Nonuniform growth of embedded silicon nanocrystals in an amorphous matrix.

The phase transformation of a metastable system occurs when islands of a second stable phase form and grow. The growth velocity of the islands controls the kinetics of the phase transformation. In this work we consider the amorphous-to-crystalline transformation in silicon as the prototype of a solid-to-solid transformation. The results of atomistic simulations are fit using an analytic model for the growth of [100]-oriented nanosized crystalline fibers embedded into an amorphous matrix. We demonstrate that the radius of the island does not grow, in general, at constant velocity. On the contrary, we identify a decelerated motion that is due to anisotropic effects of the crystal grain. Such a nonuniform growth should be taken into account in the modeling of solid-to-solid crystallization.