JPH05254883A - Production of superfine particle-dispersed material - Google Patents

Abstract

PURPOSE:To produce an superfine particle-dispersed material by embedding superfine particles synthesized in a gas phase in a glass film while maintaining characteristics of the superfine particles. CONSTITUTION:An evaporating chamber 1 is charged with an Ar gas, maintained under about 1Torr pressure and a reaction chamber 2 is charged with a mixed gas of TEOS(tetraethoxysilane) vapor diluted with an Ar gas and oxygen and kept under about 0.05Torr pressure. A CdTe polycrystal target of raw material is irradiated with a second higher harmonic wave of YAG laser in an excited state of a gas in the reaction chamber by impressing a coil 8 with a high-frequency voltage to evaporate CdTe. Consequently, superfine particle-dispersed glass of CeTe having about 6nm particle diameter and an extremely small dispersion of particle diameter is formed on a quartz substrate 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a material in which ultrafine particles are dispersed, and in particular, by enclosing ultrafine particles synthesized in the gas phase in glass synthesized in the gas phase, The present invention relates to a method for manufacturing an ultrafine particle dispersion material which facilitates the production of the ultrafine particle dispersion material and has a continuous or periodic distribution of the ultrafine particle concentration.

[0002]

2. Description of the Related Art Ultrafine particles are known to have properties different from those of bulk, and are expected to be applied as functional materials. For example, ultrafine compound semiconductor particles such as CdS have a so-called quantum size effect in which the band structure becomes discrete as the particle size decreases, and the absorption edge shifts to the high energy side (eg, AJ Nozic et.
al., J. Phys. Chem., 89, 397 (1987)). It is also known that such a material having a quantum size effect has a large nonlinear optical effect, and it is expected to be applied to an optical control element using the nonlinear optical effect such as an ultrafast optical switch or an optical logic element. Has been done. However, even if the individual particle diameters of the ultrafine particles are such that the quantum size effect is exhibited, when they are aggregated, the charge can be transferred between the ultrafine particles, and the quantum size effect disappears. Therefore, in handling such ultrafine particles, it is important to prevent aggregation of the ultrafine particles in order to enhance the effect.

In the case of a material in which ultrafine particles are dispersed in a solution, a surfactant has been conventionally used as a method for preventing agglomeration of fine particles and is applied in various fields (surfactant handbook). Optical books). This depends on the system, but the surfactant adsorbs to the surface of the ultrafine particles and prevents aggregation due to its steric hindrance.For example, hydrophobic ultrafine particles become apparently hydrophilic by adsorption of the surfactant and become hydrophilic in the hydrophilic solution. It has been explained by various effects such as being stable, or changing the internal electric field of the ultrafine particles by the surfactant to prevent aggregation. On the other hand, Steigerwald et al. Preserved the independence of the fine particles due to the steric hindrance of the phenyl group not only in the solution but also after precipitation drying by adsorbing the phenyl group on the ultrafine particles of CdSe synthesized in the liquid phase. (Steigerwald et al., J. Am. Chem. Soc., 1
10, 3046 (1988)).

As a method for producing ultrafine particles, a colloidal dispersion system using a redox reaction has long been known. For example, Au colloid can be easily produced by adding a suitable reducing agent such as hydrogen peroxide or citric acid to a potassium chloroaurate solution. Further, in the case of CdS as an example of the compound colloid, when a Na ₂ S solution is added to a Cd (ClO ₄ ) ₂ solution, a redox reaction occurs and a CdS dispersion system is obtained (for example,
R. Rossetti et al., J. Chem. Phys. 82, 552 (198
Five)). Although the particle size of the obtained ultrafine particles varies depending on the production conditions, colloidal particles having a diameter of 5 nm or less and a small dispersion can be easily produced.

As a method for producing ultrafine particles, an evaporation method in a gas is known in addition to the above method utilizing the oxidation-reduction / precipitation reaction in the liquid phase. This is because when a substance is heated and evaporated in an atmosphere of an inert gas such as Ar, the vapor collides with atmospheric gas molecules, loses kinetic energy, and is rapidly cooled to form fine particles. The size of the particles changes depending on the distance from the evaporation source, and when they are collected in the vicinity of the evaporation source, fine particles having a small particle size are obtained. In addition, the generated particles are treated with O ₂
Oxide particles can be produced by reacting with a gas.

[0006]

However, the method using a surfactant is effective in preventing the aggregation of ultrafine particles, but it is essential that the ultrafine particles are dispersed in a solution. However, the ultrafine particles obtained by the redox reaction in the liquid phase are limited to some substances such as precious metals and CdS. Further, the dry powder obtained by the method utilizing the adsorption of phenyl group has weak durability against water and is very unstable by the usual method. Further, when adsorbing phenyl groups, it is necessary that ultrafine particles are dispersed in a solution, and applicable materials are limited to sulfides and selenides. On the other hand, although it is possible to produce ultrafine particles of various materials by the gas evaporation method, it is not easy to take out the produced ultrafine particles in a form of being dispersed in a solution, and adsorption of a surfactant or a phenyl group is not possible. It cannot be applied.

The present invention solves the above-mentioned conventional problems, and manufactures an ultrafine particle dispersion material capable of being embedded in a glass film while maintaining the characteristics of ultrafine particles synthesized in a gas phase such as a gas evaporation method. The purpose is to provide a method.

[0008]

According to a first aspect of the present invention, there is provided a method for producing an ultrafine particle-dispersed material, wherein a raw material of ultrafine particles is heated and evaporated in an inert gas, and a vapor of the raw material and an inert gas collide with each other. Ultra-fine particles of the raw material are formed by rapidly cooling the steam,
A mixed gas of silicon hydride or silicon alkoxide and oxygen, or a diluted gas thereof is used for heat, plasma,
The ultrafine particles are confined in a silica glass film produced by exciting with light or the like.

The method for producing the ultrafine particle dispersed material according to claim 2 is the same as the method for producing the ultrafine particle dispersed material according to claim 1.
It is characterized by having a continuous or periodic concentration distribution of ultrafine particles in the vertical direction of the silica glass film by changing the concentration of ultrafine particles continuously or stepwise.

The method for producing the ultrafine particle dispersion material of the present invention comprises:
The raw material for the ultrafine particles is heated and evaporated in an inert gas, and the vapor is rapidly cooled by the collision between the vapor of the raw material and the inert gas to form the ultrafine particles of the raw material, silicon hydride,
Alternatively, SiO ₂ produced by utilizing a reaction in a gas phase by exciting a mixed gas of a silicon source gas such as a silicon alkoxide and oxygen with heat, plasma, light or the like.
It is characterized by being dispersed in glass.

The present invention provides ultrafine particles synthesized in a gas phase,
Silicon hydride such as monosilane or disilane, or T
In a mixed gas of silicon source gas such as silicon alkoxide such as MOS (tetramethoxysilane) and TEOS (tetraethoxysilane) and oxygen, or a gas obtained by diluting the mixed gas with a gas such as Ar or N ₂ , heat,
It is dispersed in the SiO ₂ glass produced by utilizing the reaction in the gas phase by exciting it with plasma, light or the like.

[0012]

According to the production method of the present invention, since fine particles produced in the gas phase are confined in SiO ₂ produced in the gas phase,
It is not necessary to collect the fine particles once, and it is possible to prevent aggregation of the fine particles that occurs during the collection.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a manufacturing apparatus used for producing an ultrafine particle dispersed material. This apparatus comprises an evaporation chamber 1 for producing ultrafine particles in a gas and a reaction chamber 2 for producing a glass matrix from a gas phase. The evaporation chamber 1 is equipped with a semiconductor polycrystalline target 5 as a raw material, a window 14 for introducing a laser beam 15, and an inert gas introduction pipe 6, and the raw material is vaporized by the target 5
It is performed by irradiating the laser light 15 on Reaction chamber 2
Is composed of a quartz tube 3, a coil 8 for plasma excitation, and a gas introduction tube 7 for introducing a glass source gas, and has a structure capable of exciting the gas in the reaction chamber 2 with plasma.
A quartz substrate 11 was placed on a sample support rod 9 that can move up and down. The evaporation chamber 1 and the reaction chamber 2 are connected by a pipe 4,
The pressure in the evaporation chamber 1 is set to be higher than the pressure in the reaction chamber 2 by differential evacuation. Since the pressure in the reaction chamber 2 is lower than the pressure in the evaporation chamber 1, the generated ultrafine particles are introduced into the reaction chamber 2 via the pipe 4 by the differential pressure. These pressure differences are very important factors for producing glass capsule ultrafine particles, and the pressure difference between the evaporation chamber 1 and the reaction chamber 2 is one of the parameters that determine the particle size of the ultrafine particles. In this manufacturing apparatus, the particle size of the ultrafine particles is determined by the pressure in the evaporation chamber, the power of the laser light to be irradiated, the distance from the target 5 to the pipe 4, the thickness of the pipe, etc., in addition to the pressure difference.

A method of manufacturing CdTe ultrafine particle dispersed glass using this apparatus will be described. Commercially available CdTe as raw material
A polycrystalline wafer was used. Ar gas was introduced into the evaporation chamber 1 and the pressure was controlled to about 1 Torr. The pressure in the reaction chamber 2 was set to 0.05 Torr to evaporate CdTe, and the ultrafine CdTe particles ejected from the transport pipe 4 were collected and analyzed, and it was found that the particle size was about 6 nm and the dispersion of the particle size was very small. .. Based on this result, a mixed gas of TEOS vapor diluted with Ar gas and oxygen was introduced into the reaction chamber, and the pressure thereof was set to about 0.05 Torr. High frequency voltage coil 8
The second harmonic of YAG laser (532 nm, 25 J / cm) was applied to the CdTe target in a state where the gas in the reaction chamber was excited by applying
2) was irradiated to evaporate CdTe. As a result, the intended CdTe fine particle-dispersed glass was formed on the quartz substrate 11.

When the light absorption characteristics of the CdTe fine particle-dispersed glass formed on the substrate were measured in the near infrared / visible region, the absorption edge was 760 nm, which was shifted to a shorter wavelength side than the absorption edge of 820 nm of bulk CdTe. I found out. Further observation of the CdTe ultrafine particle dispersion material produced with a transmission electron microscope showed that the particle size of C was about 6 nm.
It was found to contain fine particles of dTe. That is, in the fine particle-dispersed glass according to the present invention, it is possible to confine the generated ultrafine particles in the glass without changing them.

In addition, when the gas concentration of TEOS was changed during production to prepare a CdTe fine particle dispersion material, and while gradually scraping the surface, the fine particle concentration in the material was determined by XPS (X-ray photoelectron spectroscopy). The particle concentration varied from 1 wt% to 12 wt% in the depth direction of the film depending on the gas concentration. From this, it was confirmed that a semiconductor fine particle dispersed material having a fine particle concentration distribution in the depth direction of the film could be produced.

This time, the CdTe ultrafine particles have been described, but the present invention is not limited to this. For example, CdSSe, ZnSe, C
II-VI group compound semiconductors such as dTe, Ga
III-V group compound semiconductors such as As, InP, InGaAsP, or Fe, Co, N as magnetic storage materials
i or compounds thereof, compounds with other elements, oxides obtained by evaporation of various metals in oxygen gas, and any material capable of forming ultrafine particles in the vapor phase can be applied. In addition to the laser heating used in this embodiment, various methods such as induction heating, resistance heating, electron beam heating, and arc discharge may be applied to the heating and evaporation of the raw materials depending on the pressure in the evaporation chamber.

In this embodiment, TEO is used as a silicon raw material.
Although only the case of using S has been described, other silicon alkoxides or various silicon compounds such as silane and disilane can be used. However, high-concentration silane, disilane, etc. will react immediately by mixing with oxygen and react with S
May form iO ₂ . Therefore, in this case, it is necessary to consider dilution of each gas and mixing after dilution. Here, glass was produced using a reaction in which TEOS is decomposed by applying a high-frequency voltage to generate SiO ₂ , but the glass is not limited to this, and for example, TE in the reaction chamber is exposed to light.
SiO ₂ may be grown by exciting a mixed gas of OS and oxygen. In that case, as a light source, it is also possible to use a xenon lamp and an excimer laser capable of obtaining a large optical power density. Although SiO ₂ is used here as the material for the matrix, Si and various compound semiconductors due to gas decomposition, and oxides such as TiO ₂ , ZrO ₂ and Al ₂ O ₃ due to decomposition of metal alkoxide,
Any material that can be formed on the substrate by decomposition, condensation, or polymerization reaction without damaging the ultrafine particles produced in the reaction chamber can be used as a matrix for holding the ultrafine particles.

As a method for producing ultrafine particles in the gas phase,
In addition to the gas evaporation method described here, various methods such as a sputtering method and a plasma method have been devised and used for the production of ultrafine particles.However, in the present invention, the produced ultrafine particles are transported to a reaction chamber by using an air flow. If possible, it can be applied to any ultrafine particle manufacturing method.

In this embodiment, in order to change the concentration of fine particles in the material in the depth direction, TEOS is simply used during the material production.
Although only increasing the flow rate, the TEOS gas flow rate can also be varied during manufacture, for example periodically. Therefore, it can also be applied when manufacturing a material having a complicated fine particle concentration distribution in the depth direction of the material.

[0021]

EFFECTS OF THE INVENTION According to the present invention, it is possible to embed ultrafine particles synthesized in a gas phase, which has been difficult in the past, in a matrix while maintaining the characteristics of the ultrafine particles in a gas phase.
Further, an ultrafine particle dispersed material having a fine particle concentration distribution in the depth direction of the material can be produced.

[Brief description of drawings]

FIG. 1 is a schematic view of a manufacturing apparatus used for manufacturing an ultrafine particle dispersed material showing an example of the present invention.

[Explanation of symbols]

1 Evaporation Chamber 9 Substrate Support Rod 2 Reaction Chamber 10 Pump 3 Quartz Tube 11 Substrate (Quartz) 4 Transport Pipe 12 Valve 5 Target 13 Mass Flow Controller 6 Gas Introducing Tube 14 Window 7 Reactive Gas Introducing Tube 15 Laser Light 8 Induction Coil

Continuation of the front page (51) Int.Cl. ⁵ Identification number Reference number within the agency FI Technical indication location C03C 3/06 Z 21/00 C 7003-4G C23C 14/08 7308-4K (72) Inventor Hisao Nagata Osaka Prefecture 3-5-11 Doshomachi, Chuo-ku, Osaka, Japan Nippon Sheet Glass Co., Ltd. (72) Inventor Shuhei Tanaka 3-5-11, Doshomachi, Chuo-ku, Osaka City, Osaka Prefecture Nippon Sheet Glass Co., Ltd.

Claims (2)

[Claims] 1. A raw material for ultrafine particles is vaporized by heating in an inert gas, and the vapor is rapidly cooled by collision of the vapor of the raw material with the inert gas to form ultrafine particles of the raw material. Alternatively, production of an ultrafine particle dispersion material characterized by enclosing the ultrafine particles in a silica glass film produced by exciting a mixed gas of silicon alkoxide and oxygen or a diluted gas thereof with heat, plasma, light, etc. Method. 2. The method for producing an ultrafine particle dispersion material according to claim 1, wherein the concentration of the ultrafine particles is changed continuously or stepwise so that the ultrafine particles are continuously or periodically formed in the vertical direction of the silica glass film. A method for producing an ultrafine particle dispersed material having a concentration distribution.