3C-SiC nanowire functional composite network film on single crystal silicon and its preparation method and application

Abstract

The present invention belongs to the technical field of semiconductor nanowire material preparation, and discloses a 3C-SiC nanowire functional composite network film on single crystal silicon and its preparation method and application. The preparation method is as follows: using a single crystal silicon wafer as a cathode, using a silicon carbide nanowire suspension as an electrophoretic deposition liquid, immersing the single crystal silicon wafer in the silicon carbide nanowire suspension, and using direct current for electrophoretic deposition at a voltage of 50 to 100V to form a silicon carbide nanowire layer with a uniform and dense heterojunction structure on the single crystal silicon wafer; using plasma to weld the silicon carbide nanowire layer, that is, obtaining the 3C-SiC nanowire functional composite network film. The film prepared by the present invention in a "bottom-up" manner has a large area, a simple preparation method, low cost, high efficiency, safe and easy operation, and has a certain universality for low-dimensional nanostructures, and can be used as a reference for the preparation of other semiconductor nanofilms.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor nanowire material preparation, and in particular to a 3C-SiC nanowire functional composite network film on single crystal silicon, and a preparation method and application thereof. Background Art

[0002] As the third generation wide bandgap semiconductor, silicon carbide (SiC) is one of the most important candidate materials for high-performance semiconductor devices. When the size of SiC material enters the nanoscale, it will show many excellent properties different from bulk materials. In addition to inheriting the advantages of traditional bulk materials such as high thermal conductivity, strong thermal stability, chemical corrosion resistance, low thermal expansion coefficient, high thermal conductivity, good chemical stability, high critical breakdown electric field and high electron saturation mobility, it also has many excellent properties such as quantum confinement effect, small size effect and surface effect. Micro-nano devices constructed with SiC low-dimensional nanostructures are expected to realize the preparation of electronic devices based on single particles and single root sizes. Obviously, these micro-nano devices have low power consumption, faster electronic transmission performance, high responsiveness, high switching ratio and other properties.

[0003] In recent years, nanostructured films composed of low-dimensional nanostructures self-assembled from the bottom up have attracted widespread attention from scientific researchers. Such nanostructured films have the characteristics of high porosity, good flexibility, high specific surface area, and interconnected pore structures. The assembly of one-dimensional nanomaterials, such as nanowires and nanotubes, into macroscopic thin film materials has attracted much attention recently. Significantly different from traditional thin film materials (epitaxial single crystal films or films composed of nanoparticles), these film materials can retain the characteristics of one-dimensional nanomaterials and can be used as macroscopic two-dimensional materials, with the characteristics of two-dimensional easy processing and compatibility with semiconductor planar processing technology. It should be pointed out that this film has unique optical, electrical, and excellent mechanical properties, especially excellent mechanical properties and bendable, self-supporting structure films without supporting substrates. The synthesized nanonetwork film forms a bonded nanowire interface between the stacked nanowires, and nanopores with permeation / breathing functions can be formed between adjacent nanowires, thereby achieving excellent mechanical flexibility, ductility, processability, and breathability. In addition, given the excellent biocompatibility of silicon carbide, this nanowire network film can be perfectly combined with the organism and can be used as an electronic device implanted in the organism to monitor / amplify physiological signals in a high-fidelity manner. Therefore, the preparation of silicon carbide nanowire network films has become a research direction for many scholars at home and abroad in recent years, and has high potential application value.

[0004] However, the growth temperature of high-quality SiC nanowires is generally above 1400°C. At this temperature, it is difficult to directly prepare nanowires on single crystal substrates (such as silicon, gallium arsenide, etc.) and other flexible substrates that are not resistant to high temperatures. In order to solve this problem, the existing technology mainly prepares SiC nanowires on high melting point substrates such as crucibles, ceramic substrates, and graphite paper. The inventors found that the above-mentioned high melting point substrates such as crucibles, ceramic substrates, and graphite paper are difficult to be compatible with the semiconductor silicon plane preparation process, and these nanowire films cannot be processed into optoelectronic devices; what is more disadvantageous is that the nanowire films grown on the above-mentioned substrates are also assembled from randomly grown nanowires, mostly independently grown nanowire monomers, and the growth on the substrate is also very random. The nanowires are not cross-linked with each other, and it is difficult to form electrical contact, which makes it difficult to apply them to semiconductor integrated electronic devices. In addition, the preparation of the above-mentioned nanowire films also has high costs, cumbersome experimental processes, long cycles, high energy consumption, small output of SiC nanomaterials prepared by a single furnace, and different growth quality between furnaces, making it difficult to apply them on a large scale to future micro-nano optoelectronic devices.

[0005] To this end, the present invention provides a 3C-SiC nanowire functional composite network film on single crystal silicon and a preparation method and application thereof. Summary of the invention

[0006] In order to solve the above-mentioned deficiencies in the prior art, the present invention provides a 3C-SiC nanowire functional composite network film on single crystal silicon and a preparation method and application thereof.

[0007] The present invention provides a 3C-SiC nanowire functional composite network film on single crystal silicon and a preparation method and application thereof, which are achieved by the following technical solutions:

[0008] The first object of the present invention is to provide a method for preparing a 3C-SiC nanowire functional composite network film on single crystal silicon, comprising the following steps:

[0009] Step 1, using a single crystal silicon wafer as a cathode and a silicon carbide nanowire suspension as an electrophoretic deposition liquid, immersing the single crystal silicon wafer in the silicon carbide nanowire suspension, and performing electrophoretic deposition treatment with direct current at a voltage of 50 to 100 V to form a silicon carbide nanowire layer with a uniform and dense heterojunction structure on the single crystal silicon wafer;

[0010] Wherein, the heterojunction structure is any one of a pi junction, a pn junction and a pin junction;

[0011] Step 2: Use argon plasma to perform welding treatment on the silicon carbide nanowire layer to weld adjacent nanowires to form a silicon carbide nanowire network film, that is, to obtain the 3C-SiC nanowire functional composite network film.

[0012] Further, the pi junction is formed by a p-type single crystal silicon wafer and the silicon carbide nanowire;

[0013] The pn junction is formed by an n-type single crystal silicon wafer and a p-type silicon carbide nanowire, or by a p-type single crystal silicon wafer and an n-type silicon carbide nanowire;

[0014] The pin junction is formed by a p-type single crystal silicon wafer, the silicon carbide nanowire and the n-type silicon carbide nanowire.

[0015] Furthermore, the n-type single crystal silicon wafer is prepared from a single crystal silicon wafer and a doping source A, wherein the doping source A is any one of P, As, and Sb;

[0016] The p-type single crystal silicon wafer is prepared from a single crystal silicon wafer and a doping source B, wherein the doping source B is any one of B, Al, and Ga.

[0017] Further, the n-type silicon carbide nanowire suspension is prepared from single-crystal silicon carbide nanowires and a doping source C, wherein the doping source C is any one or more of melamine, ammonium bicarbonate, ammonium nitrate, urea, oxalic acid, red phosphorus and black phosphorus;

[0018] The p-type silicon carbide nanowires are prepared by combining a doping source D, wherein the doping source D is any one or more of boron, borane, aluminum, aluminum nitrate, aluminum chloride and boron chloride.

[0019] Furthermore, the n-type silicon carbide nanowire or the p-type silicon carbide nanowire is obtained by the following steps:

[0020] After the single crystal silicon carbide nanowires are mixed with the doping source C or the doping source D, they are heat-treated at a temperature of 1000-1400° C., and then annealed to obtain doped n-type silicon carbide nanowires or p-type silicon carbide nanowires.

[0021] Furthermore, during the electrophoretic deposition process, a platinum sheet is used as an anode, and the distance between electrodes is 0.5 to 2 cm.

[0022] Furthermore, the welding process is as follows:

[0023] At a temperature of 500-1000° C., the surface of the silicon carbide nanowire layer is treated with argon plasma for 5-60 minutes, and then a force of 5-10 MPa is applied, and the temperature is raised to 1000-1500° C. and then welded for 30-60 minutes.

[0024] Furthermore, the content of silicon carbide nanowires in the silicon carbide nanowire suspension is 0.05-0.1 g / 100 mL.

[0025] Furthermore, the silicon carbide nanowire network film obtained in step 2 is also subjected to a high-temperature bonding treatment.

[0026] Furthermore, the silicon carbide nanowire suspension is obtained by the following steps:

[0027] Undoped silicon carbide nanowires or n-type silicon carbide nanowires or p-type silicon carbide nanowires are added to an organic solvent A, and then a dispersant and a conductive solute are added, and a stable silicon carbide nanowire suspension is formed by ultraviolet ultrasonic treatment I.

[0028] Furthermore, when preparing the silicon carbide nanowire suspension, the mass ratio of the single crystal silicon carbide nanowire to the doping source is 8 to 12:1.

[0029] Furthermore, when preparing the silicon carbide nanowire suspension, the heat preservation treatment is to seal the mixture of single crystal silicon carbide nanowires and doping sources in a platinum tube, then heat the platinum tube to 1000-1400° C. at a heating rate of 3-10° C. / min, and keep it warm for 60-600 min.

[0030] Furthermore, when preparing the silicon carbide nanowire suspension, the annealing temperature is 500-1000° C., and the annealing time is 60-120 min.

[0031] Further, when preparing the silicon carbide nanowire suspension, the organic solvent A is one or both of isopropanol and ethylene glycol;

[0032] The dispersant is any one of sodium dodecylbenzene sulfonate, sodium tripolyphosphate, sodium dodecyl sulfate and polyacrylamide;

[0033] The conductive solute is any one of aluminum nitrate, sodium chloride, ammonium chloride and potassium nitrate.

[0034] Furthermore, when preparing the silicon carbide nanowire suspension, the ratio of the organic solvent A to the silicon carbide nanowire is 0.05-0.1 g:100 mL;

[0035] The mass ratio of the dispersant to the silicon carbide nanowires is 1:0.65-1.3;

[0036] The mass ratio of the conductive solute to the silicon carbide nanowires is 1:20-10.

[0037] Furthermore, the single crystal silicon carbide nanowires are obtained by the following steps:

[0038] After cleaning the silicon carbide aerogel, immerse it in an acid solution and perform ultraviolet ultrasonic treatment II, then let it stand until the solution is stratified, pour out the supernatant, add water solvent to the remaining solution, perform ultraviolet ultrasonic treatment again for 0.5 to 3 hours, let it stand again and pour out the supernatant, repeat the above steps at least 3 times, separate the solid-liquid part of the solution without the supernatant, and dry the obtained solid phase component to obtain the single crystal silicon carbide nanowire.

[0039] Furthermore, the acid solution is 98% hydrofluoric acid solution or 85% hot concentrated phosphoric acid, which removes the silicon dioxide layer on the surface of the silicon carbide aerogel, and the usage ratio of the silicon carbide aerogel to the acid solution is 1g:20-100mL.

[0040] Furthermore, the amount of the aqueous solution added is equal to the volume of the poured out supernatant.

[0041] Furthermore, the processes of each of the ultraviolet ultrasonic treatments are: the ultrasonic power is 150W, the ultrasonic time is 0.5-3h, and the ultrasonic temperature is 30-50°C; the wavelength of the ultraviolet light is 365nm, and the power is 5-10W;

[0042] Furthermore, when preparing single-crystal silicon carbide nanowires, the solid phase components are also subjected to a washing treatment before the drying treatment, wherein the washing treatment is to wash the solid phase components with an aqueous solvent until the washing liquid is neutral (pH is 7).

[0043] Furthermore, the single crystal silicon carbide nanowire has a 3C phase, a density of 3.21 g / cc, a uniform size distribution, a diameter of 50 to 300 nm, and a length of 10 to 100 μm.

[0044] Furthermore, the silicon carbide aerogel is prepared by a carbothermal reduction method.

[0045] Furthermore, the single crystal silicon wafer undergoes the following pretreatment before electrophoretic deposition:

[0046] The single crystal silicon wafer is ultrasonically cleaned in acetone, anhydrous ethanol and deionized water for 15 to 20 minutes respectively, and then taken out and placed in an oven at 60 to 80° C. to dry for 10 to 20 minutes.

[0047] The second object of the present invention is to provide a 3C-SiC nanowire functional composite network film prepared by the above preparation method.

[0048] The third object of the present invention is to provide an application of the above-mentioned 3C-SiC nanowire functional composite network film in the preparation of SiC nano-photoelectric devices.

[0049] Compared with the prior art, the present invention has the following beneficial effects:

[0050] The present invention adopts a solution method to prepare a silicon carbide nanowire heterojunction structure network film on single crystal silicon, and the prepared film can be transferred from the original substrate to a new substrate separately, and has self-supporting properties. It not only solves the technical problem that the carbon thermal reduction method and the conventional chemical vapor method cannot directly grow high-quality silicon carbide nanowire films on silicon, but also does not have the bottleneck problem encountered by lattice-mismatched epitaxial films. It can also form a high-quality heterojunction by selecting single crystal silicon substrates and silicon carbide nanowires of different conductive types, thereby hopefully realizing the research and development of electronic devices with novel properties that cannot be prepared by conventional methods and are conducive to application in flexible fields.

[0051] The film prepared by the present invention not only integrates all the advantages of one-dimensional nanowires (electrons are transmitted along the axial direction of the nanowires, which has the advantage of fast transmission) and the advantages of two-dimensional films (facilitating large-scale device integration), but also has large size, large specific surface area, uniform density, the nanowires are formed by welding, there is no contact resistance between the nanowires, and electrons can be transported from one nanowire to another along the network. In addition, this film does not require a supporting substrate, is flexible, and has a self-supporting structure. Nanopores with penetration / breathable functions can be formed between adjacent nanowires. It has excellent mechanical flexibility, ductility, processability, and breathability, and can be used to prepare high-quality silicon carbide nanowire network films with good electrical contact that can be applied to electronic devices.

[0052] The present invention provides an effective bottom-up method for assembling nanostructures. The preparation method is simple, the cost is low, the prepared film area is large, the efficiency is high, and it is safe and easy to operate. It has a certain universality for low-dimensional nanostructures and can be used as a reference for the preparation of other semiconductor nanofilms.

[0053] The silicon carbide nanowires prepared by the present invention are superior to macroscopic bulk materials in terms of mechanical properties and electrical properties. The macroscopic three-dimensional network woven structure composed of nanowires has better performance than the structure composed of micrometers or larger. At the same time, the preparation of macroscopic three-dimensional woven structures assembled by nanowires can also explore the performance of silicon carbide nanowires on a macroscopic scale and further explore the application potential of silicon carbide nanowires. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 A physical picture of the 3C-SiC nanowire functional composite network film prepared in Example 1 of the present invention;

[0055] Figure 2 XRD pattern of silicon carbide nanowire aerogel prepared in the present invention;

[0056] Figure 3 is a SEM image of the silicon carbide nanowire layer of Example 1 of the present invention;

[0057] Figure 4 This is a SEM image of the silicon carbide nanowire network film after welding in Example 1 of the present invention;

[0058] Figure 5 This is a diagram showing the mechanism of electrophoretic deposition of the present invention. DETAILED DESCRIPTION

[0059] As described in the background technology section, the prior art still faces many problems in preparing high-quality, large-size silicon carbide nanowire network films. Therefore, it is urgent to develop a universal, large-size, high-efficiency, low-cost method for preparing a silicon carbide nanowire network film, especially a method for preparing a silicon carbide nanowire network film that can be applied to SiC nano-photoelectric devices. To this end, the present invention provides a 3C-SiC nanowire functional composite network film on single crystal silicon and a preparation method and application thereof. The technical scheme in the embodiment of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiment of the present invention.

[0060] Example 1

[0061] The present embodiment provides a 3C-SiC nanowire functional composite network film, which is prepared by depositing i-type silicon carbide nanowires on p-type single crystal silicon, and is a 3C-SiC nanowire functional composite network film with a pi junction.

[0062] The preparation method of the 3C-SiC nanowire functional composite network film in this embodiment is as follows:

[0063] Step 1: Using electrophoretic deposition to form a silicon carbide nanowire layer with a uniform and dense pi heterojunction structure on a single crystal silicon wafer:

[0064] 1.1 Preparation of SiC Nanowires

[0065] The present invention does not limit the specific preparation method of silicon carbide nanowires, as long as clean silicon carbide nanowires can be obtained. Optionally, in this embodiment, a single-crystal silicon carbide nanowire with a crystal phase of 3C phase, a density of 3.21 g / cc, a uniform size distribution, a diameter of 50 to 300 nm, and a length of 10 to 100 μm is used, and the single-crystal silicon carbide nanowire used in this embodiment is obtained by the following steps:

[0066] After cleaning the silicon carbide aerogel, immerse it in an acid solution, perform ultraviolet ultrasonic treatment, then stand it until the solution is separated, pour out the supernatant, add a water solvent to the remaining solution, perform ultraviolet ultrasonic treatment again, stand it again and pour out the supernatant, repeat the above steps 5 times, separate the solution from the supernatant, and dry the obtained solid phase component to obtain the single crystal silicon carbide nanowire;

[0067] It should be noted that the present invention does not limit the specific composition and amount of the acid solution, as long as it can remove the silicon dioxide layer on the surface of the silicon carbide aerogel. In this embodiment, 98% hydrofluoric acid solution is used as the acid solution, and 300 mL of 98% hydrofluoric acid solution is weighed for standby use.

[0068] The present invention does not limit the specific process of ultraviolet ultrasonic treatment used in the preparation of single-crystal silicon carbide nanowires, as long as the silicon carbide aerogel can be dispersed and a silicon carbide aerogel suspension with uniform concentration can be prepared. In this embodiment, optionally, the following process is adopted: 5g of silicon carbide aerogel is immersed in the above-mentioned 300mL of 98% hydrofluoric acid solution, and is irradiated with an ultraviolet lamp with a wavelength of 365nm and an optical power of 7W, at a temperature of 40°C, and ultrasonically treated with an ultrasonic power of 150W for 1.5h, then allowed to stand for 200min, 270mL of the supernatant is poured out, and the remaining solution is solution A; then 270mL of deionized water is added to solution A, and then subjected to ultraviolet ultrasonic dispersion treatment and separation. After repeating the above steps 6 times, solution A is placed in a centrifuge tube and centrifuged to obtain SiC nanowires, which are then dispersed in deionized water and centrifuged again. The above operation is repeated until the pH of the solution is 7 to obtain single-crystal silicon carbide nanowires that are free of impurities, monodispersed, have a 3C phase, a density of 3.21 g / cc, and a uniform size distribution with a diameter of 50 to 300 nm and a length of 10 to 100 μm. The nanowires are dried (e.g., dried in a vacuum drying oven at 60° C. for 4 h) and set aside.

[0069] The present invention does not limit the specific operation of the cleaning treatment of silicon carbide aerogel, as long as the SiO2 layer in the silicon carbide aerogel can be removed. In this embodiment, optionally, the following process is adopted: the silicon carbide aerogel is immersed in acetone, anhydrous ethanol, and ultrasonically cleaned in deionized water (power is 150W) for 10 to 20 minutes.

[0070] The present invention does not limit the specific preparation method of silicon carbide aerogel, as long as clean silicon carbide aerogel can be obtained. In this embodiment, optionally, the silicon carbide aerogel is prepared by carbothermal reduction method.

[0071] 1.2 Preparation of electrophoretic deposition solution, i.e. silicon carbide nanowire suspension

[0072] The above-mentioned single crystal silicon carbide nanowires are added into an organic solvent A, and then a dispersant and a conductive solute are added, and a stable silicon carbide nanowire suspension is formed by ultraviolet ultrasonic treatment I.

[0073] The present invention does not limit the specific composition of the organic solvent A, as long as the silicon carbide nanowire aerogel can be dispersed in the solvent to form a uniform suspension. Optionally, in this embodiment, isopropanol is used as the organic solvent A, and 100 mL of isopropanol is weighed and set aside;

[0074] The present invention does not limit the specific composition of the dispersant, as long as it can promote the uniform dispersion of the silicon carbide nanowire aerogel in the organic solvent. Optionally, in this embodiment, sodium dodecylbenzene sulfonate is used as the dispersant, and 0.075 g of sodium dodecylbenzene sulfonate is weighed and set aside.

[0075] The present invention does not limit the specific composition of the conductive solute, as long as it can achieve the directional movement of the silicon carbide nanowires in the electrostatic field. Optionally, in this embodiment, aluminum nitrate is used as the conductive solute, and 0.0025 g of aluminum nitrate is weighed and set aside.

[0076] The present invention does not limit the specific operating parameters of the ultraviolet ultrasonic treatment I, as long as the silicon carbide nanowires can be quickly dispersed in the solvent. Optionally, in this embodiment, after adding 0.075g of sodium dodecylbenzene sulfonate and 0.0025g of aluminum nitrate to 100mL of isopropanol, the mixture is ultrasonicated for 30 to 50min at an ultrasonic power of 150W under the irradiation of an ultraviolet lamp with a wavelength of 365nm and an optical power of 5 to 10W, so that the nanowires move in a directional manner in the electrostatic field and form a stable suspension, thereby obtaining a p-type silicon carbide nanowire suspension.

[0077] 1.3 Electrophoretic deposition treatment

[0078] Using a single crystal silicon wafer as a cathode and a suspension of silicon carbide nanowires as an electrophoretic deposition liquid, the single crystal silicon wafer is immersed in the suspension of silicon carbide nanowires, and electrophoretic deposition is performed using direct current at a constant voltage of 50 to 100 V to form a silicon carbide nanowire layer with a uniform and dense heterojunction structure on the single crystal silicon wafer;

[0079] It should be noted that the present invention does not limit the types of the single crystal silicon wafer and the silicon carbide nanowires in the silicon carbide nanowire suspension, as long as a silicon carbide nanowire layer with a uniform and dense heterojunction structure can be formed on the single crystal silicon wafer. When it is necessary to obtain a silicon carbide nanowire layer with a pi junction structure, a p-type single crystal silicon wafer is selected as the cathode, and a suspension of silicon carbide nanowires (undoped) is selected as the electrophoretic deposition liquid; when it is necessary to obtain a silicon carbide nanowire layer with a pn junction structure, a p-type single crystal silicon wafer is selected, and group III boron elements are doped into the single crystal silicon to prepare a p-type single crystal silicon wafer as the cathode, and a suspension of n-type silicon carbide nanowires is selected as the electrophoretic deposition liquid, or an n-type single crystal silicon wafer is selected, and group V elements, such as phosphorus or arsenic, are doped into the single crystal silicon to prepare an n-type single crystal silicon wafer as the cathode, and a suspension of p-type silicon carbide nanowires is selected as the electrophoretic deposition liquid; when it is necessary to obtain a silicon carbide nanowire layer with a pin junction structure, a p-type single crystal silicon wafer is selected as the cathode, and a suspension of silicon carbide nanowires (undoped) + a suspension of n-type silicon carbide nanowires are selected as the electrophoretic deposition liquid. The present invention does not limit the specific types of p-type single crystal silicon wafers and n-type single crystal silicon wafers, as long as they meet the basic characteristics of p-type silicon and n-type silicon. For example: n-type single crystal silicon wafers are prepared from single crystal silicon wafers and any one of P, As, Sb doping sources; p-type single crystal silicon wafers are prepared from single crystal silicon wafers and any one of B, Al, Ga doping sources; n-type silicon carbide nanowire suspensions are prepared from single crystal silicon carbide nanowires and any one or more of melamine, ammonium bicarbonate, ammonium nitrate, urea, oxalic acid, red phosphorus and black phosphorus doping sources; p-type silicon carbide nanowire suspensions are prepared from any one or more of boron, aluminum, aluminum nitrate, aluminum chloride and boron chloride doping sources.

[0080] In this embodiment, it is necessary to prepare a silicon carbide nanowire layer with a uniform and dense pi heterojunction structure. Therefore, in this embodiment, a p-type single crystal silicon wafer is used as the cathode, and the i-type silicon carbide nanowire suspension prepared in the above step 1.2 is used as the electrophoretic deposition liquid. The above p-type single crystal silicon wafer is immersed in the above i-type silicon carbide nanowire suspension, and electrophoretic deposition is performed using direct current at a constant voltage of 70V to form a silicon carbide nanowire layer with a uniform and dense pi heterojunction structure on the single crystal silicon wafer.

[0081] The present invention does not limit the specific size of the p-type single crystal silicon wafer, which can be selected according to actual needs. Optionally, the size of the p-type single crystal silicon wafer used in this embodiment is 1×1 to 10×10 cm 2 Before the electrophoretic deposition, the p-type single crystal silicon wafer is subjected to the following pretreatment: the p-type single crystal silicon wafer is ultrasonically cleaned in acetone, anhydrous ethanol, and deionized water for 15 to 20 minutes, and then taken out and placed in an oven at 60 to 80° C. for drying for 10 to 20 minutes.

[0082] The present invention does not limit the specific process parameters of the electrophoretic deposition process, as long as the i-type silicon carbide nanowires can be deposited on the p-type single crystal silicon wafer to form a silicon carbide nanowire layer with a uniform and dense pi heterojunction structure. In this embodiment, optionally, a platinum sheet is used as an anode, and it and the above-mentioned dried p-type single crystal silicon wafer are immersed in the above-mentioned i-type silicon carbide nanowire suspension, the electrode spacing is 0.5 to 2 cm, a DC power supply is used as an electrophoresis instrument, a constant voltage of 70V is applied, and at room temperature, a magnetic stirrer stirs the solution at 100rpm for electrophoretic deposition for 10 minutes to obtain a silicon carbide nanowire layer with a uniform and dense pi heterojunction structure.

[0083] Step 2, using plasma to perform welding treatment on the silicon carbide nanowire layer to weld adjacent nanowires to form a silicon carbide nanowire network film, that is, to obtain the 3C-SiC nanowire functional composite network film;

[0084] It should be noted that the present invention does not limit the specific method and specific parameters of the welding process, as long as the adjacent nanowires on the silicon carbide nanowire layer with a uniform and dense pi heterojunction structure can be welded to form a large-area silicon carbide nanowire network film. Optionally, the present invention first treats the surface of the silicon carbide nanowire layer with argon plasma at a temperature of 700°C for 30 minutes, then applies a force of 7MPa, heats to 1250°C and welds for 45 minutes, thereby obtaining a large-area silicon carbide nanowire network film.

[0085] Example 2

[0086] This embodiment provides a 3C-SiC nanowire functional composite network film. The preparation method of the 3C-SiC nanowire functional composite network film in this embodiment is different from that in Embodiment 1 only in that:

[0087] In step 1.1 of this embodiment, when preparing silicon carbide nanowires, 5g of silicon carbide aerogel is immersed in the above-mentioned 100mL of 98% hydrofluoric acid solution, and is ultrasonically treated at 150W for 3h at a temperature of 30°C under the irradiation of an ultraviolet lamp with a wavelength of 365nm and an optical power of 5W, and then allowed to stand for 500min, 90mL of supernatant is poured out, and the remaining solution is solution A; 90mL of deionized water is added to solution A, and then ultraviolet light ultrasonic dispersion treatment and separation are performed. After repeating the above steps 5 times, solution A is placed in a centrifuge tube and centrifuged to obtain SiC nanowires, which are then dispersed in deionized water and centrifuged again. The above operation is repeated until the pH of the solution is 7 to obtain single-crystalline silicon carbide nanowires.

[0088] In step 1.2 of this embodiment, sodium tripolyphosphate is used as the dispersant, sodium chloride is used as the conductive solute, and ethylene glycol is used as the organic solvent A; and in this embodiment, the mass ratio of the dispersant to the silicon carbide nanowires is 1:1, and the mass ratio of the conductive solute to the silicon carbide nanowires is 1:0.01.

[0089] In step 1.3 of this embodiment, the electrode spacing of the electrophoretic deposition treatment is 0.5 cm, a DC power supply is used as the electrophoresis apparatus, a constant voltage of 50 V is applied, and during the deposition process, the solution is stirred at a rate of 80 r / min with a magnetic stirrer to ensure that the suspension of silicon carbide nanowires always maintains a uniform composition during the deposition process. The electrophoretic deposition is performed for 15 minutes to obtain a silicon carbide nanowire layer with a uniformly deposited and dense pi heterojunction structure.

[0090] Example 3

[0091] This embodiment provides a 3C-SiC nanowire functional composite network film. The preparation method of the 3C-SiC nanowire functional composite network film in this embodiment is different from that in Embodiment 1 only in that:

[0092] In step 1.1 of this embodiment, when preparing silicon carbide nanowires, 5g of silicon carbide aerogel is immersed in the above-mentioned 500mL weighed 85% hot concentrated phosphoric acid solution, and is ultrasonically treated at a temperature of 50°C and an ultrasonic power of 150W for 0.5h under the irradiation of an ultraviolet lamp with a wavelength of 365nm and an optical power of 10W, and then allowed to stand for 30min, 450mL of supernatant is poured out, and the remaining solution is solution A; 450mL of deionized water is added to solution A, and then ultraviolet light ultrasonic dispersion treatment and separation are performed. After repeating the above steps 8 times, solution A is placed in a centrifuge tube and centrifuged to obtain SiC nanowires, which are then dispersed in deionized water and centrifuged again. The above operation is repeated until the pH of the solution is 7 to obtain single-crystalline silicon carbide nanowires.

[0093] In step 1.2 of this embodiment, polyacrylamide is used as the dispersant, ammonium chloride is used as the conductive solute, and ethylene glycol is used as the organic solvent A; and in this embodiment, the mass ratio of the dispersant to the silicon carbide nanowires is 1:2, and the mass ratio of the conductive solute to the silicon carbide nanowires is 1:0.1.

[0094] In step 1.3 of this embodiment, the electrode spacing of the electrophoretic deposition treatment is 2 cm, a DC power supply is used as the electrophoresis apparatus, a constant voltage of 100 V is applied, and during the deposition process, the solution is stirred at a rate of 120 r / min with a magnetic stirrer to ensure that the suspension of silicon carbide nanowires always maintains a uniform composition during the deposition process. The electrophoretic deposition is performed for 6 minutes to obtain a silicon carbide nanowire layer with a uniformly deposited and dense pi heterojunction structure.

[0095] In step 2 of this embodiment, during the welding process, the surface of the silicon carbide nanowire layer is first treated with argon plasma at a temperature of 1000°C for 5 minutes, and then a force of 10 MPa is applied, the temperature is raised to 1500°C and welding is performed for 30 minutes, so that the silicon carbide nanowires are connected in many irregular crosslinks, thereby achieving nano-welding of the intersections on the silicon carbide nanowire film over a larger area.

[0096] Example 4

[0097] The present embodiment provides a 3C-SiC nanowire functional composite network film, which is prepared by depositing n-type silicon carbide nanowires on p-type single crystal silicon, and is a 3C-SiC nanowire functional composite network film with a pn junction.

[0098] The preparation method of the C-SiC nanowire functional composite network film in this embodiment 3 is different from that in embodiment 1 only in that:

[0099] In this embodiment, a suspension of n-type silicon carbide nanowires is used as the electrophoretic deposition liquid, and the present invention does not limit the specific type of the n-type silicon carbide nanowire suspension, as long as it meets the basic characteristics of the n-type silicon carbide nanowires. In this embodiment, red phosphorus is used as the n-type doping source, and the n-type silicon carbide nanowire suspension is prepared by the following steps:

[0100] After mixing the silicon carbide nanowires and the doping source, heat-treating them at a temperature of 1000 to 1400° C., and then annealing them to obtain doped single-crystal silicon carbide nanowires;

[0101] Among them, the present invention does not limit the type of doping source, and the corresponding n-type or p-type doping source can be selected according to actual needs. In this embodiment, in order to obtain n-type silicon carbide nanowires, red phosphorus is used as an n-type doping source, 0.1g of silicon carbide nanowires are weighed, and the corresponding mass of red phosphorus is weighed according to a molar ratio of 3.5:1. After mixing evenly, they are loaded into a platinum tube with a tube length of 15cm, an inner diameter of 1cm, and a wall thickness of 2mm, and the pressure inside the platinum tube is 1mTorr after sealing the tube. The sealed platinum tube is placed in a muffle furnace for heating, the heating rate is 6°C per minute, the heating temperature is 1200°C, and the insulation time is 300min. After the heating is completed, the sample is naturally cooled to room temperature with the furnace and then taken out, and annealed in a tubular furnace at a temperature of 750°C for 90min to obtain the doped n-type silicon carbide nanowires. Then, the obtained n-type silicon carbide nanowires are added to the organic solvent A according to the steps of Example 1 to form a stable suspension of n-type silicon carbide nanowires.

[0102] Example 5

[0103] This embodiment provides a 3C-SiC nanowire functional composite network film, and the preparation method of the 3C-SiC nanowire functional composite network film in this embodiment is different from that in Embodiment 4 only in that:

[0104] In this embodiment, 0.1g of silicon carbide nanowires were weighed, and the corresponding mass of red phosphorus was weighed according to the molar ratio of silicon carbide nanowires to red phosphorus of 3:1, and the mixture was evenly loaded into a platinum tube with a tube length of 15cm, an inner diameter of 1cm, and a wall thickness of 2mm, and the pressure inside the platinum tube was 1mTorr after the tube was sealed. The sealed platinum tube was placed in a muffle furnace for heating, with a heating rate of 3℃ / min, a heating temperature of 1000℃, and a holding time of 600min. After the heating was completed, the sample was naturally cooled to room temperature with the furnace and then taken out, and annealed at 500℃ for 60min in a tube furnace to obtain doped n-type silicon carbide nanowires.

[0105] Example 6

[0106] This embodiment provides a 3C-SiC nanowire functional composite network film, and the preparation method of the 3C-SiC nanowire functional composite network film in this embodiment is different from that in Embodiment 4 only in that:

[0107] In this embodiment, 0.1g of silicon carbide nanowires were weighed, and the corresponding mass of red phosphorus was weighed according to the mass ratio of silicon carbide nanowires to red phosphorus of 1:1, and the mixture was evenly loaded into a platinum tube with a tube length of 15cm, an inner diameter of 1cm, and a wall thickness of 2mm, and the pressure inside the platinum tube was 1mTorr after the tube was sealed. The sealed platinum tube was placed in a muffle furnace and heated at a heating rate of 10℃ / min per minute, a heating temperature of 1400℃, and a holding time of 60min. After the heating was completed, the sample was naturally cooled to room temperature with the furnace and then taken out, and annealed at 1000℃ for 120min in a tubular furnace to obtain doped n-type silicon carbide nanowires.

[0108] Example 7

[0109] The present embodiment provides a 3C-SiC nanowire functional composite network film, which is prepared by depositing i-type silicon carbide nanowires and n-type silicon carbide nanowires on p-type single crystal silicon, and is a 3C-SiC nanowire functional composite network film with a pin junction.

[0110] The difference between the method for preparing the C-SiC nanowire functional composite network film in Example 3 and that in Example 4 is that:

[0111] In this embodiment, the 3C-SiC nanowire functional composite network film with pi junction prepared in Example 1 is used as the cathode, and the suspension of n-type silicon carbide nanowires in Example 4 is used as the electrophoretic deposition liquid.

[0112] Example 8

[0113] The present embodiment provides a 3C-SiC nanowire functional composite network film, which is prepared by depositing p-type silicon carbide nanowires on n-type single crystal silicon, and is a 3C-SiC nanowire functional composite network film with a pn junction.

[0114] The difference between the method for preparing the C-SiC nanowire functional composite network film in Example 3 and that in Example 4 is that:

[0115] In this embodiment, an n-type single crystal silicon wafer is used as the cathode, and a suspension of p-type silicon carbide nanowires is used as the electrophoretic deposition liquid.

[0116] It should be noted that the present invention does not limit the specific type of the p-type silicon carbide nanowire suspension, as long as it meets the basic characteristics of the p-type silicon carbide nanowire. In this embodiment, borane ammonia is used as the p-type doping source, and the p-type silicon carbide nanowire suspension is prepared according to the steps in Example 4.

[0117] Example 9

[0118] The present embodiment provides a 3C-SiC nanowire functional composite network film, which is prepared by depositing p-type silicon carbide nanowires on n-type single crystal silicon, and is a 3C-SiC nanowire functional composite network film with a pn junction.

[0119] The difference between the method for preparing the C-SiC nanowire functional composite network film in Example 3 and that in Example 1 is that:

[0120] In this embodiment, aluminum chloride is used as the doping source D, and is mixed with silicon carbide nanowires according to the steps in embodiment 1 to prepare a p-type silicon carbide nanowire suspension.

[0121] Example 10

[0122] This embodiment provides a 3C-SiC nanowire functional composite network film, and the preparation method of the 3C-SiC nanowire functional composite network film in this embodiment is different from that in Embodiment 1 in that:

[0123] In this embodiment, based on Embodiments 1 to 9, the silicon carbide nanowire network film obtained in step 2 is further subjected to a high-temperature bonding treatment.

[0124] The present invention does not limit the specific process of high temperature bonding treatment, as long as it can enhance the surface bonding of the silicon carbide nanowire network film. Optionally, in this embodiment, the following process is adopted: firstly, NH3 plasma is used to treat at a temperature of 500-1000°C for 5-60 minutes, and then it is bonded at a constant temperature in a high temperature furnace under argon protection at 1000-1200°C for 30-60 minutes.

[0125] Embodiment 11

[0126] The present invention provides a SiC nano-photoelectric device based on the 3C-SiC nanowire functional composite network film prepared in the above-mentioned Examples 1 to 10, and the preparation method is as follows:

[0127] The 3C-SiC nanowire functional composite network film prepared in any one of Examples 1 to 10 is physically peeled off with a PVA glue solution to obtain a peeled film; then a layer of ordered metal electrode array is evaporated on the peeled film by a thermal electron beam evaporation method, and then annealed to obtain a SiC nano-photoelectric device;

[0128] It should be noted that the present invention does not limit the specific operation process of physical peeling using the PVA glue solution, as long as the film can be peeled off. In this embodiment, optionally, the following process is used: the 3C-SiC nanowire functional composite network film prepared in any one of Examples 1 to 10 is placed in a glue machine with a rotation speed of 500 to 900 rpm, and 3 to 6 drops of PVA glue solution are evenly coated on the surface of the film, each drop is 20 to 100 μL, and the film is physically peeled off after drying, and finally the PVA film on the surface of the film is removed by washing with deionized water.

[0129] The present invention does not limit the specific operation of the above-mentioned thermal electron beam evaporation method and the composition of the specific metal electrode, and can be selected accordingly according to actual needs, as long as a layer of orderly metal electrode array can be evaporated on the film after peeling. In this embodiment, optionally, taking nickel metal material as an example, the following steps are used to evaporate a layer of orderly nickel electrode array on the surface of the film after peeling: the evaporation time is 5 to 20 minutes, the distance between two adjacent electrodes is 40 to 200 μm, and the electrode thickness is 100 to 300 nm.

[0130] The present invention does not limit the specific process of annealing the thin film with the metal electrode evaporated, as long as the contact between the electrode and the nanowire film can be enhanced. In this embodiment, optionally, the following process is adopted: the thin film with the electrode evaporated is placed in a vacuum annealing furnace for annealing, the annealing temperature is 800-1000°C, the heating rate is 10-60°C / min, and the annealing time is 60-200min.

[0131] It should be noted that the present invention does not limit the specific operation of preparing silicon carbide aerogel by the above-mentioned carbothermal reduction method, as long as silicon carbide aerogel can be obtained. Optionally, the present invention adopts the following steps to prepare silicon carbide aerogel:

[0132] The polycarbosilane and the vinyl compound are dissolved in an organic solvent B, and the reaction is carried out under a Karstedt catalyst at 70 to 90° C. in an oxygen-free environment for 4 to 8 hours to obtain a polycarbosilane gel; the polycarbosilane gel is dried and 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 to 1800° C. in an oxygen-free argon atmosphere for 0.5 to 5 hours to obtain a silicon carbide aerogel;

[0133] Wherein, when preparing silicon carbide aerogel, the vinyl compound contains two or more vinyl groups;

[0134] The organic solvent B is one or more of cyclohexane, toluene, xylene or benzene;

[0135] 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;

[0136] The drying is supercritical drying or freeze drying;

[0137] 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;

[0138] The rice husk charcoal has a commercial particle size of less than 200 meshes and a purity of 99%.

[0139] Experimental part

[0140] (I) Physical appearance

[0141] The present invention takes a photo of the 3C-SiC nanowire functional composite network film prepared in Example 4 of the present invention. Figure 1 As shown, Figure 1 The part in the square frame is the 3C-SiC nanowire functional composite network film prepared in Example 4. It can be seen that the 3C-SiC nanowire functional composite network film prepared by the present invention is uniform and dense.

[0142] (ii) XRD test

[0143] The present invention performs XRD test on the single crystal silicon carbide nanowires prepared in Example 1 of the present invention. The test results are as follows: Figure 2 shown.

[0144] from Figure 2As shown, it can be seen that compared with the standard card (JCPSD Card No. 29-1129), all diffraction peaks of the sample are marked as cubic 3C-SiC phase, indicating the high purity of the prepared sample. The three strongest diffraction peaks of the sample are 2θ = 36°, 60° and 72°, which correspond to the diffraction planes of cubic 3C-SiC phase (111), (220) and (311). The strong and sharp peaks indicate that the sample has a high degree of crystallinity.

[0145] (III) SEM test

[0146] The present invention respectively performs SEM tests on the silicon carbide nanowire layers at different stages in the preparation process of the 3C-SiC nanowire functional composite network film in Example 1 and the silicon carbide nanowire network film after welding. The test results are as follows: Figure 3 and Figure 4 shown.

[0147] from Figure 3 and Figure 4 As shown in the figure, it can be seen that the average length of a single nanowire can reach 100μm and has good flexibility. Long silicon carbide nanowires as channels are more conducive to the preparation of high-performance films with better bonding, lower contact resistance and higher nanowire network cross-linking degree. The nanowire cross-linked network formed by welding can densify the silicon carbide aerogel-derived film, which is conducive to the development of high-stability, high-performance and flexible optoelectronic devices.

[0148] The mechanism of electrophoretic deposition of the present invention is as follows Figure 5 As shown, it can be seen that after applying a constant voltage of 60V, the silicon carbide nanowires in the suspension move toward the cathode under the action of the electrostatic field and are deposited on the substrate.

[0149] Obviously, the above embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

Claims

1. A method for preparing a 3C-SiC nanowire functional composite network film on single crystal silicon, characterized in that: The following steps are involved: Step 1, using a single crystal silicon wafer as a cathode and a suspension of silicon carbide nanowires as an electrophoretic deposition liquid, immersing the single crystal silicon wafer in the suspension of silicon carbide nanowires, and performing electrophoretic deposition treatment with direct current at a voltage of 50 to 100 V to form a silicon carbide nanowire layer with a uniform and dense heterojunction structure on the single crystal silicon wafer; Wherein, the heterojunction structure is any one of a pi junction, a pn junction and a pin junction; Step 2: Use argon plasma to perform welding treatment on the silicon carbide nanowire layer to weld adjacent nanowires to form a silicon carbide nanowire network film, that is, to obtain the 3C-SiC nanowire functional composite network film.

2. The preparation method according to claim 1, characterized in that The pi junction is formed by a p-type single crystal silicon wafer and the silicon carbide nanowire; The pn junction is formed by an n-type single crystal silicon wafer and a p-type silicon carbide nanowire, or by a p-type single crystal silicon wafer and an n-type silicon carbide nanowire; The pin junction is formed by a p-type single crystal silicon wafer, the silicon carbide nanowire and the n-type silicon carbide nanowire.

3. The preparation method according to claim 2, characterized in that: The n-type single crystal silicon wafer is prepared by the single crystal silicon wafer and a doping source A, wherein the doping source A is any one of P, As, and Sb; The p-type single crystal silicon wafer is prepared by the single crystal silicon wafer and a doping source B, and the doping source B is any one of B, Al, and Ga.

4. The preparation method according to claim 2, characterized in that: The n-type silicon carbide nanowire is prepared by the silicon carbide nanowire and a doping source C, wherein the doping source C is any one or more of melamine, ammonium bicarbonate, ammonium nitrate, urea, oxalic acid, red phosphorus and black phosphorus; The p-type silicon carbide nanowire is prepared by combining the silicon carbide nanowire with a doping source D, wherein the doping source D is any one or more of boron, aluminum, aluminum nitrate, aluminum chloride and boron chloride.

5. The preparation method according to claim 1, characterized in that: During the electrophoretic deposition treatment, a platinum sheet is used as an anode, and the distance between electrodes is 0.5 to 2 cm.

6. The preparation method according to claim 1, characterized in that: The welding process is as follows: At a temperature of 500-1000° C., the surface of the silicon carbide nanowire layer is treated with argon plasma for 5-60 minutes, and then a force of 5-10 MPa is applied, and the temperature is raised to 1000-1500° C. and then welded for 30-60 minutes.

7. The preparation method according to claim 1, characterized in that: The content of silicon carbide nanowires in the silicon carbide nanowire suspension is 0.05-0.1 g / 100 mL.

8. The preparation method according to claim 1, characterized in that: The silicon carbide nanowire network film obtained in step 2 is also subjected to a high-temperature bonding treatment.

9. A 3C-SiC nanowire functional composite network film prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the 3C-SiC nanowire functional composite network film according to claim 9 in the preparation of SiC nano-photoelectric devices.

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