A SiC nanowire core-shell heterojunction material, its preparation method and application

Abstract

The present invention belongs to the technical field of semiconductor nanowire material preparation, and discloses a SiC nanowire core-shell heterojunction material, a preparation method thereof and an application. The SiC nanowire core-shell heterojunction material comprises a core body and a shell layer, and the shell layer is uniformly coated on the core body; the core body is a silicon carbide nanowire; the shell layer is any one of graphene, carbon, silicon, silver, sulfur and boron nitride; the preparation method is as follows: after mixing silicon carbide nanowires with a shell layer raw material, under a vacuum condition, heat preservation treatment A is carried out at 500-1550 °C, and after cooling, a silicon carbide nanowire core-shell heterojunction material is obtained; the shell layer material is one or more of polystyrene, ammonium tetrachloride, nickel chloride, silver nitrate, silver carbonate, borane ammonium and sublimed sulfur powder. The method of the present invention does not need to prepare a precursor, can directly sinter a nanowire core-shell heterostructure in one step, has a simple and convenient process, effectively reduces the process cost, and is beneficial to realizing industrial large-scale production.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor nanowire material preparation, and particularly relates to a SiC nanowire core-shell heterojunction material, a preparation method thereof, and an application thereof. Background Art

[0002] As one of the most important optoelectronic devices, ultraviolet detectors have broad application prospects in the fields of military and civilian sensors, environmental and biological detection, space communication, and astronomical research, and have developed rapidly in the past few decades. As a third-generation semiconductor material, silicon carbide (SiC) is a very promising candidate material for developing high-sensitivity, high-sensitivity, high-voltage, and high-temperature ultraviolet optoelectronic detection devices in the ultraviolet region due to its wide bandgap of 2.4 - 3.3 eV and excellent thermal stability and reliability.

[0003] In the past few decades, one-dimensional (1D) semiconductor nanowires (NWs) have attracted wide attention as building blocks for various nanoscale optoelectronic detectors due to their large specific surface area, rich surface states, high light absorption efficiency, and unique electron transport characteristics compared with their corresponding bulk structures. In addition, the unique 1D structure can effectively reduce the active area of carriers while shortening the transport time, which is beneficial to the realization of high-response high-performance optoelectronic detectors. In order to achieve more excellent nanowire devices, core-shell structured nanowires have emerged and have been widely studied and concerned. Core-shell structured nanowires have both the characteristics of nanowires themselves and the physical and chemical properties of different core-shell materials. In addition, the outer shell of core-shell structured nanowires can not only protect the nanowires but also adjust the optoelectronic properties of the nanowires. Therefore, core-shell structured nanowires are regarded as a kind of "intelligent material" leading the development of the next generation of new high-performance optoelectronic devices. However, it has deficiencies such as limited material types, cumbersome and time-consuming preparation processes, and uneven thickness and quality of the shell layer materials.

[0004] Therefore, the present invention provides a SiC nanowire core-shell heterojunction material, a preparation method thereof, and an application thereof. Summary of the Invention

[0005] In order to solve the above-mentioned deficiencies in the prior art, the present invention provides a SiC nanowire core-shell heterojunction material, a preparation method thereof, and an application thereof.

[0006] The SiC nanowire core-shell heterojunction material, a preparation method thereof, and an application thereof of the present invention are realized through the following technical solutions:

[0007] The first object of the present invention is to provide a SiC nanowire core-shell heterojunction material, including a core body and a shell layer, and the shell layer is uniformly coated on the core body;

[0008] The core body is a silicon carbide nanowire;

[0009] The shell layer is any one of graphene, carbon, silicon, silver, sulfur, and boron nitride.

[0010] Furthermore, the coating thickness of the shell layer is 10 - 30 nm.

[0011] Furthermore, the silicon carbide nanowires are p-type silicon carbide nanowires doped with a p-type doping source or n-type silicon carbide nanowires doped with an n-type doping source.

[0012] Furthermore, the p-type doping source is any one or more of boron, aluminum, aluminum nitrate, aluminum chloride, and boron chloride;

[0013] The n-type doping source is any one or more of melamine, ammonium bicarbonate, ammonium nitrate, urea, oxalic acid, red phosphorus, and black phosphorus.

[0014] Furthermore, the p-type silicon carbide nanowires or n-type silicon carbide nanowires are obtained through the following steps:

[0015] After mixing single-crystal silicon carbide nanowires with a p-type doping source or an n-type doping source, under vacuum conditions, heat preservation treatment B is carried out at a temperature of 1000 - 1400 °C, followed by annealing treatment to obtain doped n-type silicon carbide nanowires or p-type silicon carbide nanowires;

[0016] Among them, the mass ratio of single-crystal silicon carbide nanowires to the p-type doping source or n-type doping source is 8 - 12:1;

[0017] The heating rate of the heat preservation treatment B is 3 - 10 °C / min, and the heat preservation time is 60 - 600 min;

[0018] The vacuum condition of the heat preservation treatment B is provided by a platinum tube. After loading single-crystal silicon carbide nanowires and a p-type doping source or an n-type doping source into the platinum tube, it is sealed so that the pressure inside the platinum tube is 1 mTorr, and then the heat preservation treatment B is directly carried out on the platinum tube sealed with single-crystal silicon carbide nanowires and a p-type doping source or an n-type doping source.

[0019] The second object of the present invention is to provide a preparation method of the above SiC nanowire core-shell heterojunction material, including the following steps:

[0020] After mixing silicon carbide nanowires with the shell layer raw material, under vacuum conditions, heat preservation treatment A is carried out at a temperature of 500 - 1550 °C, and after cooling, a silicon carbide nanowire core-shell heterojunction material is obtained.

[0021] Furthermore, the shell layer material is one or more of polystyrene, ammonium tetrachloride, nickel chloride, silver nitrate, silver carbonate, ammonium borane, and sublimed sulfur powder.

[0022] Further, the mass ratio of the silicon carbide nanowires to the shell material is 1.2 to 42:1.

[0023] Further, the heating rate of the heat preservation treatment A is 3 to 10 °C / min, and the heat preservation time is 60 to 600 min.

[0024] Further, the vacuum condition of the heat preservation treatment A is provided by a platinum tube. After loading the silicon carbide nanowires and the shell material into the platinum tube, it is sealed so that the pressure inside the platinum tube is 1 mTorr, and then the platinum tube sealed with the silicon carbide nanowires and the shell material is directly subjected to the heat preservation treatment B.

[0025] The third object of the present invention is to provide an application of the above SiC nanowire core-shell heterojunction material in the preparation of an ultraviolet photodetector.

[0026] Further, the ultraviolet photodetector is prepared by the following steps:

[0027] The SiC nanowire core-shell heterojunction material is uniformly dispersed in a solvent to obtain a nanowire suspension; and the nanowire suspension is drop-coated on a substrate. After drying, electron beam thermal evaporation is carried out to deposit electrodes and annealing treatment in sequence, and then the ultraviolet photodetector is obtained.

[0028] Further, the solvent is one or both of isopropyl alcohol and ethylene glycol;

[0029] The substrate is a silicon substrate;

[0030] The dosage ratio of the SiC nanowire core-shell heterojunction material to the solvent is 1 to 5 mg: 5 to 15 mL.

[0031] Further, the single-crystal silicon carbide nanowires are obtained by the following steps:

[0032] The silicon carbide aerogel is cleaned and then immersed in an acid solution, and subjected to ultraviolet ultrasonic treatment. Subsequently, it is left to stand until the solution is stratified, the supernatant is poured out, a water solvent is added to the remaining solution, and ultraviolet ultrasonic treatment is carried out again for 0.5 to 3 h. After standing again, the supernatant is poured out. The above steps are repeated at least 3 times. The solution part from which the supernatant is removed is subjected to solid-liquid separation. After the obtained solid-phase component is dried and then annealed, the single-crystal silicon carbide nanowires are obtained;

[0033] Among them, the temperature of the annealing treatment is 500 to 1000 °C, and the annealing time is 60 to 120 min.

[0034] Further, the acid solution is a 98% hydrofluoric acid solution or an 85% hot concentrated phosphoric acid to remove the residual silica layer on the surface of the silicon carbide nanowire aerogel prepared by the carbothermal reduction method, and the dosage ratio of the silicon carbide aerogel to the acid solution is 1 g: 20 to 100 mL.

[0035] Furthermore, the addition amount of the aqueous solution is equal to the volume of the supernatant poured out.

[0036] Furthermore, the process of each of the ultraviolet ultrasonic treatments is as follows: the ultrasonic power is 150 W, the ultrasonic time is 0.5 - 3 h, and the ultrasonic temperature is 30 - 50 °C; the wavelength of the ultraviolet light is 365 nm, and the power is 5 - 10 W.

[0037] Furthermore, when preparing the single-crystal silicon carbide nanowires, the solid-phase component is also washed before the drying treatment, and the washing treatment is to wash the solid-phase component with an aqueous solvent until the washing liquid is neutral (pH = 7).

[0038] Furthermore, the crystal phase of the single-crystal silicon carbide nanowires is the 3C phase, the density is 3.21 g / cc, the size distribution is uniform with a diameter of 50 - 300 nm and a length of 10 - 100 μm.

[0039] Furthermore, the silicon carbide aerogel is prepared by a carbothermal reduction method.

[0040] Compared with the prior art, the present invention has the following beneficial effects:

[0041] The SiC nanowire core-shell heterojunction material constructed by the present invention can realize the surface functionalization of the nanowires, which can not only improve its stability and specific surface area (the specific surface area of SiC nanowires is 5.2 m 2 / g, and the specific surface area of SiC-graphene is 22 m 2 / g), but also passivate the surface, minimizing the interference of moisture and oxygen to the greatest extent, and can contribute to the development of highly stable and highly sensitive devices.

[0042] Under vacuum conditions, the present invention conducts high-temperature heating on silicon carbide nanowires and shell layer raw materials. During the high-temperature heating process, the doping source is ablated and evaporated to form atomic clusters, which then condense on the surface of the silicon carbide nanowires upon cooling. This method does not require the preparation of a precursor, and can directly sinter the nanowire core-shell heterostructure in one step. The process is simple and convenient, effectively reducing the process cost, facilitating large-scale industrial production. Moreover, the sealed tube method can effectively isolate air, prevent the generation of impurities, and can prepare a high-quality and high-purity nanowire core-shell structure. The grown shell layer material can achieve uniform coating, and the layer thickness is controllable. The core layer and the shell layer are tightly combined. The surface of the nanowires is often the source of structural defects and electronic defects. Correctly selecting the shell material can protect the core body and significantly improve the electrical, mechanical, and optical properties of the core body. Through this method, silicon carbide nanowire core-shell heterostructures with different shell materials can be prepared, which can regulate the surface quality of the nanowires, form stable and novel advanced nanostructure properties, and are widely used in optoelectronic devices, biomedicine, catalysis, batteries, food and health products, plastics, environmental protection and other fields.

[0043] The present invention provides a simple and effective way to assemble nanostructures for fabricating ultraviolet optoelectronic devices based on single-crystalline silicon carbide (SiC) radial heterostructure core-shell nanowires. It can realize nanowires with special functional structures such as p-n core-shell heterojunctions based on single nanowires. This method has the advantages of simple process, low cost, the ability to fabricate multiple groups of single-nanowire optoelectronic devices, high efficiency, and safe and easy operation. Fabricating hybrid nanostructures composed of two or more components provides new possibilities for light detection in a wide ultraviolet spectral range.

[0044] The present invention is almost universal for all low-dimensional nanostructures and can be applied to the preparation of other semiconductor nanofilms. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 XRD pattern of the SiC nanowire aerogel prepared by the present invention;

[0046] Figure 2 XRD pattern of the SiC nanowire core-shell heterojunction material prepared in Example 3 of the present invention;

[0047] Figure 3 TEM image of the SiC nanowire core-shell heterojunction material prepared in Example 1 of the present invention;

[0048] Figure 4 TEM image of the SiC nanowire core-shell heterojunction material prepared in Example 2 of the present invention;

[0049] Figure 5 TEM image of the SiC nanowire core-shell heterojunction material prepared in Example 3 of the present invention;

[0050] Figure 6 TEM image of the SiC nanowire core-shell heterojunction material prepared in Example 5 of the present invention;

[0051] Figure 7 TEM image of the SiC nanowire core-shell heterojunction material prepared in Example 6 of the present invention;

[0052] Figure 8 Raman image of the SiC nanowire core-shell heterojunction material prepared in Example 1 of the present invention;

[0053] Figure 9 Ultraviolet optoelectronic detection performance image of the ultraviolet photodetector prepared in Example 22 of the present invention; wherein, Figure 9 (a) I-V curve of the ultraviolet photodetector prepared in Example 22 in the dark state and under irradiation of a 365 nm ultraviolet light source; Figure 9 (b) Logarithmic image of the I-V curve in Fig. (a); Figure 9(c) is the I-T curve of the device under 365 nm ultraviolet light irradiation in the on / off state at different bias voltages; Figure 9 (d) is the I-T curve of the device under irradiation with different optical power densities of 365 nm ultraviolet light;

[0054] Figure 10 This is the ultraviolet photodetection performance diagram of the ultraviolet photodetector prepared in Example 23 of the present invention; among them, Figure 10 (a) and Figure 10 (b) are the I-V curves of the ultraviolet photodetector prepared in Example 23 in the dark state and under 365 nm ultraviolet light source irradiation; Figure (c) is the I-T curve of the device under 365 nm ultraviolet light irradiation in the on / off state at different bias voltages; Figure 10 (d) is the I-T curve of the device under irradiation with different optical power densities of 365 nm ultraviolet light. Detailed implementation manners

[0055] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention.

[0056] The present invention provides a SiC nanowire core-shell heterojunction material, including silicon carbide nanowires as the core body and a shell layer coated on the surface of the silicon carbide nanowires.

[0057] It should be noted that the present invention does not limit the specific type of silicon carbide nanowires. P-type silicon carbide nanowires doped with a p-type doping source can be selected, or n-type silicon carbide nanowires doped with an n-type doping source can be selected. Moreover, the present invention does not limit the specific types of the p-type doping source and the n-type doping source, and corresponding selections can be made according to actual needs. Optionally, the p-type doping source of the present invention can be selected from any one or more of boron, aluminum, aluminum nitrate, aluminum chloride, and boron chloride. Optionally, the n-type doping source of the present invention can be selected from any one or more of melamine, ammonium bicarbonate, ammonium nitrate, urea, oxalic acid, red phosphorus, and black phosphorus.

[0058] The present invention does not limit the specific composition of the shell layer, as long as it can form a heterojunction structure with the surface of the silicon carbide nanowires. Optionally, the shell layer of the present invention can be selected from any one of graphene, carbon, silicon, silver, sulfur, and boron nitride.

[0059] The present invention does not limit the coating thickness of the shell layer on the surface of the silicon carbide nanowires, as long as a heterojunction structure can be formed after coating. Optionally, the coating thickness of the shell layer of the present invention is selected to be 10 - 30 nm to enable the device to maintain high light absorption performance and a low resistance state.

[0060] The present invention does not limit the specific preparation method of the SiC nanowire core-shell heterojunction material, as long as it can form a SiC nanowire core-shell heterojunction material with a core-shell heterojunction structure, where the core is a silicon carbide nanowire and a shell layer is coated on the core. Optionally, the present invention is prepared by the following method:

[0061] After mixing the silicon carbide nanowires with the shell layer raw material, under vacuum conditions, heat preservation treatment A is carried out at a temperature of 500 - 1550 °C, and after cooling, a silicon carbide nanowire core-shell heterojunction material is obtained;

[0062] It should be noted that the present invention does not limit the specific composition of the shell layer raw material. The corresponding shell layer raw material is selected according to the actual required shell layer composition, as long as the selected shell layer raw material can form a shell layer on the surface of the silicon carbide nanowires after heat preservation treatment A. For example, if graphene is desired as the shell layer, "polystyrene + nickel chloride" or "tetraammonium chloride + nickel chloride" can be selected as the shell layer raw material; if carbon is desired as the shell layer, polystyrene can be selected as the shell layer raw material; if silicon is desired as the shell layer, silicon powder with a particle size of 200 - 500 meshes can be selected as the shell layer raw material; if silver is desired as the shell layer, silver nitrate or silver carbonate can be selected as the shell layer raw material; if boron nitride is desired as the shell layer, ammonium borane can be selected as the shell layer raw material; if sulfur is desired as the shell layer, sublimed sulfur powder can be selected as the shell layer raw material.

[0063] The present invention does not limit the specific method of providing a vacuum condition for heat preservation treatment A, as long as it can ensure that heat preservation treatment A is carried out under vacuum conditions. Optionally, the present invention provides a vacuum condition for heat preservation treatment A in the following way: After loading the silicon carbide nanowires and the shell layer raw material into a platinum tube, the platinum tube is sealed using a hydrogen-oxygen flame vacuum tube sealing machine, so that the inside of the platinum tube is in a vacuum (such as the pressure inside the platinum tube is 1 mTorr), and then heat preservation treatment A is directly carried out on the platinum tube sealed with the silicon carbide nanowires and the shell layer raw material.

[0064] The present invention does not limit the specific heating rate and heat preservation time of heat preservation treatment A, as long as it can uniformly heat the preparation raw materials to 500 - 1550 °C at a stable rate. Optionally, the present invention controls the heating rate of heat preservation treatment A at 3 - 10 °C / min and the heat preservation time at 60 - 600 min.

[0065] The present invention also provides an ultraviolet light detector. The ultraviolet light detector of the present invention is prepared based on the above SiC nanowire core-shell heterojunction material, and its preparation method is as follows:

[0066] Step 1: Uniformly disperse the above-mentioned SiC nanowire core-shell heterojunction material in a solvent to obtain a nanowire suspension; then drop the nanowire suspension onto a substrate and subsequently perform a drying treatment to obtain a substrate with a nanowire layer coated on its surface.

[0067] It should be noted that the present invention does not limit the specific type of the solvent in Step 1, as long as it can form a homogeneous solution or suspension with the SiC nanowire core-shell heterojunction material. Optionally, the solvent used in the present invention is one or both of isopropyl alcohol and ethylene glycol.

[0068] The present invention does not limit the specific dosage relationship between the SiC nanowire core-shell heterojunction material and the solvent, as long as it can form a homogeneous solution or suspension. Optionally, the present invention controls the dosage ratio of the SiC nanowire core-shell heterojunction material to the solvent within the range of 1-5 mg:5-15 mL to ensure the full dispersion of the SiC nanowire core-shell heterojunction material in the solvent. Otherwise, too high a solution concentration will cause the nanowires to agglomerate, which is not conducive to subsequent tests.

[0069] The present invention does not limit the specific dispersion method of the SiC nanowire core-shell heterojunction material and the solvent, as long as it can help the SiC nanowire core-shell heterojunction material and the solvent to form a homogeneous solution or suspension. Optionally, the present invention uses ultrasonic waves for dispersion, and the present invention does not limit the specific power and time of ultrasonic waves, which can be flexibly selected according to the actual situation. If the power is high, the ultrasonic time is shortened, and vice versa, the ultrasonic time is extended.

[0070] The present invention does not limit the specific dosage of coating, and it can be selected accordingly according to the size of the substrate actually selected. For example, when selecting a silicon-based substrate with a size of 1 cm × 1 cm, 0.5-20 μL of the nanowire suspension is coated correspondingly.

[0071] The present invention does not limit the specific drying method in Step 1, as long as it can remove the solvent in the coated nanowire suspension to form a film. Optionally, the present invention dries in an oven at 60-80 °C for 20-60 min.

[0072] Step 2: Using the electron beam evaporation method, sequentially perform electrode evaporation and annealing treatment on the substrate with the nanowire layer coated on its surface after the drying treatment in Step 1, and then the ultraviolet photodetector is obtained.

[0073] In the present invention, by using a mask plate, high-energy electrons are used to bombard the target material in the crucible to melt it and then deposit it on the nanowire layer on the substrate, plating a high-purity and high-precision thin film, so as to realize electron beam evaporation of an electrode on the nanowire layer on the substrate, and then annealing treatment is performed in a vacuum annealing furnace at 800-1000 °C for 60-120 min, and then the ultraviolet photodetector is obtained;

[0074] The present invention does not limit the specific type and size of the mask, and can be adjusted according to the size of the substrate actually selected. Optionally, the present invention uses a nickel mesh with an electrode spacing of 10 μm as the mask.

[0075] Example 1

[0076] This example provides a SiC nanowire core-shell heterojunction material, including silicon carbide nanowires as the core and a shell layer coated on the surface of the silicon carbide nanowires.

[0077] In this example, n-type silicon carbide nanowires doped with an n-type doping source are used as the core, and graphene is used as the shell layer, and its preparation method is as follows:

[0078] 1) Preparation of n-type silicon carbide nanowires

[0079] The present invention does not limit the specific type of the n-type doping source used for preparing n-type silicon carbide nanowires, as long as n-type silicon carbide nanowires can be obtained. Optionally, in this example, red phosphorus is used as the n-type doping source. Weigh 0.1 g of single-crystal silicon carbide nanowires and 0.02 g of red phosphorus, mix them evenly and put them into a platinum tube with a tube length of 15 cm, an inner tube diameter of 1 cm, and a tube wall thickness of 2 mm. After sealing the tube, the pressure inside the platinum tube is 1 mTorr. Put the sealed platinum tube into a muffle furnace for heating, with a heating rate of 6 °C per minute, a heating temperature of 1200 °C, and a holding time of 300 min. After the heating is completed, the sample is taken out after being naturally cooled to room temperature in the furnace, and annealed at a temperature of 700 °C for 90 min in a tube furnace to obtain the doped n-type silicon carbide nanowires.

[0080] 2) Composite n-type silicon carbide nanowires with graphene

[0081] In this example, polystyrene and nickel chloride are used together as the raw materials for preparing the graphene shell layer. Weigh 0.0017 g of polystyrene, 0.0187 g of nickel chloride and the above 0.025 g of n-type silicon carbide nanowires, mix them evenly, put them into a platinum tube with a tube length of 15 cm, an inner tube diameter of 1 cm, and a tube wall thickness of 2 mm, and use a hydrogen-oxygen flame vacuum tube sealing machine to seal the platinum tube, so that the pressure inside the platinum tube is 1 mTorr. Then put the sealed platinum tube into a muffle furnace for heating, heat it to 1500 °C at a heating rate of 6 °C / min and hold for 300 min, and then take it out after being naturally cooled to room temperature in the furnace, and obtain the SiC nanowire core-shell heterojunction material, named SiC@graphene.

[0082] Example 2

[0083] This example provides a SiC nanowire core-shell heterojunction material, and the difference between this example and Example 1 is only that:

[0084] In this embodiment, carbon is used as the shell layer, and polystyrene is correspondingly selected as the raw material for the carbon shell layer. In this embodiment, the dosage of n-type silicon carbide nanowires is 0.07 g, and the dosage of polystyrene is 0.0017 g;

[0085] In this embodiment, the heat preservation temperature of the platinum tube is 900 °C.

[0086] The SiC nanowire core-shell heterojunction material obtained in this embodiment is named SiC@C.

[0087] Example 3

[0088] This embodiment provides a SiC nanowire core-shell heterojunction material, and the difference between this embodiment and Embodiment 1 is only that:

[0089] In this embodiment, silver is used as the shell layer, and silver nitrate is correspondingly selected as the raw material for the silver shell layer. In this embodiment, the dosage of n-type silicon carbide nanowires is 0.07 g, and the dosage of silver nitrate is 0.017 g;

[0090] In this embodiment, the heat preservation temperature of the platinum tube is 650 °C.

[0091] The SiC nanowire core-shell heterojunction material obtained in this embodiment is named SiC@Ag.

[0092] Example 4

[0093] This embodiment provides a SiC nanowire core-shell heterojunction material, and the difference between this embodiment and Embodiment 1 is only that:

[0094] In this embodiment, silicon is used as the shell layer, and 300-mesh silicon powder is correspondingly selected as the raw material for the silicon shell layer. In this embodiment, the dosage of n-type silicon carbide nanowires is 0.07 g, and the dosage of 300-mesh silicon powder is 0.017 g;

[0095] In this embodiment, the heat preservation temperature of the platinum tube is 1100 °C.

[0096] The SiC nanowire core-shell heterojunction material obtained in this embodiment is named SiC@Si.

[0097] Example 5

[0098] This embodiment provides a SiC nanowire core-shell heterojunction material, and the difference between this embodiment and Embodiment 1 is only that:

[0099] In this embodiment, sulfur is used as the shell layer, and sulfur powder is correspondingly selected as the raw material for the sulfur shell layer. In this embodiment, the dosage of n-type silicon carbide nanowires is 0.07 g, and the dosage of sulfur powder is 0.0017 g;

[0100] In this embodiment, the heat preservation temperature of the platinum tube is 1100 °C.

[0101] Name the SiC nanowire core-shell heterojunction material obtained in this example as SiC@S.

[0102] Example 6

[0103] This example provides a SiC nanowire core-shell heterojunction material, and the difference between this example and Example 1 is only that:

[0104] In this example, boron nitride is used as the shell layer, and borane ammonium is correspondingly selected as the raw material for the boron nitride shell layer. And in this example,

[0105] The dosage of n-type silicon carbide nanowires is 0.07 g, and the dosage of borane ammonium is 0.00318 g;

[0106] The heat preservation temperature of the platinum tube in this example is 900 °C.

[0107] Name the SiC nanowire core-shell heterojunction material obtained in this example as SiC@BN.

[0108] Example 7

[0109] This example provides a SiC nanowire core-shell heterojunction material, and the difference between this example and Example 1 is only that:

[0110] In this example, p-type silicon carbide nanowires doped with a p-type doping source are used as the core, and aluminum nitrate is used as the p-type doping source.

[0111] Example 8

[0112] This example provides a SiC nanowire core-shell heterojunction material, and the difference between this example and Example 1 is only that:

[0113] In this example, when preparing n-type silicon carbide nanowires:

[0114] Ammonium nitrate is used as the n-type doping source, the dosage of single-crystal silicon carbide nanowires is 0.05 g, and the mass ratio of ammonium nitrate to single-crystal silicon carbide nanowires is 1:8;

[0115] During the sintering treatment, the heating rate is 3 °C / min, the treatment temperature is 1000 °C, and the heat preservation time is 600 min;

[0116] The annealing temperature is 500 °C, and the annealing time is 60 min.

[0117] In this example, when compounding n-type silicon carbide nanowires and graphene:

[0118] The dosage of n-type silicon carbide nanowires is 0.01 g, the dosage of polystyrene is 0.0007 g, and the dosage of nickel chloride is 0.0075 g;

[0119] During the sintering process, the heating rate is 3 °C / min, the processing temperature is 1400 °C, and the holding time is 600 min.

[0120] Example 9

[0121] This example provides a SiC nanowire core-shell heterojunction material, and the difference between this example and Example 1 is only that:

[0122] In this example, when preparing n-type silicon carbide nanowires:

[0123] Ammonium bicarbonate is used as the n-type doping source, the amount of single-crystal silicon carbide nanowires is 0.2 g, and the mass ratio of ammonium bicarbonate to single-crystal silicon carbide nanowires is 1:12;

[0124] During the sintering process, the heating rate is 10 °C / min, the processing temperature is 1400 °C, and the holding time is 60 min;

[0125] The annealing temperature is 1000 °C and the annealing time is 120 min.

[0126] In this example, when compounding n-type silicon carbide nanowires with graphene:

[0127] The amount of n-type silicon carbide nanowires is 0.04 g, the amount of polystyrene is 0.0028 g, and the amount of nickel chloride is 0.03 g;

[0128] During the sintering process, the heating rate is 10 °C / min, the processing temperature is 1550 °C, and the holding time is 60 min.

[0129] Example 10

[0130] This example provides a SiC nanowire core-shell heterojunction material, and the difference between this example and Example 2 is only that:

[0131] In this example, the amount of n-type silicon carbide nanowires is 0.04 g, and the amount of polystyrene is 0.0007 g;

[0132] The holding temperature of the platinum tube in this example is 800 °C.

[0133] Example 11

[0134] This example provides a SiC nanowire core-shell heterojunction material, and the difference between this example and Example 2 is only that:

[0135] In this example, the amount of n-type silicon carbide nanowires is 0.1 g, and the amount of polystyrene is 0.0028 g;

[0136] In this embodiment, the heat preservation temperature of the platinum tube is 1050 °C.

[0137] Example 12

[0138] This embodiment provides a SiC nanowire core-shell heterojunction material, and the difference between this embodiment and Example 3 is only that:

[0139] In this embodiment, the dosage of n-type silicon carbide nanowires is 0.04 g, and the dosage of silver nitrate is 0.01 g;

[0140] In this embodiment, the heat preservation temperature of the platinum tube is 500 °C.

[0141] Example 13

[0142] This embodiment provides a SiC nanowire core-shell heterojunction material, and the difference between this embodiment and Example 3 is only that:

[0143] In this embodiment, the dosage of n-type silicon carbide nanowires is 0.1 g, and the dosage of silver nitrate is 0.025 g;

[0144] In this embodiment, the heat preservation temperature of the platinum tube is 800 °C.

[0145] Example 14

[0146] This embodiment provides a SiC nanowire core-shell heterojunction material, and the difference between this embodiment and Example 4 is only that:

[0147] In this embodiment, the dosage of n-type silicon carbide nanowires is 0.04 g, and the dosage of 300-mesh silicon powder is 0.01 g;

[0148] In this embodiment, the heat preservation temperature of the platinum tube is 800 °C.

[0149] Example 15

[0150] This embodiment provides a SiC nanowire core-shell heterojunction material, and the difference between this embodiment and Example 4 is only that:

[0151] In this embodiment, the dosage of n-type silicon carbide nanowires is 0.1 g, and the dosage of 300-mesh silicon powder is 0.025 g;

[0152] In this embodiment, the heat preservation temperature of the platinum tube is 1400 °C.

[0153] Example 16

[0154] This embodiment provides a SiC nanowire core-shell heterojunction material, and the difference between this embodiment and Example 5 is only that:

[0155] In this embodiment, the dosage of n-type silicon carbide nanowires is 0.04 g, and the dosage of sulfur powder is 0.001 g;

[0156] In this embodiment, the heat preservation temperature of the platinum tube is 800 °C.

[0157] Example 17

[0158] This embodiment provides a SiC nanowire core-shell heterojunction material, and the difference between this embodiment and Example 5 is only that:

[0159] In this embodiment, the amount of n-type silicon carbide nanowires used is 0.1 g, and the amount of sulfur powder used is 0.0025 g;

[0160] In this embodiment, the heat preservation temperature of the platinum tube is 1400 °C.

[0161] Example 18

[0162] This embodiment provides a SiC nanowire core-shell heterojunction material, and the difference between this embodiment and Example 6 is only that:

[0163] In this embodiment, the amount of n-type silicon carbide nanowires used is 0.04 g, and the amount of borane ammonium used is 0.00182 g;

[0164] In this embodiment, the heat preservation temperature of the platinum tube is 800 °C.

[0165] Example 19

[0166] This embodiment provides a SiC nanowire core-shell heterojunction material, and the difference between this embodiment and Example 6 is only that:

[0167] In this embodiment, the amount of n-type silicon carbide nanowires used is 0.1 g, and the amount of borane ammonium used is 0.00455 g;

[0168] In this embodiment, the heat preservation temperature of the platinum tube is 1000 °C.

[0169] Example 20

[0170] This embodiment provides a SiC nanowire core-shell heterojunction material, and the difference between this embodiment and Example 7 is only that:

[0171] In this embodiment, aluminum chloride is used as the p-type doping source.

[0172] Example 21

[0173] This embodiment provides a SiC nanowire core-shell heterojunction material, and the difference between this embodiment and Example 7 is only that:

[0174] In this embodiment, aluminum borochloride is used as the p-type doping source.

[0175] Example 22

[0176] This embodiment provides an ultraviolet light detector, and its preparation method is as follows:

[0177] 1) Prepare a nanowire suspension

[0178] In this embodiment, isopropanol is used as the solution, and 0.003 g of the SiC nanowire core-shell heterojunction material prepared in Example 1 is weighed. Through ultrasonic treatment, it is uniformly dispersed in 10 mL of isopropanol solution to obtain a nanowire suspension;

[0179] 2) Drop-coat the nanowire suspension onto the substrate

[0180] The present invention does not specifically limit the specific coating amount of the nanowire suspension on the substrate material. According to the actual selected size, the coating amount of the nanowire suspension can be flexibly adjusted. For example, in this embodiment, a 1 cm × 1 cm silicon oxide wafer is used as the substrate, and 10 μL of the above-mentioned nanowire suspension is taken with a pipette and uniformly drop-coated on the 1 cm × 1 cm silicon oxide wafer. Then, it is dried in an oven at 70 °C for 40 min, and then successively immersed in acetone, absolute ethanol, and deionized water for ultrasonic cleaning for 10 - 20 min, and the ultrasonic power is 150 - 350 W;

[0181] 3) Prepare the electrodes

[0182] The electron beam evaporation method is adopted. High-energy electrons bombard the target material in the crucible to melt it and then deposit it on the substrate to deposit a high-purity and high-precision thin film. In the present invention, using a mask, an electrode is electron beam evaporated on the ultraviolet light detector precursor, and then annealed in a vacuum annealing furnace at 900 °C for 90 min to obtain the ultraviolet light detector.

[0183] Example 23

[0184] This embodiment provides an ultraviolet light detector, and the difference in its preparation method from that of Example 22 is only that:

[0185] In this embodiment, the SiC nanowire core-shell heterojunction material of Example 2 is made into a nanowire suspension.

[0186] Example 24

[0187] This embodiment provides an ultraviolet light detector, and the difference in its preparation method from that of Example 22 is only that:

[0188] In this embodiment, the SiC nanowire core-shell heterojunction material of any one of Examples 2 - 21 is made into a nanowire suspension.

[0189] Example 25

[0190] This embodiment provides an ultraviolet light detector, and the difference in its preparation method from that of Example 22 is only that:

[0191] In this embodiment, ethylene glycol is used as the solution, and the amount of ethylene glycol is 5 mL.

[0192] In this embodiment, the amount of the SiC nanowire core-shell heterojunction material prepared in any one of Embodiments 1-21 is 0.001 g.

[0193] In this embodiment, the amount of the nanowire suspension is 0.5 μL.

[0194] In this embodiment, the drying treatment temperature is 60 °C, and the treatment time is 60 min.

[0195] In this embodiment, the annealing temperature is 800 °C, and the annealing time is 120 min.

[0196] Embodiment 26

[0197] This embodiment provides an ultraviolet photodetector, and the difference between its preparation method and that of Embodiment 22 is only that:

[0198] In this embodiment, isopropyl alcohol is used as the solution, and the amount of ethylene glycol is 15 mL.

[0199] In this embodiment, the amount of the SiC nanowire core-shell heterojunction material prepared in any one of Embodiments 1-21 is 0.005 g.

[0200] In this embodiment, the amount of the nanowire suspension is 20 μL.

[0201] In this embodiment, the drying treatment temperature is 80 °C, and the treatment time is 20 min.

[0202] In this embodiment, the annealing temperature is 1000 °C, and the annealing time is 60 min.

[0203] It should be noted that the single-crystalline silicon carbide nanowires in the above various embodiments of the present invention are obtained through the following steps: According to the dosage ratio of 1 g: 20 - 100 mL, for example, after cleaning 5 g of silicon carbide aerogel, it is immersed in 100 - 500 mL of 98% hydrofluoric acid solution of the weighed amount, under the irradiation of an ultraviolet lamp with a wavelength of 365 nm and a light power of 5 - 10 W, at a temperature of 30 - 50 °C, ultrasonic treatment is carried out with an ultrasonic power of 150 W for 0.5 - 3 h, then left standing for 30 - 500 min, the supernatant (90 - 450 mL) is poured out, and the remaining solution is solution A; then a certain amount of deionized water (90 - 450 mL) is added to solution A, and then ultrasonic dispersion treatment and separation are carried out by ultraviolet light. After repeating the above steps 5 - 8 times, solution A is placed in a centrifuge tube to obtain SiC nanowires by centrifugation, then it is dispersed into deionized water, and then centrifuged again. The above operation is repeated until the solution pH is 7, obtaining single-crystalline silicon carbide nanowires without impurities, monodispersed, with a crystal phase of 3C phase, a density of 3.21 g / cc, a diameter of 50 - 300 nm, and a length of 10 - 100 μm with a uniform size distribution, dried (such as dried in a vacuum drying oven at 60 °C for 4 h), and reserved.

[0204] It should also be noted that the present invention does not limit the specific operation of cleaning the silicon carbide aerogel, as long as the SiO2 layer on the surface of the silicon carbide aerogel can be removed. In this embodiment, optionally, the following process is adopted: The silicon carbide aerogel is respectively immersed in acetone, absolute ethanol, and deionized water and ultrasonically cleaned for 10 - 20 min.

[0205] The present invention does not limit the specific preparation method of the silicon carbide aerogel, as long as a clean silicon carbide aerogel can be obtained. In this embodiment, optionally, the silicon carbide aerogel prepared by the carbothermal reduction method is specifically prepared by the following steps:

[0206] Polysilane and vinyl compound are dissolved in organic solvent B, and under an anaerobic condition at 70 - 90 °C, Karstedt catalyst is used to catalyze the reaction for 4 - 8 h to obtain a polysilane gel; the polysilane gel is dried and then heat-treated to obtain a silicon carbide / carbon precursor aerogel, and then rice husk charcoal and silicon are added and mixed evenly, and then calcined at 1000 - 1800 °C for 0.5 - 5 h in an anaerobic argon atmosphere to obtain a silicon carbide aerogel, and the physical diagram of the obtained silicon carbide aerogel is as Figure 1 shown; wherein, when preparing the silicon carbide aerogel, the vinyl compound contains two or more vinyl groups;

[0207] The organic solvent B is one or more of cyclohexane, toluene, xylene, or benzene;

[0208] The polycarbosilane and the vinyl compound are mixed in any proportion, and the total mass of the polycarbosilane and the vinyl compound and the amount of the organic solvent B are in a ratio of 0.03 to 0.3 g:1 mL;

[0209] The drying is supercritical drying or freeze drying;

[0210] The amount ratio of the silicon carbide / carbon precursor aerogel, rice husk charcoal and silicon is 1-0.5:0.8:0.1-0.3;

[0211] The rice husk charcoal has a commercial particle size of less than 200 meshes and a purity of 99%.

[0212] Experimental part

[0213] (I) XRD test

[0214] The present invention performs XRD tests on the silicon carbide nanowire aerogel prepared by the present invention and the SiC@Ag core-shell heterojunction nanowire prepared in Example 3. The test results are as follows: Figure 1 and Figure 2 shown.

[0215] from Figure 1 and Figure 2 As shown, it can be seen that: by comparing the XRD patterns of the original silicon carbide nanowire aerogel material and the SiC@Ag core-shell heterojunction nanowire, it can be seen that diffraction peaks appear near 22°, 38°, 44°, 64°, and 77°, respectively. After comparison with the standard card and the actual situation of the sample, it is SiO2 and Ag single substances. Combined with the TEM characterization diagram, it is confirmed that the present invention successfully prepares the SiC@Ag core-shell heterojunction nanowire sample.

[0216] (II) TEM test

[0217] The present invention respectively carried out TEM tests on the SiC nanowire core-shell heterojunction materials prepared in Example 1, Example 2, Example 3, Example 4 and Example 5, and the test results are as follows: Figure 3 , Figure 4 , Figure 5 , Figure 6 and Figure 7 shown.

[0218] from Figures 3 - 7 As shown, it can be seen that a 10-30 nm epitaxial shell layer is uniformly coated on the surface of the silicon carbide nanowires.

[0219] (III) Raman test

[0220] The present invention takes the SiC nanowire core-shell heterojunction material prepared in Example 1 as an example and performs Raman testing. The test results are as follows: Figure 8 shown.

[0221] From Figure 8 As shown, it can be seen that for the typical Raman spectrum of graphene, its corresponding characteristic peaks are located at the D peak near 1350 cm -1 near, the G peak near 1582 cm -1 near, and the 2D peak near 2700 cm -1 near.

[0222] (IV) Performance Test of Ultraviolet Photodetector

[0223] Taking the ultraviolet photodetectors of Example 22 and Example 23 of the present invention as examples, they are respectively named single SiC@graphene ultraviolet photodetector and single SiC@Ag ultraviolet photodetector.

[0224] The present invention uses the Keithley 4200-SCS semiconductor characterization system to measure and its corresponding test methods to test the ultraviolet photodetection performance of the single SiC@graphene ultraviolet photodetector and the single SiC@Ag ultraviolet photodetector respectively, and the test results are respectively as Figure 9 and Figure 10 shown.

[0225] Figure 9 is the single SiC@graphene ultraviolet photodetector, that is, the ultraviolet photodetector of Example 22 of the present invention uses a continuous ultraviolet light source with an incident light wavelength of 365 nm to obtain the voltage-current and time-current curves of the device by means of on / off switching. Among them, Figure 9 (a) is the I-V curve graph of the single SiC@graphene ultraviolet photodetector device in the dark state and under the irradiation of a 365 nm ultraviolet light source, Figure 9 (b) is the logarithmic image of the I-V curve in Figure (a). It can be seen from the figure that the device current increases significantly under the irradiation of ultraviolet light, showing a strong light response; Figure 9 (c) is the I-T curve graph of the device under on / off state 365 nm ultraviolet light irradiation at different bias voltages. It can be seen that the device current increases rapidly and remains stable when irradiated with ultraviolet light, and the current drops rapidly to the initial level after turning off the light source, and the photocurrent increases with the increase of the applied bias voltage; Figure 9 (d) is the I-T curve graph of the device under irradiation with different optical power densities of 365 nm ultraviolet light. The photocurrent increases with the increase of the optical power density. According to the values of the light / dark current in the I-T curve graph, the light / dark current ratio of the device can be calculated to reach 10 3 , at a bias voltage of 5 V, the responsivity reaches 8508 A / W, the detectivity is 1.69×10 11 Jone, and the external quantum efficiency is 289618%.

[0226] Figure 10It is a single SiC@Ag ultraviolet photodetector. That is, the ultraviolet photodetector in Embodiment 23 of the present invention uses a continuous ultraviolet light source with an incident light wavelength of 365 nm, and obtains the voltage-current and time-current curves of the device by means of on / off switching. Among them, Figure 10 (a) and Figure 10 (b) are the I-V curves of a single SiC@Ag ultraviolet photodetector device in the dark state and under the irradiation of a 365-nm ultraviolet light source. It can be seen that the photocurrent of the device increases significantly compared with the dark current under the irradiation of ultraviolet light, showing a strong light response; Figure (c) is the I-T curve of the device under 365-nm ultraviolet light illumination in the on / off state at different bias voltages. It can be seen that the current of the device increases rapidly when irradiated with ultraviolet light, and drops rapidly to the initial level after turning off the light source, showing a strong light response. Repeated tests show that the device has good stability, and the photocurrent will increase significantly accordingly with the increase of the applied bias voltage. Figure 10 (d) is the I-T curve of the device under the irradiation of 365-nm ultraviolet light with different optical power densities. The photocurrent increases with the increase of the optical power density. According to the values of the light / dark current in the two I-T curves, it can be calculated that under the irradiation of ultraviolet light with an incident light wavelength of 365 nm, the single SiC@Ag ultraviolet photodetector also shows a strong light response, and the light / dark current ratio is close to 10 4 . At a bias voltage of 5 V, the responsivity reaches 9957 A / W, the detectivity is 2.55×10 11 Jone, and the external quantum efficiency is 338921%.

[0227] Obviously, the above embodiments are only a part of the embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

Claims

1. A SiC nanowire core-shell heterojunction material, characterized in that, It includes a core and a shell layer, and the shell layer uniformly coats the core; The core is a silicon carbide nanowire; The shell layer is any one of graphene, carbon, silicon, silver, sulfur, and boron nitride; The coating thickness of the shell layer is 10 - 30 nm; The silicon carbide nanowire is a p-type silicon carbide nanowire doped with a p-type doping source or an n-type silicon carbide nanowire doped with an n-type doping source; The p-type doping source is any one or more of boron, aluminum, aluminum nitrate, aluminum chloride, and boron chloride; The n-type doping source is any one or more of melamine, ammonium bicarbonate, ammonium nitrate, urea, oxalic acid, red phosphorus, and black phosphorus; The SiC nanowire core-shell heterojunction material is prepared according to the following steps: After mixing the silicon carbide nanowire with the shell layer raw material, under vacuum conditions, heat preservation treatment A is carried out at a temperature of 500 - 1550 °C, and after cooling, the SiC nanowire core-shell heterojunction material is obtained.

2. The SiC nanowire core-shell heterojunction material according to claim 1, wherein The shell layer material is one or more of polystyrene, ammonium tetrachloride, nickel chloride, silver nitrate, silver carbonate, borane ammonium, and sublimed sulfur powder; 3. The SiC nanowire core-shell heterojunction material according to claim 1, wherein The mass ratio of the silicon carbide nanowire to the shell layer raw material is 1.2 - 42:1; The time for heat preservation treatment is 60 - 600 min.

4. Application of the SiC nanowire core-shell heterojunction material according to any one of claims 1 - 3 in the preparation of an ultraviolet photodetector.

5. The application according to claim 4, wherein The ultraviolet photodetector is prepared through the following steps: The SiC nanowire core-shell heterojunction material is uniformly dispersed in a solvent to obtain a nanowire suspension; And the nanowire suspension is drop-coated on a substrate, and after drying, electron beam thermal evaporation is carried out to deposit electrodes and annealing treatment in sequence, and then the ultraviolet photodetector is obtained.

6. The application according to claim 5, wherein The solvent is one or both of isopropyl alcohol and ethylene glycol; The substrate is a silicon substrate; The dosage ratio of the SiC nanowire core-shell heterojunction material to the solvent is 1 - 5 mg:5 - 15 mL.

Images