Diamond film and preparation method thereof

Abstract

The present invention relates to the field of diamond film technology, specifically a diamond film and a preparation method thereof. The preparation method comprises: S1, preparing a zinc-doped diamond film on the surface of a substrate; S2, subjecting the zinc-doped diamond film to a high-temperature treatment in an inert atmosphere to partially evaporate the zinc to form a porous structure, thereby obtaining a zinc-doped porous diamond film; and S3, preparing a pure diamond film on the surface of the zinc-doped porous diamond film. The present invention utilizes the relatively low boiling point of zinc to dope the diamond film with zinc. Heating can evaporate a portion of the zinc to form a porous structure, which serves as a transition layer. The porous structure can be used to release thermal stress and alleviate the effects of the difference in thermal expansion coefficients between the substrate and the diamond film, thereby significantly improving the adhesion, hardness, and wear resistance of the diamond film. Furthermore, the film has good light transmittance.

Description

Technical Field

[0001] The present invention relates to the technical field of diamond films, and in particular to a diamond film and a preparation method thereof. Background Art

[0002] Diamond film is a surface functional material with a variety of excellent properties, including high hardness, low friction coefficient, high wear and corrosion resistance, wide light transmittance, and excellent biocompatibility. Therefore, diamond film has shown great application potential in the marine shipbuilding industry, aerospace engineering, automotive, printing, and biomedicine. Coating adhesion and surface finish are the main factors affecting the apparent performance of CVD diamond coatings in wear-resistant and friction-reducing devices. Due to the difference in thermal expansion coefficient and lattice constant between diamond and the substrate material, the deposited diamond coating has certain internal stresses, resulting in reduced coating adhesion and easy shedding. Because the substrate temperature during CVD deposition of diamond film is very high, around 850°C, and the thermal expansion coefficient of diamond is relatively small, generally only 1 / 3 to 1 / 4 of that of the substrate material, cooling and shrinkage will generate large internal stresses in the coating. Using a transition layer to reduce the thermal stress between the diamond film and the substrate is an effective method.

[0003] For example, patent CN201911017635.1 discloses a method for preparing a tungsten carbide transition layer-silicon-doped diamond composite coating on a steel substrate. This method is based on low-carbon steel and low-alloy steel. First, a plasma-enhanced chemical vapor deposition (PECVD) nano-tungsten carbide coating is used, and then a hot wire chemical vapor deposition method is used to deposit a nanocrystalline silicon-doped diamond coating on the tungsten carbide coating to form a double-layer transition layer. Then, an intrinsic micron or nano-diamond coating is deposited on the surface of the silicon-doped diamond coating. This method solves the problem that the steel substrate cannot be directly deposited with a CVD diamond coating due to the large difference in thermal expansion coefficient between the steel substrate and diamond, so that the steel substrate can be used to replace conventional cemented carbide for depositing diamond coatings. However, this method requires two transition layers, and too many deposition interfaces will reduce the stability of the film, and tungsten carbide leads to low transparency.

[0004] In view of this, it is necessary to design an improved diamond film and a preparation method thereof to solve the above problems. Summary of the Invention

[0005] The purpose of the present invention is to provide a diamond film and a preparation method thereof. A porous diamond film or a zinc oxide-doped porous diamond film is prepared as a transition layer between a substrate and the diamond film. The porous structure can be used to release thermal stress and alleviate the influence of the difference in thermal expansion coefficient between the substrate and the diamond film, thereby significantly improving the adhesion, hardness and wear resistance of the diamond film. The film also has good light transmittance.

[0006] To achieve the above object, the present invention provides a method for preparing a diamond film, comprising the following steps:

[0007] S1. preparing a zinc-doped diamond film on the surface of a substrate;

[0008] S2, subjecting the zinc-doped diamond film to a high-temperature treatment in an inert atmosphere to evaporate a portion of zinc to form a porous structure, thereby obtaining a zinc-doped porous diamond film;

[0009] S3. Preparing a pure diamond film on the surface of the zinc-doped porous diamond film.

[0010] As a further improvement of the present invention, step S2 further includes: subjecting the zinc-doped porous diamond film to a thermal oxidation treatment to obtain a zinc oxide-doped porous diamond film, and then performing step S3.

[0011] As a further improvement of the present invention, the thermal oxidation treatment comprises: treating in air at 200-400° C. for 1-3 hours;

[0012] Alternatively, the treatment is carried out for 1-3 hours in an atmosphere with an oxygen to nitrogen volume ratio of 10%:90% to 30%:70% and a temperature of 200-400° C.

[0013] As a further improvement of the present invention, the molar content of zinc atoms in the zinc-doped diamond film is 0.1%-10%; the zinc evaporated by the high-temperature treatment accounts for 1%-99% of the original doped zinc.

[0014] As a further improvement of the present invention, the molar content of zinc atoms in the zinc-doped diamond film is 2%-6%; the zinc evaporated by the high-temperature treatment accounts for 10%-80% of the original doped zinc.

[0015] As a further improvement of the present invention, the temperature of the high-temperature treatment is 910-1100° C., and the inert atmosphere is nitrogen or helium.

[0016] As a further improvement of the present invention, the zinc-doped porous diamond film is obtained by one or more methods selected from the group consisting of linear ion beam, magnetron sputtering, and vacuum cathode arc.

[0017] And / or, the substrate is a silicate substrate, a silicon carbide substrate, a silicon nitride substrate or a single crystal silicon substrate, and the substrate temperature is 700-900°C.

[0018] As a further improvement of the present invention, the thickness of the zinc-doped porous diamond film is 0.05-5 μm, and the thickness of the diamond film is 0.05-10 μm.

[0019] Furthermore, the present invention also provides a diamond film, comprising a substrate, a transition layer and a diamond film; the transition layer is a porous diamond film doped with zinc or a porous diamond film doped with zinc oxide.

[0020] As a further improvement of the present invention, the diamond film is prepared by the preparation method according to any one of claims 1-8.

[0021] The beneficial effects of the present invention are as follows:

[0022] 1. The method for preparing a diamond film provided by the present invention prepares a porous diamond film or a zinc oxide-doped porous diamond film as a transition layer between the substrate and the diamond film. The porous structure can be used to release thermal stress and alleviate the influence of the difference in thermal expansion coefficient between the substrate and the diamond film, thereby significantly improving the adhesion, hardness and wear resistance of the diamond film. The film also has good light transmittance.

[0023] 2. The present invention utilizes zinc's low boiling point to form a porous structure by removing some of the zinc simply by heating, resulting in a simple preparation method. Furthermore, the porous structure provides more free space for thermal expansion. By utilizing the difference in thermal expansion coefficients between zinc or zinc oxide, the substrate, and the diamond film, the thermal expansion coefficients between layers can be controlled by adjusting their contents, thereby improving the adhesion of the diamond film. Therefore, the present invention offers high controllability and provides a new approach for the preparation of high-performance diamond films. DETAILED DESCRIPTION

[0024] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention are described clearly and completely below. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0025] The invention provides a diamond film comprising a substrate, a transition layer and a diamond film; the transition layer is a porous diamond film doped with zinc or a porous diamond film doped with zinc oxide.

[0026] Furthermore, the present invention provides a method for preparing the diamond film, comprising the following steps:

[0027] S1. preparing a zinc-doped diamond film on the surface of a substrate;

[0028] S2, subjecting the zinc-doped diamond film to a high-temperature treatment in an inert atmosphere to evaporate a portion of zinc to form a porous structure, thereby obtaining a zinc-doped porous diamond film;

[0029] S3. Preparing a pure diamond film on the surface of the zinc-doped porous diamond film.

[0030] On the one hand, the thermal expansion coefficient of zinc is different from that of the substrate and the diamond film, which can adjust the thermal expansion coefficient between layers; on the other hand, the porous structure formed can provide more free space for thermal expansion, so its adhesion to the substrate is high, thereby improving the adhesion of the diamond film on its surface; moreover, the porous structure can be formed only by heating, and the method is simple and easy to operate.

[0031] Preferably, step S2 further comprises: subjecting the zinc-doped porous diamond film to a thermal oxidation treatment to obtain a zinc oxide-doped porous diamond film, and then proceeding to step S3. Zinc oxide's thermal expansion coefficient varies, allowing for flexibility in selecting either zinc or zinc oxide based on substrate type and actual needs. Furthermore, during oxidation, the incorporation of oxygen atoms can modulate the porous structure, thereby adjusting the transition layer structure.

[0032] The thermal oxidation treatment comprises: treating in air at 200-400° C. for 1-3 hours;

[0033] Alternatively, the treatment can be performed at 200-400°C for 1-3 hours in an atmosphere with an oxygen to nitrogen ratio of 10%:90% to 30%:70% by volume. Thermal oxidation treatment at 200-300°C is preferred. Under the influence of heat, zinc and oxygen undergo an oxidation reaction to form zinc oxide. Since the diamond film itself is resistant to high temperatures, the heat treatment of the present invention does not affect the diamond film itself. This demonstrates that the present invention cleverly utilizes the respective properties of the diamond film and zinc.

[0034] The molar content of zinc atoms in the zinc-doped diamond film is 0.1%-10%, preferably 2%-6%. The zinc doping amount should not be too high to avoid affecting the integrity of the diamond film.

[0035] The zinc evaporated by the high temperature treatment accounts for 1% to 99% of the original doped zinc, preferably 10% to 80%. The structure of the transition layer is adjusted by the porosity and the residual zinc content to optimize its adhesion.

[0036] The high temperature treatment temperature is 910-1100° C., and the inert atmosphere is nitrogen or helium. The high temperature treatment temperature is above the boiling point of zinc to evaporate the zinc.

[0037] The zinc-doped diamond film is obtained by one or more methods including linear ion beam, magnetron sputtering and vacuum cathode arc.

[0038] The substrate is a silicate substrate, a silicon carbide substrate, a silicon nitride substrate or a single crystal silicon substrate, and the substrate temperature is 700-900° C. The thickness of the diamond film is 0.05-5 μm; the thickness of the diamond film is 0.05-10 μm.

[0039] Example 1

[0040] A diamond film is prepared by the following steps:

[0041] S1. Using linear ion beam composite magnetron sputtering technology, a 0.6 μm thick zinc-doped diamond film was prepared on the surface of a silicon nitride substrate:

[0042] A zinc target is mounted on a magnetron sputtering source to deposit metallic zinc, while a carbon-containing gas source is introduced into a linear ion beam source to deposit a diamond film. During the coating process, both the magnetron sputtering source and the linear ion beam source are simultaneously activated to deposit a zinc-doped diamond film with a molar zinc content of 4%.

[0043] S2, treating the zinc-doped diamond film in an inert atmosphere at 950° C. to remove 40% of the doped zinc, thereby obtaining a zinc-doped porous diamond film;

[0044] S3. Using hydrogen and methane as raw materials, a pure diamond film with a thickness of 2 μm is prepared on the surface of the zinc-doped porous diamond film by hot-filament chemical vapor deposition. The hot-filament chemical vapor deposition conditions are as follows: the reaction chamber is evacuated to below 10 Pa, 20 sccm of methane and 500 sccm of hydrogen are introduced, and the pressure in the reaction chamber is controlled at 1800 Pa until the hot-filament voltage stabilizes. 10 sccm of methane, 100 sccm of hydrogen, and 92 sccm of argon are introduced, and the pressure in the reaction chamber is controlled at 1300 Pa for deposition.

[0045] Example 2

[0046] A diamond film is prepared by the following steps:

[0047] S1. Using linear ion beam composite magnetron sputtering technology, a zinc-doped diamond film with a thickness of 0.6 μm was prepared on the surface of a silicon nitride substrate:

[0048] A zinc target is mounted on a magnetron sputtering source to deposit metallic zinc, while a carbon-containing gas source is introduced into a linear ion beam source to deposit a diamond film. During the coating process, both the magnetron sputtering source and the linear ion beam source are simultaneously activated to deposit a zinc-doped diamond film with a molar zinc content of 4%.

[0049] S2, treating the zinc-doped diamond film in an inert atmosphere at 950° C. to remove 40% of the doped zinc, thereby obtaining a zinc-doped porous diamond film; and then treating the film in air at 300° C. for 1 hour to obtain a zinc oxide-doped porous diamond film;

[0050] S3. Using hydrogen and methane as raw materials, a pure diamond film with a thickness of 2 μm is prepared on the surface of the zinc oxide-doped porous diamond film by hot wire chemical vapor deposition.

[0051] Example 3

[0052] A diamond film, compared with Example 1, differs in that in step S1, the molar content of zinc is 0.2%. Other steps are the same as Example 1 and are not described again.

[0053] Example 4

[0054] A diamond film, compared with Example 1, differs in that in step S1, the molar content of zinc is 2%. Other steps are the same as Example 1 and are not described again.

[0055] Example 5

[0056] A diamond film, compared with Example 1, differs in that in step S1, the molar content of zinc is 6%. Other steps are the same as Example 1 and are not described again.

[0057] Example 6

[0058] A diamond film, compared with Example 1, differs in that in step S1, the molar content of zinc is 10%. Other steps are the same as Example 1 and are not described herein.

[0059] Example 7

[0060] A diamond film, compared with Example 1, differs in that, in step S2, 5% of the doped zinc is controlled to be removed. Other steps are the same as Example 1 and are not described again.

[0061] Example 8

[0062] A diamond film, compared with Example 1, differs in that 80% of the doped zinc is controlled to be removed. Other steps are the same as Example 1 and are not described again.

[0063] Example 9

[0064] A diamond film, compared with Example 2, differs in that in step S2, the porous diamond film doped with zinc oxide is treated in air at 300° C. for 3 hours. Other steps are the same as Example 2 and are not described again.

[0065] Example 10

[0066] A diamond film is prepared by the following steps:

[0067] S1. Using linear ion beam composite magnetron sputtering technology, zinc-doped diamond films were prepared on the surface of calcium silicate substrates:

[0068] A zinc target is mounted on a magnetron sputtering source to deposit metallic zinc, while a carbon-containing gas source is introduced into a linear ion beam source to deposit a diamond film. During the coating process, both the magnetron sputtering source and the linear ion beam source are simultaneously activated to deposit a zinc-doped diamond film with a molar zinc content of 4%.

[0069] S2, treating the zinc-doped diamond film in an inert atmosphere at 950° C. to remove 60% of the doped zinc, thereby obtaining a zinc-doped porous diamond film;

[0070] S3. Using hydrogen and methane as raw materials, a pure diamond film is prepared on the surface of the zinc-doped porous diamond film by hot-wire chemical vapor deposition.

[0071] Comparative Example 1

[0072] A diamond film is prepared on the surface of the silicon nitride substrate directly in step S3, while the other steps are the same as those in embodiment 1 and are not described in detail here.

[0073] The obtained 1 cm×1 cm diamond film was heated to 200°C, kept at this temperature for 1 hour, and then cooled to room temperature. This cycle was repeated 10 times. The surface morphology of the film was observed, and the adhesion and life of the diamond film were evaluated.

[0074] Table 1 Performance test results of diamond films prepared in Examples 1-10 and Comparative Example 1

[0075] Example Light transmittance (%) Surface morphology 1 69.8 Basically no cracks, no warping or falling off 2 69.6 Basically no cracks, no warping or falling off 3 70.1 Many cracks, no warping or falling off 4 70.0 A few cracks, no warping or falling off 5 69.5 Basically no cracks, no warping or falling off 6 69.1 A few cracks, no warping or falling off 7 69.7 A few cracks, no warping or falling off 8 69.9 Basically no cracks, no warping or falling off 9 69.2 A few cracks, no warping or falling off 10 69.7 Basically no cracks, no warping or falling off Comparative Example 1 70.2 More cracks are generated, and warping and falling off occur

[0076] As can be seen from Table 1, the light transmittance of the diamond film prepared by the present invention is close to that without a transition layer (close to the theoretical light transmittance of a diamond film), indicating that the transition layer also has good light transmittance. It can be seen that the doping of a small amount of zinc or zinc oxide has little effect on the light transmittance. As can be seen from the surface morphology, the addition of a transition layer can significantly improve the thermal stability of the film. As can be seen, the transition layer of the present invention still has a diamond film as the main body, and uses the doping of zinc or zinc oxide and the porous structure to regulate the thermal expansion coefficient and alleviate thermal stress, thereby ensuring the light transmittance of the diamond film while improving its adhesion and service life. Because the transition layer of the present invention has similar properties to diamond, it can improve the performance of the diamond film, and its hardness is basically the same as that of natural diamond.

[0077] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A method for preparing a diamond film, characterized in that: The steps include: S1. Preparing a zinc-doped diamond film on a substrate surface; the zinc-doped diamond film has a molar content of zinc atoms of 2%-6%; the substrate is a silicate substrate, a silicon carbide substrate, a silicon nitride substrate, or a single crystal silicon substrate, and the substrate temperature is 700-900° C.; S2. subjecting the zinc-doped diamond film to a high-temperature treatment in an inert atmosphere to evaporate a portion of the zinc to form a porous structure, thereby obtaining a zinc-doped porous diamond film; the high-temperature treatment temperature is 910-1100° C.; the zinc evaporated during the high-temperature treatment accounts for 10%-80% of the original doped zinc; S3. Prepare a pure diamond film on the surface of the zinc-doped porous diamond film, and use the porous structure to release thermal stress to improve the adhesion of the diamond film; the thickness of the zinc-doped porous diamond film is 0.05-5 μm, and the thickness of the diamond film is 0.05-10 μm.

2. The method for preparing a diamond thin film according to claim 1, wherein: Step S2 further includes: subjecting the zinc-doped porous diamond film to a thermal oxidation treatment to obtain a zinc oxide-doped porous diamond film, and then proceeding to step S3.

3. The method for preparing a diamond thin film according to claim 2, wherein: The thermal oxidation treatment comprises: treating in air at 200-400° C. for 1-3 hours; Alternatively, the treatment is carried out for 1-3 hours in an atmosphere with an oxygen to nitrogen volume ratio of 10%:90% to 30%:70% and a temperature of 200-400°C.

4. The method for preparing a diamond thin film according to claim 1, wherein: The inert atmosphere is nitrogen or helium.

5. The method for preparing a diamond thin film according to claim 1, wherein: The zinc-doped diamond film is obtained by one or more methods including linear ion beam, magnetron sputtering and vacuum cathode arc.

6. A diamond film prepared by the preparation method according to any one of claims 1 to 5.