The poly-Si0.85Ge0.15 layers were lithographically patterned to create nanopillar structures of various diameters (50 to 120 nm) over the buffer oxide layers and then subsequently oxidized at 900°C for 10 to 90 min to produce Ge nanocrystallites embedded within the oxide (Figure 2). It takes about 20 min to convert a 60-nm-thick, 120-nm-wide poly-Si0.85Ge0.15 pillar completely into SiO2/Ge nanocrystallites at 900°C by thermal oxidation within an H2O ambient.
this website The entire process has been selleck described together with the mechanism for Ge nanocrystallite formation in previous publications [7–9]. For yet another sample (Figure 3), the oxidized pillars were subsequently encapsulated via the conformal deposition of a thin capping layer of Si3N4. Details
of the thicknesses of the various layers are provided in the schematic diagrams of various structures. It is our contention that Si interstitials are provided both by the Si3N4 layers and by the oxidized SiGe nanopillars themselves, in the latter case, perhaps generated by the incomplete oxidation of the Si within the SiGe. Figure 1 Formation 17DMAG of Ge nanocrystallite clusters by thermally oxidizing poly-Si 0.85 Ge 0.15 pillars grown over buffer oxide. (a) Schematic diagram of the initially as-formed poly-SiGe pillars, (b) cross-sectional transmission electron microscopy (CTEM) micrograph of a self-assembled cluster of Ge nanocrystallites in the core of the oxidized pillars following 900°C 20 min oxidation in an H2O ambient, and (c) enlarged CTEM micrograph of the Ge nanocrystallites. Figure 2 Schematic diagrams and CTEM micrographs of Ge nanocrystallites growth and migration into underneath buffer Si 3 N 4 . D-malate dehydrogenase Ge nanocrystallite clusters migrate into the buffer Si3N4 underneath the original poly-Si0.85Ge0.15 pillar with coarsening and possible coalescence of these nanocrystallites after thermal annealing at 900°C for 30 min in an
H2O ambient of the previously oxidized SiGe pillars over (a) 8-nm-thick, (b) 15-nm-thick, and (c) 22-nm-thick buffer Si3N4 layers. (d) Schematic diagram illustrating the mechanism of Si interstitials generated from the Si3N4 layers enhancing the coarsening and coalescence of Ge nanocrystallites when penetrating through thin and thick Si3N4 layers, respectively. 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.