Method for preparing graphene-diamond composite material by utilizing microwaves

Abstract

The invention discloses a method for preparing a graphene-diamond composite material by utilizing microwaves, which comprises the following steps of: depositing a diamond film on the surface of a single crystal diamond by adopting a microwave chemical vapor deposition method, and respectively preparing single crystal diamond films with (111) oriented upper and lower surfaces by adopting a slicing and polishing method to obtain a diamond substrate; putting the diamond substrate into a vacuum chamber of microwave plasma chemical vapor deposition equipment to form a diamond substrate with a hydrogen terminal surface structure; and then heating a sample table where the diamond substrate is located, introducing methane, ionizing gas by using microwave energy to form microwave plasma, exciting methane and hydrogen to generate active hydrocarbon groups and hydrogen atoms, and depositing a film on the surface of the diamond to obtain the graphene-diamond composite material. According to the method disclosed by the invention, damage to the graphene layer caused by layer transfer is avoided, and the composite structure can be controlled to present conductor or semiconductor characteristics.

Description

Technical Field

[0001] The invention relates to the field of diamond composite materials, and in particular to a method for preparing a graphene-diamond composite material by utilizing microwaves. Background Art

[0002] As silicon chips gradually approach their physical limits, high-quality semiconductor chips are increasingly eager for new semiconductor materials. The diversity of carbon-based material structures and electronic adjustability give them many excellent properties. Among carbon materials, diamond has the advantages of good chemical stability, high thermal conductivity, wide bandgap, high breakdown voltage and negative electron affinity. However, the surface resistance of diamond is too high, which hinders the transfer and transportation of electrons and limits its electrical properties. As an allotrope of diamond, graphene is a two-dimensional structural material composed of carbon atoms with a high aspect ratio and excellent electrical and thermal properties, but it is easy to accumulate, which affects its practical application.

[0003] Existing graphene is mainly prepared on a copper or alloy substrate by CVD, and then prepared on a silicon or silicon carbide substrate by layer transfer technology. The transfer process will have an adverse effect on the performance of graphene, and the instability of the transfer technology itself affects the electrical properties of the graphene composite structure. Directly preparing one or more layers of graphene on the surface of diamond and combining them into a graphene-diamond composite structure can benefit from the complementary characteristics of the two components, further enhance its current carrying capacity, and greatly enhance the conductivity of the composite structure.

[0004] The surface of the existing graphene-diamond composite structure is relatively rough, the graphene quality is poor, the layers are thick and graphitized, and the conductivity is poor. Currently, most of the existing graphene preparations on the diamond surface are vertically distributed on the surface. This structure is not suitable for the semiconductor field, especially the chip preparation industry based on the lamellar structure. Although there are some reports on parallel-structured graphene-diamond composite materials, the diamond substrate used is a polycrystalline structure, and the lattice matching between different crystal planes and graphene is very different. In addition, the surface flatness of the polycrystalline structure is low, and the comprehensive performance of the composite material formed is difficult to improve. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a method for preparing a graphene-diamond composite material using microwaves, so as to achieve the purpose of preparing a graphene-diamond composite structure with a flat surface and parallel distribution. By regulating the number of graphene layers and the arrangement order, the composite structure can be controlled to exhibit conductor or semiconductor properties.

[0006] To achieve the above object, the technical solution of the present invention is as follows:

[0007] A method for preparing a graphene-diamond composite material using microwaves, characterized in that it comprises the following steps:

[0008] (1) depositing a diamond film on the surface of a single crystal diamond by microwave chemical vapor deposition, and preparing single crystal diamond films with (111) orientation on the upper and lower surfaces by slicing and polishing to obtain a diamond substrate; the surface roughness of the single crystal diamond film is less than 1.5 nm, and the crystal plane deflection angle is less than 2°;

[0009] (2) After placing the diamond substrate in a vacuum chamber of a microwave plasma chemical vapor deposition device, turning on the microwave power supply, firstly introducing hydrogen gas, using hydrogen plasma for cleaning, removing impurities adsorbed on the surface of the substrate, and forming a diamond substrate with a hydrogen-terminated surface structure;

[0010] (3) The sample stage where the diamond substrate is located is then heated. After reaching the set temperature, the microwave power is adjusted, and methane is introduced. The microwave energy is used to ionize the gas to form a microwave plasma, which excites methane and hydrogen to produce active carbon hydrogen groups and hydrogen atoms, and deposits a thin film on the diamond surface. After deposition for 5-10 minutes, the microwave power is turned off and the methane and hydrogen are turned off at the same time to obtain a graphene-diamond composite material.

[0011] In the above scheme, in step (1), after slicing and polishing, the surface of the obtained single-crystal diamond film has a single crystal plane structure that is atomically flat.

[0012] In the above scheme, in step (1), the thickness of the diamond substrate obtained is 0.3 mm.

[0013] In the above scheme, in step (2), firstly, hydrogen gas is introduced at 100 sccm-300 sccm, and cleaning is performed for 5-10 minutes.

[0014] In the above scheme, in step (2), the microwave power is 3000 watts.

[0015] In the above scheme, in step (3), after the temperature reaches 800°C-1200°C, the microwave power is adjusted.

[0016] In the above scheme, in step (3), the microwave power is adjusted to 3500-6000 watts.

[0017] In the above scheme, in step (3), the ratio of the amount of methane and hydrogen introduced is 1:10.

[0018] In the above scheme, in step (3), the time for depositing the thin film on the diamond surface is 8 minutes.

[0019] Through the above technical solution, the method for preparing a graphene-diamond composite material using microwaves provided by the present invention has the following beneficial effects:

[0020] The present invention adopts a microwave plasma chemical vapor deposition (MPCVD) method to grow graphene directly on the surface of a single crystal diamond without the action of metal catalysis, thereby avoiding the damage to the graphene layer caused by the transfer after the graphene is grown on different substrates in the past. In addition, the (111) crystal plane single crystal diamond used in the present invention has high flatness (surface roughness is less than 1.5nm) and the highest degree of matching with the graphene lattice, ensuring that the graphene layer is directly and regularly grown on the diamond surface to form a good graphene-diamond composite structure.

[0021] In addition, by controlling parameters such as temperature, carbon source amount, hydrogen amount and growth time, the number of graphene layers, arrangement order and quality can be regulated, and the composite structure can be controlled to exhibit conductor or semiconductor properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art are briefly introduced below.

[0023] Figure 1 A schematic flow chart of a method for preparing a graphene-diamond composite material using microwaves disclosed in an embodiment of the present invention;

[0024] Figure 2 This is an atomic force microscope image of the polished single crystal diamond surface;

[0025] Figure 3 This is a Raman spectrum photo of graphene-diamond composite structure;

[0026] Figure 4 This is a transmission electron microscope photo of a graphene-diamond composite structure;

[0027] Figure 5 This is an atomic force microscope image of a graphene-diamond composite structure;

[0028] Figure 6 Schematic diagram of the bonding structure of graphene and diamond with different crystal planes, (a) is the (111) crystal plane; (b) is the (100) crystal plane, and (c) is the (110) crystal plane. DETAILED DESCRIPTION

[0029] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0030] Example 1

[0031] The present invention provides a method for preparing a graphene-diamond composite material using microwaves, such as Figure 1As shown, the following steps are included:

[0032] (1) A diamond film is deposited on the surface of a single crystal diamond by microwave chemical vapor deposition, and the vapor deposition gases are methane, hydrogen, and oxygen. Single crystal diamond films with (111) orientation on the upper and lower surfaces are prepared by slicing and polishing to obtain a diamond substrate; the surface roughness of the single crystal diamond film is less than 1.5 nm, the substrate thickness is 0.3 mm, and the crystal plane deflection angle is less than 2°; Figure 2 An atomic force microscope image of the polished single crystal diamond surface is given.

[0033] (2) The diamond substrate was ultrasonically cleaned in deionized water for 10 min, ultrasonically cleaned in anhydrous ethanol for 10 min, and then dried with dry air to remove oil stains on the surface.

[0034] (3) After placing the diamond substrate in the vacuum chamber of the microwave plasma chemical vapor deposition equipment, the reaction chamber is evacuated to a vacuum degree of 10 -4 The microwave power is turned on, the microwave power is 3000 watts, hydrogen (100sccm-300sccm) is introduced first, and hydrogen plasma is used for cleaning for 5-10 minutes to remove impurities adsorbed on the surface of the substrate and form a diamond substrate with a hydrogen terminal surface structure.

[0035] (4) The sample stage on which the diamond substrate is located is then heated. After reaching the set temperature (800°C-1200°C), the microwave power is adjusted to 3500-6000 watts, and methane is introduced, and the ratio of methane to hydrogen is adjusted to 1:10. The microwave energy is used to ionize the gas to form a microwave plasma, which excites methane and hydrogen to produce active carbon hydrogen groups and hydrogen atoms, and deposits a thin film on the diamond surface.

[0036] (5) After 5-10 minutes of deposition, the microwave power is turned off, and the methane and hydrogen are turned off at the same time. After the temperature drops to room temperature, nitrogen is introduced, the vacuum is broken, and the sample is taken out to obtain a graphene-diamond composite material. By controlling parameters such as temperature, carbon source amount, hydrogen amount, and growth time, the number of graphene layers (1-3), arrangement order, and quality can be controlled, and the composite structure can be controlled to exhibit conductor or semiconductor properties.

[0037] Figure 3 The Raman spectrum of the parallel distribution graphene-diamond composite structure is given at 1580cm -1 and 2700cm -1 The G peak and 2D peak of graphene are shown in Figure 2, and the ratio of the G peak to the 2D peak is about 0.7, indicating that a single layer of graphene has grown on the diamond surface at this time.

[0038] Figure 4A transmission electron microscope photo of a multi-layer graphene composite structure on a diamond surface is given. The atoms in the lower 1 / 4 part are arranged regularly, which is a single-crystal diamond substrate. It can be seen that there is a graphene layer with a significantly larger spacing on the surface of the single-crystal diamond. The irregular atomic distribution in the photo is the metal platinum (Pt) used in the preparation of transmission electron microscope characterization samples, and the composite structure itself does not contain this part.

[0039] Figure 5 Here is an atomic force microscope image of the surface of the gold graphene-diamond composite structure. Figure 4 and Figure 5 It shows that graphene is distributed in parallel on the diamond surface, and the surface roughness of the graphene-diamond composite structure is less than 3nm.

[0040] Comparative Example 1

[0041] The difference between this comparative example and Example 1 is that no slicing and polishing is performed in step (1), and the rest is the same as Example 1. It is found that the graphene grown on the unpolished diamond surface is difficult to maintain a parallel structure, and the graphene grows on the diamond surface in a structure perpendicular to or at a certain angle to the diamond surface.

[0042] Comparative Example 2

[0043] The difference between this comparative example and Example 1 is that in step (1), after slicing and polishing, the surface roughness of the single crystal diamond film is 2 nm, the crystal plane deflection angle is 3°, and the rest is the same as Example 1. It is found that during the growth of graphene, microwave plasma will etch the diamond surface. If the deflection angle of the (111) crystal plane is too large, the substrate surface will form a slope of a certain angle along the (111) crystal plane, and steps will be formed between different slopes, thereby causing the grown graphene to be uneven, reducing the quality of the composite structure. Figure 6 (a) is a schematic diagram of the structure of graphene (yellow) and diamond (111) crystal plane.

[0044] Comparative Example 3

[0045] The difference between this comparative example and Example 1 is that in step (1), after slicing and polishing, a single crystal diamond film with upper and lower surfaces oriented (100) is prepared, and the rest is the same as Example 1. It is found that although the graphene on the (100) crystal orientation diamond surface can also present a parallel structure, due to the large lattice mismatch between the (100) plane and the graphene, it is easy to form more wrinkles on the graphene, and the quality is difficult to control. Figure 6 (b) is a schematic diagram of the structure of graphene (yellow) and diamond (100) crystal plane.

[0046] Comparative Example 4

[0047] The difference between this comparative example and Example 1 is that in step (1), after slicing and polishing, a single crystal diamond film with upper and lower surfaces oriented (110) is prepared, and the rest is the same as Example 1. It is found that similar to Comparative Example 3, the (110) surface of diamond is also relatively compatible with graphene, and it is difficult to prepare a high-quality parallel structure graphene-diamond composite structure on its surface by microwave. Figure 6 (c) is a schematic diagram of the structure of graphene (yellow) and diamond (110) crystal plane.

[0048] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a graphene-diamond composite material using microwaves, characterized in that: The steps include: (1) depositing a diamond film on the surface of a single crystal diamond by microwave chemical vapor deposition, and preparing single crystal diamond films with (111) orientation on the upper and lower surfaces by slicing and polishing to obtain a diamond substrate; the surface roughness of the single crystal diamond film is less than 1.5 nm, and the crystal plane deflection angle is less than 2°; (2) After placing the diamond substrate in a vacuum chamber of a microwave plasma chemical vapor deposition device, turning on the microwave power supply, firstly introducing hydrogen gas, using hydrogen plasma for cleaning, removing impurities adsorbed on the surface of the substrate, and forming a diamond substrate with a hydrogen-terminated surface structure; (3) The sample stage where the diamond substrate is located is then heated. After reaching the set temperature, the microwave power is adjusted, and methane is introduced. The microwave energy is used to ionize the gas to form a microwave plasma, which excites methane and hydrogen to produce active carbon hydrogen groups and hydrogen atoms, and deposits a thin film on the diamond surface. After deposition for 5-10 minutes, the microwave power is turned off and the methane and hydrogen are turned off at the same time to obtain a graphene-diamond composite material.

2. The method for preparing a graphene-diamond composite material using microwaves according to claim 1, characterized in that: In step (1), after slicing and polishing, the surface of the obtained single crystal diamond film has a single crystal plane structure that is atomically flat.

3. The method for preparing graphene-diamond composite material using microwaves according to claim 1, characterized in that: In step (1), the thickness of the diamond substrate obtained is 0.3 mm.

4. The method for preparing a graphene-diamond composite material using microwaves according to claim 1, characterized in that: In step (2), firstly, hydrogen gas is introduced at 100 sccm-300 sccm for cleaning for 5-10 minutes.

5. The method for preparing graphene-diamond composite material using microwaves according to claim 1, characterized in that: In step (2), the microwave power is 3000 watts.

6. The method for preparing a graphene-diamond composite material using microwaves according to claim 1, characterized in that: In step (3), after the temperature reaches 800°C-1200°C, the microwave power is adjusted.

7. The method for preparing graphene-diamond composite material using microwaves according to claim 1, characterized in that: In step (3), the microwave power is adjusted to 3500-6000 watts.

8. The method for preparing graphene-diamond composite material using microwaves according to claim 1, characterized in that: In step (3), the ratio of the amount of methane to hydrogen introduced is 1:

10.

9. The method for preparing graphene-diamond composite material using microwaves according to claim 1, characterized in that: In step (3), the time for depositing the thin film on the diamond surface is 8 minutes.

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