The effect of using a pulsed electric current to remove impurity iron from molten polysilicon was investigated. Using optical microscopy observation and area statistics of iron-rich content, it was found that iron tends to accumulate at the bottom of an ingot under the action of a pulsed electric current. A new separation mechanism is proposed, based on the decreased solubility of iron in polysilicon under conditions including a pulsed electric current. Thermodynamic calculations indicate the theoretical possibility of the formation of iron-rich Si clusters. These clusters sink to the bottom of an ingot under the effect of gravity and form iron-rich precipitates with silicon, thereby achieving the iron removal. This technique provides a new method for purification of polysilicon.

中文翻译：

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脉冲电流从多晶硅中分离杂质铁

研究了使用脉冲电流从熔融多晶硅中去除杂质铁的效果。用光学显微镜观察和富铁含量的面积统计发现，在脉冲电流的作用下，铁倾向于在铸锭底部积累。基于在包括脉冲电流在内的条件下铁在多晶硅中的溶解度降低，提出了一种新的分离机制。热力学计算表明形成富铁硅簇的理论可能性。这些团簇在重力作用下沉入铸锭底部，与硅形成富铁沉淀，从而达到除铁目的。该技术为多晶硅的提纯提供了一种新方法。