期刊
JOURNAL OF CRYSTAL GROWTH
卷 408, 期 -, 页码 42-48出版社
ELSEVIER
DOI: 10.1016/j.jcrysgro.2014.09.019
关键词
Numerical simulation; Segregation; Floating zone technique; Germanium
资金
- National Natural Science Foundation of China [51106059]
- Fundamental Research Funds for the Central Universities [HUST: 2013TS074]
Germanium (Ge) is a preferred material in the fabrication of high-performance gamma radiation detector for spectroscopy in nuclear physics. To maintain an intrinsic region in which electrons and holes each the contacts to produce a spectroscopic signal, germanium crystals are usually doped with lithium (Li) ions. Consequently, hyperpure germanium (HPGe) should be prepared before the doping process to eliminate the interference of unexpected impurities in the Li dopant. Zone-refining technique, widely used in purification of ultra-pure materials, is chosen as one of the purification steps during detector-grade germanium production. In the paper, numerical analysis has been conducted to analyze heat transfer, melt flow and impurity segregation during a multi-pass zone-refining process of germanium in a Cyberstar mirror furnace. By modifying the effective redistribution coefficients, axial segregations of various impurities are investigated. Marangoni convection is found dominant in the melt. It affects the purification process through modifying the boundary layer thickness. Impurity distributions along the ingot are obtained with different conditions, such as pass number, zone travel rate, initial impurity concentration, segregation coefficient, and hot-zone length. Based on the analysis, optimization of the purification process design is proposed. (C) 2014 Elsevier By. All rights reserved.
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