Laser floating region device and single crystal growth method

Abstract

The invention discloses a laser floating region device and a single crystal growth method, and belongs to the technical field of single crystal preparation. The device comprises a laser floating area furnace, a clamping assembly and a core double-heat-source assembly, the laser floating area furnace forms a furnace body through a quartz cylinder and an external heat preservation assembly, and a furnace cavity is formed in the laser floating area furnace; the clamping assembly comprises a first clamping rod and a second clamping rod which are respectively used for clamping a polycrystal bar and a seed crystal; the double-heat-source assembly comprises a laser heater used for local heating to form a melting zone and a resistance heating assembly arranged around the quartz cylinder and used for providing uniform basic temperature. The furnace body is provided with a plurality of elliptical heating through holes for laser penetration, and the resistance heating assembly comprises a first resistance heating wire and a second resistance heating wire which are arranged in different regions; and infrared temperature measurement and CCD monitoring are integrated to realize closed-loop control. According to the method based on the device, high-quality single crystal growth is achieved through the steps of vacuumizing inflation, double-heat-source cooperative preheating and melting, dynamic power regulation and control, crystal growth, in-situ annealing and the like, and thermal stress and crystal defects are effectively reduced.

Description

Technical Field

[0001] This invention relates to the field of single crystal preparation technology, and in particular to laser floating zone devices and single crystal growth methods. Background Technology

[0002] Single-crystal materials exhibit superior physicochemical properties not found in polycrystalline and amorphous materials due to the long-range, periodic arrangement of their internal atoms or molecules in space. These properties include high carrier mobility, excellent thermal stability, uniform optical properties, and high mechanical strength. These characteristics make single-crystal materials play an irreplaceable role in high-tech fields, with widespread applications in next-generation electronic power devices, high-sensitivity photodetectors, solid-state lasers, semiconductor lighting, and energy catalysis and conversion, among other cutting-edge areas.

[0003] To obtain high-quality single-crystal materials, various crystal growth techniques have emerged. Among them, the floating zone method, due to its unique crucible-free growth characteristics, has become one of the mainstream techniques for preparing high-melting-point, high-purity, and especially chemically active refractory single-crystal materials (such as oxides, silicates, and intermetallic compounds). This method melts a specific area of ​​a polycrystalline rod through localized heating, forming a suspended molten zone maintained by surface tension. By moving the heating zone or the rod, the molten zone is directionally solidified from the seed crystal, ultimately achieving continuous growth of the single crystal. The crucible-free design fundamentally avoids contamination of the melt by the container material, making it possible to obtain crystals of extremely high purity. However, with the increasing demands for single-crystal quality, traditional floating zone heating methods (such as halogen lamps and high-frequency induction heating) have shown limitations in certain applications. The laser floating zone method, as an advanced floating zone technology, has received widespread attention in recent years. It uses one or more high-energy-density laser beams as a heat source to non-contactly irradiate and heat polycrystalline rods. Compared with conventional heating methods, laser heating has outstanding advantages such as extremely high energy density, precise control of the heating area, fast thermal response, and high spatial resolution. However, while the laser floating zone method shows great potential, its inherent technical bottlenecks are becoming increasingly prominent: due to the highly concentrated laser energy, the heat input area is very limited, resulting in extremely high radial and axial temperature gradients (typically greater than 100℃ / mm) in and around the molten zone. This steep temperature distribution is the main source of stress during crystal growth. During crystal cooling, the huge thermal stress can easily cause crystal cracking, seriously affecting the integrity of the crystal and the yield. Moreover, the continuous irradiation of the high-power laser beam not only acts on the rod but also causes thermal load and potential optical damage to components such as the furnace inner wall and observation window. Summary of the Invention

[0004] The purpose of this invention is to provide a laser floating zone device and a single crystal growth method to solve the problems in the background art and achieve high-efficiency, high-quality single crystal growth.

[0005] To achieve the above objectives, the present invention provides a laser floating zone device, including a laser floating zone furnace, a clamping assembly, and a dual heat source assembly; The laser floating zone furnace is a furnace body consisting of a quartz cylinder and a heat insulation component disposed outside the quartz cylinder, with a furnace cavity formed inside the quartz cylinder; The clamping assembly is disposed in the furnace cavity, and the clamping assembly includes a first clamping rod for clamping the polycrystalline rod and a second clamping rod for clamping the seed crystal. The dual heat source assembly includes a laser heater for heating the polycrystalline rod and a resistance heating assembly for providing the base temperature. The laser floating zone furnace has a heating through hole, the laser heater is located at one end of the heating through hole, and the resistance heating assembly is located on the outside of the quartz cylinder.

[0006] Preferably, the resistance heating assembly includes a first resistance heating wire and a second resistance heating wire corresponding to the polycrystalline rod region and the seed crystal region, respectively, and the heat field generated by the first resistance heating wire and the second resistance heating wire uniformly covers the length of the polycrystalline rod and the seed crystal.

[0007] Preferably, the resistance heating component is a platinum-rhodium alloy wire, an iron-chromium-aluminum alloy wire, a nickel-chromium alloy wire, a silicon molybdenum rod heating element, or a silicon carbide rod heating element. The wavelength of the laser heater is 532nm, 808nm, 940nm, 1064nm or 1080nm.

[0008] Preferably, the laser floating area device further includes a protective component made of high-temperature resistant ceramic composite material for receiving the laser beam, the protective component being disposed at the other end of the heating through hole.

[0009] Preferably, the heating through hole has an elliptical opening structure with a major axis dimension of 10-50mm and a minor axis dimension of 5-20mm. The number of heating through holes is greater than 2, and the preset angle between each heating through hole is 60°, 72°, 90° or 120°.

[0010] Preferably, the insulation component includes a first insulation layer, a second insulation layer, and a third insulation layer. The first insulation layer is disposed on the outside of the quartz cylinder on which the resistance heating component is disposed. The second and third insulation layers are disposed above and below the first insulation layer, respectively. The first insulation layer is made of solid felt or soft felt. The second and third insulation layers are made of solid felt with a thickness of 20-200 mm. The soft felt is laid in layers with a single layer thickness of 2-15 mm.

[0011] Preferably, the material of the thermal insulation component is one or more of the following: alumina fiber, aluminum silicate fiber, zirconium oxide, magnesium oxide, high-purity graphite soft or hard felt, mullite, boron nitride, or porous silica.

[0012] Preferably, the laser floating zone device further includes an infrared thermometer for monitoring the temperature during the crystal growth process and a CCD monitor for monitoring images of the crystal growth process. The outer wall of the laser floating zone furnace is provided with an infrared device access hole and an observation device access hole for installing the infrared thermometer and the CCD monitor. Both the infrared device access hole and the observation device access hole adopt a circular opening structure with a diameter of 10-50mm.

[0013] Preferably, the height of the laser floating zone furnace is 100-600mm, and the inner diameter of the furnace is 50-400mm; the wall thickness of the quartz tube is 1-10mm, and the length of the quartz tube is 100-600mm.

[0014] The present invention also provides a single crystal growth method based on the above-mentioned laser floating region device, specifically including the following steps: Step 1: Vacuum the furnace cavity of the laser floating zone furnace, and then fill it with argon, oxygen, nitrogen or argon-oxygen mixture to maintain the furnace pressure at 0-2.0 atm. Step 2: Activate the resistance heating component to preheat the polycrystalline rod and seed crystal to 700-1600℃; Step 3: Turn on the laser heater to melt the end of the polycrystalline rod to form a molten zone, and simultaneously adjust the power of the resistance heating component to ensure that the temperature gradient around the molten zone is ≤50℃ / mm; Step 4: Drive the clamping assembly to move the polycrystalline rod and the seed crystal relative to each other and rotate in opposite directions to maintain the stability of the molten zone. At the same time, monitor the crystal growth process in real time, dynamically adjust the power of the laser heater and the resistance heating assembly, and control the temperature gradient at 10-30℃ / mm. Step 5: After crystal growth is complete, turn off the laser heater and keep the resistance heating component cooling down to room temperature at a rate of 5-10℃ / min. Then, anneal the crystal in situ in an inert atmosphere at a temperature of 1000-1400℃ for 1-5 hours.

[0015] Therefore, the laser floating zone device and single crystal growth method provided by this invention provide a uniform background temperature through a resistance heating component, and the laser heater locally melts the polycrystalline rod. The power of both is dynamically coupled to reduce the temperature gradient around the melting zone. Combined with a multi-layer insulation structure, quartz cylinder, and protective components, heat loss is reduced and equipment lifespan is extended. Infrared temperature measurement and CCD monitoring are integrated to achieve fully closed-loop control of the growth process. Based on the laser floating zone device provided above, the single crystal growth method significantly improves the efficiency and crystal quality of single crystal growth. This device and method are suitable for the growth of refractory single crystal materials, reducing defects and stress, and have broad industrial application prospects.

[0016] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0017] Figure 1 This is a cross-sectional view of the laser floating area device provided in an embodiment of the present invention; Figure 2 This is a cross-sectional view along AA of the laser floating area device provided in the embodiment of the present invention; Figure 3 This is a simulation result of the internal melt thermal field and crystal stress of the laser floating zone device without the resistance heating component; Figure 4 This is a simulation result of the melt thermal field and crystal stress inside the resistance heating component of the laser floating zone device; Figure label: 1. Laser floating zone furnace; 2. Clamping assembly; 3. Polycrystalline rod; 4. Seed crystal; 5. Dual heat source assembly; 6. Insulation assembly; 7. Quartz cylinder; 8. Protective component; 101. Heating through hole; 102. Infrared device access hole; 103. Observation device access hole; 21. First clamping rod; 22. Second clamping rod; 51. Laser heater; 52. Resistance heating assembly; 61. First insulation layer; 62. Second insulation layer; 63. Third insulation layer. Detailed Implementation

[0018] like Figure 1 and Figure 2As shown, this invention provides a laser floating zone device comprising a laser floating zone furnace 1, a clamping assembly 2, and a dual heat source assembly 5. The laser floating zone furnace 1 is a furnace body composed of a quartz cylinder 7 and a heat-insulating assembly 6 disposed outside the quartz cylinder 7, with a furnace cavity formed inside the quartz cylinder 7. The furnace body height of the laser floating zone furnace 1 is preferably 100-600 mm, and the inner diameter of the furnace body is preferably 50-400 mm. This size range can meet the needs of crystal growth of different sizes, while also considering the compactness of the furnace structure and the uniformity of the thermal field. The wall thickness of the quartz cylinder 7 is preferably 1-10 mm, and the tube length is preferably 100-600 mm. This design ensures the mechanical strength of the quartz cylinder 7 while also considering thermal conductivity and optical transmittance, providing a good process environment for crystal growth.

[0019] The clamping assembly 2 is disposed in the furnace cavity. The clamping assembly 2 includes a first clamping rod 21 for clamping the polycrystalline rod 3 and a second clamping rod 22 for clamping the seed crystal 4, and the polycrystalline rod 3 can abut against the seed crystal 4. Preferably, the polycrystalline rod 3 is prepared as a high-density preform with a relative density greater than 95%, and its shape includes, but is not limited to, strip-shaped, elliptical, or cylindrical. By optimizing the geometry and density of the preform, the melting effect of laser heating can be significantly enhanced, effectively reducing volume shrinkage and thermal stress concentration.

[0020] The dual heat source assembly 5 includes a laser heater 51 for heating the polycrystalline rod 3 and a resistance heating assembly 52 for providing a base temperature. The laser floating zone furnace 1 has at least two heating through-holes 101. The laser heater 51 is located at one end of each heating through-hole 101, and the resistance heating assembly 52 is located outside the quartz cylinder 7. The heating through-holes 101 correspond to the areas of the polycrystalline rod 3 to be heated, and the laser beam emitted by the laser heater 51 can penetrate the heating through-holes 101. The resistance heating assembly 52 and the laser heater 51 work together to heat the polycrystalline rod 3 during crystal growth to form a molten zone.

[0021] In this invention, the laser heater 51 is a fiber laser, an all-solid-state laser, a CO2 laser, or a semiconductor laser, and the wavelength of the laser heater 51 is 532nm, 808nm, 940nm, 1064nm, or 1080nm. The heating through-hole 101 is preferably an elliptical opening structure with a major axis dimension of 10-50mm and a minor axis dimension of 5-20mm. This geometric configuration can optimize heat flow symmetry and suppress local thermal stress concentration. However, those skilled in the art can choose other opening shapes, such as circular or rectangular, according to actual process requirements.

[0022] The number of heating through-holes 101 matches the number of laser heaters 51, and the specific number can be adjusted according to the actual process. By setting multiple laser heaters 51 and corresponding heating through-holes 101, multi-angle synchronous irradiation of the polycrystalline rod 3 to be heated can be achieved, significantly improving heating uniformity and energy utilization. The laser beam forms a surrounding thermal field distribution through the heating through-holes 101, effectively avoiding the local temperature gradient caused by traditional single-point or double-point heating, thereby reducing crystal cracking caused by thermal stress concentration during crystal growth. The preset angle between each heating through-hole 101 can be adjusted according to the actual process, preferably 60°, 72°, 90° or 120°.

[0023] In this invention, the resistance heating assembly 52 includes a first resistance heating wire and a second resistance heating wire. The first resistance heating wire is disposed on the outer wall of the quartz cylinder 7 on the side holding the polycrystalline rod 3, and the second resistance heating wire is disposed on the outer wall of the quartz cylinder 7 on the side holding the seed crystal 4. The heat field generated by the first and second resistance heating wires uniformly covers the length of the polycrystalline rod 3 and the seed crystal 4. The resistance heating assembly 52 is made of platinum-rhodium alloy wire, iron-chromium-aluminum alloy wire, nickel-chromium alloy wire, silicon-molybdenum rod heating element, or silicon-carbon rod heating element. The operating temperature of the resistance heating assembly 52 is 50-2000℃, and its length is 10-100mm.

[0024] In this invention, the thermal insulation component 6 includes a first thermal insulation layer 61, a second thermal insulation layer 62, and a third thermal insulation layer 63. The first thermal insulation layer 61 is disposed on the outside of the quartz cylinder 7, which has the resistance heating component 52 located on its outer side. The second and third thermal insulation layers 62 and 63 are respectively disposed above and below the first thermal insulation layer 61. The first thermal insulation layer 61 is made of solid felt or soft felt, while the second and third thermal insulation layers 62 and 63 are made of solid felt with a thickness of 20-200 mm. The soft felt is laid in layers with a single layer thickness of 2-15 mm. This multi-layer thermal insulation structure effectively reduces heat loss and improves thermal stability. The insulation component 6 is made of one or more of the following materials: alumina fiber (Al2O3), aluminosilicate fiber (Al2O3-SiO2), zirconium oxide (ZrO2), magnesium oxide (MgO), high-purity graphite soft or hard felt, mullite (3Al2O3·2SiO2), boron nitride (BN), or porous silica (SiO2). These materials possess excellent high-temperature resistance, low thermal conductivity, and good thermal stability, effectively reducing heat loss and improving the thermal uniformity of the crystal growth furnace.

[0025] The resistance heating component 52, combined with the first insulation layer 61, forms a highly efficient thermal field coupling, ensuring temperature field uniformity and reducing axial heat loss. The top second insulation layer 62 and the bottom third insulation layer 63 constitute a closed thermal barrier, effectively suppressing convective heat dissipation and maintaining longitudinal temperature gradient stability. This structural design effectively controls axial temperature fluctuations, resulting in a more stable molten zone morphology. The quartz cylinder 7 has a high melting point and thermal stability, capable of withstanding chemical reactions and thermal expansion at high temperatures, ensuring the stability of the crystal growth process. Simultaneously, it effectively isolates contaminants, protecting the crystal growth process from environmental pollution.

[0026] In this invention, the laser floating zone device also includes a protective component 8 made of high-temperature resistant ceramic composite material for receiving the laser beam. The protective component 8 is located at the other end of the heating through-hole 101. The protective component 8 acts as a physical barrier to precisely receive the laser beam penetrating the molten zone and prevents molten material from splashing and high-temperature diffusion, reducing the risk of thermal damage to the inner wall of the furnace and extending the service life of the laser floating zone device. The protective component 8 has a certain thickness and is preferably cylindrical, frustum-shaped, or arc-shaped. Furthermore, the use of high-temperature resistant ceramic composite material ensures structural stability under long-term high-temperature conditions.

[0027] In this invention, the laser floating zone device also includes an infrared thermometer. An infrared device access hole 102 is provided on the outer wall of the laser floating zone furnace 1. The infrared thermometer is disposed inside the infrared device access hole 102 and is configured to monitor the temperature during the crystal growth process. The infrared thermometer achieves non-contact real-time temperature monitoring through the infrared device access hole 102, accurately capturing the dynamic thermal field distribution at the crystal growth interface. The infrared device access hole 102 adopts a circular opening structure, and its diameter is preferably 10-50 mm.

[0028] In this invention, the laser floating zone furnace 1 also includes a CCD monitor. The laser floating zone furnace 1 is provided with an observation device access hole 103, and the CCD monitor is disposed inside the observation device access hole 103. The CCD monitor is configured to receive and monitor images of the crystal growth process. The CCD monitor of the laser floating zone furnace 1 captures high-definition images of the crystal growth interface in real time through the observation device access hole 103, which can effectively monitor the solid-liquid interface morphology, dynamic changes in the melt zone, and crystal growth. Combined with image processing algorithms, it can automatically identify diameter deviations and interface fluctuations, providing visual control assurance for high-quality crystal growth. The observation device access hole 103 adopts a circular opening structure, and its diameter is preferably 10-50 mm.

[0029] The laser floating zone device provided by this invention also includes a vacuum component, which is configured to evacuate the furnace cavity of the laser floating zone furnace 1. The vacuum component of the laser floating zone device can effectively eliminate the interference of gaseous impurities on the stability of the molten zone, suppress oxidation reactions with residual gases under high-temperature molten conditions, and significantly improve crystal growth quality. The laser floating zone furnace 1 has a connecting hole on its furnace body, which can be connected to a gas pressurizer to achieve atmosphere control.

[0030] Based on the above structure, firstly, the seed crystal 4 and the polycrystalline rod 3 are fixed inside the laser floating zone furnace 1 by the clamping assembly 2, ensuring that the polycrystalline rod 3 and the seed crystal 4 are in close contact. The resistance heating assembly 52 is then activated to provide a stable background temperature and preheat the entire growth environment. Subsequently, the laser heater 51 heats the contact area between the polycrystalline rod 3 and the seed crystal 4, forming a localized melting zone. During crystal growth, the resistance heating assembly 52 and the laser heater 51 work together to ensure a uniform and stable temperature in the melting zone, promoting directional crystal growth along the direction of the seed crystal 4. By precisely controlling the laser power and the heating area, thermal stress can be effectively reduced, and crystal quality improved. This device combines the high precision of laser heating with the stability of resistance heating, significantly improving the efficiency and quality of single crystal growth, and is suitable for the growth of refractory single crystal materials.

[0031] In this invention, the laser heater 51 can perform localized high-energy-density focused heating on the polycrystalline rod 3, achieving rapid melting and forming a stable molten zone. Simultaneously, the background temperature provided by the resistance heating component 52 significantly reduces the impact of laser power fluctuations on the crystal growth interface, minimizing thermal stress defects. This dual-heat-source coupled heating mode results in a smoother axial temperature distribution in the molten zone, facilitating the directional growth of single crystals along the seed crystal 4, ultimately yielding high-quality single crystals with low dislocation density and uniform composition. Furthermore, this dual-heat-source coupled heating design enhances the flexibility of thermal field control in the laser floating zone furnace 1. By adjusting the power ratio of different laser heaters 51, the molten zone morphology can be precisely controlled, improving crystal growth quality and yield. The modular structure of the laser heater 51 facilitates maintenance and expansion, making it suitable for the efficient preparation of various specifications of refractory crystal materials.

[0032] The present invention also provides a single crystal growth method based on the above-mentioned laser floating region device, specifically including the following steps: Step 1: Evacuate the furnace cavity of laser floating zone furnace 1 to a vacuum level of 1×10⁻⁶. -7 -1×10 -1 Pa, then argon, oxygen, nitrogen or argon-oxygen mixture is introduced to maintain the furnace pressure at 0-2.0 atm, ensuring a pure growth environment.

[0033] Step 2: Start the resistance heating component 52 to preheat the polycrystalline rod 3 and seed crystal 4 to 700-1600℃, providing a background temperature for single crystal growth.

[0034] Step 3: Turn on the laser heater 51 to melt the end of the polycrystalline rod 3 to form a molten zone. Simultaneously adjust the power of the resistance heating component 52 to ensure that the temperature gradient around the molten zone is ≤50℃ / mm.

[0035] Step 4: Drive the clamping assembly 2 to move the polycrystalline rod 3 and seed crystal 4 in the same direction at a speed of 0.1-5 mm / h and rotate in opposite directions at a speed of 1-30 rpm. This movement maintains the stability of the molten zone. At the same time, the crystal growth process is monitored in real time, and the power of the laser heater 51 and the resistance heating assembly 52 is dynamically adjusted to control the temperature gradient at 10-30℃ / mm.

[0036] Step 5: After crystal growth is completed, turn off the laser heater 51 and keep the resistance heating component 52 cooling down to room temperature at a rate of 5-10℃ / min. Then, anneal the crystal in situ in an inert atmosphere at a temperature of 1000-1400℃ for 1-5 hours to reduce residual stress in the crystal.

[0037] This laser-assisted floating zone single crystal growth method, through the coordinated control of the laser heater 51 and the resistance heating component 52, effectively suppresses high-temperature crystal decomposition and component volatilization under argon, oxygen, nitrogen, or argon-oxygen mixture and 0-2.0 atm pressure environment. Combined with dynamic power adjustment, the temperature gradient of the melting zone is precisely controlled at 10-30℃ / mm, significantly reducing the dislocation density of the crystal and improving the crystallization quality. The stepped cooling and in-situ annealing process further eliminates thermal stress, improving the integrity of the single crystal. The combination of laser local melting and resistance-assisted heating reduces energy consumption while achieving stable control of the melting zone, increasing the crystal growth rate to 5mm / h and expanding the diameter to over 50mm.

[0038] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention should be considered equivalent substitutions and are included within the protection scope of the present invention. Furthermore, it should be understood that after reading the contents of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims and are all within the protection scope of the present invention.

[0039] In this document, the term "embodiment" means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The term "embodiment" appearing in various places throughout the specification does not necessarily refer to the same embodiment, nor does it specifically limit its independence or connection with other embodiments. In principle, in this application, as long as there are no technical contradictions or conflicts, the technical features mentioned in each embodiment can be combined in any way to form corresponding implementable technical solutions.

[0040] Unless otherwise defined, the technical terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the use of related terms herein is merely for the purpose of describing particular embodiments and is not intended to limit this application.

[0041] Unless otherwise specified, the materials, instruments, and equipment used in this invention are all materials, instruments, and equipment routinely used by those skilled in the art, and the testing standards all use national or international standards commonly used in the field, without further explanation.

[0042] The single crystal growth method claimed in this invention will be further illustrated below through some embodiments. However, the embodiments and comparative examples are for explaining the implementation of the invention and do not exceed the scope of the subject matter of this invention. The scope of protection of this invention is not limited by the embodiments described. Unless otherwise specified, the materials and reagents used in this invention are all available from commercially available products in the art. The testing standards used are all common national or international standards in the art, and will not be described in detail here.

[0043] Example 1: Laser floating zone single crystal growth method applied to the growth of β-Ga2O3 crystals In this embodiment of the single crystal growth method based on a laser floating zone device, the laser floating zone furnace 1 has a furnace height of 400 mm and an inner diameter of 200 mm; the quartz cylinder 7 has a wall thickness of 5 mm and a cylinder length of 450 mm; there are three heating through holes 101, which are elliptical openings (major axis 30 mm, minor axis 15 mm) with a circumferential angle of 120°; the laser heater 51 is a fiber laser with a wavelength of 1064 nm; the resistance heating component 52 is a platinum-rhodium alloy wire with an operating temperature of 1500℃ and a length of 60 mm; the insulation component 6 is made of alumina fiber, and the first insulation layer 61 is made of alumina fiber soft felt, laid in 20 layers with a single layer thickness of 5 mm, for a total thickness of 100 mm. The second insulation layer 62 and the third insulation layer 63 are made of alumina fiber solid felt, both with a thickness of 50 mm; the protective component 8 is a cylindrical alumina ceramic component; the diameter of the infrared device access hole 102 and the observation device access hole 103 is 30 mm.

[0044] The single crystal growth method specifically includes the following steps: Step 1: Evacuate the furnace cavity of laser floating zone furnace 1 to a vacuum level of 5×10⁻⁶. -3 Pa, then high-purity argon gas (containing trace amounts of oxygen, with an oxygen partial pressure ≤0.1 atm) is introduced, and the pressure inside the furnace is maintained at 1.5 atm.

[0045] Step 2: Start the resistance heating component 52 to preheat the polycrystalline rod 3 and seed crystal 4 to 1000℃.

[0046] Step 3: Turn on the laser heater 51 to melt the end of the polycrystalline rod 3 to form a molten zone. Simultaneously adjust the power of the resistance heating component 52 to make the temperature gradient around the molten zone ≤30℃ / mm.

[0047] Step 4: Drive the polycrystalline rod 3 and seed crystal 4 to move at a low speed of 2 mm / h and rotate in opposite directions at a speed of 15 rpm. Combined with the CCD monitor to observe the molten zone morphology in real time, dynamically adjust the power of the laser heater 51 and the resistance heating component 52 to control the axial temperature gradient to 20℃ / mm.

[0048] Step 5: After crystal growth is completed, turn off the laser heater 51 and cool the resistance heating component 52 to room temperature at a rate of 10℃ / min. Then, perform in-situ annealing in an argon atmosphere (temperature 1200℃, time 3h).

[0049] Example 2: Laser floating zone single crystal growth method applied to the growth of TbYO3 crystals In this embodiment of the single crystal growth method based on a laser floating zone device, the laser floating zone furnace 1 has a furnace height of 350 mm and an inner diameter of 150 mm; the quartz cylinder 7 has a wall thickness of 4 mm and a cylinder length of 350 mm; there are 5 heating through holes 101, which are elliptical openings (major axis 25 mm, minor axis 12 mm) with a circumferential angle of 72°; the laser heater 51 is an all-solid-state laser with a wavelength of 532 nm; the resistance heating component 52 is a silicon molybdenum rod heating element with an operating temperature of 1600℃ and a length of 50 mm; the insulation component 6 is made of zirconium oxide, with the first insulation layer 61 using a zirconium oxide solid insulation board with a thickness of 80 mm, and the second and third insulation layers 62 and 63 also using zirconium oxide solid insulation boards, each with a thickness of 30 mm. The protective component 8 is a frustum-shaped alumina ceramic component; the diameters of the infrared device access hole 102 and the observation device access hole 103 are both 30 mm.

[0050] The single crystal growth method specifically includes the following steps: Step 1: Evacuate the furnace cavity of laser floating zone furnace 1 to a vacuum level of 5×10⁻⁶. -2 Pa, then high-purity argon gas (containing trace amounts of oxygen, oxygen partial pressure ≤0.1 atm) was introduced, and the furnace pressure was maintained at 2.0 atm to suppress Tb. 3+ Oxidation.

[0051] Step 2: Start the resistance heating component 52 to preheat the polycrystalline rod 3 and seed crystal 4 to 1200℃, providing a background temperature for single crystal growth.

[0052] Step 3: Turn on the laser heater 51 to melt the end of the polycrystalline rod 3 to form a molten zone. Simultaneously adjust the power of the resistance heating component 52 to ensure that the temperature gradient around the molten zone is ≤30℃ / mm to prevent the volatilization of Tb.

[0053] Step 4: Drive the polycrystalline rod 3 and seed crystal 4 to move at a low speed of 5 mm / h and rotate in opposite directions at a speed of 20 rpm. Combined with the CCD monitor to observe the molten zone morphology in real time, dynamically adjust the power of the laser heater 51 and the resistance heating component 52 to control the axial temperature gradient to 15℃ / mm.

[0054] Step 5: After crystal growth is completed, the laser heater 51 is turned off, and the resistance heating component 52 is cooled to room temperature at a rate of 8℃ / min. Then, in-situ annealing is carried out in an argon atmosphere (temperature 1000℃, time 1h) to eliminate domain wall defects and improve magneto-optical uniformity.

[0055] Example 3: Laser floating zone single crystal growth method applied to the growth of Yb:Sc x Lu 2-x O3 crystals In this embodiment of the single crystal growth method based on a laser floating zone device, the laser floating zone furnace 1 has a furnace height of 500 mm and an inner diameter of 250 mm; the quartz cylinder 7 has a wall thickness of 6 mm and a cylinder length of 500 mm; there are three heating through holes 101, which are elliptical openings (major axis 35 mm, minor axis 18 mm) with a circumferential angle of 120°; the laser heater 51 is a semiconductor laser with a wavelength of 940 nm; the resistance heating component 52 is an iron-chromium-aluminum alloy wire with an operating temperature of 1400℃ and a length of 80 mm; the insulation component 6 is made of mullite, with the first insulation layer 61 using mullite solid heat-insulating brick with a thickness of 120 mm, and the second and third insulation layers 62 and 63 also using mullite solid heat-insulating brick with a thickness of 40 mm; the diameter of the infrared device access hole 102 and the observation device access hole 103 is 30 mm.

[0056] The single crystal growth method specifically includes the following steps: Step 1: Evacuate the furnace cavity of laser floating zone furnace 1 to 1×10⁻⁶. -3 Pa, fill with high-purity argon gas (containing 0.5-1.0% O2), maintain furnace pressure at 1.5 atm, and balance Yb. 3+ / Yb 2+ Price state.

[0057] Step 2: Start the resistance heating component 52 to preheat the polycrystalline rod 3 and seed crystal 4 to 1400℃, providing a background temperature for single crystal growth.

[0058] Step 3: Turn on the laser heater 51 to melt the end of the polycrystalline rod 3 to form a molten zone. Simultaneously adjust the power of the resistance heating component 52 to make the temperature gradient around the molten zone ≤20℃ / mm to suppress Sc / Lu component segregation.

[0059] Step 4: Drive the polycrystalline rod 3 and seed crystal 4 to move at an ultra-low speed of 0.5 mm / h and rotate in opposite directions at a rotation speed of 8 rpm. Use an infrared thermometer to monitor the molten zone temperature in real time, dynamically adjust the power of the laser heater 51 and the resistance heating component 52, and control the axial temperature gradient to 30℃ / mm to ensure Yb 3+ Doping uniformity.

[0060] Step 5: After crystal growth is completed, turn off the laser heater 51 and keep the resistance heating component 52 slowly cooling down to room temperature at a rate of 5℃ / min. Then anneal in N2-H2 mixed gas (H2 volume fraction ≤5%) (temperature 1400℃, time 5h) to eliminate color center defects and improve laser output efficiency.

[0061] Example 4: Laser floating zone single crystal growth method for growing Al2O3:Cr 3+ (Ruby) Crystal In this embodiment of the single crystal growth method based on a laser floating zone device, the laser floating zone furnace 1 has a furnace height of 300 mm and an inner diameter of 120 mm; the quartz cylinder 7 has a wall thickness of 3 mm and a cylinder length of 300 mm; there are 5 heating through holes 101, which are elliptical openings (major axis 20 mm, minor axis 10 mm) with a circumferential angle of 72°; the laser heater 51 is a CO2 laser with a wavelength of 1080 nm; the resistance heating component 52 is a silicon carbide rod heating element with an operating temperature of 1700 °C and a length of 40 mm; the insulation component 6 is made of high-purity graphite, the first insulation layer 61 is made of high-purity graphite solid hard felt with a thickness of 90 mm, and the second insulation layer 62 and the third insulation layer 63 are also made of high-purity graphite solid hard felt with a thickness of 30 mm; the diameter of the infrared device access hole 102 and the observation device access hole 103 is 30 mm.

[0062] The single crystal growth method specifically includes the following steps: Step 1: Evacuate the furnace cavity of laser floating zone furnace 1 to 8×10⁻⁶. -3 Pa, then high-purity argon gas (containing trace amounts of oxygen, oxygen partial pressure ≤0.05 atm) was introduced to maintain the furnace pressure at 1.2 atm, suppressing Cr. 3+ Oxidized to Cr 4+ .

[0063] Step 2: Start the resistance heating component 52 to preheat the polycrystalline rod 3 and seed crystal 4 to 1600℃, providing a background ambient temperature for single crystal growth.

[0064] Step 3: Turn on the laser heater 51 to melt the end of the polycrystalline rod 3 to form a molten zone; synchronously adjust the power of the resistance heating component 52 to make the temperature gradient around the molten zone ≤ 10℃ / mm.

[0065] Step 4: Drive the polycrystalline rod 3 and seed crystal 4 to move at a low speed of 1.5 mm / h and rotate in opposite directions at a rotation speed of 10 rpm. Monitor the molten zone morphology through the CCD and dynamically adjust the laser power to maintain an axial temperature gradient of 15℃ / mm.

[0066] Step 5: After crystal growth is complete, the laser heater 51 is turned off, and the resistance heating component 52 is cooled to room temperature at a rate of 5℃ / min. Then, in-situ annealing is performed in argon atmosphere (temperature 1350℃, time 5h) to eliminate residual stress and enhance Cr. 3+ Ion luminescence efficiency.

[0067] Example 5: Laser-guided floating zone single crystal growth method for growing Yb:YAG crystals In this embodiment of the single crystal growth method based on a laser floating zone device, the laser floating zone furnace 1 has a furnace height of 250 mm and an inner diameter of 100 mm; the quartz cylinder 7 has a wall thickness of 2 mm and a cylinder length of 250 mm; there are three heating through holes 101, which are elliptical openings (major axis 15 mm, minor axis 8 mm) with a circumferential angle of 120°; the laser heater 51 is a fiber laser with a wavelength of 808 nm; the resistance heating component 52 is a nickel-chromium alloy wire with an operating temperature of 1200°C and a length of 30 mm; the insulation component 6 is made of boron nitride, with the first insulation layer 61 using a boron nitride solid hot press plate with a thickness of 60 mm, and the second and third insulation layers 62 and 63 using boron nitride solid hot press plates with a thickness of 25 mm; the diameters of the infrared device access hole 102 and the observation device access hole 103 are both 30 mm.

[0068] The single crystal growth method specifically includes the following steps: Step 1: Evacuate the furnace cavity of laser floating zone furnace 1 to 1×10⁻⁶. -2 Pa, then high-purity nitrogen (containing trace amounts of oxygen, oxygen partial pressure ≤0.01 atm) was introduced to maintain the furnace pressure at 1.2 atm, suppressing Yb. 3+ Price fluctuations.

[0069] Step 2: Start the resistance heating component 52 to preheat the polycrystalline rod 3 and seed crystal 4 to 700°C, providing a background ambient temperature for single crystal growth.

[0070] Step 3: Turn on the laser heater 51 to melt the end of the polycrystalline rod 3 to form a molten zone; synchronously adjust the power of the resistance heating component 52 to make the temperature gradient around the molten zone ≤ 10℃ / mm.

[0071] Step 4: Drive the polycrystalline rod 3 and seed crystal 4 to move at a low speed of 3 mm / h and rotate in opposite directions at a rotation speed of 18 rpm. Monitor the molten zone morphology through the CCD and dynamically adjust the laser power to maintain an axial temperature gradient of 18℃ / mm.

[0072] Step 5: After crystal growth is completed, the laser heater 51 is turned off, and the resistance heating component 52 is cooled to room temperature at a rate of 8℃ / min. Then, in-situ annealing is carried out in nitrogen (temperature 1100℃, time 4h). Gradient cooling reduces dislocation density and optimizes crystal optical transmittance.

[0073] Comparative Example 1 The only difference between this comparative example and Example 1 is that the laser floating zone furnace 1 is not equipped with a resistance heating component 52, while the crystal growth method is the same as that in Example 1. This will not be repeated here.

[0074] Compared to the laser floating zone furnace 1 equipped with resistance heating component 52 in Example 1, the laser floating zone furnace 1 of Comparative Example 1 exhibits more drastic temperature fluctuations at the melt and crystal edges during growth, resulting in smaller crystal sizes. The large temperature gradient around the crystal leads to unfavorable thermal stress distribution, which is a key factor causing crystal cracking and severely restricts the growth of large-size single crystals. Figure 3 As shown. In Example 1, the laser floating zone furnace 1 equipped with the resistance heating component 52 can significantly reduce the temperature gradient at the crystal edge during crystal growth, improve the interface curvature during growth, and greatly reduce the thermal stress of the crystal, such as... Figure 4 As shown.

[0075] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A laser floating zone apparatus, characterized by: The laser floating zone furnace, the clamping assembly and the double heat source assembly are provided. The laser floating zone furnace is a furnace body composed of a quartz cylinder and a heat preservation assembly arranged outside the quartz cylinder, and a furnace cavity is formed inside the quartz cylinder. The clamping assembly is arranged in the furnace cavity, and the clamping assembly comprises a first clamping rod for clamping a polycrystalline rod and a second clamping rod for clamping a seed crystal. The double heat source assembly comprises a laser heater for heating the polycrystalline rod and a resistance heating assembly for providing a basic temperature, and a heating through hole is formed in the laser floating zone furnace, the laser heater is arranged at one end of the heating through hole, and the resistance heating assembly is arranged outside the quartz cylinder.

2. A laser floating zone apparatus as claimed in claim 1, wherein: The resistance heating assembly comprises a first resistance heating wire and a second resistance heating wire corresponding to the polycrystalline rod area and the seed crystal area respectively, and the heat fields generated by the first resistance heating wire and the second resistance heating wire uniformly cover the lengths of the polycrystalline rod and the seed crystal.

3. A laser floating zone apparatus as claimed in claim 1, wherein: The resistance heating assembly is a platinum-rhodium alloy wire, a ferrochrome-aluminum alloy wire, a nickel-chromium alloy wire, a silicon-molybdenum rod electric heating element or a silicon-carbon rod electric heating element. The wavelength of the laser heater is 532 nm, 808 nm, 940 nm, 1064 nm or 1080 nm.

4. A laser floating zone apparatus as claimed in claim 1, wherein: The laser floating zone device further comprises a protective piece made of high-temperature-resistant ceramic composite material for receiving a laser beam, and the protective piece is arranged at the other end of the heating through hole.

5. A laser floating zone apparatus as claimed in claim 1, wherein: The heating through hole is an elliptical opening structure, the long axis direction size is 10-50 mm, the short axis direction size is 5-20 mm, the number of the heating through holes is greater than 2, and the preset angle between each heating through hole is 60°, 72°, 90° or 120°.

6. A laser floating zone apparatus as claimed in claim 1, wherein: The heat preservation assembly comprises a first heat preservation layer, a second heat preservation layer and a third heat preservation layer, wherein the first heat preservation layer is arranged outside the quartz cylinder outside which the resistance heating assembly is arranged, the second heat preservation layer and the third heat preservation layer are arranged above and below the first heat preservation layer respectively, the first heat preservation layer is made of solid felt or soft felt, the second heat preservation layer and the third heat preservation layer are made of solid felt, the thickness of the solid felt is 20-200 mm, the soft felt is laid in a layer-by-layer manner, and the thickness of a single layer of the soft felt is 2-15 mm.

7. A laser floating zone apparatus as claimed in claim 1, wherein: The material of the heat preservation assembly is one or more of alumina fiber, aluminum silicate fiber, zirconia, magnesium oxide, high-purity graphite soft felt or hard felt, mullite, boron nitride or porous silicon oxide.

8. A laser floating zone apparatus as claimed in claim 1, wherein: The laser floating zone device further comprises an infrared temperature detector for monitoring the temperature of the crystal growth process and a CCD monitor for monitoring the image of the crystal growth process, and the outer wall of the furnace body of the laser floating zone furnace is provided with an infrared device intervention hole and an observation device intervention hole for installing the infrared temperature detector and the CCD monitor, and the infrared device intervention hole and the observation device intervention hole are both circular opening structures with a diameter of 10-50 mm.

9. A laser floating zone apparatus as claimed in claim 1, wherein: The height of the furnace body of the laser floating zone furnace is 100-600 mm, and the inner diameter of the furnace body is 50-400 mm; the wall thickness of the quartz cylinder is 1-10 mm, and the length of the quartz cylinder is 100-600 mm.

10. A method of single crystal growth, characterized by: The laser floating zone device is implemented based on any one of claims 1-9, and specifically comprises the following steps: Step one, vacuumize the furnace cavity of the laser floating zone furnace, then fill in argon, oxygen, nitrogen or argon-oxygen mixed gas, and maintain the pressure in the furnace at 0-2.0 atm; Step two, start the resistance heating assembly, and preheat the polycrystalline rod and the seed crystal to 700-1600℃; Step three, start the laser heater, melt the end of the polycrystalline rod to form a melt zone, and simultaneously adjust the power of the resistance heating assembly so that the temperature gradient outside the melt zone is ≤50℃ / mm; Step four, drive the clamping assembly to move the polycrystalline rod and the seed crystal relative to each other and rotate in opposite directions, maintain the stability of the melt zone, and simultaneously monitor the crystal growth process in real time, dynamically adjust the power of the laser heater and the resistance heating assembly, and control the temperature gradient to be 10-30℃ / mm; Step five, after the crystal growth is completed, turn off the laser heater, keep the resistance heating assembly to cool down to room temperature at a rate of 5-10℃ / min, and in situ anneal the crystal in an inert atmosphere, with the annealing temperature being 1000-1400℃ and the annealing time being 1-5h.

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