Inhomogeneous crystallization of sputter-deposited amorphous Ge films

Crystallization of amorphous germanium films induced by electron irradiation was investigated by in-situ transmission electron microscopy under a low electron-energy of 125 keV with various pre-aging treatments at room temperature. Different microstructuies were observed depending on the aging time: coarse and spherical nanoparticles grew rapidly in samples aged for less than 3 months, while a homogeneous nanocrystalline structure with a grain size of about 10 nm appealed in samples aged for over 7 months. Analyses by the pair distribution function levealed that the initial structure is inhomogeneous, consisting of a mixture of amorphous legions and some ordered arrangements, but turned spontaneously to homogeneous random amorphous structures during aging. Such in homogeneity could be an origin of the rapid growth of nanoparticles in the samples not subjected to the long-time aging.