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

JULIO FERRÓN; RICARDO VIDAL; FERNANDO BONETTO

Aracaju

Conferencia; Autumn Meeting of the Brazilian Society of Physics 2019; 2019

Sociedad Brasilera de Física

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. In the present work we present experimental LEIS spectra of Ar+ ion scattered by a Cu(111) surface, showing unexpected features when studied via the binary collision model. We analyze the results within the frame of molecular dynamics (MD) trajectory simulations including the analysis of both, projectiles and direct recoils. 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 peaks in the Ar/Cu LEIS spectrum.