A method of producing doped two-dimensional diamond

Abstract

The application discloses a method for preparing doped two-dimensional diamond, and belongs to the technical field of diamond preparation. The method comprises the following steps: performing ball milling treatment on graphene or graphite in a gas plasma atmosphere to obtain sample A; evaporating a catalyst alloy on sodium chloride flakes to obtain sample B; alternately stacking sample A and sample B and placing them in a boron nitride tube; performing temperature and pressure preservation through a six-surface high-temperature and high-pressure technology; after pressure unloading and temperature cooling, disassembling the mold; removing residual boron nitride, and then removing sodium chloride and the catalyst alloy to obtain the doped two-dimensional diamond. The method is simple and efficient, and the prepared diamond material is in a two-dimensional single crystal state, which has important application prospects in the future nanomechanics, nanophotonic electronics and other fields.

Description

Technical Field

[0001] This invention belongs to the field of diamond preparation technology, and particularly relates to a method for preparing doped two-dimensional diamond. Background Technology

[0002] Diamond, a typical representative of carbon allotropes, is not only the hardest substance in nature, but also exhibits many outstanding properties that push the limits of materials. It possesses both the highest room-temperature thermal conductivity (2000-2200 W / m·K) and the lowest coefficient of thermal expansion (0.8 × 10⁻⁶). -6 K -1 It also possesses extremely strong resistance to radiation damage (threshold > 1×10⁻⁶). 15 cm -2 Its properties, including extreme chemical inertness, make it an ideal candidate material for high-power, high-frequency electronic devices in fourth-generation semiconductor technology. In recent years, with the deepening research on two-dimensional materials, carbon-based material systems have exhibited significant dimensional effects: when layered graphite is thinned to a single atomic layer to form graphene through exfoliation technology, its SP... 2 The hybrid honeycomb lattice can generate extraordinary mechanical strength (130 GPa) and ultra-high carrier mobility (2 × 10⁻⁶). 5 cm 2 Novel physical properties such as ( / V·s) and the quantum Hall effect have inspired researchers to explore SP. 3 Theoretical simulations show that the two-dimensional morphology of hybrid diamond allows it to maintain high thermal conductivity (>2000 W / m·K) while exhibiting tunable band gaps (1.1-4.3 eV) and anomalous quantum transport properties due to quantum confinement effects. The dangling bonds formed by surface reconstruction are more easily chemically functionalized, providing a new platform for designing novel optoelectronic devices.

[0003] However, the experimental fabrication of two-dimensional diamond faces a dual challenge: firstly, the ultra-high chemical stability and strong covalent bond network of diamond make it difficult to achieve atomic-level precision processing using traditional fabrication techniques such as mechanical exfoliation and chemical vapor deposition; secondly, when the thickness of diamond is reduced to the nanoscale, the unsaturated carbon dangling bonds on the surface will trigger drastic structural reconstruction, leading to SP... 3 Hybrid networks become unstable. Therefore, there is an urgent need to develop efficient and simple synthesis methods to achieve the precise manufacture of two-dimensional diamonds.

[0004] Two-dimensional (2D) materials refer to thin layers of material with a thickness at the atomic or molecular level, typically only a few atomic layers thick. Due to their extremely small thickness, electron movement is restricted, confined to a two-dimensional plane, thus exhibiting unique physical and chemical properties. Theoretical predictions suggest that 2D diamond is a novel carbon-based material with a Young's modulus approaching that of diamond and far exceeding that of graphene, making it one of the strongest known 2D materials. Its ultrathin structure possesses tunable electronic properties, exhibiting edge-state quantum properties, and holds potential value in quantum computing. Currently, the main method for preparing 2D diamond is high-pressure graphene followed by surface hydrogenation or fluorination. This method produces 2D diamond with only the surface layer containing hydrogen and phosphorus (H) elements, and only yields extremely small quantities of 2D diamond material at a time. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention proposes a method for preparing doped two-dimensional diamond. The method first involves ball milling and plasma treatment of graphite to obtain a uniform graphite raw material containing dopant elements (e.g., N, P). Then, the raw material undergoes high-temperature and high-pressure treatment to obtain doped two-dimensional diamond material. This method is simple, efficient, and can yield high-quality two-dimensional diamond samples.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A method for preparing doped two-dimensional diamond includes the following steps: ball milling graphene or graphite in a gas plasma atmosphere to obtain sample A; vapor-depositing a catalyst alloy on a sodium chloride sheet to obtain sample B; alternately stacking sample A and sample B and placing them in a boron nitride tube, and maintaining the temperature and pressure using a six-sided high-temperature and high-pressure technique; after the pressure is released and the temperature is cooled, disassembling the mold, removing residual boron nitride, sodium chloride, and catalyst alloy, and obtaining two-dimensional diamond.

[0008] Graphene / graphite and catalyst alloys are commonly used to catalyze the formation of diamond particles under high temperature and pressure. Therefore, in this invention, a catalyst alloy is deposited onto a sodium chloride sheet, alternately stacked with graphene / graphite, and then diamond is formed under high temperature and pressure. Because the number of graphene / graphite layers used is extremely small, separated by sodium chloride sheets coated with the catalyst alloy, the formed diamond phase is an ultrathin two-dimensional diamond. When the graphene / graphite is placed in a gaseous plasma environment, surface adsorption occurs on the graphene / graphite surface. Further, under high temperature and pressure, the adsorbed atoms diffuse into the newly formed diamond phase, forming doped diamond. Sodium chloride is highly soluble in water, and the catalyst alloy is readily soluble in acids or alkalis, thus ultimately yielding clean two-dimensional diamond.

[0009] Furthermore, the gas plasma is selected from one of N2, Ar, H2, CH4, SF6, CHF3, PH3, BH3, and SiH4.

[0010] Furthermore, the specific operation steps of the ball milling process include: the ball mill speed is 400-1500 rpm, the ball mill works for 30 minutes and then automatically stops for 30 minutes, the total ball milling time is 1-6 hours, and the pressure of the ball milling atmosphere is 0.1 MPa.

[0011] Furthermore, the thickness of the sodium chloride sheet is 1-2 mm.

[0012] Furthermore, the catalyst alloy is selected from one of Ni-Cr-Fe alloy, Ni-Fe-Mn alloy, Ni-Co alloy, Ni-Cr alloy, and Ni-Mn alloy.

[0013] In this invention, the catalyst alloy mainly serves as a catalyst for high-temperature and high-pressure reactions, catalyzing the reaction process.

[0014] Furthermore, the thickness of the catalyst alloy layer deposited on the sodium chloride sheet is 10-200 nm.

[0015] Furthermore, the total thickness of the alternately stacked samples A and B is 10 mm.

[0016] Furthermore, the specific operating steps of the six-sided high-temperature and high-pressure technology include: heating the temperature to 1500-1700℃, and after reaching the temperature value, increasing the pressure to 6-15GPa, and continuing the reaction at this temperature and pressure for 2-20 hours.

[0017] Furthermore, the specific steps for removing sodium chloride and catalyst alloy include: first placing the sample in water to dissolve the sodium chloride, and then placing the sample in an acidic or alkaline solution to dissolve the catalyst alloy, thereby achieving the removal of sodium chloride and catalyst alloy.

[0018] The present invention also discloses a two-dimensional diamond, which is prepared by the above method.

[0019] Compared with the prior art, the present invention has the following advantages and technical effects:

[0020] The method for preparing two-dimensional diamond provided by this invention is simple and efficient, and the prepared diamond material exhibits a two-dimensional single crystal state, which has important application prospects in the fields of nanomechanics and nano-optoelectronics in the future. Attached Figure Description

[0021] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0022] Figure 1 This is a flowchart of the preparation method of two-dimensional diamond according to the present invention;

[0023] Figure 2 This invention provides an experimental mold for preparing two-dimensional diamond.

[0024] Figure 3 The Raman spectrum of the two-dimensional diamond prepared in Example 1;

[0025] Figure 4 The image shows the Raman spectrum of the product prepared in Comparative Example 1. Detailed Implementation

[0026] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0027] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0028] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0029] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be readily apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0030] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0031] This invention provides a method for preparing two-dimensional diamond, comprising the following steps: ball milling graphene or graphite in a gas plasma atmosphere to obtain sample A; vapor-depositing a catalyst alloy on a sodium chloride sheet to obtain sample B; stacking sample A and sample B alternately, cutting them to the required size, placing them in a boron nitride tube, and maintaining the temperature and pressure using a six-sided high-temperature and high-pressure technique; after the pressure is released and the temperature is cooled, disassembling the mold, removing residual boron nitride, and then removing sodium chloride and the catalyst alloy to obtain two-dimensional diamond.

[0032] In this invention, the graphene or graphite is extremely thin, so its thickness is negligible during the alternating stacking process with sample B. Therefore, the thickness of the graphene or graphite is not limited in the following embodiments of this invention.

[0033] In the following embodiments of the present invention, graphene is used as an example to verify the effect.

[0034] In some preferred embodiments, the gas plasma is selected from one of N2, Ar, H2, CH4, SF6, CHF3, PH3, BH3, and SiH4. More preferably, it is N2, Ar, or BH3.

[0035] In some preferred embodiments, the specific operation steps of the ball milling process include: the ball mill speed is 400-1500 rpm (more preferably 1200 rpm), the ball mill works for 30 minutes and then automatically stops for 30 minutes, the total ball milling time is 1-6 hours (more preferably 3 hours), and the pressure of the ball milling atmosphere is 0.1 MPa.

[0036] In some preferred embodiments, the thickness of the sodium chloride sheet is 1-2 mm. More preferably, it is 2 mm.

[0037] In some preferred embodiments, the catalyst alloy is selected from one of Ni-Cr-Fe alloy, Ni-Fe-Mn alloy, Ni-Co alloy, Ni-Cr alloy, and Ni-Mn alloy. More preferably, it is a Ni-Co alloy or a Ni-Fe-Mn alloy.

[0038] In some preferred embodiments, the thickness of the catalyst alloy layer deposited on the sodium chloride sheet is 10-200 nm. More preferably, it is 50 nm.

[0039] In some preferred embodiments, the total thickness of the alternately stacked samples A and B is 10 mm. This thickness is the thickness of the experimental mold; therefore, in this invention, this total thickness does not limit the inventiveness of the invention, and the stacking thickness can be adjusted according to the height of the mold.

[0040] In some preferred embodiments, the specific operating steps of the six-sided high-temperature and high-pressure technology include: heating the temperature to 1500-1700℃ (e.g., 1500℃, 1600℃ or 1700℃), and after reaching the temperature value, increasing the pressure to 6-15GPa (more preferably 8-12GPa, e.g., 8GPa, 10GPa or 12GPa), and continuing the reaction at this temperature and pressure for 2-20h (more preferably 5-12h, e.g., 7h, 10h or 12h).

[0041] The method for removing sodium chloride is as follows: place the sample in deionized water. Sodium chloride is very soluble in water, thus achieving the removal of sodium chloride.

[0042] The method for removing the catalyst alloy is as follows: place the sample in an acidic or alkaline solution; the catalyst alloy will dissolve in the acid or alkali. For either acid or alkali, as long as the catalyst alloy is completely removed, there is no need to further limit the specific choice of acid or alkali.

[0043] In existing technologies, it is difficult to maintain the stability of diamonds with a thickness of only a few atomic layers. However, in this invention, surface-adsorbed atoms not only enter the diamond as dopant elements but also form bonds with surface carbon atoms, thus maintaining the stability of the two-dimensional diamond structure. It is worth noting that even without dopant atoms, the carbon atoms on the diamond surface can maintain the stability of the two-dimensional diamond through surface reconstruction. Plasma treatment activates the carbon atoms in graphene / graphite, making reconstruction easier to occur. This method is simple and efficient, providing a solution for the controllable doping and stable preparation of two-dimensional diamonds.

[0044] Unless otherwise specified, "room temperature" in this invention refers to 20-30℃.

[0045] All raw materials used in this invention were purchased from the market.

[0046] The technical solution of the present invention will be further illustrated by the following embodiments.

[0047] Example 1

[0048] A method for preparing two-dimensional diamond includes the following steps: Graphene is ball-milled in an N2 plasma atmosphere at a speed of 1200 rpm. The ball mill operates for 30 minutes and then automatically stops for 30 minutes, for a total milling time of 3 hours. The pressure of the milling atmosphere is 0.1 MPa, resulting in sample A. A 50 nm thick Ni-Co alloy layer is deposited on a 1.5 mm thick sodium chloride sheet, resulting in sample B. Samples A and B are stacked alternately to a thickness of 10 mm. The stacked samples are then cut to the required size and placed in a boron nitride (BN) tube. The entire experimental setup is placed in a six-sided press. The temperature is first raised to 1500 °C, then a pressure of 8 GPa is applied and held at that temperature for 5 hours. After the pressure is released and the temperature is cooled, the mold is disassembled, the mold is broken, and the residual boron nitride on the surface is removed. Finally, the sample is placed in deionized water to dissolve the sodium chloride, and then placed in acid to dissolve the Ni-Co alloy, ultimately obtaining N-doped two-dimensional diamond.

[0049] Example 2

[0050] A method for preparing two-dimensional diamond includes the following steps: Graphene is ball-milled in a BH3 plasma atmosphere at a speed of 1000 rpm. The ball mill operates for 30 minutes and then automatically stops for 30 minutes, with a total milling time of 4 hours. The pressure of the milling atmosphere is 0.1 MPa, resulting in sample A. A 100 nm thick Ni-Mn alloy layer is deposited on a 2 mm thick sodium chloride sheet, resulting in sample B. Samples A and B are stacked alternately to a thickness of 10 mm. The stacked samples are then cut to the required size and placed in a boron nitride (BN) tube. The entire experimental setup is placed in a six-sided press. The temperature is first raised to 1600 °C, then a pressure of 10 GPa is applied and the temperature is maintained for 7 hours. After the pressure is released and the temperature is cooled, the mold is disassembled, and the residual boron nitride on the surface is removed. Finally, the sample is placed in deionized water to dissolve the sodium chloride, and then placed in acid to dissolve the Ni-Mn alloy, ultimately obtaining boron-doped two-dimensional diamond.

[0051] Example 3

[0052] A method for preparing two-dimensional diamond includes the following steps: Graphene is ball-milled in an Ar plasma atmosphere at a speed of 800 rpm. The ball mill operates for 30 minutes and then automatically stops for 30 minutes, with a total milling time of 6 hours. The pressure of the milling atmosphere is 0.1 MPa, resulting in sample A. A 100 nm thick Ni-Fe-Mn alloy layer is deposited on a 2 mm thick sodium chloride sheet, resulting in sample B. Samples A and B are stacked alternately to a thickness of 10 mm. The stacked samples are then cut to the required size and placed in a boron nitride (BN) tube. The entire experimental setup is placed in a six-sided press. The temperature is first raised to 1700 °C, then a pressure of 12 GPa is applied and the temperature is maintained for 12 hours. After the pressure is released and the temperature is cooled, the mold is disassembled, and the residual boron nitride on the surface is removed. Finally, the sample is placed in deionized water to dissolve the sodium chloride, and then placed in alkali to dissolve the Ni-Fe-Mn alloy, ultimately yielding pure two-dimensional diamond.

[0053] Comparative Example 1

[0054] Same as Example 1, except that the temperature in the six-sided top press is adjusted from 1500°C to 1000°C.

[0055] Comparative Example 2

[0056] Same as Example 2, except that the pressure in the six-sided top press is adjusted from 10GPa to 4GPa.

[0057] The results showed that no diamond samples were obtained in Comparative Example 1 and Comparative Example 2; the samples remained graphite phase.

[0058] Test items and methods:

[0059] The two-dimensional diamond prepared in Example 1 was verified to be diamond using Raman spectroscopy. Figure 3 The Raman spectrum of Comparative Example 1 still contains a large amount of graphite and only a small amount of diamond. Figure 4 ).

[0060] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for preparing doped two-dimensional diamond, characterized in that, The process includes the following steps: ball milling graphene or graphite in a gas plasma atmosphere to obtain sample A; vapor deposition of a catalyst alloy on a sodium chloride sheet to obtain sample B; alternating stacking of sample A and sample B and placing them in a boron nitride tube, maintaining temperature and pressure using a six-sided high-temperature and high-pressure technique; after pressure relief and temperature cooling, disassembling the mold, removing residual boron nitride, and then removing sodium chloride and the catalyst alloy to obtain doped two-dimensional diamond. The specific operation steps of the ball milling process include: the ball mill speed is 400-1500 rpm, the ball mill works for 30 minutes and then automatically stops for 30 minutes, the total ball milling time is 1-6 hours, and the pressure of the ball milling atmosphere is 0.1 MPa; The specific operation steps of the six-sided high temperature and high pressure technology include: heating temperature of 1500-1700℃, and after reaching the temperature value, increasing the pressure to 8-12 GPa, and continuing the reaction at this temperature and pressure for 5-12 hours. The gas plasma is selected from one of N2, H2, SF6, CHF3, PH3, BH3 and SiH4; The catalyst alloy is selected from one of Ni-Cr-Fe alloy, Ni-Fe-Mn alloy, Ni-Co alloy, Ni-Cr alloy, and Ni-Mn alloy.

2. The method according to claim 1, characterized in that, The thickness of the sodium chloride sheet is 1-2 mm.

3. The method according to claim 1, characterized in that, The thickness of the catalyst alloy layer deposited on sodium chloride sheet is 10-200 nm.

4. The method according to claim 1, characterized in that, The total thickness of the samples A and B stacked alternately is 10 mm.

5. The method according to claim 1, characterized in that, The specific steps for removing sodium chloride and catalyst alloy include: first placing the sample in water to dissolve the sodium chloride, and then placing the sample in an acidic or alkaline solution to dissolve the catalyst alloy, thereby achieving the removal of sodium chloride and catalyst alloy.

6. A two-dimensional diamond, characterized in that, It is prepared by the method described in any one of claims 1-5.

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