阅读说明：本技术 一种3c-碳化硅二维单晶纳米片的制备方法 (Preparation method of 3C-silicon carbide two-dimensional single crystal nanosheet ) 是由 杜晓波 万宁 段明娜 刘红梅 尉国栋 周密 纪媛 付成伟 韩炜 于 2020-04-03 设计创作，主要内容包括：本发明公开了一种3C-碳化硅单晶二维纳米片的制备方法,包括以下步骤：先将经中子辐射的3C晶相的碳化硅纳米线用HF和HCl配置好的混合酸超声酸洗、依次通过去离子水和无水乙醇洗涤,真空干燥；然后再将酸处理过的碳化硅纳米线与氯化铵或掺杂源混合均匀后密封在石英管中；最后再将装有样品的石英管在马弗炉中加热处理,加热完成后样品随炉自然冷却到室温后取出,再将样品先后依次经无水乙醇和去离子水超声清洗,真空干燥后即可；本发明碳化硅具有纳米尺度均匀,晶体质量好,单分散性好,产量大,且制备合成过程简单、制备时间短,不需贵重设备,安全且易操作的特点,有利于实现大尺寸二维碳化硅材料的快速制备,且能实现同步掺杂和均匀掺杂。(The invention discloses a preparation method of a 3C-silicon carbide single crystal two-dimensional nanosheet, which comprises the following steps: firstly, ultrasonically pickling silicon carbide nanowires of 3C crystal phase subjected to neutron radiation by using mixed acid prepared by HF and HCl, washing the silicon carbide nanowires by deionized water and absolute ethyl alcohol in sequence, and drying the silicon carbide nanowires in vacuum; then uniformly mixing the silicon carbide nanowires subjected to acid treatment with ammonium chloride or a doping source, and sealing in a quartz tube; finally, heating the quartz tube with the sample in a muffle furnace, naturally cooling the sample to room temperature along with the furnace after heating, taking out, ultrasonically cleaning the sample with absolute ethyl alcohol and deionized water in sequence, and drying in vacuum; the silicon carbide of the invention has the characteristics of uniform nanoscale, good crystal quality, good monodispersity, high yield, simple preparation and synthesis process, short preparation time, no need of expensive equipment, safety and easy operation, is beneficial to realizing the rapid preparation of large-size two-dimensional silicon carbide materials, and can realize synchronous doping and uniform doping.)

1. A preparation method of 3C-silicon carbide two-dimensional single crystal nanosheets is characterized by comprising the following steps: the method comprises the following steps:

(1) performing neutron radiation treatment on the silicon carbide nanowire, namely putting the ultra-long 3C-SiC nanowire prepared by a chemical vapor deposition method into a fast neutron source for radiation, wherein the radiation range of the fast neutron source is 10k-10M eV, the radiation time is 70-85min, and the equivalent fast neutron fluence is 1 × 10¹³-1×10¹⁵n/cm²The total dose of gamma radiation is about 1 × 10⁵-3×10⁵rad；

(2) Acid treatment of silicon carbide nanowires: placing the 3C-SiC nanowires subjected to radiation treatment into a mixed acid solution of HF and HCl for ultrasonic dispersion for 5-20 minutes, then etching for 60-120 minutes by using ethanol and a ferric chloride solution, adding deionized water for dilution, repeating the steps for 5-8 times, washing a silicon carbide sample by using the deionized water and absolute ethanol in sequence after the pH value of the solution is greater than 4, centrifuging, and placing the silicon carbide sample into a 60-80 ℃ oven for vacuum drying for 24-36 hours for later use;

(3) doping the silicon carbide nanowires: respectively weighing a certain amount of the sample obtained in the step (2) and ammonium chloride or aluminum chloride or an n-type doping source or a p-type doping source, uniformly mixing, then placing into a quartz tube for sealing, placing the sealed quartz tube into a muffle furnace for heating, wherein the heating rate of the muffle furnace is 3-10 ℃/min, the heating temperature is 1000-1200 ℃, the heat preservation time is 60-600 minutes, and after the heating is finished, naturally cooling the sample to room temperature along with the furnace and then taking out;

(4) and (3) cleaning the sample, namely putting the sample obtained in the step (3) into 50-100m L of absolute ethyl alcohol solution for ultrasonic dispersion for 10-20 minutes, putting the centrifuged and filtered sample into 50-100m L of deionized water for ultrasonic dispersion for 10-20 minutes, and drying in vacuum to obtain the final product.

2. The preparation method of the 3C-silicon carbide two-dimensional single crystal nanosheet according to claim 1, wherein: the 3C-SiC nanowire in the step (1) is a 3C-SiC nanowire which is prepared by a chemical vapor deposition method, has the density of 3.21g/cc, the diameter of 0.1-0.6 mu m, the length of more than 100m and the length-diameter ratio of more than 200.

3. The preparation method of the 3C-silicon carbide two-dimensional single crystal nanosheet according to claim 1, wherein: the mixed acid in the step (2) is mainly prepared from the following components in a volume ratio of 1: 1 HF and HCl and contains 0.05g of sodium dodecylbenzenesulfonate per hundred milliliters of mixed acid.

4. The preparation method of the 3C-silicon carbide two-dimensional single crystal nanosheet according to claim 1, wherein: the ethanol and ferric chloride solution in the step (2) is prepared by dissolving 1-5g of ferric chloride in one hundred milliliters of ethanol solution.

5. The preparation method of the 3C-silicon carbide two-dimensional single crystal nanosheet according to claim 1, wherein: and (3) performing the silicon carbide nanowire acid treatment in the step (2) in an ultrasonic bath environment, wherein the whole solution is placed in a polytetrafluoroethylene container, the ultrasonic power of the ultrasonic bath is 150W, and the temperature of the solution is 40 ℃.

6. The preparation method of the 3C-silicon carbide two-dimensional single crystal nanosheet according to claim 1, wherein: the sample raw materials contained in the quartz tube in the step (3) are as follows: 0.05-0.2g of silicon carbide sample is obtained through the step (2), and 0.005-0.02g of ammonium chloride or aluminum chloride or n-type doping source or p-type doping source; the mass ratio of the silicon carbide sample to the ammonium chloride or aluminum chloride or the n-type doping source or the p-type doping source is 10: 1.

7. The preparation method of the 3C-silicon carbide two-dimensional single crystal nanosheet according to claim 1, wherein: the n-type doping source in the step (3) is as follows: one or more of melamine, ammonium bicarbonate, ammonium nitrate, urea, oxalic acid, red phosphorus and black phosphorus; the P-type doping source is one or more of boron, aluminum nitrate, aluminum chloride and boron chloride.

8. The preparation method of the 3C-silicon carbide two-dimensional single crystal nanosheet according to claim 1, wherein: the quartz tube in the step (3) is as follows: the length of the tube is 15cm, the inner diameter of the tube is 1cm, the wall thickness of the tube is 2mm, and the pressure in the sealed quartz tube is 1 mTorr.

Technical Field

The invention belongs to the technical field of preparation of silicon carbide nano materials, and particularly relates to a preparation method based on silicon carbide two-dimensional nanosheets.

Background

By two-dimensional material is meant a material with dimensions in two dimensions up to the nanometer scale (1-100nm), and its electrons are free to move (planar motion) only in the nanometer scale of two dimensions. Two-dimensional materials are confined to two-dimensional planes due to their carrier transport and thermal diffusion, making such materials exhibit many unique properties. So far, the two-dimensional materials mainly have structures such as nano-films, superlattices, quantum wells, nano-sheets and the like. Since the 2004 university of manchester, geom group successfully separated the two-dimensional graphene with a monoatomic layer, the two-dimensional nanomaterial has a unique nanosheet structure, a large surface area and extraordinary physicochemical properties, and has attracted great interest to researchers. Since then, many other types of two-dimensional nanomaterials, including black phosphorus, molybdenum disulfide, transition metal carbides, MXene, nitrides, carbonitrides, layered double hydroxides, MOF nanoplates, and the like, have become hot research points in the semiconductor nano field. The two-dimensional nanosheet material has a series of excellent physicochemical properties such as high mechanical flexibility, large specific surface area, rich active sites, stable chemical properties and the like, and is widely applied to various fields such as catalysis, biology, electrochemical energy storage and the like, such as photo/electro-catalysts, semiconductor photoelectric devices, lithium batteries, nuclear magnetic resonance imaging and the like.

3C-silicon carbide, as a third-generation semiconductor which is the most mature in research and has the most commercial application value, becomes a research hotspot in the field of novel semiconductor materials due to the characteristics of wide band gap, strong thermal stability, high-thermal-conductivity current carriers, high saturated transport rate, excellent radiation resistance and the like. However, the 3C-SiC nanomaterials reported at present almost focus on 3C-SiC one-dimensional nanowires and 3C-SiC thin film materials, and 3C-SiC two-dimensional nanosheets are still rarely reported, for example, document 1(acsappl. mater. interfaces,2019,11,42, 39109-. In the prior invention patent 1 (patent name: preparation method and flow of two-dimensional flaky SiC material), a microwave method is reported to synthesize a two-dimensional flaky SiC product, but the prepared two-dimensional flaky crystal structure is poor, and the sheets are mutually glued and assembled into a large-size irregular granular product. The prior invention patent 2 (patent name: synthesis of two-dimensional SiC ultrathin nano-structure by using graphene as template molten salt method and preparation method thereof) reports a method for preparing SiC ultrathin nano-sheets by using graphene as template high-temperature molten salt, but the crystallinity of SiC crystal prepared by the method is poor. Document 2(Journal of alloys and Compounds,5,345-. According to the reported invention patents and literature reports, the following defects exist in the process of preparing the two-dimensional silicon carbide nanosheet: (1) epitaxial growth on a substrate by means of a catalyst is required. By means of the catalyst epitaxial growth, not only the sample yield is small and easy to be polluted by doping of metal, but also an expensive single crystal substrate is required, and the method is obviously not suitable for industrial mass production; (2) the product is impure and has poor crystallinity. Because most of the raw materials in the carbothermic reduction technology adopt silicon dioxide, the self property of the silicon dioxide easily causes low purity of the product and is easily polluted by amorphous silicon oxide; (3) effective doping and simultaneous doping cannot be achieved. (4) The product cost is high. Most reports require expensive equipment such as chemical vapor deposition systems, precise temperature control and gas routing systems, and cumbersome manufacturing processes. Therefore, the preparation of the high-quality 3C-SiC two-dimensional single crystal nanosheet still faces a plurality of problems, and a universal, low-cost and high-quality preparation method is urgently needed to be developed.

Disclosure of Invention

The invention relates to a preparation method of a synchronously-doped 3C-silicon carbide two-dimensional single crystal nanosheet.

Specifically, 3C-silicon carbide nanowires treated by neutron radiation and mixed acid of HF and HCl are used as templates, ammonium chloride is used as an etching agent and a doping source (or aluminum chloride and an n-type or p-type doping source), and the single crystal nanowires are dissociated into two-dimensional nanosheets along a specific crystal orientation direction by a high-temperature heating method under the combined action of high-pressure chloride ions and the doping ions, so that the uniformly-doped silicon carbide two-dimensional single crystal nanosheets are finally obtained. The invention provides a preparation method of a SiC two-dimensional nanosheet, which has the advantages of high crystal quality, high yield, no need of expensive equipment, an accurate gas control system and a doping system, safety and easiness in operation. The invention is expected to solve the bottleneck problems that 3C-silicon carbide two-dimensional nano materials are difficult to prepare in high quality and synchronous doping and uniform doping cannot be effectively realized based on the traditional carbon thermal reduction technology and the single crystal substrate epitaxy technology at present.

The invention discloses a preparation method of uniformly-doped 3C-silicon carbide single crystal two-dimensional nanosheets, which comprises the following steps:

(1) weighing 10 g of ultra-long 3C-SiC nanowires prepared by a chemical vapor deposition method, putting the nanowires into a lead box, and putting the lead box into a neutron activation chamber. The nanowires are radiated in a fast neutron source (the radiation range is 10k-10M eV), the radiation time is 70-85min, and the equivalent speed is highNeutron fluence of 1 × 10¹³-1×10¹⁵n/cm2, total dose of gamma radiation of about 1 × 10⁵-3×10⁵rad。

(2) Placing the 3C-SiC nanometer subjected to radiation treatment into mixed acid for acid etching, wherein the mixed acid is formed by mixing HF and HCl solutions in a volume ratio of 1: 1, each hundred milliliters of the solution contains 0.05g of sodium dodecyl benzene sulfonate, the mixed acid solution of the silicon carbide nanowire is placed in a polytetrafluoroethylene container, ultrasonically dispersing the mixed acid solution of the silicon carbide nanowire for 5-20 minutes, then etching for 60-120 minutes through the mixed acid and ferric chloride solution, adding deionized 0-50 water for dilution, repeating the process for 5-8 times, after the pH value of the solution is more than 4, washing a silicon carbide sample by removing 50-100m L deionized water and 50-100m L absolute ethyl alcohol in sequence, centrifuging under the conditions of 40000r/min and 5-10min, and then placing in an oven at 60-80 ℃ for vacuum drying for 24-36 hours for later use.

(3) Doping the silicon carbide nanowires: 0.05-0.2g of silicon carbide obtained in the step (2) and 0.005-0.02g of ammonium chloride (or aluminum chloride, n-type or p-type doping source) are weighed respectively, and the mass ratio of the silicon carbide to the ammonium chloride (or aluminum chloride, n-type or p-type doping source) is 10: 1. And then the samples are uniformly mixed and then are put into a quartz tube with the length of 15cm, the inner diameter of the tube of 1cm and the wall thickness of the tube of 2mm, and the pressure in the quartz tube is sealed by 1 mTorr after the tube is sealed. And (3) putting the sealed quartz tube into a muffle furnace for heating, wherein the heating rate is 3-10 ℃ per minute, the heating temperature is 1000-1200 ℃, the heat preservation time is 60-600 minutes, and the sample is naturally cooled to room temperature along with the furnace and then taken out after the heating is finished.

(4) And (3) cleaning the sample, namely putting the reactant obtained in the step (3) into 50-100m L of absolute ethyl alcohol solution for ultrasonic dispersion for 10-20 minutes, then centrifuging, wherein the centrifuging condition is 4000-5000r/min, centrifuging for 5-10 minutes, putting the sample into deionized water again for purification again by the same method, repeatedly operating for 3-6 times, removing impurities such as silicon dioxide on the surface of the sample, and drying in vacuum to obtain the final product.

According to the scheme, the silicon carbide nano-wires treated by HF and HCl mixed acid are used as templates of the two-dimensional nano-sheets, ammonium chloride is used as an etching agent and a doping source (or aluminum chloride and an n-type or p-type doping source), and the nano-wires are dissociated into the two-dimensional nano-sheets along a specific crystal orientation direction under the combined action of high-pressure chloride ions and doping ions by a high-temperature heating method, so that synchronous doping and uniform doping of the silicon carbide two-dimensional single crystal nano-sheets are promoted.

Has the advantages that: compared with the reported silicon carbide two-dimensional nanosheet

1) The method has the main advantages that the prepared 3C-SiC two-dimensional single crystal nanosheet has the advantages of high crystal quality, good crystallinity, uniform nanosheet thickness, good monodispersity and the like. In addition, because the invention takes the single crystal nano wire as the template, the nano wire is dissociated along the crystal face of the silicon carbide (111) through the high-temperature dissociation reaction, so the 3C-SiC two-dimensional nano sheet also has the two-dimensional nano sheet with controllable size and capable of realizing a single atomic layer, and the preparation of the triangular, hexagonal and wafer two-dimensional nano sheet.

2) The 3C-SiC two-dimensional nanosheet prepared by the method disclosed by the invention is simple in preparation process, high in yield, low in preparation cost, safe and easy to operate, and is expected to realize industrial large-scale low-cost production.

3) The 3C-SiC two-dimensional nanosheet prepared by the method not only can realize synchronous doping, n-type doping and p-type doping in the nanosheet forming process, but also has the characteristics of simple doping process, uniform doping, various doping types, capability of realizing synchronous doping of two dopants, no need of expensive growth equipment and doping equipment and the like.

Drawings

FIG. 1 is an XRD pattern of a 3C-silicon carbide two-dimensional single-crystal nanosheet prepared in the first embodiment of the present invention;

FIG. 2 is a TEM image of a 3C-silicon carbide two-dimensional single-crystal nanosheet prepared in the first embodiment of the present invention;

fig. 3 is a transmission electron microscope Selected Area Electron Diffraction (SAED) diagram of the 3C-silicon carbide two-dimensional single crystal nanosheet prepared in the first embodiment of the present invention.

Detailed Description

In order to make the technical solution of the present invention clear, the technical solution of the present invention is fully described in detail below.