Figure 3
Rapid Ge nanocrystallites coarsening in SiO 2 without migration because of a surrounding Si 3 N 4 capping layer. The Si3N4 capping layer was deposited after the oxidation of the SiGe pillars to create the Ge nanocrystallite clusters and then thermally annealed at 900°C for 90 min in an O2 ambient. (a) Schematic diagram of initially as-formed poly-SiGe pillars. CTEM micrographs of (b) SiGe nanopillars that were thermally oxidized at 900°C for 30 min in an H2O ambient followed by the deposition of Si3N4 capping layer and (c) under further thermal annealing at 900°C for 90 min in an O2 ambient. (d) Schematic diagram showing the vertical and in-plane symmetry of Si interstitial flow that prevents the Ge nanocrystallite clusters from migrating in a preferred direction.