grown thereon, comprising: a substrate 10 , a buffer layer 20 and a diamond film 30 .

[0042] The substrate 10 has a thermal conductivity greater than or equal to 20 W / mK and a thermal expansion coefficient less than 9×10 -6 / K single material substrate 11, multi-material composite substrate 12 or multi-material multi-layer substrate 13. The single material substrate 11 here refers to a substrate made of only one material; the multi-material composite substrate 12 here refers to a board formed of at least two materials to form an integral structure, and usually the content of each material at different layer positions has a certain stable ratio; the multi-material multi-layer substrate 13 here refers to a board with multiple layers of structure superimposed and combined, and each layer of the structure is made of a single material.

[0043] Furthermore, if Figure 1 As shown, when the material of the substrate 10 is one type, that is, the substrate 10 is a single-material substrate 11, the buffer layer 20 wraps the outer surface of the substrate 10. Figure 1 , Figure 2 , Figure 3 and Figure 4 As shown, the buffer layer 20 is at least arranged on the upper surface of the substrate 10, and a diamond film 30 is grown on the buffer layer 20; the thermal expansion coefficient of the buffer layer 20 is smaller than the thermal expansion coefficient of the substrate 10; the buffer layer 20 is a single crystal film or a polycrystalline film; the diamond film 30 is a nanocrystalline diamond film and / or a microcrystalline diamond film, and the upper surface area of ​​the diamond film 30 is 13mm 2 ~465000mm 2 .

[0044] That is to say, when the substrate 10 itself is a single-material substrate 11 made of a single material, a buffer layer 20 must be added to adjust the film cracking problem caused by the single-material substrate 11 having a single performance and a certain difference in thermal expansion coefficient with the diamond film 30 during the growth of the diamond film 30. The buffer layer 20 here can serve as a transition to further buffer the thermal stress. The thermal expansion coefficient is smaller than that of the single-material substrate 11 and is closer to the thermal expansion coefficient of the diamond film 30. The buffer layer 20 transfers heat to the diamond film 30, so that the diamond film 30 grows well without film cracking.

[0045] It should be noted that, in the present invention, the outer surface of the substrate 10 includes an upper surface, a lower surface and a side surface. The upper surface is usually larger in area, relatively flat, and has a large space in contact with the reaction gas; the side surface has a small space in contact with the reaction gas, which is not conducive to the reaction, and the area of ​​the side surface is usually uneven, has an arc or is small; the lower surface is usually used for contact with the reaction vessel, and no or a very small amount of buffer layer 20 is grown; then, the buffer layer 20 of the present invention is at least grown on the upper surface of the substrate 10, and in some examples, it can also be grown on the upper surface, side surface and lower surface of the substrate 10 at the same time to completely wrap the substrate 10; and the diamond film 30 of the present invention mainly refers to the diamond film 30 grown on the upper surface of the buffer layer 20. When the diamond film 30 is grown on the side of the buffer layer 20, the surface area of ​​the diamond film 30 located on the side is not counted, and only the surface area of ​​the diamond film 30 grown on the upper surface of the buffer layer 20 is counted, that is, the upper surface area of ​​the diamond film 30 described in this application.

[0046] Since the buffer layer 20 is a single crystal film or a polycrystalline film, it is closer to the structure of the diamond film 30, which can further reduce the structural difference between the substrate 10 and the diamond film 30; the thermal expansion coefficient of its own material is lower than that of the substrate 10 and closer to the thermal expansion coefficient of the diamond film 30, and has certain thermal conductivity properties, so the buffer layer 20 has good affinity with the diamond film 30.

[0047] As can be seen from the above technical solution, the base structure 100 with the diamond film 30 grown thereon proposed in the first aspect of the present invention has excellent thermal conductivity and low thermal expansion coefficient, which can resist thermal expansion and thermal shock and provide excellent support, providing a bottom support with excellent performance for the growth of the diamond film 30, and preventing the structure from collapsing in a high-temperature environment; and the buffer layer 20 located on the surface of the substrate 10 can further reduce the difference in thermal expansion coefficient and structure between the diamond film 30 and the substrate 10, and can protect and strengthen the structure of the substrate 10 to a certain extent. The area of ​​the diamond film 30 grown on the buffer layer 20 is large, and its upper surface area is 13mm 2 ~465000mm 2 The diamond film 30 is not prone to film cracking due to temperature differences and structural differences, and the stress of the diamond film 30 is uniform during its growth.

[0048] It is understandable that compared with the defect of the prior art that a large-area diamond film 30 with excellent performance cannot be prepared, the diamond film 30 in the base structure 100 on which the diamond film 30 is grown in the present invention can achieve a large surface area and high film quality.

[0049] Optionally, the upper surface area of ​​the substrate 10 is in the range of 12 mm 2 ~460000mm2 , so that the substrate 10 used in the present application has a larger upper surface area for growing other layer structures. When the upper surface area of ​​the substrate 10 is too small and less than 12 mm 2 When the upper surface area of ​​the substrate 10 is too large to exceed 460000 mm 2 Therefore, by setting the upper surface area of ​​the substrate 10 of the present invention within the above range, the substrate 10 can not only achieve sufficient thermal buffering, but also achieve a larger upper surface area of ​​high quality, and also control the entire structure to have a reasonable preparation cost.

[0050] Further optionally, if Figures 1 to 5 As shown, the upper surface area of ​​the buffer layer 20 of the present invention is greater than or equal to the upper surface area of ​​the substrate 10. Then, the buffer layer 20 is required to at least grow on the upper surface of the substrate 10 so that the surface of the substrate 10 will not be exposed. The diamond film 30 will not be directly grown on the upper surface of the substrate 10 in these examples, but the diamond film 30 will be grown on the upper surface of the buffer layer 20. Since the thermal expansion coefficient of the buffer layer 20 is smaller than that of the substrate 10, and the thermal expansion coefficient is closer to that of the diamond film 30; and the structure of the buffer layer 20 is closer to that of the diamond film 30 than that of the substrate 10, the heat conduction effect is good, and the phenomenon of sudden increase of thermal stress on the upper surface will not occur. The buffer layer 20 can further buffer the thermal stress, so that the growth of the diamond film 30 is more uniform. The buffer layer 20 is arranged on the upper surface of the substrate 10, and the upper surface area of ​​the buffer layer 20 is greater than or equal to the upper surface area of ​​the substrate 10, and the area of ​​the diamond film 30 is greater than or equal to the upper surface area of ​​the buffer layer 20, so the diamond film 30 grown on the buffer layer 20 has a larger upper surface. Optionally, the thickness of the substrate 10 ranges from 0.5 mm to 30 mm, and the upper surface area of ​​the substrate 10 is proportional to the square of the thickness of the substrate 10. That is, in order to ensure that the upper surface area of ​​the substrate 10 is within the range of 12 mm 2 ~460000mm 2 The thickness of the substrate 10 of the present invention must be controlled within a reasonable range. If the thickness of the substrate 10 is too small and is less than 0.5 mm, a diamond film 30 with a relatively large upper surface area cannot be prepared, and sufficient thermal buffering cannot be achieved. It is also easy to crack when buffering thermal stress. If the thickness of the substrate 10 is too large and is greater than 30 mm, the overall preparation cost is too high, and the diamond film 30 prepared in the end is easy to crack. Therefore, by setting the thickness of the substrate 10 of the present invention within the above range, the substrate 10 can not only achieve sufficient thermal buffering, but also achieve a larger upper surface area, and the overall structure can be controlled to have a reasonable preparation cost.

[0051] In some examples, the upper surface area of ​​the substrate 10 is represented by S, and the thickness of the substrate 10 is represented by h. The relationship between the upper surface area S of the substrate 10 and the thickness h of the substrate 10 is expressed as: S=Ah 2 , where A is a constant with a value of 2 to 505. For example, when A is 500 and h is 8 mm, S is 32000 mm 2 For another example, when A is 490 and h is 8mm, S is 31360mm. 2 That is, in these examples, the ratio of the upper surface area S of the substrate 10 to the square of the thickness h of the substrate 10 ranges from (2 to 505):1.

[0052] Advantageously, the value of A is 5 to 50, and the value of S is 25 to 8100 mm. 2 . Thus, the manufacturing cost is controlled within a more reasonable range, and no cracks occur on the surface of each structural layer during the manufacturing process. That is, in these examples, the ratio of the upper surface area S of the substrate 10 to the square of the thickness h of the substrate 10 is in the range of (5 to 50):1.

[0053] Optionally, the surface roughness of the substrate 10 ranges from 1 nm to 1,000,000 nm. If it is too small and below 1 nm, it is not easy to grow other layers such as the buffer layer 20 or the diamond film 30 on the surface, and it is not conducive to the nucleation of the diamond seed 31 grown on the substrate 10; if it is too large and above 1,000,000 nm, it is impossible to achieve other layer structures that are relatively continuous on the surface, and the structural morphology on the interface is poor. If the surface roughness of the substrate 10 is selected within the above range, it can ensure that the structural layer grown on its surface is easy to adhere and grow, and can maintain a stable and reliable morphology. Furthermore, the surface roughness of the substrate 10 is controlled in the range of 50 to 50,000 nm, which can be more conducive to achieving the aforementioned performance.

[0054] Optionally, the thickness of the buffer layer 20 ranges from 10nm to 50000nm. When the thickness of the buffer layer 20 is too small and less than 10nm, it is easy to cause etching of the substrate 10 and cannot effectively protect the substrate 10; when the thickness of the buffer layer 20 is too large and higher than 50000nm, the effect of the substrate 10 is reduced, and the preparation cost of the buffer layer 20 is also greatly increased. Therefore, selecting the thickness of the buffer layer 20 within the above range can ensure that the substrate 10 is not etched, and can form good support and heat conduction, and the preparation cost of the buffer layer 30 is controlled within a reasonable range. Furthermore, the thickness of the buffer layer 20 is controlled in the range of 500nm to 10000nm, which is more conducive to achieving the aforementioned performance.

[0055] Optionally, the thickness of the diamond film 30 is in the range of 0.05 mm to 3 mm. If the thickness of the diamond film 30 is too thick, the deposition cost of the diamond film 30 is too high and the finished product yield is reduced; if the thickness of the diamond film 30 is too thin, the overall cost is too high and the cost performance is low. Therefore, by selecting the thickness of the diamond film 30 within the above range, the deposition cost of the diamond film 30 can be effectively controlled, the diamond film 30 can have a good finished product yield, and the overall cost can be limited within a reasonable range.

[0056] Optionally, the diamond film 30 is a nanocrystalline diamond film and / or a microcrystalline diamond film. That is, the diamond film 30 can be a single nanocrystalline diamond film, or a single microcrystalline diamond film, or the diamond film 30 can also be a combination of a nanocrystalline diamond film 30 and a microcrystalline diamond film 30, that is, a nanocrystalline-microcrystalline, microcrystalline-nanocrystal-microcrystalline, nanocrystalline-microcrystalline-nanocrystal, etc.

[0057] The nanocrystalline diamond film has a high specific surface area and high surface activity, which is beneficial for catalytic and sensor applications. The grain size of the nanocrystalline diamond film is very small, and they can provide unique size effects, such as quantum size effect and surface effect, which can be used in electronics and optics. Nanocrystalline diamond film also has semiconductor properties and can be used in electronic devices, such as field effect transistors and optoelectronic devices. Nanocrystalline diamond film can also significantly reduce the friction coefficient and reduce wear, and can be used in precision mechanical parts. Nanocrystalline diamond film can also be chemically modified to make it have good biocompatibility, so that it can be used in the biomedical field.

[0058] The micron-crystalline diamond film inherits the high hardness of diamond and has excellent wear resistance, making it suitable for manufacturing wear-resistant cutting tools and abrasives. The micron-crystalline diamond film has a high thermal conductivity and can effectively conduct heat. It can be used in thermal management systems and as a heat dissipation material. The micron-crystalline diamond film can show good stability in high temperature and chemical corrosion environments, is not easy to react with other substances, can be used in high temperature environments, and can be used in chemical equipment and processes. The micron-crystalline diamond film has high mechanical strength and good impact resistance, and can be used to manufacture high-strength and high-reliability mechanical parts. The micron-crystalline diamond film has good transparency and can be used to manufacture optical windows, lenses and laser components, especially in situations where high purity and high transparency are required. The micron-crystalline diamond film can also exhibit semiconductor properties after doping and can be used in sensors and electronic devices.

[0059] It can be seen that the large surface area and high quality diamond film 30 grown on the upper part of the base structure 100 on which the diamond film 30 is grown according to the present invention can be applied in many fields and has a good market application prospect.

[0060] Advantageously, if Figure 1 , Figure 2 , Figure 3 and Figure 4 As shown, when the substrate 10 is a single material substrate 11 or a multi-material composite substrate 12, and the substrate 10 is formed by hot pressing and sintering of at least one granular material, a buffer layer 20 is provided on the surface of the substrate 10. The buffer layer 20 of the present invention is selectively provided according to the structure of the substrate 10. For the substrate 10 formed by hot pressing and sintering, by adding the buffer layer 20, the substrate 10 can be further protected, the substrate 10 can be tightly wrapped, the overall structure of the substrate 10 can be more stable, and the internal sintered materials are not easily deformed, so that the diamond film 30 can be reliably grown on the surface of the buffer layer 20.

[0061] In some embodiments of the present invention, the material of the substrate 10 is selected from at least one of graphite, graphene, carbide, nitride, diamond particles, silicon, titanium, molybdenum, niobium, tantalum and tungsten. Fig.15 As shown, the substrate 10 made of these materials can generally achieve good thermal conductivity, is resistant to high temperatures, has a low thermal expansion coefficient, and can maintain a certain supporting force without collapsing in a high temperature environment.

[0062] In some embodiments of the present invention, the buffer layer 20 is one of carbide, nitride, silicon and iridium. Fig.15 As shown, the materials selected for the buffer layer 20 are carbides, nitrides, silicon or iridium, which are also materials with good thermal conductivity and excellent thermal expansion coefficient. The materials selected for the buffer layer 20, carbides, nitrides, silicon and iridium, all have the characteristics of strong affinity with diamond, and the structures of the above materials are single crystal or polycrystalline, similar to the structure of diamond. When the upper surface of the substrate 10 has the materials of the above materials as the buffer layer 20, the heat transfer of the substrate 10 and the buffer layer 20 can be stable, and it is not easy to cause a sudden increase in thermal stress. The difference in thermal expansion coefficient between the upper surface of the buffer layer 20 and the growing diamond film 30 is small, the stress is uniform during the growth process, and the probability of film cracking is greatly reduced. The diamond film 30 finally prepared is of high quality, large area, and excellent physical and chemical properties.

[0063] In some embodiments of the present invention, Figure 1As shown, the material of the single-material substrate 11 is one of graphite, graphene, carbide, nitride, diamond particles, silicon, titanium, molybdenum, niobium, tantalum and tungsten. In other words, any one of the above materials can be selected to make the single-material substrate 11. For example, only graphite can be used as the material of the single-material substrate 11. Since graphite is not wear-resistant and easily scratched, it is necessary to completely cover the surface of the graphite with a buffer layer 20, so as to effectively prevent the substrate 10, which is only graphite material, from contaminating the chamber when the base structure 100 is manufactured. In other words, when the upper surface of the substrate 10 is a graphite layer, the buffer layer 20 located on the surface of the graphite layer wraps the graphite layer.

[0064] like Figure 2 , Figure 3 and Figure 4 As shown, the materials of the multi-material composite substrate 12 and the multi-material multi-layer substrate 13 are selected from at least two of graphite, graphene, carbide, nitride, diamond particles, silicon, titanium, molybdenum, niobium, tantalum and tungsten. For example, it can be a combination of graphite and carbide, or a combination of nitride and a metal, or a combination of graphene and nitride, or a combination of diamond particles and silicon carbide particles, or a multilayer structure combination of carbides and graphene of different crystal forms, or a combination of silicon and nitride, etc. The combination of the above materials cannot be exhaustive, but those skilled in the art should understand that any two or more of the above materials with certain differences in heat transfer properties and thermal expansion coefficients and that are relatively easy to obtain and easy to combine can be combined, so that the entire substrate 10 has better thermal conductivity, thermal buffering capacity, high temperature tolerance and cost controllability. It should also be noted that the thermal expansion coefficient of the material of the buffer layer 20 selected in the present invention must be smaller than the thermal expansion coefficient of the material of the adjacent substrate 10, so that the advantages of the setting of the buffer layer 20 can be reflected and the upper surface of the buffer layer 20 is not prone to stress due to the large difference in thermal expansion coefficient with the diamond film 30. In other words, the buffer layer 20 can satisfy the stable growth of the diamond film 30 in a uniform thermal environment.

[0065] Optionally, the particle size of the diamond particles selected in the above substrate 10 is in the range of 5nm to 300000nm. If the particle size of the diamond particles is too small and below 5nm or too large and above 300000nm, the preparation cost will be too high. If the particle size is too high, it will be inconvenient to sinter, the uniformity of the structure after sintering will be poor, or the preparation time required will be too long. If the particle size is too fine, the purchase cost will be too high. Therefore, the particle size of the diamond particles selected in the substrate 10 of the present invention should be controlled within a reasonable range to facilitate preparation and control the cost. Further, the particle size of the above diamond particles can be controlled within 50nm to 50000nm in order to achieve the above performance.

[0066] Optionally, the carbide is one of silicon carbide, titanium carbide, tungsten carbide or tantalum carbide, and the nitride is one of aluminum nitride, boron nitride, silicon nitride, titanium nitride, tungsten nitride and tantalum nitride. These materials are readily available on the market, such as Fig.15 As shown, the above carbides and nitrides are materials with good thermal conductivity, relatively low thermal expansion coefficient and high temperature tolerance. The carbides and nitrides in the substrate 10 can be selectively combined with the carbides and nitrides in the buffer layer 20 according to actual needs. In addition, the material properties selected for the substrate 10 and the buffer layer 20 should be different, so that the material selected for the buffer layer 20 can form a better affinity with the diamond film 30 than the material selected for the substrate 10, and has a lower thermal expansion coefficient and is closer to the crystal form of the diamond film 30. Fig.15 As shown in the figure, the relatively low thermal expansion coefficient referred to in the present invention refers to a thermal expansion coefficient value of the material less than 9×10 -6 K. The thermal expansion coefficients of materials such as graphite, graphene, silicon, silicon nitride, boron nitride, molybdenum, iridium, tungsten nitride, and tungsten carbide are closer to diamond. Furthermore, the thermal conductivity of graphene, molybdenum, iridium, boron nitride, tungsten, graphite, and tungsten carbide is closer to diamond. At the same time, it is also necessary to consider whether the material is easy to obtain, whether the processing is easy, the price of the raw materials used to prepare the required material, and the similarity between the crystal form of each material and the diamond crystal form, so as to comprehensively consider which materials are used to combine and make the substrate 10 and the buffer layer 20, and then grow the diamond film 30 on the surface of the buffer layer 20.

[0067] In some embodiments of the present invention, Figure 3 and Figure 4 The multi-material composite substrate 12 shown and Figure 7 The relative mass contents of the various materials selected in the multi-material multi-layer substrate 13 shown vary gradually at different positions of the substrate 10 .

[0068] Optionally, the relative content of each material by mass changes in a gradient, including: Figure 3As shown, the mass relative content of each material changes with the height of the substrate 10 from low to high and has a plurality of gradient mass relative contents of different sizes. The gradient mass relative content of each material in each layer can be an increasing trend or a decreasing trend, or only the mass content of the materials in each gradient layer is different. Here, the structure from the substrate 10 to the buffer layer 20 and then to the diamond film 30 is mainly from bottom to top. In these examples, the substrate 10 may include a plurality of gradient layers. The mass relative content of each material selected in each gradient layer has a gradient change from low to high as the height of the substrate 10 changes. For example, two materials A1 and A2 with a certain difference in thermal expansion coefficient can be selected, the sum of the volume percentage (or mass percentage) of A1 and A2 is 1, the first gradient layer 121 is located at the bottom layer, and the content percentage of material A1 in the first gradient layer 121 is B1; the second gradient layer 122 is located above the first gradient layer 121, and the content percentage of material A1 in the second gradient layer 122 is B2; the third gradient layer 123 is located above the second gradient layer 122, and the content percentage of material A1 in the third gradient layer 123 is B3, and B3>B2>B1; at the same time, the content percentage of material A2 in the first gradient layer 121 is C1, the content percentage of material A2 in the second gradient layer 122 is C2, and the content percentage of material A2 in the third gradient layer 123 is C3, and C1>C2>C3, B1+C1=1, B2+C2=1, B3+C3=1. Then, in these examples, the relative mass content percentages of the two materials A1 and A2 of each gradient layer can have a certain gradient change, so that the thermal buffering capacity of each gradient layer can be partially adjusted, and the mechanical properties of the entire substrate 10 can be more stable, the thermal conductivity can be better, and the thermal stability can be better, so that it is more suitable for the growth of the buffer layer 20 or the diamond film 30, so that the heat changes gradually, the thermal stress will not change suddenly, and the temperature changes evenly. It should be noted that the selected materials are not necessarily only two, but can also be three or more, but it is required that each material of each gradient layer can have a certain relative mass content percentage change, and the sum of the relative mass content percentages of each material is 1. It should also be noted that the number of layers of the selected gradient layer is not necessarily limited to the above-mentioned three layers, but can also be two layers, four layers or more layers, and should be selected according to actual conditions under the conditions of reasonable cost, reasonable thickness and easy preparation. In some examples, when the substrate 10 is a multi-material multi-layer substrate 13, the mass of the material in each gradient layer accounts for a gradient of the mass content of the total substrate 10. The mass proportion of the material in the gradient layer closer to the diamond film 30 is higher, thereby increasing the amount of material in the gradient layer and making the heat transfer in the gradient layer more balanced overall.

[0069] In some specific examples, such as Figure 3As shown, the materials of the multi-material composite substrate 12 are silicon carbide and diamond particles. The multi-material composite substrate 12 is divided into an upper layer, a middle layer and a lower layer. The mass ratio of diamond particles to silicon carbide in the lower layer is (70-95): (5-30), the mass ratio of diamond particles to silicon carbide in the middle layer is (40-65): (35-60), and the mass ratio of diamond particles to silicon carbide in the upper layer is (10-35): (65-90). The buffer layer 20 is polycrystalline silicon carbide, and a diamond film 30 is grown on the buffer layer 20. Polycrystalline silicon carbide as the buffer layer 20 has a fast growth rate and low preparation cost. That is, from the lower layer, the middle layer to the upper layer, the mass proportion of diamond particles in the material decreases successively, while the mass proportion of silicon carbide in the material increases successively. For example, in the upper layer, the mass ratio of diamond particles to silicon carbide is 70:30, in the middle layer, the mass ratio of diamond particles to silicon carbide is 40:60; in the lower layer, the mass ratio of diamond particles to silicon carbide is 10:90. For another example, in the upper layer, the mass ratio of diamond particles to silicon carbide is 95:5, in the middle layer, the mass ratio of diamond particles to silicon carbide is 65:35; in the lower layer, the mass ratio of diamond particles to silicon carbide is 35:65. For another example, in the upper layer, the mass ratio of diamond particles to silicon carbide is 80:20, in the middle layer, the mass ratio of diamond particles to silicon carbide is 50:50; in the lower layer, the mass ratio of diamond particles to silicon carbide is 25:75.

[0070] Optionally, the relative mass content of each material selected in the multi-material composite substrate 12 and the multi-material multi-layer substrate 13 changes in a gradient, and further includes, for example Figure 4As shown, the relative mass content of each material has multiple gradient relative mass contents of different sizes as the distance from the geometric center of the substrate 10 changes from near to far. In these examples, the substrate 10 to the buffer layer 20 and then to the diamond film 30 is mainly an inside-out structure, that is, a stacked and wrapped structure is used between each structure. Similarly, in these examples, the substrate 10 may include multiple gradient layers. The relative content of each material selected in each gradient layer has a gradient change from the inside to the outside. For example, still taking the example of selecting two materials A1 and A2 with a certain difference in thermal expansion coefficient, and the sum of the volume content percentage (or mass content percentage) of A1 and A2 being 1, the first gradient layer 121 is located in the innermost layer, and the mass content percentage of material A1 in the first gradient layer 121 is B1; the second gradient layer 122 is located on the outside of the first gradient layer 121 and wraps the first gradient layer 121 inside, and the mass content percentage of material A1 in the second gradient layer 122 is B2; the third gradient layer 123 is located in the third gradient layer 124, and the third gradient layer 125 is located in the fourth gradient layer 126. The outer side of the second gradient layer 122 and the second gradient layer 122 is wrapped inside, the mass content percentage of material A1 in the third gradient layer 123 is B3, and B3>B2>B1; at the same time, the mass content percentage of material A2 in the first gradient layer 121 is C1, the mass content percentage of material A2 in the second gradient layer 122 is C2, and the mass content percentage of material A2 in the third gradient layer 123 is C3, and C1>C2>C3, B1+C1=1, B2+C2=1, B3+C3=1. Then, in these examples, the content percentages of the two materials A1 and A2 in each gradient layer 121 can have a certain gradient change, so that the thermal buffering capacity of each gradient layer is partially adjusted, and the mechanical properties of the entire substrate 10 are more stable, the thermal conductivity is better, and the thermal stability is better, so that it is more suitable for the growth of the buffer layer 20 or the diamond film 30, so that the heat change is gradual, the thermal stress will not change suddenly, and the temperature distribution is uniform. Similarly, in these examples, the selected materials are not necessarily limited to only two, but can also be three or more, but it is required that each material in each gradient layer can have a certain content percentage change, and the sum of the percentages of each material is 1. It should also be noted that the number of layers of the selected gradient layer is not necessarily limited to three, but can also be two, four or more layers, and should be selected according to actual conditions under the conditions of reasonable cost, reasonable thickness, and easy preparation.

[0071] In some embodiments of the present invention, the multi-material multi-layer substrate 13 includes substrate layers of multiple materials, and substrate layers of at least two materials are alternately stacked. That is, each substrate layer is made of a single material, and the materials selected for two adjacent substrate layers are different, and each substrate layer of the material is repeated at least twice.

[0072] Optionally, the multi-material multi-layer substrate 13 includes graphene and silicon carbide alternately stacked at least twice, polycrystalline silicon carbide is selected as the buffer layer 20, and a diamond film 30 is grown on the surface of the polycrystalline silicon carbide. The graphene itself has an extremely thin structure and a high in-plane thermal conductivity, which can evenly distribute the heat in the substrate 10. The graphene and silicon carbide that are alternately stacked multiple times can achieve better thermal conductivity and better thermal stress transfer for the overall structure of the substrate 10. It should be noted that the materials that are alternately stacked at least twice may not be limited to graphene and silicon carbide, but may also be other two materials or multiple materials, at least one of which has extremely excellent thermal conductivity, extremely low thermal expansion coefficient and super high temperature resistance.

[0073] In some embodiments of the present invention, the material of the substrate 10 is selected from diamond particles, silicon carbide and silicon, and the mass ratio of diamond particles, silicon carbide and silicon is 5-50%: 50-95%: 0-20%. Diamond particles have the same composition as the diamond film 30 and have good thermal conductivity. Silicon carbide and diamond have similar thermal expansion coefficients, and both have low thermal expansion coefficients. Although the thermal expansion coefficient of silicon is higher than that of silicon carbide, compared with many metals or nitrides, its thermal expansion coefficient is also lower and has good heat transfer performance.

[0074] Optionally, the material of the substrate 10 is selected from graphite and silicon carbide, and the mass ratio of graphite to silicon carbide is 30-90%:10-70%. Graphite has excellent thermal conductivity, high temperature resistance and extremely low thermal expansion coefficient, but graphite is not wear-resistant; while silicon carbide has a lower thermal expansion coefficient and better thermal conductivity. The combination of the two can achieve excellent comprehensive properties such as low thermal expansion coefficient, high thermal conductivity, high temperature resistance, and strong mechanical properties.

[0075] Optionally, the material of the substrate 10 is selected from aluminum nitride and molybdenum, and the mass ratio of aluminum nitride to molybdenum is 65-95%:5-35%. Aluminum nitride has high thermal conductivity and low expansion coefficient, fast heat transfer, and is not easily damaged or deformed by thermal stress. The thermal expansion coefficient of metal molybdenum is extremely low, which can further adjust the comprehensive properties of the thermal expansion coefficient of the entire substrate 10.

[0076] A base structure 100 that does not require an additional buffer layer 20 is described below.

[0077] The present invention proposes a substrate structure 100 on which a diamond film 30 is grown, such as Figure 6 and Figure 7 As shown, it includes a substrate 10 and a diamond film 30. That is, in these examples, there is no need to add an additional buffer layer 20. The substrate 10 has a thermal conductivity greater than or equal to 20 W / mK and a thermal expansion coefficient less than 9×10 -6The multi-material composite substrate 12 or multi-material multilayer substrate 13 of K is a multi-material composite substrate 12 or multi-material multilayer substrate 13. The material of the substrate 10 is selected from at least two of graphite, graphene, carbide, nitride, silicon, titanium, molybdenum, niobium, tantalum and tungsten; the carbide and nitride are single crystal thin films or polycrystalline thin films, and a diamond film 30 is grown on at least the upper surface of the substrate 10, and the upper surface area of ​​the diamond film is 13mm 2 ~465000mm 2 .

[0078] It should be noted that in the present invention, the outer surface of the substrate 10 includes an upper surface, a lower surface and a side surface. The upper surface is usually larger in area, relatively flat, and has a large space in contact with the reaction gas. When the substrate 10 is thin, the side surface has a small space in contact with the reaction gas, which is not conducive to the reaction. The area of ​​the side surface is usually uneven, has an arc or is small. The lower surface is usually used to contact the reaction vessel, and no or very small amounts of diamond film 30 are grown. Then, the diamond film 30 of the present invention is at least grown on the upper surface of the substrate 10. In some examples, it can also be grown on the upper surface and the side surface of the substrate 10 at the same time, completely covering the exposed surface of the substrate 10. Then, the diamond film 30 in these examples of the present invention mainly refers to the diamond film 30 grown on the upper surface of the substrate 10. When the diamond film 30 is grown on the side surface of the substrate 10, the surface area of ​​the diamond film 30 located on the side surface is not counted, and only the surface area of ​​the diamond film 30 grown on the upper surface of the substrate 10 is counted, that is, the upper surface area of ​​the diamond film 30 described in this application.

[0079] As can be seen from the above technical scheme, another substrate structure 100 with a diamond film 30 grown thereon proposed by the present invention, the substrate 10 itself is made of a variety of materials, has high thermal conductivity and support performance, the selected material has a relatively small difference in thermal expansion coefficient with diamond, and has good thermal conductivity and high temperature resistance, so when the diamond film 30 is grown on the surface of the substrate 10, the temperature can be evenly transferred, and there will be no sudden increase in thermal stress, and it is not easy to cause the surface diamond film 30 to crack due to the influence of temperature difference. Carbide and nitride are both single crystal films or polycrystalline films, and the multi-material composite substrate 12 or multi-material multi-layer substrate 13 made of a variety of materials has a strong affinity with diamond. When the substrate 10 is heated, the heat is quickly transferred on the substrate 10, the thermal stability is high, and it is not easy to cause a sudden increase in thermal stress. The difference in thermal expansion coefficient between the upper surface of the substrate 10 and the grown diamond film 30 is small, the stress is uniform during the growth process, and the probability of film cracking is greatly reduced. The diamond film 30 finally prepared is of high quality, large area, and excellent physical and chemical properties.

[0080] In these examples, carbides and nitrides may also be selected from the materials in the aforementioned examples. Carbides may be silicon carbide, titanium carbide, tungsten carbide or tantalum carbide; nitrides may be aluminum nitride, boron nitride, silicon nitride, titanium nitride, tungsten nitride or tantalum nitride.

[0081] like Fig.15 As shown, the thermal expansion coefficients of materials such as graphite, graphene, silicon, silicon nitride, boron nitride, molybdenum, tungsten nitride, and tungsten carbide selected in the present invention are closer to diamond. Furthermore, the thermal conductivity of graphene, molybdenum, boron nitride, tungsten, graphite, and tungsten carbide is closer to diamond. At the same time, it is also necessary to consider whether the material is easy to obtain, whether the processing is easy, the price of the raw materials used to prepare the required material, and the similarity between the crystal form of each material and the diamond crystal form, so as to comprehensively consider which materials to use in combination to make a multi-material composite substrate 12 or a multi-material multi-layer substrate 13, and grow a diamond film 30 on the surface of the substrate 10.

[0082] It should be noted that in the aforementioned examples of the substrate 10 provided with a buffer layer 20, the limitations on the thickness, roughness, and range of the upper surface area of ​​the substrate 10, as well as the selection of the material of the substrate 10 are all applicable to the example of growing a diamond film 30 directly on the substrate 10 in the present invention, and will not be elaborated here.

[0083] The following describes a method for preparing the diamond film 30 using the base structure 100 formed by the substrate 10 provided with the buffer layer 20 .

[0084] The present invention provides a method for preparing a diamond film 30, which is used to prepare a diamond film 30 on a substrate structure 100 on which a diamond film 30 is grown on the buffer layer 20, wherein the substrate structure 100 includes a buffer layer 20, such as Figure 8 and Fig. 9 As shown, the preparation method comprises the following steps:

[0085] The substrate 10 is prepared by chemical vapor deposition or hot pressing sintering. The structure and material of the substrate 10 can refer to the description of the substrate 10 in the above examples, and will not be repeated here. In particular, the upper surface area of ​​the substrate 10 should be within the range of 12 mm. 2 ~460000mm 2 The thickness of the substrate 10 ranges from 0.5 mm to 30 mm; the surface roughness of the substrate 10 ranges from 1 nm to 1,000,000 nm.

[0086] The buffer layer 20 is prepared on the substrate 10 by bonding method, chemical vapor deposition method or physical vapor deposition method. The structure and material selection of the buffer layer 20 are described in the above-mentioned examples, and will not be repeated here. In particular, the thickness of the buffer layer 20 ranges from 10nm to 50000nm, which needs to be controlled during the preparation process.

[0087] The substrate 10 with the buffer layer 20 is cleaned with a lotion; the substrate 10 with the buffer layer 20 is ultrasonically treated in deionized water for 10 minutes to 60 minutes, and then dried. Optionally, the lotion is one or more of deionized water, anhydrous ethanol or acetone, and the substrate 10 with the buffer layer 20 can be cleaned with the lotion to reduce impurities, increase the purity of the surface, and facilitate subsequent processing.

[0088] The substrate 10 with the buffer layer 20 is treated with a surface cleaner in an ozone atmosphere to make the surface of the buffer layer 20 active. This step can prepare for growing diamond seeds 31 on the buffer layer 20 .

[0089] A diamond particle suspension is prepared, and the buffer layer 20 and the substrate 10 with active surfaces are ultrasonically treated in the diamond particle suspension for 10 minutes to 60 minutes, so that the surface of the buffer layer 20 is provided with diamond seeds 31. Optionally, the diamond particle suspension is prepared by mixing diamond nanocrystalline liquid and deionized water in a mass ratio of 1:20 to 50. If the mass ratio is too high, higher than 1:20, the cost is high and the diamond nanocrystalline liquid is consumed more; if the mass ratio is too low, for example, lower than 1:50, it is not conducive to the rapid growth of diamond seeds 31 on the surface of the buffer layer 20, and the preparation time is long. By setting the diamond particle suspension in the above mass ratio range, the consumption of diamond nanocrystalline liquid can be moderate, and the diamond particle suspension can be kept at a certain concentration, and diamond seeds 31 can be quickly formed on the surface of the buffer layer 20, with low comprehensive preparation cost and high preparation efficiency.

[0090] Drying the buffer layer 20 and substrate 10 with diamond seeds 31. This is beneficial to subsequent chemical vapor deposition. Optionally, when drying the buffer layer 20 and substrate 10 with diamond seeds 31, it is done in a nitrogen atmosphere, using a heating table at a temperature of 60°C to 90°C. Nitrogen is a protective gas with stable properties, which prevents the diamond seeds 31, buffer layer 20 or substrate 10 from encountering other reactive gases and participating in the reaction, thereby maintaining the purity of the structure and drying quickly.

[0091] The substrate 100 is placed in a microwave plasma chemical vapor deposition device, and a mixed gas of methane, hydrogen and oxygen is introduced as a reaction gas to deposit a diamond film 30 on the surface of the buffer layer 20 to form a base structure 100 .

[0092] The diamond film 30 is obtained by grinding the base structure 100 and / or soaking the base structure 100 in an acid solution to remove the substrate 10 and the buffer layer 20. Optionally, the acid solution is one or more of a hydrochloric acid solution, a nitric acid solution, a hydrofluoric acid solution, and a sulfuric acid solution. By making a reasonable selection, some acid solutions can corrode some types of substrates 10 and buffer layers 20, and some acid solutions can quickly corrode the remaining buffer layer 20 and other substances attached to the surface of the diamond film 30 without reacting with the diamond film 30, so that the finished diamond film 30 has high purity and good stripping effect.

[0093] For example, when the acid solution is selected, when the substrate 10 or the buffer layer 20 of the present application is a silicon layer, dilute hydrofluoric acid can be selected for removal.

[0094] For example, when the substrate 10 of the present application adopts a molybdenum metal layer, concentrated nitric acid may be selected for removal.

[0095] For example, when the buffer layer 20 of the present application is an iridium metal layer, it can be removed by using aqua regia or nitric acid solution.

[0096] For example, when the substrate 10 of the present application has a titanium metal layer, a tungsten metal layer, a niobium metal layer or a tantalum metal layer, hydrofluoric acid (HF) or a mixture of hydrofluoric acid and other acids (such as nitric acid) can be selected for removal because they have high chemical stability. If necessary, a mixture of hydrofluoric acid and hydrogen peroxide solution can be used to accelerate the removal of the tantalum metal layer.

[0097] For example, when carbide is selected as the material of the substrate 10 or the buffer layer 20 of the present application, a strong acid such as hydrofluoric acid or concentrated sulfuric acid may be used for removal.

[0098] For example, when the material of the substrate 10 or the buffer layer 20 of the present application is nitride such as silicon nitride, it is generally highly resistant to acid and can be removed using a mixture of hydrofluoric acid and water.

[0099] It can be seen from the above technical solutions that the method for preparing the diamond film 30 proposed by the present invention requires few instruments during the preparation process, the preparation environment is controllable, and the temperature and gas conditions during the preparation process are easy to control. The diamond seed crystals 31 formed on the surface of the buffer layer 20 of the present invention can be used as mother crystals in the subsequent growth of the diamond film 30, and further grow together to form the diamond film 30, thereby shortening the preparation time of the diamond film 30 and improving the preparation efficiency. During the preparation process, the nucleation and growth of the diamond film 30 are uniform, the temperature is uniform during the film formation process, and the film cracking is not easy to occur. During the stripping, not only physical stripping methods can be used, but also chemical stripping methods can be used, so that the final prepared diamond film 30 has high quality and a large film forming area.

[0100] Specifically, the method for depositing the diamond film 30 is as follows: in a microwave plasma chemical vapor deposition device, the substrate 10 with the diamond seed 31 is first placed on a molybdenum table with a groove, and the height of the substrate 10 with the diamond seed 31 is 0.1 mm to 2 mm higher than the edge of the molybdenum table, so as to facilitate the deposition of the diamond film 30. The substrate 10 with the diamond seed 31 and the molybdenum table are placed together in the microwave plasma chemical vapor deposition device, and the vacuum is evacuated to 1×10 -4 Pa, hydrogen with a flow rate of 300sccm to 600sccm of hydrogen, 0.5% to 5% by volume of methane, 0.01% to 0.5% by volume of oxygen mixed gas, the total gas pressure is 9kPa to 16kPa, the working power of the microwave plasma chemical vapor deposition device is 3kW to 8kW, and surface deposition is carried out.

[0101] It should be noted that, since the base structure 100 is placed in a molybdenum table, the molybdenum table has a certain groove and depth, the substrate 10 and the buffer layer 20 are placed in the groove, and the side surface has less contact space with the gas in the reaction chamber, then the diamond seed 31 of the present invention mainly grows on the upper surface of the buffer layer 20, the density of the diamond seed 31 on the upper surface is relatively large, and part of the diamond seed 31 grows on the side of the buffer layer 20. The diamond film 30 located on the buffer layer 20 also grows mostly on the upper surface of the buffer layer 20, and grows less and thinner on the side of the buffer layer 20. If part of the diamond film 30 on the side of the buffer layer 20 needs to be removed, it can be removed by cutting and grinding.

[0102] The following describes a method for preparing the diamond film 30 grown directly on the substrate 10.

[0103] The present invention provides a method for preparing a diamond film 30, which is used to prepare a diamond film 30 in a base structure 100 having a diamond film 30 grown on the substrate 10, wherein the diamond film 30 is a nanocrystalline diamond film 30 and / or a microcrystalline diamond film 30, such as Fig.10 and Fig.11 As shown, the preparation method comprises the following steps:

[0104] The substrate 10 is prepared by chemical vapor deposition. The structure and material of the substrate 10 can refer to the description of the substrate 10 in the above examples, and will not be repeated here. In particular, the upper surface area of ​​the substrate 10 should be within the range of 12 mm. 2 ~460000mm 2 The thickness of the substrate 10 ranges from 0.5 mm to 30 mm; the surface roughness of the substrate 10 ranges from 1 nm to 1,000,000 nm.

[0105] The substrate 10 is cleaned with a lotion, ultrasonically treated in deionized water for 10 to 60 minutes, and dried. Optionally, the lotion is one or more of deionized water, anhydrous ethanol, or acetone. The lotion can clean the substrate 10, reduce impurities, increase surface purity, and facilitate subsequent processing.

[0106] The substrate 10 is treated with a surface cleaner in an ozone atmosphere to make the surface of the substrate 10 active. This step can prepare for growing diamond seeds 31 on the substrate 10 .

[0107] A diamond particle suspension is prepared, and the substrate 10 with active surface is ultrasonically placed in the diamond particle suspension for 10 minutes to 60 minutes, so that the surface of the substrate 10 is covered with diamond seeds 31 .

[0108] Optionally, the diamond particle suspension is prepared by mixing diamond nanocrystal liquid and deionized water at a mass ratio of 1:20 to 50. If the mass ratio is too high (higher than 1:20), the cost is high and the diamond nanocrystal liquid is consumed more; if the mass ratio is too low (e.g., lower than 1:50), it is not conducive to the rapid growth of diamond seeds 31 on the surface of the substrate 10, and the preparation time is long. By setting the diamond particle suspension within the above mass ratio range, the consumption of diamond nanocrystal liquid can be moderate, and the diamond particle suspension can be kept at a certain concentration, and the diamond seeds 31 can be quickly formed on the surface of the substrate 10, with low comprehensive preparation cost and high preparation efficiency.

[0109] Drying the substrate 10 with the diamond seed crystal 31 is beneficial to the subsequent chemical vapor deposition. Optionally, when drying the substrate 10 with the diamond seed crystal 31, it is dried in a nitrogen atmosphere using a heating table at a temperature of 60 to 90° C. Nitrogen is a protective gas with stable properties, which prevents the diamond seed crystal 31 or the substrate 10 from encountering other reactive gases and participating in the reaction, thereby maintaining the purity of the structure and drying quickly.

[0110] The substrate 10 is placed in a microwave plasma chemical vapor deposition device, and a mixed gas of methane, hydrogen and oxygen is introduced as a reaction gas to deposit a diamond film 30 on the surface of the substrate 10 to form a base structure 100 .

[0111] The base structure 100 is ground to obtain the diamond film 30; and / or, the base structure 100 is immersed in an acid solution to obtain the diamond film 30. Optionally, the acid solution is one or more of hydrochloric acid solution, nitric acid solution, hydrofluoric acid, and sulfuric acid. The acid solution can quickly corrode the remaining metal substances attached to the surface of the diamond film 30, and the acid solution will not react with the diamond film 30, so that the finished diamond film 30 has high purity and good stripping effect.

[0112] It can be seen from the above technical solutions that the present invention proposes a method for preparing a diamond film 30 directly on a substrate 10. The diamond seed crystal 31 formed on the surface of the substrate 10 can be used as a mother crystal when the diamond film 30 is subsequently grown, and further grows together to form a diamond film 30, thereby shortening the preparation time of the diamond film 30 and improving the preparation efficiency. During the preparation process, the nucleation and growth of the diamond film 30 located on the multi-material composite substrate 12 or the multi-material multi-layer substrate 13 are uniform, the temperature is uniform during the film formation process, and film cracks are not likely to occur. The final prepared diamond film 30 has high quality and a large film formation area.

[0113] Specifically, the method for depositing the diamond film 30 is as follows: in a microwave plasma chemical vapor deposition device, the substrate 10 with the diamond seed 31 is first placed on a molybdenum table with a groove, and the height of the substrate 10 with the diamond seed 31 is 0.1 mm to 2 mm higher than the edge of the molybdenum table, so as to facilitate the deposition of the diamond film 30. The substrate 10 with the diamond seed 31 and the molybdenum table are placed together in the microwave plasma chemical vapor deposition device, and the vacuum is evacuated to 1×10 -4 Pa, hydrogen with a flow rate of 300sccm to 600sccm of hydrogen, 0.5% to 5% by volume of methane, 0.01% to 0.5% by volume of oxygen mixed gas, the total gas pressure is 9kPa to 16kPa, the working power of the microwave plasma chemical vapor deposition device is 3kW to 8kW, and surface deposition is carried out.

[0114] It should be noted that in the case of directly growing the diamond film 30 on the multi-material multi-layer substrate 13, due to the limited space between the side of the substrate 10 and the molybdenum platform, and the squeezing of the crystals of the diamond film 30 and the crystals of some substances on the substrate 10, the diamond film 30 on the side of the substrate 10 is very thin and can be ignored.

[0115] The substrate structure 100 on which the diamond film 30 is grown and the method for preparing the diamond film 30 of the present application are further described below with reference to specific embodiments.

[0116] Example 1

[0117] like Figure 1 As shown, the substrate 10 is formed of a single material substrate 11 using sintered graphite, the buffer layer 20 is made of polycrystalline silicon carbide, a layer of polycrystalline silicon carbide is wrapped around the outside of the graphite, and a diamond film 30 is grown on the surface of the polycrystalline silicon carbide. The graphite thickness is 2 mm, the polycrystalline silicon carbide is 25 μm, and the substrate 10 is grown with a diameter of 2 inches.

[0118] like Figure 8 As shown, the specific preparation method of the diamond film 30 in this embodiment is:

[0119] The graphite particles are sintered at a high temperature to provide a graphite substrate as the single-material substrate 11 .

[0120] The silicon carbide layer is prepared as the buffer layer 20 by chemical vapor deposition.

[0121] The graphite with silicon carbide was cleaned with deionized water and anhydrous ethanol, and ultrasonically treated in deionized water for 20 minutes, and the surface was dried with nitrogen, placed in a surface cleaner and dried with ozone gas for 10 minutes to make the silicon carbide surface active, and then placed in a diamond suspension and ultrasonically treated for 20 minutes to make the silicon carbide buffer layer 20 surface with diamond seeds 31 (such as Fig. 9 As shown), the diamond suspension is prepared by mixing diamond nanocrystal liquid and deionized water in a mass ratio of 1:20.

[0122] After the ultrasonic treatment, the samples were blown dry with nitrogen and then placed on a heating platform at 80 °C for drying.

[0123] The processed silicon carbide and graphite with diamond seed 31 are placed in a molybdenum table with a groove and placed on the deposition base of the chemical vapor deposition device. -4 After the pressure drops below 0.04 Pa, hydrogen with a hydrogen flow rate of 500 sccm, methane with a methane flow rate of 10 sccm (accounting for 2% of the volume of hydrogen) and oxygen with a flow rate of 2.5 sccm (accounting for 0.5% of the volume of hydrogen) are introduced as reaction gases. The gas pressure is 14 kPa, the operating power of the microwave plasma chemical vapor deposition device is 5 kW, the temperature of the base is 900°C, the deposition time is controlled at 100 h, and a diamond film 30 is deposited on the surface of the silicon carbide to form a substrate structure 100.

[0124] like Fig. 9 As shown, physical grinding is used to remove silicon carbide and graphite to obtain a diamond film 30. Finally, the upper surface area of ​​the diamond film 30 is 2040 mm 2 .

[0125] like Fig.12 As shown in FIG. 1 , the Raman spectrum data shows that the Raman peak appears at 1332.4, the FWHM is 4.64, and the Raman peak is sharp, indicating that the diamond film 30 prepared by the present invention has high crystallinity and good purity. Fig.13 As shown, by analyzing the XRD spectrum of the diamond film 30, it can be found that the diamond peaks are mainly 220, which shows that the grain orientation of the diamond film 30 is consistent and the quality is high. Fig.14 As shown, by analyzing the data graph of transmittance from visible light to near infrared, it can be obtained that the final sample has a high transmittance (60%) in the infrared region, indicating that the diamond film 30 of the present invention can be used as an optical window.

[0126] In Example 1, graphite can also be replaced by any material selected from the group consisting of titanium carbide, tungsten carbide, tantalum carbide, aluminum nitride, boron nitride, silicon nitride, titanium nitride, tungsten nitride, tantalum nitride, graphene, diamond particles, silicon, titanium, molybdenum, niobium, tantalum and tungsten, which are different from the material of the buffer layer 20; or silicon carbide can be replaced by a material layer that is different from the material of the substrate 10 and has a lower thermal expansion coefficient, such as titanium carbide, tungsten carbide, tantalum carbide, aluminum nitride, boron nitride, silicon nitride, titanium nitride, tungsten nitride, tantalum nitride, silicon or iridium, so as to obtain a structure with similar functions to the above-mentioned base structure 100 of this embodiment. Details are not given here, and technicians in this field should understand that these should all fall within the scope of protection of the present invention.

[0127] Example 2

[0128] like Figure 2 As shown, aluminum nitride and molybdenum are used as the multi-material composite substrate 12, iridium is used as the buffer layer 20, and a diamond film 30 is grown on the surface of the iridium. The thickness of the multi-material composite substrate 12 is 2.2 mm, the thickness of the iridium is 0.1 μm, and the growth diameter of the substrate 10 is 1 inch.

[0129] like Figure 8 As shown, the specific preparation method of the diamond film 30 in this embodiment is:

[0130] The multi-material composite substrate 12 is prepared by hot pressing and sintering using 25% by volume of molybdenum with a particle size of 3 μm and 75% by volume of aluminum nitride powder with a particle size of 20 μm.

[0131] The iridium is bonded to the surface of the multi-material composite substrate 12 by a bonding method to form a buffer layer 20 .

[0132] The multi-material composite substrate 12 with iridium was ultrasonically treated in deionized water for 30 minutes, the surface was dried with nitrogen, placed in a surface cleaner and dried with ozone gas for 20 minutes to make the silicon carbide surface active, and then placed in a diamond suspension for ultrasonic treatment for 30 minutes to make the surface of the silicon carbide buffer layer 20 with diamond seeds 31 (such as Fig. 9 As shown), the diamond suspension is prepared by mixing diamond nanocrystal liquid and deionized water in a mass ratio of 1:30.

[0133] After the ultrasonic treatment, the samples were blown dry with nitrogen and then placed on a heating platform at 70 °C for drying.

[0134] The processed buffer layer 20 and substrate 10 with diamond seed crystals 31 are placed in a molybdenum table with a groove and placed on a deposition base of a chemical vapor deposition device. -4After the pressure drops below Pa, hydrogen with a hydrogen flow rate of 400sccm, methane with a methane flow rate of 10sccm (accounting for 2.5% of the volume percentage of hydrogen) and oxygen with a flow rate of 2sccm (accounting for 0.5% of the volume percentage of hydrogen) are introduced as reaction gases. The gas pressure is 13kPa, the operating power of the microwave plasma chemical vapor deposition device is 7kW, the temperature of the base is 900°C, the deposition time is controlled at 200h, and a diamond film 30 is deposited on the iridium surface to form a substrate structure 100.

[0135] like Fig. 9 As shown, physical grinding is used to remove molybdenum, aluminum nitride and part of iridium, and then nitric acid solution is used to remove the remaining iridium to obtain a diamond film 30. Finally, the upper surface area of ​​the diamond film 30 is 515mm 2 .

[0136] The aluminum nitride and molybdenum in this embodiment can also be replaced by a composite of other nitrides (such as titanium nitride, tungsten nitride, tantalum nitride or boron nitride) and iridium; or a mixture of aluminum nitride and other metals (such as titanium, niobium, tantalum and tungsten) to form other structures with similar performance to this embodiment. These will not be described in detail here. Those skilled in the art should understand that these should all fall within the scope of protection of the present invention.

[0137] Example 3

[0138] like Figure 3 As shown, the substrate 10 uses two materials, diamond particles and silicon carbide particles, as a multi-material composite substrate 12. The relative content of diamond particles and silicon carbide particles in the multi-material composite substrate 12 changes with the height range of the substrate 10 to form three gradient layers, which are the first gradient layer 121 of the lower layer, the second gradient layer 122 of the middle layer, and the third gradient layer 123 of the upper layer from bottom to top. A polycrystalline silicon carbide buffer layer 20 is used, and a diamond film 30 is grown on the surface of the buffer layer 20. In the first gradient layer 121, the mass ratio of diamond particles to silicon carbide is 70:30; in the second gradient layer 122, the mass ratio of diamond particles to silicon carbide is 40:60; in the third gradient layer 123, the mass ratio of diamond particles to silicon carbide particles is 10:90. Among them, the thickness of the multi-material composite substrate 12 is 2 mm, the diameter of the multi-material composite substrate 12 is 2 inches, and the thickness of the polycrystalline silicon carbide buffer layer is 0.2 mm.

[0139] like Figure 8 As shown, the specific preparation method of the diamond film 30 in this embodiment is:

[0140] A first gradient layer 121 is prepared by hot pressing and sintering using diamond particles with a mass percentage of 70% and a particle size of 5 μm and silicon carbide particles with a mass percentage of 30% and a particle size of 1 μm; then, 60% of diamond particles and 40% of silicon carbide particles are sintered on the first gradient layer 121 as a second gradient layer 122; finally, 10% of diamond particles and 90% of silicon carbide particles are sintered on the second gradient layer 122 as a third gradient layer 123, forming a multi-material composite substrate 12 in which the content of each material in different gradient layers varies along the height direction.

[0141] Polycrystalline silicon carbide is connected to the surface of the multi-material composite substrate 12 by chemical vapor deposition to form a buffer layer 20 .

[0142] The multi-material composite substrate 12 with polycrystalline silicon carbide was cleaned with deionized water and anhydrous ethanol, and ultrasonically treated in deionized water for 40 minutes, and the surface was dried with nitrogen, placed in a surface cleaner and dried with ozone gas for 40 minutes to make the surface of the polycrystalline silicon carbide active, and then ultrasonically treated in a diamond suspension for 40 minutes to make the surface of the buffer layer 20 of the polycrystalline silicon carbide with diamond seeds 31 (such as Fig. 9 As shown), the diamond suspension is prepared by mixing diamond nanocrystal liquid and deionized water in a mass ratio of 1:50.

[0143] After the ultrasonic treatment, the samples were blown dry with nitrogen and then placed on a heating platform at 60 °C for drying.

[0144] The processed buffer layer 20 and substrate 10 with diamond seed crystals 31 are placed in a molybdenum table with a groove and placed on a deposition base of a chemical vapor deposition device. -4 Pa, hydrogen with a hydrogen flow rate of 600sccm, methane with a methane flow rate of 30sccm (accounting for 5% of the volume percentage of hydrogen) and oxygen with a flow rate of 3sccm (accounting for 0.5% of the volume percentage of hydrogen) are introduced as reaction gases, the gas pressure is 16kPa, the operating power of the microwave plasma chemical vapor deposition device is 8kW, the temperature of the base is 900℃, the deposition time is controlled at 400h, and a diamond film 30 is deposited on the surface of the polycrystalline silicon carbide to form a substrate structure 100.

[0145] like Fig. 9 As shown, the multi-material composite substrate 12 and polycrystalline silicon carbide are removed by physical grinding to obtain a diamond film 30. Finally, the upper surface area of ​​the diamond film 30 is 2100 mm 2 .

[0146] The composite of diamond particles and silicon carbide particles in the present embodiment can also be replaced by a composite of diamond particles and other types of carbides (such as titanium carbide, tungsten carbide or tantalum carbide), or replaced by a composite of silicon carbide particles and nitride particles (such as aluminum nitride, boron nitride, silicon nitride, titanium nitride, tungsten nitride and tantalum nitride), so as to form a structure with similar functions to the above-mentioned base structure 100 of the present embodiment. Details are not given here, and those skilled in the art should understand that these should all fall within the scope of protection of the present invention.

[0147] Example 4

[0148] like Figure 4 As shown, the substrate 10 uses two materials, metal tungsten and boron nitride, as the multi-material composite substrate 12. The relative content of metal tungsten and boron nitride in the multi-material composite substrate 12 changes with the radius size and height range of the substrate 10 to form three gradient layers, which are the first gradient layer 121, the second gradient layer 122 and the third gradient layer 123 from the inside to the outside. Silicon nitride is used as the buffer layer 20, and a diamond film 30 is grown on the surface of the buffer layer 20. In the first gradient layer 121, the mass ratio of metal tungsten and boron nitride is 80:20; in the second gradient layer 122, the mass ratio of diamond particles and silicon carbide is 40:60; in the third gradient layer 123, the mass ratio of diamond particles and silicon carbide is 60:40. The diameter of the multi-material composite substrate 12 is 2 inches.

[0149] like Figure 8 As shown, the specific preparation method of the diamond film 30 in this embodiment is:

[0150] Boron nitride powder with an average particle size of 3 μm and tungsten powder with an average particle size of 6 μm were used in a mass ratio of 20:80, and the first gradient layer 121 was prepared by hot pressing and sintering; then, boron nitride powder and tungsten powder with a mass ratio of 60:40 were wrapped on the first gradient layer 121, and the second gradient layer 122 was prepared by hot pressing and sintering; finally, boron nitride powder and tungsten powder with a mass ratio of 40:60 were wrapped on the outside of the second gradient layer 122, and the third gradient layer 123 was prepared by hot pressing and sintering, forming a multi-material composite substrate 12 in which the relative content of each material changes with the radius range of the substrate 10 to form a gradient. The actual width ratio of the first gradient layer 121, the second gradient layer 122, and the third gradient layer 123 from the center of the substrate 10 is 3:4:3. In specific operations, high-temperature sintering can be performed by adopting a graded mixing technology: a cylindrical mold is made according to the three areas corresponding to the first gradient layer 121, the second gradient layer 122, and the third gradient layer 123, and each area corresponds to a part of the substrate; according to the designed mass ratio, metal tungsten powder and boron nitride powder are respectively filled into each area of ​​the mold, and the powders are compacted and sintered at high temperature; a multi-material composite substrate 12 is formed, in which the relative content of each material changes with the radius range of the substrate 10 to form a gradient.

[0151] Silicon nitride is connected to the surface of the multi-material composite substrate 12 by chemical vapor deposition to form a buffer layer 20 .

[0152] The multi-material composite substrate 12 with silicon nitride was cleaned with deionized water and anhydrous ethanol, and ultrasonically treated in deionized water for 50 minutes, and the surface was dried with nitrogen, placed in a surface cleaner and dried with ozone gas for 50 minutes to make the silicon nitride surface active, and then placed in a diamond suspension for ultrasonic treatment for 60 minutes to make the surface of the silicon nitride buffer layer 20 with diamond seeds 31 (such as Fig. 9 As shown), the diamond suspension is prepared by mixing diamond nanocrystal liquid and deionized water in a mass ratio of 1:25.

[0153] After the ultrasonic treatment, the samples were blown dry with nitrogen and then placed on a heating platform at 75°C for drying.

[0154] The processed buffer layer 20 and substrate 10 with diamond seed crystals 31 are placed in a molybdenum table with a groove and placed on a deposition base of a chemical vapor deposition device. -4Pa, hydrogen with a hydrogen flow rate of 300sccm, methane with a methane flow rate of 12sccm (accounting for 4% of the volume percentage of hydrogen) and oxygen with a flow rate of 0.09sccm (accounting for 0.3% of the volume percentage of hydrogen) are introduced as reaction gases, the gas pressure is 15kPa, the operating power of the microwave plasma chemical vapor deposition device is 7kW, the temperature of the base is 900℃, the deposition time is controlled at 350h, and a diamond film 30 is deposited on the surface of silicon nitride to form a substrate structure 100.

[0155] like Fig. 9 As shown, the multi-material composite substrate 12 and polycrystalline silicon carbide are removed by physical grinding to obtain a diamond film 30. Finally, the upper surface area of ​​the diamond film 30 is 2080 mm 2 .

[0156] The boron nitride in this embodiment can be replaced by other nitrides such as aluminum nitride, silicon nitride, titanium nitride, tungsten nitride and tantalum nitride, or tungsten can be replaced by other metals such as titanium, molybdenum, niobium, tantalum, and the buffer layer 20 can be replaced by silicon nitride with silicon carbide, thereby forming a structure with similar functions to the above-mentioned base structure 100 of this embodiment. It will not be elaborated here, and technicians in this field should understand that these should all fall within the scope of protection of the present invention.

[0157] Example 5

[0158] like Figure 5 As shown, the substrate 10 uses single-crystal silicon carbide, graphene, and polycrystalline silicon carbide as a multi-material multi-layer substrate 13, and polycrystalline silicon carbide is selected as a buffer layer 20, and a diamond film 30 is grown on the surface of the polycrystalline silicon carbide. Specifically, the multi-material multi-layer substrate 13 includes a 0.35 mm single-crystal silicon carbide layer A, a graphene layer B, a 0.2 mm polycrystalline silicon carbide layer C, a graphene layer B, a 0.35 mm single-crystal silicon carbide layer A, a graphene layer B, a 0.2 mm polycrystalline silicon carbide layer C, and a graphene layer B from bottom to top; and a layer of polycrystalline silicon carbide is grown on the surface of the top graphene layer B as a buffer layer 20, and a diamond film 30 is grown on the surface of the buffer layer 20. The diameter of the multi-material multi-layer substrate 13 is 2 inches.

[0159] like Figure 8 As shown, the specific preparation method of the diamond film 30 in this embodiment is:

[0160] The cleaned and dried single crystal silicon carbide is cleaned and dried as single crystal silicon carbide layer A. The single crystal silicon carbide layer A is fixed in a plasma enhanced chemical vapor deposition reaction chamber to ensure that the interior of the reaction chamber is clean and free of dust and impurities; the reaction chamber is evacuated to 10 -5Torr, the silicon carbide substrate is heated to a temperature of 1350°C, 15 sccm of methane is introduced as a carbon source, 1000 sccm of hydrogen is introduced as a reducing gas, and the chamber pressure is controlled to be 30 Torr. After a certain deposition time, for example, 20 minutes, methane is decomposed on the substrate surface, and a layer of graphene layer B is generated under the action of hydrogen. After the deposition is completed, the precursor gas is turned off, argon gas is continued to be introduced, and it is slowly cooled to room temperature to form a structure of a single crystal silicon carbide layer A and a graphene layer B; the substrate with the graphene layer B deposited is then fixed on the sample holder of the hot wire chemical vapor deposition reaction chamber, and the reaction chamber is evacuated to 10 -5 Torr or less; introduce 1000sccm of hydrogen as a diluent gas, and heat the entire graphene layer B and the single-crystalline silicon carbide layer A to a deposition temperature of 1100°C. Introduce reaction gas: after the temperature reaches 1100°C, introduce 100sccm of silane gas and 50sccm of methane gas as precursor gas. Control the chamber pressure to 100torr, and deposit for 10 hours to obtain a polycrystalline silicon carbide layer C. Repeat the above steps multiple times to form a higher layer of graphene layer B, a single-crystalline silicon carbide layer A, a graphene layer B, a polycrystalline silicon carbide layer C and a graphene layer B, and continue to use chemical vapor deposition to grow a layer of polycrystalline silicon carbide as a buffer layer 20 outside the top graphene layer B.

[0161] The multi-material multi-layer substrate 13 with polycrystalline silicon carbide was cleaned with deionized water and anhydrous ethanol, and ultrasonically treated in deionized water for 10 minutes, and the surface was dried with nitrogen, placed in a surface cleaner and dried with ozone gas for 25 minutes to make the surface of the polycrystalline silicon carbide active, and then ultrasonically treated in a diamond suspension for 45 minutes to make the surface of the buffer layer 20 of the polycrystalline silicon carbide with diamond seeds 31 (such as Fig. 9 As shown), the diamond suspension is prepared by mixing diamond nanocrystal liquid and deionized water in a mass ratio of 1:35.

[0162] After the ultrasonic treatment, the samples were blown dry with nitrogen and then placed on a heating platform at 85 °C for drying.

[0163] The processed buffer layer 20 and substrate 10 with diamond seed crystals 31 are placed in a molybdenum table with a groove and placed on a deposition base of a chemical vapor deposition device. -4Pa, hydrogen with a hydrogen flow rate of 350sccm, methane with a methane flow rate of 7sccm (accounting for 2% of the volume percentage of hydrogen) and oxygen with a flow rate of 1.4sccm (accounting for 0.4% of the volume percentage of hydrogen) are introduced as reaction gases, the gas pressure is 10kPa, the operating power of the microwave plasma chemical vapor deposition device is 4.5kW, the temperature of the base is 900°C, the deposition time is controlled at 600h, and a diamond film 30 is deposited on the surface of silicon nitride to form a base structure 100.

[0164] like Fig. 9 As shown, the multi-material composite substrate 12 and polycrystalline silicon carbide are removed by physical grinding to obtain a diamond film 30. Finally, the upper surface area of ​​the diamond film 30 is 2120 mm 2 .

[0165] In this embodiment, other types of carbides with various crystal forms can also be used to replace silicon carbide, so as to form a structure with similar functions to the above-mentioned base structure 100 of this embodiment. It will not be elaborated here. Those skilled in the art should understand that these should all fall within the scope of protection of the present invention.

[0166] Example 6

[0167] like Figure 6 As shown, the substrate 10 uses graphite and polycrystalline silicon carbide as a multi-material multi-layer substrate 13, and a diamond film 30 is grown on the upper surface of the outermost polycrystalline silicon carbide. Specifically, the multi-material multi-layer substrate 13 includes a graphite layer B, a polycrystalline silicon carbide layer C, a graphite layer B, a polycrystalline silicon carbide layer C, a graphite layer B, and a polycrystalline silicon carbide layer C from bottom to top, and a diamond film 30 is grown on the uppermost polycrystalline silicon carbide layer C. The diameter of the multi-material multi-layer substrate 13 is 2 inches.

[0168] like Fig.10 As shown, the specific preparation method of the diamond film 30 in this embodiment is: first prepare a graphite layer B, use chemical vapor deposition to deposit a polycrystalline silicon carbide layer C on the surface of the graphite layer B, then add a second graphite layer B, continue to use chemical vapor deposition to deposit the polycrystalline silicon carbide layer C on the surface of the graphite layer B, then add a third graphite layer B, and continue to use chemical vapor deposition to deposit the polycrystalline silicon carbide layer C on the surface of the graphite layer B.

[0169] The multi-material multi-layer substrate 13 is cleaned with deionized water and anhydrous ethanol, and ultrasonically treated in deionized water for 60 minutes, and the surface is dried with nitrogen, placed in a surface cleaner and dried with ozone gas for 40 minutes to make the silicon nitride surface active, and then ultrasonically treated in a diamond suspension for 30 minutes to make the surface of the polycrystalline silicon carbide layer C have diamond seeds 31 (such as Fig.11As shown), the diamond suspension is prepared by mixing diamond nanocrystal liquid and deionized water in a mass ratio of 1:35.

[0170] After the ultrasonic treatment, the samples were blown dry with nitrogen and then placed on a heating platform at 85 °C for drying.

[0171] The processed substrate 10 with the diamond seed 31 is placed in a molybdenum table with a groove and placed on a deposition base of a chemical vapor deposition device. -4 Pa, hydrogen with a hydrogen flow rate of 550sccm, methane with a methane flow rate of 11sccm (accounting for 2% of the volume percentage of hydrogen) and oxygen with a flow rate of 2.2sccm (accounting for 0.4% of the volume percentage of hydrogen) are introduced as reaction gases, the gas pressure is 14kPa, the working power of the microwave plasma chemical vapor deposition device is 5kW, the temperature of the base is 900℃, the deposition time is controlled at 500h, and a diamond film 30 is deposited on the surface of the polycrystalline silicon carbide layer C to form a substrate structure 100.

[0172] like Fig.11 As shown, the multi-material composite substrate 12 is removed by physical grinding to obtain a diamond film 30. Finally, the upper surface area of ​​the diamond film 30 is 2110 mm 2 .

[0173] In this embodiment, polycrystalline silicon carbide can also be replaced by single-crystalline silicon carbide or other carbides combined with graphite to produce a multi-material multi-layer substrate 13, thereby forming a structure with similar functions to the above-mentioned base structure 100 of this embodiment. It will not be elaborated here. Those skilled in the art should understand that these should all fall within the scope of protection of the present invention.

[0174] Example 7

[0175] In this implementation, please refer to Figure 6 The substrate 10 uses layers of aluminum nitride and single-crystal silicon carbide as a multi-material multi-layer substrate 13, and the aluminum nitride and the single-crystal silicon carbide are prepared by bonding. A layer of aluminum nitride is bonded to a layer of single-crystal silicon carbide, and then a layer of single-crystal silicon carbide is bonded to the surface of the aluminum nitride. Then, another layer of aluminum nitride is bonded, and another layer of single-crystal silicon carbide is bonded to the surface of the aluminum nitride layer, and a diamond film 30 is grown on the outermost single-crystal silicon carbide. The diameter of the multi-material multi-layer substrate 13 is 1 inch.

[0176] The single crystal silicon carbide and aluminum nitride in this embodiment both have high thermal conductivity and low expansion coefficient, so they can conduct heat quickly and evenly, and are not prone to stress concentration. Aluminum nitride has a high affinity with the diamond film, and film cracking at the layer plate is not prone to occur.

[0177] like Fig.10As shown, the specific preparation method of the diamond film 30 in this embodiment is:

[0178] A multi-material multi-layer substrate 13 made of a layer of two materials, aluminum nitride layer and single-crystal silicon carbide, bonded alternately, is cleaned with deionized water and anhydrous ethanol, and ultrasonically treated in deionized water for 20 minutes, and the surface is dried with nitrogen, placed in a surface cleaner and dried with ozone gas for 35 minutes to make the surface of the single-crystal silicon carbide active, and then ultrasonically treated in a diamond suspension for 30 minutes to make the surface of the single-crystal silicon carbide have diamond seeds 31 (such as Fig.11 As shown), the diamond suspension is prepared by mixing diamond nanocrystal liquid and deionized water in a mass ratio of 1:45.

[0179] After the ultrasonic treatment, the samples were blown dry with nitrogen and then placed on a heating platform at 65°C for drying.

[0180] The processed substrate 10 with the diamond seed 31 is placed in a molybdenum table with a groove and placed on a deposition base of a chemical vapor deposition device. -4 After the pressure drops below Pa, hydrogen with a hydrogen flow rate of 450sccm, methane with a methane flow rate of 13.5sccm (3% by volume of hydrogen) and oxygen with a flow rate of 0.9sccm (0.2% by volume of hydrogen) are introduced as reaction gases. The gas pressure is 13kPa, and the operating power of the microwave plasma chemical vapor deposition device is adjusted to 7kW. The temperature of the base is 900°C, and the deposition time is controlled to 800h. A diamond film 30 is deposited on the surface of the single crystal silicon carbide to form a substrate structure 100.

[0181] like Fig.11 As shown, the multi-material multi-layer substrate 13 is removed by physical grinding to obtain a diamond film 30. Finally, the upper surface area of ​​the diamond film 30 is 540 mm 2 .

[0182] The aluminum nitride in this embodiment can be replaced with other nitrides such as boron nitride, silicon nitride, titanium nitride, tungsten nitride and tantalum nitride, so as to form a structure with similar functions to the above-mentioned base structure 100 of this embodiment. It will not be elaborated here. Those skilled in the art should understand that these should all fall within the scope of protection of the present invention.

[0183] Example 8

[0184] In this embodiment, refer to Figure 7 The substrate 10 uses a layer of two materials, silicon and single-crystal silicon carbide, as a multi-material multi-layer substrate 13. Single-crystal silicon carbide is prepared on the surface of silicon by bonding method, and a diamond film 30 is further grown on the surface of the single-crystal silicon carbide. The diameter of the multi-material multi-layer substrate 13 is 2 inches.

[0185] like Fig.10 As shown, the multi-material multi-layer substrate 13 is cleaned with deionized water and anhydrous ethanol, and ultrasonically treated in deionized water for 30 minutes, the surface is dried with nitrogen, placed in a surface cleaner and dried with ozone gas for 25 minutes to make the surface of the single-crystalline silicon carbide active, and then placed in a diamond suspension for ultrasonic treatment for 35 minutes to make the surface of the single-crystalline silicon carbide have diamond seeds 31 (such as Fig.11 As shown), the diamond suspension is prepared by mixing diamond nanocrystal liquid and deionized water in a mass ratio of 1:25.

[0186] After the ultrasonic treatment, the samples were blown dry with nitrogen and then placed on a heating platform at 75°C for drying.

[0187] The processed substrate 10 with the diamond seed 31 is placed in a molybdenum table with a groove and placed on a deposition base of a chemical vapor deposition device. -4 After the pressure drops below Pa, hydrogen with a hydrogen flow rate of 500sccm, methane with a methane flow rate of 10sccm (accounting for 2% of the volume percentage of hydrogen) and oxygen with a flow rate of 0.5sccm (accounting for 0.1% of the volume percentage of hydrogen) are introduced as reaction gases. The gas pressure is 12kPa, and the working power of the microwave plasma chemical vapor deposition device is adjusted to 8kW. The temperature of the base is 900°C, and the deposition time is controlled to 600h. A diamond film 30 is deposited on the surface of the single crystal silicon carbide to form a substrate structure 100.

[0188] like Fig.11 As shown, the multi-material multi-layer substrate 13 is removed by physical grinding to obtain a diamond film 30. Finally, the upper surface area of ​​the diamond film 30 is 2120 mm 2 .

[0189] Example 9

[0190] In this embodiment, refer to Figure 7 The substrate 10 uses a layer of two materials, silicon and polycrystalline silicon carbide, as a multi-material multi-layer substrate 13, and silicon is prepared on the surface of polycrystalline silicon carbide by chemical vapor deposition, and a diamond film 30 is further grown on the surface of silicon. The substrate 10 has a growth diameter of 3 inches.

[0191] like Fig.10 As shown, the multi-material multi-layer substrate 13 is cleaned with deionized water and anhydrous ethanol, and ultrasonically treated in deionized water for 40 minutes, the surface is dried with nitrogen, placed in a surface cleaner and dried with ozone gas for 15 minutes to make the silicon surface active, and then placed in a diamond suspension for ultrasonic treatment for 45 minutes to make the silicon surface have diamond seeds 31 (such as Fig.11As shown), the diamond suspension is prepared by mixing diamond nanocrystal liquid and deionized water in a mass ratio of 1:45.

[0192] After the ultrasonic treatment, the samples were blown dry with nitrogen and then placed on a heating platform at 90 °C for drying.

[0193] The processed substrate 10 with the diamond seed 31 is placed in a molybdenum table with a groove and placed on a deposition base of a chemical vapor deposition device. -4 After the pressure drops below Pa, hydrogen with a hydrogen flow rate of 600sccm, methane with a methane flow rate of 3sccm (accounting for 0.5% of the volume percentage of hydrogen) and oxygen with a flow rate of 0.6sccm (accounting for 0.1% of the volume percentage of hydrogen) are introduced as reaction gases. The gas pressure is 11kPa, and the working power of the microwave plasma chemical vapor deposition device is adjusted to 5kW. The temperature of the base is 900°C, the deposition time is controlled to 1000h, and a diamond film 30 is deposited on the surface of the silicon to form a substrate structure 100.

[0194] like Fig.11 As shown, hydrochloric acid solution is used to remove the multi-material multi-layer substrate 13 to obtain a diamond film 30. Finally, the upper surface area of ​​the diamond film 30 is 4800 mm 2 .

[0195] Example 10

[0196] like Figure 1 As shown, a single material metal tantalum is used as the substrate 10, and aluminum nitride is selected as the transition layer 20. Tantalum and aluminum nitride are cleaned with deionized water and organic solvents such as acetone and ethanol to remove surface contaminants. A tube furnace is used to heat to 300°C in air to form a thin oxide layer. An inductively coupled plasma etcher is used to introduce argon gas into the surface of aluminum nitride for etching to increase the surface roughness. In a clean, dust-free environment, tantalum and aluminum nitride are placed in position to ensure that the two are in close contact, and heated to 1300°C at 50°C / h in a high-temperature and high-pressure reactor. A pressure of 15Mpa is applied at 1300°C to make the surfaces of tantalum and aluminum nitride in close contact to promote the formation of chemical bonds. Maintain for 3 hours in a high-temperature and high-pressure environment to ensure that a chemical bond of sufficient strength is formed. After the bonding is completed, the temperature is slowly lowered, and the sample is gradually cooled to room temperature at a cooling rate of 20°C / H to achieve chemical bonding between the two. The diameter of the substrate 10 is 2 inches.

[0197] Further, the single material substrate 11 with aluminum nitride is ultrasonically treated in deionized water for 40 minutes, the surface is dried with nitrogen, placed in a surface cleaner and dried with ozone gas for 40 minutes to make the aluminum nitride surface active, and then placed in a diamond suspension for ultrasonic treatment for 40 minutes to make the surface of the aluminum nitride buffer layer 20 with diamond seeds 31 (such as Fig. 9 As shown), the diamond suspension is prepared by mixing diamond nanocrystal liquid and deionized water in a mass ratio of 1:40.

[0198] After the ultrasonic treatment, the samples were blown dry with nitrogen and then placed on a heating platform at 80 °C for drying.

[0199] The processed buffer layer 20 and substrate 10 with diamond seed crystals 31 are placed in a molybdenum table with a groove and placed on a deposition base of a chemical vapor deposition device. -4 After the pressure drops below Pa, hydrogen with a hydrogen flow rate of 500sccm, methane with a methane flow rate of 10sccm (accounting for 2% of the volume percentage of hydrogen) and oxygen with a flow rate of 0.25sccm (accounting for 0.05% of the volume percentage of hydrogen) are introduced as reaction gases. The gas pressure is 14kPa, the operating power of the microwave plasma chemical vapor deposition device is 6kW, the temperature of the base is 900°C, the deposition time is controlled at 600h, and a diamond film 30 is deposited on the surface of aluminum nitride to form a substrate structure 100.

[0200] like Fig. 9 As shown, aluminum nitride and tantalum are removed by nitric acid to obtain a diamond film 30. Finally, the upper surface area of ​​the diamond film 30 is 2120 mm 2 .

[0201] The tantalum in this embodiment can also be replaced with other metals such as titanium, molybdenum, niobium or tungsten to form a structure with similar functions to the above-mentioned base structure 100 of this embodiment. It will not be elaborated here. Those skilled in the art should understand that these should all fall within the scope of protection of the present invention.

[0202] Embodiment 11

[0203] The preparation steps are generally the same as those in Example 1, except that a silicon carbide layer is prepared as the buffer layer 20 by a physical vapor deposition method.

[0204] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can easily think of various equivalent modifications or replacements within the technical scope disclosed by the present invention, and these modifications or replacements should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be based on the protection scope of the claims.

Claims

1. A substrate structure having a diamond film grown thereon, characterized in that: include: The substrate has a thermal conductivity greater than or equal to 20 W / mK and a thermal expansion coefficient less than 9×10 -6 / K single material substrate, multi-material composite substrate or multi-material multi-layer substrate; A buffer layer, the buffer layer is at least arranged on the upper surface of the substrate or the outer surface of the single material substrate wrapped by the buffer layer, and the diamond film is grown on the buffer layer; the thermal expansion coefficient of the buffer layer is less than the thermal expansion coefficient of the substrate; the buffer layer is a single crystal film or a polycrystalline film; the diamond film is a nanocrystalline diamond film and / or a micron crystal diamond film, and the upper surface area of ​​the diamond film is 13mm 2 ~465000mm 2 .

2. The substrate structure having a diamond film grown thereon as claimed in claim 1, characterized in that: The material of the single-material substrate is one of graphite, graphene, carbide, nitride, diamond particles, silicon, titanium, molybdenum, niobium, tantalum and tungsten; the material of the multi-material composite substrate and the multi-material multi-layer substrate is selected from at least two of graphite, graphene, carbide, nitride, diamond particles, silicon, titanium, molybdenum, niobium, tantalum and tungsten; and / or, The buffer layer is one of carbide, nitride, silicon and iridium.

3. The substrate structure having a diamond film grown thereon as claimed in claim 2, characterized in that: The carbide is one of silicon carbide, titanium carbide, tungsten carbide or tantalum carbide, and the nitride is one of aluminum nitride, boron nitride, silicon nitride, titanium nitride, tungsten nitride and tantalum nitride.

4. The substrate structure having a diamond film grown thereon as claimed in claim 3, characterized in that: The relative mass content of each material selected in the multi-material composite substrate and the multi-material multi-layer substrate varies from low to high with the height of the substrate and has a plurality of gradient relative mass contents of different sizes; or, The relative mass content of each material selected in the multi-material composite substrate and the multi-material multi-layer substrate has a plurality of gradient relative mass contents of different sizes as the distance from the geometric center of the substrate changes from near to far.

5. The substrate structure with a diamond film grown thereon as claimed in claim 4, characterized in that: The materials of the multi-material composite substrate are silicon carbide and diamond particles. The multi-material composite substrate is divided into an upper layer, a middle layer and a lower layer. The mass ratio of diamond particles and silicon carbide in the lower layer is (70-95):(5-30), the mass ratio of diamond particles and silicon carbide in the middle layer is (40-65):(35-60), and the mass ratio of diamond particles and silicon carbide in the upper layer is (10-35):(65-90). The buffer layer is made of polycrystalline silicon carbide. The buffer layer is arranged on at least the upper surface of the upper layer, and the diamond film is grown on the buffer layer.

6. The substrate structure with a diamond film grown thereon as claimed in claim 1, characterized in that: The multi-material multi-layer substrate comprises substrate layers made of multiple materials, wherein the substrate layers made of at least two materials are alternately stacked.

7. The substrate structure having a diamond film grown thereon as claimed in claim 6, characterized in that: The multi-material multi-layer substrate comprises graphene and silicon carbide which are alternately stacked at least twice, polycrystalline silicon carbide is selected as a buffer layer, and the diamond film is grown on the surface of the polycrystalline silicon carbide.

8. The substrate structure having a diamond film grown thereon as claimed in claim 1, characterized in that: The particle size of the diamond particles selected in the substrate ranges from 5 nm to 300,000 nm; and / or, when the upper surface of the substrate is a graphite layer, the buffer layer located on the surface of the graphite layer wraps the graphite layer.

9. The substrate structure with a diamond film grown thereon as claimed in claim 1, characterized in that: The material of the substrate is selected from diamond particles, silicon carbide and silicon, and the mass ratio of diamond particles, silicon carbide and silicon is 5% to 50%: 50% to 95%: 0 to 20%; Alternatively, the material of the substrate is selected from graphite and silicon carbide, and the mass ratio of graphite to silicon carbide is 30% to 90%: 10% to 70%; Alternatively, the material of the substrate is selected from aluminum nitride and molybdenum, and the mass ratio of aluminum nitride to molybdenum is 65% to 95%:5% to 35%.

10. The substrate structure with a diamond film grown thereon according to claim 1, characterized in that: The thickness of the substrate is in the range of 0.5 mm to 30 mm, and the ratio of the upper surface area of ​​the substrate to the square of the thickness of the substrate is in the range of (2 to 505):1; and / or, The upper surface area of ​​the substrate is in the range of 12 mm 2 ~460000mm 2 , the upper surface area of ​​the buffer layer is greater than or equal to the upper surface area of ​​the substrate; and / or, The thickness of the diamond film is in the range of 0.05 mm to 3 mm; and / or the thickness of the buffer layer is in the range of 10 nm to 50000 nm; And / or, the surface roughness of the substrate ranges from 1 nm to 1,000,000 nm; And / or, the diamond film is a nanocrystalline diamond film and / or a microcrystalline diamond film.

11. A substrate structure having a diamond film grown thereon, characterized in that: The substrate comprises a substrate having a thermal conductivity greater than or equal to 20 W / mK and a thermal expansion coefficient less than 9×10 -6 / K multi-material composite substrate or multi-material multi-layer substrate; the material of the substrate is selected from at least two of graphite, graphene, carbide, nitride, silicon, titanium, molybdenum, niobium, tantalum and tungsten; the carbide and the nitride are single crystal films or polycrystalline films, and a diamond film is grown on at least the upper surface of the substrate, and the upper surface area of ​​the diamond film is 13mm 2 ~465000mm 2 .

12. A method for preparing a diamond film, characterized in that: A method for preparing a diamond film on a substrate structure having a diamond film grown thereon as claimed in any one of claims 1 to 10, the preparation method comprising the following steps: A substrate is prepared by chemical vapor deposition or hot pressing sintering; a buffer layer is prepared on the substrate by bonding, chemical vapor deposition or physical vapor deposition; The substrate with the buffer layer is cleaned with a lotion; the substrate with the buffer layer is ultrasonically treated in deionized water for 10 minutes to 60 minutes, and then dried; Treating the substrate with the buffer layer with a surface cleaner in an ozone atmosphere to make the surface of the buffer layer active; A diamond particle suspension is prepared, and the buffer layer and the substrate having active surfaces are ultrasonically placed in the diamond particle suspension for 10 to 60 minutes, so that the surface of the buffer layer is provided with diamond seeds; Drying the buffer layer and substrate with diamond seeds; placing them in a microwave plasma chemical vapor deposition device, introducing a mixed gas of methane, hydrogen and oxygen as a reaction gas, and depositing a diamond film on the surface of the buffer layer to form a matrix structure; The diamond film is obtained by grinding the base structure and / or soaking the base structure in an acid solution to remove the substrate and the buffer layer.

13. The method for preparing a diamond film according to claim 12, characterized in that: The lotion is one or more of deionized water, anhydrous ethanol or acetone; and / or, The diamond particle suspension is prepared by mixing diamond nanocrystal liquid and deionized water in a mass ratio of 1:20 to 50; and / or, When drying the buffer layer and substrate with diamond seeds, drying is performed in a nitrogen atmosphere on a heating platform at a temperature of 60° C. to 90° C.; and / or, The acid solution is one or more of hydrochloric acid solution, nitric acid solution, hydrofluoric acid and sulfuric acid.

14. The method for preparing a diamond film according to claim 12, characterized in that: The substrate with diamond seeds was placed on a molybdenum table with a groove, and the height of the substrate with diamond seeds was 0.1 mm to 2 mm higher than the edge of the molybdenum table. The molybdenum table with the diamond seeds was placed together in a microwave plasma chemical vapor deposition device, and the vacuum was evacuated to 1×10 -4 Pa, hydrogen with a flow rate of 300sccm to 600sccm of hydrogen, 0.5% to 5% by volume of methane, 0.01% to 0.5% by volume of oxygen mixed gas, the total gas pressure is 9kPa to 16kPa, the working power of the microwave plasma chemical vapor deposition device is 3kW to 8kW, and surface deposition is carried out.

15. A method for preparing a diamond film, characterized in that: For preparing a diamond film on a substrate structure having a diamond film grown thereon as claimed in claim 11, wherein the diamond film is a nanocrystalline diamond film and / or a microcrystalline diamond film, the preparation method comprising the following steps: The substrate is prepared by chemical vapor deposition; The substrate is cleaned with a detergent; ultrasonically treated in deionized water for 10 to 60 minutes, and then dried; Treating the substrate with a surface cleaner in an ozone atmosphere to make the surface of the substrate active; A diamond particle suspension is prepared, and the substrate with active surface is ultrasonically placed in the diamond particle suspension for 10 minutes to 60 minutes, so that the surface of the substrate is covered with diamond seeds; The substrate with the diamond seed crystal is dried, placed in a microwave plasma chemical vapor deposition device, and a mixed gas of methane, hydrogen and oxygen is introduced as a reaction gas to deposit a diamond film on the surface of the substrate to form a matrix structure; The diamond film is obtained by grinding the base structure and / or soaking the base structure in an acid solution to remove the substrate.

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