CN1696057A - One-dimensional bamboo-shaped silicon nanomaterial and preparation method thereof - Google Patents

Abstract

A process for preparing the one-dimensional silicon nanotubes with bamboo shape includes preparing multi-pore aluminium oxide template by anodizing method, depositing Au in the pores of template by AC deposition method, dissolving the template in NaOH solution to obtain Au nanoparticles, dispersing them in absolute alcohol, loading it as catalyst in ceramic utensil as the substrate to grow silicon, putting it in the center of tubular furnace, filling the mixture of SiH4 and H2, growing said silicon nanotubes on the inner surface of ceramic utencil, closing SiH4 gas, and natural cooling.

Description

One-dimensional bamboo-shaped silicon nanomaterial and preparation method thereof

technical field

The invention relates to a silicon nanometer material, in particular to a one-dimensional bamboo-shaped silicon nanometer material and a preparation method thereof.

Background technique

Since S.Iijima (S.Iijima, Nature 1991, 354, 56.) synthesized carbon nanotubes in 1991, due to the potential application prospects in nanoelectronics, the development of one-dimensional nanomaterials, especially one-dimensional semiconductor nanomaterials Preparation research has become a hot field of nanotechnology today. Since silicon (Si) is the most widely used material in the semiconductor industry and microelectronics technology, and at the same time, the one-dimensional nanomaterials of silicon have shown some unique and excellent properties in terms of field emission and luminescence, so the one-dimensional nanomaterials of silicon The synthesis of structures has always attracted the attention of scientists.

Lieber et al. (A.M.Morales, C.M.Lieber, Science 1998, 279, 208.) of Harvard University prepared silicon nanowires (SiNWs) with a single crystal structure by using the laser-assisted catalytic growth (Laser-assisted Catalytic Growth) method. The method is to first mix silicon powder with a small amount of catalyst (such as iron, gold, etc.) and press it into a target material, and ablate it with a laser under a certain concentration of reducing atmosphere. The prepared silicon nanowires have a diameter of 6-20nm and a length greater than 1 μm. During the initial nucleation and growth process, the growth direction of silicon nanowires prepared by this method is basically <111> due to the principle of the lowest interfacial free energy. At the same time, the research group (Y.Cui, L.J.Lauhon, M.S.Gudiksen, J.Wang, C.M.Lieber, Appl.Phys.Lett.2001, 78, 2214.) also used metal-catalyzed chemical vapor deposition (Metal-catalyzed Chemical Vapor Deposition ) method to prepare silicon nanowires. Using silane as a silicon source and pre-prepared monodisperse gold nanoparticles as a catalyst, the reaction is carried out under a certain vacuum degree and temperature (450-600° C.). This method shows better selectivity and controllability, and the diameter of silicon nanowires can be controlled by adjusting the size of catalyst particles. The establishment of the above two methods is basically based on the Vapor-Liquid-Solid Growth (Vapor-Liquid-SolidGrowth) model, see (R.S.Wagner, W.C.Ellis, Appl.Phys.Lett.1964,4,89.), at first, The silicon source exists in a gaseous state under the conditions of laser irradiation or pyrolysis. When the gaseous atoms meet the catalyst, they form a liquid minimum eutectic with the catalyst in a specific proportion; Precipitation in the lowest eutectic; eventually forming a silicon nanomaterial with a one-dimensional linear structure. Li Shutang et al. (R.Q.Zhang, Y.Lifshitz, S.T.Lee, Adv. Mater, 2003, 7-8, 635) from City University of Hong Kong prepared silicon nanowires by oxide assisted growth (OAG). The team mixed high-purity silicon or its oxide powder with metal catalyst powder in a certain proportion, and performed thermal evaporation at a temperature of 1100-1400°C. In the temperature range of 900-1100°C, a large number of crystalline silicon nanometers were found. Wires are formed and the resulting product has a relatively uniform diameter. In addition, Zhang Lide et al. (X.Y. Zhang, L.D, Zhang, Adv. Mater, 2001, 13, 16, 1328.) successfully prepared highly ordered silicon nanowires using porous anodized alumina as a template and gold as a catalyst array. Zhu et al. (J.Luo, L.Zhang, Y.J.Zhang, J.Zhu, AdvMater.2002, 14, 1413.) used hydrofluoric acid to corrode silicon wafers to prepare silicon nanowires. This method is simple and easy , but the controllability is poor, and the diameter of the nanowire is large. The synthesis of silicon nanomaterials with a hollow structure has always been difficult because the bonding properties of silicon atoms determine that it tends to sp3 hybridization. Yang et al. (J.Sha, J.Niu, X.Ma, J.Xu, X.Zhang, Q.Yang, D.Yang, Adv.Mater, 2002, 14, 1219.) prepared for the first time with alumina template Crystalline silicon nanotubes with consistent dimensions. Lee et al. (W. Shi, H. Peng, N. Wang, C. P. Li, L. Xu, C. S. Lee, R. Kalish, S. T. Lee, J. Am. Chem. Soc. 2001, 123, 11095-11096.) Silicon nanoribbons (Silicon nanoribbons) grown along the <110> direction were successfully prepared using OAG.

Contents of the invention

The invention aims to provide a one-dimensional bamboo-shaped hollow silicon nanometer material and a preparation method thereof.

The one-dimensional bamboo-shaped silicon nanomaterial in the present invention is a material with a one-dimensional linear structure, and the outer diameter is 50-200nm. The interior is a hollow structure, and the internal hollow structure is a bamboo-shaped structure. The inner diameter of the bamboo-shaped structure is 10-150nm, and the shape is a cavity that is arranged in an orderly manner along the central axis of the triangular cone or trapezoidal cone or the like.

The specific steps of the preparation method of the said one-dimensional bamboo-shaped silicon nanomaterial in the present invention are as follows: 1) adopt the anodic oxidation method to prepare the porous alumina template; 2) use the alternating current electrodeposition method to deposit a 3) Dissolve the template completely with NaOH solution, leaving nano-sized gold particles, and wash with distilled water suction filtration, and transfer the gold particles to absolute ethanol to form a single gold particle with absolute ethanol as a dispersant. Disperse the solution, retain the solution and make the catalyst for growing silicon nanomaterials; 4) put the porcelain boat of the said gold catalyst in step 3) as the substrate for growing silicon, put it into the center of the tube furnace, and feed SiH , The mixed gas of H2 forms a light yellow one-dimensional bamboo-shaped hollow silicon nanomaterial on the inner wall of the porcelain boat. Turn off the SiH4 gas, stop heating, and naturally cool to room temperature, and the reaction process ends.

The said porous alumina template prepared by the anodic oxidation method can be prepared in a 0.3M oxalic acid solution at a temperature of 10°C, with aluminum foil as the positive electrode and platinum sheet as the negative electrode, and a DC voltage of 40V is applied, 2 to 3 After hours, aluminum oxide (Al2O3) with a thickness of 20-30 μm is formed on the surface of the aluminum foil.

Said alternating current electrodeposition technology method deposits a layer of metal gold at the bottom of the hole of the porous alumina template, and the aluminum foil and the platinum sheet with alumina attached to the surface of the gained in step 1) are used as two poles, and the electrolytic solution is chloroauric acid (HAuCl4 ) solution, the concentration is 10-3M, the voltage is 8-10V, the frequency is 50Hz, and the electrodeposition time is 10-15 minutes.

The concentration of said NaOH solution is 0.1M.

In step 4), the temperature of the tube furnace is 470° C. and the pressure is 1050 torr. The ratio of SiH4 and H2 mixed gas is SiH4:H2=2:1 by volume, and the total gas flow is controlled at 15-30 sccm. The entire reaction time for forming the light yellow one-dimensional bamboo-shaped hollow silicon nanometer material on the inner wall of the porcelain boat is 2 to 3 hours.

The silicon nanomaterial prepared according to the present invention exhibits a spatial one-dimensional form (similar to a line in appearance) in morphology. The diameter of this one-dimensional structure is 20-100 nm, and the length can reach hundreds of microns, but inside Cavities of tens of nanometers are distributed orderly in the axial direction, and these cavities are mostly triangular or semi-elliptical, or in between. The bottom edge of the cavity is 50nm wide and about 70nm high, and the arrangement and orientation are consistent, and the overall shape is similar to bamboo. Since the pore diameter of the porous alumina template can be adjusted according to the different pre-synthesis conditions, that is, the size of the catalyst can be changed, so the diameter of the one-dimensional silicon nanomaterial can be artificially adjusted to a certain extent. At the same time, the longer the mixed gas is introduced, that is, the longer the reaction time, the longer the length of the one-dimensional material.

So far, no one-dimensional nanomaterial of silicon with this morphology has been found in various references. Moreover, the prepared material has uniform structure, narrow size distribution, high yield and basically no other impurities. It is not difficult to imagine that this one-dimensional silicon nanomaterial, like silicon nanowires and silicon nanotubes, is bound to have potential application prospects in nanoelectronics technology. In addition, this method is relatively simple, the requirements for equipment are not high, and it is easy to master and control.

Description of drawings

Fig. 1 is a scanning electron microscope image of the one-dimensional bamboo-shaped silicon nanomaterial of the present invention. In FIG. 1 , the scale bar of (a) is 2 μm, the scale bar of (b) is 200 nm, and the scale bar of (c) is 100 nm.

Fig. 2 is a scanning transmission electron microscope (STEM) picture of the one-dimensional bamboo-shaped silicon nanomaterial of the present invention. In Fig. 2, the arrow shows the trajectory of the energy spectrum scanning, and the scale bar is 100nm.

Fig. 3 is the scanning curve of the element distribution energy spectrum of the one-dimensional bamboo-shaped silicon nanomaterial in the present invention. In FIG. 3 , the abscissa represents the position (position) passed by the electron beam during scanning, and the unit is nm, and the ordinate represents the relative intensity (intensity) of the obtained signal.

Fig. 4 is a transmission electron microscope image of the one-dimensional bamboo-shaped silicon nanomaterial of the present invention under normal conditions. In Fig. 4, the scales of ① and ② are 20nm, and the scales of ③ are 200nm.

Fig. 5 is a transmission electron microscope image of the one-dimensional bamboo-shaped silicon nanomaterial in the present invention under the condition that the SiH4 gas flow rate is reduced. In FIG. 5 , the scale of ① is 100 nm, the scale of ② is 20 nm, and the scale of ③ is 50 nm.

Fig. 6 is a transmission electron microscope image of the one-dimensional bamboo-shaped silicon nanomaterial in the present invention when the flow rate of SiH4 gas changes from large to small during the reaction process. In FIG. 6 , the scale of ① is 0.5 μm, the scale of ② is 100 nm, and the scale of ③ is 5 nm.

Fig. 7 is a transmission electron microscope image of the one-dimensional bamboo-shaped silicon nanomaterial in the present invention under the condition that the flow rate of SiH4 is further increased. In Fig. 7, the scale bar is 100 nm.

Figure 8 is a transmission electron microscope image of the as-prepared material using a smaller catalyst. Scale bar is 50nm.

Figure 9 is a transmission electron microscope image of the as-prepared material using a larger catalyst. Scale bar is 200nm.

Detailed ways

Example 1 A two-step anodic oxidation method was used to prepare an alumina template with a porous array structure. The pre-cut aluminum foil (thickness 0.2 mm, purity 99.99%) was ultrasonically cleaned in a mixed solution of ethanol, chloroform and acetone (volume ratio 1:2:1), and then in NaOH solution (concentration: 0.5M) for 10 minutes, with distilled water to clean the surface. After the above pretreatment steps are completed, the aluminum foil is electrochemically polished. Polishing is carried out under 10V DC voltage and 70°C water bath. The polishing solution is a mixture of phosphoric acid and glycerin (volume ratio: 1:1). Uniform polishing can be obtained on both sides. The polishing time is generally 10 to 15 minutes. The polished aluminum foil is placed in 0.3M oxalic acid solution at 15°C for anodic oxidation: the aluminum foil is also placed in parallel in the middle of the platinum sheet, the oxidation voltage is 40V, and the oxidation time is about 2 hours. At this time, uniform and ordered porous aluminum oxide films are formed on both sides of the aluminum foil.

Use the aluminum oxide template just prepared to carry out alternating current electrodeposition gold at room temperature, and its device is the same as the above-mentioned electrolytic cell device. 50Hz, the electrodeposition time is 10-15 minutes. Then, soak the gold-plated template in 0.1M NaOH solution until the template is completely dissolved, leaving purple-red gold nanoparticles, which are filtered and washed several times, and finally dispersed with ethanol.

One-dimensional bamboo-shaped silicon nanomaterials were prepared by chemical vapor deposition technology. Place a clean porcelain boat with gold nanoparticles attached in the center of the ceramic tube of the tube furnace. The system is a closed system, one end is air intake, and the other end is connected to the mechanical pump. Silane gas (SiH4:Ar=5:95) was used as the silicon source, and hydrogen was used as the reaction carrier gas. In order to ensure that the system is free of oxygen and other miscellaneous gases, the entire system was first vacuumed several times before the reaction, and then the temperature was raised in a hydrogen atmosphere according to a preset program. The hydrogen flow rate was 30 sccm, and the heating rate was 4 ° C / min, raised to 650°C and maintained for 2 hours to ensure full activation of the catalyst. After that, the temperature was lowered and kept at 470° C., and silane gas was started to be introduced. At this time, the silane flow rate is 10 sccm, the hydrogen gas flow rate is 5 sccm, the needle valve is adjusted to keep the system pressure at 1050 torr, and the reaction time is 2 hours.

Figure 1 is a scanning electron microscope (SEM) picture of the material. It can be seen that the material presents a one-dimensional shape, and the surface is smooth and flat without any structural defects. From the transmission electron microscope (TEM) picture of the material, it can be seen that its interior is a cavity arranged at periodic intervals. At the same time, we found that the difference of the catalyst particles largely determines the shape of the cavity, that is to say, the shape of the cavity can be regulated by changing the shape of the catalyst. From the electron energy spectrum (EDX) of the material, it can be determined that the composition of the material is elemental silicon. From the area electron diffraction image (SAED) of the material, it can be concluded that the crystalline structure of the material is amorphous. Figures 2 and 3 are the scanning transmission electron microscope (STEM) picture and element mapping of the material respectively, further illustrating the special shape of the material.

Embodiment 2 Under the condition (temperature, pressure) in embodiment 1 all constant situation, when starting to react at 470 ℃, with SiH The flow rate is set to 5 sccm, as shown in Figure 5, this moment product form changes, Compared with the previous form (as shown in Figure 4, the flow rate of SiH4 is 10 sccm), the internal cavities are arranged more tightly, and the interlayers between the cavities have structural defects, and even communicate with each other, showing a completely hollow tubular shape.

Example 3 If the SiH4 flow rate in Example 2 is quickly adjusted from 30 sccm to 10 sccm during the reaction, as shown in Figure 6, the one-dimensional structure will change from a solid linear shape to a bamboo joint shape , and its solid part presents a better crystalline structure.

Example 4 Under the condition that the conditions (temperature, pressure) in Example 1 are all constant, when the reaction is started at 470° C., the flow of SiH is set to 50 sccm, as shown in Figure 7, at this time, no The material of the cavity structure, the obtained product has completely changed from the one-dimensional bamboo-shaped silicon nanomaterial prepared in Example 1 to a silicon nanowire with a completely solid structure.

Example 5 As mentioned above, the diameter of this nano-nano material can be changed by changing the size of the catalyst. In embodiment 1, when the voltage of anodic oxidation is adjusted to 30V, other conditions are all the same as in embodiment 1, the pore diameter of porous alumina becomes smaller, and in subsequent steps, the particle diameter of the formed gold particle reduces to 50 nm, as shown in FIG. 8 , the diameter of the material prepared at this time is changed from 70-80 nm in Example 1 to 40-50 nm.

Example 6 Soak the prepared aluminum foil with a porous alumina film attached to its surface in a 6% phosphoric acid (H3PO4) solution for about 30 minutes, and expand the aperture of the alumina pores through acidic corrosion. Other experimental conditions All the same as in Example 1. As shown in FIG. 9 , the diameter of the prepared material changed from 70-80 nm in Example 1 to 180-200 nm.

Claims (10)

1. The one-dimensional bamboo-shaped silicon nanomaterial is characterized in that it is a material with a one-dimensional linear structure, the outer diameter is 50-200 nm, and the inner hollow structure is a bamboo-shaped structure. 2. The one-dimensional bamboo-shaped silicon nanomaterial according to claim 1, characterized in that the inner diameter of said bamboo-shaped structure is 10-150 nm. 3. The one-dimensional bamboo-shaped silicon nanomaterial according to claim 1 or 2, characterized in that said bamboo-shaped shape is a triangular cone or a trapezoidal cone or the like, and is arranged in an orderly manner along the central axis of the line. cavity. 4. A method for preparing a one-dimensional bamboo-shaped silicon nanomaterial, which is characterized in that the steps are: 1) using an anodic oxidation method to prepare a porous alumina template; 2) using an alternating current electrodeposition method to deposit a 3) Dissolve the template completely with NaOH solution, leaving nano-sized gold particles, and wash with distilled water suction filtration, and transfer the gold particles to absolute ethanol to form a single gold particle with absolute ethanol as a dispersant. Disperse the solution, retain the solution and make the catalyst for growing silicon nanomaterials; 4) put the porcelain boat of the said gold catalyst in step 3) as the substrate for growing silicon, put it into the center of the tube furnace, and feed SiH , The mixed gas of H2 forms a light yellow one-dimensional bamboo-shaped hollow silicon nanomaterial on the inner wall of the porcelain boat. Turn off the SiH4 gas, stop heating, and naturally cool to room temperature, and the reaction process ends. 5. The method for preparing one-dimensional bamboo-shaped silicon nanomaterials as claimed in claim 4, characterized in that the preparation of porous alumina templates by anodic oxidation refers to the preparation of porous alumina templates at a concentration of 0.3M oxalic acid solution at 10°C At a certain temperature, the aluminum foil is used as the positive electrode, the platinum sheet is used as the negative electrode, and a DC voltage of 40V is applied. After 2 to 3 hours, aluminum oxide with a thickness of 20 to 30 μm is formed on the surface of the aluminum foil. 6. The method for preparing one-dimensional bamboo-shaped silicon nanomaterials as claimed in claim 4, characterized in that said alternating current electrodeposition technique deposits a layer of metal gold at the bottom of the hole of the porous alumina template, which is based on step 1) The obtained aluminum foil and platinum sheet with alumina attached on the surface are two poles, the electrolytic solution is chloroauric acid solution, the concentration is 10-3M, the voltage is 8-10V, the frequency is 50Hz, and the electrodeposition time is 10-15 minutes. 7. The method for preparing one-dimensional bamboo-shaped silicon nanomaterials as claimed in claim 4, characterized in that the concentration of said NaOH solution is 0.1M. 8. The method for preparing one-dimensional bamboo-shaped silicon nanomaterials as claimed in claim 4, characterized in that in step 4), the temperature of the tube furnace is 470°C and the pressure is 1050 torr. 9. The method for preparing one-dimensional bamboo-shaped silicon nanomaterials as claimed in claim 4, characterized in that in step 4), the ratio of SiH4 and H2 mixed gas is SiH4: H2 = 2: 1 by volume, and the total gas The flow rate is controlled at 15-30 sccm. 10. The method for preparing one-dimensional bamboo-shaped silicon nanomaterials according to claim 4, characterized in that in step 4), said light yellow one-dimensional bamboo-shaped hollow silicon nanomaterials are formed on the inner wall of the porcelain boat The whole reaction time is 2～3 hours.

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