Graphene-diamond composite substrate, and preparation method and application thereof

Abstract

The application discloses a graphene-diamond composite substrate and a preparation method and application thereof, and belongs to the technical field of electronic device substrate materials. The preparation of the composite substrate comprises the following steps: preparing a SiC epitaxial layer on a diamond substrate with a patterned topography and being not completely flat; setting a SiC cover sheet; and performing first-stage high-temperature heat treatment on the SiC epitaxial layer and the diamond substrate together under a protective atmosphere and normal pressure. After the heat treatment pressure and temperature are reduced, second-stage high-temperature heat treatment is performed to decompose Si on the surface of the SiC epitaxial layer, and the remaining C atoms are restructured into graphene. In the composite substrate, the material interfaces can be fully bonded, and thus efficient heat conduction can be achieved; the graphene is patterned based on the substrate topography, the edges of the graphene have dangling bonds for nitride nucleation, in-situ nitriding or N plasma treatment processes are not needed, and uncontrollable defects are avoided; and the method does not need to clean the substrate, and chemical reagent pollution is avoided.

Description

Technical Field

[0001] This invention relates to the field of electronic device substrate materials technology, and more specifically, to a graphene-diamond composite substrate, its preparation method, and its application. Background Technology

[0002] Diamond substrates play an irreplaceable role in the fabrication of electronic devices. Their advantage lies in their high thermal conductivity, which, as heat dissipation substrates, significantly improves the power density and reliability of high-power, high-frequency devices and effectively mitigates self-heating effects. Furthermore, as an ultra-wide bandgap semiconductor, diamond is also an ideal material for fabricating high-temperature and high-voltage resistant devices.

[0003] However, epitaxial growth of nitrides (such as GaN) on diamond substrates faces two major challenges: first, a significant lattice mismatch, with GaN and diamond having lattice constants that differ by more than 20%, resulting in extremely high dislocation densities in the epitaxial layer, severely impacting device performance and lifespan; and second, extreme thermal mismatch, with a significant difference in their coefficients of thermal expansion. During the cooling process from high temperature to room temperature after heteroepitaxial growth, enormous thermal stress accumulates at the interface, easily leading to film cracking or substrate fragmentation. These two fundamental physical mismatch problems make obtaining high-quality, crack-free thick-film nitride epitaxial layers directly on diamond extremely challenging.

[0004] In view of this, the present invention is proposed. Summary of the Invention

[0005] The purpose of this invention is to provide a graphene-diamond composite substrate, its preparation method, and its application, so as to solve or improve the above-mentioned technical problems.

[0006] This invention can be implemented as follows: In a first aspect, the present invention provides a method for preparing a graphene-diamond composite substrate, comprising the following steps: SiC epitaxial layers are prepared on diamond substrates with patterned morphology and not completely flat. A SiC cap film is placed on the side of the SiC epitaxial layer away from the diamond substrate. Under a protective atmosphere and normal pressure, the SiC epitaxial layer and the diamond substrate are subjected to a first-stage high-temperature heat treatment to enable the SiC epitaxial layer to bond with the diamond substrate. After reducing the heat treatment pressure and temperature, a second stage of high-temperature heat treatment is carried out to decompose the Si on the surface of the SiC epitaxial layer and reconstruct the remaining C atoms into graphene. The SiC cover was removed to obtain a graphene-diamond composite substrate.

[0007] In an optional embodiment, the pattern morphology includes at least one of step morphology and mound morphology; And / or, the crystal planes of the diamond substrate include at least one of the (100) crystal plane, (110) crystal plane and (111) crystal plane.

[0008] In optional embodiments, the SiC epitaxial layer is prepared by at least one of diamond surface Si treatment, low-pressure chemical vapor deposition, and physical vapor deposition.

[0009] In an optional embodiment, the SiC epitaxial layer is prepared by low-pressure chemical vapor deposition.

[0010] In an optional implementation, low-pressure chemical vapor deposition includes at least one of the following conditions: Condition 1: The growth source includes a silicon source and a carbon source, wherein the molar ratio of Si in the silicon source to C in the carbon source is 1:4 to 4:1; Condition 2: Deposition temperature is 800℃~1200℃; Condition 3: Deposition pressure is 0.3 mbar to 70 mbar.

[0011] In an optional implementation, the first-stage high-temperature heat treatment includes at least one of the following conditions: Condition 4: The temperature of the first stage high-temperature heat treatment is 1200℃~1700℃, preferably 1300℃~1500℃; Condition 5: The time for the first stage of high-temperature heat treatment shall not be less than 0.5 hours, preferably 0.5 hours to 2 hours.

[0012] In an optional implementation, the second-stage high-temperature heat treatment includes at least one of the following conditions: Condition 6: The pressure of the second-stage high-temperature heat treatment is lower than atmospheric pressure, preferably ultra-high vacuum ~ 0.7 times atmospheric pressure; Condition 7: The temperature for the second stage of high-temperature heat treatment is 1200℃~1500℃; Condition 8: The time for the second stage of high-temperature heat treatment shall not be less than 0.5 hours, preferably 0.5 hours to 2 hours.

[0013] In an optional embodiment, the protective atmosphere includes at least one of a high-purity argon atmosphere and a high-purity nitrogen atmosphere.

[0014] In an optional implementation, the purity of high-purity argon and high-purity nitrogen is independently not less than 99.999%.

[0015] Secondly, the present invention provides a graphene-diamond composite substrate, which is prepared by any of the preparation methods described in the foregoing embodiments.

[0016] In an optional embodiment, when the thickness of the SiC epitaxial layer is ≥10nm, the graphene-diamond composite substrate is a graphene / SiC / diamond composite substrate; when the thickness of the SiC epitaxial layer is <10nm, the graphene-diamond composite substrate is a graphene / diamond composite substrate.

[0017] Thirdly, the present invention provides an electronic device comprising the graphene-diamond composite substrate of the foregoing embodiments.

[0018] The beneficial effects of this invention include: This invention utilizes the characteristic that Si atoms in SiC preferentially and orderly decompose at the step edges to generate graphene at high temperatures. A SiC layer is prepared on a diamond template, and high-temperature heat treatment is used to fully bond SiC and diamond, generating graphene material from the SiC surface. The final result is a graphene / diamond or graphene / SiC / diamond composite substrate. Because graphene bonds to the bulk material on one side and is reserved for bonding with nitride materials on the other, it eliminates the need to artificially introduce defects to promote nitride nucleation during nitride growth. Furthermore, heat can be efficiently transferred from within the graphene layer to the highly thermally conductive bulk substrate. The entire process is conducted within the material growth and high-temperature heat treatment equipment, without contact with other metals or chemical reagents. The graphene bonds fully to the bulk substrate material, the graphene generation process is orderly and controllable, and the operation steps are relatively simple, making it highly practical. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0020] Figures 1 to 6 This is a schematic diagram illustrating one preparation process of the graphene-diamond composite substrate in this invention; Figure 7 The surface morphology of the composite substrate under atomic force microscopy in Example 1; Figure 8 The surface morphology of the composite substrate under atomic force microscopy in Example 2; Figure 9 The surface morphology of the composite substrate in Comparative Example 1 is shown in the atomic force microscope image.

[0021] Icons: 10 - Diamond substrate; 20 - SiC epitaxial layer; 30 - SiC capping sheet; 40 - Graphene. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0023] The graphene-diamond composite substrate, its preparation method, and its applications provided by this invention will be described below.

[0024] This invention provides a method for preparing a graphene-diamond composite substrate. Please refer to... Figures 1 to 6 This includes the following steps: S1: On a diamond substrate 10 with a patterned morphology and not completely flat (e.g., Figure 1 On the (as shown), a SiC epitaxial layer 20 is prepared (as shown). Figure 2 (As shown).

[0025] In some alternative embodiments, the pattern morphology of the diamond substrate 10 may, by way of example but not limitation, include at least one of step morphology and mound morphology. Furthermore, the pattern morphology of the diamond substrate 10 may also include some artificially introduced specific morphologies, such as etched stripe morphology, hexagonal prisms, cylinders, hexagonal holes, circular holes, etc.

[0026] In some alternative embodiments, the crystal planes of the diamond substrate 10 may exemplary include at least one of the (100) crystal plane, (001) crystal plane, (110) crystal plane, and (111) crystal plane. It should be noted that epitaxially grown nitrides are generally in the

[0001] crystal orientation, and the (111) crystal plane of the diamond substrate 10 with the above-mentioned crystal planes is advantageous for epitaxial growth of nitrides.

[0027] In some alternative embodiments, the preparation of the SiC epitaxial layer 20 may, by way of example but not limitation, include at least one of diamond surface Si treatment, low-pressure chemical vapor deposition, and physical vapor deposition.

[0028] Taking the preparation of SiC epitaxial layer 20 by low-pressure chemical vapor deposition as an example, the growth source used in low-pressure chemical vapor deposition includes a silicon source and a carbon source. The silicon source can exemplarily include Si-containing gases such as silane and dichlorosilane, and the carbon source can exemplarily include C-containing gases such as methane and acetylene. The molar ratio of Si in the silicon source to C in the carbon source can exemplarily include 1:4 to 4:1, preferably 1:1.

[0029] The temperature for low-pressure chemical vapor deposition can be 800℃~1200℃, such as 800℃, 850℃, 900℃, 950℃, 1000℃, 1050℃, 1100℃, 1150℃ or 1200℃, or other values ​​within the range of 800℃~1200℃.

[0030] The pressure for low-pressure chemical vapor deposition can be 0.3 mbar to 70 mbar, such as 0.3 mbar, 1 mbar, 5 mbar, 10 mbar, 20 mbar, 50 mbar or 70 mbar, or other values ​​within the range of 0.3 mbar to 70 mbar.

[0031] The thickness of the SiC epitaxial layer 20 varies depending on the deposition time, and can be set according to actual needs.

[0032] High-temperature heat treatment promotes the reconstruction of C atoms on the diamond surface into graphene. However, since the diamond substrate surface is entirely composed of C atoms, the reconstruction energy of C atoms at the edges of substrate morphologies (such as steps or mound-like morphologies) is relatively similar to that of the bulk material. Therefore, graphitization easily occurs, making it impossible to control the degree of graphene formation. Consequently, graphene / diamond composite substrates cannot be directly achieved using pyrolysis of diamond. In contrast, the vapor pressure of silicon (Si) in SiC is much higher than that of carbon (C), causing atoms to actively "escape" from the surface into the gas phase. Specifically, Si atoms at the edges of steps (mound-like morphologies) preferentially desorb, while C atoms remain in situ and reconstruct into graphene 40, forming a barrier layer that slows down the desorption of atoms below, resulting in graphene 40 with controllable shape and number of layers, such as step (mound-like) patterns. Therefore, this invention employs the aforementioned selective mechanism to achieve the ordered growth of graphene 40.

[0033] Based on this, in order to form patterned and ordered graphene 40 in situ on the surface of diamond substrate 10, the present invention first prepares a SiC epitaxial layer 20 on the surface of diamond substrate 10, and further sacrifices the SiC layer to prepare graphene 40. By utilizing the fact that Si at the edge of the morphology is easier to desorb and the formed graphene 40 reduces the atomic desorption / reconstruction rate characteristics of the bulk material, a patterned graphene 40 morphology is achieved on diamond substrate 10.

[0034] For example, the method of preparing SiC epitaxial layer 20 by Si treatment of diamond surface utilizes the characteristic that diamond is composed of C element, which will react on the surface to generate SiC at high temperature. The SiC thickness is limited, which is conducive to the generation of graphene 40 directly bonded to diamond on the surface after heat treatment. Other methods such as low-pressure chemical vapor deposition are used to prepare SiC epitaxial layer 20, which mainly generate SiC by bonding Si source and C source on diamond surface. The SiC thickness is controllable, which can realize graphene / diamond composite substrate, or graphene / SiC / diamond composite substrate by thickening SiC layer.

[0035] S2: A SiC capping sheet 30 is disposed on the surface of the SiC epitaxial layer 20 away from the diamond substrate 10 (e.g., Figure 3 Under a protective atmosphere and normal pressure, the SiC epitaxial layer 20 and the diamond substrate 10 are subjected to a first-stage high-temperature heat treatment to bond the SiC epitaxial layer 20 to the diamond substrate 10.

[0036] In some optional embodiments, the temperature of the first-stage high-temperature heat treatment is 1200℃~1700℃, for example, it can be 1200℃, 1300℃, 1400℃, 1500℃, 1550℃, 1600℃, 1650℃ or 1700℃, or other values ​​within the range of 1200℃~1700℃. In some more typical embodiments, the temperature of the first-stage high-temperature heat treatment can be 1300℃~1500℃.

[0037] If the temperature is too low, it will be difficult for the SiC epitaxial layer 20 to bond well with the diamond substrate 10; if the temperature is too high, the diamond material will be easily damaged.

[0038] In some optional embodiments, the duration of the first-stage high-temperature heat treatment is not less than 0.5 hours. In some more typical embodiments, the duration of the first-stage high-temperature heat treatment can be 0.5 hours to 2 hours, such as 0.5 hours, 1 hour, 1.5 hours, or 2 hours, or other values ​​within the range of 0.5 hours to 2 hours.

[0039] In some alternative embodiments, the protective atmosphere includes at least one of a high-purity argon atmosphere and a high-purity nitrogen atmosphere. The purity of the high-purity argon and high-purity nitrogen can independently be not less than 99.999%.

[0040] S3: After reducing the heat treatment pressure and temperature, a second stage of high-temperature heat treatment is performed to decompose the Si on the surface of the SiC epitaxial layer 20, and the remaining C atoms are reconstructed into graphene 40 (e.g., Figure 4 ).

[0041] As the reaction time increases, the SiC on the diamond surface completely transforms into graphene with a certain pattern and bonded to the diamond (e.g.,Figure 5 The graphene layer retains the morphology of the original substrate, with one side well bonded to the substrate and the other side exposed to facilitate nitride nucleation and growth.

[0042] In some alternative implementations, the pressure of the second-stage high-temperature heat treatment is lower than atmospheric pressure. In some more typical implementations, the pressure of the second-stage high-temperature heat treatment is ultra-high vacuum to 0.7 times atmospheric pressure, such as 10... -4 Pa (ultra-high vacuum), 0.3 times atmospheric pressure, 0.4 times atmospheric pressure, 0.5 times atmospheric pressure, 0.6 times atmospheric pressure, or 0.7 times atmospheric pressure, or other values ​​not exceeding 0.7 times atmospheric pressure.

[0043] In some optional embodiments, the temperature of the second-stage high-temperature heat treatment can be 1200℃~1500℃, such as 1200℃, 1250℃, 1300℃, 1350℃, 1400℃, 1450℃ or 1500℃, or other values ​​within the range of 1200℃~1500℃.

[0044] In some optional embodiments, the second-stage high-temperature heat treatment lasts for no less than 0.5 hours. In some more typical embodiments, the second-stage high-temperature heat treatment lasts for 0.5 to 2 hours.

[0045] It should be noted that graphene 40 exhibits extremely high thermal conductivity due to its intralayer sp2 bonds; however, the interlayer bonds, relying solely on van der Waals forces, significantly reduce its thermal conductivity. Therefore, graphene 40 needs to be fully bonded to the substrate material to ensure efficient heat transfer through chemical bonds and leverage the advantages of the substrate material. However, SiC and diamond also exhibit some mismatch; the bonding state between SiC and diamond formed on the diamond surface through epitaxial growth may not be optimal. Therefore, in the high-temperature heat treatment process, this invention first performs a first-stage high-temperature heat treatment on SiC / diamond under atmospheric or slightly positive pressure conditions, using SiC as a cover sheet. In this step, the higher pressure inhibits SiC decomposition, promoting only sufficient bonding at the SiC-diamond interface. A second-stage high-temperature heat treatment is then performed by further reducing the pressure, promoting Si atom decomposition and forming a regular graphene 40 morphology. One end of the formed graphene 40 is fully bonded to the substrate, facilitating heat transport; the other end is exposed, providing nucleation sites for subsequent nitriding growth.

[0046] S4: Remove the SiC capping sheet 30 to obtain the graphene-diamond composite substrate (e.g., Figure 6 ).

[0047] Continuing from the above, this invention first performs Si-modification or epitaxial SiC film formation on a diamond surface with a specific surface morphology (such as step-like or mound-like morphology); then further performs high-temperature heat treatment to fully bond SiC to the diamond surface; and then further promotes the desorption of surface Si by reducing the heat treatment pressure to form patterned graphene 40, thus forming a graphene / diamond or graphene / SiC / diamond composite substrate. Based on the above two heat treatment steps, the graphene / diamond or graphene / SiC / diamond interface can be fully bonded, resulting in efficient thermal conductivity; furthermore, the graphene 40 patterned according to the substrate morphology has dangling bonds at its edges for nitride nucleation, eliminating the need for in-situ nitriding or N plasma treatment processes, thus avoiding uncontrollable defects; and this method does not require substrate cleaning, avoiding complex chemical reagent contamination. Therefore, this invention achieves efficient and stable formation of a graphene 40 layer bonded to the diamond substrate 10 on the diamond substrate 10, and nitride epitaxy can be performed without complex pretreatment.

[0048] It should be noted that even when preparing graphene-diamond composite substrates, directly transferring graphene 40 onto the diamond substrate 10 introduces a large number of uncontrollable defects during the transfer process. Furthermore, some areas require N-type defects to further form nucleation sites, which is difficult to control and affects epitaxial quality. Moreover, graphene 40 is not bonded to diamond, making it difficult to leverage diamond's high thermal conductivity. If a method is used to deposit a metal catalyst on the diamond surface and form graphene 40 material on the surface through a chemical reaction, followed by acid washing to remove the metal layer, it affects interface cleanliness and is difficult to apply efficiently in epitaxial growth. If a method is used to bombard the diamond surface with high-energy particles to reconstruct the atoms into graphene 40, it introduces a large number of defects. If a direct high-temperature pyrolysis method is used to carbonize the diamond surface using high temperatures, this method mostly forms graphite-like structures, making it difficult to controllably form graphene 40.

[0049] Accordingly, the present invention provides a graphene-diamond composite substrate, which is prepared by the above-described preparation method.

[0050] When the thickness of the SiC epitaxial layer 20 in S1 is ≥10nm, the graphene-diamond composite substrate prepared by the above preparation method is a graphene / SiC / diamond composite substrate; when the thickness of the SiC epitaxial layer 20 in S1 is <10nm, the graphene-diamond composite substrate prepared by the above preparation method is a graphene / diamond composite substrate.

[0051] In this graphene-diamond composite substrate, graphene 40 has a certain patterning, with one side bonded to diamond (or one side of graphene 40 / SiC / diamond) to facilitate heat transport; the other side is exposed, providing natural nucleation sites for nitride epitaxial growth.

[0052] This invention enables nitride epitaxy on a diamond substrate 10 by introducing graphene 40, a two-dimensional material, onto the surface of diamond. Diamond is primarily composed of carbon, and graphene 40 is also composed of C. By utilizing the absence of dangling bonds on the surface of the two-dimensional material and its weak van der Waals forces that bind it to the upper and lower layers, the lattice potential field of the substrate can be shielded. Even with significant lattice differences, the flexible lattice of the two-dimensional material can accommodate mismatch strain through its own deformation or interlayer slip, significantly reducing the density of penetrating dislocations caused by lattice mismatch. Simultaneously, the atomic-level thickness and excellent flexibility of the two-dimensional material allow it to act as a stress buffer layer, absorbing and dispersing thermal stress caused by differences in thermal expansion coefficients during cooling, thus preventing film cracking or interface delamination.

[0053] In addition, the present invention also provides an electronic device comprising the above-mentioned graphene-diamond composite substrate.

[0054] By generating patterned graphene 40 in situ on the surface of diamond, a flexible buffer layer can be provided to reduce the mismatch between diamond and nitride, which is conducive to the growth of high-quality nitride device structures. At the same time, the heat generated by the nitride device is transferred to graphene 40 through the bonding sites with the graphene 40. Due to its high thermal conductivity, graphene 40 can quickly transfer heat to the diamond composite substrate through the bonding sites between graphene 40 and the substrate, thus achieving efficient heat dissipation.

[0055] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0056] Example 1 This embodiment provides a graphene-diamond composite substrate, the preparation method of which includes: S1: SiC epitaxial layer 20 is prepared on a non-perfectly flat diamond substrate with a stepped morphology by low-pressure chemical vapor deposition.

[0057] The crystal plane of the diamond substrate 10 is (111). The conditions for low-pressure chemical vapor deposition include: the growth source is SiH4 and C2H4 with a Si:C molar ratio of 1:1; the deposition temperature is 900℃ and the deposition pressure is 50mbar; the thickness of the SiC epitaxial layer 20 is 8nm.

[0058] S2: A SiC cover plate 30 is disposed on the side of the SiC epitaxial layer 20 away from the diamond substrate 10. Under a protective atmosphere and normal pressure, the SiC epitaxial layer 20 and the diamond substrate 10 are subjected to a first-stage high-temperature heat treatment together to make the SiC epitaxial layer 20 bonded to the diamond substrate 10.

[0059] The protective atmosphere is argon gas with a purity of not less than 99.999%; the temperature of the first stage of high-temperature heat treatment is 1450℃ and the time is 1 hour.

[0060] S3: After reducing the heat treatment pressure and temperature, a second stage of high-temperature heat treatment is carried out to decompose the Si on the surface of the SiC epitaxial layer 20, and the remaining C atoms are reconstructed into graphene 40.

[0061] The second stage of high-temperature heat treatment involves a pressure of 0.5 times atmospheric pressure, a temperature of 1400℃, and a duration of 1 hour.

[0062] S4: Remove the SiC cover sheet 30 to obtain a graphene / diamond composite substrate with a stepped morphology and good bonding between graphene 40 and diamond.

[0063] The surface morphology of the composite substrate is as follows: Figure 7 As shown, the brighter parts are the wrinkles of graphene.

[0064] Example 2 This embodiment provides a graphene-SiC-diamond composite substrate, the preparation method of which includes: S1: SiC epitaxial layer 20 is prepared on a non-perfectly flat diamond substrate with irregular pore morphology by low-pressure chemical vapor deposition.

[0065] The crystal plane of the diamond substrate 10 is (111). The conditions for low-pressure chemical vapor deposition include: the growth source is SiH4 and C2H4 with a Si:C molar ratio of 1:1; the deposition temperature is 800℃ and the deposition pressure is 50 mbar; the thickness of the SiC epitaxial layer 20 is 500 nm.

[0066] S2: A SiC cover plate 30 is disposed on the side of the SiC epitaxial layer 20 away from the diamond substrate 10. Under a protective atmosphere and normal pressure, the SiC epitaxial layer 20 and the diamond substrate 10 are subjected to a first-stage high-temperature heat treatment together to make the SiC epitaxial layer 20 bonded to the diamond substrate 10.

[0067] The protective atmosphere is argon gas with a purity of not less than 99.999%; the temperature of the first stage of high-temperature heat treatment is 1500℃ and the time is 1 hour.

[0068] S3: After reducing the heat treatment pressure and temperature, a second stage of high-temperature heat treatment is carried out to decompose the Si on the surface of the SiC epitaxial layer 20, and the remaining C atoms are reconstructed into graphene 40.

[0069] The second stage of high-temperature heat treatment involves a pressure of 0.3 times atmospheric pressure, a temperature of 1500℃, and a duration of 2 hours.

[0070] S4: Remove the SiC capping sheet 30 to obtain a graphene / SiC / diamond composite substrate with irregular pore morphology and good bonding between graphene 40 and diamond, such as...Figure 8 The image shown is an image of its atomic force microscopy test results. The graphene on the surface platform will participate in subsequent epitaxial bonding; the inside of the pores (black area) is buried and has little impact on subsequent epitaxial growth.

[0071] Comparative Example 1 The difference between this comparative example and Example 2 is that the diamond substrate 10 in S1 does not have a patterned morphology and is a completely flat structure. The final surface atomic force microscopy test results are as follows. Figure 9 As shown, due to the lack of pattern induction, the graphene formation is relatively random, resulting in more thicker, uneven regions (shown in the brighter areas).

[0072] In summary, this invention utilizes the characteristic that Si atoms in SiC preferentially and orderly decompose at the step edges to generate graphene 40 at high temperatures. A SiC layer is prepared on a diamond template, and high-temperature heat treatment is used to fully bond SiC and diamond, generating graphene 40 material from the SiC surface. This ultimately yields a graphene / diamond or graphene / SiC / diamond composite substrate. Because graphene 40 is bonded to the bulk material on one side and reserved for bonding to nitride materials on the other, it eliminates the need to artificially introduce defects to promote nitride nucleation during nitride growth. Furthermore, heat can be efficiently transferred from within the graphene 40 layer to the highly thermally conductive bulk substrate. The above-mentioned scheme takes place entirely within the material growth equipment and high-temperature heat treatment equipment, without contact with other metals or chemical reagents. Furthermore, graphene 40 will fully bond with the bulk substrate material, and the graphene 40 generation process is orderly and controllable. Therefore, compared with conventional methods, this scheme does not introduce chemical reagent contamination, does not form amorphous graphite structures, and does not introduce uncontrollable N-type defects when growing nitride materials. Moreover, the operation steps are relatively simple, making it more practical.

[0073] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a graphene-diamond composite substrate, characterized in that, Includes the following steps: SiC epitaxial layers are prepared on diamond substrates with patterned morphology and not completely flat. A SiC cap is disposed on the surface of the SiC epitaxial layer away from the diamond substrate. Under a protective atmosphere and normal pressure, the SiC epitaxial layer and the diamond substrate are subjected to a first-stage high-temperature heat treatment together to bond the SiC epitaxial layer to the diamond substrate. After reducing the heat treatment pressure and temperature, a second stage of high-temperature heat treatment is carried out to decompose the Si on the surface of the SiC epitaxial layer and reconstruct the remaining C atoms into graphene. Remove the SiC cover to obtain the graphene-diamond composite substrate.

2. The preparation method according to claim 1, characterized in that, The pattern morphology includes at least one of step morphology and mound morphology; And / or, the crystal planes of the diamond substrate include at least one of the (100) crystal plane, (110) crystal plane and (111) facet.

3. The preparation method according to claim 1, characterized in that, The SiC epitaxial layer can be prepared by at least one of diamond surface Si treatment, low-pressure chemical vapor deposition, and physical vapor deposition.

4. The preparation method according to claim 3, characterized in that, The SiC epitaxial layer was prepared by low-pressure chemical vapor deposition. Preferably, low-pressure chemical vapor deposition includes at least one of the following conditions: Condition 1: The growth source includes a silicon source and a carbon source, wherein the molar ratio of Si in the silicon source to C in the carbon source is 1:4 to 4:1; Condition 2: Deposition temperature is 800℃~1200℃; Condition 3: Deposition pressure is 0.3 mbar to 70 mbar.

5. The preparation method according to claim 1, characterized in that, The first stage of high-temperature heat treatment includes at least one of the following conditions: Condition 4: The temperature of the first stage high-temperature heat treatment is 1200℃~1700℃, preferably 1300℃~1500℃; Condition 5: The time for the first stage of high-temperature heat treatment shall not be less than 0.5 hours, preferably 0.5 hours to 2 hours.

6. The preparation method according to claim 1, characterized in that, The second-stage high-temperature heat treatment includes at least one of the following conditions: Condition 6: The pressure of the second-stage high-temperature heat treatment is lower than atmospheric pressure, preferably ultra-high vacuum ~ 0.7 times atmospheric pressure; Condition 7: The temperature for the second stage of high-temperature heat treatment is 1200℃~1500℃; Condition 8: The time for the second stage of high-temperature heat treatment shall not be less than 0.5 hours, preferably 0.5 hours to 2 hours.

7. The preparation method according to claim 1, characterized in that, The protective atmosphere includes at least one of high-purity argon atmosphere and high-purity nitrogen atmosphere; Preferably, the purity of the high-purity argon and the high-purity nitrogen is independently not less than 99.999%.

8. A graphene-diamond composite substrate, characterized in that, It is prepared by the preparation method according to any one of claims 1 to 7.

9. The graphene-diamond composite substrate according to claim 8, characterized in that, When the thickness of the SiC epitaxial layer is ≥10nm, the graphene-diamond composite substrate is a graphene / SiC / diamond composite substrate; when the thickness of the SiC epitaxial layer is <10nm, the graphene-diamond composite substrate is a graphene / diamond composite substrate.

10. An electronic device, characterized in that, Includes the graphene-diamond composite substrate as described in claim 8 or 9.

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