Preparation method of graphene-diamond composite material with parallel structure

Abstract

The invention discloses a preparation method of a graphene-diamond composite material with a parallel structure, which comprises the following steps: 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; processing the surface of the monocrystal diamond film through hydrogen plasma by utilizing a microwave plasma technology to obtain monocrystal diamond with a hydrogen terminal surface; in a low-vacuum environment, mixed gas of methane and hydrogen is heated through a hot wire, carbon atoms needed by graphene growth are generated through pyrolysis, the carbon atoms are adsorbed on the surface of diamond, nucleation is carried out, two-dimensional reconstruction is carried out, and finally the graphene-diamond composite material of a parallel structure is obtained. According to the method disclosed by the invention, the damage caused by a graphene transfer technology is avoided. The surface of the composite structure can show the characteristics of a conductor or a semiconductor, and the composite structure has great application potential in the field of semiconductor chips.

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 with a parallel structure. Background Art

[0002] Graphene is a conductor material with high conductivity, mobility and excellent performance. This makes graphene have very broad application prospects in optoelectronic sensing devices, energy storage batteries and graphene composites, and has therefore attracted widespread attention and research from scientific researchers.

[0003] At present, the main methods for preparing graphene include mechanical exfoliation, chemical oxidation-reduction, chemical vapor deposition, epitaxial growth, etc. Among them, chemical vapor deposition can prepare a few layers of graphene, which are mostly prepared on substrates such as silicon carbide, silicon dioxide, and copper alloy. After the preparation is completed, in order to reduce the interference of the substrate material, it is prepared on a silicon or silicon carbide substrate by layer transfer technology. However, the transfer process will have an adverse effect on the performance of graphene, and the instability of the transfer technology itself will also affect the electrical properties of the composite structure.

[0004] Diamond is a material with excellent physical properties such as high hardness, small friction coefficient, wide forbidden band, high carrier mobility, and low field emission threshold. It also has a small size effect, large specific surface area and reactivity. If graphene is composited with diamond materials, the advantages of these two materials can be well utilized to enhance the mechanical and electrical properties, which is conducive to the application of diamond and graphene in the fields of engineering and functional materials. In the current composite structure of graphene and diamond, graphene generally grows vertically on the surface of diamond. Its structure can effectively increase the specific surface area of ​​the composite structure, but this structure is not suitable for the semiconductor field, especially the chip preparation industry based on lamellar structure. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a method for preparing a parallel-structured graphene-diamond composite material, so as to achieve the purpose of preparing a parallel-structured graphene-diamond composite material exhibiting 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 parallel-structured graphene-diamond composite material 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;

[0009] (2) Using microwave plasma technology, the surface of a single crystal diamond film is treated with hydrogen plasma to obtain a single crystal diamond with a hydrogen-terminated surface;

[0010] (3) In a low vacuum environment, a mixture of methane and hydrogen is heated by a hot wire to produce carbon atoms required for graphene growth. The carbon atoms are adsorbed on the diamond surface to form nuclei and then reconstructed in two dimensions, ultimately obtaining a graphene-diamond composite material with a parallel structure.

[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), after slicing and polishing, the surface roughness of the obtained single crystal diamond film is less than 1.5 nm.

[0013] In the above scheme, in step (2), the microwave power is 3KW, the surface temperature of the single crystal diamond film is 500-600°C, the hydrogen flow rate is 200sccm, and the hydrogenation time is 5 minutes.

[0014] In the above scheme, in step (3), the low vacuum environment is an environment with a pressure of 1000-1800Pa.

[0015] In the above scheme, in step (3), the power of the hot wire is 3000-5000w.

[0016] In the above scheme, in step (3), the flow rate of methane is 5-20 sccm, and the flow rate of hydrogen is 100-300 sccm.

[0017] In the above scheme, in step (3), the graphene growth time is 10-25 minutes.

[0018] Through the above technical solution, the method for preparing a parallel-structured graphene-diamond composite material provided by the present invention has the following beneficial effects:

[0019] The present invention uses a hot wire chemical vapor deposition method to pyrolyze a methane and hydrogen mixed gas to generate a carbon source, and directly grows a graphene-diamond composite structure with a parallel structure on the diamond surface. The high band gap width, light transmittance, thermal conductivity and stability of diamond make it directly usable as a subsequent substrate, avoiding the damage caused by the graphene transfer technology. At the same time, the present invention is different from the existing situation of graphene growing vertically on the diamond surface. Because the surface roughness of the diamond is less than 1.5nm during the preparation and polishing of the single crystal diamond film, combined with the (111) crystal plane that is highly matched with the graphene lattice, high-quality parallel growth of graphene on the diamond surface can be achieved.

[0020] In addition, the graphene in the present invention has the characteristics of controllable number of layers and stacking mode, so the obtained graphene-diamond composite structure exhibits conductor or semiconductor properties and has great application potential in the field of semiconductor chips. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] 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.

[0022] Figure 1 A schematic flow chart of a method for preparing a parallel-structured graphene-diamond composite material disclosed in an embodiment of the present invention;

[0023] Figure 2 This is an atomic force microscope image of the single crystal diamond surface after slice polishing;

[0024] Figure 3 is the Raman spectrum of the obtained parallel-structured graphene-diamond composite material;

[0025] Figure 4 This is an optical microscope image of the parallel-structured graphene-diamond composite material obtained;

[0026] Figure 5 The transmission electron microscope photo of the parallel structured graphene-diamond composite material obtained;

[0027] Figure 6 The surface atomic force microscope image of the parallel-structured graphene-diamond composite material obtained;

[0028] Figure 7 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 with a parallel structure, such as Figure 1 As 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. The surface roughness of the polished diamond is less than 1.5 nanometers, and the film thickness is 0.3 mm. Figure 2 An atomic force microscope image of the single crystal diamond surface after slicing and polishing is given.

[0033] (2) Using microwave plasma technology, single crystal diamond with a hydrogen-terminated surface was obtained by treating the surface of a single crystal diamond film with hydrogen plasma; the microwave power was 3KW, the sample surface temperature was 500-600°C, the hydrogen flow rate was 200sccm, and the hydrogenation time was 5 minutes. The main function of hydrogen termination is to keep the atomic arrangement on the diamond surface consistent with the inner layer, avoiding surface oxidation and surface atomic reconstruction.

[0034] (3) Preparation of graphene-diamond composite structure by hot wire chemical vapor deposition:

[0035] ① Open the reaction chamber of the hot wire chemical vapor deposition system, take out the base, and place the single crystal diamond sample with a hydrogen terminal surface prepared by the microwave system on the surface of the base.

[0036] ②Evacuate the chamber and introduce hydrogen for 10 minutes to discharge excess gas from the gas pipeline and mixing chamber.

[0037] ③ Turn off the hydrogen and wait for the reactor pressure to drop below 20 Pa. Then introduce methane and hydrogen. This process can exhaust the residual gas in the chamber on the one hand, and ensure the stability of the gas flow in the reaction chamber during the subsequent growth process on the other hand.

[0038] ④After 3 to 10 minutes, turn on the power and adjust the power (3000-5000w) to raise the base height. When it reaches the preset height (1-2 cm from the hot wire position), start timing the growth time and control the pressure at 1000-1800Pa.

[0039] ⑤ After 15 minutes of growth, adjust the power down to the initial value (1200w), turn off the power, lower the base height to the initial height (30 cm from the hot wire position), and turn off methane and hydrogen.

[0040] ⑥Evacuate the reactor, and turn off the vacuum pump when the pressure in the reactor drops below 20 Pa. Cool the reactor in a vacuum environment, and remove the base and sample after cooling. The experiment is over, and a parallel-structured graphene-diamond composite material is obtained.

[0041] Figure 3This is the Raman spectrum of the parallel-structured graphene-diamond composite material. The image shows that the ratio of the 2D peak to the G peak in the Raman spectrum is about 0.5, indicating that multilayer graphene has grown on the diamond surface.

[0042] Figure 4 This is an optical microscope image of a parallel-structured graphene-diamond composite material. The black shaded area in the image is the multilayer graphene area.

[0043] Figure 5 This is a transmission electron microscope photo of a parallel-structured graphene-diamond composite material. The upper half of the picture is multi-layer graphene and the lower half is the diamond layer.

[0044] Figure 6 This is an atomic force microscope image of a parallel-structured graphene-diamond composite material. The surface roughness of the graphene-diamond composite structure after growth is less than 3 nanometers.

[0045] Comparative Example 1

[0046] 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.

[0047] Comparative Example 2

[0048] 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, and the rest is the same as Example 1. It is found that roughness is the key to ensuring the parallel structure size. As the surface roughness decreases, the crystal structure of graphene and diamond (111) plane is highly similar. The parallel distribution of graphene is more stable. Figure 7 (a) is a schematic diagram of the structure of graphene (yellow) and diamond (111) crystal plane.

[0049] Comparative Example 3

[0050] 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 7 (b) is a schematic diagram of the structure of graphene (yellow) and diamond (100) crystal plane.

[0051] Comparative Example 4

[0052] 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 hot wire chemical vapor deposition. Figure 7 (c) is a schematic diagram of the structure of graphene (yellow) and diamond (110) crystal plane.

[0053] 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 parallel-structured graphene-diamond composite material, 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; (2) Using microwave plasma technology, the surface of a single crystal diamond film is treated with hydrogen plasma to obtain a single crystal diamond with a hydrogen-terminated surface; (3) In a low vacuum environment, a mixture of methane and hydrogen is heated by a hot wire to produce carbon atoms required for graphene growth. The carbon atoms are adsorbed on the diamond surface to form nuclei and then reconstructed in two dimensions, ultimately obtaining a graphene-diamond composite material with a parallel structure.

2. The method for preparing a parallel-structured graphene-diamond composite material 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 a parallel-structured graphene-diamond composite material according to claim 1, characterized in that: In step (1), after slicing and polishing, the surface roughness of the obtained single crystal diamond film is less than 1.5 nm.

4. The method for preparing a parallel-structured graphene-diamond composite material according to claim 1, characterized in that: In step (2), the microwave power is 3 KW, the surface temperature of the single crystal diamond film is 500-600° C., the hydrogen flow rate is 200 sccm, and the hydrogenation time is 5 minutes.

5. The method for preparing a parallel-structured graphene-diamond composite material according to claim 1, characterized in that: In step (3), the low vacuum environment is an environment with a pressure of 1000-1800Pa.

6. The method for preparing a parallel-structured graphene-diamond composite material according to claim 1, characterized in that: In step (3), the power of the heating wire is 3000-5000w.

7. The method for preparing a parallel-structured graphene-diamond composite material according to claim 1, characterized in that: In step (3), the flow rate of methane is 5-20 sccm, and the flow rate of hydrogen is 100-300 sccm.

8. The method for preparing a parallel-structured graphene-diamond composite material according to claim 1, characterized in that: In step (3), the graphene growth time is 10-25 minutes.

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