Figure 1.

Silicon particle characterization. (A) SEM and optical microscopy images of the porous silicon particles as prepared and (B) their size distribution. All scale bars in the insets correspond to 2 μm. (C) SEM image of a porous silicon colloid carved using the focused ion beam (FIB) technique. (D) EDX analysis of materials inside a silicon colloid as a function of the distance from the sphere center, normalized to the sphere radius (d = distance from the sphere center/sphere radius). The graph shows the counts for the Si and O peaks of the EDX spectra at five different points of analysis. The points were selected along a line travelling from the nucleus (d = 0) to the sphere surface (d = 1).