Method of growing single crystals from melt

 

The invention relates to the production of single crystals and can be used in the technology of growing single crystals from a viscous melt refractory oxides by Stepanov method for obtaining three-dimensional profiled calibrated single crystals of large diameter with a high degree of perfection patterns. The essence of the invention: a method of growing single crystal on the seed crystal of (viscous) melt refractory oxides of the crucible with the shaper when creating in the melt isotherm round shape includes growing in synchronous rotation in one direction of the crucible, shaper and the seed crystal in accordance crystallographic faces of the seed crystal form shaper, with isotherm round shape creates a heater in the shape of a crucible installed in the heater is made from slats of a U-shaped form of rods of refractory metals and alloys collected (installed) in a circle or in sections, with a total number of blades, multiple of the number of faces of the grown single crystals and a multiple of 12; the persecution is carried out in the center of the shaper and razresevanje of the single crystal is carried out from the center to the edge of formoobrazovateli in the crucible with the melt, on the shaper and the growing crystal and the increase of the yield in the manufacture of products specified profile. 1 C.p. f-crystals, 2 Il.

The invention relates to the production of single crystals and can be used in the technology of growing single crystals from a viscous melt refractory oxides by Stepanov method for obtaining three-dimensional shaped single crystals with a high degree of perfection patterns.

The technical problem solved by the invention is a method of growing a calibrated profiled bulk single crystals and increasing the yield in the manufacture of products specified profile.

There is a method of growing single crystals from melt refractory oxide type sapphire, ruby, yttrium aluminium garnet by the Czochralski method. The method includes melting the source of the charge, making the seed, the pulling of the single crystal and simultaneously cooling the melt and subsequent cooling of the grown single crystal. The temperature of the depositing of the seed set to appear on the melt surface of a single crystal, the process is conducted with the regulated speed of extrusion, cooling the melt and the single crystal (see Pat the fish.

There is a method of growing single-crystal sapphire hemispherical blanks, including the persecution on the plate around the perimeter of the tubular shaper with the formation of a hollow closed volume under the seed. While the end surface of the tubular shaper perform with a Central recess in the shape of a spherical segment, the extrusion is made from post melt and after the transition of the hollow profile in a monolithic workpiece is pulled to a length equal to the height of the segment, and produce a sharp separation of the crystal from the shaper (see RF patent 2078154, With 30 In 15/34, publ. 27.04.97, bull. 12).

The method is aimed at growing hemispherical blanks small size and cannot be used for growing bulk crystals in the shape of a square, rectangle, etc.

A known method of growing shaped single crystals of complex oxides, including persecution and pulling the seed crystal from the post of the melt at the end of the shaper, immersed in the crucible. The priming charge in the form of plates and persecution lead around the perimeter of the tubular shaper with the formation of a hollow closed volume under the plate when the pressure in the chamber is not less than 0.2 mm (see waveguide plate and razresevanje from the periphery to the center.

The method adopted for the prototype.

The disadvantage of this method is that the process of cultivation passes supercooling of the melt in the center of the crucible. This leads to the formation of low-angle boundaries in the center of the crystal and, consequently, to the growth of the polycrystal.

With the larger diameter tubular shaper probability of formation of polycrystal increases. For large tube diameters education monolithic crystal impossible.

The technical result of the invention is the possibility of growing volume shaped single crystals of large diameter and the creation of conditions ensuring the alignment of radial temperature gradients in the crucible with the melt, on the shaper and the growing crystal and allow it to grow calibrated bulk crystals of high quality and structural perfection.

The technical result is achieved in that in the method of growing single crystal on the seed crystal of (viscous) melt refractory oxides from the crucible with a shaper according to the invention, the cultivation is carried out at the establishment in the radial melt isotherm round shape and synchronous rotation in one direction of the crucible, FORMOSAT the shaper; isotherm round shape creates a heater in the shape of a crucible installed in the heater is assembled from curved lamellas U-shaped form of rods of refractory metals and alloys arranged in a circle or in sections, with a total number of blades, a multiple of the number of faces of the grown single crystals and a multiple of 12; the persecution is carried out in the center of the shaper and razresevanje of the single crystal is carried out from the center to the edge shaper, having a greater temperature.

The essence of the method lies in the fact that the claimed set of distinctive features allows centering of thermal field of a growing crystal and the crucible with the melt relative to the heater, while there are conditions the radial symmetry of the temperature field, which determine full compliance with the geometric forms of the growing single crystal (with the exception of slight melting and freezing) and shaper. In addition, the synchronous rotation of the growing single crystal and the crucible with the shaper allows you to exclude plastic deformation of the growing single crystal.

The constancy of the axial symmetry of the temperature field leads to the constancy of shape and size of the crystal, which provides the cultivation not that is travelmania carried out on the periphery, and razresevanje goes to the center, i.e. in the "cold" region, in the proposed method the persecution is carried out in the centre, and razresevanje crystal lead from the center to the periphery of the former, i.e., a "hot" area. This allows you to avoid supercooling of the melt that provides the perfect structure of single crystals.

The total number of lamellae in the heater, a multiple of 12, defines conditions for growing single crystals of cubic and hexagonal lattices of different profile, in which the number of blades and the number of faces of the grown single crystals in multiples of 12.

For example, when growing tapes (the number of faces is equal to 2), when growing single crystals of a triangular form, the number of faces is equal to 3), when growing single crystals of hexagonal shape (the number of faces is equal to 6), when growing single crystals of tetragonal form (the number of faces equal to 4), the condition of the ratio of 12.

The thinner the diameter of the rod of the blades and the larger the diameter of the crucible, the greater the number of blades, 12 times, can be assembled to the heater. The growing volume calibrated profiled single crystals of viscous melts can significantly expand the range and the PKE products.

The method is most effective when growing multi-faceted single crystals, in which the temperature difference (hypothermia) between the temperature at the center of the faces and describe the isotherm with temperature equal to Tcrit., small.

An example implementation of the method of Growing sapphire single crystals is carried out in the installation (Fig.1), comprising a housing, the heater and the crucible, structurally and shaper. The crucible is installed in the heater, made of bent U-shaped rods of refractory metals or alloys, the shape of the crucible. The shaper is placed in the crucible. The crucible and structurally mounted on the rod for rotation. Monocrystalline seed crystal cut from a large single crystal so that the side surface of the left crystallographic faces. For example, for a crystal with hexagonal lattice grown in the directionuse the seed crystal square in cross-section shape of which defines one of the side planes, the corresponding crystallographic faces (1010) and (0001), and for single crystals grown in the direction of [0001] - face (1010). For crystals section, who defined the lateral plane (110) and the output of crystal face (111), etc.

In the heater resistance, made in the form of a bowl of curved U-shaped rods of refractory metals with the total number of slats that are multiples of 12, on the lower rod set similar form crucible placed in him by the shaper (Fig.2).

Mounted on the upper rod structurally with the seed crystal oriented relative to the shaper so that the focused lateral plane of the seed crystal coincided with one of the parties shaper.

Include synchronous rotation of the rod so that the relative angular velocity of rotation does not extend beyond10'.

Melt the mixture in the crucible, conduct persecution and razresevanje with the subsequent growth of a single crystal with a constant recharge melt the charge of additional bunker.

The process of single crystal growth is conducted in the presence of all radial isotherms in the melt, i.e., when the total number of lamellae in the heater corresponds to the number of multiple of 12.

Synchronous rotation ensures the correct circular radial isotherm in rarsourcecodes.

Were grown on the sapphire crystal in the direction offaces (1010) and (0001) rectangular shape with a size of 1080 (mm) and a length of 1100 mm without structural defects in the whole volume of the crystal, without deviation in size.

Thus the invention allows to obtain the following positive effects: 1. The exception plastic deformation and getting perfect patterns in the grown single crystals.

2. The possibility of obtaining a calibrated single crystals.

3. Increased yield when grown single crystals and, consequently, in the manufacture of products from them.

4. Reducing the cost of electricity and the flow of the original expensive high-purity materials per unit of product.

Claims

1. Method of growing single crystals from melt refractory oxide on the seed crystal from the crucible with a shaper, wherein the cultivation is carried out at the establishment in the radial melt isotherm round shape and synchronous rotation in one direction of the crucible, shaper and the seed crystal in accordance crystallographic faces of the seed crystal form of molded is in the heater, assembled from strips, made of bent U-shaped rods of refractory metals and alloys arranged in a circle or in sections, with a total number of blades, a multiple of the number of faces of the grown single crystals and a multiple of 12.

2. The method according to any of paragraphs.1 and 2, characterized in that the persecution is carried out in the center of the shaper and razresevanje of the single crystal is carried out from the center to the edge of the shaper.

 

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FIELD: crystal growing.

SUBSTANCE: crystal growing apparatus comprises double-section chamber, seed holder fixed on rod, crucible, furnace provided with heater assembled on U-shaped lamellas following the crucible outline, centering ring with closed parts of lamellas attached to it, and water-cooled annular current leads. According to invention, furnace is constructed in the form of two heaters similar in shape, mass, and size, which are mirror reflection of each other; closed parts of U-shaped lamellas are attached to centering ring being moved apart to 90°; rod with seed holder is disposed inside upper heater; free ends of lamellas are connected through conducting adapters to current leads with alternation of current charge signs as follows: "++--"; crucible is supported by insulated supports disposed between heater lamellas; conducting adapters are made from refractory material having resistivity lower than that of lamellas; and ends of adapters connected with lamellas are positioned at the same distance from axis of heater.

EFFECT: enabled growing large-size monocrystals and increased their structural perfection due to lack of supercooling of melt and increased service time of units.

6 cl, 2 dwg

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