JP3413892B2 - Manufacturing method of ultrafine particle dispersion material - Google Patents

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 an ultrafine particle dispersed material utilizing a nonlinear optical effect as an ultrafast optical switch or the like.

[0002]

2. Description of the Related Art Since ultrafine particles exhibit a quantum size effect in a dispersed state without aggregation of ultrafine particles, it is known that highly useful optical characteristics such as an ultrafast optical switch can be obtained such as an increase in nonlinear optical effect. Has been.

However, in order to utilize the optical characteristics of the ultrafine particles as a device, it is necessary to prepare an ultrafine particle dispersion material in which the ultrafine particles are dispersed and fixed in some matrix, and in order to increase the non-linear characteristics thereof. It is required that the particle diameter of the ultrafine particles is equal to or less than several tens of nm where the quantum size effect appears and is uniform, and that the concentration of the ultrafine particles in the matrix is high.

A conventionally known method for producing an ultrafine particle dispersion material is a melt-quenching method in which semiconductor particles are dispersed in glass as a matrix (for example, Junji Yumoto et al .: Solid physics vol. 24 (1989)). 925).
This is a method in which a glass melt in which a compound semiconductor is uniformly dispersed is produced by rapidly cooling a solution obtained by melting a semiconductor compound together with a glass raw material, and then the glass is reheated to precipitate ultrafine particles.

The semiconductor ultrafine particle dispersion material by the melt-quenching method has already been put into practical use as a sharp cut filter having a function of blocking light in a specific wavelength range, but these filters contain compound semiconductor ultrafine particles having a particle size of about 10 nm. Therefore, it has been studied as an optical nonlinear material in recent years.

However, in the method of precipitating ultrafine particles in the matrix such as the melt quenching method, impurities from the matrix are mixed in the ultrafine particles and the growth rate of each particle during the heat treatment is high. Since it is different, it is difficult to make the particle size of the ultrafine particles uniform, and it is necessary to limit the mixing concentration of the raw materials so that the chemical properties of the matrix itself do not change, and it is difficult to disperse the ultrafine particles in a high concentration. Therefore, there is a problem in using it as an optical device such as an ultra-high-speed optical switch that requires a larger nonlinear optical effect.

In order to solve these problems, the raw material for the ultrafine particles is laser-heated and evaporated in an inert gas such as argon (Ar), and the vapor is rapidly cooled by collision with the inert gas. A method is known in which ultrafine particles of the raw material synthesized by the above are fixed in a matrix.

For example, Japanese Patent Application Laid-Open No. 5-96 by the present applicant
154 shows a method for producing cadmium telluride (CdTe) ultrafine particle-dispersed glass in which good dispersion was confirmed. This manufacturing method uses CdTe in an Ar gas atmosphere.
YAG (yttrium, aluminum,
Garnet) laser irradiation to produce ultrafine CdTe particles and irradiation of a silicon oxide (SiO) sintered body with YAG laser to produce a silica (SiO ₂ ) glass matrix in an oxygen atmosphere are alternately performed. It is a thing.

According to this manufacturing method, since the manufacturing steps of the ultrafine particles and the matrix are independent, impurities are not mixed from the matrix into the ultrafine particles, and the particle size distribution of the ultrafine particles can be easily controlled. Further, it is possible to provide a highly applicable nonlinear optical material which has a characteristic that ultrafine particles can be dispersed in a high concentration and solves the above-mentioned problems of the melt quenching method.

[0010]

However, in this method, since an inert gas such as Ar is used in the process of producing ultrafine particles, the inert gas and the matrix are mixed in the chamber used for producing the ultrafine particle dispersed material. There is a problem that the gas used in the manufacturing process must be replaced every time these processes are repeated in order to improve the manufacturing efficiency.

Further, there is a problem in manufacturing cost that a relatively large amount of relatively expensive inert gas must be used.

Particularly, in order to disperse the ultrafine particles in the matrix while avoiding the agglomeration thereof, it is desirable to repeat the production process of the ultrafine particles and the production process of the matrix frequently, and the gas exchange frequency must be high. Absent.

For example, in the above-mentioned JP-A-5-96154, CdTe having a film thickness of about 1 μm was confirmed to have good dispersion.
The number of repetitions of both manufacturing processes carried out to manufacture the ultrafine particle dispersed glass was 80 times, and it was necessary to perform suction and exhaust once in the vacuum chamber for every process.

In view of these circumstances, the present invention is a method for producing an ultrafine particle-dispersed material in which ultrafine particles are not aggregated with each other, have a uniform particle size, and are dispersed in a high concentration. It is an object of the present invention to provide a manufacturing method with further excellent manufacturing efficiency.

[0015]

The present invention is achieved by the following configurations.

That is, in the method for producing an ultrafine particle dispersed material in which the step of forming ultrafine particles and the step of forming a matrix on the substrate are alternately carried out in the same vacuum container, the step of forming the ultrafine particles Is a step of forming ultrafine particles of the raw material on a substrate by laser heating evaporation of the raw material of the ultrafine particles in an atmosphere depressurized to 5 × 10 ⁻⁵ Torr or less. It is a manufacturing method of a dispersion material.

In the conventional method, ultrafine particles are formed by laser heating evaporation of a raw material for ultrafine particles in an inert gas, capturing the energy by colliding with atoms of the inert gas, and rapidly cooling. However, in the present invention, the raw material of the ultrafine particles vaporized by laser heating under high vacuum forms the ultrafine particles through the process of nucleation and nucleus growth on the substrate.

In order to effectively carry out this process without being affected by other gas in the chamber, 5 × 10 ⁻⁵ Tor
It should be under a high vacuum of r or less, but 1 × 10 ⁻⁶ Torr
It is even more preferable under the following high vacuum.

The steps of forming a matrix include
For example, a method of forming a matrix by using a laser for heating and evaporating ultrafine particles as it is also for heating and evaporating a material that is a raw material of a matrix is preferable in terms of equipment because the laser can be shared.

At this time, it is desirable to select both so that the matrix material can sufficiently absorb the energy of the wavelength of the laser for heating and evaporating the matrix.

Further, it is known that the composite ultrafine particles further increase the nonlinear optical effect (for example,
M. H. Birnboim et al. , Mat. R
es. Soc. Symp. Proc. Vol. 164
(1990) 277), after forming the ultrafine particles and before forming the matrix, a material different from both the ultrafine particles and the matrix is formed on at least a part of the surface of the formed ultrafine particles to combine the ultrafine particles. The method for producing a composite ultrafine particle dispersion material in which the composite ultrafine particles are dispersed in a matrix may be used.

In the step of forming the material for forming the composite, this material may be formed as the second ultrafine particles on the surface of the ultrafine particles, but a large number of the second ultrafine particles are formed on each other. It may be in contact with and continuous to form a film, or in extreme cases, it may be formed so as to cover the entire surface of the first ultrafine particles. If the ultrafine particles are compounded as a whole, as long as the compounded ultrafine particles are dispersed in the matrix,
This is because the nonlinear optical effect can be expected to increase further.

[0023]

According to the present invention, in the manufacturing process of the ultrafine particle dispersed material for forming ultrafine particles by laser heating evaporation, after the matrix forming step, the gas existing in the chamber is exhausted to the outside of the chamber and the inside of the chamber is simultaneously discharged. Only by maintaining a high vacuum, it is possible to move to the next ultrafine particle forming step.

Further, after the ultrafine particle forming step, the gas used in the matrix forming step can be introduced into the chamber without exhausting the gas from the chamber, and the next matrix forming step can be performed. That is, since ultrafine particles are formed on the substrate through the process of nucleation and nucleus growth even under high vacuum, it is not necessary to have an inert gas in the chamber in the process of forming ultrafine particles, and it is possible to manufacture ultrafine particle dispersed materials. The supply and exhaust of the inert gas in the process are completely omitted.

In the manufacturing process of the ultrafine particle-dispersed material including the process of forming ultrafine particles into a composite material, the effect of not using the inert gas according to the present invention is the same.

[0026]

Embodiments of the present invention will be described below with reference to the accompanying drawings. (Example 1) A method for producing an ultrafine particle dispersion material employing CdTe as ultrafine particles and SiO ₂ glass as a matrix will be described.

FIG. 1 shows a manufacturing apparatus used in this embodiment.
As a raw material for the matrix and the ultrafine particles, a sintered body of SiO powder having a characteristic of well absorbing the second harmonic (532 nm) of the YAG laser which is a heating source of the raw material, and C
The dTe polycrystalline wafer was placed on the target holder 2 in the vacuum chamber 1. Further, quartz was placed as a substrate on the substrate holder 3 located 50 mm from the target holder 2.

First, as a preliminary experiment, SiO ₂ glass serving as a matrix was manufactured. Oxygen gas pressure in the vacuum chamber 1 from the 5 × 10 ^over 4 Torr, SiO laser pulse 20000 shots introducing a YAG laser second harmonic output 25 J / cm ^-2 from the laser beam introduction window 4 at room temperature The sintered body was irradiated. An uncolored, transparent and uniform SiO ₂ glass film having a thickness of 500 nm was obtained on the quartz substrate.
When this SiO ₂ glass film was evaluated by a spectrophotometer,
No light absorption was observed in the range of 400 nm to 1000 nm. It was also confirmed that a good SiO ₂ glass film could be produced when the substrate temperature was in the range of room temperature to 450 ° C.

Next, based on the above results, a CdTe ultrafine particle dispersed SiO ₂ glass was manufactured. According to the timing chart shown in FIG. 2, 5 × 10 5
-45 YAG laser pulse in oxygen atmosphere of ^-4 Torr
Irradiation was performed for 0 shots to form a 11.25 nm thick SiO ₂ glass film on the quartz substrate. Then, in the second step, the vacuum degree in the vacuum chamber was raised to 1 × 10 ⁻⁶ Torr and a laser pulse was irradiated on the CdTe polycrystalline wafer for 50 shots, and C was deposited on the SiO ₂ glass film produced in the first step.
The dTe microparticles were attached. By repeating the first step and the second step alternately 80 times, a CdTe ultrafine particle-dispersed glass having a film thickness of about 1 μm as shown in FIG. 4 was manufactured.

FIG. 3 shows a timing chart when this CdTe ultrafine particle-dispersed glass is manufactured by the conventional method using an inert gas in the ultrafine particle forming step, and the number of times of supply and exhaust is twice that of this embodiment. It turns out that is necessary. Further, when this CdTe ultrafine particle-dispersed glass was chemically analyzed by an inductively coupled plasma optical emission spectrometer (ICP), it was revealed that CdTe was dispersed in the glass in an amount of about 30% by weight.

Furthermore, when the manufactured ultrafine particles were observed with an electron microscope by adjusting the substrate temperature in the range of room temperature to 450 ° C., it was confirmed that the particle size was 3 nm to 50 nm.

The evaluation results of the absorption characteristics of this sample are shown in FIG. Although the absorption edge of the thin film CdTe crystal is 820 nm, a shift of the absorption edge to the high energy side due to the quantum size effect was observed in comparison with this, and it was found that good CdTe ultrafine particles were dispersed. . The concentration and particle size could be controlled with good reproducibility.

Although CdTe ultrafine particle-dispersed glass has been described in the present embodiment, the ultrafine particles are not limited to CdTe, but II-VI group compound semiconductors such as CdS, CdSSe and ZnSe and III-V such as GaAs, InP and InGaAs. It is also applicable to group compound semiconductors and single element semiconductors such as Si. Further, the matrix material is not limited to glass, and oxides or organic substances such as titanium oxide (TiO ₂ ) and aluminum oxide (Al ₂ O ₃ ) can be applied.

Some materials may not absorb the second harmonic of the YAG laser described here, but the third harmonic (354 nm) may be used, or another laser (such as an excimer laser) may be used. It is possible to produce an ultrafine particle dispersed material by heating and evaporating the material.

Since a useful matrix can be obtained by evaporating a metal such as Ti or Al in oxygen, this method may be used as a matrix forming method.

Further, a chemical vapor deposition method may be used as the method of forming the matrix. According to this method, it is possible to reduce the stress in the matrix, and even if the thickness of the matrix layer is increased, there is little risk of film peeling. A chemical vapor deposition method using the introduced gas is desirable.

(Embodiment 2) FIG. 6 shows a manufacturing apparatus used in Embodiment 2. A sintered body of SiO powder and a CdTe polycrystalline wafer were placed in a target holder 2 in a vacuum chamber 1 as a matrix and a raw material of ultrafine particles, respectively. Further, quartz was placed as a substrate on the substrate holder 3 located 50 mm from the target holder 2.

First, as the first step, the vacuum chamber 1
The CdTe polycrystalline wafer was irradiated with the second harmonic of a YAG laser having a pulse width of 10 ns and an output of 50 J / cm ^{2 with} the inside of 1 × 10 ⁻⁶ Torr to form CdTe ultrafine particles on the substrate.

Next, as a second step, gold vapor is vaporized from the electron beam gold vapor deposition gun 13 in which gold (Au) powder is put in the crucible, while maintaining the degree of vacuum in the vacuum chamber at 1 × 10 ⁻⁶ Torr. It was evaporated toward a quartz glass substrate. After evaporating for 1 minute, the shutter of the gold vapor deposition gun 13 is closed and CdT
e The vapor deposition on the ultrafine particles was completed.

Further, in the third step, oxygen gas is introduced into the chamber through the oxygen gas introducing pipe, and the gas pressure is adjusted to 5 ×.
After the 10 ^@ 5 Torr, S in YAG laser second harmonic
Irradiation of a sintered body of iO powder on a quartz glass substrate
_Two glass films were formed.

The above first to third steps were repeated 100 times to produce a CdTe ultrafine particle dispersed glass compounded by gold deposition.

When this thin film was observed with an electron microscope,
As shown in FIG. 7, CdTe is formed on the surface of the CdTe ultrafine particles 12.
Ultrafine particles 14 of a substance different from
As shown in FIG. 8, the entire surface of Te ultrafine particles is Cd.
It was covered with a film 15 of a substance different from Te.
As a result of identification with an analytical electron microscope, it was confirmed that the ultrafine particles 11 or the film 15 was gold.

Further, the non-linear effect of this thin film was evaluated, and when the ultrafine particles were not compounded, that is, CdT
e The effect was increased by a factor of 2 to 3 compared to the case where only ultrafine particles or gold ultrafine particles were dispersed.

In Example 2, CdTe was used as the ultrafine particles produced in the first step, gold was used as the ultrafine particles produced in the second step, and SiO was used as the matrix produced in the third step.
₂ glass was used, but CdTe was I as in Example 1.
It may be a group I-VI or group III-V compound semiconductor, the SiO ₂ glass may be an oxide or an organic substance such as TiO ₂ , Al ₂ O ₃ , and gold may be silver (A
It may be g), platinum (Pt), rhodium (Rh), or the like.

In this example, the ultrafine particles were manufactured by dividing them into the first step and the second step. However, if the order of the first step and the second step is reversed, they are used in the first step. Possible materials can be used in the second step, and materials that can be used in the second step can be used in the first step.

[0046]

According to the present invention, the particle size is several nm.
To a few tens nm, and there is no aggregation of particles,
A material in which ultrafine particles or composite ultrafine particles are dispersed at a high concentration can be manufactured efficiently in a timely and economical manner.

Further, since the ultrafine particles can be produced independently of the matrix, the crystallinity and particle size distribution of the ultrafine particles can be controlled, and the materials for the ultrafine particles and the matrix can be widely selected.

As described above, it is possible to provide a highly versatile nonlinear optical material by a more efficient manufacturing method than ever before.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a manufacturing apparatus for manufacturing CdTe ultrafine particle dispersed glass according to Example 1 of the present invention.

FIG. 2 is a timing chart of the first embodiment of the present invention.

FIG. 3 is a timing chart for producing CdTe ultrafine particle dispersed glass by a conventional method.

FIG. 4 is a schematic view of CdTe ultrafine particle-dispersed glass produced according to Example 1 of the present invention.

FIG. 5: Absorption characteristics of CdTe ultrafine particle dispersed glass produced according to Example 1 of the present invention

FIG. 6 is a schematic diagram of a manufacturing apparatus for manufacturing CdTe composite ultrafine particle dispersed glass according to Example 2 of the present invention.

FIG. 7 is a schematic diagram showing CdTe composite ultrafine particles produced according to Example 2 of the present invention.

FIG. 8 is a partial CdT produced according to Example 2 of the present invention.
e Schematic diagram showing composite ultrafine particles

[Explanation of symbols]

1: Vacuum chamber, 2: Target holder, 3: Substrate holder 4: Laser light introduction window, 5: Gas introduction pipe, 6: Stop valve, 7: Mass flow controller, 8: Turbo molecular pump,
9: Rotary pump 10: Quartz substrate, 11: SiO ₂ glass, 12: CdT
e Ultrafine particles 13: Gold vapor deposition gun, 14: Gold ultrafine particles, 15: Gold film 16: CdTe composite ultrafine particles

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shuhei Tanaka, 3-5-11 Doshumachi, Chuo-ku, Osaka City Nihon Sheet Glass Co., Ltd. (72) Keiji Tsuneto, 3-5 Doshomachi, Chuo-ku, Osaka No. 11 within Nihon Sheet Glass Co., Ltd. (56) Reference JP-A-4-214860 (JP, A) JP-A-5-254883 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) ) B01J 19/12 C03C 14/00-17/58

Claims (2)

(57) [Claims] 1. A step of forming ultrafine particles on a substrate,
In the method for producing an ultrafine particle dispersed material in which the step of forming a matrix on the substrate is alternately performed in the same vacuum container, the step of forming the ultrafine particles is performed at a material of 5 × 10 ⁻⁵ Torr. Laser heating and evaporation in a reduced pressure atmosphere are performed below to allow nucleation and nucleation on the substrate.
Method for producing ultrafine particle-dispersed material, characterized in Rukoto through the process of fine nucleation. 2. A material different from both the raw material of the ultrafine particles and the raw material of the matrix is formed on at least a part of the surface of the ultrafine particles as the ultrafine particles after forming the ultrafine particles and before forming the matrix. Alternatively, the method for producing an ultrafine particle dispersion material according to claim 1, wherein the ultrafine particles are formed as a continuous film to composite the ultrafine particles.