JP3086543B2 - Method for producing fine particle dispersed glass - 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 fine particle-dispersed glass.

[0002]

2. Description of the Related Art Cd having a particle size of about 100 angstroms
A sharp cut filter in which S _x Se _1-x (0 ≦ x ≦ 1) semiconductor fine particles are dispersed in a matrix glass has a relatively large third-order optical nonlinear susceptibility | χ ⁽³⁾ |
Therefore, application to optical switches and arithmetic elements for optical computers has been studied.

CdS which can be used in these nonlinear optoelectronic devices
_As xSe1 _-X fine particle-dispersed glass, for example, there is a glass described in JP-A-4-46038. The publication discloses that P ₂ O ₅ and / or B ₂ O ₃ , ZnO and / or CdO are essential components, and P ₂ O ₅ and B ₂ O ₃
Of 35 to 65 mol% and a total of 65 to 25 mol% of ZnO and CdO as a matrix, and CdS _x Se _1-x (0 ≦ x ≦ 1) fine particles were precipitated therein. A glass for a nonlinear optoelectronic device is disclosed.

[0004] Glass used for such purposes includes:
There is a demand for an optical nonlinear susceptibility (nonlinear constant) | χ ⁽³⁾ | that is sufficiently large and the nonlinear response time is short. In particular, as a practical material, a response speed of several psec is required.

[0005]

The response speed of this type of semiconductor particle-dispersed glass depends on the relaxation speed of photoexcited carriers. In a semiconductor crystal miniaturized to a size (about 100 angstroms) of the Bohr radius of electrons, holes, and excitons in a solid, a so-called quantum size effect appears, and the state density of the conduction band and the valence band is reduced. Discrete and quantized. It is considered that the energy band of the semiconductor fine particles deposited in the glass matrix is also quantized.
Recombination emission of photoexcited carriers occurs via quantized levels. FIG. 4 is a diagram for explaining the transition of the photoexcited carriers of the semiconductor fine particles.

FIG. 4A shows a typical photoexcited light emission (PL) spectrum of CdS _x Se _{1 -x} fine particle dispersed glass (P ₂ O ₅ based matrix). By photoexcitation, two emission peaks on the long-wave side from the absorption spectrum (dotted line),
It can be seen that the occurrence has occurred. In particular, the emission peak on the long wavelength side shows a dominant fluorescence intensity.

FIG. 4B is an energy band diagram for explaining the main relaxation process of the photoexcited carriers of the CdS _x Se _1-X fine particles. As described above, the quantization level E _e1 of the CdS _x Se _1-x fine particles dispersed in the glass matrix (insulator) is at a position higher in energy than the conduction band bottom of the bulk crystal. In addition, the quantization level E _h1 for holes is located at a position lower in energy than the bottom of the valence band of the bulk crystal. That is, the transition energy between the lowest quantum levels | E _e1 −E _h1 |
Is the band gap E _g of the CdS _x Se _1-X bulk crystal
Greater than. The emission peak in the PL spectrum of FIG. 4A is considered to correspond to the emission transition from E _e1 → E _{h1 in} FIG. 4B. It is considered that this interlevel transition is accompanied by a nonradiative transition as a competitive process.

On the other hand, as shown in FIG. 4B, the emission peak on the long wavelength side in FIG. 4A changes from the defect level E _D formed in the band gap to the hole level E _h1. It is thought that it corresponds to the radiation transition to. It is considered that the non-radiation competition process shown in FIG.

[0009] carriers defect levels E _D (electrons) are those supplied to the non-radiative manner E _D from electron level E _e1 by a transition indicated by. The fluorescence intensity of the emission peak is larger than the emission peak means that longer carrier lifetime in by and E _D high transition probability of the carrier to the defect level E _D. Non-radiative transitions, which are generally phonon-related thermal processes, are much faster than radiative transitions.
For example, in FIG. 4B, the process is on the order of psec, whereas the process is on the order of tens of nsec and the process is on the order of 10 μsec to 10 msec. The reason that the relaxation time of the process is several orders of magnitude longer than that of the process is the difference in carrier lifetime at the initial level.
From the above, the process relaxation time is expected to be on the order of psec.

[0010] As described above, Japanese Patent Application Laid-Open No. 4-46
Including the case of _{CdS x Se 1- x (0 ≦} x ≦ 1) particles dispersed glass 038 described in JP, conventional CdS _x Se
It was inevitable that the response speed of the _1-X fine particle-dispersed glass would be 10 μsec or more because the process was rate-determining.

As a method of increasing the response speed, there is disclosed a method of irradiating a fine particle-dispersed glass with laser light for a long time. This is because laser annealing (J. Opt.
oc. Am. B5 (1988) 1448) or photodarkening (J. Opt. Soc. Am. B4 (198)
7) 5), the mechanism of which has not been elucidated, but is thought to induce defect levels in the particulate semiconductor to predominate relaxation by a non-radiative transition process, for example.

However, in this method, since it is necessary to irradiate a high-density laser beam, there is a problem that it is difficult to uniformly and large-area photodarkening over the entire glass. In addition, a step called laser annealing is added after glass preparation, which leads to a significant increase in cost.

An object of the present invention is to provide a method capable of producing a CdS _x Se _{1 -X} fine particle dispersed glass exhibiting a fast optical response in a glass production process without requiring an additional step such as laser annealing. is there.

[0014]

In order to achieve the above object, the present invention provides a glass material serving as a matrix and Cd serving as fine particles.
Raw material of S _x Se _1-X (0 ≦ x ≦ 1) and Sb ₂ Se ₃
A method for producing a fine particle-dispersed glass, characterized by obtaining a fine-particle-dispersed glass in which CdS _x Se _1-X fine particles are dispersed in a matrix glass by cooling and heat-treating a raw material composition comprising a mixture containing I do.

[0015]

According to the present invention, Sb ₂
The point is to add Se ₃ , whereby CdS _x dispersed in the glass obtained by melting, casting, and heat treatment (slow cooling after heat treatment).
This has the effect of increasing the particle size of the Se _1-X fine particles and dispersing them uniformly.

When the particle size R of the fine particles increases in a range showing the quantum size effect, the energy difference | E _e1 −E _h1 | between the quantized levels shown in FIG. 4B decreases in inverse proportion to R ^2. It is known to That is, the emission peak energy in FIG. 4A is proportional to 1 / R ² .

The present inventors have found that as a more important effect with increasing R, the probability of the non-radiative transition process increases and the probability of the radiative process decreases. The data is shown in FIG. FIG. 1A shows the fluorescence spectra and the intensities of two examples having different radii R. The particle size R
Is represented by a particle diameter radius r (R = 2r). These two examples were measured under the same excitation conditions. A red shift of the peak wavelength and a remarkable decrease in the emission intensity are observed as the particle size R increases.

FIG. 1B collectively shows the data of the fluorescence peaks measured under the same excitation conditions while changing the particle diameter R variously. As described above, it is shown that as R increases, the peak energy red-shifts in proportion to 1 / R ² , and that the fluorescence intensity decreases significantly with the particle size in the region of r> 20 angstroms .

The present invention relies on an increase in the non-radiative transition probability with an increase in R. As the non-radiation process becomes dominant, the optical response characteristics of the fine particle-dispersed glass are significantly improved.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in more detail based on embodiments. The fine particle-dispersed glass composition of the present invention contains P ₂ O ₅ and / or B ₂ O ₃ as a glass material as a matrix.
And ZnO and / or CdO as an essential component. This is because of the thermal stability, chemical durability and the semiconductor component Cd of the glass.
This is a result in consideration of the solubility of S _x Se _1-X . Further, it is preferable to use an oxide material as the glass material. In addition to the above, materials used for ordinary melting of glass, such as hydroxides, carbonates, and nitrates, can also be used. However, these generate gas during melting and tend to volatilize sulfur and / or selenium components having a high vapor pressure, and as a result, CdS _x S dispersed in glass.
The density of e _1-X fine particles will be reduced.

The raw materials for the glass matrix, P ₂ O ₅ and / or
Alternatively, the total amount of B ₂ O ₃ is 35 to 65 mol%, and Zn
It is preferable that the total amount of O and / or CdO is 65 to 25 mol%. If the total amount of P ₂ O ₅ and B ₂ O ₃ is lower than 35 mol%, the thermal stability of the glass is deteriorated, and crystals are easily precipitated from the matrix glass in the heat treatment step after casting. P ₂ O ₅ and B ₂ O
_If the total amount of ₃ exceeds 65 mol%, the chemical durability of the glass will decrease, and this will cause a problem during use. More preferably,
The total amount of P ₂ O ₅ and B ₂ O ₃ is in the range of 40~65mol%.

Further, the total amount of ZnO and CdO is 65 mol.
%, The thermal stability of the glass is impaired, and when the total amount is less than 25 mol%, the chemical stability of the glass is impaired, so that both are not preferred. More preferably, ZnO
And the total amount of CdO is in the range of 60 to 35 mol%.

On the other hand, as other components of the matrix glass raw material, alkali metal oxides, alkaline earth metal oxides, ZrO ₂ , TiO ₂ , PbO, SiO ₂ , A
It is possible to include l ₂ O ₃ , As ₂ O ₃ , Sb ₂ O _3, etc., but the total amount must be 25 mol% or less. The reason is that the total amount of these components is 25 mol%
If the ratio exceeds 1, the solubility of sulfur and / or selenium in the glass melt decreases, and excess components are volatilized and lost, so that the density of CdS _x Se _1-X fine particles dispersed in the glass decreases.

The mixed crystal ratio x of CdS _x Se _1-X is determined by taking into account the amount of Sb ₂ Se ₃ mixed in the raw material, with CdS and C d Se.
It can be determined by mixing powders in a predetermined ratio and mixing them in a matrix. However, the state in which the CdS _x Se _1-X fine particles are precipitated in the glass matrix depends on the concentration of CdS _x Se _1-X mixed in the matrix. To explain this, FIG. 2 shows data as a comparative example of the present invention in which Sb ₂ Se ₃ was not added, and for simplicity, x = 0, that is, only CdSe was used as a semiconductor material.
FIG. 2 shows that P ₂ O ₅ , ZnO, and Cd are used as matrix glass raw materials.
The relationship between the amount of CdSe fine particles deposited in glass and the amount of CdSe added to the raw material when vitrification is performed is shown below.

The solubility of CdSe that can precipitate CdSe fine particles is, for example, that the matrix composition is 50P ₂ O ₅ -50Z.
3 to 6 mol% when nO (mol%), 50 P ₂ O ₅ −
8-16mo when 30ZnO-20CdO (mol%)
l%, 30 at the time of _{50P 2 O 5 -50CdO (mol%} )
５０50 mol%. Thus, microcrystals are unlikely to be precipitated in a low concentration region. In the higher concentration region, the glass matrix becomes unstable.

The CdSe fine crystal precipitation region is as shown in the figure, but the hatched portion is easy to obtain one having a large grain size, but is a non-uniform precipitation region. In the illustrated uniform precipitation region, the particle size is small, and therefore, the fluorescence intensity is large and the light response is poor.

When a small amount of Sb ₂ Se ₃ is added to the non-uniform precipitation region shown by the hatched portion in FIG. 2, a glass having a large particle size and uniform fine particles can be obtained. Also,
It was found that the large grain size, uniform precipitation region extended to the non-precipitation region in FIG. The particle size can be controlled by the concentration of Sb ₂ Se ₃ added, the heat treatment temperature and the time.

As compared with the matrix composition shown in FIG.
_{When the} total amount of ₂ O ₅ and B ₂ O ₃ is increased, CdS _x S
The solubility of e _1-X decreases, and conversely CdO and Cd
As the content of S and CdSe increases, the solubility of CdS _x Se _{1- x} increases, but in any case, the same tendency as in FIG. 2 is exhibited.

FIG. 3 shows an example in which Sb ₂ Se ₃ of the present invention is added.
Shown in FIG. 3 shows that the matrix composition is 50P ₂ O ₅ -30.
ZnO-20CdO (mol%) and deposited fine particles are CdS
e (mixed semiconductor material is CdSe), Sb ₂
This shows the effect of adding Se ₃ .

The hatched area in FIG. 3 is the Sb ₂ S shown in FIG.
e ₃ is nonuniform deposition region of the case of no addition. Sb ₂ Se
_{(3) In} the case of no addition, the region where the CdSe raw material is 11 to 16 mol% is a uniform precipitation region and the particle size can be controlled, but the particle size is small. In order to precipitate CdSe fine crystals having a large particle size, it is necessary to perform heat treatment for a very long time, and this is not practical. Further, the matrix becomes unstable due to the long-term heat treatment.

However, as shown in FIG.
By adding 8 mol% of Sb ₂ Se ₃ to the raw material, the precipitation region is expanded to outside the shaded region, and in the precipitation region indicated by the dotted line, uniform precipitation with a large grain size including the shaded portion in the figure is obtained. I understood. This result is completely the same in the case of depositing CdS _x Se _1-x fine particles further containing CdS.

In the homogeneous and large-diameter CdS _x Se _{1 -X} fine particle dispersed glass obtained by adding Sb ₂ Se ₃ , the fluorescence intensity of photoexcitation is about two orders of magnitude as compared with the case of no addition (FIG. 1). As a result, the non-radiative transition probability increased by that much, and the optical response was greatly improved. That is, Sb ₂ Se
₃ Homogeneous CdS _x Se showing fast photoresponse by addition
_1-X fine particle dispersed glass is obtained.

Hereinafter, a production example of the CdS _x Se _1-X fine particle-dispersed glass and a result of measurement of physical properties of the obtained fine particle-dispersed glass will be specifically described. Production Example 1 50 mol% as a raw material of glass to be a matrix
P ₂ O ₅ , 30 mol% ZnO and 20 mol% C
Using a composition consisting of dO, 100 mol% of this composition
On the other hand, a mixture obtained by adding 1.0 mol% of Sb ₂ Se ₃ and 6 mol% of CdSe as a raw material of fine particles was heated at 1200 ° C. for 15 minutes in a refractory crucible to obtain a homogeneous glass melt. It was cast on an iron plate to obtain a colorless and transparent glass. According to the chemical analysis of the glass thus obtained, the residual amount of Sb in the glass was 1.9 wt%, which was almost equivalent to the concentration of 1.8 wt% in the batch.

Next, the obtained glass was previously converted to 43
The glass was placed in an electric furnace maintained at 0 ° C., heat-treated at this temperature for 30 hours, and then gradually cooled to room temperature.

When the glass thus obtained was measured by the X-ray diffraction method, a peak of CdSe crystal was observed, and it was confirmed that CdSe fine particle dispersed glass was obtained. Furthermore, C contained in CdSe fine particle dispersed glass
The average particle size (diameter) of the CdSe crystal fine particles was determined by measuring the size of the dSe crystal fine particles using an X-ray diffraction method.
Angstrom.

The obtained CdSe fine particle-dispersed glass was optically polished to a thickness of 50 μm, and its absorption spectrum and fluorescence spectrum were measured. As shown in FIG. A subband peak is observed, and light emission near the band edge and light emission from a deep level are recognized from the fluorescence spectrum (solid line). Here, when comparing the fluorescence intensity with the case where Sb ₂ Se _{3 was} not added in FIG. 1, the relative intensity was about 1/200 (HOY).
The intensity is about 1/2000 compared to the relative value when the fluorescence intensity of R68 manufactured by A Corporation is 10 ⁴ ), indicating that the non-radiative process in the relaxation of the excited carriers is increased. . Further, luminescence of the vicinity of the absorption edge from fluorescent lifetime measurements (PLH) is about 170Psec, luminescence (PLL) from a deep level below the resolution of the measurement system, Sb ₂
It was confirmed that the length was sufficiently shorter than the case where Se _{3 was} not added. Also, the optical nonlinear susceptibility | χ ⁽³⁾ |
⁽³⁾ | / α value (α is the absorption coefficient) is 6 × 10 ⁻¹¹ esu ·
cm. This value is equivalent to the value after laser annealing.

Production Examples 2 to 20 Using the matrix raw materials shown in Tables 1 to 5, CdS _x Se
CdSe and CdS were used as raw materials for _1-X , and Sb
Glass was obtained in the same manner as in Production Example 1 using ₂ Se ₃ .
Thereafter, these glasses were each heat-treated under the conditions shown in Tables 1 to 5, and then gradually cooled to room temperature, whereby the glasses were uniformly colored.

When the colored glasses of Production Examples 2 to 20 obtained as described above were measured by an X-ray diffraction method, the glasses of Production Examples 2 to 18 had a CdSe crystal peak and Production Example 19 , 20 for CdS
_x Se _1-X mixed crystal peak of was observed, that the fine particle dispersion glass was obtained was confirmed. The particle diameter of the fine particles evaluated by the X-ray diffraction method was 70 to 150 as shown in Tables 1 to 5.
Angstrom is relatively large. Further, from the absorption spectrum, the absorption peak of the sub-band due to the quantum confinement effect was confirmed as in Production Example 1. As shown in Tables 1 to 5, the fluorescence intensity of these fine particle-dispersed glasses is smaller by 2 to 3 orders than SCF (relative value when the fluorescence intensity of R68 manufactured by HOYA Corporation is 10 ⁴ ), As in Production Example 1, it can be seen that the number of non-radiative processes in the relaxation of excited carriers is increased. In addition, the fluorescence lifetime measurement confirmed that both the emission near the absorption edge and the emission from the deep level were shorter than or about the resolution of each measurement system. The optical non-linear susceptibility | χ ⁽³⁾ | was 5８8 × 10 ⁻¹¹ esu · cm as | χ ⁽³⁾ | / α value (α is an absorption coefficient). This value is equivalent to the value after laser annealing.

Comparative Example 1 As a raw material of glass serving as a matrix, 50 mol% was used.
Of a composition comprising P ₂ O ₅ and 50 mol% of ZnO, and using a mixture of 100 mol% of this composition and 4 mol% of CdSe as a raw material of fine particles,
Glass was obtained in the same manner as in Production Example 1. This glass is Sb ₂ S
not contain e ₃ is limited outside the scope of the present invention. Thereafter, when the glass was heat-treated at 450 ° C. for 64 hours, it was uniformly colored. When the colored glass thus obtained was measured by the X-ray diffraction method, a crystal peak of CdSe was recognized, and the particle size was evaluated to be 50 Å. Further, from the absorption spectrum, the absorption peak of the sub-band due to the quantum confinement effect was confirmed as in Production Example 1. Table 5 shows the fluorescence intensity of these fine particle-dispersed glasses.
As shown in the figure, the emission is large and the emission on the low energy side is also strong, which indicates that the contribution of the radiation transition is large. From the fluorescence lifetime measurement, the emission (P
LH), which is as long as 800 psec to several tens of nsec.
And it was confirmed that it was very long. That is, it can be seen that this material cannot be used for high-speed response without laser annealing.

Comparative Example 2 In the same manner as in Comparative Example 1, except that a mixture having the composition shown in Table 5 which did not contain Sb ₂ Se ₃ as a raw material and was outside the scope of the present invention, was used. To get the glass. Thereafter, the glass was heat-treated at 450 ° C. for 64 hours, but no colored glass was obtained. No precipitation of CdSe crystal fine particles was confirmed from the X-ray diffraction method or the light absorption spectrum.

Comparative Example 3 In the same manner as in Comparative Example 1, except that a mixture having the composition shown in Table 5 which did not contain Sb ₂ Se ₃ as a raw material and was outside the scope of the present invention was used, the same procedure as in Production Example 1 was performed. To get the glass. Thereafter, when this glass was subjected to a heat treatment at 450 ° C. for 64 hours, a heterogeneous colored glass was obtained. An X-ray diffraction method showed a peak of CdSe crystal, but it was not a material capable of performing optical measurement.

Comparative Examples 4 to 8 As in Comparative Example 1, the production examples were the same as those in Comparative Examples 1 to 4 except that mixtures containing Sb ₂ Se ₃ as raw material and having compositions shown in Tables 5 and 6, which were outside the scope of the present invention, were used. Glass was obtained in the same manner as in Example 1. Thereafter, these glasses were heat-treated under the conditions shown in Tables 5 and 6, respectively.
Although the precipitation of dSe microcrystals was observed, the fluorescence lifetime was very slow as shown in Table 2. In Comparative Example 6-8, the precipitation of fine crystals of CdSe and CdS _x Se _1-X was observed.

[0043]

[Table 1]

[0044]

[Table 2]

[0045]

[Table 3]

[0046]

[Table 4]

[0047]

[Table 5]

[0048]

[Table 6]

[0049]

As described above, according to the present invention,
Weak emission intensity, i.e., can be in the relaxation process of excited carriers to obtain the contribution of the large CdS _x Se _1-X particle dispersion glass composition of the non-radiation process. This material has a short fluorescence lifetime and an optical nonlinear susceptibility |
χ ⁽³⁾ │ is | χ ⁽³⁾ │ / α value (α is the absorption coefficient), which is equivalent to the value after laser annealing, and is therefore useful as a nonlinear optoelectronic material with a fast response and good nonlinear characteristics. .

[Brief description of the drawings]

FIG. 1 is a PL data diagram showing the relationship between the particle size and fluorescence of CdS _x Se _1-X particle-dispersed glass.

FIG. 2 CdS added with raw material when Sb ₂ Se _{3 is} not added
It is a figure which shows the relationship between e quantity and CdSe fine particle precipitation amount in glass.

FIG. 3 is a diagram showing a change in a CdSe microcrystal precipitation region due to the addition of Sb ₂ Se ₃ .

FIG. 4 is a diagram showing photoexcitation relaxation of CdS _x Se _1-X fine particle dispersed glass.

FIG. 5 is an optical characteristic diagram of CdSe fine particle dispersed glass according to an example.

Claims (4)

(57) [Claims] 1. A glass material to be a matrix, a CdS _x Se _{1- x} (0 ≦ x ≦ 1) material to be fine particles, and Sb
After melting the raw material composition comprising a mixture containing ₂ Se ₃ cooled and heat treatment method for producing a particle-dispersed glass CdS _x Se _1-X fine particles and obtaining a fine particle dispersion glass dispersed in a matrix in the glass . 2. The glass raw material serving as the matrix comprises 35 to 65 mol% in total of P ₂ O ₅ and / or B ₂ O ₃ as essential components, and 65 to 25 mol% of ZnO and / or CdO in total. And the raw material composition contains the Sb ₂ S based on 100 mol% of the matrix glass.
The e ₃ containing 0.005~5.0mol%, claim 1
A method for producing the fine particle-dispersed glass according to the above. 3. The method according to claim 1, wherein the amount of CdS _x Se _1-X is 2 to 50 mol% based on 100 mol% of the matrix glass. 4. The method for producing fine particle-dispersed glass according to claim 1, wherein an oxide raw material is used as the glass raw material serving as the matrix.