Fig. 2: NanoSIMS isotopic elemental analysis on isotopically enriched samples.
From: Highly 28Si enriched silicon by localised focused ion beam implantation
a–d show depth profiles of the measured isotopic ratios for each of the three silicon isotopes from samples 1 (dotted line) and 2 (solid line), which have been normalised by dividing each by SiT = 28Si + 29Si + 30Si. b and d are enlarged from the dotted regions outlined within (a) and (c), respectively. e shows the 12C and 16O concentration depth profiles for sample 3 which was annealed following enrichment. The near-surface carbon signal shown by the dotted green line in part (e) was selected such that surface contaminants introduced during sample transfer were excluded (see Supplementary Fig. 5). This near-surface signal along with the oxygen profile shows the limited introduction of impurities within the enriched region relative to the unimplanted substrate. The figure inset to (e) illustrates 12C gettering observed near the bottom of the enriched volume where the C concentration rises above the minimum detectable limit. The concentration at each depth is the average value across the 5 μm by 5 μm area sampled within each of the enriched volumes during the SIMS analysis. The shaded grey box in each plot indicates the portion of the SIMS depth profile affected by the steady-state artefact and thus excluded from the analysis.
