In situ observation of Si faceted dendrite growth from low-degree-of-undercooling melts

We directly observed the transition of crystal growth behavior of Si in a low undercooling region. We succeeded in observing the initiation of faceted dendrite growth from a portion of parallel twins with increasing degrees of undercooling. The critical undercooling for growing a faceted dendrite was experimentally determined to be Delta T= 10 K. We also confirmed that parallel twins associated with faceted dendrite growth were formed between grain boundaries and not at grain boundaries during melt growth. The parallel-twin formation was explained in terms of a model of twin formation on the {111} facet plane at the growth interface. (C) 2008 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.