以冶金硅为原料,探索采用具有高温度梯度的真空定向凝固技术制备低成本太阳能级多晶硅,并研究其在不同生长条件下的微观组织特征、晶界与晶粒大小、固液界面形貌以及位错结构.结果表明,当凝固速率低于60 μm/s时,能获得具有高密度和良好取向的定向凝固多晶硅棒状试样,硅晶粒大小随凝固速率的增大而减小；在控制凝固过程,获得平的固液界面形貌是获得沿凝固方向排列柱状晶的关键；由于硅的小平面生长特性,微观组织中出现了位错生长台阶和孪晶结构；在晶粒中,位错分布呈现不均匀性,并且位错密度随凝固速率的增加而增加；在此基础上,讨论了多晶硅的生长行为以及位错形成机制.%A vacuum directional solidification with high temperature gradient was performed to prepare low cost solar-grade multicrystalline silicon (mc-Si) directly from metallurgical-grade mc-Si.The microstructure characteristic,grain size,boundary,solid-liquid growth interface,and dislocation structure under different growth conditions were studied.The results show that directionally solidified multicrystalline silicon rods with high density and orientation can be obtained when the solidification rate is below 60 μm/s.The grain size gradually decreases with increasing the solidification rate.The control of obtaining planar solid-liquid interface at high temperature gradient is effective to produce well-aligned columnar grains along the solidification direction.The growth step and twin boundaries are preferred to form in the microstructure due to the faceted growth characteristic of mc-Si.The dislocation distribution is inhomogeneous within crystals and the dislocation density increases with the increase of solidification rate.Furthermore,the crystal growth behavior and dislocation formation mechanism of mc-Si were discussed.
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