Nanocrystalline Ge in SiO2 by annealing of Ge<i>x</i>Si1−<i>x</i>O2 in hydrogen

Abstract

We have synthesized nanocrystalline Ge in vitreous SiO2 by annealing amorphous Ge0.38Si0.62O2 in hydrogen at 700 °C. The germanium dioxide in Ge0.38Si0.62O2 is thermodynamically unstable in the presence of hydrogen and thus precipitates out as elemental Ge. Elemental Si is not needed in this reduction process. Cross-sectional transmission electron microscopy reveals that the nucleation process is homogeneous, leading to a uniform distribution of small Ge crystallites imbedded in the remaining vitreous SiO2.