Synthesizing germanium nanocrystals in amorphous silicon oxide by rapid thermal annealing

The Raman and photoluminescence (PL) characteristics of Ge nanocrystals embedded in amorphous SiO2 films synthesized by rapid thermal annealing were presented. The nanocrystal size delta was estimated on the basis of the phonon confinement model. The Raman results showed that, for samples annealed at different annealing temperatures, a transition from amorphous to nanocrystalline Ge occurred at annealing temperature higher than 700 degrees C. delta was estimated to lie between 18 and 53 Angstrom. Two PL peaks at 1.8 and 2.2 eV were observed for Ge nanocrystals with delta = 18-53 Angstrom. The PL results of the 2.2 eV peak agreed with that published in the literature. The origin of this peak is still under investigation. A comparison of the PL peak with delta and the results of the forming-gas annealing experiments suggest that the 1.8 eV peak is possibly related to both the Ge nanocrystals and Ge related defects in the SiO2 network.