Phase field modeling of growth competition of silicon grains

The growth competition of two grains, with orientations (1 1 0) and (1 0 0), during directional solidification of silicon is simulated by using a phase field model. The two-dimensional simulations show two distinct competition mechanisms, with either interfacial or kinetic dominance, depending on the undercooling. At low undercooling, the interfacial effect is dominant so that (1 1 0) grain grows laterally, expelling the other grain. On the other hand, at high undercooling, the grain competition follows the same pattern at the beginning, but the (1 0 0) grain eventually becomes dominant, expanding its domain. In addition, the facet vanishing process and the dihedral angle evolution are discussed. The simulated results and phenomena are consistent with the experimental observations of Fujiwara et al. [Fujiwara K, Obinata Y, Ujihara T, Usami N, Sazaki G, Nakajima K. J Cryst Growth 2004;266:441] and the analytical predictions of Atwater et al. [Atwater HA, Thompson CV, Smith HI. J Mater Res 1988;6:1232].