CN1956920A - Silicon particles, silicon particle superlattices, and methods for their preparation - Google Patents

Abstract

The production method of the present invention can provide highly pure silicon nanoparticles having high practicability as a raw material powder for high-performance light-emitting elements or electronic components on an industrial scale. The preparation method comprises the following steps: the method comprises a step of synthesizing silicon oxide particles containing silicon particles by reacting a monosilane gas with an oxidizing gas for oxidizing the monosilane gas in a gas phase, and a step of holding the silicon oxide particles at 800 to 1400 ℃ in an inert atmosphere and then removing the silicon oxide particles with hydrofluoric acid.

Description

Silicon particles, silicon particle superlattices, and methods for their preparation

technical field

The invention relates to nanometer (nm) size high-purity silicon particles and a preparation method thereof.

In addition, the present invention also relates to a silicon particle superlattice formed by periodically and regularly arranging nanometer (nm) size silicon particles in a two-dimensional or three-dimensional manner and a preparation method thereof.

Background technique

Silicon particles (silicon nanoparticles) having nano-order particle diameters have significantly different physical and chemical properties from those of bulk silicon, and therefore have attracted great attention as new functional materials in recent years. For example, based on the confinement effect or surface energy effect of quantum theory, silicon nanoparticles have a different energy band structure from bulk silicon, and can see luminescence that cannot be observed in bulk silicon. Therefore, it is expected to be used as a new type of silicon Application of raw materials for light-emitting devices.

Ordinary silicon fine powder obtained by finely pulverizing silicon has almost the same physical and chemical properties as bulk silicon. In contrast, silicon nanoparticles have a fine particle size, a small particle size distribution range, and high purity. Therefore, it is considered that specific properties such as a luminescent phenomenon significantly different from those of bulk silicon are exhibited.

Conventionally, as a method for producing silicon nanoparticles, for example, (1) vaporizing the first high-temperature plasma generated between opposing silicon electrodes in the second high-temperature plasma generated by electrodeless discharge in a reduced-pressure atmosphere has been used. Method of passing silicon (Patent Document 1), (2) Separation and removal of silicon nanoparticles from an anode composed of a silicon wafer by electrochemical etching (Patent Document 2), (3) Using a reactive electrode for halogen-containing organosilicon compounds A method of performing electrode reduction (Patent Document 3) and the like.

However, in the methods (1) and (2) above, the production rate of silicon nanoparticles is remarkably low, and thus it is difficult to improve productivity. In addition, in the above-mentioned method (3), since the raw material contains halogens such as Cl, and the product is easily mixed, it is difficult to keep the total amount of Na, Fe, Al, and Cl at 10 ppm or less.

Therefore, it is very difficult to produce high-purity silicon nanoparticles that are not useful as raw material powders for high-performance light-emitting devices or electronic components on an industrial scale.

On the other hand, in order to express the luminescence phenomenon based on the above-mentioned energy band structure and surface energy level effect, etc., it is necessary to periodically and regularly arrange nano-scale silicon particles with uniform particle size in two or three dimensions, that is, to form a so-called superlattice. structure.

Therefore, as a specific method of using nanoscale silicon particles as new functional materials, it is necessary to selectively extract particles of a specific size from a large number of prepared silicon particles and arrange them two-dimensionally or three-dimensionally, that is, to form a so-called superlattice. method.

Conventionally, as methods for producing silicon particles or a superlattice containing silicon particles, or a film or molded article formed by arranging silicon particles, (a) a chemical vapor deposition (CVD) method (Patent Documents 4, 5), ( b) spin coating method (Patent Document 6), (c) method of filtering particles from a particle-containing suspension using a porous partition wall (Patent Document 7), (d) method of utilizing electrophoresis of particles (Patent Document 8), etc. .

However, the above-mentioned method (a) is mostly carried out in a high-temperature vacuum or a plasma atmosphere, so a highly controlled vacuum heating device or a plasma generator is required, and the cost increases. In addition, although the method of (b) does not require expensive equipment like the method of (a), the product yield is significantly reduced. Regarding methods (c) and (d), particles are arranged on porous partition walls or electrodes, but there is no suitable method for separating a film or molded article made of a superlattice from these materials.

In addition, the particle size of the previous superlattice containing silicon particles produced by these methods has deviations, so the energy band structure or surface energy level is unstable, and when used as a light-emitting element, the luminous efficiency is not sufficiently improved. When electronic components are used, there is a possibility of failure or the like.

Patent Document 1: Japanese Unexamined Patent Publication No. 6-279015

Patent Document 2: Special Publication No. 2003-515459

Patent Document 3: JP-A-2002-154817

Patent Document 4: Japanese Unexamined Patent Publication No. 5-62911

Patent Document 5: JP-A-6-349744

Patent Document 6: Japanese Unexamined Patent Publication No. 11-130867

Patent Document 7: JP-A-2002-279704

Patent Document 8: JP-A-2003-89896

Contents of the invention

The inventors of the present invention have intensively studied whether there is a method for producing high-purity silicon nanoparticles on an industrial scale that can realize high-performance light-emitting elements or electronic components. As a result, it was found that under specific conditions, after heat-treating silicon oxide containing silicon particles prepared by a gas phase method using a specific raw material, hydrofluoric acid was used to remove excess silicon oxide. By the above method, particles can be prepared on an industrial scale High-purity nano-sized silicon particles with relatively uniform diameters, thereby completing the present invention.

That is, the silicon particles of the present invention are characterized in that the particle diameter is 1 to 50 nm, and the total amount of Na, Fe, Al, and Cl is 10 ppm or less.

In addition, the silicon powder of the present invention is characterized by containing 90% by mass or more of silicon particles having a particle diameter of 1 to 50 nm and a total amount of Na, Fe, Al, and Cl of 10 ppm or less.

In addition, the method for producing silicon particles of the present invention is characterized by comprising the following steps: a step of reacting monosilane gas and an oxidizing gas for oxidizing the monosilane gas in a gas phase to synthesize silicon oxide particles containing silicon particles; A step of removing the silicon oxide particles with hydrofluoric acid after holding the silicon oxide particles at 800 to 1400° C. under an inert atmosphere.

In addition, the present inventors have intensively studied whether there is a low-cost and efficient method for producing a superlattice of silicon particles that can realize high-performance light-emitting devices or electronic components, and completed the present invention as a result.

That is, the silicon particle superlattice of the present invention is a silicon particle superlattice composed of multiple types of silicon particles, and is characterized in that the average particle diameter of the silicon particles is 1 to 50 nm, and the variation coefficient of the particle diameter is 20% or less.

In addition, the method for preparing a silicon particle superlattice of the present invention is characterized in that it has the following steps: adding a hydrophobic solvent to a suspension obtained by dispersing hydrophobic silicon particles in water, leaving it to stand, and separating the water phase and the organic phase The step of arranging silicon particles on the interface of , includes "the above-mentioned suspension contains hydrofluoric acid" and "the above-mentioned hydrophobic solvent is 1-octanol" as preferred embodiments.

In addition, the silicon particle superlattice structure of the present invention is characterized in that it has the above-mentioned silicon particle superlattice on the hydrophobic surface of a solid substrate having a hydrophobic surface, including "the above-mentioned solid substrate is a silicon substrate or a graphite substrate" as preferred way.

Furthermore, the light-emitting element and electronic component of the present invention are characterized by comprising at least one of the above-mentioned silicon particle superlattice and the above-mentioned silicon particle superlattice structure.

The silicon particles of the present invention are relatively uniform nanoparticles with a particle diameter of 1 to 50 nm, and the total amount of Na, Fe, Al, and Cl is 10 ppm or less, and is of high purity.

In general, silicon particles have a different energy band structure from bulk silicon due to confinement effects or surface level effects based on quantum theory, and the particle size is 1 to 5 nm when it exhibits a luminescence phenomenon that cannot be observed in bulk silicon. Quantum well structures, which are important when applied to electronic components, can be identified in aggregates of particles of 10 nm or less and having a uniform particle size. The silicon particle of the present invention has a particle diameter of 1-50 nm, including the particle diameter ranges exhibiting these quantum theory confinement effects, surface energy level effects or quantum well structures.

In addition, if silicon contains impurities such as Na, Fe, Al, or Cl, an impurity level is formed within the band structure, which causes a reduction in the luminous efficiency of the light-emitting element or failure of electronic components. The total amount of Na, Fe, Al, and Cl in the silicon particles of the present invention is 10 ppm or less, so that impurity levels are not formed, and the above-mentioned troubles of light-emitting elements or electronic components do not occur.

Therefore, unlike the conventional silicon nanoparticles, the silicon particles of the present invention have high practicability as a raw material powder for high-performance light-emitting devices or electronic components.

In addition, the method for preparing silicon particles of the present invention is to use a specific silicon-containing gas (monosilane gas) as a raw material, and react the raw material with an oxidizing gas under specific conditions. Once the silicon oxide containing silicon particles is synthesized, Further heat treatment under specific conditions, and then use hydrofluoric acid to remove excess silicon oxide, this method is different from the previous preparation method of silicon nanoparticles, the productivity is high, and industrial scale production can also be realized. Therefore, it is industrially very useful to be applicable to light-emitting devices and electronic components of silicon nanoparticles on an industrial scale.

The silicon particles constituting the superlattice of the present invention have an average particle diameter of 1 to 50 nm, are relatively uniform, and have a variation coefficient of particle diameter of 20% or less. The so-called superlattice is that the particles formed by the aggregation of atoms or molecules are further aggregated with each other, two-dimensional or three-dimensional, periodically and regularly arranged lattice-like particle aggregates, and the superlattice of the present invention with small particle diameter deviation Particles with a small surface energy level deviation can be arranged with excellent periodicity, and thus a material having a desired energy band structure can be stably produced.

In this way, silicon particle superlattice can create various energy band structures according to the purpose of use, so when it is used as a light-emitting element, it can obtain sufficient luminous efficiency, and when it is used as an electronic component, it can create a material that is less prone to failure . Therefore, it is possible to easily improve the performance of electronic devices, and it contributes greatly to the production technology of functional materials on an industrial scale, which is very useful industrially.

Description of drawings

[ Fig. 1 ] A TEM photograph showing an example of the silicon particle superlattice of the present invention.

[ Fig. 2 ] A Fourier transform image showing an example of the silicon particle superlattice of the present invention.

Detailed ways

<Silicon particles>

The silicon particle of the present invention has a particle diameter of 1 to 50 nm, preferably 1 to 30 nm. If the particle diameter is not within the above range, confinement effect, surface level effect or quantum well structure suitable for quantum theory when applied to light-emitting elements or electronic parts are not exhibited. In addition, the total amount of Na, Fe, Al, and Cl in the silicon particles of the present invention is 10 ppm or less, preferably 5 ppm or less. If the total amount of Na, Fe, Al, and Cl exceeds 10 ppm, impurities can affect the characteristics of a light-emitting element or an electronic component.

<Silicon Powder>

The silicon powder of the present invention contains 90% by mass or more of the silicon particles of the present invention. If the silicon particle content of the present invention is 90% by mass or more, unnecessary particles can be removed directly or by simple post-treatment, and if it is less than 90% by mass, it becomes difficult to remove unnecessary particles.

<Preparation method of silicon particles>

The silicon particles of the present invention can be produced, for example, by heat-treating silicon oxide particles containing silicon particles synthesized in a vapor phase using monosilane gas and an oxidizing gas under a predetermined atmosphere and temperature, followed by removal of the silicon oxide.

Specifically, first, silicon oxide particles containing silicon particles are synthesized by reacting monosilane gas and oxidizing gas in a gas phase. The reaction can be carried out by introducing monosilane gas and oxidizing gas into the reaction vessel.

Among them, the raw material used as a silicon source in the present invention is monosilane gas. If a silicon-containing gas other than monosilane gas, such as chlorosilicon (SiH _n Cl _4-n , n is an integer of 0 to 3), is used as a raw material, the total amount of Na, Fe, Al, and Cl exceeds 10 ppm.

The oxidizing gas is not particularly limited as long as it can oxidize monosilane gas. Oxygen, air, water vapor, nitrogen dioxide, carbon dioxide, etc. can be used, and oxygen is particularly preferred from the viewpoints of ease of handling and ease of reaction control. In addition, in order to easily control the reaction and achieve the purpose of diluting monosilane gas and oxidizing gas, in addition to inert gases such as argon and helium, hydrogen, Nitrogen, ammonia, carbon monoxide and other third gases.

It is preferable to carry out the reaction by maintaining the temperature of the reaction container at 500°C to 1000°C and maintaining the pressure at 10 to 1000 kPa. The reaction vessel is generally made of high-purity materials such as quartz glass, and its shape is not particularly limited, but it is preferably tubular, and the axial direction of the tube can be vertical or horizontal. As for the method of heating the reaction vessel, any method such as resistance heating, high-frequency induction heating, or infrared radiation heating can be used.

The silicon oxide particles containing silicon particles generated in the reaction vessel are discharged out of the system together with the air flow, and are collected by a powder collector such as a bag filter.

Next, the recovered silicon oxide particles are kept at 800° C. to 1400° C. under an inert atmosphere. Through the above treatment, the particle size of the silicon particles included in the silicon oxide particles is adjusted to 1 to 50 nm. If the maintenance temperature is lower than 800°C, the particle size of the silicon particles will be less than 1nm, impurities will easily remain in the silicon, and the total amount of Na, Fe, Al, and Cl will exceed 10ppm. In addition, when the temperature exceeds 1400°C, the particle size of the silicon particles exceeds 50 nm.

As the inert atmosphere gas, in addition to inert gases such as argon and helium, hydrogen, nitrogen, ammonia, carbon monoxide, and the like can be used, and argon is particularly preferable from the viewpoint of ease of handling.

After the particle size of the contained silicon particles is adjusted, silicon oxide particles are added and dispersed in water. Dispersion can be performed using ultrasonic waves or a stirrer, and it is particularly preferable to use ultrasonic waves. After the silicon oxide particles are dispersed in water to form a suspension, hydrofluoric acid is added to the suspension. The silicon particles contained in the silicon oxide particles are not dissolved by hydrofluoric acid, but the surrounding silicon oxides are dissolved and removed, so that only silicon remains, and the silicon particles of the present invention can be obtained.

<Silicon Particle Superlattice>

The average particle size of the silicon particles constituting the silicon particle superlattice of the present invention is 1 to 50 nm, preferably 5 to 20 nm. If the average particle size is below 1 nm, it is difficult to achieve regular arrangement of particles. In addition, if the average particle size exceeds 50nm, there will be almost no change in physical and chemical properties from bulk silicon, and no superlattice will be formed at all.

In addition, the coefficient of variation of the particle size of the silicon particles is 20% or less. If the coefficient of variation of the particle diameter exceeds 20%, the deviation of the particle diameter is too large to form an energy band. In addition, in the present invention, the "variation coefficient of particle diameter" is the value obtained by dividing the standard deviation of particle diameter by the average value, which is an index showing the variation of particle diameter, and the smaller the value, the smaller the variation of particle diameter.

As a specific method of measuring the average particle diameter and the coefficient of variation, for example, a method of image analysis of a transmission electron microscope (TEM) image of a superlattice can also be cited. At this time, in order to analyze a superlattice composed of a plurality of silicon particles, it is preferable to set 100 or more particles as analysis objects.

In the silicon particle superlattice of the present invention, the TEM image can be used to judge whether the particles are regularly arranged, and more specifically, the Fourier transform image of the TEM image can be used to judge. When the particles are regularly arranged, in the Fourier transform image there will be corresponding points corresponding to the lattice formation. For example, Fig. 1 is a TEM image of an example of the silicon particle superlattice of the present invention, and Fig. 2 is its Fourier transform image, and in Fig. 2, points corresponding to 6 times of the Fourier transform image can be identified, and it can be judged that the particles formed have Regularly arranged superlattices.

<Manufacturing method of silicon particle superlattice, silicon particle superlattice structure, light-emitting device, electronic component>

The method for preparing the silicon particle superlattice of the present invention is described below.

First, the method of producing a plurality of silicon particles is not particularly limited as long as the obtained silicon particles are hydrophobic. For example, the following method can be applied: using an oxidizing gas for oxidizing silane gas and silane gas to react in a gas phase to synthesize silicon oxide particles enclosing silicon particles, and maintaining the temperature at 800 to 1400°C under an inert gas. The resulting particle method. In this method, it is preferable to adjust the particle size of the silicon particles encapsulated in the silicon oxide to about 1 to 50 nm by maintaining heating in an inert atmosphere. In addition, as described above, in the step of arranging the silicon particles at the interface between the water phase and the hydrophobic solvent, since the variation in particle size can be reduced, even if the variation is relatively large at this time, there is no problem.

Silicon oxide in the silicon oxide particles containing silicon particles can be removed by hydrofluoric acid. In particular, this method is very convenient because it is a step of exposing silicon particles contained in a silicon oxide and also a step of imparting hydrophobicity to the surface of the silicon particles. The reason for imparting hydrophobicity to the surface of silicon particles by hydrofluoric acid is considered to be that hydrogen fluoride (HF) acts on the outermost surface of the exposed silicon particles while removing silicon oxide around the silicon particles by hydrofluoric acid. The silicon atoms create hydrogen bonds, and the particle surface is modified with hydrogen atoms.

At this time, silicon oxide particles are previously dispersed in water to form a suspension, and hydrofluoric acid is dropped thereinto to obtain hydrophobic homosilicon particles in the state of suspension, so the silicon particles of the present invention can be directly applied. The preparation method of the superlattice is therefore preferred. In addition, in order to improve the dispersibility of the silicon particles, it is preferable to apply oscillation to the suspension by ultrasonic waves.

Next, a hydrophobic solvent is added to the suspension. Thus, the hydrophobic silicon particles move from the aqueous phase to the organic phase (hydrophobic solvent). At this time, in order to promote the movement of particles, it is preferable to continue applying vibration by ultrasonic waves after adding hydrophobic solvents. In addition, when the silicon particles are not hydrophobic, they do not move into a hydrophobic solvent.

Then, it is allowed to stand still, and the aqueous phase and the organic phase are separated, and the silicon particles dispersed in the hydrophobic solvent slowly gather and arrange at the interface of the aqueous phase and the organic phase. The reason for this aggregation and alignment is unclear, but particles with similar particle diameters are selectively aggregated and aligned to form a superlattice composed of silicon particles at the interface between the aqueous phase and the organic phase. First, when using a powder composed of silicon particles with large variations in particle diameters, a plurality of superlattices with different average particle diameters are formed at different locations on the interface. In addition, when the solvent is not hydrophobic, the interface between the aqueous phase and the organic phase will not be formed, so that the superlattice will not be formed.

Specific examples of hydrophobic solvents include aliphatic hydrocarbon solvents such as non-water-soluble or insoluble n-hexane and n-heptane, alicyclic hydrocarbon solvents such as cyclohexane and methylcyclohexane, toluene, xylene, and the like. Aromatic hydrocarbon solvents such as 1-butanol, 1-octanol and other higher alcohols. Among them, 1-octanol having an appropriate viscosity is particularly preferable in order to smoothly aggregate and arrange silicon particles at the interface between the aqueous phase and the organic phase.

The time for applying ultrasonic vibration after adding the hydrophobic solvent, and the resting time thereafter are not particularly limited. When the hydrophobic solvent is 1-octanol, the ultrasonic vibration after adding is preferably about 30 minutes to 1 hour, and the standing time after that is preferably 30 minutes to 1 hour. Preferably it is 2 days or more.

In this way, the superlattice composed of silicon particles formed on the interface of the aqueous phase and the organic phase can be obtained on the substrate by moving it on a solid substrate with a hydrophobic surface after being picked up by a semi-permeable membrane such as a collodion film. Directly formed superlattice structures. Examples of solid substrates having a hydrophobic surface include silicon substrates (silicon wafers), graphite substrates, and the like.

In addition, after adding a hydrophobic solvent, when the aqueous phase and the organic phase are separated, a solid substrate having a hydrophobic surface is directly inserted at the interface between the two so that the hydrophobic surface faces the hydrophobic solvent side, and then, by standing still, It is also possible to form superlattices directly on substrates with hydrophobic surfaces. At this time, by using a lithography technique or the like, if a hydrophobic region and a hydrophilic region are previously patterned on the surface of the substrate, a superlattice can also be formed at a desired location on the substrate. In particular, when the superlattice structure of the present invention is directly formed on a silicon substrate, it can be used as an element for functional materials such as novel light-emitting elements and electronic parts.

Example

The present invention is further described below by enumerating examples and comparative examples.

<Example 1>

Introduce monosilane at a rate of 0.16 L/min, 0.4 L/min, and 17.5 L/min into a reaction vessel composed of a quartz glass reaction tube (inner diameter 50 mm, length 1000 mm) maintained at a temperature of 700°C and a pressure of 90 kPa. gas, oxygen and nitrogen for dilution to produce a dark brown powder. Collection is performed by a metal filter provided on the downstream side of the reaction tube.

The specific surface area of the collected produced powder was measured by the BET 1-point method and found to be 55 m ² /g. Chemical analysis shows that the main components are silicon (Si) and oxygen (O). In addition, the state of the Si bond was studied using the Si _2p spectrum of XPS (X-ray Photoelectron Spectroscopy). Packed with silicon particles.

In an argon atmosphere, 20 g of the powder was maintained at a temperature of 1100° C. for 1 hour, then cooled to room temperature, 1 L of distilled water was added, and ultrasonic waves were applied for 1 hour to disperse the powder to prepare a suspension. 0.1 L of 5% hydrofluoric acid (HF) was added to the suspension, and ultrasonic waves were applied for 30 minutes to dissolve and remove silicon oxide. Then use a membrane filter to filter and wash the suspension, separate and dry the product to obtain silicon powder.

By chemical analysis, it was confirmed that the main component of the powder was Si, and the total amount of Na, Fe, Al, and Cl was 5 ppm. In addition, when the particle size of the particles contained in the powder was measured by a transmission electron microscope (TEM), it was 10 to 40 nm.

<Example 2>

In the same reaction vessel made of quartz glass reaction tubes as in Example 1 maintained at a temperature of 750° C. and a pressure of 50 kPa, monosilane gas, silane gas, and Oxygen and argon for dilution produce a dark brown powder. Collection was performed in the same manner as in Example 1.

The specific surface area of the collected formed powder was measured and found to be 15 m ² /g. Chemical analysis shows that the main components are Si and oxygen, and the Si _2p spectrum of XPS is studied. As a result, the peak belonging to the Si-Si bond can be identified, and it can also be confirmed that the product is silicon oxide particles enclosing silicon particles.

A silicon powder was obtained in the same manner as in Example 1, except that 20 g of this powder was kept at a temperature of 900° C. for 1 hour in a helium atmosphere. By chemical analysis, it was confirmed that the main component of the powder was Si, and the total amount of Na, Fe, Al, and Cl was 8 ppm. In addition, when the particle size of the particles was measured by TEM, it was 2 to 24 nm.

<Comparative example 1>

A silicon powder was obtained in the same manner as in Example 1, except that 20 g of powder composed of Si-encapsulated silicon oxide particles was kept at a temperature of 1450° C. for 1 hour in an argon atmosphere.

By chemical analysis, it was confirmed that the main component of the powder was Si, and the total amount of Na, Fe, Al, and Cl was 4 ppm. In addition, when the particle size of the particles was measured by TEM, it was a powder composed of particles of 35 nm or more containing 12% by mass of particles exceeding 50 nm.

<Comparative example 2>

A silicon powder was obtained in the same manner as in Example 1, except that 20 g of a powder composed of Si-encapsulated silicon oxide particles was kept at a temperature of 700° C. for 1 hour in an argon atmosphere.

By chemical analysis, it was confirmed that the main component of the powder was Si, and the total amount of Na, Fe, Al, and Cl was 18 ppm. Furthermore, the particle size of the particles was measured by TEM, and it was a powder composed of particles of 10 nm or less containing 16% by mass of particles smaller than 1 nm.

<Comparative example 3>

A silicon powder was obtained in the same manner as in Example 2, except that 20 g of powder composed of Si-encapsulated silicon oxide particles was kept at a temperature of 700° C. for 1 hour in a helium atmosphere.

By chemical analysis, it was confirmed that the main component of the powder was Si, and the total amount of Na, Fe, Al, and Cl was 23 ppm. In addition, when the particle size of the particles was measured by TEM, it was confirmed that the powder was composed of particles of 6 nm or less including 40% by mass of particles smaller than 1 nm.

<Comparative example 4>

Except for using silicon tetrachloride (SiCl ₄ ) gas, which is often used as a raw material for polycrystalline silicon, instead of monosilane gas, the gas was introduced into the reaction vessel in the same manner as in Example 1 to generate a dark brown powder, which was then mixed in the same manner as in Example 1. collect.

The specific surface area of the collected formed powder was measured and found to be 45 m ² /g. Carrying out chemical analysis, the main components are Si and oxygen, and studying the Si _2p spectrum of XPS, the results can identify the peaks belonging to Si-Si bonds, and can also confirm that the product is silicon oxide powder particles containing silicon particles.

Using 20 g of this powder, silicon powder was produced in the same manner as in Example 1. The main component of the powder is Si, and the particle size measured by TEM is 5-35nm, especially contains a large amount of chlorine (Cl), and the total amount of Na, Fe, Al, and Cl is 50ppm.

<Example 3>

Introduce monosilane at a rate of 0.16L/min, 0.4L/min, and 17.5L/min into a reaction vessel composed of a quartz glass reaction tube (inner diameter 50mm, length 1000mm) maintained at a temperature of 780°C and a pressure of 90kPa. gas, oxygen and nitrogen for dilution to produce a dark brown powder. Collection is performed by a metal filter provided on the downstream side of the reaction tube.

The specific surface area of the collected produced powder was measured by the BET 1-point method and found to be 62 m ² /g. Chemical analysis shows that the main components are silicon (Si) and oxygen (O). In addition, the Si _2p spectrum of XPS (X-ray Photoelectron Spectroscopy) was used to study the bonding state of Si. As a result, in addition to the peaks belonging to the Si-O bond, the peaks belonging to the Si-Si bond could be identified, and it was also confirmed that the silicon oxidation in the generated Silicon particles are included in the material particles.

After maintaining 2 g of the powder at 1200° C. for 30 minutes under an argon atmosphere, it was cooled to room temperature, 0.1 L of distilled water was added, and ultrasonic waves were applied for 1 hour to disperse the powder to prepare a suspension. 0.01 L of 5% hydrofluoric acid (HF) was added to this suspension, and ultrasonic waves were applied for 30 minutes to dissolve and remove silicon oxide. Then, after adding 0.2 L of 1-octanol as a hydrophobic solvent, ultrasonic waves were applied for 30 minutes, and then left still for 2 days.

Then, use the carrier that adhered the collodion film on the mesh mesh (#1000) used for making the transmission electron microscope (TEM) sample, scoop out the sample near the interface of 1-octanol and aqueous solution, and the sample is 60 °C for 3 days.

As a result of observing this sample using TEM, a structure in which particles are regularly arranged as shown in FIG. 1 was recognized. Furthermore, a Fourier transform image was taken in the same field of view, and the six-order target point shown in Fig. 2 was recognized, confirming the formation of a superlattice. In addition, 115 silicon particle images were sampled and analyzed using computer software (RAZATECH Co., Ltd., SALT Ver. 3.62) for the TEM image in FIG. The coefficient is 17%.

<Example 4>

A dark brown powder was collected in the same manner as in Example 3 except that the temperature was 700°C. The specific surface area of the powder was 42 m ² /g, and the chemical analysis showed that the main components were silicon (Si) and oxygen (O). In addition, peaks belonging to Si-Si bonds were recognized by XPS in addition to peaks belonging to Si-O bonds, and it was confirmed that silicon particles were included in the formed silicon oxide particles.

Silicon oxide was dissolved and removed in the same manner as in Example 3, except that 2 g of this powder was kept at a temperature of 1100° C. for 60 minutes under an argon atmosphere. Then, after adding 0.2 liter of xylene as a hydrophobic solvent, ultrasonic waves were applied for 30 minutes, and then left still for 1 day.

Then, except drying for 1 day, it carried out similarly to Example 3, and produced the TEM sample. The structure in which particles are regularly arranged in the TEM image and six targeted points in the Fourier transform image confirmed the formation of a superlattice. In addition, 122 silicon particle images were sampled and image analyzed in the same manner as in Example 3 for the TEM images. As a result, the average particle diameter was 11 nm, and the variation coefficient of the particle diameter was 15%.

<Example 5>

A silicon wafer is irradiated with a high-power laser under vacuum, and 0.2 g of silicon particles having a particle diameter of 1 to 30 nm is produced by the above-mentioned laser ablation method. 10 ml of distilled water was added thereto, and ultrasonic waves were applied for 1 hour to disperse the powder to prepare a suspension. 0.01 L of 5% hydrofluoric acid (HF) was added to the suspension, and ultrasonic waves were applied for 1 hour. Then, after adding 20 mL of 1-octanol as a hydrophobic solvent, ultrasonic waves were applied for 30 minutes, and then left still for 2 days.

Then, a TEM sample was produced in the same manner as in Example 3. The structure in which particles are regularly arranged in the TEM image and six targeted points in the Fourier transform image confirmed the formation of a superlattice. In addition, 147 silicon particle images were sampled and analyzed in the same manner as in Example 3 for TEM images. The average particle diameter was 7 nm, and the coefficient of variation of the particle diameter was 17%.

<Example 6>

In an argon atmosphere, at a temperature of 1100°C, 2 g of a powder composed of silicon oxide particles containing silicon particles synthesized in the same manner as in Example 3 was held for 1 hour, and then dissolved and removed in the same manner as in Example 3. 0.2 L of 1-octanol was added as a hydrophobic solvent, and ultrasonic waves were applied for 30 minutes.

Then, stop applying the ultrasonic wave, the aqueous solution and the hydrophobic solvent undergo phase separation to form an interface, and at this time, directly immerse in 2%-hydrofluoric acid solution for 30 minutes to remove the natural oxide film. In addition, the ammonium fluoride (NH ₄ F) Immerse in the aqueous solution for 10 minutes, and horizontally insert the silicon wafer with the surface (111) exposed to the hydrophobic surface near the interface between the aqueous solution and the hydrophobic solvent, so that the surface after the hydrophobic treatment faces the hydrophobic solvent (ie, above) , let stand for 2 days.

After standing still, the silicon wafer was dried, and the hydrophobized surface was observed with an electric field emission scanning electron microscope (FE-SEM). It was observed that the particles had a regular arrangement structure on the surface, indicating that a superlattice of silicon particles had been formed. The 105 silicon particle images obtained by the FE-SEM image were sampled, and image analysis was performed. As a result, the average particle diameter was 5 nm, and the variation coefficient of the particle diameter was 18%.

The silicon wafer on which the silicon particles were arranged was irradiated with ultraviolet rays, and orange light emission was confirmed.

<Comparative example 5>

Silicon particles were deposited directly on the surface of the silicon wafer that had been hydrophobized in the same manner as in Example 6 by laser ablation to form a film composed of silicon particles. Using FE-SEM to observe the surface of the film, it was observed that some particles were regularly arranged on the surface, and it was confirmed that a superlattice of silicon particles was formed. In the place where the superlattice is formed, 167 silicon particle images obtained by FE-SEM image were sampled and analyzed, and the average particle diameter was 5nm, and the variation coefficient of particle diameter was 29%.

When ultraviolet rays were irradiated on the wafer where the silicon particles were arranged, light emission was not confirmed.

<Comparative example 6>

In Example 3, after adding 1-octanol without standing within 2 days, after separating the aqueous solution and 1-octanol, the silicon particles dispersed in 1-octanol were directly absorbed by a dropper, added dropwise to and implemented After being placed on the same carrier as Example 3, it was dried at 60°C for 3 days. It can be confirmed that no superlattice is formed by observing with TEM that the arrangement structure between the particles or the point in the Fourier transform image is not identified.

<Comparative example 7>

A suspension of silicon particles was prepared in the same manner as in Example 5. No hydrofluoric acid was added, 0.2 L of xylene was added, ultrasonic waves were applied for 30 minutes, and then left to stand for 1 day, it was confirmed that silicon particles did not move in xylene and did not have hydrophobicity.

This suspension was sucked up with a dropper and dropped onto the same carrier as in Example 3, followed by drying at 60° C. for 3 days. Observation by TEM showed that although silicon particles were confirmed, the arrangement structure between the particles or points in the Fourier transform image were not confirmed, and it was confirmed that no superlattice was formed.

According to the present invention, a powder composed of nano-sized silicon particles can be synthesized in large quantities with high yield and on an industrial scale without requiring a special electrolysis device or a plasma generator, and by using this powder as a raw material powder, it can contribute to new The practical application of functional materials such as high-performance light-emitting elements and electronic components.

In addition, according to the present invention, a superlattice composed of nano-sized silicon particles can be produced with high yield without requiring expensive equipment, etc., and the silicon particles constituting the superlattice can be arranged in an excellent periodicity with little variation in particle size. , and particles with small deviations in surface energy levels, so that materials with desired energy band structures can be stably produced. The superlattice of the present invention can create various energy band structures according to the purpose of use, so even when it is used for functional materials such as new light-emitting devices and electronic parts, the material properties are stable and performance can be easily improved. Therefore, it can contribute to the practical use of these functional materials.

Claims (11)

1. A silicon particle, characterized in that the particle diameter is 1-50 nm, and the total amount of Na, Fe, Al, and Cl is 10 ppm or less. 2. A silicon powder characterized by containing at least 90% by mass of silicon particles having a particle diameter of 1 to 50 nm and a total amount of Na, Fe, Al, and Cl of 10 ppm or less. 3. A method for preparing silicon particles, which is characterized in that it has the following steps: making monosilane gas and an oxidizing gas for oxidizing the monosilane gas react in a gas phase to synthesize silicon oxide particles containing silicon particles; A step of removing the silicon oxide particles with hydrofluoric acid after holding the silicon oxide particles at 800 to 1400° C. under an atmosphere. 4. A silicon particle superlattice, which is composed of a plurality of silicon particles, characterized in that the average particle size of the silicon particles is 1-50 nm, and the variation coefficient of the particle size is 20% or less. 5. The preparation method of the silicon particle superlattice is characterized in that it has the following steps: after adding a hydrophobic solvent to the suspension of silicon particles with hydrophobicity dispersed in water, leave it to stand, and place it on the interface between the water phase and the organic phase The process of aligning silicon particles. 6. The method for preparing silicon particle superlattice as claimed in claim 5, characterized in that said suspension contains hydrofluoric acid. 7. The method for preparing silicon particle superlattice according to claim 5 or 6, characterized in that the above-mentioned hydrophobic solvent is 1-octanol. 8. A silicon particle superlattice structure, characterized in that the silicon particle superlattice according to claim 4 is provided on the hydrophobic surface of a solid substrate having a hydrophobic surface. 9. The silicon particle superlattice structure according to claim 8, wherein the solid substrate is a silicon substrate or a graphite substrate. 10. A light-emitting element, characterized by comprising at least one of the silicon particle superlattice according to claim 4 and the silicon particle superlattice structure according to claim 8 or 9. 11. An electronic component comprising at least one of the silicon particle superlattice structure according to claim 4 and the silicon particle superlattice structure according to claim 8 or 9.

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