A method for improving nucleation density of large-size single crystal diamond hetero-epitaxy based on iridium-amorphous carbon pre-implantation layer
By pretreating the single-crystal silicon substrate and introducing an amorphous carbon pre-planting layer on the surface of the iridium single-crystal film, the problem of poor quality of metal oxide epitaxy was solved, and the preparation of large-size, high-quality single-crystal diamond was realized.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- TAIYUAN UNIVERSITY OF TECHNOLOGY
- Filing Date
- 2022-09-27
- Publication Date
- 2026-05-29
AI Technical Summary
In the existing technology, the epitaxial quality of metal oxides on silicon cannot meet the requirements, resulting in poor adhesion of the diamond layer. Furthermore, lattice mismatch between the epitaxial layer and the substrate material can easily lead to poor diamond layer quality, which limits the preparation of large-size single-crystal diamonds.
By performing physical and chemical pretreatment on the single-crystal silicon substrate to remove the surface oxide layer, and introducing a locally ordered amorphous carbon pre-planting layer on the surface of the metallic iridium single-crystal film, the number of nucleation sites is increased, promoting high-density uniform nucleation and enhancing the bonding force between the diamond nucleus and the heteroepitaxial substrate.
This improved the nucleation density and quality of single-crystal diamond, reduced the difference in thermal expansion coefficients and lattice mismatch between the epitaxial layer and the substrate, and enabled the fabrication of large-size, high-quality single-crystal diamond.
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Figure CN115652422B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a method for improving the nucleation density of large-size single-crystal diamond heteroepitaxial layer based on iridium-amorphous carbon pre-planting layer, belonging to the field of material surface treatment technology. Background Technology
[0002] Diamond substrate components are widely used in high-tech fields such as next-generation deep ultraviolet photodetectors, 5G communications, and military radar. Compared with polycrystalline diamond, single-crystal diamond, which is free from grain boundary constraints, has advantages such as fewer defects and superior performance, exhibiting superior electrical and mechanical properties and demonstrating enormous application potential. Furthermore, single-crystal diamond offers faster speeds, lower power consumption, and higher intrinsic mobility than traditional semiconductors, showing significant application results in cutting-edge technologies such as quantum communication, cold cathode field emission displays, semiconductor lasers, supercomputer CPU chips, multidimensional integrated circuits, and high-voltage, high-power electronic devices, making it a hot topic of international competition. However, the fabrication of large-size, high-quality single-crystal diamond is a prerequisite for its application; as a semiconductor material wafer, diamond must be at least 2 inches in size.
[0003] Currently, the main technologies for preparing large-size single-crystal diamond and wafers include mosaic growth, homoepitaxial growth, and heteroepitaxial growth. Over the past forty years, numerous experimental studies both domestically and internationally (Scientific Reports 7(2017)1-8 and Diamond and Related Materials 17(2008)1035-1038) have shown that chemical vapor deposition combined with heteroepitaxial growth is currently recognized as the only effective and feasible method for preparing high-quality, large-size single-crystal diamond. The key to heteroepitaxial single-crystal diamond technology lies in the selection of the substrate material and the nucleation density and growth of the diamond. Iridium metal has a very high nucleation density and excellent single-crystal characteristics; diamonds grown heteroepitaxially on it are of extremely high quality and are considered the most effective buffer layer for heteroepitaxial diamond growth. Theoretically, this method can grow single-crystal diamonds with sufficiently large areas to meet the industrialization needs in the field of electronic devices. However, in the existing technology, the epitaxial quality of metal oxide on silicon cannot meet the requirements. Most epitaxial growth of single crystal diamond is carried out on a heterogeneous substrate with an epitaxial iridium layer on a metal oxide single crystal wafer. This technology leads to lattice mismatch between the epitaxial layer and the substrate material, which easily causes poor adhesion of the diamond layer. Moreover, the epitaxial iridium layer and diamond layer cannot simultaneously obtain high-quality single crystal orientation.
[0004] In addition, the nucleation density of diamond on the surface of heterogeneous substrates is low. In Chinese patents CN202110732256.1 and CN111826714A, the entire substrate is covered with a metal iridium layer or a bias voltage is applied using a special power supply. This technology greatly limits the epitaxial size and quality of single-crystal diamond, becoming a key technical challenge for heteroepitaxial growth of large-size single-crystal diamond. Summary of the Invention
[0005] This invention aims to provide a method for improving the nucleation density of large-size single-crystal diamond heteroepitaxial growth based on an iridium-amorphous carbon pre-planting layer. The method involves removing the oxide layer on the surface of single-crystal silicon through physical and chemical means, thereby improving the quality of subsequent metal oxide epitaxial growth on silicon. Furthermore, a locally ordered amorphous carbon pre-planting layer is introduced onto the surface of the subsequent iridium single-crystal film to increase nucleation sites, promote nucleation, and enhance the bonding force of the diamond nuclei. This effectively improves the nucleation density on the iridium composite substrate surface and the quality and size of the subsequently epitaxially grown single-crystal diamond, while reducing the difference in thermal expansion coefficients and lattice mismatch between the epitaxial layer and the substrate, thus obtaining large-size, high-quality single-crystal diamond materials.
[0006] This invention directly pre-treats the single-crystal silicon substrate using physical and chemical methods to obtain the bottom substrate, which is easy for metal oxide epitaxial growth, effectively improving the quality of metal oxide epitaxial growth on the silicon surface; and introduces sp-containing materials onto the surface of the iridium single-crystal film. 2 and sp 3 Hybridized amorphous carbon films increase nucleation sites and improve nucleation density, thereby enabling the fabrication of large-size single-crystal diamond materials. Compared with other methods for improving the heteroepitaxial nucleation density of single-crystal diamond, this method has the following advantages: Firstly, physical and chemical treatment of the polished single-crystal silicon substrate to remove its surface silica layer reduces the difference in physical properties between the metal oxide film and the silicon surface oxide layer, thus better achieving controllable epitaxial growth of single-crystal metal oxide films on single-crystal silicon. Secondly, the fabrication of amorphous carbon films on iridium composite substrates allows for the modulation of amorphous carbon spp by changing the carbon ion excitation energy. 2 and sp 3 The hybrid bond content and ordering of the amorphous carbon pre-planting layer formed on the surface of the iridium film increase the concentration of hydrocarbon active groups on the substrate surface during subsequent bias nucleation, accelerate the dissolution-precipitation process of carbon ions entering the iridium film to form a supersaturated solid solution, increase nucleation sites, promote high-density uniform nucleation, and enhance the bonding force between the diamond nucleus and the heteroepitaxial substrate. This accelerates the rapid in-situ formation and growth of diamond micronuclei on the iridium surface until they come into contact and merge to form a single crystal diamond. This is of great significance for the preparation of high-quality, large-size single-crystal diamond semiconductor wafer materials.
[0007] This invention provides a method for improving the heteroepitaxial nucleation density of large-size single-crystal diamond based on an iridium-amorphous carbon pre-planted layer. First, a single-crystal silicon (100) substrate is pretreated by acid washing, acetone (ethanol) cleaning, ultrasonic cleaning with deionized water, and ion beam etching to remove the surface oxide layer. Then, a nanometer-thick yttrium-stabilized zirconia (YSZ) single-crystal buffer layer and an iridium single-crystal functional layer are sequentially epitaxially grown on the surface of the pretreated single-crystal silicon substrate. Next, a locally ordered amorphous carbon pre-planted layer is prepared on the surface of the iridium / YSZ composite substrate, and then subjected to vacuum annealing to relieve stress and polishing to remove large graphite particles, resulting in a smooth and flat surface. Finally, single-crystal diamond is grown epitaxially on the surface of the iridium-amorphous carbon pre-planted layer substrate under bias enhancement. The composite substrate is then cut and removed to obtain a large-size heteroepitaxial single-crystal diamond.
[0008] The above-mentioned method for improving the heteroepitaxial nucleation density of large-size single-crystal diamond based on iridium-amorphous carbon pre-planting layers specifically includes the following steps:
[0009] (1) The single crystal silicon (100) substrate is pretreated by acid washing, acetone or ethanol cleaning, deionized water ultrasonic cleaning and ion beam etching to remove the silicon dioxide layer on its surface and obtain the bottom substrate of heteroepitaxial layer.
[0010] (2) The pretreated single-crystal silicon substrate is placed in a vacuum plasma coating equipment, and a YSZ single-crystal film buffer layer with a thickness of nanometers is first epitaxially grown on the substrate surface, and then vacuum annealed under a protective atmosphere; the preparation methods of YSZ single-crystal film include electron beam evaporation, laser melt evaporation, molecular beam epitaxial deposition or magnetron sputtering technology; the crystal orientation of the prepared YSZ thin film is the same as that of the single-crystal silicon (100) substrate;
[0011] (3) An iridium single crystal film is epitaxially grown on the surface of the YSZ single crystal film buffer layer to form an iridium / YSZ composite substrate. The preparation methods of the iridium single crystal film include electron beam evaporation, molecular beam epitaxial deposition or magnetron sputtering technology; the crystal orientation of the iridium thin film is consistent with the crystal orientation of the YSZ thin film.
[0012] (4) Using high-purity graphite as the target material, an amorphous carbon film was prepared on the surface of an iridium / YSZ composite substrate. By controlling the sp... 2 and sp 3 The content and order of hybrid carbon bonds enable the formation of a locally ordered amorphous carbon pre-planting layer on the surface of the iridium film, namely the iridium-amorphous carbon pre-planting layer.
[0013] (5) The iridium-amorphous carbon pre-planted layer was subjected to vacuum annealing under a protective atmosphere, and after cooling to room temperature, it was thinned and polished to obtain a smooth and flat surface of the iridium-amorphous carbon pre-planted layer.
[0014] (6) A single-crystal diamond film was grown on the surface of an iridium-amorphous carbon pre-planted layer by bias enhancement using chemical vapor deposition. The composite substrate was removed by laser cutting to obtain a large-size single-crystal diamond film with heteroepitaxial growth.
[0015] In the above preparation method, in step (1), the acid used in the pickling process is hydrofluoric acid, nitric acid or a mixture of both, and the pickling time is 1~5 s; acetone or ethanol is used for cleaning for 5~20 min.
[0016] In the above preparation method, in step (2), the thickness of the YSZ single crystal film buffer layer is 10~100 nm, the deposition rate is greater than 10 nm / min, the growth temperature is 600~1100 ℃; the protective atmosphere is inert gas or nitrogen, and the vacuum annealing temperature is 200~800 ℃.
[0017] In the above preparation method, in step (3), the thickness of the iridium single crystal film is 50~200 nm, the deposition rate is less than 5 nm / min, and the growth temperature is 400~1000 ℃.
[0018] In the above preparation method, step (4) involves preparing the iridium-amorphous carbon pre-planting layer using magnetically filtered vacuum cathode arc or pulsed laser melting technology; the amorphous carbon pre-planting layer contains sp 3 The bond content is 50%~90%, sp 2 The bond content is 10%~50%; the thickness of the amorphous carbon pre-planting layer is 2~20 nm, and the growth temperature is room temperature.
[0019] In the above preparation method, in step (5), the protective atmosphere is an inert gas or nitrogen, the annealing temperature is 200~600 ℃, and the annealing time is 5~30 min; the surface roughness after thinning and polishing is 1~10 nm.
[0020] In the above preparation method, in step (6), the chemical vapor deposition method includes one of microwave plasma chemical vapor deposition, radio frequency plasma chemical vapor deposition, and hot filament chemical vapor deposition. The bias nucleation method uses a positive bias pulse or DC power supply with a voltage of 100~800 V.
[0021] The beneficial effects of this invention are as follows:
[0022] (1) The present invention directly pre-treats the single crystal silicon substrate by physical and chemical means to obtain the bottom substrate that is easy to grow metal oxide epitaxially, effectively improving the quality of metal oxide epitaxial growth on silicon surface and better realizing the controllable epitaxial growth of single crystal metal oxide thin film on single crystal silicon.
[0023] (2) This invention utilizes sp 3A locally ordered amorphous carbon pre-planting layer with adjustable bond content and structure achieves high concentration of sp 3 Carbon enrichment increases the concentration of hydrocarbon active groups on the substrate surface during subsequent bias nucleation by plasma bombardment, accelerates the dissolution-precipitation process of carbon ions entering the iridium film to form a supersaturated solid solution, increases nucleation sites, and improves the nucleation rate and nucleation density. At the same time, the presence of a pre-planted amorphous carbon layer can roughen the iridium substrate surface, promote nucleation, and enhance the bonding force of diamond nuclei. Attached Figure Description
[0024] Figure 1 A schematic diagram of a single-crystal silicon (100) substrate before pretreatment;
[0025] Figure 2 A schematic diagram of a smooth and flat single-crystal silicon (100) substrate after pretreatment;
[0026] Figure 3 A schematic diagram of a YSZ single crystal film epitaxially grown on a single crystal silicon substrate;
[0027] Figure 4 This is a schematic diagram of the epitaxial growth of an iridium single-crystal thin film on the surface of a YSZ single-crystal film.
[0028] Figure 5 A schematic diagram of a locally ordered amorphous carbon pre-planted layer deposited on the surface of an iridium / YSZ composite substrate;
[0029] Figure 6 A schematic diagram of the iridium-amorphous carbon pre-planted layer after polishing to remove large graphite particles;
[0030] Figure 7 Schematic diagram of epitaxial growth of single-crystal diamond film on the surface of iridium-amorphous carbon pre-planted layer;
[0031] Figure 8 A schematic diagram of single-crystal diamond after the composite substrate has been removed;
[0032] Figure 9 This is a scanning electron microscope image of the single-crystal diamond epitaxial nucleation on the surface of the iridium-amorphous carbon pre-planted layer in Example 1;
[0033] Figure 10 This is a scanning electron microscope image of the single-crystal diamond epitaxial nucleation on the surface of the iridium-amorphous carbon pre-planted layer in Example 2;
[0034] Figure 11 This is a scanning electron microscope image of the single-crystal diamond epitaxial nucleation on the surface of the iridium-amorphous carbon pre-planted layer in Example 3.
[0035] In the figure: 1. Monocrystalline silicon substrate; 2. YSZ monocrystalline thin film; 3. Metallic iridium monocrystalline film; 4. Iridium / YSZ composite substrate; 5. Amorphous carbon pre-planted layer; 6. Iridium-amorphous carbon pre-planted layer; 7. Monocrystalline diamond film; 8. Large-size monocrystalline diamond. Detailed Implementation
[0036] This invention relates to a method for improving the nucleation density of large-size single-crystal diamond heteroepitaxial structures based on an iridium-amorphous carbon pre-planting layer, specifically comprising the following steps:
[0037] (1) The monocrystalline silicon (100) substrate is pretreated by acid washing, acetone or ethanol cleaning, deionized water ultrasonic cleaning, and ion beam etching to remove the silicon dioxide layer on its surface, thereby obtaining the bottom monocrystalline silicon substrate 1 of the heteroepitaxial layer. In step (1), the acid used in the acid washing process is hydrofluoric acid, nitric acid, or a mixture of both, and the acid washing time is 1~5 s; the acetone or ethanol cleaning time is 5~20 min.
[0038] (2) The pretreated single-crystal silicon substrate 1 is placed in a vacuum plasma coating equipment, and a YSZ single-crystal film buffer layer 2 with a nanometer thickness is first epitaxially grown on the surface of the substrate, and then vacuum annealed under a protective atmosphere; the preparation methods of YSZ single-crystal thin film include electron beam evaporation, laser melt evaporation, molecular beam epitaxial deposition or magnetron sputtering technology; the crystal orientation of the prepared YSZ thin film is the same as the crystal orientation of the single-crystal silicon (100) substrate. In step (2), the thickness of the YSZ single-crystal film buffer layer is 10~100 nm, the deposition rate is greater than 20 nm / min, the growth temperature is 600~1100 ℃; the protective atmosphere is inert gas or nitrogen, and the vacuum annealing temperature is 200~800 ℃.
[0039] (3) An iridium single crystal film 3 is epitaxially grown on the surface of the YSZ single crystal film buffer layer to form an iridium / YSZ composite substrate. The preparation method of the iridium single crystal film includes electron beam evaporation, molecular beam epitaxial deposition or magnetron sputtering technology. The crystal orientation of the iridium thin film is consistent with the crystal orientation of the YSZ thin film. In step (3), the thickness of the iridium single crystal film is 50~200 nm, the deposition rate is less than 5 nm / min, and the growth temperature is 400~1000 ℃.
[0040] (4) Using high-purity graphite as the target material, an amorphous carbon film was prepared on the surface of the iridium / YSZ composite substrate 4. The sp content was adjusted. 2 and sp 3 The content and order of hybrid carbon bonds enable the formation of a locally ordered amorphous carbon pre-planted layer on the surface of the iridium film, namely the iridium-amorphous carbon pre-planted layer 6. In step (4), the amorphous carbon pre-planted layer preparation method includes magnetically filtered vacuum cathode arc or pulsed laser melting technology; the amorphous carbon pre-planted layer contains sp... 3 The bond content is 50%~90%, sp2 The bond content is 10%~50%; the thickness of the amorphous carbon pre-planting layer is 2~20 nm, and the growth temperature is room temperature.
[0041] (5) The iridium-amorphous carbon pre-planted layer 6 is subjected to vacuum annealing under a protective atmosphere, and after cooling to room temperature, it is subjected to thinning and polishing to obtain a smooth and flat surface of the amorphous carbon pre-planted layer; in step (5), the protective atmosphere is an inert gas or nitrogen, the annealing temperature is 200~600 ℃, and the annealing time is 5~30 min; the surface roughness after thinning and polishing is 1~10 nm.
[0042] (6) A single-crystal diamond film 7 is epitaxially grown on the surface of an iridium-amorphous carbon pre-planted layer 6 by bias-enhanced nucleation and chemical vapor deposition. The composite substrate is removed by laser cutting to obtain a large-size single-crystal diamond 8 by heteroepitaxial growth. In step (6), the chemical vapor deposition method includes one of microwave plasma chemical vapor deposition, radio frequency plasma chemical vapor deposition, and hot filament chemical vapor deposition. The bias nucleation method uses a positive bias pulse or DC power supply with a voltage of 100~800 V.
[0043] The present invention will be further illustrated by the following embodiments, but is not limited to the following embodiments. Example 1
[0044] This embodiment provides a method for improving the nucleation density of large-size single-crystal diamond heteroepitaxial structures based on an iridium-amorphous carbon pre-planting layer. The operation steps are as follows:
[0045] (1) Figure 1 The single-crystal silicon (100) substrate shown was pretreated by hydrofluoric acid pickling for 5 s, acetone cleaning for 15 min, ultrasonic cleaning with deionized water, and ion beam etching to remove the surface silicon dioxide layer, resulting in the bottom single-crystal silicon substrate for heteroepitaxial growth. Figure 2 As shown.
[0046] (2) The pretreated single-crystal silicon substrate is placed in an electron evaporation vacuum plasma coating apparatus to epitaxially grow a 20 nm thick YSZ single-crystal buffer layer on the substrate surface. The YSZ film deposition rate is 20 nm / min, the growth temperature is 600 ℃, the crystal orientation is 100, and the substrate is then annealed in a vacuum at 400 ℃ under an Ar atmosphere. Figure 3 As shown.
[0047] (3) A 120 nm thick iridium single crystal film was epitaxially grown on the surface of the YSZ single crystal buffer layer using high-temperature magnetron sputtering technology to form an iridium / YSZ composite substrate. The iridium film growth temperature was 600 ℃, the deposition rate was 2 nm / min, and the crystal orientation was 100. Figure 4 As shown.
[0048] (4) Using high-purity graphite as the target material, a high sp2 matrix with a thickness of 5 nm was prepared on the surface of an iridium / YSZ composite substrate by pulsed laser melting evaporation technology. 3 Locally ordered amorphous carbon pre-planting layer with high bond content, namely iridium-amorphous carbon pre-planting layer, sp 3 The bond content is 70% and sp 2 The bond content is 30%, and the growth temperature is room temperature, such as Figure 5 As shown.
[0049] (5) The iridium-amorphous carbon pre-planted layer was subjected to argon-protected vacuum annealing at a temperature of 200 °C for 5 min. After cooling to room temperature, the sample was removed, thinned, and polished to a surface roughness of 5 nm, resulting in a smooth and flat amorphous carbon film surface. Figure 6 As shown.
[0050] (6) A single-crystal diamond film was grown on the surface of an iridium-amorphous carbon pre-planted layer using microwave plasma chemical vapor deposition with enhanced nucleation and epitaxial growth under a 200 V pulsed positive bias. The methane to hydrogen flow ratio was 1:150, the growth temperature was 830 ℃, the microwave power was 6 KW, and the deposition time was 240 h. Figure 7 As shown. Laser cutting removes the composite substrate to obtain large-size single-crystal diamond heteroepitaxial material, such as... Figure 8 As shown. Example 2
[0051] This embodiment provides a method for improving the nucleation density of large-size single-crystal diamond heteroepitaxial structures based on an iridium-amorphous carbon pre-planting layer. The operation steps are as follows:
[0052] (1) Figure 1 The single-crystal silicon (100) substrate shown was pretreated by acid washing with nitric acid for 3 s, acetone cleaning for 20 min, ultrasonic cleaning with deionized water, and ion beam etching to remove the surface silicon dioxide layer, thus obtaining the bottom single-crystal silicon substrate for heteroepitaxial growth. Figure 2 As shown.
[0053] (2) The pretreated single-crystal silicon substrate is placed in a molecular beam epitaxy plasma coating apparatus, and a 30 nm thick YSZ single-crystal buffer layer is epitaxially grown on the surface of the substrate. The YSZ film layering rate is 25 nm / min, the growth temperature is 800℃, the crystal orientation is 100, and the substrate is then annealed in a vacuum at 600℃ under N2 atmosphere. Figure 3 As shown.
[0054] (3) An iridium single-crystal film with a thickness of 150 nm was epitaxially grown on the surface of the YSZ single-crystal buffer layer using electron evaporation technology to form an iridium / YSZ composite substrate. The iridium film growth temperature was 750 ℃, the deposition rate was 4 nm / min, and the crystal orientation was 100. Figure 4 As shown.
[0055] (4) Using high-purity graphite as the target material, a high sp2 matrix with a thickness of 7 nm was prepared on the surface of an iridium / YSZ composite substrate by pulsed laser melting evaporation technology. 3 Locally ordered amorphous carbon pre-planting layer with high bond content, namely iridium-amorphous carbon pre-planting layer, sp 3 The bond content is 60% and sp 2 The bond content is 40%, and the growth temperature is room temperature, such as Figure 5 As shown.
[0056] (5) The iridium-amorphous carbon pre-planted layer was subjected to argon-protected vacuum annealing at a temperature of 400 °C for 15 min. After cooling to room temperature, the sample was removed, thinned, and polished. The surface roughness after processing was 10 nm, resulting in a smooth and flat amorphous carbon film surface, as shown below. Figure 6 As shown.
[0057] (6) A single-crystal diamond film was grown on the surface of an iridium-amorphous carbon pre-planted layer using microwave plasma chemical vapor deposition with enhanced nucleation and epitaxial growth under a 400 V DC positive bias. The methane to hydrogen flow ratio was 1:200, the growth temperature was 850 ℃, the microwave power was 6 KW, and the deposition time was 300 h. Figure 7 As shown. Laser cutting removes the composite substrate to obtain large-size single-crystal diamond heteroepitaxial material, such as... Figure 8 As shown. Example 3
[0058] This embodiment provides a method for improving the nucleation density of large-size single-crystal diamond heteroepitaxial structures based on an iridium-amorphous carbon pre-planting layer. The operation steps are as follows:
[0059] (1) Figure 1 The single-crystal silicon (100) substrate shown was pretreated by acid washing with a 1:3 mixture of hydrofluoric acid and nitric acid for 4 s, acetone cleaning for 10 min, ultrasonic cleaning with deionized water, and ion beam etching to remove the surface silicon dioxide layer, thus obtaining the bottom single-crystal silicon substrate for heteroepitaxial growth, as shown. Figure 2 As shown.
[0060] (2) The pretreated single-crystal silicon substrate is placed in an electron evaporation vacuum plasma coating apparatus to epitaxially grow a 40 nm thick YSZ single-crystal buffer layer on the substrate surface. The YSZ film deposition rate is 30 nm / min, the growth temperature is 900 ℃, the crystal orientation is 100, and the substrate is then annealed in a vacuum at 800 ℃ under an Ar atmosphere. Figure 3 As shown.
[0061] (3) A 200 nm thick iridium single crystal film was epitaxially grown on the surface of the YSZ single crystal buffer layer using high-temperature magnetron sputtering technology to form an iridium / YSZ composite substrate. The iridium film growth temperature was 700 ℃, the deposition rate was 3 nm / min, and the crystal orientation was 100. Figure 4 As shown.
[0062] (4) Using high-purity graphite as the target material, a high sp2 matrix with a thickness of 5 nm was prepared on the surface of an iridium / YSZ composite substrate by magnetic filtering vacuum cathode arc evaporation technology. 3 Locally ordered amorphous carbon pre-planting layer with high bond content, namely iridium-amorphous carbon pre-planting layer, sp 3 The bond content is 50% and sp 2 The bond content is 50%, and the growth temperature is room temperature, such as Figure 5 As shown.
[0063] (5) The iridium-amorphous carbon pre-planted layer was subjected to argon-protected vacuum annealing at a temperature of 450 °C for 30 min. After cooling to room temperature, the sample was removed, thinned, and polished. The surface roughness after processing was 10 nm, resulting in a smooth and flat amorphous carbon film surface, as shown below. Figure 6 As shown.
[0064] (6) A single-crystal diamond film was grown on the surface of an iridium-amorphous carbon pre-planted layer using DC plasma chemical vapor deposition with enhanced nucleation and epitaxial growth under a 600 V pulsed positive bias. The methane to hydrogen flow ratio was 1:180, the growth temperature was 900 ℃, the microwave power was 2 KW, and the deposition time was 200 h. Figure 7 As shown. Laser cutting removes the composite substrate to obtain large-size single-crystal diamond heteroepitaxial material, such as... Figure 8 As shown.
[0065] Figures 9-11 These are scanning electron microscope (SEM) images of single-crystal diamond nucleation on the surface of the iridium-amorphous carbon pre-planted layer in Examples 1-3. As can be seen from the images, the diamond nucleation is uniform and regular, exhibiting a high nucleation density (≥10). 8 cm -2The presence of no obvious large crystal particles or interface defects, and the tight bonding of diamond crystal nuclei, indicates that the amorphous carbon pre-planting layer can effectively improve the quality of subsequent epitaxial growth of single-crystal diamond while increasing the surface nucleation density.
[0066] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; those skilled in the art should understand that there are many solutions that can actually be adopted in terms of preparation methods, and all equivalent modifications or substitutions made in accordance with the claims of the present invention are essentially within the scope of the present invention.
Claims
1. A method for improving the nucleation density of large-size single-crystal diamond heteroepitaxial growth based on an iridium-amorphous carbon pre-planting layer, characterized in that... Includes the following steps: (1) The single crystal silicon (100) substrate is pretreated by acid washing, acetone or ethanol cleaning, deionized water ultrasonic cleaning and ion beam etching to remove the silicon dioxide layer on its surface and obtain the bottom substrate of heteroepitaxial layer. The acid used in the pickling process is hydrofluoric acid, nitric acid, or a mixture of both, and the pickling time is 1-5 seconds; acetone or ethanol is used for cleaning for 5-20 minutes. (2) The pretreated single crystal silicon substrate is placed in a vacuum plasma coating equipment, and a YSZ single crystal film buffer layer with a thickness of nanometers is first epitaxially grown on the substrate surface, and then vacuum annealed under a protective atmosphere; the preparation methods of YSZ single crystal film include electron beam evaporation, laser melt evaporation, molecular beam epitaxial deposition or magnetron sputtering technology; the crystal orientation of the prepared YSZ thin film is the same as that of the single crystal silicon (100) substrate; (3) An iridium single crystal film is epitaxially grown on the surface of the YSZ single crystal film buffer layer to form an iridium / YSZ composite substrate. The preparation methods of the iridium single crystal film include electron beam evaporation, molecular beam epitaxial deposition or magnetron sputtering technology; the crystal orientation of the iridium thin film is consistent with the crystal orientation of the YSZ thin film. (4) Using high-purity graphite as the target material, an amorphous carbon film was prepared on the surface of an iridium / YSZ composite substrate. By controlling the sp... 2 and sp 3 The content and order of hybrid carbon bonds enable the formation of a locally ordered amorphous carbon pre-planted layer on the iridium film surface, namely the iridium-amorphous carbon pre-planted layer; the sp in the amorphous carbon pre-planted layer 3 The bond content is 50%~90%, sp 2 The bond content is 10%~50%; the thickness of the amorphous carbon pre-planting layer is 2~20 nm; and the growth temperature is room temperature. (5) The iridium-amorphous carbon pre-planted layer was subjected to vacuum annealing under a protective atmosphere, and after cooling to room temperature, it was thinned and polished to obtain a smooth and flat surface of the iridium-amorphous carbon pre-planted layer. The protective atmosphere was inert gas or nitrogen, the annealing temperature was 200~600 ℃, and the annealing time was 5~30 min. The surface roughness after thinning and polishing was 1~10 nm. (6) A single crystal diamond film is grown on the surface of an iridium-amorphous carbon pre-planted layer by chemical vapor deposition under bias enhancement nucleation and epitaxial growth. The composite substrate is removed by laser cutting to obtain a large-size single crystal diamond film with heteroepitaxial growth. The bias nucleation method uses a positive bias pulse or DC power supply with a voltage of 100~800 V.
2. The method for improving the nucleation density of large-size single-crystal diamond heteroepitaxial growth based on an iridium-amorphous carbon pre-planting layer according to claim 1, characterized in that: In step (2), the thickness of the YSZ single crystal film buffer layer is 10~100 nm, the deposition rate is greater than 10 nm / min, the growth temperature is 600~1100 ℃, the protective atmosphere is inert gas or nitrogen, and the vacuum annealing temperature is 200~800 ℃.
3. The method for improving the nucleation density of large-size single-crystal diamond heteroepitaxial growth based on an iridium-amorphous carbon pre-planting layer according to claim 1, characterized in that: In step (3), the thickness of the iridium single crystal film is 50~200 nm, the deposition rate is less than 5 nm / min, and the growth temperature is 400~1000 ℃.
4. The method for improving the nucleation density of large-size single-crystal diamond heteroepitaxial growth based on an iridium-amorphous carbon pre-planting layer according to claim 1, characterized in that: In step (4), the method for preparing the iridium-amorphous carbon pre-planting layer includes magnetically filtered vacuum cathode arc or pulsed laser melting technology.
5. The method for improving the nucleation density of large-size single-crystal diamond heteroepitaxial layer based on iridium-amorphous carbon pre-planting layer according to claim 1, characterized in that: In step (6), the chemical vapor deposition method includes one of microwave plasma chemical vapor deposition, radio frequency plasma chemical vapor deposition, and hot filament chemical vapor deposition.