共查询到18条相似文献,搜索用时 93 毫秒
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优质立方六面体金刚石大单晶的生长研究 总被引:1,自引:2,他引:1
高温高压静压触媒法合成的金刚石单晶,往往呈现六八面体形貌,因为立方六面体单晶{100}面的生长区间相对较小.本研究利用高温高压温度梯度法,自制Fe-Ni合金触媒,通过对合成组装和工艺进行合理调整后,控制晶体在相对低温适合{100}面生长区域内生长,得到的晶体均呈现完整立方六面体形貌;同时为抑制包裹体和其他杂质的进入,人为的提高晶体的径向平铺生长速度,抑制其轴向生长速度.以在33 h内合成的优质立方六面体晶体为例,晶体最大方向尺寸达到7.3 mm,重1.2克拉,其径向生长速度达到0.22 mm/h,轴向生长速度仅为0.08 mm/h,增重速度为7.3 mg/h. 相似文献
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针对泡生法蓝宝石单晶生长的不同生长阶段的温场、流场和固液界面形状进行数值模拟研究.并分析了加热器相对坩埚的轴向位置和不同生长速率对蓝宝石单晶生长的影响.结果表明:在蓝宝石单晶生长中,在靠近坩埚壁面和固液界面的熔体内,等温线密,温度梯度较大;在靠近坩埚底部的熔体内,等温线稀疏,温度梯度较小.随着晶体高度的增加,熔体对流由放肩阶段的两个涡胞变成等径阶段的一个涡胞,熔体平均温度有小幅度下降;加热器相对坩埚的轴向位置对晶体生长炉内温场和固液界面形状影响很大,随着加热器位置上移,晶体内平均温度升高,温度梯度减小;熔体内平均温度降低,温度梯度增大.同时固液界面凸度增大.随着晶体生长速率增大,固液界面凸度增大,界面更加凸向熔体. 相似文献
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针对不同超导水平磁场结构的磁力线分布对φ300 mm直拉硅单晶固液界面影响问题,本文采用一种基于格子Boltzmann方法的耦合热格子模型,解决温度场与速度场耦合建模问题,并对不同结构的超导磁场作用下的晶体生长进行了三维数值模拟.结果表明,采用单磁力线分布的超导磁场结构使得固液界面氧含量降低,但是容易引起熔体内部热分布不均匀;采用双磁力线分布结构能够有效地改善熔体内部沿晶体生长的轴向温度梯度和沿固液界面的径向温度梯度,然而,其对固液界面氧含量抑制作用较小.当晶转、埚转工艺作用时,超导单磁力线水平磁场结构明显优于超导双磁力线水平磁场结构,固液界面形状对称性随磁感应强度的增加而增强. 相似文献
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不同尺寸的铸锭晶体硅生长过程具有相似性,小尺寸晶体的生长规律可以迁移至大尺寸。本文采用迁移学习(TL)对G8型铸锭炉进行热场设计,设计对象为侧、顶加热器位置及体积、侧隔热笼分区块高度,主要设计目标为减少晶体内部的位错缺陷、抑制硅锭边缘多晶且使晶体生长界面微凸。首先使用神经网络对已有的G7铸锭炉建立热场几何参数与热场评价参数间的映射模型,然后将该模型迁移至G8铸锭炉,对比不同模型结构对迁移过程的影响,采用Dropout分析模型是否存在过拟合,并使用遗传算法(GA)结合聚类算法(CA)对热场几何参数进行优化,以上为G8热场设计过程。最后对优化结果采用数值模拟方法研究其在晶体生长过程中的温度分布、固液界面形状等,最终选定的优化方案能够实现较高质量的长晶。将该方案同时应用于G7和G8热场并进行对比,结果表明G8在硅熔体和硅晶体中的轴向温度梯度均小于G7,在晶体生长界面沿径向的温度梯度也小于G7,这有利于减小晶体内部的热应力。 相似文献
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冷心放肩微量提拉法大尺寸蓝宝石单晶生长过程的模拟分析 总被引:4,自引:1,他引:3
利用数值模拟方法计算了冷心放肩微量提拉法(SAPMAC)蓝宝石晶体生长过程.结合晶体直径变化、裂纹出现位置与延续方向、晶体透明性等实验现象,通过与提拉法、温梯法、坩埚移动法等相对比,分析了冷心放肩微量提拉法晶体生长各阶段的工艺特点,并根据模拟计算结果对晶体生长系统和晶体生长控制工艺进行了改进.分别利用增大热交换器的散热参数、降低加热温度、改进降温曲线、调节外加轴向和径向温度梯度的方式来实现对晶体生长的引晶、放肩、等径和收尾控制.通过实验比较证明了改进后的晶体生长系统和晶体生长控制工艺能够生长出性能较好的大尺寸蓝宝石晶体. 相似文献
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The influence of thermal conditions on the synthesis and crystallinity of ZnSiP2 is investigated. Extensive measurements lead to statements on the axial and radial distribution of temperature in the apparatus and in the reaction vessel. The axial temperature gradient in the crystallization room equals some 3 deg/cm, whereas in the ampoule a radial gradient of 4 to 5 deg/cm is ruling. — At different temperature differences the thermal conditions of deposition of ZnSiP2 are discussed, and it is found that ΔT should not fall below a minimum value of 15 deg, if ZnSiP2 is to be produced by means of gas phase transport in a finite period of time. — In a full discussion the characteristic transport effects are explained. — Condensation of ZnP2 at the end of the ampoule and by secondary transport caused by local temperature and concentration gradients in the crystallization room are stated to be responsible for different concentration profiles, for the phases present and for the crystallinity depending on the place of crystallization. — Hints for favourable variants of growing are given. 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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Liu Juncheng Song Dejie Zhang Hongying Zhai Shenqiu 《Crystal Research and Technology》2007,42(8):741-750
The temperature gradient within a furnace chamber and the crucible pull rate are the key control parameters for cadmium zinc telluride Bridgman single crystal growth. Their effects on the heat and mass transfer in front of the solid‐liquid interface and the solute segregation in the grown crystal were investigated with numerical modeling. With an increase of the temperature gradient, the convection intensity in the melt in front of the solid‐liquid interface increases almost proportionally to the temperature gradient. The interface concavity decreases rapidly at faster crucible pull rates, while it increases at slow pull rates. Moreover, the solute concentration gradient in the melt in front of the solid‐liquid interface decreases significantly, as does the radial solute segregation in the grown crystal. In general, a decrease of the pull rate leads to a strong decrease of the concavity of the solid‐liquid interface and of the radial solute segregation in the grown crystal, while the axial solute segregation in the grown crystal increases slightly. A combination of a low crucible pull rate with a medium temperature gradient within the furnace chamber will make the radial solute segregation of the grown crystal vanish. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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V. I. Strelov B. G. Zakharov V. S. Sidorov I. Zh. Bezbakh V. I. Folomeev 《Crystallography Reports》2005,50(3):490-498
Mathematical modeling of the processes of heat and mass transfer during directed crystallization under terrestrial and space conditions is performed on the basis of experimental data on the temperature distribution (boundary conditions). Convective processes are described by the system of Oberbeck-Boussinesq equations together with the heat-conduction equation (the Stefan problem). A dependence of the intensity of thermal gravitational convection on the radial and axial temperature gradients is established. It is shown that one of the necessary conditions for the growth of homogeneous semiconductor crystals under both terrestrial and zero-gravity (on board spacecraft) conditions is the absence of the free surface of a melt (the Marangoni convection) and optimization of the temperature gradients (first of all, the radial gradient). 相似文献
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借助专业晶体生长模拟软件FEMAG和自主开发的对流、传质、过饱和度及生长速率预测等有限元模块研究了物理气相传输法(PVT)同质外延生长氮化铝(AlN)单晶工艺时的初始传热及传质过程,并分析了不同形状籽晶台对生长室内的温度场、流场、过饱和度及生长速率的影响。温度场模拟结果表明籽晶台侧部角度改变可影响籽晶表面轴向及径向温度梯度,流场及传质模拟表明籽晶台侧部角度变化对籽晶台周边的传质有巨大影响。传质及过饱和度模拟结果表明,当籽晶台侧部角度为130°时,籽晶表面温度梯度较小且可以完全抑制籽晶台侧部多晶沉积,有利于通过同质外延工艺生长出无寄生、无裂纹的高质量氮化铝单晶锭。 相似文献
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Kozhemyakin G. N. Strelov V. I. Sidorov V. S. Korobeynikova E. N. 《Crystallography Reports》2020,65(5):798-804
Crystallography Reports - The influence of a low axial temperature gradient on the growth of the Ge:Ga crystal by the vertical Bridgman technique was investigated. The axial temperature gradient of... 相似文献