CN110863243B - Secondary epitaxial method for preparing high-quality diamond single crystal by adopting nano structure - Google Patents

Secondary epitaxial method for preparing high-quality diamond single crystal by adopting nano structure Download PDF

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CN110863243B
CN110863243B CN201911180429.2A CN201911180429A CN110863243B CN 110863243 B CN110863243 B CN 110863243B CN 201911180429 A CN201911180429 A CN 201911180429A CN 110863243 B CN110863243 B CN 110863243B
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diamond
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single crystal
temperature
metal
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CN110863243A (en
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智婷
陶涛
谢自力
刘斌
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Nanjing University of Posts and Telecommunications
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Nanjing University of Posts and Telecommunications
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    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B25/00—Single-crystal growth by chemical reaction of reactive gases, e.g. chemical vapour-deposition growth
    • C30B25/02—Epitaxial-layer growth
    • C30B25/18—Epitaxial-layer growth characterised by the substrate
    • C30B25/186—Epitaxial-layer growth characterised by the substrate being specially pre-treated by, e.g. chemical or physical means
    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B25/00—Single-crystal growth by chemical reaction of reactive gases, e.g. chemical vapour-deposition growth
    • C30B25/02—Epitaxial-layer growth
    • C30B25/18—Epitaxial-layer growth characterised by the substrate
    • C30B25/20—Epitaxial-layer growth characterised by the substrate the substrate being of the same materials as the epitaxial layer
    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
    • C30B29/02—Elements
    • C30B29/04—Diamond

Abstract

The invention discloses a secondary epitaxy method for preparing high-quality diamond single crystal by adopting a nano structure, which comprises the following growth steps: 1) selecting high-temperature and high-pressure diamond as seed crystal; 2) etching pretreatment is carried out on the surface defects and damages of the seed crystals; 3) controlling the pressure, microwave power, temperature, methane concentration and growth time of the reaction chamber, and extending a diamond film layer with the thickness of 2-40 mu m for the first time; 4) evaporating and evaporating a metal Ni film layer with the thickness of about 4-40 nm by using an electron beam; 5) carrying out high-temperature heat treatment to obtain a metal nanoparticle pattern; 6) plasma etching is carried out to obtain a diamond nanoparticle coating; 7) controlling the pressure, microwave power, temperature, methane concentration and growth time of the reaction chamber, and performing secondary epitaxy on the diamond film with the thickness of 5-200 mu m. The invention effectively inhibits the extension of defects in the diamond film, reduces the defect density and improves the flatness of the crystal surface.

Description

Secondary epitaxial method for preparing high-quality diamond single crystal by adopting nano structure
Technical Field
The invention relates to a growth method of diamond single crystals, in particular to a secondary epitaxy method for preparing high-quality diamond single crystals by adopting a nano structure.
Background
In recent years, diamond as a novel wide bandgap semiconductor material has many unique advantages, such as high hardness, high wear resistance, good thermal stability, high breakdown field strength, high thermal conductivity, high carrier mobility, and corrosion resistance. Therefore, the application range of the material is widely expanded, the material is greatly developed in precision machining, aerospace, semiconductor communication and the like, and the material becomes a basic material or even a unique material for solving the extreme field. The traditional artificial diamond generally adopts a high-temperature high-pressure method, and the diamond prepared by the method generally contains a large amount of impurities, has high defect density and small size, which seriously limits the application range of the single crystal diamond, so that the produced diamond can only exist in downstream industries, but not be used in high-tech fields.
In contrast, Microwave Plasma Chemical Vapor Deposition (MPCVD) is currently recognized as one of the most effective ways to produce high-quality large-size single-crystal diamond, and a diamond sample produced by MPCVD has the advantages of single crystal, low impurity concentration, low defect density, large size, and the like, and different types of semiconductor materials can be grown by controlling the intentional doping, which is very important for being an effective semiconductor material. The method adopts MPCVD method to epitaxially grow diamond, generally adopts natural diamond or monocrystal diamond prepared at high temperature and high pressure as seed crystal, forms microwave plasma discharge through microwave power, decomposes carbon-containing gas such as Chapter, generates active ion and deposits diamond film on the seed crystal. However, the problem of low flatness, high defect density, small size and the like still exists in the epitaxial diamond directly on the seed crystal by using MPCVD, and patent CN107675249 proposes a diameter-expanding growth mode of single crystal diamond to improve the crystal quality, but in the case of growing thicker diamond later, the surface has a step flow with a large drop, and then the subsequent mechanical polishing is needed, which causes a great deal of waste of single crystal diamond.
Patent CN105506576A discloses a method for preparing a high-quality diamond thick film. The invention patent is characterized in that: firstly preparing a diamond thick film by using chemical vapor deposition, then grinding and polishing the nucleation surface of the film, removing residual carbide, and then preparing the diamond thick film by taking the residual carbide as a group. In the method, a monocrystalline silicon wafer is still used as a substrate, the silicon wafer is processed by diamond grinding powder, and then the extension of a diamond film is carried out. However, this patent can only obtain polycrystalline diamond films, and cannot obtain single diamond crystal films. Thus limiting the application range and market prospect of the patent. In addition, the key step in the invention is a key factor for grinding and polishing the diamond thick film. Diamond is known to be the hardest material in nature, and therefore grinding and polishing of diamond material is very difficult. The method usually adopted is laser cutting or grinding and polishing by using diamond grinding powder. However, both laser cutting and diamond powder polishing require tens of hours or even days to process, which consumes a lot of time and labor. The invention does not need to grind and polish the diamond film, and carries out disordered natural selection by a method for preparing nano-scale patterning so as to reserve a high-quality diamond single crystal part. The method has the advantages that not only can a high-quality diamond single crystal film be obtained, but also the preparation of the nano pattern and the subsequent etching method can be finished in dozens of minutes, and a great amount of time and labor cost can be saved. Therefore, the invention has great technical advantages.
The invention CN107428541A discloses a diamond single crystal trend epitaxy method, which adopts diamond seeds or seed crystals as a substrate and selects a (100) crystal face orientation. The invention requires that the off-axis angle to the (100) orientation axis not exceed 3 degrees. And requires etching of the top surface to leak or remove surface damage, reducing defect density. Before the material growth, the substrate was cleaned in a boiling acid bath at 300 degrees celsius, followed by CVD growth. The invention does not specially design and process the substrate material, but has high requirements on the quality and performance of the substrate material.
Disclosure of Invention
The invention aims to provide a secondary epitaxy method for preparing high-quality diamond single crystals by adopting a nano structure.
The technical scheme adopted by the invention is as follows: a secondary epitaxy method for preparing high-quality diamond single crystals by adopting a nano structure comprises the following steps:
step 1, selecting octagonal diamond seed crystals prepared by a high-temperature high-pressure method as a substrate;
step 2, cleaning the diamond seed crystal:
step 3, preprocessing the diamond substrate;
step 4, performing first epitaxial growth of the diamond film on the pretreated seed crystal by adopting an MPCVD method, and growing a diamond film with the thickness of 2-40 mu m;
step 5, evaporating and plating a layer of metal mask on the diamond film which grows in the first epitaxial growth;
step 6, annealing the metal mask in a high-temperature nitrogen atmosphere, changing the metal mask into metal nano particles, and forming a metal nano pattern on the surface of the diamond film;
step 7, carrying out plasma etching on the metal nano-pattern;
step 8, removing the metal nano particles to obtain clean single crystal diamond with nano patterns;
and 9, carrying out secondary epitaxial growth of the diamond film on the single crystal diamond with the nano pattern to obtain the diamond single crystal with high quality.
Preferably, in the step 2, the single crystal diamond seed crystal is sequentially placed in acetone, absolute ethyl alcohol and water, ultrasonic cleaning is carried out for 10-30 min, the ultrasonic power is about 100-600W, organic impurities on the surface of the crystal are removed, and finally the crystal is dried in a vacuum drying oven to obtain the clean seed crystal.
Preferably, in step 3, the cleaned seed crystal is placed on a molybdenum tray in an MPCVD reaction chamber, and the vacuum degree of the reaction chamber is pumped to be less than 10-6And mbar, wherein the pressure of the reaction chamber is 50-300 mbar, the temperature is 600-1100 ℃, the microwave power is 2400-3500W, hydrogen with the flow rate of 40-350 sccm is introduced, and the conditions are stabilized for 5-40 min, so that the pretreatment of surface defects and damages of the substrate is realized.
Preferably, in the step 4, the air pressure of the reaction chamber is 80-250 mbar, the microwave power is 2500-3500W, the methane concentration is 1% -6%, the surface temperature of the sample is controlled to be 950-1200 ℃, and the cavity of the reaction chamber is circularly cooled by cooling water, so that the temperature of the outer wall of the cavity is not more than 50 ℃.
Preferably, in step 5, an electron beam evaporation technology is used to evaporate a Ni metal film with a thickness of 4-40 nm on the diamond film which is epitaxially grown for the first time, wherein the evaporation rate is 0.1-0.5 nm/s.
Preferably, in the step 6, the annealing temperature is 750-850 ℃, the annealing time is 1min, the diameter of the metal nano-particles is controlled to be 80-125 nm by adjusting the annealing temperature, the annealing time and the thickness of the metal film in a nitrogen atmosphere, and a nano-pattern layer is formed.
Preferably, in step 7, an ICP technique is adopted, the metal nanoparticles are used as a mask, oxygen is introduced for etching, and etching parameters are as follows: the flow rate of the oxygen is 5-50 sccm, the gas pressure is about 3-35 mtorr, the RF power is 50-100W, the ICP power is 200-500W, and the etching time is as follows: 1-10 min.
Preferably, in step 8, the diamond with the nano-pattern is placed in dilute HCl (with the concentration of 10% -50%), and metal Ni at the top of the nano-column is removed; and sequentially placing the diamond in acetone, absolute ethyl alcohol and water, carrying out ultrasonic cleaning for 10-30 min at the ultrasonic power of about 100-600W, and finally drying in a vacuum drying oven to obtain the clean single crystal diamond with the nano pattern.
Preferably, in the step 9, a second epitaxial growth is carried out by an MPCVD method, the air pressure of the reaction chamber is 100-300 mbar, the microwave power is 2800-3800W, the methane concentration is 1-6%, the surface temperature of the sample is 1000-1200 ℃, and a diamond film with the thickness of 5-200 μm is epitaxially grown.
The invention has the following beneficial effects:
1. the self-assembly characteristic of the metal Ni material at high temperature is utilized, the Ni film is converted into Ni nano-particles in nitrogen atmosphere at the temperature of 750-850 ℃, and the metal particles are used as masks in subsequent etching. The method is characterized in that the defect position is avoided preferentially in the self-assembly process, so that the defect position is exposed in the etching process, and the purpose of eliminating the defect is achieved. Meanwhile, surface impurity particles can be avoided, so that the impurity particles are exposed in the etching process, and the purpose of removing impurities is achieved.
2. The plasma dry etching technology is utilized to selectively etch the diamond substrate, and the metal Ni particles are used as protective masks during etching. Through the selective etching process, the defects and the impurities can be preferentially etched, so that the effect of reducing the defects and eliminating the impurities is achieved. The disordered structure of the formed diamond nano-column can become a main nucleation point in the secondary epitaxy process, and homoepitaxy is carried out on the basis of the single crystal nano-column, so that the crystal surface characteristics of diamond are guaranteed. Through the transverse growth of diamond in the secondary epitaxial process, the nano-columns are gradually combined into a single crystal film, and finally, a flat diamond single crystal film is formed.
3. In the secondary epitaxial process, the nucleation points of the nano-columns are expanded and grown by controlling conditions such as proper gas, gas pressure, power, temperature and the like, so that the transverse growth rate of the nano-columns is enhanced. And fusing the nano columns through transverse growth to form a flat surface. In the secondary epitaxy, due to the geometrical characteristics of the nano-pillar structure, the defects in the original diamond substrate do not extend into the secondary epitaxial thin film any more, so that the crystal quality of the secondary epitaxial thin film is remarkably improved.
The method carries out the nano-patterning treatment on the diamond substrate, carries out the disordered natural selection process through the patterning treatment on the surface of the substrate material, and reserves the high-quality diamond single crystal region, thereby enabling the epitaxial growth to be carried out on the high-quality single crystal region in the secondary epitaxy, effectively reducing the defect density of the epitaxial thin film, and improving the crystal quality and the surface smoothness. Meanwhile, the method can obviously inhibit the generation of diamond polycrystal in the epitaxial process, thereby being beneficial to growing large-size diamond monocrystal films. And the preparation of the nano pattern and the subsequent etching method can be finished in tens of minutes, so that a large amount of time and labor cost can be saved.
Drawings
FIG. 1 is a schematic view of a seed crystal prepared at high temperature and high pressure as a substrate;
FIG. 2 is a schematic view of a first MPCVD first epitaxial monolayer diamond film on a seed crystal of a substrate;
FIG. 3 is a schematic diagram of a single-layer diamond coated with Ni metal film by evaporation;
FIG. 4 is a schematic view of a high temperature heat treatment of a Ni metal film;
FIG. 5 is a schematic view of the nano-diamond after etching;
FIG. 6 is a schematic view of a diamond film for secondary epitaxy;
FIG. 7 shows the surface morphology of the Ni film after high-temperature heat treatment;
FIG. 8 shows the surface topography of the nano-diamond after etching;
fig. 9 shows the surface morphology of diamond after secondary epitaxy.
Fig. 10 is a schematic diagram of the principle of the present invention.
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 of the embodiments. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention.
Example 1
The secondary epitaxy method for preparing the high-quality diamond single crystal by adopting the nano structure comprises the following steps:
step 1, selecting an octagonal diamond seed crystal 1 prepared by a high-temperature high-pressure method as a substrate, as shown in figure 1.
Step 2, cleaning the diamond seed crystal: and (2) putting the single-crystal diamond seed crystal into acetone, absolute ethyl alcohol and water in sequence, ultrasonically cleaning for 20min at the ultrasonic power of 600W to remove organic impurities on the surface of the crystal, and finally drying in a vacuum drying oven to obtain the clean seed crystal.
And 3, preprocessing the diamond substrate.
Placing the cleaned seed crystal on a molybdenum tray in an MPCVD reaction chamber, and pumping the vacuum degree of the reaction chamber to be less than 10- 6And mbar, the pressure of the reaction chamber is 200mbar, the temperature is 900 ℃, the microwave power is 3000W, hydrogen with the flow rate of 200sccm is introduced, and the conditions are stabilized for 30min, so that the pretreatment of the surface defects and damages of the substrate is realized.
And 4, carrying out primary epitaxial growth of the diamond film on the seed crystal after the pretreatment.
The method adopts an MPCVD method for epitaxial growth, the air pressure of a reaction chamber is 80mbar, the microwave power is 2500W, the methane concentration is 1%, the surface temperature of a sample is measured by an optical thermodetector, the surface temperature of the sample is 950 ℃, the surface temperature of the sample is taken as the temperature of the reaction chamber instead of the temperature of the reaction chamber, the cavity of the reaction chamber is cooled by cooling water in a circulating way, the temperature of the outer wall of the cavity is ensured not to exceed 50 ℃, the diamond film 2 with the thickness of 2 μm is grown for 2 hours under the condition.
And 5, evaporating a metal mask 3 on the diamond film grown in the step one by utilizing an electron beam evaporation technology to evaporate a Ni metal film with the thickness of 4nm at the evaporation rate of 0.1 nm/s.
And 6, carrying out high-temperature heat treatment on the metal mask, and annealing in a high-temperature high-purity nitrogen environment to form metal nano particles. Aiming at the metal film, the diameter of the metal nano-particles is controlled to be 80nm by adjusting the annealing temperature to be 750 ℃, the annealing time to be 1min and the nitrogen atmosphere and by adjusting the annealing temperature, the annealing time and the thickness of the metal film, so as to form a nano-graph layer.
Step 7, carrying out plasma etching on the metal nano-pattern
Adopting ICP technology, taking the nano particles as a mask, introducing oxygen for etching, and etching parameters are as follows: the oxygen flow is 20sccm, the gas pressure is about 15mtorr, the power is 100W/500W, the etching time is as follows: for 1 min.
And 8, removing the metal nano pattern.
Placing the diamond with the nano pattern in dilute HCl with the concentration of 20 percent, and removing metal Ni at the top end of the nano column; sequentially placing the diamond in acetone, absolute ethyl alcohol and water, carrying out ultrasonic cleaning for 20min with the ultrasonic power of about 600W, and finally drying in a vacuum drying oven to obtain the clean single crystal diamond with the nano pattern.
Step 9, secondary epitaxy of the diamond with the nano pattern
And (3) carrying out epitaxial growth by adopting an MPCVD (multi-layer chemical vapor deposition) method, wherein the air pressure of a reaction chamber is 100mbar, the microwave power is 2800W, the methane concentration is 1%, the surface temperature of a sample is 1000 ℃, the growth time is 2 hours, and a diamond film 4 with the thickness of 5 mu m is obtained by secondary epitaxial growth.
Fig. 7 is a surface topography of single crystal diamond with metallic Ni nanoparticles, approximately 80nm in diameter.
FIG. 8 is a surface topography of a single crystal diamond with nanostructures, nanopillars about 80nm in diameter and 1 μm in height.
FIG. 9 shows the surface morphology of single crystal diamond after the second epitaxy, the surface roughness of the single crystal diamond is reduced from 1.83nm to 0.36nm of the substrate, and the Raman full width at half maximum is 2.7cm of the substrate-1Down to 2.1cm-1. Therefore, the quality of the single crystal diamond crystal subjected to secondary epitaxy by adopting the nano column is greatly improved, and the roughness is greatly reduced.
Example 2
The secondary epitaxy method for preparing the high-quality diamond single crystal by adopting the nano structure comprises the following steps:
step 1, selecting octagonal diamond seed crystals prepared by a high-temperature high-pressure method as a substrate.
Step 2, cleaning the diamond seed crystal: and (2) putting the single-crystal diamond seed crystal into acetone, absolute ethyl alcohol and water in sequence, ultrasonically cleaning for 30min at the ultrasonic power of about 500W to remove organic impurities on the surface of the crystal, and finally drying in a vacuum drying oven to obtain the clean seed crystal.
And 3, preprocessing the diamond substrate.
Placing the cleaned seed crystal on a molybdenum tray in an MPCVD reaction chamber, and pumping the vacuum degree of the reaction chamber to be less than 10- 6And mbar, the pressure of the reaction chamber is 300mbar, the temperature is 1100 ℃, the microwave power is 3500W, hydrogen with the flow rate of 350sccm is introduced, and the conditions are stabilized for 5min, so that the pretreatment of the surface defects and damages of the substrate is realized.
And 4, carrying out diamond film epitaxial growth on the seed crystal after the pretreatment.
And (3) carrying out epitaxial growth by adopting an MPCVD (multi-layer chemical vapor deposition) method, wherein the air pressure of a reaction chamber is 250mbar, the microwave power is 3500W, the methane concentration is 6%, the surface temperature of a sample is measured by an optical thermodetector, the surface temperature of the sample is 1200 ℃, the growth is carried out for 2h, and a diamond film with the thickness of 40 mu m is obtained by epitaxial growth.
And 5, evaporating a metal mask on the diamond film grown in the step one, and evaporating a Ni metal film with the thickness of 40nm by using an electron beam evaporation technology, wherein the evaporation rate is 0.5 nm/s.
Step 6, carrying out high-temperature heat treatment on the metal mask
And annealing at high temperature and high purity nitrogen environment to form metal nano particles. Aiming at the metal film, the diameter of the metal nano-particles is controlled to be about 125nm by adjusting the annealing temperature to 850 ℃, the annealing time to 1min and the nitrogen atmosphere and adjusting the annealing temperature, the annealing time and the thickness of the metal film to form a nano-graph layer.
Step 7, carrying out plasma etching on the metal nano-pattern
Adopting ICP technology, taking the nano particles as a mask, introducing oxygen for etching, and etching parameters are as follows: the oxygen flow is 5sccm, the gas pressure is about 3mtorr, the power is 50W/200W, the etching time is as follows: and 2 min.
And 8, removing the metal nano pattern.
Placing the diamond with the nanometer patterns in a position of 1: 1, removing metal Ni at the top end of the nano-column in dilute HCl; sequentially placing in acetone, absolute ethyl alcohol and water, ultrasonically cleaning for 10min with the ultrasonic power of about 100W, and finally drying in a vacuum drying oven to obtain the clean single crystal diamond with the nano-pattern.
Step 9, secondary epitaxy of the diamond with the nano pattern
And carrying out epitaxial growth by adopting an MPCVD (multi-layer chemical vapor deposition) method, wherein the air pressure of a reaction chamber is 300mbar, the microwave power is 3800W, the methane concentration is 6%, the surface temperature of a sample is 1200 ℃, the growth is carried out for 5h, and a diamond film with the thickness of 200 mu m is obtained by epitaxial growth.
Example 3
The secondary epitaxy method for preparing the high-quality diamond single crystal by adopting the nano structure comprises the following steps:
step 1, selecting octagonal diamond seed crystals prepared by a high-temperature high-pressure method as a substrate.
Step 2, cleaning the diamond seed crystal: and (2) putting the single-crystal diamond seed crystal into acetone, absolute ethyl alcohol and water in sequence, carrying out ultrasonic cleaning for 10min at the ultrasonic power of about 100W, removing organic impurities on the surface of the crystal, and finally drying in a vacuum drying oven to obtain the clean seed crystal.
And 3, preprocessing the diamond substrate.
Placing the cleaned seed crystal on a molybdenum tray in an MPCVD reaction chamber, and pumping the vacuum degree of the reaction chamber to be less than 10- 6mbar, the pressure of the reaction chamber is 50mbar, the temperature is 600 ℃, the microwave power is 2400W, and hydrogen with the flow rate of 40sccm is introduced to stabilize the conditions for 40min, so that the pretreatment of the surface defects and damages of the substrate is realized.
And 4, carrying out diamond film epitaxial growth on the seed crystal after the pretreatment.
The diamond film with the thickness of 18 microns is epitaxially grown by an MPCVD method, the air pressure of a reaction chamber is 200mbar, the microwave power is 3000W, the methane concentration is 2%, the surface temperature of a sample is measured by an optical thermodetector, the surface temperature of the sample is 1100 ℃, the diamond film is grown for 2 hours.
And 5, evaporating a metal mask on the diamond film grown in the step one, and evaporating a Ni metal film with the thickness of 10nm by using an electron beam evaporation technology, wherein the evaporation rate is 0.2 nm/s.
Step 6, carrying out high-temperature heat treatment on the metal mask
And annealing at high temperature and high purity nitrogen environment to form metal nano particles. Aiming at the metal film, the diameter of the metal nano-particles is controlled to be 100nm by adjusting the annealing temperature to be 800 ℃, the annealing time to be 1min and the nitrogen atmosphere and by adjusting the annealing temperature, the annealing time and the thickness of the metal film, so as to form a nano-graph layer.
Step 7, carrying out plasma etching on the metal nano-pattern
Adopting ICP technology, taking the nano particles as a mask, introducing oxygen for etching, and etching parameters are as follows: the oxygen flow is 50sccm, the gas pressure is about 35mtorr, the power is 100W/500W, the etching time is as follows: for 10 min.
And 8, removing the metal nano pattern.
Placing the diamond with the nano pattern in 30% dilute HCl, and removing metal Ni at the top end of the nano column; sequentially placing in acetone, absolute ethyl alcohol and water, ultrasonically cleaning for 30min with ultrasonic power of about 500W, and finally drying in a vacuum drying oven to obtain the clean single crystal diamond with the nano pattern.
Step 9, secondary epitaxy of the diamond with the nano pattern
And (3) carrying out epitaxial growth by adopting an MPCVD (multi-layer chemical vapor deposition) method, wherein the air pressure of a reaction chamber is 250mbar, the microwave power is 3600W, the methane concentration is 2%, the surface temperature of a sample is 1150 ℃, and a diamond film with the thickness of 100 mu m is grown for 5 hours.
The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and all such changes, modifications, substitutions, combinations, and simplifications are intended to be included in the scope of the present invention.

Claims (9)

1. A secondary epitaxy method for preparing high-quality diamond single crystals by adopting a nano structure comprises the following steps:
step 1, selecting octagonal diamond seed crystals prepared by a high-temperature high-pressure method as a substrate;
step 2, cleaning the diamond seed crystal:
step 3, preprocessing the surface defects and damages of the diamond substrate;
step 4, performing first epitaxial growth of the diamond film on the pretreated seed crystal by adopting an MPCVD method, and growing a diamond film with the thickness of 2-40 mu m;
step 5, evaporating and plating a layer of Ni metal mask on the diamond film subjected to the first epitaxial growth, wherein the thickness of the Ni metal mask is 4-40 nm;
step 6, annealing the Ni metal mask at high temperature and in a nitrogen atmosphere, wherein the annealing temperature is 750-850 ℃, the Ni metal mask is changed into metal nano particles in the nitrogen atmosphere, the diameter of the metal nano particles is controlled to be 80-125 nm, and metal nano patterns are formed on the surface of the diamond film;
step 7, carrying out plasma etching on the metal nano-pattern;
step 8, removing the metal nano particles to obtain clean single crystal diamond with nano patterns;
and 9, carrying out secondary epitaxial growth of the diamond film on the monocrystal diamond with the nano pattern to obtain the diamond monocrystal with high quality.
2. The secondary epitaxial method for preparing a high quality diamond single crystal using a nanostructure according to claim 1, wherein: and 2, sequentially placing the monocrystalline diamond seed crystals in acetone, absolute ethyl alcohol and water, carrying out ultrasonic cleaning for 10-30 min at the ultrasonic power of about 100-600W, removing organic impurities on the surfaces of the crystals, and finally drying in a vacuum drying oven to obtain the clean seed crystals.
3. The secondary epitaxial method for producing high quality diamond single crystal using nanostructure according to claim 1 or 2, characterized in thatCharacterized in that: in step 3, the cleaned seed crystal is placed on a molybdenum tray in an MPCVD reaction chamber, and the vacuum degree of the reaction chamber is pumped to be less than 10-6And mbar, wherein the pressure of the reaction chamber is 50-300 mbar, the temperature is 600-1100 ℃, the microwave power is 2400-3500W, hydrogen with the flow rate of 40-350 sccm is introduced, and the conditions are stabilized for 5-40 min, so that the pretreatment of surface defects and damages of the substrate is realized.
4. The secondary epitaxial method for preparing a high quality diamond single crystal using a nanostructure according to claim 3, wherein: in the step 4, the air pressure of the reaction chamber is 80-250 mbar, the microwave power is 2500-3500W, the methane concentration is 1% -6%, the surface temperature of the sample is controlled to be 950-1200 ℃, and the cavity of the reaction chamber is cooled by circulating cooling water, so that the temperature of the outer wall of the cavity is not more than 50 ℃.
5. The secondary epitaxial method for preparing a high quality diamond single crystal using a nanostructure according to claim 4, wherein: and 5, evaporating a Ni metal film with the thickness of 4-40 nm on the diamond film which is epitaxially grown for the first time by using an electron beam evaporation technology, wherein the evaporation rate is 0.1-0.5 nm/s.
6. The secondary epitaxial method for preparing a high quality diamond single crystal using a nanostructure according to claim 5, wherein: in the step 6, the annealing temperature is 750-850 ℃, the annealing time is 1min, the diameter of the metal nano-particles is controlled to be 80-125 nm by adjusting the annealing temperature, the annealing time and the thickness of the metal film in a nitrogen atmosphere, and a nano-pattern layer is formed.
7. The secondary epitaxial method for preparing a high quality diamond single crystal using a nanostructure according to claim 6, wherein: and 7, adopting an ICP (inductively coupled plasma) technology, taking the metal nano particles as a mask, introducing oxygen for etching, and carrying out etching parameters: the flow rate of the oxygen is 5-50 sccm, the gas pressure is about 3-35 mtorr, the RF power is 50-100W, the ICP power is 200-500W, and the etching time is as follows: 1-10 min.
8. The secondary epitaxial method for preparing a high-quality diamond single crystal using a nanostructure according to claim 7, wherein: step 8, placing the diamond with the nano pattern in dilute HCl, and removing metal Ni at the top end of the nano column; sequentially placing the diamond in acetone, absolute ethyl alcohol and water, carrying out ultrasonic cleaning for 10-30 min, wherein the ultrasonic power is about 100-600W, and finally drying in a vacuum drying oven to obtain the clean single crystal diamond with the nano pattern.
9. The secondary epitaxial method for producing a high quality diamond single crystal using a nanostructure according to claim 8, wherein: and 9, carrying out secondary epitaxial growth by adopting an MPCVD (multi-phase plasma chemical vapor deposition) method, wherein the air pressure of the reaction chamber is 100-300 mbar, the microwave power is 2800-3800W, the methane concentration is 1-6%, the surface temperature of the sample is 1000-1200 ℃, and a diamond film with the thickness of 5-200 mu m is epitaxially grown.
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