JPH0376110A - Ultra fine semiconductor particle and production thereof - Google Patents

Abstract

PURPOSE:To enable ultra fine semiconductor particles to be easily processed even in the atmospheric air thereby enabling the physical property such as notable photonon- linearity held by the ultra fine semiconductor particles to be effectively applied by a method wherein the thin films of an inert material to oxygen having almost no reactivity to semiconductor even at the maximum temperature in the manufacturing process are bonded onto the surfaces of the ultra fine semiconductor particles. CONSTITUTION:GaAs material 4 (powder or polycrystal) is contained in a crucible 5 in an evaporation chamber 1 pressure-reduced by a vacuum pump (a) (not shown) and then heated by irradiating the material 4 with the laser beams 6 of an exciner laser outside the evaporation chamber 1 through a window 7. A purified inert gas such as Ar gas or N2 gas, etc., containing not exceeding 1ppm of residual oxygen and water content, is led into the evaporation chamber 1 previously vacuumized at the pressure not exceeding 10<-7>Torr and pressurized at about 10Torr. Any evaporated GaAs vapor collides with the gas molecules to produce GaAs ultra fine particles 9. Next, the ultra fine particles 9 are carried to a pipe 10 to be discharge into a vapor deposition chamber 2 through a nozzle 11. Through these procedures, the GaAs ultra fine particles whose surfaces are covered with SiC covering material can be produced.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to semiconductor ultrafine particles and a method for producing the same, and particularly to semiconductor ultrafine particles suitable for application to electronic devices and optical devices that utilize quantum effects.

<Prior art> In recent years, it has been observed that in glass (Sharpcapto filter for photography) in which 1 to 2% of Cd55a microcrystals are dispersed, the third-order nonlinear optical effect is increased by 200 times compared to bulk CdS (Journal of 0ptic
alSociety of America 73
Vol. 647, 1983).

This is an effect produced by confining electrons, holes, or excitons in a narrow space of about IOn+n or less.

Since the nonlinear optical effect is an effect in which the refractive index changes due to light irradiation, it is expected to be applied to light-controlled optical switches and the like. However, in order to realize a practical device,
It is necessary to further increase the effect. Possible means for this purpose include dispersion at a higher concentration or dispersion of a semiconductor other than Cd55a.

However, the method for producing dispersed glass described above involves melting and mixing semiconductor constituent elements and glass, and then reheating to precipitate microcrystals. In this method, the dispersion concentration is limited to the above-mentioned level, and there is a wide variety of It is difficult to apply this method to other semiconductor materials.

Therefore, as an alternative method, it is conceivable to prepare semiconductor ultrafine particles (particle size of approximately Ions or less) and disperse them in a matrix by appropriate means.

Conventionally, as a physical method for producing ultrafine particles, evaporation in gas has been most commonly used. This method is
In an inert gas such as r or N2, the ultrafine particle raw material is heated and evaporated by means such as resistance heating, high frequency induction heating, or irradiation with an electron beam or laser light.

FIG. 4 shows a method using high-frequency induction heating among the conventional methods described above.

In the figure, a crucible 23 surrounded by an induction coil 22 connected to an external high-frequency power source 21 is placed in a vacuum chamber 20 into which an inert gas 26 is introduced. The semiconductor raw material 24 is heated by high frequency induction. Since the evaporated particles 25 gradually increase in particle size as they move away from the evaporation source (crucible 23), by collecting the particles at a certain distance from the evaporation source,
Ultrafine particles with uniform particle size can be obtained.

<Problems to be solved by the invention> However, compared to normal bulk particles, ultrafine particles have a higher proportion of atoms exposed on the surface compared to the total number of atoms, and therefore are generally highly reactive with surrounding substances. . In particular, semiconductor materials contain many oxidizable substances and often react extremely easily with oxygen in the atmosphere, making them difficult to handle after manufacture.

This is one of the major problems that has hindered the industrial use of semiconductor ultrafine particles.

Means for Solving the Problems> In order to solve the above problems, the present invention provides a material on the surface of the semiconductor ultrafine particles that has almost no reactivity with the semiconductor even at the highest temperature in the manufacturing process and is resistant to oxygen. A thin film of inert material was then deposited.

Effect> The thin film substance attached to the surface of the semiconductor ultrafine particles has no reactivity with the semiconductor and is inert to oxygen, so it remains stable even in the atmosphere without damaging the original physical properties of the semiconductor ultrafine particles. It works like this. Furthermore, if the thin film material is a material that transmits light of a wavelength corresponding to the band gap of the semiconductor, light incident from the surroundings can interact with the internal semiconductor ultrafine particles without being absorbed.

<Example> FIG. 2 is a schematic diagram of an apparatus for producing semiconductor ultrafine particles in a first example of the present invention. Evaporation chamber 1 where GaAs raw material (powder or polycrystal) is depressurized by a vacuum pump (not shown)
The raw material 4 is placed in an inner Lupo 5 and heated by irradiating the raw material 4 with laser light 6 from an excimer laser from outside the evaporation chamber through a window 7. The evaporation chamber 1 is preliminarily heated to 10-'t.

After creating a vacuum below rr level, reduce the amount of residual oxygen and moisture to l.
Ar gas purified to less than ppm or an inert gas such as N2 gas is introduced to a pressure of about 10 torr. Evaporated GaAs vapor collides with gas molecules and generates G
1^B ultrafine particles 9 are generated. The ultrafine particles 9 are pipe l
The gas is transported through O and discharged into the vapor growth chamber 2 through the nozzle 11.

The vapor phase growth chamber 2 has s+zue, 5ills (CIls
) and N2 gas inlet, and the total pressure is 5 torr.
Each gas is introduced at a constant flow rate so that the In addition, a heating means is provided in this part, and a window 12 is provided through which a portion of the excimer laser light is introduced through a semi-transparent mirror 8. When the GaAs ultrafine particles 9 pass through the vapor phase growth chamber 2, each particle A SIC film is formed on the surface by photochemical reaction. The particles are collected in the collection chamber 3.

In this way, GaAs ultrafine particles 9 whose surfaces are covered with SIC coatings 17 as shown in FIG. 1 are obtained. The optical gap of amorphous SIC is about 2 eV, and G
The bandgap of aAs is larger than 1.4 eV, and GaA
Light corresponding to the vicinity of the band gap of s can be sufficiently transmitted.

In this example, the case of GaAs was described as the semiconductor, but
This may be an elemental semiconductor such as Sl or Ge, or a compound semiconductor such as InP%CdS or CuC1. In addition, a coating 17 covering these semiconductor ultrafine particles
The material is not limited to SIC as long as it is chemically stable, and many other materials such as SiN or Zn5e can be used.

FIG. 3 is a schematic diagram of a manufacturing apparatus in a second embodiment of the present invention. G in crucible 5! ^8 The raw material 4 is evaporated by high-frequency induction heating in the same atmosphere as in the first embodiment, and sent to the plasma chamber 13 through the nozzle 11. plasma chamber 1
Styrene monomer 16 is introduced into 3, and polystyrene is produced by high frequency glow discharge. The polystyrene is G
It adheres to the surface of the aAs ultrafine particles. Collect these fine particles,
By sotering this at a temperature of about 80℃, G
A thin film or a thick film in which ultrafine aAs particles are dispersed at a high concentration of about 10% by volume or more can be formed.

In the above embodiment, as in the first embodiment, the ultrafine particle material may be a semiconductor other than GaAg. The surface protective film may also be made of other materials as long as they have a lower melting point and no reactivity than the ultrafine semiconductor. Regarding the device, the heating means may be resistance heating, laser heating, or the like.

<Effects of the Invention> The present invention allows semiconductor ultrafine particles to be easily handled even in the atmosphere, and makes it possible to effectively utilize the physical properties of semiconductor ultrafine particles, such as large optical nonlinearity.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view showing the structure of the ultrafine particles of the present invention, Fig. 2 is a cross-sectional view showing an example of the apparatus for producing ultrafine particles according to the present invention, and Fig. 3 is a cross-sectional view showing another example of the ultrafine particle production apparatus according to the present invention. FIG. 4 is a cross-sectional view showing a conventional ultrafine particle manufacturing apparatus. Figure 1 3: Collection chamber 6: Laser optical semiconductor ultrafine particles 12: Window High frequency induction coil coating l: Evaporation chamber 2: Vapor phase growth chamber 4: Semiconductor raw material 5: Crucible 7: Window 8: Semi-transparent mirror 9: lO: Vibrator 11: Nozzle 13: Plasma chamber 14. ．． 15: 16: Monomer 17: Figure 2 r2 I3 Figure r2

Claims (5)

[Claims] (1) Semiconductor ultrafine particles characterized in that the surface of the semiconductor ultrafine particles is provided with a coating made of a substance that has substantially no reactivity with the semiconductor and is inactive with respect to oxygen. (2) The semiconductor ultrafine particles according to claim 1, wherein the coating material is selected to transmit light having a wavelength corresponding to the bandgap of the semiconductor forming the ultrafine particles. (3) The semiconductor ultrafine particles according to claim 1, wherein the melting point of the coating material is lower than that of the semiconductor forming the ultrafine particles. (4) producing ultrafine particles of the semiconductor by heating and evaporating the semiconductor raw material in a reduced pressure atmosphere into which an inert gas is introduced, and sending the ultrafine particles to a vapor growth chamber into which a film-forming substance gas is introduced; A method for producing semiconductor ultrafine particles, characterized in that the ultrafine particles passing through the chamber are irradiated with a laser beam to form the substance film on the surface of the ultrafine particles through a photochemical reaction. (5) Generate ultrafine particles of the semiconductor by heating and evaporating the semiconductor raw material in a reduced pressure atmosphere into which an inert gas is introduced, send the ultrafine particles to a plasma chamber, and introduce a polymer monomer into the chamber. A method for producing ultrafine semiconductor particles, which comprises generating a polymer of monomers and simultaneously adhering them to the surface of ultrafine semiconductor particles by performing high-frequency discharge in the chamber.