“Cluster Bombardment of Solids: Atomistic, Mesoscopic and Analytic Views”
Barbara J. Garrison, Penn State
Energetic (10-40 keV) particle bombardment of solids has a number of important applications including sputtering cleaning of solids, dopant implantation, ion beam milling, elemental depth profiling, erosion of the moons of Saturn and the mass spectrometric technique of secondary ion mass spectrometry (SIMS). Of particular interest to our group is the recent experimental advance of using cluster beams such as C60 + and Au3 + for SIMS instead of atomic beams. The cluster beams have allowed new applications, including molecular depth profiling and 3D imaging. There are several aspects to the process that we have been modeling with molecular dynamics (MD) computer simulations. First, we have addressed the fundamental physics of differences in atomic vs. cluster bombardment. Second, since the simulations are computationally intensive, we have developed an analytic model to describe the basic process (fluid flow) of emission of molecules due to cluster bombardment. This model allows us to predict some of the experimental quantities without full simulations. Finally, we have developed a divide-and-conquer approach so that we can mimic the depth profiling conditions of ~5x1013 impacts/cm2 in a not unreasonable amount of computer time of several months. Examples and animations from our computational studies will be presented.
Barbara J. Garrison is head of the chemistry department at Penn State. She earned her PhD from the University of California, Berkeley in 1975. Her research interests include computer simulations of reactions at surfaces, keV particle bombardment of solids, laser ablation, diamond film growth and time-dependent Monte Carlo methods.