CN108545738B - Method for improving hardness and toughness of CVD single crystal diamond - Google Patents
Method for improving hardness and toughness of CVD single crystal diamond Download PDFInfo
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- CN108545738B CN108545738B CN201810556015.4A CN201810556015A CN108545738B CN 108545738 B CN108545738 B CN 108545738B CN 201810556015 A CN201810556015 A CN 201810556015A CN 108545738 B CN108545738 B CN 108545738B
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Abstract
The invention discloses a method for improving the hardness and toughness of CVD single crystal diamond, belonging to the field of diamond materials. The method comprises introducing nitrogen gas or mixed gas of nitrogen gas and oxygen gas or boron-containing gas intermittently when growing the single crystal diamond by Microwave Plasma Chemical Vapor Deposition (MPCVD) or Hot Filament Chemical Vapor Deposition (HFCVD) or direct current Arc Plasma Jet (DC Arc Plasma Jet CVD). The enhancement and toughening effects of the nano multilayered interface structure are realized through the alternate growth of the diamonds with different doped layers. Compared with CVD single crystal diamond which grows by non-doping, the Vickers hardness of the CVD single crystal diamond which grows by the method is improved by 5 to 25 percent, and the fracture toughness is improved by 4 to 56 percent. The hardness and toughness of the multilayer CVD single crystal diamond grown by the method are obviously improved.
Description
Technical Field
The invention relates to the technical field of mechanical properties of inorganic materials by Microwave Plasma Chemical Vapor Deposition (MPCVD), in particular to a method for improving the hardness and toughness of a CVD single crystal diamond.
Technical Field
Diamond is the hardest natural material with significant hardness and durability for applications in mechanical, biomedical, electronic and photonic applications. Diamond has ultra-high hardness and stability, but will cause brittle fracture if deformed. These limitations of diamond have motivated the study of the mechanism of the super elastic deformation of diamond due to its poor mechanical properties resulting from its poor deformability and relatively high brittleness.
The emergence of the single crystal diamond synthesized by the microwave plasma chemical vapor deposition method opens a wide situation for the application of the single crystal diamond. The grown CVD layer has high fracture toughness, extremely high fracture toughness and exceptionally high strength after high temperature and high pressure heat treatment. The advent of heat treatment introduced a novel method of hardening CVD single crystal diamond.
The incorporation of boron into CVD single crystal diamond significantly enhances its fracture toughness without affecting its high hardness (-78 GPa.) the results of spectroscopic tests confirm that boron and nitrogen coexist in the diamond structure, explaining the original enhancement of diamond fracture toughness by (Q. L ang, c.s.yan, y.meng, J. L ai, s.krassiki, h.k.mao, & r.j.hemley, engineering the mechanical properties of single crystal diamond nanoneedles, maximum tensile strain (9%) achieves theoretical elastic strain, and maximum tensile stress achieves 89GPa to 98GPa (a.balnejjd. wo., 20120. wo. c. a. with a. b. wo. c.
The improvement of the toughness of the diamond single crystal as the micro-processing cutter becomes the key for further improving the service performance of the cutter, the toughness of the diamond single crystal is very important while the hardness is improved, and the mechanical property of the CVD single crystal diamond can be obviously improved, so the invention is created.
Disclosure of Invention
The invention aims to provide a method for improving the hardness and toughness of CVD single crystal diamond, which comprises the step of introducing nitrogen or mixed gas of nitrogen and oxygen or boron-containing gas intermittently when growing the single crystal diamond by Microwave Plasma Chemical Vapor Deposition (MPCVD) or hot wire chemical vapor deposition (HFCVD) or direct current Arc Plasma Jet (DC Arc Plasma Jet CVD). Compared with CVD single crystal diamond which grows by non-doping, the Vickers hardness of the CVD single crystal diamond which grows by the method is improved by 5 to 25 percent, and the fracture toughness is improved by 4 to 56 percent. The hardness and toughness of the CVD single crystal diamond grown by the method are obviously improved.
The technical scheme adopted by the invention is as follows:
a method for improving the hardness and toughness of CVD single crystal diamond is characterized in that:
when growing the single-crystal diamond by adopting Microwave Plasma Chemical Vapor Deposition (MPCVD), hot wire chemical vapor deposition (HFCVD) or direct current Arc Plasma Jet (DC Arc Plasma Jet CVD), introducing nitrogen or mixed gas of nitrogen and oxygen or boron-containing gas discontinuously, and realizing the enhancement and toughening effects of the nano multilayered interface structure by the alternate growth of the diamond with different doped layers. The growth temperature is 700-1050 deg.C, and the pressure is 6-30KPa, CH4/H2＝2-12％。
Further, the interval time of introducing nitrogen or mixed gas of nitrogen and oxygen or boron-containing gas is 3-5 minutes;
further, the flow of the introduced nitrogen or the mixed gas of the nitrogen and the oxygen or the boron-containing gas is 0.03-0.15 sccm;
further, the thickness of the doped layer formed is from 5nm to 800 nm;
furthermore, each pair of doped layers and undoped layers form a period, and the growth period of the doped layers and the undoped layers is 30-50.
According to the technical scheme provided by the invention, the hardness and toughness of the CVD single crystal diamond can be improved by applying the method. Compared with CVD single crystal diamond which grows by the method and is not doped with CVD single crystal diamond, the Vickers hardness of the CVD single crystal diamond is improved by 5-25%, and the fracture toughness of the CVD single crystal diamond is improved by 4-56%. The hardness and toughness of the multilayer CVD single crystal diamond grown by the method are obviously improved.
Drawings
In order to more clearly illustrate the technical solution of the present invention, the drawings used in the embodiments will be briefly described below, and it is obvious that the following drawings are only one embodiment of the present invention, and for a person of ordinary skill in the art, other drawings can be obtained according to the drawings.
FIG. 1 is a schematic structural view of a CVD single-crystal diamond grown by intermittently introducing a dopant gas according to the practice of the present invention.
FIG. 2 is a cross-sectional Raman mapping graph of a sample with a nitrogen-doped layer thickness of 760 nm;
FIG. 3 is a graph of the Vickers hardness indentation of a sample with a nitrogen-doped layer thickness of 760 nm;
FIG. 4 is a cross-sectional Raman mapping chart of a sample with a nitrogen-doped layer thickness of 500 nm;
FIG. 5 is a graph of the Vickers hardness indentation of a sample with a nitrogen-doped layer thickness of 500 nm.
Detailed Description
The technical solutions in the embodiments of the present invention are clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the present invention without making any creative effort, shall fall within the protection scope of the present invention.
Referring to fig. 1, there is shown a schematic structural view of CVD single crystal diamond grown by intermittently introducing a dopant gas according to the practice of the present invention, in which doped layers 2 and undoped layers 3 are alternately grown on a seed crystal substrate 1.
Example 1
Growing single crystal diamond by microwave plasma chemical vapor deposition system at 860 deg.C under 17KPa and CH with intermittent nitrogen introduction4/H2The nitrogen gas was introduced at intervals of 4 minutes, and the flow rate of the introduced nitrogen gas was 0.12sccm, which was defined as 5%. The cross section of the grown sample was subjected to lapping and polishing treatment and the cross section was subjected to Raman mapping test, and as shown in fig. 2, the nitrogen-doped layer was about 760nm, the alternate growth period was 30, and the total thickness of the grown CVD layer was about 45 μm. FIG. 3 shows the indentation morphology of the grown sample after Vickers hardness test, with a test load of 1Kg, the Vickers hardness of 100GPa and the fracture toughness of 7.8MPa m1/2Compared with a non-nitrogen-doped CVD layer (with the Vickers hardness of 80GPa and the fracture toughness of 5.0MPa m) grown without adopting the method of the invention1/2) Has an increased Vickers hardness25 percent and the fracture toughness is improved by 56 percent.
Example 2
Growing single crystal diamond by microwave plasma chemical vapor deposition system at 860 deg.C under 17KPa and CH with intermittent nitrogen introduction4/H2The nitrogen gas was introduced at intervals of 3 minutes, and the flow rate of the introduced nitrogen gas was 0.15sccm, which was 5%. The cross section of the grown sample was subjected to lapping and polishing treatment and the cross section was subjected to Raman mapping test, and as shown in fig. 4, the nitrogen-doped layer was about 500nm, the alternate growth period was 30, and the total thickness of the grown CVD layer was about 33 μm. FIG. 5 shows the indentation morphology of the grown sample after Vickers hardness test, with a test load of 1Kg, the Vickers hardness of 100GPa and the fracture toughness of 5.9MPa m1/2Compared with a non-nitrogen-doped CVD layer (with the Vickers hardness of 80GPa and the fracture toughness of 5.0MPa m) grown without adopting the method of the invention1/2) The Vickers hardness is improved by 25 percent, and the fracture toughness is improved by 18 percent.
In summary, when the single crystal diamond is grown by Microwave Plasma Chemical Vapor Deposition (MPCVD), Hot Filament Chemical Vapor Deposition (HFCVD), or direct current Arc Plasma Jet (DC Arc Plasma Jet CVD), nitrogen gas, or a mixed gas of nitrogen gas and oxygen gas, or a boron-containing gas is intermittently introduced, and the hardness and fracture toughness of the CVD single crystal diamond are simultaneously improved by alternately growing the doped layer and the undoped layer and changing the thickness of the doped layer and the flow rate of the doped gas introduced into the doped layer. The invention has simple process and low production cost, and can be used as a new technology for enhancing the mechanical property of the diamond.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.
Claims (4)
1. A method for improving the hardness and toughness of CVD single crystal diamond is characterized in that: when the single-crystal diamond is grown by adopting microwave plasma chemical vapor deposition or hot wire chemical vapor deposition or direct current arc plasma jet, nitrogen or mixed gas of nitrogen and oxygen or boron-containing gas is intermittently introduced, the growth temperature is 700-1050 ℃, the pressure is 6-30KPa, and CH4/H2 is 2-12%, and the enhancement and toughening effects of the nano multilayered interface structure are realized by the alternate growth of the diamonds with different doped layers;
the interval time of introducing nitrogen or mixed gas of nitrogen and oxygen or boron-containing gas is 3-5 minutes.
2. A method of increasing the hardness and toughness of CVD single crystal diamond according to claim 1, wherein: the flow rate of the introduced nitrogen gas or the mixed gas of the nitrogen gas and the oxygen gas or the boron-containing gas is 0.03-0.15 sccm.
3. A method of increasing the hardness and toughness of CVD single crystal diamond according to claim 1, wherein: when growing single crystal diamond, the doped layer is formed to a thickness of from 5nm to 800 nm.
4. A method of increasing the hardness and toughness of CVD single crystal diamond according to claim 1, wherein: each pair of doped layers and undoped layers form a period, and the growth period of the doped layers and the undoped layers is 30-50.
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| CN201810556015.4A CN108545738B (en) | 2018-06-01 | 2018-06-01 | Method for improving hardness and toughness of CVD single crystal diamond |
| PCT/CN2019/088829 WO2019228351A1 (en) | 2018-06-01 | 2019-05-28 | Method for improving hardness and toughness of single crystal cvd diamond |
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| CN201810556015.4A CN108545738B (en) | 2018-06-01 | 2018-06-01 | Method for improving hardness and toughness of CVD single crystal diamond |
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| CN108545738B (en) * | 2018-06-01 | 2020-07-10 | 北京科技大学 | Method for improving hardness and toughness of CVD single crystal diamond |
| CN111099586B (en) * | 2019-11-27 | 2022-05-31 | 中国科学院金属研究所 | Preparation method of high-brightness silicon vacancy color center in nano-diamond |
| CN111172508A (en) * | 2020-02-24 | 2020-05-19 | 北京科技大学 | Method for improving pressure limit of diamond opposite-top anvil |
| CN112996209B (en) * | 2021-05-07 | 2021-08-10 | 四川大学 | Structure and array structure for microwave excitation of atmospheric pressure plasma jet |
| CN113858036B (en) * | 2021-08-23 | 2023-04-25 | 四川纳涂科技有限公司 | Hard alloy grinding rod with diamond coating and preparation method thereof |
| CN114000120B (en) * | 2022-01-05 | 2022-03-15 | 武汉大学 | Strain diamond growth doping method based on CVD method |
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| CN102084492B (en) * | 2008-05-05 | 2013-09-11 | 华盛顿卡耐基研究所 | Ultratough single crystal boron-doped diamond |
| CN103710748B (en) * | 2013-12-12 | 2016-04-06 | 王宏兴 | A kind of growth method of monocrystalline diamond film |
| CN107740184B (en) * | 2017-09-30 | 2019-07-19 | 湖北碳六科技有限公司 | A kind of gradient single-crystal diamond and preparation method thereof |
| CN108545738B (en) * | 2018-06-01 | 2020-07-10 | 北京科技大学 | Method for improving hardness and toughness of CVD single crystal diamond |
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