A method of exfoliating a diamond graphite layer

Abstract

The present application relates to a method for stripping diamond graphite layer, comprising the following steps: selecting suitable diamond; using acetone and anhydrous ethanol to ultrasonic clean the diamond respectively, then using ultrapure water to megasonic clean the diamond, and blowing the surface residual water drops by high-purity nitrogen; sending the diamond into ion implantation machine, and selecting suitable angle, energy, element and dose to carry out ion implantation; graphitizing the damage layer by high-temperature vacuum annealing method; using acetone and anhydrous ethanol to ultrasonic clean the diamond respectively, then using ultrapure water to megasonic clean the diamond, and blowing the surface residual water drops by high-purity nitrogen; sending the diamond into MPCVD machine to grow thickened upper surface diamond layer; cutting the polycrystal grown on the four sides of the diamond by laser, processing the growth surface step lines by laser milling, grinding and polishing the flat surface, and then sending into arc etching machine to separate the diamond. The method can realize rapid stripping of the graphite layer.

Description

Technical Field

[0001] This invention relates to the field of diamond stripping, and more particularly to a method for stripping the graphite layer from diamond. Background Technology

[0002] Existing diamond exfoliation methods mainly include direct laser longitudinal cutting and diamond hidden-cut exfoliation. Direct laser longitudinal cutting uses a high-energy laser beam to cut along a specific crystal plane of the diamond crystal, achieving material separation through laser thermal effect or photochemical decomposition. However, due to the V-shaped cut, material loss increases exponentially with the size of the diamond. Diamond hidden-cut exfoliation includes laser hidden-cut exfoliation and ion implantation exfoliation. Laser hidden-cut exfoliation uses an ultrafast laser to focus inside the diamond, forming a modified layer, and then achieves separation through mechanical or thermal stress. However, this method is complex and prone to chipping.

[0003] Existing ion implantation exfoliation methods include chemical etching, oxidation, and electrochemical methods. Chemical etching uses strong acids or mixed acids to etch the graphite layer at a specific temperature. Oxidation utilizes high-temperature ozone etching, exposing the sample to an ozone environment at 800 mbar pressure and 450°C; the etching process duration is strictly dependent on the size of the graphite layer, selectively removing graphite. Electrochemical methods use two electrodes spaced apart in an electrolyte solution, placing a single-crystal diamond forming a non-diamond layer between the electrodes and applying a DC voltage to the electrodes to induce a chemical reaction and exfoliate the graphite layer. However, the graphite layer formed between ion-implanted diamonds is only about 300 nm thick, extremely small. The reactions in chemical etching, electrochemical methods, and oxidation are related to the contact area, resulting in very small contact gaps. The process involves reacting from the periphery of the diamond and slowly penetrating into the diamond to exfoliate the graphite; the entire process is slow and cannot be rapidly exfoliated. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a method for rapidly peeling off diamond graphite layers, in view of the above-mentioned existing technology.

[0005] The technical solution adopted by the present invention to solve the above-mentioned technical problem is as follows: the method for peeling off the diamond graphite layer is characterized by comprising the following steps:

[0006] S1. Select the appropriate diamond;

[0007] S2. Clean the diamond;

[0008] S3. Form a damage layer at a certain depth inside the diamond and graphitize the damage layer;

[0009] S4. Clean the diamond that forms the graphite layer;

[0010] S5. Feed the diamond into the MPCVD machine to grow a thickened diamond layer on the upper surface.

[0011] S6. Use a laser to remove the polycrystalline material grown on the four sides of the diamond, and then use a swingable, extendable high-pressure probe to contact the vicinity of the graphite layer to etch the graphite by high-pressure arc ignition.

[0012] The selected diamond specifications are limited. Preferably, the total thickness deviation of the diamonds selected in step S1 is less than 100 micrometers and the surface roughness is less than 100 nanometers.

[0013] In order to better clean the diamond, the specific steps for cleaning the diamond in steps S2 and S4 are as follows: ultrasonic cleaning of the diamond is performed with acetone and anhydrous ethanol respectively, then mega-sonic cleaning of the diamond is performed with ultrapure water, and residual water droplets on the surface are blown away with high-purity nitrogen gas.

[0014] Furthermore, the ultrasonic cleaning and megaphonic cleaning times are 10–30 minutes, and the air blowing time is 5–10 minutes. This effectively removes inorganic ions and organic impurities from the diamond surface.

[0015] In order to better form a damaged layer, the method for forming a damaged layer in step S3 is to send diamond into an ion implanter and select appropriate angle, energy, elements and dosage for ion implantation.

[0016] There are various options for selecting appropriate angles, energies, elements, and doses during ion implantation. Preferably, the ion implanter selects carbon element, with an angle of 0 to 60 degrees, a dose of 0 to 1*10^17 (atom / cm^2), and an energy of 0 to 400KV to implant one layer.

[0017] Furthermore, in step S3, a high-temperature vacuum annealing method is used to graphitize the damaged layer. Of course, this is also equivalent to annealing during normal growth.

[0018] Furthermore, in step S5, the MPCVD machine uses methane with a content between 4% and 8%, nitrogen with a content between 0.1% and 1%, and the remainder is hydrogen. The microwave power is greater than or equal to 1000W, the gas pressure is between 100 and 140 torr, the growth temperature is controlled at around 800℃ to 1200℃, and the diamond growth layer is at least 0.1 mm thick. This allows for control of the diamond growth layer thickness under suitable growth conditions.

[0019] To further enhance etching precision, in step S6, a camera acquires real-time etching images, which are then transmitted to a computer to calculate the movement pattern and arc-starting output power of the high-voltage probe. Commands are then sent to the driver to activate the motor and power supply. Calculating the movement pattern and arc-starting output power of the high-voltage probe improves the accuracy of probe etching.

[0020] To improve the high-voltage arc etching effect, the voltage during high-voltage arc initiation is further controlled to be greater than 1kV.

[0021] Compared with the prior art, the advantages of this invention are as follows: This method is based on the high arc resistance of diamond material and the sublimation properties of graphite layer. It removes the graphite layer by directly etching the middle graphite layer with an electric arc. Under the action of high voltage electric arc, the end face of the graphite layer will be affected by extremely high temperature, causing the graphite layer to sublimate continuously, that is, directly change from solid to gaseous state, thereby causing the graphite layer to be consumed. The high temperature generated by the electric arc will also generate thermal stress inside the graphite layer. When these stresses exceed the graphite's bearing capacity, they will cause the graphite layer to peel off. It does not need to slowly contact and react from the periphery of diamond, but directly acts on the graphite layer, which can achieve rapid removal of the graphite layer. The diamond is not easy to crack during the whole process. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the arc etching machine in an embodiment of the present invention;

[0023] Figure 2 This is a schematic diagram of the diamond intermediate graphite layer before electrolysis in an embodiment of the present invention;

[0024] Figure 3 This is a schematic diagram of the diamond intermediate graphite layer after electrolysis in an embodiment of the present invention;

[0025] Figure 4 This is a schematic diagram of the diamond peeling surface after the graphite layer has been peeled off in an embodiment of the present invention. Detailed Implementation

[0026] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0027] like Figure 1-4 The image shows a preferred embodiment of the present invention. A method for peeling off a diamond graphite layer according to the present invention includes the following steps:

[0028] S1. Select suitable diamonds with a total thickness deviation of less than 100 micrometers and a surface roughness of less than 100 nanometers;

[0029] S2. The diamond is ultrasonically cleaned with acetone and anhydrous ethanol respectively, then ultrasonically cleaned with ultrapure water, and the residual water droplets on the surface are blown away with high-purity nitrogen. The ultrasonic cleaning and ultrasonic cleaning time is 10-30 minutes, and the blowing time is 5-10 minutes. The cleaning operation removes inorganic ions and organic impurities from the diamond surface.

[0030] S3. The diamond is fed into an ion implanter, and carbon element, angle 0-60 degrees, dose 0-1*10^17 (atom / cm^2), and energy 0-400KV are selected to implant a layer, thereby forming a damaged layer inside the diamond. The damaged layer is then graphitized by vacuum annealing at a high temperature of 400-1500℃. The thickness of the graphite layer formed by graphitization of the damaged layer is 100nm-1000nm, and the specific thickness varies depending on the process.

[0031] S4. The diamond is ultrasonically cleaned with acetone and anhydrous ethanol respectively, then ultrasonically cleaned with ultrapure water, and the residual water droplets on the surface are blown away with high-purity nitrogen gas, which is the same as step S2.

[0032] S5. The diamond is fed into the MPCVD machine to grow a thickened diamond layer on the upper surface. The proportion of methane introduced into the MPCVD machine is between 4% and 8%, the proportion of nitrogen is between 0.1% and 1%, and the remainder is hydrogen. The microwave power is greater than or equal to 1000W, the gas pressure is between 100 and 140 torr, and the growth temperature is controlled at about 800℃ to 1200℃. The diamond growth layer is at least 0.1mm thick.

[0033] Here, because the pressure resistance of diamond is related to its thickness, after ion implantation, a damage layer is formed more than 300 nanometers below the surface of the diamond. Such a thin layer is easily broken down during subsequent arc etching. Therefore, it is necessary to grow diamond above the graphite layer. At the same time, diamond preparation requires multiple diamond wafers, and two diamond wafers can be peeled off after growth, which facilitates mass production.

[0034] S6. Because the presence of polycrystalline material blocks the intermediate graphite layer and hinders the movement of the high-voltage probe, it is necessary to first use a laser to remove the polycrystalline material growing on all four sides of the diamond, then use laser milling to remove the step patterns on the growth surface, and finally grind and polish the surface to a smooth finish. Then, a oscillating, extendable high-voltage probe is used to contact the vicinity of the graphite layer, and the graphite is etched using a high-voltage arc-initiating method. The voltage during high-voltage arc-initiating is controlled to be greater than 1kV. The upper limit of this voltage is determined by the size of the diamond. The theoretical breakdown field strength of diamond is 10^7V / cm to 10^8V / cm. The larger the length and width of the diamond, the higher the voltage is ultimately required; the thicker the diamond, the more pressure-resistant it is, and it can withstand high voltage without breaking. Throughout the arc-initiating process, the voltage is not controlled at the highest level from the beginning, but rather gradually increased.

[0035] like Figure 1 As shown, in step S6, the camera 1 acquires a real-time etching image, which is transmitted to the computer to calculate the movement mode and arc-starting output power of the high-voltage probe 2, and sends a command to the driver to drive the motor and power supply to work. The retractable high-voltage probe 2 contacts the graphite layer by swinging, and the graphite is etched by high-voltage arc-starting.

[0036] Because the graphite layer blocks the light transmission of diamond, ion-implanted diamonds are black after growth. However, after arc etching, the graphite layer is etched away, restoring the light transmission of diamond. This can be used to calculate the edges that need to be etched.

[0037] In this embodiment, the ion-implanted diamond 3 is clamped onto the glass fixture 4 (ensuring light transmittance), the high-voltage probe 2 is returned to its initial position, and the position information of the diamond 3 is acquired. To acquire initial image information, the position information can be calculated based on the number of pixels in the camera 1 and the actual scale. The conventional calibration method for a camera measuring instrument is as follows: camera initialization, using a calibration card with accurate values, clamped onto the glass fixture, and then image acquisition. By calculation, the length represented by one pixel can be determined, and the position information of the high-voltage probe can be determined by real-time image acquisition during subsequent etching.

[0038] Based on the high arc resistance of diamond (negligible etching rate), the arc etching scheme in this embodiment acquires a diamond-graphite interface image through a machine vision system after the workpiece is clamped. An edge detection algorithm is used to extract contour features, and a probe trajectory is generated based on real-time data, prioritizing etching of the nearest graphite. Images of the processing area are acquired periodically, processed by an anti-arc interference algorithm, and the minimum distance between the current etching front and the target depth is calculated. Then, the motion controller generates probe trajectory correction commands based on real-time data, synchronously adjusting the displacement. Finally, the optimal arc initiation voltage under the current conditions is calculated based on Paschen's law. The machine vision system, edge detection algorithm, anti-arc interference algorithm, and Paschen's law are all existing technologies and will not be elaborated further.

[0039] During arc etching, high voltage leads to high temperatures in both the diamond and the surrounding air. High-temperature air is easily punctured, therefore the diamond also needs heat dissipation. When the diamond temperature exceeds 160 degrees Celsius, fan 5 can be turned on to cool it. During this process, a camera with temperature acquisition capabilities can be used to collect the actual temperature of the diamond after heat generation and dissipation.

[0040] Based on the sublimation properties of graphite layers, in this embodiment, under the action of a high-voltage electric arc, the end face of the graphite layer is subjected to extremely high temperatures, causing the graphite layer to continuously sublimate, that is, directly transform from a solid state to a gaseous state, thus resulting in the consumption of the graphite layer. The high temperature generated by the electric arc also generates thermal stress inside the graphite layer. When these stresses exceed the graphite's bearing capacity, it will cause the graphite layer to peel off. Specifically, during arc etching, arc patterns are formed near the graphite layer. These arc patterns are formed on both sides of the diamond-contact graphite layer, as can be seen in the details. Figure 3 and Figure 4 .

Claims

1. A method for peeling off a diamond graphite layer, characterized in that, Includes the following steps: S1. Select the appropriate diamond; S2. Clean the diamond; S3. A damage layer is formed at a certain depth inside the diamond, and the damage layer is graphitized. S4. Clean the diamond that forms the graphite layer; S5. Feed the diamond into the MPCVD machine to grow a thickened diamond layer on the upper surface. S6. Use a laser to remove the polycrystalline material grown on the four sides of the diamond, and then use a swingable, extendable high-pressure probe to contact the vicinity of the graphite layer to etch the graphite by high-pressure arc ignition.

2. The method for stripping diamond graphite layers according to claim 1, characterized in that: The diamonds selected in step S1 have a total thickness deviation of less than 100 micrometers and a surface roughness of less than 100 nanometers.

3. The method for stripping diamond graphite layers according to claim 1, characterized in that: The specific steps for cleaning the diamond in steps S2 and S4 are as follows: ultrasonic cleaning of the diamond is performed using acetone and anhydrous ethanol respectively, followed by mega-sonic cleaning of the diamond using ultrapure water, and the residual water droplets on the surface are blown away with high-purity nitrogen gas.

4. The method for stripping the diamond graphite layer according to claim 3, characterized in that: The ultrasonic cleaning and megaphonic cleaning times are 10–30 min, and the air blowing time is 5–10 min.

5. The method for stripping diamond graphite layers according to claim 1, characterized in that: The method for forming the damage layer in step S3 is to send diamond into an ion implanter and select appropriate angle, energy, elements, and dosage for ion implantation.

6. The method for stripping diamond graphite layers according to claim 5, characterized in that: The ion implanter selects carbon element during implantation, with an angle of 0 to 60 degrees, a dose of 0 to 1*10^17 (atom / cm^2), and an energy of 0 to 400KV, implanting one layer.

7. The method for stripping diamond graphite layers according to claim 1, characterized in that: In step S3, the damaged layer is graphitized using a high-temperature vacuum annealing method.

8. The method for stripping diamond graphite layers according to claim 1, characterized in that: In step S5, the MPCVD machine is supplied with methane at a rate of 4% to 8%, nitrogen at a rate of 0.1% to 1%, and the remainder is hydrogen. The microwave power is greater than or equal to 1000W, the gas pressure is between 100 and 140 torr, the growth temperature is controlled at around 800℃ to 1200℃, and the diamond growth layer is at least 0.1mm thick.

9. The method for stripping diamond graphite layers according to claim 1, characterized in that: In step S6, a camera is used to acquire real-time etching images, which are then transmitted to a computer to calculate the movement mode of the high-voltage probe and the arc-starting output power. Commands are then sent to the driver to drive the motor and power supply.

10. The method for stripping diamond graphite layers according to claim 1, characterized in that: The voltage control during high-voltage arc initiation is greater than 1kV.

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