Charge Transfer in Low-energy Collisions of Protons with a Monolayer C60 Film Deposited on Cu(111).

M. TACCA; V. QUINTERO RIASCOS; R. VIDAL; E. C. GOLDBERG; F. BONETTO

Encuentro; Autumm Meeting of the Brazilian Physical Society; 2020

Sociedade Brazileira de Fisica

Charge exchange processes in collisions between H+ projectiles and a monolayer C60 film deposited on Cu(111) are experimentally and theoretically analyzed for a wide range of energies (2-8keV) in the low-energy regime. The negative, positive and total projectile scattered ion fractions are experimentally determined by using the low energy ion scattering (LEIS) technique. Two different collisional setups are studied for a fixed backscattering angle of 135o: 45°/90° and 67.5°/67.5° incoming/exit angles, determined with respect to the target surface plane.Total ion fractions between 10% and 20% with comparable positive and negative scattered fractions are experimentally found in the whole energy range analyzed.A first-principles based theoretical model is used to describe the dynamic charge exchange processes taking place in the experimental collisional situation. A good description of the experimental results is obtained, especially for the 45°/90° collisional situation. This result is a consequence of two factors: i) the final charge state is mostly defined in the exit trajectory of the projectile and ii) in the theoretical model a normal collision is assumed.Unlike to a three-layers thick C60 film deposited on cooper, the Cu substrate plays a preponderant role in the present problem. The substrate significantly alters: i) the total DOS of the monolayer, conferring metallic properties to the film, and ii) the local state density of the C atoms located close to the Cu(111) surface, which are potential scattering centers.