Au400 Sputtering of a Polymer with Adsorbed Metal Nanoparticles: A Molecular Dynamics Study

Using molecular dynamics simulations, this article investigates the interaction of 5―40 keV Au400 projectiles with polyethylene and with gold-adsorbed nanoparticles of ∼25 A in diameter. Impacts over the Au nanoparticles and on the polymer are compared in terms of sputtered quantities, projectile penetration, and energy deposition in the substrate, and connections with experiments are made. In the considered energy range, impacts over a nanoparticle emit 1 order of magnitude more organic material than impacts on the polymeric substrate. This is explained by the large range of the heavy Au400 projectile in the polymer and the increased stopping when it first encounters an adsorbed nanoparticle. As a result, we predict that organic material sputtering and analysis with Au400 should be favored by the presence of gold nanoparticles (metal-assisted secondary ion mass spectrometry). The simulations also indicate that the average depth of emission of organic material does not exceed 20 A, and it is much less for impacts on the nanoparticles. Finally, Au400 projectiles with >10 keV of energy are able to sputter entire nanoparticles via pressure wave development and collective molecular motions in the organic substrate.