Mieszko Jaskiewicz oral presentation (SN1-Fri2-2-5)
Argon cluster-ion sputtering near the monatomic sputter threshold: Molecular Dynamics simulations
1 Newcastle University, Claremont Road, NE1 7RU NEWCASTLE UPON TYNE, United Kingdom
2 University of Cincinnati, 2600 Clifton Avenue, OH 45219 Cincinnati, United States
Molecular Dynamics (MD) simulations have been extremely useful over the last two decades in elucidating the details of monatomic and more recently cluster-ion sputtering processes[1,2,3]. From a semi-empirical point of view, a relatively simple model of cluster total sputter yield, Y, has been developed and shown to agree well with measurements;
Where 0 is the energy per atom in argon clusters containing n atoms, U is the “effective” monatomic sputter threshold, and A, s are other target material-specific parameters. U defines the transition energy-per-atom between high-energy and low-energy behavior. What experimental measurements exist suggest this is indeed related to the monatomic sputter threshold. However the real process is a complex many-body problem and improved understanding is likely to emerge from MD simulation rather than experiments or closed-form analysis.
To elucidate the role of the parameter U we have performed MD simulations using the Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS) parallel MD code on high-performance computer (HPC) clusters at Cincinnati and Newcastle. Typically we have used silicon as an archetypal inorganic substrate and for cluster sizes of between 100 and 4,000 argon atoms and 0 in the range 1 to 20eV per atom corresponding to the most important regime for experimental cluster depth-profiling in SIMS and XPS.
Figure 1 Ar1000 cluster impact on silicon at 10eV/atom
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 D Maciazek, R J Paruch, Z Postawa, B J Garrison, J Phys Chem, 120 (2016) 25473.
 R J Paruch, Z Postawa, B J Garrison, J. Vac. Sci. Tech B 34 (2016) 03H105
 P J Cumpson, J F Portoles, A J Barlow, N Sano, J. Appl. Phys. 114 (2013) 124313
 S. Plimpton, J Comp Phys, 117, 1-19 (1995), also http://lammps.sandia.gov