A method and apparatus for growing a single crystal of high quality

 

The invention can be used to obtain crystals CsLiB5O10GdxY1-xCa4O(BO3)3(0<x<1), LiNbO3, LiTaO3, NaxCO2O4. In the method of growing a single crystal by bringing the seed crystal (4) in contact with the melt (2) raw materials, molten when heated in the crucible (1) where in the melt (2) raw materials in the crucible (1) is the element (5) in the form of blades or partitions, a single crystal is grown by pulling it while rotating the crucible (1), to thereby grow from high viscosity of the melt (2) raw materials of various single crystals. Get crystals with high quality and good performance. 3 S. and 9 C.p. f-crystals, 7 Il.

The invention relates to a method and apparatus for growing a single crystal of high quality. Specifically this invention relates to a new method of growing high-quality single crystal, and with the help of this method it is possible to grow a single crystal of high quality even when using high-viscosity liquid raw materials, and device for implementing this method.

As fashion wirematerial melt when heated in the crucible, and then in contact with the melt of raw materials lead the seed crystal, and in order to grow a single crystal, during this rotation of the seed crystal pulling a single crystal in the form of a round rod. This method of stretching is used to grow single crystals as a way that allows them to effectively grow a crystal of a large diameter.

Also known, for example, another way (the way the kyropoulos method), in which raw materials are melted by heating in a crucible, and then into contact with the melt of raw materials lead the seed crystal, and the temperature below the liquid level slowly reduce to plant and grow the crystal.

However, the conventional method of growing a single crystal by bringing the seed crystal into contact with the melt of raw materials there is a problem, which is that, if the viscosity of the melt of raw materials during cultivation at the required temperature is high, the melt flow of raw materials in the crucible slows down, causing heterogeneity in the temperature, the state of supersaturation, etc., that leads to a decline in the quality of the crystal.

N the crystals to obtain ultraviolet laser radiation with high output; and it is desirable to have excellent characteristics and qualities such as very high resistance against damage by the laser, very high optical loss and high uniformity. However, as it is a crystal type of Borat, the melt has a high viscosity, making it difficult to grow a single crystal with high quality and good performance. As confirmed by these measurements, the viscosity of the solution CLBO self-fluxing composition reaches about 1000 cSt (Centistokes) at a growth temperature of about 840oC.

For example, when growing a single crystal by rotating seed rod cooling method CLBO temperature distribution in the melt of raw materials is poor, as shown in Fig.7, and the crystal growth is rapid, and therefore, inevitably there are limits on the growing crystal with high quality and good performance.

In view of this situation, the purpose of this invention is the resolution of the above-mentioned problems existing in the known methods of obtaining single crystals, and the provision of an improved new method, which allows to grow single crystals with a high for the in, as well as securing the device to implement this method.

This invention was made to solve the above problems and, first, to provide a method of growing high-quality single crystal, comprising growing a single crystal by bringing the seed crystal into contact with the melt of raw materials, which are heated and melted in a crucible, and the molten raw material in the crucible is placed element in the form of blades or element in the form of partitions, and the crystal is grown in rotation of the crucible without rotation of this element in the form of blades or partitions. Secondly, this invention also provides a method of growing by using a slow pulling of the seed crystal, which is brought into contact with the melt of raw materials; thirdly, the method of growing by using a slow cooling of the melt of raw materials, with which the seed crystal is in contact below the liquid level to grow the single crystal on the surface of the seed crystal; fourth, the way in which the seed crystal is also rotated by the rotation of the crucible; fifthly, this method, in which the grown single crystal oxide; Sixthly, JV is xicom type Borat is CsLiB5O10or oxide, obtained by partial substitution in CsLiB5O10at least one element selected from Cs and Li, at least one element of the type selected from other elements of alkali metals and alkaline earth metals; and eighth, the way in which the oxide is an oxide alloyed with at least one element selected from Al and Ga. This invention provides, in a ninth, the way in which the oxide-type borate compound represented by GdxY1-xCA4O(VO3)3(0<x<1), and the crystal is grown by the method of extrusion; and tenth, the way in which the single crystal oxide is a LiNbO3, LiT3oxide material having high-temperature superconductivity, or an oxide material that can convert heat into electricity.

In addition, this invention provides, eleventh, a device for growing high-quality single crystal by bringing the seed crystal into contact with the melt of raw materials, which are heated and melted in a crucible, comprising an element in the form of a blade or element in the form of a septum, placed in the melt of raw materials in tip which affect the mechanism for the slow pulling of the seed crystal, which is brought into contact with the melt of raw materials; in the thirteenth, a device for growing, including a cooling mechanism for the slow cooling of the melt of raw materials, with which the seed crystal is in contact below the liquid level; in the fourteenth, the device including a mechanism for rotating the seed crystal; in the fifteenth, a device for growing single crystal oxide according to any of the above devices for cultivation; and, the sixteenth, the specified device for growing single crystal oxide type Borat.

A brief description of the drawings Fig. 1 illustrates schematically the method and apparatus according to this invention.

In Fig.2 shows an example of a device for growing in the section.

In Fig.3 presents a top view illustrating the element in the form of blades.

In Fig.4 shows a side view of the element in the form of blades.

In Fig.5 shows a graph showing the hysteresis crystal growth.

In Fig. 6 presents the dependence of the temperature distribution in the melt of raw materials.

In Fig.7 shows the temperature distribution in the melt in the normal way.

Numbers in Fig.1-7 indicate the following details: 1 - Crucible 2 - Replaement 7 - Rod fixing This invention has the aforementioned characteristics, and variations of the embodiment of the present invention will be explained next.

First, the method of growing a single crystal according to this invention is based on the fact that in order to grow the single crystal, the seed crystal is brought into contact with the melt of raw materials, molten when heated in the crucible. In the production method according to this invention may use different modes, such as a method of stretching and cooling method (method of kyropoulos) using gradual cooling. Common to all these methods is that for growing a single crystal seed crystal is brought into contact with the melt (including the case of the melt), obtained by melting raw materials.

When implementing the method according to this invention a device for growing mainly includes a crucible, a heating means for heating and melting the raw material placed in the crucible, means for determining and controlling the heating temperature and the means of support of the crystal, bringing the seed crystal into contact with the melt (including melting) of raw materials, which melt is m, when for growing a single crystal seed crystal (4) supported by means of support of the crystal, such as the seed rod (3), lead in contact with the melt (2) raw materials, molten when heated in the crucible (1), melt (2) raw materials in the crucible (1) put the item (5) in the form of a blade or element in the form of partitions and rotate the crucible for single crystal growth. For rotation of the crucible (1) a device for growing equipped with rotary devices (6), which rotates the crucible (1) provided that the crucible (1) is mounted on this rotary toiletries.

In the case of the method of pulling the seed rod (3) is pulled in the upward direction while rotating seed rod (3) or in such a stationary state, so that the seed rod (3) does not rotate. On the other hand, in the case of cooling method, for example, of the way in which a hollow seed rod (3), in the hollow part serves a cooling gas, and the molten raw materials below the level of the liquid is slowly cooled to precipitate a crystal on the surface of the seed crystal (4), growing, thus, the single crystal; or you can apply the way in which the overall temperature of the liquid level. The first method is used to prevent melting of the seed crystal. In these cases, the tool support, such as the seed rod (3), may also or rotate, or be in such a stationary state, so that the seed rod (3) does not rotate. It should be noted that the present invention differs as a guideline so that rotation of the seed rod (3) mentioned above, and the seed crystal (4), which is supported by the bare stem (3), is arranged so that is irrelevant, and rotates the crucible (1). Rotate if the seed rod (3) and the seed crystal (4) or not, is specified in accordance with the need for movement relative to the rotation of the crucible (1).

In the present invention by itself, the element (5) in the form of a blade or element in the form of a partition can be in a stationary state, while the crucible (1) is designed such that it rotates with the rotary accessories (6) relative to the melt of raw materials (2), as shown for example in Fig.1.

The presence of the element (5) in the form of blades (5) or item in the form of a partition with such characteristics and the rotation of the crucible (1) improve the effect premesis what I to increase the amount of raw materials supplied to the surface of the growth, and to obtain a uniform degree of supersaturation. This allows you to grow a single crystal of high quality and high performance, even when the liquid raw material has a high viscosity at the temperature of growth.

Item (5) in the form of a blade or element in the form of a partition having a different form, can be set depending on the composition and type of the single crystal, which is the object of cultivation, and from the raw material, the composition and viscosity of the melt of raw materials, as well as the depth of immersion of the above items in the melt (2) raw materials, the distance from the center of rotation of the crucible (1), flow direction and flow velocity of the melt (2) raw materials, etc. In preferred examples of the element (5) in the form of a blade or element in the form of partitions several blades are radially and fixed in the center. Namely, in an example of the elements made in the form of a screw, and the elements obtained by the combination of several planar slices of a partition.

Although this element (5) in the form of a blade or element in the form of a dividing wall does not rotate, and is stationary is Nisha least in one direction - vertical or horizontal. Moreover, as shown in Fig.1, item (5) in the form of a blade or element in the form of partitions can be immersed in the crucible (1) above and be removed with the help of the supporting rod (7); element can be located so that, for example, the depth location of the part in the melt (2) raw materials can be adjusted and so that it can be installed and fixed relative to the bottom or other part of the crucible (1). It is considered preferable that this item had the first structure.

With regard to the rotation of the crucible (1) by turning set (6), it is considered that the crucible (1) is made to rotate in the same direction as the direction of rotation of the seed crystal (4), or alternately in both directions. Moreover, in relation to the rotation of the crucible (1), it is believed that in the course of growth, it is controlled to change the speed of rotation. It is also believed that the direction of rotation and the rotation speed is changed depending on the results of monitoring by optical methods, for example, flow and temperature of the melt and the size of the growing single crystal, or when control using methods that are sensitive to pressure and heat, for example, velocity and those who who is the subject of this invention, can be of different types, and this invention is more effective when the liquid raw material has a high viscosity at the temperatures growth. As examples of the single crystal are different oxides. In particular, this invention is applicable for the cultivation of high-viscosity-type crystals borate, such as CsLiB5O10(CLBO), which assumes a single crystal of high quality and good performance; compounds obtained by partial substitution in CsLiB5O10at least one element selected from Cs and Li, one of the atoms of other elements - alkali or alkaline-earth metals; or compositions doped in this atom, as Al or Ga. In the example below, the proposed explanations, when considering as example the case when the above-mentioned CLBO is grown by the method of cooling, although the invention is not limited to this case.

When the crystal is grown GdYCOB, namely GdY1-xCA4O(VO3)3that way pulling (Czochralski method: Cz method) according to the method of the present invention also get high-quality crystal. In particular, when the method of stretching is also effective is the use of the element in the high temperature superconducting oxide materials LiNbO3, LiTaO3- and oxide materials for conversion of heat into electricity, such as NaxCO2O4(x is about 1).

Now the invention will be explained in more detail using the following examples.

Examples
Device for growing
With regard to the device for cultivation, in General, it was designed to have a structure shown in Fig.2. When using a platinum crucible the crucible was designed so that it can be rotated by the engine. Moreover, in this device as the seed rod used hollow seed rod (3); the seed crystal (4) is supported by the lower end of the seed rod (3), and the seed crystal (4) was designed in such a way that it can be cool, feeding cooling the seed gas into the inner hollow of the seed rod (3) that protected the seed crystal (4) from melting and falling away. This device makes it possible to grow the crystal with the use of the composition of the melt, which usually brings complexity in the growing crystal as seed crystal is melted.

Item (5) screw type blade, made by the th rod (7). Item (5) in the form of blades had six blades, which were located with an inclination of 40 degrees. Item (5) in the form of blades installed so that the center of (A) the blade is in the plane corresponding to the center of rotation of the crucible. The design allowed us to control the distance (H) from the inner part of the bottom of the crucible to the center (A) of the blade. It should be noted in relation to the distance (H) that the center of (A) the blade was designed to be as close as possible to the inner part of the bottom of the crucible.

It should be noted that as the tube Alsynto and tube FKS, is shown in Fig. 4, were purchased from FURUYAMETAL Co., LTD. For the manufacture of tubes Alsynto as a source of raw material used is aluminum oxide (Al2About3), and the tube FKS consisted of a material including platinum (Pt) containing ZrO2.

Growing single crystal
When using the above mentioned device for growing crucible was rotated to obtain a single crystal CLBO the cooling method.

The seed rod is not rotated, the element in the form of the blade is also not rotated, so that the growth took place in a stationary state. The melt of raw materials was prepared in such a way as to obtain a self-fluxing status is ridino, this composition is preferred stoichiometric composition (the composition of the melt).

Maximum temperature of the melt of raw materials was set 900oC.

Conditions for the rate of temperature reduction and rotation of the crucible were as follows.

The rate of temperature decrease:
0,1oWith a day
The rotation of the crucible:
30 rpm

As the first standard point, where the measured rate of temperature decrease was the level of the melt. Then the temperature of the melt was lowered with a speed of 0.1oWith a day since the temperature at this level. The temperature at this time was measured by the control sensor, as shown in Fig.2, and the melt temperature generally decreased uniformly at the rate of 0.1oWith the day.

In Fig. 5 shows the hysteresis of the crystal compared to the crystal obtained in the usual way, and Fig.6 shows the temperature distribution in the melt of raw materials. It is evident from Fig.6 it is clear that the temperature distribution of the melt in the crucible in the direction of the height of the crucible becomes more uniform as compared with the conventional method, and the crystal grows uniformly.

Further investigation in terms of results on the temperature distribution in the melt of the raw material m is s the temperature difference (t) between the provisions from the liquid level height (depth) of about 10 cm amounted to-0.5oWith, namely from 0.5 to 0oC.

Moreover, as shown in Fig.5, when the usual method of growing, although growth in the first time is slow, the growth rate increases during the process, and the final growth rate becomes very high. This indicates that when the crystal is small, it has a small mixing effect, even when the rotation of the seed shaft, while if a large crystal, the crystal itself mixes the melt, thus immediately increasing the growth rate.

Conversely, when grown by the method of the present invention, in which the element in the form of blades, and the crucible is rotated, the growth at the initial time is faster than with conventional cultivation with the use of rotation of the seed shaft. This is due to the fact that the melt is sufficiently mixed with the rotation of the crucible and, therefore, the layer is called the diffusion boundary layer, which determines the growth rate becomes thin. In addition, it is due to the fact that the degree of supersaturation is maintained constant.

Assessment of the quality of the crystals
In order for the m and polished cut crystal in three planes, were tested using a He-Ne laser for observation of the internal diffusion in the crystal. In crystals with high quality, diffusion occurs in the inner region and the inner region is illuminated in red light so that the visible point of diffusion. In places where there are vacancies, transitions were observed.

As a result of these observations, it was confirmed that the crystal grown by the method of the present invention, where was introduced element in the form of the blades and the crucible was rotated, had good quality; observed a small number of transitions in the lower part of the seed crystal.

On the other hand, in the crystals grown in the usual way, transitions were observed in the entire volume, which led to problems associated with the quality of the crystal.

In addition, as samples for evaluation of sustainability in relation to the laser used the same samples, as mentioned above, as well as crystals with a size of 10 mm x 10 mm x 15 mm, grown in the usual way. Measurement of the threshold of damage carried out to the plane (001). As the source of laser radiation used Nd:YAG laser q-switched, with one longitudinal and transverse fashion. The estimate of p is mpulse amounted to 0.75 NS.

The light beam having the diameter of 8 mm, was focused using a lens with a focal length of 100 mm At the position of the crystal was adjusted so that the focused part was at a distance of 5 mm from the plane of incidence, and the crystal was moved before each exposure. It was confirmed that in this case there is no damage to the plane of incidence in the conditions of transformation of the world. On the same axis as that of the radiation of the Nd:YAG laser, theoretical light of He-Ne laser, in order to establish whether there is diffusion of a point on the area irradiated with laser light with every movement, and to determine visually whether there are any diffusion again points after exposure, so to find out there is damage or not. If the incident energy is higher than the threshold value of the damage at the site of convergence of light was observed plasma. Near threshold was only confirmed by the appearance of diffusion points. The intensity of the laser pulse is changed by means of the combination plates/2 (a device for rotating the plane of polarization and the polarizer. The incident energy was monitored using a two-axis solar cell and oscilloscope, which were outcalibrate is so it was determined the threshold value of the internal laser damage using the fourth harmonic (266 nm) Nd:YAG laser. The threshold value of the internal laser damage to the crystal grown according to this invention, which was introduced element in the form of blades, and the crucible was rotated, and the threshold value of the internal laser damage of the crystal grown in the usual way, and fused silica are shown below.

Method - Value threshold of damage, GW/cm2
Fused silica is 10.4
The usual way - 8,8-8,9
This invention is 10.4-20,8
Thus, it was confirmed that the threshold value of the internal laser damage of the crystal grown in the usual way, was lower than this value for fused silica, while the threshold value of the internal laser damage of the crystal grown by the method of the present invention, where was introduced element in the form of the blades and the crucible was rotated, was higher than this value for fused silica, even if the threshold value had a lower value, and is approximately two times the value for fused silica, if the threshold value was the highest.

As mentioned above, when comparing the threshold level of the internal laser of the present invention, it is seen that the crystal according to this invention is much higher than conventional crystal on the threshold value of the internal laser damage. This means that the crystallinity is significantly improved.

As detailed above, the present invention provides an opportunity to grow from the melt of a raw material having high viscosity, a variety of crystals including CLBO, high quality and good performance.


Claims

1. The method of growing a single crystal, comprising placing the item in the form of a blade or element in the form of a partition in the melt of raw materials in the crucible and growing a single crystal by rotating the crucible without rotating element in the form of a blade or element in the form of a partition during single crystal growth by bringing the seed crystal into contact with the melt of raw materials, which are heated and melted in a crucible, in which the crystal is grown at a slow cooling of the melt of raw materials, with which the seed crystal is in contact below the liquid level to grow the single crystal on the surface of the seed crystal.

2. The method according to p. 1, in which the seed is and.

4. The method according to p. 3, in which the single crystal oxide is a single crystal oxide type Borat.

5. The method according to p. 4, in which the oxide type Borat is CsLiB5O10or oxide, obtained by partial substitution in CsLiB5O10at least one element selected from Cs and Li, at least one element of the type selected from other elements - alkali metals or alkaline-earth metals.

6. The method according to p. 5, in which the oxide is an oxide alloyed with at least one element selected from Al and Ga.

7. The method according to p. 4, in which the oxide type Borat presents GdxY1-xCa4O(BO3)3(0<x<1), and the crystal is grown using the method of extrusion.

8. The method according to p. 3, in which the single crystal oxide is a LiNbO3, LiTaO3- high-temperature superconducting oxide material or an oxide material to convert heat into electricity.

9. Device for growing single crystal by bringing the seed crystal into contact with the melt of raw materials, which are heated and melted in the crucible, including the element in the form of blades or element in the form of a septum, placed in the melt of raw materials BBA raw materials, with which the seed crystal is in contact below the liquid level.

10. Device for growing on p. 9, comprising a mechanism for rotating the seed crystal.

11. Device for growing single crystal oxide, comprising a device for growing under item 9 or 10.

12. Device for growing on p. 11 used for growing a single crystal oxide type Borat.

 

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