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Abstract
A beam of negative Pt − self-ions was employed on Pt(111) at 1050–1150 K, for various impact energies in the range 60–2500 eV, to observe the way lattice sites are added to the crystal by the ion beam. The measurements were made in situ, in a low-energy electron microscope, by direct observation of surface sink (i.e. step edge) motion. The results lie in the regime in which the surface responds linearly to the ion beam intensity. An absolute calibration of the surface sputter yield is made by comparison with recent molecular dynamics (MD) simulations. Within this comparison, the results show that current MD simulations afford a good description of ion beam impacts on crystalline surfaces, and reproduce the observed neutral energy of 245 eV for Pt(111), at which sputtering balances the self-ion input. The net flow of surface steps exhibits the energy dependence expected of combined epitaxial growth and ion beam erosion processes, with bulk and surface lattice sites otherwise conserved.
Acknowledgements
We thank R. S. Averback and his coworkers for access to their molecular dynamics results for Pt − on Pt(111) prior to publication. This research was supported by US Department of Energy through grant DEFG02-02ER46011. The LEEM was maintained in the Center for Microanalysis of Materials, University of Illinois, which is partly supported by DOE grant DEFG02-91-ER45439.