CN114715898B - A kind of high-density two-dimensional silicon-based nanomaterial and its preparation method - Google Patents

Abstract

A high-density two-dimensional silicon-based nanomaterial, including silicon nanosheets and silicon substrates, and the silicon nanosheets are perpendicular to the silicon substrate and form an array; the spacing between silicon nanosheets reaches 10~100nm, and the array composed of silicon nanosheets It presents a symmetrical shape with a thickness between 5 and 150nm; it is prepared according to the following steps: the silicon substrate is pretreated and reacted with calcium in vacuum in stages, then cooled to room temperature, and then placed in manganese chloride Soak in the ethanol solution, and then place the manganese chloride particles at both ends of the sectional heating furnace respectively, feed nitrogen gas throughout the process, heat one end of the manganese chloride particles to 700~830°C, and heat the substrate end to 500~600°C for heat preservation reaction , and cooled to room temperature after the reaction. The silicon nanosheets in the nanomaterials of the present invention do not agglomerate or collapse, the thickness can be effectively adjusted between 5 and 150 nm, the height reaches about 2 μm, the yield is high, and a high-density silicon nanosheet array is formed.

Description

A kind of high-density two-dimensional silicon-based nanomaterial and its preparation method

The present invention is a divisional application of patent application number 202011308192.4 and the title of the invention is "a method for preparing a silicon nanosheet array".

technical field

The invention relates to the technical field of silicon nanomaterials, in particular to a high-density two-dimensional silicon-based nanomaterial and a preparation method thereof.

Background technique

At present, the research on low-dimensional silicon nanomaterials has been greatly developed, but there are relatively few studies on two-dimensional silicon nanosheets, which is mainly due to the sp3 hybrid cubic structure of silicon, which makes it difficult to self-assemble into atomically thick two However, silicon nanosheets exhibit excellent electrical, optical, and mechanical properties, such as semiconductor properties, large specific surface area, quantum well effect, and surface modification, making them widely used in nanoelectronics, optoelectronics, It has important application prospects in energy conversion, energy storage and biochemical detection. In particular, 2D Si-based nanostructures with internal void spaces, which have high theoretical capacities and overcome the large-scale volume change problem, are considered to be favorable choices for high-performance electrode materials in lithium batteries. For example, flakes and nanosheet arrays with multilayer structures can effectively reduce the volume change during charge and discharge, prolong cycle life; and provide more active sites for lithium ions, and provide good kinetics for lithium ions and electron transport. performance. The nanosheets (Nanosheets) refer to sheet-like structures with a thickness direction at the nanometer level, or even at the atomic layer level. The excellent performance of nanosheet arrays is closely related to its structural properties. Studies have shown that the density, thickness and arrangement of nanosheets have a great influence on the performance of nanosheet arrays. However, there are still many difficulties in the preparation of silicon nanosheets by conventional methods. For example, the use of chemical vapor deposition (CVD) (ACS Nano, 2014, 8: 6556-6562) requires relatively high temperature control and other preparation conditions. The control ability of the shape parameters such as the thickness, area and density of nanosheets is very weak, and it cannot be formed into a regular array; another example, using calcium disilicide (CaSi ₂ ) as the precursor of silicon nanosheets, through When preparing calcium by extracting calcium from metal chloride salts, it is easy to bring in metal impurities and form metal silicides. The resulting two-dimensional nanosheet structure is prone to agglomeration and self-assembly, resulting in uncontrollable morphology and structural properties. The nanosheet array has low density, poor conductivity, and its yield is low, and the yield can only reach 1% of the raw material.

Contents of the invention

The first object of the present invention is to provide a high-density two-dimensional silicon-based nanomaterial, which has the advantages of high density and controllable shape.

Another object of the present invention is to provide a method for preparing the above-mentioned high-density two-dimensional silicon-based nanomaterial, which is simple and efficient.

Above-mentioned purpose of the present invention is realized through following technical scheme:

A high-density two-dimensional silicon-based nanomaterial is characterized in that: it includes silicon nanosheets and a silicon substrate, and the silicon nanosheets are perpendicular to the silicon substrate and form an array; the spacing between the silicon nanosheets Reaching 10~100nm, the array composed of silicon nanosheets presents a symmetrical shape, and the thickness is between 5~150nm;

It is specifically prepared by the following steps:

After the pretreatment of the silicon substrate with a crystal plane of (111), put it in a vacuum with calcium to carry out a segmental heating reaction at 630~640°C and 700~720°C in turn, and after the reaction is completed, it is lowered to room temperature, and the reacted silicon The substrate is soaked in ethanol solution of manganese chloride for 2 hours, and then the soaked silicon substrate and manganese chloride particles are respectively placed at both ends of the sectional heating furnace. 830°C, one end of the substrate is heated to 500~600°C for heat preservation reaction, and cooled to room temperature after the reaction.

When preparing the CaSi ₂ precursor, there are obvious differences in the structure and performance of the silicide prepared by Si and Ca with different crystal planes. In addition, due to the slow diffusion of Si, in the ordinary chemical vapor deposition preparation process, it is difficult to form a single-phase CaSi ₂ precursor with a vertical array structure. Instead, Ca is deposited on the Si surface to form a layer of lateral growth. CaSi ₂ planar thin film structure. The present invention adopts the Si substrate of crystal plane (111). When the first stage is heated, Ca rapidly diffuses and contacts with the Si substrate, and reacts to form a CaSi layer at a relatively high Ca concentration. There is a dynamic balance of gas concentration in the quartz tube. Prevent the formation of Ca ₂ Si phase and promote the growth of CaSi layer to the critical state. With the formation of silicide, the surface lattice structure of Si is deformed, and dislocations and vacancies are formed at the contact surface. As the temperature rises, deformation and dislocations intensify, forming growth sites of CaSi ₂ . The existence of the CaSi layer makes Ca molecules only diffuse vertically along the CaSi/Si interface, and then the heating rate is lowered to further increase the temperature, and the gas concentration is dynamically adjusted to change the Ca concentration. _2. The CaSi ₂ /Si interface reacts to generate CaSi ₂ , and through the different growth rates of CaSi ₂ at the three interfaces, the CaSi ₂ array is controlled to gradually accumulate and grow in the vertical direction. In addition, the further heat treatment of CaSi during the second high-temperature heating process, as well as the subsequent control of the cooling rate, make CaSi fall off from the surface of the vertically grown CaSi ₂ by virtue of the difference in thermal expansion and lattice size of different substances, and the prepared CaSi ₂ Formed into an array without agglomeration.

As a further optimization, the above-mentioned silicon substrate is preferably a single crystal silicon substrate with a size of 8*8mm ² , a thickness of 1mm, and a crystal plane of (111), and the amount of calcium corresponding to each silicon substrate is 0.02~0.03g.

The method for preparing the above-mentioned high-density two-dimensional silicon-based nanomaterials is characterized in that: after pretreatment of the silicon substrate with a crystal plane of (111), it is placed in a vacuum with calcium at 630-640° C. and 700-720° C. Carry out segmented heating reaction, after the reaction is completed, drop to room temperature, place the reacted silicon substrate in ethanol solution of manganese chloride and soak for 2 hours, then place the soaked silicon substrate and manganese chloride particles in the compartment of the segmented heating furnace respectively At both ends, nitrogen gas is introduced throughout the whole process, and one end of the manganese chloride particles is heated to 700~830°C, and one end of the substrate is heated to 500~600°C for heat preservation reaction. After the reaction is completed, it is cooled to room temperature; the size of the silicon substrate is 8*8mm ² , a thickness of 1mm, and a single crystal silicon substrate with a crystal plane of (111), the amount of calcium corresponding to each silicon substrate is 0.02~0.03g; the mass ratio of the manganese chloride particles to calcium is 2~3:5~10 , heat one end of the manganese chloride particles to 700-830°C, heat one end of the substrate to 500-600°C, cool to room temperature after the reaction is completed, the heating rate is 10-15°C/min, the holding time is 10-20min, cool The cooling rate is the same as the heating rate; the stepwise heating reaction of the silicon substrate and calcium, specifically placing the silicon substrate and calcium metal particles in a quartz container, and keeping a certain distance, placing the quartz container in a vacuum furnace, adjusting After the vacuum degree reaches 10 ^-6 Torr, raise the temperature to 630~640°C at a rate of 5~10°C/min, keep it for 70~80 minutes, then raise the temperature to 700~720°C at a rate of 3~4°C/min, and hold it for 40~ 60min, then drop to room temperature at a rate of 15-50°C/min, and take out the silicon substrate; further preferably, the calcium metal particles are at the bottom of the quartz container, the silicon substrate is at the upper end of the calcium metal particles, face down, and the quartz container mouth Seal with quartz wool.

When using metal chloride salts to react with _CaSi2 arrays to extract Ca, it is easy to introduce other metal impurities, and even new metal silicide impurities synthesized by metal and Si remain in the nanosheet arrays, resulting in poor performance of the silicon nanosheet arrays. Moreover, during the preparation process, after the Ca is extracted, the final Si nanosheet array is prone to collapse and agglomeration, and cannot maintain its array structure; a large number of dangling bonds are formed on the Si surface and interface, which reduces the carrier lifetime. In the present invention, the silicon substrate on which the CaSi ₂ array is formed is soaked in an ethanol solution of manganese chloride to remove the residual CaSi layer, and then the CaSi ₂ array is first soaked in the process of heating up to 500-600°C and then mixed with the subsequent chlorine The reaction of manganese oxide gas makes the extraction of Ca ions more complete and fast, and effectively takes away metal manganese, reduces metal residues, avoids the synthesis of Mn-Si compounds with Si, and realizes the capping effect of chlorine elements when cooling down, and The dangling bonds on the Si surface and interface are reduced, the surface state and interface state are eliminated, the structure of the nanosheet is stabilized, and its performance is improved.

Further optimization, the ethanol solution of manganese chloride is preferably prepared by dissolving manganese chloride and ethanol according to the mass volume ratio of 5-10g:50mL.

Further optimization, the above substrate pretreatment is to immerse the single crystal silicon substrate in 50mL acetone solution for ultrasonication, evaporate to the remaining 15mL acetone solution, and then add hydrofluoric acid, nitric acid and acetic acid with a mass fraction of 50% according to the volume ratio of 1: Soak in a mixed solution of 1:2 composition for 10 seconds, rinse with pure water, and finally dip in a hydrofluoric acid aqueous solution with a volume fraction of 5-10% for cleaning, and dry in the air after washing.

A method for preparing a high-density two-dimensional silicon-based nanomaterial, characterized in that, the steps are as follows:

(1) Silicon substrate pretreatment

Soak a monocrystalline silicon substrate with a size of 8*8mm ² , a thickness of 1mm, and a crystal plane of (111) in 50mL of acetone solution, ultrasonically evaporate to the remaining 15mL of acetone solution, and then add 50% hydrofluoric acid, Soak in the mixed solution of nitric acid and acetic acid according to the volume ratio of 1:1:2 for 10 seconds, rinse with pure water, and finally dip in hydrofluoric acid aqueous solution with a volume fraction of 5-10%. Dry;

(2) Preparation of silicide precursor

Put the silicon substrate and 0.02~0.03g of calcium metal particles in a quartz container, the calcium metal particles are at the bottom of the quartz container, the silicon substrate is at the upper end of the calcium metal particles, and keep a certain distance, the silicon substrate is facing down, and the quartz container mouth is used Seal with quartz wool, place the quartz container in a vacuum furnace, adjust the vacuum degree to 10 ^-6 Torr, raise the temperature to 630-640°C at a rate of 5-10°C/min, keep it warm for 70-80min, and then increase the temperature for 3-4 Raise the temperature to 700~720℃ at a rate of ℃/min, keep it warm for 40~60min, then lower it to room temperature at a rate of 15~50℃/min to obtain a CaSi ₂ -silicon substrate, and take out the CaSi ₂ -silicon substrate;

(3) soaking treatment

Place the CaSi ₂ -silicon substrate reacted in step (2) in the ethanol solution of manganese chloride and soak for 2 hours. The mass volume ratio of manganese chloride and ethanol in the ethanol solution of manganese chloride is 5~10g:50mL;

(4) Extract calcium

Place the soaked CaSi ₂ -silicon substrate and 0.5~1g of manganese chloride particles at both ends of the sectional heating furnace respectively, and place them in a nitrogen atmosphere, heat one end of the silicon substrate to 500~600°C, and heat the end of the manganese chloride to 780~830°C, the heating rate is 10~15°C/min, keep warm for 10~20min, and then lower the temperature to room temperature at the same cooling rate as the heating rate.

The present invention has following technical effect:

The high-density two-dimensional silicon-based nanomaterials prepared by the present invention include silicon nanosheets and silicon substrates. The silicon nanosheets are perpendicular to the silicon substrate and form an array. The distance between the nanosheets reaches 10-100nm. The array can present a variety of symmetrical shapes. The nanosheets do not agglomerate or collapse. The nanosheets are uniform in size, with a thickness between 5-150nm and a height of about 2μm. The yield can reach 55.7-63.9% of the raw material, forming a high-density The silicon nanosheet array has a purity of 96.4%. The preparation method of the present invention is simple and efficient, prepares a density-controllable nanosheet array, effectively controls the area, density, symmetry, etc. of the array, and solves the problems of low density and uncontrollable shape of the prepared silicon nanosheet array. question.

Description of drawings

Fig. 1: the preparation process flowchart of the present invention.

Figure 2: Schematic diagram of the preparation device used to prepare the precursor in the present invention.

Figure 3: X-ray diffraction pattern of the silicon nanosheet array in the high-density two-dimensional silicon-based nanomaterial of the present invention.

Figure 4: SEM images of silicon nanosheet arrays in the high-density two-dimensional silicon-based nanomaterials of the present invention.

Detailed ways

The present invention is specifically described by the following examples. It is necessary to point out that the following examples are only used to further illustrate the present invention, and cannot be interpreted as limiting the protection scope of the present invention. Those skilled in the art can according to the above-mentioned description SUMMARY OF THE INVENTION Some non-essential improvements and adjustments are made to the present invention.

Example 1

A preparation method of a high-density two-dimensional silicon-based nanomaterial is carried out as follows:

(1) Silicon substrate pretreatment

A single crystal silicon substrate with a size of 8*8mm ² , a thickness of about 1mm, and a crystal plane of (111) was soaked in 50mL of acetone solution for ultrasonication, and then evaporated to the remaining 15mL of acetone solution. acid, nitric acid, and acetic acid in a volume ratio of 1:1:2, soaked for 10 seconds, rinsed with pure water, and finally dipped in an 8% hydrofluoric acid aqueous solution for cleaning. Dry;

(2) Preparation of silicide precursor

Place the pretreated silicon substrate and 0.025g of calcium metal particles in an adaptation container, the calcium metal particles are at the bottom of the quartz container, the silicon substrate is at the upper end of the calcium metal particles, and keep a certain distance, face down, and the quartz container mouth is used Seal with quartz wool, place the quartz container in a vacuum furnace, adjust the vacuum to 10 ^-6 Torr, then raise the temperature to 635°C at a rate of 6°C/min, keep it warm for 75min, and then raise the temperature to 710°C at a rate of 3.5°C/min , keep it warm for 50 minutes, then lower it to room temperature at a rate of 25°C/min, and take out the CaSi ₂ -silicon substrate;

(3) soaking treatment

Place the CaSi ₂ -silicon substrate reacted in step (2) in the ethanol solution of manganese chloride, soak for 2 hours, the mass volume ratio of manganese chloride and ethanol in the ethanol solution of manganese chloride is 7g:50mL;

(4) Extract calcium

Place the soaked CaSi ₂ -silicon substrate and 0.8g of manganese chloride particles at both ends of the sectional heating furnace respectively, feed nitrogen gas throughout, heat one end of the silicon substrate to 550°C, and one end of the manganese chloride to 800°C, then raise the temperature The rate is 12°C/min, keep warm for 10min, and then lower the temperature to room temperature at a rate of 12°C/min.

In the high-density two-dimensional silicon-based nanomaterials prepared in this example, the silicon nanosheets grow perpendicular to the silicon substrate, the vertical height of the silicon nanosheets is about 1.8-2 μm, and the silicon nanosheets are arranged in a three-way centrosymmetric manner, as shown in Fig. The X-ray diffraction energy spectrum in 3 proves the crystalline silicon material matrix of the nanosheets, (a) is the precursor of CaSi ₂ on the substrate, (b) is the silicon nanosheets generated after CaSi ₂ is extracted from the precursor on the silicon substrate array. The scanning electron microscope image of the corresponding nanosheet array is shown in Figure 4. The thickness of the nanosheets is between 78 and 120nm. The yield of the formed silicon nanosheet array accounts for 55.7% of the raw material Si, and the purity reaches 90.9%.

Example 2

A preparation method of a high-density two-dimensional silicon-based nanomaterial is carried out as follows:

(1) Silicon substrate pretreatment

A single crystal silicon substrate with a size of 8*8mm ² , a thickness of about 1mm, and a crystal plane of (111) was soaked in 50mL of acetone solution for ultrasonication, and then evaporated to the remaining 15mL of acetone solution. acid, nitric acid, and acetic acid in a volume ratio of 1:1:2, soaked for 10 seconds, rinsed with pure water, and finally dipped in hydrofluoric acid solution with a volume fraction of 10%. Dry;

(2) Preparation of silicide precursor

Place the silicon substrate and 0.03g of calcium metal particles in an adaptation container, the calcium metal particles are at the bottom of the quartz container, the silicon substrate is at the upper end of the calcium metal particles, and keep a certain distance, face down, and the quartz container mouth is sealed with quartz wool, Place the quartz container in a vacuum furnace, adjust the vacuum degree to 10 ^-6 Torr, raise the temperature to 640°C at a rate of 10°C/min, keep it for 70min, then raise the temperature to 720°C at a rate of 4°C/min, and keep it for 40min. Then cool down to room temperature at a rate of 50°C/min, and take out the CaSi ₂ -silicon substrate;

(3) soaking treatment

Place the CaSi ₂ -silicon substrate reacted in step (2) in the ethanol solution of manganese chloride, soak for 2 hours, the mass volume ratio of manganese chloride and ethanol in the ethanol solution of manganese chloride is 10g:50mL;

(4) Extract calcium

Place the soaked CaSi ₂ -silicon substrate and 1g of manganese chloride particles at both ends of the sectional heating furnace respectively, feed nitrogen gas throughout, heat one end of the silicon substrate to 600°C, and heat the end of the manganese chloride to 830°C, the heating rate 15°C/min, keep warm for 0min, then drop the temperature to room temperature at a rate of 15°C/min.

In the high-density two-dimensional silicon-based nanomaterials prepared in this example, the nanosheets grow perpendicular to the substrate, presenting a three-way centrosymmetric arrangement to form an array. The thickness of the nanosheets is between 38 and 82 nm, and the thickness of the silicon nanosheet array is The vertical height is about 2.2~2.4μm, and the yield of the formed silicon nanosheet array accounts for 60.3% of the raw material Si, and the purity reaches 93.1%.

Example 3

A preparation method of a high-density two-dimensional silicon-based nanomaterial is carried out as follows:

(1) Silicon substrate pretreatment

A single crystal silicon substrate with a size of 8*8mm ² , a thickness of about 1mm, and a crystal plane of (111) was soaked in 50mL of acetone solution for ultrasonication, and then evaporated to the remaining 15mL of acetone solution. acid, nitric acid and acetic acid in a volume ratio of 1:1:2 for 10 seconds, rinsed with pure water, and finally dipped in hydrofluoric acid solution with a volume fraction of 5%. Dry;

(2) Preparation of silicide precursor

Place the silicon substrate and 0.02g of calcium metal particles in an adaptation container, the calcium metal particles are at the bottom of the quartz container, the silicon substrate is at the upper end of the calcium metal particles, and keep a certain distance, face down, and the quartz container mouth is sealed with quartz wool, Place the quartz container in a vacuum furnace, adjust the vacuum degree to 10 ^-6 Torr, raise the temperature to 630°C at a rate of 5°C/min, keep it for 80 minutes, then raise the temperature to 700°C at a rate of 3°C/min, and keep it for 60 minutes. Then cool down to room temperature at a rate of 15°C/min, and take out the CaSi ₂ -silicon substrate;

(3) soaking treatment

Put the CaSi ₂ -silicon substrate reacted in step (2) in the ethanol solution of manganese chloride and soak for 2 hours. The mass volume ratio of manganese chloride and ethanol in the ethanol solution of manganese chloride is 5g:50mL;

(4) Extract calcium

Place the soaked CaSi ₂ -silicon substrate and 0.5g of manganese chloride particles at both ends of the sectional heating furnace respectively, feed nitrogen gas throughout the process, heat one end of the silicon substrate to 500°C, and one end of the manganese chloride to 780°C, then raise the temperature The rate is 10°C/min, keep warm for 20min, and then lower the temperature to room temperature at a rate of 10°C/min.

In the high-density two-dimensional silicon-based nanomaterials prepared in this example, the nanosheets grow perpendicular to the substrate and form an array in a three-way centrosymmetric arrangement. The thickness of the nanosheets is 110-135 nm, and the vertical height is 1.9-2.2 μm. , the yield of the formed silicon nanosheet array accounts for 63.9% of the raw material Si, and the purity reaches 96.4%.

Example 4

A preparation method of a high-density two-dimensional silicon-based nanomaterial is carried out as follows:

(1) Silicon substrate pretreatment

A single crystal silicon substrate with a size of 8*8mm ² , a thickness of about 1mm, and a crystal plane of (111) was soaked in 50mL of acetone solution for ultrasonication, and then evaporated to the remaining 15mL of acetone solution. acid, nitric acid and acetic acid in a volume ratio of 1:1:2 for 10 seconds, rinsed with pure water, and finally dipped in hydrofluoric acid solution with a volume fraction of 5%. Dry;

(2) Preparation of silicide precursor

Place the silicon substrate and 0.02g of calcium metal particles in an adaptation container, the calcium metal particles are at the bottom of the quartz container, the silicon substrate is at the upper end of the calcium metal particles, and keep a certain distance, face down, and the quartz container mouth is sealed with quartz wool, Place the quartz container in a vacuum furnace, adjust the vacuum degree to 10 ^-6 Torr, raise the temperature to 630°C at a rate of 5°C/min, keep it for 80 minutes, then raise the temperature to 700°C at a rate of 3°C/min, and keep it for 60 minutes. Then cool down to room temperature at a rate of 15°C/min, and take out the CaSi ₂ -silicon substrate;

(3) soaking treatment

Place the CaSi ₂ -silicon substrate reacted in step (2) in the ethanol solution of manganese chloride, soak for 2 hours, the mass volume ratio of manganese chloride and ethanol in the ethanol solution of manganese chloride is 5g:50mL;

(4) Extract calcium

Place the soaked CaSi ₂ -silicon substrate and 0.5g of manganese chloride particles at both ends of the sectional heating furnace respectively, feed nitrogen gas throughout the process, heat one end of the manganese chloride to 780°C, heat the end of the silicon substrate to 600°C, and raise the temperature The rate is 10°C/min, keep warm for 20min, and then lower the temperature to room temperature at a rate of 10°C/min.

In the high-density two-dimensional silicon-based nanomaterials prepared in this example, the nanosheets grow perpendicular to the substrate and form an array in a three-way centrosymmetric arrangement. The thickness of the nanosheets is 6-25 nm, and the vertical height is 1.8-2.1 μm. , the yield of the formed silicon nanosheet array accounts for 57.4% of the raw material Si, and the purity reaches 92.2%.

Claims (5)

1. A high-density two-dimensional silicon-based nanomaterial, characterized in that: it includes silicon nanosheets and silicon substrates, and the silicon nanosheets are perpendicular to the silicon substrate and form an array; between the silicon nanosheets The spacing of silicon nanosheets reaches 10~100nm, and the array composed of silicon nanosheets presents a symmetrical shape with a thickness between 5~150nm; It is specifically prepared by the following steps: After the pretreatment of the silicon substrate with a crystal plane of (111), put it in a vacuum with calcium to carry out a segmental heating reaction at 630~640°C and 700~720°C in turn, and after the reaction is completed, it is lowered to room temperature, and the reacted silicon The substrate is soaked in ethanol solution of manganese chloride for 2 hours, and then the soaked silicon substrate and manganese chloride particles are respectively placed at both ends of the sectional heating furnace. 830°C, one end of the substrate is heated to 500~600°C for heat preservation reaction, and cooled to room temperature after the reaction. 2. The high-density two-dimensional silicon-based nanomaterial according to claim 1, wherein the silicon substrate is preferably a single crystal with a size of 8*8mm ² , a thickness of 1mm, and a crystal plane of (111) For silicon substrates, the dosage of calcium for each silicon substrate is 0.02~0.03g. 3. The preparation method of high-density two-dimensional silicon-based nanomaterials according to claim 1 or 2, characterized in that: after pretreatment of the silicon substrate with a crystal plane of (111), place it in vacuum with calcium 630~640°C and 700~720°C for segmental heating reaction, after the reaction is completed, lower to room temperature, soak the reacted silicon substrate in ethanol solution of manganese chloride for 2 hours, then soak the soaked silicon substrate with chloride The manganese particles were respectively placed at both ends of the sectional heating furnace, nitrogen gas was introduced throughout the process, one end of the manganese chloride particles was heated to 700-830°C, the other end of the substrate was heated to 500-600°C for heat preservation reaction, and after the reaction was completed, it was cooled to room temperature; The silicon substrate is a single crystal silicon substrate with a size of 8*8mm ² , a thickness of 1mm, and a (111) crystal plane. The amount of calcium corresponding to each silicon substrate is 0.02~0.03g; the manganese chloride particles and calcium The mass ratio is 2~3:5~10, heat one end of the manganese chloride particles to 700~830°C, heat the substrate end to 500~600°C, cool to room temperature after the reaction, and the heating rate is 10~15°C/ min, the holding time is 10-20min, and the cooling rate is the same as the heating rate during cooling; the stepwise heating reaction of the silicon substrate and calcium, specifically, the silicon substrate and calcium metal particles are placed in a quartz container and kept at a certain distance, Place the quartz container in a vacuum furnace, adjust the vacuum degree to 10 ^-6 Torr, raise the temperature to 630~640°C at a rate of 5~10°C/min, keep it warm for 70~80min, and then increase the temperature at a rate of 3~4°C/min Raise the temperature to 700-720°C, keep it warm for 40-60min, then cool down to room temperature at a rate of 15-50°C/min, and take out the silicon substrate; the calcium metal particles are at the bottom of the quartz container, and the silicon substrate is on the upper end and front side of the calcium metal particles Downward, the mouth of the quartz container is sealed with quartz wool. 4. The preparation method of high-density two-dimensional silicon-based nanomaterials as claimed in claim 3, characterized in that: the ethanolic solution of manganese chloride is preferably manganese chloride and ethanol according to the mass volume of 5 ~ 10g: 50mL Than dissolving preparation. 5. The preparation method of high-density two-dimensional silicon-based nanomaterials as claimed in claim 3 or 4, characterized in that: the substrate pretreatment is to immerse the single crystal silicon substrate in 50mL acetone solution and ultrasonically evaporate to the remaining 15mL of acetone solution, then soak for 10 seconds in a mixed solution of hydrofluoric acid, nitric acid and acetic acid with a mass fraction of 50% in a volume ratio of 1:1:2, rinse with pure water, and finally use a volume fraction of 5- 10% hydrofluoric acid aqueous solution spot cleaning, after washing with water, let it dry in the air.

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