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Simulation of grain evolution in solidification of silicon on meso-scopic scale
摘要： We present a cellular automata model for computing the grain evolution during directional solidification of silicon on a meso-scopic scale. Firstly, the method is applied to test cases with different shapes of the melt/crystal interface. In a second step we compute the case of an experiment with in-situ observation of the interface shape evolution (Tandjaoui et al., 2012). Here we also include the effect of twinning. The interchanging appearance of two twins could be revisited by our calculations. The probabilities used correspond to those which were analytically derived for an undercooling of 0.6 K (Lin and Lan, 2017). This undercooling is a typical value for a groove with facets (Miller and Popescu, 2017).
关键词： Directional solidification,Cellular automata,Multicrystalline silicon,Lattice Boltzmann methods
更新于2025-09-23 15:23:52
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The influence of Marangoni effect on the growth quality of multi-crystalline silicon during the vacuum directional solidification process
摘要： A multi-field coupling model of heat-flow-thermal stress was established to investigate the influence of Marangoni effect on the growth quality of multi-crystalline silicon (mc-Si) during the vacuum directional solidification (VDS) process. The simulation results showed that the Marangoni effect has a significant effect on the distribution of temperature and thermal stress as well during the VDS process due to the increased velocity of melts. The enhanced flow incurred more homogeneous temperature distribution of silicon melts and reduced radial temperature gradient, which then leads to the flatter solid/liquid (s/l) interface. However, as temperature gradient of the crystal increased, thermal stress of the silicon ingot was strengthened as a result. The growth quality of crystal was more desirable when adopting a pulling-down rate of 10 μm/s, in which case the (111) surface was advantageous throughout the entire crystal growth process by XRD detection. Finally, the reliability of the numerical simulation result was verified by the experiment.
关键词： Multi-crystalline,Melt flow,Vacuum directional solidification,Numerical simulation,Marangoni effect
更新于2025-09-23 15:22:29
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Enhancement of dopant solubility in compound semiconductors during crystal growth
摘要： Doping of semiconductors is a process of intentionally incorporating impurity into the materials to adjust and optimize the electrical properties during the processing of semiconductors. The doping level has certain upper limit, which is usually corresponding to the solubility of the dopant in the host material under processing conditions. Sometimes, the maximum solubility level is still not high enough to provide the desired opto-electronic properties and a higher doping level is needed. Hence, enhancing the dopant level is one of the critical issues in the semiconductor industry, especially for those advanced devices made from compound semiconductors, including binary, ternary, as well as multi-component compounds. In this report, we designed a processing method, by simply varying a processing parameter during melt growth, to increase the doping level in the compound semiconductors well above the maximum values obtained under otherwise regular processing procedures and demonstrated it in the melt growth of Cl-doped PbTe.
关键词： Dopant,Lead telluride,Directional solidification,Solubility
更新于2025-09-23 15:21:21
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Recycling of silicon scraps by directional solidification coupled with alternating electromagnetic field and its electrical property
摘要： In this paper, alternating electromagnetic field and directional solidification are used to separate SiC and Si3N4 in polycrystalline silicon tailings. It is found the inclusion particles move downward at the center of the ingot and moving upward at the edge of the ingot by a variety of forces during the directional solidification process. The electromagnetic force accelerates the melt flow and enhances the lift force, so that larger particles can be pushed to the top of the ingot. Rod-shaped Si3N4 and block-shaped SiC particles show symbiotic relationship between each other. The aggregation of inclusion particles adsorbs metallic impurities, especially volatile metals, due to the effects of mushy region and short-circuit diffusion. The average conversion efficiency of the solar cells (Al-BSF method) prepared using the recycled silicon reached 18.56%, which meets the demand of the solar cells.
关键词： SiC,Alternating magnetic field,Directional solidification,Si3N4,Polycrystalline silicon
更新于2025-09-19 17:13:59
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Microstructure control, competitive growth and precipitation rule in faceted Al2O3/Er3Al5O12 eutectic in situ composite ceramics prepared by laser floating zone melting
摘要： Microstructure control and competitive growth of Al2O3/Er3Al5O12 eutectic/off-eutectics are explored over wide ranges of solidification rates and compositions. Gradual transformation phenomenon of microstructure morphology from complete eutectic to eutectic + coarse Er3Al5O12 phase and to eutectic + Er3Al5O12 dendrite is observed and the corresponding influence factors are evaluated. Competitive growth between single-phase Al2O3 (or Er3Al5O12) dendrite and eutectic is analyzed and coupled growth zone is mapped through comparing interface temperatures of different patterns of microstructures. The complete eutectic microstructure could be obtained at Al2O3/Er3Al5O12 hypoeutectic (Al2O3-17.5 mol% Er2O3) under fast solidification rate and the onset growth rate (~0.94 × 104 μm/s) estimated from the measured eutectic spacing (~150 nm) fits well with the result calculated on the basis of competitive growth (~1.27 × 104 μm/s). Transformation of microstructure from irregular eutectic to regular eutectic and probable adjustment mechanism of eutectic spacings are discussed when the eutectic spacings refined from micron-scale (< 10 μm) to nano-scale (~20 nm).
关键词： Competitive growth,Directional solidification,Microstructure control,Precipitation rule,Oxide ceramic
更新于2025-09-19 17:13:59
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Numerical modeling of carbon distribution and precipitation during directional solidification of photovoltaic silicon
摘要： Numerical modeling is used to investigate carbon distribution and precipitation in directional solidification of multicrystalline silicon. Computations are performed for samples of 6 cm in diameter grown in a Vertical Bridgman Freezing (VGF) system starting from silicon feedstock with different grades of contamination in carbon. The value of the unknown reaction rate coefficient governing the carbon precipitation in the silicon melt was estimated in the present work by comparing the numerically computed concentration profiles to the experimental results taken from the literature. Numerical results show that the growth rate has a significant influence on the interface deflection, melt convection and carbon precipitation. It is found that the silicon samples grown from the melts of low carbon contamination (< 1018 at/cm3) exhibit low content in SiC precipitates, even if they are solidified at high growth rates (1–2 cm/h). The samples with high initial carbon contamination (5 × 1018 at/cm3) should be solidified at much lower rates (0.2 cm/h) in order to avoid the formation of SiC precipitates.
关键词： Carbon transport and precipitation,Directional solidification,Impurities,Semiconducting silicon,Computer simulation
更新于2025-09-16 10:30:52
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Numerical Modelling on Modified Directional Solidification Process of Multi-crystalline Silicon Growth for Photovoltaic Applications
摘要： A transient global model was used to investigate the effect of bottom grooved furnace upon the directional solidification (DS) process of multi-crystalline silicon (mc-Si). The numerical simulation assumed geometry is perfect 2D axis-symmetry. The temperature distribution, crystal-melt (c-m) interface, thermal stress and dislocation density have been simulated. The modified heat exchanger block system was used for controlling the temperature gradient at the bottom of the crucible. The obtained result shows convex shape of the c-m interface. The von Mises stress and dislocation density were reduced while using the bottom grooved furnace. This work was carried out in the different grooves of radius 30 and 60 mm of the heat exchanger block of the DS furnace.
关键词： Directional solidification,Dislocation density,Thermal stress,Silicon,Solar cells,Numerical simulation
更新于2025-09-16 10:30:52
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The influence of travelling magnetic field on phosphorus distribution in n-type multi-crystalline silicon
摘要： The influence of different melt streams on the distribution of phosphorus in multi-crystalline silicon ingot was studied. Phosphorus-doped multi-crystalline silicon (mc-Si) ingots were directionally solidified using travelling magnetic fields (TMF) to alter axial phosphorus profiles. Resistivity distributions in the crystallized n-type ingots were measured along the ingot length. Different Lorentz forces were applied in order to enhance melt stirring and with that to transport phosphorus more rapid towards the melt surface. A new rectangular setup was developed, which enables simultaneous directional solidification of 4 G0-sized mc-Si ingots (80 x 80 x 60 mm3) under the influence of TMF. 900 g ingots with different initial level of phosphorus doping were grown, and dopant concentrations in ingots were related to stirring intensities. The phosphorus evaporation rate significantly affects axial dopant profile of mc-Si material, thus this approach can be used as a powerful tool to control and tailor resistivity distribution along phosphorus-doped mc-Si ingots.
关键词： A1 Directional solidification,A1 Magnetic fields,B1 Semiconducting silicon,B3 Solar cells,A1 Doping
更新于2025-09-10 09:29:36
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摘要： One commonly used system to study morphology development in multi-phase, multi-component alloys is directionally solidified ternary eutectic Al-Ag2Al-Al2Cu. One challenge in studying this system is a relatively large solubility shift of the chemical element Ag in the Al-phase after solidification, which significantly affects the observed phase fractions. The effects of this change on the microstructural patterns are not yet understood. To study these effects, directionally solidified samples of ternary eutectic Al-Ag2Al-Al2Cu were quenched, sectioned and subjected to systematic annealing. This allowed the microstructure evolution at the quenched solid-liquid interface to be recorded in cross section and quantitatively analyzed. The results show that the phase fraction changes in the micrographs are in good accordance with theoretical predictions from the thermodynamic Calphad database. Different microstructural patterns show distinct responses to the annealing. For a more highly ordered chain-like structure, the pattern is preserved even after 32 h at more than 96% of the melting temperature, as determined by the constant number and size of the intermetallic rods in the micrographs. For a less ordered cross-type structure, coarsening of the microstructure is observed, resulting in a pattern change. The outcomes underline the importance of considering post-solidification effects during the investigation of ternary eutectic Al-Ag2Al-Al2Cu and help to improve the understanding of the microstructure arrangement in complex eutectic alloys.
关键词： A1. Directional solidification,A1. Diffusion,A1. Eutectics,A1. Solubility,B1. Metals
更新于2025-09-10 09:29:36
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Reference Module in Materials Science and Materials Engineering || Monocrystalline Silicon Grown Using Floating Zone Technique ☆
摘要： The floating zone technique is the best method available for producing monocrystalline Si ingot from polycrystalline Si with the lowest amount of impurity, defect and highest resistivity. However, there are many parameters that needed to be optimised in the process to ensure high quality crystals can be produced starting from the raw materials involved, the melting and solidification rate, the surrounding atmosphere and the capability of the equipment and parts used. Without optimization, the produced Si would not be of higher quality compared to crystals produced by Czochralski and directional solidification method and it would be a waste of resources since the costs involved are much higher for the FZ technique. However, with the evolution in technology, the high cost that is associated with FZ technique and the limitation in size of ingot that can be produced will someday be solved.
关键词： Silicon Ingot,Monocrystalline Silicon,Directional Solidification,Czochralski,Floating Zone Technique
更新于2025-09-10 09:29:36