Nanoscale-crystallite nucleation and growth in amorphous solids

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Abstract
A model is proposed to describe the crystallization in disordered solids. The model is based on accounting for small statistical fluctuations in structural parameters (valence angles, bond lengths, etc.), which are shown to affect the crystallization kinetics dramatically. As opposed to the standard approach that neglects any effects due to disorder, the model reveals clearly divided stages of nucleation, growth, and ripening in the crystallization of one-component disordered solids. We show that at the nucleation stage the crystallization is nonlinear in time and is bounded by a certain small volume fraction (≊0.1). At the growth stage the radius of the crystallites depends on time logarithmically and approximately double its initial value until the ripening stage comes. The results of Raman light-scattering experiments designed to test various predictions of the model are presented for a-Si:H subjected to crystallization. Good agreement is obtained.