In order to asses the yield and origin of secondary electrons as
well as backscattered electrons in SEM, Monte Carlo simulations
using CASINO [19] have been utilized. The sample was modeled
using a 2 nm thick carbon layer on a 10 nm thick gold slab on top
of a silicon substrate. The density of the carbon layer has been
manually set to 0.5 g/cm3
. Secondary electron and backscattered
electron yields were calculated as well as the Zmax distribution.
SRIM [20] calculations have been used to obtain insight into the
contrast ratios for backscattered helium images. Backscatter yields for
nano-rods and CTA covered siliconwere calculated using the Kinchin–
Pease approximation. The same sample setup as above has been used
with the exception that the carbon layer has been replaced with a
layer of CTA stoichiometry and a density of 0.5 g/cm3
.