Novel criterion for splitting of plate-like crystal growing in undercooled silicon melts

Abstract

An undercooled drop of silicon was grown to crystals in containerless states with electromagnetic and electrostatic levitators. A high-speed video camera was used to monitor the growth rate and observe the crystal–melt interface as a function of undercooling. The morphology of the growing crystal changed from a mono-plate crystal to a multi-plate crystal, and then to faceted dendrite with increasing undercooling. The mono-plate and multi-plate crystals observed at undercooling of less than 100 K were shaped by a faceted planer interface and wavy-edge plane. The critical undercooling for the transition from mono-plate to multi-plate depends on the sample size; it was 50 and 80 K for samples of 5 and 1.7 mm in diameter, respectively. A novel criterion for the transition from mono-plate to multi-plate based on the instability of the wavy-edge plane is proposed.