Nanocrystallization of amorphous germanium films observed with nanosecond temporal resolution

Using dynamic transmission electron microscopy we measure nucleation and growth rates during laser driven crystallization of amorphous germanium (a-Ge) films supported by silicon monoxide membranes. The films were crystallized using single 532 nm laser pulses at a fluence of ∼128 mJ cm−2. Devitrification processes initiate less than 20 ns after excitation and are complete within ∼55 ns. The nucleation rate was estimated by tracking crystallite density as a function of time and reached a maximum of ∼1.6×1022 nuclei/cm3 s. This study provides information on nanocrystallization phenomena in a-Ge, which is important for the implementation of nanostructured group IV semiconductors in optoelectronics devices.