Figure 2.

Monte Carlo simulation model and results. (a) Three-dimensional geometrical model for 50 nm × 50 nm × 12.5 nm cuboids stained with 3% lead located at different depths in an 800 nm × 800 nm × 800 nm epoxy block, together with views in the x-z plane, y-z plane and x-y plane. Centers of cuboids are located 6.25 nm, 18.75 nm, 31.25 nm and 43.75 nm, respectively, from the top surface of the block from left to right. Dimension in z is not drawn to scale. (b) Simulated backscattered images at primary beam energies from 0.8 keV to 2.2 keV with an interval of 0.1 keV. (c) Corresponding intensity profiles for cuboids shown in (b). These plots provide a guide of primary voltage selection. Scale bar, 50 nm.