This study focuses on the microscopic modeling of 0–25
keV
Bi1–3–5 and C60 cluster impacts
on three different targets (Au crystal, adsorbed Au nanoparticle,
and organic solid), using molecular dynamics simulations, and on the
comparison of the calculated quantities with recent experimental results,
reported in the literature or obtained in our laboratory. The sputtering
statistics are reported, showing nonlinearity of the sputtering yields
with the number of cluster atoms at the same incident velocity for
Bi1–5 bombardment. They are compared to experiments
(especially for the organic target), and the microscopic explanation
of the observations is analyzed. The results show that the respective
behaviors and performances of the different projectiles are strongly
dependent on the target, with clusters of heavy Bi atoms being more
efficient at sputtering gold and, conversely, fullerene clusters inducing
the largest sputtering yields of the organic material (mass matching).
For organic targets, some important and novel conclusions of this
work are the following: (i) The increase of the sputtering yield when
going from Bi atoms to Bi clusters is insufficient to explain the
much larger increase of characteristic ion yields, suggesting a projectile-dependent
ionization probability. (ii) The extent of molecular fragmentation
follows the order of Bi > Bi3 > Bi5 >
C60, that is, softer emission with larger clusters. (iii)
Even
5–10 keV Bi atoms create collective molecular motions and craters
in the polymeric solid, though the collision cascades are rather dilute.
Finally, a second series of simulations performed at low energies
predict that 0.1–1 keV Bi
n
clusters
should not provide better results for sputtering and depth profiling
than isoenergetic single atoms.