NANOCRYSTALLINE GE IN SIO2 BY ANNEALING OF GEXSI1-XO2 IN HYDROGEN

We have synthesized nanocrystalline Ge in vitreous SiO2 by annealing a morphous Ge0.38Si0.62O2 in hydrogen at 700-degrees-C. The germanium di oxide 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 el ectron microscopy reveals that the nucleation process is homogeneous, leading to a uniform distribution of small Ge crystallites imbedded in the remaining vitreous SiO2.