Surface treatment method of CVD diamond

Abstract

The invention discloses a CVD diamond surface treatment method, and belongs to the technical field of crystal materials and surface treatment thereof. The surface treatment method of the CVD diamond comprises the following steps: carrying out first mechanical grinding on the CVD diamond to be treated; ti metal is introduced to the surface of the CVD diamond subjected to first mechanical grinding, so that the Ti metal and the CVD diamond are subjected to interface reaction, and a carbonization reaction layer is formed on the surface of the CVD diamond; carrying out second mechanical grinding, and removing the carbonization reaction layer to obtain the surface-treated CVD diamond, the introduction mode of the Ti metal comprises the steps that diamond is embedded with TiH2 powder or a Ti layer is formed on the surface of the diamond through magnetron sputtering. According to the method, by adjusting the introduction mode of the Ti metal and utilizing the interface reaction behavior of the Ti metal and the diamond, the carbonization reaction layer is generated on the surface of the CVD diamond, and then mechanical grinding is conducted, so that the surface quality of the CVD diamond can be effectively improved, and the surface stress of the CVD diamond is released.

Description

Technical Field

[0001] The present invention belongs to the technical field of crystal materials and their surface treatment, and particularly relates to a surface treatment method for CVD diamond. Background Art

[0002] Due to its excellent properties such as high hardness, high wear resistance, high thermal conductivity, and high light transmittance, CVD (chemical vapor deposition) diamond shows broad application prospects in the field of electronic information. Before it is applied to the manufacture of semiconductor devices, CVD diamond wafers need to go through processing procedures such as cutting, grinding, and polishing to ensure that the surface quality meets industrial requirements. However, during the deposition and growth process of CVD diamond, the crystal grows preferentially along certain crystal planes, resulting in problems such as uneven thickness, high internal stress, and large surface roughness value in the finally formed polycrystalline CVD diamond wafers. This leads to the problem that polycrystalline CVD diamond is prone to fragmentation during the grinding process, and the yield is low.

[0003] In these processing procedures, grinding processing undertakes most of the task of removing diamond materials. Its main goal is to eliminate the thickness difference of CVD diamond wafers after growth, so as to shorten the processing cycle of subsequent chemical polishing procedures. However, traditional grinding techniques are difficult to effectively remove impurities on the diamond surface, with low processing efficiency and difficult to ensure the processing surface quality of polycrystalline diamond wafers. In addition, CVD diamond fragmentation or spalling inevitably occurs during traditional grinding, which not only affects the processing 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 above problems existing in the prior art, one of the purposes of the present invention is to provide a surface treatment method for CVD diamond. By adjusting the introduction method of Ti metal, the Ti metal reacts with the diamond at the interface to form a uniform and dense reaction layer on the surface of CVD diamond, and then flattening treatment is carried out through assisted grinding, so as to effectively remove the mechanical scratches on the surface of CVD diamond, improve the processing surface quality of the workpiece and release the surface stress.

[0005] Another purpose of the present invention is to provide a surface-treated CVD diamond prepared by the above surface treatment method.

[0006] Another purpose of the present invention is to provide an application of the above surface-treated CVD diamond.

[0007] In order to achieve the above purposes, the technical solutions adopted by the present invention are 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 grinding on the CVD diamond to be treated; introducing Ti metal onto the surface of the CVD diamond after the first mechanical grinding, causing an interface reaction between the Ti metal and the CVD diamond to form a carburized reaction layer on the surface of the CVD diamond; performing a second mechanical grinding to remove the carburized reaction layer to obtain a surface-treated CVD diamond; the Ti metal is introduced by embedding the diamond with TiH2 powder or magnetron sputtering a Ti layer on the diamond surface.

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

[0010] Both the TiH2 powder-embedded diamond and magnetron sputtering of a Ti layer on the diamond surface can introduce Ti metal onto the diamond surface, forming a stable and uniform carbide reaction layer. This, in turn, allows for superior surface finish quality after removal. Furthermore, the TiH2 powder-embedded diamond method creates a more stable and uniform carbide reaction layer, resulting in a surface-treated CVD diamond with reduced surface stress and higher surface finish quality.

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

[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 among 99.9 wt.%, 99.92 wt.%, 99.95 wt.% or 99.99 wt.%, or any range between them.

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

[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 particle size of the grinding disk used in the first mechanical grinding is 20-100 μm; for example, it can be any value among 20 μm, 40 μm, 60 μm, 80 μm or 100 μm, or a range between any two values.

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

[0018] In some embodiments of the present invention, the way to make the Ti metal react with the CVD diamond at the interface is vacuum heat treatment.

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

[0020] Through further optimized design of the heat treatment process parameters, the interfacial reaction behavior between the Ti metal and the diamond can be regulated, the interfacial reaction between the Ti metal and the diamond can be optimized, a reaction layer with more stable, uniform and dense performance can be formed on the surface of the CVD diamond, thereby improving the surface quality of the CVD diamond and further releasing its surface stress.

[0021] Adopting a suitable vacuum heat treatment temperature is beneficial to obtaining a carbide reaction layer with stable performance and stable thickness, and further beneficial to removing it by subsequent grinding to obtain a diamond sample with better surface quality. Specifically, a suitable vacuum heat treatment temperature is beneficial to making the Ti metal and the diamond have a suitable reaction activation energy, thereby forming stable carbides on the diamond surface, and at the same time being able to control the solid solution and diffusion behaviors of the Ti metal and the diamond to ensure that the carbide reaction layer has a suitable thickness.

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

[0023] In some embodiments of the present invention, the vacuum degree of the vacuum heat treatment ≤ 1×10 -3 Pa; for example, it can be 0.1×10 -3 Pa, 0.5×10 -3 Pa, 0.8×10 -3 Pa or 1×10 -3 Pa or any value among them or a range value between any two of them.

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

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

[0026] In some embodiments of the present invention, the second mechanical grinding is carried out using a grinding disc; further, the grinding disc used for the second mechanical grinding is a diamond consolidated grinding disc.

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

[0028] The second aspect of the present invention provides a surface-treated CVD diamond, which is prepared by including the surface treatment method described in 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 - 140 nm; for example, it can be any value among 60 μm, 80 μm, 100 μm, 120 μm or 140 μm or a range value between any two of them.

[0030] In some embodiments of the present invention, the center value of the Raman peak of the surface-treated CVD diamond is 1332 - 1333 cm -1 ; for example, it can be 1332 cm -1 、1332.2 cm -1 、1332.4 cm -1 、1332.6 cm -1 、1332.8 cm -1 or 1333 cm -1 and any value among them or a range value between any two of them.

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

[0032] In some embodiments of the present invention, the applications of the surface-treated CVD diamond in the field of machining include being used as cutting tools, abrasives, etc.; the applications in the electronic field include being used as heat dissipation materials, semiconductor devices, etc.; the applications in the optical field include being used as window materials, optical components, etc.; the applications in the medical field include being used as biosensors, medical materials, etc.

[0033] The beneficial effects of the present invention are as follows: By adjusting the introduction method of Ti metal and utilizing the interfacial reaction behavior between Ti metal and diamond, a carbonization reaction layer is formed on the surface of CVD diamond. Then, through mechanical grinding, the mechanical scratches on the surface of CVD diamond can be effectively removed, the surface quality of CVD diamond can be effectively improved and its surface stress can be released, and the diamond grinding process becomes more controllable. The obtained surface-treated CVD diamond has good application prospects in the fields of machining, electronics, optics or medicine. Description of the Drawings

[0034] Figure 1 It is a schematic flow chart of the surface treatment method of CVD diamond in Examples 1-8.

[0035] Figure 2 It is a schematic structural diagram of the grinding machine in Examples 1-8; Marking description: 1 - polycrystalline CVD diamond sheet, 2 - diamond consolidated grinding disc, 3 - base.

[0036] Figure 3 It is a SEM morphology diagram of the sample after vacuum heat treatment in Example 1.

[0037] Figure 4 It is a surface quality diagram of TiH2 / polycrystalline CVD diamond before and after interfacial reaction-assisted grinding in Example 1.

[0038] Figure 5 It is a histogram of Raman spectral frequency shift of the diamond samples prepared in Example 1 and Comparative Examples 1-2 on the surface.

[0039] Figure 6 It is an experimental model diagram of TiH2 powder embedding diamond and the optical morphology of the sample after vacuum heat treatment in Examples 1-4.

[0040] Figure 7 It is a Raman detection spectrum of TiH2 powder embedding diamond after heat treatment in Examples 1-4.

[0041] Figure 8 It is a SEM morphology diagram of the sample after vacuum heat treatment in Example 5.

[0042] Figure 9Surface quality diagrams of sputtered Ti / polycrystalline CVD diamond before and after interface reaction-assisted grinding in Example 2.

[0043] Figure 10 Histogram of Raman spectral frequency shift of the diamond samples prepared in Example 5 and Comparative Examples 3-4.

[0044] Figure 11 Experimental model diagrams of diamond sputtered with Ti layer in Examples 5-8 and optical morphologies of the samples after vacuum heat treatment.

[0045] Figure 12 Raman detection spectra of the diamond sputtered with Ti layer after heat treatment in Examples 5-8.

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

[0047] Figure 14 Experimental model diagrams of Ti powder embedding diamond in Comparative Examples 5-8 and optical morphologies of the samples after vacuum heat treatment.

[0048] Figure 15 Raman detection spectra of the Ti powder embedding diamond after heat treatment in Comparative Examples 5-8. Detailed implementation manners

[0049] The content of the present invention will be further described in detail through specific examples below. It should be understood that the following examples are only used to further illustrate the present invention and cannot be construed as limiting the protection scope of the present invention. Some non-essential improvements and adjustments made by those skilled in the art according to the principles described in the present invention are all within the protection scope of the present invention. The specific process parameters and the like in the following examples are also only an example within a suitable range, that is, those skilled in the art can make selections within a suitable range through the description in this article, rather than being limited to the specific data in the following examples. The raw materials, reagents or devices used in the following examples and comparative examples can be obtained from conventional commercial channels or can be obtained by existing known methods without special instructions.

[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 schematic diagram is as Figure 1 , and the grinding of polycrystalline CVD diamond is assisted by the interface reaction between diamond and Ti metal. The introduction method of Ti metal is heat treatment with TiH2 powder embedding diamond. The specific steps are as follows:

[0053] S1. Mechanical grinding: Adopt asFigure 2 It is carried out with the shown grinding machine. After the growth of the polycrystalline CVD diamond blank sheet 1 is completed, it is placed on the diamond consolidated grinding disc 2, and the diamond consolidated grinding disc 2 is connected to the base 3. It is mechanically ground by the grinding machine; the particle sizes of the diamond consolidated grinding disc 2 for mechanical grinding are 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: Introduce Ti metal on the surface of the mechanically ground polycrystalline CVD diamond sheet, and make the Ti metal react with the CVD diamond at the interface to generate a uniform and dense reaction layer on the surface of the CVD diamond, and complete the interface reaction. The introduction method of Ti metal is the heat treatment of diamond embedded in TiH2 powder; the particle size of TiH2 powder is 60 μm, and the purity is 99.999 wt.%; the CVD diamond embedded with TiH2 powder is placed in a corundum crucible, and then the whole is placed in a quartz tube, and a vacuum heat treatment is carried out using a vacuum tube furnace system. The vacuum degree in the furnace during the heat treatment process is ≤1×10 -3 Pa, the temperature window for heat treatment is 700 °C, the heat treatment time is 1 hour, and the sample after heat treatment is cooled to room temperature in a vacuum environment. The formed uniform and dense reaction layer is TiC carbide. The SEM morphology diagram of the sample after this vacuum heat treatment is as Figure 3 shown. It can be seen from the figure that the morphology of the formed TiC carbide is scallop-shaped.

[0055] S3. Remove the reaction layer: Place the polycrystalline CVD diamond wafer after the interface reaction is completed on the diamond consolidated grinding disc, and assist in grinding it by the grinding machine to remove the reaction layer, and obtain the surface-treated CVD diamond, denoted as TiH2 / polycrystalline CVD diamond. The particle size of the diamond consolidated grinding disc for assisting the interface reaction is 80 μm. Coarse polishing is carried out using an 80-μm grinding disc, and fine polishing is carried out using an 80-μm grinding disc and free abrasive polishing.

[0056] Figure 4 Figure 15 shows the surface quality diagrams of TiH2 / polycrystalline CVD diamond before and after the interface reaction-assisted grinding in Example 1, where (a) is before grinding and (b) is after grinding. It can be seen from the figure that after the interface reaction-assisted grinding, the surface roughness of the polycrystalline CVD diamond is reduced from 286.0 nm before the reaction to 136.0 nm.

[0057] Comparative Example Ⅰ

[0058] A surface treatment method for CVD diamond, using an 80-μm grinding disc for coarse polishing, and the specific steps are as follows: Place the polycrystalline CVD diamond blank sheet after the growth is completed on the diamond consolidated grinding disc, and mechanically grind it by the grinding machine; the particle size of the diamond consolidated grinding disc for mechanical grinding is 80 μm.

[0059] Comparative Example 2

[0060] A surface treatment method for CVD diamond, which uses an 80-μm grinding disc and free abrasives for fine polishing. The specific steps are as follows: Place the grown polycrystalline CVD diamond blank on a diamond fixed abrasive grinding disc and mechanically grind it with a grinding machine; the particle size of the diamond fixed abrasive grinding disc used for mechanical grinding is 80 μm, and free abrasives are added for grinding at the same time.

[0061] Figure 5 It is a histogram of Raman spectral frequency shift of the diamond samples prepared in Example 1 and Comparative Examples 1-2. Among them, "80-μm rough polishing" is the sample of Comparative Example 1, "80-μm + free abrasive fine polishing" is the sample of Comparative Example 2, and "700°C - 1h reaction-assisted grinding" is the sample of Example 1. The standard diamond Raman peak spectral value is 1332.5 cm -1 , Figure 5 The standard diamond Raman peak spectral value is represented by a dotted line. Raman frequency shift can reflect surface stress. As Figure 5 can be seen, compared with the mechanical grinding of Comparative Examples 1-2, the center value of the Raman peak of the diamond sample obtained by the interface reaction-assisted grinding in Example 1 is closer to the standard value. The surface stress of the samples in Comparative Examples 1-2 is mainly compressive stress, while that in Example 1 is mainly tensile stress, indicating that the surface stress of the polycrystalline CVD diamond is released after the interface reaction-assisted grinding in Example 1.

[0062] Example 2

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

[0064] Example 3

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

[0066] Example 4

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

[0068] Figure 6Experimental model diagrams of diamond embedded in TiH2 powder and optical morphologies of samples after vacuum heat treatment in Examples 1 to 4. Among them, (a) is the experimental model diagram of diamond embedded in TiH2 powder; (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; (e) is the optical morphology of the sample after vacuum heat treatment in Example 4. From Figure 6 It can be seen that in Examples 1 to 4, using appropriate vacuum heat treatment temperatures is beneficial to obtaining a carbide reaction layer with stable performance and thickness, which is further beneficial to removing it by 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, and it is difficult to form stable carbides on the diamond surface; if the heat treatment temperature is too high, continuous solid solution and diffusion will occur between Ti metal and diamond, and it is difficult to control the thickness of the reaction layer.

[0069] Figure 7 Raman detection spectra of samples of diamond embedded in TiH2 powder after heat treatment in Examples 1 to 4. Among them, (a) is the Raman peak spectrum of Examples 1 to 4; (b) is the enlarged area of the partial peak spectrum of the sample in Example 1. From Figure 7 It can be seen that at 600 °C, only the characteristic peak of diamond at 1332 cm -1 is detected on the surface. After the reaction at 700 °C, titanium carbide peaks at 251 cm -1 , 340 cm -1 , and 609 cm -1 begin to appear on the surface. When the surface temperature is further increased to 800 °C - 900 °C, the intensity of the titanium carbide peaks on the surface further increases; in addition, the Raman peaks at 261 cm -1 and 606 cm -1 are assigned to titanium oxide. The Raman detection results are basically consistent with the aforementioned optical and scanning electron microscopy morphology results, indicating that Ti after the thermal decomposition of TiH2 adheres to the diamond surface. As the reaction progresses, some Ti at the interface reacts with diamond to form carbides, while the remaining unreacted Ti still adheres to the outer surface and oxidizes when exposed to air. Therefore, in Examples 1 to 4, using appropriate vacuum heat treatment temperatures helps diamond react with Ti at the interface to form carbides. At lower heat treatment temperatures, the unreacted Ti on the surface will adhere to the diamond surface and oxidize when exposed to air, and cannot form a stable carbide reaction layer with diamond.

[0070] Example 5

[0071] A surface treatment method for CVD diamond, which assists in the grinding of polycrystalline CVD diamond through the interfacial reaction between diamond and Ti metal. The introduction method of Ti metal is heat treatment after magnetron sputtering a Ti layer on the diamond surface. The specific steps are as follows:

[0072] S1. Mechanical grinding: Place the grown polycrystalline CVD diamond blank on a diamond-bonded grinding disc, and perform mechanical grinding on it through a grinding machine; the particle sizes of the diamond-bonded grinding discs used for mechanical grinding are 40 and 80 μm; the surface roughness of the polycrystalline CVD diamond after mechanical grinding is 139.9 nm.

[0073] S2. Solid-state reaction: Introduce Ti metal on the surface of the polycrystalline CVD diamond sheet after mechanical grinding, so that the Ti metal reacts with the CVD diamond to generate a uniform and dense reaction layer on the surface of the CVD diamond, and complete the interfacial reaction. The introduction method of Ti metal is heat treatment after magnetron sputtering a Ti layer on the diamond surface; the purity of the elemental Ti metal target is 99.999 wt.%; after the polycrystalline CVD diamond with the magnetron-sputtered Ti layer is placed in a corundum crucible, the whole is loaded into a quartz tube, and a vacuum heat treatment is carried out using a vacuum tube furnace system. The vacuum degree in the furnace during the heat treatment process is ≤1×10 -3 Pa, the temperature window for heat treatment is 700 °C, the heat treatment time is 1 hour, and the sample after heat treatment is cooled to room temperature in a vacuum environment. The formed uniform and dense reaction layer is TiC carbide. The SEM morphology diagram of the sample after this vacuum heat treatment is as Figure 8 shown. It can be seen from the figure that the morphology of the formed TiC carbide is scallop-shaped.

[0074] S3. Remove the reaction layer: Place the polycrystalline CVD diamond wafer after the interfacial reaction on a diamond-bonded grinding disc, and perform auxiliary grinding on it through a grinding machine to remove the reaction layer, and obtain the surface-treated CVD diamond, denoted as sputtered Ti / polycrystalline CVD diamond. The particle size of the diamond-bonded grinding disc used for assisting the interfacial reaction is 40 μm; rough polishing is carried out using a 40-μm grinding disc, and fine polishing is carried out using a 40-μm grinding disc and free abrasives.

[0075] Figure 9 Figure 17 is the surface quality diagram of the sputtered Ti / polycrystalline CVD diamond in Example 2 before and after the interfacial reaction-assisted grinding. Among them, (a) is before grinding, and (b) is after grinding. It can be seen from the figure that after the interfacial reaction-assisted grinding, the surface roughness of the polycrystalline CVD diamond is reduced from 139.9 nm before the reaction to 63.9 nm.

[0076] Comparative Example 3

[0077] A surface treatment method for CVD diamonds uses a 40 μm grinding disc for rough polishing. The specific steps are as follows: placing a grown polycrystalline CVD diamond blank on a diamond-consolidated grinding disc and mechanically grinding it using a grinder; the particle size of the diamond-consolidated grinding disc used for mechanical grinding is 40 μm.

[0078] Comparative Example 4

[0079] A surface treatment method for CVD diamond uses a 40μm grinding disc and free abrasives for fine polishing. The specific steps are as follows: a polycrystalline CVD diamond blank after growth is placed on a diamond consolidation grinding disc and mechanically ground by a grinder; the diamond consolidation grinding disc used for mechanical grinding has a particle size of 40μm, and free abrasives are added for grinding.

[0080] Figure 10 The Raman spectrum frequency shift histogram of the diamond samples obtained in Example 5 and Comparative Examples 3-4 is shown in the figure. The "40 μm rough polishing" is the sample of Comparative Example 3, the "40 μm + free abrasive fine polishing" is the sample of Comparative Example 4, and the "700 ° C - 1h reaction-assisted grinding" is the sample of Example 5. The standard diamond Raman peak spectrum value is 1332.5 cm -1 , Figure 1x0 The dotted line in the figure represents the Raman peak spectrum value of the standard diamond. Raman frequency shift can reflect surface stress. Figure 10 It can be seen that compared with the mechanical grinding of Comparative Examples 3 to 4, the center value of the Raman peak on the surface 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 of Comparative Examples 3 to 4 is mainly compressive stress. Compressive stress also exists in Example 5, but the stress value is smaller, indicating that the stress on the surface of the 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, yielding the statistical data shown in Table 1. Table 1 shows that the surface Raman peak center values of the diamond samples obtained through interfacial reaction-assisted polishing in Examples 1 and 5 are close to the standard values, with small peak spectrum shifts, indicating low surface stress and high surface finish quality. In comparison, TiH2 powder-embedded reaction-assisted polishing achieved superior surface finish quality.

[0082] Table 1 Statistics of Raman peak center values and offset values of standard diamond sheets and samples of Examples 1 and 5

[0083] Number Sample <![CDATA[Raman peak center value / cm -1 > <![CDATA[Peak spectrum offset value / cm -1 > / Standard diamond wafer 1332.5 0 Example 1 <![CDATA[TiH2 powder pack cementation reaction assisted grinding]]> 1332.46 -0.04 Example 5 Reactive assisted grinding of magnetron sputtered Ti layer 1332.77 0.27

[0084] Example 6

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

[0086] Example 7

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

[0088] Example 8

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

[0090] Figure 11 Figs. are the experimental model diagrams of diamond sputtered with Ti layer and the optical morphologies of samples after vacuum heat treatment in Examples 5 to 8. Among them, (a) is the experimental model diagram of diamond sputtered with 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; (e) is the optical morphology of the sample after vacuum heat treatment in Example 8. From Figure 11 It can be seen that in Examples 5 to 8, adopting appropriate vacuum heat treatment temperatures is beneficial to obtaining a stable and thickness-stable carbide reaction layer, which is further beneficial to removing it by 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, and it is difficult to form stable carbides on the diamond surface; if the heat treatment temperature is too high, continuous solid solution and diffusion will occur between Ti metal and diamond, and it is difficult to control the thickness of the reaction layer.

[0091] Figure 12 Figs. are the Raman detection spectra of samples after heat treatment of diamond sputtered with Ti layer in Examples 5 to 8. Among them, (a) is the Raman peak spectrum of Examples 5 to 8; (b) is the enlarged region of the partial peak spectrum of the sample in Example 5. From Figure 12 It can be seen that at 600°C, only the diamond peak at 1332 cm -1 on the surface is detected. This is because metals do not have the Raman effect, so the unreacted Ti layer sputtered on the diamond surface cannot be detected; after 700°C, titanium carbide peaks at 430 cm -1 and 609 cm -1 and the titanium oxide peak at 606 cm -1 begin to appear on the surface. In addition, at 1580 cm -1It is a graphite peak; when the surface temperature is further increased to 800 °C - 900 °C, the intensity of the surface titanium carbide peak is further enhanced. Therefore, using an appropriate vacuum heat treatment temperature in Examples 5 - 8 helps the diamond react with Ti at the interface to form carbides. At a lower heat treatment temperature, the Ti that fails to react on the surface will adhere to the diamond surface and oxidize when exposed to air, and it cannot form a stable carbide reaction layer with the diamond.

[0092] Comparative Example 5

[0093] A surface treatment method for CVD diamond, which is different from Example 1 in that in step S2 of this example, the TiH2 powder is replaced with Ti powder; other steps are the same as those in Example 1.

[0094] Comparative Example 6

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

[0096] Comparative Example 7

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

[0098] Comparative Example 8

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

[0100] Figure 13 It is the SEM morphology diagram of the sample after vacuum heat treatment in Comparative Example 5. Figure 14 It is the experimental model diagram of Ti powder embedding diamond and the optical morphology of the samples after vacuum heat treatment in Comparative Examples 5 - 8. Among them, (a) is the experimental model diagram of Ti powder embedding 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; (e) is the optical morphology of the sample after vacuum heat treatment in Comparative Example 8. As can be seen Figure 14 that by using the method of Ti powder embedding diamond, the Ti powder is prone to oxidation during the process of embedding diamond, and it is difficult to have solid solution and diffusion behavior with diamond during heat treatment. The reactants are discretely distributed on the diamond surface, and the reaction layer fails to adhere to the diamond surface evenly. Therefore, by using the method of Ti powder embedding diamond, it is difficult to form a carbide reaction layer on the diamond surface, and it is difficult to achieve a good diamond surface treatment effect in the present invention.

[0101] Figure 15 Raman detection spectra of the samples after heat treatment of diamond embedded in Ti powder in Comparative Examples 5-8. Among them, (a) is the Raman peak spectrum of Comparative Examples 5-8; (b) is the enlarged area of the partial peak spectrum of the sample in Comparative Example 7. It can be seen that Figure 15 after the reaction at 600 °C and 700 °C, only the Raman characteristic peak of diamond at 1332 cm -1 was detected on the surface of diamond, which is consistent with the morphological results obtained by scanning electron microscopy. After the reaction of diamond at 800 °C and 900 °C, the Raman characteristic peaks of titanium carbide at 251 cm -1 and 345 cm -1 were detected on the surface of diamond. In addition, the diamond characteristic peak at 1332 cm -1 and the graphite peak at 1580 cm -1 were detected on the surface of diamond, indicating that the diamond carbon on the surface was transformed into graphite carbon during the formation of titanium carbide. During the reaction process, the sp 3 carbon atoms of diamond were first transformed into sp 2 graphite carbon atoms diffused into titanium atoms, and some carbon atoms formed titanium carbide with the interfacial titanium atoms and adhered to the surface of the titanium layer, and finally detached from the surface of diamond to form pitting corrosion (see Figure 13 Note: There seems to be a potential error in the original text where "Figure 1x0" might be a typo. I've translated it as "Figure 10" for consistency, but it should be checked in the original context. ). During this process, some titanium carbide also remained on the pitting corrosion and the surface of diamond. Therefore, by using the method of embedding diamond in Ti powder, graphitization occurred on the surface of diamond, and some sp 3 carbon atoms of diamond were first transformed into sp 2 graphite carbon atoms diffused into titanium atoms, which eventually led to the discrete distribution of the reactants on the surface of diamond, and the reactants were easy to detach, resulting in easy formation of pitting corrosion on the surface, making it difficult to achieve good diamond surface treatment effect in the present invention.

[0102] In the embodiments of the present 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 regulated, so that Ti metal and diamond undergo an interfacial reaction to form a uniform and dense reaction layer on the surface of polycrystalline CVD diamond. Then, the surface of polycrystalline CVD diamond is flattened by assisted grinding, thereby effectively removing the mechanical scratches on the surface of polycrystalline CVD diamond, significantly improving the surface machining quality of the workpiece and releasing its surface stress.

[0103] In summary, by adjusting the introduction method of Ti metal and utilizing the interfacial reaction behavior between Ti metal and diamond, a carbonization reaction layer is formed on the surface of CVD diamond. Then, through mechanical grinding, the mechanical scratches on the surface of CVD diamond can be effectively removed, the surface quality of CVD diamond can be effectively improved, its surface stress can be released, and the diamond grinding process becomes more controllable. The surface-treated CVD diamond obtained has good application prospects in the fields of machining, electronics, optics, or medicine.

Claims

1. A surface treatment method for CVD diamond, characterized in that, It includes the following steps: Perform first mechanical grinding on the CVD diamond to be processed; Introduce Ti metal on the surface of the CVD diamond after the first mechanical grinding, cause an interfacial reaction between the Ti metal and the CVD diamond, and form a carbonization reaction layer on the surface of the CVD diamond; Perform second mechanical grinding to remove the carbonization reaction layer and obtain surface-treated CVD diamond; the introduction method of the Ti metal includes TiH2 powder embedding diamond or magnetron sputtering a Ti layer on the diamond surface.

2. The surface treatment method according to claim 1, wherein The particle size of the TiH2 powder is 60 - 80 μm; And / or, the purity of the TiH2 powder is ≥99.9 wt.%; 3. The surface treatment method according to claim 1, characterized in that, The particle size of the grinding disc used in the first mechanical grinding is 20 - 100 μm; And / or, the surface roughness of the CVD diamond after the first mechanical grinding is 100 - 400 nm; 4. The surface treatment method according to claim 1, characterized in that, The method for causing the interfacial reaction between the Ti metal and the CVD diamond is vacuum heat treatment.

5. The surface treatment method according to claim 4, wherein, The temperature of the vacuum heat treatment is 600 - 900 °C; And / or, the time of the vacuum heat treatment is 0.5 - 2 hours; and / or, the degree of vacuum in the vacuum heat treatment ≤ 1×10 -3 Pa.

6. The surface treatment method according to claim 1, characterized in that, The composition of the carbonization reaction layer includes TiC carbide; the morphology of the TiC carbide includes scallop shape, cylindrical shape or a combination thereof.

7. The surface treatment method according to claim 1, wherein, The particle size of the grinding disc used in the second mechanical grinding is 20 - 100 μm.

8. A surface-treated CVD diamond, characterized in that, The surface-treated CVD diamond is obtained by the surface treatment method described in any one of claims 1 - 8.

9. The surface-treated CVD diamond according to claim 8, wherein, The surface roughness of the surface-treated CVD diamond is 60 - 140 nm; And / or, the center value of the Raman peak of the surface-treated CVD diamond is 1332-1333 cm -1 .

10. Use of the surface-treated CVD diamond according to claim 8 or 9 in the fields of machining, electronics, optics or medicine.

Images