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

Abstract

Using molecular dynamics simulations, this article investigates the interaction of 5–40 keV Au400 projectiles with polyethylene and with gold-adsorbed nanoparticles of ∼25 Å 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 Å, 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.

Surface sputtering with nanoclusters: the relevant parameters

“…With 197 C, an elongated track is formed in the material. Comparable effects have been observed by Urbassek et al [22] and Restrepo et al [21] for gold nanoclusters impinging on various materials. In Fig.…”

“…Upon 10 keV bombardment of crystalline polyethylene (coarse-grained description [21] ), the range of *C 60 increases with the mass of the carbon 'isotopes'. In parallel, the mass of fragments ejected per impact decreases monotonically.…”

Re-print of “Sputtering of polymers by keV clusters: Microscopic views of the molecular dynamics”

“…Sample 1 was an amorphous polyethylene (PE) solid containing ∼4 × 10 5 united atoms, where each molecule was a string of 97CH 2 particles of 14 amu and capped with 2CH 3 particles of 15 amu (1.4 kDa) [36]. The crystalline PE sample (2) consisted of a box with either 4.8 × 10 5 united atoms or 9.6 × 10 5 united atoms (used to compute ranges) forming aligned chains of PE arranged horizontally in the linear zig-zag configuration [37]. Each chain was formed of 200 individual CH 2 elements, with the particles at each end being held rigid.…”

“…1. Other projectiles include Bi n [45], *C 60 with artificial atomic mass [46], Au 400 [37] and Ar n [47]. All the projectiles were modeled at the atomistic level, with hydrogen 1 H replaced by tritium 3 H for computational efficiency.…”

Cluster SIMS of Organic Materials: Theoretical Insights

“…114 Recently, two articles reported on the sputtering of a polymeric material by Au 400 projectiles with 10-40 keV of kinetic energy. 116,117 As an example, Au 400 (the polymer chains are perpendicular to the plane of the paper). 116 The Au 400 cluster implants deeply in the sample, depositing its energy in a narrow cylindrical track where the material is damaged.…”