Figure 1
Atom probe tomography analysis. (a) APT-reconstructions with Si NCs depicted as red Si iso-concentration surfaces (≥70 at%), Si-atoms in red and P-atoms in green. (b) Frequency distribution of the Si NC volumes of each sample, the solid lines (splines) are just a guide to the eye. (c) The number of P-atoms per NC as function of NC volume represents an approximately linear behaviour (small symbols: APT raw data, large symbols: average values from grouping NCs in volume classes). The inset magnifies the region around one P-atom per NC. Grey dashed lines show that NCs with 1 P-atom are on average at dNC ≈ 2 nm. (d) Comparison of the relative frequencies of NCs with n P-atoms per NC as measured by APT (bar graph) and ideal Poisson distributions with the average number of P-atoms per NC in each sample as expected value (solid lines). Due to the NC size dispersion the distributions are clearly non-Poissonian but they can be fitted as exponential probability distributions (fits not shown for the sake of clarity).
