The crystallization enthalpy measured in a large series of amorphous silicon (a-Si) materials
varies within a factor of 2 from sample to sample (Kail et al 2011 Phys. Status Solidi RRL 5
361). According to the classical theory of nucleation, this variation should produce large
differences in the crystallization kinetics leading to crystallization temperatures and activation
energies exceeding 550 C and 1.7 eV, respectively, the ‘standard’ values measured for a-Si
obtained by self-implantation. In contrast, the observed crystallization kinetics is very similar
for all the samples studied and has no correlation with the crystallization enthalpy. This
discrepancy has led us to propose that crystallization in a-Si begins in microscopic domains
that are almost identical in all samples, independently of their crystallization enthalpy.
Probably the existence of microscopic inhomogeneities also plays a crucial role in the
crystallization kinetics of other amorphous materials and glasses
