The crystallization enthalpy measured in a large series of amorphous silicon (a-Si) materialsvaries within a factor of 2 from sample to sample (Kail et al 2011 Phys. Status Solidi RRL 5361). According to the classical theory of nucleation, this variation should produce largedifferences in the crystallization kinetics leading to crystallization temperatures and activationenergies exceeding 550 C and 1.7 eV, respectively, the ‘standard’ values measured for a-Siobtained by self-implantation. In contrast, the observed crystallization kinetics is very similarfor all the samples studied and has no correlation with the crystallization enthalpy. Thisdiscrepancy has led us to propose that crystallization in a-Si begins in microscopic domainsthat are almost identical in all samples, independently of their crystallization enthalpy.Probably the existence of microscopic inhomogeneities also plays a crucial role in thecrystallization kinetics of other amorphous materials and glasses.
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