Crystallization kinetics of mixed amorphous-crystalline nanosystems

摘要

We investigate at the atomic scale the crystallization of a two-phase amorphous-crystalline system. We focus on the case of textured nanocrystalline silicon here described as a distribution of cylindrical grains embedded into an amorphous matrix. The atomistic results are used to infer a continuum model of the crystallinity evolution and to work out a comparison with Kolmogorov-Johnson-Mehl-Avrami (KJMA) model. At low crystallinity, the phase transformation is dominated by the isolated grain evolution (faceted limited growth). Conversely, at later stages we observe deviations from the KJMA that are mainly due to atomic-scale features. We prove that such effects can be included by using an improved phenomenological version of the KJMA theory.