Si1-xGex Nanocrystals Observed by EFTEM: Influence of the Dry and Wet Oxidation Process

Abstract

ABSTRACTWe report about the formation of Si1-xGex nanocrystals (NC) in an oxide matrix after oxidizing a polycrystalline Si0.7Ge0.3 layer in wet and dry conditions. We have characterized the NC by Energy Filtered Transmission Electron Microscopy (EFTEM). EFTEM images analyses show the evolution of the oxidation of polycrystalline Si0.7Ge0.3 layer. We observe that a layer with Ge-rich nanoclusters is formed. For wet oxidations we find Ge-rich Si1-xGex nanocrystals while for dry oxidations Si is oxidized faster and Ge is completely segregated. Results are contrasted with infrared and Raman spectroscopies. In conclusion, wet oxidation seems to be preferable to oxidize polycrystalline Si1-xGex to obtain Ge-rich NC embedded in an oxide matrix, as both Ge and Si are oxidized, in contrast to dry oxidation, where Ge is mainly segregated.