JPH11260621A - Bismuth-substituted garnet thick film material and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high-performance Bi-substituted garnet thick film material having various superior characteristics, such as the saturation magnetic field, etc., by mixing a specific wt.% platinum oxide in a single-crystal thick film. SOLUTION: A TbBi garnet thick film composed of Tb1.9 Bi1.1 Fe4.8 Al0.2 O3 containing 0-3.0 wt.% (excluding 0 wt.%) is grown on a neodymium-gallium- garnet(NGG) substrate to a thickness of about 600 μm by liquid phase growth by using high-purity Tb2 O3 , Fe2 O3 , Al2 O3 , Bi2 O3 , PbO, and Be2 O3 powder as raw materials and PbO-Bi2 O3 -B2 O3 as flux. Then the thick film is heat-treated in the temperature range of 950-1,130 deg.C by adjusting the oxygen concentration in the atmosphere to 10-100%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical garnet material having a Faraday effect, and more particularly to a bismuth (Bi) -substituted garnet thick film material and a method for producing the same, and more particularly to a liquid phase growth method (LPE method). (T
b, Bi) ₃ (Fe, Al) ₅ O ₁₂ -based garnet single crystal thick film material and a method for producing the same.

[0002]

2. Description of the Related Art Hitherto, devices using Faraday rotation in optical communication have been developed and put into practical use. Also,
When a semiconductor laser is used in optical communication, oscillation becomes unstable or stops when reflected light from an optical fiber cable, a connector, or the like returns to the oscillation unit. Therefore, an optical isolator is used to block return light and secure a stable oscillation state.

A Bi-substituted rare earth iron garnet having a large Faraday rotation is grown by an LPE method, a flux method, or the like, and is used as an isolator in the near infrared region. In particular, a garnet thick film grown by the LPE method has excellent productivity, and is currently mostly produced by this method.

A commercially available Bi-substituted garnet thick film produced by the LPE method is composed of GdBi-based garnet and TbBi.
Divided into garnets. The former is grown on an NGG substrate (with a lattice constant of about 12.509 angstroms) because of the large lattice constant of the crystal, and the latter is grown on an SGGG substrate (with a lattice constant of about 12.496 angstroms) because of the small lattice constant of the crystal. However, this is because it is possible to stably grow a thick film, and is common sense in manufacturing.

[0005] Commercially available GdBi-based garnets are:
Although the required applied magnetic field can be small, there is a disadvantage that the temperature characteristics (the usable temperature range is narrow in a low temperature range and the temperature change rate is large) are inferior. On the other hand, TbBi-based garnets have good temperature characteristics, but have the drawback of requiring a high applied magnetic field. In addition, since the TbBi-based garnet uses an SGGG substrate in which the variation in lattice constant is essentially large due to the large number of types of constituent elements as compared with the GdBi-based garnet, crystal defects and distortion are likely to occur and homogenization is also achieved. There was a tendency to be inferior. However, market demands are
The use of TbBi-based garnets having good temperature characteristics is increasing.

When the basic composition of a TbBi-based garnet is grown on an SGGG substrate which is considered to be suitable for its growth, the composition of the garnet is in the vicinity of Tb _2.2 Bi _0.8 Fe ₅ O ₁₂ . The optical characteristics of the TbBi-based garnet thick film include a Faraday rotation capability (θ _F ) of about 750 deg / cm, a temperature change rate (θ _{F / T} ) of Faraday rotation near room temperature of about 0.04 deg / ° C., and an insertion loss ( IL) is 0.1 to 0.1.
3 dB, a saturation magnetic field (saturation applied magnetic field which is a minimum magnetic field required for insertion loss to reach saturation) Hs is about 80
0 Oe. In this crystal, about 5
If the thickness is greater than 00 μm, the production is not easy because cracks and crystal defects occur.

Therefore, when manufacturing TbBi-based garnet, the required film thickness is reduced by improving θ _F. It grows on a SGGG substrate as before,
The Bi composition value is increased by replacing a part of Tb with Ho or Yb with respect to the basic composition of the TbBi-based garnet. That is, in order to increase the number of Bi ions having a large ion radius, Ho or Y having a small ion radius is used.
b is replaced in large quantities. Ho-based garnets and Yb-based garnets have significantly higher saturation magnetization (4πMs) near room temperature than Tb-based garnets.
Hs of oBi garnet and TbYbBi garnet
Is about 1000 to 1200 Oe. In addition, good temperature characteristics, which were characteristics of the TbBi-based garnet, tend to deteriorate.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and to provide a high-performance Bi-substituted garnet thick film material having excellent characteristics such as Hs and a method for producing the same. I do.

[0009]

Means for Solving the Problems Accordingly, the present inventors have:
By growing a TbBi-based garnet on an NGG substrate having a larger lattice constant than an SGGG substrate, Ho and Y
Do not substitute with rare earths having a small ionic radius such as b.
By increasing the Bi composition value, Hs related to 4πMs was suppressed, and an attempt was made to improve the TbBi-based garnet. As a result, in a TbBi-based garnet, including a method of substituting a part of Fe with a small amount of Al, it is possible to improve the Faraday rotation performance without a need for Yb or Ho substitution amount with a specific melt composition. Was found.

Furthermore, in a garnet thick film mainly composed of Tb, Bi, Fe, and Al, Pt is contained in the garnet.
The O ₂ by containing 0~3.0wt%, found that I.L. Is clearly reduced.

According to the present invention, the required characteristic at a wavelength of 1.55 μm as a TbBi-based garnet material is θ _F of 8
00 deg / cm or more, Hs is 1000 Oe or less, θ
_{F / T} less than 0.07 deg / ° C, Faraday rotation angle about 4
A Bi-substituted garnet thick film material having an IL of 0.2 dB or less (preferably 0.1 dB or less) at 5 deg is obtained.

That is, according to the present invention, the LP
In a Bi-substituted garnet thick film material composed of a garnet single crystal thick film mainly composed of Tb, Bi, Fe, and Al grown by the E method, PtO ₂ is reduced to 0 in the single crystal thick film.
It is a Bi-substituted garnet thick film material containing up to 3.0 wt% (excluding 0).

[0013] Further, the present invention provides the above-mentioned single crystal thick film,
This is a method for producing the above Bi-substituted garnet thick film material grown on a G substrate.

Further, the present invention provides a method for manufacturing a semiconductor device comprising:
The method for producing a Bi-substituted garnet thick film material according to the above, wherein the heat treatment is performed at a temperature in the range of 0 to 1130 ° C.

Further, the present invention provides the above-mentioned single crystal thick film,
This is a method for producing the Bi-substituted garnet material, wherein the heat treatment is performed in an oxygen concentration range of an atmosphere of about 100%.

In the present invention, PtO ₂ is added in an amount of 0 to 3.0 wt.
% (Excluding 0) means that the effect of reducing IL is recognized even when a small amount of PtO ₂ is contained, and when it exceeds 3.0 wt%, it is caused by mismatch of ion balance. This is because a remarkable increase in IL is observed.

The growth of the TbBi-based garnet of this composition on an NGG substrate is different from the growth on an SGGG substrate in that the Bi composition is not replaced by an element having a small ionic radius that provides high Ys or Ho and Hs. This is because the value can be increased.

Further, according to the present invention, the garnet film is prepared in an atmosphere having an oxygen concentration of 10 to 100% in the atmosphere of 950 to 1130.
By performing heat treatment in a temperature range of ° C., a reduction in IL is realized. Oxygen concentration in heat treatment atmosphere is 10-100
The reason for setting the percentage is that if it is less than 10%, due to lack of oxygen, correction of the ion balance of the garnet constituent elements becomes insufficient and IL increases. Further, the reason why the heat treatment temperature is in the range of 950 to 1130 ° C. is that if the temperature is lower than 950 ° C., the homogenization of the crystals is insufficient and the IL is hardly reduced. Occurs,
This is because IL is significantly increased.

The liquid phase growth of such a Bi-substituted garnet is performed as follows. In a platinum crucible, PbO, bismuth oxide (Bi ₂ O ₃ ), boron oxide (B ₂ O ₃ ) and the like are used as flux components, and garnet components [terbium oxide (Tb ₂ O ₃ ), ferric oxide (Fe)
₂ O ₃ ), aluminum oxide (Al ₂ O ₃ ) etc.
After dissolving at 1100 ° C. to prepare a solution (melt), the temperature is lowered to obtain a supersaturated solution state. By dipping the garnet substrate in the melt and rotating for a long time,
Grow i-substituted garnet thick films.

The lattice constant of the garnet single crystal to be grown is constrained to be substantially the same as the lattice constant of this substrate, and the composition ratio of atoms is determined. Therefore, it is extremely important to control the concentration of the supersaturated component, and the composition and crystallinity of the grown garnet change depending on the temperature and the flow state of the solution, resulting in a change in material properties and the occurrence of crystal defects and cracks. This L
In the current state of the PE method, the crystal growth state is managed by controlling the composition of the solution, the temperature, the lattice constant difference with the substrate, the number of rotations of the substrate, and the like. However, the optimal state of breeding is limited to a very narrow range, and it is almost impossible to adjust by independently changing the factors.

In particular, cracking of the garnet crystal thick film is caused by
The main factor is that the growth substrate and the garnet have different lattice constants and thermal expansions. Therefore, as the thickness of the grown garnet increases, the frequency of occurrence of cracks increases. Therefore, improving the Faraday rotation capability of the garnet film and reducing the required film thickness brings about the effect of reducing the occurrence of cracks, which is industrially beneficial.

The literature of the TbBi-based garnet film by the LPE method is described in Journal of the Japan Society of Applied Magnetics, Vol.
1, No. 2, 1987, p. 157 and JP-A-60-20
8730, JP-A-2-131216 and the like.
These do not suggest the contents related to the present invention.

It should be noted that the garnet showing relatively good optical characteristics according to the present invention has a main component composition ratio of Tb _3-x B
If a _{i x Fe 5-y Al y} O 12, x = 0.9~1.5,
It is obtained in the range of y = 0.02 to 0.52. However,
In the examples, among them, x =
0.9 to 1.4 and y = 0.1 to 0.5 are shown.

[0024] The characteristics shown in the present invention, I.L. garnet may smaller because it relates to the damping in the traveling direction of the light, theta _F is higher, it is possible to thin, theta _{F / The} closer _T is to 0, the better the temperature stability.
When Hs is lower, the characteristics of the permanent magnet used for the magnetization of the garnet film can be lowered, and the size and weight can be reduced. Therefore, I.L. Reduction, improve theta _F, decrease in theta _{F / T,}
Reduction of Hs is industrially beneficial.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION In a platinum crucible, PbO, Bi
₂ O ₃ , B ₂ O _3, etc. are used as flux components, and garnet components (Tb ₂ O ₃ , Fe ₂ O ₃ , Al ₂ O _3, etc.) are about 900 to 11
After dissolving at 00 ° C. to produce a melt, the temperature is lowered to a supersaturated solution state. A garnet substrate is immersed in the melt and rotated for a long time to grow a Bi-substituted garnet thick film.

[0026]

Embodiments of the present invention will be described below.

(Example 1) High purity Tb ₂ O ₃ , Fe
A powder of ₂ O ₃ , Al ₂ O ₃ , Bi ₂ O ₃ , PbO and B ₂ O ₃ is used as a raw material, and a PbO—Bi ₂ O ₃ —B ₂ O ₃ is used as a flux and an NGG substrate (with a lattice constant of 12. 509 angstroms) and the main component ratio is Tb _1.9 Bi _1.1 Fe _4.8
A TbBi-based garnet thick film having a composition containing about 1.0 wt% of PtO ₂ was grown to a thickness of about 600 μm with Al _0.2 O ₁₂ .

A garnet thick film having a thickness of about 600 μm was grown on an SGGG substrate (with a lattice constant of 12.496 angstroms) using the same melt as described above.

Next, the substrates of these samples were removed, and both surfaces were polished to adjust the thickness so that the Faraday rotation at a wavelength of 1.55 μm was about 45 deg. The above-mentioned compositions were obtained by performing EPMA analysis on each side of each of these samples at five points, and calculating the average value.

Next, after subjecting these sample plates to a non-reflective coating treatment with a SiO ₂ film, a magnetic field of about 1.
With application up to 5 kOe, Hs, IL, θ _F and θ _{F / T} were determined at a wavelength of 1.55 μm. Table 1 shows the results.

[0031]

From Table 1, the garnet thick film grown on the NGG substrate is clearly superior in IL, θ _F and θ _{F / T.} Although Hs is slightly higher, it is a difference that does not cause any problem in practical use. Therefore, N
Growing on a GG substrate is clearly beneficial.

(Embodiment 2) In the same manner as in Embodiment 1, NG
On a G substrate, the main component ratio is Tb _1.7 Bi _1.3 Fe _4.7 Al _0.3
With O ₁₂ , PtO ₂ is reduced to 0.5, 1.0, 2.0, 3.0,
After growing a TbBi-based garnet thick film having a composition containing 4.0 and 5.0 wt% to a thickness of about 600 μm, a sample was prepared and various characteristics were measured.

FIG. 1 shows the relationship between IL and PtO ₂ content. For all samples (except 0), Hs is about 750 Oe, θ _F is about 1200 deg / cm, θ
_{F / T} was about 0.05-0.06 deg / ° C.

From FIG. 1, it can be seen that the inclusion of PtO ₂ allows the IL.
Decreases in the region where PtO ₂ exceeds 3.0 wt%,
IL has increased significantly. Therefore, the content of PtO ₂ is preferably in the range of 0 to 3.0 wt% (excluding 0). Desirably, the range of 0.4 to 2.3 wt% is useful, and the IL can be set to 0.1 dB or less.

Example 3 In the same manner as in Example 1, the main component ratio was Tb _2.1 Bi _0.9 Fe _4.9 Al _0.1 O ₁₂ and PtO ₂
Garnet thick film containing about 0.7 wt%
m. Next, this sample was placed in an atmosphere of about 50% oxygen concentration at 950 ° C., 1000 ° C., 1050 ° C., and 110 ° C.
It was kept at 0 ° C., 1130 ° C., and 1150 ° C. for 10 hours and heat-treated. Next, both surfaces of these samples were polished, and Faraday rotation at a wavelength of 1.55 μm was about 4 μm.
After adjusting the thickness to 5 deg, various characteristics were measured.

FIG. 2 shows the relationship between IL and the heat treatment temperature. For all samples, Hs is about 750 Oe, θ
_F is about 900 deg / cm, θ _{F / T} is about 0.04 deg
g / ° C.

FIG. 2 shows that the heat treatment temperature was 950 to 1130.
Within the range of ° C., the effect of reducing IL by heat treatment is recognized. Therefore, it can be said that heat treatment in a temperature range of 950 to 1130 ° C. is useful.

Example 4 In the same manner as in Example 3, the main component ratio was Tb _1.6 Bi _1.4 Fe _4.5 Al _0.5 O ₁₂ and PtO ₂
Garnet thick film containing about 1.3 wt% of
m. Next, this sample was heated at a temperature of 1050 ° C.
The oxygen concentration of the atmosphere is 0, 10, 20, 40, 60, 8
After keeping the temperature at 0% and 100% and holding for 20 hours, a sample was prepared and various characteristics were measured.

FIG. 3 shows the relationship between IL and the oxygen concentration in the heat treatment atmosphere. For all samples, Hs was about 70
0 Oe and θ _F were about 1300 deg / cm, and θ _{F / T} was about 0.06 deg / ° C.

FIG. 3 shows that the oxygen concentration in the heat treatment atmosphere was 10%.
In the range of 100%, the effect of reducing the IL by the heat treatment is recognized. Therefore, the oxygen concentration in the heat treatment atmosphere is 10 to
100% is useful.

[0042]

According to the present invention, it is possible to provide a high-performance Bi-substituted garnet thick film material having excellent properties such as Hs and a method for producing the same. Therefore, a high-performance Faraday rotator can be obtained by using the Bi-substituted garnet thick film material of the present invention.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between PtO ₂ content and IL in a TbBi-based garnet thick film in Example 2.

FIG. 2 is a diagram showing a relationship between a heat treatment temperature and IL of a TbBi-based garnet thick film in Example 3.

FIG. 3 is a graph showing a relationship between an oxygen concentration and an IL in a heat treatment atmosphere of a TbBi-based garnet thick film in Example 4.

Claims (4)

[Claims] 1. A terbium (Tb), bismuth (Bi), iron (F) grown on a garnet substrate by a liquid phase growth method.
e), in a bismuth-substituted garnet thick film material composed of a garnet single crystal thick film mainly containing aluminum (Al), platinum oxide (PtO ₂ ) is contained in the single crystal thick film in an amount of 0 to 3.0 wt% (0%). (Bismuth-substituted garnet thick film material). 2. The method for producing a bismuth-substituted garnet thick film material according to claim 1, wherein the single crystal thick film is grown on a neodymium gallium garnet (NGG) substrate. 3. The method according to claim 1, wherein the single-crystal thick film is heated to 950 to 1130 °
3. The method for producing a bismuth-substituted garnet thick film material according to claim 1, wherein the heat treatment is performed in the temperature range of: 4. The method for producing a bismuth-substituted garnet material according to claim 1, wherein the single crystal thick film is subjected to a heat treatment in an oxygen concentration range of 10 to 100% atmosphere. .