Dependence of Si-Faceted Dendrite Growth Orientation on Twin Spacing and Undercooling

Abstract

Si-faceted dendrites growth orientation as a function of twin spacing and undercooling were investigated by in situ observation, and the mechanisms of the growth behaviors were discussed and clarified. The growth orientation of Si-faceted dendrites strongly depends on the twin spacing and undercooling. For a given undercooling, a dendrite with twin spacing narrower than the critical twin spacing preferentially grows in the ⟨110⟩ direction, whereas growth in the ⟨112⟩ direction preferentially occurs for a dendrite with twin spacing wider than the critical twin spacing. The critical twin spacing for stable faceted dendrite growth increases as the undercooling increases. In the case of low undercooling (∼10 K < ΔT ≲ 15 K), dendrites dominantly grow in the ⟨112⟩ direction. For high undercooling (∼25 K< ΔT ≲ 100 K), dendrites preferentially grow in the ⟨110⟩ direction. ⟨110⟩ and ⟨112⟩ growth directions occur with equal frequency for intermediate values of undercooling (∼15 K < ΔT ≤ 25 K).