JP2014214078A - Crystal growth method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a crystal growth method for manufacturing a crystal having uniform crystal properties with high yield, by using a vertical bridgman method or vertical temperature gradient solidification method.SOLUTION: A crystal growth method comprises: causing a crystal 23 to grow from a lower part toward an upper part of a crucible 21 by forming an axial temperature distribution 25 in a vertical direction, the axial temperature distribution 25 having a temperature that is high at the upper part and a low at the lower part, and cooling a molten raw material 22; and performing an over-heating process or soaking process of keeping the molten raw material 22 at a higher temperature than a crystallization temperature before starting the crystal growth. In the method, after finishing the step of the over-heating process or soaking process, the molten raw material 22 is cooled, and when a seed crystal set position 29 arranged at a bottom of the crucible 21 becomes a liquid-solid equilibrium temperature, a seed crystal grain 24 is introduced from the upper part of the crucible 21 and is delivered to the seed crystal set position 29. The molten raw material 22 is further cooled in order to grow the crystal 23 while having the seed crystal grain 24 as a core.

Description

  The present invention relates to a crystal growth method, and more specifically, in a crystal growth by a vertical Bridgman method or a vertical temperature gradient solidification method, an intermediate compound generated during heating of a raw material that is a source of a molten raw material before crystal growth is obtained. Crystal growth to produce a single crystal by controlling the orientation of the growth crystal by seed crystal grains, even though it is completely decomposed and given an overheating or soaking process to degas unnecessary components contained in the raw material Regarding the method.

  Conventionally, as a method for producing an oxide crystal material, a horizontal Bridgman method or a horizontal temperature gradient solidification method in which a molten raw material in a growth vessel is gradually solidified from a seed crystal placed on a crucible wall in a horizontal direction, and a growth vessel is vertically set. Installed to give a temperature gradient, vertical Bridgman method (for example, refer to Patent Document 1) in which the growth vessel is moved to a low temperature side to solidify the crystal, and the growth vessel is fixed vertically to keep the temperature gradient constant. However, a vertical temperature gradient solidification method is known in which the temperature of the entire furnace is cooled to solidify the crystal.

  With reference to FIG. 1, a conventional crystal manufacturing method by the vertical Bridgman method will be described. The crucible 1 is filled with the seed crystal rod 4 and the raw material and installed in the crystal production furnace. As raw materials, single elements, oxides, and carbides, which are raw materials, are weighed so as to have a desired composition ratio, and the crucible 1 is filled. As a solvent, an element, oxide, or carbide that is a constituent component of the crystal may be added excessively, or an element, oxide, or carbide that is different from the constituent component of the crystal may be additionally added. The raw material is heated and melted by the heater 6 to obtain a molten raw material 2. The crystal production furnace has an axial temperature distribution 5 in which the lower part of the crucible 1 is a low temperature region lower than the crystallization temperature and the upper part of the crucible 1 is a high temperature region higher than the crystallization temperature. The molten raw material 2 is gradually cooled from below by moving the crucible 1 to the low temperature region, that is, to the lower part while keeping the output of the heater 6 constant. The grown crystal 3 that has reached the crystallization temperature by the movement of the crucible 1 grows using the seed crystal rod 4 as a nucleus.

  At this time, since the growth crystal 3 grows sequentially with the seed crystal rod 4 as a nucleus, it inherits the crystal orientation of the seed crystal rod 4 and grows as a growth crystal 3 having the same crystal orientation as the crystal orientation of the seed crystal rod 4. be able to. In the case where there is no seed crystal rod 4, crystals grow sequentially with a growth nucleus naturally generated from the bottom of the crucible 1 as a nucleus.

  Instead of moving the crucible downward while keeping the output of the heater 6 constant, the output of the heater 6 is adjusted and cooled while adjusting so that the shape of the axial temperature distribution 5 of the heater 6 is not changed. The vertical temperature gradient solidification method is used. Specifically, in FIG. 1, the cooling is performed to the axial temperature distribution 7 without changing the shape of the axial temperature distribution 5. Since the region that reaches the crystallization temperature moves upward from the bottom of the crucible, the growth crystal 3 grows sequentially from below using the seed crystal rod 4 as a nucleus, as in the vertical Bridgman method. 4, and can be grown as a growth crystal 3 having the same crystal orientation as the crystal orientation of the seed crystal rod 4.

US Pat. No. 5,342,475

A. Reisman et al., “Phase Diagram of the System KNbO3-KTaO3 by the Methods of Differential Thermal and Resistance Analysis”, J. American Ceramic Society, Vol. 77, (1955) J. R. Carruthers et al., “Nonstoichiometry and Crystal Growth of Lithium Niobate”, J. Appl. Phys., Vol.42, No.5, pp1846-1851 (1971)

  On the other hand, crystal production by the CZ method or the TSSG method, which has an axial temperature distribution that is lower in the upper direction and lower in the upper direction and has an axial temperature distribution opposite to the vertical Bridgman method or the vertical temperature gradient solidification method, is widely used. In the case of the CZ method or the TSSG method, a seed crystal rod attached to the tip of the pulling shaft is immersed in the molten raw material from above to grow a growth crystal. Before starting crystal growth with the seed crystal rod as the nucleus, hold the material at a temperature higher than the crystallization temperature for a certain period of time to completely decompose the intermediate compound generated during heating the raw material that is the source of the molten material. In some cases, an overheating process or a soaking process is performed to degas unnecessary components contained in the raw material. This is because by performing these steps, there is an effect of suppressing precipitation of a compound other than the crystal to be produced or reducing impurities contained in the grown crystal.

  Similarly, in the vertical Bridgman method and the vertical temperature gradient solidification method, the same effect can be expected if an overheating treatment or a soaking treatment is performed before starting crystal growth using the seed crystal rod as a nucleus. However, in the vertical Bridgman method and the vertical temperature gradient solidification method, since the seed crystal rod is filled in the crucible before heating, it is difficult to heat to a temperature higher than the crystallization temperature. This is because the pre-filled seed crystal rod melts when heated to a temperature higher than the crystallization temperature.

  Therefore, in the case of crystal production by the vertical Bridgman method or the vertical temperature gradient solidification method, when the overheating or soaking process is used in combination, the seed crystal rod is not filled in advance, but the temperature is the lowest in the crucible first. The only method that can be used for crystal growth is the growth nuclei that occur naturally at the bottom of the crucible starting from the core. Since there is no seed crystal rod, the growth orientation of the growth crystal varies, and there is a problem in the yield of orientation control.

  The present invention has been made in order to overcome such problems. The object of the present invention is to provide seed crystals while using a superheating process or a soaking process in combination with a vertical Bridgman method or a vertical temperature gradient solidification method. It is an object of the present invention to provide a crystal production method for producing a crystal having uniform crystal characteristics with high yield.

  In order to achieve such an object, an embodiment of the present invention forms an axial temperature distribution in the vertical direction of upper, lower, and lower relative to a molten raw material in a crucible installed in a furnace, A crystal growth method for growing a crystal from below the crucible by cooling the molten material, and before starting the crystal growth, the molten material is constant at a temperature higher than the crystallization temperature. In a crystal growth method that performs a process of overheating treatment or soaking treatment that is held for a period of time, after finishing the overheating treatment or soaking treatment step, the molten raw material is cooled, and a seed crystal installation position installed at the bottom of a crucible When the temperature reaches the temperature at which crystal growth starts, the seed crystal grains are introduced from above the crucible so that the seed crystal grains are transported to the seed crystal grain installation position and the molten raw material is reduced. The seed crystal grains by cooling, characterized in that growing crystals as nuclei.

  According to the present invention, in the vertical Bridgman method or the vertical temperature gradient solidification method, the seed crystal grains can be introduced and the growth orientation of the grown crystal can be controlled after performing the overheating treatment or the soaking treatment, so that the crystal quality can be controlled. It is possible to produce a crystal with excellent yield and uniform growth orientation with high yield.

It is a figure explaining the crystal growth by the conventional vertical Bridgman method or the vertical temperature gradient solidification method. It is a figure explaining the crystal growth by the vertical temperature gradient solidification method concerning Example 1. FIG. It is a figure explaining the crystal growth by the vertical Bridgman method concerning Example 2. FIG. It is a figure explaining the seed crystal grain concerning Example 1 and 2, (a) is tetragonal <001> direction growth, (b) and (c) is tetragonal <110> direction growth, (d) Is a diagram showing tetragonal <111> direction growth.

[Example 1]
A method for producing a <001> direction grown KTa _x Nb _1-x O ₃ (0 ≦ x ≦ 1) single crystal by a temperature gradient solidification method will be described with reference to FIGS.

  The crystal manufacturing apparatus has an electric furnace whose furnace temperature and axial temperature distribution can be controlled by a heater 26, and a platinum crucible 21 is installed on a crucible installation base 28 in the electric furnace. The crucible 21 has a taper at the bottom and a horizontal flat portion at the bottom. The taper angle was 45 °, and the horizontal flat part was a disk shape of 5 mmφ. This horizontal flat portion is the seed crystal installation position 29, and the temperature can be measured by installing the thermocouple in thermal contact from below.

The crucible 21 is filled with a powder raw material. KTa _x Nb _1-x O ₃ (0 ≦ x ≦ 1) The solute raw material is weighed so that the raw material powders K ₂ CO ₃ , Ta ₂ O ₅ and Nb ₂ O ₅ have a desired composition ratio. . K is selected as the solvent, and excess K ₂ CO ₃ is also weighed. The weighed powder raw material is filled in the crucible 21 after mixing. The powder raw material is melted by heating the heater 26 to become a molten raw material 22. Before the start of crystal growth, the temperature was kept at a high furnace temperature 100 ° C. higher than the crystallization temperature for 24 hours to perform a soaking process.

After the soaking process, the output of the heater 26 is adjusted to realize a predetermined axial temperature distribution of upper, lower, lower and upper used for crystal growth. The temperature of the entire crucible is gradually cooled by further adjusting the output of the heater 26 while maintaining the shape of the axial temperature distribution. The temperature is measured by a thermocouple installed under the seed crystal installation position 29, and cooled to an equilibrium liquidus temperature at which the crystal does not melt and crystal growth does not occur. When this equilibrium liquidus temperature is reached, seed crystal grains 24 made of a KTa _x Nb _1-x O ₃ single crystal prepared in advance are dropped from above the crucible. FIG. 4A shows the shape of seed crystal grains. For the seed crystal grain 24, a cube having a side of 2 mm constituted by eight {001} planes was used. Here, the {001} plane is a crystal plane in a cubic structure at a high crystallization temperature. The charging was performed from the top of the electric furnace on the extension line of the crucible central axis. By dropping the seed crystal grains 24, undulations occurred on the surface of the molten raw material 22, and it was confirmed that the seed crystal grains 24 were conveyed into the molten raw material 22. Further, a temperature drop of 2 to 5 ° C. was observed on the thermocouple installed under the seed crystal installation position 29. Crystal growth starts from the crystallization temperature at which the supersaturated state is realized by cooling to a temperature lower than the equilibrium liquidus temperature. Therefore, the crystal growth does not start at a temperature drop of 2 to 5 ° C. After introducing the seed crystal grains 24, the temperature of the whole crucible is gradually cooled by adjusting the output of the heater 26 while maintaining the shape of the axial temperature distribution. By this cooling, a supersaturated state of the molten raw material 22 is realized, and the crystal 23 grows up to the crucible up to the crystallization temperature.

  The seed crystal grains 24 are rapidly heated in a few seconds from room temperature to a temperature of 1000 ° C. or more. However, when seed crystal grains prepared from a high-quality single crystal material with few defects are used, the seed crystal grains 24 function as seed crystals without being broken. did. Since the seed crystal grains are small, it is considered that the temperature difference hardly occurs between the inside and outside of the grains even when rapidly heated, and it is considered that the seed crystal grains were resistant to heat shock. Seed crystal grains having a non-uniform composition or containing crystal defects sometimes cracked in half at a frequency of once every 20 times. In the case where a taper having an angle of 45 ° is provided at the bottom of the crucible 21, the introduced seed crystal grains 24 having a side of 2 mm can be transported to a horizontal flat part of 5 mmφ at a frequency of 9 times in 10 times. The {001} plane was positioned in contact with the horizontal flat surface at the seed crystal installation position 29. It was confirmed that the growth crystal 23 was grown by inheriting the seed crystal grains 24 and the growth orientation was controlled.

  As a comparative example, heating was performed to an equilibrium liquidus temperature at which crystals were not melted and crystal growth did not occur without performing a soaking process, and seed crystals 24 were dropped from above the crucible to grow crystals. . There was a crystal in which vacancies that can be visually confirmed were found in the grown crystal. There were also crystals that crystallized during the growth process. Vacancy and polycrystallization are not observed in crystals produced after soaking before the start of growth. It was confirmed that the soaking process can sufficiently melt the intermediate compound produced during the heating of the powder raw material and can sufficiently degas unnecessary components contained in the residual raw material, thereby improving the crystal quality.

  Crucibles with variously different taper angles at the bottom of the crucible 21 were prepared, and the frequency with which the seed crystal grains 24 can be transported to the seed crystal installation position 29 was examined. When a crucible having a taper angle of 45 ° or less was used, the frequency at which it could be transported to the horizontal flat surface at the seed crystal installation position 29 was 90%. As a result of examining the transportation frequency with respect to the horizontal flat part size of the seed crystal installation position 29, when the horizontal flat part diameter of the seed crystal installation position 39 has a margin of 1 mm or more with respect to the maximum diameter of the seed crystal grain 24, it is almost At a frequency of 100%, the surface of the seed crystal grain 24 was positioned in contact with the horizontal flat surface.

  In addition, in order to set the crystal growth direction to the <110> direction, seed crystal grains composed of four {110} planes were prepared and crystals were manufactured. FIG. 4B shows the shape of seed crystal grains. Since a cube composed only of the plane cannot be produced on the {110} plane, the portion facing the other direction was formed into a curved surface so that it was difficult to stand on the horizontal flat portion at the seed crystal installation position 29. With this shape, the frequency with which the {110} plane of the seed crystal grain 24 is in contact with the horizontal flat portion at the seed crystal installation position 29 can be improved from 70% to 80%. FIG. 4C shows the shape of seed crystal grains. Changing the shape of the seed crystal grain 24 from a cube to a rectangular parallelepiped having a small plane area in the other direction also changes the frequency with which the {110} plane of the seed crystal grain 24 is in contact with the horizontal flat portion at the seed crystal installation position 29. There was an effect to improve. FIG. 4D shows the shape of seed crystal grains. In order to set the crystal growth direction to the <111> direction, regular octahedral seed crystal grains composed of eight {111} planes were prepared and crystals were manufactured. With this shape, the {111} plane of the seed crystal grain 24 was allowed to stand in contact with the horizontal flat portion at the seed crystal placement position 29, and a crystal grown in the <111> direction could be produced.

It is also possible to perform element substitution or dopant addition to the powder raw material. For example, instead of potassium carbonate as a solute raw material, a mixture of potassium carbonate and lithium carbonate or sodium carbonate is used, and a substituted single crystal of K _y M _1-y Ta _x Nb _1-x O ₃ (M = Li, Na) Can be manufactured. Alternatively, IIa group Mg, Ca, Sr, Ba may be added to the solute raw material to produce a KTa _x Nb _1-x O ₃ IIa group single crystal.

[Example 2]
A method for producing a <001> direction grown LiTaO ₃ single crystal by the vertical Bridgman method will be described with reference to FIGS.

  The crystal manufacturing apparatus has an electric furnace whose furnace temperature and axial temperature distribution can be controlled by a heater 36, and a platinum crucible 31 is installed on a crucible installation base 38 in the electric furnace. The crucible 31 has a taper at the bottom and a horizontal flat portion at the bottom. The taper angle was 30 °, a 6 mmφ pipe was provided, and the bottom of the pipe was made horizontal and flat. This horizontal flat portion is the seed crystal installation position 39, and the temperature can be measured by installing the thermocouple in thermal contact from below.

The crucible 31 is filled with a powder raw material. The LiTaO ₃ raw material is weighed so that the raw material powder Li ₂ CO ₃ and Ta ₂ O ₅ have a composition ratio of 1: 1. The weighed powder raw material is filled in the crucible 21 after mixing. The powder raw material is melted by heating the heater 36 to become a molten raw material 32. Prior to the start of crystal growth, the furnace was held at a high furnace temperature 150 ° C. higher than the crystallization temperature for 10 hours to carry out an overheating process.

After the overheating treatment, the output of the heater 36 is adjusted to realize a predetermined upper, lower, lower and higher axial temperature distribution used for crystal growth. By keeping the output of the heater 36 constant, maintaining the furnace temperature and the axial temperature distribution, and lowering the crucible installation base 38 downward, the temperature at the bottom of the crucible is gradually cooled. The temperature is measured by a thermocouple installed under the seed crystal installation position 39, and cooled to a solid-liquid equilibrium temperature at which the crystal does not melt and crystal growth does not occur. When this solid-liquid equilibrium temperature is reached, seed crystal grains 34 made of a LiTaO ₃ single crystal prepared in advance are dropped from above the crucible. FIG. 4A shows the shape of seed crystal grains. As the seed crystal grain 34, a cube having a side of 3 mm constituted by eight {001} planes was used. Here, the {001} plane is a crystal plane in a cubic structure at a high crystallization temperature. The charging was performed from the top of the electric furnace with the axis center of the crucible extended. By dropping the seed crystal grains 34, undulations were generated on the surface of the molten raw material 32, and it was confirmed that the seed crystal grains 34 were conveyed into the molten raw material 32. Furthermore, a temperature drop of 2 to 5 ° C. was observed on the thermocouple installed under the seed crystal installation position 39. Since the crystal growth starts from the crystallization temperature at which the supercooled state is realized by cooling to a temperature lower than the solid-liquid equilibrium temperature, the crystal growth does not start at a temperature drop of 2 to 5 ° C. After the seed crystal grains 34 are charged, the temperature at the lower part of the crucible is gradually cooled by lowering the crucible installation base 38 downward. By this cooling, a supercooled state of the molten raw material 32 is realized, and the crystal 33 grows up to the crucible up to the crystallization temperature.

  The seed crystal grains 34 are rapidly heated in a few seconds from room temperature to a temperature of 1000 ° C. or higher. However, when seed crystal grains prepared from a high-quality single crystal material with few defects are used, they do not break and function as seed crystals. did. Since the seed crystal grains are small, it is considered that the temperature difference hardly occurs between the inside and outside of the grains even when rapidly heated, and it is considered that the seed crystal grains were resistant to heat shock. Seed crystal grains having a non-uniform composition or containing crystal defects sometimes cracked in half at a frequency of once every 20 times. When a taper with an angle of 30 ° is provided at the bottom of the crucible 31, the introduced seed crystal grains 34 having a side of 3 mm can be conveyed to a horizontal flat part of 6 mmφ at a frequency of 10 times 10 times. The {001} plane was positioned in contact with the horizontal flat surface at the seed crystal installation position 29. It was confirmed that the growth crystal 23 was grown by inheriting the seed crystal grains 34 and the growth orientation was controlled.

  As a comparative example, without performing the overheating treatment step, the crystal was heated to a solid-liquid equilibrium temperature where the crystal did not melt and crystal growth did not occur, and the seed crystal grains 34 were dropped from above the crucible to grow the crystal. . There was a crystal in which vacancies that can be visually confirmed were found in the grown crystal. There were also crystals that crystallized during the growth process. Vacancy and polycrystallization are not observed in crystals produced after overheating before the start of growth. By overheating treatment, it was possible to sufficiently melt the intermediate compound generated during the heating of the powder raw material and degas unnecessary components contained in the residual raw material, thereby confirming the effect of improving the crystal quality.

  A crucible having variously different taper angles at the bottom of the crucible 31 was prepared, and the frequency with which the seed crystal grains 34 can be transported to the seed crystal installation position 39 was examined. When a crucible having a taper angle of 45 ° or less was used, the frequency at which the crucible was transported to the horizontal flat surface at the seed crystal installation position 39 was 90%. As a result of examining the transportation frequency with respect to the horizontal flat part size of the seed crystal installation position 39, when the horizontal flat part diameter of the seed crystal installation position 39 has a margin of 1 mm or more with respect to the maximum diameter of the seed crystal grain 34, it is almost At a frequency of 100%, the surface of the seed crystal grain 34 was positioned in contact with the horizontal flat surface.

  Moreover, in order to set the crystal growth direction to the <110> direction, seed crystal grains composed of four {110} planes were prepared and crystals were manufactured. FIG. 4B shows the shape of seed crystal grains. Since a cube composed only of the plane cannot be produced on the {110} plane, the portion facing the other direction was formed into a curved surface so that it was difficult to stand on the horizontal flat portion at the seed crystal installation position 39. With this shape, the frequency with which the {110} plane of the seed crystal grain 24 is in contact with the horizontal flat portion at the seed crystal installation position 39 can be improved from 70% to 80%. FIG. 4C shows the shape of seed crystal grains. Changing the shape of the seed crystal grain 34 from a cube to a rectangular parallelepiped with a small plane area in the other direction also changes the frequency with which the {110} plane of the seed crystal grain 34 is in contact with the horizontal flat portion at the seed crystal installation position 29. There was an effect to improve. FIG. 4D shows the shape of seed crystal grains. In order to set the crystal growth direction to the <111> direction, regular octahedral seed crystal grains composed of eight {111} planes were prepared and crystals were manufactured. With this shape, the {111} plane of the seed crystal grain 34 was allowed to stand in contact with the horizontal flat portion at the seed crystal installation position 39, and a crystal grown in the <111> direction could be manufactured.

Having thus described for the preparation of LiTaO ₃ crystal, by using Nb instead of Ta, it can of course be applied to the LiNbO ₃ crystal.

  Further, in Examples 1 and 2, a crystal whose crystal structure at the crystallization temperature is a cubic crystal has been described. However, with respect to other crystal structures, a plane perpendicular to the desired growth direction of the seed crystal grains, It goes without saying that it can be applied by increasing the probability that the seed crystal is placed on the horizontal flat part at the position where the seed crystal is placed by configuring it to the maximum possible number or by making it a plane having a larger area than other surfaces.

1, 21, 31 Crucible 2, 22, 32 Molten raw material 3, 23, 33 Crystal 4 Seed crystal rod 5, 25 Axial temperature distribution 6, 26, 36 Heater 7, 27 After cooling in the vertical temperature gradient solidification method Axial temperature distributions 24, 34 Seed crystal grains 28, 38 Crucible installation table 29, 39 Seed crystal installation position and temperature sensor

Claims (10)

By forming a vertical temperature distribution in the vertical direction with respect to the molten raw material in the crucible installed in the furnace, and cooling the molten raw material, crystals are formed upward from below the crucible. A crystal growth method for growing
And, in the crystal growth method for performing the step of overheating treatment or soaking treatment in which the molten raw material is maintained at a temperature higher than the crystallization temperature at a temperature higher than a crystallization temperature for a predetermined time before starting crystal growth,
After finishing the overheating treatment or soaking treatment, the molten raw material is cooled, and when the seed crystal installation position installed at the bottom of the crucible reaches a solid-liquid equilibrium temperature, the seed crystals from above the crucible. A crystal growth method, wherein the seed crystal is transported to the seed crystal installation position by introducing grains, and the molten raw material is further cooled to grow crystals using the seed crystal grains as nuclei.   The crucible has a cone shape and a horizontal flat surface at the bottom of the cone shape, and the seed crystal grains fall through the inside of the cone-shaped portion by gravity, The crystal growth method according to claim 1, wherein the crystal growth method can be dropped and left on the horizontal flat surface.   The crucible includes a portion having a cone shape, a portion in which a pipe is further extended from a lowermost portion of the cone shape, and a horizontal flat surface at the bottom of the pipe, and the seed crystal grains are 2. The crystal growth method according to claim 1, wherein the crystal growth method can drop through the inside of the cone-shaped portion and the inside of the pipe by gravity, and drop and stand on the horizontal flat surface.   The crystal growth method according to claim 1, wherein the seed crystal grains have a maximum diameter that is 1 mm or more smaller than a diameter of the seed crystal installation position.   The crystal growth method according to claim 1, wherein the seed crystal grains have a plane that is perpendicular to a desired growth direction. The seed crystal grains have a cubic crystal structure at a crystallization temperature and the desired growth direction is a <001> direction,
The crystal growth method according to claim 4, comprising eight {001} planes. The seed crystal grain has a cubic crystal structure at a crystallization temperature, and the desired growth direction is a <110> direction,
The crystal growth method according to claim 4, wherein a surface formed of four {110} planes and directed in a direction other than the <110> direction is a curved surface. The seed crystal grain has a cubic crystal structure at a crystallization temperature, and the desired growth direction is a <110> direction,
The shape of the seed crystal grain is a rectangular parallelepiped, is configured by four {110} planes, and an area of a plane facing an orientation other than the <110> direction is smaller than the {110} plane. Crystal growth method. The seed crystal grains, when the crystal structure at the crystallization temperature is cubic and the desired growth direction is <111> direction,
The crystal growth method according to claim 4, comprising eight {111} planes. If the seed crystal is not cubic crystal structure at the crystallization temperature,
5. The crystal growth method according to claim 4, wherein the crystal growth method comprises a plane perpendicular to the desired growth direction.

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