Nickel silicide nanowire in-situ preparation method and obtained nickel silicide nanowire

Abstract

The invention discloses an in-situ preparation method of a nickel silicide nanowire and the obtained nickel silicide nanowire, and belongs to the technical field of nano materials. The in-situ preparation method comprises the following steps: adding a nickel salt into a SiCw dispersion liquid for dissolving, then adding an NH4HCO3 aqueous solution, stirring for reaction, washing and drying a solid product obtained after the reaction, and then heating to 550-650 DEG C in an H2 atmosphere for calcining, thereby obtaining the nickel-nickel composite material. According to the preparation method, the silicon carbide whisker (SiCw) is used as a silicon source, the SiCw-coated Ni (CO3) 2.2 Ni (OH) 2.2 H2O precipitate is prepared through a heterogeneous precipitation method, then the nickel silicide nanowire is obtained through H2 calcination, the overall preparation process is simple, multiple high-temperature treatment is not needed, the requirement for equipment is low, and the obtained nickel silicide nanowire is high in purity and suitable for large-scale production.

Description

Technical Field

[0001] The present invention relates to the technical field of nanomaterials, and particularly to an in-situ preparation method of nickel silicide nanowires and the obtained nickel silicide nanowires. Background Art

[0002] The information disclosed in the background art of the present invention is only intended to enhance the overall understanding of the present invention, and is not necessarily regarded as an admission or an implication in any form that this information constitutes the prior art already known to those of ordinary skill in the art.

[0003] Metal silicides have been widely used in the semiconductor field due to their low resistivity and high thermal stability. Typical applications include electrical components, gate electrodes, and photovoltaic and thermoelectric devices, etc. With the continuous miniaturization of the size of microelectronic devices, the development of nanoscale silicide structures has become an urgent need for technological development.

[0004] Nickel silicide nanowires have a low silicidation temperature, consume less silicon during the reaction, and can conduct one-dimensional transport, so they have become a research hotspot in recent years. At present, the synthesis method of nickel silicide mainly focuses on chemical vapor deposition. For example, the patent with the publication number CN101555016A discloses a preparation method of nickel silicide nanowires. It forms a silicon dioxide layer on the surface of a silicon substrate, then deposits a titanium layer, places the silicon substrate with the titanium layer in a reaction chamber, and heats it to 500 - 1000 °C to sputter nickel clusters and deposit the nickel clusters on the surface of the silicon substrate to grow nickel silicide nanowires. However, this method has complex preparation steps, a relatively high heating temperature, high requirements for equipment, and it is difficult to ensure the production efficiency of nickel silicide nanowires.

[0005] The paper "Formation and evolution of nickel silicide in silicon nanowires" (IEEE Transactions on Electron Devices, 2014, 61(10): 3363 - 3371) provides a preparation method of nickel silicide nanowires. In an ultra-high vacuum chemical vapor deposition chamber, using silane as the silicon precursor and gold as the catalyst, adopting the vapor-liquid-solid growth technique, and then annealing to generate nickel silicide nanowires. This method requires a harsh high-vacuum environment, and the preparation process is complex and cumbersome.

[0006] The paper "Growth of single-crystalline nickel silicide nanowires with excellent physical properties" (CrystEngComm, 2015, 17(9): 1911 - 1916) provides a method for preparing nickel silicide nanowires. It ultrasonically cleans the silicon substrate in acetone and isopropyl alcohol, then removes the native oxide with dilute hydrofluoric acid. After washing with deionized water, a Ni film is deposited. In a chemical vapor deposition chamber, nickel silicide nanowire materials are synthesized by SiH 4 / H 2 gas on the Ni film evaporated by electron beam. The SiH 4 selected in this method is toxic, which limits its large-scale production.

[0007] The patent with the authorization announcement number CN106558474B discloses a method for preparing nickel silicide nanowires. It forms silicon-containing nanowires by chemical vapor deposition, then deposits a nickel layer on its surface by chemical vapor deposition, subsequently deposits a constraint layer by vapor deposition, and finally performs annealing treatment to obtain nickel silicide nanowires. This method requires multiple vapor deposition steps, has high requirements for equipment, complex steps, high costs, and low production efficiency.

[0008] Therefore, it is necessary to provide a method for preparing nickel silicide nanowire materials that is simple, efficient, and low-cost. Summary of the Invention

[0009] In view of this, the present invention provides an in-situ preparation method for nickel silicide nanowires and the obtained nickel silicide nanowires, which solves the problems of high energy consumption, cumbersome steps, and low production efficiency caused by the multi-layer vapor deposition method in the prior art.

[0010] In the first aspect, the present invention provides an in-situ preparation method for nickel silicide nanowires, including the following steps: Adding nickel salt to the SiC w dispersion liquid for dissolution, and the mass ratio of the nickel salt to SiC w is (1.4 - 1.8) : (0.9 - 1.1); then adding NH 4 HCO 3 aqueous solution, stirring and reacting, washing and drying the solid product obtained after the reaction, and then calcining at 550 - 650 °C in an H 2 atmosphere to obtain.

[0011] In the second aspect, the present invention provides nickel silicide nanowires prepared by the above in-situ preparation method.

[0012] Compared with the prior art, the present invention has achieved the following beneficial effects: The present invention uses silicon carbide whiskers (SiC w ) as a silicon source and prepares SiC w @Ni(CO 3 ) 2 ·2Ni(OH) 2 ·2H 2 O precipitate by heterogeneous precipitation method, and then calcine it in H 2 to obtain nickel silicide nanowires. The overall preparation process is simple, without the need for multiple high-temperature treatments, and has low requirements for equipment. The obtained nickel silicide nanowires have high purity and are suitable for large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The accompanying drawings forming a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments and descriptions thereof of the present invention are used to explain the present invention and do not constitute an improper limitation of the present invention. Obviously, for those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0014] Figure 1 are the transmission electron microscope image and energy dispersive spectrometer elemental analysis diagram of the nickel silicide nanowires in Example 1 of the present invention. Among them, a is the microscopic morphology of the nickel silicide nanowires, b is the partial enlarged view of the morphology of a, c is the Ni element distribution diagram, and d is the Si element distribution diagram; Figure 2 is the X-ray diffraction pattern of the nickel silicide nanowires in Example 1 of the present invention; Figure 3 is the X-ray diffraction pattern of the product in Comparative Example 1 of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0015] It should be noted that the following detailed descriptions are all exemplary and are intended to provide further explanations of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention belongs.

[0016] The present invention provides an in-situ preparation method of nickel silicide nanowires, which includes the following steps: Add nickel salt to the SiC w dispersion solution to dissolve, then add NH 4 HCO 3 aqueous solution, stir and react, wash and dry the solid product obtained after the reaction, and then calcine it in H 2 atmosphere at 550-650 °C to obtain the product.

[0017] In the present invention, silicon carbide whiskers (SiC w) is a silicon-containing precursor. Using the heterogeneous precipitation method, nickel salt reacts with NH 4 HCO 3 in solution, and Ni(CO w ) 3 ·2Ni(OH) 2 ·2H 2 O precipitate is formed on the outer layer of SiC 2 to obtain SiC w @Ni(CO 3 ) 2 ·2Ni(OH) 2 ·2H 2 O precipitate (precursor), and it shows a layered state. The water-soluble ammonium salts are removed by washing to purify the precursor. After drying, it is calcined in an H 2 atmosphere to avoid the influence of oxygen on the synthesis of nickel silicide nanowires, and at the same time, the excess CO 3 2- and OH - are removed under the reduction of hydrogen; Ni has strong reducibility, and it will react with silicon carbide whiskers to obtain nickel silicide nanowires.

[0018] In the present invention, the length of the SiC w is 2 - 10 μm, and the diameter of the SiC w is 20 - 80 nm.

[0019] In the present invention, the nickel salt is selected from nickel nitrate hexahydrate or nickel sulfate hexahydrate; the specific reactions in the heterogeneous precipitation process are as follows: SiC w +Ni(NO 3 ) 2 ·6H 2 O+NH 4 HCO 3 →SiC w @Ni(CO 3 ) 2 ·2Ni(OH) 2 ·2H 2 O↓+NH 4 NO 3 +CO 2 ↑; SiC w +NiSO 4 ·6H 2 O+NH 4 HCO 3 →SiC w @Ni(CO 3 ) 2 ·2Ni(OH) 2 ·2H 2 O↓+(NH4 ) 2 SO 4 +CO 2 ↑。

[0020] In the present invention, the mass ratio of the nickel salt to SiC w is (1.4~1.8) : (0.9~1.1). If the mass of SiC w is excessive, there will be uncoated silicon carbide whiskers, which do not participate in the reduction process and thus affect the purity. If the mass of the nickel salt is excessive, there will be nickel salt residues during the reduction process, which will also reduce the purity. A suitable mass ratio is beneficial to the synthesis of nickel silicide nanowires with higher purity.

[0021] In the present invention, the SiC w dispersion liquid includes SiC w , water and a dispersant; the mass ratio of the SiC w to the dispersant is 1 :(1~5). Since SiC w has a large aspect ratio and is prone to agglomeration, it needs to be uniformly dispersed in the solution with the assistance of a dispersant. The present invention does not impose special restrictions on the preparation method of the SiC w dispersion liquid, and a conventional preparation method in the art can be used, for example, dispersion can be promoted by ultrasonic, stirring, heating, etc.

[0022] In the present invention, the dispersant is selected from one or two of polyethylene glycol or polyvinylpyrrolidone, which can increase the viscosity of the aqueous solution and has good water solubility, and is easily removed through subsequent washing steps. When the dispersant is polyethylene glycol (PEG), the molecular weight of the polyethylene glycol is 2000~10000, and most preferably PEG6000. Further, the concentration of the dispersant is 1~20 g / L, which can be selected according to the specific dispersion situation.

[0023] In the present invention, the concentration of the NH 4 HCO 3 aqueous solution is 40~100 g / L, and the NH 4 HCO 3 aqueous solution is added at a set flow rate. Further, the stirring reaction is specifically: when stirring to a pH of 7.2~7.8, stop adding the NH 4 HCO 3 aqueous solution, and then continue stirring for 40~80 min. The stirring reaction can be carried out at room temperature (10~40 °C) without providing an additional heat source. The addition flow rate of the NH 4 HCO 3 aqueous solution is 0.001~0.01 L / min.

[0024] In the present invention, in the step of washing and drying the solid product obtained after the reaction, the solid product is obtained by means of standing, filtration or centrifugation. The present invention preferably adopts centrifugation to obtain the solid product. The washing is carried out by washing with water and ethanol in sequence, and the number of washing times is 2 to 5 times to remove water-soluble impurities and obtain a high-purity silicon-nickel precursor. The present invention does not impose special restrictions on the drying method, and any commonly used drying method in the art can be adopted, such as ordinary drying, vacuum drying, freeze drying, supercritical CO 2 drying, etc. The present invention preferably adopts vacuum drying. After the drying is completed, the present invention further includes a step of sieving the obtained powder to make it have a larger reaction area.

[0025] In the present invention, the calcination time is 1 to 5 h, more preferably 1.5 to 2.5 h; the flow rate of H 2 is 0.3 to 0.8 L / min. The heating rate of the present invention to the calcination temperature is 2 to 8 °C / min.

[0026] The present invention also provides nickel silicide nanowires prepared by the above in-situ preparation method. The main compound forms of the obtained nickel silicide nanowires are Ni 3 Si, Ni 2 Si and Ni 31 Si 12 etc.

[0027] The technical solution of the present invention will be further described below in conjunction with specific embodiments. Unless otherwise specified, the present invention does not impose special restrictions on the sources of the reagents used in the following embodiments, and commercially available products well-known to those skilled in the art can be adopted. The SiC w adopted in the following embodiments has an average length of 4 μm and an average diameter of 50 nm.

[0028] Example 1 This example provides an in-situ preparation method of nickel silicide nanowires.

[0029] (1) Take distilled water and place it in a beaker. Weigh and add polyethylene glycol 6000 (PEG6000). Place the beaker in a water bath and magnetically stir at a constant temperature of 55 °C for 15 min until PEG6000 is completely dissolved. Cool to room temperature to obtain a PEG aqueous solution with a concentration of 7.5 g / L.

[0030] (2) Add 1 g of SiC w powder to the PEG aqueous solution prepared in step (1) (containing 2.3 g of PEG6000), and ultrasonically disperse and mechanically stir. The ultrasonic time is 30 min to obtain a SiC w dispersion.

[0031] (3) Add 1.4 g of Ni(NO3 ) 2 ·6H 2 O is added to the SiC in step (2) w dispersion liquid, and stirred until completely dissolved to obtain a mixed solution.

[0032] (4) NH 4 HCO 3 is dissolved in distilled water to prepare an aqueous solution of NH 4 HCO 3 with a concentration of 79 g / L.

[0033] (5) The aqueous solution of NH 4 HCO 3 with a concentration of 79 g / L prepared in step (4) is slowly dropped into the mixed solution prepared in step (3) at a rate of 0.003 L / min, continuously stirred and the pH is monitored until pH = 7.5; then the addition of NH 4 HCO 3 is stopped to obtain a reaction mixture.

[0034] (6) The reaction mixture obtained in step (5) is continuously stirred for 60 min, and after the stirring is completed, it is left standing for 24 h.

[0035] (7) The supernatant is poured out, distilled water is added and left standing, and the supernatant is poured out after stratification. This step of washing with distilled water is repeated 3 times in total; then it is washed with absolute ethanol 3 times, and the washing procedure is the same as that of washing with distilled water; after washing, it is vacuum dried at 100 °C for 24 h, and then sieved (the sieve mesh is 50 meshes) to obtain a silicon-nickel precursor.

[0036] (8) The silicon-nickel precursor in step (7) is heated to 600 °C at a heating rate of 5 °C / min in an H 2 atmosphere (the flow rate of H 2 is controlled to be 0.6 L / min), and calcined at a constant temperature for 2 h to obtain nickel silicide nanowires.

[0037] The transmission electron microscope image and the energy dispersive spectrometer (EDS) elemental analysis diagram of the nickel silicide nanowires in this example are as Figure 1 shown. a is the microscopic morphology of the nickel silicide nanowires, b is a partial enlarged view of the morphology of a. It can be seen that the nickel silicide material is in a nanowire structure, Figure 1 c and d in

[0038] are the scanning elemental distribution diagrams of b. It can be seen that the elemental distribution of the nanowires shows that the inner layer is Ni element and the outer layer is Si element. Figure 2As shown, it can be seen that no other impurity peaks appear, indicating that high-purity nickel silicide material is in-situ prepared on the material surface. There are three forms of the nickel silicide compound, namely Ni 3 Si, Ni 2 Si, and Ni 31 Si 12 .

[0039] Example 2 This example provides a method for in-situ preparation of nickel silicide nanowires.

[0040] (1) Take distilled water and place it in a beaker. Weigh and add polyvinylpyrrolidone (PVP). Place the beaker in a water bath and magnetically stir at a constant temperature of 55 °C for 15 min until the PVP is completely dissolved. Cool to room temperature to obtain a PVP aqueous solution with a concentration of 7.5 g / L.

[0041] (2) Add 1 g of SiC w powder to the PVP aqueous solution prepared in step (1) (containing 2.3 g of PVP). Ultrasonically disperse and mechanically stir for 30 min to obtain a SiC w dispersion.

[0042] (3) Add 1.4 g of NiSO 4 ·6H 2 O to the SiC w dispersion in step (2) and stir until completely dissolved to obtain a mixed solution.

[0043] (4) Dissolve NH 4 HCO 3 in distilled water to prepare an aqueous solution of NH 4 HCO 3 with a concentration of 79 g / L.

[0044] (5) Slowly drip the aqueous solution of NH 4 HCO 3 with a concentration of 79 g / L prepared in step (4) into the mixed solution prepared in step (3) at a rate of 0.003 L / min, continuously stir and monitor the pH until pH = 7.5; then stop adding NH 4 HCO 3 to obtain a reaction mixture.

[0045] (6) Continue to stir the reaction mixture obtained in step (5) for 60 min, and after the stirring ends, let it stand for 24 h.

[0046] (7) Pour out the supernatant, continue to add distilled water and let it stand. After layering, pour out the supernatant. This distilled water washing step is repeated 3 times in total; then wash with absolute ethanol 3 times, and the steps are the same as those for washing with distilled water; after washing, vacuum dry at 100 °C for 24 h, and then screen (the sieve mesh is 50 meshes) to obtain the silicon-nickel precursor.

[0047] (8) Heat the silicon-nickel precursor in step (7) in an H 2 atmosphere (control the flow rate of H 2 to be 0.6 L / min) at a heating rate of 5 °C / min to 580 °C, and keep it calcined for 2 h to obtain nickel silicide nanowires.

[0048] Through X-ray diffraction analysis, the compound form of the nickel silicide nanowires prepared in this example is Ni 3 Si, Ni 2 Si and Ni 31 Si 12 .

[0049] Comparative Example 1 Compared with Example 1, the difference in this comparative example is that the mass of the SiC w powder is 1.4 g.

[0050] The X-ray diffraction pattern of the reduced powder is as Figure 3 shown. It can be seen that there are nickel silicide nanowires and excess silicon carbide whiskers, and the purity decreases.

[0051] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. An in-situ preparation method of nickel silicide nanowires, characterized in that: The steps include: Adding nickel salt to SiC w The nickel salt and SiC w The mass ratio of is (1.4~1.8): (0.9~1.1); then add NH4HCO3 aqueous solution, stir to react, wash and dry the solid product obtained after the reaction, and then heat to 550~650℃ in H2 atmosphere and calcine to obtain the product.

2. The in-situ preparation method according to claim 1, characterized in that: The SiC w The length is 2~10μm, SiC w The diameter is 20~80nm.

3. The in-situ preparation method according to claim 1, characterized in that: The nickel salt is nickel nitrate hexahydrate or nickel sulfate hexahydrate.

4. The in-situ preparation method according to claim 1, characterized in that: The SiC w The dispersion includes SiC w , water and a dispersant; the SiC w The mass ratio of the dispersant is 1: (1~5).

5. The in-situ preparation method according to claim 4, characterized in that: The dispersant is selected from one or both of polyethylene glycol and polyvinyl pyrrolidone.

6. The in-situ preparation method according to claim 4, characterized in that: The concentration of the dispersant is 1-20 g / L.

7. The in-situ preparation method according to claim 1, characterized in that: The concentration of the NH4HCO3 aqueous solution is 40-100 g / L, and the NH4HCO3 aqueous solution is added at a set flow rate.

8. The in-situ preparation method according to claim 7, characterized in that: The stirring reaction is specifically as follows: when the pH value is 7.2-7.8, the addition of the NH4HCO3 aqueous solution is stopped, and then stirring is continued for 40-80 minutes; and the washing is performed by washing with water and ethanol in sequence.

9. The in-situ preparation method according to claim 1, characterized in that: The calcination time is 1-5 hours; the flow rate of H2 is 0.3-0.8 L / min.

10. Nickel silicide nanowires prepared by the in-situ preparation method according to any one of claims 1 to 9.

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