JPH06292826A - Production of composite super fine particles - Google Patents

Abstract

PURPOSE:To increase the degree of freedom of the selection for making the composite material of super fine particles and to enable its use in a stable form by forming the super fine particles in vapor phase, sticking the obtained super fine particles on a substrate and depositing the material different from the super fine particles. CONSTITUTION:Gaseous argon is introduced into a vacuum chamber 8 from a gaseous argon introducing pipe 6, and YAG laser 5 is irradiated to a cadmium telluride single crystal target 2 under a prescribed pressure to evaporate the target material to form semiconductor super fine particles of the first material, and to stick the super fine particles 12 on a quartz glass substrate 1. Then, using gold powder as the second material, gold vapor is evaporated from a gold depositing gun 4 under the prescribed pressure in the vacuum chamber 8, and composite super fine particles 13 are formed on the super fine particles 12. Then, the gaseous argon is evacuated and gaseous oxygen is introduced, the SiO2 of a SiO2 target 3 evaporated by a laser evaporation to form a SiO2 thin film, and the composite super fine particles 13 are covered with a SiO2 glass 14.

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 composite ultrafine particles, and in particular, ultrafine particles formed in a gas phase are vapor-deposited with materials of different substances to be composited to exhibit new characteristics. A method for producing composite ultrafine particles. The fields of application of such composite ultrafine particles include fields of nonlinear optical materials and catalyst materials.

[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, cadmium sulfide (Cd
Compound semiconductor ultrafine particles such as (S) 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 (for example, 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,
It is expected to be applied to optical control elements using nonlinear optical effects such as ultrafast optical switches and optical logic elements.

The following methods are known as methods for producing ultrafine particles. As a method for producing ultrafine particles in a solution, there is colloid generation using a redox reaction. For example, gold (Au) colloid can be easily produced by adding an appropriate reducing agent such as hydrogen peroxide or citric acid to a potassium chloroaurate solution. In the case of CdS as an example of the compound colloid, when a sodium sulfide (Na ₂ S) solution is added to a cadmium perchlorate (Cd (ClO ₄ ) ₂ ) solution, a redox reaction occurs to obtain a CdS colloid (for example, , R.
Rossetti et al., J. Chem. Phys. 82, 552 (1985)
). Although the particle size of the obtained fine particles varies depending on the manufacturing conditions, colloidal particles having a diameter of 5 nm or less and a small particle size distribution dispersion can be easily manufactured.

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 a liquid phase. This is because when a substance is heated and evaporated in an atmosphere of an inert gas such as argon (Ar), the vapor collides with atmosphere gas molecules, loses kinetic energy, and is rapidly cooled to form ultrafine particles. The size of the particles depends mainly on the pressure of the inert gas. Further, ultrafine oxide particles can be produced by reacting the produced particles with, for example, oxygen (O ₂ ) gas.

The above method is a method for producing ultrafine particles relating to one material. As a method for producing composite ultrafine particles, a method of precipitating zinc sulfide (ZnS) on CdS ultrafine particles produced in a solution is used. Known (eg,
Hyeong-Chan Youn, et al., J. Phys. Chem. 92 (1988)
6320.). This is Cd by blowing hydrogen sulfide (H ₂ S) gas into a solution containing cadmium ions (Cd ²⁺ ).
S is generated, zinc ions (Zn ²⁺ ) are further added, and H ₂ S gas is blown again to precipitate ZnS on CdS. A method of depositing a metal such as rhodium (Rh) on CdS is known (for example, Yves-M
Tricot, et al., J. Phys. Chem. 84 (1980) 7359
). Also in this case, a CdS colloid is similarly prepared in a solution and Rh is deposited on the surface of the fine particles. It has been reported that such composite ultrafine particles have a significantly improved catalytic action in photolysis of water. On the other hand, as a nonlinear optical material, it is theoretically predicted that the effect will increase in such composite ultrafine particles (for example, MH Birnboim et al., Mat. Res. Soc. Sy.
mp.Proc. Vol. 164 (1990) 277).

[0006]

However, since the conventional method for producing composite ultrafine particles uses a reaction in a solution, there is a problem in handling and stability, and the characteristics are sufficiently utilized. It was difficult to do. In addition, the materials that can be used for reaction in solution are limited,
It is not a widely used method. The above-mentioned serious drawbacks exist in the previously reported methods.

The present invention solves the above-mentioned conventional problems, dramatically increases the degree of freedom in selecting ultrafine particles as a composite material, and can be used in a more stable form. The purpose is to provide a method.

[0008]

The above object of the present invention can be achieved by the following constitutions.

That is, in the method for producing composite ultrafine particles, ultrafine particles are formed in a gas phase, the formed ultrafine particles are attached to a substrate, and then a material of a substance different from the ultrafine particles is vapor-deposited on the ultrafine particles. is there.

Ultrafine particles of the first material are produced by using a fine particle forming method in a gas phase which can be applied to a wide variety of materials as an ultrafine particle forming method, and the obtained fine particles are attached to a substrate.
Further, the second material is vapor-deposited on the surface of the ultrafine particles of the first material, or the ultrafine particles of the first material are covered therewith to produce composite ultrafine particles of the first material and the second material. .

[0011]

According to the present invention, the formation of the ultrafine particles of the first material and the formation of the composite of the second material are carried out on the substrate via the gas phase, so that the present invention can be applied to most materials. , The degree of freedom of the combination increases dramatically.
In addition, since the ultrafine particles of the first material act as a precipitation point of the second material, it is difficult to form ultrafine particles of the second material alone, and it is easy to obtain only composite ultrafine particles.
Further, the third material or the first material can be composited again on the second material, and it has an effect of making it possible to obtain ultrafine particles which could not be obtained conventionally.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a schematic view of a manufacturing apparatus used for manufacturing composite ultrafine particles. This apparatus is an apparatus for producing ultrafine particles in a gas. In this case, a high-power pulse laser was used as the first method for vaporizing the ultrafine particle raw material.

Argon gas is introduced into the vacuum chamber 8 through the argon gas introduction pipe 6 to reduce the pressure in the chamber to 0.
5 Torr, wavelength 532 nm, pulse width 10 n
A cadmium telluride (CdTe) single crystal target 2 was irradiated with an Nd: YAG laser 5 having a pulse power of 50 J / cm ² for s, and the material was evaporated to form semiconductor ultrafine particles as a first material. 50 mm from CdTe target 2
The quartz glass substrate 1 was placed at a distance and formed C
The dTe ultrafine particles 12 were attached. At this time, the pulse energy and the number of irradiations were taken into consideration so that the ultrafine particle density was such that the CdTe ultrafine particles 12 did not adhere to each other. The particle size of the CdTe ultrafine particles in forming the ultrafine particles under these conditions was analyzed by an electron microscope, and it was found that the particle size was about 6 nm and the dispersion of the particle size distribution was very small.

Next, using gold (Au) powder as the second raw material, after putting the above powder into the crucible of the electron beam gold vapor deposition gun 4 installed in the chamber, the vacuum degree of the vacuum chamber 8 was set to 1 × 10. -Reached to ^-6 Torr. After the degree of vacuum reached a predetermined value, gold vapor was evaporated from the gold vapor deposition gun 4 toward the quartz glass substrate 1. After evaporating for 1 minute, the shutter was closed and the vapor deposition on the CdTe ultrafine particles 12 was completed to form composite ultrafine particles 13.

Further, the argon gas was exhausted, and the oxygen gas was introduced through the oxygen gas introducing pipe 7 at a pressure of 5 × 10 ⁻⁴ Torr. Then, the SiO of the SiO target 3 was evaporated by laser evaporation to form a SiO ₂ thin film, and the composite ultrafine particles 13 were covered with the SiO ₂ glass 14. By stacking 100 such layers,
As shown in, a glass thin film 1 in which composite ultrafine particles are dispersed
5 was obtained. When the non-linear optical characteristics of this thin film were evaluated, when it was not composited, that is, ultrafine gold particles or C
Compared with the case where only dTe ultrafine particles are dispersed,
The nonlinear optical effect was observed to increase 2 to 3 times.
On the other hand, as a result of observing the obtained thin film with an electron microscope, as shown in FIG. 2, another ultrafine particle 11 or layer was observed on the surface of the CdTe ultrafine particle 12 and was identified by an analytical electron microscope. It was confirmed that the layer was gold. Therefore, it was found that the composite ultrafine particles 13 in which the gold ultrafine particles 11 were vapor-deposited on the CdTe ultrafine particles 12 were obtained by the above manufacturing method.

This time, the case of using CdTe ultrafine particles and gold has been described, but the present invention is not limited to this. For example, cadmium selenide (CdSe), zinc selenide (ZnSe), Cd.
2-6 group compound semiconductors such as S, GaAs, I
A Group 3-5 compound semiconductor such as nP or InGaAsP, a noble metal such as silver (Ag), platinum (Pt), Rh, or the like, or iron (Fe), cobalt (Co), nickel (Ni), or the like as a magnetic recording material, or copper. (Cu), vanadium (V), niobium (Nb) and other metals and their alloys, compounds with other elements, oxides obtained by evaporation of various metals in oxygen gas, etc. Any material that can be made into fine particles can be applied as the first ultrafine particle material. Of course, those materials can also be used as the second material,
By combining these, various types of composite ultrafine particles can be obtained.

In this embodiment, laser heating evaporation was used for heating evaporation of the first raw material, and electron beam heating was used for evaporation of the second raw material. However, in addition to this, sputtering for forming ultrafine particles and vapor deposition. Method, induction heating method, resistance heating method, CV
D method etc. can be applied. Of course, it is also possible to evaporate the first raw material and the second raw material in the same manner,
It is also possible to combine various methods.

A quartz glass substrate was used for collecting the produced composite ultrafine particles, but the present invention is not limited to this, and various single crystal and glass substrates can be used as the substrate.

[0019]

EFFECTS OF THE INVENTION According to the present invention, the composite material of ultrafine particles, which has been conventionally limited by selection, is formed on the substrate through the gas phase, thereby dramatically increasing the degree of freedom and further stabilizing the stability. Available in shape. By producing such composite ultrafine particles, it was possible to obtain a non-linear optical characteristic that could not be obtained by conventional single ultrafine particles.

[Brief description of drawings]

FIG. 1 is a schematic view of an apparatus for producing composite ultrafine particles used in an example of the present invention.

FIG. 2 is a schematic view of composite ultrafine particles obtained in an example of the present invention.

FIG. 3 is a schematic view of glass in which composite ultrafine particles obtained in an example of the present invention are dispersed.

[Explanation of symbols]

1 ... Quartz glass substrate, 2 ... CdTe target, 3 ... S
iO target, 4 ... gold vapor deposition gun, 5 ... laser beam,
6 ... Argon gas introduction pipe, 7 ... Oxygen gas introduction pipe, 8 ... Vacuum chamber, 9 ... Gate valve, 10 ... Laser light introduction window, 11 ... Gold ultrafine particles, 12 ... CdTe ultrafine particles, 1
3 ... Composite ultrafine particles, 14 ... SiO ₂ glass, 15 ... Glass thin film in which composite ultrafine particles are dispersed.

Claims (1)

[Claims] A composite ultrafine particle characterized by forming ultrafine particles in a gas phase, adhering the formed ultrafine particles to a substrate, and then depositing a material of a substance different from the ultrafine particles on the ultrafine particles. Manufacturing method.