共查询到20条相似文献,搜索用时 31 毫秒
1.
Liu Juncheng 《Crystal Research and Technology》2008,43(4):396-408
A numerical simulation study was carried out for CdZnTe vertical Bridgman method crystal growth with the accelerated crucible rotation technique (ACRT). The convection, heat and mass transfer in front of the solid‐liquid interface, and their effects on the solute segregation of the grown crystal can be characterized with the following. ACRT brings about a periodic forced convection in the melt, of which the intensity and the incidence are far above the ones of the natural convection without ACRT. This forced convection is of multiformity due to the changes of the ACRT parameters. It can result in the increases of both the solid‐liquid interface concavity and the temperature gradient of the melt in front of the solid‐liquid interface, of which magnitudes vary from a little to many times as the ACRT wave parameters change. It also enhances the mass transfer in the melt in a great deal, almost results in the complete uniformity of the solute distribution in the melt. With suitable wave parameters, ACRT forced convection decreases the radial solute segregation of the crystal in a great deal, even makes it disappear completely. However, it increases both the axial solute segregation and the radial one notably with bad wave parameters. An excellent single crystal could be gotten, of which the most part is with no segregation, by adjusting both the ACRT wave parameters and the crystal growth control parameters, e.g. the initial temperature of the melt, the temperature gradient, and the crucible withdrawal rate. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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The thermal and flow transport in an inductively heated Czochralski crystal growth furnace during a crystal growth process is investigated numerically. The temperature and flow fields inside the furnace, coupled with the heat generation in the iridium crucible induced by the electromagnetic field generated by the RF coil, are computed. The results indicate that for an RF coil fixed in position during the growth process, although the maximum value of the magnetic, temperature and velocity fields decrease, the convexity of the crystal‐melt interface increases for longer crystal growth lengths. The convexity of the crystal‐melt interface and the power consumption can be reduced by adjusting the relative position between the crucible and the induction coil during growth. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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Li Hongjun Xu Jun Su Liangbi Jiang Benxue Zhao Guangjun Zhou Guoqing Dong Yongjun 《Crystal Research and Technology》2007,42(2):107-113
A finite‐element model is employed to analysis the thermal environments in Temperature Gradient Technique (TGT) furnace during the growth of large‐sized Nd:YAG crystal. The obtained results show that when the crucible is located at the lower position inside of the heater, a flatter solid‐liquid interface is established, which makes it easier to obtain the core‐free Nd:YAG crystal. Meanwhile, the lower crucible position can induce higher axial temperature gradient, which is beneficial to the release of latent heat. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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For the seeding process of oxide Czochralski crystal growth, influence of the crucible bottom shape on the heat generation, temperature and flow field of the system and the seed‐melt interface shape have been studied numerically using the finite element method. The configuration usually used in a real Czochralski crystal growth process consists of a crucible, active afterheater, induction coil with two parts, insulation, melt, gas and seed crystal. At first, the volumetric distribution of heat inside the metal crucible and afterheater inducted by the RF‐coil was calculated. Using this heat generation in the crucible wall as a source the fluid flow and temperature field of the entire system as well as the seed‐melt interface shape were determined. We have considered two cases, flat and rounded crucible bottom shape. It was observed that using a crucible with a rounded bottom has several advantages such as: (i) The position of the heat generation maximum at the crucible side wall moves upwards, compared to the flat bottom shape. (ii) The location of the temperature maximum at the crucible side wall rises and as a result the temperature gradient along the melt surface increases. (iii) The streamlines of the melt flow are parallel to the crucible bottom and have a curved shape which is similar to the rounded bottom shape. These important features lead to increasing thermal convection in the system and influence the velocity field in the melt and gas domain which help preventing some serious growth problems such as spiral growth. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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In order to understand the effects of the thermophysical properties of the melt on the transport phenomena in the Czochralski (Cz) furnace for the single crystal growth of silicon, a set of global analyses of momentum, heat and mass transfer in small Cz furnace (crucible diameter: 7.2 cm, crystal diameter: 3.5 cm, operated in a 10 Torr argon flow environment) was carried out using the finite‐element method. The global analysis assumed a pseudosteady axisymmetric state with laminar flow. The results show that different thermophysical properties will bring different variations of the heater power, the deflection of the melt/crystal interface, the axial temperature gradient in the crystal on the center of the melt/crystal interface and the average oxygen concentration along the melt/crystal interface. The application of the axial magnetic field is insensitive to this effect. This analysis reveals the importance of the determination of the thermophysical property in numerical simulation. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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Huijie Li Xianglin Liu Yuxia Feng Hongyuan Wei Shaoyan Yang 《Crystal Research and Technology》2013,48(5):321-327
A large radial temperature gradient in the AlN sublimation growth system would lead to non‐uniform growth rate along the radial direction and introduce thermal stress in the as grown crystal. In this paper, we have numerically studied the radial thermal uniformity in the crucible of a AlN sublimation growth system. The temperature difference on the source top surface is insignificant while the radial temperature gradient on the lid surface is too large to be neglected. The simulation results showed that the crucible material with a large thermal conductivity is beneficial to obtain a uniform temperature distribution on the lid surface. Moreover, it was found that the temperature gradient on the lid surface decreases with increased lid thickness and decreased top window size. 相似文献
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3D simulations using the commercial CFDRC and FIDAP code, which are based on finite element techniques, were performed to investigate the effects of anisotropic conductivity on the convexity of the melt–crystal interface and the hot spots of sapphire crystal in a heat‐exchanger‐method crystal growth system. The convection boundary conditions of both the energy input to the crucible by the radiation as well as convection inside the furnace and the energy output through the heat exchanger are modeled. The cross‐sectional flow pattern and the shape of the melt–crystal interface are confirmed by comparing the 3‐D modeling results with previous 2D simulation results. In the 3D model, the “hot spots” in the corners of the crucible are donut shaped, and the shape changes with the value of the conductivity of anisotropic crystal. The outline of the crystal becomes more convex as the conductivity in the z direction (ksz) increases. The outline of melt–crystal interface is elliptical when the anisotropic conductivity is moving in the radial direction (ksx and ksy). The portion at the outline touching the bottom of the crucible is smaller than the maximum outline of the crystal, meaning that the shape at the “hot spot”, changes with the value of the conductivities of anisotropic crystal. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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Bridgman growth of Nd:SGG (Sr3Ga2Ge4O14) crystals has been investigated for the first time. Pt crucible of ∅︁25mm×250mm with a seed well of ∅︁10mm×80 mm is used, and seed is SGG crystal of ∅︁10mm×50mm grown by Bridgman method in advance. The growth parameters are optimized as the furnace temperature is set to 1450∼1500°C, temperature gradient in the crystal‐melt interface is less than 25 K/cm and growth rate is less than 0.5mm/h. The Nd:SGG crystals with 25mm in diameter and 60mm in length are grown successfully from 1.5 to 8at% Nd3+ doped stoichiometric Sr3Ga2Ge4O14 melt. The distribution coefficient and concentration of Nd3+ in Nd:SGG crystals are obviously higher than those of Nd:YAG crystal. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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The paper is the second in a series which presentes results on the small-signal diametral response of a Czochralski crystal grown in a resistively heated furnace to variations in heater temperature and pull rate. Here it is shown that the small-signal bulk melt temperature variation is related to the small-signal furnace temperature variation via a first order linear differential equation. 相似文献
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Radiative Heat Transfer in a Resistance Heated Floating Zone Furnace: A Numerical Study with FIDAPTM
This paper presents a numerical study of radiative heat transfer in a floating zone (FZ) furnace which was performed by using the commercial finite element program FIDAPTM. This resistance furnace should provide a temperature higher than the melting temperature of silicon (i.e. Tmax ≈ 1500 °C) and a variable temperature gradient at the liquid/solid interface (≥ 25 K/cm). Due to the high working temperatures, heat radiation plays the dominant role for the heat transfer in the furnace. For this reason, the quality of view factors used in the wall‐to‐wall model was carefully inspected with energy‐balance checks. A numerical model with two control parameters is applied to study the influence of material and geometrical parameters on the temperature field. In addition, this model allows us to estimate the internal thermal conditions which were used as thermal boundary conditions for partial 3D simulations. The influences of an optical lens system on the radial symmetry of the temperature field were examined with these partial 3D simulations. Furthermore, we used the inverse modeling method to achieve maximum possible temperature gradients at the liquid/solid interface according to the limitation of maximum available power and the maximum stable height of a melt zone. 相似文献
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The optimization of the InP liquid encapsulated Czochralski systems is usually difficult, time consuming and very expensive. Here, the relative importance of the different growth parameters (e.g., pull rate, system temperatures and geometry) on the growth interface deflection, the temperature gradients within the melt and the crystal and the dislocation density has been investigated through a sensitivity analysis. The sensitivity coefficients have been calculated by means of a mathematical model, previously validated, based on the thermoelastic theory for the dislocation formation and on the thermal capillary theory for the temperature field within the system. The crucible temperature profile has been selected as the more important parameter to control the crystal quality during the growth. 相似文献
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Heat transfer and fluid flow in HEM crystal growth of silicon in cylindrical cavity is studied numerically. The walls of the crucible are heated to a fixed temperature. The exchanger that causes and induces natural convection is seated at the middle‐bottom of the crucible. The finite‐volume method is employed to solve the governing equations with proper boundary conditions. The effects of transport mechanism on the temperature distribution, melt flow, pressure and stream function are presented. We focus our work on the pressure field which has not yet been studied in HEM crucible. Also, we extend our work on a wide range Grashof number and for large numbers until 1012 not yet studied in HEM furnace. It is found that the onset of flow fluctuations appears at Gr = 1010. Uniform temperature is observed in the entire melt at high Grashof number with development of a thermal boundary layer close to the exchanger. The thermal boundary layer thickness is calculated for strong buoyancy regime. Besides, for very high Gr number, buoyancy has less effect on temperature and then on melt‐crystal interface shape. During enlarging Gr, pressure evolution is related to temperature variation more than flow pattern. 相似文献
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K. Kakimoto L. Liu H. Miyazawa S. Nakano D. Kashiwagi X. J. Chen Y. Kangawa 《Crystal Research and Technology》2007,42(12):1185-1189
Heat and mass transfer during crystal growth of bulk Si and nitrides by using numerical analysis was studied. A three‐dimensional analysis was carried out to investigate temperature distribution and solid‐liquid interface shape of silicon for large‐scale integrated circuits and photovoltaic silicon. The analysis enables prediction of the solid‐liquid interface shape of silicon crystals. The result shows that the interface shape became bevel like structure in the case without crystal rotation. We also carried out analysis of nitrogen transfer in gallium melt during crystal growth of gallium nitride using liquid‐phase epitaxy. The result shows that the growth rate at the center was smaller than that at the center. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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Ying-Yang Teng Jyh-Chen Chen Cheng-Chuan Huang Chung-Wei Lu Wan-Ting Wun Chi-Yung Chen 《Journal of Crystal Growth》2012,352(1):167-172
In this study, a numerical simulation is performed to investigate the effect of the shape of the heat shield on the oxygen concentration in the melt. The results show that the oxygen concentration in the melt can be significantly decreased by increasing the speed of the argon gas near the crucible wall. This can be achieved by enlarging the horizontal length of the heat shield. The oxygen concentration at the melt–crystal interface varies with the length of the crystal growth. In the initial stage, there is a significant decrease in the oxygen concentration as the growth length increases. There is also a significant reduction in the emission of oxygen from the crucible wall due to the lower melt depth and crucible temperature. The transportation of oxygen impurity towards the melt–crystal interface is suppressed by the vortex motion in the melt. When the crystal exceeds a certain length, the oxygen concentration in the melt–crystal interface starts to increase with increasing crystal length, due to the drop in vortex motion in the melt. 相似文献
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J. N. Koster 《Crystal Research and Technology》1999,34(9):1129-1140
Eutectic gallium-indium is studied in a horizontal Bridgman furnace geometry. Differential temperature gradients are applied to solidify and melt the alloy while observing in-situ the interface morphology and the chemical segregation in the melt and in the solid as well. Upon cooling, a wedge-type indium-rich mushy zone develops at the cold wall. The melt is initially stirred by convective flow. After solidification starts the roll cell recedes to be replaced by a chemically layered conductive melt that eventually solidifies with rather uniform eutectic structure. Upon re-melting, the morphology of the interface adopts a profile that is predetermined by the original solid structure. Those patterns, as well as the flow, are different from single element solid melting experiments and have yet to be modeled. Under high thermal gradient the convective flow mixes the binary melt and the visualized density pattern eventually becomes that of a homogeneous melt. 相似文献
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E. V. Yakovlev V. V. Kalaev E. N. Bystrova O. V. Smirnova Yu. N. Makarov Ch. Frank‐Rotsch M. Neubert P. Rudolph 《Crystal Research and Technology》2003,38(6):506-514
The results of three‐dimensional unsteady modeling of melt turbulent convection with prediction of the crystallization front geometry in liquid encapsulated Czochralski growth of InP bulk crystals and vapor pressure controlled Czochralski growth of GaAs bulk crystals are presented. The three‐dimensional model is combined with axisymmetric calculations of heat and mass transfer in the entire furnace. A comprehensive numerical analysis using various two‐dimensional steady and three‐dimensional unsteady models is also performed to explore their possibilities in predicting the melt/crystal interface geometry. The results obtained with different numerical approaches are analyzed and compared with available experimental data. It has been found that three‐dimensional unsteady consideration of heat and mass transfer in the crystallization zone provides a good reproduction of the solidification front geometry for both GaAs and InP crystal growth. 相似文献