JPH07175095A - Production of nonlinear optical material - Google Patents

Abstract

PURPOSE:To decrease a grain size distribution in the micranization by heat treatment by specifying a temp. of a substrate at the time of forming an amor phous thin film on the substrate. CONSTITUTION:A sputtering device 7 is composed of a target 1 made of a metal, the target 2 made of an amorphous material, a substrate 3, a substrate holder 4 and high-frequency power sources 5 and 6 supplying high frequency power to each targets 1 and 2. The sputtering is executed by supplying the high-frequency power to form the amorphous thin film in which a metal is dispersed. Au is used as the metal used to the target 1, Al2O3 is used as the amorphous material used for the target 2 and a quartz glass is used as the substrate 3. In this case, the temp. of the substrate at the time of forming the amorphous thin film on the substrate is set at room temp. to 200 deg.C. In this way, a nonlinear optical material excellent in nonlinear optical characteristic is produced easily. That is, a metal or a semiconductor is dispersed uniformly in the thin film without being atomized.

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 non-linear optical material which forms the basis of an optical device utilizing a non-linear optical effect, and more particularly to a metal fine particle or semiconductor fine particle dispersed thin film.

[0002]

2. Description of the Related Art As a conventional technique, for example, a journal
Of Optical Society Of America 7th
Volume 3, Page 647 (Journal of Optica
l Society of America 73,
647 CdS _x Se listed in (1983))
_{There is one} using a cut-off filter glass obtained by doping _1-x (0 ≦ X ≦ 1) in borosilicate glass as a nonlinear optical material. In this glass, CdS _x Se _1-x and borosilicate glass are melted, quenched in the ionic state of Cd, S, and Se, and dispersed in the borosilicate glass. After that, through a reheat treatment process at about 600 to 700 ° C., CdS _x Se _1-x fine particles are deposited in the glass.

The average particle diameter of the fine particles is controlled by the temperature and time of the reheat treatment process, and the relationship between the average particle diameter and the heat treatment time is that the average particle diameter is proportional to the 1/3 power of the heat treatment time. .

Also, the Journal of Applied Physics, Vol. 63, page 957 (Journal
of Applied Physics 63, 95
7 (1988)). First, this thin-film glass is a target made of Corning "7059 glass" (Ba-containing borosilicate glass) and CdS by a high frequency magnetron sputtering method to disperse CdS in "7059 glass" in an amount of 2 to 4% by weight. I am letting you. Then, the thin film is heat-treated at 400 to 500 ° C. for about 24 hours to deposit CdS fine particles in the glass. At this time, the relationship between the particle size of the fine particles and the heat treatment time is the same as the 1/3 power law as shown above.

On the other hand, as a conventional technique for dispersing fine metal particles in glass, Optics Letters No. 1 is used.
Volume 0, page 511 (Optics Letters, 1
0, p. 511 (1985)). Au and Ag are used as the metal fine particles, and a metal salt reduction method is used as a method for producing the metal fine particle-dispersed glass. When the melting method is used, metal fine particles are mixed into a glass raw material to be shaped, and then heat-treated to deposit a specific metal, and a metal called a colored glass in which a metal colloid such as gold, silver, or copper is deposited. A fine particle dispersed glass was manufactured. At this time, the relationship between the particle size of the fine particles and the heat treatment time is the same as the 1/3 power law as shown above.

[0006]

In a non-linear optical material utilizing a non-linear optical effect containing fine semiconductor particles or fine metal particles, the finer the particles are uniformly dispersed in the glass of the matrix, the smaller the particle size distribution is. A nonlinear optical effect can be expected. Further, it is also important that the one having a large content and a small composition deviation is excellent.

However, the conventional non-linear optical material made of semiconductor or glass in which fine metal particles are dispersed or the manufacturing method thereof has the following problems. In the case of semiconductor fine particles, since CdS _x Se _1-x and borosilicate glass are melted at a high temperature and then reheated, the particle size control is not easy and the particle size distribution of the semiconductor fine particles becomes large. When the content of the semiconductor is 2 to 4% by weight or more, the particle size becomes too large to exist as fine particles, and the glass is devitrified, or the emission spectrum intensity near the light absorption edge of the semiconductor is lowered. It adversely affects the expression of the nonlinear optical effect.

Further, in the case of manufacturing by using the high frequency magnetron sputtering method, the surface temperature of the substrate is raised by being heated by the irradiation of ions in the plasma to the surface of the substrate during the manufacturing. Therefore, some semiconductors and metals in the amorphous thin film become island-shaped fine particles and are ubiquitous in the film. After that, since heat treatment is performed for a long time, the ubiquitous island-shaped fine particles become nuclei and grow large. On the other hand, some particles are made fine during the heat treatment, and these particles are mixed in the thin film, and the particle size distribution is enlarged. Further, in the sputtering method, there is a deviation in composition of the semiconductor due to re-evaporation of the semiconductor during production. That is, there is a possibility that an element that easily vaporizes or sublimes among the semiconductor constituent elements may deviate from the initial composition due to vaporization or sublimation.

On the other hand, a thin metal particle-dispersed thin film has the same problems as the semiconductor fine particle-dispersed thin film. further,
The third-order nonlinear susceptibility of the Au fine particle-dispersed glass produced by the conventional method is a value of 10 ⁻¹³ to 10 ⁻¹² esu, which is much smaller than other nonlinear optical materials. It is considered that this is because the value of the third-order nonlinear susceptibility was small because the dispersion amount of the metal fine particles was 5 ppm or less. Therefore, when the amount of dispersion was increased by the conventional manufacturing method, it was not possible to disperse uniformly.

In order to solve the above problems, the present invention provides a method for producing a non-linear optical material in which semiconductor fine particles or metal fine particles are dispersed in a large amount in a thin film and the particle size distribution of the fine particles is narrowed. To aim.

[0011]

In order to achieve the above object, the method for producing a non-linear optical material of the present invention comprises a step of forming an amorphous thin film containing a metal or a semiconductor on a substrate and then heat-treating the fine metal particles or In the method of manufacturing a nonlinear optical material by dispersing semiconductor fine particles in an amorphous thin film, the substrate temperature when the amorphous thin film is formed on the substrate is room temperature to
It is characterized in that the temperature is 200 ° C.

In the above-mentioned manufacturing method, it is preferable that after the amorphous thin film containing a metal or a semiconductor is formed on a substrate, heat treatment is performed by heating at a temperature rising rate of 1 to 250 ° C./sec.

[0013]

According to the method for producing a nonlinear optical material of the present invention, an amorphous thin film containing a metal or a semiconductor is formed on a substrate and then heat-treated to disperse the metal fine particles or the semiconductor fine particles in the amorphous thin film. In the method for producing a non-linear optical material by setting the substrate temperature at the time of forming the amorphous thin film on the substrate to room temperature to 200 ° C., a non-linear optical material having excellent non-linear optical characteristics can be easily produced. That is, since the metal or semiconductor is dispersed in the thin film in an ionic state or an atomic state in a homogeneous manner without forming fine particles,
It is possible to disperse a large amount in the thin film.

Further, an amorphous thin film containing a metal or a semiconductor is formed on a substrate, and then the temperature rising rate is 1 ° C./sec to 250.
According to the preferable configuration of the present invention in which the heat treatment is performed by heating at ° C / sec, a nonlinear optical material having excellent nonlinear optical characteristics can be easily manufactured. That is, the ionic or atomically dispersed metal or semiconductor in the thin film is rapidly made into fine particles to form uniform fine particles and the particle size distribution can be narrowed.

[0015]

EXAMPLE As the amorphous material of this example, a suitable type of amorphous material varies depending on the type of semiconductor used.
For example, glass materials such as silicon oxide, aluminum oxide, zinc oxide, titanium oxide, indium oxide and borosilicate glass, silicon nitride, aluminum nitride, titanium nitride, nitrides such as boron nitride, silicon carbide, carbides such as boron carbide. It is more preferable to use it because the dispersibility of the semiconductor is good.

The semiconductor of this embodiment depends on the type of the amorphous material used, but is, for example, CuCl, which is a group I-VII compound semiconductor, or G, which is a group III-V compound semiconductor.
ZnSe, ZnS, ZnTe, CdSe, Cd of II-VI group compound semiconductors such as aAs, InP and GaAlAs.
S, CdTe, ZnO, MnO, ZnCdSe, ZnS
It is preferable to use Group IV semiconductors such as Se such as Se, Ge, and SiGe because they show good nonlinear optical characteristics.

The metal used in this embodiment depends on the type of amorphous material used, but is, for example, gold (Au), silver (Ag), copper (Cu), platinum (Pt), tin (Sn), or the like. It is preferable to use it because it shows good nonlinear optical characteristics.

In this embodiment, as a means for producing an amorphous thin film, a sputtering method or a CVD method (Chemical Vap) is used.
or Deposition method, that is, chemical vapor deposition method), vacuum deposition method, and the like. The substrate temperature of this embodiment differs depending on the type of metal, semiconductor, and amorphous material used, so it is difficult to specify in a general way, but a temperature that can be normally performed in the above method, for example, room temperature (about 20 ° C.) From 2
It is not higher than 00 ° C.

When the sputtering method is adopted, argon gas is preferably used as the inert gas. The pressure condition for sputtering is not particularly limited, but a suitable pressure may be usually adopted within a pressure range of about 1 to 20 Pa. The power applied to the target varies depending on the type of the target material and the dispersion ratio of the metal or semiconductor fine particles to the target amorphous material, and thus is difficult to specify in general, but is, for example, about 20 to 500 W. .
A high-frequency sputtering method is generally used as the sputtering method, but a direct-current sputtering method or an electron cyclotron resonance sputtering method may be used depending on the type of target.

When the CVD method is adopted as a means for producing a semiconductor, a metal and an amorphous material, a metal used,
Since it depends on the type of semiconductor and the type of amorphous material, it is difficult to specify in general.
Se can be easily produced by the high frequency plasma CVD method. As another manufacturing method, thermal CVD
Method, laser CVD method or the like.

As the raw material gas when the high frequency plasma CVD method is adopted, a known raw material gas which can synthesize a metal or a semiconductor suitable as an amorphous material by the high frequency plasma CVD method may be used, and a III-V group compound semiconductor is used. As a gas for synthesizing, for example, AR ₃ (where A is
It represents a group III or group V element, and R represents a lower alkyl group such as a methyl group or an ethyl group. ), PH ₃ , AsH _{3 and the} like. Moreover, as a gas for synthesizing a II-VI group compound semiconductor, for example, DR ₂ (where D is
It represents a Group II or VI element, and R represents a lower alkyl group such as a methyl group or an ethyl group. ), H ₂ S, H ₂ Se and the like. Further, as the gas for synthesizing the group IV semiconductor, for example, SiH ₄ , GeH ₄ , SiC
l ₄ , GeCl _{4 and the} like.

When an oxide is used as the amorphous material,
As constituent gases other than oxygen, for example, TiCl ₄ ,
And group IV semiconductor gas, group III element gas, V
Examples of the gas include Group I elements, and oxygen includes oxygen gas.

When nitride is used as the amorphous material, the source gas other than nitrogen can be the same source gas as in the case of producing an oxide. The gas containing nitrogen may be NH ₃ or nitrogen gas.

Further, when the high frequency plasma CVD method is adopted as the means for producing the non-linear optical material, the above-mentioned gas may be used within a pressure range of about 13 to 1330 Pa. The high-frequency power varies depending on the type of gas used, etc., so it is difficult to specify in a general way, but for example, 20 to 200
It is about W.

The heat treatment temperature in this embodiment differs depending on the type of metal, semiconductor, and amorphous material used, and is therefore difficult to specify in general, but, for example, 600 to 1000.
It is about ℃.

The substrate used for depositing the nonlinear optical material of this embodiment may be a solid substrate used as this type of substrate, and a substrate made of an inorganic material is preferable in terms of heat resistance. It is not always necessary for the substrate to be transparent, but it is necessary to use it in applications where it is necessary to allow light to pass through the substrate, or for the evaluation and measurement of the obtained nonlinear optical material. When an evaluation or measurement method that requires transmission is adopted, the substrate is preferably transparent in the visible region, for example, glass, quartz, alumina, MgO and other transparent substrates can be used.

The amount of the fine semiconductor particles dispersed in the oxide layer is not particularly limited, but is preferably in the range of, for example, about 10 to 50 atom%. Of course, it may be used in an amount of 10 atomic% or less depending on the use, purpose, required performance and the like.

The present invention will be described below with reference to specific examples. Example 1 FIG. 1 is a schematic configuration diagram of a sputtering apparatus used in this example. The sputtering apparatus 7 includes a metal target 1, an amorphous material target 2, a substrate 3, a substrate holder 4, and high-frequency power sources 5 and 6 that supply high-frequency power to the respective targets.

High frequency power was supplied to the targets 1 and 2 to carry out sputtering to form an amorphous thin film in which metal was dispersed. The metal used for the target 1 was Au, the amorphous material used for the target 2 was AlO ₂ , and the substrate 3 was quartz glass. Argon gas was used as the sputtering gas, and the pressure was 2 Pa. 20 W of high frequency power was supplied to the target 1 and 200 W to the target 2, and sputtering was performed. The substrate temperature was 150 ° C. The thickness of the obtained amorphous thin film containing gold was 2 μm.

A constituent component of a thin film deposited on a substrate
Au and an amorphous material AlO ₂Al existing in
When measured with a Micro Beam Narizer, Au and Al source
The offspring ratio was approximately 1: 4 in terms of the number of atoms. In amorphous thin film
The content of Au was 20 atomic%.

Thereafter, the obtained amorphous thin film was heat-treated at 900 ° C. for 1 hour to obtain a nonlinear optical material. 90 at this time
The heating rate for reaching 0 ° C was 250 ° C / sec. The thin film after the heat treatment was examined by a transmission electron microscope for the particle size and absorption spectrum of the metal fine particles. FIG. 2 shows the absorption spectrum of the thin film of this example. (A) in FIG. 2 is an absorption spectrum between 400 nm and 800 nm, and plasmon resonance absorption of gold and band absorption of gold itself were observed. Figure 2
(B) shows only plasmon resonance absorption obtained by removing the band absorption spectrum from (a). The more symmetrical the absorption spectrum is, the smaller the particle size distribution is.

For comparison, the temperature rising rate is 90 ° C./sec.
The case of 0.5 ° C./sec is shown in FIGS. Comparing the plasmon resonance absorptions of the respective thin films in FIG. 3B and FIG. 4B, the higher the heating rate, the more symmetrical. Particularly, in the case of 0.5 ° C./second, the tail of plasmon resonance absorption extends to around 800 nm. From these results, it is considered that the effect of increasing the temperature rising rate to 1 ° C./second or more is produced. Further, even if the temperature rising rate is higher than 250 ° C./sec, a remarkable effect cannot be found because the diffusion limit of heat to the thin film occurs.

Further, in the case of the absorption spectrum of FIG. 2, an amorphous thin film was formed at a substrate temperature of 150 ° C. FIG. 5 shows the case where the substrate temperature is 250 ° C. in order to see the effect of the substrate temperature.
Plasmon resonance absorption was also observed in the as-depo state, but it is found that there is a tail of absorption on the long wavelength side and the particle size distribution is large. Furthermore, even if the thin film of FIG. 5 was heat-treated at a high temperature rising rate, there was no change in the absorption spectrum.

FIG. 6 shows a temperature rising rate of 250 ° C./sec and 0.5 ° C.
3 shows a histogram of the particle size distribution of a thin film per second. Both have a peak at a particle size of 10 nm, but the thin film at 0.5 ° C./sec had a distribution in which the particle size reached 16 nm. on the other hand,
In the thin film of this example, the grain size was distributed up to about 12 nm, but the grain size was almost 16 nm. This is shown in Figure 2.
Similar to the results of 3 and 4, it is considered that this was caused by the high temperature rising rate.

From these results, it is possible to form a thin film at a substrate temperature of 200 ° C. or lower and to raise the temperature of the heat treatment from 1 ° C./sec to 25 ° C.
The effect of increasing the temperature to 0 ° C./second was recognized. Furthermore, as a result of the third-order nonlinear susceptibility measurement by the degenerate four-wave mixing method using a nitrogen laser-excited dye laser, the third-order nonlinear susceptibility of the thin film at a temperature rising rate of 0.5 ° C./sec is 1 × 10 ⁻⁷ esu. On the other hand, the third-order nonlinear susceptibility of the nonlinear optical material of this example is 1 × 10 ^−6.
It was esu.

Example 2 A target 1 was used as a semiconductor target by using the same apparatus as the sputtering apparatus 7 used in Example 1. High frequency power was supplied to the semiconductor target 1 and the amorphous material target 2 to perform sputtering to form an amorphous thin film in which the semiconductor was dispersed. The semiconductor used for the target 1 is Zn
Te, the amorphous material used for the target 2 was SiO ₂ , and the substrate 3 was quartz glass. Argon gas was used as the sputtering gas, and the pressure was 2 Pa. Target 1
50 W and 300 W of high frequency power were supplied to the target 2 for sputtering. The substrate temperature was 100 ° C. The thickness of the obtained amorphous thin film containing ZnTe was 0.
It was 5 μm.

Zn, which is a constituent of the fine particles in the thin film deposited on the quartz glass substrate, and S in the amorphous material SiO ₂
Zn atom when i is measured by a microbeam analyzer,
The ratio of Si atoms was about 1: 3 in number of atoms. The content of ZnTe fine particles in the nonlinear optical material was 25 atom%.

Thereafter, the obtained amorphous thin film was heat-treated at 600 ° C. for 1 hour to obtain a nonlinear optical material. At this time 60
The heating rate for reaching 0 ° C. was 100 ° C./sec. The thin film after the heat treatment was examined by a transmission electron microscope for the particle size distribution of the semiconductor fine particles.

FIG. 7 shows a histogram of the grain size distribution of a thin film having a temperature rising rate of 100 ° C./sec and a comparative example of 0.5 ° C./sec.
Both have a peak at a particle size of 8 nm, but
In the thin film at 5 ° C./sec, the particle size was distributed up to 12 nm. On the other hand, in the thin film of this example, the particle size was distributed up to about 10 nm, but the particle size was almost 12 nm. It is considered that this is because the particle size distribution was reduced due to the high temperature rising rate.

Further, when the substrate was manufactured at a temperature higher than 200 ° C., the peak of the absorption spectrum due to the ZnTe fine particles was observed, but when the particle diameter of the ZnTe fine particles was examined by observation with a transmission electron microscope, as compared with the thin film of this example. The particle size distribution was large.

From these results, a thin film is formed at a substrate temperature of 200 ° C. or lower, and the heat treatment temperature is raised from 1 ° C./sec to 2 ° C.
The effect of 50 ° C./sec was recognized. Furthermore, as a result of the third-order nonlinear susceptibility measurement by the degenerate four-wave mixing method using a nitrogen laser-excited dye laser, the third-order nonlinear susceptibility of the thin film with a temperature rising rate of 0.5 ° C./sec is 5 × 10 ⁻⁷ esu. On the other hand, the third-order nonlinear susceptibility of the nonlinear optical material of this example is 2 × 10.
It was ^-6 esu.

[0042]

As described above, according to the method for producing a nonlinear optical material of the present invention, an amorphous thin film containing a metal or a semiconductor is formed on a substrate and then heat-treated to remove the metal fine particles or the semiconductor fine particles. A method for producing a non-linear optical material dispersed in a crystalline thin film, wherein a substrate temperature when forming the amorphous thin film on a substrate is set to room temperature or higher and 200 ° C. or lower. Without it, it can be dispersed homogeneously in an amorphous thin film, the particle size distribution can be made smaller by atomization by heat treatment, and a nonlinear optical material having a large nonlinear optical effect can be manufactured.

When an amorphous thin film containing a metal or a semiconductor is formed on a substrate and then the heat treatment is performed at a temperature rising rate of 1 ° C./sec to 250 ° C./sec to perform the heat treatment, the ions are formed in the thin film. Since the metal or semiconductor dispersed in the form of particles or atoms is rapidly made into fine particles to form uniform fine particles and the particle size distribution can be made small, a nonlinear optical material having a large nonlinear optical effect can be manufactured.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a sputtering apparatus used in an embodiment of the present invention.

FIG. 2 is a diagram showing an absorption spectrum of a nonlinear optical material obtained in one example of the present invention.

FIG. 3 is a diagram showing an absorption spectrum of a nonlinear optical material obtained in one example of the present invention.

FIG. 4 is a diagram showing an absorption spectrum of a thin film of AlO ₂ dispersed with gold fine particles obtained in a comparative example.

FIG. 5 is a diagram showing an absorption spectrum of a thin film of gold fine particle-dispersed AlO ₂ obtained in a comparative example.

FIG. 6 is a histogram of the particle size distribution of gold fine particles in the nonlinear optical material obtained in one example of the present invention and in the gold fine particle-dispersed AlO ₂ thin film obtained in the comparative example.

FIG. 7 is a histogram of the particle size distribution of ZnTe fine particles in the nonlinear optical material obtained in one example of the present invention and in the ZnTe fine particle-dispersed SiO ₂ thin film obtained in the comparative example.

[Explanation of symbols]

 1 Target of Metal or Semiconductor 2 Target of Amorphous Material 3 Substrate 4 Substrate Holder 5 High Frequency Power Supply 6 High Frequency Power Supply 7 Sputtering Equipment

Claims (2)

[Claims] 1. A method for producing a non-linear optical material by forming an amorphous thin film containing a metal or a semiconductor on a substrate and then heat-treating the amorphous fine film to disperse the metal fine particles or the semiconductor fine particles in the amorphous thin film. A method for producing a non-linear optical material, characterized in that the substrate temperature at the time of forming the crystalline thin film on the substrate is room temperature or higher and 200 ° C. or lower. 2. After forming an amorphous thin film containing a metal or a semiconductor on a substrate, the heating rate is 1 ° C./sec or more and 250 or more.
The method for producing a non-linear optical material according to claim 1, wherein the heat treatment is performed by heating at a rate of not higher than C / sec.