Synthesizing germanium nanocrystals in amorphous silicon oxide by rapid thermal annealing

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Abstract
The Raman and photoluminescence (PL) characteristics of Ge nanocrystals embedded in amorphous SiO2 films synthesized by rapid thermal annealing were presented. The nanocrystal size δ 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 nano-crystalline Ge occurred at annealing temperature higher than 700°C. δ was estimated to lie between 18 and 53 A. Two PL peaks at 1.8 and 2.2 eV were observed for Ge nanocrystals with δ= 18-53 Å. The PL results of the 2.2eV peak agreed with that published in the literature. The origin of this peak is still under investigation. A comparison of the PL peak with δ 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.