Method for depositing diamond film on graphite sheet based on microwave plasma chemical vapor deposition method

Abstract

The invention discloses a method for depositing a diamond film on a graphite sheet based on a microwave plasma chemical vapor deposition method, which comprises the following steps of: firstly, depositing a transition layer on the graphite sheet by adopting ALD (Atomic Layer Deposition), performing ultrasonic seed crystal treatment, and growing in MPCVD (Microwave Plasma Chemical Vapor Deposition) equipment to obtain a graphite-diamond composite film; according to the method, the excellent performance of graphite and diamond is combined, and the composite material with wide application prospects is obtained.

Description

Technical Field

[0001] The invention relates to a method for depositing a diamond film on a graphite sheet based on a microwave plasma chemical vapor deposition method. Background Art

[0002] Graphite is widely used to make electrodes in electrical discharge machining (EDM) and electrochemical reactions, brushes in direct current (DC) motors, molds in casting, etc., thanks to its light weight, low thermal expansion coefficient, high temperature resistance, good thermal and electrical conductivity, good corrosion resistance, good lubricity and good machinability. The lack of wear resistance of graphite, combined with its low hardness and interlaminar strength, limits the service life of graphite parts in certain applications, for example, when the DC motor is running, the brushes are constantly sliding on the metal. Chemical vapor deposition (CVD) diamond films can be used as an effective protective coating on graphite parts.

[0003] Graphite is an allotrope of diamond, and the nucleation and growth of diamond on it are limited by the reaction principle of the CVD process. The hydrogen-rich plasma environment during diamond deposition has a great influence on the graphite phase (sp 2 Carbon) produces a strong etching effect, making it very difficult to deposit a continuous diamond film directly on a graphite substrate. Such etching may even directly damage the graphite substrate instead of diamond growth. Using an intermediate layer between the diamond film and graphite may be an effective solution for depositing high-quality diamond films on graphite substrates. Beijing University of Science and Technology used multi-arc ion plating and magnetron sputtering to plate a metal transition layer of several hundred nanometers on the graphite surface. However, during the cooling process, the film layer fell off due to the high thermal expansion coefficient and low elastic modulus of the metal transition layer. Atomic layer deposition (ALD) can achieve highly uniform and continuous film coverage on complex three-dimensional structures and high aspect ratio surfaces. The metal oxide film we deposited using ALD protects the substrate from being corroded by atomic hydrogen, and due to its thin thickness, it avoids the risk of film shedding or cracking due to the thermal residual stress formed between the transition layer and the diamond film.

[0004] The present invention adopts atomic layer deposition (ALD) to generate a metal oxide film on the surface of a graphite sheet, then puts the graphite sheet into a diamond seeding liquid for ultrasonic seeding to increase the nucleation sites of diamond during growth, and then uses microwave plasma chemical vapor deposition (MPCVD) to deposit a diamond film on the graphite sheet to obtain a graphite-diamond composite film. Summary of the invention

[0005] The present invention relates to a new method for depositing a diamond film on a graphite substrate. First, a tantalum pentoxide, titanium dioxide or tungsten trioxide film is deposited on a graphite sheet by ALD as a transition layer, and then the film is grown in an MPCVD device after ultrasonic seeding to obtain a graphite-diamond composite film.

[0006] The technical solution of the present invention is as follows:

[0007] A method for depositing a diamond film on a graphite sheet based on microwave plasma chemical vapor deposition comprises the following steps:

[0008] (1) ultrasonically cleaning the graphite sheet and drying it for later use;

[0009] The specific operation is as follows: the graphite sheet is ultrasonically cleaned in 95% ethanol for 25 to 35 minutes (preferably 30 minutes), and the cleaning is repeated twice, and then the graphite sheet is dried in a drying oven at 100 to 200° C. (preferably 150° C.) for 0.5 to 1.5 hours (preferably 1 hour) for use;

[0010] (2) placing the graphite sheet pretreated in step (1) into an atomic layer deposition device for film coating to obtain a graphite sheet coated with a metal oxide thin film (transition layer);

[0011] The metal oxide is tantalum pentoxide, titanium dioxide or tungsten trioxide;

[0012] The coating conditions of the tantalum pentoxide film are as follows: the precursor is t-butylimino tris(ethylmethylamino)tantalum, the precursor heating temperature is 35-45°C (preferably 40°C), the residence time of the precursor in the cavity is 0.3-0.7s (preferably 0.5s), the nitrogen flushing time is 8-12s (preferably 10s), the water residence time in the cavity is 0.3-0.7s (preferably 0.5s), and the nitrogen flushing time is 6-10s (preferably 8s); the above is taken as a cycle, the number of cycles is 200-300 times (preferably 250 times), the sample stage temperature is set at 200-300°C (preferably 250°C), the sample stage preheating time is set at 30-40min (preferably 35min), and the graphite sheet coated with the tantalum pentoxide film is obtained after the deposition is completed;

[0013] The coating conditions of the titanium dioxide film are as follows: the precursor is isopropyl titanate, the precursor heating temperature is 70-80°C (preferably 75°C), the residence time of the precursor in the cavity is 0.7-1.1s (preferably 0.9s), the nitrogen flushing time is 3-7s (preferably 5s), the water residence time in the cavity is 1-3s (preferably 2s), and the nitrogen flushing time is 6-10s (preferably 8s); the above is regarded as a cycle, the number of cycles is 200-300 times (preferably 250 times), the sample stage temperature is set at 200-300°C (preferably 250°C), the sample stage preheating time is set at 30-40min (preferably 35min), and the graphite sheet coated with the titanium dioxide film is obtained after the deposition is completed;

[0014] The coating conditions of tungsten trioxide film are as follows: the precursor is bis(tert-butylimide)bis(dimethylamino)tungsten, the precursor heating temperature is 50-60°C (preferably 55°C), the residence time of the precursor in the chamber is 1-3s (preferably 2s), the nitrogen flushing time is 8-12s (preferably 10s), the water residence time in the chamber is 0.3-0.7s (preferably 0.5s), and the nitrogen flushing time is 3-7s (preferably 5s); the above is taken as a cycle, the number of cycles is 200-300 times (preferably 250 times), the sample stage temperature is set at 300-400°C (preferably 350°C), the sample stage preheating time is set at 30-40min (preferably 35min), and the graphite sheet coated with tungsten trioxide film is obtained after the deposition is completed;

[0015] (3) subjecting the graphite sheet coated with the metal oxide film obtained in step (2) to ultrasonic seeding to obtain a seeded graphite sheet;

[0016] The specific operation is as follows: diamond micropowder is evenly dispersed in acetone to obtain a seed crystal solution, a graphite sheet coated with a metal oxide film is placed in the seed crystal solution, and ultrasonicated for 5 to 10 minutes (preferably 5 minutes) to obtain a seed crystal graphite sheet; wherein the particle size of the diamond micropowder is 55nm; the concentration of the seed crystal solution is 0.8 to 1.2g / L (preferably 1g / L);

[0017] (4) Place the seed crystal graphite sheet obtained in step (3) into a microwave plasma chemical vapor deposition device, set the base height to 4.8 cm, the pure hydrogen flow rate to 200-250 sccm (preferably 200 sccm), the methane flow rate to 20-40 sccm (preferably 30 sccm), the working gas pressure to 90-120 torr (preferably 100 torr), the microwave power to 2500-4000 W (preferably 3500 W), and grow for 7-9 h (preferably 8 h) to obtain a graphite-diamond composite film.

[0018] The beneficial effects of the present invention are embodied in:

[0019] (1) This method can avoid the etching of graphite by hydrogen plasma, and during the growth process, the metal oxide is converted into metal carbide, which accelerates the deposition rate of the diamond film.

[0020] (2) ALD has atomic-level precision control of film thickness and can achieve uniform deposition on nanostructured surfaces with high depth ratios through a self-limiting reaction mechanism. This method can reduce stress during diamond film deposition, reduce the risk of diamond film breakage, and improve the quality of diamond films.

[0021] (3) The graphite sheets used in this method are simple and easy to obtain, which can reduce the cost of diamond film deposition. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1SEM image of diamond film deposited on graphite substrate in comparative example.

[0023] Figure 2 Raman spectrum of diamond film deposited on graphite substrate in comparative example.

[0024] Figure 3 SEM image of the diamond film deposited on the graphite substrate in Example 1.

[0025] Figure 4 Raman spectrum of the diamond film deposited on the graphite substrate in Example 1.

[0026] Figure 5 SEM image of the diamond film deposited on the graphite substrate in Example 2.

[0027] Figure 6 Raman spectrum of the diamond film deposited on the graphite substrate in Example 2.

[0028] Figure 7 SEM image of the diamond film deposited on the graphite substrate in Example 3.

[0029] Figure 8 Raman spectrum of the diamond film deposited on the graphite substrate in Example 3.

[0030] Fig. 9 SEM image of the diamond film deposited on the graphite substrate in Example 4.

[0031] Fig.10 Raman spectrum of the diamond film deposited on the graphite substrate in Example 4.

[0032] Fig.11 SEM image of the diamond film deposited on the graphite substrate in Example 5.

[0033] Fig.12 Raman spectrum of the diamond film deposited on the graphite substrate in Example 5.

[0034] Fig.13 SEM image of the diamond film deposited on the graphite substrate in Example 6.

[0035] Fig.14 Raman spectrum of the diamond film deposited on the graphite substrate in Example 6.

[0036] Fig.15 SEM image of the diamond film deposited on the graphite substrate in Example 7.

[0037] Fig.16 Raman spectrum of the diamond film deposited on the graphite substrate in Example 7.

[0038] Fig.17 SEM image of the diamond film deposited on the graphite substrate in Example 8.

[0039] Fig.18 Raman spectrum of the diamond film deposited on the graphite substrate in Example 8.

[0040] Fig.19 SEM image of the diamond film deposited on the graphite substrate in Example 9.

[0041] Fig. 20 Raman spectrum of the diamond film deposited on the graphite substrate in Example 9. DETAILED DESCRIPTION

[0042] The present invention is further described below by means of specific embodiments, but the protection scope of the present invention is not limited thereto.

[0043] In the following embodiments,

[0044] The graphite sheets were purchased from Baojun Refractory Materials Business Department in Zhoucun, with a purity of more than 99.95%; the size of the graphite sheets was: 14 mm in diameter and 2 mm in thickness;

[0045] Tert-butyliminotris(ethylmethylamino)tantalum was purchased from Shenzhen Yuansu Optoelectronics Technology Co., Ltd. with a purity of 99.9999%;

[0046] Isopropyl titanate was purchased from Shenzhen Yuansu Optoelectronics Technology Co., Ltd. with a purity of 99.9999%;

[0047] Bis(tert-butylimino)bis(dimethylamino)tungsten was purchased from Shenzhen Yuansu Optoelectronics Technology Co., Ltd. with a purity of 99.9999%;

[0048] The atomic layer deposition equipment was purchased from Shenzhen Yuansu Optoelectronics Technology Co., Ltd., model E200SP;

[0049] The microwave plasma chemical vapor deposition equipment was purchased from Shenzhen Super Magnetic Robot Co., Ltd., model MPCVD-6A;

[0050] The ultrasonic cleaning machine was purchased from Kunshan Ultrasonic Instrument Co., Ltd., model KQ3200DE;

[0051] The drying oven was purchased from Shanghai Jinghong Experimental Equipment Co., Ltd., model DHG-9053A.

[0052] Comparative Example

[0053] (1) Graphite sheet pretreatment: The graphite sheet was ultrasonically cleaned in 95% ethanol for 30 min, twice to remove graphite particles and oil stains on the graphite surface. After cleaning, the graphite sheet was dried in a 150° C. drying oven for 1 h to remove alcohol on the graphite sheet and obtain a clean graphite sheet.

[0054] (2) Growth of diamond film: The graphite sheet described in step 1 is placed in a microwave plasma chemical vapor deposition device for growth, with the pure hydrogen flow rate set to 200 sccm, the methane flow rate set to 30 sccm, the working gas pressure set to 100 torr, the microwave power set to 2500 W, and the growth time set to 8 hours. After the reaction is completed, only etched graphite is obtained.

[0055] SEM and Raman spectroscopy were used to characterize the surface morphology and growth of the samples after the experiment.

[0056] Figure 1 The SEM image for the comparative example shows that the sample surface presents an obvious porous structure. The small micropores are caused by hydrogen plasma etching in the microwave environment. No diamond particles were observed on the sample surface, indicating that the graphite sheet without ALD treatment failed to successfully deposit diamonds in microwave chemical vapor deposition.

[0057] Figure 2 The Raman spectrum of the comparative example shows that the D peak (1350 cm -1 ) and G peak (1580cm -1 ), no diamond appeared at 1332cm -1 The characteristic peak at the position indicates that diamond deposition was not successful this time.

[0058] Example 1

[0059] (1) Graphite sheet pretreatment: The graphite sheet was ultrasonically cleaned in 95% ethanol for 30 min, twice to remove graphite particles and oil stains on the graphite surface. After cleaning, the graphite sheet was dried in a 150° C. drying oven for 1 h to remove alcohol on the graphite sheet and obtain a clean graphite sheet.

[0060] (2) Preparation of tantalum pentoxide film on graphite sheet: Open the ALD equipment chamber, place the graphite sheet into the chamber, close the chamber, and pump the chamber pressure to 0.03 torr. Set the deposition parameters: use t-butyl imino tris (ethylmethylamino) tantalum as the tantalum precursor, heat the tantalum precursor to 40°C, the residence time of the tantalum precursor in the chamber is 0.5s, the nitrogen flushing time is 10s, the residence time of water in the chamber is 0.5s, the second nitrogen flushing time is 8s, and the above is considered as a cycle. The cycle is repeated 250 times, the sample stage temperature is set to 250°C, and the sample stage preheating time is set to 35min. After the deposition is completed, a graphite sheet coated with tantalum pentoxide film is obtained.

[0061] (3) Seeding treatment: The sample obtained in step 2 is placed in a seeding solution in which diamond micropowder with a diamond particle size of 55 nm and acetone are uniformly mixed in a ratio of 1 g:1 L. The seeding solution is ultrasonically treated for 5 min, and the sample is taken out and placed in a drying oven at 150° C. for 1 h to obtain a seeded graphite sheet.

[0062] (4) Growth of diamond film: The graphite sheet described in step 3 is placed in a microwave plasma chemical vapor deposition device for growth, with the pure hydrogen flow rate set to 200 sccm, the methane flow rate set to 30 sccm, the working gas pressure set to 100 torr, the microwave power set to 2500 W, and the growth time set to 8 hours. After the reaction is completed, a graphite-diamond composite film is obtained.

[0063] SEM and Raman spectroscopy were used to characterize the surface morphology and growth quality of the samples after the experiment.

[0064] Figure 3 This is the SEM image in Example 1. It can be observed that the sample surface is composed of irregular grains. The grains are polyhedral in shape and have obvious edges and plane features. There are obvious gaps between the grains, and the grain size is between 8 and 12 μm.

[0065] Figure 4 The Raman spectrum in Example 1 is at 1330.2 cm -1 The obvious diamond characteristic peak appears at 1350cm, indicating that the diamond film was successfully deposited by microwave chemical vapor deposition after being coated with tantalum pentoxide. The diamond peak shifts to the left, indicating that there is tensile stress in the diamond film. The D peak (1350cm -1 ) and G peak (1580cm -1 ), indicating that the non-diamond phase content in the sample is low and the diamond purity is high. At the same time, the half-peak width of the characteristic peak is narrow, reflecting that the sample has a high degree of crystallinity.

[0066] Example 2

[0067] (1) Graphite sheet pretreatment: The graphite sheet was ultrasonically cleaned in 95% ethanol for 30 min, twice to remove graphite particles and oil stains on the graphite surface. After cleaning, the graphite sheet was dried in a 150° C. drying oven for 1 h to remove alcohol on the graphite sheet and obtain a clean graphite sheet.

[0068] (2) Preparation of tantalum pentoxide film on graphite sheet: Open the ALD equipment chamber, place the graphite sheet into the chamber, close the chamber, and pump the chamber pressure to 0.03 torr. Set the deposition parameters: use t-butyl imino tris (ethylmethylamino) tantalum as the tantalum precursor, heat the tantalum precursor to 40°C, the residence time of the tantalum precursor in the chamber is 0.5s, the nitrogen flushing time is 10s, the residence time of water in the chamber is 0.5s, the second nitrogen flushing time is 8s, and the above is considered as a cycle. The cycle is repeated 250 times, the sample stage temperature is set to 250°C, and the sample stage preheating time is set to 35min. After the deposition is completed, a graphite sheet coated with tantalum pentoxide film is obtained.

[0069] (3) Seeding treatment: The sample obtained in step 2 is placed in a seeding solution in which diamond micropowder with a diamond particle size of 55 nm and acetone are uniformly mixed in a ratio of 1 g:1 L. The seeding solution is ultrasonically treated for 5 min, and the sample is taken out and placed in a drying oven at 150° C. for 1 h to obtain a seeded graphite sheet.

[0070] (4) Growth of diamond film: The graphite sheet described in step 3 is placed in a microwave plasma chemical vapor deposition device for growth, with the pure hydrogen flow rate set to 200 sccm, the methane flow rate set to 30 sccm, the working gas pressure set to 100 torr, the microwave power set to 3000 W, and the growth time set to 8 hours. After the reaction is completed, a graphite-diamond composite film is obtained.

[0071] SEM and Raman spectroscopy were used to characterize the surface morphology and growth quality of the samples after the experiment.

[0072] Figure 5 This is the SEM image in Example 2. It can be observed that the sample surface exhibits a regular polyhedral morphology and is evenly distributed on the film surface without obvious holes or grain accumulation, indicating that the film surface has good continuity; the grain size is mainly distributed in the range of 5 to 9 μm.

[0073] Figure 6 The Raman spectrum in Example 2 is at 1333.5 cm -1 There is an obvious diamond characteristic peak at 1500cm, which belongs to the Raman scattering characteristic peak of sp3 hybridized CC bond in diamond crystal, indicating that the diamond film was successfully deposited by microwave chemical vapor deposition after coating with tantalum pentoxide. The diamond peak position shifts to a high wave number, indicating that there is compressive stress in the diamond film. -1 A weak broad peak appears near the sample, indicating that there is a small amount of non-diamond phase in the sample. At the same time, the half-peak width of the characteristic peak is narrow, indicating that the sample has a high degree of crystallinity and a good crystal structure.

[0074] Example 3

[0075] (1) Pretreatment of graphite sheets: The graphite sheets were ultrasonically cleaned in 95% ethanol for 30 min, twice to remove graphite particles and oil stains on the graphite surface. After cleaning, the sheets were dried in a 150° C. drying oven for 1 h to remove the ethanol on the graphite sheets and obtain clean graphite sheets.

[0076] (2) Preparation of tantalum pentoxide film on graphite sheet: Open the ALD equipment chamber, place the graphite sheet into the chamber, close the chamber, and pump the chamber pressure to 0.03 torr. Set the deposition parameters: use t-butyl imino tris (ethylmethylamino) tantalum as the tantalum precursor, heat the tantalum precursor to 40°C, the residence time of the tantalum precursor in the chamber is 0.5s, the nitrogen flushing time is 10s, the residence time of water in the chamber is 0.5s, the second nitrogen flushing time is 8s, and the above is considered as a cycle. The cycle is repeated 250 times, the sample stage temperature is set to 250°C, and the sample stage preheating time is set to 35min. After the deposition is completed, a graphite sheet coated with tantalum pentoxide film is obtained.

[0077] (3) Seeding treatment: The sample obtained in step 2 is placed in a seeding solution in which diamond micropowder with a diamond particle size of 55 nm and acetone are uniformly mixed in a ratio of 1 g:1 L. The seeding solution is ultrasonically treated for 5 min, and the sample is taken out and placed in a drying oven at 150° C. for 1 h to obtain a seeded graphite sheet.

[0078] (4) Growth of diamond film: The graphite sheet described in step 3 is placed in a microwave plasma chemical vapor deposition device for growth, with the pure hydrogen flow rate set to 200 sccm, the methane flow rate set to 30 sccm, the working gas pressure set to 100 torr, the microwave power set to 3500 W, and the growth time set to 8 hours. After the reaction is completed, a graphite-diamond composite film is obtained.

[0079] SEM and Raman spectroscopy were used to characterize the surface morphology and growth quality of the samples after the experiment.

[0080] Figure 7 This is the SEM image in Example 3. It can be observed that the sample surface is an irregular polyhedron morphology, there are no obvious holes on the film surface, and the film density is relatively high; the grain size is between 5 and 8 μm, indicating that the diamond film has a high nucleation density. At the same time, there is a competition effect between grains in crystal growth, which leads to differences in the distribution of grain sizes.

[0081] Figure 8 The Raman spectrum in Example 3 is at 1331.1 cm -1There is an obvious diamond characteristic peak at 1350cm, which belongs to the Raman scattering characteristic peak of the sp3 hybridized CC bond in the diamond crystal, indicating that the diamond film was successfully deposited by microwave chemical vapor deposition after being coated with tantalum pentoxide. The diamond peak position shifts to a lower wave number, indicating that there is tensile stress in the diamond film. The D peak (1350cm -1 ) and G peak (1580cm -1 ), indicating that the non-diamond phase content in the sample is low and the diamond purity is high. The half-peak width of the diamond characteristic peak is narrow, indicating that the sample has a high degree of crystallinity and fewer grain defects.

[0082] Example 4

[0083] (1) Graphite sheet pretreatment: The graphite sheet was ultrasonically cleaned in 95% ethanol for 30 min, twice to remove graphite particles and oil stains on the graphite surface. After cleaning, the graphite sheet was dried in a 150° C. drying oven for 1 h to remove alcohol on the graphite sheet and obtain a clean graphite sheet.

[0084] (2) Preparation of titanium dioxide film on graphite sheet: Open the ALD equipment chamber, place the graphite sheet in the chamber, close the chamber, and pump the chamber pressure to 0.03 torr. Set the deposition parameters: use isopropyl titanate as the titanium precursor, heat the titanium precursor to 75°C, the residence time of the titanium precursor in the chamber is 0.9s, the nitrogen flushing time is 5s, the residence time of water in the chamber is 2s, the second nitrogen flushing time is 8s, and the above is considered as a cycle. The cycle is repeated 250 times, the sample stage temperature is set to 250°C, and the sample stage preheating time is set to 35min. After the deposition is completed, a graphite sheet coated with titanium dioxide film is obtained.

[0085] (3) Seeding treatment: The sample obtained in step 2 is placed in a seeding solution in which diamond micropowder with a diamond particle size of 55 nm and acetone are uniformly mixed in a ratio of 1 g:1 L. The seeding solution is ultrasonically treated for 5 min, and the sample is taken out and placed in a drying oven at 150° C. for 1 h to obtain a seeded graphite sheet.

[0086] (4) Growth of diamond film: The graphite sheet described in step 3 is placed in a microwave plasma chemical vapor deposition device for growth, with the pure hydrogen flow rate set to 200 sccm, the methane flow rate set to 30 sccm, the working gas pressure set to 100 torr, the microwave power set to 2500 W, and the growth time set to 8 hours. After the reaction is completed, a graphite-diamond composite film is obtained.

[0087] SEM and Raman spectroscopy were used to characterize the surface morphology and growth quality of the samples after the experiment.

[0088] Fig. 9This is the SEM image of Example 4. It can be observed that the sample surface is composed of a large number of blocky grains of irregular size. The grains present a regular polyhedral shape with relatively obvious edges and plane features. The surface of the grains is relatively flat, and no obvious holes and cracks are observed, showing a high density. The grain size is between 1 and 10 μm.

[0089] Fig.10 The Raman spectrum in Example 4 is at 1331.6 cm -1 The obvious diamond characteristic peak appears at , indicating that the diamond film was successfully deposited by microwave chemical vapor deposition after being coated with titanium dioxide. The diamond peak shifts to the left, indicating that there is tensile stress in the diamond film. The background baseline of the spectrum is relatively flat, and there is no D peak (1350cm -1 ) and G peak (1580cm -1 ), indicating that the non-diamond phase content in the sample is low and the diamond purity is high. The half-height width of the characteristic peak is narrow, reflecting that the sample has a high degree of crystallinity.

[0090] Example 5

[0091] (1) Graphite sheet pretreatment: The graphite sheet was ultrasonically cleaned in 95% ethanol for 30 min, twice to remove graphite particles and oil stains on the graphite surface. After cleaning, the graphite sheet was dried in a 150° C. drying oven for 1 h to remove alcohol on the graphite sheet and obtain a clean graphite sheet.

[0092] (2) Preparation of titanium dioxide film on graphite sheet: Open the ALD equipment chamber, place the graphite sheet in the chamber, close the chamber, and pump the chamber pressure to 0.03 torr. Set the deposition parameters: use isopropyl titanate as the titanium precursor, heat the titanium precursor to 75°C, the residence time of the titanium precursor in the chamber is 0.9s, the nitrogen flushing time is 5s, the residence time of water in the chamber is 2s, the second nitrogen flushing time is 8s, and the above is considered as a cycle. The cycle is repeated 250 times, the sample stage temperature is set to 250°C, and the sample stage preheating time is set to 35min. After the deposition is completed, a graphite sheet coated with titanium dioxide film is obtained.

[0093] (3) Seeding treatment: The sample obtained in step 2 is placed in a seeding solution in which diamond micropowder with a diamond particle size of 55 nm and acetone are uniformly mixed in a ratio of 1 g:1 L. The seeding solution is ultrasonically treated for 5 min, and the sample is taken out and placed in a drying oven at 150° C. for 1 h to obtain a seeded graphite sheet.

[0094] (4) Growth of diamond film: The graphite sheet described in step 3 is placed in a microwave plasma chemical vapor deposition device for growth, with the pure hydrogen flow rate set to 200 sccm, the methane flow rate set to 30 sccm, the working gas pressure set to 100 torr, the microwave power set to 3000 W, and the growth time set to 8 hours. After the reaction is completed, a graphite-diamond composite film is obtained.

[0095] SEM and Raman spectroscopy were used to characterize the surface morphology and growth quality of the samples after the experiment.

[0096] Fig.11 This is the SEM image of Example 5. It can be observed that the sample surface exhibits a particle aggregation structure. Some particles form a larger cluster structure. The gaps between the particles are small, showing a dense stacking feature; the grain size is between 3 and 5 μm.

[0097] Fig.12 The Raman spectrum in Example 5 is at 1331.6 cm -1 There is an obvious diamond characteristic peak at , which belongs to the Raman scattering characteristic peak of sp3 hybridized CC bond in diamond crystal, indicating that the diamond film was successfully deposited by microwave chemical vapor deposition after being coated with titanium dioxide. The diamond peak position shifts slightly to low wavenumber, indicating that the tensile stress in the diamond film is small. The background baseline of the spectrum is relatively flat, and there is no D peak (1350cm -1 ) and G peak (1580cm -1 ), indicating that the non-diamond phase content in the sample is low and the diamond purity is high. At the same time, the half-peak width of the characteristic peak is narrow, indicating that the sample has a high degree of crystallinity and a good crystal structure.

[0098] Example 6

[0099] (1) Graphite sheet pretreatment: The graphite sheet was ultrasonically cleaned in 95% ethanol for 30 min, twice to remove graphite particles and oil stains on the graphite surface. After cleaning, the graphite sheet was dried in a 150° C. drying oven for 1 h to remove alcohol on the graphite sheet and obtain a clean graphite sheet.

[0100] (2) Preparation of titanium dioxide film on graphite sheet: Open the ALD equipment chamber, place the graphite sheet in the chamber, close the chamber, and pump the chamber pressure to 0.03 torr. Set the deposition parameters: use isopropyl titanate as the titanium precursor, heat the titanium precursor to 75°C, the residence time of the titanium precursor in the chamber is 0.9s, the nitrogen flushing time is 5s, the residence time of water in the chamber is 2s, the second nitrogen flushing time is 8s, and the above is considered as a cycle. The cycle is repeated 250 times, the sample stage temperature is set to 250°C, and the sample stage preheating time is set to 35min. After the deposition is completed, a graphite sheet coated with titanium dioxide film is obtained.

[0101] (3) Seeding treatment: The sample obtained in step 2 is placed in a seeding solution in which diamond micropowder with a diamond particle size of 55 nm and acetone are uniformly mixed in a ratio of 1 g:1 L. The seeding solution is ultrasonically treated for 5 min, and the sample is taken out and placed in a drying oven at 150° C. for 1 h to obtain a seeded graphite sheet.

[0102] (4) Growth of diamond film: The graphite sheet described in step 3 is placed in a microwave plasma chemical vapor deposition device for growth, with the pure hydrogen flow rate set to 200 sccm, the methane flow rate set to 30 sccm, the working gas pressure set to 100 torr, the microwave power set to 3500 W, and the growth time set to 8 hours. After the reaction is completed, a graphite-diamond composite film is obtained.

[0103] SEM and Raman spectroscopy were used to characterize the surface morphology and growth quality of the samples after the experiment.

[0104] Fig.13 This is the SEM image in Example 6. It can be observed that the sample surface is an irregular polyhedron morphology. The particle surface shows irregular corners and relatively sharp edges, indicating that the particles have a high surface roughness; the grain size is between 5 and 12 μm.

[0105] Fig.14 The Raman spectrum in Example 6 is at 1331.6 cm -1 There is an obvious diamond characteristic peak at the 400 nm, which belongs to the Raman scattering characteristic peak of the sp3 hybridized CC bond in the diamond crystal, indicating that the diamond film was successfully deposited using microwave chemical vapor deposition after being coated with titanium dioxide. The diamond peak position shifts to a lower wave number, indicating that there is tensile stress in the diamond film. The background baseline of the spectrum is relatively flat, and there is no D peak (1350 cm -1 ) and G peak (1580cm -1 ), indicating that the non-diamond phase content in the sample is low and the diamond purity is high. At the same time, the half-peak width of the characteristic peak is narrow, indicating that the sample has a high degree of crystallinity and fewer grain defects.

[0106] Example 7

[0107] (1) Graphite sheet pretreatment: The graphite sheet was ultrasonically cleaned in 95% ethanol for 30 min, twice to remove graphite particles and oil stains on the graphite surface. After cleaning, the graphite sheet was dried in a 150° C. drying oven for 1 h to remove alcohol on the graphite sheet and obtain a clean graphite sheet.

[0108] (2) Preparation of tungsten trioxide film on graphite sheet: Open the ALD equipment chamber, place the graphite sheet into the chamber, close the chamber, and pump the chamber pressure to 0.03 torr. Set the deposition parameters: use bis(tert-butylimino)bis(dimethylamino)tungsten as the tungsten precursor, heat the tungsten precursor to 55°C, the residence time of the tungsten precursor in the chamber is 2s, the nitrogen flushing time is 10s, the residence time of water in the chamber is 0.5s, the second nitrogen flushing time is 5s, and the above is considered as a cycle. The cycle is repeated 250 times, the sample stage temperature is set to 350°C, and the sample stage preheating time is set to 35min. After the deposition is completed, a graphite sheet coated with a tungsten trioxide film is obtained.

[0109] (3) Seeding treatment: The sample obtained in step 2 is placed in a seeding solution in which diamond micropowder with a diamond particle size of 55 nm and acetone are uniformly mixed in a ratio of 1 g:1 L. The seeding solution is ultrasonically treated for 5 min, and the sample is taken out and placed in a drying oven at 150° C. for 1 h to obtain a seeded graphite sheet.

[0110] (4) Growth of diamond film: The graphite sheet described in step 3 is placed in a microwave plasma chemical vapor deposition device for growth, with the pure hydrogen flow rate set to 200 sccm, the methane flow rate set to 30 sccm, the working gas pressure set to 100 torr, the microwave power set to 2500 W, and the growth time set to 8 hours. After the reaction is completed, a graphite-diamond composite film is obtained.

[0111] SEM and Raman spectroscopy were used to characterize the surface morphology and growth quality of the samples after the experiment.

[0112] Fig.15 This is the SEM image in Example 7. It can be observed that the sample surface is composed of irregular block-shaped grains. The grains are polyhedral in shape and have obvious edges and plane features. Cluster structures are formed between the grains, and the grain size is between 6 and 8 μm.

[0113] Fig.16 The Raman spectrum in Example 7 is at 1330.6 cm -1 The obvious diamond characteristic peak appears at 1350cm, indicating that the diamond film was successfully deposited by microwave chemical vapor deposition after being coated with tungsten trioxide. The diamond peak shifts to the left, indicating that there is tensile stress in the diamond film. The D peak (1350cm -1 ) and G peak (1580cm -1 ), indicating that the content of non-diamond phase in the sample is low. At the same time, the half-peak width of the characteristic peak is narrow, reflecting that the sample has a high degree of crystallinity.

[0114] Example 8

[0115] (1) Graphite sheet pretreatment: The graphite sheet was ultrasonically cleaned in 95% ethanol for 30 min, twice to remove graphite particles and oil stains on the graphite surface. After cleaning, the graphite sheet was dried in a 150° C. drying oven for 1 h to remove alcohol on the graphite sheet and obtain a clean graphite sheet.

[0116] (2) Preparation of tungsten trioxide film on graphite sheet: Open the ALD equipment chamber, place the graphite sheet into the chamber, close the chamber, and pump the chamber pressure to 0.03 torr. Set the deposition parameters: use bis(tert-butylimino)bis(dimethylamino)tungsten as the tungsten precursor, heat the tungsten precursor to 55°C, the residence time of the tungsten precursor in the chamber is 2s, the nitrogen flushing time is 10s, the residence time of water in the chamber is 0.5s, the second nitrogen flushing time is 5s, and the above is considered as a cycle. The cycle is repeated 250 times, the sample stage temperature is set to 350°C, and the sample stage preheating time is set to 35min. After the deposition is completed, a graphite sheet coated with a tungsten trioxide film is obtained.

[0117] (3) Seeding treatment: The sample obtained in step 2 is placed in a seeding solution in which diamond micropowder with a diamond particle size of 55 nm and acetone are uniformly mixed in a ratio of 1 g:1 L. The seeding solution is ultrasonically treated for 5 min, and the sample is taken out and placed in a drying oven at 150° C. for 1 h to obtain a seeded graphite sheet.

[0118] (4) Growth of diamond film: The graphite sheet described in step 3 is placed in a microwave plasma chemical vapor deposition device for growth, with the pure hydrogen flow rate set to 200 sccm, the methane flow rate set to 30 sccm, the working gas pressure set to 100 torr, the microwave power set to 3000 W, and the growth time set to 8 hours. After the reaction is completed, a graphite-diamond composite film is obtained.

[0119] SEM and Raman spectroscopy were used to characterize the surface morphology and growth quality of the samples after the experiment.

[0120] Fig.17 This is the SEM image of Example 8. It can be observed that the surface of the grains is relatively flat and has clear edges and corners, indicating that the quality of diamond crystallization is high; there are certain gaps between the grains; and some grains are large in size, indicating that there is a problem of low nucleation density.

[0121] Fig.18 The Raman spectrum in Example 8 is at 1332.5 cm -1 There is an obvious diamond characteristic peak at the bottom, which belongs to the Raman scattering characteristic peak of the sp3 hybridized CC bond in the diamond crystal, indicating that the diamond film was successfully deposited using microwave chemical vapor deposition after being coated with tungsten trioxide and the crystal quality is high. The increase in the background signal is caused by a small amount of disordered carbon in the sample.

[0122] Example 9

[0123] (1) Pretreatment of graphite sheets: The graphite sheets were ultrasonically cleaned in 95% ethanol for 30 min, twice to remove graphite particles and oil stains on the graphite surface. After cleaning, the sheets were dried in a 150° C. drying oven for 1 h to remove the ethanol on the graphite sheets and obtain clean graphite sheets.

[0124] (2) Preparation of tungsten trioxide film on graphite sheet: Open the ALD equipment chamber, place the graphite sheet into the chamber, close the chamber, and pump the chamber pressure to 0.03 torr. Set the deposition parameters: use bis(tert-butylimino)bis(dimethylamino)tungsten as the tungsten precursor, heat the tungsten precursor to 55°C, the residence time of the tungsten precursor in the chamber is 2s, the nitrogen flushing time is 10s, the residence time of water in the chamber is 0.5s, the second nitrogen flushing time is 5s, and the above is considered as a cycle. The cycle is repeated 250 times, the sample stage temperature is set to 350°C, and the sample stage preheating time is set to 35min. After the deposition is completed, a graphite sheet coated with a tungsten trioxide film is obtained.

[0125] (3) Seeding treatment: The sample obtained in step 2 is placed in a seeding solution in which diamond micropowder with a diamond particle size of 55 nm and acetone are uniformly mixed in a ratio of 1 g:1 L. The seeding solution is ultrasonically treated for 5 min, and the sample is taken out and placed in a drying oven at 150° C. for 1 h to obtain a seeded graphite sheet.

[0126] (4) Growth of diamond film: The graphite sheet described in step 3 is placed in a microwave plasma chemical vapor deposition device for growth, with the pure hydrogen flow rate set to 200 sccm, the methane flow rate set to 30 sccm, the working gas pressure set to 100 torr, the microwave power set to 3500 W, and the growth time set to 8 hours. After the reaction is completed, a graphite-diamond composite film is obtained.

[0127] SEM and Raman spectroscopy were used to characterize the surface morphology and growth quality of the samples after the experiment.

[0128] Fig.19 This is the SEM image in Example 9. It can be observed that the sample surface is an irregular polyhedron morphology; a cluster structure is formed between the grains, and the grain size is between 6 and 10 μm, indicating that there is a competition effect between the grains in crystal growth, resulting in differences in the distribution of grain sizes.

[0129] Fig. 20 The Raman spectrum in Example 9 is at 1332.0 cm -1There is an obvious diamond characteristic peak at , which belongs to the Raman scattering characteristic peak of sp3 hybridized CC bond in diamond crystal, indicating that the diamond film was successfully deposited by microwave chemical vapor deposition after being coated with tungsten trioxide. The diamond peak position shifts to a low wave number, indicating that there is tensile stress in the diamond film. There is no D peak (1350cm -1 ) and G peak (1580cm -1 ), indicating that the non-diamond phase content in the sample is low and the diamond purity is high. The half-peak width of the diamond characteristic peak is narrow, indicating that the sample has a high degree of crystallinity and fewer grain defects.

Claims

1. A method for depositing a diamond film on a graphite sheet based on microwave plasma chemical vapor deposition, characterized in that: The following steps are involved: (1) ultrasonically cleaning the graphite sheet and drying it for later use; (2) placing the graphite sheet pretreated in step (1) into an atomic layer deposition device for film coating to obtain a graphite sheet coated with a metal oxide film; The metal oxide is tantalum pentoxide, titanium dioxide or tungsten trioxide; (3) subjecting the graphite sheet coated with the metal oxide film obtained in step (2) to ultrasonic seeding to obtain a seeded graphite sheet; (4) Place the seed crystal graphite sheet obtained in step (3) into a microwave plasma chemical vapor deposition device, set the base height to 4.8 cm, the pure hydrogen flow rate to 200-250 sccm, the methane flow rate to 20-40 sccm, the working gas pressure to 90-120 torr, the microwave power to 2500-4000 W, and grow for 7-9 hours to obtain a graphite-diamond composite film.

2. The method for depositing a diamond film on a graphite sheet based on microwave plasma chemical vapor deposition as claimed in claim 1, characterized in that: The operation of step (1) is as follows: the graphite sheet is ultrasonically cleaned in 95% ethanol for 25 to 35 minutes, the cleaning is repeated twice, and then the sheet is dried in a drying oven at 100 to 200° C. for 0.5 to 1.5 hours for standby use.

3. The method for depositing a diamond film on a graphite sheet based on microwave plasma chemical vapor deposition as claimed in claim 1, characterized in that: In step (2), the coating conditions of the tantalum pentoxide film are as follows: the precursor is t-butylimino tris(ethylmethylamino)tantalum, the precursor heating temperature is 35-45°C, the residence time of the precursor in the chamber is 0.3-0.7s, the nitrogen flushing time is 8-12s, the water residence time in the chamber is 0.3-0.7s, and the nitrogen flushing time is 6-10s again; the above is regarded as a cycle, the number of cycles is 200-300 times, the sample stage temperature is set at 200-300°C, the sample stage preheating time is set at 30-40min, and the deposition is completed to obtain a graphite sheet coated with a tantalum pentoxide film.

4. The method for depositing a diamond film on a graphite sheet based on microwave plasma chemical vapor deposition as claimed in claim 1, characterized in that: In step (2), the coating conditions of the titanium dioxide film are as follows: the precursor is isopropyl titanate, the precursor heating temperature is 70-80°C, the residence time of the precursor in the chamber is 0.7-1.1s, the nitrogen flushing time is 3-7s, the water residence time in the chamber is 1-3s, and the nitrogen flushing time is 6-10s again; the above is regarded as a cycle, the number of cycles is 200-300 times, the sample stage temperature is set at 200-300°C, the sample stage preheating time is set at 30-40min, and a graphite sheet coated with a titanium dioxide film is obtained after the deposition is completed.

5. The method for depositing a diamond film on a graphite sheet based on microwave plasma chemical vapor deposition as claimed in claim 1, characterized in that: In step (2), the coating conditions of the tungsten trioxide film are as follows: the precursor is bis(tert-butylimide)bis(dimethylamino)tungsten, the precursor heating temperature is 50-60°C, the residence time of the precursor in the chamber is 1-3s, the nitrogen flushing time is 8-12s, the water residence time in the chamber is 0.3-0.7s, and the nitrogen flushing time is 3-7s again; the above is regarded as a cycle, the number of cycles is 200-300 times, the sample stage temperature is set at 300-400°C, the sample stage preheating time is set at 30-40min, and the deposition is completed to obtain a graphite sheet coated with a tungsten trioxide film.

6. The method for depositing a diamond film on a graphite sheet based on microwave plasma chemical vapor deposition as claimed in claim 1, characterized in that: The operation of step (3) is as follows: diamond powder is uniformly dispersed in acetone to obtain a seeding solution, a graphite sheet coated with a metal oxide film is placed in the seeding solution, and ultrasonicated for 5 to 10 minutes to obtain a seeding graphite sheet; wherein the diamond powder has a particle size of 55 nm; and the concentration of the seeding solution is 0.8 to 1.2 g / L.

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