JP4090345B2 - Liquid phase crystal growth method - Google Patents

Description

表からわかる通り、本発明に従って結晶成長中の溶液中の白金濃度を１ｍａｓｓ％以下とすれば、得られる結晶中の白金濃度を０．５ｍａｓｓ％以下とすることができ、１００μｍ以上のピット数も少なく、割れのないＦＲ膜を得ることが可能である。
【００２０】
（比較例１〜７）
溶液の一部に窒素を吹き当てることなく実施例１と同様にしてＦＲ膜１１（比較例１）、１２（比較例２）、１３（比較例３）、１４（比較例４）、１５（比較例５）、１６（比較例６）、１７（比較例７）を作製した。
【００２１】
いずれのＦＲ膜１１〜１７にも同心円状の亀裂が見られた。また、各FR膜に全面に存在する１００μｍ以上のピット状欠陥数を求めた。また、結晶成長中の溶液中の白金濃度とＦＲ膜の白金濃度とを求めた。これらの結果を表２に示した。
【００２２】
【表２】

【００２３】
表２よりわかる通り、本発明に従って結晶成長中の溶液中の白金濃度を１ｍａｓｓ％以下としなければ、良好なＦＲ膜が得られない。
【００２４】
【発明の効果】
本発明は白金容器を用いて液相結晶成長する際に、溶液の一部の温度を冷却することにより溶液中の白金濃度を低減させ、もって目的結晶中への白金混入量を低減化させ、目的結晶の結晶品質を向上させる。本発明を、磁性ガーネット結晶に適用した実施例の結果からわかるように、本発明による溶液から成長した磁性ガーネット結晶の品質が向上することは明らかである。
【図面の簡単な説明】
【図１】液相エピタキシャル成長にて得られる磁性ガーネット厚膜結晶に見られる同心円状の亀裂の様子を表す模式図である。
【図２】本発明の検討で得られたＦＲ膜における、同心円状亀裂、ピット状欠陥とＦＲ膜中の白金濃度との関係を示す図である。
【図３】実施例の磁性ガーネット厚膜結晶成長に用いた成長炉の構成図である。
【符号の説明】
１：ＦＲ膜
２：割れ
３：Pt製坩堝
４：成長溶液
５：耐火物
６：電熱ヒーター
７：窒素ガス導入管[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a liquid phase crystal growth method, and more particularly, to a liquid phase crystal growth method in which a substrate material is immersed in a supersaturated solution to precipitate a solute on the substrate.
[0002]
[Prior art]
The liquid phase crystal growth method is one type of crystal growth methods that have been widely known. In general, a substance serving as a solvent is maintained in a liquid state at a constant temperature, and a solute component is dissolved in the solvent in a saturated state. Thereafter, the temperature is gradually increased in a state where a material serving as a substrate is immersed in the solution. This is a method of creating a supersaturated state by lowering and precipitating a solute component that cannot be dissolved as crystals on the substrate surface.
[0003]
This method has the disadvantage that when a disk-shaped single crystal is used as a substrate, the crystal deposited on the substrate surface has the same orientation as the substrate crystal, and the growth rate is extremely low compared to the pulling method. Crystals with very good crystal quality can be obtained. For this reason, it is a technique that is widely used in the manufacturing process of light emitting diodes and laser diodes.
[0004]
In the liquid phase growth method, since a solution in a liquid state is used, some kind of container is used. The container is often eroded by the solution, and the elements constituting the container often precipitate as impurities in the target crystal. In the growth of a magnetic garnet film used in an optical isolator, lead oxide and boron oxide as solvents are held in a liquid state in a platinum container, and various oxides as solutes are dissolved therein. Then, a magnetic carnet film is obtained on the substrate. At this time, it is known that the container is attacked and platinum is eluted into the solution and mixed into the magnetic garnet film. It is known that platinum mixed in affects the Faraday rotation angle and insertion loss, which are the basic performance of an optical isolator, depending on the concentration.
[0005]
Further, according to the examination results of the present inventors, platinum that is present as an impurity is one of the causes of generating concentric cracks, that is, when 1% or more of Pt is mixed in the YbTbBiFe-based garnet crystal. Since the composition differs from that of the intended magnetic garnet crystal, the lattice constant thereof changes, the lattice constant difference from the substrate material increases, and concentric cracks as shown in FIG. 1 are generated.
[0006]
In order to eliminate the disadvantages of the liquid phase growth method, the main species are being studied. For example, using a container made of a material having a very low solubility in a solvent. This method is common. However, no matter how low the solubility of the container material in the solution, the mixing amount does not become zero thermodynamically. For this reason, when it is inevitably desired to avoid contamination from the container, the crystal is grown by a method other than the liquid phase growth method, for example, vapor phase growth. However, not all crystal materials can be obtained by vapor phase growth.
[0007]
[Problems to be solved by the invention]
The present invention provides a method in which the material of the solution holding container is not mixed into the target crystal when the magnetic garnet crystal is obtained by the liquid phase crystal growth method, and specifically, a Pt container is used as the solution holding material. An object of the present invention is to provide a method for reducing the Pt concentration in a target crystal when a crystal such as a magnetic garnet film is grown by liquid phase crystal growth.
[0008]
[Means for solving problems]
The first aspect of the present invention for solving the above-mentioned problem is a method for obtaining a magnetic garnet film by a liquid phase crystal growth method using a platinum container as a solution holding material and using a solution containing no platinum exceeding an inevitable impurity concentration. In order to keep the platinum concentration in the solution during crystal growth below the saturation concentration at all times, a part of the vessel is forcibly cooled and Pt eluted from the vessel is continuously deposited on the cooling part, so that the solution during crystal growth The concentration inside is maintained at less than 1 mass%.
The invention according to the second aspect is characterized in that the solution is composed of lead oxide, boron oxide, terbium oxide, ytterbium oxide, iron oxide, bismuth oxide, and a magnetic material grown using this solution. The liquid crystal growth method according to claim 1, wherein the composition of the garnet is composed of YbTbBiFe.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
In the liquid crystal growth method, when the target crystal is an oxide crystal such as a magnetic garnet thick film crystal, a platinum crucible is often used. In liquid phase epitaxial growth using a platinum crucible, it is unavoidable that platinum is dissolved in a solvent component at the crystal growth temperature, so that platinum is mixed into the target crystal as an impurity. When platinum is mixed as an impurity in the magnetic garnet thick film crystal, if the ratio exceeds 0.5 mass%, concentric cracks are generated, resulting in a decrease in yield.
[0010]
FIG. 2 shows this relationship. Figure 2 shows a 3 inch diameter garnet wafer with a lattice constant of 1.2497 ± 0.0003 nm, while maintaining the platinum concentration in the solution at various values, soaking only one side of the substrate in the solution, and simultaneously rotating the substrate. While the solution temperature is lowered at a rate of 0.6 ° C. per hour, liquid phase crystal growth is performed for 20 hours to produce a TbTbBiFe-based magnetic garnet epitaxial film (hereinafter referred to as FR film), and platinum in the FR film. This shows the relationship between the concentration, the number of pit-like defects of 100 μm or more in the FR film, and the presence or absence of crack defects. FIG. 2 clearly shows that when the platinum ratio exceeds 0.5 mass%, concentric cracks are generated and the yield is reduced.
[0011]
In the invention according to the first claim, the platinum concentration in the solution at the time of crystal growth is maintained at a saturation concentration or less, preferably less than 1 mass%. This is because the amount of platinum mixed into the target crystal is reduced by using a solution having a reduced platinum concentration because it is proportional. What is important here is to keep the platinum concentration in the solution below 1 mass% while the target crystal grows.
[0012]
The method for reducing the Pt concentration in the solution is not particularly limited. Basically, as described in claim 1 , the platinum concentration in the solution can be maintained at less than 1 mass% by cooling a part of the solution and aggregating Pt dissolved in the cooling part. It is important that, as before reporting, is to maintain during such aggregation process purpose crystal grows. That is, the elution of platinum into the solution from the platinum container is continued during the growth period of the target crystal.
[0013]
The present invention is effective in a liquid phase crystal growth method in which platinum is not contained in a target crystal by using a platinum container, and in particular, lead oxide, boron oxide, terbium oxide, ytterbium oxide, iron oxide, bismuth oxide. It is effective when growing a magnetic garnet thick film crystal from a solution in which the smelt is melted.
[0014]
In the present invention, what can be used as a method for cooling a part of the solution includes blowing an inert gas, adopting a heat pump, etc. Even if the part of the solution is directly cooled, the container part containing the solution is used. Some may be cooled.
[0015]
【Example】
Examples and comparative examples in which the present invention is applied to a magnetic garnet thick film crystal are shown below.
(Examples 1-7)
A platinum container was charged with 2300 g of lead oxide, 140 g of boron oxide, 3100 g of bismuth oxide, 460 g of iron oxide, 56.6 g of terbium oxide, and 4.4 g of ytterbium oxide. This was installed in a vertical tubular furnace, the whole was heated to 950 ° C., sufficiently stirred and mixed uniformly to obtain a magnetic garnet epitaxial film growth solution.
[0016]
The temperature of this solution is lowered to the crystal growth temperature, and at the same time, as shown in FIG. 3, nitrogen gas is blown onto a part of the solution surface to forcibly cool the part, and a part of the dissolved platinum is removed. Solution 1 (Example 1), 2 (Example 2), 3 (Example 3), 4 (Example 4), 5 (Example 5) in which the platinum concentration in the solution is 1 mass% or less. ), 6 (Example 6), and 7 (Example 7).
[0017]
Next, a 3 inch diameter garnet wafer having a lattice constant of 1.2497 ± 0.0003 nm was used as the substrate, and only one side of the substrate was immersed in the solution, and the substrate was simultaneously rotated.
In this state, while the solution temperature was lowered at a rate of 0.6 ° C. per hour, epitaxial growth was performed for 20 hours, and FR films 1 (Example 1), 2 (Example 2), and 3 (Example 3). ), 4 (Example 4), 5 (Example 5), 6 (Example 6), and 7 (Example 7).
[0018]
None of the FR films 1 to 7 had concentric cracks. Further, the number of pit-like defects of 100 μm or more existing on the entire surface of each FR film was determined. Further, the platinum concentration in the solution during crystal growth and the platinum concentration in the FR film were determined. These results are shown in Table 1.
[0019]
[Table 1]

As can be seen from the table, if the platinum concentration in the solution during crystal growth is 1 mass% or less according to the present invention, the platinum concentration in the resulting crystal can be 0.5 mass% or less, and the number of pits of 100 μm or more is also possible. It is possible to obtain an FR film with few and no cracks.
[0020]
(Comparative Examples 1-7)
FR film 11 (Comparative Example 1), 12 (Comparative Example 2), 13 (Comparative Example 3), 14 (Comparative Example 4), 15 (similar to Example 1 without blowing nitrogen to part of the solution) Comparative Examples 5), 16 (Comparative Example 6), and 17 (Comparative Example 7) were produced.
[0021]
Concentric cracks were observed in any of the FR films 11-17. Further, the number of pit-like defects of 100 μm or more existing on the entire surface of each FR film was determined. Further, the platinum concentration in the solution during crystal growth and the platinum concentration in the FR film were determined. These results are shown in Table 2.
[0022]
[Table 2]

[0023]
As can be seen from Table 2, a good FR film cannot be obtained unless the platinum concentration in the solution during crystal growth is 1 mass% or less according to the present invention.
[0024]
【The invention's effect】
The present invention reduces the platinum concentration in the solution by cooling the temperature of a part of the solution during liquid phase crystal growth using a platinum container, thereby reducing the amount of platinum mixed into the target crystal, Improve the crystal quality of the target crystal. As can be seen from the results of the examples in which the present invention was applied to magnetic garnet crystals, it is clear that the quality of magnetic garnet crystals grown from solutions according to the present invention is improved.
[Brief description of the drawings]
FIG. 1 is a schematic view showing a concentric crack seen in a magnetic garnet thick film crystal obtained by liquid phase epitaxial growth.
FIG. 2 is a diagram showing the relationship between concentric cracks, pit-like defects and platinum concentration in the FR film in the FR film obtained by the study of the present invention.
FIG. 3 is a structural diagram of a growth furnace used for magnetic garnet thick film crystal growth in an example.
[Explanation of symbols]
1: FR film 2: Crack 3: Pt crucible 4: Growth solution 5: Refractory 6: Electric heater 7: Nitrogen gas introduction tube

Claims (2)

In a method for obtaining a magnetic garnet film by a liquid phase crystal growth method using a platinum container as a solution holding material and using a solution that does not contain platinum exceeding the concentration of inevitable impurities, the concentration of platinum in the solution during crystal growth is always saturated. In order to suppress the following, the concentration in the solution at the time of crystal growth is maintained at less than 1 mass% by forcibly cooling a part of the container and continuously precipitating Pt eluted from the container in the cooling part. Liquid phase crystal growth method. The solution is composed of lead oxide, boron oxide, terbium oxide, ytterbium oxide, iron oxide, bismuth oxide, and the composition of magnetic garnet grown using this solution is composed of YbTbBiFe. The liquid phase crystal growth method according to 1.

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