NANOCRYSTALLINE GERMANIUM SYNTHESIS FROM HYDROTHERMALLY OXIDIZED SI1-XGEX ALLOYS

We have used low temperature (475-degrees-C), high pressure (25 MPa) hydrothermal oxidation to form compositionally congruent oxides from epitaxial thin film alloys of Si90Ge10. The resulting Si90Ge10O2 oxide alloys are shown to be thermodynamically unstable when in contact with Si but remain microstructurally unchanged on annealing at 700-degrees-C for 1 h. After annealing for 1 h at 800-degrees-C, Raman spectroscopy and cross-sectional transmission electron microscopy reveal the presence of crystalline Ge precipitates in the oxide. Transmission electron microscopy was used to show that these precipitates are distributed through the oxide thickness, and range in size from 1 to 20 nm after a 1 h. 800-degrees-C anneal.