Figure 3
From: Directed Self-Assembly of Ge Quantum Dots Using Focused Si2+ Ion Beam Patterning
Bright field transmission electron microscopy (TEM) images obtained along the [011] axis from samples in which Si2+ was implanted in a pattern of lines along [011], each made up of 50 nm steps with ~1 × 105 ions implanted per step. The dose is thus 2 × 103 ions per nm. Cross sections were cut after (a) implantation, and after annealing at (b) 500 °C and (c) at 600 °C for 30 minutes. As-implanted (a), the amorphized area is ~370 nm wide and 140 nm deep. After (b) annealing at 500 °C, the amorphous area reduces to ~245 nm wide and 63 nm deep. After (c) annealing at 600 °C, recrystallization occurs but leaves a pair of residual defects, highlighted with black circles. The defect on the left makes an angle of ~55° with the surface, whereas the defect on the right has a kink with an angle of ~100°, consistent with the angle between {111} facets. In (c), the surface pit expected for these implant/anneal conditions would be too shallow to be visible. (d) A schematic of recrystallization via multi-directional solid phase epitaxial regrowth where the growth fronts form {111} nanofacets. Fully amorphous areas are shown in white and crystalline Si in blue. The transition area in the first panel indicates a partially amorphized region.
