The influence of surface defects on the low energy scattering of Ar ions from a Cu(111) surface

Abstract

Low-energy ion scattering (LEIS) is distinguished by its acute surface sensitivity. Depending on the projectile/target system under analysis and the incoming energy of the projectile, it can provide information on the outermost atomic layer of the target surface. Due to the range of energies involved in LEIS, an elemental model based on a two-body classical elastic collision is generally accepted to describe the energy-position of all the peaks appearing in a LEIS spectrum. Here, we show that, under specific experimental conditions for Ar+ ions colliding with a Cu(111) surface, there exist certain peaks in the LEIS spectra that cannot be explained by the binary collision model. We experimentally show also that the appearance of these peaks is strongly dependent on the experimental conditions. We use molecular dynamics simulations to describe and understand the physical processes behind these particular features in the LEIS spectrum. We determine that surface defects such as islands or steps, inherent to any real physical surface, are crucial to the existence of the mentioned singular features in the Ar/Cu LEIS spectrum.