A surface treatment method for CVD diamond

Abstract

The application discloses a surface treatment method of CVD diamond, and belongs to the technical field of crystal materials and surface treatment thereof. The surface treatment method of CVD diamond comprises the following steps: first mechanical grinding of the CVD diamond to be treated; introducing Ti metal on the surface of the CVD diamond after the first mechanical grinding, so that the Ti metal and the CVD diamond have an interface reaction, and a carbonization reaction layer is formed on the surface of the CVD diamond; second mechanical grinding is performed to remove the carbonization reaction layer, and a surface-treated CVD diamond is obtained; and the introduction mode of the Ti metal comprises embedding TiH2 powder into the diamond or magnetron sputtering of a Ti layer on the surface of the diamond. By adjusting the introduction mode of the Ti metal, the interface reaction behavior of the Ti metal and the diamond is utilized to generate a carbonization reaction layer on the surface of the CVD diamond, and then the mechanical grinding is performed, so that the surface quality of the CVD diamond can be effectively improved, and the surface stress of the CVD diamond can be released.

Description

Technical Field

[0001] This invention belongs to the field of crystal materials and their surface treatment technology, and particularly relates to a surface treatment method for CVD diamond. Background Technology

[0002] CVD (Chemical Vapor Deposition) diamond exhibits broad application prospects in the electronics and information field due to its superior properties such as high hardness, high wear resistance, high thermal conductivity, and high light transmittance. Before its application in semiconductor device manufacturing, CVD diamond wafers require processing steps such as cutting, grinding, and polishing to ensure surface quality meets industrial requirements. However, during the deposition and growth process of CVD diamond, the crystals preferentially grow along certain crystal planes, leading to problems such as uneven thickness, high internal stress, and large surface roughness in the final polycrystalline CVD diamond wafers. This results in fragmentation during the grinding process, leading to a low yield.

[0003] In these processing steps, grinding undertakes the majority of the diamond material removal task. Its main goal is to eliminate thickness variations in CVD diamond wafers after growth, thereby shortening the processing cycle of subsequent chemical polishing. However, traditional grinding techniques are difficult to effectively remove impurities from the diamond surface, resulting in low processing efficiency and difficulty in guaranteeing the surface quality of polycrystalline diamond wafers. Furthermore, CVD diamond fragmentation or peeling inevitably occurs during traditional grinding processes, which not only affects the surface quality of the wafers but also severely restricts the large-scale industrial application of CVD diamond wafers. Summary of the Invention

[0004] In order to overcome at least one of the problems existing in the prior art, one of the objectives of the present invention is to provide a surface treatment method for CVD diamond. By adjusting the way Ti metal is introduced, Ti metal and diamond undergo an interfacial reaction, generating a uniform and dense reaction layer on the surface of CVD diamond. Then, planarization is performed by auxiliary grinding, thereby effectively removing mechanical wear marks on the surface of CVD diamond, improving the surface quality of the workpiece and releasing surface stress.

[0005] A second objective of this invention is to provide a surface-treated CVD diamond obtained by the above-described surface treatment method.

[0006] The third objective of this invention is to provide an application of the above-mentioned surface-treated CVD diamond.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] The first aspect of the present invention provides a surface treatment method for CVD diamond, comprising the following steps: performing a first mechanical polishing on the CVD diamond to be treated; introducing Ti metal onto the surface of the CVD diamond after the first mechanical polishing, causing the Ti metal to react with the CVD diamond at the interface and forming a carbonized reaction layer on the surface of the CVD diamond; performing a second mechanical polishing to remove the carbonized reaction layer, thereby obtaining a surface-treated CVD diamond; wherein the Ti metal is introduced by means of embedding diamond with TiH2 powder or magnetron sputtering a Ti layer onto the diamond surface.

[0009] In some embodiments of the present invention, the Ti metal is introduced by means of TiH2 powder embedded diamond.

[0010] Both embedding diamond with TiH2 powder and magnetron sputtering of a Ti layer on the diamond surface can introduce Ti metal into the diamond surface, forming a stable and uniform carbide reaction layer. This allows for the removal of the carbide reaction layer and the achievement of good surface finish. Furthermore, compared to other methods, embedding diamond with TiH2 powder results in a more stable and uniform carbide reaction layer, leading to lower surface stress and higher surface finish in the surface-treated CVD diamond.

[0011] In some embodiments of the present invention, the particle size of the TiH2 powder is 60 to 80 μm; for example, it can be any value of 60 μm, 65 μm, 70 μm, 75 μm or 80 μm or a range between any two.

[0012] In some embodiments of the present invention, the purity of the TiH2 powder is ≥99.9 wt.%; for example, it can be any value of 99.9 wt.%, 99.92 wt.%, 99.95 wt.%, or 99.99 wt.%, or a range between any two.

[0013] In some embodiments of the present invention, the CVD diamond is a polycrystalline CVD diamond.

[0014] In some embodiments of the present invention, the CVD diamond to be processed is a polycrystalline CVD diamond blank after CVD growth.

[0015] In some embodiments of the present invention, the first mechanical grinding is performed using a grinding disc; further, the grinding disc used in the first mechanical grinding is a diamond bonded grinding disc.

[0016] In some embodiments of the present invention, the grinding disc used in the first mechanical grinding has a particle size of 20 to 100 μm; for example, it can be any value of 20 μm, 40 μm, 60 μm, 80 μm or 100 μm or a range between any two.

[0017] In some embodiments of the present invention, the surface roughness of the CVD diamond after the first mechanical polishing is 100 to 400 nm; for example, it can be any value or a range between 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm or 400 nm.

[0018] In some embodiments of the present invention, the method for causing the Ti metal to undergo an interfacial reaction with CVD diamond is vacuum heat treatment.

[0019] In some embodiments of the present invention, the temperature of the vacuum heat treatment is 600 to 900°C; for example, it can be any value or a range between any two of 600°C, 650°C, 700°C, 750°C, 800°C, 850°C, or 900°C, such as 650 to 900°C, 700 to 900°C, 700 to 800°C, etc.

[0020] By further optimizing the heat treatment process parameters, the interfacial reaction behavior between Ti metal and diamond can be controlled, thereby optimizing the interfacial reaction between Ti metal and diamond and generating a more stable, uniform and dense reaction layer on the surface of CVD diamond. This improves the surface quality of CVD diamond and further releases its surface stress.

[0021] Using a suitable vacuum heat treatment temperature is beneficial for obtaining a stable and thick carbonized reaction layer, which in turn facilitates the removal of the carbonized reaction layer through subsequent grinding, resulting in diamond samples with better surface quality. Specifically, a suitable vacuum heat treatment temperature helps to give Ti metal and diamond a suitable reaction activation energy, thereby generating stable carbides on the diamond surface. At the same time, it can control the solid solution and diffusion behavior of Ti metal and diamond, ensuring that the carbonized reaction layer has a suitable thickness.

[0022] In some embodiments of the present invention, the vacuum heat treatment time is 0.5 to 2 hours; for example, it can be any value of 0.5 hours, 0.8 hours, 1 hour, 1.5 hours or 2 hours or a range between any two.

[0023] In some embodiments of the present invention, the vacuum degree of the vacuum heat treatment is ≤1×10⁻⁶. -3 Pa; for example, it could be 0.1 × 10⁻⁶ Pa. -3 Pa, 0.5×10 -3 Pa, 0.8×10 -3 Pa or 1×10 -3 Pa is any value in Pa or a range of values ​​between any two.

[0024] In some embodiments of the present invention, the carbonization reaction layer comprises TiC carbide; in some specific embodiments of the present invention, the morphology of the TiC carbide comprises scallop-shaped, cylindrical, or a combination thereof; in some more specific embodiments of the present invention, the morphology of the TiC carbide is scallop-shaped.

[0025] In some embodiments of the present invention, the vacuum heat treatment further includes a step of cooling to room temperature; specifically, the room temperature is 20 to 30°C; the cooling is carried out in a vacuum environment.

[0026] In some embodiments of the present invention, the second mechanical polishing is performed using a polishing disc; further, the polishing disc used in the second mechanical polishing is a diamond bonded polishing disc.

[0027] In some embodiments of the present invention, the grinding disc used in the second mechanical grinding has a particle size of 20 to 100 μm; for example, it can be any value of 20 μm, 40 μm, 60 μm, 80 μm or 100 μm or a range between any two.

[0028] A second aspect of the present invention provides a surface-treated CVD diamond, said surface-treated CVD diamond being prepared by a surface treatment method comprising the first aspect of the present invention.

[0029] In some embodiments of the present invention, the surface roughness of the surface-treated CVD diamond is 60 to 140 nm; for example, it can be any value of 60 μm, 80 μm, 100 μm, 120 μm or 140 μm or a range between any two.

[0030] In some embodiments of the present invention, the Raman peak center value of the surface-treated CVD diamond is 1332–1333 cm⁻¹. -1 For example, it could be 1332cm. -1 1332.2cm -1 1332.4cm -1 1332.6cm -1 1332.8cm -1 Or 1333cm -1 Any value in or a range of values ​​between any two.

[0031] A third aspect of the present invention provides the application of surface-treated CVD diamond as described in the second aspect of the present invention in the fields of machining, electronics, optics or medical applications.

[0032] In some embodiments of the present invention, the surface-treated CVD diamond is used in the field of machining as cutting tools, abrasives, etc.; in the field of electronics as heat dissipation materials, semiconductor devices, etc.; in the field of optics as window materials, optical elements, etc.; and in the field of medicine as biosensors, medical materials, etc.

[0033] The beneficial effects of this invention are as follows: By adjusting the way Ti metal is introduced, this invention utilizes the interfacial reaction behavior between Ti metal and diamond to generate a carbonized reaction layer on the surface of CVD diamond. Then, through mechanical polishing, mechanical scratches on the surface of CVD diamond can be effectively removed, effectively improving the surface quality of CVD diamond and releasing its surface stress. Furthermore, it makes the diamond polishing process more controllable. The resulting surface-treated CVD diamond has good application prospects in the fields of machining, electronics, optics, or medicine. Attached Figure Description

[0034] Figure 1 The above are schematic diagrams of the surface treatment methods for CVD diamond in Examples 1 to 8.

[0035] Figure 2 The diagram shows the structure of the grinding machine in Examples 1 to 8; the markings are as follows: 1-polycrystalline CVD diamond sheet, 2-diamond bonded grinding disc, 3-base.

[0036] Figure 3 This is a SEM image of the sample after vacuum heat treatment in Example 1.

[0037] Figure 4 The image shows the surface quality of TiH2 / polycrystalline CVD diamond before and after interfacial reaction-assisted grinding in Example 1.

[0038] Figure 5 The image shows the Raman spectral frequency shift histogram of the diamond samples obtained in Example 1 and Comparative Examples 1-2.

[0039] Figure 6 The images show experimental models of diamond embedded in TiH2 powder in Examples 1-4 and the optical morphology of the samples after vacuum heat treatment.

[0040] Figure 7 The images show the Raman spectra of diamond embedded in TiH2 powder after heat treatment in Examples 1-4.

[0041] Figure 8 This is a SEM image of the sample after vacuum heat treatment in Example 5.

[0042] Figure 9The image shows the surface quality of sputtered Ti / polycrystalline CVD diamond before and after interfacial reaction-assisted grinding in Example 2.

[0043] Figure 10 The image shows the Raman spectral frequency shift histograms of the diamond samples obtained in Example 5 and Comparative Examples 3-4.

[0044] Figure 11 The images show experimental model diagrams of diamond sputtered Ti layers in Examples 5-8 and the optical morphology of the samples after vacuum heat treatment.

[0045] Figure 12 The images are Raman spectra of the diamond sputtered Ti layers after heat treatment in Examples 5-8.

[0046] Figure 13 The image shows the SEM morphology of the sample after vacuum heat treatment in Comparative Example 5.

[0047] Figure 14 The experimental model diagrams of Ti powder-embedded diamond in Comparative Examples 5-8 and the optical morphology of the samples after vacuum heat treatment are shown.

[0048] Figure 15 The images show the Raman spectra of Ti powder-embedded diamond after heat treatment in Comparative Examples 5–8. Detailed Implementation

[0049] The following specific embodiments further illustrate the content of the present invention in detail. It should also be understood that the following embodiments are only for further explanation of the present invention and should not be construed as limiting the scope of protection of the present invention. Non-essential improvements and adjustments made by those skilled in the art based on the principles described herein are all within the scope of protection of the present invention. The specific process parameters, etc., in the following examples are merely examples within a suitable range; that is, those skilled in the art can make selections within a suitable range based on the description herein, and are not intended to be limited to the specific data in the examples below. Unless otherwise specified, the raw materials, reagents, or apparatus used in the following embodiments and comparative examples can be obtained from conventional commercial sources or by existing known methods.

[0050] It should be noted that in the following examples and comparative examples, room temperature refers to 20–30°C.

[0051] Example 1

[0052] A surface treatment method for CVD diamond, the process diagram is as follows: Figure 1 The grinding of polycrystalline CVD diamond is aided by the interfacial reaction between diamond and Ti metal. The Ti metal is introduced by embedding diamond in TiH2 powder and then heat-treating it. The specific steps are as follows:

[0053] S1. Mechanical grinding: using methods such as... Figure 2 The grinding process is performed using the grinding machine shown. The grown polycrystalline CVD diamond blank 1 is placed on the diamond-bonded grinding disc 2, which is connected to the base 3. Mechanical grinding is then performed using the grinding machine; the diamond-bonded grinding disc 2 used for mechanical grinding has a particle size of 40 μm and 80 μm; the surface roughness of the polycrystalline CVD diamond after mechanical grinding is 286.0 nm.

[0054] S2. Solid-state reaction: Ti metal is introduced onto the surface of the mechanically ground polycrystalline CVD diamond wafer, causing an interfacial reaction between the Ti metal and the CVD diamond. This produces a uniform and dense reaction layer on the CVD diamond surface, completing the interfacial reaction. The Ti metal is introduced by embedding TiH2 powder in diamond and then heat-treating it. The TiH2 powder has a particle size of 60 μm and a purity of 99.999 wt.%. The CVD diamond embedded with TiH2 powder is placed in a corundum crucible, then the entire structure is placed in a quartz tube and vacuum heat-treated using a vacuum tube furnace system. The vacuum level inside the furnace during the heat treatment process is ≤1×10⁻⁶. -3 The heat treatment temperature window was 700℃, and the heat treatment time was 1 hour. The heat-treated sample was then cooled to room temperature in a vacuum environment, resulting in a uniform and dense reaction layer of TiC carbide. The SEM morphology of the sample after vacuum heat treatment is shown below. Figure 3 As shown in the figure, the TiC carbides formed have a scallop-like morphology.

[0055] S3. Removal of the reaction layer: The polycrystalline CVD diamond wafer after the interface reaction is completed is placed on a diamond-bonded polishing pad, and the reaction layer is removed by auxiliary polishing with a polishing machine to obtain the surface-treated CVD diamond, denoted as TiH2 / polycrystalline CVD diamond. The diamond-bonded polishing pad used for interface reaction assistance has a particle size of 80μm. Coarse polishing is performed using an 80μm polishing pad, and fine polishing is performed using an 80μm polishing pad and free abrasive.

[0056] Figure 4 The figures show the surface quality of TiH2 / polycrystalline CVD diamond before and after interface reaction-assisted polishing in Example 1, where (a) is before polishing and (b) is after polishing. As can be seen from the figures, after interface reaction-assisted polishing, the surface roughness of the polycrystalline CVD diamond decreased from 286.0 nm before the reaction to 136.0 nm.

[0057] Comparative Example 1

[0058] A surface treatment method for CVD diamond, using an 80μm polishing disc for rough polishing, includes the following steps: placing the grown polycrystalline CVD diamond blank onto a diamond bonded polishing disc and mechanically polishing it using a polishing machine; the diamond bonded polishing disc used for mechanical polishing has a particle size of 80μm.

[0059] Comparative Example 2

[0060] A surface treatment method for CVD diamond, using an 80μm polishing disc and free abrasive for fine polishing, the specific steps are as follows: the polycrystalline CVD diamond blank after growth is placed on a diamond bonded polishing disc and mechanically polished by a polishing machine; the diamond bonded polishing disc used for mechanical polishing has a particle size of 80μm, and free abrasive is added at the same time for polishing.

[0061] Figure 5 The table shows the Raman spectral frequency shift histograms of the diamond samples prepared in Example 1 and Comparative Examples 1-2. The sample from Comparative Example 1 is described as having undergone "80μm coarse polishing," the sample from Comparative Example 2 is described as having undergone "80μm + free abrasive fine polishing," and the sample from Example 1 is described as having undergone "700℃-1h reaction-assisted grinding." The standard diamond Raman peak value is 1332.5 cm⁻¹. -1 , Figure 5 The peak values ​​of the standard diamond Raman spectral data are represented by dashed lines. The Raman frequency shift can reflect surface stress. Figure 5 As can be seen, compared with the mechanical grinding of Comparative Examples 1 and 2, the Raman peak center value of the diamond sample obtained by interfacial reaction-assisted grinding in Example 1 is closer to the standard value. The stress on the surface of the samples in Comparative Examples 1 and 2 is mainly compressive stress, while that in Example 1 is mainly tensile stress, indicating that the stress on the surface of polycrystalline CVD diamond was released after interfacial reaction-assisted grinding in Example 1.

[0062] Example 2

[0063] A surface treatment method for CVD diamond differs from Example 1 in that the temperature window for heat treatment in step S2 of this example is 600°C; the other steps are the same as in Example 1.

[0064] Example 3

[0065] A surface treatment method for CVD diamond differs from Example 1 in that the temperature window for heat treatment in step S2 of this example is 800°C; the other steps are the same as in Example 1.

[0066] Example 4

[0067] A surface treatment method for CVD diamond differs from Example 1 in that the temperature window for heat treatment in step S2 of this example is 900°C; the other steps are the same as in Example 1.

[0068] Figure 6The images show experimental model diagrams of TiH2 powder-embedded diamond in Examples 1-4 and the optical morphology of the samples after vacuum heat treatment. Specifically, (a) is an experimental model diagram of TiH2 powder-embedded diamond; (b) is the optical morphology of the sample after vacuum heat treatment in Example 2; (c) is the optical morphology of the sample after vacuum heat treatment in Example 1; (d) is the optical morphology of the sample after vacuum heat treatment in Example 3; and (e) is the optical morphology of the sample after vacuum heat treatment in Example 4. Figure 6 It is evident that using appropriate vacuum heat treatment temperatures in Examples 1-4 is beneficial for obtaining a carbonized reaction layer with stable performance and thickness, which in turn facilitates removal through subsequent grinding to obtain diamond samples with better surface quality. In contrast, if the heat treatment temperature is too low, the activation energy for the reaction between Ti metal and diamond is insufficient, making it difficult to form stable carbides on the diamond surface. If the heat treatment temperature is too high, solid solution and diffusion will continue to occur between Ti metal and diamond, making it difficult to control the thickness of the reaction layer.

[0069] Figure 7 The images show the Raman spectra of the TiH2 powder-embedded diamond samples after heat treatment in Examples 1-4, where (a) is the Raman peak spectrum of Examples 1-4; and (b) is a magnified area of ​​a portion of the peak spectrum of the sample from Example 1. Figure 7 It can be seen that at 600℃, only 1332 cm² of the surface was detected. -1 The characteristic peaks of diamond begin to appear on the surface after the reaction at 700℃, with a peak length of 251 cm⁻¹. -1 340cm -1 609cm -1 The titanium carbide peak, further increased by raising the surface temperature to 800℃~900℃, further enhances the intensity of the surface titanium carbide peak; in addition, 261cm -1 606cm -1 The Raman peak was assigned to titanium dioxide. The Raman detection results were basically consistent with the aforementioned optical and scanning electron microscopy morphology results, indicating that Ti, after thermal decomposition of TiH2, adhered to the diamond surface. As the reaction proceeded, some Ti at the interface reacted with diamond to form carbides, while the remaining unreacted Ti remained attached to the outer surface and oxidized upon contact with air. Therefore, the appropriate vacuum heat treatment temperature used in Examples 1-4 facilitated the reaction between diamond and Ti at the interface to form carbides. At lower heat treatment temperatures, unreacted Ti adhered to the diamond surface and oxidized upon contact with air, failing to form a stable carbide reaction layer with diamond.

[0070] Example 5

[0071] A surface treatment method for CVD diamond utilizes the interfacial reaction between diamond and Ti metal to assist in the grinding of polycrystalline CVD diamond. The Ti metal is introduced by magnetron sputtering a Ti layer onto the diamond surface followed by heat treatment. The specific steps are as follows:

[0072] S1. Mechanical polishing: The polycrystalline CVD diamond blank after growth is placed on a diamond bonded polishing disc and mechanically polished by a polishing machine; the diamond bonded polishing disc used for mechanical polishing has a particle size of 40 and 80 μm; the surface roughness of the polycrystalline CVD diamond after mechanical polishing is 139.9 nm.

[0073] S2. Solid-state reaction: Ti metal is introduced onto the surface of the mechanically ground polycrystalline CVD diamond wafer, causing an interfacial reaction between the Ti metal and the CVD diamond. This results in a uniform and dense reaction layer on the CVD diamond surface, completing the interfacial reaction. The Ti metal is introduced by magnetron sputtering a Ti layer onto the diamond surface followed by heat treatment; the purity of the elemental Ti metal target is 99.999 wt.%. After the magnetron sputtered Ti layer on the polycrystalline CVD diamond is placed in an alumina crucible, the entire assembly is placed in a quartz tube and vacuum heat-treated using a vacuum tube furnace system. The vacuum level inside the furnace during the heat treatment process is ≤1×10⁻⁶. -3 The heat treatment temperature window was 700℃, and the heat treatment time was 1 hour. The heat-treated sample was then cooled to room temperature in a vacuum environment, resulting in a uniform and dense reaction layer of TiC carbide. The SEM morphology of the sample after vacuum heat treatment is shown below. Figure 8 As shown in the figure, the TiC carbides formed have a scallop-like morphology.

[0074] S3. Removal of the reaction layer: The polycrystalline CVD diamond wafer after the interface reaction is completed is placed on a diamond-bonded polishing pad, and the reaction layer is removed by auxiliary polishing with a polishing machine to obtain a surface-treated CVD diamond, denoted as sputtered Ti / polycrystalline CVD diamond. The diamond-bonded polishing pad used for interface reaction assistance has a particle size of 40μm; rough polishing is performed using a 40μm polishing pad, and fine polishing is performed using a 40μm polishing pad and free abrasive.

[0075] Figure 9 The figures show the surface quality of sputtered Ti / polycrystalline CVD diamond before and after interface reaction-assisted polishing in Example 2, where (a) is before polishing and (b) is after polishing. As can be seen from the figures, after interface reaction-assisted polishing, the surface roughness of the polycrystalline CVD diamond decreased from 139.9 nm before the reaction to 63.9 nm.

[0076] Comparative Example 3

[0077] A surface treatment method for CVD diamond, using a 40μm polishing disc for rough polishing, the specific steps are as follows: the grown polycrystalline CVD diamond blank is placed on a diamond bonded polishing disc and mechanically polished by a polishing machine; the particle size of the diamond bonded polishing disc used for mechanical polishing is 40μm.

[0078] Comparative Example 4

[0079] A surface treatment method for CVD diamond, using a 40μm polishing disc and free abrasive for fine polishing, the specific steps are as follows: the grown polycrystalline CVD diamond blank is placed on a diamond bonded polishing disc and mechanically polished by a polishing machine; the diamond bonded polishing disc used for mechanical polishing has a particle size of 40μm, and free abrasive is added at the same time for polishing.

[0080] Figure 10 The table shows the Raman spectral frequency shift histograms of the diamond samples prepared in Example 5 and Comparative Examples 3-4. The sample from Comparative Example 3 is described as having a "40μm coarse polishing" finish, the sample from Comparative Example 4 is described as having a "40μm + free abrasive fine polishing" finish, and the sample from Example 5 is described as having a "700℃-1h reaction-assisted grinding" finish. The standard diamond Raman peak value is 1332.5 cm⁻¹. -1 , Figure 10 The peak values ​​of the standard diamond Raman spectral data are represented by dashed lines. The Raman frequency shift can reflect surface stress. Figure 10 As can be seen, compared with the mechanical grinding of Comparative Examples 3-4, the Raman peak center value of the diamond sample obtained by interface reaction-assisted grinding in Example 5 is closer to the standard value. The stress on the surface of the samples in Comparative Examples 3-4 is mainly compressive stress. Comparative stress also exists in Example 5, but the stress value is smaller, indicating that the stress on the surface of polycrystalline CVD diamond is released after interface reaction-assisted grinding.

[0081] The polycrystalline CVD diamond samples obtained in Examples 1 and 5 were compared with standard diamond sheets, and the statistical results are shown in Table 1. Table 1 shows that the diamond samples obtained in Examples 1 and 5 through interface reaction-assisted grinding have Raman peak center values ​​close to the standard values, and small peak shift values, indicating low surface stress and high surface processing quality. In comparison, TiH2 powder-embedded reaction-assisted grinding achieves even better surface processing quality.

[0082] Table 1. Statistical table of Raman peak center values ​​and offset values ​​for standard diamond sheets and samples from Examples 1 and 5.

[0083] serial number sample <![CDATA[Raman peak center value / cm -1 > <![CDATA[Peak spectrum offset value / cm -1 > / Standard diamond sheet 1332.5 0 Example 1 <![CDATA[TiH2 powder packeting reaction-assisted grinding]]> 1332.46 -0.04 Example 5 Reactive grinding of Ti layers by magnetron sputtering 1332.77 0.27

[0084] Example 6

[0085] A surface treatment method for CVD diamond differs from Example 5 in that the temperature window for heat treatment in step S2 of this example is 600°C; the other steps are the same as in Example 5.

[0086] Example 7

[0087] A surface treatment method for CVD diamond differs from Example 5 in that the temperature window for heat treatment in step S2 of this example is 800°C; the other steps are the same as in Example 5.

[0088] Example 8

[0089] A surface treatment method for CVD diamond differs from Example 5 in that the temperature window for heat treatment in step S2 of this example is 900°C; the other steps are the same as in Example 5.

[0090] Figure 11 The images show experimental model diagrams of diamond-sputtered Ti layers from Examples 5 to 8, and the optical morphology of the samples after vacuum heat treatment. Specifically, (a) is an experimental model diagram of the diamond-sputtered Ti layer; (b) is the optical morphology of the sample after vacuum heat treatment in Example 6; (c) is the optical morphology of the sample after vacuum heat treatment in Example 5; (d) is the optical morphology of the sample after vacuum heat treatment in Example 7; and (e) is the optical morphology of the sample after vacuum heat treatment in Example 8. Figure 11 It is evident that using appropriate vacuum heat treatment temperatures in Examples 5-8 is beneficial for obtaining a carbonized reaction layer with stable performance and thickness, which in turn facilitates removal through subsequent grinding to obtain diamond samples with better surface quality. In contrast, if the heat treatment temperature is too low, the activation energy for the reaction between Ti metal and diamond is insufficient, making it difficult to form stable carbides on the diamond surface. If the heat treatment temperature is too high, solid solution and diffusion will continue to occur between Ti metal and diamond, making it difficult to control the thickness of the reaction layer.

[0091] Figure 12 The images show the Raman spectra of the samples after heat treatment of the diamond sputtered Ti layer in Examples 5-8, where (a) is the Raman peak spectrum of Examples 5-8; and (b) is a magnified area of ​​a portion of the peak spectrum of the sample in Example 5. Figure 12 It can be seen that at 600℃, only 1332 cm² of the surface was detected. -1 The diamond peak is due to the fact that metals do not exhibit the Raman effect, thus the unreacted Ti layer after sputtering onto the diamond surface cannot be detected; after 700℃, a 430cm peak begins to appear on the surface. -1 609cm -1 Titanium carbide peak and 606 cm⁻¹ -1 In addition to the titanium oxide peak, there is also the 1580 cm⁻¹ peak. -1The graphite peak is observed; further increasing the surface temperature to 800℃~900℃ further enhances the intensity of the surface titanium carbide peak. Therefore, the appropriate vacuum heat treatment temperature used in Examples 5-8 facilitates the reaction between diamond and Ti at the interface to form carbides. Ti that fails to react on the surface at lower heat treatment temperatures will adhere to the diamond surface and oxidize upon contact with air, failing to form a stable carbide reaction layer with diamond.

[0092] Comparative Example 5

[0093] A surface treatment method for CVD diamond differs from Example 1 in that TiH2 powder is replaced with Ti powder in step S2; the other steps are the same as in Example 1.

[0094] Comparative Example 6

[0095] A surface treatment method for CVD diamond differs from Comparative Example 5 in that the temperature window for heat treatment in step S2 of this example is 600℃; the other steps are the same as those in Comparative Example 5.

[0096] Comparative Example 7

[0097] A surface treatment method for CVD diamond differs from Comparative Example 5 in that the temperature window for heat treatment in step S2 of this example is 800℃; the other steps are the same as those in Comparative Example 5.

[0098] Comparative Example 8

[0099] A surface treatment method for CVD diamond differs from Comparative Example 5 in that the temperature window for heat treatment in step S2 of this example is 900℃; the other steps are the same as those in Comparative Example 5.

[0100] Figure 13 The image shows the SEM morphology of the sample after vacuum heat treatment in Comparative Example 5. Figure 14 The images show experimental model diagrams of Ti powder-embedded diamond in Comparative Examples 5-8 and the optical morphology of the samples after vacuum heat treatment. Specifically, (a) is an experimental model diagram of Ti powder-embedded diamond; (b) is the optical morphology of the sample after vacuum heat treatment in Comparative Example 6; (c) is the optical morphology of the sample after vacuum heat treatment in Comparative Example 5; (d) is the optical morphology of the sample after vacuum heat treatment in Comparative Example 7; and (e) is the optical morphology of the sample after vacuum heat treatment in Comparative Example 8. Figure 14 As can be seen, when using Ti powder to embed diamond, the Ti powder is prone to oxidation during the embedding process, making it difficult to achieve solid solution and diffusion with the diamond during heat treatment. The reactants are dispersed on the diamond surface, and the reaction layer fails to adhere uniformly. Therefore, the method of embedding diamond with Ti powder is difficult to form a carbonized reaction layer on the diamond surface, making it difficult to achieve good diamond surface treatment results in this invention.

[0101] Figure 15 Raman spectra of Ti powder-embedded diamond samples after heat treatment in Comparative Examples 5–8 are shown. (a) shows the Raman peak spectra of Comparative Examples 5–8; (b) shows a magnified portion of the peak spectrum of Comparative Example 7. Figure 15 It is evident that after the reaction at 600℃ and 700℃, only 1332 cm⁻¹ was detected on the surface of the diamond. -1 The characteristic Raman peaks of diamond were observed, which are consistent with the morphological results obtained by scanning electron microscopy. After reacting diamond at 800℃ and 900℃, a 251 cm⁻¹ peak was detected on the diamond surface. -1 345cm -1 In addition to the characteristic Raman peaks of titanium carbide, a 1332 cm⁻¹ peak was detected on the diamond surface. -1 The diamond characteristic peak at 1580cm -1 The presence of a graphite peak indicates that during the formation of titanium carbide, the diamond carbon on the surface transforms into graphite carbon. During the reaction, diamond sp... 3 Carbon atoms are first converted into sp 2 Graphite carbon atoms diffuse into titanium atoms, and some carbon atoms combine with interfacial titanium atoms to form titanium carbide, which adheres to the surface of the titanium layer and eventually detaches from the diamond surface, forming pitting (see...). Figure 13 During this process, some titanium carbide remains on the pitting and diamond surface. Therefore, by using Ti powder to embed diamond, graphitization occurs on the diamond surface, and some of the diamond sp... 3 Carbon atoms are first converted into sp 2 The diffusion of graphite carbon atoms into titanium atoms eventually leads to a discrete distribution of reactants on the diamond surface. Furthermore, the reactants are prone to detachment, resulting in pitting corrosion on the surface. Therefore, it is difficult to achieve a good diamond surface treatment effect in this invention.

[0102] In this embodiment of the invention, by adjusting the introduction method of Ti metal and optimizing the design of heat treatment process parameters, the interfacial reaction behavior between Ti metal and diamond is controlled, so that Ti metal and diamond undergo an interfacial reaction, generating a uniform and dense reaction layer on the surface of polycrystalline CVD diamond. Then, the surface of polycrystalline CVD diamond is planarized by auxiliary grinding, thereby effectively removing mechanical wear marks on the surface of polycrystalline CVD diamond, significantly improving the surface processing quality of the workpiece and releasing its surface stress.

[0103] In summary, this invention, by adjusting the introduction method of Ti metal and utilizing the interfacial reaction behavior between Ti metal and diamond, generates a carbonized reaction layer on the surface of CVD diamond. Then, through mechanical polishing, it effectively removes mechanical scratches from the CVD diamond surface, significantly improves the surface quality of the CVD diamond, releases its surface stress, and makes the diamond polishing process more controllable. The resulting surface-treated CVD diamond has promising application prospects in the fields of machining, electronics, optics, and medicine.

Claims

1. A surface treatment method for CVD diamond, characterized in that, Includes the following steps: The CVD diamond to be processed is subjected to a first mechanical grinding; Ti metal is introduced into the surface of CVD diamond after the first mechanical polishing, so that Ti metal reacts with CVD diamond at the interface and forms a carbonized reaction layer on the surface of CVD diamond. A second mechanical grinding process is performed to remove the carbonized reaction layer, resulting in surface-treated CVD diamond. The Ti metal is introduced by embedding diamond in TiH2 powder; the particle size of the TiH2 powder is 60~80μm. The method for inducing an interfacial reaction between Ti metal and CVD diamond is vacuum heat treatment; the temperature of the vacuum heat treatment is 650~750℃; and the vacuum degree of the vacuum heat treatment is ≤1×10⁻⁶. -3 Pa; The second mechanical grinding is performed using a grinding disc; The surface roughness of the surface-treated CVD diamond is 60~140 nm; the Raman peak center value of the surface-treated CVD diamond is 1332.4~1332.6 cm. -1 .

2. The surface treatment method according to claim 1, characterized in that, The purity of the TiH2 powder is ≥99.9 wt.%.

3. The surface treatment method according to claim 1, characterized in that, The first mechanical grinding uses a grinding disc with a particle size of 20~100μm; And / or, the surface roughness of the CVD diamond after the first mechanical polishing is 100~400nm.

4. The surface treatment method according to claim 1, characterized in that, The vacuum heat treatment time is 0.5 to 2 hours.

5. The surface treatment method according to claim 1, characterized in that, The carbonization reaction layer comprises TiC carbides; the morphology of the TiC carbides includes scalloped, cylindrical, or a combination thereof.

6. The surface treatment method according to claim 1, characterized in that, The grinding disc used in the second mechanical grinding process has a particle size of 20~100μm.

7. A surface-treated CVD diamond, characterized in that, The surface-treated CVD diamond is prepared by the surface treatment method according to any one of claims 1 to 6.

8. The application of the surface-treated CVD diamond as described in claim 7 in the fields of machining, electronics, optics or medicine.

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