A crystal growth apparatus and method for separating crystal and melt.

Abstract

This invention provides a crystal growth apparatus and method with crystal and melt separation, overcoming the shortcomings of current crystal growth methods that easily produce polycrystalline structures. The growth apparatus includes a holding furnace, a heater, a crystal growth crucible, an inner liner crucible, a pulling mechanism, a ceramic pulling seat, a pressing graphite, a thermally conductive graphite ring, and a holding ring. The crystal growth crucible is coaxially arranged in the holding furnace; the heater is coaxially arranged between the crystal growth crucible and the holding furnace; the inner liner crucible is coaxially arranged in the crystal growth crucible, and from bottom to top includes a coaxial and connected crucible base plate, a melt transfer channel, and a crucible body. To reduce the influence of the melt on the crystal during growth, this invention physically separates the crystal from the melt, designing a growth apparatus with two crucibles. Considering the importance of a stable thermal environment for crystal growth, the heat transfer between the two crucibles is isolated by the holding ring, and the thermally conductive graphite is used to uniformly heat the center and edges of the melt, avoiding the formation of a concave liquid surface.

Description

Technical Field

[0001] This invention belongs to the field of crystal growth technology, specifically relating to a crystal growth apparatus and method that separates crystals and melts. Background Technology

[0002] During crystal growth, the molten region at the top of the crystal is typically located in a high-temperature zone. Thermal radiation and conduction from the heater cause this region to continuously absorb heat, leading to heat accumulation. Heat in the central melt region is difficult to diffuse rapidly to the edges, resulting in a significantly higher central temperature than the surrounding areas. This makes it easy for a concave interface to form at the solid-liquid interface during growth, which is detrimental to single crystal growth. Simultaneously, complex convection currents exist within the melt, which can couple to form turbulence. The presence of turbulence constantly disturbs the solid-liquid interface, creating an unstable crystal growth environment that easily leads to polycrystalline growth.

[0003] Therefore, it is necessary to explore a solution to avoid the above situation from occurring. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of current crystal growth methods that easily produce polycrystalline structures, and to provide a crystal growth apparatus and method that separates the crystal from the melt.

[0005] To address the problems existing in the background technology, this invention, through in-depth analysis, reveals that the key reasons why the crystal growth process is susceptible to the influence of high-temperature melts are mainly reflected in two aspects: 1. Temperature gradient and interface morphology issues; when a large amount of melt accumulates above the solid-liquid interface, the high-temperature melt will form a thermal accumulation effect in the central region, resulting in a distribution characteristic of high temperature at the center and low temperature at the edge of the solid-liquid interface. This temperature gradient will cause the interface isotherms to exhibit a concave shape, while the ideal interface required for single crystal growth should be a flat interface or a slightly convex interface. 2. Melt turbulence disturbance issues; the strong turbulence present in the high-temperature melt will significantly disturb the solid-liquid interface, leading to instability of the solid-liquid interface and inducing polycrystalline formation, which seriously affects the quality of single crystals.

[0006] To suppress the impact of melt convection on crystal growth, compromises in crystal growth conditions are necessary. This invention evaluates the feasibility of two traditional improvement approaches: ① Melt temperature control: Controlling the melt temperature can improve uniformity. Although a more uniform melt temperature results in a smaller internal temperature difference and a smaller density difference due to the temperature difference, which can slightly reduce convection intensity, it hinders heat dissipation at the crystal tail and cannot fundamentally eliminate the inherent temperature gradient, thus offering limited improvement. ② Crystal diameter reduction: Reducing the crystal diameter creates numerous turbulent flows along the vertical direction. While this reduces the maximum flow velocity, it limits crystal size and cannot meet the growth requirements of large-size single crystals.

[0007] To solve the above problems, new approaches need to be explored. By reducing the amount of melt above the solid-liquid interface, the melt height can be reduced, thereby effectively reducing the turbulence scale and convection velocity. However, shortening the crystal length and increasing the number of crystals will significantly increase the cost of equipment and consumables, making it less economical.

[0008] Based on the above analysis, this invention proposes a groundbreaking solution, innovatively adopting a design concept of separating the melt from the crystal, thereby minimizing the influence of the melt during crystal growth.

[0009] Based on the above inventive concept, and to achieve the above objectives, the technical solution provided by this invention is as follows:

[0010] A crystal growth apparatus that separates crystals and melts is characterized by comprising a holding furnace, a heater, a crystal growth crucible, an inner liner crucible, a pulling mechanism, a ceramic pulling seat, a pressing graphite, a thermally conductive graphite ring, and a holding ring.

[0011] The heat preservation furnace includes a furnace body and a furnace cover; wherein, a limiting groove is coaxially provided at the bottom of the furnace body, and the ceramic lifting seat is coaxially and sealed on the furnace cover.

[0012] The crystal growth crucible is coaxially arranged in the furnace body, and its bottom dimensions are adapted to the limiting groove. The inner liner crucible, from bottom to top, includes a coaxial and connected crucible bottom plate, a melt transfer channel, and a crucible body, which are coaxially arranged in the crystal growth crucible, and the diameter of the crucible bottom plate is equal to the outer diameter of the crucible body. The height of the inner liner crucible is not less than the height of the crystal growth crucible, and the inner diameter of the crystal growth crucible is 0.1-0.5 mm larger than the outer diameter of the crucible body. A flange is provided on the top of the crucible body. The bottom surface of the crucible bottom plate and the crystal growth crucible form a crystal growth space. The diameter of the melt transfer channel is 5-10 mm, and its outer circumference, together with the inner circumference of the crystal growth crucible, the bottom surface of the crucible body, and the top surface of the crucible bottom plate, form an installation cavity. The installation cavity is filled from bottom to top with the thermally conductive graphite ring and the heat-insulating ring. The thermally conductive graphite ring and the heat-insulating ring are both designed with a split structure, so that they can be smoothly installed into the installation cavity.

[0013] The heater is coaxially positioned between the crystal growth crucible and the furnace body to provide heat for crystal growth; the lifting mechanism is sealed and vertically mounted on the furnace cover, with its lower end connected to the flange at the top of the crucible body; the pressing graphite is coaxially mounted at the lower end of the ceramic lifting seat and is coaxially located inside the crucible body; the inner diameter of the crucible body is 0.1-0.5 mm larger than the outer diameter of the pressing graphite; during crystal growth, the bottom surface of the pressing graphite is in contact with the melt inside the crucible body.

[0014] Under the action of the lifting mechanism, the inner liner crucible can move up and down in the crystal growth crucible, thereby adjusting the size of the crystal growth space. When the lifting mechanism pulls the inner liner crucible upwards, it presses down the graphite, which can push the melt in the crucible body down into the crystal growth space through the melt transfer channel. During crystal growth, the melt in the crystal growth space is controlled to be 3-5mm.

[0015] Furthermore, the thickness dc of the thermally conductive graphite ring and the inner diameter Dc of the crystal growth crucible (equivalent to the crystal diameter) satisfy the condition: Dc / 4≤dc≤Dc / 2; the thickness di of the heat-insulating ring and the thickness dc of the thermally conductive graphite ring satisfy the condition: 2dc≤di≤5dc.

[0016] Furthermore, the insulation ring is prepared by filling alumina insulation fiber cotton into a hollow quartz block, vacuum sealing it, and then frosting the outer surface.

[0017] Furthermore, to facilitate temperature control, the heater is a segmented heater, including an upper heater and a lower heater, and the operating status of the heater is controlled by a heater controller.

[0018] Furthermore, the lifting mechanism includes a lifting assembly and a lifting assembly; the lifting assembly is connected to the upper end of the lifting assembly, and the lifting assembly is provided with a bellows near the furnace cover to ensure sealing; the lower end of the lifting assembly is connected to the flange at the top of the crucible body; the lifting assembly is made of alumina ceramic.

[0019] Furthermore, the crystal growth crucible is made of high-purity quartz, and its inner wall is treated with a carbon coating; the inner lining crucible is also made of high-purity quartz.

[0020] Furthermore, both the thermally conductive graphite ring and the heat-insulating ring are divided into two substructures along the axis and assembled together for easy installation.

[0021] Furthermore, the height of the inner liner crucible is 20-50 cm greater than the height of the crystal growth crucible.

[0022] Furthermore, the thermal conductivity of the insulation ring is 0.02-0.2 W / (m·K).

[0023] Meanwhile, this invention provides a method for crystal growth using the crystal growth apparatus with the above-mentioned separation of crystal and melt, characterized by the following steps: S1. Loading the crystal growth material into the inner liner crucible and installing each component of the crystal growth apparatus in place; S2. Evacuating the vacuum in the holding furnace to 0 Pa, introducing nitrogen gas until the standard atmospheric pressure is reached, and then adjusting the heater temperature to melt all the crystal growth material into a melt; S3. Using a lifting mechanism, slowly lifting the inner liner crucible, with the pressing graphite moving downwards relative to the crucible body, and the melt in the crucible body flowing into the crystal growth space through the melt transfer channel under the action of the pressing graphite, adjusting the heater temperature to allow the crystal to grow slowly until the crystal growth is completed.

[0024] Further, S1 specifically involves: S1.1 sealing and vertically installing the lifting mechanism and ceramic lifting seat on the furnace cover of the holding furnace, with the ceramic lifting seat coaxial with the furnace cover, and then installing the pressing graphite at the lower end of the ceramic lifting seat; S1.2 installing the heat-conducting graphite ring and the heat-insulating ring on the outside of the melt transfer channel of the inner lining crucible, and loading the crystal growth raw material into the crucible body; S1.3 inserting the pressing graphite into the crucible body of the inner lining crucible, and connecting the lower end of the lifting mechanism to the flange at the top of the crucible body; S1.4 inserting the inner lining crucible into the crystal growth crucible (the crystal growth crucible and heater have been pre-installed in the furnace body of the holding furnace), and tightening the furnace cover and the furnace body.

[0025] Compared with traditional crystal growth methods, the technical difficulties of this invention mainly lie in the following two aspects.

[0026] I. Structural Optimization Design of the Growth Device

[0027] In order to reduce the influence of the melt on the crystal during the growth process, this invention physically separates the crystal from the melt and designs a growth device with two crucibles. Considering the importance of a stable thermal environment for crystal growth, the heat transfer between the two crucibles is isolated by a heat-insulating ring, and thermally conductive graphite is used to uniformly heat the center and edge of the melt to avoid the formation of a concave liquid surface.

[0028] II. Selection of Materials and Parameters for Each Component of the Growth Device

[0029] 1. Inner lining crucible

[0030] The inner crucible, from bottom to top, comprises a coaxial and interconnected crucible base plate, a melt transport channel, and the crucible body, all made of high-purity quartz. A thermally conductive graphite ring and a heat-insulating ring are fitted around the outside of the melt transport channel from bottom to top. The thermally conductive graphite ring provides uniform heat distribution, ensuring a uniform temperature between the center and edges of the melt film in the crystal growth space, eliminating concave liquid surfaces, and facilitating single crystal growth. The heat-insulating ring separates the area below from the area above, blocking heat transfer and ensuring a stable thermal environment near the interface.

[0031] Given the requirement for crystal growth, which allows the crystal to grow from start to finish, it is important to note when designing the crucible size that the height of the inner liner crucible should not be less than the height of the crystal growth crucible, and ideally the inner liner crucible should be 20-50mm taller than the crystal growth crucible.

[0032] The inner-lined crucible contains a pressing graphite core, which is connected to a ceramic lifting seat via a threaded connection. The ceramic lifting seat pulls the pressing graphite core. As the inner-lined crucible slowly rises, the pressing graphite core also descends at the same speed relative to the tail of the melt. This ensures that there are no gaps between the pressing graphite core and the melt, eliminating voids within the crucible body, suppressing raw material volatilization, and completely eliminating gas convection above the tail of the melt, resulting in a more stable temperature field within the crucible body.

[0033] The melt transport channel is a transport channel connecting a large amount of melt at the top with the crystals below. Because the melt has a certain viscosity, its diameter is controlled between 5-10 mm. If it is less than 5 mm, the melt will have difficulty passing through the melt transport channel smoothly under the large melt viscosity and capillary force. If it is greater than 10 mm, it will not be able to play a solid-liquid separation role.

[0034] The main function of the thermally conductive graphite ring is to homogenize the heat at the crystal growth interface. Graphite has a high thermal conductivity, and through its homogenizing effect, the crystal growth interface exhibits a uniform temperature along the radial direction, thus achieving a smooth crystal growth interface, which is beneficial for growing large-sized single crystals. The thickness of the thermally conductive graphite ring is denoted as dc, and the inner diameter of the crystal growth crucible (equivalent to the crystal diameter) is denoted as Dc. A thicker thermally conductive graphite ring results in better thermal conductivity and a smoother solid-liquid interface; however, excessive thickness will lead to a larger inner crucible volume. To obtain a smooth and stable crystal growth interface, dc is typically no greater than Dc / 2 and no less than Dc / 4.

[0035] The insulating ring serves as a thermal insulator, its purpose being to isolate the high-temperature zone at the top from the lower crystal, preventing the high temperature from the top from transferring to the bottom and causing instability in the crystal growth environment. The thickness of the insulating ring is denoted as di. As described above, after the insulating ring is fabricated, its thermal conductivity should be 0.02-0.2 W / (m·K), a value much smaller than that of a thermally conductive graphite ring. To achieve better thermal insulation, di should be no less than 2dc, at which point the insulation effect is good. However, it should not be too thick, otherwise the melt transport channel will be too long, which can easily cause a large number of turbulent rings inside. Therefore, di should also not exceed 5dc. Since this structure is located inside the crystal growth crucible, a high degree of cleanliness is required, and there should be no slag or dust falling off to avoid introducing contamination. Therefore, refractory bricks cannot be used as insulation materials for insulation rings. Through exploration, it has been found that hollow quartz blocks can be used, filled with alumina insulation fiber cotton, vacuum sealed, and finally the outer surface is frosted. Insulation rings obtained in this way have good heat insulation effect and fully meet the requirements of the application scenario.

[0036] 2. Crystal growth crucible

[0037] The crystal growth crucible is made of high-purity quartz. Because it needs to come into contact with other components and will undergo relative movement, a carbon film is applied to the inner wall of the crystal growth crucible to increase the smoothness of the inner surface, reduce the frictional resistance during relative movement, and make the crystal growth process more stable.

[0038] During crystal growth, a layer of melt exists between the crystal and the bottom plate of the inner crucible. This layer of melt, referred to as the melt film, is the part in contact with the crystallization interface, and its thickness needs to be precisely controlled. If the thickness is too thin, due to the viscous resistance of the fluid, the melt added from the top will be difficult to spread evenly, causing the crystal diameter to change continuously. If it is too thick, convection will occur within the melt film due to temperature differences in different parts, which is not conducive to the stability of the crystal growth interface. Therefore, the thickness needs to be controlled within 3-5 mm.

[0039] The solid medium above the melt at the crystallization interface, namely the crucible bottom plate of the inner lining crucible, can produce a sudden temperature change. Therefore, a large temperature gradient can be introduced into the melt, which is beneficial to increasing the crystal growth rate.

[0040] The pressing graphite and ceramic lifting seat at the top of the crucible body has a limiting effect on the crystal growth crucible. At the same time, the crucible can fall into the limiting groove at the bottom of the holding furnace body. By constraining from the bottom and top at the same time, the crystal growth crucible can always be kept in the center of the furnace body, and the temperature field symmetry is good.

[0041] 3. Lifting mechanism

[0042] The lifting mechanism includes a lifting component and a lifting component. Since the lifting component needs to be connected to the inner lining crucible, it should have a certain structural strength and cleanliness. Its material can be alumina ceramic, etc.

[0043] Advantages of this invention:

[0044] This invention effectively avoids the influence of high melt temperature on the solid-liquid interface shape by separating the melt and crystal, and also avoids polycrystalline formation at the interface caused by melt convection. During crystal growth, only a millimeter-scale melt film slowly solidifies above the crystal, suppressing turbulence within the melt film and eliminating compositional segregation caused by turbulent flow, resulting in a more uniform crystal composition. Furthermore, the melt at the crystallization interface is in contact with the bottom of the inner lining crucible, thus introducing a larger temperature gradient into the melt, which is beneficial for increasing the crystal growth rate. Attached Figure Description

[0045] Figure 1 This is a schematic diagram of the crystal growth apparatus for separating crystal and melt according to the present invention.

[0046] Figure 2 This is a schematic diagram of the crystal growth apparatus used for comparison.

[0047] Figure 3 The solid-liquid interface results for Examples 1-2 and Comparative Examples 1-2 are shown below. (a) is a solid-liquid interface diagram of Example 1, (b) is a solid-liquid interface diagram of Comparative Example 1, (c) is a solid-liquid interface diagram of Example 2, and (d) is a solid-liquid interface diagram of Comparative Example 2.

[0048] Figure 4 The results are for Examples 1-2 and Comparative Examples 1-2, where (a) is the grain result of Example 1, (b) is the grain result of Comparative Example 1, (c) is the grain result of Example 2, and (d) is the grain result of Comparative Example 2.

[0049] The attached figures are labeled as follows: 1-Crystal; 2-Melted liquid film; 3-Melted transport channel; 4-Melted liquid; 5-Pressing graphite; 6-Heat-conducting graphite ring; 7-Insulating ring; 8-Inner liner crucible; 9-Pulling mechanism; 10-Crystal growth crucible; 11-Lower heater; 12-Upper heater; 13-Insulating furnace; 14-Ceramic pulling seat. Detailed Implementation

[0050] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0051] Example 1

[0052] This embodiment provides a 2-inch cadmium zinc telluride (Cd) 0.7 Zn 0.3 A crystal growth method for Te, comprising the following steps:

[0053] S1. Assembly of the charging and crystal growth apparatus

[0054] Reference Figure 1 Place the furnace body of the holding furnace 13 on a horizontal platform, and then install the lower heater 11 and upper heater 12 inside the furnace body. Clean and dry the crystal growth crucible 10, and place it inside the furnace body. Seal and vertically install the lifting mechanism 9 and ceramic lifting seat 14 on the furnace cover of the holding furnace 13, and install the pressing graphite 5 at the lower end of the ceramic lifting seat 14. Install the heat-conducting graphite ring 6 and the heat-insulating ring 7 on the outside of the melt transfer channel 3 of the inner liner crucible 8, and load the crystal growth raw material into the crucible body. Insert the pressing graphite 5 into the crucible body, and connect the lower end of the lifting mechanism 9 to the flange at the top of the crucible body. Insert the inner liner crucible 8 into the crystal growth crucible 10, and tighten the furnace cover and furnace body. Evacuate the vacuum inside the holding furnace to 0 Pa, and introduce nitrogen until the standard atmospheric pressure is reached. Ensure that all components are coaxial.

[0055] S2, Crystal growth

[0056] Temperature control programs for the lower heater 11 and upper heater 12 were set, and the furnace was started to heat up. After 72 hours of heating, the target temperature of the lower heater 11 was 1160℃, and the target temperature of the upper heater 12 was 1180℃. At this time, the crystal growth material in the inner liner crucible 8 would be fully melted at high temperature, becoming melt 4. The temperature control program of the lower heater 11 was then modified so that the temperature would be reduced to 1000℃ after 50 hours, with the entire process being a uniform cooling rate. At the same time, the lifting mechanism 9 was activated, allowing it to rise at a uniform speed of 2 mm / h. During this process, melt 4 would be transported downwards from the main crucible of the inner liner crucible 8 along the melt transport channel 3 under the pressure of the lower graphite 5, flowing into the crystal growth crucible 10. As the lower heater 11 gradually cooled down, the isothermal surface inside the furnace, equal to the melting point of the crystal, would gradually move upwards at the same speed as the upward speed of the lifting mechanism 9. The melt 4 in the crystal growth crucible 10 would gradually crystallize, ultimately completing the entire growth process.

[0057] To facilitate observation of the results, the entire crystal growth process is not completed. A 20mm section of melt 4 is left at the end. The inner liner crucible 8 is then quickly lifted, and the lower heater 11 and upper heater 12 are turned off at the same time. This allows the unfinished melt 4 to flow over the crystal in the crystal growth crucible 10 and solidify rapidly.

[0058] Example 2

[0059] This application provides a 3-inch cadmium zinc telluride (Cd) alloy. 0.7 Zn 0.3 A crystal growth method for Te, comprising the following steps:

[0060] S1. Assembly of the charging and crystal growth apparatus

[0061] Reference Figure 1 Place the furnace body of the holding furnace 13 on a horizontal platform, and then install the lower heater 11 and upper heater 12 inside the furnace body. Clean and dry the crystal growth crucible 10, and place it inside the furnace body. Seal and vertically install the lifting mechanism 9 and ceramic lifting seat 14 on the furnace cover of the holding furnace 13, and install the pressing graphite 5 at the lower end of the ceramic lifting seat 14. Install the heat-conducting graphite ring 6 and the heat-insulating ring 7 on the outside of the melt transfer channel 3 of the inner liner crucible 8, and load the crystal growth raw material into the crucible body. Insert the pressing graphite 5 into the crucible body, and connect the lower end of the lifting mechanism 9 to the flange at the top of the crucible body. Insert the inner liner crucible 8 into the crystal growth crucible 10, and tighten the furnace cover and furnace body. Evacuate the vacuum inside the holding furnace to 0 Pa, and introduce nitrogen until the standard atmospheric pressure is reached. Ensure that all components are coaxial.

[0062] S2, Crystal growth

[0063] Temperature control programs for the lower heater 11 and upper heater 12 were set, and the furnace was started to heat up. After 72 hours of heating, the target temperature of the lower heater 11 was 1160℃, and the target temperature of the upper heater 12 was 1180℃. At this time, the crystal growth material in the inner liner crucible 8 would be fully melted at high temperature, becoming melt 4. The temperature control program of the lower heater 11 was then modified so that the temperature would be reduced to 1000℃ after 50 hours, with the entire process being a uniform cooling rate. At the same time, the lifting mechanism 9 was activated, allowing it to rise at a uniform speed of 2 mm / h. During this process, melt 4 would be transported downwards from the main crucible of the inner liner crucible 8 along the melt transport channel 3 under the pressure of the lower graphite 5, flowing into the crystal growth crucible 10. As the lower heater 11 gradually cooled down, the isothermal surface inside the furnace, equal to the melting point of the crystal, would gradually move upwards at the same speed as the upward speed of the lifting mechanism 9. The melt 4 in the crystal growth crucible 10 would gradually crystallize, ultimately completing the entire growth process.

[0064] To facilitate observation of the results, the entire crystal growth process is not completed. A 20mm section of melt 4 is left at the end. The inner liner crucible 8 is then quickly lifted, and the lower heater 11 and upper heater 12 are turned off at the same time. This allows the unfinished melt 4 to flow over the crystal in the crystal growth crucible 10 and solidify rapidly.

[0065] Comparative Example 1

[0066] This comparative example provides a 2-inch cadmium zinc telluride (Cd) 0.7 Zn 0.3 A crystal growth method for Te, comprising the following steps:

[0067] S1. Assembly of the charging and crystal growth apparatus

[0068] Reference Figure 2Place the furnace body of the holding furnace 13 on a horizontal platform, and then install the lower heater 11 and upper heater 12 inside the furnace body. Clean and dry the crystal growth crucible 10, load the crystal growth raw material into the crystal growth crucible 10, and then seal the tail of the crystal growth crucible 10 with a quartz plug. Tighten the furnace lid and furnace body, evacuate the vacuum inside the holding furnace to 0 Pa, and then introduce nitrogen gas until the pressure reaches standard atmospheric pressure. Ensure that all components are coaxial.

[0069] S2, Crystal growth

[0070] Temperature control programs for the lower heater 11 and upper heater 12 were set, and the furnace was started to heat up. After 72 hours of heating, the target temperature for the lower heater 11 was 1160℃, and the target temperature for the upper heater 12 was 1180℃. At this point, the crystal growth material in the crystal growth crucible 10 would fully melt at the high temperature, becoming melt 4. The temperature control program for the lower heater 11 was then modified so that the temperature would decrease to 1000℃ after 50 hours, with the entire process involving uniform cooling. As the lower heater 11 gradually cooled down, the isothermal surface within the furnace, equal to the crystal melting point, would gradually move upwards, and the melt 4 in the crystal growth crucible 10 would gradually crystallize, ultimately completing the entire growth process.

[0071] To facilitate observation of the results, the entire crystal growth process is not completed. The last 20mm of melt 4 is left ungrown, and the lower heater 11 and the upper heater 12 are turned off to allow the ungrown melt 4 to solidify rapidly.

[0072] Comparative Example 2

[0073] This application provides a comparative example of a 3-inch cadmium zinc telluride (Cd) alloy. 0.7 Zn 0.3 A crystal growth method for Te, comprising the following steps:

[0074] S1. Assembly of the charging and crystal growth apparatus

[0075] Reference Figure 2 Place the furnace body of the holding furnace 13 on a horizontal platform, and then install the lower heater 11 and upper heater 12 inside the furnace body. Clean and dry the crystal growth crucible 10, load the crystal growth raw material into the crystal growth crucible 10, and then seal the tail of the crystal growth crucible 10 with a quartz plug. Tighten the furnace lid and furnace body, evacuate the vacuum inside the holding furnace to 0 Pa, and then introduce nitrogen gas until the pressure reaches standard atmospheric pressure. Ensure that all components are coaxial.

[0076] S2, Crystal growth

[0077] Temperature control programs for the lower heater 11 and upper heater 12 were set, and the furnace was started to heat up. After 72 hours of heating, the target temperature for the lower heater 11 was 1160℃, and the target temperature for the upper heater 12 was 1180℃. At this point, the crystal growth material in the crystal growth crucible 10 would fully melt at the high temperature, becoming melt 4. The temperature control program for the lower heater 11 was then modified so that the temperature would decrease to 1000℃ after 50 hours, with the entire process involving uniform cooling. As the lower heater 11 gradually cooled down, the isothermal surface within the furnace, equal to the crystal melting point, would gradually move upwards, and the melt 4 in the crystal growth crucible 10 would gradually crystallize, ultimately completing the entire growth process.

[0078] To facilitate observation of the results, the entire crystal growth process is not completed. The last 20mm of melt 4 is left ungrown, and the lower heater 11 and the upper heater 12 are turned off to allow the ungrown melt 4 to solidify rapidly.

[0079] To verify the effectiveness of the invention, the following tests were also conducted.

[0080] 1. Take out the crystals from Examples 1-2 and Comparative Examples 1-2, and cut the crystals along their length, with the cutting surface perpendicular to the crystal axis. Cut the upper half along the axis. Since a 20mm high section of melt 4 was left ungrown, after rapid solidification, melt 4 will become many small, disordered flower-like crystals, while the crystal below, having undergone crystal growth, will be a large, blocky crystal. Therefore, there will be a clear interface between these two parts. After cutting the crystal along the axis, the solid-liquid interface can be clearly seen.

[0081] Figure 3 (a), (b), (c), and (d) correspond to the results of Example 1, Comparative Example 1, Example 2, and Comparative Example 2, respectively. From Figure 3 It can be seen that the solid-liquid interface of Examples 1-2 is relatively flat, while the solid-liquid interface of Comparative Examples 1-2 is obviously concave.

[0082] 2. Take out the crystals of Examples 1-2 and Comparative Examples 1-2, cut the crystals along the length direction, with the cut surface perpendicular to the crystal axis, and observe the grain condition of the segmented cut surface.

[0083] Figure 4 (a), (b), (c), and (d) correspond to the results of Example 1, Comparative Example 1, Example 2, and Comparative Example 2, respectively. From Figure 4 It can be seen that the interface grains of Examples 1-2 are better, with no polycrystalline or grain boundary observed, and the entire crystal is a single crystal, while the interface of Comparative Examples 1-2 has two or more grains.

[0084] The results of Examples 1-2 and Comparative Examples 1-2 show that the 2-inch and 3-inch cadmium zinc telluride crystals prepared by using the technical solution of the present invention have a better smooth solid-liquid interface, can grow large-size single crystals, and the grain quality is significantly improved.

[0085] In summary, the crystal growth apparatus designed in this invention can significantly reduce the impact of the melt on the crystal growth process, achieving synergistic optimization of growth quality and production efficiency. This solution offers a systematic innovation from two dimensions: melt control and crystal growth, providing a novel approach to solving industry challenges.

[0086] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the scope of the technology disclosed in the present invention, and such modifications or substitutions should all be covered within the scope of protection of the present invention.

Claims

1. A crystal growth device with crystal and melt separation, comprising: a heat-insulating furnace, a heater, a crystal growth crucible, an inner-lining crucible, a pulling mechanism, a ceramic pulling seat, a lower pressing graphite, a heat-conducting graphite ring, and a heat-insulating ring; the heat-insulating furnace comprises a furnace body and a furnace cover, wherein a limiting groove is coaxially arranged on the inner bottom of the furnace body, and the ceramic pulling seat is coaxially and sealingly arranged on the furnace cover; the crystal growth crucible is coaxially arranged in the furnace body, and the bottom size of the crystal growth crucible is adapted to the limiting groove; the inner-lining crucible comprises a crucible bottom plate, a melt transmission channel, and a crucible main body which are coaxially and continuously arranged in the crystal growth crucible, and the diameter of the crucible bottom plate is equal to the outer diameter of the crucible main body; the height of the inner-lining crucible is not less than the height of the crystal growth crucible, and the inner diameter of the crystal growth crucible is 0.1-0.5 mm larger than the outer diameter of the crucible main body; the top of the crucible main body is provided with a flange; the bottom surface of the crucible bottom plate forms a crystal growth space with the crystal growth crucible; the diameter of the melt transmission channel is 5-10 mm, and the outer peripheral surface of the melt transmission channel, the inner peripheral surface of the crystal growth crucible, the bottom surface of the crucible main body, and the top surface of the crucible bottom plate jointly form an installation cavity which is filled with the heat-conducting graphite ring and the heat-insulating ring from bottom to top; the heat-conducting graphite ring and the heat-insulating ring are designed in a split structure; the heater is coaxially arranged between the crystal growth crucible and the furnace body; the pulling mechanism is sealingly and vertically arranged on the furnace cover, and comprises a lifting assembly and a pulling assembly; the lifting assembly is connected to the upper end of the pulling assembly, the pulling assembly is provided with a bellows near the furnace cover, and the lower end of the pulling assembly is connected to the flange on the top of the crucible main body; the lower pressing graphite is coaxially arranged at the lower end of the ceramic pulling seat and in the crucible main body; the inner diameter of the crucible main body is 0.1-0.5 mm larger than the outer diameter of the lower pressing graphite; during crystal growth, the bottom surface of the lower pressing graphite is in contact with the melt in the crucible main body; under the action of the pulling mechanism, the inner-lining crucible can move up and down in the crystal growth crucible, so as to adjust the size of the crystal growth space; while the pulling mechanism pulls the inner-lining crucible upward, the lower pressing graphite can press the melt in the crucible main body downward through the melt transmission channel and into the crystal growth space; during crystal growth, the melt in the crystal growth space is controlled to be 3-5 mm. 2.The crystal growth device with crystal and melt separation according to claim 1, wherein: the thickness dc of the heat-conducting graphite ring and the inner diameter Dc of the crystal growth crucible satisfy the following condition: Dc / 4≤dc≤Dc / 2; and the thickness di of the heat-insulating ring and the thickness dc of the heat-conducting graphite ring satisfy the following condition: 2dc≤di≤5dc. 3.The crystal growth device with crystal and melt separation according to claim 1 or 2, wherein: the heat-insulating ring is prepared by filling alumina heat-insulating fiber cotton in a hollow quartz block, vacuumizing and sealing, and grinding the outer surface. 4.The crystal growth device with crystal and melt separation according to claim 3, wherein: the heater is a segmented heater comprising an upper heater and a lower heater. 5.The crystal growth device with crystal and melt separation according to claim 4, wherein: the material of the pulling assembly is alumina ceramic. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 6. The crystal growth apparatus for separating crystals from melt according to claim 5, wherein: the material of the crystal growing crucible is high-purity quartz, and the inner wall of the crystal growing crucible is coated with carbon film.

7. The crystal growth apparatus for separating crystals from melt according to claim 6, wherein: the heat-conducting graphite ring and the heat-insulating ring are both split into two sub-structures along the axis, and are combined by splicing.

8. The crystal growth apparatus for separating crystals from melt according to claim 1, wherein: the height of the inner lining crucible is 20-50 cm greater than the height of the crystal growing crucible.

9. The crystal growth apparatus for separating crystals from melt according to claim 1, wherein: the thermal conductivity of the heat-insulating ring is 0.02-0.2 W / (m·K). The method comprises the following steps: S1. loading the crystal growing raw material into the inner lining crucible, and installing each component of the crystal growth apparatus in place; S2. vacuumizing the inner lining crucible to 0 Pa, introducing nitrogen gas until the standard atmospheric pressure, and then adjusting the temperature of the heater to melt the crystal growing raw material into melt; S3. using the pulling mechanism to pull the inner lining crucible, pressing the graphite downward relative to the crucible body, and adjusting the temperature of the heater to grow the crystal until the crystal growing is completed. ​ 10. A method of growing a crystal using a crystal growth apparatus in which the crystal and melt are separated as claimed in any one of claims 1 to 9, characterised in that, ​ ​ ​ ​

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