Interactions of germanium atoms with silica surfaces

GeH4 is thermally cracked over a hot filament depositing 0.7-15 ML Ge onto 2-7 nm SiO2/Si(1 0 0) at substrate temperatures of 300-970 K. Ge bonding changes are analyzed during annealing with X-ray photoelectron spectroscopy. Ge, GeHx, GeO, and GeO2 desorption is monitored through temperature programmed desorption in the temperature range 300-1000 K. Low temperature desorption features are attributed to GeO and GeH4. No GeO2 desorption is observed, but GeO2 decomposition to Ge through high temperature pathways is seen above 750 K. Germanium oxidization results from Ge etching of the oxide substrate. With these results, explanations for the failure of conventional chemical vapor deposition to produce Ge nanocrystals on SiO2 surfaces are proposed.