Molecular dynamics study of the sputtering of nanostructured metal-organic surfaces

(eng) Using molecular dynamics simulations, the present research has been focused on the elucidation of the mechanisms of sputtering of hybrid metal-organic surfaces. This study takes place in the context of surface analysis by secondary ion mass spectrometry, a method in which kiloelectronvolt projectiles are used to bombard the samples and the ions emitted by the surface are mass-analyzed. The central question here was to understand the beneficial effect of the presence of gold nanoparticles (NPs) in organic surfaces for molecular and fragment ion emission enhancement, experimentally observed when atomic projectiles were used, and why a different behavior occurred upon polyatomic projectile bombardment. In the process of answering this question, some of the most fundamental aspects involved in the keV bombardment, by monoatomic and polyatomic projectiles (Ga, C60, Aun and Arn), of a polymeric solid covered by gold NPs as well as of the interface between a gold crystal and a polymer, have been unveiled. Special attention was given to the influence of the metal in the energy deposition process and in the formation of the sputtered organic species. Two important results of this research, valid for atoms and clusters, are that (1) the sputter yield is proportional to the quantity of energy deposited in the extreme surface of the polymer, which depends directly on the stopping power and inversely on the range of the projectile, and (2) the sputtering maximizes when the atomic masses of the cluster projectile and target match, i.e. when the energy transfer and the angular dispersion in diatomic collisions are maximum. In addition, the detailed analysis of the simulations provides abundant information concerning, e.g., the projectile implantation, damage produced in the target, induced pressure waves, crater sizes, and mass, energy and origin of the emitted fragments, as a function of the initial conditions, which should be useful for experimentalists.