JP3369394B2 - Crystal preparation method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a crystal producing method for producing a crystal used in an optical device or the like.

[0002]

2. Description of the Related Art The following are the major conventional single crystal production methods.

FIG. 7 shows an indirect heating laser melting pedestal (I
LHPG) method is schematically shown. In FIG. 7, a part of a glass tube 706 made of quartz glass or the like is heated by infrared light 701 such as a CO ₂ laser. The upper portion of the base material 702 is heated and melted by the radiant heat 707 from the high temperature portion of the straight pipe. The molten portion 705 is attached to the seed crystal 704, the seed crystal 704 is moved at a speed V ₂ , and the base material 702 is moved at a speed V ₁ to draw a single crystal 70.
3 is produced. Here, the crystal orientation of the single crystal 703 is the same as the orientation of the seed crystal 704. Next, a method for producing a base material will be described.
First, the powder crystal material 708 is filled in the container 709.
Next, the container 709 is heated by a heating furnace 710 to melt the powder crystal material 708 to form a melt 711. Heating furnace 710
The container 709 is taken out from the container and cooled from one end, and the melt is made into crystals 712. Remove the crystal 712 from the container 709,
Use as base material. At this time, the base material does not have to be a single crystal, but crystallization needs to proceed continuously in one direction of the melt in order to obtain a continuous base material.

FIG. 8 shows the Bridgeman-Stockburger method, in which a heating heater 802 is used.
A heating furnace 801 composed of a heat insulating material 804 and a heat insulating material 804 is maintained at a melting point of a desired material or higher. Then, after encapsulating this material in a growth vessel 806 made of quartz glass or the like having a thin tube portion, a taper portion, and a thick tube portion, this growth vessel 80
6 is put in the heating furnace 801. Material melts, melt 8
It will be 05. Then, one end of the container thin tube portion of the growth container 806 is gradually drawn from the heating furnace 801 to a region kept at a temperature lower than the melting point of this material. After the single-crystal nuclei are formed in the container thin tube part, the container large tube part is drawn out to the low temperature region. Then, a single crystal 80 having the same orientation as the nucleus of the single crystal
3 grows.

FIG. 9 shows a method for producing a single crystal by the Czochralski method (Cz method). In FIG. 9, a target material is heated and melted by a heating heater 902 in a heating furnace 901. The seed crystal 9 is formed on the surface of the melt 905.
04 is brought into contact with the heating furnace 90 kept at a temperature equal to or higher than the melting point.
A single crystal 903 is grown by pulling from 1 toward a region having a temperature equal to or lower than the melting point.

[0006]

In order to use a single crystal material for an optical signal processing element and an optical storage element, a single crystal having high crystal quality is required. Therefore, a single crystallization technique that does not depend on the physical properties peculiar to the material such as the melting point, heat resistance, and crystallinity of the material to be single crystallized must be provided.

However, in the above-mentioned single crystallization technique, for a material which easily exhibits supercooling property such as an organic material and is easily decomposed by heat, the production of a high quality crystal which is not affected by the decomposition is There were the following problems.

That is, in the ILHPG method, it is necessary to produce the base material 702 before producing a single crystal. At this time, the base material 702 needs to be continuous, but in the case of a material having a supercooling property, even if the temperature of the melt falls below the melting point, solidification does not start and it takes a long time to form a plurality of places in the melt. In the nucleus,
Since crystallization progresses independently at each place, crystallization that proceeds in one direction as described above cannot be achieved. as a result,
The base material after crystallization becomes discontinuous, and the ILHPG method cannot be used.

Further, in the Bridgeman-Stockberger method, in order to obtain a single crystal, it is necessary to pull out the thick tube portion of the container to a low temperature region after the single crystal is formed in the thin tube portion of the container. However, in the case of a material having a supercooling property, it takes time until a single crystal is formed in the container thin tube portion, and during that time, the melt 805 is exposed to a temperature higher than the melting point in the container thick tube portion and the decomposition of the material progresses. Quality single crystal cannot be obtained.

Also in the Czochralski method, since there is no means for reheating the supercooled melt 905, crystallization cannot be controlled and a high quality single crystal cannot be obtained.

In this way, in particular, even if the temperature of the melt having a temperature above the melting point is lowered to below the melting point, solidification does not begin, and a plurality of portions of the melt after being kept at the temperature below the melting point for a very long time. In the crystallization of an organic material having a supercooling property that solidifies from the above, it is difficult to obtain a high quality single crystal by the conventional single crystal growth method as described above.

The present invention has been made to solve the above-mentioned problems, and it is possible to obtain a single crystal which is capable of crystal growth while suppressing thermal decomposition, has no defects or dislocations, and is excellent in electrical characteristics and optical characteristics. It is an object of the present invention to provide a crystal production method for

[0013]

[Means for Solving the Problems] A first step of heating an organic material to a melting point or above to obtain a molten liquid, and cooling at least a part of the molten liquid to a first temperature below the melting point to supercool it. A second step of forming a melt and reheating at least a portion of the supercooled melt to a second temperature between the melting point and the first temperature to crystallize the supercooled melt. And a third step of

In the third step, one end of the supercooled molten liquid is reheated to grow a seed crystal, and then a reheating region for crystallization is moved toward the other end.

Further, it has a first region having a small inner diameter, a second region having a large inner diameter, and a region located between the first region and the second region where the inner diameter changes in a tapered shape. A container is loaded with the organic material, and the seed crystal is grown in the first region.

In the third step, after the single crystal is brought into contact with one end of the supercooled melt, the region where the single crystal is brought into contact is reheated to the second temperature and reheated. Move the area towards the other end.

In the third step, after the single crystal is brought into contact with one end of the supercooled melt, a part of the supercooled solution adhered to the single crystal is pulled up together with the single crystal, Crystallize by passing through a reheat zone heated to a second temperature.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic view showing one embodiment of the crystal production method according to the present invention.

As shown in the figure, the crystal material 101 in the container 109 is once heated by the heater 106 until it reaches a temperature higher than its melting point (first step). After the crystal material is completely melted and becomes the melt 102, the container 109 is set to the heater 1
Then, the melt 102 is rapidly cooled to a first temperature equal to or lower than the melting point to obtain a supercooled melt 103 (second step). After that, the supercooled melt 103 can be crystallized by reheating with the heater 106 until the second temperature is reached. By such a crystal production method, crystallization of a material having a high supercooling property can be controlled.

Alternatively, the seed crystal 104 is then reheated by the heater 107 until one end of the supercooled melt 103 reaches a second temperature between the melting point and the first temperature (third step). Is generated. After that, the heater 105 is moved from the seed crystal 104 toward the supercooled melt 103, whereby the crystal 105 can be manufactured. FIG. 2 shows temperature changes at points 110 and 111 of the crystalline material 101. By such a crystal production method,
The supercooled melt 103 near the crystal can be continuously crystallized, crystallization can be prevented from proceeding from a plurality of locations in the melt 102, and continuous crystals can be obtained.

FIG. 3 is a schematic view showing another embodiment of the crystal producing method according to the present invention. As shown in the figure, the first heater 306, the second heater 307, and the third heater 308 are formed by using a container 309 having a thin tube portion (first region), a tapered portion, and a thick tube portion (second region). The temperature distribution is set as shown in FIG. First, the crystal material 301 is placed in the container 309 and heated to a temperature equal to or higher than the melting point by the first heater 306. After the crystal material 301 is completely melted and becomes the melt 302, the container 309 is moved toward the second heater 307. The tip of the thin tube is second
When it reaches the heater 307, it is rapidly cooled, and the supercooled melt 303
Becomes Further, it is moved toward the third heater 308. The supercooled melt 303 is reheated by the third heater 308, and the seed crystal 304 is generated. By continuing the movement, the single crystal 305 can be manufactured.

By such a crystal manufacturing method, the supercooled melt 303 near the crystal can be continuously crystallized,
Crystals with higher single crystallinity can be obtained. In addition, since it takes a shorter time to generate the seed crystal 304 than when using the conventional Bridgeman-Stockburger method, it is possible to suppress the time in which the material is exposed to a temperature equal to or higher than the melting point, which is high quality with less thermal decomposition. Can be obtained.

FIG. 5 is a schematic view showing another embodiment of the crystal producing method according to the present invention. As shown in the figure, in an example using a seed crystal 504, a crystal material 501 in a container 509 is heated by a heater 506 to a temperature equal to or higher than a melting point. After the crystal material 501 is completely melted and becomes the melt 502, the container 509 is taken out from the heater 506,
It is cooled to obtain a supercooled melt 503. The seed crystal 504 is brought into contact with the supercooled melt at the end of the container. Ring-shaped heater 507
Is aligned with the position of contact between the seed crystal and the supercooled melt. While adjusting the output of the ring-shaped heater 507 and reheating the temperature of the supercooled melt to a predetermined temperature (second temperature) below the melting point (third step), the ring-shaped heater is moved to the container 509.
By moving the seed crystal 504 from the seed crystal 504 toward the supercooled melt 503, a single crystal 505 having the same growth direction as that of the seed crystal 504 is produced.

By such a crystal production method, the supercooled melt 503 near the crystal can be continuously crystallized,
A crystal having the same crystal orientation as the external seed crystal 504 and having a crystal orientation according to the application can be obtained.

FIG. 6 is a schematic view showing another embodiment of the crystal producing method according to the present invention. As shown in the figure, in the example using the seed crystal 604, the crystal material 601 in the container 609 is used.
Is heated to a temperature equal to or higher than the melting point by a heater 606.
After the crystal material 601 is completely melted and becomes a melt 602, the output of the heater 606 is reduced and the container 609 is rapidly cooled.
Let it be a supercooled melt 603. Next, the seed crystal 604 is passed through the center of the ring-shaped heater 607 and brought into contact with the supercooled melt 603. By adjusting the output of the ring-shaped heater 607 and reheating the temperature of the supercooled melt below the seed crystal 604 to a predetermined temperature (second temperature) below the melting point (third step), the seed crystal 604 was overheated. By moving it away from the cooling melt 603, a single crystal 605 having the same growth direction as the seed crystal 604 is produced.

By such a crystal producing method, the supercooled melt 603 near the crystal can be continuously crystallized,
A crystal having the same crystal orientation as the external seed crystal 604 and having a crystal orientation according to the application can be obtained.

The materials used in the example of the present embodiment are as follows. That is, as a material, 3-methyl-4-nitropyridine-1-oxide (PO
M), N- (4-nitrophenyl) -L-prolinol (NPP), N- (nitrophenyl) -N-methylaminoacetonitrile (NPAN), 4-N, N-dimethylamino-2-acetamide-4. -Nitroaniline (DA
N), 2-cycloacetylamino-5-nitropyridine (COANP), 3,9-dinitro-5a, 6,11
a, 12-Tetrahydro- [1,4] benzoxazino [3,2-b] [1,4] benzoxazine (DNB
B) 4'-nitrobenzylidene-3-acetamino-
4-methoxyaniline (MNBA), (-) 4- (4 '
-Dimethylaminophenyl) -3- (2'-hydroxypropylamino) cyclobutene-3,4-dione (DA
D), 2-methoxy-5-nitrophenol (MN
P), 3,5-dimethyl-1- (4-nitrophenyl)
Pyrazole (DMNP), 2-adamantylamino 5-
Nitropyridine (AANP), 3-nitroaniline (m
-NA), 2-methyl-4-nitroaniline (MN
A), 3-methyl- (2,4-dinitrophenyl) -aminopropanoate (MAP), 4-nitrophenylcarbamic acid isopropyl ester (PCNB) and the like.

While such a technique is expected to be applied to an optical device such as an optical non-linear effect, it is particularly suitable for producing a single crystal of an organic material which has been difficult to produce due to its high supercooling property. It is valid.

[0029]

EXAMPLE An example according to the present invention will now be described. Example 1
1 is the method shown in FIG. 1, Example 2 is the method shown in FIG. 3, Example 3 is the method shown in FIG. 5, and Example 4 is the method shown in FIG.

(Example 1) Teflon tube (inner diameter: 2 mm, wall thickness: 1 mm) as a container, NPP as a crystal material
(Melting point 116 ° C.) was used. Fill the container with NPP powder and heat to 120 ° C. with a heater to completely melt the material. The container was taken out of the heater and cooled to 35 ° C. to bring the NPP melt into a supercooled state. When one end of this container was heated to 70 ° C. by a heater, crystallization started. By moving the heating part, a crystal base material having a diameter of 2 mm and a length of 20 mm was obtained. With the conventional crystal base material manufacturing method, it was only possible to obtain a material having a length of 3 mm. An NPP single crystal having a diameter of 2 mm and a length of 18 mm could be produced by the ILHPG method using the crystal base material obtained by this production method.

(Embodiment 2) The thin tube portion has an inner diameter of 1 mm, a wall thickness of 0.5 mm, a length of 40 mm, and a taper portion having a length of 40 m.
m, inner diameter of thick tube is 10 mm, wall thickness is 1 mm, length is 30 mm
Was filled with COANP (melting point: 73 ° C.). The heating furnace has a first heater (120 mm long,
74 ° C), 2nd heater (length 5mm, 25 ° C), 3rd
A heater equipped with a heater (length 10 mm, 45 ° C.) was used. The container was placed in the first heater to completely melt the material. The container was moved toward the second heater, the tip of the thin tube portion was cooled by the second heater portion, and the melt was supercooled. Further, it was moved toward the third heater and reheated to be crystallized. The movement was continued until the rear end of the thick tube portion passed through the third heater. A single crystal with a diameter of 10 mm and a length of 30 mm was obtained.

(Embodiment 3) Outer diameter 2 mm, inner diameter 100 μ
MAP (melting point 81
(° C). The thin tube was heated to 83 ° C. by a heater and completely melted. Next, heating by the heater was stopped and the melt was cooled to 25 ° C. to be in a supercooled state. The seed crystal (diameter 0.5 mm, length 3 mm) is brought into contact with the supercooled melt at the end of the thin tube, and the position of the ring-shaped heater (outer diameter 10 mm, inner diameter 6 mm, height 2 mm) is adjusted with the seed crystal and the supercooled melt. It was adjusted to the position of the contact part of. By adjusting the output of the ring-shaped heater and moving the supercooled melt to 50 ° C. while moving the ring-shaped heater along the narrow tube, a single crystal with a length of 25 mm and a diameter of 100 μm was produced in the glass thin tube. Was obtained. The orientation of the obtained crystal coincided with that of the seed crystal.

Example 4 MNA (melting point 132 ° C.) was used as a crystal material. Glass crucible (15m inside diameter)
(m, depth 10 mm), the material powder was put therein and heated by a heater to be completely melted. Next, heating by the heater was stopped and the melt was cooled to 40 ° C. to be in a supercooled state. Ring-shaped heater (outer diameter 10 mm, inner diameter 6 mm, height 2 m
Seed crystal from the center of m) (diameter 0.5 mm, length 3 mm)
Was put into contact with the supercooled melt. The output of the ring-shaped heater was adjusted, and the supercooled melt near the seed crystal was reheated to 75 ° C. A single crystal having a diameter of 4 mm and a length of 10 mm could be produced by pulling the seed crystal upward while reheating. As a result of X-ray analysis, the growth direction of this single crystal coincided with the direction of the seed crystal.

Table 1 shows the results when the above-mentioned materials were manufactured according to the present invention.

[0035]

[Table 1]

[0036]

As described above, in the crystal manufacturing method according to the present invention, after the melt of the crystal material having supercooling property is cooled to a supercooled state, the temperature of a part or all of the melt is By reheating to a predetermined temperature below the melting point, it is possible to control the crystallization of a material having a high supercooling property.

Further, a part of the supercooled melt is reheated to a predetermined temperature lower than the melting point and first crystallized to form a seed crystal, and then the reheat range is changed from the seed crystal to the supercooled melt. By moving, it is possible to continuously crystallize the supercooled melt near the crystal, prevent crystallization from progressing from a plurality of positions in the melt, and obtain a continuous crystal.

Further, the crystal material is made into a supercooled melt in a container having a thin tube portion, a tapered portion, and a thick tube portion, and a part of the supercooled melt of the thin tube portion is reheated to a predetermined temperature below the melting point, After first crystallizing in the narrow tube to make a seed crystal with high single crystallinity,
By moving the reheating range from the thin tube portion to the thick tube portion, the supercooled melt near the crystal can be continuously crystallized, and a crystal with higher single crystallinity can be obtained. Further, since the time required for seed crystal formation is shorter than that when using the conventional Bridgeman-Stockburger method, the time when the material is exposed to a temperature equal to or higher than the melting point can be suppressed to be short, and high-quality with little thermal decomposition. Crystals can be obtained.

An external single crystal is used as a seed crystal,
After contacting a part of the supercooled melt with the seed crystal, move the reheat range from the seed crystal to the supercooled melt, or while reheating the boundary between the single crystal and the supercooled melt. ,
By moving the seed crystal away from the supercooled melt, the supercooled melt in the vicinity of the crystal can be continuously crystallized, and the crystal orientation that matches the crystal orientation of the external seed crystal and the application It is possible to obtain a crystal having a desired quality.

By the above-mentioned method, crystal growth which suppresses thermal decomposition is possible, so that there are no defects or transitions, and electrical characteristics,
It is possible to obtain a single crystal having excellent optical characteristics.

[Brief description of drawings]

FIG. 1 is a schematic view showing one embodiment of a crystal production method according to the present invention.

FIG. 2 is a diagram showing a temperature change with time of a point inside a container.

FIG. 3 is a schematic view showing another embodiment of the crystal production method according to the present invention.

FIG. 4 is a schematic diagram showing an example of heater temperature setting.

FIG. 5 is a schematic view showing another embodiment of the crystal production method according to the present invention.

FIG. 6 is a schematic view showing still another embodiment of the crystal production method according to the present invention.

FIG. 7 is a schematic diagram showing a single crystal production method by an indirect heating laser pedestal method.

FIG. 8 is a schematic diagram showing a single crystal production method by the Bridgeman-Stockburger method.

FIG. 9 is a schematic view showing a single crystal production method by the Czochralski method.

[Explanation of symbols]

101, 301, 501, 601 ... Crystal material 701 ... Infrared light 801, 901 ... Heating furnace 102, 302, 502, 602 ... Melt 702 ... Base material 802, 902 ... Heating heater 103, 303, 503, 603 ... Supercooled melt 703, 803, 903 ... Single crystal 104, 304, 504, 604, 704, 904 ... Seed crystal 804 ... Insulating material 105 ... Crystal 305, 505, 605 ... Single crystal 705 ... Melting part 805, 905 ... Melt Liquid 106, 506, 606 ... Heater 306 ... First heater 706 ... Glass tube 806 ... Growing crystal 107 ... Heater 307 ... Second heater 507, 607 ... Ring heater 707 ... Radiant heat 308 ... Third heater 708 ... Crystal base material powder 109, 309, 509, 609, 709 ... Container 110 ... Point inside container 710 ... Heating furnace 111 ... Volume Point of the inner 711 ... melt 712 ... crystal

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-63-319297 (JP, A) JP-A-61-197495 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) C30B 11/02 C30B 13/00 C30B 29/54 G02F 1/361

Claims (5)

(57) [Claims] 1. A first step of heating an organic material to a melting point or above to obtain a melt, and cooling at least a part of the melt to a first temperature below the melting point to obtain a supercooled melt. A second step and a third step of reheating at least a portion of the supercooled melt to a second temperature between the melting point and the first temperature to crystallize the supercooled melt. A method for producing a crystal, including the steps of. 2. In the third step, one end of the supercooled melt is reheated to grow a seed crystal, and then a reheat region for crystallization is moved toward the other end. The method for producing a crystal according to claim 1, which is characterized in that. 3. A first region having a small inner diameter and a second region having a large inner diameter.
And a region having an inner diameter that is located between the first region and the second region and changes in a tapered shape,
The crystal manufacturing method according to claim 2, wherein the organic material is loaded and the seed crystal is grown in the first region. 4. In the third step, after the single crystal is brought into contact with one end of the supercooled melt, the region where the single crystal is brought into contact is reheated to the second temperature and reheated. The crystal manufacturing method according to claim 1, wherein the region is moved toward the other end. 5. In the third step, a single crystal is brought into contact with one end of the supercooled melt, and then a part of the supercooled solution adhered to the single crystal is pulled up together with the single crystal. The crystal production method according to claim 1, wherein the crystal is made to pass through a reheating region heated to a second temperature for crystallization.